// The constant UpperLower has an otherwise impossible delta value.
type CaseRange struct {
	Lo    uint32
	Hi    uint32
	Delta d
}

// SpecialCase represents language-specific case mappings such as Turkish.
// Methods of SpecialCase customize (by overriding) the standard mappings.
type SpecialCase []CaseRange

// BUG(r): There is no mechanism for full case folding, that is, for
// characters that involve multiple runes in the input or output.

// 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

		{"UnixMilli", Func, 17},
		{"Until", Func, 8},
		{"Wednesday", Const, 0},
		{"Weekday", Type, 0},
	},
	"unicode": {
		{"(SpecialCase).ToLower", Method, 0},
		{"(SpecialCase).ToTitle", Method, 0},
		{"(SpecialCase).ToUpper", Method, 0},
		{"ASCII_Hex_Digit", Var, 0},
		{"Adlam", Var, 7},
		{"Ahom", Var, 5},
		{"Anatolian_Hieroglyphs", Var, 5},
		{"Arabic", Var, 0},