--- /dev/null
+package main
+
+import (
+ "errors"
+ "fmt"
+)
+
+type someError struct {
+ Msg string
+}
+
+func (e *someError) Error() string {
+ return "someError: " + e.Msg
+}
+
+func calculate() (int, *someError) {
+ return 42, nil
+}
+
+func main() {
+ err := errors.New("ERROR")
+ num, err := calculate()
+ fmt.Println(num, err, err == nil) // want `this comparison is never true`
+}