hphp/hack/test/typecheck/typing_fail_duck.php

   1 <?hh // strict
   2 /**
   3  * Copyright (c) 2014, Facebook, Inc.
   4  * All rights reserved.
   5  *
   6  * This source code is licensed under the BSD-style license found in the
   7  * LICENSE file in the "hack" directory of this source tree. An additional grant
   8  * of patent rights can be found in the PATENTS file in the same directory.
   9  *
  10  */
  11
  12 // A simple duck typing example
  13
  14 class DoesRender {
  15
  16   public function render(): string {
  17     return "";
  18   }
  19 }
  20
  21 class MyClass1 {
  22
  23   public function otherStuff(): string {
  24     return "I know how to do other stuff too!";
  25   }
  26
  27   public function render(string $x = ""): string {
  28     return "Yoohoo I know how to render";
  29   }
  30 }
  31
  32 function test(DoesRender $obj): string {
  33   return $obj->render();
  34 }
  35
  36 function main(): void {
  37   $my_string = test(new MyClass1());
  38 }