Rollup merge of rust-lang#131197 - EFanZh:avoid-emptyness-check-in-peekmut-pop, r=Amanieu

matthiaskrgr · web-flow · commit 1bd16cdc12dc · 2024-10-03T21:52:47.000+02:00
Avoid emptiness check in `PeekMut::pop`

This PR avoids an unnecessary emptiness check in `PeekMut::pop` by replacing `Option::unwrap` with `Option::unwrap_unchecked`.
diff --git a/alloc/src/collections/binary_heap/mod.rs b/alloc/src/collections/binary_heap/mod.rs
@@ -374,7 +374,10 @@ impl<'a, T: Ord, A: Allocator> PeekMut<'a, T, A> {
             // the caller could've mutated the element. It is removed from the
             // heap on the next line and pop() is not sensitive to its value.
         }
-        this.heap.pop().unwrap()
+
+        // SAFETY: Have a `PeekMut` element proves that the associated binary heap being non-empty,
+        // so the `pop` operation will not fail.
+        unsafe { this.heap.pop().unwrap_unchecked() }
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -374,7 +374,10 @@ impl<'a, T: Ord, A: Allocator> PeekMut<'a, T, A> {`
`374`	`374`	`// the caller could've mutated the element. It is removed from the`
`375`	`375`	`// heap on the next line and pop() is not sensitive to its value.`
`376`	`376`	`}`
`377`		`- this.heap.pop().unwrap()`
	`377`	`+`
	`378`	+ // SAFETY: Have a `PeekMut` element proves that the associated binary heap being non-empty,
	`379`	+ // so the `pop` operation will not fail.
	`380`	`+ unsafe { this.heap.pop().unwrap_unchecked() }`
`378`	`381`	`}`
`379`	`382`	`}`
`380`	`383`