Use throw_exception in Optional

Summary: [Folly] Use `throw_exception` in `Optional`, which also respects all stated reasons why the `throw` statement is moved to a separate `.cpp` - to outline it and to permit replacement of its implementation with a call to `std::terminate`.

Reviewed By: akrieger

Differential Revision: D7728129

fbshipit-source-id: 0539f9d16a719b52f5a81b13b5d2ce2b61d36de0

folly/Optional.cpp

-/*
- * Copyright 2017-present Facebook, Inc.
- *
- * 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 <folly/Optional.h>
-
-namespace folly {
-namespace detail {
-
-void throw_optional_empty_exception() {
-  throw OptionalEmptyException();
-}
-
-} // namespace detail
-} // namespace folly

folly/Optional.h

@@ -63,6 +63,7 @@
 #include <folly/Portability.h>
 #include <folly/Traits.h>
 #include <folly/Utility.h>
+#include <folly/lang/Exception.h>
 
 namespace folly {
 
@@ -72,11 +73,6 @@ class Optional;
 namespace detail {
 struct NoneHelper {};
 
-// Allow each translation unit to control its own -fexceptions setting.
-// If exceptions are disabled, std::terminate() will be called instead of
-// throwing OptionalEmptyException when the condition fails.
-[[noreturn]] void throw_optional_empty_exception();
-
 template <class Value>
 struct OptionalPromiseReturn;
 } // namespace detail
@@ -321,7 +317,7 @@ class Optional {
  private:
   void require_value() const {
     if (!storage_.hasValue) {
-      detail::throw_optional_empty_exception();
+      throw_exception<OptionalEmptyException>();
     }
   }