Did you know TypeScript is Turing complete? In this post, I will approach type definitions as writing a program.

marmelab

TypeScript's type system is Turing complete and can be approached as a programming language. Generic types function like type-level functions, conditional types enable branching logic with the extends keyword, the infer keyword acts as variable assignment for extracting types, recursion allows iteration over arrays and complex structures, template literals enable string manipulation at the type level, and mapped types provide iteration over object properties. These capabilities enable creating sophisticated type utilities like CRUD generators, middleware type inference, and dynamic method generation that reduce code duplication while improving type safety and IDE autocomplete.

TypeScript Types as a Programming Language

String Manipulation: Template Literal Types

And that’s why I dislike it. Same as Rust’s type system.
You can get stuck writing types or satisfying* them instead of solving the actual problem imperatively, declaratively.
* And sometimes understanding them, some types are amazing but they require some intense type theory knowledge to understand them, let alone find a bug or improve them.