Support ?Trait bounds in supertraits and dyn Trait under a feature gate

1 files changed, 21 insertions, 7 deletions

diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 1088db74cc9..9b063a330b7 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -1345,14 +1345,28 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         match bound {
             GenericBound::Trait(trait_ref, modifiers) => {
                 match (ctxt, modifiers.constness, modifiers.polarity) {
-                    (BoundKind::SuperTraits, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
-                        self.dcx().emit_err(errors::OptionalTraitSupertrait {
-                            span: trait_ref.span,
-                            path_str: pprust::path_to_string(&trait_ref.trait_ref.path),
-                        });
+                    (BoundKind::SuperTraits, BoundConstness::Never, BoundPolarity::Maybe(_))
+                        if !self.features.more_maybe_bounds =>
+                    {
+                        self.session
+                            .create_feature_err(
+                                errors::OptionalTraitSupertrait {
+                                    span: trait_ref.span,
+                                    path_str: pprust::path_to_string(&trait_ref.trait_ref.path),
+                                },
+                                sym::more_maybe_bounds,
+                            )
+                            .emit();
                     }
-                    (BoundKind::TraitObject, BoundConstness::Never, BoundPolarity::Maybe(_)) => {
-                        self.dcx().emit_err(errors::OptionalTraitObject { span: trait_ref.span });
+                    (BoundKind::TraitObject, BoundConstness::Never, BoundPolarity::Maybe(_))
+                        if !self.features.more_maybe_bounds =>
+                    {
+                        self.session
+                            .create_feature_err(
+                                errors::OptionalTraitObject { span: trait_ref.span },
+                                sym::more_maybe_bounds,
+                            )
+                            .emit();
                     }
                     (
                         BoundKind::TraitObject,