The use case is going to be something like this.

In CPS transformer, check if expression contains yield/await. If so transform expression into normalized comma expression, Then transform that into a state machine. Something like:

```js
if (a.b + yield c.d) {
```
becomes
```js
$0 = a.b;
$1 = yield c.d;
if ($0 + $1) {  // $0 + $1 is the last expression in the normalized comma expression
```



plus CPS transformed of course.