1 files changed, 19 insertions, 0 deletions
diff --git a/library/std/src/os/fd/tests.rs b/library/std/src/os/fd/tests.rs
index 26ef93e3d71..b39863644f1 100644
--- a/library/std/src/os/fd/tests.rs
+++ b/library/std/src/os/fd/tests.rs
@@ -32,3 +32,22 @@ fn test_fd() {
     assert_eq!(stdin_as_file.as_fd().as_raw_fd(), raw_fd);
     assert_eq!(Into::<OwnedFd>::into(stdin_as_file).into_raw_fd(), raw_fd);
 }
+
+#[cfg(any(unix, target_os = "wasi"))]
+#[test]
+fn test_niche_optimizations() {
+    use crate::mem::size_of;
+    #[cfg(unix)]
+    use crate::os::unix::io::{BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
+    #[cfg(target_os = "wasi")]
+    use crate::os::wasi::io::{BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
+
+    assert_eq!(size_of::<Option<OwnedFd>>(), size_of::<RawFd>());
+    assert_eq!(size_of::<Option<BorrowedFd<'static>>>(), size_of::<RawFd>());
+    unsafe {
+        assert_eq!(OwnedFd::from_raw_fd(RawFd::MIN).into_raw_fd(), RawFd::MIN);
+        assert_eq!(OwnedFd::from_raw_fd(RawFd::MAX).into_raw_fd(), RawFd::MAX);
+        assert_eq!(Some(OwnedFd::from_raw_fd(RawFd::MIN)).unwrap().into_raw_fd(), RawFd::MIN);
+        assert_eq!(Some(OwnedFd::from_raw_fd(RawFd::MAX)).unwrap().into_raw_fd(), RawFd::MAX);
+    }
+}