Try it

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAIg9gcyg...

type Mutt = Dog & Cat

const imposter: Mutt = { bark: () => console.log("woof"), meow: () => console.log("meow"), }

You're both misunderstanding parent's point as well as the original point. Nobody ever claimed your link wouldn't compile.