[GHC] #14498: GHC internal error: "not in scope during TC but it passed the renamer"

[GHC]

#14498: GHC internal error: "not in scope during TC but it passed the renamer"
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |             Keywords:
      Resolution:                    |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14288            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I suppose we wouldn't have to break anything for now if we went with
 another option: create a separate copy `hsScopedTvs` intended only for use
 with pattern synonyms and only apply the fix to that copy for now. That
 way, `g` would still continue to compile, as it would use the old
 codepath.

 Of course, we wouldn't want to maintain this `hsScopedTvs` split forever,
 but we can merge them back together when #14288 is implemented (where we
 have the liberty of changing the semantics of existing programs).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14498#comment:7>
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