CoreLint error in safe program

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.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	goldfire
Operating system
Architecture