Make convert_null_to() take the container type as a template argument

Passing array_t or object_t instead of a value_t makes an invalid target
a compile error instead of a runtime assertion, and removes the branch.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.clang-tidy

@@ -1,11 +1,9 @@
-# TODO: The first three checks are only removed to get the CI going. They have to be addressed at some point.
+# TODO: portability-template-virtual-member-function is only removed to get the CI going. It has to be addressed at some point.
 # TODO: portability-avoid-pragma-once: should be fixed eventually
 
 Checks: '*,
 
          -portability-template-virtual-member-function,
-         -bugprone-use-after-move,
-         -hicpp-invalid-access-moved,
 
          -altera-id-dependent-backward-branch,
          -altera-struct-pack-align,

docs/mkdocs/docs/api/basic_json/meta.md

@@ -13,7 +13,7 @@ JSON object holding version information
 
 | key         | description                                                                                                                                                                                                                                                                    |
 |-------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `compiler`  | Information on the used compiler. It is an object with the following keys: `c++` (the used C++ standard), `family` (the compiler family; possible values are `clang`, `icc`, `gcc`, `ilecpp`, `msvc`, `pgcpp`, `sunpro`, and `unknown`), and `version` (the compiler version). On HP aCC compilers, `compiler` is instead the plain string `hp`. |
+| `compiler`  | Information on the used compiler. It is an object with the following keys: `c++` (the used C++ standard), `family` (the compiler family; possible values are `clang`, `icc`, `gcc`, `hp`, `ilecpp`, `msvc`, `pgcpp`, `sunpro`, and `unknown`), and `version` (the compiler version). |
 | `copyright` | The copyright line for the library as string.                                                                                                                                                                                                                                  |
 | `name`      | The name of the library as string.                                                                                                                                                                                                                                             |
 | `platform`  | The used platform as string. Possible values are `win32`, `linux`, `apple`, `unix`, and `unknown`.                                                                                                                                                                             |

include/nlohmann/detail/conversions/from_json.hpp

@@ -353,7 +353,7 @@ template < typename BasicJsonType, typename T, std::size_t... Idx >
 std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(BasicJsonType&& j,
                      identity_tag<std::array<T, sizeof...(Idx)>> /*unused*/, index_sequence<Idx...> /*unused*/)
 {
-    return { { std::forward<BasicJsonType>(j).at(Idx).template get<T>()... } };
+    return { { j.at(Idx).template get<T>()... } };
 }
 
 template < typename BasicJsonType, typename T, std::size_t N >
@@ -502,7 +502,7 @@ using tuple_type = std::tuple < decltype(from_json_tuple_get_impl(std::declval<B
 template<std::size_t PTagValue, typename... Args, typename BasicJsonType, std::size_t... Idx>
 tuple_type<PTagValue, BasicJsonType, Args...> from_json_tuple_impl_base(BasicJsonType&& j, index_sequence<Idx...> /*unused*/)
 {
-    return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(std::forward<BasicJsonType>(j).at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
+    return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(j.at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
 }
 
 template<std::size_t PTagValue, typename BasicJsonType>
@@ -514,8 +514,8 @@ std::tuple<> from_json_tuple_impl_base(BasicJsonType& /*unused*/, index_sequence
 template < typename BasicJsonType, class A1, class A2 >
 std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
 {
-    return {std::forward<BasicJsonType>(j).at(0).template get<A1>(),
-            std::forward<BasicJsonType>(j).at(1).template get<A2>()};
+    return {j.at(0).template get<A1>(),
+            j.at(1).template get<A2>()};
 }
 
 template<typename BasicJsonType, typename A1, typename A2>

include/nlohmann/detail/input/binary_reader.hpp

@@ -3344,8 +3344,8 @@ class binary_reader
         return enter_object(detail::unknown_size());
     }
 
-    // Note, UBJSON has no binary type of its own; BJData, which shares this
-    // reader, decodes optimized 'B' arrays as binary in get_ubjson_array().
+    // Note, no reader for UBJSON binary types is implemented because they do
+    // not exist
 
     bool get_ubjson_high_precision_number()
     {
@@ -4052,7 +4052,7 @@ class binary_reader
 #endif
     }
 
-    /*!
+    /*
     @brief read a number from the input
 
     @tparam NumberType the type of the number
@@ -4062,10 +4062,10 @@ class binary_reader
     @return whether conversion completed
 
     @note This function needs to respect the system's endianness, because
-          bytes in CBOR, MessagePack, UBJSON, and BON8 are stored in network
-          order (big endian) and therefore need reordering on little endian
-          systems. On the other hand, BSON and BJData use little endian and
-          should reorder on big endian systems.
+          bytes in CBOR, MessagePack, and UBJSON are stored in network order
+          (big endian) and therefore need reordering on little endian systems.
+          On the other hand, BSON and BJData use little endian and should reorder
+          on big endian systems.
     */
     template<typename NumberType, bool InputIsLittleEndian = false>
     bool get_number(const input_format_t format, NumberType& result)

include/nlohmann/detail/input/input_adapters.hpp

@@ -8,12 +8,12 @@
 
 #pragma once
 
-#include <algorithm> // min
 #include <array> // array
 #include <cstddef> // size_t
-#include <cstdint> // uint32_t
 #include <cstring> // strlen
 #include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next
+#include <memory> // shared_ptr, make_shared, addressof
+#include <numeric> // accumulate
 #include <streambuf> // streambuf
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
@@ -28,7 +28,6 @@
 #include <nlohmann/detail/iterators/iterator_traits.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
-#include <nlohmann/detail/string_utils.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -83,9 +82,8 @@ class file_input_adapter
 };
 
 /*!
-Input adapter for a (caching) istream. Does not skip a UTF Byte Order Mark
-itself; that is done by the lexer's skip_bom(). Does not support changing
-the underlying std::streambuf
+Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
+beginning of input. Does not support changing the underlying std::streambuf
 in mid-input. Maintains underlying std::istream and std::streambuf to support
 subsequent use of standard std::istream operations to process any input
 characters following those used in parsing the JSON input.  Clears the
@@ -450,14 +448,32 @@ struct wide_string_input_helper<BaseInputAdapter, 4>
             // get the current character
             const auto wc = input.get_character();
 
-            if (wc <= 0x10FFFF)
+            // UTF-32 to UTF-8 encoding
+            if (wc < 0x80)
             {
-                // UTF-32 to UTF-8 encoding
-                utf8_bytes_filled = 0;
-                encode_utf8(static_cast<std::uint32_t>(wc), [&utf8_bytes, &utf8_bytes_filled](std::uint32_t byte)
-                {
-                    utf8_bytes[utf8_bytes_filled++] = static_cast<std::char_traits<char>::int_type>(byte);
-                });
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u) & 0x1Fu));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
+                utf8_bytes_filled = 2;
+            }
+            else if (wc <= 0xFFFF)
+            {
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u) & 0x0Fu));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
+                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
+                utf8_bytes_filled = 3;
+            }
+            else if (wc <= 0x10FFFF)
+            {
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | ((static_cast<unsigned int>(wc) >> 18u) & 0x07u));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 12u) & 0x3Fu));
+                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
+                utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
+                utf8_bytes_filled = 4;
             }
             else
             {
@@ -494,15 +510,24 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
             // get the current character
             const auto wc = input.get_character();
 
-            if (0xD800 > wc || wc >= 0xE000)
+            // UTF-16 to UTF-8 encoding
+            if (wc < 0x80)
             {
-                // a UTF-16 code unit outside the surrogate range is a valid
-                // code point (at most U+FFFF) on its own
-                utf8_bytes_filled = 0;
-                encode_utf8(static_cast<std::uint32_t>(wc), [&utf8_bytes, &utf8_bytes_filled](std::uint32_t byte)
-                {
-                    utf8_bytes[utf8_bytes_filled++] = static_cast<std::char_traits<char>::int_type>(byte);
-                });
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
+                utf8_bytes_filled = 2;
+            }
+            else if (0xD800 > wc || wc >= 0xE000)
+            {
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
+                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
+                utf8_bytes_filled = 3;
             }
             else
             {
@@ -520,11 +545,11 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
                     if (0xDC00 <= wc2 && wc2 <= 0xDFFF)
                     {
                         const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
-                        utf8_bytes_filled = 0;
-                        encode_utf8(charcode, [&utf8_bytes, &utf8_bytes_filled](std::uint32_t byte)
-                        {
-                            utf8_bytes[utf8_bytes_filled++] = static_cast<std::char_traits<char>::int_type>(byte);
-                        });
+                        utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
+                        utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
+                        utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
+                        utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
+                        utf8_bytes_filled = 4;
                         valid_pair = true;
                     }
                 }
@@ -738,6 +763,7 @@ struct container_input_adapter_factory< ContainerType,
 
            static adapter_type create(ContainerType&& container)
 {
+    // NOLINTNEXTLINE(bugprone-use-after-move,hicpp-invalid-access-moved) forwarded twice on purpose, so begin() and end() see the same value category and yield matching iterator types
     return input_adapter(begin(std::forward<ContainerType>(container)), end(std::forward<ContainerType>(container)));
 }
        };
@@ -837,9 +863,9 @@ auto input_adapter(T (&array)[N]) -> decltype(input_adapter(array, array + N)) /
     return input_adapter(array, array + N);
 }
 
-// This class only handles inputs that construct a contiguous_bytes_input_adapter
-// (e.g. span_input_adapter). It's required so that expressions like {ptr, len}
-// can be implicitly cast to the correct adapter.
+// This class only handles inputs of input_buffer_adapter type.
+// It's required so that expressions like {ptr, len} can be implicitly cast
+// to the correct adapter.
 class span_input_adapter
 {
   public:

include/nlohmann/detail/input/json_sax.hpp

@@ -10,7 +10,6 @@
 
 #include <algorithm> // find_if, min
 #include <cstddef>
-#include <limits> // numeric_limits
 #include <string> // string
 #include <type_traits> // enable_if_t
 #include <utility> // move, pair
@@ -176,88 +175,6 @@ template<typename ArrayType>
 inline void reserve_array(ArrayType& /*arr*/, std::size_t /*len*/, priority_tag<0> /*unused*/)
 {}
 
-#if JSON_DIAGNOSTIC_POSITIONS
-/*!
-@brief set the diagnostic positions of a value the DOM SAX parsers just stored
-
-Shared by json_sax_dom_parser and json_sax_dom_callback_parser. basic_json
-befriends this struct, as the position members are private.
-*/
-struct diagnostic_positions
-{
-    /*!
-    @param[in,out] v  the value that was just parsed
-    @param[in] lexer  the lexer that read it, or nullptr to leave @a v alone
-    */
-    template<typename BasicJsonType, typename LexerType>
-    static void set_from_lexer(BasicJsonType& v, LexerType* lexer)
-    {
-        if (lexer)
-        {
-            // Lexer has read past the current field value, so set the end position to the current position.
-            // The start position will be set below based on the length of the string representation
-            // of the value.
-            v.end_position = lexer->get_position();
-
-            switch (v.type())
-            {
-                case value_t::boolean:
-                {
-                    // 4 and 5 are the string length of "true" and "false"
-                    v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
-                    break;
-                }
-
-                case value_t::null:
-                {
-                    // 4 is the string length of "null"
-                    v.start_position = v.end_position - 4;
-                    break;
-                }
-
-                case value_t::string:
-                {
-                    // escape sequences make the token longer than the value it
-                    // parses to, so the start position cannot be derived from
-                    // the value; use the offset the lexer recorded instead
-                    v.start_position = lexer->get_token_start_position();
-                    break;
-                }
-
-                case value_t::discarded:
-                {
-                    // an object or array the callback of
-                    // json_sax_dom_callback_parser rejected has no position
-                    v.end_position = std::string::npos;
-                    v.start_position = v.end_position;
-                    break;
-                }
-
-                case value_t::binary:
-                case value_t::number_integer:
-                case value_t::number_unsigned:
-                case value_t::number_float:
-                {
-                    v.start_position = v.end_position - lexer->get_string().size();
-                    break;
-                }
-
-                case value_t::object:
-                case value_t::array:
-                {
-                    // object and array are handled in start_object() and start_array() handlers
-                    // skip setting the values here.
-                    break;
-                }
-                default: // LCOV_EXCL_LINE
-                    // Handle all possible types discretely, default handler should never be reached.
-                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
-            }
-        }
-    }
-};
-#endif
-
 /*!
 @brief SAX implementation to create a JSON value from SAX events
 
@@ -459,6 +376,76 @@ class json_sax_dom_parser
 
   private:
 
+#if JSON_DIAGNOSTIC_POSITIONS
+    void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
+    {
+        if (m_lexer_ref)
+        {
+            // Lexer has read past the current field value, so set the end position to the current position.
+            // The start position will be set below based on the length of the string representation
+            // of the value.
+            v.end_position = m_lexer_ref->get_position();
+
+            switch (v.type())
+            {
+                case value_t::boolean:
+                {
+                    // 4 and 5 are the string length of "true" and "false"
+                    v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
+                    break;
+                }
+
+                case value_t::null:
+                {
+                    // 4 is the string length of "null"
+                    v.start_position = v.end_position - 4;
+                    break;
+                }
+
+                case value_t::string:
+                {
+                    // escape sequences make the token longer than the value it
+                    // parses to, so the start position cannot be derived from
+                    // the value; use the offset the lexer recorded instead
+                    v.start_position = m_lexer_ref->get_token_start_position();
+                    break;
+                }
+
+                // As we handle the start and end positions for values created during parsing,
+                // we do not expect the following value type to be called. Regardless, set the positions
+                // in case this is created manually or through a different constructor. Exclude from lcov
+                // since the exact condition of this switch is esoteric.
+                // LCOV_EXCL_START
+                case value_t::discarded:
+                {
+                    v.end_position = std::string::npos;
+                    v.start_position = v.end_position;
+                    break;
+                }
+                // LCOV_EXCL_STOP
+                case value_t::binary:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                {
+                    v.start_position = v.end_position - m_lexer_ref->get_string().size();
+                    break;
+                }
+                case value_t::object:
+                case value_t::array:
+                {
+                    // object and array are handled in start_object() and start_array() handlers
+                    // skip setting the values here.
+                    break;
+                }
+                default: // LCOV_EXCL_LINE
+                    // Handle all possible types discretely, default handler should never be reached.
+                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
+            }
+        }
+    }
+#endif
+
     /*!
     @invariant If the ref stack is empty, then the passed value will be the new
                root.
@@ -474,7 +461,7 @@ class json_sax_dom_parser
             root = BasicJsonType(std::forward<Value>(v));
 
 #if JSON_DIAGNOSTIC_POSITIONS
-            diagnostic_positions::set_from_lexer(root, m_lexer_ref);
+            handle_diagnostic_positions_for_json_value(root);
 #endif
 
             return &root;
@@ -487,7 +474,7 @@ class json_sax_dom_parser
             ref_stack.back()->m_data.m_value.array->emplace_back(std::forward<Value>(v));
 
 #if JSON_DIAGNOSTIC_POSITIONS
-            diagnostic_positions::set_from_lexer(ref_stack.back()->m_data.m_value.array->back(), m_lexer_ref);
+            handle_diagnostic_positions_for_json_value(ref_stack.back()->m_data.m_value.array->back());
 #endif
 
             return &(ref_stack.back()->m_data.m_value.array->back());
@@ -498,7 +485,7 @@ class json_sax_dom_parser
         *object_element = BasicJsonType(std::forward<Value>(v));
 
 #if JSON_DIAGNOSTIC_POSITIONS
-        diagnostic_positions::set_from_lexer(*object_element, m_lexer_ref);
+        handle_diagnostic_positions_for_json_value(*object_element);
 #endif
 
         return object_element;
@@ -675,7 +662,7 @@ class json_sax_dom_callback_parser
 
 #if JSON_DIAGNOSTIC_POSITIONS
                     // Set start/end positions for discarded object.
-                    diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
+                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
                 }
             }
@@ -791,7 +778,7 @@ class json_sax_dom_callback_parser
 
 #if JSON_DIAGNOSTIC_POSITIONS
                     // Set start/end positions for discarded array.
-                    diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
+                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
                 }
             }
@@ -844,6 +831,72 @@ class json_sax_dom_callback_parser
 
   private:
 
+#if JSON_DIAGNOSTIC_POSITIONS
+    void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
+    {
+        if (m_lexer_ref)
+        {
+            // Lexer has read past the current field value, so set the end position to the current position.
+            // The start position will be set below based on the length of the string representation
+            // of the value.
+            v.end_position = m_lexer_ref->get_position();
+
+            switch (v.type())
+            {
+                case value_t::boolean:
+                {
+                    // 4 and 5 are the string length of "true" and "false"
+                    v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
+                    break;
+                }
+
+                case value_t::null:
+                {
+                    // 4 is the string length of "null"
+                    v.start_position = v.end_position - 4;
+                    break;
+                }
+
+                case value_t::string:
+                {
+                    // escape sequences make the token longer than the value it
+                    // parses to, so the start position cannot be derived from
+                    // the value; use the offset the lexer recorded instead
+                    v.start_position = m_lexer_ref->get_token_start_position();
+                    break;
+                }
+
+                case value_t::discarded:
+                {
+                    v.end_position = std::string::npos;
+                    v.start_position = v.end_position;
+                    break;
+                }
+
+                case value_t::binary:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                {
+                    v.start_position = v.end_position - m_lexer_ref->get_string().size();
+                    break;
+                }
+
+                case value_t::object:
+                case value_t::array:
+                {
+                    // object and array are handled in start_object() and start_array() handlers
+                    // skip setting the values here.
+                    break;
+                }
+                default: // LCOV_EXCL_LINE
+                    // Handle all possible types discretely, default handler should never be reached.
+                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
+            }
+        }
+    }
+#endif
+
     /// if there is a pending duplicate-key stash entry for this exact slot,
     /// remove it from the stash; if restore_value is true, the stashed
     /// previous value is moved back into the slot first (use this when the
@@ -965,7 +1018,7 @@ class json_sax_dom_callback_parser
         auto value = BasicJsonType(std::forward<Value>(v));
 
 #if JSON_DIAGNOSTIC_POSITIONS
-        diagnostic_positions::set_from_lexer(value, m_lexer_ref);
+        handle_diagnostic_positions_for_json_value(value);
 #endif
 
         // check callback

include/nlohmann/detail/input/lexer.hpp

@@ -11,7 +11,6 @@
 #include <array> // array
 #include <clocale> // localeconv
 #include <cstddef> // size_t
-#include <cstdint> // uint32_t
 #include <cstdio> // snprintf
 #include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
 #include <initializer_list> // initializer_list
@@ -25,7 +24,6 @@
 #include <nlohmann/detail/input/string_scan.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
-#include <nlohmann/detail/string_utils.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -502,10 +500,32 @@ class lexer : public lexer_base<BasicJsonType>
                             JSON_ASSERT(0x00 <= codepoint && codepoint <= 0x10FFFF);
 
                             // translate codepoint into bytes
-                            encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
+                            if (codepoint < 0x80)
                             {
-                                add(static_cast<char_int_type>(byte));
-                            });
+                                // 1-byte characters: 0xxxxxxx (ASCII)
+                                add(static_cast<char_int_type>(codepoint));
+                            }
+                            else if (codepoint <= 0x7FF)
+                            {
+                                // 2-byte characters: 110xxxxx 10xxxxxx
+                                add(static_cast<char_int_type>(0xC0u | (static_cast<unsigned int>(codepoint) >> 6u)));
+                                add(static_cast<char_int_type>(0x80u | (static_cast<unsigned int>(codepoint) & 0x3Fu)));
+                            }
+                            else if (codepoint <= 0xFFFF)
+                            {
+                                // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx
+                                add(static_cast<char_int_type>(0xE0u | (static_cast<unsigned int>(codepoint) >> 12u)));
+                                add(static_cast<char_int_type>(0x80u | ((static_cast<unsigned int>(codepoint) >> 6u) & 0x3Fu)));
+                                add(static_cast<char_int_type>(0x80u | (static_cast<unsigned int>(codepoint) & 0x3Fu)));
+                            }
+                            else
+                            {
+                                // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+                                add(static_cast<char_int_type>(0xF0u | (static_cast<unsigned int>(codepoint) >> 18u)));
+                                add(static_cast<char_int_type>(0x80u | ((static_cast<unsigned int>(codepoint) >> 12u) & 0x3Fu)));
+                                add(static_cast<char_int_type>(0x80u | ((static_cast<unsigned int>(codepoint) >> 6u) & 0x3Fu)));
+                                add(static_cast<char_int_type>(0x80u | (static_cast<unsigned int>(codepoint) & 0x3Fu)));
+                            }
 
                             break;
                         }
@@ -1474,30 +1494,45 @@ scan_number_done:
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
-        // accept() only needs to know whether the input is valid, so it sets
-        // discard_number_values (see json.hpp), and an integer token whose
-        // digit count shows that it fits is reported without calling
-        // convert_integer(). A number with up to 18 digits always fits into
-        // both std::uint64_t and std::int64_t (18 nines is about 1e18, below
-        // INT64_MAX, which is about 9.2e18). Longer tokens take the exact path
-        // below, including the fallback to floating point when the value does
-        // not fit.
+        // If the caller does not need the converted value (only whether the
+        // input is syntactically valid; see json_sax_acceptor/accept()), an
+        // unsigned/integer token can be reported without calling
+        // strtoull()/strtoll() at all, *provided* we can already tell from
+        // the digit count alone that the conversion cannot overflow 64 bits.
+        // Such tokens are always finite and are accepted unconditionally by
+        // the parser regardless of their actual value (parser::sax_parse_internal()
+        // never checks finiteness for value_unsigned/value_integer), so the
+        // classification below is all that is needed.
         //
-        // With a narrower number_unsigned_t/number_integer_t (e.g.
-        // std::uint32_t), the exact path would reclassify some of these tokens
-        // as (finite) floats, while this check reports integers. That does not
-        // change the result of accept(): it always parses through
-        // json_sax_acceptor, whose number callbacks discard their argument and
-        // return true, and the parser rejects neither integers nor finite
-        // floats. value_unsigned/value_integer are left unset here, so a caller
-        // that reads the converted value must not set discard_number_values.
+        // A decimal number with up to 18 digits is always representable in
+        // both std::uint64_t and std::int64_t (18 nines is ~1e18, well below
+        // both UINT64_MAX ~1.8e19 and INT64_MAX ~9.2e18), so strtoull()/strtoll()
+        // could not have set errno to ERANGE for it. Numbers with more digits
+        // (rare in practice) fall through to the exact code below, unchanged,
+        // so their handling -- including reclassification to value_float when
+        // the value overflows 64 bits, and rejection when it is not even
+        // finite as a double -- is bit-for-bit identical to before this
+        // optimization.
         //
-        // On contiguous input, scan_number_bulk_contiguous() converts integer
-        // tokens itself and does not pass them to this function, unless
-        // JSON_DIAGNOSTIC_POSITIONS is enabled. This check is therefore only
-        // reached for input without bulk access (e.g. streams), with
-        // JSON_DIAGNOSTIC_POSITIONS, or when scan_number_bulk_contiguous()
-        // falls back to scan_number().
+        // Note this reasons about std::uint64_t/std::int64_t, not about
+        // number_unsigned_t/number_integer_t (BasicJsonType's own, possibly
+        // narrower, template parameters -- e.g. std::uint32_t). That is fine
+        // *only* because discard_number_values is exclusively set by
+        // accept() (see json.hpp), and accept() always parses through the
+        // library's own json_sax_acceptor -- never a user-supplied SAX
+        // consumer -- whose number_unsigned()/number_integer()/number_float()
+        // callbacks unconditionally discard their argument and return true.
+        // So for every caller that can reach this branch, neither the token
+        // classification below nor the eventual (possibly narrowed, and on
+        // this fast path left stale/unset) value_unsigned/value_integer is
+        // ever consulted -- an unsigned/integer token is accepted outright,
+        // and even a >18-digit token that this fast path deliberately falls
+        // through for is, once reclassified to value_float, still finite
+        // (and thus accepted) for any digit count that fits in number_unsigned_t
+        // or number_integer_t regardless of that type's width. If this
+        // function is ever taught to run with discard_number_values true for
+        // a caller that *does* read the converted value, this reasoning (and
+        // the fast path below) would need to be revisited.
         if (discard_number_values)
         {
             constexpr std::size_t safe_digit_count = 18;
@@ -1988,7 +2023,7 @@ scan_number_done:
         return value_float;
     }
 
-    /// return current string value
+    /// return current string value (implicitly resets the token; useful only once)
     string_t& get_string()
     {
         // a number token holds '.' regardless of the locale (#4084)
@@ -2290,11 +2325,11 @@ scan_number_done:
     /// the position of the decimal point in token_buffer
     std::size_t decimal_point_position = std::string::npos;
 
-    /// whether the caller only needs the token types and never looks at the
-    /// converted numeric values; set only by accept(), which parses through
-    /// json_sax_acceptor. When set, convert_number() skips converting integer
-    /// tokens whose digit count guarantees that they fit into 64 bits (see
-    /// there)
+    /// whether the caller (e.g. accept()/json_sax_acceptor) only needs the
+    /// token classification and never looks at the converted numeric value;
+    /// when set, scan_number() may skip strtoull()/strtoll() for
+    /// value_unsigned/value_integer tokens whose digit count guarantees they
+    /// fit into 64 bits (see scan_number())
     const bool discard_number_values = false;
 };
 

include/nlohmann/detail/input/parser.hpp

@@ -54,8 +54,7 @@ using parser_callback_t =
 /*!
 @brief syntax analysis
 
-This class implements an iterative parser that keeps the open containers on
-an explicit stack and reports what it reads as SAX events.
+This class implements a recursive descent parser.
 */
 template<typename BasicJsonType, typename InputAdapterType>
 class parser
@@ -99,9 +98,28 @@ class parser
         if (callback)
         {
             json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
+            sax_parse_internal(&sdp);
+
+            if (strict)
+            {
+                // in strict mode, input must be completely read
+                if (get_token() != token_type::end_of_input)
+                {
+                    sdp.parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(),
+                                                        exception_message(token_type::end_of_input, "value"), nullptr));
+                }
+            }
+            else
+            {
+                // the caller keeps using the input: position it right after
+                // the value by leaving the character that terminated it
+                m_lexer.release_lookahead();
+            }
 
             // in case of an error, return a discarded value
-            if (!parse_dom(sdp, strict))
+            if (sdp.is_errored())
             {
                 result = value_t::discarded;
                 return;
@@ -117,9 +135,26 @@ class parser
         else
         {
             json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
+            sax_parse_internal(&sdp);
+
+            if (strict)
+            {
+                // in strict mode, input must be completely read
+                if (get_token() != token_type::end_of_input)
+                {
+                    sdp.parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
+                }
+            }
+            else
+            {
+                // see above
+                m_lexer.release_lookahead();
+            }
 
             // in case of an error, return a discarded value
-            if (!parse_dom(sdp, strict))
+            if (sdp.is_errored())
             {
                 result = value_t::discarded;
                 return;
@@ -172,46 +207,6 @@ class parser
     }
 
   private:
-    /*!
-    @brief run a DOM SAX parser to completion and position the lexer
-
-    Shared by both branches of @ref parse(): builds no SAX parser itself,
-    but drives an already-constructed @a json_sax_dom_parser or
-    @ref json_sax_dom_callback_parser through @ref sax_parse_internal(),
-    then applies the strict-EOF check (reporting parse_error.101 through
-    @a sdp on failure) or, in non-strict mode, releases the lookahead so
-    the caller can keep reading the input right after the parsed value.
-
-    @param[in,out] sdp     the DOM SAX parser to run
-    @param[in] strict      whether to expect the last token to be EOF
-    @return whether @a sdp did not report an error
-    */
-    template<typename DomSax>
-    bool parse_dom(DomSax& sdp, const bool strict)
-    {
-        sax_parse_internal(&sdp);
-
-        if (strict)
-        {
-            // in strict mode, input must be completely read
-            if (get_token() != token_type::end_of_input)
-            {
-                sdp.parse_error(m_lexer.get_position(),
-                                m_lexer.get_token_string(),
-                                parse_error::create(101, m_lexer.get_position(),
-                                                    exception_message(token_type::end_of_input, "value"), nullptr));
-            }
-        }
-        else
-        {
-            // the caller keeps using the input: position it right after
-            // the value by leaving the character that terminated it
-            m_lexer.release_lookahead();
-        }
-
-        return !sdp.is_errored();
-    }
-
     template<typename SAX>
     JSON_HEDLEY_NON_NULL(2)
     bool sax_parse_internal(SAX* sax)
@@ -444,9 +439,8 @@ class parser
 
                     // We are done with this array. Before we can parse a
                     // new value, we need to evaluate the new state first.
-                    // By setting skip_to_state_evaluation to true, the next
-                    // iteration skips parsing a value and evaluates the
-                    // enclosing state directly.
+                    // By setting skip_to_state_evaluation to false, we
+                    // are effectively jumping to the beginning of this if.
                     JSON_ASSERT(!states.empty());
                     states.pop_back();
                     skip_to_state_evaluation = true;
@@ -506,9 +500,8 @@ class parser
 
                 // We are done with this object. Before we can parse a
                 // new value, we need to evaluate the new state first.
-                // By setting skip_to_state_evaluation to true, the next
-                // iteration skips parsing a value and evaluates the
-                // enclosing state directly.
+                // By setting skip_to_state_evaluation to false, we
+                // are effectively jumping to the beginning of this if.
                 JSON_ASSERT(!states.empty());
                 states.pop_back();
                 skip_to_state_evaluation = true;

include/nlohmann/detail/string_concat.hpp

@@ -39,7 +39,6 @@ inline std::size_t concat_length(const char /*c*/, const Args& ... rest)
 template<typename... Args>
 inline std::size_t concat_length(const char* cstr, const Args& ... rest)
 {
-    // cppcheck-suppress ignoredReturnValue
     return ::strlen(cstr) + concat_length(rest...);
 }
 

include/nlohmann/detail/string_utils.hpp

@@ -36,61 +36,6 @@ StringType to_string(std::size_t value)
     return result;
 }
 
-///////////////////
-// UTF-8 encoding //
-///////////////////
-
-/*!
-@brief encode a Unicode code point as UTF-8
-
-Used to turn a decoded code point back into bytes: by the wide-string input
-adapters in input_adapters.hpp (one code point per UTF-32 unit, per UTF-16
-unit outside the surrogate range, and per valid UTF-16 surrogate pair), and
-by the lexer's `\uXXXX`/`\uXXXX\uYYYY` handling in lexer.hpp. Passing a
-code point above U+10FFFF, or one in the surrogate range U+D800..U+DFFF, is
-undefined behavior; callers are expected to have rejected those already
-(the wide-string adapters pass malformed units through unencoded instead of
-calling this function, and the lexer rejects unpaired surrogates before
-reaching it).
-
-@tparam Out    a callable invoked with one byte (as std::uint32_t, 0x00..0xFF)
-               at a time, most significant byte first
-@param[in] cp   the code point to encode (at most U+10FFFF)
-@param[in] out  called once for each byte of the UTF-8 encoding of @a cp
-*/
-template<typename Out>
-void encode_utf8(std::uint32_t cp, Out&& out)
-{
-    JSON_ASSERT(cp <= 0x10FFFF);
-
-    if (cp < 0x80)
-    {
-        // 1-byte characters: 0xxxxxxx (ASCII)
-        out(cp);
-    }
-    else if (cp <= 0x7FF)
-    {
-        // 2-byte characters: 110xxxxx 10xxxxxx
-        out(0xC0u | (cp >> 6u));
-        out(0x80u | (cp & 0x3Fu));
-    }
-    else if (cp <= 0xFFFF)
-    {
-        // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx
-        out(0xE0u | (cp >> 12u));
-        out(0x80u | ((cp >> 6u) & 0x3Fu));
-        out(0x80u | (cp & 0x3Fu));
-    }
-    else
-    {
-        // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
-        out(0xF0u | (cp >> 18u));
-        out(0x80u | ((cp >> 12u) & 0x3Fu));
-        out(0x80u | ((cp >> 6u) & 0x3Fu));
-        out(0x80u | (cp & 0x3Fu));
-    }
-}
-
 ///////////////////
 // UTF-8 decoding //
 ///////////////////
@@ -106,23 +51,11 @@ This is a single-byte step of a "shift-based" UTF-8 decoder originally
 written by Björn Hoehrmann. See
 http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
 
-The library checks UTF-8 well-formedness (RFC 3629, section 4) in four
-places, which differ in speed, diagnostics, and how they read the input:
-
-- decode() and @ref is_valid_utf8 below: the serializer (to escape and, in
-  strict mode, reject ill-formed UTF-8 when dumping a string) and the CBOR,
-  MessagePack, BSON, UBJSON and BJData readers (to reject ill-formed UTF-8 in
-  text strings at decode time).
-- the per-lead-byte switch in lexer::scan_string(): JSON text, with a
-  diagnostic for each kind of error.
-- validate_one_utf8() and valid_utf8_prefix() in string_scan.hpp: the lexer's
-  bulk string scan, the bulk path of the BON8 reader, and the BON8 writer.
-  They must accept exactly what the lexer's switch accepts.
-- the byte path of binary_reader::get_bon8_string(): BON8 input without bulk
-  access, and the bytes the bulk path leaves to it.
-
-All four must accept the same set of sequences, so a change to one needs a
-matching change to the others.
+This decoder is the single source of truth for UTF-8 validation in this
+library: it is used both by the serializer (to escape and, in strict mode,
+reject ill-formed UTF-8 when dumping a string) and by the binary readers
+(to reject ill-formed UTF-8 in CBOR/MessagePack/BSON/UBJSON text strings at
+decode time; see @ref is_valid_utf8 below).
 
 @param[in,out] state  the current decoder state
 @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)

include/nlohmann/ordered_map.hpp

@@ -70,14 +70,41 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
         return *this;
     }
 
+private:
+    /// @brief find the entry for @a key, for either constness of @a self
+    /// @note the single place that performs the linear key search
+    template<typename Self, typename KeyType>
+    static auto find_impl(Self& self, KeyType&& key) -> decltype(self.begin())
+    {
+        for (auto it = self.begin(); it != self.end(); ++it)
+        {
+            if (self.m_compare(it->first, key))
+            {
+                return it;
+            }
+        }
+        return self.end();
+    }
+
+    /// @brief remove the entry @a it points to, preserving order
+    /// @note keys are not movable, so the tail is destroyed and re-constructed in place
+    void erase_at(iterator it)
+    {
+        for (auto next = it; ++next != this->end(); ++it)
+        {
+            it->~value_type(); // Destroy but keep allocation
+            new (&*it) value_type{std::move(*next)};
+        }
+        Container::pop_back();
+    }
+
+public:
     std::pair<iterator, bool> emplace(const key_type& key, T&& t)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return {it, false};
-            }
+            return {it, false};
         }
         Container::emplace_back(key, std::forward<T>(t));
         return {std::prev(this->end()), true};
@@ -87,12 +114,10 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     std::pair<iterator, bool> emplace(KeyType && key, T && t)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return {it, false};
-            }
+            return {it, false};
         }
         Container::emplace_back(std::forward<KeyType>(key), std::forward<T>(t));
         return {std::prev(this->end()), true};
@@ -124,75 +149,55 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
 
     T& at(const key_type& key)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return it->second;
-            }
+            JSON_THROW(std::out_of_range("key not found"));
         }
-
-        JSON_THROW(std::out_of_range("key not found"));
+        return it->second;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     T & at(KeyType && key) // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return it->second;
-            }
+            JSON_THROW(std::out_of_range("key not found"));
         }
-
-        JSON_THROW(std::out_of_range("key not found"));
+        return it->second;
     }
 
     const T& at(const key_type& key) const
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return it->second;
-            }
+            JSON_THROW(std::out_of_range("key not found"));
         }
-
-        JSON_THROW(std::out_of_range("key not found"));
+        return it->second;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     const T & at(KeyType && key) const // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                return it->second;
-            }
+            JSON_THROW(std::out_of_range("key not found"));
         }
-
-        JSON_THROW(std::out_of_range("key not found"));
+        return it->second;
     }
 
     size_type erase(const key_type& key)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                // Since we cannot move const Keys, re-construct them in place
-                for (auto next = it; ++next != this->end(); ++it)
-                {
-                    it->~value_type(); // Destroy but keep allocation
-                    new (&*it) value_type{std::move(*next)};
-                }
-                Container::pop_back();
-                return 1;
-            }
+            erase_at(it);
+            return 1;
         }
         return 0;
     }
@@ -201,19 +206,11 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     size_type erase(KeyType && key) // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, key);
+        if (it != this->end())
         {
-            if (m_compare(it->first, key))
-            {
-                // Since we cannot move const Keys, re-construct them in place
-                for (auto next = it; ++next != this->end(); ++it)
-                {
-                    it->~value_type(); // Destroy but keep allocation
-                    new (&*it) value_type{std::move(*next)};
-                }
-                Container::pop_back();
-                return 1;
-            }
+            erase_at(it);
+            return 1;
         }
         return 0;
     }
@@ -278,80 +275,38 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
 
     size_type count(const key_type& key) const
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return 1;
-            }
-        }
-        return 0;
+        return find_impl(*this, key) != this->end() ? 1 : 0;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     size_type count(KeyType && key) const // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return 1;
-            }
-        }
-        return 0;
+        return find_impl(*this, key) != this->end() ? 1 : 0;
     }
 
     iterator find(const key_type& key)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return it;
-            }
-        }
-        return Container::end();
+        return find_impl(*this, key);
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     iterator find(KeyType && key) // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return it;
-            }
-        }
-        return Container::end();
+        return find_impl(*this, key);
     }
 
     const_iterator find(const key_type& key) const
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return it;
-            }
-        }
-        return Container::end();
+        return find_impl(*this, key);
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     const_iterator find(KeyType && key) const // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
-        {
-            if (m_compare(it->first, key))
-            {
-                return it;
-            }
-        }
-        return Container::end();
+        return find_impl(*this, key);
     }
 
     std::pair<iterator, bool> insert( value_type&& value )
@@ -361,12 +316,10 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
 
     std::pair<iterator, bool> insert( const value_type& value )
     {
-        for (auto it = this->begin(); it != this->end(); ++it)
+        const auto it = find_impl(*this, value.first);
+        if (it != this->end())
         {
-            if (m_compare(it->first, value.first))
-            {
-                return {it, false};
-            }
+            return {it, false};
         }
         Container::push_back(value);
         return {--this->end(), true};

tests/src/unit-class_parser.cpp

@@ -2525,12 +2525,10 @@ TEST_CASE("diagnostic positions: value lifetime, input adapters, and SAX")
 
         SECTION("move constructor resets the moved-from value to npos")
         {
-            // basic_json(basic_json&&) (json.hpp, around line 1265) copies
+            // basic_json(basic_json&&) (json.hpp, around line 1944) copies
             // other's start_position/end_position into *this and then resets
-            // other's to npos (see the cppcheck-suppress[accessForwarded]
-            // annotation there, which flags this reset as worth a second
-            // look). Only the top-level moved-from value is affected; its
-            // (moved-away) children are gone along with it.
+            // other's to npos. Only the top-level moved-from value is
+            // affected; its (moved-away) children are gone along with it.
             const std::string s = R"({"a":1,"b":[1,2,3]})";
             json a = json::parse(s);
             const auto a_start = a.start_pos();

tests/src/unit-modifiers.cpp

@@ -618,6 +618,49 @@ TEST_CASE("modifiers")
             }
         }
 
+        SECTION("rvalue at position moves rather than copies")
+        {
+            // regression test: insert(pos, basic_json&&) used to forward to
+            // insert(pos, const basic_json&) because the named rvalue
+            // reference parameter is itself an lvalue, so it always
+            // deep-copied its argument instead of moving it
+            json j_big = std::string(1000, 'x');
+            const auto* const original_buffer = j_big.get_ref<const std::string&>().data();
+
+            auto it = j_array.insert(j_array.begin(), std::move(j_big));
+            CHECK(j_array.size() == 5);
+            CHECK(*it == json(std::string(1000, 'x')));
+            CHECK((*it).get_ref<const std::string&>().data() == original_buffer);
+
+            // the moved-from value is null, the same as after push_back(&&)
+            CHECK(j_big.is_null()); // NOLINT(bugprone-use-after-move,hicpp-invalid-access-moved)
+        }
+
+        SECTION("self-aliasing insertion")
+        {
+            SECTION("without reallocation")
+            {
+                json j_self = {1, 2, 3, 4};
+                j_self.get_ref<json::array_t&>().reserve(j_self.size() + 1);
+
+                auto it = j_self.insert(j_self.begin(), std::move(j_self[1]));
+                CHECK(j_self.size() == 5);
+                CHECK(*it == json(2));
+                CHECK(j_self == json({2, 1, nullptr, 3, 4}));
+            }
+
+            SECTION("with reallocation")
+            {
+                json j_self = {1, 2, 3, 4};
+                j_self.get_ref<json::array_t&>().shrink_to_fit();
+
+                auto it = j_self.insert(j_self.begin(), std::move(j_self[1]));
+                CHECK(j_self.size() == 5);
+                CHECK(*it == json(2));
+                CHECK(j_self == json({2, 1, nullptr, 3, 4}));
+            }
+        }
+
         SECTION("copies at position")
         {
             SECTION("insert before begin()")