stabilize const_cell_into_inner

Author: RalfJung

Diff for: library/core/src/cell.rs

@@ -514,7 +514,8 @@ impl<T> Cell<T> {
     /// assert_eq!(five, 5);
     /// ```
     #[stable(feature = "move_cell", since = "1.17.0")]
-    #[rustc_const_unstable(feature = "const_cell_into_inner", issue = "78729")]
+    #[rustc_const_stable(feature = "const_cell_into_inner", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
     pub const fn into_inner(self) -> T {
         self.value.into_inner()
     }
@@ -857,7 +858,8 @@ impl<T> RefCell<T> {
     /// let five = c.into_inner();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_cell_into_inner", issue = "78729")]
+    #[rustc_const_stable(feature = "const_cell_into_inner", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
     #[inline]
     pub const fn into_inner(self) -> T {
         // Since this function takes `self` (the `RefCell`) by value, the
@@ -2098,8 +2100,8 @@ impl<T> UnsafeCell<T> {
     /// ```
     #[inline(always)]
     #[stable(feature = "rust1", since = "1.0.0")]
-    // When this is const stabilized, please remove `primitive_into_inner` below.
-    #[rustc_const_unstable(feature = "const_cell_into_inner", issue = "78729")]
+    #[rustc_const_stable(feature = "const_cell_into_inner", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
     pub const fn into_inner(self) -> T {
         self.value
     }
@@ -2245,47 +2247,6 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> {}
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T> {}
 
-// Special cases of UnsafeCell::into_inner where T is a primitive. These are
-// used by Atomic*::into_inner.
-//
-// The real UnsafeCell::into_inner cannot be used yet in a stable const function.
-// That is blocked on a "precise drop analysis" unstable const feature.
-// https://github.com/rust-lang/rust/issues/73255
-macro_rules! unsafe_cell_primitive_into_inner {
-    ($($primitive:ident $atomic:literal)*) => {
-        $(
-            #[cfg(target_has_atomic_load_store = $atomic)]
-            impl UnsafeCell<$primitive> {
-                pub(crate) const fn primitive_into_inner(self) -> $primitive {
-                    self.value
-                }
-            }
-        )*
-    };
-}
-
-unsafe_cell_primitive_into_inner! {
-    i8 "8"
-    u8 "8"
-    i16 "16"
-    u16 "16"
-    i32 "32"
-    u32 "32"
-    i64 "64"
-    u64 "64"
-    i128 "128"
-    u128 "128"
-    isize "ptr"
-    usize "ptr"
-}
-
-#[cfg(target_has_atomic_load_store = "ptr")]
-impl<T> UnsafeCell<*mut T> {
-    pub(crate) const fn primitive_into_inner(self) -> *mut T {
-        self.value
-    }
-}
-
 /// [`UnsafeCell`], but [`Sync`].
 ///
 /// This is just an `UnsafeCell`, except it implements `Sync`

Diff for: library/core/src/cell/once.rs

@@ -309,7 +309,8 @@ impl<T> OnceCell<T> {
     /// ```
     #[inline]
     #[stable(feature = "once_cell", since = "1.70.0")]
-    #[rustc_const_unstable(feature = "const_cell_into_inner", issue = "78729")]
+    #[rustc_const_stable(feature = "const_cell_into_inner", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
     pub const fn into_inner(self) -> Option<T> {
         // Because `into_inner` takes `self` by value, the compiler statically verifies
         // that it is not currently borrowed. So it is safe to move out `Option<T>`.

Diff for: library/core/src/lib.rs

@@ -118,7 +118,6 @@
 #![feature(const_array_into_iter_constructors)]
 #![feature(const_bigint_helper_methods)]
 #![feature(const_black_box)]
-#![feature(const_cell_into_inner)]
 #![feature(const_char_encode_utf16)]
 #![feature(const_char_encode_utf8)]
 #![feature(const_eval_select)]

Diff for: library/core/src/sync/atomic.rs

@@ -577,7 +577,7 @@ impl AtomicBool {
     #[stable(feature = "atomic_access", since = "1.15.0")]
     #[rustc_const_stable(feature = "const_atomic_into_inner", since = "1.79.0")]
     pub const fn into_inner(self) -> bool {
-        self.v.primitive_into_inner() != 0
+        self.v.into_inner() != 0
     }
 
     /// Loads a value from the bool.
@@ -1394,7 +1394,7 @@ impl<T> AtomicPtr<T> {
     #[stable(feature = "atomic_access", since = "1.15.0")]
     #[rustc_const_stable(feature = "const_atomic_into_inner", since = "1.79.0")]
     pub const fn into_inner(self) -> *mut T {
-        self.p.primitive_into_inner()
+        self.p.into_inner()
     }
 
     /// Loads a value from the pointer.
@@ -2389,7 +2389,7 @@ macro_rules! atomic_int {
             #[$stable_access]
             #[rustc_const_stable(feature = "const_atomic_into_inner", since = "1.79.0")]
             pub const fn into_inner(self) -> $int_type {
-                self.v.primitive_into_inner()
+                self.v.into_inner()
             }
 
             /// Loads a value from the atomic integer.

Diff for: library/core/tests/lib.rs

@@ -18,7 +18,6 @@
 #![feature(const_align_offset)]
 #![feature(const_array_from_ref)]
 #![feature(const_black_box)]
-#![feature(const_cell_into_inner)]
 #![feature(const_hash)]
 #![feature(const_heap)]
 #![feature(const_ip)]