[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 simonpj):

 >  Is "a coercion variable shall not appear as a template variable" an
 invariant of Rule? This wasn't clear to me.

 In effect, yes.  Matching the LHS will never bind coercion variables
 (certainly not ones used in types), so they'd better not appear on the
 RHS.

 Boiling out a small test case would be jolly useful.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14270#comment:13>
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