[GHC] #14608: Different GHCi error messages for similar scenarios

[GHC]

#14608: Different GHCi error messages for similar scenarios
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        Reporter:  mb64              |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Ah. I believe the culprit is the fact that these two lines were removed:
 https://github.com/ghc/ghc/commit/714bebff44076061d0a719c4eda2cfd213b7ac3d
 #diff-6fd42166fdf8d397ba9081bb24661f1fL851

 Previously, this would check that in interpreted code, any alternatives in
 a pattern match would not scrutinize unboxed tuples. But since that check
 was removed, it falls through and eventually results in the disastrous
 panic shown above.

 Luckily, we should be able to reinstate this check with relative ease.
 Patch coming soon.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14608#comment:2>
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