Given this exhaustive switch, what is the purpose of the `never` assignment in the `default` branch?
type Shape =
| { kind: "circle"; r: number }
| { kind: "square"; s: number };
function area(sh: Shape): number {
switch (sh.kind) {
case "circle": return Math.PI * sh.r ** 2;
case "square": return sh.s ** 2;
default:
const _exhaustive: never = sh;
return _exhaustive;
}
}