reify yields incorrect TupleT at higher-kinds

Line 1175 of changeset:0237ed67 introduces a bug where reify yields an application of TupleT where its argument is too small when the type being reified is of a higher-kind than *.

For example, in the Applicative instance for ((,) a); the (,) gets reified as TupleT 1 instead of TupleT 2.

Here's some code that duplicates its C instance to be a D instance.

{-# LANGUAGE TemplateHaskell, KindSignatures, FlexibleInstances #-}

module ReifyTupleBug where

import Language.Haskell.TH

class C (f :: * -> *)
class D (f :: * -> *)

instance C ((,) Int)

reify ''C >>= \(ClassI _ [i]) ->
  return [InstanceD (ci_cxt i) (foldl AppT (ConT ''D) (ci_tys i)) []]

It results in a kind mis-match:

ReifyTupleBug.hs:13:1: Kind mis-match The first argument ofD' should have kind * -> *', but Int' has kind *' In the instance declaration for D Int' Failed, modules loaded: none.`

I'm not sure how reify_tc_app should be adjusted; perhaps it needs to know the kind at which it is operating and then increment n_tys based on the number of arrows?

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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