Refactor yet another part of the expression visitor

That terrible "setTypesForEventualCall" function is now gone entirely.
It has been replaced by recursive calls to the expression visitor,
which leads to less code duplication, less special-case-handling, and
less bugs. Oh, and probably less performance, too.
I think this was the last required step to make the expressionvisitor code
halfway sane, hope it works okay now.