Bug 315198 – Fix WTF::Variant build with GCC 15

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Loïc Yhuel]

Build is broken after https://commits.webkit.org/313528@main.

[Loïc Yhuel]

Pull request: https://github.com/WebKit/WebKit/pull/65293

[Loïc Yhuel]

In file included from /home/src/upstream/webkit/Source/WTF/wtf/StdLibExtras.h:52,
                 from /home/src/upstream/webkit/Source/WTF/wtf/MallocCommon.h:29,
                 from /home/src/upstream/webkit/Source/WTF/wtf/FastMalloc.h:28,
                 from /home/src/upstream/webkit/Source/WTF/config.h:31,
                 from /home/src/upstream/webkit/Source/WTF/wtf/JSONValues.cpp:33:
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h: In instantiation of ‘constexpr mpark::detail::base<Ts>::alt_at<I>& mpark::detail::base<Ts>::get_alt() const & [with long unsigned int I = 6; Ts = {std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag}]’:
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h:1475:66: error: use of built-in trait ‘__type_pack_element<I, std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag>’ in function signature; use library traits instead
 1475 |       template <std::size_t I> inline constexpr const alt_at<I> &get_alt() const & noexcept {
      |                                                                  ^~~~~~~
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h: In instantiation of ‘constexpr mpark::detail::base<Ts>::alt_at<I>& mpark::detail::base<Ts>::get_alt() const & [with long unsigned int I = 5; Ts = {std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag}]’:
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h:1475:66: error: use of built-in trait ‘__type_pack_element<I, std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag>’ in function signature; use library traits instead
...
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h: In instantiation of ‘constexpr mpark::detail::base<Ts>::alt_at<I>& mpark::detail::base<Ts>::get_alt() & [with long unsigned int I = 6; Ts = {std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag}]’:
/home/src/upstream/webkit/Source/WTF/wtf/Variant.h:1472:60: error: use of built-in trait ‘__type_pack_element<I, std::monostate, bool, double, int, WTF::String, WTF::JSONImpl::Value::ObjectTypeTag, WTF::JSONImpl::Value::ArrayTypeTag>’ in function signature; use library traits instead
 1472 |       template <std::size_t I> inline constexpr alt_at<I> &get_alt() & noexcept {
      |                                                            ^~~~~~~
...

[EWS]

Committed 313666@main (3917eb489bf7): <https://commits.webkit.org/313666@main>

Reviewed commits have been landed. Closing PR #65293 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/177626501>