Auto merge of #28729 - retep998:canonical-dir, r=alexcrichton

cc #27706

Author: bors

src/libstd/fs.rs

@@ -2083,6 +2083,15 @@ mod tests {
         check!(fs::create_dir_all(&path.join("a/")));
     }
 
+    #[test]
+    fn canonicalize_works_simple() {
+        let tmpdir = tmpdir();
+        let tmpdir = fs::canonicalize(tmpdir.path()).unwrap();
+        let file = tmpdir.join("test");
+        File::create(&file).unwrap();
+        assert_eq!(fs::canonicalize(&file).unwrap(), file);
+    }
+
     #[test]
     #[cfg(not(windows))]
     fn realpath_works() {

src/libstd/sys/windows/fs.rs

@@ -583,6 +583,8 @@ fn get_path(f: &File) -> io::Result<PathBuf> {
 pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
     let mut opts = OpenOptions::new();
     opts.read(true);
+    // This flag is so we can open directories too
+    opts.flags_and_attributes(c::FILE_FLAG_BACKUP_SEMANTICS);
     let f = try!(File::open(p, &opts));
     get_path(&f)
 }