diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs index 82236d2e306..409aef9185d 100644 --- a/compiler/rustc_ast_passes/src/feature_gate.rs +++ b/compiler/rustc_ast_passes/src/feature_gate.rs @@ -362,6 +362,19 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> { } } + fn visit_generic_args(&mut self, args: &'a ast::GenericArgs) { + // This check needs to happen here because the never type can be returned from a function, + // but cannot be used in any other context. If this check was in `visit_fn_ret_ty`, it + // include both functions and generics like `impl Fn() -> !`. + if let ast::GenericArgs::Parenthesized(generic_args) = args + && let ast::FnRetTy::Ty(ref ty) = generic_args.output + && matches!(ty.kind, ast::TyKind::Never) + { + gate!(&self, never_type, ty.span, "the `!` type is experimental"); + } + visit::walk_generic_args(self, args); + } + fn visit_expr(&mut self, e: &'a ast::Expr) { match e.kind { ast::ExprKind::TryBlock(_) => {