ftl: add comparison operators to Optional

Add comparison operators and tests for Optional

Test: build
Bug: 185536303
Change-Id: Ic2002489f5fa04cbb8b4c7aba57c8213b9719944

2 files changed, 41 insertions, 0 deletions

diff --git a/include/ftl/optional.h b/include/ftl/optional.h
index 626507fd8f..7b02bac340 100644
--- a/include/ftl/optional.h
+++ b/include/ftl/optional.h
@@ -97,6 +97,16 @@ struct Optional final : std::optional<T> {
   }
 };
 
+template <typename T, typename U>
+constexpr bool operator==(const Optional<T>& lhs, const Optional<U>& rhs) {
+  return static_cast<std::optional<T>>(lhs) == static_cast<std::optional<U>>(rhs);
+}
+
+template <typename T, typename U>
+constexpr bool operator!=(const Optional<T>& lhs, const Optional<U>& rhs) {
+  return !(lhs == rhs);
+}
+
 // Deduction guides.
 template <typename T>
 Optional(T) -> Optional<T>;
diff --git a/libs/ftl/optional_test.cpp b/libs/ftl/optional_test.cpp
index f7410c2aa9..6b3b6c49e5 100644
--- a/libs/ftl/optional_test.cpp
+++ b/libs/ftl/optional_test.cpp
@@ -164,4 +164,35 @@ TEST(Optional, AndThen) {
                      }));
 }
 
+// Comparison.
+namespace {
+
+constexpr Optional<int> kOptional1 = 1;
+constexpr Optional<int> kAnotherOptional1 = 1;
+constexpr Optional<int> kOptional2 = 2;
+constexpr Optional<int> kOptionalEmpty, kAnotherOptionalEmpty;
+
+constexpr std::optional<int> kStdOptional1 = 1;
+
+static_assert(kOptional1 == kAnotherOptional1);
+
+static_assert(kOptional1 != kOptional2);
+static_assert(kOptional2 != kOptional1);
+
+static_assert(kOptional1 != kOptionalEmpty);
+static_assert(kOptionalEmpty != kOptional1);
+
+static_assert(kOptionalEmpty == kAnotherOptionalEmpty);
+
+static_assert(kOptional1 == kStdOptional1);
+static_assert(kStdOptional1 == kOptional1);
+
+static_assert(kOptional2 != kStdOptional1);
+static_assert(kStdOptional1 != kOptional2);
+
+static_assert(kOptional2 != kOptionalEmpty);
+static_assert(kOptionalEmpty != kOptional2);
+
+} // namespace
+
 }  // namespace android::test