diff --git a/src/librustc_error_codes/error_codes.rs b/src/librustc_error_codes/error_codes.rs index 5865042859d..7abe75a375a 100644 --- a/src/librustc_error_codes/error_codes.rs +++ b/src/librustc_error_codes/error_codes.rs @@ -437,6 +437,7 @@ E0751: include_str!("./error_codes/E0751.md"), E0752: include_str!("./error_codes/E0752.md"), E0753: include_str!("./error_codes/E0753.md"), E0754: include_str!("./error_codes/E0754.md"), +E0760: include_str!("./error_codes/E0760.md"), ; // E0006, // merged with E0005 // E0008, // cannot bind by-move into a pattern guard diff --git a/src/librustc_error_codes/error_codes/E0760.md b/src/librustc_error_codes/error_codes/E0760.md new file mode 100644 index 00000000000..e1dcfefebcd --- /dev/null +++ b/src/librustc_error_codes/error_codes/E0760.md @@ -0,0 +1,32 @@ +`async fn`/`impl trait` return type cannot contain a projection +or `Self` that references lifetimes from a parent scope. + +Erroneous code example: + +```compile_fail,E0760,edition2018 +struct S<'a>(&'a i32); + +impl<'a> S<'a> { + async fn new(i: &'a i32) -> Self { + S(&22) + } +} +``` + +To fix this error we need to spell out `Self` to `S<'a>`: + +```edition2018 +struct S<'a>(&'a i32); + +impl<'a> S<'a> { + async fn new(i: &'a i32) -> S<'a> { + S(&22) + } +} +``` + +This will be allowed at some point in the future, +but the implementation is not yet complete. +See the [issue-61949] for this limitation. + +[issue-61949]: https://github.com/rust-lang/rust/issues/61949 diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index ba4bca8cd99..634f2f78c70 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -1623,12 +1623,17 @@ fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: LocalDefId, struct ProhibitOpaqueVisitor<'tcx> { opaque_identity_ty: Ty<'tcx>, generics: &'tcx ty::Generics, + ty: Option>, }; impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> { fn visit_ty(&mut self, t: Ty<'tcx>) -> bool { debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t); - if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) } + if t != self.opaque_identity_ty && t.super_visit_with(self) { + self.ty = Some(t); + return true; + } + false } fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool { @@ -1651,46 +1656,61 @@ fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: LocalDefId, } } - let prohibit_opaque = match item.kind { - ItemKind::OpaqueTy(hir::OpaqueTy { - origin: hir::OpaqueTyOrigin::AsyncFn | hir::OpaqueTyOrigin::FnReturn, - .. - }) => { - let mut visitor = ProhibitOpaqueVisitor { - opaque_identity_ty: tcx.mk_opaque( - def_id.to_def_id(), - InternalSubsts::identity_for_item(tcx, def_id.to_def_id()), - ), - generics: tcx.generics_of(def_id), - }; - debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor); - - tcx.predicates_of(def_id) - .predicates - .iter() - .any(|(predicate, _)| predicate.visit_with(&mut visitor)) - } - _ => false, - }; - - debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque); - if prohibit_opaque { - let is_async = match item.kind { - ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin { - hir::OpaqueTyOrigin::AsyncFn => true, - _ => false, - }, - _ => unreachable!(), + if let ItemKind::OpaqueTy(hir::OpaqueTy { + origin: hir::OpaqueTyOrigin::AsyncFn | hir::OpaqueTyOrigin::FnReturn, + .. + }) = item.kind + { + let mut visitor = ProhibitOpaqueVisitor { + opaque_identity_ty: tcx.mk_opaque( + def_id.to_def_id(), + InternalSubsts::identity_for_item(tcx, def_id.to_def_id()), + ), + generics: tcx.generics_of(def_id), + ty: None, }; - - tcx.sess.span_err( - span, - &format!( - "`{}` return type cannot contain a projection or `Self` that references lifetimes from \ - a parent scope", - if is_async { "async fn" } else { "impl Trait" }, - ), + let prohibit_opaque = tcx + .predicates_of(def_id) + .predicates + .iter() + .any(|(predicate, _)| predicate.visit_with(&mut visitor)); + debug!( + "check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor={:?}", + prohibit_opaque, visitor ); + + if prohibit_opaque { + let is_async = match item.kind { + ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin { + hir::OpaqueTyOrigin::AsyncFn => true, + _ => false, + }, + _ => unreachable!(), + }; + + let mut err = struct_span_err!( + tcx.sess, + span, + E0760, + "`{}` return type cannot contain a projection or `Self` that references lifetimes from \ + a parent scope", + if is_async { "async fn" } else { "impl Trait" }, + ); + + if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(span) { + if snippet == "Self" { + if let Some(ty) = visitor.ty { + err.span_suggestion( + span, + "consider spelling out the type instead", + format!("{:?}", ty), + Applicability::MaybeIncorrect, + ); + } + } + } + err.emit(); + } } } diff --git a/src/test/ui/async-await/issue-61949-self-return-type.stderr b/src/test/ui/async-await/issue-61949-self-return-type.stderr index 12fb77d8dd6..4eeef871c5b 100644 --- a/src/test/ui/async-await/issue-61949-self-return-type.stderr +++ b/src/test/ui/async-await/issue-61949-self-return-type.stderr @@ -1,8 +1,9 @@ -error: `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope +error[E0760]: `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope --> $DIR/issue-61949-self-return-type.rs:11:40 | LL | pub async fn new(_bar: &'a i32) -> Self { - | ^^^^ + | ^^^^ help: consider spelling out the type instead: `Foo<'a>` error: aborting due to previous error +For more information about this error, try `rustc --explain E0760`. diff --git a/src/test/ui/impl-trait/bound-normalization-fail.stderr b/src/test/ui/impl-trait/bound-normalization-fail.stderr index 36b4ebca4df..03aba10cc79 100644 --- a/src/test/ui/impl-trait/bound-normalization-fail.stderr +++ b/src/test/ui/impl-trait/bound-normalization-fail.stderr @@ -21,7 +21,7 @@ help: consider constraining the associated type `::Assoc LL | fn foo_fail>() -> impl FooLike { | ^^^^^^^^^^^^ -error: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope +error[E0760]: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope --> $DIR/bound-normalization-fail.rs:43:41 | LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike { @@ -43,4 +43,5 @@ LL | fn foo2_fail<'a, T: Trait<'a, Assoc = ()>>() -> impl FooLike