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Auto merge of #121679 - lcnr:opaque-wf-check-2, r=oli-obk

stricter hidden type wf-check [based on #115008]

Original work by `@aliemjay` in #115008. A huge thanks to them for originally figuring out this approach ❤️

Fixes https://github.com/rust-lang/rust/issues/114728
Fixes https://github.com/rust-lang/rust/issues/114572

Instead of adding the `WellFormed` obligations when relating opaque types, we now always emit such an obligation when defining the hidden type.

This causes nested opaque types which aren't wf to error, see the comment below for the described impact. I believe this change to be desirable as it significantly reduces complexity by removing special-cases.

It also caused an issue with RPITIT: in defaulted trait methods, we add a `Projection(synthetic_assoc, rpit_of_trait_method)` clause to the `param_env`. This clause is not added to the `ParamEnv` of the nested coroutines. This caused a normalization failure in `fn check_coroutine_obligations` with the new solver. I fixed that by using the env of the typeck root instead.

r? `@oli-obk`
This commit is contained in:
bors 2024-03-06 10:04:26 +00:00
commit 09bc67b915
21 changed files with 313 additions and 136 deletions

View file

@ -121,18 +121,7 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
}
}
DefKind::AssocConst | DefKind::AssocTy => tcx.assumed_wf_types(tcx.local_parent(def_id)),
DefKind::OpaqueTy => match tcx.def_kind(tcx.local_parent(def_id)) {
DefKind::TyAlias => ty::List::empty(),
DefKind::AssocTy => tcx.assumed_wf_types(tcx.local_parent(def_id)),
// Nested opaque types only occur in associated types:
// ` type Opaque<T> = impl Trait<&'static T, AssocTy = impl Nested>; `
// assumed_wf_types should include those of `Opaque<T>`, `Opaque<T>` itself
// and `&'static T`.
DefKind::OpaqueTy => bug!("unimplemented implied bounds for nested opaque types"),
def_kind => {
bug!("unimplemented implied bounds for opaque types with parent {def_kind:?}")
}
},
DefKind::OpaqueTy => bug!("implied bounds are not defined for opaques"),
DefKind::Mod
| DefKind::Struct
| DefKind::Union