No newline after arrow when the expression is one-line

[yukukotani]

Fixes #586

Do not insert newline after arrow, when following expression is one-line.

Current

fun test(status: A): B {
    return when (status) {
        A.A,
        // Missing newline after "->"
        A.B -> B.A
    }
}

// Formatted
fun test(status: A): B? {
    return when (status) {
        A.A,
        A.B ->
            B.A
    }
}

Patched

fun test(status: A): B {
    return when (status) {
        A.A,
        //  No error
        A.B -> B.A
    }
}

[Tapchicoma]

Thank you for your contribution 👍