hphp/hack/test/typecheck/eq_constraint.php

   1 <?hh // strict
   2
   3 class Foo {
   4   public function assertIsFoo(): void {}
   5 }
   6
   7 class Boxing<Tclass> {
   8   public function __construct(
   9     private Tclass $member,
  10   ) {}
  11
  12   public function getWithDefault<Tinner>(
  13     Tinner $default,
  14   ): Tinner where
  15     Tclass = ?Tinner,
  16   {
  17     return $this->member ?: $default;
  18   }
  19
  20   public function getOrExcept<Tinner>(): Tinner where Tclass = ?Tinner {
  21     if ($this->member === null) {
  22       throw new Exception('Member is null and can\'t be got.');
  23     }
  24     return $this->member;
  25   }
  26
  27   public function getAsIs(): Tclass {
  28     return $this->member;
  29   }
  30
  31   public static function caller(Boxing<?Foo> $c, Foo $f): void {
  32     $c->getWithDefault($f)->assertIsFoo(); // Must succeed
  33     $c->getOrExcept()->assertIsFoo();      // Must succeed
  34     $c->getAsIs()->assertIsFoo();          // Must fail, because may be null
  35   }
  36 }