[refactor] Cleanup switch statements (#71)

Taking additional suggestion from #65

crypto/ed25519.go

@@ -184,7 +184,7 @@ type Ed25519PublicKey struct {
 // Implements:
 //   - [VerifyingKey]
 func (key *Ed25519PublicKey) Verify(msg []byte, sig Signature) bool {
-	switch sig.(type) {
+	switch sig := sig.(type) {
 	case *Ed25519Signature:
 		return ed25519.Verify(key.Inner, msg, sig.Bytes())
 	default:

crypto/multiEd25519.go

@@ -34,9 +34,8 @@ type MultiEd25519PublicKey struct {
 // Implements:
 //   - [VerifyingKey]
 func (key *MultiEd25519PublicKey) Verify(msg []byte, signature Signature) bool {
-	switch signature.(type) {
+	switch sig := signature.(type) {
 	case *MultiEd25519Signature:
-		sig := signature.(*MultiEd25519Signature)
 		verified := uint8(0)
 		// TODO: Verify with bitmap, and check that this works properly
 		for i, pubKey := range key.PubKeys {

crypto/multiKey.go

@@ -30,9 +30,8 @@ type MultiKey struct {
 // Implements:
 //   - [VerifyingKey]
 func (key *MultiKey) Verify(msg []byte, signature Signature) bool {
-	switch signature.(type) {
+	switch sig := signature.(type) {
 	case *MultiKeySignature:
-		sig := signature.(*MultiKeySignature)
 		verified := uint8(0)
 		for i, pub := range key.PubKeys {
 			if pub.Verify(msg, sig.Signatures[i]) {

crypto/secp256k1.go

@@ -148,13 +148,11 @@ type Secp256k1PublicKey struct {
 // Implements:
 //   - [VerifyingKey]
 func (key *Secp256k1PublicKey) Verify(msg []byte, sig Signature) bool {
-	switch sig.(type) {
+	switch sig := sig.(type) {
 	case *Secp256k1Signature:
-		typedSig := sig.(*Secp256k1Signature)
-
 		// Verification requires to pass the SHA-256 hash of the message
 		msg = util.Sha3256Hash([][]byte{msg})
-		return ethCrypto.VerifySignature(key.Bytes(), msg, typedSig.Bytes())
+		return ethCrypto.VerifySignature(key.Bytes(), msg, sig.Bytes())
 	default:
 		return false
 	}

crypto/singleKey.go

@@ -134,10 +134,9 @@ func ToAnyPublicKey(key VerifyingKey) (*AnyPublicKey, error) {
 // Implements:
 //   - [VerifyingKey]
 func (key *AnyPublicKey) Verify(msg []byte, sig Signature) bool {
-	switch sig.(type) {
+	switch sig := sig.(type) {
 	case *AnySignature:
-		anySig := sig.(*AnySignature)
-		return key.PubKey.Verify(msg, anySig.Signature)
+		return key.PubKey.Verify(msg, sig.Signature)
 	default:
 		return false
 	}

transactionSubmission.go

@@ -141,12 +141,11 @@ func (rc *NodeClient) BuildSignAndSubmitTransactions(
 	buildOptions ...any,
 ) {
 	singleSigner := func(rawTxn RawTransactionImpl) (*SignedTransaction, error) {
-		switch rawTxn.(type) {
+		switch rawTxn := rawTxn.(type) {
 		case *RawTransaction:
-			return rawTxn.(*RawTransaction).SignedTransaction(sender)
+			return rawTxn.SignedTransaction(sender)
 		case *RawTransactionWithData:
-			rawTxnWithData := rawTxn.(*RawTransactionWithData)
-			switch rawTxnWithData.Variant {
+			switch rawTxn.Variant {
 			case MultiAgentRawTransactionWithDataVariant:
 				return nil, fmt.Errorf("multi agent not supported, please provide a signer function")
 			case MultiAgentWithFeePayerRawTransactionWithDataVariant: