Hard Engineer SpeedRun interfaces nil type-assertions

Go: The Nil Interface That Isn't Nil

+250 XP · 6 min · attempt 1

Problem

What does this Go program print?

    type myErr struct{}
    func (*myErr) Error() string { return "boom" }

    func doWork() error {
        var e *myErr = nil
        return e
    }

    func main() {
        err := doWork()
        if err == nil {
            fmt.Println("all good")
        } else {
            fmt.Println("got error")
        }
    }

Enter the exact output line.

Starter

// An interface value is nil only when BOTH its type and value are nil.
// Returning a typed nil pointer wraps it in an interface with a non-nil type.

Your answer

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