Compiler should reject doubly declared function

[morganthomas]

I expect the following example to fail to compile because it declares a twice with the same type signature:

    fn a() -> 1 {
        return 0;
    }

    fn a() -> 1 {
        return 1;
    }

    fn main() {
        a();
        return;
    }

This example appears to compile. To illustrate the issue, I made this draft PR where I added a failing test case: #43

Question: What is the expected behavior in the case of two function declarations with the same name and different type signatures? Is it allowed to overload the same name and allow the types to disambiguate, or should all functions be required to have distinct names?

[TomWambsgans]

Thanks for catching this. I think we can agree that all functions should have distinct names?

[morganthomas]

Ok! PR #43 updated with the name distinctness checks and marked ready for review.