Handling of type parameters for effects

[marzipankaiser]

If we declare an effect with type parameters, e.g.

effect Eff[A] {
  def use(): A
}

Then the number of type parameters is not checked at the usage site, so all of those compile:

def foo(): Int / Eff = <>
def foo2(): Int / Eff[Int, Unit] = <>

Only if we ever use do use, it will complain that Eff[Int] is not allowed in that context, or that the number of type parameters does not match up for the use call.
EDIT: If we ever try to define a handler with try ... with ..., then we get the appropriate error message there.

[b-studios]

Really??? I would have assumed that the kind checker would catch this

[marzipankaiser]

I would have assumed so, too, but apparently not:

[marzipankaiser]

Ah, interesting: At a try ... with ..., this check is made (we get a Interface ... expects ... parameters, but ... with something like try {...} with Eff { ... } if Eff was declared with type parameters)

[b-studios]

We could add a pretyper phase (at one point we had it) to establish wellformedness before typing. There is Wellformedness but it only runs after typer.