[GHC] #15428: GHC 8.6+ panics (piResultTys2), older GHCs don't

[GHC]

#15428: GHC 8.6+ panics (piResultTys2), older GHCs don't
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:  TypeInType,
                                     |  TypeFamilies
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 monoidal):

 Simpler version, also panicks 8.4:

 {{{
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeInType #-}
 module Bug where

 data Flurmp
 type family Pure (x :: a) :: f a

 type T = Pure Flurmp Flurmp
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15428#comment:1>
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