src/Log.php
public function formError($field, $message = '')
    {
        $formErrors = &$this->getFormErrors();
        if ($message) {
            if (is_int($message) && isset($this->errorList[$message])) {
                // Use predefined error
                $formErrors[$field] = $this->errorList[$message];
            }else{
                // Use given error message
                $formErrors[$field] = $message;
            }
            $this->error($message);
        } else {
            // if the message if omitted use the field as a generic message
            $formErrors[$field] = $message;
            $this->error($field);
        }

        return $this;
    }
public function formError($field, $message = '')
    {
        $formErrors = &$this->getFormErrors();
        if ($message) {
            if (is_int($message) && isset($this->errorList[$message])) {
                // Use predefined error
                $formErrors[$field] = $this->errorList[$message];
            }else{
                // Use given error message
                $formErrors[$field] = $message;
            }
            $this->error($message);
        } else {
            // if the message if omitted use the field as a generic message
            $formErrors[$field] = $message;
            $this->error($field);
        }

        return $this;
    }
Log an error to a form field error
Note: Only one error per field in a channel namespace

@param string $field   - The form field name
@param string|int $message - The error message to link to the field or an ID of a predefined error message

@return $this