Missing excess property errors when assigning to intersection

[OliverJAsh]

Bug Report

🔎 Search Terms

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about excess property checking

⏯ Playground Link

Playground link with relevant code

💻 Code

type Props = { foo: string };

type Demo = {
    props: Props;
} & {
    props: Props;
};

type Collection = {
    demo: Demo;
} & {
    demo: Demo;
};

const t1: Collection = {
    demo: {
        props: {
            foo: 'foo',
            bar: 1, // expected error due to excess prop, but got none ❌
        },
    },
};

If we remove one of the intersections, excess property checks kick in again.

This is clearly a contrived example however I have reduced it from a much more complicated example where we do actually need to use intersections in a similar way. I can elaborate if needed.

I have been able to workaround the issue using this Compact helper:

type Compact<A> = A extends Function ? A : { [K in keyof A]: A[K] } & {};

type Collection = Compact<{
    demo: Demo;
} & {
    demo: Demo;
}>;

🙁 Actual behavior

See comment in code above.

🙂 Expected behavior

See comment in code above.

[Andarist]

This was fixed in 4.9, likely by #51140 (4.9.0-dev.20221014 is the first one to report the correct error)