[GHC] #15918: GHC panic from QuantifiedConstraints(?)

[GHC]

#15918: GHC panic from QuantifiedConstraints(?)
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.2
      Resolution:                    |             Keywords:
                                     |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 This appears to no longer happen on a recent `devel2`-flavoured GHC HEAD:

 {{{
 GHCi, version 8.9.20190227: https://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Main             ( ../Bug.hs, interpreted )

 ../Bug.hs:18:19: error:
     • Expected kind ‘(k0 -> *) -> Constraint’,
         but ‘[]’ has kind ‘* -> *’
     • In the first argument of ‘Build’, namely ‘[]’
       In an expression type signature: Build [] a
       In the expression: rev :: Build [] a
    |
 18 | uu = rev :: Build [] a
    |                   ^^
 }}}

 Should we add a test case for this and call it fixed?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15918#comment:11>
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