SingletonDetails.md

partial class Singleton
{
  private Singleton _root;

  private Service1? _scopedService1;
  private Service4? _scopedService4;

  [OrdinalAttribute(256)]
  public Singleton()
  {
    _root = this;
  }

  internal Singleton(Singleton parentScope)
  {
    if (Object.ReferenceEquals(parentScope, null)) throw new ArgumentNullException(nameof(parentScope));
    _root = parentScope._root ?? parentScope;
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public partial CompositionRoot TestPureDIByCR()
  {
    if (_scopedService1 is null)
    {
      if (_scopedService4 is null)
      {
        _scopedService4 = new Service4();
      }

      _scopedService1 = new Service1(new Service2(new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4)));
    }

    if (_scopedService4 is null)
    {
      _scopedService4 = new Service4();
    }

    return new CompositionRoot(_scopedService1, new Service2(new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4)), new Service2(new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4)), new Service2(new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4), new Service3(_scopedService4, _scopedService4)), new Service3(_scopedService4, _scopedService4), _scopedService4, _scopedService4);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public T Resolve<T>()
  {
    return Resolver<T>.Value.Resolve(this);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public T Resolve<T>(object? tag)
  {
    return Resolver<T>.Value.ResolveByTag(this, tag);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public object Resolve(Type type)
  {
    #if NETCOREAPP3_0_OR_GREATER
    var index = (int)(_bucketSize * (((uint)type.TypeHandle.GetHashCode()) % 1));
    #else
    var index = (int)(_bucketSize * (((uint)RuntimeHelpers.GetHashCode(type)) % 1));
    #endif
    ref var pair = ref _buckets[index];
    return Object.ReferenceEquals(pair.Key, type) ? pair.Value.Resolve(this) : Resolve(type, index);
  }

  [MethodImpl(MethodImplOptions.NoInlining)]
  private object Resolve(Type type, int index)
  {
    var finish = index + _bucketSize;
    while (++index < finish)
    {
      ref var pair = ref _buckets[index];
      if (Object.ReferenceEquals(pair.Key, type))
      {
        return pair.Value.Resolve(this);
      }
    }

    throw new CannotResolveException($"{CannotResolveMessage} {OfTypeMessage} {type}.", type, null);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public object Resolve(Type type, object? tag)
  {
    #if NETCOREAPP3_0_OR_GREATER
    var index = (int)(_bucketSize * (((uint)type.TypeHandle.GetHashCode()) % 1));
    #else
    var index = (int)(_bucketSize * (((uint)RuntimeHelpers.GetHashCode(type)) % 1));
    #endif
    ref var pair = ref _buckets[index];
    return Object.ReferenceEquals(pair.Key, type) ? pair.Value.ResolveByTag(this, tag) : Resolve(type, tag, index);
  }

  [MethodImpl(MethodImplOptions.NoInlining)]
  private object Resolve(Type type, object? tag, int index)
  {
    var finish = index + _bucketSize;
    while (++index < finish)
    {
      ref var pair = ref _buckets[index];
      if (Object.ReferenceEquals(pair.Key, type))
      {
        return pair.Value.ResolveByTag(this, tag);
      }
    }

    throw new CannotResolveException($"{CannotResolveMessage} \"{tag}\" {OfTypeMessage} {type}.", type, tag);
  }

  private readonly static uint _bucketSize;
  private readonly static Pair<IResolver<Singleton, object>>[] _buckets;

  static Singleton()
  {
    var valResolver_0000 = new Resolver_0000();
    Resolver<CompositionRoot>.Value = valResolver_0000;
    _buckets = Buckets<IResolver<Singleton, object>>.Create(
      1,
      out _bucketSize,
      new Pair<IResolver<Singleton, object>>[1]
      {
         new Pair<IResolver<Singleton, object>>(typeof(CompositionRoot), valResolver_0000)
      });
  }

  private const string CannotResolveMessage = "Cannot resolve composition root ";
  private const string OfTypeMessage = "of type ";

  private class Resolver<T>: IResolver<Singleton, T>
  {
    public static IResolver<Singleton, T> Value = new Resolver<T>();

    public virtual T Resolve(Singleton composite)
    {
      throw new CannotResolveException($"{CannotResolveMessage}{OfTypeMessage}{typeof(T)}.", typeof(T), null);
    }

    public virtual T ResolveByTag(Singleton composite, object tag)
    {
      throw new CannotResolveException($"{CannotResolveMessage}\"{tag}\" {OfTypeMessage}{typeof(T)}.", typeof(T), tag);
    }
  }

  private sealed class Resolver_0000: Resolver<CompositionRoot>
  {
    public override CompositionRoot Resolve(Singleton composition)
    {
      return composition.TestPureDIByCR();
    }

    public override CompositionRoot ResolveByTag(Singleton composition, object tag)
    {
      switch (tag)
      {
        case null:
          return composition.TestPureDIByCR();

        default:
          return base.ResolveByTag(composition, tag);
      }
    }
  }
}