# V8023\. It is possible that a wrong variable of the 'error' type is checked for 'nil'\.

The analyzer has detected code where the wrong variable of the error type is checked for nil\. Due to their frequent use and the similarity in the names of the error type variables, the risk of making a mistake when dealing with them increases\. 

The example:

```cpp
func decodeUser(data []byte) (err error) {
  var u map[string] any

  if e := json.Unmarshal(data, &u); err != nil {
    return e
  }

  ....
}
```

The result of the `json.Unmarshal(data, &u)` call is assigned to the `e` variable\. However, the condition checks the `err` named return value\. So, the result of `json.Unmarshal(data, &u)` is not checked at all, and a different value affects the function's return value\.

To fix this, check `e` in the `if` statement:

```cpp
func decodeUser(data []byte) (err error) {
  var u map[string] any

  if e := json.Unmarshal(data, &u); e != nil {
   return e
  }

  ....
}
```

Another example:

```cpp
func decodeUser(data []byte) error {
  var u map[string] any

  e := validatePayload(data)

  if e != nil {
    return e
  }

  err := json.Unmarshal(data, &u)
  if e != nil {
    e = err
  }

  ....
}
```

The `data` parameter is checked via the `validatePayload` function before being used\. If the data contains an error, the function stops executing\. Otherwise, the result of the `json.Unmarshal(data, &u)` call is assigned to the `err` variable, and then `e` is checked again\. If an error occurs while executing `json.Unmarshal(data, &u)`, the information will not be overwritten\.

To fix this, check `err` in the `if` statement:

```cpp
func decodeUser(data []byte) error {
  var u map[string]any

  e := validatePayload(data)

  if e != nil {
    return e
  }

  err := json.Unmarshal(data, &u)
  if err != nil {
    e = err
  }

  ....
}
```