From c957c4e7043169743355066640d4c18d93264b3e Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 19 Aug 2025 18:51:08 +0000
Subject: [PATCH 01/10] Account for impossible bounds making seemingly
 unsatisfyable dyn-to-dyn casts

---
 compiler/rustc_borrowck/src/type_check/mod.rs | 33 ++++++++++++-------
 tests/ui/coercion/fake-sized-ptr-cast.rs      | 16 +++++++++
 2 files changed, 38 insertions(+), 11 deletions(-)
 create mode 100644 tests/ui/coercion/fake-sized-ptr-cast.rs

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 0e1dd5c701fe5..7d19b57e40c53 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -34,6 +34,7 @@ use rustc_mir_dataflow::points::DenseLocationMap;
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::source_map::Spanned;
 use rustc_span::{Span, sym};
+use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 use tracing::{debug, instrument, trace};
@@ -1457,22 +1458,32 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
+
                         match (cast_ty_from, cast_ty_to) {
                             (Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => {
-                                let src_tail = self.struct_tail(src.ty, location);
-                                let dst_tail = self.struct_tail(dst.ty, location);
-
-                                // This checks (lifetime part of) vtable validity for pointer casts,
-                                // which is irrelevant when there are aren't principal traits on
-                                // both sides (aka only auto traits).
-                                //
-                                // Note that other checks (such as denying `dyn Send` -> `dyn
-                                // Debug`) are in `rustc_hir_typeck`.
-                                if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) = *src_tail.kind()
-                                    && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) = *dst_tail.kind()
+                                if self
+                                    .infcx
+                                    .type_is_sized_modulo_regions(self.infcx.param_env, dst.ty)
+                                {
+                                    // Wide to thin ptr cast. This may even occur in an env with
+                                    // impossible predicates, such as `where dyn Trait: Sized`.
+                                    // In this case, we don't want to fall into the case below,
+                                    // since the types may not actually be equatable, but it's
+                                    // fine to perform this operation in an impossible env.
+                                } else if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) =
+                                    *self.struct_tail(src.ty, location).kind()
+                                    && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) =
+                                        *self.struct_tail(dst.ty, location).kind()
                                     && src_tty.principal().is_some()
                                     && dst_tty.principal().is_some()
                                 {
+                                    // This checks (lifetime part of) vtable validity for pointer casts,
+                                    // which is irrelevant when there are aren't principal traits on
+                                    // both sides (aka only auto traits).
+                                    //
+                                    // Note that other checks (such as denying `dyn Send` -> `dyn
+                                    // Debug`) are in `rustc_hir_typeck`.
+
                                     // Remove auto traits.
                                     // Auto trait checks are handled in `rustc_hir_typeck` as FCW.
                                     let src_obj = Ty::new_dynamic(
diff --git a/tests/ui/coercion/fake-sized-ptr-cast.rs b/tests/ui/coercion/fake-sized-ptr-cast.rs
new file mode 100644
index 0000000000000..4b6bf0eb5168e
--- /dev/null
+++ b/tests/ui/coercion/fake-sized-ptr-cast.rs
@@ -0,0 +1,16 @@
+// Make sure borrowck doesn't ICE because it thinks a pointer cast is a metadata-preserving
+// wide-to-wide ptr cast when it's actually (falsely) a wide-to-thin ptr cast due to an
+// impossible dyn sized bound.
+
+//@ check-pass
+
+trait Trait<T> {}
+
+fn func<'a>(x: *const (dyn Trait<()> + 'a))
+where
+    dyn Trait<u8> + 'a: Sized,
+{
+    let _x: *const dyn Trait<u8> = x as _;
+}
+
+fn main() {}

From e0fb6ebf7ba47eb67642e83186736149d5083e7d Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sat, 23 Aug 2025 17:13:03 +0000
Subject: [PATCH 02/10] Nits

---
 compiler/rustc_borrowck/src/type_check/mod.rs | 143 +++++++++---------
 1 file changed, 72 insertions(+), 71 deletions(-)

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 7d19b57e40c53..d661fb6403c91 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1456,78 +1456,79 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     }
                     CastKind::PtrToPtr => {
                         let ty_from = op.ty(self.body, tcx);
-                        let cast_ty_from = CastTy::from_ty(ty_from);
-                        let cast_ty_to = CastTy::from_ty(*ty);
+                        let Some(CastTy::Ptr(src)) = CastTy::from_ty(ty_from) else {
+                            unreachable!();
+                        };
+                        let Some(CastTy::Ptr(dst)) = CastTy::from_ty(*ty) else {
+                            unreachable!();
+                        };
 
-                        match (cast_ty_from, cast_ty_to) {
-                            (Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => {
-                                if self
-                                    .infcx
-                                    .type_is_sized_modulo_regions(self.infcx.param_env, dst.ty)
-                                {
-                                    // Wide to thin ptr cast. This may even occur in an env with
-                                    // impossible predicates, such as `where dyn Trait: Sized`.
-                                    // In this case, we don't want to fall into the case below,
-                                    // since the types may not actually be equatable, but it's
-                                    // fine to perform this operation in an impossible env.
-                                } else if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) =
-                                    *self.struct_tail(src.ty, location).kind()
-                                    && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) =
-                                        *self.struct_tail(dst.ty, location).kind()
-                                    && src_tty.principal().is_some()
-                                    && dst_tty.principal().is_some()
-                                {
-                                    // This checks (lifetime part of) vtable validity for pointer casts,
-                                    // which is irrelevant when there are aren't principal traits on
-                                    // both sides (aka only auto traits).
-                                    //
-                                    // Note that other checks (such as denying `dyn Send` -> `dyn
-                                    // Debug`) are in `rustc_hir_typeck`.
-
-                                    // Remove auto traits.
-                                    // Auto trait checks are handled in `rustc_hir_typeck` as FCW.
-                                    let src_obj = Ty::new_dynamic(
-                                        tcx,
-                                        tcx.mk_poly_existential_predicates(
-                                            &src_tty.without_auto_traits().collect::<Vec<_>>(),
-                                        ),
-                                        // FIXME: Once we disallow casting `*const dyn Trait + 'short`
-                                        // to `*const dyn Trait + 'long`, then this can just be `src_lt`.
-                                        dst_lt,
-                                        ty::Dyn,
-                                    );
-                                    let dst_obj = Ty::new_dynamic(
-                                        tcx,
-                                        tcx.mk_poly_existential_predicates(
-                                            &dst_tty.without_auto_traits().collect::<Vec<_>>(),
-                                        ),
-                                        dst_lt,
-                                        ty::Dyn,
-                                    );
-
-                                    debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);
-
-                                    self.sub_types(
-                                        src_obj,
-                                        dst_obj,
-                                        location.to_locations(),
-                                        ConstraintCategory::Cast {
-                                            is_implicit_coercion: false,
-                                            unsize_to: None,
-                                        },
-                                    )
-                                    .unwrap();
-                                }
-                            }
-                            _ => {
-                                span_mirbug!(
-                                    self,
-                                    rvalue,
-                                    "Invalid PtrToPtr cast {:?} -> {:?}",
-                                    ty_from,
-                                    ty
-                                )
-                            }
+                        if self.infcx.type_is_sized_modulo_regions(self.infcx.param_env, dst.ty) {
+                            // Wide to thin ptr cast. This may even occur in an env with
+                            // impossible predicates, such as `where dyn Trait: Sized`.
+                            // In this case, we don't want to fall into the case below,
+                            // since the types may not actually be equatable, but it's
+                            // fine to perform this operation in an impossible env.
+                            let trait_ref = ty::TraitRef::new(
+                                tcx,
+                                tcx.require_lang_item(LangItem::Sized, self.last_span),
+                                [dst.ty],
+                            );
+                            self.prove_trait_ref(
+                                trait_ref,
+                                location.to_locations(),
+                                ConstraintCategory::Cast {
+                                    is_implicit_coercion: true,
+                                    unsize_to: None,
+                                },
+                            );
+                        } else if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) =
+                            *self.struct_tail(src.ty, location).kind()
+                            && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) =
+                                *self.struct_tail(dst.ty, location).kind()
+                            && src_tty.principal().is_some()
+                            && dst_tty.principal().is_some()
+                        {
+                            // This checks (lifetime part of) vtable validity for pointer casts,
+                            // which is irrelevant when there are aren't principal traits on
+                            // both sides (aka only auto traits).
+                            //
+                            // Note that other checks (such as denying `dyn Send` -> `dyn
+                            // Debug`) are in `rustc_hir_typeck`.
+
+                            // Remove auto traits.
+                            // Auto trait checks are handled in `rustc_hir_typeck` as FCW.
+                            let src_obj = Ty::new_dynamic(
+                                tcx,
+                                tcx.mk_poly_existential_predicates(
+                                    &src_tty.without_auto_traits().collect::<Vec<_>>(),
+                                ),
+                                // FIXME: Once we disallow casting `*const dyn Trait + 'short`
+                                // to `*const dyn Trait + 'long`, then this can just be `src_lt`.
+                                dst_lt,
+                                ty::Dyn,
+                            );
+                            let dst_obj = Ty::new_dynamic(
+                                tcx,
+                                tcx.mk_poly_existential_predicates(
+                                    &dst_tty.without_auto_traits().collect::<Vec<_>>(),
+                                ),
+                                dst_lt,
+                                ty::Dyn,
+                            );
+
+                            debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);
+
+                            self.sub_types(
+                                src_obj,
+                                dst_obj,
+                                location.to_locations(),
+                                ConstraintCategory::Cast {
+                                    is_implicit_coercion: false,
+                                    unsize_to: None,
+                                },
+                            )
+                            .unwrap();
                         }
                     }
                     CastKind::Transmute => {

From 03ab22415a57a488e81414cc08a685cc77e6b72c Mon Sep 17 00:00:00 2001
From: Valdemar Erk <valdemar@erk.dev>
Date: Sat, 23 Aug 2025 11:37:53 +0200
Subject: [PATCH 03/10] add span to struct pattern rest (..)

---
 compiler/rustc_ast/src/ast.rs                        |  6 +++---
 compiler/rustc_ast_lowering/src/expr.rs              |  6 +++---
 compiler/rustc_ast_lowering/src/lib.rs               |  2 +-
 compiler/rustc_ast_lowering/src/pat.rs               |  9 +++++----
 compiler/rustc_ast_pretty/src/pprust/state.rs        |  2 +-
 compiler/rustc_hir/src/hir.rs                        |  8 ++++----
 compiler/rustc_hir_pretty/src/lib.rs                 |  4 ++--
 compiler/rustc_hir_typeck/src/pat.rs                 | 12 ++++++++++--
 compiler/rustc_parse/src/parser/pat.rs               |  2 +-
 compiler/rustc_passes/src/liveness.rs                |  2 +-
 compiler/rustc_resolve/src/late.rs                   |  2 +-
 .../clippy/clippy_lints/src/equatable_if_let.rs      |  2 +-
 src/tools/clippy/clippy_lints/src/manual_let_else.rs |  4 ++--
 .../src/matches/rest_pat_in_fully_bound_struct.rs    |  2 +-
 src/tools/clippy/clippy_lints/src/utils/author.rs    |  3 ++-
 src/tools/clippy/clippy_utils/src/lib.rs             |  2 +-
 src/tools/rustfmt/src/patterns.rs                    |  2 +-
 17 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index de3e0e0c87f5a..802a6fa324984 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -937,7 +937,7 @@ pub enum PatKind {
 #[derive(Clone, Copy, Encodable, Decodable, Debug, PartialEq, Walkable)]
 pub enum PatFieldsRest {
     /// `module::StructName { field, ..}`
-    Rest,
+    Rest(Span),
     /// `module::StructName { field, syntax error }`
     Recovered(ErrorGuaranteed),
     /// `module::StructName { field }`
@@ -4051,8 +4051,8 @@ mod size_asserts {
     static_assert_size!(Local, 96);
     static_assert_size!(MetaItemLit, 40);
     static_assert_size!(Param, 40);
-    static_assert_size!(Pat, 72);
-    static_assert_size!(PatKind, 48);
+    static_assert_size!(Pat, 80);
+    static_assert_size!(PatKind, 56);
     static_assert_size!(Path, 24);
     static_assert_size!(PathSegment, 24);
     static_assert_size!(Stmt, 32);
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index cbd17d66b7548..3674814b796c2 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1434,10 +1434,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         self.dcx().emit_err(FunctionalRecordUpdateDestructuringAssignment {
                             span: e.span,
                         });
-                        true
+                        Some(self.lower_span(e.span))
                     }
-                    StructRest::Rest(_) => true,
-                    StructRest::None => false,
+                    StructRest::Rest(span) => Some(self.lower_span(*span)),
+                    StructRest::None => None,
                 };
                 let struct_pat = hir::PatKind::Struct(qpath, field_pats, fields_omitted);
                 return self.pat_without_dbm(lhs.span, struct_pat);
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 70595391b85bc..137207bde1f12 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -2508,7 +2508,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         fields: &'hir [hir::PatField<'hir>],
     ) -> &'hir hir::Pat<'hir> {
         let qpath = hir::QPath::LangItem(lang_item, self.lower_span(span));
-        self.pat(span, hir::PatKind::Struct(qpath, fields, false))
+        self.pat(span, hir::PatKind::Struct(qpath, fields, None))
     }
 
     fn pat_ident(&mut self, span: Span, ident: Ident) -> (&'hir hir::Pat<'hir>, HirId) {
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index b8f8624787565..ed159f37051c1 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -106,10 +106,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         break hir::PatKind::Struct(
                             qpath,
                             fs,
-                            matches!(
-                                etc,
-                                ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_)
-                            ),
+                            match etc {
+                                ast::PatFieldsRest::Rest(sp) => Some(self.lower_span(*sp)),
+                                ast::PatFieldsRest::Recovered(_) => Some(Span::default()),
+                                _ => None,
+                            },
                         );
                     }
                     PatKind::Tuple(pats) => {
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index a056ce3e29d28..41b520b04c993 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1769,7 +1769,7 @@ impl<'a> State<'a> {
                     },
                     |f| f.pat.span,
                 );
-                if let ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) = etc {
+                if let ast::PatFieldsRest::Rest(_) | ast::PatFieldsRest::Recovered(_) = etc {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index e397c286de289..e3c27c73638c1 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1884,8 +1884,8 @@ pub enum PatKind<'hir> {
     Binding(BindingMode, HirId, Ident, Option<&'hir Pat<'hir>>),
 
     /// A struct or struct variant pattern (e.g., `Variant {x, y, ..}`).
-    /// The `bool` is `true` in the presence of a `..`.
-    Struct(QPath<'hir>, &'hir [PatField<'hir>], bool),
+    /// The `Option` contains the span of a possible `..`.
+    Struct(QPath<'hir>, &'hir [PatField<'hir>], Option<Span>),
 
     /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
     /// If the `..` pattern fragment is present, then `DotDotPos` denotes its position.
@@ -4979,8 +4979,8 @@ mod size_asserts {
     static_assert_size!(ItemKind<'_>, 64);
     static_assert_size!(LetStmt<'_>, 72);
     static_assert_size!(Param<'_>, 32);
-    static_assert_size!(Pat<'_>, 72);
-    static_assert_size!(PatKind<'_>, 48);
+    static_assert_size!(Pat<'_>, 80);
+    static_assert_size!(PatKind<'_>, 56);
     static_assert_size!(Path<'_>, 40);
     static_assert_size!(PathSegment<'_>, 48);
     static_assert_size!(QPath<'_>, 24);
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index be5859b57c5e0..52b29e05dcb0e 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -1958,12 +1958,12 @@ impl<'a> State<'a> {
                 self.print_qpath(qpath, true);
                 self.nbsp();
                 self.word("{");
-                let empty = fields.is_empty() && !etc;
+                let empty = fields.is_empty() && etc.is_none();
                 if !empty {
                     self.space();
                 }
                 self.commasep_cmnt(Consistent, fields, |s, f| s.print_patfield(f), |f| f.pat.span);
-                if etc {
+                if etc.is_some() {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 7dc736e5e6b14..f735c0a416099 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -605,7 +605,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             },
             PatKind::Struct(_, fields, has_rest_pat) => match opt_path_res.unwrap() {
                 Ok(ResolvedPat { ty, kind: ResolvedPatKind::Struct { variant } }) => self
-                    .check_pat_struct(pat, fields, has_rest_pat, ty, variant, expected, pat_info),
+                    .check_pat_struct(
+                        pat,
+                        fields,
+                        has_rest_pat.is_some(),
+                        ty,
+                        variant,
+                        expected,
+                        pat_info,
+                    ),
                 Err(guar) => {
                     let ty_err = Ty::new_error(self.tcx, guar);
                     for field in fields {
@@ -2428,7 +2436,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let len = unmentioned_fields.len();
         let (prefix, postfix, sp) = match fields {
             [] => match &pat.kind {
-                PatKind::Struct(path, [], false) => {
+                PatKind::Struct(path, [], None) => {
                     (" { ", " }", path.span().shrink_to_hi().until(pat.span.shrink_to_hi()))
                 }
                 _ => return err,
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 9754691a0b9ca..c4d30b3d32832 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -1516,7 +1516,7 @@ impl<'a> Parser<'a> {
                 || self.check_noexpect(&token::DotDotDot)
                 || self.check_keyword(exp!(Underscore))
             {
-                etc = PatFieldsRest::Rest;
+                etc = PatFieldsRest::Rest(self.token.span);
                 let mut etc_sp = self.token.span;
                 if first_etc_and_maybe_comma_span.is_none() {
                     if let Some(comma_tok) =
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 801a533c94338..ae16a51bc693c 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -1583,7 +1583,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
         });
 
         let can_remove = match pat.kind {
-            hir::PatKind::Struct(_, fields, true) => {
+            hir::PatKind::Struct(_, fields, Some(_)) => {
                 // if all fields are shorthand, remove the struct field, otherwise, mark with _ as prefix
                 fields.iter().all(|f| f.is_shorthand)
             }
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 679e663f88614..84108f0b8663d 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -3922,7 +3922,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
     fn record_patterns_with_skipped_bindings(&mut self, pat: &Pat, rest: &ast::PatFieldsRest) {
         match rest {
-            ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) => {
+            ast::PatFieldsRest::Rest(_) | ast::PatFieldsRest::Recovered(_) => {
                 // Record that the pattern doesn't introduce all the bindings it could.
                 if let Some(partial_res) = self.r.partial_res_map.get(&pat.id)
                     && let Some(res) = partial_res.full_res()
diff --git a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
index 72f5eaf8a4bcc..c3fc09343dbfe 100644
--- a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
+++ b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
@@ -53,7 +53,7 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
         | PatKind::Never
         | PatKind::Or(_)
         | PatKind::Err(_) => false,
-        PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),
+        PatKind::Struct(_, a, etc) => etc.is_none() && a.iter().all(|x| unary_pattern(x.pat)),
         PatKind::Tuple(a, etc) | PatKind::TupleStruct(_, a, etc) => etc.as_opt_usize().is_none() && array_rec(a),
         PatKind::Ref(x, _) | PatKind::Box(x) | PatKind::Deref(x) | PatKind::Guard(x, _) => unary_pattern(x),
         PatKind::Expr(_) => true,
diff --git a/src/tools/clippy/clippy_lints/src/manual_let_else.rs b/src/tools/clippy/clippy_lints/src/manual_let_else.rs
index 5a7967bbf9468..2705ef20b795d 100644
--- a/src/tools/clippy/clippy_lints/src/manual_let_else.rs
+++ b/src/tools/clippy/clippy_lints/src/manual_let_else.rs
@@ -287,7 +287,7 @@ fn replace_in_pattern(
                 }
                 return or_pat;
             },
-            PatKind::Struct(path, fields, has_dot_dot) => {
+            PatKind::Struct(path, fields, dot_dot) => {
                 let fields = fields
                     .iter()
                     .map(|fld| {
@@ -311,7 +311,7 @@ fn replace_in_pattern(
                     .collect::<Vec<_>>();
                 let fields_string = fields.join(", ");
 
-                let dot_dot_str = if has_dot_dot { " .." } else { "" };
+                let dot_dot_str = if dot_dot.is_some() { " .." } else { "" };
                 let (sn_pth, _) = snippet_with_context(cx, path.span(), span.ctxt(), "", app);
                 return format!("{sn_pth} {{ {fields_string}{dot_dot_str} }}");
             },
diff --git a/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs b/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
index 2154cd5b24a54..ae09c2e87d6b7 100644
--- a/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
@@ -7,7 +7,7 @@ use super::REST_PAT_IN_FULLY_BOUND_STRUCTS;
 
 pub(crate) fn check(cx: &LateContext<'_>, pat: &Pat<'_>) {
     if !pat.span.from_expansion()
-        && let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind
+        && let PatKind::Struct(QPath::Resolved(_, path), fields, Some(_)) = pat.kind
         && let Some(def_id) = path.res.opt_def_id()
         && let ty = cx.tcx.type_of(def_id).instantiate_identity()
         && let ty::Adt(def, _) = ty.kind()
diff --git a/src/tools/clippy/clippy_lints/src/utils/author.rs b/src/tools/clippy/clippy_lints/src/utils/author.rs
index 2113cb92137eb..ece29362a39f9 100644
--- a/src/tools/clippy/clippy_lints/src/utils/author.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/author.rs
@@ -754,7 +754,8 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 self.ident(name);
                 sub.if_some(|p| self.pat(p));
             },
-            PatKind::Struct(ref qpath, fields, ignore) => {
+            PatKind::Struct(ref qpath, fields, etc) => {
+                let ignore = etc.is_some();
                 bind!(self, qpath, fields);
                 kind!("Struct(ref {qpath}, {fields}, {ignore})");
                 self.qpath(qpath, pat);
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 8533fa8554199..011c9b2f931ae 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -2011,7 +2011,7 @@ pub fn is_expr_identity_of_pat(cx: &LateContext<'_>, pat: &Pat<'_>, expr: &Expr<
                 false
             }
         },
-        (PatKind::Struct(pat_ident, field_pats, false), ExprKind::Struct(ident, fields, hir::StructTailExpr::None))
+        (PatKind::Struct(pat_ident, field_pats, None), ExprKind::Struct(ident, fields, hir::StructTailExpr::None))
             if field_pats.len() == fields.len() =>
         {
             // check ident
diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs
index d212ecf392a7f..848bd0766e786 100644
--- a/src/tools/rustfmt/src/patterns.rs
+++ b/src/tools/rustfmt/src/patterns.rs
@@ -303,7 +303,7 @@ impl Rewrite for Pat {
                 qself,
                 path,
                 fields,
-                rest == ast::PatFieldsRest::Rest,
+                matches!(rest, ast::PatFieldsRest::Rest(_)),
                 self.span,
                 context,
                 shape,

From 4e4325c47701081dab1a32a7c9217f80ae5284c6 Mon Sep 17 00:00:00 2001
From: Marijn Schouten <mhkbst@gmail.com>
Date: Sat, 23 Aug 2025 19:36:19 +0000
Subject: [PATCH 04/10] remove deprecated Error::description in impls

---
 compiler/rustc_thread_pool/src/lib.rs         | 15 ++-----
 library/alloc/src/boxed.rs                    |  5 ---
 library/alloc/src/boxed/convert.rs            |  7 +--
 .../alloc/src/collections/btree/map/entry.rs  |  4 --
 library/alloc/src/ffi/c_str.rs                | 21 +--------
 library/alloc/src/string.rs                   | 14 +-----
 library/alloc/src/sync.rs                     |  5 ---
 library/core/src/array/mod.rs                 | 10 +----
 library/core/src/char/convert.rs              | 17 +++----
 library/core/src/char/decode.rs               |  7 +--
 library/core/src/convert/mod.rs               |  6 +--
 library/core/src/error.rs                     | 33 ++------------
 library/core/src/net/parser.rs                | 15 +++----
 library/core/src/num/dec2flt/mod.rs           | 17 +++----
 library/core/src/num/error.rs                 | 25 +++--------
 library/core/src/str/error.rs                 | 14 +-----
 library/core/src/time.rs                      | 17 +++----
 library/std/src/collections/hash/map.rs       |  7 +--
 library/std/src/env.rs                        | 10 +----
 library/std/src/io/buffered/bufwriter.rs      | 12 +----
 library/std/src/io/buffered/mod.rs            |  7 +--
 library/std/src/io/error.rs                   |  9 ----
 library/std/src/path.rs                       | 10 +----
 library/std/src/sync/mpsc.rs                  | 44 +++----------------
 library/std/src/sync/poison.rs                | 18 +-------
 library/std/src/sys/net/connection/sgx.rs     |  7 +--
 library/std/src/sys/pal/hermit/os.rs          |  8 +---
 library/std/src/sys/pal/sgx/mod.rs            |  3 +-
 library/std/src/sys/pal/sgx/os.rs             | 17 +++----
 library/std/src/sys/pal/solid/os.rs           |  8 +---
 library/std/src/sys/pal/teeos/os.rs           |  8 +---
 library/std/src/sys/pal/uefi/os.rs            |  3 +-
 library/std/src/sys/pal/unix/os.rs            |  8 +---
 library/std/src/sys/pal/unsupported/os.rs     |  8 +---
 library/std/src/sys/pal/wasi/os.rs            |  8 +---
 library/std/src/sys/pal/windows/os.rs         |  8 +---
 library/std/src/sys/pal/xous/os.rs            |  8 +---
 library/std/src/sys/pal/zkvm/os.rs            |  8 +---
 library/std/src/time.rs                       |  7 +--
 tests/ui/resolve/issue-102946.rs              |  1 -
 .../issue-87455-static-lifetime-ice.rs        |  6 +--
 41 files changed, 83 insertions(+), 382 deletions(-)

diff --git a/compiler/rustc_thread_pool/src/lib.rs b/compiler/rustc_thread_pool/src/lib.rs
index 34252d919e38e..7ce7fbc27eabe 100644
--- a/compiler/rustc_thread_pool/src/lib.rs
+++ b/compiler/rustc_thread_pool/src/lib.rs
@@ -787,18 +787,7 @@ impl ThreadPoolBuildError {
     }
 }
 
-const GLOBAL_POOL_ALREADY_INITIALIZED: &str =
-    "The global thread pool has already been initialized.";
-
 impl Error for ThreadPoolBuildError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match self.kind {
-            ErrorKind::GlobalPoolAlreadyInitialized => GLOBAL_POOL_ALREADY_INITIALIZED,
-            ErrorKind::IOError(ref e) => e.description(),
-        }
-    }
-
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match &self.kind {
             ErrorKind::GlobalPoolAlreadyInitialized => None,
@@ -810,7 +799,9 @@ impl Error for ThreadPoolBuildError {
 impl fmt::Display for ThreadPoolBuildError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.kind {
-            ErrorKind::GlobalPoolAlreadyInitialized => GLOBAL_POOL_ALREADY_INITIALIZED.fmt(f),
+            ErrorKind::GlobalPoolAlreadyInitialized => {
+                "The global thread pool has already been initialized.".fmt(f)
+            }
             ErrorKind::IOError(e) => e.fmt(f),
         }
     }
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index fa12d379c8cae..98c9f6b51ab86 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -2128,11 +2128,6 @@ impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> {
 
 #[stable(feature = "box_error", since = "1.8.0")]
 impl<E: Error> Error for Box<E> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn Error> {
         Error::cause(&**self)
diff --git a/library/alloc/src/boxed/convert.rs b/library/alloc/src/boxed/convert.rs
index 8062658020239..45c46fb526365 100644
--- a/library/alloc/src/boxed/convert.rs
+++ b/library/alloc/src/boxed/convert.rs
@@ -608,12 +608,7 @@ impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a> {
     fn from(err: String) -> Box<dyn Error + Send + Sync + 'a> {
         struct StringError(String);
 
-        impl Error for StringError {
-            #[allow(deprecated)]
-            fn description(&self) -> &str {
-                &self.0
-            }
-        }
+        impl Error for StringError {}
 
         impl fmt::Display for StringError {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/library/alloc/src/collections/btree/map/entry.rs b/library/alloc/src/collections/btree/map/entry.rs
index ea8fa363c3805..ec9b774c30877 100644
--- a/library/alloc/src/collections/btree/map/entry.rs
+++ b/library/alloc/src/collections/btree/map/entry.rs
@@ -136,10 +136,6 @@ impl<'a, K: Debug + Ord, V: Debug, A: Allocator + Clone> fmt::Display
 impl<'a, K: core::fmt::Debug + Ord, V: core::fmt::Debug> core::error::Error
     for crate::collections::btree_map::OccupiedError<'a, K, V>
 {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "key already exists"
-    }
 }
 
 impl<'a, K: Ord, V, A: Allocator + Clone> Entry<'a, K, V, A> {
diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index fe6c89a30949d..b0c8c4b1ca4a7 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -1061,17 +1061,10 @@ impl IntoStringError {
     }
 }
 
-impl IntoStringError {
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-}
-
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl fmt::Display for IntoStringError {
-    #[allow(deprecated, deprecated_in_future)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.description().fmt(f)
+        "C string contained non-utf8 bytes".fmt(f)
     }
 }
 
@@ -1291,23 +1284,13 @@ impl PartialEq<CString> for Cow<'_, CStr> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl core::error::Error for NulError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "nul byte found in data"
-    }
-}
+impl core::error::Error for NulError {}
 
 #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
 impl core::error::Error for FromVecWithNulError {}
 
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl core::error::Error for IntoStringError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-
     fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
         Some(&self.error)
     }
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 9eacbf00e4233..11fd4346ff504 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -2285,20 +2285,10 @@ impl fmt::Display for FromUtf16Error {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for FromUtf8Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "invalid utf-8"
-    }
-}
+impl Error for FromUtf8Error {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for FromUtf16Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "invalid utf-16"
-    }
-}
+impl Error for FromUtf16Error {}
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 29caa7bc5393c..a21b6880674c6 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -4113,11 +4113,6 @@ impl<T: ?Sized, A: Allocator> Drop for UniqueArcUninit<T, A> {
 
 #[stable(feature = "arc_error", since = "1.52.0")]
 impl<T: core::error::Error + ?Sized> core::error::Error for Arc<T> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        core::error::Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn core::error::Error> {
         core::error::Error::cause(&**self)
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index bb75ec74c8177..835ee57ce230b 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -184,18 +184,12 @@ pub struct TryFromSliceError(());
 impl fmt::Display for TryFromSliceError {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[allow(deprecated)]
-        self.description().fmt(f)
+        "could not convert slice to array".fmt(f)
     }
 }
 
 #[stable(feature = "try_from", since = "1.34.0")]
-impl Error for TryFromSliceError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "could not convert slice to array"
-    }
-}
+impl Error for TryFromSliceError {}
 
 #[stable(feature = "try_from_slice_error", since = "1.36.0")]
 #[rustc_const_unstable(feature = "const_try", issue = "74935")]
diff --git a/library/core/src/char/convert.rs b/library/core/src/char/convert.rs
index 23061cb663bc6..cf5a91bf8ddb5 100644
--- a/library/core/src/char/convert.rs
+++ b/library/core/src/char/convert.rs
@@ -193,21 +193,16 @@ enum CharErrorKind {
 }
 
 #[stable(feature = "char_from_str", since = "1.20.0")]
-impl Error for ParseCharError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match self.kind {
-            CharErrorKind::EmptyString => "cannot parse char from empty string",
-            CharErrorKind::TooManyChars => "too many characters in string",
-        }
-    }
-}
+impl Error for ParseCharError {}
 
 #[stable(feature = "char_from_str", since = "1.20.0")]
 impl fmt::Display for ParseCharError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[allow(deprecated)]
-        self.description().fmt(f)
+        match self.kind {
+            CharErrorKind::EmptyString => "cannot parse char from empty string",
+            CharErrorKind::TooManyChars => "too many characters in string",
+        }
+        .fmt(f)
     }
 }
 
diff --git a/library/core/src/char/decode.rs b/library/core/src/char/decode.rs
index 23319fbe5ddc4..d7c5f45ae4ed7 100644
--- a/library/core/src/char/decode.rs
+++ b/library/core/src/char/decode.rs
@@ -126,9 +126,4 @@ impl fmt::Display for DecodeUtf16Error {
 }
 
 #[stable(feature = "decode_utf16", since = "1.9.0")]
-impl Error for DecodeUtf16Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "unpaired surrogate found"
-    }
-}
+impl Error for DecodeUtf16Error {}
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index 0c3034c3d4cf2..a0a7b7928d16c 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -958,11 +958,7 @@ impl fmt::Display for Infallible {
 }
 
 #[stable(feature = "str_parse_error2", since = "1.8.0")]
-impl Error for Infallible {
-    fn description(&self) -> &str {
-        match *self {}
-    }
-}
+impl Error for Infallible {}
 
 #[stable(feature = "convert_infallible", since = "1.34.0")]
 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
diff --git a/library/core/src/error.rs b/library/core/src/error.rs
index 88e633c9eef3f..92b3c83d1bf34 100644
--- a/library/core/src/error.rs
+++ b/library/core/src/error.rs
@@ -1042,11 +1042,6 @@ impl<'a> crate::iter::FusedIterator for Source<'a> {}
 
 #[stable(feature = "error_by_ref", since = "1.51.0")]
 impl<'a, T: Error + ?Sized> Error for &'a T {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn Error> {
         Error::cause(&**self)
@@ -1062,36 +1057,16 @@ impl<'a, T: Error + ?Sized> Error for &'a T {
 }
 
 #[stable(feature = "fmt_error", since = "1.11.0")]
-impl Error for crate::fmt::Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "an error occurred when formatting an argument"
-    }
-}
+impl Error for crate::fmt::Error {}
 
 #[stable(feature = "try_borrow", since = "1.13.0")]
-impl Error for crate::cell::BorrowError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "already mutably borrowed"
-    }
-}
+impl Error for crate::cell::BorrowError {}
 
 #[stable(feature = "try_borrow", since = "1.13.0")]
-impl Error for crate::cell::BorrowMutError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "already borrowed"
-    }
-}
+impl Error for crate::cell::BorrowMutError {}
 
 #[stable(feature = "try_from", since = "1.34.0")]
-impl Error for crate::char::CharTryFromError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "converted integer out of range for `char`"
-    }
-}
+impl Error for crate::char::CharTryFromError {}
 
 #[stable(feature = "duration_checked_float", since = "1.66.0")]
 impl Error for crate::time::TryFromFloatSecsError {}
diff --git a/library/core/src/net/parser.rs b/library/core/src/net/parser.rs
index 73230f6ee5b03..3aab24a90d817 100644
--- a/library/core/src/net/parser.rs
+++ b/library/core/src/net/parser.rs
@@ -497,16 +497,7 @@ pub struct AddrParseError(AddrKind);
 
 #[stable(feature = "addr_parse_error_error", since = "1.4.0")]
 impl fmt::Display for AddrParseError {
-    #[allow(deprecated, deprecated_in_future)]
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt.write_str(self.description())
-    }
-}
-
-#[stable(feature = "addr_parse_error_error", since = "1.4.0")]
-impl Error for AddrParseError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.0 {
             AddrKind::Ip => "invalid IP address syntax",
             AddrKind::Ipv4 => "invalid IPv4 address syntax",
@@ -515,5 +506,9 @@ impl Error for AddrParseError {
             AddrKind::SocketV4 => "invalid IPv4 socket address syntax",
             AddrKind::SocketV6 => "invalid IPv6 socket address syntax",
         }
+        .fmt(f)
     }
 }
+
+#[stable(feature = "addr_parse_error_error", since = "1.4.0")]
+impl Error for AddrParseError {}
diff --git a/library/core/src/num/dec2flt/mod.rs b/library/core/src/num/dec2flt/mod.rs
index 3118a6e5ca62e..dd4eccd24de03 100644
--- a/library/core/src/num/dec2flt/mod.rs
+++ b/library/core/src/num/dec2flt/mod.rs
@@ -219,21 +219,16 @@ enum FloatErrorKind {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseFloatError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match self.kind {
-            FloatErrorKind::Empty => "cannot parse float from empty string",
-            FloatErrorKind::Invalid => "invalid float literal",
-        }
-    }
-}
+impl Error for ParseFloatError {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for ParseFloatError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[allow(deprecated)]
-        self.description().fmt(f)
+        match self.kind {
+            FloatErrorKind::Empty => "cannot parse float from empty string",
+            FloatErrorKind::Invalid => "invalid float literal",
+        }
+        .fmt(f)
     }
 }
 
diff --git a/library/core/src/num/error.rs b/library/core/src/num/error.rs
index cfedd465cab0b..faa52329827c1 100644
--- a/library/core/src/num/error.rs
+++ b/library/core/src/num/error.rs
@@ -11,19 +11,13 @@ pub struct TryFromIntError(pub(crate) ());
 
 #[stable(feature = "try_from", since = "1.34.0")]
 impl fmt::Display for TryFromIntError {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[allow(deprecated)]
-        self.description().fmt(fmt)
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "out of range integral type conversion attempted".fmt(f)
     }
 }
 
 #[stable(feature = "try_from", since = "1.34.0")]
-impl Error for TryFromIntError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "out of range integral type conversion attempted"
-    }
-}
+impl Error for TryFromIntError {}
 
 #[stable(feature = "try_from", since = "1.34.0")]
 #[rustc_const_unstable(feature = "const_try", issue = "74935")]
@@ -128,15 +122,6 @@ impl ParseIntError {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for ParseIntError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[allow(deprecated)]
-        self.description().fmt(f)
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseIntError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
         match self.kind {
             IntErrorKind::Empty => "cannot parse integer from empty string",
             IntErrorKind::InvalidDigit => "invalid digit found in string",
@@ -144,5 +129,9 @@ impl Error for ParseIntError {
             IntErrorKind::NegOverflow => "number too small to fit in target type",
             IntErrorKind::Zero => "number would be zero for non-zero type",
         }
+        .fmt(f)
     }
 }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Error for ParseIntError {}
diff --git a/library/core/src/str/error.rs b/library/core/src/str/error.rs
index 4c8231a2286e1..1677c849ae4bf 100644
--- a/library/core/src/str/error.rs
+++ b/library/core/src/str/error.rs
@@ -124,12 +124,7 @@ impl fmt::Display for Utf8Error {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for Utf8Error {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "invalid utf-8: corrupt contents"
-    }
-}
+impl Error for Utf8Error {}
 
 /// An error returned when parsing a `bool` using [`from_str`] fails
 ///
@@ -147,9 +142,4 @@ impl fmt::Display for ParseBoolError {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseBoolError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "failed to parse bool"
-    }
-}
+impl Error for ParseBoolError {}
diff --git a/library/core/src/time.rs b/library/core/src/time.rs
index 0cc570f4b7335..f37e47f132d54 100644
--- a/library/core/src/time.rs
+++ b/library/core/src/time.rs
@@ -927,7 +927,7 @@ impl Duration {
     pub fn from_secs_f64(secs: f64) -> Duration {
         match Duration::try_from_secs_f64(secs) {
             Ok(v) => v,
-            Err(e) => panic!("{}", e.description()),
+            Err(e) => panic!("{e}"),
         }
     }
 
@@ -964,7 +964,7 @@ impl Duration {
     pub fn from_secs_f32(secs: f32) -> Duration {
         match Duration::try_from_secs_f32(secs) {
             Ok(v) => v,
-            Err(e) => panic!("{}", e.description()),
+            Err(e) => panic!("{e}"),
         }
     }
 
@@ -1445,8 +1445,9 @@ pub struct TryFromFloatSecsError {
     kind: TryFromFloatSecsErrorKind,
 }
 
-impl TryFromFloatSecsError {
-    const fn description(&self) -> &'static str {
+#[stable(feature = "duration_checked_float", since = "1.66.0")]
+impl fmt::Display for TryFromFloatSecsError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.kind {
             TryFromFloatSecsErrorKind::Negative => {
                 "cannot convert float seconds to Duration: value is negative"
@@ -1455,13 +1456,7 @@ impl TryFromFloatSecsError {
                 "cannot convert float seconds to Duration: value is either too big or NaN"
             }
         }
-    }
-}
-
-#[stable(feature = "duration_checked_float", since = "1.66.0")]
-impl fmt::Display for TryFromFloatSecsError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.description().fmt(f)
+        .fmt(f)
     }
 }
 
diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index 15a7a770d1a87..fc0fef620e3b6 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -1875,12 +1875,7 @@ impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V> {
 }
 
 #[unstable(feature = "map_try_insert", issue = "82766")]
-impl<'a, K: fmt::Debug, V: fmt::Debug> Error for OccupiedError<'a, K, V> {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "key already exists"
-    }
-}
+impl<'a, K: Debug, V: Debug> Error for OccupiedError<'a, K, V> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> {
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 9f17ff7644557..e457cd61c7596 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -296,15 +296,7 @@ impl fmt::Display for VarError {
 }
 
 #[stable(feature = "env", since = "1.0.0")]
-impl Error for VarError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match *self {
-            VarError::NotPresent => "environment variable not found",
-            VarError::NotUnicode(..) => "environment variable was not valid unicode",
-        }
-    }
-}
+impl Error for VarError {}
 
 /// Sets the environment variable `key` to the value `value` for the currently running
 /// process.
diff --git a/library/std/src/io/buffered/bufwriter.rs b/library/std/src/io/buffered/bufwriter.rs
index 574eb83dc5649..d569fed24c561 100644
--- a/library/std/src/io/buffered/bufwriter.rs
+++ b/library/std/src/io/buffered/bufwriter.rs
@@ -492,23 +492,15 @@ impl WriterPanicked {
     pub fn into_inner(self) -> Vec<u8> {
         self.buf
     }
-
-    const DESCRIPTION: &'static str =
-        "BufWriter inner writer panicked, what data remains unwritten is not known";
 }
 
 #[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
-impl error::Error for WriterPanicked {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        Self::DESCRIPTION
-    }
-}
+impl error::Error for WriterPanicked {}
 
 #[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
 impl fmt::Display for WriterPanicked {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", Self::DESCRIPTION)
+        "BufWriter inner writer panicked, what data remains unwritten is not known".fmt(f)
     }
 }
 
diff --git a/library/std/src/io/buffered/mod.rs b/library/std/src/io/buffered/mod.rs
index 475d877528f7f..e36f2d92108d0 100644
--- a/library/std/src/io/buffered/mod.rs
+++ b/library/std/src/io/buffered/mod.rs
@@ -179,12 +179,7 @@ impl<W> From<IntoInnerError<W>> for Error {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        error::Error::description(self.error())
-    }
-}
+impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W> fmt::Display for IntoInnerError<W> {
diff --git a/library/std/src/io/error.rs b/library/std/src/io/error.rs
index dcfa189823f89..57a980d6acdb5 100644
--- a/library/std/src/io/error.rs
+++ b/library/std/src/io/error.rs
@@ -1049,15 +1049,6 @@ impl fmt::Display for Error {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl error::Error for Error {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        match self.repr.data() {
-            ErrorData::Os(..) | ErrorData::Simple(..) => self.kind().as_str(),
-            ErrorData::SimpleMessage(msg) => msg.message,
-            ErrorData::Custom(c) => c.error.description(),
-        }
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn error::Error> {
         match self.repr.data() {
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 3899fbf86db8c..470d300d2d95b 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -3677,19 +3677,13 @@ impl_cmp_os_str!(<'a> Cow<'a, Path>, OsString);
 
 #[stable(since = "1.7.0", feature = "strip_prefix")]
 impl fmt::Display for StripPrefixError {
-    #[allow(deprecated, deprecated_in_future)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.description().fmt(f)
+        "prefix not found".fmt(f)
     }
 }
 
 #[stable(since = "1.7.0", feature = "strip_prefix")]
-impl Error for StripPrefixError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "prefix not found"
-    }
-}
+impl Error for StripPrefixError {}
 
 #[unstable(feature = "normalize_lexically", issue = "134694")]
 impl fmt::Display for NormalizeError {
diff --git a/library/std/src/sync/mpsc.rs b/library/std/src/sync/mpsc.rs
index 03d7fddc2faef..f91c26aa22cf8 100644
--- a/library/std/src/sync/mpsc.rs
+++ b/library/std/src/sync/mpsc.rs
@@ -1108,12 +1108,7 @@ impl<T> fmt::Display for SendError<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> error::Error for SendError<T> {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "sending on a closed channel"
-    }
-}
+impl<T> error::Error for SendError<T> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> fmt::Debug for TrySendError<T> {
@@ -1136,15 +1131,7 @@ impl<T> fmt::Display for TrySendError<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> error::Error for TrySendError<T> {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match *self {
-            TrySendError::Full(..) => "sending on a full channel",
-            TrySendError::Disconnected(..) => "sending on a closed channel",
-        }
-    }
-}
+impl<T> error::Error for TrySendError<T> {}
 
 #[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
 impl<T> From<SendError<T>> for TrySendError<T> {
@@ -1168,12 +1155,7 @@ impl fmt::Display for RecvError {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl error::Error for RecvError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "receiving on a closed channel"
-    }
-}
+impl error::Error for RecvError {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for TryRecvError {
@@ -1186,15 +1168,7 @@ impl fmt::Display for TryRecvError {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl error::Error for TryRecvError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match *self {
-            TryRecvError::Empty => "receiving on an empty channel",
-            TryRecvError::Disconnected => "receiving on a closed channel",
-        }
-    }
-}
+impl error::Error for TryRecvError {}
 
 #[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
 impl From<RecvError> for TryRecvError {
@@ -1221,15 +1195,7 @@ impl fmt::Display for RecvTimeoutError {
 }
 
 #[stable(feature = "mpsc_recv_timeout_error", since = "1.15.0")]
-impl error::Error for RecvTimeoutError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match *self {
-            RecvTimeoutError::Timeout => "timed out waiting on channel",
-            RecvTimeoutError::Disconnected => "channel is empty and sending half is closed",
-        }
-    }
-}
+impl error::Error for RecvTimeoutError {}
 
 #[stable(feature = "mpsc_error_conversions", since = "1.24.0")]
 impl From<RecvError> for RecvTimeoutError {
diff --git a/library/std/src/sync/poison.rs b/library/std/src/sync/poison.rs
index 31889dcc10fad..49a71b9ad10bd 100644
--- a/library/std/src/sync/poison.rs
+++ b/library/std/src/sync/poison.rs
@@ -263,12 +263,7 @@ impl<T> fmt::Display for PoisonError<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Error for PoisonError<T> {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "poisoned lock: another task failed inside"
-    }
-}
+impl<T> Error for PoisonError<T> {}
 
 impl<T> PoisonError<T> {
     /// Creates a `PoisonError`.
@@ -376,17 +371,6 @@ impl<T> fmt::Display for TryLockError<T> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Error for TryLockError<T> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        match *self {
-            #[cfg(panic = "unwind")]
-            TryLockError::Poisoned(ref p) => p.description(),
-            #[cfg(not(panic = "unwind"))]
-            TryLockError::Poisoned(ref p) => match p._never {},
-            TryLockError::WouldBlock => "try_lock failed because the operation would block",
-        }
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn Error> {
         match *self {
diff --git a/library/std/src/sys/net/connection/sgx.rs b/library/std/src/sys/net/connection/sgx.rs
index 242df10bc3270..2389fd1bcb6ca 100644
--- a/library/std/src/sys/net/connection/sgx.rs
+++ b/library/std/src/sys/net/connection/sgx.rs
@@ -452,12 +452,7 @@ pub struct NonIpSockAddr {
     host: String,
 }
 
-impl error::Error for NonIpSockAddr {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "Failed to convert address to SocketAddr"
-    }
-}
+impl error::Error for NonIpSockAddr {}
 
 impl fmt::Display for NonIpSockAddr {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/library/std/src/sys/pal/hermit/os.rs b/library/std/src/sys/pal/hermit/os.rs
index a998c3165e52f..0fe713a503bd0 100644
--- a/library/std/src/sys/pal/hermit/os.rs
+++ b/library/std/src/sys/pal/hermit/os.rs
@@ -1,5 +1,4 @@
 use super::hermit_abi;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
@@ -52,12 +51,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on hermit yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/sgx/mod.rs b/library/std/src/sys/pal/sgx/mod.rs
index 6e43a79ddec2c..4a297b6823f20 100644
--- a/library/std/src/sys/pal/sgx/mod.rs
+++ b/library/std/src/sys/pal/sgx/mod.rs
@@ -59,8 +59,7 @@ pub fn sgx_ineffective<T>(v: T) -> crate::io::Result<T> {
 
 #[inline]
 pub fn is_interrupted(code: i32) -> bool {
-    use fortanix_sgx_abi::Error;
-    code == Error::Interrupted as _
+    code == fortanix_sgx_abi::Error::Interrupted as _
 }
 
 pub fn decode_error_kind(code: i32) -> ErrorKind {
diff --git a/library/std/src/sys/pal/sgx/os.rs b/library/std/src/sys/pal/sgx/os.rs
index 70f838679c9ca..6b62320a0862a 100644
--- a/library/std/src/sys/pal/sgx/os.rs
+++ b/library/std/src/sys/pal/sgx/os.rs
@@ -1,6 +1,3 @@
-use fortanix_sgx_abi::{Error, RESULT_SUCCESS};
-
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
@@ -12,9 +9,12 @@ pub fn errno() -> i32 {
 }
 
 pub fn error_string(errno: i32) -> String {
-    if errno == RESULT_SUCCESS {
+    use fortanix_sgx_abi as abi;
+
+    if errno == abi::RESULT_SUCCESS {
         "operation successful".into()
-    } else if ((Error::UserRangeStart as _)..=(Error::UserRangeEnd as _)).contains(&errno) {
+    } else if ((abi::Error::UserRangeStart as _)..=(abi::Error::UserRangeEnd as _)).contains(&errno)
+    {
         format!("user-specified error {errno:08x}")
     } else {
         decode_error_kind(errno).as_str().into()
@@ -59,12 +59,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported in SGX yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/solid/os.rs b/library/std/src/sys/pal/solid/os.rs
index 8f5976b0592ec..cb6e2cbceae6c 100644
--- a/library/std/src/sys/pal/solid/os.rs
+++ b/library/std/src/sys/pal/solid/os.rs
@@ -1,5 +1,4 @@
 use super::{error, itron, unsupported};
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::path::{self, PathBuf};
 use crate::{fmt, io};
@@ -58,12 +57,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/teeos/os.rs b/library/std/src/sys/pal/teeos/os.rs
index 03f3c72b0229a..512b3e2885bf0 100644
--- a/library/std/src/sys/pal/teeos/os.rs
+++ b/library/std/src/sys/pal/teeos/os.rs
@@ -3,7 +3,6 @@
 use core::marker::PhantomData;
 
 use super::unsupported;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::path::PathBuf;
 use crate::{fmt, io, path};
@@ -62,12 +61,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/uefi/os.rs b/library/std/src/sys/pal/uefi/os.rs
index bfd4dc81cb44f..aae6cb9e06462 100644
--- a/library/std/src/sys/pal/uefi/os.rs
+++ b/library/std/src/sys/pal/uefi/os.rs
@@ -2,7 +2,6 @@ use r_efi::efi::Status;
 use r_efi::efi::protocols::{device_path, loaded_image_device_path};
 
 use super::{RawOsError, helpers, unsupported_err};
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::os::uefi;
@@ -122,7 +121,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     let protocol = helpers::image_handle_protocol::<device_path::Protocol>(
diff --git a/library/std/src/sys/pal/unix/os.rs b/library/std/src/sys/pal/unix/os.rs
index 1110b775c0953..81275afa70777 100644
--- a/library/std/src/sys/pal/unix/os.rs
+++ b/library/std/src/sys/pal/unix/os.rs
@@ -7,7 +7,6 @@ mod tests;
 
 use libc::{c_char, c_int, c_void};
 
-use crate::error::Error as StdError;
 use crate::ffi::{CStr, OsStr, OsString};
 use crate::os::unix::prelude::*;
 use crate::path::{self, PathBuf};
@@ -248,12 +247,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "failed to join paths"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 #[cfg(target_os = "aix")]
 pub fn current_exe() -> io::Result<PathBuf> {
diff --git a/library/std/src/sys/pal/unsupported/os.rs b/library/std/src/sys/pal/unsupported/os.rs
index a8ef97ecf67ac..13d2a2044f48a 100644
--- a/library/std/src/sys/pal/unsupported/os.rs
+++ b/library/std/src/sys/pal/unsupported/os.rs
@@ -1,5 +1,4 @@
 use super::unsupported;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
@@ -51,12 +50,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/wasi/os.rs b/library/std/src/sys/pal/wasi/os.rs
index 672cf70d1a5b2..151ba254ec4cf 100644
--- a/library/std/src/sys/pal/wasi/os.rs
+++ b/library/std/src/sys/pal/wasi/os.rs
@@ -1,6 +1,5 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-use crate::error::Error as StdError;
 use crate::ffi::{CStr, OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::os::wasi::prelude::*;
@@ -105,12 +104,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on wasm yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/windows/os.rs b/library/std/src/sys/pal/windows/os.rs
index f331282d2d72a..1b3c80c079bef 100644
--- a/library/std/src/sys/pal/windows/os.rs
+++ b/library/std/src/sys/pal/windows/os.rs
@@ -8,7 +8,6 @@ mod tests;
 use super::api;
 #[cfg(not(target_vendor = "uwp"))]
 use super::api::WinError;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::os::windows::ffi::EncodeWide;
 use crate::os::windows::prelude::*;
@@ -162,12 +161,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "failed to join paths"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     super::fill_utf16_buf(
diff --git a/library/std/src/sys/pal/xous/os.rs b/library/std/src/sys/pal/xous/os.rs
index d612a27d2bdb6..d9b8418e6c33c 100644
--- a/library/std/src/sys/pal/xous/os.rs
+++ b/library/std/src/sys/pal/xous/os.rs
@@ -1,5 +1,4 @@
 use super::unsupported;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::os::xous::ffi::Error as XousError;
@@ -110,12 +109,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/sys/pal/zkvm/os.rs b/library/std/src/sys/pal/zkvm/os.rs
index a8ef97ecf67ac..13d2a2044f48a 100644
--- a/library/std/src/sys/pal/zkvm/os.rs
+++ b/library/std/src/sys/pal/zkvm/os.rs
@@ -1,5 +1,4 @@
 use super::unsupported;
-use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
@@ -51,12 +50,7 @@ impl fmt::Display for JoinPathsError {
     }
 }
 
-impl StdError for JoinPathsError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "not supported on this platform yet"
-    }
-}
+impl crate::error::Error for JoinPathsError {}
 
 pub fn current_exe() -> io::Result<PathBuf> {
     unsupported()
diff --git a/library/std/src/time.rs b/library/std/src/time.rs
index 07bb41f14961b..84fbb4c2fe4b1 100644
--- a/library/std/src/time.rs
+++ b/library/std/src/time.rs
@@ -717,12 +717,7 @@ impl SystemTimeError {
 }
 
 #[stable(feature = "time2", since = "1.8.0")]
-impl Error for SystemTimeError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "other time was not earlier than self"
-    }
-}
+impl Error for SystemTimeError {}
 
 #[stable(feature = "time2", since = "1.8.0")]
 impl fmt::Display for SystemTimeError {
diff --git a/tests/ui/resolve/issue-102946.rs b/tests/ui/resolve/issue-102946.rs
index c6feca6f32f60..8d90e61bb5d3f 100644
--- a/tests/ui/resolve/issue-102946.rs
+++ b/tests/ui/resolve/issue-102946.rs
@@ -1,7 +1,6 @@
 impl Error for str::Utf8Error {
     //~^ ERROR cannot find trait `Error` in this scope
     //~| ERROR ambiguous associated type
-    fn description(&self)  {}
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-87455-static-lifetime-ice.rs b/tests/ui/type-alias-impl-trait/issue-87455-static-lifetime-ice.rs
index 987fad2efeadb..476babdfb0512 100644
--- a/tests/ui/type-alias-impl-trait/issue-87455-static-lifetime-ice.rs
+++ b/tests/ui/type-alias-impl-trait/issue-87455-static-lifetime-ice.rs
@@ -1,6 +1,6 @@
 //@ check-pass
 
-use std::error::Error as StdError;
+use std::error::Error;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
@@ -51,7 +51,7 @@ impl<S> Stream for SseKeepAlive<S>
 where
     S: TryStream + Send + 'static,
     S::Ok: ServerSentEvent,
-    S::Error: StdError + Send + Sync + 'static,
+    S::Error: Error + Send + Sync + 'static,
 {
     type Item = Result<SseComment<&'static str>, ()>;
     fn poll_next(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Option<Self::Item>> {
@@ -65,7 +65,7 @@ pub fn keep<S>(
 where
     S: TryStream + Send + 'static,
     S::Ok: ServerSentEvent + Send,
-    S::Error: StdError + Send + Sync + 'static,
+    S::Error: Error + Send + Sync + 'static,
 {
     SseKeepAlive { event_stream }
 }

From 3f339ab84926eaf34d2caaa7394bb84744017960 Mon Sep 17 00:00:00 2001
From: Marijn Schouten <hkBst@users.noreply.github.com>
Date: Mon, 20 Jan 2025 10:59:42 +0100
Subject: [PATCH 05/10] Dial down detail of B-tree description

fixes 134088, though it is a shame to lose some of this wonderful detail.
---
 library/alloc/src/collections/btree/map.rs | 29 ++++------------------
 1 file changed, 5 insertions(+), 24 deletions(-)

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index c4e599222e501..673487549fcad 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -40,30 +40,10 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 /// An ordered map based on a [B-Tree].
 ///
-/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
-/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
-/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
-/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
-/// is done is *very* inefficient for modern computer architectures. In particular, every element
-/// is stored in its own individually heap-allocated node. This means that every single insertion
-/// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
-/// are both notably expensive things to do in practice, we are forced to, at the very least,
-/// reconsider the BST strategy.
-///
-/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
-/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
-/// searches. However, this does mean that searches will have to do *more* comparisons on average.
-/// The precise number of comparisons depends on the node search strategy used. For optimal cache
-/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
-/// the node using binary search. As a compromise, one could also perform a linear search
-/// that initially only checks every i<sup>th</sup> element for some choice of i.
-///
-/// Currently, our implementation simply performs naive linear search. This provides excellent
-/// performance on *small* nodes of elements which are cheap to compare. However in the future we
-/// would like to further explore choosing the optimal search strategy based on the choice of B,
-/// and possibly other factors. Using linear search, searching for a random element is expected
-/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
-/// however, performance is excellent.
+/// A B-tree resembles a [binary search tree], but each leaf (node) contains
+/// an entire array (of unspecified size) of elements, instead of just a single element.
+/// A search first traverses the tree structure to find, in logarithmic time, the correct leaf.
+/// This leaf is then searched linearly, which is very fast on modern hardware.
 ///
 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
@@ -77,6 +57,7 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// amortized constant time per item returned.
 ///
 /// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
+/// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
 ///

From bb7993f80793ee4dce16f77532dc44c0048b3261 Mon Sep 17 00:00:00 2001
From: Marijn Schouten <hkBst@users.noreply.github.com>
Date: Tue, 21 Jan 2025 12:00:44 +0100
Subject: [PATCH 06/10] focus more on ordered aspect and restore old comments

---
 library/alloc/src/collections/btree/map.rs | 58 +++++++++++++++++-----
 1 file changed, 45 insertions(+), 13 deletions(-)

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 673487549fcad..b23a62c55459a 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -40,10 +40,15 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 /// An ordered map based on a [B-Tree].
 ///
-/// A B-tree resembles a [binary search tree], but each leaf (node) contains
-/// an entire array (of unspecified size) of elements, instead of just a single element.
-/// A search first traverses the tree structure to find, in logarithmic time, the correct leaf.
-/// This leaf is then searched linearly, which is very fast on modern hardware.
+/// An ordered map is a map in which the keys are totally ordered.
+/// That means that keys must be of a type that implements the [`Ord`] trait,
+/// such that two keys can always be compared to determine their [`Ordering`].
+/// Examples of totally ordered keys are strings with lexicographical order,
+/// and numbers with their natural order.
+///
+/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
+/// [`BTreeMap::keys`] produce their items in key order, and take worst-case logarithmic and
+/// amortized constant time per item returned.
 ///
 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
@@ -52,15 +57,6 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// `BTreeMap` that observed the logic error and not result in undefined behavior. This could
 /// include panics, incorrect results, aborts, memory leaks, and non-termination.
 ///
-/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
-/// [`BTreeMap::keys`] produce their items in order by key, and take worst-case logarithmic and
-/// amortized constant time per item returned.
-///
-/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
-/// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
-/// [`Cell`]: core::cell::Cell
-/// [`RefCell`]: core::cell::RefCell
-///
 /// # Examples
 ///
 /// ```
@@ -150,6 +146,42 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// // modify an entry before an insert with in-place mutation
 /// player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
 /// ```
+///
+/// # Background
+///
+/// A B-tree is (like) a [binary search tree], but adapted to the natural granularity that modern
+/// machines like to consume data at. This means that each node contains an entire array of elements,
+/// instead of just a single element.
+///
+/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
+/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
+/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum number of
+/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
+/// is done is *very* inefficient for modern computer architectures. In particular, every element
+/// is stored in its own individually heap-allocated node. This means that every single insertion
+/// triggers a heap-allocation, and every comparison is a potential cache-miss due to the indirection.
+/// Since both heap-allocations and cache-misses are notably expensive in practice, we are forced to,
+/// at the very least, reconsider the BST strategy.
+///
+/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
+/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
+/// searches. However, this does mean that searches will have to do *more* comparisons on average.
+/// The precise number of comparisons depends on the node search strategy used. For optimal cache
+/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
+/// the node using binary search. As a compromise, one could also perform a linear search
+/// that initially only checks every i<sup>th</sup> element for some choice of i.
+///
+/// Currently, our implementation simply performs naive linear search. This provides excellent
+/// performance on *small* nodes of elements which are cheap to compare. However in the future we
+/// would like to further explore choosing the optimal search strategy based on the choice of B,
+/// and possibly other factors. Using linear search, searching for a random element is expected
+/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
+/// however, performance is excellent.
+///
+/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
+/// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
+/// [`Cell`]: core::cell::Cell
+/// [`RefCell`]: core::cell::RefCell
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "BTreeMap")]
 #[rustc_insignificant_dtor]

From 1b773870854bac0fa898be2e5d1ba7d44d16b83c Mon Sep 17 00:00:00 2001
From: Marijn Schouten <hkBst@users.noreply.github.com>
Date: Wed, 22 Jan 2025 10:05:55 +0100
Subject: [PATCH 07/10] Prevent confusion with insertion-ordered maps.

---
 library/alloc/src/collections/btree/map.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index b23a62c55459a..8b6d86a288866 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -40,10 +40,10 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 /// An ordered map based on a [B-Tree].
 ///
-/// An ordered map is a map in which the keys are totally ordered.
+/// Given a key type with a [total order], an ordered map stores its entries in key order.
 /// That means that keys must be of a type that implements the [`Ord`] trait,
 /// such that two keys can always be compared to determine their [`Ordering`].
-/// Examples of totally ordered keys are strings with lexicographical order,
+/// Examples of keys with a total order are strings with lexicographical order,
 /// and numbers with their natural order.
 ///
 /// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
@@ -180,6 +180,7 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 ///
 /// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
 /// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
+/// [total order]: https://en.wikipedia.org/wiki/Total_order
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
 #[stable(feature = "rust1", since = "1.0.0")]

From 455a67bd4f38b10e613fc6e2103598db10ad57fe Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Sun, 24 Aug 2025 15:05:26 +1000
Subject: [PATCH 08/10] Replace the `llvm::Bool` typedef with a proper newtype

---
 compiler/rustc_codegen_llvm/src/asm.rs       | 11 ++--
 compiler/rustc_codegen_llvm/src/builder.rs   | 21 +++-----
 compiler/rustc_codegen_llvm/src/common.rs    |  4 +-
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs  | 57 ++++++++++++++++++--
 compiler/rustc_codegen_llvm/src/llvm/mod.rs  |  4 +-
 compiler/rustc_codegen_llvm/src/llvm_util.rs |  2 +-
 compiler/rustc_codegen_llvm/src/mono_item.rs |  2 +-
 compiler/rustc_codegen_llvm/src/type_.rs     |  8 +--
 8 files changed, 75 insertions(+), 34 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index a643a91141e19..38c1d3b53e87c 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -16,6 +16,7 @@ use tracing::debug;
 use crate::builder::Builder;
 use crate::common::Funclet;
 use crate::context::CodegenCx;
+use crate::llvm::ToLlvmBool;
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
@@ -470,10 +471,6 @@ pub(crate) fn inline_asm_call<'ll>(
     dest: Option<&'ll llvm::BasicBlock>,
     catch_funclet: Option<(&'ll llvm::BasicBlock, Option<&Funclet<'ll>>)>,
 ) -> Option<&'ll Value> {
-    let volatile = if volatile { llvm::True } else { llvm::False };
-    let alignstack = if alignstack { llvm::True } else { llvm::False };
-    let can_throw = if unwind { llvm::True } else { llvm::False };
-
     let argtys = inputs
         .iter()
         .map(|v| {
@@ -500,10 +497,10 @@ pub(crate) fn inline_asm_call<'ll>(
             asm.len(),
             cons.as_ptr(),
             cons.len(),
-            volatile,
-            alignstack,
+            volatile.to_llvm_bool(),
+            alignstack.to_llvm_bool(),
             dia,
-            can_throw,
+            unwind.to_llvm_bool(),
         )
     };
 
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 427c75d40e9c6..836d227456c40 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -35,7 +35,7 @@ use crate::attributes;
 use crate::common::Funclet;
 use crate::context::{CodegenCx, FullCx, GenericCx, SCx};
 use crate::llvm::{
-    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, False, GEPNoWrapFlags, Metadata, True,
+    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, GEPNoWrapFlags, Metadata, ToLlvmBool, True,
 };
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
@@ -717,7 +717,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             let mut const_llval = None;
             let llty = place.layout.llvm_type(self);
             if let Some(global) = llvm::LLVMIsAGlobalVariable(place.val.llval) {
-                if llvm::LLVMIsGlobalConstant(global) == llvm::True {
+                if llvm::LLVMIsGlobalConstant(global).is_true() {
                     if let Some(init) = llvm::LLVMGetInitializer(global) {
                         if self.val_ty(init) == llty {
                             const_llval = Some(init);
@@ -1067,13 +1067,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
 
     fn intcast(&mut self, val: &'ll Value, dest_ty: &'ll Type, is_signed: bool) -> &'ll Value {
         unsafe {
-            llvm::LLVMBuildIntCast2(
-                self.llbuilder,
-                val,
-                dest_ty,
-                if is_signed { True } else { False },
-                UNNAMED,
-            )
+            llvm::LLVMBuildIntCast2(self.llbuilder, val, dest_ty, is_signed.to_llvm_bool(), UNNAMED)
         }
     }
 
@@ -1317,7 +1311,6 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         failure_order: rustc_middle::ty::AtomicOrdering,
         weak: bool,
     ) -> (&'ll Value, &'ll Value) {
-        let weak = if weak { llvm::True } else { llvm::False };
         unsafe {
             let value = llvm::LLVMBuildAtomicCmpXchg(
                 self.llbuilder,
@@ -1328,7 +1321,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 AtomicOrdering::from_generic(failure_order),
                 llvm::False, // SingleThreaded
             );
-            llvm::LLVMSetWeak(value, weak);
+            llvm::LLVMSetWeak(value, weak.to_llvm_bool());
             let val = self.extract_value(value, 0);
             let success = self.extract_value(value, 1);
             (val, success)
@@ -1368,14 +1361,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         scope: SynchronizationScope,
     ) {
         let single_threaded = match scope {
-            SynchronizationScope::SingleThread => llvm::True,
-            SynchronizationScope::CrossThread => llvm::False,
+            SynchronizationScope::SingleThread => true,
+            SynchronizationScope::CrossThread => false,
         };
         unsafe {
             llvm::LLVMBuildFence(
                 self.llbuilder,
                 AtomicOrdering::from_generic(order),
-                single_threaded,
+                single_threaded.to_llvm_bool(),
                 UNNAMED,
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index f29fefb66f0fe..1b341c1f6afe3 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -20,7 +20,7 @@ use tracing::debug;
 use crate::consts::const_alloc_to_llvm;
 pub(crate) use crate::context::CodegenCx;
 use crate::context::{GenericCx, SCx};
-use crate::llvm::{self, BasicBlock, Bool, ConstantInt, False, Metadata, True};
+use crate::llvm::{self, BasicBlock, ConstantInt, False, Metadata, ToLlvmBool, True};
 use crate::type_::Type;
 use crate::value::Value;
 
@@ -392,7 +392,7 @@ fn struct_in_context<'ll>(
     packed: bool,
 ) -> &'ll Value {
     let len = c_uint::try_from(elts.len()).expect("LLVMConstStructInContext elements len overflow");
-    unsafe { llvm::LLVMConstStructInContext(llcx, elts.as_ptr(), len, packed as Bool) }
+    unsafe { llvm::LLVMConstStructInContext(llcx, elts.as_ptr(), len, packed.to_llvm_bool()) }
 }
 
 #[inline]
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 2461f70a86e35..912e3d6ff2424 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -13,7 +13,7 @@
 #![allow(non_camel_case_types)]
 #![allow(non_upper_case_globals)]
 
-use std::fmt::Debug;
+use std::fmt::{self, Debug};
 use std::marker::PhantomData;
 use std::num::NonZero;
 use std::ptr;
@@ -33,10 +33,59 @@ use crate::llvm;
 
 /// In the LLVM-C API, boolean values are passed as `typedef int LLVMBool`,
 /// which has a different ABI from Rust or C++ `bool`.
-pub(crate) type Bool = c_int;
+///
+/// This wrapper does not implement `PartialEq`.
+/// To test the underlying boolean value, use [`Self::is_true`].
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+pub(crate) struct Bool {
+    value: c_int,
+}
+
+pub(crate) const True: Bool = Bool::TRUE;
+pub(crate) const False: Bool = Bool::FALSE;
+
+impl Bool {
+    pub(crate) const TRUE: Self = Self { value: 1 };
+    pub(crate) const FALSE: Self = Self { value: 0 };
+
+    pub(crate) const fn from_bool(rust_bool: bool) -> Self {
+        if rust_bool { Self::TRUE } else { Self::FALSE }
+    }
+
+    /// Converts this LLVM-C boolean to a Rust `bool`
+    pub(crate) fn is_true(self) -> bool {
+        // Since we're interacting with a C API, follow the C convention of
+        // treating any nonzero value as true.
+        self.value != Self::FALSE.value
+    }
+}
 
-pub(crate) const True: Bool = 1 as Bool;
-pub(crate) const False: Bool = 0 as Bool;
+impl Debug for Bool {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.value {
+            0 => f.write_str("FALSE"),
+            1 => f.write_str("TRUE"),
+            // As with `Self::is_true`, treat any nonzero value as true.
+            v => write!(f, "TRUE ({v})"),
+        }
+    }
+}
+
+/// Convenience trait to convert `bool` to `llvm::Bool` with an explicit method call.
+///
+/// Being able to write `b.to_llvm_bool()` is less noisy than `llvm::Bool::from(b)`,
+/// while being more explicit and less mistake-prone than something like `b.into()`.
+pub(crate) trait ToLlvmBool: Copy {
+    fn to_llvm_bool(self) -> llvm::Bool;
+}
+
+impl ToLlvmBool for bool {
+    #[inline(always)]
+    fn to_llvm_bool(self) -> llvm::Bool {
+        llvm::Bool::from_bool(self)
+    }
+}
 
 /// Wrapper for a raw enum value returned from LLVM's C APIs.
 ///
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 7fea7b79a8cfb..6adabe5312969 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -215,7 +215,7 @@ pub(crate) fn set_initializer(llglobal: &Value, constant_val: &Value) {
 }
 
 pub(crate) fn set_global_constant(llglobal: &Value, is_constant: bool) {
-    LLVMSetGlobalConstant(llglobal, if is_constant { ffi::True } else { ffi::False });
+    LLVMSetGlobalConstant(llglobal, is_constant.to_llvm_bool());
 }
 
 pub(crate) fn get_linkage(llglobal: &Value) -> Linkage {
@@ -229,7 +229,7 @@ pub(crate) fn set_linkage(llglobal: &Value, linkage: Linkage) {
 }
 
 pub(crate) fn is_declaration(llglobal: &Value) -> bool {
-    unsafe { LLVMIsDeclaration(llglobal) == ffi::True }
+    unsafe { LLVMIsDeclaration(llglobal) }.is_true()
 }
 
 pub(crate) fn get_visibility(llglobal: &Value) -> Visibility {
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index 90f7cd43268fa..d5025bb405cc5 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -26,7 +26,7 @@ static INIT: Once = Once::new();
 pub(crate) fn init(sess: &Session) {
     unsafe {
         // Before we touch LLVM, make sure that multithreading is enabled.
-        if llvm::LLVMIsMultithreaded() != 1 {
+        if !llvm::LLVMIsMultithreaded().is_true() {
             bug!("LLVM compiled without support for threads");
         }
         INIT.call_once(|| {
diff --git a/compiler/rustc_codegen_llvm/src/mono_item.rs b/compiler/rustc_codegen_llvm/src/mono_item.rs
index 5075befae8a54..52eefe2d4d243 100644
--- a/compiler/rustc_codegen_llvm/src/mono_item.rs
+++ b/compiler/rustc_codegen_llvm/src/mono_item.rs
@@ -133,7 +133,7 @@ impl CodegenCx<'_, '_> {
 
         // Thread-local variables generally don't support copy relocations.
         let is_thread_local_var = llvm::LLVMIsAGlobalVariable(llval)
-            .is_some_and(|v| llvm::LLVMIsThreadLocal(v) == llvm::True);
+            .is_some_and(|v| llvm::LLVMIsThreadLocal(v).is_true());
         if is_thread_local_var {
             return false;
         }
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index f02d16baf94e7..499771aa12427 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -15,7 +15,7 @@ use rustc_target::callconv::{CastTarget, FnAbi};
 use crate::abi::{FnAbiLlvmExt, LlvmType};
 use crate::context::{CodegenCx, GenericCx, SCx};
 pub(crate) use crate::llvm::Type;
-use crate::llvm::{Bool, False, Metadata, True};
+use crate::llvm::{False, Metadata, ToLlvmBool, True};
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use crate::{common, llvm};
@@ -53,7 +53,9 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn set_struct_body(&self, ty: &'ll Type, els: &[&'ll Type], packed: bool) {
-        unsafe { llvm::LLVMStructSetBody(ty, els.as_ptr(), els.len() as c_uint, packed as Bool) }
+        unsafe {
+            llvm::LLVMStructSetBody(ty, els.as_ptr(), els.len() as c_uint, packed.to_llvm_bool())
+        }
     }
     pub(crate) fn type_void(&self) -> &'ll Type {
         unsafe { llvm::LLVMVoidTypeInContext(self.llcx()) }
@@ -152,7 +154,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
                 self.llcx(),
                 els.as_ptr(),
                 els.len() as c_uint,
-                packed as Bool,
+                packed.to_llvm_bool(),
             )
         }
     }

From b4e97e5d866dd43c110d337affc419d5ac482765 Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Sun, 24 Aug 2025 20:49:32 +1000
Subject: [PATCH 09/10] Rename `llvm::Bool` aliases to standard const case

This avoids the need for `#![allow(non_upper_case_globals)]`.
---
 compiler/rustc_codegen_llvm/src/allocator.rs  |  6 ++--
 compiler/rustc_codegen_llvm/src/back/write.rs |  2 +-
 compiler/rustc_codegen_llvm/src/builder.rs    | 30 +++++++++----------
 .../src/builder/autodiff.rs                   |  4 +--
 compiler/rustc_codegen_llvm/src/common.rs     |  8 ++---
 compiler/rustc_codegen_llvm/src/context.rs    |  2 +-
 .../rustc_codegen_llvm/src/debuginfo/gdb.rs   |  2 +-
 .../src/debuginfo/namespace.rs                |  2 +-
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs   |  5 ++--
 compiler/rustc_codegen_llvm/src/type_.rs      |  6 ++--
 10 files changed, 33 insertions(+), 34 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 23610aa856cb1..df3e49279d976 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -12,7 +12,7 @@ use smallvec::SmallVec;
 
 use crate::builder::SBuilder;
 use crate::declare::declare_simple_fn;
-use crate::llvm::{self, False, True, Type, Value};
+use crate::llvm::{self, FALSE, TRUE, Type, Value};
 use crate::{SimpleCx, attributes, debuginfo, llvm_util};
 
 pub(crate) unsafe fn codegen(
@@ -80,7 +80,7 @@ pub(crate) unsafe fn codegen(
             &cx,
             &mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
             &i8,
-            &llvm::LLVMConstInt(i8, tcx.sess.opts.unstable_opts.oom.should_panic() as u64, False),
+            &llvm::LLVMConstInt(i8, tcx.sess.opts.unstable_opts.oom.should_panic() as u64, FALSE),
         );
 
         // __rust_no_alloc_shim_is_unstable_v2
@@ -201,7 +201,7 @@ fn create_wrapper_function(
             .map(|(i, _)| llvm::get_param(llfn, i as c_uint))
             .collect::<Vec<_>>();
         let ret = bx.call(ty, callee, &args, None);
-        llvm::LLVMSetTailCall(ret, True);
+        llvm::LLVMSetTailCall(ret, TRUE);
         if output.is_some() {
             bx.ret(ret);
         } else {
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 62998003ca114..7c65d667bda88 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -1110,7 +1110,7 @@ fn embed_bitcode(
 
         llvm::set_section(llglobal, bitcode_section_name(cgcx));
         llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
-        llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
+        llvm::LLVMSetGlobalConstant(llglobal, llvm::TRUE);
 
         let llconst = common::bytes_in_context(llcx, &[]);
         let llglobal = llvm::add_global(llmod, common::val_ty(llconst), c"rustc.embedded.cmdline");
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 836d227456c40..37379586d5828 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -35,7 +35,7 @@ use crate::attributes;
 use crate::common::Funclet;
 use crate::context::{CodegenCx, FullCx, GenericCx, SCx};
 use crate::llvm::{
-    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, GEPNoWrapFlags, Metadata, ToLlvmBool, True,
+    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, GEPNoWrapFlags, Metadata, TRUE, ToLlvmBool,
 };
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
@@ -493,8 +493,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let add = llvm::LLVMBuildAdd(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(add).is_some() {
-                llvm::LLVMSetNUW(add, True);
-                llvm::LLVMSetNSW(add, True);
+                llvm::LLVMSetNUW(add, TRUE);
+                llvm::LLVMSetNSW(add, TRUE);
             }
             add
         }
@@ -503,8 +503,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let sub = llvm::LLVMBuildSub(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(sub).is_some() {
-                llvm::LLVMSetNUW(sub, True);
-                llvm::LLVMSetNSW(sub, True);
+                llvm::LLVMSetNUW(sub, TRUE);
+                llvm::LLVMSetNSW(sub, TRUE);
             }
             sub
         }
@@ -513,8 +513,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let mul = llvm::LLVMBuildMul(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(mul).is_some() {
-                llvm::LLVMSetNUW(mul, True);
-                llvm::LLVMSetNSW(mul, True);
+                llvm::LLVMSetNUW(mul, TRUE);
+                llvm::LLVMSetNSW(mul, TRUE);
             }
             mul
         }
@@ -528,7 +528,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             // an instruction, so we need to check before setting the flag.
             // (See also `LLVMBuildNUWNeg` which also needs a check.)
             if llvm::LLVMIsAInstruction(or).is_some() {
-                llvm::LLVMSetIsDisjoint(or, True);
+                llvm::LLVMSetIsDisjoint(or, TRUE);
             }
             or
         }
@@ -629,7 +629,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn volatile_load(&mut self, ty: &'ll Type, ptr: &'ll Value) -> &'ll Value {
         unsafe {
             let load = llvm::LLVMBuildLoad2(self.llbuilder, ty, ptr, UNNAMED);
-            llvm::LLVMSetVolatile(load, llvm::True);
+            llvm::LLVMSetVolatile(load, llvm::TRUE);
             load
         }
     }
@@ -838,7 +838,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 if flags.contains(MemFlags::UNALIGNED) { 1 } else { align.bytes() as c_uint };
             llvm::LLVMSetAlignment(store, align);
             if flags.contains(MemFlags::VOLATILE) {
-                llvm::LLVMSetVolatile(store, llvm::True);
+                llvm::LLVMSetVolatile(store, llvm::TRUE);
             }
             if flags.contains(MemFlags::NONTEMPORAL) {
                 // Make sure that the current target architectures supports "sane" non-temporal
@@ -956,7 +956,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let trunc = self.trunc(val, dest_ty);
         unsafe {
             if llvm::LLVMIsAInstruction(trunc).is_some() {
-                llvm::LLVMSetNUW(trunc, True);
+                llvm::LLVMSetNUW(trunc, TRUE);
             }
         }
         trunc
@@ -968,7 +968,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let trunc = self.trunc(val, dest_ty);
         unsafe {
             if llvm::LLVMIsAInstruction(trunc).is_some() {
-                llvm::LLVMSetNSW(trunc, True);
+                llvm::LLVMSetNSW(trunc, TRUE);
             }
         }
         trunc
@@ -1223,7 +1223,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let ty = self.type_struct(&[self.type_ptr(), self.type_i32()], false);
         let landing_pad = self.landing_pad(ty, pers_fn, 0);
         unsafe {
-            llvm::LLVMSetCleanup(landing_pad, llvm::True);
+            llvm::LLVMSetCleanup(landing_pad, llvm::TRUE);
         }
         (self.extract_value(landing_pad, 0), self.extract_value(landing_pad, 1))
     }
@@ -1319,7 +1319,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 src,
                 AtomicOrdering::from_generic(order),
                 AtomicOrdering::from_generic(failure_order),
-                llvm::False, // SingleThreaded
+                llvm::FALSE, // SingleThreaded
             );
             llvm::LLVMSetWeak(value, weak.to_llvm_bool());
             let val = self.extract_value(value, 0);
@@ -1346,7 +1346,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 dst,
                 src,
                 AtomicOrdering::from_generic(order),
-                llvm::False, // SingleThreaded
+                llvm::FALSE, // SingleThreaded
             )
         };
         if ret_ptr && self.val_ty(res) != self.type_ptr() {
diff --git a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
index e2df3265f6f7d..6ddf53cdc87f0 100644
--- a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
+++ b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
@@ -11,7 +11,7 @@ use crate::builder::{Builder, PlaceRef, UNNAMED};
 use crate::context::SimpleCx;
 use crate::declare::declare_simple_fn;
 use crate::llvm;
-use crate::llvm::{Metadata, True, Type};
+use crate::llvm::{Metadata, TRUE, Type};
 use crate::value::Value;
 
 pub(crate) fn adjust_activity_to_abi<'tcx>(
@@ -293,7 +293,7 @@ pub(crate) fn generate_enzyme_call<'ll, 'tcx>(
     //   ret double %0
     // }
     // ```
-    let enzyme_ty = unsafe { llvm::LLVMFunctionType(ret_ty, ptr::null(), 0, True) };
+    let enzyme_ty = unsafe { llvm::LLVMFunctionType(ret_ty, ptr::null(), 0, TRUE) };
 
     // FIXME(ZuseZ4): the CC/Addr/Vis values are best effort guesses, we should look at tests and
     // think a bit more about what should go here.
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index 1b341c1f6afe3..11b79a7fe68c6 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -20,7 +20,7 @@ use tracing::debug;
 use crate::consts::const_alloc_to_llvm;
 pub(crate) use crate::context::CodegenCx;
 use crate::context::{GenericCx, SCx};
-use crate::llvm::{self, BasicBlock, ConstantInt, False, Metadata, ToLlvmBool, True};
+use crate::llvm::{self, BasicBlock, ConstantInt, FALSE, Metadata, TRUE, ToLlvmBool};
 use crate::type_::Type;
 use crate::value::Value;
 
@@ -158,7 +158,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
             self.type_kind(t) == TypeKind::Integer,
             "only allows integer types in const_int"
         );
-        unsafe { llvm::LLVMConstInt(t, i as u64, True) }
+        unsafe { llvm::LLVMConstInt(t, i as u64, TRUE) }
     }
 
     fn const_u8(&self, i: u8) -> &'ll Value {
@@ -192,7 +192,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
             self.type_kind(t) == TypeKind::Integer,
             "only allows integer types in const_uint"
         );
-        unsafe { llvm::LLVMConstInt(t, i, False) }
+        unsafe { llvm::LLVMConstInt(t, i, FALSE) }
     }
 
     fn const_uint_big(&self, t: &'ll Type, u: u128) -> &'ll Value {
@@ -377,7 +377,7 @@ pub(crate) fn val_ty(v: &Value) -> &Type {
 pub(crate) fn bytes_in_context<'ll>(llcx: &'ll llvm::Context, bytes: &[u8]) -> &'ll Value {
     unsafe {
         let ptr = bytes.as_ptr() as *const c_char;
-        llvm::LLVMConstStringInContext2(llcx, ptr, bytes.len(), True)
+        llvm::LLVMConstStringInContext2(llcx, ptr, bytes.len(), TRUE)
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 4a7de7d2e69e2..4fd6110ac4a11 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -701,7 +701,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn get_const_int(&self, ty: &'ll Type, val: u64) -> &'ll Value {
-        unsafe { llvm::LLVMConstInt(ty, val, llvm::False) }
+        unsafe { llvm::LLVMConstInt(ty, val, llvm::FALSE) }
     }
 
     pub(crate) fn get_const_i64(&self, n: u64) -> &'ll Value {
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 6eb7042da6171..7a6dc008c7b9e 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -72,7 +72,7 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
                 .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
             llvm::set_section(section_var, c".debug_gdb_scripts");
             llvm::set_initializer(section_var, cx.const_bytes(section_contents));
-            llvm::LLVMSetGlobalConstant(section_var, llvm::True);
+            llvm::LLVMSetGlobalConstant(section_var, llvm::TRUE);
             llvm::set_unnamed_address(section_var, llvm::UnnamedAddr::Global);
             llvm::set_linkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
             // This should make sure that the whole section is not larger than
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
index b4d639368b005..1dcf4ff3062a2 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
@@ -38,7 +38,7 @@ pub(crate) fn item_namespace<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'l
             parent_scope,
             namespace_name_string.as_ptr(),
             namespace_name_string.len(),
-            llvm::False, // ExportSymbols (only relevant for C++ anonymous namespaces)
+            llvm::FALSE, // ExportSymbols (only relevant for C++ anonymous namespaces)
         )
     };
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 912e3d6ff2424..fa2802a891fbd 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -11,7 +11,6 @@
 //! the need for an extra cast from `*const u8` on the Rust side.
 
 #![allow(non_camel_case_types)]
-#![allow(non_upper_case_globals)]
 
 use std::fmt::{self, Debug};
 use std::marker::PhantomData;
@@ -42,8 +41,8 @@ pub(crate) struct Bool {
     value: c_int,
 }
 
-pub(crate) const True: Bool = Bool::TRUE;
-pub(crate) const False: Bool = Bool::FALSE;
+pub(crate) const TRUE: Bool = Bool::TRUE;
+pub(crate) const FALSE: Bool = Bool::FALSE;
 
 impl Bool {
     pub(crate) const TRUE: Self = Self { value: 1 };
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index 499771aa12427..9ecaf5f24fe15 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -15,7 +15,7 @@ use rustc_target::callconv::{CastTarget, FnAbi};
 use crate::abi::{FnAbiLlvmExt, LlvmType};
 use crate::context::{CodegenCx, GenericCx, SCx};
 pub(crate) use crate::llvm::Type;
-use crate::llvm::{False, Metadata, ToLlvmBool, True};
+use crate::llvm::{FALSE, Metadata, TRUE, ToLlvmBool};
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use crate::{common, llvm};
@@ -141,7 +141,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn type_variadic_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
-        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, True) }
+        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, TRUE) }
     }
 
     pub(crate) fn type_i1(&self) -> &'ll Type {
@@ -202,7 +202,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> BaseTypeCodegenMethods for GenericCx<'ll, CX> {
     }
 
     fn type_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
-        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, False) }
+        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, FALSE) }
     }
 
     fn type_kind(&self, ty: &'ll Type) -> TypeKind {

From b1be775dd67b2b9a871f6e7076d7d2f2c7f1c8ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Miku=C5=82a?= <oss@mateuszmikula.dev>
Date: Sat, 23 Aug 2025 18:26:11 +0200
Subject: [PATCH 10/10] raw-dylib-elf: set correct `DT_VERDEFNUM`

Previously it indicated a single version, regardless of their count.
Observed in: https://github.com/davidlattimore/wild/pull/1041
---
 .../rustc_codegen_ssa/src/back/link/raw_dylib.rs    | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs b/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
index b9e0c95736331..509168b2cd283 100644
--- a/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
@@ -307,11 +307,14 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
     stub.reserve_section_headers();
     stub.reserve_dynsym();
     stub.reserve_dynstr();
+    let verdef_count = 1 + vers.len();
+    let mut dynamic_entries = 2; // DT_SONAME, DT_NULL
     if !vers.is_empty() {
         stub.reserve_gnu_versym();
-        stub.reserve_gnu_verdef(1 + vers.len(), 1 + vers.len());
+        stub.reserve_gnu_verdef(verdef_count, verdef_count);
+        dynamic_entries += 1; // DT_VERDEFNUM
     }
-    stub.reserve_dynamic(2); // DT_SONAME, DT_NULL
+    stub.reserve_dynamic(dynamic_entries);
 
     // First write the ELF header with the arch information.
     let e_machine = match (arch, sub_arch) {
@@ -443,9 +446,13 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
     // .dynamic
     // the DT_SONAME will be used by the linker to populate DT_NEEDED
     // which the loader uses to find the library.
-    // DT_NULL terminates the .dynamic table.
     stub.write_align_dynamic();
     stub.write_dynamic_string(elf::DT_SONAME, soname);
+    // LSB section "2.7. Symbol Versioning" requires `DT_VERDEFNUM` to be reliable.
+    if verdef_count > 1 {
+        stub.write_dynamic(elf::DT_VERDEFNUM, verdef_count as u64);
+    }
+    // DT_NULL terminates the .dynamic table.
     stub.write_dynamic(elf::DT_NULL, 0);
 
     stub_buf