Reassigning data doesn't type-check correctly in interpolation

[octref]

When upgrading to TS 4.0.2, this no longer causes error:

<template>
  <div>
    <button @click="test = 'test'">Invalid Update Type</button>
  </div>
</template>

<script lang="ts">
import Vue from 'vue'

export default Vue.extend({
  data() {
    return {
      test: 0
    }
  }
})
</script>

@ktsn, I commented this test out for now: bc07565

Woud you have time to take a look?

[ktsn]

Ok, let me investigate on it.

[ktsn]

Strangely, it works correctly in the raw typescript file.

https://www.typescriptlang.org/play?checkJs=true&allowJs=true&target=99#code/CYUwxgNghgTiAEYD2A7AzgF3gfWwNwjQGEkBbAB1RBQwC54BvAKHnhRAHd4AKASnobwWreBhCZ6KAK6kARiBjCAvkxVMMAT3IISFKjQAyAS0zUFaADwAVAHzwAvI2EBtANLwjKeAGsQGpABm8FYAugD89NwAJCB41HTBbiG8DnZQKBoA3KrZnmIwAVBgOmSU7DQAIlAYUNZ2zKzkMEjkaPQASuBIMMAWmDCeAOYANPDpGjbZrKj0umXxxqbsMJa2U-DARnBgGEZxbWMZziHZKiAAHpQwWKCQsAjI6Fi4BGidKKAwABIgENowAmEdW4c30CW47C43AAdLDYIMDuNjil7HYrLxRgEUJEMAALEz0dGpQ4afgk07ZC5XG7gaBwRCoTA4fCEUHlDA-P4KQGsYHCVh4UiE4b80RQQb0fpDEUiDbVKCzUpgqo1CydZA9PoYAYoEYkmx2ABkwXxaCsWhAdRlIjA+IgwDg2JJx2EZPGFKYTBehHen05-243uISvZmKkKB2RlQPBSgmEQbZ8X9Cm4eJMowARJs8BnRoImi0DgwlKMZowSxstuBdvt6Md4BXnKKEyGk78A2m0JnZFIMBhULnGEJZY1mq0BBXRdMnYIM5AjGBvBn6AFw5Ho9FYvFY6JTdCxEzHBmDxgM5kGw3RlPK9sa+I6yFhyJGxmAJIoPBQCBGYDwACq5DANUCDmtoGbJMIyTnqovDZEAA

[octref]

🤷‍♂️ That's weird. I'll take a look when I have time...