Merge branch 'develop' into fix/scalar-comparison-noexcept

Conflict in operator_ne.md: took develop's corrected page (#5638 documents that there is no C++20 member operator!=) and re-added this branch's conditional noexcept for overload (2) and its version history note. Ran make amalgamate.

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

docs/mkdocs/docs/api/basic_json/operator_eq.md

@@ -5,17 +5,17 @@
 bool operator==(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator==(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator==(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator==(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator==(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 
 // since C++20
 class basic_json {
     bool operator==(const_reference rhs) const noexcept;              // (1)
 
     template<typename ScalarType>
-    bool operator==(ScalarType rhs) const noexcept;                   // (2)
+    bool operator==(ScalarType rhs) const noexcept(/* see below */); // (2)
 };
 ```
 
@@ -46,7 +46,12 @@ whether the values `lhs`/`*this` and `rhs` are equal
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -171,3 +176,4 @@ Linear.
 
 1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
 2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_ge.md

@@ -5,10 +5,10 @@
 bool operator>=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator>=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator>=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator>=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator>=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is greater than or equal to another JSON value `rhs` according to the following
@@ -39,7 +39,12 @@ whether `lhs` is greater than or equal to `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -94,3 +99,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_gt.md

@@ -5,10 +5,10 @@
 bool operator>(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator>(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator>(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator>(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator>(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is greater than another JSON value `rhs` according to the
@@ -39,7 +39,12 @@ whether `lhs` is greater than `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -84,3 +89,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_le.md

@@ -5,10 +5,10 @@
 bool operator<=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator<=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator<=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator<=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator<=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is less than or equal to another JSON value `rhs`
@@ -40,7 +40,12 @@ whether `lhs` is less than or equal to `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -95,3 +100,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_lt.md

@@ -5,10 +5,10 @@
 bool operator<(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator<(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator<(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator<(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator<(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is less than another JSON value `rhs` according to the
@@ -49,7 +49,12 @@ whether `lhs` is less than `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -94,3 +99,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_ne.md

@@ -5,10 +5,10 @@
 bool operator!=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator!=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator!=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator!=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator!=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares two JSON values for inequality. Returns `#!cpp !(lhs == rhs)`.
@@ -36,7 +36,12 @@ whether the values `lhs`/`*this` and `rhs` are not equal
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -98,3 +103,4 @@ Linear.
    member function in version 3.13.0; since C++20, the compiler rewrites `a != b` using `operator==`.
 2. Added in version 1.0.0. Changed in version 3.13.0 to remove special-casing for `NaN` and `discarded` values;
    `operator!=` now consistently means `!(a == b)`. Since C++20, the compiler rewrites `a != b` using `operator==`.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

docs/mkdocs/docs/api/basic_json/operator_spaceship.md

@@ -6,7 +6,7 @@ class basic_json {
     std::partial_ordering operator<=>(const_reference rhs) const noexcept;  // (1)
 
     template<typename ScalarType>
-    std::partial_ordering operator<=>(const ScalarType rhs) const noexcept; // (2)
+    std::partial_ordering operator<=>(const ScalarType rhs) const noexcept(/* see below */); // (2)
 };
 ```
 
@@ -39,7 +39,12 @@ the `std::partial_ordering` of the 3-way comparison of `*this` and `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -98,3 +103,4 @@ Linear.
 
 1. Added in version 3.11.0.
 2. Added in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

include/nlohmann/json.hpp

@@ -4865,7 +4865,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator==(ScalarType rhs) const noexcept
+    bool operator==(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this == basic_json(rhs);
     }
@@ -4888,7 +4888,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_spaceship/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    std::partial_ordering operator<=>(ScalarType rhs) const noexcept // *NOPAD*
+    std::partial_ordering operator<=>(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value) // *NOPAD*
     {
         return *this <=> basic_json(rhs); // *NOPAD*
     }
@@ -4913,7 +4913,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator<=(ScalarType rhs) const noexcept
+    bool operator<=(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this <= basic_json(rhs);
     }
@@ -4934,7 +4934,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator>=(ScalarType rhs) const noexcept
+    bool operator>=(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this >= basic_json(rhs);
     }
@@ -4959,7 +4959,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator==(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator==(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs == basic_json(rhs);
     }
@@ -4968,7 +4968,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator==(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator==(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) == rhs;
     }
@@ -4984,7 +4984,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ne/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator!=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator!=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs != basic_json(rhs);
     }
@@ -4993,7 +4993,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ne/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator!=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator!=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) != rhs;
     }
@@ -5013,7 +5013,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_lt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator<(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs < basic_json(rhs);
     }
@@ -5022,7 +5022,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_lt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator<(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) < rhs;
     }
@@ -5042,7 +5042,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator<=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs <= basic_json(rhs);
     }
@@ -5051,7 +5051,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) <= rhs;
     }
@@ -5072,7 +5072,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator>(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs > basic_json(rhs);
     }
@@ -5081,7 +5081,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator>(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) > rhs;
     }
@@ -5101,7 +5101,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator>=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs >= basic_json(rhs);
     }
@@ -5110,7 +5110,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) >= rhs;
     }

single_include/nlohmann/json.hpp

@@ -31564,7 +31564,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator==(ScalarType rhs) const noexcept
+    bool operator==(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this == basic_json(rhs);
     }
@@ -31587,7 +31587,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_spaceship/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    std::partial_ordering operator<=>(ScalarType rhs) const noexcept // *NOPAD*
+    std::partial_ordering operator<=>(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value) // *NOPAD*
     {
         return *this <=> basic_json(rhs); // *NOPAD*
     }
@@ -31612,7 +31612,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator<=(ScalarType rhs) const noexcept
+    bool operator<=(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this <= basic_json(rhs);
     }
@@ -31633,7 +31633,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    bool operator>=(ScalarType rhs) const noexcept
+    bool operator>=(ScalarType rhs) const noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return *this >= basic_json(rhs);
     }
@@ -31658,7 +31658,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator==(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator==(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs == basic_json(rhs);
     }
@@ -31667,7 +31667,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_eq/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator==(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator==(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) == rhs;
     }
@@ -31683,7 +31683,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ne/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator!=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator!=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs != basic_json(rhs);
     }
@@ -31692,7 +31692,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ne/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator!=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator!=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) != rhs;
     }
@@ -31712,7 +31712,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_lt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator<(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs < basic_json(rhs);
     }
@@ -31721,7 +31721,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_lt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator<(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) < rhs;
     }
@@ -31741,7 +31741,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator<=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs <= basic_json(rhs);
     }
@@ -31750,7 +31750,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) <= rhs;
     }
@@ -31771,7 +31771,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator>(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs > basic_json(rhs);
     }
@@ -31780,7 +31780,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gt/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator>(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) > rhs;
     }
@@ -31800,7 +31800,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>=(const_reference lhs, ScalarType rhs) noexcept
+    friend bool operator>=(const_reference lhs, ScalarType rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return lhs >= basic_json(rhs);
     }
@@ -31809,7 +31809,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType, typename std::enable_if<
                  std::is_scalar<ScalarType>::value, int>::type = 0>
-    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) >= rhs;
     }

tests/src/unit-conversions.cpp

@@ -1764,6 +1764,12 @@ TEST_CASE("Strict JSON to enum mapping")
         CHECK(json("herz").get<strict_cards>() == strict_cards::herz);
         CHECK(json("karo").get<strict_cards>() == strict_cards::karo);
 
+        // comparison of enum and json
+        CHECK(strict_cards::kreuz == json("kreuz"));
+        CHECK(strict_cards::pik == json("pik"));
+        CHECK(strict_cards::herz == json("herz"));
+        CHECK(strict_cards::karo == json("karo"));
+
         // invalid json -> exception thrown
         json _;
         CHECK_THROWS_WITH_AS(_ = json("what?").get<strict_cards>(), "[json.exception.out_of_range.410] enum value out of range for strict_cards: \"what?\"", json::out_of_range&);
@@ -1771,6 +1777,12 @@ TEST_CASE("Strict JSON to enum mapping")
         // conversion of unmapped enum -> exception thrown
         CHECK_THROWS_WITH_AS(json(strict_cards::andere), "[json.exception.out_of_range.410] enum value out of range for strict_cards", json::out_of_range&);
 
+        // comparing an unmapped enum with json throws the same exception
+        // (the scalar comparison operators used to be noexcept, so this
+        // called std::terminate)
+        CHECK_THROWS_WITH_AS(static_cast<void>(strict_cards::andere == json("andere")), "[json.exception.out_of_range.410] enum value out of range for strict_cards", json::out_of_range&);
+        CHECK_THROWS_WITH_AS(static_cast<void>(json("andere") != strict_cards::andere), "[json.exception.out_of_range.410] enum value out of range for strict_cards", json::out_of_range&);
+
         // invalid UTF-8 -> out_of_range.410, not the type_error.316 thrown while building the
         // message (regression test for #5667); such strings can reach get<Enum>() unvalidated,
         // e.g. from from_cbor()/from_msgpack() (#5529)
@@ -1792,12 +1804,21 @@ TEST_CASE("Strict JSON to enum mapping")
         CHECK(json("completed").get<StrictTaskState>() == STRICT_TS_COMPLETED);
         CHECK(json().get<StrictTaskState>() == STRICT_TS_INVALID);
 
+        // comparison of enum and json
+        CHECK(STRICT_TS_STOPPED == json("stopped"));
+        CHECK(STRICT_TS_RUNNING == json("running"));
+        CHECK(STRICT_TS_COMPLETED == json("completed"));
+        CHECK(STRICT_TS_INVALID == json());
+
         // invalid json -> exception thrown
         json _;
         CHECK_THROWS_WITH_AS(_ = json("what?").get<StrictTaskState>(), "[json.exception.out_of_range.410] enum value out of range for StrictTaskState: \"what?\"", json::out_of_range&);
 
         // conversion of unmapped enum -> exception thrown
         CHECK_THROWS_WITH_AS(json(STRICT_TS_OTHER), "[json.exception.out_of_range.410] enum value out of range for StrictTaskState", json::out_of_range&);
+
+        // comparing an unmapped enum with json throws the same exception
+        CHECK_THROWS_WITH_AS(static_cast<void>(STRICT_TS_OTHER < json("x")), "[json.exception.out_of_range.410] enum value out of range for StrictTaskState", json::out_of_range&);
     }
 }
 

tests/src/unit-noexcept.cpp

@@ -54,6 +54,15 @@ static_assert(noexcept(json(pod {})), "");
 static_assert(noexcept(std::declval<json>().get<pod>()), "");
 static_assert(!noexcept(std::declval<json>().get<pod_bis>()), "");
 static_assert(noexcept(json(pod{})), "");
+
+// comparing with a scalar is noexcept exactly when converting the scalar is
+static_assert(noexcept(std::declval<const json&>() == 1), "");
+static_assert(noexcept(1 != std::declval<const json&>()), "");
+static_assert(noexcept(std::declval<const json&>() < 2.5), "");
+static_assert(noexcept(nullptr == std::declval<const json&>()), "");
+static_assert(!noexcept(std::declval<const json&>() == "foo"), "");
+static_assert(!noexcept("foo" >= std::declval<const json&>()), "");
+static_assert(noexcept(std::declval<const json&>() == std::declval<const json&>()), "");
 } // namespace
 
 TEST_CASE("noexcept")