Optional key with initializer still declared as possibly undefined

[kazarmy]

Bug Report

🔎 Search Terms

"Object is possibly" undefined object key

(Sorry couldn't check all relevant issues)

🕗 Version & Regression Information

4.7.3

• I was unable to test this on prior versions because it occurred on new code.

⏯ Playground Link

Playground link (Nightly version) with relevant code

💻 Code

  const anObject: {abc?: string} = {
    abc: '123',
  };
  console.log(anObject.abc.length);

🙁 Actual behavior

anObject.abc clearly is not undefined.

🙂 Expected behavior

There is no error. The actual code has basically typeof anotherVar for the type, and anotherVar's type has a considerable number of keys so it's not just a matter of removing a question mark.

[RyanCavanaugh]

See discussion at #47920

[kazarmy]

Thanks for the reply. Ok saw the "Optional Member Conformance" section and can make do with

const anObject: Required<Pick<typeof anotherVar, LongListOfKeys>> = {
  // object initializer with keys from LongListOfKeys
}

which allows dropping of the assert(anObject.key).