Feature request: mark dynamic scopes a reference passes through

[bakkot]

For example:

let x;
function f() {
  {
    let x;
    x; // 1
    with (o) {
      x; // 2
    }
  }
  eval(s);
  x; // 3
}

would mark 1 as passing through no dynamic scopes, would mark 2 as passing through the with, and would mark 3 as passing through the function.

[michaelficarra]

Can't this already be derived?

[bakkot]

Not trivially, especially when the dynamism comes from a sloppy direct eval.