code: private void removeFromUseIfLocal(String name, ReachingUses use) {
      Var var = allVarsInFn.get(name);
      if (var == null) {
        return;
      }
      if (!escaped.contains(var)) {
        use.mayUseMap.removeAll(var);
      }
    }
docs: Removes the variable for the given name from the node value in the upward
  exposed lattice. Do nothing if the variable name is one of the escaped
  variable.