Antlr4.Misc.TreeParserExtensions.InContext C# (CSharp) Method

        private static bool InContext(
            ITreeAdaptor adaptor,
            string[] tokenNames,
            object t,
            string context)
        {
            if (Regex.IsMatch(context, DotDot))
            {
                // don't allow "..", must be "..."
                throw new ArgumentException("invalid syntax: ..");
            }

            if (Regex.IsMatch(context, DoubleEtc))
            {
                // don't allow double "..."
                throw new ArgumentException("invalid syntax: ... ...");
            }

            context = context.Replace("...", " ... "); // ensure spaces around ...
            context = context.Trim();
            string[] nodes = context.Split(new[] { ' ', '\t', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
            int ni = nodes.Length - 1;
            t = adaptor.GetParent(t);
            while (ni >= 0 && t != null)
            {
                if (nodes[ni].Equals("..."))
                {
                    // walk upwards until we see nodes[ni-1] then continue walking
                    if (ni == 0)
                    {
                        // ... at start is no-op
                        return true;
                    }

                    string goal = nodes[ni - 1];
                    object ancestor = GetAncestor(adaptor, tokenNames, t, goal);
                    if (ancestor == null)
                        return false;

                    t = ancestor;
                    ni--;
                }

                string name = tokenNames[adaptor.GetType(t)];
                if (!name.Equals(nodes[ni]))
                {
                    //System.Console.Error.WriteLine("not matched: " + nodes[ni] + " at " + t);
                    return false;
                }

                // advance to parent and to previous element in context node list
                ni--;
                t = adaptor.GetParent(t);
            }

            if (t == null && ni >= 0)
                return false; // at root but more nodes to match
            return true;
        }