[GHC] #13901: Lift the "Illegal polymorphic type" restriction on type families

[GHC]

#13901: Lift the "Illegal polymorphic type" restriction on type families
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11962            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 The reference to wrapper is more of an implementation detail. GHC uses a
 `HsWrapper` type to denote things that happen to expressions
 (instantiations, type abstractions, dictionary applications, etc.) that
 are invisible in user-written Haskell. That's all I was referring to
 there.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13901#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler