--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vendor/github.com/dlclark/regexp2/syntax/prefix.go	Sun Jul 23 13:18:53 2023 +0000
@@ -0,0 +1,896 @@
+package syntax
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"unicode"
+	"unicode/utf8"
+)
+
+type Prefix struct {
+	PrefixStr       []rune
+	PrefixSet       CharSet
+	CaseInsensitive bool
+}
+
+// It takes a RegexTree and computes the set of chars that can start it.
+func getFirstCharsPrefix(tree *RegexTree) *Prefix {
+	s := regexFcd{
+		fcStack:  make([]regexFc, 32),
+		intStack: make([]int, 32),
+	}
+	fc := s.regexFCFromRegexTree(tree)
+
+	if fc == nil || fc.nullable || fc.cc.IsEmpty() {
+		return nil
+	}
+	fcSet := fc.getFirstChars()
+	return &Prefix{PrefixSet: fcSet, CaseInsensitive: fc.caseInsensitive}
+}
+
+type regexFcd struct {
+	intStack        []int
+	intDepth        int
+	fcStack         []regexFc
+	fcDepth         int
+	skipAllChildren bool // don't process any more children at the current level
+	skipchild       bool // don't process the current child.
+	failed          bool
+}
+
+/*
+ * The main FC computation. It does a shortcutted depth-first walk
+ * through the tree and calls CalculateFC to emits code before
+ * and after each child of an interior node, and at each leaf.
+ */
+func (s *regexFcd) regexFCFromRegexTree(tree *RegexTree) *regexFc {
+	curNode := tree.root
+	curChild := 0
+
+	for {
+		if len(curNode.children) == 0 {
+			// This is a leaf node
+			s.calculateFC(curNode.t, curNode, 0)
+		} else if curChild < len(curNode.children) && !s.skipAllChildren {
+			// This is an interior node, and we have more children to analyze
+			s.calculateFC(curNode.t|beforeChild, curNode, curChild)
+
+			if !s.skipchild {
+				curNode = curNode.children[curChild]
+				// this stack is how we get a depth first walk of the tree.
+				s.pushInt(curChild)
+				curChild = 0
+			} else {
+				curChild++
+				s.skipchild = false
+			}
+			continue
+		}
+
+		// This is an interior node where we've finished analyzing all the children, or
+		// the end of a leaf node.
+		s.skipAllChildren = false
+
+		if s.intIsEmpty() {
+			break
+		}
+
+		curChild = s.popInt()
+		curNode = curNode.next
+
+		s.calculateFC(curNode.t|afterChild, curNode, curChild)
+		if s.failed {
+			return nil
+		}
+
+		curChild++
+	}
+
+	if s.fcIsEmpty() {
+		return nil
+	}
+
+	return s.popFC()
+}
+
+// To avoid recursion, we use a simple integer stack.
+// This is the push.
+func (s *regexFcd) pushInt(I int) {
+	if s.intDepth >= len(s.intStack) {
+		expanded := make([]int, s.intDepth*2)
+		copy(expanded, s.intStack)
+		s.intStack = expanded
+	}
+
+	s.intStack[s.intDepth] = I
+	s.intDepth++
+}
+
+// True if the stack is empty.
+func (s *regexFcd) intIsEmpty() bool {
+	return s.intDepth == 0
+}
+
+// This is the pop.
+func (s *regexFcd) popInt() int {
+	s.intDepth--
+	return s.intStack[s.intDepth]
+}
+
+// We also use a stack of RegexFC objects.
+// This is the push.
+func (s *regexFcd) pushFC(fc regexFc) {
+	if s.fcDepth >= len(s.fcStack) {
+		expanded := make([]regexFc, s.fcDepth*2)
+		copy(expanded, s.fcStack)
+		s.fcStack = expanded
+	}
+
+	s.fcStack[s.fcDepth] = fc
+	s.fcDepth++
+}
+
+// True if the stack is empty.
+func (s *regexFcd) fcIsEmpty() bool {
+	return s.fcDepth == 0
+}
+
+// This is the pop.
+func (s *regexFcd) popFC() *regexFc {
+	s.fcDepth--
+	return &s.fcStack[s.fcDepth]
+}
+
+// This is the top.
+func (s *regexFcd) topFC() *regexFc {
+	return &s.fcStack[s.fcDepth-1]
+}
+
+// Called in Beforechild to prevent further processing of the current child
+func (s *regexFcd) skipChild() {
+	s.skipchild = true
+}
+
+// FC computation and shortcut cases for each node type
+func (s *regexFcd) calculateFC(nt nodeType, node *regexNode, CurIndex int) {
+	//fmt.Printf("NodeType: %v, CurIndex: %v, Desc: %v\n", nt, CurIndex, node.description())
+	ci := false
+	rtl := false
+
+	if nt <= ntRef {
+		if (node.options & IgnoreCase) != 0 {
+			ci = true
+		}
+		if (node.options & RightToLeft) != 0 {
+			rtl = true
+		}
+	}
+
+	switch nt {
+	case ntConcatenate | beforeChild, ntAlternate | beforeChild, ntTestref | beforeChild, ntLoop | beforeChild, ntLazyloop | beforeChild:
+		break
+
+	case ntTestgroup | beforeChild:
+		if CurIndex == 0 {
+			s.skipChild()
+		}
+		break
+
+	case ntEmpty:
+		s.pushFC(regexFc{nullable: true})
+		break
+
+	case ntConcatenate | afterChild:
+		if CurIndex != 0 {
+			child := s.popFC()
+			cumul := s.topFC()
+
+			s.failed = !cumul.addFC(*child, true)
+		}
+
+		fc := s.topFC()
+		if !fc.nullable {
+			s.skipAllChildren = true
+		}
+		break
+
+	case ntTestgroup | afterChild:
+		if CurIndex > 1 {
+			child := s.popFC()
+			cumul := s.topFC()
+
+			s.failed = !cumul.addFC(*child, false)
+		}
+		break
+
+	case ntAlternate | afterChild, ntTestref | afterChild:
+		if CurIndex != 0 {
+			child := s.popFC()
+			cumul := s.topFC()
+
+			s.failed = !cumul.addFC(*child, false)
+		}
+		break
+
+	case ntLoop | afterChild, ntLazyloop | afterChild:
+		if node.m == 0 {
+			fc := s.topFC()
+			fc.nullable = true
+		}
+		break
+
+	case ntGroup | beforeChild, ntGroup | afterChild, ntCapture | beforeChild, ntCapture | afterChild, ntGreedy | beforeChild, ntGreedy | afterChild:
+		break
+
+	case ntRequire | beforeChild, ntPrevent | beforeChild:
+		s.skipChild()
+		s.pushFC(regexFc{nullable: true})
+		break
+
+	case ntRequire | afterChild, ntPrevent | afterChild:
+		break
+
+	case ntOne, ntNotone:
+		s.pushFC(newRegexFc(node.ch, nt == ntNotone, false, ci))
+		break
+
+	case ntOneloop, ntOnelazy:
+		s.pushFC(newRegexFc(node.ch, false, node.m == 0, ci))
+		break
+
+	case ntNotoneloop, ntNotonelazy:
+		s.pushFC(newRegexFc(node.ch, true, node.m == 0, ci))
+		break
+
+	case ntMulti:
+		if len(node.str) == 0 {
+			s.pushFC(regexFc{nullable: true})
+		} else if !rtl {
+			s.pushFC(newRegexFc(node.str[0], false, false, ci))
+		} else {
+			s.pushFC(newRegexFc(node.str[len(node.str)-1], false, false, ci))
+		}
+		break
+
+	case ntSet:
+		s.pushFC(regexFc{cc: node.set.Copy(), nullable: false, caseInsensitive: ci})
+		break
+
+	case ntSetloop, ntSetlazy:
+		s.pushFC(regexFc{cc: node.set.Copy(), nullable: node.m == 0, caseInsensitive: ci})
+		break
+
+	case ntRef:
+		s.pushFC(regexFc{cc: *AnyClass(), nullable: true, caseInsensitive: false})
+		break
+
+	case ntNothing, ntBol, ntEol, ntBoundary, ntNonboundary, ntECMABoundary, ntNonECMABoundary, ntBeginning, ntStart, ntEndZ, ntEnd:
+		s.pushFC(regexFc{nullable: true})
+		break
+
+	default:
+		panic(fmt.Sprintf("unexpected op code: %v", nt))
+	}
+}
+
+type regexFc struct {
+	cc              CharSet
+	nullable        bool
+	caseInsensitive bool
+}
+
+func newRegexFc(ch rune, not, nullable, caseInsensitive bool) regexFc {
+	r := regexFc{
+		caseInsensitive: caseInsensitive,
+		nullable:        nullable,
+	}
+	if not {
+		if ch > 0 {
+			r.cc.addRange('\x00', ch-1)
+		}
+		if ch < 0xFFFF {
+			r.cc.addRange(ch+1, utf8.MaxRune)
+		}
+	} else {
+		r.cc.addRange(ch, ch)
+	}
+	return r
+}
+
+func (r *regexFc) getFirstChars() CharSet {
+	if r.caseInsensitive {
+		r.cc.addLowercase()
+	}
+
+	return r.cc
+}
+
+func (r *regexFc) addFC(fc regexFc, concatenate bool) bool {
+	if !r.cc.IsMergeable() || !fc.cc.IsMergeable() {
+		return false
+	}
+
+	if concatenate {
+		if !r.nullable {
+			return true
+		}
+
+		if !fc.nullable {
+			r.nullable = false
+		}
+	} else {
+		if fc.nullable {
+			r.nullable = true
+		}
+	}
+
+	r.caseInsensitive = r.caseInsensitive || fc.caseInsensitive
+	r.cc.addSet(fc.cc)
+
+	return true
+}
+
+// This is a related computation: it takes a RegexTree and computes the
+// leading substring if it sees one. It's quite trivial and gives up easily.
+func getPrefix(tree *RegexTree) *Prefix {
+	var concatNode *regexNode
+	nextChild := 0
+
+	curNode := tree.root
+
+	for {
+		switch curNode.t {
+		case ntConcatenate:
+			if len(curNode.children) > 0 {
+				concatNode = curNode
+				nextChild = 0
+			}
+
+		case ntGreedy, ntCapture:
+			curNode = curNode.children[0]
+			concatNode = nil
+			continue
+
+		case ntOneloop, ntOnelazy:
+			if curNode.m > 0 {
+				return &Prefix{
+					PrefixStr:       repeat(curNode.ch, curNode.m),
+					CaseInsensitive: (curNode.options & IgnoreCase) != 0,
+				}
+			}
+			return nil
+
+		case ntOne:
+			return &Prefix{
+				PrefixStr:       []rune{curNode.ch},
+				CaseInsensitive: (curNode.options & IgnoreCase) != 0,
+			}
+
+		case ntMulti:
+			return &Prefix{
+				PrefixStr:       curNode.str,
+				CaseInsensitive: (curNode.options & IgnoreCase) != 0,
+			}
+
+		case ntBol, ntEol, ntBoundary, ntECMABoundary, ntBeginning, ntStart,
+			ntEndZ, ntEnd, ntEmpty, ntRequire, ntPrevent:
+
+		default:
+			return nil
+		}
+
+		if concatNode == nil || nextChild >= len(concatNode.children) {
+			return nil
+		}
+
+		curNode = concatNode.children[nextChild]
+		nextChild++
+	}
+}
+
+// repeat the rune r, c times... up to the max of MaxPrefixSize
+func repeat(r rune, c int) []rune {
+	if c > MaxPrefixSize {
+		c = MaxPrefixSize
+	}
+
+	ret := make([]rune, c)
+
+	// binary growth using copy for speed
+	ret[0] = r
+	bp := 1
+	for bp < len(ret) {
+		copy(ret[bp:], ret[:bp])
+		bp *= 2
+	}
+
+	return ret
+}
+
+// BmPrefix precomputes the Boyer-Moore
+// tables for fast string scanning. These tables allow
+// you to scan for the first occurrence of a string within
+// a large body of text without examining every character.
+// The performance of the heuristic depends on the actual
+// string and the text being searched, but usually, the longer
+// the string that is being searched for, the fewer characters
+// need to be examined.
+type BmPrefix struct {
+	positive        []int
+	negativeASCII   []int
+	negativeUnicode [][]int
+	pattern         []rune
+	lowASCII        rune
+	highASCII       rune
+	rightToLeft     bool
+	caseInsensitive bool
+}
+
+func newBmPrefix(pattern []rune, caseInsensitive, rightToLeft bool) *BmPrefix {
+
+	b := &BmPrefix{
+		rightToLeft:     rightToLeft,
+		caseInsensitive: caseInsensitive,
+		pattern:         pattern,
+	}
+
+	if caseInsensitive {
+		for i := 0; i < len(b.pattern); i++ {
+			// We do the ToLower character by character for consistency.  With surrogate chars, doing
+			// a ToLower on the entire string could actually change the surrogate pair.  This is more correct
+			// linguistically, but since Regex doesn't support surrogates, it's more important to be
+			// consistent.
+
+			b.pattern[i] = unicode.ToLower(b.pattern[i])
+		}
+	}
+
+	var beforefirst, last, bump int
+	var scan, match int
+
+	if !rightToLeft {
+		beforefirst = -1
+		last = len(b.pattern) - 1
+		bump = 1
+	} else {
+		beforefirst = len(b.pattern)
+		last = 0
+		bump = -1
+	}
+
+	// PART I - the good-suffix shift table
+	//
+	// compute the positive requirement:
+	// if char "i" is the first one from the right that doesn't match,
+	// then we know the matcher can advance by _positive[i].
+	//
+	// This algorithm is a simplified variant of the standard
+	// Boyer-Moore good suffix calculation.
+
+	b.positive = make([]int, len(b.pattern))
+
+	examine := last
+	ch := b.pattern[examine]
+	b.positive[examine] = bump
+	examine -= bump
+
+Outerloop:
+	for {
+		// find an internal char (examine) that matches the tail
+
+		for {
+			if examine == beforefirst {
+				break Outerloop
+			}
+			if b.pattern[examine] == ch {
+				break
+			}
+			examine -= bump
+		}
+
+		match = last
+		scan = examine
+
+		// find the length of the match
+		for {
+			if scan == beforefirst || b.pattern[match] != b.pattern[scan] {
+				// at the end of the match, note the difference in _positive
+				// this is not the length of the match, but the distance from the internal match
+				// to the tail suffix.
+				if b.positive[match] == 0 {
+					b.positive[match] = match - scan
+				}
+
+				// System.Diagnostics.Debug.WriteLine("Set positive[" + match + "] to " + (match - scan));
+
+				break
+			}
+
+			scan -= bump
+			match -= bump
+		}
+
+		examine -= bump
+	}
+
+	match = last - bump
+
+	// scan for the chars for which there are no shifts that yield a different candidate
+
+	// The inside of the if statement used to say
+	// "_positive[match] = last - beforefirst;"
+	// This is slightly less aggressive in how much we skip, but at worst it
+	// should mean a little more work rather than skipping a potential match.
+	for match != beforefirst {
+		if b.positive[match] == 0 {
+			b.positive[match] = bump
+		}
+
+		match -= bump
+	}
+
+	// PART II - the bad-character shift table
+	//
+	// compute the negative requirement:
+	// if char "ch" is the reject character when testing position "i",
+	// we can slide up by _negative[ch];
+	// (_negative[ch] = str.Length - 1 - str.LastIndexOf(ch))
+	//
+	// the lookup table is divided into ASCII and Unicode portions;
+	// only those parts of the Unicode 16-bit code set that actually
+	// appear in the string are in the table. (Maximum size with
+	// Unicode is 65K; ASCII only case is 512 bytes.)
+
+	b.negativeASCII = make([]int, 128)
+
+	for i := 0; i < len(b.negativeASCII); i++ {
+		b.negativeASCII[i] = last - beforefirst
+	}
+
+	b.lowASCII = 127
+	b.highASCII = 0
+
+	for examine = last; examine != beforefirst; examine -= bump {
+		ch = b.pattern[examine]
+
+		switch {
+		case ch < 128:
+			if b.lowASCII > ch {
+				b.lowASCII = ch
+			}
+
+			if b.highASCII < ch {
+				b.highASCII = ch
+			}
+
+			if b.negativeASCII[ch] == last-beforefirst {
+				b.negativeASCII[ch] = last - examine
+			}
+		case ch <= 0xffff:
+			i, j := ch>>8, ch&0xFF
+
+			if b.negativeUnicode == nil {
+				b.negativeUnicode = make([][]int, 256)
+			}
+
+			if b.negativeUnicode[i] == nil {
+				newarray := make([]int, 256)
+
+				for k := 0; k < len(newarray); k++ {
+					newarray[k] = last - beforefirst
+				}
+
+				if i == 0 {
+					copy(newarray, b.negativeASCII)
+					//TODO: this line needed?
+					b.negativeASCII = newarray
+				}
+
+				b.negativeUnicode[i] = newarray
+			}
+
+			if b.negativeUnicode[i][j] == last-beforefirst {
+				b.negativeUnicode[i][j] = last - examine
+			}
+		default:
+			// we can't do the filter because this algo doesn't support
+			// unicode chars >0xffff
+			return nil
+		}
+	}
+
+	return b
+}
+
+func (b *BmPrefix) String() string {
+	return string(b.pattern)
+}
+
+// Dump returns the contents of the filter as a human readable string
+func (b *BmPrefix) Dump(indent string) string {
+	buf := &bytes.Buffer{}
+
+	fmt.Fprintf(buf, "%sBM Pattern: %s\n%sPositive: ", indent, string(b.pattern), indent)
+	for i := 0; i < len(b.positive); i++ {
+		buf.WriteString(strconv.Itoa(b.positive[i]))
+		buf.WriteRune(' ')
+	}
+	buf.WriteRune('\n')
+
+	if b.negativeASCII != nil {
+		buf.WriteString(indent)
+		buf.WriteString("Negative table\n")
+		for i := 0; i < len(b.negativeASCII); i++ {
+			if b.negativeASCII[i] != len(b.pattern) {
+				fmt.Fprintf(buf, "%s  %s %s\n", indent, Escape(string(rune(i))), strconv.Itoa(b.negativeASCII[i]))
+			}
+		}
+	}
+
+	return buf.String()
+}
+
+// Scan uses the Boyer-Moore algorithm to find the first occurrence
+// of the specified string within text, beginning at index, and
+// constrained within beglimit and endlimit.
+//
+// The direction and case-sensitivity of the match is determined
+// by the arguments to the RegexBoyerMoore constructor.
+func (b *BmPrefix) Scan(text []rune, index, beglimit, endlimit int) int {
+	var (
+		defadv, test, test2         int
+		match, startmatch, endmatch int
+		bump, advance               int
+		chTest                      rune
+		unicodeLookup               []int
+	)
+
+	if !b.rightToLeft {
+		defadv = len(b.pattern)
+		startmatch = len(b.pattern) - 1
+		endmatch = 0
+		test = index + defadv - 1
+		bump = 1
+	} else {
+		defadv = -len(b.pattern)
+		startmatch = 0
+		endmatch = -defadv - 1
+		test = index + defadv
+		bump = -1
+	}
+
+	chMatch := b.pattern[startmatch]
+
+	for {
+		if test >= endlimit || test < beglimit {
+			return -1
+		}
+
+		chTest = text[test]
+
+		if b.caseInsensitive {
+			chTest = unicode.ToLower(chTest)
+		}
+
+		if chTest != chMatch {
+			if chTest < 128 {
+				advance = b.negativeASCII[chTest]
+			} else if chTest < 0xffff && len(b.negativeUnicode) > 0 {
+				unicodeLookup = b.negativeUnicode[chTest>>8]
+				if len(unicodeLookup) > 0 {
+					advance = unicodeLookup[chTest&0xFF]
+				} else {
+					advance = defadv
+				}
+			} else {
+				advance = defadv
+			}
+
+			test += advance
+		} else { // if (chTest == chMatch)
+			test2 = test
+			match = startmatch
+
+			for {
+				if match == endmatch {
+					if b.rightToLeft {
+						return test2 + 1
+					} else {
+						return test2
+					}
+				}
+
+				match -= bump
+				test2 -= bump
+
+				chTest = text[test2]
+
+				if b.caseInsensitive {
+					chTest = unicode.ToLower(chTest)
+				}
+
+				if chTest != b.pattern[match] {
+					advance = b.positive[match]
+					if (chTest & 0xFF80) == 0 {
+						test2 = (match - startmatch) + b.negativeASCII[chTest]
+					} else if chTest < 0xffff && len(b.negativeUnicode) > 0 {
+						unicodeLookup = b.negativeUnicode[chTest>>8]
+						if len(unicodeLookup) > 0 {
+							test2 = (match - startmatch) + unicodeLookup[chTest&0xFF]
+						} else {
+							test += advance
+							break
+						}
+					} else {
+						test += advance
+						break
+					}
+
+					if b.rightToLeft {
+						if test2 < advance {
+							advance = test2
+						}
+					} else if test2 > advance {
+						advance = test2
+					}
+
+					test += advance
+					break
+				}
+			}
+		}
+	}
+}
+
+// When a regex is anchored, we can do a quick IsMatch test instead of a Scan
+func (b *BmPrefix) IsMatch(text []rune, index, beglimit, endlimit int) bool {
+	if !b.rightToLeft {
+		if index < beglimit || endlimit-index < len(b.pattern) {
+			return false
+		}
+
+		return b.matchPattern(text, index)
+	} else {
+		if index > endlimit || index-beglimit < len(b.pattern) {
+			return false
+		}
+
+		return b.matchPattern(text, index-len(b.pattern))
+	}
+}
+
+func (b *BmPrefix) matchPattern(text []rune, index int) bool {
+	if len(text)-index < len(b.pattern) {
+		return false
+	}
+
+	if b.caseInsensitive {
+		for i := 0; i < len(b.pattern); i++ {
+			//Debug.Assert(textinfo.ToLower(_pattern[i]) == _pattern[i], "pattern should be converted to lower case in constructor!");
+			if unicode.ToLower(text[index+i]) != b.pattern[i] {
+				return false
+			}
+		}
+		return true
+	} else {
+		for i := 0; i < len(b.pattern); i++ {
+			if text[index+i] != b.pattern[i] {
+				return false
+			}
+		}
+		return true
+	}
+}
+
+type AnchorLoc int16
+
+// where the regex can be pegged
+const (
+	AnchorBeginning    AnchorLoc = 0x0001
+	AnchorBol                    = 0x0002
+	AnchorStart                  = 0x0004
+	AnchorEol                    = 0x0008
+	AnchorEndZ                   = 0x0010
+	AnchorEnd                    = 0x0020
+	AnchorBoundary               = 0x0040
+	AnchorECMABoundary           = 0x0080
+)
+
+func getAnchors(tree *RegexTree) AnchorLoc {
+
+	var concatNode *regexNode
+	nextChild, result := 0, AnchorLoc(0)
+
+	curNode := tree.root
+
+	for {
+		switch curNode.t {
+		case ntConcatenate:
+			if len(curNode.children) > 0 {
+				concatNode = curNode
+				nextChild = 0
+			}
+
+		case ntGreedy, ntCapture:
+			curNode = curNode.children[0]
+			concatNode = nil
+			continue
+
+		case ntBol, ntEol, ntBoundary, ntECMABoundary, ntBeginning,
+			ntStart, ntEndZ, ntEnd:
+			return result | anchorFromType(curNode.t)
+
+		case ntEmpty, ntRequire, ntPrevent:
+
+		default:
+			return result
+		}
+
+		if concatNode == nil || nextChild >= len(concatNode.children) {
+			return result
+		}
+
+		curNode = concatNode.children[nextChild]
+		nextChild++
+	}
+}
+
+func anchorFromType(t nodeType) AnchorLoc {
+	switch t {
+	case ntBol:
+		return AnchorBol
+	case ntEol:
+		return AnchorEol
+	case ntBoundary:
+		return AnchorBoundary
+	case ntECMABoundary:
+		return AnchorECMABoundary
+	case ntBeginning:
+		return AnchorBeginning
+	case ntStart:
+		return AnchorStart
+	case ntEndZ:
+		return AnchorEndZ
+	case ntEnd:
+		return AnchorEnd
+	default:
+		return 0
+	}
+}
+
+// anchorDescription returns a human-readable description of the anchors
+func (anchors AnchorLoc) String() string {
+	buf := &bytes.Buffer{}
+
+	if 0 != (anchors & AnchorBeginning) {
+		buf.WriteString(", Beginning")
+	}
+	if 0 != (anchors & AnchorStart) {
+		buf.WriteString(", Start")
+	}
+	if 0 != (anchors & AnchorBol) {
+		buf.WriteString(", Bol")
+	}
+	if 0 != (anchors & AnchorBoundary) {
+		buf.WriteString(", Boundary")
+	}
+	if 0 != (anchors & AnchorECMABoundary) {
+		buf.WriteString(", ECMABoundary")
+	}
+	if 0 != (anchors & AnchorEol) {
+		buf.WriteString(", Eol")
+	}
+	if 0 != (anchors & AnchorEnd) {
+		buf.WriteString(", End")
+	}
+	if 0 != (anchors & AnchorEndZ) {
+		buf.WriteString(", EndZ")
+	}
+
+	// trim off comma
+	if buf.Len() >= 2 {
+		return buf.String()[2:]
+	}
+	return "None"
+}