@Override
            public Memory invoke(PropertyEntity prop, Memory o1, Memory o2) {
                if (oldValue != null)
                    oldValue.assign(o1.toValue());

                if (prop != null && prop.isTyped() && prop.getType() == HintType.INT) {
                    long x = o1.toLong(), y = o2.toLong();
                    long r = x - y;

                    if (((x ^ y) & (x ^ r)) < 0L) {
                        env.exception(trace,
                                BaseTypeError.class,
                                "Cannot math subtract for property %s::$%s of type int past its minimal value",
                                prop.getClazz().getName(), prop.getName()
                        );
                    }
                }

                return o1.minus(o2);
            }
return empty list if success else list with not valid implemented methods in class

@param _interface
@return
jphp-runtime/src/php/runtime/reflection/ClassEntity.java