Bug 1404972 - To Result add operator==. r=glandium

This is needed for using Result with gtest matchers.

Differential Revision: https://phabricator.services.mozilla.com/D205958

mfbt/Result.h

@@ -834,6 +834,15 @@ class [[nodiscard]] Result final {
   constexpr auto andThen(F f) -> std::invoke_result_t<F, V&&> {
     return MOZ_LIKELY(isOk()) ? f(unwrap()) : propagateErr();
   }
+
+  bool operator==(const Result<V, E>& aOther) const {
+    return (isOk() && aOther.isOk() && inspect() == aOther.inspect()) ||
+           (isErr() && aOther.isErr() && inspectErr() == aOther.inspectErr());
+  }
+
+  bool operator!=(const Result<V, E>& aOther) const {
+    return !(*this == aOther);
+  }
 };
 
 /**

mfbt/tests/TestResult.cpp

@@ -852,6 +852,50 @@ void UpcastTest() {
   }
 }
 
+void EqualityTest() {
+  {
+    Result<int, bool> result(1);
+    Result<int, bool> other(1);
+
+    MOZ_RELEASE_ASSERT(result == other);
+  }
+
+  {
+    Result<int, bool> result(true);
+    Result<int, bool> other(true);
+
+    MOZ_RELEASE_ASSERT(result == other);
+  }
+
+  {
+    Result<int, bool> result(1);
+    Result<int, bool> other(2);
+
+    MOZ_RELEASE_ASSERT(result != other);
+  }
+
+  {
+    Result<int, bool> result(true);
+    Result<int, bool> other(false);
+
+    MOZ_RELEASE_ASSERT(result != other);
+  }
+
+  {
+    Result<int, bool> result(0);
+    Result<int, bool> other(false);
+
+    MOZ_RELEASE_ASSERT(result != other);
+  }
+
+  {
+    Result<int, unsigned int> result(1);
+    Result<int, unsigned int> other(1u);
+
+    MOZ_RELEASE_ASSERT(result != other);
+  }
+}
+
 /* * */
 
 int main() {
@@ -866,5 +910,6 @@ int main() {
   UniquePtrTest();
   ZeroIsEmptyErrorTest();
   UpcastTest();
+  EqualityTest();
   return 0;
 }