[GHC] #13474: GHC HEAD regression: Prelude.!!: index too large

[GHC]

#13474: GHC HEAD regression: Prelude.!!: index too large
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 I would be happy to.

 Unfortunately there are some testsuite issues in Phab:D3316 which will
 need to be resolved before it can be merged. Namely, `T11480b` fails with,
 {{{
 T11480b.hs:131:10: error:
     • Couldn't match kind ‘*’ with ‘Constraint’
         arising from a use of ‘T11480b.$dmop’
     • In the expression: T11480b.$dmop @Constraint @(:-)
       In an equation for ‘op’: op = T11480b.$dmop @Constraint @(:-)
       In the instance declaration for ‘Category (:-)’
 }}}
 which I'm reasonably confident will break user code (namely Edward
 Kmetts's `constraints` library).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13474#comment:7>
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