refactor serialization tuple into an enum (#31679)

runtime/src/serde_snapshot/newer.rs

@@ -202,7 +202,7 @@ impl<'a> TypeContext<'a> for Context {
         let ancestors = HashMap::from(&serializable_bank.bank.ancestors);
         let fields = serializable_bank.bank.get_fields_to_serialize(&ancestors);
         let lamports_per_signature = fields.fee_rate_governor.lamports_per_signature;
-        (
+        match get_serialize_bank_fields(
             SerializableVersionedBank::from(fields),
             SerializableAccountsDb::<'a, Self> {
                 accounts_db: &serializable_bank.bank.rc.accounts.accounts_db,
@@ -219,8 +219,9 @@ impl<'a> TypeContext<'a> for Context {
                 .bank
                 .get_epoch_accounts_hash_to_serialize()
                 .map(|epoch_accounts_hash| *epoch_accounts_hash.as_ref()),
-        )
-            .serialize(serializer)
+        ) {
+            BankFieldsToSerialize::WithoutEpochRewardStatus(data) => data.serialize(serializer),
+        }
     }
 
     #[cfg(test)]
@@ -411,15 +412,47 @@ impl<'a> TypeContext<'a> for Context {
             is_delta: rhs.is_delta,
         };
 
-        bincode::serialize_into(
-            stream_writer,
-            &(
+        match get_serialize_bank_fields(
+            bank,
+            accounts_db_fields,
+            lamports_per_signature,
+            incremental_snapshot_persistence.cloned(),
+            epoch_accounts_hash.copied(),
+        ) {
+            BankFieldsToSerialize::WithoutEpochRewardStatus(data) => {
+                bincode::serialize_into(stream_writer, &data)
+            }
+        }
+    }
+}
+
+enum BankFieldsToSerialize<'a, T: Serialize> {
+    /// this is compatible with 1.14
+    WithoutEpochRewardStatus(
+        (
+            SerializableVersionedBank<'a>,
+            T,
+            u64,
+            Option<BankIncrementalSnapshotPersistence>,
+            Option<Hash>,
+        ),
+    ),
+}
+
+/// serializing involves building these fields into a tuple
+/// This occurs during normal serialization and again during re-serialization.
+fn get_serialize_bank_fields<T: Serialize>(
+    bank: SerializableVersionedBank<'_>,
+    accounts_db_fields: T,
+    lamports_per_signature: u64,
+    incremental_snapshot_persistence: Option<BankIncrementalSnapshotPersistence>,
+    epoch_accounts_hash: Option<Hash>,
+) -> BankFieldsToSerialize<'_, T> {
+    BankFieldsToSerialize::WithoutEpochRewardStatus((
         bank,
         accounts_db_fields,
         lamports_per_signature,
         incremental_snapshot_persistence,
         epoch_accounts_hash,
-            ),
-        )
-    }
+    ))
 }