Hi, my proposal is to have something to tell the `...

# language-proposals

[louiscad]

Hi, my proposal is to have something to tell the when expression to fail if no case matches, in a syntax similar to !! for non null assertions.

Currently, I have to add a else case and throw an IllegalArgumentException or an IllegalStateException, which adds a line for each when clause, which is quite a lot for 2-3 cases when expressions.

How about a syntax like the following?

val message: String = when!! {
    code == 0 -> "Ok"
    result.failed -> "Some error ;)"
}

val text: String = when(number)!! {
    0 -> "Zero"
    1 -> "One"
}