wrong scoping of `let` variables declared in loop header

[mminea]

A let in a loop header should create a new binding for each iteration.
This code should print out 0 1 2

let fa = [];
for (let i = 0; i < 3; ++i) {
  fa.push(() => i);
}
fa.forEach(f => console.log(f()));

However, it prints 3 three times.

[generic-github-user]

I think this might have to do with the for loop desugaring in Stopify (this would be the relevant code) - I'm still looking through the code but it seems that the AST might be rewritten in a way that only declares the variable once before the generated while loop is executed, then updates this (instead of initializing a new variable with the value from the previous iteration). Hopefully I'll have some time next week to take a closer look.