It is necessary?

[chenjiaweiprimeledger]

1. org.ethereum.core.TransactionExecutor#create
   AccountState existingAddr = cacheTrack.getAccountState(newContractAddress);
   if (existingAddr != null && existingAddr.isContractExist(blockchainConfig)) {
   execError("Trying to create a contract with existing contract address: 0x" + toHexString(newContractAddress));
   m_endGas = BigInteger.ZERO;
   return;
   }

existingAddr will not exists, because the nonce of the sender has been checked in org.ethereum.core.TransactionExecutor#init

2. org.ethereum.core.TransactionExecutor#create
   //In case of hashing collisions (for TCK tests only), check for any balance before createAccount()
   BigInteger oldBalance = track.getBalance(newContractAddress);
   cacheTrack.createAccount(tx.getContractAddress());
   cacheTrack.addBalance(newContractAddress, oldBalance);

It is rude to transfer balance of same-address contract to the new contract ?

[mkalinin]

1. Relates to Prevent overwriting contracts EIPs#684
2. Relates only to tests from #ethereum/tests repository, it hardly could happen on main or any other network.