@typedef can access function type parameters

[ghost]

TypeScript Version: 2.7.0-dev.20171220

Code

/** @typedef {U} T */

/**
 * @template U
 * @param {U} x
 * @return {T}
 */
function f(x) {
    return x;
}

/** @type T */
const x = 3;

Expected behavior:

We shouldn't be able to access U in the definition for T. Doing so leads to strange behavior later on.

Actual behavior:

We can. But then we can't use T anywhere because it leaks U.