address comments

lib/scale/encode.go

@@ -100,20 +100,24 @@ func (se *Encoder) EncodeCustom(in interface{}) (int, error) {
 	someType := reflect.TypeOf(in)
 	// TODO: if not a pointer, check if type pointer has Encode method
 	_, ok := someType.MethodByName("Encode")
-	if ok {
-		res := reflect.ValueOf(in).MethodByName("Encode").Call([]reflect.Value{})
-		val := res[0].Interface()
-		if len(res) < 2 {
-			return se.Writer.Write(val.([]byte))
-		}
+	if !ok {
+		return 0, fmt.Errorf("cannot call EncodeCustom")
+	}
 
-		err := res[1].Interface()
-		if err != nil {
-			return 0, err.(error)
-		}
+	res := reflect.ValueOf(in).MethodByName("Encode").Call([]reflect.Value{})
+	if len(res) == 0 {
+		return 0, fmt.Errorf("method Encode does not have any return values")
+	}
+	val := res[0].Interface()
+	if len(res) < 2 {
 		return se.Writer.Write(val.([]byte))
 	}
-	return 0, fmt.Errorf("cannot call EncodeCustom")
+
+	err := res[1].Interface()
+	if err != nil {
+		return 0, err.(error)
+	}
+	return se.Writer.Write(val.([]byte))
 }
 
 // encodeCustomOrEncode tries to use EncodeCustom, if that fails, it reverts to Encode