Stabilize const_impl_trait as well

Author: eholk

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -356,7 +356,6 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
 
             match *ty.kind() {
                 ty::Ref(_, _, hir::Mutability::Mut) => self.check_op(ops::ty::MutRef(kind)),
-                ty::Opaque(..) => self.check_op(ops::ty::ImplTrait),
                 _ => {}
             }
         }

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -795,25 +795,4 @@ pub mod ty {
             )
         }
     }
-
-    #[derive(Debug)]
-    pub struct ImplTrait;
-    impl<'tcx> NonConstOp<'tcx> for ImplTrait {
-        fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status {
-            Status::Unstable(sym::const_impl_trait)
-        }
-
-        fn build_error(
-            &self,
-            ccx: &ConstCx<'_, 'tcx>,
-            span: Span,
-        ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-            feature_err(
-                &ccx.tcx.sess.parse_sess,
-                sym::const_impl_trait,
-                span,
-                &format!("`impl Trait` is not allowed in {}s", ccx.const_kind()),
-            )
-        }
-    }
 }

compiler/rustc_feature/src/accepted.rs

@@ -100,6 +100,8 @@ declare_features! (
     (accepted, const_generics_defaults, "1.59.0", Some(44580), None),
     /// Allows the use of `if` and `match` in constants.
     (accepted, const_if_match, "1.46.0", Some(49146), None),
+    /// Allows argument and return position `impl Trait` in a `const fn`.
+    (accepted, const_impl_trait, "1.60.0", Some(77463), None),
     /// Allows indexing into constant arrays.
     (accepted, const_indexing, "1.26.0", Some(29947), None),
     /// Allows let bindings, assignments and destructuring in `const` functions and constants.

compiler/rustc_feature/src/active.rs

@@ -340,8 +340,6 @@ declare_features! (
     (active, const_fn_floating_point_arithmetic, "1.48.0", Some(57241), None),
     /// Allows `for _ in _` loops in const contexts.
     (active, const_for, "1.56.0", Some(87575), None),
-    /// Allows argument and return position `impl Trait` in a `const fn`.
-    (active, const_impl_trait, "1.48.0", Some(77463), None),
     /// Allows using `&mut` in constant functions.
     (active, const_mut_refs, "1.41.0", Some(57349), None),
     /// Be more precise when looking for live drops in a const context.

library/core/src/lib.rs

@@ -160,7 +160,7 @@
 #![feature(const_fn_floating_point_arithmetic)]
 #![cfg_attr(bootstrap, feature(const_fn_fn_ptr_basics))]
 #![cfg_attr(bootstrap, feature(const_fn_trait_bound))]
-#![feature(const_impl_trait)]
+#![cfg_attr(bootstrap, feature(const_impl_trait))]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
 #![feature(const_refs_to_cell)]

src/test/ui/consts/min_const_fn/min_const_fn_impl_trait.rs

@@ -1,4 +1,4 @@
-#![feature(const_impl_trait, rustc_attrs)]
+#![feature(rustc_attrs)]
 #![feature(type_alias_impl_trait)]
 
 type Foo = impl Fn() -> usize;

src/test/ui/consts/min_const_fn/min_const_fn_impl_trait.stderr

@@ -1,4 +1,4 @@
-#![feature(const_impl_trait, generators, generator_trait, rustc_attrs)]
+#![feature(generators, generator_trait, rustc_attrs)]
 #![feature(type_alias_impl_trait)]
 
 use std::ops::Generator;