[GHC] #12115: CoreLint error in safe program

[GHC]

#12115: CoreLint error in safe program
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           Reporter:  osa1           |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           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:
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 This correct program is failing with a CoreLint error:

 {{{
 {-# LANGUAGE MagicHash, UnboxedTuples #-}

 module Main where

 import GHC.Prim
 import GHC.Types

 showAlt0 :: (# Void#, (# #) #) -> String
 showAlt0 (# _, (# #) #) = "()"

 main :: IO ()
 main = return ()
 }}}

 Error:

 {{{
 *** Core Lint errors : in result of Desugar (after optimization) ***
 <no location info>: warning:
     In the type ‘(# Void#, (# #) #) -> String’
     Kind application error in type ‘(# Void#, (# #) #)’
       Function kind = * -> * -> TYPE 'UnboxedTupleRep
       Arg kinds = [('VoidRep, RuntimeRep),
                    ('UnboxedTupleRep, RuntimeRep), (Void#, TYPE 'VoidRep),
                    ((# #), TYPE 'VoidRep)]
 core_err.hs:13:1: warning:
     [RHS of showAlt0 :: (# Void#, (# #) #) -> String]
     The type of this binder doesn't match the type of its RHS: showAlt0
     Binder's type: (# Void#, (# #) #) -> String
     Rhs type: (# Void#, (# #) #) -> String
 }}}

 Tried with: GHC HEAD, 8.0.1.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12115>
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