non-empty-string.ts

// Here we check if our custom type "Stringy" extends a narrow type of ''
// If it does, the type is never
// If it doesnt, the type is "Strinfy", which is just a string type
function getItem<Stringy extends string>(
  id: Stringy extends '' ? never : Stringy
) {
  // code here
}
// works:
getItem('abc123'); // No error

// Error
getItem('');
getItem();
getItem(123); // fail