Correct, the compiler allows you to generate the Rust bindings automatically. Worth noting that the compiler is at an earlier stage of development (the library was started six years ago, the compiler started roughly two years ago). So there are features that aren't used or supported by the compiler that are available in the library.

Yes writing the definitions by hand can time consuming and error-prone, but I designed the library in mind around the declarative API to make it easy to both manually write and generate, I also personally prefer writing Rust whenever possible, so nowadays I would sooner write an ASN.1 module in Rust and then if needed build a generator for the ASN.1 textual representation than write ASN.1 directly since I get access to much better and stronger tooling.

Also in my research when designing the crate, there are often requests in other ASN.1 or X.509 libraries to allow decoding semantically invalid messages because in the wild there are often services sending incorrect data, and so I designed rasn to allow you mix and match and easily build your own ASN.1 types from definitions so that when you do need something bespoke, it's easy and safe.

> Yes writing the definitions by hand can time consuming and error-prone

With the proper environment, this isn't that time consuming or error-prone anymore, based on my recent experiments. When I initially started exploring with the library, it was a bit difficult at first (mostly because back then there was no reference documentation and you had to rely on tests), but after some time API gets easy to understand. Actual type definitions remain very small because of the derive macros.

Nowadays LLMs are pretty good at handling ASN.1 definitions. If you provide the context correctly, by giving e.g. the reference from the rasn's README, maybe even some type definitions from the library itself, and just give the ASN.1 schemas, LLMs can generate the bindings very accurately. The workflow switches from being the manual writer to be just the reviewer. Compiler is also already good at generating the basic definitions on most cases.

I really like the idea that then standard can be published as a crate, and nobody needs to ever touch for the same standard again, unless there is a bug or standard gets an update. Crates can be then used with different open-source projects with the same types. What I known about commercial ASN.1 usage, different companies buy these products to compile the same standards over and over again.

I bet that there are no many companies that define their internal APIs with ASN.1 and buys commercial tool just to support ASN.1 usage in their own business, without any international standards included.