[core] Simplify Thread::invokeSync (#6128)

platform/default/default_file_source.cpp

@@ -156,7 +156,7 @@ void DefaultFileSource::setAccessToken(const std::string& accessToken) {
 }
 
 std::string DefaultFileSource::getAccessToken() const {
-    return thread->invokeSync<std::string>(&Impl::getAccessToken);
+    return thread->invokeSync(&Impl::getAccessToken);
 }
 
 std::unique_ptr<AsyncRequest> DefaultFileSource::request(const Resource& resource, Callback callback) {

src/mbgl/util/thread.hpp

@@ -44,23 +44,15 @@ public:
     }
 
     // Invoke object->fn(args...) in the runloop thread, and wait for the result.
-    template <class R, typename Fn, class... Args>
-    R invokeSync(Fn fn, Args&&... args) {
+    template <typename Fn, class... Args>
+    auto invokeSync(Fn fn, Args&&... args) {
+        using R = std::result_of_t<Fn(Object, Args&&...)>;
         std::packaged_task<R ()> task(std::bind(fn, object, args...));
         std::future<R> future = task.get_future();
         loop->invoke(std::move(task));
         return future.get();
     }
 
-    // Invoke object->fn(args...) in the runloop thread, and wait for it to complete.
-    template <typename Fn, class... Args>
-    void invokeSync(Fn fn, Args&&... args) {
-        std::packaged_task<void ()> task(std::bind(fn, object, args...));
-        std::future<void> future = task.get_future();
-        loop->invoke(std::move(task));
-        future.get();
-    }
-
 private:
     Thread(const Thread&) = delete;
     Thread(Thread&&) = delete;

test/util/thread_local.cpp

@@ -43,9 +43,9 @@ TEST(ThreadLocalStorage, Basic) {
     Thread<TestThread> thread2(context, &number2);
     Thread<TestThread> thread3(context, &number3);
 
-    EXPECT_EQ(number1, thread1.invokeSync<int>(&TestThread::getNumber));
-    EXPECT_EQ(number2, thread2.invokeSync<int>(&TestThread::getNumber));
-    EXPECT_EQ(number3, thread3.invokeSync<int>(&TestThread::getNumber));
+    EXPECT_EQ(number1, thread1.invokeSync(&TestThread::getNumber));
+    EXPECT_EQ(number2, thread2.invokeSync(&TestThread::getNumber));
+    EXPECT_EQ(number3, thread3.invokeSync(&TestThread::getNumber));
 }
 
 TEST(ThreadLocalStorage, NotSetReturnsNull) {