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")]
+implFrom<TryLockError>for io::Error{
+fnfrom(err:TryLockError) -> io::Error{
+match err {
+TryLockError::Error(err) => err,
+TryLockError::WouldBlock => io::ErrorKind::WouldBlock.into(),
+}
+}
+}
+
 implFile{
 /// 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(())
 /// }