src/cmd/compile/internal/types2/typestring.go

   1 // Copyright 2013 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // This file implements printing of types.
   6
   7 package types2
   8
   9 import (
  10         "bytes"
  11         "fmt"
  12         "sort"
  13         "strconv"
  14         "strings"
  15         "unicode/utf8"
  16 )
  17
  18 // A Qualifier controls how named package-level objects are printed in
  19 // calls to TypeString, ObjectString, and SelectionString.
  20 //
  21 // These three formatting routines call the Qualifier for each
  22 // package-level object O, and if the Qualifier returns a non-empty
  23 // string p, the object is printed in the form p.O.
  24 // If it returns an empty string, only the object name O is printed.
  25 //
  26 // Using a nil Qualifier is equivalent to using (*Package).Path: the
  27 // object is qualified by the import path, e.g., "encoding/json.Marshal".
  28 type Qualifier func(*Package) string
  29
  30 // RelativeTo returns a Qualifier that fully qualifies members of
  31 // all packages other than pkg.
  32 func RelativeTo(pkg *Package) Qualifier {
  33         if pkg == nil {
  34                 return nil
  35         }
  36         return func(other *Package) string {
  37                 if pkg == other {
  38                         return "" // same package; unqualified
  39                 }
  40                 return other.Path()
  41         }
  42 }
  43
  44 // TypeString returns the string representation of typ.
  45 // The Qualifier controls the printing of
  46 // package-level objects, and may be nil.
  47 func TypeString(typ Type, qf Qualifier) string {
  48         var buf bytes.Buffer
  49         WriteType(&buf, typ, qf)
  50         return buf.String()
  51 }
  52
  53 // WriteType writes the string representation of typ to buf.
  54 // The Qualifier controls the printing of
  55 // package-level objects, and may be nil.
  56 func WriteType(buf *bytes.Buffer, typ Type, qf Qualifier) {
  57         newTypeWriter(buf, qf).typ(typ)
  58 }
  59
  60 // WriteSignature writes the representation of the signature sig to buf,
  61 // without a leading "func" keyword. The Qualifier controls the printing
  62 // of package-level objects, and may be nil.
  63 func WriteSignature(buf *bytes.Buffer, sig *Signature, qf Qualifier) {
  64         newTypeWriter(buf, qf).signature(sig)
  65 }
  66
  67 type typeWriter struct {
  68         buf          *bytes.Buffer
  69         seen         map[Type]bool
  70         qf           Qualifier
  71         ctxt         *Context       // if non-nil, we are type hashing
  72         tparams      *TypeParamList // local type parameters
  73         paramNames   bool           // if set, write function parameter names, otherwise, write types only
  74         tpSubscripts bool           // if set, write type parameter indices as subscripts
  75         pkgInfo      bool           // package-annotate first unexported-type field to avoid confusing type description
  76 }
  77
  78 func newTypeWriter(buf *bytes.Buffer, qf Qualifier) *typeWriter {
  79         return &typeWriter{buf, make(map[Type]bool), qf, nil, nil, true, false, false}
  80 }
  81
  82 func newTypeHasher(buf *bytes.Buffer, ctxt *Context) *typeWriter {
  83         assert(ctxt != nil)
  84         return &typeWriter{buf, make(map[Type]bool), nil, ctxt, nil, false, false, false}
  85 }
  86
  87 func (w *typeWriter) byte(b byte) {
  88         if w.ctxt != nil {
  89                 if b == ' ' {
  90                         b = '#'
  91                 }
  92                 w.buf.WriteByte(b)
  93                 return
  94         }
  95         w.buf.WriteByte(b)
  96         if b == ',' || b == ';' {
  97                 w.buf.WriteByte(' ')
  98         }
  99 }
 100
 101 func (w *typeWriter) string(s string) {
 102         w.buf.WriteString(s)
 103 }
 104
 105 func (w *typeWriter) error(msg string) {
 106         if w.ctxt != nil {
 107                 panic(msg)
 108         }
 109         w.buf.WriteString("<" + msg + ">")
 110 }
 111
 112 func (w *typeWriter) typ(typ Type) {
 113         if w.seen[typ] {
 114                 w.error("cycle to " + goTypeName(typ))
 115                 return
 116         }
 117         w.seen[typ] = true
 118         defer delete(w.seen, typ)
 119
 120         switch t := typ.(type) {
 121         case nil:
 122                 w.error("nil")
 123
 124         case *Basic:
 125                 // exported basic types go into package unsafe
 126                 // (currently this is just unsafe.Pointer)
 127                 if isExported(t.name) {
 128                         if obj, _ := Unsafe.scope.Lookup(t.name).(*TypeName); obj != nil {
 129                                 w.typeName(obj)
 130                                 break
 131                         }
 132                 }
 133                 w.string(t.name)
 134
 135         case *Array:
 136                 w.byte('[')
 137                 w.string(strconv.FormatInt(t.len, 10))
 138                 w.byte(']')
 139                 w.typ(t.elem)
 140
 141         case *Slice:
 142                 w.string("[]")
 143                 w.typ(t.elem)
 144
 145         case *Struct:
 146                 w.string("struct{")
 147                 for i, f := range t.fields {
 148                         if i > 0 {
 149                                 w.byte(';')
 150                         }
 151
 152                         // If disambiguating one struct for another, look for the first unexported field.
 153                         // Do this first in case of nested structs; tag the first-outermost field.
 154                         pkgAnnotate := false
 155                         if w.qf == nil && w.pkgInfo && !isExported(f.name) {
 156                                 // note for embedded types, type name is field name, and "string" etc are lower case hence unexported.
 157                                 pkgAnnotate = true
 158                                 w.pkgInfo = false // only tag once
 159                         }
 160
 161                         // This doesn't do the right thing for embedded type
 162                         // aliases where we should print the alias name, not
 163                         // the aliased type (see go.dev/issue/44410).
 164                         if !f.embedded {
 165                                 w.string(f.name)
 166                                 w.byte(' ')
 167                         }
 168                         w.typ(f.typ)
 169                         if pkgAnnotate {
 170                                 w.string(" /* package ")
 171                                 w.string(f.pkg.Path())
 172                                 w.string(" */ ")
 173                         }
 174                         if tag := t.Tag(i); tag != "" {
 175                                 w.byte(' ')
 176                                 // TODO(gri) If tag contains blanks, replacing them with '#'
 177                                 //           in Context.TypeHash may produce another tag
 178                                 //           accidentally.
 179                                 w.string(strconv.Quote(tag))
 180                         }
 181                 }
 182                 w.byte('}')
 183
 184         case *Pointer:
 185                 w.byte('*')
 186                 w.typ(t.base)
 187
 188         case *Tuple:
 189                 w.tuple(t, false)
 190
 191         case *Signature:
 192                 w.string("func")
 193                 w.signature(t)
 194
 195         case *Union:
 196                 // Unions only appear as (syntactic) embedded elements
 197                 // in interfaces and syntactically cannot be empty.
 198                 if t.Len() == 0 {
 199                         w.error("empty union")
 200                         break
 201                 }
 202                 for i, t := range t.terms {
 203                         if i > 0 {
 204                                 w.string(termSep)
 205                         }
 206                         if t.tilde {
 207                                 w.byte('~')
 208                         }
 209                         w.typ(t.typ)
 210                 }
 211
 212         case *Interface:
 213                 if w.ctxt == nil {
 214                         if t == universeAny.Type() {
 215                                 // When not hashing, we can try to improve type strings by writing "any"
 216                                 // for a type that is pointer-identical to universeAny. This logic should
 217                                 // be deprecated by more robust handling for aliases.
 218                                 w.string("any")
 219                                 break
 220                         }
 221                         if t == asNamed(universeComparable.Type()).underlying {
 222                                 w.string("interface{comparable}")
 223                                 break
 224                         }
 225                 }
 226                 if t.implicit {
 227                         if len(t.methods) == 0 && len(t.embeddeds) == 1 {
 228                                 w.typ(t.embeddeds[0])
 229                                 break
 230                         }
 231                         // Something's wrong with the implicit interface.
 232                         // Print it as such and continue.
 233                         w.string("/* implicit */ ")
 234                 }
 235                 w.string("interface{")
 236                 first := true
 237                 if w.ctxt != nil {
 238                         w.typeSet(t.typeSet())
 239                 } else {
 240                         for _, m := range t.methods {
 241                                 if !first {
 242                                         w.byte(';')
 243                                 }
 244                                 first = false
 245                                 w.string(m.name)
 246                                 w.signature(m.typ.(*Signature))
 247                         }
 248                         for _, typ := range t.embeddeds {
 249                                 if !first {
 250                                         w.byte(';')
 251                                 }
 252                                 first = false
 253                                 w.typ(typ)
 254                         }
 255                 }
 256                 w.byte('}')
 257
 258         case *Map:
 259                 w.string("map[")
 260                 w.typ(t.key)
 261                 w.byte(']')
 262                 w.typ(t.elem)
 263
 264         case *Chan:
 265                 var s string
 266                 var parens bool
 267                 switch t.dir {
 268                 case SendRecv:
 269                         s = "chan "
 270                         // chan (<-chan T) requires parentheses
 271                         if c, _ := t.elem.(*Chan); c != nil && c.dir == RecvOnly {
 272                                 parens = true
 273                         }
 274                 case SendOnly:
 275                         s = "chan<- "
 276                 case RecvOnly:
 277                         s = "<-chan "
 278                 default:
 279                         w.error("unknown channel direction")
 280                 }
 281                 w.string(s)
 282                 if parens {
 283                         w.byte('(')
 284                 }
 285                 w.typ(t.elem)
 286                 if parens {
 287                         w.byte(')')
 288                 }
 289
 290         case *Named:
 291                 // If hashing, write a unique prefix for t to represent its identity, since
 292                 // named type identity is pointer identity.
 293                 if w.ctxt != nil {
 294                         w.string(strconv.Itoa(w.ctxt.getID(t)))
 295                 }
 296                 w.typeName(t.obj) // when hashing written for readability of the hash only
 297                 if t.inst != nil {
 298                         // instantiated type
 299                         w.typeList(t.inst.targs.list())
 300                 } else if w.ctxt == nil && t.TypeParams().Len() != 0 { // For type hashing, don't need to format the TypeParams
 301                         // parameterized type
 302                         w.tParamList(t.TypeParams().list())
 303                 }
 304
 305         case *TypeParam:
 306                 if t.obj == nil {
 307                         w.error("unnamed type parameter")
 308                         break
 309                 }
 310                 if i := tparamIndex(w.tparams.list(), t); i >= 0 {
 311                         // The names of type parameters that are declared by the type being
 312                         // hashed are not part of the type identity. Replace them with a
 313                         // placeholder indicating their index.
 314                         w.string(fmt.Sprintf("$%d", i))
 315                 } else {
 316                         w.string(t.obj.name)
 317                         if w.tpSubscripts || w.ctxt != nil {
 318                                 w.string(subscript(t.id))
 319                         }
 320                         // If the type parameter name is the same as a predeclared object
 321                         // (say int), point out where it is declared to avoid confusing
 322                         // error messages. This doesn't need to be super-elegant; we just
 323                         // need a clear indication that this is not a predeclared name.
 324                         if w.ctxt == nil && Universe.Lookup(t.obj.name) != nil {
 325                                 w.string(sprintf(nil, false, " /* with %s declared at %s */", t.obj.name, t.obj.Pos()))
 326                         }
 327                 }
 328
 329         default:
 330                 // For externally defined implementations of Type.
 331                 // Note: In this case cycles won't be caught.
 332                 w.string(t.String())
 333         }
 334 }
 335
 336 // typeSet writes a canonical hash for an interface type set.
 337 func (w *typeWriter) typeSet(s *_TypeSet) {
 338         assert(w.ctxt != nil)
 339         first := true
 340         for _, m := range s.methods {
 341                 if !first {
 342                         w.byte(';')
 343                 }
 344                 first = false
 345                 w.string(m.name)
 346                 w.signature(m.typ.(*Signature))
 347         }
 348         switch {
 349         case s.terms.isAll():
 350                 // nothing to do
 351         case s.terms.isEmpty():
 352                 w.string(s.terms.String())
 353         default:
 354                 var termHashes []string
 355                 for _, term := range s.terms {
 356                         // terms are not canonically sorted, so we sort their hashes instead.
 357                         var buf bytes.Buffer
 358                         if term.tilde {
 359                                 buf.WriteByte('~')
 360                         }
 361                         newTypeHasher(&buf, w.ctxt).typ(term.typ)
 362                         termHashes = append(termHashes, buf.String())
 363                 }
 364                 sort.Strings(termHashes)
 365                 if !first {
 366                         w.byte(';')
 367                 }
 368                 w.string(strings.Join(termHashes, "|"))
 369         }
 370 }
 371
 372 func (w *typeWriter) typeList(list []Type) {
 373         w.byte('[')
 374         for i, typ := range list {
 375                 if i > 0 {
 376                         w.byte(',')
 377                 }
 378                 w.typ(typ)
 379         }
 380         w.byte(']')
 381 }
 382
 383 func (w *typeWriter) tParamList(list []*TypeParam) {
 384         w.byte('[')
 385         var prev Type
 386         for i, tpar := range list {
 387                 // Determine the type parameter and its constraint.
 388                 // list is expected to hold type parameter names,
 389                 // but don't crash if that's not the case.
 390                 if tpar == nil {
 391                         w.error("nil type parameter")
 392                         continue
 393                 }
 394                 if i > 0 {
 395                         if tpar.bound != prev {
 396                                 // bound changed - write previous one before advancing
 397                                 w.byte(' ')
 398                                 w.typ(prev)
 399                         }
 400                         w.byte(',')
 401                 }
 402                 prev = tpar.bound
 403                 w.typ(tpar)
 404         }
 405         if prev != nil {
 406                 w.byte(' ')
 407                 w.typ(prev)
 408         }
 409         w.byte(']')
 410 }
 411
 412 func (w *typeWriter) typeName(obj *TypeName) {
 413         w.string(packagePrefix(obj.pkg, w.qf))
 414         w.string(obj.name)
 415 }
 416
 417 func (w *typeWriter) tuple(tup *Tuple, variadic bool) {
 418         w.byte('(')
 419         if tup != nil {
 420                 for i, v := range tup.vars {
 421                         if i > 0 {
 422                                 w.byte(',')
 423                         }
 424                         // parameter names are ignored for type identity and thus type hashes
 425                         if w.ctxt == nil && v.name != "" && w.paramNames {
 426                                 w.string(v.name)
 427                                 w.byte(' ')
 428                         }
 429                         typ := v.typ
 430                         if variadic && i == len(tup.vars)-1 {
 431                                 if s, ok := typ.(*Slice); ok {
 432                                         w.string("...")
 433                                         typ = s.elem
 434                                 } else {
 435                                         // special case:
 436                                         // append(s, "foo"...) leads to signature func([]byte, string...)
 437                                         if t, _ := under(typ).(*Basic); t == nil || t.kind != String {
 438                                                 w.error("expected string type")
 439                                                 continue
 440                                         }
 441                                         w.typ(typ)
 442                                         w.string("...")
 443                                         continue
 444                                 }
 445                         }
 446                         w.typ(typ)
 447                 }
 448         }
 449         w.byte(')')
 450 }
 451
 452 func (w *typeWriter) signature(sig *Signature) {
 453         if sig.TypeParams().Len() != 0 {
 454                 if w.ctxt != nil {
 455                         assert(w.tparams == nil)
 456                         w.tparams = sig.TypeParams()
 457                         defer func() {
 458                                 w.tparams = nil
 459                         }()
 460                 }
 461                 w.tParamList(sig.TypeParams().list())
 462         }
 463
 464         w.tuple(sig.params, sig.variadic)
 465
 466         n := sig.results.Len()
 467         if n == 0 {
 468                 // no result
 469                 return
 470         }
 471
 472         w.byte(' ')
 473         if n == 1 && (w.ctxt != nil || sig.results.vars[0].name == "") {
 474                 // single unnamed result (if type hashing, name must be ignored)
 475                 w.typ(sig.results.vars[0].typ)
 476                 return
 477         }
 478
 479         // multiple or named result(s)
 480         w.tuple(sig.results, false)
 481 }
 482
 483 // subscript returns the decimal (utf8) representation of x using subscript digits.
 484 func subscript(x uint64) string {
 485         const w = len("₀") // all digits 0...9 have the same utf8 width
 486         var buf [32 * w]byte
 487         i := len(buf)
 488         for {
 489                 i -= w
 490                 utf8.EncodeRune(buf[i:], '₀'+rune(x%10)) // '₀' == U+2080
 491                 x /= 10
 492                 if x == 0 {
 493                         break
 494                 }
 495         }
 496         return string(buf[i:])
 497 }