presto-spi/src/main/java/io/prestosql/spi/type/RowType.java/RowType/anonymous
class RowType:    public static RowType anonymous(List<Type> types)
    {
        List<Field> fields = types.stream()
                .map(type -> new Field(Optional.empty(), type))
                .collect(Collectors.toList());

        return new RowType(makeSignature(fields), fields);
    }