sequence as class property breaks everything

Valid JS code

```js
class Foo {
  [(1, Symbol.asyncIterator)]() {}
}
```

obfuscated as 

```js
class Foo {
    [0x1, Symbol['asyncIterator']]() {
    }
}
```

invalid js code. The bug exists in the latest 0.x.x and latest 1.x.x versions.

It's very important bug, TypeScript generates such code, i can't even fix it.