Auto merge of #86595 - a1phyr:allocator_api_for_vecdeque, r=Amanieu

Add support for custom allocator in `VecDeque`

This follows the [roadmap](rust-lang/wg-allocators#7) of the allocator WG to add custom allocators to collections.

`@rustbot` modify labels: +A-allocators +T-libs

library/alloc/src/collections/vec_deque/drain.rs

@@ -2,6 +2,8 @@ use core::iter::FusedIterator;
 use core::ptr::{self, NonNull};
 use core::{fmt, mem};
 
+use crate::alloc::{Allocator, Global};
+
 use super::{count, Iter, VecDeque};
 
 /// A draining iterator over the elements of a `VecDeque`.
@@ -11,15 +13,19 @@ use super::{count, Iter, VecDeque};
 ///
 /// [`drain`]: VecDeque::drain
 #[stable(feature = "drain", since = "1.6.0")]
-pub struct Drain<'a, T: 'a> {
+pub struct Drain<
+    'a,
+    T: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
     pub(crate) after_tail: usize,
     pub(crate) after_head: usize,
     pub(crate) iter: Iter<'a, T>,
-    pub(crate) deque: NonNull<VecDeque<T>>,
+    pub(crate) deque: NonNull<VecDeque<T, A>>,
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
-impl<T: fmt::Debug> fmt::Debug for Drain<'_, T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("Drain")
             .field(&self.after_tail)
@@ -30,16 +36,16 @@ impl<T: fmt::Debug> fmt::Debug for Drain<'_, T> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-unsafe impl<T: Sync> Sync for Drain<'_, T> {}
+unsafe impl<T: Sync, A: Allocator + Sync> Sync for Drain<'_, T, A> {}
 #[stable(feature = "drain", since = "1.6.0")]
-unsafe impl<T: Send> Send for Drain<'_, T> {}
+unsafe impl<T: Send, A: Allocator + Send> Send for Drain<'_, T, A> {}
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<T> Drop for Drain<'_, T> {
+impl<T, A: Allocator> Drop for Drain<'_, T, A> {
     fn drop(&mut self) {
-        struct DropGuard<'r, 'a, T>(&'r mut Drain<'a, T>);
+        struct DropGuard<'r, 'a, T, A: Allocator>(&'r mut Drain<'a, T, A>);
 
-        impl<'r, 'a, T> Drop for DropGuard<'r, 'a, T> {
+        impl<'r, 'a, T, A: Allocator> Drop for DropGuard<'r, 'a, T, A> {
             fn drop(&mut self) {
                 self.0.for_each(drop);
 
@@ -96,7 +102,7 @@ impl<T> Drop for Drain<'_, T> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<T> Iterator for Drain<'_, T> {
+impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
     type Item = T;
 
     #[inline]
@@ -111,15 +117,15 @@ impl<T> Iterator for Drain<'_, T> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<T> DoubleEndedIterator for Drain<'_, T> {
+impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.iter.next_back().map(|elt| unsafe { ptr::read(elt) })
     }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<T> ExactSizeIterator for Drain<'_, T> {}
+impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {}
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<T> FusedIterator for Drain<'_, T> {}
+impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}

library/alloc/src/collections/vec_deque/into_iter.rs

@@ -1,6 +1,8 @@
 use core::fmt;
 use core::iter::{FusedIterator, TrustedLen};
 
+use crate::alloc::{Allocator, Global};
+
 use super::VecDeque;
 
 /// An owning iterator over the elements of a `VecDeque`.
@@ -11,19 +13,22 @@ use super::VecDeque;
 /// [`into_iter`]: VecDeque::into_iter
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct IntoIter<T> {
-    pub(crate) inner: VecDeque<T>,
+pub struct IntoIter<
+    T,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
+    pub(crate) inner: VecDeque<T, A>,
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
-impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("IntoIter").field(&self.inner).finish()
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Iterator for IntoIter<T> {
+impl<T, A: Allocator> Iterator for IntoIter<T, A> {
     type Item = T;
 
     #[inline]
@@ -39,22 +44,22 @@ impl<T> Iterator for IntoIter<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> DoubleEndedIterator for IntoIter<T> {
+impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.inner.pop_back()
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> ExactSizeIterator for IntoIter<T> {
+impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
     fn is_empty(&self) -> bool {
         self.inner.is_empty()
     }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<T> FusedIterator for IntoIter<T> {}
+impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<T> TrustedLen for IntoIter<T> {}
+unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}

library/alloc/src/collections/vec_deque/macros.rs

@@ -1,9 +1,9 @@
 macro_rules! __impl_slice_eq1 {
     ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => {
         #[stable(feature = "vec_deque_partial_eq_slice", since = "1.17.0")]
-        impl<A, B, $($vars)*> PartialEq<$rhs> for $lhs
+        impl<T, U, A: Allocator, $($vars)*> PartialEq<$rhs> for $lhs
         where
-            A: PartialEq<B>,
+            T: PartialEq<U>,
             $($constraints)*
         {
             fn eq(&self, other: &$rhs) -> bool {