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Set sift=true only when PeekMut yields a mutable reference

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This commit is contained in:
Giacomo Stevanato 2020-08-26 23:52:20 +02:00
parent 924cd135b6
commit af1e3633f7
1 changed files with 2 additions and 1 deletions
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library/alloc/src/collections/binary_heap.rs
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@ -293,6 +293,7 @@ impl<T: Ord> Deref for PeekMut<'_, T> {
impl<T: Ord> DerefMut for PeekMut<'_, T> { impl<T: Ord> DerefMut for PeekMut<'_, T> {
fn deref_mut(&mut self) -> &mut T { fn deref_mut(&mut self) -> &mut T {
debug_assert!(!self.heap.is_empty()); debug_assert!(!self.heap.is_empty());
self.sift = true;
// SAFE: PeekMut is only instantiated for non-empty heaps // SAFE: PeekMut is only instantiated for non-empty heaps
unsafe { self.heap.data.get_unchecked_mut(0) } unsafe { self.heap.data.get_unchecked_mut(0) }
} }
@ -401,7 +402,7 @@ impl<T: Ord> BinaryHeap<T> {
/// Cost is *O*(1) in the worst case. /// Cost is *O*(1) in the worst case.
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> { pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> {
if self.is_empty() { None } else { Some(PeekMut { heap: self, sift: true }) } if self.is_empty() { None } else { Some(PeekMut { heap: self, sift: false }) }
} }
/// Removes the greatest item from the binary heap and returns it, or `None` if it /// Removes the greatest item from the binary heap and returns it, or `None` if it