Tuple Support

[rtulip]

Allows users to create anonymous structures. For example:

fn main() {
    1 true cast([u64 bool]) as [x]
    x    println // prints `[1 2]`
    x::0 println // prints `1`
    x::1 println // prints `true` 
}

The empty tuple is the first zero-sized type and can be created like this for now:

fn main() {
    cast([]) println // prints `[]`
}

So you can now make your own zero sized types like so:

struct PhantomData<T> { []: _ 
impl:
    fn PhantomData.new<T>() -> [PhantomData<T>] {
        cast([]) cast(PhantomData<T>)
    }
}

Type inference doesn't work with the example above as of yet.

This is an important step for making sum types. Next we'll be able to define a sum type like this:

enum struct SumType {
    []           : NoData
    Str          : PlainOldData
    [u64 u64 u64]: RGB
}