Rename shutdown method on {Tcp,Unix}Stream to shutdown_std and make it private, to avoid clash with AsyncWriteExt::shutdown

[aknuds1]

Motivation

#3294 describes that the shutdown method should be removed from the {Tcp,Unix}Stream types in favour of the one on AsyncWriteExt. However, plain removing it lead to some compilation failures that were difficult to resolve, so @Darksonn suggested we instead rename the method (to shutdown_std) and make it private. Closes #3294.

Solution

Rename {Tcp,Unix}Stream::shutdown to shutdown_std and make it private.

[Darksonn]

Looks good to me. 👍

[MikailBag]

I think is should be mentioned in docs how one can achieve Read and Both shutdown behaviors.

[Darksonn]

With this change, that isn't possible. However @carllerche suggested on Discord to an .as_std() method that returns a &std::net::TcpStream. It would be possible to access those behaviors through such a method with .as_std().shutdown(how). This would be added in a follow-up PR.

Note that the behavior of shutdown(Read) and shutdown(Both) is platform-dependent and should normally be avoided. The receiver shutting down its read channel doesn't really exist in the tcp protocol in the same way as shutdown(Write) does (as I understand it) and would correspond to an abnormal shutdown of the connection similar to if the connection was lost.

[carllerche]

@MikailBag what do you expect happens when shutdown(Read) is called?

[MikailBag]

I've never used shutdown() so I can't answer this question.

But I think someone else used them. IMHO it'd be good to provide some docs to them, such as "shutdown(Read) is never correct, fix your code" or "use this function", or something else.

This is just an opinion, feel free to ignore :)