Cut Futures private invocability helpers

Summary: [Folly] Cut Futures private invocability helpers, which can be replaced with invoke_result, is_invocable, etc.

Reviewed By: marshallcline

Differential Revision: D8087901

fbshipit-source-id: 17282d77aaff61350d1e7f1b0c363c25db8fb5b1

folly/futures/Future-inl.h

@@ -980,7 +980,7 @@ Future<Unit> Future<T>::then() {
 template <class T>
 template <class F>
 typename std::enable_if<
-    !futures::detail::callableWith<F, exception_wrapper>::value &&
+    !is_invocable<F, exception_wrapper>::value &&
         !futures::detail::Extract<F>::ReturnsFuture::value,
     Future<T>>::type
 Future<T>::onError(F&& func) {
@@ -1015,7 +1015,7 @@ Future<T>::onError(F&& func) {
 template <class T>
 template <class F>
 typename std::enable_if<
-    !futures::detail::callableWith<F, exception_wrapper>::value &&
+    !is_invocable<F, exception_wrapper>::value &&
         futures::detail::Extract<F>::ReturnsFuture::value,
     Future<T>>::type
 Future<T>::onError(F&& func) {
@@ -1074,7 +1074,7 @@ Future<T> Future<T>::onTimeout(Duration dur, F&& func, Timekeeper* tk) {
 template <class T>
 template <class F>
 typename std::enable_if<
-    futures::detail::callableWith<F, exception_wrapper>::value &&
+    is_invocable<F, exception_wrapper>::value &&
         futures::detail::Extract<F>::ReturnsFuture::value,
     Future<T>>::type
 Future<T>::onError(F&& func) {
@@ -1112,7 +1112,7 @@ Future<T>::onError(F&& func) {
 template <class T>
 template <class F>
 typename std::enable_if<
-    futures::detail::callableWith<F, exception_wrapper>::value &&
+    is_invocable<F, exception_wrapper>::value &&
         !futures::detail::Extract<F>::ReturnsFuture::value,
     Future<T>>::type
 Future<T>::onError(F&& func) {
@@ -1496,10 +1496,9 @@ Future<T> reduce(It first, It last, T&& initial, F&& func) {
   }
 
   typedef typename std::iterator_traits<It>::value_type::value_type ItT;
-  typedef typename std::conditional<
-      futures::detail::callableWith<F, T&&, Try<ItT>&&>::value,
-      Try<ItT>,
-      ItT>::type Arg;
+  typedef typename std::
+      conditional<is_invocable<F, T&&, Try<ItT>&&>::value, Try<ItT>, ItT>::type
+          Arg;
   typedef isTry<Arg> IsTry;
 
   auto sfunc = std::make_shared<F>(std::move(func));

folly/futures/Future-pre.h

@@ -76,9 +76,6 @@ template <class...> struct CollectAllVariadicContext;
 template <class...> struct CollectVariadicContext;
 template <class> struct CollectContext;
 
-template <typename F, typename... Args>
-using resultOf = decltype(std::declval<F>()(std::declval<Args>()...));
-
 template <typename...>
 struct ArgType;
 
@@ -95,30 +92,16 @@ struct ArgType<> {
 template <bool isTry, typename F, typename... Args>
 struct argResult {
   using ArgList = ArgType<Args...>;
-  using Result = resultOf<F, Args...>;
-};
-
-template <typename F, typename... Args>
-struct callableWith {
-    template <typename T, typename = detail::resultOf<T, Args...>>
-    static constexpr std::true_type
-    check(std::nullptr_t) { return std::true_type{}; }
-
-    template <typename>
-    static constexpr std::false_type
-    check(...) { return std::false_type{}; }
-
-    typedef decltype(check<F>(nullptr)) type;
-    static constexpr bool value = type::value;
+  using Result = invoke_result_t<F, Args...>;
 };
 
 template <typename T, typename F>
 struct callableResult {
   typedef typename std::conditional<
-      callableWith<F>::value,
+      is_invocable<F>::value,
       detail::argResult<false, F>,
       typename std::conditional<
-          callableWith<F, T&&>::value,
+          is_invocable<F, T&&>::value,
           detail::argResult<false, F, T&&>,
           detail::argResult<true, F, Try<T>&&>>::type>::type Arg;
   typedef isFutureOrSemiFuture<typename Arg::Result> ReturnsFuture;
@@ -128,7 +111,7 @@ struct callableResult {
 template <typename T, typename F>
 struct tryCallableResult {
   typedef typename std::conditional<
-      callableWith<F>::value,
+      is_invocable<F>::value,
       detail::argResult<false, F>,
       detail::argResult<true, F, Try<T>&&>>::type Arg;
   typedef isFutureOrSemiFuture<typename Arg::Result> ReturnsFuture;
@@ -138,7 +121,7 @@ struct tryCallableResult {
 template <typename T, typename F>
 struct valueCallableResult {
   typedef typename std::conditional<
-      callableWith<F>::value,
+      is_invocable<F>::value,
       detail::argResult<false, F>,
       detail::argResult<false, F, T&&>>::type Arg;
   typedef isFutureOrSemiFuture<typename Arg::Result> ReturnsFuture;

folly/futures/Future.h

@@ -33,6 +33,7 @@
 #include <folly/Utility.h>
 #include <folly/executors/DrivableExecutor.h>
 #include <folly/executors/TimedDrivableExecutor.h>
+#include <folly/functional/Invoke.h>
 #include <folly/futures/Promise.h>
 #include <folly/futures/detail/Types.h>
 #include <folly/lang/Exception.h>
@@ -871,7 +872,7 @@ class Future : private futures::detail::FutureBase<T> {
   ///   });
   template <class F>
   typename std::enable_if<
-      !futures::detail::callableWith<F, exception_wrapper>::value &&
+      !is_invocable<F, exception_wrapper>::value &&
           !futures::detail::Extract<F>::ReturnsFuture::value,
       Future<T>>::type
   onError(F&& func);
@@ -879,7 +880,7 @@ class Future : private futures::detail::FutureBase<T> {
   /// Overload of onError where the error callback returns a Future<T>
   template <class F>
   typename std::enable_if<
-      !futures::detail::callableWith<F, exception_wrapper>::value &&
+      !is_invocable<F, exception_wrapper>::value &&
           futures::detail::Extract<F>::ReturnsFuture::value,
       Future<T>>::type
   onError(F&& func);
@@ -887,7 +888,7 @@ class Future : private futures::detail::FutureBase<T> {
   /// Overload of onError that takes exception_wrapper and returns Future<T>
   template <class F>
   typename std::enable_if<
-      futures::detail::callableWith<F, exception_wrapper>::value &&
+      is_invocable<F, exception_wrapper>::value &&
           futures::detail::Extract<F>::ReturnsFuture::value,
       Future<T>>::type
   onError(F&& func);
@@ -895,7 +896,7 @@ class Future : private futures::detail::FutureBase<T> {
   /// Overload of onError that takes exception_wrapper and returns T
   template <class F>
   typename std::enable_if<
-      futures::detail::callableWith<F, exception_wrapper>::value &&
+      is_invocable<F, exception_wrapper>::value &&
           !futures::detail::Extract<F>::ReturnsFuture::value,
       Future<T>>::type
   onError(F&& func);

folly/futures/helpers.h

@@ -437,7 +437,7 @@ template <
     class F,
     class ItT = typename std::iterator_traits<
         typename Collection::iterator>::value_type,
-    class Result = typename futures::detail::resultOf<F, ItT&&>::value_type>
+    class Result = typename invoke_result_t<F, ItT&&>::value_type>
 std::vector<Future<Result>> window(Collection input, F func, size_t n);
 
 template <
@@ -445,15 +445,13 @@ template <
     class F,
     class ItT = typename std::iterator_traits<
         typename Collection::iterator>::value_type,
-    class Result = typename futures::detail::resultOf<F, ItT&&>::value_type>
+    class Result = typename invoke_result_t<F, ItT&&>::value_type>
 std::vector<Future<Result>>
 window(Executor* executor, Collection input, F func, size_t n);
 
 template <typename F, typename T, typename ItT>
-using MaybeTryArg = typename std::conditional<
-    futures::detail::callableWith<F, T&&, Try<ItT>&&>::value,
-    Try<ItT>,
-    ItT>::type;
+using MaybeTryArg = typename std::
+    conditional<is_invocable<F, T&&, Try<ItT>&&>::value, Try<ItT>, ItT>::type;
 
 /** repeatedly calls func on every result, e.g.
     reduce(reduce(reduce(T initial, result of first), result of second), ...)