Function overloading can create unreachable functions

[OliveIsAWord]

The Jakt compiler currently accepts these functions:

fn example() => ...
fn example(my_default_arg: u32 = 42) => ...

However, any call to example() will always call the second function. As far as I can tell, the first function cannot be called. This code should probably give an error.

[cg-jl]

Good catch, verified it still happens. Test case I'm using:

fn example() -> u32 => 3

fn example(my_default_arg: u32 = 42) -> u32 => my_default_arg


fn main() {

    let something = example()

    println("what: {}", something)

}

Typechecker seems to prefer the one with a default argument, since it thinks it's more specific:

(debug) function called: example
(debug) overload candidates: [FunctionId(module: ModuleId(id: 1), id: 23), FunctionId(module: ModuleId(id: 1), id: 24)]
(debug)  ()
(debug)  (my_default_arg: u32 = ParsedExpression::NumericConstant(val: NumericConstant::UnknownSigned(42), span: Span(file_id: FileId(id: 1), start: 60, end: 62)))
(debug) found match with specificity: 0
(debug) found match with specificity: 2147483648

(I added log statements manually)

I have yet to explore the space, but I guess we want it to err with "ambiguous call". Will be thinking of more possible examples throughout the week, since this one's pretty trivial but there could be other cases. Nice job on the minimization!