TypeScript cannot correctly infer non undefined object property

[micheleangioni]

TypeScript Version:
3.7.5 and previous ones

Search Terms:
infer undefined object property

Code

type Test = {
  [s: string]: {
    optionalFunction?: (aString: string) => void
  }
}

const test: Test = {
  myString: { optionalFunction: (aString: string) => { console.log(aString); } }
}

const testTheFunction = (inputString: string) => {

  if (test[inputString] && test[inputString].optionalFunction) {
    test[inputString].optionalFunction(inputString);
 }
}

Expected behavior:
No error

Actual behavior:
Cannot invoke an object which is possibly undefined

Playground Link:
Playground example

[RyanCavanaugh]

Duplicate #36230

[typescript-bot]

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