[libc++] P3379R1: Constrain 'std::expected' equality operators

Author: xiaoyang-sde

libcxx/docs/ReleaseNotes/20.rst

@@ -45,6 +45,7 @@ Implemented Papers
 - ``std::jthread`` and ``<stop_token>`` are not guarded behind ``-fexperimental-library`` anymore
 - P2674R1: A trait for implicit lifetime types (`Github <https://github.com/llvm/llvm-project/issues/105259>`__)
 - P0429R9: A Standard ``flat_map`` is partially implemented and ``flat_map`` is provided (`Github <https://github.com/llvm/llvm-project/issues/105190>`__)
+- P3379R1: Constrain ``std::expected`` equality operators
 
 Improvements and New Features
 -----------------------------

libcxx/test/std/utilities/expected/expected.expected/equality/equality.other_expected.pass.cpp

@@ -23,15 +23,12 @@
 template <class T1, class T2>
 concept CanCompare = requires(T1 t1, T2 t2) { t1 == t2; };
 
-struct Foo{};
+struct Foo {};
 static_assert(!CanCompare<Foo, Foo>);
 
 static_assert(CanCompare<std::expected<int, int>, std::expected<int, int>>);
 static_assert(CanCompare<std::expected<int, int>, std::expected<short, short>>);
 
-// Note this is true because other overloads are unconstrained
-static_assert(CanCompare<std::expected<int, int>, std::expected<void, int>>);
-
 constexpr bool test() {
   // x.has_value() && y.has_value()
   {