hphp/hack/test/typecheck/coalesce_bug.php

   1 <?hh // strict
   2 // Copyright 2004-present Facebook. All Rights Reserved.
   3
   4 function coalesce3<Tr, Ta as Tr, Tb as Tr, Tc as Tr>(
   5   ?Ta $a,
   6   ?Tb $b,
   7   Tc $c,
   8 ): Tr {
   9   return $a ?? $b ?? $c;
  10 }
  11
  12 class C {}
  13 interface I {}
  14 function genI(): ?I {
  15   return null;
  16 }
  17 function genC(bool $f, ?C $a, ?C $b, ?I $c): ?C {
  18   $r = coalesce3($f ? $a : null, $b, genI());
  19   return $r;
  20 }