let coro::get_awaiter be a function-object and evade ADL

Reviewed By: cjhawley Differential Revision: D69710057 fbshipit-source-id: 5e8d92d41f36e62ee90eec15d6b283c5bbbd010b
novitae · Feb 17, 2025 · 513e1b9 · 513e1b9
1 parent 58b6c5a
commit 513e1b9
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Showing 3 changed files with 41 additions and 39 deletions.
diff --git a/folly/coro/Traits.h b/folly/coro/Traits.h
@@ -143,39 +143,42 @@ constexpr bool is_awaitable_v = is_awaitable<T>::value;
 /// for that type.
 ///
 /// This encapsulates calling 'operator co_await()' if it exists.
-template <
-    typename Awaitable,
-    std::enable_if_t<
-        folly::Conjunction<
-            is_awaiter<Awaitable>,
-            folly::Negation<detail::_has_free_operator_co_await<Awaitable>>,
-            folly::Negation<detail::_has_member_operator_co_await<Awaitable>>>::
-            value,
-        int> = 0>
-Awaitable& get_awaiter(Awaitable&& awaitable) {
-  return static_cast<Awaitable&>(awaitable);
-}
-
-template <
-    typename Awaitable,
-    std::enable_if_t<
-        detail::_has_member_operator_co_await<Awaitable>::value,
-        int> = 0>
-decltype(auto) get_awaiter(Awaitable&& awaitable) {
-  return static_cast<Awaitable&&>(awaitable).operator co_await();
-}
-
-template <
-    typename Awaitable,
-    std::enable_if_t<
-        folly::Conjunction<
-            detail::_has_free_operator_co_await<Awaitable>,
-            folly::Negation<detail::_has_member_operator_co_await<Awaitable>>>::
-            value,
-        int> = 0>
-decltype(auto) get_awaiter(Awaitable&& awaitable) {
-  return operator co_await(static_cast<Awaitable&&>(awaitable));
-}
+struct get_awaiter_fn {
+  template <
+      typename Awaitable,
+      std::enable_if_t<
+          folly::Conjunction<
+              is_awaiter<Awaitable>,
+              folly::Negation<detail::_has_free_operator_co_await<Awaitable>>,
+              folly::Negation<
+                  detail::_has_member_operator_co_await<Awaitable>>>::value,
+          int> = 0>
+  Awaitable& operator()(Awaitable&& awaitable) const {
+    return static_cast<Awaitable&>(awaitable);
+  }
+
+  template <
+      typename Awaitable,
+      std::enable_if_t<
+          detail::_has_member_operator_co_await<Awaitable>::value,
+          int> = 0>
+  decltype(auto) operator()(Awaitable&& awaitable) const {
+    return static_cast<Awaitable&&>(awaitable).operator co_await();
+  }
+
+  template <
+      typename Awaitable,
+      std::enable_if_t<
+          folly::Conjunction<
+              detail::_has_free_operator_co_await<Awaitable>,
+              folly::Negation<
+                  detail::_has_member_operator_co_await<Awaitable>>>::value,
+          int> = 0>
+  decltype(auto) operator()(Awaitable&& awaitable) const {
+    return operator co_await(static_cast<Awaitable&&>(awaitable));
+  }
+};
+constexpr inline get_awaiter_fn get_awaiter{};
 
 /// awaiter_type<Awaitable>
 ///

diff --git a/folly/coro/ViaIfAsync.h b/folly/coro/ViaIfAsync.h
@@ -242,8 +242,8 @@ class StackAwareViaIfAsyncAwaiter {
       : viaCoroutine_(CoroutineType::create(std::move(executor))),
         awaitable_(folly::coro::co_withAsyncStack(
             static_cast<Awaitable&&>(awaitable))),
-        awaiter_(folly::coro::get_awaiter(
-            static_cast<WithAsyncStackAwaitable&&>(awaitable_))) {}
+        awaiter_(
+            get_awaiter(static_cast<WithAsyncStackAwaitable&&>(awaitable_))) {}
 
   decltype(auto) await_ready() noexcept(noexcept(awaiter_.await_ready())) {
     return awaiter_.await_ready();
@@ -301,8 +301,7 @@ class ViaIfAsyncAwaiter {
   explicit ViaIfAsyncAwaiter(
       folly::Executor::KeepAlive<> executor, Awaitable&& awaitable)
       : viaCoroutine_(CoroutineType::create(std::move(executor))),
-        awaiter_(
-            folly::coro::get_awaiter(static_cast<Awaitable&&>(awaitable))) {}
+        awaiter_(get_awaiter(static_cast<Awaitable&&>(awaitable))) {}
 
   decltype(auto) await_ready() noexcept(noexcept(awaiter_.await_ready())) {
     return awaiter_.await_ready();
@@ -581,7 +580,7 @@ class TryAwaiter {
 
  public:
   explicit TryAwaiter(Awaitable&& awaiter)
-      : awaiter_(folly::coro::get_awaiter(static_cast<Awaitable&&>(awaiter))) {}
+      : awaiter_(get_awaiter(static_cast<Awaitable&&>(awaiter))) {}
 
   auto await_ready() noexcept(noexcept(std::declval<Awaiter&>().await_ready()))
       -> decltype(std::declval<Awaiter&>().await_ready()) {

diff --git a/folly/coro/WithAsyncStack.h b/folly/coro/WithAsyncStack.h
@@ -118,7 +118,7 @@ class WithAsyncStackAwaiter {
 
  public:
   explicit WithAsyncStackAwaiter(Awaitable&& awaitable)
-      : awaiter_(folly::coro::get_awaiter(static_cast<Awaitable&&>(awaitable))),
+      : awaiter_(get_awaiter(static_cast<Awaitable&&>(awaitable))),
         coroWrapper_(WithAsyncStackCoroutine::create()) {}
 
   auto await_ready() noexcept(noexcept(std::declval<Awaiter&>().await_ready()))