Rollup merge of #141312 - cberner:filelock_from, r=joshtriplett

Add From<TryLockError> for io::Error

Adds a `From` impl to make error propagation easier, as discussed in the tracking issue

`TryLockError` is unstable under the "file_lock" feature. The related tracking issue is https://github.com/rust-lang/rust/issues/130994

This PR also cleanups the Windows implementation of `try_lock()` and `try_lock_shared()` as [discussed here](https://github.com/rust-lang/rust/pull/140718#discussion_r2076678485)

1 files changed, 16 insertions, 0 deletions

diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 8047c0c03ad..8ed5800e9d0 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -391,6 +391,16 @@ impl fmt::Display for TryLockError {
     }
 }
 
+#[unstable(feature = "file_lock", issue = "130994")]
+impl From<TryLockError> for io::Error {
+    fn from(err: TryLockError) -> io::Error {
+        match err {
+            TryLockError::Error(err) => err,
+            TryLockError::WouldBlock => io::ErrorKind::WouldBlock.into(),
+        }
+    }
+}
+
 impl File {
     /// Attempts to open a file in read-only mode.
     ///
@@ -820,11 +830,14 @@ impl File {
     ///
     /// fn main() -> std::io::Result<()> {
     ///     let f = File::create("foo.txt")?;
+    ///     // Explicit handling of the WouldBlock error
     ///     match f.try_lock() {
     ///         Ok(_) => (),
     ///         Err(TryLockError::WouldBlock) => (), // Lock not acquired
     ///         Err(TryLockError::Error(err)) => return Err(err),
     ///     }
+    ///     // Alternately, propagate the error as an io::Error
+    ///     f.try_lock()?;
     ///     Ok(())
     /// }
     /// ```
@@ -881,11 +894,14 @@ impl File {
     ///
     /// fn main() -> std::io::Result<()> {
     ///     let f = File::open("foo.txt")?;
+    ///     // Explicit handling of the WouldBlock error
     ///     match f.try_lock_shared() {
     ///         Ok(_) => (),
     ///         Err(TryLockError::WouldBlock) => (), // Lock not acquired
     ///         Err(TryLockError::Error(err)) => return Err(err),
     ///     }
+    ///     // Alternately, propagate the error as an io::Error
+    ///     f.try_lock_shared()?;
     ///
     ///     Ok(())
     /// }