Tuple predicates in Template Haskell

[Yorick Laupa]

Hi,

I try to make my way through #7021 [1]. Unfortunately, there is nothing in
the ticket about what should be expected from the code given as example.

I came with an implementation and I would like feedback from you guys. So,
considering this snippet:

--

{-# LANGUAGE ConstraintKinds #-}

type IOable a = (Show a, Read a)

foo :: IOable a => a
foo = undefined

-- 

This is what I got now when pretty-printing TH.Info after reify "foo" call:

VarI Tuple.foo (ForallT [PlainTV a_1627398594] [TupleP 2 [AppT (ConT
GHC.Show.Show) (VarT a_1627398594),AppT (ConT GHC.Read.Read) (VarT
a_1627398594)]] (VarT a_1627398594)) Nothing (Fixity 9 InfixL)

Does that sound right to you ?

Thanks for your time

-- Yorick

[1] https://ghc.haskell.org/trac/ghc/ticket/7021
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