Rollup of 5 pull requests

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -7,6 +7,7 @@ use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, Upcast};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
+use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
 use rustc_trait_selection::traits::ObligationCause;
 
@@ -165,6 +166,52 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         result.unwrap_or(value)
     }
 
+    #[instrument(skip(self), level = "debug")]
+    pub(super) fn struct_tail(
+        &mut self,
+        ty: Ty<'tcx>,
+        location: impl NormalizeLocation,
+    ) -> Ty<'tcx> {
+        let tcx = self.tcx();
+        if self.infcx.next_trait_solver() {
+            let body = self.body;
+            let param_env = self.param_env;
+            self.fully_perform_op(
+                location.to_locations(),
+                ConstraintCategory::Boring,
+                CustomTypeOp::new(
+                    |ocx| {
+                        let structurally_normalize = |ty| {
+                            ocx.structurally_normalize(
+                                &ObligationCause::misc(
+                                    location.to_locations().span(body),
+                                    body.source.def_id().expect_local(),
+                                ),
+                                param_env,
+                                ty,
+                            )
+                            .unwrap_or_else(|_| bug!("struct tail should have been computable, since we computed it in HIR"))
+                        };
+
+                        let tail = tcx.struct_tail_raw(
+                            ty,
+                            structurally_normalize,
+                            || {},
+                        );
+
+                        Ok(tail)
+                    },
+                    "normalizing struct tail",
+                ),
+            )
+            .unwrap_or_else(|guar| Ty::new_error(tcx, guar))
+        } else {
+            let mut normalize = |ty| self.normalize(ty, location);
+            let tail = tcx.struct_tail_raw(ty, &mut normalize, || {});
+            normalize(tail)
+        }
+    }
+
     #[instrument(skip(self), level = "debug")]
     pub(super) fn ascribe_user_type(
         &mut self,

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2329,17 +2329,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
                             (Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => {
-                                let mut normalize = |t| self.normalize(t, location);
-
-                                // N.B. `struct_tail_with_normalize` only "structurally resolves"
-                                // the type. It is not fully normalized, so we have to normalize it
-                                // afterwards.
-                                let src_tail =
-                                    tcx.struct_tail_with_normalize(src.ty, &mut normalize, || ());
-                                let src_tail = normalize(src_tail);
-                                let dst_tail =
-                                    tcx.struct_tail_with_normalize(dst.ty, &mut normalize, || ());
-                                let dst_tail = normalize(dst_tail);
+                                let src_tail = self.struct_tail(src.ty, location);
+                                let dst_tail = self.struct_tail(dst.ty, location);
 
                                 // This checks (lifetime part of) vtable validity for pointer casts,
                                 // which is irrelevant when there are aren't principal traits on both sides (aka only auto traits).

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -226,7 +226,7 @@ pub(super) fn op_to_const<'tcx>(
                 let pointee_ty = imm.layout.ty.builtin_deref(false).unwrap(); // `false` = no raw ptrs
                 debug_assert!(
                     matches!(
-                        ecx.tcx.struct_tail_without_normalization(pointee_ty).kind(),
+                        ecx.tcx.struct_tail_for_codegen(pointee_ty, ecx.param_env).kind(),
                         ty::Str | ty::Slice(..),
                     ),
                     "`ConstValue::Slice` is for slice-tailed types only, but got {}",

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -195,7 +195,7 @@ fn reconstruct_place_meta<'tcx>(
 
     let mut last_valtree = valtree;
     // Traverse the type, and update `last_valtree` as we go.
-    let tail = tcx.struct_tail_with_normalize(
+    let tail = tcx.struct_tail_raw(
         layout.ty,
         |ty| ty,
         || {

compiler/rustc_hir_analysis/src/collect.rs

@@ -1700,6 +1700,8 @@ fn impl_trait_header(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::ImplTrai
             trait_ref: ty::EarlyBinder::bind(trait_ref),
             safety: impl_.safety,
             polarity: polarity_of_impl(tcx, def_id, impl_, item.span),
+            do_not_recommend: tcx.features().do_not_recommend
+                && tcx.has_attrs_with_path(def_id, &[sym::diagnostic, sym::do_not_recommend]),
         }
     })
 }

compiler/rustc_hir_typeck/src/cast.rs

@@ -97,6 +97,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return Ok(Some(PointerKind::Thin));
         }
 
+        let t = self.try_structurally_resolve_type(span, t);
+
         Ok(match *t.kind() {
             ty::Slice(_) | ty::Str => Some(PointerKind::Length),
             ty::Dynamic(tty, _, ty::Dyn) => Some(PointerKind::VTable(tty)),

compiler/rustc_hir_typeck/src/expectation.rs

@@ -70,7 +70,8 @@ impl<'a, 'tcx> Expectation<'tcx> {
     /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
     /// for examples of where this comes up,.
     pub(super) fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
-        match fcx.tcx.struct_tail_without_normalization(ty).kind() {
+        // FIXME: This is not right, even in the old solver...
+        match fcx.tcx.struct_tail_raw(ty, |ty| ty, || {}).kind() {
             ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
             _ => ExpectHasType(ty),
         }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -404,7 +404,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         code: traits::ObligationCauseCode<'tcx>,
     ) {
         if !ty.references_error() {
-            let tail = self.tcx.struct_tail_with_normalize(
+            let tail = self.tcx.struct_tail_raw(
                 ty,
                 |ty| {
                     if self.next_trait_solver() {

compiler/rustc_middle/src/ty/context.rs

@@ -3176,6 +3176,12 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn impl_polarity(self, def_id: impl IntoQueryParam<DefId>) -> ty::ImplPolarity {
         self.impl_trait_header(def_id).map_or(ty::ImplPolarity::Positive, |h| h.polarity)
     }
+
+    /// Whether this is a trait implementation that has `#[diagnostic::do_not_recommend]`
+    pub fn do_not_recommend_impl(self, def_id: DefId) -> bool {
+        matches!(self.def_kind(def_id), DefKind::Impl { of_trait: true })
+            && self.impl_trait_header(def_id).is_some_and(|header| header.do_not_recommend)
+    }
 }
 
 /// Parameter attributes that can only be determined by examining the body of a function instead

compiler/rustc_middle/src/ty/layout.rs

@@ -362,7 +362,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
             ty::Ref(_, pointee, _) | ty::RawPtr(pointee, _) => {
                 let non_zero = !ty.is_unsafe_ptr();
 
-                let tail = tcx.struct_tail_with_normalize(
+                let tail = tcx.struct_tail_raw(
                     pointee,
                     |ty| match tcx.try_normalize_erasing_regions(param_env, ty) {
                         Ok(ty) => ty,

compiler/rustc_middle/src/ty/mod.rs

@@ -262,6 +262,7 @@ pub struct ImplTraitHeader<'tcx> {
     pub trait_ref: ty::EarlyBinder<'tcx, ty::TraitRef<'tcx>>,
     pub polarity: ImplPolarity,
     pub safety: hir::Safety,
+    pub do_not_recommend: bool,
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TypeFoldable, TypeVisitable)]

compiler/rustc_middle/src/ty/sty.rs

@@ -1590,7 +1590,7 @@ impl<'tcx> Ty<'tcx> {
         tcx: TyCtxt<'tcx>,
         normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
     ) -> Result<Ty<'tcx>, Ty<'tcx>> {
-        let tail = tcx.struct_tail_with_normalize(self, normalize, || {});
+        let tail = tcx.struct_tail_raw(self, normalize, || {});
         match tail.kind() {
             // Sized types
             ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
@@ -1614,10 +1614,10 @@ impl<'tcx> Ty<'tcx> {
             | ty::Foreign(..)
             // `dyn*` has metadata = ().
             | ty::Dynamic(_, _, ty::DynStar)
-            // If returned by `struct_tail_with_normalize` this is a unit struct
+            // If returned by `struct_tail_raw` this is a unit struct
             // without any fields, or not a struct, and therefore is Sized.
             | ty::Adt(..)
-            // If returned by `struct_tail_with_normalize` this is the empty tuple,
+            // If returned by `struct_tail_raw` this is the empty tuple,
             // a.k.a. unit type, which is Sized
             | ty::Tuple(..) => Ok(tcx.types.unit),
 

compiler/rustc_middle/src/ty/util.rs

@@ -171,14 +171,6 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    /// Attempts to returns the deeply last field of nested structures, but
-    /// does not apply any normalization in its search. Returns the same type
-    /// if input `ty` is not a structure at all.
-    pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let tcx = self;
-        tcx.struct_tail_with_normalize(ty, |ty| ty, || {})
-    }
-
     /// Returns the deeply last field of nested structures, or the same type if
     /// not a structure at all. Corresponds to the only possible unsized field,
     /// and its type can be used to determine unsizing strategy.
@@ -188,20 +180,22 @@ impl<'tcx> TyCtxt<'tcx> {
     /// normalization attempt may cause compiler bugs.
     pub fn struct_tail_for_codegen(self, ty: Ty<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
         let tcx = self;
-        tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
+        tcx.struct_tail_raw(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
     }
 
     /// Returns the deeply last field of nested structures, or the same type if
     /// not a structure at all. Corresponds to the only possible unsized field,
     /// and its type can be used to determine unsizing strategy.
     ///
     /// This is parameterized over the normalization strategy (i.e. how to
-    /// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity
-    /// function to indicate no normalization should take place.
+    /// handle `<T as Trait>::Assoc` and `impl Trait`). You almost certainly do
+    /// **NOT** want to pass the identity function here, unless you know what
+    /// you're doing, or you're within normalization code itself and will handle
+    /// an unnormalized tail recursively.
     ///
     /// See also `struct_tail_for_codegen`, which is suitable for use
     /// during codegen.
-    pub fn struct_tail_with_normalize(
+    pub fn struct_tail_raw(
         self,
         mut ty: Ty<'tcx>,
         mut normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
@@ -281,7 +275,7 @@ impl<'tcx> TyCtxt<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
     ) -> (Ty<'tcx>, Ty<'tcx>) {
         let tcx = self;
-        tcx.struct_lockstep_tails_with_normalize(source, target, |ty| {
+        tcx.struct_lockstep_tails_raw(source, target, |ty| {
             tcx.normalize_erasing_regions(param_env, ty)
         })
     }
@@ -294,7 +288,7 @@ impl<'tcx> TyCtxt<'tcx> {
     ///
     /// See also `struct_lockstep_tails_for_codegen`, which is suitable for use
     /// during codegen.
-    pub fn struct_lockstep_tails_with_normalize(
+    pub fn struct_lockstep_tails_raw(
         self,
         source: Ty<'tcx>,
         target: Ty<'tcx>,

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

@@ -687,10 +687,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let mut applied_do_not_recommend = false;
         loop {
             if let ObligationCauseCode::ImplDerived(ref c) = base_cause {
-                if self.tcx.has_attrs_with_path(
-                    c.impl_or_alias_def_id,
-                    &[sym::diagnostic, sym::do_not_recommend],
-                ) {
+                if self.tcx.do_not_recommend_impl(c.impl_or_alias_def_id) {
                     let code = (*c.derived.parent_code).clone();
                     obligation.cause.map_code(|_| code);
                     obligation.predicate = c.derived.parent_trait_pred.upcast(self.tcx);
@@ -1629,11 +1626,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 .tcx
                 .all_impls(def_id)
                 // ignore `do_not_recommend` items
-                .filter(|def_id| {
-                    !self
-                        .tcx
-                        .has_attrs_with_path(*def_id, &[sym::diagnostic, sym::do_not_recommend])
-                })
+                .filter(|def_id| !self.tcx.do_not_recommend_impl(*def_id))
                 // Ignore automatically derived impls and `!Trait` impls.
                 .filter_map(|def_id| self.tcx.impl_trait_header(def_id))
                 .filter_map(|header| {
@@ -1903,12 +1896,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let impl_candidates = impl_candidates
             .into_iter()
             .cloned()
-            .filter(|cand| {
-                !self.tcx.has_attrs_with_path(
-                    cand.impl_def_id,
-                    &[sym::diagnostic, sym::do_not_recommend],
-                )
-            })
+            .filter(|cand| !self.tcx.do_not_recommend_impl(cand.impl_def_id))
             .collect::<Vec<_>>();
 
         let def_id = trait_ref.def_id();

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -13,7 +13,6 @@ use rustc_middle::bug;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_next_trait_solver::solve::{GenerateProofTree, SolverDelegateEvalExt as _};
-use rustc_span::symbol::sym;
 
 use super::delegate::SolverDelegate;
 use super::inspect::{self, ProofTreeInferCtxtExt, ProofTreeVisitor};
@@ -440,10 +439,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             source: CandidateSource::Impl(impl_def_id),
             result: _,
         } = candidate.kind()
-            && goal
-                .infcx()
-                .tcx
-                .has_attrs_with_path(impl_def_id, &[sym::diagnostic, sym::do_not_recommend])
+            && goal.infcx().tcx.do_not_recommend_impl(impl_def_id)
         {
             return ControlFlow::Break(self.obligation.clone());
         }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1110,7 +1110,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                         | ty::Error(_) => false,
                     }
                 } else if tcx.is_lang_item(trait_ref.def_id, LangItem::PointeeTrait) {
-                    let tail = selcx.tcx().struct_tail_with_normalize(
+                    let tail = selcx.tcx().struct_tail_raw(
                         self_ty,
                         |ty| {
                             // We throw away any obligations we get from this, since we normalize
@@ -1149,10 +1149,10 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                         | ty::Never
                         // Extern types have unit metadata, according to RFC 2850
                         | ty::Foreign(_)
-                        // If returned by `struct_tail_without_normalization` this is a unit struct
+                        // If returned by `struct_tail` this is a unit struct
                         // without any fields, or not a struct, and therefore is Sized.
                         | ty::Adt(..)
-                        // If returned by `struct_tail_without_normalization` this is the empty tuple.
+                        // If returned by `struct_tail` this is the empty tuple.
                         | ty::Tuple(..)
                         // Integers and floats are always Sized, and so have unit type metadata.
                         | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true,

compiler/rustc_ty_utils/src/layout.rs

@@ -219,9 +219,13 @@ fn layout_of_uncached<'tcx>(
                             // its struct tail cannot be normalized either, so try to get a
                             // more descriptive layout error here, which will lead to less confusing
                             // diagnostics.
+                            //
+                            // We use the raw struct tail function here to get the first tail
+                            // that is an alias, which is likely the cause of the normalization
+                            // error.
                             match tcx.try_normalize_erasing_regions(
                                 param_env,
-                                tcx.struct_tail_without_normalization(pointee),
+                                tcx.struct_tail_raw(pointee, |ty| ty, || {}),
                             ) {
                                 Ok(_) => {}
                                 Err(better_err) => {

library/alloc/src/fmt.rs

@@ -581,7 +581,7 @@ pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::Error;
 #[unstable(feature = "debug_closure_helpers", issue = "117729")]
-pub use core::fmt::FormatterFn;
+pub use core::fmt::{from_fn, FromFn};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{write, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]