[SR-5993] Cannot subclass to a nested class ('Super' is not a member type of 'Baz').

[DevAndArtist]

Previous ID	SR-5993
Radar	None
Original Reporter	@DevAndArtist
Type	Bug
Status	Resolved
Resolution	Done

Attachment: Download

Environment

Xcode Version 9.0 (9A235), Swift 4

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug
Assignee	@slavapestov
Priority	Medium

md5: 8d6c77fe197d852dcf28d4056069c764

duplicates:

• SR-631 Extensions in different files do not recognize each other

relates to:

• SR-631 Extensions in different files do not recognize each other

Issue Description:

A class that is nested inside a different type through extensions from a different file cannot be subclassed as another nested sub-class in yet another different file. `typealias` cannot be used as a workaround.

See `Bar.Sub1` and `Bar.Sub2` in the attached playground.

This might be related to: https://bugs.swift.org/browse/SR-631

[belkadan]

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

[DevAndArtist]

@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.

[DevAndArtist]

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

[belkadan]

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

[belkadan]

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

[slavapestov]

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

[DougGregor]

The example here is fixed by #18364

[DevAndArtist]

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

[DougGregor]

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

[DevAndArtist]

@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?

[DougGregor]

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.

[DevAndArtist]

Okay thank you for confirming it.