[GHC] #12652: Type checker no longer accepting code using function composition and rank-n types

[GHC]

#12652: Type checker no longer accepting code using function composition and rank-n
types
-------------------------------------+-------------------------------------
        Reporter:  ezyang            |                Owner:  simonpj
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 Agree with Richard. If we can impredicatively use `($)` without
 `ImpredicativeTypes`, I don't see why we'd need it for `(.)`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12652#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler