System.Text.RegularExpressions.RegexParser.AddGroup C# (CSharp) Method

        internal void AddGroup()
        {
            if (_group.Type() == RegexNode.Testgroup || _group.Type() == RegexNode.Testref)
            {
                _group.AddChild(_concatenation.ReverseLeft());

                if (_group.Type() == RegexNode.Testref && _group.ChildCount() > 2 || _group.ChildCount() > 3)
                    throw MakeException(SR.TooManyAlternates);
            }
            else
            {
                _alternation.AddChild(_concatenation.ReverseLeft());
                _group.AddChild(_alternation);
            }

            _unit = _group;
        }