emptyMatchEncountered = rulen
			continue
		}

		duplicateMatches := 0
		for matchn, match := range route.Match {
			dupn, ok := matchesEncountered[asJSON(match)]
			if ok {
				reportIneffective(routeName(route, rulen), requestName(match, matchn), routeName(routes[dupn], dupn))
				duplicateMatches++
				// no need to handle for totally duplicated match rules
				continue
			}

	"≿":                         "\u227f",
	"∑":                             "\u2211",
	"♪":                            "\u266a",
	"¹":                            "\u00b9",
	"²":                            "\u00b2",
	"³":                            "\u00b3",
	"⊃":                             "\u2283",
	"⫆":                            "\u2ac6",

// it panics.
func Register(name string, driver driver.Driver) {
	driversMu.Lock()
	defer driversMu.Unlock()
	if driver == nil {
		panic("sql: Register driver is nil")
	}
	if _, dup := drivers[name]; dup {
		panic("sql: Register called twice for driver " + name)
	}
	drivers[name] = driver
}

func unregisterAllDrivers() {
	driversMu.Lock()
	defer driversMu.Unlock()
	// For tests.