Add android::base::expected
android::base::expected is an Android implementation of the
std::expected proposal.
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0323r7.html
For usage, refer to the expected.h header file and
expected_test.cpp
Bug: 132145659
Test: libbase_test
Change-Id: I65d3a1ecf8654d9858989755dfd0065c81f7b209
diff --git a/base/expected_test.cpp b/base/expected_test.cpp
new file mode 100644
index 0000000..490ced4
--- /dev/null
+++ b/base/expected_test.cpp
@@ -0,0 +1,745 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "android-base/expected.h"
+
+#include <cstdio>
+#include <memory>
+#include <string>
+
+#include <gtest/gtest.h>
+
+using android::base::expected;
+using android::base::unexpected;
+
+typedef expected<int, int> exp_int;
+typedef expected<double, double> exp_double;
+typedef expected<std::string, std::string> exp_string;
+typedef expected<std::pair<std::string, int>, int> exp_pair;
+
+struct T {
+ int a;
+ int b;
+ T() = default;
+ T(int a, int b) noexcept : a(a), b(b) {}
+};
+bool operator==(const T& x, const T& y) {
+ return x.a == y.a && x.b == y.b;
+}
+bool operator!=(const T& x, const T& y) {
+ return x.a != y.a || x.b != y.b;
+}
+
+struct E {
+ std::string message;
+ int cause;
+ E(const std::string& message, int cause) : message(message), cause(cause) {}
+};
+
+typedef expected<T,E> exp_complex;
+
+TEST(Expected, testDefaultConstructible) {
+ exp_int e;
+ EXPECT_TRUE(e.has_value());
+ EXPECT_EQ(0, e.value());
+
+ exp_complex e2;
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(T(0,0), e2.value());
+}
+
+TEST(Expected, testCopyConstructible) {
+ exp_int e;
+ exp_int e2 = e;
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(0, e.value());
+ EXPECT_EQ(0, e2.value());
+}
+
+TEST(Expected, testMoveConstructible) {
+ exp_int e;
+ exp_int e2 = std::move(e);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(0, e.value());
+ EXPECT_EQ(0, e2.value());
+
+ exp_string e3(std::string("hello"));
+ exp_string e4 = std::move(e3);
+
+ EXPECT_TRUE(e3.has_value());
+ EXPECT_TRUE(e4.has_value());
+ EXPECT_EQ("", e3.value()); // e3 is moved
+ EXPECT_EQ("hello", e4.value());
+}
+
+TEST(Expected, testCopyConstructibleFromConvertibleType) {
+ exp_double e = 3.3f;
+ exp_int e2 = e;
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(3.3f, e.value());
+ EXPECT_EQ(3, e2.value());
+}
+
+TEST(Expected, testMoveConstructibleFromConvertibleType) {
+ exp_double e = 3.3f;
+ exp_int e2 = std::move(e);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(3.3f, e.value());
+ EXPECT_EQ(3, e2.value());
+}
+
+TEST(Expected, testConstructibleFromValue) {
+ exp_int e = 3;
+ exp_double e2 = 5.5f;
+ exp_string e3 = std::string("hello");
+ exp_complex e4 = T(10, 20);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_TRUE(e3.has_value());
+ EXPECT_TRUE(e4.has_value());
+ EXPECT_EQ(3, e.value());
+ EXPECT_EQ(5.5f, e2.value());
+ EXPECT_EQ("hello", e3.value());
+ EXPECT_EQ(T(10,20), e4.value());
+}
+
+TEST(Expected, testConstructibleFromMovedValue) {
+ std::string hello = "hello";
+ exp_string e = std::move(hello);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_EQ("hello", e.value());
+ EXPECT_EQ("", hello);
+}
+
+TEST(Expected, testConstructibleFromConvertibleValue) {
+ exp_int e = 3.3f; // double to int
+ exp_string e2 = "hello"; // char* to std::string
+ EXPECT_TRUE(e.has_value());
+ EXPECT_EQ(3, e.value());
+
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ("hello", e2.value());
+}
+
+TEST(Expected, testConstructibleFromUnexpected) {
+ exp_int::unexpected_type unexp = unexpected(10);
+ exp_int e = unexp;
+
+ exp_double::unexpected_type unexp2 = unexpected(10.5f);
+ exp_double e2 = unexp2;
+
+ exp_string::unexpected_type unexp3 = unexpected(std::string("error"));
+ exp_string e3 = unexp3;
+
+ EXPECT_FALSE(e.has_value());
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_FALSE(e3.has_value());
+ EXPECT_EQ(10, e.error());
+ EXPECT_EQ(10.5f, e2.error());
+ EXPECT_EQ("error", e3.error());
+}
+
+TEST(Expected, testMoveConstructibleFromUnexpected) {
+ exp_int e = unexpected(10);
+ exp_double e2 = unexpected(10.5f);
+ exp_string e3 = unexpected(std::string("error"));
+
+ EXPECT_FALSE(e.has_value());
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_FALSE(e3.has_value());
+ EXPECT_EQ(10, e.error());
+ EXPECT_EQ(10.5f, e2.error());
+ EXPECT_EQ("error", e3.error());
+}
+
+TEST(Expected, testConstructibleByForwarding) {
+ exp_string e(std::in_place, 5, 'a');
+ EXPECT_TRUE(e.has_value());
+ EXPECT_EQ("aaaaa", e.value());
+
+ exp_string e2({'a', 'b', 'c'});
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ("abc", e2.value());
+
+ exp_pair e3({"hello", 30});
+ EXPECT_TRUE(e3.has_value());
+ EXPECT_EQ("hello",e3->first);
+ EXPECT_EQ(30,e3->second);
+}
+
+TEST(Expected, testDestructible) {
+ bool destroyed = false;
+ struct T {
+ bool* flag_;
+ T(bool* flag) : flag_(flag) {}
+ ~T() { *flag_ = true; }
+ };
+ {
+ expected<T, int> exp = T(&destroyed);
+ }
+ EXPECT_TRUE(destroyed);
+}
+
+TEST(Expected, testAssignable) {
+ exp_int e = 10;
+ exp_int e2 = 20;
+ e = e2;
+
+ EXPECT_EQ(20, e.value());
+ EXPECT_EQ(20, e2.value());
+
+ exp_int e3 = 10;
+ exp_int e4 = 20;
+ e3 = std::move(e4);
+
+ EXPECT_EQ(20, e3.value());
+ EXPECT_EQ(20, e4.value());
+}
+
+TEST(Expected, testAssignableFromValue) {
+ exp_int e = 10;
+ e = 20;
+ EXPECT_EQ(20, e.value());
+
+ exp_double e2 = 3.5f;
+ e2 = 10.5f;
+ EXPECT_EQ(10.5f, e2.value());
+
+ exp_string e3 = "hello";
+ e3 = "world";
+ EXPECT_EQ("world", e3.value());
+}
+
+TEST(Expected, testAssignableFromUnexpected) {
+ exp_int e = 10;
+ e = unexpected(30);
+ EXPECT_FALSE(e.has_value());
+ EXPECT_EQ(30, e.error());
+
+ exp_double e2 = 3.5f;
+ e2 = unexpected(10.5f);
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_EQ(10.5f, e2.error());
+
+ exp_string e3 = "hello";
+ e3 = unexpected("world");
+ EXPECT_FALSE(e3.has_value());
+ EXPECT_EQ("world", e3.error());
+}
+
+TEST(Expected, testAssignableFromMovedValue) {
+ std::string world = "world";
+ exp_string e = "hello";
+ e = std::move(world);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_EQ("world", e.value());
+ EXPECT_EQ("", world);
+}
+
+TEST(Expected, testAssignableFromMovedUnexpected) {
+ std::string world = "world";
+ exp_string e = "hello";
+ e = unexpected(std::move(world));
+
+ EXPECT_FALSE(e.has_value());
+ EXPECT_EQ("world", e.error());
+ EXPECT_EQ("", world);
+}
+
+TEST(Expected, testEmplace) {
+ struct T {
+ int a;
+ double b;
+ T() {}
+ T(int a, double b) noexcept : a(a), b(b) {}
+ };
+ expected<T, int> exp;
+ T& t = exp.emplace(3, 10.5f);
+
+ EXPECT_TRUE(exp.has_value());
+ EXPECT_EQ(3, t.a);
+ EXPECT_EQ(10.5f, t.b);
+ EXPECT_EQ(3, exp.value().a);
+ EXPECT_EQ(10.5, exp.value().b);
+}
+
+TEST(Expected, testSwapExpectedExpected) {
+ exp_int e = 10;
+ exp_int e2 = 20;
+ e.swap(e2);
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(20, e.value());
+ EXPECT_EQ(10, e2.value());
+}
+
+TEST(Expected, testSwapUnexpectedUnexpected) {
+ exp_int e = unexpected(10);
+ exp_int e2 = unexpected(20);
+ e.swap(e2);
+ EXPECT_FALSE(e.has_value());
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_EQ(20, e.error());
+ EXPECT_EQ(10, e2.error());
+}
+
+TEST(Expected, testSwapExpectedUnepected) {
+ exp_int e = 10;
+ exp_int e2 = unexpected(30);
+ e.swap(e2);
+ EXPECT_FALSE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(30, e.error());
+ EXPECT_EQ(10, e2.value());
+}
+
+TEST(Expected, testDereference) {
+ struct T {
+ int a;
+ double b;
+ T() {}
+ T(int a, double b) : a(a), b(b) {}
+ };
+ expected<T, int> exp = T(3, 10.5f);
+
+ EXPECT_EQ(3, exp->a);
+ EXPECT_EQ(10.5f, exp->b);
+
+ EXPECT_EQ(3, (*exp).a);
+ EXPECT_EQ(10.5f, (*exp).b);
+}
+
+TEST(Expected, testTest) {
+ exp_int e = 10;
+ EXPECT_TRUE(e);
+ EXPECT_TRUE(e.has_value());
+
+ exp_int e2 = unexpected(10);
+ EXPECT_FALSE(e2);
+ EXPECT_FALSE(e2.has_value());
+}
+
+TEST(Expected, testGetValue) {
+ exp_int e = 10;
+ EXPECT_EQ(10, e.value());
+ EXPECT_EQ(10, e.value_or(20));
+
+ exp_int e2 = unexpected(10);
+ EXPECT_EQ(10, e2.error());
+ EXPECT_EQ(20, e2.value_or(20));
+}
+
+TEST(Expected, testSameValues) {
+ exp_int e = 10;
+ exp_int e2 = 10;
+ EXPECT_TRUE(e == e2);
+ EXPECT_TRUE(e2 == e);
+ EXPECT_FALSE(e != e2);
+ EXPECT_FALSE(e2 != e);
+}
+
+TEST(Expected, testDifferentValues) {
+ exp_int e = 10;
+ exp_int e2 = 20;
+ EXPECT_FALSE(e == e2);
+ EXPECT_FALSE(e2 == e);
+ EXPECT_TRUE(e != e2);
+ EXPECT_TRUE(e2 != e);
+}
+
+TEST(Expected, testValueWithError) {
+ exp_int e = 10;
+ exp_int e2 = unexpected(10);
+ EXPECT_FALSE(e == e2);
+ EXPECT_FALSE(e2 == e);
+ EXPECT_TRUE(e != e2);
+ EXPECT_TRUE(e2 != e);
+}
+
+TEST(Expected, testSameErrors) {
+ exp_int e = unexpected(10);
+ exp_int e2 = unexpected(10);
+ EXPECT_TRUE(e == e2);
+ EXPECT_TRUE(e2 == e);
+ EXPECT_FALSE(e != e2);
+ EXPECT_FALSE(e2 != e);
+}
+
+TEST(Expected, testDifferentErrors) {
+ exp_int e = unexpected(10);
+ exp_int e2 = unexpected(20);
+ EXPECT_FALSE(e == e2);
+ EXPECT_FALSE(e2 == e);
+ EXPECT_TRUE(e != e2);
+ EXPECT_TRUE(e2 != e);
+}
+
+TEST(Expected, testCompareWithSameValue) {
+ exp_int e = 10;
+ int value = 10;
+ EXPECT_TRUE(e == value);
+ EXPECT_TRUE(value == e);
+ EXPECT_FALSE(e != value);
+ EXPECT_FALSE(value != e);
+}
+
+TEST(Expected, testCompareWithDifferentValue) {
+ exp_int e = 10;
+ int value = 20;
+ EXPECT_FALSE(e == value);
+ EXPECT_FALSE(value == e);
+ EXPECT_TRUE(e != value);
+ EXPECT_TRUE(value != e);
+}
+
+TEST(Expected, testCompareWithSameError) {
+ exp_int e = unexpected(10);
+ exp_int::unexpected_type error = 10;
+ EXPECT_TRUE(e == error);
+ EXPECT_TRUE(error == e);
+ EXPECT_FALSE(e != error);
+ EXPECT_FALSE(error != e);
+}
+
+TEST(Expected, testCompareWithDifferentError) {
+ exp_int e = unexpected(10);
+ exp_int::unexpected_type error = 20;
+ EXPECT_FALSE(e == error);
+ EXPECT_FALSE(error == e);
+ EXPECT_TRUE(e != error);
+ EXPECT_TRUE(error != e);
+}
+
+TEST(Expected, testDivideExample) {
+ struct QR {
+ int quotient;
+ int remainder;
+ QR(int q, int r) noexcept : quotient(q), remainder(r) {}
+ bool operator==(const QR& rhs) const {
+ return quotient == rhs.quotient && remainder == rhs.remainder;
+ }
+ bool operator!=(const QR& rhs) const {
+ return quotient != rhs.quotient || remainder == rhs.remainder;
+ }
+ };
+
+ auto divide = [](int x, int y) -> expected<QR,E> {
+ if (y == 0) {
+ return unexpected(E("divide by zero", -1));
+ } else {
+ return QR(x / y, x % y);
+ }
+ };
+
+ EXPECT_FALSE(divide(10, 0));
+ EXPECT_EQ("divide by zero", divide(10, 0).error().message);
+ EXPECT_EQ(-1, divide(10, 0).error().cause);
+
+ EXPECT_TRUE(divide(10, 3));
+ EXPECT_EQ(QR(3, 1), divide(10, 3));
+}
+
+TEST(Expected, testPair) {
+ auto test = [](bool yes) -> exp_pair {
+ if (yes) {
+ return exp_pair({"yes", 42});
+ } else {
+ return unexpected(42);
+ }
+ };
+
+ auto r = test(true);
+ EXPECT_TRUE(r);
+ EXPECT_EQ("yes", r->first);
+}
+
+// copied from result_test.cpp
+struct ConstructorTracker {
+ static size_t constructor_called;
+ static size_t copy_constructor_called;
+ static size_t move_constructor_called;
+ static size_t copy_assignment_called;
+ static size_t move_assignment_called;
+
+ template <typename T,
+ typename std::enable_if_t<std::is_convertible_v<T, std::string>>* = nullptr>
+ ConstructorTracker(T&& string) : string(string) {
+ ++constructor_called;
+ }
+ ConstructorTracker(const ConstructorTracker& ct) {
+ ++copy_constructor_called;
+ string = ct.string;
+ }
+ ConstructorTracker(ConstructorTracker&& ct) noexcept {
+ ++move_constructor_called;
+ string = std::move(ct.string);
+ }
+ ConstructorTracker& operator=(const ConstructorTracker& ct) {
+ ++copy_assignment_called;
+ string = ct.string;
+ return *this;
+ }
+ ConstructorTracker& operator=(ConstructorTracker&& ct) noexcept {
+ ++move_assignment_called;
+ string = std::move(ct.string);
+ return *this;
+ }
+ static void Reset() {
+ constructor_called = 0;
+ copy_constructor_called = 0;
+ move_constructor_called = 0;
+ copy_assignment_called = 0;
+ move_assignment_called = 0;
+ }
+ std::string string;
+};
+
+size_t ConstructorTracker::constructor_called = 0;
+size_t ConstructorTracker::copy_constructor_called = 0;
+size_t ConstructorTracker::move_constructor_called = 0;
+size_t ConstructorTracker::copy_assignment_called = 0;
+size_t ConstructorTracker::move_assignment_called = 0;
+
+typedef expected<ConstructorTracker, int> exp_track;
+
+TEST(Expected, testNumberOfCopies) {
+ // default constructor
+ ConstructorTracker::Reset();
+ exp_track e("hello");
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // copy constructor
+ ConstructorTracker::Reset();
+ exp_track e2 = e;
+ EXPECT_EQ(0U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // move constructor
+ ConstructorTracker::Reset();
+ exp_track e3 = std::move(e);
+ EXPECT_EQ(0U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // construct from lvalue
+ ConstructorTracker::Reset();
+ ConstructorTracker ct = "hello";
+ exp_track e4(ct);
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // construct from rvalue
+ ConstructorTracker::Reset();
+ ConstructorTracker ct2 = "hello";
+ exp_track e5(std::move(ct2));
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // copy assignment
+ ConstructorTracker::Reset();
+ exp_track e6 = "hello";
+ exp_track e7 = "world";
+ e7 = e6;
+ EXPECT_EQ(2U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ // move assignment
+ ConstructorTracker::Reset();
+ exp_track e8 = "hello";
+ exp_track e9 = "world";
+ e9 = std::move(e8);
+ EXPECT_EQ(2U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_assignment_called);
+
+ // swap
+ ConstructorTracker::Reset();
+ exp_track e10 = "hello";
+ exp_track e11 = "world";
+ std::swap(e10, e11);
+ EXPECT_EQ(2U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(2U, ConstructorTracker::move_assignment_called);
+}
+
+TEST(Expected, testNoCopyOnReturn) {
+ auto test = [](const std::string& in) -> exp_track {
+ if (in.empty()) {
+ return "literal string";
+ }
+ if (in == "test2") {
+ return ConstructorTracker(in + in + "2");
+ }
+ ConstructorTracker result(in + " " + in);
+ return result;
+ };
+
+ ConstructorTracker::Reset();
+ auto result1 = test("");
+ ASSERT_TRUE(result1);
+ EXPECT_EQ("literal string", result1->string);
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ ConstructorTracker::Reset();
+ auto result2 = test("test2");
+ ASSERT_TRUE(result2);
+ EXPECT_EQ("test2test22", result2->string);
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+ ConstructorTracker::Reset();
+ auto result3 = test("test3");
+ ASSERT_TRUE(result3);
+ EXPECT_EQ("test3 test3", result3->string);
+ EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+ EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+ EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+ EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+}
+
+TEST(Expected, testNested) {
+ expected<exp_string, std::string> e = "hello";
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e.value().has_value());
+ EXPECT_TRUE(e);
+ EXPECT_TRUE(*e);
+ EXPECT_EQ("hello", e.value().value());
+
+ expected<exp_string, std::string> e2 = unexpected("world");
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_FALSE(e2);
+ EXPECT_EQ("world", e2.error());
+
+ expected<exp_string, std::string> e3 = exp_string(unexpected("world"));
+ EXPECT_TRUE(e3.has_value());
+ EXPECT_FALSE(e3.value().has_value());
+ EXPECT_TRUE(e3);
+ EXPECT_FALSE(*e3);
+ EXPECT_EQ("world", e3.value().error());
+}
+
+constexpr bool equals(const char* a, const char* b) {
+ return (a == nullptr && b == nullptr) ||
+ (a != nullptr && b != nullptr && *a == *b &&
+ (*a == '\0' || equals(a + 1, b + 1)));
+}
+
+TEST(Expected, testConstexpr) {
+ // Compliation error will occur if these expressions can't be
+ // evaluated at compile time
+ constexpr exp_int e(3);
+ constexpr exp_int::unexpected_type err(3);
+ constexpr int i = 4;
+
+ // default constructor
+ static_assert(exp_int().value() == 0);
+ // copy constructor
+ static_assert(exp_int(e).value() == 3);
+ // move constructor
+ static_assert(exp_int(exp_int(4)).value() == 4);
+ // copy construct from value
+ static_assert(exp_int(i).value() == 4);
+ // copy construct from unexpected
+ static_assert(exp_int(err).error() == 3);
+ // move costruct from unexpected
+ static_assert(exp_int(unexpected(3)).error() == 3);
+ // observers
+ static_assert(*exp_int(3) == 3);
+ static_assert(exp_int(3).has_value() == true);
+ static_assert(exp_int(3).value_or(4) == 3);
+
+ typedef expected<const char*, int> exp_s;
+ constexpr exp_s s("hello");
+ constexpr const char* c = "hello";
+ static_assert(equals(exp_s().value(), nullptr));
+ static_assert(equals(exp_s(s).value(), "hello"));
+ static_assert(equals(exp_s(exp_s("hello")).value(), "hello"));
+ static_assert(equals(exp_s("hello").value(), "hello"));
+ static_assert(equals(exp_s(c).value(), "hello"));
+}
+
+TEST(Expected, testWithNonConstructible) {
+ struct AssertNotConstructed {
+ AssertNotConstructed() = delete;
+ };
+
+ expected<int, AssertNotConstructed> v(42);
+ EXPECT_TRUE(v.has_value());
+ EXPECT_EQ(42, v.value());
+
+ expected<AssertNotConstructed, int> e(unexpected(42));
+ EXPECT_FALSE(e.has_value());
+ EXPECT_EQ(42, e.error());
+}
+
+TEST(Expected, testWithMoveOnlyType) {
+ typedef expected<std::unique_ptr<int>,std::unique_ptr<int>> exp_ptr;
+ exp_ptr e(std::make_unique<int>(3));
+ exp_ptr e2(unexpected(std::make_unique<int>(4)));
+
+ EXPECT_TRUE(e.has_value());
+ EXPECT_FALSE(e2.has_value());
+ EXPECT_EQ(3, *(e.value()));
+ EXPECT_EQ(4, *(e2.error()));
+
+ e2 = std::move(e);
+ EXPECT_TRUE(e.has_value());
+ EXPECT_TRUE(e2.has_value());
+ EXPECT_EQ(3, *(e2.value()));
+}