phadej

import Data.Typeable (Typeable, typeRep)
import Data.Proxy (Proxy (..))
import Text.Read (readMaybe)
import GHC.Stack (HasCallStack)

import Prelude hiding (read)

read :: forall a. (Typeable a, Read a, HasCallStack) => String -> a
read s = case readMaybe s of
    Just x  -> x

phadej

{-# LANGUAGE DeriveFunctor #-}

-- This are are fine
newtype F a = F ((a -> Bool) -> Bool) deriving Functor
newtype T a = T (a,a,a) deriving Functor

-- but if we define

newtype Fun a b   = Fun (a -> b) -- and
data    Tri a b c = Tri a b c

phadej

module Main (main) where

import System.FilePath.Glob (glob)
import Control.Monad (foldM)
import Distribution.Simple.Utils (fromUTF8BS)

import qualified Data.ByteString as BS
import qualified Data.Map.Strict as Map

import GHC.Hs.Expr

phadej

[polinukli] ~ % ghc-pkg list --package-db=/cabal/store/ghc-8.6.5/package.db|grep hashable
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0
    hashable-1.2.7.0

phadej

First build:

% cabal v2-build -w ghc-8.8.3

(I tried at v2.6 tag)

Then run test

phadej

{-# LANGUAGE TemplateHaskell #-}
module Bar where

import System.Process (readProcess)
import Control.Monad.IO.Class (liftIO)
import Language.Haskell.TH.Syntax (lift)

fooBar :: String
fooBar = $(liftIO (readProcess "foo" [] "") >>= lift)

phadej

modelTest
    :: forall a b f g c.
    ( c a, c b
    , QC.Arbitrary (f b), Eq (g a)
    , Show (f a), Show (f b), Show (g a), Show (g b)
    , Functor f, Functor g
    )
    => (b -> a)
    -> Proxy c
    -> TestName

phadej

-- this is so wrong.
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE DerivingStrategies, GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MagicHash, UnboxedTuples #-}
{-# LANGUAGE ScopedTypeVariables #-}
module ExceptST (
    ExceptST, runExceptST, liftST, throwExceptST,
    -- * examples
    allNonNegative,
    ) where

phadej

{-# LANGUAGE DeriveTraversable #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# OPTIONS_GHC -Wall #-}
module Unification where

import Control.Monad (ap, forM, forM_)
import Data.Foldable (toList)

import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map

phadej

{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE DerivingVia #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes #-}