TS2322 not work on some strange situations

[FlareZh]

Bug Report

🔎 Search Terms

type or, adding undefined, TS2322

🕗 Version & Regression Information

Maybe it is from the beginning

⏯ Playground Link

Playground link with relevant code

💻 Code

type A = {
    name: string
}
type B = {
    name: string
    id: number
}

type C = A | B

const a: C = {
    name: '1',
    id: undefined, // expect an error
}

const b: C = {
    name: '1',
    id: undefined, // an ts2322 error
    value: 2,
}

🙁 Actual behavior

The var a does not report any error, but the var b report error "Type 'undefined' is not assignable to type 'number'(2322)".
Before v3.7.5, it will report error "Type '{ name: string; id: undefined; value: number; }' is not assignable to type 'C'.
Object literal may only specify known properties, and 'value' does not exist in type 'C'.(2322)" on b.
But I think the error should occur on var a too.

🙂 Expected behavior

The error reported on b should also be reported on var a.

[MartinJohns]

Excess property checks are not working for unions without a discriminant. See #20863.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.