var golang.org/x/text/internal/language.altLangIndex

2 uses

	golang.org/x/text/internal/language (current package)
		lookup.go#L114: 			return Language(altLangIndex[altLangISO3.Elem(i)[3]]), nil
		tables.go#L581: var altLangIndex = [6]uint16{

The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)