Auto merge of #130732 - matthiaskrgr:rollup-ke1j314, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #129550 (Add str.as_str() for easy Deref to string slices)
 - #130344 (Handle unsized consts with type `str`  in v0 symbol mangling)
 - #130659 (Support `char::encode_utf16` in const scenarios.)
 - #130705 (No longer mark RTN as incomplete)
 - #130712 (Don't call `ty::Const::normalize` in error reporting)
 - #130713 (Mark `u8::make_ascii_uppercase` and `u8::make_ascii_lowercase` as const.)
 - #130714 (Introduce `structurally_normalize_const`, use it in `rustc_hir_typeck`)
 - #130715 (Replace calls to `ty::Const::{try_}eval` in mir build/pattern analysis)
 - #130723 (Add test for `available_parallelism()`)
 - #130726 (tests: Remove spuriously failing vec-tryinto-array codegen test)

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

compiler/rustc_feature/src/unstable.rs

@@ -578,7 +578,7 @@ declare_features! (
     /// be used to describe E or vise-versa.
     (unstable, result_ffi_guarantees, "1.80.0", Some(110503)),
     /// Allows bounding the return type of AFIT/RPITIT.
-    (incomplete, return_type_notation, "1.70.0", Some(109417)),
+    (unstable, return_type_notation, "1.70.0", Some(109417)),
     /// Allows `extern "rust-cold"`.
     (unstable, rust_cold_cc, "1.63.0", Some(97544)),
     /// Allows use of x86 SHA512, SM3 and SM4 target-features and intrinsics

compiler/rustc_hir/src/hir.rs

@@ -1668,10 +1668,17 @@ pub enum ArrayLen<'hir> {
 }
 
 impl ArrayLen<'_> {
-    pub fn hir_id(&self) -> HirId {
+    pub fn span(self) -> Span {
         match self {
-            ArrayLen::Infer(InferArg { hir_id, .. }) | ArrayLen::Body(ConstArg { hir_id, .. }) => {
-                *hir_id
+            ArrayLen::Infer(arg) => arg.span,
+            ArrayLen::Body(body) => body.span(),
+        }
+    }
+
+    pub fn hir_id(self) -> HirId {
+        match self {
+            ArrayLen::Infer(InferArg { hir_id, .. }) | ArrayLen::Body(&ConstArg { hir_id, .. }) => {
+                hir_id
             }
         }
     }

compiler/rustc_hir_typeck/src/expr.rs

@@ -1491,8 +1491,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expr: &'tcx hir::Expr<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
-        let count = self.lower_array_length(count);
-        if let Some(count) = count.try_eval_target_usize(tcx, self.param_env) {
+        let count_span = count.span();
+        let count = self.try_structurally_resolve_const(count_span, self.lower_array_length(count));
+
+        if let Some(count) = count.try_to_target_usize(tcx) {
             self.suggest_array_len(expr, count);
         }
 
@@ -1520,19 +1522,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return Ty::new_error(tcx, guar);
         }
 
-        self.check_repeat_element_needs_copy_bound(element, count, element_ty);
+        // If the length is 0, we don't create any elements, so we don't copy any.
+        // If the length is 1, we don't copy that one element, we move it. Only check
+        // for `Copy` if the length is larger, or unevaluated.
+        // FIXME(min_const_generic_exprs): We could perhaps defer this check so that
+        // we don't require `<?0t as Tr>::CONST` doesn't unnecessarily require `Copy`.
+        if count.try_to_target_usize(tcx).is_none_or(|x| x > 1) {
+            self.enforce_repeat_element_needs_copy_bound(element, element_ty);
+        }
 
         let ty = Ty::new_array_with_const_len(tcx, t, count);
-
         self.register_wf_obligation(ty.into(), expr.span, ObligationCauseCode::WellFormed(None));
-
         ty
     }
 
-    fn check_repeat_element_needs_copy_bound(
+    /// Requires that `element_ty` is `Copy` (unless it's a const expression itself).
+    fn enforce_repeat_element_needs_copy_bound(
         &self,
         element: &hir::Expr<'_>,
-        count: ty::Const<'tcx>,
         element_ty: Ty<'tcx>,
     ) {
         let tcx = self.tcx;
@@ -1565,27 +1572,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ => traits::IsConstable::No,
         };
 
-        // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
-        // don't copy that one element, we move it. Only check for Copy if the length is larger.
-        if count.try_eval_target_usize(tcx, self.param_env).is_none_or(|len| len > 1) {
-            let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
-            let code = traits::ObligationCauseCode::RepeatElementCopy {
-                is_constable,
-                elt_type: element_ty,
-                elt_span: element.span,
-                elt_stmt_span: self
-                    .tcx
-                    .hir()
-                    .parent_iter(element.hir_id)
-                    .find_map(|(_, node)| match node {
-                        hir::Node::Item(it) => Some(it.span),
-                        hir::Node::Stmt(stmt) => Some(stmt.span),
-                        _ => None,
-                    })
-                    .expect("array repeat expressions must be inside an item or statement"),
-            };
-            self.require_type_meets(element_ty, element.span, code, lang_item);
-        }
+        let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
+        let code = traits::ObligationCauseCode::RepeatElementCopy {
+            is_constable,
+            elt_type: element_ty,
+            elt_span: element.span,
+            elt_stmt_span: self
+                .tcx
+                .hir()
+                .parent_iter(element.hir_id)
+                .find_map(|(_, node)| match node {
+                    hir::Node::Item(it) => Some(it.span),
+                    hir::Node::Stmt(stmt) => Some(stmt.span),
+                    _ => None,
+                })
+                .expect("array repeat expressions must be inside an item or statement"),
+        };
+        self.require_type_meets(element_ty, element.span, code, lang_item);
     }
 
     fn check_expr_tuple(
@@ -2800,9 +2803,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         len: ty::Const<'tcx>,
     ) {
         err.span_label(field.span, "unknown field");
-        if let (Some(len), Ok(user_index)) =
-            (len.try_eval_target_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
-        {
+        if let (Some(len), Ok(user_index)) = (
+            self.try_structurally_resolve_const(base.span, len).try_to_target_usize(self.tcx),
+            field.as_str().parse::<u64>(),
+        ) {
             let help = "instead of using tuple indexing, use array indexing";
             let applicability = if len < user_index {
                 Applicability::MachineApplicable

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -1470,6 +1470,33 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip(self, sp), ret)]
+    pub fn try_structurally_resolve_const(&self, sp: Span, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
+        // FIXME(min_const_generic_exprs): We could process obligations here if `ct` is a var.
+
+        if self.next_trait_solver()
+            && let ty::ConstKind::Unevaluated(..) = ct.kind()
+        {
+            // We need to use a separate variable here as otherwise the temporary for
+            // `self.fulfillment_cx.borrow_mut()` is alive in the `Err` branch, resulting
+            // in a reentrant borrow, causing an ICE.
+            let result = self
+                .at(&self.misc(sp), self.param_env)
+                .structurally_normalize_const(ct, &mut **self.fulfillment_cx.borrow_mut());
+            match result {
+                Ok(normalized_ct) => normalized_ct,
+                Err(errors) => {
+                    let guar = self.err_ctxt().report_fulfillment_errors(errors);
+                    return ty::Const::new_error(self.tcx, guar);
+                }
+            }
+        } else if self.tcx.features().generic_const_exprs {
+            ct.normalize(self.tcx, self.param_env)
+        } else {
+            ct
+        }
+    }
+
     /// Resolves `ty` by a single level if `ty` is a type variable.
     ///
     /// When the new solver is enabled, this will also attempt to normalize

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1502,7 +1502,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Create an dummy type `&[_]` so that both &[] and `&Vec<T>` can coerce to it.
         let dummy_ty = if let ty::Array(elem_ty, size) = peeled.kind()
             && let ty::Infer(_) = elem_ty.kind()
-            && size.try_eval_target_usize(self.tcx, self.param_env) == Some(0)
+            && self
+                .try_structurally_resolve_const(provided_expr.span, *size)
+                .try_to_target_usize(self.tcx)
+                == Some(0)
         {
             let slice = Ty::new_slice(self.tcx, *elem_ty);
             Ty::new_imm_ref(self.tcx, self.tcx.lifetimes.re_static, slice)

compiler/rustc_hir_typeck/src/intrinsicck.rs

@@ -101,7 +101,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
             Ok(SizeSkeleton::Generic(size)) => {
-                if let Some(size) = size.try_eval_target_usize(tcx, self.param_env) {
+                if let Some(size) =
+                    self.try_structurally_resolve_const(span, size).try_to_target_usize(tcx)
+                {
                     format!("{size} bytes")
                 } else {
                     format!("generic size {size}")

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1721,20 +1721,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        if item_name.name == sym::as_str && rcvr_ty.peel_refs().is_str() {
-            let msg = "remove this method call";
-            let mut fallback_span = true;
-            if let SelfSource::MethodCall(expr) = source {
-                let call_expr = self.tcx.hir().expect_expr(self.tcx.parent_hir_id(expr.hir_id));
-                if let Some(span) = call_expr.span.trim_start(expr.span) {
-                    err.span_suggestion(span, msg, "", Applicability::MachineApplicable);
-                    fallback_span = false;
-                }
-            }
-            if fallback_span {
-                err.span_label(span, msg);
-            }
-        } else if let Some(similar_candidate) = similar_candidate {
+        if let Some(similar_candidate) = similar_candidate {
             // Don't emit a suggestion if we found an actual method
             // that had unsatisfied trait bounds
             if unsatisfied_predicates.is_empty()

compiler/rustc_hir_typeck/src/pat.rs

@@ -2412,7 +2412,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         len: ty::Const<'tcx>,
         min_len: u64,
     ) -> (Option<Ty<'tcx>>, Ty<'tcx>) {
-        let len = len.try_eval_target_usize(self.tcx, self.param_env);
+        let len = self.try_structurally_resolve_const(span, len).try_to_target_usize(self.tcx);
 
         let guar = if let Some(len) = len {
             // Now we know the length...

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -57,7 +57,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 this.in_scope(region_scope, lint_level, |this| this.as_rvalue(block, scope, value))
             }
             ExprKind::Repeat { value, count } => {
-                if Some(0) == count.try_eval_target_usize(this.tcx, this.param_env) {
+                if Some(0) == count.try_to_target_usize(this.tcx) {
                     this.build_zero_repeat(block, value, scope, source_info)
                 } else {
                     let value_operand = unpack!(

compiler/rustc_mir_build/src/build/matches/match_pair.rs

@@ -42,7 +42,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let tcx = self.tcx;
         let (min_length, exact_size) = if let Some(place_resolved) = place.try_to_place(self) {
             match place_resolved.ty(&self.local_decls, tcx).ty.kind() {
-                ty::Array(_, length) => (length.eval_target_usize(tcx, self.param_env), true),
+                ty::Array(_, length) => (
+                    length
+                        .try_to_target_usize(tcx)
+                        .expect("expected len of array pat to be definite"),
+                    true,
+                ),
                 _ => ((prefix.len() + suffix.len()).try_into().unwrap(), false),
             }
         } else {

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -441,7 +441,9 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
             ty::Slice(..) => PatKind::Slice { prefix, slice, suffix },
             // Fixed-length array, `[T; len]`.
             ty::Array(_, len) => {
-                let len = len.eval_target_usize(self.tcx, self.param_env);
+                let len = len
+                    .try_to_target_usize(self.tcx)
+                    .expect("expected len of array pat to be definite");
                 assert!(len >= prefix.len() as u64 + suffix.len() as u64);
                 PatKind::Array { prefix, slice, suffix }
             }

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -352,7 +352,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
             ty::Array(sub_ty, len) => {
                 // We treat arrays of a constant but unknown length like slices.
                 ConstructorSet::Slice {
-                    array_len: len.try_eval_target_usize(cx.tcx, cx.param_env).map(|l| l as usize),
+                    array_len: len.try_to_target_usize(cx.tcx).map(|l| l as usize),
                     subtype_is_empty: cx.is_uninhabited(*sub_ty),
                 }
             }
@@ -685,9 +685,12 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
             }
             PatKind::Array { prefix, slice, suffix } | PatKind::Slice { prefix, slice, suffix } => {
                 let array_len = match ty.kind() {
-                    ty::Array(_, length) => {
-                        Some(length.eval_target_usize(cx.tcx, cx.param_env) as usize)
-                    }
+                    ty::Array(_, length) => Some(
+                        length
+                            .try_to_target_usize(cx.tcx)
+                            .expect("expected len of array pat to be definite")
+                            as usize,
+                    ),
                     ty::Slice(_) => None,
                     _ => span_bug!(pat.span, "bad ty {} for slice pattern", ty.inner()),
                 };

compiler/rustc_symbol_mangling/src/v0.rs

@@ -607,45 +607,40 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                 let _ = write!(self.out, "{bits:x}_");
             }
 
+            // Handle `str` as partial support for unsized constants
+            ty::Str => {
+                let tcx = self.tcx();
+                // HACK(jaic1): hide the `str` type behind a reference
+                // for the following transformation from valtree to raw bytes
+                let ref_ty = Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, ct_ty);
+                let slice = valtree.try_to_raw_bytes(tcx, ref_ty).unwrap_or_else(|| {
+                    bug!("expected to get raw bytes from valtree {:?} for type {:}", valtree, ct_ty)
+                });
+                let s = std::str::from_utf8(slice).expect("non utf8 str from MIR interpreter");
+
+                // "e" for str as a basic type
+                self.push("e");
+
+                // FIXME(eddyb) use a specialized hex-encoding loop.
+                for byte in s.bytes() {
+                    let _ = write!(self.out, "{byte:02x}");
+                }
+
+                self.push("_");
+            }
+
             // FIXME(valtrees): Remove the special case for `str`
             // here and fully support unsized constants.
-            ty::Ref(_, inner_ty, mutbl) => {
+            ty::Ref(_, _, mutbl) => {
                 self.push(match mutbl {
                     hir::Mutability::Not => "R",
                     hir::Mutability::Mut => "Q",
                 });
 
-                match inner_ty.kind() {
-                    ty::Str if mutbl.is_not() => {
-                        let slice =
-                            valtree.try_to_raw_bytes(self.tcx(), ct_ty).unwrap_or_else(|| {
-                                bug!(
-                                    "expected to get raw bytes from valtree {:?} for type {:}",
-                                    valtree,
-                                    ct_ty
-                                )
-                            });
-                        let s =
-                            std::str::from_utf8(slice).expect("non utf8 str from MIR interpreter");
-
-                        self.push("e");
-
-                        // FIXME(eddyb) use a specialized hex-encoding loop.
-                        for byte in s.bytes() {
-                            let _ = write!(self.out, "{byte:02x}");
-                        }
-
-                        self.push("_");
-                    }
-                    _ => {
-                        let pointee_ty = ct_ty
-                            .builtin_deref(true)
-                            .expect("tried to dereference on non-ptr type");
-                        let dereferenced_const =
-                            ty::Const::new_value(self.tcx, valtree, pointee_ty);
-                        dereferenced_const.print(self)?;
-                    }
-                }
+                let pointee_ty =
+                    ct_ty.builtin_deref(true).expect("tried to dereference on non-ptr type");
+                let dereferenced_const = ty::Const::new_value(self.tcx, valtree, pointee_ty);
+                dereferenced_const.print(self)?;
             }
 
             ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -17,7 +17,7 @@ use rustc_middle::traits::SignatureMismatchData;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::{BottomUpFolder, TypeFolder, TypeSuperFoldable};
+use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::print::{
     FmtPrinter, Print, PrintTraitPredicateExt as _, PrintTraitRefExt as _,
     with_forced_trimmed_paths,
@@ -1788,22 +1788,18 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         return false;
                     }
 
-                    let cand = self.resolve_vars_if_possible(impl_trait_ref).fold_with(
-                        &mut BottomUpFolder {
-                            tcx: self.tcx,
-                            ty_op: |ty| ty,
-                            lt_op: |lt| lt,
-                            ct_op: |ct| ct.normalize(self.tcx, ty::ParamEnv::empty()),
-                        },
-                    );
-                    if cand.references_error() {
+                    let impl_trait_ref = self.resolve_vars_if_possible(impl_trait_ref);
+                    if impl_trait_ref.references_error() {
                         return false;
                     }
                     err.highlighted_help(vec![
-                        StringPart::normal(format!("the trait `{}` ", cand.print_trait_sugared())),
+                        StringPart::normal(format!(
+                            "the trait `{}` ",
+                            impl_trait_ref.print_trait_sugared()
+                        )),
                         StringPart::highlighted("is"),
                         StringPart::normal(" implemented for `"),
-                        StringPart::highlighted(cand.self_ty().to_string()),
+                        StringPart::highlighted(impl_trait_ref.self_ty().to_string()),
                         StringPart::normal("`"),
                     ]);
 
@@ -1915,15 +1911,18 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let mut impl_candidates: Vec<_> = impl_candidates
             .iter()
             .cloned()
+            .filter(|cand| !cand.trait_ref.references_error())
             .map(|mut cand| {
-                // Fold the consts so that they shows up as, e.g., `10`
-                // instead of `core::::array::{impl#30}::{constant#0}`.
-                cand.trait_ref = cand.trait_ref.fold_with(&mut BottomUpFolder {
-                    tcx: self.tcx,
-                    ty_op: |ty| ty,
-                    lt_op: |lt| lt,
-                    ct_op: |ct| ct.normalize(self.tcx, ty::ParamEnv::empty()),
-                });
+                // Normalize the trait ref in its *own* param-env so
+                // that consts are folded and any trivial projections
+                // are normalized.
+                cand.trait_ref = self
+                    .tcx
+                    .try_normalize_erasing_regions(
+                        self.tcx.param_env(cand.impl_def_id),
+                        cand.trait_ref,
+                    )
+                    .unwrap_or(cand.trait_ref);
                 cand
             })
             .collect();

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -4620,7 +4620,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     format!("&{}{ty}", mutability.prefix_str())
                 }
             }
-            ty::Array(ty, len) if let Some(len) = len.try_eval_target_usize(tcx, param_env) => {
+            ty::Array(ty, len) if let Some(len) = len.try_to_target_usize(tcx) => {
                 if len == 0 {
                     "[]".to_string()
                 } else if self.type_is_copy_modulo_regions(param_env, ty) || len == 1 {

compiler/rustc_trait_selection/src/traits/structural_normalize.rs

@@ -46,4 +46,44 @@ impl<'tcx> At<'_, 'tcx> {
             Ok(self.normalize(ty).into_value_registering_obligations(self.infcx, fulfill_cx))
         }
     }
+
+    fn structurally_normalize_const<E: 'tcx>(
+        &self,
+        ct: ty::Const<'tcx>,
+        fulfill_cx: &mut dyn TraitEngine<'tcx, E>,
+    ) -> Result<ty::Const<'tcx>, Vec<E>> {
+        assert!(!ct.is_ct_infer(), "should have resolved vars before calling");
+
+        if self.infcx.next_trait_solver() {
+            let ty::ConstKind::Unevaluated(..) = ct.kind() else {
+                return Ok(ct);
+            };
+
+            let new_infer_ct = self.infcx.next_const_var(self.cause.span);
+
+            // We simply emit an `alias-eq` goal here, since that will take care of
+            // normalizing the LHS of the projection until it is a rigid projection
+            // (or a not-yet-defined opaque in scope).
+            let obligation = Obligation::new(
+                self.infcx.tcx,
+                self.cause.clone(),
+                self.param_env,
+                ty::PredicateKind::AliasRelate(
+                    ct.into(),
+                    new_infer_ct.into(),
+                    ty::AliasRelationDirection::Equate,
+                ),
+            );
+
+            fulfill_cx.register_predicate_obligation(self.infcx, obligation);
+            let errors = fulfill_cx.select_where_possible(self.infcx);
+            if !errors.is_empty() {
+                return Err(errors);
+            }
+
+            Ok(self.infcx.resolve_vars_if_possible(new_infer_ct))
+        } else {
+            Ok(self.normalize(ct).into_value_registering_obligations(self.infcx, fulfill_cx))
+        }
+    }
 }

library/alloc/src/lib.rs

@@ -93,6 +93,7 @@
 // tidy-alphabetical-start
 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
 #![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
+#![cfg_attr(test, feature(str_as_str))]
 #![feature(alloc_layout_extra)]
 #![feature(allocator_api)]
 #![feature(array_chunks)]

library/alloc/src/rc/tests.rs

@@ -448,7 +448,11 @@ fn test_from_box_str() {
     use std::string::String;
 
     let s = String::from("foo").into_boxed_str();
+    assert_eq!((&&&s).as_str(), "foo");
+
     let r: Rc<str> = Rc::from(s);
+    assert_eq!((&r).as_str(), "foo");
+    assert_eq!(r.as_str(), "foo");
 
     assert_eq!(&r[..], "foo");
 }

library/core/src/char/methods.rs

@@ -638,8 +638,7 @@ impl char {
     #[rustc_const_stable(feature = "const_char_len_utf", since = "1.52.0")]
     #[inline]
     pub const fn len_utf16(self) -> usize {
-        let ch = self as u32;
-        if (ch & 0xFFFF) == ch { 1 } else { 2 }
+        len_utf16(self as u32)
     }
 
     /// Encodes this character as UTF-8 into the provided byte buffer,
@@ -709,8 +708,9 @@ impl char {
     /// '𝕊'.encode_utf16(&mut b);
     /// ```
     #[stable(feature = "unicode_encode_char", since = "1.15.0")]
+    #[rustc_const_unstable(feature = "const_char_encode_utf16", issue = "130660")]
     #[inline]
-    pub fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16] {
+    pub const fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16] {
         encode_utf16_raw(self as u32, dst)
     }
 
@@ -1279,7 +1279,7 @@ impl char {
     ///
     /// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
-    #[rustc_const_unstable(feature = "const_char_make_ascii", issue = "130698")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
     pub const fn make_ascii_uppercase(&mut self) {
         *self = self.to_ascii_uppercase();
@@ -1305,7 +1305,7 @@ impl char {
     ///
     /// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
-    #[rustc_const_unstable(feature = "const_char_make_ascii", issue = "130698")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
     pub const fn make_ascii_lowercase(&mut self) {
         *self = self.to_ascii_lowercase();
@@ -1747,7 +1747,12 @@ const fn len_utf8(code: u32) -> usize {
     }
 }
 
-/// Encodes a raw u32 value as UTF-8 into the provided byte buffer,
+#[inline]
+const fn len_utf16(code: u32) -> usize {
+    if (code & 0xFFFF) == code { 1 } else { 2 }
+}
+
+/// Encodes a raw `u32` value as UTF-8 into the provided byte buffer,
 /// and then returns the subslice of the buffer that contains the encoded character.
 ///
 /// Unlike `char::encode_utf8`, this method also handles codepoints in the surrogate range.
@@ -1801,7 +1806,7 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] {
     unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) }
 }
 
-/// Encodes a raw u32 value as UTF-16 into the provided `u16` buffer,
+/// Encodes a raw `u32` value as UTF-16 into the provided `u16` buffer,
 /// and then returns the subslice of the buffer that contains the encoded character.
 ///
 /// Unlike `char::encode_utf16`, this method also handles codepoints in the surrogate range.
@@ -1812,28 +1817,33 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] {
 /// Panics if the buffer is not large enough.
 /// A buffer of length 2 is large enough to encode any `char`.
 #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
+#[rustc_const_unstable(feature = "const_char_encode_utf16", issue = "130660")]
 #[doc(hidden)]
 #[inline]
-pub fn encode_utf16_raw(mut code: u32, dst: &mut [u16]) -> &mut [u16] {
-    // SAFETY: each arm checks whether there are enough bits to write into
-    unsafe {
-        if (code & 0xFFFF) == code && !dst.is_empty() {
-            // The BMP falls through
-            *dst.get_unchecked_mut(0) = code as u16;
-            slice::from_raw_parts_mut(dst.as_mut_ptr(), 1)
-        } else if dst.len() >= 2 {
-            // Supplementary planes break into surrogates.
-            code -= 0x1_0000;
-            *dst.get_unchecked_mut(0) = 0xD800 | ((code >> 10) as u16);
-            *dst.get_unchecked_mut(1) = 0xDC00 | ((code as u16) & 0x3FF);
-            slice::from_raw_parts_mut(dst.as_mut_ptr(), 2)
-        } else {
-            panic!(
-                "encode_utf16: need {} units to encode U+{:X}, but the buffer has {}",
-                char::from_u32_unchecked(code).len_utf16(),
-                code,
-                dst.len(),
-            )
-        }
+pub const fn encode_utf16_raw(mut code: u32, dst: &mut [u16]) -> &mut [u16] {
+    const fn panic_at_const(_code: u32, _len: usize, _dst_len: usize) {
+        // Note that we cannot format in constant expressions.
+        panic!("encode_utf16: buffer does not have enough bytes to encode code point");
     }
+    fn panic_at_rt(code: u32, len: usize, dst_len: usize) {
+        panic!(
+            "encode_utf16: need {len} bytes to encode U+{code:04X} but buffer has just {dst_len}",
+        );
+    }
+    let len = len_utf16(code);
+    match (len, &mut *dst) {
+        (1, [a, ..]) => {
+            *a = code as u16;
+        }
+        (2, [a, b, ..]) => {
+            code -= 0x1_0000;
+
+            *a = (code >> 10) as u16 | 0xD800;
+            *b = (code & 0x3FF) as u16 | 0xDC00;
+        }
+        // FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly.
+        _ => const_eval_select((code, len, dst.len()), panic_at_const, panic_at_rt),
+    };
+    // SAFETY: `<&mut [u16]>::as_mut_ptr` is guaranteed to return a valid pointer and `len` has been tested to be within bounds.
+    unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) }
 }

library/core/src/lib.rs

@@ -119,6 +119,7 @@
 #![feature(const_bigint_helper_methods)]
 #![feature(const_black_box)]
 #![feature(const_cell_into_inner)]
+#![feature(const_char_encode_utf16)]
 #![feature(const_char_encode_utf8)]
 #![feature(const_eval_select)]
 #![feature(const_exact_div)]

library/core/src/num/mod.rs

@@ -624,8 +624,9 @@ impl u8 {
     ///
     /// [`to_ascii_uppercase`]: Self::to_ascii_uppercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
-    pub fn make_ascii_uppercase(&mut self) {
+    pub const fn make_ascii_uppercase(&mut self) {
         *self = self.to_ascii_uppercase();
     }
 
@@ -649,8 +650,9 @@ impl u8 {
     ///
     /// [`to_ascii_lowercase`]: Self::to_ascii_lowercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
-    pub fn make_ascii_lowercase(&mut self) {
+    pub const fn make_ascii_lowercase(&mut self) {
         *self = self.to_ascii_lowercase();
     }
 

library/core/src/str/mod.rs

@@ -2740,6 +2740,17 @@ impl str {
     pub fn substr_range(&self, substr: &str) -> Option<Range<usize>> {
         self.as_bytes().subslice_range(substr.as_bytes())
     }
+
+    /// Returns the same string as a string slice `&str`.
+    ///
+    /// This method is redundant when used directly on `&str`, but
+    /// it helps dereferencing other string-like types to string slices,
+    /// for example references to `Box<str>` or `Arc<str>`.
+    #[inline]
+    #[unstable(feature = "str_as_str", issue = "130366")]
+    pub fn as_str(&self) -> &str {
+        self
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

library/std/tests/thread.rs

@@ -37,3 +37,21 @@ fn thread_local_containing_const_statements() {
     assert_eq!(CELL.get(), 1);
     assert_eq!(REFCELL.take(), 1);
 }
+
+#[test]
+// Include an ignore list on purpose, so that new platforms don't miss it
+#[cfg_attr(
+    any(
+        target_os = "redox",
+        target_os = "l4re",
+        target_env = "sgx",
+        target_os = "solid_asp3",
+        target_os = "teeos",
+        target_os = "wasi"
+    ),
+    should_panic
+)]
+fn available_parallelism() {
+    // check that std::thread::available_parallelism() returns a valid value
+    assert!(thread::available_parallelism().is_ok());
+}

tests/codegen/issues/issue-111508-vec-tryinto-array.rs

@@ -1,22 +0,0 @@
-//@ compile-flags: -O
-// This regress since Rust version 1.72.
-//@ min-llvm-version: 18.1.4
-
-#![crate_type = "lib"]
-
-use std::convert::TryInto;
-
-const N: usize = 24;
-
-// CHECK-LABEL: @example
-// CHECK-NOT: unwrap_failed
-#[no_mangle]
-pub fn example(a: Vec<u8>) -> u8 {
-    if a.len() != 32 {
-        return 0;
-    }
-
-    let a: [u8; 32] = a.try_into().unwrap();
-
-    a[15] + a[N]
-}

tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs

@@ -1,7 +1,6 @@
 //@ edition: 2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     async fn method() {}

tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr

@@ -1,66 +1,57 @@
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:28:36
+  --> $DIR/bad-inputs-and-output.rs:27:36
    |
 LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:31:36
+  --> $DIR/bad-inputs-and-output.rs:30:36
    |
 LL | fn bar_qualified<T: Trait>() where <T as Trait>::method() -> (): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:34:36
+  --> $DIR/bad-inputs-and-output.rs:33:36
    |
 LL | fn baz_qualified<T: Trait>() where <T as Trait>::method(): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^ not a associated type
 
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/bad-inputs-and-output.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:10:23
+  --> $DIR/bad-inputs-and-output.rs:9:23
    |
 LL | fn foo<T: Trait<method(i32): Send>>() {}
    |                       ^^^^^ help: remove the input types: `()`
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:13:25
+  --> $DIR/bad-inputs-and-output.rs:12:25
    |
 LL | fn bar<T: Trait<method() -> (): Send>>() {}
    |                         ^^^^^^ help: remove the return type
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:16:23
+  --> $DIR/bad-inputs-and-output.rs:15:23
    |
 LL | fn baz<T: Trait<method(): Send>>() {}
    |                       ^^ help: add `..`: `(..)`
 
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:19:40
+  --> $DIR/bad-inputs-and-output.rs:18:40
    |
 LL | fn foo_path<T: Trait>() where T::method(i32): Send {}
    |                                        ^^^^^ help: remove the input types: `()`
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:22:42
+  --> $DIR/bad-inputs-and-output.rs:21:42
    |
 LL | fn bar_path<T: Trait>() where T::method() -> (): Send {}
    |                                          ^^^^^^ help: remove the return type
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:25:40
+  --> $DIR/bad-inputs-and-output.rs:24:40
    |
 LL | fn baz_path<T: Trait>() where T::method(): Send {}
    |                                        ^^ help: add `..`: `(..)`
 
-error: aborting due to 9 previous errors; 1 warning emitted
+error: aborting due to 9 previous errors
 
 For more information about this error, try `rustc --explain E0575`.

tests/ui/associated-type-bounds/return-type-notation/bare-path.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Tr {
     const CONST: usize;

tests/ui/associated-type-bounds/return-type-notation/bare-path.stderr

@@ -1,23 +1,14 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/bare-path.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation not allowed in this position yet
-  --> $DIR/bare-path.rs:15:23
+  --> $DIR/bare-path.rs:14:23
    |
 LL |     let _ = T::CONST::(..);
    |                       ^^^^
 
 error: return type notation not allowed in this position yet
-  --> $DIR/bare-path.rs:17:12
+  --> $DIR/bare-path.rs:16:12
    |
 LL |     let _: T::method(..);
    |            ^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/associated-type-bounds/return-type-notation/basic.rs

@@ -3,7 +3,6 @@
 //@ [with] check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     async fn method() -> Result<(), ()>;

tests/ui/associated-type-bounds/return-type-notation/basic.with.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/basic.rs:5:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/associated-type-bounds/return-type-notation/basic.without.stderr

@@ -1,29 +1,20 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/basic.rs:5:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: future cannot be sent between threads safely
-  --> $DIR/basic.rs:23:13
+  --> $DIR/basic.rs:22:13
    |
 LL |     is_send(foo::<T>());
    |             ^^^^^^^^^^ future returned by `foo` is not `Send`
    |
    = help: within `impl Future<Output = Result<(), ()>>`, the trait `Send` is not implemented for `impl Future<Output = Result<(), ()>> { <T as Foo>::method(..) }`, which is required by `impl Future<Output = Result<(), ()>>: Send`
 note: future is not `Send` as it awaits another future which is not `Send`
-  --> $DIR/basic.rs:13:5
+  --> $DIR/basic.rs:12:5
    |
 LL |     T::method().await?;
    |     ^^^^^^^^^^^ await occurs here on type `impl Future<Output = Result<(), ()>> { <T as Foo>::method(..) }`, which is not `Send`
 note: required by a bound in `is_send`
-  --> $DIR/basic.rs:17:20
+  --> $DIR/basic.rs:16:20
    |
 LL | fn is_send(_: impl Send) {}
    |                    ^^^^ required by this bound in `is_send`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 

tests/ui/associated-type-bounds/return-type-notation/display.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {}
 fn needs_trait(_: impl Trait) {}

tests/ui/associated-type-bounds/return-type-notation/display.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/display.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0277]: the trait bound `impl Sized { <T as Assoc>::method(..) }: Trait` is not satisfied
-  --> $DIR/display.rs:15:17
+  --> $DIR/display.rs:14:17
    |
 LL |     needs_trait(T::method());
    |     ----------- ^^^^^^^^^^^ the trait `Trait` is not implemented for `impl Sized { <T as Assoc>::method(..) }`
@@ -16,13 +7,13 @@ LL |     needs_trait(T::method());
    |     required by a bound introduced by this call
    |
 note: required by a bound in `needs_trait`
-  --> $DIR/display.rs:5:24
+  --> $DIR/display.rs:4:24
    |
 LL | fn needs_trait(_: impl Trait) {}
    |                        ^^^^^ required by this bound in `needs_trait`
 
 error[E0277]: the trait bound `impl Sized { <T as Assoc>::method_with_lt(..) }: Trait` is not satisfied
-  --> $DIR/display.rs:17:17
+  --> $DIR/display.rs:16:17
    |
 LL |     needs_trait(T::method_with_lt());
    |     ----------- ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `impl Sized { <T as Assoc>::method_with_lt(..) }`
@@ -30,13 +21,13 @@ LL |     needs_trait(T::method_with_lt());
    |     required by a bound introduced by this call
    |
 note: required by a bound in `needs_trait`
-  --> $DIR/display.rs:5:24
+  --> $DIR/display.rs:4:24
    |
 LL | fn needs_trait(_: impl Trait) {}
    |                        ^^^^^ required by this bound in `needs_trait`
 
 error[E0277]: the trait bound `impl Sized: Trait` is not satisfied
-  --> $DIR/display.rs:19:17
+  --> $DIR/display.rs:18:17
    |
 LL |     needs_trait(T::method_with_ty());
    |     ----------- ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `impl Sized`
@@ -44,18 +35,18 @@ LL |     needs_trait(T::method_with_ty());
    |     required by a bound introduced by this call
    |
 help: this trait has no implementations, consider adding one
-  --> $DIR/display.rs:4:1
+  --> $DIR/display.rs:3:1
    |
 LL | trait Trait {}
    | ^^^^^^^^^^^
 note: required by a bound in `needs_trait`
-  --> $DIR/display.rs:5:24
+  --> $DIR/display.rs:4:24
    |
 LL | fn needs_trait(_: impl Trait) {}
    |                        ^^^^^ required by this bound in `needs_trait`
 
 error[E0277]: the trait bound `impl Sized: Trait` is not satisfied
-  --> $DIR/display.rs:21:17
+  --> $DIR/display.rs:20:17
    |
 LL |     needs_trait(T::method_with_ct());
    |     ----------- ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `impl Sized`
@@ -63,16 +54,16 @@ LL |     needs_trait(T::method_with_ct());
    |     required by a bound introduced by this call
    |
 help: this trait has no implementations, consider adding one
-  --> $DIR/display.rs:4:1
+  --> $DIR/display.rs:3:1
    |
 LL | trait Trait {}
    | ^^^^^^^^^^^
 note: required by a bound in `needs_trait`
-  --> $DIR/display.rs:5:24
+  --> $DIR/display.rs:4:24
    |
 LL | fn needs_trait(_: impl Trait) {}
    |                        ^^^^^ required by this bound in `needs_trait`
 
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/associated-type-bounds/return-type-notation/equality.rs

@@ -1,7 +1,6 @@
 //@ edition: 2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 use std::future::Future;
 

tests/ui/associated-type-bounds/return-type-notation/equality.stderr

@@ -1,17 +1,8 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/equality.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation is not allowed to use type equality
-  --> $DIR/equality.rs:12:18
+  --> $DIR/equality.rs:11:18
    |
 LL | fn test<T: Trait<method(..) = Box<dyn Future<Output = ()>>>>() {}
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 

tests/ui/associated-type-bounds/return-type-notation/higher-ranked-bound-works.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait<'a> {
     fn late<'b>(&'b self, _: &'a ()) -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/higher-ranked-bound-works.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/higher-ranked-bound-works.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/associated-type-bounds/return-type-notation/issue-120208-higher-ranked-const.rs

@@ -1,7 +1,6 @@
 //@ edition: 2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait HealthCheck {
     async fn check<const N: usize>() -> bool;

tests/ui/associated-type-bounds/return-type-notation/issue-120208-higher-ranked-const.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/issue-120208-higher-ranked-const.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation is not allowed for functions that have const parameters
-  --> $DIR/issue-120208-higher-ranked-const.rs:12:21
+  --> $DIR/issue-120208-higher-ranked-const.rs:11:21
    |
 LL |     async fn check<const N: usize>() -> bool;
    |                    -------------- const parameter declared here
@@ -16,5 +7,5 @@ LL |     async fn check<const N: usize>() -> bool;
 LL |     HC: HealthCheck<check(..): Send> + Send + 'static,
    |                     ^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 

tests/ui/associated-type-bounds/return-type-notation/missing.rs

@@ -1,7 +1,6 @@
 //@ edition: 2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     async fn method() {}

tests/ui/associated-type-bounds/return-type-notation/missing.stderr

@@ -1,18 +1,9 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/missing.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0220]: associated function `methid` not found for `Trait`
-  --> $DIR/missing.rs:10:17
+  --> $DIR/missing.rs:9:17
    |
 LL | fn bar<T: Trait<methid(..): Send>>() {}
    |                 ^^^^^^ help: there is an associated function with a similar name: `method`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0220`.

tests/ui/associated-type-bounds/return-type-notation/namespace-conflict.rs

@@ -2,7 +2,6 @@
 
 #![allow(non_camel_case_types)]
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     type test;

tests/ui/associated-type-bounds/return-type-notation/namespace-conflict.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/namespace-conflict.rs:4:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/associated-type-bounds/return-type-notation/non-rpitit.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() {}

tests/ui/associated-type-bounds/return-type-notation/non-rpitit.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/non-rpitit.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation used on function that is not `async` and does not return `impl Trait`
-  --> $DIR/non-rpitit.rs:8:19
+  --> $DIR/non-rpitit.rs:7:19
    |
 LL |     fn method() {}
    |     ----------- this function must be `async` or return `impl Trait`
@@ -19,7 +10,7 @@ LL | fn bound<T: Trait<method(..): Send>>() {}
    = note: function returns `()`, which is not compatible with associated type return bounds
 
 error: return type notation used on function that is not `async` and does not return `impl Trait`
-  --> $DIR/non-rpitit.rs:11:30
+  --> $DIR/non-rpitit.rs:10:30
    |
 LL |     fn method() {}
    |     ----------- this function must be `async` or return `impl Trait`
@@ -29,5 +20,5 @@ LL | fn path<T>() where T: Trait, T::method(..): Send {}
    |
    = note: function returns `()`, which is not compatible with associated type return bounds
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/associated-type-bounds/return-type-notation/not-a-method.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 fn function() {}
 

tests/ui/associated-type-bounds/return-type-notation/not-a-method.stderr

@@ -1,49 +1,40 @@
 error[E0575]: expected function, found function `function`
-  --> $DIR/not-a-method.rs:8:5
+  --> $DIR/not-a-method.rs:7:5
    |
 LL |     function(..): Send,
    |     ^^^^^^^^^^^^ not a function
 
 error[E0573]: expected type, found function `function`
-  --> $DIR/not-a-method.rs:16:5
+  --> $DIR/not-a-method.rs:15:5
    |
 LL |     function(): Send,
    |     ^^^^^^^^^^ not a type
 
 error[E0576]: cannot find function `method` in this scope
-  --> $DIR/not-a-method.rs:28:5
+  --> $DIR/not-a-method.rs:27:5
    |
 LL |     method(..): Send,
    |     ^^^^^^ not found in this scope
 
 error[E0412]: cannot find type `method` in this scope
-  --> $DIR/not-a-method.rs:37:5
+  --> $DIR/not-a-method.rs:36:5
    |
 LL |     method(): Send,
    |     ^^^^^^ not found in this scope
 
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/not-a-method.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation not allowed in this position yet
-  --> $DIR/not-a-method.rs:8:5
+  --> $DIR/not-a-method.rs:7:5
    |
 LL |     function(..): Send,
    |     ^^^^^^^^^^^^
 
 error: return type notation not allowed in this position yet
-  --> $DIR/not-a-method.rs:28:5
+  --> $DIR/not-a-method.rs:27:5
    |
 LL |     method(..): Send,
    |     ^^^^^^^^^^
 
-error: aborting due to 6 previous errors; 1 warning emitted
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0412, E0573, E0575, E0576.
 For more information about an error, try `rustc --explain E0412`.

tests/ui/associated-type-bounds/return-type-notation/path-ambiguous.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait A {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-ambiguous.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-ambiguous.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0221]: ambiguous associated function `method` in bounds of `T`
-  --> $DIR/path-ambiguous.rs:13:5
+  --> $DIR/path-ambiguous.rs:12:5
    |
 LL |     fn method() -> impl Sized;
    |     -------------------------- ambiguous `method` from `A`
@@ -29,7 +20,7 @@ LL |     <T as A>::method(..): Send,
    |     ~~~~~~~~~~
 
 error[E0221]: ambiguous associated function `method` in bounds of `T`
-  --> $DIR/path-ambiguous.rs:22:5
+  --> $DIR/path-ambiguous.rs:21:5
    |
 LL |     fn method() -> impl Sized;
    |     -------------------------- ambiguous `method` from `A`
@@ -49,6 +40,6 @@ help: use fully-qualified syntax to disambiguate
 LL |     <T as A>::method(..): Send,
    |     ~~~~~~~~~~
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0221`.

tests/ui/associated-type-bounds/return-type-notation/path-constrained-in-method.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-constrained-in-method.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-constrained-in-method.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/associated-type-bounds/return-type-notation/path-higher-ranked.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait A<'a> {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-higher-ranked.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-higher-ranked.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0212]: cannot use the associated function of a trait with uninferred generic parameters
-  --> $DIR/path-higher-ranked.rs:12:5
+  --> $DIR/path-higher-ranked.rs:11:5
    |
 LL |     T::method(..): Send,
    |     ^^^^^^^^^^^^^
@@ -19,7 +10,7 @@ LL |     <T as A<'_>>::method(..): Send,
    |     ~~~~~~~~~~~~~~
 
 error[E0212]: cannot use the associated function of a trait with uninferred generic parameters
-  --> $DIR/path-higher-ranked.rs:20:5
+  --> $DIR/path-higher-ranked.rs:19:5
    |
 LL |     T::method(..): Send,
    |     ^^^^^^^^^^^^^
@@ -29,6 +20,6 @@ help: use a fully qualified path with inferred lifetimes
 LL |     <T as A<'_>>::method(..): Send,
    |     ~~~~~~~~~~~~~~
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0212`.

tests/ui/associated-type-bounds/return-type-notation/path-missing.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait A {
     #[allow(non_camel_case_types)]

tests/ui/associated-type-bounds/return-type-notation/path-missing.stderr

@@ -1,33 +1,24 @@
 error[E0576]: cannot find method or associated constant `method` in trait `A`
-  --> $DIR/path-missing.rs:11:15
+  --> $DIR/path-missing.rs:10:15
    |
 LL |     <T as A>::method(..): Send,
    |               ^^^^^^ not found in `A`
 
 error[E0575]: expected method or associated constant, found associated type `A::bad`
-  --> $DIR/path-missing.rs:13:5
+  --> $DIR/path-missing.rs:12:5
    |
 LL |     <T as A>::bad(..): Send,
    |     ^^^^^^^^^^^^^^^^^
    |
    = note: can't use a type alias as a constructor
 
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-missing.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0220]: associated function `method` not found for `T`
-  --> $DIR/path-missing.rs:20:8
+  --> $DIR/path-missing.rs:19:8
    |
 LL |     T::method(..): Send,
    |        ^^^^^^ associated function `method` not found
 
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0220, E0575, E0576.
 For more information about an error, try `rustc --explain E0220`.

tests/ui/associated-type-bounds/return-type-notation/path-no-qself.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-no-qself.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-no-qself.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0223]: ambiguous associated type
-  --> $DIR/path-no-qself.rs:10:5
+  --> $DIR/path-no-qself.rs:9:5
    |
 LL |     Trait::method(..): Send,
    |     ^^^^^^^^^^^^^^^^^
@@ -18,6 +9,6 @@ help: if there were a type named `Example` that implemented `Trait`, you could u
 LL |     <Example as Trait>::method: Send,
    |     ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0223`.

tests/ui/associated-type-bounds/return-type-notation/path-non-param-qself.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-non-param-qself.stderr

@@ -1,30 +1,21 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-non-param-qself.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0223]: ambiguous associated function
-  --> $DIR/path-non-param-qself.rs:12:5
+  --> $DIR/path-non-param-qself.rs:11:5
    |
 LL |     <()>::method(..): Send,
    |     ^^^^^^^^^^^^^^^^
 
 error[E0223]: ambiguous associated function
-  --> $DIR/path-non-param-qself.rs:14:5
+  --> $DIR/path-non-param-qself.rs:13:5
    |
 LL |     i32::method(..): Send,
    |     ^^^^^^^^^^^^^^^
 
 error[E0223]: ambiguous associated function
-  --> $DIR/path-non-param-qself.rs:16:5
+  --> $DIR/path-non-param-qself.rs:15:5
    |
 LL |     Adt::method(..): Send,
    |     ^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0223`.

tests/ui/associated-type-bounds/return-type-notation/path-self-qself.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-self-qself.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-self-qself.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/associated-type-bounds/return-type-notation/path-type-param.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     fn method<T>() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-type-param.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-type-param.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation is not allowed for functions that have type parameters
-  --> $DIR/path-type-param.rs:10:5
+  --> $DIR/path-type-param.rs:9:5
    |
 LL |     fn method<T>() -> impl Sized;
    |               - type parameter declared here
@@ -17,7 +8,7 @@ LL |     <T as Foo>::method(..): Send,
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 error: return type notation is not allowed for functions that have type parameters
-  --> $DIR/path-type-param.rs:17:5
+  --> $DIR/path-type-param.rs:16:5
    |
 LL |     fn method<T>() -> impl Sized;
    |               - type parameter declared here
@@ -25,5 +16,5 @@ LL |     fn method<T>() -> impl Sized;
 LL |     <T as Foo>::method(..): Send,
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/associated-type-bounds/return-type-notation/path-unsatisfied.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-unsatisfied.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-unsatisfied.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0277]: `*mut ()` cannot be sent between threads safely
-  --> $DIR/path-unsatisfied.rs:23:12
+  --> $DIR/path-unsatisfied.rs:22:12
    |
 LL |     fn method() -> impl Sized {
    |                    ---------- within this `impl Sized`
@@ -18,12 +9,12 @@ LL |     test::<DoesntWork>();
    |
    = help: within `impl Sized`, the trait `Send` is not implemented for `*mut ()`, which is required by `impl Sized: Send`
 note: required because it appears within the type `impl Sized`
-  --> $DIR/path-unsatisfied.rs:10:20
+  --> $DIR/path-unsatisfied.rs:9:20
    |
 LL |     fn method() -> impl Sized {
    |                    ^^^^^^^^^^
 note: required by a bound in `test`
-  --> $DIR/path-unsatisfied.rs:18:20
+  --> $DIR/path-unsatisfied.rs:17:20
    |
 LL | fn test<T: Trait>()
    |    ---- required by a bound in this function
@@ -31,6 +22,6 @@ LL | where
 LL |     T::method(..): Send,
    |                    ^^^^ required by this bound in `test`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/associated-type-bounds/return-type-notation/path-works.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Trait {
     fn method() -> impl Sized;

tests/ui/associated-type-bounds/return-type-notation/path-works.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/path-works.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/issue-110963-early.stderr

@@ -1,12 +1,3 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/issue-110963-early.rs:4:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: implementation of `Send` is not general enough
   --> $DIR/issue-110963-early.rs:14:5
    |
@@ -36,5 +27,5 @@ LL | |     });
    = note: ...but `Send` is actually implemented for the type `impl Future<Output = bool> { <HC as HealthCheck>::check<'2>(..) }`, for some specific lifetime `'2`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/async-await/return-type-notation/issue-110963-late.rs

@@ -2,7 +2,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait HealthCheck {
     async fn check(&mut self) -> bool;

tests/ui/async-await/return-type-notation/issue-110963-late.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/issue-110963-late.rs:4:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/normalizing-self-auto-trait-issue-109924.current.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/normalizing-self-auto-trait-issue-109924.rs:7:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/normalizing-self-auto-trait-issue-109924.next.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/normalizing-self-auto-trait-issue-109924.rs:7:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/normalizing-self-auto-trait-issue-109924.rs

@@ -5,7 +5,6 @@
 //@ edition:2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     async fn bar(&self);

tests/ui/async-await/return-type-notation/rtn-implied-in-supertrait.rs

@@ -2,7 +2,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 use std::future::Future;
 

tests/ui/async-await/return-type-notation/rtn-implied-in-supertrait.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/rtn-implied-in-supertrait.rs:4:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/rtn-in-impl-signature.rs

@@ -1,5 +1,4 @@
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 // Shouldn't ICE when we have a (bad) RTN in an impl header
 

tests/ui/async-await/return-type-notation/rtn-in-impl-signature.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/rtn-in-impl-signature.rs:1:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0229]: associated item constraints are not allowed here
-  --> $DIR/rtn-in-impl-signature.rs:10:17
+  --> $DIR/rtn-in-impl-signature.rs:9:17
    |
 LL | impl Super1<'_, bar(..): Send> for () {}
    |                 ^^^^^^^^^^^^^ associated item constraint not allowed here
@@ -20,7 +11,7 @@ LL + impl Super1<'_> for () {}
    |
 
 error[E0046]: not all trait items implemented, missing: `bar`
-  --> $DIR/rtn-in-impl-signature.rs:10:1
+  --> $DIR/rtn-in-impl-signature.rs:9:1
    |
 LL |     fn bar<'b>() -> bool;
    |     --------------------- `bar` from trait
@@ -28,7 +19,7 @@ LL |     fn bar<'b>() -> bool;
 LL | impl Super1<'_, bar(..): Send> for () {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `bar` in implementation
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0046, E0229.
 For more information about an error, try `rustc --explain E0046`.

tests/ui/async-await/return-type-notation/super-method-bound-ambig.rs

@@ -1,7 +1,6 @@
 //@ edition:2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Super1<'a> {
     async fn test();

tests/ui/async-await/return-type-notation/super-method-bound-ambig.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/super-method-bound-ambig.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error[E0221]: ambiguous associated function `test` in bounds of `Foo`
-  --> $DIR/super-method-bound-ambig.rs:25:12
+  --> $DIR/super-method-bound-ambig.rs:24:12
    |
 LL |     async fn test();
    |     ---------------- ambiguous `test` from `for<'a> Super1<'a>`
@@ -19,6 +10,6 @@ LL |     async fn test();
 LL |     T: Foo<test(..): Send>,
    |            ^^^^^^^^^^^^^^ ambiguous associated function `test`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0221`.

tests/ui/async-await/return-type-notation/super-method-bound.rs

@@ -2,7 +2,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Super<'a> {
     async fn test();

tests/ui/async-await/return-type-notation/super-method-bound.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/super-method-bound.rs:4:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/supertrait-bound.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete and may not be safe to use
 
 trait IntFactory {
     fn stream(&self) -> impl Iterator<Item = i32>;

tests/ui/async-await/return-type-notation/supertrait-bound.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/supertrait-bound.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/async-await/return-type-notation/ty-or-ct-params.rs

@@ -1,7 +1,6 @@
 //@ edition: 2021
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     async fn bar<T>() {}

tests/ui/async-await/return-type-notation/ty-or-ct-params.stderr

@@ -1,14 +1,5 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/ty-or-ct-params.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
 error: return type notation is not allowed for functions that have type parameters
-  --> $DIR/ty-or-ct-params.rs:14:12
+  --> $DIR/ty-or-ct-params.rs:13:12
    |
 LL |     async fn bar<T>() {}
    |                  - type parameter declared here
@@ -17,7 +8,7 @@ LL |     T: Foo<bar(..): Send, baz(..): Send>,
    |            ^^^^^^^^^^^^^
 
 error: return type notation is not allowed for functions that have const parameters
-  --> $DIR/ty-or-ct-params.rs:14:27
+  --> $DIR/ty-or-ct-params.rs:13:27
    |
 LL |     async fn baz<const N: usize>() {}
    |                  -------------- const parameter declared here
@@ -25,5 +16,5 @@ LL |     async fn baz<const N: usize>() {}
 LL |     T: Foo<bar(..): Send, baz(..): Send>,
    |                           ^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/binop/binary-op-suggest-deref.stderr

@@ -303,8 +303,8 @@ LL |     let _ = FOO & (*"Sized".to_string().into_boxed_str());
    |
    = help: the trait `BitAnd<str>` is not implemented for `i32`
    = help: the following other types implement trait `BitAnd<Rhs>`:
-             `&'a i32` implements `BitAnd<i32>`
-             `&i32` implements `BitAnd<&i32>`
+             `&i32` implements `BitAnd<i32>`
+             `&i32` implements `BitAnd`
              `i32` implements `BitAnd<&i32>`
              `i32` implements `BitAnd`
 

tests/ui/binop/binop-mul-i32-f32.stderr

@@ -6,8 +6,8 @@ LL |     x * y
    |
    = help: the trait `Mul<f32>` is not implemented for `i32`
    = help: the following other types implement trait `Mul<Rhs>`:
-             `&'a i32` implements `Mul<i32>`
-             `&i32` implements `Mul<&i32>`
+             `&i32` implements `Mul<i32>`
+             `&i32` implements `Mul`
              `i32` implements `Mul<&i32>`
              `i32` implements `Mul`
 

tests/ui/binop/shift-various-bad-types.stderr

@@ -6,14 +6,14 @@ LL |     22 >> p.char;
    |
    = help: the trait `Shr<char>` is not implemented for `{integer}`
    = help: the following other types implement trait `Shr<Rhs>`:
-             `&'a i128` implements `Shr<i128>`
-             `&'a i128` implements `Shr<i16>`
-             `&'a i128` implements `Shr<i32>`
-             `&'a i128` implements `Shr<i64>`
-             `&'a i128` implements `Shr<i8>`
-             `&'a i128` implements `Shr<isize>`
-             `&'a i128` implements `Shr<u128>`
-             `&'a i128` implements `Shr<u16>`
+             `&i128` implements `Shr<&i16>`
+             `&i128` implements `Shr<&i32>`
+             `&i128` implements `Shr<&i64>`
+             `&i128` implements `Shr<&i8>`
+             `&i128` implements `Shr<&isize>`
+             `&i128` implements `Shr<&u128>`
+             `&i128` implements `Shr<&u16>`
+             `&i128` implements `Shr<&u32>`
            and 568 others
 
 error[E0277]: no implementation for `{integer} >> &str`
@@ -24,14 +24,14 @@ LL |     22 >> p.str;
    |
    = help: the trait `Shr<&str>` is not implemented for `{integer}`
    = help: the following other types implement trait `Shr<Rhs>`:
-             `&'a i128` implements `Shr<i128>`
-             `&'a i128` implements `Shr<i16>`
-             `&'a i128` implements `Shr<i32>`
-             `&'a i128` implements `Shr<i64>`
-             `&'a i128` implements `Shr<i8>`
-             `&'a i128` implements `Shr<isize>`
-             `&'a i128` implements `Shr<u128>`
-             `&'a i128` implements `Shr<u16>`
+             `&i128` implements `Shr<&i16>`
+             `&i128` implements `Shr<&i32>`
+             `&i128` implements `Shr<&i64>`
+             `&i128` implements `Shr<&i8>`
+             `&i128` implements `Shr<&isize>`
+             `&i128` implements `Shr<&u128>`
+             `&i128` implements `Shr<&u16>`
+             `&i128` implements `Shr<&u32>`
            and 568 others
 
 error[E0277]: no implementation for `{integer} >> &Panolpy`
@@ -42,14 +42,14 @@ LL |     22 >> p;
    |
    = help: the trait `Shr<&Panolpy>` is not implemented for `{integer}`
    = help: the following other types implement trait `Shr<Rhs>`:
-             `&'a i128` implements `Shr<i128>`
-             `&'a i128` implements `Shr<i16>`
-             `&'a i128` implements `Shr<i32>`
-             `&'a i128` implements `Shr<i64>`
-             `&'a i128` implements `Shr<i8>`
-             `&'a i128` implements `Shr<isize>`
-             `&'a i128` implements `Shr<u128>`
-             `&'a i128` implements `Shr<u16>`
+             `&i128` implements `Shr<&i16>`
+             `&i128` implements `Shr<&i32>`
+             `&i128` implements `Shr<&i64>`
+             `&i128` implements `Shr<&i8>`
+             `&i128` implements `Shr<&isize>`
+             `&i128` implements `Shr<&u128>`
+             `&i128` implements `Shr<&u16>`
+             `&i128` implements `Shr<&u32>`
            and 568 others
 
 error[E0308]: mismatched types

tests/ui/borrowck/alias-liveness/rtn-static.rs

@@ -1,7 +1,6 @@
 //@ check-pass
 
 #![feature(return_type_notation)]
-//~^ WARN the feature `return_type_notation` is incomplete
 
 trait Foo {
     fn borrow(&mut self) -> impl Sized + '_;

tests/ui/borrowck/alias-liveness/rtn-static.stderr

@@ -1,11 +0,0 @@
-warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/rtn-static.rs:3:12
-   |
-LL | #![feature(return_type_notation)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-warning: 1 warning emitted
-

tests/ui/const-generics/generic_const_exprs/different-fn.stderr

@@ -2,10 +2,10 @@ error[E0308]: mismatched types
   --> $DIR/different-fn.rs:10:5
    |
 LL |     [0; size_of::<Foo<T>>()]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ expected `size_of::<T>()`, found `size_of::<Foo<T>>()`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ expected `size_of::<T>()`, found `0`
    |
    = note: expected constant `size_of::<T>()`
-              found constant `size_of::<Foo<T>>()`
+              found constant `0`
 
 error: unconstrained generic constant
   --> $DIR/different-fn.rs:10:9

tests/ui/const-generics/occurs-check/unused-substs-1.stderr

@@ -4,7 +4,7 @@ error[E0277]: the trait bound `A<_>: Bar<_>` is not satisfied
 LL |     let _ = A;
    |             ^ the trait `Bar<_>` is not implemented for `A<_>`
    |
-   = help: the trait `Bar<_>` is implemented for `A<7>`
+   = help: the trait `Bar<_>` is implemented for `A<{ 6 + 1 }>`
 note: required by a bound in `A`
   --> $DIR/unused-substs-1.rs:9:11
    |

tests/ui/const-generics/unsized_const_params/symbol_mangling_v0_str.rs

@@ -0,0 +1,24 @@
+//@ check-pass
+//@ compile-flags: -Csymbol-mangling-version=v0
+#![allow(incomplete_features)]
+#![feature(unsized_const_params)]
+
+// Regression test for #116303
+
+#[derive(PartialEq, Eq)]
+struct MyStr(str);
+impl std::marker::UnsizedConstParamTy for MyStr {}
+
+fn function_with_my_str<const S: &'static MyStr>() -> &'static MyStr {
+    S
+}
+
+impl MyStr {
+    const fn new(s: &'static str) -> &'static MyStr {
+        unsafe { std::mem::transmute(s) }
+    }
+}
+
+pub fn main() {
+    let f = function_with_my_str::<{ MyStr::new("hello") }>();
+}

tests/ui/consts/const-eval/const-eval-overflow-3b.stderr

@@ -12,8 +12,8 @@ LL |     = [0; (i8::MAX + 1u8) as usize];
    |
    = help: the trait `Add<u8>` is not implemented for `i8`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a i8` implements `Add<i8>`
-             `&i8` implements `Add<&i8>`
+             `&i8` implements `Add<i8>`
+             `&i8` implements `Add`
              `i8` implements `Add<&i8>`
              `i8` implements `Add`
 

tests/ui/consts/const-eval/const-eval-overflow-4b.stderr

@@ -12,8 +12,8 @@ LL |     : [u32; (i8::MAX as i8 + 1u8) as usize]
    |
    = help: the trait `Add<u8>` is not implemented for `i8`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a i8` implements `Add<i8>`
-             `&i8` implements `Add<&i8>`
+             `&i8` implements `Add<i8>`
+             `&i8` implements `Add`
              `i8` implements `Add<&i8>`
              `i8` implements `Add`
 

tests/ui/impl-trait/equality.stderr

@@ -30,8 +30,8 @@ LL |         n + sum_to(n - 1)
    |
    = help: the trait `Add<impl Foo>` is not implemented for `u32`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a u32` implements `Add<u32>`
-             `&u32` implements `Add<&u32>`
+             `&u32` implements `Add<u32>`
+             `&u32` implements `Add`
              `u32` implements `Add<&u32>`
              `u32` implements `Add`
 

tests/ui/issues/issue-11771.stderr

@@ -6,14 +6,14 @@ LL |     1 +
    |
    = help: the trait `Add<()>` is not implemented for `{integer}`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a f128` implements `Add<f128>`
-             `&'a f16` implements `Add<f16>`
-             `&'a f32` implements `Add<f32>`
-             `&'a f64` implements `Add<f64>`
-             `&'a i128` implements `Add<i128>`
-             `&'a i16` implements `Add<i16>`
-             `&'a i32` implements `Add<i32>`
-             `&'a i64` implements `Add<i64>`
+             `&f128` implements `Add<f128>`
+             `&f128` implements `Add`
+             `&f16` implements `Add<f16>`
+             `&f16` implements `Add`
+             `&f32` implements `Add<f32>`
+             `&f32` implements `Add`
+             `&f64` implements `Add<f64>`
+             `&f64` implements `Add`
            and 56 others
 
 error[E0277]: cannot add `()` to `{integer}`
@@ -24,14 +24,14 @@ LL |     1 +
    |
    = help: the trait `Add<()>` is not implemented for `{integer}`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a f128` implements `Add<f128>`
-             `&'a f16` implements `Add<f16>`
-             `&'a f32` implements `Add<f32>`
-             `&'a f64` implements `Add<f64>`
-             `&'a i128` implements `Add<i128>`
-             `&'a i16` implements `Add<i16>`
-             `&'a i32` implements `Add<i32>`
-             `&'a i64` implements `Add<i64>`
+             `&f128` implements `Add<f128>`
+             `&f128` implements `Add`
+             `&f16` implements `Add<f16>`
+             `&f16` implements `Add`
+             `&f32` implements `Add<f32>`
+             `&f32` implements `Add`
+             `&f64` implements `Add<f64>`
+             `&f64` implements `Add`
            and 56 others
 
 error: aborting due to 2 previous errors

tests/ui/issues/issue-24352.stderr

@@ -6,8 +6,8 @@ LL |     1.0f64 - 1
    |
    = help: the trait `Sub<{integer}>` is not implemented for `f64`
    = help: the following other types implement trait `Sub<Rhs>`:
-             `&'a f64` implements `Sub<f64>`
-             `&f64` implements `Sub<&f64>`
+             `&f64` implements `Sub<f64>`
+             `&f64` implements `Sub`
              `f64` implements `Sub<&f64>`
              `f64` implements `Sub`
 help: consider using a floating-point literal by writing it with `.0`

tests/ui/issues/issue-50582.stderr

@@ -16,14 +16,14 @@ LL |     Vec::<[(); 1 + for x in 0..1 {}]>::new();
    |
    = help: the trait `Add<()>` is not implemented for `{integer}`
    = help: the following other types implement trait `Add<Rhs>`:
-             `&'a f128` implements `Add<f128>`
-             `&'a f16` implements `Add<f16>`
-             `&'a f32` implements `Add<f32>`
-             `&'a f64` implements `Add<f64>`
-             `&'a i128` implements `Add<i128>`
-             `&'a i16` implements `Add<i16>`
-             `&'a i32` implements `Add<i32>`
-             `&'a i64` implements `Add<i64>`
+             `&f128` implements `Add<f128>`
+             `&f128` implements `Add`
+             `&f16` implements `Add<f16>`
+             `&f16` implements `Add`
+             `&f32` implements `Add<f32>`
+             `&f32` implements `Add`
+             `&f64` implements `Add<f64>`
+             `&f64` implements `Add`
            and 56 others
 
 error: aborting due to 2 previous errors

tests/ui/iterators/invalid-iterator-chain-fixable.stderr

@@ -33,7 +33,7 @@ LL |     println!("{}", scores.sum::<i32>());
    |
    = help: the trait `Sum<()>` is not implemented for `i32`
    = help: the following other types implement trait `Sum<A>`:
-             `i32` implements `Sum<&'a i32>`
+             `i32` implements `Sum<&i32>`
              `i32` implements `Sum`
 note: the method call chain might not have had the expected associated types
   --> $DIR/invalid-iterator-chain-fixable.rs:14:10
@@ -66,7 +66,7 @@ LL |             .sum::<i32>(),
    |
    = help: the trait `Sum<()>` is not implemented for `i32`
    = help: the following other types implement trait `Sum<A>`:
-             `i32` implements `Sum<&'a i32>`
+             `i32` implements `Sum<&i32>`
              `i32` implements `Sum`
 note: the method call chain might not have had the expected associated types
   --> $DIR/invalid-iterator-chain-fixable.rs:23:14
@@ -99,7 +99,7 @@ LL |     println!("{}", vec![0, 1].iter().map(|x| { x; }).sum::<i32>());
    |
    = help: the trait `Sum<()>` is not implemented for `i32`
    = help: the following other types implement trait `Sum<A>`:
-             `i32` implements `Sum<&'a i32>`
+             `i32` implements `Sum<&i32>`
              `i32` implements `Sum`
 note: the method call chain might not have had the expected associated types
   --> $DIR/invalid-iterator-chain-fixable.rs:27:38