From 8315295917d0cfbabaaccaf4f0826a6304acc9be Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 29 Sep 2023 02:40:30 -0400
Subject: [PATCH] Stabilize `const_mem_zeroed`

Make `core::mem::zeroed` const stable. Newly stable API:

    // core::mem
    pub const unsafe fn zeroed<T>() -> T;

This is stabilized with `const_maybe_uninit_zeroed` since it is a simple
wrapper.

In order to make this possible, intrinsics `assert_zero_valid` was made
const stable under `const_assert_type2`.
`assert_mem_uninitialized_valid` was also made const stable since it is
under the same gate.
---
 library/core/src/intrinsics.rs            | 4 ++--
 library/core/src/mem/mod.rs               | 3 ++-
 tests/ui/consts/assert-type-intrinsics.rs | 1 -
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index 4c76662ac0975..40dc323032eda 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -1072,7 +1072,7 @@ extern "rust-intrinsic" {
     /// zero-initialization: This will statically either panic, or do nothing.
     ///
     /// This intrinsic does not have a stable counterpart.
-    #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
+    #[rustc_const_stable(feature = "const_assert_type2", since = "CURRENT_RUSTC_VERSION")]
     #[rustc_safe_intrinsic]
     #[rustc_nounwind]
     pub fn assert_zero_valid<T>();
@@ -1080,7 +1080,7 @@ extern "rust-intrinsic" {
     /// A guard for `std::mem::uninitialized`. This will statically either panic, or do nothing.
     ///
     /// This intrinsic does not have a stable counterpart.
-    #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
+    #[rustc_const_stable(feature = "const_assert_type2", since = "CURRENT_RUSTC_VERSION")]
     #[rustc_safe_intrinsic]
     #[rustc_nounwind]
     pub fn assert_mem_uninitialized_valid<T>();
diff --git a/library/core/src/mem/mod.rs b/library/core/src/mem/mod.rs
index d7abc9a0e23aa..82ce901140ada 100644
--- a/library/core/src/mem/mod.rs
+++ b/library/core/src/mem/mod.rs
@@ -647,7 +647,8 @@ pub const fn needs_drop<T: ?Sized>() -> bool {
 #[allow(deprecated)]
 #[rustc_diagnostic_item = "mem_zeroed"]
 #[track_caller]
-pub unsafe fn zeroed<T>() -> T {
+#[rustc_const_stable(feature = "const_mem_zeroed", since = "CURRENT_RUSTC_VERSION")]
+pub const unsafe fn zeroed<T>() -> T {
     // SAFETY: the caller must guarantee that an all-zero value is valid for `T`.
     unsafe {
         intrinsics::assert_zero_valid::<T>();
diff --git a/tests/ui/consts/assert-type-intrinsics.rs b/tests/ui/consts/assert-type-intrinsics.rs
index b4fd423becd9d..32b5f5c92c52d 100644
--- a/tests/ui/consts/assert-type-intrinsics.rs
+++ b/tests/ui/consts/assert-type-intrinsics.rs
@@ -1,5 +1,4 @@
 #![feature(never_type)]
-#![feature(const_assert_type2)]
 #![feature(core_intrinsics)]
 
 use std::intrinsics;