make_batch_type: return Result instead of Option

Result is more idiomatic in Rust to represent a fallible operation.
Converting an integer to a Rust enum can definitely fail, so using
`Result` is more appropriate than `Option`.

Author: wprzytula

scylla-rust-wrapper/src/batch.rs

@@ -35,7 +35,7 @@ pub(crate) struct CassBatchState {
 pub unsafe extern "C" fn cass_batch_new(
     type_: CassBatchType,
 ) -> CassOwnedExclusivePtr<CassBatch, CMut> {
-    if let Some(batch_type) = make_batch_type(type_) {
+    if let Ok(batch_type) = make_batch_type(type_) {
         BoxFFI::into_ptr(Box::new(CassBatch {
             state: Arc::new(CassBatchState {
                 batch: Batch::new(batch_type),

scylla-rust-wrapper/src/cass_types.rs

@@ -898,11 +898,11 @@ pub unsafe extern "C" fn cass_data_type_add_sub_value_type_by_name_n(
     }
 }
 
-pub(crate) fn make_batch_type(type_: CassBatchType) -> Option<BatchType> {
+pub(crate) fn make_batch_type(type_: CassBatchType) -> Result<BatchType, ()> {
     match type_ {
-        CassBatchType::CASS_BATCH_TYPE_LOGGED => Some(BatchType::Logged),
-        CassBatchType::CASS_BATCH_TYPE_UNLOGGED => Some(BatchType::Unlogged),
-        CassBatchType::CASS_BATCH_TYPE_COUNTER => Some(BatchType::Counter),
-        _ => None,
+        CassBatchType::CASS_BATCH_TYPE_LOGGED => Ok(BatchType::Logged),
+        CassBatchType::CASS_BATCH_TYPE_UNLOGGED => Ok(BatchType::Unlogged),
+        CassBatchType::CASS_BATCH_TYPE_COUNTER => Ok(BatchType::Counter),
+        _ => Err(()),
     }
 }