Swiftlint: Class Delegate Protocol rule conflicting with Xcode 9.1 warnings

[esteluk]

New Issue Checklist

• [x] Updated SwiftLint to the latest version
• [x] I searched for existing GitHub issues

Bug Report

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint
Protocols.swift:16:1: warning: Test Violation: Delegate protocols should be class-only so they can be weakly referenced. (class_delegate_protocol)

Environment

• SwiftLint version (run swiftlint version to be sure)?

0.23.1

• Installation method used (Homebrew, CocoaPods, building from source, etc)?

Brew

• Paste your configuration file:

• Are you using nested configurations?
  If so, paste their relative paths and respective contents.

No

• Which Xcode version are you using (check xcode-select -p)?

9.1

• Do you have a sample that shows the issue? Run echo "[string here]" | swiftlint lint --no-cache --use-stdin --enable-all-rules
  to quickly test if your example is really demonstrating the issue. If your example is more
  complex, you can use swiftlint lint --path [file here] --no-cache --enable-all-rules.

// This triggers a violation:
protocol A: class {}

protocol BDelegate: A {}

Description

In the example above this triggers a violation as expected. The suggested way to fix this would be to change the code to:

// This does not trigger a violation
protocol A: class {}

protocol BDelegate: class, A {}

However this invokes a new warning in Xcode 9.1:

warning: redundant layout constraint 'Self' : 'AnyObject'
protocol BDelegate: class, A {

So it's not possible to satisfy both the Swift requirement and the Swiftlint rule unless the dependent protocol is renamed to *Delegate. This seems more restrictive than this rule was originally intended to be.

1856 is similar but appears to have addressed a slightly different issue.

[inahuelzapata]

I have the same issue with Xcode version 9.1. I had to disable the rule in order to stop getting warnings that didn't appear on Xcode 9.0.

Hope to get a solution.

[eduardourso]

Same for me, only happens on Xcode 9.1.

[TheSwifter]

Same for me too, only happens for Xcode 9.1.

[jpsim]

PRs welcome.

[marcelofabri]

The only solution I could come up with would be adding an extra configuration to explicitly allow certain protocols inheritance. This is not ideal, but at least would avoid the warning.

[eneko]

I'm not 100% sure about this, but I feel the warning is triggered without protocol inheritance.

// This triggers a violation "Delegate protocols should be class-only so they can be weakly referenced."
protocol MyClassDelegate: class {}
class MyClass: NSObject {
    weak var delegate: MyClassDelegate?
}

This might have been fixed recently, but still shows up for Danger running swiftlint (checking the version now).

[marcelofabri]

@eneko That didn't trigger a warning for me.

[soleares]

@eneko Your case also triggers warnings for me when run from Danger on CI but not locally. I'm using the latest versions of Danger and SwiftLint on CI and locally.

[eneko]

Ok, so it might have been fixed recently, I would assume the danger-swiftlint gem has not been updated yet. Thanks!

[stale[bot]]

This issue has been automatically marked as stale because it has not had any recent activity. Please comment to prevent this issue from being closed. Thank you for your contributions!