cannot use void as template argument

[kazuho]

User-defined template classes should accept void as type arguments, while at least some built-tin classes (e.g. Array.<T> and Map.<T> should not).

The code snippet below fails to compile with the error message: 'void' cannot be used here.

class Foo.<T> {
    static function callIt(f : () -> T) : void {
        f();
    }
}

class _Main {
    static function main(args : string[]) : void {
        Foo.<void>.callIt(function () {});
    }
}

[kazuho]

Looking at https://gist.github.com/kazuho/3b25bda2b916830c7bbc the only built-in classes that should not accept void seem to be Array and Map.

Whether we should allow the use of Nullable.<void> is another issue.

[nyuichi]

@kazuho

If you will not allow Nullable.<void>, defining native class bindings would be pretty difficult.

native class Foo.<T> {
    function foo () : void;
    function foo (optional : Nullable.<T>) : void;
}

If Nullable.<void> is illegal in the JSX world, when native template class has a method overloaded for optional T value, it'd be absolutely impossible to define such class in the JSX world.

[kazuho]

closing as fixed