Move type checking to a static_assert

[esteve]

VS2015 still fails to compile when callbacks have only two arguments, as it insists on checking for a non-existent third argument (causing an index out of bounds error on std::tuple_element).

This change just moves the check to a static_assert in the body of the method.

@dirk-thomas @tfoote @wjwwood

[esteve]

While trying to fix this, I came up with the following code for checking several conditions on a single std::enable_if, maybe with a bit more of work we can move the check to the template section instead of static_assert back, but at this point I don't think it's worth us spending more time on this.

template <typename... T>
struct All : std::true_type {};

template <typename First, typename... Last>
struct All<First, Last...> :
std::conditional<First::value, All<Last...>, std::false_type>::type
{};

template<
  typename FunctorT,
  typename std::enable_if<All<
    std::is_same<
      typename function_traits<FunctorT>::template argument_type<0>,
      int>,
    typename std::conditional<function_traits<FunctorT>::arity == 1, std::true_type, std::false_type>::type
  >::value>::type * = nullptr
>
void
test1(FunctorT callback) {}

I also think we could whip up something with std::forward, but as I said, there's no real benefit spending more time on this. If anyone feels like giving it a chance, just let me know.

[wjwwood]

I agree, if it works around the issue for now then we should just move on. Thanks for taking time to look into it.

[esteve]

Thanks @wjwwood for your review. I'm merging this so we can continue working on Windows.

[wjwwood]

@esteve FYI there was a style issue with this pr:

http://54.183.26.131:8080/job/ros2_batch_ci_linux/141/testReport/junit/rclcpp/uncrustify/__include_rclcpp_node_hpp/

Can you just push an update to fix that directly?

[esteve]

Fixed, thanks for noticing @wjwwood

On Wed, Jun 10, 2015 at 2:15 PM, William Woodall [email protected]
wrote:

@esteve https://github.com/esteve FYI there was a style issue with this
pr:

http://54.183.26.131:8080/job/ros2_batch_ci_linux/141/testReport/junit/rclcpp/uncrustify/__include_rclcpp_node_hpp/

Can you just push an update to fix that directly?

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