Consider the following case:

type MyInt int

func (mi *MyInt) Show() {
	fmt.Println(*mi)
}

func main() {
	ms := []MyInt{50, 60, 70, 80, 90}
	for _, m := range ms {
		go m.Show() // go (&m).Show()
	}

	time.Sleep(100 * time.Millisecond)
}

Result:

90
90
90
90
90

Show() has a pointer type receiver, and loop variable m is of type MyInt. In m.Show(), m will be implicitly converted to a pointer ((&m).Show()), thus implicitly creating a reference to the loop variable that are then passed to go/defer function.

This mistake is more subtle than accidentally capturing loop variables with function literals since it's impossible to detect if only looking at the for loop without also checking the receiver type of Show(). So I think this is worth vetting for.

I imagine a implementation of such check would look a lot like loopclosure. And would share a lot of the same logics (such as maybe? the recent #57173). But it isn't technically caused by "closure" so I'm not sure that's the right place to do it.