[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):

 I have good news and bad news.

 The bad news is that this still does not typecheck on GHC HEAD.

 The good news is that it no longer panics! It now gives the following,
 lovely error message:

 {{{
 $ /opt/ghc/head/bin/ghci Bug.hs
 GHCi, version 8.7.20180621: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Bug              ( Bug.hs, interpreted )

 Bug.hs:8:42: error:
     • Expected a type, but ‘k’ has kind ‘k’
     • In the kind ‘[(k, Type)]’
   |
 8 | class ListTuple (tuple :: Type) (as :: [(k, Type)]) where
   |                                          ^
 }}}

 So that's... nice, I guess.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15142#comment:13>
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