deferError was not r-value qualified but should have been.

Summary: When cleaning up the interface with r-value qualification for SemiFuture it seems we missed deferError.

Reviewed By: yfeldblum

Differential Revision: D7942259

fbshipit-source-id: c0cf05eb2b6357e6f6eb3fab6aef87ec6416caf7

folly/futures/Future-inl.h

@@ -755,7 +755,7 @@ typename std::enable_if<
         !futures::detail::callableWith<F, exception_wrapper&>::value &&
         !futures::detail::Extract<F>::ReturnsFuture::value,
     SemiFuture<T>>::type
-SemiFuture<T>::deferError(F&& func) {
+SemiFuture<T>::deferError(F&& func) && {
   using Exn =
       std::remove_reference_t<typename futures::detail::Extract<F>::FirstArg>;
   return std::move(*this).defer(
@@ -775,7 +775,7 @@ typename std::enable_if<
         !futures::detail::callableWith<F, exception_wrapper&>::value &&
         futures::detail::Extract<F>::ReturnsFuture::value,
     SemiFuture<T>>::type
-SemiFuture<T>::deferError(F&& func) {
+SemiFuture<T>::deferError(F&& func) && {
   using Exn =
       std::remove_reference_t<typename futures::detail::Extract<F>::FirstArg>;
   return std::move(*this).defer(
@@ -794,7 +794,7 @@ typename std::enable_if<
     futures::detail::callableWith<F, exception_wrapper>::value &&
         !futures::detail::Extract<F>::ReturnsFuture::value,
     SemiFuture<T>>::type
-SemiFuture<T>::deferError(F&& func) {
+SemiFuture<T>::deferError(F&& func) && {
   return std::move(*this).defer(
       [func = std::forward<F>(func)](Try<T> t) mutable {
         if (t.hasException()) {
@@ -811,7 +811,7 @@ typename std::enable_if<
     futures::detail::callableWith<F, exception_wrapper>::value &&
         futures::detail::Extract<F>::ReturnsFuture::value,
     SemiFuture<T>>::type
-SemiFuture<T>::deferError(F&& func) {
+SemiFuture<T>::deferError(F&& func) && {
   return std::move(*this).defer(
       [func = std::forward<F>(func)](Try<T> t) mutable {
         if (t.hasException()) {

folly/futures/Future.h

@@ -364,7 +364,7 @@ class SemiFuture : private futures::detail::FutureBase<T> {
           !futures::detail::callableWith<F, exception_wrapper&>::value &&
           !futures::detail::Extract<F>::ReturnsFuture::value,
       SemiFuture<T>>::type
-  deferError(F&& func);
+  deferError(F&& func) &&;
 
   /// Overload of deferError where the error callback returns a Future<T>
   template <class F>
@@ -373,7 +373,7 @@ class SemiFuture : private futures::detail::FutureBase<T> {
           !futures::detail::callableWith<F, exception_wrapper&>::value &&
           futures::detail::Extract<F>::ReturnsFuture::value,
       SemiFuture<T>>::type
-  deferError(F&& func);
+  deferError(F&& func) &&;
 
   /// Overload of deferError that takes exception_wrapper and returns T
   template <class F>
@@ -381,7 +381,7 @@ class SemiFuture : private futures::detail::FutureBase<T> {
       futures::detail::callableWith<F, exception_wrapper>::value &&
           !futures::detail::Extract<F>::ReturnsFuture::value,
       SemiFuture<T>>::type
-  deferError(F&& func);
+  deferError(F&& func) &&;
 
   /// Overload of deferError that takes exception_wrapper and returns Future<T>
   template <class F>
@@ -389,7 +389,7 @@ class SemiFuture : private futures::detail::FutureBase<T> {
       futures::detail::callableWith<F, exception_wrapper>::value &&
           futures::detail::Extract<F>::ReturnsFuture::value,
       SemiFuture<T>>::type
-  deferError(F&& func);
+  deferError(F&& func) &&;
 
   /// Return a future that completes inline, as if the future had no executor.
   /// Intended for porting legacy code without behavioural change, and for rare