JSDoc '@this' not actually used to enforce thisArg at callsite

Bug Report

🔎 Search Terms

JSDoc this

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about @this

⏯ Playground Link

Playground Link: Provided

💻 Code

/** @this {string} */
export function firstCharOfThis() {
  return this.charAt(0);
}

firstCharOfThis(); // invalid
firstCharOfThis.call(1); // invalid
firstCharOfThis.call('foo'); // valid

🙁 Actual behavior

No compile error, but a runtime error.

🙂 Expected behavior

First two calls should be an error, last call should be fine. Expected the same behavior as if it was written in TS with an explicit this-parameter

Start with the provided TypeScript Playground reproduction and compare the JSDoc @this function with an equivalent explicit this-parameter declaration. The fix is complete when calling firstCharOfThis() and firstCharOfThis.call(1) produces errors while firstCharOfThis.call('foo') remains valid.