export assert_unsafe_precondition macro for std-internal use

library/core/src/intrinsics.rs

@@ -2720,7 +2720,7 @@ pub const fn is_val_statically_known<T: Copy>(_arg: T) -> bool {
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[inline(always)]
 #[cfg_attr(not(bootstrap), rustc_intrinsic)] // just make it a regular fn in bootstrap
-pub(crate) const fn ub_checks() -> bool {
+pub const fn ub_checks() -> bool {
     cfg!(debug_assertions)
 }
 

library/core/src/lib.rs

@@ -193,6 +193,7 @@
 #![feature(str_split_inclusive_remainder)]
 #![feature(str_split_remainder)]
 #![feature(strict_provenance)]
+#![feature(ub_checks)]
 #![feature(unchecked_shifts)]
 #![feature(utf16_extra)]
 #![feature(utf16_extra_const)]
@@ -370,7 +371,8 @@ pub mod assert_matches {
 pub mod intrinsics;
 pub mod mem;
 pub mod ptr;
-mod ub_checks;
+#[unstable(feature = "ub_checks", issue = "none")]
+pub mod ub_checks;
 
 /* Core language traits */
 

library/core/src/ub_checks.rs

@@ -46,6 +46,8 @@
 /// variables cannot be optimized out in MIR, an innocent-looking `let` can produce enough
 /// debuginfo to have a measurable compile-time impact on debug builds.
 #[allow_internal_unstable(const_ub_checks)] // permit this to be called in stably-const fn
+#[macro_export]
+#[unstable(feature = "ub_checks", issue = "none")]
 macro_rules! assert_unsafe_precondition {
     ($kind:ident, $message:expr, ($($name:ident:$ty:ty = $arg:expr),*$(,)?) => $e:expr $(,)?) => {
         {
@@ -75,11 +77,13 @@ const fn precondition_check($($name:$ty),*) {
         }
     };
 }
-pub(crate) use assert_unsafe_precondition;
+#[unstable(feature = "ub_checks", issue = "none")]
+pub use assert_unsafe_precondition;
 
 /// Checking library UB is always enabled when UB-checking is done
 /// (and we use a reexport so that there is no unnecessary wrapper function).
-pub(crate) use intrinsics::ub_checks as check_library_ub;
+#[unstable(feature = "ub_checks", issue = "none")]
+pub use intrinsics::ub_checks as check_library_ub;
 
 /// Determines whether we should check for language UB.
 ///

library/std/src/lib.rs

@@ -358,6 +358,7 @@
 #![feature(str_internals)]
 #![feature(strict_provenance)]
 #![feature(strict_provenance_atomic_ptr)]
+#![feature(ub_checks)]
 // tidy-alphabetical-end
 //
 // Library features (alloc):