hphp/hack/test/typecheck/covariance7.php

   1 //// file1.php
   2 <?hh // partial
   3
   4 newtype ID<+T> = int;
   5 newtype UID<+T> as ID<T> = int;
   6 newtype OID<+T> as ID<T> = int;
   7
   8 //// file2.php
   9 <?hh // partial
  10
  11 class A {}
  12 class B extends A {}
  13
  14 function takesIDA(ID<A> $x): void {}
  15 function test(UID<B> $x): void {
  16   takesIDA($x);
  17 }