[GHC] #11549: Add -fshow-runtime-rep

[GHC]

#11549: Add -fshow-runtime-rep
-------------------------------------+-------------------------------------
           Reporter:  goldfire       |             Owner:  goldfire
               Type:  bug            |            Status:  new
           Priority:  highest        |         Milestone:  8.0.1
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 As discussed in several interwoven threads
 ([https://mail.haskell.org/pipermail/ghc-devs/2016-February/011268.html
 original], [https://mail.haskell.org/pipermail/haskell-
 cafe/2016-February/122914.html café]), it has been suggested to add a flag
 `-fshow-runtime-rep`. Without this flag enabled, the pretty printer will
 instantiate any `RuntimeRep` type parameters to `PtrRep Lifted`. This has
 the effect of changing

 {{{
 ($) :: forall (r :: RuntimeRep) (a :: *) (b :: TYPE r). (a -> b) -> a -> b
 }}}

 to

 {{{
 ($) :: (a -> b) -> a -> b
 }}}

 under the default GHCi settings.

 Note that `Levity` becomes `RuntimeRep` after #11471 is complete.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11549>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler