The negative type proposition constructor incorrectly simplifies
(! Any ...) to tt instead of (! Nothing ..) to ff.
Implement and/or test these optimisations:
(is Any ..) = tt
(is Nothing ..) = ff
(! Any ..) = ff
(! Nothing ..) = ff
Pull request: 46
Patch: ctyp-258.patch
Commit: 00b8d5
Release: 0.3.9