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         "unicode/utf8"
  13 )
  14
  15 // A Qualifier controls how named package-level objects are printed in
  16 // calls to TypeString, ObjectString, and SelectionString.
  17 //
  18 // These three formatting routines call the Qualifier for each
  19 // package-level object O, and if the Qualifier returns a non-empty
  20 // string p, the object is printed in the form p.O.
  21 // If it returns an empty string, only the object name O is printed.
  22 //
  23 // Using a nil Qualifier is equivalent to using (*Package).Path: the
  24 // object is qualified by the import path, e.g., "encoding/json.Marshal".
  25 //
  26 type Qualifier func(*Package) string
  27
  28 // RelativeTo returns a Qualifier that fully qualifies members of
  29 // all packages other than pkg.
  30 func RelativeTo(pkg *Package) Qualifier {
  31         if pkg == nil {
  32                 return nil
  33         }
  34         return func(other *Package) string {
  35                 if pkg == other {
  36                         return "" // same package; unqualified
  37                 }
  38                 return other.Path()
  39         }
  40 }
  41
  42 // If gcCompatibilityMode is set, printing of types is modified
  43 // to match the representation of some types in the gc compiler:
  44 //
  45 //      - byte and rune lose their alias name and simply stand for
  46 //        uint8 and int32 respectively
  47 //      - embedded interfaces get flattened (the embedding info is lost,
  48 //        and certain recursive interface types cannot be printed anymore)
  49 //
  50 // This makes it easier to compare packages computed with the type-
  51 // checker vs packages imported from gc export data.
  52 //
  53 // Caution: This flag affects all uses of WriteType, globally.
  54 // It is only provided for testing in conjunction with
  55 // gc-generated data.
  56 //
  57 // This flag is exported in the x/tools/go/types package. We don't
  58 // need it at the moment in the std repo and so we don't export it
  59 // anymore. We should eventually try to remove it altogether.
  60 // TODO(gri) remove this
  61 var gcCompatibilityMode bool
  62
  63 // TypeString returns the string representation of typ.
  64 // The Qualifier controls the printing of
  65 // package-level objects, and may be nil.
  66 func TypeString(typ Type, qf Qualifier) string {
  67         var buf bytes.Buffer
  68         WriteType(&buf, typ, qf)
  69         return buf.String()
  70 }
  71
  72 // WriteType writes the string representation of typ to buf.
  73 // The Qualifier controls the printing of
  74 // package-level objects, and may be nil.
  75 func WriteType(buf *bytes.Buffer, typ Type, qf Qualifier) {
  76         writeType(buf, typ, qf, make([]Type, 0, 8))
  77 }
  78
  79 // instanceMarker is the prefix for an instantiated type
  80 // in "non-evaluated" instance form.
  81 const instanceMarker = '#'
  82
  83 func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
  84         // Theoretically, this is a quadratic lookup algorithm, but in
  85         // practice deeply nested composite types with unnamed component
  86         // types are uncommon. This code is likely more efficient than
  87         // using a map.
  88         for _, t := range visited {
  89                 if t == typ {
  90                         fmt.Fprintf(buf, "○%T", goTypeName(typ)) // cycle to typ
  91                         return
  92                 }
  93         }
  94         visited = append(visited, typ)
  95
  96         switch t := typ.(type) {
  97         case nil:
  98                 buf.WriteString("<nil>")
  99
 100         case *Basic:
 101                 // exported basic types go into package unsafe
 102                 // (currently this is just unsafe.Pointer)
 103                 if isExported(t.name) {
 104                         if obj, _ := Unsafe.scope.Lookup(t.name).(*TypeName); obj != nil {
 105                                 writeTypeName(buf, obj, qf)
 106                                 break
 107                         }
 108                 }
 109
 110                 if gcCompatibilityMode {
 111                         // forget the alias names
 112                         switch t.kind {
 113                         case Byte:
 114                                 t = Typ[Uint8]
 115                         case Rune:
 116                                 t = Typ[Int32]
 117                         }
 118                 }
 119                 buf.WriteString(t.name)
 120
 121         case *Array:
 122                 fmt.Fprintf(buf, "[%d]", t.len)
 123                 writeType(buf, t.elem, qf, visited)
 124
 125         case *Slice:
 126                 buf.WriteString("[]")
 127                 writeType(buf, t.elem, qf, visited)
 128
 129         case *Struct:
 130                 buf.WriteString("struct{")
 131                 for i, f := range t.fields {
 132                         if i > 0 {
 133                                 buf.WriteString("; ")
 134                         }
 135                         // This doesn't do the right thing for embedded type
 136                         // aliases where we should print the alias name, not
 137                         // the aliased type (see issue #44410).
 138                         if !f.embedded {
 139                                 buf.WriteString(f.name)
 140                                 buf.WriteByte(' ')
 141                         }
 142                         writeType(buf, f.typ, qf, visited)
 143                         if tag := t.Tag(i); tag != "" {
 144                                 fmt.Fprintf(buf, " %q", tag)
 145                         }
 146                 }
 147                 buf.WriteByte('}')
 148
 149         case *Pointer:
 150                 buf.WriteByte('*')
 151                 writeType(buf, t.base, qf, visited)
 152
 153         case *Tuple:
 154                 writeTuple(buf, t, false, qf, visited)
 155
 156         case *Signature:
 157                 buf.WriteString("func")
 158                 writeSignature(buf, t, qf, visited)
 159
 160         case *Sum:
 161                 for i, t := range t.types {
 162                         if i > 0 {
 163                                 buf.WriteString(", ")
 164                         }
 165                         writeType(buf, t, qf, visited)
 166                 }
 167
 168         case *Interface:
 169                 // We write the source-level methods and embedded types rather
 170                 // than the actual method set since resolved method signatures
 171                 // may have non-printable cycles if parameters have embedded
 172                 // interface types that (directly or indirectly) embed the
 173                 // current interface. For instance, consider the result type
 174                 // of m:
 175                 //
 176                 //     type T interface{
 177                 //         m() interface{ T }
 178                 //     }
 179                 //
 180                 buf.WriteString("interface{")
 181                 empty := true
 182                 if gcCompatibilityMode {
 183                         // print flattened interface
 184                         // (useful to compare against gc-generated interfaces)
 185                         for i, m := range t.allMethods {
 186                                 if i > 0 {
 187                                         buf.WriteString("; ")
 188                                 }
 189                                 buf.WriteString(m.name)
 190                                 writeSignature(buf, m.typ.(*Signature), qf, visited)
 191                                 empty = false
 192                         }
 193                         if !empty && t.allTypes != nil {
 194                                 buf.WriteString("; ")
 195                         }
 196                         if t.allTypes != nil {
 197                                 buf.WriteString("type ")
 198                                 writeType(buf, t.allTypes, qf, visited)
 199                         }
 200                 } else {
 201                         // print explicit interface methods and embedded types
 202                         for i, m := range t.methods {
 203                                 if i > 0 {
 204                                         buf.WriteString("; ")
 205                                 }
 206                                 buf.WriteString(m.name)
 207                                 writeSignature(buf, m.typ.(*Signature), qf, visited)
 208                                 empty = false
 209                         }
 210                         if !empty && t.types != nil {
 211                                 buf.WriteString("; ")
 212                         }
 213                         if t.types != nil {
 214                                 buf.WriteString("type ")
 215                                 writeType(buf, t.types, qf, visited)
 216                                 empty = false
 217                         }
 218                         if !empty && len(t.embeddeds) > 0 {
 219                                 buf.WriteString("; ")
 220                         }
 221                         for i, typ := range t.embeddeds {
 222                                 if i > 0 {
 223                                         buf.WriteString("; ")
 224                                 }
 225                                 writeType(buf, typ, qf, visited)
 226                                 empty = false
 227                         }
 228                 }
 229                 if debug && (t.allMethods == nil || len(t.methods) > len(t.allMethods)) {
 230                         if !empty {
 231                                 buf.WriteByte(' ')
 232                         }
 233                         buf.WriteString("/* incomplete */")
 234                 }
 235                 buf.WriteByte('}')
 236
 237         case *Map:
 238                 buf.WriteString("map[")
 239                 writeType(buf, t.key, qf, visited)
 240                 buf.WriteByte(']')
 241                 writeType(buf, t.elem, qf, visited)
 242
 243         case *Chan:
 244                 var s string
 245                 var parens bool
 246                 switch t.dir {
 247                 case SendRecv:
 248                         s = "chan "
 249                         // chan (<-chan T) requires parentheses
 250                         if c, _ := t.elem.(*Chan); c != nil && c.dir == RecvOnly {
 251                                 parens = true
 252                         }
 253                 case SendOnly:
 254                         s = "chan<- "
 255                 case RecvOnly:
 256                         s = "<-chan "
 257                 default:
 258                         panic("unreachable")
 259                 }
 260                 buf.WriteString(s)
 261                 if parens {
 262                         buf.WriteByte('(')
 263                 }
 264                 writeType(buf, t.elem, qf, visited)
 265                 if parens {
 266                         buf.WriteByte(')')
 267                 }
 268
 269         case *Named:
 270                 writeTypeName(buf, t.obj, qf)
 271                 if t.targs != nil {
 272                         // instantiated type
 273                         buf.WriteByte('[')
 274                         writeTypeList(buf, t.targs, qf, visited)
 275                         buf.WriteByte(']')
 276                 } else if t.tparams != nil {
 277                         // parameterized type
 278                         writeTParamList(buf, t.tparams, qf, visited)
 279                 }
 280
 281         case *TypeParam:
 282                 s := "?"
 283                 if t.obj != nil {
 284                         // Optionally write out package for typeparams (like Named).
 285                         // TODO(danscales): this is required for import/export, so
 286                         // we maybe need a separate function that won't be changed
 287                         // for debugging purposes.
 288                         if t.obj.pkg != nil {
 289                                 writePackage(buf, t.obj.pkg, qf)
 290                         }
 291                         s = t.obj.name
 292                 }
 293                 buf.WriteString(s + subscript(t.id))
 294
 295         case *instance:
 296                 buf.WriteByte(instanceMarker) // indicate "non-evaluated" syntactic instance
 297                 writeTypeName(buf, t.base.obj, qf)
 298                 buf.WriteByte('[')
 299                 writeTypeList(buf, t.targs, qf, visited)
 300                 buf.WriteByte(']')
 301
 302         case *bottom:
 303                 buf.WriteString("⊥")
 304
 305         case *top:
 306                 buf.WriteString("⊤")
 307
 308         default:
 309                 // For externally defined implementations of Type.
 310                 buf.WriteString(t.String())
 311         }
 312 }
 313
 314 func writeTypeList(buf *bytes.Buffer, list []Type, qf Qualifier, visited []Type) {
 315         for i, typ := range list {
 316                 if i > 0 {
 317                         buf.WriteString(", ")
 318                 }
 319                 writeType(buf, typ, qf, visited)
 320         }
 321 }
 322
 323 func writeTParamList(buf *bytes.Buffer, list []*TypeName, qf Qualifier, visited []Type) {
 324         buf.WriteString("[")
 325         var prev Type
 326         for i, p := range list {
 327                 // TODO(gri) support 'any' sugar here.
 328                 var b Type = &emptyInterface
 329                 if t, _ := p.typ.(*TypeParam); t != nil && t.bound != nil {
 330                         b = t.bound
 331                 }
 332                 if i > 0 {
 333                         if b != prev {
 334                                 // type bound changed - write previous one before advancing
 335                                 buf.WriteByte(' ')
 336                                 writeType(buf, prev, qf, visited)
 337                         }
 338                         buf.WriteString(", ")
 339                 }
 340                 prev = b
 341
 342                 if t, _ := p.typ.(*TypeParam); t != nil {
 343                         writeType(buf, t, qf, visited)
 344                 } else {
 345                         buf.WriteString(p.name)
 346                 }
 347         }
 348         if prev != nil {
 349                 buf.WriteByte(' ')
 350                 writeType(buf, prev, qf, visited)
 351         }
 352         buf.WriteByte(']')
 353 }
 354
 355 func writeTypeName(buf *bytes.Buffer, obj *TypeName, qf Qualifier) {
 356         s := "<Named w/o object>"
 357         if obj != nil {
 358                 if obj.pkg != nil {
 359                         writePackage(buf, obj.pkg, qf)
 360                 }
 361                 // TODO(gri): function-local named types should be displayed
 362                 // differently from named types at package level to avoid
 363                 // ambiguity.
 364                 s = obj.name
 365         }
 366         buf.WriteString(s)
 367 }
 368
 369 func writeTuple(buf *bytes.Buffer, tup *Tuple, variadic bool, qf Qualifier, visited []Type) {
 370         buf.WriteByte('(')
 371         if tup != nil {
 372                 for i, v := range tup.vars {
 373                         if i > 0 {
 374                                 buf.WriteString(", ")
 375                         }
 376                         if v.name != "" {
 377                                 buf.WriteString(v.name)
 378                                 buf.WriteByte(' ')
 379                         }
 380                         typ := v.typ
 381                         if variadic && i == len(tup.vars)-1 {
 382                                 if s, ok := typ.(*Slice); ok {
 383                                         buf.WriteString("...")
 384                                         typ = s.elem
 385                                 } else {
 386                                         // special case:
 387                                         // append(s, "foo"...) leads to signature func([]byte, string...)
 388                                         if t := asBasic(typ); t == nil || t.kind != String {
 389                                                 panic("internal error: string type expected")
 390                                         }
 391                                         writeType(buf, typ, qf, visited)
 392                                         buf.WriteString("...")
 393                                         continue
 394                                 }
 395                         }
 396                         writeType(buf, typ, qf, visited)
 397                 }
 398         }
 399         buf.WriteByte(')')
 400 }
 401
 402 // WriteSignature writes the representation of the signature sig to buf,
 403 // without a leading "func" keyword.
 404 // The Qualifier controls the printing of
 405 // package-level objects, and may be nil.
 406 func WriteSignature(buf *bytes.Buffer, sig *Signature, qf Qualifier) {
 407         writeSignature(buf, sig, qf, make([]Type, 0, 8))
 408 }
 409
 410 func writeSignature(buf *bytes.Buffer, sig *Signature, qf Qualifier, visited []Type) {
 411         if sig.tparams != nil {
 412                 writeTParamList(buf, sig.tparams, qf, visited)
 413         }
 414
 415         writeTuple(buf, sig.params, sig.variadic, qf, visited)
 416
 417         n := sig.results.Len()
 418         if n == 0 {
 419                 // no result
 420                 return
 421         }
 422
 423         buf.WriteByte(' ')
 424         if n == 1 && sig.results.vars[0].name == "" {
 425                 // single unnamed result
 426                 writeType(buf, sig.results.vars[0].typ, qf, visited)
 427                 return
 428         }
 429
 430         // multiple or named result(s)
 431         writeTuple(buf, sig.results, false, qf, visited)
 432 }
 433
 434 // subscript returns the decimal (utf8) representation of x using subscript digits.
 435 func subscript(x uint64) string {
 436         const w = len("₀") // all digits 0...9 have the same utf8 width
 437         var buf [32 * w]byte
 438         i := len(buf)
 439         for {
 440                 i -= w
 441                 utf8.EncodeRune(buf[i:], '₀'+rune(x%10)) // '₀' == U+2080
 442                 x /= 10
 443                 if x == 0 {
 444                         break
 445                 }
 446         }
 447         return string(buf[i:])
 448 }