id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5937	Kind variables not allowed in data declaration kind annotation	goldfire		"GHC won't accept kind variables stated directly in a data declaration. For example, the following does not compile:

{{{
data SMaybe :: (k -> *) -> Maybe k -> * where
  SNothing :: SMaybe s 'Nothing
  SJust :: s a -> SMaybe s ('Just a)
}}}

However, the following does compile:

{{{
data SMaybe' (s :: k -> *) (m :: Maybe k) where
  SNothing' :: SMaybe' s 'Nothing
  SJust' :: s a -> SMaybe' s ('Just a)
}}}"	bug	closed	normal		Compiler (Type checker)	7.5	fixed	PolyKinds		Unknown/Multiple	Unknown/Multiple	GHC rejects valid program	Unknown	polykinds/T5937