Change std::io::FilePermission to a typesafe representation

This patch changes `std::io::FilePermissions` from an exposed `u32`
representation to a typesafe representation (that only allows valid
flag combinations) using the `std::bitflags`, thus ensuring a greater
degree of safety on the Rust side.

Despite the change to the type, most code should continue to work
as-is, sincde the new type provides bit operations in the style of C
flags. To get at the underlying integer representation, use the `bits`
method; to (unsafely) convert to `FilePermissions`, use
`FilePermissions::from_bits`.

Closes #6085.

[breaking-change]

2 files changed, 9 insertions, 5 deletions

diff --git a/src/libnative/io/file_unix.rs b/src/libnative/io/file_unix.rs
index 7c19eb54326..94ca6027841 100644
--- a/src/libnative/io/file_unix.rs
+++ b/src/libnative/io/file_unix.rs
@@ -335,7 +335,7 @@ pub fn open(path: &CString, fm: io::FileMode, fa: io::FileAccess)
 
 pub fn mkdir(p: &CString, mode: io::FilePermission) -> IoResult<()> {
     super::mkerr_libc(retry(|| unsafe {
-        libc::mkdir(p.with_ref(|p| p), mode as libc::mode_t)
+        libc::mkdir(p.with_ref(|p| p), mode.bits() as libc::mode_t)
     }))
 }
 
@@ -392,7 +392,7 @@ pub fn rename(old: &CString, new: &CString) -> IoResult<()> {
 
 pub fn chmod(p: &CString, mode: io::FilePermission) -> IoResult<()> {
     super::mkerr_libc(retry(|| unsafe {
-        libc::chmod(p.with_ref(|p| p), mode as libc::mode_t)
+        libc::chmod(p.with_ref(|p| p), mode.bits() as libc::mode_t)
     }))
 }
 
@@ -470,7 +470,9 @@ fn mkstat(stat: &libc::stat, path: &CString) -> io::FileStat {
         path: Path::new(path),
         size: stat.st_size as u64,
         kind: kind,
-        perm: (stat.st_mode) as io::FilePermission & io::AllPermissions,
+        perm: unsafe {
+            io::FilePermission::from_bits(stat.st_mode as u32) & io::AllPermissions
+        },
         created: mktime(stat.st_ctime as u64, stat.st_ctime_nsec as u64),
         modified: mktime(stat.st_mtime as u64, stat.st_mtime_nsec as u64),
         accessed: mktime(stat.st_atime as u64, stat.st_atime_nsec as u64),
diff --git a/src/libnative/io/file_win32.rs b/src/libnative/io/file_win32.rs
index 88ba6dcbc7e..945a1f0d612 100644
--- a/src/libnative/io/file_win32.rs
+++ b/src/libnative/io/file_win32.rs
@@ -391,7 +391,7 @@ pub fn rename(old: &CString, new: &CString) -> IoResult<()> {
 
 pub fn chmod(p: &CString, mode: io::FilePermission) -> IoResult<()> {
     super::mkerr_libc(as_utf16_p(p.as_str().unwrap(), |p| unsafe {
-        libc::wchmod(p, mode as libc::c_int)
+        libc::wchmod(p, mode.bits() as libc::c_int)
     }))
 }
 
@@ -470,7 +470,9 @@ fn mkstat(stat: &libc::stat, path: &CString) -> io::FileStat {
         path: Path::new(path),
         size: stat.st_size as u64,
         kind: kind,
-        perm: (stat.st_mode) as io::FilePermission & io::AllPermissions,
+        perm: unsafe {
+          io::FilePermission::from_bits(stat.st_mode as u32)  & io::AllPermissions
+        },
         created: stat.st_ctime as u64,
         modified: stat.st_mtime as u64,
         accessed: stat.st_atime as u64,