[libcxx-commits] [libcxx] [libc++] Correct `optional<T&>` implementation (PR #174537)

[A. Jiang via libcxx-commits]

================
@@ -32,40 +33,60 @@ struct Y
     int test() const {return 2;}
 };
 
-int main(int, char**)
-{
-    {
-        const optional<X> opt; ((void)opt);
-        ASSERT_SAME_TYPE(decltype(*opt), X const&);
-        ASSERT_NOEXCEPT(*opt);
-    }
-    {
-        constexpr optional<X> opt(X{});
-        static_assert((*opt).test() == 3, "");
-    }
 #if TEST_STD_VER >= 26
-    {
-      X x{};
-      const optional<X&> opt{x};
-      ASSERT_SAME_TYPE(decltype(*opt), X&);
-      ASSERT_NOEXCEPT(*opt);
-    }
-    {
-      X x{};
-      const optional<const X&> opt{x};
-      ASSERT_SAME_TYPE(decltype(*opt), const X&);
-      ASSERT_NOEXCEPT(*opt);
-    }
-    {
-      static constexpr X x{};
-      constexpr optional<const X&> opt(x);
-      static_assert((*opt).test() == 3);
-    }
+constexpr bool test_ref() {
+  using T = TracedCopyMove;
+  {
+    T x{};
+    const std::optional<T&> opt(x);
+    ASSERT_NOEXCEPT(*opt);
+    ASSERT_SAME_TYPE(decltype(*opt), TracedCopyMove&);
+
+    assert(std::addressof(*opt) == std::addressof(x));
+    assert((*opt).constMove == 0);
+    assert((*opt).nonConstMove == 0);
+    assert((*opt).constCopy == 0);
+    assert((*opt).nonConstCopy == 0);
+  }
+
+  {
+    T x{};
+    const std::optional<const T&> opt(x);
+    ASSERT_NOEXCEPT(*opt);
+    ASSERT_SAME_TYPE(decltype(*opt), const TracedCopyMove&);
+
+    assert(std::addressof(*opt) == std::addressof(x));
+    assert((*opt).constMove == 0);
+    assert((*opt).nonConstMove == 0);
+    assert((*opt).constCopy == 0);
+    assert((*opt).nonConstCopy == 0);
+  }
+
+  return true;
+}
+
+#endif
+
+int main(int, char**) {
+  {
+    const optional<X> opt;
+    ((void)opt);
+    ASSERT_SAME_TYPE(decltype(*opt), X const&);
+    ASSERT_NOEXCEPT(*opt);
+  }
+  {
+    constexpr optional<X> opt(X{});
+    static_assert((*opt).test() == 3, "");
+  }
+  {
+    constexpr optional<Y> opt(Y{});
+    assert((*opt).test() == 2);
+  }
----------------
frederick-vs-ja wrote:

These 2 cases are suitable for both constant and runtime evaluation. I think we should use both `static_assert` and `assert` consistently.
(Top-level constant evaluation seems a bit mattering. So perhaps it makes some sense not to put them in `test_ref`.)

https://github.com/llvm/llvm-project/pull/174537