[SR-13857] indexstore missing references for superclass / protocol when using composition

[keith]

Previous ID	SR-13857
Radar	rdar://problem/71447059
Original Reporter	@keith
Type	Bug

Attachment: Download

Environment

Xcode 12.2 (12B45b)

Additional Detail from JIRA

Votes	0
Component/s	Source Tooling
Labels	Bug
Assignee	None
Priority	Medium

md5: 3d2406440cd5302076477f42903a56d5

Issue Description:

With this code:

class ZZ1 {}
typealias BaseAlias = ZZ1 & Protocol
protocol Protocol {}

class Subclass: BaseAlias {}

The index store produced by building does not contain references from Subclass to ZZ1 as the superclass, or Protocol. This causes Xcode to not display the superclasses / protocol connections in the UI, and also impacts custom tooling built on index store data.

The difference is specifically a few symbols. With this code:

class ZZ1 {}
typealias BaseAlias = ZZ1 & Protocol
protocol Protocol {}

class Subclass: ZZ1 {}

You have this (normalized for display) reference which is missing when building the original snippet: s:10superclass3ZZ1C baseOf s:10superclass8SubclassC

If you use this code:

class ZZ1 {}
typealias BaseAlias = ZZ1
protocol Protocol {}

class Subclass: BaseAlias, Protocol {}

You end up with both the reference to the superclass, and a protocol reference: s:10superclass8ProtocolP baseOf s:10superclass8SubclassC.

Attached are the screenshots of how this ends up affecting Xcode's UI

[keith]

Turns out you don't actually need the type alias here, using this code has the same issue:

class ZZ1 {}
protocol Protocol {}

class Subclass: ZZ1 & Protocol {}

[typesanitizer]

@swift-ci create

[keith]

I'd be happy to take a stab at this if someone could offer some guidance!

[akyrtzi]

Interesting, as you pointed out it's not the typealias the problem, it's that it uses composition. The code is in lib/Index/Index.cpp, look for references of SymbolRole::RelationBaseOf if you want to take a stab. Related tests are in test/Index.

[keith]

Thanks for the tip! I got to it eventually! 🙃 #64997

[keith]

take 2 after a revert #65550