Unable to catch type error when using spread operator

[richardliu-db]

🔎 Search Terms

spread operator

#38657 (comment)

🕗 Version & Regression Information

• typescript version: 5.2.2

⏯ Playground Link

No response

💻 Code

type Type = {
  a: string
}

const foo = ({ a }: Type) => {
  console.log(a)
}

foo({ a: 'hello', b: 'world' }) // Compile error. Expected

foo({ ...{ a: 'hello', b: 'world' } }) // No compile error. Not expected.

🙁 Actual behavior

The spread operator can fool the type check, as shown in the line with "No compile error. Not expected.".

🙂 Expected behavior

The type check should show compile error as b field is not expected

Additional information about the issue

No response

[fatcerberus]

Duplicate of #39998.

Note that an excess property error is not a type error per se - objects can legally have more properties than the type declares. This is more of a lint check and you shouldn’t rely on it to enforce runtime invariants. See #12936.

[typescript-bot]

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