Constant STAGE_WRONG_ERROR 

pub(crate) const STAGE_WRONG_ERROR: ErrorCode = _; // 18_446_744_073_709_551_556usize

The error code zstd itself returns for an operation the context is in no state to perform (-ZSTD_error_stage_wrong as a size_t), for the places where that has to be decided on the Rust side of a call.