Comment by _flux
I'm not a practioner of cryptography, but I would be wary about timing attacks that might become possible if such a dynamic runtime is introduced. At least relevant pieces of code would need to be re-evaluated in the Fil-C environment.
But maybe you could use C as the "glue language" and then the build better performing libraries in Rust for C to use. Like in Python!
Good call! Fil-C does in fact have a way to let you build and run OpenSSL with its constant time crypto. I don't know how this works exactly but I guess it's relatively easy to guarantee it's safe.