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Comment by shepherdjerred | Hacker News Reader

I love how far Java has come. I still prefer TypeScript since I do a lot of frontend work and prefer to use the same language across the stack.

With the said, you can do exhaustive pattern matching in TypeScript! https://github.com/gvergnaud/ts-pattern

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Isn't that overkill? You can check exhaustiveness with a trivial little helper:

    function exhaustive(witness: never): never {
      return witness
    }

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

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

[0]: https://docs.python.org/3/library/typing.html#typing.assert_...

In the example you don't even need the default clause and the helper (the error message without it is worse though).

you can just to

    default:
        matched satisfies never
        throw new Error(...)

You don't even need a function.

> I still prefer TypeScript since I do a lot of frontend work and prefer to use the same language across the stack.

If you perfer using the same language for both frontend and backend work, yet would like to have one more semantically rich than TypeScript, consider Scala.

For the frontend, ScalaJS[0].

For the backend, Scala[1].

0 - https://www.scala-js.org/

1 - https://scala-lang.org/

Or Java: https://github.com/konsoletyper/teavm

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.

https://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.

I rather use something more beefy than V8 JIT with a dynamic language on the server side when given the option, after all they even had to rewrite the compiler.

On the other hand, at least I get an excuse to write native addons.

If it wasn't for the projects that require Next.js I would never bother with Node.

I knew I should've written a disclaimer about doing this in vanilla TypeScript

Yes, 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.

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