[clang] [Clang] make most enums trivially equality comparable (PR #169079)

[Mariya Podchishchaeva via cfe-commits]

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@@ -4321,6 +4305,38 @@ struct TriviallyEqualityComparable {
 };
 static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparable));
 
+template <class T>
+struct TriviallyEqualityComparableContains {
+  T t;
+
+  friend bool operator==(const TriviallyEqualityComparableContains&, const TriviallyEqualityComparableContains&) = default;
+};
+
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<int>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<int&>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<float>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<double>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<long double>));
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<int[4]>));
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<int[4][4]>));
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<Enum>));
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<Enum[2]>));
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContains<Enum[2][2]>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<EnumWithOpEq>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<EnumWithOpEq[2]>));
+static_assert(!__is_trivially_equality_comparable(TriviallyEqualityComparableContains<EnumWithOpEq[2][2]>));
+
+auto GetNonCapturingLambda() { return [](){ return 42; }; }
+
+struct TriviallyEqualityComparableContainsLambda {
+  [[no_unique_address]] decltype(GetNonCapturingLambda()) l;
+  int i;
+
+  friend bool operator==(const TriviallyEqualityComparableContainsLambda&, const TriviallyEqualityComparableContainsLambda&) = default;
+};
+static_assert(!__is_trivially_equality_comparable(decltype(GetNonCapturingLambda()))); // padding
+static_assert(__is_trivially_equality_comparable(TriviallyEqualityComparableContainsLambda));
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Fznamznon wrote:

The patch is modifying how `__is_trivially_equality_comparable` works with enums whereas I don't see any enums in these test cases. This IMOI makes it hard for someone who will be looking at this without context of this pr via git blame to understand what is going on. The same way it was hard for me yesterday to understand how these cases are related to the patch. Could you please create a separate PR for these? The patch is otherwise LGTM and I'm ready to land it for you once it is focused on enums.

https://github.com/llvm/llvm-project/pull/169079