[GHC] #5395: Context reduction stack overflow without undecidable instances

[GHC]

#5395: Context reduction stack overflow without undecidable instances
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    Reporter:  guest                     |        Owner:                           
        Type:  bug                       |       Status:  new                      
    Priority:  normal                    |    Milestone:                           
   Component:  Compiler                  |      Version:  7.0.4                    
    Keywords:  type family, termination  |     Testcase:                           
   Blockedby:                            |   Difficulty:                           
          Os:  Unknown/Multiple          |     Blocking:                           
Architecture:  Unknown/Multiple          |      Failure:  GHC rejects valid program
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Comment(by simonpj@…):

 commit d3a31e480ace72a82a301ffb11fd5f73d9ede5bd
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Fri Sep 2 09:07:46 2011 +0100

     Increase the "context stack depth" to 200 (from 20)

     This parameter controls the allowed depth of reasoning in the
     type constraint solver.  Perfectly well-behaved programs can
     use deep stacks, and 20 is obviously too small.  (Indeed, if
     you don't have UndecidableInstances, the constraint solver
     is supposed to terminate, so no limit should be needed.)

     Responding to Trac #5395 this patch increases the default
     to 200.

  includes/HaskellConstants.hs |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5395#comment:3>
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