Angular 角度9常春藤误差<；垫形式字段>；有多个垫子提示

在升级到angular9 Ivy之前，我曾经在一个

<div class="example-container">
  <mat-form-field hintLabel="Max 10 characters" appearance="fill">
    <mat-label>Enter some input</mat-label>
    <input matInput #input maxlength="10" placeholder="Ex. Nougat">
    <mat-hint align="end">{{input.value?.length || 0}}/10</mat-hint>

    <mat-label>Select me</mat-label>
    <mat-select>
      <mat-option value="option">Option</mat-option>
    </mat-select>
    <mat-hint align="end">Here's the dropdown arrow ^</mat-hint>
  </mat-form-field>
</div>

以前

  function (hint) {
                if (hint.align === 'start') {
                    if (startHint_1 || _this.hintLabel) {
                        throw getMatFormFieldDuplicatedHintError('start');
                    }
                    startHint_1 = hint;
                }
                else if (hint.align === 'end') {
                    if (endHint_1) {
                        throw getMatFormFieldDuplicatedHintError('end');
                    }
                    endHint_1 = hint;
                }

也许这就是那个错误的原因

  function (hint) {
                if (hint.align === 'start') {
                    if (startHint_1 || _this.hintLabel) {
                        throw getMatFormFieldDuplicatedHintError('start');
                    }
                    startHint_1 = hint;
                }
                else if (hint.align === 'end') {
                    if (endHint_1) {
                        throw getMatFormFieldDuplicatedHintError('end');
                    }
                    endHint_1 = hint;
                }