Make scalar comparisons noexcept only when converting the scalar cannot throw

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;
     }