NRE when printing failure report with a generated None value

[samritchie]

I’m seeing crashes when rendering the failure report for a property with a Gen.option that has generated None. A minimal failing case (using NUnit):

    [<Test>]
    member _.TestOptionReport () =
        property {
            let! opt = Gen.option (Gen.int32 (Range.linear 0 10))
            return opt.IsSome
        }
        |> Property.check

throws the following:

 Error Message:
   System.NullReferenceException : Object reference not set to an instance of an object.
  Stack Trace:
     at System.Object.GetType()
   at Hedgehog.Property.prepareForPrinting@103(Object value)
   at Hedgehog.Property.printValue[a](a value)
   at Microsoft.FSharp.Collections.Internal.IEnumerator.map@75.DoMoveNext(b& curr) in D:\a\_work\1\s\src\fsharp\FSharp.Core\seq.fs:line 78
   at Microsoft.FSharp.Collections.Internal.IEnumerator.MapEnumerator`1.System.Collections.IEnumerator.MoveNext() in D:\a\_work\1\s\src\fsharp\FSharp.Core\seq.fs:line 64
   at Microsoft.FSharp.Collections.SeqModule.Iterate[T](FSharpFunc`2 action, IEnumerable`1 source) in D:\a\_work\1\s\src\fsharp\FSharp.Core\seq.fs:line 496
   at Hedgehog.ReportModule.renderFailed(FailureData failure, Report report)
   at Hedgehog.ReportModule.tryRaise(Report report)
   at Hedgehog.Property.check(Property`1 p)

I’m using dotnet 6.0.100, macOS 11.6.1, Hedgehog 0.11, NUnit 3.13.2, NUnitTestAdapter 4.1

[TysonMN]

PR #382 fixes this bug and release 0.11.1 contains the fix

[TysonMN]

Thanks @samritchie for the bug report and simple reproduction :)

[samritchie]

Thanks for the quick fix!