Typescript optional chaining error: Expression expected.ts(1109)

I am trying to do optional chaining in Typescript + React Native.

Let's say I have the following interfaces:

interface Bar {
  y: number
}

interface Foo {
  x?: Bar
}

and I try to run the following:

 const test: Foo = {x: {y: 3}};
 console.log(test.x?.y);

VSCode will show an error under the ?. saying the following: Expression expected.ts(1109)

Do you have any idea why this is happening or how should I fix it? Thanks.