[GHC] #15472: GHC HEAD type inference regression post-"Remove decideKindGeneralisationPlan"

[GHC]

#15472: GHC HEAD type inference regression post-"Remove
decideKindGeneralisationPlan"
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  highest           |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |
      Resolution:  invalid           |             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 monoidal):

 Thanks. I have simplified the code.

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

 import Data.Kind (Type)

 data Proxy b

 type family LetGo :: k

 foo :: Proxy (LetGo :: Type)
 foo = undefined

 sSconcat :: forall x. x
 sSconcat = undefined
    where sGo :: x -> Proxy LetGo
          sGo _ = foo
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15472#comment:7>
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