go*: one go module for the repo, no more nested

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

vendor/github.com/BurntSushi/toml/parse.go

@@ -0,0 +1,811 @@
+package toml
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/BurntSushi/toml/internal"
+)
+
+type parser struct {
+	lx         *lexer
+	context    Key      // Full key for the current hash in scope.
+	currentKey string   // Base key name for everything except hashes.
+	pos        Position // Current position in the TOML file.
+	tomlNext   bool
+
+	ordered []Key // List of keys in the order that they appear in the TOML data.
+
+	keyInfo   map[string]keyInfo     // Map keyname → info about the TOML key.
+	mapping   map[string]interface{} // Map keyname → key value.
+	implicits map[string]struct{}    // Record implicit keys (e.g. "key.group.names").
+}
+
+type keyInfo struct {
+	pos      Position
+	tomlType tomlType
+}
+
+func parse(data string) (p *parser, err error) {
+	_, tomlNext := os.LookupEnv("BURNTSUSHI_TOML_110")
+
+	defer func() {
+		if r := recover(); r != nil {
+			if pErr, ok := r.(ParseError); ok {
+				pErr.input = data
+				err = pErr
+				return
+			}
+			panic(r)
+		}
+	}()
+
+	// Read over BOM; do this here as the lexer calls utf8.DecodeRuneInString()
+	// which mangles stuff. UTF-16 BOM isn't strictly valid, but some tools add
+	// it anyway.
+	if strings.HasPrefix(data, "\xff\xfe") || strings.HasPrefix(data, "\xfe\xff") { // UTF-16
+		data = data[2:]
+	} else if strings.HasPrefix(data, "\xef\xbb\xbf") { // UTF-8
+		data = data[3:]
+	}
+
+	// Examine first few bytes for NULL bytes; this probably means it's a UTF-16
+	// file (second byte in surrogate pair being NULL). Again, do this here to
+	// avoid having to deal with UTF-8/16 stuff in the lexer.
+	ex := 6
+	if len(data) < 6 {
+		ex = len(data)
+	}
+	if i := strings.IndexRune(data[:ex], 0); i > -1 {
+		return nil, ParseError{
+			Message:  "files cannot contain NULL bytes; probably using UTF-16; TOML files must be UTF-8",
+			Position: Position{Line: 1, Start: i, Len: 1},
+			Line:     1,
+			input:    data,
+		}
+	}
+
+	p = &parser{
+		keyInfo:   make(map[string]keyInfo),
+		mapping:   make(map[string]interface{}),
+		lx:        lex(data, tomlNext),
+		ordered:   make([]Key, 0),
+		implicits: make(map[string]struct{}),
+		tomlNext:  tomlNext,
+	}
+	for {
+		item := p.next()
+		if item.typ == itemEOF {
+			break
+		}
+		p.topLevel(item)
+	}
+
+	return p, nil
+}
+
+func (p *parser) panicErr(it item, err error) {
+	panic(ParseError{
+		err:      err,
+		Position: it.pos,
+		Line:     it.pos.Len,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) panicItemf(it item, format string, v ...interface{}) {
+	panic(ParseError{
+		Message:  fmt.Sprintf(format, v...),
+		Position: it.pos,
+		Line:     it.pos.Len,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) panicf(format string, v ...interface{}) {
+	panic(ParseError{
+		Message:  fmt.Sprintf(format, v...),
+		Position: p.pos,
+		Line:     p.pos.Line,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) next() item {
+	it := p.lx.nextItem()
+	//fmt.Printf("ITEM %-18s line %-3d │ %q\n", it.typ, it.pos.Line, it.val)
+	if it.typ == itemError {
+		if it.err != nil {
+			panic(ParseError{
+				Position: it.pos,
+				Line:     it.pos.Line,
+				LastKey:  p.current(),
+				err:      it.err,
+			})
+		}
+
+		p.panicItemf(it, "%s", it.val)
+	}
+	return it
+}
+
+func (p *parser) nextPos() item {
+	it := p.next()
+	p.pos = it.pos
+	return it
+}
+
+func (p *parser) bug(format string, v ...interface{}) {
+	panic(fmt.Sprintf("BUG: "+format+"\n\n", v...))
+}
+
+func (p *parser) expect(typ itemType) item {
+	it := p.next()
+	p.assertEqual(typ, it.typ)
+	return it
+}
+
+func (p *parser) assertEqual(expected, got itemType) {
+	if expected != got {
+		p.bug("Expected '%s' but got '%s'.", expected, got)
+	}
+}
+
+func (p *parser) topLevel(item item) {
+	switch item.typ {
+	case itemCommentStart: // # ..
+		p.expect(itemText)
+	case itemTableStart: // [ .. ]
+		name := p.nextPos()
+
+		var key Key
+		for ; name.typ != itemTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemTableEnd, name.typ)
+
+		p.addContext(key, false)
+		p.setType("", tomlHash, item.pos)
+		p.ordered = append(p.ordered, key)
+	case itemArrayTableStart: // [[ .. ]]
+		name := p.nextPos()
+
+		var key Key
+		for ; name.typ != itemArrayTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemArrayTableEnd, name.typ)
+
+		p.addContext(key, true)
+		p.setType("", tomlArrayHash, item.pos)
+		p.ordered = append(p.ordered, key)
+	case itemKeyStart: // key = ..
+		outerContext := p.context
+		/// Read all the key parts (e.g. 'a' and 'b' in 'a.b')
+		k := p.nextPos()
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key[len(key)-1]
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key[:len(key)-1]
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+
+		/// Set value.
+		vItem := p.next()
+		val, typ := p.value(vItem, false)
+		p.set(p.currentKey, val, typ, vItem.pos)
+
+		/// Remove the context we added (preserving any context from [tbl] lines).
+		p.context = outerContext
+		p.currentKey = ""
+	default:
+		p.bug("Unexpected type at top level: %s", item.typ)
+	}
+}
+
+// Gets a string for a key (or part of a key in a table name).
+func (p *parser) keyString(it item) string {
+	switch it.typ {
+	case itemText:
+		return it.val
+	case itemString, itemMultilineString,
+		itemRawString, itemRawMultilineString:
+		s, _ := p.value(it, false)
+		return s.(string)
+	default:
+		p.bug("Unexpected key type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+var datetimeRepl = strings.NewReplacer(
+	"z", "Z",
+	"t", "T",
+	" ", "T")
+
+// value translates an expected value from the lexer into a Go value wrapped
+// as an empty interface.
+func (p *parser) value(it item, parentIsArray bool) (interface{}, tomlType) {
+	switch it.typ {
+	case itemString:
+		return p.replaceEscapes(it, it.val), p.typeOfPrimitive(it)
+	case itemMultilineString:
+		return p.replaceEscapes(it, p.stripEscapedNewlines(stripFirstNewline(it.val))), p.typeOfPrimitive(it)
+	case itemRawString:
+		return it.val, p.typeOfPrimitive(it)
+	case itemRawMultilineString:
+		return stripFirstNewline(it.val), p.typeOfPrimitive(it)
+	case itemInteger:
+		return p.valueInteger(it)
+	case itemFloat:
+		return p.valueFloat(it)
+	case itemBool:
+		switch it.val {
+		case "true":
+			return true, p.typeOfPrimitive(it)
+		case "false":
+			return false, p.typeOfPrimitive(it)
+		default:
+			p.bug("Expected boolean value, but got '%s'.", it.val)
+		}
+	case itemDatetime:
+		return p.valueDatetime(it)
+	case itemArray:
+		return p.valueArray(it)
+	case itemInlineTableStart:
+		return p.valueInlineTable(it, parentIsArray)
+	default:
+		p.bug("Unexpected value type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+func (p *parser) valueInteger(it item) (interface{}, tomlType) {
+	if !numUnderscoresOK(it.val) {
+		p.panicItemf(it, "Invalid integer %q: underscores must be surrounded by digits", it.val)
+	}
+	if numHasLeadingZero(it.val) {
+		p.panicItemf(it, "Invalid integer %q: cannot have leading zeroes", it.val)
+	}
+
+	num, err := strconv.ParseInt(it.val, 0, 64)
+	if err != nil {
+		// Distinguish integer values. Normally, it'd be a bug if the lexer
+		// provides an invalid integer, but it's possible that the number is
+		// out of range of valid values (which the lexer cannot determine).
+		// So mark the former as a bug but the latter as a legitimate user
+		// error.
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicErr(it, errParseRange{i: it.val, size: "int64"})
+		} else {
+			p.bug("Expected integer value, but got '%s'.", it.val)
+		}
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+func (p *parser) valueFloat(it item) (interface{}, tomlType) {
+	parts := strings.FieldsFunc(it.val, func(r rune) bool {
+		switch r {
+		case '.', 'e', 'E':
+			return true
+		}
+		return false
+	})
+	for _, part := range parts {
+		if !numUnderscoresOK(part) {
+			p.panicItemf(it, "Invalid float %q: underscores must be surrounded by digits", it.val)
+		}
+	}
+	if len(parts) > 0 && numHasLeadingZero(parts[0]) {
+		p.panicItemf(it, "Invalid float %q: cannot have leading zeroes", it.val)
+	}
+	if !numPeriodsOK(it.val) {
+		// As a special case, numbers like '123.' or '1.e2',
+		// which are valid as far as Go/strconv are concerned,
+		// must be rejected because TOML says that a fractional
+		// part consists of '.' followed by 1+ digits.
+		p.panicItemf(it, "Invalid float %q: '.' must be followed by one or more digits", it.val)
+	}
+	val := strings.Replace(it.val, "_", "", -1)
+	if val == "+nan" || val == "-nan" { // Go doesn't support this, but TOML spec does.
+		val = "nan"
+	}
+	num, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicErr(it, errParseRange{i: it.val, size: "float64"})
+		} else {
+			p.panicItemf(it, "Invalid float value: %q", it.val)
+		}
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+var dtTypes = []struct {
+	fmt  string
+	zone *time.Location
+	next bool
+}{
+	{time.RFC3339Nano, time.Local, false},
+	{"2006-01-02T15:04:05.999999999", internal.LocalDatetime, false},
+	{"2006-01-02", internal.LocalDate, false},
+	{"15:04:05.999999999", internal.LocalTime, false},
+
+	// tomlNext
+	{"2006-01-02T15:04Z07:00", time.Local, true},
+	{"2006-01-02T15:04", internal.LocalDatetime, true},
+	{"15:04", internal.LocalTime, true},
+}
+
+func (p *parser) valueDatetime(it item) (interface{}, tomlType) {
+	it.val = datetimeRepl.Replace(it.val)
+	var (
+		t   time.Time
+		ok  bool
+		err error
+	)
+	for _, dt := range dtTypes {
+		if dt.next && !p.tomlNext {
+			continue
+		}
+		t, err = time.ParseInLocation(dt.fmt, it.val, dt.zone)
+		if err == nil {
+			ok = true
+			break
+		}
+	}
+	if !ok {
+		p.panicItemf(it, "Invalid TOML Datetime: %q.", it.val)
+	}
+	return t, p.typeOfPrimitive(it)
+}
+
+func (p *parser) valueArray(it item) (interface{}, tomlType) {
+	p.setType(p.currentKey, tomlArray, it.pos)
+
+	var (
+		types []tomlType
+
+		// Initialize to a non-nil empty slice. This makes it consistent with
+		// how S = [] decodes into a non-nil slice inside something like struct
+		// { S []string }. See #338
+		array = []interface{}{}
+	)
+	for it = p.next(); it.typ != itemArrayEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		val, typ := p.value(it, true)
+		array = append(array, val)
+		types = append(types, typ)
+
+		// XXX: types isn't used here, we need it to record the accurate type
+		// information.
+		//
+		// Not entirely sure how to best store this; could use "key[0]",
+		// "key[1]" notation, or maybe store it on the Array type?
+		_ = types
+	}
+	return array, tomlArray
+}
+
+func (p *parser) valueInlineTable(it item, parentIsArray bool) (interface{}, tomlType) {
+	var (
+		hash         = make(map[string]interface{})
+		outerContext = p.context
+		outerKey     = p.currentKey
+	)
+
+	p.context = append(p.context, p.currentKey)
+	prevContext := p.context
+	p.currentKey = ""
+
+	p.addImplicit(p.context)
+	p.addContext(p.context, parentIsArray)
+
+	/// Loop over all table key/value pairs.
+	for it := p.next(); it.typ != itemInlineTableEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		/// Read all key parts.
+		k := p.nextPos()
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key[len(key)-1]
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key[:len(key)-1]
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+
+		/// Set the value.
+		val, typ := p.value(p.next(), false)
+		p.set(p.currentKey, val, typ, it.pos)
+		hash[p.currentKey] = val
+
+		/// Restore context.
+		p.context = prevContext
+	}
+	p.context = outerContext
+	p.currentKey = outerKey
+	return hash, tomlHash
+}
+
+// numHasLeadingZero checks if this number has leading zeroes, allowing for '0',
+// +/- signs, and base prefixes.
+func numHasLeadingZero(s string) bool {
+	if len(s) > 1 && s[0] == '0' && !(s[1] == 'b' || s[1] == 'o' || s[1] == 'x') { // Allow 0b, 0o, 0x
+		return true
+	}
+	if len(s) > 2 && (s[0] == '-' || s[0] == '+') && s[1] == '0' {
+		return true
+	}
+	return false
+}
+
+// numUnderscoresOK checks whether each underscore in s is surrounded by
+// characters that are not underscores.
+func numUnderscoresOK(s string) bool {
+	switch s {
+	case "nan", "+nan", "-nan", "inf", "-inf", "+inf":
+		return true
+	}
+	accept := false
+	for _, r := range s {
+		if r == '_' {
+			if !accept {
+				return false
+			}
+		}
+
+		// isHexadecimal is a superset of all the permissable characters
+		// surrounding an underscore.
+		accept = isHexadecimal(r)
+	}
+	return accept
+}
+
+// numPeriodsOK checks whether every period in s is followed by a digit.
+func numPeriodsOK(s string) bool {
+	period := false
+	for _, r := range s {
+		if period && !isDigit(r) {
+			return false
+		}
+		period = r == '.'
+	}
+	return !period
+}
+
+// Set the current context of the parser, where the context is either a hash or
+// an array of hashes, depending on the value of the `array` parameter.
+//
+// Establishing the context also makes sure that the key isn't a duplicate, and
+// will create implicit hashes automatically.
+func (p *parser) addContext(key Key, array bool) {
+	var ok bool
+
+	// Always start at the top level and drill down for our context.
+	hashContext := p.mapping
+	keyContext := make(Key, 0)
+
+	// We only need implicit hashes for key[0:-1]
+	for _, k := range key[0 : len(key)-1] {
+		_, ok = hashContext[k]
+		keyContext = append(keyContext, k)
+
+		// No key? Make an implicit hash and move on.
+		if !ok {
+			p.addImplicit(keyContext)
+			hashContext[k] = make(map[string]interface{})
+		}
+
+		// If the hash context is actually an array of tables, then set
+		// the hash context to the last element in that array.
+		//
+		// Otherwise, it better be a table, since this MUST be a key group (by
+		// virtue of it not being the last element in a key).
+		switch t := hashContext[k].(type) {
+		case []map[string]interface{}:
+			hashContext = t[len(t)-1]
+		case map[string]interface{}:
+			hashContext = t
+		default:
+			p.panicf("Key '%s' was already created as a hash.", keyContext)
+		}
+	}
+
+	p.context = keyContext
+	if array {
+		// If this is the first element for this array, then allocate a new
+		// list of tables for it.
+		k := key[len(key)-1]
+		if _, ok := hashContext[k]; !ok {
+			hashContext[k] = make([]map[string]interface{}, 0, 4)
+		}
+
+		// Add a new table. But make sure the key hasn't already been used
+		// for something else.
+		if hash, ok := hashContext[k].([]map[string]interface{}); ok {
+			hashContext[k] = append(hash, make(map[string]interface{}))
+		} else {
+			p.panicf("Key '%s' was already created and cannot be used as an array.", key)
+		}
+	} else {
+		p.setValue(key[len(key)-1], make(map[string]interface{}))
+	}
+	p.context = append(p.context, key[len(key)-1])
+}
+
+// set calls setValue and setType.
+func (p *parser) set(key string, val interface{}, typ tomlType, pos Position) {
+	p.setValue(key, val)
+	p.setType(key, typ, pos)
+}
+
+// setValue sets the given key to the given value in the current context.
+// It will make sure that the key hasn't already been defined, account for
+// implicit key groups.
+func (p *parser) setValue(key string, value interface{}) {
+	var (
+		tmpHash    interface{}
+		ok         bool
+		hash       = p.mapping
+		keyContext Key
+	)
+	for _, k := range p.context {
+		keyContext = append(keyContext, k)
+		if tmpHash, ok = hash[k]; !ok {
+			p.bug("Context for key '%s' has not been established.", keyContext)
+		}
+		switch t := tmpHash.(type) {
+		case []map[string]interface{}:
+			// The context is a table of hashes. Pick the most recent table
+			// defined as the current hash.
+			hash = t[len(t)-1]
+		case map[string]interface{}:
+			hash = t
+		default:
+			p.panicf("Key '%s' has already been defined.", keyContext)
+		}
+	}
+	keyContext = append(keyContext, key)
+
+	if _, ok := hash[key]; ok {
+		// Normally redefining keys isn't allowed, but the key could have been
+		// defined implicitly and it's allowed to be redefined concretely. (See
+		// the `valid/implicit-and-explicit-after.toml` in toml-test)
+		//
+		// But we have to make sure to stop marking it as an implicit. (So that
+		// another redefinition provokes an error.)
+		//
+		// Note that since it has already been defined (as a hash), we don't
+		// want to overwrite it. So our business is done.
+		if p.isArray(keyContext) {
+			p.removeImplicit(keyContext)
+			hash[key] = value
+			return
+		}
+		if p.isImplicit(keyContext) {
+			p.removeImplicit(keyContext)
+			return
+		}
+
+		// Otherwise, we have a concrete key trying to override a previous
+		// key, which is *always* wrong.
+		p.panicf("Key '%s' has already been defined.", keyContext)
+	}
+
+	hash[key] = value
+}
+
+// setType sets the type of a particular value at a given key. It should be
+// called immediately AFTER setValue.
+//
+// Note that if `key` is empty, then the type given will be applied to the
+// current context (which is either a table or an array of tables).
+func (p *parser) setType(key string, typ tomlType, pos Position) {
+	keyContext := make(Key, 0, len(p.context)+1)
+	keyContext = append(keyContext, p.context...)
+	if len(key) > 0 { // allow type setting for hashes
+		keyContext = append(keyContext, key)
+	}
+	// Special case to make empty keys ("" = 1) work.
+	// Without it it will set "" rather than `""`.
+	// TODO: why is this needed? And why is this only needed here?
+	if len(keyContext) == 0 {
+		keyContext = Key{""}
+	}
+	p.keyInfo[keyContext.String()] = keyInfo{tomlType: typ, pos: pos}
+}
+
+// Implicit keys need to be created when tables are implied in "a.b.c.d = 1" and
+// "[a.b.c]" (the "a", "b", and "c" hashes are never created explicitly).
+func (p *parser) addImplicit(key Key)        { p.implicits[key.String()] = struct{}{} }
+func (p *parser) removeImplicit(key Key)     { delete(p.implicits, key.String()) }
+func (p *parser) isImplicit(key Key) bool    { _, ok := p.implicits[key.String()]; return ok }
+func (p *parser) isArray(key Key) bool       { return p.keyInfo[key.String()].tomlType == tomlArray }
+func (p *parser) addImplicitContext(key Key) { p.addImplicit(key); p.addContext(key, false) }
+
+// current returns the full key name of the current context.
+func (p *parser) current() string {
+	if len(p.currentKey) == 0 {
+		return p.context.String()
+	}
+	if len(p.context) == 0 {
+		return p.currentKey
+	}
+	return fmt.Sprintf("%s.%s", p.context, p.currentKey)
+}
+
+func stripFirstNewline(s string) string {
+	if len(s) > 0 && s[0] == '\n' {
+		return s[1:]
+	}
+	if len(s) > 1 && s[0] == '\r' && s[1] == '\n' {
+		return s[2:]
+	}
+	return s
+}
+
+// stripEscapedNewlines removes whitespace after line-ending backslashes in
+// multiline strings.
+//
+// A line-ending backslash is an unescaped \ followed only by whitespace until
+// the next newline. After a line-ending backslash, all whitespace is removed
+// until the next non-whitespace character.
+func (p *parser) stripEscapedNewlines(s string) string {
+	var b strings.Builder
+	var i int
+	for {
+		ix := strings.Index(s[i:], `\`)
+		if ix < 0 {
+			b.WriteString(s)
+			return b.String()
+		}
+		i += ix
+
+		if len(s) > i+1 && s[i+1] == '\\' {
+			// Escaped backslash.
+			i += 2
+			continue
+		}
+		// Scan until the next non-whitespace.
+		j := i + 1
+	whitespaceLoop:
+		for ; j < len(s); j++ {
+			switch s[j] {
+			case ' ', '\t', '\r', '\n':
+			default:
+				break whitespaceLoop
+			}
+		}
+		if j == i+1 {
+			// Not a whitespace escape.
+			i++
+			continue
+		}
+		if !strings.Contains(s[i:j], "\n") {
+			// This is not a line-ending backslash.
+			// (It's a bad escape sequence, but we can let
+			// replaceEscapes catch it.)
+			i++
+			continue
+		}
+		b.WriteString(s[:i])
+		s = s[j:]
+		i = 0
+	}
+}
+
+func (p *parser) replaceEscapes(it item, str string) string {
+	replaced := make([]rune, 0, len(str))
+	s := []byte(str)
+	r := 0
+	for r < len(s) {
+		if s[r] != '\\' {
+			c, size := utf8.DecodeRune(s[r:])
+			r += size
+			replaced = append(replaced, c)
+			continue
+		}
+		r += 1
+		if r >= len(s) {
+			p.bug("Escape sequence at end of string.")
+			return ""
+		}
+		switch s[r] {
+		default:
+			p.bug("Expected valid escape code after \\, but got %q.", s[r])
+		case ' ', '\t':
+			p.panicItemf(it, "invalid escape: '\\%c'", s[r])
+		case 'b':
+			replaced = append(replaced, rune(0x0008))
+			r += 1
+		case 't':
+			replaced = append(replaced, rune(0x0009))
+			r += 1
+		case 'n':
+			replaced = append(replaced, rune(0x000A))
+			r += 1
+		case 'f':
+			replaced = append(replaced, rune(0x000C))
+			r += 1
+		case 'r':
+			replaced = append(replaced, rune(0x000D))
+			r += 1
+		case 'e':
+			if p.tomlNext {
+				replaced = append(replaced, rune(0x001B))
+				r += 1
+			}
+		case '"':
+			replaced = append(replaced, rune(0x0022))
+			r += 1
+		case '\\':
+			replaced = append(replaced, rune(0x005C))
+			r += 1
+		case 'x':
+			if p.tomlNext {
+				escaped := p.asciiEscapeToUnicode(it, s[r+1:r+3])
+				replaced = append(replaced, escaped)
+				r += 3
+			}
+		case 'u':
+			// At this point, we know we have a Unicode escape of the form
+			// `uXXXX` at [r, r+5). (Because the lexer guarantees this
+			// for us.)
+			escaped := p.asciiEscapeToUnicode(it, s[r+1:r+5])
+			replaced = append(replaced, escaped)
+			r += 5
+		case 'U':
+			// At this point, we know we have a Unicode escape of the form
+			// `uXXXX` at [r, r+9). (Because the lexer guarantees this
+			// for us.)
+			escaped := p.asciiEscapeToUnicode(it, s[r+1:r+9])
+			replaced = append(replaced, escaped)
+			r += 9
+		}
+	}
+	return string(replaced)
+}
+
+func (p *parser) asciiEscapeToUnicode(it item, bs []byte) rune {
+	s := string(bs)
+	hex, err := strconv.ParseUint(strings.ToLower(s), 16, 32)
+	if err != nil {
+		p.bug("Could not parse '%s' as a hexadecimal number, but the lexer claims it's OK: %s", s, err)
+	}
+	if !utf8.ValidRune(rune(hex)) {
+		p.panicItemf(it, "Escaped character '\\u%s' is not valid UTF-8.", s)
+	}
+	return rune(hex)
+}