forward.hpp

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// Copyright (C) 2020-2023 Jonathan Müller and lexy contributors
// SPDX-License-Identifier: BSL-1.0
 
#ifndef LEXY_CALLBACK_FORWARD_HPP_INCLUDED
#define LEXY_CALLBACK_FORWARD_HPP_INCLUDED
 
#include <lexy/callback/base.hpp>
 
namespace lexy
{
struct nullopt;
 
template <typename T>
struct _fwd
{
    using return_type = T;
 
    constexpr T operator()(T&& t) const
    {
        return LEXY_MOV(t);
    }
    constexpr T operator()(const T& t) const
    {
        return t;
    }
};
template <>
struct _fwd<void>
{
    using return_type = void;
 
    template <typename... Args>
    constexpr auto sink(const Args&...) const
    {
        // We don't need a separate type, forward itself can have the required functions.
        return *this;
    }
 
    constexpr void operator()() const {}
    constexpr void operator()(const lexy::nullopt&) const {}
 
    constexpr void finish() && {}
};
 
template <typename T>
constexpr auto forward = _fwd<T>{};
} // namespace lexy
 
#endif // LEXY_CALLBACK_FORWARD_HPP_INCLUDED