[GHC] #8743: The impossible happened : Prelude.(!!): index too large

[GHC]

#8743: The impossible happened : Prelude.(!!): index too large
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        Reporter:  erikd             |                   Owner:  nomeata
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.8.1
       Component:  Compiler          |                 Version:  7.8.1-rc1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash                              |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by nomeata):

 I’m confused. The harbormaster build for Phab:D860 at
 https://phabricator.haskell.org/harbormaster/build/3863/ does not list
 8743 as failing.

 Also, this looks like a different bug, unrelated to the demand analyzer,
 and related to the lint check introduced in #10181. I suggest to discuss
 this in a separate ticket.

 Also feel free to go ahead with your patches, marking the test case as
 `expect_broken`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8743#comment:13>
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