Rule Request: unused control flow labels

[masters3d]

Rule Request

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

Typescript just added a way to identify labels which are not being used. I think this would be really nice to have in swift as lint rule.

https://github.com/Microsoft/TypeScript/pull/24037/files

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

label2:  /// label2 not being used. Consider removing
    while (true) {}

do, while, repeat should be supported

non triggering examples:

label2: 
    while (true) { break label2}

3. Should the rule be configurable, if so what parameters should be configurable?

none

4. Should the rule be opt-in or enabled by default? Why?
   See README.md for guidelines on when to mark a
   rule as opt-in.

probably opt in

[jpsim]

It took me a bit to understand that this was about unused control flow labels, not closure parameters.