init: fix hiding of move constructors of Result<T>
This is needed to have Result<Result<T>> work correctly.
Test: init unit tests
Change-Id: If7d23d1ea13f3727b567d3baf0eee1d8d0e5a196
diff --git a/init/result.h b/init/result.h
index 36c3b83..fc03962 100644
--- a/init/result.h
+++ b/init/result.h
@@ -153,8 +153,14 @@
template <typename T>
class Result {
public:
- template <typename... U>
- Result(U&&... result) : contents_(std::in_place_index_t<0>(), std::forward<U>(result)...) {}
+ Result() {}
+
+ template <typename U, typename... V,
+ typename = std::enable_if_t<!(std::is_same_v<std::decay_t<U>, Result<T>> &&
+ sizeof...(V) == 0)>>
+ Result(U&& result, V&&... results)
+ : contents_(std::in_place_index_t<0>(), std::forward<U>(result),
+ std::forward<V>(results)...) {}
Result(Error&& error) : contents_(std::in_place_index_t<1>(), error.str(), error.get_errno()) {}
Result(const ResultError& result_error)
diff --git a/init/result_test.cpp b/init/result_test.cpp
index 19caaf5..327b444 100644
--- a/init/result_test.cpp
+++ b/init/result_test.cpp
@@ -276,6 +276,49 @@
EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
}
+// Below two tests require that we do not hide the move constructor with our forwarding reference
+// constructor. This is done with by disabling the forwarding reference constructor if its first
+// and only type is Result<T>.
+TEST(result, result_result_with_success) {
+ auto return_result_result_with_success = []() -> Result<Result<Success>> {
+ return Result<Success>();
+ };
+ auto result = return_result_result_with_success();
+ ASSERT_TRUE(result);
+ ASSERT_TRUE(*result);
+
+ auto inner_result = result.value();
+ ASSERT_TRUE(inner_result);
+}
+
+TEST(result, result_result_with_failure) {
+ auto return_result_result_with_error = []() -> Result<Result<Success>> {
+ return Result<Success>(ResultError("failure string", 6));
+ };
+ auto result = return_result_result_with_error();
+ ASSERT_TRUE(result);
+ ASSERT_FALSE(*result);
+ EXPECT_EQ("failure string", result->error_string());
+ EXPECT_EQ(6, result->error_errno());
+}
+
+// This test requires that we disable the forwarding reference constructor if Result<T> is the
+// *only* type that we are forwarding. In otherwords, if we are forwarding Result<T>, int to
+// construct a Result<T>, then we still need the constructor.
+TEST(result, result_two_parameter_constructor_same_type) {
+ struct TestStruct {
+ TestStruct(int value) : value_(value) {}
+ TestStruct(Result<TestStruct> result, int value) : value_(result->value_ * value) {}
+ int value_;
+ };
+
+ auto return_test_struct = []() -> Result<TestStruct> { return {Result<TestStruct>(6), 6}; };
+
+ auto result = return_test_struct();
+ ASSERT_TRUE(result);
+ EXPECT_EQ(36, result->value_);
+}
+
TEST(result, die_on_access_failed_result) {
Result<std::string> result = Error();
ASSERT_DEATH(*result, "");