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  • #9081

Closed
Open
Opened May 06, 2014 by Richard Eisenberg@raeDeveloper

Template Haskell gets confused with scoped kind variables in a class declaration

When I say

{-# LANGUAGE TemplateHaskell, DataKinds, PolyKinds, TypeFamilies #-}

module Bug where

import Data.Proxy

$( [d|
  class kproxy ~ 'KProxy => C (kproxy :: KProxy a) where
    type TF (x :: a) :: Bool
  |])

I get

/Users/rae/temp/Bug.hs:7:4:
    Kind variable also used as type variable: ‘a_asJA’
    In the declaration for class C_asJy

/Users/rae/temp/Bug.hs:7:4:
    The exact Name ‘kproxy_asJB’ is not in scope
      Probable cause: you used a unique Template Haskell name (NameU), 
      perhaps via newName, but did not bind it
      If that's it, then -ddump-splices might be useful

The code in the TH quote compiles fine on its own.

Trac metadata
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Version 7.8.2
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Template Haskell
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Reference: ghc/ghc#9081