Specify vectors are non-empty at compile time?

[JSAbrahams]

Summary of current issue

So I'd been wondering whether there was a way that we can specify that a vector always contains at least one element.
Found a cool wrapper which guarantees this at compile time.

Proposed change

If we use this in as many places as possible, then we can guarantee a lot of extra properties at compile time.
This prevents us from implementing superfluous logic for syntax errors in the

• Check and...
• ...Generate stages

This should also greatly reduce the amount of unreachable branches in the current implementation.