hphp/hack/test/typecheck/instanceof_static_with_reqs.php

   1 <?hh
   2
   3 abstract class BaseField<T> {
   4
   5   final public function __construct() {}
   6
   7   final public static function fromType($type): this {
   8     $class_name = $type->getClassName();
   9     $field = new $class_name();
  10     hh_show($field);
  11     invariant(
  12       $field instanceof static,
  13       '%s is not a valid %s',
  14       $class_name,
  15       get_called_class(),
  16     );
  17     hh_show($field);
  18
  19     if ($type instanceof HasFoo) {
  20       // This illustrates a limitation of the typechecker:
  21       // - intersection of this<BaseField> and INeedsFoo
  22       invariant(
  23         $field instanceof INeedsFoo,
  24         'The context arg was provided, but the field doesn\'t support one',
  25       );
  26       hh_show($field);
  27       $field->setFoo($type->getFoo());
  28     }
  29
  30     hh_show($field);
  31     return $field;
  32   }
  33 }
  34
  35 interface INeedsFoo<T> {
  36   require extends Base;
  37
  38   public function setFoo(T $arg): this;
  39 }