diff --git a/compiler/rustc_abi/src/extern_abi.rs b/compiler/rustc_abi/src/extern_abi.rs
index 543c2f8ab12cf..4d70afd4e0bca 100644
--- a/compiler/rustc_abi/src/extern_abi.rs
+++ b/compiler/rustc_abi/src/extern_abi.rs
@@ -191,6 +191,17 @@ impl StableOrd for ExternAbi {
 }
 
 impl ExternAbi {
+    /// An ABI "like Rust"
+    ///
+    /// These ABIs are fully controlled by the Rust compiler, which means they
+    /// - support unwinding with `-Cpanic=unwind`, unlike `extern "C"`
+    /// - often diverge from the C ABI
+    /// - are subject to change between compiler versions
+    pub fn is_rustic_abi(self) -> bool {
+        use ExternAbi::*;
+        matches!(self, Rust | RustCall | RustIntrinsic | RustCold)
+    }
+
     pub fn supports_varargs(self) -> bool {
         // * C and Cdecl obviously support varargs.
         // * C can be based on Aapcs, SysV64 or Win64, so they must support varargs.
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 2197dd68eaf69..a59dc870aa33d 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -1812,7 +1812,7 @@ where
         f.debug_struct("Layout")
             .field("size", size)
             .field("align", align)
-            .field("abi", backend_repr)
+            .field("backend_repr", backend_repr)
             .field("fields", fields)
             .field("largest_niche", largest_niche)
             .field("uninhabited", uninhabited)
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index c0188dde56518..4d4585145ef03 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -926,7 +926,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     if let Some(first_char) = constraint.ident.as_str().chars().next()
                         && first_char.is_ascii_lowercase()
                     {
-                        tracing::info!(?data, ?data.inputs);
                         let err = match (&data.inputs[..], &data.output) {
                             ([_, ..], FnRetTy::Default(_)) => {
                                 errors::BadReturnTypeNotation::Inputs { span: data.inputs_span }
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index 6b6244b05aa9b..d00c797755f3f 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -268,7 +268,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 }
                 GenericArgs::Parenthesized(data) => match generic_args_mode {
                     GenericArgsMode::ReturnTypeNotation => {
-                        tracing::info!(?data, ?data.inputs);
                         let err = match (&data.inputs[..], &data.output) {
                             ([_, ..], FnRetTy::Default(_)) => {
                                 BadReturnTypeNotation::Inputs { span: data.inputs_span }
diff --git a/compiler/rustc_attr_parsing/src/parser.rs b/compiler/rustc_attr_parsing/src/parser.rs
index 96fc9d7d9ac47..f0cce26f4e248 100644
--- a/compiler/rustc_attr_parsing/src/parser.rs
+++ b/compiler/rustc_attr_parsing/src/parser.rs
@@ -473,6 +473,15 @@ impl<'a> MetaItemListParserContext<'a> {
         {
             self.inside_delimiters.next();
             return Some(MetaItemOrLitParser::Lit(lit));
+        } else if let Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) =
+            self.inside_delimiters.peek()
+        {
+            self.inside_delimiters.next();
+            return MetaItemListParserContext {
+                inside_delimiters: inner_tokens.iter().peekable(),
+                dcx: self.dcx,
+            }
+            .next();
         }
 
         // or a path.
diff --git a/compiler/rustc_data_structures/src/marker.rs b/compiler/rustc_data_structures/src/marker.rs
index 6ae97222f77fd..4cacc269709a9 100644
--- a/compiler/rustc_data_structures/src/marker.rs
+++ b/compiler/rustc_data_structures/src/marker.rs
@@ -1,3 +1,5 @@
+use std::alloc::Allocator;
+
 #[rustc_on_unimplemented(message = "`{Self}` doesn't implement `DynSend`. \
             Add it to `rustc_data_structures::marker` or use `IntoDynSyncSend` if it's already `Send`")]
 // This is an auto trait for types which can be sent across threads if `sync::is_dyn_thread_safe()`
@@ -28,8 +30,8 @@ impls_dyn_send_neg!(
     [*const T where T: ?Sized]
     [*mut T where T: ?Sized]
     [std::ptr::NonNull<T> where T: ?Sized]
-    [std::rc::Rc<T> where T: ?Sized]
-    [std::rc::Weak<T> where T: ?Sized]
+    [std::rc::Rc<T, A> where T: ?Sized, A: Allocator]
+    [std::rc::Weak<T, A> where T: ?Sized, A: Allocator]
     [std::sync::MutexGuard<'_, T> where T: ?Sized]
     [std::sync::RwLockReadGuard<'_, T> where T: ?Sized]
     [std::sync::RwLockWriteGuard<'_, T> where T: ?Sized]
@@ -96,8 +98,8 @@ impls_dyn_sync_neg!(
     [std::cell::RefCell<T> where T: ?Sized]
     [std::cell::UnsafeCell<T> where T: ?Sized]
     [std::ptr::NonNull<T> where T: ?Sized]
-    [std::rc::Rc<T> where T: ?Sized]
-    [std::rc::Weak<T> where T: ?Sized]
+    [std::rc::Rc<T, A> where T: ?Sized, A: Allocator]
+    [std::rc::Weak<T, A> where T: ?Sized, A: Allocator]
     [std::cell::OnceCell<T> where T]
     [std::sync::mpsc::Receiver<T> where T]
     [std::sync::mpsc::Sender<T> where T]
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index f2b133f56773b..f69e756a3e1b5 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -626,7 +626,6 @@ pub enum StashKey {
     MaybeFruTypo,
     CallAssocMethod,
     AssociatedTypeSuggestion,
-    MaybeForgetReturn,
     /// Query cycle detected, stashing in favor of a better error.
     Cycle,
     UndeterminedMacroResolution,
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 3f75cce009225..c30666d9b4572 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -278,13 +278,6 @@ hir_analysis_invalid_union_field =
 hir_analysis_invalid_union_field_sugg =
     wrap the field type in `ManuallyDrop<...>`
 
-hir_analysis_invalid_unsafe_field =
-    field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be unsafe
-    .note = unsafe fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
-
-hir_analysis_invalid_unsafe_field_sugg =
-    wrap the field type in `ManuallyDrop<...>`
-
 hir_analysis_late_bound_const_in_apit = `impl Trait` can only mention const parameters from an fn or impl
     .label = const parameter declared here
 
@@ -620,6 +613,8 @@ hir_analysis_variances_of = {$variances}
 hir_analysis_where_clause_on_main = `main` function is not allowed to have a `where` clause
     .label = `main` cannot have a `where` clause
 
+hir_analysis_within_macro = due to this macro variable
+
 hir_analysis_wrong_number_of_generic_arguments_to_intrinsic =
     intrinsic has wrong number of {$descr} parameters: found {$found}, expected {$expected}
     .label = expected {$expected} {$descr} {$expected ->
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/always_applicable.rs
similarity index 62%
rename from compiler/rustc_hir_analysis/src/check/dropck.rs
rename to compiler/rustc_hir_analysis/src/check/always_applicable.rs
index d7dfe482da449..ba5b61d3fce0b 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/always_applicable.rs
@@ -1,8 +1,15 @@
+//! This module contains methods that assist in checking that impls are general
+//! enough, i.e. that they always apply to every valid instantaiton of the ADT
+//! they're implemented for.
+//!
+//! This is necessary for `Drop` and negative impls to be well-formed.
+
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::codes::*;
 use rustc_errors::{ErrorGuaranteed, struct_span_code_err};
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
 use rustc_infer::traits::{ObligationCause, ObligationCauseCode};
+use rustc_middle::span_bug;
 use rustc_middle::ty::util::CheckRegions;
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypingMode};
 use rustc_trait_selection::regions::InferCtxtRegionExt;
@@ -27,11 +34,12 @@ use crate::hir::def_id::{DefId, LocalDefId};
 /// 3. Any bounds on the generic parameters must be reflected in the
 ///    struct/enum definition for the nominal type itself (i.e.
 ///    cannot do `struct S<T>; impl<T:Clone> Drop for S<T> { ... }`).
-///
 pub(crate) fn check_drop_impl(
     tcx: TyCtxt<'_>,
     drop_impl_did: DefId,
 ) -> Result<(), ErrorGuaranteed> {
+    let drop_impl_did = drop_impl_did.expect_local();
+
     match tcx.impl_polarity(drop_impl_did) {
         ty::ImplPolarity::Positive => {}
         ty::ImplPolarity::Negative => {
@@ -45,55 +53,107 @@ pub(crate) fn check_drop_impl(
             }));
         }
     }
-    let dtor_self_type = tcx.type_of(drop_impl_did).instantiate_identity();
-    match dtor_self_type.kind() {
+
+    tcx.ensure_ok().orphan_check_impl(drop_impl_did)?;
+
+    let dtor_impl_trait_ref = tcx.impl_trait_ref(drop_impl_did).unwrap().instantiate_identity();
+
+    match dtor_impl_trait_ref.self_ty().kind() {
         ty::Adt(adt_def, adt_to_impl_args) => {
-            ensure_drop_params_and_item_params_correspond(
+            ensure_impl_params_and_item_params_correspond(
                 tcx,
-                drop_impl_did.expect_local(),
+                drop_impl_did,
                 adt_def.did(),
                 adt_to_impl_args,
             )?;
 
-            ensure_drop_predicates_are_implied_by_item_defn(
+            ensure_impl_predicates_are_implied_by_item_defn(
                 tcx,
-                drop_impl_did.expect_local(),
-                adt_def.did().expect_local(),
+                drop_impl_did,
+                adt_def.did(),
                 adt_to_impl_args,
             )
         }
         _ => {
-            // Destructors only work on nominal types. This was
-            // already checked by coherence, but compilation may
-            // not have been terminated.
-            let span = tcx.def_span(drop_impl_did);
-            let reported = tcx.dcx().span_delayed_bug(
-                span,
-                format!("should have been rejected by coherence check: {dtor_self_type}"),
-            );
-            Err(reported)
+            span_bug!(tcx.def_span(drop_impl_did), "incoherent impl of Drop");
         }
     }
 }
 
-fn ensure_drop_params_and_item_params_correspond<'tcx>(
+pub(crate) fn check_negative_auto_trait_impl<'tcx>(
     tcx: TyCtxt<'tcx>,
-    drop_impl_did: LocalDefId,
-    self_type_did: DefId,
+    impl_def_id: LocalDefId,
+    impl_trait_ref: ty::TraitRef<'tcx>,
+    polarity: ty::ImplPolarity,
+) -> Result<(), ErrorGuaranteed> {
+    let ty::ImplPolarity::Negative = polarity else {
+        return Ok(());
+    };
+
+    if !tcx.trait_is_auto(impl_trait_ref.def_id) {
+        return Ok(());
+    }
+
+    if tcx.defaultness(impl_def_id).is_default() {
+        tcx.dcx().span_delayed_bug(tcx.def_span(impl_def_id), "default impl cannot be negative");
+    }
+
+    tcx.ensure_ok().orphan_check_impl(impl_def_id)?;
+
+    match impl_trait_ref.self_ty().kind() {
+        ty::Adt(adt_def, adt_to_impl_args) => {
+            ensure_impl_params_and_item_params_correspond(
+                tcx,
+                impl_def_id,
+                adt_def.did(),
+                adt_to_impl_args,
+            )?;
+
+            ensure_impl_predicates_are_implied_by_item_defn(
+                tcx,
+                impl_def_id,
+                adt_def.did(),
+                adt_to_impl_args,
+            )
+        }
+        _ => {
+            if tcx.features().auto_traits() {
+                // NOTE: We ignore the applicability check for negative auto impls
+                // defined in libcore. In the (almost impossible) future where we
+                // stabilize auto impls, then the proper applicability check MUST
+                // be implemented here to handle non-ADT rigid types.
+                Ok(())
+            } else {
+                span_bug!(tcx.def_span(impl_def_id), "incoherent impl of negative auto trait");
+            }
+        }
+    }
+}
+
+fn ensure_impl_params_and_item_params_correspond<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    impl_def_id: LocalDefId,
+    adt_def_id: DefId,
     adt_to_impl_args: GenericArgsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
     let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_args, CheckRegions::OnlyParam) else {
         return Ok(());
     };
 
-    let drop_impl_span = tcx.def_span(drop_impl_did);
-    let item_span = tcx.def_span(self_type_did);
-    let self_descr = tcx.def_descr(self_type_did);
+    let impl_span = tcx.def_span(impl_def_id);
+    let item_span = tcx.def_span(adt_def_id);
+    let self_descr = tcx.def_descr(adt_def_id);
+    let polarity = match tcx.impl_polarity(impl_def_id) {
+        ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => "",
+        ty::ImplPolarity::Negative => "!",
+    };
+    let trait_name = tcx
+        .item_name(tcx.trait_id_of_impl(impl_def_id.to_def_id()).expect("expected impl of trait"));
     let mut err = struct_span_code_err!(
         tcx.dcx(),
-        drop_impl_span,
+        impl_span,
         E0366,
-        "`Drop` impls cannot be specialized"
+        "`{polarity}{trait_name}` impls cannot be specialized",
     );
     match arg {
         ty::util::NotUniqueParam::DuplicateParam(arg) => {
@@ -116,17 +176,22 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
 /// Confirms that all predicates defined on the `Drop` impl (`drop_impl_def_id`) are able to be
 /// proven from within `adt_def_id`'s environment. I.e. all the predicates on the impl are
 /// implied by the ADT being well formed.
-fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
+fn ensure_impl_predicates_are_implied_by_item_defn<'tcx>(
     tcx: TyCtxt<'tcx>,
-    drop_impl_def_id: LocalDefId,
-    adt_def_id: LocalDefId,
+    impl_def_id: LocalDefId,
+    adt_def_id: DefId,
     adt_to_impl_args: GenericArgsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
     let infcx = tcx.infer_ctxt().build(TypingMode::non_body_analysis());
     let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
 
-    let impl_span = tcx.def_span(drop_impl_def_id.to_def_id());
-
+    let impl_span = tcx.def_span(impl_def_id.to_def_id());
+    let trait_name = tcx
+        .item_name(tcx.trait_id_of_impl(impl_def_id.to_def_id()).expect("expected impl of trait"));
+    let polarity = match tcx.impl_polarity(impl_def_id) {
+        ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => "",
+        ty::ImplPolarity::Negative => "!",
+    };
     // Take the param-env of the adt and instantiate the args that show up in
     // the implementation's self type. This gives us the assumptions that the
     // self ty of the implementation is allowed to know just from it being a
@@ -145,17 +210,21 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
     let adt_env =
         ty::EarlyBinder::bind(tcx.param_env(adt_def_id)).instantiate(tcx, adt_to_impl_args);
 
-    let fresh_impl_args = infcx.fresh_args_for_item(impl_span, drop_impl_def_id.to_def_id());
+    let fresh_impl_args = infcx.fresh_args_for_item(impl_span, impl_def_id.to_def_id());
     let fresh_adt_ty =
-        tcx.impl_trait_ref(drop_impl_def_id).unwrap().instantiate(tcx, fresh_impl_args).self_ty();
+        tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(tcx, fresh_impl_args).self_ty();
 
     ocx.eq(&ObligationCause::dummy_with_span(impl_span), adt_env, fresh_adt_ty, impl_adt_ty)
-        .unwrap();
+        .expect("equating fully generic trait ref should never fail");
 
-    for (clause, span) in tcx.predicates_of(drop_impl_def_id).instantiate(tcx, fresh_impl_args) {
-        let normalize_cause = traits::ObligationCause::misc(span, adt_def_id);
+    for (clause, span) in tcx.predicates_of(impl_def_id).instantiate(tcx, fresh_impl_args) {
+        let normalize_cause = traits::ObligationCause::misc(span, impl_def_id);
         let pred = ocx.normalize(&normalize_cause, adt_env, clause);
-        let cause = traits::ObligationCause::new(span, adt_def_id, ObligationCauseCode::DropImpl);
+        let cause = traits::ObligationCause::new(
+            span,
+            impl_def_id,
+            ObligationCauseCode::AlwaysApplicableImpl,
+        );
         ocx.register_obligation(traits::Obligation::new(tcx, cause, adt_env, pred));
     }
 
@@ -173,13 +242,13 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
             let root_predicate = error.root_obligation.predicate;
             if root_predicates.insert(root_predicate) {
                 let item_span = tcx.def_span(adt_def_id);
-                let self_descr = tcx.def_descr(adt_def_id.to_def_id());
+                let self_descr = tcx.def_descr(adt_def_id);
                 guar = Some(
                     struct_span_code_err!(
                         tcx.dcx(),
                         error.root_obligation.cause.span,
                         E0367,
-                        "`Drop` impl requires `{root_predicate}` \
+                        "`{polarity}{trait_name}` impl requires `{root_predicate}` \
                         but the {self_descr} it is implemented for does not",
                     )
                     .with_span_note(item_span, "the implementor must specify the same requirement")
@@ -190,12 +259,12 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
         return Err(guar.unwrap());
     }
 
-    let errors = ocx.infcx.resolve_regions(adt_def_id, adt_env, []);
+    let errors = ocx.infcx.resolve_regions(impl_def_id, adt_env, []);
     if !errors.is_empty() {
         let mut guar = None;
         for error in errors {
             let item_span = tcx.def_span(adt_def_id);
-            let self_descr = tcx.def_descr(adt_def_id.to_def_id());
+            let self_descr = tcx.def_descr(adt_def_id);
             let outlives = match error {
                 RegionResolutionError::ConcreteFailure(_, a, b) => format!("{b}: {a}"),
                 RegionResolutionError::GenericBoundFailure(_, generic, r) => {
@@ -212,7 +281,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
                     tcx.dcx(),
                     error.origin().span(),
                     E0367,
-                    "`Drop` impl requires `{outlives}` \
+                    "`{polarity}{trait_name}` impl requires `{outlives}` \
                     but the {self_descr} it is implemented for does not",
                 )
                 .with_span_note(item_span, "the implementor must specify the same requirement")
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index f2331f3fd8e13..25dc6b7954b21 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -70,7 +70,6 @@ fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     check_transparent(tcx, def);
     check_packed(tcx, span, def);
-    check_unsafe_fields(tcx, def_id);
 }
 
 fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
@@ -144,36 +143,6 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
     true
 }
 
-/// Check that the unsafe fields do not need dropping.
-fn check_unsafe_fields(tcx: TyCtxt<'_>, item_def_id: LocalDefId) {
-    let span = tcx.def_span(item_def_id);
-    let def = tcx.adt_def(item_def_id);
-
-    let typing_env = ty::TypingEnv::non_body_analysis(tcx, item_def_id);
-    let args = ty::GenericArgs::identity_for_item(tcx, item_def_id);
-
-    for field in def.all_fields() {
-        if !field.safety.is_unsafe() {
-            continue;
-        }
-
-        if !allowed_union_or_unsafe_field(tcx, field.ty(tcx, args), typing_env, span) {
-            let hir::Node::Field(field) = tcx.hir_node_by_def_id(field.did.expect_local()) else {
-                unreachable!("field has to correspond to hir field")
-            };
-            let ty_span = field.ty.span;
-            tcx.dcx().emit_err(errors::InvalidUnsafeField {
-                field_span: field.span,
-                sugg: errors::InvalidUnsafeFieldSuggestion {
-                    lo: ty_span.shrink_to_lo(),
-                    hi: ty_span.shrink_to_hi(),
-                },
-                note: (),
-            });
-        }
-    }
-}
-
 /// Check that a `static` is inhabited.
 fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     // Make sure statics are inhabited.
@@ -1517,7 +1486,6 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     detect_discriminant_duplicate(tcx, def);
     check_transparent(tcx, def);
-    check_unsafe_fields(tcx, def_id);
 }
 
 /// Part of enum check. Given the discriminants of an enum, errors if two or more discriminants are equal
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 1c5455710db8a..d72d5b4fa19d4 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -62,9 +62,9 @@ a type parameter).
 
 */
 
+pub mod always_applicable;
 mod check;
 mod compare_impl_item;
-pub mod dropck;
 mod entry;
 pub mod intrinsic;
 pub mod intrinsicck;
@@ -113,11 +113,11 @@ pub fn provide(providers: &mut Providers) {
 }
 
 fn adt_destructor(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Destructor> {
-    tcx.calculate_dtor(def_id.to_def_id(), dropck::check_drop_impl)
+    tcx.calculate_dtor(def_id.to_def_id(), always_applicable::check_drop_impl)
 }
 
 fn adt_async_destructor(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::AsyncDestructor> {
-    tcx.calculate_async_dtor(def_id.to_def_id(), dropck::check_drop_impl)
+    tcx.calculate_async_dtor(def_id.to_def_id(), always_applicable::check_drop_impl)
 }
 
 /// Given a `DefId` for an opaque type in return position, find its parent item's return
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index d72cf00293f0c..ec137bb1fcae7 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -126,13 +126,14 @@ where
 
     let infcx_compat = infcx.fork();
 
-    // We specifically want to call the non-compat version of `implied_bounds_tys`; we do this always.
+    // We specifically want to *disable* the implied bounds hack, first,
+    // so we can detect when failures are due to bevy's implied bounds.
     let outlives_env = OutlivesEnvironment::new_with_implied_bounds_compat(
         &infcx,
         body_def_id,
         param_env,
         assumed_wf_types.iter().copied(),
-        false,
+        true,
     );
 
     lint_redundant_lifetimes(tcx, body_def_id, &outlives_env);
@@ -142,53 +143,22 @@ where
         return Ok(());
     }
 
-    let is_bevy = assumed_wf_types.visit_with(&mut ContainsBevyParamSet { tcx }).is_break();
-
-    // If we have set `no_implied_bounds_compat`, then do not attempt compatibility.
-    // We could also just always enter if `is_bevy`, and call `implied_bounds_tys`,
-    // but that does result in slightly more work when this option is set and
-    // just obscures what we mean here anyways. Let's just be explicit.
-    if is_bevy && !infcx.tcx.sess.opts.unstable_opts.no_implied_bounds_compat {
-        let outlives_env = OutlivesEnvironment::new_with_implied_bounds_compat(
-            &infcx,
-            body_def_id,
-            param_env,
-            assumed_wf_types,
-            true,
-        );
-        let errors_compat = infcx_compat.resolve_regions_with_outlives_env(&outlives_env);
-        if errors_compat.is_empty() {
-            Ok(())
-        } else {
-            Err(infcx_compat.err_ctxt().report_region_errors(body_def_id, &errors_compat))
-        }
+    let outlives_env = OutlivesEnvironment::new_with_implied_bounds_compat(
+        &infcx_compat,
+        body_def_id,
+        param_env,
+        assumed_wf_types,
+        // Don't *disable* the implied bounds hack; though this will only apply
+        // the implied bounds hack if this contains `bevy_ecs`'s `ParamSet` type.
+        false,
+    );
+    let errors_compat = infcx_compat.resolve_regions_with_outlives_env(&outlives_env);
+    if errors_compat.is_empty() {
+        // FIXME: Once we fix bevy, this would be the place to insert a warning
+        // to upgrade bevy.
+        Ok(())
     } else {
-        Err(infcx.err_ctxt().report_region_errors(body_def_id, &errors))
-    }
-}
-
-struct ContainsBevyParamSet<'tcx> {
-    tcx: TyCtxt<'tcx>,
-}
-
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsBevyParamSet<'tcx> {
-    type Result = ControlFlow<()>;
-
-    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
-        // We only care to match `ParamSet<T>` or `&ParamSet<T>`.
-        match t.kind() {
-            ty::Adt(def, _) => {
-                if self.tcx.item_name(def.did()) == sym::ParamSet
-                    && self.tcx.crate_name(def.did().krate) == sym::bevy_ecs
-                {
-                    return ControlFlow::Break(());
-                }
-            }
-            ty::Ref(_, ty, _) => ty.visit_with(self)?,
-            _ => {}
-        }
-
-        ControlFlow::Continue(())
+        Err(infcx_compat.err_ctxt().report_region_errors(body_def_id, &errors_compat))
     }
 }
 
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 0245d4c9fe4b6..b5c6c2f386192 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -16,6 +16,7 @@ use rustc_span::{ErrorGuaranteed, sym};
 use rustc_type_ir::elaborate;
 use tracing::debug;
 
+use crate::check::always_applicable;
 use crate::errors;
 
 mod builtin;
@@ -24,11 +25,12 @@ mod inherent_impls_overlap;
 mod orphan;
 mod unsafety;
 
-fn check_impl(
-    tcx: TyCtxt<'_>,
+fn check_impl<'tcx>(
+    tcx: TyCtxt<'tcx>,
     impl_def_id: LocalDefId,
-    trait_ref: ty::TraitRef<'_>,
-    trait_def: &ty::TraitDef,
+    trait_ref: ty::TraitRef<'tcx>,
+    trait_def: &'tcx ty::TraitDef,
+    polarity: ty::ImplPolarity,
 ) -> Result<(), ErrorGuaranteed> {
     debug!(
         "(checking implementation) adding impl for trait '{:?}', item '{}'",
@@ -44,6 +46,12 @@ fn check_impl(
 
     enforce_trait_manually_implementable(tcx, impl_def_id, trait_ref.def_id, trait_def)
         .and(enforce_empty_impls_for_marker_traits(tcx, impl_def_id, trait_ref.def_id, trait_def))
+        .and(always_applicable::check_negative_auto_trait_impl(
+            tcx,
+            impl_def_id,
+            trait_ref,
+            polarity,
+        ))
 }
 
 fn enforce_trait_manually_implementable(
@@ -154,16 +162,16 @@ fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) -> Result<(), ErrorGuaranteed>
     let mut res = tcx.ensure_ok().specialization_graph_of(def_id);
 
     for &impl_def_id in impls {
-        let trait_header = tcx.impl_trait_header(impl_def_id).unwrap();
-        let trait_ref = trait_header.trait_ref.instantiate_identity();
+        let impl_header = tcx.impl_trait_header(impl_def_id).unwrap();
+        let trait_ref = impl_header.trait_ref.instantiate_identity();
         let trait_def = tcx.trait_def(trait_ref.def_id);
 
         res = res
-            .and(check_impl(tcx, impl_def_id, trait_ref, trait_def))
+            .and(check_impl(tcx, impl_def_id, trait_ref, trait_def, impl_header.polarity))
             .and(check_object_overlap(tcx, impl_def_id, trait_ref))
-            .and(unsafety::check_item(tcx, impl_def_id, trait_header, trait_def))
+            .and(unsafety::check_item(tcx, impl_def_id, impl_header, trait_def))
             .and(tcx.ensure_ok().orphan_check_impl(impl_def_id))
-            .and(builtin::check_trait(tcx, def_id, impl_def_id, trait_header));
+            .and(builtin::check_trait(tcx, def_id, impl_def_id, impl_header));
     }
 
     res
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 852533ff5c954..390450b5885aa 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -84,6 +84,8 @@ pub(crate) struct AssocItemNotFound<'a> {
     pub label: Option<AssocItemNotFoundLabel<'a>>,
     #[subdiagnostic]
     pub sugg: Option<AssocItemNotFoundSugg<'a>>,
+    #[label(hir_analysis_within_macro)]
+    pub within_macro_span: Option<Span>,
 }
 
 #[derive(Subdiagnostic)]
@@ -710,17 +712,6 @@ pub(crate) struct InvalidUnionField {
     pub note: (),
 }
 
-#[derive(Diagnostic)]
-#[diag(hir_analysis_invalid_unsafe_field, code = E0740)]
-pub(crate) struct InvalidUnsafeField {
-    #[primary_span]
-    pub field_span: Span,
-    #[subdiagnostic]
-    pub sugg: InvalidUnsafeFieldSuggestion,
-    #[note]
-    pub note: (),
-}
-
 #[derive(Diagnostic)]
 #[diag(hir_analysis_return_type_notation_on_non_rpitit)]
 pub(crate) struct ReturnTypeNotationOnNonRpitit<'tcx> {
@@ -742,18 +733,6 @@ pub(crate) struct InvalidUnionFieldSuggestion {
     pub hi: Span,
 }
 
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    hir_analysis_invalid_unsafe_field_sugg,
-    applicability = "machine-applicable"
-)]
-pub(crate) struct InvalidUnsafeFieldSuggestion {
-    #[suggestion_part(code = "std::mem::ManuallyDrop<")]
-    pub lo: Span,
-    #[suggestion_part(code = ">")]
-    pub hi: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(hir_analysis_return_type_notation_equality_bound)]
 pub(crate) struct ReturnTypeNotationEqualityBound {
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index d51fd7f7e78ab..ace5e34b38249 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -151,6 +151,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             qself: &qself_str,
             label: None,
             sugg: None,
+            // Try to get the span of the identifier within the path's syntax context
+            // (if that's different).
+            within_macro_span: assoc_name.span.within_macro(span, tcx.sess.source_map()),
         };
 
         if is_dummy {
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index dec1779d92ca4..7f67e524fc4a8 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -3069,7 +3069,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
             ident, base, expr, base_ty
         );
-        let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
+        let mut err = self.no_such_field_err(ident, base_ty, expr);
 
         match *base_ty.peel_refs().kind() {
             ty::Array(_, len) => {
@@ -3282,18 +3282,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
     }
 
-    fn no_such_field_err(&self, field: Ident, expr_t: Ty<'tcx>, id: HirId) -> Diag<'_> {
+    fn no_such_field_err(
+        &self,
+        field: Ident,
+        base_ty: Ty<'tcx>,
+        expr: &hir::Expr<'tcx>,
+    ) -> Diag<'_> {
         let span = field.span;
-        debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
+        debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, base_ty);
 
-        let mut err = self.dcx().create_err(NoFieldOnType { span, ty: expr_t, field });
-        if expr_t.references_error() {
+        let mut err = self.dcx().create_err(NoFieldOnType { span, ty: base_ty, field });
+        if base_ty.references_error() {
             err.downgrade_to_delayed_bug();
         }
 
+        if let Some(within_macro_span) = span.within_macro(expr.span, self.tcx.sess.source_map()) {
+            err.span_label(within_macro_span, "due to this macro variable");
+        }
+
         // try to add a suggestion in case the field is a nested field of a field of the Adt
-        let mod_id = self.tcx.parent_module(id).to_def_id();
-        let (ty, unwrap) = if let ty::Adt(def, args) = expr_t.kind()
+        let mod_id = self.tcx.parent_module(expr.hir_id).to_def_id();
+        let (ty, unwrap) = if let ty::Adt(def, args) = base_ty.kind()
             && (self.tcx.is_diagnostic_item(sym::Result, def.did())
                 || self.tcx.is_diagnostic_item(sym::Option, def.did()))
             && let Some(arg) = args.get(0)
@@ -3301,10 +3310,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             (ty, "unwrap().")
         } else {
-            (expr_t, "")
+            (base_ty, "")
         };
         for (found_fields, args) in
-            self.get_field_candidates_considering_privacy_for_diag(span, ty, mod_id, id)
+            self.get_field_candidates_considering_privacy_for_diag(span, ty, mod_id, expr.hir_id)
         {
             let field_names = found_fields.iter().map(|field| field.name).collect::<Vec<_>>();
             let mut candidate_fields: Vec<_> = found_fields
@@ -3317,7 +3326,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         args,
                         vec![],
                         mod_id,
-                        id,
+                        expr.hir_id,
                     )
                 })
                 .map(|mut field_path| {
@@ -3328,7 +3337,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             candidate_fields.sort();
 
             let len = candidate_fields.len();
-            if len > 0 {
+            // Don't suggest `.field` if the base expr is from a different
+            // syntax context than the field.
+            if len > 0 && expr.span.eq_ctxt(field.span) {
                 err.span_suggestions(
                     field.span.shrink_to_lo(),
                     format!(
@@ -3963,7 +3974,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 _ => (),
             };
 
-            self.no_such_field_err(field, container, expr.hir_id).emit();
+            self.no_such_field_err(field, container, expr).emit();
 
             break;
         }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 054e3bcb67c3d..c46a42c5de1e3 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -669,12 +669,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         if !errors.is_empty() {
             self.adjust_fulfillment_errors_for_expr_obligation(&mut errors);
-            let errors_causecode = errors
-                .iter()
-                .map(|e| (e.obligation.cause.span, e.root_obligation.cause.code().clone()))
-                .collect::<Vec<_>>();
             self.err_ctxt().report_fulfillment_errors(errors);
-            self.collect_unused_stmts_for_coerce_return_ty(errors_causecode);
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 82e99ca7afa2f..db947b6744da6 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -3,9 +3,7 @@ use std::{fmt, iter, mem};
 use itertools::Itertools;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::codes::*;
-use rustc_errors::{
-    Applicability, Diag, ErrorGuaranteed, MultiSpan, StashKey, a_or_an, listify, pluralize,
-};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan, a_or_an, listify, pluralize};
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
@@ -2193,62 +2191,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(super) fn collect_unused_stmts_for_coerce_return_ty(
-        &self,
-        errors_causecode: Vec<(Span, ObligationCauseCode<'tcx>)>,
-    ) {
-        for (span, code) in errors_causecode {
-            self.dcx().try_steal_modify_and_emit_err(span, StashKey::MaybeForgetReturn, |err| {
-                if let Some(fn_sig) = self.body_fn_sig()
-                    && let ObligationCauseCode::WhereClauseInExpr(_, _, binding_hir_id, ..) = code
-                    && !fn_sig.output().is_unit()
-                {
-                    let mut block_num = 0;
-                    let mut found_semi = false;
-                    for (hir_id, node) in self.tcx.hir_parent_iter(binding_hir_id) {
-                        // Don't proceed into parent bodies
-                        if hir_id.owner != binding_hir_id.owner {
-                            break;
-                        }
-                        match node {
-                            hir::Node::Stmt(stmt) => {
-                                if let hir::StmtKind::Semi(expr) = stmt.kind {
-                                    let expr_ty = self.typeck_results.borrow().expr_ty(expr);
-                                    let return_ty = fn_sig.output();
-                                    if !matches!(expr.kind, hir::ExprKind::Ret(..))
-                                        && self.may_coerce(expr_ty, return_ty)
-                                    {
-                                        found_semi = true;
-                                    }
-                                }
-                            }
-                            hir::Node::Block(_block) => {
-                                if found_semi {
-                                    block_num += 1;
-                                }
-                            }
-                            hir::Node::Item(item) => {
-                                if let hir::ItemKind::Fn { .. } = item.kind {
-                                    break;
-                                }
-                            }
-                            _ => {}
-                        }
-                    }
-                    if block_num > 1 && found_semi {
-                        err.span_suggestion_verbose(
-                            // use the span of the *whole* expr
-                            self.tcx.hir().span(binding_hir_id).shrink_to_lo(),
-                            "you might have meant to return this to infer its type parameters",
-                            "return ",
-                            Applicability::MaybeIncorrect,
-                        );
-                    }
-                }
-            });
-        }
-    }
-
     /// Given a vector of fulfillment errors, try to adjust the spans of the
     /// errors to more accurately point at the cause of the failure.
     ///
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 18218a7a0a641..cb1e89fb9e593 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -158,7 +158,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.typeck_results.borrow_mut().used_trait_imports.insert(import_id);
         }
 
-        let (span, sugg_span, source, item_name, args) = match self.tcx.hir_node(call_id) {
+        let (span, expr_span, source, item_name, args) = match self.tcx.hir_node(call_id) {
             hir::Node::Expr(&hir::Expr {
                 kind: hir::ExprKind::MethodCall(segment, rcvr, args, _),
                 span,
@@ -194,6 +194,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             node => unreachable!("{node:?}"),
         };
 
+        // Try to get the span of the identifier within the expression's syntax context
+        // (if that's different).
+        let within_macro_span = span.within_macro(expr_span, self.tcx.sess.source_map());
+
         // Avoid suggestions when we don't know what's going on.
         if let Err(guar) = rcvr_ty.error_reported() {
             return guar;
@@ -207,10 +211,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 call_id,
                 source,
                 args,
-                sugg_span,
+                expr_span,
                 &mut no_match_data,
                 expected,
                 trait_missing_method,
+                within_macro_span,
             ),
 
             MethodError::Ambiguity(mut sources) => {
@@ -221,6 +226,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     "multiple applicable items in scope"
                 );
                 err.span_label(item_name.span, format!("multiple `{item_name}` found"));
+                if let Some(within_macro_span) = within_macro_span {
+                    err.span_label(within_macro_span, "due to this macro variable");
+                }
 
                 self.note_candidates_on_method_error(
                     rcvr_ty,
@@ -230,7 +238,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     span,
                     &mut err,
                     &mut sources,
-                    Some(sugg_span),
+                    Some(expr_span),
                 );
                 err.emit()
             }
@@ -252,6 +260,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .span_if_local(def_id)
                     .unwrap_or_else(|| self.tcx.def_span(def_id));
                 err.span_label(sp, format!("private {kind} defined here"));
+                if let Some(within_macro_span) = within_macro_span {
+                    err.span_label(within_macro_span, "due to this macro variable");
+                }
                 self.suggest_valid_traits(&mut err, item_name, out_of_scope_traits, true);
                 err.emit()
             }
@@ -268,6 +279,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if !needs_mut {
                     err.span_label(bound_span, "this has a `Sized` requirement");
                 }
+                if let Some(within_macro_span) = within_macro_span {
+                    err.span_label(within_macro_span, "due to this macro variable");
+                }
                 if !candidates.is_empty() {
                     let help = format!(
                         "{an}other candidate{s} {were} found in the following trait{s}",
@@ -581,6 +595,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         no_match_data: &mut NoMatchData<'tcx>,
         expected: Expectation<'tcx>,
         trait_missing_method: bool,
+        within_macro_span: Option<Span>,
     ) -> ErrorGuaranteed {
         let mode = no_match_data.mode;
         let tcx = self.tcx;
@@ -721,6 +736,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if tcx.sess.source_map().is_multiline(sugg_span) {
             err.span_label(sugg_span.with_hi(span.lo()), "");
         }
+        if let Some(within_macro_span) = within_macro_span {
+            err.span_label(within_macro_span, "due to this macro variable");
+        }
 
         if short_ty_str.len() < ty_str.len() && ty_str.len() > 10 {
             ty_str = short_ty_str;
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index cb83d405cc3ed..d2b08eab47916 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -1,7 +1,7 @@
 use std::iter;
 use std::ops::ControlFlow;
 
-use rustc_abi::{BackendRepr, ExternAbi, TagEncoding, VariantIdx, Variants, WrappingRange};
+use rustc_abi::{BackendRepr, TagEncoding, VariantIdx, Variants, WrappingRange};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::DiagMessage;
 use rustc_hir::intravisit::VisitorExt;
@@ -1349,7 +1349,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
             ty::FnPtr(sig_tys, hdr) => {
                 let sig = sig_tys.with(hdr);
-                if self.is_internal_abi(sig.abi()) {
+                if sig.abi().is_rustic_abi() {
                     return FfiUnsafe {
                         ty,
                         reason: fluent::lint_improper_ctypes_fnptr_reason,
@@ -1552,13 +1552,6 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         self.check_type_for_ffi_and_report_errors(span, ty, true, false);
     }
 
-    fn is_internal_abi(&self, abi: ExternAbi) -> bool {
-        matches!(
-            abi,
-            ExternAbi::Rust | ExternAbi::RustCall | ExternAbi::RustCold | ExternAbi::RustIntrinsic
-        )
-    }
-
     /// Find any fn-ptr types with external ABIs in `ty`.
     ///
     /// For example, `Option<extern "C" fn()>` returns `extern "C" fn()`
@@ -1567,17 +1560,16 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         hir_ty: &hir::Ty<'tcx>,
         ty: Ty<'tcx>,
     ) -> Vec<(Ty<'tcx>, Span)> {
-        struct FnPtrFinder<'a, 'b, 'tcx> {
-            visitor: &'a ImproperCTypesVisitor<'b, 'tcx>,
+        struct FnPtrFinder<'tcx> {
             spans: Vec<Span>,
             tys: Vec<Ty<'tcx>>,
         }
 
-        impl<'a, 'b, 'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'a, 'b, 'tcx> {
+        impl<'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'tcx> {
             fn visit_ty(&mut self, ty: &'_ hir::Ty<'_, AmbigArg>) {
                 debug!(?ty);
                 if let hir::TyKind::BareFn(hir::BareFnTy { abi, .. }) = ty.kind
-                    && !self.visitor.is_internal_abi(*abi)
+                    && !abi.is_rustic_abi()
                 {
                     self.spans.push(ty.span);
                 }
@@ -1586,12 +1578,12 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             }
         }
 
-        impl<'a, 'b, 'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'a, 'b, 'tcx> {
+        impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'tcx> {
             type Result = ();
 
             fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
                 if let ty::FnPtr(_, hdr) = ty.kind()
-                    && !self.visitor.is_internal_abi(hdr.abi)
+                    && !hdr.abi.is_rustic_abi()
                 {
                     self.tys.push(ty);
                 }
@@ -1600,7 +1592,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             }
         }
 
-        let mut visitor = FnPtrFinder { visitor: self, spans: Vec::new(), tys: Vec::new() };
+        let mut visitor = FnPtrFinder { spans: Vec::new(), tys: Vec::new() };
         ty.visit_with(&mut visitor);
         visitor.visit_ty_unambig(hir_ty);
 
@@ -1615,13 +1607,13 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
 
         match it.kind {
             hir::ForeignItemKind::Fn(sig, _, _) => {
-                if vis.is_internal_abi(abi) {
+                if abi.is_rustic_abi() {
                     vis.check_fn(it.owner_id.def_id, sig.decl)
                 } else {
                     vis.check_foreign_fn(it.owner_id.def_id, sig.decl);
                 }
             }
-            hir::ForeignItemKind::Static(ty, _, _) if !vis.is_internal_abi(abi) => {
+            hir::ForeignItemKind::Static(ty, _, _) if !abi.is_rustic_abi() => {
                 vis.check_foreign_static(it.owner_id, ty.span);
             }
             hir::ForeignItemKind::Static(..) | hir::ForeignItemKind::Type => (),
@@ -1775,7 +1767,7 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
         };
 
         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
-        if vis.is_internal_abi(abi) {
+        if abi.is_rustic_abi() {
             vis.check_fn(id, decl);
         } else {
             vis.check_foreign_fn(id, decl);
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index 1489d57aba645..98314b5abfda1 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -508,6 +508,14 @@ impl<'tcx, T: Clone> Key for CanonicalQueryInput<'tcx, T> {
     }
 }
 
+impl<'tcx, T: Clone> Key for (CanonicalQueryInput<'tcx, T>, bool) {
+    type Cache<V> = DefaultCache<Self, V>;
+
+    fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl Key for (Symbol, u32, u32) {
     type Cache<V> = DefaultCache<Self, V>;
 
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 1302027aabb36..4ad4427594cf2 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -2262,22 +2262,13 @@ rustc_queries! {
         desc { "normalizing `{}`", goal.value }
     }
 
-    query implied_outlives_bounds_compat(
-        goal: CanonicalImpliedOutlivesBoundsGoal<'tcx>
-    ) -> Result<
-        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
-        NoSolution,
-    > {
-        desc { "computing implied outlives bounds for `{}`", goal.canonical.value.value.ty }
-    }
-
     query implied_outlives_bounds(
-        goal: CanonicalImpliedOutlivesBoundsGoal<'tcx>
+        key: (CanonicalImpliedOutlivesBoundsGoal<'tcx>, bool)
     ) -> Result<
         &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
         NoSolution,
     > {
-        desc { "computing implied outlives bounds v2 for `{}`", goal.canonical.value.value.ty }
+        desc { "computing implied outlives bounds for `{}` (hack disabled = {:?})", key.0.canonical.value.value.ty, key.1 }
     }
 
     /// Do not call this query directly:
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index d033ecc75dbe5..af38748d5b2a6 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -397,9 +397,9 @@ pub enum ObligationCauseCode<'tcx> {
 
     RustCall,
 
-    /// Obligations to prove that a `std::ops::Drop` impl is not stronger than
+    /// Obligations to prove that a `Drop` or negative auto trait impl is not stronger than
     /// the ADT it's being implemented for.
-    DropImpl,
+    AlwaysApplicableImpl,
 
     /// Requirement for a `const N: Ty` to implement `Ty: ConstParamTy`
     ConstParam(Ty<'tcx>),
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
index 505c7278176f3..953ad62be0a86 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
@@ -236,6 +236,11 @@ impl<'tcx> InhabitedPredicate<'tcx> {
         self.instantiate_opt(tcx, args).unwrap_or(self)
     }
 
+    /// Same as [`Self::instantiate`], but if there is no generics to
+    /// instantiate, returns `None`. This is useful because it lets us avoid
+    /// allocating a recursive copy of everything when the result is unchanged.
+    ///
+    /// Only used to implement `instantiate` itself.
     fn instantiate_opt(self, tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> Option<Self> {
         match self {
             Self::ConstIsZero(c) => {
@@ -260,7 +265,10 @@ impl<'tcx> InhabitedPredicate<'tcx> {
                 Some(InhabitedPredicate::True) => Some(InhabitedPredicate::True),
                 Some(a) => Some(a.or(tcx, b.instantiate_opt(tcx, args).unwrap_or(b))),
             },
-            _ => None,
+            Self::True | Self::False | Self::NotInModule(_) => None,
+            Self::OpaqueType(_) => {
+                bug!("unexpected OpaqueType in InhabitedPredicate");
+            }
         }
     }
 }
diff --git a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
index 7b3553e7afd06..abbff1c48dd9a 100644
--- a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
+++ b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
@@ -53,11 +53,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
 
         // Rust calls cannot themselves create foreign unwinds.
         // We assume this is true for intrinsics as well.
-        if let ExternAbi::RustIntrinsic
-        | ExternAbi::Rust
-        | ExternAbi::RustCall
-        | ExternAbi::RustCold = sig.abi()
-        {
+        if sig.abi().is_rustic_abi() {
             continue;
         };
 
diff --git a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
index 9f26da7d5c64b..06d6c3ab8050e 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
@@ -1,6 +1,6 @@
 //! This module ensures that if a function's ABI requires a particular target feature,
 //! that target feature is enabled both on the callee and all callers.
-use rustc_abi::{BackendRepr, ExternAbi, RegKind};
+use rustc_abi::{BackendRepr, RegKind};
 use rustc_hir::CRATE_HIR_ID;
 use rustc_middle::mir::{self, traversal};
 use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TyCtxt};
@@ -115,8 +115,8 @@ fn check_call_site_abi<'tcx>(
     span: Span,
     caller: InstanceKind<'tcx>,
 ) {
-    if callee.fn_sig(tcx).abi() == ExternAbi::Rust {
-        // "Rust" ABI never passes arguments in vector registers.
+    if callee.fn_sig(tcx).abi().is_rustic_abi() {
+        // we directly handle the soundness of Rust ABIs
         return;
     }
     let typing_env = ty::TypingEnv::fully_monomorphized();
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 1e86b9721d4a6..42199891847f4 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -623,7 +623,7 @@ pub(crate) struct UnnecessaryQualification<'ra> {
     pub removal_span: Span,
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 struct DiagMetadata<'ast> {
     /// The current trait's associated items' ident, used for diagnostic suggestions.
     current_trait_assoc_items: Option<&'ast [P<AssocItem>]>,
@@ -3146,6 +3146,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 PathSource::Trait(AliasPossibility::No),
                 Finalize::new(trait_ref.ref_id, trait_ref.path.span),
                 RecordPartialRes::Yes,
+                None,
             );
             self.diag_metadata.currently_processing_impl_trait = None;
             if let Some(def_id) = res.expect_full_res().opt_def_id() {
@@ -4072,6 +4073,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             source,
             Finalize::new(id, path.span),
             RecordPartialRes::Yes,
+            None,
         );
     }
 
@@ -4083,14 +4085,21 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         source: PathSource<'ast>,
         finalize: Finalize,
         record_partial_res: RecordPartialRes,
+        parent_qself: Option<&QSelf>,
     ) -> PartialRes {
         let ns = source.namespace();
 
         let Finalize { node_id, path_span, .. } = finalize;
         let report_errors = |this: &mut Self, res: Option<Res>| {
             if this.should_report_errs() {
-                let (err, candidates) =
-                    this.smart_resolve_report_errors(path, None, path_span, source, res);
+                let (err, candidates) = this.smart_resolve_report_errors(
+                    path,
+                    None,
+                    path_span,
+                    source,
+                    res,
+                    parent_qself,
+                );
 
                 let def_id = this.parent_scope.module.nearest_parent_mod();
                 let instead = res.is_some();
@@ -4159,6 +4168,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     path_span,
                     PathSource::Type,
                     None,
+                    parent_qself,
                 );
 
                 // There are two different error messages user might receive at
@@ -4436,6 +4446,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 PathSource::Trait(AliasPossibility::No),
                 Finalize::new(finalize.node_id, qself.path_span),
                 RecordPartialRes::No,
+                Some(&qself),
             );
 
             if trait_res.expect_full_res() == Res::Err {
@@ -4460,6 +4471,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 PathSource::TraitItem(ns),
                 Finalize::with_root_span(finalize.node_id, finalize.path_span, qself.path_span),
                 RecordPartialRes::No,
+                Some(&qself),
             );
 
             // The remaining segments (the `C` in our example) will
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 0e14e7671b176..7de4645533632 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -35,7 +35,7 @@ use super::NoConstantGenericsReason;
 use crate::diagnostics::{ImportSuggestion, LabelSuggestion, TypoSuggestion};
 use crate::late::{
     AliasPossibility, LateResolutionVisitor, LifetimeBinderKind, LifetimeRes, LifetimeRibKind,
-    LifetimeUseSet, RibKind,
+    LifetimeUseSet, QSelf, RibKind,
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::{
@@ -421,6 +421,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         span: Span,
         source: PathSource<'_>,
         res: Option<Res>,
+        qself: Option<&QSelf>,
     ) -> (Diag<'tcx>, Vec<ImportSuggestion>) {
         debug!(?res, ?source);
         let base_error = self.make_base_error(path, span, source, res);
@@ -429,6 +430,14 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         let mut err = self.r.dcx().struct_span_err(base_error.span, base_error.msg.clone());
         err.code(code);
 
+        // Try to get the span of the identifier within the path's syntax context
+        // (if that's different).
+        if let Some(within_macro_span) =
+            base_error.span.within_macro(span, self.r.tcx.sess.source_map())
+        {
+            err.span_label(within_macro_span, "due to this macro variable");
+        }
+
         self.detect_missing_binding_available_from_pattern(&mut err, path, following_seg);
         self.suggest_at_operator_in_slice_pat_with_range(&mut err, path);
         self.suggest_swapping_misplaced_self_ty_and_trait(&mut err, source, res, base_error.span);
@@ -453,6 +462,15 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
 
         self.suggest_self_or_self_ref(&mut err, path, span);
         self.detect_assoc_type_constraint_meant_as_path(&mut err, &base_error);
+        self.detect_rtn_with_fully_qualified_path(
+            &mut err,
+            path,
+            following_seg,
+            span,
+            source,
+            res,
+            qself,
+        );
         if self.suggest_self_ty(&mut err, source, path, span)
             || self.suggest_self_value(&mut err, source, path, span)
         {
@@ -501,6 +519,33 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         (err, candidates)
     }
 
+    fn detect_rtn_with_fully_qualified_path(
+        &self,
+        err: &mut Diag<'_>,
+        path: &[Segment],
+        following_seg: Option<&Segment>,
+        span: Span,
+        source: PathSource<'_>,
+        res: Option<Res>,
+        qself: Option<&QSelf>,
+    ) {
+        if let Some(Res::Def(DefKind::AssocFn, _)) = res
+            && let PathSource::TraitItem(TypeNS) = source
+            && let None = following_seg
+            && let Some(qself) = qself
+            && let TyKind::Path(None, ty_path) = &qself.ty.kind
+            && ty_path.segments.len() == 1
+            && self.diag_metadata.current_where_predicate.is_some()
+        {
+            err.span_suggestion_verbose(
+                span,
+                "you might have meant to use the return type notation syntax",
+                format!("{}::{}(..)", ty_path.segments[0].ident, path[path.len() - 1].ident),
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
     fn detect_assoc_type_constraint_meant_as_path(
         &self,
         err: &mut Diag<'_>,
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index bca9323a50d4c..798e186a94b1a 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -1057,6 +1057,37 @@ impl Span {
         }
     }
 
+    /// Returns the `Span` within the syntax context of "within". This is useful when
+    /// "self" is an expansion from a macro variable, since this can be used for
+    /// providing extra macro expansion context for certain errors.
+    ///
+    /// ```text
+    /// macro_rules! m {
+    ///     ($ident:ident) => { ($ident,) }
+    /// }
+    ///
+    /// m!(outer_ident);
+    /// ```
+    ///
+    /// If "self" is the span of the outer_ident, and "within" is the span of the `($ident,)`
+    /// expr, then this will return the span of the `$ident` macro variable.
+    pub fn within_macro(self, within: Span, sm: &SourceMap) -> Option<Span> {
+        match Span::prepare_to_combine(self, within) {
+            // Only return something if it doesn't overlap with the original span,
+            // and the span isn't "imported" (i.e. from unavailable sources).
+            // FIXME: This does limit the usefulness of the error when the macro is
+            // from a foreign crate; we could also take into account `-Zmacro-backtrace`,
+            // which doesn't redact this span (but that would mean passing in even more
+            // args to this function, lol).
+            Ok((self_, _, parent))
+                if self_.hi < self.lo() || self.hi() < self_.lo && !sm.is_imported(within) =>
+            {
+                Some(Span::new(self_.lo, self_.hi, self_.ctxt, parent))
+            }
+            _ => None,
+        }
+    }
+
     pub fn from_inner(self, inner: InnerSpan) -> Span {
         let span = self.data();
         Span::new(
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index f15f1b78b5282..d673e5672a00b 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -1,8 +1,6 @@
 use std::ops::ControlFlow;
 
-use rustc_errors::{
-    Applicability, Diag, E0283, E0284, E0790, MultiSpan, StashKey, struct_span_code_err,
-};
+use rustc_errors::{Applicability, Diag, E0283, E0284, E0790, MultiSpan, struct_span_code_err};
 use rustc_hir as hir;
 use rustc_hir::LangItem;
 use rustc_hir::def::{DefKind, Res};
@@ -197,7 +195,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 // be ignoring the fact that we don't KNOW the type works
                 // out. Though even that would probably be harmless, given that
                 // we're only talking about builtin traits, which are known to be
-                // inhabited. We used to check for `self.tcx.sess.has_errors()` to
+                // inhabited. We used to check for `self.tainted_by_errors()` to
                 // avoid inundating the user with unnecessary errors, but we now
                 // check upstream for type errors and don't add the obligations to
                 // begin with in those cases.
@@ -211,7 +209,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 TypeAnnotationNeeded::E0282,
                                 false,
                             );
-                            return err.stash(span, StashKey::MaybeForgetReturn).unwrap();
+                            return err.emit();
                         }
                         Some(e) => return e,
                     }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index b85c18c53121f..0178400414cb2 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2695,7 +2695,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             | ObligationCauseCode::LetElse
             | ObligationCauseCode::BinOp { .. }
             | ObligationCauseCode::AscribeUserTypeProvePredicate(..)
-            | ObligationCauseCode::DropImpl
+            | ObligationCauseCode::AlwaysApplicableImpl
             | ObligationCauseCode::ConstParam(_)
             | ObligationCauseCode::ReferenceOutlivesReferent(..)
             | ObligationCauseCode::ObjectTypeBound(..) => {}
diff --git a/compiler/rustc_trait_selection/src/regions.rs b/compiler/rustc_trait_selection/src/regions.rs
index 5517175461876..068e90b00b8d1 100644
--- a/compiler/rustc_trait_selection/src/regions.rs
+++ b/compiler/rustc_trait_selection/src/regions.rs
@@ -17,13 +17,7 @@ impl<'tcx> OutlivesEnvironment<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
     ) -> Self {
-        Self::new_with_implied_bounds_compat(
-            infcx,
-            body_id,
-            param_env,
-            assumed_wf_tys,
-            !infcx.tcx.sess.opts.unstable_opts.no_implied_bounds_compat,
-        )
+        Self::new_with_implied_bounds_compat(infcx, body_id, param_env, assumed_wf_tys, false)
     }
 
     fn new_with_implied_bounds_compat(
@@ -31,7 +25,7 @@ impl<'tcx> OutlivesEnvironment<'tcx> {
         body_id: LocalDefId,
         param_env: ty::ParamEnv<'tcx>,
         assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
-        implied_bounds_compat: bool,
+        disable_implied_bounds_hack: bool,
     ) -> Self {
         let mut bounds = vec![];
 
@@ -59,11 +53,11 @@ impl<'tcx> OutlivesEnvironment<'tcx> {
         OutlivesEnvironment::from_normalized_bounds(
             param_env,
             bounds,
-            infcx.implied_bounds_tys_with_compat(
+            infcx.implied_bounds_tys(
                 body_id,
                 param_env,
                 assumed_wf_tys,
-                implied_bounds_compat,
+                disable_implied_bounds_hack,
             ),
         )
     }
diff --git a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
index 189326958078d..68983ef80fa48 100644
--- a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -36,7 +36,7 @@ fn implied_outlives_bounds<'a, 'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     body_id: LocalDefId,
     ty: Ty<'tcx>,
-    compat: bool,
+    disable_implied_bounds_hack: bool,
 ) -> Vec<OutlivesBound<'tcx>> {
     let ty = infcx.resolve_vars_if_possible(ty);
     let ty = OpportunisticRegionResolver::new(infcx).fold_ty(ty);
@@ -52,11 +52,8 @@ fn implied_outlives_bounds<'a, 'tcx>(
     let mut canonical_var_values = OriginalQueryValues::default();
     let input = ImpliedOutlivesBounds { ty };
     let canonical = infcx.canonicalize_query(param_env.and(input), &mut canonical_var_values);
-    let implied_bounds_result = if compat {
-        infcx.tcx.implied_outlives_bounds_compat(canonical)
-    } else {
-        infcx.tcx.implied_outlives_bounds(canonical)
-    };
+    let implied_bounds_result =
+        infcx.tcx.implied_outlives_bounds((canonical, disable_implied_bounds_hack));
     let Ok(canonical_result) = implied_bounds_result else {
         return vec![];
     };
@@ -110,14 +107,15 @@ fn implied_outlives_bounds<'a, 'tcx>(
 impl<'tcx> InferCtxt<'tcx> {
     /// Do *NOT* call this directly. You probably want to construct a `OutlivesEnvironment`
     /// instead if you're interested in the implied bounds for a given signature.
-    fn implied_bounds_tys_with_compat<Tys: IntoIterator<Item = Ty<'tcx>>>(
+    fn implied_bounds_tys<Tys: IntoIterator<Item = Ty<'tcx>>>(
         &self,
         body_id: LocalDefId,
         param_env: ParamEnv<'tcx>,
         tys: Tys,
-        compat: bool,
+        disable_implied_bounds_hack: bool,
     ) -> impl Iterator<Item = OutlivesBound<'tcx>> {
-        tys.into_iter()
-            .flat_map(move |ty| implied_outlives_bounds(self, param_env, body_id, ty, compat))
+        tys.into_iter().flat_map(move |ty| {
+            implied_outlives_bounds(self, param_env, body_id, ty, disable_implied_bounds_hack)
+        })
     }
 }
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
index ec0b790339691..f98529860ff81 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
@@ -1,15 +1,16 @@
+use std::ops::ControlFlow;
+
+use rustc_infer::infer::RegionObligation;
 use rustc_infer::infer::canonical::CanonicalQueryInput;
-use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::traits::query::OutlivesBound;
 use rustc_infer::traits::query::type_op::ImpliedOutlivesBounds;
 use rustc_middle::infer::canonical::CanonicalQueryResponse;
 use rustc_middle::traits::ObligationCause;
-use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, TypeFolder, TypeVisitableExt};
+use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, TypeVisitable, TypeVisitor};
 use rustc_span::def_id::CRATE_DEF_ID;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, sym};
 use rustc_type_ir::outlives::{Component, push_outlives_components};
 use smallvec::{SmallVec, smallvec};
-use tracing::debug;
 
 use crate::traits::query::NoSolution;
 use crate::traits::{ObligationCtxt, wf};
@@ -35,11 +36,7 @@ impl<'tcx> super::QueryTypeOp<'tcx> for ImpliedOutlivesBounds<'tcx> {
         tcx: TyCtxt<'tcx>,
         canonicalized: CanonicalQueryInput<'tcx, ParamEnvAnd<'tcx, Self>>,
     ) -> Result<CanonicalQueryResponse<'tcx, Self::QueryResponse>, NoSolution> {
-        if tcx.sess.opts.unstable_opts.no_implied_bounds_compat {
-            tcx.implied_outlives_bounds(canonicalized)
-        } else {
-            tcx.implied_outlives_bounds_compat(canonicalized)
-        }
+        tcx.implied_outlives_bounds((canonicalized, false))
     }
 
     fn perform_locally_with_next_solver(
@@ -47,11 +44,7 @@ impl<'tcx> super::QueryTypeOp<'tcx> for ImpliedOutlivesBounds<'tcx> {
         key: ParamEnvAnd<'tcx, Self>,
         span: Span,
     ) -> Result<Self::QueryResponse, NoSolution> {
-        if ocx.infcx.tcx.sess.opts.unstable_opts.no_implied_bounds_compat {
-            compute_implied_outlives_bounds_inner(ocx, key.param_env, key.value.ty, span)
-        } else {
-            compute_implied_outlives_bounds_compat_inner(ocx, key.param_env, key.value.ty, span)
-        }
+        compute_implied_outlives_bounds_inner(ocx, key.param_env, key.value.ty, span, false)
     }
 }
 
@@ -60,18 +53,15 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     ty: Ty<'tcx>,
     span: Span,
+    disable_implied_bounds_hack: bool,
 ) -> Result<Vec<OutlivesBound<'tcx>>, NoSolution> {
-    let normalize_op = |ty| -> Result<_, NoSolution> {
+    let normalize_ty = |ty| -> Result<_, NoSolution> {
         // We must normalize the type so we can compute the right outlives components.
         // for example, if we have some constrained param type like `T: Trait<Out = U>`,
         // and we know that `&'a T::Out` is WF, then we want to imply `U: 'a`.
         let ty = ocx
             .deeply_normalize(&ObligationCause::dummy_with_span(span), param_env, ty)
             .map_err(|_| NoSolution)?;
-        if !ocx.select_all_or_error().is_empty() {
-            return Err(NoSolution);
-        }
-        let ty = OpportunisticRegionResolver::new(&ocx.infcx).fold_ty(ty);
         Ok(ty)
     };
 
@@ -81,7 +71,7 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
     // guaranteed to be a subset of the original type, so we need to store the
     // WF args we've computed in a set.
     let mut checked_wf_args = rustc_data_structures::fx::FxHashSet::default();
-    let mut wf_args = vec![ty.into(), normalize_op(ty)?.into()];
+    let mut wf_args = vec![ty.into(), normalize_ty(ty)?.into()];
 
     let mut outlives_bounds: Vec<OutlivesBound<'tcx>> = vec![];
 
@@ -96,8 +86,14 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
                 .into_iter()
                 .flatten()
         {
-            assert!(!obligation.has_escaping_bound_vars());
-            let Some(pred) = obligation.predicate.kind().no_bound_vars() else {
+            let pred = ocx
+                .deeply_normalize(
+                    &ObligationCause::dummy_with_span(span),
+                    param_env,
+                    obligation.predicate,
+                )
+                .map_err(|_| NoSolution)?;
+            let Some(pred) = pred.kind().no_bound_vars() else {
                 continue;
             };
             match pred {
@@ -130,7 +126,6 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
                     ty_a,
                     r_b,
                 ))) => {
-                    let ty_a = normalize_op(ty_a)?;
                     let mut components = smallvec![];
                     push_outlives_components(ocx.infcx.tcx, ty_a, &mut components);
                     outlives_bounds.extend(implied_bounds_from_components(r_b, components))
@@ -139,141 +134,48 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
         }
     }
 
-    Ok(outlives_bounds)
-}
-
-pub fn compute_implied_outlives_bounds_compat_inner<'tcx>(
-    ocx: &ObligationCtxt<'_, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
-    span: Span,
-) -> Result<Vec<OutlivesBound<'tcx>>, NoSolution> {
-    let tcx = ocx.infcx.tcx;
-
-    // Sometimes when we ask what it takes for T: WF, we get back that
-    // U: WF is required; in that case, we push U onto this stack and
-    // process it next. Because the resulting predicates aren't always
-    // guaranteed to be a subset of the original type, so we need to store the
-    // WF args we've computed in a set.
-    let mut checked_wf_args = rustc_data_structures::fx::FxHashSet::default();
-    let mut wf_args = vec![ty.into()];
-
-    let mut outlives_bounds: Vec<ty::OutlivesPredicate<'tcx, ty::GenericArg<'tcx>>> = vec![];
-
-    while let Some(arg) = wf_args.pop() {
-        if !checked_wf_args.insert(arg) {
-            continue;
+    // If we detect `bevy_ecs::*::ParamSet` in the WF args list (and `disable_implied_bounds_hack`
+    // or `-Zno-implied-bounds-compat` are not set), then use the registered outlives obligations
+    // as implied bounds.
+    if !disable_implied_bounds_hack
+        && !ocx.infcx.tcx.sess.opts.unstable_opts.no_implied_bounds_compat
+        && ty.visit_with(&mut ContainsBevyParamSet { tcx: ocx.infcx.tcx }).is_break()
+    {
+        for RegionObligation { sup_type, sub_region, .. } in
+            ocx.infcx.take_registered_region_obligations()
+        {
+            let mut components = smallvec![];
+            push_outlives_components(ocx.infcx.tcx, sup_type, &mut components);
+            outlives_bounds.extend(implied_bounds_from_components(sub_region, components));
         }
+    }
 
-        // Compute the obligations for `arg` to be well-formed. If `arg` is
-        // an unresolved inference variable, just instantiated an empty set
-        // -- because the return type here is going to be things we *add*
-        // to the environment, it's always ok for this set to be smaller
-        // than the ultimate set. (Note: normally there won't be
-        // unresolved inference variables here anyway, but there might be
-        // during typeck under some circumstances.)
-        //
-        // FIXME(@lcnr): It's not really "always fine", having fewer implied
-        // bounds can be backward incompatible, e.g. #101951 was caused by
-        // us not dealing with inference vars in `TypeOutlives` predicates.
-        let obligations =
-            wf::obligations(ocx.infcx, param_env, CRATE_DEF_ID, 0, arg, span).unwrap_or_default();
+    Ok(outlives_bounds)
+}
 
-        for obligation in obligations {
-            debug!(?obligation);
-            assert!(!obligation.has_escaping_bound_vars());
+struct ContainsBevyParamSet<'tcx> {
+    tcx: TyCtxt<'tcx>,
+}
 
-            // While these predicates should all be implied by other parts of
-            // the program, they are still relevant as they may constrain
-            // inference variables, which is necessary to add the correct
-            // implied bounds in some cases, mostly when dealing with projections.
-            //
-            // Another important point here: we only register `Projection`
-            // predicates, since otherwise we might register outlives
-            // predicates containing inference variables, and we don't
-            // learn anything new from those.
-            if obligation.predicate.has_non_region_infer() {
-                match obligation.predicate.kind().skip_binder() {
-                    ty::PredicateKind::Clause(ty::ClauseKind::Projection(..))
-                    | ty::PredicateKind::AliasRelate(..) => {
-                        ocx.register_obligation(obligation.clone());
-                    }
-                    _ => {}
-                }
-            }
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsBevyParamSet<'tcx> {
+    type Result = ControlFlow<()>;
 
-            let pred = match obligation.predicate.kind().no_bound_vars() {
-                None => continue,
-                Some(pred) => pred,
-            };
-            match pred {
-                // FIXME(const_generics): Make sure that `<'a, 'b, const N: &'a &'b u32>` is sound
-                // if we ever support that
-                ty::PredicateKind::Clause(ty::ClauseKind::Trait(..))
-                | ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(..))
-                | ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(..))
-                | ty::PredicateKind::Subtype(..)
-                | ty::PredicateKind::Coerce(..)
-                | ty::PredicateKind::Clause(ty::ClauseKind::Projection(..))
-                | ty::PredicateKind::DynCompatible(..)
-                | ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..))
-                | ty::PredicateKind::ConstEquate(..)
-                | ty::PredicateKind::Ambiguous
-                | ty::PredicateKind::NormalizesTo(..)
-                | ty::PredicateKind::AliasRelate(..) => {}
-
-                // We need to search through *all* WellFormed predicates
-                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
-                    wf_args.push(arg);
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
+        // We only care to match `ParamSet<T>` or `&ParamSet<T>`.
+        match t.kind() {
+            ty::Adt(def, _) => {
+                if self.tcx.item_name(def.did()) == sym::ParamSet
+                    && self.tcx.crate_name(def.did().krate) == sym::bevy_ecs
+                {
+                    return ControlFlow::Break(());
                 }
-
-                // We need to register region relationships
-                ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(
-                    ty::OutlivesPredicate(r_a, r_b),
-                )) => outlives_bounds.push(ty::OutlivesPredicate(r_a.into(), r_b)),
-
-                ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(
-                    ty_a,
-                    r_b,
-                ))) => outlives_bounds.push(ty::OutlivesPredicate(ty_a.into(), r_b)),
             }
+            ty::Ref(_, ty, _) => ty.visit_with(self)?,
+            _ => {}
         }
-    }
 
-    // This call to `select_all_or_error` is necessary to constrain inference variables, which we
-    // use further down when computing the implied bounds.
-    match ocx.select_all_or_error().as_slice() {
-        [] => (),
-        _ => return Err(NoSolution),
+        ControlFlow::Continue(())
     }
-
-    // We lazily compute the outlives components as
-    // `select_all_or_error` constrains inference variables.
-    let mut implied_bounds = Vec::new();
-    for ty::OutlivesPredicate(a, r_b) in outlives_bounds {
-        match a.unpack() {
-            ty::GenericArgKind::Lifetime(r_a) => {
-                implied_bounds.push(OutlivesBound::RegionSubRegion(r_b, r_a))
-            }
-            ty::GenericArgKind::Type(ty_a) => {
-                let mut ty_a = ocx.infcx.resolve_vars_if_possible(ty_a);
-                // Need to manually normalize in the new solver as `wf::obligations` does not.
-                if ocx.infcx.next_trait_solver() {
-                    ty_a = ocx
-                        .deeply_normalize(&ObligationCause::dummy_with_span(span), param_env, ty_a)
-                        .map_err(|_| NoSolution)?;
-                }
-                let mut components = smallvec![];
-                push_outlives_components(tcx, ty_a, &mut components);
-                implied_bounds.extend(implied_bounds_from_components(r_b, components))
-            }
-            ty::GenericArgKind::Const(_) => {
-                unreachable!("consts do not participate in outlives bounds")
-            }
-        }
-    }
-
-    Ok(implied_bounds)
 }
 
 /// When we have an implied bound that `T: 'a`, we can further break
diff --git a/compiler/rustc_traits/src/implied_outlives_bounds.rs b/compiler/rustc_traits/src/implied_outlives_bounds.rs
index 5f75e242a50fb..6fb483e6dac93 100644
--- a/compiler/rustc_traits/src/implied_outlives_bounds.rs
+++ b/compiler/rustc_traits/src/implied_outlives_bounds.rs
@@ -10,38 +10,28 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
-use rustc_trait_selection::traits::query::type_op::implied_outlives_bounds::{
-    compute_implied_outlives_bounds_compat_inner, compute_implied_outlives_bounds_inner,
-};
+use rustc_trait_selection::traits::query::type_op::implied_outlives_bounds::compute_implied_outlives_bounds_inner;
 use rustc_trait_selection::traits::query::{CanonicalImpliedOutlivesBoundsGoal, NoSolution};
 
 pub(crate) fn provide(p: &mut Providers) {
-    *p = Providers { implied_outlives_bounds_compat, ..*p };
     *p = Providers { implied_outlives_bounds, ..*p };
 }
 
-fn implied_outlives_bounds_compat<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    goal: CanonicalImpliedOutlivesBoundsGoal<'tcx>,
-) -> Result<
-    &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
-    NoSolution,
-> {
-    tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
-        let (param_env, ImpliedOutlivesBounds { ty }) = key.into_parts();
-        compute_implied_outlives_bounds_compat_inner(ocx, param_env, ty, DUMMY_SP)
-    })
-}
-
 fn implied_outlives_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
-    goal: CanonicalImpliedOutlivesBoundsGoal<'tcx>,
+    (goal, disable_implied_bounds_hack): (CanonicalImpliedOutlivesBoundsGoal<'tcx>, bool),
 ) -> Result<
     &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
     NoSolution,
 > {
     tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
         let (param_env, ImpliedOutlivesBounds { ty }) = key.into_parts();
-        compute_implied_outlives_bounds_inner(ocx, param_env, ty, DUMMY_SP)
+        compute_implied_outlives_bounds_inner(
+            ocx,
+            param_env,
+            ty,
+            DUMMY_SP,
+            disable_implied_bounds_hack,
+        )
     })
 }
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
index e317768ff602c..a726ebae6fe1b 100644
--- a/compiler/rustc_ty_utils/src/abi.rs
+++ b/compiler/rustc_ty_utils/src/abi.rs
@@ -436,10 +436,7 @@ fn fn_abi_sanity_check<'tcx>(
     ) {
         let tcx = cx.tcx();
 
-        if spec_abi == ExternAbi::Rust
-            || spec_abi == ExternAbi::RustCall
-            || spec_abi == ExternAbi::RustCold
-        {
+        if spec_abi.is_rustic_abi() {
             if arg.layout.is_zst() {
                 // Casting closures to function pointers depends on ZST closure types being
                 // omitted entirely in the calling convention.
@@ -687,7 +684,7 @@ fn fn_abi_adjust_for_abi<'tcx>(
 
     let tcx = cx.tcx();
 
-    if abi == ExternAbi::Rust || abi == ExternAbi::RustCall || abi == ExternAbi::RustIntrinsic {
+    if abi.is_rustic_abi() {
         fn_abi.adjust_for_rust_abi(cx, abi);
 
         // Look up the deduced parameter attributes for this function, if we have its def ID and
diff --git a/config.example.toml b/config.example.toml
index 2e26c024865db..ac5e491b4b520 100644
--- a/config.example.toml
+++ b/config.example.toml
@@ -189,6 +189,17 @@
 # The default stage to use for the `bench` subcommand
 #bench-stage = 2
 
+# A descriptive string to be appended to version output (e.g., `rustc --version`),
+# which is also used in places like debuginfo `DW_AT_producer`. This may be useful for
+# supplementary build information, like distro-specific package versions.
+#
+# The Rust compiler will differentiate between versions of itself, including
+# based on this string, which means that if you wish to be compatible with
+# upstream Rust you need to set this to "". However, note that if you set this to "" but
+# are not actually compatible -- for example if you've backported patches that change
+# behavior -- this may lead to miscompilations or other bugs.
+#description = ""
+
 # Build triple for the pre-compiled snapshot compiler. If `rustc` is set, this must match its host
 # triple (see `rustc --version --verbose`; cross-compiling the rust build system itself is NOT
 # supported). If `rustc` is unset, this must be a platform with pre-compiled host tools
@@ -615,17 +626,6 @@
 # If using tarball sources, default value is "auto-detect", otherwise, it's "dev".
 #channel = if "is a tarball source" { "auto-detect" } else { "dev" }
 
-# A descriptive string to be appended to `rustc --version` output, which is
-# also used in places like debuginfo `DW_AT_producer`. This may be useful for
-# supplementary build information, like distro-specific package versions.
-#
-# The Rust compiler will differentiate between versions of itself, including
-# based on this string, which means that if you wish to be compatible with
-# upstream Rust you need to set this to "". However, note that if you are not
-# actually compatible -- for example if you've backported patches that change
-# behavior -- this may lead to miscompilations or other bugs.
-#description = ""
-
 # The root location of the musl installation directory. The library directory
 # will also need to contain libunwind.a for an unwinding implementation. Note
 # that this option only makes sense for musl targets that produce statically
diff --git a/library/Cargo.lock b/library/Cargo.lock
index 37b10649ced4b..efb6b83a093ec 100644
--- a/library/Cargo.lock
+++ b/library/Cargo.lock
@@ -151,9 +151,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.169"
+version = "0.2.170"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b5aba8db14291edd000dfcc4d620c7ebfb122c613afb886ca8803fa4e128a20a"
+checksum = "875b3680cb2f8f71bdcf9a30f38d48282f5d3c95cbf9b3fa57269bb5d5c06828"
 dependencies = [
  "rustc-std-workspace-core",
 ]
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index f10ef1fca1377..fc4b93ccf8c20 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -1134,7 +1134,6 @@ impl String {
     /// # Examples
     ///
     /// ```
-    /// #![feature(string_extend_from_within)]
     /// let mut string = String::from("abcde");
     ///
     /// string.extend_from_within(2..);
@@ -1147,7 +1146,7 @@ impl String {
     /// assert_eq!(string, "abcdecdeabecde");
     /// ```
     #[cfg(not(no_global_oom_handling))]
-    #[unstable(feature = "string_extend_from_within", issue = "103806")]
+    #[stable(feature = "string_extend_from_within", since = "CURRENT_RUSTC_VERSION")]
     pub fn extend_from_within<R>(&mut self, src: R)
     where
         R: RangeBounds<usize>,
diff --git a/library/core/src/bstr.rs b/library/core/src/bstr.rs
index 74e07f3d242cd..ae84fd8adb61c 100644
--- a/library/core/src/bstr.rs
+++ b/library/core/src/bstr.rs
@@ -151,7 +151,9 @@ impl fmt::Display for ByteStr {
         };
         let nchars: usize = self
             .utf8_chunks()
-            .map(|chunk| chunk.valid().len() + if chunk.invalid().is_empty() { 0 } else { 1 })
+            .map(|chunk| {
+                chunk.valid().chars().count() + if chunk.invalid().is_empty() { 0 } else { 1 }
+            })
             .sum();
         let padding = f.width().unwrap_or(0).saturating_sub(nchars);
         let fill = f.fill();
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index e468f4f0f7e66..43fd54f881dae 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -778,7 +778,6 @@ impl<T> From<T> for T {
 ///
 /// [#64715]: https://github.com/rust-lang/rust/issues/64715
 #[stable(feature = "convert_infallible", since = "1.34.0")]
-#[allow(unused_attributes)] // FIXME(#58633): do a principled fix instead.
 #[rustc_reservation_impl = "permitting this impl would forbid us from adding \
                             `impl<T> From<!> for T` later; see rust-lang/rust#64715 for details"]
 impl<T> From<!> for T {
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index 764e7fff33ec7..3f60bb067d6e6 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -1693,49 +1693,41 @@ impl<'a> Formatter<'a> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn pad(&mut self, s: &str) -> Result {
-        // Make sure there's a fast path up front
+        // Make sure there's a fast path up front.
         if self.options.width.is_none() && self.options.precision.is_none() {
             return self.buf.write_str(s);
         }
-        // The `precision` field can be interpreted as a `max-width` for the
+
+        // The `precision` field can be interpreted as a maximum width for the
         // string being formatted.
-        let s = if let Some(max) = self.options.precision {
-            // If our string is longer that the precision, then we must have
-            // truncation. However other flags like `fill`, `width` and `align`
-            // must act as always.
-            if let Some((i, _)) = s.char_indices().nth(max) {
-                // LLVM here can't prove that `..i` won't panic `&s[..i]`, but
-                // we know that it can't panic. Use `get` + `unwrap_or` to avoid
-                // `unsafe` and otherwise don't emit any panic-related code
-                // here.
-                s.get(..i).unwrap_or(s)
-            } else {
-                &s
-            }
+        let (s, char_count) = if let Some(max_char_count) = self.options.precision {
+            let mut iter = s.char_indices();
+            let remaining = match iter.advance_by(max_char_count) {
+                Ok(()) => 0,
+                Err(remaining) => remaining.get(),
+            };
+            // SAFETY: The offset of `.char_indices()` is guaranteed to be
+            // in-bounds and between character boundaries.
+            let truncated = unsafe { s.get_unchecked(..iter.offset()) };
+            (truncated, max_char_count - remaining)
         } else {
-            &s
+            // Use the optimized char counting algorithm for the full string.
+            (s, s.chars().count())
         };
-        // The `width` field is more of a `min-width` parameter at this point.
-        match self.options.width {
-            // If we're under the maximum length, and there's no minimum length
-            // requirements, then we can just emit the string
-            None => self.buf.write_str(s),
-            Some(width) => {
-                let chars_count = s.chars().count();
-                // If we're under the maximum width, check if we're over the minimum
-                // width, if so it's as easy as just emitting the string.
-                if chars_count >= width {
-                    self.buf.write_str(s)
-                }
-                // If we're under both the maximum and the minimum width, then fill
-                // up the minimum width with the specified string + some alignment.
-                else {
-                    let align = Alignment::Left;
-                    let post_padding = self.padding(width - chars_count, align)?;
-                    self.buf.write_str(s)?;
-                    post_padding.write(self)
-                }
-            }
+
+        // The `width` field is more of a minimum width parameter at this point.
+        if let Some(width) = self.options.width
+            && char_count < width
+        {
+            // If we're under the minimum width, then fill up the minimum width
+            // with the specified string + some alignment.
+            let post_padding = self.padding(width - char_count, Alignment::Left)?;
+            self.buf.write_str(s)?;
+            post_padding.write(self)
+        } else {
+            // If we're over the minimum width or there is no minimum width, we
+            // can just emit the string.
+            self.buf.write_str(s)
         }
     }
 
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index b0571bf7247af..e2dd813981d04 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -453,8 +453,8 @@ impl Copy for ! {}
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> Copy for &T {}
 
-/// Marker trait for the types that are allowed in union fields, unsafe fields,
-/// and unsafe binder types.
+/// Marker trait for the types that are allowed in union fields and unsafe
+/// binder types.
 ///
 /// Implemented for:
 /// * `&T`, `&mut T` for all `T`,
diff --git a/library/core/src/num/dec2flt/common.rs b/library/core/src/num/dec2flt/common.rs
index 4dadf406ae8c7..a140a311c452f 100644
--- a/library/core/src/num/dec2flt/common.rs
+++ b/library/core/src/num/dec2flt/common.rs
@@ -8,12 +8,12 @@ pub(crate) trait ByteSlice {
     /// Writes a 64-bit integer as 8 bytes in little-endian order.
     fn write_u64(&mut self, value: u64);
 
-    /// Calculate the offset of a slice from another.
+    /// Calculate the difference in length between two slices.
     fn offset_from(&self, other: &Self) -> isize;
 
     /// Iteratively parse and consume digits from bytes.
-    /// Returns the same bytes with consumed digits being
-    /// elided.
+    ///
+    /// Returns the same bytes with consumed digits being elided. Breaks on invalid digits.
     fn parse_digits(&self, func: impl FnMut(u8)) -> &Self;
 }
 
@@ -39,11 +39,11 @@ impl ByteSlice for [u8] {
     fn parse_digits(&self, mut func: impl FnMut(u8)) -> &Self {
         let mut s = self;
 
-        while let Some((c, s_next)) = s.split_first() {
+        while let Some((c, rest)) = s.split_first() {
             let c = c.wrapping_sub(b'0');
             if c < 10 {
                 func(c);
-                s = s_next;
+                s = rest;
             } else {
                 break;
             }
@@ -53,7 +53,9 @@ impl ByteSlice for [u8] {
     }
 }
 
-/// Determine if 8 bytes are all decimal digits.
+/// Determine if all characters in an 8-byte byte string (represented as a `u64`) are all decimal
+/// digits.
+///
 /// This does not care about the order in which the bytes were loaded.
 pub(crate) fn is_8digits(v: u64) -> bool {
     let a = v.wrapping_add(0x4646_4646_4646_4646);
@@ -61,19 +63,20 @@ pub(crate) fn is_8digits(v: u64) -> bool {
     (a | b) & 0x8080_8080_8080_8080 == 0
 }
 
-/// A custom 64-bit floating point type, representing `f * 2^e`.
-/// e is biased, so it be directly shifted into the exponent bits.
+/// A custom 64-bit floating point type, representing `m * 2^p`.
+/// p is biased, so it be directly shifted into the exponent bits.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Default)]
 pub struct BiasedFp {
     /// The significant digits.
-    pub f: u64,
+    pub m: u64,
     /// The biased, binary exponent.
-    pub e: i32,
+    pub p_biased: i32,
 }
 
 impl BiasedFp {
+    /// Represent `0 ^ p`
     #[inline]
-    pub const fn zero_pow2(e: i32) -> Self {
-        Self { f: 0, e }
+    pub const fn zero_pow2(p_biased: i32) -> Self {
+        Self { m: 0, p_biased }
     }
 }
diff --git a/library/core/src/num/dec2flt/decimal.rs b/library/core/src/num/dec2flt/decimal.rs
index b37724ba62d5e..db7176c124318 100644
--- a/library/core/src/num/dec2flt/decimal.rs
+++ b/library/core/src/num/dec2flt/decimal.rs
@@ -1,358 +1,87 @@
-//! Arbitrary-precision decimal class for fallback algorithms.
-//!
-//! This is only used if the fast-path (native floats) and
-//! the Eisel-Lemire algorithm are unable to unambiguously
-//! determine the float.
-//!
-//! The technique used is "Simple Decimal Conversion", developed
-//! by Nigel Tao and Ken Thompson. A detailed description of the
-//! algorithm can be found in "ParseNumberF64 by Simple Decimal Conversion",
-//! available online: <https://nigeltao.github.io/blog/2020/parse-number-f64-simple.html>.
-
-use crate::num::dec2flt::common::{ByteSlice, is_8digits};
-
-#[derive(Clone)]
-pub(super) struct Decimal {
-    /// The number of significant digits in the decimal.
-    pub num_digits: usize,
-    /// The offset of the decimal point in the significant digits.
-    pub decimal_point: i32,
-    /// If the number of significant digits stored in the decimal is truncated.
-    pub truncated: bool,
-    /// Buffer of the raw digits, in the range [0, 9].
-    pub digits: [u8; Self::MAX_DIGITS],
+//! Representation of a float as the significant digits and exponent.
+
+use crate::num::dec2flt::float::RawFloat;
+use crate::num::dec2flt::fpu::set_precision;
+
+const INT_POW10: [u64; 16] = [
+    1,
+    10,
+    100,
+    1000,
+    10000,
+    100000,
+    1000000,
+    10000000,
+    100000000,
+    1000000000,
+    10000000000,
+    100000000000,
+    1000000000000,
+    10000000000000,
+    100000000000000,
+    1000000000000000,
+];
+
+/// A floating point number with up to 64 bits of mantissa and an `i64` exponent.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct Decimal {
+    pub exponent: i64,
+    pub mantissa: u64,
+    pub negative: bool,
+    pub many_digits: bool,
 }
 
-impl Default for Decimal {
-    fn default() -> Self {
-        Self { num_digits: 0, decimal_point: 0, truncated: false, digits: [0; Self::MAX_DIGITS] }
+impl Decimal {
+    /// Detect if the float can be accurately reconstructed from native floats.
+    #[inline]
+    fn can_use_fast_path<F: RawFloat>(&self) -> bool {
+        F::MIN_EXPONENT_FAST_PATH <= self.exponent
+            && self.exponent <= F::MAX_EXPONENT_DISGUISED_FAST_PATH
+            && self.mantissa <= F::MAX_MANTISSA_FAST_PATH
+            && !self.many_digits
     }
-}
 
-impl Decimal {
-    /// The maximum number of digits required to unambiguously round a float.
-    ///
-    /// For a double-precision IEEE 754 float, this required 767 digits,
-    /// so we store the max digits + 1.
-    ///
-    /// We can exactly represent a float in radix `b` from radix 2 if
-    /// `b` is divisible by 2. This function calculates the exact number of
-    /// digits required to exactly represent that float.
-    ///
-    /// According to the "Handbook of Floating Point Arithmetic",
-    /// for IEEE754, with emin being the min exponent, p2 being the
-    /// precision, and b being the radix, the number of digits follows as:
+    /// Try turning the decimal into an exact float representation, using machine-sized integers
+    /// and floats.
     ///
-    /// `−emin + p2 + ⌊(emin + 1) log(2, b) − log(1 − 2^(−p2), b)⌋`
+    /// This is extracted into a separate function so that it can be attempted before constructing
+    /// a Decimal. This only works if both the mantissa and the exponent
+    /// can be exactly represented as a machine float, since IEE-754 guarantees
+    /// no rounding will occur.
     ///
-    /// For f32, this follows as:
-    ///     emin = -126
-    ///     p2 = 24
-    ///
-    /// For f64, this follows as:
-    ///     emin = -1022
-    ///     p2 = 53
-    ///
-    /// In Python:
-    ///     `-emin + p2 + math.floor((emin+ 1)*math.log(2, b)-math.log(1-2**(-p2), b))`
-    pub(super) const MAX_DIGITS: usize = 768;
-    /// The max digits that can be exactly represented in a 64-bit integer.
-    pub(super) const MAX_DIGITS_WITHOUT_OVERFLOW: usize = 19;
-    pub(super) const DECIMAL_POINT_RANGE: i32 = 2047;
-
-    /// Append a digit to the buffer.
-    pub(super) fn try_add_digit(&mut self, digit: u8) {
-        if self.num_digits < Self::MAX_DIGITS {
-            self.digits[self.num_digits] = digit;
-        }
-        self.num_digits += 1;
-    }
-
-    /// Trim trailing zeros from the buffer.
-    pub(super) fn trim(&mut self) {
-        // All of the following calls to `Decimal::trim` can't panic because:
-        //
-        //  1. `parse_decimal` sets `num_digits` to a max of `Decimal::MAX_DIGITS`.
-        //  2. `right_shift` sets `num_digits` to `write_index`, which is bounded by `num_digits`.
-        //  3. `left_shift` `num_digits` to a max of `Decimal::MAX_DIGITS`.
-        //
-        // Trim is only called in `right_shift` and `left_shift`.
-        debug_assert!(self.num_digits <= Self::MAX_DIGITS);
-        while self.num_digits != 0 && self.digits[self.num_digits - 1] == 0 {
-            self.num_digits -= 1;
-        }
-    }
-
-    pub(super) fn round(&self) -> u64 {
-        if self.num_digits == 0 || self.decimal_point < 0 {
-            return 0;
-        } else if self.decimal_point > 18 {
-            return 0xFFFF_FFFF_FFFF_FFFF_u64;
-        }
-        let dp = self.decimal_point as usize;
-        let mut n = 0_u64;
-        for i in 0..dp {
-            n *= 10;
-            if i < self.num_digits {
-                n += self.digits[i] as u64;
-            }
-        }
-        let mut round_up = false;
-        if dp < self.num_digits {
-            round_up = self.digits[dp] >= 5;
-            if self.digits[dp] == 5 && dp + 1 == self.num_digits {
-                round_up = self.truncated || ((dp != 0) && (1 & self.digits[dp - 1] != 0))
-            }
-        }
-        if round_up {
-            n += 1;
-        }
-        n
-    }
-
-    /// Computes decimal * 2^shift.
-    pub(super) fn left_shift(&mut self, shift: usize) {
-        if self.num_digits == 0 {
-            return;
-        }
-        let num_new_digits = number_of_digits_decimal_left_shift(self, shift);
-        let mut read_index = self.num_digits;
-        let mut write_index = self.num_digits + num_new_digits;
-        let mut n = 0_u64;
-        while read_index != 0 {
-            read_index -= 1;
-            write_index -= 1;
-            n += (self.digits[read_index] as u64) << shift;
-            let quotient = n / 10;
-            let remainder = n - (10 * quotient);
-            if write_index < Self::MAX_DIGITS {
-                self.digits[write_index] = remainder as u8;
-            } else if remainder > 0 {
-                self.truncated = true;
-            }
-            n = quotient;
-        }
-        while n > 0 {
-            write_index -= 1;
-            let quotient = n / 10;
-            let remainder = n - (10 * quotient);
-            if write_index < Self::MAX_DIGITS {
-                self.digits[write_index] = remainder as u8;
-            } else if remainder > 0 {
-                self.truncated = true;
-            }
-            n = quotient;
-        }
-        self.num_digits += num_new_digits;
-        if self.num_digits > Self::MAX_DIGITS {
-            self.num_digits = Self::MAX_DIGITS;
-        }
-        self.decimal_point += num_new_digits as i32;
-        self.trim();
-    }
-
-    /// Computes decimal * 2^-shift.
-    pub(super) fn right_shift(&mut self, shift: usize) {
-        let mut read_index = 0;
-        let mut write_index = 0;
-        let mut n = 0_u64;
-        while (n >> shift) == 0 {
-            if read_index < self.num_digits {
-                n = (10 * n) + self.digits[read_index] as u64;
-                read_index += 1;
-            } else if n == 0 {
-                return;
+    /// There is an exception: disguised fast-path cases, where we can shift
+    /// powers-of-10 from the exponent to the significant digits.
+    pub fn try_fast_path<F: RawFloat>(&self) -> Option<F> {
+        // Here we need to work around <https://github.com/rust-lang/rust/issues/114479>.
+        // The fast path crucially depends on arithmetic being rounded to the correct number of bits
+        // without any intermediate rounding. On x86 (without SSE or SSE2) this requires the precision
+        // of the x87 FPU stack to be changed so that it directly rounds to 64/32 bit.
+        // The `set_precision` function takes care of setting the precision on architectures which
+        // require setting it by changing the global state (like the control word of the x87 FPU).
+        let _cw = set_precision::<F>();
+
+        if !self.can_use_fast_path::<F>() {
+            return None;
+        }
+
+        let value = if self.exponent <= F::MAX_EXPONENT_FAST_PATH {
+            // normal fast path
+            let value = F::from_u64(self.mantissa);
+            if self.exponent < 0 {
+                value / F::pow10_fast_path((-self.exponent) as _)
             } else {
-                while (n >> shift) == 0 {
-                    n *= 10;
-                    read_index += 1;
-                }
-                break;
-            }
-        }
-        self.decimal_point -= read_index as i32 - 1;
-        if self.decimal_point < -Self::DECIMAL_POINT_RANGE {
-            // `self = Self::Default()`, but without the overhead of clearing `digits`.
-            self.num_digits = 0;
-            self.decimal_point = 0;
-            self.truncated = false;
-            return;
-        }
-        let mask = (1_u64 << shift) - 1;
-        while read_index < self.num_digits {
-            let new_digit = (n >> shift) as u8;
-            n = (10 * (n & mask)) + self.digits[read_index] as u64;
-            read_index += 1;
-            self.digits[write_index] = new_digit;
-            write_index += 1;
-        }
-        while n > 0 {
-            let new_digit = (n >> shift) as u8;
-            n = 10 * (n & mask);
-            if write_index < Self::MAX_DIGITS {
-                self.digits[write_index] = new_digit;
-                write_index += 1;
-            } else if new_digit > 0 {
-                self.truncated = true;
-            }
-        }
-        self.num_digits = write_index;
-        self.trim();
-    }
-}
-
-/// Parse a big integer representation of the float as a decimal.
-pub(super) fn parse_decimal(mut s: &[u8]) -> Decimal {
-    let mut d = Decimal::default();
-    let start = s;
-
-    while let Some((&b'0', s_next)) = s.split_first() {
-        s = s_next;
-    }
-
-    s = s.parse_digits(|digit| d.try_add_digit(digit));
-
-    if let Some((b'.', s_next)) = s.split_first() {
-        s = s_next;
-        let first = s;
-        // Skip leading zeros.
-        if d.num_digits == 0 {
-            while let Some((&b'0', s_next)) = s.split_first() {
-                s = s_next;
-            }
-        }
-        while s.len() >= 8 && d.num_digits + 8 < Decimal::MAX_DIGITS {
-            let v = s.read_u64();
-            if !is_8digits(v) {
-                break;
+                value * F::pow10_fast_path(self.exponent as _)
             }
-            d.digits[d.num_digits..].write_u64(v - 0x3030_3030_3030_3030);
-            d.num_digits += 8;
-            s = &s[8..];
-        }
-        s = s.parse_digits(|digit| d.try_add_digit(digit));
-        d.decimal_point = s.len() as i32 - first.len() as i32;
-    }
-    if d.num_digits != 0 {
-        // Ignore the trailing zeros if there are any
-        let mut n_trailing_zeros = 0;
-        for &c in start[..(start.len() - s.len())].iter().rev() {
-            if c == b'0' {
-                n_trailing_zeros += 1;
-            } else if c != b'.' {
-                break;
-            }
-        }
-        d.decimal_point += n_trailing_zeros as i32;
-        d.num_digits -= n_trailing_zeros;
-        d.decimal_point += d.num_digits as i32;
-        if d.num_digits > Decimal::MAX_DIGITS {
-            d.truncated = true;
-            d.num_digits = Decimal::MAX_DIGITS;
-        }
-    }
-    if let Some((&ch, s_next)) = s.split_first() {
-        if ch == b'e' || ch == b'E' {
-            s = s_next;
-            let mut neg_exp = false;
-            if let Some((&ch, s_next)) = s.split_first() {
-                neg_exp = ch == b'-';
-                if ch == b'-' || ch == b'+' {
-                    s = s_next;
-                }
+        } else {
+            // disguised fast path
+            let shift = self.exponent - F::MAX_EXPONENT_FAST_PATH;
+            let mantissa = self.mantissa.checked_mul(INT_POW10[shift as usize])?;
+            if mantissa > F::MAX_MANTISSA_FAST_PATH {
+                return None;
             }
-            let mut exp_num = 0_i32;
-
-            s.parse_digits(|digit| {
-                if exp_num < 0x10000 {
-                    exp_num = 10 * exp_num + digit as i32;
-                }
-            });
+            F::from_u64(mantissa) * F::pow10_fast_path(F::MAX_EXPONENT_FAST_PATH as _)
+        };
 
-            d.decimal_point += if neg_exp { -exp_num } else { exp_num };
-        }
-    }
-    for i in d.num_digits..Decimal::MAX_DIGITS_WITHOUT_OVERFLOW {
-        d.digits[i] = 0;
-    }
-    d
-}
-
-fn number_of_digits_decimal_left_shift(d: &Decimal, mut shift: usize) -> usize {
-    #[rustfmt::skip]
-    const TABLE: [u16; 65] = [
-        0x0000, 0x0800, 0x0801, 0x0803, 0x1006, 0x1009, 0x100D, 0x1812, 0x1817, 0x181D, 0x2024,
-        0x202B, 0x2033, 0x203C, 0x2846, 0x2850, 0x285B, 0x3067, 0x3073, 0x3080, 0x388E, 0x389C,
-        0x38AB, 0x38BB, 0x40CC, 0x40DD, 0x40EF, 0x4902, 0x4915, 0x4929, 0x513E, 0x5153, 0x5169,
-        0x5180, 0x5998, 0x59B0, 0x59C9, 0x61E3, 0x61FD, 0x6218, 0x6A34, 0x6A50, 0x6A6D, 0x6A8B,
-        0x72AA, 0x72C9, 0x72E9, 0x7B0A, 0x7B2B, 0x7B4D, 0x8370, 0x8393, 0x83B7, 0x83DC, 0x8C02,
-        0x8C28, 0x8C4F, 0x9477, 0x949F, 0x94C8, 0x9CF2, 0x051C, 0x051C, 0x051C, 0x051C,
-    ];
-    #[rustfmt::skip]
-    const TABLE_POW5: [u8; 0x051C] = [
-        5, 2, 5, 1, 2, 5, 6, 2, 5, 3, 1, 2, 5, 1, 5, 6, 2, 5, 7, 8, 1, 2, 5, 3, 9, 0, 6, 2, 5, 1,
-        9, 5, 3, 1, 2, 5, 9, 7, 6, 5, 6, 2, 5, 4, 8, 8, 2, 8, 1, 2, 5, 2, 4, 4, 1, 4, 0, 6, 2, 5,
-        1, 2, 2, 0, 7, 0, 3, 1, 2, 5, 6, 1, 0, 3, 5, 1, 5, 6, 2, 5, 3, 0, 5, 1, 7, 5, 7, 8, 1, 2,
-        5, 1, 5, 2, 5, 8, 7, 8, 9, 0, 6, 2, 5, 7, 6, 2, 9, 3, 9, 4, 5, 3, 1, 2, 5, 3, 8, 1, 4, 6,
-        9, 7, 2, 6, 5, 6, 2, 5, 1, 9, 0, 7, 3, 4, 8, 6, 3, 2, 8, 1, 2, 5, 9, 5, 3, 6, 7, 4, 3, 1,
-        6, 4, 0, 6, 2, 5, 4, 7, 6, 8, 3, 7, 1, 5, 8, 2, 0, 3, 1, 2, 5, 2, 3, 8, 4, 1, 8, 5, 7, 9,
-        1, 0, 1, 5, 6, 2, 5, 1, 1, 9, 2, 0, 9, 2, 8, 9, 5, 5, 0, 7, 8, 1, 2, 5, 5, 9, 6, 0, 4, 6,
-        4, 4, 7, 7, 5, 3, 9, 0, 6, 2, 5, 2, 9, 8, 0, 2, 3, 2, 2, 3, 8, 7, 6, 9, 5, 3, 1, 2, 5, 1,
-        4, 9, 0, 1, 1, 6, 1, 1, 9, 3, 8, 4, 7, 6, 5, 6, 2, 5, 7, 4, 5, 0, 5, 8, 0, 5, 9, 6, 9, 2,
-        3, 8, 2, 8, 1, 2, 5, 3, 7, 2, 5, 2, 9, 0, 2, 9, 8, 4, 6, 1, 9, 1, 4, 0, 6, 2, 5, 1, 8, 6,
-        2, 6, 4, 5, 1, 4, 9, 2, 3, 0, 9, 5, 7, 0, 3, 1, 2, 5, 9, 3, 1, 3, 2, 2, 5, 7, 4, 6, 1, 5,
-        4, 7, 8, 5, 1, 5, 6, 2, 5, 4, 6, 5, 6, 6, 1, 2, 8, 7, 3, 0, 7, 7, 3, 9, 2, 5, 7, 8, 1, 2,
-        5, 2, 3, 2, 8, 3, 0, 6, 4, 3, 6, 5, 3, 8, 6, 9, 6, 2, 8, 9, 0, 6, 2, 5, 1, 1, 6, 4, 1, 5,
-        3, 2, 1, 8, 2, 6, 9, 3, 4, 8, 1, 4, 4, 5, 3, 1, 2, 5, 5, 8, 2, 0, 7, 6, 6, 0, 9, 1, 3, 4,
-        6, 7, 4, 0, 7, 2, 2, 6, 5, 6, 2, 5, 2, 9, 1, 0, 3, 8, 3, 0, 4, 5, 6, 7, 3, 3, 7, 0, 3, 6,
-        1, 3, 2, 8, 1, 2, 5, 1, 4, 5, 5, 1, 9, 1, 5, 2, 2, 8, 3, 6, 6, 8, 5, 1, 8, 0, 6, 6, 4, 0,
-        6, 2, 5, 7, 2, 7, 5, 9, 5, 7, 6, 1, 4, 1, 8, 3, 4, 2, 5, 9, 0, 3, 3, 2, 0, 3, 1, 2, 5, 3,
-        6, 3, 7, 9, 7, 8, 8, 0, 7, 0, 9, 1, 7, 1, 2, 9, 5, 1, 6, 6, 0, 1, 5, 6, 2, 5, 1, 8, 1, 8,
-        9, 8, 9, 4, 0, 3, 5, 4, 5, 8, 5, 6, 4, 7, 5, 8, 3, 0, 0, 7, 8, 1, 2, 5, 9, 0, 9, 4, 9, 4,
-        7, 0, 1, 7, 7, 2, 9, 2, 8, 2, 3, 7, 9, 1, 5, 0, 3, 9, 0, 6, 2, 5, 4, 5, 4, 7, 4, 7, 3, 5,
-        0, 8, 8, 6, 4, 6, 4, 1, 1, 8, 9, 5, 7, 5, 1, 9, 5, 3, 1, 2, 5, 2, 2, 7, 3, 7, 3, 6, 7, 5,
-        4, 4, 3, 2, 3, 2, 0, 5, 9, 4, 7, 8, 7, 5, 9, 7, 6, 5, 6, 2, 5, 1, 1, 3, 6, 8, 6, 8, 3, 7,
-        7, 2, 1, 6, 1, 6, 0, 2, 9, 7, 3, 9, 3, 7, 9, 8, 8, 2, 8, 1, 2, 5, 5, 6, 8, 4, 3, 4, 1, 8,
-        8, 6, 0, 8, 0, 8, 0, 1, 4, 8, 6, 9, 6, 8, 9, 9, 4, 1, 4, 0, 6, 2, 5, 2, 8, 4, 2, 1, 7, 0,
-        9, 4, 3, 0, 4, 0, 4, 0, 0, 7, 4, 3, 4, 8, 4, 4, 9, 7, 0, 7, 0, 3, 1, 2, 5, 1, 4, 2, 1, 0,
-        8, 5, 4, 7, 1, 5, 2, 0, 2, 0, 0, 3, 7, 1, 7, 4, 2, 2, 4, 8, 5, 3, 5, 1, 5, 6, 2, 5, 7, 1,
-        0, 5, 4, 2, 7, 3, 5, 7, 6, 0, 1, 0, 0, 1, 8, 5, 8, 7, 1, 1, 2, 4, 2, 6, 7, 5, 7, 8, 1, 2,
-        5, 3, 5, 5, 2, 7, 1, 3, 6, 7, 8, 8, 0, 0, 5, 0, 0, 9, 2, 9, 3, 5, 5, 6, 2, 1, 3, 3, 7, 8,
-        9, 0, 6, 2, 5, 1, 7, 7, 6, 3, 5, 6, 8, 3, 9, 4, 0, 0, 2, 5, 0, 4, 6, 4, 6, 7, 7, 8, 1, 0,
-        6, 6, 8, 9, 4, 5, 3, 1, 2, 5, 8, 8, 8, 1, 7, 8, 4, 1, 9, 7, 0, 0, 1, 2, 5, 2, 3, 2, 3, 3,
-        8, 9, 0, 5, 3, 3, 4, 4, 7, 2, 6, 5, 6, 2, 5, 4, 4, 4, 0, 8, 9, 2, 0, 9, 8, 5, 0, 0, 6, 2,
-        6, 1, 6, 1, 6, 9, 4, 5, 2, 6, 6, 7, 2, 3, 6, 3, 2, 8, 1, 2, 5, 2, 2, 2, 0, 4, 4, 6, 0, 4,
-        9, 2, 5, 0, 3, 1, 3, 0, 8, 0, 8, 4, 7, 2, 6, 3, 3, 3, 6, 1, 8, 1, 6, 4, 0, 6, 2, 5, 1, 1,
-        1, 0, 2, 2, 3, 0, 2, 4, 6, 2, 5, 1, 5, 6, 5, 4, 0, 4, 2, 3, 6, 3, 1, 6, 6, 8, 0, 9, 0, 8,
-        2, 0, 3, 1, 2, 5, 5, 5, 5, 1, 1, 1, 5, 1, 2, 3, 1, 2, 5, 7, 8, 2, 7, 0, 2, 1, 1, 8, 1, 5,
-        8, 3, 4, 0, 4, 5, 4, 1, 0, 1, 5, 6, 2, 5, 2, 7, 7, 5, 5, 5, 7, 5, 6, 1, 5, 6, 2, 8, 9, 1,
-        3, 5, 1, 0, 5, 9, 0, 7, 9, 1, 7, 0, 2, 2, 7, 0, 5, 0, 7, 8, 1, 2, 5, 1, 3, 8, 7, 7, 7, 8,
-        7, 8, 0, 7, 8, 1, 4, 4, 5, 6, 7, 5, 5, 2, 9, 5, 3, 9, 5, 8, 5, 1, 1, 3, 5, 2, 5, 3, 9, 0,
-        6, 2, 5, 6, 9, 3, 8, 8, 9, 3, 9, 0, 3, 9, 0, 7, 2, 2, 8, 3, 7, 7, 6, 4, 7, 6, 9, 7, 9, 2,
-        5, 5, 6, 7, 6, 2, 6, 9, 5, 3, 1, 2, 5, 3, 4, 6, 9, 4, 4, 6, 9, 5, 1, 9, 5, 3, 6, 1, 4, 1,
-        8, 8, 8, 2, 3, 8, 4, 8, 9, 6, 2, 7, 8, 3, 8, 1, 3, 4, 7, 6, 5, 6, 2, 5, 1, 7, 3, 4, 7, 2,
-        3, 4, 7, 5, 9, 7, 6, 8, 0, 7, 0, 9, 4, 4, 1, 1, 9, 2, 4, 4, 8, 1, 3, 9, 1, 9, 0, 6, 7, 3,
-        8, 2, 8, 1, 2, 5, 8, 6, 7, 3, 6, 1, 7, 3, 7, 9, 8, 8, 4, 0, 3, 5, 4, 7, 2, 0, 5, 9, 6, 2,
-        2, 4, 0, 6, 9, 5, 9, 5, 3, 3, 6, 9, 1, 4, 0, 6, 2, 5,
-    ];
-
-    shift &= 63;
-    let x_a = TABLE[shift];
-    let x_b = TABLE[shift + 1];
-    let num_new_digits = (x_a >> 11) as _;
-    let pow5_a = (0x7FF & x_a) as usize;
-    let pow5_b = (0x7FF & x_b) as usize;
-    let pow5 = &TABLE_POW5[pow5_a..];
-    for (i, &p5) in pow5.iter().enumerate().take(pow5_b - pow5_a) {
-        if i >= d.num_digits {
-            return num_new_digits - 1;
-        } else if d.digits[i] == p5 {
-            continue;
-        } else if d.digits[i] < p5 {
-            return num_new_digits - 1;
-        } else {
-            return num_new_digits;
-        }
+        if self.negative { Some(-value) } else { Some(value) }
     }
-    num_new_digits
 }
diff --git a/library/core/src/num/dec2flt/decimal_seq.rs b/library/core/src/num/dec2flt/decimal_seq.rs
new file mode 100644
index 0000000000000..de22280c001c9
--- /dev/null
+++ b/library/core/src/num/dec2flt/decimal_seq.rs
@@ -0,0 +1,379 @@
+//! Arbitrary-precision decimal type used by fallback algorithms.
+//!
+//! This is only used if the fast-path (native floats) and
+//! the Eisel-Lemire algorithm are unable to unambiguously
+//! determine the float.
+//!
+//! The technique used is "Simple Decimal Conversion", developed
+//! by Nigel Tao and Ken Thompson. A detailed description of the
+//! algorithm can be found in "ParseNumberF64 by Simple Decimal Conversion",
+//! available online: <https://nigeltao.github.io/blog/2020/parse-number-f64-simple.html>.
+
+use crate::num::dec2flt::common::{ByteSlice, is_8digits};
+
+/// A decimal floating-point number, represented as a sequence of decimal digits.
+#[derive(Clone, Debug, PartialEq)]
+pub struct DecimalSeq {
+    /// The number of significant digits in the decimal.
+    pub num_digits: usize,
+    /// The offset of the decimal point in the significant digits.
+    pub decimal_point: i32,
+    /// If the number of significant digits stored in the decimal is truncated.
+    pub truncated: bool,
+    /// Buffer of the raw digits, in the range [0, 9].
+    pub digits: [u8; Self::MAX_DIGITS],
+}
+
+impl Default for DecimalSeq {
+    fn default() -> Self {
+        Self { num_digits: 0, decimal_point: 0, truncated: false, digits: [0; Self::MAX_DIGITS] }
+    }
+}
+
+impl DecimalSeq {
+    /// The maximum number of digits required to unambiguously round up to a 64-bit float.
+    ///
+    /// For an IEEE 754 binary64 float, this required 767 digits. So we store the max digits + 1.
+    ///
+    /// We can exactly represent a float in radix `b` from radix 2 if
+    /// `b` is divisible by 2. This function calculates the exact number of
+    /// digits required to exactly represent that float.
+    ///
+    /// According to the "Handbook of Floating Point Arithmetic",
+    /// for IEEE754, with `emin` being the min exponent, `p2` being the
+    /// precision, and `b` being the radix, the number of digits follows as:
+    ///
+    /// `−emin + p2 + ⌊(emin + 1) log(2, b) − log(1 − 2^(−p2), b)⌋`
+    ///
+    /// For f32, this follows as:
+    ///     emin = -126
+    ///     p2 = 24
+    ///
+    /// For f64, this follows as:
+    ///     emin = -1022
+    ///     p2 = 53
+    ///
+    /// In Python:
+    ///     `-emin + p2 + math.floor((emin+ 1)*math.log(2, b)-math.log(1-2**(-p2), b))`
+    pub const MAX_DIGITS: usize = 768;
+
+    /// The max decimal digits that can be exactly represented in a 64-bit integer.
+    pub(super) const MAX_DIGITS_WITHOUT_OVERFLOW: usize = 19;
+    pub(super) const DECIMAL_POINT_RANGE: i32 = 2047;
+
+    /// Append a digit to the buffer if it fits.
+    // FIXME(tgross35): it may be better for this to return an option
+    // FIXME(tgross35): incrementing the digit counter even if we don't push anything
+    // seems incorrect.
+    pub(super) fn try_add_digit(&mut self, digit: u8) {
+        if self.num_digits < Self::MAX_DIGITS {
+            self.digits[self.num_digits] = digit;
+        }
+        self.num_digits += 1;
+    }
+
+    /// Trim trailing zeros from the buffer.
+    // FIXME(tgross35): this could be `.rev().position()` if perf is okay
+    pub fn trim(&mut self) {
+        // All of the following calls to `DecimalSeq::trim` can't panic because:
+        //
+        //  1. `parse_decimal` sets `num_digits` to a max of `DecimalSeq::MAX_DIGITS`.
+        //  2. `right_shift` sets `num_digits` to `write_index`, which is bounded by `num_digits`.
+        //  3. `left_shift` `num_digits` to a max of `DecimalSeq::MAX_DIGITS`.
+        //
+        // Trim is only called in `right_shift` and `left_shift`.
+        debug_assert!(self.num_digits <= Self::MAX_DIGITS);
+        while self.num_digits != 0 && self.digits[self.num_digits - 1] == 0 {
+            self.num_digits -= 1;
+        }
+    }
+
+    pub(super) fn round(&self) -> u64 {
+        if self.num_digits == 0 || self.decimal_point < 0 {
+            return 0;
+        } else if self.decimal_point >= Self::MAX_DIGITS_WITHOUT_OVERFLOW as i32 {
+            return 0xFFFF_FFFF_FFFF_FFFF_u64;
+        }
+
+        let dp = self.decimal_point as usize;
+        let mut n = 0_u64;
+
+        for i in 0..dp {
+            n *= 10;
+            if i < self.num_digits {
+                n += self.digits[i] as u64;
+            }
+        }
+
+        let mut round_up = false;
+
+        if dp < self.num_digits {
+            round_up = self.digits[dp] >= 5;
+            if self.digits[dp] == 5 && dp + 1 == self.num_digits {
+                round_up = self.truncated || ((dp != 0) && (1 & self.digits[dp - 1] != 0))
+            }
+        }
+
+        if round_up {
+            n += 1;
+        }
+        n
+    }
+
+    /// Computes decimal * 2^shift.
+    pub(super) fn left_shift(&mut self, shift: usize) {
+        if self.num_digits == 0 {
+            return;
+        }
+        let num_new_digits = number_of_digits_decimal_left_shift(self, shift);
+        let mut read_index = self.num_digits;
+        let mut write_index = self.num_digits + num_new_digits;
+        let mut n = 0_u64;
+
+        while read_index != 0 {
+            read_index -= 1;
+            write_index -= 1;
+            n += (self.digits[read_index] as u64) << shift;
+            let quotient = n / 10;
+            let remainder = n - (10 * quotient);
+            if write_index < Self::MAX_DIGITS {
+                self.digits[write_index] = remainder as u8;
+            } else if remainder > 0 {
+                self.truncated = true;
+            }
+            n = quotient;
+        }
+
+        while n > 0 {
+            write_index -= 1;
+            let quotient = n / 10;
+            let remainder = n - (10 * quotient);
+            if write_index < Self::MAX_DIGITS {
+                self.digits[write_index] = remainder as u8;
+            } else if remainder > 0 {
+                self.truncated = true;
+            }
+            n = quotient;
+        }
+
+        self.num_digits += num_new_digits;
+
+        if self.num_digits > Self::MAX_DIGITS {
+            self.num_digits = Self::MAX_DIGITS;
+        }
+
+        self.decimal_point += num_new_digits as i32;
+        self.trim();
+    }
+
+    /// Computes decimal * 2^-shift.
+    pub(super) fn right_shift(&mut self, shift: usize) {
+        let mut read_index = 0;
+        let mut write_index = 0;
+        let mut n = 0_u64;
+        while (n >> shift) == 0 {
+            if read_index < self.num_digits {
+                n = (10 * n) + self.digits[read_index] as u64;
+                read_index += 1;
+            } else if n == 0 {
+                return;
+            } else {
+                while (n >> shift) == 0 {
+                    n *= 10;
+                    read_index += 1;
+                }
+                break;
+            }
+        }
+        self.decimal_point -= read_index as i32 - 1;
+        if self.decimal_point < -Self::DECIMAL_POINT_RANGE {
+            // `self = Self::Default()`, but without the overhead of clearing `digits`.
+            self.num_digits = 0;
+            self.decimal_point = 0;
+            self.truncated = false;
+            return;
+        }
+        let mask = (1_u64 << shift) - 1;
+        while read_index < self.num_digits {
+            let new_digit = (n >> shift) as u8;
+            n = (10 * (n & mask)) + self.digits[read_index] as u64;
+            read_index += 1;
+            self.digits[write_index] = new_digit;
+            write_index += 1;
+        }
+        while n > 0 {
+            let new_digit = (n >> shift) as u8;
+            n = 10 * (n & mask);
+            if write_index < Self::MAX_DIGITS {
+                self.digits[write_index] = new_digit;
+                write_index += 1;
+            } else if new_digit > 0 {
+                self.truncated = true;
+            }
+        }
+        self.num_digits = write_index;
+        self.trim();
+    }
+}
+
+/// Parse a big integer representation of the float as a decimal.
+pub fn parse_decimal_seq(mut s: &[u8]) -> DecimalSeq {
+    let mut d = DecimalSeq::default();
+    let start = s;
+
+    while let Some((&b'0', s_next)) = s.split_first() {
+        s = s_next;
+    }
+
+    s = s.parse_digits(|digit| d.try_add_digit(digit));
+
+    if let Some((b'.', s_next)) = s.split_first() {
+        s = s_next;
+        let first = s;
+        // Skip leading zeros.
+        if d.num_digits == 0 {
+            while let Some((&b'0', s_next)) = s.split_first() {
+                s = s_next;
+            }
+        }
+        while s.len() >= 8 && d.num_digits + 8 < DecimalSeq::MAX_DIGITS {
+            let v = s.read_u64();
+            if !is_8digits(v) {
+                break;
+            }
+            d.digits[d.num_digits..].write_u64(v - 0x3030_3030_3030_3030);
+            d.num_digits += 8;
+            s = &s[8..];
+        }
+        s = s.parse_digits(|digit| d.try_add_digit(digit));
+        d.decimal_point = s.len() as i32 - first.len() as i32;
+    }
+
+    if d.num_digits != 0 {
+        // Ignore the trailing zeros if there are any
+        let mut n_trailing_zeros = 0;
+        for &c in start[..(start.len() - s.len())].iter().rev() {
+            if c == b'0' {
+                n_trailing_zeros += 1;
+            } else if c != b'.' {
+                break;
+            }
+        }
+        d.decimal_point += n_trailing_zeros as i32;
+        d.num_digits -= n_trailing_zeros;
+        d.decimal_point += d.num_digits as i32;
+        if d.num_digits > DecimalSeq::MAX_DIGITS {
+            d.truncated = true;
+            d.num_digits = DecimalSeq::MAX_DIGITS;
+        }
+    }
+
+    if let Some((&ch, s_next)) = s.split_first() {
+        if ch == b'e' || ch == b'E' {
+            s = s_next;
+            let mut neg_exp = false;
+            if let Some((&ch, s_next)) = s.split_first() {
+                neg_exp = ch == b'-';
+                if ch == b'-' || ch == b'+' {
+                    s = s_next;
+                }
+            }
+            let mut exp_num = 0_i32;
+
+            s.parse_digits(|digit| {
+                if exp_num < 0x10000 {
+                    exp_num = 10 * exp_num + digit as i32;
+                }
+            });
+
+            d.decimal_point += if neg_exp { -exp_num } else { exp_num };
+        }
+    }
+
+    for i in d.num_digits..DecimalSeq::MAX_DIGITS_WITHOUT_OVERFLOW {
+        d.digits[i] = 0;
+    }
+
+    d
+}
+
+fn number_of_digits_decimal_left_shift(d: &DecimalSeq, mut shift: usize) -> usize {
+    #[rustfmt::skip]
+    const TABLE: [u16; 65] = [
+        0x0000, 0x0800, 0x0801, 0x0803, 0x1006, 0x1009, 0x100D, 0x1812, 0x1817, 0x181D, 0x2024,
+        0x202B, 0x2033, 0x203C, 0x2846, 0x2850, 0x285B, 0x3067, 0x3073, 0x3080, 0x388E, 0x389C,
+        0x38AB, 0x38BB, 0x40CC, 0x40DD, 0x40EF, 0x4902, 0x4915, 0x4929, 0x513E, 0x5153, 0x5169,
+        0x5180, 0x5998, 0x59B0, 0x59C9, 0x61E3, 0x61FD, 0x6218, 0x6A34, 0x6A50, 0x6A6D, 0x6A8B,
+        0x72AA, 0x72C9, 0x72E9, 0x7B0A, 0x7B2B, 0x7B4D, 0x8370, 0x8393, 0x83B7, 0x83DC, 0x8C02,
+        0x8C28, 0x8C4F, 0x9477, 0x949F, 0x94C8, 0x9CF2, 0x051C, 0x051C, 0x051C, 0x051C,
+    ];
+    #[rustfmt::skip]
+    const TABLE_POW5: [u8; 0x051C] = [
+        5, 2, 5, 1, 2, 5, 6, 2, 5, 3, 1, 2, 5, 1, 5, 6, 2, 5, 7, 8, 1, 2, 5, 3, 9, 0, 6, 2, 5, 1,
+        9, 5, 3, 1, 2, 5, 9, 7, 6, 5, 6, 2, 5, 4, 8, 8, 2, 8, 1, 2, 5, 2, 4, 4, 1, 4, 0, 6, 2, 5,
+        1, 2, 2, 0, 7, 0, 3, 1, 2, 5, 6, 1, 0, 3, 5, 1, 5, 6, 2, 5, 3, 0, 5, 1, 7, 5, 7, 8, 1, 2,
+        5, 1, 5, 2, 5, 8, 7, 8, 9, 0, 6, 2, 5, 7, 6, 2, 9, 3, 9, 4, 5, 3, 1, 2, 5, 3, 8, 1, 4, 6,
+        9, 7, 2, 6, 5, 6, 2, 5, 1, 9, 0, 7, 3, 4, 8, 6, 3, 2, 8, 1, 2, 5, 9, 5, 3, 6, 7, 4, 3, 1,
+        6, 4, 0, 6, 2, 5, 4, 7, 6, 8, 3, 7, 1, 5, 8, 2, 0, 3, 1, 2, 5, 2, 3, 8, 4, 1, 8, 5, 7, 9,
+        1, 0, 1, 5, 6, 2, 5, 1, 1, 9, 2, 0, 9, 2, 8, 9, 5, 5, 0, 7, 8, 1, 2, 5, 5, 9, 6, 0, 4, 6,
+        4, 4, 7, 7, 5, 3, 9, 0, 6, 2, 5, 2, 9, 8, 0, 2, 3, 2, 2, 3, 8, 7, 6, 9, 5, 3, 1, 2, 5, 1,
+        4, 9, 0, 1, 1, 6, 1, 1, 9, 3, 8, 4, 7, 6, 5, 6, 2, 5, 7, 4, 5, 0, 5, 8, 0, 5, 9, 6, 9, 2,
+        3, 8, 2, 8, 1, 2, 5, 3, 7, 2, 5, 2, 9, 0, 2, 9, 8, 4, 6, 1, 9, 1, 4, 0, 6, 2, 5, 1, 8, 6,
+        2, 6, 4, 5, 1, 4, 9, 2, 3, 0, 9, 5, 7, 0, 3, 1, 2, 5, 9, 3, 1, 3, 2, 2, 5, 7, 4, 6, 1, 5,
+        4, 7, 8, 5, 1, 5, 6, 2, 5, 4, 6, 5, 6, 6, 1, 2, 8, 7, 3, 0, 7, 7, 3, 9, 2, 5, 7, 8, 1, 2,
+        5, 2, 3, 2, 8, 3, 0, 6, 4, 3, 6, 5, 3, 8, 6, 9, 6, 2, 8, 9, 0, 6, 2, 5, 1, 1, 6, 4, 1, 5,
+        3, 2, 1, 8, 2, 6, 9, 3, 4, 8, 1, 4, 4, 5, 3, 1, 2, 5, 5, 8, 2, 0, 7, 6, 6, 0, 9, 1, 3, 4,
+        6, 7, 4, 0, 7, 2, 2, 6, 5, 6, 2, 5, 2, 9, 1, 0, 3, 8, 3, 0, 4, 5, 6, 7, 3, 3, 7, 0, 3, 6,
+        1, 3, 2, 8, 1, 2, 5, 1, 4, 5, 5, 1, 9, 1, 5, 2, 2, 8, 3, 6, 6, 8, 5, 1, 8, 0, 6, 6, 4, 0,
+        6, 2, 5, 7, 2, 7, 5, 9, 5, 7, 6, 1, 4, 1, 8, 3, 4, 2, 5, 9, 0, 3, 3, 2, 0, 3, 1, 2, 5, 3,
+        6, 3, 7, 9, 7, 8, 8, 0, 7, 0, 9, 1, 7, 1, 2, 9, 5, 1, 6, 6, 0, 1, 5, 6, 2, 5, 1, 8, 1, 8,
+        9, 8, 9, 4, 0, 3, 5, 4, 5, 8, 5, 6, 4, 7, 5, 8, 3, 0, 0, 7, 8, 1, 2, 5, 9, 0, 9, 4, 9, 4,
+        7, 0, 1, 7, 7, 2, 9, 2, 8, 2, 3, 7, 9, 1, 5, 0, 3, 9, 0, 6, 2, 5, 4, 5, 4, 7, 4, 7, 3, 5,
+        0, 8, 8, 6, 4, 6, 4, 1, 1, 8, 9, 5, 7, 5, 1, 9, 5, 3, 1, 2, 5, 2, 2, 7, 3, 7, 3, 6, 7, 5,
+        4, 4, 3, 2, 3, 2, 0, 5, 9, 4, 7, 8, 7, 5, 9, 7, 6, 5, 6, 2, 5, 1, 1, 3, 6, 8, 6, 8, 3, 7,
+        7, 2, 1, 6, 1, 6, 0, 2, 9, 7, 3, 9, 3, 7, 9, 8, 8, 2, 8, 1, 2, 5, 5, 6, 8, 4, 3, 4, 1, 8,
+        8, 6, 0, 8, 0, 8, 0, 1, 4, 8, 6, 9, 6, 8, 9, 9, 4, 1, 4, 0, 6, 2, 5, 2, 8, 4, 2, 1, 7, 0,
+        9, 4, 3, 0, 4, 0, 4, 0, 0, 7, 4, 3, 4, 8, 4, 4, 9, 7, 0, 7, 0, 3, 1, 2, 5, 1, 4, 2, 1, 0,
+        8, 5, 4, 7, 1, 5, 2, 0, 2, 0, 0, 3, 7, 1, 7, 4, 2, 2, 4, 8, 5, 3, 5, 1, 5, 6, 2, 5, 7, 1,
+        0, 5, 4, 2, 7, 3, 5, 7, 6, 0, 1, 0, 0, 1, 8, 5, 8, 7, 1, 1, 2, 4, 2, 6, 7, 5, 7, 8, 1, 2,
+        5, 3, 5, 5, 2, 7, 1, 3, 6, 7, 8, 8, 0, 0, 5, 0, 0, 9, 2, 9, 3, 5, 5, 6, 2, 1, 3, 3, 7, 8,
+        9, 0, 6, 2, 5, 1, 7, 7, 6, 3, 5, 6, 8, 3, 9, 4, 0, 0, 2, 5, 0, 4, 6, 4, 6, 7, 7, 8, 1, 0,
+        6, 6, 8, 9, 4, 5, 3, 1, 2, 5, 8, 8, 8, 1, 7, 8, 4, 1, 9, 7, 0, 0, 1, 2, 5, 2, 3, 2, 3, 3,
+        8, 9, 0, 5, 3, 3, 4, 4, 7, 2, 6, 5, 6, 2, 5, 4, 4, 4, 0, 8, 9, 2, 0, 9, 8, 5, 0, 0, 6, 2,
+        6, 1, 6, 1, 6, 9, 4, 5, 2, 6, 6, 7, 2, 3, 6, 3, 2, 8, 1, 2, 5, 2, 2, 2, 0, 4, 4, 6, 0, 4,
+        9, 2, 5, 0, 3, 1, 3, 0, 8, 0, 8, 4, 7, 2, 6, 3, 3, 3, 6, 1, 8, 1, 6, 4, 0, 6, 2, 5, 1, 1,
+        1, 0, 2, 2, 3, 0, 2, 4, 6, 2, 5, 1, 5, 6, 5, 4, 0, 4, 2, 3, 6, 3, 1, 6, 6, 8, 0, 9, 0, 8,
+        2, 0, 3, 1, 2, 5, 5, 5, 5, 1, 1, 1, 5, 1, 2, 3, 1, 2, 5, 7, 8, 2, 7, 0, 2, 1, 1, 8, 1, 5,
+        8, 3, 4, 0, 4, 5, 4, 1, 0, 1, 5, 6, 2, 5, 2, 7, 7, 5, 5, 5, 7, 5, 6, 1, 5, 6, 2, 8, 9, 1,
+        3, 5, 1, 0, 5, 9, 0, 7, 9, 1, 7, 0, 2, 2, 7, 0, 5, 0, 7, 8, 1, 2, 5, 1, 3, 8, 7, 7, 7, 8,
+        7, 8, 0, 7, 8, 1, 4, 4, 5, 6, 7, 5, 5, 2, 9, 5, 3, 9, 5, 8, 5, 1, 1, 3, 5, 2, 5, 3, 9, 0,
+        6, 2, 5, 6, 9, 3, 8, 8, 9, 3, 9, 0, 3, 9, 0, 7, 2, 2, 8, 3, 7, 7, 6, 4, 7, 6, 9, 7, 9, 2,
+        5, 5, 6, 7, 6, 2, 6, 9, 5, 3, 1, 2, 5, 3, 4, 6, 9, 4, 4, 6, 9, 5, 1, 9, 5, 3, 6, 1, 4, 1,
+        8, 8, 8, 2, 3, 8, 4, 8, 9, 6, 2, 7, 8, 3, 8, 1, 3, 4, 7, 6, 5, 6, 2, 5, 1, 7, 3, 4, 7, 2,
+        3, 4, 7, 5, 9, 7, 6, 8, 0, 7, 0, 9, 4, 4, 1, 1, 9, 2, 4, 4, 8, 1, 3, 9, 1, 9, 0, 6, 7, 3,
+        8, 2, 8, 1, 2, 5, 8, 6, 7, 3, 6, 1, 7, 3, 7, 9, 8, 8, 4, 0, 3, 5, 4, 7, 2, 0, 5, 9, 6, 2,
+        2, 4, 0, 6, 9, 5, 9, 5, 3, 3, 6, 9, 1, 4, 0, 6, 2, 5,
+    ];
+
+    shift &= 63;
+    let x_a = TABLE[shift];
+    let x_b = TABLE[shift + 1];
+    let num_new_digits = (x_a >> 11) as _;
+    let pow5_a = (0x7FF & x_a) as usize;
+    let pow5_b = (0x7FF & x_b) as usize;
+    let pow5 = &TABLE_POW5[pow5_a..];
+
+    for (i, &p5) in pow5.iter().enumerate().take(pow5_b - pow5_a) {
+        if i >= d.num_digits {
+            return num_new_digits - 1;
+        } else if d.digits[i] == p5 {
+            continue;
+        } else if d.digits[i] < p5 {
+            return num_new_digits - 1;
+        } else {
+            return num_new_digits;
+        }
+    }
+
+    num_new_digits
+}
diff --git a/library/core/src/num/dec2flt/float.rs b/library/core/src/num/dec2flt/float.rs
index da57aa9a546af..b8a28a6756917 100644
--- a/library/core/src/num/dec2flt/float.rs
+++ b/library/core/src/num/dec2flt/float.rs
@@ -1,14 +1,57 @@
 //! Helper trait for generic float types.
 
+use core::f64;
+
 use crate::fmt::{Debug, LowerExp};
 use crate::num::FpCategory;
-use crate::ops::{Add, Div, Mul, Neg};
+use crate::ops::{self, Add, Div, Mul, Neg};
+
+/// Lossy `as` casting between two types.
+pub trait CastInto<T: Copy>: Copy {
+    fn cast(self) -> T;
+}
+
+/// Collection of traits that allow us to be generic over integer size.
+pub trait Integer:
+    Sized
+    + Clone
+    + Copy
+    + Debug
+    + ops::Shr<u32, Output = Self>
+    + ops::Shl<u32, Output = Self>
+    + ops::BitAnd<Output = Self>
+    + ops::BitOr<Output = Self>
+    + PartialEq
+    + CastInto<i16>
+{
+    const ZERO: Self;
+    const ONE: Self;
+}
+
+macro_rules! int {
+    ($($ty:ty),+) => {
+        $(
+            impl CastInto<i16> for $ty {
+                fn cast(self) -> i16 {
+                    self as i16
+                }
+            }
+
+            impl Integer for $ty {
+                const ZERO: Self = 0;
+                const ONE: Self = 1;
+            }
+        )+
+    }
+}
+
+int!(u32, u64);
 
-/// A helper trait to avoid duplicating basically all the conversion code for `f32` and `f64`.
+/// A helper trait to avoid duplicating basically all the conversion code for IEEE floats.
 ///
 /// See the parent module's doc comment for why this is necessary.
 ///
-/// Should **never ever** be implemented for other types or be used outside the dec2flt module.
+/// Should **never ever** be implemented for other types or be used outside the `dec2flt` module.
 #[doc(hidden)]
 pub trait RawFloat:
     Sized
@@ -24,62 +67,107 @@ pub trait RawFloat:
     + Copy
     + Debug
 {
+    /// The unsigned integer with the same size as the float
+    type Int: Integer + Into<u64>;
+
+    /* general constants */
+
     const INFINITY: Self;
     const NEG_INFINITY: Self;
     const NAN: Self;
     const NEG_NAN: Self;
 
-    /// The number of bits in the significand, *excluding* the hidden bit.
-    const MANTISSA_EXPLICIT_BITS: usize;
-
-    // Round-to-even only happens for negative values of q
-    // when q ≥ −4 in the 64-bit case and when q ≥ −17 in
-    // the 32-bitcase.
-    //
-    // When q ≥ 0,we have that 5^q ≤ 2m+1. In the 64-bit case,we
-    // have 5^q ≤ 2m+1 ≤ 2^54 or q ≤ 23. In the 32-bit case,we have
-    // 5^q ≤ 2m+1 ≤ 2^25 or q ≤ 10.
-    //
-    // When q < 0, we have w ≥ (2m+1)×5^−q. We must have that w < 2^64
-    // so (2m+1)×5^−q < 2^64. We have that 2m+1 > 2^53 (64-bit case)
-    // or 2m+1 > 2^24 (32-bit case). Hence,we must have 2^53×5^−q < 2^64
-    // (64-bit) and 2^24×5^−q < 2^64 (32-bit). Hence we have 5^−q < 2^11
-    // or q ≥ −4 (64-bit case) and 5^−q < 2^40 or q ≥ −17 (32-bitcase).
-    //
-    // Thus we have that we only need to round ties to even when
-    // we have that q ∈ [−4,23](in the 64-bit case) or q∈[−17,10]
-    // (in the 32-bit case). In both cases,the power of five(5^|q|)
-    // fits in a 64-bit word.
-    const MIN_EXPONENT_ROUND_TO_EVEN: i32;
-    const MAX_EXPONENT_ROUND_TO_EVEN: i32;
+    /// Bit width of the float
+    const BITS: u32;
 
-    // Minimum exponent that for a fast path case, or `-⌊(MANTISSA_EXPLICIT_BITS+1)/log2(5)⌋`
-    const MIN_EXPONENT_FAST_PATH: i64;
+    /// The number of bits in the significand, *including* the hidden bit.
+    const SIG_TOTAL_BITS: u32;
 
-    // Maximum exponent that for a fast path case, or `⌊(MANTISSA_EXPLICIT_BITS+1)/log2(5)⌋`
-    const MAX_EXPONENT_FAST_PATH: i64;
+    const EXP_MASK: Self::Int;
+    const SIG_MASK: Self::Int;
 
-    // Maximum exponent that can be represented for a disguised-fast path case.
-    // This is `MAX_EXPONENT_FAST_PATH + ⌊(MANTISSA_EXPLICIT_BITS+1)/log2(10)⌋`
-    const MAX_EXPONENT_DISGUISED_FAST_PATH: i64;
-
-    // Minimum exponent value `-(1 << (EXP_BITS - 1)) + 1`.
-    const MINIMUM_EXPONENT: i32;
+    /// The number of bits in the significand, *excluding* the hidden bit.
+    const SIG_BITS: u32 = Self::SIG_TOTAL_BITS - 1;
+
+    /// Number of bits in the exponent.
+    const EXP_BITS: u32 = Self::BITS - Self::SIG_BITS - 1;
+
+    /// The saturated (maximum bitpattern) value of the exponent, i.e. the infinite
+    /// representation.
+    ///
+    /// This shifted fully right, use `EXP_MASK` for the shifted value.
+    const EXP_SAT: u32 = (1 << Self::EXP_BITS) - 1;
+
+    /// Signed version of `EXP_SAT` since we convert a lot.
+    const INFINITE_POWER: i32 = Self::EXP_SAT as i32;
+
+    /// The exponent bias value. This is also the maximum value of the exponent.
+    const EXP_BIAS: u32 = Self::EXP_SAT >> 1;
+
+    /// Minimum exponent value of normal values.
+    const EXP_MIN: i32 = -(Self::EXP_BIAS as i32 - 1);
+
+    /// Round-to-even only happens for negative values of q
+    /// when q ≥ −4 in the 64-bit case and when q ≥ −17 in
+    /// the 32-bitcase.
+    ///
+    /// When q ≥ 0,we have that 5^q ≤ 2m+1. In the 64-bit case,we
+    /// have 5^q ≤ 2m+1 ≤ 2^54 or q ≤ 23. In the 32-bit case,we have
+    /// 5^q ≤ 2m+1 ≤ 2^25 or q ≤ 10.
+    ///
+    /// When q < 0, we have w ≥ (2m+1)×5^−q. We must have that w < 2^64
+    /// so (2m+1)×5^−q < 2^64. We have that 2m+1 > 2^53 (64-bit case)
+    /// or 2m+1 > 2^24 (32-bit case). Hence,we must have 2^53×5^−q < 2^64
+    /// (64-bit) and 2^24×5^−q < 2^64 (32-bit). Hence we have 5^−q < 2^11
+    /// or q ≥ −4 (64-bit case) and 5^−q < 2^40 or q ≥ −17 (32-bitcase).
+    ///
+    /// Thus we have that we only need to round ties to even when
+    /// we have that q ∈ [−4,23](in the 64-bit case) or q∈[−17,10]
+    /// (in the 32-bit case). In both cases,the power of five(5^|q|)
+    /// fits in a 64-bit word.
+    const MIN_EXPONENT_ROUND_TO_EVEN: i32;
+    const MAX_EXPONENT_ROUND_TO_EVEN: i32;
 
-    // Largest exponent value `(1 << EXP_BITS) - 1`.
-    const INFINITE_POWER: i32;
+    /* limits related to Fast pathing */
+
+    /// Largest decimal exponent for a non-infinite value.
+    ///
+    /// This is the max exponent in binary converted to the max exponent in decimal. Allows fast
+    /// pathing anything larger than `10^LARGEST_POWER_OF_TEN`, which will round to infinity.
+    const LARGEST_POWER_OF_TEN: i32 = {
+        let largest_pow2 = Self::EXP_BIAS + 1;
+        pow2_to_pow10(largest_pow2 as i64) as i32
+    };
+
+    /// Smallest decimal exponent for a non-zero value. This allows for fast pathing anything
+    /// smaller than `10^SMALLEST_POWER_OF_TEN`, which will round to zero.
+    ///
+    /// The smallest power of ten is represented by `⌊log10(2^-n / (2^64 - 1))⌋`, where `n` is
+    /// the smallest power of two. The `2^64 - 1)` denomenator comes from the number of values
+    /// that are representable by the intermediate storage format. I don't actually know _why_
+    /// the storage format is relevant here.
+    ///
+    /// The values may be calculated using the formula. Unfortunately we cannot calculate them at
+    /// compile time since intermediates exceed the range of an `f64`.
+    const SMALLEST_POWER_OF_TEN: i32;
 
-    // Index (in bits) of the sign.
-    const SIGN_INDEX: usize;
+    /// Maximum exponent for a fast path case, or `⌊(SIG_BITS+1)/log2(5)⌋`
+    // assuming FLT_EVAL_METHOD = 0
+    const MAX_EXPONENT_FAST_PATH: i64 = {
+        let log2_5 = f64::consts::LOG2_10 - 1.0;
+        (Self::SIG_TOTAL_BITS as f64 / log2_5) as i64
+    };
 
-    // Smallest decimal exponent for a non-zero value.
-    const SMALLEST_POWER_OF_TEN: i32;
+    /// Minimum exponent for a fast path case, or `-⌊(SIG_BITS+1)/log2(5)⌋`
+    const MIN_EXPONENT_FAST_PATH: i64 = -Self::MAX_EXPONENT_FAST_PATH;
 
-    // Largest decimal exponent for a non-infinite value.
-    const LARGEST_POWER_OF_TEN: i32;
+    /// Maximum exponent that can be represented for a disguised-fast path case.
+    /// This is `MAX_EXPONENT_FAST_PATH + ⌊(SIG_BITS+1)/log2(10)⌋`
+    const MAX_EXPONENT_DISGUISED_FAST_PATH: i64 =
+        Self::MAX_EXPONENT_FAST_PATH + (Self::SIG_TOTAL_BITS as f64 / f64::consts::LOG2_10) as i64;
 
-    // Maximum mantissa for the fast-path (`1 << 53` for f64).
-    const MAX_MANTISSA_FAST_PATH: u64 = 2_u64 << Self::MANTISSA_EXPLICIT_BITS;
+    /// Maximum mantissa for the fast-path (`1 << 53` for f64).
+    const MAX_MANTISSA_FAST_PATH: u64 = 1 << Self::SIG_TOTAL_BITS;
 
     /// Converts integer into float through an as cast.
     /// This is only called in the fast-path algorithm, and therefore
@@ -96,27 +184,51 @@ pub trait RawFloat:
     /// Returns the category that this number falls into.
     fn classify(self) -> FpCategory;
 
+    /// Transmute to the integer representation
+    fn to_bits(self) -> Self::Int;
+
     /// Returns the mantissa, exponent and sign as integers.
-    fn integer_decode(self) -> (u64, i16, i8);
+    ///
+    /// That is, this returns `(m, p, s)` such that `s * m * 2^p` represents the original float.
+    /// For 0, the exponent will be `-(EXP_BIAS + SIG_BITS`, which is the
+    /// minimum subnormal power.
+    fn integer_decode(self) -> (u64, i16, i8) {
+        let bits = self.to_bits();
+        let sign: i8 = if bits >> (Self::BITS - 1) == Self::Int::ZERO { 1 } else { -1 };
+        let mut exponent: i16 = ((bits & Self::EXP_MASK) >> Self::SIG_BITS).cast();
+        let mantissa = if exponent == 0 {
+            (bits & Self::SIG_MASK) << 1
+        } else {
+            (bits & Self::SIG_MASK) | (Self::Int::ONE << Self::SIG_BITS)
+        };
+        // Exponent bias + mantissa shift
+        exponent -= (Self::EXP_BIAS + Self::SIG_BITS) as i16;
+        (mantissa.into(), exponent, sign)
+    }
+}
+
+/// Solve for `b` in `10^b = 2^a`
+const fn pow2_to_pow10(a: i64) -> i64 {
+    let res = (a as f64) / f64::consts::LOG2_10;
+    res as i64
 }
 
 impl RawFloat for f32 {
+    type Int = u32;
+
     const INFINITY: Self = f32::INFINITY;
     const NEG_INFINITY: Self = f32::NEG_INFINITY;
     const NAN: Self = f32::NAN;
     const NEG_NAN: Self = -f32::NAN;
 
-    const MANTISSA_EXPLICIT_BITS: usize = 23;
+    const BITS: u32 = 32;
+    const SIG_TOTAL_BITS: u32 = Self::MANTISSA_DIGITS;
+    const EXP_MASK: Self::Int = Self::EXP_MASK;
+    const SIG_MASK: Self::Int = Self::MAN_MASK;
+
     const MIN_EXPONENT_ROUND_TO_EVEN: i32 = -17;
     const MAX_EXPONENT_ROUND_TO_EVEN: i32 = 10;
-    const MIN_EXPONENT_FAST_PATH: i64 = -10; // assuming FLT_EVAL_METHOD = 0
-    const MAX_EXPONENT_FAST_PATH: i64 = 10;
-    const MAX_EXPONENT_DISGUISED_FAST_PATH: i64 = 17;
-    const MINIMUM_EXPONENT: i32 = -127;
-    const INFINITE_POWER: i32 = 0xFF;
-    const SIGN_INDEX: usize = 31;
     const SMALLEST_POWER_OF_TEN: i32 = -65;
-    const LARGEST_POWER_OF_TEN: i32 = 38;
 
     #[inline]
     fn from_u64(v: u64) -> Self {
@@ -136,16 +248,8 @@ impl RawFloat for f32 {
         TABLE[exponent & 15]
     }
 
-    /// Returns the mantissa, exponent and sign as integers.
-    fn integer_decode(self) -> (u64, i16, i8) {
-        let bits = self.to_bits();
-        let sign: i8 = if bits >> 31 == 0 { 1 } else { -1 };
-        let mut exponent: i16 = ((bits >> 23) & 0xff) as i16;
-        let mantissa =
-            if exponent == 0 { (bits & 0x7fffff) << 1 } else { (bits & 0x7fffff) | 0x800000 };
-        // Exponent bias + mantissa shift
-        exponent -= 127 + 23;
-        (mantissa as u64, exponent, sign)
+    fn to_bits(self) -> Self::Int {
+        self.to_bits()
     }
 
     fn classify(self) -> FpCategory {
@@ -154,22 +258,21 @@ impl RawFloat for f32 {
 }
 
 impl RawFloat for f64 {
-    const INFINITY: Self = f64::INFINITY;
-    const NEG_INFINITY: Self = f64::NEG_INFINITY;
-    const NAN: Self = f64::NAN;
-    const NEG_NAN: Self = -f64::NAN;
+    type Int = u64;
+
+    const INFINITY: Self = Self::INFINITY;
+    const NEG_INFINITY: Self = Self::NEG_INFINITY;
+    const NAN: Self = Self::NAN;
+    const NEG_NAN: Self = -Self::NAN;
+
+    const BITS: u32 = 64;
+    const SIG_TOTAL_BITS: u32 = Self::MANTISSA_DIGITS;
+    const EXP_MASK: Self::Int = Self::EXP_MASK;
+    const SIG_MASK: Self::Int = Self::MAN_MASK;
 
-    const MANTISSA_EXPLICIT_BITS: usize = 52;
     const MIN_EXPONENT_ROUND_TO_EVEN: i32 = -4;
     const MAX_EXPONENT_ROUND_TO_EVEN: i32 = 23;
-    const MIN_EXPONENT_FAST_PATH: i64 = -22; // assuming FLT_EVAL_METHOD = 0
-    const MAX_EXPONENT_FAST_PATH: i64 = 22;
-    const MAX_EXPONENT_DISGUISED_FAST_PATH: i64 = 37;
-    const MINIMUM_EXPONENT: i32 = -1023;
-    const INFINITE_POWER: i32 = 0x7FF;
-    const SIGN_INDEX: usize = 63;
     const SMALLEST_POWER_OF_TEN: i32 = -342;
-    const LARGEST_POWER_OF_TEN: i32 = 308;
 
     #[inline]
     fn from_u64(v: u64) -> Self {
@@ -190,19 +293,8 @@ impl RawFloat for f64 {
         TABLE[exponent & 31]
     }
 
-    /// Returns the mantissa, exponent and sign as integers.
-    fn integer_decode(self) -> (u64, i16, i8) {
-        let bits = self.to_bits();
-        let sign: i8 = if bits >> 63 == 0 { 1 } else { -1 };
-        let mut exponent: i16 = ((bits >> 52) & 0x7ff) as i16;
-        let mantissa = if exponent == 0 {
-            (bits & 0xfffffffffffff) << 1
-        } else {
-            (bits & 0xfffffffffffff) | 0x10000000000000
-        };
-        // Exponent bias + mantissa shift
-        exponent -= 1023 + 52;
-        (mantissa, exponent, sign)
+    fn to_bits(self) -> Self::Int {
+        self.to_bits()
     }
 
     fn classify(self) -> FpCategory {
diff --git a/library/core/src/num/dec2flt/lemire.rs b/library/core/src/num/dec2flt/lemire.rs
index 01642e1b1112a..f84929a03c172 100644
--- a/library/core/src/num/dec2flt/lemire.rs
+++ b/library/core/src/num/dec2flt/lemire.rs
@@ -38,7 +38,7 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
     // Normalize our significant digits, so the most-significant bit is set.
     let lz = w.leading_zeros();
     w <<= lz;
-    let (lo, hi) = compute_product_approx(q, w, F::MANTISSA_EXPLICIT_BITS + 3);
+    let (lo, hi) = compute_product_approx(q, w, F::SIG_BITS as usize + 3);
     if lo == 0xFFFF_FFFF_FFFF_FFFF {
         // If we have failed to approximate w x 5^-q with our 128-bit value.
         // Since the addition of 1 could lead to an overflow which could then
@@ -61,8 +61,8 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
         }
     }
     let upperbit = (hi >> 63) as i32;
-    let mut mantissa = hi >> (upperbit + 64 - F::MANTISSA_EXPLICIT_BITS as i32 - 3);
-    let mut power2 = power(q as i32) + upperbit - lz as i32 - F::MINIMUM_EXPONENT;
+    let mut mantissa = hi >> (upperbit + 64 - F::SIG_BITS as i32 - 3);
+    let mut power2 = power(q as i32) + upperbit - lz as i32 - F::EXP_MIN + 1;
     if power2 <= 0 {
         if -power2 + 1 >= 64 {
             // Have more than 64 bits below the minimum exponent, must be 0.
@@ -72,8 +72,8 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
         mantissa >>= -power2 + 1;
         mantissa += mantissa & 1;
         mantissa >>= 1;
-        power2 = (mantissa >= (1_u64 << F::MANTISSA_EXPLICIT_BITS)) as i32;
-        return BiasedFp { f: mantissa, e: power2 };
+        power2 = (mantissa >= (1_u64 << F::SIG_BITS)) as i32;
+        return BiasedFp { m: mantissa, p_biased: power2 };
     }
     // Need to handle rounding ties. Normally, we need to round up,
     // but if we fall right in between and we have an even basis, we
@@ -89,8 +89,8 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
     if lo <= 1
         && q >= F::MIN_EXPONENT_ROUND_TO_EVEN as i64
         && q <= F::MAX_EXPONENT_ROUND_TO_EVEN as i64
-        && mantissa & 3 == 1
-        && (mantissa << (upperbit + 64 - F::MANTISSA_EXPLICIT_BITS as i32 - 3)) == hi
+        && mantissa & 0b11 == 0b01
+        && (mantissa << (upperbit + 64 - F::SIG_BITS as i32 - 3)) == hi
     {
         // Zero the lowest bit, so we don't round up.
         mantissa &= !1_u64;
@@ -98,20 +98,20 @@ pub fn compute_float<F: RawFloat>(q: i64, mut w: u64) -> BiasedFp {
     // Round-to-even, then shift the significant digits into place.
     mantissa += mantissa & 1;
     mantissa >>= 1;
-    if mantissa >= (2_u64 << F::MANTISSA_EXPLICIT_BITS) {
+    if mantissa >= (2_u64 << F::SIG_BITS) {
         // Rounding up overflowed, so the carry bit is set. Set the
         // mantissa to 1 (only the implicit, hidden bit is set) and
         // increase the exponent.
-        mantissa = 1_u64 << F::MANTISSA_EXPLICIT_BITS;
+        mantissa = 1_u64 << F::SIG_BITS;
         power2 += 1;
     }
     // Zero out the hidden bit.
-    mantissa &= !(1_u64 << F::MANTISSA_EXPLICIT_BITS);
+    mantissa &= !(1_u64 << F::SIG_BITS);
     if power2 >= F::INFINITE_POWER {
         // Exponent is above largest normal value, must be infinite.
         return fp_inf;
     }
-    BiasedFp { f: mantissa, e: power2 }
+    BiasedFp { m: mantissa, p_biased: power2 }
 }
 
 /// Calculate a base 2 exponent from a decimal exponent.
diff --git a/library/core/src/num/dec2flt/mod.rs b/library/core/src/num/dec2flt/mod.rs
index 6dca740684537..d1a0e1db31314 100644
--- a/library/core/src/num/dec2flt/mod.rs
+++ b/library/core/src/num/dec2flt/mod.rs
@@ -3,8 +3,8 @@
 //! # Problem statement
 //!
 //! We are given a decimal string such as `12.34e56`. This string consists of integral (`12`),
-//! fractional (`34`), and exponent (`56`) parts. All parts are optional and interpreted as zero
-//! when missing.
+//! fractional (`34`), and exponent (`56`) parts. All parts are optional and interpreted as a
+//! default value (1 or 0) when missing.
 //!
 //! We seek the IEEE 754 floating point number that is closest to the exact value of the decimal
 //! string. It is well-known that many decimal strings do not have terminating representations in
@@ -67,6 +67,18 @@
 //! "such that the exponent +/- the number of decimal digits fits into a 64 bit integer".
 //! Larger exponents are accepted, but we don't do arithmetic with them, they are immediately
 //! turned into {positive,negative} {zero,infinity}.
+//!
+//! # Notation
+//!
+//! This module uses the same notation as the Lemire paper:
+//!
+//! - `m`: binary mantissa; always nonnegative
+//! - `p`: binary exponent; a signed integer
+//! - `w`: decimal significand; always nonnegative
+//! - `q`: decimal exponent; a signed integer
+//!
+//! This gives `m * 2^p` for the binary floating-point number, with `w * 10^q` as the decimal
+//! equivalent.
 
 #![doc(hidden)]
 #![unstable(
@@ -85,14 +97,14 @@ use crate::fmt;
 use crate::str::FromStr;
 
 mod common;
-mod decimal;
+pub mod decimal;
+pub mod decimal_seq;
 mod fpu;
 mod slow;
 mod table;
 // float is used in flt2dec, and all are used in unit tests.
 pub mod float;
 pub mod lemire;
-pub mod number;
 pub mod parse;
 
 macro_rules! from_str_float_impl {
@@ -220,10 +232,10 @@ pub fn pfe_invalid() -> ParseFloatError {
 }
 
 /// Converts a `BiasedFp` to the closest machine float type.
-fn biased_fp_to_float<T: RawFloat>(x: BiasedFp) -> T {
-    let mut word = x.f;
-    word |= (x.e as u64) << T::MANTISSA_EXPLICIT_BITS;
-    T::from_u64_bits(word)
+fn biased_fp_to_float<F: RawFloat>(x: BiasedFp) -> F {
+    let mut word = x.m;
+    word |= (x.p_biased as u64) << F::SIG_BITS;
+    F::from_u64_bits(word)
 }
 
 /// Converts a decimal string into a floating point number.
@@ -260,12 +272,15 @@ pub fn dec2flt<F: RawFloat>(s: &str) -> Result<F, ParseFloatError> {
     // redundantly using the Eisel-Lemire algorithm if it was unable to
     // correctly round on the first pass.
     let mut fp = compute_float::<F>(num.exponent, num.mantissa);
-    if num.many_digits && fp.e >= 0 && fp != compute_float::<F>(num.exponent, num.mantissa + 1) {
-        fp.e = -1;
+    if num.many_digits
+        && fp.p_biased >= 0
+        && fp != compute_float::<F>(num.exponent, num.mantissa + 1)
+    {
+        fp.p_biased = -1;
     }
     // Unable to correctly round the float using the Eisel-Lemire algorithm.
     // Fallback to a slower, but always correct algorithm.
-    if fp.e < 0 {
+    if fp.p_biased < 0 {
         fp = parse_long_mantissa::<F>(s);
     }
 
diff --git a/library/core/src/num/dec2flt/number.rs b/library/core/src/num/dec2flt/number.rs
deleted file mode 100644
index 2538991564ae4..0000000000000
--- a/library/core/src/num/dec2flt/number.rs
+++ /dev/null
@@ -1,88 +0,0 @@
-//! Representation of a float as the significant digits and exponent.
-
-use crate::num::dec2flt::float::RawFloat;
-use crate::num::dec2flt::fpu::set_precision;
-
-#[rustfmt::skip]
-const INT_POW10: [u64; 16] = [
-    1,
-    10,
-    100,
-    1000,
-    10000,
-    100000,
-    1000000,
-    10000000,
-    100000000,
-    1000000000,
-    10000000000,
-    100000000000,
-    1000000000000,
-    10000000000000,
-    100000000000000,
-    1000000000000000,
-];
-
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-pub struct Number {
-    pub exponent: i64,
-    pub mantissa: u64,
-    pub negative: bool,
-    pub many_digits: bool,
-}
-
-impl Number {
-    /// Detect if the float can be accurately reconstructed from native floats.
-    #[inline]
-    fn is_fast_path<F: RawFloat>(&self) -> bool {
-        F::MIN_EXPONENT_FAST_PATH <= self.exponent
-            && self.exponent <= F::MAX_EXPONENT_DISGUISED_FAST_PATH
-            && self.mantissa <= F::MAX_MANTISSA_FAST_PATH
-            && !self.many_digits
-    }
-
-    /// The fast path algorithm using machine-sized integers and floats.
-    ///
-    /// This is extracted into a separate function so that it can be attempted before constructing
-    /// a Decimal. This only works if both the mantissa and the exponent
-    /// can be exactly represented as a machine float, since IEE-754 guarantees
-    /// no rounding will occur.
-    ///
-    /// There is an exception: disguised fast-path cases, where we can shift
-    /// powers-of-10 from the exponent to the significant digits.
-    pub fn try_fast_path<F: RawFloat>(&self) -> Option<F> {
-        // Here we need to work around <https://github.com/rust-lang/rust/issues/114479>.
-        // The fast path crucially depends on arithmetic being rounded to the correct number of bits
-        // without any intermediate rounding. On x86 (without SSE or SSE2) this requires the precision
-        // of the x87 FPU stack to be changed so that it directly rounds to 64/32 bit.
-        // The `set_precision` function takes care of setting the precision on architectures which
-        // require setting it by changing the global state (like the control word of the x87 FPU).
-        let _cw = set_precision::<F>();
-
-        if self.is_fast_path::<F>() {
-            let mut value = if self.exponent <= F::MAX_EXPONENT_FAST_PATH {
-                // normal fast path
-                let value = F::from_u64(self.mantissa);
-                if self.exponent < 0 {
-                    value / F::pow10_fast_path((-self.exponent) as _)
-                } else {
-                    value * F::pow10_fast_path(self.exponent as _)
-                }
-            } else {
-                // disguised fast path
-                let shift = self.exponent - F::MAX_EXPONENT_FAST_PATH;
-                let mantissa = self.mantissa.checked_mul(INT_POW10[shift as usize])?;
-                if mantissa > F::MAX_MANTISSA_FAST_PATH {
-                    return None;
-                }
-                F::from_u64(mantissa) * F::pow10_fast_path(F::MAX_EXPONENT_FAST_PATH as _)
-            };
-            if self.negative {
-                value = -value;
-            }
-            Some(value)
-        } else {
-            None
-        }
-    }
-}
diff --git a/library/core/src/num/dec2flt/parse.rs b/library/core/src/num/dec2flt/parse.rs
index 06ee8e95fbc47..e38fedc58bec0 100644
--- a/library/core/src/num/dec2flt/parse.rs
+++ b/library/core/src/num/dec2flt/parse.rs
@@ -1,8 +1,8 @@
 //! Functions to parse floating-point numbers.
 
 use crate::num::dec2flt::common::{ByteSlice, is_8digits};
+use crate::num::dec2flt::decimal::Decimal;
 use crate::num::dec2flt::float::RawFloat;
-use crate::num::dec2flt::number::Number;
 
 const MIN_19DIGIT_INT: u64 = 100_0000_0000_0000_0000;
 
@@ -100,7 +100,7 @@ fn parse_scientific(s_ref: &mut &[u8]) -> Option<i64> {
 ///
 /// This creates a representation of the float as the
 /// significant digits and the decimal exponent.
-fn parse_partial_number(mut s: &[u8]) -> Option<(Number, usize)> {
+fn parse_partial_number(mut s: &[u8]) -> Option<(Decimal, usize)> {
     debug_assert!(!s.is_empty());
 
     // parse initial digits before dot
@@ -146,7 +146,7 @@ fn parse_partial_number(mut s: &[u8]) -> Option<(Number, usize)> {
 
     // handle uncommon case with many digits
     if n_digits <= 19 {
-        return Some((Number { exponent, mantissa, negative: false, many_digits: false }, len));
+        return Some((Decimal { exponent, mantissa, negative: false, many_digits: false }, len));
     }
 
     n_digits -= 19;
@@ -179,13 +179,13 @@ fn parse_partial_number(mut s: &[u8]) -> Option<(Number, usize)> {
         exponent += exp_number;
     }
 
-    Some((Number { exponent, mantissa, negative: false, many_digits }, len))
+    Some((Decimal { exponent, mantissa, negative: false, many_digits }, len))
 }
 
 /// Try to parse a non-special floating point number,
 /// as well as two slices with integer and fractional parts
 /// and the parsed exponent.
-pub fn parse_number(s: &[u8]) -> Option<Number> {
+pub fn parse_number(s: &[u8]) -> Option<Decimal> {
     if let Some((float, rest)) = parse_partial_number(s) {
         if rest == s.len() {
             return Some(float);
diff --git a/library/core/src/num/dec2flt/slow.rs b/library/core/src/num/dec2flt/slow.rs
index 85d4b13284b7d..3baed42652393 100644
--- a/library/core/src/num/dec2flt/slow.rs
+++ b/library/core/src/num/dec2flt/slow.rs
@@ -1,7 +1,7 @@
 //! Slow, fallback algorithm for cases the Eisel-Lemire algorithm cannot round.
 
 use crate::num::dec2flt::common::BiasedFp;
-use crate::num::dec2flt::decimal::{Decimal, parse_decimal};
+use crate::num::dec2flt::decimal_seq::{DecimalSeq, parse_decimal_seq};
 use crate::num::dec2flt::float::RawFloat;
 
 /// Parse the significant digits and biased, binary exponent of a float.
@@ -36,7 +36,7 @@ pub(crate) fn parse_long_mantissa<F: RawFloat>(s: &[u8]) -> BiasedFp {
     let fp_zero = BiasedFp::zero_pow2(0);
     let fp_inf = BiasedFp::zero_pow2(F::INFINITE_POWER);
 
-    let mut d = parse_decimal(s);
+    let mut d = parse_decimal_seq(s);
 
     // Short-circuit if the value can only be a literal 0 or infinity.
     if d.num_digits == 0 || d.decimal_point < -324 {
@@ -50,7 +50,7 @@ pub(crate) fn parse_long_mantissa<F: RawFloat>(s: &[u8]) -> BiasedFp {
         let n = d.decimal_point as usize;
         let shift = get_shift(n);
         d.right_shift(shift);
-        if d.decimal_point < -Decimal::DECIMAL_POINT_RANGE {
+        if d.decimal_point < -DecimalSeq::DECIMAL_POINT_RANGE {
             return fp_zero;
         }
         exp2 += shift as i32;
@@ -67,43 +67,43 @@ pub(crate) fn parse_long_mantissa<F: RawFloat>(s: &[u8]) -> BiasedFp {
             get_shift((-d.decimal_point) as _)
         };
         d.left_shift(shift);
-        if d.decimal_point > Decimal::DECIMAL_POINT_RANGE {
+        if d.decimal_point > DecimalSeq::DECIMAL_POINT_RANGE {
             return fp_inf;
         }
         exp2 -= shift as i32;
     }
     // We are now in the range [1/2 ... 1] but the binary format uses [1 ... 2].
     exp2 -= 1;
-    while (F::MINIMUM_EXPONENT + 1) > exp2 {
-        let mut n = ((F::MINIMUM_EXPONENT + 1) - exp2) as usize;
+    while F::EXP_MIN > exp2 {
+        let mut n = (F::EXP_MIN - exp2) as usize;
         if n > MAX_SHIFT {
             n = MAX_SHIFT;
         }
         d.right_shift(n);
         exp2 += n as i32;
     }
-    if (exp2 - F::MINIMUM_EXPONENT) >= F::INFINITE_POWER {
+    if (exp2 - F::EXP_MIN + 1) >= F::INFINITE_POWER {
         return fp_inf;
     }
     // Shift the decimal to the hidden bit, and then round the value
     // to get the high mantissa+1 bits.
-    d.left_shift(F::MANTISSA_EXPLICIT_BITS + 1);
+    d.left_shift(F::SIG_BITS as usize + 1);
     let mut mantissa = d.round();
-    if mantissa >= (1_u64 << (F::MANTISSA_EXPLICIT_BITS + 1)) {
+    if mantissa >= (1_u64 << (F::SIG_BITS + 1)) {
         // Rounding up overflowed to the carry bit, need to
         // shift back to the hidden bit.
         d.right_shift(1);
         exp2 += 1;
         mantissa = d.round();
-        if (exp2 - F::MINIMUM_EXPONENT) >= F::INFINITE_POWER {
+        if (exp2 - F::EXP_MIN + 1) >= F::INFINITE_POWER {
             return fp_inf;
         }
     }
-    let mut power2 = exp2 - F::MINIMUM_EXPONENT;
-    if mantissa < (1_u64 << F::MANTISSA_EXPLICIT_BITS) {
+    let mut power2 = exp2 - F::EXP_MIN + 1;
+    if mantissa < (1_u64 << F::SIG_BITS) {
         power2 -= 1;
     }
     // Zero out all the bits above the explicit mantissa bits.
-    mantissa &= (1_u64 << F::MANTISSA_EXPLICIT_BITS) - 1;
-    BiasedFp { f: mantissa, e: power2 }
+    mantissa &= (1_u64 << F::SIG_BITS) - 1;
+    BiasedFp { m: mantissa, p_biased: power2 }
 }
diff --git a/library/core/src/num/f32.rs b/library/core/src/num/f32.rs
index a200fd5318669..de1557ccc9028 100644
--- a/library/core/src/num/f32.rs
+++ b/library/core/src/num/f32.rs
@@ -493,13 +493,13 @@ impl f32 {
     pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
 
     /// Sign bit
-    const SIGN_MASK: u32 = 0x8000_0000;
+    pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
 
     /// Exponent mask
-    const EXP_MASK: u32 = 0x7f80_0000;
+    pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
 
     /// Mantissa mask
-    const MAN_MASK: u32 = 0x007f_ffff;
+    pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
 
     /// Minimum representable positive value (min subnormal)
     const TINY_BITS: u32 = 0x1;
diff --git a/library/core/src/num/f64.rs b/library/core/src/num/f64.rs
index de63a462b61ac..65b5f3b9af093 100644
--- a/library/core/src/num/f64.rs
+++ b/library/core/src/num/f64.rs
@@ -492,13 +492,13 @@ impl f64 {
     pub const NEG_INFINITY: f64 = -1.0_f64 / 0.0_f64;
 
     /// Sign bit
-    const SIGN_MASK: u64 = 0x8000_0000_0000_0000;
+    pub(crate) const SIGN_MASK: u64 = 0x8000_0000_0000_0000;
 
     /// Exponent mask
-    const EXP_MASK: u64 = 0x7ff0_0000_0000_0000;
+    pub(crate) const EXP_MASK: u64 = 0x7ff0_0000_0000_0000;
 
     /// Mantissa mask
-    const MAN_MASK: u64 = 0x000f_ffff_ffff_ffff;
+    pub(crate) const MAN_MASK: u64 = 0x000f_ffff_ffff_ffff;
 
     /// Minimum representable positive value (min subnormal)
     const TINY_BITS: u64 = 0x1;
diff --git a/library/coretests/tests/num/dec2flt/decimal.rs b/library/coretests/tests/num/dec2flt/decimal.rs
new file mode 100644
index 0000000000000..1fa06de692e07
--- /dev/null
+++ b/library/coretests/tests/num/dec2flt/decimal.rs
@@ -0,0 +1,28 @@
+use core::num::dec2flt::decimal::Decimal;
+
+type FPath<F> = ((i64, u64, bool, bool), Option<F>);
+
+const FPATHS_F32: &[FPath<f32>] =
+    &[((0, 0, false, false), Some(0.0)), ((0, 0, false, false), Some(0.0))];
+const FPATHS_F64: &[FPath<f64>] =
+    &[((0, 0, false, false), Some(0.0)), ((0, 0, false, false), Some(0.0))];
+
+#[test]
+fn check_fast_path_f32() {
+    for ((exponent, mantissa, negative, many_digits), expected) in FPATHS_F32.iter().copied() {
+        let dec = Decimal { exponent, mantissa, negative, many_digits };
+        let actual = dec.try_fast_path::<f32>();
+
+        assert_eq!(actual, expected);
+    }
+}
+
+#[test]
+fn check_fast_path_f64() {
+    for ((exponent, mantissa, negative, many_digits), expected) in FPATHS_F64.iter().copied() {
+        let dec = Decimal { exponent, mantissa, negative, many_digits };
+        let actual = dec.try_fast_path::<f64>();
+
+        assert_eq!(actual, expected);
+    }
+}
diff --git a/library/coretests/tests/num/dec2flt/decimal_seq.rs b/library/coretests/tests/num/dec2flt/decimal_seq.rs
new file mode 100644
index 0000000000000..f46ba7c465a6e
--- /dev/null
+++ b/library/coretests/tests/num/dec2flt/decimal_seq.rs
@@ -0,0 +1,30 @@
+use core::num::dec2flt::decimal_seq::{DecimalSeq, parse_decimal_seq};
+
+#[test]
+fn test_trim() {
+    let mut dec = DecimalSeq::default();
+    let digits = [1, 2, 3, 4];
+
+    dec.digits[0..4].copy_from_slice(&digits);
+    dec.num_digits = 8;
+    dec.trim();
+
+    assert_eq!(dec.digits[0..4], digits);
+    assert_eq!(dec.num_digits, 4);
+}
+
+#[test]
+fn test_parse() {
+    let tests = [("1.234", [1, 2, 3, 4], 1)];
+
+    for (s, exp_digits, decimal_point) in tests {
+        let actual = parse_decimal_seq(s.as_bytes());
+        let mut digits = [0; DecimalSeq::MAX_DIGITS];
+        digits[..exp_digits.len()].copy_from_slice(&exp_digits);
+
+        let expected =
+            DecimalSeq { num_digits: exp_digits.len(), decimal_point, truncated: false, digits };
+
+        assert_eq!(actual, expected);
+    }
+}
diff --git a/library/coretests/tests/num/dec2flt/float.rs b/library/coretests/tests/num/dec2flt/float.rs
index 7a9587a18d030..b5afd3e3b2436 100644
--- a/library/coretests/tests/num/dec2flt/float.rs
+++ b/library/coretests/tests/num/dec2flt/float.rs
@@ -12,8 +12,8 @@ fn test_f32_integer_decode() {
 
     // Ignore the "sign" (quiet / signalling flag) of NAN.
     // It can vary between runtime operations and LLVM folding.
-    let (nan_m, nan_e, _nan_s) = f32::NAN.integer_decode();
-    assert_eq!((nan_m, nan_e), (12582912, 105));
+    let (nan_m, nan_p, _nan_s) = f32::NAN.integer_decode();
+    assert_eq!((nan_m, nan_p), (12582912, 105));
 }
 
 #[test]
@@ -28,6 +28,46 @@ fn test_f64_integer_decode() {
 
     // Ignore the "sign" (quiet / signalling flag) of NAN.
     // It can vary between runtime operations and LLVM folding.
-    let (nan_m, nan_e, _nan_s) = f64::NAN.integer_decode();
-    assert_eq!((nan_m, nan_e), (6755399441055744, 972));
+    let (nan_m, nan_p, _nan_s) = f64::NAN.integer_decode();
+    assert_eq!((nan_m, nan_p), (6755399441055744, 972));
+}
+
+/* Sanity checks of computed magic numbers */
+
+#[test]
+fn test_f32_consts() {
+    assert_eq!(<f32 as RawFloat>::INFINITY, f32::INFINITY);
+    assert_eq!(<f32 as RawFloat>::NEG_INFINITY, -f32::INFINITY);
+    assert_eq!(<f32 as RawFloat>::NAN.to_bits(), f32::NAN.to_bits());
+    assert_eq!(<f32 as RawFloat>::NEG_NAN.to_bits(), (-f32::NAN).to_bits());
+    assert_eq!(<f32 as RawFloat>::SIG_BITS, 23);
+    assert_eq!(<f32 as RawFloat>::MIN_EXPONENT_ROUND_TO_EVEN, -17);
+    assert_eq!(<f32 as RawFloat>::MAX_EXPONENT_ROUND_TO_EVEN, 10);
+    assert_eq!(<f32 as RawFloat>::MIN_EXPONENT_FAST_PATH, -10);
+    assert_eq!(<f32 as RawFloat>::MAX_EXPONENT_FAST_PATH, 10);
+    assert_eq!(<f32 as RawFloat>::MAX_EXPONENT_DISGUISED_FAST_PATH, 17);
+    assert_eq!(<f32 as RawFloat>::EXP_MIN, -126);
+    assert_eq!(<f32 as RawFloat>::EXP_SAT, 0xff);
+    assert_eq!(<f32 as RawFloat>::SMALLEST_POWER_OF_TEN, -65);
+    assert_eq!(<f32 as RawFloat>::LARGEST_POWER_OF_TEN, 38);
+    assert_eq!(<f32 as RawFloat>::MAX_MANTISSA_FAST_PATH, 16777216);
+}
+
+#[test]
+fn test_f64_consts() {
+    assert_eq!(<f64 as RawFloat>::INFINITY, f64::INFINITY);
+    assert_eq!(<f64 as RawFloat>::NEG_INFINITY, -f64::INFINITY);
+    assert_eq!(<f64 as RawFloat>::NAN.to_bits(), f64::NAN.to_bits());
+    assert_eq!(<f64 as RawFloat>::NEG_NAN.to_bits(), (-f64::NAN).to_bits());
+    assert_eq!(<f64 as RawFloat>::SIG_BITS, 52);
+    assert_eq!(<f64 as RawFloat>::MIN_EXPONENT_ROUND_TO_EVEN, -4);
+    assert_eq!(<f64 as RawFloat>::MAX_EXPONENT_ROUND_TO_EVEN, 23);
+    assert_eq!(<f64 as RawFloat>::MIN_EXPONENT_FAST_PATH, -22);
+    assert_eq!(<f64 as RawFloat>::MAX_EXPONENT_FAST_PATH, 22);
+    assert_eq!(<f64 as RawFloat>::MAX_EXPONENT_DISGUISED_FAST_PATH, 37);
+    assert_eq!(<f64 as RawFloat>::EXP_MIN, -1022);
+    assert_eq!(<f64 as RawFloat>::EXP_SAT, 0x7ff);
+    assert_eq!(<f64 as RawFloat>::SMALLEST_POWER_OF_TEN, -342);
+    assert_eq!(<f64 as RawFloat>::LARGEST_POWER_OF_TEN, 308);
+    assert_eq!(<f64 as RawFloat>::MAX_MANTISSA_FAST_PATH, 9007199254740992);
 }
diff --git a/library/coretests/tests/num/dec2flt/lemire.rs b/library/coretests/tests/num/dec2flt/lemire.rs
index f71bbb7c7a318..0db80fbd52506 100644
--- a/library/coretests/tests/num/dec2flt/lemire.rs
+++ b/library/coretests/tests/num/dec2flt/lemire.rs
@@ -1,13 +1,14 @@
+use core::num::dec2flt::float::RawFloat;
 use core::num::dec2flt::lemire::compute_float;
 
 fn compute_float32(q: i64, w: u64) -> (i32, u64) {
     let fp = compute_float::<f32>(q, w);
-    (fp.e, fp.f)
+    (fp.p_biased, fp.m)
 }
 
 fn compute_float64(q: i64, w: u64) -> (i32, u64) {
     let fp = compute_float::<f64>(q, w);
-    (fp.e, fp.f)
+    (fp.p_biased, fp.m)
 }
 
 #[test]
@@ -27,6 +28,11 @@ fn compute_float_f32_rounding() {
     // Let's check the lines to see if anything is different in table...
     assert_eq!(compute_float32(-10, 167772190000000000), (151, 2));
     assert_eq!(compute_float32(-10, 167772200000000000), (151, 2));
+
+    // Check the rounding point between infinity and the next representable number down
+    assert_eq!(compute_float32(38, 3), (f32::INFINITE_POWER - 1, 6402534));
+    assert_eq!(compute_float32(38, 4), (f32::INFINITE_POWER, 0)); // infinity
+    assert_eq!(compute_float32(20, 3402823470000000000), (f32::INFINITE_POWER - 1, 8388607));
 }
 
 #[test]
diff --git a/library/coretests/tests/num/dec2flt/mod.rs b/library/coretests/tests/num/dec2flt/mod.rs
index 874e0ec7093c7..a9025be5ca7f1 100644
--- a/library/coretests/tests/num/dec2flt/mod.rs
+++ b/library/coretests/tests/num/dec2flt/mod.rs
@@ -1,5 +1,7 @@
 #![allow(overflowing_literals)]
 
+mod decimal;
+mod decimal_seq;
 mod float;
 mod lemire;
 mod parse;
diff --git a/library/coretests/tests/num/dec2flt/parse.rs b/library/coretests/tests/num/dec2flt/parse.rs
index 4a5d24ba7d5fa..59be3915052d8 100644
--- a/library/coretests/tests/num/dec2flt/parse.rs
+++ b/library/coretests/tests/num/dec2flt/parse.rs
@@ -1,9 +1,9 @@
-use core::num::dec2flt::number::Number;
+use core::num::dec2flt::decimal::Decimal;
 use core::num::dec2flt::parse::parse_number;
 use core::num::dec2flt::{dec2flt, pfe_invalid};
 
-fn new_number(e: i64, m: u64) -> Number {
-    Number { exponent: e, mantissa: m, negative: false, many_digits: false }
+fn new_dec(e: i64, m: u64) -> Decimal {
+    Decimal { exponent: e, mantissa: m, negative: false, many_digits: false }
 }
 
 #[test]
@@ -31,23 +31,23 @@ fn invalid_chars() {
     }
 }
 
-fn parse_positive(s: &[u8]) -> Option<Number> {
+fn parse_positive(s: &[u8]) -> Option<Decimal> {
     parse_number(s)
 }
 
 #[test]
 fn valid() {
-    assert_eq!(parse_positive(b"123.456e789"), Some(new_number(786, 123456)));
-    assert_eq!(parse_positive(b"123.456e+789"), Some(new_number(786, 123456)));
-    assert_eq!(parse_positive(b"123.456e-789"), Some(new_number(-792, 123456)));
-    assert_eq!(parse_positive(b".050"), Some(new_number(-3, 50)));
-    assert_eq!(parse_positive(b"999"), Some(new_number(0, 999)));
-    assert_eq!(parse_positive(b"1.e300"), Some(new_number(300, 1)));
-    assert_eq!(parse_positive(b".1e300"), Some(new_number(299, 1)));
-    assert_eq!(parse_positive(b"101e-33"), Some(new_number(-33, 101)));
+    assert_eq!(parse_positive(b"123.456e789"), Some(new_dec(786, 123456)));
+    assert_eq!(parse_positive(b"123.456e+789"), Some(new_dec(786, 123456)));
+    assert_eq!(parse_positive(b"123.456e-789"), Some(new_dec(-792, 123456)));
+    assert_eq!(parse_positive(b".050"), Some(new_dec(-3, 50)));
+    assert_eq!(parse_positive(b"999"), Some(new_dec(0, 999)));
+    assert_eq!(parse_positive(b"1.e300"), Some(new_dec(300, 1)));
+    assert_eq!(parse_positive(b".1e300"), Some(new_dec(299, 1)));
+    assert_eq!(parse_positive(b"101e-33"), Some(new_dec(-33, 101)));
     let zeros = "0".repeat(25);
     let s = format!("1.5e{zeros}");
-    assert_eq!(parse_positive(s.as_bytes()), Some(new_number(-1, 15)));
+    assert_eq!(parse_positive(s.as_bytes()), Some(new_dec(-1, 15)));
 }
 
 macro_rules! assert_float_result_bits_eq {
@@ -57,6 +57,21 @@ macro_rules! assert_float_result_bits_eq {
     }};
 }
 
+#[test]
+fn regression() {
+    // These showed up in fuzz tests when the minimum exponent was incorrect.
+    assert_float_result_bits_eq!(
+        0x0,
+        f64,
+        "3313756768023998018398807867233977556112078681253148176737587500333136120852692315608454494981109839693784033457129423181787087843504060087613228932431e-475"
+    );
+    assert_float_result_bits_eq!(
+        0x0,
+        f64,
+        "5298127456259331337220.92759278003098321644501973966679724599271041396379712108366679824365568578569680024083293475291869842408884554511641179110778276695274832779269225510492006696321279587846006535230380114430977056662212751544508159333199129106162019382177820713609e-346"
+    );
+}
+
 #[test]
 fn issue31109() {
     // Regression test for #31109.
diff --git a/library/coretests/tests/slice.rs b/library/coretests/tests/slice.rs
index 1c5c8a9ebf258..fe356dcc43c7b 100644
--- a/library/coretests/tests/slice.rs
+++ b/library/coretests/tests/slice.rs
@@ -5,8 +5,6 @@ use core::num::NonZero;
 use core::ops::{Range, RangeInclusive};
 use core::slice;
 
-use rand::seq::IndexedRandom;
-
 #[test]
 fn test_position() {
     let b = [1, 2, 3, 5, 5];
@@ -1810,6 +1808,7 @@ fn select_nth_unstable() {
     use core::cmp::Ordering::{Equal, Greater, Less};
 
     use rand::Rng;
+    use rand::seq::IndexedRandom;
 
     let mut rng = crate::test_rng();
 
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 8e4dd0f2bf480..f762d20546311 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -35,7 +35,7 @@ miniz_oxide = { version = "0.8.0", optional = true, default-features = false }
 addr2line = { version = "0.24.0", optional = true, default-features = false }
 
 [target.'cfg(not(all(windows, target_env = "msvc")))'.dependencies]
-libc = { version = "0.2.169", default-features = false, features = [
+libc = { version = "0.2.170", default-features = false, features = [
     'rustc-dep-of-std',
 ], public = true }
 
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 4a071b4e1faec..e62aeb2ede0ad 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -641,11 +641,6 @@ impl Error for JoinPathsError {
 ///     None => println!("Impossible to get your home dir!"),
 /// }
 /// ```
-#[deprecated(
-    since = "1.29.0",
-    note = "This function's behavior may be unexpected on Windows. \
-            Consider using a crate from crates.io instead."
-)]
 #[must_use]
 #[stable(feature = "env", since = "1.0.0")]
 pub fn home_dir() -> Option<PathBuf> {
diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 57e235c3efe1d..4314c8a0b1825 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -2857,9 +2857,11 @@ pub fn remove_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
 ///
 /// See [`fs::remove_file`] and [`fs::remove_dir`].
 ///
-/// `remove_dir_all` will fail if `remove_dir` or `remove_file` fail on any constituent paths, including the root `path`.
-/// As a result, the directory you are deleting must exist, meaning that this function is not idempotent.
-/// Additionally, `remove_dir_all` will also fail if the `path` is not a directory.
+/// [`remove_dir_all`] will fail if [`remove_dir`] or [`remove_file`] fail on *any* constituent
+/// paths, *including* the root `path`. Consequently,
+///
+/// - The directory you are deleting *must* exist, meaning that this function is *not idempotent*.
+/// - [`remove_dir_all`] will fail if the `path` is *not* a directory.
 ///
 /// Consider ignoring the error if validating the removal is not required for your use case.
 ///
diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
index 017862c7f3aac..ce46241f8e84d 100644
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -575,6 +575,11 @@ impl fmt::Debug for StdinLock<'_> {
 /// output stream. Access is also synchronized via a lock and explicit control
 /// over locking is available via the [`lock`] method.
 ///
+/// By default, the handle is line-buffered when connected to a terminal, meaning
+/// it flushes automatically when a newline (`\n`) is encountered. For immediate
+/// output, you can manually call the [`flush`] method. When the handle goes out
+/// of scope, the buffer is automatically flushed.
+///
 /// Created by the [`io::stdout`] method.
 ///
 /// ### Note: Windows Portability Considerations
@@ -590,6 +595,7 @@ impl fmt::Debug for StdinLock<'_> {
 /// standard library or via raw Windows API calls, will fail.
 ///
 /// [`lock`]: Stdout::lock
+/// [`flush`]: Write::flush
 /// [`io::stdout`]: stdout
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Stdout {
@@ -604,6 +610,11 @@ pub struct Stdout {
 /// This handle implements the [`Write`] trait, and is constructed via
 /// the [`Stdout::lock`] method. See its documentation for more.
 ///
+/// By default, the handle is line-buffered when connected to a terminal, meaning
+/// it flushes automatically when a newline (`\n`) is encountered. For immediate
+/// output, you can manually call the [`flush`] method. When the handle goes out
+/// of scope, the buffer is automatically flushed.
+///
 /// ### Note: Windows Portability Considerations
 ///
 /// When operating in a console, the Windows implementation of this stream does not support
@@ -615,6 +626,8 @@ pub struct Stdout {
 /// the contained handle will be null. In such cases, the standard library's `Read` and
 /// `Write` will do nothing and silently succeed. All other I/O operations, via the
 /// standard library or via raw Windows API calls, will fail.
+///
+/// [`flush`]: Write::flush
 #[must_use = "if unused stdout will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct StdoutLock<'a> {
@@ -629,6 +642,11 @@ static STDOUT: OnceLock<ReentrantLock<RefCell<LineWriter<StdoutRaw>>>> = OnceLoc
 /// is synchronized via a mutex. If you need more explicit control over
 /// locking, see the [`Stdout::lock`] method.
 ///
+/// By default, the handle is line-buffered when connected to a terminal, meaning
+/// it flushes automatically when a newline (`\n`) is encountered. For immediate
+/// output, you can manually call the [`flush`] method. When the handle goes out
+/// of scope, the buffer is automatically flushed.
+///
 /// ### Note: Windows Portability Considerations
 ///
 /// When operating in a console, the Windows implementation of this stream does not support
@@ -669,6 +687,22 @@ static STDOUT: OnceLock<ReentrantLock<RefCell<LineWriter<StdoutRaw>>>> = OnceLoc
 ///     Ok(())
 /// }
 /// ```
+///
+/// Ensuring output is flushed immediately:
+///
+/// ```no_run
+/// use std::io::{self, Write};
+///
+/// fn main() -> io::Result<()> {
+///     let mut stdout = io::stdout();
+///     stdout.write_all(b"hello, ")?;
+///     stdout.flush()?;                // Manual flush
+///     stdout.write_all(b"world!\n")?; // Automatically flushed
+///     Ok(())
+/// }
+/// ```
+///
+/// [`flush`]: Write::flush
 #[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "io_stdout")]
diff --git a/library/std/src/sys/pal/uefi/helpers.rs b/library/std/src/sys/pal/uefi/helpers.rs
index cb6aacd0063d4..cca2312c4f923 100644
--- a/library/std/src/sys/pal/uefi/helpers.rs
+++ b/library/std/src/sys/pal/uefi/helpers.rs
@@ -10,7 +10,7 @@
 //! - More information about protocols can be found [here](https://edk2-docs.gitbook.io/edk-ii-uefi-driver-writer-s-guide/3_foundation/36_protocols_and_handles)
 
 use r_efi::efi::{self, Guid};
-use r_efi::protocols::{device_path, device_path_to_text, shell};
+use r_efi::protocols::{device_path, device_path_to_text, service_binding, shell};
 
 use crate::ffi::{OsStr, OsString};
 use crate::io::{self, const_error};
@@ -500,3 +500,62 @@ pub(crate) fn get_device_path_from_map(map: &Path) -> io::Result<BorrowedDeviceP
 
     Ok(BorrowedDevicePath::new(protocol))
 }
+
+/// Helper for UEFI Protocols which are created and destroyed using
+/// [EFI_SERVICE_BINDING_PROTCOL](https://uefi.org/specs/UEFI/2.11/11_Protocols_UEFI_Driver_Model.html#efi-service-binding-protocol)
+pub(crate) struct ServiceProtocol {
+    service_guid: r_efi::efi::Guid,
+    handle: NonNull<crate::ffi::c_void>,
+    child_handle: NonNull<crate::ffi::c_void>,
+}
+
+impl ServiceProtocol {
+    #[expect(dead_code)]
+    pub(crate) fn open(service_guid: r_efi::efi::Guid) -> io::Result<Self> {
+        let handles = locate_handles(service_guid)?;
+
+        for handle in handles {
+            if let Ok(protocol) = open_protocol::<service_binding::Protocol>(handle, service_guid) {
+                let Ok(child_handle) = Self::create_child(protocol) else {
+                    continue;
+                };
+
+                return Ok(Self { service_guid, handle, child_handle });
+            }
+        }
+
+        Err(io::const_error!(io::ErrorKind::NotFound, "no service binding protocol found"))
+    }
+
+    #[expect(dead_code)]
+    pub(crate) fn child_handle(&self) -> NonNull<crate::ffi::c_void> {
+        self.child_handle
+    }
+
+    fn create_child(
+        sbp: NonNull<service_binding::Protocol>,
+    ) -> io::Result<NonNull<crate::ffi::c_void>> {
+        let mut child_handle: r_efi::efi::Handle = crate::ptr::null_mut();
+        // SAFETY: A new handle is allocated if a pointer to NULL is passed.
+        let r = unsafe { ((*sbp.as_ptr()).create_child)(sbp.as_ptr(), &mut child_handle) };
+
+        if r.is_error() {
+            Err(crate::io::Error::from_raw_os_error(r.as_usize()))
+        } else {
+            NonNull::new(child_handle)
+                .ok_or(const_error!(io::ErrorKind::Other, "null child handle"))
+        }
+    }
+}
+
+impl Drop for ServiceProtocol {
+    fn drop(&mut self) {
+        if let Ok(sbp) = open_protocol::<service_binding::Protocol>(self.handle, self.service_guid)
+        {
+            // SAFETY: Child handle must be allocated by the current service binding protocol.
+            let _ = unsafe {
+                ((*sbp.as_ptr()).destroy_child)(sbp.as_ptr(), self.child_handle.as_ptr())
+            };
+        }
+    }
+}
diff --git a/library/std/src/sys/pal/unix/process/process_unix.rs b/library/std/src/sys/pal/unix/process/process_unix.rs
index 1f3abd4cc1286..ddea445bb17e4 100644
--- a/library/std/src/sys/pal/unix/process/process_unix.rs
+++ b/library/std/src/sys/pal/unix/process/process_unix.rs
@@ -410,6 +410,7 @@ impl Command {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "illumos",
         all(target_os = "linux", target_env = "gnu"),
         all(target_os = "linux", target_env = "musl"),
         target_os = "nto",
@@ -427,6 +428,7 @@ impl Command {
     // directly.
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "illumos",
         all(target_os = "linux", target_env = "gnu"),
         all(target_os = "linux", target_env = "musl"),
         target_os = "nto",
@@ -584,6 +586,10 @@ impl Command {
         fn get_posix_spawn_addchdir() -> Option<PosixSpawnAddChdirFn> {
             use crate::sys::weak::weak;
 
+            // POSIX.1-2024 standardizes this function:
+            // https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_spawn_file_actions_addchdir.html.
+            // The _np version is more widely available, though, so try that first.
+
             weak! {
                 fn posix_spawn_file_actions_addchdir_np(
                     *mut libc::posix_spawn_file_actions_t,
@@ -591,7 +597,16 @@ impl Command {
                 ) -> libc::c_int
             }
 
-            posix_spawn_file_actions_addchdir_np.get()
+            weak! {
+                fn posix_spawn_file_actions_addchdir(
+                    *mut libc::posix_spawn_file_actions_t,
+                    *const libc::c_char
+                ) -> libc::c_int
+            }
+
+            posix_spawn_file_actions_addchdir_np
+                .get()
+                .or_else(|| posix_spawn_file_actions_addchdir.get())
         }
 
         /// Get the function pointer for adding a chdir action to a
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 2c1d85b01e6af..2ea2596088fd5 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "bootstrap"
 version = "0.0.0"
-edition = "2021"
+edition = "2024"
 build = "build.rs"
 default-run = "bootstrap"
 
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index e3f58d97cbc4c..c3b256464396f 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -292,7 +292,7 @@ def v(*args):
 v("release-channel", "rust.channel", "the name of the release channel to build")
 v(
     "release-description",
-    "rust.description",
+    "build.description",
     "optional descriptive string for version output",
 )
 v("dist-compression-formats", None, "List of compression formats to use")
diff --git a/src/bootstrap/src/bin/sccache-plus-cl.rs b/src/bootstrap/src/bin/sccache-plus-cl.rs
index 6e87d4222e863..c161d69d5f73b 100644
--- a/src/bootstrap/src/bin/sccache-plus-cl.rs
+++ b/src/bootstrap/src/bin/sccache-plus-cl.rs
@@ -4,8 +4,13 @@ use std::process::{self, Command};
 fn main() {
     let target = env::var("SCCACHE_TARGET").unwrap();
     // Locate the actual compiler that we're invoking
-    env::set_var("CC", env::var_os("SCCACHE_CC").unwrap());
-    env::set_var("CXX", env::var_os("SCCACHE_CXX").unwrap());
+
+    // SAFETY: we're in main, there are no other threads
+    unsafe {
+        env::set_var("CC", env::var_os("SCCACHE_CC").unwrap());
+        env::set_var("CXX", env::var_os("SCCACHE_CXX").unwrap());
+    }
+
     let mut cfg = cc::Build::new();
     cfg.cargo_metadata(false)
         .out_dir("/")
diff --git a/src/bootstrap/src/core/build_steps/format.rs b/src/bootstrap/src/core/build_steps/format.rs
index c7eafadee2df3..9817e47baa101 100644
--- a/src/bootstrap/src/core/build_steps/format.rs
+++ b/src/bootstrap/src/core/build_steps/format.rs
@@ -27,7 +27,7 @@ fn rustfmt(
     rustfmt: &Path,
     paths: &[PathBuf],
     check: bool,
-) -> impl FnMut(bool) -> RustfmtStatus {
+) -> impl FnMut(bool) -> RustfmtStatus + use<> {
     let mut cmd = Command::new(rustfmt);
     // Avoid the submodule config paths from coming into play. We only allow a single global config
     // for the workspace for now.
diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index d84ade21caf29..4b7c8d5770e4e 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -90,7 +90,7 @@ impl Step for CrateBootstrap {
         );
 
         let crate_name = path.rsplit_once('/').unwrap().1;
-        run_cargo_test(cargo, &[], &[], crate_name, crate_name, bootstrap_host, builder);
+        run_cargo_test(cargo, &[], &[], crate_name, bootstrap_host, builder);
     }
 }
 
@@ -140,15 +140,7 @@ You can skip linkcheck with --skip src/tools/linkchecker"
             SourceType::InTree,
             &[],
         );
-        run_cargo_test(
-            cargo,
-            &[],
-            &[],
-            "linkchecker",
-            "linkchecker self tests",
-            bootstrap_host,
-            builder,
-        );
+        run_cargo_test(cargo, &[], &[], "linkchecker self tests", bootstrap_host, builder);
 
         if builder.doc_tests == DocTests::No {
             return;
@@ -337,7 +329,7 @@ impl Step for Cargo {
         );
 
         // NOTE: can't use `run_cargo_test` because we need to overwrite `PATH`
-        let mut cargo = prepare_cargo_test(cargo, &[], &[], "cargo", self.host, builder);
+        let mut cargo = prepare_cargo_test(cargo, &[], &[], self.host, builder);
 
         // Don't run cross-compile tests, we may not have cross-compiled libstd libs
         // available.
@@ -423,7 +415,7 @@ impl Step for RustAnalyzer {
         cargo.env("SKIP_SLOW_TESTS", "1");
 
         cargo.add_rustc_lib_path(builder);
-        run_cargo_test(cargo, &[], &[], "rust-analyzer", "rust-analyzer", host, builder);
+        run_cargo_test(cargo, &[], &[], "rust-analyzer", host, builder);
     }
 }
 
@@ -472,7 +464,7 @@ impl Step for Rustfmt {
 
         cargo.add_rustc_lib_path(builder);
 
-        run_cargo_test(cargo, &[], &[], "rustfmt", "rustfmt", host, builder);
+        run_cargo_test(cargo, &[], &[], "rustfmt", host, builder);
     }
 }
 
@@ -588,7 +580,7 @@ impl Step for Miri {
 
         // We can NOT use `run_cargo_test` since Miri's integration tests do not use the usual test
         // harness and therefore do not understand the flags added by `add_flags_and_try_run_test`.
-        let mut cargo = prepare_cargo_test(cargo, &[], &[], "miri", host, builder);
+        let mut cargo = prepare_cargo_test(cargo, &[], &[], host, builder);
 
         // miri tests need to know about the stage sysroot
         cargo.env("MIRI_SYSROOT", &miri_sysroot);
@@ -736,7 +728,7 @@ impl Step for CompiletestTest {
             &[],
         );
         cargo.allow_features("test");
-        run_cargo_test(cargo, &[], &[], "compiletest", "compiletest self test", host, builder);
+        run_cargo_test(cargo, &[], &[], "compiletest self test", host, builder);
     }
 }
 
@@ -797,7 +789,7 @@ impl Step for Clippy {
         cargo.env("HOST_LIBS", host_libs);
 
         cargo.add_rustc_lib_path(builder);
-        let cargo = prepare_cargo_test(cargo, &[], &[], "clippy", host, builder);
+        let cargo = prepare_cargo_test(cargo, &[], &[], host, builder);
 
         let _guard = builder.msg_sysroot_tool(Kind::Test, compiler.stage, "clippy", host, host);
 
@@ -1277,15 +1269,7 @@ impl Step for CrateRunMakeSupport {
             &[],
         );
         cargo.allow_features("test");
-        run_cargo_test(
-            cargo,
-            &[],
-            &[],
-            "run-make-support",
-            "run-make-support self test",
-            host,
-            builder,
-        );
+        run_cargo_test(cargo, &[], &[], "run-make-support self test", host, builder);
     }
 }
 
@@ -1322,7 +1306,7 @@ impl Step for CrateBuildHelper {
             &[],
         );
         cargo.allow_features("test");
-        run_cargo_test(cargo, &[], &[], "build_helper", "build_helper self test", host, builder);
+        run_cargo_test(cargo, &[], &[], "build_helper self test", host, builder);
     }
 }
 
@@ -2507,13 +2491,12 @@ fn run_cargo_test<'a>(
     cargo: builder::Cargo,
     libtest_args: &[&str],
     crates: &[String],
-    primary_crate: &str,
     description: impl Into<Option<&'a str>>,
     target: TargetSelection,
     builder: &Builder<'_>,
 ) -> bool {
     let compiler = cargo.compiler();
-    let mut cargo = prepare_cargo_test(cargo, libtest_args, crates, primary_crate, target, builder);
+    let mut cargo = prepare_cargo_test(cargo, libtest_args, crates, target, builder);
     let _time = helpers::timeit(builder);
     let _group = description.into().and_then(|what| {
         builder.msg_sysroot_tool(Kind::Test, compiler.stage, what, compiler.host, target)
@@ -2537,7 +2520,6 @@ fn prepare_cargo_test(
     cargo: builder::Cargo,
     libtest_args: &[&str],
     crates: &[String],
-    primary_crate: &str,
     target: TargetSelection,
     builder: &Builder<'_>,
 ) -> BootstrapCommand {
@@ -2567,13 +2549,6 @@ fn prepare_cargo_test(
             cargo.arg("--doc");
         }
         DocTests::No => {
-            let krate = &builder
-                .crates
-                .get(primary_crate)
-                .unwrap_or_else(|| panic!("missing crate {primary_crate}"));
-            if krate.has_lib {
-                cargo.arg("--lib");
-            }
             cargo.args(["--bins", "--examples", "--tests", "--benches"]);
         }
         DocTests::Yes => {}
@@ -2748,15 +2723,15 @@ impl Step for Crate {
             _ => panic!("can only test libraries"),
         };
 
-        run_cargo_test(
-            cargo,
-            &[],
-            &self.crates,
-            &self.crates[0],
-            &*crate_description(&self.crates),
-            target,
-            builder,
-        );
+        let mut crates = self.crates.clone();
+        // The core crate can't directly be tested. We could silently
+        // ignore it, but adding it's own test crate is less confusing
+        // for users. We still keep core itself for doctests.
+        if crates.iter().any(|crate_| crate_ == "core") {
+            crates.push("coretests".to_owned());
+        }
+
+        run_cargo_test(cargo, &[], &crates, &*crate_description(&self.crates), target, builder);
     }
 }
 
@@ -2849,15 +2824,7 @@ impl Step for CrateRustdoc {
         dylib_path.insert(0, PathBuf::from(&*libdir));
         cargo.env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
-        run_cargo_test(
-            cargo,
-            &[],
-            &["rustdoc:0.0.0".to_string()],
-            "rustdoc",
-            "rustdoc",
-            target,
-            builder,
-        );
+        run_cargo_test(cargo, &[], &["rustdoc:0.0.0".to_string()], "rustdoc", target, builder);
     }
 }
 
@@ -2914,7 +2881,6 @@ impl Step for CrateRustdocJsonTypes {
             libtest_args,
             &["rustdoc-json-types".to_string()],
             "rustdoc-json-types",
-            "rustdoc-json-types",
             target,
             builder,
         );
@@ -3094,7 +3060,7 @@ impl Step for Bootstrap {
 
         // bootstrap tests are racy on directory creation so just run them one at a time.
         // Since there's not many this shouldn't be a problem.
-        run_cargo_test(cargo, &["--test-threads=1"], &[], "bootstrap", None, host, builder);
+        run_cargo_test(cargo, &["--test-threads=1"], &[], None, host, builder);
     }
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
@@ -3219,7 +3185,7 @@ impl Step for RustInstaller {
             bootstrap_host,
             bootstrap_host,
         );
-        run_cargo_test(cargo, &[], &[], "installer", None, bootstrap_host, builder);
+        run_cargo_test(cargo, &[], &[], None, bootstrap_host, builder);
 
         // We currently don't support running the test.sh script outside linux(?) environments.
         // Eventually this should likely migrate to #[test]s in rust-installer proper rather than a
@@ -3610,7 +3576,7 @@ impl Step for TestFloatParse {
             &[],
         );
 
-        run_cargo_test(cargo_test, &[], &[], crate_name, crate_name, bootstrap_host, builder);
+        run_cargo_test(cargo_test, &[], &[], crate_name, bootstrap_host, builder);
 
         // Run the actual parse tests.
         let mut cargo_run = tool::prepare_tool_cargo(
diff --git a/src/bootstrap/src/core/build_steps/tool.rs b/src/bootstrap/src/core/build_steps/tool.rs
index 0149709f5c51b..6a9e373fbc949 100644
--- a/src/bootstrap/src/core/build_steps/tool.rs
+++ b/src/bootstrap/src/core/build_steps/tool.rs
@@ -248,23 +248,32 @@ pub fn prepare_tool_cargo(
     cargo.env("CFG_VERSION", builder.rust_version());
     cargo.env("CFG_RELEASE_NUM", &builder.version);
     cargo.env("DOC_RUST_LANG_ORG_CHANNEL", builder.doc_rust_lang_org_channel());
+
     if let Some(ref ver_date) = builder.rust_info().commit_date() {
         cargo.env("CFG_VER_DATE", ver_date);
     }
+
     if let Some(ref ver_hash) = builder.rust_info().sha() {
         cargo.env("CFG_VER_HASH", ver_hash);
     }
 
+    if let Some(description) = &builder.config.description {
+        cargo.env("CFG_VER_DESCRIPTION", description);
+    }
+
     let info = GitInfo::new(builder.config.omit_git_hash, &dir);
     if let Some(sha) = info.sha() {
         cargo.env("CFG_COMMIT_HASH", sha);
     }
+
     if let Some(sha_short) = info.sha_short() {
         cargo.env("CFG_SHORT_COMMIT_HASH", sha_short);
     }
+
     if let Some(date) = info.commit_date() {
         cargo.env("CFG_COMMIT_DATE", date);
     }
+
     if !features.is_empty() {
         cargo.arg("--features").arg(features.join(", "));
     }
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index d0e0ed50ad89f..ac24da9f86b25 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -894,6 +894,7 @@ define_config! {
     #[derive(Default)]
     struct Build {
         build: Option<String> = "build",
+        description: Option<String> = "description",
         host: Option<Vec<String>> = "host",
         target: Option<Vec<String>> = "target",
         build_dir: Option<String> = "build-dir",
@@ -1176,6 +1177,7 @@ define_config! {
         incremental: Option<bool> = "incremental",
         default_linker: Option<String> = "default-linker",
         channel: Option<String> = "channel",
+        // FIXME: Remove this field at Q2 2025, it has been replaced by build.description
         description: Option<String> = "description",
         musl_root: Option<String> = "musl-root",
         rpath: Option<bool> = "rpath",
@@ -1583,6 +1585,7 @@ impl Config {
         config.change_id = toml.change_id.inner;
 
         let Build {
+            mut description,
             build,
             host,
             target,
@@ -1831,7 +1834,7 @@ impl Config {
                 randomize_layout,
                 default_linker,
                 channel: _, // already handled above
-                description,
+                description: rust_description,
                 musl_root,
                 rpath,
                 verbose_tests,
@@ -1924,7 +1927,12 @@ impl Config {
             set(&mut config.jemalloc, jemalloc);
             set(&mut config.test_compare_mode, test_compare_mode);
             set(&mut config.backtrace, backtrace);
-            config.description = description;
+            if rust_description.is_some() {
+                eprintln!(
+                    "Warning: rust.description is deprecated. Use build.description instead."
+                );
+            }
+            description = description.or(rust_description);
             set(&mut config.rust_dist_src, dist_src);
             set(&mut config.verbose_tests, verbose_tests);
             // in the case "false" is set explicitly, do not overwrite the command line args
@@ -1990,6 +1998,7 @@ impl Config {
         }
 
         config.reproducible_artifacts = flags.reproducible_artifact;
+        config.description = description;
 
         // We need to override `rust.channel` if it's manually specified when using the CI rustc.
         // This is because if the compiler uses a different channel than the one specified in config.toml,
diff --git a/src/bootstrap/src/core/metadata.rs b/src/bootstrap/src/core/metadata.rs
index 01cbf6629408d..2706aba5ffc8d 100644
--- a/src/bootstrap/src/core/metadata.rs
+++ b/src/bootstrap/src/core/metadata.rs
@@ -28,7 +28,6 @@ struct Package {
     source: Option<String>,
     manifest_path: String,
     dependencies: Vec<Dependency>,
-    targets: Vec<Target>,
     features: BTreeMap<String, Vec<String>>,
 }
 
@@ -40,11 +39,6 @@ struct Dependency {
     source: Option<String>,
 }
 
-#[derive(Debug, Deserialize)]
-struct Target {
-    kind: Vec<String>,
-}
-
 /// Collects and stores package metadata of each workspace members into `build`,
 /// by executing `cargo metadata` commands.
 pub fn build(build: &mut Build) {
@@ -59,12 +53,10 @@ pub fn build(build: &mut Build) {
                 .filter(|dep| dep.source.is_none())
                 .map(|dep| dep.name)
                 .collect();
-            let has_lib = package.targets.iter().any(|t| t.kind.iter().any(|k| k == "lib"));
             let krate = Crate {
                 name: name.clone(),
                 deps,
                 path,
-                has_lib,
                 features: package.features.keys().cloned().collect(),
             };
             let relative_path = krate.local_path(build);
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 351e67f6702d1..4ea711c1325e8 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -185,7 +185,6 @@ struct Crate {
     name: String,
     deps: HashSet<String>,
     path: PathBuf,
-    has_lib: bool,
     features: Vec<String>,
 }
 
diff --git a/src/bootstrap/src/utils/cc_detect/tests.rs b/src/bootstrap/src/utils/cc_detect/tests.rs
index 006dfe7e5d7b3..715ce90e2e1e3 100644
--- a/src/bootstrap/src/utils/cc_detect/tests.rs
+++ b/src/bootstrap/src/utils/cc_detect/tests.rs
@@ -9,20 +9,24 @@ use crate::{Build, Config, Flags};
 fn test_cc2ar_env_specific() {
     let triple = "x86_64-unknown-linux-gnu";
     let key = "AR_x86_64_unknown_linux_gnu";
-    env::set_var(key, "custom-ar");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::set_var(key, "custom-ar") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
     let result = cc2ar(cc, target, default_ar);
-    env::remove_var(key);
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var(key) };
     assert_eq!(result, Some(PathBuf::from("custom-ar")));
 }
 
 #[test]
 fn test_cc2ar_musl() {
     let triple = "x86_64-unknown-linux-musl";
-    env::remove_var("AR_x86_64_unknown_linux_musl");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_x86_64_unknown_linux_musl") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -33,8 +37,10 @@ fn test_cc2ar_musl() {
 #[test]
 fn test_cc2ar_openbsd() {
     let triple = "x86_64-unknown-openbsd";
-    env::remove_var("AR_x86_64_unknown_openbsd");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_x86_64_unknown_openbsd") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/cc");
     let default_ar = PathBuf::from("default-ar");
@@ -45,8 +51,10 @@ fn test_cc2ar_openbsd() {
 #[test]
 fn test_cc2ar_vxworks() {
     let triple = "armv7-wrs-vxworks";
-    env::remove_var("AR_armv7_wrs_vxworks");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_armv7_wrs_vxworks") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -57,8 +65,10 @@ fn test_cc2ar_vxworks() {
 #[test]
 fn test_cc2ar_nto_i586() {
     let triple = "i586-unknown-nto-something";
-    env::remove_var("AR_i586_unknown_nto_something");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_i586_unknown_nto_something") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -69,8 +79,10 @@ fn test_cc2ar_nto_i586() {
 #[test]
 fn test_cc2ar_nto_aarch64() {
     let triple = "aarch64-unknown-nto-something";
-    env::remove_var("AR_aarch64_unknown_nto_something");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_aarch64_unknown_nto_something") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -81,8 +93,10 @@ fn test_cc2ar_nto_aarch64() {
 #[test]
 fn test_cc2ar_nto_x86_64() {
     let triple = "x86_64-unknown-nto-something";
-    env::remove_var("AR_x86_64_unknown_nto_something");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_x86_64_unknown_nto_something") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -94,8 +108,10 @@ fn test_cc2ar_nto_x86_64() {
 #[should_panic(expected = "Unknown architecture, cannot determine archiver for Neutrino QNX")]
 fn test_cc2ar_nto_unknown() {
     let triple = "powerpc-unknown-nto-something";
-    env::remove_var("AR_powerpc_unknown_nto_something");
-    env::remove_var("AR");
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR_powerpc_unknown_nto_something") };
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::remove_var("AR") };
     let target = TargetSelection::from_user(triple);
     let cc = Path::new("/usr/bin/clang");
     let default_ar = PathBuf::from("default-ar");
@@ -177,7 +193,8 @@ fn test_default_compiler_wasi() {
     let build = Build::new(Config { ..Config::parse(Flags::parse(&["check".to_owned()])) });
     let target = TargetSelection::from_user("wasm32-wasi");
     let wasi_sdk = PathBuf::from("/wasi-sdk");
-    env::set_var("WASI_SDK_PATH", &wasi_sdk);
+    // SAFETY: bootstrap tests run on a single thread
+    unsafe { env::set_var("WASI_SDK_PATH", &wasi_sdk) };
     let mut cfg = cc::Build::new();
     if let Some(result) = default_compiler(&mut cfg, Language::C, target.clone(), &build) {
         let expected = {
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index 5f49c50c5ad3a..425ffdccad57f 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -365,4 +365,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "`rust.channel` now supports \"auto-detect\" to load the channel from `src/ci/channel`",
     },
+    ChangeInfo {
+        change_id: 137723,
+        severity: ChangeSeverity::Info,
+        summary: "The rust.description option has moved to build.description and rust.description is now deprecated.",
+    },
 ];
diff --git a/src/bootstrap/src/utils/helpers.rs b/src/bootstrap/src/utils/helpers.rs
index 7ad308cd06728..89d93a29acbca 100644
--- a/src/bootstrap/src/utils/helpers.rs
+++ b/src/bootstrap/src/utils/helpers.rs
@@ -286,7 +286,7 @@ pub fn output(cmd: &mut Command) -> String {
 /// to finish and then return its output. This allows the spawned process
 /// to do work without immediately blocking bootstrap.
 #[track_caller]
-pub fn start_process(cmd: &mut Command) -> impl FnOnce() -> String {
+pub fn start_process(cmd: &mut Command) -> impl FnOnce() -> String + use<> {
     let child = match cmd.stderr(Stdio::inherit()).stdout(Stdio::piped()).spawn() {
         Ok(child) => child,
         Err(e) => fail(&format!("failed to execute command: {cmd:?}\nERROR: {e}")),
diff --git a/src/bootstrap/src/utils/job.rs b/src/bootstrap/src/utils/job.rs
index 10efed130d624..2ad5aa8e798dc 100644
--- a/src/bootstrap/src/utils/job.rs
+++ b/src/bootstrap/src/utils/job.rs
@@ -7,7 +7,9 @@ pub unsafe fn setup(_build: &mut crate::Build) {}
 #[cfg(all(unix, not(target_os = "haiku")))]
 pub unsafe fn setup(build: &mut crate::Build) {
     if build.config.low_priority {
-        libc::setpriority(libc::PRIO_PGRP as _, 0, 10);
+        unsafe {
+            libc::setpriority(libc::PRIO_PGRP as _, 0, 10);
+        }
     }
 }
 
diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index bbcc01a0c2998..6b88c26e3a276 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -54,7 +54,7 @@ runners:
     <<: *base-job
 
   - &job-aarch64-linux-8c
-    os: ubuntu-22.04-arm64-8core-32gb
+    os: ubuntu-24.04-arm64-8core-32gb
     <<: *base-job
 envs:
   env-x86_64-apple-tests: &env-x86_64-apple-tests
diff --git a/src/doc/rustc-dev-guide/src/tests/compiletest.md b/src/doc/rustc-dev-guide/src/tests/compiletest.md
index 459c082906eba..2905e470fabd3 100644
--- a/src/doc/rustc-dev-guide/src/tests/compiletest.md
+++ b/src/doc/rustc-dev-guide/src/tests/compiletest.md
@@ -74,8 +74,7 @@ The following test suites are available, with links for more information:
 
 ### General purpose test suite
 
-[`run-make`](#run-make-tests) are general purpose tests using Rust programs (or
-Makefiles (legacy)).
+[`run-make`](#run-make-tests) are general purpose tests using Rust programs.
 
 ### Rustdoc test suites
 
@@ -396,14 +395,6 @@ your test, causing separate files to be generated for 32bit and 64bit systems.
 
 ### `run-make` tests
 
-> **Note on phasing out `Makefile`s**
-> 
-> We are planning to migrate all existing Makefile-based `run-make` tests
-> to Rust programs. You should not be adding new Makefile-based `run-make`
-> tests.
->
-> See <https://github.com/rust-lang/rust/issues/121876>.
-
 The tests in [`tests/run-make`] are general-purpose tests using Rust *recipes*,
 which are small programs (`rmake.rs`) allowing arbitrary Rust code such as
 `rustc` invocations, and is supported by a [`run_make_support`] library. Using
@@ -424,11 +415,6 @@ Compiletest directives like `//@ only-<target>` or `//@ ignore-<target>` are
 supported in `rmake.rs`, like in UI tests. However, revisions or building
 auxiliary via directives are not currently supported.
 
-Two `run-make` tests are ported over to Rust recipes as examples:
-
-- <https://github.com/rust-lang/rust/tree/master/tests/run-make/CURRENT_RUSTC_VERSION>
-- <https://github.com/rust-lang/rust/tree/master/tests/run-make/a-b-a-linker-guard>
-
 #### Quickly check if `rmake.rs` tests can be compiled
 
 You can quickly check if `rmake.rs` tests can be compiled without having to
@@ -481,20 +467,6 @@ Then add a corresponding entry to `"rust-analyzer.linkedProjects"`
 ],
 ```
 
-#### Using Makefiles (legacy)
-
-<div class="warning">
-You should avoid writing new Makefile-based `run-make` tests.
-</div>
-
-Each test should be in a separate directory with a `Makefile` indicating the
-commands to run.
-
-There is a [`tools.mk`] Makefile which you can include which provides a bunch of
-utilities to make it easier to run commands and compare outputs. Take a look at
-some of the other tests for some examples on how to get started.
-
-[`tools.mk`]: https://github.com/rust-lang/rust/blob/master/tests/run-make/tools.mk
 [`tests/run-make`]: https://github.com/rust-lang/rust/tree/master/tests/run-make
 [`run_make_support`]: https://github.com/rust-lang/rust/tree/master/src/tools/run-make-support
 
diff --git a/src/doc/rustc-dev-guide/src/tests/directives.md b/src/doc/rustc-dev-guide/src/tests/directives.md
index af9cb85d27b53..14f18a7ecf714 100644
--- a/src/doc/rustc-dev-guide/src/tests/directives.md
+++ b/src/doc/rustc-dev-guide/src/tests/directives.md
@@ -6,10 +6,7 @@
 FIXME(jieyouxu) completely revise this chapter.
 -->
 
-Directives are special comments that tell compiletest how to build and interpret
-a test. They must appear before the Rust source in the test. They may also
-appear in `rmake.rs` or legacy Makefiles for [run-make
-tests](compiletest.md#run-make-tests).
+Directives are special comments that tell compiletest how to build and interpret a test. They must appear before the Rust source in the test. They may also appear in `rmake.rs` [run-make tests](compiletest.md#run-make-tests).
 
 They are normally put after the short comment that explains the point of this
 test. Compiletest test suites use `//@` to signal that a comment is a directive.
@@ -222,8 +219,6 @@ The following directives will check LLVM support:
     [`aarch64-gnu-debug`]), which only runs a
     subset of `run-make` tests. Other tests with this directive will not
     run at all, which is usually not what you want.
-  - Notably, the [`aarch64-gnu-debug`] CI job *currently* only runs `run-make`
-    tests which additionally contain `clang` in their test name.
 
 See also [Debuginfo tests](compiletest.md#debuginfo-tests) for directives for
 ignoring debuggers.
diff --git a/src/doc/rustc-dev-guide/src/tests/running.md b/src/doc/rustc-dev-guide/src/tests/running.md
index 6ce65092389bd..9ddf0afee0c77 100644
--- a/src/doc/rustc-dev-guide/src/tests/running.md
+++ b/src/doc/rustc-dev-guide/src/tests/running.md
@@ -238,30 +238,6 @@ This is much faster, but doesn't always work. For example, some tests include
 directives that specify specific compiler flags, or which rely on other crates,
 and they may not run the same without those options.
 
-## Running `run-make` tests
-
-### Windows
-
-Running the `run-make` test suite on Windows is a currently bit more involved.
-There are numerous prerequisites and environmental requirements:
-
-- Install msys2: <https://www.msys2.org/>
-- Specify `MSYS2_PATH_TYPE=inherit` in `msys2.ini` in the msys2 installation directory, run the
-  following with `MSYS2 MSYS`:
-  - `pacman -Syuu`
-  - `pacman -S make`
-  - `pacman -S diffutils`
-  - `pacman -S binutils`
-  - `./x test run-make` (`./x test tests/run-make` doesn't work)
-
-There is [on-going work][port-run-make] to not rely on `Makefile`s in the
-run-make test suite. Once this work is completed, you can run the entire
-`run-make` test suite on native Windows inside `cmd` or `PowerShell` without
-needing to install and use MSYS2. As of <!--date-check --> Oct 2024, it is
-already possible to run the vast majority of the `run-make` test suite outside
-of MSYS2, but there will be failures for the tests that still use `Makefile`s
-due to not finding `make`.
-
 ## Running tests on a remote machine
 
 Tests may be run on a remote machine (e.g. to test builds for a different
@@ -406,4 +382,3 @@ If you encounter bugs or problems, don't hesitate to open issues on the
 repository](https://github.com/rust-lang/rustc_codegen_gcc/).
 
 [`tests/ui`]: https://github.com/rust-lang/rust/tree/master/tests/ui
-[port-run-make]: https://github.com/rust-lang/rust/issues/121876
diff --git a/src/etc/test-float-parse/src/traits.rs b/src/etc/test-float-parse/src/traits.rs
index c8407ba7cc50a..57e702b7d0913 100644
--- a/src/etc/test-float-parse/src/traits.rs
+++ b/src/etc/test-float-parse/src/traits.rs
@@ -147,12 +147,12 @@ pub trait Float:
 }
 
 macro_rules! impl_float {
-    ($($fty:ty, $ity:ty, $bits:literal);+) => {
+    ($($fty:ty, $ity:ty);+) => {
         $(
             impl Float for $fty {
                 type Int = $ity;
                 type SInt = <Self::Int as Int>::Signed;
-                const BITS: u32 = $bits;
+                const BITS: u32 = <$ity>::BITS;
                 const MAN_BITS: u32 = Self::MANTISSA_DIGITS - 1;
                 const MAN_MASK: Self::Int = (Self::Int::ONE << Self::MAN_BITS) - Self::Int::ONE;
                 const SIGN_MASK: Self::Int = Self::Int::ONE << (Self::BITS-1);
@@ -168,7 +168,7 @@ macro_rules! impl_float {
     }
 }
 
-impl_float!(f32, u32, 32; f64, u64, 64);
+impl_float!(f32, u32; f64, u64);
 
 /// A test generator. Should provide an iterator that produces unique patterns to parse.
 ///
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index 53ee901b8bc48..7675e13990d6c 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -709,11 +709,11 @@ impl TestProps {
 /// returns a struct containing various parts of the directive.
 fn line_directive<'line>(
     line_number: usize,
-    comment: &str,
     original_line: &'line str,
 ) -> Option<DirectiveLine<'line>> {
     // Ignore lines that don't start with the comment prefix.
-    let after_comment = original_line.trim_start().strip_prefix(comment)?.trim_start();
+    let after_comment =
+        original_line.trim_start().strip_prefix(COMPILETEST_DIRECTIVE_PREFIX)?.trim_start();
 
     let revision;
     let raw_directive;
@@ -722,7 +722,7 @@ fn line_directive<'line>(
         // A comment like `//@[foo]` only applies to revision `foo`.
         let Some((line_revision, after_close_bracket)) = after_open_bracket.split_once(']') else {
             panic!(
-                "malformed condition directive: expected `{comment}[foo]`, found `{original_line}`"
+                "malformed condition directive: expected `{COMPILETEST_DIRECTIVE_PREFIX}[foo]`, found `{original_line}`"
             )
         };
 
@@ -836,6 +836,8 @@ pub(crate) fn check_directive<'a>(
     CheckDirectiveResult { is_known_directive: is_known(&directive_name), trailing_directive }
 }
 
+const COMPILETEST_DIRECTIVE_PREFIX: &str = "//@";
+
 fn iter_header(
     mode: Mode,
     _suite: &str,
@@ -849,8 +851,7 @@ fn iter_header(
     }
 
     // Coverage tests in coverage-run mode always have these extra directives, without needing to
-    // specify them manually in every test file. (Some of the comments below have been copied over
-    // from the old `tests/run-make/coverage-reports/Makefile`, which no longer exists.)
+    // specify them manually in every test file.
     //
     // FIXME(jieyouxu): I feel like there's a better way to do this, leaving for later.
     if mode == Mode::CoverageRun {
@@ -867,9 +868,6 @@ fn iter_header(
         }
     }
 
-    // NOTE(jieyouxu): once we get rid of `Makefile`s we can unconditionally check for `//@`.
-    let comment = if testfile.extension().is_some_and(|e| e == "rs") { "//@" } else { "#" };
-
     let mut rdr = BufReader::with_capacity(1024, rdr);
     let mut ln = String::new();
     let mut line_number = 0;
@@ -882,7 +880,7 @@ fn iter_header(
         }
         let ln = ln.trim();
 
-        let Some(directive_line) = line_directive(line_number, comment, ln) else {
+        let Some(directive_line) = line_directive(line_number, ln) else {
             continue;
         };
 
diff --git a/src/tools/compiletest/src/header/tests.rs b/src/tools/compiletest/src/header/tests.rs
index d7079fdeee6c3..007318be7cc39 100644
--- a/src/tools/compiletest/src/header/tests.rs
+++ b/src/tools/compiletest/src/header/tests.rs
@@ -239,11 +239,6 @@ fn check_ignore(config: &Config, contents: &str) -> bool {
     d.ignore
 }
 
-fn parse_makefile(config: &Config, contents: &str) -> EarlyProps {
-    let bytes = contents.as_bytes();
-    EarlyProps::from_reader(config, Path::new("Makefile"), bytes)
-}
-
 #[test]
 fn should_fail() {
     let config: Config = cfg().build();
@@ -261,10 +256,6 @@ fn revisions() {
     let config: Config = cfg().build();
 
     assert_eq!(parse_rs(&config, "//@ revisions: a b c").revisions, vec!["a", "b", "c"],);
-    assert_eq!(
-        parse_makefile(&config, "# revisions: hello there").revisions,
-        vec!["hello", "there"],
-    );
 }
 
 #[test]
diff --git a/src/tools/compiletest/src/lib.rs b/src/tools/compiletest/src/lib.rs
index e93f32c86bc41..dd611b19a8d0d 100644
--- a/src/tools/compiletest/src/lib.rs
+++ b/src/tools/compiletest/src/lib.rs
@@ -21,7 +21,7 @@ pub mod util;
 
 use core::panic;
 use std::collections::HashSet;
-use std::ffi::{OsStr, OsString};
+use std::ffi::OsString;
 use std::io::{self, ErrorKind};
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
@@ -274,12 +274,8 @@ pub fn parse_config(args: Vec<String>) -> Config {
                 let path = Path::new(f);
                 let mut iter = path.iter().skip(1);
 
-                // We skip the test folder and check if the user passed `rmake.rs` or `Makefile`.
-                if iter
-                    .next()
-                    .is_some_and(|s| s == OsStr::new("rmake.rs") || s == OsStr::new("Makefile"))
-                    && iter.next().is_none()
-                {
+                // We skip the test folder and check if the user passed `rmake.rs`.
+                if iter.next().is_some_and(|s| s == "rmake.rs") && iter.next().is_none() {
                     path.parent().unwrap().to_str().unwrap().to_string()
                 } else {
                     f.to_string()
@@ -783,16 +779,9 @@ fn collect_tests_from_dir(
         return Ok(());
     }
 
-    // For run-make tests, a "test file" is actually a directory that contains
-    // an `rmake.rs` or `Makefile`"
+    // For run-make tests, a "test file" is actually a directory that contains an `rmake.rs`.
     if cx.config.mode == Mode::RunMake {
-        if dir.join("Makefile").exists() && dir.join("rmake.rs").exists() {
-            return Err(io::Error::other(
-                "run-make tests cannot have both `Makefile` and `rmake.rs`",
-            ));
-        }
-
-        if dir.join("Makefile").exists() || dir.join("rmake.rs").exists() {
+        if dir.join("rmake.rs").exists() {
             let paths = TestPaths {
                 file: dir.to_path_buf(),
                 relative_dir: relative_dir_path.parent().unwrap().to_path_buf(),
@@ -861,24 +850,14 @@ pub fn is_test(file_name: &OsString) -> bool {
     !invalid_prefixes.iter().any(|p| file_name.starts_with(p))
 }
 
-/// For a single test file, creates one or more test structures (one per revision)
-/// that can be handed over to libtest to run, possibly in parallel.
+/// For a single test file, creates one or more test structures (one per revision) that can be
+/// handed over to libtest to run, possibly in parallel.
 fn make_test(cx: &TestCollectorCx, collector: &mut TestCollector, testpaths: &TestPaths) {
-    // For run-make tests, each "test file" is actually a _directory_ containing
-    // an `rmake.rs` or `Makefile`. But for the purposes of directive parsing,
-    // we want to look at that recipe file, not the directory itself.
+    // For run-make tests, each "test file" is actually a _directory_ containing an `rmake.rs`. But
+    // for the purposes of directive parsing, we want to look at that recipe file, not the directory
+    // itself.
     let test_path = if cx.config.mode == Mode::RunMake {
-        if testpaths.file.join("rmake.rs").exists() && testpaths.file.join("Makefile").exists() {
-            panic!("run-make tests cannot have both `rmake.rs` and `Makefile`");
-        }
-
-        if testpaths.file.join("rmake.rs").exists() {
-            // Parse directives in rmake.rs.
-            testpaths.file.join("rmake.rs")
-        } else {
-            // Parse directives in the Makefile.
-            testpaths.file.join("Makefile")
-        }
+        testpaths.file.join("rmake.rs")
     } else {
         PathBuf::from(&testpaths.file)
     };
diff --git a/src/tools/compiletest/src/runtest/run_make.rs b/src/tools/compiletest/src/runtest/run_make.rs
index 07f4d7c494265..8900752bd4be8 100644
--- a/src/tools/compiletest/src/runtest/run_make.rs
+++ b/src/tools/compiletest/src/runtest/run_make.rs
@@ -9,168 +9,6 @@ use crate::util::{copy_dir_all, dylib_env_var};
 
 impl TestCx<'_> {
     pub(super) fn run_rmake_test(&self) {
-        let test_dir = &self.testpaths.file;
-        if test_dir.join("rmake.rs").exists() {
-            self.run_rmake_v2_test();
-        } else if test_dir.join("Makefile").exists() {
-            self.run_rmake_legacy_test();
-        } else {
-            self.fatal("failed to find either `rmake.rs` or `Makefile`")
-        }
-    }
-
-    fn run_rmake_legacy_test(&self) {
-        let cwd = env::current_dir().unwrap();
-
-        // FIXME(Zalathar): This should probably be `output_base_dir` to avoid
-        // an unnecessary extra subdirectory, but since legacy Makefile tests
-        // are hopefully going away, it seems safer to leave this perilous code
-        // as-is until it can all be deleted.
-        let tmpdir = cwd.join(self.output_base_name());
-        ignore_not_found(|| recursive_remove(&tmpdir)).unwrap();
-
-        fs::create_dir_all(&tmpdir).unwrap();
-
-        let host = &self.config.host;
-        let make = if host.contains("dragonfly")
-            || host.contains("freebsd")
-            || host.contains("netbsd")
-            || host.contains("openbsd")
-            || host.contains("aix")
-        {
-            "gmake"
-        } else {
-            "make"
-        };
-
-        let mut cmd = Command::new(make);
-        cmd.current_dir(&self.testpaths.file)
-            .stdout(Stdio::piped())
-            .stderr(Stdio::piped())
-            .env("TARGET", &self.config.target)
-            .env("PYTHON", &self.config.python)
-            .env("S", &self.config.src_root)
-            .env("RUST_BUILD_STAGE", &self.config.stage_id)
-            .env("RUSTC", cwd.join(&self.config.rustc_path))
-            .env("TMPDIR", &tmpdir)
-            .env("LD_LIB_PATH_ENVVAR", dylib_env_var())
-            .env("HOST_RPATH_DIR", cwd.join(&self.config.compile_lib_path))
-            .env("TARGET_RPATH_DIR", cwd.join(&self.config.run_lib_path))
-            .env("LLVM_COMPONENTS", &self.config.llvm_components)
-            // We for sure don't want these tests to run in parallel, so make
-            // sure they don't have access to these vars if we run via `make`
-            // at the top level
-            .env_remove("MAKEFLAGS")
-            .env_remove("MFLAGS")
-            .env_remove("CARGO_MAKEFLAGS");
-
-        if let Some(ref cargo) = self.config.cargo_path {
-            cmd.env("CARGO", cwd.join(cargo));
-        }
-
-        if let Some(ref rustdoc) = self.config.rustdoc_path {
-            cmd.env("RUSTDOC", cwd.join(rustdoc));
-        }
-
-        if let Some(ref node) = self.config.nodejs {
-            cmd.env("NODE", node);
-        }
-
-        if let Some(ref linker) = self.config.target_linker {
-            cmd.env("RUSTC_LINKER", linker);
-        }
-
-        if let Some(ref clang) = self.config.run_clang_based_tests_with {
-            cmd.env("CLANG", clang);
-        }
-
-        if let Some(ref filecheck) = self.config.llvm_filecheck {
-            cmd.env("LLVM_FILECHECK", filecheck);
-        }
-
-        if let Some(ref llvm_bin_dir) = self.config.llvm_bin_dir {
-            cmd.env("LLVM_BIN_DIR", llvm_bin_dir);
-        }
-
-        if let Some(ref remote_test_client) = self.config.remote_test_client {
-            cmd.env("REMOTE_TEST_CLIENT", remote_test_client);
-        }
-
-        // We don't want RUSTFLAGS set from the outside to interfere with
-        // compiler flags set in the test cases:
-        cmd.env_remove("RUSTFLAGS");
-
-        // Use dynamic musl for tests because static doesn't allow creating dylibs
-        if self.config.host.contains("musl") {
-            cmd.env("RUSTFLAGS", "-Ctarget-feature=-crt-static").env("IS_MUSL_HOST", "1");
-        }
-
-        if self.config.bless {
-            cmd.env("RUSTC_BLESS_TEST", "--bless");
-            // Assume this option is active if the environment variable is "defined", with _any_ value.
-            // As an example, a `Makefile` can use this option by:
-            //
-            //   ifdef RUSTC_BLESS_TEST
-            //       cp "$(TMPDIR)"/actual_something.ext expected_something.ext
-            //   else
-            //       $(DIFF) expected_something.ext "$(TMPDIR)"/actual_something.ext
-            //   endif
-        }
-
-        if self.config.target.contains("msvc") && !self.config.cc.is_empty() {
-            // We need to pass a path to `lib.exe`, so assume that `cc` is `cl.exe`
-            // and that `lib.exe` lives next to it.
-            let lib = Path::new(&self.config.cc).parent().unwrap().join("lib.exe");
-
-            // MSYS doesn't like passing flags of the form `/foo` as it thinks it's
-            // a path and instead passes `C:\msys64\foo`, so convert all
-            // `/`-arguments to MSVC here to `-` arguments.
-            let cflags = self
-                .config
-                .cflags
-                .split(' ')
-                .map(|s| s.replace("/", "-"))
-                .collect::<Vec<_>>()
-                .join(" ");
-            let cxxflags = self
-                .config
-                .cxxflags
-                .split(' ')
-                .map(|s| s.replace("/", "-"))
-                .collect::<Vec<_>>()
-                .join(" ");
-
-            cmd.env("IS_MSVC", "1")
-                .env("IS_WINDOWS", "1")
-                .env("MSVC_LIB", format!("'{}' -nologo", lib.display()))
-                .env("MSVC_LIB_PATH", format!("{}", lib.display()))
-                .env("CC", format!("'{}' {}", self.config.cc, cflags))
-                .env("CXX", format!("'{}' {}", &self.config.cxx, cxxflags));
-        } else {
-            cmd.env("CC", format!("{} {}", self.config.cc, self.config.cflags))
-                .env("CXX", format!("{} {}", self.config.cxx, self.config.cxxflags))
-                .env("AR", &self.config.ar);
-
-            if self.config.target.contains("windows") {
-                cmd.env("IS_WINDOWS", "1");
-            }
-        }
-
-        let (output, truncated) =
-            self.read2_abbreviated(cmd.spawn().expect("failed to spawn `make`"));
-        if !output.status.success() {
-            let res = ProcRes {
-                status: output.status,
-                stdout: String::from_utf8_lossy(&output.stdout).into_owned(),
-                stderr: String::from_utf8_lossy(&output.stderr).into_owned(),
-                truncated,
-                cmdline: format!("{:?}", cmd),
-            };
-            self.fatal_proc_rec("make failed", &res);
-        }
-    }
-
-    fn run_rmake_v2_test(&self) {
         // For `run-make` V2, we need to perform 2 steps to build and run a `run-make` V2 recipe
         // (`rmake.rs`) to run the actual tests. The support library is already built as a tool rust
         // library and is available under
@@ -192,8 +30,6 @@ impl TestCx<'_> {
         // recipes to `remove_dir_all($TMPDIR)` without running into issues related trying to remove
         // a currently running executable because the recipe executable is not under the
         // `rmake_out/` directory.
-        //
-        // This setup intentionally diverges from legacy Makefile run-make tests.
         let base_dir = self.output_base_dir();
         ignore_not_found(|| recursive_remove(&base_dir)).unwrap();
 
diff --git a/src/tools/run-make-support/src/artifact_names.rs b/src/tools/run-make-support/src/artifact_names.rs
index 0d7b5cb98388e..8968f831542e6 100644
--- a/src/tools/run-make-support/src/artifact_names.rs
+++ b/src/tools/run-make-support/src/artifact_names.rs
@@ -8,23 +8,6 @@ use crate::targets::is_msvc;
 /// Construct the static library name based on the target.
 #[must_use]
 pub fn static_lib_name(name: &str) -> String {
-    // See tools.mk (irrelevant lines omitted):
-    //
-    // ```makefile
-    // ifeq ($(UNAME),Darwin)
-    //     STATICLIB = $(TMPDIR)/lib$(1).a
-    // else
-    //     ifdef IS_WINDOWS
-    //         ifdef IS_MSVC
-    //             STATICLIB = $(TMPDIR)/$(1).lib
-    //         else
-    //             STATICLIB = $(TMPDIR)/lib$(1).a
-    //         endif
-    //     else
-    //         STATICLIB = $(TMPDIR)/lib$(1).a
-    //     endif
-    // endif
-    // ```
     assert!(!name.contains(char::is_whitespace), "static library name cannot contain whitespace");
 
     if is_msvc() { format!("{name}.lib") } else { format!("lib{name}.a") }
diff --git a/src/tools/run-make-support/src/external_deps/c_cxx_compiler/cc.rs b/src/tools/run-make-support/src/external_deps/c_cxx_compiler/cc.rs
index becb91ae989cc..0e6d6ea6075d2 100644
--- a/src/tools/run-make-support/src/external_deps/c_cxx_compiler/cc.rs
+++ b/src/tools/run-make-support/src/external_deps/c_cxx_compiler/cc.rs
@@ -80,17 +80,6 @@ impl Cc {
 
     /// Specify `-o` or `-Fe`/`-Fo` depending on platform/compiler.
     pub fn out_exe(&mut self, name: &str) -> &mut Self {
-        // Ref: tools.mk (irrelevant lines omitted):
-        //
-        // ```makefile
-        // ifdef IS_MSVC
-        //     OUT_EXE=-Fe:`cygpath -w $(TMPDIR)/$(call BIN,$(1))` \
-        //         -Fo:`cygpath -w $(TMPDIR)/$(1).obj`
-        // else
-        //     OUT_EXE=-o $(TMPDIR)/$(1)
-        // endif
-        // ```
-
         let mut path = std::path::PathBuf::from(name);
 
         if is_msvc() {
diff --git a/src/tools/run-make-support/src/external_deps/c_cxx_compiler/extras.rs b/src/tools/run-make-support/src/external_deps/c_cxx_compiler/extras.rs
index 49210d75e063f..ca6ab3275c4d6 100644
--- a/src/tools/run-make-support/src/external_deps/c_cxx_compiler/extras.rs
+++ b/src/tools/run-make-support/src/external_deps/c_cxx_compiler/extras.rs
@@ -2,36 +2,6 @@ use crate::{is_msvc, is_windows, uname};
 
 /// `EXTRACFLAGS`
 pub fn extra_c_flags() -> Vec<&'static str> {
-    // Adapted from tools.mk (trimmed):
-    //
-    // ```makefile
-    // ifdef IS_WINDOWS
-    //     ifdef IS_MSVC
-    //         EXTRACFLAGS := ws2_32.lib userenv.lib advapi32.lib bcrypt.lib ntdll.lib synchronization.lib
-    //     else
-    //         EXTRACFLAGS := -lws2_32 -luserenv -lbcrypt -lntdll -lsynchronization
-    //     endif
-    // else
-    //     ifeq ($(UNAME),Darwin)
-    //         EXTRACFLAGS := -lresolv
-    //     else
-    //         ifeq ($(UNAME),FreeBSD)
-    //             EXTRACFLAGS := -lm -lpthread -lgcc_s
-    //         else
-    //             ifeq ($(UNAME),SunOS)
-    //                 EXTRACFLAGS := -lm -lpthread -lposix4 -lsocket -lresolv
-    //             else
-    //                 ifeq ($(UNAME),OpenBSD)
-    //                     EXTRACFLAGS := -lm -lpthread -lc++abi
-    //                 else
-    //                     EXTRACFLAGS := -lm -lrt -ldl -lpthread
-    //                 endif
-    //             endif
-    //         endif
-    //     endif
-    // endif
-    // ```
-
     if is_windows() {
         if is_msvc() {
             vec![
@@ -60,31 +30,6 @@ pub fn extra_c_flags() -> Vec<&'static str> {
 
 /// `EXTRACXXFLAGS`
 pub fn extra_cxx_flags() -> Vec<&'static str> {
-    // Adapted from tools.mk (trimmed):
-    //
-    // ```makefile
-    // ifdef IS_WINDOWS
-    //     ifdef IS_MSVC
-    //     else
-    //         EXTRACXXFLAGS := -lstdc++
-    //     endif
-    // else
-    //     ifeq ($(UNAME),Darwin)
-    //         EXTRACXXFLAGS := -lc++
-    //     else
-    //         ifeq ($(UNAME),FreeBSD)
-    //         else
-    //             ifeq ($(UNAME),SunOS)
-    //             else
-    //                 ifeq ($(UNAME),OpenBSD)
-    //                 else
-    //                     EXTRACXXFLAGS := -lstdc++
-    //                 endif
-    //             endif
-    //         endif
-    //     endif
-    // endif
-    // ```
     if is_windows() {
         if is_msvc() { vec![] } else { vec!["-lstdc++"] }
     } else {
diff --git a/src/tools/run-make-support/src/external_deps/rustc.rs b/src/tools/run-make-support/src/external_deps/rustc.rs
index cb2bd83815a35..0e2239147f122 100644
--- a/src/tools/run-make-support/src/external_deps/rustc.rs
+++ b/src/tools/run-make-support/src/external_deps/rustc.rs
@@ -365,31 +365,6 @@ impl Rustc {
 
     /// `EXTRARSCXXFLAGS`
     pub fn extra_rs_cxx_flags(&mut self) -> &mut Self {
-        // Adapted from tools.mk (trimmed):
-        //
-        // ```makefile
-        // ifdef IS_WINDOWS
-        //     ifdef IS_MSVC
-        //     else
-        //         EXTRARSCXXFLAGS := -lstatic:-bundle=stdc++
-        //     endif
-        // else
-        //     ifeq ($(UNAME),Darwin)
-        //         EXTRARSCXXFLAGS := -lc++
-        //     else
-        //         ifeq ($(UNAME),FreeBSD)
-        //         else
-        //             ifeq ($(UNAME),SunOS)
-        //             else
-        //                 ifeq ($(UNAME),OpenBSD)
-        //                 else
-        //                     EXTRARSCXXFLAGS := -lstdc++
-        //                 endif
-        //             endif
-        //         endif
-        //     endif
-        // endif
-        // ```
         if is_windows() {
             // So this is a bit hacky: we can't use the DLL version of libstdc++ because
             // it pulls in the DLL version of libgcc, which means that we end up with 2
diff --git a/src/tools/tidy/src/allowed_run_make_makefiles.txt b/src/tools/tidy/src/allowed_run_make_makefiles.txt
deleted file mode 100644
index e69de29bb2d1d..0000000000000
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index 1e7eb82b83e98..9f6d563166e2b 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -79,7 +79,6 @@ pub(crate) mod iter_header;
 pub mod known_bug;
 pub mod mir_opt_tests;
 pub mod pal;
-pub mod run_make_tests;
 pub mod rustdoc_css_themes;
 pub mod rustdoc_gui_tests;
 pub mod rustdoc_templates;
diff --git a/src/tools/tidy/src/main.rs b/src/tools/tidy/src/main.rs
index 13a558fea48ea..1d8514ef4c9c4 100644
--- a/src/tools/tidy/src/main.rs
+++ b/src/tools/tidy/src/main.rs
@@ -103,8 +103,6 @@ fn main() {
         check!(tests_revision_unpaired_stdout_stderr, &tests_path);
         check!(debug_artifacts, &tests_path);
         check!(ui_tests, &root_path, bless);
-        // FIXME(jieyouxu): remove this check once all run-make tests are ported over to rmake.rs.
-        check!(run_make_tests, &tests_path, &src_path, bless);
         check!(mir_opt_tests, &tests_path, bless);
         check!(rustdoc_gui_tests, &tests_path);
         check!(rustdoc_css_themes, &librustdoc_path);
diff --git a/src/tools/tidy/src/run_make_tests.rs b/src/tools/tidy/src/run_make_tests.rs
deleted file mode 100644
index 8d1767878378c..0000000000000
--- a/src/tools/tidy/src/run_make_tests.rs
+++ /dev/null
@@ -1,104 +0,0 @@
-//! Tidy check to ensure that no new Makefiles are added under `tests/run-make/`.
-
-use std::collections::BTreeSet;
-use std::fs::File;
-use std::io::Write;
-use std::path::{Path, PathBuf};
-
-pub fn check(tests_path: &Path, src_path: &Path, bless: bool, bad: &mut bool) {
-    let mut is_sorted = true;
-
-    let allowed_makefiles = {
-        let mut total_lines = 0;
-        let mut prev_line = "";
-        let allowed_makefiles: BTreeSet<&str> = include_str!("allowed_run_make_makefiles.txt")
-            .lines()
-            .map(|line| {
-                total_lines += 1;
-
-                if prev_line > line {
-                    is_sorted = false;
-                }
-
-                prev_line = line;
-
-                line
-            })
-            .collect();
-
-        if !is_sorted && !bless {
-            tidy_error!(
-                bad,
-                "`src/tools/tidy/src/allowed_run_make_makefiles.txt` is not in order, likely \
-                because you modified it manually, please only update it with command \
-                `x test tidy --bless`"
-            );
-        }
-        if allowed_makefiles.len() != total_lines {
-            tidy_error!(
-                bad,
-                "`src/tools/tidy/src/allowed_run_make_makefiles.txt` contains duplicate entries, \
-                likely because you modified it manually, please only update it with command \
-                `x test tidy --bless`"
-            );
-        }
-
-        allowed_makefiles
-    };
-
-    let mut remaining_makefiles = allowed_makefiles.clone();
-
-    crate::walk::walk_no_read(
-        &[tests_path.join("run-make").as_ref()],
-        |_, _| false,
-        &mut |entry| {
-            if entry.file_type().map_or(true, |t| t.is_dir()) {
-                return;
-            }
-
-            if entry.file_name().to_str().map_or(true, |f| f != "Makefile") {
-                return;
-            }
-
-            let makefile_path = entry.path().strip_prefix(&tests_path).unwrap();
-            let makefile_path = makefile_path.to_str().unwrap().replace('\\', "/");
-
-            if !remaining_makefiles.remove(makefile_path.as_str()) {
-                tidy_error!(
-                    bad,
-                    "found run-make Makefile not permitted in \
-                `src/tools/tidy/src/allowed_run_make_makefiles.txt`, please write new run-make \
-                tests with `rmake.rs` instead: {}",
-                    entry.path().display()
-                );
-            }
-        },
-    );
-
-    // If there are any expected Makefiles remaining, they were moved or deleted.
-    // Our data must remain up to date, so they must be removed from
-    // `src/tools/tidy/src/allowed_run_make_makefiles.txt`.
-    // This can be done automatically on --bless, or else a tidy error will be issued.
-    if bless && (!remaining_makefiles.is_empty() || !is_sorted) {
-        let tidy_src = src_path.join("tools").join("tidy").join("src");
-        let org_file_path = tidy_src.join("allowed_run_make_makefiles.txt");
-        let temp_file_path = tidy_src.join("blessed_allowed_run_make_makefiles.txt");
-        let mut temp_file = t!(File::create_new(&temp_file_path));
-        for file in allowed_makefiles.difference(&remaining_makefiles) {
-            t!(writeln!(temp_file, "{file}"));
-        }
-        t!(std::fs::rename(&temp_file_path, &org_file_path));
-    } else {
-        for file in remaining_makefiles {
-            let mut p = PathBuf::from(tests_path);
-            p.push(file);
-            tidy_error!(
-                bad,
-                "Makefile `{}` no longer exists and should be removed from the exclusions in \
-                `src/tools/tidy/src/allowed_run_make_makefiles.txt`, you can run `x test tidy --bless` to update \
-                the allow list",
-                p.display()
-            );
-        }
-    }
-}
diff --git a/tests/crashes/132981.rs b/tests/crashes/132981.rs
deleted file mode 100644
index 916c15592404c..0000000000000
--- a/tests/crashes/132981.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-//@ known-bug: #132981
-//@compile-flags: -Clink-dead-code=true --crate-type lib
-//@ only-x86_64
-//@ ignore-windows
-// The set of targets this crashes on is really fiddly, because it is deep in our ABI logic. It
-// crashes on x86_64-unknown-linux-gnu, and i686-pc-windows-msvc, but not on
-// x86_64-pc-windows-msvc. If you are trying to fix this crash, don't pay too much attention to the
-// directives.
-
-#![feature(rust_cold_cc)]
-pub extern "rust-cold" fn foo(_: [usize; 3]) {}
diff --git a/tests/run-make/README.md b/tests/run-make/README.md
index 4035990347389..5cdd2fdc523cf 100644
--- a/tests/run-make/README.md
+++ b/tests/run-make/README.md
@@ -1,32 +1,17 @@
 # The `run-make` test suite
 
-The `run-make` test suite contains tests which are the most flexible out of all
-the [rust-lang/rust](https://github.com/rust-lang/rust) test suites. `run-make`
-tests can basically contain arbitrary code, and are supported by the
-[`run_make_support`] library.
+The `run-make` test suite contains tests which are the most flexible out of all the [rust-lang/rust](https://github.com/rust-lang/rust) test suites. `run-make` tests can basically contain arbitrary code, and are supported by the [`run_make_support`] library.
 
 ## Infrastructure
 
-There are two kinds of run-make tests:
+A `run-make` test is a test recipe source file `rmake.rs` accompanied by its parent directory (e.g. `tests/run-make/foo/rmake.rs` is the `foo` `run-make` test).
 
-1. The new `rmake.rs` version: this allows run-make tests to be written in Rust
-   (with `rmake.rs` as the main test file).
-2. The legacy `Makefile` version: this is what run-make tests were written with
-   before support for `rmake.rs` was introduced.
+The implementation for collecting and building the `rmake.rs` recipes are in [`src/tools/compiletest/src/runtest.rs`](../../src/tools/compiletest/src/runtest.rs), in `run_rmake_test`.
 
-The implementation for collecting and building the `rmake.rs` recipes (or
-`Makefile`s) are in
-[`src/tools/compiletest/src/runtest.rs`](../../src/tools/compiletest/src/runtest.rs),
-in `run_rmake_v2_test` and `run_rmake_legacy_test`.
-
-### Rust-based `run-make` tests: `rmake.rs`
-
-The setup for the `rmake.rs` version is a 3-stage process:
+The setup for the `rmake.rs` can be summarized as a 3-stage process:
 
 1. First, we build the [`run_make_support`] library in bootstrap as a tool lib.
-2. Then, we compile the `rmake.rs` "recipe" linking the support library and its
-   dependencies in, and provide a bunch of env vars. We setup a directory
-   structure within `build/<target>/test/run-make/`
+2. Then, we compile the `rmake.rs` "recipe" linking the support library and its dependencies in, and provide a bunch of env vars. We setup a directory structure within `build/<target>/test/run-make/`
 
    ```
    <test-name>/
@@ -34,15 +19,8 @@ The setup for the `rmake.rs` version is a 3-stage process:
        rmake_out/             # sources from test sources copied over
    ```
 
-   and copy non-`rmake.rs` input support files over to `rmake_out/`. The
-   support library is made available as an [*extern prelude*][extern_prelude].
-3. Finally, we run the recipe binary and set `rmake_out/` as the working
-   directory.
+   and copy non-`rmake.rs` input support files over to `rmake_out/`. The support library is made available as an [*extern prelude*][extern_prelude].
+3. Finally, we run the recipe binary and set `rmake_out/` as the working directory.
 
 [`run_make_support`]: ../../src/tools/run-make-support
 [extern_prelude]: https://doc.rust-lang.org/reference/names/preludes.html#extern-prelude
-
-### Formatting
-
-Note that files under `tests/` are not formatted by `./x fmt`,
-use `rustfmt tests/path/to/file.rs` to format a specific file if desired.
diff --git a/tests/run-make/repr128-dwarf/main.rs b/tests/run-make/repr128-dwarf/main.rs
index 57923a8386db9..9842ab4a3426f 100644
--- a/tests/run-make/repr128-dwarf/main.rs
+++ b/tests/run-make/repr128-dwarf/main.rs
@@ -19,8 +19,33 @@ pub enum I128Enum {
     I128D = i128::MAX.to_le(),
 }
 
+#[cfg(not(old_llvm))]
+#[repr(u128)]
+pub enum U128VariantEnum {
+    VariantU128A(u8) = 0_u128.to_le(),
+    VariantU128B = 1_u128.to_le(),
+    VariantU128C = (u64::MAX as u128 + 1).to_le(),
+    VariantU128D = u128::MAX.to_le(),
+}
+
+#[cfg(not(old_llvm))]
+#[repr(i128)]
+pub enum I128VariantEnum {
+    VariantI128A(u8) = 0_i128.to_le(),
+    VariantI128B = (-1_i128).to_le(),
+    VariantI128C = i128::MIN.to_le(),
+    VariantI128D = i128::MAX.to_le(),
+}
+
 pub fn f(_: U128Enum, _: I128Enum) {}
 
+#[cfg(not(old_llvm))]
+pub fn g(_: U128VariantEnum, _: I128VariantEnum) {}
+
 fn main() {
     f(U128Enum::U128A, I128Enum::I128A);
+    #[cfg(not(old_llvm))]
+    {
+        g(U128VariantEnum::VariantU128A(1), I128VariantEnum::VariantI128A(2));
+    }
 }
diff --git a/tests/run-make/repr128-dwarf/rmake.rs b/tests/run-make/repr128-dwarf/rmake.rs
index 2fd54c186b934..15eb186717f6d 100644
--- a/tests/run-make/repr128-dwarf/rmake.rs
+++ b/tests/run-make/repr128-dwarf/rmake.rs
@@ -5,13 +5,32 @@ use std::collections::HashMap;
 use std::path::PathBuf;
 use std::rc::Rc;
 
+use gimli::read::DebuggingInformationEntry;
 use gimli::{AttributeValue, EndianRcSlice, Reader, RunTimeEndian};
 use object::{Object, ObjectSection};
 use run_make_support::{gimli, object, rfs, rustc};
 
 fn main() {
+    // Before LLVM 20, 128-bit enums with variants didn't emit debuginfo correctly.
+    // This check can be removed once Rust no longer supports LLVM 18 and 19.
+    let llvm_version = rustc()
+        .verbose()
+        .arg("--version")
+        .run()
+        .stdout_utf8()
+        .lines()
+        .filter_map(|line| line.strip_prefix("LLVM version: "))
+        .map(|version| version.split(".").next().unwrap().parse::<u32>().unwrap())
+        .next()
+        .unwrap();
+    let is_old_llvm = llvm_version < 20;
+
     let output = PathBuf::from("repr128");
-    rustc().input("main.rs").output(&output).arg("-Cdebuginfo=2").run();
+    let mut rustc = rustc();
+    if is_old_llvm {
+        rustc.cfg("old_llvm");
+    }
+    rustc.input("main.rs").output(&output).arg("-Cdebuginfo=2").run();
     // Mach-O uses packed debug info
     let dsym_location = output
         .with_extension("dSYM")
@@ -29,7 +48,8 @@ fn main() {
     })
     .unwrap();
     let mut iter = dwarf.units();
-    let mut still_to_find = HashMap::from([
+
+    let mut enumerators_to_find = HashMap::from([
         ("U128A", 0_u128),
         ("U128B", 1_u128),
         ("U128C", u64::MAX as u128 + 1),
@@ -39,35 +59,88 @@ fn main() {
         ("I128C", i128::MIN as u128),
         ("I128D", i128::MAX as u128),
     ]);
+    let mut variants_to_find = HashMap::from([
+        ("VariantU128A", 0_u128),
+        ("VariantU128B", 1_u128),
+        ("VariantU128C", u64::MAX as u128 + 1),
+        ("VariantU128D", u128::MAX),
+        ("VariantI128A", 0_i128 as u128),
+        ("VariantI128B", (-1_i128) as u128),
+        ("VariantI128C", i128::MIN as u128),
+        ("VariantI128D", i128::MAX as u128),
+    ]);
+
     while let Some(header) = iter.next().unwrap() {
         let unit = dwarf.unit(header).unwrap();
         let mut cursor = unit.entries();
+
+        let get_name = |entry: &DebuggingInformationEntry<'_, '_, _>| {
+            let name = dwarf
+                .attr_string(
+                    &unit,
+                    entry.attr(gimli::constants::DW_AT_name).unwrap().unwrap().value(),
+                )
+                .unwrap();
+            name.to_string().unwrap().to_string()
+        };
+
         while let Some((_, entry)) = cursor.next_dfs().unwrap() {
-            if entry.tag() == gimli::constants::DW_TAG_enumerator {
-                let name = dwarf
-                    .attr_string(
-                        &unit,
-                        entry.attr(gimli::constants::DW_AT_name).unwrap().unwrap().value(),
-                    )
-                    .unwrap();
-                let name = name.to_string().unwrap();
-                if let Some(expected) = still_to_find.remove(name.as_ref()) {
-                    match entry.attr(gimli::constants::DW_AT_const_value).unwrap().unwrap().value()
+            match entry.tag() {
+                gimli::constants::DW_TAG_variant if !is_old_llvm => {
+                    let value = match entry
+                        .attr(gimli::constants::DW_AT_discr_value)
+                        .unwrap()
+                        .unwrap()
+                        .value()
                     {
-                        AttributeValue::Block(value) => {
-                            assert_eq!(
-                                value.to_slice().unwrap(),
-                                expected.to_le_bytes().as_slice(),
-                                "{name}"
-                            );
+                        AttributeValue::Block(value) => value.to_slice().unwrap().to_vec(),
+                        value => panic!("unexpected DW_AT_discr_value of {value:?}"),
+                    };
+                    // The `DW_TAG_member` that is a child of `DW_TAG_variant` will contain the
+                    // variant's name.
+                    let Some((1, child_entry)) = cursor.next_dfs().unwrap() else {
+                        panic!("Missing child of DW_TAG_variant");
+                    };
+                    assert_eq!(child_entry.tag(), gimli::constants::DW_TAG_member);
+                    let name = get_name(child_entry);
+                    if let Some(expected) = variants_to_find.remove(name.as_str()) {
+                        // This test uses LE byte order is used for consistent values across
+                        // architectures.
+                        assert_eq!(value.as_slice(), expected.to_le_bytes().as_slice(), "{name}");
+                    }
+                }
+
+                gimli::constants::DW_TAG_enumerator => {
+                    let name = get_name(entry);
+                    if let Some(expected) = enumerators_to_find.remove(name.as_str()) {
+                        match entry
+                            .attr(gimli::constants::DW_AT_const_value)
+                            .unwrap()
+                            .unwrap()
+                            .value()
+                        {
+                            AttributeValue::Block(value) => {
+                                // This test uses LE byte order is used for consistent values across
+                                // architectures.
+                                assert_eq!(
+                                    value.to_slice().unwrap(),
+                                    expected.to_le_bytes().as_slice(),
+                                    "{name}"
+                                );
+                            }
+                            value => panic!("{name}: unexpected DW_AT_const_value of {value:?}"),
                         }
-                        value => panic!("{name}: unexpected DW_AT_const_value of {value:?}"),
                     }
                 }
+
+                _ => {}
             }
         }
     }
-    if !still_to_find.is_empty() {
-        panic!("Didn't find debug entries for {still_to_find:?}");
+    if !enumerators_to_find.is_empty() {
+        panic!("Didn't find debug enumerator entries for {enumerators_to_find:?}");
+    }
+    if !is_old_llvm && !variants_to_find.is_empty() {
+        panic!("Didn't find debug variant entries for {variants_to_find:?}");
     }
 }
diff --git a/tests/run-make/tools.mk b/tests/run-make/tools.mk
deleted file mode 100644
index b1e872a202af5..0000000000000
--- a/tests/run-make/tools.mk
+++ /dev/null
@@ -1,209 +0,0 @@
-# These deliberately use `=` and not `:=` so that client makefiles can
-# augment HOST_RPATH_DIR / TARGET_RPATH_DIR.
-HOST_RPATH_ENV = \
-    $(LD_LIB_PATH_ENVVAR)="$(TMPDIR):$(HOST_RPATH_DIR):$($(LD_LIB_PATH_ENVVAR))"
-TARGET_RPATH_ENV = \
-    $(LD_LIB_PATH_ENVVAR)="$(TMPDIR):$(TARGET_RPATH_DIR):$($(LD_LIB_PATH_ENVVAR))"
-
-RUSTC_ORIGINAL := $(RUSTC)
-BARE_RUSTC := $(HOST_RPATH_ENV) '$(RUSTC)'
-BARE_RUSTDOC := $(HOST_RPATH_ENV) '$(RUSTDOC)'
-RUSTC := $(BARE_RUSTC) --out-dir $(TMPDIR) -L $(TMPDIR) $(RUSTFLAGS) -Ainternal_features
-RUSTDOC := $(BARE_RUSTDOC) -L $(TARGET_RPATH_DIR)
-ifdef RUSTC_LINKER
-RUSTC := $(RUSTC) -Clinker='$(RUSTC_LINKER)'
-RUSTDOC := $(RUSTDOC) -Clinker='$(RUSTC_LINKER)'
-endif
-#CC := $(CC) -L $(TMPDIR)
-HTMLDOCCK := '$(PYTHON)' '$(S)/src/etc/htmldocck.py'
-CGREP := "$(S)/src/etc/cat-and-grep.sh"
-
-# diff with common flags for multi-platform diffs against text output
-DIFF := diff -u --strip-trailing-cr
-
-# With RUSTC_TEST_OP you can elegantly support blessing of run-make tests. Do
-# like this in a Makefile recipe:
-#
-#   "$(TMPDIR)"/your-test > "$(TMPDIR)"/your-test.run.stdout
-#   $(RUSTC_TEST_OP) "$(TMPDIR)"/your-test.run.stdout your-test.run.stdout
-#
-# When running the test normally with
-#
-#   ./x test tests/run-make/your-test
-#
-# the actual output will be diffed against the expected output. When running in
-# bless-mode with
-#
-#   ./x test --bless tests/run-make/your-test
-#
-# the actual output will be blessed as the expected output.
-ifdef RUSTC_BLESS_TEST
-    RUSTC_TEST_OP = cp
-else
-    RUSTC_TEST_OP = $(DIFF)
-endif
-
-# Some of the Rust CI platforms use `/bin/dash` to run `shell` script in
-# Makefiles. Other platforms, including many developer platforms, default to
-# `/bin/bash`. (In many cases, `make` is actually using `/bin/sh`, but `sh`
-# is configured to execute one or the other shell binary). `dash` features
-# support only a small subset of `bash` features, so `dash` can be thought of as
-# the lowest common denominator, and tests should be validated against `dash`
-# whenever possible. Most developer platforms include `/bin/dash`, but to ensure
-# tests still work when `/bin/dash`, if not available, this `SHELL` override is
-# conditional:
-ifndef IS_WINDOWS # dash interprets backslashes in executable paths incorrectly
-ifneq (,$(wildcard /bin/dash))
-SHELL := /bin/dash
-endif
-endif
-
-# This is the name of the binary we will generate and run; use this
-# e.g. for `$(CC) -o $(RUN_BINFILE)`.
-RUN_BINFILE = $(TMPDIR)/$(1)
-
-# Invoke the generated binary on the remote machine if compiletest was
-# configured to use a remote test device, otherwise run it on the current host.
-ifdef REMOTE_TEST_CLIENT
-# FIXME: if a test requires additional files, this will need to be changed to
-# also push them (by changing the 0 to the number of additional files, and
-# providing the path of the additional files as the last arguments).
-EXECUTE = $(REMOTE_TEST_CLIENT) run 0 $(RUN_BINFILE)
-else
-EXECUTE = $(RUN_BINFILE)
-endif
-
-# RUN and FAIL are basic way we will invoke the generated binary.  On
-# non-windows platforms, they set the LD_LIBRARY_PATH environment
-# variable before running the binary.
-
-RLIB_GLOB = lib$(1)*.rlib
-BIN = $(1)
-
-UNAME = $(shell uname)
-
-ifeq ($(UNAME),Darwin)
-RUN = $(TARGET_RPATH_ENV) $(EXECUTE)
-FAIL = $(TARGET_RPATH_ENV) $(EXECUTE) && exit 1 || exit 0
-DYLIB_GLOB = lib$(1)*.dylib
-DYLIB = $(TMPDIR)/lib$(1).dylib
-STATICLIB = $(TMPDIR)/lib$(1).a
-STATICLIB_GLOB = lib$(1)*.a
-else
-ifdef IS_WINDOWS
-RUN = PATH="$(PATH):$(TARGET_RPATH_DIR)" $(EXECUTE)
-FAIL = PATH="$(PATH):$(TARGET_RPATH_DIR)" $(EXECUTE) && exit 1 || exit 0
-DYLIB_GLOB = $(1)*.dll
-DYLIB = $(TMPDIR)/$(1).dll
-ifdef IS_MSVC
-STATICLIB = $(TMPDIR)/$(1).lib
-STATICLIB_GLOB = $(1)*.lib
-else
-IMPLIB = $(TMPDIR)/lib$(1).dll.a
-STATICLIB = $(TMPDIR)/lib$(1).a
-STATICLIB_GLOB = lib$(1)*.a
-endif
-BIN = $(1).exe
-LLVM_FILECHECK := $(shell cygpath -u "$(LLVM_FILECHECK)")
-else
-RUN = $(TARGET_RPATH_ENV) $(EXECUTE)
-FAIL = $(TARGET_RPATH_ENV) $(EXECUTE) && exit 1 || exit 0
-DYLIB_GLOB = lib$(1)*.so
-DYLIB = $(TMPDIR)/lib$(1).so
-STATICLIB = $(TMPDIR)/lib$(1).a
-STATICLIB_GLOB = lib$(1)*.a
-endif
-endif
-
-ifdef IS_MSVC
-COMPILE_OBJ = $(CC) -c -Fo:`cygpath -w $(1)` $(2)
-COMPILE_OBJ_CXX = $(CXX) -EHs -c -Fo:`cygpath -w $(1)` $(2)
-NATIVE_STATICLIB_FILE = $(1).lib
-NATIVE_STATICLIB = $(TMPDIR)/$(call NATIVE_STATICLIB_FILE,$(1))
-OUT_EXE=-Fe:`cygpath -w $(TMPDIR)/$(call BIN,$(1))` \
-	-Fo:`cygpath -w $(TMPDIR)/$(1).obj`
-else
-COMPILE_OBJ = $(CC) -v -c -o $(1) $(2)
-COMPILE_OBJ_CXX = $(CXX) -c -o $(1) $(2)
-NATIVE_STATICLIB_FILE = lib$(1).a
-NATIVE_STATICLIB = $(call STATICLIB,$(1))
-OUT_EXE=-o $(TMPDIR)/$(1)
-endif
-
-
-# Extra flags needed to compile a working executable with the standard library
-ifdef IS_WINDOWS
-ifdef IS_MSVC
-	EXTRACFLAGS := ws2_32.lib userenv.lib advapi32.lib bcrypt.lib ntdll.lib synchronization.lib
-else
-	EXTRACFLAGS := -lws2_32 -luserenv -lbcrypt -lntdll -lsynchronization
-	EXTRACXXFLAGS := -lstdc++
-	# So this is a bit hacky: we can't use the DLL version of libstdc++ because
-	# it pulls in the DLL version of libgcc, which means that we end up with 2
-	# instances of the DW2 unwinding implementation. This is a problem on
-	# i686-pc-windows-gnu because each module (DLL/EXE) needs to register its
-	# unwind information with the unwinding implementation, and libstdc++'s
-	# __cxa_throw won't see the unwinding info we registered with our statically
-	# linked libgcc.
-	#
-	# Now, simply statically linking libstdc++ would fix this problem, except
-	# that it is compiled with the expectation that pthreads is dynamically
-	# linked as a DLL and will fail to link with a statically linked libpthread.
-	#
-	# So we end up with the following hack: we link use static:-bundle to only
-	# link the parts of libstdc++ that we actually use, which doesn't include
-	# the dependency on the pthreads DLL.
-	EXTRARSCXXFLAGS := -l static:-bundle=stdc++
-endif
-else
-ifeq ($(UNAME),Darwin)
-	EXTRACFLAGS := -lresolv
-	EXTRACXXFLAGS := -lc++
-	EXTRARSCXXFLAGS := -lc++
-else
-ifeq ($(UNAME),FreeBSD)
-	EXTRACFLAGS := -lm -lpthread -lgcc_s
-else
-ifeq ($(UNAME),SunOS)
-	EXTRACFLAGS := -lm -lpthread -lposix4 -lsocket -lresolv
-else
-ifeq ($(UNAME),OpenBSD)
-	EXTRACFLAGS := -lm -lpthread -lc++abi
-	RUSTC := $(RUSTC) -C linker="$(word 1,$(CC:ccache=))"
-else
-	EXTRACFLAGS := -lm -lrt -ldl -lpthread
-	EXTRACXXFLAGS := -lstdc++
-	EXTRARSCXXFLAGS := -lstdc++
-endif
-endif
-endif
-endif
-endif
-
-REMOVE_DYLIBS     = rm $(TMPDIR)/$(call DYLIB_GLOB,$(1))
-REMOVE_RLIBS      = rm $(TMPDIR)/$(call RLIB_GLOB,$(1))
-
-%.a: %.o
-	$(AR) crus $@ $<
-ifdef IS_MSVC
-%.lib: lib%.o
-	$(MSVC_LIB) -out:`cygpath -w $@` $<
-else
-%.lib: lib%.o
-	$(AR) crus $@ $<
-endif
-%.dylib: %.o
-	$(CC) -dynamiclib -Wl,-dylib -o $@ $<
-%.so: %.o
-	$(CC) -o $@ $< -shared
-
-ifdef IS_MSVC
-%.dll: lib%.o
-	$(CC) $< -link -dll -out:`cygpath -w $@`
-else
-%.dll: lib%.o
-	$(CC) -o $@ $< -shared -Wl,--out-implib=$@.a
-endif
-
-$(TMPDIR)/lib%.o: %.c
-	$(call COMPILE_OBJ,$@,$<)
diff --git a/tests/rustdoc/impl-parts-crosscrate.rs b/tests/rustdoc/impl-parts-crosscrate.rs
index 49752ab75d512..631c8bb3eb318 100644
--- a/tests/rustdoc/impl-parts-crosscrate.rs
+++ b/tests/rustdoc/impl-parts-crosscrate.rs
@@ -5,7 +5,7 @@
 
 extern crate rustdoc_impl_parts_crosscrate;
 
-pub struct Bar<T> { t: T }
+pub struct Bar<T: Copy + Send> { t: T }
 
 // The output file is html embedded in javascript, so the html tags
 // aren't stripped by the processing script and we can't check for the
diff --git a/tests/rustdoc/impl-parts.rs b/tests/rustdoc/impl-parts.rs
index 820f51008a40c..4f281bfd63c83 100644
--- a/tests/rustdoc/impl-parts.rs
+++ b/tests/rustdoc/impl-parts.rs
@@ -3,7 +3,7 @@
 
 pub auto trait AnAutoTrait {}
 
-pub struct Foo<T> { field: T }
+pub struct Foo<T: Clone + Sync> { field: T }
 
 //@ has impl_parts/struct.Foo.html '//*[@class="impl"]//h3[@class="code-header"]' \
 //     "impl<T> !AnAutoTrait for Foo<T>where T: Sync + Clone,"
diff --git a/tests/ui/abi/c-zst.aarch64-darwin.stderr b/tests/ui/abi/c-zst.aarch64-darwin.stderr
index 57cc48aa9cf47..48fa2bf29bc40 100644
--- a/tests/ui/abi/c-zst.aarch64-darwin.stderr
+++ b/tests/ui/abi/c-zst.aarch64-darwin.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -38,7 +38,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/c-zst.powerpc-linux.stderr b/tests/ui/abi/c-zst.powerpc-linux.stderr
index 6738017673003..bfdf94c99007c 100644
--- a/tests/ui/abi/c-zst.powerpc-linux.stderr
+++ b/tests/ui/abi/c-zst.powerpc-linux.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -49,7 +49,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/c-zst.s390x-linux.stderr b/tests/ui/abi/c-zst.s390x-linux.stderr
index 6738017673003..bfdf94c99007c 100644
--- a/tests/ui/abi/c-zst.s390x-linux.stderr
+++ b/tests/ui/abi/c-zst.s390x-linux.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -49,7 +49,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/c-zst.sparc64-linux.stderr b/tests/ui/abi/c-zst.sparc64-linux.stderr
index 6738017673003..bfdf94c99007c 100644
--- a/tests/ui/abi/c-zst.sparc64-linux.stderr
+++ b/tests/ui/abi/c-zst.sparc64-linux.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -49,7 +49,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/c-zst.x86_64-linux.stderr b/tests/ui/abi/c-zst.x86_64-linux.stderr
index 57cc48aa9cf47..48fa2bf29bc40 100644
--- a/tests/ui/abi/c-zst.x86_64-linux.stderr
+++ b/tests/ui/abi/c-zst.x86_64-linux.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -38,7 +38,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/c-zst.x86_64-pc-windows-gnu.stderr b/tests/ui/abi/c-zst.x86_64-pc-windows-gnu.stderr
index 6738017673003..bfdf94c99007c 100644
--- a/tests/ui/abi/c-zst.x86_64-pc-windows-gnu.stderr
+++ b/tests/ui/abi/c-zst.x86_64-pc-windows-gnu.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -49,7 +49,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/debug.stderr b/tests/ui/abi/debug.stderr
index 5f73ff7d6bd58..2239ba0e5880a 100644
--- a/tests/ui/abi/debug.stderr
+++ b/tests/ui/abi/debug.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(test) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I8,
@@ -48,7 +48,7 @@ error: fn_abi_of(test) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I8,
@@ -107,7 +107,7 @@ error: fn_abi_of(TestFnPtr) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I8,
@@ -155,7 +155,7 @@ error: fn_abi_of(TestFnPtr) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I8,
@@ -205,7 +205,7 @@ error: fn_abi_of(test_generic) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Pointer(
                                        AddressSpace(
@@ -245,7 +245,7 @@ error: fn_abi_of(test_generic) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -292,7 +292,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I8,
@@ -331,7 +331,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -366,7 +366,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I32,
@@ -405,7 +405,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -446,7 +446,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Array {
@@ -486,7 +486,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -521,7 +521,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Array {
@@ -561,7 +561,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -602,7 +602,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Float(
                                        F32,
@@ -640,7 +640,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -675,7 +675,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I32,
@@ -714,7 +714,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -755,7 +755,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I32,
@@ -794,7 +794,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -829,7 +829,7 @@ error: ABIs are not compatible
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Int(
                                        I32,
@@ -868,7 +868,7 @@ error: ABIs are not compatible
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -923,7 +923,7 @@ error: fn_abi_of(assoc_test) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Scalar(
+                           backend_repr: Scalar(
                                Initialized {
                                    value: Pointer(
                                        AddressSpace(
@@ -975,7 +975,7 @@ error: fn_abi_of(assoc_test) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/abi/rust-cold-works-with-rustic-args.rs b/tests/ui/abi/rust-cold-works-with-rustic-args.rs
new file mode 100644
index 0000000000000..5702736469965
--- /dev/null
+++ b/tests/ui/abi/rust-cold-works-with-rustic-args.rs
@@ -0,0 +1,6 @@
+//@build-pass
+//@compile-flags: -Clink-dead-code=true --crate-type lib
+// We used to not handle all "rustic" ABIs in a (relatively) uniform way,
+// so we failed to fix up arguments for actually passing through the ABI...
+#![feature(rust_cold_cc)]
+pub extern "rust-cold" fn foo(_: [usize; 3]) {}
diff --git a/tests/ui/abi/sysv64-zst.stderr b/tests/ui/abi/sysv64-zst.stderr
index ec85030c10686..59d7b00441790 100644
--- a/tests/ui/abi/sysv64-zst.stderr
+++ b/tests/ui/abi/sysv64-zst.stderr
@@ -9,7 +9,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                                abi: $SOME_ALIGN,
                                pref: $SOME_ALIGN,
                            },
-                           abi: Memory {
+                           backend_repr: Memory {
                                sized: true,
                            },
                            fields: Arbitrary {
@@ -38,7 +38,7 @@ error: fn_abi_of(pass_zst) = FnAbi {
                            abi: $SOME_ALIGN,
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/associated-inherent-types/issue-109789.rs b/tests/ui/associated-inherent-types/issue-109789.rs
index 46dd4590141d0..e3c490b2dc842 100644
--- a/tests/ui/associated-inherent-types/issue-109789.rs
+++ b/tests/ui/associated-inherent-types/issue-109789.rs
@@ -20,5 +20,6 @@ fn bar(_: Foo<for<'a> fn(&'a ())>::Assoc) {}
 //~| ERROR mismatched types
 //~| ERROR higher-ranked subtype error
 //~| ERROR higher-ranked subtype error
+//~| ERROR higher-ranked subtype error
 
 fn main() {}
diff --git a/tests/ui/associated-inherent-types/issue-109789.stderr b/tests/ui/associated-inherent-types/issue-109789.stderr
index c6ea6c5541d23..db860a64826d6 100644
--- a/tests/ui/associated-inherent-types/issue-109789.stderr
+++ b/tests/ui/associated-inherent-types/issue-109789.stderr
@@ -31,6 +31,14 @@ LL | fn bar(_: Foo<for<'a> fn(&'a ())>::Assoc) {}
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 4 previous errors
+error: higher-ranked subtype error
+  --> $DIR/issue-109789.rs:18:1
+   |
+LL | fn bar(_: Foo<for<'a> fn(&'a ())>::Assoc) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/associated-inherent-types/issue-111404-1.rs b/tests/ui/associated-inherent-types/issue-111404-1.rs
index 3255bf20ebd1b..cad6d48b1c5af 100644
--- a/tests/ui/associated-inherent-types/issue-111404-1.rs
+++ b/tests/ui/associated-inherent-types/issue-111404-1.rs
@@ -12,5 +12,6 @@ fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
 //~| ERROR mismatched types [E0308]
 //~| ERROR higher-ranked subtype error
 //~| ERROR higher-ranked subtype error
+//~| ERROR higher-ranked subtype error
 
 fn main() {}
diff --git a/tests/ui/associated-inherent-types/issue-111404-1.stderr b/tests/ui/associated-inherent-types/issue-111404-1.stderr
index 5074c877a8ee8..ce49126c316c2 100644
--- a/tests/ui/associated-inherent-types/issue-111404-1.stderr
+++ b/tests/ui/associated-inherent-types/issue-111404-1.stderr
@@ -31,6 +31,14 @@ LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 4 previous errors
+error: higher-ranked subtype error
+  --> $DIR/issue-111404-1.rs:10:1
+   |
+LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed
new file mode 100644
index 0000000000000..7af986267aa67
--- /dev/null
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed
@@ -0,0 +1,40 @@
+//@ edition: 2021
+//@ run-rustfix
+#![feature(return_type_notation)]
+#![allow(dead_code)]
+
+trait Trait {
+    async fn method() {}
+}
+
+fn foo<T: Trait<method(..): Send>>() {}
+//~^ ERROR argument types not allowed with return type notation
+
+fn bar<T: Trait<method(..): Send>>() {}
+//~^ ERROR return type not allowed with return type notation
+
+fn baz<T: Trait<method(..): Send>>() {}
+//~^ ERROR return type notation arguments must be elided with `..`
+
+fn foo_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR argument types not allowed with return type notation
+
+fn bar_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type not allowed with return type notation
+
+fn bay_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type not allowed with return type notation
+
+fn baz_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type notation arguments must be elided with `..`
+
+fn foo_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn bar_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn baz_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn main() {}
diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
index 90fd2c2b4f326..983836e6433f0 100644
--- a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
@@ -1,6 +1,7 @@
 //@ edition: 2021
-
+//@ run-rustfix
 #![feature(return_type_notation)]
+#![allow(dead_code)]
 
 trait Trait {
     async fn method() {}
diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
index bd02b7d6534a9..e1245a04c7f7d 100644
--- a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
@@ -1,5 +1,5 @@
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:24:45
+  --> $DIR/bad-inputs-and-output.rs:25:45
    |
 LL | fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
    |                                             ^^^^^
@@ -11,25 +11,43 @@ LL + fn bay_path<T: Trait>() where T::method(..): Send {}
    |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:30:36
+  --> $DIR/bad-inputs-and-output.rs:31:36
    |
 LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
+LL + fn foo_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:33:36
+  --> $DIR/bad-inputs-and-output.rs:34:36
    |
 LL | fn bar_qualified<T: Trait>() where <T as Trait>::method() -> (): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn bar_qualified<T: Trait>() where <T as Trait>::method() -> (): Send {}
+LL + fn bar_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:36:36
+  --> $DIR/bad-inputs-and-output.rs:37:36
    |
 LL | fn baz_qualified<T: Trait>() where <T as Trait>::method(): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn baz_qualified<T: Trait>() where <T as Trait>::method(): Send {}
+LL + fn baz_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:9:23
+  --> $DIR/bad-inputs-and-output.rs:10:23
    |
 LL | fn foo<T: Trait<method(i32): Send>>() {}
    |                       ^^^^^
@@ -41,7 +59,7 @@ LL + fn foo<T: Trait<method(..): Send>>() {}
    |
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:12:25
+  --> $DIR/bad-inputs-and-output.rs:13:25
    |
 LL | fn bar<T: Trait<method() -> (): Send>>() {}
    |                         ^^^^^^
@@ -53,7 +71,7 @@ LL + fn bar<T: Trait<method(..): Send>>() {}
    |
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:15:23
+  --> $DIR/bad-inputs-and-output.rs:16:23
    |
 LL | fn baz<T: Trait<method(): Send>>() {}
    |                       ^^
@@ -64,7 +82,7 @@ LL | fn baz<T: Trait<method(..): Send>>() {}
    |                        ++
 
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:18:40
+  --> $DIR/bad-inputs-and-output.rs:19:40
    |
 LL | fn foo_path<T: Trait>() where T::method(i32): Send {}
    |                                        ^^^^^
@@ -76,7 +94,7 @@ LL + fn foo_path<T: Trait>() where T::method(..): Send {}
    |
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:21:42
+  --> $DIR/bad-inputs-and-output.rs:22:42
    |
 LL | fn bar_path<T: Trait>() where T::method() -> (): Send {}
    |                                          ^^^^^^
@@ -88,7 +106,7 @@ LL + fn bar_path<T: Trait>() where T::method(..): Send {}
    |
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:27:40
+  --> $DIR/bad-inputs-and-output.rs:28:40
    |
 LL | fn baz_path<T: Trait>() where T::method(): Send {}
    |                                        ^^
diff --git a/tests/ui/associated-types/ident-from-macro-expansion.rs b/tests/ui/associated-types/ident-from-macro-expansion.rs
new file mode 100644
index 0000000000000..6aabe4571406c
--- /dev/null
+++ b/tests/ui/associated-types/ident-from-macro-expansion.rs
@@ -0,0 +1,23 @@
+trait Trait {}
+impl Trait for () {}
+
+macro_rules! fully_qualified {
+    ($id:ident) => {
+        <() as Trait>::$id
+    }
+}
+
+macro_rules! type_dependent {
+    ($t:ident, $id:ident) => {
+        T::$id
+    }
+}
+
+fn t<T: Trait>() {
+    let x: fully_qualified!(Assoc);
+    //~^ ERROR cannot find associated type `Assoc` in trait `Trait`
+    let x: type_dependent!(T, Assoc);
+    //~^ ERROR associated type `Assoc` not found for `T`
+}
+
+fn main() {}
diff --git a/tests/ui/associated-types/ident-from-macro-expansion.stderr b/tests/ui/associated-types/ident-from-macro-expansion.stderr
new file mode 100644
index 0000000000000..dabf13c2c1726
--- /dev/null
+++ b/tests/ui/associated-types/ident-from-macro-expansion.stderr
@@ -0,0 +1,22 @@
+error[E0576]: cannot find associated type `Assoc` in trait `Trait`
+  --> $DIR/ident-from-macro-expansion.rs:17:29
+   |
+LL |         <() as Trait>::$id
+   |                        --- due to this macro variable
+...
+LL |     let x: fully_qualified!(Assoc);
+   |                             ^^^^^ not found in `Trait`
+
+error[E0220]: associated type `Assoc` not found for `T`
+  --> $DIR/ident-from-macro-expansion.rs:19:31
+   |
+LL |         T::$id
+   |            --- due to this macro variable
+...
+LL |     let x: type_dependent!(T, Assoc);
+   |                               ^^^^^ associated type `Assoc` not found
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0220, E0576.
+For more information about an error, try `rustc --explain E0220`.
diff --git a/tests/ui/attributes/decl_macro_ty_in_attr_macro.rs b/tests/ui/attributes/decl_macro_ty_in_attr_macro.rs
new file mode 100644
index 0000000000000..e633c08be3ad2
--- /dev/null
+++ b/tests/ui/attributes/decl_macro_ty_in_attr_macro.rs
@@ -0,0 +1,20 @@
+// tests for #137662: using a ty or (or most other) fragment inside an attr macro wouldn't work
+// because of a missing code path. With $repr: tt it did work.
+//@ check-pass
+
+macro_rules! foo {
+    {
+        $repr:ty
+    } => {
+        #[repr($repr)]
+        pub enum Foo {
+            Bar = 0i32,
+        }
+    }
+}
+
+foo! {
+    i32
+}
+
+fn main() {}
diff --git a/tests/ui/coherence/coherence-conflicting-negative-trait-impl.rs b/tests/ui/coherence/coherence-conflicting-negative-trait-impl.rs
index 24b878927530c..15ca0577e4acb 100644
--- a/tests/ui/coherence/coherence-conflicting-negative-trait-impl.rs
+++ b/tests/ui/coherence/coherence-conflicting-negative-trait-impl.rs
@@ -8,10 +8,14 @@ struct TestType<T>(::std::marker::PhantomData<T>);
 
 unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
 
-impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR found both positive and negative implementation
+impl<T: MyTrait> !Send for TestType<T> {}
+//~^ ERROR found both positive and negative implementation
+//~| ERROR `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
 
-unsafe impl<T: 'static> Send for TestType<T> {} //~ ERROR conflicting implementations
+unsafe impl<T: 'static> Send for TestType<T> {}
+//~^ ERROR conflicting implementations
 
 impl !Send for TestType<i32> {}
+//~^ ERROR `!Send` impls cannot be specialized
 
 fn main() {}
diff --git a/tests/ui/coherence/coherence-conflicting-negative-trait-impl.stderr b/tests/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
index 2463f38a92251..c6aed150201d8 100644
--- a/tests/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
+++ b/tests/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
@@ -8,7 +8,7 @@ LL | impl<T: MyTrait> !Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error[E0119]: conflicting implementations of trait `Send` for type `TestType<_>`
-  --> $DIR/coherence-conflicting-negative-trait-impl.rs:13:1
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:15:1
    |
 LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
    | ------------------------------------------------------ first implementation here
@@ -16,7 +16,32 @@ LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
 LL | unsafe impl<T: 'static> Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
 
-error: aborting due to 2 previous errors
+error[E0367]: `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:11:9
+   |
+LL | impl<T: MyTrait> !Send for TestType<T> {}
+   |         ^^^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:7:1
+   |
+LL | struct TestType<T>(::std::marker::PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^
+
+error[E0366]: `!Send` impls cannot be specialized
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:18:1
+   |
+LL | impl !Send for TestType<i32> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `i32` is not a generic parameter
+note: use the same sequence of generic lifetime, type and const parameters as the struct definition
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:7:1
+   |
+LL | struct TestType<T>(::std::marker::PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
 
-Some errors have detailed explanations: E0119, E0751.
+Some errors have detailed explanations: E0119, E0366, E0367, E0751.
 For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr
index 77d1bdee5acf1..bc81dd6f286dd 100644
--- a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr
+++ b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr
@@ -1,9 +1,3 @@
-error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker1`
-  --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1
-   |
-LL | impl !Marker1 for dyn Object + Marker2 {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1`
-
 error[E0321]: traits with a default impl, like `Marker1`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
   --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1
    |
@@ -12,11 +6,11 @@ LL | impl !Marker1 for dyn Object + Marker2 {}
    |
    = note: a trait object implements `Marker1` if and only if `Marker1` is one of the trait object's trait bounds
 
-error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2`
-  --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1
+error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker1`
+  --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1
    |
-LL | impl !Marker2 for dyn Object + Marker2 {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2`
+LL | impl !Marker1 for dyn Object + Marker2 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1`
 
 error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
   --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1
@@ -26,6 +20,12 @@ LL | impl !Marker2 for dyn Object + Marker2 {}
    |
    = note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds
 
+error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2`
+  --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1
+   |
+LL | impl !Marker2 for dyn Object + Marker2 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2`
+
 error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + 'static)`
   --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:26:1
    |
diff --git a/tests/ui/coherence/coherence-orphan.rs b/tests/ui/coherence/coherence-orphan.rs
index aee6647a78819..665fa15c56e53 100644
--- a/tests/ui/coherence/coherence-orphan.rs
+++ b/tests/ui/coherence/coherence-orphan.rs
@@ -8,12 +8,13 @@ use lib::TheTrait;
 struct TheType;
 
 impl TheTrait<usize> for isize {}
-//~^ ERROR E0117
+//~^ ERROR  only traits defined in the current crate can be implemented for primitive types
 
 impl TheTrait<TheType> for isize {}
 
 impl TheTrait<isize> for TheType {}
 
-impl !Send for Vec<isize> {} //~ ERROR E0117
+impl !Send for Vec<isize> {}
+//~^ ERROR only traits defined in the current crate can be implemented for types defined outside of the crate
 
 fn main() {}
diff --git a/tests/ui/coherence/coherence-overlap-negative-impls.rs b/tests/ui/coherence/coherence-overlap-negative-impls.rs
deleted file mode 100644
index ffcd56817e5c2..0000000000000
--- a/tests/ui/coherence/coherence-overlap-negative-impls.rs
+++ /dev/null
@@ -1,44 +0,0 @@
-//@ check-pass
-//@ known-bug: #74629
-
-// Should fail. The `0` and `1` impls overlap, violating coherence. Eg, with
-// `T = Test, F = ()`, all bounds are true, making both impls applicable.
-// `Test: Fold<Nil>`, `Test: Fold<()>` are true because of `2`.
-// `Is<Test>: NotNil` is true because of `auto trait` and lack of negative impl.
-
-#![feature(negative_impls)]
-#![feature(auto_traits)]
-
-struct Nil;
-struct Cons<H>(H);
-struct Test;
-
-trait Fold<F> {}
-
-impl<T, F> Fold<F> for Cons<T>
-// 0
-where
-    T: Fold<Nil>,
-{
-}
-
-impl<T, F> Fold<F> for Cons<T>
-// 1
-where
-    T: Fold<F>,
-    private::Is<T>: private::NotNil,
-{
-}
-
-impl<F> Fold<F> for Test {} // 2
-
-mod private {
-    use crate::Nil;
-
-    pub struct Is<T>(T);
-    pub auto trait NotNil {}
-
-    impl !NotNil for Is<Nil> {}
-}
-
-fn main() {}
diff --git a/tests/ui/hygiene/generate-mod.stderr b/tests/ui/hygiene/generate-mod.stderr
index 32a2e145ca942..58b9c642dabe3 100644
--- a/tests/ui/hygiene/generate-mod.stderr
+++ b/tests/ui/hygiene/generate-mod.stderr
@@ -1,12 +1,18 @@
 error[E0412]: cannot find type `FromOutside` in this scope
   --> $DIR/generate-mod.rs:35:13
    |
+LL |     type A = $FromOutside;
+   |              ------------ due to this macro variable
+...
 LL |     genmod!(FromOutside, Outer);
    |             ^^^^^^^^^^^ not found in this scope
 
 error[E0412]: cannot find type `Outer` in this scope
   --> $DIR/generate-mod.rs:35:26
    |
+LL |     struct $Outer;
+   |            ------ due to this macro variable
+...
 LL |     genmod!(FromOutside, Outer);
    |                          ^^^^^ not found in this scope
 
diff --git a/tests/ui/hygiene/globs.stderr b/tests/ui/hygiene/globs.stderr
index 3f7a0ae7efa1b..31f25b182f1f5 100644
--- a/tests/ui/hygiene/globs.stderr
+++ b/tests/ui/hygiene/globs.stderr
@@ -50,6 +50,9 @@ error[E0425]: cannot find function `f` in this scope
 LL | n!(f);
    | ----- in this macro invocation
 ...
+LL |                     $j();
+   |                     -- due to this macro variable
+...
 LL |         n!(f);
    |            ^ not found in this scope
    |
@@ -63,6 +66,9 @@ error[E0425]: cannot find function `f` in this scope
 LL | n!(f);
    | ----- in this macro invocation
 ...
+LL |                     $j();
+   |                     -- due to this macro variable
+...
 LL |                 f
    |                 ^ not found in this scope
    |
diff --git a/tests/ui/implied-bounds/from-trait-impl.rs b/tests/ui/implied-bounds/from-trait-impl.rs
index 6e126575aa9a2..5822c5474bdcb 100644
--- a/tests/ui/implied-bounds/from-trait-impl.rs
+++ b/tests/ui/implied-bounds/from-trait-impl.rs
@@ -12,6 +12,7 @@ where
 
 fn func1(foo: Foo<(&str,)>) {
     //~^ ERROR `&str` does not fulfill the required lifetime
+    //~| ERROR lifetime may not live long enough
     let _: &'static str = foo.0.0;
 }
 
@@ -19,5 +20,6 @@ trait TestTrait {}
 
 impl<X> TestTrait for [Foo<(X,)>; 1] {}
 //~^ ERROR `X` may not live long enough
+//~| ERROR `X` may not live long enough
 
 fn main() {}
diff --git a/tests/ui/implied-bounds/from-trait-impl.stderr b/tests/ui/implied-bounds/from-trait-impl.stderr
index 4151d206ae25f..5f189d3385ac1 100644
--- a/tests/ui/implied-bounds/from-trait-impl.stderr
+++ b/tests/ui/implied-bounds/from-trait-impl.stderr
@@ -7,7 +7,21 @@ LL | fn func1(foo: Foo<(&str,)>) {
    = note: type must satisfy the static lifetime
 
 error[E0310]: the parameter type `X` may not live long enough
-  --> $DIR/from-trait-impl.rs:20:23
+  --> $DIR/from-trait-impl.rs:21:1
+   |
+LL | impl<X> TestTrait for [Foo<(X,)>; 1] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | |
+   | the parameter type `X` must be valid for the static lifetime...
+   | ...so that the type `X` will meet its required lifetime bounds
+   |
+help: consider adding an explicit lifetime bound
+   |
+LL | impl<X: 'static> TestTrait for [Foo<(X,)>; 1] {}
+   |       +++++++++
+
+error[E0310]: the parameter type `X` may not live long enough
+  --> $DIR/from-trait-impl.rs:21:23
    |
 LL | impl<X> TestTrait for [Foo<(X,)>; 1] {}
    |                       ^^^^^^^^^^^^^^
@@ -20,7 +34,16 @@ help: consider adding an explicit lifetime bound
 LL | impl<X: 'static> TestTrait for [Foo<(X,)>; 1] {}
    |       +++++++++
 
-error: aborting due to 2 previous errors
+error: lifetime may not live long enough
+  --> $DIR/from-trait-impl.rs:13:1
+   |
+LL | fn func1(foo: Foo<(&str,)>) {
+   | ^^^^^^^^^^^^^^^^^^^-^^^^^^^
+   | |                  |
+   | |                  let's call the lifetime of this reference `'1`
+   | requires that `'1` must outlive `'static`
+
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0310, E0477.
 For more information about an error, try `rustc --explain E0310`.
diff --git a/tests/ui/implied-bounds/normalization-nested.lifetime.stderr b/tests/ui/implied-bounds/normalization-nested.lifetime.stderr
deleted file mode 100644
index c43cc0999f1d7..0000000000000
--- a/tests/ui/implied-bounds/normalization-nested.lifetime.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: lifetime may not live long enough
-  --> $DIR/normalization-nested.rs:40:5
-   |
-LL | pub fn test_borrowck<'x>(_: Map<Vec<&'x ()>>, s: &'x str) -> &'static str {
-   |                      -- lifetime `'x` defined here
-LL |     s
-   |     ^ returning this value requires that `'x` must outlive `'static`
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/implied-bounds/normalization-nested.rs b/tests/ui/implied-bounds/normalization-nested.rs
index 4527e33a291bb..9a0defd16675a 100644
--- a/tests/ui/implied-bounds/normalization-nested.rs
+++ b/tests/ui/implied-bounds/normalization-nested.rs
@@ -3,9 +3,7 @@
 //
 //@ revisions: param_ty lifetime param_ty_no_compat lifetime_no_compat
 
-//@[param_ty] check-pass
-//@[param_ty_no_compat] check-pass
-//@[lifetime_no_compat] check-pass
+//@ check-pass
 //@[param_ty_no_compat] compile-flags: -Zno-implied-bounds-compat
 //@[lifetime_no_compat] compile-flags: -Zno-implied-bounds-compat
 
@@ -38,7 +36,6 @@ pub fn test_wfcheck<'x>(_: Map<Vec<&'x ()>>) {}
 
 pub fn test_borrowck<'x>(_: Map<Vec<&'x ()>>, s: &'x str) -> &'static str {
     s
-    //[lifetime]~^ ERROR lifetime may not live long enough
 }
 
 fn main() {}
diff --git a/tests/ui/implied-bounds/normalization-placeholder-leak.fail.stderr b/tests/ui/implied-bounds/normalization-placeholder-leak.fail.stderr
index a591d0f5d4d0a..8919919d04e5c 100644
--- a/tests/ui/implied-bounds/normalization-placeholder-leak.fail.stderr
+++ b/tests/ui/implied-bounds/normalization-placeholder-leak.fail.stderr
@@ -1,3 +1,9 @@
+error[E0477]: the type `&'lt u8` does not fulfill the required lifetime
+  --> $DIR/normalization-placeholder-leak.rs:31:5
+   |
+LL |     fn test_lifetime<'lt, T: Trait>(_: Foo<&'lt u8>) {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0477]: the type `&'lt u8` does not fulfill the required lifetime
   --> $DIR/normalization-placeholder-leak.rs:31:40
    |
@@ -5,11 +11,35 @@ LL |     fn test_lifetime<'lt, T: Trait>(_: Foo<&'lt u8>) {}
    |                                        ^^^^^^^^^^^^
 
 error[E0477]: the type `<T as AnotherTrait>::Ty2<'lt>` does not fulfill the required lifetime
-  --> $DIR/normalization-placeholder-leak.rs:36:44
+  --> $DIR/normalization-placeholder-leak.rs:38:5
+   |
+LL |     fn test_alias<'lt, T: AnotherTrait>(_: Foo<T::Ty2::<'lt>>) {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0477]: the type `<T as AnotherTrait>::Ty2<'lt>` does not fulfill the required lifetime
+  --> $DIR/normalization-placeholder-leak.rs:38:44
    |
 LL |     fn test_alias<'lt, T: AnotherTrait>(_: Foo<T::Ty2::<'lt>>) {}
    |                                            ^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: lifetime may not live long enough
+  --> $DIR/normalization-placeholder-leak.rs:31:5
+   |
+LL |     fn test_lifetime<'lt, T: Trait>(_: Foo<&'lt u8>) {}
+   |     ^^^^^^^^^^^^^^^^^---^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |                |
+   |     |                lifetime `'lt` defined here
+   |     requires that `'lt` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/normalization-placeholder-leak.rs:38:5
+   |
+LL |     fn test_alias<'lt, T: AnotherTrait>(_: Foo<T::Ty2::<'lt>>) {}
+   |     ^^^^^^^^^^^^^^---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |             |
+   |     |             lifetime `'lt` defined here
+   |     requires that `'lt` must outlive `'static`
+
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0477`.
diff --git a/tests/ui/implied-bounds/normalization-placeholder-leak.rs b/tests/ui/implied-bounds/normalization-placeholder-leak.rs
index a9dfa69cfd6a4..3a15897db8211 100644
--- a/tests/ui/implied-bounds/normalization-placeholder-leak.rs
+++ b/tests/ui/implied-bounds/normalization-placeholder-leak.rs
@@ -30,11 +30,15 @@ mod fail {
     // don't use the bound to prove `'lt: 'static`.
     fn test_lifetime<'lt, T: Trait>(_: Foo<&'lt u8>) {}
     //[fail]~^ ERROR `&'lt u8` does not fulfill the required lifetime
+    //[fail]~| ERROR `&'lt u8` does not fulfill the required lifetime
+    //[fail]~| ERROR may not live long enough
 
     // implied bound: `T::Ty2<'lt>: placeholder('x)`.
     // don't use the bound to prove `T::Ty2<'lt>: 'static`.
     fn test_alias<'lt, T: AnotherTrait>(_: Foo<T::Ty2::<'lt>>) {}
     //[fail]~^ ERROR `<T as AnotherTrait>::Ty2<'lt>` does not fulfill the required lifetime
+    //[fail]~| ERROR `<T as AnotherTrait>::Ty2<'lt>` does not fulfill the required lifetime
+    //[fail]~| ERROR may not live long enough
 }
 
 
diff --git a/tests/ui/implied-bounds/sod_service_chain.rs b/tests/ui/implied-bounds/sod_service_chain.rs
index 7443a29f30cbd..032483e1be48f 100644
--- a/tests/ui/implied-bounds/sod_service_chain.rs
+++ b/tests/ui/implied-bounds/sod_service_chain.rs
@@ -27,11 +27,19 @@ pub struct ServiceChainBuilder<P: Service, S: Service<Input = P::Output>> {
 }
 impl<P: Service, S: Service<Input = P::Output>> ServiceChainBuilder<P, S> {
     pub fn next<NS: Service<Input = S::Output>>(
+        //~^ the associated type
+        //~| the associated type
+        //~| the associated type
+        //~| the associated type
+        //~| the associated type
+        //~| the associated type
+        //~| may not live long enough
         self,
     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
         //~^ the associated type
         //~| the associated type
         //~| the associated type
+        //~| the associated type
         panic!();
     }
 }
diff --git a/tests/ui/implied-bounds/sod_service_chain.stderr b/tests/ui/implied-bounds/sod_service_chain.stderr
index 1c0ef573e7d33..f5221fc11056c 100644
--- a/tests/ui/implied-bounds/sod_service_chain.stderr
+++ b/tests/ui/implied-bounds/sod_service_chain.stderr
@@ -1,5 +1,39 @@
 error[E0310]: the associated type `<P as Service>::Error` may not live long enough
-  --> $DIR/sod_service_chain.rs:31:10
+  --> $DIR/sod_service_chain.rs:29:5
+   |
+LL | /     pub fn next<NS: Service<Input = S::Output>>(
+...  |
+LL | |         self,
+LL | |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
+   | |                                                    ^
+   | |                                                    |
+   | |____________________________________________________the associated type `<P as Service>::Error` must be valid for the static lifetime...
+   |                                                      ...so that the type `<P as Service>::Error` will meet its required lifetime bounds
+   |
+help: consider adding an explicit lifetime bound
+   |
+LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <P as Service>::Error: 'static {
+   |                                                      ++++++++++++++++++++++++++++++++++++
+
+error[E0310]: the associated type `<S as Service>::Error` may not live long enough
+  --> $DIR/sod_service_chain.rs:29:5
+   |
+LL | /     pub fn next<NS: Service<Input = S::Output>>(
+...  |
+LL | |         self,
+LL | |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
+   | |                                                    ^
+   | |                                                    |
+   | |____________________________________________________the associated type `<S as Service>::Error` must be valid for the static lifetime...
+   |                                                      ...so that the type `<S as Service>::Error` will meet its required lifetime bounds
+   |
+help: consider adding an explicit lifetime bound
+   |
+LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <S as Service>::Error: 'static {
+   |                                                      ++++++++++++++++++++++++++++++++++++
+
+error[E0310]: the associated type `<P as Service>::Error` may not live long enough
+  --> $DIR/sod_service_chain.rs:38:10
    |
 LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -13,7 +47,7 @@ LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <P as Service>::
    |                                                      ++++++++++++++++++++++++++++++++++++
 
 error[E0310]: the associated type `<S as Service>::Error` may not live long enough
-  --> $DIR/sod_service_chain.rs:31:10
+  --> $DIR/sod_service_chain.rs:38:10
    |
 LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -26,6 +60,42 @@ help: consider adding an explicit lifetime bound
 LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <S as Service>::Error: 'static {
    |                                                      ++++++++++++++++++++++++++++++++++++
 
-error: aborting due to 2 previous errors
+error[E0310]: the associated type `<P as Service>::Error` may not live long enough
+  --> $DIR/sod_service_chain.rs:29:5
+   |
+LL | /     pub fn next<NS: Service<Input = S::Output>>(
+...  |
+LL | |         self,
+LL | |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
+   | |                                                    ^
+   | |                                                    |
+   | |____________________________________________________the associated type `<P as Service>::Error` must be valid for the static lifetime...
+   |                                                      ...so that the type `<P as Service>::Error` will meet its required lifetime bounds
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: consider adding an explicit lifetime bound
+   |
+LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <P as Service>::Error: 'static {
+   |                                                      ++++++++++++++++++++++++++++++++++++
+
+error[E0310]: the associated type `<S as Service>::Error` may not live long enough
+  --> $DIR/sod_service_chain.rs:29:5
+   |
+LL | /     pub fn next<NS: Service<Input = S::Output>>(
+...  |
+LL | |         self,
+LL | |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> {
+   | |                                                    ^
+   | |                                                    |
+   | |____________________________________________________the associated type `<S as Service>::Error` must be valid for the static lifetime...
+   |                                                      ...so that the type `<S as Service>::Error` will meet its required lifetime bounds
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: consider adding an explicit lifetime bound
+   |
+LL |     ) -> ServiceChainBuilder<ServiceChain<P, S>, NS> where <S as Service>::Error: 'static {
+   |                                                      ++++++++++++++++++++++++++++++++++++
+
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0310`.
diff --git a/tests/ui/inference/issue-86094-suggest-add-return-to-coerce-ret-ty.stderr b/tests/ui/inference/issue-86094-suggest-add-return-to-coerce-ret-ty.stderr
index 1fea73529a8a2..c61ca699b0d35 100644
--- a/tests/ui/inference/issue-86094-suggest-add-return-to-coerce-ret-ty.stderr
+++ b/tests/ui/inference/issue-86094-suggest-add-return-to-coerce-ret-ty.stderr
@@ -8,10 +8,6 @@ help: consider specifying the generic arguments
    |
 LL |         Err::<T, MyError>(MyError);
    |            ++++++++++++++
-help: you might have meant to return this to infer its type parameters
-   |
-LL |         return Err(MyError);
-   |         ++++++
 
 error[E0282]: type annotations needed
   --> $DIR/issue-86094-suggest-add-return-to-coerce-ret-ty.rs:14:9
@@ -23,10 +19,6 @@ help: consider specifying the generic arguments
    |
 LL |         Ok::<(), E>(());
    |           +++++++++
-help: you might have meant to return this to infer its type parameters
-   |
-LL |         return Ok(());
-   |         ++++++
 
 error[E0308]: mismatched types
   --> $DIR/issue-86094-suggest-add-return-to-coerce-ret-ty.rs:21:20
diff --git a/tests/ui/issues/issue-106755.rs b/tests/ui/issues/issue-106755.rs
index 689b1d885ae60..d7e7122ebda16 100644
--- a/tests/ui/issues/issue-106755.rs
+++ b/tests/ui/issues/issue-106755.rs
@@ -10,10 +10,13 @@ struct TestType<T>(::std::marker::PhantomData<T>);
 
 unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
 
-impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR found both positive and negative implementation
+impl<T: MyTrait> !Send for TestType<T> {}
+//~^ ERROR found both positive and negative implementation
+//~| ERROR `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
 
 unsafe impl<T: 'static> Send for TestType<T> {} //~ ERROR conflicting implementations
 
 impl !Send for TestType<i32> {}
+//~^ ERROR `!Send` impls cannot be specialized
 
 fn main() {}
diff --git a/tests/ui/issues/issue-106755.stderr b/tests/ui/issues/issue-106755.stderr
index 543970340620d..da6b8c5c56325 100644
--- a/tests/ui/issues/issue-106755.stderr
+++ b/tests/ui/issues/issue-106755.stderr
@@ -8,7 +8,7 @@ LL | impl<T: MyTrait> !Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error[E0119]: conflicting implementations of trait `Send` for type `TestType<_>`
-  --> $DIR/issue-106755.rs:15:1
+  --> $DIR/issue-106755.rs:17:1
    |
 LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
    | ------------------------------------------------------ first implementation here
@@ -16,7 +16,32 @@ LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
 LL | unsafe impl<T: 'static> Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
 
-error: aborting due to 2 previous errors
+error[E0367]: `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
+  --> $DIR/issue-106755.rs:13:9
+   |
+LL | impl<T: MyTrait> !Send for TestType<T> {}
+   |         ^^^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/issue-106755.rs:9:1
+   |
+LL | struct TestType<T>(::std::marker::PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^
+
+error[E0366]: `!Send` impls cannot be specialized
+  --> $DIR/issue-106755.rs:19:1
+   |
+LL | impl !Send for TestType<i32> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `i32` is not a generic parameter
+note: use the same sequence of generic lifetime, type and const parameters as the struct definition
+  --> $DIR/issue-106755.rs:9:1
+   |
+LL | struct TestType<T>(::std::marker::PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
 
-Some errors have detailed explanations: E0119, E0751.
+Some errors have detailed explanations: E0119, E0366, E0367, E0751.
 For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/ui/layout/debug.stderr b/tests/ui/layout/debug.stderr
index 07cad7766920f..80b35ff6ad49e 100644
--- a/tests/ui/layout/debug.stderr
+++ b/tests/ui/layout/debug.stderr
@@ -10,7 +10,7 @@ error: layout_of(E) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -49,7 +49,7 @@ error: layout_of(E) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -71,7 +71,7 @@ error: layout_of(E) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -112,7 +112,7 @@ error: layout_of(S) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I32,
@@ -160,7 +160,7 @@ error: layout_of(U) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -186,7 +186,7 @@ error: layout_of(Result<i32, i32>) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I32,
@@ -238,7 +238,7 @@ error: layout_of(Result<i32, i32>) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -277,7 +277,7 @@ error: layout_of(Result<i32, i32>) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -327,7 +327,7 @@ error: layout_of(i32) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -357,7 +357,7 @@ error: layout_of(V) = Layout {
                abi: Align(2 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -383,7 +383,7 @@ error: layout_of(W) = Layout {
                abi: Align(2 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -409,7 +409,7 @@ error: layout_of(Y) = Layout {
                abi: Align(2 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -435,7 +435,7 @@ error: layout_of(P1) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -461,7 +461,7 @@ error: layout_of(P2) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -487,7 +487,7 @@ error: layout_of(P3) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -513,7 +513,7 @@ error: layout_of(P4) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Union(
@@ -539,7 +539,7 @@ error: layout_of(P5) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Union {
                    value: Int(
                        I8,
@@ -570,7 +570,7 @@ error: layout_of(MaybeUninit<u8>) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Union {
                    value: Int(
                        I8,
diff --git a/tests/ui/layout/hexagon-enum.stderr b/tests/ui/layout/hexagon-enum.stderr
index b802b400b18b8..9c3a8662d4f08 100644
--- a/tests/ui/layout/hexagon-enum.stderr
+++ b/tests/ui/layout/hexagon-enum.stderr
@@ -4,7 +4,7 @@ error: layout_of(A) = Layout {
                abi: Align(1 bytes),
                pref: Align(1 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -49,7 +49,7 @@ error: layout_of(A) = Layout {
                            abi: Align(1 bytes),
                            pref: Align(1 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -82,7 +82,7 @@ error: layout_of(B) = Layout {
                abi: Align(1 bytes),
                pref: Align(1 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -127,7 +127,7 @@ error: layout_of(B) = Layout {
                            abi: Align(1 bytes),
                            pref: Align(1 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -160,7 +160,7 @@ error: layout_of(C) = Layout {
                abi: Align(2 bytes),
                pref: Align(2 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I16,
@@ -205,7 +205,7 @@ error: layout_of(C) = Layout {
                            abi: Align(2 bytes),
                            pref: Align(2 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -238,7 +238,7 @@ error: layout_of(P) = Layout {
                abi: Align(4 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -283,7 +283,7 @@ error: layout_of(P) = Layout {
                            abi: Align(4 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -316,7 +316,7 @@ error: layout_of(T) = Layout {
                abi: Align(4 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -361,7 +361,7 @@ error: layout_of(T) = Layout {
                            abi: Align(4 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr b/tests/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
index 3bdb9c5c143e4..ef7f0cd2d1c34 100644
--- a/tests/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
+++ b/tests/ui/layout/issue-96158-scalarpair-payload-might-be-uninit.stderr
@@ -4,7 +4,7 @@ error: layout_of(MissingPayloadField) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -55,7 +55,7 @@ error: layout_of(MissingPayloadField) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -93,7 +93,7 @@ error: layout_of(MissingPayloadField) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -126,7 +126,7 @@ error: layout_of(CommonPayloadField) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -178,7 +178,7 @@ error: layout_of(CommonPayloadField) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -217,7 +217,7 @@ error: layout_of(CommonPayloadField) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -267,7 +267,7 @@ error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -318,7 +318,7 @@ error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -356,7 +356,7 @@ error: layout_of(CommonPayloadFieldIsMaybeUninit) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -405,7 +405,7 @@ error: layout_of(NicheFirst) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -460,7 +460,7 @@ error: layout_of(NicheFirst) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -510,7 +510,7 @@ error: layout_of(NicheFirst) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -532,7 +532,7 @@ error: layout_of(NicheFirst) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -565,7 +565,7 @@ error: layout_of(NicheSecond) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -620,7 +620,7 @@ error: layout_of(NicheSecond) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -670,7 +670,7 @@ error: layout_of(NicheSecond) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -692,7 +692,7 @@ error: layout_of(NicheSecond) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/layout/issue-96185-overaligned-enum.stderr b/tests/ui/layout/issue-96185-overaligned-enum.stderr
index 1d4e443644826..a9081afc50944 100644
--- a/tests/ui/layout/issue-96185-overaligned-enum.stderr
+++ b/tests/ui/layout/issue-96185-overaligned-enum.stderr
@@ -4,7 +4,7 @@ error: layout_of(Aligned1) = Layout {
                abi: Align(8 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -43,7 +43,7 @@ error: layout_of(Aligned1) = Layout {
                            abi: Align(8 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -67,7 +67,7 @@ error: layout_of(Aligned1) = Layout {
                            abi: Align(8 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -104,7 +104,7 @@ error: layout_of(Aligned2) = Layout {
                abi: Align(1 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -149,7 +149,7 @@ error: layout_of(Aligned2) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -173,7 +173,7 @@ error: layout_of(Aligned2) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/layout/thumb-enum.stderr b/tests/ui/layout/thumb-enum.stderr
index 07153fee02736..b635d1a45bb7a 100644
--- a/tests/ui/layout/thumb-enum.stderr
+++ b/tests/ui/layout/thumb-enum.stderr
@@ -4,7 +4,7 @@ error: layout_of(A) = Layout {
                abi: Align(1 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -49,7 +49,7 @@ error: layout_of(A) = Layout {
                            abi: Align(1 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -82,7 +82,7 @@ error: layout_of(B) = Layout {
                abi: Align(1 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -127,7 +127,7 @@ error: layout_of(B) = Layout {
                            abi: Align(1 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -160,7 +160,7 @@ error: layout_of(C) = Layout {
                abi: Align(2 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I16,
@@ -205,7 +205,7 @@ error: layout_of(C) = Layout {
                            abi: Align(2 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -238,7 +238,7 @@ error: layout_of(P) = Layout {
                abi: Align(4 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -283,7 +283,7 @@ error: layout_of(P) = Layout {
                            abi: Align(4 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -316,7 +316,7 @@ error: layout_of(T) = Layout {
                abi: Align(4 bytes),
                pref: Align(4 bytes),
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -361,7 +361,7 @@ error: layout_of(T) = Layout {
                            abi: Align(4 bytes),
                            pref: Align(4 bytes),
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/layout/zero-sized-array-enum-niche.stderr b/tests/ui/layout/zero-sized-array-enum-niche.stderr
index 33d2eede22090..1ba184bdacefb 100644
--- a/tests/ui/layout/zero-sized-array-enum-niche.stderr
+++ b/tests/ui/layout/zero-sized-array-enum-niche.stderr
@@ -4,7 +4,7 @@ error: layout_of(Result<[u32; 0], bool>) = Layout {
                abi: Align(4 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -43,7 +43,7 @@ error: layout_of(Result<[u32; 0], bool>) = Layout {
                            abi: Align(4 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -69,7 +69,7 @@ error: layout_of(Result<[u32; 0], bool>) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -115,7 +115,7 @@ error: layout_of(MultipleAlignments) = Layout {
                abi: Align(4 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -154,7 +154,7 @@ error: layout_of(MultipleAlignments) = Layout {
                            abi: Align(2 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -180,7 +180,7 @@ error: layout_of(MultipleAlignments) = Layout {
                            abi: Align(4 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -206,7 +206,7 @@ error: layout_of(MultipleAlignments) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -252,7 +252,7 @@ error: layout_of(Result<[u32; 0], Packed<NonZero<u16>>>) = Layout {
                abi: Align(4 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -291,7 +291,7 @@ error: layout_of(Result<[u32; 0], Packed<NonZero<u16>>>) = Layout {
                            abi: Align(4 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -317,7 +317,7 @@ error: layout_of(Result<[u32; 0], Packed<NonZero<u16>>>) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -363,7 +363,7 @@ error: layout_of(Result<[u32; 0], Packed<U16IsZero>>) = Layout {
                abi: Align(4 bytes),
                pref: $PREF_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -406,7 +406,7 @@ error: layout_of(Result<[u32; 0], Packed<U16IsZero>>) = Layout {
                            abi: Align(4 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -432,7 +432,7 @@ error: layout_of(Result<[u32; 0], Packed<U16IsZero>>) = Layout {
                            abi: Align(1 bytes),
                            pref: $PREF_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/macros/macro-parameter-span.stderr b/tests/ui/macros/macro-parameter-span.stderr
index 247750a8ad705..44c8c56dff999 100644
--- a/tests/ui/macros/macro-parameter-span.stderr
+++ b/tests/ui/macros/macro-parameter-span.stderr
@@ -1,6 +1,9 @@
 error[E0425]: cannot find value `x` in this scope
   --> $DIR/macro-parameter-span.rs:11:9
    |
+LL |         $id
+   |         --- due to this macro variable
+...
 LL |         x
    |         ^ not found in this scope
 
diff --git a/tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.stderr b/tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.stderr
index ce7694ecb1da3..d9646760cea92 100644
--- a/tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.stderr
+++ b/tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.stderr
@@ -338,6 +338,9 @@ LL |     no_curly__no_rhs_dollar__no_round!(a);
 error[E0425]: cannot find value `a` in this scope
   --> $DIR/syntax-errors.rs:152:37
    |
+LL |     ( $i:ident ) => { count($i) };
+   |                             -- due to this macro variable
+...
 LL |     no_curly__rhs_dollar__no_round!(a);
    |                                     ^ not found in this scope
 
diff --git a/tests/ui/methods/ident-from-macro-expansion.rs b/tests/ui/methods/ident-from-macro-expansion.rs
new file mode 100644
index 0000000000000..38d2fee0e53c0
--- /dev/null
+++ b/tests/ui/methods/ident-from-macro-expansion.rs
@@ -0,0 +1,18 @@
+macro_rules! dot {
+    ($id:ident) => {
+        ().$id();
+    }
+}
+
+macro_rules! dispatch {
+    ($id:ident) => {
+        <()>::$id();
+    }
+}
+
+fn main() {
+    dot!(hello);
+    //~^ ERROR no method named `hello` found for unit type `()` in the current scope
+    dispatch!(hello);
+    //~^ ERROR no function or associated item named `hello` found for unit type `()` in the current scope
+}
diff --git a/tests/ui/methods/ident-from-macro-expansion.stderr b/tests/ui/methods/ident-from-macro-expansion.stderr
new file mode 100644
index 0000000000000..b596ce29f6fee
--- /dev/null
+++ b/tests/ui/methods/ident-from-macro-expansion.stderr
@@ -0,0 +1,21 @@
+error[E0599]: no method named `hello` found for unit type `()` in the current scope
+  --> $DIR/ident-from-macro-expansion.rs:14:10
+   |
+LL |         ().$id();
+   |            --- due to this macro variable
+...
+LL |     dot!(hello);
+   |          ^^^^^ method not found in `()`
+
+error[E0599]: no function or associated item named `hello` found for unit type `()` in the current scope
+  --> $DIR/ident-from-macro-expansion.rs:16:15
+   |
+LL |         <()>::$id();
+   |               --- due to this macro variable
+...
+LL |     dispatch!(hello);
+   |               ^^^^^ function or associated item not found in `()`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/tests/ui/repr/repr-c-dead-variants.aarch64-unknown-linux-gnu.stderr b/tests/ui/repr/repr-c-dead-variants.aarch64-unknown-linux-gnu.stderr
index 42fcaee2d4aa4..c11acc98637df 100644
--- a/tests/ui/repr/repr-c-dead-variants.aarch64-unknown-linux-gnu.stderr
+++ b/tests/ui/repr/repr-c-dead-variants.aarch64-unknown-linux-gnu.stderr
@@ -4,7 +4,7 @@ error: layout_of(Univariant) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -49,7 +49,7 @@ error: layout_of(Univariant) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I32,
@@ -92,7 +92,7 @@ error: layout_of(TwoVariants) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I32,
@@ -143,7 +143,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -181,7 +181,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -230,7 +230,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                abi: Align(8 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -269,7 +269,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -299,7 +299,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/repr/repr-c-dead-variants.armebv7r-none-eabi.stderr b/tests/ui/repr/repr-c-dead-variants.armebv7r-none-eabi.stderr
index bb2c6e70dc7ab..a7888155deaf7 100644
--- a/tests/ui/repr/repr-c-dead-variants.armebv7r-none-eabi.stderr
+++ b/tests/ui/repr/repr-c-dead-variants.armebv7r-none-eabi.stderr
@@ -4,7 +4,7 @@ error: layout_of(Univariant) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -49,7 +49,7 @@ error: layout_of(Univariant) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I8,
@@ -92,7 +92,7 @@ error: layout_of(TwoVariants) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -143,7 +143,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -181,7 +181,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -230,7 +230,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                abi: Align(8 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -269,7 +269,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -299,7 +299,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/repr/repr-c-dead-variants.i686-pc-windows-msvc.stderr b/tests/ui/repr/repr-c-dead-variants.i686-pc-windows-msvc.stderr
index 42fcaee2d4aa4..c11acc98637df 100644
--- a/tests/ui/repr/repr-c-dead-variants.i686-pc-windows-msvc.stderr
+++ b/tests/ui/repr/repr-c-dead-variants.i686-pc-windows-msvc.stderr
@@ -4,7 +4,7 @@ error: layout_of(Univariant) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -49,7 +49,7 @@ error: layout_of(Univariant) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I32,
@@ -92,7 +92,7 @@ error: layout_of(TwoVariants) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I32,
@@ -143,7 +143,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -181,7 +181,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -230,7 +230,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                abi: Align(8 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -269,7 +269,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -299,7 +299,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/repr/repr-c-dead-variants.x86_64-unknown-linux-gnu.stderr b/tests/ui/repr/repr-c-dead-variants.x86_64-unknown-linux-gnu.stderr
index 42fcaee2d4aa4..c11acc98637df 100644
--- a/tests/ui/repr/repr-c-dead-variants.x86_64-unknown-linux-gnu.stderr
+++ b/tests/ui/repr/repr-c-dead-variants.x86_64-unknown-linux-gnu.stderr
@@ -4,7 +4,7 @@ error: layout_of(Univariant) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -49,7 +49,7 @@ error: layout_of(Univariant) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I32,
@@ -92,7 +92,7 @@ error: layout_of(TwoVariants) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I32,
@@ -143,7 +143,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -181,7 +181,7 @@ error: layout_of(TwoVariants) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I32,
@@ -230,7 +230,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                abi: Align(8 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -269,7 +269,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -299,7 +299,7 @@ error: layout_of(DeadBranchHasOtherField) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/repr/repr-c-int-dead-variants.stderr b/tests/ui/repr/repr-c-int-dead-variants.stderr
index f852212deb908..f63574182c25f 100644
--- a/tests/ui/repr/repr-c-int-dead-variants.stderr
+++ b/tests/ui/repr/repr-c-int-dead-variants.stderr
@@ -4,7 +4,7 @@ error: layout_of(UnivariantU8) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I8,
@@ -49,7 +49,7 @@ error: layout_of(UnivariantU8) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I8,
@@ -92,7 +92,7 @@ error: layout_of(TwoVariantsU8) = Layout {
                abi: Align(1 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: ScalarPair(
+           backend_repr: ScalarPair(
                Initialized {
                    value: Int(
                        I8,
@@ -143,7 +143,7 @@ error: layout_of(TwoVariantsU8) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -181,7 +181,7 @@ error: layout_of(TwoVariantsU8) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: ScalarPair(
+                       backend_repr: ScalarPair(
                            Initialized {
                                value: Int(
                                    I8,
@@ -230,7 +230,7 @@ error: layout_of(DeadBranchHasOtherFieldU8) = Layout {
                abi: Align(8 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Memory {
+           backend_repr: Memory {
                sized: true,
            },
            fields: Arbitrary {
@@ -269,7 +269,7 @@ error: layout_of(DeadBranchHasOtherFieldU8) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -299,7 +299,7 @@ error: layout_of(DeadBranchHasOtherFieldU8) = Layout {
                            abi: Align(8 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
diff --git a/tests/ui/return/tail-expr-as-potential-return.rs b/tests/ui/return/tail-expr-as-potential-return.rs
index 11ecddb049b57..2e638f1897c22 100644
--- a/tests/ui/return/tail-expr-as-potential-return.rs
+++ b/tests/ui/return/tail-expr-as-potential-return.rs
@@ -60,7 +60,6 @@ fn method() -> Option<i32> {
         Receiver.generic();
         //~^ ERROR type annotations needed
         //~| HELP consider specifying the generic argument
-        //~| HELP you might have meant to return this to infer its type parameters
     }
 
     None
diff --git a/tests/ui/return/tail-expr-as-potential-return.stderr b/tests/ui/return/tail-expr-as-potential-return.stderr
index 756de2b5a1668..8105b2df3fea6 100644
--- a/tests/ui/return/tail-expr-as-potential-return.stderr
+++ b/tests/ui/return/tail-expr-as-potential-return.stderr
@@ -57,10 +57,6 @@ help: consider specifying the generic argument
    |
 LL |         Receiver.generic::<T>();
    |                         +++++
-help: you might have meant to return this to infer its type parameters
-   |
-LL |         return Receiver.generic();
-   |         ++++++
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/specialization/defaultimpl/validation.rs b/tests/ui/specialization/defaultimpl/validation.rs
index 4049c4ea14c5b..14771be8982dd 100644
--- a/tests/ui/specialization/defaultimpl/validation.rs
+++ b/tests/ui/specialization/defaultimpl/validation.rs
@@ -6,12 +6,17 @@ struct Z;
 
 default impl S {} //~ ERROR inherent impls cannot be `default`
 
-default unsafe impl Send for S {} //~ ERROR impls of auto traits cannot be default
-//~^ ERROR `S` cannot be sent between threads safely
-default impl !Send for Z {} //~ ERROR impls of auto traits cannot be default
-                            //~^ ERROR negative impls cannot be default impls
+default unsafe impl Send for S {}
+//~^ ERROR impls of auto traits cannot be default
+
+default impl !Send for Z {}
+//~^ ERROR impls of auto traits cannot be default
+//~| ERROR negative impls cannot be default impls
+//~| ERROR `!Send` impl requires `Z: Send` but the struct it is implemented for does not
 
 trait Tr {}
-default impl !Tr for S {} //~ ERROR negative impls cannot be default impls
+
+default impl !Tr for S {}
+//~^ ERROR negative impls cannot be default impls
 
 fn main() {}
diff --git a/tests/ui/specialization/defaultimpl/validation.stderr b/tests/ui/specialization/defaultimpl/validation.stderr
index f56f16162a27f..d034386b842f3 100644
--- a/tests/ui/specialization/defaultimpl/validation.stderr
+++ b/tests/ui/specialization/defaultimpl/validation.stderr
@@ -26,22 +26,20 @@ LL | default unsafe impl Send for S {}
    | |
    | default because of this
 
-error[E0277]: `S` cannot be sent between threads safely
-  --> $DIR/validation.rs:9:1
+error[E0367]: `!Send` impl requires `Z: Send` but the struct it is implemented for does not
+  --> $DIR/validation.rs:12:1
    |
-LL | default unsafe impl Send for S {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `S` cannot be sent between threads safely
-   |
-   = help: the trait `Send` is not implemented for `S`
-   = help: the trait `Send` is implemented for `S`
-   = help: see issue #48214
-help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
+LL | default impl !Send for Z {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
    |
-LL + #![feature(trivial_bounds)]
+note: the implementor must specify the same requirement
+  --> $DIR/validation.rs:5:1
    |
+LL | struct Z;
+   | ^^^^^^^^
 
 error: impls of auto traits cannot be default
-  --> $DIR/validation.rs:11:15
+  --> $DIR/validation.rs:12:15
    |
 LL | default impl !Send for Z {}
    | -------       ^^^^ auto trait
@@ -49,18 +47,18 @@ LL | default impl !Send for Z {}
    | default because of this
 
 error[E0750]: negative impls cannot be default impls
-  --> $DIR/validation.rs:11:1
+  --> $DIR/validation.rs:12:1
    |
 LL | default impl !Send for Z {}
    | ^^^^^^^      ^
 
 error[E0750]: negative impls cannot be default impls
-  --> $DIR/validation.rs:15:1
+  --> $DIR/validation.rs:19:1
    |
 LL | default impl !Tr for S {}
    | ^^^^^^^      ^
 
 error: aborting due to 6 previous errors; 1 warning emitted
 
-Some errors have detailed explanations: E0277, E0750.
-For more information about an error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0367, E0750.
+For more information about an error, try `rustc --explain E0367`.
diff --git a/tests/ui/specialization/specialization-overlap-negative.rs b/tests/ui/specialization/specialization-overlap-negative.rs
index 550d370829539..244f21c7ba905 100644
--- a/tests/ui/specialization/specialization-overlap-negative.rs
+++ b/tests/ui/specialization/specialization-overlap-negative.rs
@@ -6,6 +6,8 @@ trait MyTrait {}
 struct TestType<T>(::std::marker::PhantomData<T>);
 
 unsafe impl<T: Clone> Send for TestType<T> {}
-impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR E0751
+impl<T: MyTrait> !Send for TestType<T> {}
+//~^ ERROR found both positive and negative implementation of trait `Send` for type `TestType<_>`
+//~| ERROR `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
 
 fn main() {}
diff --git a/tests/ui/specialization/specialization-overlap-negative.stderr b/tests/ui/specialization/specialization-overlap-negative.stderr
index a8e99953e2b65..4874e897726fc 100644
--- a/tests/ui/specialization/specialization-overlap-negative.stderr
+++ b/tests/ui/specialization/specialization-overlap-negative.stderr
@@ -16,6 +16,19 @@ LL | unsafe impl<T: Clone> Send for TestType<T> {}
 LL | impl<T: MyTrait> !Send for TestType<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
-error: aborting due to 1 previous error; 1 warning emitted
+error[E0367]: `!Send` impl requires `T: MyTrait` but the struct it is implemented for does not
+  --> $DIR/specialization-overlap-negative.rs:9:9
+   |
+LL | impl<T: MyTrait> !Send for TestType<T> {}
+   |         ^^^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/specialization-overlap-negative.rs:6:1
+   |
+LL | struct TestType<T>(::std::marker::PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0751`.
+Some errors have detailed explanations: E0367, E0751.
+For more information about an error, try `rustc --explain E0367`.
diff --git a/tests/ui/structs/ident-from-macro-expansion.rs b/tests/ui/structs/ident-from-macro-expansion.rs
new file mode 100644
index 0000000000000..56d31a4256168
--- /dev/null
+++ b/tests/ui/structs/ident-from-macro-expansion.rs
@@ -0,0 +1,19 @@
+struct Foo {
+    inner: Inner,
+}
+
+struct Inner {
+    y: i32,
+}
+
+macro_rules! access {
+    ($expr:expr, $ident:ident) => {
+        $expr.$ident
+    }
+}
+
+fn main() {
+    let k = Foo { inner: Inner { y: 0 } };
+    access!(k, y);
+    //~^ ERROR no field `y` on type `Foo`
+}
diff --git a/tests/ui/structs/ident-from-macro-expansion.stderr b/tests/ui/structs/ident-from-macro-expansion.stderr
new file mode 100644
index 0000000000000..be2ab7c2e9966
--- /dev/null
+++ b/tests/ui/structs/ident-from-macro-expansion.stderr
@@ -0,0 +1,14 @@
+error[E0609]: no field `y` on type `Foo`
+  --> $DIR/ident-from-macro-expansion.rs:17:16
+   |
+LL |         $expr.$ident
+   |               ------ due to this macro variable
+...
+LL |     access!(k, y);
+   |                ^ unknown field
+   |
+   = note: available field is: `inner`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0609`.
diff --git a/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.rs b/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.rs
new file mode 100644
index 0000000000000..cd675a5efd162
--- /dev/null
+++ b/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.rs
@@ -0,0 +1,22 @@
+#![feature(auto_traits, negative_impls)]
+
+auto trait Foo {}
+
+struct AdditionalLt<'a, T>(&'a (), T);
+impl<'a, T: 'a> !Foo for AdditionalLt<'a, T> {}
+//~^ ERROR `!Foo` impl requires `T: 'a` but the struct it is implemented for does not
+
+struct AdditionalBound<T>(T);
+trait Bound {}
+impl<T: Bound> !Foo for AdditionalBound<T> {}
+//~^ ERROR `!Foo` impl requires `T: Bound` but the struct it is implemented for does not
+
+struct TwoParam<T, U>(T, U);
+impl<T> !Foo for TwoParam<T, T> {}
+//~^ ERROR `!Foo` impls cannot be specialized
+
+struct ConcreteParam<T>(T);
+impl !Foo for ConcreteParam<i32> {}
+//~^ ERROR `!Foo` impls cannot be specialized
+
+fn main() {}
diff --git a/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.stderr b/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.stderr
new file mode 100644
index 0000000000000..ef783e9015592
--- /dev/null
+++ b/tests/ui/traits/negative-impls/negated-auto-traits-validity-error.stderr
@@ -0,0 +1,54 @@
+error[E0367]: `!Foo` impl requires `T: 'a` but the struct it is implemented for does not
+  --> $DIR/negated-auto-traits-validity-error.rs:6:13
+   |
+LL | impl<'a, T: 'a> !Foo for AdditionalLt<'a, T> {}
+   |             ^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/negated-auto-traits-validity-error.rs:5:1
+   |
+LL | struct AdditionalLt<'a, T>(&'a (), T);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0367]: `!Foo` impl requires `T: Bound` but the struct it is implemented for does not
+  --> $DIR/negated-auto-traits-validity-error.rs:11:9
+   |
+LL | impl<T: Bound> !Foo for AdditionalBound<T> {}
+   |         ^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> $DIR/negated-auto-traits-validity-error.rs:9:1
+   |
+LL | struct AdditionalBound<T>(T);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0366]: `!Foo` impls cannot be specialized
+  --> $DIR/negated-auto-traits-validity-error.rs:15:1
+   |
+LL | impl<T> !Foo for TwoParam<T, T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `T` is mentioned multiple times
+note: use the same sequence of generic lifetime, type and const parameters as the struct definition
+  --> $DIR/negated-auto-traits-validity-error.rs:14:1
+   |
+LL | struct TwoParam<T, U>(T, U);
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+error[E0366]: `!Foo` impls cannot be specialized
+  --> $DIR/negated-auto-traits-validity-error.rs:19:1
+   |
+LL | impl !Foo for ConcreteParam<i32> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `i32` is not a generic parameter
+note: use the same sequence of generic lifetime, type and const parameters as the struct definition
+  --> $DIR/negated-auto-traits-validity-error.rs:18:1
+   |
+LL | struct ConcreteParam<T>(T);
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0366, E0367.
+For more information about an error, try `rustc --explain E0366`.
diff --git a/tests/ui/traits/negative-impls/negated-auto-traits-validity.rs b/tests/ui/traits/negative-impls/negated-auto-traits-validity.rs
new file mode 100644
index 0000000000000..76996b5593e60
--- /dev/null
+++ b/tests/ui/traits/negative-impls/negated-auto-traits-validity.rs
@@ -0,0 +1,22 @@
+//@ check-pass
+
+#![feature(auto_traits, negative_impls)]
+
+auto trait Foo {}
+auto trait Bar {}
+
+struct NeedsOutlives<'a, T>(&'a T);
+
+impl<'a, T: 'a> !Foo for NeedsOutlives<'a, T> {}
+
+// Leaving out the lifetime bound
+impl<'a, T> !Bar for NeedsOutlives<'a, T> {}
+
+struct NeedsSend<T: Send>(T);
+
+impl<T: Send> !Foo for NeedsSend<T> {}
+
+// Leaving off the trait bound
+impl<T> !Bar for NeedsSend<T> {}
+
+fn main() {}
diff --git a/tests/ui/type/pattern_types/range_patterns.stderr b/tests/ui/type/pattern_types/range_patterns.stderr
index 690592ba0b8da..7eda50fd12116 100644
--- a/tests/ui/type/pattern_types/range_patterns.stderr
+++ b/tests/ui/type/pattern_types/range_patterns.stderr
@@ -4,7 +4,7 @@ error: layout_of(NonZero<u32>) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -50,7 +50,7 @@ error: layout_of((u32) is 1..=) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -89,7 +89,7 @@ error: layout_of(Option<(u32) is 1..=>) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -129,7 +129,7 @@ error: layout_of(Option<(u32) is 1..=>) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -151,7 +151,7 @@ error: layout_of(Option<(u32) is 1..=>) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I32,
@@ -203,7 +203,7 @@ error: layout_of(Option<NonZero<u32>>) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
@@ -243,7 +243,7 @@ error: layout_of(Option<NonZero<u32>>) = Layout {
                            abi: Align(1 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Memory {
+                       backend_repr: Memory {
                            sized: true,
                        },
                        fields: Arbitrary {
@@ -265,7 +265,7 @@ error: layout_of(Option<NonZero<u32>>) = Layout {
                            abi: Align(4 bytes),
                            pref: $SOME_ALIGN,
                        },
-                       abi: Scalar(
+                       backend_repr: Scalar(
                            Initialized {
                                value: Int(
                                    I32,
@@ -317,7 +317,7 @@ error: layout_of(NonZeroU32New) = Layout {
                abi: Align(4 bytes),
                pref: $SOME_ALIGN,
            },
-           abi: Scalar(
+           backend_repr: Scalar(
                Initialized {
                    value: Int(
                        I32,
diff --git a/tests/ui/unsafe-fields/unsafe-fields.rs b/tests/ui/unsafe-fields/unsafe-fields.rs
index 637471582d7e4..cb86479bb20d3 100644
--- a/tests/ui/unsafe-fields/unsafe-fields.rs
+++ b/tests/ui/unsafe-fields/unsafe-fields.rs
@@ -17,7 +17,7 @@ fn f(a: A) {
 }
 
 struct WithInvalidUnsafeField {
-    unsafe unsafe_noncopy_field: Vec<u32>, //~ ERROR
+    unsafe unsafe_noncopy_field: Vec<u32>,
 }
 
 struct WithManuallyDropUnsafeField {
diff --git a/tests/ui/unsafe-fields/unsafe-fields.stderr b/tests/ui/unsafe-fields/unsafe-fields.stderr
index a1c5d2b44cdf1..d0e2dc16a13d5 100644
--- a/tests/ui/unsafe-fields/unsafe-fields.stderr
+++ b/tests/ui/unsafe-fields/unsafe-fields.stderr
@@ -1,15 +1,3 @@
-error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be unsafe
-  --> $DIR/unsafe-fields.rs:20:5
-   |
-LL |     unsafe unsafe_noncopy_field: Vec<u32>,
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: unsafe fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
-help: wrap the field type in `ManuallyDrop<...>`
-   |
-LL |     unsafe unsafe_noncopy_field: std::mem::ManuallyDrop<Vec<u32>>,
-   |                                  +++++++++++++++++++++++        +
-
 error[E0133]: use of unsafe field is unsafe and requires unsafe block
   --> $DIR/unsafe-fields.rs:15:30
    |
@@ -69,7 +57,6 @@ LL |         &raw const self.unsafe_field
    |
    = note: unsafe fields may carry library invariants
 
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0133, E0740.
-For more information about an error, try `rustc --explain E0133`.
+For more information about this error, try `rustc --explain E0133`.
diff --git a/triagebot.toml b/triagebot.toml
index cab4e232dc044..ff789e6e36265 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -838,13 +838,7 @@ message = "Some changes occurred in GUI tests."
 cc = ["@GuillaumeGomez"]
 
 [mentions."tests/run-make/"]
-message = """
-This PR modifies `tests/run-make/`. If this PR is trying to port a Makefile
-run-make test to use rmake.rs, please update the
-[run-make port tracking issue](https://github.com/rust-lang/rust/issues/121876)
-so we can track our progress. You can either modify the tracking issue
-directly, or you can comment on the tracking issue and link this PR.
-"""
+message = "This PR modifies `run-make` tests."
 cc = ["@jieyouxu"]
 
 [mentions."src/rustdoc-json-types"]