[GHC] #4497: hmatrix-0.10.0.0 fails to build with GHC 7.0.1 (worked with 7.0.0.20101111)

[GHC]

#4497: hmatrix-0.10.0.0 fails to build with GHC 7.0.1 (worked with 7.0.0.20101111)
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    Reporter:  luite                                     |        Owner:              
        Type:  bug                                       |       Status:  new         
    Priority:  normal                                    |    Milestone:              
   Component:  Compiler                                  |      Version:  7.0.1       
    Keywords:  hmatrix context reduction stack overflow  |     Testcase:              
   Blockedby:                                            |   Difficulty:              
          Os:  Windows                                   |     Blocking:              
Architecture:  Unknown/Multiple                          |      Failure:  None/Unknown
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Comment(by simonpj):

 OK here's a tiny program with no dependencies that demonstrates the bug.
 {{{
 {-# LANGUAGE FlexibleContexts, MultiParamTypeClasses, TypeFamilies #-}
 module T4497 where

 norm2PropR a = twiddle (norm2 a) a

 twiddle :: Normed a => a -> a -> Double
 twiddle a b = undefined

 norm2 :: e -> RealOf e
 norm2 = undefined

 class (Num (RealOf t)) => Normed t

 type family RealOf x
 }}}
 Great.  Dimitrios and I know what's happening. Patch coming.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4497#comment:8>
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