Add more niche-optimization tests.

This ports in the new tests added in rust-lang/rust#96947.

tests/niche-optimizations.rs

@@ -10,17 +10,33 @@ use io_lifetimes::{BorrowedFd, OwnedFd};
 use io_lifetimes::{BorrowedSocket, OwnedSocket};
 
 #[cfg(unix)]
-use std::os::unix::io::RawFd;
+use std::os::unix::io::{FromRawFd, IntoRawFd, RawFd};
 #[cfg(target_os = "wasi")]
-use std::os::wasi::io::RawFd;
+use std::os::wasi::io::{FromRawSocket, IntoRawSocket, RawFd};
 #[cfg(windows)]
-use std::os::windows::io::RawSocket;
+use std::os::windows::io::{FromRawSocket, IntoRawSocket, RawSocket};
 
 #[cfg(all(rustc_attrs, any(unix, target_os = "wasi")))]
 #[test]
 fn test_niche_optimizations() {
     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
+        );
+    }
 }
 
 #[cfg(all(rustc_attrs, windows))]
@@ -31,4 +47,26 @@ fn test_niche_optimizations_socket() {
         size_of::<Option<BorrowedSocket<'static>>>(),
         size_of::<RawSocket>(),
     );
+    unsafe {
+        assert_eq!(
+            OwnedSocket::from_raw_socket(RawSocket::MIN).into_raw_socket(),
+            RawSocket::MIN
+        );
+        assert_eq!(
+            OwnedSocket::from_raw_socket(RawSocket::MAX).into_raw_socket(),
+            RawSocket::MAX
+        );
+        assert_eq!(
+            Some(OwnedSocket::from_raw_socket(RawSocket::MIN))
+                .unwrap()
+                .into_raw_socket(),
+            RawSocket::MIN
+        );
+        assert_eq!(
+            Some(OwnedSocket::from_raw_socket(RawSocket::MAX))
+                .unwrap()
+                .into_raw_socket(),
+            RawSocket::MAX
+        );
+    }
 }