Perhaps you've heard of `assertUnreachable` or even used the `ts-assert-unreachable` npm. For most of us, we first saw it on a Stack Overflow post (https://stackoverflow.com/questions/39419170/how-do-i-check-that-a-switch-block-is-exhaustive-in-typescript/39419171#39419171) from Ryan Cavanaugh from the TypeScript team.
So then when this topic came up in our theorycrafting video on T[number], we thought "who better to do a short theorycraft video on assertUnreachable than Ryan himself?!". So.. here you go! Enjoy!
0:00 what `assertUnreachable` does
0:41 where'd the idea come from?
1:29 the problem it solves
1:56 how `assertUnreachable` works
2:20 thinking about `noImplicitReturns` being in the mix
3:31 interesting subtleties
4:30 should unreachable code even be allowed?
6:02 other variations on `assertUnreachable`
7:20 variations on adding a message or not throwing
To see the code from this episode, check out the TheoryCraft GitHub: https://github.com/MichiganTypeScript/theorycraft/blob/main/episodes/assert-unreachable/code.tsx
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