Auto merge of #155863 - jhpratt:rollup-6wWyVPM, r=jhpratt

Rollup of 3 pull requests

Successful merges:

 - rust-lang/rust#155772 (Check closure's constness validity in the constness query)
 - rust-lang/rust#155833 (CI: rfl: move job forward to Linux v7.0)
 - rust-lang/rust#155839 (Remove unnecessary requires_lto: false for eBPF)

compiler/rustc_ast_lowering/src/expr.rs

@@ -1052,7 +1052,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         binder: &ClosureBinder,
         capture_clause: CaptureBy,
         closure_id: NodeId,
-        mut constness: Const,
+        constness: Const,
         movability: Movability,
         decl: &FnDecl,
         body: &Expr,
@@ -1062,18 +1062,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let closure_def_id = self.local_def_id(closure_id);
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
-        if let Const::Yes(span) = constness {
-            if !self.is_in_const_context {
-                self.dcx().span_err(span, "cannot use `const` closures outside of const contexts");
-                constness = Const::No;
-            }
-        }
-
         let (body_id, closure_kind) = self.with_new_scopes(fn_decl_span, move |this| {
             let mut coroutine_kind = find_attr!(attrs, Coroutine(_) => hir::CoroutineKind::Coroutine(Movability::Movable));
 
             // FIXME(contracts): Support contracts on closures?
-            let body_id = this.lower_fn_body(decl, None, constness, |this| {
+            let body_id = this.lower_fn_body(decl, None, |this| {
                 this.coroutine_kind = coroutine_kind;
                 let e = this.lower_expr_mut(body);
                 coroutine_kind = this.coroutine_kind;

compiler/rustc_ast_lowering/src/item.rs

@@ -1,5 +1,3 @@
-use std::mem;
-
 use rustc_abi::ExternAbi;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
@@ -378,7 +376,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         body.as_deref(),
                         attrs,
                         contract.as_deref(),
-                        header.constness,
                     );
 
                     let itctx = ImplTraitContext::Universal;
@@ -1068,7 +1065,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     Some(body),
                     attrs,
                     contract.as_deref(),
-                    sig.header.constness,
                 );
                 let (generics, sig) = self.lower_method_sig(
                     generics,
@@ -1262,7 +1258,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     body.as_deref(),
                     attrs,
                     contract.as_deref(),
-                    sig.header.constness,
                 );
                 let (generics, sig) = self.lower_method_sig(
                     generics,
@@ -1391,13 +1386,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
     ) -> hir::BodyId {
         let prev_coroutine_kind = self.coroutine_kind.take();
-        let prev_is_in_const_context = mem::take(&mut self.is_in_const_context);
         let task_context = self.task_context.take();
         let (parameters, result) = f(self);
         let body_id = self.record_body(parameters, result);
         self.task_context = task_context;
         self.coroutine_kind = prev_coroutine_kind;
-        self.is_in_const_context = prev_is_in_const_context;
         body_id
     }
 
@@ -1416,13 +1409,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         decl: &FnDecl,
         contract: Option<&FnContract>,
-        constness: Const,
         body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
     ) -> hir::BodyId {
         self.lower_body(|this| {
-            if let Const::Yes(_) = constness {
-                this.is_in_const_context = true;
-            }
             let params =
                 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x)));
 
@@ -1440,9 +1429,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         decl: &FnDecl,
         body: &Block,
         contract: Option<&FnContract>,
-        constness: Const,
     ) -> hir::BodyId {
-        self.lower_fn_body(decl, contract, constness, |this| this.lower_block_expr(body))
+        self.lower_fn_body(decl, contract, |this| this.lower_block_expr(body))
     }
 
     pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
@@ -1450,10 +1438,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             (
                 &[],
                 match expr {
-                    Some(expr) => {
-                        this.is_in_const_context = true;
-                        this.lower_expr_mut(expr)
-                    }
+                    Some(expr) => this.lower_expr_mut(expr),
                     None => this.expr_err(span, this.dcx().span_delayed_bug(span, "no block")),
                 },
             )
@@ -1472,13 +1457,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         body: Option<&Block>,
         attrs: &'hir [hir::Attribute],
         contract: Option<&FnContract>,
-        constness: Const,
     ) -> hir::BodyId {
         let Some(body) = body else {
             // Functions without a body are an error, except if this is an intrinsic. For those we
             // create a fake body so that the entire rest of the compiler doesn't have to deal with
             // this as a special case.
-            return self.lower_fn_body(decl, contract, constness, |this| {
+            return self.lower_fn_body(decl, contract, |this| {
                 if find_attr!(attrs, RustcIntrinsic) || this.tcx.is_sdylib_interface_build() {
                     let span = this.lower_span(span);
                     let empty_block = hir::Block {
@@ -1503,7 +1487,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
         let Some(coroutine_kind) = coroutine_kind else {
             // Typical case: not a coroutine.
-            return self.lower_fn_body_block(decl, body, contract, constness);
+            return self.lower_fn_body_block(decl, body, contract);
         };
         // FIXME(contracts): Support contracts on async fn.
         self.lower_body(|this| {

compiler/rustc_ast_lowering/src/lib.rs

@@ -124,7 +124,6 @@ struct LoweringContext<'a, 'hir> {
     loop_scope: Option<HirId>,
     is_in_loop_condition: bool,
     is_in_dyn_type: bool,
-    is_in_const_context: bool,
 
     current_hir_id_owner: hir::OwnerId,
     item_local_id_counter: hir::ItemLocalId,
@@ -193,7 +192,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             loop_scope: None,
             is_in_loop_condition: false,
             is_in_dyn_type: false,
-            is_in_const_context: false,
             coroutine_kind: None,
             task_context: None,
             current_item: None,

compiler/rustc_attr_parsing/src/attributes/diagnostic/mod.rs

@@ -236,9 +236,11 @@ fn parse_directive_items<'p, S: Stage>(
         }}
 
         macro or_malformed($($code:tt)*) {{
-            let Some(ret) = (||{
-                Some($($code)*)
-            })() else {
+            let Some(ret) = (
+                try {
+                    $($code)*
+                }
+            ) else {
                 malformed!()
             };
             ret

compiler/rustc_attr_parsing/src/context.rs

@@ -84,8 +84,7 @@ pub(super) struct GroupTypeInnerAccept<S: Stage> {
 
 pub(crate) type AcceptFn<S> =
     Box<dyn for<'sess, 'a> Fn(&mut AcceptContext<'_, 'sess, S>, &ArgParser) + Send + Sync>;
-pub(crate) type FinalizeFn<S> =
-    Box<dyn Send + Sync + Fn(&mut FinalizeContext<'_, '_, S>) -> Option<AttributeKind>>;
+pub(crate) type FinalizeFn<S> = fn(&mut FinalizeContext<'_, '_, S>) -> Option<AttributeKind>;
 
 macro_rules! attribute_parsers {
     (
@@ -131,10 +130,10 @@ macro_rules! attribute_parsers {
                                     }),
                                     safety: <$names as crate::attributes::AttributeParser<$stage>>::SAFETY,
                                     allowed_targets: <$names as crate::attributes::AttributeParser<$stage>>::ALLOWED_TARGETS,
-                                    finalizer: Box::new(|cx| {
+                                    finalizer: |cx| {
                                         let state = STATE_OBJECT.take();
                                         state.finalize(cx)
-                                    })
+                                    }
                                 });
                             }
                             Entry::Occupied(_) => panic!("Attribute {path:?} has multiple accepters"),

compiler/rustc_attr_parsing/src/interface.rs

@@ -297,7 +297,7 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
         let mut attr_paths: Vec<RefPathParser<'_>> = Vec::new();
         let mut early_parsed_state = EarlyParsedState::default();
 
-        let mut finalizers: Vec<&FinalizeFn<S>> = Vec::with_capacity(attrs.len());
+        let mut finalizers: Vec<FinalizeFn<S>> = Vec::with_capacity(attrs.len());
 
         for attr in attrs {
             // If we're only looking for a single attribute, skip all the ones we don't care about.
@@ -413,7 +413,7 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                         };
 
                         (accept.accept_fn)(&mut cx, &args);
-                        finalizers.push(&accept.finalizer);
+                        finalizers.push(accept.finalizer);
 
                         if !matches!(cx.stage.should_emit(), ShouldEmit::Nothing) {
                             Self::check_target(&accept.allowed_targets, target, &mut cx);

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -153,7 +153,7 @@ impl ModuleConfig {
             // `#![no_builtins]` is assumed to not participate in LTO and
             // instead goes on to generate object code.
             EmitObj::Bitcode
-        } else if need_bitcode_in_object(tcx) {
+        } else if need_bitcode_in_object(tcx) || sess.target.requires_lto {
             EmitObj::ObjectCode(BitcodeSection::Full)
         } else {
             EmitObj::ObjectCode(BitcodeSection::None)

compiler/rustc_const_eval/src/const_eval/fn_queries.rs

@@ -16,7 +16,13 @@ fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Constness {
             // Foreign functions cannot be evaluated at compile-time.
             Constness::NotConst
         }
-        Node::Expr(e) if let ExprKind::Closure(c) = e.kind => c.constness,
+        Node::Expr(e) if let ExprKind::Closure(c) = e.kind => {
+            if let Constness::Const = c.constness && tcx.hir_body_const_context(tcx.local_parent(def_id)).is_none() {
+                tcx.dcx().span_err(tcx.def_span(def_id), "cannot use `const` closures outside of const contexts");
+                return Constness::NotConst;
+            }
+            c.constness
+        },
         // FIXME(fee1-dead): extract this one out and rename this query to `fn_constness` so we don't need `is_const_fn` anymore.
         Node::Item(i) if let ItemKind::Impl(impl_) = i.kind => impl_.constness,
         Node::Item(Item { kind: ItemKind::Fn { sig, .. }, .. }) => sig.header.constness,

compiler/rustc_hir_typeck/src/coercion.rs

@@ -2009,6 +2009,9 @@ impl<'tcx> CoerceMany<'tcx> {
             // note in this case, since it would be incorrect.
             && let Some(fn_sig) = fcx.body_fn_sig()
             && fn_sig.output().is_ty_var()
+            && fcx.ret_coercion.as_ref().is_some_and(|ret_coercion| {
+                fcx.resolve_vars_if_possible(ret_coercion.borrow().expected_ty()) == expected
+            })
         {
             err.span_note(sp, format!("return type inferred to be `{expected}` here"));
         }

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -7,6 +7,7 @@ use rustc_ast::util::parser::ExprPrecedence;
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::{Applicability, Diag, MultiSpan, listify, msg};
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
+use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
     self as hir, Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind,
@@ -26,13 +27,14 @@ use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::{ExpnKind, Ident, MacroKind, Span, Spanned, Symbol, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::DefIdOrName;
+use rustc_trait_selection::error_reporting::traits::suggestions::ReturnsVisitor;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
 use tracing::{debug, instrument};
 
 use super::FnCtxt;
-use crate::errors;
+use crate::errors::{self, SuggestBoxingForReturnImplTrait};
 use crate::fn_ctxt::rustc_span::BytePos;
 use crate::method::probe;
 use crate::method::probe::{IsSuggestion, Mode, ProbeScope};
@@ -963,6 +965,40 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         );
                     }
 
+                    let trait_def_id = trait_ref.trait_ref.path.res.def_id();
+                    if self.tcx.is_dyn_compatible(trait_def_id) {
+                        err.subdiagnostic(SuggestBoxingForReturnImplTrait::ChangeReturnType {
+                            start_sp: hir_ty.span.with_hi(hir_ty.span.lo() + BytePos(4)),
+                            end_sp: hir_ty.span.shrink_to_hi(),
+                        });
+
+                        let body = self.tcx.hir_body_owned_by(fn_id);
+                        let mut visitor = ReturnsVisitor::default();
+                        visitor.visit_body(&body);
+
+                        if !visitor.returns.is_empty() {
+                            let starts: Vec<Span> = visitor
+                                .returns
+                                .iter()
+                                .filter(|expr| expr.span.can_be_used_for_suggestions())
+                                .map(|expr| expr.span.shrink_to_lo())
+                                .collect();
+                            let ends: Vec<Span> = visitor
+                                .returns
+                                .iter()
+                                .filter(|expr| expr.span.can_be_used_for_suggestions())
+                                .map(|expr| expr.span.shrink_to_hi())
+                                .collect();
+
+                            if !starts.is_empty() {
+                                err.subdiagnostic(SuggestBoxingForReturnImplTrait::BoxReturnExpr {
+                                    starts,
+                                    ends,
+                                });
+                            }
+                        }
+                    }
+
                     self.try_suggest_return_impl_trait(err, expected, found, fn_id);
                     self.try_note_caller_chooses_ty_for_ty_param(err, expected, found);
                     return true;

compiler/rustc_middle/src/error.rs

@@ -143,7 +143,7 @@ pub(crate) struct Reentrant;
 #[note(
     "an ideal reproduction consists of the code before and some patch that then triggers the bug when applied and compiled again"
 )]
-#[note("as a workaround, you can run {$run_cmd} to allow your project to compile")]
+#[note("as a workaround, you can {$run_cmd} to allow your project to compile")]
 pub(crate) struct IncrementCompilation {
     pub run_cmd: String,
     pub dep_node: String,

compiler/rustc_middle/src/hir/map.rs

@@ -319,17 +319,7 @@ impl<'tcx> TyCtxt<'tcx> {
             BodyOwnerKind::Fn if self.is_constructor(def_id) => return None,
             // Const closures use their parent's const context
             BodyOwnerKind::Closure if self.is_const_fn(def_id) => {
-                return Some(
-                    self.hir_body_const_context(self.local_parent(local_def_id)).unwrap_or_else(
-                        || {
-                            assert!(
-                                self.dcx().has_errors().is_some(),
-                                "`const` closure with no enclosing const context",
-                            );
-                            ConstContext::ConstFn
-                        },
-                    ),
-                );
+                return self.hir_body_const_context(self.local_parent(local_def_id));
             }
             BodyOwnerKind::Fn if self.is_const_fn(def_id) => ConstContext::ConstFn,
             BodyOwnerKind::Fn | BodyOwnerKind::Closure | BodyOwnerKind::GlobalAsm => return None,

compiler/rustc_middle/src/ty/context.rs

@@ -2416,10 +2416,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// to build a full `Place` it's just a convenient way to grab a projection and modify it in
     /// flight.
     pub fn mk_place_elem(self, place: Place<'tcx>, elem: PlaceElem<'tcx>) -> Place<'tcx> {
-        let mut projection = place.projection.to_vec();
-        projection.push(elem);
-
-        Place { local: place.local, projection: self.mk_place_elems(&projection) }
+        Place {
+            local: place.local,
+            projection: self.mk_place_elems_from_iter(place.projection.iter().chain([elem])),
+        }
     }
 
     pub fn mk_poly_existential_predicates(

compiler/rustc_middle/src/verify_ich.rs

@@ -1,6 +1,8 @@
 use std::cell::Cell;
 
 use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_session::utils::was_invoked_from_cargo;
 use tracing::instrument;
 
 use crate::dep_graph::{DepGraphData, SerializedDepNodeIndex};
@@ -66,10 +68,10 @@ fn incremental_verify_ich_failed<'tcx>(
     if old_in_panic {
         tcx.dcx().emit_err(crate::error::Reentrant);
     } else {
-        let run_cmd = if let Some(crate_name) = &tcx.sess.opts.crate_name {
-            format!("`cargo clean -p {crate_name}` or `cargo clean`")
+        let run_cmd = if was_invoked_from_cargo() {
+            format!("run `cargo clean -p {}` or `cargo clean`", tcx.crate_name(LOCAL_CRATE))
         } else {
-            "`cargo clean`".to_string()
+            "clean your build cache".to_owned()
         };
 
         let dep_node = tcx.dep_graph.data().unwrap().prev_node_of(prev_index);

compiler/rustc_session/src/config.rs

@@ -1205,6 +1205,7 @@ impl OutputFilenames {
     }
 
     pub fn interface_path(&self) -> PathBuf {
+        debug!("using crate_name={} for interface_path", self.crate_stem);
         self.out_directory.join(format!("lib{}.rs", self.crate_stem))
     }
 
@@ -1214,6 +1215,7 @@ impl OutputFilenames {
         let extension = flavor.extension();
         match flavor {
             OutputType::Metadata => {
+                debug!("using crate_name={} for {extension}", self.crate_stem);
                 self.out_directory.join(format!("lib{}.{}", self.crate_stem, extension))
             }
             _ => self.with_directory_and_extension(&self.out_directory, extension),
@@ -1288,6 +1290,7 @@ impl OutputFilenames {
     }
 
     pub fn with_directory_and_extension(&self, directory: &Path, extension: &str) -> PathBuf {
+        debug!("using filestem={} for {extension}", self.filestem);
         let mut path = directory.join(&self.filestem);
         path.set_extension(extension);
         path

compiler/rustc_target/src/spec/base/bpf.rs

@@ -18,7 +18,6 @@ pub(crate) fn opts(endian: Endian) -> TargetOptions {
         //   BPF_PROG_LOAD and not all BPF libraries do that yet
         merge_functions: MergeFunctions::Disabled,
         obj_is_bitcode: true,
-        requires_lto: false,
         singlethread: true,
         // When targeting the `v3` cpu in llvm, 32-bit atomics are also supported.
         // But making this value change based on the target cpu can be mostly confusing

library/alloc/src/rc.rs

@@ -2615,7 +2615,7 @@ impl<T: ?Sized + PartialEq, A: Allocator> RcEqIdent<T, A> for Rc<T, A> {
 #[rustc_unsafe_specialization_marker]
 pub(crate) trait MarkerEq: PartialEq<Self> {}
 
-impl<T: Eq> MarkerEq for T {}
+impl<T: ?Sized + Eq> MarkerEq for T {}
 
 /// We're doing this specialization here, and not as a more general optimization on `&T`, because it
 /// would otherwise add a cost to all equality checks on refs. We assume that `Rc`s are used to
@@ -2628,12 +2628,12 @@ impl<T: Eq> MarkerEq for T {}
 impl<T: ?Sized + MarkerEq, A: Allocator> RcEqIdent<T, A> for Rc<T, A> {
     #[inline]
     fn eq(&self, other: &Rc<T, A>) -> bool {
-        Rc::ptr_eq(self, other) || **self == **other
+        ptr::eq(self.ptr.as_ptr(), other.ptr.as_ptr()) || **self == **other
     }
 
     #[inline]
     fn ne(&self, other: &Rc<T, A>) -> bool {
-        !Rc::ptr_eq(self, other) && **self != **other
+        !ptr::eq(self.ptr.as_ptr(), other.ptr.as_ptr()) && **self != **other
     }
 }
 

library/alloc/src/str.rs

@@ -126,6 +126,26 @@ macro_rules! copy_slice_and_advance {
 // the bounds for String-join are S: Borrow<str> and for Vec-join Borrow<[T]>
 // [T] and str both impl AsRef<[T]> for some T
 // => s.borrow().as_ref() and we always have slices
+//
+// # Safety notes
+//
+// `Borrow` is a safe trait, and implementations are not required
+// to be deterministic. An inconsistent `Borrow` implementation could return slices
+// of different lengths on consecutive calls (e.g. by using interior mutability).
+//
+// This implementation calls `borrow()` multiple times:
+// 1. To calculate `reserved_len`, all elements are borrowed once.
+// 2. The first element is borrowed again when copied via `extend_from_slice`.
+// 3. Subsequent elements are borrowed a second time when building the mapped iterator.
+//
+// Risks and Mitigations:
+// - If the first element GROWS on the second borrow, the length subtraction underflows.
+//   We mitigate this by doing a `checked_sub` to panic rather than allowing an underflow
+//   that fabricates a huge destination slice.
+// - If elements 2..N GROW on their second borrow, the target slice bounds set by `checked_sub`
+//   means that `split_at_mut` inside `copy_slice_and_advance!` will correctly panic.
+// - If elements SHRINK on their second borrow, the spare space is never written, and the final
+//   length set via `set_len` masks trailing uninitialized bytes.
 #[cfg(not(no_global_oom_handling))]
 fn join_generic_copy<B, T, S>(slice: &[S], sep: &[T]) -> Vec<T>
 where
@@ -161,19 +181,21 @@ where
 
     unsafe {
         let pos = result.len();
-        let target = result.spare_capacity_mut().get_unchecked_mut(..reserved_len - pos);
+        let target_len = reserved_len.checked_sub(pos).expect("inconsistent Borrow implementation");
+        let target = result.spare_capacity_mut().get_unchecked_mut(..target_len);
 
         // Convert the separator and slices to slices of MaybeUninit
-        // to simplify implementation in specialize_for_lengths
+        // to simplify implementation in specialize_for_lengths.
         let sep_uninit = core::slice::from_raw_parts(sep.as_ptr().cast(), sep.len());
         let iter_uninit = iter.map(|it| {
             let it = it.borrow().as_ref();
             core::slice::from_raw_parts(it.as_ptr().cast(), it.len())
         });
 
-        // copy separator and slices over without bounds checks
-        // generate loops with hardcoded offsets for small separators
-        // massive improvements possible (~ x2)
+        // copy separator and slices over without bounds checks.
+        // `specialize_for_lengths!` internally calls `s.borrow()`, but because it uses
+        // the bounds-checked `split_at_mut` any misbehaving implementation
+        // will not write out of bounds.
         let remain = specialize_for_lengths!(sep_uninit, target, iter_uninit; 0, 1, 2, 3, 4);
 
         // A weird borrow implementation may return different

library/alloc/src/sync.rs

@@ -3549,12 +3549,12 @@ impl<T: ?Sized + PartialEq, A: Allocator> ArcEqIdent<T, A> for Arc<T, A> {
 impl<T: ?Sized + crate::rc::MarkerEq, A: Allocator> ArcEqIdent<T, A> for Arc<T, A> {
     #[inline]
     fn eq(&self, other: &Arc<T, A>) -> bool {
-        Arc::ptr_eq(self, other) || **self == **other
+        ptr::eq(self.ptr.as_ptr(), other.ptr.as_ptr()) || **self == **other
     }
 
     #[inline]
     fn ne(&self, other: &Arc<T, A>) -> bool {
-        !Arc::ptr_eq(self, other) && **self != **other
+        !ptr::eq(self.ptr.as_ptr(), other.ptr.as_ptr()) && **self != **other
     }
 }
 

library/alloctests/tests/arc.rs

@@ -86,6 +86,34 @@ fn eq() {
     assert_eq!(*x.0.borrow(), 0);
 }
 
+#[test]
+fn eq_unsized() {
+    #[derive(Eq)]
+    struct TestEq<T: ?Sized>(RefCell<usize>, T);
+    impl<T: ?Sized> PartialEq for TestEq<T> {
+        fn eq(&self, other: &TestEq<T>) -> bool {
+            *self.0.borrow_mut() += 1;
+            *other.0.borrow_mut() += 1;
+            true
+        }
+    }
+    let x = Arc::<TestEq<[u8; 3]>>::new(TestEq(RefCell::new(0), [0, 1, 2])) as Arc<TestEq<[u8]>>;
+    assert!(x == x);
+    assert!(!(x != x));
+    assert_eq!(*x.0.borrow(), 0);
+}
+
+#[test]
+fn eq_unsized_slice() {
+    let a: Arc<[()]> = Arc::new([(); 3]);
+    let ptr: *const () = Arc::into_raw(a.clone()).cast();
+    let b: Arc<[()]> = unsafe { Arc::from_raw(core::ptr::slice_from_raw_parts(ptr, 42)) };
+    assert!(a == a);
+    assert!(!(a != a));
+    assert!(a != b);
+    assert!(!(a == b));
+}
+
 // The test code below is identical to that in `rc.rs`.
 // For better maintainability we therefore define this type alias.
 type Rc<T, A = std::alloc::Global> = Arc<T, A>;

library/alloctests/tests/rc.rs

@@ -87,6 +87,34 @@ fn eq() {
     assert_eq!(*x.0.borrow(), 0);
 }
 
+#[test]
+fn eq_unsized() {
+    #[derive(Eq)]
+    struct TestEq<T: ?Sized>(RefCell<usize>, T);
+    impl<T: ?Sized> PartialEq for TestEq<T> {
+        fn eq(&self, other: &TestEq<T>) -> bool {
+            *self.0.borrow_mut() += 1;
+            *other.0.borrow_mut() += 1;
+            true
+        }
+    }
+    let x = Rc::<TestEq<[u8; 3]>>::new(TestEq(RefCell::new(0), [0, 1, 2])) as Rc<TestEq<[u8]>>;
+    assert!(x == x);
+    assert!(!(x != x));
+    assert_eq!(*x.0.borrow(), 0);
+}
+
+#[test]
+fn eq_unsized_slice() {
+    let a: Rc<[()]> = Rc::new([(); 3]);
+    let ptr: *const () = Rc::into_raw(a.clone()).cast();
+    let b: Rc<[()]> = unsafe { Rc::from_raw(core::ptr::slice_from_raw_parts(ptr, 42)) };
+    assert!(a == a);
+    assert!(!(a != a));
+    assert!(a != b);
+    assert!(!(a == b));
+}
+
 const SHARED_ITER_MAX: u16 = 100;
 
 fn assert_trusted_len<I: TrustedLen>(_: &I) {}

library/alloctests/tests/str.rs

@@ -194,6 +194,25 @@ fn test_join_issue_80335() {
     test_join!("0-0-0", arr, "-");
 }
 
+#[test]
+#[should_panic(expected = "inconsistent Borrow implementation")]
+fn test_join_inconsistent_borrow() {
+    use std::borrow::Borrow;
+    use std::cell::Cell;
+
+    struct E(Cell<u32>);
+
+    impl Borrow<str> for E {
+        fn borrow(&self) -> &str {
+            let count = self.0.get();
+            self.0.set(count + 1);
+            if count == 0 { "" } else { "longer string" }
+        }
+    }
+
+    let _s = [E(Cell::new(0)), E(Cell::new(0))].join("");
+}
+
 #[test]
 #[cfg_attr(miri, ignore)] // Miri is too slow
 fn test_unsafe_slice() {

library/core/src/field.rs

@@ -1,11 +1,12 @@
 //! Field Reflection
 
+use crate::fmt;
+use crate::hash::{Hash, Hasher};
 use crate::marker::PhantomData;
 
 /// Field Representing Type
 #[unstable(feature = "field_representing_type_raw", issue = "none")]
 #[lang = "field_representing_type"]
-#[expect(missing_debug_implementations)]
 #[fundamental]
 pub struct FieldRepresentingType<T: ?Sized, const VARIANT: u32, const FIELD: u32> {
     // We want this type to be invariant over `T`, because otherwise `field_of!(Struct<'short>,
@@ -14,16 +15,50 @@ pub struct FieldRepresentingType<T: ?Sized, const VARIANT: u32, const FIELD: u32
     _phantom: PhantomData<fn(T) -> T>,
 }
 
-// SAFETY: `FieldRepresentingType` doesn't contain any `T`
-unsafe impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Send
-    for FieldRepresentingType<T, VARIANT, FIELD>
-{
-}
-
-// SAFETY: `FieldRepresentingType` doesn't contain any `T`
-unsafe impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Sync
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> fmt::Debug
     for FieldRepresentingType<T, VARIANT, FIELD>
 {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        enum Member {
+            Name(&'static str),
+            Index(u32),
+        }
+        impl fmt::Display for Member {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                match self {
+                    Self::Name(name) => fmt::Display::fmt(name, f),
+                    Self::Index(idx) => fmt::Display::fmt(idx, f),
+                }
+            }
+        }
+        let (variant, field) = const {
+            use crate::mem::type_info::{Type, TypeKind};
+            match Type::of::<T>().kind {
+                TypeKind::Struct(struct_) => {
+                    (None, Member::Name(struct_.fields[FIELD as usize].name))
+                }
+                TypeKind::Tuple(_) => (None, Member::Index(FIELD)),
+                TypeKind::Enum(enum_) => {
+                    let variant = &enum_.variants[VARIANT as usize];
+                    (Some(variant.name), Member::Name(variant.fields[FIELD as usize].name))
+                }
+                TypeKind::Union(union) => (None, Member::Name(union.fields[FIELD as usize].name)),
+                _ => unreachable!(),
+            }
+        };
+        let type_name = const { crate::any::type_name::<T>() };
+        match variant {
+            Some(variant) => write!(f, "field_of!({type_name}, {variant}.{field})"),
+            None => write!(f, "field_of!({type_name}, {field})"),
+        }
+        // NOTE: if there are changes in the reflection work and the above no
+        // longer compiles, then the following debug impl could also work in
+        // the meantime:
+        // ```rust
+        // let type_name = const { type_name::<T>() };
+        // write!(f, "field_of!({type_name}, {VARIANT}.{FIELD})")
+        // ```
+    }
 }
 
 impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Copy
@@ -39,6 +74,51 @@ impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Clone
     }
 }
 
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Default
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+    fn default() -> Self {
+        Self { _phantom: PhantomData::default() }
+    }
+}
+
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Hash
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self._phantom.hash(state);
+    }
+}
+
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> PartialEq
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+    fn eq(&self, other: &Self) -> bool {
+        self._phantom == other._phantom
+    }
+}
+
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Eq
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+}
+
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> PartialOrd
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+    fn partial_cmp(&self, other: &Self) -> Option<crate::cmp::Ordering> {
+        self._phantom.partial_cmp(&other._phantom)
+    }
+}
+
+impl<T: ?Sized, const VARIANT: u32, const FIELD: u32> Ord
+    for FieldRepresentingType<T, VARIANT, FIELD>
+{
+    fn cmp(&self, other: &Self) -> crate::cmp::Ordering {
+        self._phantom.cmp(&other._phantom)
+    }
+}
+
 /// Expands to the field representing type of the given field.
 ///
 /// The container type may be a tuple, `struct`, `union` or `enum`. In the case of an enum, the

library/std/src/io/mod.rs

@@ -3098,9 +3098,7 @@ impl<T: Read> Read for Take<T> {
             let is_init = buf.is_init();
 
             // SAFETY: no uninit data is written to ibuf
-            let ibuf = unsafe { &mut buf.as_mut()[..limit] };
-
-            let mut sliced_buf: BorrowedBuf<'_> = ibuf.into();
+            let mut sliced_buf = BorrowedBuf::from(unsafe { &mut buf.as_mut()[..limit] });
 
             if is_init {
                 // SAFETY: `sliced_buf` is a subslice of `buf`, so if `buf` was initialized then
@@ -3108,22 +3106,23 @@ impl<T: Read> Read for Take<T> {
                 unsafe { sliced_buf.set_init() };
             }
 
-            let mut cursor = sliced_buf.unfilled();
-            let result = self.inner.read_buf(cursor.reborrow());
+            let result = self.inner.read_buf(sliced_buf.unfilled());
 
-            let should_init = cursor.is_init();
+            let did_init_up_to_limit = sliced_buf.is_init();
             let filled = sliced_buf.len();
 
-            // cursor / sliced_buf / ibuf must drop here
+            // sliced_buf must drop here
 
             // Avoid accidentally quadratic behaviour by initializing the whole
             // cursor if only part of it was initialized.
-            if should_init {
-                // SAFETY: no uninit data is written
-                let uninit = unsafe { &mut buf.as_mut()[limit..] };
-                uninit.write_filled(0);
-                // SAFETY: all bytes that were not initialized by `T::read_buf`
-                // have just been written to.
+            if did_init_up_to_limit && !is_init {
+                // SAFETY: No uninit data will be written.
+                let unfilled_before_advance = unsafe { buf.as_mut() };
+
+                unfilled_before_advance[limit..].write_filled(0);
+
+                // SAFETY: `unfilled_before_advance[..limit]` was initialized by `T::read_buf`, and
+                // `unfilled_before_advance[limit..]` was just initialized.
                 unsafe { buf.set_init() };
             }
 

library/std/src/sys/process/uefi.rs

@@ -5,7 +5,7 @@ use crate::collections::BTreeMap;
 pub use crate::ffi::OsString as EnvKey;
 use crate::ffi::{OsStr, OsString};
 use crate::num::{NonZero, NonZeroI32};
-use crate::path::Path;
+use crate::path::{Path, PathBuf};
 use crate::process::StdioPipes;
 use crate::sys::fs::File;
 use crate::sys::io::error_string;
@@ -138,7 +138,9 @@ impl Command {
 }
 
 pub fn output(command: &mut Command) -> io::Result<(ExitStatus, Vec<u8>, Vec<u8>)> {
-    let mut cmd = uefi_command_internal::Image::load_image(&command.prog)?;
+    let prog_path = resolve_program(&command.prog)
+        .ok_or(io::const_error!(io::ErrorKind::NotFound, "could not find the program."))?;
+    let mut cmd = uefi_command_internal::Image::load_image(prog_path.as_os_str())?;
 
     // UEFI adds the bin name by default
     if !command.args.is_empty() {
@@ -366,6 +368,36 @@ pub fn read_output(
     match out.diverge() {}
 }
 
+// Search for programs similar to UEFI Shell defined in Section 3.6.1. It follows the following flow:
+// 1. If program is already absolute path, just check if it exists.
+// 2. For non-absolute path, search relative to current directory.
+// 3. Search the path list sequentially.
+//
+// [UEFI Shell Specification](https://uefi.org/sites/default/files/resources/UEFI_Shell_2_2.pdf).
+fn resolve_program<S: AsRef<OsStr> + ?Sized>(prog: &S) -> Option<PathBuf> {
+    let absolute_prog_path = crate::path::absolute(prog.as_ref()).ok()?;
+
+    match crate::fs::exists(&absolute_prog_path) {
+        Ok(true) => return Some(absolute_prog_path),
+        // If program path was already absolute and is not found, then stop.
+        Ok(false) if Path::new(prog.as_ref()).is_absolute() => return None,
+        _ => {}
+    }
+
+    // Search for the program in path.
+    if let Ok(path_var) = crate::env::var("path") {
+        for p in crate::env::split_paths(&path_var) {
+            let temp = p.join(prog.as_ref());
+
+            if let Ok(true) = crate::fs::exists(&temp) {
+                return Some(temp);
+            }
+        }
+    }
+
+    None
+}
+
 #[allow(dead_code)]
 mod uefi_command_internal {
     use r_efi::protocols::{loaded_image, simple_text_input, simple_text_output};

src/ci/docker/scripts/rfl-build.sh

@@ -2,9 +2,7 @@
 
 set -euo pipefail
 
-# https://github.com/rust-lang/rust/pull/151534
-# https://github.com/rust-lang/rust/pull/149389
-LINUX_VERSION=167ea5357eb7c3a39200627a36dfbfe249576192
+LINUX_VERSION=v7.0
 
 # Build rustc, rustdoc, cargo, clippy-driver and rustfmt
 ../x.py build --stage 2 library rustdoc clippy rustfmt

src/doc/rustc/src/platform-support/amdgcn-amd-amdhsa.md

@@ -59,11 +59,6 @@ Build the library as `cdylib`:
 # Cargo.toml
 [lib]
 crate-type = ["cdylib"]
-
-[profile.dev]
-lto = true # LTO must be explicitly enabled for now
-[profile.release]
-lto = true
 ```
 
 The target-cpu must be from the list [supported by LLVM] (or printed with `rustc --target amdgcn-amd-amdhsa --print target-cpus`).

tests/run-make-cargo/amdgpu-lto/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "amdgpu_lto"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+path = "lib.rs"
+crate-type = ["cdylib"]

tests/run-make-cargo/amdgpu-lto/lib.rs

@@ -0,0 +1,15 @@
+#![feature(abi_gpu_kernel)]
+#![no_std]
+
+#[panic_handler]
+fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[unsafe(no_mangle)]
+fn foo(a: i32, b: i32) -> i32 {
+    a + b
+}
+
+#[unsafe(no_mangle)]
+extern "gpu-kernel" fn kernel() {}

tests/run-make-cargo/amdgpu-lto/rmake.rs

@@ -0,0 +1,28 @@
+// Check that compiling for the amdgpu target which needs LTO works with a default
+// cargo configuration.
+
+//@ needs-llvm-components: amdgpu
+//@ needs-rust-lld
+
+#![deny(warnings)]
+
+use run_make_support::{cargo, path};
+
+fn main() {
+    let target_dir = path("target");
+
+    cargo()
+        .args(&[
+            "build",
+            "--release",
+            "--lib",
+            "--manifest-path",
+            "Cargo.toml",
+            "-Zbuild-std=core",
+            "--target",
+            "amdgcn-amd-amdhsa",
+        ])
+        .env("RUSTFLAGS", "-Ctarget-cpu=gfx900")
+        .env("CARGO_TARGET_DIR", &target_dir)
+        .run();
+}

tests/ui/closures/closure-return-block-note-issue-155670.rs

@@ -0,0 +1,14 @@
+struct SmolStr;
+
+const _: fn() = || {
+    match Some(()) {
+        Some(()) => (),
+        None => return,
+    };
+    let _: String = {
+        SmolStr
+        //~^ ERROR mismatched types
+    };
+};
+
+fn main() {}

tests/ui/closures/closure-return-block-note-issue-155670.stderr

@@ -0,0 +1,9 @@
+error[E0308]: mismatched types
+  --> $DIR/closure-return-block-note-issue-155670.rs:9:9
+   |
+LL |         SmolStr
+   |         ^^^^^^^ expected `String`, found `SmolStr`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/consts/const-closure-in-trait-impl.rs

@@ -0,0 +1,25 @@
+//@ check-pass
+
+#![feature(const_closures, const_destruct, const_trait_impl)]
+
+use std::marker::Destruct;
+use std::num::NonZero;
+
+const trait T {
+    fn a(&mut self, f: impl [const] Fn() + [const] Destruct);
+    fn b(&mut self);
+}
+
+struct S;
+
+impl const T for S {
+    fn a(&mut self, f: impl [const] Fn() + [const] Destruct) {
+        f()
+    }
+
+    fn b(&mut self) {
+        self.a(const || {});
+    }
+}
+
+fn main() {}

tests/ui/field_representing_types/not-field-if-unsized.next.stderr

@@ -0,0 +1,27 @@
+error[E0277]: the trait bound `field_of!(MyStruct, 0): std::field::Field` is not satisfied
+  --> $DIR/not-field-if-unsized.rs:17:20
+   |
+LL |     assert_field::<field_of!(MyStruct, 0)>();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::field::Field` is not implemented for `field_of!(MyStruct, 0)`
+   |
+note: required by a bound in `assert_field`
+  --> $DIR/not-field-if-unsized.rs:12:20
+   |
+LL | fn assert_field<F: Field>() {}
+   |                    ^^^^^ required by this bound in `assert_field`
+
+error[E0277]: the trait bound `field_of!(MyStruct, 1): std::field::Field` is not satisfied
+  --> $DIR/not-field-if-unsized.rs:21:20
+   |
+LL |     assert_field::<field_of!(MyStruct, 1)>();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::field::Field` is not implemented for `field_of!(MyStruct, 1)`
+   |
+note: required by a bound in `assert_field`
+  --> $DIR/not-field-if-unsized.rs:12:20
+   |
+LL | fn assert_field<F: Field>() {}
+   |                    ^^^^^ required by this bound in `assert_field`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/field_representing_types/not-field-if-unsized.old.stderr

@@ -0,0 +1,27 @@
+error[E0277]: the trait bound `field_of!(MyStruct, 0): std::field::Field` is not satisfied
+  --> $DIR/not-field-if-unsized.rs:17:20
+   |
+LL |     assert_field::<field_of!(MyStruct, 0)>();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::field::Field` is not implemented for `field_of!(MyStruct, 0)`
+   |
+note: required by a bound in `assert_field`
+  --> $DIR/not-field-if-unsized.rs:12:20
+   |
+LL | fn assert_field<F: Field>() {}
+   |                    ^^^^^ required by this bound in `assert_field`
+
+error[E0277]: the trait bound `field_of!(MyStruct, 1): std::field::Field` is not satisfied
+  --> $DIR/not-field-if-unsized.rs:21:20
+   |
+LL |     assert_field::<field_of!(MyStruct, 1)>();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::field::Field` is not implemented for `field_of!(MyStruct, 1)`
+   |
+note: required by a bound in `assert_field`
+  --> $DIR/not-field-if-unsized.rs:12:20
+   |
+LL | fn assert_field<F: Field>() {}
+   |                    ^^^^^ required by this bound in `assert_field`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/field_representing_types/not-field-if-unsized.rs

@@ -0,0 +1,23 @@
+//@ revisions: old next
+//@ [next] compile-flags: -Znext-solver
+#![expect(incomplete_features)]
+#![feature(field_projections)]
+
+use std::field::{Field, field_of};
+
+pub trait Trait {}
+
+pub struct MyStruct(usize, dyn Trait);
+
+fn assert_field<F: Field>() {}
+
+fn main() {
+    // FIXME(FRTs): this requires relaxing the `Base: ?Sized` bound in the
+    // `Field` trait & compiler changes.
+    assert_field::<field_of!(MyStruct, 0)>();
+    //~^ ERROR: the trait bound `field_of!(MyStruct, 0): std::field::Field` is not satisfied [E0277]
+
+    // FIXME(FRTs): improve this error message, point to the `dyn Trait` span.
+    assert_field::<field_of!(MyStruct, 1)>();
+    //~^ ERROR: the trait bound `field_of!(MyStruct, 1): std::field::Field` is not satisfied [E0277]
+}

tests/ui/field_representing_types/traits.rs

@@ -1,13 +1,17 @@
 //@ revisions: old next
 //@ [next] compile-flags: -Znext-solver
 //@ run-pass
-#![feature(field_projections, freeze)]
+#![feature(field_projections, freeze, unsafe_unpin)]
 #![expect(incomplete_features, dead_code)]
 use std::field::field_of;
-use std::marker::{Freeze, Unpin};
+use std::fmt::Debug;
+use std::hash::Hash;
+use std::marker::{Freeze, Unpin, UnsafeUnpin};
+use std::panic::{RefUnwindSafe, UnwindSafe};
 
 struct Struct {
     field: u32,
+    tail: [u32],
 }
 
 union Union {
@@ -19,11 +23,37 @@ enum Enum {
     Variant2(u32),
 }
 
-fn assert_traits<T: Send + Sync + Unpin + Copy + Clone + Sized + Freeze>() {}
+type Tuple = ((), usize, String, dyn Debug);
+
+fn assert_traits<
+    T: Sized
+        + Freeze
+        + RefUnwindSafe
+        + Send
+        + Sync
+        + Unpin
+        + UnsafeUnpin
+        + UnwindSafe
+        + Copy
+        + Debug
+        + Default
+        + Eq
+        + Hash
+        + Ord,
+>() {
+}
 
 fn main() {
     assert_traits::<field_of!(Struct, field)>();
+    assert_traits::<field_of!(Struct, tail)>();
+
     assert_traits::<field_of!(Union, field)>();
+
     assert_traits::<field_of!(Enum, Variant1.field)>();
     assert_traits::<field_of!(Enum, Variant2.0)>();
+
+    assert_traits::<field_of!(Tuple, 0)>();
+    assert_traits::<field_of!(Tuple, 1)>();
+    assert_traits::<field_of!(Tuple, 2)>();
+    assert_traits::<field_of!(Tuple, 3)>();
 }

tests/ui/impl-trait/dyn-incompatible-trait-in-return-position-impl-trait.stderr

@@ -21,6 +21,18 @@ LL |         return A;
 LL |     }
 LL |     B
    |     ^ expected `A`, found `B`
+   |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn cat() -> impl DynCompatible {
+LL + fn cat() -> Box<dyn DynCompatible> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         return Box::new(A);
+LL |     }
+LL ~     Box::new(B)
+   |
 
 error: aborting due to 2 previous errors
 

tests/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr

@@ -72,6 +72,17 @@ LL |     }
 LL |     1u32
    |     ^^^^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn foo() -> impl std::fmt::Display {
+LL + fn foo() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         return Box::new(0i32);
+LL |     }
+LL ~     Box::new(1u32)
+   |
 help: change the type of the numeric literal from `u32` to `i32`
    |
 LL -     1u32
@@ -90,6 +101,17 @@ LL |     } else {
 LL |         return 1u32;
    |                ^^^^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn bar() -> impl std::fmt::Display {
+LL + fn bar() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         return Box::new(0i32);
+LL |     } else {
+LL ~         return Box::new(1u32);
+   |
 help: change the type of the numeric literal from `u32` to `i32`
    |
 LL -         return 1u32;
@@ -108,6 +130,17 @@ LL |     } else {
 LL |         1u32
    |         ^^^^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn baz() -> impl std::fmt::Display {
+LL + fn baz() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         return Box::new(0i32);
+LL |     } else {
+LL ~         Box::new(1u32)
+   |
 help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
    |
 LL |     }.try_into().unwrap()
@@ -153,6 +186,16 @@ LL |         0 => return 0i32,
 LL |         _ => 1u32,
    |              ^^^^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn bat() -> impl std::fmt::Display {
+LL + fn bat() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         0 => return Box::new(0i32),
+LL ~         _ => Box::new(1u32),
+   |
 help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
    |
 LL |     }.try_into().unwrap()
@@ -171,6 +214,17 @@ LL | |         _ => 2u32,
 LL | |     }
    | |_____^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn can() -> impl std::fmt::Display {
+LL + fn can() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~         0 => return Box::new(0i32),
+LL ~         1 => Box::new(1u32),
+LL ~         _ => Box::new(2u32),
+   |
 help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
    |
 LL |     }.try_into().unwrap()
@@ -188,6 +242,18 @@ LL |             return 0i32;
 LL |             1u32
    |             ^^^^ expected `i32`, found `u32`
    |
+help: you could change the return type to be a boxed trait object
+   |
+LL - fn cat() -> impl std::fmt::Display {
+LL + fn cat() -> Box<dyn std::fmt::Display> {
+   |
+help: if you change the return type to expect trait objects, box the returned expressions
+   |
+LL ~             return Box::new(0i32);
+LL |         }
+LL |         _ => {
+LL ~             Box::new(1u32)
+   |
 help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
    |
 LL |     }.try_into().unwrap()

tests/ui/traits/const-traits/const-closure-in-non-const-trait-impl-method.rs

@@ -11,6 +11,7 @@ impl<T: Foo> Foo for &mut T {
     const fn test() -> impl [const] Fn() {
         //~^ ERROR functions in trait impls cannot be declared const
         const move || {}
+        //~^ ERROR: cannot use `const` closures outside of const contexts
     }
 }
 

tests/ui/traits/const-traits/const-closure-in-non-const-trait-impl-method.stderr

@@ -14,6 +14,12 @@ help: ... and declare the impl to be const instead
 LL | impl<T: Foo> const Foo for &mut T {
    |              +++++
 
-error: aborting due to 1 previous error
+error: cannot use `const` closures outside of const contexts
+  --> $DIR/const-closure-in-non-const-trait-impl-method.rs:13:9
+   |
+LL |         const move || {}
+   |         ^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0379`.

tests/ui/traits/const-traits/const-closure-in-non-const-trait-method.rs

@@ -6,6 +6,7 @@ trait Tr {
     const fn test() {
         //~^ ERROR functions in traits cannot be declared const
         (const || {})()
+        //~^ ERROR cannot use `const` closures outside of const contexts
     }
 }
 

tests/ui/traits/const-traits/const-closure-in-non-const-trait-method.stderr

@@ -7,6 +7,12 @@ LL |     const fn test() {
    |     functions in traits cannot be const
    |     help: remove the `const`
 
-error: aborting due to 1 previous error
+error: cannot use `const` closures outside of const contexts
+  --> $DIR/const-closure-in-non-const-trait-method.rs:8:10
+   |
+LL |         (const || {})()
+   |          ^^^^^^^^
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0379`.

tests/ui/traits/const-traits/non-const-op-const-closure-non-const-outer.stderr

@@ -2,7 +2,7 @@ error: cannot use `const` closures outside of const contexts
   --> $DIR/non-const-op-const-closure-non-const-outer.rs:14:6
    |
 LL |     (const || { (()).foo() })();
-   |      ^^^^^
+   |      ^^^^^^^^
 
 error: aborting due to 1 previous error