Exhaustiveness checking in TypeScript

Unreachable code path optimization hint for Swift

A Rust macro xkcd_unreachable!() inspired by https://xkcd.com/2200/

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A syntax extension that denotes unreachable code and prints descriptive errors when the code is reached

unreachable compiler hint for C

Compile time asserts and other utilities for code validation

Exception types for marking unreachable/unimplemented code