[GHC] #15436: Compile-time panic, Prelude.!!: negative index

[GHC]

#15436: Compile-time panic, Prelude.!!: negative index
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        Reporter:  pbrisbin          |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash or panic                     |  simplCore/should_run/T15436
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5008
       Wiki Page:                    |
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Comment (by hvr):

 I was just about to finally file this bug I ran into back in May already
 w/ GHC 8.4.2 but didn't have time to investigate and instead workarounded
 via

 https://github.com/text-utf8/text-
 utf8/commit/5ba8f5d1d4c0f39399d8c32f069e4132c92ef099


 It'd be great to have this fixed in GHC 8.4.4

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15436#comment:10>
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