Some ideas

include/continuable/detail/core/base.hpp

@@ -486,10 +486,8 @@ void on_executor(Executor&& executor, Invoker&& invoker, Args&&... args) {
 
   // Create a worker object which when invoked calls the callback with the
   // the returned arguments.
-  auto work = [
-    invoker = std::forward<Invoker>(invoker),
-    args = std::make_tuple(std::forward<Args>(args)...)
-  ]() mutable {
+  auto work = [invoker = std::forward<Invoker>(invoker),
+               args = std::make_tuple(std::forward<Args>(args)...)]() mutable {
     traits::unpack(
         [&](auto&&... captured_args) {
           // Just use the packed dispatch method which dispatches the work on
@@ -557,6 +555,8 @@ template <typename Base>
 struct error_handler_base<handle_errors::no, Base> {
   /// The operator which is called when an error occurred
   void operator()(exception_arg_t tag, exception_t exception) && {
+    // TODO Add control flow info here
+
     // Forward the error to the next callback
     std::move(static_cast<Base*>(this)->next_callback_)(tag,
                                                         std::move(exception));
@@ -606,6 +606,7 @@ struct callback_base<identity<Args...>, HandleResults, HandleErrors, Callback,
   Callback callback_;
   Executor executor_;
   NextCallback next_callback_;
+  int callstack_;
 
   explicit callback_base(Callback callback, Executor executor,
                          NextCallback next_callback)
@@ -751,6 +752,7 @@ struct chained_continuation<identity<Args...>, identity<NextArgs...>,
   Continuation continuation_;
   Callback callback_;
   Executor executor_;
+  int callstack_;
 
   explicit chained_continuation(Continuation continuation, Callback callback,
                                 Executor executor)

include/continuable/detail/operations/async.hpp

@@ -73,7 +73,6 @@ auto async(Callable&& callable, Executor&& executor, Args&&... args) {
                                      hint, util::ownership{});
 }
 } // namespace operations
-
 } // namespace detail
 } // namespace cti
 

test/playground/test-playground.cpp

@@ -20,10 +20,53 @@
   SOFTWARE.
 **/
 
+#include <exception>
+#include <vector>
 #include <continuable/continuable.hpp>
 
 using namespace cti;
 
-int main(int, char**) {
-  // ...
+continuable<std::string> http_request(std::string /*url*/) {
+  return async([]() -> std::string {
+    throw std::exception{}; //
+  });
+}
+
+struct ResultSet {};
+struct Buffer {};
+
+continuable<ResultSet> mysql_query(std::string /*url*/) {
+  return make_ready_continuable(ResultSet{});
+}
+
+continuable<Buffer> read_file(std::string /*url*/) {
+  return make_ready_continuable(Buffer{});
+}
+
+struct exception_trait {};
+
+struct unhandled_exception_trait {};
+
+struct stacktrace_trait {
+  using stacktrace_type = std::vector<void const*>;
+
+  static stacktrace_type gather(std::size_t offset) noexcept {
+    return {};
+  }
+
+  static exception_t annotate(stacktrace_type stacktrace,
+                              exception_t&& exception) noexcept {
+    return exception;
+  }
+};
+
+int main(int, char**) {
+  when_all(http_request("github.com"), http_request("atom.io"))
+      .then([](std::string /*github*/, std::string /*atom*/) {
+        // ...
+        return mysql_query("select * from `users`");
+      })
+      .then([](ResultSet /*result*/) {
+        // ...
+      });
 }