Your playground has a whole bunch of different examples in it, and I can't reproduce the issue in isolation. Which ones are relevant?

@belkadan The playground contains exactly two examples with the reproducible project structure, which I tried to describe above.

There are two files which will trigger the issue, you can test them individually.

• Bar.Sub1.swift

• Bar.Sub2.swift

In each file it's only necessary to uncomment the last commented line to trigger the error. The error will be appear in a different place, on the line where the nested subclass is defined.

@belkadan Here are two screenshots of both of the cases.

Whoops, you did mention Bar.Sub1.swift and Bar.Sub2.swift. My bad for jumping to the attachment.

Yeah, I think this is another SR-631, then.

Re-opening this because the interaction between extension binding and subclassing is a bit more subtle than just SR-631.

The example here is fixed by #18364

@DougGregor I assume the comment is the same as on twitter recently. This fix won't land in Swift 4.2?

That's correct. This will not go into Swift 4.2.

@DougGregor Any chance this might go into Swift 4.x (4.3) a couple of month later, or is it something for a major release like Swift 5?

It will have to wait for a major release. This bug fix is a consequence of some significant architectural changes that don't fit into a dot release.

Okay thank you for confirming it.