for c.next() {
		foldFull(&c)
		c.checkpoint()
	}
	return c.ret()
}

func (t *caseFolder) Span(src []byte, atEOF bool) (n int, err error) {
	c := context{src: src, atEOF: atEOF}
	for c.next() && isFoldFull(&c) {
		c.checkpoint()
	}
	return c.retSpan()
}

func makeFold(o options) transform.SpanningTransformer {
	// TODO: Special case folding, through option Language, Special/Turkic, or
	// both.

	if n == 0 {
		if ct == cLower {
			return c.copy()
		}
		n = (e[1] >> lengthBits) & lengthMask
	}
	return c.writeString(e[2 : 2+n])
}

// isFoldFull reports whether the current run is mapped to foldFull
func isFoldFull(c *context) bool {
	if c.info&hasMappingMask == 0 {
		return true
	}
	ct := c.caseType()
	if c.info&exceptionBit == 0 {
		if ct != cLower || c.info&inverseFoldBit != 0 {