x.mode = mapindex
		x.typ = typ.elem
		x.expr = e
		return false

	case *Interface:
		if !isTypeParam(x.typ) {
			break
		}
		// TODO(gri) report detailed failure cause for better error messages
		var key, elem Type // key != nil: we must have all maps
		mode := variable   // non-maps result mode
		// TODO(gri) factor out closure and use it for non-typeparam cases as well

	// not specified in the certificate itself.
	constraint func([]*Certificate) error

	// getCert returns the certificate.
	//
	// It is not meant to do network operations or anything else
	// where a failure is likely; the func is meant to lazily
	// parse/decompress data that is already known to be good. The
	// error in the signature primarily is meant for use in the
	// case where a cert file existed on local disk when the program

through the fmt package.  For example, if a String method
calls panic("bad"), the resulting formatted message will look
like

	%!s(PANIC=bad)

The %!s just shows the print verb in use when the failure
occurred. If the panic is caused by a nil receiver to an Error
or String method, however, the output is the undecorated
string, "<nil>".

# Scanning

An analogous set of functions scans formatted text to yield

	{26, "SIGVTALRM", "virtual timer expired"},
	{27, "SIGPROF", "profiling timer expired"},
	{28, "SIGWINCH", "window changed"},
	{29, "SIGIO", "I/O possible"},
	{30, "SIGPWR", "power failure"},
	{31, "SIGSYS", "bad system call"},

	{26, "SIGVTALRM", "virtual timer expired"},
	{27, "SIGPROF", "profiling timer expired"},
	{28, "SIGWINCH", "window changed"},
	{29, "SIGIO", "I/O possible"},
	{30, "SIGPWR", "power failure"},
	{31, "SIGSYS", "bad system call"},

	{26, "SIGVTALRM", "virtual timer expired"},
	{27, "SIGPROF", "profiling timer expired"},
	{28, "SIGWINCH", "window changed"},
	{29, "SIGIO", "I/O possible"},
	{30, "SIGPWR", "power failure"},
	{31, "SIGSYS", "bad system call"},

	{26, "SIGVTALRM", "virtual timer expired"},
	{27, "SIGPROF", "profiling timer expired"},
	{28, "SIGWINCH", "window changed"},
	{29, "SIGIO", "I/O possible"},
	{30, "SIGPWR", "power failure"},
	{31, "SIGSYS", "bad system call"},

	tests = append(tests, setStringTests2...)

	for i, test := range tests {
		x, ok := new(Rat).SetString(test.in)

		if ok {
			if !test.ok {
				t.Errorf("#%d SetString(%q) expected failure", i, test.in)
			} else if x.RatString() != test.out {
				t.Errorf("#%d SetString(%q) got %s want %s", i, test.in, x.RatString(), test.out)
			}
		} else {
			if test.ok {

	l.updateLocked(now)
	l.gcEnabled = enableGC
	l.transitioning = true
	// N.B. finishGCTransition releases the lock.
	//
	// We don't release here to increase the chance that if there's a failure
	// to finish the transition, that we throw on failing to acquire the lock.
}

// finishGCTransition notifies the limiter that the GC transition is complete

	{14, "SIGALRM", "alarm clock"},
	{15, "SIGTERM", "terminated"},
	{16, "SIGUSR1", "user defined signal 1"},
	{17, "SIGUSR2", "user defined signal 2"},
	{18, "SIGCHLD", "child exited"},
	{19, "SIGPWR", "power failure"},
	{20, "SIGWINCH", "window changed"},
	{21, "SIGURG", "urgent I/O condition"},
	{22, "SIGIO", "I/O possible"},
	{23, "SIGSTOP", "stopped (signal)"},
	{24, "SIGTSTP", "stopped"},
	{25, "SIGCONT", "continued"},