hphp/hack/test/typecheck/iface_require_incompat4.php

   1 <?hh
   2
   3 class Super<T> {
   4   public ?T $x;
   5 }
   6
   7 interface I1 {
   8   require extends Super<int>;
   9 }
  10
  11 interface I2 {
  12   require extends Super<float>;
  13 }
  14
  15 // On its own this is not an error
  16 interface I3 extends I1, I2 {}
  17
  18 // But as soon as it is used, we fail to extend Super<float>
  19 class C extends Super<int> implements I3 { }