Warn implicit self for weak self captures, after self is unwrapped

New Issue Checklist

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

New rule request

Implicit self is now permitted for weak self captures, after self is unwrapped. For example:

class ViewController {
  let button: Button

  func setup() {
      button.tapHandler = { [weak self] in
          guard let self else { return }
          dismiss() // refers to `self.dismiss()`
      }
  }

  func dismiss() { ... }
}

Is it possible to have a rule that warns if an implicit self is used?

The issue names no files, tests, or entry points. Start by reviewing SwiftLint’s existing rule implementations and test layout, then trace how closure captures and implicit self references are analyzed. Done means the rule detects implicit self after weak self is unwrapped and has coverage for the example behavior.