Add transfer processing to BeaconChain

eth2/state_processing/src/per_block_processing/errors.rs

@@ -365,7 +365,9 @@ pub enum TransferInvalid {
     /// (from_validator)
     FromValidatorIneligableForTransfer(u64),
     /// The validators withdrawal credentials do not match `transfer.pubkey`.
-    WithdrawalCredentialsMismatch,
+    ///
+    /// (state_credentials, transfer_pubkey_credentials)
+    WithdrawalCredentialsMismatch(Hash256, Hash256),
     /// The deposit was not signed by `deposit.pubkey`.
     BadSignature,
     /// Overflow when adding to `transfer.to` balance.

eth2/state_processing/src/per_block_processing/verify_transfer.rs

@@ -64,7 +64,10 @@ pub fn verify_transfer(
     );
     verify!(
         from_validator.withdrawal_credentials == transfer_withdrawal_credentials,
-        Invalid::WithdrawalCredentialsMismatch
+        Invalid::WithdrawalCredentialsMismatch(
+            from_validator.withdrawal_credentials,
+            transfer_withdrawal_credentials
+        )
     );
 
     let message = transfer.signed_root();