stabilize const_cttz

Author: andjo403

library/core/src/intrinsics.rs

@@ -1543,7 +1543,7 @@ extern "rust-intrinsic" {
     /// let num_trailing = unsafe { cttz_nonzero(x) };
     /// assert_eq!(num_trailing, 3);
     /// ```
-    #[rustc_const_unstable(feature = "const_cttz", issue = "none")]
+    #[rustc_const_stable(feature = "const_cttz", since = "1.53.0")]
     pub fn cttz_nonzero<T: Copy>(x: T) -> T;
 
     /// Reverses the bytes in an integer type `T`.

library/core/src/lib.rs

@@ -79,7 +79,6 @@
 #![feature(const_int_unchecked_arith)]
 #![feature(const_mut_refs)]
 #![feature(const_refs_to_cell)]
-#![feature(const_cttz)]
 #![feature(const_panic)]
 #![feature(const_pin)]
 #![feature(const_fn)]

src/test/ui/consts/const-int-unchecked.rs

@@ -186,4 +186,13 @@ const _: i32 = unsafe { std::intrinsics::unchecked_rem(i32::MIN, -1) };
 //~^ ERROR any use of this value will cause an error
 //~| WARN this was previously accepted by the compiler but is being phased out
 
+// capture fault with zero value
+
+const _: u32 = unsafe { std::intrinsics::ctlz_nonzero(0) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+const _: u32 = unsafe { std::intrinsics::cttz_nonzero(0) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+
 fn main() {}

src/test/ui/consts/const-int-unchecked.stderr

@@ -516,5 +516,27 @@ LL | const _: i32 = unsafe { std::intrinsics::unchecked_rem(i32::MIN, -1) };
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
-error: aborting due to 47 previous errors
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:191:25
+   |
+LL | const _: u32 = unsafe { std::intrinsics::ctlz_nonzero(0) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         `ctlz_nonzero` called on 0
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:194:25
+   |
+LL | const _: u32 = unsafe { std::intrinsics::cttz_nonzero(0) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         `cttz_nonzero` called on 0
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: aborting due to 49 previous errors