Antlr4.Parse.ScopeParser.ParseAttributeDef C# (CSharp) Method

        public static Attribute ParseAttributeDef([Nullable] ActionAST action, [NotNull] System.Tuple<string, int> decl, Grammar g)
        {
            if (decl.Item1 == null)
                return null;

            Attribute attr = new Attribute();
            int rightEdgeOfDeclarator = decl.Item1.Length - 1;
            int equalsIndex = decl.Item1.IndexOf('=');
            if (equalsIndex > 0)
            {
                // everything after the '=' is the init value
                attr.initValue = decl.Item1.Substring(equalsIndex + 1).Trim();
                rightEdgeOfDeclarator = equalsIndex - 1;
            }

            string declarator = decl.Item1.Substring(0, rightEdgeOfDeclarator + 1);
            System.Tuple<int, int> p;
            string text = decl.Item1;
            text = text.Replace("::", "");
            if (text.Contains(":"))
            {
                // declarator has type appearing after the name like "x:T"
                p = _ParsePostfixDecl(attr, declarator, action, g);
            }
            else
            {
                // declarator has type appearing before the name like "T x"
                p = _ParsePrefixDecl(attr, declarator, action, g);
            }
            int idStart = p.Item1;
            int idStop = p.Item2;

            attr.decl = decl.Item1;

            if (action != null)
            {
                string actionText = action.Text;
                int[] lines = new int[actionText.Length];
                int[] charPositionInLines = new int[actionText.Length];
                for (int i = 0, line1 = 0, col = 0; i < actionText.Length; i++, col++)
                {
                    lines[i] = line1;
                    charPositionInLines[i] = col;
                    if (actionText[i] == '\n')
                    {
                        line1++;
                        col = -1;
                    }
                }

                int[] charIndexes = new int[actionText.Length];
                for (int i = 0, j = 0; i < actionText.Length; i++, j++)
                {
                    charIndexes[j] = i;
                    // skip comments
                    if (i < actionText.Length - 1 && actionText[i] == '/' && actionText[i + 1] == '/')
                    {
                        while (i < actionText.Length && actionText[i] != '\n')
                        {
                            i++;
                        }
                    }
                }

                int declOffset = charIndexes[decl.Item2];
                int declLine = lines[declOffset + idStart];

                int line = action.Token.Line + declLine;
                int charPositionInLine = charPositionInLines[declOffset + idStart];
                if (declLine == 0)
                {
                    /* offset for the start position of the ARG_ACTION token, plus 1
                     * since the ARG_ACTION text had the leading '[' stripped before
                     * reaching the scope parser.
                     */
                    charPositionInLine += action.Token.CharPositionInLine + 1;
                }

                int offset = ((CommonToken)action.Token).StartIndex;
                attr.token = new CommonToken(action.Token.InputStream, ANTLRParser.ID, BaseRecognizer.DefaultTokenChannel, offset + declOffset + idStart + 1, offset + declOffset + idStop);
                attr.token.Line = line;
                attr.token.CharPositionInLine = charPositionInLine;
                Debug.Assert(attr.name.Equals(attr.token.Text), "Attribute text should match the pseudo-token text at this point.");
            }

            return attr;
        }