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How do you do exhaustiveness checking?

Q: How do you do exhaustiveness checking?

In a `switch` over a discriminated union, add a `default` that assigns the value to a `never` variable: `const _exhaustive: never = value`. If you add a new variant and forget a case, the compiler errors — catching missed handling.

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Explain exhaustive switch.

neverexhaustive

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In a switch over a discriminated union, add a default that assigns the value to a never variable: const _exhaustive: never = value. If you add a new variant and forget a case, the compiler errors — catching missed handling.

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