Safety

Building composable type guard systems in TypeScript where runtime validation seamlessly integrates with compile-time type narrowing. Type guards like isString(x): x is string enable safe runtime checks, but composing them requires careful design. This explores combinators for union guards or(isNumber, isString): x is number | string, intersection guards and(hasName, hasAge): x is Person, and variadic patterns that preserve type inference. The result: elegant runtime validation that TypeScript’s control flow fully understands.