diff options
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs | 5 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/project.rs | 7 |
2 files changed, 8 insertions, 4 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs index 571963fa735..b0bdeb7d2a7 100644 --- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs @@ -410,7 +410,10 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> { } ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => { - // FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints. + // This is the "fallback impl" for type parameters, unnormalizable projections + // and opaque types: If the `self_ty` is `Sized`, then the metadata is `()`. + // FIXME(ptr_metadata): This impl overlaps with the other impls and shouldn't + // exist. Instead, `Pointee<Metadata = ()>` should be a supertrait of `Sized`. let sized_predicate = ty::TraitRef::from_lang_item( tcx, LangItem::Sized, diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index 33298c4b750..ecaab0e0085 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -2302,9 +2302,10 @@ fn confirm_builtin_candidate<'cx, 'tcx>( }; let metadata_ty = self_ty.ptr_metadata_ty_or_tail(tcx, normalize).unwrap_or_else(|tail| { if tail == self_ty { - // This is the fallback case for type parameters, unnormalizable projections - // and opaque types. - // If the `self_ty` is `Sized`, then the metadata is `()`. + // This is the "fallback impl" for type parameters, unnormalizable projections + // and opaque types: If the `self_ty` is `Sized`, then the metadata is `()`. + // FIXME(ptr_metadata): This impl overlaps with the other impls and shouldn't + // exist. Instead, `Pointee<Metadata = ()>` should be a supertrait of `Sized`. let sized_predicate = ty::TraitRef::from_lang_item( tcx, LangItem::Sized, |