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Disallow dyn Trait -> dyn Auto back

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I think it's fine, but let's ask T-lang separately.
This commit is contained in:
Waffle Lapkin 2024-06-04 14:39:51 +02:00 committed by Maybe Lapkin
parent bb651d358d
commit eac4916c90
1 changed files with 16 additions and 6 deletions
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22
compiler/rustc_hir_typeck/src/cast.rs
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@ -840,8 +840,16 @@ fn check_ptr_ptr_cast(
// contain wrappers, which we do not care about.
//
// e.g. we want to allow `dyn T -> (dyn T,)`, etc.
let src_obj = tcx.mk_ty_from_kind(ty::Dynamic(src_tty, tcx.lifetimes.re_erased, ty::Dyn));
let dst_obj = tcx.mk_ty_from_kind(ty::Dynamic(dst_tty, tcx.lifetimes.re_erased, ty::Dyn));
let src_obj = tcx.mk_ty_from_kind(ty::Dynamic(
src_tty,
tcx.lifetimes.re_erased,
ty::Dyn,
));
let dst_obj = tcx.mk_ty_from_kind(ty::Dynamic(
dst_tty,
tcx.lifetimes.re_erased,
ty::Dyn,
));
// `dyn Src: Unsize<dyn Dst>`
let cause = fcx.misc(self.span);
@ -853,7 +861,7 @@ fn check_ptr_ptr_cast(
tcx,
tcx.require_lang_item(LangItem::Unsize, Some(self.span)),
[src_obj, dst_obj],
)
),
);
fcx.register_predicate(obligation);
@ -866,9 +874,11 @@ fn check_ptr_ptr_cast(
}
// dyn Auto -> dyn Auto'? ok.
(None, None)
// dyn Trait -> dyn Auto? ok.
| (Some(_), None)=> Ok(CastKind::PtrPtrCast),
(None, None) => Ok(CastKind::PtrPtrCast),
// dyn Trait -> dyn Auto? should be ok, but we used to not allow it.
// FIXME: allow this
(Some(_), None) => Err(CastError::DifferingKinds),
// dyn Auto -> dyn Trait? not ok.
(None, Some(_)) => Err(CastError::DifferingKinds),