You don't even need that. The code exactly as presented acts as a discriminator. TypeScript is smart enough to handle that logic in the if block and know whether animal has been validated as Dog vs Cat. GP is complaining about a feature that already exists in TypeScript

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littlecranky67 4 hours ago | parent [-]

It depends how you construct Dog and Cat. With Javascripts dynamic prototype chain, you could never know for sure.

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culi 4 hours ago | parent [-]

Try it

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

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reitzensteinm 4 hours ago | parent | next [-]

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.

	▲	culi 2 hours ago \| parent [-]
		I see what you mean, thanks Well imo GP is fundamentally misunderstanding TypeScript. It's explicitly a structural language not a nominal one. It goes against the entire design philosophy of TS

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4 hours ago | parent | prev [-]

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