Function refuse_unlinkable 

pub fn refuse_unlinkable(
    program: &CompiledProgram,
    interner: &Interner,
    backend: Backend,
) -> Result<(), String>

The entry gate of every backend that lowers bytecode WITHOUT the Rust runtime (C, RISC-V, WebAssembly, the soft core): refuse — by name — what only the interpreter, the VM, and the Rust tier provide, rather than lower it as something else. A standard-library native kernel is Rust code; a CRDT kind the backend does not lower is refused by its type name. Only code that can run is judged (crate::vm::reach): the loader splices whole standard-library modules, and a function nothing calls refuses nothing.