In JS, `@template` types on constructor functions do not resolve in prototype methods

[sandersn]

var Multimap = function() {
  /** @type {!Map.<K, !Set.<!V>>} */
  this._map = new Map();
};

/**
 * @param {K} key the key ok
 * @returns {Set<V>} the value ok
 */
Multimap.prototype.get = function (key) {
    return this._map.get(key) || new Set();
}

Expected behavior:
No errors, and Multimap<K,V>.get: (key: K) => Set<V>

Actual behavior:
K and V in @param {K} and @returns {Set<V>} are not found and get: (key: any) => any.

Works fine if Multimap is declared as function Multimap ....

Should work with prototype assignments too, eg Multimap.prototype = { get() { ... } }. Discovered while fixing #24230