code: private void addToDefIfLocal(String name, @Nullable Node node,
        @Nullable Node rValue, MustDef def) {
      Var var = allVarsInFn.get(name);
  
      // var might be null if the variable is defined in the externs
      if (var == null) {
        return;
      }
  
      for (Var other : def.reachingDef.keySet()) {
        Definition otherDef = def.reachingDef.get(other);
        if (otherDef == null) {
          continue;
        }
        if (otherDef.depends.contains(var)) {
          def.reachingDef.put(other, null);
        }
      }
  
      if (!escaped.contains(var)) {
        if (node == null) {
          def.reachingDef.put(var, null);
        } else {
          Definition definition = new Definition(node);
          if (rValue != null) {
            computeDependence(definition, rValue);
          }
          def.reachingDef.put(var, definition);
        }
      }
    }
docs: Set the variable lattice for the given name to the node value in the def
  lattice. Do nothing if the variable name is one of the escaped variable.
  
  @param node The CFG node where the definition should be record to.
  {@code null} if this is a conditional define.