makeBound chokes on types containing tuples of constants

[Daniel Fox Franke]

The following makeBound invocation chokes:

{-# LANGUAGE DeriveFunctor, TemplateHaskell #-}

import Bound
import Bound.Name
import Data.Text

type Named b = Name Text b

data Term v
  = EVar v
  | EApp (Term v) (Term v)
  | EAbs (Named ()) (Scope (Named ()) Term v)
  deriving (Functor)

makeBound ''Term

boundbug.hs:1:1: error:
    Exception when trying to run compile-time code:
      This is bad: AppT (ConT Main.Named) (TupleT 0) False
CallStack (from HasCallStack):
  error, called at src/Bound/TH.hs:269:35 in bound-2.0.1-13f2bf83f03b2fd0ec7401893dd97861fab71a8bfa55e6a9cf9d765f1a520a4f:Bound.TH
    Code: makeBound ''Term

But the following works fine:

data MyUnit = MyUnit deriving (Eq)

data Term v
  = EVar v
  | EApp (Term v) (Term v)
  | EAbs (Named MyUnit) (Scope (Named ()) Term v)
  deriving (Functor)

makeBound ''Term

The problem is that makeBound doesn't recognize () as a constant because it parses as an empty tuple, and isKonst is missing a rule for tuples. The other, remaining occurrence of Named () is okay because it gets handled by boundInstance rather than isKonst.

[Oleg Grenrus]

I guess it's easy enough to extend the isKonst, do you want to try?