E0309: unexpected '?' when destructuring

In TypeScript, ? can be used to mark a function parameter as optional. It is a syntax error to write ? when destructuring:

type OneOrTwo<T> = [T] | [T, T];
function join1Or2(
  [first, second?]: OneOrTwo<string>,
) {
  return second ? first+second : first;
}

To fix this error, remove the ?:

type OneOrTwo<T> = [T] | [T, T];
function join1Or2(
  [first, second]: OneOrTwo<string>,
) {
  return second ? first+second : first;
}

Introduced in quick-lint-js version 2.10.0.