Template Haskell gets confused with scoped kind variables in a class declaration (#9081) · Issues · Glasgow Haskell Compiler / GHC

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

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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