I don't think the idea here is to use it on third party dependencies, I think the idea is "we have this C code base that we maintain, and we really wish it was a rust codebase instead".
It's a nice idea, but in my experience very few people want to do that, even with a tool to help. What they do want is to be able to seamlessly interact with their existing code base the way it is.
Examples: C and C++, Java and Kotlin. The latter advertises: "Write concise and expressive code while maintaining full compatibility and interoperability with Java" and has been very successful with that.
Yes, interop is a much more common use case, but this just isn't the tool for that.
Rust-bindgen is. Which "just" tries to translate header files, since rustc can link to C object files just fine. And for what it's worth, I'm pretty sure most of your complaints do apply to that tool.
I agree that in general most want to integrate new languages with their existing code bases (rust-bindgen automatically generates C bindings, ABI tests, etc. using libclang to access C and C++ from Rust, and for each language there are tools to generate bindings and ABI tests for Rust code, e.g., the cpp crate generates C++ wrappers around Rust libraries).
The consultancy company developing c2rust specifically helps clients translate their apps to Rust. IIUC these clients want to move from C to a memory and thread safe language without loosing performance.
c2rust is the first step in that process. It mechanically translates C into "C-looking unsafe Rust".
The engineers then go and start migrating from unsafe Rust to safe Rust incrementally.
This is a long process, c2rust speeds up a small fraction of it, but most of the engineers time is spent into translating unsafe Rust into safe Rust, and then refactoring safe Rust into idiomatic Rust.
> It's a nice idea, but in my experience very few people want to do that
Maybe it's relatively few, but they exist, and this is targeting serving their needs. There are other tools serving C/Rust interop use cases, and at a certain point the “this isn't the most common use case” dismissal is just tedious.
HN shouldn't be a place where things targeting real but narrow technical niches are dismissed because the niche is narrow or there is a much bigger superficially related one around.
