From f6febbe359f0936c411fac9788985118aa82fdef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Tue, 24 Jul 2018 13:22:44 +0200
Subject: [PATCH 1/5] split meta.hpp, add detected_t (used to define concepts)

---
 Makefile                                      |  5 +-
 .../nlohmann/detail/conversions/from_json.hpp |  3 +-
 .../nlohmann/detail/conversions/to_json.hpp   |  3 +-
 .../nlohmann/detail/iterators/iter_impl.hpp   |  2 +-
 include/nlohmann/detail/meta/cpp_future.hpp   | 83 ++++++++++++++++
 include/nlohmann/detail/meta/detected.hpp     | 56 +++++++++++
 .../detail/{meta.hpp => meta/type_traits.hpp} | 76 +--------------
 include/nlohmann/detail/meta/void_t.hpp       | 10 ++
 include/nlohmann/detail/output/serializer.hpp |  2 +-
 include/nlohmann/json.hpp                     |  3 +-
 single_include/nlohmann/json.hpp              | 96 +++++++++++--------
 test/src/unit-inspection.cpp                  |  4 +-
 12 files changed, 222 insertions(+), 121 deletions(-)
 create mode 100644 include/nlohmann/detail/meta/cpp_future.hpp
 create mode 100644 include/nlohmann/detail/meta/detected.hpp
 rename include/nlohmann/detail/{meta.hpp => meta/type_traits.hpp} (74%)
 create mode 100644 include/nlohmann/detail/meta/void_t.hpp

diff --git a/Makefile b/Makefile
index 1e12178804..36b01450de 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,10 @@ SRCS = include/nlohmann/json.hpp \
        include/nlohmann/detail/json_ref.hpp \
        include/nlohmann/detail/macro_scope.hpp \
        include/nlohmann/detail/macro_unscope.hpp \
-       include/nlohmann/detail/meta.hpp \
+       include/nlohmann/detail/meta/cpp_future.hpp \
+       include/nlohmann/detail/meta/detected.hpp \
+       include/nlohmann/detail/meta/type_traits.hpp \
+       include/nlohmann/detail/meta/void_t.hpp \
        include/nlohmann/detail/output/binary_writer.hpp \
        include/nlohmann/detail/output/output_adapters.hpp \
        include/nlohmann/detail/output/serializer.hpp \
diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
index b092c8cc32..5956352fb9 100644
--- a/include/nlohmann/detail/conversions/from_json.hpp
+++ b/include/nlohmann/detail/conversions/from_json.hpp
@@ -15,7 +15,8 @@
 
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
index 07946f55ac..35be5de468 100644
--- a/include/nlohmann/detail/conversions/to_json.hpp
+++ b/include/nlohmann/detail/conversions/to_json.hpp
@@ -8,7 +8,8 @@
 #include <valarray> // valarray
 #include <vector> // vector
 
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/value_t.hpp>
 #include <nlohmann/detail/iterators/iteration_proxy.hpp>
 
diff --git a/include/nlohmann/detail/iterators/iter_impl.hpp b/include/nlohmann/detail/iterators/iter_impl.hpp
index f34f7a5540..adcd8a37bb 100644
--- a/include/nlohmann/detail/iterators/iter_impl.hpp
+++ b/include/nlohmann/detail/iterators/iter_impl.hpp
@@ -8,7 +8,7 @@
 #include <nlohmann/detail/iterators/internal_iterator.hpp>
 #include <nlohmann/detail/iterators/primitive_iterator.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
diff --git a/include/nlohmann/detail/meta/cpp_future.hpp b/include/nlohmann/detail/meta/cpp_future.hpp
new file mode 100644
index 0000000000..d12d6bdb76
--- /dev/null
+++ b/include/nlohmann/detail/meta/cpp_future.hpp
@@ -0,0 +1,83 @@
+#pragma once
+
+#include <ciso646> // not
+#include <cstddef> // size_t
+#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
+
+namespace nlohmann
+{
+namespace detail
+{
+// alias templates to reduce boilerplate
+template<bool B, typename T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+
+template<typename T>
+using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+
+// implementation of C++14 index_sequence and affiliates
+// source: https://stackoverflow.com/a/32223343
+template<std::size_t... Ints>
+struct index_sequence
+{
+    using type = index_sequence;
+    using value_type = std::size_t;
+    static constexpr std::size_t size() noexcept
+    {
+        return sizeof...(Ints);
+    }
+};
+
+template<class Sequence1, class Sequence2>
+struct merge_and_renumber;
+
+template<std::size_t... I1, std::size_t... I2>
+struct merge_and_renumber<index_sequence<I1...>, index_sequence<I2...>>
+        : index_sequence < I1..., (sizeof...(I1) + I2)... > {};
+
+template<std::size_t N>
+struct make_index_sequence
+    : merge_and_renumber < typename make_index_sequence < N / 2 >::type,
+      typename make_index_sequence < N - N / 2 >::type > {};
+
+template<> struct make_index_sequence<0> : index_sequence<> {};
+template<> struct make_index_sequence<1> : index_sequence<0> {};
+
+template<typename... Ts>
+using index_sequence_for = make_index_sequence<sizeof...(Ts)>;
+
+/*
+Implementation of two C++17 constructs: conjunction, negation. This is needed
+to avoid evaluating all the traits in a condition
+
+For example: not std::is_same<void, T>::value and has_value_type<T>::value
+will not compile when T = void (on MSVC at least). Whereas
+conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value will
+stop evaluating if negation<...>::value == false
+
+Please note that those constructs must be used with caution, since symbols can
+become very long quickly (which can slow down compilation and cause MSVC
+internal compiler errors). Only use it when you have to (see example ahead).
+*/
+template<class...> struct conjunction : std::true_type {};
+template<class B1> struct conjunction<B1> : B1 {};
+template<class B1, class... Bn>
+struct conjunction<B1, Bn...> : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};
+
+template<class B> struct negation : std::integral_constant<bool, not B::value> {};
+
+// dispatch utility (taken from ranges-v3)
+template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
+template<> struct priority_tag<0> {};
+
+// taken from ranges-v3
+template<typename T>
+struct static_const
+{
+    static constexpr T value{};
+};
+
+template<typename T>
+constexpr T static_const<T>::value;
+}
+}
diff --git a/include/nlohmann/detail/meta/detected.hpp b/include/nlohmann/detail/meta/detected.hpp
new file mode 100644
index 0000000000..ed1d6ac71d
--- /dev/null
+++ b/include/nlohmann/detail/meta/detected.hpp
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <type_traits>
+
+#include <nlohmann/detail/meta/void_t.hpp>
+
+// http://en.cppreference.com/w/cpp/experimental/is_detected
+namespace nlohmann
+{
+namespace detail
+{
+struct nonesuch
+{
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(nonesuch const&) = delete;
+    void operator=(nonesuch const&) = 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>
+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>;
+}
+}
diff --git a/include/nlohmann/detail/meta.hpp b/include/nlohmann/detail/meta/type_traits.hpp
similarity index 74%
rename from include/nlohmann/detail/meta.hpp
rename to include/nlohmann/detail/meta/type_traits.hpp
index 50200304da..caf8122261 100644
--- a/include/nlohmann/detail/meta.hpp
+++ b/include/nlohmann/detail/meta/type_traits.hpp
@@ -1,12 +1,12 @@
 #pragma once
 
 #include <ciso646> // not
-#include <cstddef> // size_t
 #include <limits> // numeric_limits
-#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
+#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
 #include <utility> // declval
 
 #include <nlohmann/json_fwd.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 namespace nlohmann
@@ -30,68 +30,6 @@ template<typename> struct is_basic_json : std::false_type {};
 NLOHMANN_BASIC_JSON_TPL_DECLARATION
 struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
 
-// alias templates to reduce boilerplate
-template<bool B, typename T = void>
-using enable_if_t = typename std::enable_if<B, T>::type;
-
-template<typename T>
-using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
-
-// implementation of C++14 index_sequence and affiliates
-// source: https://stackoverflow.com/a/32223343
-template<std::size_t... Ints>
-struct index_sequence
-{
-    using type = index_sequence;
-    using value_type = std::size_t;
-    static constexpr std::size_t size() noexcept
-    {
-        return sizeof...(Ints);
-    }
-};
-
-template<class Sequence1, class Sequence2>
-struct merge_and_renumber;
-
-template<std::size_t... I1, std::size_t... I2>
-struct merge_and_renumber<index_sequence<I1...>, index_sequence<I2...>>
-        : index_sequence < I1..., (sizeof...(I1) + I2)... > {};
-
-template<std::size_t N>
-struct make_index_sequence
-    : merge_and_renumber < typename make_index_sequence < N / 2 >::type,
-      typename make_index_sequence < N - N / 2 >::type > {};
-
-template<> struct make_index_sequence<0> : index_sequence<> {};
-template<> struct make_index_sequence<1> : index_sequence<0> {};
-
-template<typename... Ts>
-using index_sequence_for = make_index_sequence<sizeof...(Ts)>;
-
-/*
-Implementation of two C++17 constructs: conjunction, negation. This is needed
-to avoid evaluating all the traits in a condition
-
-For example: not std::is_same<void, T>::value and has_value_type<T>::value
-will not compile when T = void (on MSVC at least). Whereas
-conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value will
-stop evaluating if negation<...>::value == false
-
-Please note that those constructs must be used with caution, since symbols can
-become very long quickly (which can slow down compilation and cause MSVC
-internal compiler errors). Only use it when you have to (see example ahead).
-*/
-template<class...> struct conjunction : std::true_type {};
-template<class B1> struct conjunction<B1> : B1 {};
-template<class B1, class... Bn>
-struct conjunction<B1, Bn...> : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};
-
-template<class B> struct negation : std::integral_constant<bool, not B::value> {};
-
-// dispatch utility (taken from ranges-v3)
-template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
-template<> struct priority_tag<0> {};
-
 ////////////////////////
 // has_/is_ functions //
 ////////////////////////
@@ -264,15 +202,5 @@ struct is_compatible_type
       is_compatible_complete_type<BasicJsonType, CompatibleType>>
 {
 };
-
-// taken from ranges-v3
-template<typename T>
-struct static_const
-{
-    static constexpr T value{};
-};
-
-template<typename T>
-constexpr T static_const<T>::value;
 }
 }
diff --git a/include/nlohmann/detail/meta/void_t.hpp b/include/nlohmann/detail/meta/void_t.hpp
new file mode 100644
index 0000000000..66c4a359e4
--- /dev/null
+++ b/include/nlohmann/detail/meta/void_t.hpp
@@ -0,0 +1,10 @@
+#pragma once
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename...>
+using void_t = void;
+}
+}
diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index c0f8177663..de3676ac59 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -16,7 +16,7 @@
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/conversions/to_chars.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 85868f639c..9621e2ba31 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -48,7 +48,8 @@ SOFTWARE.
 
 #include <nlohmann/json_fwd.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
-#include <nlohmann/detail/meta.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/value_t.hpp>
 #include <nlohmann/detail/conversions/from_json.hpp>
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index d0c1f02ffa..9350590ced 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -238,41 +238,17 @@ contains a `mapped_type`, whereas `std::vector` fails the test.
                 std::is_integral<decltype(detect(std::declval<T>()))>::value; \
     }
 
-// #include <nlohmann/detail/meta.hpp>
+// #include <nlohmann/detail/meta/cpp_future.hpp>
 
 
 #include <ciso646> // not
 #include <cstddef> // size_t
-#include <limits> // numeric_limits
 #include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
-#include <utility> // declval
-
-// #include <nlohmann/json_fwd.hpp>
-
-// #include <nlohmann/detail/macro_scope.hpp>
-
 
 namespace nlohmann
 {
-/*!
-@brief detail namespace with internal helper functions
-
-This namespace collects functions that should not be exposed,
-implementations of some @ref basic_json methods, and meta-programming helpers.
-
-@since version 2.1.0
-*/
 namespace detail
 {
-/////////////
-// helpers //
-/////////////
-
-template<typename> struct is_basic_json : std::false_type {};
-
-NLOHMANN_BASIC_JSON_TPL_DECLARATION
-struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
-
 // alias templates to reduce boilerplate
 template<bool B, typename T = void>
 using enable_if_t = typename std::enable_if<B, T>::type;
@@ -335,6 +311,54 @@ template<class B> struct negation : std::integral_constant<bool, not B::value> {
 template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
 template<> struct priority_tag<0> {};
 
+// taken from ranges-v3
+template<typename T>
+struct static_const
+{
+    static constexpr T value{};
+};
+
+template<typename T>
+constexpr T static_const<T>::value;
+}
+}
+
+// #include <nlohmann/detail/meta/type_traits.hpp>
+
+
+#include <ciso646> // not
+#include <limits> // numeric_limits
+#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
+#include <utility> // declval
+
+// #include <nlohmann/json_fwd.hpp>
+
+// #include <nlohmann/detail/meta/cpp_future.hpp>
+
+// #include <nlohmann/detail/macro_scope.hpp>
+
+
+namespace nlohmann
+{
+/*!
+@brief detail namespace with internal helper functions
+
+This namespace collects functions that should not be exposed,
+implementations of some @ref basic_json methods, and meta-programming helpers.
+
+@since version 2.1.0
+*/
+namespace detail
+{
+/////////////
+// helpers //
+/////////////
+
+template<typename> struct is_basic_json : std::false_type {};
+
+NLOHMANN_BASIC_JSON_TPL_DECLARATION
+struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
+
 ////////////////////////
 // has_/is_ functions //
 ////////////////////////
@@ -507,16 +531,6 @@ struct is_compatible_type
       is_compatible_complete_type<BasicJsonType, CompatibleType>>
 {
 };
-
-// taken from ranges-v3
-template<typename T>
-struct static_const
-{
-    static constexpr T value{};
-};
-
-template<typename T>
-constexpr T static_const<T>::value;
 }
 }
 
@@ -950,7 +964,9 @@ inline bool operator<(const value_t lhs, const value_t rhs) noexcept
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
-// #include <nlohmann/detail/meta.hpp>
+// #include <nlohmann/detail/meta/cpp_future.hpp>
+
+// #include <nlohmann/detail/meta/type_traits.hpp>
 
 // #include <nlohmann/detail/value_t.hpp>
 
@@ -1335,7 +1351,9 @@ constexpr const auto& from_json = detail::static_const<detail::from_json_fn>::va
 #include <valarray> // valarray
 #include <vector> // vector
 
-// #include <nlohmann/detail/meta.hpp>
+// #include <nlohmann/detail/meta/cpp_future.hpp>
+
+// #include <nlohmann/detail/meta/type_traits.hpp>
 
 // #include <nlohmann/detail/value_t.hpp>
 
@@ -4873,7 +4891,7 @@ template<typename BasicJsonType> struct internal_iterator
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
-// #include <nlohmann/detail/meta.hpp>
+// #include <nlohmann/detail/meta/cpp_future.hpp>
 
 // #include <nlohmann/detail/value_t.hpp>
 
@@ -9488,7 +9506,7 @@ char* to_chars(char* first, char* last, FloatType value)
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
-// #include <nlohmann/detail/meta.hpp>
+// #include <nlohmann/detail/meta/cpp_future.hpp>
 
 // #include <nlohmann/detail/output/output_adapters.hpp>
 
diff --git a/test/src/unit-inspection.cpp b/test/src/unit-inspection.cpp
index 4c03cf968f..e50c7338eb 100644
--- a/test/src/unit-inspection.cpp
+++ b/test/src/unit-inspection.cpp
@@ -317,8 +317,8 @@ TEST_CASE("object inspection")
     SECTION("round trips")
     {
         for (const auto& s :
-                {"3.141592653589793", "1000000000000000010E5"
-                })
+    {"3.141592653589793", "1000000000000000010E5"
+    })
         {
             json j1 = json::parse(s);
             std::string s1 = j1.dump();

From 442886d0404a268299a253ccc7fa0d4fc1f94ad4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Mon, 2 Jul 2018 10:14:37 +0200
Subject: [PATCH 2/5] use templates in the sax interface instead of virtuals

---
 .../nlohmann/detail/input/binary_reader.hpp   |  20 +--
 include/nlohmann/detail/input/json_sax.hpp    |  78 +++++------
 include/nlohmann/detail/input/parser.hpp      |  12 +-
 include/nlohmann/json.hpp                     |  13 +-
 single_include/nlohmann/json.hpp              | 123 +++++++++---------
 test/src/unit-cbor.cpp                        |  26 ++--
 test/src/unit-class_parser.cpp                |  56 ++++----
 test/src/unit-deserialization.cpp             |  36 ++---
 test/src/unit-msgpack.cpp                     |  26 ++--
 test/src/unit-ubjson.cpp                      |  26 ++--
 10 files changed, 207 insertions(+), 209 deletions(-)

diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index 726e552dd3..cc3c3adac5 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -30,14 +30,14 @@ namespace detail
 /*!
 @brief deserialization of CBOR, MessagePack, and UBJSON values
 */
-template<typename BasicJsonType>
+template<typename BasicJsonType, typename SAX = json_sax_dom_parser<BasicJsonType>>
 class binary_reader
 {
     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 json_sax_t = json_sax<BasicJsonType>;
+    using json_sax_t = SAX;
 
   public:
     /*!
@@ -321,7 +321,7 @@ class binary_reader
             }
 
             case 0x9F: // array (indefinite length)
-                return get_cbor_array(json_sax_t::no_limit);
+                return get_cbor_array(std::size_t(-1));
 
             // map (0x00..0x17 pairs of data items follow)
             case 0xA0:
@@ -375,7 +375,7 @@ class binary_reader
             }
 
             case 0xBF: // map (indefinite length)
-                return get_cbor_object(json_sax_t::no_limit);
+                return get_cbor_object(std::size_t(-1));
 
             case 0xF4: // false
                 return sax->boolean(false);
@@ -1020,7 +1020,7 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the array or json_sax_t::no_limit for an
+    @param[in] len  the length of the array or std::size_t(-1) for an
                     array of indefinite size
     @return whether array creation completed
     */
@@ -1031,7 +1031,7 @@ class binary_reader
             return false;
         }
 
-        if (len != json_sax_t::no_limit)
+        if (len != std::size_t(-1))
             for (std::size_t i = 0; i < len; ++i)
             {
                 if (JSON_UNLIKELY(not parse_cbor_internal()))
@@ -1054,7 +1054,7 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the object or json_sax_t::no_limit for an
+    @param[in] len  the length of the object or std::size_t(-1) for an
                     object of indefinite size
     @return whether object creation completed
     */
@@ -1066,7 +1066,7 @@ class binary_reader
         }
 
         string_t key;
-        if (len != json_sax_t::no_limit)
+        if (len != std::size_t(-1))
         {
             for (std::size_t i = 0; i < len; ++i)
             {
@@ -1558,7 +1558,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_array()))
+            if (JSON_UNLIKELY(not sax->start_array(-1)))
             {
                 return false;
             }
@@ -1628,7 +1628,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_object()))
+            if (JSON_UNLIKELY(not sax->start_object(-1)))
             {
                 return false;
             }
diff --git a/include/nlohmann/detail/input/json_sax.hpp b/include/nlohmann/detail/input/json_sax.hpp
index 563eac312a..9d96a20e15 100644
--- a/include/nlohmann/detail/input/json_sax.hpp
+++ b/include/nlohmann/detail/input/json_sax.hpp
@@ -136,7 +136,7 @@ constructor contains the parsed value.
 @tparam BasicJsonType  the JSON type
 */
 template<typename BasicJsonType>
-class json_sax_dom_parser : public json_sax<BasicJsonType>
+class json_sax_dom_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -153,43 +153,43 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         : root(r), allow_exceptions(allow_exceptions_)
     {}
 
-    bool null() override
+    bool null()
     {
         handle_value(nullptr);
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_integer(number_integer_t val) override
+    bool number_integer(number_integer_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t val) override
+    bool number_unsigned(number_unsigned_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_float(number_float_t val, const string_t&) override
+    bool number_float(number_float_t val, const string_t&)
     {
         handle_value(val);
         return true;
     }
 
-    bool string(string_t& val) override
+    bool string(string_t& val)
     {
         handle_value(val);
         return true;
     }
 
-    bool start_object(std::size_t len) override
+    bool start_object(std::size_t len = -1)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
@@ -202,20 +202,20 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool key(string_t& val) override
+    bool key(string_t& val)
     {
         // add null at given key and store the reference for later
         object_element = &(ref_stack.back()->m_value.object->operator[](val));
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         ref_stack.pop_back();
         return true;
     }
 
-    bool start_array(std::size_t len) override
+    bool start_array(std::size_t len = -1)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
@@ -228,14 +228,14 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         ref_stack.pop_back();
         return true;
     }
 
     bool parse_error(std::size_t, const std::string&,
-                     const detail::exception& ex) override
+                     const detail::exception& ex)
     {
         errored = true;
         if (allow_exceptions)
@@ -310,7 +310,7 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
 };
 
 template<typename BasicJsonType>
-class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
+class json_sax_dom_callback_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -328,43 +328,43 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         keep_stack.push_back(true);
     }
 
-    bool null() override
+    bool null()
     {
         handle_value(nullptr);
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_integer(number_integer_t val) override
+    bool number_integer(number_integer_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t val) override
+    bool number_unsigned(number_unsigned_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_float(number_float_t val, const string_t&) override
+    bool number_float(number_float_t val, const string_t&)
     {
         handle_value(val);
         return true;
     }
 
-    bool string(string_t& val) override
+    bool string(string_t& val)
     {
         handle_value(val);
         return true;
     }
 
-    bool start_object(std::size_t len) override
+    bool start_object(std::size_t len = -1)
     {
         // check callback for object start
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
@@ -386,7 +386,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool key(string_t& val) override
+    bool key(string_t& val)
     {
         BasicJsonType k = BasicJsonType(val);
 
@@ -403,7 +403,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         if (ref_stack.back())
         {
@@ -438,7 +438,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool start_array(std::size_t len) override
+    bool start_array(std::size_t len = -1)
     {
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
@@ -459,7 +459,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         bool keep = true;
 
@@ -491,7 +491,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
     }
 
     bool parse_error(std::size_t, const std::string&,
-                     const detail::exception& ex) override
+                     const detail::exception& ex)
     {
         errored = true;
         if (allow_exceptions)
@@ -614,7 +614,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
 };
 
 template<typename BasicJsonType>
-class json_sax_acceptor : public json_sax<BasicJsonType>
+class json_sax_acceptor
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -622,62 +622,62 @@ class json_sax_acceptor : public json_sax<BasicJsonType>
     using number_float_t = typename BasicJsonType::number_float_t;
     using string_t = typename BasicJsonType::string_t;
 
-    bool null() override
+    bool null()
     {
         return true;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return true;
     }
 
-    bool number_integer(number_integer_t) override
+    bool number_integer(number_integer_t)
     {
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t) override
+    bool number_unsigned(number_unsigned_t)
     {
         return true;
     }
 
-    bool number_float(number_float_t, const string_t&) override
+    bool number_float(number_float_t, const string_t&)
     {
         return true;
     }
 
-    bool string(string_t&) override
+    bool string(string_t&)
     {
         return true;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t = -1)
     {
         return true;
     }
 
-    bool key(string_t&) override
+    bool key(string_t&)
     {
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return true;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t = -1)
     {
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return true;
     }
 
-    bool parse_error(std::size_t, const std::string&, const detail::exception&) override
+    bool parse_error(std::size_t, const std::string&, const detail::exception&)
     {
         return false;
     }
diff --git a/include/nlohmann/detail/input/parser.hpp b/include/nlohmann/detail/input/parser.hpp
index c3cfcd5325..93d1dc4a32 100644
--- a/include/nlohmann/detail/input/parser.hpp
+++ b/include/nlohmann/detail/input/parser.hpp
@@ -54,8 +54,6 @@ class parser
         value
     };
 
-    using json_sax_t = json_sax<BasicJsonType>;
-
     using parser_callback_t =
         std::function<bool(int depth, parse_event_t event, BasicJsonType& parsed)>;
 
@@ -144,7 +142,8 @@ class parser
         return sax_parse(&sax_acceptor, strict);
     }
 
-    bool sax_parse(json_sax_t* sax, const bool strict = true)
+    template <typename SAX>
+    bool sax_parse(SAX* sax, const bool strict = true)
     {
         const bool result = sax_parse_internal(sax);
 
@@ -160,7 +159,8 @@ class parser
     }
 
   private:
-    bool sax_parse_internal(json_sax_t* sax)
+    template <typename SAX>
+    bool sax_parse_internal(SAX* sax)
     {
         // stack to remember the hieararchy of structured values we are parsing
         // true = array; false = object
@@ -177,7 +177,7 @@ class parser
                 {
                     case token_type::begin_object:
                     {
-                        if (JSON_UNLIKELY(not sax->start_object()))
+                        if (JSON_UNLIKELY(not sax->start_object(-1)))
                         {
                             return false;
                         }
@@ -225,7 +225,7 @@ class parser
 
                     case token_type::begin_array:
                     {
-                        if (JSON_UNLIKELY(not sax->start_array()))
+                        if (JSON_UNLIKELY(not sax->start_array(-1)))
                         {
                             return false;
                         }
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 9621e2ba31..8c4cb159ee 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -171,7 +171,7 @@ class basic_json
     friend class ::nlohmann::detail::iter_impl;
     template<typename BasicJsonType, typename CharType>
     friend class ::nlohmann::detail::binary_writer;
-    template<typename BasicJsonType>
+    template<typename BasicJsonType, typename SAX>
     friend class ::nlohmann::detail::binary_reader;
     template<typename BasicJsonType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
@@ -1113,8 +1113,6 @@ class basic_json
     */
     using parser_callback_t = typename parser::parser_callback_t;
 
-    using json_sax_t = typename parser::json_sax_t;
-
     //////////////////
     // constructors //
     //////////////////
@@ -6014,7 +6012,8 @@ class basic_json
         return parser(i).accept(true);
     }
 
-    static bool sax_parse(detail::input_adapter&& i, json_sax_t* sax,
+    template <typename SAX>
+    static bool sax_parse(detail::input_adapter&& i, SAX* sax,
                           input_format_t format = input_format_t::json,
                           const bool strict = true)
     {
@@ -6024,7 +6023,7 @@ class basic_json
             case input_format_t::json:
                 return parser(std::move(i)).sax_parse(sax, strict);
             default:
-                return binary_reader(std::move(i)).sax_parse(format, sax, strict);
+                return detail::binary_reader<basic_json, SAX>(std::move(i)).sax_parse(format, sax, strict);
         }
     }
 
@@ -6097,11 +6096,11 @@ class basic_json
         return parser(detail::input_adapter(first, last)).accept(true);
     }
 
-    template<class IteratorType, typename std::enable_if<
+    template<class IteratorType, class SAX, typename std::enable_if<
                  std::is_base_of<
                      std::random_access_iterator_tag,
                      typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
-    static bool sax_parse(IteratorType first, IteratorType last, json_sax_t* sax)
+    static bool sax_parse(IteratorType first, IteratorType last, SAX* sax)
     {
         return parser(detail::input_adapter(first, last)).sax_parse(sax);
     }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 9350590ced..33e864e1bf 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3700,7 +3700,7 @@ constructor contains the parsed value.
 @tparam BasicJsonType  the JSON type
 */
 template<typename BasicJsonType>
-class json_sax_dom_parser : public json_sax<BasicJsonType>
+class json_sax_dom_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -3717,43 +3717,43 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         : root(r), allow_exceptions(allow_exceptions_)
     {}
 
-    bool null() override
+    bool null()
     {
         handle_value(nullptr);
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_integer(number_integer_t val) override
+    bool number_integer(number_integer_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t val) override
+    bool number_unsigned(number_unsigned_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_float(number_float_t val, const string_t&) override
+    bool number_float(number_float_t val, const string_t&)
     {
         handle_value(val);
         return true;
     }
 
-    bool string(string_t& val) override
+    bool string(string_t& val)
     {
         handle_value(val);
         return true;
     }
 
-    bool start_object(std::size_t len) override
+    bool start_object(std::size_t len = -1)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
@@ -3766,20 +3766,20 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool key(string_t& val) override
+    bool key(string_t& val)
     {
         // add null at given key and store the reference for later
         object_element = &(ref_stack.back()->m_value.object->operator[](val));
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         ref_stack.pop_back();
         return true;
     }
 
-    bool start_array(std::size_t len) override
+    bool start_array(std::size_t len = -1)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
@@ -3792,14 +3792,14 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         ref_stack.pop_back();
         return true;
     }
 
     bool parse_error(std::size_t, const std::string&,
-                     const detail::exception& ex) override
+                     const detail::exception& ex)
     {
         errored = true;
         if (allow_exceptions)
@@ -3874,7 +3874,7 @@ class json_sax_dom_parser : public json_sax<BasicJsonType>
 };
 
 template<typename BasicJsonType>
-class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
+class json_sax_dom_callback_parser
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -3892,43 +3892,43 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         keep_stack.push_back(true);
     }
 
-    bool null() override
+    bool null()
     {
         handle_value(nullptr);
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_integer(number_integer_t val) override
+    bool number_integer(number_integer_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t val) override
+    bool number_unsigned(number_unsigned_t val)
     {
         handle_value(val);
         return true;
     }
 
-    bool number_float(number_float_t val, const string_t&) override
+    bool number_float(number_float_t val, const string_t&)
     {
         handle_value(val);
         return true;
     }
 
-    bool string(string_t& val) override
+    bool string(string_t& val)
     {
         handle_value(val);
         return true;
     }
 
-    bool start_object(std::size_t len) override
+    bool start_object(std::size_t len = -1)
     {
         // check callback for object start
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
@@ -3950,7 +3950,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool key(string_t& val) override
+    bool key(string_t& val)
     {
         BasicJsonType k = BasicJsonType(val);
 
@@ -3967,7 +3967,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         if (ref_stack.back())
         {
@@ -4002,7 +4002,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool start_array(std::size_t len) override
+    bool start_array(std::size_t len = -1)
     {
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
@@ -4023,7 +4023,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         bool keep = true;
 
@@ -4055,7 +4055,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
     }
 
     bool parse_error(std::size_t, const std::string&,
-                     const detail::exception& ex) override
+                     const detail::exception& ex)
     {
         errored = true;
         if (allow_exceptions)
@@ -4178,7 +4178,7 @@ class json_sax_dom_callback_parser : public json_sax<BasicJsonType>
 };
 
 template<typename BasicJsonType>
-class json_sax_acceptor : public json_sax<BasicJsonType>
+class json_sax_acceptor
 {
   public:
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -4186,62 +4186,62 @@ class json_sax_acceptor : public json_sax<BasicJsonType>
     using number_float_t = typename BasicJsonType::number_float_t;
     using string_t = typename BasicJsonType::string_t;
 
-    bool null() override
+    bool null()
     {
         return true;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return true;
     }
 
-    bool number_integer(number_integer_t) override
+    bool number_integer(number_integer_t)
     {
         return true;
     }
 
-    bool number_unsigned(number_unsigned_t) override
+    bool number_unsigned(number_unsigned_t)
     {
         return true;
     }
 
-    bool number_float(number_float_t, const string_t&) override
+    bool number_float(number_float_t, const string_t&)
     {
         return true;
     }
 
-    bool string(string_t&) override
+    bool string(string_t&)
     {
         return true;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t = -1)
     {
         return true;
     }
 
-    bool key(string_t&) override
+    bool key(string_t&)
     {
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return true;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t = -1)
     {
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return true;
     }
 
-    bool parse_error(std::size_t, const std::string&, const detail::exception&) override
+    bool parse_error(std::size_t, const std::string&, const detail::exception&)
     {
         return false;
     }
@@ -4295,8 +4295,6 @@ class parser
         value
     };
 
-    using json_sax_t = json_sax<BasicJsonType>;
-
     using parser_callback_t =
         std::function<bool(int depth, parse_event_t event, BasicJsonType& parsed)>;
 
@@ -4385,7 +4383,8 @@ class parser
         return sax_parse(&sax_acceptor, strict);
     }
 
-    bool sax_parse(json_sax_t* sax, const bool strict = true)
+    template <typename SAX>
+    bool sax_parse(SAX* sax, const bool strict = true)
     {
         const bool result = sax_parse_internal(sax);
 
@@ -4401,7 +4400,8 @@ class parser
     }
 
   private:
-    bool sax_parse_internal(json_sax_t* sax)
+    template <typename SAX>
+    bool sax_parse_internal(SAX* sax)
     {
         // stack to remember the hieararchy of structured values we are parsing
         // true = array; false = object
@@ -4418,7 +4418,7 @@ class parser
                 {
                     case token_type::begin_object:
                     {
-                        if (JSON_UNLIKELY(not sax->start_object()))
+                        if (JSON_UNLIKELY(not sax->start_object(-1)))
                         {
                             return false;
                         }
@@ -4466,7 +4466,7 @@ class parser
 
                     case token_type::begin_array:
                     {
-                        if (JSON_UNLIKELY(not sax->start_array()))
+                        if (JSON_UNLIKELY(not sax->start_array(-1)))
                         {
                             return false;
                         }
@@ -5774,14 +5774,14 @@ namespace detail
 /*!
 @brief deserialization of CBOR, MessagePack, and UBJSON values
 */
-template<typename BasicJsonType>
+template<typename BasicJsonType, typename SAX = json_sax_dom_parser<BasicJsonType>>
 class binary_reader
 {
     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 json_sax_t = json_sax<BasicJsonType>;
+    using json_sax_t = SAX;
 
   public:
     /*!
@@ -6065,7 +6065,7 @@ class binary_reader
             }
 
             case 0x9F: // array (indefinite length)
-                return get_cbor_array(json_sax_t::no_limit);
+                return get_cbor_array(std::size_t(-1));
 
             // map (0x00..0x17 pairs of data items follow)
             case 0xA0:
@@ -6119,7 +6119,7 @@ class binary_reader
             }
 
             case 0xBF: // map (indefinite length)
-                return get_cbor_object(json_sax_t::no_limit);
+                return get_cbor_object(std::size_t(-1));
 
             case 0xF4: // false
                 return sax->boolean(false);
@@ -6764,7 +6764,7 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the array or json_sax_t::no_limit for an
+    @param[in] len  the length of the array or std::size_t(-1) for an
                     array of indefinite size
     @return whether array creation completed
     */
@@ -6775,7 +6775,7 @@ class binary_reader
             return false;
         }
 
-        if (len != json_sax_t::no_limit)
+        if (len != std::size_t(-1))
             for (std::size_t i = 0; i < len; ++i)
             {
                 if (JSON_UNLIKELY(not parse_cbor_internal()))
@@ -6798,7 +6798,7 @@ class binary_reader
     }
 
     /*!
-    @param[in] len  the length of the object or json_sax_t::no_limit for an
+    @param[in] len  the length of the object or std::size_t(-1) for an
                     object of indefinite size
     @return whether object creation completed
     */
@@ -6810,7 +6810,7 @@ class binary_reader
         }
 
         string_t key;
-        if (len != json_sax_t::no_limit)
+        if (len != std::size_t(-1))
         {
             for (std::size_t i = 0; i < len; ++i)
             {
@@ -7302,7 +7302,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_array()))
+            if (JSON_UNLIKELY(not sax->start_array(-1)))
             {
                 return false;
             }
@@ -7372,7 +7372,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_object()))
+            if (JSON_UNLIKELY(not sax->start_object(-1)))
             {
                 return false;
             }
@@ -11040,7 +11040,7 @@ class basic_json
     friend class ::nlohmann::detail::iter_impl;
     template<typename BasicJsonType, typename CharType>
     friend class ::nlohmann::detail::binary_writer;
-    template<typename BasicJsonType>
+    template<typename BasicJsonType, typename SAX>
     friend class ::nlohmann::detail::binary_reader;
     template<typename BasicJsonType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
@@ -11982,8 +11982,6 @@ class basic_json
     */
     using parser_callback_t = typename parser::parser_callback_t;
 
-    using json_sax_t = typename parser::json_sax_t;
-
     //////////////////
     // constructors //
     //////////////////
@@ -16883,7 +16881,8 @@ class basic_json
         return parser(i).accept(true);
     }
 
-    static bool sax_parse(detail::input_adapter&& i, json_sax_t* sax,
+    template <typename SAX>
+    static bool sax_parse(detail::input_adapter&& i, SAX* sax,
                           input_format_t format = input_format_t::json,
                           const bool strict = true)
     {
@@ -16893,7 +16892,7 @@ class basic_json
             case input_format_t::json:
                 return parser(std::move(i)).sax_parse(sax, strict);
             default:
-                return binary_reader(std::move(i)).sax_parse(format, sax, strict);
+                return detail::binary_reader<basic_json, SAX>(std::move(i)).sax_parse(format, sax, strict);
         }
     }
 
@@ -16966,11 +16965,11 @@ class basic_json
         return parser(detail::input_adapter(first, last)).accept(true);
     }
 
-    template<class IteratorType, typename std::enable_if<
+    template<class IteratorType, class SAX, typename std::enable_if<
                  std::is_base_of<
                      std::random_access_iterator_tag,
                      typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
-    static bool sax_parse(IteratorType first, IteratorType last, json_sax_t* sax)
+    static bool sax_parse(IteratorType first, IteratorType last, SAX* sax)
     {
         return parser(detail::input_adapter(first, last)).sax_parse(sax);
     }
diff --git a/test/src/unit-cbor.cpp b/test/src/unit-cbor.cpp
index 9ad5997ce9..dd40099d38 100644
--- a/test/src/unit-cbor.cpp
+++ b/test/src/unit-cbor.cpp
@@ -34,68 +34,68 @@ using nlohmann::json;
 
 #include <fstream>
 
-class SaxCountdown : public nlohmann::json::json_sax_t
+class SaxCountdown
 {
   public:
     explicit SaxCountdown(const int count) : events_left(count)
     {}
 
-    bool null() override
+    bool null()
     {
         return events_left-- > 0;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return events_left-- > 0;
     }
 
-    bool number_integer(json::number_integer_t) override
+    bool number_integer(json::number_integer_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_unsigned(json::number_unsigned_t) override
+    bool number_unsigned(json::number_unsigned_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_float(json::number_float_t, const std::string&) override
+    bool number_float(json::number_float_t, const std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool string(std::string&) override
+    bool string(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t)
     {
         return events_left-- > 0;
     }
 
-    bool key(std::string&) override
+    bool key(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t)
     {
         return events_left-- > 0;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return events_left-- > 0;
     }
 
-    bool parse_error(std::size_t, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t, const std::string&, const json::exception&)
     {
         return false;
     }
diff --git a/test/src/unit-class_parser.cpp b/test/src/unit-class_parser.cpp
index 6edb0a2e79..73c5be8325 100644
--- a/test/src/unit-class_parser.cpp
+++ b/test/src/unit-class_parser.cpp
@@ -35,48 +35,48 @@ using nlohmann::json;
 
 #include <valarray>
 
-class SaxEventLogger : public nlohmann::json::json_sax_t
+class SaxEventLogger
 {
   public:
-    bool null() override
+    bool null()
     {
         events.push_back("null()");
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         events.push_back(val ? "boolean(true)" : "boolean(false)");
         return true;
     }
 
-    bool number_integer(json::number_integer_t val) override
+    bool number_integer(json::number_integer_t val)
     {
         events.push_back("number_integer(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_unsigned(json::number_unsigned_t val) override
+    bool number_unsigned(json::number_unsigned_t val)
     {
         events.push_back("number_unsigned(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_float(json::number_float_t, const std::string& s) override
+    bool number_float(json::number_float_t, const std::string& s)
     {
         events.push_back("number_float(" + s + ")");
         return true;
     }
 
-    bool string(std::string& val) override
+    bool string(std::string& val)
     {
         events.push_back("string(" + val + ")");
         return true;
     }
 
-    bool start_object(std::size_t elements) override
+    bool start_object(std::size_t elements = -1)
     {
-        if (elements == no_limit)
+        if (elements == std::size_t(-1))
         {
             events.push_back("start_object()");
         }
@@ -87,21 +87,21 @@ class SaxEventLogger : public nlohmann::json::json_sax_t
         return true;
     }
 
-    bool key(std::string& val) override
+    bool key(std::string& val)
     {
         events.push_back("key(" + val + ")");
         return true;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         events.push_back("end_object()");
         return true;
     }
 
-    bool start_array(std::size_t elements) override
+    bool start_array(std::size_t elements = -1)
     {
-        if (elements == no_limit)
+        if (elements == std::size_t(-1))
         {
             events.push_back("start_array()");
         }
@@ -112,13 +112,13 @@ class SaxEventLogger : public nlohmann::json::json_sax_t
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         events.push_back("end_array()");
         return true;
     }
 
-    bool parse_error(std::size_t position, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t position, const std::string&, const json::exception&)
     {
         errored = true;
         events.push_back("parse_error(" + std::to_string(position) + ")");
@@ -129,68 +129,68 @@ class SaxEventLogger : public nlohmann::json::json_sax_t
     bool errored = false;
 };
 
-class SaxCountdown : public nlohmann::json::json_sax_t
+class SaxCountdown
 {
   public:
     explicit SaxCountdown(const int count) : events_left(count)
     {}
 
-    bool null() override
+    bool null()
     {
         return events_left-- > 0;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return events_left-- > 0;
     }
 
-    bool number_integer(json::number_integer_t) override
+    bool number_integer(json::number_integer_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_unsigned(json::number_unsigned_t) override
+    bool number_unsigned(json::number_unsigned_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_float(json::number_float_t, const std::string&) override
+    bool number_float(json::number_float_t, const std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool string(std::string&) override
+    bool string(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t = -1)
     {
         return events_left-- > 0;
     }
 
-    bool key(std::string&) override
+    bool key(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t = -1)
     {
         return events_left-- > 0;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return events_left-- > 0;
     }
 
-    bool parse_error(std::size_t, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t, const std::string&, const json::exception&)
     {
         return false;
     }
diff --git a/test/src/unit-deserialization.cpp b/test/src/unit-deserialization.cpp
index 09d5395a60..e122628ed6 100644
--- a/test/src/unit-deserialization.cpp
+++ b/test/src/unit-deserialization.cpp
@@ -35,45 +35,45 @@ using nlohmann::json;
 #include <iostream>
 #include <valarray>
 
-struct SaxEventLogger : public nlohmann::json::json_sax_t
+struct SaxEventLogger
 {
-    bool null() override
+    bool null()
     {
         events.push_back("null()");
         return true;
     }
 
-    bool boolean(bool val) override
+    bool boolean(bool val)
     {
         events.push_back(val ? "boolean(true)" : "boolean(false)");
         return true;
     }
 
-    bool number_integer(json::number_integer_t val) override
+    bool number_integer(json::number_integer_t val)
     {
         events.push_back("number_integer(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_unsigned(json::number_unsigned_t val) override
+    bool number_unsigned(json::number_unsigned_t val)
     {
         events.push_back("number_unsigned(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_float(json::number_float_t, const std::string& s) override
+    bool number_float(json::number_float_t, const std::string& s)
     {
         events.push_back("number_float(" + s + ")");
         return true;
     }
 
-    bool string(std::string& val) override
+    bool string(std::string& val)
     {
         events.push_back("string(" + val + ")");
         return true;
     }
 
-    bool start_object(std::size_t elements) override
+    bool start_object(std::size_t elements)
     {
         if (elements == std::size_t(-1))
         {
@@ -86,19 +86,19 @@ struct SaxEventLogger : public nlohmann::json::json_sax_t
         return true;
     }
 
-    bool key(std::string& val) override
+    bool key(std::string& val)
     {
         events.push_back("key(" + val + ")");
         return true;
     }
 
-    bool end_object()override
+    bool end_object()
     {
         events.push_back("end_object()");
         return true;
     }
 
-    bool start_array(std::size_t elements) override
+    bool start_array(std::size_t elements)
     {
         if (elements == std::size_t(-1))
         {
@@ -111,13 +111,13 @@ struct SaxEventLogger : public nlohmann::json::json_sax_t
         return true;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         events.push_back("end_array()");
         return true;
     }
 
-    bool parse_error(std::size_t position, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t position, const std::string&, const json::exception&)
     {
         events.push_back("parse_error(" + std::to_string(position) + ")");
         return false;
@@ -128,9 +128,9 @@ struct SaxEventLogger : public nlohmann::json::json_sax_t
 
 struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
 {
-    bool start_object(std::size_t elements) override
+    bool start_object(std::size_t elements)
     {
-        if (elements == no_limit)
+        if (elements == -1)
         {
             events.push_back("start_object()");
         }
@@ -144,7 +144,7 @@ struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
 
 struct SaxEventLoggerExitAfterKey : public SaxEventLogger
 {
-    bool key(std::string& val) override
+    bool key(std::string& val)
     {
         events.push_back("key(" + val + ")");
         return false;
@@ -153,9 +153,9 @@ struct SaxEventLoggerExitAfterKey : public SaxEventLogger
 
 struct SaxEventLoggerExitAfterStartArray : public SaxEventLogger
 {
-    bool start_array(std::size_t elements) override
+    bool start_array(std::size_t elements)
     {
-        if (elements == no_limit)
+        if (elements == -1)
         {
             events.push_back("start_array()");
         }
diff --git a/test/src/unit-msgpack.cpp b/test/src/unit-msgpack.cpp
index e3672d1fe4..c8bfe0bb80 100644
--- a/test/src/unit-msgpack.cpp
+++ b/test/src/unit-msgpack.cpp
@@ -34,68 +34,68 @@ using nlohmann::json;
 
 #include <fstream>
 
-class SaxCountdown : public nlohmann::json::json_sax_t
+class SaxCountdown
 {
   public:
     explicit SaxCountdown(const int count) : events_left(count)
     {}
 
-    bool null() override
+    bool null()
     {
         return events_left-- > 0;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return events_left-- > 0;
     }
 
-    bool number_integer(json::number_integer_t) override
+    bool number_integer(json::number_integer_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_unsigned(json::number_unsigned_t) override
+    bool number_unsigned(json::number_unsigned_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_float(json::number_float_t, const std::string&) override
+    bool number_float(json::number_float_t, const std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool string(std::string&) override
+    bool string(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t)
     {
         return events_left-- > 0;
     }
 
-    bool key(std::string&) override
+    bool key(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t)
     {
         return events_left-- > 0;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return events_left-- > 0;
     }
 
-    bool parse_error(std::size_t, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t, const std::string&, const json::exception&)
     {
         return false;
     }
diff --git a/test/src/unit-ubjson.cpp b/test/src/unit-ubjson.cpp
index 73a9186865..d57593117f 100644
--- a/test/src/unit-ubjson.cpp
+++ b/test/src/unit-ubjson.cpp
@@ -34,68 +34,68 @@ using nlohmann::json;
 
 #include <fstream>
 
-class SaxCountdown : public nlohmann::json::json_sax_t
+class SaxCountdown
 {
   public:
     explicit SaxCountdown(const int count) : events_left(count)
     {}
 
-    bool null() override
+    bool null()
     {
         return events_left-- > 0;
     }
 
-    bool boolean(bool) override
+    bool boolean(bool)
     {
         return events_left-- > 0;
     }
 
-    bool number_integer(json::number_integer_t) override
+    bool number_integer(json::number_integer_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_unsigned(json::number_unsigned_t) override
+    bool number_unsigned(json::number_unsigned_t)
     {
         return events_left-- > 0;
     }
 
-    bool number_float(json::number_float_t, const std::string&) override
+    bool number_float(json::number_float_t, const std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool string(std::string&) override
+    bool string(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t) override
+    bool start_object(std::size_t = -1)
     {
         return events_left-- > 0;
     }
 
-    bool key(std::string&) override
+    bool key(std::string&)
     {
         return events_left-- > 0;
     }
 
-    bool end_object() override
+    bool end_object()
     {
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t) override
+    bool start_array(std::size_t = -1)
     {
         return events_left-- > 0;
     }
 
-    bool end_array() override
+    bool end_array()
     {
         return events_left-- > 0;
     }
 
-    bool parse_error(std::size_t, const std::string&, const json::exception&) override
+    bool parse_error(std::size_t, const std::string&, const json::exception&)
     {
         return false;
     }

From 9bbb133094d62299bea79d008e7c69a81d457c7c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Tue, 24 Jul 2018 13:09:08 +0200
Subject: [PATCH 3/5] remove no_limit constant and default values

---
 include/nlohmann/detail/input/json_sax.hpp | 27 ++++++++++------------
 single_include/nlohmann/json.hpp           | 27 ++++++++++------------
 test/src/unit-class_parser.cpp             |  8 +++----
 test/src/unit-ubjson.cpp                   |  4 ++--
 4 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/include/nlohmann/detail/input/json_sax.hpp b/include/nlohmann/detail/input/json_sax.hpp
index 9d96a20e15..fe1cf7c5b6 100644
--- a/include/nlohmann/detail/input/json_sax.hpp
+++ b/include/nlohmann/detail/input/json_sax.hpp
@@ -25,9 +25,6 @@ struct json_sax
     /// type for strings
     using string_t = typename BasicJsonType::string_t;
 
-    /// constant to indicate that no size limit is given for array or object
-    static constexpr auto no_limit = std::size_t(-1);
-
     /*!
     @brief a null value was read
     @return whether parsing should proceed
@@ -72,11 +69,11 @@ struct json_sax
 
     /*!
     @brief the beginning of an object was read
-    @param[in] elements  number of object elements or no_limit if unknown
+    @param[in] elements  number of object elements or -1 if unknown
     @return whether parsing should proceed
     @note binary formats may report the number of elements
     */
-    virtual bool start_object(std::size_t elements = no_limit) = 0;
+    virtual bool start_object(std::size_t elements) = 0;
 
     /*!
     @brief an object key was read
@@ -93,11 +90,11 @@ struct json_sax
 
     /*!
     @brief the beginning of an array was read
-    @param[in] elements  number of array elements or no_limit if unknown
+    @param[in] elements  number of array elements or -1 if unknown
     @return whether parsing should proceed
     @note binary formats may report the number of elements
     */
-    virtual bool start_array(std::size_t elements = no_limit) = 0;
+    virtual bool start_array(std::size_t elements) = 0;
 
     /*!
     @brief the end of an array was read
@@ -189,11 +186,11 @@ class json_sax_dom_parser
         return true;
     }
 
-    bool start_object(std::size_t len = -1)
+    bool start_object(std::size_t len)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
-        if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive object size: " + std::to_string(len)));
@@ -215,11 +212,11 @@ class json_sax_dom_parser
         return true;
     }
 
-    bool start_array(std::size_t len = -1)
+    bool start_array(std::size_t len)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
-        if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive array size: " + std::to_string(len)));
@@ -364,7 +361,7 @@ class json_sax_dom_callback_parser
         return true;
     }
 
-    bool start_object(std::size_t len = -1)
+    bool start_object(std::size_t len)
     {
         // check callback for object start
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
@@ -376,7 +373,7 @@ class json_sax_dom_callback_parser
         // check object limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive object size: " + std::to_string(len)));
@@ -438,7 +435,7 @@ class json_sax_dom_callback_parser
         return true;
     }
 
-    bool start_array(std::size_t len = -1)
+    bool start_array(std::size_t len)
     {
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
@@ -449,7 +446,7 @@ class json_sax_dom_callback_parser
         // check array limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive array size: " + std::to_string(len)));
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 33e864e1bf..6e6ef85d88 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3589,9 +3589,6 @@ struct json_sax
     /// type for strings
     using string_t = typename BasicJsonType::string_t;
 
-    /// constant to indicate that no size limit is given for array or object
-    static constexpr auto no_limit = std::size_t(-1);
-
     /*!
     @brief a null value was read
     @return whether parsing should proceed
@@ -3636,11 +3633,11 @@ struct json_sax
 
     /*!
     @brief the beginning of an object was read
-    @param[in] elements  number of object elements or no_limit if unknown
+    @param[in] elements  number of object elements or -1 if unknown
     @return whether parsing should proceed
     @note binary formats may report the number of elements
     */
-    virtual bool start_object(std::size_t elements = no_limit) = 0;
+    virtual bool start_object(std::size_t elements) = 0;
 
     /*!
     @brief an object key was read
@@ -3657,11 +3654,11 @@ struct json_sax
 
     /*!
     @brief the beginning of an array was read
-    @param[in] elements  number of array elements or no_limit if unknown
+    @param[in] elements  number of array elements or -1 if unknown
     @return whether parsing should proceed
     @note binary formats may report the number of elements
     */
-    virtual bool start_array(std::size_t elements = no_limit) = 0;
+    virtual bool start_array(std::size_t elements) = 0;
 
     /*!
     @brief the end of an array was read
@@ -3753,11 +3750,11 @@ class json_sax_dom_parser
         return true;
     }
 
-    bool start_object(std::size_t len = -1)
+    bool start_object(std::size_t len)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
-        if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive object size: " + std::to_string(len)));
@@ -3779,11 +3776,11 @@ class json_sax_dom_parser
         return true;
     }
 
-    bool start_array(std::size_t len = -1)
+    bool start_array(std::size_t len)
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
-        if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive array size: " + std::to_string(len)));
@@ -3928,7 +3925,7 @@ class json_sax_dom_callback_parser
         return true;
     }
 
-    bool start_object(std::size_t len = -1)
+    bool start_object(std::size_t len)
     {
         // check callback for object start
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
@@ -3940,7 +3937,7 @@ class json_sax_dom_callback_parser
         // check object limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive object size: " + std::to_string(len)));
@@ -4002,7 +3999,7 @@ class json_sax_dom_callback_parser
         return true;
     }
 
-    bool start_array(std::size_t len = -1)
+    bool start_array(std::size_t len)
     {
         const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
@@ -4013,7 +4010,7 @@ class json_sax_dom_callback_parser
         // check array limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != json_sax<BasicJsonType>::no_limit and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive array size: " + std::to_string(len)));
diff --git a/test/src/unit-class_parser.cpp b/test/src/unit-class_parser.cpp
index 73c5be8325..e08099da0f 100644
--- a/test/src/unit-class_parser.cpp
+++ b/test/src/unit-class_parser.cpp
@@ -74,7 +74,7 @@ class SaxEventLogger
         return true;
     }
 
-    bool start_object(std::size_t elements = -1)
+    bool start_object(std::size_t elements)
     {
         if (elements == std::size_t(-1))
         {
@@ -99,7 +99,7 @@ class SaxEventLogger
         return true;
     }
 
-    bool start_array(std::size_t elements = -1)
+    bool start_array(std::size_t elements)
     {
         if (elements == std::size_t(-1))
         {
@@ -165,7 +165,7 @@ class SaxCountdown
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t = -1)
+    bool start_object(std::size_t)
     {
         return events_left-- > 0;
     }
@@ -180,7 +180,7 @@ class SaxCountdown
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t = -1)
+    bool start_array(std::size_t)
     {
         return events_left-- > 0;
     }
diff --git a/test/src/unit-ubjson.cpp b/test/src/unit-ubjson.cpp
index d57593117f..524d60b9c5 100644
--- a/test/src/unit-ubjson.cpp
+++ b/test/src/unit-ubjson.cpp
@@ -70,7 +70,7 @@ class SaxCountdown
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t = -1)
+    bool start_object(std::size_t)
     {
         return events_left-- > 0;
     }
@@ -85,7 +85,7 @@ class SaxCountdown
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t = -1)
+    bool start_array(std::size_t)
     {
         return events_left-- > 0;
     }

From 38f8a51a8f049a98936f0f3eeabdb1f6080e5f37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Thu, 16 Aug 2018 10:52:33 +0200
Subject: [PATCH 4/5] use abstract sax class in parser tests

---
 include/nlohmann/json.hpp        |  1 +
 single_include/nlohmann/json.hpp |  1 +
 test/src/unit-class_parser.cpp   | 26 +++++++++++++-------------
 3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 8c4cb159ee..54638d72d4 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -212,6 +212,7 @@ class basic_json
     using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
 
     using input_format_t = detail::input_format_t;
+    using json_sax_t = json_sax<basic_json>;
 
     ////////////////
     // exceptions //
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 6e6ef85d88..cbd1a34d78 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -11078,6 +11078,7 @@ class basic_json
     using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
 
     using input_format_t = detail::input_format_t;
+    using json_sax_t = json_sax<basic_json>;
 
     ////////////////
     // exceptions //
diff --git a/test/src/unit-class_parser.cpp b/test/src/unit-class_parser.cpp
index e08099da0f..74abd472e0 100644
--- a/test/src/unit-class_parser.cpp
+++ b/test/src/unit-class_parser.cpp
@@ -129,68 +129,68 @@ class SaxEventLogger
     bool errored = false;
 };
 
-class SaxCountdown
+class SaxCountdown : public nlohmann::json::json_sax_t
 {
   public:
     explicit SaxCountdown(const int count) : events_left(count)
     {}
 
-    bool null()
+    bool null() override
     {
         return events_left-- > 0;
     }
 
-    bool boolean(bool)
+    bool boolean(bool) override
     {
         return events_left-- > 0;
     }
 
-    bool number_integer(json::number_integer_t)
+    bool number_integer(json::number_integer_t) override
     {
         return events_left-- > 0;
     }
 
-    bool number_unsigned(json::number_unsigned_t)
+    bool number_unsigned(json::number_unsigned_t) override
     {
         return events_left-- > 0;
     }
 
-    bool number_float(json::number_float_t, const std::string&)
+    bool number_float(json::number_float_t, const std::string&) override
     {
         return events_left-- > 0;
     }
 
-    bool string(std::string&)
+    bool string(std::string&) override
     {
         return events_left-- > 0;
     }
 
-    bool start_object(std::size_t)
+    bool start_object(std::size_t) override
     {
         return events_left-- > 0;
     }
 
-    bool key(std::string&)
+    bool key(std::string&) override
     {
         return events_left-- > 0;
     }
 
-    bool end_object()
+    bool end_object() override
     {
         return events_left-- > 0;
     }
 
-    bool start_array(std::size_t)
+    bool start_array(std::size_t) override
     {
         return events_left-- > 0;
     }
 
-    bool end_array()
+    bool end_array() override
     {
         return events_left-- > 0;
     }
 
-    bool parse_error(std::size_t, const std::string&, const json::exception&)
+    bool parse_error(std::size_t, const std::string&, const json::exception&) override
     {
         return false;
     }

From 0cc3db4f153d376d324eeb859c5ed0583d256e47 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Tue, 24 Jul 2018 14:47:41 +0200
Subject: [PATCH 5/5] add static_asserts on SAX interface

---
 .../nlohmann/detail/input/binary_reader.hpp   |   2 +
 include/nlohmann/detail/input/parser.hpp      |   2 +
 include/nlohmann/detail/meta/is_sax.hpp       | 141 ++++++++++++
 single_include/nlohmann/json.hpp              | 216 ++++++++++++++++++
 4 files changed, 361 insertions(+)
 create mode 100644 include/nlohmann/detail/meta/is_sax.hpp

diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index cc3c3adac5..27c34edbc6 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -17,6 +17,7 @@
 #include <nlohmann/detail/input/json_sax.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
+#include <nlohmann/detail/meta/is_sax.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
@@ -47,6 +48,7 @@ class binary_reader
     */
     explicit binary_reader(input_adapter_t adapter) : ia(std::move(adapter))
     {
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
         assert(ia);
     }
 
diff --git a/include/nlohmann/detail/input/parser.hpp b/include/nlohmann/detail/input/parser.hpp
index 93d1dc4a32..cfb8b65e87 100644
--- a/include/nlohmann/detail/input/parser.hpp
+++ b/include/nlohmann/detail/input/parser.hpp
@@ -9,6 +9,7 @@
 
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
+#include <nlohmann/detail/meta/is_sax.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
 #include <nlohmann/detail/input/json_sax.hpp>
 #include <nlohmann/detail/input/lexer.hpp>
@@ -145,6 +146,7 @@ class parser
     template <typename SAX>
     bool sax_parse(SAX* sax, const bool strict = true)
     {
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType>{};
         const bool result = sax_parse_internal(sax);
 
         // strict mode: next byte must be EOF
diff --git a/include/nlohmann/detail/meta/is_sax.hpp b/include/nlohmann/detail/meta/is_sax.hpp
new file mode 100644
index 0000000000..b4e1f3fda1
--- /dev/null
+++ b/include/nlohmann/detail/meta/is_sax.hpp
@@ -0,0 +1,141 @@
+#pragma once
+
+#include <cstdint> // size_t
+#include <utility> // declval
+
+#include <nlohmann/detail/meta/detected.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename T>
+using null_function_t = decltype(std::declval<T&>().null());
+
+template <typename T>
+using boolean_function_t =
+    decltype(std::declval<T&>().boolean(std::declval<bool>()));
+
+template <typename T, typename Integer>
+using number_integer_function_t =
+    decltype(std::declval<T&>().number_integer(std::declval<Integer>()));
+
+template <typename T, typename Unsigned>
+using number_unsigned_function_t =
+    decltype(std::declval<T &>().number_unsigned(std::declval<Unsigned>()));
+
+template <typename T, typename Float, typename String>
+using number_float_function_t = decltype(std::declval<T &>().number_float(
+    std::declval<Float>(), std::declval<const String &>()));
+
+template <typename T, typename String>
+using string_function_t =
+    decltype(std::declval<T &>().string(std::declval<String &>()));
+
+template <typename T>
+using start_object_function_t =
+    decltype(std::declval<T &>().start_object(std::declval<std::size_t>()));
+
+template <typename T, typename String>
+using key_function_t =
+    decltype(std::declval<T &>().key(std::declval<String &>()));
+
+template <typename T>
+using end_object_function_t = decltype(std::declval<T &>().end_object());
+
+template <typename T>
+using start_array_function_t =
+    decltype(std::declval<T &>().start_array(std::declval<std::size_t>()));
+
+template <typename T>
+using end_array_function_t = decltype(std::declval<T &>().end_array());
+
+template <typename T, typename Exception>
+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 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, 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
+{
+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 exception_t = typename BasicJsonType::exception;
+
+public:
+  static_assert(is_detected_exact<bool, null_function_t, SAX>::value,
+                "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,
+      "Missing/invalid function: bool number_integer(number_integer_t)");
+  static_assert(
+      is_detected_exact<bool, number_unsigned_function_t, SAX,
+                        number_unsigned_t>::value,
+      "Missing/invalid function: bool number_unsigned(number_unsigned_t)");
+  static_assert(is_detected_exact<bool, number_float_function_t, SAX,
+                                  number_float_t, string_t>::value,
+                "Missing/invalid function: bool number_float(number_float_t, const string_t&)");
+  static_assert(
+      is_detected_exact<bool, string_function_t, SAX, string_t>::value,
+      "Missing/invalid function: bool string(string_t&)");
+  static_assert(is_detected_exact<bool, start_object_function_t, SAX>::value,
+                "Missing/invalid function: bool start_object(std::size_t)");
+  static_assert(is_detected_exact<bool, key_function_t, SAX, string_t>::value,
+                "Missing/invalid function: bool key(string_t&)");
+  static_assert(is_detected_exact<bool, end_object_function_t, SAX>::value,
+                "Missing/invalid function: bool end_object()");
+  static_assert(is_detected_exact<bool, start_array_function_t, SAX>::value,
+                "Missing/invalid function: bool start_array(std::size_t)");
+  static_assert(is_detected_exact<bool, end_array_function_t, SAX>::value,
+                "Missing/invalid function: bool end_array()");
+  static_assert(
+      is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value,
+      "Missing/invalid function: bool parse_error(std::size_t, const "
+      "std::string&, const exception&)");
+};
+}
+}
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index cbd1a34d78..2e73d98f38 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3557,6 +3557,218 @@ class lexer
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
+// #include <nlohmann/detail/meta/is_sax.hpp>
+
+
+#include <cstdint> // size_t
+#include <utility> // declval
+
+// #include <nlohmann/detail/meta/detected.hpp>
+
+
+#include <type_traits>
+
+// #include <nlohmann/detail/meta/void_t.hpp>
+
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename...>
+using void_t = void;
+}
+}
+
+
+// http://en.cppreference.com/w/cpp/experimental/is_detected
+namespace nlohmann
+{
+namespace detail
+{
+struct nonesuch
+{
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(nonesuch const&) = delete;
+    void operator=(nonesuch const&) = 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>
+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>;
+}
+}
+
+// #include <nlohmann/detail/meta/type_traits.hpp>
+
+
+namespace nlohmann
+{
+namespace detail
+{
+template <typename T>
+using null_function_t = decltype(std::declval<T&>().null());
+
+template <typename T>
+using boolean_function_t =
+    decltype(std::declval<T&>().boolean(std::declval<bool>()));
+
+template <typename T, typename Integer>
+using number_integer_function_t =
+    decltype(std::declval<T&>().number_integer(std::declval<Integer>()));
+
+template <typename T, typename Unsigned>
+using number_unsigned_function_t =
+    decltype(std::declval<T&>().number_unsigned(std::declval<Unsigned>()));
+
+template <typename T, typename Float, typename String>
+using number_float_function_t = decltype(std::declval<T&>().number_float(
+                                    std::declval<Float>(), std::declval<const String&>()));
+
+template <typename T, typename String>
+using string_function_t =
+    decltype(std::declval<T&>().string(std::declval<String&>()));
+
+template <typename T>
+using start_object_function_t =
+    decltype(std::declval<T&>().start_object(std::declval<std::size_t>()));
+
+template <typename T, typename String>
+using key_function_t =
+    decltype(std::declval<T&>().key(std::declval<String&>()));
+
+template <typename T>
+using end_object_function_t = decltype(std::declval<T&>().end_object());
+
+template <typename T>
+using start_array_function_t =
+    decltype(std::declval<T&>().start_array(std::declval<std::size_t>()));
+
+template <typename T>
+using end_array_function_t = decltype(std::declval<T&>().end_array());
+
+template <typename T, typename Exception>
+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 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, 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
+{
+  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 exception_t = typename BasicJsonType::exception;
+
+  public:
+    static_assert(is_detected_exact<bool, null_function_t, SAX>::value,
+                  "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,
+        "Missing/invalid function: bool number_integer(number_integer_t)");
+    static_assert(
+        is_detected_exact<bool, number_unsigned_function_t, SAX,
+        number_unsigned_t>::value,
+        "Missing/invalid function: bool number_unsigned(number_unsigned_t)");
+    static_assert(is_detected_exact<bool, number_float_function_t, SAX,
+                  number_float_t, string_t>::value,
+                  "Missing/invalid function: bool number_float(number_float_t, const string_t&)");
+    static_assert(
+        is_detected_exact<bool, string_function_t, SAX, string_t>::value,
+        "Missing/invalid function: bool string(string_t&)");
+    static_assert(is_detected_exact<bool, start_object_function_t, SAX>::value,
+                  "Missing/invalid function: bool start_object(std::size_t)");
+    static_assert(is_detected_exact<bool, key_function_t, SAX, string_t>::value,
+                  "Missing/invalid function: bool key(string_t&)");
+    static_assert(is_detected_exact<bool, end_object_function_t, SAX>::value,
+                  "Missing/invalid function: bool end_object()");
+    static_assert(is_detected_exact<bool, start_array_function_t, SAX>::value,
+                  "Missing/invalid function: bool start_array(std::size_t)");
+    static_assert(is_detected_exact<bool, end_array_function_t, SAX>::value,
+                  "Missing/invalid function: bool end_array()");
+    static_assert(
+        is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value,
+        "Missing/invalid function: bool parse_error(std::size_t, const "
+        "std::string&, const exception&)");
+};
+}
+}
+
 // #include <nlohmann/detail/input/input_adapters.hpp>
 
 // #include <nlohmann/detail/input/json_sax.hpp>
@@ -4383,6 +4595,7 @@ class parser
     template <typename SAX>
     bool sax_parse(SAX* sax, const bool strict = true)
     {
+        // (void)detail::is_sax_static_asserts<SAX, BasicJsonType>{};
         const bool result = sax_parse_internal(sax);
 
         // strict mode: next byte must be EOF
@@ -5757,6 +5970,8 @@ class output_adapter
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
+// #include <nlohmann/detail/meta/is_sax.hpp>
+
 // #include <nlohmann/detail/value_t.hpp>
 
 
@@ -5788,6 +6003,7 @@ class binary_reader
     */
     explicit binary_reader(input_adapter_t adapter) : ia(std::move(adapter))
     {
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
         assert(ia);
     }