Rule Request: Deinit Required

[BenStaveleyTaylor]

New Issue Checklist

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

New rule request

I would like to have the ability to require classes to have a deinit method.

1. Why should this rule be added? Share links to existing discussion about what
   the community thinks about this.

When investigating memory leaks it is useful to be able to set a breakpoint on the deinit method. Our house style is that all classes should have a deinit even if it is empty, to facilitate debugging.
Frequently the class does not have a method, so you have to quit, add the method and rebuild in order to proceed.

2. Provide several examples of what would and wouldn't trigger violations.

// Would trigger
class Apple {
}

class Banana
{
   func peel() {
   }
}

class Cherry: NSObject {
}

class Damson: Protocol1, Protocol2 {
}

// Would not trigger
class Apple {
   deinit {
   }
}

class Banana
{
   func peel() {
   }  
   deinit {
      print("Deinit of Banana: \(self)")
   }
}

struct Cherry {
}

enum Damson {
}

protocol Elderberry {
}

3. Should the rule be configurable, if so what parameters should be configurable?
   No, I don't think anything beyond the standard error/warning, enable/disable is needed.

4. Should the rule be opt-in or enabled by default? Why?
   opt-in. Clearly not everybody wants this all the time.

[BenStaveleyTaylor]

@marcelofabri I'd be prepared to have a go at this. Before I invest time in it, is this a rule that would be accepted if it worked as described? If the feedback is that people don't want it, that's OK.

[marcelofabri]

I think it makes sense as an opt-in rule.

[marcelofabri]

Implemented in #2624.