hphp/hack/test/typecheck/recursive_type_1.php

   1 <?hh // strict
   2 // Copyright 2004-present Facebook. All Rights Reserved.
   3
   4 final class MyMap<Tk, Tv> {
   5   public function get(Tk $k): ?Tv {
   6     return null;
   7   }
   8 }
   9
  10 function coalesce2<Tr, Ta as Tr, Tb as Tr>(?Ta $a, Tb $b): Tr {
  11   return $a ?? $b;
  12 }
  13
  14 function ForceString(string $x): void {}
  15 function Test(MyMap<string, string> $extra_data): void {
  16   $ref_id = (string)coalesce2(
  17     $extra_data->get('ref_id'), // This has type ?var_1
  18     $extra_data->get('attachment_id'), // this also has type ?var_1
  19   );
  20   ForceString($ref_id);
  21
  22 }