1 files changed, 64 insertions, 0 deletions
diff --git a/src/test/ui/stdlib-unit-tests/minmax-stability-issue-23687.rs b/src/test/ui/stdlib-unit-tests/minmax-stability-issue-23687.rs
new file mode 100644
index 000000000..9100bfbde
--- /dev/null
+++ b/src/test/ui/stdlib-unit-tests/minmax-stability-issue-23687.rs
@@ -0,0 +1,64 @@
+// run-pass
+
+use std::fmt::Debug;
+use std::cmp::{self, PartialOrd, Ordering};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+struct Foo {
+    n: u8,
+    name: &'static str
+}
+
+impl PartialOrd for Foo {
+    fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Foo {
+    fn cmp(&self, other: &Foo) -> Ordering {
+        self.n.cmp(&other.n)
+    }
+}
+
+fn main() {
+    let a = Foo { n: 4, name: "a" };
+    let b = Foo { n: 4, name: "b" };
+    let c = Foo { n: 8, name: "c" };
+    let d = Foo { n: 8, name: "d" };
+    let e = Foo { n: 22, name: "e" };
+    let f = Foo { n: 22, name: "f" };
+
+    let data = [a, b, c, d, e, f];
+
+    // `min` should return the left when the values are equal
+    assert_eq!(data.iter().min(), Some(&a));
+    assert_eq!(data.iter().min_by_key(|a| a.n), Some(&a));
+    assert_eq!(cmp::min(a, b), a);
+    assert_eq!(cmp::min(b, a), b);
+
+    // `max` should return the right when the values are equal
+    assert_eq!(data.iter().max(), Some(&f));
+    assert_eq!(data.iter().max_by_key(|a| a.n), Some(&f));
+    assert_eq!(cmp::max(e, f), f);
+    assert_eq!(cmp::max(f, e), e);
+
+    let mut presorted = data.to_vec();
+    presorted.sort();
+    assert_stable(&presorted);
+
+    let mut presorted = data.to_vec();
+    presorted.sort_by(|a, b| a.cmp(b));
+    assert_stable(&presorted);
+
+    // Assert that sorted and min/max are the same
+    fn assert_stable<T: Ord + Debug>(presorted: &[T]) {
+        for slice in presorted.windows(2) {
+            let a = &slice[0];
+            let b = &slice[1];
+
+            assert_eq!(a, cmp::min(a, b));
+            assert_eq!(b, cmp::max(a, b));
+        }
+    }
+}