satisfies allows excess properties via object spread

[robpalme]

Bug Report

🔎 Search Terms

satisfies object spread excess properties

🕗 Version & Regression Information

• Tested on 4.9.0-dev.20220921

⏯ Playground Link

Playground link with relevant code

💻 Code

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

const favoriteColors = {
    "red": "yes",
    "green": false,
    "blue": "kinda",
    ...{ platypus: false },   // No error, despite it being a known excess property
} satisfies Record<Colors, unknown>;

🙁 Actual behavior

No error. The use of object spread causes the excess property to be permitted.

Hovering over favoriteColors, you can see that TypeScript understands it has generated a type with all four properties.

🙂 Expected behavior

An error. The issue introducing satisfies and release notes suggest excess property detection is an intended feature of satisfies.

[robpalme]

This issue is not specific to satisfies and is a known limitation of the existing excess property checks.

There is already a request to make the checking stricter to include object spread.