Support IfConfigDecl clauses in UseEnumForNamespacing

[klaaspieter]

Anything inside a IfConfigDecl was ignored when determining if a struct
could be an enum. This looks for IfConfigDeclSyntax in the
MemberDeclListSyntax and only turns the struct into an enum when all of
the clauses have namespace compatible members.

Fixes: https://bugs.swift.org/browse/SR-11830

[allevato]

Thanks for tackling this!

The implementation looks good. For completeness' sake, can you add a couple more tests to make sure we've covered everything?

• A test that uses an #else instead of an #elseif
• A test that involves two nested #if blocks in some fashion to verify that we recurse through them properly.

Based on the implementation I think both of those should work, but it'll be good to have the extra test coverage for potential future changes.

[allevato]

It looks like the commit history here has commits from the 5.1 branch included in it, which may be the case if you were doing work there. Can you clean that up?

[klaaspieter]

@allevato Yeah. I'm in the middle of adding those extra tests. I wanted to actually try and test against master so I've been trying to get the swift-DEVELOPMENT-SNAPSHOT-2019-09-26-a toolchain.

Is the only way to get it to build it from source?

[klaaspieter]

Should be fixed now. Although I still haven't been able to test this against master 😞

[dylansturg]

@allevato Yeah. I'm in the middle of adding those extra tests. I wanted to actually try and test against master so I've been trying to get the swift-DEVELOPMENT-SNAPSHOT-2019-09-26-a toolchain.

Is the only way to get it to build it from source?

You can still download that snapshot from Swift.org, it's just hard to find since the link has long-since been removed from the UI. You can just change the date in the download URL to match any snapshot. For example, here's the link for 2019-09-26-a snapshot for use in Xcode:
https://swift.org/builds/development/xcode/swift-DEVELOPMENT-SNAPSHOT-2019-09-26-a/swift-DEVELOPMENT-SNAPSHOT-2019-09-26-a-osx.pkg

[klaaspieter]

@dylansturg is it worth updating the README with that link?

[dylansturg]

@dylansturg is it worth updating the README with that link?

I think we want to get away from that old snapshot and onto a newer one that supports the latest Swift-Syntax soonish™️ so it may not be relevant for too much longer.

[allevato]

Sorry for the delay—the new tests look great, thanks!

I just pulled the change down myself and tested it against 09-26 to verify, and everything checks out, so this is good to merge.