Rule request: unneeded break in switch

[marcelofabri]

New Issue Checklist

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

Rule Request

When using switch statements, avoid adding explicit break.

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

From Erica Sadun's Swift Style book:

Avoid adding unneeded break statements. Swift naturally ends evaluation at the end of a case. Don’t pad your code to look like other languages that don’t offer this safety feature.

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

// should trigger
switch foo {
case .bar:
  something()
  ↓break
default:
  break
}

// shouldn't trigger
switch foo {
case .bar:
  something()
case .bar2:
  somethingElse()
}

switch foo {
case .bar:
  break
case .bar2:
  somethingElse()
}

switch foo {
case .bar:
  for i in [0, 1, 2] {
    break
  }
case .bar2:
  somethingElse()
}

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

Just the severity.

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.

Enabled by default.