🐛 ReadonlyCollectionPropertiesBehavior causes InvalidCastException when used with OmitOnRecursionBehavior

[ArturDorochowicz]

Describe the Bug

When ReadonlyCollectionPropertiesBehavior and OmitOnRecursionBehavior are used together, there may be an InvalidCastException thrown from CreateMany call in ReadonlyCollectionPropertiesCommand

InvalidCastException
Unable to cast object of type 'AutoFixture.Kernel.OmitSpecimen' to type 'System.Collections.Generic.IEnumerable1[System.Object]'.

AutoFixture/Src/AutoFixture/Kernel/ReadonlyCollectionPropertiesCommand.cs

Lines 64 to 66 in 730b478

	var valuesToAdd = SpecimenFactory.CreateMany(
	context,
	addMethod.Parameters.Single().ParameterType);

Scenario

using System.Collections.Generic;
using System.Linq;
using AutoFixture;
using Xunit;

#nullable enable

public class Bugs
{

public class RecursionModel
{
    public RecursionItem? Item { get; set; }
}

public class RecursionItem
{
    public List<RecursionItem> Items { get; } = new();
}

    [Fact]
    public void OmitRecursion()
    {
        var fixture = new Fixture();
        fixture.Behaviors.Add(new ReadonlyCollectionPropertiesBehavior());
        fixture.Behaviors.OfType<ThrowingRecursionBehavior>().ToList()
            .ForEach(b => fixture.Behaviors.Remove(b));
        fixture.Behaviors.Add(new OmitOnRecursionBehavior());
 
        // Throws
        fixture.Create<RecursionModel>();
    }
}
/*
System.InvalidCastException
Unable to cast object of type 'AutoFixture.Kernel.OmitSpecimen' to type 'System.Collections.Generic.IEnumerable`1[System.Object]'.
   at AutoFixture.SpecimenFactory.CreateMany(ISpecimenContext context, Type type)
   at AutoFixture.Kernel.ReadonlyCollectionPropertiesCommand.Execute(Object specimen, ISpecimenContext context)
   at AutoFixture.Kernel.Postprocessor`1.Create(Object request, ISpecimenContext context)
   at AutoFixture.Fixture.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.SpecimenContext.Resolve(Object request)
   at AutoFixture.Kernel.SeedIgnoringRelay.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.CompositeSpecimenBuilder.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.CompositeSpecimenBuilder.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.Postprocessor`1.Create(Object request, ISpecimenContext context)
   at AutoFixture.AutoPropertiesTarget.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.CompositeSpecimenBuilder.Create(Object request, ISpecimenContext context)
   at AutoFixture.Kernel.TerminatingWithPathSpecimenBuilder.Create(Object request, ISpecimenContext context)
*/

Expected Behavior

The code above should not throw. The first level collection should probably be empty

More Information

Using AutoFixture 4.17