diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs index 0258f8fd2d9..f05a441ff81 100644 --- a/compiler/rustc_ast_lowering/src/lib.rs +++ b/compiler/rustc_ast_lowering/src/lib.rs @@ -259,6 +259,8 @@ enum ImplTraitContext { }, /// Impl trait in type aliases. TypeAliasesOpaqueTy, + /// `impl Trait` is unstably accepted in this position. + FeatureGated(ImplTraitPosition, Symbol), /// `impl Trait` is not accepted in this position. Disallowed(ImplTraitPosition), } @@ -1372,17 +1374,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { } path } - ImplTraitContext::Disallowed( - position @ (ImplTraitPosition::TraitReturn | ImplTraitPosition::ImplReturn), - ) => { + ImplTraitContext::FeatureGated(position, feature) => { self.tcx .sess .create_feature_err( MisplacedImplTrait { span: t.span, - position: DiagnosticArgFromDisplay(&position), + position: DiagnosticArgFromDisplay(position), }, - sym::return_position_impl_trait_in_trait, + *feature, ) .emit(); hir::TyKind::Err @@ -1390,7 +1390,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { ImplTraitContext::Disallowed(position) => { self.tcx.sess.emit_err(MisplacedImplTrait { span: t.span, - position: DiagnosticArgFromDisplay(&position), + position: DiagnosticArgFromDisplay(position), }); hir::TyKind::Err } @@ -1739,14 +1739,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { } else { match &decl.output { FnRetTy::Ty(ty) => { - let mut context = if kind.return_impl_trait_allowed(self.tcx) { + let context = if kind.return_impl_trait_allowed(self.tcx) { let fn_def_id = self.local_def_id(fn_node_id); ImplTraitContext::ReturnPositionOpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id), in_trait: matches!(kind, FnDeclKind::Trait), } } else { - ImplTraitContext::Disallowed(match kind { + let position = match kind { FnDeclKind::Fn | FnDeclKind::Inherent => { unreachable!("fn should allow in-band lifetimes") } @@ -1755,9 +1755,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { FnDeclKind::Pointer => ImplTraitPosition::PointerReturn, FnDeclKind::Trait => ImplTraitPosition::TraitReturn, FnDeclKind::Impl => ImplTraitPosition::ImplReturn, - }) + }; + match kind { + FnDeclKind::Trait | FnDeclKind::Impl => ImplTraitContext::FeatureGated( + position, + sym::return_position_impl_trait_in_trait, + ), + _ => ImplTraitContext::Disallowed(position), + } }; - hir::FnRetTy::Return(self.lower_ty(ty, &mut context)) + hir::FnRetTy::Return(self.lower_ty(ty, &context)) } FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(self.lower_span(*span)), } @@ -1938,7 +1945,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { output, span, if in_trait && !this.tcx.features().return_position_impl_trait_in_trait { - ImplTraitContext::Disallowed(ImplTraitPosition::TraitReturn) + ImplTraitContext::FeatureGated( + ImplTraitPosition::TraitReturn, + sym::return_position_impl_trait_in_trait, + ) } else { ImplTraitContext::ReturnPositionOpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id), diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs index 8d23c26e603..592fc5aa645 100644 --- a/compiler/rustc_ast_lowering/src/path.rs +++ b/compiler/rustc_ast_lowering/src/path.rs @@ -9,7 +9,7 @@ use rustc_ast::{self as ast, *}; use rustc_hir as hir; use rustc_hir::def::{DefKind, PartialRes, Res}; use rustc_hir::GenericArg; -use rustc_span::symbol::{kw, Ident}; +use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::{BytePos, Span, DUMMY_SP}; use smallvec::{smallvec, SmallVec}; @@ -352,11 +352,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> { // fn f(_: impl Fn() -> impl Debug) -> impl Fn() -> impl Debug // // disallowed --^^^^^^^^^^ allowed --^^^^^^^^^^ // ``` - FnRetTy::Ty(ty) - if matches!(itctx, ImplTraitContext::ReturnPositionOpaqueTy { .. }) - && self.tcx.features().impl_trait_in_fn_trait_return => - { - self.lower_ty(&ty, itctx) + FnRetTy::Ty(ty) if matches!(itctx, ImplTraitContext::ReturnPositionOpaqueTy { .. }) => { + if self.tcx.features().impl_trait_in_fn_trait_return { + self.lower_ty(&ty, itctx) + } else { + self.lower_ty( + &ty, + &ImplTraitContext::FeatureGated( + ImplTraitPosition::FnTraitReturn, + sym::impl_trait_in_fn_trait_return, + ), + ) + } } FnRetTy::Ty(ty) => { self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn)) diff --git a/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr index c485bc5c3ab..760dcb615c8 100644 --- a/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr +++ b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr @@ -3,12 +3,18 @@ error[E0562]: `impl Trait` only allowed in function and inherent method return t | LL | fn f() -> impl Fn() -> impl Sized { || () } | ^^^^^^^^^^ + | + = note: see issue #99697 for more information + = help: add `#![feature(impl_trait_in_fn_trait_return)]` to the crate attributes to enable error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return --> $DIR/feature-gate-impl_trait_in_fn_trait_return.rs:3:32 | LL | fn g() -> &'static dyn Fn() -> impl Sized { &|| () } | ^^^^^^^^^^ + | + = note: see issue #99697 for more information + = help: add `#![feature(impl_trait_in_fn_trait_return)]` to the crate attributes to enable error: aborting due to 2 previous errors