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

[GHC]

#11549: Add -fshow-runtime-rep
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        Reporter:  goldfire          |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.1
      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:                    |
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Comment (by RyanGlScott):

 One thing isn't clear to me about how `-fshow-runtime-rep` works. I'm
 assuming that without `-fshow-runtime-rep` on, you won't see any mention
 of `RuntimeRep` in error messages. If so, what kind of error would this
 produce?

 {{{#!hs
 import GHC.Exts

 bad :: forall (w :: RuntimeRep) (a :: TYPE w). a -> Int
 bad _ = 42
 }}}

 The error would probably mention the type signature of `bad`, but would it
 be truncated to `a -> Int` instead of the full shebang?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11549#comment:1>
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