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This repository was archived by the owner on May 28, 2025. It is now read-only.

Commit ab5b1be

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Auto merge of rust-lang#138892 - compiler-errors:revert-ptr-ptr, r=oli-obk
Revert "Rollup merge of rust-lang#136127 - WaffleLapkin:dyn_ptr_unwrap_cast, r=compiler-errors" ...not permanently tho. Just until we can land something like rust-lang#138542, which will fix the underlying perf issues (rust-lang#136127 (comment)). I just don't want this to land on beta and have people rely on this behavior if it'll need some reworking for it to be implemented performantly. r? `@WaffleLapkin` or reassign -- sorry for reverting ur pr! i'm working on getting it re-landed soon :>
2 parents 10a76d6 + e06d50c commit ab5b1be

8 files changed

+8
-436
lines changed

‎compiler/rustc_hir_typeck/src/coercion.rs

Lines changed: 8 additions & 60 deletions
Original file line numberDiff line numberDiff line change
@@ -41,8 +41,8 @@ use rustc_abi::ExternAbi;
4141
use rustc_attr_parsing::InlineAttr;
4242
use rustc_errors::codes::*;
4343
use rustc_errors::{Applicability, Diag, struct_span_code_err};
44+
use rustc_hir as hir;
4445
use rustc_hir::def_id::{DefId, LocalDefId};
45-
use rustc_hir::{self as hir, LangItem};
4646
use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
4747
use rustc_infer::infer::relate::RelateResult;
4848
use rustc_infer::infer::{Coercion, DefineOpaqueTypes, InferOk, InferResult};
@@ -55,7 +55,7 @@ use rustc_middle::ty::adjustment::{
5555
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCoercion,
5656
};
5757
use rustc_middle::ty::error::TypeError;
58-
use rustc_middle::ty::{self, AliasTy,GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
58+
use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
5959
use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span};
6060
use rustc_trait_selection::infer::InferCtxtExt as _;
6161
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
@@ -592,63 +592,6 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
592592

593593
// Create an obligation for `Source: CoerceUnsized<Target>`.
594594
let cause = self.cause(self.cause.span, ObligationCauseCode::Coercion { source, target });
595-
let root_obligation = Obligation::new(
596-
self.tcx,
597-
cause.clone(),
598-
self.fcx.param_env,
599-
ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target]),
600-
);
601-
602-
// If the root `Source: CoerceUnsized<Target>` obligation can't possibly hold,
603-
// we don't have to assume that this is unsizing coercion (it will always lead to an error)
604-
//
605-
// However, we don't want to bail early all the time, since the unholdable obligations
606-
// may be interesting for diagnostics (such as trying to coerce `&T` to `&dyn Id<This = U>`),
607-
// so we only bail if there (likely) is another way to convert the types.
608-
if !self.infcx.predicate_may_hold(&root_obligation) {
609-
if let Some(dyn_metadata_adt_def_id) = self.tcx.lang_items().get(LangItem::DynMetadata)
610-
&& let Some(metadata_type_def_id) = self.tcx.lang_items().get(LangItem::Metadata)
611-
{
612-
self.probe(|_| {
613-
let ocx = ObligationCtxt::new(&self.infcx);
614-
615-
// returns `true` if `<ty as Pointee>::Metadata` is `DynMetadata<_>`
616-
let has_dyn_trait_metadata = |ty| {
617-
let metadata_ty: Result<_, _> = ocx.structurally_normalize_ty(
618-
&ObligationCause::dummy(),
619-
self.fcx.param_env,
620-
Ty::new_alias(
621-
self.tcx,
622-
ty::AliasTyKind::Projection,
623-
AliasTy::new(self.tcx, metadata_type_def_id, [ty]),
624-
),
625-
);
626-
627-
metadata_ty.is_ok_and(|metadata_ty| {
628-
metadata_ty
629-
.ty_adt_def()
630-
.is_some_and(|d| d.did() == dyn_metadata_adt_def_id)
631-
})
632-
};
633-
634-
// If both types are raw pointers to a (wrapper over a) trait object,
635-
// this might be a cast like `*const W<dyn Trait> -> *const dyn Trait`.
636-
// So it's better to bail and try that. (even if the cast is not possible, for
637-
// example due to vtables not matching, cast diagnostic will likely still be better)
638-
//
639-
// N.B. use `target`, not `coerce_target` (the latter is a var)
640-
if let &ty::RawPtr(source_pointee, _) = coerce_source.kind()
641-
&& let &ty::RawPtr(target_pointee, _) = target.kind()
642-
&& has_dyn_trait_metadata(source_pointee)
643-
&& has_dyn_trait_metadata(target_pointee)
644-
{
645-
return Err(TypeError::Mismatch);
646-
}
647-
648-
Ok(())
649-
})?;
650-
}
651-
}
652595

653596
// Use a FIFO queue for this custom fulfillment procedure.
654597
//
@@ -657,7 +600,12 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
657600
// and almost never more than 3. By using a SmallVec we avoid an
658601
// allocation, at the (very small) cost of (occasionally) having to
659602
// shift subsequent elements down when removing the front element.
660-
let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![root_obligation];
603+
let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![Obligation::new(
604+
self.tcx,
605+
cause,
606+
self.fcx.param_env,
607+
ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target])
608+
)];
661609

662610
// Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid
663611
// emitting a coercion in cases like `Foo<1ドル>` -> `Foo<2ドル>`, where

‎tests/ui/cast/ptr-to-trait-obj-wrap-add-auto.rs

Lines changed: 0 additions & 36 deletions
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‎tests/ui/cast/ptr-to-trait-obj-wrap-add-auto.stderr

Lines changed: 0 additions & 48 deletions
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‎tests/ui/cast/ptr-to-trait-obj-wrap-different-args.rs

Lines changed: 0 additions & 36 deletions
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‎tests/ui/cast/ptr-to-trait-obj-wrap-different-args.stderr

Lines changed: 0 additions & 43 deletions
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‎tests/ui/cast/ptr-to-trait-obj-wrap-different-regions.rs

Lines changed: 0 additions & 41 deletions
This file was deleted.

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