Enforce syntactical stability of const traits in HIR

Author: compiler-errors

core/src/intrinsics/fallback.rs

@@ -8,6 +8,7 @@
 #![allow(missing_docs)]
 
 #[const_trait]
+#[rustc_const_unstable(feature = "core_intrinsics_fallbacks", issue = "none")]
 pub trait CarryingMulAdd: Copy + 'static {
     type Unsigned: Copy + 'static;
     fn carrying_mul_add(

core/src/marker.rs

@@ -952,6 +952,7 @@ marker_impls! {
 /// This should be used for `~const` bounds,
 /// as non-const bounds will always hold for every type.
 #[unstable(feature = "const_destruct", issue = "133214")]
+#[rustc_const_unstable(feature = "const_destruct", issue = "133214")]
 #[lang = "destruct"]
 #[rustc_on_unimplemented(message = "can't drop `{Self}`", append_const_msg)]
 #[rustc_deny_explicit_impl]

core/src/ops/arith.rs

@@ -65,6 +65,7 @@
 /// ```
 #[lang = "add"]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_ops", issue = "90080")]
 #[rustc_on_unimplemented(
     on(all(_Self = "{integer}", Rhs = "{float}"), message = "cannot add a float to an integer",),
     on(all(_Self = "{float}", Rhs = "{integer}"), message = "cannot add an integer to a float",),

core/src/ops/deref.rs

@@ -134,6 +134,7 @@
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "Deref"]
 #[const_trait]
+#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
 pub trait Deref {
     /// The resulting type after dereferencing.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -263,6 +264,7 @@ impl<T: ?Sized> const Deref for &mut T {
 #[doc(alias = "*")]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[const_trait]
+#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
 pub trait DerefMut: ~const Deref {
     /// Mutably dereferences the value.
     #[stable(feature = "rust1", since = "1.0.0")]

core/src/ops/drop.rs

@@ -204,6 +204,7 @@
 #[lang = "drop"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[const_trait]
+#[rustc_const_unstable(feature = "const_destruct", issue = "133214")]
 pub trait Drop {
     /// Executes the destructor for this type.
     ///