[GHC] #908: Deriving MPTC panic: tcSplitTyConApp

[GHC]

#908: Deriving MPTC panic: tcSplitTyConApp
-----------------------------------+----------------------------------------
    Reporter:  bjorn at bringert.net  |        Owner:         
        Type:  bug                 |       Status:  new    
    Priority:  normal              |    Milestone:         
   Component:  Compiler            |      Version:  6.5    
    Severity:  normal              |     Keywords:         
          Os:  Unknown             |   Difficulty:  Unknown
Architecture:  Unknown             |  
-----------------------------------+----------------------------------------
Current GHC HEAD panics when trying to compile test
 [http://darcs.haskell.org/testsuite/tests/ghc-
 regress/deriving/should_compile/drv020.hs drv020] (added by me):

 {{{
 $ compiler/stage1/ghc-inplace -no-recomp -c -fglasgow-exts testsuite/tests
 /ghc-regress/deriving/should_compile/drv020.hs
 ghc-6.5: panic! (the 'impossible' happened)
   (GHC version 6.5 for i386-apple-darwin):
         tcSplitTyConApp
     {main:ShouldSucceed.MonadState{tc rdb} base:GHC.Base.Int{(w) tc 3J}
                                            <nt>main:ShouldSucceed.Foo{tc
 rat}}
 }}}

 It seems to have problems with this declaration:

 {{{
 newtype Foo a = MkFoo (State Int a)
  deriving (Monad, MonadState Int)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/908>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler