hphp/hack/test/typecheck/reactive/test_mutable_assign.php

   1 <?hh // strict
   2 class C {
   3   <<__Rx>>
   4   public function __construct(public int $val) {}
   5 }
   6
   7 <<__Rx>>
   8 function basic(): void {
   9   $z = \HH\Rx\mutable(new C(7)); // $z is mutable
  10   $z->val = 5; // okay
  11   $z = 7; // error, cannot change mutability flavor of the local
  12   $b = $z; // can reassign an immutable object
  13
  14   // $x is mutable(mutably owned)
  15   $x = \HH\Rx\mutable(returnsMut());
  16   // error, cannot reassign a mutable object
  17   $y = $x;
  18 }
  19
  20 <<__Rx, __MutableReturn>>
  21 function returnsMut(): C {
  22   // UNSAFE
  23 }