It appears that you can't define an unary operator for a tuple. Consider this example:

```
@prefix func - (tuple: (Int, Int)) -> (Int, Int) {
    return (-tuple.0, -tuple.1)
}

let t = (1, 2)
-t

```

And I get an error: *could not find an overload for '-' that accepts the supplied arguments*. Is this an expected behavior?

It's worth noting that binary operators work fine, e.g. you can define `==` for tuples and it works as expected.