[GHC] #14498: GHC internal error: "not in scope during TC but it passed the renamer"

[GHC]

#14498: GHC internal error: "not in scope during TC but it passed the renamer"
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |             Keywords:
      Resolution:                    |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14288            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Here's a much simpler way to reproduce the bug, for debugging purposes:

 {{{#!hs
 {-# LANGUAGE PatternSynonyms, PolyKinds, ScopedTypeVariables #-}
 module Bug where

 import Data.Proxy

 pattern Foo :: forall (a :: j). () => forall (b :: k). () => Proxy a
 pattern Foo = (Proxy :: Proxy (b :: k))
 }}}
 {{{
 GHCi, version 8.2.1: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Bug              ( Bug.hs, interpreted )

 Bug.hs:7:37: error:
     • GHC internal error: ‘k’ is not in scope during type checking, but it
 passed the renamer
       tcl_env of environment: [a1vz :-> Type variable ‘j’ = j,
                                a1vB :-> Type variable ‘a’ = a, a1vD :->
 Type variable ‘b’ = b]
     • In the kind ‘k’
       In the first argument of ‘Proxy’, namely ‘(b :: k)’
       In the type ‘Proxy (b :: k)’
   |
 7 | pattern Foo = (Proxy :: Proxy (b :: k))
   |                                     ^
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14498#comment:5>
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