hphp/hack/test/typecheck/class_prop_as_this.php

   1 <?hh // strict
   2
   3 // The test proves that it is safe to allow the 'this' type as a public
   4 // property. Attempting to assign to a property of type 'this' will fail
   5 // if they are not the same expression dependent type.
   6 abstract class C {
   7   public function __construct(public this $x) {}
   8
   9   public function test(C $c1, C $c2, this $static): void {
  10     // This works because both are known to be of type <static>
  11     $static->x = $this->x;
  12     hh_show($static->x);
  13     hh_show($this->x);
  14
  15     // But since we don't know if $c1 and $c2 refer to the same type this is an
  16     // error.
  17     $c1->x = $c2->x;
  18   }
  19 }