As of at least recently, empty cases are entirely permitted (and used for e.g. Void / nullary types).

On Wed, Jun 26, 2019 at 3:08 PM Johannes Waldmann <johannes.waldmann@htwk-leipzig.de> wrote:
> The rule "alt" allows "(empty alternative)"

Ah, yes. But no? The standard says

> A case expression must have at least one alternative
> and each alternative must have at least one body.

Should this be "each non-empty alternative must have ..."?

I think the intention is to allow

    case () of () | False -> () | True -> ()

(one alternative, two bodies) but to disallow

    case () of ()

(one alternative, no body)

- J.
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--
brandon s allbery kf8nh
allbery.b@gmail.com