Auto merge of #130016 - matthiaskrgr:rollup-fopistw, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #129021 (Check WF of source type's signature on fn pointer cast)
 - #129781 (Make `./x.py <cmd> compiler/<crate>` aware of the crate's features)
 - #129963 (Inaccurate `{Path,OsStr}::to_string_lossy()` documentation)
 - #129969 (Make `Ty::boxed_ty` return an `Option`)
 - #129995 (Remove wasm32-wasip2's tier 2 status from release notes)
 - #130013 (coverage: Count await when the Future is immediately ready )

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

RELEASES.md

@@ -34,7 +34,6 @@ Compiler
   - [Add Tier 3 `std` Xtensa targets:](https://github.com/rust-lang/rust/pull/126380/) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf`
   - [Add Tier 3 i686 Redox OS target:](https://github.com/rust-lang/rust/pull/126192/) `i686-unknown-redox`
   - [Promote `arm64ec-pc-windows-msvc` to Tier 2.](https://github.com/rust-lang/rust/pull/126039/)
-  - [Promote `wasm32-wasip2` to Tier 2.](https://github.com/rust-lang/rust/pull/126967/)
   - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.](https://github.com/rust-lang/rust/pull/126298/)
   - [Enable full tools and profiler for LoongArch Linux targets.](https://github.com/rust-lang/rust/pull/127078/)
   - [Unconditionally warn on usage of `wasm32-wasi`.](https://github.com/rust-lang/rust/pull/126662/) (see compatibility note below)

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -662,9 +662,10 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
                                                 // `&dyn Trait`
                                                 ty::Ref(_, ty, _) if ty.is_trait() => true,
                                                 // `Box<dyn Trait>`
-                                                _ if ty.is_box() && ty.boxed_ty().is_trait() => {
+                                                _ if ty.boxed_ty().is_some_and(Ty::is_trait) => {
                                                     true
                                                 }
+
                                                 // `dyn Trait`
                                                 _ if ty.is_trait() => true,
                                                 // Anything else.

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -345,9 +345,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
         variant_index: Option<VariantIdx>,
         including_tuple_field: IncludingTupleField,
     ) -> Option<String> {
-        if ty.is_box() {
+        if let Some(boxed_ty) = ty.boxed_ty() {
             // If the type is a box, the field is described from the boxed type
-            self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field)
+            self.describe_field_from_ty(boxed_ty, field, variant_index, including_tuple_field)
         } else {
             match *ty.kind() {
                 ty::Adt(def, _) => {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1979,19 +1979,76 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                 match cast_kind {
                     CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
-                        let fn_sig = op.ty(body, tcx).fn_sig(tcx);
+                        let src_sig = op.ty(body, tcx).fn_sig(tcx);
+
+                        // HACK: This shouldn't be necessary... We can remove this when we actually
+                        // get binders with where clauses, then elaborate implied bounds into that
+                        // binder, and implement a higher-ranked subtyping algorithm that actually
+                        // respects these implied bounds.
+                        //
+                        // This protects against the case where we are casting from a higher-ranked
+                        // fn item to a non-higher-ranked fn pointer, where the cast throws away
+                        // implied bounds that would've needed to be checked at the call site. This
+                        // only works when we're casting to a non-higher-ranked fn ptr, since
+                        // placeholders in the target signature could have untracked implied
+                        // bounds, resulting in incorrect errors.
+                        //
+                        // We check that this signature is WF before subtyping the signature with
+                        // the target fn sig.
+                        if src_sig.has_bound_regions()
+                            && let ty::FnPtr(target_fn_tys, target_hdr) = *ty.kind()
+                            && let target_sig = target_fn_tys.with(target_hdr)
+                            && let Some(target_sig) = target_sig.no_bound_vars()
+                        {
+                            let src_sig = self.infcx.instantiate_binder_with_fresh_vars(
+                                span,
+                                BoundRegionConversionTime::HigherRankedType,
+                                src_sig,
+                            );
+                            let src_ty = Ty::new_fn_ptr(self.tcx(), ty::Binder::dummy(src_sig));
+                            self.prove_predicate(
+                                ty::ClauseKind::WellFormed(src_ty.into()),
+                                location.to_locations(),
+                                ConstraintCategory::Cast { unsize_to: None },
+                            );
+
+                            let src_ty = self.normalize(src_ty, location);
+                            if let Err(terr) = self.sub_types(
+                                src_ty,
+                                *ty,
+                                location.to_locations(),
+                                ConstraintCategory::Cast { unsize_to: None },
+                            ) {
+                                span_mirbug!(
+                                    self,
+                                    rvalue,
+                                    "equating {:?} with {:?} yields {:?}",
+                                    target_sig,
+                                    src_sig,
+                                    terr
+                                );
+                            };
+                        }
+
+                        let src_ty = Ty::new_fn_ptr(tcx, src_sig);
+                        // HACK: We want to assert that the signature of the source fn is
+                        // well-formed, because we don't enforce that via the WF of FnDef
+                        // types normally. This should be removed when we improve the tracking
+                        // of implied bounds of fn signatures.
+                        self.prove_predicate(
+                            ty::ClauseKind::WellFormed(src_ty.into()),
+                            location.to_locations(),
+                            ConstraintCategory::Cast { unsize_to: None },
+                        );
 
                         // The type that we see in the fcx is like
                         // `foo::<'a, 'b>`, where `foo` is the path to a
                         // function definition. When we extract the
                         // signature, it comes from the `fn_sig` query,
                         // and hence may contain unnormalized results.
-                        let fn_sig = self.normalize(fn_sig, location);
-
-                        let ty_fn_ptr_from = Ty::new_fn_ptr(tcx, fn_sig);
-
+                        let src_ty = self.normalize(src_ty, location);
                         if let Err(terr) = self.sub_types(
-                            ty_fn_ptr_from,
+                            src_ty,
                             *ty,
                             location.to_locations(),
                             ConstraintCategory::Cast { unsize_to: None },
@@ -2000,7 +2057,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 self,
                                 rvalue,
                                 "equating {:?} with {:?} yields {:?}",
-                                ty_fn_ptr_from,
+                                src_ty,
                                 ty,
                                 terr
                             );

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -456,7 +456,7 @@ pub(crate) fn type_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>) ->
             if def.is_box()
                 && args.get(1).map_or(true, |arg| cx.layout_of(arg.expect_ty()).is_1zst()) =>
         {
-            build_pointer_or_reference_di_node(cx, t, t.boxed_ty(), unique_type_id)
+            build_pointer_or_reference_di_node(cx, t, t.expect_boxed_ty(), unique_type_id)
         }
         ty::FnDef(..) | ty::FnPtr(..) => build_subroutine_type_di_node(cx, unique_type_id),
         ty::Closure(..) => build_closure_env_di_node(cx, unique_type_id),

compiler/rustc_const_eval/src/interpret/call.rs

@@ -189,7 +189,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 ty::Ref(_, ty, _) => *ty,
                 ty::RawPtr(ty, _) => *ty,
                 // We only accept `Box` with the default allocator.
-                _ if ty.is_box_global(*self.tcx) => ty.boxed_ty(),
+                _ if ty.is_box_global(*self.tcx) => ty.expect_boxed_ty(),
                 _ => return Ok(None),
             }))
         };

compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs

@@ -63,8 +63,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // Instead, the problem is that the array-into_iter hack will no longer
                     // apply in Rust 2021.
                     (ARRAY_INTO_ITER, "2021")
-                } else if self_ty.is_box()
-                    && self_ty.boxed_ty().is_slice()
+                } else if self_ty.boxed_ty().is_some_and(Ty::is_slice)
                     && !span.at_least_rust_2024()
                 {
                     // In this case, it wasn't really a prelude addition that was the problem.

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1485,8 +1485,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
                         // Some trait methods are excluded for boxed slices before 2024.
                         // (`boxed_slice.into_iter()` wants a slice iterator for compatibility.)
-                        if self_ty.is_box()
-                            && self_ty.boxed_ty().is_slice()
+                        if self_ty.boxed_ty().is_some_and(Ty::is_slice)
                             && !method_name.span.at_least_rust_2024()
                         {
                             let trait_def = self.tcx.trait_def(poly_trait_ref.def_id());

compiler/rustc_lint/src/shadowed_into_iter.rs

@@ -94,12 +94,9 @@ impl<'tcx> LateLintPass<'tcx> for ShadowedIntoIter {
         fn is_ref_to_array(ty: Ty<'_>) -> bool {
             if let ty::Ref(_, pointee_ty, _) = *ty.kind() { pointee_ty.is_array() } else { false }
         }
-        fn is_boxed_slice(ty: Ty<'_>) -> bool {
-            ty.is_box() && ty.boxed_ty().is_slice()
-        }
         fn is_ref_to_boxed_slice(ty: Ty<'_>) -> bool {
             if let ty::Ref(_, pointee_ty, _) = *ty.kind() {
-                is_boxed_slice(pointee_ty)
+                pointee_ty.boxed_ty().is_some_and(Ty::is_slice)
             } else {
                 false
             }
@@ -119,7 +116,7 @@ impl<'tcx> LateLintPass<'tcx> for ShadowedIntoIter {
                     .iter()
                     .copied()
                     .take_while(|ty| !is_ref_to_boxed_slice(*ty))
-                    .position(|ty| is_boxed_slice(ty))
+                    .position(|ty| ty.boxed_ty().is_some_and(Ty::is_slice))
             {
                 (BOXED_SLICE_INTO_ITER, "Box<[T]>", "2024", idx == 0)
             } else {

compiler/rustc_lint/src/types.rs

@@ -1304,8 +1304,10 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
         match *ty.kind() {
             ty::Adt(def, args) => {
-                if def.is_box() && matches!(self.mode, CItemKind::Definition) {
-                    if ty.boxed_ty().is_sized(tcx, self.cx.param_env) {
+                if let Some(boxed) = ty.boxed_ty()
+                    && matches!(self.mode, CItemKind::Definition)
+                {
+                    if boxed.is_sized(tcx, self.cx.param_env) {
                         return FfiSafe;
                     } else {
                         return FfiUnsafe {

compiler/rustc_lint/src/unused.rs

@@ -283,9 +283,8 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
             }
 
             match *ty.kind() {
-                ty::Adt(..) if ty.is_box() => {
-                    let boxed_ty = ty.boxed_ty();
-                    is_ty_must_use(cx, boxed_ty, expr, span)
+                ty::Adt(..) if let Some(boxed) = ty.boxed_ty() => {
+                    is_ty_must_use(cx, boxed, expr, span)
                         .map(|inner| MustUsePath::Boxed(Box::new(inner)))
                 }
                 ty::Adt(def, args) if cx.tcx.is_lang_item(def.did(), LangItem::Pin) => {

compiler/rustc_middle/src/ty/layout.rs

@@ -1075,11 +1075,13 @@ where
                 // the raw pointer, so size and align are set to the boxed type, but `pointee.safe`
                 // will still be `None`.
                 if let Some(ref mut pointee) = result {
-                    if offset.bytes() == 0 && this.ty.is_box() {
+                    if offset.bytes() == 0
+                        && let Some(boxed_ty) = this.ty.boxed_ty()
+                    {
                         debug_assert!(pointee.safe.is_none());
                         let optimize = tcx.sess.opts.optimize != OptLevel::No;
                         pointee.safe = Some(PointerKind::Box {
-                            unpin: optimize && this.ty.boxed_ty().is_unpin(tcx, cx.param_env()),
+                            unpin: optimize && boxed_ty.is_unpin(tcx, cx.param_env()),
                             global: this.ty.is_box_global(tcx),
                         });
                     }

compiler/rustc_middle/src/ty/sty.rs

@@ -1170,14 +1170,19 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
-    /// Panics if called on any type other than `Box<T>`.
-    pub fn boxed_ty(self) -> Ty<'tcx> {
+    pub fn boxed_ty(self) -> Option<Ty<'tcx>> {
         match self.kind() {
-            Adt(def, args) if def.is_box() => args.type_at(0),
-            _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
+            Adt(def, args) if def.is_box() => Some(args.type_at(0)),
+            _ => None,
         }
     }
 
+    /// Panics if called on any type other than `Box<T>`.
+    pub fn expect_boxed_ty(self) -> Ty<'tcx> {
+        self.boxed_ty()
+            .unwrap_or_else(|| bug!("`expect_boxed_ty` is called on non-box type {:?}", self))
+    }
+
     /// A scalar type is one that denotes an atomic datum, with no sub-components.
     /// (A RawPtr is scalar because it represents a non-managed pointer, so its
     /// contents are abstract to rustc.)
@@ -1323,7 +1328,7 @@ impl<'tcx> Ty<'tcx> {
     /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
     pub fn builtin_deref(self, explicit: bool) -> Option<Ty<'tcx>> {
         match *self.kind() {
-            Adt(def, _) if def.is_box() => Some(self.boxed_ty()),
+            _ if let Some(boxed) = self.boxed_ty() => Some(boxed),
             Ref(_, ty, _) => Some(ty),
             RawPtr(ty, _) if explicit => Some(ty),
             _ => None,

compiler/rustc_middle/src/ty/util.rs

@@ -1628,7 +1628,7 @@ impl<'tcx> ExplicitSelf<'tcx> {
             _ if is_self_ty(self_arg_ty) => ByValue,
             ty::Ref(region, ty, mutbl) if is_self_ty(ty) => ByReference(region, mutbl),
             ty::RawPtr(ty, mutbl) if is_self_ty(ty) => ByRawPointer(mutbl),
-            ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
+            _ if self_arg_ty.boxed_ty().is_some_and(is_self_ty) => ByBox,
             _ => Other,
         }
     }

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -3,7 +3,7 @@ use std::collections::VecDeque;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir;
-use rustc_span::Span;
+use rustc_span::{DesugaringKind, ExpnKind, MacroKind, Span};
 use tracing::{debug, debug_span, instrument};
 
 use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
@@ -25,7 +25,7 @@ pub(super) fn extract_refined_covspans(
 
     // First, perform the passes that need macro information.
     covspans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
-    remove_unwanted_macro_spans(&mut covspans);
+    remove_unwanted_expansion_spans(&mut covspans);
     split_visible_macro_spans(&mut covspans);
 
     // We no longer need the extra information in `SpanFromMir`, so convert to `Covspan`.
@@ -76,18 +76,24 @@ pub(super) fn extract_refined_covspans(
 /// invocation, which is unhelpful. Keeping only the first such span seems to
 /// give better mappings, so remove the others.
 ///
+/// Similarly, `await` expands to a branch on the discriminant of `Poll`, which
+/// leads to incorrect coverage if the `Future` is immediately ready (#98712).
+///
 /// (The input spans should be sorted in BCB dominator order, so that the
 /// retained "first" span is likely to dominate the others.)
-fn remove_unwanted_macro_spans(covspans: &mut Vec<SpanFromMir>) {
-    let mut seen_macro_spans = FxHashSet::default();
+fn remove_unwanted_expansion_spans(covspans: &mut Vec<SpanFromMir>) {
+    let mut deduplicated_spans = FxHashSet::default();
+
     covspans.retain(|covspan| {
-        // Ignore (retain) non-macro-expansion spans.
-        if covspan.visible_macro.is_none() {
-            return true;
+        match covspan.expn_kind {
+            // Retain only the first await-related or macro-expanded covspan with this span.
+            Some(ExpnKind::Desugaring(kind)) if kind == DesugaringKind::Await => {
+                deduplicated_spans.insert(covspan.span)
+            }
+            Some(ExpnKind::Macro(MacroKind::Bang, _)) => deduplicated_spans.insert(covspan.span),
+            // Ignore (retain) other spans.
+            _ => true,
         }
-
-        // Retain only the first macro-expanded covspan with this span.
-        seen_macro_spans.insert(covspan.span)
     });
 }
 
@@ -99,7 +105,9 @@ fn split_visible_macro_spans(covspans: &mut Vec<SpanFromMir>) {
     let mut extra_spans = vec![];
 
     covspans.retain(|covspan| {
-        let Some(visible_macro) = covspan.visible_macro else { return true };
+        let Some(ExpnKind::Macro(MacroKind::Bang, visible_macro)) = covspan.expn_kind else {
+            return true;
+        };
 
         let split_len = visible_macro.as_str().len() as u32 + 1;
         let (before, after) = covspan.span.split_at(split_len);
@@ -111,8 +119,8 @@ fn split_visible_macro_spans(covspans: &mut Vec<SpanFromMir>) {
             return true;
         }
 
-        extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb));
-        extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb));
+        extra_spans.push(SpanFromMir::new(before, covspan.expn_kind.clone(), covspan.bcb));
+        extra_spans.push(SpanFromMir::new(after, covspan.expn_kind.clone(), covspan.bcb));
         false // Discard the original covspan that we just split.
     });