[GHC] #8678: Derivin `Functor` complains about existential type

[GHC]

#8678: Derivin `Functor` complains about existential type
-------------------------------------+------------------------------------
        Reporter:  heisenbug         |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
-------------------------------------+------------------------------------

Comment (by carter):

 where does the variable {{{n}}} get introduced in {{{Standard :: a ->
 NonStandard (S n) a}}} ? That seems existential

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8678#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler