[解決済み] フレックスアイテムが行の幅いっぱいに広がるようにする

.parent {
  display: flex;
  align-items: center;
  width: 100%;
  background-color: #ececec;
}

.parent * {
  width: 100%;
}

.parent #text {
  min-width: 75px;
  flex-shrink: 2.25;
}

<div class="parent">
  <input type="range" id="range">
  <input type="text" id="text">
  <label class="error">Error message</label>
</div>

.parent {
  display: flex;
  flex-wrap: wrap;
}

#range, #text {
  flex: 1;
}

.error {
  flex: 0 0 100%; /* flex-grow, flex-shrink, flex-basis */
  border: 1px dashed black;
}

<div class="parent">
  <input type="range" id="range">
  <input type="text" id="text">
  <label class="error">Error message (takes full width)</label>
</div>