for silent downvoter: this line "Next create a file src/serde_types.in.rs to hold all the types for which we need code generation." sounds ridiculous for web projects with hundreds of entities, needed to be transferred as json objects trough API.
The idea would be that these types would be put into a library (or just another module) that's used by the rest of the app. There wouldn't be duplication of these structures. It's not ideal, which is why we are working on stabilizing the compiler features to do away from codegen.