isBlockReceipt incorrectly called on non derived logs

[piersy]

The deriveLogFields function hydrates a log with information such as block number, transaction hash, block hash ...etc

But in the code below, before deriving the fields isBlockReceipt is called which checks whether the log's transaction hash matches the log's block hash ( block receipts are receipts that are not generated through a transaction, but instead track logs emitted by system calls, as such there is no corresponding transaction so the block hash is used in place of the transaction hash) of course because the fields are not yet defined they will both be zero values and so always match.

I think there is a further problem which is that in the case that len(txs) == len(receipts) the first part of the or condition will not be triggered, so the the next part of the or condition will be triggered, and that will return an error if the last receipt is not a block receipt, even though when len(txs) == len(receipts) no block receipt is expected. This problem probably hasn't been encountered since isBlockReceipt is always returning true in this context.

celo-blockchain/core/rawdb/accessors_chain.go

Lines 700 to 705 in 91a4db9

	func deriveLogFields(receipts []*receiptLogs, hash common.Hash, number uint64, txs types.Transactions) error {
	logIndex := uint(0)
	// The receipts may include an additional "block finalization" receipt (only IBFT)
	if len(txs) != len(receipts) && (len(txs)+1 != len(receipts) || !isBlockReceipt(receipts[len(receipts)-1])) {
	return errors.New("transaction and receipt count mismatch")
	}