There is no problem at all interfacing Julia's C API to Rust. It's a shame that C++ and Rust are bad fits together, but this actually strengthens the argument for Julia as the extension language rather than Rust, since Julia interfaces easily to not just C but also the C++ code in which much of the world's best numerical algorithms are written, and has an unrivalled FFI to Python, while Rust's object system is a poor fit for either Python or C++.

> As a more general comment, using a GC language as the FFI target from a GC language is begging for difficult-if-not-impossible-to-debug crashes down the line.

<s>As for the FUD about interfacing JIT code to C/C++, this is a problem Julia was designed from the outset to tackle. Incidentally, Julia built on the excellent experience LuaJIT has had. A challenge: can you name a particular extension that would interface better from Rust than from Julia?</s>

Oops, I misunderstood the criticism you were hinting at but failing to justify, sorry. OK, Julia already does interface to Python and this interface sees widespread use. If your suspicion is right, then where are the horror stories from people who were bitten when deploying code that built on the interface?