Fix invoker when UnmarshalCBOR errors

Underlying issue: https://git.io/fjXU6

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>

chain/invoker.go

@@ -124,7 +124,9 @@ func (*invoker) transform(instance Invokee) (nativeCode, error) {
 				if err != nil {
 					return []reflect.Value{
 						reflect.ValueOf(InvokeRet{}),
-						reflect.ValueOf(err),
+						// Below is a hack, fixed in Go 1.13
+						// https://git.io/fjXU6
+						reflect.ValueOf(&err).Elem(),
 					}
 				}
 				return meth.Call([]reflect.Value{

chain/invoker_test.go

@@ -1,6 +1,7 @@
 package chain
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -18,10 +19,17 @@ func (b *basicParams) UnmarshalCBOR(in []byte) (int, error) {
 	return 1, nil
 }
 
+type badParam struct {
+}
+
+func (b *badParam) UnmarshalCBOR(in []byte) (int, error) {
+	return -1, errors.New("some error")
+}
+
 func (b basicContract) Exports() []interface{} {
 	return []interface{}{
 		b.InvokeSomething0,
-		nil,
+		b.BadParam,
 		nil,
 		nil,
 		nil,
@@ -40,6 +48,11 @@ func (basicContract) InvokeSomething0(act *types.Actor, vmctx types.VMContext,
 		returnCode: params.b,
 	}, nil
 }
+func (basicContract) BadParam(act *types.Actor, vmctx types.VMContext,
+	params *badParam) (InvokeRet, error) {
+	panic("should not execute")
+}
+
 func (basicContract) InvokeSomething10(act *types.Actor, vmctx types.VMContext,
 	params *basicParams) (InvokeRet, error) {
 	return InvokeRet{
@@ -58,4 +71,7 @@ func TestInvokerBasic(t *testing.T) {
 	ret, err = code[10](nil, &VMContext{}, []byte{2})
 	assert.NoError(t, err)
 	assert.Equal(t, byte(12), ret.returnCode, "return code should be 1")
+
+	ret, err = code[1](nil, &VMContext{}, []byte{2})
+	assert.Error(t, err)
 }