Support C++17 noexcept function type in base::Bind

In C++17, noexcept keyword is a part of the function type, and that
causes a pattern match failure on base::Bind implementation.
This CL fixes the failure by falling it back to bare function cases.

Bug: 752720
Change-Id: I98c71977fa3fd759956c86e394fb9e30179c951c
Reviewed-on: https://chromium-review.googlesource.com/1027530
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553913}

base/bind_internal.h

@@ -397,9 +397,9 @@ struct FunctorTraits<R (*)(Args...)> {
   static constexpr bool is_method = false;
   static constexpr bool is_nullable = true;
 
-  template <typename... RunArgs>
-  static R Invoke(R (*function)(Args...), RunArgs&&... args) {
-    return function(std::forward<RunArgs>(args)...);
+  template <typename Function, typename... RunArgs>
+  static R Invoke(Function&& function, RunArgs&&... args) {
+    return std::forward<Function>(function)(std::forward<RunArgs>(args)...);
   }
 };
 
@@ -440,8 +440,8 @@ struct FunctorTraits<R (Receiver::*)(Args...)> {
   static constexpr bool is_method = true;
   static constexpr bool is_nullable = true;
 
-  template <typename ReceiverPtr, typename... RunArgs>
-  static R Invoke(R (Receiver::*method)(Args...),
+  template <typename Method, typename ReceiverPtr, typename... RunArgs>
+  static R Invoke(Method method,
                   ReceiverPtr&& receiver_ptr,
                   RunArgs&&... args) {
     return ((*receiver_ptr).*method)(std::forward<RunArgs>(args)...);
@@ -455,14 +455,31 @@ struct FunctorTraits<R (Receiver::*)(Args...) const> {
   static constexpr bool is_method = true;
   static constexpr bool is_nullable = true;
 
-  template <typename ReceiverPtr, typename... RunArgs>
-  static R Invoke(R (Receiver::*method)(Args...) const,
+  template <typename Method, typename ReceiverPtr, typename... RunArgs>
+  static R Invoke(Method method,
                   ReceiverPtr&& receiver_ptr,
                   RunArgs&&... args) {
     return ((*receiver_ptr).*method)(std::forward<RunArgs>(args)...);
   }
 };
 
+#ifdef __cpp_noexcept_function_type
+// noexcept makes a distinct function type in C++17.
+// I.e. `void(*)()` and `void(*)() noexcept` are same in pre-C++17, and
+// different in C++17.
+template <typename R, typename... Args>
+struct FunctorTraits<R (*)(Args...) noexcept> : FunctorTraits<R (*)(Args...)> {
+};
+
+template <typename R, typename Receiver, typename... Args>
+struct FunctorTraits<R (Receiver::*)(Args...) noexcept>
+    : FunctorTraits<R (Receiver::*)(Args...)> {};
+
+template <typename R, typename Receiver, typename... Args>
+struct FunctorTraits<R (Receiver::*)(Args...) const noexcept>
+    : FunctorTraits<R (Receiver::*)(Args...) const> {};
+#endif
+
 // For IgnoreResults.
 template <typename T>
 struct FunctorTraits<IgnoreResultHelper<T>> : FunctorTraits<T> {

base/bind_unittest.cc

@@ -311,6 +311,10 @@ void TakesACallback(const Closure& callback) {
   callback.Run();
 }
 
+int Noexcept() noexcept {
+  return 42;
+}
+
 class BindTest : public ::testing::Test {
  public:
   BindTest() {
@@ -326,6 +330,8 @@ class BindTest : public ::testing::Test {
   }
 
   static int IntFunc0() { return static_func_mock_ptr->IntMethod0(); }
+  int NoexceptMethod() noexcept { return 42; }
+  int ConstNoexceptMethod() const noexcept { return 42; }
 
  protected:
   StrictMock<NoRef> no_ref_;
@@ -1469,6 +1475,16 @@ TEST_F(BindTest, UnwrapPassed) {
   EXPECT_EQ(p, internal::Unwrap(Passed(WrapUnique(p))).get());
 }
 
+TEST_F(BindTest, BindNoexcept) {
+  EXPECT_EQ(42, base::BindOnce(&Noexcept).Run());
+  EXPECT_EQ(
+      42,
+      base::BindOnce(&BindTest::NoexceptMethod, base::Unretained(this)).Run());
+  EXPECT_EQ(
+      42, base::BindOnce(&BindTest::ConstNoexceptMethod, base::Unretained(this))
+              .Run());
+}
+
 // Test null callbacks cause a DCHECK.
 TEST(BindDeathTest, NullCallback) {
   base::Callback<void(int)> null_cb;