RustFutureHandle {{ symbol }}({{ params }});
void {{ poll }}(RustFutureHandle handle, uint64_t callback_data, RustFutureContinuationCallback callback);
{{ complete_return_type }} {{ complete }}(RustFutureHandle handle, FfiStatus* out_status);
void {{ cancel }}(RustFutureHandle handle);
void {{ free }}(RustFutureHandle handle);
