src/cmd/compile/internal/types2/typestring.go - go - Git at Google

 // Copyright 2013 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.

 // This file implements printing of types.

 package types2

 import (
 	"bytes"
 	"strconv"
 	"unicode/utf8"
 )

 // A Qualifier controls how named package-level objects are printed in
 // calls to TypeString, ObjectString, and SelectionString.
 //
 // These three formatting routines call the Qualifier for each
 // package-level object O, and if the Qualifier returns a non-empty
 // string p, the object is printed in the form p.O.
 // If it returns an empty string, only the object name O is printed.
 //
 // Using a nil Qualifier is equivalent to using (*Package).Path: the
 // object is qualified by the import path, e.g., "encoding/json.Marshal".
 //
 type Qualifier func(*Package) string

 // RelativeTo returns a Qualifier that fully qualifies members of
 // all packages other than pkg.
 func RelativeTo(pkg *Package) Qualifier {
 	if pkg == nil {
 		return nil
 	}
 	return func(other *Package) string {
 		if pkg == other {
 			return "" // same package; unqualified
 		}
 		return other.Path()
 	}
 }

 // TypeString returns the string representation of typ.
 // The Qualifier controls the printing of
 // package-level objects, and may be nil.
 func TypeString(typ Type, qf Qualifier) string {
 	var buf bytes.Buffer
 	WriteType(&buf, typ, qf)
 	return buf.String()
 }

 // WriteType writes the string representation of typ to buf.
 // The Qualifier controls the printing of
 // package-level objects, and may be nil.
 func WriteType(buf *bytes.Buffer, typ Type, qf Qualifier) {
 	newTypeWriter(buf, qf).typ(typ)
 }

 // WriteSignature writes the representation of the signature sig to buf,
 // without a leading "func" keyword.
 // The Qualifier controls the printing of
 // package-level objects, and may be nil.
 func WriteSignature(buf *bytes.Buffer, sig *Signature, qf Qualifier) {
 	newTypeWriter(buf, qf).signature(sig)
 }

 // instanceMarker is the prefix for an instantiated type in unexpanded form.
 const instanceMarker = '#'

 type typeWriter struct {
 	buf  *bytes.Buffer
 	seen map[Type]bool
 	qf   Qualifier
 	env  *Environment // if non-nil, we are type hashing
 }

 func newTypeWriter(buf *bytes.Buffer, qf Qualifier) *typeWriter {
 	return &typeWriter{buf, make(map[Type]bool), qf, nil}
 }

 func newTypeHasher(buf *bytes.Buffer, env *Environment) *typeWriter {
 	assert(env != nil)
 	return &typeWriter{buf, make(map[Type]bool), nil, env}
 }

 func (w *typeWriter) byte(b byte) {
 	if w.env != nil {
 		if b == ' ' {
 			b = '#'
 		}
 		w.buf.WriteByte(b)
 		return
 	}
 	w.buf.WriteByte(b)
 	if b == ',' || b == ';' {
 		w.buf.WriteByte(' ')
 	}
 }

 func (w *typeWriter) string(s string) {
 	w.buf.WriteString(s)
 }

 func (w *typeWriter) error(msg string) {
 	if w.env != nil {
 		panic(msg)
 	}
 	w.buf.WriteString("<" + msg + ">")
 }

 func (w *typeWriter) typ(typ Type) {
 	if w.seen[typ] {
 		w.error("cycle to " + goTypeName(typ))
 		return
 	}
 	w.seen[typ] = true
 	defer delete(w.seen, typ)

 	switch t := typ.(type) {
 	case nil:
 		w.error("nil")

 	case *Basic:
 		// exported basic types go into package unsafe
 		// (currently this is just unsafe.Pointer)
 		if isExported(t.name) {
 			if obj, _ := Unsafe.scope.Lookup(t.name).(*TypeName); obj != nil {
 				w.typeName(obj)
 				break
 			}
 		}
 		w.string(t.name)

 	case *Array:
 		w.byte('[')
 		w.string(strconv.FormatInt(t.len, 10))
 		w.byte(']')
 		w.typ(t.elem)

 	case *Slice:
 		w.string("[]")
 		w.typ(t.elem)

 	case *Struct:
 		w.string("struct{")
 		for i, f := range t.fields {
 			if i > 0 {
 				w.byte(';')
 			}
 			// This doesn't do the right thing for embedded type
 			// aliases where we should print the alias name, not
 			// the aliased type (see issue #44410).
 			if !f.embedded {
 				w.string(f.name)
 				w.byte(' ')
 			}
 			w.typ(f.typ)
 			if tag := t.Tag(i); tag != "" {
 				w.byte(' ')
 				// TODO(gri) If tag contains blanks, replacing them with '#'
 				//           in Environment.TypeHash may produce another tag
 				//           accidentally.
 				w.string(strconv.Quote(tag))
 			}
 		}
 		w.byte('}')

 	case *Pointer:
 		w.byte('*')
 		w.typ(t.base)

 	case *Tuple:
 		w.tuple(t, false)

 	case *Signature:
 		w.string("func")
 		w.signature(t)

 	case *Union:
 		// Unions only appear as (syntactic) embedded elements
 		// in interfaces and syntactically cannot be empty.
 		if t.Len() == 0 {
 			w.error("empty union")
 			break
 		}
 		for i, t := range t.terms {
 			if i > 0 {
 				w.byte('|')
 			}
 			if t.tilde {
 				w.byte('~')
 			}
 			w.typ(t.typ)
 		}

 	case *Interface:
 		w.string("interface{")
 		first := true
 		for _, m := range t.methods {
 			if !first {
 				w.byte(';')
 			}
 			first = false
 			w.string(m.name)
 			w.signature(m.typ.(*Signature))
 		}
 		for _, typ := range t.embeddeds {
 			if !first {
 				w.byte(';')
 			}
 			first = false
 			w.typ(typ)
 		}
 		w.byte('}')

 	case *Map:
 		w.string("map[")
 		w.typ(t.key)
 		w.byte(']')
 		w.typ(t.elem)

 	case *Chan:
 		var s string
 		var parens bool
 		switch t.dir {
 		case SendRecv:
 			s = "chan "
 			// chan (<-chan T) requires parentheses
 			if c, _ := t.elem.(*Chan); c != nil && c.dir == RecvOnly {
 				parens = true
 			}
 		case SendOnly:
 			s = "chan<- "
 		case RecvOnly:
 			s = "<-chan "
 		default:
 			w.error("unknown channel direction")
 		}
 		w.string(s)
 		if parens {
 			w.byte('(')
 		}
 		w.typ(t.elem)
 		if parens {
 			w.byte(')')
 		}

 	case *Named:
 		// Instance markers indicate unexpanded instantiated
 		// types. Write them to aid debugging, but don't write
 		// them when we need an instance hash: whether a type
 		// is fully expanded or not doesn't matter for identity.
 		if w.env == nil && t.instPos != nil {
 			w.byte(instanceMarker)
 		}
 		w.typePrefix(t)
 		w.typeName(t.obj)
 		if t.targs != nil {
 			// instantiated type
 			w.typeList(t.targs.list())
 		} else if w.env == nil && t.TypeParams().Len() != 0 { // For type hashing, don't need to format the TParams
 			// parameterized type
 			w.tParamList(t.TypeParams().list())
 		}

 	case *TypeParam:
 		if t.obj == nil {
 			w.error("unnamed type parameter")
 			break
 		}
 		// Optionally write out package for typeparams (like Named).
 		// TODO(danscales): this is required for import/export, so
 		// we maybe need a separate function that won't be changed
 		// for debugging purposes.
 		if t.obj.pkg != nil {
 			writePackage(w.buf, t.obj.pkg, w.qf)
 		}
 		w.string(t.obj.name + subscript(t.id))

 	case *top:
 		w.error("⊤")

 	default:
 		// For externally defined implementations of Type.
 		// Note: In this case cycles won't be caught.
 		w.string(t.String())
 	}
 }

 // If w.env is non-nil, typePrefix writes a unique prefix for the named type t
 // based on the types already observed by w.env. If w.env is nil, it does
 // nothing.
 func (w *typeWriter) typePrefix(t *Named) {
 	if w.env != nil {
 		w.string(strconv.Itoa(w.env.idForType(t)))
 	}
 }

 func (w *typeWriter) typeList(list []Type) {
 	w.byte('[')
 	for i, typ := range list {
 		if i > 0 {
 			w.byte(',')
 		}
 		w.typ(typ)
 	}
 	w.byte(']')
 }

 func (w *typeWriter) tParamList(list []*TypeParam) {
 	w.byte('[')
 	var prev Type
 	for i, tpar := range list {
 		// Determine the type parameter and its constraint.
 		// list is expected to hold type parameter names,
 		// but don't crash if that's not the case.
 		if tpar == nil {
 			w.error("nil type parameter")
 			continue
 		}
 		if i > 0 {
 			if tpar.bound != prev {
 				// bound changed - write previous one before advancing
 				w.byte(' ')
 				w.typ(prev)
 			}
 			w.byte(',')
 		}
 		prev = tpar.bound
 		w.typ(tpar)
 	}
 	if prev != nil {
 		w.byte(' ')
 		w.typ(prev)
 	}
 	w.byte(']')
 }

 func (w *typeWriter) typeName(obj *TypeName) {
 	if obj.pkg != nil {
 		writePackage(w.buf, obj.pkg, w.qf)
 	}
 	w.string(obj.name)
 }

 func (w *typeWriter) tuple(tup *Tuple, variadic bool) {
 	w.byte('(')
 	if tup != nil {
 		for i, v := range tup.vars {
 			if i > 0 {
 				w.byte(',')
 			}
 			// parameter names are ignored for type identity and thus type hashes
 			if w.env == nil && v.name != "" {
 				w.string(v.name)
 				w.byte(' ')
 			}
 			typ := v.typ
 			if variadic && i == len(tup.vars)-1 {
 				if s, ok := typ.(*Slice); ok {
 					w.string("...")
 					typ = s.elem
 				} else {
 					// special case:
 					// append(s, "foo"...) leads to signature func([]byte, string...)
 					if t := asBasic(typ); t == nil || t.kind != String {
 						w.error("expected string type")
 						continue
 					}
 					w.typ(typ)
 					w.string("...")
 					continue
 				}
 			}
 			w.typ(typ)
 		}
 	}
 	w.byte(')')
 }

 func (w *typeWriter) signature(sig *Signature) {
 	if sig.TypeParams().Len() != 0 {
 		w.tParamList(sig.TypeParams().list())
 	}

 	w.tuple(sig.params, sig.variadic)

 	n := sig.results.Len()
 	if n == 0 {
 		// no result
 		return
 	}

 	w.byte(' ')
 	if n == 1 && (w.env != nil || sig.results.vars[0].name == "") {
 		// single unnamed result (if type hashing, name must be ignored)
 		w.typ(sig.results.vars[0].typ)
 		return
 	}

 	// multiple or named result(s)
 	w.tuple(sig.results, false)
 }

 // subscript returns the decimal (utf8) representation of x using subscript digits.
 func subscript(x uint64) string {
 	const w = len("₀") // all digits 0...9 have the same utf8 width
 	var buf [32 * w]byte
 	i := len(buf)
 	for {
 		i -= w
 		utf8.EncodeRune(buf[i:], '₀'+rune(x%10)) // '₀' == U+2080
 		x /= 10
 		if x == 0 {
 			break
 		}
 	}
 	return string(buf[i:])
 }
	// Copyright 2013 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.

	// This file implements printing of types.

	package types2

	import (
	"bytes"
	"strconv"
	"unicode/utf8"
	)

	// A Qualifier controls how named package-level objects are printed in
	// calls to TypeString, ObjectString, and SelectionString.
	//
	// These three formatting routines call the Qualifier for each
	// package-level object O, and if the Qualifier returns a non-empty
	// string p, the object is printed in the form p.O.
	// If it returns an empty string, only the object name O is printed.
	//
	// Using a nil Qualifier is equivalent to using (*Package).Path: the
	// object is qualified by the import path, e.g., "encoding/json.Marshal".
	//
	type Qualifier func(*Package) string

	// RelativeTo returns a Qualifier that fully qualifies members of
	// all packages other than pkg.
	func RelativeTo(pkg *Package) Qualifier {
	if pkg == nil {
	return nil
	}
	return func(other *Package) string {
	if pkg == other {
	return "" // same package; unqualified
	}
	return other.Path()
	}
	}

	// TypeString returns the string representation of typ.
	// The Qualifier controls the printing of
	// package-level objects, and may be nil.
	func TypeString(typ Type, qf Qualifier) string {
	var buf bytes.Buffer
	WriteType(&buf, typ, qf)
	return buf.String()
	}

	// WriteType writes the string representation of typ to buf.
	// The Qualifier controls the printing of
	// package-level objects, and may be nil.
	func WriteType(buf *bytes.Buffer, typ Type, qf Qualifier) {
	newTypeWriter(buf, qf).typ(typ)
	}

	// WriteSignature writes the representation of the signature sig to buf,
	// without a leading "func" keyword.
	// The Qualifier controls the printing of
	// package-level objects, and may be nil.
	func WriteSignature(buf bytes.Buffer, sig Signature, qf Qualifier) {
	newTypeWriter(buf, qf).signature(sig)
	}

	// instanceMarker is the prefix for an instantiated type in unexpanded form.
	const instanceMarker = '#'

	type typeWriter struct {
	buf *bytes.Buffer
	seen map[Type]bool
	qf Qualifier
	env *Environment // if non-nil, we are type hashing
	}

	func newTypeWriter(buf bytes.Buffer, qf Qualifier) typeWriter {
	return &typeWriter{buf, make(map[Type]bool), qf, nil}
	}

	func newTypeHasher(buf bytes.Buffer, env Environment) *typeWriter {
	assert(env != nil)
	return &typeWriter{buf, make(map[Type]bool), nil, env}
	}

	func (w *typeWriter) byte(b byte) {
	if w.env != nil {
	if b == ' ' {
	b = '#'
	}
	w.buf.WriteByte(b)
	return
	}
	w.buf.WriteByte(b)
	if b == ',' \|\| b == ';' {
	w.buf.WriteByte(' ')
	}
	}

	func (w *typeWriter) string(s string) {
	w.buf.WriteString(s)
	}

	func (w *typeWriter) error(msg string) {
	if w.env != nil {
	panic(msg)
	}
	w.buf.WriteString("<" + msg + ">")
	}

	func (w *typeWriter) typ(typ Type) {
	if w.seen[typ] {
	w.error("cycle to " + goTypeName(typ))
	return
	}
	w.seen[typ] = true
	defer delete(w.seen, typ)

	switch t := typ.(type) {
	case nil:
	w.error("nil")

	case *Basic:
	// exported basic types go into package unsafe
	// (currently this is just unsafe.Pointer)
	if isExported(t.name) {
	if obj, _ := Unsafe.scope.Lookup(t.name).(*TypeName); obj != nil {
	w.typeName(obj)
	break
	}
	}
	w.string(t.name)

	case *Array:
	w.byte('[')
	w.string(strconv.FormatInt(t.len, 10))
	w.byte(']')
	w.typ(t.elem)

	case *Slice:
	w.string("[]")
	w.typ(t.elem)

	case *Struct:
	w.string("struct{")
	for i, f := range t.fields {
	if i > 0 {
	w.byte(';')
	}
	// This doesn't do the right thing for embedded type
	// aliases where we should print the alias name, not
	// the aliased type (see issue #44410).
	if !f.embedded {
	w.string(f.name)
	w.byte(' ')
	}
	w.typ(f.typ)
	if tag := t.Tag(i); tag != "" {
	w.byte(' ')
	// TODO(gri) If tag contains blanks, replacing them with '#'
	// in Environment.TypeHash may produce another tag
	// accidentally.
	w.string(strconv.Quote(tag))
	}
	}
	w.byte('}')

	case *Pointer:
	w.byte('*')
	w.typ(t.base)

	case *Tuple:
	w.tuple(t, false)

	case *Signature:
	w.string("func")
	w.signature(t)

	case *Union:
	// Unions only appear as (syntactic) embedded elements
	// in interfaces and syntactically cannot be empty.
	if t.Len() == 0 {
	w.error("empty union")
	break
	}
	for i, t := range t.terms {
	if i > 0 {
	w.byte('\|')
	}
	if t.tilde {
	w.byte('~')
	}
	w.typ(t.typ)
	}

	case *Interface:
	w.string("interface{")
	first := true
	for _, m := range t.methods {
	if !first {
	w.byte(';')
	}
	first = false
	w.string(m.name)
	w.signature(m.typ.(*Signature))
	}
	for _, typ := range t.embeddeds {
	if !first {
	w.byte(';')
	}
	first = false
	w.typ(typ)
	}
	w.byte('}')

	case *Map:
	w.string("map[")
	w.typ(t.key)
	w.byte(']')
	w.typ(t.elem)

	case *Chan:
	var s string
	var parens bool
	switch t.dir {
	case SendRecv:
	s = "chan "
	// chan (<-chan T) requires parentheses
	if c, _ := t.elem.(*Chan); c != nil && c.dir == RecvOnly {
	parens = true
	}
	case SendOnly:
	s = "chan<- "
	case RecvOnly:
	s = "<-chan "
	default:
	w.error("unknown channel direction")
	}
	w.string(s)
	if parens {
	w.byte('(')
	}
	w.typ(t.elem)
	if parens {
	w.byte(')')
	}

	case *Named:
	// Instance markers indicate unexpanded instantiated
	// types. Write them to aid debugging, but don't write
	// them when we need an instance hash: whether a type
	// is fully expanded or not doesn't matter for identity.
	if w.env == nil && t.instPos != nil {
	w.byte(instanceMarker)
	}
	w.typePrefix(t)
	w.typeName(t.obj)
	if t.targs != nil {
	// instantiated type
	w.typeList(t.targs.list())
	} else if w.env == nil && t.TypeParams().Len() != 0 { // For type hashing, don't need to format the TParams
	// parameterized type
	w.tParamList(t.TypeParams().list())
	}

	case *TypeParam:
	if t.obj == nil {
	w.error("unnamed type parameter")
	break
	}
	// Optionally write out package for typeparams (like Named).
	// TODO(danscales): this is required for import/export, so
	// we maybe need a separate function that won't be changed
	// for debugging purposes.
	if t.obj.pkg != nil {
	writePackage(w.buf, t.obj.pkg, w.qf)
	}
	w.string(t.obj.name + subscript(t.id))

	case *top:
	w.error("⊤")

	default:
	// For externally defined implementations of Type.
	// Note: In this case cycles won't be caught.
	w.string(t.String())
	}
	}

	// If w.env is non-nil, typePrefix writes a unique prefix for the named type t
	// based on the types already observed by w.env. If w.env is nil, it does
	// nothing.
	func (w typeWriter) typePrefix(t Named) {
	if w.env != nil {
	w.string(strconv.Itoa(w.env.idForType(t)))
	}
	}

	func (w *typeWriter) typeList(list []Type) {
	w.byte('[')
	for i, typ := range list {
	if i > 0 {
	w.byte(',')
	}
	w.typ(typ)
	}
	w.byte(']')
	}

	func (w typeWriter) tParamList(list []TypeParam) {
	w.byte('[')
	var prev Type
	for i, tpar := range list {
	// Determine the type parameter and its constraint.
	// list is expected to hold type parameter names,
	// but don't crash if that's not the case.
	if tpar == nil {
	w.error("nil type parameter")
	continue
	}
	if i > 0 {
	if tpar.bound != prev {
	// bound changed - write previous one before advancing
	w.byte(' ')
	w.typ(prev)
	}
	w.byte(',')
	}
	prev = tpar.bound
	w.typ(tpar)
	}
	if prev != nil {
	w.byte(' ')
	w.typ(prev)
	}
	w.byte(']')
	}

	func (w typeWriter) typeName(obj TypeName) {
	if obj.pkg != nil {
	writePackage(w.buf, obj.pkg, w.qf)
	}
	w.string(obj.name)
	}

	func (w typeWriter) tuple(tup Tuple, variadic bool) {
	w.byte('(')
	if tup != nil {
	for i, v := range tup.vars {
	if i > 0 {
	w.byte(',')
	}
	// parameter names are ignored for type identity and thus type hashes
	if w.env == nil && v.name != "" {
	w.string(v.name)
	w.byte(' ')
	}
	typ := v.typ
	if variadic && i == len(tup.vars)-1 {
	if s, ok := typ.(*Slice); ok {
	w.string("...")
	typ = s.elem
	} else {
	// special case:
	// append(s, "foo"...) leads to signature func([]byte, string...)
	if t := asBasic(typ); t == nil \|\| t.kind != String {
	w.error("expected string type")
	continue
	}
	w.typ(typ)
	w.string("...")
	continue
	}
	}
	w.typ(typ)
	}
	}
	w.byte(')')
	}

	func (w typeWriter) signature(sig Signature) {
	if sig.TypeParams().Len() != 0 {
	w.tParamList(sig.TypeParams().list())
	}

	w.tuple(sig.params, sig.variadic)

	n := sig.results.Len()
	if n == 0 {
	// no result
	return
	}

	w.byte(' ')
	if n == 1 && (w.env != nil \|\| sig.results.vars[0].name == "") {
	// single unnamed result (if type hashing, name must be ignored)
	w.typ(sig.results.vars[0].typ)
	return
	}

	// multiple or named result(s)
	w.tuple(sig.results, false)
	}

	// subscript returns the decimal (utf8) representation of x using subscript digits.
	func subscript(x uint64) string {
	const w = len("₀") // all digits 0...9 have the same utf8 width
	var buf [32 * w]byte
	i := len(buf)
	for {
	i -= w
	utf8.EncodeRune(buf[i:], '₀'+rune(x%10)) // '₀' == U+2080
	x /= 10
	if x == 0 {
	break
	}
	}
	return string(buf[i:])
	}