[GHC] #5252: UNPACK without optimisation leads to panic

[GHC]

#5252: UNPACK without optimisation leads to panic
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  Reporter:  simonpj                                   |          Owner:                  
      Type:  bug                                       |         Status:  merge           
  Priority:  normal                                    |      Milestone:                  
 Component:  Compiler                                  |        Version:  7.6.1           
Resolution:                                            |       Keywords:                  
        Os:  Unknown/Multiple                          |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown                              |     Difficulty:  Unknown         
  Testcase:  deSugar/should_compile/T5252, T5252Take2  |      Blockedby:                  
  Blocking:                                            |        Related:                  
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Changes (by simonpj):

  * status:  new => merge
  * testcase:  deSugar/should_compile/T5252 =>
               deSugar/should_compile/T5252, T5252Take2


Comment:

 Needs this patch too:
 {{{
 commit ba8fd081ba9b222dd5f93604d7deeaca372e4511
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Mon Sep 17 18:22:10 2012 +0100

     Make the call to chooseBoxingStrategy lazy again

     I made it strict, as an incidental consequence of this patch:

       commit 5bae803a18b17bdb158a7780e6b6ac3c520e5b39
       Author: Simon Peyton Jones <simonpj at microsoft.com>
       Date:   Sat Sep 15 23:09:25 2012 +0100
           Fix UNPACK with -fomit-interface-pragmas.

     But it's very important that chooseBoxingStrategy is lazy, else
     (in bigger programs with lots of recursion in types) GHC can
     loop. This showed up in Data.Sequence; and I think it was making
     haddock loop as well.

     Anyway this patch makes it lazy again.

  compiler/typecheck/TcTyClsDecls.lhs |   34
 +++++++++++++++++-----------------
  1 file changed, 17 insertions(+), 17 deletions(-)
 }}}
 Regression test added.

 Merge to 7.6 branch.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5252#comment:6>
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