Some identical types not being merged when one is optional in an object spread

Bug Report

🔎 Search Terms

merging object spread

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about object spreads

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const A: {foo: () => void}
declare const B: {foo?: () => void}

const C = {...A, ...B};

🙁 Actual behavior

const C: {
    foo: (() => void) | (() => void);
}

🙂 Expected behavior

const C: {
    foo: () => void;
}

Notes

Note that this merges primitives, but not functions or objects as far as I can tell