before this transition step: the plus operator's generator code should implicitly convert both operands to a number. however, after this, we want to make sure that this implicit conversion does not happen (therefore, we will probably have type mismatch errors).
how do we want to handle type mismatch errors? similar to #15
before this transition step: the plus operator's generator code should implicitly convert both operands to a number. however, after this, we want to make sure that this implicit conversion does not happen (therefore, we will probably have type mismatch errors).