diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index 9325d4c413941..9079e26eb509e 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -273,7 +273,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         if !generic_args.parenthesized && !has_lifetimes {
             generic_args.args = self
                 .elided_path_lifetimes(
-                    first_generic_span.map(|s| s.shrink_to_lo()).unwrap_or(segment.ident.span),
+                    first_generic_span.map_or(segment.ident.span, |s| s.shrink_to_lo()),
                     expected_lifetimes,
                 )
                 .map(GenericArg::Lifetime)
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index d65bc820f8fb1..7bd805f91c857 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -370,7 +370,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     gate_feature_post!(
                         &self,
                         negative_impls,
-                        span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(span)),
+                        span.to(of_trait.as_ref().map_or(span, |t| t.path.span)),
                         "negative trait bounds are not yet fully implemented; \
                          use marker types for now"
                     );
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 68f319ade1e79..e225730dce061 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -1002,8 +1002,7 @@ pub unsafe fn with_llvm_pmb(
     // reasonable defaults and prepare it to actually populate the pass
     // manager.
     let builder = llvm::LLVMPassManagerBuilderCreate();
-    let opt_size =
-        config.opt_size.map(|x| to_llvm_opt_settings(x).1).unwrap_or(llvm::CodeGenOptSizeNone);
+    let opt_size = config.opt_size.map_or(llvm::CodeGenOptSizeNone, |x| to_llvm_opt_settings(x).1);
     let inline_threshold = config.inline_threshold;
     let pgo_gen_path = get_pgo_gen_path(config);
     let pgo_use_path = get_pgo_use_path(config);
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index ccbe7325cc6c2..955e739b2c126 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -552,7 +552,6 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         unsafe {
             llvm::LLVMRustDIBuilderCreateDebugLocation(
-                utils::debug_context(self).llcontext,
                 line.unwrap_or(UNKNOWN_LINE_NUMBER),
                 col.unwrap_or(UNKNOWN_COLUMN_NUMBER),
                 scope,
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index e359d9f8c9c77..eb4f36266dbae 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2102,7 +2102,6 @@ extern "C" {
     );
 
     pub fn LLVMRustDIBuilderCreateDebugLocation(
-        Context: &'a Context,
         Line: c_uint,
         Column: c_uint,
         Scope: &'a DIScope,
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 728795cf50b85..ff77db9eab852 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -166,7 +166,7 @@ fn get_linker(
         _ => match flavor {
             LinkerFlavor::Lld(f) => Command::lld(linker, f),
             LinkerFlavor::Msvc if sess.opts.cg.linker.is_none() && sess.target.linker.is_none() => {
-                Command::new(msvc_tool.as_ref().map(|t| t.path()).unwrap_or(linker))
+                Command::new(msvc_tool.as_ref().map_or(linker, |t| t.path()))
             }
             _ => Command::new(linker),
         },
diff --git a/compiler/rustc_data_structures/src/profiling.rs b/compiler/rustc_data_structures/src/profiling.rs
index 5d13b7f27c704..b16d5a9e2b421 100644
--- a/compiler/rustc_data_structures/src/profiling.rs
+++ b/compiler/rustc_data_structures/src/profiling.rs
@@ -166,7 +166,7 @@ impl SelfProfilerRef {
         // If there is no SelfProfiler then the filter mask is set to NONE,
         // ensuring that nothing ever tries to actually access it.
         let event_filter_mask =
-            profiler.as_ref().map(|p| p.event_filter_mask).unwrap_or(EventFilter::empty());
+            profiler.as_ref().map_or(EventFilter::empty(), |p| p.event_filter_mask);
 
         SelfProfilerRef {
             profiler,
diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index 509f81e16536b..15b984acac590 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -798,7 +798,7 @@ pub fn version(binary: &str, matches: &getopts::Matches) {
         println!("commit-date: {}", unw(util::commit_date_str()));
         println!("host: {}", config::host_triple());
         println!("release: {}", unw(util::release_str()));
-        if cfg!(llvm) {
+        if cfg!(feature = "llvm") {
             get_builtin_codegen_backend("llvm")().print_version();
         }
     }
@@ -1087,7 +1087,7 @@ pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
     }
 
     if cg_flags.iter().any(|x| *x == "passes=list") {
-        if cfg!(llvm) {
+        if cfg!(feature = "llvm") {
             get_builtin_codegen_backend("llvm")().print_passes();
         }
         return None;
@@ -1236,7 +1236,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     }
 
     // If backtraces are enabled, also print the query stack
-    let backtrace = env::var_os("RUST_BACKTRACE").map(|x| &x != "0").unwrap_or(false);
+    let backtrace = env::var_os("RUST_BACKTRACE").map_or(false, |x| &x != "0");
 
     let num_frames = if backtrace { None } else { Some(2) };
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 593e0d92031ff..e184e929b0745 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -804,7 +804,7 @@ impl HandlerInner {
     }
 
     fn treat_err_as_bug(&self) -> bool {
-        self.flags.treat_err_as_bug.map(|c| self.err_count() >= c).unwrap_or(false)
+        self.flags.treat_err_as_bug.map_or(false, |c| self.err_count() >= c)
     }
 
     fn print_error_count(&mut self, registry: &Registry) {
@@ -913,7 +913,7 @@ impl HandlerInner {
         // This is technically `self.treat_err_as_bug()` but `delay_span_bug` is called before
         // incrementing `err_count` by one, so we need to +1 the comparing.
         // FIXME: Would be nice to increment err_count in a more coherent way.
-        if self.flags.treat_err_as_bug.map(|c| self.err_count() + 1 >= c).unwrap_or(false) {
+        if self.flags.treat_err_as_bug.map_or(false, |c| self.err_count() + 1 >= c) {
             // FIXME: don't abort here if report_delayed_bugs is off
             self.span_bug(sp, msg);
         }
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 1193f66651ce9..b07bce94870c1 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -423,7 +423,7 @@ impl<'a> StripUnconfigured<'a> {
 
     /// If attributes are not allowed on expressions, emit an error for `attr`
     pub fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
-        if !self.features.map(|features| features.stmt_expr_attributes).unwrap_or(true) {
+        if !self.features.map_or(true, |features| features.stmt_expr_attributes) {
             let mut err = feature_err(
                 &self.sess.parse_sess,
                 sym::stmt_expr_attributes,
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs
index e76cc6f1fed7b..1aed42a24e2b3 100644
--- a/compiler/rustc_expand/src/mbe/macro_parser.rs
+++ b/compiler/rustc_expand/src/mbe/macro_parser.rs
@@ -500,7 +500,7 @@ fn inner_parse_loop<'root, 'tt>(
                 if idx == len && item.sep.is_some() {
                     // We have a separator, and it is the current token. We can advance past the
                     // separator token.
-                    if item.sep.as_ref().map(|sep| token_name_eq(token, sep)).unwrap_or(false) {
+                    if item.sep.as_ref().map_or(false, |sep| token_name_eq(token, sep)) {
                         item.idx += 1;
                         next_items.push(item);
                     }
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 3d126749d541d..8373304ea9134 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -203,7 +203,7 @@ fn macro_rules_dummy_expander<'cx>(
 }
 
 fn trace_macros_note(cx_expansions: &mut FxHashMap<Span, Vec<String>>, sp: Span, message: String) {
-    let sp = sp.macro_backtrace().last().map(|trace| trace.call_site).unwrap_or(sp);
+    let sp = sp.macro_backtrace().last().map_or(sp, |trace| trace.call_site);
     cx_expansions.entry(sp).or_default().push(message);
 }
 
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs
index a4b44931fc1ae..c8049495d223c 100644
--- a/compiler/rustc_expand/src/mbe/quoted.rs
+++ b/compiler/rustc_expand/src/mbe/quoted.rs
@@ -99,10 +99,10 @@ pub(super) fn parse(
                                 }
                                 _ => token.span,
                             },
-                            tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span),
+                            tree => tree.as_ref().map_or(span, tokenstream::TokenTree::span),
                         }
                     }
-                    tree => tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(start_sp),
+                    tree => tree.as_ref().map_or(start_sp, tokenstream::TokenTree::span),
                 };
                 if node_id != DUMMY_NODE_ID {
                     // Macros loaded from other crates have dummy node ids.
@@ -250,7 +250,7 @@ fn parse_kleene_op(
             Some(op) => Ok(Ok((op, token.span))),
             None => Ok(Err(token)),
         },
-        tree => Err(tree.as_ref().map(tokenstream::TokenTree::span).unwrap_or(span)),
+        tree => Err(tree.as_ref().map_or(span, tokenstream::TokenTree::span)),
     }
 }
 
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 269916390ed45..5c3c1591b1ce5 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -561,7 +561,7 @@ impl WhereClause<'_> {
     ///  in `fn foo<T>(t: T) where T: Foo,` so we don't suggest two trailing commas.
     pub fn tail_span_for_suggestion(&self) -> Span {
         let end = self.span_for_predicates_or_empty_place().shrink_to_hi();
-        self.predicates.last().map(|p| p.span()).unwrap_or(end).shrink_to_hi().to(end)
+        self.predicates.last().map_or(end, |p| p.span()).shrink_to_hi().to(end)
     }
 }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 5d56744805f89..fee6f87ae42c3 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2118,7 +2118,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 let consider = format!(
                     "{} {}...",
                     msg,
-                    if type_param_span.map(|(_, _, is_impl_trait)| is_impl_trait).unwrap_or(false) {
+                    if type_param_span.map_or(false, |(_, _, is_impl_trait)| is_impl_trait) {
                         format!(" `{}` to `{}`", sub, bound_kind)
                     } else {
                         format!("`{}: {}`", bound_kind, sub)
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 56d9634213ae5..27545c126857b 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -1533,7 +1533,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 // Note: if these two lines are combined into one we get
                 // dynamic borrow errors on `self.inner`.
                 let known = self.inner.borrow_mut().type_variables().probe(v).known();
-                known.map(|t| self.shallow_resolve_ty(t)).unwrap_or(typ)
+                known.map_or(typ, |t| self.shallow_resolve_ty(t))
             }
 
             ty::Infer(ty::IntVar(v)) => self
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index 9ad9d53cd0db3..424f91b3f883e 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -647,8 +647,7 @@ pub fn transparent_newtype_field<'a, 'tcx>(
     let param_env = tcx.param_env(variant.def_id);
     for field in &variant.fields {
         let field_ty = tcx.type_of(field.did);
-        let is_zst =
-            tcx.layout_of(param_env.and(field_ty)).map(|layout| layout.is_zst()).unwrap_or(false);
+        let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
 
         if !is_zst {
             return Some(field);
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 35915dc7a9753..bc7363a69a6e8 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -529,8 +529,8 @@ trait UnusedDelimLint {
             pprust::expr_to_string(value)
         };
         let keep_space = (
-            left_pos.map(|s| s >= value.span.lo()).unwrap_or(false),
-            right_pos.map(|s| s <= value.span.hi()).unwrap_or(false),
+            left_pos.map_or(false, |s| s >= value.span.lo()),
+            right_pos.map_or(false, |s| s <= value.span.hi()),
         );
         self.emit_unused_delims(cx, value.span, &expr_text, ctx.into(), keep_space);
     }
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index c0ff62c17beb5..1d6f00562f136 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -994,11 +994,9 @@ LLVMRustDICompositeTypeReplaceArrays(LLVMRustDIBuilderRef Builder,
 }
 
 extern "C" LLVMMetadataRef
-LLVMRustDIBuilderCreateDebugLocation(LLVMContextRef ContextRef, unsigned Line,
-                                     unsigned Column, LLVMMetadataRef Scope,
+LLVMRustDIBuilderCreateDebugLocation(unsigned Line, unsigned Column,
+                                     LLVMMetadataRef Scope,
                                      LLVMMetadataRef InlinedAt) {
-  LLVMContext &Context = *unwrap(ContextRef);
-
   DebugLoc debug_loc = DebugLoc::get(Line, Column, unwrapDIPtr<MDNode>(Scope),
                                      unwrapDIPtr<MDNode>(InlinedAt));
 
diff --git a/compiler/rustc_macros/src/query.rs b/compiler/rustc_macros/src/query.rs
index 6d876784be653..d264462bf0895 100644
--- a/compiler/rustc_macros/src/query.rs
+++ b/compiler/rustc_macros/src/query.rs
@@ -429,7 +429,7 @@ fn add_query_description_impl(
     };
 
     let (tcx, desc) = modifiers.desc;
-    let tcx = tcx.as_ref().map(|t| quote! { #t }).unwrap_or(quote! { _ });
+    let tcx = tcx.as_ref().map_or(quote! { _ }, |t| quote! { #t });
 
     let desc = quote! {
         #[allow(unused_variables)]
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index 019ca5174a223..a7bf79d7e6743 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -326,7 +326,7 @@ impl<'a> CrateLoader<'a> {
         self.verify_no_symbol_conflicts(&crate_root)?;
 
         let private_dep =
-            self.sess.opts.externs.get(&name.as_str()).map(|e| e.is_private_dep).unwrap_or(false);
+            self.sess.opts.externs.get(&name.as_str()).map_or(false, |e| e.is_private_dep);
 
         // Claim this crate number and cache it
         let cnum = self.cstore.alloc_new_crate_num();
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index 5b33678b25ae2..8d0994320e383 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -132,7 +132,7 @@ impl ItemLikeVisitor<'tcx> for Collector<'tcx> {
 
 impl Collector<'tcx> {
     fn register_native_lib(&mut self, span: Option<Span>, lib: NativeLib) {
-        if lib.name.as_ref().map(|&s| s == kw::Empty).unwrap_or(false) {
+        if lib.name.as_ref().map_or(false, |&s| s == kw::Empty) {
             match span {
                 Some(span) => {
                     struct_span_err!(
diff --git a/compiler/rustc_middle/src/dep_graph/dep_node.rs b/compiler/rustc_middle/src/dep_graph/dep_node.rs
index b775846bba452..65e5301c96e9e 100644
--- a/compiler/rustc_middle/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_middle/src/dep_graph/dep_node.rs
@@ -29,9 +29,10 @@
 //!   contained no `DefId` for thing that had been removed.
 //!
 //! `DepNode` definition happens in the `define_dep_nodes!()` macro. This macro
-//! defines the `DepKind` enum and a corresponding `dep_constructor` module. The
-//! `dep_constructor` module links a `DepKind` to the parameters that are needed at
-//! runtime in order to construct a valid `DepNode` fingerprint.
+//! defines the `DepKind` enum. Each `DepKind` has its own parameters that are
+//! needed at runtime in order to construct a valid `DepNode` fingerprint.
+//! However, only `CompileCodegenUnit` is constructed explicitly (with
+//! `make_compile_codegen_unit`).
 //!
 //! Because the macro sees what parameters a given `DepKind` requires, it can
 //! "infer" some properties for each kind of `DepNode`:
@@ -44,22 +45,14 @@
 //!   `DefId` it was computed from. In other cases, too much information gets
 //!   lost during fingerprint computation.
 //!
-//! The `dep_constructor` module, together with `DepNode::new()`, ensures that only
+//! `make_compile_codegen_unit`, together with `DepNode::new()`, ensures that only
 //! valid `DepNode` instances can be constructed. For example, the API does not
 //! allow for constructing parameterless `DepNode`s with anything other
 //! than a zeroed out fingerprint. More generally speaking, it relieves the
 //! user of the `DepNode` API of having to know how to compute the expected
 //! fingerprint for a given set of node parameters.
 
-use crate::mir::interpret::{GlobalId, LitToConstInput};
-use crate::traits;
-use crate::traits::query::{
-    CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
-    CanonicalTypeOpAscribeUserTypeGoal, CanonicalTypeOpEqGoal, CanonicalTypeOpNormalizeGoal,
-    CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpSubtypeGoal,
-};
-use crate::ty::subst::{GenericArg, SubstsRef};
-use crate::ty::{self, ParamEnvAnd, Ty, TyCtxt};
+use crate::ty::TyCtxt;
 
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
@@ -338,25 +331,6 @@ macro_rules! define_dep_nodes {
             $($variant),*
         }
 
-        #[allow(non_camel_case_types)]
-        pub mod dep_constructor {
-            use super::*;
-
-            $(
-                #[inline(always)]
-                #[allow(unreachable_code, non_snake_case)]
-                pub fn $variant(_tcx: TyCtxt<'_>, $(arg: $tuple_arg_ty)*) -> DepNode {
-                    // tuple args
-                    $({
-                        erase!($tuple_arg_ty);
-                        return DepNode::construct(_tcx, DepKind::$variant, &arg)
-                    })*
-
-                    return DepNode::construct(_tcx, DepKind::$variant, &())
-                }
-            )*
-        }
-
         fn dep_kind_from_label_string(label: &str) -> Result<DepKind, ()> {
             match label {
                 $(stringify!($variant) => Ok(DepKind::$variant),)*
@@ -384,9 +358,16 @@ rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
 
     [anon] TraitSelect,
 
+    // WARNING: if `Symbol` is changed, make sure you update `make_compile_codegen_unit` below.
     [] CompileCodegenUnit(Symbol),
 ]);
 
+// WARNING: `construct` is generic and does not know that `CompileCodegenUnit` takes `Symbol`s as keys.
+// Be very careful changing this type signature!
+crate fn make_compile_codegen_unit(tcx: TyCtxt<'_>, name: Symbol) -> DepNode {
+    DepNode::construct(tcx, DepKind::CompileCodegenUnit, &name)
+}
+
 pub type DepNode = rustc_query_system::dep_graph::DepNode<DepKind>;
 
 // We keep a lot of `DepNode`s in memory during compilation. It's not
diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 22e9cc1cd3ee4..ea4d8c1299709 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -13,7 +13,8 @@ pub use rustc_query_system::dep_graph::{
     WorkProduct, WorkProductId,
 };
 
-pub use dep_node::{dep_constructor, label_strs, DepKind, DepNode, DepNodeExt};
+crate use dep_node::make_compile_codegen_unit;
+pub use dep_node::{label_strs, DepKind, DepNode, DepNodeExt};
 
 pub type DepGraph = rustc_query_system::dep_graph::DepGraph<DepKind>;
 pub type TaskDeps = rustc_query_system::dep_graph::TaskDeps<DepKind>;
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 209d1838e3ebc..2568af23ef506 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -813,7 +813,7 @@ impl<'hir> Map<'hir> {
     /// Given a node ID, gets a list of attributes associated with the AST
     /// corresponding to the node-ID.
     pub fn attrs(&self, id: HirId) -> &'hir [ast::Attribute] {
-        let attrs = self.find_entry(id).map(|entry| match entry.node {
+        self.find_entry(id).map_or(&[], |entry| match entry.node {
             Node::Param(a) => &a.attrs[..],
             Node::Local(l) => &l.attrs[..],
             Node::Item(i) => &i.attrs[..],
@@ -840,8 +840,7 @@ impl<'hir> Map<'hir> {
             | Node::Block(..)
             | Node::Lifetime(..)
             | Node::Visibility(..) => &[],
-        });
-        attrs.unwrap_or(&[])
+        })
     }
 
     /// Gets the span of the definition of the specified HIR node.
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index f810f6a56a520..6d5d408f86c15 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -1,4 +1,4 @@
-use crate::dep_graph::{dep_constructor, DepNode, WorkProduct, WorkProductId};
+use crate::dep_graph::{DepNode, WorkProduct, WorkProductId};
 use crate::ich::{NodeIdHashingMode, StableHashingContext};
 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
 use rustc_attr::InlineAttr;
@@ -362,7 +362,7 @@ impl<'tcx> CodegenUnit<'tcx> {
     }
 
     pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
-        dep_constructor::CompileCodegenUnit(tcx, self.name())
+        crate::dep_graph::make_compile_codegen_unit(tcx, self.name())
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index ecf2837b3e423..a2638d8bddad0 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -82,7 +82,7 @@ impl<'tcx> ConstKind<'tcx> {
     /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
     /// unevaluated constant.
     pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Self {
-        self.try_eval(tcx, param_env).and_then(Result::ok).map(ConstKind::Value).unwrap_or(self)
+        self.try_eval(tcx, param_env).and_then(Result::ok).map_or(self, ConstKind::Value)
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 3540f0f06b6e6..c3ad4c1c126d2 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1338,7 +1338,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn serialize_query_result_cache(self, encoder: &mut FileEncoder) -> FileEncodeResult {
-        self.queries.on_disk_cache.as_ref().map(|c| c.serialize(self, encoder)).unwrap_or(Ok(()))
+        self.queries.on_disk_cache.as_ref().map_or(Ok(()), |c| c.serialize(self, encoder))
     }
 
     /// If `true`, we should use the MIR-based borrowck, but also
@@ -2601,7 +2601,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn is_late_bound(self, id: HirId) -> bool {
-        self.is_late_bound_map(id.owner).map(|set| set.contains(&id.local_id)).unwrap_or(false)
+        self.is_late_bound_map(id.owner).map_or(false, |set| set.contains(&id.local_id))
     }
 
     pub fn object_lifetime_defaults(self, id: HirId) -> Option<&'tcx [ObjectLifetimeDefault]> {
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 413c9cca589d9..6ca5dcc532d22 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -535,7 +535,7 @@ fn polymorphize<'tcx>(
     } else {
         None
     };
-    let has_upvars = upvars_ty.map(|ty| ty.tuple_fields().count() > 0).unwrap_or(false);
+    let has_upvars = upvars_ty.map_or(false, |ty| ty.tuple_fields().count() > 0);
     debug!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty, has_upvars);
 
     struct PolymorphizationFolder<'tcx> {
diff --git a/compiler/rustc_mir/src/borrow_check/borrow_set.rs b/compiler/rustc_mir/src/borrow_check/borrow_set.rs
index b4299fbc5a1fe..288eda32e414e 100644
--- a/compiler/rustc_mir/src/borrow_check/borrow_set.rs
+++ b/compiler/rustc_mir/src/borrow_check/borrow_set.rs
@@ -149,7 +149,7 @@ impl<'tcx> BorrowSet<'tcx> {
     }
 
     crate fn activations_at_location(&self, location: Location) -> &[BorrowIndex] {
-        self.activation_map.get(&location).map(|activations| &activations[..]).unwrap_or(&[])
+        self.activation_map.get(&location).map_or(&[], |activations| &activations[..])
     }
 
     crate fn len(&self) -> usize {
diff --git a/compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs b/compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs
index eccb6168229c2..a3d09c3a8d4c1 100644
--- a/compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_mir/src/borrow_check/diagnostics/explain_borrow.rs
@@ -75,7 +75,7 @@ impl BorrowExplanation {
                     LaterUseKind::FakeLetRead => "stored here",
                     LaterUseKind::Other => "used here",
                 };
-                if !borrow_span.map(|sp| sp.overlaps(var_or_use_span)).unwrap_or(false) {
+                if !borrow_span.map_or(false, |sp| sp.overlaps(var_or_use_span)) {
                     err.span_label(
                         var_or_use_span,
                         format!("{}borrow later {}", borrow_desc, message),
diff --git a/compiler/rustc_mir/src/interpret/eval_context.rs b/compiler/rustc_mir/src/interpret/eval_context.rs
index 6d7781671d8cc..7e9594dd6bfd7 100644
--- a/compiler/rustc_mir/src/interpret/eval_context.rs
+++ b/compiler/rustc_mir/src/interpret/eval_context.rs
@@ -370,7 +370,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
     #[inline(always)]
     pub fn cur_span(&self) -> Span {
-        self.stack().last().map(|f| f.current_span()).unwrap_or(self.tcx.span)
+        self.stack().last().map_or(self.tcx.span, |f| f.current_span())
     }
 
     #[inline(always)]
diff --git a/compiler/rustc_mir/src/interpret/util.rs b/compiler/rustc_mir/src/interpret/util.rs
index c2165db278fa0..89f34cd07aa4b 100644
--- a/compiler/rustc_mir/src/interpret/util.rs
+++ b/compiler/rustc_mir/src/interpret/util.rs
@@ -47,8 +47,7 @@ where
                         let index = index
                             .try_into()
                             .expect("more generic parameters than can fit into a `u32`");
-                        let is_used =
-                            unused_params.contains(index).map(|unused| !unused).unwrap_or(true);
+                        let is_used = unused_params.contains(index).map_or(true, |unused| !unused);
                         // Only recurse when generic parameters in fns, closures and generators
                         // are used and require substitution.
                         match (is_used, subst.needs_subst()) {
diff --git a/compiler/rustc_mir/src/monomorphize/collector.rs b/compiler/rustc_mir/src/monomorphize/collector.rs
index a8f2b4d60e140..75f80f69beafc 100644
--- a/compiler/rustc_mir/src/monomorphize/collector.rs
+++ b/compiler/rustc_mir/src/monomorphize/collector.rs
@@ -823,7 +823,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: &Instance<'tcx>) ->
     }
 
     if !tcx.is_mir_available(def_id) {
-        bug!("cannot create local mono-item for {:?}", def_id)
+        bug!("no MIR available for {:?}", def_id);
     }
 
     true
diff --git a/compiler/rustc_mir/src/monomorphize/partitioning/mod.rs b/compiler/rustc_mir/src/monomorphize/partitioning/mod.rs
index db6d3b2d912d6..b9fcd32250dcf 100644
--- a/compiler/rustc_mir/src/monomorphize/partitioning/mod.rs
+++ b/compiler/rustc_mir/src/monomorphize/partitioning/mod.rs
@@ -247,8 +247,7 @@ where
             for (mono_item, linkage) in cgu.items() {
                 let symbol_name = mono_item.symbol_name(tcx).name;
                 let symbol_hash_start = symbol_name.rfind('h');
-                let symbol_hash =
-                    symbol_hash_start.map(|i| &symbol_name[i..]).unwrap_or("<no hash>");
+                let symbol_hash = symbol_hash_start.map_or("<no hash>", |i| &symbol_name[i..]);
 
                 debug!(
                     " - {} [{:?}] [{}] estimated size {}",
diff --git a/compiler/rustc_mir/src/transform/simplify_try.rs b/compiler/rustc_mir/src/transform/simplify_try.rs
index a3459887a9a75..05a88828070fb 100644
--- a/compiler/rustc_mir/src/transform/simplify_try.rs
+++ b/compiler/rustc_mir/src/transform/simplify_try.rs
@@ -113,7 +113,7 @@ fn get_arm_identity_info<'a, 'tcx>(
         test: impl Fn(&'a Statement<'tcx>) -> bool,
         mut action: impl FnMut(usize, &'a Statement<'tcx>),
     ) {
-        while stmt_iter.peek().map(|(_, stmt)| test(stmt)).unwrap_or(false) {
+        while stmt_iter.peek().map_or(false, |(_, stmt)| test(stmt)) {
             let (idx, stmt) = stmt_iter.next().unwrap();
 
             action(idx, stmt);
@@ -635,7 +635,7 @@ impl<'a, 'tcx> SimplifyBranchSameOptimizationFinder<'a, 'tcx> {
                     })
                     .peekable();
 
-                let bb_first = iter_bbs_reachable.peek().map(|(idx, _)| *idx).unwrap_or(&targets_and_values[0]);
+                let bb_first = iter_bbs_reachable.peek().map_or(&targets_and_values[0], |(idx, _)| *idx);
                 let mut all_successors_equivalent = StatementEquality::TrivialEqual;
 
                 // All successor basic blocks must be equal or contain statements that are pairwise considered equal.
diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
index 83fee380ccce7..d7c08a2d1af6b 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
@@ -952,7 +952,7 @@ fn is_useful<'p, 'tcx>(
     assert!(rows.iter().all(|r| r.len() == v.len()));
 
     // FIXME(Nadrieril): Hack to work around type normalization issues (see #72476).
-    let ty = matrix.heads().next().map(|r| r.ty).unwrap_or(v.head().ty);
+    let ty = matrix.heads().next().map_or(v.head().ty, |r| r.ty);
     let pcx = PatCtxt { cx, ty, span: v.head().span, is_top_level };
 
     debug!("is_useful_expand_first_col: ty={:#?}, expanding {:#?}", pcx.ty, v.head());
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 98c7b9a63a55f..35435baea7019 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -511,7 +511,7 @@ impl<'a> Parser<'a> {
         //
         // `x.foo::<u32>>>(3)`
         let parsed_angle_bracket_args =
-            segment.args.as_ref().map(|args| args.is_angle_bracketed()).unwrap_or(false);
+            segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
 
         debug!(
             "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 25e3e67e28e6c..f7b16bd991bfd 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -347,7 +347,7 @@ impl<'a> Parser<'a> {
         let mut pos = pos;
         // This handles the raw string case, the raw argument is the number of #
         // in r###"..."### (we need to add one because of the `r`).
-        let raw = self.style.map(|raw| raw + 1).unwrap_or(0);
+        let raw = self.style.map_or(0, |raw| raw + 1);
         for skip in &self.skips {
             if pos > *skip {
                 pos += 1;
@@ -814,7 +814,7 @@ fn find_skips_from_snippet(
         skips
     }
 
-    let r_start = str_style.map(|r| r + 1).unwrap_or(0);
+    let r_start = str_style.map_or(0, |r| r + 1);
     let r_end = str_style.unwrap_or(0);
     let s = &snippet[r_start + 1..snippet.len() - r_end - 1];
     (find_skips(s, str_style.is_some()), true)
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 605d7ae4af678..151e056a5b356 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -953,7 +953,7 @@ impl<K: DepKind> DepGraph<K> {
     // Returns true if the given node has been marked as green during the
     // current compilation session. Used in various assertions
     pub fn is_green(&self, dep_node: &DepNode<K>) -> bool {
-        self.node_color(dep_node).map(|c| c.is_green()).unwrap_or(false)
+        self.node_color(dep_node).map_or(false, |c| c.is_green())
     }
 
     // This method loads all on-disk cacheable query results into memory, so
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 6219d1b08eb68..9de35a8006123 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -1925,7 +1925,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     {
                         // Check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
                         let item_span =
-                            path.iter().last().map(|segment| segment.ident.span).unwrap_or(span);
+                            path.iter().last().map_or(span, |segment| segment.ident.span);
 
                         let mut hm = self.r.session.confused_type_with_std_module.borrow_mut();
                         hm.insert(item_span, span);
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 55623c9bd9cf6..3945afb4724a8 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -264,7 +264,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                 // The current function has a `self' parameter, but we were unable to resolve
                 // a reference to `self`. This can only happen if the `self` identifier we
                 // are resolving came from a different hygiene context.
-                if fn_kind.decl().inputs.get(0).map(|p| p.is_self()).unwrap_or(false) {
+                if fn_kind.decl().inputs.get(0).map_or(false, |p| p.is_self()) {
                     err.span_label(*span, "this function has a `self` parameter, but a macro invocation can only access identifiers it receives from parameters");
                 } else {
                     let doesnt = if is_assoc_fn {
@@ -1452,8 +1452,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
             }
         } else {
             let needs_placeholder = |def_id: DefId, kind: CtorKind| {
-                let has_no_fields =
-                    self.r.field_names.get(&def_id).map(|f| f.is_empty()).unwrap_or(false);
+                let has_no_fields = self.r.field_names.get(&def_id).map_or(false, |f| f.is_empty());
                 match kind {
                     CtorKind::Const => false,
                     CtorKind::Fn | CtorKind::Fictive if has_no_fields => false,
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs
index cc0e99dc6b10c..aab5c3cf8f59d 100644
--- a/compiler/rustc_resolve/src/late/lifetimes.rs
+++ b/compiler/rustc_resolve/src/late/lifetimes.rs
@@ -644,17 +644,17 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                             } else {
                                 bug!();
                             };
-                            if let hir::ParamName::Plain(param_name) = name {
-                                if param_name.name == kw::UnderscoreLifetime {
-                                    // Pick the elided lifetime "definition" if one exists
-                                    // and use it to make an elision scope.
-                                    self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
-                                    elision = Some(reg);
-                                } else {
-                                    lifetimes.insert(name, reg);
-                                }
+                            // We cannot predict what lifetimes are unused in opaque type.
+                            self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
+                            if let hir::ParamName::Plain(Ident {
+                                name: kw::UnderscoreLifetime,
+                                ..
+                            }) = name
+                            {
+                                // Pick the elided lifetime "definition" if one exists
+                                // and use it to make an elision scope.
+                                elision = Some(reg);
                             } else {
-                                self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
                                 lifetimes.insert(name, reg);
                             }
                         }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index fb364053e241e..c5b8f7d647ca7 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1052,7 +1052,7 @@ pub struct ResolverArenas<'a> {
 impl<'a> ResolverArenas<'a> {
     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
         let module = self.modules.alloc(module);
-        if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
+        if module.def_id().map_or(true, |def_id| def_id.is_local()) {
             self.local_modules.borrow_mut().push(module);
         }
         module
@@ -3031,7 +3031,7 @@ impl<'a> Resolver<'a> {
         let duplicate = new_binding.res().opt_def_id() == old_binding.res().opt_def_id();
         let has_dummy_span = new_binding.span.is_dummy() || old_binding.span.is_dummy();
         let from_item =
-            self.extern_prelude.get(&ident).map(|entry| entry.introduced_by_item).unwrap_or(true);
+            self.extern_prelude.get(&ident).map_or(true, |entry| entry.introduced_by_item);
         // Only suggest removing an import if both bindings are to the same def, if both spans
         // aren't dummy spans. Further, if both bindings are imports, then the ident must have
         // been introduced by a item.
diff --git a/compiler/rustc_save_analysis/src/lib.rs b/compiler/rustc_save_analysis/src/lib.rs
index c8cdff4f7e5d3..129123349a028 100644
--- a/compiler/rustc_save_analysis/src/lib.rs
+++ b/compiler/rustc_save_analysis/src/lib.rs
@@ -670,7 +670,7 @@ impl<'tcx> SaveContext<'tcx> {
     ) -> Option<Ref> {
         // Returns true if the path is function type sugar, e.g., `Fn(A) -> B`.
         fn fn_type(seg: &hir::PathSegment<'_>) -> bool {
-            seg.args.map(|args| args.parenthesized).unwrap_or(false)
+            seg.args.map_or(false, |args| args.parenthesized)
         }
 
         let res = self.get_path_res(id);
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 1f9a1af0f6872..6d01854228662 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1358,7 +1358,7 @@ pub fn build_session(
 
     let optimization_fuel_crate = sopts.debugging_opts.fuel.as_ref().map(|i| i.0.clone());
     let optimization_fuel = Lock::new(OptimizationFuel {
-        remaining: sopts.debugging_opts.fuel.as_ref().map(|i| i.1).unwrap_or(0),
+        remaining: sopts.debugging_opts.fuel.as_ref().map_or(0, |i| i.1),
         out_of_fuel: false,
     });
     let print_fuel_crate = sopts.debugging_opts.print_fuel.clone();
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index 842ccda6ea8b0..4e0ce0d344de4 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -539,7 +539,7 @@ impl SourceMap {
 
     pub fn is_line_before_span_empty(&self, sp: Span) -> bool {
         match self.span_to_prev_source(sp) {
-            Ok(s) => s.split('\n').last().map(|l| l.trim_start().is_empty()).unwrap_or(false),
+            Ok(s) => s.split('\n').last().map_or(false, |l| l.trim_start().is_empty()),
             Err(_) => false,
         }
     }
@@ -568,7 +568,7 @@ impl SourceMap {
         // asserting that the line numbers here are all indeed 1-based.
         let hi_line = hi.line.saturating_sub(1);
         for line_index in lo.line.saturating_sub(1)..hi_line {
-            let line_len = lo.file.get_line(line_index).map(|s| s.chars().count()).unwrap_or(0);
+            let line_len = lo.file.get_line(line_index).map_or(0, |s| s.chars().count());
             lines.push(LineInfo { line_index, start_col, end_col: CharPos::from_usize(line_len) });
             start_col = CharPos::from_usize(0);
         }
diff --git a/compiler/rustc_span/src/source_map/tests.rs b/compiler/rustc_span/src/source_map/tests.rs
index b8459eee4ecf0..3f22829b049fe 100644
--- a/compiler/rustc_span/src/source_map/tests.rs
+++ b/compiler/rustc_span/src/source_map/tests.rs
@@ -107,7 +107,7 @@ fn t7() {
 fn span_from_selection(input: &str, selection: &str) -> Span {
     assert_eq!(input.len(), selection.len());
     let left_index = selection.find('~').unwrap() as u32;
-    let right_index = selection.rfind('~').map(|x| x as u32).unwrap_or(left_index);
+    let right_index = selection.rfind('~').map_or(left_index, |x| x as u32);
     Span::with_root_ctxt(BytePos(left_index), BytePos(right_index + 1))
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 0186d164a4c53..795cf2e19decc 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -830,7 +830,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     .collect::<Vec<ArgKind>>(),
             ),
             Node::Ctor(ref variant_data) => {
-                let span = variant_data.ctor_hir_id().map(|id| hir.span(id)).unwrap_or(DUMMY_SP);
+                let span = variant_data.ctor_hir_id().map_or(DUMMY_SP, |id| hir.span(id));
                 let span = sm.guess_head_span(span);
                 (span, vec![ArgKind::empty(); variant_data.fields().len()])
             }
diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs
index f1fb2b800232d..8e339eb26b26c 100644
--- a/compiler/rustc_typeck/src/check/check.rs
+++ b/compiler/rustc_typeck/src/check/check.rs
@@ -1259,8 +1259,8 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: &'tcx ty
         let layout = tcx.layout_of(param_env.and(ty));
         // We are currently checking the type this field came from, so it must be local
         let span = tcx.hir().span_if_local(field.did).unwrap();
-        let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
-        let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
+        let zst = layout.map_or(false, |layout| layout.is_zst());
+        let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
         (span, zst, align1)
     });
 
diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
index 320ded5334e21..0036edda36da5 100644
--- a/compiler/rustc_typeck/src/check/compare_method.rs
+++ b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -364,13 +364,14 @@ fn check_region_bounds_on_impl_item<'tcx>(
     if trait_params != impl_params {
         let item_kind = assoc_item_kind_str(impl_m);
         let def_span = tcx.sess.source_map().guess_head_span(span);
-        let span = tcx.hir().get_generics(impl_m.def_id).map(|g| g.span).unwrap_or(def_span);
+        let span = tcx.hir().get_generics(impl_m.def_id).map_or(def_span, |g| g.span);
         let generics_span = if let Some(sp) = tcx.hir().span_if_local(trait_m.def_id) {
             let def_sp = tcx.sess.source_map().guess_head_span(sp);
-            Some(tcx.hir().get_generics(trait_m.def_id).map(|g| g.span).unwrap_or(def_sp))
+            Some(tcx.hir().get_generics(trait_m.def_id).map_or(def_sp, |g| g.span))
         } else {
             None
         };
+
         tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait {
             span,
             item_kind,
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
index c3166ce8164f4..47799c95fc0a7 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
@@ -904,8 +904,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             // Return directly on cache hit. This is useful to avoid doubly reporting
             // errors with default match binding modes. See #44614.
-            let def =
-                cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
+            let def = cached_result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
             return (def, Some(ty), slice::from_ref(&**item_segment));
         }
         let item_name = item_segment.ident;
@@ -932,7 +931,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Write back the new resolution.
         self.write_resolution(hir_id, result);
         (
-            result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
+            result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
             Some(ty),
             slice::from_ref(&**item_segment),
         )
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
index 94f8bfa3fc04b..ba944599653fa 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/checks.rs
@@ -821,7 +821,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 Some(match &arm.body.kind {
                                     // Point at the tail expression when possible.
                                     hir::ExprKind::Block(block, _) => {
-                                        block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
+                                        block.expr.as_ref().map_or(block.span, |e| e.span)
                                     }
                                     _ => arm.body.span,
                                 })
@@ -882,7 +882,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // Write back the new resolution.
                 self.write_resolution(hir_id, result);
 
-                (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
+                (result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)), ty)
             }
             QPath::LangItem(lang_item, span) => {
                 self.resolve_lang_item_path(lang_item, span, hir_id)
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 5cfd78ebeacad..e6bfa5e1497fe 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -1193,7 +1193,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .any(|imp_did| {
                             let imp = self.tcx.impl_trait_ref(imp_did).unwrap();
                             let imp_simp = simplify_type(self.tcx, imp.self_ty(), true);
-                            imp_simp.map(|s| s == simp_rcvr_ty).unwrap_or(false)
+                            imp_simp.map_or(false, |s| s == simp_rcvr_ty)
                         })
                     {
                         explicitly_negative.push(candidate);
@@ -1270,11 +1270,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             match ty.kind() {
                 ty::Adt(def, _) => def.did.is_local(),
                 ty::Foreign(did) => did.is_local(),
-
-                ty::Dynamic(ref tr, ..) => {
-                    tr.principal().map(|d| d.def_id().is_local()).unwrap_or(false)
-                }
-
+                ty::Dynamic(ref tr, ..) => tr.principal().map_or(false, |d| d.def_id().is_local()),
                 ty::Param(_) => true,
 
                 // Everything else (primitive types, etc.) is effectively
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index 5fc573a57ad0b..ecc6e8599ad01 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -15,6 +15,7 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::{Span, Spanned};
 use rustc_span::symbol::Ident;
+use rustc_span::{BytePos, DUMMY_SP};
 use rustc_trait_selection::traits::{ObligationCause, Pattern};
 
 use std::cmp;
@@ -1001,7 +1002,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // More generally, the expected type wants a tuple variant with one field of an
         // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern
         // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
-        let missing_parenthesis = match (&expected.kind(), fields, had_err) {
+        let missing_parentheses = match (&expected.kind(), fields, had_err) {
             // #67037: only do this if we could successfully type-check the expected type against
             // the tuple struct pattern. Otherwise the substs could get out of range on e.g.,
             // `let P() = U;` where `P != U` with `struct P<T>(T);`.
@@ -1014,13 +1015,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             _ => false,
         };
-        if missing_parenthesis {
+        if missing_parentheses {
             let (left, right) = match subpats {
                 // This is the zero case; we aim to get the "hi" part of the `QPath`'s
                 // span as the "lo" and then the "hi" part of the pattern's span as the "hi".
                 // This looks like:
                 //
-                // help: missing parenthesis
+                // help: missing parentheses
                 //   |
                 // L |     let A(()) = A(());
                 //   |          ^  ^
@@ -1029,17 +1030,63 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // last sub-pattern. In the case of `A(x)` the first and last may coincide.
                 // This looks like:
                 //
-                // help: missing parenthesis
+                // help: missing parentheses
                 //   |
                 // L |     let A((x, y)) = A((1, 2));
                 //   |           ^    ^
                 [first, ..] => (first.span.shrink_to_lo(), subpats.last().unwrap().span),
             };
             err.multipart_suggestion(
-                "missing parenthesis",
+                "missing parentheses",
                 vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())],
                 Applicability::MachineApplicable,
             );
+        } else if fields.len() > subpats.len() {
+            let after_fields_span = if pat_span == DUMMY_SP {
+                pat_span
+            } else {
+                pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi()
+            };
+            let all_fields_span = match subpats {
+                [] => after_fields_span,
+                [field] => field.span,
+                [first, .., last] => first.span.to(last.span),
+            };
+
+            // Check if all the fields in the pattern are wildcards.
+            let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild));
+
+            let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", ");
+            if !subpats.is_empty() {
+                wildcard_sugg = String::from(", ") + &wildcard_sugg;
+            }
+
+            err.span_suggestion_verbose(
+                after_fields_span,
+                "use `_` to explicitly ignore each field",
+                wildcard_sugg,
+                Applicability::MaybeIncorrect,
+            );
+
+            // Only suggest `..` if more than one field is missing
+            // or the pattern consists of all wildcards.
+            if fields.len() - subpats.len() > 1 || all_wildcards {
+                if subpats.is_empty() || all_wildcards {
+                    err.span_suggestion_verbose(
+                        all_fields_span,
+                        "use `..` to ignore all fields",
+                        String::from(".."),
+                        Applicability::MaybeIncorrect,
+                    );
+                } else {
+                    err.span_suggestion_verbose(
+                        after_fields_span,
+                        "use `..` to ignore the rest of the fields",
+                        String::from(", .."),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+            }
         }
 
         err.emit();
diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs
index fc3dff2654257..2c720ce025b0b 100644
--- a/compiler/rustc_typeck/src/check/wfcheck.rs
+++ b/compiler/rustc_typeck/src/check/wfcheck.rs
@@ -108,7 +108,7 @@ pub fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
                 .impl_trait_ref(tcx.hir().local_def_id(item.hir_id))
                 .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.def_id));
             if let (hir::Defaultness::Default { .. }, true) = (impl_.defaultness, is_auto) {
-                let sp = impl_.of_trait.as_ref().map(|t| t.path.span).unwrap_or(item.span);
+                let sp = impl_.of_trait.as_ref().map_or(item.span, |t| t.path.span);
                 let mut err =
                     tcx.sess.struct_span_err(sp, "impls of auto traits cannot be default");
                 err.span_labels(impl_.defaultness_span, "default because of this");
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 1626a0116a7eb..a6677328f8f88 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -1656,7 +1656,7 @@ fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
             ..
         }) => {
             if is_rustc_reservation {
-                let span = span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(*span));
+                let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
                 tcx.sess.span_err(span, "reservation impls can't be negative");
             }
             ty::ImplPolarity::Negative
diff --git a/compiler/rustc_typeck/src/mem_categorization.rs b/compiler/rustc_typeck/src/mem_categorization.rs
index a601123c8d055..4f11594d39813 100644
--- a/compiler/rustc_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_typeck/src/mem_categorization.rs
@@ -653,9 +653,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         // Then we see that to get the same result, we must start with
         // `deref { deref { place_foo }}` instead of `place_foo` since the pattern is now `Some(x,)`
         // and not `&&Some(x,)`, even though its assigned type is that of `&&Some(x,)`.
-        for _ in
-            0..self.typeck_results.pat_adjustments().get(pat.hir_id).map(|v| v.len()).unwrap_or(0)
-        {
+        for _ in 0..self.typeck_results.pat_adjustments().get(pat.hir_id).map_or(0, |v| v.len()) {
             debug!("cat_pattern: applying adjustment to place_with_id={:?}", place_with_id);
             place_with_id = self.cat_deref(pat, place_with_id)?;
         }
diff --git a/compiler/rustc_typeck/src/outlives/implicit_infer.rs b/compiler/rustc_typeck/src/outlives/implicit_infer.rs
index 3d0635e3fe437..02008e180b34d 100644
--- a/compiler/rustc_typeck/src/outlives/implicit_infer.rs
+++ b/compiler/rustc_typeck/src/outlives/implicit_infer.rs
@@ -99,7 +99,7 @@ impl<'cx, 'tcx> ItemLikeVisitor<'tcx> for InferVisitor<'cx, 'tcx> {
         // we walk the crates again and re-calculate predicates for all
         // items.
         let item_predicates_len: usize =
-            self.global_inferred_outlives.get(&item_did.to_def_id()).map(|p| p.len()).unwrap_or(0);
+            self.global_inferred_outlives.get(&item_did.to_def_id()).map_or(0, |p| p.len());
         if item_required_predicates.len() > item_predicates_len {
             *self.predicates_added = true;
             self.global_inferred_outlives.insert(item_did.to_def_id(), item_required_predicates);
diff --git a/library/alloc/src/sync/tests.rs b/library/alloc/src/sync/tests.rs
index e8e1e66da5ed4..5067af1d4ff68 100644
--- a/library/alloc/src/sync/tests.rs
+++ b/library/alloc/src/sync/tests.rs
@@ -370,7 +370,7 @@ fn test_weak_count_locked() {
         let n = Arc::weak_count(&a2);
         assert!(n < 2, "bad weak count: {}", n);
         #[cfg(miri)] // Miri's scheduler does not guarantee liveness, and thus needs this hint.
-        atomic::spin_loop_hint();
+        std::hint::spin_loop();
     }
     t.join().unwrap();
 }
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 1ca194c336112..ccc4f03a1e505 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -1953,27 +1953,6 @@ impl<T: PartialEq, A: Allocator> Vec<T, A> {
     }
 }
 
-impl<T, A: Allocator> Vec<T, A> {
-    /// Removes the first instance of `item` from the vector if the item exists.
-    ///
-    /// This method will be removed soon.
-    #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
-    #[rustc_deprecated(
-        reason = "Removing the first item equal to a needle is already easily possible \
-            with iterators and the current Vec methods. Furthermore, having a method for \
-            one particular case of removal (linear search, only the first item, no swap remove) \
-            but not for others is inconsistent. This method will be removed soon.",
-        since = "1.46.0"
-    )]
-    pub fn remove_item<V>(&mut self, item: &V) -> Option<T>
-    where
-        T: PartialEq<V>,
-    {
-        let pos = self.iter().position(|x| *x == *item)?;
-        Some(self.remove(pos))
-    }
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 // Internal methods and functions
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index 0c65c1c9eb7e9..73cf5d138bf75 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -456,7 +456,9 @@ impl Display for Arguments<'_> {
 ///
 /// When used with the alternate format specifier `#?`, the output is pretty-printed.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// This trait can be used with `#[derive]` if all fields implement `Debug`. When
 /// `derive`d for structs, it will use the name of the `struct`, then `{`, then a
@@ -602,7 +604,9 @@ pub use macros::Debug;
 /// `Display` is similar to [`Debug`], but `Display` is for user-facing
 /// output, and so cannot be derived.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -674,7 +678,9 @@ pub trait Display {
 ///
 /// The alternate flag, `#`, adds a `0o` in front of the output.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -726,7 +732,9 @@ pub trait Octal {
 ///
 /// The alternate flag, `#`, adds a `0b` in front of the output.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -782,7 +790,9 @@ pub trait Binary {
 ///
 /// The alternate flag, `#`, adds a `0x` in front of the output.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -835,7 +845,9 @@ pub trait LowerHex {
 ///
 /// The alternate flag, `#`, adds a `0x` in front of the output.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -883,7 +895,9 @@ pub trait UpperHex {
 /// The `Pointer` trait should format its output as a memory location. This is commonly presented
 /// as hexadecimal.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -932,7 +946,9 @@ pub trait Pointer {
 ///
 /// The `LowerExp` trait should format its output in scientific notation with a lower-case `e`.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -981,7 +997,9 @@ pub trait LowerExp {
 ///
 /// The `UpperExp` trait should format its output in scientific notation with an upper-case `E`.
 ///
-/// For more information on formatters, see [the module-level documentation][self].
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -1555,7 +1573,7 @@ impl<'a> Formatter<'a> {
     ///     }
     /// }
     ///
-    /// // We set alignment to the left with ">".
+    /// // We set alignment to the right with ">".
     /// assert_eq!(&format!("{:G>3}", Foo), "GGG");
     /// assert_eq!(&format!("{:t>6}", Foo), "tttttt");
     /// ```
diff --git a/library/core/src/iter/adapters/intersperse.rs b/library/core/src/iter/adapters/intersperse.rs
index 362326725490f..1d01e9b5fb7dc 100644
--- a/library/core/src/iter/adapters/intersperse.rs
+++ b/library/core/src/iter/adapters/intersperse.rs
@@ -1,6 +1,9 @@
 use super::Peekable;
 
 /// An iterator adapter that places a separator between all elements.
+///
+/// This `struct` is created by [`Iterator::intersperse`]. See its documentation
+/// for more information.
 #[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
 #[derive(Debug, Clone)]
 pub struct Intersperse<I: Iterator>
@@ -40,37 +43,146 @@ where
         }
     }
 
-    fn fold<B, F>(mut self, init: B, mut f: F) -> B
+    fn fold<B, F>(self, init: B, f: F) -> B
     where
         Self: Sized,
         F: FnMut(B, Self::Item) -> B,
     {
-        let mut accum = init;
+        let separator = self.separator;
+        intersperse_fold(self.iter, init, f, move || separator.clone(), self.needs_sep)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        intersperse_size_hint(&self.iter, self.needs_sep)
+    }
+}
+
+/// An iterator adapter that places a separator between all elements.
+///
+/// This `struct` is created by [`Iterator::intersperse_with`]. See its
+/// documentation for more information.
+#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+pub struct IntersperseWith<I, G>
+where
+    I: Iterator,
+{
+    separator: G,
+    iter: Peekable<I>,
+    needs_sep: bool,
+}
+
+#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+impl<I, G> crate::fmt::Debug for IntersperseWith<I, G>
+where
+    I: Iterator + crate::fmt::Debug,
+    I::Item: crate::fmt::Debug,
+    G: crate::fmt::Debug,
+{
+    fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
+        f.debug_struct("IntersperseWith")
+            .field("separator", &self.separator)
+            .field("iter", &self.iter)
+            .field("needs_sep", &self.needs_sep)
+            .finish()
+    }
+}
 
-        // Use `peek()` first to avoid calling `next()` on an empty iterator.
-        if !self.needs_sep || self.iter.peek().is_some() {
-            if let Some(x) = self.iter.next() {
-                accum = f(accum, x);
-            }
+#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+impl<I, G> crate::clone::Clone for IntersperseWith<I, G>
+where
+    I: Iterator + crate::clone::Clone,
+    I::Item: crate::clone::Clone,
+    G: Clone,
+{
+    fn clone(&self) -> Self {
+        IntersperseWith {
+            separator: self.separator.clone(),
+            iter: self.iter.clone(),
+            needs_sep: self.needs_sep.clone(),
         }
+    }
+}
 
-        let element = &self.separator;
+impl<I, G> IntersperseWith<I, G>
+where
+    I: Iterator,
+    G: FnMut() -> I::Item,
+{
+    pub(in crate::iter) fn new(iter: I, separator: G) -> Self {
+        Self { iter: iter.peekable(), separator, needs_sep: false }
+    }
+}
 
-        self.iter.fold(accum, |mut accum, x| {
-            accum = f(accum, element.clone());
-            accum = f(accum, x);
-            accum
-        })
+#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+impl<I, G> Iterator for IntersperseWith<I, G>
+where
+    I: Iterator,
+    G: FnMut() -> I::Item,
+{
+    type Item = I::Item;
+
+    #[inline]
+    fn next(&mut self) -> Option<I::Item> {
+        if self.needs_sep && self.iter.peek().is_some() {
+            self.needs_sep = false;
+            Some((self.separator)())
+        } else {
+            self.needs_sep = true;
+            self.iter.next()
+        }
+    }
+
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        intersperse_fold(self.iter, init, f, self.separator, self.needs_sep)
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let (lo, hi) = self.iter.size_hint();
-        let next_is_elem = !self.needs_sep;
-        let lo = lo.saturating_sub(next_is_elem as usize).saturating_add(lo);
-        let hi = match hi {
-            Some(hi) => hi.saturating_sub(next_is_elem as usize).checked_add(hi),
-            None => None,
-        };
-        (lo, hi)
+        intersperse_size_hint(&self.iter, self.needs_sep)
     }
 }
+
+fn intersperse_size_hint<I>(iter: &I, needs_sep: bool) -> (usize, Option<usize>)
+where
+    I: Iterator,
+{
+    let (lo, hi) = iter.size_hint();
+    let next_is_elem = !needs_sep;
+    let lo = lo.saturating_sub(next_is_elem as usize).saturating_add(lo);
+    let hi = match hi {
+        Some(hi) => hi.saturating_sub(next_is_elem as usize).checked_add(hi),
+        None => None,
+    };
+    (lo, hi)
+}
+
+fn intersperse_fold<I, B, F, G>(
+    mut iter: Peekable<I>,
+    init: B,
+    mut f: F,
+    mut separator: G,
+    needs_sep: bool,
+) -> B
+where
+    I: Iterator,
+    F: FnMut(B, I::Item) -> B,
+    G: FnMut() -> I::Item,
+{
+    let mut accum = init;
+
+    // Use `peek()` first to avoid calling `next()` on an empty iterator.
+    if !needs_sep || iter.peek().is_some() {
+        if let Some(x) = iter.next() {
+            accum = f(accum, x);
+        }
+    }
+
+    iter.fold(accum, |mut accum, x| {
+        accum = f(accum, separator());
+        accum = f(accum, x);
+        accum
+    })
+}
diff --git a/library/core/src/iter/adapters/mod.rs b/library/core/src/iter/adapters/mod.rs
index 7dfbf32cea7b8..41a7b13232adf 100644
--- a/library/core/src/iter/adapters/mod.rs
+++ b/library/core/src/iter/adapters/mod.rs
@@ -43,7 +43,7 @@ pub use self::flatten::Flatten;
 pub use self::copied::Copied;
 
 #[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
-pub use self::intersperse::Intersperse;
+pub use self::intersperse::{Intersperse, IntersperseWith};
 
 #[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")]
 pub use self::map_while::MapWhile;
diff --git a/library/core/src/iter/mod.rs b/library/core/src/iter/mod.rs
index 569de719d03d6..c57ba2bf62645 100644
--- a/library/core/src/iter/mod.rs
+++ b/library/core/src/iter/mod.rs
@@ -395,8 +395,6 @@ pub use self::adapters::Cloned;
 pub use self::adapters::Copied;
 #[stable(feature = "iterator_flatten", since = "1.29.0")]
 pub use self::adapters::Flatten;
-#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
-pub use self::adapters::Intersperse;
 #[unstable(feature = "iter_map_while", reason = "recently added", issue = "68537")]
 pub use self::adapters::MapWhile;
 #[unstable(feature = "inplace_iteration", issue = "none")]
@@ -410,6 +408,8 @@ pub use self::adapters::{
     Chain, Cycle, Enumerate, Filter, FilterMap, FlatMap, Fuse, Inspect, Map, Peekable, Rev, Scan,
     Skip, SkipWhile, Take, TakeWhile, Zip,
 };
+#[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+pub use self::adapters::{Intersperse, IntersperseWith};
 
 pub(crate) use self::adapters::process_results;
 
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 0023de65d2b3b..83d339d8f40a5 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -8,7 +8,7 @@ use crate::ops::{Add, ControlFlow, Try};
 use super::super::TrustedRandomAccess;
 use super::super::{Chain, Cloned, Copied, Cycle, Enumerate, Filter, FilterMap, Fuse};
 use super::super::{FlatMap, Flatten};
-use super::super::{FromIterator, Intersperse, Product, Sum, Zip};
+use super::super::{FromIterator, Intersperse, IntersperseWith, Product, Sum, Zip};
 use super::super::{
     Inspect, Map, MapWhile, Peekable, Rev, Scan, Skip, SkipWhile, StepBy, Take, TakeWhile,
 };
@@ -571,6 +571,9 @@ pub trait Iterator {
 
     /// Places a copy of `separator` between all elements.
     ///
+    /// In case the separator does not implement [`Clone`] or needs to be
+    /// computed every time, use [`intersperse_with`].
+    ///
     /// # Examples
     ///
     /// Basic usage:
@@ -578,9 +581,12 @@ pub trait Iterator {
     /// ```
     /// #![feature(iter_intersperse)]
     ///
-    /// let hello = ["Hello", "World"].iter().copied().intersperse(" ").collect::<String>();
-    /// assert_eq!(hello, "Hello World");
+    /// let hello = ["Hello", "World", "!"].iter().copied().intersperse(" ").collect::<String>();
+    /// assert_eq!(hello, "Hello World !");
     /// ```
+    ///
+    /// [`Clone`]: crate::clone::Clone
+    /// [`intersperse_with`]: Iterator::intersperse_with
     #[inline]
     #[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
     fn intersperse(self, separator: Self::Item) -> Intersperse<Self>
@@ -591,6 +597,33 @@ pub trait Iterator {
         Intersperse::new(self, separator)
     }
 
+    /// Places an element generated by `separator` between all elements.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(iter_intersperse)]
+    ///
+    /// let src = ["Hello", "to", "all", "people", "!!"].iter().copied();
+    ///
+    /// let mut happy_emojis = [" ❤️ ", " 😀 "].iter().copied();
+    /// let separator = || happy_emojis.next().unwrap_or(" 🦀 ");
+    ///
+    /// let result = src.intersperse_with(separator).collect::<String>();
+    /// assert_eq!(result, "Hello ❤️ to 😀 all 🦀 people 🦀 !!");
+    /// ```
+    #[inline]
+    #[unstable(feature = "iter_intersperse", reason = "recently added", issue = "79524")]
+    fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
+    where
+        Self: Sized,
+        G: FnMut() -> Self::Item,
+    {
+        IntersperseWith::new(self, separator)
+    }
+
     /// Takes a closure and creates an iterator which calls that closure on each
     /// element.
     ///
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 1634aff7b4dc9..90964bae98c89 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -401,7 +401,7 @@ macro_rules! write {
 /// For more information, see [`write!`]. For information on the format string syntax, see
 /// [`std::fmt`].
 ///
-/// [`std::fmt`]: crate::fmt
+/// [`std::fmt`]: ../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -730,7 +730,7 @@ pub(crate) mod builtin {
     /// [`Display`]: crate::fmt::Display
     /// [`Debug`]: crate::fmt::Debug
     /// [`fmt::Arguments`]: crate::fmt::Arguments
-    /// [`std::fmt`]: crate::fmt
+    /// [`std::fmt`]: ../std/fmt/index.html
     /// [`format!`]: ../std/macro.format.html
     /// [`println!`]: ../std/macro.println.html
     ///
@@ -1194,7 +1194,7 @@ pub(crate) mod builtin {
     /// be provided with or without arguments for formatting. See [`std::fmt`]
     /// for syntax for this form.
     ///
-    /// [`std::fmt`]: crate::fmt
+    /// [`std::fmt`]: ../std/fmt/index.html
     ///
     /// # Examples
     ///
diff --git a/library/core/src/ops/range.rs b/library/core/src/ops/range.rs
index 1d67e65e51f5f..0571dc74b9af9 100644
--- a/library/core/src/ops/range.rs
+++ b/library/core/src/ops/range.rs
@@ -678,6 +678,29 @@ pub enum Bound<T> {
     Unbounded,
 }
 
+#[unstable(feature = "bound_as_ref", issue = "80996")]
+impl<T> Bound<T> {
+    /// Converts from `&Bound<T>` to `Bound<&T>`.
+    #[inline]
+    pub fn as_ref(&self) -> Bound<&T> {
+        match *self {
+            Included(ref x) => Included(x),
+            Excluded(ref x) => Excluded(x),
+            Unbounded => Unbounded,
+        }
+    }
+
+    /// Converts from `&mut Bound<T>` to `Bound<&T>`.
+    #[inline]
+    pub fn as_mut(&mut self) -> Bound<&mut T> {
+        match *self {
+            Included(ref mut x) => Included(x),
+            Excluded(ref mut x) => Excluded(x),
+            Unbounded => Unbounded,
+        }
+    }
+}
+
 impl<T: Clone> Bound<&T> {
     /// Map a `Bound<&T>` to a `Bound<T>` by cloning the contents of the bound.
     ///
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 081d80f487605..6de2714059480 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -1877,7 +1877,7 @@ impl<T> [T] {
     ///            Some(b"llo".as_ref()));
     /// ```
     #[must_use = "returns the subslice without modifying the original"]
-    #[stable(feature = "slice_strip", since = "1.50.0")]
+    #[stable(feature = "slice_strip", since = "1.51.0")]
     pub fn strip_prefix<P: SlicePattern<Item = T> + ?Sized>(&self, prefix: &P) -> Option<&[T]>
     where
         T: PartialEq,
@@ -1911,7 +1911,7 @@ impl<T> [T] {
     /// assert_eq!(v.strip_suffix(&[50, 30]), None);
     /// ```
     #[must_use = "returns the subslice without modifying the original"]
-    #[stable(feature = "slice_strip", since = "1.50.0")]
+    #[stable(feature = "slice_strip", since = "1.51.0")]
     pub fn strip_suffix<P: SlicePattern<Item = T> + ?Sized>(&self, suffix: &P) -> Option<&[T]>
     where
         T: PartialEq,
@@ -3323,7 +3323,7 @@ pub trait SlicePattern {
     fn as_slice(&self) -> &[Self::Item];
 }
 
-#[stable(feature = "slice_strip", since = "1.50.0")]
+#[stable(feature = "slice_strip", since = "1.51.0")]
 impl<T> SlicePattern for [T] {
     type Item = T;
 
@@ -3333,7 +3333,7 @@ impl<T> SlicePattern for [T] {
     }
 }
 
-#[stable(feature = "slice_strip", since = "1.50.0")]
+#[stable(feature = "slice_strip", since = "1.51.0")]
 impl<T, const N: usize> SlicePattern for [T; N] {
     type Item = T;
 
diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
index a167f0ffa09ec..81c9e1d1c10b2 100644
--- a/library/core/src/sync/atomic.rs
+++ b/library/core/src/sync/atomic.rs
@@ -120,21 +120,6 @@ use crate::intrinsics;
 
 use crate::hint::spin_loop;
 
-/// Signals the processor that it is inside a busy-wait spin-loop ("spin lock").
-///
-/// This function is expected to be deprecated in favor of
-/// [`hint::spin_loop`].
-///
-/// **Note**: On platforms that do not support receiving spin-loop hints this function does not
-/// do anything at all.
-///
-/// [`hint::spin_loop`]: crate::hint::spin_loop
-#[inline]
-#[stable(feature = "spin_loop_hint", since = "1.24.0")]
-pub fn spin_loop_hint() {
-    spin_loop()
-}
-
 /// A boolean type which can be safely shared between threads.
 ///
 /// This type has the same in-memory representation as a [`bool`].
@@ -2791,3 +2776,15 @@ impl<T> fmt::Pointer for AtomicPtr<T> {
         fmt::Pointer::fmt(&self.load(Ordering::SeqCst), f)
     }
 }
+
+/// Signals the processor that it is inside a busy-wait spin-loop ("spin lock").
+///
+/// This function is deprecated in favor of [`hint::spin_loop`].
+///
+/// [`hint::spin_loop`]: crate::hint::spin_loop
+#[inline]
+#[stable(feature = "spin_loop_hint", since = "1.24.0")]
+#[rustc_deprecated(since = "1.51.0", reason = "use hint::spin_loop instead")]
+pub fn spin_loop_hint() {
+    spin_loop()
+}
diff --git a/library/core/tests/iter.rs b/library/core/tests/iter.rs
index 7376e7848eff5..691767edea6d9 100644
--- a/library/core/tests/iter.rs
+++ b/library/core/tests/iter.rs
@@ -3508,6 +3508,12 @@ pub fn extend_for_unit() {
 
 #[test]
 fn test_intersperse() {
+    let v = std::iter::empty().intersperse(0u32).collect::<Vec<_>>();
+    assert_eq!(v, vec![]);
+
+    let v = std::iter::once(1).intersperse(0).collect::<Vec<_>>();
+    assert_eq!(v, vec![1]);
+
     let xs = ["a", "", "b", "c"];
     let v: Vec<&str> = xs.iter().map(|x| x.clone()).intersperse(", ").collect();
     let text: String = v.concat();
@@ -3520,6 +3526,9 @@ fn test_intersperse() {
 
 #[test]
 fn test_intersperse_size_hint() {
+    let iter = std::iter::empty::<i32>().intersperse(0);
+    assert_eq!(iter.size_hint(), (0, Some(0)));
+
     let xs = ["a", "", "b", "c"];
     let mut iter = xs.iter().map(|x| x.clone()).intersperse(", ");
     assert_eq!(iter.size_hint(), (7, Some(7)));
@@ -3587,3 +3596,24 @@ fn test_try_fold_specialization_intersperse_err() {
     iter.try_for_each(|item| if item == "b" { None } else { Some(()) });
     assert_eq!(iter.next(), None);
 }
+
+#[test]
+fn test_intersperse_with() {
+    #[derive(PartialEq, Debug)]
+    struct NotClone {
+        u: u32,
+    }
+    let r = vec![NotClone { u: 0 }, NotClone { u: 1 }]
+        .into_iter()
+        .intersperse_with(|| NotClone { u: 2 })
+        .collect::<Vec<_>>();
+    assert_eq!(r, vec![NotClone { u: 0 }, NotClone { u: 2 }, NotClone { u: 1 }]);
+
+    let mut ctr = 100;
+    let separator = || {
+        ctr *= 2;
+        ctr
+    };
+    let r = (0..3).intersperse_with(separator).collect::<Vec<_>>();
+    assert_eq!(r, vec![0, 200, 1, 400, 2]);
+}
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 7ad9e446c5997..3f5b7c0b29be6 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -366,7 +366,6 @@ where
 {
     let start_len = buf.len();
     let mut g = Guard { len: buf.len(), buf };
-    let ret;
     loop {
         if g.len == g.buf.len() {
             unsafe {
@@ -385,21 +384,20 @@ where
             }
         }
 
-        match r.read(&mut g.buf[g.len..]) {
-            Ok(0) => {
-                ret = Ok(g.len - start_len);
-                break;
+        let buf = &mut g.buf[g.len..];
+        match r.read(buf) {
+            Ok(0) => return Ok(g.len - start_len),
+            Ok(n) => {
+                // We can't allow bogus values from read. If it is too large, the returned vec could have its length
+                // set past its capacity, or if it overflows the vec could be shortened which could create an invalid
+                // string if this is called via read_to_string.
+                assert!(n <= buf.len());
+                g.len += n;
             }
-            Ok(n) => g.len += n,
             Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
-            Err(e) => {
-                ret = Err(e);
-                break;
-            }
+            Err(e) => return Err(e),
         }
     }
-
-    ret
 }
 
 pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>
@@ -944,6 +942,54 @@ pub trait Read {
     }
 }
 
+/// Read all bytes from a [reader][Read] into a new [`String`].
+///
+/// This is a convenience function for [`Read::read_to_string`]. Using this
+/// function avoids having to create a variable first and provides more type
+/// safety since you can only get the buffer out if there were no errors. (If you
+/// use [`Read::read_to_string`] you have to remember to check whether the read
+/// succeeded because otherwise your buffer will be empty or only partially full.)
+///
+/// # Performance
+///
+/// The downside of this function's increased ease of use and type safety is
+/// that it gives you less control over performance. For example, you can't
+/// pre-allocate memory like you can using [`String::with_capacity`] and
+/// [`Read::read_to_string`]. Also, you can't re-use the buffer if an error
+/// occurs while reading.
+///
+/// In many cases, this function's performance will be adequate and the ease of use
+/// and type safety tradeoffs will be worth it. However, there are cases where you
+/// need more control over performance, and in those cases you should definitely use
+/// [`Read::read_to_string`] directly.
+///
+/// # Errors
+///
+/// This function forces you to handle errors because the output (the `String`)
+/// is wrapped in a [`Result`]. See [`Read::read_to_string`] for the errors
+/// that can occur. If any error occurs, you will get an [`Err`], so you
+/// don't have to worry about your buffer being empty or partially full.
+///
+/// # Examples
+///
+/// ```no_run
+/// #![feature(io_read_to_string)]
+///
+/// # use std::io;
+/// fn main() -> io::Result<()> {
+///     let stdin = io::read_to_string(&mut io::stdin())?;
+///     println!("Stdin was:");
+///     println!("{}", stdin);
+///     Ok(())
+/// }
+/// ```
+#[unstable(feature = "io_read_to_string", issue = "80218")]
+pub fn read_to_string<R: Read>(reader: &mut R) -> Result<String> {
+    let mut buf = String::new();
+    reader.read_to_string(&mut buf)?;
+    Ok(buf)
+}
+
 /// A buffer type used with `Read::read_vectored`.
 ///
 /// It is semantically a wrapper around an `&mut [u8]`, but is guaranteed to be
diff --git a/library/std/src/sys/hermit/mutex.rs b/library/std/src/sys/hermit/mutex.rs
index f988a019cfedb..885389ca54cd4 100644
--- a/library/std/src/sys/hermit/mutex.rs
+++ b/library/std/src/sys/hermit/mutex.rs
@@ -1,9 +1,10 @@
 use crate::cell::UnsafeCell;
 use crate::collections::VecDeque;
 use crate::ffi::c_void;
+use crate::hint;
 use crate::ops::{Deref, DerefMut, Drop};
 use crate::ptr;
-use crate::sync::atomic::{spin_loop_hint, AtomicUsize, Ordering};
+use crate::sync::atomic::{AtomicUsize, Ordering};
 use crate::sys::hermit::abi;
 
 /// This type provides a lock based on busy waiting to realize mutual exclusion
@@ -46,7 +47,7 @@ impl<T> Spinlock<T> {
     fn obtain_lock(&self) {
         let ticket = self.queue.fetch_add(1, Ordering::SeqCst) + 1;
         while self.dequeue.load(Ordering::SeqCst) != ticket {
-            spin_loop_hint();
+            hint::spin_loop();
         }
     }
 
diff --git a/library/std/src/sys/sgx/waitqueue/spin_mutex.rs b/library/std/src/sys/sgx/waitqueue/spin_mutex.rs
index 9140041c58414..7f1a671bab4eb 100644
--- a/library/std/src/sys/sgx/waitqueue/spin_mutex.rs
+++ b/library/std/src/sys/sgx/waitqueue/spin_mutex.rs
@@ -2,8 +2,9 @@
 mod tests;
 
 use crate::cell::UnsafeCell;
+use crate::hint;
 use crate::ops::{Deref, DerefMut};
-use crate::sync::atomic::{spin_loop_hint, AtomicBool, Ordering};
+use crate::sync::atomic::{AtomicBool, Ordering};
 
 #[derive(Default)]
 pub struct SpinMutex<T> {
@@ -32,7 +33,7 @@ impl<T> SpinMutex<T> {
             match self.try_lock() {
                 None => {
                     while self.lock.load(Ordering::Relaxed) {
-                        spin_loop_hint()
+                        hint::spin_loop()
                     }
                 }
                 Some(guard) => return guard,
diff --git a/library/std/src/sys/unix/ext/process.rs b/library/std/src/sys/unix/ext/process.rs
index 3615a8a5ee8b0..f4c67b225e6e1 100644
--- a/library/std/src/sys/unix/ext/process.rs
+++ b/library/std/src/sys/unix/ext/process.rs
@@ -9,6 +9,14 @@ use crate::process;
 use crate::sys;
 use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
 
+mod private {
+    /// This trait being unreachable from outside the crate
+    /// prevents other implementations of the `ExitStatusExt` trait,
+    /// which allows potentially adding more trait methods in the future.
+    #[stable(feature = "none", since = "1.51.0")]
+    pub trait Sealed {}
+}
+
 /// Unix-specific extensions to the [`process::Command`] builder.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait CommandExt {
@@ -163,18 +171,48 @@ impl CommandExt for process::Command {
 }
 
 /// Unix-specific extensions to [`process::ExitStatus`].
+///
+/// This trait is sealed: it cannot be implemented outside the standard library.
+/// This is so that future additional methods are not breaking changes.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub trait ExitStatusExt {
+pub trait ExitStatusExt: private::Sealed {
     /// Creates a new `ExitStatus` from the raw underlying `i32` return value of
     /// a process.
     #[stable(feature = "exit_status_from", since = "1.12.0")]
     fn from_raw(raw: i32) -> Self;
 
     /// If the process was terminated by a signal, returns that signal.
+    ///
+    /// In other words, if `WIFSIGNALED`, this returns `WTERMSIG`.
     #[stable(feature = "rust1", since = "1.0.0")]
     fn signal(&self) -> Option<i32>;
+
+    /// If the process was terminated by a signal, says whether it dumped core.
+    #[unstable(feature = "unix_process_wait_more", issue = "80695")]
+    fn core_dumped(&self) -> bool;
+
+    /// If the process was stopped by a signal, returns that signal.
+    ///
+    /// In other words, if `WIFSTOPPED`, this returns `WSTOPSIG`.  This is only possible if the status came from
+    /// a `wait` system call which was passed `WUNTRACED`, was then converted into an `ExitStatus`.
+    #[unstable(feature = "unix_process_wait_more", issue = "80695")]
+    fn stopped_signal(&self) -> Option<i32>;
+
+    /// Whether the process was continued from a stopped status.
+    ///
+    /// Ie, `WIFCONTINUED`.  This is only possible if the status came from a `wait` system call
+    /// which was passed `WCONTINUED`, was then converted into an `ExitStatus`.
+    #[unstable(feature = "unix_process_wait_more", issue = "80695")]
+    fn continued(&self) -> bool;
+
+    /// Returns the underlying raw `wait` status.
+    #[unstable(feature = "unix_process_wait_more", issue = "80695")]
+    fn into_raw(self) -> i32;
 }
 
+#[stable(feature = "none", since = "1.51.0")]
+impl private::Sealed for process::ExitStatus {}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl ExitStatusExt for process::ExitStatus {
     fn from_raw(raw: i32) -> Self {
@@ -184,6 +222,22 @@ impl ExitStatusExt for process::ExitStatus {
     fn signal(&self) -> Option<i32> {
         self.as_inner().signal()
     }
+
+    fn core_dumped(&self) -> bool {
+        self.as_inner().core_dumped()
+    }
+
+    fn stopped_signal(&self) -> Option<i32> {
+        self.as_inner().stopped_signal()
+    }
+
+    fn continued(&self) -> bool {
+        self.as_inner().continued()
+    }
+
+    fn into_raw(self) -> i32 {
+        self.as_inner().into_raw().into()
+    }
 }
 
 #[stable(feature = "process_extensions", since = "1.2.0")]
diff --git a/library/std/src/sys/unix/process/process_fuchsia.rs b/library/std/src/sys/unix/process/process_fuchsia.rs
index b64636c3f3d15..0d4703d7f503a 100644
--- a/library/std/src/sys/unix/process/process_fuchsia.rs
+++ b/library/std/src/sys/unix/process/process_fuchsia.rs
@@ -245,6 +245,50 @@ impl ExitStatus {
     pub fn signal(&self) -> Option<i32> {
         None
     }
+
+    // FIXME: The actually-Unix implementation in process_unix.rs uses WSTOPSIG, WCOREDUMP et al.
+    // I infer from the implementation of `success`, `code` and `signal` above that these are not
+    // available on Fuchsia.
+    //
+    // It does not appear that Fuchsia is Unix-like enough to implement ExitStatus (or indeed many
+    // other things from std::os::unix) properly.  This veneer is always going to be a bodge.  So
+    // while I don't know if these implementations are actually correct, I think they will do for
+    // now at least.
+    pub fn core_dumped(&self) -> bool {
+        false
+    }
+    pub fn stopped_signal(&self) -> Option<i32> {
+        None
+    }
+    pub fn continued(&self) -> bool {
+        false
+    }
+
+    pub fn into_raw(&self) -> c_int {
+        // We don't know what someone who calls into_raw() will do with this value, but it should
+        // have the conventional Unix representation.  Despite the fact that this is not
+        // standardised in SuS or POSIX, all Unix systems encode the signal and exit status the
+        // same way.  (Ie the WIFEXITED, WEXITSTATUS etc. macros have identical behaviour on every
+        // Unix.)
+        //
+        // The caller of `std::os::unix::into_raw` is probably wanting a Unix exit status, and may
+        // do their own shifting and masking, or even pass the status to another computer running a
+        // different Unix variant.
+        //
+        // The other view would be to say that the caller on Fuchsia ought to know that `into_raw`
+        // will give a raw Fuchsia status (whatever that is - I don't know, personally).  That is
+        // not possible here becaause we must return a c_int because that's what Unix (including
+        // SuS and POSIX) say a wait status is, but Fuchsia apparently uses a u64, so it won't
+        // necessarily fit.
+        //
+        // It seems to me that that the right answer would be to provide std::os::fuchsia with its
+        // own ExitStatusExt, rather that trying to provide a not very convincing imitation of
+        // Unix.  Ie, std::os::unix::process:ExitStatusExt ought not to exist on Fuchsia.  But
+        // fixing this up that is beyond the scope of my efforts now.
+        let exit_status_as_if_unix: u8 = self.0.try_into().expect("Fuchsia process return code bigger than 8 bits, but std::os::unix::ExitStatusExt::into_raw() was called to try to convert the value into a traditional Unix-style wait status, which cannot represent values greater than 255.");
+        let wait_status_as_if_unix = (exit_status_as_if_unix as c_int) << 8;
+        wait_status_as_if_unix
+    }
 }
 
 /// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying.
diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs
index a590c74435639..945b43678a919 100644
--- a/library/std/src/sys/unix/process/process_unix.rs
+++ b/library/std/src/sys/unix/process/process_unix.rs
@@ -479,7 +479,23 @@ impl ExitStatus {
     }
 
     pub fn signal(&self) -> Option<i32> {
-        if !self.exited() { Some(libc::WTERMSIG(self.0)) } else { None }
+        if libc::WIFSIGNALED(self.0) { Some(libc::WTERMSIG(self.0)) } else { None }
+    }
+
+    pub fn core_dumped(&self) -> bool {
+        libc::WIFSIGNALED(self.0) && libc::WCOREDUMP(self.0)
+    }
+
+    pub fn stopped_signal(&self) -> Option<i32> {
+        if libc::WIFSTOPPED(self.0) { Some(libc::WSTOPSIG(self.0)) } else { None }
+    }
+
+    pub fn continued(&self) -> bool {
+        libc::WIFCONTINUED(self.0)
+    }
+
+    pub fn into_raw(&self) -> c_int {
+        self.0
     }
 }
 
diff --git a/library/std/src/sys/windows/ext/process.rs b/library/std/src/sys/windows/ext/process.rs
index 61e4c6a1d1718..7a92381d6609b 100644
--- a/library/std/src/sys/windows/ext/process.rs
+++ b/library/std/src/sys/windows/ext/process.rs
@@ -7,6 +7,14 @@ use crate::process;
 use crate::sys;
 use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
 
+mod private {
+    /// This trait being unreachable from outside the crate
+    /// prevents other implementations of the `ExitStatusExt` trait,
+    /// which allows potentially adding more trait methods in the future.
+    #[stable(feature = "none", since = "1.51.0")]
+    pub trait Sealed {}
+}
+
 #[stable(feature = "process_extensions", since = "1.2.0")]
 impl FromRawHandle for process::Stdio {
     unsafe fn from_raw_handle(handle: RawHandle) -> process::Stdio {
@@ -73,8 +81,11 @@ impl IntoRawHandle for process::ChildStderr {
 }
 
 /// Windows-specific extensions to [`process::ExitStatus`].
+///
+/// This trait is sealed: it cannot be implemented outside the standard library.
+/// This is so that future additional methods are not breaking changes.
 #[stable(feature = "exit_status_from", since = "1.12.0")]
-pub trait ExitStatusExt {
+pub trait ExitStatusExt: private::Sealed {
     /// Creates a new `ExitStatus` from the raw underlying `u32` return value of
     /// a process.
     #[stable(feature = "exit_status_from", since = "1.12.0")]
@@ -88,6 +99,9 @@ impl ExitStatusExt for process::ExitStatus {
     }
 }
 
+#[stable(feature = "none", since = "1.51.0")]
+impl private::Sealed for process::ExitStatus {}
+
 /// Windows-specific extensions to the [`process::Command`] builder.
 #[stable(feature = "windows_process_extensions", since = "1.16.0")]
 pub trait CommandExt {
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index 5d65f960fcd39..0d004a516f594 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -1186,32 +1186,37 @@ impl fmt::Debug for Thread {
 /// the [`Error`](crate::error::Error) trait.
 ///
 /// Thus, a sensible way to handle a thread panic is to either:
-/// 1. `unwrap` the `Result<T>`, propagating the panic
+///
+/// 1. propagate the panic with [`std::panic::resume_unwind`]
 /// 2. or in case the thread is intended to be a subsystem boundary
 /// that is supposed to isolate system-level failures,
-/// match on the `Err` variant and handle the panic in an appropriate way.
+/// match on the `Err` variant and handle the panic in an appropriate way
 ///
 /// A thread that completes without panicking is considered to exit successfully.
 ///
 /// # Examples
 ///
+/// Matching on the result of a joined thread:
+///
 /// ```no_run
-/// use std::thread;
-/// use std::fs;
+/// use std::{fs, thread, panic};
 ///
 /// fn copy_in_thread() -> thread::Result<()> {
-///     thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join()
+///     thread::spawn(|| {
+///         fs::copy("foo.txt", "bar.txt").unwrap();
+///     }).join()
 /// }
 ///
 /// fn main() {
 ///     match copy_in_thread() {
-///         Ok(_) => println!("this is fine"),
-///         Err(_) => println!("thread panicked"),
+///         Ok(_) => println!("copy succeeded"),
+///         Err(e) => panic::resume_unwind(e),
 ///     }
 /// }
 /// ```
 ///
 /// [`Result`]: crate::result::Result
+/// [`std::panic::resume_unwind`]: crate::panic::resume_unwind
 #[stable(feature = "rust1", since = "1.0.0")]
 pub type Result<T> = crate::result::Result<T, Box<dyn Any + Send + 'static>>;
 
diff --git a/src/doc/book b/src/doc/book
index 5bb44f8b5b0aa..ac57a0ddd23d1 160000
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit 5bb44f8b5b0aa105c8b22602e9b18800484afa21
+Subproject commit ac57a0ddd23d173b26731ccf939f3ba729753275
diff --git a/src/doc/embedded-book b/src/doc/embedded-book
index ba34b8a968f95..ceec19e873be8 160000
--- a/src/doc/embedded-book
+++ b/src/doc/embedded-book
@@ -1 +1 @@
-Subproject commit ba34b8a968f9531d38c4dc4411d5568b7c076bfe
+Subproject commit ceec19e873be87c6ee5666b030c6bb612f889a96
diff --git a/src/doc/nomicon b/src/doc/nomicon
index a5a48441d411f..a8584998eacde 160000
--- a/src/doc/nomicon
+++ b/src/doc/nomicon
@@ -1 +1 @@
-Subproject commit a5a48441d411f61556b57d762b03d6874afe575d
+Subproject commit a8584998eacdea7106a1dfafcbf6c1c06fcdf925
diff --git a/src/doc/reference b/src/doc/reference
index b278478b76617..50af691f83893 160000
--- a/src/doc/reference
+++ b/src/doc/reference
@@ -1 +1 @@
-Subproject commit b278478b766178491a8b6f67afa4bcd6b64d977a
+Subproject commit 50af691f838937c300b47812d0507c6d88c14f97
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
index 1cce0737d6a7d..03e23af01f0b4 160000
--- a/src/doc/rust-by-example
+++ b/src/doc/rust-by-example
@@ -1 +1 @@
-Subproject commit 1cce0737d6a7d3ceafb139b4a206861fb1dcb2ab
+Subproject commit 03e23af01f0b4f83a3a513da280e1ca92587f2ec
diff --git a/src/test/ui/async-await/unused-lifetime.rs b/src/test/ui/async-await/unused-lifetime.rs
index 1cf546bcb4266..5bd6ae8d3a42d 100644
--- a/src/test/ui/async-await/unused-lifetime.rs
+++ b/src/test/ui/async-await/unused-lifetime.rs
@@ -1,42 +1,47 @@
-// edition:2018
+// Check "unused_lifetimes" lint on both async and sync functions
 
-// Avoid spurious warnings of unused lifetime. The below async functions
-// are desugered to have an unused lifetime
-// but we don't want to warn about that as there's nothing they can do about it.
+// edition:2018
 
 #![deny(unused_lifetimes)]
-#![allow(dead_code)]
-
-pub async fn october(s: &str) {
-    println!("{}", s);
-}
-
-pub async fn async_fn(&mut ref s: &mut[i32]) {
-    println!("{:?}", s);
-}
-
-macro_rules! foo_macro {
-    () => {
-        pub async fn async_fn_in_macro(&mut ref _s: &mut[i32]) {}
-    };
-}
-
-foo_macro!();
-
-pub async fn func_with_unused_lifetime<'a>(s: &'a str) {
-    //~^ ERROR lifetime parameter `'a` never used
-    println!("{}", s);
-}
-
-pub async fn func_with_two_unused_lifetime<'a, 'b>(s: &'a str, t: &'b str) {
-    //~^ ERROR lifetime parameter `'a` never used
-    //~^^ ERROR lifetime parameter `'b` never used
-    println!("{}", s);
-}
-
-pub async fn func_with_unused_lifetime_in_two_params<'c>(s: &'c str, t: &'c str) {
-    //~^ ERROR lifetime parameter `'c` never used
-    println!("{}", s);
-}
+
+
+// Async part with unused lifetimes
+//
+// Even wrong cases don't cause errors because async functions are desugared with all lifetimes
+// involved in the signature. So, we cannot predict what lifetimes are unused in async function.
+async fn async_wrong_without_args<'a>() {}
+
+async fn async_wrong_1_lifetime<'a>(_: &i32) {}
+
+async fn async_wrong_2_lifetimes<'a, 'b>(_: &'a i32, _: &i32) {}
+
+async fn async_right_1_lifetime<'a>(_: &'a i32) {}
+
+async fn async_right_2_lifetimes<'a, 'b>(_: &'a i32, _: &'b i32) {}
+
+async fn async_right_trait_bound_lifetime<'a, I>(_: I)
+where
+    I: Iterator<Item = &'a i32>
+{}
+
+
+// Sync part with unused lifetimes
+//
+// These functions are compiled as supposed
+fn wrong_without_args<'a>() {} //~ ERROR lifetime parameter `'a` never used
+
+fn wrong_1_lifetime<'a>(_: &i32) {} //~ ERROR lifetime parameter `'a` never used
+
+fn wrong_2_lifetimes<'a, 'b>(_: &'a i32, _: &i32) {} //~ ERROR lifetime parameter `'b` never used
+
+fn right_1_lifetime<'a>(_: &'a i32) {}
+
+fn right_2_lifetimes<'a, 'b>(_: &'a i32, _: &'b i32) {}
+
+fn right_trait_bound_lifetime<'a, I>(_: I)
+where
+    I: Iterator<Item = &'a i32>
+{}
+
 
 fn main() {}
diff --git a/src/test/ui/async-await/unused-lifetime.stderr b/src/test/ui/async-await/unused-lifetime.stderr
index 2a7a12a364346..4e90f43fdd07b 100644
--- a/src/test/ui/async-await/unused-lifetime.stderr
+++ b/src/test/ui/async-await/unused-lifetime.stderr
@@ -1,32 +1,28 @@
 error: lifetime parameter `'a` never used
-  --> $DIR/unused-lifetime.rs:26:40
+  --> $DIR/unused-lifetime.rs:31:23
    |
-LL | pub async fn func_with_unused_lifetime<'a>(s: &'a str) {
-   |                                        ^^
+LL | fn wrong_without_args<'a>() {}
+   |                      -^^- help: elide the unused lifetime
    |
 note: the lint level is defined here
-  --> $DIR/unused-lifetime.rs:7:9
+  --> $DIR/unused-lifetime.rs:5:9
    |
 LL | #![deny(unused_lifetimes)]
    |         ^^^^^^^^^^^^^^^^
 
 error: lifetime parameter `'a` never used
-  --> $DIR/unused-lifetime.rs:31:44
+  --> $DIR/unused-lifetime.rs:33:21
    |
-LL | pub async fn func_with_two_unused_lifetime<'a, 'b>(s: &'a str, t: &'b str) {
-   |                                            ^^
+LL | fn wrong_1_lifetime<'a>(_: &i32) {}
+   |                    -^^- help: elide the unused lifetime
 
 error: lifetime parameter `'b` never used
-  --> $DIR/unused-lifetime.rs:31:48
+  --> $DIR/unused-lifetime.rs:35:26
    |
-LL | pub async fn func_with_two_unused_lifetime<'a, 'b>(s: &'a str, t: &'b str) {
-   |                                                ^^
+LL | fn wrong_2_lifetimes<'a, 'b>(_: &'a i32, _: &i32) {}
+   |                        --^^
+   |                        |
+   |                        help: elide the unused lifetime
 
-error: lifetime parameter `'c` never used
-  --> $DIR/unused-lifetime.rs:37:54
-   |
-LL | pub async fn func_with_unused_lifetime_in_two_params<'c>(s: &'c str, t: &'c str) {
-   |                                                      ^^
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.stderr b/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.stderr
index 0e7174e5b19d6..c270593cac741 100644
--- a/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.stderr
+++ b/src/test/ui/destructuring-assignment/tuple_struct_destructure_fail.stderr
@@ -31,6 +31,15 @@ LL | struct TupleStruct<S, T>(S, T);
 ...
 LL |     TupleStruct(_) = TupleStruct(1, 2);
    |     ^^^^^^^^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |     TupleStruct(_, _) = TupleStruct(1, 2);
+   |                  ^^^
+help: use `..` to ignore all fields
+   |
+LL |     TupleStruct(..) = TupleStruct(1, 2);
+   |                 ^^
 
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/tuple_struct_destructure_fail.rs:34:5
@@ -49,6 +58,15 @@ LL |     SingleVariant(S, T)
 ...
 LL |     Enum::SingleVariant(_) = Enum::SingleVariant(1, 2);
    |     ^^^^^^^^^^^^^^^^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |     Enum::SingleVariant(_, _) = Enum::SingleVariant(1, 2);
+   |                          ^^^
+help: use `..` to ignore all fields
+   |
+LL |     Enum::SingleVariant(..) = Enum::SingleVariant(1, 2);
+   |                         ^^
 
 error[E0070]: invalid left-hand side of assignment
   --> $DIR/tuple_struct_destructure_fail.rs:40:12
diff --git a/src/test/ui/error-codes/E0023.stderr b/src/test/ui/error-codes/E0023.stderr
index a3610099294da..832eba6972213 100644
--- a/src/test/ui/error-codes/E0023.stderr
+++ b/src/test/ui/error-codes/E0023.stderr
@@ -6,6 +6,11 @@ LL |     Apple(String, String),
 ...
 LL |         Fruit::Apple(a) => {},
    |         ^^^^^^^^^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         Fruit::Apple(a, _) => {},
+   |                       ^^^
 
 error[E0023]: this pattern has 3 fields, but the corresponding tuple variant has 2 fields
   --> $DIR/E0023.rs:12:9
@@ -34,7 +39,7 @@ LL |     Orange((String, String)),
 LL |         Fruit::Orange(a, b) => {},
    |         ^^^^^^^^^^^^^^^^^^^ expected 1 field, found 2
    |
-help: missing parenthesis
+help: missing parentheses
    |
 LL |         Fruit::Orange((a, b)) => {},
    |                       ^    ^
@@ -48,7 +53,7 @@ LL |     Banana(()),
 LL |         Fruit::Banana() => {},
    |         ^^^^^^^^^^^^^^^ expected 1 field, found 0
    |
-help: missing parenthesis
+help: missing parentheses
    |
 LL |         Fruit::Banana(()) => {},
    |                      ^  ^
diff --git a/src/test/ui/issues/issue-67037-pat-tup-scrut-ty-diff-less-fields.stderr b/src/test/ui/issues/issue-67037-pat-tup-scrut-ty-diff-less-fields.stderr
index 6e8ea6bf618f2..9bdbf0bf9f40d 100644
--- a/src/test/ui/issues/issue-67037-pat-tup-scrut-ty-diff-less-fields.stderr
+++ b/src/test/ui/issues/issue-67037-pat-tup-scrut-ty-diff-less-fields.stderr
@@ -17,6 +17,15 @@ LL | struct P<T>(T); // 1 type parameter wanted
 ...
 LL |     let P() = U {};
    |         ^^^ expected 1 field, found 0
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |     let P(_) = U {};
+   |           ^
+help: use `..` to ignore all fields
+   |
+LL |     let P(..) = U {};
+   |           ^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/issues/issue-72574-2.stderr b/src/test/ui/issues/issue-72574-2.stderr
index 0a9c868af7af8..a1e8ec1677db5 100644
--- a/src/test/ui/issues/issue-72574-2.stderr
+++ b/src/test/ui/issues/issue-72574-2.stderr
@@ -26,6 +26,11 @@ LL | struct Binder(i32, i32, i32);
 ...
 LL |         Binder(_a, _x @ ..) => {}
    |         ^^^^^^^^^^^^^^^^^^^ expected 3 fields, found 2
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         Binder(_a, _x @ .., _) => {}
+   |                           ^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/match/match-pattern-field-mismatch.stderr b/src/test/ui/match/match-pattern-field-mismatch.stderr
index c2298d6fbbf02..37839482b31a2 100644
--- a/src/test/ui/match/match-pattern-field-mismatch.stderr
+++ b/src/test/ui/match/match-pattern-field-mismatch.stderr
@@ -6,6 +6,15 @@ LL |         Rgb(usize, usize, usize),
 ...
 LL |           Color::Rgb(_, _) => { }
    |           ^^^^^^^^^^^^^^^^ expected 3 fields, found 2
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |           Color::Rgb(_, _, _) => { }
+   |                          ^^^
+help: use `..` to ignore all fields
+   |
+LL |           Color::Rgb(..) => { }
+   |                      ^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/pattern/issue-74539.stderr b/src/test/ui/pattern/issue-74539.stderr
index cbc90b5397d8b..f7644c19ea0d9 100644
--- a/src/test/ui/pattern/issue-74539.stderr
+++ b/src/test/ui/pattern/issue-74539.stderr
@@ -26,6 +26,11 @@ LL |     A(u8, u8),
 ...
 LL |         E::A(x @ ..) => {
    |         ^^^^^^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         E::A(x @ .., _) => {
+   |                    ^^^
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/pattern/pat-tuple-underfield.rs b/src/test/ui/pattern/pat-tuple-underfield.rs
new file mode 100644
index 0000000000000..ed852a47bb4ee
--- /dev/null
+++ b/src/test/ui/pattern/pat-tuple-underfield.rs
@@ -0,0 +1,55 @@
+struct S(i32, f32);
+enum E {
+    S(i32, f32),
+}
+struct Point4(i32, i32, i32, i32);
+
+fn main() {
+    match S(0, 1.0) {
+        S(x) => {}
+        //~^ ERROR this pattern has 1 field, but the corresponding tuple struct has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+    }
+    match S(0, 1.0) {
+        S(_) => {}
+        //~^ ERROR this pattern has 1 field, but the corresponding tuple struct has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+        //~| HELP use `..` to ignore all fields
+    }
+    match S(0, 1.0) {
+        S() => {}
+        //~^ ERROR this pattern has 0 fields, but the corresponding tuple struct has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+        //~| HELP use `..` to ignore all fields
+    }
+
+    match E::S(0, 1.0) {
+        E::S(x) => {}
+        //~^ ERROR this pattern has 1 field, but the corresponding tuple variant has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+    }
+    match E::S(0, 1.0) {
+        E::S(_) => {}
+        //~^ ERROR this pattern has 1 field, but the corresponding tuple variant has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+        //~| HELP use `..` to ignore all fields
+    }
+    match E::S(0, 1.0) {
+        E::S() => {}
+        //~^ ERROR this pattern has 0 fields, but the corresponding tuple variant has 2 fields
+        //~| HELP use `_` to explicitly ignore each field
+        //~| HELP use `..` to ignore all fields
+    }
+    match E::S(0, 1.0) {
+        E::S => {}
+        //~^ ERROR expected unit struct, unit variant or constant, found tuple variant `E::S`
+        //~| HELP use the tuple variant pattern syntax instead
+    }
+
+    match Point4(0, 1, 2, 3) {
+        Point4(   a   ,     _    ) => {}
+        //~^ ERROR this pattern has 2 fields, but the corresponding tuple struct has 4 fields
+        //~| HELP use `_` to explicitly ignore each field
+        //~| HELP use `..` to ignore the rest of the fields
+    }
+}
diff --git a/src/test/ui/pattern/pat-tuple-underfield.stderr b/src/test/ui/pattern/pat-tuple-underfield.stderr
new file mode 100644
index 0000000000000..76323d9a7bf56
--- /dev/null
+++ b/src/test/ui/pattern/pat-tuple-underfield.stderr
@@ -0,0 +1,131 @@
+error[E0532]: expected unit struct, unit variant or constant, found tuple variant `E::S`
+  --> $DIR/pat-tuple-underfield.rs:44:9
+   |
+LL |     S(i32, f32),
+   |     ----------- `E::S` defined here
+...
+LL |         E::S => {}
+   |         ^^^^ help: use the tuple variant pattern syntax instead: `E::S(_, _)`
+
+error[E0023]: this pattern has 1 field, but the corresponding tuple struct has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:9:9
+   |
+LL | struct S(i32, f32);
+   | ------------------- tuple struct defined here
+...
+LL |         S(x) => {}
+   |         ^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         S(x, _) => {}
+   |            ^^^
+
+error[E0023]: this pattern has 1 field, but the corresponding tuple struct has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:14:9
+   |
+LL | struct S(i32, f32);
+   | ------------------- tuple struct defined here
+...
+LL |         S(_) => {}
+   |         ^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         S(_, _) => {}
+   |            ^^^
+help: use `..` to ignore all fields
+   |
+LL |         S(..) => {}
+   |           ^^
+
+error[E0023]: this pattern has 0 fields, but the corresponding tuple struct has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:20:9
+   |
+LL | struct S(i32, f32);
+   | ------------------- tuple struct defined here
+...
+LL |         S() => {}
+   |         ^^^ expected 2 fields, found 0
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         S(_, _) => {}
+   |           ^^^^
+help: use `..` to ignore all fields
+   |
+LL |         S(..) => {}
+   |           ^^
+
+error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:27:9
+   |
+LL |     S(i32, f32),
+   |     ----------- tuple variant defined here
+...
+LL |         E::S(x) => {}
+   |         ^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         E::S(x, _) => {}
+   |               ^^^
+
+error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:32:9
+   |
+LL |     S(i32, f32),
+   |     ----------- tuple variant defined here
+...
+LL |         E::S(_) => {}
+   |         ^^^^^^^ expected 2 fields, found 1
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         E::S(_, _) => {}
+   |               ^^^
+help: use `..` to ignore all fields
+   |
+LL |         E::S(..) => {}
+   |              ^^
+
+error[E0023]: this pattern has 0 fields, but the corresponding tuple variant has 2 fields
+  --> $DIR/pat-tuple-underfield.rs:38:9
+   |
+LL |     S(i32, f32),
+   |     ----------- tuple variant defined here
+...
+LL |         E::S() => {}
+   |         ^^^^^^ expected 2 fields, found 0
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         E::S(_, _) => {}
+   |              ^^^^
+help: use `..` to ignore all fields
+   |
+LL |         E::S(..) => {}
+   |              ^^
+
+error[E0023]: this pattern has 2 fields, but the corresponding tuple struct has 4 fields
+  --> $DIR/pat-tuple-underfield.rs:50:9
+   |
+LL | struct Point4(i32, i32, i32, i32);
+   | ---------------------------------- tuple struct defined here
+...
+LL |         Point4(   a   ,     _    ) => {}
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected 4 fields, found 2
+   |
+help: use `_` to explicitly ignore each field
+   |
+LL |         Point4(   a   ,     _    , _, _) => {}
+   |                                  ^^^^^^
+help: use `..` to ignore the rest of the fields
+   |
+LL |         Point4(   a   ,     _    , ..) => {}
+   |                                  ^^^^
+
+error: aborting due to 8 previous errors
+
+Some errors have detailed explanations: E0023, E0532.
+For more information about an error, try `rustc --explain E0023`.