gcc/go/gofrontend/gogo.cc

   1 // gogo.cc -- Go frontend parsed representation.
   2
   3 // Copyright 2009 The Go Authors. All rights reserved.
   4 // Use of this source code is governed by a BSD-style
   5 // license that can be found in the LICENSE file.
   6
   7 #include "go-system.h"
   8
   9 #include "go-c.h"
  10 #include "go-dump.h"
  11 #include "lex.h"
  12 #include "types.h"
  13 #include "statements.h"
  14 #include "expressions.h"
  15 #include "dataflow.h"
  16 #include "runtime.h"
  17 #include "import.h"
  18 #include "export.h"
  19 #include "backend.h"
  20 #include "gogo.h"
  21
  22 // Class Gogo.
  23
  24 Gogo::Gogo(Backend* backend, Linemap* linemap, int int_type_size,
  25            int pointer_size)
  26   : backend_(backend),
  27     linemap_(linemap),
  28     package_(NULL),
  29     functions_(),
  30     globals_(new Bindings(NULL)),
  31     imports_(),
  32     imported_unsafe_(false),
  33     packages_(),
  34     init_functions_(),
  35     need_init_fn_(false),
  36     init_fn_name_(),
  37     imported_init_fns_(),
  38     unique_prefix_(),
  39     unique_prefix_specified_(false),
  40     verify_types_(),
  41     interface_types_(),
  42     specific_type_functions_(),
  43     specific_type_functions_are_written_(false),
  44     named_types_are_converted_(false)
  45 {
  46   const Location loc = Linemap::predeclared_location();
  47
  48   Named_type* uint8_type = Type::make_integer_type("uint8", true, 8,
  49                                                    RUNTIME_TYPE_KIND_UINT8);
  50   this->add_named_type(uint8_type);
  51   this->add_named_type(Type::make_integer_type("uint16", true,  16,
  52                                                RUNTIME_TYPE_KIND_UINT16));
  53   this->add_named_type(Type::make_integer_type("uint32", true,  32,
  54                                                RUNTIME_TYPE_KIND_UINT32));
  55   this->add_named_type(Type::make_integer_type("uint64", true,  64,
  56                                                RUNTIME_TYPE_KIND_UINT64));
  57
  58   this->add_named_type(Type::make_integer_type("int8",  false,   8,
  59                                                RUNTIME_TYPE_KIND_INT8));
  60   this->add_named_type(Type::make_integer_type("int16", false,  16,
  61                                                RUNTIME_TYPE_KIND_INT16));
  62   Named_type* int32_type = Type::make_integer_type("int32", false,  32,
  63                                                    RUNTIME_TYPE_KIND_INT32);
  64   this->add_named_type(int32_type);
  65   this->add_named_type(Type::make_integer_type("int64", false,  64,
  66                                                RUNTIME_TYPE_KIND_INT64));
  67
  68   this->add_named_type(Type::make_float_type("float32", 32,
  69                                              RUNTIME_TYPE_KIND_FLOAT32));
  70   this->add_named_type(Type::make_float_type("float64", 64,
  71                                              RUNTIME_TYPE_KIND_FLOAT64));
  72
  73   this->add_named_type(Type::make_complex_type("complex64", 64,
  74                                                RUNTIME_TYPE_KIND_COMPLEX64));
  75   this->add_named_type(Type::make_complex_type("complex128", 128,
  76                                                RUNTIME_TYPE_KIND_COMPLEX128));
  77
  78   if (int_type_size < 32)
  79     int_type_size = 32;
  80   this->add_named_type(Type::make_integer_type("uint", true,
  81                                                int_type_size,
  82                                                RUNTIME_TYPE_KIND_UINT));
  83   Named_type* int_type = Type::make_integer_type("int", false, int_type_size,
  84                                                  RUNTIME_TYPE_KIND_INT);
  85   this->add_named_type(int_type);
  86
  87   this->add_named_type(Type::make_integer_type("uintptr", true,
  88                                                pointer_size,
  89                                                RUNTIME_TYPE_KIND_UINTPTR));
  90
  91   // "byte" is an alias for "uint8".
  92   uint8_type->integer_type()->set_is_byte();
  93   Named_object* byte_type = Named_object::make_type("byte", NULL, uint8_type,
  94                                                     loc);
  95   this->add_named_type(byte_type->type_value());
  96
  97   // "rune" is an alias for "int32".
  98   int32_type->integer_type()->set_is_rune();
  99   Named_object* rune_type = Named_object::make_type("rune", NULL, int32_type,
 100                                                     loc);
 101   this->add_named_type(rune_type->type_value());
 102
 103   this->add_named_type(Type::make_named_bool_type());
 104
 105   this->add_named_type(Type::make_named_string_type());
 106
 107   // "error" is interface { Error() string }.
 108   {
 109     Typed_identifier_list *methods = new Typed_identifier_list;
 110     Typed_identifier_list *results = new Typed_identifier_list;
 111     results->push_back(Typed_identifier("", Type::lookup_string_type(), loc));
 112     Type *method_type = Type::make_function_type(NULL, NULL, results, loc);
 113     methods->push_back(Typed_identifier("Error", method_type, loc));
 114     Interface_type *error_iface = Type::make_interface_type(methods, loc);
 115     error_iface->finalize_methods();
 116     Named_type *error_type = Named_object::make_type("error", NULL, error_iface, loc)->type_value();
 117     this->add_named_type(error_type);
 118   }
 119
 120   this->globals_->add_constant(Typed_identifier("true",
 121                                                 Type::make_boolean_type(),
 122                                                 loc),
 123                                NULL,
 124                                Expression::make_boolean(true, loc),
 125                                0);
 126   this->globals_->add_constant(Typed_identifier("false",
 127                                                 Type::make_boolean_type(),
 128                                                 loc),
 129                                NULL,
 130                                Expression::make_boolean(false, loc),
 131                                0);
 132
 133   this->globals_->add_constant(Typed_identifier("nil", Type::make_nil_type(),
 134                                                 loc),
 135                                NULL,
 136                                Expression::make_nil(loc),
 137                                0);
 138
 139   Type* abstract_int_type = Type::make_abstract_integer_type();
 140   this->globals_->add_constant(Typed_identifier("iota", abstract_int_type,
 141                                                 loc),
 142                                NULL,
 143                                Expression::make_iota(),
 144                                0);
 145
 146   Function_type* new_type = Type::make_function_type(NULL, NULL, NULL, loc);
 147   new_type->set_is_varargs();
 148   new_type->set_is_builtin();
 149   this->globals_->add_function_declaration("new", NULL, new_type, loc);
 150
 151   Function_type* make_type = Type::make_function_type(NULL, NULL, NULL, loc);
 152   make_type->set_is_varargs();
 153   make_type->set_is_builtin();
 154   this->globals_->add_function_declaration("make", NULL, make_type, loc);
 155
 156   Typed_identifier_list* len_result = new Typed_identifier_list();
 157   len_result->push_back(Typed_identifier("", int_type, loc));
 158   Function_type* len_type = Type::make_function_type(NULL, NULL, len_result,
 159                                                      loc);
 160   len_type->set_is_builtin();
 161   this->globals_->add_function_declaration("len", NULL, len_type, loc);
 162
 163   Typed_identifier_list* cap_result = new Typed_identifier_list();
 164   cap_result->push_back(Typed_identifier("", int_type, loc));
 165   Function_type* cap_type = Type::make_function_type(NULL, NULL, len_result,
 166                                                      loc);
 167   cap_type->set_is_builtin();
 168   this->globals_->add_function_declaration("cap", NULL, cap_type, loc);
 169
 170   Function_type* print_type = Type::make_function_type(NULL, NULL, NULL, loc);
 171   print_type->set_is_varargs();
 172   print_type->set_is_builtin();
 173   this->globals_->add_function_declaration("print", NULL, print_type, loc);
 174
 175   print_type = Type::make_function_type(NULL, NULL, NULL, loc);
 176   print_type->set_is_varargs();
 177   print_type->set_is_builtin();
 178   this->globals_->add_function_declaration("println", NULL, print_type, loc);
 179
 180   Type *empty = Type::make_empty_interface_type(loc);
 181   Typed_identifier_list* panic_parms = new Typed_identifier_list();
 182   panic_parms->push_back(Typed_identifier("e", empty, loc));
 183   Function_type *panic_type = Type::make_function_type(NULL, panic_parms,
 184                                                        NULL, loc);
 185   panic_type->set_is_builtin();
 186   this->globals_->add_function_declaration("panic", NULL, panic_type, loc);
 187
 188   Typed_identifier_list* recover_result = new Typed_identifier_list();
 189   recover_result->push_back(Typed_identifier("", empty, loc));
 190   Function_type* recover_type = Type::make_function_type(NULL, NULL,
 191                                                          recover_result,
 192                                                          loc);
 193   recover_type->set_is_builtin();
 194   this->globals_->add_function_declaration("recover", NULL, recover_type, loc);
 195
 196   Function_type* close_type = Type::make_function_type(NULL, NULL, NULL, loc);
 197   close_type->set_is_varargs();
 198   close_type->set_is_builtin();
 199   this->globals_->add_function_declaration("close", NULL, close_type, loc);
 200
 201   Typed_identifier_list* copy_result = new Typed_identifier_list();
 202   copy_result->push_back(Typed_identifier("", int_type, loc));
 203   Function_type* copy_type = Type::make_function_type(NULL, NULL,
 204                                                       copy_result, loc);
 205   copy_type->set_is_varargs();
 206   copy_type->set_is_builtin();
 207   this->globals_->add_function_declaration("copy", NULL, copy_type, loc);
 208
 209   Function_type* append_type = Type::make_function_type(NULL, NULL, NULL, loc);
 210   append_type->set_is_varargs();
 211   append_type->set_is_builtin();
 212   this->globals_->add_function_declaration("append", NULL, append_type, loc);
 213
 214   Function_type* complex_type = Type::make_function_type(NULL, NULL, NULL, loc);
 215   complex_type->set_is_varargs();
 216   complex_type->set_is_builtin();
 217   this->globals_->add_function_declaration("complex", NULL, complex_type, loc);
 218
 219   Function_type* real_type = Type::make_function_type(NULL, NULL, NULL, loc);
 220   real_type->set_is_varargs();
 221   real_type->set_is_builtin();
 222   this->globals_->add_function_declaration("real", NULL, real_type, loc);
 223
 224   Function_type* imag_type = Type::make_function_type(NULL, NULL, NULL, loc);
 225   imag_type->set_is_varargs();
 226   imag_type->set_is_builtin();
 227   this->globals_->add_function_declaration("imag", NULL, imag_type, loc);
 228
 229   Function_type* delete_type = Type::make_function_type(NULL, NULL, NULL, loc);
 230   delete_type->set_is_varargs();
 231   delete_type->set_is_builtin();
 232   this->globals_->add_function_declaration("delete", NULL, delete_type, loc);
 233 }
 234
 235 // Munge name for use in an error message.
 236
 237 std::string
 238 Gogo::message_name(const std::string& name)
 239 {
 240   return go_localize_identifier(Gogo::unpack_hidden_name(name).c_str());
 241 }
 242
 243 // Get the package name.
 244
 245 const std::string&
 246 Gogo::package_name() const
 247 {
 248   go_assert(this->package_ != NULL);
 249   return this->package_->name();
 250 }
 251
 252 // Set the package name.
 253
 254 void
 255 Gogo::set_package_name(const std::string& package_name,
 256                        Location location)
 257 {
 258   if (this->package_ != NULL && this->package_->name() != package_name)
 259     {
 260       error_at(location, "expected package %<%s%>",
 261                Gogo::message_name(this->package_->name()).c_str());
 262       return;
 263     }
 264
 265   // If the user did not specify a unique prefix, we always use "go".
 266   // This in effect requires that the package name be unique.
 267   if (this->unique_prefix_.empty())
 268     this->unique_prefix_ = "go";
 269
 270   this->package_ = this->register_package(package_name, this->unique_prefix_,
 271                                           location);
 272
 273   // We used to permit people to qualify symbols with the current
 274   // package name (e.g., P.x), but we no longer do.
 275   // this->globals_->add_package(package_name, this->package_);
 276
 277   if (this->is_main_package())
 278     {
 279       // Declare "main" as a function which takes no parameters and
 280       // returns no value.
 281       Location uloc = Linemap::unknown_location();
 282       this->declare_function("main",
 283                              Type::make_function_type (NULL, NULL, NULL, uloc),
 284                              uloc);
 285     }
 286 }
 287
 288 // Return whether this is the "main" package.  This is not true if
 289 // -fgo-prefix was used.
 290
 291 bool
 292 Gogo::is_main_package() const
 293 {
 294   return this->package_name() == "main" && !this->unique_prefix_specified_;
 295 }
 296
 297 // Import a package.
 298
 299 void
 300 Gogo::import_package(const std::string& filename,
 301                      const std::string& local_name,
 302                      bool is_local_name_exported,
 303                      Location location)
 304 {
 305   if (filename == "unsafe")
 306     {
 307       this->import_unsafe(local_name, is_local_name_exported, location);
 308       return;
 309     }
 310
 311   Imports::const_iterator p = this->imports_.find(filename);
 312   if (p != this->imports_.end())
 313     {
 314       Package* package = p->second;
 315       package->set_location(location);
 316       package->set_is_imported();
 317       std::string ln = local_name;
 318       bool is_ln_exported = is_local_name_exported;
 319       if (ln.empty())
 320         {
 321           ln = package->name();
 322           is_ln_exported = Lex::is_exported_name(ln);
 323         }
 324       if (ln == ".")
 325         {
 326           Bindings* bindings = package->bindings();
 327           for (Bindings::const_declarations_iterator p =
 328                  bindings->begin_declarations();
 329                p != bindings->end_declarations();
 330                ++p)
 331             this->add_named_object(p->second);
 332         }
 333       else if (ln == "_")
 334         package->set_uses_sink_alias();
 335       else
 336         {
 337           ln = this->pack_hidden_name(ln, is_ln_exported);
 338           this->package_->bindings()->add_package(ln, package);
 339         }
 340       return;
 341     }
 342
 343   Import::Stream* stream = Import::open_package(filename, location);
 344   if (stream == NULL)
 345     {
 346       error_at(location, "import file %qs not found", filename.c_str());
 347       return;
 348     }
 349
 350   Import imp(stream, location);
 351   imp.register_builtin_types(this);
 352   Package* package = imp.import(this, local_name, is_local_name_exported);
 353   if (package != NULL)
 354     {
 355       if (package->name() == this->package_name()
 356           && package->unique_prefix() == this->unique_prefix())
 357         error_at(location,
 358                  ("imported package uses same package name and prefix "
 359                   "as package being compiled (see -fgo-prefix option)"));
 360
 361       this->imports_.insert(std::make_pair(filename, package));
 362       package->set_is_imported();
 363     }
 364
 365   delete stream;
 366 }
 367
 368 // Add an import control function for an imported package to the list.
 369
 370 void
 371 Gogo::add_import_init_fn(const std::string& package_name,
 372                          const std::string& init_name, int prio)
 373 {
 374   for (std::set<Import_init>::const_iterator p =
 375          this->imported_init_fns_.begin();
 376        p != this->imported_init_fns_.end();
 377        ++p)
 378     {
 379       if (p->init_name() == init_name
 380           && (p->package_name() != package_name || p->priority() != prio))
 381         {
 382           error("duplicate package initialization name %qs",
 383                 Gogo::message_name(init_name).c_str());
 384           inform(UNKNOWN_LOCATION, "used by package %qs at priority %d",
 385                  Gogo::message_name(p->package_name()).c_str(),
 386                  p->priority());
 387           inform(UNKNOWN_LOCATION, " and by package %qs at priority %d",
 388                  Gogo::message_name(package_name).c_str(), prio);
 389           return;
 390         }
 391     }
 392
 393   this->imported_init_fns_.insert(Import_init(package_name, init_name,
 394                                               prio));
 395 }
 396
 397 // Return whether we are at the global binding level.
 398
 399 bool
 400 Gogo::in_global_scope() const
 401 {
 402   return this->functions_.empty();
 403 }
 404
 405 // Return the current binding contour.
 406
 407 Bindings*
 408 Gogo::current_bindings()
 409 {
 410   if (!this->functions_.empty())
 411     return this->functions_.back().blocks.back()->bindings();
 412   else if (this->package_ != NULL)
 413     return this->package_->bindings();
 414   else
 415     return this->globals_;
 416 }
 417
 418 const Bindings*
 419 Gogo::current_bindings() const
 420 {
 421   if (!this->functions_.empty())
 422     return this->functions_.back().blocks.back()->bindings();
 423   else if (this->package_ != NULL)
 424     return this->package_->bindings();
 425   else
 426     return this->globals_;
 427 }
 428
 429 // Return the current block.
 430
 431 Block*
 432 Gogo::current_block()
 433 {
 434   if (this->functions_.empty())
 435     return NULL;
 436   else
 437     return this->functions_.back().blocks.back();
 438 }
 439
 440 // Look up a name in the current binding contour.  If PFUNCTION is not
 441 // NULL, set it to the function in which the name is defined, or NULL
 442 // if the name is defined in global scope.
 443
 444 Named_object*
 445 Gogo::lookup(const std::string& name, Named_object** pfunction) const
 446 {
 447   if (pfunction != NULL)
 448     *pfunction = NULL;
 449
 450   if (Gogo::is_sink_name(name))
 451     return Named_object::make_sink();
 452
 453   for (Open_functions::const_reverse_iterator p = this->functions_.rbegin();
 454        p != this->functions_.rend();
 455        ++p)
 456     {
 457       Named_object* ret = p->blocks.back()->bindings()->lookup(name);
 458       if (ret != NULL)
 459         {
 460           if (pfunction != NULL)
 461             *pfunction = p->function;
 462           return ret;
 463         }
 464     }
 465
 466   if (this->package_ != NULL)
 467     {
 468       Named_object* ret = this->package_->bindings()->lookup(name);
 469       if (ret != NULL)
 470         {
 471           if (ret->package() != NULL)
 472             ret->package()->set_used();
 473           return ret;
 474         }
 475     }
 476
 477   // We do not look in the global namespace.  If we did, the global
 478   // namespace would effectively hide names which were defined in
 479   // package scope which we have not yet seen.  Instead,
 480   // define_global_names is called after parsing is over to connect
 481   // undefined names at package scope with names defined at global
 482   // scope.
 483
 484   return NULL;
 485 }
 486
 487 // Look up a name in the current block, without searching enclosing
 488 // blocks.
 489
 490 Named_object*
 491 Gogo::lookup_in_block(const std::string& name) const
 492 {
 493   go_assert(!this->functions_.empty());
 494   go_assert(!this->functions_.back().blocks.empty());
 495   return this->functions_.back().blocks.back()->bindings()->lookup_local(name);
 496 }
 497
 498 // Look up a name in the global namespace.
 499
 500 Named_object*
 501 Gogo::lookup_global(const char* name) const
 502 {
 503   return this->globals_->lookup(name);
 504 }
 505
 506 // Add an imported package.
 507
 508 Package*
 509 Gogo::add_imported_package(const std::string& real_name,
 510                            const std::string& alias_arg,
 511                            bool is_alias_exported,
 512                            const std::string& unique_prefix,
 513                            Location location,
 514                            bool* padd_to_globals)
 515 {
 516   // FIXME: Now that we compile packages as a whole, should we permit
 517   // importing the current package?
 518   if (this->package_name() == real_name
 519       && this->unique_prefix() == unique_prefix)
 520     {
 521       *padd_to_globals = false;
 522       if (!alias_arg.empty() && alias_arg != ".")
 523         {
 524           std::string alias = this->pack_hidden_name(alias_arg,
 525                                                      is_alias_exported);
 526           this->package_->bindings()->add_package(alias, this->package_);
 527         }
 528       return this->package_;
 529     }
 530   else if (alias_arg == ".")
 531     {
 532       *padd_to_globals = true;
 533       return this->register_package(real_name, unique_prefix, location);
 534     }
 535   else if (alias_arg == "_")
 536     {
 537       Package* ret = this->register_package(real_name, unique_prefix, location);
 538       ret->set_uses_sink_alias();
 539       return ret;
 540     }
 541   else
 542     {
 543       *padd_to_globals = false;
 544       std::string alias = alias_arg;
 545       if (alias.empty())
 546         {
 547           alias = real_name;
 548           is_alias_exported = Lex::is_exported_name(alias);
 549         }
 550       alias = this->pack_hidden_name(alias, is_alias_exported);
 551       Named_object* no = this->add_package(real_name, alias, unique_prefix,
 552                                            location);
 553       if (!no->is_package())
 554         return NULL;
 555       return no->package_value();
 556     }
 557 }
 558
 559 // Add a package.
 560
 561 Named_object*
 562 Gogo::add_package(const std::string& real_name, const std::string& alias,
 563                   const std::string& unique_prefix, Location location)
 564 {
 565   go_assert(this->in_global_scope());
 566
 567   // Register the package.  Note that we might have already seen it in
 568   // an earlier import.
 569   Package* package = this->register_package(real_name, unique_prefix, location);
 570
 571   return this->package_->bindings()->add_package(alias, package);
 572 }
 573
 574 // Register a package.  This package may or may not be imported.  This
 575 // returns the Package structure for the package, creating if it
 576 // necessary.
 577
 578 Package*
 579 Gogo::register_package(const std::string& package_name,
 580                        const std::string& unique_prefix,
 581                        Location location)
 582 {
 583   go_assert(!unique_prefix.empty() && !package_name.empty());
 584   std::string name = unique_prefix + '.' + package_name;
 585   Package* package = NULL;
 586   std::pair<Packages::iterator, bool> ins =
 587     this->packages_.insert(std::make_pair(name, package));
 588   if (!ins.second)
 589     {
 590       // We have seen this package name before.
 591       package = ins.first->second;
 592       go_assert(package != NULL);
 593       go_assert(package->name() == package_name
 594                  && package->unique_prefix() == unique_prefix);
 595       if (Linemap::is_unknown_location(package->location()))
 596         package->set_location(location);
 597     }
 598   else
 599     {
 600       // First time we have seen this package name.
 601       package = new Package(package_name, unique_prefix, location);
 602       go_assert(ins.first->second == NULL);
 603       ins.first->second = package;
 604     }
 605
 606   return package;
 607 }
 608
 609 // Start compiling a function.
 610
 611 Named_object*
 612 Gogo::start_function(const std::string& name, Function_type* type,
 613                      bool add_method_to_type, Location location)
 614 {
 615   bool at_top_level = this->functions_.empty();
 616
 617   Block* block = new Block(NULL, location);
 618
 619   Function* enclosing = (at_top_level
 620                          ? NULL
 621                          : this->functions_.back().function->func_value());
 622
 623   Function* function = new Function(type, enclosing, block, location);
 624
 625   if (type->is_method())
 626     {
 627       const Typed_identifier* receiver = type->receiver();
 628       Variable* this_param = new Variable(receiver->type(), NULL, false,
 629                                           true, true, location);
 630       std::string rname = receiver->name();
 631       if (rname.empty() || Gogo::is_sink_name(rname))
 632         {
 633           // We need to give receivers a name since they wind up in
 634           // DECL_ARGUMENTS.  FIXME.
 635           static unsigned int count;
 636           char buf[50];
 637           snprintf(buf, sizeof buf, "r.%u", count);
 638           ++count;
 639           rname = buf;
 640         }
 641       block->bindings()->add_variable(rname, NULL, this_param);
 642     }
 643
 644   const Typed_identifier_list* parameters = type->parameters();
 645   bool is_varargs = type->is_varargs();
 646   if (parameters != NULL)
 647     {
 648       for (Typed_identifier_list::const_iterator p = parameters->begin();
 649            p != parameters->end();
 650            ++p)
 651         {
 652           Variable* param = new Variable(p->type(), NULL, false, true, false,
 653                                          location);
 654           if (is_varargs && p + 1 == parameters->end())
 655             param->set_is_varargs_parameter();
 656
 657           std::string pname = p->name();
 658           if (pname.empty() || Gogo::is_sink_name(pname))
 659             {
 660               // We need to give parameters a name since they wind up
 661               // in DECL_ARGUMENTS.  FIXME.
 662               static unsigned int count;
 663               char buf[50];
 664               snprintf(buf, sizeof buf, "p.%u", count);
 665               ++count;
 666               pname = buf;
 667             }
 668           block->bindings()->add_variable(pname, NULL, param);
 669         }
 670     }
 671
 672   function->create_result_variables(this);
 673
 674   const std::string* pname;
 675   std::string nested_name;
 676   bool is_init = false;
 677   if (Gogo::unpack_hidden_name(name) == "init" && !type->is_method())
 678     {
 679       if ((type->parameters() != NULL && !type->parameters()->empty())
 680           || (type->results() != NULL && !type->results()->empty()))
 681         error_at(location,
 682                  "func init must have no arguments and no return values");
 683       // There can be multiple "init" functions, so give them each a
 684       // different name.
 685       static int init_count;
 686       char buf[30];
 687       snprintf(buf, sizeof buf, ".$init%d", init_count);
 688       ++init_count;
 689       nested_name = buf;
 690       pname = &nested_name;
 691       is_init = true;
 692     }
 693   else if (!name.empty())
 694     pname = &name;
 695   else
 696     {
 697       // Invent a name for a nested function.
 698       static int nested_count;
 699       char buf[30];
 700       snprintf(buf, sizeof buf, ".$nested%d", nested_count);
 701       ++nested_count;
 702       nested_name = buf;
 703       pname = &nested_name;
 704     }
 705
 706   Named_object* ret;
 707   if (Gogo::is_sink_name(*pname))
 708     {
 709       static int sink_count;
 710       char buf[30];
 711       snprintf(buf, sizeof buf, ".$sink%d", sink_count);
 712       ++sink_count;
 713       ret = Named_object::make_function(buf, NULL, function);
 714     }
 715   else if (!type->is_method())
 716     {
 717       ret = this->package_->bindings()->add_function(*pname, NULL, function);
 718       if (!ret->is_function() || ret->func_value() != function)
 719         {
 720           // Redefinition error.  Invent a name to avoid knockon
 721           // errors.
 722           static int redefinition_count;
 723           char buf[30];
 724           snprintf(buf, sizeof buf, ".$redefined%d", redefinition_count);
 725           ++redefinition_count;
 726           ret = this->package_->bindings()->add_function(buf, NULL, function);
 727         }
 728     }
 729   else
 730     {
 731       if (!add_method_to_type)
 732         ret = Named_object::make_function(name, NULL, function);
 733       else
 734         {
 735           go_assert(at_top_level);
 736           Type* rtype = type->receiver()->type();
 737
 738           // We want to look through the pointer created by the
 739           // parser, without getting an error if the type is not yet
 740           // defined.
 741           if (rtype->classification() == Type::TYPE_POINTER)
 742             rtype = rtype->points_to();
 743
 744           if (rtype->is_error_type())
 745             ret = Named_object::make_function(name, NULL, function);
 746           else if (rtype->named_type() != NULL)
 747             {
 748               ret = rtype->named_type()->add_method(name, function);
 749               if (!ret->is_function())
 750                 {
 751                   // Redefinition error.
 752                   ret = Named_object::make_function(name, NULL, function);
 753                 }
 754             }
 755           else if (rtype->forward_declaration_type() != NULL)
 756             {
 757               Named_object* type_no =
 758                 rtype->forward_declaration_type()->named_object();
 759               if (type_no->is_unknown())
 760                 {
 761                   // If we are seeing methods it really must be a
 762                   // type.  Declare it as such.  An alternative would
 763                   // be to support lists of methods for unknown
 764                   // expressions.  Either way the error messages if
 765                   // this is not a type are going to get confusing.
 766                   Named_object* declared =
 767                     this->declare_package_type(type_no->name(),
 768                                                type_no->location());
 769                   go_assert(declared
 770                              == type_no->unknown_value()->real_named_object());
 771                 }
 772               ret = rtype->forward_declaration_type()->add_method(name,
 773                                                                   function);
 774             }
 775           else
 776             go_unreachable();
 777         }
 778       this->package_->bindings()->add_method(ret);
 779     }
 780
 781   this->functions_.resize(this->functions_.size() + 1);
 782   Open_function& of(this->functions_.back());
 783   of.function = ret;
 784   of.blocks.push_back(block);
 785
 786   if (is_init)
 787     {
 788       this->init_functions_.push_back(ret);
 789       this->need_init_fn_ = true;
 790     }
 791
 792   return ret;
 793 }
 794
 795 // Finish compiling a function.
 796
 797 void
 798 Gogo::finish_function(Location location)
 799 {
 800   this->finish_block(location);
 801   go_assert(this->functions_.back().blocks.empty());
 802   this->functions_.pop_back();
 803 }
 804
 805 // Return the current function.
 806
 807 Named_object*
 808 Gogo::current_function() const
 809 {
 810   go_assert(!this->functions_.empty());
 811   return this->functions_.back().function;
 812 }
 813
 814 // Start a new block.
 815
 816 void
 817 Gogo::start_block(Location location)
 818 {
 819   go_assert(!this->functions_.empty());
 820   Block* block = new Block(this->current_block(), location);
 821   this->functions_.back().blocks.push_back(block);
 822 }
 823
 824 // Finish a block.
 825
 826 Block*
 827 Gogo::finish_block(Location location)
 828 {
 829   go_assert(!this->functions_.empty());
 830   go_assert(!this->functions_.back().blocks.empty());
 831   Block* block = this->functions_.back().blocks.back();
 832   this->functions_.back().blocks.pop_back();
 833   block->set_end_location(location);
 834   return block;
 835 }
 836
 837 // Add an erroneous name.
 838
 839 Named_object*
 840 Gogo::add_erroneous_name(const std::string& name)
 841 {
 842   return this->package_->bindings()->add_erroneous_name(name);
 843 }
 844
 845 // Add an unknown name.
 846
 847 Named_object*
 848 Gogo::add_unknown_name(const std::string& name, Location location)
 849 {
 850   return this->package_->bindings()->add_unknown_name(name, location);
 851 }
 852
 853 // Declare a function.
 854
 855 Named_object*
 856 Gogo::declare_function(const std::string& name, Function_type* type,
 857                        Location location)
 858 {
 859   if (!type->is_method())
 860     return this->current_bindings()->add_function_declaration(name, NULL, type,
 861                                                               location);
 862   else
 863     {
 864       // We don't bother to add this to the list of global
 865       // declarations.
 866       Type* rtype = type->receiver()->type();
 867
 868       // We want to look through the pointer created by the
 869       // parser, without getting an error if the type is not yet
 870       // defined.
 871       if (rtype->classification() == Type::TYPE_POINTER)
 872         rtype = rtype->points_to();
 873
 874       if (rtype->is_error_type())
 875         return NULL;
 876       else if (rtype->named_type() != NULL)
 877         return rtype->named_type()->add_method_declaration(name, NULL, type,
 878                                                            location);
 879       else if (rtype->forward_declaration_type() != NULL)
 880         {
 881           Forward_declaration_type* ftype = rtype->forward_declaration_type();
 882           return ftype->add_method_declaration(name, NULL, type, location);
 883         }
 884       else
 885         go_unreachable();
 886     }
 887 }
 888
 889 // Add a label definition.
 890
 891 Label*
 892 Gogo::add_label_definition(const std::string& label_name,
 893                            Location location)
 894 {
 895   go_assert(!this->functions_.empty());
 896   Function* func = this->functions_.back().function->func_value();
 897   Label* label = func->add_label_definition(this, label_name, location);
 898   this->add_statement(Statement::make_label_statement(label, location));
 899   return label;
 900 }
 901
 902 // Add a label reference.
 903
 904 Label*
 905 Gogo::add_label_reference(const std::string& label_name,
 906                           Location location, bool issue_goto_errors)
 907 {
 908   go_assert(!this->functions_.empty());
 909   Function* func = this->functions_.back().function->func_value();
 910   return func->add_label_reference(this, label_name, location,
 911                                    issue_goto_errors);
 912 }
 913
 914 // Return the current binding state.
 915
 916 Bindings_snapshot*
 917 Gogo::bindings_snapshot(Location location)
 918 {
 919   return new Bindings_snapshot(this->current_block(), location);
 920 }
 921
 922 // Add a statement.
 923
 924 void
 925 Gogo::add_statement(Statement* statement)
 926 {
 927   go_assert(!this->functions_.empty()
 928              && !this->functions_.back().blocks.empty());
 929   this->functions_.back().blocks.back()->add_statement(statement);
 930 }
 931
 932 // Add a block.
 933
 934 void
 935 Gogo::add_block(Block* block, Location location)
 936 {
 937   go_assert(!this->functions_.empty()
 938              && !this->functions_.back().blocks.empty());
 939   Statement* statement = Statement::make_block_statement(block, location);
 940   this->functions_.back().blocks.back()->add_statement(statement);
 941 }
 942
 943 // Add a constant.
 944
 945 Named_object*
 946 Gogo::add_constant(const Typed_identifier& tid, Expression* expr,
 947                    int iota_value)
 948 {
 949   return this->current_bindings()->add_constant(tid, NULL, expr, iota_value);
 950 }
 951
 952 // Add a type.
 953
 954 void
 955 Gogo::add_type(const std::string& name, Type* type, Location location)
 956 {
 957   Named_object* no = this->current_bindings()->add_type(name, NULL, type,
 958                                                         location);
 959   if (!this->in_global_scope() && no->is_type())
 960     no->type_value()->set_in_function(this->functions_.back().function);
 961 }
 962
 963 // Add a named type.
 964
 965 void
 966 Gogo::add_named_type(Named_type* type)
 967 {
 968   go_assert(this->in_global_scope());
 969   this->current_bindings()->add_named_type(type);
 970 }
 971
 972 // Declare a type.
 973
 974 Named_object*
 975 Gogo::declare_type(const std::string& name, Location location)
 976 {
 977   Bindings* bindings = this->current_bindings();
 978   Named_object* no = bindings->add_type_declaration(name, NULL, location);
 979   if (!this->in_global_scope() && no->is_type_declaration())
 980     {
 981       Named_object* f = this->functions_.back().function;
 982       no->type_declaration_value()->set_in_function(f);
 983     }
 984   return no;
 985 }
 986
 987 // Declare a type at the package level.
 988
 989 Named_object*
 990 Gogo::declare_package_type(const std::string& name, Location location)
 991 {
 992   return this->package_->bindings()->add_type_declaration(name, NULL, location);
 993 }
 994
 995 // Declare a function at the package level.
 996
 997 Named_object*
 998 Gogo::declare_package_function(const std::string& name, Function_type* type,
 999                                Location location)
1000 {
1001   return this->package_->bindings()->add_function_declaration(name, NULL, type,
1002                                                               location);
1003 }
1004
1005 // Define a type which was already declared.
1006
1007 void
1008 Gogo::define_type(Named_object* no, Named_type* type)
1009 {
1010   this->current_bindings()->define_type(no, type);
1011 }
1012
1013 // Add a variable.
1014
1015 Named_object*
1016 Gogo::add_variable(const std::string& name, Variable* variable)
1017 {
1018   Named_object* no = this->current_bindings()->add_variable(name, NULL,
1019                                                             variable);
1020
1021   // In a function the middle-end wants to see a DECL_EXPR node.
1022   if (no != NULL
1023       && no->is_variable()
1024       && !no->var_value()->is_parameter()
1025       && !this->functions_.empty())
1026     this->add_statement(Statement::make_variable_declaration(no));
1027
1028   return no;
1029 }
1030
1031 // Add a sink--a reference to the blank identifier _.
1032
1033 Named_object*
1034 Gogo::add_sink()
1035 {
1036   return Named_object::make_sink();
1037 }
1038
1039 // Add a named object.
1040
1041 void
1042 Gogo::add_named_object(Named_object* no)
1043 {
1044   this->current_bindings()->add_named_object(no);
1045 }
1046
1047 // Mark all local variables used.  This is used when some types of
1048 // parse error occur.
1049
1050 void
1051 Gogo::mark_locals_used()
1052 {
1053   for (Open_functions::iterator pf = this->functions_.begin();
1054        pf != this->functions_.end();
1055        ++pf)
1056     {
1057       for (std::vector<Block*>::iterator pb = pf->blocks.begin();
1058            pb != pf->blocks.end();
1059            ++pb)
1060         (*pb)->bindings()->mark_locals_used();
1061     }
1062 }
1063
1064 // Record that we've seen an interface type.
1065
1066 void
1067 Gogo::record_interface_type(Interface_type* itype)
1068 {
1069   this->interface_types_.push_back(itype);
1070 }
1071
1072 // Return a name for a thunk object.
1073
1074 std::string
1075 Gogo::thunk_name()
1076 {
1077   static int thunk_count;
1078   char thunk_name[50];
1079   snprintf(thunk_name, sizeof thunk_name, "$thunk%d", thunk_count);
1080   ++thunk_count;
1081   return thunk_name;
1082 }
1083
1084 // Return whether a function is a thunk.
1085
1086 bool
1087 Gogo::is_thunk(const Named_object* no)
1088 {
1089   return no->name().compare(0, 6, "$thunk") == 0;
1090 }
1091
1092 // Define the global names.  We do this only after parsing all the
1093 // input files, because the program might define the global names
1094 // itself.
1095
1096 void
1097 Gogo::define_global_names()
1098 {
1099   for (Bindings::const_declarations_iterator p =
1100          this->globals_->begin_declarations();
1101        p != this->globals_->end_declarations();
1102        ++p)
1103     {
1104       Named_object* global_no = p->second;
1105       std::string name(Gogo::pack_hidden_name(global_no->name(), false));
1106       Named_object* no = this->package_->bindings()->lookup(name);
1107       if (no == NULL)
1108         continue;
1109       no = no->resolve();
1110       if (no->is_type_declaration())
1111         {
1112           if (global_no->is_type())
1113             {
1114               if (no->type_declaration_value()->has_methods())
1115                 error_at(no->location(),
1116                          "may not define methods for global type");
1117               no->set_type_value(global_no->type_value());
1118             }
1119           else
1120             {
1121               error_at(no->location(), "expected type");
1122               Type* errtype = Type::make_error_type();
1123               Named_object* err =
1124                 Named_object::make_type("erroneous_type", NULL, errtype,
1125                                         Linemap::predeclared_location());
1126               no->set_type_value(err->type_value());
1127             }
1128         }
1129       else if (no->is_unknown())
1130         no->unknown_value()->set_real_named_object(global_no);
1131     }
1132 }
1133
1134 // Clear out names in file scope.
1135
1136 void
1137 Gogo::clear_file_scope()
1138 {
1139   this->package_->bindings()->clear_file_scope();
1140
1141   // Warn about packages which were imported but not used.
1142   for (Packages::iterator p = this->packages_.begin();
1143        p != this->packages_.end();
1144        ++p)
1145     {
1146       Package* package = p->second;
1147       if (package != this->package_
1148           && package->is_imported()
1149           && !package->used()
1150           && !package->uses_sink_alias()
1151           && !saw_errors())
1152         error_at(package->location(), "imported and not used: %s",
1153                  Gogo::message_name(package->name()).c_str());
1154       package->clear_is_imported();
1155       package->clear_uses_sink_alias();
1156       package->clear_used();
1157     }
1158 }
1159
1160 // Queue up a type specific function for later writing.  These are
1161 // written out in write_specific_type_functions, called after the
1162 // parse tree is lowered.
1163
1164 void
1165 Gogo::queue_specific_type_function(Type* type, Named_type* name,
1166                                    const std::string& hash_name,
1167                                    Function_type* hash_fntype,
1168                                    const std::string& equal_name,
1169                                    Function_type* equal_fntype)
1170 {
1171   go_assert(!this->specific_type_functions_are_written_);
1172   go_assert(!this->in_global_scope());
1173   Specific_type_function* tsf = new Specific_type_function(type, name,
1174                                                            hash_name,
1175                                                            hash_fntype,
1176                                                            equal_name,
1177                                                            equal_fntype);
1178   this->specific_type_functions_.push_back(tsf);
1179 }
1180
1181 // Look for types which need specific hash or equality functions.
1182
1183 class Specific_type_functions : public Traverse
1184 {
1185  public:
1186   Specific_type_functions(Gogo* gogo)
1187     : Traverse(traverse_types),
1188       gogo_(gogo)
1189   { }
1190
1191   int
1192   type(Type*);
1193
1194  private:
1195   Gogo* gogo_;
1196 };
1197
1198 int
1199 Specific_type_functions::type(Type* t)
1200 {
1201   Named_object* hash_fn;
1202   Named_object* equal_fn;
1203   switch (t->classification())
1204     {
1205     case Type::TYPE_NAMED:
1206       {
1207         Named_type* nt = t->named_type();
1208         if (!t->compare_is_identity(this->gogo_) && t->is_comparable())
1209           t->type_functions(this->gogo_, nt, NULL, NULL, &hash_fn, &equal_fn);
1210
1211         // If this is a struct type, we don't want to make functions
1212         // for the unnamed struct.
1213         Type* rt = nt->real_type();
1214         if (rt->struct_type() == NULL)
1215           {
1216             if (Type::traverse(rt, this) == TRAVERSE_EXIT)
1217               return TRAVERSE_EXIT;
1218           }
1219         else
1220           {
1221             // If this type is defined in another package, then we don't
1222             // need to worry about the unexported fields.
1223             bool is_defined_elsewhere = nt->named_object()->package() != NULL;
1224             const Struct_field_list* fields = rt->struct_type()->fields();
1225             for (Struct_field_list::const_iterator p = fields->begin();
1226                  p != fields->end();
1227                  ++p)
1228               {
1229                 if (is_defined_elsewhere
1230                     && Gogo::is_hidden_name(p->field_name()))
1231                   continue;
1232                 if (Type::traverse(p->type(), this) == TRAVERSE_EXIT)
1233                   return TRAVERSE_EXIT;
1234               }
1235           }
1236
1237         return TRAVERSE_SKIP_COMPONENTS;
1238       }
1239
1240     case Type::TYPE_STRUCT:
1241     case Type::TYPE_ARRAY:
1242       if (!t->compare_is_identity(this->gogo_) && t->is_comparable())
1243         t->type_functions(this->gogo_, NULL, NULL, NULL, &hash_fn, &equal_fn);
1244       break;
1245
1246     default:
1247       break;
1248     }
1249
1250   return TRAVERSE_CONTINUE;
1251 }
1252
1253 // Write out type specific functions.
1254
1255 void
1256 Gogo::write_specific_type_functions()
1257 {
1258   Specific_type_functions stf(this);
1259   this->traverse(&stf);
1260
1261   while (!this->specific_type_functions_.empty())
1262     {
1263       Specific_type_function* tsf = this->specific_type_functions_.back();
1264       this->specific_type_functions_.pop_back();
1265       tsf->type->write_specific_type_functions(this, tsf->name,
1266                                                tsf->hash_name,
1267                                                tsf->hash_fntype,
1268                                                tsf->equal_name,
1269                                                tsf->equal_fntype);
1270       delete tsf;
1271     }
1272   this->specific_type_functions_are_written_ = true;
1273 }
1274
1275 // Traverse the tree.
1276
1277 void
1278 Gogo::traverse(Traverse* traverse)
1279 {
1280   // Traverse the current package first for consistency.  The other
1281   // packages will only contain imported types, constants, and
1282   // declarations.
1283   if (this->package_->bindings()->traverse(traverse, true) == TRAVERSE_EXIT)
1284     return;
1285   for (Packages::const_iterator p = this->packages_.begin();
1286        p != this->packages_.end();
1287        ++p)
1288     {
1289       if (p->second != this->package_)
1290         {
1291           if (p->second->bindings()->traverse(traverse, true) == TRAVERSE_EXIT)
1292             break;
1293         }
1294     }
1295 }
1296
1297 // Add a type to verify.  This is used for types of sink variables, in
1298 // order to give appropriate error messages.
1299
1300 void
1301 Gogo::add_type_to_verify(Type* type)
1302 {
1303   this->verify_types_.push_back(type);
1304 }
1305
1306 // Traversal class used to verify types.
1307
1308 class Verify_types : public Traverse
1309 {
1310  public:
1311   Verify_types()
1312     : Traverse(traverse_types)
1313   { }
1314
1315   int
1316   type(Type*);
1317 };
1318
1319 // Verify that a type is correct.
1320
1321 int
1322 Verify_types::type(Type* t)
1323 {
1324   if (!t->verify())
1325     return TRAVERSE_SKIP_COMPONENTS;
1326   return TRAVERSE_CONTINUE;
1327 }
1328
1329 // Verify that all types are correct.
1330
1331 void
1332 Gogo::verify_types()
1333 {
1334   Verify_types traverse;
1335   this->traverse(&traverse);
1336
1337   for (std::vector<Type*>::iterator p = this->verify_types_.begin();
1338        p != this->verify_types_.end();
1339        ++p)
1340     (*p)->verify();
1341   this->verify_types_.clear();
1342 }
1343
1344 // Traversal class used to lower parse tree.
1345
1346 class Lower_parse_tree : public Traverse
1347 {
1348  public:
1349   Lower_parse_tree(Gogo* gogo, Named_object* function)
1350     : Traverse(traverse_variables
1351                | traverse_constants
1352                | traverse_functions
1353                | traverse_statements
1354                | traverse_expressions),
1355       gogo_(gogo), function_(function), iota_value_(-1), inserter_()
1356   { }
1357
1358   void
1359   set_inserter(const Statement_inserter* inserter)
1360   { this->inserter_ = *inserter; }
1361
1362   int
1363   variable(Named_object*);
1364
1365   int
1366   constant(Named_object*, bool);
1367
1368   int
1369   function(Named_object*);
1370
1371   int
1372   statement(Block*, size_t* pindex, Statement*);
1373
1374   int
1375   expression(Expression**);
1376
1377  private:
1378   // General IR.
1379   Gogo* gogo_;
1380   // The function we are traversing.
1381   Named_object* function_;
1382   // Value to use for the predeclared constant iota.
1383   int iota_value_;
1384   // Current statement inserter for use by expressions.
1385   Statement_inserter inserter_;
1386 };
1387
1388 // Lower variables.
1389
1390 int
1391 Lower_parse_tree::variable(Named_object* no)
1392 {
1393   if (!no->is_variable())
1394     return TRAVERSE_CONTINUE;
1395
1396   if (no->is_variable() && no->var_value()->is_global())
1397     {
1398       // Global variables can have loops in their initialization
1399       // expressions.  This is handled in lower_init_expression.
1400       no->var_value()->lower_init_expression(this->gogo_, this->function_,
1401                                              &this->inserter_);
1402       return TRAVERSE_CONTINUE;
1403     }
1404
1405   // This is a local variable.  We are going to return
1406   // TRAVERSE_SKIP_COMPONENTS here because we want to traverse the
1407   // initialization expression when we reach the variable declaration
1408   // statement.  However, that means that we need to traverse the type
1409   // ourselves.
1410   if (no->var_value()->has_type())
1411     {
1412       Type* type = no->var_value()->type();
1413       if (type != NULL)
1414         {
1415           if (Type::traverse(type, this) == TRAVERSE_EXIT)
1416             return TRAVERSE_EXIT;
1417         }
1418     }
1419   go_assert(!no->var_value()->has_pre_init());
1420
1421   return TRAVERSE_SKIP_COMPONENTS;
1422 }
1423
1424 // Lower constants.  We handle constants specially so that we can set
1425 // the right value for the predeclared constant iota.  This works in
1426 // conjunction with the way we lower Const_expression objects.
1427
1428 int
1429 Lower_parse_tree::constant(Named_object* no, bool)
1430 {
1431   Named_constant* nc = no->const_value();
1432
1433   // Don't get into trouble if the constant's initializer expression
1434   // refers to the constant itself.
1435   if (nc->lowering())
1436     return TRAVERSE_CONTINUE;
1437   nc->set_lowering();
1438
1439   go_assert(this->iota_value_ == -1);
1440   this->iota_value_ = nc->iota_value();
1441   nc->traverse_expression(this);
1442   this->iota_value_ = -1;
1443
1444   nc->clear_lowering();
1445
1446   // We will traverse the expression a second time, but that will be
1447   // fast.
1448
1449   return TRAVERSE_CONTINUE;
1450 }
1451
1452 // Lower function closure types.  Record the function while lowering
1453 // it, so that we can pass it down when lowering an expression.
1454
1455 int
1456 Lower_parse_tree::function(Named_object* no)
1457 {
1458   no->func_value()->set_closure_type();
1459
1460   go_assert(this->function_ == NULL);
1461   this->function_ = no;
1462   int t = no->func_value()->traverse(this);
1463   this->function_ = NULL;
1464
1465   if (t == TRAVERSE_EXIT)
1466     return t;
1467   return TRAVERSE_SKIP_COMPONENTS;
1468 }
1469
1470 // Lower statement parse trees.
1471
1472 int
1473 Lower_parse_tree::statement(Block* block, size_t* pindex, Statement* sorig)
1474 {
1475   // Because we explicitly traverse the statement's contents
1476   // ourselves, we want to skip block statements here.  There is
1477   // nothing to lower in a block statement.
1478   if (sorig->is_block_statement())
1479     return TRAVERSE_CONTINUE;
1480
1481   Statement_inserter hold_inserter(this->inserter_);
1482   this->inserter_ = Statement_inserter(block, pindex);
1483
1484   // Lower the expressions first.
1485   int t = sorig->traverse_contents(this);
1486   if (t == TRAVERSE_EXIT)
1487     {
1488       this->inserter_ = hold_inserter;
1489       return t;
1490     }
1491
1492   // Keep lowering until nothing changes.
1493   Statement* s = sorig;
1494   while (true)
1495     {
1496       Statement* snew = s->lower(this->gogo_, this->function_, block,
1497                                  &this->inserter_);
1498       if (snew == s)
1499         break;
1500       s = snew;
1501       t = s->traverse_contents(this);
1502       if (t == TRAVERSE_EXIT)
1503         {
1504           this->inserter_ = hold_inserter;
1505           return t;
1506         }
1507     }
1508
1509   if (s != sorig)
1510     block->replace_statement(*pindex, s);
1511
1512   this->inserter_ = hold_inserter;
1513   return TRAVERSE_SKIP_COMPONENTS;
1514 }
1515
1516 // Lower expression parse trees.
1517
1518 int
1519 Lower_parse_tree::expression(Expression** pexpr)
1520 {
1521   // We have to lower all subexpressions first, so that we can get
1522   // their type if necessary.  This is awkward, because we don't have
1523   // a postorder traversal pass.
1524   if ((*pexpr)->traverse_subexpressions(this) == TRAVERSE_EXIT)
1525     return TRAVERSE_EXIT;
1526   // Keep lowering until nothing changes.
1527   while (true)
1528     {
1529       Expression* e = *pexpr;
1530       Expression* enew = e->lower(this->gogo_, this->function_,
1531                                   &this->inserter_, this->iota_value_);
1532       if (enew == e)
1533         break;
1534       if (enew->traverse_subexpressions(this) == TRAVERSE_EXIT)
1535         return TRAVERSE_EXIT;
1536       *pexpr = enew;
1537     }
1538   return TRAVERSE_SKIP_COMPONENTS;
1539 }
1540
1541 // Lower the parse tree.  This is called after the parse is complete,
1542 // when all names should be resolved.
1543
1544 void
1545 Gogo::lower_parse_tree()
1546 {
1547   Lower_parse_tree lower_parse_tree(this, NULL);
1548   this->traverse(&lower_parse_tree);
1549 }
1550
1551 // Lower a block.
1552
1553 void
1554 Gogo::lower_block(Named_object* function, Block* block)
1555 {
1556   Lower_parse_tree lower_parse_tree(this, function);
1557   block->traverse(&lower_parse_tree);
1558 }
1559
1560 // Lower an expression.  INSERTER may be NULL, in which case the
1561 // expression had better not need to create any temporaries.
1562
1563 void
1564 Gogo::lower_expression(Named_object* function, Statement_inserter* inserter,
1565                        Expression** pexpr)
1566 {
1567   Lower_parse_tree lower_parse_tree(this, function);
1568   if (inserter != NULL)
1569     lower_parse_tree.set_inserter(inserter);
1570   lower_parse_tree.expression(pexpr);
1571 }
1572
1573 // Lower a constant.  This is called when lowering a reference to a
1574 // constant.  We have to make sure that the constant has already been
1575 // lowered.
1576
1577 void
1578 Gogo::lower_constant(Named_object* no)
1579 {
1580   go_assert(no->is_const());
1581   Lower_parse_tree lower(this, NULL);
1582   lower.constant(no, false);
1583 }
1584
1585 // Look for interface types to finalize methods of inherited
1586 // interfaces.
1587
1588 class Finalize_methods : public Traverse
1589 {
1590  public:
1591   Finalize_methods(Gogo* gogo)
1592     : Traverse(traverse_types),
1593       gogo_(gogo)
1594   { }
1595
1596   int
1597   type(Type*);
1598
1599  private:
1600   Gogo* gogo_;
1601 };
1602
1603 // Finalize the methods of an interface type.
1604
1605 int
1606 Finalize_methods::type(Type* t)
1607 {
1608   // Check the classification so that we don't finalize the methods
1609   // twice for a named interface type.
1610   switch (t->classification())
1611     {
1612     case Type::TYPE_INTERFACE:
1613       t->interface_type()->finalize_methods();
1614       break;
1615
1616     case Type::TYPE_NAMED:
1617       {
1618         // We have to finalize the methods of the real type first.
1619         // But if the real type is a struct type, then we only want to
1620         // finalize the methods of the field types, not of the struct
1621         // type itself.  We don't want to add methods to the struct,
1622         // since it has a name.
1623         Named_type* nt = t->named_type();
1624         Type* rt = nt->real_type();
1625         if (rt->classification() != Type::TYPE_STRUCT)
1626           {
1627             if (Type::traverse(rt, this) == TRAVERSE_EXIT)
1628               return TRAVERSE_EXIT;
1629           }
1630         else
1631           {
1632             if (rt->struct_type()->traverse_field_types(this) == TRAVERSE_EXIT)
1633               return TRAVERSE_EXIT;
1634           }
1635
1636         nt->finalize_methods(this->gogo_);
1637
1638         // If this type is defined in a different package, then finalize the
1639         // types of all the methods, since we won't see them otherwise.
1640         if (nt->named_object()->package() != NULL && nt->has_any_methods())
1641           {
1642             const Methods* methods = nt->methods();
1643             for (Methods::const_iterator p = methods->begin();
1644                  p != methods->end();
1645                  ++p)
1646               {
1647                 if (Type::traverse(p->second->type(), this) == TRAVERSE_EXIT)
1648                   return TRAVERSE_EXIT;
1649               }
1650           }
1651
1652         return TRAVERSE_SKIP_COMPONENTS;
1653       }
1654
1655     case Type::TYPE_STRUCT:
1656       // Traverse the field types first in case there is an embedded
1657       // field with methods that the struct should inherit.
1658       if (t->struct_type()->traverse_field_types(this) == TRAVERSE_EXIT)
1659           return TRAVERSE_EXIT;
1660       t->struct_type()->finalize_methods(this->gogo_);
1661       return TRAVERSE_SKIP_COMPONENTS;
1662
1663     default:
1664       break;
1665     }
1666
1667   return TRAVERSE_CONTINUE;
1668 }
1669
1670 // Finalize method lists and build stub methods for types.
1671
1672 void
1673 Gogo::finalize_methods()
1674 {
1675   Finalize_methods finalize(this);
1676   this->traverse(&finalize);
1677 }
1678
1679 // Set types for unspecified variables and constants.
1680
1681 void
1682 Gogo::determine_types()
1683 {
1684   Bindings* bindings = this->current_bindings();
1685   for (Bindings::const_definitions_iterator p = bindings->begin_definitions();
1686        p != bindings->end_definitions();
1687        ++p)
1688     {
1689       if ((*p)->is_function())
1690         (*p)->func_value()->determine_types();
1691       else if ((*p)->is_variable())
1692         (*p)->var_value()->determine_type();
1693       else if ((*p)->is_const())
1694         (*p)->const_value()->determine_type();
1695
1696       // See if a variable requires us to build an initialization
1697       // function.  We know that we will see all global variables
1698       // here.
1699       if (!this->need_init_fn_ && (*p)->is_variable())
1700         {
1701           Variable* variable = (*p)->var_value();
1702
1703           // If this is a global variable which requires runtime
1704           // initialization, we need an initialization function.
1705           if (!variable->is_global())
1706             ;
1707           else if (variable->init() == NULL)
1708             ;
1709           else if (variable->type()->interface_type() != NULL)
1710             this->need_init_fn_ = true;
1711           else if (variable->init()->is_constant())
1712             ;
1713           else if (!variable->init()->is_composite_literal())
1714             this->need_init_fn_ = true;
1715           else if (variable->init()->is_nonconstant_composite_literal())
1716             this->need_init_fn_ = true;
1717
1718           // If this is a global variable which holds a pointer value,
1719           // then we need an initialization function to register it as a
1720           // GC root.
1721           if (variable->is_global() && variable->type()->has_pointer())
1722             this->need_init_fn_ = true;
1723         }
1724     }
1725
1726   // Determine the types of constants in packages.
1727   for (Packages::const_iterator p = this->packages_.begin();
1728        p != this->packages_.end();
1729        ++p)
1730     p->second->determine_types();
1731 }
1732
1733 // Traversal class used for type checking.
1734
1735 class Check_types_traverse : public Traverse
1736 {
1737  public:
1738   Check_types_traverse(Gogo* gogo)
1739     : Traverse(traverse_variables
1740                | traverse_constants
1741                | traverse_functions
1742                | traverse_statements
1743                | traverse_expressions),
1744       gogo_(gogo)
1745   { }
1746
1747   int
1748   variable(Named_object*);
1749
1750   int
1751   constant(Named_object*, bool);
1752
1753   int
1754   function(Named_object*);
1755
1756   int
1757   statement(Block*, size_t* pindex, Statement*);
1758
1759   int
1760   expression(Expression**);
1761
1762  private:
1763   // General IR.
1764   Gogo* gogo_;
1765 };
1766
1767 // Check that a variable initializer has the right type.
1768
1769 int
1770 Check_types_traverse::variable(Named_object* named_object)
1771 {
1772   if (named_object->is_variable())
1773     {
1774       Variable* var = named_object->var_value();
1775
1776       // Give error if variable type is not defined.
1777       var->type()->base();
1778
1779       Expression* init = var->init();
1780       std::string reason;
1781       if (init != NULL
1782           && !Type::are_assignable(var->type(), init->type(), &reason))
1783         {
1784           if (reason.empty())
1785             error_at(var->location(), "incompatible type in initialization");
1786           else
1787             error_at(var->location(),
1788                      "incompatible type in initialization (%s)",
1789                      reason.c_str());
1790           var->clear_init();
1791         }
1792       else if (!var->is_used()
1793                && !var->is_global()
1794                && !var->is_parameter()
1795                && !var->is_receiver()
1796                && !var->type()->is_error()
1797                && (init == NULL || !init->is_error_expression())
1798                && !Lex::is_invalid_identifier(named_object->name()))
1799         error_at(var->location(), "%qs declared and not used",
1800                  named_object->message_name().c_str());
1801     }
1802   return TRAVERSE_CONTINUE;
1803 }
1804
1805 // Check that a constant initializer has the right type.
1806
1807 int
1808 Check_types_traverse::constant(Named_object* named_object, bool)
1809 {
1810   Named_constant* constant = named_object->const_value();
1811   Type* ctype = constant->type();
1812   if (ctype->integer_type() == NULL
1813       && ctype->float_type() == NULL
1814       && ctype->complex_type() == NULL
1815       && !ctype->is_boolean_type()
1816       && !ctype->is_string_type())
1817     {
1818       if (ctype->is_nil_type())
1819         error_at(constant->location(), "const initializer cannot be nil");
1820       else if (!ctype->is_error())
1821         error_at(constant->location(), "invalid constant type");
1822       constant->set_error();
1823     }
1824   else if (!constant->expr()->is_constant())
1825     {
1826       error_at(constant->expr()->location(), "expression is not constant");
1827       constant->set_error();
1828     }
1829   else if (!Type::are_assignable(constant->type(), constant->expr()->type(),
1830                                  NULL))
1831     {
1832       error_at(constant->location(),
1833                "initialization expression has wrong type");
1834       constant->set_error();
1835     }
1836   return TRAVERSE_CONTINUE;
1837 }
1838
1839 // There are no types to check in a function, but this is where we
1840 // issue warnings about labels which are defined but not referenced.
1841
1842 int
1843 Check_types_traverse::function(Named_object* no)
1844 {
1845   no->func_value()->check_labels();
1846   return TRAVERSE_CONTINUE;
1847 }
1848
1849 // Check that types are valid in a statement.
1850
1851 int
1852 Check_types_traverse::statement(Block*, size_t*, Statement* s)
1853 {
1854   s->check_types(this->gogo_);
1855   return TRAVERSE_CONTINUE;
1856 }
1857
1858 // Check that types are valid in an expression.
1859
1860 int
1861 Check_types_traverse::expression(Expression** expr)
1862 {
1863   (*expr)->check_types(this->gogo_);
1864   return TRAVERSE_CONTINUE;
1865 }
1866
1867 // Check that types are valid.
1868
1869 void
1870 Gogo::check_types()
1871 {
1872   Check_types_traverse traverse(this);
1873   this->traverse(&traverse);
1874 }
1875
1876 // Check the types in a single block.
1877
1878 void
1879 Gogo::check_types_in_block(Block* block)
1880 {
1881   Check_types_traverse traverse(this);
1882   block->traverse(&traverse);
1883 }
1884
1885 // A traversal class used to find a single shortcut operator within an
1886 // expression.
1887
1888 class Find_shortcut : public Traverse
1889 {
1890  public:
1891   Find_shortcut()
1892     : Traverse(traverse_blocks
1893                | traverse_statements
1894                | traverse_expressions),
1895       found_(NULL)
1896   { }
1897
1898   // A pointer to the expression which was found, or NULL if none was
1899   // found.
1900   Expression**
1901   found() const
1902   { return this->found_; }
1903
1904  protected:
1905   int
1906   block(Block*)
1907   { return TRAVERSE_SKIP_COMPONENTS; }
1908
1909   int
1910   statement(Block*, size_t*, Statement*)
1911   { return TRAVERSE_SKIP_COMPONENTS; }
1912
1913   int
1914   expression(Expression**);
1915
1916  private:
1917   Expression** found_;
1918 };
1919
1920 // Find a shortcut expression.
1921
1922 int
1923 Find_shortcut::expression(Expression** pexpr)
1924 {
1925   Expression* expr = *pexpr;
1926   Binary_expression* be = expr->binary_expression();
1927   if (be == NULL)
1928     return TRAVERSE_CONTINUE;
1929   Operator op = be->op();
1930   if (op != OPERATOR_OROR && op != OPERATOR_ANDAND)
1931     return TRAVERSE_CONTINUE;
1932   go_assert(this->found_ == NULL);
1933   this->found_ = pexpr;
1934   return TRAVERSE_EXIT;
1935 }
1936
1937 // A traversal class used to turn shortcut operators into explicit if
1938 // statements.
1939
1940 class Shortcuts : public Traverse
1941 {
1942  public:
1943   Shortcuts(Gogo* gogo)
1944     : Traverse(traverse_variables
1945                | traverse_statements),
1946       gogo_(gogo)
1947   { }
1948
1949  protected:
1950   int
1951   variable(Named_object*);
1952
1953   int
1954   statement(Block*, size_t*, Statement*);
1955
1956  private:
1957   // Convert a shortcut operator.
1958   Statement*
1959   convert_shortcut(Block* enclosing, Expression** pshortcut);
1960
1961   // The IR.
1962   Gogo* gogo_;
1963 };
1964
1965 // Remove shortcut operators in a single statement.
1966
1967 int
1968 Shortcuts::statement(Block* block, size_t* pindex, Statement* s)
1969 {
1970   // FIXME: This approach doesn't work for switch statements, because
1971   // we add the new statements before the whole switch when we need to
1972   // instead add them just before the switch expression.  The right
1973   // fix is probably to lower switch statements with nonconstant cases
1974   // to a series of conditionals.
1975   if (s->switch_statement() != NULL)
1976     return TRAVERSE_CONTINUE;
1977
1978   while (true)
1979     {
1980       Find_shortcut find_shortcut;
1981
1982       // If S is a variable declaration, then ordinary traversal won't
1983       // do anything.  We want to explicitly traverse the
1984       // initialization expression if there is one.
1985       Variable_declaration_statement* vds = s->variable_declaration_statement();
1986       Expression* init = NULL;
1987       if (vds == NULL)
1988         s->traverse_contents(&find_shortcut);
1989       else
1990         {
1991           init = vds->var()->var_value()->init();
1992           if (init == NULL)
1993             return TRAVERSE_CONTINUE;
1994           init->traverse(&init, &find_shortcut);
1995         }
1996       Expression** pshortcut = find_shortcut.found();
1997       if (pshortcut == NULL)
1998         return TRAVERSE_CONTINUE;
1999
2000       Statement* snew = this->convert_shortcut(block, pshortcut);
2001       block->insert_statement_before(*pindex, snew);
2002       ++*pindex;
2003
2004       if (pshortcut == &init)
2005         vds->var()->var_value()->set_init(init);
2006     }
2007 }
2008
2009 // Remove shortcut operators in the initializer of a global variable.
2010
2011 int
2012 Shortcuts::variable(Named_object* no)
2013 {
2014   if (no->is_result_variable())
2015     return TRAVERSE_CONTINUE;
2016   Variable* var = no->var_value();
2017   Expression* init = var->init();
2018   if (!var->is_global() || init == NULL)
2019     return TRAVERSE_CONTINUE;
2020
2021   while (true)
2022     {
2023       Find_shortcut find_shortcut;
2024       init->traverse(&init, &find_shortcut);
2025       Expression** pshortcut = find_shortcut.found();
2026       if (pshortcut == NULL)
2027         return TRAVERSE_CONTINUE;
2028
2029       Statement* snew = this->convert_shortcut(NULL, pshortcut);
2030       var->add_preinit_statement(this->gogo_, snew);
2031       if (pshortcut == &init)
2032         var->set_init(init);
2033     }
2034 }
2035
2036 // Given an expression which uses a shortcut operator, return a
2037 // statement which implements it, and update *PSHORTCUT accordingly.
2038
2039 Statement*
2040 Shortcuts::convert_shortcut(Block* enclosing, Expression** pshortcut)
2041 {
2042   Binary_expression* shortcut = (*pshortcut)->binary_expression();
2043   Expression* left = shortcut->left();
2044   Expression* right = shortcut->right();
2045   Location loc = shortcut->location();
2046
2047   Block* retblock = new Block(enclosing, loc);
2048   retblock->set_end_location(loc);
2049
2050   Temporary_statement* ts = Statement::make_temporary(Type::lookup_bool_type(),
2051                                                       left, loc);
2052   retblock->add_statement(ts);
2053
2054   Block* block = new Block(retblock, loc);
2055   block->set_end_location(loc);
2056   Expression* tmpref = Expression::make_temporary_reference(ts, loc);
2057   Statement* assign = Statement::make_assignment(tmpref, right, loc);
2058   block->add_statement(assign);
2059
2060   Expression* cond = Expression::make_temporary_reference(ts, loc);
2061   if (shortcut->binary_expression()->op() == OPERATOR_OROR)
2062     cond = Expression::make_unary(OPERATOR_NOT, cond, loc);
2063
2064   Statement* if_statement = Statement::make_if_statement(cond, block, NULL,
2065                                                          loc);
2066   retblock->add_statement(if_statement);
2067
2068   *pshortcut = Expression::make_temporary_reference(ts, loc);
2069
2070   delete shortcut;
2071
2072   // Now convert any shortcut operators in LEFT and RIGHT.
2073   Shortcuts shortcuts(this->gogo_);
2074   retblock->traverse(&shortcuts);
2075
2076   return Statement::make_block_statement(retblock, loc);
2077 }
2078
2079 // Turn shortcut operators into explicit if statements.  Doing this
2080 // considerably simplifies the order of evaluation rules.
2081
2082 void
2083 Gogo::remove_shortcuts()
2084 {
2085   Shortcuts shortcuts(this);
2086   this->traverse(&shortcuts);
2087 }
2088
2089 // A traversal class which finds all the expressions which must be
2090 // evaluated in order within a statement or larger expression.  This
2091 // is used to implement the rules about order of evaluation.
2092
2093 class Find_eval_ordering : public Traverse
2094 {
2095  private:
2096   typedef std::vector<Expression**> Expression_pointers;
2097
2098  public:
2099   Find_eval_ordering()
2100     : Traverse(traverse_blocks
2101                | traverse_statements
2102                | traverse_expressions),
2103       exprs_()
2104   { }
2105
2106   size_t
2107   size() const
2108   { return this->exprs_.size(); }
2109
2110   typedef Expression_pointers::const_iterator const_iterator;
2111
2112   const_iterator
2113   begin() const
2114   { return this->exprs_.begin(); }
2115
2116   const_iterator
2117   end() const
2118   { return this->exprs_.end(); }
2119
2120  protected:
2121   int
2122   block(Block*)
2123   { return TRAVERSE_SKIP_COMPONENTS; }
2124
2125   int
2126   statement(Block*, size_t*, Statement*)
2127   { return TRAVERSE_SKIP_COMPONENTS; }
2128
2129   int
2130   expression(Expression**);
2131
2132  private:
2133   // A list of pointers to expressions with side-effects.
2134   Expression_pointers exprs_;
2135 };
2136
2137 // If an expression must be evaluated in order, put it on the list.
2138
2139 int
2140 Find_eval_ordering::expression(Expression** expression_pointer)
2141 {
2142   // We have to look at subexpressions before this one.
2143   if ((*expression_pointer)->traverse_subexpressions(this) == TRAVERSE_EXIT)
2144     return TRAVERSE_EXIT;
2145   if ((*expression_pointer)->must_eval_in_order())
2146     this->exprs_.push_back(expression_pointer);
2147   return TRAVERSE_SKIP_COMPONENTS;
2148 }
2149
2150 // A traversal class for ordering evaluations.
2151
2152 class Order_eval : public Traverse
2153 {
2154  public:
2155   Order_eval(Gogo* gogo)
2156     : Traverse(traverse_variables
2157                | traverse_statements),
2158       gogo_(gogo)
2159   { }
2160
2161   int
2162   variable(Named_object*);
2163
2164   int
2165   statement(Block*, size_t*, Statement*);
2166
2167  private:
2168   // The IR.
2169   Gogo* gogo_;
2170 };
2171
2172 // Implement the order of evaluation rules for a statement.
2173
2174 int
2175 Order_eval::statement(Block* block, size_t* pindex, Statement* s)
2176 {
2177   // FIXME: This approach doesn't work for switch statements, because
2178   // we add the new statements before the whole switch when we need to
2179   // instead add them just before the switch expression.  The right
2180   // fix is probably to lower switch statements with nonconstant cases
2181   // to a series of conditionals.
2182   if (s->switch_statement() != NULL)
2183     return TRAVERSE_CONTINUE;
2184
2185   Find_eval_ordering find_eval_ordering;
2186
2187   // If S is a variable declaration, then ordinary traversal won't do
2188   // anything.  We want to explicitly traverse the initialization
2189   // expression if there is one.
2190   Variable_declaration_statement* vds = s->variable_declaration_statement();
2191   Expression* init = NULL;
2192   Expression* orig_init = NULL;
2193   if (vds == NULL)
2194     s->traverse_contents(&find_eval_ordering);
2195   else
2196     {
2197       init = vds->var()->var_value()->init();
2198       if (init == NULL)
2199         return TRAVERSE_CONTINUE;
2200       orig_init = init;
2201
2202       // It might seem that this could be
2203       // init->traverse_subexpressions.  Unfortunately that can fail
2204       // in a case like
2205       //   var err os.Error
2206       //   newvar, err := call(arg())
2207       // Here newvar will have an init of call result 0 of
2208       // call(arg()).  If we only traverse subexpressions, we will
2209       // only find arg(), and we won't bother to move anything out.
2210       // Then we get to the assignment to err, we will traverse the
2211       // whole statement, and this time we will find both call() and
2212       // arg(), and so we will move them out.  This will cause them to
2213       // be put into temporary variables before the assignment to err
2214       // but after the declaration of newvar.  To avoid that problem,
2215       // we traverse the entire expression here.
2216       Expression::traverse(&init, &find_eval_ordering);
2217     }
2218
2219   if (find_eval_ordering.size() <= 1)
2220     {
2221       // If there is only one expression with a side-effect, we can
2222       // leave it in place.
2223       return TRAVERSE_CONTINUE;
2224     }
2225
2226   bool is_thunk = s->thunk_statement() != NULL;
2227   for (Find_eval_ordering::const_iterator p = find_eval_ordering.begin();
2228        p != find_eval_ordering.end();
2229        ++p)
2230     {
2231       Expression** pexpr = *p;
2232
2233       // The last expression in a thunk will be the call passed to go
2234       // or defer, which we must not evaluate early.
2235       if (is_thunk && p + 1 == find_eval_ordering.end())
2236         break;
2237
2238       Location loc = (*pexpr)->location();
2239       Statement* s;
2240       if ((*pexpr)->call_expression() == NULL
2241           || (*pexpr)->call_expression()->result_count() < 2)
2242         {
2243           Temporary_statement* ts = Statement::make_temporary(NULL, *pexpr,
2244                                                               loc);
2245           s = ts;
2246           *pexpr = Expression::make_temporary_reference(ts, loc);
2247         }
2248       else
2249         {
2250           // A call expression which returns multiple results needs to
2251           // be handled specially.  We can't create a temporary
2252           // because there is no type to give it.  Any actual uses of
2253           // the values will be done via Call_result_expressions.
2254           s = Statement::make_statement(*pexpr, true);
2255         }
2256
2257       block->insert_statement_before(*pindex, s);
2258       ++*pindex;
2259     }
2260
2261   if (init != orig_init)
2262     vds->var()->var_value()->set_init(init);
2263
2264   return TRAVERSE_CONTINUE;
2265 }
2266
2267 // Implement the order of evaluation rules for the initializer of a
2268 // global variable.
2269
2270 int
2271 Order_eval::variable(Named_object* no)
2272 {
2273   if (no->is_result_variable())
2274     return TRAVERSE_CONTINUE;
2275   Variable* var = no->var_value();
2276   Expression* init = var->init();
2277   if (!var->is_global() || init == NULL)
2278     return TRAVERSE_CONTINUE;
2279
2280   Find_eval_ordering find_eval_ordering;
2281   Expression::traverse(&init, &find_eval_ordering);
2282
2283   if (find_eval_ordering.size() <= 1)
2284     {
2285       // If there is only one expression with a side-effect, we can
2286       // leave it in place.
2287       return TRAVERSE_SKIP_COMPONENTS;
2288     }
2289
2290   Expression* orig_init = init;
2291
2292   for (Find_eval_ordering::const_iterator p = find_eval_ordering.begin();
2293        p != find_eval_ordering.end();
2294        ++p)
2295     {
2296       Expression** pexpr = *p;
2297       Location loc = (*pexpr)->location();
2298       Statement* s;
2299       if ((*pexpr)->call_expression() == NULL
2300           || (*pexpr)->call_expression()->result_count() < 2)
2301         {
2302           Temporary_statement* ts = Statement::make_temporary(NULL, *pexpr,
2303                                                               loc);
2304           s = ts;
2305           *pexpr = Expression::make_temporary_reference(ts, loc);
2306         }
2307       else
2308         {
2309           // A call expression which returns multiple results needs to
2310           // be handled specially.
2311           s = Statement::make_statement(*pexpr, true);
2312         }
2313       var->add_preinit_statement(this->gogo_, s);
2314     }
2315
2316   if (init != orig_init)
2317     var->set_init(init);
2318
2319   return TRAVERSE_SKIP_COMPONENTS;
2320 }
2321
2322 // Use temporary variables to implement the order of evaluation rules.
2323
2324 void
2325 Gogo::order_evaluations()
2326 {
2327   Order_eval order_eval(this);
2328   this->traverse(&order_eval);
2329 }
2330
2331 // Traversal to convert calls to the predeclared recover function to
2332 // pass in an argument indicating whether it can recover from a panic
2333 // or not.
2334
2335 class Convert_recover : public Traverse
2336 {
2337  public:
2338   Convert_recover(Named_object* arg)
2339     : Traverse(traverse_expressions),
2340       arg_(arg)
2341   { }
2342
2343  protected:
2344   int
2345   expression(Expression**);
2346
2347  private:
2348   // The argument to pass to the function.
2349   Named_object* arg_;
2350 };
2351
2352 // Convert calls to recover.
2353
2354 int
2355 Convert_recover::expression(Expression** pp)
2356 {
2357   Call_expression* ce = (*pp)->call_expression();
2358   if (ce != NULL && ce->is_recover_call())
2359     ce->set_recover_arg(Expression::make_var_reference(this->arg_,
2360                                                        ce->location()));
2361   return TRAVERSE_CONTINUE;
2362 }
2363
2364 // Traversal for build_recover_thunks.
2365
2366 class Build_recover_thunks : public Traverse
2367 {
2368  public:
2369   Build_recover_thunks(Gogo* gogo)
2370     : Traverse(traverse_functions),
2371       gogo_(gogo)
2372   { }
2373
2374   int
2375   function(Named_object*);
2376
2377  private:
2378   Expression*
2379   can_recover_arg(Location);
2380
2381   // General IR.
2382   Gogo* gogo_;
2383 };
2384
2385 // If this function calls recover, turn it into a thunk.
2386
2387 int
2388 Build_recover_thunks::function(Named_object* orig_no)
2389 {
2390   Function* orig_func = orig_no->func_value();
2391   if (!orig_func->calls_recover()
2392       || orig_func->is_recover_thunk()
2393       || orig_func->has_recover_thunk())
2394     return TRAVERSE_CONTINUE;
2395
2396   Gogo* gogo = this->gogo_;
2397   Location location = orig_func->location();
2398
2399   static int count;
2400   char buf[50];
2401
2402   Function_type* orig_fntype = orig_func->type();
2403   Typed_identifier_list* new_params = new Typed_identifier_list();
2404   std::string receiver_name;
2405   if (orig_fntype->is_method())
2406     {
2407       const Typed_identifier* receiver = orig_fntype->receiver();
2408       snprintf(buf, sizeof buf, "rt.%u", count);
2409       ++count;
2410       receiver_name = buf;
2411       new_params->push_back(Typed_identifier(receiver_name, receiver->type(),
2412                                              receiver->location()));
2413     }
2414   const Typed_identifier_list* orig_params = orig_fntype->parameters();
2415   if (orig_params != NULL && !orig_params->empty())
2416     {
2417       for (Typed_identifier_list::const_iterator p = orig_params->begin();
2418            p != orig_params->end();
2419            ++p)
2420         {
2421           snprintf(buf, sizeof buf, "pt.%u", count);
2422           ++count;
2423           new_params->push_back(Typed_identifier(buf, p->type(),
2424                                                  p->location()));
2425         }
2426     }
2427   snprintf(buf, sizeof buf, "pr.%u", count);
2428   ++count;
2429   std::string can_recover_name = buf;
2430   new_params->push_back(Typed_identifier(can_recover_name,
2431                                          Type::lookup_bool_type(),
2432                                          orig_fntype->location()));
2433
2434   const Typed_identifier_list* orig_results = orig_fntype->results();
2435   Typed_identifier_list* new_results;
2436   if (orig_results == NULL || orig_results->empty())
2437     new_results = NULL;
2438   else
2439     {
2440       new_results = new Typed_identifier_list();
2441       for (Typed_identifier_list::const_iterator p = orig_results->begin();
2442            p != orig_results->end();
2443            ++p)
2444         new_results->push_back(Typed_identifier("", p->type(), p->location()));
2445     }
2446
2447   Function_type *new_fntype = Type::make_function_type(NULL, new_params,
2448                                                        new_results,
2449                                                        orig_fntype->location());
2450   if (orig_fntype->is_varargs())
2451     new_fntype->set_is_varargs();
2452
2453   std::string name = orig_no->name() + "$recover";
2454   Named_object *new_no = gogo->start_function(name, new_fntype, false,
2455                                               location);
2456   Function *new_func = new_no->func_value();
2457   if (orig_func->enclosing() != NULL)
2458     new_func->set_enclosing(orig_func->enclosing());
2459
2460   // We build the code for the original function attached to the new
2461   // function, and then swap the original and new function bodies.
2462   // This means that existing references to the original function will
2463   // then refer to the new function.  That makes this code a little
2464   // confusing, in that the reference to NEW_NO really refers to the
2465   // other function, not the one we are building.
2466
2467   Expression* closure = NULL;
2468   if (orig_func->needs_closure())
2469     {
2470       Named_object* orig_closure_no = orig_func->closure_var();
2471       Variable* orig_closure_var = orig_closure_no->var_value();
2472       Variable* new_var = new Variable(orig_closure_var->type(), NULL, false,
2473                                        true, false, location);
2474       snprintf(buf, sizeof buf, "closure.%u", count);
2475       ++count;
2476       Named_object* new_closure_no = Named_object::make_variable(buf, NULL,
2477                                                                  new_var);
2478       new_func->set_closure_var(new_closure_no);
2479       closure = Expression::make_var_reference(new_closure_no, location);
2480     }
2481
2482   Expression* fn = Expression::make_func_reference(new_no, closure, location);
2483
2484   Expression_list* args = new Expression_list();
2485   if (new_params != NULL)
2486     {
2487       // Note that we skip the last parameter, which is the boolean
2488       // indicating whether recover can succed.
2489       for (Typed_identifier_list::const_iterator p = new_params->begin();
2490            p + 1 != new_params->end();
2491            ++p)
2492         {
2493           Named_object* p_no = gogo->lookup(p->name(), NULL);
2494           go_assert(p_no != NULL
2495                      && p_no->is_variable()
2496                      && p_no->var_value()->is_parameter());
2497           args->push_back(Expression::make_var_reference(p_no, location));
2498         }
2499     }
2500   args->push_back(this->can_recover_arg(location));
2501
2502   gogo->start_block(location);
2503
2504   Call_expression* call = Expression::make_call(fn, args, false, location);
2505
2506   // Any varargs call has already been lowered.
2507   call->set_varargs_are_lowered();
2508
2509   Statement* s;
2510   if (orig_fntype->results() == NULL || orig_fntype->results()->empty())
2511     s = Statement::make_statement(call, true);
2512   else
2513     {
2514       Expression_list* vals = new Expression_list();
2515       size_t rc = orig_fntype->results()->size();
2516       if (rc == 1)
2517         vals->push_back(call);
2518       else
2519         {
2520           for (size_t i = 0; i < rc; ++i)
2521             vals->push_back(Expression::make_call_result(call, i));
2522         }
2523       s = Statement::make_return_statement(vals, location);
2524     }
2525   s->determine_types();
2526   gogo->add_statement(s);
2527
2528   Block* b = gogo->finish_block(location);
2529
2530   gogo->add_block(b, location);
2531
2532   // Lower the call in case it returns multiple results.
2533   gogo->lower_block(new_no, b);
2534
2535   gogo->finish_function(location);
2536
2537   // Swap the function bodies and types.
2538   new_func->swap_for_recover(orig_func);
2539   orig_func->set_is_recover_thunk();
2540   new_func->set_calls_recover();
2541   new_func->set_has_recover_thunk();
2542
2543   Bindings* orig_bindings = orig_func->block()->bindings();
2544   Bindings* new_bindings = new_func->block()->bindings();
2545   if (orig_fntype->is_method())
2546     {
2547       // We changed the receiver to be a regular parameter.  We have
2548       // to update the binding accordingly in both functions.
2549       Named_object* orig_rec_no = orig_bindings->lookup_local(receiver_name);
2550       go_assert(orig_rec_no != NULL
2551                  && orig_rec_no->is_variable()
2552                  && !orig_rec_no->var_value()->is_receiver());
2553       orig_rec_no->var_value()->set_is_receiver();
2554
2555       const std::string& new_receiver_name(orig_fntype->receiver()->name());
2556       Named_object* new_rec_no = new_bindings->lookup_local(new_receiver_name);
2557       if (new_rec_no == NULL)
2558         go_assert(saw_errors());
2559       else
2560         {
2561           go_assert(new_rec_no->is_variable()
2562                      && new_rec_no->var_value()->is_receiver());
2563           new_rec_no->var_value()->set_is_not_receiver();
2564         }
2565     }
2566
2567   // Because we flipped blocks but not types, the can_recover
2568   // parameter appears in the (now) old bindings as a parameter.
2569   // Change it to a local variable, whereupon it will be discarded.
2570   Named_object* can_recover_no = orig_bindings->lookup_local(can_recover_name);
2571   go_assert(can_recover_no != NULL
2572              && can_recover_no->is_variable()
2573              && can_recover_no->var_value()->is_parameter());
2574   orig_bindings->remove_binding(can_recover_no);
2575
2576   // Add the can_recover argument to the (now) new bindings, and
2577   // attach it to any recover statements.
2578   Variable* can_recover_var = new Variable(Type::lookup_bool_type(), NULL,
2579                                            false, true, false, location);
2580   can_recover_no = new_bindings->add_variable(can_recover_name, NULL,
2581                                               can_recover_var);
2582   Convert_recover convert_recover(can_recover_no);
2583   new_func->traverse(&convert_recover);
2584
2585   // Update the function pointers in any named results.
2586   new_func->update_result_variables();
2587   orig_func->update_result_variables();
2588
2589   return TRAVERSE_CONTINUE;
2590 }
2591
2592 // Return the expression to pass for the .can_recover parameter to the
2593 // new function.  This indicates whether a call to recover may return
2594 // non-nil.  The expression is
2595 // __go_can_recover(__builtin_return_address()).
2596
2597 Expression*
2598 Build_recover_thunks::can_recover_arg(Location location)
2599 {
2600   static Named_object* builtin_return_address;
2601   if (builtin_return_address == NULL)
2602     {
2603       const Location bloc = Linemap::predeclared_location();
2604
2605       Typed_identifier_list* param_types = new Typed_identifier_list();
2606       Type* uint_type = Type::lookup_integer_type("uint");
2607       param_types->push_back(Typed_identifier("l", uint_type, bloc));
2608
2609       Typed_identifier_list* return_types = new Typed_identifier_list();
2610       Type* voidptr_type = Type::make_pointer_type(Type::make_void_type());
2611       return_types->push_back(Typed_identifier("", voidptr_type, bloc));
2612
2613       Function_type* fntype = Type::make_function_type(NULL, param_types,
2614                                                        return_types, bloc);
2615       builtin_return_address =
2616         Named_object::make_function_declaration("__builtin_return_address",
2617                                                 NULL, fntype, bloc);
2618       const char* n = "__builtin_return_address";
2619       builtin_return_address->func_declaration_value()->set_asm_name(n);
2620     }
2621
2622   static Named_object* can_recover;
2623   if (can_recover == NULL)
2624     {
2625       const Location bloc = Linemap::predeclared_location();
2626       Typed_identifier_list* param_types = new Typed_identifier_list();
2627       Type* voidptr_type = Type::make_pointer_type(Type::make_void_type());
2628       param_types->push_back(Typed_identifier("a", voidptr_type, bloc));
2629       Type* boolean_type = Type::lookup_bool_type();
2630       Typed_identifier_list* results = new Typed_identifier_list();
2631       results->push_back(Typed_identifier("", boolean_type, bloc));
2632       Function_type* fntype = Type::make_function_type(NULL, param_types,
2633                                                        results, bloc);
2634       can_recover = Named_object::make_function_declaration("__go_can_recover",
2635                                                             NULL, fntype,
2636                                                             bloc);
2637       can_recover->func_declaration_value()->set_asm_name("__go_can_recover");
2638     }
2639
2640   Expression* fn = Expression::make_func_reference(builtin_return_address,
2641                                                    NULL, location);
2642
2643   mpz_t zval;
2644   mpz_init_set_ui(zval, 0UL);
2645   Expression* zexpr = Expression::make_integer(&zval, NULL, location);
2646   mpz_clear(zval);
2647   Expression_list *args = new Expression_list();
2648   args->push_back(zexpr);
2649
2650   Expression* call = Expression::make_call(fn, args, false, location);
2651
2652   args = new Expression_list();
2653   args->push_back(call);
2654
2655   fn = Expression::make_func_reference(can_recover, NULL, location);
2656   return Expression::make_call(fn, args, false, location);
2657 }
2658
2659 // Build thunks for functions which call recover.  We build a new
2660 // function with an extra parameter, which is whether a call to
2661 // recover can succeed.  We then move the body of this function to
2662 // that one.  We then turn this function into a thunk which calls the
2663 // new one, passing the value of
2664 // __go_can_recover(__builtin_return_address()).  The function will be
2665 // marked as not splitting the stack.  This will cooperate with the
2666 // implementation of defer to make recover do the right thing.
2667
2668 void
2669 Gogo::build_recover_thunks()
2670 {
2671   Build_recover_thunks build_recover_thunks(this);
2672   this->traverse(&build_recover_thunks);
2673 }
2674
2675 // Look for named types to see whether we need to create an interface
2676 // method table.
2677
2678 class Build_method_tables : public Traverse
2679 {
2680  public:
2681   Build_method_tables(Gogo* gogo,
2682                       const std::vector<Interface_type*>& interfaces)
2683     : Traverse(traverse_types),
2684       gogo_(gogo), interfaces_(interfaces)
2685   { }
2686
2687   int
2688   type(Type*);
2689
2690  private:
2691   // The IR.
2692   Gogo* gogo_;
2693   // A list of locally defined interfaces which have hidden methods.
2694   const std::vector<Interface_type*>& interfaces_;
2695 };
2696
2697 // Build all required interface method tables for types.  We need to
2698 // ensure that we have an interface method table for every interface
2699 // which has a hidden method, for every named type which implements
2700 // that interface.  Normally we can just build interface method tables
2701 // as we need them.  However, in some cases we can require an
2702 // interface method table for an interface defined in a different
2703 // package for a type defined in that package.  If that interface and
2704 // type both use a hidden method, that is OK.  However, we will not be
2705 // able to build that interface method table when we need it, because
2706 // the type's hidden method will be static.  So we have to build it
2707 // here, and just refer it from other packages as needed.
2708
2709 void
2710 Gogo::build_interface_method_tables()
2711 {
2712   if (saw_errors())
2713     return;
2714
2715   std::vector<Interface_type*> hidden_interfaces;
2716   hidden_interfaces.reserve(this->interface_types_.size());
2717   for (std::vector<Interface_type*>::const_iterator pi =
2718          this->interface_types_.begin();
2719        pi != this->interface_types_.end();
2720        ++pi)
2721     {
2722       const Typed_identifier_list* methods = (*pi)->methods();
2723       if (methods == NULL)
2724         continue;
2725       for (Typed_identifier_list::const_iterator pm = methods->begin();
2726            pm != methods->end();
2727            ++pm)
2728         {
2729           if (Gogo::is_hidden_name(pm->name()))
2730             {
2731               hidden_interfaces.push_back(*pi);
2732               break;
2733             }
2734         }
2735     }
2736
2737   if (!hidden_interfaces.empty())
2738     {
2739       // Now traverse the tree looking for all named types.
2740       Build_method_tables bmt(this, hidden_interfaces);
2741       this->traverse(&bmt);
2742     }
2743
2744   // We no longer need the list of interfaces.
2745
2746   this->interface_types_.clear();
2747 }
2748
2749 // This is called for each type.  For a named type, for each of the
2750 // interfaces with hidden methods that it implements, create the
2751 // method table.
2752
2753 int
2754 Build_method_tables::type(Type* type)
2755 {
2756   Named_type* nt = type->named_type();
2757   if (nt != NULL)
2758     {
2759       for (std::vector<Interface_type*>::const_iterator p =
2760              this->interfaces_.begin();
2761            p != this->interfaces_.end();
2762            ++p)
2763         {
2764           // We ask whether a pointer to the named type implements the
2765           // interface, because a pointer can implement more methods
2766           // than a value.
2767           if ((*p)->implements_interface(Type::make_pointer_type(nt), NULL))
2768             {
2769               nt->interface_method_table(this->gogo_, *p, false);
2770               nt->interface_method_table(this->gogo_, *p, true);
2771             }
2772         }
2773     }
2774   return TRAVERSE_CONTINUE;
2775 }
2776
2777 // Traversal class used to check for return statements.
2778
2779 class Check_return_statements_traverse : public Traverse
2780 {
2781  public:
2782   Check_return_statements_traverse()
2783     : Traverse(traverse_functions)
2784   { }
2785
2786   int
2787   function(Named_object*);
2788 };
2789
2790 // Check that a function has a return statement if it needs one.
2791
2792 int
2793 Check_return_statements_traverse::function(Named_object* no)
2794 {
2795   Function* func = no->func_value();
2796   const Function_type* fntype = func->type();
2797   const Typed_identifier_list* results = fntype->results();
2798
2799   // We only need a return statement if there is a return value.
2800   if (results == NULL || results->empty())
2801     return TRAVERSE_CONTINUE;
2802
2803   if (func->block()->may_fall_through())
2804     error_at(func->location(), "control reaches end of non-void function");
2805
2806   return TRAVERSE_CONTINUE;
2807 }
2808
2809 // Check return statements.
2810
2811 void
2812 Gogo::check_return_statements()
2813 {
2814   Check_return_statements_traverse traverse;
2815   this->traverse(&traverse);
2816 }
2817
2818 // Get the unique prefix to use before all exported symbols.  This
2819 // must be unique across the entire link.
2820
2821 const std::string&
2822 Gogo::unique_prefix() const
2823 {
2824   go_assert(!this->unique_prefix_.empty());
2825   return this->unique_prefix_;
2826 }
2827
2828 // Set the unique prefix to use before all exported symbols.  This
2829 // comes from the command line option -fgo-prefix=XXX.
2830
2831 void
2832 Gogo::set_unique_prefix(const std::string& arg)
2833 {
2834   go_assert(this->unique_prefix_.empty());
2835   this->unique_prefix_ = arg;
2836   this->unique_prefix_specified_ = true;
2837 }
2838
2839 // Work out the package priority.  It is one more than the maximum
2840 // priority of an imported package.
2841
2842 int
2843 Gogo::package_priority() const
2844 {
2845   int priority = 0;
2846   for (Packages::const_iterator p = this->packages_.begin();
2847        p != this->packages_.end();
2848        ++p)
2849     if (p->second->priority() > priority)
2850       priority = p->second->priority();
2851   return priority + 1;
2852 }
2853
2854 // Export identifiers as requested.
2855
2856 void
2857 Gogo::do_exports()
2858 {
2859   // For now we always stream to a section.  Later we may want to
2860   // support streaming to a separate file.
2861   Stream_to_section stream;
2862
2863   Export exp(&stream);
2864   exp.register_builtin_types(this);
2865   exp.export_globals(this->package_name(),
2866                      this->unique_prefix(),
2867                      this->package_priority(),
2868                      this->imports_,
2869                      (this->need_init_fn_ && !this->is_main_package()
2870                       ? this->get_init_fn_name()
2871                       : ""),
2872                      this->imported_init_fns_,
2873                      this->package_->bindings());
2874 }
2875
2876 // Find the blocks in order to convert named types defined in blocks.
2877
2878 class Convert_named_types : public Traverse
2879 {
2880  public:
2881   Convert_named_types(Gogo* gogo)
2882     : Traverse(traverse_blocks),
2883       gogo_(gogo)
2884   { }
2885
2886  protected:
2887   int
2888   block(Block* block);
2889
2890  private:
2891   Gogo* gogo_;
2892 };
2893
2894 int
2895 Convert_named_types::block(Block* block)
2896 {
2897   this->gogo_->convert_named_types_in_bindings(block->bindings());
2898   return TRAVERSE_CONTINUE;
2899 }
2900
2901 // Convert all named types to the backend representation.  Since named
2902 // types can refer to other types, this needs to be done in the right
2903 // sequence, which is handled by Named_type::convert.  Here we arrange
2904 // to call that for each named type.
2905
2906 void
2907 Gogo::convert_named_types()
2908 {
2909   this->convert_named_types_in_bindings(this->globals_);
2910   for (Packages::iterator p = this->packages_.begin();
2911        p != this->packages_.end();
2912        ++p)
2913     {
2914       Package* package = p->second;
2915       this->convert_named_types_in_bindings(package->bindings());
2916     }
2917
2918   Convert_named_types cnt(this);
2919   this->traverse(&cnt);
2920
2921   // Make all the builtin named types used for type descriptors, and
2922   // then convert them.  They will only be written out if they are
2923   // needed.
2924   Type::make_type_descriptor_type();
2925   Type::make_type_descriptor_ptr_type();
2926   Function_type::make_function_type_descriptor_type();
2927   Pointer_type::make_pointer_type_descriptor_type();
2928   Struct_type::make_struct_type_descriptor_type();
2929   Array_type::make_array_type_descriptor_type();
2930   Array_type::make_slice_type_descriptor_type();
2931   Map_type::make_map_type_descriptor_type();
2932   Map_type::make_map_descriptor_type();
2933   Channel_type::make_chan_type_descriptor_type();
2934   Interface_type::make_interface_type_descriptor_type();
2935   Type::convert_builtin_named_types(this);
2936
2937   Runtime::convert_types(this);
2938
2939   this->named_types_are_converted_ = true;
2940 }
2941
2942 // Convert all names types in a set of bindings.
2943
2944 void
2945 Gogo::convert_named_types_in_bindings(Bindings* bindings)
2946 {
2947   for (Bindings::const_definitions_iterator p = bindings->begin_definitions();
2948        p != bindings->end_definitions();
2949        ++p)
2950     {
2951       if ((*p)->is_type())
2952         (*p)->type_value()->convert(this);
2953     }
2954 }
2955
2956 // Class Function.
2957
2958 Function::Function(Function_type* type, Function* enclosing, Block* block,
2959                    Location location)
2960   : type_(type), enclosing_(enclosing), results_(NULL),
2961     closure_var_(NULL), block_(block), location_(location), fndecl_(NULL),
2962     defer_stack_(NULL), results_are_named_(false), calls_recover_(false),
2963     is_recover_thunk_(false), has_recover_thunk_(false)
2964 {
2965 }
2966
2967 // Create the named result variables.
2968
2969 void
2970 Function::create_result_variables(Gogo* gogo)
2971 {
2972   const Typed_identifier_list* results = this->type_->results();
2973   if (results == NULL || results->empty())
2974     return;
2975
2976   if (!results->front().name().empty())
2977     this->results_are_named_ = true;
2978
2979   this->results_ = new Results();
2980   this->results_->reserve(results->size());
2981
2982   Block* block = this->block_;
2983   int index = 0;
2984   for (Typed_identifier_list::const_iterator p = results->begin();
2985        p != results->end();
2986        ++p, ++index)
2987     {
2988       std::string name = p->name();
2989       if (name.empty() || Gogo::is_sink_name(name))
2990         {
2991           static int result_counter;
2992           char buf[100];
2993           snprintf(buf, sizeof buf, "$ret%d", result_counter);
2994           ++result_counter;
2995           name = gogo->pack_hidden_name(buf, false);
2996         }
2997       Result_variable* result = new Result_variable(p->type(), this, index,
2998                                                     p->location());
2999       Named_object* no = block->bindings()->add_result_variable(name, result);
3000       if (no->is_result_variable())
3001         this->results_->push_back(no);
3002       else
3003         {
3004           static int dummy_result_count;
3005           char buf[100];
3006           snprintf(buf, sizeof buf, "$dret%d", dummy_result_count);
3007           ++dummy_result_count;
3008           name = gogo->pack_hidden_name(buf, false);
3009           no = block->bindings()->add_result_variable(name, result);
3010           go_assert(no->is_result_variable());
3011           this->results_->push_back(no);
3012         }
3013     }
3014 }
3015
3016 // Update the named result variables when cloning a function which
3017 // calls recover.
3018
3019 void
3020 Function::update_result_variables()
3021 {
3022   if (this->results_ == NULL)
3023     return;
3024
3025   for (Results::iterator p = this->results_->begin();
3026        p != this->results_->end();
3027        ++p)
3028     (*p)->result_var_value()->set_function(this);
3029 }
3030
3031 // Return the closure variable, creating it if necessary.
3032
3033 Named_object*
3034 Function::closure_var()
3035 {
3036   if (this->closure_var_ == NULL)
3037     {
3038       // We don't know the type of the variable yet.  We add fields as
3039       // we find them.
3040       Location loc = this->type_->location();
3041       Struct_field_list* sfl = new Struct_field_list;
3042       Type* struct_type = Type::make_struct_type(sfl, loc);
3043       Variable* var = new Variable(Type::make_pointer_type(struct_type),
3044                                    NULL, false, true, false, loc);
3045       var->set_is_used();
3046       this->closure_var_ = Named_object::make_variable("closure", NULL, var);
3047       // Note that the new variable is not in any binding contour.
3048     }
3049   return this->closure_var_;
3050 }
3051
3052 // Set the type of the closure variable.
3053
3054 void
3055 Function::set_closure_type()
3056 {
3057   if (this->closure_var_ == NULL)
3058     return;
3059   Named_object* closure = this->closure_var_;
3060   Struct_type* st = closure->var_value()->type()->deref()->struct_type();
3061   unsigned int index = 0;
3062   for (Closure_fields::const_iterator p = this->closure_fields_.begin();
3063        p != this->closure_fields_.end();
3064        ++p, ++index)
3065     {
3066       Named_object* no = p->first;
3067       char buf[20];
3068       snprintf(buf, sizeof buf, "%u", index);
3069       std::string n = no->name() + buf;
3070       Type* var_type;
3071       if (no->is_variable())
3072         var_type = no->var_value()->type();
3073       else
3074         var_type = no->result_var_value()->type();
3075       Type* field_type = Type::make_pointer_type(var_type);
3076       st->push_field(Struct_field(Typed_identifier(n, field_type, p->second)));
3077     }
3078 }
3079
3080 // Return whether this function is a method.
3081
3082 bool
3083 Function::is_method() const
3084 {
3085   return this->type_->is_method();
3086 }
3087
3088 // Add a label definition.
3089
3090 Label*
3091 Function::add_label_definition(Gogo* gogo, const std::string& label_name,
3092                                Location location)
3093 {
3094   Label* lnull = NULL;
3095   std::pair<Labels::iterator, bool> ins =
3096     this->labels_.insert(std::make_pair(label_name, lnull));
3097   Label* label;
3098   if (ins.second)
3099     {
3100       // This is a new label.
3101       label = new Label(label_name);
3102       ins.first->second = label;
3103     }
3104   else
3105     {
3106       // The label was already in the hash table.
3107       label = ins.first->second;
3108       if (label->is_defined())
3109         {
3110           error_at(location, "label %qs already defined",
3111                    Gogo::message_name(label_name).c_str());
3112           inform(label->location(), "previous definition of %qs was here",
3113                  Gogo::message_name(label_name).c_str());
3114           return new Label(label_name);
3115         }
3116     }
3117
3118   label->define(location, gogo->bindings_snapshot(location));
3119
3120   // Issue any errors appropriate for any previous goto's to this
3121   // label.
3122   const std::vector<Bindings_snapshot*>& refs(label->refs());
3123   for (std::vector<Bindings_snapshot*>::const_iterator p = refs.begin();
3124        p != refs.end();
3125        ++p)
3126     (*p)->check_goto_to(gogo->current_block());
3127   label->clear_refs();
3128
3129   return label;
3130 }
3131
3132 // Add a reference to a label.
3133
3134 Label*
3135 Function::add_label_reference(Gogo* gogo, const std::string& label_name,
3136                               Location location, bool issue_goto_errors)
3137 {
3138   Label* lnull = NULL;
3139   std::pair<Labels::iterator, bool> ins =
3140     this->labels_.insert(std::make_pair(label_name, lnull));
3141   Label* label;
3142   if (!ins.second)
3143     {
3144       // The label was already in the hash table.
3145       label = ins.first->second;
3146     }
3147   else
3148     {
3149       go_assert(ins.first->second == NULL);
3150       label = new Label(label_name);
3151       ins.first->second = label;
3152     }
3153
3154   label->set_is_used();
3155
3156   if (issue_goto_errors)
3157     {
3158       Bindings_snapshot* snapshot = label->snapshot();
3159       if (snapshot != NULL)
3160         snapshot->check_goto_from(gogo->current_block(), location);
3161       else
3162         label->add_snapshot_ref(gogo->bindings_snapshot(location));
3163     }
3164
3165   return label;
3166 }
3167
3168 // Warn about labels that are defined but not used.
3169
3170 void
3171 Function::check_labels() const
3172 {
3173   for (Labels::const_iterator p = this->labels_.begin();
3174        p != this->labels_.end();
3175        p++)
3176     {
3177       Label* label = p->second;
3178       if (!label->is_used())
3179         error_at(label->location(), "label %qs defined and not used",
3180                  Gogo::message_name(label->name()).c_str());
3181     }
3182 }
3183
3184 // Swap one function with another.  This is used when building the
3185 // thunk we use to call a function which calls recover.  It may not
3186 // work for any other case.
3187
3188 void
3189 Function::swap_for_recover(Function *x)
3190 {
3191   go_assert(this->enclosing_ == x->enclosing_);
3192   std::swap(this->results_, x->results_);
3193   std::swap(this->closure_var_, x->closure_var_);
3194   std::swap(this->block_, x->block_);
3195   go_assert(this->location_ == x->location_);
3196   go_assert(this->fndecl_ == NULL && x->fndecl_ == NULL);
3197   go_assert(this->defer_stack_ == NULL && x->defer_stack_ == NULL);
3198 }
3199
3200 // Traverse the tree.
3201
3202 int
3203 Function::traverse(Traverse* traverse)
3204 {
3205   unsigned int traverse_mask = traverse->traverse_mask();
3206
3207   if ((traverse_mask
3208        & (Traverse::traverse_types | Traverse::traverse_expressions))
3209       != 0)
3210     {
3211       if (Type::traverse(this->type_, traverse) == TRAVERSE_EXIT)
3212         return TRAVERSE_EXIT;
3213     }
3214
3215   // FIXME: We should check traverse_functions here if nested
3216   // functions are stored in block bindings.
3217   if (this->block_ != NULL
3218       && (traverse_mask
3219           & (Traverse::traverse_variables
3220              | Traverse::traverse_constants
3221              | Traverse::traverse_blocks
3222              | Traverse::traverse_statements
3223              | Traverse::traverse_expressions
3224              | Traverse::traverse_types)) != 0)
3225     {
3226       if (this->block_->traverse(traverse) == TRAVERSE_EXIT)
3227         return TRAVERSE_EXIT;
3228     }
3229
3230   return TRAVERSE_CONTINUE;
3231 }
3232
3233 // Work out types for unspecified variables and constants.
3234
3235 void
3236 Function::determine_types()
3237 {
3238   if (this->block_ != NULL)
3239     this->block_->determine_types();
3240 }
3241
3242 // Get a pointer to the variable representing the defer stack for this
3243 // function, making it if necessary.  The value of the variable is set
3244 // by the runtime routines to true if the function is returning,
3245 // rather than panicing through.  A pointer to this variable is used
3246 // as a marker for the functions on the defer stack associated with
3247 // this function.  A function-specific variable permits inlining a
3248 // function which uses defer.
3249
3250 Expression*
3251 Function::defer_stack(Location location)
3252 {
3253   if (this->defer_stack_ == NULL)
3254     {
3255       Type* t = Type::lookup_bool_type();
3256       Expression* n = Expression::make_boolean(false, location);
3257       this->defer_stack_ = Statement::make_temporary(t, n, location);
3258       this->defer_stack_->set_is_address_taken();
3259     }
3260   Expression* ref = Expression::make_temporary_reference(this->defer_stack_,
3261                                                          location);
3262   return Expression::make_unary(OPERATOR_AND, ref, location);
3263 }
3264
3265 // Export the function.
3266
3267 void
3268 Function::export_func(Export* exp, const std::string& name) const
3269 {
3270   Function::export_func_with_type(exp, name, this->type_);
3271 }
3272
3273 // Export a function with a type.
3274
3275 void
3276 Function::export_func_with_type(Export* exp, const std::string& name,
3277                                 const Function_type* fntype)
3278 {
3279   exp->write_c_string("func ");
3280
3281   if (fntype->is_method())
3282     {
3283       exp->write_c_string("(");
3284       const Typed_identifier* receiver = fntype->receiver();
3285       exp->write_name(receiver->name());
3286       exp->write_c_string(" ");
3287       exp->write_type(receiver->type());
3288       exp->write_c_string(") ");
3289     }
3290
3291   exp->write_string(name);
3292
3293   exp->write_c_string(" (");
3294   const Typed_identifier_list* parameters = fntype->parameters();
3295   if (parameters != NULL)
3296     {
3297       bool is_varargs = fntype->is_varargs();
3298       bool first = true;
3299       for (Typed_identifier_list::const_iterator p = parameters->begin();
3300            p != parameters->end();
3301            ++p)
3302         {
3303           if (first)
3304             first = false;
3305           else
3306             exp->write_c_string(", ");
3307           exp->write_name(p->name());
3308           exp->write_c_string(" ");
3309           if (!is_varargs || p + 1 != parameters->end())
3310             exp->write_type(p->type());
3311           else
3312             {
3313               exp->write_c_string("...");
3314               exp->write_type(p->type()->array_type()->element_type());
3315             }
3316         }
3317     }
3318   exp->write_c_string(")");
3319
3320   const Typed_identifier_list* results = fntype->results();
3321   if (results != NULL)
3322     {
3323       if (results->size() == 1 && results->begin()->name().empty())
3324         {
3325           exp->write_c_string(" ");
3326           exp->write_type(results->begin()->type());
3327         }
3328       else
3329         {
3330           exp->write_c_string(" (");
3331           bool first = true;
3332           for (Typed_identifier_list::const_iterator p = results->begin();
3333                p != results->end();
3334                ++p)
3335             {
3336               if (first)
3337                 first = false;
3338               else
3339                 exp->write_c_string(", ");
3340               exp->write_name(p->name());
3341               exp->write_c_string(" ");
3342               exp->write_type(p->type());
3343             }
3344           exp->write_c_string(")");
3345         }
3346     }
3347   exp->write_c_string(";\n");
3348 }
3349
3350 // Import a function.
3351
3352 void
3353 Function::import_func(Import* imp, std::string* pname,
3354                       Typed_identifier** preceiver,
3355                       Typed_identifier_list** pparameters,
3356                       Typed_identifier_list** presults,
3357                       bool* is_varargs)
3358 {
3359   imp->require_c_string("func ");
3360
3361   *preceiver = NULL;
3362   if (imp->peek_char() == '(')
3363     {
3364       imp->require_c_string("(");
3365       std::string name = imp->read_name();
3366       imp->require_c_string(" ");
3367       Type* rtype = imp->read_type();
3368       *preceiver = new Typed_identifier(name, rtype, imp->location());
3369       imp->require_c_string(") ");
3370     }
3371
3372   *pname = imp->read_identifier();
3373
3374   Typed_identifier_list* parameters;
3375   *is_varargs = false;
3376   imp->require_c_string(" (");
3377   if (imp->peek_char() == ')')
3378     parameters = NULL;
3379   else
3380     {
3381       parameters = new Typed_identifier_list();
3382       while (true)
3383         {
3384           std::string name = imp->read_name();
3385           imp->require_c_string(" ");
3386
3387           if (imp->match_c_string("..."))
3388             {
3389               imp->advance(3);
3390               *is_varargs = true;
3391             }
3392
3393           Type* ptype = imp->read_type();
3394           if (*is_varargs)
3395             ptype = Type::make_array_type(ptype, NULL);
3396           parameters->push_back(Typed_identifier(name, ptype,
3397                                                  imp->location()));
3398           if (imp->peek_char() != ',')
3399             break;
3400           go_assert(!*is_varargs);
3401           imp->require_c_string(", ");
3402         }
3403     }
3404   imp->require_c_string(")");
3405   *pparameters = parameters;
3406
3407   Typed_identifier_list* results;
3408   if (imp->peek_char() != ' ')
3409     results = NULL;
3410   else
3411     {
3412       results = new Typed_identifier_list();
3413       imp->require_c_string(" ");
3414       if (imp->peek_char() != '(')
3415         {
3416           Type* rtype = imp->read_type();
3417           results->push_back(Typed_identifier("", rtype, imp->location()));
3418         }
3419       else
3420         {
3421           imp->require_c_string("(");
3422           while (true)
3423             {
3424               std::string name = imp->read_name();
3425               imp->require_c_string(" ");
3426               Type* rtype = imp->read_type();
3427               results->push_back(Typed_identifier(name, rtype,
3428                                                   imp->location()));
3429               if (imp->peek_char() != ',')
3430                 break;
3431               imp->require_c_string(", ");
3432             }
3433           imp->require_c_string(")");
3434         }
3435     }
3436   imp->require_c_string(";\n");
3437   *presults = results;
3438 }
3439
3440 // Class Block.
3441
3442 Block::Block(Block* enclosing, Location location)
3443   : enclosing_(enclosing), statements_(),
3444     bindings_(new Bindings(enclosing == NULL
3445                            ? NULL
3446                            : enclosing->bindings())),
3447     start_location_(location),
3448     end_location_(UNKNOWN_LOCATION)
3449 {
3450 }
3451
3452 // Add a statement to a block.
3453
3454 void
3455 Block::add_statement(Statement* statement)
3456 {
3457   this->statements_.push_back(statement);
3458 }
3459
3460 // Add a statement to the front of a block.  This is slow but is only
3461 // used for reference counts of parameters.
3462
3463 void
3464 Block::add_statement_at_front(Statement* statement)
3465 {
3466   this->statements_.insert(this->statements_.begin(), statement);
3467 }
3468
3469 // Replace a statement in a block.
3470
3471 void
3472 Block::replace_statement(size_t index, Statement* s)
3473 {
3474   go_assert(index < this->statements_.size());
3475   this->statements_[index] = s;
3476 }
3477
3478 // Add a statement before another statement.
3479
3480 void
3481 Block::insert_statement_before(size_t index, Statement* s)
3482 {
3483   go_assert(index < this->statements_.size());
3484   this->statements_.insert(this->statements_.begin() + index, s);
3485 }
3486
3487 // Add a statement after another statement.
3488
3489 void
3490 Block::insert_statement_after(size_t index, Statement* s)
3491 {
3492   go_assert(index < this->statements_.size());
3493   this->statements_.insert(this->statements_.begin() + index + 1, s);
3494 }
3495
3496 // Traverse the tree.
3497
3498 int
3499 Block::traverse(Traverse* traverse)
3500 {
3501   unsigned int traverse_mask = traverse->traverse_mask();
3502
3503   if ((traverse_mask & Traverse::traverse_blocks) != 0)
3504     {
3505       int t = traverse->block(this);
3506       if (t == TRAVERSE_EXIT)
3507         return TRAVERSE_EXIT;
3508       else if (t == TRAVERSE_SKIP_COMPONENTS)
3509         return TRAVERSE_CONTINUE;
3510     }
3511
3512   if ((traverse_mask
3513        & (Traverse::traverse_variables
3514           | Traverse::traverse_constants
3515           | Traverse::traverse_expressions
3516           | Traverse::traverse_types)) != 0)
3517     {
3518       const unsigned int e_or_t = (Traverse::traverse_expressions
3519                                    | Traverse::traverse_types);
3520       const unsigned int e_or_t_or_s = (e_or_t
3521                                         | Traverse::traverse_statements);
3522       for (Bindings::const_definitions_iterator pb =
3523              this->bindings_->begin_definitions();
3524            pb != this->bindings_->end_definitions();
3525            ++pb)
3526         {
3527           int t = TRAVERSE_CONTINUE;
3528           switch ((*pb)->classification())
3529             {
3530             case Named_object::NAMED_OBJECT_CONST:
3531               if ((traverse_mask & Traverse::traverse_constants) != 0)
3532                 t = traverse->constant(*pb, false);
3533               if (t == TRAVERSE_CONTINUE
3534                   && (traverse_mask & e_or_t) != 0)
3535                 {
3536                   Type* tc = (*pb)->const_value()->type();