PHP7 Return Type Declarations with interfaces

php7-return-type-declarations-interface.php

<?php

class User {}

interface UserFactoryContract {
  public static function generate() : User;
}

class UserFactory implements UserFactoryContract {
  public static function generate() {
    // PHP Fatal error:  Declaration of UserFactory::generate() must be compatible with UserFactoryContract::generate(): User
  }
  
  public static function generate() : User {
    return [];
    // PHP Warning:  Uncaught TypeError: Return value of UserFactory::getUserWrong() must be an instance of User
  }
  
  public static function generate() : User {
    return new User;
  }
}