[GHC] #9200: Milner-Mycroft failure at the kind level

[GHC]

#9200: Milner-Mycroft failure at the kind level
-------------------------------------+-------------------------------------
              Reporter:  ekmett      |            Owner:  goldfire
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.2
  (Type checker)                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  GHC         |  Related Tickets:
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 What about

 {{{
 type S (a :: k) = Proxy (T (Just a))
 data T a = MkT (S a)
 }}}

 Does that `S` have a CUSK? If it does, the code should be accepted, I
 think. Or, would a user have to put in a totally-superfluous ` :: *` at
 the end of `S`'s RHS? Regardless of the kind of `T`, a proxy is always in
 kind `*`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9200#comment:34>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler