Slotted Redistribution Question

date-combo-box.html

<!-- Reference implementation for date-combo-box
Reference link: https://github.com/w3c/webcomponents/wiki/Proposal-for-changes-to-manage-Shadow-DOM-content-distribution/641b524e633678c2b25e7cb8ba31005350f36c9d#proposal-part-2-filling-and-re-exposing-named-insertion-points
-->

<!-- For date-combo-box, which inherits from combo-box -->
<template>
  <input type="date" content-slot="inputElement">
  <img src="calendarIcon.png" content-slot="icon">
  <month-calendar content-slot="dropdown"></month-calendar>
</template>

date-range-combo-box.html

<!-- instance -->
<date-range-combo-box>
  <input type="date" content-slot="start">
  <input type="date" content-slot="end">
</date-range-combo-box>

<!-- implementation -->
<template>
  <shadow>
    <date-combo-box>
       <!--
       How can input[content-slot="start"] end up in the <content slot="inputElement">
       in the <date-combo-box> ?
       -->
      <content slot="start"></content>
    </date-combo-box>
    <date-combo-box>
      <content slot="end"></content>
    </date-combo-box>
  </shadow>
</template>