TypeScript Advanced Types

Use this skill when generic inference, conditional/mapped types, template literals, or a reusable type utility is the actual problem. Ordinary typed API, form, and state work uses its domain guidance unless advanced type behavior needs attention.

Concern being changed	Reference
Generics, conditional/mapped/template-literal and utility types	references/core-concepts.md
Reusable emitters, builders, clients, deep utilities, or discriminated models	references/advanced-patterns.md
infer, narrowing, assertion functions, and type-contract tests	references/type-inference.md
Compiler configuration, type complexity, and maintainability	references/best-practices.md

Prefer the simplest type that expresses the contract. Use unknown and real narrowing at untrusted boundaries; preserve discriminants and readonly intent. Let inference handle local values and follow repository conventions for public annotations, interface, and type.

Use the existing tsconfig; reference configurations are examples, not instructions to change it. Add compile-time tests only when type behavior is a product/library contract, using its owning suite. Avoid a new type framework or elaborate generic abstraction for a single ordinary call site. Run the repository's affected typecheck gate.