Description:
------------
In debug mode, when we define return type info as object and specify class for it, e.g.

ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(test_arginfo, ZEND_RETURN_VALUE, 0, IS_OBJECT, "ClassName", 0)
ZEND_END_ARG_INFO()

and then throw exception from function, e.g.

PHP_FUNCTION(test) {
    if (zend_parse_parameters_none() == FAILURE) {
        return;
    }
    
    zend_throw_exception(zend_exception_get_default(), "Test exception", 0);
}

we have fatal error "Fatal error: Return value of test() must be an instance of ClassName, null returned in Unknown on line 0"

While allow_null set to 1 fixes this problem, it is clearly a bug, while after exception thrown, method returned value not used, so no type check after exception should be performed (debug mode affected only).