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

        internal void PopGroup()
        {
            _concatenation = _stack;
            _alternation = _concatenation._next;
            _group = _alternation._next;
            _stack = _group._next;

            // The first () inside a Testgroup group goes directly to the group
            if (_group.Type() == RegexNode.Testgroup && _group.ChildCount() == 0)
            {
                if (_unit == null)
                    throw MakeException(SR.IllegalCondition);

                _group.AddChild(_unit);
                _unit = null;
            }
        }