ast.go

// 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 demangle

import (
	"fmt"
	"strings"
)

// AST is an abstract syntax tree representing a C++ declaration.
// This is sufficient for the demangler but is by no means a general C++ AST.
// This abstract syntax tree is only used for C++ symbols, not Rust symbols.
type AST interface {
	// Internal method to convert to demangled string.
	print(*printState)

	// Traverse each element of an AST.  If the function returns
	// false, traversal of children of that element is skipped.
	Traverse(func(AST) bool)

	// Copy an AST with possible transformations.
	// If the skip function returns true, no copy is required.
	// If the copy function returns nil, no copy is required.
	// The Copy method will do the right thing if copy returns nil
	// for some components of an AST but not others, so a good
	// copy function will only return non-nil for AST values that
	// need to change.
	// Copy itself returns either a copy or nil.
	Copy(copy func(AST) AST, skip func(AST) bool) AST

	// Implement the fmt.GoStringer interface.
	GoString() string
	goString(indent int, field string) string
}

// ASTToString returns the demangled name of the AST.
func ASTToString(a AST, options ...Option) string {
	tparams := true
	enclosingParams := true
	llvmStyle := false
	max := 0
	for _, o := range options {
		switch {
		case o == NoTemplateParams:
			tparams = false
		case o == NoEnclosingParams:
			enclosingParams = false
		case o == LLVMStyle:
			llvmStyle = true
		case isMaxLength(o):
			max = maxLength(o)
		}
	}

	ps := printState{
		tparams:         tparams,
		enclosingParams: enclosingParams,
		llvmStyle:       llvmStyle,
		max:             max,
		scopes:          1,
	}
	a.print(&ps)
	s := ps.buf.String()
	if max > 0 && len(s) > max {
		s = s[:max]
	}
	return s
}

// The printState type holds information needed to print an AST.
type printState struct {
	tparams         bool // whether to print template parameters
	enclosingParams bool // whether to print enclosing parameters
	llvmStyle       bool
	max             int // maximum output length

	// The scopes field is used to avoid unnecessary parentheses
	// around expressions that use > (or >>). It is incremented if
	// we output a parenthesis or something else that means that >
	// or >> won't be treated as ending a template. It starts out
	// as 1, and is set to 0 when we start writing template
	// arguments. We add parentheses around expressions using > if
	// scopes is 0. The effect is that an expression with > gets
	// parentheses if used as a template argument that is not
	// inside some other set of parentheses.
	scopes int

	buf  strings.Builder
	last byte // Last byte written to buffer.

	// The inner field is a list of items to print for a type
	// name.  This is used by types to implement the inside-out
	// C++ declaration syntax.
	inner []AST

	// The printing field is a list of items we are currently
	// printing.  This avoids endless recursion if a substitution
	// reference creates a cycle in the graph.
	printing []AST
}

// writeByte adds a byte to the string being printed.
func (ps *printState) writeByte(b byte) {
	ps.last = b
	ps.buf.WriteByte(b)
}

// writeString adds a string to the string being printed.
func (ps *printState) writeString(s string) {
	if len(s) > 0 {
		ps.last = s[len(s)-1]
	}
	ps.buf.WriteString(s)
}

// Print an AST.
func (ps *printState) print(a AST) {
	if ps.max > 0 && ps.buf.Len() > ps.max {
		return
	}

	c := 0
	for _, v := range ps.printing {
		if v == a {
			// We permit the type to appear once, and
			// return without printing anything if we see
			// it twice.  This is for a case like
			// _Z6outer2IsEPFilES1_, where the
			// substitution is printed differently the
			// second time because the set of inner types
			// is different.
			c++
			if c > 1 {
				return
			}
		}
	}
	ps.printing = append(ps.printing, a)

	a.print(ps)

	ps.printing = ps.printing[:len(ps.printing)-1]
}

// printList prints a list of AST values separated by commas,
// optionally skipping some.
func (ps *printState) printList(args []AST, skip func(AST) bool) {
	first := true
	for _, a := range args {
		if skip != nil && skip(a) {
			continue
		}
		if !first {
			ps.writeString(", ")
		}

		needsParen := false
		if ps.llvmStyle {
			if p, ok := a.(hasPrec); ok {
				if p.prec() >= precComma {
					needsParen = true
				}
			}
		}
		if needsParen {
			ps.startScope('(')
		}

		ps.print(a)

		if needsParen {
			ps.endScope(')')
		}

		first = false
	}
}

// startScope starts a scope. This is used to decide whether we need
// to parenthesize an expression using > or >>.
func (ps *printState) startScope(b byte) {
	ps.scopes++
	ps.writeByte(b)
}

// endScope closes a scope.
func (ps *printState) endScope(b byte) {
	ps.scopes--
	ps.writeByte(b)
}

// precedence is used for operator precedence. This is used to avoid
// unnecessary parentheses when printing expressions in the LLVM style.
type precedence int

// The precedence values, in order from high to low.
const (
	precPrimary precedence = iota
	precPostfix
	precUnary
	precCast
	precPtrMem
	precMul
	precAdd
	precShift
	precSpaceship
	precRel
	precEqual
	precAnd
	precXor
	precOr
	precLogicalAnd
	precLogicalOr
	precCond
	precAssign
	precComma
	precDefault
)

// hasPrec matches the AST nodes that have a prec method that returns
// the node's precedence.
type hasPrec interface {
	prec() precedence
}

// Name is an unqualified name.
type Name struct {
	Name string
}

func (n *Name) print(ps *printState) {
	ps.writeString(n.Name)
}

func (n *Name) Traverse(fn func(AST) bool) {
	fn(n)
}

func (n *Name) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(n) {
		return nil
	}
	return fn(n)
}

func (n *Name) GoString() string {
	return n.goString(0, "Name: ")
}

func (n *Name) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%s%s", indent, "", field, n.Name)
}

func (n *Name) prec() precedence {
	return precPrimary
}

// Typed is a typed name.
type Typed struct {
	Name AST
	Type AST
}

func (t *Typed) print(ps *printState) {
	// We are printing a typed name, so ignore the current set of
	// inner names to print.  Pass down our name as the one to use.
	holdInner := ps.inner
	defer func() { ps.inner = holdInner }()

	ps.inner = []AST{t}
	ps.print(t.Type)
	if len(ps.inner) > 0 {
		// The type did not print the name; print it now in
		// the default location.
		ps.writeByte(' ')
		ps.print(t.Name)
	}
}

func (t *Typed) printInner(ps *printState) {
	ps.print(t.Name)
}

func (t *Typed) Traverse(fn func(AST) bool) {
	if fn(t) {
		t.Name.Traverse(fn)
		t.Type.Traverse(fn)
	}
}

func (t *Typed) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(t) {
		return nil
	}
	name := t.Name.Copy(fn, skip)
	typ := t.Type.Copy(fn, skip)
	if name == nil && typ == nil {
		return fn(t)
	}
	if name == nil {
		name = t.Name
	}
	if typ == nil {
		typ = t.Type
	}
	t = &Typed{Name: name, Type: typ}
	if r := fn(t); r != nil {
		return r
	}
	return t
}

func (t *Typed) GoString() string {
	return t.goString(0, "")
}

func (t *Typed) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTyped:\n%s\n%s", indent, "", field,
		t.Name.goString(indent+2, "Name: "),
		t.Type.goString(indent+2, "Type: "))
}

// Qualified is a name in a scope.
type Qualified struct {
	Scope AST
	Name  AST

	// The LocalName field is true if this is parsed as a
	// <local-name>.  We shouldn't really need this, but in some
	// cases (for the unary sizeof operator) the standard
	// demangler prints a local name slightly differently.  We
	// keep track of this for compatibility.
	LocalName bool // A full local name encoding
}

func (q *Qualified) print(ps *printState) {
	ps.print(q.Scope)
	ps.writeString("::")
	ps.print(q.Name)
}

func (q *Qualified) Traverse(fn func(AST) bool) {
	if fn(q) {
		q.Scope.Traverse(fn)
		q.Name.Traverse(fn)
	}
}

func (q *Qualified) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(q) {
		return nil
	}
	scope := q.Scope.Copy(fn, skip)
	name := q.Name.Copy(fn, skip)
	if scope == nil && name == nil {
		return fn(q)
	}
	if scope == nil {
		scope = q.Scope
	}
	if name == nil {
		name = q.Name
	}
	q = &Qualified{Scope: scope, Name: name, LocalName: q.LocalName}
	if r := fn(q); r != nil {
		return r
	}
	return q
}

func (q *Qualified) GoString() string {
	return q.goString(0, "")
}

func (q *Qualified) goString(indent int, field string) string {
	s := ""
	if q.LocalName {
		s = " LocalName: true"
	}
	return fmt.Sprintf("%*s%sQualified:%s\n%s\n%s", indent, "", field,
		s, q.Scope.goString(indent+2, "Scope: "),
		q.Name.goString(indent+2, "Name: "))
}

func (q *Qualified) prec() precedence {
	return precPrimary
}

// Template is a template with arguments.
type Template struct {
	Name AST
	Args []AST
}

func (t *Template) print(ps *printState) {
	// Inner types apply to the template as a whole, they don't
	// cross over into the template.
	holdInner := ps.inner
	defer func() { ps.inner = holdInner }()

	ps.inner = nil
	ps.print(t.Name)

	if !ps.tparams {
		// Do not print template parameters.
		return
	}
	// We need an extra space after operator<.
	if ps.last == '<' {
		ps.writeByte(' ')
	}

	scopes := ps.scopes
	ps.scopes = 0

	ps.writeByte('<')
	ps.printList(t.Args, ps.isEmpty)
	if ps.last == '>' && !ps.llvmStyle {
		// Avoid syntactic ambiguity in old versions of C++.
		ps.writeByte(' ')
	}
	ps.writeByte('>')

	ps.scopes = scopes
}

func (t *Template) Traverse(fn func(AST) bool) {
	if fn(t) {
		t.Name.Traverse(fn)
		for _, a := range t.Args {
			a.Traverse(fn)
		}
	}
}

func (t *Template) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(t) {
		return nil
	}
	name := t.Name.Copy(fn, skip)
	changed := name != nil
	args := make([]AST, len(t.Args))
	for i, a := range t.Args {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			changed = true
		}
	}
	if !changed {
		return fn(t)
	}
	if name == nil {
		name = t.Name
	}
	t = &Template{Name: name, Args: args}
	if r := fn(t); r != nil {
		return r
	}
	return t
}

func (t *Template) GoString() string {
	return t.goString(0, "")
}

func (t *Template) goString(indent int, field string) string {
	var args string
	if len(t.Args) == 0 {
		args = fmt.Sprintf("%*sArgs: nil", indent+2, "")
	} else {
		args = fmt.Sprintf("%*sArgs:", indent+2, "")
		for i, a := range t.Args {
			args += "\n"
			args += a.goString(indent+4, fmt.Sprintf("%d: ", i))
		}
	}
	return fmt.Sprintf("%*s%sTemplate (%p):\n%s\n%s", indent, "", field, t,
		t.Name.goString(indent+2, "Name: "), args)
}

// TemplateParam is a template parameter.  The Template field is
// filled in while parsing the demangled string.  We don't normally
// see these while printing--they are replaced by the simplify
// function.
type TemplateParam struct {
	Index    int
	Template *Template
}

func (tp *TemplateParam) print(ps *printState) {
	if tp.Template == nil {
		panic("TemplateParam Template field is nil")
	}
	if tp.Index >= len(tp.Template.Args) {
		panic("TemplateParam Index out of bounds")
	}
	ps.print(tp.Template.Args[tp.Index])
}

func (tp *TemplateParam) Traverse(fn func(AST) bool) {
	fn(tp)
	// Don't traverse Template--it points elsewhere in the AST.
}

func (tp *TemplateParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tp) {
		return nil
	}
	return fn(tp)
}

func (tp *TemplateParam) GoString() string {
	return tp.goString(0, "")
}

func (tp *TemplateParam) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTemplateParam: Template: %p; Index %d", indent, "", field, tp.Template, tp.Index)
}

// LambdaAuto is a lambda auto parameter.
type LambdaAuto struct {
	Index int
}

func (la *LambdaAuto) print(ps *printState) {
	// We print the index plus 1 because that is what the standard
	// demangler does.
	if ps.llvmStyle {
		ps.writeString("auto")
	} else {
		fmt.Fprintf(&ps.buf, "auto:%d", la.Index+1)
	}
}

func (la *LambdaAuto) Traverse(fn func(AST) bool) {
	fn(la)
}

func (la *LambdaAuto) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(la) {
		return nil
	}
	return fn(la)
}

func (la *LambdaAuto) GoString() string {
	return la.goString(0, "")
}

func (la *LambdaAuto) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sLambdaAuto: Index %d", indent, "", field, la.Index)
}

// TemplateParamQualifiedArg is used when the mangled name includes
// both the template parameter declaration and the template argument.
// See https://github.com/itanium-cxx-abi/cxx-abi/issues/47.
type TemplateParamQualifiedArg struct {
	Param AST
	Arg   AST
}

func (tpqa *TemplateParamQualifiedArg) print(ps *printState) {
	// We only demangle the actual template argument.
	// That is what the LLVM demangler does.
	// The parameter disambiguates the argument,
	// but is hopefully not required by a human reader.
	ps.print(tpqa.Arg)
}

func (tpqa *TemplateParamQualifiedArg) Traverse(fn func(AST) bool) {
	if fn(tpqa) {
		tpqa.Param.Traverse(fn)
		tpqa.Arg.Traverse(fn)
	}
}

func (tpqa *TemplateParamQualifiedArg) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tpqa) {
		return nil
	}
	param := tpqa.Param.Copy(fn, skip)
	arg := tpqa.Arg.Copy(fn, skip)
	if param == nil && arg == nil {
		return fn(tpqa)
	}
	if param == nil {
		param = tpqa.Param
	}
	if arg == nil {
		arg = tpqa.Arg
	}
	tpqa = &TemplateParamQualifiedArg{Param: param, Arg: arg}
	if r := fn(tpqa); r != nil {
		return r
	}
	return tpqa
}

func (tpqa *TemplateParamQualifiedArg) GoString() string {
	return tpqa.goString(0, "")
}

func (tpqa *TemplateParamQualifiedArg) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTemplateParamQualifiedArg:\n%s\n%s", indent, "", field,
		tpqa.Param.goString(indent+2, "Param: "),
		tpqa.Arg.goString(indent+2, "Arg: "))
}

// Qualifiers is an ordered list of type qualifiers.
type Qualifiers struct {
	Qualifiers []AST
}

func (qs *Qualifiers) print(ps *printState) {
	first := true
	for _, q := range qs.Qualifiers {
		if !first {
			ps.writeByte(' ')
		}
		q.print(ps)
		first = false
	}
}

func (qs *Qualifiers) Traverse(fn func(AST) bool) {
	if fn(qs) {
		for _, q := range qs.Qualifiers {
			q.Traverse(fn)
		}
	}
}

func (qs *Qualifiers) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(qs) {
		return nil
	}
	changed := false
	qualifiers := make([]AST, len(qs.Qualifiers))
	for i, q := range qs.Qualifiers {
		qc := q.Copy(fn, skip)
		if qc == nil {
			qualifiers[i] = q
		} else {
			qualifiers[i] = qc
			changed = true
		}
	}
	if !changed {
		return fn(qs)
	}
	qs = &Qualifiers{Qualifiers: qualifiers}
	if r := fn(qs); r != nil {
		return r
	}
	return qs
}

func (qs *Qualifiers) GoString() string {
	return qs.goString(0, "")
}

func (qs *Qualifiers) goString(indent int, field string) string {
	quals := fmt.Sprintf("%*s%s", indent, "", field)
	for _, q := range qs.Qualifiers {
		quals += "\n"
		quals += q.goString(indent+2, "")
	}
	return quals
}

// Qualifier is a single type qualifier.
type Qualifier struct {
	Name  string // qualifier name: const, volatile, etc.
	Exprs []AST  // can be non-nil for noexcept and throw
}

func (q *Qualifier) print(ps *printState) {
	ps.writeString(q.Name)
	if len(q.Exprs) > 0 {
		ps.startScope('(')
		first := true
		for _, e := range q.Exprs {
			if el, ok := e.(*ExprList); ok && len(el.Exprs) == 0 {
				continue
			}
			if !first {
				ps.writeString(", ")
			}
			ps.print(e)
			first = false
		}
		ps.endScope(')')
	}
}

func (q *Qualifier) Traverse(fn func(AST) bool) {
	if fn(q) {
		for _, e := range q.Exprs {
			e.Traverse(fn)
		}
	}
}

func (q *Qualifier) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(q) {
		return nil
	}
	exprs := make([]AST, len(q.Exprs))
	changed := false
	for i, e := range q.Exprs {
		ec := e.Copy(fn, skip)
		if ec == nil {
			exprs[i] = e
		} else {
			exprs[i] = ec
			changed = true
		}
	}
	if !changed {
		return fn(q)
	}
	q = &Qualifier{Name: q.Name, Exprs: exprs}
	if r := fn(q); r != nil {
		return r
	}
	return q
}

func (q *Qualifier) GoString() string {
	return q.goString(0, "Qualifier: ")
}

func (q *Qualifier) goString(indent int, field string) string {
	qs := fmt.Sprintf("%*s%s%s", indent, "", field, q.Name)
	if len(q.Exprs) > 0 {
		for i, e := range q.Exprs {
			qs += "\n"
			qs += e.goString(indent+2, fmt.Sprintf("%d: ", i))
		}
	}
	return qs
}

// TypeWithQualifiers is a type with standard qualifiers.
type TypeWithQualifiers struct {
	Base       AST
	Qualifiers AST
}

func (twq *TypeWithQualifiers) print(ps *printState) {
	// Give the base type a chance to print the inner types.
	ps.inner = append(ps.inner, twq)
	ps.print(twq.Base)
	if len(ps.inner) > 0 {
		// The qualifier wasn't printed by Base.
		ps.writeByte(' ')
		ps.print(twq.Qualifiers)
		ps.inner = ps.inner[:len(ps.inner)-1]
	}
}

// Print qualifiers as an inner type by just printing the qualifiers.
func (twq *TypeWithQualifiers) printInner(ps *printState) {
	ps.writeByte(' ')
	ps.print(twq.Qualifiers)
}

func (twq *TypeWithQualifiers) Traverse(fn func(AST) bool) {
	if fn(twq) {
		twq.Base.Traverse(fn)
	}
}

func (twq *TypeWithQualifiers) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(twq) {
		return nil
	}
	base := twq.Base.Copy(fn, skip)
	quals := twq.Qualifiers.Copy(fn, skip)
	if base == nil && quals == nil {
		return fn(twq)
	}
	if base == nil {
		base = twq.Base
	}
	if quals == nil {
		quals = twq.Qualifiers
	}
	twq = &TypeWithQualifiers{Base: base, Qualifiers: quals}
	if r := fn(twq); r != nil {
		return r
	}
	return twq
}

func (twq *TypeWithQualifiers) GoString() string {
	return twq.goString(0, "")
}

func (twq *TypeWithQualifiers) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTypeWithQualifiers:\n%s\n%s", indent, "", field,
		twq.Qualifiers.goString(indent+2, "Qualifiers: "),
		twq.Base.goString(indent+2, "Base: "))
}

// MethodWithQualifiers is a method with qualifiers.
type MethodWithQualifiers struct {
	Method       AST
	Qualifiers   AST
	RefQualifier string // "" or "&" or "&&"
}

func (mwq *MethodWithQualifiers) print(ps *printState) {
	// Give the base type a chance to print the inner types.
	ps.inner = append(ps.inner, mwq)
	ps.print(mwq.Method)
	if len(ps.inner) > 0 {
		if mwq.Qualifiers != nil {
			ps.writeByte(' ')
			ps.print(mwq.Qualifiers)
		}
		if mwq.RefQualifier != "" {
			ps.writeByte(' ')
			ps.writeString(mwq.RefQualifier)
		}
		ps.inner = ps.inner[:len(ps.inner)-1]
	}
}

func (mwq *MethodWithQualifiers) printInner(ps *printState) {
	if mwq.Qualifiers != nil {
		ps.writeByte(' ')
		ps.print(mwq.Qualifiers)
	}
	if mwq.RefQualifier != "" {
		ps.writeByte(' ')
		ps.writeString(mwq.RefQualifier)
	}
}

func (mwq *MethodWithQualifiers) Traverse(fn func(AST) bool) {
	if fn(mwq) {
		mwq.Method.Traverse(fn)
	}
}

func (mwq *MethodWithQualifiers) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(mwq) {
		return nil
	}
	method := mwq.Method.Copy(fn, skip)
	var quals AST
	if mwq.Qualifiers != nil {
		quals = mwq.Qualifiers.Copy(fn, skip)
	}
	if method == nil && quals == nil {
		return fn(mwq)
	}
	if method == nil {
		method = mwq.Method
	}
	if quals == nil {
		quals = mwq.Qualifiers
	}
	mwq = &MethodWithQualifiers{Method: method, Qualifiers: quals, RefQualifier: mwq.RefQualifier}
	if r := fn(mwq); r != nil {
		return r
	}
	return mwq
}

func (mwq *MethodWithQualifiers) GoString() string {
	return mwq.goString(0, "")
}

func (mwq *MethodWithQualifiers) goString(indent int, field string) string {
	var q string
	if mwq.Qualifiers != nil {
		q += "\n" + mwq.Qualifiers.goString(indent+2, "Qualifiers: ")
	}
	if mwq.RefQualifier != "" {
		if q != "" {
			q += "\n"
		}
		q += fmt.Sprintf("%*s%s%s", indent+2, "", "RefQualifier: ", mwq.RefQualifier)
	}
	return fmt.Sprintf("%*s%sMethodWithQualifiers:%s\n%s", indent, "", field,
		q, mwq.Method.goString(indent+2, "Method: "))
}

// BuiltinType is a builtin type, like "int".
type BuiltinType struct {
	Name string
}

func (bt *BuiltinType) print(ps *printState) {
	name := bt.Name
	if ps.llvmStyle && name == "decltype(nullptr)" {
		name = "std::nullptr_t"
	}
	ps.writeString(name)
}

func (bt *BuiltinType) Traverse(fn func(AST) bool) {
	fn(bt)
}

func (bt *BuiltinType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(bt) {
		return nil
	}
	return fn(bt)
}

func (bt *BuiltinType) GoString() string {
	return bt.goString(0, "")
}

func (bt *BuiltinType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sBuiltinType: %s", indent, "", field, bt.Name)
}

func (bt *BuiltinType) prec() precedence {
	return precPrimary
}

// printBase is common print code for types that are printed with a
// simple suffix.
func printBase(ps *printState, qual, base AST) {
	ps.inner = append(ps.inner, qual)
	ps.print(base)
	if len(ps.inner) > 0 {
		qual.(innerPrinter).printInner(ps)
		ps.inner = ps.inner[:len(ps.inner)-1]
	}
}

// PointerType is a pointer type.
type PointerType struct {
	Base AST
}

func (pt *PointerType) print(ps *printState) {
	printBase(ps, pt, pt.Base)
}

func (pt *PointerType) printInner(ps *printState) {
	ps.writeString("*")
}

func (pt *PointerType) Traverse(fn func(AST) bool) {
	if fn(pt) {
		pt.Base.Traverse(fn)
	}
}

func (pt *PointerType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(pt) {
		return nil
	}
	base := pt.Base.Copy(fn, skip)
	if base == nil {
		return fn(pt)
	}
	pt = &PointerType{Base: base}
	if r := fn(pt); r != nil {
		return r
	}
	return pt
}

func (pt *PointerType) GoString() string {
	return pt.goString(0, "")
}

func (pt *PointerType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sPointerType:\n%s", indent, "", field,
		pt.Base.goString(indent+2, ""))
}

// ReferenceType is a reference type.
type ReferenceType struct {
	Base AST
}

func (rt *ReferenceType) print(ps *printState) {
	printBase(ps, rt, rt.Base)
}

func (rt *ReferenceType) printInner(ps *printState) {
	ps.writeString("&")
}

func (rt *ReferenceType) Traverse(fn func(AST) bool) {
	if fn(rt) {
		rt.Base.Traverse(fn)
	}
}

func (rt *ReferenceType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(rt) {
		return nil
	}
	base := rt.Base.Copy(fn, skip)
	if base == nil {
		return fn(rt)
	}
	rt = &ReferenceType{Base: base}
	if r := fn(rt); r != nil {
		return r
	}
	return rt
}

func (rt *ReferenceType) GoString() string {
	return rt.goString(0, "")
}

func (rt *ReferenceType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sReferenceType:\n%s", indent, "", field,
		rt.Base.goString(indent+2, ""))
}

// RvalueReferenceType is an rvalue reference type.
type RvalueReferenceType struct {
	Base AST
}

func (rt *RvalueReferenceType) print(ps *printState) {
	printBase(ps, rt, rt.Base)
}

func (rt *RvalueReferenceType) printInner(ps *printState) {
	ps.writeString("&&")
}

func (rt *RvalueReferenceType) Traverse(fn func(AST) bool) {
	if fn(rt) {
		rt.Base.Traverse(fn)
	}
}

func (rt *RvalueReferenceType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(rt) {
		return nil
	}
	base := rt.Base.Copy(fn, skip)
	if base == nil {
		return fn(rt)
	}
	rt = &RvalueReferenceType{Base: base}
	if r := fn(rt); r != nil {
		return r
	}
	return rt
}

func (rt *RvalueReferenceType) GoString() string {
	return rt.goString(0, "")
}

func (rt *RvalueReferenceType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sRvalueReferenceType:\n%s", indent, "", field,
		rt.Base.goString(indent+2, ""))
}

// ComplexType is a complex type.
type ComplexType struct {
	Base AST
}

func (ct *ComplexType) print(ps *printState) {
	printBase(ps, ct, ct.Base)
}

func (ct *ComplexType) printInner(ps *printState) {
	ps.writeString(" _Complex")
}

func (ct *ComplexType) Traverse(fn func(AST) bool) {
	if fn(ct) {
		ct.Base.Traverse(fn)
	}
}

func (ct *ComplexType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ct) {
		return nil
	}
	base := ct.Base.Copy(fn, skip)
	if base == nil {
		return fn(ct)
	}
	ct = &ComplexType{Base: base}
	if r := fn(ct); r != nil {
		return r
	}
	return ct
}

func (ct *ComplexType) GoString() string {
	return ct.goString(0, "")
}

func (ct *ComplexType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sComplexType:\n%s", indent, "", field,
		ct.Base.goString(indent+2, ""))
}

// ImaginaryType is an imaginary type.
type ImaginaryType struct {
	Base AST
}

func (it *ImaginaryType) print(ps *printState) {
	printBase(ps, it, it.Base)
}

func (it *ImaginaryType) printInner(ps *printState) {
	ps.writeString(" _Imaginary")
}

func (it *ImaginaryType) Traverse(fn func(AST) bool) {
	if fn(it) {
		it.Base.Traverse(fn)
	}
}

func (it *ImaginaryType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(it) {
		return nil
	}
	base := it.Base.Copy(fn, skip)
	if base == nil {
		return fn(it)
	}
	it = &ImaginaryType{Base: base}
	if r := fn(it); r != nil {
		return r
	}
	return it
}

func (it *ImaginaryType) GoString() string {
	return it.goString(0, "")
}

func (it *ImaginaryType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sImaginaryType:\n%s", indent, "", field,
		it.Base.goString(indent+2, ""))
}

// SuffixType is an type with an arbitrary suffix.
type SuffixType struct {
	Base   AST
	Suffix string
}

func (st *SuffixType) print(ps *printState) {
	printBase(ps, st, st.Base)
}

func (st *SuffixType) printInner(ps *printState) {
	ps.writeByte(' ')
	ps.writeString(st.Suffix)
}

func (st *SuffixType) Traverse(fn func(AST) bool) {
	if fn(st) {
		st.Base.Traverse(fn)
	}
}

func (st *SuffixType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(st) {
		return nil
	}
	base := st.Base.Copy(fn, skip)
	if base == nil {
		return fn(st)
	}
	st = &SuffixType{Base: base, Suffix: st.Suffix}
	if r := fn(st); r != nil {
		return r
	}
	return st
}

func (st *SuffixType) GoString() string {
	return st.goString(0, "")
}

func (st *SuffixType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sSuffixType: %s\n%s", indent, "", field,
		st.Suffix, st.Base.goString(indent+2, "Base: "))
}

// TransformedType is a builtin type with a template argument.
type TransformedType struct {
	Name string
	Base AST
}

func (tt *TransformedType) print(ps *printState) {
	ps.writeString(tt.Name)
	ps.startScope('(')
	ps.print(tt.Base)
	ps.endScope(')')
}

func (tt *TransformedType) Traverse(fn func(AST) bool) {
	if fn(tt) {
		tt.Base.Traverse(fn)
	}
}

func (tt *TransformedType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tt) {
		return nil
	}
	base := tt.Base.Copy(fn, skip)
	if base == nil {
		return fn(tt)
	}
	tt = &TransformedType{Name: tt.Name, Base: base}
	if r := fn(tt); r != nil {
		return r
	}
	return tt
}

func (tt *TransformedType) GoString() string {
	return tt.goString(0, "")
}

func (tt *TransformedType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTransformedType: %s\n%s", indent, "", field,
		tt.Name, tt.Base.goString(indent+2, "Base: "))
}

// VendorQualifier is a type qualified by a vendor-specific qualifier.
type VendorQualifier struct {
	Qualifier AST
	Type      AST
}

func (vq *VendorQualifier) print(ps *printState) {
	if ps.llvmStyle {
		ps.print(vq.Type)
		vq.printInner(ps)
	} else {
		ps.inner = append(ps.inner, vq)
		ps.print(vq.Type)
		if len(ps.inner) > 0 {
			ps.printOneInner(nil)
		}
	}
}

func (vq *VendorQualifier) printInner(ps *printState) {
	ps.writeByte(' ')
	ps.print(vq.Qualifier)
}

func (vq *VendorQualifier) Traverse(fn func(AST) bool) {
	if fn(vq) {
		vq.Qualifier.Traverse(fn)
		vq.Type.Traverse(fn)
	}
}

func (vq *VendorQualifier) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(vq) {
		return nil
	}
	qualifier := vq.Qualifier.Copy(fn, skip)
	typ := vq.Type.Copy(fn, skip)
	if qualifier == nil && typ == nil {
		return fn(vq)
	}
	if qualifier == nil {
		qualifier = vq.Qualifier
	}
	if typ == nil {
		typ = vq.Type
	}
	vq = &VendorQualifier{Qualifier: qualifier, Type: vq.Type}
	if r := fn(vq); r != nil {
		return r
	}
	return vq
}

func (vq *VendorQualifier) GoString() string {
	return vq.goString(0, "")
}

func (vq *VendorQualifier) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sVendorQualifier:\n%s\n%s", indent, "", field,
		vq.Qualifier.goString(indent+2, "Qualifier: "),
		vq.Type.goString(indent+2, "Type: "))
}

// ArrayType is an array type.
type ArrayType struct {
	Dimension AST
	Element   AST
}

func (at *ArrayType) print(ps *printState) {
	// Pass the array type down as an inner type so that we print
	// multi-dimensional arrays correctly.
	ps.inner = append(ps.inner, at)
	ps.print(at.Element)
	if ln := len(ps.inner); ln > 0 {
		ps.inner = ps.inner[:ln-1]
		at.printDimension(ps)
	}
}

func (at *ArrayType) printInner(ps *printState) {
	at.printDimension(ps)
}

// Print the array dimension.
func (at *ArrayType) printDimension(ps *printState) {
	space := " "
	for len(ps.inner) > 0 {
		// We haven't gotten to the real type yet.  Use
		// parentheses around that type, except that if it is
		// an array type we print it as a multi-dimensional
		// array
		in := ps.inner[len(ps.inner)-1]
		if twq, ok := in.(*TypeWithQualifiers); ok {
			in = twq.Base
		}
		if _, ok := in.(*ArrayType); ok {
			if in == ps.inner[len(ps.inner)-1] {
				space = ""
			}
			ps.printOneInner(nil)
		} else {
			ps.writeByte(' ')
			ps.startScope('(')
			ps.printInner(false)
			ps.endScope(')')
		}
	}
	ps.writeString(space)
	ps.writeByte('[')
	ps.print(at.Dimension)
	ps.writeByte(']')
}

func (at *ArrayType) Traverse(fn func(AST) bool) {
	if fn(at) {
		at.Dimension.Traverse(fn)
		at.Element.Traverse(fn)
	}
}

func (at *ArrayType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(at) {
		return nil
	}
	dimension := at.Dimension.Copy(fn, skip)
	element := at.Element.Copy(fn, skip)
	if dimension == nil && element == nil {
		return fn(at)
	}
	if dimension == nil {
		dimension = at.Dimension
	}
	if element == nil {
		element = at.Element
	}
	at = &ArrayType{Dimension: dimension, Element: element}
	if r := fn(at); r != nil {
		return r
	}
	return at
}

func (at *ArrayType) GoString() string {
	return at.goString(0, "")
}

func (at *ArrayType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sArrayType:\n%s\n%s", indent, "", field,
		at.Dimension.goString(indent+2, "Dimension: "),
		at.Element.goString(indent+2, "Element: "))
}

// FunctionType is a function type.
type FunctionType struct {
	Return AST
	Args   []AST

	// The forLocalName field reports whether this FunctionType
	// was created for a local name. With the default GNU demangling
	// output we don't print the return type in that case.
	ForLocalName bool
}

func (ft *FunctionType) print(ps *printState) {
	retType := ft.Return
	if ft.ForLocalName && (!ps.enclosingParams || !ps.llvmStyle) {
		retType = nil
	}
	if retType != nil {
		// Pass the return type as an inner type in order to
		// print the arguments in the right location.
		ps.inner = append(ps.inner, ft)
		ps.print(retType)
		if len(ps.inner) == 0 {
			// Everything was printed.
			return
		}
		ps.inner = ps.inner[:len(ps.inner)-1]
		ps.writeByte(' ')
	}
	ft.printArgs(ps)
}

func (ft *FunctionType) printInner(ps *printState) {
	ft.printArgs(ps)
}

// printArgs prints the arguments of a function type.  It looks at the
// inner types for spacing.
func (ft *FunctionType) printArgs(ps *printState) {
	paren := false
	space := false
	for i := len(ps.inner) - 1; i >= 0; i-- {
		switch ps.inner[i].(type) {
		case *PointerType, *ReferenceType, *RvalueReferenceType:
			paren = true
		case *TypeWithQualifiers, *ComplexType, *ImaginaryType, *PtrMem:
			space = true
			paren = true
		}
		if paren {
			break
		}
	}

	if paren {
		if !space && (ps.last != '(' && ps.last != '*') {
			space = true
		}
		if space && ps.last != ' ' {
			ps.writeByte(' ')
		}
		ps.startScope('(')
	}

	save := ps.printInner(true)

	if paren {
		ps.endScope(')')
	}

	ps.startScope('(')
	if !ft.ForLocalName || ps.enclosingParams {
		first := true
		for _, a := range ft.Args {
			if ps.isEmpty(a) {
				continue
			}
			if !first {
				ps.writeString(", ")
			}
			ps.print(a)
			first = false
		}
	}
	ps.endScope(')')

	ps.inner = save
	ps.printInner(false)
}

func (ft *FunctionType) Traverse(fn func(AST) bool) {
	if fn(ft) {
		if ft.Return != nil {
			ft.Return.Traverse(fn)
		}
		for _, a := range ft.Args {
			a.Traverse(fn)
		}
	}
}

func (ft *FunctionType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ft) {
		return nil
	}
	changed := false
	var ret AST
	if ft.Return != nil {
		ret = ft.Return.Copy(fn, skip)
		if ret == nil {
			ret = ft.Return
		} else {
			changed = true
		}
	}
	args := make([]AST, len(ft.Args))
	for i, a := range ft.Args {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			changed = true
		}
	}
	if !changed {
		return fn(ft)
	}
	ft = &FunctionType{
		Return:       ret,
		Args:         args,
		ForLocalName: ft.ForLocalName,
	}
	if r := fn(ft); r != nil {
		return r
	}
	return ft
}

func (ft *FunctionType) GoString() string {
	return ft.goString(0, "")
}

func (ft *FunctionType) goString(indent int, field string) string {
	var forLocalName string
	if ft.ForLocalName {
		forLocalName = " ForLocalName: true"
	}
	var r string
	if ft.Return == nil {
		r = fmt.Sprintf("%*sReturn: nil", indent+2, "")
	} else {
		r = ft.Return.goString(indent+2, "Return: ")
	}
	var args string
	if len(ft.Args) == 0 {
		args = fmt.Sprintf("%*sArgs: nil", indent+2, "")
	} else {
		args = fmt.Sprintf("%*sArgs:", indent+2, "")
		for i, a := range ft.Args {
			args += "\n"
			args += a.goString(indent+4, fmt.Sprintf("%d: ", i))
		}
	}
	return fmt.Sprintf("%*s%sFunctionType:%s\n%s\n%s", indent, "", field,
		forLocalName, r, args)
}

// FunctionParam is a parameter of a function, used for last-specified
// return type in a closure.
type FunctionParam struct {
	Index int
}

func (fp *FunctionParam) print(ps *printState) {
	if fp.Index == 0 {
		ps.writeString("this")
	} else if ps.llvmStyle {
		if fp.Index == 1 {
			ps.writeString("fp")
		} else {
			fmt.Fprintf(&ps.buf, "fp%d", fp.Index-2)
		}
	} else {
		fmt.Fprintf(&ps.buf, "{parm#%d}", fp.Index)
	}
}

func (fp *FunctionParam) Traverse(fn func(AST) bool) {
	fn(fp)
}

func (fp *FunctionParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(fp) {
		return nil
	}
	return fn(fp)
}

func (fp *FunctionParam) GoString() string {
	return fp.goString(0, "")
}

func (fp *FunctionParam) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sFunctionParam: %d", indent, "", field, fp.Index)
}

func (fp *FunctionParam) prec() precedence {
	return precPrimary
}

// PtrMem is a pointer-to-member expression.
type PtrMem struct {
	Class  AST
	Member AST
}

func (pm *PtrMem) print(ps *printState) {
	ps.inner = append(ps.inner, pm)
	ps.print(pm.Member)
	if len(ps.inner) > 0 {
		ps.printOneInner(nil)
	}
}

func (pm *PtrMem) printInner(ps *printState) {
	if ps.last != '(' {
		ps.writeByte(' ')
	}
	ps.print(pm.Class)
	ps.writeString("::*")
}

func (pm *PtrMem) Traverse(fn func(AST) bool) {
	if fn(pm) {
		pm.Class.Traverse(fn)
		pm.Member.Traverse(fn)
	}
}

func (pm *PtrMem) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(pm) {
		return nil
	}
	class := pm.Class.Copy(fn, skip)
	member := pm.Member.Copy(fn, skip)
	if class == nil && member == nil {
		return fn(pm)
	}
	if class == nil {
		class = pm.Class
	}
	if member == nil {
		member = pm.Member
	}
	pm = &PtrMem{Class: class, Member: member}
	if r := fn(pm); r != nil {
		return r
	}
	return pm
}

func (pm *PtrMem) GoString() string {
	return pm.goString(0, "")
}

func (pm *PtrMem) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sPtrMem:\n%s\n%s", indent, "", field,
		pm.Class.goString(indent+2, "Class: "),
		pm.Member.goString(indent+2, "Member: "))
}

// FixedType is a fixed numeric type of unknown size.
type FixedType struct {
	Base  AST
	Accum bool
	Sat   bool
}

func (ft *FixedType) print(ps *printState) {
	if ft.Sat {
		ps.writeString("_Sat ")
	}
	if bt, ok := ft.Base.(*BuiltinType); ok && bt.Name == "int" {
		// The standard demangler skips printing "int".
	} else {
		ps.print(ft.Base)
		ps.writeByte(' ')
	}
	if ft.Accum {
		ps.writeString("_Accum")
	} else {
		ps.writeString("_Fract")
	}
}

func (ft *FixedType) Traverse(fn func(AST) bool) {
	if fn(ft) {
		ft.Base.Traverse(fn)
	}
}

func (ft *FixedType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ft) {
		return nil
	}
	base := ft.Base.Copy(fn, skip)
	if base == nil {
		return fn(ft)
	}
	ft = &FixedType{Base: base, Accum: ft.Accum, Sat: ft.Sat}
	if r := fn(ft); r != nil {
		return r
	}
	return ft
}

func (ft *FixedType) GoString() string {
	return ft.goString(0, "")
}

func (ft *FixedType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sFixedType: Accum: %t; Sat: %t\n%s", indent, "", field,
		ft.Accum, ft.Sat,
		ft.Base.goString(indent+2, "Base: "))
}

// BinaryFP is a binary floating-point type.
type BinaryFP struct {
	Bits int
}

func (bfp *BinaryFP) print(ps *printState) {
	fmt.Fprintf(&ps.buf, "_Float%d", bfp.Bits)
}

func (bfp *BinaryFP) Traverse(fn func(AST) bool) {
	fn(bfp)
}

func (bfp *BinaryFP) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(bfp) {
		return nil
	}
	return fn(bfp)
}

func (bfp *BinaryFP) GoString() string {
	return bfp.goString(0, "")
}

func (bfp *BinaryFP) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sBinaryFP: %d", indent, "", field, bfp.Bits)
}

// BitIntType is the C++23 _BitInt(N) type.
type BitIntType struct {
	Size   AST
	Signed bool
}

func (bt *BitIntType) print(ps *printState) {
	if !bt.Signed {
		ps.writeString("unsigned ")
	}
	ps.writeString("_BitInt")
	ps.startScope('(')
	ps.print(bt.Size)
	ps.endScope(')')
}

func (bt *BitIntType) Traverse(fn func(AST) bool) {
	if fn(bt) {
		bt.Size.Traverse(fn)
	}
}

func (bt *BitIntType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(bt) {
		return nil
	}
	size := bt.Size.Copy(fn, skip)
	if size == nil {
		return fn(bt)
	}
	bt = &BitIntType{Size: size, Signed: bt.Signed}
	if r := fn(bt); r != nil {
		return r
	}
	return bt
}

func (bt *BitIntType) GoString() string {
	return bt.goString(0, "")
}

func (bt *BitIntType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sBitIntType: Signed: %t\n%s", indent, "", field,
		bt.Signed,
		bt.Size.goString(indent+2, "Size: "))
}

// VectorType is a vector type.
type VectorType struct {
	Dimension AST
	Base      AST
}

func (vt *VectorType) print(ps *printState) {
	ps.inner = append(ps.inner, vt)
	ps.print(vt.Base)
	if len(ps.inner) > 0 {
		ps.printOneInner(nil)
	}
}

func (vt *VectorType) printInner(ps *printState) {
	end := byte(')')
	if ps.llvmStyle {
		ps.writeString(" vector[")
		end = ']'
	} else {
		ps.writeString(" __vector(")
	}
	ps.print(vt.Dimension)
	ps.writeByte(end)
}

func (vt *VectorType) Traverse(fn func(AST) bool) {
	if fn(vt) {
		vt.Dimension.Traverse(fn)
		vt.Base.Traverse(fn)
	}
}

func (vt *VectorType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(vt) {
		return nil
	}
	dimension := vt.Dimension.Copy(fn, skip)
	base := vt.Base.Copy(fn, skip)
	if dimension == nil && base == nil {
		return fn(vt)
	}
	if dimension == nil {
		dimension = vt.Dimension
	}
	if base == nil {
		base = vt.Base
	}
	vt = &VectorType{Dimension: dimension, Base: base}
	if r := fn(vt); r != nil {
		return r
	}
	return vt
}

func (vt *VectorType) GoString() string {
	return vt.goString(0, "")
}

func (vt *VectorType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sVectorType:\n%s\n%s", indent, "", field,
		vt.Dimension.goString(indent+2, "Dimension: "),
		vt.Base.goString(indent+2, "Base: "))
}

// ElaboratedType is an elaborated struct/union/enum type.
type ElaboratedType struct {
	Kind string
	Type AST
}

func (et *ElaboratedType) print(ps *printState) {
	ps.writeString(et.Kind)
	ps.writeString(" ")
	et.Type.print(ps)
}

func (et *ElaboratedType) Traverse(fn func(AST) bool) {
	if fn(et) {
		et.Type.Traverse(fn)
	}
}

func (et *ElaboratedType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(et) {
		return nil
	}
	typ := et.Type.Copy(fn, skip)
	if typ == nil {
		return fn(et)
	}
	et = &ElaboratedType{Kind: et.Kind, Type: typ}
	if r := fn(et); r != nil {
		return r
	}
	return et
}

func (et *ElaboratedType) GoString() string {
	return et.goString(0, "")
}

func (et *ElaboratedType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sElaboratedtype: Kind: %s\n%s", indent, "", field,
		et.Kind, et.Type.goString(indent+2, "Expr: "))
}

// Decltype is the decltype operator.
type Decltype struct {
	Expr AST
}

func (dt *Decltype) print(ps *printState) {
	ps.writeString("decltype")
	if !ps.llvmStyle {
		ps.writeString(" ")
	}
	ps.startScope('(')
	ps.print(dt.Expr)
	ps.endScope(')')
}

func (dt *Decltype) Traverse(fn func(AST) bool) {
	if fn(dt) {
		dt.Expr.Traverse(fn)
	}
}

func (dt *Decltype) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(dt) {
		return nil
	}
	expr := dt.Expr.Copy(fn, skip)
	if expr == nil {
		return fn(dt)
	}
	dt = &Decltype{Expr: expr}
	if r := fn(dt); r != nil {
		return r
	}
	return dt
}

func (dt *Decltype) GoString() string {
	return dt.goString(0, "")
}

func (dt *Decltype) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sDecltype:\n%s", indent, "", field,
		dt.Expr.goString(indent+2, "Expr: "))
}

// Operator is an operator.
type Operator struct {
	Name       string
	precedence precedence
}

func (op *Operator) print(ps *printState) {
	ps.writeString("operator")
	if isLower(op.Name[0]) {
		ps.writeByte(' ')
	}
	n := op.Name
	n = strings.TrimSuffix(n, " ")
	ps.writeString(n)
}

func (op *Operator) Traverse(fn func(AST) bool) {
	fn(op)
}

func (op *Operator) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(op) {
		return nil
	}
	return fn(op)
}

func (op *Operator) GoString() string {
	return op.goString(0, "")
}

func (op *Operator) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sOperator: %s", indent, "", field, op.Name)
}

func (op *Operator) prec() precedence {
	return op.precedence
}

// Constructor is a constructor.
type Constructor struct {
	Name AST
	Base AST // base class of inheriting constructor
}

func (c *Constructor) print(ps *printState) {
	ps.print(c.Name)
	// We don't include the base class in the demangled string.
}

func (c *Constructor) Traverse(fn func(AST) bool) {
	if fn(c) {
		c.Name.Traverse(fn)
		if c.Base != nil {
			c.Base.Traverse(fn)
		}
	}
}

func (c *Constructor) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(c) {
		return nil
	}
	name := c.Name.Copy(fn, skip)
	var base AST
	if c.Base != nil {
		base = c.Base.Copy(fn, skip)
	}
	if name == nil && base == nil {
		return fn(c)
	}
	if name == nil {
		name = c.Name
	}
	if base == nil {
		base = c.Base
	}
	c = &Constructor{Name: name, Base: base}
	if r := fn(c); r != nil {
		return r
	}
	return c
}

func (c *Constructor) GoString() string {
	return c.goString(0, "")
}

func (c *Constructor) goString(indent int, field string) string {
	var sb strings.Builder
	fmt.Fprintf(&sb, "%*s%sConstructor:\n", indent, "", field)
	if c.Base != nil {
		fmt.Fprintf(&sb, "%s\n", c.Base.goString(indent+2, "Base: "))
	}
	fmt.Fprintf(&sb, "%s", c.Name.goString(indent+2, "Name: "))
	return sb.String()
}

// Destructor is a destructor.
type Destructor struct {
	Name AST
}

func (d *Destructor) print(ps *printState) {
	ps.writeByte('~')
	ps.print(d.Name)
}

func (d *Destructor) Traverse(fn func(AST) bool) {
	if fn(d) {
		d.Name.Traverse(fn)
	}
}

func (d *Destructor) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(d) {
		return nil
	}
	name := d.Name.Copy(fn, skip)
	if name == nil {
		return fn(d)
	}
	d = &Destructor{Name: name}
	if r := fn(d); r != nil {
		return r
	}
	return d
}

func (d *Destructor) GoString() string {
	return d.goString(0, "")
}

func (d *Destructor) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sDestructor:\n%s", indent, "", field, d.Name.goString(indent+2, "Name: "))
}

// GlobalCDtor is a global constructor or destructor.
type GlobalCDtor struct {
	Ctor bool
	Key  AST
}

func (gcd *GlobalCDtor) print(ps *printState) {
	ps.writeString("global ")
	if gcd.Ctor {
		ps.writeString("constructors")
	} else {
		ps.writeString("destructors")
	}
	ps.writeString(" keyed to ")
	ps.print(gcd.Key)
}

func (gcd *GlobalCDtor) Traverse(fn func(AST) bool) {
	if fn(gcd) {
		gcd.Key.Traverse(fn)
	}
}

func (gcd *GlobalCDtor) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(gcd) {
		return nil
	}
	key := gcd.Key.Copy(fn, skip)
	if key == nil {
		return fn(gcd)
	}
	gcd = &GlobalCDtor{Ctor: gcd.Ctor, Key: key}
	if r := fn(gcd); r != nil {
		return r
	}
	return gcd
}

func (gcd *GlobalCDtor) GoString() string {
	return gcd.goString(0, "")
}

func (gcd *GlobalCDtor) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sGlobalCDtor: Ctor: %t\n%s", indent, "", field,
		gcd.Ctor, gcd.Key.goString(indent+2, "Key: "))
}

// TaggedName is a name with an ABI tag.
type TaggedName struct {
	Name AST
	Tag  AST
}

func (t *TaggedName) print(ps *printState) {
	ps.print(t.Name)
	ps.writeString("[abi:")
	ps.print(t.Tag)
	ps.writeByte(']')
}

func (t *TaggedName) Traverse(fn func(AST) bool) {
	if fn(t) {
		t.Name.Traverse(fn)
		t.Tag.Traverse(fn)
	}
}

func (t *TaggedName) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(t) {
		return nil
	}
	name := t.Name.Copy(fn, skip)
	tag := t.Tag.Copy(fn, skip)
	if name == nil && tag == nil {
		return fn(t)
	}
	if name == nil {
		name = t.Name
	}
	if tag == nil {
		tag = t.Tag
	}
	t = &TaggedName{Name: name, Tag: tag}
	if r := fn(t); r != nil {
		return r
	}
	return t
}

func (t *TaggedName) GoString() string {
	return t.goString(0, "")
}

func (t *TaggedName) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTaggedName:\n%s\n%s", indent, "", field,
		t.Name.goString(indent+2, "Name: "),
		t.Tag.goString(indent+2, "Tag: "))
}

// PackExpansion is a pack expansion.  The Pack field may be nil.
type PackExpansion struct {
	Base AST
	Pack *ArgumentPack
}

func (pe *PackExpansion) print(ps *printState) {
	// We normally only get here if the simplify function was
	// unable to locate and expand the pack.
	if pe.Pack == nil {
		if ps.llvmStyle {
			ps.print(pe.Base)
		} else {
			parenthesize(ps, pe.Base)
			ps.writeString("...")
		}
	} else {
		ps.print(pe.Base)
	}
}

func (pe *PackExpansion) Traverse(fn func(AST) bool) {
	if fn(pe) {
		pe.Base.Traverse(fn)
		// Don't traverse Template--it points elsewhere in the AST.
	}
}

func (pe *PackExpansion) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(pe) {
		return nil
	}
	base := pe.Base.Copy(fn, skip)
	if base == nil {
		return fn(pe)
	}
	pe = &PackExpansion{Base: base, Pack: pe.Pack}
	if r := fn(pe); r != nil {
		return r
	}
	return pe
}

func (pe *PackExpansion) GoString() string {
	return pe.goString(0, "")
}

func (pe *PackExpansion) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sPackExpansion: Pack: %p\n%s", indent, "", field,
		pe.Pack, pe.Base.goString(indent+2, "Base: "))
}

// ArgumentPack is an argument pack.
type ArgumentPack struct {
	Args []AST
}

func (ap *ArgumentPack) print(ps *printState) {
	for i, a := range ap.Args {
		if i > 0 {
			ps.writeString(", ")
		}
		ps.print(a)
	}
}

func (ap *ArgumentPack) Traverse(fn func(AST) bool) {
	if fn(ap) {
		for _, a := range ap.Args {
			a.Traverse(fn)
		}
	}
}

func (ap *ArgumentPack) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ap) {
		return nil
	}
	args := make([]AST, len(ap.Args))
	changed := false
	for i, a := range ap.Args {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			changed = true
		}
	}
	if !changed {
		return fn(ap)
	}
	ap = &ArgumentPack{Args: args}
	if r := fn(ap); r != nil {
		return r
	}
	return ap
}

func (ap *ArgumentPack) GoString() string {
	return ap.goString(0, "")
}

func (ap *ArgumentPack) goString(indent int, field string) string {
	if len(ap.Args) == 0 {
		return fmt.Sprintf("%*s%sArgumentPack: nil", indent, "", field)
	}
	s := fmt.Sprintf("%*s%sArgumentPack:", indent, "", field)
	for i, a := range ap.Args {
		s += "\n"
		s += a.goString(indent+2, fmt.Sprintf("%d: ", i))
	}
	return s
}

// SizeofPack is the sizeof operator applied to an argument pack.
type SizeofPack struct {
	Pack *ArgumentPack
}

func (sp *SizeofPack) print(ps *printState) {
	if ps.llvmStyle {
		ps.writeString("sizeof...")
		ps.startScope('(')
		ps.print(sp.Pack)
		ps.endScope(')')
	} else {
		ps.writeString(fmt.Sprintf("%d", len(sp.Pack.Args)))
	}
}

func (sp *SizeofPack) Traverse(fn func(AST) bool) {
	fn(sp)
	// Don't traverse the pack--it points elsewhere in the AST.
}

func (sp *SizeofPack) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(sp) {
		return nil
	}
	sp = &SizeofPack{Pack: sp.Pack}
	if r := fn(sp); r != nil {
		return r
	}
	return sp
}

func (sp *SizeofPack) GoString() string {
	return sp.goString(0, "")
}

func (sp *SizeofPack) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sSizeofPack: Pack: %p", indent, "", field, sp.Pack)
}

// SizeofArgs is the size of a captured template parameter pack from
// an alias template.
type SizeofArgs struct {
	Args []AST
}

func (sa *SizeofArgs) print(ps *printState) {
	c := 0
	for _, a := range sa.Args {
		if ap, ok := a.(*ArgumentPack); ok {
			c += len(ap.Args)
		} else if el, ok := a.(*ExprList); ok {
			c += len(el.Exprs)
		} else {
			c++
		}
	}
	ps.writeString(fmt.Sprintf("%d", c))
}

func (sa *SizeofArgs) Traverse(fn func(AST) bool) {
	if fn(sa) {
		for _, a := range sa.Args {
			a.Traverse(fn)
		}
	}
}

func (sa *SizeofArgs) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(sa) {
		return nil
	}
	changed := false
	args := make([]AST, len(sa.Args))
	for i, a := range sa.Args {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			changed = true
		}
	}
	if !changed {
		return fn(sa)
	}
	sa = &SizeofArgs{Args: args}
	if r := fn(sa); r != nil {
		return r
	}
	return sa
}

func (sa *SizeofArgs) GoString() string {
	return sa.goString(0, "")
}

func (sa *SizeofArgs) goString(indent int, field string) string {
	var args string
	if len(sa.Args) == 0 {
		args = fmt.Sprintf("%*sArgs: nil", indent+2, "")
	} else {
		args = fmt.Sprintf("%*sArgs:", indent+2, "")
		for i, a := range sa.Args {
			args += "\n"
			args += a.goString(indent+4, fmt.Sprintf("%d: ", i))
		}
	}
	return fmt.Sprintf("%*s%sSizeofArgs:\n%s", indent, "", field, args)
}

// TemplateParamName is the name of a template parameter that the
// demangler introduced for a lambda that has explicit template
// parameters.  This is a prefix with an index.
type TemplateParamName struct {
	Prefix string
	Index  int
}

func (tpn *TemplateParamName) print(ps *printState) {
	ps.writeString(tpn.Prefix)
	if tpn.Index > 0 {
		ps.writeString(fmt.Sprintf("%d", tpn.Index-1))
	}
}

func (tpn *TemplateParamName) Traverse(fn func(AST) bool) {
	fn(tpn)
}

func (tpn *TemplateParamName) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tpn) {
		return nil
	}
	return fn(tpn)
}

func (tpn *TemplateParamName) GoString() string {
	return tpn.goString(0, "")
}

func (tpn *TemplateParamName) goString(indent int, field string) string {
	name := tpn.Prefix
	if tpn.Index > 0 {
		name += fmt.Sprintf("%d", tpn.Index-1)
	}
	return fmt.Sprintf("%*s%sTemplateParamName: %s", indent, "", field, name)
}

// TypeTemplateParam is a type template parameter that appears in a
// lambda with explicit template parameters.
type TypeTemplateParam struct {
	Name AST
}

func (ttp *TypeTemplateParam) print(ps *printState) {
	ps.writeString("typename ")
	ps.printInner(false)
	ps.print(ttp.Name)
}

func (ttp *TypeTemplateParam) Traverse(fn func(AST) bool) {
	if fn(ttp) {
		ttp.Name.Traverse(fn)
	}
}

func (ttp *TypeTemplateParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ttp) {
		return nil
	}
	name := ttp.Name.Copy(fn, skip)
	if name == nil {
		return fn(ttp)
	}
	ttp = &TypeTemplateParam{Name: name}
	if r := fn(ttp); r != nil {
		return r
	}
	return ttp
}

func (ttp *TypeTemplateParam) GoString() string {
	return ttp.goString(0, "")
}

func (ttp *TypeTemplateParam) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTypeTemplateParam:\n%s", indent, "", field,
		ttp.Name.goString(indent+2, "Name"))
}

// NonTypeTemplateParam is a non-type template parameter that appears
// in a lambda with explicit template parameters.
type NonTypeTemplateParam struct {
	Name AST
	Type AST
}

func (nttp *NonTypeTemplateParam) print(ps *printState) {
	ps.inner = append(ps.inner, nttp)
	ps.print(nttp.Type)
	if len(ps.inner) > 0 {
		ps.writeByte(' ')
		ps.print(nttp.Name)
		ps.inner = ps.inner[:len(ps.inner)-1]
	}
}

func (nttp *NonTypeTemplateParam) printInner(ps *printState) {
	ps.print(nttp.Name)
}

func (nttp *NonTypeTemplateParam) Traverse(fn func(AST) bool) {
	if fn(nttp) {
		nttp.Name.Traverse(fn)
		nttp.Type.Traverse(fn)
	}
}

func (nttp *NonTypeTemplateParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(nttp) {
		return nil
	}
	name := nttp.Name.Copy(fn, skip)
	typ := nttp.Type.Copy(fn, skip)
	if name == nil && typ == nil {
		return fn(nttp)
	}
	if name == nil {
		name = nttp.Name
	}
	if typ == nil {
		typ = nttp.Type
	}
	nttp = &NonTypeTemplateParam{Name: name, Type: typ}
	if r := fn(nttp); r != nil {
		return r
	}
	return nttp
}

func (nttp *NonTypeTemplateParam) GoString() string {
	return nttp.goString(0, "")
}

func (nttp *NonTypeTemplateParam) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sNonTypeTemplateParam:\n%s\n%s", indent, "", field,
		nttp.Name.goString(indent+2, "Name: "),
		nttp.Type.goString(indent+2, "Type: "))
}

// TemplateTemplateParam is a template template parameter that appears
// in a lambda with explicit template parameters.
type TemplateTemplateParam struct {
	Name       AST
	Params     []AST
	Constraint AST
}

func (ttp *TemplateTemplateParam) print(ps *printState) {
	scopes := ps.scopes
	ps.scopes = 0

	ps.writeString("template<")
	ps.printList(ttp.Params, nil)
	ps.writeString("> typename ")

	ps.scopes = scopes

	ps.print(ttp.Name)

	if ttp.Constraint != nil {
		ps.writeString(" requires ")
		ps.print(ttp.Constraint)
	}
}

func (ttp *TemplateTemplateParam) Traverse(fn func(AST) bool) {
	if fn(ttp) {
		ttp.Name.Traverse(fn)
		for _, param := range ttp.Params {
			param.Traverse(fn)
		}
		if ttp.Constraint != nil {
			ttp.Constraint.Traverse(fn)
		}
	}
}

func (ttp *TemplateTemplateParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ttp) {
		return nil
	}

	changed := false

	name := ttp.Name.Copy(fn, skip)
	if name == nil {
		name = ttp.Name
	} else {
		changed = true
	}

	params := make([]AST, len(ttp.Params))
	for i, p := range ttp.Params {
		pc := p.Copy(fn, skip)
		if pc == nil {
			params[i] = p
		} else {
			params[i] = pc
			changed = true
		}
	}

	var constraint AST
	if ttp.Constraint != nil {
		constraint = ttp.Constraint.Copy(fn, skip)
		if constraint == nil {
			constraint = ttp.Constraint
		} else {
			changed = true
		}
	}

	if !changed {
		return fn(ttp)
	}

	ttp = &TemplateTemplateParam{
		Name:       name,
		Params:     params,
		Constraint: constraint,
	}
	if r := fn(ttp); r != nil {
		return r
	}
	return ttp
}

func (ttp *TemplateTemplateParam) GoString() string {
	return ttp.goString(0, "")
}

func (ttp *TemplateTemplateParam) goString(indent int, field string) string {
	var params strings.Builder
	fmt.Fprintf(&params, "%*sParams:", indent+2, "")
	for i, p := range ttp.Params {
		params.WriteByte('\n')
		params.WriteString(p.goString(indent+4, fmt.Sprintf("%d: ", i)))
	}
	var constraint string
	if ttp.Constraint == nil {
		constraint = fmt.Sprintf("%*sConstraint: nil", indent+2, "")
	} else {
		constraint = ttp.Constraint.goString(indent+2, "Constraint: ")
	}
	return fmt.Sprintf("%*s%sTemplateTemplateParam:\n%s\n%s\n%s", indent, "", field,
		ttp.Name.goString(indent+2, "Name: "),
		params.String(),
		constraint)
}

// ConstrainedTypeTemplateParam is a constrained template type
// parameter declaration.
type ConstrainedTypeTemplateParam struct {
	Name       AST
	Constraint AST
}

func (cttp *ConstrainedTypeTemplateParam) print(ps *printState) {
	ps.inner = append(ps.inner, cttp)
	ps.print(cttp.Constraint)
	if len(ps.inner) > 0 {
		ps.writeByte(' ')
		ps.print(cttp.Name)
		ps.inner = ps.inner[:len(ps.inner)-1]
	}
}

func (cttp *ConstrainedTypeTemplateParam) printInner(ps *printState) {
	ps.print(cttp.Name)
}

func (cttp *ConstrainedTypeTemplateParam) Traverse(fn func(AST) bool) {
	if fn(cttp) {
		cttp.Name.Traverse(fn)
		cttp.Constraint.Traverse(fn)
	}
}

func (cttp *ConstrainedTypeTemplateParam) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(cttp) {
		return nil
	}
	name := cttp.Name.Copy(fn, skip)
	constraint := cttp.Constraint.Copy(fn, skip)
	if name == nil && constraint == nil {
		return fn(cttp)
	}
	if name == nil {
		name = cttp.Name
	}
	if constraint == nil {
		constraint = cttp.Constraint
	}
	cttp = &ConstrainedTypeTemplateParam{Name: name, Constraint: constraint}
	if r := fn(cttp); r != nil {
		return r
	}
	return cttp
}

func (cttp *ConstrainedTypeTemplateParam) GoString() string {
	return cttp.goString(0, "")
}

func (cttp *ConstrainedTypeTemplateParam) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sConstrainedTypeTemplateParam\n%s\n%s", indent, "", field,
		cttp.Name.goString(indent+2, "Name: "),
		cttp.Constraint.goString(indent+2, "Constraint: "))
}

// TemplateParamPack is a template parameter pack that appears in a
// lambda with explicit template parameters.
type TemplateParamPack struct {
	Param AST
}

func (tpp *TemplateParamPack) print(ps *printState) {
	holdInner := ps.inner
	defer func() { ps.inner = holdInner }()

	ps.inner = []AST{tpp}
	if nttp, ok := tpp.Param.(*NonTypeTemplateParam); ok {
		ps.print(nttp.Type)
	} else {
		ps.print(tpp.Param)
	}
	if len(ps.inner) > 0 {
		ps.writeString("...")
	}
}

func (tpp *TemplateParamPack) printInner(ps *printState) {
	ps.writeString("...")
	if nttp, ok := tpp.Param.(*NonTypeTemplateParam); ok {
		ps.print(nttp.Name)
	}
}

func (tpp *TemplateParamPack) Traverse(fn func(AST) bool) {
	if fn(tpp) {
		tpp.Param.Traverse(fn)
	}
}

func (tpp *TemplateParamPack) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tpp) {
		return nil
	}
	param := tpp.Param.Copy(fn, skip)
	if param == nil {
		return fn(tpp)
	}
	tpp = &TemplateParamPack{Param: param}
	if r := fn(tpp); r != nil {
		return r
	}
	return tpp
}

func (tpp *TemplateParamPack) GoString() string {
	return tpp.goString(0, "")
}

func (tpp *TemplateParamPack) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTemplateParamPack:\n%s", indent, "", field,
		tpp.Param.goString(indent+2, "Param: "))
}

// Cast is a type cast.
type Cast struct {
	To AST
}

func (c *Cast) print(ps *printState) {
	ps.writeString("operator ")
	ps.print(c.To)
}

func (c *Cast) Traverse(fn func(AST) bool) {
	if fn(c) {
		c.To.Traverse(fn)
	}
}

func (c *Cast) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(c) {
		return nil
	}
	to := c.To.Copy(fn, skip)
	if to == nil {
		return fn(c)
	}
	c = &Cast{To: to}
	if r := fn(c); r != nil {
		return r
	}
	return c
}

func (c *Cast) GoString() string {
	return c.goString(0, "")
}

func (c *Cast) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sCast\n%s", indent, "", field,
		c.To.goString(indent+2, "To: "))
}

func (c *Cast) prec() precedence {
	return precCast
}

// The parenthesize function prints the string for val, wrapped in
// parentheses if necessary.
func parenthesize(ps *printState, val AST) {
	paren := false
	switch v := val.(type) {
	case *Name, *InitializerList:
	case *FunctionParam:
		if ps.llvmStyle {
			paren = true
		}
	case *Qualified:
		if v.LocalName {
			paren = true
		}
	default:
		paren = true
	}
	if paren {
		ps.startScope('(')
	}
	ps.print(val)
	if paren {
		ps.endScope(')')
	}
}

// Nullary is an operator in an expression with no arguments, such as
// throw.
type Nullary struct {
	Op AST
}

func (n *Nullary) print(ps *printState) {
	if op, ok := n.Op.(*Operator); ok {
		ps.writeString(op.Name)
	} else {
		ps.print(n.Op)
	}
}

func (n *Nullary) Traverse(fn func(AST) bool) {
	if fn(n) {
		n.Op.Traverse(fn)
	}
}

func (n *Nullary) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(n) {
		return nil
	}
	op := n.Op.Copy(fn, skip)
	if op == nil {
		return fn(n)
	}
	n = &Nullary{Op: op}
	if r := fn(n); r != nil {
		return r
	}
	return n
}

func (n *Nullary) GoString() string {
	return n.goString(0, "")
}

func (n *Nullary) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sNullary:\n%s", indent, "", field,
		n.Op.goString(indent+2, "Op: "))
}

// Unary is a unary operation in an expression.
type Unary struct {
	Op         AST
	Expr       AST
	Suffix     bool // true for ++ -- when used as postfix
	SizeofType bool // true for sizeof (type)
}

func (u *Unary) print(ps *printState) {
	op, _ := u.Op.(*Operator)
	expr := u.Expr

	// Don't print the argument list when taking the address of a
	// function.
	if !ps.llvmStyle {
		if op != nil && op.Name == "&" {
			if t, ok := expr.(*Typed); ok {
				if _, ok := t.Type.(*FunctionType); ok {
					expr = t.Name
				}
			}
		}
	}

	if u.Suffix {
		if ps.llvmStyle {
			wantParens := true
			opPrec := precUnary
			if op != nil {
				opPrec = op.precedence
			}
			if p, ok := expr.(hasPrec); ok {
				if p.prec() < opPrec {
					wantParens = false
				}
			}
			if wantParens {
				ps.startScope('(')
			}
			ps.print(expr)
			if wantParens {
				ps.endScope(')')
			}
		} else {
			parenthesize(ps, expr)
		}
	}

	if op != nil {
		ps.writeString(op.Name)
		if ps.llvmStyle && op.Name == "noexcept" {
			ps.writeByte(' ')
		}
	} else if c, ok := u.Op.(*Cast); ok {
		ps.startScope('(')
		ps.print(c.To)
		ps.endScope(')')
	} else {
		ps.print(u.Op)
	}

	if !u.Suffix {
		isDelete := op != nil && (op.Name == "delete " || op.Name == "delete[] ")
		if op != nil && op.Name == "::" {
			// Don't use parentheses after ::.
			ps.print(expr)
		} else if u.SizeofType {
			// Always use parentheses for sizeof argument.
			ps.startScope('(')
			ps.print(expr)
			ps.endScope(')')
		} else if op != nil && op.Name == "__alignof__" {
			// Always use parentheses for __alignof__ argument.
			ps.startScope('(')
			ps.print(expr)
			ps.endScope(')')
		} else if ps.llvmStyle {
			var wantParens bool
			switch {
			case op == nil:
				wantParens = true
			case op.Name == `operator"" `:
				wantParens = false
			case op.Name == "&":
				wantParens = false
			case isDelete:
				wantParens = false
			case op.Name == "alignof ":
				wantParens = true
			case op.Name == "sizeof ":
				wantParens = true
			case op.Name == "typeid ":
				wantParens = true
			default:
				wantParens = true
				if p, ok := expr.(hasPrec); ok {
					if p.prec() < op.precedence {
						wantParens = false
					}
				}
			}
			if wantParens {
				ps.startScope('(')
			}
			ps.print(expr)
			if wantParens {
				ps.endScope(')')
			}
		} else {
			parenthesize(ps, expr)
		}
	}
}

func (u *Unary) Traverse(fn func(AST) bool) {
	if fn(u) {
		u.Op.Traverse(fn)
		u.Expr.Traverse(fn)
	}
}

func (u *Unary) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(u) {
		return nil
	}
	op := u.Op.Copy(fn, skip)
	expr := u.Expr.Copy(fn, skip)
	if op == nil && expr == nil {
		return fn(u)
	}
	if op == nil {
		op = u.Op
	}
	if expr == nil {
		expr = u.Expr
	}
	u = &Unary{Op: op, Expr: expr, Suffix: u.Suffix, SizeofType: u.SizeofType}
	if r := fn(u); r != nil {
		return r
	}
	return u
}

func (u *Unary) GoString() string {
	return u.goString(0, "")
}

func (u *Unary) goString(indent int, field string) string {
	var s string
	if u.Suffix {
		s = " Suffix: true"
	}
	if u.SizeofType {
		s += " SizeofType: true"
	}
	return fmt.Sprintf("%*s%sUnary:%s\n%s\n%s", indent, "", field,
		s, u.Op.goString(indent+2, "Op: "),
		u.Expr.goString(indent+2, "Expr: "))
}

func (u *Unary) prec() precedence {
	if p, ok := u.Op.(hasPrec); ok {
		return p.prec()
	}
	return precDefault
}

// isDesignatedInitializer reports whether x is a designated
// initializer.
func isDesignatedInitializer(x AST) bool {
	switch x := x.(type) {
	case *Binary:
		if op, ok := x.Op.(*Operator); ok {
			if op.Name == "]=" {
				return true
			}
			if op.Name != "=" {
				return false
			}
			if _, ok := x.Left.(*Literal); ok {
				return false
			}
			return true
		}
	case *Trinary:
		if op, ok := x.Op.(*Operator); ok {
			return op.Name == "[...]="
		}
	}
	return false
}

// Binary is a binary operation in an expression.
type Binary struct {
	Op    AST
	Left  AST
	Right AST
}

func (b *Binary) print(ps *printState) {
	op, _ := b.Op.(*Operator)

	if op != nil && strings.Contains(op.Name, "cast") {
		ps.writeString(op.Name)

		scopes := ps.scopes
		ps.scopes = 0

		ps.writeByte('<')
		ps.print(b.Left)
		ps.writeString(">")

		ps.scopes = scopes

		ps.startScope('(')
		ps.print(b.Right)
		ps.endScope(')')
		return
	}

	if isDesignatedInitializer(b) {
		if op.Name == "=" {
			ps.writeByte('.')
		} else {
			ps.writeByte('[')
		}
		ps.print(b.Left)
		if op.Name == "]=" {
			ps.writeByte(']')
		}
		if isDesignatedInitializer(b.Right) {
			// Don't add anything between designated
			// initializer chains.
			ps.print(b.Right)
		} else {
			if ps.llvmStyle {
				ps.writeString(" = ")
				ps.print(b.Right)
			} else {
				ps.writeByte('=')
				parenthesize(ps, b.Right)
			}
		}
		return
	}

	// Use an extra set of parentheses around an expression that
	// uses the greater-than operator, so that it does not get
	// confused with the '>' that ends template parameters.
	needsOuterParen := op != nil && (op.Name == ">" || op.Name == ">>")
	if ps.llvmStyle && ps.scopes > 0 {
		needsOuterParen = false
	}
	if needsOuterParen {
		ps.startScope('(')
	}

	left := b.Left

	skipParens := false
	addSpaces := ps.llvmStyle
	if ps.llvmStyle && op != nil {
		switch op.Name {
		case ".", "->", "->*":
			addSpaces = false
		}
	}

	// For a function call in an expression, don't print the types
	// of the arguments unless there is a return type.
	if op != nil && op.Name == "()" {
		if ty, ok := b.Left.(*Typed); ok {
			if ft, ok := ty.Type.(*FunctionType); ok {
				if ft.Return == nil {
					left = ty.Name
				} else {
					skipParens = true
				}
			} else {
				left = ty.Name
			}
		}
		if ps.llvmStyle {
			skipParens = true
		}
	}

	if skipParens {
		ps.print(left)
	} else if ps.llvmStyle {
		prec := precPrimary
		if p, ok := left.(hasPrec); ok {
			prec = p.prec()
		}
		needsParen := false
		if prec > b.prec() {
			needsParen = true
		}
		if needsParen {
			ps.startScope('(')
		}

		ps.print(left)

		if needsParen {
			ps.endScope(')')
		}
	} else {
		parenthesize(ps, left)
	}

	if op != nil && op.Name == "[]" {
		ps.writeByte('[')
		ps.print(b.Right)
		ps.writeByte(']')
		return
	}

	if op != nil {
		if op.Name != "()" {
			if addSpaces && op.Name != "," {
				ps.writeByte(' ')
			}
			ps.writeString(op.Name)
			if addSpaces {
				ps.writeByte(' ')
			}
		}
	} else {
		ps.print(b.Op)
	}

	if ps.llvmStyle {
		prec := precPrimary
		if p, ok := b.Right.(hasPrec); ok {
			prec = p.prec()
		}
		needsParen := false
		if prec >= b.prec() {
			needsParen = true
		}
		if needsParen {
			ps.startScope('(')
		}

		ps.print(b.Right)

		if needsParen {
			ps.endScope(')')
		}
	} else {
		parenthesize(ps, b.Right)
	}

	if needsOuterParen {
		ps.endScope(')')
	}
}

func (b *Binary) Traverse(fn func(AST) bool) {
	if fn(b) {
		b.Op.Traverse(fn)
		b.Left.Traverse(fn)
		b.Right.Traverse(fn)
	}
}

func (b *Binary) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(b) {
		return nil
	}
	op := b.Op.Copy(fn, skip)
	left := b.Left.Copy(fn, skip)
	right := b.Right.Copy(fn, skip)
	if op == nil && left == nil && right == nil {
		return fn(b)
	}
	if op == nil {
		op = b.Op
	}
	if left == nil {
		left = b.Left
	}
	if right == nil {
		right = b.Right
	}
	b = &Binary{Op: op, Left: left, Right: right}
	if r := fn(b); r != nil {
		return r
	}
	return b
}

func (b *Binary) GoString() string {
	return b.goString(0, "")
}

func (b *Binary) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sBinary:\n%s\n%s\n%s", indent, "", field,
		b.Op.goString(indent+2, "Op: "),
		b.Left.goString(indent+2, "Left: "),
		b.Right.goString(indent+2, "Right: "))
}

func (b *Binary) prec() precedence {
	if p, ok := b.Op.(hasPrec); ok {
		return p.prec()
	}
	return precDefault
}

// Trinary is the ?: trinary operation in an expression.
type Trinary struct {
	Op     AST
	First  AST
	Second AST
	Third  AST
}

func (t *Trinary) print(ps *printState) {
	if isDesignatedInitializer(t) {
		ps.writeByte('[')
		ps.print(t.First)
		ps.writeString(" ... ")
		ps.print(t.Second)
		ps.writeByte(']')
		if isDesignatedInitializer(t.Third) {
			// Don't add anything between designated
			// initializer chains.
			ps.print(t.Third)
		} else {
			if ps.llvmStyle {
				ps.writeString(" = ")
				ps.print(t.Third)
			} else {
				ps.writeByte('=')
				parenthesize(ps, t.Third)
			}
		}
		return
	}

	if ps.llvmStyle {
		wantParens := true
		opPrec := precPrimary
		if op, ok := t.Op.(*Operator); ok {
			opPrec = op.precedence
		}
		if p, ok := t.First.(hasPrec); ok {
			if p.prec() < opPrec {
				wantParens = false
			}
		}
		if wantParens {
			ps.startScope('(')
		}
		ps.print(t.First)
		if wantParens {
			ps.endScope(')')
		}
	} else {
		parenthesize(ps, t.First)
	}

	if ps.llvmStyle {
		ps.writeString(" ? ")
	} else {
		ps.writeByte('?')
	}

	if ps.llvmStyle {
		wantParens := true
		if p, ok := t.Second.(hasPrec); ok {
			if p.prec() < precDefault {
				wantParens = false
			}
		}
		if wantParens {
			ps.startScope('(')
		}
		ps.print(t.Second)
		if wantParens {
			ps.endScope(')')
		}
	} else {
		parenthesize(ps, t.Second)
	}

	ps.writeString(" : ")

	if ps.llvmStyle {
		wantParens := true
		if p, ok := t.Third.(hasPrec); ok {
			if p.prec() < precAssign {
				wantParens = false
			}
		}
		if wantParens {
			ps.startScope('(')
		}
		ps.print(t.Third)
		if wantParens {
			ps.endScope(')')
		}
	} else {
		parenthesize(ps, t.Third)
	}
}

func (t *Trinary) Traverse(fn func(AST) bool) {
	if fn(t) {
		t.Op.Traverse(fn)
		t.First.Traverse(fn)
		t.Second.Traverse(fn)
		t.Third.Traverse(fn)
	}
}

func (t *Trinary) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(t) {
		return nil
	}
	op := t.Op.Copy(fn, skip)
	first := t.First.Copy(fn, skip)
	second := t.Second.Copy(fn, skip)
	third := t.Third.Copy(fn, skip)
	if op == nil && first == nil && second == nil && third == nil {
		return fn(t)
	}
	if op == nil {
		op = t.Op
	}
	if first == nil {
		first = t.First
	}
	if second == nil {
		second = t.Second
	}
	if third == nil {
		third = t.Third
	}
	t = &Trinary{Op: op, First: first, Second: second, Third: third}
	if r := fn(t); r != nil {
		return r
	}
	return t
}

func (t *Trinary) GoString() string {
	return t.goString(0, "")
}

func (t *Trinary) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTrinary:\n%s\n%s\n%s\n%s", indent, "", field,
		t.Op.goString(indent+2, "Op: "),
		t.First.goString(indent+2, "First: "),
		t.Second.goString(indent+2, "Second: "),
		t.Third.goString(indent+2, "Third: "))
}

// Fold is a C++17 fold-expression.  Arg2 is nil for a unary operator.
type Fold struct {
	Left bool
	Op   AST
	Arg1 AST
	Arg2 AST
}

func (f *Fold) print(ps *printState) {
	op, _ := f.Op.(*Operator)
	printOp := func() {
		if op != nil {
			if ps.llvmStyle {
				ps.writeByte(' ')
			}
			ps.writeString(op.Name)
			if ps.llvmStyle {
				ps.writeByte(' ')
			}
		} else {
			ps.print(f.Op)
		}
	}
	foldParenthesize := func(a AST) {
		if ps.llvmStyle {
			prec := precDefault
			if p, ok := a.(hasPrec); ok {
				prec = p.prec()
			}
			needsParen := false
			if prec > precCast {
				needsParen = true
			}
			if needsParen {
				ps.startScope('(')
			}
			ps.print(a)
			if needsParen {
				ps.endScope(')')
			}
		} else {
			parenthesize(ps, a)
		}
	}

	if f.Arg2 == nil {
		if f.Left {
			ps.startScope('(')
			ps.writeString("...")
			printOp()
			foldParenthesize(f.Arg1)
			ps.endScope(')')
		} else {
			ps.startScope('(')
			foldParenthesize(f.Arg1)
			printOp()
			ps.writeString("...")
			ps.endScope(')')
		}
	} else {
		ps.startScope('(')
		foldParenthesize(f.Arg1)
		printOp()
		ps.writeString("...")
		printOp()
		foldParenthesize(f.Arg2)
		ps.endScope(')')
	}
}

func (f *Fold) Traverse(fn func(AST) bool) {
	if fn(f) {
		f.Op.Traverse(fn)
		f.Arg1.Traverse(fn)
		if f.Arg2 != nil {
			f.Arg2.Traverse(fn)
		}
	}
}

func (f *Fold) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(f) {
		return nil
	}
	op := f.Op.Copy(fn, skip)
	arg1 := f.Arg1.Copy(fn, skip)
	var arg2 AST
	if f.Arg2 != nil {
		arg2 = f.Arg2.Copy(fn, skip)
	}
	if op == nil && arg1 == nil && arg2 == nil {
		return fn(f)
	}
	if op == nil {
		op = f.Op
	}
	if arg1 == nil {
		arg1 = f.Arg1
	}
	if arg2 == nil {
		arg2 = f.Arg2
	}
	f = &Fold{Left: f.Left, Op: op, Arg1: arg1, Arg2: arg2}
	if r := fn(f); r != nil {
		return r
	}
	return f
}

func (f *Fold) GoString() string {
	return f.goString(0, "")
}

func (f *Fold) goString(indent int, field string) string {
	if f.Arg2 == nil {
		return fmt.Sprintf("%*s%sFold: Left: %t\n%s\n%s", indent, "", field,
			f.Left, f.Op.goString(indent+2, "Op: "),
			f.Arg1.goString(indent+2, "Arg1: "))
	} else {
		return fmt.Sprintf("%*s%sFold: Left: %t\n%s\n%s\n%s", indent, "", field,
			f.Left, f.Op.goString(indent+2, "Op: "),
			f.Arg1.goString(indent+2, "Arg1: "),
			f.Arg2.goString(indent+2, "Arg2: "))
	}
}

// Subobject is a a reference to an offset in an expression.  This is
// used for C++20 manglings of class types used as the type of
// non-type template arguments.
//
// See https://github.com/itanium-cxx-abi/cxx-abi/issues/47.
type Subobject struct {
	Type      AST
	SubExpr   AST
	Offset    int
	Selectors []int
	PastEnd   bool
}

func (so *Subobject) print(ps *printState) {
	ps.print(so.SubExpr)
	ps.writeString(".<")
	ps.print(so.Type)
	ps.writeString(fmt.Sprintf(" at offset %d>", so.Offset))
}

func (so *Subobject) Traverse(fn func(AST) bool) {
	if fn(so) {
		so.Type.Traverse(fn)
		so.SubExpr.Traverse(fn)
	}
}

func (so *Subobject) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(so) {
		return nil
	}
	typ := so.Type.Copy(fn, skip)
	subExpr := so.SubExpr.Copy(fn, skip)
	if typ == nil && subExpr == nil {
		return nil
	}
	if typ == nil {
		typ = so.Type
	}
	if subExpr == nil {
		subExpr = so.SubExpr
	}
	so = &Subobject{
		Type:      typ,
		SubExpr:   subExpr,
		Offset:    so.Offset,
		Selectors: so.Selectors,
		PastEnd:   so.PastEnd,
	}
	if r := fn(so); r != nil {
		return r
	}
	return so
}

func (so *Subobject) GoString() string {
	return so.goString(0, "")
}

func (so *Subobject) goString(indent int, field string) string {
	var selectors string
	for _, s := range so.Selectors {
		selectors += fmt.Sprintf(" %d", s)
	}
	return fmt.Sprintf("%*s%sSubobject:\n%s\n%s\n%*sOffset: %d\n%*sSelectors:%s\n%*sPastEnd: %t",
		indent, "", field,
		so.Type.goString(indent+2, "Type: "),
		so.SubExpr.goString(indent+2, "SubExpr: "),
		indent+2, "", so.Offset,
		indent+2, "", selectors,
		indent+2, "", so.PastEnd)
}

// PtrMemCast is a conversion of an expression to a pointer-to-member
// type.  This is used for C++20 manglings of class types used as the
// type of non-type template arguments.
//
// See https://github.com/itanium-cxx-abi/cxx-abi/issues/47.
type PtrMemCast struct {
	Type   AST
	Expr   AST
	Offset int
}

func (pmc *PtrMemCast) print(ps *printState) {
	ps.startScope('(')
	ps.print(pmc.Type)
	ps.writeString(")(")
	ps.print(pmc.Expr)
	ps.endScope(')')
}

func (pmc *PtrMemCast) Traverse(fn func(AST) bool) {
	if fn(pmc) {
		pmc.Type.Traverse(fn)
		pmc.Expr.Traverse(fn)
	}
}

func (pmc *PtrMemCast) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(pmc) {
		return nil
	}
	typ := pmc.Type.Copy(fn, skip)
	expr := pmc.Expr.Copy(fn, skip)
	if typ == nil && expr == nil {
		return nil
	}
	if typ == nil {
		typ = pmc.Type
	}
	if expr == nil {
		expr = pmc.Expr
	}
	pmc = &PtrMemCast{
		Type:   typ,
		Expr:   expr,
		Offset: pmc.Offset,
	}
	if r := fn(pmc); r != nil {
		return r
	}
	return pmc
}

func (pmc *PtrMemCast) GoString() string {
	return pmc.goString(0, "")
}

func (pmc *PtrMemCast) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sPtrMemCast:\n%s\n%s\n%*sOffset: %d",
		indent, "", field,
		pmc.Type.goString(indent+2, "Type: "),
		pmc.Expr.goString(indent+2, "Expr: "),
		indent+2, "", pmc.Offset)
}

// New is a use of operator new in an expression.
type New struct {
	Op    AST
	Place AST
	Type  AST
	Init  AST
}

func (n *New) print(ps *printState) {
	if !ps.llvmStyle {
		// Op doesn't really matter for printing--we always print "new".
		ps.writeString("new ")
	} else {
		op, _ := n.Op.(*Operator)
		if op != nil {
			ps.writeString(op.Name)
			if n.Place == nil {
				ps.writeByte(' ')
			}
		} else {
			ps.print(n.Op)
		}
	}
	if n.Place != nil {
		parenthesize(ps, n.Place)
		ps.writeByte(' ')
	}
	ps.print(n.Type)
	if n.Init != nil {
		parenthesize(ps, n.Init)
	}
}

func (n *New) Traverse(fn func(AST) bool) {
	if fn(n) {
		n.Op.Traverse(fn)
		if n.Place != nil {
			n.Place.Traverse(fn)
		}
		n.Type.Traverse(fn)
		if n.Init != nil {
			n.Init.Traverse(fn)
		}
	}
}

func (n *New) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(n) {
		return nil
	}
	op := n.Op.Copy(fn, skip)
	var place AST
	if n.Place != nil {
		place = n.Place.Copy(fn, skip)
	}
	typ := n.Type.Copy(fn, skip)
	var ini AST
	if n.Init != nil {
		ini = n.Init.Copy(fn, skip)
	}
	if op == nil && place == nil && typ == nil && ini == nil {
		return fn(n)
	}
	if op == nil {
		op = n.Op
	}
	if place == nil {
		place = n.Place
	}
	if typ == nil {
		typ = n.Type
	}
	if ini == nil {
		ini = n.Init
	}
	n = &New{Op: op, Place: place, Type: typ, Init: ini}
	if r := fn(n); r != nil {
		return r
	}
	return n
}

func (n *New) GoString() string {
	return n.goString(0, "")
}

func (n *New) goString(indent int, field string) string {
	var place string
	if n.Place == nil {
		place = fmt.Sprintf("%*sPlace: nil", indent, "")
	} else {
		place = n.Place.goString(indent+2, "Place: ")
	}
	var ini string
	if n.Init == nil {
		ini = fmt.Sprintf("%*sInit: nil", indent, "")
	} else {
		ini = n.Init.goString(indent+2, "Init: ")
	}
	return fmt.Sprintf("%*s%sNew:\n%s\n%s\n%s\n%s", indent, "", field,
		n.Op.goString(indent+2, "Op: "), place,
		n.Type.goString(indent+2, "Type: "), ini)
}

// Literal is a literal in an expression.
type Literal struct {
	Type AST
	Val  string
	Neg  bool
}

// Suffixes to use for constants of the given integer type.
var builtinTypeSuffix = map[string]string{
	"int":                "",
	"unsigned int":       "u",
	"long":               "l",
	"unsigned long":      "ul",
	"long long":          "ll",
	"unsigned long long": "ull",
}

// Builtin float types.
var builtinTypeFloat = map[string]bool{
	"double":      true,
	"long double": true,
	"float":       true,
	"__float128":  true,
	"half":        true,
}

func (l *Literal) print(ps *printState) {
	isFloat := false
	if b, ok := l.Type.(*BuiltinType); ok {
		if suffix, ok := builtinTypeSuffix[b.Name]; ok {
			if l.Neg {
				ps.writeByte('-')
			}
			ps.writeString(l.Val)
			ps.writeString(suffix)
			return
		} else if b.Name == "bool" && !l.Neg {
			switch l.Val {
			case "0":
				ps.writeString("false")
				return
			case "1":
				ps.writeString("true")
				return
			}
		} else if b.Name == "decltype(nullptr)" && (l.Val == "" || l.Val == "0") {
			if ps.llvmStyle {
				ps.writeString("nullptr")
			} else {
				ps.print(l.Type)
			}
			return
		} else {
			isFloat = builtinTypeFloat[b.Name]
		}
	}

	ps.startScope('(')
	ps.print(l.Type)
	ps.endScope(')')

	if isFloat {
		ps.writeByte('[')
	}
	if l.Neg {
		ps.writeByte('-')
	}
	ps.writeString(l.Val)
	if isFloat {
		ps.writeByte(']')
	}
}

func (l *Literal) Traverse(fn func(AST) bool) {
	if fn(l) {
		l.Type.Traverse(fn)
	}
}

func (l *Literal) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(l) {
		return nil
	}
	typ := l.Type.Copy(fn, skip)
	if typ == nil {
		return fn(l)
	}
	l = &Literal{Type: typ, Val: l.Val, Neg: l.Neg}
	if r := fn(l); r != nil {
		return r
	}
	return l
}

func (l *Literal) GoString() string {
	return l.goString(0, "")
}

func (l *Literal) goString(indent int, field string) string {
	var neg string
	if l.Neg {
		neg = " Neg: true"
	}
	return fmt.Sprintf("%*s%sLiteral:%s\n%s\n%*sVal: %s", indent, "", field,
		neg, l.Type.goString(indent+2, "Type: "),
		indent+2, "", l.Val)
}

func (l *Literal) prec() precedence {
	return precPrimary
}

// StringLiteral is a string literal.
type StringLiteral struct {
	Type AST
}

func (sl *StringLiteral) print(ps *printState) {
	ps.writeString(`"<`)
	sl.Type.print(ps)
	ps.writeString(`>"`)
}

func (sl *StringLiteral) Traverse(fn func(AST) bool) {
	if fn(sl) {
		sl.Type.Traverse(fn)
	}
}

func (sl *StringLiteral) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(sl) {
		return nil
	}
	typ := sl.Type.Copy(fn, skip)
	if typ == nil {
		return fn(sl)
	}
	sl = &StringLiteral{Type: typ}
	if r := fn(sl); r != nil {
		return r
	}
	return sl
}

func (sl *StringLiteral) GoString() string {
	return sl.goString(0, "")
}

func (sl *StringLiteral) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sStringLiteral:\n%s", indent, "", field,
		sl.Type.goString(indent+2, ""))
}

// LambdaExpr is a literal that is a lambda expression.
type LambdaExpr struct {
	Type AST
}

func (le *LambdaExpr) print(ps *printState) {
	ps.writeString("[]")
	if cl, ok := le.Type.(*Closure); ok {
		cl.printTypes(ps)
	}
	ps.writeString("{...}")
}

func (le *LambdaExpr) Traverse(fn func(AST) bool) {
	if fn(le) {
		le.Type.Traverse(fn)
	}
}

func (le *LambdaExpr) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(le) {
		return nil
	}
	typ := le.Type.Copy(fn, skip)
	if typ == nil {
		return fn(le)
	}
	le = &LambdaExpr{Type: typ}
	if r := fn(le); r != nil {
		return r
	}
	return le
}

func (le *LambdaExpr) GoString() string {
	return le.goString(0, "")
}

func (le *LambdaExpr) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sLambdaExpr:\n%s", indent, "", field,
		le.Type.goString(indent+2, ""))
}

// ExprList is a list of expressions, typically arguments to a
// function call in an expression.
type ExprList struct {
	Exprs []AST
}

func (el *ExprList) print(ps *printState) {
	ps.printList(el.Exprs, nil)
}

func (el *ExprList) Traverse(fn func(AST) bool) {
	if fn(el) {
		for _, e := range el.Exprs {
			e.Traverse(fn)
		}
	}
}

func (el *ExprList) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(el) {
		return nil
	}
	exprs := make([]AST, len(el.Exprs))
	changed := false
	for i, e := range el.Exprs {
		ec := e.Copy(fn, skip)
		if ec == nil {
			exprs[i] = e
		} else {
			exprs[i] = ec
			changed = true
		}
	}
	if !changed {
		return fn(el)
	}
	el = &ExprList{Exprs: exprs}
	if r := fn(el); r != nil {
		return r
	}
	return el
}

func (el *ExprList) GoString() string {
	return el.goString(0, "")
}

func (el *ExprList) goString(indent int, field string) string {
	if len(el.Exprs) == 0 {
		return fmt.Sprintf("%*s%sExprList: nil", indent, "", field)
	}
	s := fmt.Sprintf("%*s%sExprList:", indent, "", field)
	for i, e := range el.Exprs {
		s += "\n"
		s += e.goString(indent+2, fmt.Sprintf("%d: ", i))
	}
	return s
}

func (el *ExprList) prec() precedence {
	return precComma
}

// InitializerList is an initializer list: an optional type with a
// list of expressions.
type InitializerList struct {
	Type  AST
	Exprs AST
}

func (il *InitializerList) print(ps *printState) {
	if il.Type != nil {
		ps.print(il.Type)
	}
	ps.writeByte('{')
	ps.print(il.Exprs)
	ps.writeByte('}')
}

func (il *InitializerList) Traverse(fn func(AST) bool) {
	if fn(il) {
		if il.Type != nil {
			il.Type.Traverse(fn)
		}
		il.Exprs.Traverse(fn)
	}
}

func (il *InitializerList) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(il) {
		return nil
	}
	var typ AST
	if il.Type != nil {
		typ = il.Type.Copy(fn, skip)
	}
	exprs := il.Exprs.Copy(fn, skip)
	if typ == nil && exprs == nil {
		return fn(il)
	}
	if typ == nil {
		typ = il.Type
	}
	if exprs == nil {
		exprs = il.Exprs
	}
	il = &InitializerList{Type: typ, Exprs: exprs}
	if r := fn(il); r != nil {
		return r
	}
	return il
}

func (il *InitializerList) GoString() string {
	return il.goString(0, "")
}

func (il *InitializerList) goString(indent int, field string) string {
	var t string
	if il.Type == nil {
		t = fmt.Sprintf("%*sType: nil", indent+2, "")
	} else {
		t = il.Type.goString(indent+2, "Type: ")
	}
	return fmt.Sprintf("%*s%sInitializerList:\n%s\n%s", indent, "", field,
		t, il.Exprs.goString(indent+2, "Exprs: "))
}

// DefaultArg holds a default argument for a local name.
type DefaultArg struct {
	Num int
	Arg AST
}

func (da *DefaultArg) print(ps *printState) {
	if !ps.llvmStyle {
		fmt.Fprintf(&ps.buf, "{default arg#%d}::", da.Num+1)
	}
	ps.print(da.Arg)
}

func (da *DefaultArg) Traverse(fn func(AST) bool) {
	if fn(da) {
		da.Arg.Traverse(fn)
	}
}

func (da *DefaultArg) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(da) {
		return nil
	}
	arg := da.Arg.Copy(fn, skip)
	if arg == nil {
		return fn(da)
	}
	da = &DefaultArg{Num: da.Num, Arg: arg}
	if r := fn(da); r != nil {
		return r
	}
	return da
}

func (da *DefaultArg) GoString() string {
	return da.goString(0, "")
}

func (da *DefaultArg) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sDefaultArg: Num: %d\n%s", indent, "", field, da.Num,
		da.Arg.goString(indent+2, "Arg: "))
}

// Closure is a closure, or lambda expression.
type Closure struct {
	TemplateArgs           []AST
	TemplateArgsConstraint AST
	Types                  []AST
	Num                    int
	CallConstraint         AST
}

func (cl *Closure) print(ps *printState) {
	if ps.llvmStyle {
		if cl.Num == 0 {
			ps.writeString("'lambda'")
		} else {
			ps.writeString(fmt.Sprintf("'lambda%d'", cl.Num-1))
		}
	} else {
		ps.writeString("{lambda")
	}
	cl.printTypes(ps)
	if !ps.llvmStyle {
		ps.writeString(fmt.Sprintf("#%d}", cl.Num+1))
	}
}

func (cl *Closure) printTypes(ps *printState) {
	if len(cl.TemplateArgs) > 0 {
		scopes := ps.scopes
		ps.scopes = 0

		ps.writeString("<")
		ps.printList(cl.TemplateArgs, nil)
		ps.writeString(">")

		ps.scopes = scopes
	}

	if cl.TemplateArgsConstraint != nil {
		ps.writeString(" requires ")
		ps.print(cl.TemplateArgsConstraint)
		ps.writeByte(' ')
	}

	ps.startScope('(')
	ps.printList(cl.Types, nil)
	ps.endScope(')')

	if cl.CallConstraint != nil {
		ps.writeString(" requires ")
		ps.print(cl.CallConstraint)
	}
}

func (cl *Closure) Traverse(fn func(AST) bool) {
	if fn(cl) {
		for _, a := range cl.TemplateArgs {
			a.Traverse(fn)
		}
		if cl.TemplateArgsConstraint != nil {
			cl.TemplateArgsConstraint.Traverse(fn)
		}
		for _, t := range cl.Types {
			t.Traverse(fn)
		}
		if cl.CallConstraint != nil {
			cl.CallConstraint.Traverse(fn)
		}
	}
}

func (cl *Closure) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(cl) {
		return nil
	}
	changed := false

	args := make([]AST, len(cl.TemplateArgs))
	for i, a := range cl.TemplateArgs {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			changed = true
		}
	}

	var templateArgsConstraint AST
	if cl.TemplateArgsConstraint != nil {
		templateArgsConstraint = cl.TemplateArgsConstraint.Copy(fn, skip)
		if templateArgsConstraint == nil {
			templateArgsConstraint = cl.TemplateArgsConstraint
		} else {
			changed = true
		}
	}

	types := make([]AST, len(cl.Types))
	for i, t := range cl.Types {
		tc := t.Copy(fn, skip)
		if tc == nil {
			types[i] = t
		} else {
			types[i] = tc
			changed = true
		}
	}

	var callConstraint AST
	if cl.CallConstraint != nil {
		callConstraint = cl.CallConstraint.Copy(fn, skip)
		if callConstraint == nil {
			callConstraint = cl.CallConstraint
		} else {
			changed = true
		}
	}

	if !changed {
		return fn(cl)
	}
	cl = &Closure{
		TemplateArgs:           args,
		TemplateArgsConstraint: templateArgsConstraint,
		Types:                  types,
		Num:                    cl.Num,
		CallConstraint:         callConstraint,
	}
	if r := fn(cl); r != nil {
		return r
	}
	return cl
}

func (cl *Closure) GoString() string {
	return cl.goString(0, "")
}

func (cl *Closure) goString(indent int, field string) string {
	var args strings.Builder
	if len(cl.TemplateArgs) == 0 {
		fmt.Fprintf(&args, "%*sTemplateArgs: nil", indent+2, "")
	} else {
		fmt.Fprintf(&args, "%*sTemplateArgs:", indent+2, "")
		for i, a := range cl.TemplateArgs {
			args.WriteByte('\n')
			args.WriteString(a.goString(indent+4, fmt.Sprintf("%d: ", i)))
		}
	}

	var templateArgsConstraint string
	if cl.TemplateArgsConstraint != nil {
		templateArgsConstraint = "\n" + cl.TemplateArgsConstraint.goString(indent+2, "TemplateArgsConstraint: ")
	}

	var types strings.Builder
	if len(cl.Types) == 0 {
		fmt.Fprintf(&types, "%*sTypes: nil", indent+2, "")
	} else {
		fmt.Fprintf(&types, "%*sTypes:", indent+2, "")
		for i, t := range cl.Types {
			types.WriteByte('\n')
			types.WriteString(t.goString(indent+4, fmt.Sprintf("%d: ", i)))
		}
	}

	var callConstraint string
	if cl.CallConstraint != nil {
		callConstraint = "\n" + cl.CallConstraint.goString(indent+2, "CallConstraint: ")
	}

	return fmt.Sprintf("%*s%sClosure: Num: %d\n%s\n%s%s%s", indent, "", field,
		cl.Num, args.String(), templateArgsConstraint, types.String(),
		callConstraint)
}

// StructuredBindings is a structured binding declaration.
type StructuredBindings struct {
	Bindings []AST
}

func (sb *StructuredBindings) print(ps *printState) {
	ps.writeString("[")
	ps.printList(sb.Bindings, nil)
	ps.writeString("]")
}

func (sb *StructuredBindings) Traverse(fn func(AST) bool) {
	if fn(sb) {
		for _, b := range sb.Bindings {
			b.Traverse(fn)
		}
	}
}

func (sb *StructuredBindings) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(sb) {
		return nil
	}
	changed := false
	bindings := make([]AST, len(sb.Bindings))
	for i, b := range sb.Bindings {
		bc := b.Copy(fn, skip)
		if bc == nil {
			bindings[i] = b
		} else {
			bindings[i] = bc
			changed = true
		}
	}
	if !changed {
		return fn(sb)
	}
	sb = &StructuredBindings{Bindings: bindings}
	if r := fn(sb); r != nil {
		return r
	}
	return sb
}

func (sb *StructuredBindings) GoString() string {
	return sb.goString(0, "")
}

func (sb *StructuredBindings) goString(indent int, field string) string {
	var strb strings.Builder
	fmt.Fprintf(&strb, "%*s%sStructuredBinding:", indent, "", field)
	for _, b := range sb.Bindings {
		strb.WriteByte('\n')
		strb.WriteString(b.goString(indent+2, ""))
	}
	return strb.String()
}

// UnnamedType is an unnamed type, that just has an index.
type UnnamedType struct {
	Num int
}

func (ut *UnnamedType) print(ps *printState) {
	if ps.llvmStyle {
		if ut.Num == 0 {
			ps.writeString("'unnamed'")
		} else {
			ps.writeString(fmt.Sprintf("'unnamed%d'", ut.Num-1))
		}
	} else {
		ps.writeString(fmt.Sprintf("{unnamed type#%d}", ut.Num+1))
	}
}

func (ut *UnnamedType) Traverse(fn func(AST) bool) {
	fn(ut)
}

func (ut *UnnamedType) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ut) {
		return nil
	}
	return fn(ut)
}

func (ut *UnnamedType) GoString() string {
	return ut.goString(0, "")
}

func (ut *UnnamedType) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sUnnamedType: Num: %d", indent, "", field, ut.Num)
}

// Clone is a clone of a function, with a distinguishing suffix.
type Clone struct {
	Base   AST
	Suffix string
}

func (c *Clone) print(ps *printState) {
	ps.print(c.Base)
	if ps.llvmStyle {
		ps.writeByte(' ')
		ps.startScope('(')
		ps.writeString(c.Suffix)
		ps.endScope(')')
	} else {
		ps.writeString(fmt.Sprintf(" [clone %s]", c.Suffix))
	}
}

func (c *Clone) Traverse(fn func(AST) bool) {
	if fn(c) {
		c.Base.Traverse(fn)
	}
}

func (c *Clone) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(c) {
		return nil
	}
	base := c.Base.Copy(fn, skip)
	if base == nil {
		return fn(c)
	}
	c = &Clone{Base: base, Suffix: c.Suffix}
	if r := fn(c); r != nil {
		return r
	}
	return c
}

func (c *Clone) GoString() string {
	return c.goString(0, "")
}

func (c *Clone) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sClone: Suffix: %s\n%s", indent, "", field,
		c.Suffix, c.Base.goString(indent+2, "Base: "))
}

// Special is a special symbol, printed as a prefix plus another
// value.
type Special struct {
	Prefix string
	Val    AST
}

func (s *Special) print(ps *printState) {
	prefix := s.Prefix
	if ps.llvmStyle {
		switch prefix {
		case "TLS wrapper function for ":
			prefix = "thread-local wrapper routine for "
		case "TLS init function for ":
			prefix = "thread-local initialization routine for "
		}
	}
	ps.writeString(prefix)
	ps.print(s.Val)
}

func (s *Special) Traverse(fn func(AST) bool) {
	if fn(s) {
		s.Val.Traverse(fn)
	}
}

func (s *Special) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(s) {
		return nil
	}
	val := s.Val.Copy(fn, skip)
	if val == nil {
		return fn(s)
	}
	s = &Special{Prefix: s.Prefix, Val: val}
	if r := fn(s); r != nil {
		return r
	}
	return s
}

func (s *Special) GoString() string {
	return s.goString(0, "")
}

func (s *Special) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sSpecial: Prefix: %s\n%s", indent, "", field,
		s.Prefix, s.Val.goString(indent+2, "Val: "))
}

// Special2 is like special, but uses two values.
type Special2 struct {
	Prefix string
	Val1   AST
	Middle string
	Val2   AST
}

func (s *Special2) print(ps *printState) {
	ps.writeString(s.Prefix)
	ps.print(s.Val1)
	ps.writeString(s.Middle)
	ps.print(s.Val2)
}

func (s *Special2) Traverse(fn func(AST) bool) {
	if fn(s) {
		s.Val1.Traverse(fn)
		s.Val2.Traverse(fn)
	}
}

func (s *Special2) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(s) {
		return nil
	}
	val1 := s.Val1.Copy(fn, skip)
	val2 := s.Val2.Copy(fn, skip)
	if val1 == nil && val2 == nil {
		return fn(s)
	}
	if val1 == nil {
		val1 = s.Val1
	}
	if val2 == nil {
		val2 = s.Val2
	}
	s = &Special2{Prefix: s.Prefix, Val1: val1, Middle: s.Middle, Val2: val2}
	if r := fn(s); r != nil {
		return r
	}
	return s
}

func (s *Special2) GoString() string {
	return s.goString(0, "")
}

func (s *Special2) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sSpecial2: Prefix: %s\n%s\n%*sMiddle: %s\n%s", indent, "", field,
		s.Prefix, s.Val1.goString(indent+2, "Val1: "),
		indent+2, "", s.Middle, s.Val2.goString(indent+2, "Val2: "))
}

// EnableIf is used by clang for an enable_if attribute.
type EnableIf struct {
	Type AST
	Args []AST
}

func (ei *EnableIf) print(ps *printState) {
	ps.print(ei.Type)
	ps.writeString(" [enable_if:")
	ps.printList(ei.Args, nil)
	ps.writeString("]")
}

func (ei *EnableIf) Traverse(fn func(AST) bool) {
	if fn(ei) {
		ei.Type.Traverse(fn)
		for _, a := range ei.Args {
			a.Traverse(fn)
		}
	}
}

func (ei *EnableIf) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(ei) {
		return nil
	}
	typ := ei.Type.Copy(fn, skip)
	argsChanged := false
	args := make([]AST, len(ei.Args))
	for i, a := range ei.Args {
		ac := a.Copy(fn, skip)
		if ac == nil {
			args[i] = a
		} else {
			args[i] = ac
			argsChanged = true
		}
	}
	if typ == nil && !argsChanged {
		return fn(ei)
	}
	if typ == nil {
		typ = ei.Type
	}
	ei = &EnableIf{Type: typ, Args: args}
	if r := fn(ei); r != nil {
		return r
	}
	return ei
}

func (ei *EnableIf) GoString() string {
	return ei.goString(0, "")
}

func (ei *EnableIf) goString(indent int, field string) string {
	var args string
	if len(ei.Args) == 0 {
		args = fmt.Sprintf("%*sArgs: nil", indent+2, "")
	} else {
		args = fmt.Sprintf("%*sArgs:", indent+2, "")
		for i, a := range ei.Args {
			args += "\n"
			args += a.goString(indent+4, fmt.Sprintf("%d: ", i))
		}
	}
	return fmt.Sprintf("%*s%sEnableIf:\n%s\n%s", indent, "", field,
		ei.Type.goString(indent+2, "Type: "), args)
}

// ModuleName is a C++20 module.
type ModuleName struct {
	Parent      AST
	Name        AST
	IsPartition bool
}

func (mn *ModuleName) print(ps *printState) {
	if mn.Parent != nil {
		ps.print(mn.Parent)
	}
	if mn.IsPartition {
		ps.writeByte(':')
	} else if mn.Parent != nil {
		ps.writeByte('.')
	}
	ps.print(mn.Name)
}

func (mn *ModuleName) Traverse(fn func(AST) bool) {
	if fn(mn) {
		mn.Parent.Traverse(fn)
		mn.Name.Traverse(fn)
	}
}

func (mn *ModuleName) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(mn) {
		return nil
	}
	var parent AST
	if mn.Parent != nil {
		parent = mn.Parent.Copy(fn, skip)
	}
	name := mn.Name.Copy(fn, skip)
	if parent == nil && name == nil {
		return fn(mn)
	}
	if parent == nil {
		parent = mn.Parent
	}
	if name == nil {
		name = mn.Name
	}
	mn = &ModuleName{Parent: parent, Name: name, IsPartition: mn.IsPartition}
	if r := fn(mn); r != nil {
		return r
	}
	return mn
}

func (mn *ModuleName) GoString() string {
	return mn.goString(0, "")
}

func (mn *ModuleName) goString(indent int, field string) string {
	var parent string
	if mn.Parent == nil {
		parent = fmt.Sprintf("%*sParent: nil", indent+2, "")
	} else {
		parent = mn.Parent.goString(indent+2, "Parent: ")
	}
	return fmt.Sprintf("%*s%sModuleName: IsPartition: %t\n%s\n%s", indent, "", field,
		mn.IsPartition, parent,
		mn.Name.goString(indent+2, "Name: "))
}

// ModuleEntity is a name inside a module.
type ModuleEntity struct {
	Module AST
	Name   AST
}

func (me *ModuleEntity) print(ps *printState) {
	ps.print(me.Name)
	ps.writeByte('@')
	ps.print(me.Module)
}

func (me *ModuleEntity) Traverse(fn func(AST) bool) {
	if fn(me) {
		me.Module.Traverse(fn)
		me.Name.Traverse(fn)
	}
}

func (me *ModuleEntity) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(me) {
		return nil
	}
	module := me.Module.Copy(fn, skip)
	name := me.Name.Copy(fn, skip)
	if module == nil && name == nil {
		return fn(me)
	}
	if module == nil {
		module = me.Module
	}
	if name == nil {
		name = me.Name
	}
	me = &ModuleEntity{Module: module, Name: name}
	if r := fn(me); r != nil {
		return r
	}
	return me
}

func (me *ModuleEntity) GoString() string {
	return me.goString(0, "")
}

func (me *ModuleEntity) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sModuleEntity:\n%s\n%s", indent, "", field,
		me.Module.goString(indent+2, "Module: "),
		me.Name.goString(indent+2, "Name: "))
}

// Friend is a member like friend name.
type Friend struct {
	Name AST
}

func (f *Friend) print(ps *printState) {
	ps.writeString("friend ")
	ps.print(f.Name)
}

func (f *Friend) Traverse(fn func(AST) bool) {
	if fn(f) {
		f.Name.Traverse(fn)
	}
}

func (f *Friend) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(f) {
		return nil
	}
	name := f.Name.Copy(fn, skip)
	if name == nil {
		return fn(f)
	}
	f = &Friend{Name: name}
	if r := fn(f); r != nil {
		return r
	}
	return f
}

func (f *Friend) GoString() string {
	return f.goString(0, "")
}

func (f *Friend) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sFriend:\n%s", indent, "", field,
		f.Name.goString(indent+2, "Name: "))
}

// Constraint represents an AST with a constraint.
type Constraint struct {
	Name     AST
	Requires AST
}

func (c *Constraint) print(ps *printState) {
	ps.print(c.Name)
	ps.writeString(" requires ")
	ps.print(c.Requires)
}

func (c *Constraint) Traverse(fn func(AST) bool) {
	if fn(c) {
		c.Name.Traverse(fn)
		c.Requires.Traverse(fn)
	}
}

func (c *Constraint) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(c) {
		return nil
	}
	name := c.Name.Copy(fn, skip)
	requires := c.Requires.Copy(fn, skip)
	if name == nil && requires == nil {
		return fn(c)
	}
	if name == nil {
		name = c.Name
	}
	if requires == nil {
		requires = c.Requires
	}
	c = &Constraint{Name: name, Requires: requires}
	if r := fn(c); r != nil {
		return r
	}
	return c
}

func (c *Constraint) GoString() string {
	return c.goString(0, "")
}

func (c *Constraint) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sConstraint:\n%s\n%s", indent, "", field,
		c.Name.goString(indent+2, "Name: "),
		c.Requires.goString(indent+2, "Requires: "))
}

// RequiresExpr is a C++20 requires expression.
type RequiresExpr struct {
	Params       []AST
	Requirements []AST
}

func (re *RequiresExpr) print(ps *printState) {
	ps.writeString("requires")
	if len(re.Params) > 0 {
		ps.writeByte(' ')
		ps.startScope('(')
		ps.printList(re.Params, nil)
		ps.endScope(')')
	}
	ps.writeByte(' ')
	ps.startScope('{')
	for _, req := range re.Requirements {
		ps.print(req)
	}
	ps.writeByte(' ')
	ps.endScope('}')
}

func (re *RequiresExpr) Traverse(fn func(AST) bool) {
	if fn(re) {
		for _, p := range re.Params {
			p.Traverse(fn)
		}
		for _, r := range re.Requirements {
			r.Traverse(fn)
		}
	}
}

func (re *RequiresExpr) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(re) {
		return nil
	}

	changed := false

	var params []AST
	if len(re.Params) > 0 {
		params = make([]AST, len(re.Params))
		for i, p := range re.Params {
			pc := p.Copy(fn, skip)
			if pc == nil {
				params[i] = p
			} else {
				params[i] = pc
				changed = true
			}
		}
	}

	requirements := make([]AST, len(re.Requirements))
	for i, r := range re.Requirements {
		rc := r.Copy(fn, skip)
		if rc == nil {
			requirements[i] = r
		} else {
			requirements[i] = rc
			changed = true
		}
	}

	if !changed {
		return fn(re)
	}

	re = &RequiresExpr{Params: params, Requirements: requirements}
	if r := fn(re); r != nil {
		return r
	}
	return re
}

func (re *RequiresExpr) GoString() string {
	return re.goString(0, "")
}

func (re *RequiresExpr) goString(indent int, field string) string {
	var params strings.Builder
	if len(re.Params) == 0 {
		fmt.Fprintf(&params, "%*sParams: nil", indent+2, "")
	} else {
		fmt.Fprintf(&params, "%*sParams:", indent+2, "")
		for i, p := range re.Params {
			params.WriteByte('\n')
			params.WriteString(p.goString(indent+4, fmt.Sprintf("%d: ", i)))
		}
	}

	var requirements strings.Builder
	fmt.Fprintf(&requirements, "%*sRequirements:", indent+2, "")
	for i, r := range re.Requirements {
		requirements.WriteByte('\n')
		requirements.WriteString(r.goString(indent+4, fmt.Sprintf("%d: ", i)))
	}

	return fmt.Sprintf("%*s%sRequirements:\n%s\n%s", indent, "", field,
		params.String(), requirements.String())
}

// ExprRequirement is a simple requirement in a requires expression.
// This is an arbitrary expression.
type ExprRequirement struct {
	Expr     AST
	Noexcept bool
	TypeReq  AST
}

func (er *ExprRequirement) print(ps *printState) {
	ps.writeByte(' ')
	if er.Noexcept || er.TypeReq != nil {
		ps.startScope('{')
	}
	ps.print(er.Expr)
	if er.Noexcept || er.TypeReq != nil {
		ps.endScope('}')
	}
	if er.Noexcept {
		ps.writeString(" noexcept")
	}
	if er.TypeReq != nil {
		ps.writeString(" -> ")
		ps.print(er.TypeReq)
	}
	ps.writeByte(';')
}

func (er *ExprRequirement) Traverse(fn func(AST) bool) {
	if fn(er) {
		er.Expr.Traverse(fn)
		if er.TypeReq != nil {
			er.TypeReq.Traverse(fn)
		}
	}
}

func (er *ExprRequirement) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(er) {
		return nil
	}
	expr := er.Expr.Copy(fn, skip)
	var typeReq AST
	if er.TypeReq != nil {
		typeReq = er.TypeReq.Copy(fn, skip)
	}
	if expr == nil && typeReq == nil {
		return fn(er)
	}
	if expr == nil {
		expr = er.Expr
	}
	if typeReq == nil {
		typeReq = er.TypeReq
	}
	er = &ExprRequirement{Expr: expr, TypeReq: typeReq}
	if r := fn(er); r != nil {
		return r
	}
	return er
}

func (er *ExprRequirement) GoString() string {
	return er.goString(0, "")
}

func (er *ExprRequirement) goString(indent int, field string) string {
	var typeReq string
	if er.TypeReq != nil {
		typeReq = "\n" + er.TypeReq.goString(indent+2, "TypeReq: ")
	}

	return fmt.Sprintf("%*s%sExprRequirement: Noexcept: %t\n%s%s", indent, "", field,
		er.Noexcept,
		er.Expr.goString(indent+2, "Expr: "),
		typeReq)
}

// TypeRequirement is a type requirement in a requires expression.
type TypeRequirement struct {
	Type AST
}

func (tr *TypeRequirement) print(ps *printState) {
	ps.writeString(" typename ")
	ps.print(tr.Type)
	ps.writeByte(';')
}

func (tr *TypeRequirement) Traverse(fn func(AST) bool) {
	if fn(tr) {
		tr.Type.Traverse(fn)
	}
}

func (tr *TypeRequirement) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(tr) {
		return nil
	}
	typ := tr.Type.Copy(fn, skip)
	if typ == nil {
		return fn(tr)
	}
	tr = &TypeRequirement{Type: typ}
	if r := fn(tr); r != nil {
		return r
	}
	return tr
}

func (tr *TypeRequirement) GoString() string {
	return tr.goString(0, "")
}

func (tr *TypeRequirement) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sTypeRequirement:\n%s", indent, "", field,
		tr.Type.goString(indent+2, ""))
}

// NestedRequirement is a nested requirement in a requires expression.
type NestedRequirement struct {
	Constraint AST
}

func (nr *NestedRequirement) print(ps *printState) {
	ps.writeString(" requires ")
	ps.print(nr.Constraint)
	ps.writeByte(';')
}

func (nr *NestedRequirement) Traverse(fn func(AST) bool) {
	if fn(nr) {
		nr.Constraint.Traverse(fn)
	}
}

func (nr *NestedRequirement) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(nr) {
		return nil
	}
	constraint := nr.Constraint.Copy(fn, skip)
	if constraint == nil {
		return fn(nr)
	}
	nr = &NestedRequirement{Constraint: constraint}
	if r := fn(nr); r != nil {
		return r
	}
	return nr
}

func (nr *NestedRequirement) GoString() string {
	return nr.goString(0, "")
}

func (nr *NestedRequirement) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sNestedRequirement:\n%s", indent, "", field,
		nr.Constraint.goString(indent+2, ""))
}

// ExplicitObjectParameter represents a C++23 explicit object parameter.
type ExplicitObjectParameter struct {
	Base AST
}

func (eop *ExplicitObjectParameter) print(ps *printState) {
	ps.writeString("this ")
	ps.print(eop.Base)
}

func (eop *ExplicitObjectParameter) Traverse(fn func(AST) bool) {
	if fn(eop) {
		eop.Base.Traverse(fn)
	}
}

func (eop *ExplicitObjectParameter) Copy(fn func(AST) AST, skip func(AST) bool) AST {
	if skip(eop) {
		return nil
	}
	base := eop.Base.Copy(fn, skip)
	if base == nil {
		return fn(eop)
	}
	eop = &ExplicitObjectParameter{Base: base}
	if r := fn(eop); r != nil {
		return r
	}
	return eop
}

func (eop *ExplicitObjectParameter) GoString() string {
	return eop.goString(0, "")
}

func (eop *ExplicitObjectParameter) goString(indent int, field string) string {
	return fmt.Sprintf("%*s%sExplicitObjectParameter:\n%s", indent, "", field,
		eop.Base.goString(indent+2, ""))
}

// Print the inner types.
func (ps *printState) printInner(prefixOnly bool) []AST {
	var save []AST
	var psave *[]AST
	if prefixOnly {
		psave = &save
	}
	for len(ps.inner) > 0 {
		ps.printOneInner(psave)
	}
	return save
}

// innerPrinter is an interface for types that can print themselves as
// inner types.
type innerPrinter interface {
	printInner(*printState)
}

// Print the most recent inner type.  If save is not nil, only print
// prefixes.
func (ps *printState) printOneInner(save *[]AST) {
	if len(ps.inner) == 0 {
		panic("printOneInner called with no inner types")
	}
	ln := len(ps.inner)
	a := ps.inner[ln-1]
	ps.inner = ps.inner[:ln-1]

	if save != nil {
		if _, ok := a.(*MethodWithQualifiers); ok {
			*save = append(*save, a)
			return
		}
	}

	if ip, ok := a.(innerPrinter); ok {
		ip.printInner(ps)
	} else {
		ps.print(a)
	}
}

// isEmpty returns whether printing a will not print anything.
func (ps *printState) isEmpty(a AST) bool {
	switch a := a.(type) {
	case *ArgumentPack:
		for _, a := range a.Args {
			if !ps.isEmpty(a) {
				return false
			}
		}
		return true
	case *ExprList:
		return len(a.Exprs) == 0
	case *PackExpansion:
		return a.Pack != nil && ps.isEmpty(a.Base)
	default:
		return false
	}
}