seniorTypeScript
What is 'Discriminated Unions' and exhaustive checking?
Updated May 4, 2026
Short answer
It uses the 'never' type to ensure every member of a union is handled in a switch/if statement.
Deep explanation
By assigning the remaining variable to never in a default case, the compiler throws an error if any part of the union is unhandled. This ensures 100% code coverage for complex logic[cite: 1].
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