Overload resolution picks wrong function

[bbannier]

If I implement the same function multiple times for integer types which are coercible into each other, the wrong overload is picked, e.g.,

module foo;

function fn(x: uint8) {
    print "uint8";
}

function fn(x: uint64) {
    print "uint64";
}

global x: uint8 = 0;
fn(x);

$ spicyc -dj foo.spicy
uint64

I would have expected this to print uint8.

Adding a fn taking a string has no effect one these.

It seems we consider overloads with coercible args before we check for explicitly matching ones. We should resolve the correct overload, and also check whether this behaves reasonable for functions taking multiple arguments (where non/some/all require coercions).