Для чего можно использовать тип

function throwError(message: string): never {
  throw new Error(message);
}

function infiniteLoop(): never {
  while(true) { /* ... */ }
}

type Shape = 'circle' | 'square';

function getArea(shape: Shape): number {
  switch(shape) {
    case 'circle': return Math.PI * 2;
    case 'square': return 4;
    default: 
      const _exhaustiveCheck: never = shape;
      return _exhaustiveCheck;
  }
}