[libc++] Module fixes for __synth_three_way.

[Mordante]

Summary

These changes make it possible to use __synth_three_way in modules. The
change from a lambda to a function is a Clang issue.

The change is list was needed since the compiler couldn't deduce the
comparison template argument.

Adds a few missing includes too.

[Mordante]

CI fixes.

[Mordante]

CI fixes, __synth_three_way is used in more places now.

[ldionne]

libcxx/include/__compare/synth_three_way.h

28–48

Do we have a clang bug report for that? If not, let's make one and link it here.

[Mordante]

libcxx/include/__compare/synth_three_way.h

28–48

Yes I've added the link to https://github.com/llvm/llvm-project/issues/57222

libcxx/include/__compare/synth_three_way.h

 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 20
 
 // [expos.only.func]
 
-_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way =
-  []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u)
-    requires requires {
-      { __t < __u } -> __boolean_testable;
-      { __u < __t } -> __boolean_testable;
-    }
-  {
-    if constexpr (three_way_comparable_with<_Tp, _Up>) {
-      return __t <=> __u;
-    } else {
-      if (__t < __u) return weak_ordering::less;
-      if (__u < __t) return weak_ordering::greater;
-      return weak_ordering::equivalent;
-    }
-  };
+// TODO MODULES restore the lamba to match the Standard.
+// See https://github.com/llvm/llvm-project/issues/57222
+//_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way =
+//  []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u)
+template <class _Tp, class _Up>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __synth_three_way(const _Tp& __t, const _Up& __u)
+    if (__t < __u)
+      return weak_ordering::less;
+    if (__u < __t)
+      return weak_ordering::greater;
+}
 
 template <class _Tp, class _Up = _Tp>
 using __synth_three_way_result = decltype(std::__synth_three_way(std::declval<_Tp&>(), std::declval<_Up&>()));
 
 #endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H

libcxx/include/compare

 #include <__compare/compare_strong_order_fallback.h>
 #include <__compare/compare_three_way.h>
 #include <__compare/compare_three_way_result.h>
 #include <__compare/compare_weak_order_fallback.h>
 #include <__compare/is_eq.h>
 #include <__compare/ordering.h>
 #include <__compare/partial_order.h>
 #include <__compare/strong_order.h>
+#include <__compare/synth_three_way.h>
 #include <__compare/three_way_comparable.h>
 #include <__compare/weak_order.h>
 #include <__config>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <type_traits>
 #endif
 
 #endif // _LIBCPP_COMPARE

libcxx/include/deque

 #else // _LIBCPP_STD_VER <= 17
 
 template<class _Tp, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 __synth_three_way_result<_Tp>
 operator<=>(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
 {
     return std::lexicographical_compare_three_way(
-        __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+        __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way<_Tp, _Tp>);
 }
 
 #endif // _LIBCPP_STD_VER <= 17
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 void
 swap(deque<_Tp, _Allocator>& __x, deque<_Tp, _Allocator>& __y)

libcxx/include/forward_list

 
 template<class _Tp, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 __synth_three_way_result<_Tp>
 operator<=>(const forward_list<_Tp, _Allocator>& __x,
             const forward_list<_Tp, _Allocator>& __y)
 {
     return std::lexicographical_compare_three_way(
-        __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+        __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way<_Tp, _Tp>);
 }
 
 #endif // #if _LIBCPP_STD_VER <= 17
 
 template <class _Tp, class _Alloc>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 swap(forward_list<_Tp, _Alloc>& __x, forward_list<_Tp, _Alloc>& __y)

libcxx/include/list

 #else // _LIBCPP_STD_VER <= 17
 
 template<class _Tp, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 __synth_three_way_result<_Tp>
 operator<=>(const list<_Tp, _Allocator>& __x, const list<_Tp, _Allocator>& __y)
 {
     return std::lexicographical_compare_three_way(
-        __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+        __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way<_Tp, _Tp>);
 }
 
 #endif // _LIBCPP_STD_VER <= 17
 
 template <class _Tp, class _Alloc>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 swap(list<_Tp, _Alloc>& __x, list<_Tp, _Alloc>& __y)

libcxx/include/map

 
 template<class _Key, class _Tp, class _Compare, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 __synth_three_way_result<pair<const _Key, _Tp>>
 operator<=>(const map<_Key, _Tp, _Compare, _Allocator>& __x,
             const map<_Key, _Tp, _Compare, _Allocator>& __y)
 {
     return std::lexicographical_compare_three_way(
-        __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+        __x.begin(),
+        __x.end(),
+        __y.begin(),
+        __y.end(),
+        std::__synth_three_way<pair<const _Key, _Tp>, pair<const _Key, _Tp>>);
 }
 
 #endif // #if _LIBCPP_STD_VER <= 17
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 swap(map<_Key, _Tp, _Compare, _Allocator>& __x,

 
 template<class _Key, class _Tp, class _Compare, class _Allocator>
 inline _LIBCPP_HIDE_FROM_ABI
 __synth_three_way_result<pair<const _Key, _Tp>>
 operator<=>(const multimap<_Key, _Tp, _Compare, _Allocator>& __x,
             const multimap<_Key, _Tp, _Compare, _Allocator>& __y)
 {
     return std::lexicographical_compare_three_way(
-        __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+        __x.begin(),
+        __x.end(),
+        __y.begin(),
+        __y.end(),
+        std::__synth_three_way<pair<const _Key, _Tp>, pair<const _Key, _Tp>>);
 }
 
 #endif // #if _LIBCPP_STD_VER <= 17
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 swap(multimap<_Key, _Tp, _Compare, _Allocator>& __x,

libcxx/utils/data/ignore_format.txt

 libcxx/include/__compare/compare_partial_order_fallback.h
 libcxx/include/__compare/compare_strong_order_fallback.h
 libcxx/include/__compare/compare_three_way.h
 libcxx/include/__compare/compare_three_way_result.h
 libcxx/include/__compare/compare_weak_order_fallback.h
 libcxx/include/__compare/ordering.h
 libcxx/include/__compare/partial_order.h
 libcxx/include/__compare/strong_order.h
-libcxx/include/__compare/synth_three_way.h
 libcxx/include/__compare/three_way_comparable.h
 libcxx/include/__compare/weak_order.h
 libcxx/include/complex
 libcxx/include/__concepts/arithmetic.h
 libcxx/include/__concepts/assignable.h
 libcxx/include/__concepts/boolean_testable.h
 libcxx/include/__concepts/class_or_enum.h
 libcxx/include/__concepts/common_reference_with.h