[GHC] #15142: GHC HEAD regression: tcTyVarDetails

[GHC]

#15142: GHC HEAD regression: tcTyVarDetails
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |             Keywords:  TypeInType,
      Resolution:                    |  TypeFamilies, CUSKs
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 As far as I can tell, the only available workaround for this issue is to
 explicitly quantify `k`, like so:

 {{{#!hs
 class ListTuple (tuple :: Type) k (as :: [(k, Type)]) where
   type ListToTuple as :: Type
 }}}

 `generic-lens` may need to employ this hack if this issue hasn't been
 fixed by 8.6.1's release.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15142#comment:14>
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