Type safety / static async check

[fed239]

Would it possible to do so that when @async is used with a function, its type is change, so if @await is not used when calling the function type checking would fail?

Example

@async function returnZero(): Int {
  return 0;
}

var i: Int = @await returnZero(); // compilation succeeds
var p: Promise<Int> = returnZero(); // compilation succeeds
var i2: Int = returnZero(); // compilation fails

[botsman]

I've tried to implement type checking, but did not manage to do that, unfortunately.
I guess that I am not good enough with Haxe macro system.