Then why not use libraries like io-ts [0] to define interfaces, which survive the compilation, can test untyped objects against the given schema and could also

Then why not use libraries like io-ts [0] to define interfaces, which survive the compilation, can test untyped objects against the given schema and could also be used as DI tokens. Still, depending on structural typing here feels like a hack, but I never did this so maybe someone with experience in a large codebase can chime in. Anyway, IMHO, Typescript isn't designed for dependency injection in mind. Microsoft also has a DI library [1] but it feels like too much wiring to compensate for the lack of compiled interfaces. [0]: https://github.com/gcanti/io-ts https://github.com/gcanti/io-ts [1]: https://github.com/Microsoft/tsyringe https://github.com/Microsoft/tsyringe