code: function countIdentifiers (node) {
      if (!node.children) return 0;
      var count = 0, i = 0, len = node.children.length, type;
      for (; i < len; i++) {
        type = node.children[i].type;
        if (type === "identifier" || type === "binder" || type === "key") count += 1;
        else count += countIdentifiers(node.children[i]);
      }
      return count;
    }
docs: Scans all children for a node and counts the number of identifier patterns. Identifier patterns include captures and object keys.