Breaking lexical scope to prevent finding all references

问题

Apart from text-to-code methods, like eval/Function, or adding additional scripts, are there any more ways to shroud lexical scoping, which would invalidate a basic lexical search for an identifier's declaration, and all references?

This is related to e.g. vs-code's "rename" (F2 by default), more precisely, implementing similar functionality. In other words, locally observing a snippet from a larger program, and renaming an identifier - not in a normal "best practice" situation, but where an obfuscator deliberately tries to sabotage you.

An example of a problematic case with eval would be this:

function f() {
  try { v; } catch(_) { console.log("weewoo"); }
}
{
  let v = 1;
  function g() {
    v; // entering here, trying to rename this "v"
  }
  eval(`(${f.toString()})()`);
}

In vs-code, renaming the marked v would semantically change the code, which can be detected.

If there should be no eval/Function usage in the entire code, and it's certain, that no additional code is being loaded, is a lexical renaming always safe? Are there more such pitfalls?

---

Edit: There are two other cases, which i forgot to mention, because they typically don't apply, and are far easier to detect. However, they are still very related:

• using the fact, that global scope variables are added to the global object:

  var v = 1;
  v; // renaming here
  if (!window[String.fromCharCode(118)])
    console.log("weewoo");
  

• non-strict mode legacy with statement (which vs-code does detect!):

  var v = 0;
  with({ v: 1 }) {
    v; // renaming here
    if (!v) console.log("weewoo");
  }
  

来源：https://stackoverflow.com/questions/61560852/breaking-lexical-scope-to-prevent-finding-all-references