[GHC] #14270: GHC HEAD's ghc-stage1 panics on Data.Typeable.Internal

[GHC]

#14270: GHC HEAD's ghc-stage1 panics on Data.Typeable.Internal
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        Reporter:  hvr               |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14236            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Uck. This is nasty. And I'm sure it's actually my fault, not Ben's.

 I think we should revert the offending commit while sorting this out, as
 I'm not convinced that this will have an easy fix.

 Ben, could you paste here what the offending rule is? I know that GHC
 already does some faffing about with rules to make sure their LHSs are
 convenient to match with (see, e.g., `DsBinds.decomposeRuleLhs` and
 `Desugar.unfold_coerce`); maybe we can extend that algorithm to handle
 this case.

 The long-term solution is, I believe comment:9:ticket:14119.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14270#comment:7>
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