code: function BlockStatement(node, print) {
    this.push("{");
    if (node.body.length) {
      this.newline();
      print.sequence(node.body, { indent: true });
      if (!this.format.retainLines) this.removeLast("\n");
      this.rightBrace();
    } else {
      print.printInnerComments();
      this.push("}");
    }
  }
docs: Print BlockStatement, collapses empty blocks, prints body.