[GHC] #5962: Data.Typeable: types which should compare equal don't

[GHC]

#5962: Data.Typeable: types which should compare equal don't
------------------------------------------+---------------------------------
  Reporter:  NickSmallbone                |          Owner:  simonpj         
      Type:  bug                          |         Status:  closed          
  Priority:  normal                       |      Milestone:                  
 Component:  libraries/base               |        Version:  7.4.1           
Resolution:  fixed                        |       Keywords:                  
        Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
   Failure:  Incorrect result at runtime  |     Difficulty:  Unknown         
  Testcase:  base/tests/T5962             |      Blockedby:                  
  Blocking:                               |        Related:                  
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Changes (by simonpj):

  * status:  new => closed
  * testcase:  => base/tests/T5962
  * resolution:  => fixed


Comment:

 Excellent point thank you.  Fixed by
 {{{
 commit f35ebbd5dfd108487efa7912349e9802f6029897
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Fri Mar 30 12:51:14 2012 +0100

     Fix an egregious bug in the fingerprint calculation for TypeRep

     Given (T ty1) and ty2, we were computing the fingerprint of the
     application (T ty1 ty2) by combining the two fingerprints from (T ty1)
     and ty2.  But that gives a different answer to combinging the three
     fingerprints from T, ty1, and ty2, which is what happens if you
     build the type all at once.  Urk!

     Fixes Trac #5962

  Data/Typeable/Internal.hs |    9 ++++++---
  1 files changed, 6 insertions(+), 3 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5962#comment:2>
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