TS8020

JSDoc types can only be used inside documentation comments.

Broken Code ❌

function add(a: number, b: number, c: number?): number {  return a + b; }

Fixed Code ✔️

If you wanted to make c optional:

function add(a: number, b: number, c?: number): number {  return a + b; }

If you wanted to document c with JSDoc:

/**  * @param a Initial quantity  * @param b Amount to add  * @param [c] Optional number to add  */ function add(a: number, b: number, c: number): number {  return a + b; }