use better unstable attribs

Author: xacrimon

library/core/src/cmp/pattern.rs

@@ -12,7 +12,7 @@ where
     fn do_match(&self, other: &Rhs) -> bool;
 }
 
-macro_rules ! impl_match_lowered_cmp_for_primitive {
+macro_rules ! impl_for_primitive {
     ($($t:ty),*) => {
         $(
             impl const MatchLoweredCmp for $t {
@@ -24,15 +24,14 @@ macro_rules ! impl_match_lowered_cmp_for_primitive {
     };
 }
 
-impl_match_lowered_cmp_for_primitive! {
+impl_for_primitive! {
     bool, char,
     u8, u16, u32, u64, u128, usize,
     i8, i16, i32, i64, i128, isize,
     f32, f64
 }
 
 impl const MatchLoweredCmp for str {
-    #[rustc_allow_const_fn_unstable(const_trait_impl)]
     fn do_match(&self, other: &Self) -> bool {
         <[u8] as MatchLoweredCmp>::do_match((*self).as_bytes(), (*other).as_bytes())
     }
@@ -42,7 +41,6 @@ impl<T> const MatchLoweredCmp for [T]
 where
     T: ~const MatchLoweredCmp,
 {
-    #[rustc_allow_const_fn_unstable(const_trait_impl)]
     default fn do_match(&self, other: &Self) -> bool {
         if self.len() != other.len() {
             return false;
@@ -62,11 +60,11 @@ where
     }
 }
 
+#[rustc_const_unstable(feature = "core_intrinsics", issue = "none")]
 impl<T> const MatchLoweredCmp for [T]
 where
     T: ~const MatchLoweredCmp + BytewiseEq<T>,
 {
-    #[rustc_allow_const_fn_unstable(core_intrinsics, const_trait_impl)]
     fn do_match(&self, other: &Self) -> bool {
         if self.len() != other.len() {
             return false;