member.hpp

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// Copyright (C) 2020-2024 Jonathan Müller and lexy contributors
// SPDX-License-Identifier: BSL-1.0
 
#ifndef LEXY_DSL_MEMBER_HPP_INCLUDED
#define LEXY_DSL_MEMBER_HPP_INCLUDED
 
#include <lexy/_detail/stateless_lambda.hpp>
#include <lexy/dsl/base.hpp>
#include <lexy/dsl/branch.hpp>
 
namespace lexy
{
template <auto Ptr>
struct _mem_ptr_fn
{
    template <typename Object, typename Value>
    constexpr void operator()(Object& object, Value&& value) const
    {
        object.*Ptr = LEXY_FWD(value);
    }
};
 
template <typename Fn>
struct member
{};
 
template <auto Ptr>
using make_member_ptr = member<_mem_ptr_fn<Ptr>>;
} // namespace lexy
 
namespace lexyd
{
template <typename Fn, typename Rule>
struct _mem : _copy_base<Rule>
{
    template <typename Reader>
    struct bp
    {
        lexy::branch_parser_for<Rule, Reader> rule;
 
        template <typename ControlBlock>
        constexpr auto try_parse(const ControlBlock* cb, const Reader& reader)
        {
            return rule.try_parse(cb, reader);
        }
 
        template <typename Context>
        constexpr void cancel(Context& context)
        {
            rule.cancel(context);
        }
 
        template <typename NextParser, typename Context, typename... Args>
        LEXY_PARSER_FUNC auto finish(Context& context, Reader& reader, Args&&... args)
        {
            // Add member tag here.
            return rule.template finish<NextParser>(context, reader, LEXY_FWD(args)...,
                                                    lexy::member<Fn>{});
        }
    };
 
    template <typename NextParser>
    struct p
    {
        template <typename Context, typename Reader, typename... Args>
        LEXY_PARSER_FUNC static bool parse(Context& context, Reader& reader, Args&&... args)
        {
            // Forward to the rule, but add member tag.
            using parser = lexy::parser_for<Rule, NextParser>;
            return parser::parse(context, reader, LEXY_FWD(args)..., lexy::member<Fn>{});
        }
    };
};
 
template <typename Fn>
struct _mem_dsl
{
    constexpr _mem_dsl(Fn = {}) {}
 
    template <typename Rule>
    constexpr auto operator=(Rule) const // NOLINT: it _is_ an unconventional assignment operator
    {
        using lambda = std::conditional_t<std::is_default_constructible_v<Fn>, Fn,
                                          lexy::_detail::stateless_lambda<Fn>>;
        return _mem<lambda, Rule>{};
    }
};
 
template <auto MemPtr>
constexpr auto member = _mem_dsl<lexy::_mem_ptr_fn<MemPtr>>{};
 
#define LEXY_MEM(Name)                                                                             \
    ::lexyd::_mem_dsl([](auto& obj, auto&& value) { obj.Name = LEXY_FWD(value); })
} // namespace lexyd
 
#endif // LEXY_DSL_MEMBER_HPP_INCLUDED