Comment by Sergo Beruashvili (JIRA)

@belkadan @phausler What do you think about marking all the NSUnimplemented functions with @available(*, unavailable, message: "Not available on non-Darwin platforms")

@parkera @millenomi, would you accept a PR that adds an available annotation to all of the currently NSUnimplemented functions? I think the upside of compile-time errors would outway the downside of the code-spam, and having spoken to other Swift on Linux developers it is a source of annoyance to have the runtime crash instead.

@spevans only after we remove as many as possible before the end of 5.0.

Is that primarily to avoid wasted effort? It's something we're planning on doing regardless.

One thing about this - we have to be careful about it being an availability thing in scenarios like this, totally contrived, example:

public func a(_ v: Int) {
{{ if v % 2 == 0 { b() }}}{{ }}

{{ else { c() }}}

{{}}}

internal func b() { /* available */ }

internal func c() { /* unimplemented */ }

Bleh. I give up on JIRA's formatting. But you get the idea. 🙂

I'd only apply it to the public function declarations and try to avoid any that I think will be implemented for 5.0 or are in the PR queue.

Ok, so basically top-level stuff only?

The thing I wanted to avoid was some kind of "viral unavailability", where one lower level function being unavailable causes a bunch of higher level stuff that may call it only in specific scenarios to become unavailable always.

I guess discovering if there are any key functions in that path would be a useful side effect.

We've done this as part of https://bugs.swift.org/browse/SR-10347.