exception_wrapper::handle should accommodate noexcept lambdas in C++17

Summary: `exception_wrapper::handle` uses the signature of `Fn::operator()` to pick apart the function type and deduce the exception type for the handler. We use specializations of an `arg_type_` class template to do this. In C++17, `noexcept` is a part of the type system, but there were no specializations of `arg_type_` to handle `noexcept`-qualified callables.

Reviewed By: ispeters

Differential Revision: D24733871

fbshipit-source-id: 344e735e653296c9344b6c09662fccd94953e8a7

folly/ExceptionWrapper-inl.h

@@ -59,6 +59,41 @@ struct exception_wrapper::arg_type_<Ret (*)(...)> {
   using type = AnyException;
 };
 
+#ifdef FOLLY_HAVE_NOEXCEPT_FUNCTION_TYPE
+template <class Ret, class Class, class Arg>
+struct exception_wrapper::arg_type_<Ret (Class::*)(Arg) noexcept> {
+  using type = Arg;
+};
+template <class Ret, class Class, class Arg>
+struct exception_wrapper::arg_type_<Ret (Class::*)(Arg) const noexcept> {
+  using type = Arg;
+};
+template <class Ret, class Arg>
+struct exception_wrapper::arg_type_<Ret(Arg) noexcept> {
+  using type = Arg;
+};
+template <class Ret, class Arg>
+struct exception_wrapper::arg_type_<Ret (*)(Arg) noexcept> {
+  using type = Arg;
+};
+template <class Ret, class Class>
+struct exception_wrapper::arg_type_<Ret (Class::*)(...) noexcept> {
+  using type = AnyException;
+};
+template <class Ret, class Class>
+struct exception_wrapper::arg_type_<Ret (Class::*)(...) const noexcept> {
+  using type = AnyException;
+};
+template <class Ret>
+struct exception_wrapper::arg_type_<Ret(...) noexcept> {
+  using type = AnyException;
+};
+template <class Ret>
+struct exception_wrapper::arg_type_<Ret (*)(...) noexcept> {
+  using type = AnyException;
+};
+#endif
+
 template <class Ret, class... Args>
 inline Ret exception_wrapper::noop_(Args...) {
   return Ret();

folly/test/ExceptionWrapperTest.cpp

@@ -589,7 +589,7 @@ TEST(ExceptionWrapper, handle_std_exception) {
   auto expect_runtime_error_yes_catch_all = [&](const exception_wrapper& ew) {
     ew.handle(
         [](const std::logic_error&) { ADD_FAILURE(); },
-        [&](const std::runtime_error&) { handled = true; },
+        [&](const std::runtime_error&) noexcept { handled = true; },
         [](const std::exception&) { ADD_FAILURE(); },
         [](...) { ADD_FAILURE(); });
   };
@@ -606,7 +606,7 @@ TEST(ExceptionWrapper, handle_std_exception) {
 
   auto expect_runtime_error_no_catch_all = [&](const exception_wrapper& ew) {
     ew.handle(
-        [](const std::logic_error&) { ADD_FAILURE(); },
+        [](const std::logic_error&) noexcept { ADD_FAILURE(); },
         [&](const std::runtime_error&) { handled = true; },
         [](const std::exception&) { ADD_FAILURE(); });
   };