Rollup merge of #109693 - workingjubilee:maybe-unconstify-alloc, r=fee1-dead

Remove ~const from alloc

There is currently an effort underway to stop using `~const Trait`, temporarily, so as to refactor the logic underlying const traits with relative ease. This means it has to go from the standard library, as well.

I have taken the initial step of just removing these impls from alloc, as removing them from core is a much more tangled task. In addition, all of these implementations are one more-or-less logically-connected group, so reverting their deconstification as a group seems like it will also be sensible.

r? `@fee1-dead`

Author: matthiaskrgr

library/alloc/src/alloc.rs

@@ -14,8 +14,6 @@ use core::ptr::{self, NonNull};
 #[doc(inline)]
 pub use core::alloc::*;
 
-use core::marker::Destruct;
-
 #[cfg(test)]
 mod tests;
 
@@ -331,16 +329,12 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
 
 #[cfg_attr(not(test), lang = "box_free")]
 #[inline]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
 // This signature has to be the same as `Box`, otherwise an ICE will happen.
 // When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
 // well.
 // For example if `Box` is changed to  `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
 // this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
-pub(crate) const unsafe fn box_free<T: ?Sized, A: ~const Allocator + ~const Destruct>(
-    ptr: Unique<T>,
-    alloc: A,
-) {
+pub(crate) unsafe fn box_free<T: ?Sized, A: Allocator>(ptr: Unique<T>, alloc: A) {
     unsafe {
         let size = size_of_val(ptr.as_ref());
         let align = min_align_of_val(ptr.as_ref());

library/alloc/src/borrow.rs

@@ -328,10 +328,9 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
-impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B>
+impl<B: ?Sized + ToOwned> Deref for Cow<'_, B>
 where
-    B::Owned: ~const Borrow<B>,
+    B::Owned: Borrow<B>,
 {
     type Target = B;
 

library/alloc/src/boxed.rs

@@ -159,7 +159,7 @@ use core::hash::{Hash, Hasher};
 use core::iter::FromIterator;
 use core::iter::{FusedIterator, Iterator};
 use core::marker::Tuple;
-use core::marker::{Destruct, Unpin, Unsize};
+use core::marker::{Unpin, Unsize};
 use core::mem;
 use core::ops::{
     CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver,
@@ -376,12 +376,11 @@ impl<T, A: Allocator> Box<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[must_use]
     #[inline]
-    pub const fn new_in(x: T, alloc: A) -> Self
+    pub fn new_in(x: T, alloc: A) -> Self
     where
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let mut boxed = Self::new_uninit_in(alloc);
         unsafe {
@@ -406,12 +405,10 @@ impl<T, A: Allocator> Box<T, A> {
     /// # Ok::<(), std::alloc::AllocError>(())
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>
+    pub fn try_new_in(x: T, alloc: A) -> Result<Self, AllocError>
     where
-        T: ~const Destruct,
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let mut boxed = Self::try_new_uninit_in(alloc)?;
         unsafe {
@@ -441,13 +438,12 @@ impl<T, A: Allocator> Box<T, A> {
     /// assert_eq!(*five, 5)
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[cfg(not(no_global_oom_handling))]
     #[must_use]
     // #[unstable(feature = "new_uninit", issue = "63291")]
-    pub const fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
+    pub fn new_uninit_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
     where
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
         // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
@@ -482,10 +478,9 @@ impl<T, A: Allocator> Box<T, A> {
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
     // #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
-    pub const fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
+    pub fn try_new_uninit_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
     where
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
         let ptr = alloc.allocate(layout)?.cast();
@@ -513,13 +508,12 @@ impl<T, A: Allocator> Box<T, A> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[cfg(not(no_global_oom_handling))]
     // #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
-    pub const fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
+    pub fn new_zeroed_in(alloc: A) -> Box<mem::MaybeUninit<T>, A>
     where
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
         // NOTE: Prefer match over unwrap_or_else since closure sometimes not inlineable.
@@ -554,10 +548,9 @@ impl<T, A: Allocator> Box<T, A> {
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[unstable(feature = "allocator_api", issue = "32838")]
     // #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
-    pub const fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
+    pub fn try_new_zeroed_in(alloc: A) -> Result<Box<mem::MaybeUninit<T>, A>, AllocError>
     where
-        A: ~const Allocator + ~const Destruct,
+        A: Allocator,
     {
         let layout = Layout::new::<mem::MaybeUninit<T>>();
         let ptr = alloc.allocate_zeroed(layout)?.cast();
@@ -573,12 +566,11 @@ impl<T, A: Allocator> Box<T, A> {
     /// construct a (pinned) `Box` in a different way than with [`Box::new_in`].
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[must_use]
     #[inline(always)]
-    pub const fn pin_in(x: T, alloc: A) -> Pin<Self>
+    pub fn pin_in(x: T, alloc: A) -> Pin<Self>
     where
-        A: 'static + ~const Allocator + ~const Destruct,
+        A: 'static + Allocator,
     {
         Self::into_pin(Self::new_in(x, alloc))
     }
@@ -605,12 +597,8 @@ impl<T, A: Allocator> Box<T, A> {
     /// assert_eq!(Box::into_inner(c), 5);
     /// ```
     #[unstable(feature = "box_into_inner", issue = "80437")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn into_inner(boxed: Self) -> T
-    where
-        Self: ~const Destruct,
-    {
+    pub fn into_inner(boxed: Self) -> T {
         *boxed
     }
 }

library/alloc/tests/boxed.rs

@@ -179,18 +179,3 @@ unsafe impl const Allocator for ConstAllocator {
         self
     }
 }
-
-#[test]
-fn const_box() {
-    const VALUE: u32 = {
-        let mut boxed = Box::new_in(1u32, ConstAllocator);
-        assert!(*boxed == 1);
-
-        *boxed = 42;
-        assert!(*boxed == 42);
-
-        *Box::leak(boxed)
-    };
-
-    assert!(VALUE == 42);
-}

library/alloc/tests/lib.rs

@@ -3,7 +3,6 @@
 #![feature(assert_matches)]
 #![feature(btree_drain_filter)]
 #![feature(cow_is_borrowed)]
-#![feature(const_box)]
 #![feature(const_convert)]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_heap)]