src/librustc_resolve/build_reduced_graph.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Reduced graph building
  12 //!
  13 //! Here we build the "reduced graph": the graph of the module tree without
  14 //! any imports resolved.
  15
  16 use {DefModifiers, PUBLIC, IMPORTABLE};
  17 use ImportDirective;
  18 use ImportDirectiveSubclass::{self, SingleImport, GlobImport};
  19 use ImportResolution;
  20 use Module;
  21 use ModuleKind::*;
  22 use Namespace::{TypeNS, ValueNS};
  23 use NameBindings;
  24 use ParentLink::{self, ModuleParentLink, BlockParentLink};
  25 use Resolver;
  26 use RibKind::*;
  27 use Shadowable;
  28 use TypeNsDef;
  29 use TypeParameters::HasTypeParameters;
  30
  31 use self::DuplicateCheckingMode::*;
  32 use self::NamespaceError::*;
  33
  34 use rustc::metadata::csearch;
  35 use rustc::metadata::decoder::{DefLike, DlDef, DlField, DlImpl};
  36 use rustc::middle::def::*;
  37 use rustc::middle::subst::FnSpace;
  38
  39 use syntax::ast::{Block, Crate};
  40 use syntax::ast::{DeclItem, DefId};
  41 use syntax::ast::{ForeignItem, ForeignItemFn, ForeignItemStatic};
  42 use syntax::ast::{Item, ItemConst, ItemEnum, ItemFn};
  43 use syntax::ast::{ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic};
  44 use syntax::ast::{ItemStruct, ItemTrait, ItemTy};
  45 use syntax::ast::{MethodImplItem, Name, NamedField, NodeId};
  46 use syntax::ast::{PathListIdent, PathListMod};
  47 use syntax::ast::{Public, SelfStatic};
  48 use syntax::ast::StmtDecl;
  49 use syntax::ast::StructVariantKind;
  50 use syntax::ast::TupleVariantKind;
  51 use syntax::ast::TyObjectSum;
  52 use syntax::ast::{TypeImplItem, UnnamedField};
  53 use syntax::ast::{Variant, ViewItem, ViewItemExternCrate};
  54 use syntax::ast::{ViewItemUse, ViewPathGlob, ViewPathList, ViewPathSimple};
  55 use syntax::ast::{Visibility};
  56 use syntax::ast::TyPath;
  57 use syntax::ast;
  58 use syntax::ast_util::{self, PostExpansionMethod, local_def};
  59 use syntax::attr::AttrMetaMethods;
  60 use syntax::parse::token::{self, special_idents};
  61 use syntax::codemap::{Span, DUMMY_SP};
  62 use syntax::visit::{self, Visitor};
  63
  64 use std::mem::replace;
  65 use std::ops::{Deref, DerefMut};
  66 use std::rc::Rc;
  67
  68 // Specifies how duplicates should be handled when adding a child item if
  69 // another item exists with the same name in some namespace.
  70 #[derive(Copy, PartialEq)]
  71 enum DuplicateCheckingMode {
  72     ForbidDuplicateModules,
  73     ForbidDuplicateTypesAndModules,
  74     ForbidDuplicateValues,
  75     ForbidDuplicateTypesAndValues,
  76     OverwriteDuplicates
  77 }
  78
  79 #[derive(Copy, PartialEq)]
  80 enum NamespaceError {
  81     NoError,
  82     ModuleError,
  83     TypeError,
  84     ValueError
  85 }
  86
  87 fn namespace_error_to_string(ns: NamespaceError) -> &'static str {
  88     match ns {
  89         NoError                 => "",
  90         ModuleError | TypeError => "type or module",
  91         ValueError              => "value",
  92     }
  93 }
  94
  95 struct GraphBuilder<'a, 'b:'a, 'tcx:'b> {
  96     resolver: &'a mut Resolver<'b, 'tcx>
  97 }
  98
  99 impl<'a, 'b:'a, 'tcx:'b> Deref for GraphBuilder<'a, 'b, 'tcx> {
 100     type Target = Resolver<'b, 'tcx>;
 101
 102     fn deref(&self) -> &Resolver<'b, 'tcx> {
 103         &*self.resolver
 104     }
 105 }
 106
 107 impl<'a, 'b:'a, 'tcx:'b> DerefMut for GraphBuilder<'a, 'b, 'tcx> {
 108     fn deref_mut(&mut self) -> &mut Resolver<'b, 'tcx> {
 109         &mut *self.resolver
 110     }
 111 }
 112
 113 impl<'a, 'b:'a, 'tcx:'b> GraphBuilder<'a, 'b, 'tcx> {
 114     /// Constructs the reduced graph for the entire crate.
 115     fn build_reduced_graph(self, krate: &ast::Crate) {
 116         let parent = self.graph_root.get_module();
 117         let mut visitor = BuildReducedGraphVisitor {
 118             builder: self,
 119             parent: parent
 120         };
 121         visit::walk_crate(&mut visitor, krate);
 122     }
 123
 124     /// Adds a new child item to the module definition of the parent node and
 125     /// returns its corresponding name bindings as well as the current parent.
 126     /// Or, if we're inside a block, creates (or reuses) an anonymous module
 127     /// corresponding to the innermost block ID and returns the name bindings
 128     /// as well as the newly-created parent.
 129     ///
 130     /// # Panics
 131     ///
 132     /// Panics if this node does not have a module definition and we are not inside
 133     /// a block.
 134     fn add_child(&self,
 135                  name: Name,
 136                  parent: &Rc<Module>,
 137                  duplicate_checking_mode: DuplicateCheckingMode,
 138                  // For printing errors
 139                  sp: Span)
 140                  -> Rc<NameBindings> {
 141         // If this is the immediate descendant of a module, then we add the
 142         // child name directly. Otherwise, we create or reuse an anonymous
 143         // module and add the child to that.
 144
 145         self.check_for_conflicts_between_external_crates_and_items(&**parent,
 146                                                                    name,
 147                                                                    sp);
 148
 149         // Add or reuse the child.
 150         let child = parent.children.borrow().get(&name).cloned();
 151         match child {
 152             None => {
 153                 let child = Rc::new(NameBindings::new());
 154                 parent.children.borrow_mut().insert(name, child.clone());
 155                 child
 156             }
 157             Some(child) => {
 158                 // Enforce the duplicate checking mode:
 159                 //
 160                 // * If we're requesting duplicate module checking, check that
 161                 //   there isn't a module in the module with the same name.
 162                 //
 163                 // * If we're requesting duplicate type checking, check that
 164                 //   there isn't a type in the module with the same name.
 165                 //
 166                 // * If we're requesting duplicate value checking, check that
 167                 //   there isn't a value in the module with the same name.
 168                 //
 169                 // * If we're requesting duplicate type checking and duplicate
 170                 //   value checking, check that there isn't a duplicate type
 171                 //   and a duplicate value with the same name.
 172                 //
 173                 // * If no duplicate checking was requested at all, do
 174                 //   nothing.
 175
 176                 let mut duplicate_type = NoError;
 177                 let ns = match duplicate_checking_mode {
 178                     ForbidDuplicateModules => {
 179                         if child.get_module_if_available().is_some() {
 180                             duplicate_type = ModuleError;
 181                         }
 182                         Some(TypeNS)
 183                     }
 184                     ForbidDuplicateTypesAndModules => {
 185                         match child.def_for_namespace(TypeNS) {
 186                             None => {}
 187                             Some(_) if child.get_module_if_available()
 188                                             .map(|m| m.kind.get()) ==
 189                                        Some(ImplModuleKind) => {}
 190                             Some(_) => duplicate_type = TypeError
 191                         }
 192                         Some(TypeNS)
 193                     }
 194                     ForbidDuplicateValues => {
 195                         if child.defined_in_namespace(ValueNS) {
 196                             duplicate_type = ValueError;
 197                         }
 198                         Some(ValueNS)
 199                     }
 200                     ForbidDuplicateTypesAndValues => {
 201                         let mut n = None;
 202                         match child.def_for_namespace(TypeNS) {
 203                             Some(DefMod(_)) | None => {}
 204                             Some(_) => {
 205                                 n = Some(TypeNS);
 206                                 duplicate_type = TypeError;
 207                             }
 208                         };
 209                         if child.defined_in_namespace(ValueNS) {
 210                             duplicate_type = ValueError;
 211                             n = Some(ValueNS);
 212                         }
 213                         n
 214                     }
 215                     OverwriteDuplicates => None
 216                 };
 217                 if duplicate_type != NoError {
 218                     // Return an error here by looking up the namespace that
 219                     // had the duplicate.
 220                     let ns = ns.unwrap();
 221                     self.resolve_error(sp,
 222                         format!("duplicate definition of {} `{}`",
 223                              namespace_error_to_string(duplicate_type),
 224                              token::get_name(name))[]);
 225                     {
 226                         let r = child.span_for_namespace(ns);
 227                         for sp in r.iter() {
 228                             self.session.span_note(*sp,
 229                                  format!("first definition of {} `{}` here",
 230                                       namespace_error_to_string(duplicate_type),
 231                                       token::get_name(name))[]);
 232                         }
 233                     }
 234                 }
 235                 child
 236             }
 237         }
 238     }
 239
 240     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 241         // If the block has view items, we need an anonymous module.
 242         if block.view_items.len() > 0 {
 243             return true;
 244         }
 245
 246         // Check each statement.
 247         for statement in block.stmts.iter() {
 248             match statement.node {
 249                 StmtDecl(ref declaration, _) => {
 250                     match declaration.node {
 251                         DeclItem(_) => {
 252                             return true;
 253                         }
 254                         _ => {
 255                             // Keep searching.
 256                         }
 257                     }
 258                 }
 259                 _ => {
 260                     // Keep searching.
 261                 }
 262             }
 263         }
 264
 265         // If we found neither view items nor items, we don't need to create
 266         // an anonymous module.
 267
 268         return false;
 269     }
 270
 271     fn get_parent_link(&mut self, parent: &Rc<Module>, name: Name) -> ParentLink {
 272         ModuleParentLink(parent.downgrade(), name)
 273     }
 274
 275     /// Constructs the reduced graph for one item.
 276     fn build_reduced_graph_for_item(&mut self, item: &Item, parent: &Rc<Module>) -> Rc<Module> {
 277         let name = item.ident.name;
 278         let sp = item.span;
 279         let is_public = item.vis == ast::Public;
 280         let modifiers = if is_public { PUBLIC } else { DefModifiers::empty() } | IMPORTABLE;
 281
 282         match item.node {
 283             ItemMod(..) => {
 284                 let name_bindings = self.add_child(name, parent, ForbidDuplicateModules, sp);
 285
 286                 let parent_link = self.get_parent_link(parent, name);
 287                 let def_id = DefId { krate: 0, node: item.id };
 288                 name_bindings.define_module(parent_link,
 289                                             Some(def_id),
 290                                             NormalModuleKind,
 291                                             false,
 292                                             item.vis == ast::Public,
 293                                             sp);
 294
 295                 name_bindings.get_module()
 296             }
 297
 298             ItemForeignMod(..) => parent.clone(),
 299
 300             // These items live in the value namespace.
 301             ItemStatic(_, m, _) => {
 302                 let name_bindings = self.add_child(name, parent, ForbidDuplicateValues, sp);
 303                 let mutbl = m == ast::MutMutable;
 304
 305                 name_bindings.define_value(DefStatic(local_def(item.id), mutbl), sp, modifiers);
 306                 parent.clone()
 307             }
 308             ItemConst(_, _) => {
 309                 self.add_child(name, parent, ForbidDuplicateValues, sp)
 310                     .define_value(DefConst(local_def(item.id)), sp, modifiers);
 311                 parent.clone()
 312             }
 313             ItemFn(_, _, _, _, _) => {
 314                 let name_bindings = self.add_child(name, parent, ForbidDuplicateValues, sp);
 315
 316                 let def = DefFn(local_def(item.id), false);
 317                 name_bindings.define_value(def, sp, modifiers);
 318                 parent.clone()
 319             }
 320
 321             // These items live in the type namespace.
 322             ItemTy(..) => {
 323                 let name_bindings =
 324                     self.add_child(name, parent, ForbidDuplicateTypesAndModules, sp);
 325
 326                 name_bindings.define_type(DefTy(local_def(item.id), false), sp, modifiers);
 327                 parent.clone()
 328             }
 329
 330             ItemEnum(ref enum_definition, _) => {
 331                 let name_bindings =
 332                     self.add_child(name, parent, ForbidDuplicateTypesAndModules, sp);
 333
 334                 name_bindings.define_type(DefTy(local_def(item.id), true), sp, modifiers);
 335
 336                 let parent_link = self.get_parent_link(parent, name);
 337                 // We want to make sure the module type is EnumModuleKind
 338                 // even if there's already an ImplModuleKind module defined,
 339                 // since that's how we prevent duplicate enum definitions
 340                 name_bindings.set_module_kind(parent_link,
 341                                               Some(local_def(item.id)),
 342                                               EnumModuleKind,
 343                                               false,
 344                                               is_public,
 345                                               sp);
 346
 347                 let module = name_bindings.get_module();
 348
 349                 for variant in (*enum_definition).variants.iter() {
 350                     self.build_reduced_graph_for_variant(
 351                         &**variant,
 352                         local_def(item.id),
 353                         &module);
 354                 }
 355                 parent.clone()
 356             }
 357
 358             // These items live in both the type and value namespaces.
 359             ItemStruct(ref struct_def, _) => {
 360                 // Adding to both Type and Value namespaces or just Type?
 361                 let (forbid, ctor_id) = match struct_def.ctor_id {
 362                     Some(ctor_id)   => (ForbidDuplicateTypesAndValues, Some(ctor_id)),
 363                     None            => (ForbidDuplicateTypesAndModules, None)
 364                 };
 365
 366                 let name_bindings = self.add_child(name, parent, forbid, sp);
 367
 368                 // Define a name in the type namespace.
 369                 name_bindings.define_type(DefTy(local_def(item.id), false), sp, modifiers);
 370
 371                 // If this is a newtype or unit-like struct, define a name
 372                 // in the value namespace as well
 373                 if let Some(cid) = ctor_id {
 374                     name_bindings.define_value(DefStruct(local_def(cid)), sp, modifiers);
 375                 }
 376
 377                 // Record the def ID and fields of this struct.
 378                 let named_fields = struct_def.fields.iter().filter_map(|f| {
 379                     match f.node.kind {
 380                         NamedField(ident, _) => Some(ident.name),
 381                         UnnamedField(_) => None
 382                     }
 383                 }).collect();
 384                 self.structs.insert(local_def(item.id), named_fields);
 385
 386                 parent.clone()
 387             }
 388
 389             ItemImpl(_, _, None, ref ty, ref impl_items) => {
 390                 // If this implements an anonymous trait, then add all the
 391                 // methods within to a new module, if the type was defined
 392                 // within this module.
 393
 394                 let mod_name = match ty.node {
 395                     TyPath(ref path, _) if path.segments.len() == 1 => {
 396                         // FIXME(18446) we should distinguish between the name of
 397                         // a trait and the name of an impl of that trait.
 398                         Some(path.segments.last().unwrap().identifier.name)
 399                     }
 400                     TyObjectSum(ref lhs_ty, _) => {
 401                         match lhs_ty.node {
 402                             TyPath(ref path, _) if path.segments.len() == 1 => {
 403                                 Some(path.segments.last().unwrap().identifier.name)
 404                             }
 405                             _ => {
 406                                 None
 407                             }
 408                         }
 409                     }
 410                     _ => {
 411                         None
 412                     }
 413                 };
 414
 415                 match mod_name {
 416                     None => {
 417                         self.resolve_error(ty.span,
 418                                            "inherent implementations may \
 419                                             only be implemented in the same \
 420                                             module as the type they are \
 421                                             implemented for")
 422                     }
 423                     Some(mod_name) => {
 424                         // Create the module and add all methods.
 425                         let parent_opt = parent.children.borrow().get(&mod_name).cloned();
 426                         let new_parent = match parent_opt {
 427                             // It already exists
 428                             Some(ref child) if child.get_module_if_available()
 429                                 .is_some() &&
 430                                 (child.get_module().kind.get() == ImplModuleKind ||
 431                                  child.get_module().kind.get() == TraitModuleKind) => {
 432                                     child.get_module()
 433                                 }
 434                             Some(ref child) if child.get_module_if_available()
 435                                 .is_some() &&
 436                                 child.get_module().kind.get() ==
 437                                 EnumModuleKind => child.get_module(),
 438                             // Create the module
 439                             _ => {
 440                                 let name_bindings =
 441                                     self.add_child(mod_name, parent, ForbidDuplicateModules, sp);
 442
 443                                 let parent_link = self.get_parent_link(parent, name);
 444                                 let def_id = local_def(item.id);
 445                                 let ns = TypeNS;
 446                                 let is_public =
 447                                     !name_bindings.defined_in_namespace(ns) ||
 448                                     name_bindings.defined_in_public_namespace(ns);
 449
 450                                 name_bindings.define_module(parent_link,
 451                                                             Some(def_id),
 452                                                             ImplModuleKind,
 453                                                             false,
 454                                                             is_public,
 455                                                             sp);
 456
 457                                 name_bindings.get_module()
 458                             }
 459                         };
 460
 461                         // For each implementation item...
 462                         for impl_item in impl_items.iter() {
 463                             match *impl_item {
 464                                 MethodImplItem(ref method) => {
 465                                     // Add the method to the module.
 466                                     let name = method.pe_ident().name;
 467                                     let method_name_bindings =
 468                                         self.add_child(name,
 469                                                        &new_parent,
 470                                                        ForbidDuplicateValues,
 471                                                        method.span);
 472                                     let def = match method.pe_explicit_self()
 473                                         .node {
 474                                             SelfStatic => {
 475                                                 // Static methods become
 476                                                 // `DefStaticMethod`s.
 477                                                 DefStaticMethod(local_def(method.id),
 478                                                                 FromImpl(local_def(item.id)))
 479                                             }
 480                                             _ => {
 481                                                 // Non-static methods become
 482                                                 // `DefMethod`s.
 483                                                 DefMethod(local_def(method.id),
 484                                                           None,
 485                                                           FromImpl(local_def(item.id)))
 486                                             }
 487                                         };
 488
 489                                     // NB: not IMPORTABLE
 490                                     let modifiers = if method.pe_vis() == ast::Public {
 491                                         PUBLIC
 492                                     } else {
 493                                         DefModifiers::empty()
 494                                     };
 495                                     method_name_bindings.define_value(
 496                                         def,
 497                                         method.span,
 498                                         modifiers);
 499                                 }
 500                                 TypeImplItem(ref typedef) => {
 501                                     // Add the typedef to the module.
 502                                     let name = typedef.ident.name;
 503                                     let typedef_name_bindings =
 504                                         self.add_child(
 505                                             name,
 506                                             &new_parent,
 507                                             ForbidDuplicateTypesAndModules,
 508                                             typedef.span);
 509                                     let def = DefAssociatedTy(local_def(
 510                                         typedef.id));
 511                                     // NB: not IMPORTABLE
 512                                     let modifiers = if typedef.vis == ast::Public {
 513                                         PUBLIC
 514                                     } else {
 515                                         DefModifiers::empty()
 516                                     };
 517                                     typedef_name_bindings.define_type(
 518                                         def,
 519                                         typedef.span,
 520                                         modifiers);
 521                                 }
 522                             }
 523                         }
 524                     }
 525                 }
 526
 527                 parent.clone()
 528             }
 529
 530             ItemImpl(_, _, Some(_), _, _) => parent.clone(),
 531
 532             ItemTrait(_, _, _, ref items) => {
 533                 let name_bindings =
 534                     self.add_child(name, parent, ForbidDuplicateTypesAndModules, sp);
 535
 536                 // Add all the items within to a new module.
 537                 let parent_link = self.get_parent_link(parent, name);
 538                 name_bindings.define_module(parent_link,
 539                                             Some(local_def(item.id)),
 540                                             TraitModuleKind,
 541                                             false,
 542                                             item.vis == ast::Public,
 543                                             sp);
 544                 let module_parent = name_bindings.get_module();
 545
 546                 let def_id = local_def(item.id);
 547
 548                 // Add the names of all the items to the trait info.
 549                 for trait_item in items.iter() {
 550                     let (name, kind) = match *trait_item {
 551                         ast::RequiredMethod(_) |
 552                         ast::ProvidedMethod(_) => {
 553                             let ty_m = ast_util::trait_item_to_ty_method(trait_item);
 554
 555                             let name = ty_m.ident.name;
 556
 557                             // Add it as a name in the trait module.
 558                             let (def, static_flag) = match ty_m.explicit_self
 559                                                                .node {
 560                                 SelfStatic => {
 561                                     // Static methods become `DefStaticMethod`s.
 562                                     (DefStaticMethod(
 563                                             local_def(ty_m.id),
 564                                             FromTrait(local_def(item.id))),
 565                                      StaticMethodTraitItemKind)
 566                                 }
 567                                 _ => {
 568                                     // Non-static methods become `DefMethod`s.
 569                                     (DefMethod(local_def(ty_m.id),
 570                                                Some(local_def(item.id)),
 571                                                FromTrait(local_def(item.id))),
 572                                      NonstaticMethodTraitItemKind)
 573                                 }
 574                             };
 575
 576                             let method_name_bindings =
 577                                 self.add_child(name,
 578                                                &module_parent,
 579                                                ForbidDuplicateTypesAndValues,
 580                                                ty_m.span);
 581                             // NB: not IMPORTABLE
 582                             method_name_bindings.define_value(def,
 583                                                               ty_m.span,
 584                                                               PUBLIC);
 585
 586                             (name, static_flag)
 587                         }
 588                         ast::TypeTraitItem(ref associated_type) => {
 589                             let def = DefAssociatedTy(local_def(
 590                                     associated_type.ty_param.id));
 591
 592                             let name_bindings =
 593                                 self.add_child(associated_type.ty_param.ident.name,
 594                                                &module_parent,
 595                                                ForbidDuplicateTypesAndValues,
 596                                                associated_type.ty_param.span);
 597                             // NB: not IMPORTABLE
 598                             name_bindings.define_type(def,
 599                                                       associated_type.ty_param.span,
 600                                                       PUBLIC);
 601
 602                             (associated_type.ty_param.ident.name, TypeTraitItemKind)
 603                         }
 604                     };
 605
 606                     self.trait_item_map.insert((name, def_id), kind);
 607                 }
 608
 609                 name_bindings.define_type(DefTrait(def_id), sp, modifiers);
 610                 parent.clone()
 611             }
 612             ItemMac(..) => parent.clone()
 613         }
 614     }
 615
 616     // Constructs the reduced graph for one variant. Variants exist in the
 617     // type and value namespaces.
 618     fn build_reduced_graph_for_variant(&mut self,
 619                                        variant: &Variant,
 620                                        item_id: DefId,
 621                                        parent: &Rc<Module>) {
 622         let name = variant.node.name.name;
 623         let is_exported = match variant.node.kind {
 624             TupleVariantKind(_) => false,
 625             StructVariantKind(_) => {
 626                 // Not adding fields for variants as they are not accessed with a self receiver
 627                 self.structs.insert(local_def(variant.node.id), Vec::new());
 628                 true
 629             }
 630         };
 631
 632         let child = self.add_child(name, parent,
 633                                    ForbidDuplicateTypesAndValues,
 634                                    variant.span);
 635         // variants are always treated as importable to allow them to be glob
 636         // used
 637         child.define_value(DefVariant(item_id,
 638                                       local_def(variant.node.id), is_exported),
 639                            variant.span, PUBLIC | IMPORTABLE);
 640         child.define_type(DefVariant(item_id,
 641                                      local_def(variant.node.id), is_exported),
 642                           variant.span, PUBLIC | IMPORTABLE);
 643     }
 644
 645     /// Constructs the reduced graph for one 'view item'. View items consist
 646     /// of imports and use directives.
 647     fn build_reduced_graph_for_view_item(&mut self, view_item: &ViewItem, parent: &Rc<Module>) {
 648         match view_item.node {
 649             ViewItemUse(ref view_path) => {
 650                 // Extract and intern the module part of the path. For
 651                 // globs and lists, the path is found directly in the AST;
 652                 // for simple paths we have to munge the path a little.
 653                 let module_path = match view_path.node {
 654                     ViewPathSimple(_, ref full_path, _) => {
 655                         full_path.segments
 656                             .init()
 657                             .iter().map(|ident| ident.identifier.name)
 658                             .collect()
 659                     }
 660
 661                     ViewPathGlob(ref module_ident_path, _) |
 662                     ViewPathList(ref module_ident_path, _, _) => {
 663                         module_ident_path.segments
 664                             .iter().map(|ident| ident.identifier.name).collect()
 665                     }
 666                 };
 667
 668                 // Build up the import directives.
 669                 let is_public = view_item.vis == ast::Public;
 670                 let shadowable =
 671                     view_item.attrs
 672                              .iter()
 673                              .any(|attr| {
 674                                  attr.name() == token::get_name(
 675                                     special_idents::prelude_import.name)
 676                              });
 677                 let shadowable = if shadowable {
 678                     Shadowable::Always
 679                 } else {
 680                     Shadowable::Never
 681                 };
 682
 683                 match view_path.node {
 684                     ViewPathSimple(binding, ref full_path, id) => {
 685                         let source_name =
 686                             full_path.segments.last().unwrap().identifier.name;
 687                         if token::get_name(source_name).get() == "mod" ||
 688                            token::get_name(source_name).get() == "self" {
 689                             self.resolve_error(view_path.span,
 690                                 "`self` imports are only allowed within a { } list");
 691                         }
 692
 693                         let subclass = SingleImport(binding.name,
 694                                                     source_name);
 695                         self.build_import_directive(&**parent,
 696                                                     module_path,
 697                                                     subclass,
 698                                                     view_path.span,
 699                                                     id,
 700                                                     is_public,
 701                                                     shadowable);
 702                     }
 703                     ViewPathList(_, ref source_items, _) => {
 704                         // Make sure there's at most one `mod` import in the list.
 705                         let mod_spans = source_items.iter().filter_map(|item| match item.node {
 706                             PathListMod { .. } => Some(item.span),
 707                             _ => None
 708                         }).collect::<Vec<Span>>();
 709                         if mod_spans.len() > 1 {
 710                             self.resolve_error(mod_spans[0],
 711                                 "`self` import can only appear once in the list");
 712                             for other_span in mod_spans.iter().skip(1) {
 713                                 self.session.span_note(*other_span,
 714                                     "another `self` import appears here");
 715                             }
 716                         }
 717
 718                         for source_item in source_items.iter() {
 719                             let (module_path, name) = match source_item.node {
 720                                 PathListIdent { name, .. } =>
 721                                     (module_path.clone(), name.name),
 722                                 PathListMod { .. } => {
 723                                     let name = match module_path.last() {
 724                                         Some(name) => *name,
 725                                         None => {
 726                                             self.resolve_error(source_item.span,
 727                                                 "`self` import can only appear in an import list \
 728                                                  with a non-empty prefix");
 729                                             continue;
 730                                         }
 731                                     };
 732                                     let module_path = module_path.init();
 733                                     (module_path.to_vec(), name)
 734                                 }
 735                             };
 736                             self.build_import_directive(
 737                                 &**parent,
 738                                 module_path,
 739                                 SingleImport(name, name),
 740                                 source_item.span,
 741                                 source_item.node.id(),
 742                                 is_public,
 743                                 shadowable);
 744                         }
 745                     }
 746                     ViewPathGlob(_, id) => {
 747                         self.build_import_directive(&**parent,
 748                                                     module_path,
 749                                                     GlobImport,
 750                                                     view_path.span,
 751                                                     id,
 752                                                     is_public,
 753                                                     shadowable);
 754                     }
 755                 }
 756             }
 757
 758             ViewItemExternCrate(name, _, node_id) => {
 759                 // n.b. we don't need to look at the path option here, because cstore already did
 760                 for &crate_id in self.session.cstore
 761                                      .find_extern_mod_stmt_cnum(node_id).iter() {
 762                     let def_id = DefId { krate: crate_id, node: 0 };
 763                     self.external_exports.insert(def_id);
 764                     let parent_link = ModuleParentLink(parent.downgrade(), name.name);
 765                     let external_module = Rc::new(Module::new(parent_link,
 766                                                               Some(def_id),
 767                                                               NormalModuleKind,
 768                                                               false,
 769                                                               true));
 770                     debug!("(build reduced graph for item) found extern `{}`",
 771                             self.module_to_string(&*external_module));
 772                     self.check_for_conflicts_between_external_crates(
 773                         &**parent,
 774                         name.name,
 775                         view_item.span);
 776                     parent.external_module_children.borrow_mut()
 777                           .insert(name.name, external_module.clone());
 778                     self.build_reduced_graph_for_external_crate(&external_module);
 779                 }
 780             }
 781         }
 782     }
 783
 784     /// Constructs the reduced graph for one foreign item.
 785     fn build_reduced_graph_for_foreign_item<F>(&mut self,
 786                                                foreign_item: &ForeignItem,
 787                                                parent: &Rc<Module>,
 788                                                f: F) where
 789         F: FnOnce(&mut Resolver),
 790     {
 791         let name = foreign_item.ident.name;
 792         let is_public = foreign_item.vis == ast::Public;
 793         let modifiers = if is_public { PUBLIC } else { DefModifiers::empty() } | IMPORTABLE;
 794         let name_bindings =
 795             self.add_child(name, parent, ForbidDuplicateValues,
 796                            foreign_item.span);
 797
 798         match foreign_item.node {
 799             ForeignItemFn(_, ref generics) => {
 800                 let def = DefFn(local_def(foreign_item.id), false);
 801                 name_bindings.define_value(def, foreign_item.span, modifiers);
 802
 803                 self.with_type_parameter_rib(
 804                     HasTypeParameters(generics,
 805                                       FnSpace,
 806                                       foreign_item.id,
 807                                       NormalRibKind),
 808                     f);
 809             }
 810             ForeignItemStatic(_, m) => {
 811                 let def = DefStatic(local_def(foreign_item.id), m);
 812                 name_bindings.define_value(def, foreign_item.span, modifiers);
 813
 814                 f(self.resolver)
 815             }
 816         }
 817     }
 818
 819     fn build_reduced_graph_for_block(&mut self, block: &Block, parent: &Rc<Module>) -> Rc<Module> {
 820         if self.block_needs_anonymous_module(block) {
 821             let block_id = block.id;
 822
 823             debug!("(building reduced graph for block) creating a new \
 824                     anonymous module for block {}",
 825                    block_id);
 826
 827             let new_module = Rc::new(Module::new(
 828                 BlockParentLink(parent.downgrade(), block_id),
 829                 None,
 830                 AnonymousModuleKind,
 831                 false,
 832                 false));
 833             parent.anonymous_children.borrow_mut().insert(block_id, new_module.clone());
 834             new_module
 835         } else {
 836             parent.clone()
 837         }
 838     }
 839
 840     fn handle_external_def(&mut self,
 841                            def: Def,
 842                            vis: Visibility,
 843                            child_name_bindings: &NameBindings,
 844                            final_ident: &str,
 845                            name: Name,
 846                            new_parent: &Rc<Module>) {
 847         debug!("(building reduced graph for \
 848                 external crate) building external def, priv {}",
 849                vis);
 850         let is_public = vis == ast::Public;
 851         let modifiers = if is_public { PUBLIC } else { DefModifiers::empty() } | IMPORTABLE;
 852         let is_exported = is_public && match new_parent.def_id.get() {
 853             None => true,
 854             Some(did) => self.external_exports.contains(&did)
 855         };
 856         if is_exported {
 857             self.external_exports.insert(def.def_id());
 858         }
 859
 860         let kind = match def {
 861             DefTy(_, true) => EnumModuleKind,
 862             DefStruct(..) | DefTy(..) => ImplModuleKind,
 863             _ => NormalModuleKind
 864         };
 865
 866         match def {
 867           DefMod(def_id) | DefForeignMod(def_id) | DefStruct(def_id) |
 868           DefTy(def_id, _) => {
 869             let type_def = child_name_bindings.type_def.borrow().clone();
 870             match type_def {
 871               Some(TypeNsDef { module_def: Some(module_def), .. }) => {
 872                 debug!("(building reduced graph for external crate) \
 873                         already created module");
 874                 module_def.def_id.set(Some(def_id));
 875               }
 876               Some(_) | None => {
 877                 debug!("(building reduced graph for \
 878                         external crate) building module \
 879                         {}", final_ident);
 880                 let parent_link = self.get_parent_link(new_parent, name);
 881
 882                 child_name_bindings.define_module(parent_link,
 883                                                   Some(def_id),
 884                                                   kind,
 885                                                   true,
 886                                                   is_public,
 887                                                   DUMMY_SP);
 888               }
 889             }
 890           }
 891           _ => {}
 892         }
 893
 894         match def {
 895           DefMod(_) | DefForeignMod(_) => {}
 896           DefVariant(_, variant_id, is_struct) => {
 897               debug!("(building reduced graph for external crate) building \
 898                       variant {}",
 899                       final_ident);
 900               // variants are always treated as importable to allow them to be
 901               // glob used
 902               let modifiers = PUBLIC | IMPORTABLE;
 903               if is_struct {
 904                   child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 905                   // Not adding fields for variants as they are not accessed with a self receiver
 906                   self.structs.insert(variant_id, Vec::new());
 907               } else {
 908                   child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 909               }
 910           }
 911           DefFn(ctor_id, true) => {
 912             child_name_bindings.define_value(
 913                 csearch::get_tuple_struct_definition_if_ctor(&self.session.cstore, ctor_id)
 914                     .map_or(def, |_| DefStruct(ctor_id)), DUMMY_SP, modifiers);
 915           }
 916           DefFn(..) | DefStaticMethod(..) | DefStatic(..) | DefConst(..) | DefMethod(..) => {
 917             debug!("(building reduced graph for external \
 918                     crate) building value (fn/static) {}", final_ident);
 919             // impl methods have already been defined with the correct importability modifier
 920             let mut modifiers = match *child_name_bindings.value_def.borrow() {
 921                 Some(ref def) => (modifiers & !IMPORTABLE) | (def.modifiers & IMPORTABLE),
 922                 None => modifiers
 923             };
 924             if new_parent.kind.get() != NormalModuleKind {
 925                 modifiers = modifiers & !IMPORTABLE;
 926             }
 927             child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 928           }
 929           DefTrait(def_id) => {
 930               debug!("(building reduced graph for external \
 931                       crate) building type {}", final_ident);
 932
 933               // If this is a trait, add all the trait item names to the trait
 934               // info.
 935
 936               let trait_item_def_ids =
 937                 csearch::get_trait_item_def_ids(&self.session.cstore, def_id);
 938               for trait_item_def_id in trait_item_def_ids.iter() {
 939                   let (trait_item_name, trait_item_kind) =
 940                       csearch::get_trait_item_name_and_kind(
 941                           &self.session.cstore,
 942                           trait_item_def_id.def_id());
 943
 944                   debug!("(building reduced graph for external crate) ... \
 945                           adding trait item '{}'",
 946                          token::get_name(trait_item_name));
 947
 948                   self.trait_item_map.insert((trait_item_name, def_id), trait_item_kind);
 949
 950                   if is_exported {
 951                       self.external_exports
 952                           .insert(trait_item_def_id.def_id());
 953                   }
 954               }
 955
 956               child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 957
 958               // Define a module if necessary.
 959               let parent_link = self.get_parent_link(new_parent, name);
 960               child_name_bindings.set_module_kind(parent_link,
 961                                                   Some(def_id),
 962                                                   TraitModuleKind,
 963                                                   true,
 964                                                   is_public,
 965                                                   DUMMY_SP)
 966           }
 967           DefTy(..) | DefAssociatedTy(..) | DefAssociatedPath(..) => {
 968               debug!("(building reduced graph for external \
 969                       crate) building type {}", final_ident);
 970
 971               child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 972           }
 973           DefStruct(def_id) => {
 974             debug!("(building reduced graph for external \
 975                     crate) building type and value for {}",
 976                    final_ident);
 977             child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 978             let fields = csearch::get_struct_fields(&self.session.cstore, def_id).iter().map(|f| {
 979                 f.name
 980             }).collect::<Vec<_>>();
 981
 982             if fields.len() == 0 {
 983                 child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 984             }
 985
 986             // Record the def ID and fields of this struct.
 987             self.structs.insert(def_id, fields);
 988           }
 989           DefLocal(..) | DefPrimTy(..) | DefTyParam(..) |
 990           DefUse(..) | DefUpvar(..) | DefRegion(..) |
 991           DefTyParamBinder(..) | DefLabel(..) | DefSelfTy(..) => {
 992             panic!("didn't expect `{}`", def);
 993           }
 994         }
 995     }
 996
 997     /// Builds the reduced graph for a single item in an external crate.
 998     fn build_reduced_graph_for_external_crate_def(&mut self,
 999                                                   root: &Rc<Module>,
1000                                                   def_like: DefLike,
1001                                                   name: Name,
1002                                                   visibility: Visibility) {
1003         match def_like {
1004             DlDef(def) => {
1005                 // Add the new child item, if necessary.
1006                 match def {
1007                     DefForeignMod(def_id) => {
1008                         // Foreign modules have no names. Recur and populate
1009                         // eagerly.
1010                         csearch::each_child_of_item(&self.session.cstore,
1011                                                     def_id,
1012                                                     |def_like,
1013                                                      child_name,
1014                                                      vis| {
1015                             self.build_reduced_graph_for_external_crate_def(
1016                                 root,
1017                                 def_like,
1018                                 child_name,
1019                                 vis)
1020                         });
1021                     }
1022                     _ => {
1023                         let child_name_bindings =
1024                             self.add_child(name,
1025                                            root,
1026                                            OverwriteDuplicates,
1027                                            DUMMY_SP);
1028
1029                         self.handle_external_def(def,
1030                                                  visibility,
1031                                                  &*child_name_bindings,
1032                                                  token::get_name(name).get(),
1033                                                  name,
1034                                                  root);
1035                     }
1036                 }
1037             }
1038             DlImpl(def) => {
1039                 match csearch::get_type_name_if_impl(&self.session.cstore, def) {
1040                     None => {}
1041                     Some(final_name) => {
1042                         let methods_opt =
1043                             csearch::get_methods_if_impl(&self.session.cstore, def);
1044                         match methods_opt {
1045                             Some(ref methods) if
1046                                 methods.len() >= 1 => {
1047                                 debug!("(building reduced graph for \
1048                                         external crate) processing \
1049                                         static methods for type name {}",
1050                                         token::get_name(final_name));
1051
1052                                 let child_name_bindings =
1053                                     self.add_child(
1054                                         final_name,
1055                                         root,
1056                                         OverwriteDuplicates,
1057                                         DUMMY_SP);
1058
1059                                 // Process the static methods. First,
1060                                 // create the module.
1061                                 let type_module;
1062                                 let type_def = child_name_bindings.type_def.borrow().clone();
1063                                 match type_def {
1064                                     Some(TypeNsDef {
1065                                         module_def: Some(module_def),
1066                                         ..
1067                                     }) => {
1068                                         // We already have a module. This
1069                                         // is OK.
1070                                         type_module = module_def;
1071
1072                                         // Mark it as an impl module if
1073                                         // necessary.
1074                                         type_module.kind.set(ImplModuleKind);
1075                                     }
1076                                     Some(_) | None => {
1077                                         let parent_link =
1078                                             self.get_parent_link(root, final_name);
1079                                         child_name_bindings.define_module(
1080                                             parent_link,
1081                                             Some(def),
1082                                             ImplModuleKind,
1083                                             true,
1084                                             true,
1085                                             DUMMY_SP);
1086                                         type_module =
1087                                             child_name_bindings.
1088                                                 get_module();
1089                                     }
1090                                 }
1091
1092                                 // Add each static method to the module.
1093                                 let new_parent = type_module;
1094                                 for method_info in methods.iter() {
1095                                     let name = method_info.name;
1096                                     debug!("(building reduced graph for \
1097                                              external crate) creating \
1098                                              static method '{}'",
1099                                            token::get_name(name));
1100
1101                                     let method_name_bindings =
1102                                         self.add_child(name,
1103                                                        &new_parent,
1104                                                        OverwriteDuplicates,
1105                                                        DUMMY_SP);
1106                                     let def = DefFn(method_info.def_id, false);
1107
1108                                     // NB: not IMPORTABLE
1109                                     let modifiers = if visibility == ast::Public {
1110                                         PUBLIC
1111                                     } else {
1112                                         DefModifiers::empty()
1113                                     };
1114                                     method_name_bindings.define_value(
1115                                         def, DUMMY_SP, modifiers);
1116                                 }
1117                             }
1118
1119                             // Otherwise, do nothing.
1120                             Some(_) | None => {}
1121                         }
1122                     }
1123                 }
1124             }
1125             DlField => {
1126                 debug!("(building reduced graph for external crate) \
1127                         ignoring field");
1128             }
1129         }
1130     }
1131
1132     /// Builds the reduced graph rooted at the given external module.
1133     fn populate_external_module(&mut self, module: &Rc<Module>) {
1134         debug!("(populating external module) attempting to populate {}",
1135                self.module_to_string(&**module));
1136
1137         let def_id = match module.def_id.get() {
1138             None => {
1139                 debug!("(populating external module) ... no def ID!");
1140                 return
1141             }
1142             Some(def_id) => def_id,
1143         };
1144
1145         csearch::each_child_of_item(&self.session.cstore,
1146                                     def_id,
1147                                     |def_like, child_name, visibility| {
1148             debug!("(populating external module) ... found ident: {}",
1149                    token::get_name(child_name));
1150             self.build_reduced_graph_for_external_crate_def(module,
1151                                                             def_like,
1152                                                             child_name,
1153                                                             visibility)
1154         });
1155         module.populated.set(true)
1156     }
1157
1158     /// Ensures that the reduced graph rooted at the given external module
1159     /// is built, building it if it is not.
1160     fn populate_module_if_necessary(&mut self, module: &Rc<Module>) {
1161         if !module.populated.get() {
1162             self.populate_external_module(module)
1163         }
1164         assert!(module.populated.get())
1165     }
1166
1167     /// Builds the reduced graph rooted at the 'use' directive for an external
1168     /// crate.
1169     fn build_reduced_graph_for_external_crate(&mut self, root: &Rc<Module>) {
1170         csearch::each_top_level_item_of_crate(&self.session.cstore,
1171                                               root.def_id
1172                                                   .get()
1173                                                   .unwrap()
1174                                                   .krate,
1175                                               |def_like, name, visibility| {
1176             self.build_reduced_graph_for_external_crate_def(root, def_like, name, visibility)
1177         });
1178     }
1179
1180     /// Creates and adds an import directive to the given module.
1181     fn build_import_directive(&mut self,
1182                               module_: &Module,
1183                               module_path: Vec<Name>,
1184                               subclass: ImportDirectiveSubclass,
1185                               span: Span,
1186                               id: NodeId,
1187                               is_public: bool,
1188                               shadowable: Shadowable) {
1189         module_.imports.borrow_mut().push(ImportDirective::new(module_path,
1190                                                                subclass,
1191                                                                span,
1192                                                                id,
1193                                                                is_public,
1194                                                                shadowable));
1195         self.unresolved_imports += 1;
1196         // Bump the reference count on the name. Or, if this is a glob, set
1197         // the appropriate flag.
1198
1199         match subclass {
1200             SingleImport(target, _) => {
1201                 debug!("(building import directive) building import \
1202                         directive: {}::{}",
1203                        self.names_to_string(module_.imports.borrow().last().unwrap()
1204                                                  .module_path[]),
1205                        token::get_name(target));
1206
1207                 let mut import_resolutions = module_.import_resolutions
1208                                                     .borrow_mut();
1209                 match import_resolutions.get_mut(&target) {
1210                     Some(resolution) => {
1211                         debug!("(building import directive) bumping \
1212                                 reference");
1213                         resolution.outstanding_references += 1;
1214
1215                         // the source of this name is different now
1216                         resolution.type_id = id;
1217                         resolution.value_id = id;
1218                         resolution.is_public = is_public;
1219                         return;
1220                     }
1221                     None => {}
1222                 }
1223                 debug!("(building import directive) creating new");
1224                 let mut resolution = ImportResolution::new(id, is_public);
1225                 resolution.outstanding_references = 1;
1226                 import_resolutions.insert(target, resolution);
1227             }
1228             GlobImport => {
1229                 // Set the glob flag. This tells us that we don't know the
1230                 // module's exports ahead of time.
1231
1232                 module_.glob_count.set(module_.glob_count.get() + 1);
1233             }
1234         }
1235     }
1236 }
1237
1238 struct BuildReducedGraphVisitor<'a, 'b:'a, 'tcx:'b> {
1239     builder: GraphBuilder<'a, 'b, 'tcx>,
1240     parent: Rc<Module>
1241 }
1242
1243 impl<'a, 'b, 'v, 'tcx> Visitor<'v> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
1244     fn visit_item(&mut self, item: &Item) {
1245         let p = self.builder.build_reduced_graph_for_item(item, &self.parent);
1246         let old_parent = replace(&mut self.parent, p);
1247         visit::walk_item(self, item);
1248         self.parent = old_parent;
1249     }
1250
1251     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
1252         let parent = &self.parent;
1253         self.builder.build_reduced_graph_for_foreign_item(foreign_item,
1254                                                           parent,
1255                                                           |r| {
1256             let mut v = BuildReducedGraphVisitor {
1257                 builder: GraphBuilder { resolver: r },
1258                 parent: parent.clone()
1259             };
1260             visit::walk_foreign_item(&mut v, foreign_item);
1261         })
1262     }
1263
1264     fn visit_view_item(&mut self, view_item: &ViewItem) {
1265         self.builder.build_reduced_graph_for_view_item(view_item, &self.parent);
1266     }
1267
1268     fn visit_block(&mut self, block: &Block) {
1269         let np = self.builder.build_reduced_graph_for_block(block, &self.parent);
1270         let old_parent = replace(&mut self.parent, np);
1271         visit::walk_block(self, block);
1272         self.parent = old_parent;
1273     }
1274 }
1275
1276 pub fn build_reduced_graph(resolver: &mut Resolver, krate: &ast::Crate) {
1277     GraphBuilder {
1278         resolver: resolver
1279     }.build_reduced_graph(krate);
1280 }
1281
1282 pub fn populate_module_if_necessary(resolver: &mut Resolver, module: &Rc<Module>) {
1283     GraphBuilder {
1284         resolver: resolver
1285     }.populate_module_if_necessary(module);
1286 }