Arguments sometimes not checked or evaluated because of defaults

```rs
fn foo(a: u32 = 123456, b: u32) {
    println("a={}, b={}", a, b)
}

fn main() {
    foo(a: 123, b: 456) // Prints "a=123, b=456" as expected.
    foo(b: 456, a: 123) // Prints "a=123456, b=456". What?
    foo(b: 456, real_arg: abort() - real_var) // Wait, this argument is completely ignored!
}
```
Function overload resolution seems to catch all the errors if the call has too many arguments.