code: private Node tryFoldAssignment(Node subtree) {
      checkState(subtree.isAssign());
      Node left = subtree.getFirstChild();
      Node right = subtree.getLastChild();
      if (left.isName()
          && right.isName()
          && left.getString().equals(right.getString())) {
        // Only names
        subtree.replaceWith(right.detach());
        reportChangeToEnclosingScope(right);
        return right;
      } else if (left.isDestructuringPattern() && !left.hasChildren()) {
        // `[] = <expr>` becomes `<expr>`
        // Note that this does potentially change behavior. If `<expr>` is not iterable and this
        // code originally threw, it will no longer throw.
        subtree.replaceWith(right.detach());
        reportChangeToEnclosingScope(right);
        return right;
      }
      return subtree;
    }
docs: Try removing identity assignments and empty destructuring pattern assignments
  
  @return the replacement node, if changed, or the original if not