Assertion failure when freeing rvalue of ASSIGN_OBJ with typed refs and __toString() #20316

Description

The following code:

<?php

class C {
    public string $a = '';
    public $b;
    function __toString() {
        global $c; // turns rvalue into a ref
        return '';
    }
}

$c = new C;
$c->b = &$c->a;
$c->b = $c;

Resulted in this output:

zend_execute.c:4093: i_zval_ptr_dtor_noref: Assertion `zval_get_type(&(*(zval_ptr))) != 10' failed.

Root cause is that we call zend_assign_to_variable_ex() / zend_assign_to_typed_ref_ex() with value_type=IS_TMP_VAR, when value may be a CV slot here:

Therefore the slot may have been modified when reaching this call:

With the code above, the assertion fails because orig_value is now a ref.

PHP Version

PHP 8.3

Operating System

No response