class A {
    readonly kind = 'a';
}
type U = A; // <-- supposed to be a single case union
declare var u: U;
declare function never(never: never): never;
function fn() {
    switch (u.kind) {
        case 'a': return 1;
        default: return never(u); // <-- u expected to be never, actually is A
    }
}