Apply review feedback; Fix no_global_oom_handling build

Author: scottmcm

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

@@ -590,6 +590,9 @@ impl<T, A: Allocator> VecDeque<T, A> {
         VecDeque { head: 0, len: 0, buf: RawVec::with_capacity_in(capacity, alloc) }
     }
 
+    /// Creates a `VecDeque` from a raw allocation, when the initialized
+    /// part of that allocation forms a *contiguous* subslice thereof.
+    ///
     /// For use by `vec::IntoIter::into_vecdeque`
     ///
     /// # Safety

library/alloc/src/vec/into_iter.rs

@@ -1,6 +1,7 @@
 #[cfg(not(no_global_oom_handling))]
 use super::AsVecIntoIter;
 use crate::alloc::{Allocator, Global};
+#[cfg(not(no_global_oom_handling))]
 use crate::collections::VecDeque;
 use crate::raw_vec::RawVec;
 use core::array;
@@ -134,6 +135,7 @@ impl<T, A: Allocator> IntoIter<T, A> {
         self.ptr = self.end;
     }
 
+    #[cfg(not(no_global_oom_handling))]
     #[inline]
     pub(crate) fn into_vecdeque(self) -> VecDeque<T, A> {
         // Keep our `Drop` impl from dropping the elements and the allocator

library/alloc/tests/vec_deque.rs

@@ -1741,22 +1741,32 @@ fn test_resize_keeps_reserved_space_from_item() {
 fn test_collect_from_into_iter_keeps_allocation() {
     let mut v = Vec::with_capacity(13);
     v.extend(0..7);
-    check(v.into_iter());
+    check(v.as_ptr(), v.last().unwrap(), v.into_iter());
 
     let mut v = VecDeque::with_capacity(13);
     v.extend(0..7);
-    check(v.into_iter());
+    check(&v[0], &v[v.len() - 1], v.into_iter());
 
-    fn check(mut it: impl Iterator<Item = i32>) {
+    fn check(buf: *const i32, last: *const i32, mut it: impl Iterator<Item = i32>) {
         assert_eq!(it.next(), Some(0));
         assert_eq!(it.next(), Some(1));
+
         let mut v: VecDeque<i32> = it.collect();
         assert_eq!(v.capacity(), 13);
+        assert_eq!(v.as_slices().0.as_ptr(), buf.wrapping_add(2));
+        assert_eq!(&v[v.len() - 1] as *const _, last);
+
         assert_eq!(v.as_slices(), ([2, 3, 4, 5, 6].as_slice(), [].as_slice()));
         v.push_front(7);
         assert_eq!(v.as_slices(), ([7, 2, 3, 4, 5, 6].as_slice(), [].as_slice()));
         v.push_front(8);
         assert_eq!(v.as_slices(), ([8, 7, 2, 3, 4, 5, 6].as_slice(), [].as_slice()));
+
+        // Now that we've adding thing in place of the two that we removed from
+        // the front of the iterator, we're back to matching the buffer pointer.
+        assert_eq!(v.as_slices().0.as_ptr(), buf);
+        assert_eq!(&v[v.len() - 1] as *const _, last);
+
         v.push_front(9);
         assert_eq!(v.as_slices(), ([9].as_slice(), [8, 7, 2, 3, 4, 5, 6].as_slice()));
         assert_eq!(v.capacity(), 13);