Rollup merge of rust-lang#136552 - ChrisDenton:option-find-handle, r=Mark-Simulacrum

Use an `Option` for `FindNextFileHandle` in `ReadDir` instead of `INVALID_FILE_HANDLE` sentinel value

Sometimes we store an invalid handle when we don't want to return an error. We then check the handle before use in order to avoid actually using the invalid handle. However, using an `Option` for this is better and avoids us forgetting to check the handle is valid. This was noticed due to us closing the handle without checking for validity: https://github.com/rust-lang/rust/blob/bd6a6777f5cbbec549f123995026cef76d1e6b84/library/std/src/sys/pal/windows/fs.rs#L148-L151

Author: workingjubilee

library/std/src/sys/pal/windows/fs.rs

@@ -44,7 +44,7 @@ pub struct FileType {
 }
 
 pub struct ReadDir {
-    handle: FindNextFileHandle,
+    handle: Option<FindNextFileHandle>,
     root: Arc<PathBuf>,
     first: Option<c::WIN32_FIND_DATAW>,
 }
@@ -113,13 +113,13 @@ impl fmt::Debug for ReadDir {
 impl Iterator for ReadDir {
     type Item = io::Result<DirEntry>;
     fn next(&mut self) -> Option<io::Result<DirEntry>> {
-        if self.handle.0 == c::INVALID_HANDLE_VALUE {
+        let Some(handle) = self.handle.as_ref() else {
             // This iterator was initialized with an `INVALID_HANDLE_VALUE` as its handle.
             // Simply return `None` because this is only the case when `FindFirstFileExW` in
             // the construction of this iterator returns `ERROR_FILE_NOT_FOUND` which means
             // no matchhing files can be found.
             return None;
-        }
+        };
         if let Some(first) = self.first.take() {
             if let Some(e) = DirEntry::new(&self.root, &first) {
                 return Some(Ok(e));
@@ -128,7 +128,7 @@ impl Iterator for ReadDir {
         unsafe {
             let mut wfd = mem::zeroed();
             loop {
-                if c::FindNextFileW(self.handle.0, &mut wfd) == 0 {
+                if c::FindNextFileW(handle.0, &mut wfd) == 0 {
                     match api::get_last_error() {
                         WinError::NO_MORE_FILES => return None,
                         WinError { code } => {
@@ -1194,7 +1194,7 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
 
         if find_handle != c::INVALID_HANDLE_VALUE {
             Ok(ReadDir {
-                handle: FindNextFileHandle(find_handle),
+                handle: Some(FindNextFileHandle(find_handle)),
                 root: Arc::new(root),
                 first: Some(wfd),
             })
@@ -1212,11 +1212,7 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
             // See issue #120040: https://github.com/rust-lang/rust/issues/120040.
             let last_error = api::get_last_error();
             if last_error == WinError::FILE_NOT_FOUND {
-                return Ok(ReadDir {
-                    handle: FindNextFileHandle(find_handle),
-                    root: Arc::new(root),
-                    first: None,
-                });
+                return Ok(ReadDir { handle: None, root: Arc::new(root), first: None });
             }
 
             // Just return the error constructed from the raw OS error if the above is not the case.