Is it possible to extend ProxyHandler interface?

[ikabirov]

I'll try to write externs for Record from Immutable.js.

When class contains only get method it's ok, but it's ignored when object contains custom methods

[brad4d]

It looks like ProxyHandler is defined as an @record in es6_proxy.js, so it should be possible to extend it like this.

/**
 * @extends {ProxyHandler}
 * @record
 */
function MyProxyHandler() {}

/**
 * @param {number} n
 * @return {string}
 */
MyProxyHandler.prototype.myMethod = function(n) {};

What does your code look like?

[ikabirov]

Extending ProxyHandler work only if we have no additional methods:

/**
 * @extends {ProxyHandler<T>}
 * @record
 * @template T
 */
function MyProxyHandler() {}

/**
 * @typedef {{
 *   src: string,
 * }}
 */
var MyData;

/**
 * @param {MyProxyHandler<MyData>} proxy
 */
function foo(proxy) {
	proxy.myMethod(1); // WARNING - Property myMethod never defined on MyProxyHandler
	console.log(proxy.src); // OK
}

But if we add custom method extending ProxyHandler does not work:

/**
 * @extends {ProxyHandler<T>}
 * @record
 * @template T
 */
function MyProxyHandler() {}

/**
 * @param {number} n
 * @return {string}
 */
MyProxyHandler.prototype.myMethod = function(n) {};

/**
 * @typedef {{
 *   src: string,
 * }}
 */
var MyData;

/**
 * @param {MyProxyHandler<MyData>} proxy
 */
function foo(proxy) {
	proxy.myMethod(1); // OK
	console.log(proxy.src); // WARNING - Property src never defined on MyProxyHandler
}

[brad4d]

@ikabirov thanks for the detailed repro.
I've created an internal bug to track fixing this.