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Auto merge of #13750 - lowr:fix/rpit-in-projection, r=flodiebold
fix: normalize projection after discarding free `BoundVar`s in RPIT
Fixes #13307
When we lower the return type of a function, it may contain free `BoundVar`s in `OpaqueType`'s substitution, which would cause panic during canonicalization as part of projection normalization. Those `BoundVar`s are irrelevant in this context and will be discarded, and we should defer projection normalization until then.
| -rw-r--r-- | crates/hir-ty/src/infer.rs | 38 | ||||
| -rw-r--r-- | crates/hir-ty/src/tests/traits.rs | 16 |
2 files changed, 34 insertions, 20 deletions
diff --git a/crates/hir-ty/src/infer.rs b/crates/hir-ty/src/infer.rs index 874a54fc3e..ad7ec485e9 100644 --- a/crates/hir-ty/src/infer.rs +++ b/crates/hir-ty/src/infer.rs @@ -503,7 +503,7 @@ impl<'a> InferenceContext<'a> { result: InferenceResult::default(), table: unify::InferenceTable::new(db, trait_env.clone()), trait_env, - return_ty: TyKind::Error.intern(Interner), // set in collect_fn_signature + return_ty: TyKind::Error.intern(Interner), // set in collect_* calls resume_yield_tys: None, db, owner, @@ -582,14 +582,17 @@ impl<'a> InferenceContext<'a> { } else { &*data.ret_type }; - let return_ty = self.make_ty_with_mode(return_ty, ImplTraitLoweringMode::Opaque); - self.return_ty = return_ty; - if let Some(rpits) = self.db.return_type_impl_traits(func) { + let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver) + .with_impl_trait_mode(ImplTraitLoweringMode::Opaque); + let return_ty = ctx.lower_ty(return_ty); + let return_ty = self.insert_type_vars(return_ty); + + let return_ty = if let Some(rpits) = self.db.return_type_impl_traits(func) { // RPIT opaque types use substitution of their parent function. let fn_placeholders = TyBuilder::placeholder_subst(self.db, func); - self.return_ty = fold_tys( - self.return_ty.clone(), + fold_tys( + return_ty, |ty, _| { let opaque_ty_id = match ty.kind(Interner) { TyKind::OpaqueType(opaque_ty_id, _) => *opaque_ty_id, @@ -610,14 +613,18 @@ impl<'a> InferenceContext<'a> { let (var_predicate, binders) = predicate .substitute(Interner, &var_subst) .into_value_and_skipped_binders(); - always!(binders.len(Interner) == 0); // quantified where clauses not yet handled + always!(binders.is_empty(Interner)); // quantified where clauses not yet handled self.push_obligation(var_predicate.cast(Interner)); } var }, DebruijnIndex::INNERMOST, - ); - } + ) + } else { + return_ty + }; + + self.return_ty = self.normalize_associated_types_in(return_ty); } fn infer_body(&mut self) { @@ -652,23 +659,14 @@ impl<'a> InferenceContext<'a> { self.result.diagnostics.push(diagnostic); } - fn make_ty_with_mode( - &mut self, - type_ref: &TypeRef, - impl_trait_mode: ImplTraitLoweringMode, - ) -> Ty { + fn make_ty(&mut self, type_ref: &TypeRef) -> Ty { // FIXME use right resolver for block - let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver) - .with_impl_trait_mode(impl_trait_mode); + let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver); let ty = ctx.lower_ty(type_ref); let ty = self.insert_type_vars(ty); self.normalize_associated_types_in(ty) } - fn make_ty(&mut self, type_ref: &TypeRef) -> Ty { - self.make_ty_with_mode(type_ref, ImplTraitLoweringMode::Disallowed) - } - fn err_ty(&self) -> Ty { self.result.standard_types.unknown.clone() } diff --git a/crates/hir-ty/src/tests/traits.rs b/crates/hir-ty/src/tests/traits.rs index 3d7194b6f4..a9fd01ee01 100644 --- a/crates/hir-ty/src/tests/traits.rs +++ b/crates/hir-ty/src/tests/traits.rs @@ -1389,6 +1389,22 @@ fn foo<const C: u8, T>() -> (impl FnOnce(&str, T), impl Trait<u8>) { } #[test] +fn return_pos_impl_trait_in_projection() { + // Note that the unused type param `X` is significant; see #13307. + check_no_mismatches( + r#" +//- minicore: sized +trait Future { type Output; } +impl Future for () { type Output = i32; } +type Foo<F> = (<F as Future>::Output, F); +fn foo<X>() -> Foo<impl Future<Output = ()>> { + (0, ()) +} +"#, + ) +} + +#[test] fn dyn_trait() { check_infer( r#" |