Using BOOST Spirit X3 with custom lexer

Question

How a X3 parser could use an already generated vector of tokens. How the rules could be defined, having something like

enum class token { aa, bb, cc};    
auto rule = token::aa >> token::bb >> -token::cc;
std::vector<token> tokens{token::aa, token:bb, token:cc};
auto ok = parse(tokens.cbegin(), tokens.cend(), rule);

I'm interested to validate the input. The idea is to avoid any lexical analysis (x3::lit, x3::char_, x3::lexeme, x3::alpha, etc.) following the zero-overhead principle of C++.

Answer 1

Based on @sehe's reply, the implementation could be

#include <boost/fusion/adapted.hpp>
#include <boost/spirit/home/x3.hpp>
#include <cassert>
#include <iostream>
#include <utility>
#include <vector>

namespace my_parser
{
    enum class token
    {
        unknown,
        aa,
        bb,
        cc
    };

    namespace ast
    {
        struct my_seq
        {
            token m1 {};
            token m2 {};
            std::optional<token> m3 {};
        };
    }

    namespace x3 = boost::spirit::x3;

    struct dummy_token_parser: x3::parser<dummy_token_parser>
    {
        using attribute_type = token;
        static const bool has_attribute = true;

        constexpr dummy_token_parser(const token tok): tok(tok) {}

        template <typename It, typename Ctx, typename A>
        bool parse(It& first, const It& last, const Ctx& /*ctx*/, x3::unused_type, A& attr) const
        {
            if (first != last && *first == tok)
            {
                attr = *first;
                ++first;
                return true;
            }

            return false;
        }

        token tok;
    };

    void parse_tokens(const std::vector<token>& input, auto& rule, ast::my_seq& my_seq_data, bool expected_result)
    {
        my_seq_data = {};
        const bool result = x3::parse(input.cbegin(), input.cend(), rule, my_seq_data);
        assert(result == expected_result);
        std::cout << result << std::endl;
    }

    using tp = dummy_token_parser;

    const x3::rule<struct my_seq_rule, ast::my_seq> my_seq {"my_seq"};
    const auto my_seq_def = tp(token::aa) >> tp(token::bb) >> -tp(token::cc);

    BOOST_SPIRIT_DEFINE(my_seq);
}

BOOST_FUSION_ADAPT_STRUCT(my_parser::ast::my_seq, m1, m2, m3);

int main()
{
    using namespace my_parser;

    ast::my_seq my_seq_data {};
    parse_tokens({token::aa, token::bb, token::cc}, my_seq, my_seq_data, true);
    parse_tokens({token::aa, token::cc}, my_seq, my_seq_data, false);
    parse_tokens({token::bb, token::cc}, my_seq, my_seq_data, false);
    parse_tokens({token::aa, token::bb}, my_seq, my_seq_data, true);

    return 0;
}