Diff coverage report for

//

//

// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)

// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)

// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)

// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)

// Copyright (c) 2022 Dmitry Arkhipov (grisumbras@gmail.com)

// Copyright (c) 2022 Dmitry Arkhipov (grisumbras@gmail.com)

//

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

//

// Official repository: https://github.com/boostorg/json

// Official repository: https://github.com/boostorg/json

//

//

#ifndef BOOST_JSON_VALUE_TO_HPP

#ifndef BOOST_JSON_VALUE_TO_HPP

#define BOOST_JSON_VALUE_TO_HPP

#define BOOST_JSON_VALUE_TO_HPP

#include <boost/core/detail/static_assert.hpp>

#include <boost/core/detail/static_assert.hpp>

#include <boost/json/detail/value_to.hpp>

#include <boost/json/detail/value_to.hpp>

namespace boost {

namespace boost {

namespace json {

namespace json {

/** Convert a @ref value to an object of type `T`.

/** Convert a @ref value to an object of type `T`.

    This function attempts to convert a @ref value

    This function attempts to convert a @ref value

    to `T` using

    to `T` using

    @li one of @ref value's accessors, or

    @li one of @ref value's accessors, or

    @li a library-provided generic conversion, or

    @li a library-provided generic conversion, or

    @li a user-provided overload of `tag_invoke`.

    @li a user-provided overload of `tag_invoke`.

    Out of the box the function supports default constructible types satisfying

    Out of the box the function supports default constructible types satisfying

    {req_SequenceContainer}, arrays, arithmetic types, `bool`, `std::tuple`,

    {req_SequenceContainer}, arrays, arithmetic types, `bool`, `std::tuple`,

    `std::pair`, `std::optional`, `std::variant`, `std::nullptr_t`, and structs

    `std::pair`, `std::optional`, `std::variant`, `std::nullptr_t`, and structs

    and enums described using Boost.Describe.

    and enums described using Boost.Describe.

    Conversion of other types is done by calling an overload of `tag_invoke`

    Conversion of other types is done by calling an overload of `tag_invoke`

    found by argument-dependent lookup. Its signature should be similar to:

    found by argument-dependent lookup. Its signature should be similar to:

    @code

    @code

    template< class FullContext >

    template< class FullContext >

    T tag_invoke( value_to_tag<T>, const value&, const Context& , const FullContext& );

    T tag_invoke( value_to_tag<T>, const value&, const Context& , const FullContext& );

    @endcode

    @endcode

    or

    or

    @code

    @code

    T tag_invoke( value_to_tag<T>, const value&, const Context& );

    T tag_invoke( value_to_tag<T>, const value&, const Context& );

    @endcode

    @endcode

    or

    or

    @code

    @code

    result<T> tag_invoke( value_to_tag<T>, const value& );

    result<T> tag_invoke( value_to_tag<T>, const value& );

    @endcode

    @endcode

    The overloads are checked for existence in that order and the first that

    The overloads are checked for existence in that order and the first that

    matches will be selected.

    matches will be selected.

    The object returned by the function call is returned by @ref value_to as

    The object returned by the function call is returned by @ref value_to as

    the result of the conversion.

    the result of the conversion.

    The `ctx` argument can be used either as a tag type to provide conversions

    The `ctx` argument can be used either as a tag type to provide conversions

    for third-party types, or to pass extra data to the conversion function.

    for third-party types, or to pass extra data to the conversion function.

    Overload **(3)** is **deleted** and participates in overload resolution

    Overload **(3)** is **deleted** and participates in overload resolution

    only when `U` is not @ref value. The overload exists to prevent unintented

    only when `U` is not @ref value. The overload exists to prevent unintented

    creation of temporary @ref value instances, e.g.

    creation of temporary @ref value instances, e.g.

    @code

    @code

    auto flag = value_to<bool>(true);

    auto flag = value_to<bool>(true);

    @endcode

    @endcode

    @par Constraints

    @par Constraints

    @code

    @code

    ! std::is_reference< T >::value

    ! std::is_reference< T >::value

    @endcode

    @endcode

    @par Exception Safety

    @par Exception Safety

    Strong guarantee.

    Strong guarantee.

    @tparam T The type to convert to.

    @tparam T The type to convert to.

    @tparam Context The type of context passed to the conversion function.

    @tparam Context The type of context passed to the conversion function.

    @returns `jv` converted to `result<T>`.

    @returns `jv` converted to `result<T>`.

    @param jv The @ref value to convert.

    @param jv The @ref value to convert.

    @param ctx Context passed to the conversion function.

    @param ctx Context passed to the conversion function.

    @see @ref value_to_tag, @ref value_from,

    @see @ref value_to_tag, @ref value_from,

    <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf">

    <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf">

        tag_invoke: A general pattern for supporting customisable functions</a>

        tag_invoke: A general pattern for supporting customisable functions</a>

    @{

    @{

*/

*/

template< class T, class Context >

template< class T, class Context >

T

T

{

{

    BOOST_CORE_STATIC_ASSERT( ! std::is_reference<T>::value );

    BOOST_CORE_STATIC_ASSERT( ! std::is_reference<T>::value );

    using bare_T = detail::remove_cvref<T>;

    using bare_T = detail::remove_cvref<T>;

    BOOST_CORE_STATIC_ASSERT((

    BOOST_CORE_STATIC_ASSERT((

        detail::conversion_round_trips<

        detail::conversion_round_trips<

            Context, bare_T, detail::value_to_conversion>::value));

            Context, bare_T, detail::value_to_conversion>::value));

    using cat = detail::value_to_category<Context, bare_T>;

    using cat = detail::value_to_category<Context, bare_T>;

}

}

/// Overload

/// Overload

template<class T>

template<class T>

T

T

{

{

}

}

/// Overload

/// Overload

template<class T, class U

template<class T, class U

#ifndef BOOST_JSON_DOCS

#ifndef BOOST_JSON_DOCS

    , class = typename std::enable_if<!std::is_same<U, value>::value>::type

    , class = typename std::enable_if<!std::is_same<U, value>::value>::type

#endif

#endif

>

>

T

T

value_to(U const& jv) = delete;

value_to(U const& jv) = delete;

/// @}

/// @}

/** Convert a @ref value to a @ref boost::system::result.

/** Convert a @ref value to a @ref boost::system::result.

    This function attempts to convert a @ref value to `result<T>` using

    This function attempts to convert a @ref value to `result<T>` using

    @li one of @ref value's accessors, or

    @li one of @ref value's accessors, or

    @li a library-provided generic conversion, or

    @li a library-provided generic conversion, or

    @li a user-provided overload of `tag_invoke`.

    @li a user-provided overload of `tag_invoke`.

    Out of the box the function supports default constructible types satisfying

    Out of the box the function supports default constructible types satisfying

    {req_SequenceContainer}, arrays, arithmetic types, `bool`, `std::tuple`,

    {req_SequenceContainer}, arrays, arithmetic types, `bool`, `std::tuple`,

    `std::pair`, `std::optional`, `std::variant`, `std::nullptr_t`, and structs

    `std::pair`, `std::optional`, `std::variant`, `std::nullptr_t`, and structs

    and enums described using Boost.Describe.

    and enums described using Boost.Describe.

    Conversion of other types is done by calling an overload of `tag_invoke`

    Conversion of other types is done by calling an overload of `tag_invoke`

    found by argument-dependent lookup. Its signature should be similar to:

    found by argument-dependent lookup. Its signature should be similar to:

    @code

    @code

    template< class FullContext >

    template< class FullContext >

    result<T> tag_invoke( try_value_to_tag<T>, const value&, const Context& , const FullContext& );

    result<T> tag_invoke( try_value_to_tag<T>, const value&, const Context& , const FullContext& );

    @endcode

    @endcode

    or

    or

    @code

    @code

    result<T> tag_invoke( try_value_to_tag<T>, const value&, const Context& );

    result<T> tag_invoke( try_value_to_tag<T>, const value&, const Context& );

    @endcode

    @endcode

    or

    or

    @code

    @code

    result<T> tag_invoke( try_value_to_tag<T>, const value& );

    result<T> tag_invoke( try_value_to_tag<T>, const value& );

    @endcode

    @endcode

    The overloads are checked for existence in that order and the first that

    The overloads are checked for existence in that order and the first that

    matches will be selected.

    matches will be selected.

    If an error occurs during conversion, the result will store the error code

    If an error occurs during conversion, the result will store the error code

    associated with the error. If an exception is thrown, the function will

    associated with the error. If an exception is thrown, the function will

    attempt to retrieve the associated error code and return it, otherwise it

    attempt to retrieve the associated error code and return it, otherwise it

    will return `error::exception`, unless the exception type is

    will return `error::exception`, unless the exception type is

    @ref std::bad_alloc, which will be allowed to propagate.

    @ref std::bad_alloc, which will be allowed to propagate.

    The `ctx` argument can be used either as a tag type to provide conversions

    The `ctx` argument can be used either as a tag type to provide conversions

    for third-party types, or to pass extra data to the conversion function.

    for third-party types, or to pass extra data to the conversion function.

    @par Constraints

    @par Constraints

    @code

    @code

    ! std::is_reference< T >::value

    ! std::is_reference< T >::value

    @endcode

    @endcode

    @par Exception Safety

    @par Exception Safety

    Strong guarantee.

    Strong guarantee.

    @tparam T The type to convert to.

    @tparam T The type to convert to.

    @tparam Context The type of context passed to the conversion function.

    @tparam Context The type of context passed to the conversion function.

    @param jv The @ref value to convert.

    @param jv The @ref value to convert.

    @param ctx Context passed to the conversion function.

    @param ctx Context passed to the conversion function.

    @returns `jv` converted to `result<T>`.

    @returns `jv` converted to `result<T>`.

    @see @ref value_to_tag, @ref value_to, @ref value_from,

    @see @ref value_to_tag, @ref value_to, @ref value_from,

         [tag_invoke: A general pattern for supporting customisable functions](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf).

         [tag_invoke: A general pattern for supporting customisable functions](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf).

    @{

    @{

*/

*/

template< class T, class Context >

template< class T, class Context >

typename result_for<T, value>::type

typename result_for<T, value>::type

{

{

    BOOST_CORE_STATIC_ASSERT( ! std::is_reference<T>::value );

    BOOST_CORE_STATIC_ASSERT( ! std::is_reference<T>::value );

    using bare_T = detail::remove_cvref<T>;

    using bare_T = detail::remove_cvref<T>;

    BOOST_CORE_STATIC_ASSERT((

    BOOST_CORE_STATIC_ASSERT((

        detail::conversion_round_trips<

        detail::conversion_round_trips<

            Context, bare_T, detail::value_to_conversion>::value));

            Context, bare_T, detail::value_to_conversion>::value));

    using cat = detail::value_to_category<Context, bare_T>;

    using cat = detail::value_to_category<Context, bare_T>;

}

}

/// Overload

/// Overload

template<class T>

template<class T>

typename result_for<T, value>::type

typename result_for<T, value>::type

{

{

}

}

/// @}

/// @}

/** Determine if a @ref value can be converted to `T`.

/** Determine if a @ref value can be converted to `T`.

    If @ref value can be converted to `T` via a

    If @ref value can be converted to `T` via a

    call to @ref value_to, the static data member `value`

    call to @ref value_to, the static data member `value`

    is defined as `true`. Otherwise, `value` is

    is defined as `true`. Otherwise, `value` is

    defined as `false`.

    defined as `false`.

    @see @ref value_to

    @see @ref value_to

*/

*/

#ifdef BOOST_JSON_DOCS

#ifdef BOOST_JSON_DOCS

template<class T>

template<class T>

using has_value_to = __see_below__;

using has_value_to = __see_below__;

#else

#else

template<class T>

template<class T>

using has_value_to = detail::can_convert<

using has_value_to = detail::can_convert<

    detail::remove_cvref<T>, detail::value_to_conversion>;

    detail::remove_cvref<T>, detail::value_to_conversion>;

#endif

#endif

} // namespace json

} // namespace json

} // namespace boost

} // namespace boost

#endif

#endif