Auto merge of #129595 - matthiaskrgr:rollup-4udn7nn, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #129288 (Use subtyping for `UnsafeFnPointer` coercion, too)
 - #129405 (Fixing span manipulation and indentation of the suggestion introduced by #126187)
 - #129518 (gitignore: ignore ICE reports regardless of directory)
 - #129519 (Remove redundant flags from `lower_ty_common` that can be inferred from the HIR)
 - #129525 (rustdoc: clean up tuple <-> primitive conversion docs)
 - #129526 (Use `FxHasher` on new solver unconditionally)
 - #129544 (Removes dead code from the compiler)
 - #129553 (add back test for stable-const-can-only-call-stable-const)
 - #129590 (Avoid taking reference of &TyKind)

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

.gitignore

@@ -56,7 +56,9 @@ build/
 /src/tools/x/target
 # Created by default with `src/ci/docker/run.sh`
 /obj/
-/rustc-ice*
+
+## ICE reports
+rustc-ice-*.txt
 
 ## Temporary files
 *~

Cargo.lock

@@ -4536,6 +4536,7 @@ dependencies = [
  "bitflags 2.6.0",
  "derive-where",
  "indexmap",
+ "rustc-hash",
  "rustc_ast_ir",
  "rustc_data_structures",
  "rustc_index",

compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -290,7 +290,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
         ty: Ty<'_>,
         is_index: Option<bool>,
     ) -> Diag<'infcx> {
-        let type_name = match (&ty.kind(), is_index) {
+        let type_name = match (ty.kind(), is_index) {
             (&ty::Array(_, _), Some(true)) | (&ty::Array(_, _), None) => "array",
             (&ty::Slice(_), _) => "slice",
             _ => span_bug!(move_from_span, "this path should not cause illegal move"),

compiler/rustc_borrowck/src/places_conflict.rs

@@ -201,7 +201,7 @@ fn place_components_conflict<'tcx>(
 
             let base_ty = base.ty(body, tcx).ty;
 
-            match (elem, &base_ty.kind(), access) {
+            match (elem, base_ty.kind(), access) {
                 (_, _, Shallow(Some(ArtificialField::ArrayLength)))
                 | (_, _, Shallow(Some(ArtificialField::FakeBorrow))) => {
                     // The array length is like additional fields on the

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2043,9 +2043,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
 
-                        if let Err(terr) = self.eq_types(
-                            *ty,
+                        if let Err(terr) = self.sub_types(
                             ty_fn_ptr_from,
+                            *ty,
                             location.to_locations(),
                             ConstraintCategory::Cast { unsize_to: None },
                         ) {

compiler/rustc_const_eval/messages.ftl

@@ -419,7 +419,7 @@ const_eval_unstable_const_fn = `{$def_path}` is not yet stable as a const fn
 const_eval_unstable_in_stable =
     const-stable function cannot use `#[feature({$gate})]`
     .unstable_sugg = if it is not part of the public API, make this function unstably const
-    .bypass_sugg = otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
+    .bypass_sugg = otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks (but requires team approval)
 
 const_eval_unterminated_c_string =
     reading a null-terminated string starting at {$pointer} with no null found before end of allocation

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -388,7 +388,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let (src_pointee_ty, dest_pointee_ty) =
             self.tcx.struct_lockstep_tails_for_codegen(source_ty, cast_ty, self.param_env);
 
-        match (&src_pointee_ty.kind(), &dest_pointee_ty.kind()) {
+        match (src_pointee_ty.kind(), dest_pointee_ty.kind()) {
             (&ty::Array(_, length), &ty::Slice(_)) => {
                 let ptr = self.read_pointer(src)?;
                 let val = Immediate::new_slice(
@@ -478,9 +478,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         dest: &PlaceTy<'tcx, M::Provenance>,
     ) -> InterpResult<'tcx> {
         trace!("Unsizing {:?} of type {} into {}", *src, src.layout.ty, cast_ty.ty);
-        match (&src.layout.ty.kind(), &cast_ty.ty.kind()) {
+        match (src.layout.ty.kind(), cast_ty.ty.kind()) {
             (&ty::Ref(_, s, _), &ty::Ref(_, c, _) | &ty::RawPtr(c, _))
-            | (&ty::RawPtr(s, _), &ty::RawPtr(c, _)) => self.unsize_into_ptr(src, dest, *s, *c),
+            | (&ty::RawPtr(s, _), &ty::RawPtr(c, _)) => self.unsize_into_ptr(src, dest, s, c),
             (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
                 assert_eq!(def_a, def_b); // implies same number of fields
 

compiler/rustc_hir_analysis/src/collect.rs

@@ -392,7 +392,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
     }
 
     fn re_infer(&self, span: Span, reason: RegionInferReason<'_>) -> ty::Region<'tcx> {
-        if let RegionInferReason::BorrowedObjectLifetimeDefault = reason {
+        if let RegionInferReason::ObjectLifetimeDefault = reason {
             let e = struct_span_code_err!(
                 self.dcx(),
                 span,

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -608,7 +608,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let mut bound_span_label = |self_ty: Ty<'_>, obligation: &str, quiet: &str| {
             let msg = format!("`{}`", if obligation.len() > 50 { quiet } else { obligation });
-            match &self_ty.kind() {
+            match self_ty.kind() {
                 // Point at the type that couldn't satisfy the bound.
                 ty::Adt(def, _) => {
                     bound_spans.get_mut_or_insert_default(tcx.def_span(def.did())).push(msg)

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -15,11 +15,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ///
     /// *Bare* trait object types are ones that aren't preceded by the keyword `dyn`.
     /// In edition 2021 and onward we emit a hard error for them.
-    pub(super) fn prohibit_or_lint_bare_trait_object_ty(
-        &self,
-        self_ty: &hir::Ty<'_>,
-        in_path: bool,
-    ) {
+    pub(super) fn prohibit_or_lint_bare_trait_object_ty(&self, self_ty: &hir::Ty<'_>) {
         let tcx = self.tcx();
 
         let hir::TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
@@ -28,6 +24,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             return;
         };
 
+        let in_path = match tcx.parent_hir_node(self_ty.hir_id) {
+            hir::Node::Ty(hir::Ty {
+                kind: hir::TyKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            })
+            | hir::Node::Expr(hir::Expr {
+                kind: hir::ExprKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            })
+            | hir::Node::Pat(hir::Pat {
+                kind: hir::PatKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            }) if qself.hir_id == self_ty.hir_id => true,
+            _ => false,
+        };
         let needs_bracket = in_path
             && !tcx
                 .sess

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -85,10 +85,9 @@ pub enum PredicateFilter {
 
 #[derive(Debug)]
 pub enum RegionInferReason<'a> {
-    /// Lifetime on a trait object behind a reference.
-    /// This allows inferring information from the reference.
-    BorrowedObjectLifetimeDefault,
-    /// A trait object's lifetime.
+    /// Lifetime on a trait object that is spelled explicitly, e.g. `+ 'a` or `+ '_`.
+    ExplicitObjectLifetime,
+    /// A trait object's lifetime when it is elided, e.g. `dyn Any`.
     ObjectLifetimeDefault,
     /// Generic lifetime parameter
     Param(&'a ty::GenericParamDef),
@@ -1057,7 +1056,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         // Find the type of the associated item, and the trait where the associated
         // item is declared.
-        let bound = match (&qself_ty.kind(), qself_res) {
+        let bound = match (qself_ty.kind(), qself_res) {
             (_, Res::SelfTyAlias { alias_to: impl_def_id, is_trait_impl: true, .. }) => {
                 // `Self` in an impl of a trait -- we have a concrete self type and a
                 // trait reference.
@@ -1999,16 +1998,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
-    /// Lower a type from the HIR to our internal notion of a type.
-    pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
-        self.lower_ty_common(hir_ty, false, false)
-    }
-
-    /// Lower a type inside of a path from the HIR to our internal notion of a type.
-    pub fn lower_ty_in_path(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
-        self.lower_ty_common(hir_ty, false, true)
-    }
-
     fn lower_delegation_ty(&self, idx: hir::InferDelegationKind) -> Ty<'tcx> {
         let delegation_sig = self.tcx().inherit_sig_for_delegation_item(self.item_def_id());
         match idx {
@@ -2026,7 +2015,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// 2. `in_path`: Whether the type appears inside of a path.
     ///    Used to provide correct diagnostics for bare trait object types.
     #[instrument(level = "debug", skip(self), ret)]
-    fn lower_ty_common(&self, hir_ty: &hir::Ty<'tcx>, borrowed: bool, in_path: bool) -> Ty<'tcx> {
+    pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
         let tcx = self.tcx();
 
         let result_ty = match &hir_ty.kind {
@@ -2036,7 +2025,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             hir::TyKind::Ref(region, mt) => {
                 let r = self.lower_lifetime(region, RegionInferReason::Reference);
                 debug!(?r);
-                let t = self.lower_ty_common(mt.ty, true, false);
+                let t = self.lower_ty(mt.ty);
                 Ty::new_ref(tcx, r, t, mt.mutbl)
             }
             hir::TyKind::Never => tcx.types.never,
@@ -2065,20 +2054,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 )
             }
             hir::TyKind::TraitObject(bounds, lifetime, repr) => {
-                self.prohibit_or_lint_bare_trait_object_ty(hir_ty, in_path);
+                self.prohibit_or_lint_bare_trait_object_ty(hir_ty);
 
                 let repr = match repr {
                     TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
                     TraitObjectSyntax::DynStar => ty::DynStar,
                 };
-                self.lower_trait_object_ty(
-                    hir_ty.span,
-                    hir_ty.hir_id,
-                    bounds,
-                    lifetime,
-                    borrowed,
-                    repr,
-                )
+                self.lower_trait_object_ty(hir_ty.span, hir_ty.hir_id, bounds, lifetime, repr)
             }
             hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
                 debug!(?maybe_qself, ?path);
@@ -2106,7 +2088,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
             hir::TyKind::Path(hir::QPath::TypeRelative(qself, segment)) => {
                 debug!(?qself, ?segment);
-                let ty = self.lower_ty_common(qself, false, true);
+                let ty = self.lower_ty(qself);
                 self.lower_assoc_path(hir_ty.hir_id, hir_ty.span, ty, qself, segment, false)
                     .map(|(ty, _, _)| ty)
                     .unwrap_or_else(|guar| Ty::new_error(tcx, guar))

compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs

@@ -30,7 +30,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         hir_id: hir::HirId,
         hir_trait_bounds: &[(hir::PolyTraitRef<'tcx>, hir::TraitBoundModifier)],
         lifetime: &hir::Lifetime,
-        borrowed: bool,
         representation: DynKind,
     ) -> Ty<'tcx> {
         let tcx = self.tcx();
@@ -325,22 +324,32 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         v.dedup();
         let existential_predicates = tcx.mk_poly_existential_predicates(&v);
 
-        // Use explicitly-specified region bound.
+        // Use explicitly-specified region bound, unless the bound is missing.
         let region_bound = if !lifetime.is_elided() {
-            self.lower_lifetime(lifetime, RegionInferReason::ObjectLifetimeDefault)
+            self.lower_lifetime(lifetime, RegionInferReason::ExplicitObjectLifetime)
         } else {
             self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
+                // Curiously, we prefer object lifetime default for `+ '_`...
                 if tcx.named_bound_var(lifetime.hir_id).is_some() {
-                    self.lower_lifetime(lifetime, RegionInferReason::ObjectLifetimeDefault)
+                    self.lower_lifetime(lifetime, RegionInferReason::ExplicitObjectLifetime)
                 } else {
-                    self.re_infer(
-                        span,
-                        if borrowed {
-                            RegionInferReason::ObjectLifetimeDefault
+                    let reason =
+                        if let hir::LifetimeName::ImplicitObjectLifetimeDefault = lifetime.res {
+                            if let hir::Node::Ty(hir::Ty {
+                                kind: hir::TyKind::Ref(parent_lifetime, _),
+                                ..
+                            }) = tcx.parent_hir_node(hir_id)
+                                && tcx.named_bound_var(parent_lifetime.hir_id).is_none()
+                            {
+                                // Parent lifetime must have failed to resolve. Don't emit a redundant error.
+                                RegionInferReason::ExplicitObjectLifetime
+                            } else {
+                                RegionInferReason::ObjectLifetimeDefault
+                            }
                         } else {
-                            RegionInferReason::BorrowedObjectLifetimeDefault
-                        },
-                    )
+                            RegionInferReason::ExplicitObjectLifetime
+                        };
+                    self.re_infer(span, reason)
                 }
             })
         };

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -798,7 +798,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // to be object-safe.
                 // We manually call `register_wf_obligation` in the success path
                 // below.
-                let ty = self.lowerer().lower_ty_in_path(qself);
+                let ty = self.lowerer().lower_ty(qself);
                 (LoweredTy::from_raw(self, span, ty), qself, segment)
             }
             QPath::LangItem(..) => {

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -2975,7 +2975,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut suffix_suggestion = sugg.clone();
         suffix_suggestion.push((
             if matches!(
-                (&expected_ty.kind(), &checked_ty.kind()),
+                (expected_ty.kind(), checked_ty.kind()),
                 (ty::Int(_) | ty::Uint(_), ty::Float(_))
             ) {
                 // Remove fractional part from literal, for example `42.0f32` into `42`
@@ -3077,7 +3077,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
             };
 
-        match (&expected_ty.kind(), &checked_ty.kind()) {
+        match (expected_ty.kind(), checked_ty.kind()) {
             (ty::Int(exp), ty::Int(found)) => {
                 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
                 {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1012,7 +1012,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
             let mut bound_span_label = |self_ty: Ty<'_>, obligation: &str, quiet: &str| {
                 let msg = format!("`{}`", if obligation.len() > 50 { quiet } else { obligation });
-                match &self_ty.kind() {
+                match self_ty.kind() {
                     // Point at the type that couldn't satisfy the bound.
                     ty::Adt(def, _) => {
                         bound_spans.get_mut_or_insert_default(tcx.def_span(def.did())).push(msg)

compiler/rustc_hir_typeck/src/pat.rs

@@ -1336,7 +1336,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // More generally, the expected type wants a tuple variant with one field of an
         // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern
         // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
-        let missing_parentheses = match (&expected.kind(), fields, had_err) {
+        let missing_parentheses = match (expected.kind(), fields, had_err) {
             // #67037: only do this if we could successfully type-check the expected type against
             // the tuple struct pattern. Otherwise the args could get out of range on e.g.,
             // `let P() = U;` where `P != U` with `struct P<T>(T);`.

compiler/rustc_incremental/messages.ftl

@@ -99,6 +99,4 @@ incremental_unrecognized_depnode = unrecognized `DepNode` variant: {$name}
 
 incremental_unrecognized_depnode_label = dep-node label `{$label}` not recognized
 
-incremental_write_dep_graph = failed to write dependency graph to `{$path}`: {$err}
-
 incremental_write_new = failed to write {$name} to `{$path}`: {$err}

compiler/rustc_incremental/src/errors.rs

@@ -272,13 +272,6 @@ pub struct LoadDepGraph {
     pub err: std::io::Error,
 }
 
-#[derive(Diagnostic)]
-#[diag(incremental_write_dep_graph)]
-pub struct WriteDepGraph<'a> {
-    pub path: &'a Path,
-    pub err: std::io::Error,
-}
-
 #[derive(Diagnostic)]
 #[diag(incremental_move_dep_graph)]
 pub struct MoveDepGraph<'a> {

compiler/rustc_middle/src/ty/layout.rs

@@ -1104,7 +1104,7 @@ where
     }
 
     fn is_never(this: TyAndLayout<'tcx>) -> bool {
-        this.ty.kind() == &ty::Never
+        matches!(this.ty.kind(), ty::Never)
     }
 
     fn is_tuple(this: TyAndLayout<'tcx>) -> bool {

compiler/rustc_middle/src/ty/util.rs

@@ -296,7 +296,7 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> (Ty<'tcx>, Ty<'tcx>) {
         let (mut a, mut b) = (source, target);
         loop {
-            match (&a.kind(), &b.kind()) {
+            match (a.kind(), b.kind()) {
                 (&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args))
                     if a_def == b_def && a_def.is_struct() =>
                 {

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

@@ -127,7 +127,7 @@ fn lit_to_mir_constant<'tcx>(
         Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
     };
 
-    let value = match (lit, &ty.kind()) {
+    let value = match (lit, ty.kind()) {
         (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
             let s = s.as_str();
             let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes());

compiler/rustc_mir_build/src/thir/constant.rs

@@ -29,7 +29,7 @@ pub(crate) fn lit_to_const<'tcx>(
             .unwrap_or_else(|| bug!("expected to create ScalarInt from uint {:?}", result)))
     };
 
-    let valtree = match (lit, &ty.kind()) {
+    let valtree = match (lit, ty.kind()) {
         (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
             let str_bytes = s.as_str().as_bytes();
             ty::ValTree::from_raw_bytes(tcx, str_bytes)

compiler/rustc_monomorphize/src/collector.rs

@@ -1035,9 +1035,9 @@ fn find_vtable_types_for_unsizing<'tcx>(
         }
     };
 
-    match (&source_ty.kind(), &target_ty.kind()) {
+    match (source_ty.kind(), target_ty.kind()) {
         (&ty::Ref(_, a, _), &ty::Ref(_, b, _) | &ty::RawPtr(b, _))
-        | (&ty::RawPtr(a, _), &ty::RawPtr(b, _)) => ptr_vtable(*a, *b),
+        | (&ty::RawPtr(a, _), &ty::RawPtr(b, _)) => ptr_vtable(a, b),
         (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
             ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
         }

compiler/rustc_passes/messages.ftl

@@ -481,10 +481,6 @@ passes_must_not_suspend =
     `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
     .label = is not a struct, enum, union, or trait
 
-passes_must_use_async =
-    `must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within
-    .label = this attribute does nothing, the `Future`s returned by async functions are already `must_use`
-
 passes_must_use_no_effect =
     `#[must_use]` has no effect when applied to {$article} {$target}