prevent unicode-confusion in password by applying PRECIS, and username/email address by applying unicode NFC normalization

an é (e with accent) can also be written as e+\u0301. the first form is NFC,
the second NFD. when logging in, we transform usernames (email addresses) to
NFC. so both forms will be accepted. if a client is using NFD, they can log
in too.

for passwords, we apply the PRECIS "opaquestring", which (despite the name)
transforms the value too: unicode spaces are replaced with ascii spaces. the
string is also normalized to NFC. PRECIS may reject confusing passwords when
you set a password.

imapserver/append_test.go

@@ -18,11 +18,11 @@ func TestAppend(t *testing.T) {
 	tc3 := startNoSwitchboard(t)
 	defer tc3.close()
 
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
-	tc3.client.Login("mjl@mox.example", "testtest")
+	tc3.client.Login("mjl@mox.example", password0)
 
 	tc2.transactf("bad", "append")              // Missing params.
 	tc2.transactf("bad", `append inbox`)        // Missing message.
@@ -32,13 +32,13 @@ func TestAppend(t *testing.T) {
 	tc2.transactf("bad", "append inbox (\\Badflag) {1+}\r\nx") // Unknown flag.
 	tc2 = startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
 
 	tc2.transactf("bad", "append inbox () \"bad time\" {1+}\r\nx") // Bad time.
 	tc2 = startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
 
 	tc2.transactf("no", "append nobox (\\Seen) \" 1-Jan-2022 10:10:00 +0100\" {1}")
@@ -81,7 +81,7 @@ func TestAppend(t *testing.T) {
 
 	tclimit := startArgs(t, false, false, true, true, "limit")
 	defer tclimit.close()
-	tclimit.client.Login("limit@mox.example", "testtest")
+	tclimit.client.Login("limit@mox.example", password0)
 	tclimit.client.Select("inbox")
 	// First message of 1 byte is within limits.
 	tclimit.transactf("ok", "append inbox (\\Seen Label1 $label2) \" 1-Jan-2022 10:10:00 +0100\" {1+}\r\nx")

imapserver/authenticate_test.go

@@ -12,9 +12,18 @@ import (
 	"strings"
 	"testing"
 
+	"golang.org/x/text/secure/precis"
+
 	"github.com/mjl-/mox/scram"
 )
 
+func TestAuthenticateLogin(t *testing.T) {
+	// NFD username and PRECIS-cleaned password.
+	tc := start(t)
+	tc.client.Login("mo\u0301x@mox.example", password1)
+	tc.close()
+}
+
 func TestAuthenticatePlain(t *testing.T) {
 	tc := start(t)
 
@@ -28,21 +37,26 @@ func TestAuthenticatePlain(t *testing.T) {
 	tc.xcode("AUTHENTICATIONFAILED")
 	tc.transactf("no", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000test")))
 	tc.xcode("AUTHENTICATIONFAILED")
-	tc.transactf("no", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000testtesttest")))
+	tc.transactf("no", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000test"+password0)))
 	tc.xcode("AUTHENTICATIONFAILED")
 	tc.transactf("bad", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000")))
 	tc.xcode("")
-	tc.transactf("no", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("other\u0000mjl@mox.example\u0000testtest")))
+	tc.transactf("no", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("other\u0000mjl@mox.example\u0000"+password0)))
 	tc.xcode("AUTHORIZATIONFAILED")
-	tc.transactf("ok", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000testtest")))
+	tc.transactf("ok", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000"+password0)))
 	tc.close()
 
 	tc = start(t)
-	tc.transactf("ok", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("mjl@mox.example\u0000mjl@mox.example\u0000testtest")))
+	tc.transactf("ok", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("mjl@mox.example\u0000mjl@mox.example\u0000"+password0)))
+	tc.close()
+
+	// NFD username and PRECIS-cleaned password.
+	tc = start(t)
+	tc.transactf("ok", "authenticate plain %s", base64.StdEncoding.EncodeToString([]byte("mo\u0301x@mox.example\u0000mo\u0301x@mox.example\u0000"+password1)))
 	tc.close()
 
 	tc = start(t)
-	tc.client.AuthenticatePlain("mjl@mox.example", "testtest")
+	tc.client.AuthenticatePlain("mjl@mox.example", password0)
 	tc.close()
 
 	tc = start(t)
@@ -55,7 +69,7 @@ func TestAuthenticatePlain(t *testing.T) {
 
 	tc.cmdf("", "authenticate plain")
 	tc.readprefixline("+ ")
-	tc.writelinef("%s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000testtest")))
+	tc.writelinef("%s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000"+password0)))
 	tc.readstatus("ok")
 }
 
@@ -77,7 +91,7 @@ func TestAuthenticateSCRAMSHA256PLUS(t *testing.T) {
 
 func testAuthenticateSCRAM(t *testing.T, tls bool, method string, h func() hash.Hash) {
 	tc := startArgs(t, true, tls, true, true, "mjl")
-	tc.client.AuthenticateSCRAM(method, h, "mjl@mox.example", "testtest")
+	tc.client.AuthenticateSCRAM(method, h, "mjl@mox.example", password0)
 	tc.close()
 
 	auth := func(status string, serverFinalError error, username, password string) {
@@ -129,11 +143,15 @@ func testAuthenticateSCRAM(t *testing.T, tls bool, method string, h func() hash.
 	auth("no", scram.ErrInvalidProof, "mjl@mox.example", "badpass")
 	auth("no", scram.ErrInvalidProof, "mjl@mox.example", "")
 	// todo: server aborts due to invalid username. we should probably make client continue with fake determinisitically generated salt and result in error in the end.
-	// auth("no", nil, "other@mox.example", "testtest")
+	// auth("no", nil, "other@mox.example", password0)
 
 	tc.transactf("no", "authenticate bogus ")
 	tc.transactf("bad", "authenticate %s not base64...", method)
 	tc.transactf("bad", "authenticate %s %s", method, base64.StdEncoding.EncodeToString([]byte("bad data")))
+
+	// NFD username, with PRECIS-cleaned password.
+	auth("ok", nil, "mo\u0301x@mox.example", password1)
+
 	tc.close()
 }
 
@@ -163,6 +181,10 @@ func TestAuthenticateCRAMMD5(t *testing.T) {
 		}
 
 		chal := xreadContinuation()
+		pw, err := precis.OpaqueString.String(password)
+		if err == nil {
+			password = pw
+		}
 		h := hmac.New(md5.New, []byte(password))
 		h.Write([]byte(chal))
 		resp := fmt.Sprintf("%s %x", username, h.Sum(nil))
@@ -177,9 +199,14 @@ func TestAuthenticateCRAMMD5(t *testing.T) {
 
 	auth("no", "mjl@mox.example", "badpass")
 	auth("no", "mjl@mox.example", "")
-	auth("no", "other@mox.example", "testtest")
+	auth("no", "other@mox.example", password0)
 
-	auth("ok", "mjl@mox.example", "testtest")
+	auth("ok", "mjl@mox.example", password0)
 
 	tc.close()
+
+	// NFD username, with PRECIS-cleaned password.
+	tc = start(t)
+	auth("ok", "mo\u0301x@mox.example", password1)
+	tc.close()
 }

imapserver/condstore_test.go

@@ -34,7 +34,7 @@ func testCondstoreQresync(t *testing.T, qresync bool) {
 		capability = "Qresync"
 	}
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Enable(capability)
 	tc.transactf("ok", "Select inbox")
 	tc.xuntaggedOpt(false, imapclient.UntaggedResult{Status: imapclient.OK, RespText: imapclient.RespText{Code: "HIGHESTMODSEQ", CodeArg: imapclient.CodeHighestModSeq(1), More: "x"}})
@@ -101,13 +101,13 @@ func testCondstoreQresync(t *testing.T, qresync bool) {
 	// tc2 is a client without condstore, so no modseq responses.
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
 
 	// tc3 is a client with condstore, so with modseq responses.
 	tc3 := startNoSwitchboard(t)
 	defer tc3.close()
-	tc3.client.Login("mjl@mox.example", "testtest")
+	tc3.client.Login("mjl@mox.example", password0)
 	tc3.client.Enable(capability)
 	tc3.client.Select("inbox")
 
@@ -357,7 +357,7 @@ func testCondstoreQresync(t *testing.T, qresync bool) {
 			xtc.close()
 			store.CheckConsistencyOnClose = true
 		}()
-		xtc.client.Login("mjl@mox.example", "testtest")
+		xtc.client.Login("mjl@mox.example", password0)
 		fn(xtc)
 		tagcount++
 		label := fmt.Sprintf("l%d", tagcount)
@@ -444,13 +444,13 @@ func testCondstoreQresync(t *testing.T, qresync bool) {
 	// tc2o is a client without condstore, so no modseq responses.
 	tc2o := startNoSwitchboard(t)
 	defer tc2o.close()
-	tc2o.client.Login("mjl@mox.example", "testtest")
+	tc2o.client.Login("mjl@mox.example", password0)
 	tc2o.client.Select("otherbox")
 
 	// tc3o is a client with condstore, so with modseq responses.
 	tc3o := startNoSwitchboard(t)
 	defer tc3o.close()
-	tc3o.client.Login("mjl@mox.example", "testtest")
+	tc3o.client.Login("mjl@mox.example", password0)
 	tc3o.client.Enable(capability)
 	tc3o.client.Select("otherbox")
 
@@ -529,7 +529,7 @@ func testQresync(t *testing.T, tc *testconn, clientModseq int64) {
 
 	// Vanished not allowed without first enabling qresync. ../rfc/7162:1697
 	xtc := startNoSwitchboard(t)
-	xtc.client.Login("mjl@mox.example", "testtest")
+	xtc.client.Login("mjl@mox.example", password0)
 	xtc.transactf("ok", "Select inbox (Condstore)")
 	xtc.transactf("bad", "Uid Fetch 1:* (Flags) (Changedsince 1 Vanished)")
 	// Prevent triggering the consistency checker, we still have modseq/createseq at 0.
@@ -553,7 +553,7 @@ func testQresync(t *testing.T, tc *testconn, clientModseq int64) {
 
 	// Must enable qresync explicitly before using. ../rfc/7162:1446
 	xtc = startNoSwitchboard(t)
-	xtc.client.Login("mjl@mox.example", "testtest")
+	xtc.client.Login("mjl@mox.example", password0)
 	xtc.transactf("bad", "Select inbox (Qresync 1 0)")
 	// Prevent triggering the consistency checker, we still have modseq/createseq at 0.
 	store.CheckConsistencyOnClose = false

imapserver/copy_test.go

@@ -14,10 +14,10 @@ func TestCopy(t *testing.T) {
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("Trash")
 
 	tc.transactf("bad", "copy")          // Missing params.
@@ -61,7 +61,7 @@ func TestCopy(t *testing.T) {
 
 	tclimit := startArgs(t, false, false, true, true, "limit")
 	defer tclimit.close()
-	tclimit.client.Login("limit@mox.example", "testtest")
+	tclimit.client.Login("limit@mox.example", password0)
 	tclimit.client.Select("inbox")
 	// First message of 1 byte is within limits.
 	tclimit.transactf("ok", "append inbox (\\Seen Label1 $label2) \" 1-Jan-2022 10:10:00 +0100\" {1+}\r\nx")

imapserver/create_test.go

@@ -13,8 +13,8 @@ func TestCreate(t *testing.T) {
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("no", "create inbox") // Already exists and not allowed. ../rfc/9051:1913
 	tc.transactf("no", "create Inbox") // Idem.

imapserver/delete_test.go

@@ -16,9 +16,9 @@ func TestDelete(t *testing.T) {
 	tc3 := startNoSwitchboard(t)
 	defer tc3.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
-	tc3.client.Login("mjl@mox.example", "testtest")
+	tc3.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "delete")              // Missing mailbox.
 	tc.transactf("no", "delete inbox")         // Cannot delete inbox.

imapserver/expunge_test.go

@@ -14,10 +14,10 @@ func TestExpunge(t *testing.T) {
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
 
 	tc.transactf("bad", "expunge leftover") // Leftover data.

imapserver/fetch_test.go

@@ -12,7 +12,7 @@ func TestFetch(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Enable("imap4rev2")
 	received, err := time.Parse(time.RFC3339, "2022-11-16T10:01:00+01:00")
 	tc.check(err, "parse time")

imapserver/fuzz_test.go

@@ -70,7 +70,7 @@ func FuzzServer(f *testing.F) {
 		f.Fatalf("open account: %v", err)
 	}
 	defer acc.Close()
-	err = acc.SetPassword(log, "testtest")
+	err = acc.SetPassword(log, password0)
 	if err != nil {
 		f.Fatalf("set password: %v", err)
 	}

imapserver/idle_test.go

@@ -11,11 +11,11 @@ import (
 func TestIdle(t *testing.T) {
 	tc1 := start(t)
 	defer tc1.close()
-	tc1.transactf("ok", "login mjl@mox.example testtest")
+	tc1.client.Login("mjl@mox.example", password0)
 
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.transactf("ok", "login mjl@mox.example testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 
 	tc1.transactf("ok", "select inbox")
 	tc2.transactf("ok", "select inbox")

imapserver/list_test.go

@@ -11,7 +11,7 @@ func TestListBasic(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	ulist := func(name string, flags ...string) imapclient.UntaggedList {
 		if len(flags) == 0 {
@@ -61,7 +61,7 @@ func TestListExtended(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	ulist := func(name string, flags ...string) imapclient.UntaggedList {
 		if len(flags) == 0 {

imapserver/lsub_test.go

@@ -10,7 +10,7 @@ func TestLsub(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "lsub")       // Missing params.
 	tc.transactf("bad", `lsub ""`)    // Missing param.

imapserver/move_test.go

@@ -17,13 +17,13 @@ func TestMove(t *testing.T) {
 	tc3 := startNoSwitchboard(t)
 	defer tc3.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("Trash")
 
-	tc3.client.Login("mjl@mox.example", "testtest")
+	tc3.client.Login("mjl@mox.example", password0)
 	tc3.client.Select("inbox")
 
 	tc.transactf("bad", "move")          // Missing params.

imapserver/rename_test.go

@@ -14,8 +14,8 @@ func TestRename(t *testing.T) {
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "rename")      // Missing parameters.
 	tc.transactf("bad", "rename x")    // Missing destination.

imapserver/search_test.go

@@ -59,7 +59,7 @@ func (tc *testconn) xesearch(exp imapclient.UntaggedEsearch) {
 func TestSearch(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
 	// Add 5 and delete first 4 messages. So UIDs start at 5.

imapserver/selectexamine_test.go

@@ -21,7 +21,7 @@ func testSelectExamine(t *testing.T, examine bool) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	cmd := "select"
 	okcode := "READ-WRITE"

imapserver/server_test.go

@@ -334,6 +334,9 @@ func startNoSwitchboard(t *testing.T) *testconn {
 	return startArgs(t, false, false, true, false, "mjl")
 }
 
+const password0 = "te\u0301st \u00a0\u2002\u200a" // NFD and various unicode spaces.
+const password1 = "tést    "                      // PRECIS normalized, with NFC.
+
 func startArgs(t *testing.T, first, isTLS, allowLoginWithoutTLS, setPassword bool, accname string) *testconn {
 	limitersInit() // Reset rate limiters.
 
@@ -346,7 +349,7 @@ func startArgs(t *testing.T, first, isTLS, allowLoginWithoutTLS, setPassword boo
 	acc, err := store.OpenAccount(pkglog, accname)
 	tcheck(t, err, "open account")
 	if setPassword {
-		err = acc.SetPassword(pkglog, "testtest")
+		err = acc.SetPassword(pkglog, password0)
 		tcheck(t, err, "set password")
 	}
 	switchStop := func() {}
@@ -405,20 +408,20 @@ func TestLogin(t *testing.T) {
 	tc.transactf("bad", "login too many args")
 	tc.transactf("bad", "login") // no args
 	tc.transactf("no", "login mjl@mox.example badpass")
-	tc.transactf("no", "login mjl testtest") // must use email, not account
+	tc.transactf("no", `login mjl "%s"`, password0) // must use email, not account
 	tc.transactf("no", "login mjl@mox.example test")
 	tc.transactf("no", "login mjl@mox.example testtesttest")
 	tc.transactf("no", `login "mjl@mox.example" "testtesttest"`)
 	tc.transactf("no", "login \"m\xf8x@mox.example\" \"testtesttest\"")
-	tc.transactf("ok", "login mjl@mox.example testtest")
+	tc.transactf("ok", `login mjl@mox.example "%s"`, password0)
 	tc.close()
 
 	tc = start(t)
-	tc.transactf("ok", `login "mjl@mox.example" "testtest"`)
+	tc.transactf("ok", `login "mjl@mox.example" "%s"`, password0)
 	tc.close()
 
 	tc = start(t)
-	tc.transactf("ok", `login "\"\"@mox.example" "testtest"`)
+	tc.transactf("ok", `login "\"\"@mox.example" "%s"`, password0)
 	defer tc.close()
 
 	tc.transactf("bad", "logout badarg")
@@ -447,7 +450,7 @@ func TestState(t *testing.T) {
 	}
 
 	// Some commands not allowed when authenticated.
-	tc.transactf("ok", "login mjl@mox.example testtest")
+	tc.transactf("ok", `login mjl@mox.example "%s"`, password0)
 	for _, cmd := range append(append([]string{}, notAuthenticated...), selected...) {
 		tc.transactf("no", "%s", cmd)
 	}
@@ -472,7 +475,7 @@ func TestLiterals(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Create("tmpbox")
 
 	tc.transactf("ok", "rename {6+}\r\ntmpbox {7+}\r\nntmpbox")
@@ -495,7 +498,7 @@ func TestLiterals(t *testing.T) {
 func TestScenario(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.transactf("ok", "login mjl@mox.example testtest")
+	tc.transactf("ok", `login mjl@mox.example "%s"`, password0)
 
 	tc.transactf("bad", " missingcommand")
 
@@ -573,7 +576,7 @@ func TestScenario(t *testing.T) {
 func TestMailbox(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	invalid := []string{
 		"e\u0301", // é but as e + acute, not unicode-normalized
@@ -595,11 +598,11 @@ func TestMailbox(t *testing.T) {
 func TestMailboxDeleted(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 
 	tc.client.Create("testbox")
 	tc2.client.Select("testbox")
@@ -631,7 +634,7 @@ func TestMailboxDeleted(t *testing.T) {
 func TestID(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("ok", "id nil")
 	tc.xuntagged(imapclient.UntaggedID{"name": "mox", "version": moxvar.Version})
@@ -645,7 +648,7 @@ func TestID(t *testing.T) {
 func TestSequence(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
 	tc.transactf("bad", "fetch * all") // ../rfc/9051:7018
@@ -673,13 +676,13 @@ func TestSequence(t *testing.T) {
 func DisabledTestReference(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 	tc.client.Append("inbox", nil, nil, []byte(exampleMsg))
 
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 	tc2.client.Select("inbox")
 
 	tc.client.StoreFlagsSet("1", true, `\Deleted`)
@@ -687,7 +690,7 @@ func DisabledTestReference(t *testing.T) {
 
 	tc3 := startNoSwitchboard(t)
 	defer tc3.close()
-	tc3.client.Login("mjl@mox.example", "testtest")
+	tc3.client.Login("mjl@mox.example", password0)
 	tc3.transactf("ok", `list "" "inbox" return (status (messages))`)
 	tc3.xuntagged(imapclient.UntaggedList{Separator: '/', Mailbox: "Inbox"}, imapclient.UntaggedStatus{Mailbox: "Inbox", Attrs: map[string]int64{"MESSAGES": 0}})
 

imapserver/starttls_test.go

@@ -10,7 +10,7 @@ func TestStarttls(t *testing.T) {
 	tc := start(t)
 	tc.client.Starttls(&tls.Config{InsecureSkipVerify: true})
 	tc.transactf("bad", "starttls") // TLS already active.
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.close()
 
 	tc = startArgs(t, true, true, false, true, "mjl")
@@ -18,11 +18,11 @@ func TestStarttls(t *testing.T) {
 	tc.close()
 
 	tc = startArgs(t, true, false, false, true, "mjl")
-	tc.transactf("no", `login "mjl@mox.example" "testtest"`)
+	tc.transactf("no", `login "mjl@mox.example" "%s"`, password0)
 	tc.xcode("PRIVACYREQUIRED")
-	tc.transactf("no", "authenticate PLAIN %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000testtest")))
+	tc.transactf("no", "authenticate PLAIN %s", base64.StdEncoding.EncodeToString([]byte("\u0000mjl@mox.example\u0000"+password0)))
 	tc.xcode("PRIVACYREQUIRED")
 	tc.client.Starttls(&tls.Config{InsecureSkipVerify: true})
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.close()
 }

imapserver/status_test.go

@@ -11,7 +11,7 @@ func TestStatus(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "status")                      // Missing param.
 	tc.transactf("bad", "status inbox")                // Missing param.

imapserver/store_test.go

@@ -11,7 +11,7 @@ func TestStore(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Enable("imap4rev2")
 
 	tc.client.Append("inbox", nil, nil, []byte(exampleMsg))

imapserver/subscribe_test.go

@@ -13,8 +13,8 @@ func TestSubscribe(t *testing.T) {
 	tc2 := startNoSwitchboard(t)
 	defer tc2.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
-	tc2.client.Login("mjl@mox.example", "testtest")
+	tc2.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "subscribe")       // Missing param.
 	tc.transactf("bad", "subscribe ")      // Missing param.

imapserver/unselect_test.go

@@ -10,7 +10,7 @@ func TestUnselect(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 	tc.client.Select("inbox")
 
 	tc.transactf("bad", "unselect bogus") // Leftover data.

imapserver/unsubscribe_test.go

@@ -8,7 +8,7 @@ func TestUnsubscribe(t *testing.T) {
 	tc := start(t)
 	defer tc.close()
 
-	tc.client.Login("mjl@mox.example", "testtest")
+	tc.client.Login("mjl@mox.example", password0)
 
 	tc.transactf("bad", "unsubscribe")       // Missing param.
 	tc.transactf("bad", "unsubscribe ")      // Missing param.

main.go

@@ -33,6 +33,7 @@ import (
 	"time"
 
 	"golang.org/x/crypto/bcrypt"
+	"golang.org/x/text/secure/precis"
 
 	"github.com/mjl-/adns"
 
@@ -1246,6 +1247,8 @@ The password is read from stdin. Its bcrypt hash is stored in a file named
 	}
 
 	pw := xreadpassword()
+	pw, err := precis.OpaqueString.String(pw)
+	xcheckf(err, `checking password with "precis" requirements`)
 	hash, err := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.DefaultCost)
 	xcheckf(err, "generating hash for password")
 	err = os.WriteFile(path, hash, 0660)

sasl/sasl.go

@@ -10,6 +10,8 @@ import (
 	"hash"
 	"strings"
 
+	"golang.org/x/text/secure/precis"
+
 	"github.com/mjl-/mox/scram"
 )
 
@@ -52,6 +54,7 @@ var _ Client = (*clientPlain)(nil)
 // PLAIN is specified in RFC 4616, The PLAIN Simple Authentication and Security
 // Layer (SASL) Mechanism.
 func NewClientPlain(username, password string) Client {
+	// No "precis" processing, remote can clean password up. ../rfc/8265:679
 	return &clientPlain{username, password, 0}
 }
 
@@ -80,6 +83,7 @@ var _ Client = (*clientLogin)(nil)
 //
 // See https://datatracker.ietf.org/doc/html/draft-murchison-sasl-login-00
 func NewClientLogin(username, password string) Client {
+	// No "precis" processing, remote can clean password up. ../rfc/8265:679
 	return &clientLogin{username, password, 0}
 }
 
@@ -99,6 +103,17 @@ func (a *clientLogin) Next(fromServer []byte) (toServer []byte, last bool, rerr
 	}
 }
 
+// Cleanup password with precis, like remote should have done. If the password
+// appears invalid, we'll return the original, there is a chance the server also
+// doesn't enforce requirements and accepts it. ../rfc/8265:679
+func precisPassword(password string) string {
+	pw, err := precis.OpaqueString.String(password)
+	if err != nil {
+		return password
+	}
+	return pw
+}
+
 type clientCRAMMD5 struct {
 	Username, Password string
 	step               int
@@ -111,6 +126,7 @@ var _ Client = (*clientCRAMMD5)(nil)
 // CRAM-MD5 is specified in RFC 2195, IMAP/POP AUTHorize Extension for Simple
 // Challenge/Response.
 func NewClientCRAMMD5(username, password string) Client {
+	password = precisPassword(password)
 	return &clientCRAMMD5{username, password, 0}
 }
 
@@ -199,6 +215,7 @@ var _ Client = (*clientSCRAMSHA)(nil)
 // SCRAM-SHA-1 is specified in RFC 5802, "Salted Challenge Response Authentication
 // Mechanism (SCRAM) SASL and GSS-API Mechanisms".
 func NewClientSCRAMSHA1(username, password string, noServerPlus bool) Client {
+	password = precisPassword(password)
 	return &clientSCRAMSHA{username, password, sha1.New, false, tls.ConnectionState{}, noServerPlus, "SCRAM-SHA-1", 0, nil}
 }
 
@@ -210,6 +227,7 @@ func NewClientSCRAMSHA1(username, password string, noServerPlus bool) Client {
 // SCRAM-SHA-1-PLUS is specified in RFC 5802, "Salted Challenge Response
 // Authentication Mechanism (SCRAM) SASL and GSS-API Mechanisms".
 func NewClientSCRAMSHA1PLUS(username, password string, cs tls.ConnectionState) Client {
+	password = precisPassword(password)
 	return &clientSCRAMSHA{username, password, sha1.New, true, cs, false, "SCRAM-SHA-1-PLUS", 0, nil}
 }
 
@@ -224,6 +242,7 @@ func NewClientSCRAMSHA1PLUS(username, password string, cs tls.ConnectionState) C
 // SCRAM-SHA-256 is specified in RFC 7677, "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS
 // Simple Authentication and Security Layer (SASL) Mechanisms".
 func NewClientSCRAMSHA256(username, password string, noServerPlus bool) Client {
+	password = precisPassword(password)
 	return &clientSCRAMSHA{username, password, sha256.New, false, tls.ConnectionState{}, noServerPlus, "SCRAM-SHA-256", 0, nil}
 }
 
@@ -235,6 +254,7 @@ func NewClientSCRAMSHA256(username, password string, noServerPlus bool) Client {
 // SCRAM-SHA-256-PLUS is specified in RFC 7677, "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS
 // Simple Authentication and Security Layer (SASL) Mechanisms".
 func NewClientSCRAMSHA256PLUS(username, password string, cs tls.ConnectionState) Client {
+	password = precisPassword(password)
 	return &clientSCRAMSHA{username, password, sha256.New, true, cs, false, "SCRAM-SHA-256-PLUS", 0, nil}
 }
 

scram/scram.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"golang.org/x/crypto/pbkdf2"
+	"golang.org/x/text/secure/precis"
 	"golang.org/x/text/unicode/norm"
 )
 
@@ -84,9 +85,20 @@ func MakeRandom() []byte {
 	return buf
 }
 
+// Cleanup password with precis, like remote should have done. If the password
+// appears invalid, we'll return the original, there is a chance the server also
+// doesn't enforce requirements and accepts it. ../rfc/8265:679
+func precisPassword(password string) string {
+	pw, err := precis.OpaqueString.String(password)
+	if err != nil {
+		return password
+	}
+	return pw
+}
+
 // SaltPassword returns a salted password.
 func SaltPassword(h func() hash.Hash, password string, salt []byte, iterations int) []byte {
-	password = norm.NFC.String(password)
+	password = precisPassword(password)
 	return pbkdf2.Key([]byte(password), salt, iterations, h().Size(), h)
 }
 

smtpserver/server.go

@@ -28,6 +28,7 @@ import (
 	"time"
 
 	"golang.org/x/exp/maps"
+	"golang.org/x/text/unicode/norm"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
@@ -962,8 +963,6 @@ func (c *conn) cmdAuth(p *parser) {
 		xsmtpUserErrorf(smtp.C503BadCmdSeq, smtp.SeProto5BadCmdOrSeq1, "authentication not allowed during mail transaction")
 	}
 
-	// todo future: we may want to normalize usernames and passwords, see stringprep in ../rfc/4013:38 and possibly newer mechanisms (though they are opt-in and that may not have happened yet).
-
 	// If authentication fails due to missing derived secrets, we don't hold it against
 	// the connection. There is no way to indicate server support for an authentication
 	// mechanism, but that a mechanism won't work for an account.
@@ -1071,8 +1070,8 @@ func (c *conn) cmdAuth(p *parser) {
 		if len(plain) != 3 {
 			xsmtpUserErrorf(smtp.C501BadParamSyntax, smtp.SeProto5BadParams4, "auth data should have 3 nul-separated tokens, got %d", len(plain))
 		}
-		authz := string(plain[0])
+		authz := norm.NFC.String(string(plain[0]))
-		authc := string(plain[1])
+		authc := norm.NFC.String(string(plain[1]))
 		password := string(plain[2])
 
 		if authz != "" && authz != authc {
@@ -1115,6 +1114,7 @@ func (c *conn) cmdAuth(p *parser) {
 		// I-D says maximum length must be 64 bytes. We allow more, for long user names
 		// (domains).
 		username := string(xreadInitial())
+		username = norm.NFC.String(username)
 
 		// Again, client should ignore the challenge, we send the same as the example in
 		// the I-D.
@@ -1156,7 +1156,7 @@ func (c *conn) cmdAuth(p *parser) {
 		if len(t) != 2 || len(t[1]) != 2*md5.Size {
 			xsmtpUserErrorf(smtp.C501BadParamSyntax, smtp.SeProto5BadParams4, "malformed cram-md5 response")
 		}
-		addr := t[0]
+		addr := norm.NFC.String(t[0])
 		c.log.Debug("cram-md5 auth", slog.String("address", addr))
 		acc, _, err := store.OpenEmail(c.log, addr)
 		if err != nil {
@@ -1245,13 +1245,14 @@ func (c *conn) cmdAuth(p *parser) {
 		c0 := xreadInitial()
 		ss, err := scram.NewServer(h, c0, cs, channelBindingRequired)
 		xcheckf(err, "starting scram")
-		c.log.Debug("scram auth", slog.String("authentication", ss.Authentication))
+		authc := norm.NFC.String(ss.Authentication)
-		acc, _, err := store.OpenEmail(c.log, ss.Authentication)
+		c.log.Debug("scram auth", slog.String("authentication", authc))
+		acc, _, err := store.OpenEmail(c.log, authc)
 		if err != nil {
 			// todo: we could continue scram with a generated salt, deterministically generated
 			// from the username. that way we don't have to store anything but attackers cannot
 			// learn if an account exists. same for absent scram saltedpassword below.
-			c.log.Info("failed authentication attempt", slog.String("username", ss.Authentication), slog.Any("remote", c.remoteIP))
+			c.log.Info("failed authentication attempt", slog.String("username", authc), slog.Any("remote", c.remoteIP))
 			xsmtpUserErrorf(smtp.C454TempAuthFail, smtp.SeSys3Other0, "scram not possible")
 		}
 		defer func() {
@@ -1268,7 +1269,7 @@ func (c *conn) cmdAuth(p *parser) {
 			err := acc.DB.Read(context.TODO(), func(tx *bstore.Tx) error {
 				password, err := bstore.QueryTx[store.Password](tx).Get()
 				if err == bstore.ErrAbsent {
-					c.log.Info("failed authentication attempt", slog.String("username", ss.Authentication), slog.Any("remote", c.remoteIP))
+					c.log.Info("failed authentication attempt", slog.String("username", authc), slog.Any("remote", c.remoteIP))
 					xsmtpUserErrorf(smtp.C535AuthBadCreds, smtp.SePol7AuthBadCreds8, "bad user/pass")
 				}
 				xcheckf(err, "fetching credentials")
@@ -1282,8 +1283,8 @@ func (c *conn) cmdAuth(p *parser) {
 				}
 				if len(xscram.Salt) == 0 || xscram.Iterations == 0 || len(xscram.SaltedPassword) == 0 {
 					missingDerivedSecrets = true
-					c.log.Info("scram auth attempt without derived secrets set, save password again to store secrets", slog.String("address", ss.Authentication))
+					c.log.Info("scram auth attempt without derived secrets set, save password again to store secrets", slog.String("address", authc))
-					c.log.Info("failed authentication attempt", slog.String("username", ss.Authentication), slog.Any("remote", c.remoteIP))
+					c.log.Info("failed authentication attempt", slog.String("username", authc), slog.Any("remote", c.remoteIP))
 					xsmtpUserErrorf(smtp.C454TempAuthFail, smtp.SeSys3Other0, "scram not possible")
 				}
 				return nil
@@ -1302,7 +1303,7 @@ func (c *conn) cmdAuth(p *parser) {
 			c.readline() // Should be "*" for cancellation.
 			if errors.Is(err, scram.ErrInvalidProof) {
 				authResult = "badcreds"
-				c.log.Info("failed authentication attempt", slog.String("username", ss.Authentication), slog.Any("remote", c.remoteIP))
+				c.log.Info("failed authentication attempt", slog.String("username", authc), slog.Any("remote", c.remoteIP))
 				xsmtpUserErrorf(smtp.C535AuthBadCreds, smtp.SePol7AuthBadCreds8, "bad credentials")
 			}
 			xcheckf(err, "server final")
@@ -1317,7 +1318,7 @@ func (c *conn) cmdAuth(p *parser) {
 		c.setSlow(false)
 		c.account = acc
 		acc = nil // Cancel cleanup.
-		c.username = ss.Authentication
+		c.username = authc
 		// ../rfc/4954:276
 		c.writecodeline(smtp.C235AuthSuccess, smtp.SePol7Other0, "nice", nil)
 

smtpserver/server_test.go

@@ -97,6 +97,9 @@ type testserver struct {
 	tlspkix    bool
 }
 
+const password0 = "te\u0301st \u00a0\u2002\u200a" // NFD and various unicode spaces.
+const password1 = "tést    "                      // PRECIS normalized, with NFC.
+
 func newTestServer(t *testing.T, configPath string, resolver dns.Resolver) *testserver {
 	limitersInit() // Reset rate limiters.
 
@@ -116,7 +119,7 @@ func newTestServer(t *testing.T, configPath string, resolver dns.Resolver) *test
 	var err error
 	ts.acc, err = store.OpenAccount(log, "mjl")
 	tcheck(t, err, "open account")
-	err = ts.acc.SetPassword(log, "testtest")
+	err = ts.acc.SetPassword(log, password0)
 	tcheck(t, err, "set password")
 	ts.switchStop = store.Switchboard()
 	err = queue.Init()
@@ -285,9 +288,14 @@ func TestSubmission(t *testing.T) {
 		},
 	}
 	for _, fn := range authfns {
-		testAuth(fn, "mjl@mox.example", "test", &smtpclient.Error{Secode: smtp.SePol7AuthBadCreds8})         // Bad (short) password.
+		testAuth(fn, "mjl@mox.example", "test", &smtpclient.Error{Secode: smtp.SePol7AuthBadCreds8})           // Bad (short) password.
-		testAuth(fn, "mjl@mox.example", "testtesttest", &smtpclient.Error{Secode: smtp.SePol7AuthBadCreds8}) // Bad password.
+		testAuth(fn, "mjl@mox.example", password0+"test", &smtpclient.Error{Secode: smtp.SePol7AuthBadCreds8}) // Bad password.
-		testAuth(fn, "mjl@mox.example", "testtest", nil)
+		testAuth(fn, "mjl@mox.example", password0, nil)
+		testAuth(fn, "mjl@mox.example", password1, nil)
+		testAuth(fn, "móx@mox.example", password0, nil)
+		testAuth(fn, "móx@mox.example", password1, nil)
+		testAuth(fn, "mo\u0301x@mox.example", password0, nil)
+		testAuth(fn, "mo\u0301x@mox.example", password1, nil)
 	}
 }
 
@@ -370,12 +378,12 @@ func TestDelivery(t *testing.T) {
 	ts.run(func(err error, client *smtpclient.Client) {
 		recipients := []string{
 			"mjl@mox.example",
-			"o@mox.example",          // ascii o, as configured
+			"o@mox.example",         // ascii o, as configured
-			"\u2126@mox.example",     // ohm sign, as configured
+			"\u2126@mox.example",    // ohm sign, as configured
-			"ω@mox.example",          // lower-case omega, we match case-insensitively and this is the lowercase of ohm (!)
+			"ω@mox.example",         // lower-case omega, we match case-insensitively and this is the lowercase of ohm (!)
-			"\u03a9@mox.example",     // capital omega, also lowercased to omega.
+			"\u03a9@mox.example",    // capital omega, also lowercased to omega.
-			"tést@mox.example",       // NFC
+			"móx@mox.example",       // NFC
-			"te\u0301st@mox.example", // not NFC, but normalized as tést@, see https://go.dev/blog/normalization
+			"mo\u0301x@mox.example", // not NFC, but normalized as móx@, see https://go.dev/blog/normalization
 		}
 
 		for _, rcptTo := range recipients {
@@ -1258,7 +1266,7 @@ func TestLimitOutgoing(t *testing.T) {
 	defer ts.close()
 
 	ts.user = "mjl@mox.example"
-	ts.pass = "testtest"
+	ts.pass = password0
 	ts.submission = true
 
 	err := ts.acc.DB.Insert(ctxbg, &store.Outgoing{Recipient: "a@other.example", Submitted: time.Now().Add(-24*time.Hour - time.Minute)})
@@ -1413,7 +1421,7 @@ func TestDKIMSign(t *testing.T) {
 
 	ts.submission = true
 	ts.user = "mjl@mox.example"
-	ts.pass = "testtest"
+	ts.pass = password0
 
 	n := 0
 	testSubmit := func(mailFrom, msgFrom string) {
@@ -1541,7 +1549,7 @@ func TestRequireTLS(t *testing.T) {
 	ts.submission = true
 	ts.requiretls = true
 	ts.user = "mjl@mox.example"
-	ts.pass = "testtest"
+	ts.pass = password0
 
 	no := false
 	yes := true
@@ -1692,7 +1700,7 @@ func TestFutureRelease(t *testing.T) {
 	ts := newTestServer(t, filepath.FromSlash("../testdata/smtp/mox.conf"), dns.MockResolver{})
 	ts.tlsmode = smtpclient.TLSSkip
 	ts.user = "mjl@mox.example"
-	ts.pass = "testtest"
+	ts.pass = password0
 	ts.submission = true
 	defer ts.close()
 

store/account.go

@@ -45,6 +45,7 @@ import (
 	"time"
 
 	"golang.org/x/crypto/bcrypt"
+	"golang.org/x/text/secure/precis"
 	"golang.org/x/text/unicode/norm"
 
 	"github.com/mjl-/bstore"
@@ -1473,6 +1474,16 @@ func (a *Account) DeliverMessage(log mlog.Log, tx *bstore.Tx, m *Message, msgFil
 // SetPassword saves a new password for this account. This password is used for
 // IMAP, SMTP (submission) sessions and the HTTP account web page.
 func (a *Account) SetPassword(log mlog.Log, password string) error {
+	password, err := precis.OpaqueString.String(password)
+	if err != nil {
+		return fmt.Errorf(`password not allowed by "precis"`)
+	}
+
+	if len(password) < 8 {
+		// We actually check for bytes...
+		return fmt.Errorf("password must be at least 8 characters long")
+	}
+
 	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
 	if err != nil {
 		return fmt.Errorf("generating password hash: %w", err)
@@ -2080,6 +2091,11 @@ func manageAuthCache() {
 //
 // The email address may contain a catchall separator.
 func OpenEmailAuth(log mlog.Log, email string, password string) (acc *Account, rerr error) {
+	password, err := precis.OpaqueString.String(password)
+	if err != nil {
+		return nil, ErrUnknownCredentials
+	}
+
 	acc, _, rerr = OpenEmail(log, email)
 	if rerr != nil {
 		return

testdata/imap/domains.conf

@@ -7,6 +7,7 @@ Accounts:
 		Destinations:
 			mjl@mox.example: nil
 			""@mox.example: nil
+			móx@mox.example: nil
 		JunkFilter:
 			Threshold: 0.95
 			Params:

testdata/smtp/domains.conf

@@ -12,7 +12,7 @@ Accounts:
 			o@mox.example: nil
 			# ohm sign, \u2126
 			Ω@mox.example: nil
-			tést@mox.example: nil
+			móx@mox.example: nil
 		JunkFilter:
 			Threshold: 0.9
 			Params:

testdata/webmail/domains.conf

@@ -18,6 +18,7 @@ Accounts:
 		Destinations:
 			mjl@mox.example: nil
 			møx@mox.example: nil
+			móx@mox.example: nil
 		RejectsMailbox: Rejects
 		JunkFilter:
 			Threshold: 0.95

vendor/golang.org/x/text/cases/cases.go

@@ -0,0 +1,162 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run gen.go gen_trieval.go
+
+// Package cases provides general and language-specific case mappers.
+package cases // import "golang.org/x/text/cases"
+
+import (
+	"golang.org/x/text/language"
+	"golang.org/x/text/transform"
+)
+
+// References:
+// - Unicode Reference Manual Chapter 3.13, 4.2, and 5.18.
+// - https://www.unicode.org/reports/tr29/
+// - https://www.unicode.org/Public/6.3.0/ucd/CaseFolding.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/SpecialCasing.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/DerivedCoreProperties.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakProperty.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakTest.txt
+// - http://userguide.icu-project.org/transforms/casemappings
+
+// TODO:
+// - Case folding
+// - Wide and Narrow?
+// - Segmenter option for title casing.
+// - ASCII fast paths
+// - Encode Soft-Dotted property within trie somehow.
+
+// A Caser transforms given input to a certain case. It implements
+// transform.Transformer.
+//
+// A Caser may be stateful and should therefore not be shared between
+// goroutines.
+type Caser struct {
+	t transform.SpanningTransformer
+}
+
+// Bytes returns a new byte slice with the result of converting b to the case
+// form implemented by c.
+func (c Caser) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(c.t, b)
+	return b
+}
+
+// String returns a string with the result of transforming s to the case form
+// implemented by c.
+func (c Caser) String(s string) string {
+	s, _, _ = transform.String(c.t, s)
+	return s
+}
+
+// Reset resets the Caser to be reused for new input after a previous call to
+// Transform.
+func (c Caser) Reset() { c.t.Reset() }
+
+// Transform implements the transform.Transformer interface and transforms the
+// given input to the case form implemented by c.
+func (c Caser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return c.t.Transform(dst, src, atEOF)
+}
+
+// Span implements the transform.SpanningTransformer interface.
+func (c Caser) Span(src []byte, atEOF bool) (n int, err error) {
+	return c.t.Span(src, atEOF)
+}
+
+// Upper returns a Caser for language-specific uppercasing.
+func Upper(t language.Tag, opts ...Option) Caser {
+	return Caser{makeUpper(t, getOpts(opts...))}
+}
+
+// Lower returns a Caser for language-specific lowercasing.
+func Lower(t language.Tag, opts ...Option) Caser {
+	return Caser{makeLower(t, getOpts(opts...))}
+}
+
+// Title returns a Caser for language-specific title casing. It uses an
+// approximation of the default Unicode Word Break algorithm.
+func Title(t language.Tag, opts ...Option) Caser {
+	return Caser{makeTitle(t, getOpts(opts...))}
+}
+
+// Fold returns a Caser that implements Unicode case folding. The returned Caser
+// is stateless and safe to use concurrently by multiple goroutines.
+//
+// Case folding does not normalize the input and may not preserve a normal form.
+// Use the collate or search package for more convenient and linguistically
+// sound comparisons. Use golang.org/x/text/secure/precis for string comparisons
+// where security aspects are a concern.
+func Fold(opts ...Option) Caser {
+	return Caser{makeFold(getOpts(opts...))}
+}
+
+// An Option is used to modify the behavior of a Caser.
+type Option func(o options) options
+
+// TODO: consider these options to take a boolean as well, like FinalSigma.
+// The advantage of using this approach is that other providers of a lower-case
+// algorithm could set different defaults by prefixing a user-provided slice
+// of options with their own. This is handy, for instance, for the precis
+// package which would override the default to not handle the Greek final sigma.
+
+var (
+	// NoLower disables the lowercasing of non-leading letters for a title
+	// caser.
+	NoLower Option = noLower
+
+	// Compact omits mappings in case folding for characters that would grow the
+	// input. (Unimplemented.)
+	Compact Option = compact
+)
+
+// TODO: option to preserve a normal form, if applicable?
+
+type options struct {
+	noLower bool
+	simple  bool
+
+	// TODO: segmenter, max ignorable, alternative versions, etc.
+
+	ignoreFinalSigma bool
+}
+
+func getOpts(o ...Option) (res options) {
+	for _, f := range o {
+		res = f(res)
+	}
+	return
+}
+
+func noLower(o options) options {
+	o.noLower = true
+	return o
+}
+
+func compact(o options) options {
+	o.simple = true
+	return o
+}
+
+// HandleFinalSigma specifies whether the special handling of Greek final sigma
+// should be enabled. Unicode prescribes handling the Greek final sigma for all
+// locales, but standards like IDNA and PRECIS override this default.
+func HandleFinalSigma(enable bool) Option {
+	if enable {
+		return handleFinalSigma
+	}
+	return ignoreFinalSigma
+}
+
+func ignoreFinalSigma(o options) options {
+	o.ignoreFinalSigma = true
+	return o
+}
+
+func handleFinalSigma(o options) options {
+	o.ignoreFinalSigma = false
+	return o
+}

vendor/golang.org/x/text/cases/context.go

@@ -0,0 +1,376 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+import "golang.org/x/text/transform"
+
+// A context is used for iterating over source bytes, fetching case info and
+// writing to a destination buffer.
+//
+// Casing operations may need more than one rune of context to decide how a rune
+// should be cased. Casing implementations should call checkpoint on context
+// whenever it is known to be safe to return the runes processed so far.
+//
+// It is recommended for implementations to not allow for more than 30 case
+// ignorables as lookahead (analogous to the limit in norm) and to use state if
+// unbounded lookahead is needed for cased runes.
+type context struct {
+	dst, src []byte
+	atEOF    bool
+
+	pDst int // pDst points past the last written rune in dst.
+	pSrc int // pSrc points to the start of the currently scanned rune.
+
+	// checkpoints safe to return in Transform, where nDst <= pDst and nSrc <= pSrc.
+	nDst, nSrc int
+	err        error
+
+	sz   int  // size of current rune
+	info info // case information of currently scanned rune
+
+	// State preserved across calls to Transform.
+	isMidWord bool // false if next cased letter needs to be title-cased.
+}
+
+func (c *context) Reset() {
+	c.isMidWord = false
+}
+
+// ret returns the return values for the Transform method. It checks whether
+// there were insufficient bytes in src to complete and introduces an error
+// accordingly, if necessary.
+func (c *context) ret() (nDst, nSrc int, err error) {
+	if c.err != nil || c.nSrc == len(c.src) {
+		return c.nDst, c.nSrc, c.err
+	}
+	// This point is only reached by mappers if there was no short destination
+	// buffer. This means that the source buffer was exhausted and that c.sz was
+	// set to 0 by next.
+	if c.atEOF && c.pSrc == len(c.src) {
+		return c.pDst, c.pSrc, nil
+	}
+	return c.nDst, c.nSrc, transform.ErrShortSrc
+}
+
+// retSpan returns the return values for the Span method. It checks whether
+// there were insufficient bytes in src to complete and introduces an error
+// accordingly, if necessary.
+func (c *context) retSpan() (n int, err error) {
+	_, nSrc, err := c.ret()
+	return nSrc, err
+}
+
+// checkpoint sets the return value buffer points for Transform to the current
+// positions.
+func (c *context) checkpoint() {
+	if c.err == nil {
+		c.nDst, c.nSrc = c.pDst, c.pSrc+c.sz
+	}
+}
+
+// unreadRune causes the last rune read by next to be reread on the next
+// invocation of next. Only one unreadRune may be called after a call to next.
+func (c *context) unreadRune() {
+	c.sz = 0
+}
+
+func (c *context) next() bool {
+	c.pSrc += c.sz
+	if c.pSrc == len(c.src) || c.err != nil {
+		c.info, c.sz = 0, 0
+		return false
+	}
+	v, sz := trie.lookup(c.src[c.pSrc:])
+	c.info, c.sz = info(v), sz
+	if c.sz == 0 {
+		if c.atEOF {
+			// A zero size means we have an incomplete rune. If we are atEOF,
+			// this means it is an illegal rune, which we will consume one
+			// byte at a time.
+			c.sz = 1
+		} else {
+			c.err = transform.ErrShortSrc
+			return false
+		}
+	}
+	return true
+}
+
+// writeBytes adds bytes to dst.
+func (c *context) writeBytes(b []byte) bool {
+	if len(c.dst)-c.pDst < len(b) {
+		c.err = transform.ErrShortDst
+		return false
+	}
+	// This loop is faster than using copy.
+	for _, ch := range b {
+		c.dst[c.pDst] = ch
+		c.pDst++
+	}
+	return true
+}
+
+// writeString writes the given string to dst.
+func (c *context) writeString(s string) bool {
+	if len(c.dst)-c.pDst < len(s) {
+		c.err = transform.ErrShortDst
+		return false
+	}
+	// This loop is faster than using copy.
+	for i := 0; i < len(s); i++ {
+		c.dst[c.pDst] = s[i]
+		c.pDst++
+	}
+	return true
+}
+
+// copy writes the current rune to dst.
+func (c *context) copy() bool {
+	return c.writeBytes(c.src[c.pSrc : c.pSrc+c.sz])
+}
+
+// copyXOR copies the current rune to dst and modifies it by applying the XOR
+// pattern of the case info. It is the responsibility of the caller to ensure
+// that this is a rune with a XOR pattern defined.
+func (c *context) copyXOR() bool {
+	if !c.copy() {
+		return false
+	}
+	if c.info&xorIndexBit == 0 {
+		// Fast path for 6-bit XOR pattern, which covers most cases.
+		c.dst[c.pDst-1] ^= byte(c.info >> xorShift)
+	} else {
+		// Interpret XOR bits as an index.
+		// TODO: test performance for unrolling this loop. Verify that we have
+		// at least two bytes and at most three.
+		idx := c.info >> xorShift
+		for p := c.pDst - 1; ; p-- {
+			c.dst[p] ^= xorData[idx]
+			idx--
+			if xorData[idx] == 0 {
+				break
+			}
+		}
+	}
+	return true
+}
+
+// hasPrefix returns true if src[pSrc:] starts with the given string.
+func (c *context) hasPrefix(s string) bool {
+	b := c.src[c.pSrc:]
+	if len(b) < len(s) {
+		return false
+	}
+	for i, c := range b[:len(s)] {
+		if c != s[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// caseType returns an info with only the case bits, normalized to either
+// cLower, cUpper, cTitle or cUncased.
+func (c *context) caseType() info {
+	cm := c.info & 0x7
+	if cm < 4 {
+		return cm
+	}
+	if cm >= cXORCase {
+		// xor the last bit of the rune with the case type bits.
+		b := c.src[c.pSrc+c.sz-1]
+		return info(b&1) ^ cm&0x3
+	}
+	if cm == cIgnorableCased {
+		return cLower
+	}
+	return cUncased
+}
+
+// lower writes the lowercase version of the current rune to dst.
+func lower(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cLower {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		return c.copyXOR()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+	if nLower := (e[1] >> lengthBits) & lengthMask; nLower != noChange {
+		return c.writeString(e[offset : offset+nLower])
+	}
+	return c.copy()
+}
+
+func isLower(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cLower {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	if nLower := (e[1] >> lengthBits) & lengthMask; nLower != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// upper writes the uppercase version of the current rune to dst.
+func upper(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cUpper {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		return c.copyXOR()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+	// Get length of first special case mapping.
+	n := (e[1] >> lengthBits) & lengthMask
+	if ct == cTitle {
+		// The first special case mapping is for lower. Set n to the second.
+		if n == noChange {
+			n = 0
+		}
+		n, e = e[1]&lengthMask, e[n:]
+	}
+	if n != noChange {
+		return c.writeString(e[offset : offset+n])
+	}
+	return c.copy()
+}
+
+// isUpper writes the isUppercase version of the current rune to dst.
+func isUpper(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cUpper {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	// Get length of first special case mapping.
+	n := (e[1] >> lengthBits) & lengthMask
+	if ct == cTitle {
+		n = e[1] & lengthMask
+	}
+	if n != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// title writes the title case version of the current rune to dst.
+func title(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cTitle {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		if ct == cLower {
+			return c.copyXOR()
+		}
+		return c.copy()
+	}
+	// Get the exception data.
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+
+	nFirst := (e[1] >> lengthBits) & lengthMask
+	if nTitle := e[1] & lengthMask; nTitle != noChange {
+		if nFirst != noChange {
+			e = e[nFirst:]
+		}
+		return c.writeString(e[offset : offset+nTitle])
+	}
+	if ct == cLower && nFirst != noChange {
+		// Use the uppercase version instead.
+		return c.writeString(e[offset : offset+nFirst])
+	}
+	// Already in correct case.
+	return c.copy()
+}
+
+// isTitle reports whether the current rune is in title case.
+func isTitle(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cTitle {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		if ct == cLower {
+			c.err = transform.ErrEndOfSpan
+			return false
+		}
+		return true
+	}
+	// Get the exception data.
+	e := exceptions[c.info>>exceptionShift:]
+	if nTitle := e[1] & lengthMask; nTitle != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	nFirst := (e[1] >> lengthBits) & lengthMask
+	if ct == cLower && nFirst != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// foldFull writes the foldFull version of the current rune to dst.
+func foldFull(c *context) bool {
+	if c.info&hasMappingMask == 0 {
+		return c.copy()
+	}
+	ct := c.caseType()
+	if c.info&exceptionBit == 0 {
+		if ct != cLower || c.info&inverseFoldBit != 0 {
+			return c.copyXOR()
+		}
+		return c.copy()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	n := e[0] & lengthMask
+	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 {
+			c.err = transform.ErrEndOfSpan
+			return false
+		}
+		return true
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	n := e[0] & lengthMask
+	if n == 0 && ct == cLower {
+		return true
+	}
+	c.err = transform.ErrEndOfSpan
+	return false
+}

vendor/golang.org/x/text/cases/fold.go

@@ -0,0 +1,34 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+import "golang.org/x/text/transform"
+
+type caseFolder struct{ transform.NopResetter }
+
+// caseFolder implements the Transformer interface for doing case folding.
+func (t *caseFolder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	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.
+	// TODO: Implement Compact options.
+	return &caseFolder{}
+}

vendor/golang.org/x/text/cases/icu.go

@@ -0,0 +1,61 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build icu
+
+package cases
+
+// Ideally these functions would be defined in a test file, but go test doesn't
+// allow CGO in tests. The build tag should ensure either way that these
+// functions will not end up in the package.
+
+// TODO: Ensure that the correct ICU version is set.
+
+/*
+#cgo LDFLAGS: -licui18n.57 -licuuc.57
+#include <stdlib.h>
+#include <unicode/ustring.h>
+#include <unicode/utypes.h>
+#include <unicode/localpointer.h>
+#include <unicode/ucasemap.h>
+*/
+import "C"
+
+import "unsafe"
+
+func doICU(tag, caser, input string) string {
+	err := C.UErrorCode(0)
+	loc := C.CString(tag)
+	cm := C.ucasemap_open(loc, C.uint32_t(0), &err)
+
+	buf := make([]byte, len(input)*4)
+	dst := (*C.char)(unsafe.Pointer(&buf[0]))
+	src := C.CString(input)
+
+	cn := C.int32_t(0)
+
+	switch caser {
+	case "fold":
+		cn = C.ucasemap_utf8FoldCase(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "lower":
+		cn = C.ucasemap_utf8ToLower(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "upper":
+		cn = C.ucasemap_utf8ToUpper(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "title":
+		cn = C.ucasemap_utf8ToTitle(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	}
+	return string(buf[:cn])
+}

vendor/golang.org/x/text/cases/info.go

@@ -0,0 +1,82 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+func (c info) cccVal() info {
+	if c&exceptionBit != 0 {
+		return info(exceptions[c>>exceptionShift]) & cccMask
+	}
+	return c & cccMask
+}
+
+func (c info) cccType() info {
+	ccc := c.cccVal()
+	if ccc <= cccZero {
+		return cccZero
+	}
+	return ccc
+}
+
+// TODO: Implement full Unicode breaking algorithm:
+// 1) Implement breaking in separate package.
+// 2) Use the breaker here.
+// 3) Compare table size and performance of using the more generic breaker.
+//
+// Note that we can extend the current algorithm to be much more accurate. This
+// only makes sense, though, if the performance and/or space penalty of using
+// the generic breaker is big. Extra data will only be needed for non-cased
+// runes, which means there are sufficient bits left in the caseType.
+// ICU prohibits breaking in such cases as well.
+
+// For the purpose of title casing we use an approximation of the Unicode Word
+// Breaking algorithm defined in Annex #29:
+// https://www.unicode.org/reports/tr29/#Default_Grapheme_Cluster_Table.
+//
+// For our approximation, we group the Word Break types into the following
+// categories, with associated rules:
+//
+// 1) Letter:
+//    ALetter, Hebrew_Letter, Numeric, ExtendNumLet, Extend, Format_FE, ZWJ.
+//    Rule: Never break between consecutive runes of this category.
+//
+// 2) Mid:
+//    MidLetter, MidNumLet, Single_Quote.
+//    (Cf. case-ignorable: MidLetter, MidNumLet, Single_Quote or cat is Mn,
+//    Me, Cf, Lm or Sk).
+//    Rule: Don't break between Letter and Mid, but break between two Mids.
+//
+// 3) Break:
+//    Any other category: NewLine, MidNum, CR, LF, Double_Quote, Katakana, and
+//    Other.
+//    These categories should always result in a break between two cased letters.
+//    Rule: Always break.
+//
+// Note 1: the Katakana and MidNum categories can, in esoteric cases, result in
+// preventing a break between two cased letters. For now we will ignore this
+// (e.g. [ALetter] [ExtendNumLet] [Katakana] [ExtendNumLet] [ALetter] and
+// [ALetter] [Numeric] [MidNum] [Numeric] [ALetter].)
+//
+// Note 2: the rule for Mid is very approximate, but works in most cases. To
+// improve, we could store the categories in the trie value and use a FA to
+// manage breaks. See TODO comment above.
+//
+// Note 3: according to the spec, it is possible for the Extend category to
+// introduce breaks between other categories grouped in Letter. However, this
+// is undesirable for our purposes. ICU prevents breaks in such cases as well.
+
+// isBreak returns whether this rune should introduce a break.
+func (c info) isBreak() bool {
+	return c.cccVal() == cccBreak
+}
+
+// isLetter returns whether the rune is of break type ALetter, Hebrew_Letter,
+// Numeric, ExtendNumLet, or Extend.
+func (c info) isLetter() bool {
+	ccc := c.cccVal()
+	if ccc == cccZero {
+		return !c.isCaseIgnorable()
+	}
+	return ccc != cccBreak
+}

vendor/golang.org/x/text/cases/map.go

@@ -0,0 +1,816 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+// This file contains the definitions of case mappings for all supported
+// languages. The rules for the language-specific tailorings were taken and
+// modified from the CLDR transform definitions in common/transforms.
+
+import (
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/internal"
+	"golang.org/x/text/language"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+// A mapFunc takes a context set to the current rune and writes the mapped
+// version to the same context. It may advance the context to the next rune. It
+// returns whether a checkpoint is possible: whether the pDst bytes written to
+// dst so far won't need changing as we see more source bytes.
+type mapFunc func(*context) bool
+
+// A spanFunc takes a context set to the current rune and returns whether this
+// rune would be altered when written to the output. It may advance the context
+// to the next rune. It returns whether a checkpoint is possible.
+type spanFunc func(*context) bool
+
+// maxIgnorable defines the maximum number of ignorables to consider for
+// lookahead operations.
+const maxIgnorable = 30
+
+// supported lists the language tags for which we have tailorings.
+const supported = "und af az el lt nl tr"
+
+func init() {
+	tags := []language.Tag{}
+	for _, s := range strings.Split(supported, " ") {
+		tags = append(tags, language.MustParse(s))
+	}
+	matcher = internal.NewInheritanceMatcher(tags)
+	Supported = language.NewCoverage(tags)
+}
+
+var (
+	matcher *internal.InheritanceMatcher
+
+	Supported language.Coverage
+
+	// We keep the following lists separate, instead of having a single per-
+	// language struct, to give the compiler a chance to remove unused code.
+
+	// Some uppercase mappers are stateless, so we can precompute the
+	// Transformers and save a bit on runtime allocations.
+	upperFunc = []struct {
+		upper mapFunc
+		span  spanFunc
+	}{
+		{nil, nil},                  // und
+		{nil, nil},                  // af
+		{aztrUpper(upper), isUpper}, // az
+		{elUpper, noSpan},           // el
+		{ltUpper(upper), noSpan},    // lt
+		{nil, nil},                  // nl
+		{aztrUpper(upper), isUpper}, // tr
+	}
+
+	undUpper            transform.SpanningTransformer = &undUpperCaser{}
+	undLower            transform.SpanningTransformer = &undLowerCaser{}
+	undLowerIgnoreSigma transform.SpanningTransformer = &undLowerIgnoreSigmaCaser{}
+
+	lowerFunc = []mapFunc{
+		nil,       // und
+		nil,       // af
+		aztrLower, // az
+		nil,       // el
+		ltLower,   // lt
+		nil,       // nl
+		aztrLower, // tr
+	}
+
+	titleInfos = []struct {
+		title     mapFunc
+		lower     mapFunc
+		titleSpan spanFunc
+		rewrite   func(*context)
+	}{
+		{title, lower, isTitle, nil},                // und
+		{title, lower, isTitle, afnlRewrite},        // af
+		{aztrUpper(title), aztrLower, isTitle, nil}, // az
+		{title, lower, isTitle, nil},                // el
+		{ltUpper(title), ltLower, noSpan, nil},      // lt
+		{nlTitle, lower, nlTitleSpan, afnlRewrite},  // nl
+		{aztrUpper(title), aztrLower, isTitle, nil}, // tr
+	}
+)
+
+func makeUpper(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	f := upperFunc[i].upper
+	if f == nil {
+		return undUpper
+	}
+	return &simpleCaser{f: f, span: upperFunc[i].span}
+}
+
+func makeLower(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	f := lowerFunc[i]
+	if f == nil {
+		if o.ignoreFinalSigma {
+			return undLowerIgnoreSigma
+		}
+		return undLower
+	}
+	if o.ignoreFinalSigma {
+		return &simpleCaser{f: f, span: isLower}
+	}
+	return &lowerCaser{
+		first:   f,
+		midWord: finalSigma(f),
+	}
+}
+
+func makeTitle(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	x := &titleInfos[i]
+	lower := x.lower
+	if o.noLower {
+		lower = (*context).copy
+	} else if !o.ignoreFinalSigma {
+		lower = finalSigma(lower)
+	}
+	return &titleCaser{
+		title:     x.title,
+		lower:     lower,
+		titleSpan: x.titleSpan,
+		rewrite:   x.rewrite,
+	}
+}
+
+func noSpan(c *context) bool {
+	c.err = transform.ErrEndOfSpan
+	return false
+}
+
+// TODO: consider a similar special case for the fast majority lower case. This
+// is a bit more involved so will require some more precise benchmarking to
+// justify it.
+
+type undUpperCaser struct{ transform.NopResetter }
+
+// undUpperCaser implements the Transformer interface for doing an upper case
+// mapping for the root locale (und). It eliminates the need for an allocation
+// as it prevents escaping by not using function pointers.
+func (t undUpperCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() {
+		upper(&c)
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t undUpperCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isUpper(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// undLowerIgnoreSigmaCaser implements the Transformer interface for doing
+// a lower case mapping for the root locale (und) ignoring final sigma
+// handling. This casing algorithm is used in some performance-critical packages
+// like secure/precis and x/net/http/idna, which warrants its special-casing.
+type undLowerIgnoreSigmaCaser struct{ transform.NopResetter }
+
+func (t undLowerIgnoreSigmaCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() && lower(&c) {
+		c.checkpoint()
+	}
+	return c.ret()
+
+}
+
+// Span implements a generic lower-casing. This is possible as isLower works
+// for all lowercasing variants. All lowercase variants only vary in how they
+// transform a non-lowercase letter. They will never change an already lowercase
+// letter. In addition, there is no state.
+func (t undLowerIgnoreSigmaCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isLower(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+type simpleCaser struct {
+	context
+	f    mapFunc
+	span spanFunc
+}
+
+// simpleCaser implements the Transformer interface for doing a case operation
+// on a rune-by-rune basis.
+func (t *simpleCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() && t.f(&c) {
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t *simpleCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && t.span(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// undLowerCaser implements the Transformer interface for doing a lower case
+// mapping for the root locale (und) ignoring final sigma handling. This casing
+// algorithm is used in some performance-critical packages like secure/precis
+// and x/net/http/idna, which warrants its special-casing.
+type undLowerCaser struct{ transform.NopResetter }
+
+func (t undLowerCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+
+	for isInterWord := true; c.next(); {
+		if isInterWord {
+			if c.info.isCased() {
+				if !lower(&c) {
+					break
+				}
+				isInterWord = false
+			} else if !c.copy() {
+				break
+			}
+		} else {
+			if c.info.isNotCasedAndNotCaseIgnorable() {
+				if !c.copy() {
+					break
+				}
+				isInterWord = true
+			} else if !c.hasPrefix("Σ") {
+				if !lower(&c) {
+					break
+				}
+			} else if !finalSigmaBody(&c) {
+				break
+			}
+		}
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t undLowerCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isLower(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// lowerCaser implements the Transformer interface. The default Unicode lower
+// casing requires different treatment for the first and subsequent characters
+// of a word, most notably to handle the Greek final Sigma.
+type lowerCaser struct {
+	undLowerIgnoreSigmaCaser
+
+	context
+
+	first, midWord mapFunc
+}
+
+func (t *lowerCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	t.context = context{dst: dst, src: src, atEOF: atEOF}
+	c := &t.context
+
+	for isInterWord := true; c.next(); {
+		if isInterWord {
+			if c.info.isCased() {
+				if !t.first(c) {
+					break
+				}
+				isInterWord = false
+			} else if !c.copy() {
+				break
+			}
+		} else {
+			if c.info.isNotCasedAndNotCaseIgnorable() {
+				if !c.copy() {
+					break
+				}
+				isInterWord = true
+			} else if !t.midWord(c) {
+				break
+			}
+		}
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+// titleCaser implements the Transformer interface. Title casing algorithms
+// distinguish between the first letter of a word and subsequent letters of the
+// same word. It uses state to avoid requiring a potentially infinite lookahead.
+type titleCaser struct {
+	context
+
+	// rune mappings used by the actual casing algorithms.
+	title     mapFunc
+	lower     mapFunc
+	titleSpan spanFunc
+
+	rewrite func(*context)
+}
+
+// Transform implements the standard Unicode title case algorithm as defined in
+// Chapter 3 of The Unicode Standard:
+// toTitlecase(X): Find the word boundaries in X according to Unicode Standard
+// Annex #29, "Unicode Text Segmentation." For each word boundary, find the
+// first cased character F following the word boundary. If F exists, map F to
+// Titlecase_Mapping(F); then map all characters C between F and the following
+// word boundary to Lowercase_Mapping(C).
+func (t *titleCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	t.context = context{dst: dst, src: src, atEOF: atEOF, isMidWord: t.isMidWord}
+	c := &t.context
+
+	if !c.next() {
+		return c.ret()
+	}
+
+	for {
+		p := c.info
+		if t.rewrite != nil {
+			t.rewrite(c)
+		}
+
+		wasMid := p.isMid()
+		// Break out of this loop on failure to ensure we do not modify the
+		// state incorrectly.
+		if p.isCased() {
+			if !c.isMidWord {
+				if !t.title(c) {
+					break
+				}
+				c.isMidWord = true
+			} else if !t.lower(c) {
+				break
+			}
+		} else if !c.copy() {
+			break
+		} else if p.isBreak() {
+			c.isMidWord = false
+		}
+
+		// As we save the state of the transformer, it is safe to call
+		// checkpoint after any successful write.
+		if !(c.isMidWord && wasMid) {
+			c.checkpoint()
+		}
+
+		if !c.next() {
+			break
+		}
+		if wasMid && c.info.isMid() {
+			c.isMidWord = false
+		}
+	}
+	return c.ret()
+}
+
+func (t *titleCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	t.context = context{src: src, atEOF: atEOF, isMidWord: t.isMidWord}
+	c := &t.context
+
+	if !c.next() {
+		return c.retSpan()
+	}
+
+	for {
+		p := c.info
+		if t.rewrite != nil {
+			t.rewrite(c)
+		}
+
+		wasMid := p.isMid()
+		// Break out of this loop on failure to ensure we do not modify the
+		// state incorrectly.
+		if p.isCased() {
+			if !c.isMidWord {
+				if !t.titleSpan(c) {
+					break
+				}
+				c.isMidWord = true
+			} else if !isLower(c) {
+				break
+			}
+		} else if p.isBreak() {
+			c.isMidWord = false
+		}
+		// As we save the state of the transformer, it is safe to call
+		// checkpoint after any successful write.
+		if !(c.isMidWord && wasMid) {
+			c.checkpoint()
+		}
+
+		if !c.next() {
+			break
+		}
+		if wasMid && c.info.isMid() {
+			c.isMidWord = false
+		}
+	}
+	return c.retSpan()
+}
+
+// finalSigma adds Greek final Sigma handing to another casing function. It
+// determines whether a lowercased sigma should be σ or ς, by looking ahead for
+// case-ignorables and a cased letters.
+func finalSigma(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		if !c.hasPrefix("Σ") {
+			return f(c)
+		}
+		return finalSigmaBody(c)
+	}
+}
+
+func finalSigmaBody(c *context) bool {
+	// Current rune must be ∑.
+
+	// ::NFD();
+	// # 03A3; 03C2; 03A3; 03A3; Final_Sigma; # GREEK CAPITAL LETTER SIGMA
+	// Σ } [:case-ignorable:]* [:cased:] → σ;
+	// [:cased:] [:case-ignorable:]* { Σ → ς;
+	// ::Any-Lower;
+	// ::NFC();
+
+	p := c.pDst
+	c.writeString("ς")
+
+	// TODO: we should do this here, but right now this will never have an
+	// effect as this is called when the prefix is Sigma, whereas Dutch and
+	// Afrikaans only test for an apostrophe.
+	//
+	// if t.rewrite != nil {
+	// 	t.rewrite(c)
+	// }
+
+	// We need to do one more iteration after maxIgnorable, as a cased
+	// letter is not an ignorable and may modify the result.
+	wasMid := false
+	for i := 0; i < maxIgnorable+1; i++ {
+		if !c.next() {
+			return false
+		}
+		if !c.info.isCaseIgnorable() {
+			// All Midword runes are also case ignorable, so we are
+			// guaranteed to have a letter or word break here. As we are
+			// unreading the run, there is no need to unset c.isMidWord;
+			// the title caser will handle this.
+			if c.info.isCased() {
+				// p+1 is guaranteed to be in bounds: if writing ς was
+				// successful, p+1 will contain the second byte of ς. If not,
+				// this function will have returned after c.next returned false.
+				c.dst[p+1]++ // ς → σ
+			}
+			c.unreadRune()
+			return true
+		}
+		// A case ignorable may also introduce a word break, so we may need
+		// to continue searching even after detecting a break.
+		isMid := c.info.isMid()
+		if (wasMid && isMid) || c.info.isBreak() {
+			c.isMidWord = false
+		}
+		wasMid = isMid
+		c.copy()
+	}
+	return true
+}
+
+// finalSigmaSpan would be the same as isLower.
+
+// elUpper implements Greek upper casing, which entails removing a predefined
+// set of non-blocked modifiers. Note that these accents should not be removed
+// for title casing!
+// Example: "Οδός" -> "ΟΔΟΣ".
+func elUpper(c *context) bool {
+	// From CLDR:
+	// [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Above:]]*? { [\u0313\u0314\u0301\u0300\u0306\u0342\u0308\u0304] → ;
+	// [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Iota_Subscript:]]*? { \u0345 → ;
+
+	r, _ := utf8.DecodeRune(c.src[c.pSrc:])
+	oldPDst := c.pDst
+	if !upper(c) {
+		return false
+	}
+	if !unicode.Is(unicode.Greek, r) {
+		return true
+	}
+	i := 0
+	// Take the properties of the uppercased rune that is already written to the
+	// destination. This saves us the trouble of having to uppercase the
+	// decomposed rune again.
+	if b := norm.NFD.Properties(c.dst[oldPDst:]).Decomposition(); b != nil {
+		// Restore the destination position and process the decomposed rune.
+		r, sz := utf8.DecodeRune(b)
+		if r <= 0xFF { // See A.6.1
+			return true
+		}
+		c.pDst = oldPDst
+		// Insert the first rune and ignore the modifiers. See A.6.2.
+		c.writeBytes(b[:sz])
+		i = len(b[sz:]) / 2 // Greek modifiers are always of length 2.
+	}
+
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch r, _ := utf8.DecodeRune(c.src[c.pSrc:]); r {
+		// Above and Iota Subscript
+		case 0x0300, // U+0300 COMBINING GRAVE ACCENT
+			0x0301, // U+0301 COMBINING ACUTE ACCENT
+			0x0304, // U+0304 COMBINING MACRON
+			0x0306, // U+0306 COMBINING BREVE
+			0x0308, // U+0308 COMBINING DIAERESIS
+			0x0313, // U+0313 COMBINING COMMA ABOVE
+			0x0314, // U+0314 COMBINING REVERSED COMMA ABOVE
+			0x0342, // U+0342 COMBINING GREEK PERISPOMENI
+			0x0345: // U+0345 COMBINING GREEK YPOGEGRAMMENI
+			// No-op. Gobble the modifier.
+
+		default:
+			switch v, _ := trie.lookup(c.src[c.pSrc:]); info(v).cccType() {
+			case cccZero:
+				c.unreadRune()
+				return true
+
+			// We don't need to test for IotaSubscript as the only rune that
+			// qualifies (U+0345) was already excluded in the switch statement
+			// above. See A.4.
+
+			case cccAbove:
+				return c.copy()
+			default:
+				// Some other modifier. We're still allowed to gobble Greek
+				// modifiers after this.
+				c.copy()
+			}
+		}
+	}
+	return i == maxIgnorable
+}
+
+// TODO: implement elUpperSpan (low-priority: complex and infrequent).
+
+func ltLower(c *context) bool {
+	// From CLDR:
+	// # Introduce an explicit dot above when lowercasing capital I's and J's
+	// # whenever there are more accents above.
+	// # (of the accents used in Lithuanian: grave, acute, tilde above, and ogonek)
+	// # 0049; 0069 0307; 0049; 0049; lt More_Above; # LATIN CAPITAL LETTER I
+	// # 004A; 006A 0307; 004A; 004A; lt More_Above; # LATIN CAPITAL LETTER J
+	// # 012E; 012F 0307; 012E; 012E; lt More_Above; # LATIN CAPITAL LETTER I WITH OGONEK
+	// # 00CC; 0069 0307 0300; 00CC; 00CC; lt; # LATIN CAPITAL LETTER I WITH GRAVE
+	// # 00CD; 0069 0307 0301; 00CD; 00CD; lt; # LATIN CAPITAL LETTER I WITH ACUTE
+	// # 0128; 0069 0307 0303; 0128; 0128; lt; # LATIN CAPITAL LETTER I WITH TILDE
+	// ::NFD();
+	// I } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → i \u0307;
+	// J } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → j \u0307;
+	// I \u0328 (Į) } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → i \u0328 \u0307;
+	// I \u0300 (Ì) → i \u0307 \u0300;
+	// I \u0301 (Í) → i \u0307 \u0301;
+	// I \u0303 (Ĩ) → i \u0307 \u0303;
+	// ::Any-Lower();
+	// ::NFC();
+
+	i := 0
+	if r := c.src[c.pSrc]; r < utf8.RuneSelf {
+		lower(c)
+		if r != 'I' && r != 'J' {
+			return true
+		}
+	} else {
+		p := norm.NFD.Properties(c.src[c.pSrc:])
+		if d := p.Decomposition(); len(d) >= 3 && (d[0] == 'I' || d[0] == 'J') {
+			// UTF-8 optimization: the decomposition will only have an above
+			// modifier if the last rune of the decomposition is in [U+300-U+311].
+			// In all other cases, a decomposition starting with I is always
+			// an I followed by modifiers that are not cased themselves. See A.2.
+			if d[1] == 0xCC && d[2] <= 0x91 { // A.2.4.
+				if !c.writeBytes(d[:1]) {
+					return false
+				}
+				c.dst[c.pDst-1] += 'a' - 'A' // lower
+
+				// Assumption: modifier never changes on lowercase. See A.1.
+				// Assumption: all modifiers added have CCC = Above. See A.2.3.
+				return c.writeString("\u0307") && c.writeBytes(d[1:])
+			}
+			// In all other cases the additional modifiers will have a CCC
+			// that is less than 230 (Above). We will insert the U+0307, if
+			// needed, after these modifiers so that a string in FCD form
+			// will remain so. See A.2.2.
+			lower(c)
+			i = 1
+		} else {
+			return lower(c)
+		}
+	}
+
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch c.info.cccType() {
+		case cccZero:
+			c.unreadRune()
+			return true
+		case cccAbove:
+			return c.writeString("\u0307") && c.copy() // See A.1.
+		default:
+			c.copy() // See A.1.
+		}
+	}
+	return i == maxIgnorable
+}
+
+// ltLowerSpan would be the same as isLower.
+
+func ltUpper(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		// Unicode:
+		// 0307; 0307; ; ; lt After_Soft_Dotted; # COMBINING DOT ABOVE
+		//
+		// From CLDR:
+		// # Remove \u0307 following soft-dotteds (i, j, and the like), with possible
+		// # intervening non-230 marks.
+		// ::NFD();
+		// [:Soft_Dotted:] [^[:ccc=Not_Reordered:][:ccc=Above:]]* { \u0307 → ;
+		// ::Any-Upper();
+		// ::NFC();
+
+		// TODO: See A.5. A soft-dotted rune never has an exception. This would
+		// allow us to overload the exception bit and encode this property in
+		// info. Need to measure performance impact of this.
+		r, _ := utf8.DecodeRune(c.src[c.pSrc:])
+		oldPDst := c.pDst
+		if !f(c) {
+			return false
+		}
+		if !unicode.Is(unicode.Soft_Dotted, r) {
+			return true
+		}
+
+		// We don't need to do an NFD normalization, as a soft-dotted rune never
+		// contains U+0307. See A.3.
+
+		i := 0
+		for ; i < maxIgnorable && c.next(); i++ {
+			switch c.info.cccType() {
+			case cccZero:
+				c.unreadRune()
+				return true
+			case cccAbove:
+				if c.hasPrefix("\u0307") {
+					// We don't do a full NFC, but rather combine runes for
+					// some of the common cases. (Returning NFC or
+					// preserving normal form is neither a requirement nor
+					// a possibility anyway).
+					if !c.next() {
+						return false
+					}
+					if c.dst[oldPDst] == 'I' && c.pDst == oldPDst+1 && c.src[c.pSrc] == 0xcc {
+						s := ""
+						switch c.src[c.pSrc+1] {
+						case 0x80: // U+0300 COMBINING GRAVE ACCENT
+							s = "\u00cc" // U+00CC LATIN CAPITAL LETTER I WITH GRAVE
+						case 0x81: // U+0301 COMBINING ACUTE ACCENT
+							s = "\u00cd" // U+00CD LATIN CAPITAL LETTER I WITH ACUTE
+						case 0x83: // U+0303 COMBINING TILDE
+							s = "\u0128" // U+0128 LATIN CAPITAL LETTER I WITH TILDE
+						case 0x88: // U+0308 COMBINING DIAERESIS
+							s = "\u00cf" // U+00CF LATIN CAPITAL LETTER I WITH DIAERESIS
+						default:
+						}
+						if s != "" {
+							c.pDst = oldPDst
+							return c.writeString(s)
+						}
+					}
+				}
+				return c.copy()
+			default:
+				c.copy()
+			}
+		}
+		return i == maxIgnorable
+	}
+}
+
+// TODO: implement ltUpperSpan (low priority: complex and infrequent).
+
+func aztrUpper(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		// i→İ;
+		if c.src[c.pSrc] == 'i' {
+			return c.writeString("İ")
+		}
+		return f(c)
+	}
+}
+
+func aztrLower(c *context) (done bool) {
+	// From CLDR:
+	// # I and i-dotless; I-dot and i are case pairs in Turkish and Azeri
+	// # 0130; 0069; 0130; 0130; tr; # LATIN CAPITAL LETTER I WITH DOT ABOVE
+	// İ→i;
+	// # When lowercasing, remove dot_above in the sequence I + dot_above, which will turn into i.
+	// # This matches the behavior of the canonically equivalent I-dot_above
+	// # 0307; ; 0307; 0307; tr After_I; # COMBINING DOT ABOVE
+	// # When lowercasing, unless an I is before a dot_above, it turns into a dotless i.
+	// # 0049; 0131; 0049; 0049; tr Not_Before_Dot; # LATIN CAPITAL LETTER I
+	// I([^[:ccc=Not_Reordered:][:ccc=Above:]]*)\u0307 → i$1 ;
+	// I→ı ;
+	// ::Any-Lower();
+	if c.hasPrefix("\u0130") { // İ
+		return c.writeString("i")
+	}
+	if c.src[c.pSrc] != 'I' {
+		return lower(c)
+	}
+
+	// We ignore the lower-case I for now, but insert it later when we know
+	// which form we need.
+	start := c.pSrc + c.sz
+
+	i := 0
+Loop:
+	// We check for up to n ignorables before \u0307. As \u0307 is an
+	// ignorable as well, n is maxIgnorable-1.
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch c.info.cccType() {
+		case cccAbove:
+			if c.hasPrefix("\u0307") {
+				return c.writeString("i") && c.writeBytes(c.src[start:c.pSrc]) // ignore U+0307
+			}
+			done = true
+			break Loop
+		case cccZero:
+			c.unreadRune()
+			done = true
+			break Loop
+		default:
+			// We'll write this rune after we know which starter to use.
+		}
+	}
+	if i == maxIgnorable {
+		done = true
+	}
+	return c.writeString("ı") && c.writeBytes(c.src[start:c.pSrc+c.sz]) && done
+}
+
+// aztrLowerSpan would be the same as isLower.
+
+func nlTitle(c *context) bool {
+	// From CLDR:
+	// # Special titlecasing for Dutch initial "ij".
+	// ::Any-Title();
+	// # Fix up Ij at the beginning of a "word" (per Any-Title, notUAX #29)
+	// [:^WB=ALetter:] [:WB=Extend:]* [[:WB=MidLetter:][:WB=MidNumLet:]]? { Ij } → IJ ;
+	if c.src[c.pSrc] != 'I' && c.src[c.pSrc] != 'i' {
+		return title(c)
+	}
+
+	if !c.writeString("I") || !c.next() {
+		return false
+	}
+	if c.src[c.pSrc] == 'j' || c.src[c.pSrc] == 'J' {
+		return c.writeString("J")
+	}
+	c.unreadRune()
+	return true
+}
+
+func nlTitleSpan(c *context) bool {
+	// From CLDR:
+	// # Special titlecasing for Dutch initial "ij".
+	// ::Any-Title();
+	// # Fix up Ij at the beginning of a "word" (per Any-Title, notUAX #29)
+	// [:^WB=ALetter:] [:WB=Extend:]* [[:WB=MidLetter:][:WB=MidNumLet:]]? { Ij } → IJ ;
+	if c.src[c.pSrc] != 'I' {
+		return isTitle(c)
+	}
+	if !c.next() || c.src[c.pSrc] == 'j' {
+		return false
+	}
+	if c.src[c.pSrc] != 'J' {
+		c.unreadRune()
+	}
+	return true
+}
+
+// Not part of CLDR, but see https://unicode.org/cldr/trac/ticket/7078.
+func afnlRewrite(c *context) {
+	if c.hasPrefix("'") || c.hasPrefix("’") {
+		c.isMidWord = true
+	}
+}

vendor/golang.org/x/text/cases/trieval.go

@@ -0,0 +1,217 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package cases
+
+// This file contains definitions for interpreting the trie value of the case
+// trie generated by "go run gen*.go". It is shared by both the generator
+// program and the resultant package. Sharing is achieved by the generator
+// copying gen_trieval.go to trieval.go and changing what's above this comment.
+
+// info holds case information for a single rune. It is the value returned
+// by a trie lookup. Most mapping information can be stored in a single 16-bit
+// value. If not, for example when a rune is mapped to multiple runes, the value
+// stores some basic case data and an index into an array with additional data.
+//
+// The per-rune values have the following format:
+//
+//	if (exception) {
+//	  15..4  unsigned exception index
+//	} else {
+//	  15..8  XOR pattern or index to XOR pattern for case mapping
+//	         Only 13..8 are used for XOR patterns.
+//	      7  inverseFold (fold to upper, not to lower)
+//	      6  index: interpret the XOR pattern as an index
+//	         or isMid if case mode is cIgnorableUncased.
+//	   5..4  CCC: zero (normal or break), above or other
+//	}
+//	   3  exception: interpret this value as an exception index
+//	      (TODO: is this bit necessary? Probably implied from case mode.)
+//	2..0  case mode
+//
+// For the non-exceptional cases, a rune must be either uncased, lowercase or
+// uppercase. If the rune is cased, the XOR pattern maps either a lowercase
+// rune to uppercase or an uppercase rune to lowercase (applied to the 10
+// least-significant bits of the rune).
+//
+// See the definitions below for a more detailed description of the various
+// bits.
+type info uint16
+
+const (
+	casedMask      = 0x0003
+	fullCasedMask  = 0x0007
+	ignorableMask  = 0x0006
+	ignorableValue = 0x0004
+
+	inverseFoldBit = 1 << 7
+	isMidBit       = 1 << 6
+
+	exceptionBit     = 1 << 3
+	exceptionShift   = 4
+	numExceptionBits = 12
+
+	xorIndexBit = 1 << 6
+	xorShift    = 8
+
+	// There is no mapping if all xor bits and the exception bit are zero.
+	hasMappingMask = 0xff80 | exceptionBit
+)
+
+// The case mode bits encodes the case type of a rune. This includes uncased,
+// title, upper and lower case and case ignorable. (For a definition of these
+// terms see Chapter 3 of The Unicode Standard Core Specification.) In some rare
+// cases, a rune can be both cased and case-ignorable. This is encoded by
+// cIgnorableCased. A rune of this type is always lower case. Some runes are
+// cased while not having a mapping.
+//
+// A common pattern for scripts in the Unicode standard is for upper and lower
+// case runes to alternate for increasing rune values (e.g. the accented Latin
+// ranges starting from U+0100 and U+1E00 among others and some Cyrillic
+// characters). We use this property by defining a cXORCase mode, where the case
+// mode (always upper or lower case) is derived from the rune value. As the XOR
+// pattern for case mappings is often identical for successive runes, using
+// cXORCase can result in large series of identical trie values. This, in turn,
+// allows us to better compress the trie blocks.
+const (
+	cUncased          info = iota // 000
+	cTitle                        // 001
+	cLower                        // 010
+	cUpper                        // 011
+	cIgnorableUncased             // 100
+	cIgnorableCased               // 101 // lower case if mappings exist
+	cXORCase                      // 11x // case is cLower | ((rune&1) ^ x)
+
+	maxCaseMode = cUpper
+)
+
+func (c info) isCased() bool {
+	return c&casedMask != 0
+}
+
+func (c info) isCaseIgnorable() bool {
+	return c&ignorableMask == ignorableValue
+}
+
+func (c info) isNotCasedAndNotCaseIgnorable() bool {
+	return c&fullCasedMask == 0
+}
+
+func (c info) isCaseIgnorableAndNotCased() bool {
+	return c&fullCasedMask == cIgnorableUncased
+}
+
+func (c info) isMid() bool {
+	return c&(fullCasedMask|isMidBit) == isMidBit|cIgnorableUncased
+}
+
+// The case mapping implementation will need to know about various Canonical
+// Combining Class (CCC) values. We encode two of these in the trie value:
+// cccZero (0) and cccAbove (230). If the value is cccOther, it means that
+// CCC(r) > 0, but not 230. A value of cccBreak means that CCC(r) == 0 and that
+// the rune also has the break category Break (see below).
+const (
+	cccBreak info = iota << 4
+	cccZero
+	cccAbove
+	cccOther
+
+	cccMask = cccBreak | cccZero | cccAbove | cccOther
+)
+
+const (
+	starter       = 0
+	above         = 230
+	iotaSubscript = 240
+)
+
+// The exceptions slice holds data that does not fit in a normal info entry.
+// The entry is pointed to by the exception index in an entry. It has the
+// following format:
+//
+// Header:
+//
+//	byte 0:
+//	 7..6  unused
+//	 5..4  CCC type (same bits as entry)
+//	    3  unused
+//	 2..0  length of fold
+//
+//	byte 1:
+//	  7..6  unused
+//	  5..3  length of 1st mapping of case type
+//	  2..0  length of 2nd mapping of case type
+//
+//	  case     1st    2nd
+//	  lower -> upper, title
+//	  upper -> lower, title
+//	  title -> lower, upper
+//
+// Lengths with the value 0x7 indicate no value and implies no change.
+// A length of 0 indicates a mapping to zero-length string.
+//
+// Body bytes:
+//
+//	case folding bytes
+//	lowercase mapping bytes
+//	uppercase mapping bytes
+//	titlecase mapping bytes
+//	closure mapping bytes (for NFKC_Casefold). (TODO)
+//
+// Fallbacks:
+//
+//	missing fold  -> lower
+//	missing title -> upper
+//	all missing   -> original rune
+//
+// exceptions starts with a dummy byte to enforce that there is no zero index
+// value.
+const (
+	lengthMask = 0x07
+	lengthBits = 3
+	noChange   = 0
+)
+
+// References to generated trie.
+
+var trie = newCaseTrie(0)
+
+var sparse = sparseBlocks{
+	values:  sparseValues[:],
+	offsets: sparseOffsets[:],
+}
+
+// Sparse block lookup code.
+
+// valueRange is an entry in a sparse block.
+type valueRange struct {
+	value  uint16
+	lo, hi byte
+}
+
+type sparseBlocks struct {
+	values  []valueRange
+	offsets []uint16
+}
+
+// lookup returns the value from values block n for byte b using binary search.
+func (s *sparseBlocks) lookup(n uint32, b byte) uint16 {
+	lo := s.offsets[n]
+	hi := s.offsets[n+1]
+	for lo < hi {
+		m := lo + (hi-lo)/2
+		r := s.values[m]
+		if r.lo <= b && b <= r.hi {
+			return r.value
+		}
+		if b < r.lo {
+			hi = m
+		} else {
+			lo = m + 1
+		}
+	}
+	return 0
+}
+
+// lastRuneForTesting is the last rune used for testing. Everything after this
+// is boring.
+const lastRuneForTesting = rune(0x1FFFF)

vendor/golang.org/x/text/internal/internal.go

@@ -0,0 +1,49 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package internal contains non-exported functionality that are used by
+// packages in the text repository.
+package internal // import "golang.org/x/text/internal"
+
+import (
+	"sort"
+
+	"golang.org/x/text/language"
+)
+
+// SortTags sorts tags in place.
+func SortTags(tags []language.Tag) {
+	sort.Sort(sorter(tags))
+}
+
+type sorter []language.Tag
+
+func (s sorter) Len() int {
+	return len(s)
+}
+
+func (s sorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s sorter) Less(i, j int) bool {
+	return s[i].String() < s[j].String()
+}
+
+// UniqueTags sorts and filters duplicate tags in place and returns a slice with
+// only unique tags.
+func UniqueTags(tags []language.Tag) []language.Tag {
+	if len(tags) <= 1 {
+		return tags
+	}
+	SortTags(tags)
+	k := 0
+	for i := 1; i < len(tags); i++ {
+		if tags[k].String() < tags[i].String() {
+			k++
+			tags[k] = tags[i]
+		}
+	}
+	return tags[:k+1]
+}

vendor/golang.org/x/text/internal/language/common.go

@@ -0,0 +1,16 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package language
+
+// This file contains code common to the maketables.go and the package code.
+
+// AliasType is the type of an alias in AliasMap.
+type AliasType int8
+
+const (
+	Deprecated AliasType = iota
+	Macro
+	Legacy
+
+	AliasTypeUnknown AliasType = -1
+)

vendor/golang.org/x/text/internal/language/compact.go

@@ -0,0 +1,29 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+// CompactCoreInfo is a compact integer with the three core tags encoded.
+type CompactCoreInfo uint32
+
+// GetCompactCore generates a uint32 value that is guaranteed to be unique for
+// different language, region, and script values.
+func GetCompactCore(t Tag) (cci CompactCoreInfo, ok bool) {
+	if t.LangID > langNoIndexOffset {
+		return 0, false
+	}
+	cci |= CompactCoreInfo(t.LangID) << (8 + 12)
+	cci |= CompactCoreInfo(t.ScriptID) << 12
+	cci |= CompactCoreInfo(t.RegionID)
+	return cci, true
+}
+
+// Tag generates a tag from c.
+func (c CompactCoreInfo) Tag() Tag {
+	return Tag{
+		LangID:   Language(c >> 20),
+		RegionID: Region(c & 0x3ff),
+		ScriptID: Script(c>>12) & 0xff,
+	}
+}

vendor/golang.org/x/text/internal/language/compact/compact.go

@@ -0,0 +1,61 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package compact defines a compact representation of language tags.
+//
+// Common language tags (at least all for which locale information is defined
+// in CLDR) are assigned a unique index. Each Tag is associated with such an
+// ID for selecting language-related resources (such as translations) as well
+// as one for selecting regional defaults (currency, number formatting, etc.)
+//
+// It may want to export this functionality at some point, but at this point
+// this is only available for use within x/text.
+package compact // import "golang.org/x/text/internal/language/compact"
+
+import (
+	"sort"
+	"strings"
+
+	"golang.org/x/text/internal/language"
+)
+
+// ID is an integer identifying a single tag.
+type ID uint16
+
+func getCoreIndex(t language.Tag) (id ID, ok bool) {
+	cci, ok := language.GetCompactCore(t)
+	if !ok {
+		return 0, false
+	}
+	i := sort.Search(len(coreTags), func(i int) bool {
+		return cci <= coreTags[i]
+	})
+	if i == len(coreTags) || coreTags[i] != cci {
+		return 0, false
+	}
+	return ID(i), true
+}
+
+// Parent returns the ID of the parent or the root ID if id is already the root.
+func (id ID) Parent() ID {
+	return parents[id]
+}
+
+// Tag converts id to an internal language Tag.
+func (id ID) Tag() language.Tag {
+	if int(id) >= len(coreTags) {
+		return specialTags[int(id)-len(coreTags)]
+	}
+	return coreTags[id].Tag()
+}
+
+var specialTags []language.Tag
+
+func init() {
+	tags := strings.Split(specialTagsStr, " ")
+	specialTags = make([]language.Tag, len(tags))
+	for i, t := range tags {
+		specialTags[i] = language.MustParse(t)
+	}
+}

vendor/golang.org/x/text/internal/language/compact/language.go

@@ -0,0 +1,260 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run gen.go gen_index.go -output tables.go
+//go:generate go run gen_parents.go
+
+package compact
+
+// TODO: Remove above NOTE after:
+// - verifying that tables are dropped correctly (most notably matcher tables).
+
+import (
+	"strings"
+
+	"golang.org/x/text/internal/language"
+)
+
+// Tag represents a BCP 47 language tag. It is used to specify an instance of a
+// specific language or locale. All language tag values are guaranteed to be
+// well-formed.
+type Tag struct {
+	// NOTE: exported tags will become part of the public API.
+	language ID
+	locale   ID
+	full     fullTag // always a language.Tag for now.
+}
+
+const _und = 0
+
+type fullTag interface {
+	IsRoot() bool
+	Parent() language.Tag
+}
+
+// Make a compact Tag from a fully specified internal language Tag.
+func Make(t language.Tag) (tag Tag) {
+	if region := t.TypeForKey("rg"); len(region) == 6 && region[2:] == "zzzz" {
+		if r, err := language.ParseRegion(region[:2]); err == nil {
+			tFull := t
+			t, _ = t.SetTypeForKey("rg", "")
+			// TODO: should we not consider "va" for the language tag?
+			var exact1, exact2 bool
+			tag.language, exact1 = FromTag(t)
+			t.RegionID = r
+			tag.locale, exact2 = FromTag(t)
+			if !exact1 || !exact2 {
+				tag.full = tFull
+			}
+			return tag
+		}
+	}
+	lang, ok := FromTag(t)
+	tag.language = lang
+	tag.locale = lang
+	if !ok {
+		tag.full = t
+	}
+	return tag
+}
+
+// Tag returns an internal language Tag version of this tag.
+func (t Tag) Tag() language.Tag {
+	if t.full != nil {
+		return t.full.(language.Tag)
+	}
+	tag := t.language.Tag()
+	if t.language != t.locale {
+		loc := t.locale.Tag()
+		tag, _ = tag.SetTypeForKey("rg", strings.ToLower(loc.RegionID.String())+"zzzz")
+	}
+	return tag
+}
+
+// IsCompact reports whether this tag is fully defined in terms of ID.
+func (t *Tag) IsCompact() bool {
+	return t.full == nil
+}
+
+// MayHaveVariants reports whether a tag may have variants. If it returns false
+// it is guaranteed the tag does not have variants.
+func (t Tag) MayHaveVariants() bool {
+	return t.full != nil || int(t.language) >= len(coreTags)
+}
+
+// MayHaveExtensions reports whether a tag may have extensions. If it returns
+// false it is guaranteed the tag does not have them.
+func (t Tag) MayHaveExtensions() bool {
+	return t.full != nil ||
+		int(t.language) >= len(coreTags) ||
+		t.language != t.locale
+}
+
+// IsRoot returns true if t is equal to language "und".
+func (t Tag) IsRoot() bool {
+	if t.full != nil {
+		return t.full.IsRoot()
+	}
+	return t.language == _und
+}
+
+// Parent returns the CLDR parent of t. In CLDR, missing fields in data for a
+// specific language are substituted with fields from the parent language.
+// The parent for a language may change for newer versions of CLDR.
+func (t Tag) Parent() Tag {
+	if t.full != nil {
+		return Make(t.full.Parent())
+	}
+	if t.language != t.locale {
+		// Simulate stripping -u-rg-xxxxxx
+		return Tag{language: t.language, locale: t.language}
+	}
+	// TODO: use parent lookup table once cycle from internal package is
+	// removed. Probably by internalizing the table and declaring this fast
+	// enough.
+	// lang := compactID(internal.Parent(uint16(t.language)))
+	lang, _ := FromTag(t.language.Tag().Parent())
+	return Tag{language: lang, locale: lang}
+}
+
+// nextToken returns token t and the rest of the string.
+func nextToken(s string) (t, tail string) {
+	p := strings.Index(s[1:], "-")
+	if p == -1 {
+		return s[1:], ""
+	}
+	p++
+	return s[1:p], s[p:]
+}
+
+// LanguageID returns an index, where 0 <= index < NumCompactTags, for tags
+// for which data exists in the text repository.The index will change over time
+// and should not be stored in persistent storage. If t does not match a compact
+// index, exact will be false and the compact index will be returned for the
+// first match after repeatedly taking the Parent of t.
+func LanguageID(t Tag) (id ID, exact bool) {
+	return t.language, t.full == nil
+}
+
+// RegionalID returns the ID for the regional variant of this tag. This index is
+// used to indicate region-specific overrides, such as default currency, default
+// calendar and week data, default time cycle, and default measurement system
+// and unit preferences.
+//
+// For instance, the tag en-GB-u-rg-uszzzz specifies British English with US
+// settings for currency, number formatting, etc. The CompactIndex for this tag
+// will be that for en-GB, while the RegionalID will be the one corresponding to
+// en-US.
+func RegionalID(t Tag) (id ID, exact bool) {
+	return t.locale, t.full == nil
+}
+
+// LanguageTag returns t stripped of regional variant indicators.
+//
+// At the moment this means it is stripped of a regional and variant subtag "rg"
+// and "va" in the "u" extension.
+func (t Tag) LanguageTag() Tag {
+	if t.full == nil {
+		return Tag{language: t.language, locale: t.language}
+	}
+	tt := t.Tag()
+	tt.SetTypeForKey("rg", "")
+	tt.SetTypeForKey("va", "")
+	return Make(tt)
+}
+
+// RegionalTag returns the regional variant of the tag.
+//
+// At the moment this means that the region is set from the regional subtag
+// "rg" in the "u" extension.
+func (t Tag) RegionalTag() Tag {
+	rt := Tag{language: t.locale, locale: t.locale}
+	if t.full == nil {
+		return rt
+	}
+	b := language.Builder{}
+	tag := t.Tag()
+	// tag, _ = tag.SetTypeForKey("rg", "")
+	b.SetTag(t.locale.Tag())
+	if v := tag.Variants(); v != "" {
+		for _, v := range strings.Split(v, "-") {
+			b.AddVariant(v)
+		}
+	}
+	for _, e := range tag.Extensions() {
+		b.AddExt(e)
+	}
+	return t
+}
+
+// FromTag reports closest matching ID for an internal language Tag.
+func FromTag(t language.Tag) (id ID, exact bool) {
+	// TODO: perhaps give more frequent tags a lower index.
+	// TODO: we could make the indexes stable. This will excluded some
+	//       possibilities for optimization, so don't do this quite yet.
+	exact = true
+
+	b, s, r := t.Raw()
+	if t.HasString() {
+		if t.IsPrivateUse() {
+			// We have no entries for user-defined tags.
+			return 0, false
+		}
+		hasExtra := false
+		if t.HasVariants() {
+			if t.HasExtensions() {
+				build := language.Builder{}
+				build.SetTag(language.Tag{LangID: b, ScriptID: s, RegionID: r})
+				build.AddVariant(t.Variants())
+				exact = false
+				t = build.Make()
+			}
+			hasExtra = true
+		} else if _, ok := t.Extension('u'); ok {
+			// TODO: va may mean something else. Consider not considering it.
+			// Strip all but the 'va' entry.
+			old := t
+			variant := t.TypeForKey("va")
+			t = language.Tag{LangID: b, ScriptID: s, RegionID: r}
+			if variant != "" {
+				t, _ = t.SetTypeForKey("va", variant)
+				hasExtra = true
+			}
+			exact = old == t
+		} else {
+			exact = false
+		}
+		if hasExtra {
+			// We have some variants.
+			for i, s := range specialTags {
+				if s == t {
+					return ID(i + len(coreTags)), exact
+				}
+			}
+			exact = false
+		}
+	}
+	if x, ok := getCoreIndex(t); ok {
+		return x, exact
+	}
+	exact = false
+	if r != 0 && s == 0 {
+		// Deal with cases where an extra script is inserted for the region.
+		t, _ := t.Maximize()
+		if x, ok := getCoreIndex(t); ok {
+			return x, exact
+		}
+	}
+	for t = t.Parent(); t != root; t = t.Parent() {
+		// No variants specified: just compare core components.
+		// The key has the form lllssrrr, where l, s, and r are nibbles for
+		// respectively the langID, scriptID, and regionID.
+		if x, ok := getCoreIndex(t); ok {
+			return x, exact
+		}
+	}
+	return 0, exact
+}
+
+var root = language.Tag{}

vendor/golang.org/x/text/internal/language/compact/parents.go

@@ -0,0 +1,120 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package compact
+
+// parents maps a compact index of a tag to the compact index of the parent of
+// this tag.
+var parents = []ID{ // 775 elements
+	// Entry 0 - 3F
+	0x0000, 0x0000, 0x0001, 0x0001, 0x0000, 0x0004, 0x0000, 0x0006,
+	0x0000, 0x0008, 0x0000, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a,
+	0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a,
+	0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a,
+	0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x000a, 0x0000,
+	0x0000, 0x0028, 0x0000, 0x002a, 0x0000, 0x002c, 0x0000, 0x0000,
+	0x002f, 0x002e, 0x002e, 0x0000, 0x0033, 0x0000, 0x0035, 0x0000,
+	0x0037, 0x0000, 0x0039, 0x0000, 0x003b, 0x0000, 0x0000, 0x003e,
+	// Entry 40 - 7F
+	0x0000, 0x0040, 0x0040, 0x0000, 0x0043, 0x0043, 0x0000, 0x0046,
+	0x0000, 0x0048, 0x0000, 0x0000, 0x004b, 0x004a, 0x004a, 0x0000,
+	0x004f, 0x004f, 0x004f, 0x004f, 0x0000, 0x0054, 0x0054, 0x0000,
+	0x0057, 0x0000, 0x0059, 0x0000, 0x005b, 0x0000, 0x005d, 0x005d,
+	0x0000, 0x0060, 0x0000, 0x0062, 0x0000, 0x0064, 0x0000, 0x0066,
+	0x0066, 0x0000, 0x0069, 0x0000, 0x006b, 0x006b, 0x006b, 0x006b,
+	0x006b, 0x006b, 0x006b, 0x0000, 0x0073, 0x0000, 0x0075, 0x0000,
+	0x0077, 0x0000, 0x0000, 0x007a, 0x0000, 0x007c, 0x0000, 0x007e,
+	// Entry 80 - BF
+	0x0000, 0x0080, 0x0080, 0x0000, 0x0083, 0x0083, 0x0000, 0x0086,
+	0x0087, 0x0087, 0x0087, 0x0086, 0x0088, 0x0087, 0x0087, 0x0087,
+	0x0086, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0088,
+	0x0087, 0x0087, 0x0087, 0x0087, 0x0088, 0x0087, 0x0088, 0x0087,
+	0x0087, 0x0088, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0087, 0x0087, 0x0087, 0x0086, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0086, 0x0087, 0x0086,
+	// Entry C0 - FF
+	0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0088, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0086, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0088, 0x0087,
+	0x0087, 0x0088, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087,
+	0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0086, 0x0086, 0x0087,
+	0x0087, 0x0086, 0x0087, 0x0087, 0x0087, 0x0087, 0x0087, 0x0000,
+	0x00ef, 0x0000, 0x00f1, 0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x00f2,
+	0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x00f1, 0x00f2, 0x00f1, 0x00f1,
+	// Entry 100 - 13F
+	0x00f2, 0x00f2, 0x00f1, 0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x00f1,
+	0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x00f2, 0x0000, 0x010e,
+	0x0000, 0x0110, 0x0000, 0x0112, 0x0000, 0x0114, 0x0114, 0x0000,
+	0x0117, 0x0117, 0x0117, 0x0117, 0x0000, 0x011c, 0x0000, 0x011e,
+	0x0000, 0x0120, 0x0120, 0x0000, 0x0123, 0x0123, 0x0123, 0x0123,
+	0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123,
+	0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123,
+	0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123,
+	// Entry 140 - 17F
+	0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123,
+	0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123, 0x0123,
+	0x0123, 0x0123, 0x0000, 0x0152, 0x0000, 0x0154, 0x0000, 0x0156,
+	0x0000, 0x0158, 0x0000, 0x015a, 0x0000, 0x015c, 0x015c, 0x015c,
+	0x0000, 0x0160, 0x0000, 0x0000, 0x0163, 0x0000, 0x0165, 0x0000,
+	0x0167, 0x0167, 0x0167, 0x0000, 0x016b, 0x0000, 0x016d, 0x0000,
+	0x016f, 0x0000, 0x0171, 0x0171, 0x0000, 0x0174, 0x0000, 0x0176,
+	0x0000, 0x0178, 0x0000, 0x017a, 0x0000, 0x017c, 0x0000, 0x017e,
+	// Entry 180 - 1BF
+	0x0000, 0x0000, 0x0000, 0x0182, 0x0000, 0x0184, 0x0184, 0x0184,
+	0x0184, 0x0000, 0x0000, 0x0000, 0x018b, 0x0000, 0x0000, 0x018e,
+	0x0000, 0x0000, 0x0191, 0x0000, 0x0000, 0x0000, 0x0195, 0x0000,
+	0x0197, 0x0000, 0x0000, 0x019a, 0x0000, 0x0000, 0x019d, 0x0000,
+	0x019f, 0x0000, 0x01a1, 0x0000, 0x01a3, 0x0000, 0x01a5, 0x0000,
+	0x01a7, 0x0000, 0x01a9, 0x0000, 0x01ab, 0x0000, 0x01ad, 0x0000,
+	0x01af, 0x0000, 0x01b1, 0x01b1, 0x0000, 0x01b4, 0x0000, 0x01b6,
+	0x0000, 0x01b8, 0x0000, 0x01ba, 0x0000, 0x01bc, 0x0000, 0x0000,
+	// Entry 1C0 - 1FF
+	0x01bf, 0x0000, 0x01c1, 0x0000, 0x01c3, 0x0000, 0x01c5, 0x0000,
+	0x01c7, 0x0000, 0x01c9, 0x0000, 0x01cb, 0x01cb, 0x01cb, 0x01cb,
+	0x0000, 0x01d0, 0x0000, 0x01d2, 0x01d2, 0x0000, 0x01d5, 0x0000,
+	0x01d7, 0x0000, 0x01d9, 0x0000, 0x01db, 0x0000, 0x01dd, 0x0000,
+	0x01df, 0x01df, 0x0000, 0x01e2, 0x0000, 0x01e4, 0x0000, 0x01e6,
+	0x0000, 0x01e8, 0x0000, 0x01ea, 0x0000, 0x01ec, 0x0000, 0x01ee,
+	0x0000, 0x01f0, 0x0000, 0x0000, 0x01f3, 0x0000, 0x01f5, 0x01f5,
+	0x01f5, 0x0000, 0x01f9, 0x0000, 0x01fb, 0x0000, 0x01fd, 0x0000,
+	// Entry 200 - 23F
+	0x01ff, 0x0000, 0x0000, 0x0202, 0x0000, 0x0204, 0x0204, 0x0000,
+	0x0207, 0x0000, 0x0209, 0x0209, 0x0000, 0x020c, 0x020c, 0x0000,
+	0x020f, 0x020f, 0x020f, 0x020f, 0x020f, 0x020f, 0x020f, 0x0000,
+	0x0217, 0x0000, 0x0219, 0x0000, 0x021b, 0x0000, 0x0000, 0x0000,
+	0x0000, 0x0000, 0x0221, 0x0000, 0x0000, 0x0224, 0x0000, 0x0226,
+	0x0226, 0x0000, 0x0229, 0x0000, 0x022b, 0x022b, 0x0000, 0x0000,
+	0x022f, 0x022e, 0x022e, 0x0000, 0x0000, 0x0234, 0x0000, 0x0236,
+	0x0000, 0x0238, 0x0000, 0x0244, 0x023a, 0x0244, 0x0244, 0x0244,
+	// Entry 240 - 27F
+	0x0244, 0x0244, 0x0244, 0x0244, 0x023a, 0x0244, 0x0244, 0x0000,
+	0x0247, 0x0247, 0x0247, 0x0000, 0x024b, 0x0000, 0x024d, 0x0000,
+	0x024f, 0x024f, 0x0000, 0x0252, 0x0000, 0x0254, 0x0254, 0x0254,
+	0x0254, 0x0254, 0x0254, 0x0000, 0x025b, 0x0000, 0x025d, 0x0000,
+	0x025f, 0x0000, 0x0261, 0x0000, 0x0263, 0x0000, 0x0265, 0x0000,
+	0x0000, 0x0268, 0x0268, 0x0268, 0x0000, 0x026c, 0x0000, 0x026e,
+	0x0000, 0x0270, 0x0000, 0x0000, 0x0000, 0x0274, 0x0273, 0x0273,
+	0x0000, 0x0278, 0x0000, 0x027a, 0x0000, 0x027c, 0x0000, 0x0000,
+	// Entry 280 - 2BF
+	0x0000, 0x0000, 0x0281, 0x0000, 0x0000, 0x0284, 0x0000, 0x0286,
+	0x0286, 0x0286, 0x0286, 0x0000, 0x028b, 0x028b, 0x028b, 0x0000,
+	0x028f, 0x028f, 0x028f, 0x028f, 0x028f, 0x0000, 0x0295, 0x0295,
+	0x0295, 0x0295, 0x0000, 0x0000, 0x0000, 0x0000, 0x029d, 0x029d,
+	0x029d, 0x0000, 0x02a1, 0x02a1, 0x02a1, 0x02a1, 0x0000, 0x0000,
+	0x02a7, 0x02a7, 0x02a7, 0x02a7, 0x0000, 0x02ac, 0x0000, 0x02ae,
+	0x02ae, 0x0000, 0x02b1, 0x0000, 0x02b3, 0x0000, 0x02b5, 0x02b5,
+	0x0000, 0x0000, 0x02b9, 0x0000, 0x0000, 0x0000, 0x02bd, 0x0000,
+	// Entry 2C0 - 2FF
+	0x02bf, 0x02bf, 0x0000, 0x0000, 0x02c3, 0x0000, 0x02c5, 0x0000,
+	0x02c7, 0x0000, 0x02c9, 0x0000, 0x02cb, 0x0000, 0x02cd, 0x02cd,
+	0x0000, 0x0000, 0x02d1, 0x0000, 0x02d3, 0x02d0, 0x02d0, 0x0000,
+	0x0000, 0x02d8, 0x02d7, 0x02d7, 0x0000, 0x0000, 0x02dd, 0x0000,
+	0x02df, 0x0000, 0x02e1, 0x0000, 0x0000, 0x02e4, 0x0000, 0x02e6,
+	0x0000, 0x0000, 0x02e9, 0x0000, 0x02eb, 0x0000, 0x02ed, 0x0000,
+	0x02ef, 0x02ef, 0x0000, 0x0000, 0x02f3, 0x02f2, 0x02f2, 0x0000,
+	0x02f7, 0x0000, 0x02f9, 0x02f9, 0x02f9, 0x02f9, 0x02f9, 0x0000,
+	// Entry 300 - 33F
+	0x02ff, 0x0300, 0x02ff, 0x0000, 0x0303, 0x0051, 0x00e6,
+} // Size: 1574 bytes
+
+// Total table size 1574 bytes (1KiB); checksum: 895AAF0B

vendor/golang.org/x/text/internal/language/compact/tags.go

@@ -0,0 +1,91 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package compact
+
+var (
+	und = Tag{}
+
+	Und Tag = Tag{}
+
+	Afrikaans            Tag = Tag{language: afIndex, locale: afIndex}
+	Amharic              Tag = Tag{language: amIndex, locale: amIndex}
+	Arabic               Tag = Tag{language: arIndex, locale: arIndex}
+	ModernStandardArabic Tag = Tag{language: ar001Index, locale: ar001Index}
+	Azerbaijani          Tag = Tag{language: azIndex, locale: azIndex}
+	Bulgarian            Tag = Tag{language: bgIndex, locale: bgIndex}
+	Bengali              Tag = Tag{language: bnIndex, locale: bnIndex}
+	Catalan              Tag = Tag{language: caIndex, locale: caIndex}
+	Czech                Tag = Tag{language: csIndex, locale: csIndex}
+	Danish               Tag = Tag{language: daIndex, locale: daIndex}
+	German               Tag = Tag{language: deIndex, locale: deIndex}
+	Greek                Tag = Tag{language: elIndex, locale: elIndex}
+	English              Tag = Tag{language: enIndex, locale: enIndex}
+	AmericanEnglish      Tag = Tag{language: enUSIndex, locale: enUSIndex}
+	BritishEnglish       Tag = Tag{language: enGBIndex, locale: enGBIndex}
+	Spanish              Tag = Tag{language: esIndex, locale: esIndex}
+	EuropeanSpanish      Tag = Tag{language: esESIndex, locale: esESIndex}
+	LatinAmericanSpanish Tag = Tag{language: es419Index, locale: es419Index}
+	Estonian             Tag = Tag{language: etIndex, locale: etIndex}
+	Persian              Tag = Tag{language: faIndex, locale: faIndex}
+	Finnish              Tag = Tag{language: fiIndex, locale: fiIndex}
+	Filipino             Tag = Tag{language: filIndex, locale: filIndex}
+	French               Tag = Tag{language: frIndex, locale: frIndex}
+	CanadianFrench       Tag = Tag{language: frCAIndex, locale: frCAIndex}
+	Gujarati             Tag = Tag{language: guIndex, locale: guIndex}
+	Hebrew               Tag = Tag{language: heIndex, locale: heIndex}
+	Hindi                Tag = Tag{language: hiIndex, locale: hiIndex}
+	Croatian             Tag = Tag{language: hrIndex, locale: hrIndex}
+	Hungarian            Tag = Tag{language: huIndex, locale: huIndex}
+	Armenian             Tag = Tag{language: hyIndex, locale: hyIndex}
+	Indonesian           Tag = Tag{language: idIndex, locale: idIndex}
+	Icelandic            Tag = Tag{language: isIndex, locale: isIndex}
+	Italian              Tag = Tag{language: itIndex, locale: itIndex}
+	Japanese             Tag = Tag{language: jaIndex, locale: jaIndex}
+	Georgian             Tag = Tag{language: kaIndex, locale: kaIndex}
+	Kazakh               Tag = Tag{language: kkIndex, locale: kkIndex}
+	Khmer                Tag = Tag{language: kmIndex, locale: kmIndex}
+	Kannada              Tag = Tag{language: knIndex, locale: knIndex}
+	Korean               Tag = Tag{language: koIndex, locale: koIndex}
+	Kirghiz              Tag = Tag{language: kyIndex, locale: kyIndex}
+	Lao                  Tag = Tag{language: loIndex, locale: loIndex}
+	Lithuanian           Tag = Tag{language: ltIndex, locale: ltIndex}
+	Latvian              Tag = Tag{language: lvIndex, locale: lvIndex}
+	Macedonian           Tag = Tag{language: mkIndex, locale: mkIndex}
+	Malayalam            Tag = Tag{language: mlIndex, locale: mlIndex}
+	Mongolian            Tag = Tag{language: mnIndex, locale: mnIndex}
+	Marathi              Tag = Tag{language: mrIndex, locale: mrIndex}
+	Malay                Tag = Tag{language: msIndex, locale: msIndex}
+	Burmese              Tag = Tag{language: myIndex, locale: myIndex}
+	Nepali               Tag = Tag{language: neIndex, locale: neIndex}
+	Dutch                Tag = Tag{language: nlIndex, locale: nlIndex}
+	Norwegian            Tag = Tag{language: noIndex, locale: noIndex}
+	Punjabi              Tag = Tag{language: paIndex, locale: paIndex}
+	Polish               Tag = Tag{language: plIndex, locale: plIndex}
+	Portuguese           Tag = Tag{language: ptIndex, locale: ptIndex}
+	BrazilianPortuguese  Tag = Tag{language: ptBRIndex, locale: ptBRIndex}
+	EuropeanPortuguese   Tag = Tag{language: ptPTIndex, locale: ptPTIndex}
+	Romanian             Tag = Tag{language: roIndex, locale: roIndex}
+	Russian              Tag = Tag{language: ruIndex, locale: ruIndex}
+	Sinhala              Tag = Tag{language: siIndex, locale: siIndex}
+	Slovak               Tag = Tag{language: skIndex, locale: skIndex}
+	Slovenian            Tag = Tag{language: slIndex, locale: slIndex}
+	Albanian             Tag = Tag{language: sqIndex, locale: sqIndex}
+	Serbian              Tag = Tag{language: srIndex, locale: srIndex}
+	SerbianLatin         Tag = Tag{language: srLatnIndex, locale: srLatnIndex}
+	Swedish              Tag = Tag{language: svIndex, locale: svIndex}
+	Swahili              Tag = Tag{language: swIndex, locale: swIndex}
+	Tamil                Tag = Tag{language: taIndex, locale: taIndex}
+	Telugu               Tag = Tag{language: teIndex, locale: teIndex}
+	Thai                 Tag = Tag{language: thIndex, locale: thIndex}
+	Turkish              Tag = Tag{language: trIndex, locale: trIndex}
+	Ukrainian            Tag = Tag{language: ukIndex, locale: ukIndex}
+	Urdu                 Tag = Tag{language: urIndex, locale: urIndex}
+	Uzbek                Tag = Tag{language: uzIndex, locale: uzIndex}
+	Vietnamese           Tag = Tag{language: viIndex, locale: viIndex}
+	Chinese              Tag = Tag{language: zhIndex, locale: zhIndex}
+	SimplifiedChinese    Tag = Tag{language: zhHansIndex, locale: zhHansIndex}
+	TraditionalChinese   Tag = Tag{language: zhHantIndex, locale: zhHantIndex}
+	Zulu                 Tag = Tag{language: zuIndex, locale: zuIndex}
+)

vendor/golang.org/x/text/internal/language/compose.go

@@ -0,0 +1,167 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"sort"
+	"strings"
+)
+
+// A Builder allows constructing a Tag from individual components.
+// Its main user is Compose in the top-level language package.
+type Builder struct {
+	Tag Tag
+
+	private    string // the x extension
+	variants   []string
+	extensions []string
+}
+
+// Make returns a new Tag from the current settings.
+func (b *Builder) Make() Tag {
+	t := b.Tag
+
+	if len(b.extensions) > 0 || len(b.variants) > 0 {
+		sort.Sort(sortVariants(b.variants))
+		sort.Strings(b.extensions)
+
+		if b.private != "" {
+			b.extensions = append(b.extensions, b.private)
+		}
+		n := maxCoreSize + tokenLen(b.variants...) + tokenLen(b.extensions...)
+		buf := make([]byte, n)
+		p := t.genCoreBytes(buf)
+		t.pVariant = byte(p)
+		p += appendTokens(buf[p:], b.variants...)
+		t.pExt = uint16(p)
+		p += appendTokens(buf[p:], b.extensions...)
+		t.str = string(buf[:p])
+		// We may not always need to remake the string, but when or when not
+		// to do so is rather tricky.
+		scan := makeScanner(buf[:p])
+		t, _ = parse(&scan, "")
+		return t
+
+	} else if b.private != "" {
+		t.str = b.private
+		t.RemakeString()
+	}
+	return t
+}
+
+// SetTag copies all the settings from a given Tag. Any previously set values
+// are discarded.
+func (b *Builder) SetTag(t Tag) {
+	b.Tag.LangID = t.LangID
+	b.Tag.RegionID = t.RegionID
+	b.Tag.ScriptID = t.ScriptID
+	// TODO: optimize
+	b.variants = b.variants[:0]
+	if variants := t.Variants(); variants != "" {
+		for _, vr := range strings.Split(variants[1:], "-") {
+			b.variants = append(b.variants, vr)
+		}
+	}
+	b.extensions, b.private = b.extensions[:0], ""
+	for _, e := range t.Extensions() {
+		b.AddExt(e)
+	}
+}
+
+// AddExt adds extension e to the tag. e must be a valid extension as returned
+// by Tag.Extension. If the extension already exists, it will be discarded,
+// except for a -u extension, where non-existing key-type pairs will added.
+func (b *Builder) AddExt(e string) {
+	if e[0] == 'x' {
+		if b.private == "" {
+			b.private = e
+		}
+		return
+	}
+	for i, s := range b.extensions {
+		if s[0] == e[0] {
+			if e[0] == 'u' {
+				b.extensions[i] += e[1:]
+			}
+			return
+		}
+	}
+	b.extensions = append(b.extensions, e)
+}
+
+// SetExt sets the extension e to the tag. e must be a valid extension as
+// returned by Tag.Extension. If the extension already exists, it will be
+// overwritten, except for a -u extension, where the individual key-type pairs
+// will be set.
+func (b *Builder) SetExt(e string) {
+	if e[0] == 'x' {
+		b.private = e
+		return
+	}
+	for i, s := range b.extensions {
+		if s[0] == e[0] {
+			if e[0] == 'u' {
+				b.extensions[i] = e + s[1:]
+			} else {
+				b.extensions[i] = e
+			}
+			return
+		}
+	}
+	b.extensions = append(b.extensions, e)
+}
+
+// AddVariant adds any number of variants.
+func (b *Builder) AddVariant(v ...string) {
+	for _, v := range v {
+		if v != "" {
+			b.variants = append(b.variants, v)
+		}
+	}
+}
+
+// ClearVariants removes any variants previously added, including those
+// copied from a Tag in SetTag.
+func (b *Builder) ClearVariants() {
+	b.variants = b.variants[:0]
+}
+
+// ClearExtensions removes any extensions previously added, including those
+// copied from a Tag in SetTag.
+func (b *Builder) ClearExtensions() {
+	b.private = ""
+	b.extensions = b.extensions[:0]
+}
+
+func tokenLen(token ...string) (n int) {
+	for _, t := range token {
+		n += len(t) + 1
+	}
+	return
+}
+
+func appendTokens(b []byte, token ...string) int {
+	p := 0
+	for _, t := range token {
+		b[p] = '-'
+		copy(b[p+1:], t)
+		p += 1 + len(t)
+	}
+	return p
+}
+
+type sortVariants []string
+
+func (s sortVariants) Len() int {
+	return len(s)
+}
+
+func (s sortVariants) Swap(i, j int) {
+	s[j], s[i] = s[i], s[j]
+}
+
+func (s sortVariants) Less(i, j int) bool {
+	return variantIndex[s[i]] < variantIndex[s[j]]
+}

vendor/golang.org/x/text/internal/language/coverage.go

@@ -0,0 +1,28 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+// BaseLanguages returns the list of all supported base languages. It generates
+// the list by traversing the internal structures.
+func BaseLanguages() []Language {
+	base := make([]Language, 0, NumLanguages)
+	for i := 0; i < langNoIndexOffset; i++ {
+		// We included "und" already for the value 0.
+		if i != nonCanonicalUnd {
+			base = append(base, Language(i))
+		}
+	}
+	i := langNoIndexOffset
+	for _, v := range langNoIndex {
+		for k := 0; k < 8; k++ {
+			if v&1 == 1 {
+				base = append(base, Language(i))
+			}
+			v >>= 1
+			i++
+		}
+	}
+	return base
+}

vendor/golang.org/x/text/internal/language/language.go

@@ -0,0 +1,627 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run gen.go gen_common.go -output tables.go
+
+package language // import "golang.org/x/text/internal/language"
+
+// TODO: Remove above NOTE after:
+// - verifying that tables are dropped correctly (most notably matcher tables).
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+const (
+	// maxCoreSize is the maximum size of a BCP 47 tag without variants and
+	// extensions. Equals max lang (3) + script (4) + max reg (3) + 2 dashes.
+	maxCoreSize = 12
+
+	// max99thPercentileSize is a somewhat arbitrary buffer size that presumably
+	// is large enough to hold at least 99% of the BCP 47 tags.
+	max99thPercentileSize = 32
+
+	// maxSimpleUExtensionSize is the maximum size of a -u extension with one
+	// key-type pair. Equals len("-u-") + key (2) + dash + max value (8).
+	maxSimpleUExtensionSize = 14
+)
+
+// Tag represents a BCP 47 language tag. It is used to specify an instance of a
+// specific language or locale. All language tag values are guaranteed to be
+// well-formed. The zero value of Tag is Und.
+type Tag struct {
+	// TODO: the following fields have the form TagTypeID. This name is chosen
+	// to allow refactoring the public package without conflicting with its
+	// Base, Script, and Region methods. Once the transition is fully completed
+	// the ID can be stripped from the name.
+
+	LangID   Language
+	RegionID Region
+	// TODO: we will soon run out of positions for ScriptID. Idea: instead of
+	// storing lang, region, and ScriptID codes, store only the compact index and
+	// have a lookup table from this code to its expansion. This greatly speeds
+	// up table lookup, speed up common variant cases.
+	// This will also immediately free up 3 extra bytes. Also, the pVariant
+	// field can now be moved to the lookup table, as the compact index uniquely
+	// determines the offset of a possible variant.
+	ScriptID Script
+	pVariant byte   // offset in str, includes preceding '-'
+	pExt     uint16 // offset of first extension, includes preceding '-'
+
+	// str is the string representation of the Tag. It will only be used if the
+	// tag has variants or extensions.
+	str string
+}
+
+// Make is a convenience wrapper for Parse that omits the error.
+// In case of an error, a sensible default is returned.
+func Make(s string) Tag {
+	t, _ := Parse(s)
+	return t
+}
+
+// Raw returns the raw base language, script and region, without making an
+// attempt to infer their values.
+// TODO: consider removing
+func (t Tag) Raw() (b Language, s Script, r Region) {
+	return t.LangID, t.ScriptID, t.RegionID
+}
+
+// equalTags compares language, script and region subtags only.
+func (t Tag) equalTags(a Tag) bool {
+	return t.LangID == a.LangID && t.ScriptID == a.ScriptID && t.RegionID == a.RegionID
+}
+
+// IsRoot returns true if t is equal to language "und".
+func (t Tag) IsRoot() bool {
+	if int(t.pVariant) < len(t.str) {
+		return false
+	}
+	return t.equalTags(Und)
+}
+
+// IsPrivateUse reports whether the Tag consists solely of an IsPrivateUse use
+// tag.
+func (t Tag) IsPrivateUse() bool {
+	return t.str != "" && t.pVariant == 0
+}
+
+// RemakeString is used to update t.str in case lang, script or region changed.
+// It is assumed that pExt and pVariant still point to the start of the
+// respective parts.
+func (t *Tag) RemakeString() {
+	if t.str == "" {
+		return
+	}
+	extra := t.str[t.pVariant:]
+	if t.pVariant > 0 {
+		extra = extra[1:]
+	}
+	if t.equalTags(Und) && strings.HasPrefix(extra, "x-") {
+		t.str = extra
+		t.pVariant = 0
+		t.pExt = 0
+		return
+	}
+	var buf [max99thPercentileSize]byte // avoid extra memory allocation in most cases.
+	b := buf[:t.genCoreBytes(buf[:])]
+	if extra != "" {
+		diff := len(b) - int(t.pVariant)
+		b = append(b, '-')
+		b = append(b, extra...)
+		t.pVariant = uint8(int(t.pVariant) + diff)
+		t.pExt = uint16(int(t.pExt) + diff)
+	} else {
+		t.pVariant = uint8(len(b))
+		t.pExt = uint16(len(b))
+	}
+	t.str = string(b)
+}
+
+// genCoreBytes writes a string for the base languages, script and region tags
+// to the given buffer and returns the number of bytes written. It will never
+// write more than maxCoreSize bytes.
+func (t *Tag) genCoreBytes(buf []byte) int {
+	n := t.LangID.StringToBuf(buf[:])
+	if t.ScriptID != 0 {
+		n += copy(buf[n:], "-")
+		n += copy(buf[n:], t.ScriptID.String())
+	}
+	if t.RegionID != 0 {
+		n += copy(buf[n:], "-")
+		n += copy(buf[n:], t.RegionID.String())
+	}
+	return n
+}
+
+// String returns the canonical string representation of the language tag.
+func (t Tag) String() string {
+	if t.str != "" {
+		return t.str
+	}
+	if t.ScriptID == 0 && t.RegionID == 0 {
+		return t.LangID.String()
+	}
+	buf := [maxCoreSize]byte{}
+	return string(buf[:t.genCoreBytes(buf[:])])
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (t Tag) MarshalText() (text []byte, err error) {
+	if t.str != "" {
+		text = append(text, t.str...)
+	} else if t.ScriptID == 0 && t.RegionID == 0 {
+		text = append(text, t.LangID.String()...)
+	} else {
+		buf := [maxCoreSize]byte{}
+		text = buf[:t.genCoreBytes(buf[:])]
+	}
+	return text, nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (t *Tag) UnmarshalText(text []byte) error {
+	tag, err := Parse(string(text))
+	*t = tag
+	return err
+}
+
+// Variants returns the part of the tag holding all variants or the empty string
+// if there are no variants defined.
+func (t Tag) Variants() string {
+	if t.pVariant == 0 {
+		return ""
+	}
+	return t.str[t.pVariant:t.pExt]
+}
+
+// VariantOrPrivateUseTags returns variants or private use tags.
+func (t Tag) VariantOrPrivateUseTags() string {
+	if t.pExt > 0 {
+		return t.str[t.pVariant:t.pExt]
+	}
+	return t.str[t.pVariant:]
+}
+
+// HasString reports whether this tag defines more than just the raw
+// components.
+func (t Tag) HasString() bool {
+	return t.str != ""
+}
+
+// Parent returns the CLDR parent of t. In CLDR, missing fields in data for a
+// specific language are substituted with fields from the parent language.
+// The parent for a language may change for newer versions of CLDR.
+func (t Tag) Parent() Tag {
+	if t.str != "" {
+		// Strip the variants and extensions.
+		b, s, r := t.Raw()
+		t = Tag{LangID: b, ScriptID: s, RegionID: r}
+		if t.RegionID == 0 && t.ScriptID != 0 && t.LangID != 0 {
+			base, _ := addTags(Tag{LangID: t.LangID})
+			if base.ScriptID == t.ScriptID {
+				return Tag{LangID: t.LangID}
+			}
+		}
+		return t
+	}
+	if t.LangID != 0 {
+		if t.RegionID != 0 {
+			maxScript := t.ScriptID
+			if maxScript == 0 {
+				max, _ := addTags(t)
+				maxScript = max.ScriptID
+			}
+
+			for i := range parents {
+				if Language(parents[i].lang) == t.LangID && Script(parents[i].maxScript) == maxScript {
+					for _, r := range parents[i].fromRegion {
+						if Region(r) == t.RegionID {
+							return Tag{
+								LangID:   t.LangID,
+								ScriptID: Script(parents[i].script),
+								RegionID: Region(parents[i].toRegion),
+							}
+						}
+					}
+				}
+			}
+
+			// Strip the script if it is the default one.
+			base, _ := addTags(Tag{LangID: t.LangID})
+			if base.ScriptID != maxScript {
+				return Tag{LangID: t.LangID, ScriptID: maxScript}
+			}
+			return Tag{LangID: t.LangID}
+		} else if t.ScriptID != 0 {
+			// The parent for an base-script pair with a non-default script is
+			// "und" instead of the base language.
+			base, _ := addTags(Tag{LangID: t.LangID})
+			if base.ScriptID != t.ScriptID {
+				return Und
+			}
+			return Tag{LangID: t.LangID}
+		}
+	}
+	return Und
+}
+
+// ParseExtension parses s as an extension and returns it on success.
+func ParseExtension(s string) (ext string, err error) {
+	defer func() {
+		if recover() != nil {
+			ext = ""
+			err = ErrSyntax
+		}
+	}()
+
+	scan := makeScannerString(s)
+	var end int
+	if n := len(scan.token); n != 1 {
+		return "", ErrSyntax
+	}
+	scan.toLower(0, len(scan.b))
+	end = parseExtension(&scan)
+	if end != len(s) {
+		return "", ErrSyntax
+	}
+	return string(scan.b), nil
+}
+
+// HasVariants reports whether t has variants.
+func (t Tag) HasVariants() bool {
+	return uint16(t.pVariant) < t.pExt
+}
+
+// HasExtensions reports whether t has extensions.
+func (t Tag) HasExtensions() bool {
+	return int(t.pExt) < len(t.str)
+}
+
+// Extension returns the extension of type x for tag t. It will return
+// false for ok if t does not have the requested extension. The returned
+// extension will be invalid in this case.
+func (t Tag) Extension(x byte) (ext string, ok bool) {
+	for i := int(t.pExt); i < len(t.str)-1; {
+		var ext string
+		i, ext = getExtension(t.str, i)
+		if ext[0] == x {
+			return ext, true
+		}
+	}
+	return "", false
+}
+
+// Extensions returns all extensions of t.
+func (t Tag) Extensions() []string {
+	e := []string{}
+	for i := int(t.pExt); i < len(t.str)-1; {
+		var ext string
+		i, ext = getExtension(t.str, i)
+		e = append(e, ext)
+	}
+	return e
+}
+
+// TypeForKey returns the type associated with the given key, where key and type
+// are of the allowed values defined for the Unicode locale extension ('u') in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// TypeForKey will traverse the inheritance chain to get the correct value.
+//
+// If there are multiple types associated with a key, only the first will be
+// returned. If there is no type associated with a key, it returns the empty
+// string.
+func (t Tag) TypeForKey(key string) string {
+	if _, start, end, _ := t.findTypeForKey(key); end != start {
+		s := t.str[start:end]
+		if p := strings.IndexByte(s, '-'); p >= 0 {
+			s = s[:p]
+		}
+		return s
+	}
+	return ""
+}
+
+var (
+	errPrivateUse       = errors.New("cannot set a key on a private use tag")
+	errInvalidArguments = errors.New("invalid key or type")
+)
+
+// SetTypeForKey returns a new Tag with the key set to type, where key and type
+// are of the allowed values defined for the Unicode locale extension ('u') in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// An empty value removes an existing pair with the same key.
+func (t Tag) SetTypeForKey(key, value string) (Tag, error) {
+	if t.IsPrivateUse() {
+		return t, errPrivateUse
+	}
+	if len(key) != 2 {
+		return t, errInvalidArguments
+	}
+
+	// Remove the setting if value is "".
+	if value == "" {
+		start, sep, end, _ := t.findTypeForKey(key)
+		if start != sep {
+			// Remove a possible empty extension.
+			switch {
+			case t.str[start-2] != '-': // has previous elements.
+			case end == len(t.str), // end of string
+				end+2 < len(t.str) && t.str[end+2] == '-': // end of extension
+				start -= 2
+			}
+			if start == int(t.pVariant) && end == len(t.str) {
+				t.str = ""
+				t.pVariant, t.pExt = 0, 0
+			} else {
+				t.str = fmt.Sprintf("%s%s", t.str[:start], t.str[end:])
+			}
+		}
+		return t, nil
+	}
+
+	if len(value) < 3 || len(value) > 8 {
+		return t, errInvalidArguments
+	}
+
+	var (
+		buf    [maxCoreSize + maxSimpleUExtensionSize]byte
+		uStart int // start of the -u extension.
+	)
+
+	// Generate the tag string if needed.
+	if t.str == "" {
+		uStart = t.genCoreBytes(buf[:])
+		buf[uStart] = '-'
+		uStart++
+	}
+
+	// Create new key-type pair and parse it to verify.
+	b := buf[uStart:]
+	copy(b, "u-")
+	copy(b[2:], key)
+	b[4] = '-'
+	b = b[:5+copy(b[5:], value)]
+	scan := makeScanner(b)
+	if parseExtensions(&scan); scan.err != nil {
+		return t, scan.err
+	}
+
+	// Assemble the replacement string.
+	if t.str == "" {
+		t.pVariant, t.pExt = byte(uStart-1), uint16(uStart-1)
+		t.str = string(buf[:uStart+len(b)])
+	} else {
+		s := t.str
+		start, sep, end, hasExt := t.findTypeForKey(key)
+		if start == sep {
+			if hasExt {
+				b = b[2:]
+			}
+			t.str = fmt.Sprintf("%s-%s%s", s[:sep], b, s[end:])
+		} else {
+			t.str = fmt.Sprintf("%s-%s%s", s[:start+3], value, s[end:])
+		}
+	}
+	return t, nil
+}
+
+// findTypeForKey returns the start and end position for the type corresponding
+// to key or the point at which to insert the key-value pair if the type
+// wasn't found. The hasExt return value reports whether an -u extension was present.
+// Note: the extensions are typically very small and are likely to contain
+// only one key-type pair.
+func (t Tag) findTypeForKey(key string) (start, sep, end int, hasExt bool) {
+	p := int(t.pExt)
+	if len(key) != 2 || p == len(t.str) || p == 0 {
+		return p, p, p, false
+	}
+	s := t.str
+
+	// Find the correct extension.
+	for p++; s[p] != 'u'; p++ {
+		if s[p] > 'u' {
+			p--
+			return p, p, p, false
+		}
+		if p = nextExtension(s, p); p == len(s) {
+			return len(s), len(s), len(s), false
+		}
+	}
+	// Proceed to the hyphen following the extension name.
+	p++
+
+	// curKey is the key currently being processed.
+	curKey := ""
+
+	// Iterate over keys until we get the end of a section.
+	for {
+		end = p
+		for p++; p < len(s) && s[p] != '-'; p++ {
+		}
+		n := p - end - 1
+		if n <= 2 && curKey == key {
+			if sep < end {
+				sep++
+			}
+			return start, sep, end, true
+		}
+		switch n {
+		case 0, // invalid string
+			1: // next extension
+			return end, end, end, true
+		case 2:
+			// next key
+			curKey = s[end+1 : p]
+			if curKey > key {
+				return end, end, end, true
+			}
+			start = end
+			sep = p
+		}
+	}
+}
+
+// ParseBase parses a 2- or 3-letter ISO 639 code.
+// It returns a ValueError if s is a well-formed but unknown language identifier
+// or another error if another error occurred.
+func ParseBase(s string) (l Language, err error) {
+	defer func() {
+		if recover() != nil {
+			l = 0
+			err = ErrSyntax
+		}
+	}()
+
+	if n := len(s); n < 2 || 3 < n {
+		return 0, ErrSyntax
+	}
+	var buf [3]byte
+	return getLangID(buf[:copy(buf[:], s)])
+}
+
+// ParseScript parses a 4-letter ISO 15924 code.
+// It returns a ValueError if s is a well-formed but unknown script identifier
+// or another error if another error occurred.
+func ParseScript(s string) (scr Script, err error) {
+	defer func() {
+		if recover() != nil {
+			scr = 0
+			err = ErrSyntax
+		}
+	}()
+
+	if len(s) != 4 {
+		return 0, ErrSyntax
+	}
+	var buf [4]byte
+	return getScriptID(script, buf[:copy(buf[:], s)])
+}
+
+// EncodeM49 returns the Region for the given UN M.49 code.
+// It returns an error if r is not a valid code.
+func EncodeM49(r int) (Region, error) {
+	return getRegionM49(r)
+}
+
+// ParseRegion parses a 2- or 3-letter ISO 3166-1 or a UN M.49 code.
+// It returns a ValueError if s is a well-formed but unknown region identifier
+// or another error if another error occurred.
+func ParseRegion(s string) (r Region, err error) {
+	defer func() {
+		if recover() != nil {
+			r = 0
+			err = ErrSyntax
+		}
+	}()
+
+	if n := len(s); n < 2 || 3 < n {
+		return 0, ErrSyntax
+	}
+	var buf [3]byte
+	return getRegionID(buf[:copy(buf[:], s)])
+}
+
+// IsCountry returns whether this region is a country or autonomous area. This
+// includes non-standard definitions from CLDR.
+func (r Region) IsCountry() bool {
+	if r == 0 || r.IsGroup() || r.IsPrivateUse() && r != _XK {
+		return false
+	}
+	return true
+}
+
+// IsGroup returns whether this region defines a collection of regions. This
+// includes non-standard definitions from CLDR.
+func (r Region) IsGroup() bool {
+	if r == 0 {
+		return false
+	}
+	return int(regionInclusion[r]) < len(regionContainment)
+}
+
+// Contains returns whether Region c is contained by Region r. It returns true
+// if c == r.
+func (r Region) Contains(c Region) bool {
+	if r == c {
+		return true
+	}
+	g := regionInclusion[r]
+	if g >= nRegionGroups {
+		return false
+	}
+	m := regionContainment[g]
+
+	d := regionInclusion[c]
+	b := regionInclusionBits[d]
+
+	// A contained country may belong to multiple disjoint groups. Matching any
+	// of these indicates containment. If the contained region is a group, it
+	// must strictly be a subset.
+	if d >= nRegionGroups {
+		return b&m != 0
+	}
+	return b&^m == 0
+}
+
+var errNoTLD = errors.New("language: region is not a valid ccTLD")
+
+// TLD returns the country code top-level domain (ccTLD). UK is returned for GB.
+// In all other cases it returns either the region itself or an error.
+//
+// This method may return an error for a region for which there exists a
+// canonical form with a ccTLD. To get that ccTLD canonicalize r first. The
+// region will already be canonicalized it was obtained from a Tag that was
+// obtained using any of the default methods.
+func (r Region) TLD() (Region, error) {
+	// See http://en.wikipedia.org/wiki/Country_code_top-level_domain for the
+	// difference between ISO 3166-1 and IANA ccTLD.
+	if r == _GB {
+		r = _UK
+	}
+	if (r.typ() & ccTLD) == 0 {
+		return 0, errNoTLD
+	}
+	return r, nil
+}
+
+// Canonicalize returns the region or a possible replacement if the region is
+// deprecated. It will not return a replacement for deprecated regions that
+// are split into multiple regions.
+func (r Region) Canonicalize() Region {
+	if cr := normRegion(r); cr != 0 {
+		return cr
+	}
+	return r
+}
+
+// Variant represents a registered variant of a language as defined by BCP 47.
+type Variant struct {
+	ID  uint8
+	str string
+}
+
+// ParseVariant parses and returns a Variant. An error is returned if s is not
+// a valid variant.
+func ParseVariant(s string) (v Variant, err error) {
+	defer func() {
+		if recover() != nil {
+			v = Variant{}
+			err = ErrSyntax
+		}
+	}()
+
+	s = strings.ToLower(s)
+	if id, ok := variantIndex[s]; ok {
+		return Variant{id, s}, nil
+	}
+	return Variant{}, NewValueError([]byte(s))
+}
+
+// String returns the string representation of the variant.
+func (v Variant) String() string {
+	return v.str
+}

vendor/golang.org/x/text/internal/language/lookup.go

@@ -0,0 +1,412 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+	"strconv"
+
+	"golang.org/x/text/internal/tag"
+)
+
+// findIndex tries to find the given tag in idx and returns a standardized error
+// if it could not be found.
+func findIndex(idx tag.Index, key []byte, form string) (index int, err error) {
+	if !tag.FixCase(form, key) {
+		return 0, ErrSyntax
+	}
+	i := idx.Index(key)
+	if i == -1 {
+		return 0, NewValueError(key)
+	}
+	return i, nil
+}
+
+func searchUint(imap []uint16, key uint16) int {
+	return sort.Search(len(imap), func(i int) bool {
+		return imap[i] >= key
+	})
+}
+
+type Language uint16
+
+// getLangID returns the langID of s if s is a canonical subtag
+// or langUnknown if s is not a canonical subtag.
+func getLangID(s []byte) (Language, error) {
+	if len(s) == 2 {
+		return getLangISO2(s)
+	}
+	return getLangISO3(s)
+}
+
+// TODO language normalization as well as the AliasMaps could be moved to the
+// higher level package, but it is a bit tricky to separate the generation.
+
+func (id Language) Canonicalize() (Language, AliasType) {
+	return normLang(id)
+}
+
+// normLang returns the mapped langID of id according to mapping m.
+func normLang(id Language) (Language, AliasType) {
+	k := sort.Search(len(AliasMap), func(i int) bool {
+		return AliasMap[i].From >= uint16(id)
+	})
+	if k < len(AliasMap) && AliasMap[k].From == uint16(id) {
+		return Language(AliasMap[k].To), AliasTypes[k]
+	}
+	return id, AliasTypeUnknown
+}
+
+// getLangISO2 returns the langID for the given 2-letter ISO language code
+// or unknownLang if this does not exist.
+func getLangISO2(s []byte) (Language, error) {
+	if !tag.FixCase("zz", s) {
+		return 0, ErrSyntax
+	}
+	if i := lang.Index(s); i != -1 && lang.Elem(i)[3] != 0 {
+		return Language(i), nil
+	}
+	return 0, NewValueError(s)
+}
+
+const base = 'z' - 'a' + 1
+
+func strToInt(s []byte) uint {
+	v := uint(0)
+	for i := 0; i < len(s); i++ {
+		v *= base
+		v += uint(s[i] - 'a')
+	}
+	return v
+}
+
+// converts the given integer to the original ASCII string passed to strToInt.
+// len(s) must match the number of characters obtained.
+func intToStr(v uint, s []byte) {
+	for i := len(s) - 1; i >= 0; i-- {
+		s[i] = byte(v%base) + 'a'
+		v /= base
+	}
+}
+
+// getLangISO3 returns the langID for the given 3-letter ISO language code
+// or unknownLang if this does not exist.
+func getLangISO3(s []byte) (Language, error) {
+	if tag.FixCase("und", s) {
+		// first try to match canonical 3-letter entries
+		for i := lang.Index(s[:2]); i != -1; i = lang.Next(s[:2], i) {
+			if e := lang.Elem(i); e[3] == 0 && e[2] == s[2] {
+				// We treat "und" as special and always translate it to "unspecified".
+				// Note that ZZ and Zzzz are private use and are not treated as
+				// unspecified by default.
+				id := Language(i)
+				if id == nonCanonicalUnd {
+					return 0, nil
+				}
+				return id, nil
+			}
+		}
+		if i := altLangISO3.Index(s); i != -1 {
+			return Language(altLangIndex[altLangISO3.Elem(i)[3]]), nil
+		}
+		n := strToInt(s)
+		if langNoIndex[n/8]&(1<<(n%8)) != 0 {
+			return Language(n) + langNoIndexOffset, nil
+		}
+		// Check for non-canonical uses of ISO3.
+		for i := lang.Index(s[:1]); i != -1; i = lang.Next(s[:1], i) {
+			if e := lang.Elem(i); e[2] == s[1] && e[3] == s[2] {
+				return Language(i), nil
+			}
+		}
+		return 0, NewValueError(s)
+	}
+	return 0, ErrSyntax
+}
+
+// StringToBuf writes the string to b and returns the number of bytes
+// written.  cap(b) must be >= 3.
+func (id Language) StringToBuf(b []byte) int {
+	if id >= langNoIndexOffset {
+		intToStr(uint(id)-langNoIndexOffset, b[:3])
+		return 3
+	} else if id == 0 {
+		return copy(b, "und")
+	}
+	l := lang[id<<2:]
+	if l[3] == 0 {
+		return copy(b, l[:3])
+	}
+	return copy(b, l[:2])
+}
+
+// String returns the BCP 47 representation of the langID.
+// Use b as variable name, instead of id, to ensure the variable
+// used is consistent with that of Base in which this type is embedded.
+func (b Language) String() string {
+	if b == 0 {
+		return "und"
+	} else if b >= langNoIndexOffset {
+		b -= langNoIndexOffset
+		buf := [3]byte{}
+		intToStr(uint(b), buf[:])
+		return string(buf[:])
+	}
+	l := lang.Elem(int(b))
+	if l[3] == 0 {
+		return l[:3]
+	}
+	return l[:2]
+}
+
+// ISO3 returns the ISO 639-3 language code.
+func (b Language) ISO3() string {
+	if b == 0 || b >= langNoIndexOffset {
+		return b.String()
+	}
+	l := lang.Elem(int(b))
+	if l[3] == 0 {
+		return l[:3]
+	} else if l[2] == 0 {
+		return altLangISO3.Elem(int(l[3]))[:3]
+	}
+	// This allocation will only happen for 3-letter ISO codes
+	// that are non-canonical BCP 47 language identifiers.
+	return l[0:1] + l[2:4]
+}
+
+// IsPrivateUse reports whether this language code is reserved for private use.
+func (b Language) IsPrivateUse() bool {
+	return langPrivateStart <= b && b <= langPrivateEnd
+}
+
+// SuppressScript returns the script marked as SuppressScript in the IANA
+// language tag repository, or 0 if there is no such script.
+func (b Language) SuppressScript() Script {
+	if b < langNoIndexOffset {
+		return Script(suppressScript[b])
+	}
+	return 0
+}
+
+type Region uint16
+
+// getRegionID returns the region id for s if s is a valid 2-letter region code
+// or unknownRegion.
+func getRegionID(s []byte) (Region, error) {
+	if len(s) == 3 {
+		if isAlpha(s[0]) {
+			return getRegionISO3(s)
+		}
+		if i, err := strconv.ParseUint(string(s), 10, 10); err == nil {
+			return getRegionM49(int(i))
+		}
+	}
+	return getRegionISO2(s)
+}
+
+// getRegionISO2 returns the regionID for the given 2-letter ISO country code
+// or unknownRegion if this does not exist.
+func getRegionISO2(s []byte) (Region, error) {
+	i, err := findIndex(regionISO, s, "ZZ")
+	if err != nil {
+		return 0, err
+	}
+	return Region(i) + isoRegionOffset, nil
+}
+
+// getRegionISO3 returns the regionID for the given 3-letter ISO country code
+// or unknownRegion if this does not exist.
+func getRegionISO3(s []byte) (Region, error) {
+	if tag.FixCase("ZZZ", s) {
+		for i := regionISO.Index(s[:1]); i != -1; i = regionISO.Next(s[:1], i) {
+			if e := regionISO.Elem(i); e[2] == s[1] && e[3] == s[2] {
+				return Region(i) + isoRegionOffset, nil
+			}
+		}
+		for i := 0; i < len(altRegionISO3); i += 3 {
+			if tag.Compare(altRegionISO3[i:i+3], s) == 0 {
+				return Region(altRegionIDs[i/3]), nil
+			}
+		}
+		return 0, NewValueError(s)
+	}
+	return 0, ErrSyntax
+}
+
+func getRegionM49(n int) (Region, error) {
+	if 0 < n && n <= 999 {
+		const (
+			searchBits = 7
+			regionBits = 9
+			regionMask = 1<<regionBits - 1
+		)
+		idx := n >> searchBits
+		buf := fromM49[m49Index[idx]:m49Index[idx+1]]
+		val := uint16(n) << regionBits // we rely on bits shifting out
+		i := sort.Search(len(buf), func(i int) bool {
+			return buf[i] >= val
+		})
+		if r := fromM49[int(m49Index[idx])+i]; r&^regionMask == val {
+			return Region(r & regionMask), nil
+		}
+	}
+	var e ValueError
+	fmt.Fprint(bytes.NewBuffer([]byte(e.v[:])), n)
+	return 0, e
+}
+
+// normRegion returns a region if r is deprecated or 0 otherwise.
+// TODO: consider supporting BYS (-> BLR), CSK (-> 200 or CZ), PHI (-> PHL) and AFI (-> DJ).
+// TODO: consider mapping split up regions to new most populous one (like CLDR).
+func normRegion(r Region) Region {
+	m := regionOldMap
+	k := sort.Search(len(m), func(i int) bool {
+		return m[i].From >= uint16(r)
+	})
+	if k < len(m) && m[k].From == uint16(r) {
+		return Region(m[k].To)
+	}
+	return 0
+}
+
+const (
+	iso3166UserAssigned = 1 << iota
+	ccTLD
+	bcp47Region
+)
+
+func (r Region) typ() byte {
+	return regionTypes[r]
+}
+
+// String returns the BCP 47 representation for the region.
+// It returns "ZZ" for an unspecified region.
+func (r Region) String() string {
+	if r < isoRegionOffset {
+		if r == 0 {
+			return "ZZ"
+		}
+		return fmt.Sprintf("%03d", r.M49())
+	}
+	r -= isoRegionOffset
+	return regionISO.Elem(int(r))[:2]
+}
+
+// ISO3 returns the 3-letter ISO code of r.
+// Note that not all regions have a 3-letter ISO code.
+// In such cases this method returns "ZZZ".
+func (r Region) ISO3() string {
+	if r < isoRegionOffset {
+		return "ZZZ"
+	}
+	r -= isoRegionOffset
+	reg := regionISO.Elem(int(r))
+	switch reg[2] {
+	case 0:
+		return altRegionISO3[reg[3]:][:3]
+	case ' ':
+		return "ZZZ"
+	}
+	return reg[0:1] + reg[2:4]
+}
+
+// M49 returns the UN M.49 encoding of r, or 0 if this encoding
+// is not defined for r.
+func (r Region) M49() int {
+	return int(m49[r])
+}
+
+// IsPrivateUse reports whether r has the ISO 3166 User-assigned status. This
+// may include private-use tags that are assigned by CLDR and used in this
+// implementation. So IsPrivateUse and IsCountry can be simultaneously true.
+func (r Region) IsPrivateUse() bool {
+	return r.typ()&iso3166UserAssigned != 0
+}
+
+type Script uint16
+
+// getScriptID returns the script id for string s. It assumes that s
+// is of the format [A-Z][a-z]{3}.
+func getScriptID(idx tag.Index, s []byte) (Script, error) {
+	i, err := findIndex(idx, s, "Zzzz")
+	return Script(i), err
+}
+
+// String returns the script code in title case.
+// It returns "Zzzz" for an unspecified script.
+func (s Script) String() string {
+	if s == 0 {
+		return "Zzzz"
+	}
+	return script.Elem(int(s))
+}
+
+// IsPrivateUse reports whether this script code is reserved for private use.
+func (s Script) IsPrivateUse() bool {
+	return _Qaaa <= s && s <= _Qabx
+}
+
+const (
+	maxAltTaglen = len("en-US-POSIX")
+	maxLen       = maxAltTaglen
+)
+
+var (
+	// grandfatheredMap holds a mapping from legacy and grandfathered tags to
+	// their base language or index to more elaborate tag.
+	grandfatheredMap = map[[maxLen]byte]int16{
+		[maxLen]byte{'a', 'r', 't', '-', 'l', 'o', 'j', 'b', 'a', 'n'}: _jbo, // art-lojban
+		[maxLen]byte{'i', '-', 'a', 'm', 'i'}:                          _ami, // i-ami
+		[maxLen]byte{'i', '-', 'b', 'n', 'n'}:                          _bnn, // i-bnn
+		[maxLen]byte{'i', '-', 'h', 'a', 'k'}:                          _hak, // i-hak
+		[maxLen]byte{'i', '-', 'k', 'l', 'i', 'n', 'g', 'o', 'n'}:      _tlh, // i-klingon
+		[maxLen]byte{'i', '-', 'l', 'u', 'x'}:                          _lb,  // i-lux
+		[maxLen]byte{'i', '-', 'n', 'a', 'v', 'a', 'j', 'o'}:           _nv,  // i-navajo
+		[maxLen]byte{'i', '-', 'p', 'w', 'n'}:                          _pwn, // i-pwn
+		[maxLen]byte{'i', '-', 't', 'a', 'o'}:                          _tao, // i-tao
+		[maxLen]byte{'i', '-', 't', 'a', 'y'}:                          _tay, // i-tay
+		[maxLen]byte{'i', '-', 't', 's', 'u'}:                          _tsu, // i-tsu
+		[maxLen]byte{'n', 'o', '-', 'b', 'o', 'k'}:                     _nb,  // no-bok
+		[maxLen]byte{'n', 'o', '-', 'n', 'y', 'n'}:                     _nn,  // no-nyn
+		[maxLen]byte{'s', 'g', 'n', '-', 'b', 'e', '-', 'f', 'r'}:      _sfb, // sgn-BE-FR
+		[maxLen]byte{'s', 'g', 'n', '-', 'b', 'e', '-', 'n', 'l'}:      _vgt, // sgn-BE-NL
+		[maxLen]byte{'s', 'g', 'n', '-', 'c', 'h', '-', 'd', 'e'}:      _sgg, // sgn-CH-DE
+		[maxLen]byte{'z', 'h', '-', 'g', 'u', 'o', 'y', 'u'}:           _cmn, // zh-guoyu
+		[maxLen]byte{'z', 'h', '-', 'h', 'a', 'k', 'k', 'a'}:           _hak, // zh-hakka
+		[maxLen]byte{'z', 'h', '-', 'm', 'i', 'n', '-', 'n', 'a', 'n'}: _nan, // zh-min-nan
+		[maxLen]byte{'z', 'h', '-', 'x', 'i', 'a', 'n', 'g'}:           _hsn, // zh-xiang
+
+		// Grandfathered tags with no modern replacement will be converted as
+		// follows:
+		[maxLen]byte{'c', 'e', 'l', '-', 'g', 'a', 'u', 'l', 'i', 's', 'h'}: -1, // cel-gaulish
+		[maxLen]byte{'e', 'n', '-', 'g', 'b', '-', 'o', 'e', 'd'}:           -2, // en-GB-oed
+		[maxLen]byte{'i', '-', 'd', 'e', 'f', 'a', 'u', 'l', 't'}:           -3, // i-default
+		[maxLen]byte{'i', '-', 'e', 'n', 'o', 'c', 'h', 'i', 'a', 'n'}:      -4, // i-enochian
+		[maxLen]byte{'i', '-', 'm', 'i', 'n', 'g', 'o'}:                     -5, // i-mingo
+		[maxLen]byte{'z', 'h', '-', 'm', 'i', 'n'}:                          -6, // zh-min
+
+		// CLDR-specific tag.
+		[maxLen]byte{'r', 'o', 'o', 't'}:                                    0,  // root
+		[maxLen]byte{'e', 'n', '-', 'u', 's', '-', 'p', 'o', 's', 'i', 'x'}: -7, // en_US_POSIX"
+	}
+
+	altTagIndex = [...]uint8{0, 17, 31, 45, 61, 74, 86, 102}
+
+	altTags = "xtg-x-cel-gaulishen-GB-oxendicten-x-i-defaultund-x-i-enochiansee-x-i-mingonan-x-zh-minen-US-u-va-posix"
+)
+
+func grandfathered(s [maxAltTaglen]byte) (t Tag, ok bool) {
+	if v, ok := grandfatheredMap[s]; ok {
+		if v < 0 {
+			return Make(altTags[altTagIndex[-v-1]:altTagIndex[-v]]), true
+		}
+		t.LangID = Language(v)
+		return t, true
+	}
+	return t, false
+}

vendor/golang.org/x/text/internal/language/match.go

@@ -0,0 +1,226 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import "errors"
+
+type scriptRegionFlags uint8
+
+const (
+	isList = 1 << iota
+	scriptInFrom
+	regionInFrom
+)
+
+func (t *Tag) setUndefinedLang(id Language) {
+	if t.LangID == 0 {
+		t.LangID = id
+	}
+}
+
+func (t *Tag) setUndefinedScript(id Script) {
+	if t.ScriptID == 0 {
+		t.ScriptID = id
+	}
+}
+
+func (t *Tag) setUndefinedRegion(id Region) {
+	if t.RegionID == 0 || t.RegionID.Contains(id) {
+		t.RegionID = id
+	}
+}
+
+// ErrMissingLikelyTagsData indicates no information was available
+// to compute likely values of missing tags.
+var ErrMissingLikelyTagsData = errors.New("missing likely tags data")
+
+// addLikelySubtags sets subtags to their most likely value, given the locale.
+// In most cases this means setting fields for unknown values, but in some
+// cases it may alter a value.  It returns an ErrMissingLikelyTagsData error
+// if the given locale cannot be expanded.
+func (t Tag) addLikelySubtags() (Tag, error) {
+	id, err := addTags(t)
+	if err != nil {
+		return t, err
+	} else if id.equalTags(t) {
+		return t, nil
+	}
+	id.RemakeString()
+	return id, nil
+}
+
+// specializeRegion attempts to specialize a group region.
+func specializeRegion(t *Tag) bool {
+	if i := regionInclusion[t.RegionID]; i < nRegionGroups {
+		x := likelyRegionGroup[i]
+		if Language(x.lang) == t.LangID && Script(x.script) == t.ScriptID {
+			t.RegionID = Region(x.region)
+		}
+		return true
+	}
+	return false
+}
+
+// Maximize returns a new tag with missing tags filled in.
+func (t Tag) Maximize() (Tag, error) {
+	return addTags(t)
+}
+
+func addTags(t Tag) (Tag, error) {
+	// We leave private use identifiers alone.
+	if t.IsPrivateUse() {
+		return t, nil
+	}
+	if t.ScriptID != 0 && t.RegionID != 0 {
+		if t.LangID != 0 {
+			// already fully specified
+			specializeRegion(&t)
+			return t, nil
+		}
+		// Search matches for und-script-region. Note that for these cases
+		// region will never be a group so there is no need to check for this.
+		list := likelyRegion[t.RegionID : t.RegionID+1]
+		if x := list[0]; x.flags&isList != 0 {
+			list = likelyRegionList[x.lang : x.lang+uint16(x.script)]
+		}
+		for _, x := range list {
+			// Deviating from the spec. See match_test.go for details.
+			if Script(x.script) == t.ScriptID {
+				t.setUndefinedLang(Language(x.lang))
+				return t, nil
+			}
+		}
+	}
+	if t.LangID != 0 {
+		// Search matches for lang-script and lang-region, where lang != und.
+		if t.LangID < langNoIndexOffset {
+			x := likelyLang[t.LangID]
+			if x.flags&isList != 0 {
+				list := likelyLangList[x.region : x.region+uint16(x.script)]
+				if t.ScriptID != 0 {
+					for _, x := range list {
+						if Script(x.script) == t.ScriptID && x.flags&scriptInFrom != 0 {
+							t.setUndefinedRegion(Region(x.region))
+							return t, nil
+						}
+					}
+				} else if t.RegionID != 0 {
+					count := 0
+					goodScript := true
+					tt := t
+					for _, x := range list {
+						// We visit all entries for which the script was not
+						// defined, including the ones where the region was not
+						// defined. This allows for proper disambiguation within
+						// regions.
+						if x.flags&scriptInFrom == 0 && t.RegionID.Contains(Region(x.region)) {
+							tt.RegionID = Region(x.region)
+							tt.setUndefinedScript(Script(x.script))
+							goodScript = goodScript && tt.ScriptID == Script(x.script)
+							count++
+						}
+					}
+					if count == 1 {
+						return tt, nil
+					}
+					// Even if we fail to find a unique Region, we might have
+					// an unambiguous script.
+					if goodScript {
+						t.ScriptID = tt.ScriptID
+					}
+				}
+			}
+		}
+	} else {
+		// Search matches for und-script.
+		if t.ScriptID != 0 {
+			x := likelyScript[t.ScriptID]
+			if x.region != 0 {
+				t.setUndefinedRegion(Region(x.region))
+				t.setUndefinedLang(Language(x.lang))
+				return t, nil
+			}
+		}
+		// Search matches for und-region. If und-script-region exists, it would
+		// have been found earlier.
+		if t.RegionID != 0 {
+			if i := regionInclusion[t.RegionID]; i < nRegionGroups {
+				x := likelyRegionGroup[i]
+				if x.region != 0 {
+					t.setUndefinedLang(Language(x.lang))
+					t.setUndefinedScript(Script(x.script))
+					t.RegionID = Region(x.region)
+				}
+			} else {
+				x := likelyRegion[t.RegionID]
+				if x.flags&isList != 0 {
+					x = likelyRegionList[x.lang]
+				}
+				if x.script != 0 && x.flags != scriptInFrom {
+					t.setUndefinedLang(Language(x.lang))
+					t.setUndefinedScript(Script(x.script))
+					return t, nil
+				}
+			}
+		}
+	}
+
+	// Search matches for lang.
+	if t.LangID < langNoIndexOffset {
+		x := likelyLang[t.LangID]
+		if x.flags&isList != 0 {
+			x = likelyLangList[x.region]
+		}
+		if x.region != 0 {
+			t.setUndefinedScript(Script(x.script))
+			t.setUndefinedRegion(Region(x.region))
+		}
+		specializeRegion(&t)
+		if t.LangID == 0 {
+			t.LangID = _en // default language
+		}
+		return t, nil
+	}
+	return t, ErrMissingLikelyTagsData
+}
+
+func (t *Tag) setTagsFrom(id Tag) {
+	t.LangID = id.LangID
+	t.ScriptID = id.ScriptID
+	t.RegionID = id.RegionID
+}
+
+// minimize removes the region or script subtags from t such that
+// t.addLikelySubtags() == t.minimize().addLikelySubtags().
+func (t Tag) minimize() (Tag, error) {
+	t, err := minimizeTags(t)
+	if err != nil {
+		return t, err
+	}
+	t.RemakeString()
+	return t, nil
+}
+
+// minimizeTags mimics the behavior of the ICU 51 C implementation.
+func minimizeTags(t Tag) (Tag, error) {
+	if t.equalTags(Und) {
+		return t, nil
+	}
+	max, err := addTags(t)
+	if err != nil {
+		return t, err
+	}
+	for _, id := range [...]Tag{
+		{LangID: t.LangID},
+		{LangID: t.LangID, RegionID: t.RegionID},
+		{LangID: t.LangID, ScriptID: t.ScriptID},
+	} {
+		if x, err := addTags(id); err == nil && max.equalTags(x) {
+			t.setTagsFrom(id)
+			break
+		}
+	}
+	return t, nil
+}

vendor/golang.org/x/text/internal/language/parse.go

@@ -0,0 +1,608 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"sort"
+
+	"golang.org/x/text/internal/tag"
+)
+
+// isAlpha returns true if the byte is not a digit.
+// b must be an ASCII letter or digit.
+func isAlpha(b byte) bool {
+	return b > '9'
+}
+
+// isAlphaNum returns true if the string contains only ASCII letters or digits.
+func isAlphaNum(s []byte) bool {
+	for _, c := range s {
+		if !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9') {
+			return false
+		}
+	}
+	return true
+}
+
+// ErrSyntax is returned by any of the parsing functions when the
+// input is not well-formed, according to BCP 47.
+// TODO: return the position at which the syntax error occurred?
+var ErrSyntax = errors.New("language: tag is not well-formed")
+
+// ErrDuplicateKey is returned when a tag contains the same key twice with
+// different values in the -u section.
+var ErrDuplicateKey = errors.New("language: different values for same key in -u extension")
+
+// ValueError is returned by any of the parsing functions when the
+// input is well-formed but the respective subtag is not recognized
+// as a valid value.
+type ValueError struct {
+	v [8]byte
+}
+
+// NewValueError creates a new ValueError.
+func NewValueError(tag []byte) ValueError {
+	var e ValueError
+	copy(e.v[:], tag)
+	return e
+}
+
+func (e ValueError) tag() []byte {
+	n := bytes.IndexByte(e.v[:], 0)
+	if n == -1 {
+		n = 8
+	}
+	return e.v[:n]
+}
+
+// Error implements the error interface.
+func (e ValueError) Error() string {
+	return fmt.Sprintf("language: subtag %q is well-formed but unknown", e.tag())
+}
+
+// Subtag returns the subtag for which the error occurred.
+func (e ValueError) Subtag() string {
+	return string(e.tag())
+}
+
+// scanner is used to scan BCP 47 tokens, which are separated by _ or -.
+type scanner struct {
+	b     []byte
+	bytes [max99thPercentileSize]byte
+	token []byte
+	start int // start position of the current token
+	end   int // end position of the current token
+	next  int // next point for scan
+	err   error
+	done  bool
+}
+
+func makeScannerString(s string) scanner {
+	scan := scanner{}
+	if len(s) <= len(scan.bytes) {
+		scan.b = scan.bytes[:copy(scan.bytes[:], s)]
+	} else {
+		scan.b = []byte(s)
+	}
+	scan.init()
+	return scan
+}
+
+// makeScanner returns a scanner using b as the input buffer.
+// b is not copied and may be modified by the scanner routines.
+func makeScanner(b []byte) scanner {
+	scan := scanner{b: b}
+	scan.init()
+	return scan
+}
+
+func (s *scanner) init() {
+	for i, c := range s.b {
+		if c == '_' {
+			s.b[i] = '-'
+		}
+	}
+	s.scan()
+}
+
+// restToLower converts the string between start and end to lower case.
+func (s *scanner) toLower(start, end int) {
+	for i := start; i < end; i++ {
+		c := s.b[i]
+		if 'A' <= c && c <= 'Z' {
+			s.b[i] += 'a' - 'A'
+		}
+	}
+}
+
+func (s *scanner) setError(e error) {
+	if s.err == nil || (e == ErrSyntax && s.err != ErrSyntax) {
+		s.err = e
+	}
+}
+
+// resizeRange shrinks or grows the array at position oldStart such that
+// a new string of size newSize can fit between oldStart and oldEnd.
+// Sets the scan point to after the resized range.
+func (s *scanner) resizeRange(oldStart, oldEnd, newSize int) {
+	s.start = oldStart
+	if end := oldStart + newSize; end != oldEnd {
+		diff := end - oldEnd
+		var b []byte
+		if n := len(s.b) + diff; n > cap(s.b) {
+			b = make([]byte, n)
+			copy(b, s.b[:oldStart])
+		} else {
+			b = s.b[:n]
+		}
+		copy(b[end:], s.b[oldEnd:])
+		s.b = b
+		s.next = end + (s.next - s.end)
+		s.end = end
+	}
+}
+
+// replace replaces the current token with repl.
+func (s *scanner) replace(repl string) {
+	s.resizeRange(s.start, s.end, len(repl))
+	copy(s.b[s.start:], repl)
+}
+
+// gobble removes the current token from the input.
+// Caller must call scan after calling gobble.
+func (s *scanner) gobble(e error) {
+	s.setError(e)
+	if s.start == 0 {
+		s.b = s.b[:+copy(s.b, s.b[s.next:])]
+		s.end = 0
+	} else {
+		s.b = s.b[:s.start-1+copy(s.b[s.start-1:], s.b[s.end:])]
+		s.end = s.start - 1
+	}
+	s.next = s.start
+}
+
+// deleteRange removes the given range from s.b before the current token.
+func (s *scanner) deleteRange(start, end int) {
+	s.b = s.b[:start+copy(s.b[start:], s.b[end:])]
+	diff := end - start
+	s.next -= diff
+	s.start -= diff
+	s.end -= diff
+}
+
+// scan parses the next token of a BCP 47 string.  Tokens that are larger
+// than 8 characters or include non-alphanumeric characters result in an error
+// and are gobbled and removed from the output.
+// It returns the end position of the last token consumed.
+func (s *scanner) scan() (end int) {
+	end = s.end
+	s.token = nil
+	for s.start = s.next; s.next < len(s.b); {
+		i := bytes.IndexByte(s.b[s.next:], '-')
+		if i == -1 {
+			s.end = len(s.b)
+			s.next = len(s.b)
+			i = s.end - s.start
+		} else {
+			s.end = s.next + i
+			s.next = s.end + 1
+		}
+		token := s.b[s.start:s.end]
+		if i < 1 || i > 8 || !isAlphaNum(token) {
+			s.gobble(ErrSyntax)
+			continue
+		}
+		s.token = token
+		return end
+	}
+	if n := len(s.b); n > 0 && s.b[n-1] == '-' {
+		s.setError(ErrSyntax)
+		s.b = s.b[:len(s.b)-1]
+	}
+	s.done = true
+	return end
+}
+
+// acceptMinSize parses multiple tokens of the given size or greater.
+// It returns the end position of the last token consumed.
+func (s *scanner) acceptMinSize(min int) (end int) {
+	end = s.end
+	s.scan()
+	for ; len(s.token) >= min; s.scan() {
+		end = s.end
+	}
+	return end
+}
+
+// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
+// failed it returns an error and any part of the tag that could be parsed.
+// If parsing succeeded but an unknown value was found, it returns
+// ValueError. The Tag returned in this case is just stripped of the unknown
+// value. All other values are preserved. It accepts tags in the BCP 47 format
+// and extensions to this standard defined in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+func Parse(s string) (t Tag, err error) {
+	// TODO: consider supporting old-style locale key-value pairs.
+	if s == "" {
+		return Und, ErrSyntax
+	}
+	defer func() {
+		if recover() != nil {
+			t = Und
+			err = ErrSyntax
+			return
+		}
+	}()
+	if len(s) <= maxAltTaglen {
+		b := [maxAltTaglen]byte{}
+		for i, c := range s {
+			// Generating invalid UTF-8 is okay as it won't match.
+			if 'A' <= c && c <= 'Z' {
+				c += 'a' - 'A'
+			} else if c == '_' {
+				c = '-'
+			}
+			b[i] = byte(c)
+		}
+		if t, ok := grandfathered(b); ok {
+			return t, nil
+		}
+	}
+	scan := makeScannerString(s)
+	return parse(&scan, s)
+}
+
+func parse(scan *scanner, s string) (t Tag, err error) {
+	t = Und
+	var end int
+	if n := len(scan.token); n <= 1 {
+		scan.toLower(0, len(scan.b))
+		if n == 0 || scan.token[0] != 'x' {
+			return t, ErrSyntax
+		}
+		end = parseExtensions(scan)
+	} else if n >= 4 {
+		return Und, ErrSyntax
+	} else { // the usual case
+		t, end = parseTag(scan, true)
+		if n := len(scan.token); n == 1 {
+			t.pExt = uint16(end)
+			end = parseExtensions(scan)
+		} else if end < len(scan.b) {
+			scan.setError(ErrSyntax)
+			scan.b = scan.b[:end]
+		}
+	}
+	if int(t.pVariant) < len(scan.b) {
+		if end < len(s) {
+			s = s[:end]
+		}
+		if len(s) > 0 && tag.Compare(s, scan.b) == 0 {
+			t.str = s
+		} else {
+			t.str = string(scan.b)
+		}
+	} else {
+		t.pVariant, t.pExt = 0, 0
+	}
+	return t, scan.err
+}
+
+// parseTag parses language, script, region and variants.
+// It returns a Tag and the end position in the input that was parsed.
+// If doNorm is true, then <lang>-<extlang> will be normalized to <extlang>.
+func parseTag(scan *scanner, doNorm bool) (t Tag, end int) {
+	var e error
+	// TODO: set an error if an unknown lang, script or region is encountered.
+	t.LangID, e = getLangID(scan.token)
+	scan.setError(e)
+	scan.replace(t.LangID.String())
+	langStart := scan.start
+	end = scan.scan()
+	for len(scan.token) == 3 && isAlpha(scan.token[0]) {
+		// From http://tools.ietf.org/html/bcp47, <lang>-<extlang> tags are equivalent
+		// to a tag of the form <extlang>.
+		if doNorm {
+			lang, e := getLangID(scan.token)
+			if lang != 0 {
+				t.LangID = lang
+				langStr := lang.String()
+				copy(scan.b[langStart:], langStr)
+				scan.b[langStart+len(langStr)] = '-'
+				scan.start = langStart + len(langStr) + 1
+			}
+			scan.gobble(e)
+		}
+		end = scan.scan()
+	}
+	if len(scan.token) == 4 && isAlpha(scan.token[0]) {
+		t.ScriptID, e = getScriptID(script, scan.token)
+		if t.ScriptID == 0 {
+			scan.gobble(e)
+		}
+		end = scan.scan()
+	}
+	if n := len(scan.token); n >= 2 && n <= 3 {
+		t.RegionID, e = getRegionID(scan.token)
+		if t.RegionID == 0 {
+			scan.gobble(e)
+		} else {
+			scan.replace(t.RegionID.String())
+		}
+		end = scan.scan()
+	}
+	scan.toLower(scan.start, len(scan.b))
+	t.pVariant = byte(end)
+	end = parseVariants(scan, end, t)
+	t.pExt = uint16(end)
+	return t, end
+}
+
+var separator = []byte{'-'}
+
+// parseVariants scans tokens as long as each token is a valid variant string.
+// Duplicate variants are removed.
+func parseVariants(scan *scanner, end int, t Tag) int {
+	start := scan.start
+	varIDBuf := [4]uint8{}
+	variantBuf := [4][]byte{}
+	varID := varIDBuf[:0]
+	variant := variantBuf[:0]
+	last := -1
+	needSort := false
+	for ; len(scan.token) >= 4; scan.scan() {
+		// TODO: measure the impact of needing this conversion and redesign
+		// the data structure if there is an issue.
+		v, ok := variantIndex[string(scan.token)]
+		if !ok {
+			// unknown variant
+			// TODO: allow user-defined variants?
+			scan.gobble(NewValueError(scan.token))
+			continue
+		}
+		varID = append(varID, v)
+		variant = append(variant, scan.token)
+		if !needSort {
+			if last < int(v) {
+				last = int(v)
+			} else {
+				needSort = true
+				// There is no legal combinations of more than 7 variants
+				// (and this is by no means a useful sequence).
+				const maxVariants = 8
+				if len(varID) > maxVariants {
+					break
+				}
+			}
+		}
+		end = scan.end
+	}
+	if needSort {
+		sort.Sort(variantsSort{varID, variant})
+		k, l := 0, -1
+		for i, v := range varID {
+			w := int(v)
+			if l == w {
+				// Remove duplicates.
+				continue
+			}
+			varID[k] = varID[i]
+			variant[k] = variant[i]
+			k++
+			l = w
+		}
+		if str := bytes.Join(variant[:k], separator); len(str) == 0 {
+			end = start - 1
+		} else {
+			scan.resizeRange(start, end, len(str))
+			copy(scan.b[scan.start:], str)
+			end = scan.end
+		}
+	}
+	return end
+}
+
+type variantsSort struct {
+	i []uint8
+	v [][]byte
+}
+
+func (s variantsSort) Len() int {
+	return len(s.i)
+}
+
+func (s variantsSort) Swap(i, j int) {
+	s.i[i], s.i[j] = s.i[j], s.i[i]
+	s.v[i], s.v[j] = s.v[j], s.v[i]
+}
+
+func (s variantsSort) Less(i, j int) bool {
+	return s.i[i] < s.i[j]
+}
+
+type bytesSort struct {
+	b [][]byte
+	n int // first n bytes to compare
+}
+
+func (b bytesSort) Len() int {
+	return len(b.b)
+}
+
+func (b bytesSort) Swap(i, j int) {
+	b.b[i], b.b[j] = b.b[j], b.b[i]
+}
+
+func (b bytesSort) Less(i, j int) bool {
+	for k := 0; k < b.n; k++ {
+		if b.b[i][k] == b.b[j][k] {
+			continue
+		}
+		return b.b[i][k] < b.b[j][k]
+	}
+	return false
+}
+
+// parseExtensions parses and normalizes the extensions in the buffer.
+// It returns the last position of scan.b that is part of any extension.
+// It also trims scan.b to remove excess parts accordingly.
+func parseExtensions(scan *scanner) int {
+	start := scan.start
+	exts := [][]byte{}
+	private := []byte{}
+	end := scan.end
+	for len(scan.token) == 1 {
+		extStart := scan.start
+		ext := scan.token[0]
+		end = parseExtension(scan)
+		extension := scan.b[extStart:end]
+		if len(extension) < 3 || (ext != 'x' && len(extension) < 4) {
+			scan.setError(ErrSyntax)
+			end = extStart
+			continue
+		} else if start == extStart && (ext == 'x' || scan.start == len(scan.b)) {
+			scan.b = scan.b[:end]
+			return end
+		} else if ext == 'x' {
+			private = extension
+			break
+		}
+		exts = append(exts, extension)
+	}
+	sort.Sort(bytesSort{exts, 1})
+	if len(private) > 0 {
+		exts = append(exts, private)
+	}
+	scan.b = scan.b[:start]
+	if len(exts) > 0 {
+		scan.b = append(scan.b, bytes.Join(exts, separator)...)
+	} else if start > 0 {
+		// Strip trailing '-'.
+		scan.b = scan.b[:start-1]
+	}
+	return end
+}
+
+// parseExtension parses a single extension and returns the position of
+// the extension end.
+func parseExtension(scan *scanner) int {
+	start, end := scan.start, scan.end
+	switch scan.token[0] {
+	case 'u': // https://www.ietf.org/rfc/rfc6067.txt
+		attrStart := end
+		scan.scan()
+		for last := []byte{}; len(scan.token) > 2; scan.scan() {
+			if bytes.Compare(scan.token, last) != -1 {
+				// Attributes are unsorted. Start over from scratch.
+				p := attrStart + 1
+				scan.next = p
+				attrs := [][]byte{}
+				for scan.scan(); len(scan.token) > 2; scan.scan() {
+					attrs = append(attrs, scan.token)
+					end = scan.end
+				}
+				sort.Sort(bytesSort{attrs, 3})
+				copy(scan.b[p:], bytes.Join(attrs, separator))
+				break
+			}
+			last = scan.token
+			end = scan.end
+		}
+		// Scan key-type sequences. A key is of length 2 and may be followed
+		// by 0 or more "type" subtags from 3 to the maximum of 8 letters.
+		var last, key []byte
+		for attrEnd := end; len(scan.token) == 2; last = key {
+			key = scan.token
+			end = scan.end
+			for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
+				end = scan.end
+			}
+			// TODO: check key value validity
+			if bytes.Compare(key, last) != 1 || scan.err != nil {
+				// We have an invalid key or the keys are not sorted.
+				// Start scanning keys from scratch and reorder.
+				p := attrEnd + 1
+				scan.next = p
+				keys := [][]byte{}
+				for scan.scan(); len(scan.token) == 2; {
+					keyStart := scan.start
+					end = scan.end
+					for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
+						end = scan.end
+					}
+					keys = append(keys, scan.b[keyStart:end])
+				}
+				sort.Stable(bytesSort{keys, 2})
+				if n := len(keys); n > 0 {
+					k := 0
+					for i := 1; i < n; i++ {
+						if !bytes.Equal(keys[k][:2], keys[i][:2]) {
+							k++
+							keys[k] = keys[i]
+						} else if !bytes.Equal(keys[k], keys[i]) {
+							scan.setError(ErrDuplicateKey)
+						}
+					}
+					keys = keys[:k+1]
+				}
+				reordered := bytes.Join(keys, separator)
+				if e := p + len(reordered); e < end {
+					scan.deleteRange(e, end)
+					end = e
+				}
+				copy(scan.b[p:], reordered)
+				break
+			}
+		}
+	case 't': // https://www.ietf.org/rfc/rfc6497.txt
+		scan.scan()
+		if n := len(scan.token); n >= 2 && n <= 3 && isAlpha(scan.token[1]) {
+			_, end = parseTag(scan, false)
+			scan.toLower(start, end)
+		}
+		for len(scan.token) == 2 && !isAlpha(scan.token[1]) {
+			end = scan.acceptMinSize(3)
+		}
+	case 'x':
+		end = scan.acceptMinSize(1)
+	default:
+		end = scan.acceptMinSize(2)
+	}
+	return end
+}
+
+// getExtension returns the name, body and end position of the extension.
+func getExtension(s string, p int) (end int, ext string) {
+	if s[p] == '-' {
+		p++
+	}
+	if s[p] == 'x' {
+		return len(s), s[p:]
+	}
+	end = nextExtension(s, p)
+	return end, s[p:end]
+}
+
+// nextExtension finds the next extension within the string, searching
+// for the -<char>- pattern from position p.
+// In the fast majority of cases, language tags will have at most
+// one extension and extensions tend to be small.
+func nextExtension(s string, p int) int {
+	for n := len(s) - 3; p < n; {
+		if s[p] == '-' {
+			if s[p+2] == '-' {
+				return p
+			}
+			p += 3
+		} else {
+			p++
+		}
+	}
+	return len(s)
+}

vendor/golang.org/x/text/internal/language/tags.go

@@ -0,0 +1,48 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+// MustParse is like Parse, but panics if the given BCP 47 tag cannot be parsed.
+// It simplifies safe initialization of Tag values.
+func MustParse(s string) Tag {
+	t, err := Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+// MustParseBase is like ParseBase, but panics if the given base cannot be parsed.
+// It simplifies safe initialization of Base values.
+func MustParseBase(s string) Language {
+	b, err := ParseBase(s)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+// MustParseScript is like ParseScript, but panics if the given script cannot be
+// parsed. It simplifies safe initialization of Script values.
+func MustParseScript(s string) Script {
+	scr, err := ParseScript(s)
+	if err != nil {
+		panic(err)
+	}
+	return scr
+}
+
+// MustParseRegion is like ParseRegion, but panics if the given region cannot be
+// parsed. It simplifies safe initialization of Region values.
+func MustParseRegion(s string) Region {
+	r, err := ParseRegion(s)
+	if err != nil {
+		panic(err)
+	}
+	return r
+}
+
+// Und is the root language.
+var Und Tag

vendor/golang.org/x/text/internal/match.go

@@ -0,0 +1,67 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package internal
+
+// This file contains matchers that implement CLDR inheritance.
+//
+//     See https://unicode.org/reports/tr35/#Locale_Inheritance.
+//
+// Some of the inheritance described in this document is already handled by
+// the cldr package.
+
+import (
+	"golang.org/x/text/language"
+)
+
+// TODO: consider if (some of the) matching algorithm needs to be public after
+// getting some feel about what is generic and what is specific.
+
+// NewInheritanceMatcher returns a matcher that matches based on the inheritance
+// chain.
+//
+// The matcher uses canonicalization and the parent relationship to find a
+// match. The resulting match will always be either Und or a language with the
+// same language and script as the requested language. It will not match
+// languages for which there is understood to be mutual or one-directional
+// intelligibility.
+//
+// A Match will indicate an Exact match if the language matches after
+// canonicalization and High if the matched tag is a parent.
+func NewInheritanceMatcher(t []language.Tag) *InheritanceMatcher {
+	tags := &InheritanceMatcher{make(map[language.Tag]int)}
+	for i, tag := range t {
+		ct, err := language.All.Canonicalize(tag)
+		if err != nil {
+			ct = tag
+		}
+		tags.index[ct] = i
+	}
+	return tags
+}
+
+type InheritanceMatcher struct {
+	index map[language.Tag]int
+}
+
+func (m InheritanceMatcher) Match(want ...language.Tag) (language.Tag, int, language.Confidence) {
+	for _, t := range want {
+		ct, err := language.All.Canonicalize(t)
+		if err != nil {
+			ct = t
+		}
+		conf := language.Exact
+		for {
+			if index, ok := m.index[ct]; ok {
+				return ct, index, conf
+			}
+			if ct == language.Und {
+				break
+			}
+			ct = ct.Parent()
+			conf = language.High
+		}
+	}
+	return language.Und, 0, language.No
+}

vendor/golang.org/x/text/internal/tag/tag.go

@@ -0,0 +1,100 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tag contains functionality handling tags and related data.
+package tag // import "golang.org/x/text/internal/tag"
+
+import "sort"
+
+// An Index converts tags to a compact numeric value.
+//
+// All elements are of size 4. Tags may be up to 4 bytes long. Excess bytes can
+// be used to store additional information about the tag.
+type Index string
+
+// Elem returns the element data at the given index.
+func (s Index) Elem(x int) string {
+	return string(s[x*4 : x*4+4])
+}
+
+// Index reports the index of the given key or -1 if it could not be found.
+// Only the first len(key) bytes from the start of the 4-byte entries will be
+// considered for the search and the first match in Index will be returned.
+func (s Index) Index(key []byte) int {
+	n := len(key)
+	// search the index of the first entry with an equal or higher value than
+	// key in s.
+	index := sort.Search(len(s)/4, func(i int) bool {
+		return cmp(s[i*4:i*4+n], key) != -1
+	})
+	i := index * 4
+	if cmp(s[i:i+len(key)], key) != 0 {
+		return -1
+	}
+	return index
+}
+
+// Next finds the next occurrence of key after index x, which must have been
+// obtained from a call to Index using the same key. It returns x+1 or -1.
+func (s Index) Next(key []byte, x int) int {
+	if x++; x*4 < len(s) && cmp(s[x*4:x*4+len(key)], key) == 0 {
+		return x
+	}
+	return -1
+}
+
+// cmp returns an integer comparing a and b lexicographically.
+func cmp(a Index, b []byte) int {
+	n := len(a)
+	if len(b) < n {
+		n = len(b)
+	}
+	for i, c := range b[:n] {
+		switch {
+		case a[i] > c:
+			return 1
+		case a[i] < c:
+			return -1
+		}
+	}
+	switch {
+	case len(a) < len(b):
+		return -1
+	case len(a) > len(b):
+		return 1
+	}
+	return 0
+}
+
+// Compare returns an integer comparing a and b lexicographically.
+func Compare(a string, b []byte) int {
+	return cmp(Index(a), b)
+}
+
+// FixCase reformats b to the same pattern of cases as form.
+// If returns false if string b is malformed.
+func FixCase(form string, b []byte) bool {
+	if len(form) != len(b) {
+		return false
+	}
+	for i, c := range b {
+		if form[i] <= 'Z' {
+			if c >= 'a' {
+				c -= 'z' - 'Z'
+			}
+			if c < 'A' || 'Z' < c {
+				return false
+			}
+		} else {
+			if c <= 'Z' {
+				c += 'z' - 'Z'
+			}
+			if c < 'a' || 'z' < c {
+				return false
+			}
+		}
+		b[i] = c
+	}
+	return true
+}

vendor/golang.org/x/text/language/coverage.go

@@ -0,0 +1,187 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"fmt"
+	"sort"
+
+	"golang.org/x/text/internal/language"
+)
+
+// The Coverage interface is used to define the level of coverage of an
+// internationalization service. Note that not all types are supported by all
+// services. As lists may be generated on the fly, it is recommended that users
+// of a Coverage cache the results.
+type Coverage interface {
+	// Tags returns the list of supported tags.
+	Tags() []Tag
+
+	// BaseLanguages returns the list of supported base languages.
+	BaseLanguages() []Base
+
+	// Scripts returns the list of supported scripts.
+	Scripts() []Script
+
+	// Regions returns the list of supported regions.
+	Regions() []Region
+}
+
+var (
+	// Supported defines a Coverage that lists all supported subtags. Tags
+	// always returns nil.
+	Supported Coverage = allSubtags{}
+)
+
+// TODO:
+// - Support Variants, numbering systems.
+// - CLDR coverage levels.
+// - Set of common tags defined in this package.
+
+type allSubtags struct{}
+
+// Regions returns the list of supported regions. As all regions are in a
+// consecutive range, it simply returns a slice of numbers in increasing order.
+// The "undefined" region is not returned.
+func (s allSubtags) Regions() []Region {
+	reg := make([]Region, language.NumRegions)
+	for i := range reg {
+		reg[i] = Region{language.Region(i + 1)}
+	}
+	return reg
+}
+
+// Scripts returns the list of supported scripts. As all scripts are in a
+// consecutive range, it simply returns a slice of numbers in increasing order.
+// The "undefined" script is not returned.
+func (s allSubtags) Scripts() []Script {
+	scr := make([]Script, language.NumScripts)
+	for i := range scr {
+		scr[i] = Script{language.Script(i + 1)}
+	}
+	return scr
+}
+
+// BaseLanguages returns the list of all supported base languages. It generates
+// the list by traversing the internal structures.
+func (s allSubtags) BaseLanguages() []Base {
+	bs := language.BaseLanguages()
+	base := make([]Base, len(bs))
+	for i, b := range bs {
+		base[i] = Base{b}
+	}
+	return base
+}
+
+// Tags always returns nil.
+func (s allSubtags) Tags() []Tag {
+	return nil
+}
+
+// coverage is used by NewCoverage which is used as a convenient way for
+// creating Coverage implementations for partially defined data. Very often a
+// package will only need to define a subset of slices. coverage provides a
+// convenient way to do this. Moreover, packages using NewCoverage, instead of
+// their own implementation, will not break if later new slice types are added.
+type coverage struct {
+	tags    func() []Tag
+	bases   func() []Base
+	scripts func() []Script
+	regions func() []Region
+}
+
+func (s *coverage) Tags() []Tag {
+	if s.tags == nil {
+		return nil
+	}
+	return s.tags()
+}
+
+// bases implements sort.Interface and is used to sort base languages.
+type bases []Base
+
+func (b bases) Len() int {
+	return len(b)
+}
+
+func (b bases) Swap(i, j int) {
+	b[i], b[j] = b[j], b[i]
+}
+
+func (b bases) Less(i, j int) bool {
+	return b[i].langID < b[j].langID
+}
+
+// BaseLanguages returns the result from calling s.bases if it is specified or
+// otherwise derives the set of supported base languages from tags.
+func (s *coverage) BaseLanguages() []Base {
+	if s.bases == nil {
+		tags := s.Tags()
+		if len(tags) == 0 {
+			return nil
+		}
+		a := make([]Base, len(tags))
+		for i, t := range tags {
+			a[i] = Base{language.Language(t.lang())}
+		}
+		sort.Sort(bases(a))
+		k := 0
+		for i := 1; i < len(a); i++ {
+			if a[k] != a[i] {
+				k++
+				a[k] = a[i]
+			}
+		}
+		return a[:k+1]
+	}
+	return s.bases()
+}
+
+func (s *coverage) Scripts() []Script {
+	if s.scripts == nil {
+		return nil
+	}
+	return s.scripts()
+}
+
+func (s *coverage) Regions() []Region {
+	if s.regions == nil {
+		return nil
+	}
+	return s.regions()
+}
+
+// NewCoverage returns a Coverage for the given lists. It is typically used by
+// packages providing internationalization services to define their level of
+// coverage. A list may be of type []T or func() []T, where T is either Tag,
+// Base, Script or Region. The returned Coverage derives the value for Bases
+// from Tags if no func or slice for []Base is specified. For other unspecified
+// types the returned Coverage will return nil for the respective methods.
+func NewCoverage(list ...interface{}) Coverage {
+	s := &coverage{}
+	for _, x := range list {
+		switch v := x.(type) {
+		case func() []Base:
+			s.bases = v
+		case func() []Script:
+			s.scripts = v
+		case func() []Region:
+			s.regions = v
+		case func() []Tag:
+			s.tags = v
+		case []Base:
+			s.bases = func() []Base { return v }
+		case []Script:
+			s.scripts = func() []Script { return v }
+		case []Region:
+			s.regions = func() []Region { return v }
+		case []Tag:
+			s.tags = func() []Tag { return v }
+		default:
+			panic(fmt.Sprintf("language: unsupported set type %T", v))
+		}
+	}
+	return s
+}

vendor/golang.org/x/text/language/doc.go

@@ -0,0 +1,98 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package language implements BCP 47 language tags and related functionality.
+//
+// The most important function of package language is to match a list of
+// user-preferred languages to a list of supported languages.
+// It alleviates the developer of dealing with the complexity of this process
+// and provides the user with the best experience
+// (see https://blog.golang.org/matchlang).
+//
+// # Matching preferred against supported languages
+//
+// A Matcher for an application that supports English, Australian English,
+// Danish, and standard Mandarin can be created as follows:
+//
+//	var matcher = language.NewMatcher([]language.Tag{
+//	    language.English,   // The first language is used as fallback.
+//	    language.MustParse("en-AU"),
+//	    language.Danish,
+//	    language.Chinese,
+//	})
+//
+// This list of supported languages is typically implied by the languages for
+// which there exists translations of the user interface.
+//
+// User-preferred languages usually come as a comma-separated list of BCP 47
+// language tags.
+// The MatchString finds best matches for such strings:
+//
+//	handler(w http.ResponseWriter, r *http.Request) {
+//	    lang, _ := r.Cookie("lang")
+//	    accept := r.Header.Get("Accept-Language")
+//	    tag, _ := language.MatchStrings(matcher, lang.String(), accept)
+//
+//	    // tag should now be used for the initialization of any
+//	    // locale-specific service.
+//	}
+//
+// The Matcher's Match method can be used to match Tags directly.
+//
+// Matchers are aware of the intricacies of equivalence between languages, such
+// as deprecated subtags, legacy tags, macro languages, mutual
+// intelligibility between scripts and languages, and transparently passing
+// BCP 47 user configuration.
+// For instance, it will know that a reader of Bokmål Danish can read Norwegian
+// and will know that Cantonese ("yue") is a good match for "zh-HK".
+//
+// # Using match results
+//
+// To guarantee a consistent user experience to the user it is important to
+// use the same language tag for the selection of any locale-specific services.
+// For example, it is utterly confusing to substitute spelled-out numbers
+// or dates in one language in text of another language.
+// More subtly confusing is using the wrong sorting order or casing
+// algorithm for a certain language.
+//
+// All the packages in x/text that provide locale-specific services
+// (e.g. collate, cases) should be initialized with the tag that was
+// obtained at the start of an interaction with the user.
+//
+// Note that Tag that is returned by Match and MatchString may differ from any
+// of the supported languages, as it may contain carried over settings from
+// the user tags.
+// This may be inconvenient when your application has some additional
+// locale-specific data for your supported languages.
+// Match and MatchString both return the index of the matched supported tag
+// to simplify associating such data with the matched tag.
+//
+// # Canonicalization
+//
+// If one uses the Matcher to compare languages one does not need to
+// worry about canonicalization.
+//
+// The meaning of a Tag varies per application. The language package
+// therefore delays canonicalization and preserves information as much
+// as possible. The Matcher, however, will always take into account that
+// two different tags may represent the same language.
+//
+// By default, only legacy and deprecated tags are converted into their
+// canonical equivalent. All other information is preserved. This approach makes
+// the confidence scores more accurate and allows matchers to distinguish
+// between variants that are otherwise lost.
+//
+// As a consequence, two tags that should be treated as identical according to
+// BCP 47 or CLDR, like "en-Latn" and "en", will be represented differently. The
+// Matcher handles such distinctions, though, and is aware of the
+// equivalence relations. The CanonType type can be used to alter the
+// canonicalization form.
+//
+// # References
+//
+// BCP 47 - Tags for Identifying Languages http://tools.ietf.org/html/bcp47
+package language // import "golang.org/x/text/language"
+
+// TODO: explanation on how to match languages for your own locale-specific
+// service.

vendor/golang.org/x/text/language/language.go

@@ -0,0 +1,605 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run gen.go -output tables.go
+
+package language
+
+// TODO: Remove above NOTE after:
+// - verifying that tables are dropped correctly (most notably matcher tables).
+
+import (
+	"strings"
+
+	"golang.org/x/text/internal/language"
+	"golang.org/x/text/internal/language/compact"
+)
+
+// Tag represents a BCP 47 language tag. It is used to specify an instance of a
+// specific language or locale. All language tag values are guaranteed to be
+// well-formed.
+type Tag compact.Tag
+
+func makeTag(t language.Tag) (tag Tag) {
+	return Tag(compact.Make(t))
+}
+
+func (t *Tag) tag() language.Tag {
+	return (*compact.Tag)(t).Tag()
+}
+
+func (t *Tag) isCompact() bool {
+	return (*compact.Tag)(t).IsCompact()
+}
+
+// TODO: improve performance.
+func (t *Tag) lang() language.Language { return t.tag().LangID }
+func (t *Tag) region() language.Region { return t.tag().RegionID }
+func (t *Tag) script() language.Script { return t.tag().ScriptID }
+
+// Make is a convenience wrapper for Parse that omits the error.
+// In case of an error, a sensible default is returned.
+func Make(s string) Tag {
+	return Default.Make(s)
+}
+
+// Make is a convenience wrapper for c.Parse that omits the error.
+// In case of an error, a sensible default is returned.
+func (c CanonType) Make(s string) Tag {
+	t, _ := c.Parse(s)
+	return t
+}
+
+// Raw returns the raw base language, script and region, without making an
+// attempt to infer their values.
+func (t Tag) Raw() (b Base, s Script, r Region) {
+	tt := t.tag()
+	return Base{tt.LangID}, Script{tt.ScriptID}, Region{tt.RegionID}
+}
+
+// IsRoot returns true if t is equal to language "und".
+func (t Tag) IsRoot() bool {
+	return compact.Tag(t).IsRoot()
+}
+
+// CanonType can be used to enable or disable various types of canonicalization.
+type CanonType int
+
+const (
+	// Replace deprecated base languages with their preferred replacements.
+	DeprecatedBase CanonType = 1 << iota
+	// Replace deprecated scripts with their preferred replacements.
+	DeprecatedScript
+	// Replace deprecated regions with their preferred replacements.
+	DeprecatedRegion
+	// Remove redundant scripts.
+	SuppressScript
+	// Normalize legacy encodings. This includes legacy languages defined in
+	// CLDR as well as bibliographic codes defined in ISO-639.
+	Legacy
+	// Map the dominant language of a macro language group to the macro language
+	// subtag. For example cmn -> zh.
+	Macro
+	// The CLDR flag should be used if full compatibility with CLDR is required.
+	// There are a few cases where language.Tag may differ from CLDR. To follow all
+	// of CLDR's suggestions, use All|CLDR.
+	CLDR
+
+	// Raw can be used to Compose or Parse without Canonicalization.
+	Raw CanonType = 0
+
+	// Replace all deprecated tags with their preferred replacements.
+	Deprecated = DeprecatedBase | DeprecatedScript | DeprecatedRegion
+
+	// All canonicalizations recommended by BCP 47.
+	BCP47 = Deprecated | SuppressScript
+
+	// All canonicalizations.
+	All = BCP47 | Legacy | Macro
+
+	// Default is the canonicalization used by Parse, Make and Compose. To
+	// preserve as much information as possible, canonicalizations that remove
+	// potentially valuable information are not included. The Matcher is
+	// designed to recognize similar tags that would be the same if
+	// they were canonicalized using All.
+	Default = Deprecated | Legacy
+
+	canonLang = DeprecatedBase | Legacy | Macro
+
+	// TODO: LikelyScript, LikelyRegion: suppress similar to ICU.
+)
+
+// canonicalize returns the canonicalized equivalent of the tag and
+// whether there was any change.
+func canonicalize(c CanonType, t language.Tag) (language.Tag, bool) {
+	if c == Raw {
+		return t, false
+	}
+	changed := false
+	if c&SuppressScript != 0 {
+		if t.LangID.SuppressScript() == t.ScriptID {
+			t.ScriptID = 0
+			changed = true
+		}
+	}
+	if c&canonLang != 0 {
+		for {
+			if l, aliasType := t.LangID.Canonicalize(); l != t.LangID {
+				switch aliasType {
+				case language.Legacy:
+					if c&Legacy != 0 {
+						if t.LangID == _sh && t.ScriptID == 0 {
+							t.ScriptID = _Latn
+						}
+						t.LangID = l
+						changed = true
+					}
+				case language.Macro:
+					if c&Macro != 0 {
+						// We deviate here from CLDR. The mapping "nb" -> "no"
+						// qualifies as a typical Macro language mapping.  However,
+						// for legacy reasons, CLDR maps "no", the macro language
+						// code for Norwegian, to the dominant variant "nb". This
+						// change is currently under consideration for CLDR as well.
+						// See https://unicode.org/cldr/trac/ticket/2698 and also
+						// https://unicode.org/cldr/trac/ticket/1790 for some of the
+						// practical implications. TODO: this check could be removed
+						// if CLDR adopts this change.
+						if c&CLDR == 0 || t.LangID != _nb {
+							changed = true
+							t.LangID = l
+						}
+					}
+				case language.Deprecated:
+					if c&DeprecatedBase != 0 {
+						if t.LangID == _mo && t.RegionID == 0 {
+							t.RegionID = _MD
+						}
+						t.LangID = l
+						changed = true
+						// Other canonicalization types may still apply.
+						continue
+					}
+				}
+			} else if c&Legacy != 0 && t.LangID == _no && c&CLDR != 0 {
+				t.LangID = _nb
+				changed = true
+			}
+			break
+		}
+	}
+	if c&DeprecatedScript != 0 {
+		if t.ScriptID == _Qaai {
+			changed = true
+			t.ScriptID = _Zinh
+		}
+	}
+	if c&DeprecatedRegion != 0 {
+		if r := t.RegionID.Canonicalize(); r != t.RegionID {
+			changed = true
+			t.RegionID = r
+		}
+	}
+	return t, changed
+}
+
+// Canonicalize returns the canonicalized equivalent of the tag.
+func (c CanonType) Canonicalize(t Tag) (Tag, error) {
+	// First try fast path.
+	if t.isCompact() {
+		if _, changed := canonicalize(c, compact.Tag(t).Tag()); !changed {
+			return t, nil
+		}
+	}
+	// It is unlikely that one will canonicalize a tag after matching. So do
+	// a slow but simple approach here.
+	if tag, changed := canonicalize(c, t.tag()); changed {
+		tag.RemakeString()
+		return makeTag(tag), nil
+	}
+	return t, nil
+
+}
+
+// Confidence indicates the level of certainty for a given return value.
+// For example, Serbian may be written in Cyrillic or Latin script.
+// The confidence level indicates whether a value was explicitly specified,
+// whether it is typically the only possible value, or whether there is
+// an ambiguity.
+type Confidence int
+
+const (
+	No    Confidence = iota // full confidence that there was no match
+	Low                     // most likely value picked out of a set of alternatives
+	High                    // value is generally assumed to be the correct match
+	Exact                   // exact match or explicitly specified value
+)
+
+var confName = []string{"No", "Low", "High", "Exact"}
+
+func (c Confidence) String() string {
+	return confName[c]
+}
+
+// String returns the canonical string representation of the language tag.
+func (t Tag) String() string {
+	return t.tag().String()
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (t Tag) MarshalText() (text []byte, err error) {
+	return t.tag().MarshalText()
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (t *Tag) UnmarshalText(text []byte) error {
+	var tag language.Tag
+	err := tag.UnmarshalText(text)
+	*t = makeTag(tag)
+	return err
+}
+
+// Base returns the base language of the language tag. If the base language is
+// unspecified, an attempt will be made to infer it from the context.
+// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
+func (t Tag) Base() (Base, Confidence) {
+	if b := t.lang(); b != 0 {
+		return Base{b}, Exact
+	}
+	tt := t.tag()
+	c := High
+	if tt.ScriptID == 0 && !tt.RegionID.IsCountry() {
+		c = Low
+	}
+	if tag, err := tt.Maximize(); err == nil && tag.LangID != 0 {
+		return Base{tag.LangID}, c
+	}
+	return Base{0}, No
+}
+
+// Script infers the script for the language tag. If it was not explicitly given, it will infer
+// a most likely candidate.
+// If more than one script is commonly used for a language, the most likely one
+// is returned with a low confidence indication. For example, it returns (Cyrl, Low)
+// for Serbian.
+// If a script cannot be inferred (Zzzz, No) is returned. We do not use Zyyy (undetermined)
+// as one would suspect from the IANA registry for BCP 47. In a Unicode context Zyyy marks
+// common characters (like 1, 2, 3, '.', etc.) and is therefore more like multiple scripts.
+// See https://www.unicode.org/reports/tr24/#Values for more details. Zzzz is also used for
+// unknown value in CLDR.  (Zzzz, Exact) is returned if Zzzz was explicitly specified.
+// Note that an inferred script is never guaranteed to be the correct one. Latin is
+// almost exclusively used for Afrikaans, but Arabic has been used for some texts
+// in the past.  Also, the script that is commonly used may change over time.
+// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
+func (t Tag) Script() (Script, Confidence) {
+	if scr := t.script(); scr != 0 {
+		return Script{scr}, Exact
+	}
+	tt := t.tag()
+	sc, c := language.Script(_Zzzz), No
+	if scr := tt.LangID.SuppressScript(); scr != 0 {
+		// Note: it is not always the case that a language with a suppress
+		// script value is only written in one script (e.g. kk, ms, pa).
+		if tt.RegionID == 0 {
+			return Script{scr}, High
+		}
+		sc, c = scr, High
+	}
+	if tag, err := tt.Maximize(); err == nil {
+		if tag.ScriptID != sc {
+			sc, c = tag.ScriptID, Low
+		}
+	} else {
+		tt, _ = canonicalize(Deprecated|Macro, tt)
+		if tag, err := tt.Maximize(); err == nil && tag.ScriptID != sc {
+			sc, c = tag.ScriptID, Low
+		}
+	}
+	return Script{sc}, c
+}
+
+// Region returns the region for the language tag. If it was not explicitly given, it will
+// infer a most likely candidate from the context.
+// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
+func (t Tag) Region() (Region, Confidence) {
+	if r := t.region(); r != 0 {
+		return Region{r}, Exact
+	}
+	tt := t.tag()
+	if tt, err := tt.Maximize(); err == nil {
+		return Region{tt.RegionID}, Low // TODO: differentiate between high and low.
+	}
+	tt, _ = canonicalize(Deprecated|Macro, tt)
+	if tag, err := tt.Maximize(); err == nil {
+		return Region{tag.RegionID}, Low
+	}
+	return Region{_ZZ}, No // TODO: return world instead of undetermined?
+}
+
+// Variants returns the variants specified explicitly for this language tag.
+// or nil if no variant was specified.
+func (t Tag) Variants() []Variant {
+	if !compact.Tag(t).MayHaveVariants() {
+		return nil
+	}
+	v := []Variant{}
+	x, str := "", t.tag().Variants()
+	for str != "" {
+		x, str = nextToken(str)
+		v = append(v, Variant{x})
+	}
+	return v
+}
+
+// Parent returns the CLDR parent of t. In CLDR, missing fields in data for a
+// specific language are substituted with fields from the parent language.
+// The parent for a language may change for newer versions of CLDR.
+//
+// Parent returns a tag for a less specific language that is mutually
+// intelligible or Und if there is no such language. This may not be the same as
+// simply stripping the last BCP 47 subtag. For instance, the parent of "zh-TW"
+// is "zh-Hant", and the parent of "zh-Hant" is "und".
+func (t Tag) Parent() Tag {
+	return Tag(compact.Tag(t).Parent())
+}
+
+// nextToken returns token t and the rest of the string.
+func nextToken(s string) (t, tail string) {
+	p := strings.Index(s[1:], "-")
+	if p == -1 {
+		return s[1:], ""
+	}
+	p++
+	return s[1:p], s[p:]
+}
+
+// Extension is a single BCP 47 extension.
+type Extension struct {
+	s string
+}
+
+// String returns the string representation of the extension, including the
+// type tag.
+func (e Extension) String() string {
+	return e.s
+}
+
+// ParseExtension parses s as an extension and returns it on success.
+func ParseExtension(s string) (e Extension, err error) {
+	ext, err := language.ParseExtension(s)
+	return Extension{ext}, err
+}
+
+// Type returns the one-byte extension type of e. It returns 0 for the zero
+// exception.
+func (e Extension) Type() byte {
+	if e.s == "" {
+		return 0
+	}
+	return e.s[0]
+}
+
+// Tokens returns the list of tokens of e.
+func (e Extension) Tokens() []string {
+	return strings.Split(e.s, "-")
+}
+
+// Extension returns the extension of type x for tag t. It will return
+// false for ok if t does not have the requested extension. The returned
+// extension will be invalid in this case.
+func (t Tag) Extension(x byte) (ext Extension, ok bool) {
+	if !compact.Tag(t).MayHaveExtensions() {
+		return Extension{}, false
+	}
+	e, ok := t.tag().Extension(x)
+	return Extension{e}, ok
+}
+
+// Extensions returns all extensions of t.
+func (t Tag) Extensions() []Extension {
+	if !compact.Tag(t).MayHaveExtensions() {
+		return nil
+	}
+	e := []Extension{}
+	for _, ext := range t.tag().Extensions() {
+		e = append(e, Extension{ext})
+	}
+	return e
+}
+
+// TypeForKey returns the type associated with the given key, where key and type
+// are of the allowed values defined for the Unicode locale extension ('u') in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// TypeForKey will traverse the inheritance chain to get the correct value.
+//
+// If there are multiple types associated with a key, only the first will be
+// returned. If there is no type associated with a key, it returns the empty
+// string.
+func (t Tag) TypeForKey(key string) string {
+	if !compact.Tag(t).MayHaveExtensions() {
+		if key != "rg" && key != "va" {
+			return ""
+		}
+	}
+	return t.tag().TypeForKey(key)
+}
+
+// SetTypeForKey returns a new Tag with the key set to type, where key and type
+// are of the allowed values defined for the Unicode locale extension ('u') in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// An empty value removes an existing pair with the same key.
+func (t Tag) SetTypeForKey(key, value string) (Tag, error) {
+	tt, err := t.tag().SetTypeForKey(key, value)
+	return makeTag(tt), err
+}
+
+// NumCompactTags is the number of compact tags. The maximum tag is
+// NumCompactTags-1.
+const NumCompactTags = compact.NumCompactTags
+
+// CompactIndex returns an index, where 0 <= index < NumCompactTags, for tags
+// for which data exists in the text repository.The index will change over time
+// and should not be stored in persistent storage. If t does not match a compact
+// index, exact will be false and the compact index will be returned for the
+// first match after repeatedly taking the Parent of t.
+func CompactIndex(t Tag) (index int, exact bool) {
+	id, exact := compact.LanguageID(compact.Tag(t))
+	return int(id), exact
+}
+
+var root = language.Tag{}
+
+// Base is an ISO 639 language code, used for encoding the base language
+// of a language tag.
+type Base struct {
+	langID language.Language
+}
+
+// ParseBase parses a 2- or 3-letter ISO 639 code.
+// It returns a ValueError if s is a well-formed but unknown language identifier
+// or another error if another error occurred.
+func ParseBase(s string) (Base, error) {
+	l, err := language.ParseBase(s)
+	return Base{l}, err
+}
+
+// String returns the BCP 47 representation of the base language.
+func (b Base) String() string {
+	return b.langID.String()
+}
+
+// ISO3 returns the ISO 639-3 language code.
+func (b Base) ISO3() string {
+	return b.langID.ISO3()
+}
+
+// IsPrivateUse reports whether this language code is reserved for private use.
+func (b Base) IsPrivateUse() bool {
+	return b.langID.IsPrivateUse()
+}
+
+// Script is a 4-letter ISO 15924 code for representing scripts.
+// It is idiomatically represented in title case.
+type Script struct {
+	scriptID language.Script
+}
+
+// ParseScript parses a 4-letter ISO 15924 code.
+// It returns a ValueError if s is a well-formed but unknown script identifier
+// or another error if another error occurred.
+func ParseScript(s string) (Script, error) {
+	sc, err := language.ParseScript(s)
+	return Script{sc}, err
+}
+
+// String returns the script code in title case.
+// It returns "Zzzz" for an unspecified script.
+func (s Script) String() string {
+	return s.scriptID.String()
+}
+
+// IsPrivateUse reports whether this script code is reserved for private use.
+func (s Script) IsPrivateUse() bool {
+	return s.scriptID.IsPrivateUse()
+}
+
+// Region is an ISO 3166-1 or UN M.49 code for representing countries and regions.
+type Region struct {
+	regionID language.Region
+}
+
+// EncodeM49 returns the Region for the given UN M.49 code.
+// It returns an error if r is not a valid code.
+func EncodeM49(r int) (Region, error) {
+	rid, err := language.EncodeM49(r)
+	return Region{rid}, err
+}
+
+// ParseRegion parses a 2- or 3-letter ISO 3166-1 or a UN M.49 code.
+// It returns a ValueError if s is a well-formed but unknown region identifier
+// or another error if another error occurred.
+func ParseRegion(s string) (Region, error) {
+	r, err := language.ParseRegion(s)
+	return Region{r}, err
+}
+
+// String returns the BCP 47 representation for the region.
+// It returns "ZZ" for an unspecified region.
+func (r Region) String() string {
+	return r.regionID.String()
+}
+
+// ISO3 returns the 3-letter ISO code of r.
+// Note that not all regions have a 3-letter ISO code.
+// In such cases this method returns "ZZZ".
+func (r Region) ISO3() string {
+	return r.regionID.ISO3()
+}
+
+// M49 returns the UN M.49 encoding of r, or 0 if this encoding
+// is not defined for r.
+func (r Region) M49() int {
+	return r.regionID.M49()
+}
+
+// IsPrivateUse reports whether r has the ISO 3166 User-assigned status. This
+// may include private-use tags that are assigned by CLDR and used in this
+// implementation. So IsPrivateUse and IsCountry can be simultaneously true.
+func (r Region) IsPrivateUse() bool {
+	return r.regionID.IsPrivateUse()
+}
+
+// IsCountry returns whether this region is a country or autonomous area. This
+// includes non-standard definitions from CLDR.
+func (r Region) IsCountry() bool {
+	return r.regionID.IsCountry()
+}
+
+// IsGroup returns whether this region defines a collection of regions. This
+// includes non-standard definitions from CLDR.
+func (r Region) IsGroup() bool {
+	return r.regionID.IsGroup()
+}
+
+// Contains returns whether Region c is contained by Region r. It returns true
+// if c == r.
+func (r Region) Contains(c Region) bool {
+	return r.regionID.Contains(c.regionID)
+}
+
+// TLD returns the country code top-level domain (ccTLD). UK is returned for GB.
+// In all other cases it returns either the region itself or an error.
+//
+// This method may return an error for a region for which there exists a
+// canonical form with a ccTLD. To get that ccTLD canonicalize r first. The
+// region will already be canonicalized it was obtained from a Tag that was
+// obtained using any of the default methods.
+func (r Region) TLD() (Region, error) {
+	tld, err := r.regionID.TLD()
+	return Region{tld}, err
+}
+
+// Canonicalize returns the region or a possible replacement if the region is
+// deprecated. It will not return a replacement for deprecated regions that
+// are split into multiple regions.
+func (r Region) Canonicalize() Region {
+	return Region{r.regionID.Canonicalize()}
+}
+
+// Variant represents a registered variant of a language as defined by BCP 47.
+type Variant struct {
+	variant string
+}
+
+// ParseVariant parses and returns a Variant. An error is returned if s is not
+// a valid variant.
+func ParseVariant(s string) (Variant, error) {
+	v, err := language.ParseVariant(s)
+	return Variant{v.String()}, err
+}
+
+// String returns the string representation of the variant.
+func (v Variant) String() string {
+	return v.variant
+}

vendor/golang.org/x/text/language/match.go

@@ -0,0 +1,735 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"errors"
+	"strings"
+
+	"golang.org/x/text/internal/language"
+)
+
+// A MatchOption configures a Matcher.
+type MatchOption func(*matcher)
+
+// PreferSameScript will, in the absence of a match, result in the first
+// preferred tag with the same script as a supported tag to match this supported
+// tag. The default is currently true, but this may change in the future.
+func PreferSameScript(preferSame bool) MatchOption {
+	return func(m *matcher) { m.preferSameScript = preferSame }
+}
+
+// TODO(v1.0.0): consider making Matcher a concrete type, instead of interface.
+// There doesn't seem to be too much need for multiple types.
+// Making it a concrete type allows MatchStrings to be a method, which will
+// improve its discoverability.
+
+// MatchStrings parses and matches the given strings until one of them matches
+// the language in the Matcher. A string may be an Accept-Language header as
+// handled by ParseAcceptLanguage. The default language is returned if no
+// other language matched.
+func MatchStrings(m Matcher, lang ...string) (tag Tag, index int) {
+	for _, accept := range lang {
+		desired, _, err := ParseAcceptLanguage(accept)
+		if err != nil {
+			continue
+		}
+		if tag, index, conf := m.Match(desired...); conf != No {
+			return tag, index
+		}
+	}
+	tag, index, _ = m.Match()
+	return
+}
+
+// Matcher is the interface that wraps the Match method.
+//
+// Match returns the best match for any of the given tags, along with
+// a unique index associated with the returned tag and a confidence
+// score.
+type Matcher interface {
+	Match(t ...Tag) (tag Tag, index int, c Confidence)
+}
+
+// Comprehends reports the confidence score for a speaker of a given language
+// to being able to comprehend the written form of an alternative language.
+func Comprehends(speaker, alternative Tag) Confidence {
+	_, _, c := NewMatcher([]Tag{alternative}).Match(speaker)
+	return c
+}
+
+// NewMatcher returns a Matcher that matches an ordered list of preferred tags
+// against a list of supported tags based on written intelligibility, closeness
+// of dialect, equivalence of subtags and various other rules. It is initialized
+// with the list of supported tags. The first element is used as the default
+// value in case no match is found.
+//
+// Its Match method matches the first of the given Tags to reach a certain
+// confidence threshold. The tags passed to Match should therefore be specified
+// in order of preference. Extensions are ignored for matching.
+//
+// The index returned by the Match method corresponds to the index of the
+// matched tag in t, but is augmented with the Unicode extension ('u')of the
+// corresponding preferred tag. This allows user locale options to be passed
+// transparently.
+func NewMatcher(t []Tag, options ...MatchOption) Matcher {
+	return newMatcher(t, options)
+}
+
+func (m *matcher) Match(want ...Tag) (t Tag, index int, c Confidence) {
+	var tt language.Tag
+	match, w, c := m.getBest(want...)
+	if match != nil {
+		tt, index = match.tag, match.index
+	} else {
+		// TODO: this should be an option
+		tt = m.default_.tag
+		if m.preferSameScript {
+		outer:
+			for _, w := range want {
+				script, _ := w.Script()
+				if script.scriptID == 0 {
+					// Don't do anything if there is no script, such as with
+					// private subtags.
+					continue
+				}
+				for i, h := range m.supported {
+					if script.scriptID == h.maxScript {
+						tt, index = h.tag, i
+						break outer
+					}
+				}
+			}
+		}
+		// TODO: select first language tag based on script.
+	}
+	if w.RegionID != tt.RegionID && w.RegionID != 0 {
+		if w.RegionID != 0 && tt.RegionID != 0 && tt.RegionID.Contains(w.RegionID) {
+			tt.RegionID = w.RegionID
+			tt.RemakeString()
+		} else if r := w.RegionID.String(); len(r) == 2 {
+			// TODO: also filter macro and deprecated.
+			tt, _ = tt.SetTypeForKey("rg", strings.ToLower(r)+"zzzz")
+		}
+	}
+	// Copy options from the user-provided tag into the result tag. This is hard
+	// to do after the fact, so we do it here.
+	// TODO: add in alternative variants to -u-va-.
+	// TODO: add preferred region to -u-rg-.
+	if e := w.Extensions(); len(e) > 0 {
+		b := language.Builder{}
+		b.SetTag(tt)
+		for _, e := range e {
+			b.AddExt(e)
+		}
+		tt = b.Make()
+	}
+	return makeTag(tt), index, c
+}
+
+// ErrMissingLikelyTagsData indicates no information was available
+// to compute likely values of missing tags.
+var ErrMissingLikelyTagsData = errors.New("missing likely tags data")
+
+// func (t *Tag) setTagsFrom(id Tag) {
+// 	t.LangID = id.LangID
+// 	t.ScriptID = id.ScriptID
+// 	t.RegionID = id.RegionID
+// }
+
+// Tag Matching
+// CLDR defines an algorithm for finding the best match between two sets of language
+// tags. The basic algorithm defines how to score a possible match and then find
+// the match with the best score
+// (see https://www.unicode.org/reports/tr35/#LanguageMatching).
+// Using scoring has several disadvantages. The scoring obfuscates the importance of
+// the various factors considered, making the algorithm harder to understand. Using
+// scoring also requires the full score to be computed for each pair of tags.
+//
+// We will use a different algorithm which aims to have the following properties:
+// - clarity on the precedence of the various selection factors, and
+// - improved performance by allowing early termination of a comparison.
+//
+// Matching algorithm (overview)
+// Input:
+//   - supported: a set of supported tags
+//   - default:   the default tag to return in case there is no match
+//   - desired:   list of desired tags, ordered by preference, starting with
+//                the most-preferred.
+//
+// Algorithm:
+//   1) Set the best match to the lowest confidence level
+//   2) For each tag in "desired":
+//     a) For each tag in "supported":
+//        1) compute the match between the two tags.
+//        2) if the match is better than the previous best match, replace it
+//           with the new match. (see next section)
+//     b) if the current best match is Exact and pin is true the result will be
+//        frozen to the language found thusfar, although better matches may
+//        still be found for the same language.
+//   3) If the best match so far is below a certain threshold, return "default".
+//
+// Ranking:
+// We use two phases to determine whether one pair of tags are a better match
+// than another pair of tags. First, we determine a rough confidence level. If the
+// levels are different, the one with the highest confidence wins.
+// Second, if the rough confidence levels are identical, we use a set of tie-breaker
+// rules.
+//
+// The confidence level of matching a pair of tags is determined by finding the
+// lowest confidence level of any matches of the corresponding subtags (the
+// result is deemed as good as its weakest link).
+// We define the following levels:
+//   Exact    - An exact match of a subtag, before adding likely subtags.
+//   MaxExact - An exact match of a subtag, after adding likely subtags.
+//              [See Note 2].
+//   High     - High level of mutual intelligibility between different subtag
+//              variants.
+//   Low      - Low level of mutual intelligibility between different subtag
+//              variants.
+//   No       - No mutual intelligibility.
+//
+// The following levels can occur for each type of subtag:
+//   Base:    Exact, MaxExact, High, Low, No
+//   Script:  Exact, MaxExact [see Note 3], Low, No
+//   Region:  Exact, MaxExact, High
+//   Variant: Exact, High
+//   Private: Exact, No
+//
+// Any result with a confidence level of Low or higher is deemed a possible match.
+// Once a desired tag matches any of the supported tags with a level of MaxExact
+// or higher, the next desired tag is not considered (see Step 2.b).
+// Note that CLDR provides languageMatching data that defines close equivalence
+// classes for base languages, scripts and regions.
+//
+// Tie-breaking
+// If we get the same confidence level for two matches, we apply a sequence of
+// tie-breaking rules. The first that succeeds defines the result. The rules are
+// applied in the following order.
+//   1) Original language was defined and was identical.
+//   2) Original region was defined and was identical.
+//   3) Distance between two maximized regions was the smallest.
+//   4) Original script was defined and was identical.
+//   5) Distance from want tag to have tag using the parent relation [see Note 5.]
+// If there is still no winner after these rules are applied, the first match
+// found wins.
+//
+// Notes:
+// [2] In practice, as matching of Exact is done in a separate phase from
+//     matching the other levels, we reuse the Exact level to mean MaxExact in
+//     the second phase. As a consequence, we only need the levels defined by
+//     the Confidence type. The MaxExact confidence level is mapped to High in
+//     the public API.
+// [3] We do not differentiate between maximized script values that were derived
+//     from suppressScript versus most likely tag data. We determined that in
+//     ranking the two, one ranks just after the other. Moreover, the two cannot
+//     occur concurrently. As a consequence, they are identical for practical
+//     purposes.
+// [4] In case of deprecated, macro-equivalents and legacy mappings, we assign
+//     the MaxExact level to allow iw vs he to still be a closer match than
+//     en-AU vs en-US, for example.
+// [5] In CLDR a locale inherits fields that are unspecified for this locale
+//     from its parent. Therefore, if a locale is a parent of another locale,
+//     it is a strong measure for closeness, especially when no other tie
+//     breaker rule applies. One could also argue it is inconsistent, for
+//     example, when pt-AO matches pt (which CLDR equates with pt-BR), even
+//     though its parent is pt-PT according to the inheritance rules.
+//
+// Implementation Details:
+// There are several performance considerations worth pointing out. Most notably,
+// we preprocess as much as possible (within reason) at the time of creation of a
+// matcher. This includes:
+//   - creating a per-language map, which includes data for the raw base language
+//     and its canonicalized variant (if applicable),
+//   - expanding entries for the equivalence classes defined in CLDR's
+//     languageMatch data.
+// The per-language map ensures that typically only a very small number of tags
+// need to be considered. The pre-expansion of canonicalized subtags and
+// equivalence classes reduces the amount of map lookups that need to be done at
+// runtime.
+
+// matcher keeps a set of supported language tags, indexed by language.
+type matcher struct {
+	default_         *haveTag
+	supported        []*haveTag
+	index            map[language.Language]*matchHeader
+	passSettings     bool
+	preferSameScript bool
+}
+
+// matchHeader has the lists of tags for exact matches and matches based on
+// maximized and canonicalized tags for a given language.
+type matchHeader struct {
+	haveTags []*haveTag
+	original bool
+}
+
+// haveTag holds a supported Tag and its maximized script and region. The maximized
+// or canonicalized language is not stored as it is not needed during matching.
+type haveTag struct {
+	tag language.Tag
+
+	// index of this tag in the original list of supported tags.
+	index int
+
+	// conf is the maximum confidence that can result from matching this haveTag.
+	// When conf < Exact this means it was inserted after applying a CLDR equivalence rule.
+	conf Confidence
+
+	// Maximized region and script.
+	maxRegion language.Region
+	maxScript language.Script
+
+	// altScript may be checked as an alternative match to maxScript. If altScript
+	// matches, the confidence level for this match is Low. Theoretically there
+	// could be multiple alternative scripts. This does not occur in practice.
+	altScript language.Script
+
+	// nextMax is the index of the next haveTag with the same maximized tags.
+	nextMax uint16
+}
+
+func makeHaveTag(tag language.Tag, index int) (haveTag, language.Language) {
+	max := tag
+	if tag.LangID != 0 || tag.RegionID != 0 || tag.ScriptID != 0 {
+		max, _ = canonicalize(All, max)
+		max, _ = max.Maximize()
+		max.RemakeString()
+	}
+	return haveTag{tag, index, Exact, max.RegionID, max.ScriptID, altScript(max.LangID, max.ScriptID), 0}, max.LangID
+}
+
+// altScript returns an alternative script that may match the given script with
+// a low confidence.  At the moment, the langMatch data allows for at most one
+// script to map to another and we rely on this to keep the code simple.
+func altScript(l language.Language, s language.Script) language.Script {
+	for _, alt := range matchScript {
+		// TODO: also match cases where language is not the same.
+		if (language.Language(alt.wantLang) == l || language.Language(alt.haveLang) == l) &&
+			language.Script(alt.haveScript) == s {
+			return language.Script(alt.wantScript)
+		}
+	}
+	return 0
+}
+
+// addIfNew adds a haveTag to the list of tags only if it is a unique tag.
+// Tags that have the same maximized values are linked by index.
+func (h *matchHeader) addIfNew(n haveTag, exact bool) {
+	h.original = h.original || exact
+	// Don't add new exact matches.
+	for _, v := range h.haveTags {
+		if equalsRest(v.tag, n.tag) {
+			return
+		}
+	}
+	// Allow duplicate maximized tags, but create a linked list to allow quickly
+	// comparing the equivalents and bail out.
+	for i, v := range h.haveTags {
+		if v.maxScript == n.maxScript &&
+			v.maxRegion == n.maxRegion &&
+			v.tag.VariantOrPrivateUseTags() == n.tag.VariantOrPrivateUseTags() {
+			for h.haveTags[i].nextMax != 0 {
+				i = int(h.haveTags[i].nextMax)
+			}
+			h.haveTags[i].nextMax = uint16(len(h.haveTags))
+			break
+		}
+	}
+	h.haveTags = append(h.haveTags, &n)
+}
+
+// header returns the matchHeader for the given language. It creates one if
+// it doesn't already exist.
+func (m *matcher) header(l language.Language) *matchHeader {
+	if h := m.index[l]; h != nil {
+		return h
+	}
+	h := &matchHeader{}
+	m.index[l] = h
+	return h
+}
+
+func toConf(d uint8) Confidence {
+	if d <= 10 {
+		return High
+	}
+	if d < 30 {
+		return Low
+	}
+	return No
+}
+
+// newMatcher builds an index for the given supported tags and returns it as
+// a matcher. It also expands the index by considering various equivalence classes
+// for a given tag.
+func newMatcher(supported []Tag, options []MatchOption) *matcher {
+	m := &matcher{
+		index:            make(map[language.Language]*matchHeader),
+		preferSameScript: true,
+	}
+	for _, o := range options {
+		o(m)
+	}
+	if len(supported) == 0 {
+		m.default_ = &haveTag{}
+		return m
+	}
+	// Add supported languages to the index. Add exact matches first to give
+	// them precedence.
+	for i, tag := range supported {
+		tt := tag.tag()
+		pair, _ := makeHaveTag(tt, i)
+		m.header(tt.LangID).addIfNew(pair, true)
+		m.supported = append(m.supported, &pair)
+	}
+	m.default_ = m.header(supported[0].lang()).haveTags[0]
+	// Keep these in two different loops to support the case that two equivalent
+	// languages are distinguished, such as iw and he.
+	for i, tag := range supported {
+		tt := tag.tag()
+		pair, max := makeHaveTag(tt, i)
+		if max != tt.LangID {
+			m.header(max).addIfNew(pair, true)
+		}
+	}
+
+	// update is used to add indexes in the map for equivalent languages.
+	// update will only add entries to original indexes, thus not computing any
+	// transitive relations.
+	update := func(want, have uint16, conf Confidence) {
+		if hh := m.index[language.Language(have)]; hh != nil {
+			if !hh.original {
+				return
+			}
+			hw := m.header(language.Language(want))
+			for _, ht := range hh.haveTags {
+				v := *ht
+				if conf < v.conf {
+					v.conf = conf
+				}
+				v.nextMax = 0 // this value needs to be recomputed
+				if v.altScript != 0 {
+					v.altScript = altScript(language.Language(want), v.maxScript)
+				}
+				hw.addIfNew(v, conf == Exact && hh.original)
+			}
+		}
+	}
+
+	// Add entries for languages with mutual intelligibility as defined by CLDR's
+	// languageMatch data.
+	for _, ml := range matchLang {
+		update(ml.want, ml.have, toConf(ml.distance))
+		if !ml.oneway {
+			update(ml.have, ml.want, toConf(ml.distance))
+		}
+	}
+
+	// Add entries for possible canonicalizations. This is an optimization to
+	// ensure that only one map lookup needs to be done at runtime per desired tag.
+	// First we match deprecated equivalents. If they are perfect equivalents
+	// (their canonicalization simply substitutes a different language code, but
+	// nothing else), the match confidence is Exact, otherwise it is High.
+	for i, lm := range language.AliasMap {
+		// If deprecated codes match and there is no fiddling with the script
+		// or region, we consider it an exact match.
+		conf := Exact
+		if language.AliasTypes[i] != language.Macro {
+			if !isExactEquivalent(language.Language(lm.From)) {
+				conf = High
+			}
+			update(lm.To, lm.From, conf)
+		}
+		update(lm.From, lm.To, conf)
+	}
+	return m
+}
+
+// getBest gets the best matching tag in m for any of the given tags, taking into
+// account the order of preference of the given tags.
+func (m *matcher) getBest(want ...Tag) (got *haveTag, orig language.Tag, c Confidence) {
+	best := bestMatch{}
+	for i, ww := range want {
+		w := ww.tag()
+		var max language.Tag
+		// Check for exact match first.
+		h := m.index[w.LangID]
+		if w.LangID != 0 {
+			if h == nil {
+				continue
+			}
+			// Base language is defined.
+			max, _ = canonicalize(Legacy|Deprecated|Macro, w)
+			// A region that is added through canonicalization is stronger than
+			// a maximized region: set it in the original (e.g. mo -> ro-MD).
+			if w.RegionID != max.RegionID {
+				w.RegionID = max.RegionID
+			}
+			// TODO: should we do the same for scripts?
+			// See test case: en, sr, nl ; sh ; sr
+			max, _ = max.Maximize()
+		} else {
+			// Base language is not defined.
+			if h != nil {
+				for i := range h.haveTags {
+					have := h.haveTags[i]
+					if equalsRest(have.tag, w) {
+						return have, w, Exact
+					}
+				}
+			}
+			if w.ScriptID == 0 && w.RegionID == 0 {
+				// We skip all tags matching und for approximate matching, including
+				// private tags.
+				continue
+			}
+			max, _ = w.Maximize()
+			if h = m.index[max.LangID]; h == nil {
+				continue
+			}
+		}
+		pin := true
+		for _, t := range want[i+1:] {
+			if w.LangID == t.lang() {
+				pin = false
+				break
+			}
+		}
+		// Check for match based on maximized tag.
+		for i := range h.haveTags {
+			have := h.haveTags[i]
+			best.update(have, w, max.ScriptID, max.RegionID, pin)
+			if best.conf == Exact {
+				for have.nextMax != 0 {
+					have = h.haveTags[have.nextMax]
+					best.update(have, w, max.ScriptID, max.RegionID, pin)
+				}
+				return best.have, best.want, best.conf
+			}
+		}
+	}
+	if best.conf <= No {
+		if len(want) != 0 {
+			return nil, want[0].tag(), No
+		}
+		return nil, language.Tag{}, No
+	}
+	return best.have, best.want, best.conf
+}
+
+// bestMatch accumulates the best match so far.
+type bestMatch struct {
+	have            *haveTag
+	want            language.Tag
+	conf            Confidence
+	pinnedRegion    language.Region
+	pinLanguage     bool
+	sameRegionGroup bool
+	// Cached results from applying tie-breaking rules.
+	origLang     bool
+	origReg      bool
+	paradigmReg  bool
+	regGroupDist uint8
+	origScript   bool
+}
+
+// update updates the existing best match if the new pair is considered to be a
+// better match. To determine if the given pair is a better match, it first
+// computes the rough confidence level. If this surpasses the current match, it
+// will replace it and update the tie-breaker rule cache. If there is a tie, it
+// proceeds with applying a series of tie-breaker rules. If there is no
+// conclusive winner after applying the tie-breaker rules, it leaves the current
+// match as the preferred match.
+//
+// If pin is true and have and tag are a strong match, it will henceforth only
+// consider matches for this language. This corresponds to the idea that most
+// users have a strong preference for the first defined language. A user can
+// still prefer a second language over a dialect of the preferred language by
+// explicitly specifying dialects, e.g. "en, nl, en-GB". In this case pin should
+// be false.
+func (m *bestMatch) update(have *haveTag, tag language.Tag, maxScript language.Script, maxRegion language.Region, pin bool) {
+	// Bail if the maximum attainable confidence is below that of the current best match.
+	c := have.conf
+	if c < m.conf {
+		return
+	}
+	// Don't change the language once we already have found an exact match.
+	if m.pinLanguage && tag.LangID != m.want.LangID {
+		return
+	}
+	// Pin the region group if we are comparing tags for the same language.
+	if tag.LangID == m.want.LangID && m.sameRegionGroup {
+		_, sameGroup := regionGroupDist(m.pinnedRegion, have.maxRegion, have.maxScript, m.want.LangID)
+		if !sameGroup {
+			return
+		}
+	}
+	if c == Exact && have.maxScript == maxScript {
+		// If there is another language and then another entry of this language,
+		// don't pin anything, otherwise pin the language.
+		m.pinLanguage = pin
+	}
+	if equalsRest(have.tag, tag) {
+	} else if have.maxScript != maxScript {
+		// There is usually very little comprehension between different scripts.
+		// In a few cases there may still be Low comprehension. This possibility
+		// is pre-computed and stored in have.altScript.
+		if Low < m.conf || have.altScript != maxScript {
+			return
+		}
+		c = Low
+	} else if have.maxRegion != maxRegion {
+		if High < c {
+			// There is usually a small difference between languages across regions.
+			c = High
+		}
+	}
+
+	// We store the results of the computations of the tie-breaker rules along
+	// with the best match. There is no need to do the checks once we determine
+	// we have a winner, but we do still need to do the tie-breaker computations.
+	// We use "beaten" to keep track if we still need to do the checks.
+	beaten := false // true if the new pair defeats the current one.
+	if c != m.conf {
+		if c < m.conf {
+			return
+		}
+		beaten = true
+	}
+
+	// Tie-breaker rules:
+	// We prefer if the pre-maximized language was specified and identical.
+	origLang := have.tag.LangID == tag.LangID && tag.LangID != 0
+	if !beaten && m.origLang != origLang {
+		if m.origLang {
+			return
+		}
+		beaten = true
+	}
+
+	// We prefer if the pre-maximized region was specified and identical.
+	origReg := have.tag.RegionID == tag.RegionID && tag.RegionID != 0
+	if !beaten && m.origReg != origReg {
+		if m.origReg {
+			return
+		}
+		beaten = true
+	}
+
+	regGroupDist, sameGroup := regionGroupDist(have.maxRegion, maxRegion, maxScript, tag.LangID)
+	if !beaten && m.regGroupDist != regGroupDist {
+		if regGroupDist > m.regGroupDist {
+			return
+		}
+		beaten = true
+	}
+
+	paradigmReg := isParadigmLocale(tag.LangID, have.maxRegion)
+	if !beaten && m.paradigmReg != paradigmReg {
+		if !paradigmReg {
+			return
+		}
+		beaten = true
+	}
+
+	// Next we prefer if the pre-maximized script was specified and identical.
+	origScript := have.tag.ScriptID == tag.ScriptID && tag.ScriptID != 0
+	if !beaten && m.origScript != origScript {
+		if m.origScript {
+			return
+		}
+		beaten = true
+	}
+
+	// Update m to the newly found best match.
+	if beaten {
+		m.have = have
+		m.want = tag
+		m.conf = c
+		m.pinnedRegion = maxRegion
+		m.sameRegionGroup = sameGroup
+		m.origLang = origLang
+		m.origReg = origReg
+		m.paradigmReg = paradigmReg
+		m.origScript = origScript
+		m.regGroupDist = regGroupDist
+	}
+}
+
+func isParadigmLocale(lang language.Language, r language.Region) bool {
+	for _, e := range paradigmLocales {
+		if language.Language(e[0]) == lang && (r == language.Region(e[1]) || r == language.Region(e[2])) {
+			return true
+		}
+	}
+	return false
+}
+
+// regionGroupDist computes the distance between two regions based on their
+// CLDR grouping.
+func regionGroupDist(a, b language.Region, script language.Script, lang language.Language) (dist uint8, same bool) {
+	const defaultDistance = 4
+
+	aGroup := uint(regionToGroups[a]) << 1
+	bGroup := uint(regionToGroups[b]) << 1
+	for _, ri := range matchRegion {
+		if language.Language(ri.lang) == lang && (ri.script == 0 || language.Script(ri.script) == script) {
+			group := uint(1 << (ri.group &^ 0x80))
+			if 0x80&ri.group == 0 {
+				if aGroup&bGroup&group != 0 { // Both regions are in the group.
+					return ri.distance, ri.distance == defaultDistance
+				}
+			} else {
+				if (aGroup|bGroup)&group == 0 { // Both regions are not in the group.
+					return ri.distance, ri.distance == defaultDistance
+				}
+			}
+		}
+	}
+	return defaultDistance, true
+}
+
+// equalsRest compares everything except the language.
+func equalsRest(a, b language.Tag) bool {
+	// TODO: don't include extensions in this comparison. To do this efficiently,
+	// though, we should handle private tags separately.
+	return a.ScriptID == b.ScriptID && a.RegionID == b.RegionID && a.VariantOrPrivateUseTags() == b.VariantOrPrivateUseTags()
+}
+
+// isExactEquivalent returns true if canonicalizing the language will not alter
+// the script or region of a tag.
+func isExactEquivalent(l language.Language) bool {
+	for _, o := range notEquivalent {
+		if o == l {
+			return false
+		}
+	}
+	return true
+}
+
+var notEquivalent []language.Language
+
+func init() {
+	// Create a list of all languages for which canonicalization may alter the
+	// script or region.
+	for _, lm := range language.AliasMap {
+		tag := language.Tag{LangID: language.Language(lm.From)}
+		if tag, _ = canonicalize(All, tag); tag.ScriptID != 0 || tag.RegionID != 0 {
+			notEquivalent = append(notEquivalent, language.Language(lm.From))
+		}
+	}
+	// Maximize undefined regions of paradigm locales.
+	for i, v := range paradigmLocales {
+		t := language.Tag{LangID: language.Language(v[0])}
+		max, _ := t.Maximize()
+		if v[1] == 0 {
+			paradigmLocales[i][1] = uint16(max.RegionID)
+		}
+		if v[2] == 0 {
+			paradigmLocales[i][2] = uint16(max.RegionID)
+		}
+	}
+}

vendor/golang.org/x/text/language/parse.go

@@ -0,0 +1,256 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import (
+	"errors"
+	"sort"
+	"strconv"
+	"strings"
+
+	"golang.org/x/text/internal/language"
+)
+
+// ValueError is returned by any of the parsing functions when the
+// input is well-formed but the respective subtag is not recognized
+// as a valid value.
+type ValueError interface {
+	error
+
+	// Subtag returns the subtag for which the error occurred.
+	Subtag() string
+}
+
+// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
+// failed it returns an error and any part of the tag that could be parsed.
+// If parsing succeeded but an unknown value was found, it returns
+// ValueError. The Tag returned in this case is just stripped of the unknown
+// value. All other values are preserved. It accepts tags in the BCP 47 format
+// and extensions to this standard defined in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// The resulting tag is canonicalized using the default canonicalization type.
+func Parse(s string) (t Tag, err error) {
+	return Default.Parse(s)
+}
+
+// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
+// failed it returns an error and any part of the tag that could be parsed.
+// If parsing succeeded but an unknown value was found, it returns
+// ValueError. The Tag returned in this case is just stripped of the unknown
+// value. All other values are preserved. It accepts tags in the BCP 47 format
+// and extensions to this standard defined in
+// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
+// The resulting tag is canonicalized using the canonicalization type c.
+func (c CanonType) Parse(s string) (t Tag, err error) {
+	defer func() {
+		if recover() != nil {
+			t = Tag{}
+			err = language.ErrSyntax
+		}
+	}()
+
+	tt, err := language.Parse(s)
+	if err != nil {
+		return makeTag(tt), err
+	}
+	tt, changed := canonicalize(c, tt)
+	if changed {
+		tt.RemakeString()
+	}
+	return makeTag(tt), err
+}
+
+// Compose creates a Tag from individual parts, which may be of type Tag, Base,
+// Script, Region, Variant, []Variant, Extension, []Extension or error. If a
+// Base, Script or Region or slice of type Variant or Extension is passed more
+// than once, the latter will overwrite the former. Variants and Extensions are
+// accumulated, but if two extensions of the same type are passed, the latter
+// will replace the former. For -u extensions, though, the key-type pairs are
+// added, where later values overwrite older ones. A Tag overwrites all former
+// values and typically only makes sense as the first argument. The resulting
+// tag is returned after canonicalizing using the Default CanonType. If one or
+// more errors are encountered, one of the errors is returned.
+func Compose(part ...interface{}) (t Tag, err error) {
+	return Default.Compose(part...)
+}
+
+// Compose creates a Tag from individual parts, which may be of type Tag, Base,
+// Script, Region, Variant, []Variant, Extension, []Extension or error. If a
+// Base, Script or Region or slice of type Variant or Extension is passed more
+// than once, the latter will overwrite the former. Variants and Extensions are
+// accumulated, but if two extensions of the same type are passed, the latter
+// will replace the former. For -u extensions, though, the key-type pairs are
+// added, where later values overwrite older ones. A Tag overwrites all former
+// values and typically only makes sense as the first argument. The resulting
+// tag is returned after canonicalizing using CanonType c. If one or more errors
+// are encountered, one of the errors is returned.
+func (c CanonType) Compose(part ...interface{}) (t Tag, err error) {
+	defer func() {
+		if recover() != nil {
+			t = Tag{}
+			err = language.ErrSyntax
+		}
+	}()
+
+	var b language.Builder
+	if err = update(&b, part...); err != nil {
+		return und, err
+	}
+	b.Tag, _ = canonicalize(c, b.Tag)
+	return makeTag(b.Make()), err
+}
+
+var errInvalidArgument = errors.New("invalid Extension or Variant")
+
+func update(b *language.Builder, part ...interface{}) (err error) {
+	for _, x := range part {
+		switch v := x.(type) {
+		case Tag:
+			b.SetTag(v.tag())
+		case Base:
+			b.Tag.LangID = v.langID
+		case Script:
+			b.Tag.ScriptID = v.scriptID
+		case Region:
+			b.Tag.RegionID = v.regionID
+		case Variant:
+			if v.variant == "" {
+				err = errInvalidArgument
+				break
+			}
+			b.AddVariant(v.variant)
+		case Extension:
+			if v.s == "" {
+				err = errInvalidArgument
+				break
+			}
+			b.SetExt(v.s)
+		case []Variant:
+			b.ClearVariants()
+			for _, v := range v {
+				b.AddVariant(v.variant)
+			}
+		case []Extension:
+			b.ClearExtensions()
+			for _, e := range v {
+				b.SetExt(e.s)
+			}
+		// TODO: support parsing of raw strings based on morphology or just extensions?
+		case error:
+			if v != nil {
+				err = v
+			}
+		}
+	}
+	return
+}
+
+var errInvalidWeight = errors.New("ParseAcceptLanguage: invalid weight")
+var errTagListTooLarge = errors.New("tag list exceeds max length")
+
+// ParseAcceptLanguage parses the contents of an Accept-Language header as
+// defined in http://www.ietf.org/rfc/rfc2616.txt and returns a list of Tags and
+// a list of corresponding quality weights. It is more permissive than RFC 2616
+// and may return non-nil slices even if the input is not valid.
+// The Tags will be sorted by highest weight first and then by first occurrence.
+// Tags with a weight of zero will be dropped. An error will be returned if the
+// input could not be parsed.
+func ParseAcceptLanguage(s string) (tag []Tag, q []float32, err error) {
+	defer func() {
+		if recover() != nil {
+			tag = nil
+			q = nil
+			err = language.ErrSyntax
+		}
+	}()
+
+	if strings.Count(s, "-") > 1000 {
+		return nil, nil, errTagListTooLarge
+	}
+
+	var entry string
+	for s != "" {
+		if entry, s = split(s, ','); entry == "" {
+			continue
+		}
+
+		entry, weight := split(entry, ';')
+
+		// Scan the language.
+		t, err := Parse(entry)
+		if err != nil {
+			id, ok := acceptFallback[entry]
+			if !ok {
+				return nil, nil, err
+			}
+			t = makeTag(language.Tag{LangID: id})
+		}
+
+		// Scan the optional weight.
+		w := 1.0
+		if weight != "" {
+			weight = consume(weight, 'q')
+			weight = consume(weight, '=')
+			// consume returns the empty string when a token could not be
+			// consumed, resulting in an error for ParseFloat.
+			if w, err = strconv.ParseFloat(weight, 32); err != nil {
+				return nil, nil, errInvalidWeight
+			}
+			// Drop tags with a quality weight of 0.
+			if w <= 0 {
+				continue
+			}
+		}
+
+		tag = append(tag, t)
+		q = append(q, float32(w))
+	}
+	sort.Stable(&tagSort{tag, q})
+	return tag, q, nil
+}
+
+// consume removes a leading token c from s and returns the result or the empty
+// string if there is no such token.
+func consume(s string, c byte) string {
+	if s == "" || s[0] != c {
+		return ""
+	}
+	return strings.TrimSpace(s[1:])
+}
+
+func split(s string, c byte) (head, tail string) {
+	if i := strings.IndexByte(s, c); i >= 0 {
+		return strings.TrimSpace(s[:i]), strings.TrimSpace(s[i+1:])
+	}
+	return strings.TrimSpace(s), ""
+}
+
+// Add hack mapping to deal with a small number of cases that occur
+// in Accept-Language (with reasonable frequency).
+var acceptFallback = map[string]language.Language{
+	"english": _en,
+	"deutsch": _de,
+	"italian": _it,
+	"french":  _fr,
+	"*":       _mul, // defined in the spec to match all languages.
+}
+
+type tagSort struct {
+	tag []Tag
+	q   []float32
+}
+
+func (s *tagSort) Len() int {
+	return len(s.q)
+}
+
+func (s *tagSort) Less(i, j int) bool {
+	return s.q[i] > s.q[j]
+}
+
+func (s *tagSort) Swap(i, j int) {
+	s.tag[i], s.tag[j] = s.tag[j], s.tag[i]
+	s.q[i], s.q[j] = s.q[j], s.q[i]
+}

vendor/golang.org/x/text/language/tables.go

@@ -0,0 +1,298 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package language
+
+// CLDRVersion is the CLDR version from which the tables in this package are derived.
+const CLDRVersion = "32"
+
+const (
+	_de  = 269
+	_en  = 313
+	_fr  = 350
+	_it  = 505
+	_mo  = 784
+	_no  = 879
+	_nb  = 839
+	_pt  = 960
+	_sh  = 1031
+	_mul = 806
+	_und = 0
+)
+const (
+	_001 = 1
+	_419 = 31
+	_BR  = 65
+	_CA  = 73
+	_ES  = 111
+	_GB  = 124
+	_MD  = 189
+	_PT  = 239
+	_UK  = 307
+	_US  = 310
+	_ZZ  = 358
+	_XA  = 324
+	_XC  = 326
+	_XK  = 334
+)
+const (
+	_Latn = 91
+	_Hani = 57
+	_Hans = 59
+	_Hant = 60
+	_Qaaa = 149
+	_Qaai = 157
+	_Qabx = 198
+	_Zinh = 255
+	_Zyyy = 260
+	_Zzzz = 261
+)
+
+var regionToGroups = []uint8{ // 359 elements
+	// Entry 0 - 3F
+	0x00, 0x00, 0x00, 0x04, 0x04, 0x00, 0x00, 0x04,
+	0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x04, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x00,
+	0x00, 0x04, 0x00, 0x00, 0x04, 0x01, 0x00, 0x00,
+	0x04, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x00, 0x04,
+	// Entry 40 - 7F
+	0x04, 0x04, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x04, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x04, 0x00, 0x00, 0x04, 0x00, 0x00, 0x04,
+	0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x00,
+	0x08, 0x00, 0x04, 0x00, 0x00, 0x08, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04,
+	// Entry 80 - BF
+	0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x04, 0x00,
+	0x00, 0x00, 0x04, 0x01, 0x00, 0x04, 0x02, 0x00,
+	0x04, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x04, 0x00,
+	0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x08, 0x08, 0x00, 0x00, 0x00, 0x04,
+	// Entry C0 - FF
+	0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02,
+	0x01, 0x04, 0x08, 0x04, 0x00, 0x00, 0x00, 0x00,
+	0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x04, 0x00, 0x05, 0x00, 0x00,
+	0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	// Entry 100 - 13F
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04,
+	0x00, 0x00, 0x00, 0x04, 0x04, 0x00, 0x00, 0x00,
+	0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x08, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x05, 0x04,
+	0x00, 0x00, 0x04, 0x00, 0x04, 0x04, 0x05, 0x00,
+	// Entry 140 - 17F
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+} // Size: 383 bytes
+
+var paradigmLocales = [][3]uint16{ // 3 elements
+	0: [3]uint16{0x139, 0x0, 0x7c},
+	1: [3]uint16{0x13e, 0x0, 0x1f},
+	2: [3]uint16{0x3c0, 0x41, 0xef},
+} // Size: 42 bytes
+
+type mutualIntelligibility struct {
+	want     uint16
+	have     uint16
+	distance uint8
+	oneway   bool
+}
+type scriptIntelligibility struct {
+	wantLang   uint16
+	haveLang   uint16
+	wantScript uint8
+	haveScript uint8
+	distance   uint8
+}
+type regionIntelligibility struct {
+	lang     uint16
+	script   uint8
+	group    uint8
+	distance uint8
+}
+
+// matchLang holds pairs of langIDs of base languages that are typically
+// mutually intelligible. Each pair is associated with a confidence and
+// whether the intelligibility goes one or both ways.
+var matchLang = []mutualIntelligibility{ // 113 elements
+	0:   {want: 0x1d1, have: 0xb7, distance: 0x4, oneway: false},
+	1:   {want: 0x407, have: 0xb7, distance: 0x4, oneway: false},
+	2:   {want: 0x407, have: 0x1d1, distance: 0x4, oneway: false},
+	3:   {want: 0x407, have: 0x432, distance: 0x4, oneway: false},
+	4:   {want: 0x43a, have: 0x1, distance: 0x4, oneway: false},
+	5:   {want: 0x1a3, have: 0x10d, distance: 0x4, oneway: true},
+	6:   {want: 0x295, have: 0x10d, distance: 0x4, oneway: true},
+	7:   {want: 0x101, have: 0x36f, distance: 0x8, oneway: false},
+	8:   {want: 0x101, have: 0x347, distance: 0x8, oneway: false},
+	9:   {want: 0x5, have: 0x3e2, distance: 0xa, oneway: true},
+	10:  {want: 0xd, have: 0x139, distance: 0xa, oneway: true},
+	11:  {want: 0x16, have: 0x367, distance: 0xa, oneway: true},
+	12:  {want: 0x21, have: 0x139, distance: 0xa, oneway: true},
+	13:  {want: 0x56, have: 0x13e, distance: 0xa, oneway: true},
+	14:  {want: 0x58, have: 0x3e2, distance: 0xa, oneway: true},
+	15:  {want: 0x71, have: 0x3e2, distance: 0xa, oneway: true},
+	16:  {want: 0x75, have: 0x139, distance: 0xa, oneway: true},
+	17:  {want: 0x82, have: 0x1be, distance: 0xa, oneway: true},
+	18:  {want: 0xa5, have: 0x139, distance: 0xa, oneway: true},
+	19:  {want: 0xb2, have: 0x15e, distance: 0xa, oneway: true},
+	20:  {want: 0xdd, have: 0x153, distance: 0xa, oneway: true},
+	21:  {want: 0xe5, have: 0x139, distance: 0xa, oneway: true},
+	22:  {want: 0xe9, have: 0x3a, distance: 0xa, oneway: true},
+	23:  {want: 0xf0, have: 0x15e, distance: 0xa, oneway: true},
+	24:  {want: 0xf9, have: 0x15e, distance: 0xa, oneway: true},
+	25:  {want: 0x100, have: 0x139, distance: 0xa, oneway: true},
+	26:  {want: 0x130, have: 0x139, distance: 0xa, oneway: true},
+	27:  {want: 0x13c, have: 0x139, distance: 0xa, oneway: true},
+	28:  {want: 0x140, have: 0x151, distance: 0xa, oneway: true},
+	29:  {want: 0x145, have: 0x13e, distance: 0xa, oneway: true},
+	30:  {want: 0x158, have: 0x101, distance: 0xa, oneway: true},
+	31:  {want: 0x16d, have: 0x367, distance: 0xa, oneway: true},
+	32:  {want: 0x16e, have: 0x139, distance: 0xa, oneway: true},
+	33:  {want: 0x16f, have: 0x139, distance: 0xa, oneway: true},
+	34:  {want: 0x17e, have: 0x139, distance: 0xa, oneway: true},
+	35:  {want: 0x190, have: 0x13e, distance: 0xa, oneway: true},
+	36:  {want: 0x194, have: 0x13e, distance: 0xa, oneway: true},
+	37:  {want: 0x1a4, have: 0x1be, distance: 0xa, oneway: true},
+	38:  {want: 0x1b4, have: 0x139, distance: 0xa, oneway: true},
+	39:  {want: 0x1b8, have: 0x139, distance: 0xa, oneway: true},
+	40:  {want: 0x1d4, have: 0x15e, distance: 0xa, oneway: true},
+	41:  {want: 0x1d7, have: 0x3e2, distance: 0xa, oneway: true},
+	42:  {want: 0x1d9, have: 0x139, distance: 0xa, oneway: true},
+	43:  {want: 0x1e7, have: 0x139, distance: 0xa, oneway: true},
+	44:  {want: 0x1f8, have: 0x139, distance: 0xa, oneway: true},
+	45:  {want: 0x20e, have: 0x1e1, distance: 0xa, oneway: true},
+	46:  {want: 0x210, have: 0x139, distance: 0xa, oneway: true},
+	47:  {want: 0x22d, have: 0x15e, distance: 0xa, oneway: true},
+	48:  {want: 0x242, have: 0x3e2, distance: 0xa, oneway: true},
+	49:  {want: 0x24a, have: 0x139, distance: 0xa, oneway: true},
+	50:  {want: 0x251, have: 0x139, distance: 0xa, oneway: true},
+	51:  {want: 0x265, have: 0x139, distance: 0xa, oneway: true},
+	52:  {want: 0x274, have: 0x48a, distance: 0xa, oneway: true},
+	53:  {want: 0x28a, have: 0x3e2, distance: 0xa, oneway: true},
+	54:  {want: 0x28e, have: 0x1f9, distance: 0xa, oneway: true},
+	55:  {want: 0x2a3, have: 0x139, distance: 0xa, oneway: true},
+	56:  {want: 0x2b5, have: 0x15e, distance: 0xa, oneway: true},
+	57:  {want: 0x2b8, have: 0x139, distance: 0xa, oneway: true},
+	58:  {want: 0x2be, have: 0x139, distance: 0xa, oneway: true},
+	59:  {want: 0x2c3, have: 0x15e, distance: 0xa, oneway: true},
+	60:  {want: 0x2ed, have: 0x139, distance: 0xa, oneway: true},
+	61:  {want: 0x2f1, have: 0x15e, distance: 0xa, oneway: true},
+	62:  {want: 0x2fa, have: 0x139, distance: 0xa, oneway: true},
+	63:  {want: 0x2ff, have: 0x7e, distance: 0xa, oneway: true},
+	64:  {want: 0x304, have: 0x139, distance: 0xa, oneway: true},
+	65:  {want: 0x30b, have: 0x3e2, distance: 0xa, oneway: true},
+	66:  {want: 0x31b, have: 0x1be, distance: 0xa, oneway: true},
+	67:  {want: 0x31f, have: 0x1e1, distance: 0xa, oneway: true},
+	68:  {want: 0x320, have: 0x139, distance: 0xa, oneway: true},
+	69:  {want: 0x331, have: 0x139, distance: 0xa, oneway: true},
+	70:  {want: 0x351, have: 0x139, distance: 0xa, oneway: true},
+	71:  {want: 0x36a, have: 0x347, distance: 0xa, oneway: false},
+	72:  {want: 0x36a, have: 0x36f, distance: 0xa, oneway: true},
+	73:  {want: 0x37a, have: 0x139, distance: 0xa, oneway: true},
+	74:  {want: 0x387, have: 0x139, distance: 0xa, oneway: true},
+	75:  {want: 0x389, have: 0x139, distance: 0xa, oneway: true},
+	76:  {want: 0x38b, have: 0x15e, distance: 0xa, oneway: true},
+	77:  {want: 0x390, have: 0x139, distance: 0xa, oneway: true},
+	78:  {want: 0x395, have: 0x139, distance: 0xa, oneway: true},
+	79:  {want: 0x39d, have: 0x139, distance: 0xa, oneway: true},
+	80:  {want: 0x3a5, have: 0x139, distance: 0xa, oneway: true},
+	81:  {want: 0x3be, have: 0x139, distance: 0xa, oneway: true},
+	82:  {want: 0x3c4, have: 0x13e, distance: 0xa, oneway: true},
+	83:  {want: 0x3d4, have: 0x10d, distance: 0xa, oneway: true},
+	84:  {want: 0x3d9, have: 0x139, distance: 0xa, oneway: true},
+	85:  {want: 0x3e5, have: 0x15e, distance: 0xa, oneway: true},
+	86:  {want: 0x3e9, have: 0x1be, distance: 0xa, oneway: true},
+	87:  {want: 0x3fa, have: 0x139, distance: 0xa, oneway: true},
+	88:  {want: 0x40c, have: 0x139, distance: 0xa, oneway: true},
+	89:  {want: 0x423, have: 0x139, distance: 0xa, oneway: true},
+	90:  {want: 0x429, have: 0x139, distance: 0xa, oneway: true},
+	91:  {want: 0x431, have: 0x139, distance: 0xa, oneway: true},
+	92:  {want: 0x43b, have: 0x139, distance: 0xa, oneway: true},
+	93:  {want: 0x43e, have: 0x1e1, distance: 0xa, oneway: true},
+	94:  {want: 0x445, have: 0x139, distance: 0xa, oneway: true},
+	95:  {want: 0x450, have: 0x139, distance: 0xa, oneway: true},
+	96:  {want: 0x461, have: 0x139, distance: 0xa, oneway: true},
+	97:  {want: 0x467, have: 0x3e2, distance: 0xa, oneway: true},
+	98:  {want: 0x46f, have: 0x139, distance: 0xa, oneway: true},
+	99:  {want: 0x476, have: 0x3e2, distance: 0xa, oneway: true},
+	100: {want: 0x3883, have: 0x139, distance: 0xa, oneway: true},
+	101: {want: 0x480, have: 0x139, distance: 0xa, oneway: true},
+	102: {want: 0x482, have: 0x139, distance: 0xa, oneway: true},
+	103: {want: 0x494, have: 0x3e2, distance: 0xa, oneway: true},
+	104: {want: 0x49d, have: 0x139, distance: 0xa, oneway: true},
+	105: {want: 0x4ac, have: 0x529, distance: 0xa, oneway: true},
+	106: {want: 0x4b4, have: 0x139, distance: 0xa, oneway: true},
+	107: {want: 0x4bc, have: 0x3e2, distance: 0xa, oneway: true},
+	108: {want: 0x4e5, have: 0x15e, distance: 0xa, oneway: true},
+	109: {want: 0x4f2, have: 0x139, distance: 0xa, oneway: true},
+	110: {want: 0x512, have: 0x139, distance: 0xa, oneway: true},
+	111: {want: 0x518, have: 0x139, distance: 0xa, oneway: true},
+	112: {want: 0x52f, have: 0x139, distance: 0xa, oneway: true},
+} // Size: 702 bytes
+
+// matchScript holds pairs of scriptIDs where readers of one script
+// can typically also read the other. Each is associated with a confidence.
+var matchScript = []scriptIntelligibility{ // 26 elements
+	0:  {wantLang: 0x432, haveLang: 0x432, wantScript: 0x5b, haveScript: 0x20, distance: 0x5},
+	1:  {wantLang: 0x432, haveLang: 0x432, wantScript: 0x20, haveScript: 0x5b, distance: 0x5},
+	2:  {wantLang: 0x58, haveLang: 0x3e2, wantScript: 0x5b, haveScript: 0x20, distance: 0xa},
+	3:  {wantLang: 0xa5, haveLang: 0x139, wantScript: 0xe, haveScript: 0x5b, distance: 0xa},
+	4:  {wantLang: 0x1d7, haveLang: 0x3e2, wantScript: 0x8, haveScript: 0x20, distance: 0xa},
+	5:  {wantLang: 0x210, haveLang: 0x139, wantScript: 0x2e, haveScript: 0x5b, distance: 0xa},
+	6:  {wantLang: 0x24a, haveLang: 0x139, wantScript: 0x4f, haveScript: 0x5b, distance: 0xa},
+	7:  {wantLang: 0x251, haveLang: 0x139, wantScript: 0x53, haveScript: 0x5b, distance: 0xa},
+	8:  {wantLang: 0x2b8, haveLang: 0x139, wantScript: 0x58, haveScript: 0x5b, distance: 0xa},
+	9:  {wantLang: 0x304, haveLang: 0x139, wantScript: 0x6f, haveScript: 0x5b, distance: 0xa},
+	10: {wantLang: 0x331, haveLang: 0x139, wantScript: 0x76, haveScript: 0x5b, distance: 0xa},
+	11: {wantLang: 0x351, haveLang: 0x139, wantScript: 0x22, haveScript: 0x5b, distance: 0xa},
+	12: {wantLang: 0x395, haveLang: 0x139, wantScript: 0x83, haveScript: 0x5b, distance: 0xa},
+	13: {wantLang: 0x39d, haveLang: 0x139, wantScript: 0x36, haveScript: 0x5b, distance: 0xa},
+	14: {wantLang: 0x3be, haveLang: 0x139, wantScript: 0x5, haveScript: 0x5b, distance: 0xa},
+	15: {wantLang: 0x3fa, haveLang: 0x139, wantScript: 0x5, haveScript: 0x5b, distance: 0xa},
+	16: {wantLang: 0x40c, haveLang: 0x139, wantScript: 0xd6, haveScript: 0x5b, distance: 0xa},
+	17: {wantLang: 0x450, haveLang: 0x139, wantScript: 0xe6, haveScript: 0x5b, distance: 0xa},
+	18: {wantLang: 0x461, haveLang: 0x139, wantScript: 0xe9, haveScript: 0x5b, distance: 0xa},
+	19: {wantLang: 0x46f, haveLang: 0x139, wantScript: 0x2c, haveScript: 0x5b, distance: 0xa},
+	20: {wantLang: 0x476, haveLang: 0x3e2, wantScript: 0x5b, haveScript: 0x20, distance: 0xa},
+	21: {wantLang: 0x4b4, haveLang: 0x139, wantScript: 0x5, haveScript: 0x5b, distance: 0xa},
+	22: {wantLang: 0x4bc, haveLang: 0x3e2, wantScript: 0x5b, haveScript: 0x20, distance: 0xa},
+	23: {wantLang: 0x512, haveLang: 0x139, wantScript: 0x3e, haveScript: 0x5b, distance: 0xa},
+	24: {wantLang: 0x529, haveLang: 0x529, wantScript: 0x3b, haveScript: 0x3c, distance: 0xf},
+	25: {wantLang: 0x529, haveLang: 0x529, wantScript: 0x3c, haveScript: 0x3b, distance: 0x13},
+} // Size: 232 bytes
+
+var matchRegion = []regionIntelligibility{ // 15 elements
+	0:  {lang: 0x3a, script: 0x0, group: 0x4, distance: 0x4},
+	1:  {lang: 0x3a, script: 0x0, group: 0x84, distance: 0x4},
+	2:  {lang: 0x139, script: 0x0, group: 0x1, distance: 0x4},
+	3:  {lang: 0x139, script: 0x0, group: 0x81, distance: 0x4},
+	4:  {lang: 0x13e, script: 0x0, group: 0x3, distance: 0x4},
+	5:  {lang: 0x13e, script: 0x0, group: 0x83, distance: 0x4},
+	6:  {lang: 0x3c0, script: 0x0, group: 0x3, distance: 0x4},
+	7:  {lang: 0x3c0, script: 0x0, group: 0x83, distance: 0x4},
+	8:  {lang: 0x529, script: 0x3c, group: 0x2, distance: 0x4},
+	9:  {lang: 0x529, script: 0x3c, group: 0x82, distance: 0x4},
+	10: {lang: 0x3a, script: 0x0, group: 0x80, distance: 0x5},
+	11: {lang: 0x139, script: 0x0, group: 0x80, distance: 0x5},
+	12: {lang: 0x13e, script: 0x0, group: 0x80, distance: 0x5},
+	13: {lang: 0x3c0, script: 0x0, group: 0x80, distance: 0x5},
+	14: {lang: 0x529, script: 0x3c, group: 0x80, distance: 0x5},
+} // Size: 114 bytes
+
+// Total table size 1473 bytes (1KiB); checksum: 7BB90B5C

vendor/golang.org/x/text/language/tags.go

@@ -0,0 +1,145 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package language
+
+import "golang.org/x/text/internal/language/compact"
+
+// TODO: Various sets of commonly use tags and regions.
+
+// MustParse is like Parse, but panics if the given BCP 47 tag cannot be parsed.
+// It simplifies safe initialization of Tag values.
+func MustParse(s string) Tag {
+	t, err := Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+// MustParse is like Parse, but panics if the given BCP 47 tag cannot be parsed.
+// It simplifies safe initialization of Tag values.
+func (c CanonType) MustParse(s string) Tag {
+	t, err := c.Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+// MustParseBase is like ParseBase, but panics if the given base cannot be parsed.
+// It simplifies safe initialization of Base values.
+func MustParseBase(s string) Base {
+	b, err := ParseBase(s)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+// MustParseScript is like ParseScript, but panics if the given script cannot be
+// parsed. It simplifies safe initialization of Script values.
+func MustParseScript(s string) Script {
+	scr, err := ParseScript(s)
+	if err != nil {
+		panic(err)
+	}
+	return scr
+}
+
+// MustParseRegion is like ParseRegion, but panics if the given region cannot be
+// parsed. It simplifies safe initialization of Region values.
+func MustParseRegion(s string) Region {
+	r, err := ParseRegion(s)
+	if err != nil {
+		panic(err)
+	}
+	return r
+}
+
+var (
+	und = Tag{}
+
+	Und Tag = Tag{}
+
+	Afrikaans            Tag = Tag(compact.Afrikaans)
+	Amharic              Tag = Tag(compact.Amharic)
+	Arabic               Tag = Tag(compact.Arabic)
+	ModernStandardArabic Tag = Tag(compact.ModernStandardArabic)
+	Azerbaijani          Tag = Tag(compact.Azerbaijani)
+	Bulgarian            Tag = Tag(compact.Bulgarian)
+	Bengali              Tag = Tag(compact.Bengali)
+	Catalan              Tag = Tag(compact.Catalan)
+	Czech                Tag = Tag(compact.Czech)
+	Danish               Tag = Tag(compact.Danish)
+	German               Tag = Tag(compact.German)
+	Greek                Tag = Tag(compact.Greek)
+	English              Tag = Tag(compact.English)
+	AmericanEnglish      Tag = Tag(compact.AmericanEnglish)
+	BritishEnglish       Tag = Tag(compact.BritishEnglish)
+	Spanish              Tag = Tag(compact.Spanish)
+	EuropeanSpanish      Tag = Tag(compact.EuropeanSpanish)
+	LatinAmericanSpanish Tag = Tag(compact.LatinAmericanSpanish)
+	Estonian             Tag = Tag(compact.Estonian)
+	Persian              Tag = Tag(compact.Persian)
+	Finnish              Tag = Tag(compact.Finnish)
+	Filipino             Tag = Tag(compact.Filipino)
+	French               Tag = Tag(compact.French)
+	CanadianFrench       Tag = Tag(compact.CanadianFrench)
+	Gujarati             Tag = Tag(compact.Gujarati)
+	Hebrew               Tag = Tag(compact.Hebrew)
+	Hindi                Tag = Tag(compact.Hindi)
+	Croatian             Tag = Tag(compact.Croatian)
+	Hungarian            Tag = Tag(compact.Hungarian)
+	Armenian             Tag = Tag(compact.Armenian)
+	Indonesian           Tag = Tag(compact.Indonesian)
+	Icelandic            Tag = Tag(compact.Icelandic)
+	Italian              Tag = Tag(compact.Italian)
+	Japanese             Tag = Tag(compact.Japanese)
+	Georgian             Tag = Tag(compact.Georgian)
+	Kazakh               Tag = Tag(compact.Kazakh)
+	Khmer                Tag = Tag(compact.Khmer)
+	Kannada              Tag = Tag(compact.Kannada)
+	Korean               Tag = Tag(compact.Korean)
+	Kirghiz              Tag = Tag(compact.Kirghiz)
+	Lao                  Tag = Tag(compact.Lao)
+	Lithuanian           Tag = Tag(compact.Lithuanian)
+	Latvian              Tag = Tag(compact.Latvian)
+	Macedonian           Tag = Tag(compact.Macedonian)
+	Malayalam            Tag = Tag(compact.Malayalam)
+	Mongolian            Tag = Tag(compact.Mongolian)
+	Marathi              Tag = Tag(compact.Marathi)
+	Malay                Tag = Tag(compact.Malay)
+	Burmese              Tag = Tag(compact.Burmese)
+	Nepali               Tag = Tag(compact.Nepali)
+	Dutch                Tag = Tag(compact.Dutch)
+	Norwegian            Tag = Tag(compact.Norwegian)
+	Punjabi              Tag = Tag(compact.Punjabi)
+	Polish               Tag = Tag(compact.Polish)
+	Portuguese           Tag = Tag(compact.Portuguese)
+	BrazilianPortuguese  Tag = Tag(compact.BrazilianPortuguese)
+	EuropeanPortuguese   Tag = Tag(compact.EuropeanPortuguese)
+	Romanian             Tag = Tag(compact.Romanian)
+	Russian              Tag = Tag(compact.Russian)
+	Sinhala              Tag = Tag(compact.Sinhala)
+	Slovak               Tag = Tag(compact.Slovak)
+	Slovenian            Tag = Tag(compact.Slovenian)
+	Albanian             Tag = Tag(compact.Albanian)
+	Serbian              Tag = Tag(compact.Serbian)
+	SerbianLatin         Tag = Tag(compact.SerbianLatin)
+	Swedish              Tag = Tag(compact.Swedish)
+	Swahili              Tag = Tag(compact.Swahili)
+	Tamil                Tag = Tag(compact.Tamil)
+	Telugu               Tag = Tag(compact.Telugu)
+	Thai                 Tag = Tag(compact.Thai)
+	Turkish              Tag = Tag(compact.Turkish)
+	Ukrainian            Tag = Tag(compact.Ukrainian)
+	Urdu                 Tag = Tag(compact.Urdu)
+	Uzbek                Tag = Tag(compact.Uzbek)
+	Vietnamese           Tag = Tag(compact.Vietnamese)
+	Chinese              Tag = Tag(compact.Chinese)
+	SimplifiedChinese    Tag = Tag(compact.SimplifiedChinese)
+	TraditionalChinese   Tag = Tag(compact.TraditionalChinese)
+	Zulu                 Tag = Tag(compact.Zulu)
+)

vendor/golang.org/x/text/secure/precis/class.go

@@ -0,0 +1,36 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode/utf8"
+)
+
+// TODO: Add contextual character rules from Appendix A of RFC5892.
+
+// A class is a set of characters that match certain derived properties. The
+// PRECIS framework defines two classes: The Freeform class and the Identifier
+// class. The freeform class should be used for profiles where expressiveness is
+// prioritized over safety such as nicknames or passwords. The identifier class
+// should be used for profiles where safety is the first priority such as
+// addressable network labels and usernames.
+type class struct {
+	validFrom property
+}
+
+// Contains satisfies the runes.Set interface and returns whether the given rune
+// is a member of the class.
+func (c class) Contains(r rune) bool {
+	b := make([]byte, 4)
+	n := utf8.EncodeRune(b, r)
+
+	trieval, _ := dpTrie.lookup(b[:n])
+	return c.validFrom <= property(trieval)
+}
+
+var (
+	identifier = &class{validFrom: pValid}
+	freeform   = &class{validFrom: idDisOrFreePVal}
+)

vendor/golang.org/x/text/secure/precis/context.go

@@ -0,0 +1,139 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import "errors"
+
+// This file contains tables and code related to context rules.
+
+type catBitmap uint16
+
+const (
+	// These bits, once set depending on the current value, are never unset.
+	bJapanese catBitmap = 1 << iota
+	bArabicIndicDigit
+	bExtendedArabicIndicDigit
+
+	// These bits are set on each iteration depending on the current value.
+	bJoinStart
+	bJoinMid
+	bJoinEnd
+	bVirama
+	bLatinSmallL
+	bGreek
+	bHebrew
+
+	// These bits indicated which of the permanent bits need to be set at the
+	// end of the checks.
+	bMustHaveJapn
+
+	permanent = bJapanese | bArabicIndicDigit | bExtendedArabicIndicDigit | bMustHaveJapn
+)
+
+const finalShift = 10
+
+var errContext = errors.New("precis: contextual rule violated")
+
+func init() {
+	// Programmatically set these required bits as, manually setting them seems
+	// too error prone.
+	for i, ct := range categoryTransitions {
+		categoryTransitions[i].keep |= permanent
+		categoryTransitions[i].accept |= ct.term
+	}
+}
+
+var categoryTransitions = []struct {
+	keep catBitmap // mask selecting which bits to keep from the previous state
+	set  catBitmap // mask for which bits to set for this transition
+
+	// These bitmaps are used for rules that require lookahead.
+	// term&accept == term must be true, which is enforced programmatically.
+	term   catBitmap // bits accepted as termination condition
+	accept catBitmap // bits that pass, but not sufficient as termination
+
+	// The rule function cannot take a *context as an argument, as it would
+	// cause the context to escape, adding significant overhead.
+	rule func(beforeBits catBitmap) (doLookahead bool, err error)
+}{
+	joiningL:          {set: bJoinStart},
+	joiningD:          {set: bJoinStart | bJoinEnd},
+	joiningT:          {keep: bJoinStart, set: bJoinMid},
+	joiningR:          {set: bJoinEnd},
+	viramaModifier:    {set: bVirama},
+	viramaJoinT:       {set: bVirama | bJoinMid},
+	latinSmallL:       {set: bLatinSmallL},
+	greek:             {set: bGreek},
+	greekJoinT:        {set: bGreek | bJoinMid},
+	hebrew:            {set: bHebrew},
+	hebrewJoinT:       {set: bHebrew | bJoinMid},
+	japanese:          {set: bJapanese},
+	katakanaMiddleDot: {set: bMustHaveJapn},
+
+	zeroWidthNonJoiner: {
+		term:   bJoinEnd,
+		accept: bJoinMid,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bVirama != 0 {
+				return false, nil
+			}
+			if before&bJoinStart == 0 {
+				return false, errContext
+			}
+			return true, nil
+		},
+	},
+	zeroWidthJoiner: {
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bVirama == 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	middleDot: {
+		term: bLatinSmallL,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bLatinSmallL == 0 {
+				return false, errContext
+			}
+			return true, nil
+		},
+	},
+	greekLowerNumeralSign: {
+		set:  bGreek,
+		term: bGreek,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			return true, nil
+		},
+	},
+	hebrewPreceding: {
+		set: bHebrew,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bHebrew == 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	arabicIndicDigit: {
+		set: bArabicIndicDigit,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bExtendedArabicIndicDigit != 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	extendedArabicIndicDigit: {
+		set: bExtendedArabicIndicDigit,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bArabicIndicDigit != 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+}

vendor/golang.org/x/text/secure/precis/doc.go

@@ -0,0 +1,14 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package precis contains types and functions for the preparation,
+// enforcement, and comparison of internationalized strings ("PRECIS") as
+// defined in RFC 8264. It also contains several pre-defined profiles for
+// passwords, nicknames, and usernames as defined in RFC 8265 and RFC 8266.
+//
+// BE ADVISED: This package is under construction and the API may change in
+// backwards incompatible ways and without notice.
+package precis // import "golang.org/x/text/secure/precis"
+
+//go:generate go run gen.go gen_trieval.go

vendor/golang.org/x/text/secure/precis/nickname.go

@@ -0,0 +1,72 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+type nickAdditionalMapping struct {
+	// TODO: This transformer needs to be stateless somehow…
+	notStart  bool
+	prevSpace bool
+}
+
+func (t *nickAdditionalMapping) Reset() {
+	t.prevSpace = false
+	t.notStart = false
+}
+
+func (t *nickAdditionalMapping) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	// RFC 8266 §2.1.  Rules
+	//
+	// 2.  Additional Mapping Rule: The additional mapping rule consists of
+	//     the following sub-rules.
+	//
+	//     a.  Map any instances of non-ASCII space to SPACE (U+0020); a
+	//         non-ASCII space is any Unicode code point having a general
+	//         category of "Zs", naturally with the exception of SPACE
+	//         (U+0020).  (The inclusion of only ASCII space prevents
+	//         confusion with various non-ASCII space code points, many of
+	//         which are difficult to reproduce across different input
+	//         methods.)
+	//
+	//     b.  Remove any instances of the ASCII space character at the
+	//         beginning or end of a nickname (e.g., "stpeter " is mapped to
+	//         "stpeter").
+	//
+	//     c.  Map interior sequences of more than one ASCII space character
+	//         to a single ASCII space character (e.g., "St  Peter" is
+	//         mapped to "St Peter").
+	for nSrc < len(src) {
+		r, size := utf8.DecodeRune(src[nSrc:])
+		if size == 0 { // Incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1
+		}
+		if unicode.Is(unicode.Zs, r) {
+			t.prevSpace = true
+		} else {
+			if t.prevSpace && t.notStart {
+				dst[nDst] = ' '
+				nDst += 1
+			}
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				nDst += size
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+			t.prevSpace = false
+			t.notStart = true
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}

vendor/golang.org/x/text/secure/precis/options.go

@@ -0,0 +1,157 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+// An Option is used to define the behavior and rules of a Profile.
+type Option func(*options)
+
+type options struct {
+	// Preparation options
+	foldWidth bool
+
+	// Enforcement options
+	asciiLower    bool
+	cases         transform.SpanningTransformer
+	disallow      runes.Set
+	norm          transform.SpanningTransformer
+	additional    []func() transform.SpanningTransformer
+	width         transform.SpanningTransformer
+	disallowEmpty bool
+	bidiRule      bool
+	repeat        bool
+
+	// Comparison options
+	ignorecase bool
+}
+
+func getOpts(o ...Option) (res options) {
+	for _, f := range o {
+		f(&res)
+	}
+	// Using a SpanningTransformer, instead of norm.Form prevents an allocation
+	// down the road.
+	if res.norm == nil {
+		res.norm = norm.NFC
+	}
+	return
+}
+
+var (
+	// The IgnoreCase option causes the profile to perform a case insensitive
+	// comparison during the PRECIS comparison step.
+	IgnoreCase Option = ignoreCase
+
+	// The FoldWidth option causes the profile to map non-canonical wide and
+	// narrow variants to their decomposition mapping. This is useful for
+	// profiles that are based on the identifier class which would otherwise
+	// disallow such characters.
+	FoldWidth Option = foldWidth
+
+	// The DisallowEmpty option causes the enforcement step to return an error if
+	// the resulting string would be empty.
+	DisallowEmpty Option = disallowEmpty
+
+	// The BidiRule option causes the Bidi Rule defined in RFC 5893 to be
+	// applied.
+	BidiRule Option = bidiRule
+)
+
+var (
+	ignoreCase = func(o *options) {
+		o.ignorecase = true
+	}
+	foldWidth = func(o *options) {
+		o.foldWidth = true
+	}
+	disallowEmpty = func(o *options) {
+		o.disallowEmpty = true
+	}
+	bidiRule = func(o *options) {
+		o.bidiRule = true
+	}
+	repeat = func(o *options) {
+		o.repeat = true
+	}
+)
+
+// TODO: move this logic to package transform
+
+type spanWrap struct{ transform.Transformer }
+
+func (s spanWrap) Span(src []byte, atEOF bool) (n int, err error) {
+	return 0, transform.ErrEndOfSpan
+}
+
+// TODO: allow different types? For instance:
+//     func() transform.Transformer
+//     func() transform.SpanningTransformer
+//     func([]byte) bool  // validation only
+//
+// Also, would be great if we could detect if a transformer is reentrant.
+
+// The AdditionalMapping option defines the additional mapping rule for the
+// Profile by applying Transformer's in sequence.
+func AdditionalMapping(t ...func() transform.Transformer) Option {
+	return func(o *options) {
+		for _, f := range t {
+			sf := func() transform.SpanningTransformer {
+				return f().(transform.SpanningTransformer)
+			}
+			if _, ok := f().(transform.SpanningTransformer); !ok {
+				sf = func() transform.SpanningTransformer {
+					return spanWrap{f()}
+				}
+			}
+			o.additional = append(o.additional, sf)
+		}
+	}
+}
+
+// The Norm option defines a Profile's normalization rule. Defaults to NFC.
+func Norm(f norm.Form) Option {
+	return func(o *options) {
+		o.norm = f
+	}
+}
+
+// The FoldCase option defines a Profile's case mapping rule. Options can be
+// provided to determine the type of case folding used.
+func FoldCase(opts ...cases.Option) Option {
+	return func(o *options) {
+		o.asciiLower = true
+		o.cases = cases.Fold(opts...)
+	}
+}
+
+// The LowerCase option defines a Profile's case mapping rule. Options can be
+// provided to determine the type of case folding used.
+func LowerCase(opts ...cases.Option) Option {
+	return func(o *options) {
+		o.asciiLower = true
+		if len(opts) == 0 {
+			o.cases = cases.Lower(language.Und, cases.HandleFinalSigma(false))
+			return
+		}
+
+		opts = append([]cases.Option{cases.HandleFinalSigma(false)}, opts...)
+		o.cases = cases.Lower(language.Und, opts...)
+	}
+}
+
+// The Disallow option further restricts a Profile's allowed characters beyond
+// what is disallowed by the underlying string class.
+func Disallow(set runes.Set) Option {
+	return func(o *options) {
+		o.disallow = set
+	}
+}

vendor/golang.org/x/text/secure/precis/profile.go

@@ -0,0 +1,412 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"bytes"
+	"errors"
+	"unicode/utf8"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/secure/bidirule"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/width"
+)
+
+var (
+	errDisallowedRune = errors.New("precis: disallowed rune encountered")
+)
+
+var dpTrie = newDerivedPropertiesTrie(0)
+
+// A Profile represents a set of rules for normalizing and validating strings in
+// the PRECIS framework.
+type Profile struct {
+	options
+	class *class
+}
+
+// NewIdentifier creates a new PRECIS profile based on the Identifier string
+// class. Profiles created from this class are suitable for use where safety is
+// prioritized over expressiveness like network identifiers, user accounts, chat
+// rooms, and file names.
+func NewIdentifier(opts ...Option) *Profile {
+	return &Profile{
+		options: getOpts(opts...),
+		class:   identifier,
+	}
+}
+
+// NewFreeform creates a new PRECIS profile based on the Freeform string class.
+// Profiles created from this class are suitable for use where expressiveness is
+// prioritized over safety like passwords, and display-elements such as
+// nicknames in a chat room.
+func NewFreeform(opts ...Option) *Profile {
+	return &Profile{
+		options: getOpts(opts...),
+		class:   freeform,
+	}
+}
+
+// NewRestrictedProfile creates a new PRECIS profile based on an existing
+// profile.
+// If the parent profile already had the Disallow option set, the new rule
+// overrides the parents rule.
+func NewRestrictedProfile(parent *Profile, disallow runes.Set) *Profile {
+	p := *parent
+	Disallow(disallow)(&p.options)
+	return &p
+}
+
+// NewTransformer creates a new transform.Transformer that performs the PRECIS
+// preparation and enforcement steps on the given UTF-8 encoded bytes.
+func (p *Profile) NewTransformer() *Transformer {
+	var ts []transform.Transformer
+
+	// These transforms are applied in the order defined in
+	// https://tools.ietf.org/html/rfc7564#section-7
+
+	// RFC 8266 §2.1:
+	//
+	//     Implementation experience has shown that applying the rules for the
+	//     Nickname profile is not an idempotent procedure for all code points.
+	//     Therefore, an implementation SHOULD apply the rules repeatedly until
+	//     the output string is stable; if the output string does not stabilize
+	//     after reapplying the rules three (3) additional times after the first
+	//     application, the implementation SHOULD terminate application of the
+	//     rules and reject the input string as invalid.
+	//
+	// There is no known string that will change indefinitely, so repeat 4 times
+	// and rely on the Span method to keep things relatively performant.
+	r := 1
+	if p.options.repeat {
+		r = 4
+	}
+	for ; r > 0; r-- {
+		if p.options.foldWidth {
+			ts = append(ts, width.Fold)
+		}
+
+		for _, f := range p.options.additional {
+			ts = append(ts, f())
+		}
+
+		if p.options.cases != nil {
+			ts = append(ts, p.options.cases)
+		}
+
+		ts = append(ts, p.options.norm)
+
+		if p.options.bidiRule {
+			ts = append(ts, bidirule.New())
+		}
+
+		ts = append(ts, &checker{p: p, allowed: p.Allowed()})
+	}
+
+	// TODO: Add the disallow empty rule with a dummy transformer?
+
+	return &Transformer{transform.Chain(ts...)}
+}
+
+var errEmptyString = errors.New("precis: transformation resulted in empty string")
+
+type buffers struct {
+	src  []byte
+	buf  [2][]byte
+	next int
+}
+
+func (b *buffers) apply(t transform.SpanningTransformer) (err error) {
+	n, err := t.Span(b.src, true)
+	if err != transform.ErrEndOfSpan {
+		return err
+	}
+	x := b.next & 1
+	if b.buf[x] == nil {
+		b.buf[x] = make([]byte, 0, 8+len(b.src)+len(b.src)>>2)
+	}
+	span := append(b.buf[x][:0], b.src[:n]...)
+	b.src, _, err = transform.Append(t, span, b.src[n:])
+	b.buf[x] = b.src
+	b.next++
+	return err
+}
+
+// Pre-allocate transformers when possible. In some cases this avoids allocation.
+var (
+	foldWidthT transform.SpanningTransformer = width.Fold
+	lowerCaseT transform.SpanningTransformer = cases.Lower(language.Und, cases.HandleFinalSigma(false))
+)
+
+// TODO: make this a method on profile.
+
+func (b *buffers) enforce(p *Profile, src []byte, comparing bool) (str []byte, err error) {
+	b.src = src
+
+	ascii := true
+	for _, c := range src {
+		if c >= utf8.RuneSelf {
+			ascii = false
+			break
+		}
+	}
+	// ASCII fast path.
+	if ascii {
+		for _, f := range p.options.additional {
+			if err = b.apply(f()); err != nil {
+				return nil, err
+			}
+		}
+		switch {
+		case p.options.asciiLower || (comparing && p.options.ignorecase):
+			for i, c := range b.src {
+				if 'A' <= c && c <= 'Z' {
+					b.src[i] = c ^ 1<<5
+				}
+			}
+		case p.options.cases != nil:
+			b.apply(p.options.cases)
+		}
+		c := checker{p: p}
+		if _, err := c.span(b.src, true); err != nil {
+			return nil, err
+		}
+		if p.disallow != nil {
+			for _, c := range b.src {
+				if p.disallow.Contains(rune(c)) {
+					return nil, errDisallowedRune
+				}
+			}
+		}
+		if p.options.disallowEmpty && len(b.src) == 0 {
+			return nil, errEmptyString
+		}
+		return b.src, nil
+	}
+
+	// These transforms are applied in the order defined in
+	// https://tools.ietf.org/html/rfc8264#section-7
+
+	r := 1
+	if p.options.repeat {
+		r = 4
+	}
+	for ; r > 0; r-- {
+		// TODO: allow different width transforms options.
+		if p.options.foldWidth || (p.options.ignorecase && comparing) {
+			b.apply(foldWidthT)
+		}
+		for _, f := range p.options.additional {
+			if err = b.apply(f()); err != nil {
+				return nil, err
+			}
+		}
+		if p.options.cases != nil {
+			b.apply(p.options.cases)
+		}
+		if comparing && p.options.ignorecase {
+			b.apply(lowerCaseT)
+		}
+		b.apply(p.norm)
+		if p.options.bidiRule && !bidirule.Valid(b.src) {
+			return nil, bidirule.ErrInvalid
+		}
+		c := checker{p: p}
+		if _, err := c.span(b.src, true); err != nil {
+			return nil, err
+		}
+		if p.disallow != nil {
+			for i := 0; i < len(b.src); {
+				r, size := utf8.DecodeRune(b.src[i:])
+				if p.disallow.Contains(r) {
+					return nil, errDisallowedRune
+				}
+				i += size
+			}
+		}
+		if p.options.disallowEmpty && len(b.src) == 0 {
+			return nil, errEmptyString
+		}
+	}
+	return b.src, nil
+}
+
+// Append appends the result of applying p to src writing the result to dst.
+// It returns an error if the input string is invalid.
+func (p *Profile) Append(dst, src []byte) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, src, false)
+	if err != nil {
+		return nil, err
+	}
+	return append(dst, b...), nil
+}
+
+func processBytes(p *Profile, b []byte, key bool) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, b, key)
+	if err != nil {
+		return nil, err
+	}
+	if buf.next == 0 {
+		c := make([]byte, len(b))
+		copy(c, b)
+		return c, nil
+	}
+	return b, nil
+}
+
+// Bytes returns a new byte slice with the result of applying the profile to b.
+func (p *Profile) Bytes(b []byte) ([]byte, error) {
+	return processBytes(p, b, false)
+}
+
+// AppendCompareKey appends the result of applying p to src (including any
+// optional rules to make strings comparable or useful in a map key such as
+// applying lowercasing) writing the result to dst. It returns an error if the
+// input string is invalid.
+func (p *Profile) AppendCompareKey(dst, src []byte) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, src, true)
+	if err != nil {
+		return nil, err
+	}
+	return append(dst, b...), nil
+}
+
+func processString(p *Profile, s string, key bool) (string, error) {
+	var buf buffers
+	b, err := buf.enforce(p, []byte(s), key)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}
+
+// String returns a string with the result of applying the profile to s.
+func (p *Profile) String(s string) (string, error) {
+	return processString(p, s, false)
+}
+
+// CompareKey returns a string that can be used for comparison, hashing, or
+// collation.
+func (p *Profile) CompareKey(s string) (string, error) {
+	return processString(p, s, true)
+}
+
+// Compare enforces both strings, and then compares them for bit-string identity
+// (byte-for-byte equality). If either string cannot be enforced, the comparison
+// is false.
+func (p *Profile) Compare(a, b string) bool {
+	var buf buffers
+
+	akey, err := buf.enforce(p, []byte(a), true)
+	if err != nil {
+		return false
+	}
+
+	buf = buffers{}
+	bkey, err := buf.enforce(p, []byte(b), true)
+	if err != nil {
+		return false
+	}
+
+	return bytes.Equal(akey, bkey)
+}
+
+// Allowed returns a runes.Set containing every rune that is a member of the
+// underlying profile's string class and not disallowed by any profile specific
+// rules.
+func (p *Profile) Allowed() runes.Set {
+	if p.options.disallow != nil {
+		return runes.Predicate(func(r rune) bool {
+			return p.class.Contains(r) && !p.options.disallow.Contains(r)
+		})
+	}
+	return p.class
+}
+
+type checker struct {
+	p       *Profile
+	allowed runes.Set
+
+	beforeBits catBitmap
+	termBits   catBitmap
+	acceptBits catBitmap
+}
+
+func (c *checker) Reset() {
+	c.beforeBits = 0
+	c.termBits = 0
+	c.acceptBits = 0
+}
+
+func (c *checker) span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		e, sz := dpTrie.lookup(src[n:])
+		d := categoryTransitions[category(e&catMask)]
+		if sz == 0 {
+			if !atEOF {
+				return n, transform.ErrShortSrc
+			}
+			return n, errDisallowedRune
+		}
+		doLookAhead := false
+		if property(e) < c.p.class.validFrom {
+			if d.rule == nil {
+				return n, errDisallowedRune
+			}
+			doLookAhead, err = d.rule(c.beforeBits)
+			if err != nil {
+				return n, err
+			}
+		}
+		c.beforeBits &= d.keep
+		c.beforeBits |= d.set
+		if c.termBits != 0 {
+			// We are currently in an unterminated lookahead.
+			if c.beforeBits&c.termBits != 0 {
+				c.termBits = 0
+				c.acceptBits = 0
+			} else if c.beforeBits&c.acceptBits == 0 {
+				// Invalid continuation of the unterminated lookahead sequence.
+				return n, errContext
+			}
+		}
+		if doLookAhead {
+			if c.termBits != 0 {
+				// A previous lookahead run has not been terminated yet.
+				return n, errContext
+			}
+			c.termBits = d.term
+			c.acceptBits = d.accept
+		}
+		n += sz
+	}
+	if m := c.beforeBits >> finalShift; c.beforeBits&m != m || c.termBits != 0 {
+		err = errContext
+	}
+	return n, err
+}
+
+// TODO: we may get rid of this transform if transform.Chain understands
+// something like a Spanner interface.
+func (c checker) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	short := false
+	if len(dst) < len(src) {
+		src = src[:len(dst)]
+		atEOF = false
+		short = true
+	}
+	nSrc, err = c.span(src, atEOF)
+	nDst = copy(dst, src[:nSrc])
+	if short && (err == transform.ErrShortSrc || err == nil) {
+		err = transform.ErrShortDst
+	}
+	return nDst, nSrc, err
+}

vendor/golang.org/x/text/secure/precis/profiles.go

@@ -0,0 +1,78 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode"
+
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+var (
+	// Implements the Nickname profile specified in RFC 8266.
+	Nickname *Profile = nickname
+
+	// Implements the UsernameCaseMapped profile specified in RFC 8265.
+	UsernameCaseMapped *Profile = usernameCaseMap
+
+	// Implements the UsernameCasePreserved profile specified in RFC 8265.
+	UsernameCasePreserved *Profile = usernameNoCaseMap
+
+	// Implements the OpaqueString profile defined in RFC 8265 for passwords and
+	// other secure labels.
+	OpaqueString *Profile = opaquestring
+)
+
+var (
+	nickname = &Profile{
+		options: getOpts(
+			AdditionalMapping(func() transform.Transformer {
+				return &nickAdditionalMapping{}
+			}),
+			IgnoreCase,
+			Norm(norm.NFKC),
+			DisallowEmpty,
+			repeat,
+		),
+		class: freeform,
+	}
+	usernameCaseMap = &Profile{
+		options: getOpts(
+			FoldWidth,
+			LowerCase(),
+			Norm(norm.NFC),
+			BidiRule,
+		),
+		class: identifier,
+	}
+	usernameNoCaseMap = &Profile{
+		options: getOpts(
+			FoldWidth,
+			Norm(norm.NFC),
+			BidiRule,
+		),
+		class: identifier,
+	}
+	opaquestring = &Profile{
+		options: getOpts(
+			AdditionalMapping(func() transform.Transformer {
+				return mapSpaces
+			}),
+			Norm(norm.NFC),
+			DisallowEmpty,
+		),
+		class: freeform,
+	}
+)
+
+// mapSpaces is a shared value of a runes.Map transformer.
+var mapSpaces transform.Transformer = runes.Map(func(r rune) rune {
+	if unicode.Is(unicode.Zs, r) {
+		return ' '
+	}
+	return r
+})

vendor/golang.org/x/text/secure/precis/transformer.go

@@ -0,0 +1,32 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import "golang.org/x/text/transform"
+
+// Transformer implements the transform.Transformer interface.
+type Transformer struct {
+	t transform.Transformer
+}
+
+// Reset implements the transform.Transformer interface.
+func (t Transformer) Reset() { t.t.Reset() }
+
+// Transform implements the transform.Transformer interface.
+func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return t.t.Transform(dst, src, atEOF)
+}
+
+// Bytes returns a new byte slice with the result of applying t to b.
+func (t Transformer) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(t, b)
+	return b
+}
+
+// String returns a string with the result of applying t to s.
+func (t Transformer) String(s string) string {
+	s, _, _ = transform.String(t, s)
+	return s
+}

vendor/golang.org/x/text/secure/precis/trieval.go

@@ -0,0 +1,64 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package precis
+
+// entry is the entry of a trie table
+// 7..6   property (unassigned, disallowed, maybe, valid)
+// 5..0   category
+type entry uint8
+
+const (
+	propShift = 6
+	propMask  = 0xc0
+	catMask   = 0x3f
+)
+
+func (e entry) property() property { return property(e & propMask) }
+func (e entry) category() category { return category(e & catMask) }
+
+type property uint8
+
+// The order of these constants matter. A Profile may consider runes to be
+// allowed either from pValid or idDisOrFreePVal.
+const (
+	unassigned property = iota << propShift
+	disallowed
+	idDisOrFreePVal // disallowed for Identifier, pValid for FreeForm
+	pValid
+)
+
+// compute permutations of all properties and specialCategories.
+type category uint8
+
+const (
+	other category = iota
+
+	// Special rune types
+	joiningL
+	joiningD
+	joiningT
+	joiningR
+	viramaModifier
+	viramaJoinT // Virama + JoiningT
+	latinSmallL // U+006c
+	greek
+	greekJoinT // Greek + JoiningT
+	hebrew
+	hebrewJoinT // Hebrew + JoiningT
+	japanese    // hirigana, katakana, han
+
+	// Special rune types associated with contextual rules defined in
+	// https://tools.ietf.org/html/rfc5892#appendix-A.
+	// ContextO
+	zeroWidthNonJoiner // rule 1
+	zeroWidthJoiner    // rule 2
+	// ContextJ
+	middleDot                // rule 3
+	greekLowerNumeralSign    // rule 4
+	hebrewPreceding          // rule 5 and 6
+	katakanaMiddleDot        // rule 7
+	arabicIndicDigit         // rule 8
+	extendedArabicIndicDigit // rule 9
+
+	numCategories
+)

vendor/golang.org/x/text/width/kind_string.go

@@ -0,0 +1,28 @@
+// Code generated by "stringer -type=Kind"; DO NOT EDIT.
+
+package width
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Neutral-0]
+	_ = x[EastAsianAmbiguous-1]
+	_ = x[EastAsianWide-2]
+	_ = x[EastAsianNarrow-3]
+	_ = x[EastAsianFullwidth-4]
+	_ = x[EastAsianHalfwidth-5]
+}
+
+const _Kind_name = "NeutralEastAsianAmbiguousEastAsianWideEastAsianNarrowEastAsianFullwidthEastAsianHalfwidth"
+
+var _Kind_index = [...]uint8{0, 7, 25, 38, 53, 71, 89}
+
+func (i Kind) String() string {
+	if i < 0 || i >= Kind(len(_Kind_index)-1) {
+		return "Kind(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Kind_name[_Kind_index[i]:_Kind_index[i+1]]
+}

vendor/golang.org/x/text/width/transform.go

@@ -0,0 +1,239 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package width
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+type foldTransform struct {
+	transform.NopResetter
+}
+
+func (foldTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		if src[n] < utf8.RuneSelf {
+			// ASCII fast path.
+			for n++; n < len(src) && src[n] < utf8.RuneSelf; n++ {
+			}
+			continue
+		}
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if elem(v)&tagNeedsFold != 0 {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (foldTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		if src[nSrc] < utf8.RuneSelf {
+			// ASCII fast path.
+			start, end := nSrc, len(src)
+			if d := len(dst) - nDst; d < end-start {
+				end = nSrc + d
+			}
+			for nSrc++; nSrc < end && src[nSrc] < utf8.RuneSelf; nSrc++ {
+			}
+			n := copy(dst[nDst:], src[start:nSrc])
+			if nDst += n; nDst == len(dst) {
+				nSrc = start + n
+				if nSrc == len(src) {
+					return nDst, nSrc, nil
+				}
+				if src[nSrc] < utf8.RuneSelf {
+					return nDst, nSrc, transform.ErrShortDst
+				}
+			}
+			continue
+		}
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if elem(v)&tagNeedsFold == 0 {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}
+
+type narrowTransform struct {
+	transform.NopResetter
+}
+
+func (narrowTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		if src[n] < utf8.RuneSelf {
+			// ASCII fast path.
+			for n++; n < len(src) && src[n] < utf8.RuneSelf; n++ {
+			}
+			continue
+		}
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianFullwidth && k != EastAsianWide && k != EastAsianAmbiguous {
+		} else {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (narrowTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		if src[nSrc] < utf8.RuneSelf {
+			// ASCII fast path.
+			start, end := nSrc, len(src)
+			if d := len(dst) - nDst; d < end-start {
+				end = nSrc + d
+			}
+			for nSrc++; nSrc < end && src[nSrc] < utf8.RuneSelf; nSrc++ {
+			}
+			n := copy(dst[nDst:], src[start:nSrc])
+			if nDst += n; nDst == len(dst) {
+				nSrc = start + n
+				if nSrc == len(src) {
+					return nDst, nSrc, nil
+				}
+				if src[nSrc] < utf8.RuneSelf {
+					return nDst, nSrc, transform.ErrShortDst
+				}
+			}
+			continue
+		}
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianFullwidth && k != EastAsianWide && k != EastAsianAmbiguous {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}
+
+type wideTransform struct {
+	transform.NopResetter
+}
+
+func (wideTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		// TODO: Consider ASCII fast path. Special-casing ASCII handling can
+		// reduce the ns/op of BenchmarkWideASCII by about 30%. This is probably
+		// not enough to warrant the extra code and complexity.
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianHalfwidth && k != EastAsianNarrow {
+		} else {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (wideTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		// TODO: Consider ASCII fast path. Special-casing ASCII handling can
+		// reduce the ns/op of BenchmarkWideASCII by about 30%. This is probably
+		// not enough to warrant the extra code and complexity.
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianHalfwidth && k != EastAsianNarrow {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}

vendor/golang.org/x/text/width/trieval.go

@@ -0,0 +1,30 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package width
+
+// elem is an entry of the width trie. The high byte is used to encode the type
+// of the rune. The low byte is used to store the index to a mapping entry in
+// the inverseData array.
+type elem uint16
+
+const (
+	tagNeutral elem = iota << typeShift
+	tagAmbiguous
+	tagWide
+	tagNarrow
+	tagFullwidth
+	tagHalfwidth
+)
+
+const (
+	numTypeBits = 3
+	typeShift   = 16 - numTypeBits
+
+	// tagNeedsFold is true for all fullwidth and halfwidth runes except for
+	// the Won sign U+20A9.
+	tagNeedsFold = 0x1000
+
+	// The Korean Won sign is halfwidth, but SHOULD NOT be mapped to a wide
+	// variant.
+	wonSign rune = 0x20A9
+)

vendor/golang.org/x/text/width/width.go

@@ -0,0 +1,206 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate stringer -type=Kind
+//go:generate go run gen.go gen_common.go gen_trieval.go
+
+// Package width provides functionality for handling different widths in text.
+//
+// Wide characters behave like ideographs; they tend to allow line breaks after
+// each character and remain upright in vertical text layout. Narrow characters
+// are kept together in words or runs that are rotated sideways in vertical text
+// layout.
+//
+// For more information, see https://unicode.org/reports/tr11/.
+package width // import "golang.org/x/text/width"
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+// TODO
+// 1) Reduce table size by compressing blocks.
+// 2) API proposition for computing display length
+//    (approximation, fixed pitch only).
+// 3) Implement display length.
+
+// Kind indicates the type of width property as defined in https://unicode.org/reports/tr11/.
+type Kind int
+
+const (
+	// Neutral characters do not occur in legacy East Asian character sets.
+	Neutral Kind = iota
+
+	// EastAsianAmbiguous characters that can be sometimes wide and sometimes
+	// narrow and require additional information not contained in the character
+	// code to further resolve their width.
+	EastAsianAmbiguous
+
+	// EastAsianWide characters are wide in its usual form. They occur only in
+	// the context of East Asian typography. These runes may have explicit
+	// halfwidth counterparts.
+	EastAsianWide
+
+	// EastAsianNarrow characters are narrow in its usual form. They often have
+	// fullwidth counterparts.
+	EastAsianNarrow
+
+	// Note: there exist Narrow runes that do not have fullwidth or wide
+	// counterparts, despite what the definition says (e.g. U+27E6).
+
+	// EastAsianFullwidth characters have a compatibility decompositions of type
+	// wide that map to a narrow counterpart.
+	EastAsianFullwidth
+
+	// EastAsianHalfwidth characters have a compatibility decomposition of type
+	// narrow that map to a wide or ambiguous counterpart, plus U+20A9 ₩ WON
+	// SIGN.
+	EastAsianHalfwidth
+
+	// Note: there exist runes that have a halfwidth counterparts but that are
+	// classified as Ambiguous, rather than wide (e.g. U+2190).
+)
+
+// TODO: the generated tries need to return size 1 for invalid runes for the
+// width to be computed correctly (each byte should render width 1)
+
+var trie = newWidthTrie(0)
+
+// Lookup reports the Properties of the first rune in b and the number of bytes
+// of its UTF-8 encoding.
+func Lookup(b []byte) (p Properties, size int) {
+	v, sz := trie.lookup(b)
+	return Properties{elem(v), b[sz-1]}, sz
+}
+
+// LookupString reports the Properties of the first rune in s and the number of
+// bytes of its UTF-8 encoding.
+func LookupString(s string) (p Properties, size int) {
+	v, sz := trie.lookupString(s)
+	return Properties{elem(v), s[sz-1]}, sz
+}
+
+// LookupRune reports the Properties of rune r.
+func LookupRune(r rune) Properties {
+	var buf [4]byte
+	n := utf8.EncodeRune(buf[:], r)
+	v, _ := trie.lookup(buf[:n])
+	last := byte(r)
+	if r >= utf8.RuneSelf {
+		last = 0x80 + byte(r&0x3f)
+	}
+	return Properties{elem(v), last}
+}
+
+// Properties provides access to width properties of a rune.
+type Properties struct {
+	elem elem
+	last byte
+}
+
+func (e elem) kind() Kind {
+	return Kind(e >> typeShift)
+}
+
+// Kind returns the Kind of a rune as defined in Unicode TR #11.
+// See https://unicode.org/reports/tr11/ for more details.
+func (p Properties) Kind() Kind {
+	return p.elem.kind()
+}
+
+// Folded returns the folded variant of a rune or 0 if the rune is canonical.
+func (p Properties) Folded() rune {
+	if p.elem&tagNeedsFold != 0 {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// Narrow returns the narrow variant of a rune or 0 if the rune is already
+// narrow or doesn't have a narrow variant.
+func (p Properties) Narrow() rune {
+	if k := p.elem.kind(); byte(p.elem) != 0 && (k == EastAsianFullwidth || k == EastAsianWide || k == EastAsianAmbiguous) {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// Wide returns the wide variant of a rune or 0 if the rune is already
+// wide or doesn't have a wide variant.
+func (p Properties) Wide() rune {
+	if k := p.elem.kind(); byte(p.elem) != 0 && (k == EastAsianHalfwidth || k == EastAsianNarrow) {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// TODO for Properties:
+// - Add Fullwidth/Halfwidth or Inverted methods for computing variants
+// mapping.
+// - Add width information (including information on non-spacing runes).
+
+// Transformer implements the transform.Transformer interface.
+type Transformer struct {
+	t transform.SpanningTransformer
+}
+
+// Reset implements the transform.Transformer interface.
+func (t Transformer) Reset() { t.t.Reset() }
+
+// Transform implements the transform.Transformer interface.
+func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return t.t.Transform(dst, src, atEOF)
+}
+
+// Span implements the transform.SpanningTransformer interface.
+func (t Transformer) Span(src []byte, atEOF bool) (n int, err error) {
+	return t.t.Span(src, atEOF)
+}
+
+// Bytes returns a new byte slice with the result of applying t to b.
+func (t Transformer) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(t, b)
+	return b
+}
+
+// String returns a string with the result of applying t to s.
+func (t Transformer) String(s string) string {
+	s, _, _ = transform.String(t, s)
+	return s
+}
+
+var (
+	// Fold is a transform that maps all runes to their canonical width.
+	//
+	// Note that the NFKC and NFKD transforms in golang.org/x/text/unicode/norm
+	// provide a more generic folding mechanism.
+	Fold Transformer = Transformer{foldTransform{}}
+
+	// Widen is a transform that maps runes to their wide variant, if
+	// available.
+	Widen Transformer = Transformer{wideTransform{}}
+
+	// Narrow is a transform that maps runes to their narrow variant, if
+	// available.
+	Narrow Transformer = Transformer{narrowTransform{}}
+)
+
+// TODO: Consider the following options:
+// - Treat Ambiguous runes that have a halfwidth counterpart as wide, or some
+//   generalized variant of this.
+// - Consider a wide Won character to be the default width (or some generalized
+//   variant of this).
+// - Filter the set of characters that gets converted (the preferred approach is
+//   to allow applying filters to transforms).

vendor/modules.txt

@@ -96,6 +96,7 @@ golang.org/x/sys/unix
 golang.org/x/sys/windows
 # golang.org/x/text v0.14.0
 ## explicit; go 1.18
+golang.org/x/text/cases
 golang.org/x/text/encoding
 golang.org/x/text/encoding/charmap
 golang.org/x/text/encoding/ianaindex
@@ -106,12 +107,19 @@ golang.org/x/text/encoding/korean
 golang.org/x/text/encoding/simplifiedchinese
 golang.org/x/text/encoding/traditionalchinese
 golang.org/x/text/encoding/unicode
+golang.org/x/text/internal
+golang.org/x/text/internal/language
+golang.org/x/text/internal/language/compact
+golang.org/x/text/internal/tag
 golang.org/x/text/internal/utf8internal
+golang.org/x/text/language
 golang.org/x/text/runes
 golang.org/x/text/secure/bidirule
+golang.org/x/text/secure/precis
 golang.org/x/text/transform
 golang.org/x/text/unicode/bidi
 golang.org/x/text/unicode/norm
+golang.org/x/text/width
 # golang.org/x/tools v0.19.0
 ## explicit; go 1.19
 golang.org/x/tools/go/gcexportdata

webauth/admin.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"golang.org/x/crypto/bcrypt"
+	"golang.org/x/text/secure/precis"
 
 	"github.com/mjl-/mox/mlog"
 	"github.com/mjl-/mox/mox-"
@@ -48,6 +49,11 @@ func (a *adminSessionAuth) login(ctx context.Context, log mlog.Log, username, pa
 		return false, "", fmt.Errorf("reading password file: %v", err)
 	}
 	passwordhash := strings.TrimSpace(string(buf))
+	// Transform with precis, if valid. ../rfc/8265:679
+	pw, err := precis.OpaqueString.String(password)
+	if err == nil {
+		password = pw
+	}
 	if err := bcrypt.CompareHashAndPassword([]byte(passwordhash), []byte(password)); err != nil {
 		return false, "", nil
 	}

webauth/webauth.go

@@ -266,7 +266,7 @@ func Login(ctx context.Context, log mlog.Log, sessionAuth SessionAuth, kind, coo
 		// We don't set a max-age. These makes cookies per-session. Browsers are rarely
 		// restarted nowadays, and they have "continue where you left off", keeping session
 		// cookies. Our sessions are only valid for max 1 day. Convenience can come from
-		// the browser remember the password.
+		// the browser remembering the password.
 	})
 	// Remove cookie used during login.
 	http.SetCookie(w, &http.Cookie{

webmail/api_test.go

@@ -59,7 +59,9 @@ func TestAPI(t *testing.T) {
 	log := mlog.New("webmail", nil)
 	acc, err := store.OpenAccount(log, "mjl")
 	tcheck(t, err, "open account")
-	err = acc.SetPassword(log, "test1234")
+	const pw0 = "te\u0301st \u00a0\u2002\u200a" // NFD and various unicode spaces.
+	const pw1 = "tést    "                      // PRECIS normalized, with NFC.
+	err = acc.SetPassword(log, pw0)
 	tcheck(t, err, "set password")
 	defer func() {
 		err := acc.Close()
@@ -90,7 +92,7 @@ func TestAPI(t *testing.T) {
 	loginctx := context.WithValue(ctxbg, requestInfoCtxKey, loginReqInfo)
 
 	// Missing login token.
-	tneedErrorCode(t, "user:error", func() { api.Login(loginctx, "", "mjl@mox.example", "test1234") })
+	tneedErrorCode(t, "user:error", func() { api.Login(loginctx, "", "mjl@mox.example", pw0) })
 
 	// Login with loginToken.
 	loginCookie := &http.Cookie{Name: "webmaillogin"}
@@ -104,7 +106,7 @@ func TestAPI(t *testing.T) {
 			x := recover()
 			expErr := len(expErrCodes) > 0
 			if (x != nil) != expErr {
-				t.Fatalf("got %v, expected codes %v", x, expErrCodes)
+				t.Fatalf("got %v, expected codes %v, for username %q, password %q", x, expErrCodes, username, password)
 			}
 			if x == nil {
 				return
@@ -117,18 +119,21 @@ func TestAPI(t *testing.T) {
 
 		api.Login(loginctx, loginCookie.Value, username, password)
 	}
-	testLogin("mjl@mox.example", "test1234")
+	testLogin("mjl@mox.example", pw0)
-	testLogin("mjl@mox.example", "bad", "user:loginFailed")
+	testLogin("mjl@mox.example", pw1)
-	testLogin("nouser@mox.example", "test1234", "user:loginFailed")
+	testLogin("móx@mox.example", pw1)       // NFC username
-	testLogin("nouser@bad.example", "test1234", "user:loginFailed")
+	testLogin("mo\u0301x@mox.example", pw1) // NFD username
+	testLogin("mjl@mox.example", pw1+" ", "user:loginFailed")
+	testLogin("nouser@mox.example", pw0, "user:loginFailed")
+	testLogin("nouser@bad.example", pw0, "user:loginFailed")
 	for i := 3; i < 10; i++ {
-		testLogin("bad@bad.example", "test1234", "user:loginFailed")
+		testLogin("bad@bad.example", pw0, "user:loginFailed")
 	}
 	// Ensure rate limiter is triggered, also for slow tests.
 	for i := 0; i < 10; i++ {
-		testLogin("bad@bad.example", "test1234", "user:loginFailed", "user:error")
+		testLogin("bad@bad.example", pw0, "user:loginFailed", "user:error")
 	}
-	testLogin("bad@bad.example", "test1234", "user:error")
+	testLogin("bad@bad.example", pw0, "user:error")
 
 	// Context with different IP, for clear rate limit history.
 	reqInfo := requestInfo{"mjl@mox.example", "mjl", "", nil, &http.Request{RemoteAddr: "127.0.0.1:1234"}}