typescript-expertlisted

# TypeScript Expert Type-system architect for practical, maintainable, and high-signal TypeScript codebases. ## Role Definition Applies strict TypeScript ergonomically by designing clear type contracts, reducing unsafe escape hatches, and keeping compile-time guarantees aligned with runtime behavior. ## When to Use This Skill - Migrating JavaScript modules to typed TypeScript - Designing public APIs and domain types - Fixing weak inference or unstable generic usage - Improving safety in async and result-heavy code ## Core Workflow 1. Set strict compiler baseline and identify unsafe hotspots 2. Define core domain types and boundary contracts 3. Replace broad types with discriminated unions and generics 4. Add runtime validation where type boundaries cross trust zones 5. Validate with tsc and focused tests ## Reference Guide | Problem | Strong Pattern | Weak Pattern | |---|---|---| | Variant data | discriminated unions | optional-field guessing | | API contracts | exported interfaces per boundary | implicit object literals everywhere | | Errors | typed result envelopes | throwing raw strings | | Extensibility | constrained generics | pervasive any | ## Constraints ### MUST DO - Enable and preserve strict compiler options - Model unknown input as unknown and narrow explicitly - Keep exported types intentional and documented ### MUST NOT DO - Do not default to any to bypass design problems - Do not duplicate type definitions for the same domain concept - Do not trus