code: function printVueFor(value, textToDoc) {
    const { left, operator, right } = parseVueFor(value);
    return concat([
      group(
        textToDoc(`function _(${left}) {}`, {
          parser: "babel",
          __isVueForBindingLeft: true
        })
      ),
      " ",
      operator,
      " ",
      textToDoc(right, { parser: "__js_expression" })
    ]);
  }
docs: v-for="... in ..."
  v-for="... of ..."
  v-for="(..., ...) in ..."
  v-for="(..., ...) of ..."