The following program <div class="highlight highlight-source-haskell notranslate p

<a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/us

Possibly related: <a href="https://ghc.haskell.org/trac/ghc/ticket/13306" rel="nofollo

I think this is closed in <a class="issue-link js-issue-link" data-error-text="Failed

`withStatic` instance fails when type families appear in constraints about distributed-closure HOT 4 CLOSED

tweag commented on July 17, 2024

`withStatic` instance fails when type families appear in constraints

from distributed-closure.

Comments (4)

facundominguez commented on July 17, 2024 1

@alpmestan, note this issue

from distributed-closure.

facundominguez commented on July 17, 2024

from distributed-closure.

edsko commented on July 17, 2024

I think this is closed in #10 since the following version of the @facundominguez 's test code works just fine:

{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StaticPointers #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TemplateHaskell #-}

import Control.Distributed.Closure.TH

data T a = T
  deriving Show

type family F a where
  F Int = Int
  F a = a

class C a where
  m :: Maybe a

instance C Int where m = Just 0

withStatic [d|
  instance C (F a) => C (T a) where
    m = Just T
  |]

main :: IO ()
main = print (m :: Maybe (T Int))