// EN, ES, CS, ET, ON, BN, or NSM are allowed.
		// We exclude the entries from [2.6].
		{ruleLTR, 1<<bidi.ES | 1<<bidi.CS | 1<<bidi.ET | 1<<bidi.ON | 1<<bidi.BN},
	},
	ruleInvalid: {
		{ruleInvalid, 0},
		{ruleInvalid, 0},
	},
}

// [2.4] In an RTL label, if an EN is present, no AN may be present, and
// vice versa.
const exclusiveRTL = uint16(1<<bidi.EN | 1<<bidi.AN)

// From RFC 5893

	// provided (e.g. empty strings, null values, or empty arrays).  See
	// Required().
	ErrorTypeRequired ErrorType = "RuleRequired"
	// ErrorTypeInvalid is used to report malformed values
	ErrorTypeInvalid ErrorType = "RuleInvalid"
	// ErrorTypeInternal is used to report other errors that are not related
	// to user input.  See InternalError().
	ErrorTypeInternal ErrorType = "InternalError"