Function gen_unimplemented_body 

pub fn gen_unimplemented_body(
    return_type: &TypeRef,
    fn_name: &str,
    has_error: bool,
    cfg: &RustBindingConfig<'_>,
    params: &[ParamDef],
    opaque_types: &AHashSet<String>,
) -> String

Generate a compilable body for functions that can’t be auto-delegated. Returns a default value or error instead of todo!() which would panic.

opaque_types is the set of opaque type names (Arc-wrapped). Opaque types do not implement Default, so returning Default::default() for their Named return types would fail to compile. For those cases a todo!() body is emitted instead.