DivideByZeroException in Gen.Choose

Hello. I’m started trying to use FsCheck in C# Project. And I use simple example in test to generate any number from all range of int values:

    [Test]
    public void Test_MinMax()
    {
        var generator = Gen.Choose(int.MinValue, int.MaxValue);
        foreach (var val in generator.Sample(10, 10))
            Console.WriteLine(val);
    }

And I got exception in test output in FsCheck:

System.DivideByZeroException : Attempted to divide by zero.
   at FsCheck.Random.stdRange(Int32 l, Int32 h, StdGen rng)
   at [e-mail](StdGen rng)
   at [e-mail](Int32 _arg1, StdGen r)
   at FsCheck.Gen.sample@170[a](Int32 size, Gen`1 generator, Int32 i, StdGen seed, FSharpList`1 samples)
   at FsCheck.Gen.Sample[a](Int32 size, Int32 n, Gen`1 generator)
   at FsCheck.GenExtensions.Sample[a](Gen`1 generator, Int32 size, Int32 numberOfSamples)

Is this a bug? Or, i’m doing something wrong?

[Kharacternyk]

DoNotSize<T> types are just a way to tell FsCheck that you want T in the whole range. They are wrappers around T without any additional behaviour.

I see you are an Russian speaker, so you may contact me on The Telegram if you have additional questions (I think issues on GitHub should be readable for everyone and using English here is the right way).

http://t.me/Kharacternyk

Удачи!

[Kharacternyk]

It seems right, except that F# version firstly create an arbitrary for int and then uses Arb.convert to create an arbitrary for DoNotSize<int>. I think shrinking wouldn’t work in your version because Arb.Shrink tries to find an Arbitrary<DoNotSize<int>> that doesn’t exist yet. The F# version is closer to

//your code
return Arb.From(gen, i => (Arb.Shrink i.Item).Select(DoNotSize<int>.NewDoNotSize));