Why argument is null in CallSiteVisitor<TArgument, TResult> in ExpressionResolverBuilder

[peterykt]

I'm researching the Dependency Injection library for Net 8.
Here's a simple code example:
`
public class CreateServiceByExpressionTest
{
[Fact]
private void CreateServiceByServiceProviderTest()
{
var serviceScopedCollection = new ServiceCollection();
serviceScopedCollection.AddScoped<IBaz, Baz>();
var serviceProvider = serviceScopedCollection.BuildServiceProvider();
var scope = serviceProvider.CreateScope();
// First call
var bazFromScopeFirst = scope.ServiceProvider.GetService();
// Second call
var bazFromScopeSecond = scope.ServiceProvider.GetService();
Assert.True(ReferenceEquals(bazFromScopeFirst, bazFromScopeSecond));
}

public interface IBaz
{
    
}

public class Baz : IBaz
{
    
}

}
`
Let's say we'll use ExpressionResolverBuilder to replace the ServiceAccessor object's delegate, Func<ServiceProviderEngineScope, object?> RealizedService (Expression build)
in DynamicServiceProviderEngine (as I understand it, this is for netstandard2.0).
For CallSiteRuntimeResolver, I understand that RuntimeResolverContext is needed to optimize locking for CallSiteVisitor methods with recursion on the same thread.
Why is TArgument null for ExpressionResolverBuilder, since it also has recursion?

[peterykt]

I mean when call VisitCallSite in RuntimeResolverContext argument is not null