[GHC] #746: ghc panic! with foreign import wrapper involving Bool

[GHC]

#746: ghc panic! with foreign import wrapper involving Bool
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    Reporter:  brianh at metamilk.com  |        Owner:                    
        Type:  bug                  |       Status:  new               
    Priority:  normal               |    Milestone:                    
   Component:  Compiler             |      Version:  6.4               
    Severity:  normal               |     Keywords:  DsForeign Bool FFI
          Os:  Windows              |   Difficulty:  Unknown           
Architecture:  x86                  |  
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I encounter a strange 'ghc panic' bug when I try to export the function
 onKeyDown below. I'm using ghc 6.4 and WindowsXP on x86.

 The bug seems to be caused by the use of {{{Bool}}} in
 {{{DumaKeyCallback}}}, because when I change the {{{Bool}}} to an
 {{{Int}}} everything compiles ok. Therefore I wonder if this is something
 to do with the compilation of "wrapper" imports not liking a Bool in the
 type signature?

 Anyway here is the full standalone example and session transcript:
 {{{
 module Keyboard
         ( Key(..)
         , KeyCallback

         , onKeyDown -- compiles fine if this export is commented out

         ) where

 import Foreign.Ptr

 data Key
         = KeyLButton -- other keys ommitted
         | KeyDown
         deriving (Enum)

 type KeyCallback = Key -> IO ()

 type DumaKeyCallback = Bool -> Int -> IO () -- Crashes GHC

 -- type DumaKeyCallback = Int -> Int -> IO () -- But this compiles
 fine!!!! ?

 foreign import ccall "wrapper" mkDumaKeyCallback :: DumaKeyCallback -> IO
 (FunPtr DumaKeyCallback)

 toDumaKeyCallback :: KeyCallback -> DumaKeyCallback
 toDumaKeyCallback f = \alt key -> f (toEnum key)

 foreign import ccall duma_onKeyDown :: FunPtr DumaKeyCallback -> IO ()

 onKeyDown :: KeyCallback -> IO ()
 onKeyDown f = mkDumaKeyCallback (toDumaKeyCallback f) >>= duma_onKeyDown
 }}}
 Transcript:
 {{{
 >ghc -fglasgow-exts -fffi -v keyboard.hs
 Glasgow Haskell Compiler, Version 6.4, for Haskell 98, compiled by GHC
 version 6.2.2
 Using package config file: c:\ghc\ghc-6.4\package.conf
 Hsc static flags: -static
 *** Checking old interface for Keyboard:
 *** Parser:
 *** Renamer/typechecker:
 *** Desugar:
     Result size = 354
 *** Simplify:
     Result size = 528
     Result size = 443
     Result size = 415
 *** Tidy Core:
     Result size = 415
 *** CorePrep:
     Result size = 500
 *** Stg2Stg:
 *** CodeGen:
 *** CodeOutput:
 *** Deleting temp files
 Deleting: C:/DOCUME~1/TYPHON~1/LOCALS~1/Temp/ghc4084.s
 Warning: deleting non-existent
 C:/DOCUME~1/TYPHON~1/LOCALS~1/Temp/ghc4084.s
 ghc: panic! (the `impossible' happened, GHC version 6.4):
         DsForeign.getPrimTyOf GHCziBase.Bool{(w) tc 3c}

 Please report it as a compiler bug to glasgow-haskell-bugs at haskell.org,
 or http://sourceforge.net/projects/ghc/.
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/746>
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