[GHC] #7703: GHCI crashes when loading a file, Windows 7 64 bit

[GHC]

#7703: GHCI crashes when loading a file, Windows 7 64 bit
-------------------------------+--------------------------------------------
    Reporter:  crntaylor       |        Owner:            
        Type:  bug             |       Status:  closed    
    Priority:  normal          |    Component:  GHCi      
     Version:  7.6.2           |   Resolution:  fixed     
    Keywords:                  |           Os:  Windows   
Architecture:  x86_64 (amd64)  |      Failure:  GHCi crash
   Blockedby:                  |     Blocking:            
     Related:                  |  
-------------------------------+--------------------------------------------
Changes (by monoidal):

  * status:  new => closed
  * resolution:  => fixed


Comment:

 Here's a small version:

 {{{
 newtype O f g a = Compose { getCompose :: f (g a) }

 mapC :: cat a b -> cat (O g f a) (O g f b)
 mapC (Compose f) = mapC (mapC f)
 }}}

 GHC 7.4 and 7.6 panic, but HEAD correctly reports:

 {{{
 cat.hs:11:7:
     Couldn't match kind `* -> *' with `*'
     When matching types
       t0 :: * -> *
       a :: *
     Expected type: cat a b
       Actual type: O (cat a0) t0 b
     In the pattern: Compose f
     In an equation for `mapC': mapC (Compose f) = mapC (mapC f)
 }}}

 (it also reports unrelated ambiguity in your code related to fundeps)

 I think the underlying cause is the same as #7368.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7703#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler