buggy type inference for props with array type

[indus]

Version

2.5.16

Reproduction link

https://raw.githubusercontent.com/indus/stuff/master/vue_issue.jpg
(sorry - haven't found an online tool that shows type annotations)

Steps to reproduce

type the following in an TS enabled Editor like VS Code:

new Vue({
    el: '#app',
    props: {
        object: {
            type: Array,
            required: true,
            default: () => []
        }
    },
    data: function () {
        return {
            message: 'Hello Vue.js!'
        }
    },
    created: function () {
        this.message;
    }
})

What is expected?

correct type inference (at least) for 'message'

What is actually happening?

getting Error: "Property 'message' doesn't exist"

---

This doesn't happen when the type of the prop is Object:

new Vue({
    el: '#app',
    props: {
        object: {
            type: Object,
            required: true,
            default: () => {}
        }
    },
    data: function () {
        return {
            message: 'Hello Vue.js!'
        }
    },
    created: function () {
        this.message;
    }
})

or 'data' is just a simple object and not a function

new Vue({
    el: '#app',
    props: {
        object: {
            type: Array,
            required: true,
            default: () => []
        }
    },
    data: {
        message: 'Hello Vue.js!'
    },
    created: function () {
        this.message;
    }
})

[ktsn]

This looks like duplicate of #7640 if you are using TypeScript 2.7.
If it's not the same issue, please provide a example github repo that reproduce it.

[HerringtonDarkholme]

This is exactly the duplicate of #7640.

type: Array breaks the overloading function Vue.extend. The last alternative of overloading is picked so this-type isn't included.

The workaround is manual annotation.

import Vue, {PropOptions} from "vue"

Vue.extend({
    props: {
        myProp: {
            type: Array,
        } as PropOptions<any[]>,
    },
})

[ffxsam]

@HerringtonDarkholme Thanks for that workaround. Kind of hard to believe this is still an issue.