5z5-비어있지-않은-배열-타입

https://type-level-typescript.com/arrays-and-tuples

/**
 * Create a generic `NonEmptyArray` type that represents 
 * Arrays that contain at least one element.
 */
namespace nonEmptyArray {
  type NonEmptyArray<T> = [T, ...T[]]
 
  function sendMail(addresses: NonEmptyArray<string>) {
    /* ... */
  }
 
  sendMail(["123 5th Ave"]); // ✅
  sendMail(["75 rue Quincampoix", "75003 Paris"]); // ✅
  // @ts-expect-error
  sendMail([]);
  //       ^ ❌ `[]` isn't assignable to `NonEmptyArray<string>`
}