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tests/unit-iterators2: use std::ranges::equals for range comparisons - #3950
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This fixes a build error on GCC 13:
/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp: In function ‘void _DOCTEST_ANON_FUNC_2()’:
/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp:946:32: error: no match for ‘operator==’ (operand types are ‘doctest::detail::Expression_lhs<std::ranges::reverse_view<std::ranges::ref_view<nlohmann::json_abi_v3_11_2::basic_json<> > >&>’ and ‘nlohmann::json_abi_v3_11_2::json’ {aka ‘nlohmann::json_abi_v3_11_2::basic_json<>’})
946 | CHECK(reversed == j_expected);
| ^~ ~~~~~~~~~~
| |
| nlohmann::json_abi_v3_11_2::json {aka nlohmann::json_abi_v3_11_2::basic_json<>}
Bug: https://bugs.gentoo.org/895692
Closes: nlohmann#3927
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nlohmann
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…nthesis Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's rewritten-candidate synthesis for operator==, preventing heterogeneous comparisons like `std::string s; json j; s == j;` from compiling. Fix by removing the hand-written operator!=, allowing the compiler to synthesize != as !(a==b) in all language modes (C++20 member functions and pre-C++20 friend functions). Behavior change: operator!= now returns !(a==b) unconditionally, including for special values like NaN and discarded. This means: - NaN != NaN now returns true (matches IEEE-754 semantics) - discarded != x now returns true for any x (matches !(discarded == x)) This also fixes underlying defects in previously-working code: - Restores direct == comparison for views vs json (reverts std::ranges::equal workaround added in PR #3950 to dodge this bug) - Re-enables std::string == json comparisons (uncomments check in unit-constructor1.cpp) Fixes: #3868, #3979 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me>
nlohmann
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…nthesis (#5253) * Fix #3868: Remove operator!= to enable P2468R2 rewritten candidate synthesis Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's rewritten-candidate synthesis for operator==, preventing heterogeneous comparisons like `std::string s; json j; s == j;` from compiling. Fix by removing the hand-written operator!=, allowing the compiler to synthesize != as !(a==b) in all language modes (C++20 member functions and pre-C++20 friend functions). Behavior change: operator!= now returns !(a==b) unconditionally, including for special values like NaN and discarded. This means: - NaN != NaN now returns true (matches IEEE-754 semantics) - discarded != x now returns true for any x (matches !(discarded == x)) This also fixes underlying defects in previously-working code: - Restores direct == comparison for views vs json (reverts std::ranges::equal workaround added in PR #3950 to dodge this bug) - Re-enables std::string == json comparisons (uncomments check in unit-constructor1.cpp) Fixes: #3868, #3979 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me> * 🚨 fix warning Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
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Sep 21, 2026
…idate synthesis (nlohmann#5253) * Fix nlohmann#3868: Remove operator!= to enable P2468R2 rewritten candidate synthesis Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's rewritten-candidate synthesis for operator==, preventing heterogeneous comparisons like `std::string s; json j; s == j;` from compiling. Fix by removing the hand-written operator!=, allowing the compiler to synthesize != as !(a==b) in all language modes (C++20 member functions and pre-C++20 friend functions). Behavior change: operator!= now returns !(a==b) unconditionally, including for special values like NaN and discarded. This means: - NaN != NaN now returns true (matches IEEE-754 semantics) - discarded != x now returns true for any x (matches !(discarded == x)) This also fixes underlying defects in previously-working code: - Restores direct == comparison for views vs json (reverts std::ranges::equal workaround added in PR nlohmann#3950 to dodge this bug) - Re-enables std::string == json comparisons (uncomments check in unit-constructor1.cpp) Fixes: nlohmann#3868, nlohmann#3979 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Signed-off-by: Niels Lohmann <mail@nlohmann.me> * 🚨 fix warning Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
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This fixes a build error on GCC 13:
/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp: In function ‘void _DOCTEST_ANON_FUNC_2()’:
/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp:946:32: error: no match for ‘operator==’ (operand types are ‘doctest::detail::Expression_lhs<std::ranges::reverse_view<std::ranges::ref_view<nlohmann::json_abi_v3_11_2::basic_json<> > >&>’ and ‘nlohmann::json_abi_v3_11_2::json’ {aka ‘nlohmann::json_abi_v3_11_2::basic_json<>’})
946 | CHECK(reversed == j_expected);
| ^~ ~~~~~~~~~~
| |
| nlohmann::json_abi_v3_11_2::json {aka nlohmann::json_abi_v3_11_2::basic_json<>}
Bug: https://bugs.gentoo.org/895692
Closes: #3927
This PR also depends on trofis PR: #3895
Tested on x86_64-pc-linux-gnu in the default CMake configuration.
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