Unable to access scoped variables

[sfmskywalker]

Originally posted by @dodyg in #760 (comment)

Why does in this workflow "CurrentValue" variable is missing from IfTrue

public class Loop : IWorkflow
{
    public void Build(IWorkflowBuilder builder) =>
        builder
        .ForEach(x => new int[] { 10, 20, 30, 40 }, x =>
        {
            x.IfTrue(condition: (ActivityExecutionContext m) =>
            {
                var has = m.HasVariable("CurrentValue");
                Console.WriteLine("Has variable " + has);
                var value = m.GetVariable<int>("CurrentValue");
                Console.WriteLine("Debug Value " + value);
                return value == 40;
            }, whenTrue: (y) =>
            {
                y.WriteLine("The last value");
            });
        });
}

but if I implement a custom activity, the variable are accessible

using Elsa;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Elsa.Builders;
using Elsa.Services;
using Elsa.ActivityResults;
using Elsa.Services.Models;
using System;
using Elsa.Activities.ControlFlow;
using Elsa.Activities.Console;
using Elsa.Activities.Primitives;

using var host = new HostBuilder()
    .ConfigureServices(services =>
    {
        services.AddElsa(elsa =>
        {
            elsa
                .AddConsoleActivities()
                .AddQuartzTemporalActivities()
                .AddWorkflow<Loop>()
                .AddActivity<Print>();
        });
    })
    .UseConsoleLifetime()
    .Build();

await host.Services.GetService<IBuildsAndStartsWorkflow>().BuildAndStartWorkflowAsync<Loop>();
await host.WaitForShutdownAsync();

public class Loop : IWorkflow
{
    public void Build(IWorkflowBuilder builder) =>
        builder
        .ForEach(x => new int[] { 10, 20, 30, 40 }, x =>
        {
            x.Then<Print>();
        });
}

public class Print : Activity
{
    protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
    {
        try
        {
            var index = context.GetVariable("CurrentIndex");
            var value = context.GetVariable("CurrentValue");
            System.Console.WriteLine($"Index {index} values {value} type {value.GetType()}");
            return Done("No");
        }
        catch(Exception ex)
        {
            return Fault(ex.Message);
        }
    }
}