Behavior of `let` inside a loop

[Dickson Wong]

I'm running into some strange behavior where a variable declared with `let` inside a loop retains the value from a previous iteration if it hasn't been initialized in the current iteration.

For instance, the following code:

for (var i of [0, 1]) {
  let x;
  if (i % 2 === 0) {
    x = i;
  }

  console.log(`x: ${x}`);
}

Outputs:

x: 0
x: 0

And more strangely, the following code:

for (var i of [0, 1]) {
  let x;
  if (i % 2 === 0) {
    x = i;
  }

  console.log(`x: ${x}`);

  var f = function() {
    var y = x;
  };
}

Outputs:

x: 0
x: undefined

According to let declaration section of the ES6 draft, I was expecting a value of `undefined` in the second iteration in both cases.

I'm wondering if the ES6 spec specifies whether a variable declared using `let` inside a loop should be scoped to the current iteration of the loop or if it should be scoped to the loop block with the variable shared between all iterations.

[Erik Arvidsson]

This has been fixed:

https://github.com/google/traceur-compiler/issues/1567

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--
erik