internal/core/debug/debug.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 debug prints a given ADT node.
 //
 // Note that the result is not valid CUE, but instead prints the internals
 // of an ADT node in human-readable form. It uses a simple indentation algorithm
 // for improved readability and diffing.
 //
 package debug

 import (
 	"fmt"
 	"io"
 	"strconv"
 	"strings"

 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/literal"
 	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/core/adt"
 )

 const (
 	openTuple  = "\u3008"
 	closeTuple = "\u3009"
 )

 type Config struct {
 	Cwd     string
 	Compact bool
 	Raw     bool
 }

 func WriteNode(w io.Writer, i adt.StringIndexer, n adt.Node, config *Config) {
 	if config == nil {
 		config = &Config{}
 	}
 	p := printer{Writer: w, index: i, cfg: config}
 	if config.Compact {
 		p := compactPrinter{p}
 		p.node(n)
 	} else {
 		p.node(n)
 	}
 }

 func NodeString(i adt.StringIndexer, n adt.Node, config *Config) string {
 	b := &strings.Builder{}
 	WriteNode(b, i, n, config)
 	return b.String()
 }

 type printer struct {
 	io.Writer
 	index  adt.StringIndexer
 	indent string
 	cfg    *Config

 	// modes:
 	// - show vertex
 	// - show original conjuncts
 	// - show unevaluated
 	// - auto
 }

 func (w *printer) string(s string) {
 	s = strings.Replace(s, "\n", "\n"+w.indent, -1)
 	_, _ = io.WriteString(w, s)
 }

 func (w *printer) label(f adt.Feature) {
 	w.string(w.labelString(f))
 }

 func (w *printer) ident(f adt.Feature) {
 	w.string(f.IdentString(w.index))
 }

 // TODO: fold into label once :: is no longer supported.
 func (w *printer) labelString(f adt.Feature) string {
 	if f.IsHidden() {
 		ident := f.IdentString(w.index)
 		if pkgName := f.PkgID(w.index); pkgName != "_" {
 			ident = fmt.Sprintf("%s(%s)", ident, pkgName)
 		}
 		return ident
 	}
 	return f.SelectorString(w.index)
 }

 func (w *printer) shortError(errs errors.Error) {
 	for {
 		msg, args := errs.Msg()
 		fmt.Fprintf(w, msg, args...)

 		err := errors.Unwrap(errs)
 		if err == nil {
 			break
 		}

 		if errs, _ = err.(errors.Error); errs != nil {
 			w.string(err.Error())
 			break
 		}
 	}
 }

 func (w *printer) interpolation(x *adt.Interpolation) {
 	quote := `"`
 	if x.K == adt.BytesKind {
 		quote = `'`
 	}
 	w.string(quote)
 	for i := 0; i < len(x.Parts); i += 2 {
 		switch x.K {
 		case adt.StringKind:
 			if s, ok := x.Parts[i].(*adt.String); ok {
 				w.string(s.Str)
 			} else {
 				w.string("<bad string>")
 			}
 		case adt.BytesKind:
 			if s, ok := x.Parts[i].(*adt.Bytes); ok {
 				_, _ = w.Write(s.B)
 			} else {
 				w.string("<bad bytes>")
 			}
 		}
 		if i+1 < len(x.Parts) {
 			w.string(`\(`)
 			w.node(x.Parts[i+1])
 			w.string(`)`)
 		}
 	}
 	w.string(quote)
 }

 func (w *printer) node(n adt.Node) {
 	switch x := n.(type) {
 	case *adt.Vertex:
 		var kind adt.Kind
 		if x.BaseValue != nil {
 			kind = x.BaseValue.Kind()
 		}

 		kindStr := kind.String()

 		// TODO: replace with showing full closedness data.
 		if x.IsClosedList() || x.IsClosedStruct() {
 			if kind == adt.ListKind || kind == adt.StructKind {
 				kindStr = "#" + kindStr
 			}
 		}

 		fmt.Fprintf(w, "(%s){", kindStr)

 		saved := w.indent
 		w.indent += "  "
 		defer func() { w.indent = saved }()

 		switch v := x.BaseValue.(type) {
 		case nil:
 		case *adt.Bottom:
 			// TODO: reuse bottom.
 			saved := w.indent
 			w.indent += "// "
 			w.string("\n")
 			fmt.Fprintf(w, "[%v]", v.Code)
 			if !v.ChildError {
 				msg := errors.Details(v.Err, &errors.Config{
 					Cwd:     w.cfg.Cwd,
 					ToSlash: true,
 				})
 				msg = strings.TrimSpace(msg)
 				if msg != "" {
 					w.string(" ")
 					w.string(msg)
 				}
 			}
 			w.indent = saved

 		case *adt.StructMarker, *adt.ListMarker:
 			// if len(x.Arcs) == 0 {
 			// 	// w.string("}")
 			// 	// return
 			// }

 		case adt.Value:
 			if len(x.Arcs) == 0 {
 				w.string(" ")
 				w.node(v)
 				w.string(" }")
 				return
 			}
 			w.string("\n")
 			w.node(v)
 		}

 		for _, a := range x.Arcs {
 			w.string("\n")
 			w.label(a.Label)
 			w.string(": ")
 			w.node(a)
 		}

 		if x.BaseValue == nil {
 			w.indent += "// "
 			w.string("// ")
 			for i, c := range x.Conjuncts {
 				if i > 0 {
 					w.string(" & ")
 				}
 				w.node(c.Expr()) // TODO: also include env?
 			}
 		}

 		w.indent = saved
 		w.string("\n")
 		w.string("}")

 	case *adt.StructMarker:
 		w.string("struct")

 	case *adt.ListMarker:
 		w.string("list")

 	case *adt.StructLit:
 		if len(x.Decls) == 0 {
 			w.string("{}")
 			break
 		}
 		w.string("{")
 		w.indent += "  "
 		for _, d := range x.Decls {
 			w.string("\n")
 			w.node(d)
 		}
 		w.indent = w.indent[:len(w.indent)-2]
 		w.string("\n}")

 	case *adt.ListLit:
 		if len(x.Elems) == 0 {
 			w.string("[]")
 			break
 		}
 		w.string("[")
 		w.indent += "  "
 		for _, d := range x.Elems {
 			w.string("\n")
 			w.node(d)
 			w.string(",")
 		}
 		w.indent = w.indent[:len(w.indent)-2]
 		w.string("\n]")

 	case *adt.Field:
 		s := w.labelString(x.Label)
 		w.string(s)
 		w.string(":")
 		if x.Label.IsDef() && !internal.IsDef(s) {
 			w.string(":")
 		}
 		w.string(" ")
 		w.node(x.Value)

 	case *adt.OptionalField:
 		s := w.labelString(x.Label)
 		w.string(s)
 		w.string("?:")
 		if x.Label.IsDef() && !internal.IsDef(s) {
 			w.string(":")
 		}
 		w.string(" ")
 		w.node(x.Value)

 	case *adt.BulkOptionalField:
 		w.string("[")
 		w.node(x.Filter)
 		w.string("]: ")
 		w.node(x.Value)

 	case *adt.DynamicField:
 		w.node(x.Key)
 		if x.IsOptional() {
 			w.string("?")
 		}
 		w.string(": ")
 		w.node(x.Value)

 	case *adt.Ellipsis:
 		w.string("...")
 		if x.Value != nil {
 			w.node(x.Value)
 		}

 	case *adt.Bottom:
 		w.string(`_|_`)
 		if x.Err != nil {
 			w.string("(")
 			w.shortError(x.Err)
 			w.string(")")
 		}

 	case *adt.Null:
 		w.string("null")

 	case *adt.Bool:
 		fmt.Fprint(w, x.B)

 	case *adt.Num:
 		fmt.Fprint(w, &x.X)

 	case *adt.String:
 		w.string(literal.String.Quote(x.Str))

 	case *adt.Bytes:
 		w.string(literal.Bytes.Quote(string(x.B)))

 	case *adt.Top:
 		w.string("_")

 	case *adt.BasicType:
 		fmt.Fprint(w, x.K)

 	case *adt.BoundExpr:
 		fmt.Fprint(w, x.Op)
 		w.node(x.Expr)

 	case *adt.BoundValue:
 		fmt.Fprint(w, x.Op)
 		w.node(x.Value)

 	case *adt.NodeLink:
 		w.string(openTuple)
 		for i, f := range x.Node.Path() {
 			if i > 0 {
 				w.string(".")
 			}
 			w.label(f)
 		}
 		w.string(closeTuple)

 	case *adt.FieldReference:
 		w.string(openTuple)
 		w.string(strconv.Itoa(int(x.UpCount)))
 		w.string(";")
 		w.label(x.Label)
 		w.string(closeTuple)

 	case *adt.LabelReference:
 		w.string(openTuple)
 		w.string(strconv.Itoa(int(x.UpCount)))
 		w.string(";-")
 		w.string(closeTuple)

 	case *adt.DynamicReference:
 		w.string(openTuple)
 		w.string(strconv.Itoa(int(x.UpCount)))
 		w.string(";(")
 		w.node(x.Label)
 		w.string(")")
 		w.string(closeTuple)

 	case *adt.ImportReference:
 		w.string(openTuple + "import;")
 		w.label(x.ImportPath)
 		w.string(closeTuple)

 	case *adt.LetReference:
 		w.string(openTuple)
 		w.string(strconv.Itoa(int(x.UpCount)))
 		w.string(";let ")
 		w.ident(x.Label)
 		w.string(closeTuple)

 	case *adt.SelectorExpr:
 		w.node(x.X)
 		w.string(".")
 		w.label(x.Sel)

 	case *adt.IndexExpr:
 		w.node(x.X)
 		w.string("[")
 		w.node(x.Index)
 		w.string("]")

 	case *adt.SliceExpr:
 		w.node(x.X)
 		w.string("[")
 		if x.Lo != nil {
 			w.node(x.Lo)
 		}
 		w.string(":")
 		if x.Hi != nil {
 			w.node(x.Hi)
 		}
 		if x.Stride != nil {
 			w.string(":")
 			w.node(x.Stride)
 		}
 		w.string("]")

 	case *adt.Interpolation:
 		w.interpolation(x)

 	case *adt.UnaryExpr:
 		fmt.Fprint(w, x.Op)
 		w.node(x.X)

 	case *adt.BinaryExpr:
 		w.string("(")
 		w.node(x.X)
 		fmt.Fprint(w, " ", x.Op, " ")
 		w.node(x.Y)
 		w.string(")")

 	case *adt.CallExpr:
 		w.node(x.Fun)
 		w.string("(")
 		for i, a := range x.Args {
 			if i > 0 {
 				w.string(", ")
 			}
 			w.node(a)
 		}
 		w.string(")")

 	case *adt.Builtin:
 		if x.Package != 0 {
 			w.label(x.Package)
 			w.string(".")
 		}
 		w.string(x.Name)

 	case *adt.BuiltinValidator:
 		w.node(x.Builtin)
 		w.string("(")
 		for i, a := range x.Args {
 			if i > 0 {
 				w.string(", ")
 			}
 			w.node(a)
 		}
 		w.string(")")

 	case *adt.DisjunctionExpr:
 		w.string("(")
 		for i, a := range x.Values {
 			if i > 0 {
 				w.string("|")
 			}
 			// Disjunct
 			if a.Default {
 				w.string("*")
 			}
 			w.node(a.Val)
 		}
 		w.string(")")

 	case *adt.Conjunction:
 		w.string("&(")
 		for i, c := range x.Values {
 			if i > 0 {
 				w.string(", ")
 			}
 			w.node(c)
 		}
 		w.string(")")

 	case *adt.Disjunction:
 		w.string("|(")
 		for i, c := range x.Values {
 			if i > 0 {
 				w.string(", ")
 			}
 			if i < x.NumDefaults {
 				w.string("*")
 			}
 			w.node(c)
 		}
 		w.string(")")

 	case *adt.ForClause:
 		w.string("for ")
 		w.ident(x.Key)
 		w.string(", ")
 		w.ident(x.Value)
 		w.string(" in ")
 		w.node(x.Src)
 		w.string(" ")
 		w.node(x.Dst)

 	case *adt.IfClause:
 		w.string("if ")
 		w.node(x.Condition)
 		w.string(" ")
 		w.node(x.Dst)

 	case *adt.LetClause:
 		w.string("let ")
 		w.ident(x.Label)
 		w.string(" = ")
 		w.node(x.Expr)
 		w.string(" ")
 		w.node(x.Dst)

 	case *adt.ValueClause:
 		w.node(x.StructLit)

 	default:
 		panic(fmt.Sprintf("unknown type %T", x))
 	}
 }
	// 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 debug prints a given ADT node.
	//
	// Note that the result is not valid CUE, but instead prints the internals
	// of an ADT node in human-readable form. It uses a simple indentation algorithm
	// for improved readability and diffing.
	//
	package debug

	import (
	"fmt"
	"io"
	"strconv"
	"strings"

	"cuelang.org/go/cue/errors"
	"cuelang.org/go/cue/literal"
	"cuelang.org/go/internal"
	"cuelang.org/go/internal/core/adt"
	)

	const (
	openTuple = "\u3008"
	closeTuple = "\u3009"
	)

	type Config struct {
	Cwd string
	Compact bool
	Raw bool
	}

	func WriteNode(w io.Writer, i adt.StringIndexer, n adt.Node, config *Config) {
	if config == nil {
	config = &Config{}
	}
	p := printer{Writer: w, index: i, cfg: config}
	if config.Compact {
	p := compactPrinter{p}
	p.node(n)
	} else {
	p.node(n)
	}
	}

	func NodeString(i adt.StringIndexer, n adt.Node, config *Config) string {
	b := &strings.Builder{}
	WriteNode(b, i, n, config)
	return b.String()
	}

	type printer struct {
	io.Writer
	index adt.StringIndexer
	indent string
	cfg *Config

	// modes:
	// - show vertex
	// - show original conjuncts
	// - show unevaluated
	// - auto
	}

	func (w *printer) string(s string) {
	s = strings.Replace(s, "\n", "\n"+w.indent, -1)
	_, _ = io.WriteString(w, s)
	}

	func (w *printer) label(f adt.Feature) {
	w.string(w.labelString(f))
	}

	func (w *printer) ident(f adt.Feature) {
	w.string(f.IdentString(w.index))
	}

	// TODO: fold into label once :: is no longer supported.
	func (w *printer) labelString(f adt.Feature) string {
	if f.IsHidden() {
	ident := f.IdentString(w.index)
	if pkgName := f.PkgID(w.index); pkgName != "_" {
	ident = fmt.Sprintf("%s(%s)", ident, pkgName)
	}
	return ident
	}
	return f.SelectorString(w.index)
	}

	func (w *printer) shortError(errs errors.Error) {
	for {
	msg, args := errs.Msg()
	fmt.Fprintf(w, msg, args...)

	err := errors.Unwrap(errs)
	if err == nil {
	break
	}

	if errs, _ = err.(errors.Error); errs != nil {
	w.string(err.Error())
	break
	}
	}
	}

	func (w printer) interpolation(x adt.Interpolation) {
	quote := `"`
	if x.K == adt.BytesKind {
	quote = `'`
	}
	w.string(quote)
	for i := 0; i < len(x.Parts); i += 2 {
	switch x.K {
	case adt.StringKind:
	if s, ok := x.Parts[i].(*adt.String); ok {
	w.string(s.Str)
	} else {
	w.string("<bad string>")
	}
	case adt.BytesKind:
	if s, ok := x.Parts[i].(*adt.Bytes); ok {
	_, _ = w.Write(s.B)
	} else {
	w.string("<bad bytes>")
	}
	}
	if i+1 < len(x.Parts) {
	w.string(`\(`)
	w.node(x.Parts[i+1])
	w.string(`)`)
	}
	}
	w.string(quote)
	}

	func (w *printer) node(n adt.Node) {
	switch x := n.(type) {
	case *adt.Vertex:
	var kind adt.Kind
	if x.BaseValue != nil {
	kind = x.BaseValue.Kind()
	}

	kindStr := kind.String()

	// TODO: replace with showing full closedness data.
	if x.IsClosedList() \|\| x.IsClosedStruct() {
	if kind == adt.ListKind \|\| kind == adt.StructKind {
	kindStr = "#" + kindStr
	}
	}

	fmt.Fprintf(w, "(%s){", kindStr)

	saved := w.indent
	w.indent += " "
	defer func() { w.indent = saved }()

	switch v := x.BaseValue.(type) {
	case nil:
	case *adt.Bottom:
	// TODO: reuse bottom.
	saved := w.indent
	w.indent += "// "
	w.string("\n")
	fmt.Fprintf(w, "[%v]", v.Code)
	if !v.ChildError {
	msg := errors.Details(v.Err, &errors.Config{
	Cwd: w.cfg.Cwd,
	ToSlash: true,
	})
	msg = strings.TrimSpace(msg)
	if msg != "" {
	w.string(" ")
	w.string(msg)
	}
	}
	w.indent = saved

	case adt.StructMarker, adt.ListMarker:
	// if len(x.Arcs) == 0 {
	// // w.string("}")
	// // return
	// }

	case adt.Value:
	if len(x.Arcs) == 0 {
	w.string(" ")
	w.node(v)
	w.string(" }")
	return
	}
	w.string("\n")
	w.node(v)
	}

	for _, a := range x.Arcs {
	w.string("\n")
	w.label(a.Label)
	w.string(": ")
	w.node(a)
	}

	if x.BaseValue == nil {
	w.indent += "// "
	w.string("// ")
	for i, c := range x.Conjuncts {
	if i > 0 {
	w.string(" & ")
	}
	w.node(c.Expr()) // TODO: also include env?
	}
	}

	w.indent = saved
	w.string("\n")
	w.string("}")

	case *adt.StructMarker:
	w.string("struct")

	case *adt.ListMarker:
	w.string("list")

	case *adt.StructLit:
	if len(x.Decls) == 0 {
	w.string("{}")
	break
	}
	w.string("{")
	w.indent += " "
	for _, d := range x.Decls {
	w.string("\n")
	w.node(d)
	}
	w.indent = w.indent[:len(w.indent)-2]
	w.string("\n}")

	case *adt.ListLit:
	if len(x.Elems) == 0 {
	w.string("[]")
	break
	}
	w.string("[")
	w.indent += " "
	for _, d := range x.Elems {
	w.string("\n")
	w.node(d)
	w.string(",")
	}
	w.indent = w.indent[:len(w.indent)-2]
	w.string("\n]")

	case *adt.Field:
	s := w.labelString(x.Label)
	w.string(s)
	w.string(":")
	if x.Label.IsDef() && !internal.IsDef(s) {
	w.string(":")
	}
	w.string(" ")
	w.node(x.Value)

	case *adt.OptionalField:
	s := w.labelString(x.Label)
	w.string(s)
	w.string("?:")
	if x.Label.IsDef() && !internal.IsDef(s) {
	w.string(":")
	}
	w.string(" ")
	w.node(x.Value)

	case *adt.BulkOptionalField:
	w.string("[")
	w.node(x.Filter)
	w.string("]: ")
	w.node(x.Value)

	case *adt.DynamicField:
	w.node(x.Key)
	if x.IsOptional() {
	w.string("?")
	}
	w.string(": ")
	w.node(x.Value)

	case *adt.Ellipsis:
	w.string("...")
	if x.Value != nil {
	w.node(x.Value)
	}

	case *adt.Bottom:
	w.string(`_\|_`)
	if x.Err != nil {
	w.string("(")
	w.shortError(x.Err)
	w.string(")")
	}

	case *adt.Null:
	w.string("null")

	case *adt.Bool:
	fmt.Fprint(w, x.B)

	case *adt.Num:
	fmt.Fprint(w, &x.X)

	case *adt.String:
	w.string(literal.String.Quote(x.Str))

	case *adt.Bytes:
	w.string(literal.Bytes.Quote(string(x.B)))

	case *adt.Top:
	w.string("_")

	case *adt.BasicType:
	fmt.Fprint(w, x.K)

	case *adt.BoundExpr:
	fmt.Fprint(w, x.Op)
	w.node(x.Expr)

	case *adt.BoundValue:
	fmt.Fprint(w, x.Op)
	w.node(x.Value)

	case *adt.NodeLink:
	w.string(openTuple)
	for i, f := range x.Node.Path() {
	if i > 0 {
	w.string(".")
	}
	w.label(f)
	}
	w.string(closeTuple)

	case *adt.FieldReference:
	w.string(openTuple)
	w.string(strconv.Itoa(int(x.UpCount)))
	w.string(";")
	w.label(x.Label)
	w.string(closeTuple)

	case *adt.LabelReference:
	w.string(openTuple)
	w.string(strconv.Itoa(int(x.UpCount)))
	w.string(";-")
	w.string(closeTuple)

	case *adt.DynamicReference:
	w.string(openTuple)
	w.string(strconv.Itoa(int(x.UpCount)))
	w.string(";(")
	w.node(x.Label)
	w.string(")")
	w.string(closeTuple)

	case *adt.ImportReference:
	w.string(openTuple + "import;")
	w.label(x.ImportPath)
	w.string(closeTuple)

	case *adt.LetReference:
	w.string(openTuple)
	w.string(strconv.Itoa(int(x.UpCount)))
	w.string(";let ")
	w.ident(x.Label)
	w.string(closeTuple)

	case *adt.SelectorExpr:
	w.node(x.X)
	w.string(".")
	w.label(x.Sel)

	case *adt.IndexExpr:
	w.node(x.X)
	w.string("[")
	w.node(x.Index)
	w.string("]")

	case *adt.SliceExpr:
	w.node(x.X)
	w.string("[")
	if x.Lo != nil {
	w.node(x.Lo)
	}
	w.string(":")
	if x.Hi != nil {
	w.node(x.Hi)
	}
	if x.Stride != nil {
	w.string(":")
	w.node(x.Stride)
	}
	w.string("]")

	case *adt.Interpolation:
	w.interpolation(x)

	case *adt.UnaryExpr:
	fmt.Fprint(w, x.Op)
	w.node(x.X)

	case *adt.BinaryExpr:
	w.string("(")
	w.node(x.X)
	fmt.Fprint(w, " ", x.Op, " ")
	w.node(x.Y)
	w.string(")")

	case *adt.CallExpr:
	w.node(x.Fun)
	w.string("(")
	for i, a := range x.Args {
	if i > 0 {
	w.string(", ")
	}
	w.node(a)
	}
	w.string(")")

	case *adt.Builtin:
	if x.Package != 0 {
	w.label(x.Package)
	w.string(".")
	}
	w.string(x.Name)

	case *adt.BuiltinValidator:
	w.node(x.Builtin)
	w.string("(")
	for i, a := range x.Args {
	if i > 0 {
	w.string(", ")
	}
	w.node(a)
	}
	w.string(")")

	case *adt.DisjunctionExpr:
	w.string("(")
	for i, a := range x.Values {
	if i > 0 {
	w.string("\|")
	}
	// Disjunct
	if a.Default {
	w.string("*")
	}
	w.node(a.Val)
	}
	w.string(")")

	case *adt.Conjunction:
	w.string("&(")
	for i, c := range x.Values {
	if i > 0 {
	w.string(", ")
	}
	w.node(c)
	}
	w.string(")")

	case *adt.Disjunction:
	w.string("\|(")
	for i, c := range x.Values {
	if i > 0 {
	w.string(", ")
	}
	if i < x.NumDefaults {
	w.string("*")
	}
	w.node(c)
	}
	w.string(")")

	case *adt.ForClause:
	w.string("for ")
	w.ident(x.Key)
	w.string(", ")
	w.ident(x.Value)
	w.string(" in ")
	w.node(x.Src)
	w.string(" ")
	w.node(x.Dst)

	case *adt.IfClause:
	w.string("if ")
	w.node(x.Condition)
	w.string(" ")
	w.node(x.Dst)

	case *adt.LetClause:
	w.string("let ")
	w.ident(x.Label)
	w.string(" = ")
	w.node(x.Expr)
	w.string(" ")
	w.node(x.Dst)

	case *adt.ValueClause:
	w.node(x.StructLit)

	default:
	panic(fmt.Sprintf("unknown type %T", x))
	}
	}