[Bug]: Inheriting from a generic class in a non-generic subclass causes internal error

[jabraham17]

Inheriting from a generic class in a class that is otherwise not generic results in an internal error.

class Generic {
  param x = 1;
}

class Parent {
  var x: borrowed Generic(?);
  proc init(x: borrowed Generic(?)) {
    this.x = x;
  }
}

class Child: Parent(?) {
  proc init(x: borrowed Generic(?)) {
    super.init(x);
  }
}

var g = new Generic();
var c = new Child(g);

This hits an internal error on new Child(g) in resolvePromotionType while trying to resolve type constructors. Making the Child class explicitly generic by adding param dummy = 1; to resolves the issue. Note that this bug occurs regardless of if Generic is generic-with-defaults or not.