switch {
		case 'A' <= r && r <= 'Z', 'a' <= r && r <= 'z',
			'0' <= r && r <= '9':
			return r
		}
		return '_'
	}
	return strings.Map(clean, ppath)
}

// toSymbolV2 converts a package path using the second mangling scheme.
func toSymbolV2(ppath string) string {
	var bsl strings.Builder
	changed := false
	for _, c := range ppath {
		if ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z') || ('0' <= c && c <= '9') || c == '_' {

			t.Errorf("toSymbolV1(%q) = %q, want %q", test.input, got, want)
		}
	}
}

func TestV2(t *testing.T) {
	for _, test := range symbolTests {
		if got, want := toSymbolV2(test.input), test.v2; got != want {
			t.Errorf("toSymbolV2(%q) = %q, want %q", test.input, got, want)
		}
	}
}

func TestV3(t *testing.T) {
	for _, test := range symbolTests {