Rule Definition
The 'else' part is executed when none of the when part is executed. Having no else keyword means that there is no backup. The cases that are "impossible" today are those most likely to be the causes of untraceable bugs in the future. Software should follow the principles of structured programming or else it degrades comprehensibility.

Remediation
Add else block to every when statement or expression

Violation Code Sample

fun  main(args: Array<String>){
    println("hello")
    val x = 20
    when (x) {
        1 -> print("x == 1")
        2 -> print("x == 2")

        }
    }

Fixed Code Sample

fun  main(args: Array<String>){
    println("hello")
    val x = 20
    when (x) {
        1 -> print("x == 1")
        2 -> print("x == 2")
        else -> println("x is neither 1 not 2")
        }
    }

CISQ rule: ASCMM-MNT-1.