1 files changed, 23 insertions, 2 deletions
diff --git a/src/libstd/fs.rs b/src/libstd/fs.rs
index 25f2dd73504..8c3d0da0a7e 100644
--- a/src/libstd/fs.rs
+++ b/src/libstd/fs.rs
@@ -211,7 +211,7 @@ pub struct DirBuilder {
     recursive: bool,
 }
 
-/// How large a buffer to pre-allocate before reading the entire file.
+/// Indicates how large a buffer to pre-allocate before reading the entire file.
 fn initial_buffer_size(file: &File) -> usize {
     // Allocate one extra byte so the buffer doesn't need to grow before the
     // final `read` call at the end of the file.  Don't worry about `usize`
@@ -1581,7 +1581,8 @@ pub fn rename<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> io::Result<()>
 /// `O_CLOEXEC` is set for returned file descriptors.
 /// On Windows, this function currently corresponds to `CopyFileEx`. Alternate
 /// NTFS streams are copied but only the size of the main stream is returned by
-/// this function.
+/// this function. On MacOS, this function corresponds to `copyfile` with
+/// `COPYFILE_ALL`.
 /// Note that, this [may change in the future][changes].
 ///
 /// [changes]: ../io/index.html#platform-specific-behavior
@@ -2837,6 +2838,26 @@ mod tests {
     }
 
     #[test]
+    fn copy_file_follows_dst_symlink() {
+        let tmp = tmpdir();
+        if !got_symlink_permission(&tmp) { return };
+
+        let in_path = tmp.join("in.txt");
+        let out_path = tmp.join("out.txt");
+        let out_path_symlink = tmp.join("out_symlink.txt");
+
+        check!(fs::write(&in_path, "foo"));
+        check!(fs::write(&out_path, "bar"));
+        check!(symlink_file(&out_path, &out_path_symlink));
+
+        check!(fs::copy(&in_path, &out_path_symlink));
+
+        assert!(check!(out_path_symlink.symlink_metadata()).file_type().is_symlink());
+        assert_eq!(check!(fs::read(&out_path_symlink)), b"foo".to_vec());
+        assert_eq!(check!(fs::read(&out_path)), b"foo".to_vec());
+    }
+
+    #[test]
     fn symlinks_work() {
         let tmpdir = tmpdir();
         if !got_symlink_permission(&tmpdir) { return };