Handle access list txs at espresso hardfork (#213)

Ideally we would be able to leave signing of non celo transaction types to the upstream code. But in this case the the upstream support for this transaction type was added in the London hardfork which also contained lots of other changes which we are enabling at the cel2 transition point. We can't enable the London hardfork earlier, as it will make our migrated blocks invalid. From the celo side we added support for these transactions in the Espresso hardfork which came before the London hardfork and so we need support from espresso onwards for this transaction type and therefore we add it to the celo legacy meta fork (which contains signing logic for all forks before cel2).

core/types/celo_transaction_signing_forks.go

@@ -103,6 +103,10 @@ func (c *celoLegacy) txFuncs(tx *Transaction) *txFuncs {
 		// changes that were not part of Espresso. So instead we ned to handle
 		// DynamicFeeTxTypes here.
 		return dynamicFeeTxFuncs
+	case t == AccessListTxType:
+		// Similar to the dynamic fee tx type, we need to handle the access list tx type that was also enabled by the
+		// espresso hardfork.
+		return accessListTxFuncs
 	case t == CeloDynamicFeeTxV2Type:
 		return celoDynamicFeeTxV2Funcs
 	case t == CeloDynamicFeeTxType:

core/types/celo_transaction_signing_tx_funcs.go

@@ -60,6 +60,18 @@ var (
 		},
 	}
 
+	accessListTxFuncs = &txFuncs{
+		hash: func(tx *Transaction, chainID *big.Int) common.Hash {
+			return NewEIP2930Signer(chainID).Hash(tx)
+		},
+		signatureValues: func(tx *Transaction, sig []byte, signerChainID *big.Int) (r *big.Int, s *big.Int, v *big.Int, err error) {
+			return NewEIP2930Signer(signerChainID).SignatureValues(tx, sig)
+		},
+		sender: func(tx *Transaction, hashFunc func(tx *Transaction, chainID *big.Int) common.Hash, signerChainID *big.Int) (common.Address, error) {
+			return NewEIP2930Signer(tx.ChainId()).Sender(tx)
+		},
+	}
+
 	dynamicFeeTxFuncs = &txFuncs{
 		hash: func(tx *Transaction, chainID *big.Int) common.Hash {
 			return NewLondonSigner(chainID).Hash(tx)