internal/core/export/export.go - cue - Git at Google

 // Copyright 2020 CUE Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package export

 import (
 	"fmt"
 	"math/rand"

 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/ast/astutil"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/core/adt"
 	"cuelang.org/go/internal/core/eval"
 	"cuelang.org/go/internal/core/walk"
 )

 const debug = false

 type Profile struct {
 	Simplify bool

 	// Final reports incomplete errors as errors.
 	Final bool

 	// TakeDefaults is used in Value mode to drop non-default values.
 	TakeDefaults bool

 	ShowOptional    bool
 	ShowDefinitions bool

 	// ShowHidden forces the inclusion of hidden fields when these would
 	// otherwise be omitted. Only hidden fields from the current package are
 	// included.
 	ShowHidden     bool
 	ShowDocs       bool
 	ShowAttributes bool

 	// ShowErrors treats errors as values and will not percolate errors up.
 	ShowErrors bool
 	// Use unevaluated conjuncts for these error types
 	// IgnoreRecursive

 	// TODO: recurse over entire tree to determine transitive closure
 	// of what needs to be printed.
 	// IncludeDependencies bool
 }

 var Simplified = &Profile{
 	Simplify: true,
 	ShowDocs: true,
 }

 var Final = &Profile{
 	Simplify:     true,
 	TakeDefaults: true,
 	Final:        true,
 }

 var Raw = &Profile{
 	ShowOptional:    true,
 	ShowDefinitions: true,
 	ShowHidden:      true,
 	ShowDocs:        true,
 }

 var All = &Profile{
 	Simplify:        true,
 	ShowOptional:    true,
 	ShowDefinitions: true,
 	ShowHidden:      true,
 	ShowDocs:        true,
 	ShowAttributes:  true,
 }

 // Concrete

 // Def exports v as a definition.
 func Def(r adt.Runtime, pkgID string, v *adt.Vertex) (*ast.File, errors.Error) {
 	return All.Def(r, pkgID, v)
 }

 // Def exports v as a definition.
 func (p *Profile) Def(r adt.Runtime, pkgID string, v *adt.Vertex) (*ast.File, errors.Error) {
 	e := newExporter(p, r, pkgID, v)
 	e.markUsedFeatures(v)

 	isDef := v.IsRecursivelyClosed()
 	if isDef {
 		e.inDefinition++
 	}

 	expr := e.expr(v)

 	if isDef {
 		e.inDefinition--
 		if v.Kind() == adt.StructKind {
 			expr = ast.NewStruct(
 				ast.Embed(ast.NewIdent("_#def")),
 				ast.NewIdent("_#def"), expr,
 			)
 		}
 	}
 	return e.toFile(v, expr)
 }

 func Expr(r adt.Runtime, pkgID string, n adt.Expr) (ast.Expr, errors.Error) {
 	return Simplified.Expr(r, pkgID, n)
 }

 func (p *Profile) Expr(r adt.Runtime, pkgID string, n adt.Expr) (ast.Expr, errors.Error) {
 	e := newExporter(p, r, pkgID, nil)
 	e.markUsedFeatures(n)

 	return e.expr(n), nil
 }

 func (e *exporter) toFile(v *adt.Vertex, x ast.Expr) (*ast.File, errors.Error) {
 	f := &ast.File{}

 	pkgName := ""
 	pkg := &ast.Package{}
 	for _, c := range v.Conjuncts {
 		f, _ := c.Source().(*ast.File)
 		if f == nil {
 			continue
 		}

 		if _, name, _ := internal.PackageInfo(f); name != "" {
 			pkgName = name
 		}

 		if e.cfg.ShowDocs {
 			if doc := internal.FileComment(f); doc != nil {
 				ast.AddComment(pkg, doc)
 			}
 		}
 	}

 	if pkgName != "" {
 		pkg.Name = ast.NewIdent(pkgName)
 		f.Decls = append(f.Decls, pkg)
 	}

 	switch st := x.(type) {
 	case nil:
 		panic("null input")

 	case *ast.StructLit:
 		f.Decls = append(f.Decls, st.Elts...)

 	default:
 		f.Decls = append(f.Decls, &ast.EmbedDecl{Expr: x})
 	}
 	if err := astutil.Sanitize(f); err != nil {
 		err := errors.Promote(err, "export")
 		return f, errors.Append(e.errs, err)
 	}

 	return f, nil
 }

 // File

 func Vertex(r adt.Runtime, pkgID string, n *adt.Vertex) (*ast.File, errors.Error) {
 	return Simplified.Vertex(r, pkgID, n)
 }

 func (p *Profile) Vertex(r adt.Runtime, pkgID string, n *adt.Vertex) (*ast.File, errors.Error) {
 	e := exporter{
 		ctx:   eval.NewContext(r, nil),
 		cfg:   p,
 		index: r,
 		pkgID: pkgID,
 	}
 	e.markUsedFeatures(n)
 	v := e.value(n, n.Conjuncts...)

 	return e.toFile(n, v)
 }

 func Value(r adt.Runtime, pkgID string, n adt.Value) (ast.Expr, errors.Error) {
 	return Simplified.Value(r, pkgID, n)
 }

 // Should take context.
 func (p *Profile) Value(r adt.Runtime, pkgID string, n adt.Value) (ast.Expr, errors.Error) {
 	e := exporter{
 		ctx:   eval.NewContext(r, nil),
 		cfg:   p,
 		index: r,
 		pkgID: pkgID,
 	}
 	e.markUsedFeatures(n)
 	v := e.value(n)
 	return v, e.errs
 }

 type exporter struct {
 	cfg  *Profile // Make value todo
 	errs errors.Error

 	ctx *adt.OpContext

 	index adt.StringIndexer
 	rand  *rand.Rand

 	// For resolving up references.
 	stack []frame

 	inDefinition int // for close() wrapping.

 	// hidden label handling
 	pkgID  string
 	hidden map[string]adt.Feature // adt.InvalidFeatures means more than one.

 	// If a used feature maps to an expression, it means it is assigned to a
 	// unique let expression.
 	usedFeature map[adt.Feature]adt.Expr
 	labelAlias  map[adt.Expr]adt.Feature
 	valueAlias  map[*ast.Alias]*ast.Alias

 	usedHidden map[string]bool
 }

 func newExporter(p *Profile, r adt.Runtime, pkgID string, v *adt.Vertex) *exporter {
 	return &exporter{
 		cfg:   p,
 		ctx:   eval.NewContext(r, v),
 		index: r,
 		pkgID: pkgID,
 	}
 }

 func (e *exporter) markUsedFeatures(x adt.Expr) {
 	e.usedFeature = make(map[adt.Feature]adt.Expr)

 	w := &walk.Visitor{}
 	w.Before = func(n adt.Node) bool {
 		switch x := n.(type) {
 		case *adt.Vertex:
 			if !x.IsData() {
 				for _, c := range x.Conjuncts {
 					w.Expr(c.Expr())
 				}
 			}

 		case *adt.DynamicReference:
 			if e.labelAlias == nil {
 				e.labelAlias = make(map[adt.Expr]adt.Feature)
 			}
 			// TODO: add preferred label.
 			e.labelAlias[x.Label] = adt.InvalidLabel

 		case *adt.LabelReference:
 		}
 		return true
 	}

 	w.Feature = func(f adt.Feature, src adt.Node) {
 		_, ok := e.usedFeature[f]

 		switch x := src.(type) {
 		case *adt.LetReference:
 			if !ok {
 				e.usedFeature[f] = x.X
 			}

 		default:
 			e.usedFeature[f] = nil
 		}
 	}

 	w.Expr(x)
 }

 func (e *exporter) getFieldAlias(f *ast.Field, name string) string {
 	a, ok := f.Label.(*ast.Alias)
 	if !ok {
 		a = &ast.Alias{
 			Ident: ast.NewIdent(e.uniqueAlias(name)),
 			Expr:  f.Label.(ast.Expr),
 		}
 		f.Label = a
 	}
 	return a.Ident.Name
 }

 func setFieldAlias(f *ast.Field, name string) {
 	if _, ok := f.Label.(*ast.Alias); !ok {
 		f.Label = &ast.Alias{
 			Ident: ast.NewIdent(name),
 			Expr:  f.Label.(ast.Expr),
 		}
 	}
 }

 // uniqueLetIdent returns a name for a let identifier that uniquely identifies
 // the given expression. If the preferred name is already taken, a new globally
 // unique name of the form base_X ... base_XXXXXXXXXXXXXX is generated.
 //
 // It prefers short extensions over large ones, while ensuring the likelihood of
 // fast termination is high. There are at least two digits to make it visually
 // clearer this concerns a generated number.
 //
 func (e exporter) uniqueLetIdent(f adt.Feature, x adt.Expr) adt.Feature {
 	if e.usedFeature[f] == x {
 		return f
 	}

 	f, _ = e.uniqueFeature(f.IdentString(e.ctx))
 	e.usedFeature[f] = x
 	return f
 }

 func (e exporter) uniqueAlias(name string) string {
 	f := adt.MakeIdentLabel(e.ctx, name, "")

 	if _, ok := e.usedFeature[f]; !ok {
 		e.usedFeature[f] = nil
 		return name
 	}

 	_, name = e.uniqueFeature(f.IdentString(e.ctx))
 	return name
 }

 func (e exporter) uniqueFeature(base string) (f adt.Feature, name string) {
 	if e.rand == nil {
 		e.rand = rand.New(rand.NewSource(808))
 	}

 	const mask = 0xff_ffff_ffff_ffff // max bits; stay clear of int64 overflow
 	const shift = 4                  // rate of growth
 	for n := int64(0x10); ; n = int64(mask&((n<<shift)-1)) + 1 {
 		num := e.rand.Intn(int(n))
 		name := fmt.Sprintf("%s_%01X", base, num)
 		f := adt.MakeIdentLabel(e.ctx, name, "")
 		if _, ok := e.usedFeature[f]; !ok {
 			e.usedFeature[f] = nil
 			return f, name
 		}
 	}
 }

 type completeFunc func(scope *ast.StructLit, m adt.Node)

 type frame struct {
 	scope *ast.StructLit
 	todo  []completeFunc

 	docSources []adt.Conjunct

 	// For resolving dynamic fields.
 	field     *ast.Field
 	labelExpr ast.Expr
 	upCount   int32 // for off-by-one handling

 	// labeled fields
 	fields map[adt.Feature]entry
 	let    map[adt.Expr]*ast.LetClause

 	// field to new field
 	mapped map[adt.Node]ast.Node
 }

 type entry struct {
 	alias      string
 	field      *ast.Field
 	node       ast.Node // How to reference. See astutil.Resolve
 	references []*ast.Ident
 }

 func (e *exporter) addField(label adt.Feature, f *ast.Field, n ast.Node) {
 	frame := e.top()
 	entry := frame.fields[label]
 	entry.field = f
 	entry.node = n
 	frame.fields[label] = entry
 }

 func (e *exporter) addEmbed(x ast.Expr) {
 	frame := e.top()
 	frame.scope.Elts = append(frame.scope.Elts, x)
 }

 func (e *exporter) pushFrame(conjuncts []adt.Conjunct) (s *ast.StructLit, saved []frame) {
 	saved = e.stack
 	s = &ast.StructLit{}
 	e.stack = append(e.stack, frame{
 		scope:      s,
 		mapped:     map[adt.Node]ast.Node{},
 		fields:     map[adt.Feature]entry{},
 		docSources: conjuncts,
 	})
 	return s, saved
 }

 func (e *exporter) popFrame(saved []frame) {
 	top := e.stack[len(e.stack)-1]

 	for _, f := range top.fields {
 		node := f.node
 		if f.alias != "" && f.field != nil {
 			setFieldAlias(f.field, f.alias)
 			node = f.field
 		}
 		for _, r := range f.references {
 			r.Node = node
 		}
 	}

 	e.stack = saved
 }

 func (e *exporter) top() *frame {
 	return &(e.stack[len(e.stack)-1])
 }

 func (e *exporter) frame(upCount int32) *frame {
 	for i := len(e.stack) - 1; i >= 0; i-- {
 		f := &(e.stack[i])
 		if upCount <= (f.upCount - 1) {
 			return f
 		}
 		upCount -= f.upCount
 	}
 	if debug {
 		// This may be valid when exporting incomplete references. These are
 		// not yet handled though, so find a way to catch them when debugging
 		// printing of values that are supposed to be complete.
 		panic("unreachable reference")
 	}

 	return &frame{}
 }

 func (e *exporter) setDocs(x adt.Node) {
 	f := e.stack[len(e.stack)-1]
 	f.docSources = []adt.Conjunct{adt.MakeRootConjunct(nil, x)}
 	e.stack[len(e.stack)-1] = f
 }

 // func (e *Exporter) promise(upCount int32, f completeFunc) {
 // 	e.todo = append(e.todo, f)
 // }

 func (e *exporter) errf(format string, args ...interface{}) *ast.BottomLit {
 	err := &exporterError{}
 	e.errs = errors.Append(e.errs, err)
 	return &ast.BottomLit{}
 }

 type errTODO errors.Error

 type exporterError struct {
 	errTODO
 }
	// Copyright 2020 CUE Authors
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package export

	import (
	"fmt"
	"math/rand"

	"cuelang.org/go/cue/ast"
	"cuelang.org/go/cue/ast/astutil"
	"cuelang.org/go/cue/errors"
	"cuelang.org/go/internal"
	"cuelang.org/go/internal/core/adt"
	"cuelang.org/go/internal/core/eval"
	"cuelang.org/go/internal/core/walk"
	)

	const debug = false

	type Profile struct {
	Simplify bool

	// Final reports incomplete errors as errors.
	Final bool

	// TakeDefaults is used in Value mode to drop non-default values.
	TakeDefaults bool

	ShowOptional bool
	ShowDefinitions bool

	// ShowHidden forces the inclusion of hidden fields when these would
	// otherwise be omitted. Only hidden fields from the current package are
	// included.
	ShowHidden bool
	ShowDocs bool
	ShowAttributes bool

	// ShowErrors treats errors as values and will not percolate errors up.
	ShowErrors bool
	// Use unevaluated conjuncts for these error types
	// IgnoreRecursive

	// TODO: recurse over entire tree to determine transitive closure
	// of what needs to be printed.
	// IncludeDependencies bool
	}

	var Simplified = &Profile{
	Simplify: true,
	ShowDocs: true,
	}

	var Final = &Profile{
	Simplify: true,
	TakeDefaults: true,
	Final: true,
	}

	var Raw = &Profile{
	ShowOptional: true,
	ShowDefinitions: true,
	ShowHidden: true,
	ShowDocs: true,
	}

	var All = &Profile{
	Simplify: true,
	ShowOptional: true,
	ShowDefinitions: true,
	ShowHidden: true,
	ShowDocs: true,
	ShowAttributes: true,
	}

	// Concrete

	// Def exports v as a definition.
	func Def(r adt.Runtime, pkgID string, v adt.Vertex) (ast.File, errors.Error) {
	return All.Def(r, pkgID, v)
	}

	// Def exports v as a definition.
	func (p Profile) Def(r adt.Runtime, pkgID string, v adt.Vertex) (*ast.File, errors.Error) {
	e := newExporter(p, r, pkgID, v)
	e.markUsedFeatures(v)

	isDef := v.IsRecursivelyClosed()
	if isDef {
	e.inDefinition++
	}

	expr := e.expr(v)

	if isDef {
	e.inDefinition--
	if v.Kind() == adt.StructKind {
	expr = ast.NewStruct(
	ast.Embed(ast.NewIdent("_#def")),
	ast.NewIdent("_#def"), expr,
	)
	}
	}
	return e.toFile(v, expr)
	}

	func Expr(r adt.Runtime, pkgID string, n adt.Expr) (ast.Expr, errors.Error) {
	return Simplified.Expr(r, pkgID, n)
	}

	func (p *Profile) Expr(r adt.Runtime, pkgID string, n adt.Expr) (ast.Expr, errors.Error) {
	e := newExporter(p, r, pkgID, nil)
	e.markUsedFeatures(n)

	return e.expr(n), nil
	}

	func (e exporter) toFile(v adt.Vertex, x ast.Expr) (*ast.File, errors.Error) {
	f := &ast.File{}

	pkgName := ""
	pkg := &ast.Package{}
	for _, c := range v.Conjuncts {
	f, _ := c.Source().(*ast.File)
	if f == nil {
	continue
	}

	if _, name, _ := internal.PackageInfo(f); name != "" {
	pkgName = name
	}

	if e.cfg.ShowDocs {
	if doc := internal.FileComment(f); doc != nil {
	ast.AddComment(pkg, doc)
	}
	}
	}

	if pkgName != "" {
	pkg.Name = ast.NewIdent(pkgName)
	f.Decls = append(f.Decls, pkg)
	}

	switch st := x.(type) {
	case nil:
	panic("null input")

	case *ast.StructLit:
	f.Decls = append(f.Decls, st.Elts...)

	default:
	f.Decls = append(f.Decls, &ast.EmbedDecl{Expr: x})
	}
	if err := astutil.Sanitize(f); err != nil {
	err := errors.Promote(err, "export")
	return f, errors.Append(e.errs, err)
	}

	return f, nil
	}

	// File

	func Vertex(r adt.Runtime, pkgID string, n adt.Vertex) (ast.File, errors.Error) {
	return Simplified.Vertex(r, pkgID, n)
	}

	func (p Profile) Vertex(r adt.Runtime, pkgID string, n adt.Vertex) (*ast.File, errors.Error) {
	e := exporter{
	ctx: eval.NewContext(r, nil),
	cfg: p,
	index: r,
	pkgID: pkgID,
	}
	e.markUsedFeatures(n)
	v := e.value(n, n.Conjuncts...)

	return e.toFile(n, v)
	}

	func Value(r adt.Runtime, pkgID string, n adt.Value) (ast.Expr, errors.Error) {
	return Simplified.Value(r, pkgID, n)
	}

	// Should take context.
	func (p *Profile) Value(r adt.Runtime, pkgID string, n adt.Value) (ast.Expr, errors.Error) {
	e := exporter{
	ctx: eval.NewContext(r, nil),
	cfg: p,
	index: r,
	pkgID: pkgID,
	}
	e.markUsedFeatures(n)
	v := e.value(n)
	return v, e.errs
	}

	type exporter struct {
	cfg *Profile // Make value todo
	errs errors.Error

	ctx *adt.OpContext

	index adt.StringIndexer
	rand *rand.Rand

	// For resolving up references.
	stack []frame

	inDefinition int // for close() wrapping.

	// hidden label handling
	pkgID string
	hidden map[string]adt.Feature // adt.InvalidFeatures means more than one.

	// If a used feature maps to an expression, it means it is assigned to a
	// unique let expression.
	usedFeature map[adt.Feature]adt.Expr
	labelAlias map[adt.Expr]adt.Feature
	valueAlias map[ast.Alias]ast.Alias

	usedHidden map[string]bool
	}

	func newExporter(p Profile, r adt.Runtime, pkgID string, v adt.Vertex) *exporter {
	return &exporter{
	cfg: p,
	ctx: eval.NewContext(r, v),
	index: r,
	pkgID: pkgID,
	}
	}

	func (e *exporter) markUsedFeatures(x adt.Expr) {
	e.usedFeature = make(map[adt.Feature]adt.Expr)

	w := &walk.Visitor{}
	w.Before = func(n adt.Node) bool {
	switch x := n.(type) {
	case *adt.Vertex:
	if !x.IsData() {
	for _, c := range x.Conjuncts {
	w.Expr(c.Expr())
	}
	}

	case *adt.DynamicReference:
	if e.labelAlias == nil {
	e.labelAlias = make(map[adt.Expr]adt.Feature)
	}
	// TODO: add preferred label.
	e.labelAlias[x.Label] = adt.InvalidLabel

	case *adt.LabelReference:
	}
	return true
	}

	w.Feature = func(f adt.Feature, src adt.Node) {
	_, ok := e.usedFeature[f]

	switch x := src.(type) {
	case *adt.LetReference:
	if !ok {
	e.usedFeature[f] = x.X
	}

	default:
	e.usedFeature[f] = nil
	}
	}

	w.Expr(x)
	}

	func (e exporter) getFieldAlias(f ast.Field, name string) string {
	a, ok := f.Label.(*ast.Alias)
	if !ok {
	a = &ast.Alias{
	Ident: ast.NewIdent(e.uniqueAlias(name)),
	Expr: f.Label.(ast.Expr),
	}
	f.Label = a
	}
	return a.Ident.Name
	}

	func setFieldAlias(f *ast.Field, name string) {
	if _, ok := f.Label.(*ast.Alias); !ok {
	f.Label = &ast.Alias{
	Ident: ast.NewIdent(name),
	Expr: f.Label.(ast.Expr),
	}
	}
	}

	// uniqueLetIdent returns a name for a let identifier that uniquely identifies
	// the given expression. If the preferred name is already taken, a new globally
	// unique name of the form base_X ... base_XXXXXXXXXXXXXX is generated.
	//
	// It prefers short extensions over large ones, while ensuring the likelihood of
	// fast termination is high. There are at least two digits to make it visually
	// clearer this concerns a generated number.
	//
	func (e exporter) uniqueLetIdent(f adt.Feature, x adt.Expr) adt.Feature {
	if e.usedFeature[f] == x {
	return f
	}

	f, _ = e.uniqueFeature(f.IdentString(e.ctx))
	e.usedFeature[f] = x
	return f
	}

	func (e exporter) uniqueAlias(name string) string {
	f := adt.MakeIdentLabel(e.ctx, name, "")

	if _, ok := e.usedFeature[f]; !ok {
	e.usedFeature[f] = nil
	return name
	}

	_, name = e.uniqueFeature(f.IdentString(e.ctx))
	return name
	}

	func (e exporter) uniqueFeature(base string) (f adt.Feature, name string) {
	if e.rand == nil {
	e.rand = rand.New(rand.NewSource(808))
	}

	const mask = 0xff_ffff_ffff_ffff // max bits; stay clear of int64 overflow
	const shift = 4 // rate of growth
	for n := int64(0x10); ; n = int64(mask&((n<<shift)-1)) + 1 {
	num := e.rand.Intn(int(n))
	name := fmt.Sprintf("%s_%01X", base, num)
	f := adt.MakeIdentLabel(e.ctx, name, "")
	if _, ok := e.usedFeature[f]; !ok {
	e.usedFeature[f] = nil
	return f, name
	}
	}
	}

	type completeFunc func(scope *ast.StructLit, m adt.Node)

	type frame struct {
	scope *ast.StructLit
	todo []completeFunc

	docSources []adt.Conjunct

	// For resolving dynamic fields.
	field *ast.Field
	labelExpr ast.Expr
	upCount int32 // for off-by-one handling

	// labeled fields
	fields map[adt.Feature]entry
	let map[adt.Expr]*ast.LetClause

	// field to new field
	mapped map[adt.Node]ast.Node
	}

	type entry struct {
	alias string
	field *ast.Field
	node ast.Node // How to reference. See astutil.Resolve
	references []*ast.Ident
	}

	func (e exporter) addField(label adt.Feature, f ast.Field, n ast.Node) {
	frame := e.top()
	entry := frame.fields[label]
	entry.field = f
	entry.node = n
	frame.fields[label] = entry
	}

	func (e *exporter) addEmbed(x ast.Expr) {
	frame := e.top()
	frame.scope.Elts = append(frame.scope.Elts, x)
	}

	func (e exporter) pushFrame(conjuncts []adt.Conjunct) (s ast.StructLit, saved []frame) {
	saved = e.stack
	s = &ast.StructLit{}
	e.stack = append(e.stack, frame{
	scope: s,
	mapped: map[adt.Node]ast.Node{},
	fields: map[adt.Feature]entry{},
	docSources: conjuncts,
	})
	return s, saved
	}

	func (e *exporter) popFrame(saved []frame) {
	top := e.stack[len(e.stack)-1]

	for _, f := range top.fields {
	node := f.node
	if f.alias != "" && f.field != nil {
	setFieldAlias(f.field, f.alias)
	node = f.field
	}
	for _, r := range f.references {
	r.Node = node
	}
	}

	e.stack = saved
	}

	func (e exporter) top() frame {
	return &(e.stack[len(e.stack)-1])
	}

	func (e exporter) frame(upCount int32) frame {
	for i := len(e.stack) - 1; i >= 0; i-- {
	f := &(e.stack[i])
	if upCount <= (f.upCount - 1) {
	return f
	}
	upCount -= f.upCount
	}
	if debug {
	// This may be valid when exporting incomplete references. These are
	// not yet handled though, so find a way to catch them when debugging
	// printing of values that are supposed to be complete.
	panic("unreachable reference")
	}

	return &frame{}
	}

	func (e *exporter) setDocs(x adt.Node) {
	f := e.stack[len(e.stack)-1]
	f.docSources = []adt.Conjunct{adt.MakeRootConjunct(nil, x)}
	e.stack[len(e.stack)-1] = f
	}

	// func (e *Exporter) promise(upCount int32, f completeFunc) {
	// e.todo = append(e.todo, f)
	// }

	func (e exporter) errf(format string, args ...interface{}) ast.BottomLit {
	err := &exporterError{}
	e.errs = errors.Append(e.errs, err)
	return &ast.BottomLit{}
	}

	type errTODO errors.Error

	type exporterError struct {
	errTODO
	}