If what could be written in C? The FFI library allows for dynamic binding of library methods for execution from Ruby without the need to write a native extension. That's a huge productivity boost and makes for code that can be shared across CRuby, JRuby, and TruffleRuby.

I suppose if you could statically determine all of the bindings at boot up you could write a stub and insert into the method table. But, that still would happen at runtime, making it JIT. And it wouldn't be able to adapt to the types flowing through the system, so it'd have to be conservative in what it accepts or what it optimizes, which is what libffi already does today. The AOT approach is to write a native extension.