public override IMatched <Unit> Parse(ParseState state, Token[] tokens, ExpressionBuilder builder) { var source = tokens[2].Text; state.Colorize(tokens, Color.Whitespace, Color.Identifier); if (state.DefExpression(source).If(out var defExpression)) { builder.Add(defExpression); } else { builder.Add(builder.Flags[ExpressionFlags.Comparisand] ? new PlaceholderSymbol($"-{source}") : new FieldSymbol(source)); } return(Unit.Matched()); }