Implement Debug for File

This patch adds a `Debug` impl for `std::fs::File`.

On all platforms (Unix and Windows) it shows the file descriptor.

On Linux, it displays the path and access mode as well.

Ideally we should show the path/mode for all platforms, not just Linux,
but this will do for now.

cc #24570

1 files changed, 7 insertions, 0 deletions

diff --git a/src/libstd/fs.rs b/src/libstd/fs.rs
index 8af3311c426..e8cdee9aca4 100644
--- a/src/libstd/fs.rs
+++ b/src/libstd/fs.rs
@@ -19,6 +19,7 @@
 
 use core::prelude::*;
 
+use fmt;
 use io::{self, Error, ErrorKind, SeekFrom, Seek, Read, Write};
 use path::{Path, PathBuf};
 use sys::fs2 as fs_imp;
@@ -305,6 +306,12 @@ impl FromInner<fs_imp::File> for File {
     }
 }
 
+impl fmt::Debug for File {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.inner.fmt(f)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Read for File {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {