1 files changed, 212 insertions, 0 deletions
diff --git a/mfbt/tests/TestResult.cpp b/mfbt/tests/TestResult.cpp
new file mode 100644
index 0000000000..b02e710003
--- /dev/null
+++ b/mfbt/tests/TestResult.cpp
@@ -0,0 +1,212 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 <string.h>
+#include "mozilla/Result.h"
+
+using mozilla::GenericErrorResult;
+using mozilla::MakeGenericErrorResult;
+using mozilla::Ok;
+using mozilla::Result;
+
+struct Failed
+{
+  int x;
+};
+
+static_assert(sizeof(Result<Ok, Failed&>) == sizeof(uintptr_t),
+              "Result with empty value type should be pointer-sized");
+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");
+
+static GenericErrorResult<Failed&>
+Fail()
+{
+  static Failed failed;
+  return MakeGenericErrorResult<Failed&>(failed);
+}
+
+static Result<Ok, Failed&>
+Task1(bool pass)
+{
+  if (!pass) {
+    return Fail();  // implicit conversion from GenericErrorResult to Result
+  }
+  return Ok();
+}
+
+static 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 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_RELEASE_ASSERT(Task1(true).isOk());
+  MOZ_RELEASE_ASSERT(!Task1(true).isErr());
+  MOZ_RELEASE_ASSERT(!Task1(false).isOk());
+  MOZ_RELEASE_ASSERT(Task1(false).isErr());
+
+  // MOZ_TRY works.
+  MOZ_RELEASE_ASSERT(Task2(true, 3).isOk());
+  MOZ_RELEASE_ASSERT(Task2(true, 3).unwrap() == 3);
+  MOZ_RELEASE_ASSERT(Task2(false, 3).isErr());
+
+  // 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());
+
+  // Lvalues should work too.
+  {
+    Result<Ok, Failed&> res = Task1(true);
+    MOZ_RELEASE_ASSERT(res.isOk());
+    MOZ_RELEASE_ASSERT(!res.isErr());
+
+    res = Task1(false);
+    MOZ_RELEASE_ASSERT(!res.isOk());
+    MOZ_RELEASE_ASSERT(res.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;
+    double d = 3.14;
+
+    Result<int*, double&> 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 = MakeGenericErrorResult(d);
+    MOZ_RELEASE_ASSERT(res.isErr());
+    MOZ_RELEASE_ASSERT(&res.unwrapErr() == &d);
+    MOZ_RELEASE_ASSERT(res.unwrapErr() == 3.14);
+  }
+}
+
+
+/* * */
+
+struct Snafu : Failed {};
+
+static Result<Ok, Snafu*>
+Explode()
+{
+  static Snafu snafu;
+  return MakeGenericErrorResult(&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());
+}
+
+static void
+EmptyValueTest()
+{
+  struct Fine {};
+  mozilla::Result<Fine, int&> res((Fine()));
+  res.unwrap();
+  MOZ_RELEASE_ASSERT(res.isOk());
+  static_assert(sizeof(res) == sizeof(uintptr_t),
+                "Result with empty value type should be pointer-sized");
+}
+
+static void
+ReferenceTest()
+{
+  struct MyError { int x = 0; };
+  MyError merror;
+  Result<int, MyError&> res(merror);
+  MOZ_RELEASE_ASSERT(&res.unwrapErr() == &merror);
+}
+
+static void
+MapTest()
+{
+  struct MyError {
+    int x;
+
+    explicit MyError(int y) : x(y) { }
+  };
+
+  // Mapping over success values.
+  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 error values.
+  MyError err(1);
+  Result<char, MyError> res3(err);
+  MOZ_RELEASE_ASSERT(res3.isErr());
+  Result<char, MyError> res4 = res3.map([](int x) {
+    MOZ_RELEASE_ASSERT(false);
+    return 'a';
+  });
+  MOZ_RELEASE_ASSERT(res4.isErr());
+  MOZ_RELEASE_ASSERT(res4.unwrapErr().x == err.x);
+
+  // Function pointers instead of lamdbas as the mapping function.
+  Result<const char*, MyError> res5("hello");
+  auto res6 = res5.map(strlen);
+  MOZ_RELEASE_ASSERT(res6.isOk());
+  MOZ_RELEASE_ASSERT(res6.unwrap() == 5);
+}
+
+/* * */
+
+int main()
+{
+  BasicTests();
+  TypeConversionTests();
+  EmptyValueTest();
+  ReferenceTest();
+  MapTest();
+  return 0;
+}