title: Vuejs typescript this.$refs.<refField>.value does not exist
body: <p>While rewriting my VueJs project in typescript, I came across a TypeScript error.</p>
  
  <p>This is a part of the component that has a custom v-model.</p>
  
  <p>An input field in the html has a ref called 'plate' and I want to access the value of that. The @input on that field calls the update method written below.</p>
  
  <p>Typescript is complaining that value does not exist on plate. </p>
  
  <pre><code>@Prop() value: any;
  
  update() {
      this.$emit('input',
          plate: this.$refs.plate.value
      });
  }
  </code></pre>
  
  <p>template:</p>
  
  <pre><code>&lt;template&gt;  
  &lt;div&gt;
      &lt;div class="form-group"&gt;
          &lt;label for="inputPlate" class="col-sm-2 control-label"&gt;Plate&lt;/label&gt;
  
          &lt;div class="col-sm-10"&gt;
              &lt;input type="text" class="form-control" id="inputPlate" ref="plate" :value="value.plate" @input="update"&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  
  &lt;/div&gt;
  &lt;/template&gt;
  </code></pre>