satisfies should work when an object is spread into another

[arcticmatt]

Suggestion

It looks like satisfies doesn't work when you spread an object into another

TypeScript errors as expected

type Colors = "red" | "green" | "blue";

// Ensure that we have exactly the keys from 'Colors'.
const favoriteColors = {
    "red": "yes",
    "green": false,
    "blue": "kinda",
    "platypus": false
//  ~~~~~~~~~~ error - "platypus" was never listed in 'Colors'.
} satisfies Record<Colors, unknown>;

TypeScript does not error, but I think it should

type Colors = "red" | "green" | "blue";

const foo = {
    "platypus": false
}

// Ensure that we have exactly the keys from 'Colors'.
const favoriteColors = {
    "red": "yes",
    "green": false,
    "blue": "kinda",
    ...foo
} satisfies Record<Colors, unknown>;

I would expect the latter to also have a TypeScript error, to prevent favoriteColors from having undesired extra properties.

Why? Well, because sometimes passing extra properties can break stuff.

🔍 Search Terms

satisfies, spread

[fatcerberus]

Duplicate of #50938; interestingly the examples are almost identical.

See also #39998

[fatcerberus]

Why? Well, because sometimes passing extra properties can break stuff.

Just FWIW, you probably shouldn't rely on this check to prevent runtime errors due to excess properties. It's a fairly limited lint check primarily designed to catch typos in object literals; it's still very easy to end up with extra properties:

const faves = {
    "red": "yes",
    "green": false,
    "blue": "kinda",
    "platypus": false
};
const favoriteColors = faves satisfies Record<Colors, unknown>;  // no error

[RyanCavanaugh]

Spreads aren't subject to excess property checks and it's not clear to me that they ever could be in an ergonomic way.

[fatcerberus]

@RyanCavanaugh If this is Working As Intended, shouldn't #39998 be closed then? 😉

[RyanCavanaugh]

Awaiting More Feedback isn't the same as closed? 🙃

[typescript-bot]

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