Add enum_intrinsics_non_enums lint

Author: Flying-Toast

core/src/mem/mod.rs

@@ -1053,6 +1053,7 @@ pub const fn discriminant<T>(v: &T) -> Discriminant<T> {
 #[inline(always)]
 #[unstable(feature = "variant_count", issue = "73662")]
 #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
+#[rustc_diagnostic_item = "mem_variant_count"]
 pub const fn variant_count<T>() -> usize {
     intrinsics::variant_count::<T>()
 }