`this` type inference doesnt work in `data` method

[ReinisV]

Version

2.6.14

Reproduction link

github.com

Steps to reproduce

create a Vue app using vue create either 2.x or 3.x doesnt matter, as long as it is with TypeScript and object style component syntax go to HelloWorld.vue and right below the props definition paste this:

  data (): { hellStringType: string, hellNumberType: number, hellInvalid: string} {
    debugger;
    return {
      hellStringType: this.getNumber(),
      // should fail due to field type and return type not matching
      hellNumberType: this.getNumber(),
      // should fail due to there being no such function
      hellInvalid: this.buildSomethingElse(),
    }
  },
  methods: {
    getNumber (): number {
      return 42
    }
  }

What is expected?

type inference for the method calls should work, and thus the compilation should fail

What is actually happening?

type inference doesnt work, the invalid code compiles fine. Type inference works only for props.

---

running the code in a browser with debug statement, the methods called are accessible

[bl3ndd]

I have this issue too

[Yan-Doshchinskiy]

I have the same issue

interface IDropdownItem {
  selector: string,
  handler: number,
  title: string,
}

interface HeaderData {
  isShowDropdown: boolean
  dropdownItems: Array<IDropdownItem>
}

I have such interfaces for describing the data

  data(): HeaderData {
    return {
      isShowDropdown: false,
      dropdownItems: [
        {
          selector: 'SELECTOR-1',
          handler: '123',
          title: 'TITLE-1',
        },
        {
          selector: 'SELECTOR-1',
          handler: '123',
          title: 'TITLE-1',
        },
      ]
    };
  },

in this case, the typescript highlights the incorrect typing of the "handler" field if I change one of the "handler" fields to the expected type, only the wrong field will be highlighted. This corresponds to the expected behavior But if I pass a function to one of the fields, and leave the second field with the wrong type, then both fields will be considered correct

If the function is set as a callback, then typing works fine

[4xii]

可以看看这个demo，好像ts是会有这个问题