Add From<TryLockError> for io::Error

This makes error propagation from try_lock() and try_lock_shared()
more convenient

Author: cberner

library/std/src/fs.rs

@@ -392,6 +392,16 @@ 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.
     ///
@@ -821,11 +831,14 @@ 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(())
     /// }
     /// ```
@@ -882,11 +895,14 @@ 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(())
     /// }