Isn't that overkill? You can check exhaustiveness with a trivial little helper:
reply function exhaustive(witness: never): never {
return witness
}
Agree, python calls this little helper assert_never[0]. I opened an PR to add it to the TypeScript docs some time ago: https://github.com/microsoft/TypeScript-Website/pull/3599
reply[0]: https://docs.python.org/3/library/typing.html#typing.assert_...
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replyIn the example you don't even need the default clause and the helper (the error message without it is worse though).
replyyou can just to
reply default:
matched satisfies never
throw new Error(...)
I knew I should've written a disclaimer about doing this in vanilla TypeScript
replyYes, you can do it via an assert never in a switch. That isn't pattern matching. That's an exhaustive switch enforced at compile time
Which is nice, but again, it's not pattern matching.
You don't need a library for this; the idiomatic approach is to lean on TypeScript's narrowing and native control flow (ifs and switches, or maybe IIFEs), along with (maybe) the never type to enforce exhaustiveness.
replyhttps://www.typescriptlang.org/play/?jsx=4#code/JYWwDg9gTgLg...
I guess the library is slightly nicer, arguably, but I don't think it's worth the external dependency and added complexity.
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reply