[GHC] #11250: GHC shows core with error

[GHC]

#11250: GHC shows core with error
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           Reporter:  crockeea       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect
  Unknown/Multiple                   |  warning at compile-time
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The following code intentionally does not compile:


 {{{
 {-# LANGUAGE DataKinds, KindSignatures, PolyKinds #-}

 data Proxy (p :: k) = Proxy
 data Tagged (t :: k) s = Tagged s

 proxy :: Tagged t s -> Proxy t -> s
 proxy = undefined

 bar :: Tagged (gad :: *) Int
 bar = undefined

 foo :: Int
 foo = proxy bar (Proxy::Proxy 'True)
 }}}

 but it produces the following output with GHC and GHCi:


 {{{
 [1 of 1] Compiling Main             ( Bug.hs, interpreted )
 RAE1
   [W] cobox_aLM :: t0_aK4[tau:1] ~ 'True (CNonCanonical)
   t0_aK4[tau:1]
   'True
   False

 Bug.hs:13:18:
     Couldn't match kind ‘Bool’ with ‘*’
     Expected type: Proxy t0
       Actual type: Proxy 'True
     In the second argument of ‘proxy’, namely ‘(Proxy :: Proxy True)’
     In the expression: proxy bar (Proxy :: Proxy True)
     In an equation for ‘foo’: foo = proxy bar (Proxy :: Proxy True)
 Failed, modules loaded: none.
 }}}

 This ticket is about the first block printed out. It seems to be a random
 section of core, and is completely useless to debugging the problem.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11250>
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