Fix issues found by golangci-linter v1.56.2, small optimization of Fe…

…lt.UnmarshalJSON() (#1743)

core/felt/felt.go

@@ -52,20 +52,19 @@ func (z *Felt) Impl() *fp.Element {
 //
 // [gnark-crypto]: https://github.com/ConsenSys/gnark-crypto/blob/master/ecc/stark-curve/fp/element.go
 func (z *Felt) UnmarshalJSON(data []byte) error {
-	s := string(data)
-	if len(s) > fp.Bits*3 {
+	if len(data) > fp.Bits*3 {
 		return errors.New("value too large (max = Element.Bits * 3)")
 	}
 
 	// we accept numbers and strings, remove leading and trailing quotes if any
-	if len(s) > 0 && s[0] == '"' {
-		s = s[1:]
+	if len(data) > 0 && data[0] == '"' {
+		data = data[1:]
 	}
-	if len(s) > 0 && s[len(s)-1] == '"' {
-		s = s[:len(s)-1]
+	if len(data) > 0 && data[len(data)-1] == '"' {
+		data = data[:len(data)-1]
 	}
 
-	_, err := z.SetString(s)
+	_, err := z.SetString(string(data))
 	return err
 }
 

rpc/handlers.go

@@ -1145,7 +1145,7 @@ func (h *Handler) Events(args EventsArg) (*EventsChunk, *jsonrpc.Error) {
 	defer h.callAndLogErr(filter.Close, "Error closing event filter in events")
 
 	var cToken *blockchain.ContinuationToken
-	if len(args.ContinuationToken) > 0 {
+	if args.ContinuationToken != "" {
 		cToken = new(blockchain.ContinuationToken)
 		if err = cToken.FromString(args.ContinuationToken); err != nil {
 			return nil, ErrInvalidContinuationToken

vm/vm.go

@@ -234,7 +234,7 @@ func (v *vm) Call(callInfo *CallInfo, blockInfo *BlockInfo, state core.StateRead
 	C.free(unsafe.Pointer(chainID))
 	C.free(unsafe.Pointer(cBlockInfo.version))
 
-	if len(context.err) > 0 {
+	if context.err != "" {
 		return nil, errors.New(context.err)
 	}
 	return context.response, nil