T extends U ? X : Y — type-level if/else for powerful type transformations and inference.
Five passes over the same idea, each from a different angle. Do them in order, or jump to whichever you need.
Conditional types enable type-level branching. The syntax T extends U ? X : Y checks if T is assignable to U. Combined with infer keyword, they extract types from complex structures. Distributive conditional types map over unions. They power most advanced utility types under the hood.
