[GHC] #14720: GHC 8.4.1-alpha regression with TypeInType

[GHC]

#14720: GHC 8.4.1-alpha regression with TypeInType
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler (Type    |              Version:  8.4.1-alpha1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I'm pretty sure this is #12919. It works on my branch, held up due to
 performance problems. It's being actively worked on by @alexvieth, to whom
 I've gratefully delegated fixing those performance problems. But when I
 say active, I mean it: Alex sent me some results offline this morning.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14720#comment:2>
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