union type bug

[damon-kwok]

use "collections"

primitive Seqx[A: Seq[B] ref = Array[I32], B: Comparable[B] #read = I32]
  fun each(a: A, f: ({(B)} val | {(B): B} val) ): A^ => a
  fun map(a: A, f: ({(B): B} val | {(USize, B): B} val)): A^ =>  a

primitive Num[A: (Real[A] val & Number) = I32]
  fun print(a: A): A => a

actor Main
  new create(env: Env) =>
    let arr_i: Array[I32] ref = [1; 2; 3]
    Seqx.>map(arr_i, Num~print())   // allow
    //Seqx.each(arr_i, Num~print()) // don't allow

• playground: https://playground.ponylang.io/?gist=2a69d0a5f35b19d49445f56ebf426345
• zulip: https://ponylang.zulipchat.com/#narrow/stream/189985-beginner-help/topic/reference.20capability.20bug.3F/near/196746595

[SeanTAllen]

@damon-kwok please include all the information in the issue rather than referring to Zulip otherwise people will have to refer to the zulip and someone else will have to copy it over. You can provide a link for additional context but enough information to start addressing the issue should be included. This is missing valuable information.

Thanks.

[damon-kwok]

Here are some zulip discussions that may be helpful in analyzing bugs：

@jasoncarr0
To add onto this: it does not work with:
fun each(a: A, f: ({(B)} val | {(B): B} val) ): A^ => a
but does work with:
fun each(a: A, f: ({(B): B} val) ): A^ => a
So I think there's an issue with unions here as the former should accept more arguments

@SeanTAllen: Yeah it appears to be a bug with the union type there, as it is rejecting it because it doesnt match one of them, rather than accepting it.