// upper case using the case mapping specified by c.
func ToUpperSpecial(c unicode.SpecialCase, s string) string {
	return Map(c.ToUpper, s)
}

// ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their
// lower case using the case mapping specified by c.
func ToLowerSpecial(c unicode.SpecialCase, s string) string {
	return Map(c.ToLower, s)
}

	// Issue 25636
	// no change for rune 'A', zero delta, under upper/lower/title case change.
	var noChangeForCapitalA = CaseRange{'A', 'A', [MaxCase]rune{0, 0, 0}}
	got := strings.ToLowerSpecial(SpecialCase([]CaseRange{noChangeForCapitalA}), "ABC")
	want := "Abc"
	if got != want {
		t.Errorf("got %q; want %q", got, want)
	}
}

func TestNegativeRune(t *testing.T) {
	// Issue 43254