diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_hir_typeck/src/coercion.rs | 68 |
1 files changed, 8 insertions, 60 deletions
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs index 4cbc42b99ea..f42ca3af2b3 100644 --- a/compiler/rustc_hir_typeck/src/coercion.rs +++ b/compiler/rustc_hir_typeck/src/coercion.rs @@ -41,8 +41,8 @@ use rustc_abi::ExternAbi; use rustc_attr_parsing::InlineAttr; use rustc_errors::codes::*; use rustc_errors::{Applicability, Diag, struct_span_code_err}; +use rustc_hir as hir; use rustc_hir::def_id::{DefId, LocalDefId}; -use rustc_hir::{self as hir, LangItem}; use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer; use rustc_infer::infer::relate::RelateResult; use rustc_infer::infer::{Coercion, DefineOpaqueTypes, InferOk, InferResult}; @@ -55,7 +55,7 @@ use rustc_middle::ty::adjustment::{ Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCoercion, }; use rustc_middle::ty::error::TypeError; -use rustc_middle::ty::{self, AliasTy, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt}; +use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt}; use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span}; use rustc_trait_selection::infer::InferCtxtExt as _; use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt; @@ -592,63 +592,6 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // Create an obligation for `Source: CoerceUnsized<Target>`. let cause = self.cause(self.cause.span, ObligationCauseCode::Coercion { source, target }); - let root_obligation = Obligation::new( - self.tcx, - cause.clone(), - self.fcx.param_env, - ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target]), - ); - - // If the root `Source: CoerceUnsized<Target>` obligation can't possibly hold, - // we don't have to assume that this is unsizing coercion (it will always lead to an error) - // - // However, we don't want to bail early all the time, since the unholdable obligations - // may be interesting for diagnostics (such as trying to coerce `&T` to `&dyn Id<This = U>`), - // so we only bail if there (likely) is another way to convert the types. - if !self.infcx.predicate_may_hold(&root_obligation) { - if let Some(dyn_metadata_adt_def_id) = self.tcx.lang_items().get(LangItem::DynMetadata) - && let Some(metadata_type_def_id) = self.tcx.lang_items().get(LangItem::Metadata) - { - self.probe(|_| { - let ocx = ObligationCtxt::new(&self.infcx); - - // returns `true` if `<ty as Pointee>::Metadata` is `DynMetadata<_>` - let has_dyn_trait_metadata = |ty| { - let metadata_ty: Result<_, _> = ocx.structurally_normalize_ty( - &ObligationCause::dummy(), - self.fcx.param_env, - Ty::new_alias( - self.tcx, - ty::AliasTyKind::Projection, - AliasTy::new(self.tcx, metadata_type_def_id, [ty]), - ), - ); - - metadata_ty.is_ok_and(|metadata_ty| { - metadata_ty - .ty_adt_def() - .is_some_and(|d| d.did() == dyn_metadata_adt_def_id) - }) - }; - - // If both types are raw pointers to a (wrapper over a) trait object, - // this might be a cast like `*const W<dyn Trait> -> *const dyn Trait`. - // So it's better to bail and try that. (even if the cast is not possible, for - // example due to vtables not matching, cast diagnostic will likely still be better) - // - // N.B. use `target`, not `coerce_target` (the latter is a var) - if let &ty::RawPtr(source_pointee, _) = coerce_source.kind() - && let &ty::RawPtr(target_pointee, _) = target.kind() - && has_dyn_trait_metadata(source_pointee) - && has_dyn_trait_metadata(target_pointee) - { - return Err(TypeError::Mismatch); - } - - Ok(()) - })?; - } - } // Use a FIFO queue for this custom fulfillment procedure. // @@ -657,7 +600,12 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> { // and almost never more than 3. By using a SmallVec we avoid an // allocation, at the (very small) cost of (occasionally) having to // shift subsequent elements down when removing the front element. - let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![root_obligation]; + let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![Obligation::new( + self.tcx, + cause, + self.fcx.param_env, + ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target]) + )]; // Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid // emitting a coercion in cases like `Foo<$1>` -> `Foo<$2>`, where |