no_fallthrough_only.md

Pattern: Use of case with fallthrough only

Issue: -

Description

Fall-throughs can only be used if the case contains at least one other statement.

Examples of correct code:

switch myvar {
case 1:
    var a = 1
    fallthrough
case 2:
    var a = 2
}


switch myvar {
case "a":
    var one = 1
    var two = 2
    fallthrough
case "b": /* comment */
    var three = 3
}


switch myvar {
case 1:
   let one = 1
case 2:
   // comment
   var two = 2
}


switch myvar {
case MyFunc(x: [1, 2, YourFunc(a: 23)], y: 2):
    var three = 3
    fallthrough
default:
    var three = 4
}


switch myvar {
case .alpha:
    var one = 1
case .beta:
    var three = 3
    fallthrough
default:
    var four = 4
}


let aPoint = (1, -1)
switch aPoint {
case let (x, y) where x == y:
    let A = "A"
case let (x, y) where x == -y:
    let B = "B"
    fallthrough
default:
    let C = "C"
}


switch myvar {
case MyFun(with: { $1 }):
    let one = 1
    fallthrough
case "abc":
    let two = 2
}

Examples of incorrect code:

switch myvar {
case 1:
    ↓fallthrough
case 2:
    var a = 1
}


switch myvar {
case 1:
    var a = 2
case 2:
    ↓fallthrough
case 3:
    var a = 3
}


switch myvar {
case 1: // comment
    ↓fallthrough
}


switch myvar {
case 1: /* multi
    line
    comment */
    ↓fallthrough
case 2:
    var a = 2
}


switch myvar {
case MyFunc(x: [1, 2, YourFunc(a: 23)], y: 2):
    ↓fallthrough
default:
    var three = 4
}


switch myvar {
case .alpha:
    var one = 1
case .beta:
    ↓fallthrough
case .gamma:
    var three = 3
default:
  var four = 4
}


let aPoint = (1, -1)
switch aPoint {
case let (x, y) where x == y:
    let A = "A"
case let (x, y) where x == -y:
    ↓fallthrough
default:
    let B = "B"
}


switch myvar {
case MyFun(with: { $1 }):
    ↓fallthrough
case "abc":
    let two = 2
}

Further Reading

• SwiftLint - No Fallthrough Only