#### defer (1 of 3 overloads)

Submits a completion token or function object for execution.

    template<
        typename CompletionToken>
    DEDUCED defer(
        CompletionToken && token);

This function submits an object for execution using the object's associated executor. The function object is queued for execution, and is never called from the current thread prior to returning from `defer()`.

The use of `defer()`, rather than `post` , indicates the caller's preference that the executor defer the queueing of the function object. This may allow the executor to optimise queueing for cases when the function object represents a continuation of the current call context.

This function has the following effects:

- Constructs a function object handler of type `Handler`, initialized with `handler(forward<CompletionToken>(token))`.
- Constructs an object `result` of type `async_result<Handler>`, initializing the object as `result(handler)`.
- Obtains the handler's associated executor object `ex` by performing `get_associated_executor(handler)`.
- Obtains the handler's associated allocator object `alloc` by performing `get_associated_allocator(handler)`.
- Performs `ex.defer(std::move(handler), alloc)`.
- Returns `result.get()`.