Fix misplaced and stale comments in JSON_HAS_RANGES and conversions

The JSON_HAS_RANGES feature-detection block had its libc++ comment sitting above the clang+libstdc++ branch it does not describe, leaving the libc++ branch uncommented and the clang+libstdc++ branch without its own rationale. Move each comment to sit under its own branch, and give the clang+libstdc++ branch (added in issue 5161) its own one-line reason referencing that issue instead of reusing the libc++ branch's comment. Also fix a duplicated-word typo ("in large in large cpp files") in from_json.hpp, drop two unanswered 2017 design questions left as comments in type_traits.hpp and from_json.hpp that no longer reflect open questions, and correct NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's @since tag from 3.12.0 to 3.13.0, the release it was actually introduced in. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Fix tautological clause in iter_impl's iterator category assertion
2026-09-30 11:40:30 +00:00 · 2026-09-30 10:11:36 +02:00 · 2026-09-30 09:54:59 +02:00 · 2026-09-30 09:53:14 +02:00 · 2026-09-30 09:50:52 +02:00 · 2026-09-30 09:46:04 +02:00
13 changed files with 152 additions and 506 deletions
@@ -51,7 +51,6 @@ cc_library(
        "include/nlohmann/detail/meta/detected.hpp",
        "include/nlohmann/detail/meta/identity_tag.hpp",
        "include/nlohmann/detail/meta/is_sax.hpp",
-        "include/nlohmann/detail/meta/logic.hpp",
        "include/nlohmann/detail/meta/std_fs.hpp",
        "include/nlohmann/detail/meta/type_traits.hpp",
        "include/nlohmann/detail/meta/void_t.hpp",
@@ -27,7 +27,6 @@
 #include <nlohmann/detail/meta/identity_tag.hpp>
 #include <nlohmann/detail/meta/std_fs.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
-#include <nlohmann/detail/meta/logic.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 #include <nlohmann/detail/value_t.hpp>

@@ -429,9 +428,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
 }

 // overload for arithmetic types, not chosen for basic_json template arguments
-// (BooleanType, etc.); note: Is it really necessary to provide explicit
-// overloads for boolean_t etc. in case of a custom BooleanType which is not
-// an arithmetic type?
+// (BooleanType, etc.)
 template < typename BasicJsonType, typename ArithmeticType,
           enable_if_t <
               std::is_arithmetic<ArithmeticType>::value&&
@@ -527,7 +524,7 @@ inline void from_json_tuple_impl(BasicJsonType&& j, std::pair<A1, A2>& p, priori
 template<typename BasicJsonType, typename... Args>
 std::tuple<Args...> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::tuple<Args...>> /*unused*/, priority_tag<2> /*unused*/)
 {
-    static_assert(cxpr_and<cxpr_or<cxpr_not<std::is_reference<Args>>, is_compatible_reference_type<BasicJsonType, Args>>...>::value,
+    static_assert(conjunction<disjunction<negation<std::is_reference<Args>>, is_compatible_reference_type<BasicJsonType, Args>>...>::value,
                  "Can not return a tuple containing references to types not contained in a Json, try Json::get_to()");
    return from_json_tuple_impl_base<1, Args...>(std::forward<BasicJsonType>(j), index_sequence_for<Args...> {});
 }
@@ -592,7 +589,7 @@ inline void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Has

 #if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM

-// Workaround for MSVC 19.51 (and possibly later): in large in large cpp files, the compiler may fail to resolve with generic has_from_json (issue #4996)
+// Workaround for MSVC 19.51 (and possibly later): in large cpp files, the compiler may fail to resolve with generic has_from_json (issue #4996)
 template<typename BasicJsonType>
 struct has_from_json<BasicJsonType, std_fs::path, void> : std::true_type {};

@@ -60,9 +60,11 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
    static_assert(is_basic_json<typename std::remove_const<BasicJsonType>::type>::value,
                  "iter_impl only accepts (const) basic_json");
    // superficial check for the LegacyBidirectionalIterator named requirement
-    static_assert(std::is_base_of<std::bidirectional_iterator_tag, std::bidirectional_iterator_tag>::value
-                  &&  std::is_base_of<std::bidirectional_iterator_tag, typename std::iterator_traits<typename array_t::iterator>::iterator_category>::value,
-                  "basic_json iterator assumes array and object type iterators satisfy the LegacyBidirectionalIterator named requirement.");
+    // note: only array_t::iterator is checked here; object_t::iterator may be
+    // a forward-only iterator as long as reverse iteration and operator--
+    // are never used on it
+    static_assert(std::is_base_of<std::bidirectional_iterator_tag, typename std::iterator_traits<typename array_t::iterator>::iterator_category>::value,
+                  "basic_json iterator assumes array type iterators satisfy the LegacyBidirectionalIterator named requirement.");

  public:
    /// The std::iterator class template (used as a base class to provide typedefs) is deprecated in C++17.
@@ -583,63 +583,6 @@ class json_pointer
        return *ptr;
    }

-    /*!
-    @throw parse_error.106   if an array index begins with '0'
-    @throw parse_error.109   if an array index was not a number
-    @throw out_of_range.402  if the array index '-' is used
-    @throw out_of_range.404  if the JSON pointer can not be resolved
-    */
-    template<typename BasicJsonType>
-    const BasicJsonType& get_checked(const BasicJsonType* ptr) const
-    {
-        for (const auto& reference_token : reference_tokens)
-        {
-            switch (ptr->type())
-            {
-                case detail::value_t::object:
-                {
-                    // note: at performs range check
-                    ptr = &ptr->at(reference_token);
-                    break;
-                }
-
-                case detail::value_t::array:
-                {
-                    if (JSON_HEDLEY_UNLIKELY(reference_token == "-"))
-                    {
-                        // "-" always fails the range check
-                        JSON_THROW(detail::out_of_range::create(402, detail::concat(
-                                "array index '-' (", std::to_string(ptr->m_data.m_value.array->size()),
-                                ") is out of range"), ptr));
-                    }
-
-                    const auto idx = array_index<BasicJsonType>(reference_token);
-                    // Bounds check before access to avoid exception with JSON_NOEXCEPTION
-                    if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
-                    {
-                        JSON_THROW(detail::out_of_range::create(401, detail::concat(
-                                "array index ", std::to_string(idx), " is out of range"), ptr));
-                    }
-                    ptr = &ptr->operator[](idx);
-                    break;
-                }
-
-                case detail::value_t::null:
-                case detail::value_t::string:
-                case detail::value_t::boolean:
-                case detail::value_t::number_integer:
-                case detail::value_t::number_unsigned:
-                case detail::value_t::number_float:
-                case detail::value_t::binary:
-                case detail::value_t::discarded:
-                default:
-                    JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", reference_token, "'"), ptr));
-            }
-        }
-
-        return *ptr;
-    }
-
    /*!
    @brief return a pointer to the pointed to value, or `nullptr` if the
           pointer cannot be resolved because a key is missing, an array
@@ -9,7 +9,6 @@
 #pragma once

 #include <utility> // declval, pair
-#include <nlohmann/detail/meta/detected.hpp>
 #include <nlohmann/thirdparty/hedley/hedley.hpp>

 // This file contains all internal macro definitions (except those affecting ABI)
@@ -140,10 +139,12 @@
        // libstdc++ < 11 has incomplete C++20 ranges (issue #4440)
    #elif defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 11
        #define JSON_HAS_RANGES 0
-        // libc++ < 16 has incomplete C++20 ranges (issue #4440)
+        // clang < 16 with libstdc++ does not implement the ranges customization
+        // points libstdc++ declares, so its C++20 ranges support is incomplete (issue #5161)
    #elif defined(__clang__) && !defined(__apple_build_version__) \
        && __clang_major__ < 16 && defined(__GLIBCXX__)
        #define JSON_HAS_RANGES 0
+        // libc++ < 16 has incomplete C++20 ranges (issue #4440)
    #elif defined(_LIBCPP_VERSION) && _LIBCPP_VERSION < 160000
        #define JSON_HAS_RANGES 0
        // nvcc CUDA 12.0/12.1 chokes on the enable_borrowed_range variable-template
@@ -305,7 +306,7 @@ void templated_json_throw(ExceptionType exception)
@brief macro to briefly define a mapping between an enum and JSON with exception
       on invalid input
@def NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
-@since version 3.12.0
+@since version 3.13.0
 */
 #define NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(ENUM_TYPE, ...)                                     \
    template<typename BasicJsonType>                                                            \
@@ -876,30 +877,6 @@ void templated_json_throw(ExceptionType exception)
    \
    template<typename... T>                                                       \
    using result_of_##std_name = decltype(std_name(std::declval<T>()...));        \
-    }                                                                             \
-    \
-    namespace detail2 {                                                           \
-    struct std_name##_tag                                                         \
-    {                                                                             \
-    };                                                                            \
-    \
-    template<typename... T>                                                       \
-    std_name##_tag std_name(T&&...);                                              \
-    \
-    template<typename... T>                                                       \
-    using result_of_##std_name = decltype(std_name(std::declval<T>()...));        \
-    \
-    template<typename... T>                                                       \
-    struct would_call_std_##std_name                                              \
-    {                                                                             \
-        static constexpr auto const value = ::nlohmann::detail::                  \
-                                            is_detected_exact<std_name##_tag, result_of_##std_name, T...>::value; \
-    };                                                                            \
-    } /* namespace detail2 */ \
-    \
-    template<typename... T>                                                       \
-    struct would_call_std_##std_name : detail2::would_call_std_##std_name<T...>   \
-    {                                                                             \
    }

 #ifndef JSON_USE_IMPLICIT_CONVERSIONS
@@ -12,6 +12,6 @@

 NLOHMANN_JSON_NAMESPACE_BEGIN

-NLOHMANN_CAN_CALL_STD_FUNC_IMPL(begin);
+NLOHMANN_CAN_CALL_STD_FUNC_IMPL(begin)

 NLOHMANN_JSON_NAMESPACE_END
@@ -12,6 +12,6 @@

 NLOHMANN_JSON_NAMESPACE_BEGIN

-NLOHMANN_CAN_CALL_STD_FUNC_IMPL(end);
+NLOHMANN_CAN_CALL_STD_FUNC_IMPL(end)

 NLOHMANN_JSON_NAMESPACE_END
@@ -62,9 +62,5 @@ using detected_or_t = typename detected_or<Default, Op, Args...>::type;
 template<class Expected, template<class...> class Op, class... Args>
 using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;

-template<class To, template<class...> class Op, class... Args>
-using is_detected_convertible =
-    std::is_convertible<detected_t<Op, Args...>, To>;
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -8,7 +8,7 @@

 #pragma once

-#include <cstdint> // size_t
+#include <cstddef> // size_t
 #include <utility> // declval
 #include <string> // string

@@ -70,37 +70,6 @@ using parse_error_function_t = decltype(std::declval<T&>().parse_error(
        std::declval<std::size_t>(), std::declval<const std::string&>(),
        std::declval<const Exception&>()));

-template<typename SAX, typename BasicJsonType>
-struct is_sax
-{
-  private:
-    static_assert(is_basic_json<BasicJsonType>::value,
-                  "BasicJsonType must be of type basic_json<...>");
-
-    using number_integer_t = typename BasicJsonType::number_integer_t;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-    using number_float_t = typename BasicJsonType::number_float_t;
-    using string_t = typename BasicJsonType::string_t;
-    using binary_t = typename BasicJsonType::binary_t;
-    using exception_t = typename BasicJsonType::exception;
-
-  public:
-    static constexpr bool value =
-        is_detected_exact<bool, null_function_t, SAX>::value &&
-        is_detected_exact<bool, boolean_function_t, SAX>::value &&
-        is_detected_exact<bool, number_integer_function_t, SAX, number_integer_t>::value &&
-        is_detected_exact<bool, number_unsigned_function_t, SAX, number_unsigned_t>::value &&
-        is_detected_exact<bool, number_float_function_t, SAX, number_float_t, string_t>::value &&
-        is_detected_exact<bool, string_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, binary_function_t, SAX, binary_t>::value &&
-        is_detected_exact<bool, start_object_function_t, SAX>::value &&
-        is_detected_exact<bool, key_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, end_object_function_t, SAX>::value &&
-        is_detected_exact<bool, start_array_function_t, SAX>::value &&
-        is_detected_exact<bool, end_array_function_t, SAX>::value &&
-        is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value;
-};
-
 template<typename SAX, typename BasicJsonType>
 struct is_sax_static_asserts
 {
@@ -120,8 +89,6 @@ struct is_sax_static_asserts
                  "Missing/invalid function: bool null()");
    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
                  "Missing/invalid function: bool boolean(bool)");
-    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
-                  "Missing/invalid function: bool boolean(bool)");
    static_assert(
        is_detected_exact<bool, number_integer_function_t, SAX,
        number_integer_t>::value,
@@ -1,54 +0,0 @@
-#pragma once
-
-#include <nlohmann/detail/macro_scope.hpp>
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-#ifdef JSON_HAS_CPP_17
-
-template<bool... Booleans>
-struct cxpr_or_impl : std::integral_constant < bool, (Booleans || ...) > {};
-
-template<bool... Booleans>
-struct cxpr_and_impl : std::integral_constant < bool, (Booleans &&...) > {};
-
-#else
-
-template<bool... Booleans>
-struct cxpr_or_impl : std::false_type {};
-
-template<bool... Booleans>
-struct cxpr_or_impl<true, Booleans...> : std::true_type {};
-
-template<bool... Booleans>
-struct cxpr_or_impl<false, Booleans...> : cxpr_or_impl<Booleans...> {};
-
-template<bool... Booleans>
-struct cxpr_and_impl : std::true_type {};
-
-template<bool... Booleans>
-struct cxpr_and_impl<true, Booleans...> : cxpr_and_impl<Booleans...> {};
-
-template<bool... Booleans>
-struct cxpr_and_impl<false, Booleans...> : std::false_type {};
-
-#endif
-
-template<class Boolean>
-struct cxpr_not : std::integral_constant < bool, !Boolean::value > {};
-
-template<class... Booleans>
-struct cxpr_or : cxpr_or_impl<Booleans::value...> {};
-
-template<bool... Booleans>
-struct cxpr_or_c : cxpr_or_impl<Booleans...> {};
-
-template<class... Booleans>
-struct cxpr_and : cxpr_and_impl<Booleans::value...> {};
-
-template<bool... Booleans>
-struct cxpr_and_c : cxpr_and_impl<Booleans...> {};
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END
@@ -283,6 +283,13 @@ template<class B, class... Bn>
 struct conjunction<B, Bn...>
 : std::conditional<static_cast<bool>(B::value), conjunction<Bn...>, B>::type {};

+// https://en.cppreference.com/w/cpp/types/disjunction
+template<class...> struct disjunction : std::false_type { };
+template<class B> struct disjunction<B> : B { };
+template<class B, class... Bn>
+struct disjunction<B, Bn...>
+: std::conditional<static_cast<bool>(B::value), B, disjunction<Bn...>>::type {};
+
 // https://en.cppreference.com/w/cpp/types/negation
 template<class B> struct negation : std::integral_constant < bool, !B::value > { };

@@ -604,7 +611,6 @@ struct is_compatible_integer_type_impl <
    std::is_integral<CompatibleNumberIntegerType>::value&&
    !std::is_same<bool, CompatibleNumberIntegerType>::value >>
 {
-    // is there an assert somewhere on overflows?
    using RealLimits = std::numeric_limits<RealIntegerType>;
    using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;

@@ -798,20 +804,7 @@ struct has_capacity : std::integral_constant<bool, is_detected<detect_capacity,
 // a naive helper to check if a type is an ordered_map (exploits the fact that
 // ordered_map inherits capacity() from std::vector)
 template <typename T>
-struct is_ordered_map
-{
-    using one = char;
-
-    struct two
-    {
-        char x[2]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
-    };
-
-    template <typename C> static one test( decltype(&C::capacity) ) ;
-    template <typename C> static two test(...);
-
-    enum { value = sizeof(test<T>(nullptr)) == sizeof(char) }; // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg,cppcoreguidelines-use-enum-class)
-};
+struct is_ordered_map : has_capacity<T> {};

 // to avoid useless casts (see https://github.com/nlohmann/json/issues/2893#issuecomment-889152324)
 template < typename T, typename U, enable_if_t < !std::is_same<T, U>::value, int > = 0 >
@@ -835,10 +828,8 @@ using all_signed = conjunction<std::is_signed<Types>...>;
 template<typename... Types>
 using all_unsigned = conjunction<std::is_unsigned<Types>...>;

-// there's a disjunction trait in another PR; replace when merged
 template<typename... Types>
-using same_sign = std::integral_constant < bool,
-      all_signed<Types...>::value || all_unsigned<Types...>::value >;
+using same_sign = disjunction<all_signed<Types...>, all_unsigned<Types...>>;

 template<typename OfType, typename T>
 using never_out_of_range = std::integral_constant < bool,
@@ -275,104 +275,6 @@


 #include <utility> // declval, pair
-// #include <nlohmann/detail/meta/detected.hpp>
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-
-
-#include <type_traits>
-
-// #include <nlohmann/detail/meta/void_t.hpp>
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-
-
-// #include <nlohmann/detail/abi_macros.hpp>
-
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-
-template<typename ...Ts> struct make_void
-{
-    using type = void;
-};
-template<typename ...Ts> using void_t = typename make_void<Ts...>::type;
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END
-
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-
-// https://en.cppreference.com/w/cpp/experimental/is_detected
-struct nonesuch
-{
-    nonesuch() = delete;
-    ~nonesuch() = delete;
-    nonesuch(nonesuch const&) = delete;
-    nonesuch(nonesuch const&&) = delete;
-    void operator=(nonesuch const&) = delete;
-    void operator=(nonesuch&&) = delete;
-};
-
-template<class Default,
-         class AlwaysVoid,
-         template<class...> class Op,
-         class... Args>
-struct detector
-{
-    using value_t = std::false_type;
-    using type = Default;
-};
-
-template<class Default, template<class...> class Op, class... Args>
-struct detector<Default, void_t<Op<Args...>>, Op, Args...>
-{
-    using value_t = std::true_type;
-    using type = Op<Args...>;
-};
-
-template<template<class...> class Op, class... Args>
-using is_detected = typename detector<nonesuch, void, Op, Args...>::value_t;
-
-template<template<class...> class Op, class... Args>
-struct is_detected_lazy : is_detected<Op, Args...> { };
-
-template<template<class...> class Op, class... Args>
-using detected_t = typename detector<nonesuch, void, Op, Args...>::type;
-
-template<class Default, template<class...> class Op, class... Args>
-using detected_or = detector<Default, void, Op, Args...>;
-
-template<class Default, template<class...> class Op, class... Args>
-using detected_or_t = typename detected_or<Default, Op, Args...>::type;
-
-template<class Expected, template<class...> class Op, class... Args>
-using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
-
-template<class To, template<class...> class Op, class... Args>
-using is_detected_convertible =
-    std::is_convertible<detected_t<Op, Args...>, To>;
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END
-
 // #include <nlohmann/thirdparty/hedley/hedley.hpp>


@@ -2551,10 +2453,12 @@ JSON_HEDLEY_DIAGNOSTIC_POP
        // libstdc++ < 11 has incomplete C++20 ranges (issue #4440)
    #elif defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 11
        #define JSON_HAS_RANGES 0
-        // libc++ < 16 has incomplete C++20 ranges (issue #4440)
+        // clang < 16 with libstdc++ does not implement the ranges customization
+        // points libstdc++ declares, so its C++20 ranges support is incomplete (issue #5161)
    #elif defined(__clang__) && !defined(__apple_build_version__) \
        && __clang_major__ < 16 && defined(__GLIBCXX__)
        #define JSON_HAS_RANGES 0
+        // libc++ < 16 has incomplete C++20 ranges (issue #4440)
    #elif defined(_LIBCPP_VERSION) && _LIBCPP_VERSION < 160000
        #define JSON_HAS_RANGES 0
        // nvcc CUDA 12.0/12.1 chokes on the enable_borrowed_range variable-template
@@ -2716,7 +2620,7 @@ void templated_json_throw(ExceptionType exception)
@brief macro to briefly define a mapping between an enum and JSON with exception
       on invalid input
@def NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
-@since version 3.12.0
+@since version 3.13.0
 */
 #define NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(ENUM_TYPE, ...)                                     \
    template<typename BasicJsonType>                                                            \
@@ -3287,30 +3191,6 @@ void templated_json_throw(ExceptionType exception)
    \
    template<typename... T>                                                       \
    using result_of_##std_name = decltype(std_name(std::declval<T>()...));        \
-    }                                                                             \
-    \
-    namespace detail2 {                                                           \
-    struct std_name##_tag                                                         \
-    {                                                                             \
-    };                                                                            \
-    \
-    template<typename... T>                                                       \
-    std_name##_tag std_name(T&&...);                                              \
-    \
-    template<typename... T>                                                       \
-    using result_of_##std_name = decltype(std_name(std::declval<T>()...));        \
-    \
-    template<typename... T>                                                       \
-    struct would_call_std_##std_name                                              \
-    {                                                                             \
-        static constexpr auto const value = ::nlohmann::detail::                  \
-                                            is_detected_exact<std_name##_tag, result_of_##std_name, T...>::value; \
-    };                                                                            \
-    } /* namespace detail2 */ \
-    \
-    template<typename... T>                                                       \
-    struct would_call_std_##std_name : detail2::would_call_std_##std_name<T...>   \
-    {                                                                             \
    }

 #ifndef JSON_USE_IMPLICIT_CONVERSIONS
@@ -3860,6 +3740,31 @@ NLOHMANN_JSON_NAMESPACE_END
 // #include <nlohmann/detail/abi_macros.hpp>

 // #include <nlohmann/detail/meta/void_t.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+
+// #include <nlohmann/detail/abi_macros.hpp>
+
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+template<typename ...Ts> struct make_void
+{
+    using type = void;
+};
+template<typename ...Ts> using void_t = typename make_void<Ts...>::type;
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

 // #include <nlohmann/detail/meta/cpp_future.hpp>

@@ -3931,7 +3836,7 @@ NLOHMANN_JSON_NAMESPACE_END

 NLOHMANN_JSON_NAMESPACE_BEGIN

-NLOHMANN_CAN_CALL_STD_FUNC_IMPL(begin);
+NLOHMANN_CAN_CALL_STD_FUNC_IMPL(begin)

 NLOHMANN_JSON_NAMESPACE_END

@@ -3951,13 +3856,80 @@ NLOHMANN_JSON_NAMESPACE_END

 NLOHMANN_JSON_NAMESPACE_BEGIN

-NLOHMANN_CAN_CALL_STD_FUNC_IMPL(end);
+NLOHMANN_CAN_CALL_STD_FUNC_IMPL(end)

 NLOHMANN_JSON_NAMESPACE_END

 // #include <nlohmann/detail/meta/cpp_future.hpp>

 // #include <nlohmann/detail/meta/detected.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+
+#include <type_traits>
+
+// #include <nlohmann/detail/meta/void_t.hpp>
+
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+// https://en.cppreference.com/w/cpp/experimental/is_detected
+struct nonesuch
+{
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(nonesuch const&) = delete;
+    nonesuch(nonesuch const&&) = delete;
+    void operator=(nonesuch const&) = delete;
+    void operator=(nonesuch&&) = delete;
+};
+
+template<class Default,
+         class AlwaysVoid,
+         template<class...> class Op,
+         class... Args>
+struct detector
+{
+    using value_t = std::false_type;
+    using type = Default;
+};
+
+template<class Default, template<class...> class Op, class... Args>
+struct detector<Default, void_t<Op<Args...>>, Op, Args...>
+{
+    using value_t = std::true_type;
+    using type = Op<Args...>;
+};
+
+template<template<class...> class Op, class... Args>
+using is_detected = typename detector<nonesuch, void, Op, Args...>::value_t;
+
+template<template<class...> class Op, class... Args>
+struct is_detected_lazy : is_detected<Op, Args...> { };
+
+template<template<class...> class Op, class... Args>
+using detected_t = typename detector<nonesuch, void, Op, Args...>::type;
+
+template<class Default, template<class...> class Op, class... Args>
+using detected_or = detector<Default, void, Op, Args...>;
+
+template<class Default, template<class...> class Op, class... Args>
+using detected_or_t = typename detected_or<Default, Op, Args...>::type;
+
+template<class Expected, template<class...> class Op, class... Args>
+using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

 // #include <nlohmann/json_fwd.hpp>
 //     __ _____ _____ _____
@@ -4293,6 +4265,13 @@ template<class B, class... Bn>
 struct conjunction<B, Bn...>
 : std::conditional<static_cast<bool>(B::value), conjunction<Bn...>, B>::type {};

+// https://en.cppreference.com/w/cpp/types/disjunction
+template<class...> struct disjunction : std::false_type { };
+template<class B> struct disjunction<B> : B { };
+template<class B, class... Bn>
+struct disjunction<B, Bn...>
+: std::conditional<static_cast<bool>(B::value), B, disjunction<Bn...>>::type {};
+
 // https://en.cppreference.com/w/cpp/types/negation
 template<class B> struct negation : std::integral_constant < bool, !B::value > { };

@@ -4614,7 +4593,6 @@ struct is_compatible_integer_type_impl <
    std::is_integral<CompatibleNumberIntegerType>::value&&
    !std::is_same<bool, CompatibleNumberIntegerType>::value >>
 {
-    // is there an assert somewhere on overflows?
    using RealLimits = std::numeric_limits<RealIntegerType>;
    using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;

@@ -4808,20 +4786,7 @@ struct has_capacity : std::integral_constant<bool, is_detected<detect_capacity,
 // a naive helper to check if a type is an ordered_map (exploits the fact that
 // ordered_map inherits capacity() from std::vector)
 template <typename T>
-struct is_ordered_map
-{
-    using one = char;
-
-    struct two
-    {
-        char x[2]; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
-    };
-
-    template <typename C> static one test( decltype(&C::capacity) ) ;
-    template <typename C> static two test(...);
-
-    enum { value = sizeof(test<T>(nullptr)) == sizeof(char) }; // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg,cppcoreguidelines-use-enum-class)
-};
+struct is_ordered_map : has_capacity<T> {};

 // to avoid useless casts (see https://github.com/nlohmann/json/issues/2893#issuecomment-889152324)
 template < typename T, typename U, enable_if_t < !std::is_same<T, U>::value, int > = 0 >
@@ -4845,10 +4810,8 @@ using all_signed = conjunction<std::is_signed<Types>...>;
 template<typename... Types>
 using all_unsigned = conjunction<std::is_unsigned<Types>...>;

-// there's a disjunction trait in another PR; replace when merged
 template<typename... Types>
-using same_sign = std::integral_constant < bool,
-      all_signed<Types...>::value || all_unsigned<Types...>::value >;
+using same_sign = disjunction<all_signed<Types...>, all_unsigned<Types...>>;

 template<typename OfType, typename T>
 using never_out_of_range = std::integral_constant < bool,
@@ -5466,63 +5429,6 @@ NLOHMANN_JSON_NAMESPACE_END

 // #include <nlohmann/detail/meta/type_traits.hpp>

-// #include <nlohmann/detail/meta/logic.hpp>
-
-
-// #include <nlohmann/detail/macro_scope.hpp>
-
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-#ifdef JSON_HAS_CPP_17
-
-template<bool... Booleans>
-struct cxpr_or_impl : std::integral_constant < bool, (Booleans || ...) > {};
-
-template<bool... Booleans>
-struct cxpr_and_impl : std::integral_constant < bool, (Booleans &&...) > {};
-
-#else
-
-template<bool... Booleans>
-struct cxpr_or_impl : std::false_type {};
-
-template<bool... Booleans>
-struct cxpr_or_impl<true, Booleans...> : std::true_type {};
-
-template<bool... Booleans>
-struct cxpr_or_impl<false, Booleans...> : cxpr_or_impl<Booleans...> {};
-
-template<bool... Booleans>
-struct cxpr_and_impl : std::true_type {};
-
-template<bool... Booleans>
-struct cxpr_and_impl<true, Booleans...> : cxpr_and_impl<Booleans...> {};
-
-template<bool... Booleans>
-struct cxpr_and_impl<false, Booleans...> : std::false_type {};
-
-#endif
-
-template<class Boolean>
-struct cxpr_not : std::integral_constant < bool, !Boolean::value > {};
-
-template<class... Booleans>
-struct cxpr_or : cxpr_or_impl<Booleans::value...> {};
-
-template<bool... Booleans>
-struct cxpr_or_c : cxpr_or_impl<Booleans...> {};
-
-template<class... Booleans>
-struct cxpr_and : cxpr_and_impl<Booleans::value...> {};
-
-template<bool... Booleans>
-struct cxpr_and_c : cxpr_and_impl<Booleans...> {};
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END
-
 // #include <nlohmann/detail/string_concat.hpp>

 // #include <nlohmann/detail/value_t.hpp>
@@ -5926,9 +5832,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
 }

 // overload for arithmetic types, not chosen for basic_json template arguments
-// (BooleanType, etc.); note: Is it really necessary to provide explicit
-// overloads for boolean_t etc. in case of a custom BooleanType which is not
-// an arithmetic type?
+// (BooleanType, etc.)
 template < typename BasicJsonType, typename ArithmeticType,
           enable_if_t <
               std::is_arithmetic<ArithmeticType>::value&&
@@ -6024,7 +5928,7 @@ inline void from_json_tuple_impl(BasicJsonType&& j, std::pair<A1, A2>& p, priori
 template<typename BasicJsonType, typename... Args>
 std::tuple<Args...> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::tuple<Args...>> /*unused*/, priority_tag<2> /*unused*/)
 {
-    static_assert(cxpr_and<cxpr_or<cxpr_not<std::is_reference<Args>>, is_compatible_reference_type<BasicJsonType, Args>>...>::value,
+    static_assert(conjunction<disjunction<negation<std::is_reference<Args>>, is_compatible_reference_type<BasicJsonType, Args>>...>::value,
                  "Can not return a tuple containing references to types not contained in a Json, try Json::get_to()");
    return from_json_tuple_impl_base<1, Args...>(std::forward<BasicJsonType>(j), index_sequence_for<Args...> {});
 }
@@ -6089,7 +5993,7 @@ inline void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Has

 #if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM

-// Workaround for MSVC 19.51 (and possibly later): in large in large cpp files, the compiler may fail to resolve with generic has_from_json (issue #4996)
+// Workaround for MSVC 19.51 (and possibly later): in large cpp files, the compiler may fail to resolve with generic has_from_json (issue #4996)
 template<typename BasicJsonType>
 struct has_from_json<BasicJsonType, std_fs::path, void> : std::true_type {};

@@ -12641,7 +12545,7 @@ NLOHMANN_JSON_NAMESPACE_END



-#include <cstdint> // size_t
+#include <cstddef> // size_t
 #include <utility> // declval
 #include <string> // string

@@ -12706,37 +12610,6 @@ using parse_error_function_t = decltype(std::declval<T&>().parse_error(
        std::declval<std::size_t>(), std::declval<const std::string&>(),
        std::declval<const Exception&>()));

-template<typename SAX, typename BasicJsonType>
-struct is_sax
-{
-  private:
-    static_assert(is_basic_json<BasicJsonType>::value,
-                  "BasicJsonType must be of type basic_json<...>");
-
-    using number_integer_t = typename BasicJsonType::number_integer_t;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-    using number_float_t = typename BasicJsonType::number_float_t;
-    using string_t = typename BasicJsonType::string_t;
-    using binary_t = typename BasicJsonType::binary_t;
-    using exception_t = typename BasicJsonType::exception;
-
-  public:
-    static constexpr bool value =
-        is_detected_exact<bool, null_function_t, SAX>::value &&
-        is_detected_exact<bool, boolean_function_t, SAX>::value &&
-        is_detected_exact<bool, number_integer_function_t, SAX, number_integer_t>::value &&
-        is_detected_exact<bool, number_unsigned_function_t, SAX, number_unsigned_t>::value &&
-        is_detected_exact<bool, number_float_function_t, SAX, number_float_t, string_t>::value &&
-        is_detected_exact<bool, string_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, binary_function_t, SAX, binary_t>::value &&
-        is_detected_exact<bool, start_object_function_t, SAX>::value &&
-        is_detected_exact<bool, key_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, end_object_function_t, SAX>::value &&
-        is_detected_exact<bool, start_array_function_t, SAX>::value &&
-        is_detected_exact<bool, end_array_function_t, SAX>::value &&
-        is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value;
-};
-
 template<typename SAX, typename BasicJsonType>
 struct is_sax_static_asserts
 {
@@ -12756,8 +12629,6 @@ struct is_sax_static_asserts
                  "Missing/invalid function: bool null()");
    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
                  "Missing/invalid function: bool boolean(bool)");
-    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
-                  "Missing/invalid function: bool boolean(bool)");
    static_assert(
        is_detected_exact<bool, number_integer_function_t, SAX,
        number_integer_t>::value,
@@ -17939,9 +17810,11 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
    static_assert(is_basic_json<typename std::remove_const<BasicJsonType>::type>::value,
                  "iter_impl only accepts (const) basic_json");
    // superficial check for the LegacyBidirectionalIterator named requirement
-    static_assert(std::is_base_of<std::bidirectional_iterator_tag, std::bidirectional_iterator_tag>::value
-                  &&  std::is_base_of<std::bidirectional_iterator_tag, typename std::iterator_traits<typename array_t::iterator>::iterator_category>::value,
-                  "basic_json iterator assumes array and object type iterators satisfy the LegacyBidirectionalIterator named requirement.");
+    // note: only array_t::iterator is checked here; object_t::iterator may be
+    // a forward-only iterator as long as reverse iteration and operator--
+    // are never used on it
+    static_assert(std::is_base_of<std::bidirectional_iterator_tag, typename std::iterator_traits<typename array_t::iterator>::iterator_category>::value,
+                  "basic_json iterator assumes array type iterators satisfy the LegacyBidirectionalIterator named requirement.");

  public:
    /// The std::iterator class template (used as a base class to provide typedefs) is deprecated in C++17.
@@ -19425,63 +19298,6 @@ class json_pointer
        return *ptr;
    }

-    /*!
-    @throw parse_error.106   if an array index begins with '0'
-    @throw parse_error.109   if an array index was not a number
-    @throw out_of_range.402  if the array index '-' is used
-    @throw out_of_range.404  if the JSON pointer can not be resolved
-    */
-    template<typename BasicJsonType>
-    const BasicJsonType& get_checked(const BasicJsonType* ptr) const
-    {
-        for (const auto& reference_token : reference_tokens)
-        {
-            switch (ptr->type())
-            {
-                case detail::value_t::object:
-                {
-                    // note: at performs range check
-                    ptr = &ptr->at(reference_token);
-                    break;
-                }
-
-                case detail::value_t::array:
-                {
-                    if (JSON_HEDLEY_UNLIKELY(reference_token == "-"))
-                    {
-                        // "-" always fails the range check
-                        JSON_THROW(detail::out_of_range::create(402, detail::concat(
-                                "array index '-' (", std::to_string(ptr->m_data.m_value.array->size()),
-                                ") is out of range"), ptr));
-                    }
-
-                    const auto idx = array_index<BasicJsonType>(reference_token);
-                    // Bounds check before access to avoid exception with JSON_NOEXCEPTION
-                    if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
-                    {
-                        JSON_THROW(detail::out_of_range::create(401, detail::concat(
-                                "array index ", std::to_string(idx), " is out of range"), ptr));
-                    }
-                    ptr = &ptr->operator[](idx);
-                    break;
-                }
-
-                case detail::value_t::null:
-                case detail::value_t::string:
-                case detail::value_t::boolean:
-                case detail::value_t::number_integer:
-                case detail::value_t::number_unsigned:
-                case detail::value_t::number_float:
-                case detail::value_t::binary:
-                case detail::value_t::discarded:
-                default:
-                    JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", reference_token, "'"), ptr));
-            }
-        }
-
-        return *ptr;
-    }
-
    /*!
    @brief return a pointer to the pointed to value, or `nullptr` if the
           pointer cannot be resolved because a key is missing, an array
@@ -10,10 +10,14 @@

 #if JSON_TEST_USING_MULTIPLE_HEADERS
    #include <nlohmann/detail/meta/type_traits.hpp>
+    #include <nlohmann/ordered_map.hpp>
 #else
    #include <nlohmann/json.hpp>
 #endif

+#include <map>
+#include <string>
+
 TEST_CASE("type traits")
 {
    SECTION("is_c_string")
@@ -83,4 +87,12 @@ TEST_CASE("type traits")
            }
        }
    }
+
+    SECTION("is_ordered_map")
+    {
+        using nlohmann::detail::is_ordered_map;
+
+        CHECK(is_ordered_map<nlohmann::ordered_map<std::string, int>>::value);
+        CHECK_FALSE(is_ordered_map<std::map<std::string, int>>::value);
+    }
 }
Author	SHA1	Message	Date
Niels Lohmann	b5fad30499	Fix misplaced and stale comments in JSON_HAS_RANGES and conversions The JSON_HAS_RANGES feature-detection block had its libc++ comment sitting above the clang+libstdc++ branch it does not describe, leaving the libc++ branch uncommented and the clang+libstdc++ branch without its own rationale. Move each comment to sit under its own branch, and give the clang+libstdc++ branch (added in issue 5161) its own one-line reason referencing that issue instead of reusing the libc++ branch's comment. Also fix a duplicated-word typo ("in large in large cpp files") in from_json.hpp, drop two unanswered 2017 design questions left as comments in type_traits.hpp and from_json.hpp that no longer reflect open questions, and correct NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's @since tag from 3.12.0 to 3.13.0, the release it was actually introduced in. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 10:11:36 +02:00
Niels Lohmann	a9cc4243b7	Fix tautological clause in iter_impl's iterator category assertion The static_assert meant to check the LegacyBidirectionalIterator named requirement had a first clause comparing std::bidirectional_iterator_tag to itself, which is always true and checks nothing; only array_t::iterator was actually being checked, despite the message claiming object iterators were checked too. Drop the tautological clause, reword the message to describe what is actually checked, and note that object_t may use a forward-only iterator as long as reverse iteration and operator-- are unused. The check is intentionally not extended to object_t::iterator, since that would reject object types with forward-only iterators that compile and work correctly today. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:54:59 +02:00
Niels Lohmann	03319da529	Remove duplicate const overload of json_pointer::get_checked The const and non-const get_checked() overloads had byte-identical 50-line bodies, differing only in the signature. The remaining template deduces a const-qualified BasicJsonType for const callers, so at(), the out_of_range::create() calls and the bounds check all still work. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:53:14 +02:00
Niels Lohmann	ae9ef9dde1	Simplify is_ordered_map to reuse has_capacity is_ordered_map re-detected capacity() with a C++03 sizeof/vararg trick right after has_capacity did the same detection through is_detected. For ordered_map, the old trick took the address of std::vector::capacity, which [namespace.std]/6 makes unspecified. Reuse has_capacity instead, which removes the unspecified-behavior pointer-to-std-member and two NOLINT suppressions. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:50:52 +02:00
Niels Lohmann	f9d4b51455	Remove unused would_call_std_* from NLOHMANN_CAN_CALL_STD_FUNC_IMPL Besides detail::result_of_begin/end, which is_range and iterator_t use, the macro defined a namespace detail2 with a tag type, a catch-all overload and would_call_std_begin/end, plus would_call_std_begin/end structs directly in namespace nlohmann. Nothing has used them since they were added in #3020. Reduce the macro to its detail part. Without the trailing struct the ';' after the two invocations would be an empty declaration that -Wextra-semi flags, so drop it. macro_scope.hpp included meta/detected.hpp only for this macro; all users of detected.hpp include it (or type_traits.hpp) themselves, so remove the include. Behavior and ABI are unchanged. The undocumented, untested and unused names nlohmann::would_call_std_begin, nlohmann::would_call_std_end and namespace nlohmann::detail2 are no longer declared. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:46:04 +02:00
Niels Lohmann	31883d06a8	Replace meta/logic.hpp with a disjunction trait meta/logic.hpp added a second set of type-level boolean helpers (cxpr_and, cxpr_or, cxpr_not, ...) next to the existing conjunction and negation in type_traits.hpp. It was used only by one static_assert in from_json_tuple_impl, two of its templates were never used, and it was the only header without the license banner and relied on transitive includes for <type_traits>. Add the missing disjunction next to conjunction and negation, use the three in the static_assert, and delete logic.hpp together with its BUILD.bazel entry. same_sign now uses disjunction as well, which resolves the 2022 TODO waiting for such a trait. The static_assert accepts and rejects the same types as before. Only names in nlohmann::detail change; behavior, public API and ABI are unchanged. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:42:12 +02:00
Niels Lohmann	4c208728e7	Remove unused is_sax and is_detected_convertible detail::is_sax had no user: the parser and the binary reader only use is_sax_static_asserts, so is_sax was a second, unchecked copy of the SAX event list. is_sax_static_asserts asserted boolean(bool) twice in a row, and detail::is_detected_convertible was never used anywhere. Remove all three and include <cstddef> for size_t instead of <cstdint>. Only names in nlohmann::detail are removed; behavior, public API and ABI are unchanged. The diagnostics for an incomplete SAX handler are the same, apart from the duplicated boolean() message. Part of #5708 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 09:38:54 +02:00