Auto merge of rust-lang#137040 - jhpratt:rollup-lr17zya, r=jhpratt

Rollup of 11 pull requests

Successful merges:

 - rust-lang#133312 (triagebot: automatically add more rustdoc related labels)
 - rust-lang#134016 (Stabilize `const_is_char_boundary` and `const_str_split_at`.)
 - rust-lang#135813 (CI: split i686-mingw job to three free runners)
 - rust-lang#136879 (Add safe new() to NotAllOnes)
 - rust-lang#136971 (Add a new check-pass UI test for returning `impl Fn(T) -> impl Trait`)
 - rust-lang#136983 (Prepare standard library for Rust 2024 migration)
 - rust-lang#137002 (Fix early lint check desc in query)
 - rust-lang#137006 (borrowck diagnostics cleanup: remove an unused and a barely-used field)
 - rust-lang#137026 (Stabilize (and const-stabilize) `integer_sign_cast`)
 - rust-lang#137028 (mir_build: Clarify some code for lowering `hir::PatExpr` to THIR)
 - rust-lang#137032 (Decode metadata buffer in one go)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

Diff for: compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -147,9 +147,7 @@ pub(crate) enum RegionErrorKind<'tcx> {
 pub(crate) struct ErrorConstraintInfo<'tcx> {
     // fr: outlived_fr
     pub(super) fr: RegionVid,
-    pub(super) fr_is_local: bool,
     pub(super) outlived_fr: RegionVid,
-    pub(super) outlived_fr_is_local: bool,
 
     // Category and span for best blame constraint
     pub(super) category: ConstraintCategory<'tcx>,
@@ -471,14 +469,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             fr_is_local, outlived_fr_is_local, category
         );
 
-        let errci = ErrorConstraintInfo {
-            fr,
-            outlived_fr,
-            fr_is_local,
-            outlived_fr_is_local,
-            category,
-            span: cause.span,
-        };
+        let errci = ErrorConstraintInfo { fr, outlived_fr, category, span: cause.span };
 
         let mut diag = match (category, fr_is_local, outlived_fr_is_local) {
             (ConstraintCategory::Return(kind), true, false) if self.is_closure_fn_mut(fr) => {
@@ -680,11 +671,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 && self.regioncx.universal_regions().defining_ty.is_fn_def())
             || self.regioncx.universal_regions().defining_ty.is_const()
         {
-            return self.report_general_error(&ErrorConstraintInfo {
-                fr_is_local: true,
-                outlived_fr_is_local: false,
-                ..*errci
-            });
+            return self.report_general_error(errci);
         }
 
         let mut diag =
@@ -762,15 +749,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     /// ```
     #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
     fn report_general_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> Diag<'infcx> {
-        let ErrorConstraintInfo {
-            fr,
-            fr_is_local,
-            outlived_fr,
-            outlived_fr_is_local,
-            span,
-            category,
-            ..
-        } = errci;
+        let ErrorConstraintInfo { fr, outlived_fr, span, category, .. } = errci;
 
         let mir_def_name = self.infcx.tcx.def_descr(self.mir_def_id().to_def_id());
 
@@ -789,19 +768,22 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         let outlived_fr_name = self.give_region_a_name(*outlived_fr).unwrap();
         outlived_fr_name.highlight_region_name(&mut diag);
 
-        let err_category = match (category, outlived_fr_is_local, fr_is_local) {
-            (ConstraintCategory::Return(_), true, _) => LifetimeReturnCategoryErr::WrongReturn {
+        let err_category = if matches!(category, ConstraintCategory::Return(_))
+            && self.regioncx.universal_regions().is_local_free_region(*outlived_fr)
+        {
+            LifetimeReturnCategoryErr::WrongReturn {
                 span: *span,
                 mir_def_name,
                 outlived_fr_name,
                 fr_name: &fr_name,
-            },
-            _ => LifetimeReturnCategoryErr::ShortReturn {
+            }
+        } else {
+            LifetimeReturnCategoryErr::ShortReturn {
                 span: *span,
                 category_desc: category.description(),
                 free_region_name: &fr_name,
                 outlived_fr_name,
-            },
+            }
         };
 
         diag.subdiagnostic(err_category);

Diff for: compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2272,10 +2272,7 @@ impl<D: Decoder> Decodable<D> for EncodedMetadata {
         let len = d.read_usize();
         let mmap = if len > 0 {
             let mut mmap = MmapMut::map_anon(len).unwrap();
-            for _ in 0..len {
-                (&mut mmap[..]).write_all(&[d.read_u8()]).unwrap();
-            }
-            mmap.flush().unwrap();
+            mmap.copy_from_slice(d.read_raw_bytes(len));
             Some(mmap.make_read_only().unwrap())
         } else {
             None

Diff for: compiler/rustc_middle/src/query/mod.rs

@@ -116,7 +116,7 @@ rustc_queries! {
     }
 
     query early_lint_checks(_: ()) {
-        desc { "perform lints prior to macro expansion" }
+        desc { "perform lints prior to AST lowering" }
     }
 
     query resolutions(_: ()) -> &'tcx ty::ResolverGlobalCtxt {

Diff for: compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -189,7 +189,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 
         // Lower the endpoint into a temporary `PatKind` that will then be
         // deconstructed to obtain the constant value and other data.
-        let mut kind: PatKind<'tcx> = self.lower_lit(expr);
+        let mut kind: PatKind<'tcx> = self.lower_pat_expr(expr);
 
         // Unpeel any ascription or inline-const wrapper nodes.
         loop {
@@ -353,7 +353,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 
             hir::PatKind::Never => PatKind::Never,
 
-            hir::PatKind::Expr(value) => self.lower_lit(value),
+            hir::PatKind::Expr(value) => self.lower_pat_expr(value),
 
             hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {
                 let (lo_expr, hi_expr) = (lo_expr.as_deref(), hi_expr.as_deref());
@@ -638,54 +638,57 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let ty = self.typeck_results.node_type(id);
         let res = self.typeck_results.qpath_res(qpath, id);
 
-        let pat_from_kind = |kind| Box::new(Pat { span, ty, kind });
-
-        let (def_id, is_associated_const) = match res {
-            Res::Def(DefKind::Const, def_id) => (def_id, false),
-            Res::Def(DefKind::AssocConst, def_id) => (def_id, true),
+        let (def_id, user_ty) = match res {
+            Res::Def(DefKind::Const, def_id) => (def_id, None),
+            Res::Def(DefKind::AssocConst, def_id) => {
+                (def_id, self.typeck_results.user_provided_types().get(id))
+            }
 
-            _ => return pat_from_kind(self.lower_variant_or_leaf(res, id, span, ty, vec![])),
+            _ => {
+                // The path isn't the name of a constant, so it must actually
+                // be a unit struct or unit variant (e.g. `Option::None`).
+                let kind = self.lower_variant_or_leaf(res, id, span, ty, vec![]);
+                return Box::new(Pat { span, ty, kind });
+            }
         };
 
+        // Lower the named constant to a THIR pattern.
         let args = self.typeck_results.node_args(id);
         let c = ty::Const::new_unevaluated(self.tcx, ty::UnevaluatedConst { def: def_id, args });
         let subpattern = self.const_to_pat(c, ty, id, span);
-        let pattern = Box::new(Pat {
-            span,
-            ty,
-            kind: PatKind::ExpandedConstant { subpattern, def_id, is_inline: false },
-        });
 
-        if !is_associated_const {
-            return pattern;
-        }
+        // Wrap the pattern in a marker node to indicate that it is the result
+        // of lowering a named constant. This marker is used for improved
+        // diagnostics in some situations, but has no effect at runtime.
+        let mut pattern = {
+            let kind = PatKind::ExpandedConstant { subpattern, def_id, is_inline: false };
+            Box::new(Pat { span, ty, kind })
+        };
 
-        let user_provided_types = self.typeck_results.user_provided_types();
-        if let Some(&user_ty) = user_provided_types.get(id) {
+        // If this is an associated constant with an explicit user-written
+        // type, add an ascription node (e.g. `<Foo<'a> as MyTrait>::CONST`).
+        if let Some(&user_ty) = user_ty {
             let annotation = CanonicalUserTypeAnnotation {
                 user_ty: Box::new(user_ty),
                 span,
                 inferred_ty: self.typeck_results.node_type(id),
             };
-            Box::new(Pat {
-                span,
-                kind: PatKind::AscribeUserType {
-                    subpattern: pattern,
-                    ascription: Ascription {
-                        annotation,
-                        // Note that use `Contravariant` here. See the
-                        // `variance` field documentation for details.
-                        variance: ty::Contravariant,
-                    },
+            let kind = PatKind::AscribeUserType {
+                subpattern: pattern,
+                ascription: Ascription {
+                    annotation,
+                    // Note that we use `Contravariant` here. See the
+                    // `variance` field documentation for details.
+                    variance: ty::Contravariant,
                 },
-                ty,
-            })
-        } else {
-            pattern
+            };
+            pattern = Box::new(Pat { span, kind, ty });
         }
+
+        pattern
     }
 
-    /// Converts inline const patterns.
+    /// Lowers an inline const block (e.g. `const { 1 + 1 }`) to a pattern.
     fn lower_inline_const(
         &mut self,
         block: &'tcx hir::ConstBlock,
@@ -705,14 +708,17 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 
         let ct = ty::UnevaluatedConst { def: def_id.to_def_id(), args };
         let subpattern = self.const_to_pat(ty::Const::new_unevaluated(self.tcx, ct), ty, id, span);
+
+        // Wrap the pattern in a marker node to indicate that it is the result
+        // of lowering an inline const block.
         PatKind::ExpandedConstant { subpattern, def_id: def_id.to_def_id(), is_inline: true }
     }
 
-    /// Converts literals, paths and negation of literals to patterns.
-    /// The special case for negation exists to allow things like `-128_i8`
-    /// which would overflow if we tried to evaluate `128_i8` and then negate
-    /// afterwards.
-    fn lower_lit(&mut self, expr: &'tcx hir::PatExpr<'tcx>) -> PatKind<'tcx> {
+    /// Lowers the kinds of "expression" that can appear in a HIR pattern:
+    /// - Paths (e.g. `FOO`, `foo::BAR`, `Option::None`)
+    /// - Inline const blocks (e.g. `const { 1 + 1 }`)
+    /// - Literals, possibly negated (e.g. `-128u8`, `"hello"`)
+    fn lower_pat_expr(&mut self, expr: &'tcx hir::PatExpr<'tcx>) -> PatKind<'tcx> {
         let (lit, neg) = match &expr.kind {
             hir::PatExprKind::Path(qpath) => {
                 return self.lower_path(qpath, expr.hir_id, expr.span).kind;

Diff for: library/Cargo.lock

@@ -215,6 +215,15 @@ dependencies = [
  "unwind",
 ]
 
+[[package]]
+name = "proc-macro2"
+version = "1.0.93"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60946a68e5f9d28b0dc1c21bb8a97ee7d018a8b322fa57838ba31cc878e22d99"
+dependencies = [
+ "unicode-ident",
+]
+
 [[package]]
 name = "proc_macro"
 version = "0.0.0"
@@ -230,6 +239,15 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "quote"
+version = "1.0.38"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e4dccaaaf89514f546c693ddc140f729f958c247918a13380cccc6078391acc"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "r-efi"
 version = "4.5.0"
@@ -253,24 +271,28 @@ dependencies = [
 
 [[package]]
 name = "rand"
-version = "0.8.5"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+checksum = "3779b94aeb87e8bd4e834cee3650289ee9e0d5677f976ecdb6d219e5f4f6cd94"
 dependencies = [
  "rand_core",
+ "zerocopy",
 ]
 
 [[package]]
 name = "rand_core"
-version = "0.6.4"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+checksum = "b08f3c9802962f7e1b25113931d94f43ed9725bebc59db9d0c3e9a23b67e15ff"
+dependencies = [
+ "zerocopy",
+]
 
 [[package]]
 name = "rand_xorshift"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
+checksum = "513962919efc330f829edb2535844d1b912b0fbe2ca165d613e4e8788bb05a5a"
 dependencies = [
  "rand_core",
 ]
@@ -352,6 +374,17 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "syn"
+version = "2.0.98"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "36147f1a48ae0ec2b5b3bc5b537d267457555a10dc06f3dbc8cb11ba3006d3b1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "sysroot"
 version = "0.0.0"
@@ -372,6 +405,12 @@ dependencies = [
  "std",
 ]
 
+[[package]]
+name = "unicode-ident"
+version = "1.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a210d160f08b701c8721ba1c726c11662f877ea6b7094007e1ca9a1041945034"
+
 [[package]]
 name = "unicode-width"
 version = "0.1.14"
@@ -492,3 +531,23 @@ name = "windows_x86_64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
+
+[[package]]
+name = "zerocopy"
+version = "0.8.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa91407dacce3a68c56de03abe2760159582b846c6a4acd2f456618087f12713"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06718a168365cad3d5ff0bb133aad346959a2074bd4a85c121255a11304a8626"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]

Diff for: library/alloc/Cargo.toml

@@ -13,8 +13,8 @@ core = { path = "../core" }
 compiler_builtins = { version = "=0.1.146", features = ['rustc-dep-of-std'] }
 
 [dev-dependencies]
-rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
-rand_xorshift = "0.3.0"
+rand = { version = "0.9.0", default-features = false, features = ["alloc"] }
+rand_xorshift = "0.4.0"
 
 [[test]]
 name = "alloctests"