Rollup merge of rust-lang#132445 - RalfJung:const-unchecked-shifts, r=tgross35

Cleanup attributes around unchecked shifts and unchecked negation in const

The underlying intrinsic is marked as "safe to expose on stable", so we shouldn't need any `rustc_allow_const_fn_unstable(unchecked_shifts)` anywhere. However, bootstrap rustc doesn't yet have the new const stability checks, so these changes only apply under `cfg(not(bootstrap))`.

Author: GuillaumeGomez

Diff for: core/src/num/int_macros.rs

@@ -1161,7 +1161,7 @@ macro_rules! int_impl {
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
-        #[rustc_const_unstable(feature = "unchecked_neg", issue = "85122")]
+        #[cfg_attr(bootstrap, rustc_const_unstable(feature = "unchecked_neg", issue = "85122"))]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
         pub const unsafe fn unchecked_neg(self) -> Self {
@@ -1227,8 +1227,7 @@ macro_rules! int_impl {
         /// ```
         #[stable(feature = "wrapping", since = "1.7.0")]
         #[rustc_const_stable(feature = "const_checked_int_methods", since = "1.47.0")]
-        // We could always go back to wrapping
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -1294,7 +1293,7 @@ macro_rules! int_impl {
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
-        #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
+        #[cfg_attr(bootstrap, rustc_const_unstable(feature = "unchecked_shifts", issue = "85122"))]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
         pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self {
@@ -1353,8 +1352,7 @@ macro_rules! int_impl {
         /// ```
         #[stable(feature = "wrapping", since = "1.7.0")]
         #[rustc_const_stable(feature = "const_checked_int_methods", since = "1.47.0")]
-        // We could always go back to wrapping
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -1420,7 +1418,7 @@ macro_rules! int_impl {
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
-        #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
+        #[cfg_attr(bootstrap, rustc_const_unstable(feature = "unchecked_shifts", issue = "85122"))]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
@@ -2151,7 +2149,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         pub const fn wrapping_shl(self, rhs: u32) -> Self {
             // SAFETY: the masking by the bitsize of the type ensures that we do not shift
             // out of bounds
@@ -2181,7 +2179,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         pub const fn wrapping_shr(self, rhs: u32) -> Self {
             // SAFETY: the masking by the bitsize of the type ensures that we do not shift
             // out of bounds

Diff for: core/src/num/uint_macros.rs

@@ -1416,8 +1416,7 @@ macro_rules! uint_impl {
         /// ```
         #[stable(feature = "wrapping", since = "1.7.0")]
         #[rustc_const_stable(feature = "const_checked_int_methods", since = "1.47.0")]
-        // We could always go back to wrapping
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -1483,7 +1482,7 @@ macro_rules! uint_impl {
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
-        #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
+        #[cfg_attr(bootstrap, rustc_const_unstable(feature = "unchecked_shifts", issue = "85122"))]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
         pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self {
@@ -1542,8 +1541,7 @@ macro_rules! uint_impl {
         /// ```
         #[stable(feature = "wrapping", since = "1.7.0")]
         #[rustc_const_stable(feature = "const_checked_int_methods", since = "1.47.0")]
-        // We could always go back to wrapping
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -1609,7 +1607,7 @@ macro_rules! uint_impl {
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
-        #[rustc_const_unstable(feature = "unchecked_shifts", issue = "85122")]
+        #[cfg_attr(bootstrap, rustc_const_unstable(feature = "unchecked_shifts", issue = "85122"))]
         #[inline(always)]
         #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
@@ -2132,7 +2130,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         pub const fn wrapping_shl(self, rhs: u32) -> Self {
             // SAFETY: the masking by the bitsize of the type ensures that we do not shift
             // out of bounds
@@ -2165,7 +2163,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[rustc_allow_const_fn_unstable(unchecked_shifts)]
+        #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_shifts))]
         pub const fn wrapping_shr(self, rhs: u32) -> Self {
             // SAFETY: the masking by the bitsize of the type ensures that we do not shift
             // out of bounds

Diff for: core/src/ptr/const_ptr.rs

@@ -1005,7 +1005,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
-    #[rustc_allow_const_fn_unstable(unchecked_neg)]
+    #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_neg))]
     #[inline(always)]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn sub(self, count: usize) -> Self

Diff for: core/src/ptr/mut_ptr.rs

@@ -1085,7 +1085,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
-    #[rustc_allow_const_fn_unstable(unchecked_neg)]
+    #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_neg))]
     #[inline(always)]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn sub(self, count: usize) -> Self

Diff for: core/src/ptr/non_null.rs

@@ -635,7 +635,7 @@ impl<T: ?Sized> NonNull<T> {
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[stable(feature = "non_null_convenience", since = "1.80.0")]
     #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
-    #[rustc_allow_const_fn_unstable(unchecked_neg)]
+    #[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(unchecked_neg))]
     pub const unsafe fn sub(self, count: usize) -> Self
     where
         T: Sized,