Description:
------------
See test script

Test script:
---------------
<?php

trait Foo
{
    function bar($a = self::class) {}
}

class B {
    use Foo;
}

$b = new B;

$b->bar();

Expected result:
----------------
string(1) "C"

Actual result:
--------------
PHP-5.6: Fatal error: Invalid opcode 64/8/2. in /tmp/1.php on line 5
PHP-7.0: NULL
[Mon Nov 23 12:39:01 2015]  Script:  '/tmp/1.php'
/home/huixinchen/opensource/php-7.0/Zend/zend_string.h(121) :  Freeing 0x7FFFF8059B80 (32 bytes), script=/tmp/1.php
=== Total 1 memory leaks detected ===