Do newtypes make a difference? E.g let N x = e in ...
where N is the data contructor of a newtype?
I don't think it has too. So for the moment, I vote to stick to the current proposal and consider this like all lazy non-variable patterns: must be unrestricted.
I suspect that there's a possible refinement where we say that a happy pattern is either:
- A variable
- Strict
- A newtype constructor where the inner pattern is happy.
(then if pat is an unhappy pattern, `let pat` must be unrestricted).
But I don't think I'm quite ready to go there for the time being, and that'll be a backward compatible change if we change our mind.