From 4c208728e7541c4c16c2b2d75f27b707afc4dc1e Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Wed, 30 Sep 2026 09:38:54 +0200
Subject: [PATCH] Remove unused is_sax and is_detected_convertible

detail::is_sax had no user: the parser and the binary reader only use
is_sax_static_asserts, so is_sax was a second, unchecked copy of the
SAX event list. is_sax_static_asserts asserted boolean(bool) twice in
a row, and detail::is_detected_convertible was never used anywhere.

Remove all three and include <cstddef> for size_t instead of <cstdint>.
Only names in nlohmann::detail are removed; behavior, public API and ABI
are unchanged. The diagnostics for an incomplete SAX handler are the
same, apart from the duplicated boolean() message.

Part of #5708

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 include/nlohmann/detail/meta/detected.hpp |  4 ---
 include/nlohmann/detail/meta/is_sax.hpp   | 35 +-------------------
 single_include/nlohmann/json.hpp          | 39 +----------------------
 3 files changed, 2 insertions(+), 76 deletions(-)

diff --git a/include/nlohmann/detail/meta/detected.hpp b/include/nlohmann/detail/meta/detected.hpp
index 8da22eb9b..c41fe657e 100644
--- a/include/nlohmann/detail/meta/detected.hpp
+++ b/include/nlohmann/detail/meta/detected.hpp
@@ -62,9 +62,5 @@ using detected_or_t = typename detected_or<Default, Op, Args...>::type;
 template<class Expected, template<class...> class Op, class... Args>
 using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
 
-template<class To, template<class...> class Op, class... Args>
-using is_detected_convertible =
-    std::is_convertible<detected_t<Op, Args...>, To>;
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
diff --git a/include/nlohmann/detail/meta/is_sax.hpp b/include/nlohmann/detail/meta/is_sax.hpp
index 8e8a0de24..ac238b0c2 100644
--- a/include/nlohmann/detail/meta/is_sax.hpp
+++ b/include/nlohmann/detail/meta/is_sax.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include <cstdint> // size_t
+#include <cstddef> // size_t
 #include <utility> // declval
 #include <string> // string
 
@@ -70,37 +70,6 @@ using parse_error_function_t = decltype(std::declval<T&>().parse_error(
         std::declval<std::size_t>(), std::declval<const std::string&>(),
         std::declval<const Exception&>()));
 
-template<typename SAX, typename BasicJsonType>
-struct is_sax
-{
-  private:
-    static_assert(is_basic_json<BasicJsonType>::value,
-                  "BasicJsonType must be of type basic_json<...>");
-
-    using number_integer_t = typename BasicJsonType::number_integer_t;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-    using number_float_t = typename BasicJsonType::number_float_t;
-    using string_t = typename BasicJsonType::string_t;
-    using binary_t = typename BasicJsonType::binary_t;
-    using exception_t = typename BasicJsonType::exception;
-
-  public:
-    static constexpr bool value =
-        is_detected_exact<bool, null_function_t, SAX>::value &&
-        is_detected_exact<bool, boolean_function_t, SAX>::value &&
-        is_detected_exact<bool, number_integer_function_t, SAX, number_integer_t>::value &&
-        is_detected_exact<bool, number_unsigned_function_t, SAX, number_unsigned_t>::value &&
-        is_detected_exact<bool, number_float_function_t, SAX, number_float_t, string_t>::value &&
-        is_detected_exact<bool, string_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, binary_function_t, SAX, binary_t>::value &&
-        is_detected_exact<bool, start_object_function_t, SAX>::value &&
-        is_detected_exact<bool, key_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, end_object_function_t, SAX>::value &&
-        is_detected_exact<bool, start_array_function_t, SAX>::value &&
-        is_detected_exact<bool, end_array_function_t, SAX>::value &&
-        is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value;
-};
-
 template<typename SAX, typename BasicJsonType>
 struct is_sax_static_asserts
 {
@@ -120,8 +89,6 @@ struct is_sax_static_asserts
                   "Missing/invalid function: bool null()");
     static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
                   "Missing/invalid function: bool boolean(bool)");
-    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
-                  "Missing/invalid function: bool boolean(bool)");
     static_assert(
         is_detected_exact<bool, number_integer_function_t, SAX,
         number_integer_t>::value,
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 576498738..a1c02c488 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -366,10 +366,6 @@ using detected_or_t = typename detected_or<Default, Op, Args...>::type;
 template<class Expected, template<class...> class Op, class... Args>
 using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
 
-template<class To, template<class...> class Op, class... Args>
-using is_detected_convertible =
-    std::is_convertible<detected_t<Op, Args...>, To>;
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
 
@@ -12641,7 +12637,7 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 
-#include <cstdint> // size_t
+#include <cstddef> // size_t
 #include <utility> // declval
 #include <string> // string
 
@@ -12706,37 +12702,6 @@ using parse_error_function_t = decltype(std::declval<T&>().parse_error(
         std::declval<std::size_t>(), std::declval<const std::string&>(),
         std::declval<const Exception&>()));
 
-template<typename SAX, typename BasicJsonType>
-struct is_sax
-{
-  private:
-    static_assert(is_basic_json<BasicJsonType>::value,
-                  "BasicJsonType must be of type basic_json<...>");
-
-    using number_integer_t = typename BasicJsonType::number_integer_t;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-    using number_float_t = typename BasicJsonType::number_float_t;
-    using string_t = typename BasicJsonType::string_t;
-    using binary_t = typename BasicJsonType::binary_t;
-    using exception_t = typename BasicJsonType::exception;
-
-  public:
-    static constexpr bool value =
-        is_detected_exact<bool, null_function_t, SAX>::value &&
-        is_detected_exact<bool, boolean_function_t, SAX>::value &&
-        is_detected_exact<bool, number_integer_function_t, SAX, number_integer_t>::value &&
-        is_detected_exact<bool, number_unsigned_function_t, SAX, number_unsigned_t>::value &&
-        is_detected_exact<bool, number_float_function_t, SAX, number_float_t, string_t>::value &&
-        is_detected_exact<bool, string_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, binary_function_t, SAX, binary_t>::value &&
-        is_detected_exact<bool, start_object_function_t, SAX>::value &&
-        is_detected_exact<bool, key_function_t, SAX, string_t>::value &&
-        is_detected_exact<bool, end_object_function_t, SAX>::value &&
-        is_detected_exact<bool, start_array_function_t, SAX>::value &&
-        is_detected_exact<bool, end_array_function_t, SAX>::value &&
-        is_detected_exact<bool, parse_error_function_t, SAX, exception_t>::value;
-};
-
 template<typename SAX, typename BasicJsonType>
 struct is_sax_static_asserts
 {
@@ -12756,8 +12721,6 @@ struct is_sax_static_asserts
                   "Missing/invalid function: bool null()");
     static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
                   "Missing/invalid function: bool boolean(bool)");
-    static_assert(is_detected_exact<bool, boolean_function_t, SAX>::value,
-                  "Missing/invalid function: bool boolean(bool)");
     static_assert(
         is_detected_exact<bool, number_integer_function_t, SAX,
         number_integer_t>::value,