Type inference of coroutines

[WiseIndian]

It would be nice if we could create coroutines like so:

class A 
class B extends A
coroutine {
  yieldval(new A()) 
  yieldval(new B())
}

so that this code would return a coroutine with the tightest type (Coroutine[A] in this case) out of the yieldval and join operations within that coroutine body.

[liufengyun]

It can be done with white-box macros. Maybe make it low priority, and focus on other use cases.

[liufengyun]

Another subtlety with inference in Dotty is that you can always produce a union type A | B, even if A and B are disjoint.

[WiseIndian]

thanks for the feedback.