Brendan Eich wrote:
>>     let["a"].foo() // Fine in ES5 non-strict, fails in ES6?
>
> That old chestnut! (Unquote "a" for better ambiguity.) 

Truly hard case:

   let[x] = y;

where 'var let' or something worse, e.g., at global scope, this.let = 
[], has been evaluated.

/be

Brendan Eich wrote:
>>     let["a"].foo() // Fine in ES5 non-strict, fails in ES6?
>
> That old chestnut! (Unquote "a" for better ambiguity.) 

Truly hard case:

```js
let[x] = y;
```

where `var let` or something worse, e.g., at global scope, `this.let = []`, has been evaluated.