Incorrect type cast for FutureOr

[iarkh]

Dart SDK Version: 2.1.0-dev.2.0
OS: Windows 10 (64 bit)

I am not 100% sure that this is not a duplicate of #34264, however on the firs glance these cases looks different.

The following code sample assign FutureOr variable (without type parameter specified) to int and then prints it:

import "dart:async";

main() {
 FutureOr fff;
 int i = fff;
 print(i);
}

It passes both with analyzer and dart,no compiler errors and dart prints null value here.

I'm just wandering - should not it fail here in the strong mode?

Please note that if I change FutureOr to Future this test starts to fail both with analyzer and dart,, from my point of view this is expected behavior both for Future and FutureOr.

[matanlurey]

This is (unfortunately) WAI: #31410.

FutureOr really means FutureOr<dynamic> (#33119), and FutureOr<dynamic> is a poor-man's "union type" of Future<dynamic> and dynamic. Of course, dynamic is statically assignable to int (with a runtime check), and it succeeds because everything is nullable right now (null is valid for anything).

/cc @lrhn if you have anything else to add, but I'll close for now.

[iarkh]

In this case, should not case with Future (instead of FutureOr) in the example above statically pass in the same way? Now it fails both with analyzer and dart.

[matanlurey]

No, Future is not assignable to int. FutureOr is.