Vollständige Musterübereinstimmung mit Diskriminierten Unionen und Never

type Circle = { kind: "circle"; radius: number };
type Square = { kind: "square"; sideLength: number };
type Rectangle = { kind: "rectangle"; width: number; height: number };
 
type Shape = Circle | Square | Rectangle;
 
function assertUnreachable(x: never): never {
  throw new Error(`Unexpected object: ${JSON.stringify(x)}`);
}
 
function calculateArea(shape: Shape): number {
  switch (shape.kind) {
    case "circle":
      return Math.PI * shape.radius ** 2;
    case "square":
      return shape.sideLength ** 2;
    case "rectangle":
      return shape.width * shape.height;
    default:
      return assertUnreachable(shape);
  }
}