Module Test.QuickCheck.Instances collides with a module of the same name from quickcheck-instances

[sol]

From a users perspective this is a pain, esp. when using a global package database and GHCi. checkers was first, quickcheck-instances is more widely used, not sure how to resolve this.

[sol]

I'm cross-filing this at aslatter/qc-instances#9.

[russmatney]

(repost from same linked issue). Is there are movement on this? I just ran into it, but it seems quite old - if there's a systemic way to solve this I'd love to know about it!

[russmatney]

Just discovered PackageImports, which totally solved this for me.

import "quickcheck-instances" Test.QuickCheck.Instances()
import "checkers" Test.QuickCheck.Instances()

Sorry for the noise!

[sjakobi]

Since there hasn't been any more input on this issue for over 2 years, I currently tend to do nothing about it.

[conal]

I completely forgot about this issue. Is there still interest in addressing? How do the contents of these two modules relate?

[sjakobi]

How do the contents of these two modules relate?

To my surprise they actually don't relate much at all:

• The quickcheck-instances version actually contains lots of instances.
• The checkers version contains instances for Array but mostly generators and combinators for generators:

> :browse Test.QuickCheck.Instances
(Test.QuickCheck.Instances.Tuple.>****<) ::
  Test.QuickCheck.Gen.Gen a
  -> Test.QuickCheck.Gen.Gen b
  -> Test.QuickCheck.Gen.Gen c
  -> Test.QuickCheck.Gen.Gen d
  -> Test.QuickCheck.Gen.Gen e
  -> Test.QuickCheck.Gen.Gen (a, b, c, d, e)
(Test.QuickCheck.Instances.Tuple.>***<) ::
  Test.QuickCheck.Gen.Gen a
  -> Test.QuickCheck.Gen.Gen b
  -> Test.QuickCheck.Gen.Gen c
  -> Test.QuickCheck.Gen.Gen d
  -> Test.QuickCheck.Gen.Gen (a, b, c, d)
(Test.QuickCheck.Instances.Tuple.>**<) ::
  Test.QuickCheck.Gen.Gen a
  -> Test.QuickCheck.Gen.Gen b
  -> Test.QuickCheck.Gen.Gen c
  -> Test.QuickCheck.Gen.Gen (a, b, c)
(Test.QuickCheck.Instances.Tuple.>*<) ::
  Test.QuickCheck.Gen.Gen a
  -> Test.QuickCheck.Gen.Gen b -> Test.QuickCheck.Gen.Gen (a, b)
Test.QuickCheck.Instances.List.anyList ::
  Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Char.brace ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Char.bracket ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.List.decreasing ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Eq a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.decreasingInf ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Eq a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Ord.greaterThan ::
  Ord a =>
  a -> Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.List.increasing ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Eq a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.increasingInf ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Eq a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.infiniteList ::
  Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Ord.lessThan ::
  Ord a =>
  a -> Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Char.lowerAlpha ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Maybe.maybeGen ::
  Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen (Maybe a)
Test.QuickCheck.Instances.Num.negative ::
  (Eq a, Num a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Char.newline ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.List.nonEmpty ::
  Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Num.nonNegative ::
  (Num a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Num.nonPositive ::
  (Num a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Char.nonSpace ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Num.nonZero ::
  (Eq a, Num a) =>
  Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Num.nonZero_ ::
  (Eq a, Num a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.List.nondecreasing ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.nondecreasingInf ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.nonincreasing ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.List.nonincreasingInf ::
  (Test.QuickCheck.Arbitrary.Arbitrary a, Num a) =>
  Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Eq.notEqualTo ::
  Eq a => a -> Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Eq.notOneof ::
  (Eq a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  [a] -> Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.Char.numeric ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Char.operator ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Char.parenthesis ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Num.positive ::
  (Eq a, Num a, Test.QuickCheck.Arbitrary.Arbitrary a) =>
  Test.QuickCheck.Gen.Gen a
Test.QuickCheck.Instances.List.setLength ::
  Int -> Test.QuickCheck.Gen.Gen a -> Test.QuickCheck.Gen.Gen [a]
Test.QuickCheck.Instances.Char.space ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Char.upperAlpha ::
  Test.QuickCheck.Gen.Gen Char
Test.QuickCheck.Instances.Char.whitespace ::
  Test.QuickCheck.Gen.Gen Char

We could probably get rid of the Array instances – quickcheck-instances provides these too.

The generators seem rather hidden in an Instances module – we could try moving these to a module with a more appropriate name.