Async Polyfill for javascript using eval and async function transform

asynceval.js

/* Idea for allowing async-style functions in vanilla JS
 * This transforms a function which uses await into a function
 * which returns an ES6-style promise
 *
 * eval has the property of running the string of javascript
 * with the same closure scope chain as the method it is called
 * from, which is why it is necessary to call eval on the output
 * of the async function, which returns a string representing
 * the transformed function.
 */

// Real ES7 Async JS function:
var asyncFunction = async function() {
    var x = await somePromiseNumber;
    var y = await somePromiseNumberFunction();

    return x + y;
};

// Proposed Example
var asyncFunction = eval(async(function() {
    var x = await(somePromiseNumber);
    var y = await(somePromiseNumberFunction());

    return x + y;
}));

// Becomes the equivalent of this
var asyncFunction = function() {
    return new Promise(function(resolve, reject) {
        somePromiseNumber.then(function(x) {
            somePromiseNumberFunction().then(function(y) {
                resolve(x + y);
                return;
            }, reject);
        }, reject);
    });
}

// Transformation Rules/Examples

// ----------------------------------
// this
async(function() {
  
});

// becomes this
function() {
  return Promise.resolve();
}

// ----------------------------------
// this
async(function() {
  return x;
});

// becomes this
function() {
  return new Promise(function(resolve, reject) {
    resolve(x);
    return;
  });
}

// ----------------------------------
// this
var x = await(promise)

//becomes this
promise.then(function(x) {
  /* rest of function */
}, reject);

// ----------------------------------
// this
x = await(promise)

//becomes this
promise.then(function(__) {
  x = __;
  /* rest of function */
}, reject);

// ----------------------------------
// this
await(promise)

//becomes this
promise.then(function() {
  /* rest of function */
}, reject);

// ----------------------------------
// this
return await(promise)

// ----------------------------------
//becomes this
promise.then(resolve, reject);