diff options
Diffstat (limited to 'compiler/rustc_borrowck/src')
| -rw-r--r-- | compiler/rustc_borrowck/src/type_check/mod.rs | 136 |
1 files changed, 74 insertions, 62 deletions
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs index e55f5b7b43e..0d363935f14 100644 --- a/compiler/rustc_borrowck/src/type_check/mod.rs +++ b/compiler/rustc_borrowck/src/type_check/mod.rs @@ -34,6 +34,7 @@ use rustc_mir_dataflow::points::DenseLocationMap; use rustc_span::def_id::CRATE_DEF_ID; use rustc_span::source_map::Spanned; use rustc_span::{Span, sym}; +use rustc_trait_selection::infer::InferCtxtExt; use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints; use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput}; use tracing::{debug, instrument, trace}; @@ -1454,68 +1455,79 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> { } CastKind::PtrToPtr => { let ty_from = op.ty(self.body, tcx); - let cast_ty_from = CastTy::from_ty(ty_from); - let cast_ty_to = CastTy::from_ty(*ty); - match (cast_ty_from, cast_ty_to) { - (Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => { - 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). - // - // Note that other checks (such as denying `dyn Send` -> `dyn - // Debug`) are in `rustc_hir_typeck`. - if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) = *src_tail.kind() - && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) = *dst_tail.kind() - && src_tty.principal().is_some() - && dst_tty.principal().is_some() - { - // Remove auto traits. - // Auto trait checks are handled in `rustc_hir_typeck` as FCW. - let src_obj = Ty::new_dynamic( - tcx, - tcx.mk_poly_existential_predicates( - &src_tty.without_auto_traits().collect::<Vec<_>>(), - ), - // FIXME: Once we disallow casting `*const dyn Trait + 'short` - // to `*const dyn Trait + 'long`, then this can just be `src_lt`. - dst_lt, - ty::Dyn, - ); - let dst_obj = Ty::new_dynamic( - tcx, - tcx.mk_poly_existential_predicates( - &dst_tty.without_auto_traits().collect::<Vec<_>>(), - ), - dst_lt, - ty::Dyn, - ); - - debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj); - - self.sub_types( - src_obj, - dst_obj, - location.to_locations(), - ConstraintCategory::Cast { - is_implicit_coercion: false, - unsize_to: None, - }, - ) - .unwrap(); - } - } - _ => { - span_mirbug!( - self, - rvalue, - "Invalid PtrToPtr cast {:?} -> {:?}", - ty_from, - ty - ) - } + let Some(CastTy::Ptr(src)) = CastTy::from_ty(ty_from) else { + unreachable!(); + }; + let Some(CastTy::Ptr(dst)) = CastTy::from_ty(*ty) else { + unreachable!(); + }; + + if self.infcx.type_is_sized_modulo_regions(self.infcx.param_env, dst.ty) { + // Wide to thin ptr cast. This may even occur in an env with + // impossible predicates, such as `where dyn Trait: Sized`. + // In this case, we don't want to fall into the case below, + // since the types may not actually be equatable, but it's + // fine to perform this operation in an impossible env. + let trait_ref = ty::TraitRef::new( + tcx, + tcx.require_lang_item(LangItem::Sized, self.last_span), + [dst.ty], + ); + self.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::Cast { + is_implicit_coercion: true, + unsize_to: None, + }, + ); + } else if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) = + *self.struct_tail(src.ty, location).kind() + && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) = + *self.struct_tail(dst.ty, location).kind() + && src_tty.principal().is_some() + && dst_tty.principal().is_some() + { + // 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). + // + // Note that other checks (such as denying `dyn Send` -> `dyn + // Debug`) are in `rustc_hir_typeck`. + + // Remove auto traits. + // Auto trait checks are handled in `rustc_hir_typeck` as FCW. + let src_obj = Ty::new_dynamic( + tcx, + tcx.mk_poly_existential_predicates( + &src_tty.without_auto_traits().collect::<Vec<_>>(), + ), + // FIXME: Once we disallow casting `*const dyn Trait + 'short` + // to `*const dyn Trait + 'long`, then this can just be `src_lt`. + dst_lt, + ty::Dyn, + ); + let dst_obj = Ty::new_dynamic( + tcx, + tcx.mk_poly_existential_predicates( + &dst_tty.without_auto_traits().collect::<Vec<_>>(), + ), + dst_lt, + ty::Dyn, + ); + + debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj); + + self.sub_types( + src_obj, + dst_obj, + location.to_locations(), + ConstraintCategory::Cast { + is_implicit_coercion: false, + unsize_to: None, + }, + ) + .unwrap(); } } CastKind::Transmute => { |