presto-main/src/main/java/io/prestosql/sql/rewrite/DescribeInputRewrite.java/Visitor/createDescribeInputRow
class Visitor:        private static Row createDescribeInputRow(Parameter parameter, Analysis queryAnalysis)
        {
            Type type = queryAnalysis.getCoercion(parameter);
            if (type == null) {
                type = UNKNOWN;
            }

            return row(
                    new LongLiteral(Integer.toString(parameter.getPosition())),
                    new StringLiteral(type.getBaseName()));
        }