Rollup merge of #71485 - arlopurcell:binary_heap_retain, r=Amanieu

Add BinaryHeap::retain as suggested in #42849

This PR implements retain for BinaryHeap as suggested in #42849.

This is my first PR for Rust, so please let me know if I should be doing anything differently, thanks!

2 files changed, 9 insertions, 0 deletions

diff --git a/src/liballoc/tests/binary_heap.rs b/src/liballoc/tests/binary_heap.rs
index 057afd41824..62084ccf53c 100644
--- a/src/liballoc/tests/binary_heap.rs
+++ b/src/liballoc/tests/binary_heap.rs
@@ -372,6 +372,14 @@ fn assert_covariance() {
     }
 }
 
+#[test]
+fn test_retain() {
+    let mut a = BinaryHeap::from(vec![-10, -5, 1, 2, 4, 13]);
+    a.retain(|x| x % 2 == 0);
+
+    assert_eq!(a.into_sorted_vec(), [-10, 2, 4])
+}
+
 // old binaryheap failed this test
 //
 // Integrity means that all elements are present after a comparison panics,
diff --git a/src/liballoc/tests/lib.rs b/src/liballoc/tests/lib.rs
index ad6feaeebc6..78d49558262 100644
--- a/src/liballoc/tests/lib.rs
+++ b/src/liballoc/tests/lib.rs
@@ -14,6 +14,7 @@
 #![feature(binary_heap_drain_sorted)]
 #![feature(vec_remove_item)]
 #![feature(split_inclusive)]
+#![feature(binary_heap_retain)]
 
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};