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author | Jonathan Wakely <jwakely@redhat.com> | 2024-04-19 17:42:04 +0100 |
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committer | Jonathan Wakely <jwakely@redhat.com> | 2024-04-19 21:06:29 +0100 |
commit | d86472a6f041ccf3d1be0cf6bb15d1e0ad8f6dbe (patch) | |
tree | b5f7e34cc51e995143a6499e72d83f35d523803c /libstdc++-v3/include | |
parent | eed7fb1b2fe72150cd6af10dd3b8f7fc4f0a4da1 (diff) | |
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libstdc++: Simplify constraints on <=> for std::reference_wrapper
Instead of constraining these overloads in terms of synth-three-way we
can just check that the value_type is less-than-comparable, which is
what synth-three-way's constraints check.
The reason that I implemented these with constraints has now been filed
as LWG 4071, so add a comment about that too.
libstdc++-v3/ChangeLog:
* include/bits/refwrap.h (operator<=>): Simplify constraints.
Diffstat (limited to 'libstdc++-v3/include')
-rw-r--r-- | libstdc++-v3/include/bits/refwrap.h | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/libstdc++-v3/include/bits/refwrap.h b/libstdc++-v3/include/bits/refwrap.h index fd1cc2b..71ec2b2 100644 --- a/libstdc++-v3/include/bits/refwrap.h +++ b/libstdc++-v3/include/bits/refwrap.h @@ -384,23 +384,29 @@ _GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type) && requires { { __x.get() == __y.get() } -> convertible_to<bool>; } { return __x.get() == __y.get(); } + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 4071. reference_wrapper comparisons are not SFINAE-friendly + [[nodiscard]] friend constexpr auto - operator<=>(reference_wrapper __x, reference_wrapper<_Tp> __y) - requires requires { __detail::__synth3way(__x.get(), __y.get()); } + operator<=>(reference_wrapper __x, reference_wrapper __y) + requires requires (const _Tp __t) { + { __t < __t } -> __detail::__boolean_testable; + } { return __detail::__synth3way(__x.get(), __y.get()); } [[nodiscard]] friend constexpr auto operator<=>(reference_wrapper __x, const _Tp& __y) - requires requires { __detail::__synth3way(__x.get(), __y); } + requires requires { { __y < __y } -> __detail::__boolean_testable; } { return __detail::__synth3way(__x.get(), __y); } [[nodiscard]] friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper<const _Tp> __y) - requires (!is_const_v<_Tp>) - && requires { __detail::__synth3way(__x.get(), __y.get()); } + requires (!is_const_v<_Tp>) && requires (const _Tp __t) { + { __t < __t } -> __detail::__boolean_testable; + } { return __detail::__synth3way(__x.get(), __y.get()); } #endif }; |