The let-declarations are hoisted even though they should not:

function foo() {
    n = 0;
    console.log(n);  // should give a ReferenceError, but it doesn't
    let n;
}

ECMA-262, 7th Edition, §13.3.1:

The variables are created when their containing Lexical Environment is instantiated but may not be accessed in any way until the variable's LexicalBinding is evaluated.