[GHC] #7147: programatica fails to compile

[GHC]

#7147: programatica fails to compile
-------------------------+--------------------------------------------------
    Reporter:  maeder    |       Owner:                           
        Type:  bug       |      Status:  infoneeded               
    Priority:  normal    |   Milestone:                           
   Component:  Compiler  |     Version:  7.6.1-rc1                
    Keywords:            |          Os:  Solaris                  
Architecture:  x86       |     Failure:  GHC rejects valid program
  Difficulty:  Unknown   |    Testcase:                           
   Blockedby:            |    Blocking:                           
     Related:            |  
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Comment(by simonpj@…):

 commit de07bf2657fc5709331ad933b5563fac97b1a05b
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Wed Aug 15 18:10:54 2012 +0100

     Use TcMType.growThetaTyVars (which works) rather than
 TcSimplify.growPreds (which doesn't)

     I think this got left behind when we simplified and improved
 TcSimplify.  The effect
     was that we had a function like
        class P a b | a -> b
        class Q b c | b -> c

        f :: (P a b, Q b c) => a -> a

     and were were failing to quanitfy over 'c', even though it is
 (indirectly) determined
     by 'a'.

     This make Programatica fail to compile: Trac #7147

  compiler/typecheck/TcSimplify.lhs |   40
 +++++++++++++------------------------
  1 files changed, 14 insertions(+), 26 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7147#comment:4>
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