reexport remaining coroutine names

Summary: Reexport remaining names, including `noop_coroutine`, from `folly/experimental/coro/Coroutine.h`, which wraps inclusion of `experimental/coroutine`.

Differential Revision: D26227580

fbshipit-source-id: b7ea0bb0bb7447bf4327b2f178c51db544f70f46

folly/experimental/coro/Coroutine.h

@@ -29,6 +29,10 @@
 namespace folly::coro {
 
 using std::experimental::coroutine_handle;
+using std::experimental::coroutine_traits;
+using std::experimental::noop_coroutine;
+using std::experimental::noop_coroutine_handle;
+using std::experimental::noop_coroutine_promise;
 using std::experimental::suspend_always;
 using std::experimental::suspend_never;
 

folly/experimental/coro/Utils.h

@@ -63,12 +63,11 @@ struct await_suspend_return_coroutine_fn {
   coroutine_handle<> operator()(A& a, coroutine_handle<P> coro) const
       noexcept(noexcept(a.await_suspend(coro))) {
     using result = decltype(a.await_suspend(coro));
-    auto noop = std::experimental::noop_coroutine();
     if constexpr (std::is_same_v<void, result>) {
       a.await_suspend(coro);
-      return noop;
+      return noop_coroutine();
     } else if constexpr (std::is_same_v<bool, result>) {
-      return a.await_suspend(coro) ? noop : coro;
+      return a.await_suspend(coro) ? noop_coroutine() : coro;
     } else {
       return a.await_suspend(coro);
     }

folly/experimental/coro/detail/Barrier.h

@@ -80,7 +80,7 @@ class Barrier {
       }
       return std::exchange(continuation_, {});
     } else {
-      return std::experimental::noop_coroutine();
+      return noop_coroutine();
     }
   }
 
@@ -95,12 +95,12 @@ class Barrier {
       auto coro = std::exchange(continuation_, {});
       if (asyncFrame_ != nullptr) {
         folly::resumeCoroutineWithNewAsyncStackRoot(coro, *asyncFrame_);
-        return std::experimental::noop_coroutine();
+        return noop_coroutine();
       } else {
         return coro;
       }
     } else {
-      return std::experimental::noop_coroutine();
+      return noop_coroutine();
     }
   }