Conditional keys added to Partial<T> are not checked

[pierpo]

Search Terms:

conditional keys object properties not checked

Code

interface MyInterface {
    a: number;
    b: number;
}

const myFunc = (): Partial<MyInterface> => {
    return {
        a: 1,
        b: 2,
        ...(true && { c: 'oops, no error' }),
    }
}

Expected behavior:

I should have an error saying "c key does not exist in MyInterface".

Actual behavior:

I do not get an error.

Playground Link:

Playground Link

Related Issues:

I could not find any.

---

Please note that the values are checked. This does produce an error:

interface MyInterface {
    a: number;
    b: number;
}

const myFunc = (): Partial<MyInterface> => {
    return {
        a: 1,
        ...(true && { b: 'okay I get an error' }),
    }
}

[MartinJohns]

Excess property checks do not occur for spread objects. This is intentional, see #19775.

[pierpo]

Oh! Indeed. I did not pinpoint the problem precisely enough, I should've known it was related to spread operators.

Thank you for your very quick and helpful answer! We may close the issue! Sorry about the duplicate 😊