[GHC] #11715: There's something fishy going on with Constraint

[GHC]

#11715: There's something fishy going on with Constraint
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  high           |         Milestone:  8.0.1
          Component:  Compiler       |           Version:  8.0.1-rc1
  (Type checker)                     |
           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:
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 I first noticed something was a bit odd with `Constraint` when chasing
 #11334. Consider this testcase,
 {{{#!hs
 import Data.Typeable

 main = do
     print $ typeRep (Proxy :: Proxy Eq)
     print $ typeOf (Proxy :: Proxy Eq)
 }}}
 With `ghc-8.0` this will produce,
 {{{
 Eq
 Proxy (* -> *) Eq
 }}}
 Notice the second line; GHC seems to be claiming that `Eq :: * -> *`,
 which is clearly nonsense.

 I believe this issue may be the cause of some of the testsuite failures
 that I'm seeing on #11011. Unfortunately I haven't the foggiest where this
 issue might originate.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11715>
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