[SE-0290] Add #unavailable (Negative platform checks)

[rockbruno]

Implementation for SE-0290: https://github.com/apple/swift-evolution/blob/main/proposals/0290-negative-availability.md

Swift evolution thread: https://forums.swift.org/t/support-negative-availability-literals/

[shahmishal]

Please update the base branch to main by Oct 5th otherwise the pull request will be closed automatically.

• How to change the base branch: (Link)
• More detail about the branch update: (Link)

[rockbruno]

I notice now that that the underlying _stdlib_isOSVersionAtLeast emission needs to be reverted as well. I'll add this change along with some SIL tests as the review progresses.

[rockbruno]

I updated the implementation to match the final revision (imply the wildcard). The implementation now rejects explicit *s and injecting a fake one to the spec list so that the rest of the logic works as expected.

I was unsure how to proceed with #unavailable() though. This is technically correct if the wildcard is implied but right now it's being rejected by the parser.

[rockbruno]

@tkremenek Any updates on the plan for this feature? I'd like to keep the branch updated, but only when this actually moves forward.

[varungandhi-apple]

Sorry this got missed. Could you please fix the merge conflicts? I've left some comments and have asked other folks to chime in as well.

In the future, please feel free to ping someone who has modified the surrounding code for review, or ask on the Swift forums for review.

[varungandhi-apple]

cc @rintaro for parser changes, cc @amartini51 as there may be potential TSPL changes.

[rockbruno]

Thanks @varungandhi-apple! I'll rebase it and apply the changes.

[rockbruno]

@varungandhi-apple I've updated it. Had to lose the commit history though because it was 3000 commits behind main 😢

[varungandhi-apple]

Nit: Please use C++ lambda syntax instead of using block syntax. (I'm not sure if MSVC supports the latter, also we use lambda syntax with [ ... ] elsewhere in the code.)

[varungandhi-apple]

It doesn't look like Queries is getting used later.

Suggested change

	auto Queries = available->getQueries();
	for (auto *Spec : Queries) {
	for (auto *Spec : available->getQueries()) {

[varungandhi-apple]

Thanks for your patience with the review. Mostly LGTM, left a couple of minor comments. You may want to squash some of the later commits.

[varungandhi-apple]

@swift-ci smoke test

[rockbruno]

@varungandhi-apple There was a typo in the result builder logic, I cleaned it up further and squashed the rest.

[varungandhi-apple]

@swift-ci smoke test

[rockbruno]

Hm it failed because of SwiftSyntax not knowing the keyword, do I need to push something in its repo first for it to pass here?

[ahoppen]

Hm it failed because of SwiftSyntax not knowing the keyword, do I need to push something in its repo first for it to pass here?

You need to re-generate the files in the SwiftSyntax repo. For this:

• Check out https://github.com/apple/swift-syntax next to your swift repository
• Run ./build-script.py --toolchain /path/to/anywhere --degyb-only in the swift-syntax repository
• Set up a PR to the swift-syntax repository and mention it in this PR
• Not to people triggering CI: You need to reference the corresponding swift-syntax PR when testing swift and the swift PR when testing swift-syntax like here. Also the two PRs need to be merged at the same time.

[rockbruno]

@ahoppen Thanks! I tried that but I get errors about python imports. Do I need a specific python version?

    from .Classification import classification_by_name
ImportError: attempted relative import with no known parent package

[ahoppen]

I haven’t seen that error message before. I’m using Python 2. Could you share the entire error message? Maybe I’ll be able to figure out what’s going on from there.

[rockbruno]

With Python 2, I get a slightly different error:

** Generating gyb Files **
Traceback (most recent call last):
  File "/Users/rochab/Desktop/Other/swift-sources/swift/utils/gyb", line 3, in <module>
    gyb.main()
  File "/Users/rochab/Desktop/Other/swift-sources/swift/utils/gyb.py", line 1267, in main
    f.write(execute_template(ast, args.line_directive, **bindings))
  File "/Users/rochab/Desktop/Other/swift-sources/swift/utils/gyb.py", line 1137, in execute_template
    ast.execute(execution_context)
  File "/Users/rochab/Desktop/Other/swift-sources/swift/utils/gyb.py", line 639, in execute
    x.execute(context)
  File "/Users/rochab/Desktop/Other/swift-sources/swift/utils/gyb.py", line 725, in execute
    result = eval(self.code, context.local_bindings)
  File "/Users/rochab/Desktop/Other/swift-sources/swift-syntax/Sources/SwiftSyntaxBuilder/Buildables.swift.gyb", line 5, in <module>
    from gyb_syntax_support.kinds import syntax_buildable_child_type, syntax_buildable_default_init_value
ImportError: cannot import name syntax_buildable_default_init_value
FAIL: Generating .gyb files failed

[ahoppen]

That’s probably because syntax_buildable_default_init_value was added fairly recently (~1 month ago) in b7d4dec. Could you try rebasing your swift branch?

[rockbruno]

Should've tried that first. It worked, thanks!

swiftlang/swift-syntax#296

[ahoppen]

Nice! Let’s see what CI has to say now.

swiftlang/swift-syntax#296
@swift-ci Please smoke test

[ahoppen]

Changes to gyb_syntax_support are looking good to me. I didn’t look at the other changes.

[varungandhi-apple]

@swift-ci test and merge

[rockbruno]

I think we need to merge swiftlang/swift-syntax#296 first for this to become green, right?

[ahoppen]

You need to merge them at the same time. Make sure that both have a green CI status before merging either.

[rockbruno]

Ah I see, it failed because we needed to reference the PR in the command.

[ahoppen]

Yeah, so they've always been tested in unison in PR testing so far (because you referenced the other PR) and thus you also need to merge them together.

[varungandhi-apple]

My bad, sorry about that. I should've paid more attention.

swiftlang/swift-syntax#296

@swift-ci please test

[varungandhi-apple]

@rockbruno could you submit a PR adding a "Swift Next" entry to the ChangeLog and mentioning this new feature there? Here's an example PR which does that.

[rockbruno]

Done: #38390