Default values on parameters should not force the parameter type

[jakebailey]

Take:

def add(a=1, b=2):
    return a + b

With x = add(), we get int. But, with y = add("a", "b"), we also get int.

The presence of a default value doesn't necessarily mean that is what is going to be passed in. The second example should have the opportunity to evaluate with both strings and end up with a final string.

The old LS could "do" this, but only because all possible input and output types were unioned together (giving the appearance of the return type making sense).