Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 870 insertions, 0 deletions

diff --git a/mfbt/tests/TestResult.cpp b/mfbt/tests/TestResult.cpp
new file mode 100644
index 0000000000..a2e10640c5
--- /dev/null
+++ b/mfbt/tests/TestResult.cpp
@@ -0,0 +1,870 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdint.h>
+#include <string.h>
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Try.h"
+#include "mozilla/UniquePtr.h"
+
+using mozilla::Err;
+using mozilla::GenericErrorResult;
+using mozilla::Ok;
+using mozilla::Result;
+using mozilla::UniquePtr;
+
+#define MOZ_STATIC_AND_RELEASE_ASSERT(expr) \
+  static_assert(expr);                      \
+  MOZ_RELEASE_ASSERT(expr)
+
+enum struct TestUnusedZeroEnum : int16_t { Ok = 0, NotOk = 1 };
+
+namespace mozilla::detail {
+template <>
+struct UnusedZero<TestUnusedZeroEnum> : UnusedZeroEnum<TestUnusedZeroEnum> {};
+}  // namespace mozilla::detail
+
+struct Failed {};
+
+namespace mozilla::detail {
+template <>
+struct UnusedZero<Failed> {
+  using StorageType = uintptr_t;
+
+  static constexpr bool value = true;
+  static constexpr StorageType nullValue = 0;
+  static constexpr StorageType GetDefaultValue() { return 2; }
+
+  static constexpr void AssertValid(StorageType aValue) {}
+  static constexpr Failed Inspect(const StorageType& aValue) {
+    return Failed{};
+  }
+  static constexpr Failed Unwrap(StorageType aValue) { return Failed{}; }
+  static constexpr StorageType Store(Failed aValue) {
+    return GetDefaultValue();
+  }
+};
+
+}  // namespace mozilla::detail
+
+// V is trivially default-constructible, and E has UnusedZero<E>::value == true,
+// for a reference type and for a non-reference type
+static_assert(mozilla::detail::SelectResultImpl<uintptr_t, Failed>::value ==
+              mozilla::detail::PackingStrategy::NullIsOk);
+static_assert(
+    mozilla::detail::SelectResultImpl<Ok, TestUnusedZeroEnum>::value ==
+    mozilla::detail::PackingStrategy::NullIsOk);
+static_assert(mozilla::detail::SelectResultImpl<Ok, Failed>::value ==
+              mozilla::detail::PackingStrategy::LowBitTagIsError);
+
+static_assert(std::is_trivially_destructible_v<Result<uintptr_t, Failed>>);
+static_assert(std::is_trivially_destructible_v<Result<Ok, TestUnusedZeroEnum>>);
+static_assert(std::is_trivially_destructible_v<Result<Ok, Failed>>);
+
+static_assert(
+    sizeof(Result<bool, TestUnusedZeroEnum>) <= sizeof(uintptr_t),
+    "Result with bool value type should not be larger than pointer-sized");
+static_assert(sizeof(Result<Ok, Failed>) == sizeof(uint8_t),
+              "Result with empty value type should be size 1");
+static_assert(sizeof(Result<int*, Failed>) == sizeof(uintptr_t),
+              "Result with two aligned pointer types should be pointer-sized");
+static_assert(
+    sizeof(Result<char*, Failed*>) > sizeof(char*),
+    "Result with unaligned success type `char*` must not be pointer-sized");
+static_assert(
+    sizeof(Result<int*, char*>) > sizeof(char*),
+    "Result with unaligned error type `char*` must not be pointer-sized");
+
+enum Foo8 : uint8_t {};
+enum Foo16 : uint16_t {};
+enum Foo32 : uint32_t {};
+static_assert(sizeof(Result<Ok, Foo8>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+static_assert(sizeof(Result<Ok, Foo16>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+static_assert(sizeof(Foo32) >= sizeof(uintptr_t) ||
+                  sizeof(Result<Ok, Foo32>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+
+static_assert(sizeof(Result<Foo16, Foo8>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+static_assert(sizeof(Result<Foo8, Foo16>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+static_assert(sizeof(Foo32) >= sizeof(uintptr_t) ||
+                  sizeof(Result<Foo32, Foo16>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+static_assert(sizeof(Foo32) >= sizeof(uintptr_t) ||
+                  sizeof(Result<Foo16, Foo32>) <= sizeof(uintptr_t),
+              "Result with small types should be pointer-sized");
+
+#if __cplusplus < 202002L
+static_assert(std::is_literal_type_v<Result<int*, Failed>>);
+static_assert(std::is_literal_type_v<Result<Ok, Failed>>);
+static_assert(std::is_literal_type_v<Result<Ok, Foo8>>);
+static_assert(std::is_literal_type_v<Result<Foo8, Foo16>>);
+static_assert(!std::is_literal_type_v<Result<Ok, UniquePtr<int>>>);
+#endif
+
+static constexpr GenericErrorResult<Failed> Fail() { return Err(Failed{}); }
+
+static constexpr GenericErrorResult<TestUnusedZeroEnum>
+FailTestUnusedZeroEnum() {
+  return Err(TestUnusedZeroEnum::NotOk);
+}
+
+static constexpr Result<Ok, Failed> Task1(bool pass) {
+  if (!pass) {
+    return Fail();  // implicit conversion from GenericErrorResult to Result
+  }
+  return Ok();
+}
+
+static constexpr Result<Ok, TestUnusedZeroEnum> Task1UnusedZeroEnumErr(
+    bool pass) {
+  if (!pass) {
+    return FailTestUnusedZeroEnum();  // implicit conversion from
+                                      // GenericErrorResult to Result
+  }
+  return Ok();
+}
+
+static constexpr Result<int, Failed> Task2(bool pass, int value) {
+  MOZ_TRY(
+      Task1(pass));  // converts one type of result to another in the error case
+  return value;      // implicit conversion from T to Result<T, E>
+}
+
+static constexpr Result<int, TestUnusedZeroEnum> Task2UnusedZeroEnumErr(
+    bool pass, int value) {
+  MOZ_TRY(Task1UnusedZeroEnumErr(
+      pass));    // converts one type of result to another in the error case
+  return value;  // implicit conversion from T to Result<T, E>
+}
+
+static Result<int, Failed> Task3(bool pass1, bool pass2, int value) {
+  int x, y;
+  MOZ_TRY_VAR(x, Task2(pass1, value));
+  MOZ_TRY_VAR(y, Task2(pass2, value));
+  return x + y;
+}
+
+static void BasicTests() {
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task1(true).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(!Task1(true).isErr());
+  MOZ_STATIC_AND_RELEASE_ASSERT(!Task1(false).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task1(false).isErr());
+
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task1UnusedZeroEnumErr(true).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(!Task1UnusedZeroEnumErr(true).isErr());
+  MOZ_STATIC_AND_RELEASE_ASSERT(!Task1UnusedZeroEnumErr(false).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task1UnusedZeroEnumErr(false).isErr());
+  MOZ_STATIC_AND_RELEASE_ASSERT(TestUnusedZeroEnum::NotOk ==
+                                Task1UnusedZeroEnumErr(false).inspectErr());
+  MOZ_STATIC_AND_RELEASE_ASSERT(TestUnusedZeroEnum::NotOk ==
+                                Task1UnusedZeroEnumErr(false).unwrapErr());
+
+  // MOZ_TRY works.
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2(true, 3).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2(true, 3).unwrap() == 3);
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2(true, 3).unwrapOr(6) == 3);
+  MOZ_RELEASE_ASSERT(Task2(false, 3).isErr());
+  MOZ_RELEASE_ASSERT(Task2(false, 3).unwrapOr(6) == 6);
+
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2UnusedZeroEnumErr(true, 3).isOk());
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2UnusedZeroEnumErr(true, 3).unwrap() == 3);
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2UnusedZeroEnumErr(true, 3).unwrapOr(6) ==
+                                3);
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2UnusedZeroEnumErr(false, 3).isErr());
+  MOZ_STATIC_AND_RELEASE_ASSERT(Task2UnusedZeroEnumErr(false, 3).unwrapOr(6) ==
+                                6);
+
+  // MOZ_TRY_VAR works.
+  MOZ_RELEASE_ASSERT(Task3(true, true, 3).isOk());
+  MOZ_RELEASE_ASSERT(Task3(true, true, 3).unwrap() == 6);
+  MOZ_RELEASE_ASSERT(Task3(true, false, 3).isErr());
+  MOZ_RELEASE_ASSERT(Task3(false, true, 3).isErr());
+  MOZ_RELEASE_ASSERT(Task3(false, true, 3).unwrapOr(6) == 6);
+
+  // Lvalues should work too.
+  {
+    constexpr Result<Ok, Failed> res1 = Task1(true);
+    MOZ_STATIC_AND_RELEASE_ASSERT(res1.isOk());
+    MOZ_STATIC_AND_RELEASE_ASSERT(!res1.isErr());
+
+    constexpr Result<Ok, Failed> res2 = Task1(false);
+    MOZ_STATIC_AND_RELEASE_ASSERT(!res2.isOk());
+    MOZ_STATIC_AND_RELEASE_ASSERT(res2.isErr());
+  }
+
+  {
+    Result<int, Failed> res = Task2(true, 3);
+    MOZ_RELEASE_ASSERT(res.isOk());
+    MOZ_RELEASE_ASSERT(res.unwrap() == 3);
+
+    res = Task2(false, 4);
+    MOZ_RELEASE_ASSERT(res.isErr());
+  }
+
+  // Some tests for pointer tagging.
+  {
+    int i = 123;
+
+    Result<int*, Failed> res = &i;
+    static_assert(sizeof(res) == sizeof(uintptr_t),
+                  "should use pointer tagging to fit in a word");
+
+    MOZ_RELEASE_ASSERT(res.isOk());
+    MOZ_RELEASE_ASSERT(*res.unwrap() == 123);
+
+    res = Err(Failed());
+    MOZ_RELEASE_ASSERT(res.isErr());
+  }
+}
+
+struct NonCopyableNonMovable {
+  explicit constexpr NonCopyableNonMovable(uint32_t aValue) : mValue(aValue) {}
+
+  NonCopyableNonMovable(const NonCopyableNonMovable&) = delete;
+  NonCopyableNonMovable(NonCopyableNonMovable&&) = delete;
+  NonCopyableNonMovable& operator=(const NonCopyableNonMovable&) = delete;
+  NonCopyableNonMovable& operator=(NonCopyableNonMovable&&) = delete;
+
+  uint32_t mValue;
+};
+
+static void InPlaceConstructionTests() {
+  {
+    // PackingStrategy == NullIsOk
+    static_assert(mozilla::detail::SelectResultImpl<NonCopyableNonMovable,
+                                                    Failed>::value ==
+                  mozilla::detail::PackingStrategy::NullIsOk);
+    constexpr Result<NonCopyableNonMovable, Failed> result{std::in_place, 42u};
+    MOZ_STATIC_AND_RELEASE_ASSERT(42 == result.inspect().mValue);
+  }
+
+  {
+    // PackingStrategy == Variant
+    static_assert(
+        mozilla::detail::SelectResultImpl<NonCopyableNonMovable, int>::value ==
+        mozilla::detail::PackingStrategy::Variant);
+    const Result<NonCopyableNonMovable, int> result{std::in_place, 42};
+    MOZ_RELEASE_ASSERT(42 == result.inspect().mValue);
+  }
+}
+
+/* * */
+
+struct Snafu : Failed {};
+
+static Result<Ok, Snafu*> Explode() {
+  static Snafu snafu;
+  return Err(&snafu);
+}
+
+static Result<Ok, Failed*> ErrorGeneralization() {
+  MOZ_TRY(Explode());  // change error type from Snafu* to more general Failed*
+  return Ok();
+}
+
+static void TypeConversionTests() {
+  MOZ_RELEASE_ASSERT(ErrorGeneralization().isErr());
+
+  {
+    const Result<Ok, Failed*> res = Explode();
+    MOZ_RELEASE_ASSERT(res.isErr());
+  }
+
+  {
+    const Result<Ok, Failed*> res = Result<Ok, Snafu*>{Ok{}};
+    MOZ_RELEASE_ASSERT(res.isOk());
+  }
+}
+
+static void EmptyValueTest() {
+  struct Fine {};
+  mozilla::Result<Fine, Failed> res((Fine()));
+  res.unwrap();
+  MOZ_RELEASE_ASSERT(res.isOk());
+  static_assert(sizeof(res) == sizeof(uint8_t),
+                "Result with empty value and error types should be size 1");
+}
+
+static void MapTest() {
+  struct MyError {
+    int x;
+
+    explicit MyError(int y) : x(y) {}
+  };
+
+  // Mapping over success values, to the same success type.
+  {
+    Result<int, MyError> res(5);
+    bool invoked = false;
+    auto res2 = res.map([&invoked](int x) {
+      MOZ_RELEASE_ASSERT(x == 5);
+      invoked = true;
+      return 6;
+    });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 6);
+  }
+
+  // Mapping over success values, to a different success type.
+  {
+    Result<int, MyError> res(5);
+    bool invoked = false;
+    auto res2 = res.map([&invoked](int x) {
+      MOZ_RELEASE_ASSERT(x == 5);
+      invoked = true;
+      return "hello";
+    });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(strcmp(res2.unwrap(), "hello") == 0);
+  }
+
+  // Mapping over success values (constexpr).
+  {
+    constexpr uint64_t kValue = 42u;
+    constexpr auto res2a = Result<int32_t, Failed>{5}.map([](int32_t x) {
+      MOZ_RELEASE_ASSERT(x == 5);
+      return kValue;
+    });
+    MOZ_STATIC_AND_RELEASE_ASSERT(res2a.isOk());
+    MOZ_STATIC_AND_RELEASE_ASSERT(kValue == res2a.inspect());
+  }
+
+  // Mapping over error values.
+  {
+    MyError err(1);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    Result<char, MyError> res2 = res.map([](int x) {
+      MOZ_RELEASE_ASSERT(false);
+      return 'a';
+    });
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(res2.unwrapErr().x == err.x);
+  }
+
+  // Function pointers instead of lambdas as the mapping function.
+  {
+    Result<const char*, MyError> res("hello");
+    auto res2 = res.map(strlen);
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 5);
+  }
+}
+
+static void MapErrTest() {
+  struct MyError {
+    int x;
+
+    explicit MyError(int y) : x(y) {}
+  };
+
+  struct MyError2 {
+    int a;
+
+    explicit MyError2(int b) : a(b) {}
+  };
+
+  // Mapping over error values, to the same error type.
+  {
+    MyError err(1);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 = res.mapErr([&invoked](const auto err) {
+      MOZ_RELEASE_ASSERT(err.x == 1);
+      invoked = true;
+      return MyError(2);
+    });
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrapErr().x == 2);
+  }
+
+  // Mapping over error values, to a different error type.
+  {
+    MyError err(1);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 = res.mapErr([&invoked](const auto err) {
+      MOZ_RELEASE_ASSERT(err.x == 1);
+      invoked = true;
+      return MyError2(2);
+    });
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrapErr().a == 2);
+  }
+
+  // Mapping over success values.
+  {
+    Result<int, MyError> res(5);
+    auto res2 = res.mapErr([](const auto err) {
+      MOZ_RELEASE_ASSERT(false);
+      return MyError(1);
+    });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 5);
+  }
+
+  // Function pointers instead of lambdas as the mapping function.
+  {
+    Result<Ok, const char*> res("hello");
+    auto res2 = res.mapErr(strlen);
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(res2.unwrapErr() == 5);
+  }
+}
+
+static Result<Ok, size_t> strlen_ResultWrapper(const char* aValue) {
+  return Err(strlen(aValue));
+}
+
+static void OrElseTest() {
+  struct MyError {
+    int x;
+
+    explicit constexpr MyError(int y) : x(y) {}
+  };
+
+  struct MyError2 {
+    int a;
+
+    explicit constexpr MyError2(int b) : a(b) {}
+  };
+
+  // `orElse`ing over error values, to Result<V, E> (the same error type) error
+  // variant.
+  {
+    MyError err(1);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 = res.orElse([&invoked](const auto err) -> Result<char, MyError> {
+      MOZ_RELEASE_ASSERT(err.x == 1);
+      invoked = true;
+      if (err.x != 42) {
+        return Err(MyError(2));
+      }
+      return 'a';
+    });
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrapErr().x == 2);
+  }
+
+  // `orElse`ing over error values, to Result<V, E> (the same error type)
+  // success variant.
+  {
+    MyError err(42);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 = res.orElse([&invoked](const auto err) -> Result<char, MyError> {
+      MOZ_RELEASE_ASSERT(err.x == 42);
+      invoked = true;
+      if (err.x != 42) {
+        return Err(MyError(2));
+      }
+      return 'a';
+    });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 'a');
+  }
+
+  // `orElse`ing over error values, to Result<V, E2> (a different error type)
+  // error variant.
+  {
+    MyError err(1);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 =
+        res.orElse([&invoked](const auto err) -> Result<char, MyError2> {
+          MOZ_RELEASE_ASSERT(err.x == 1);
+          invoked = true;
+          if (err.x != 42) {
+            return Err(MyError2(2));
+          }
+          return 'a';
+        });
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrapErr().a == 2);
+  }
+
+  // `orElse`ing over error values, to Result<V, E2> (a different error type)
+  // success variant.
+  {
+    MyError err(42);
+    Result<char, MyError> res(err);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    bool invoked = false;
+    auto res2 =
+        res.orElse([&invoked](const auto err) -> Result<char, MyError2> {
+          MOZ_RELEASE_ASSERT(err.x == 42);
+          invoked = true;
+          if (err.x != 42) {
+            return Err(MyError2(2));
+          }
+          return 'a';
+        });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(invoked);
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 'a');
+  }
+
+  // `orElse`ing over success values.
+  {
+    Result<int, MyError> res(5);
+    auto res2 = res.orElse([](const auto err) -> Result<int, MyError> {
+      MOZ_RELEASE_ASSERT(false);
+      return Err(MyError(1));
+    });
+    MOZ_RELEASE_ASSERT(res2.isOk());
+    MOZ_RELEASE_ASSERT(res2.unwrap() == 5);
+  }
+
+  // Function pointers instead of lambdas as the `orElse`ing function.
+  {
+    Result<Ok, const char*> res("hello");
+    auto res2 = res.orElse(strlen_ResultWrapper);
+    MOZ_RELEASE_ASSERT(res2.isErr());
+    MOZ_RELEASE_ASSERT(res2.unwrapErr() == 5);
+  }
+}
+
+static void AndThenTest() {
+  // `andThen`ing over success results.
+  {
+    Result<int, const char*> r1(10);
+    Result<int, const char*> r2 =
+        r1.andThen([](int x) { return Result<int, const char*>(x + 1); });
+    MOZ_RELEASE_ASSERT(r2.isOk());
+    MOZ_RELEASE_ASSERT(r2.unwrap() == 11);
+  }
+
+  // `andThen`ing over success results (constexpr).
+  {
+    constexpr Result<int, Failed> r2a = Result<int, Failed>{10}.andThen(
+        [](int x) { return Result<int, Failed>(x + 1); });
+    MOZ_STATIC_AND_RELEASE_ASSERT(r2a.isOk());
+    MOZ_STATIC_AND_RELEASE_ASSERT(r2a.inspect() == 11);
+  }
+
+  // `andThen`ing over error results.
+  {
+    Result<int, const char*> r3("error");
+    Result<int, const char*> r4 = r3.andThen([](int x) {
+      MOZ_RELEASE_ASSERT(false);
+      return Result<int, const char*>(1);
+    });
+    MOZ_RELEASE_ASSERT(r4.isErr());
+    MOZ_RELEASE_ASSERT(r3.unwrapErr() == r4.unwrapErr());
+  }
+
+  // andThen with a function accepting an rvalue
+  {
+    Result<int, const char*> r1(10);
+    Result<int, const char*> r2 =
+        r1.andThen([](int&& x) { return Result<int, const char*>(x + 1); });
+    MOZ_RELEASE_ASSERT(r2.isOk());
+    MOZ_RELEASE_ASSERT(r2.unwrap() == 11);
+  }
+
+  // `andThen`ing over error results (constexpr).
+  {
+    constexpr Result<int, Failed> r4a =
+        Result<int, Failed>{Failed{}}.andThen([](int x) {
+          MOZ_RELEASE_ASSERT(false);
+          return Result<int, Failed>(1);
+        });
+    MOZ_STATIC_AND_RELEASE_ASSERT(r4a.isErr());
+  }
+}
+
+using UniqueResult = Result<UniquePtr<int>, const char*>;
+
+static UniqueResult UniqueTask() { return mozilla::MakeUnique<int>(3); }
+static UniqueResult UniqueTaskError() { return Err("bad"); }
+
+using UniqueErrorResult = Result<int, UniquePtr<int>>;
+static UniqueErrorResult UniqueError() {
+  return Err(mozilla::MakeUnique<int>(4));
+}
+
+static Result<Ok, UniquePtr<int>> TryUniqueErrorResult() {
+  MOZ_TRY(UniqueError());
+  return Ok();
+}
+
+static void UniquePtrTest() {
+  {
+    auto result = UniqueTask();
+    MOZ_RELEASE_ASSERT(result.isOk());
+    auto ptr = result.unwrap();
+    MOZ_RELEASE_ASSERT(ptr);
+    MOZ_RELEASE_ASSERT(*ptr == 3);
+    auto moved = result.unwrap();
+    MOZ_RELEASE_ASSERT(!moved);
+  }
+
+  {
+    auto err = UniqueTaskError();
+    MOZ_RELEASE_ASSERT(err.isErr());
+    auto ptr = err.unwrapOr(mozilla::MakeUnique<int>(4));
+    MOZ_RELEASE_ASSERT(ptr);
+    MOZ_RELEASE_ASSERT(*ptr == 4);
+  }
+
+  {
+    auto result = UniqueTaskError();
+    result = UniqueResult(mozilla::MakeUnique<int>(6));
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() && *result.inspect() == 6);
+  }
+
+  {
+    auto result = UniqueError();
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(result.inspectErr());
+    MOZ_RELEASE_ASSERT(*result.inspectErr() == 4);
+    auto err = result.unwrapErr();
+    MOZ_RELEASE_ASSERT(!result.inspectErr());
+    MOZ_RELEASE_ASSERT(err);
+    MOZ_RELEASE_ASSERT(*err == 4);
+
+    result = UniqueErrorResult(0);
+    MOZ_RELEASE_ASSERT(result.isOk() && result.unwrap() == 0);
+  }
+
+  {
+    auto result = TryUniqueErrorResult();
+    MOZ_RELEASE_ASSERT(result.isErr());
+    auto err = result.unwrapErr();
+    MOZ_RELEASE_ASSERT(err && *err == 4);
+    MOZ_RELEASE_ASSERT(!result.inspectErr());
+  }
+}
+
+struct ZeroIsUnusedStructForPointer {
+  int x = 1;
+};
+enum class ZeroIsUnusedEnum1 : uint8_t {
+  V1 = 1,
+  V2 = 2,
+};
+enum class ZeroIsUnusedEnum2 : uint16_t {
+  V1 = 1,
+  V2 = 2,
+};
+enum class ZeroIsUnusedEnum4 : uint32_t {
+  V1 = 1,
+  V2 = 2,
+};
+enum class ZeroIsUnusedEnum8 : uint64_t {
+  V1 = 1,
+  V2 = 2,
+};
+struct EmptyErrorStruct {};
+
+template <>
+struct mozilla::detail::UnusedZero<ZeroIsUnusedStructForPointer*> {
+  static const bool value = true;
+};
+template <>
+struct mozilla::detail::UnusedZero<ZeroIsUnusedEnum1> {
+  static const bool value = true;
+};
+template <>
+struct mozilla::detail::UnusedZero<ZeroIsUnusedEnum2> {
+  static const bool value = true;
+};
+template <>
+struct mozilla::detail::UnusedZero<ZeroIsUnusedEnum4> {
+  static const bool value = true;
+};
+template <>
+struct mozilla::detail::UnusedZero<ZeroIsUnusedEnum8> {
+  static const bool value = true;
+};
+
+static void ZeroIsEmptyErrorTest() {
+  {
+    ZeroIsUnusedStructForPointer s;
+
+    using V = ZeroIsUnusedStructForPointer*;
+
+    mozilla::Result<V, EmptyErrorStruct> result(&s);
+    MOZ_RELEASE_ASSERT(sizeof(result) == sizeof(V));
+
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() == &s);
+  }
+
+  {
+    using V = ZeroIsUnusedStructForPointer*;
+
+    mozilla::Result<V, EmptyErrorStruct> result(Err(EmptyErrorStruct{}));
+
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(*reinterpret_cast<V*>(&result) == nullptr);
+  }
+
+  {
+    ZeroIsUnusedEnum1 e = ZeroIsUnusedEnum1::V1;
+
+    using V = ZeroIsUnusedEnum1;
+
+    mozilla::Result<V, EmptyErrorStruct> result(e);
+    MOZ_RELEASE_ASSERT(sizeof(result) == sizeof(V));
+
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() == e);
+  }
+
+  {
+    using V = ZeroIsUnusedEnum1;
+
+    mozilla::Result<V, EmptyErrorStruct> result(Err(EmptyErrorStruct()));
+
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(*reinterpret_cast<uint8_t*>(&result) == 0);
+  }
+
+  {
+    ZeroIsUnusedEnum2 e = ZeroIsUnusedEnum2::V1;
+
+    using V = ZeroIsUnusedEnum2;
+
+    mozilla::Result<V, EmptyErrorStruct> result(e);
+    MOZ_RELEASE_ASSERT(sizeof(result) == sizeof(V));
+
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() == e);
+  }
+
+  {
+    using V = ZeroIsUnusedEnum2;
+
+    mozilla::Result<V, EmptyErrorStruct> result(Err(EmptyErrorStruct()));
+
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(*reinterpret_cast<uint16_t*>(&result) == 0);
+  }
+
+  {
+    ZeroIsUnusedEnum4 e = ZeroIsUnusedEnum4::V1;
+
+    using V = ZeroIsUnusedEnum4;
+
+    mozilla::Result<V, EmptyErrorStruct> result(e);
+    MOZ_RELEASE_ASSERT(sizeof(result) == sizeof(V));
+
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() == e);
+  }
+
+  {
+    using V = ZeroIsUnusedEnum4;
+
+    mozilla::Result<V, EmptyErrorStruct> result(Err(EmptyErrorStruct()));
+
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(*reinterpret_cast<uint32_t*>(&result) == 0);
+  }
+
+  {
+    ZeroIsUnusedEnum8 e = ZeroIsUnusedEnum8::V1;
+
+    using V = ZeroIsUnusedEnum8;
+
+    mozilla::Result<V, EmptyErrorStruct> result(e);
+    MOZ_RELEASE_ASSERT(sizeof(result) == sizeof(V));
+
+    MOZ_RELEASE_ASSERT(result.isOk());
+    MOZ_RELEASE_ASSERT(result.inspect() == e);
+  }
+
+  {
+    using V = ZeroIsUnusedEnum8;
+
+    mozilla::Result<V, EmptyErrorStruct> result(Err(EmptyErrorStruct()));
+
+    MOZ_RELEASE_ASSERT(result.isErr());
+    MOZ_RELEASE_ASSERT(*reinterpret_cast<uint64_t*>(&result) == 0);
+  }
+}
+
+class Foo {};
+
+class C1 {};
+class C2 : public C1 {};
+
+class E1 {};
+class E2 : public E1 {};
+
+void UpcastTest() {
+  {
+    C2 c2;
+
+    mozilla::Result<C2*, Failed> result(&c2);
+    mozilla::Result<C1*, Failed> copied(std::move(result));
+
+    MOZ_RELEASE_ASSERT(copied.inspect() == &c2);
+  }
+
+  {
+    E2 e2;
+
+    mozilla::Result<Foo, E2*> result(Err(&e2));
+    mozilla::Result<Foo, E1*> copied(std::move(result));
+
+    MOZ_RELEASE_ASSERT(copied.inspectErr() == &e2);
+  }
+
+  {
+    C2 c2;
+
+    mozilla::Result<C2*, E2*> result(&c2);
+    mozilla::Result<C1*, E1*> copied(std::move(result));
+
+    MOZ_RELEASE_ASSERT(copied.inspect() == &c2);
+  }
+
+  {
+    E2 e2;
+
+    mozilla::Result<C2*, E2*> result(Err(&e2));
+    mozilla::Result<C1*, E1*> copied(std::move(result));
+
+    MOZ_RELEASE_ASSERT(copied.inspectErr() == &e2);
+  }
+}
+
+/* * */
+
+int main() {
+  BasicTests();
+  InPlaceConstructionTests();
+  TypeConversionTests();
+  EmptyValueTest();
+  MapTest();
+  MapErrTest();
+  OrElseTest();
+  AndThenTest();
+  UniquePtrTest();
+  ZeroIsEmptyErrorTest();
+  UpcastTest();
+  return 0;
+}