PropType doesn't take undefined for optional props into account

Version

2.6.11

Steps to reproduce

Create component with optional prop being an object and try to access its property

import Vue, { PropType } from 'vue';

Vue.extend({
  props: {
    container: Object as PropType<{ n: number }>,
    // or container: Number
  },

  mounted () {
    // should fail because this.container could be undefined
    console.log(this.container.n);
  },
});

What is expected?

TS error: Object is possibly undefined

What is actually happening?

No error

Note

It works as expected with Composition API plugin

[jacekkarczmarczyk]

Yeah, I guess I didn’t emphasised actual problem clear enough, sorry and thanks

[jacekkarczmarczyk]

@posva you mean vue behaviour is correct and VCA behaviour is not?