test-framework-th does not work with GeneralizedNewtypeDeriving or TypeSynonymInstances

[adamgordonbell]

$(defaultMainGenerator) is not seeing the arbitary instance of Results.

Yet $quickCheckAll, from quickchek, works for these, so must be possible

Example TypeSynonymInstances Code:

{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE OverlappingInstances #-}
module Main where

import ClassyPrelude
import qualified Data.Map as Map
import Test.HUnit
import Data.Number.Fixed
import Test.QuickCheck hiding (Result)
import Test.QuickCheck.All
import Test.Framework.TH
import Test.Framework
import Test.Framework.Providers.QuickCheck2

type Result = (Int,Int)

instance Arbitrary Result where
    arbitrary = elements resultElements

resultMax = 3

resultElements :: [Result]
resultElements = [(h,a)| h <- [0..resultMax], a <- [0..resultMax]]

type Results = Map Result Rational

instance Monoid Results where
    mempty = empty
    mappend = Map.unionWith (+)

instance Arbitrary Results where
    arbitrary = do
      rs <-listOf $ elements resultElements
      ws <-listOf $ elements [1, 1.5 .. 2]
      return $ Map.fromListWith (+) $ zip rs ws

main = do
    runTests1
    runTests2
    return ()


prop_resultsAdd :: Results -> Results -> Bool
prop_resultsAdd rs1 rs2 = mappend rs1 rs2 == mappend rs2 rs1

runTests1 = $quickCheckAll
runTests2 = $(defaultMainGenerator)

Error: No instance for (Arbitrary (Map Result Rational))

Example GeneralizedNewtypeDeriving Code:

{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Main2 where

import ClassyPrelude
import qualified Data.Map as Map
import Test.HUnit
import Data.Number.Fixed
import Test.QuickCheck hiding (Result)
import Test.QuickCheck.All
import Test.Framework.TH
import Test.Framework
import Test.Framework.Providers.QuickCheck2

newtype Result = Result (Int,Int) deriving (Show,Eq,Ord)


instance Arbitrary Result where
    arbitrary = elements resultElements

resultMax = 3

resultElements :: [Result]
resultElements = [Result (h,a)| h <- [0..resultMax], a <- [0..resultMax]]

newtype Results = Results (Map Result Rational) deriving (Eq,Ord, Show)

instance Monoid Results where
    mempty = Results empty
    mappend (Results r1)(Results r2) = Results $ Map.unionWith (+) r1 r2

instance Arbitrary Results where
    arbitrary = do
      rs <-listOf $ elements resultElements
      ws <-listOf $ elements [1, 1.5 .. 2]
      return . Results . Map.fromListWith (+) $ zip rs ws

main = do
    runTests1
    runTests2
    return ()

runTests1 = $quickCheckAll
runTests2 = $(defaultMainGenerator)

prop_resultsAdd :: Results -> Results -> Bool
prop_resultsAdd rs1 rs2 = mappend rs1 rs2 == mappend rs2 rs1

Error: No instance for (Arbitrary Results)