> Ring is mostly C/Assembly
Crypto needs to be written in Assembly to ensure that operations take a constant time, regardless of input. Writing it in a high level language like C or Rust opens you up to the compiler "optimising" routines and making them no longer constant time.
But you already knew this. And you also knew that the security audit (https://github.com/rustls/rustls/blob/master/audit/TLS-01-re...) of ring was favourable
> No issues were found with regards to the cryptographic engineering of rustls or its underlying ring library. A recommendation is provided in TLS-01-001 to optionally supplement the already solid cryptographic library with another cryptographic provider (EverCrypt) with an added benefit of formally verified cryptographic primitives. Overall, it is very clear that the developers of rustls have an extensive knowledge on how to correctly implement the TLS stack whilst avoiding the common pitfalls that surround the TLS ecosystem. This knowledge has translated reliably into an implementation of exceptional quality.
As a bonus, rustls is under active development with sponsorship from Google, AWS and fly.io, with the aim of making a high quality, memory-safe TLS stack - https://www.memorysafety.org/initiative/rustls/
You said
> a standard library with feature flags and editions would make rust ridiculously much more productive
What's the difference between opting into a library with a feature flag and opting in with a line in Cargo.toml? Let's say you want to use the de-facto regex library. Would it really be ridiculously productive if you said you wanted the "regex" feature flag instead of the "regex" crate?
I do agree that the standard library does need a versioning story so they can remove long deprecated functions. Where it gets complicated is if a new method is reintroduced using the same name in a later edition.