This is by design. ECMAScript block scoped declarations generally conform to
the principle that within a single block or statement a name may have only a
single binding. For example,
```js
let x=0;
{
let x = x+1; //access to uninitialized variable error because both the RHS
and LHS refer to the inner x
//which has not yet been initialized when the RHS is
evaluated
}
```
The same principle also applies to
```js
let n = {a:[]};
for (let n of n.a) ;
```
although the actual scoping of the `for` statement is more complex. Basically,
such `for` statements consider all names bound by the `let` part of of the
`for` header to be undefined while the `of` expression is being evaluated.
This is done to avoid any confusion about which `n` the expression references.
Such confusion is avoid by all references to the `let` bound names from the RHS
errors.
Allen
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