diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/outlives/components.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/components.rs | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/compiler/rustc_infer/src/infer/outlives/components.rs b/compiler/rustc_infer/src/infer/outlives/components.rs index b2d7f4a66..14ee9f051 100644 --- a/compiler/rustc_infer/src/infer/outlives/components.rs +++ b/compiler/rustc_infer/src/infer/outlives/components.rs @@ -3,8 +3,9 @@ // RFC for reference. use rustc_data_structures::sso::SsoHashSet; +use rustc_hir::def_id::DefId; use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; -use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable}; +use rustc_middle::ty::{self, SubstsRef, Ty, TyCtxt, TypeVisitable}; use smallvec::{smallvec, SmallVec}; #[derive(Debug)] @@ -45,6 +46,8 @@ pub enum Component<'tcx> { // them. This gives us room to improve the regionck reasoning in // the future without breaking backwards compat. EscapingProjection(Vec<Component<'tcx>>), + + Opaque(DefId, SubstsRef<'tcx>), } /// Push onto `out` all the things that must outlive `'a` for the condition @@ -120,6 +123,17 @@ fn compute_components<'tcx>( out.push(Component::Param(p)); } + // Ignore lifetimes found in opaque types. Opaque types can + // have lifetimes in their substs which their hidden type doesn't + // actually use. If we inferred that an opaque type is outlived by + // its parameter lifetimes, then we could prove that any lifetime + // outlives any other lifetime, which is unsound. + // See https://github.com/rust-lang/rust/issues/84305 for + // more details. + ty::Opaque(def_id, substs) => { + out.push(Component::Opaque(def_id, substs)); + }, + // For projections, we prefer to generate an obligation like // `<P0 as Trait<P1...Pn>>::Foo: 'a`, because this gives the // regionck more ways to prove that it holds. However, @@ -168,7 +182,6 @@ fn compute_components<'tcx>( ty::Float(..) | // OutlivesScalar ty::Never | // ... ty::Adt(..) | // OutlivesNominalType - ty::Opaque(..) | // OutlivesNominalType (ish) ty::Foreign(..) | // OutlivesNominalType ty::Str | // OutlivesScalar (ish) ty::Slice(..) | // ... |