using being too strict to throw on Function type

[rixtox]

Bug Report

Currently the polyfilled implementation for using performs the following check:

var __addDisposableResource = (this && this.__addDisposableResource) || function (env, value, async) {
    if (value !== null && value !== void 0) {
        if (typeof value !== "object") throw new TypeError("Object expected.");
// ...

In the spec, the value used with using needs to be an "Object type", but we know in JavaScript an Object type can have typeof value other than "object", for example, a function has typeof value === "function" while also being a valid JavaScript Object.

The implementation should use the check similar to underscore.js's isObject() check:

export default function isObject(obj) {
  var type = typeof obj;
  return type === 'function' || (type === 'object' && !!obj);
}

⏯ Playground Link

function createHandle(): Writer & Disposable {
    const write: Writer = (data) => {};
    const close = (): void => {};
    return Object.assign(write, { [Symbol.dispose]: close });
}

{
    using write = createHandle();
}

type Writer = {
    (data: string): void;
};

Playground link with relevant code

[rixtox]

CC @rbuckton