add @async.is_cancellation_error

Author: Guest0x0

src/async.mbt

@@ -48,6 +48,18 @@ pub using @coroutine {pause}
 /// In this case, `is_being_cancelled` can be used to avoid dead loop.
 pub using @coroutine {is_being_cancelled}
 
+///|
+/// `is_cancellation_error(err)` return `true`
+/// if `err` is the special error used to represent cancellation internally.
+///
+/// Note that `is_cancellation_error` may not be accurate:
+/// async code may fail and raise other error during cancellation handling,
+/// in this case the error may be replaced by something else.
+/// For accurate detection of cancellation, use `is_being_cancelled` instead.
+pub fn is_cancellation_error(error : Error) -> Bool {
+  error is @coroutine.Cancelled
+}
+
 ///|
 pub suberror TimeoutError derive(Show, ToJson)
 

src/pkg.generated.mbti

@@ -10,6 +10,8 @@ import(
 // Values
 fn is_being_cancelled() -> Bool
 
+fn is_cancellation_error(Error) -> Bool
+
 fn now() -> Int64
 
 async fn pause() -> Unit