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

21 Nov 2017


      #14498: GHC internal error: "not in scope during TC but it passed the renamer"
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 {-# Language PatternSynonyms, ViewPatterns, GADTs, ConstraintKinds,
 RankNTypes, KindSignatures, PolyKinds, ScopedTypeVariables, DataKinds #-}

 import Type.Reflection
 import Data.Kind

 data Dict c where Dict :: c => Dict c

 asTypeable :: TypeRep a -> Dict (Typeable a)
 asTypeable rep =
   withTypeable rep
     Dict

 pattern Typeable :: () => Typeable a => TypeRep a
 pattern Typeable <- (asTypeable -> Dict)
   where Typeable = typeRep

 data N = O | S N

 type SN = (TypeRep :: N -> Type)

 pattern SO = (Typeable :: TypeRep (O::N))

 pattern SS ::
      forall (t :: k').
      ()
   => forall (a :: kk -> k') (n :: kk).
      (t ~ a n)
   =>
   TypeRep n -> TypeRep t
 pattern SS n <- (App (Typeable :: TypeRep (a::kk -> k')) n)
 }}}

 fails with **GHC internal error**

 {{{
 $ ghci -ignore-dot-ghci Bug.hs
 GHCi, version 8.3.20170920: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Bug.hs, interpreted )

 Bug.hs:31:47: error:
     • GHC internal error: ‘kk’ is not in scope during type checking, but
 it passed the renamer
       tcl_env of environment: [a1Ao :-> Type variable ‘k'’ = k' :: *,
                                a1Aq :-> Type variable ‘t’ = t :: k',
                                a1Hs :-> Type variable ‘a’ = a :: k0,
                                r1v4 :-> Identifier[asTypeable::forall k (a
 :: k).
                                                                TypeRep a
                                                                -> Dict
 (Typeable a), TopLevelLet]]
     • In the kind ‘kk -> k'’
       In the first argument of ‘TypeRep’, namely ‘(a :: kk -> k')’
       In the type ‘TypeRep (a :: kk -> k')’
    |
 31 | pattern SS n <- (App (Typeable :: TypeRep (a::kk -> k')) n)
    |                                               ^^
 Failed, 0 modules loaded.
 Prelude>
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14498
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