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assertNever

Callable

  • assertNever<V>(subject): V

  • Raise a compile error when accessing this function and throws a TypeError at runtime This is useful for exhaustive switch check.

    const print = (fruit: 'banana'|'kiwi') => {
      switch (fruit) {
        case 'banana': return '🍌 Banana';
        case 'kiwi': return '🥝 Kiwi';
        default: return assertNever(fruit); // <- This line will report an error if a case is missing
      }
    }