[GHC] #8205: the 'impossible' happened : expectJust block_order

[GHC]

#8205: the 'impossible' happened : expectJust block_order
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        Reporter:  erikd                |            Owner:  jstolarek
            Type:  bug                  |           Status:  closed
        Priority:  normal               |        Milestone:
       Component:  Compiler             |          Version:  7.7
      Resolution:  fixed                |         Keywords:
Operating System:  Unknown/Multiple     |     Architecture:
 Type of failure:  Building GHC failed  |  Unknown/Multiple
       Test Case:                       |       Difficulty:  Unknown
        Blocking:                       |       Blocked By:
                                        |  Related Tickets:
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Comment (by jstolarek):

 Well, actually we don't have a test because I couldn't reproduce the
 problem on my machine and I wasn't able to check whether the test really
 catches the bug. I just pushed a speculative test into testsuite. Kazu,
 can you test whether it does the job? Here's what you need to do:

 {{{
 ./sync-all pull
 make -j4
 cd testsuite/tests
 make TEST=T8205
 }}}
 Since the problem is fixed, this test should pass. Now you need to tests
 whether the test fails without my fix:
 {{{
 cd ../..
 git revert bec3c0497fa55e84005d175e0fc6b1d72df961e1
 }}}
 Now build only stage2 compiler:
 {{{
 make stage=2 -j4
 }}}
 This will give you a broken stage2 compiler. Run the test again:
 {{{
 cd testsuite/test
 make TEST=T8205
 }}}
 This time it should fail with a panic. If it does, then all is well and we
 have the test that catches the bug.

 Could you try doing this and report the results?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8205#comment:29>
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