Bug Report

🔎 Search Terms

spread
spread operator
spread any
spread object assign

🕗 Version & Regression Information

This is the behavior in every version I tried, and I reviewed the FAQ for entries about the spread operator

⏯ Playground Link

Playground link with relevant code

💻 Code

const x: any = { a: 5 }

interface I {
  b?: string
}

let spread: I;
spread = {
  ...x,
  b: 5
}

🙁 Actual behavior

Type mismatch is missed after use of spread operator.

🙂 Expected behavior

I expect a "Type 'number' is not assignable to type 'string | undefined'.(2322)" error for b: 5.

Similar bug #46128 indicates that after spread the type is not kept.
The main difference between the bugs is that in this case, the type is declared beforehand.