x/playground: no error reported for stack overflow (due to infinite recursion)

[benhoyt]

When running the following infinitely-recursive code on the Go Playground (with Go 1.18, but 1.17 and dev do the same):

func f() string {
	return f()
}

func main() {
	fmt.Printf("%q", f())
}

Instead of printing a "stack overflow" or any other kind of error, it prints nothing except the usual "Program exited" message. This is confusing because it appears the program ran successfully. Presumably the Playground runtime can tell whether a program exited successfully or with some kind of error (stack overflow / out of memory in this case) and print "fatal error: stack overflow" or similar.

See related golang-nuts thread.

[cherrymui]

cc @toothrot