Description:
------------
magic method are called in a special way, if those methods
was defined as generator, most of them will not work as expected.

We could disallow them when compiling.


Test script:
---------------
class A {
     public function __construct(array $data) {
           $this->initData = $data;
           // maybe more initialization...

           var_dump($this->initData);
           foreach$(this->initData as $v) {
               yield $v;
           }
     }
}

$a = new A(array(1, 2)); //  constructor didn't get called.

so does the that magic methods:
http://www.php.net/manual/en/language.oop5.magic.php

most of them are meanning less if they are generators.
*some of them* maybe useful if they return value but not void.


Those could be allowed: __call(), __callStatic(), __get(), __invoke()

but those seems meaningless to be generators
__construct(), __destruct(), __set(), __isset(), __unset(), __sleep(), __wakeup(), __toString(), __set_state() and __clone(),