Hide Channel internal implementation methods

[j8r]

Some methods should not be part of the public API, being internal implementation details.
Obviously, receive_impl and receive_internal are ones.

Return type annotations are also added for receive and receive? to have them in the API docs.

[waj]

Thanks! Channel's interface and docs is needing some love. There are other methods I'd like to hide from docs. select_impl looks obvious, but I think we could hide anything related to SelectAction as well. @bcardiff what do you think? Methods to create instances of SelectAction are not even public anyway and it's an implementation detail right now. Other structs like SelectState and DeliveryState should be marked as :nodoc: as well.

@j8r would you like to make those updates as part of this PR?

[j8r]

What about methods receiving SelectAction or Indexabel(SelectAction) as an argument?

[waj]

I think those should be :nodoc: as well. Those methods are called when a select statement is used.

[j8r]

I agree with you @waj , and it will definitely be good to to enhance Channel API before 1.0.0.

Also some methods/classes can be changed from :nodoc: to private - which is better.

[bcardiff]

I agree that the self.non_blocking_select/self.select can be made :nodoc:. They are used by the compiler so private will not work on them. But for the user the api should be to use the select statement.

We are leaving doing send + receive on array as a public API but I think it's safe to do so.

I don't follow why you are changing Channel to AChannel though.

[j8r]

Sorry @bcardiff , I was testing something and pushed accidentally.

[waj]

@j8r this looks great. Could you please run crystal tool format?

Also, def self.select(ops : Indexable(SelectAction), has_else) can be removed now. It was deprecated for some versions but it's not needed anymore and it was always internal anyway.

[straight-shoota]

Thanks @j8r