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,
 325                                    sp);
 326
 327                 name_bindings.define_type(DefTy(local_def(item.id), false), sp,
 328                                           modifiers);
 329
 330                 let parent_link = self.get_parent_link(parent, name);
 331                 name_bindings.set_module_kind(parent_link,
 332                                               Some(local_def(item.id)),
 333                                               TypeModuleKind,
 334                                               false,
 335                                               is_public,
 336                                               sp);
 337                 parent.clone()
 338             }
 339
 340             ItemEnum(ref enum_definition, _) => {
 341                 let name_bindings =
 342                     self.add_child(name, parent, ForbidDuplicateTypesAndModules, sp);
 343
 344                 name_bindings.define_type(DefTy(local_def(item.id), true), sp, modifiers);
 345
 346                 let parent_link = self.get_parent_link(parent, name);
 347                 // We want to make sure the module type is EnumModuleKind
 348                 // even if there's already an ImplModuleKind module defined,
 349                 // since that's how we prevent duplicate enum definitions
 350                 name_bindings.set_module_kind(parent_link,
 351                                               Some(local_def(item.id)),
 352                                               EnumModuleKind,
 353                                               false,
 354                                               is_public,
 355                                               sp);
 356
 357                 let module = name_bindings.get_module();
 358
 359                 for variant in (*enum_definition).variants.iter() {
 360                     self.build_reduced_graph_for_variant(
 361                         &**variant,
 362                         local_def(item.id),
 363                         &module);
 364                 }
 365                 parent.clone()
 366             }
 367
 368             // These items live in both the type and value namespaces.
 369             ItemStruct(ref struct_def, _) => {
 370                 // Adding to both Type and Value namespaces or just Type?
 371                 let (forbid, ctor_id) = match struct_def.ctor_id {
 372                     Some(ctor_id)   => (ForbidDuplicateTypesAndValues, Some(ctor_id)),
 373                     None            => (ForbidDuplicateTypesAndModules, None)
 374                 };
 375
 376                 let name_bindings = self.add_child(name, parent, forbid, sp);
 377
 378                 // Define a name in the type namespace.
 379                 name_bindings.define_type(DefTy(local_def(item.id), false), sp, modifiers);
 380
 381                 // If this is a newtype or unit-like struct, define a name
 382                 // in the value namespace as well
 383                 if let Some(cid) = ctor_id {
 384                     name_bindings.define_value(DefStruct(local_def(cid)), sp, modifiers);
 385                 }
 386
 387                 // Record the def ID and fields of this struct.
 388                 let named_fields = struct_def.fields.iter().filter_map(|f| {
 389                     match f.node.kind {
 390                         NamedField(ident, _) => Some(ident.name),
 391                         UnnamedField(_) => None
 392                     }
 393                 }).collect();
 394                 self.structs.insert(local_def(item.id), named_fields);
 395
 396                 parent.clone()
 397             }
 398
 399             ItemImpl(_, _, _, None, ref ty, ref impl_items) => {
 400                 // If this implements an anonymous trait, then add all the
 401                 // methods within to a new module, if the type was defined
 402                 // within this module.
 403
 404                 let mod_name = match ty.node {
 405                     TyPath(ref path, _) if path.segments.len() == 1 => {
 406                         // FIXME(18446) we should distinguish between the name of
 407                         // a trait and the name of an impl of that trait.
 408                         Some(path.segments.last().unwrap().identifier.name)
 409                     }
 410                     TyObjectSum(ref lhs_ty, _) => {
 411                         match lhs_ty.node {
 412                             TyPath(ref path, _) if path.segments.len() == 1 => {
 413                                 Some(path.segments.last().unwrap().identifier.name)
 414                             }
 415                             _ => {
 416                                 None
 417                             }
 418                         }
 419                     }
 420                     _ => {
 421                         None
 422                     }
 423                 };
 424
 425                 let mod_name = match mod_name {
 426                     Some(mod_name) => mod_name,
 427                     None => {
 428                         self.resolve_error(ty.span,
 429                                            "inherent implementations may \
 430                                             only be implemented in the same \
 431                                             module as the type they are \
 432                                             implemented for");
 433                         return parent.clone();
 434                     }
 435                 };
 436                 // Create the module and add all methods.
 437                 let child_opt = parent.children.borrow().get(&mod_name)
 438                                        .and_then(|m| m.get_module_if_available());
 439                 let new_parent = match child_opt {
 440                     // It already exists
 441                     Some(ref child) if (child.kind.get() == ImplModuleKind ||
 442                                         child.kind.get() == TraitModuleKind) => {
 443                         child.clone()
 444                     }
 445                     Some(ref child) if child.kind.get() == EnumModuleKind ||
 446                                        child.kind.get() == TypeModuleKind => {
 447                         child.clone()
 448                     }
 449                     // Create the module
 450                     _ => {
 451                         let name_bindings =
 452                             self.add_child(mod_name, parent, ForbidDuplicateModules, sp);
 453
 454                         let parent_link = self.get_parent_link(parent, name);
 455                         let def_id = local_def(item.id);
 456                         let ns = TypeNS;
 457                         let is_public =
 458                             !name_bindings.defined_in_namespace(ns) ||
 459                             name_bindings.defined_in_public_namespace(ns);
 460
 461                         name_bindings.define_module(parent_link,
 462                                                     Some(def_id),
 463                                                     ImplModuleKind,
 464                                                     false,
 465                                                     is_public,
 466                                                     sp);
 467
 468                         name_bindings.get_module()
 469                     }
 470                 };
 471
 472                 // For each implementation item...
 473                 for impl_item in impl_items.iter() {
 474                     match *impl_item {
 475                         MethodImplItem(ref method) => {
 476                             // Add the method to the module.
 477                             let name = method.pe_ident().name;
 478                             let method_name_bindings =
 479                                 self.add_child(name,
 480                                                &new_parent,
 481                                                ForbidDuplicateValues,
 482                                                method.span);
 483                             let def = match method.pe_explicit_self()
 484                                 .node {
 485                                     SelfStatic => {
 486                                         // Static methods become
 487                                         // `DefStaticMethod`s.
 488                                         DefStaticMethod(local_def(method.id),
 489                                                         FromImpl(local_def(item.id)))
 490                                     }
 491                                     _ => {
 492                                         // Non-static methods become
 493                                         // `DefMethod`s.
 494                                         DefMethod(local_def(method.id),
 495                                                   None,
 496                                                   FromImpl(local_def(item.id)))
 497                                     }
 498                                 };
 499
 500                             // NB: not IMPORTABLE
 501                             let modifiers = if method.pe_vis() == ast::Public {
 502                                 PUBLIC
 503                             } else {
 504                                 DefModifiers::empty()
 505                             };
 506                             method_name_bindings.define_value(
 507                                 def,
 508                                 method.span,
 509                                 modifiers);
 510                         }
 511                         TypeImplItem(ref typedef) => {
 512                             // Add the typedef to the module.
 513                             let name = typedef.ident.name;
 514                             let typedef_name_bindings =
 515                                 self.add_child(
 516                                     name,
 517                                     &new_parent,
 518                                     ForbidDuplicateTypesAndModules,
 519                                     typedef.span);
 520                             let def = DefAssociatedTy(local_def(
 521                                 typedef.id));
 522                             // NB: not IMPORTABLE
 523                             let modifiers = if typedef.vis == ast::Public {
 524                                 PUBLIC
 525                             } else {
 526                                 DefModifiers::empty()
 527                             };
 528                             typedef_name_bindings.define_type(
 529                                 def,
 530                                 typedef.span,
 531                                 modifiers);
 532                         }
 533                     }
 534                 }
 535                 parent.clone()
 536             }
 537
 538             ItemImpl(_, _, _, Some(_), _, _) => parent.clone(),
 539
 540             ItemTrait(_, _, _, ref items) => {
 541                 let name_bindings =
 542                     self.add_child(name, parent, ForbidDuplicateTypesAndModules, sp);
 543
 544                 // Add all the items within to a new module.
 545                 let parent_link = self.get_parent_link(parent, name);
 546                 name_bindings.define_module(parent_link,
 547                                             Some(local_def(item.id)),
 548                                             TraitModuleKind,
 549                                             false,
 550                                             item.vis == ast::Public,
 551                                             sp);
 552                 let module_parent = name_bindings.get_module();
 553
 554                 let def_id = local_def(item.id);
 555
 556                 // Add the names of all the items to the trait info.
 557                 for trait_item in items.iter() {
 558                     let (name, kind) = match *trait_item {
 559                         ast::RequiredMethod(_) |
 560                         ast::ProvidedMethod(_) => {
 561                             let ty_m = ast_util::trait_item_to_ty_method(trait_item);
 562
 563                             let name = ty_m.ident.name;
 564
 565                             // Add it as a name in the trait module.
 566                             let (def, static_flag) = match ty_m.explicit_self
 567                                                                .node {
 568                                 SelfStatic => {
 569                                     // Static methods become `DefStaticMethod`s.
 570                                     (DefStaticMethod(
 571                                             local_def(ty_m.id),
 572                                             FromTrait(local_def(item.id))),
 573                                      StaticMethodTraitItemKind)
 574                                 }
 575                                 _ => {
 576                                     // Non-static methods become `DefMethod`s.
 577                                     (DefMethod(local_def(ty_m.id),
 578                                                Some(local_def(item.id)),
 579                                                FromTrait(local_def(item.id))),
 580                                      NonstaticMethodTraitItemKind)
 581                                 }
 582                             };
 583
 584                             let method_name_bindings =
 585                                 self.add_child(name,
 586                                                &module_parent,
 587                                                ForbidDuplicateTypesAndValues,
 588                                                ty_m.span);
 589                             // NB: not IMPORTABLE
 590                             method_name_bindings.define_value(def,
 591                                                               ty_m.span,
 592                                                               PUBLIC);
 593
 594                             (name, static_flag)
 595                         }
 596                         ast::TypeTraitItem(ref associated_type) => {
 597                             let def = DefAssociatedTy(local_def(
 598                                     associated_type.ty_param.id));
 599
 600                             let name_bindings =
 601                                 self.add_child(associated_type.ty_param.ident.name,
 602                                                &module_parent,
 603                                                ForbidDuplicateTypesAndValues,
 604                                                associated_type.ty_param.span);
 605                             // NB: not IMPORTABLE
 606                             name_bindings.define_type(def,
 607                                                       associated_type.ty_param.span,
 608                                                       PUBLIC);
 609
 610                             (associated_type.ty_param.ident.name, TypeTraitItemKind)
 611                         }
 612                     };
 613
 614                     self.trait_item_map.insert((name, def_id), kind);
 615                 }
 616
 617                 name_bindings.define_type(DefTrait(def_id), sp, modifiers);
 618                 parent.clone()
 619             }
 620             ItemMac(..) => parent.clone()
 621         }
 622     }
 623
 624     // Constructs the reduced graph for one variant. Variants exist in the
 625     // type and value namespaces.
 626     fn build_reduced_graph_for_variant(&mut self,
 627                                        variant: &Variant,
 628                                        item_id: DefId,
 629                                        parent: &Rc<Module>) {
 630         let name = variant.node.name.name;
 631         let is_exported = match variant.node.kind {
 632             TupleVariantKind(_) => false,
 633             StructVariantKind(_) => {
 634                 // Not adding fields for variants as they are not accessed with a self receiver
 635                 self.structs.insert(local_def(variant.node.id), Vec::new());
 636                 true
 637             }
 638         };
 639
 640         let child = self.add_child(name, parent,
 641                                    ForbidDuplicateTypesAndValues,
 642                                    variant.span);
 643         // variants are always treated as importable to allow them to be glob
 644         // used
 645         child.define_value(DefVariant(item_id,
 646                                       local_def(variant.node.id), is_exported),
 647                            variant.span, PUBLIC | IMPORTABLE);
 648         child.define_type(DefVariant(item_id,
 649                                      local_def(variant.node.id), is_exported),
 650                           variant.span, PUBLIC | IMPORTABLE);
 651     }
 652
 653     /// Constructs the reduced graph for one 'view item'. View items consist
 654     /// of imports and use directives.
 655     fn build_reduced_graph_for_view_item(&mut self, view_item: &ViewItem, parent: &Rc<Module>) {
 656         match view_item.node {
 657             ViewItemUse(ref view_path) => {
 658                 // Extract and intern the module part of the path. For
 659                 // globs and lists, the path is found directly in the AST;
 660                 // for simple paths we have to munge the path a little.
 661                 let module_path = match view_path.node {
 662                     ViewPathSimple(_, ref full_path, _) => {
 663                         full_path.segments
 664                             .init()
 665                             .iter().map(|ident| ident.identifier.name)
 666                             .collect()
 667                     }
 668
 669                     ViewPathGlob(ref module_ident_path, _) |
 670                     ViewPathList(ref module_ident_path, _, _) => {
 671                         module_ident_path.segments
 672                             .iter().map(|ident| ident.identifier.name).collect()
 673                     }
 674                 };
 675
 676                 // Build up the import directives.
 677                 let is_public = view_item.vis == ast::Public;
 678                 let shadowable =
 679                     view_item.attrs
 680                              .iter()
 681                              .any(|attr| {
 682                                  attr.name() == token::get_name(
 683                                     special_idents::prelude_import.name)
 684                              });
 685                 let shadowable = if shadowable {
 686                     Shadowable::Always
 687                 } else {
 688                     Shadowable::Never
 689                 };
 690
 691                 match view_path.node {
 692                     ViewPathSimple(binding, ref full_path, id) => {
 693                         let source_name =
 694                             full_path.segments.last().unwrap().identifier.name;
 695                         if token::get_name(source_name).get() == "mod" ||
 696                            token::get_name(source_name).get() == "self" {
 697                             self.resolve_error(view_path.span,
 698                                 "`self` imports are only allowed within a { } list");
 699                         }
 700
 701                         let subclass = SingleImport(binding.name,
 702                                                     source_name);
 703                         self.build_import_directive(&**parent,
 704                                                     module_path,
 705                                                     subclass,
 706                                                     view_path.span,
 707                                                     id,
 708                                                     is_public,
 709                                                     shadowable);
 710                     }
 711                     ViewPathList(_, ref source_items, _) => {
 712                         // Make sure there's at most one `mod` import in the list.
 713                         let mod_spans = source_items.iter().filter_map(|item| match item.node {
 714                             PathListMod { .. } => Some(item.span),
 715                             _ => None
 716                         }).collect::<Vec<Span>>();
 717                         if mod_spans.len() > 1 {
 718                             self.resolve_error(mod_spans[0],
 719                                 "`self` import can only appear once in the list");
 720                             for other_span in mod_spans.iter().skip(1) {
 721                                 self.session.span_note(*other_span,
 722                                     "another `self` import appears here");
 723                             }
 724                         }
 725
 726                         for source_item in source_items.iter() {
 727                             let (module_path, name) = match source_item.node {
 728                                 PathListIdent { name, .. } =>
 729                                     (module_path.clone(), name.name),
 730                                 PathListMod { .. } => {
 731                                     let name = match module_path.last() {
 732                                         Some(name) => *name,
 733                                         None => {
 734                                             self.resolve_error(source_item.span,
 735                                                 "`self` import can only appear in an import list \
 736                                                  with a non-empty prefix");
 737                                             continue;
 738                                         }
 739                                     };
 740                                     let module_path = module_path.init();
 741                                     (module_path.to_vec(), name)
 742                                 }
 743                             };
 744                             self.build_import_directive(
 745                                 &**parent,
 746                                 module_path,
 747                                 SingleImport(name, name),
 748                                 source_item.span,
 749                                 source_item.node.id(),
 750                                 is_public,
 751                                 shadowable);
 752                         }
 753                     }
 754                     ViewPathGlob(_, id) => {
 755                         self.build_import_directive(&**parent,
 756                                                     module_path,
 757                                                     GlobImport,
 758                                                     view_path.span,
 759                                                     id,
 760                                                     is_public,
 761                                                     shadowable);
 762                     }
 763                 }
 764             }
 765
 766             ViewItemExternCrate(name, _, node_id) => {
 767                 // n.b. we don't need to look at the path option here, because cstore already did
 768                 for &crate_id in self.session.cstore
 769                                      .find_extern_mod_stmt_cnum(node_id).iter() {
 770                     let def_id = DefId { krate: crate_id, node: 0 };
 771                     self.external_exports.insert(def_id);
 772                     let parent_link = ModuleParentLink(parent.downgrade(), name.name);
 773                     let external_module = Rc::new(Module::new(parent_link,
 774                                                               Some(def_id),
 775                                                               NormalModuleKind,
 776                                                               false,
 777                                                               true));
 778                     debug!("(build reduced graph for item) found extern `{}`",
 779                             self.module_to_string(&*external_module));
 780                     self.check_for_conflicts_between_external_crates(
 781                         &**parent,
 782                         name.name,
 783                         view_item.span);
 784                     parent.external_module_children.borrow_mut()
 785                           .insert(name.name, external_module.clone());
 786                     self.build_reduced_graph_for_external_crate(&external_module);
 787                 }
 788             }
 789         }
 790     }
 791
 792     /// Constructs the reduced graph for one foreign item.
 793     fn build_reduced_graph_for_foreign_item<F>(&mut self,
 794                                                foreign_item: &ForeignItem,
 795                                                parent: &Rc<Module>,
 796                                                f: F) where
 797         F: FnOnce(&mut Resolver),
 798     {
 799         let name = foreign_item.ident.name;
 800         let is_public = foreign_item.vis == ast::Public;
 801         let modifiers = if is_public { PUBLIC } else { DefModifiers::empty() } | IMPORTABLE;
 802         let name_bindings =
 803             self.add_child(name, parent, ForbidDuplicateValues,
 804                            foreign_item.span);
 805
 806         match foreign_item.node {
 807             ForeignItemFn(_, ref generics) => {
 808                 let def = DefFn(local_def(foreign_item.id), false);
 809                 name_bindings.define_value(def, foreign_item.span, modifiers);
 810
 811                 self.with_type_parameter_rib(
 812                     HasTypeParameters(generics,
 813                                       FnSpace,
 814                                       foreign_item.id,
 815                                       NormalRibKind),
 816                     f);
 817             }
 818             ForeignItemStatic(_, m) => {
 819                 let def = DefStatic(local_def(foreign_item.id), m);
 820                 name_bindings.define_value(def, foreign_item.span, modifiers);
 821
 822                 f(self.resolver)
 823             }
 824         }
 825     }
 826
 827     fn build_reduced_graph_for_block(&mut self, block: &Block, parent: &Rc<Module>) -> Rc<Module> {
 828         if self.block_needs_anonymous_module(block) {
 829             let block_id = block.id;
 830
 831             debug!("(building reduced graph for block) creating a new \
 832                     anonymous module for block {}",
 833                    block_id);
 834
 835             let new_module = Rc::new(Module::new(
 836                 BlockParentLink(parent.downgrade(), block_id),
 837                 None,
 838                 AnonymousModuleKind,
 839                 false,
 840                 false));
 841             parent.anonymous_children.borrow_mut().insert(block_id, new_module.clone());
 842             new_module
 843         } else {
 844             parent.clone()
 845         }
 846     }
 847
 848     fn handle_external_def(&mut self,
 849                            def: Def,
 850                            vis: Visibility,
 851                            child_name_bindings: &NameBindings,
 852                            final_ident: &str,
 853                            name: Name,
 854                            new_parent: &Rc<Module>) {
 855         debug!("(building reduced graph for \
 856                 external crate) building external def, priv {:?}",
 857                vis);
 858         let is_public = vis == ast::Public;
 859         let modifiers = if is_public { PUBLIC } else { DefModifiers::empty() } | IMPORTABLE;
 860         let is_exported = is_public && match new_parent.def_id.get() {
 861             None => true,
 862             Some(did) => self.external_exports.contains(&did)
 863         };
 864         if is_exported {
 865             self.external_exports.insert(def.def_id());
 866         }
 867
 868         let kind = match def {
 869             DefTy(_, true) => EnumModuleKind,
 870             DefTy(_, false) => TypeModuleKind,
 871             DefStruct(..) => ImplModuleKind,
 872             _ => NormalModuleKind
 873         };
 874
 875         match def {
 876           DefMod(def_id) | DefForeignMod(def_id) | DefStruct(def_id) |
 877           DefTy(def_id, _) => {
 878             let type_def = child_name_bindings.type_def.borrow().clone();
 879             match type_def {
 880               Some(TypeNsDef { module_def: Some(module_def), .. }) => {
 881                 debug!("(building reduced graph for external crate) \
 882                         already created module");
 883                 module_def.def_id.set(Some(def_id));
 884               }
 885               Some(_) | None => {
 886                 debug!("(building reduced graph for \
 887                         external crate) building module \
 888                         {}", final_ident);
 889                 let parent_link = self.get_parent_link(new_parent, name);
 890
 891                 child_name_bindings.define_module(parent_link,
 892                                                   Some(def_id),
 893                                                   kind,
 894                                                   true,
 895                                                   is_public,
 896                                                   DUMMY_SP);
 897               }
 898             }
 899           }
 900           _ => {}
 901         }
 902
 903         match def {
 904           DefMod(_) | DefForeignMod(_) => {}
 905           DefVariant(_, variant_id, is_struct) => {
 906               debug!("(building reduced graph for external crate) building \
 907                       variant {}",
 908                       final_ident);
 909               // variants are always treated as importable to allow them to be
 910               // glob used
 911               let modifiers = PUBLIC | IMPORTABLE;
 912               if is_struct {
 913                   child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 914                   // Not adding fields for variants as they are not accessed with a self receiver
 915                   self.structs.insert(variant_id, Vec::new());
 916               } else {
 917                   child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 918               }
 919           }
 920           DefFn(ctor_id, true) => {
 921             child_name_bindings.define_value(
 922                 csearch::get_tuple_struct_definition_if_ctor(&self.session.cstore, ctor_id)
 923                     .map_or(def, |_| DefStruct(ctor_id)), DUMMY_SP, modifiers);
 924           }
 925           DefFn(..) | DefStaticMethod(..) | DefStatic(..) | DefConst(..) | DefMethod(..) => {
 926             debug!("(building reduced graph for external \
 927                     crate) building value (fn/static) {}", final_ident);
 928             // impl methods have already been defined with the correct importability modifier
 929             let mut modifiers = match *child_name_bindings.value_def.borrow() {
 930                 Some(ref def) => (modifiers & !IMPORTABLE) | (def.modifiers & IMPORTABLE),
 931                 None => modifiers
 932             };
 933             if new_parent.kind.get() != NormalModuleKind {
 934                 modifiers = modifiers & !IMPORTABLE;
 935             }
 936             child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 937           }
 938           DefTrait(def_id) => {
 939               debug!("(building reduced graph for external \
 940                       crate) building type {}", final_ident);
 941
 942               // If this is a trait, add all the trait item names to the trait
 943               // info.
 944
 945               let trait_item_def_ids =
 946                 csearch::get_trait_item_def_ids(&self.session.cstore, def_id);
 947               for trait_item_def_id in trait_item_def_ids.iter() {
 948                   let (trait_item_name, trait_item_kind) =
 949                       csearch::get_trait_item_name_and_kind(
 950                           &self.session.cstore,
 951                           trait_item_def_id.def_id());
 952
 953                   debug!("(building reduced graph for external crate) ... \
 954                           adding trait item '{}'",
 955                          token::get_name(trait_item_name));
 956
 957                   self.trait_item_map.insert((trait_item_name, def_id), trait_item_kind);
 958
 959                   if is_exported {
 960                       self.external_exports
 961                           .insert(trait_item_def_id.def_id());
 962                   }
 963               }
 964
 965               child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 966
 967               // Define a module if necessary.
 968               let parent_link = self.get_parent_link(new_parent, name);
 969               child_name_bindings.set_module_kind(parent_link,
 970                                                   Some(def_id),
 971                                                   TraitModuleKind,
 972                                                   true,
 973                                                   is_public,
 974                                                   DUMMY_SP)
 975           }
 976           DefTy(..) | DefAssociatedTy(..) | DefAssociatedPath(..) => {
 977               debug!("(building reduced graph for external \
 978                       crate) building type {}", final_ident);
 979
 980               child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 981           }
 982           DefStruct(def_id) => {
 983             debug!("(building reduced graph for external \
 984                     crate) building type and value for {}",
 985                    final_ident);
 986             child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 987             let fields = csearch::get_struct_fields(&self.session.cstore, def_id).iter().map(|f| {
 988                 f.name
 989             }).collect::<Vec<_>>();
 990
 991             if fields.len() == 0 {
 992                 child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 993             }
 994
 995             // Record the def ID and fields of this struct.
 996             self.structs.insert(def_id, fields);
 997           }
 998           DefLocal(..) | DefPrimTy(..) | DefTyParam(..) |
 999           DefUse(..) | DefUpvar(..) | DefRegion(..) |
1000           DefTyParamBinder(..) | DefLabel(..) | DefSelfTy(..) => {
1001             panic!("didn't expect `{:?}`", def);
1002           }
1003         }
1004     }
1005
1006     /// Builds the reduced graph for a single item in an external crate.
1007     fn build_reduced_graph_for_external_crate_def(&mut self,
1008                                                   root: &Rc<Module>,
1009                                                   def_like: DefLike,
1010                                                   name: Name,
1011                                                   def_visibility: Visibility) {
1012         match def_like {
1013             DlDef(def) => {
1014                 // Add the new child item, if necessary.
1015                 match def {
1016                     DefForeignMod(def_id) => {
1017                         // Foreign modules have no names. Recur and populate
1018                         // eagerly.
1019                         csearch::each_child_of_item(&self.session.cstore,
1020                                                     def_id,
1021                                                     |def_like,
1022                                                      child_name,
1023                                                      vis| {
1024                             self.build_reduced_graph_for_external_crate_def(
1025                                 root,
1026                                 def_like,
1027                                 child_name,
1028                                 vis)
1029                         });
1030                     }
1031                     _ => {
1032                         let child_name_bindings =
1033                             self.add_child(name,
1034                                            root,
1035                                            OverwriteDuplicates,
1036                                            DUMMY_SP);
1037
1038                         self.handle_external_def(def,
1039                                                  def_visibility,
1040                                                  &*child_name_bindings,
1041                                                  token::get_name(name).get(),
1042                                                  name,
1043                                                  root);
1044                     }
1045                 }
1046             }
1047             DlImpl(def) => {
1048                 match csearch::get_type_name_if_impl(&self.session.cstore, def) {
1049                     None => {}
1050                     Some(final_name) => {
1051                         let methods_opt =
1052                             csearch::get_methods_if_impl(&self.session.cstore, def);
1053                         match methods_opt {
1054                             Some(ref methods) if
1055                                 methods.len() >= 1 => {
1056                                 debug!("(building reduced graph for \
1057                                         external crate) processing \
1058                                         static methods for type name {}",
1059                                         token::get_name(final_name));
1060
1061                                 let child_name_bindings =
1062                                     self.add_child(
1063                                         final_name,
1064                                         root,
1065                                         OverwriteDuplicates,
1066                                         DUMMY_SP);
1067
1068                                 // Process the static methods. First,
1069                                 // create the module.
1070                                 let type_module;
1071                                 let type_def = child_name_bindings.type_def.borrow().clone();
1072                                 match type_def {
1073                                     Some(TypeNsDef {
1074                                         module_def: Some(module_def),
1075                                         ..
1076                                     }) => {
1077                                         // We already have a module. This
1078                                         // is OK.
1079                                         type_module = module_def;
1080
1081                                         // Mark it as an impl module if
1082                                         // necessary.
1083                                         type_module.kind.set(ImplModuleKind);
1084                                     }
1085                                     Some(_) | None => {
1086                                         let parent_link =
1087                                             self.get_parent_link(root, final_name);
1088                                         child_name_bindings.define_module(
1089                                             parent_link,
1090                                             Some(def),
1091                                             ImplModuleKind,
1092                                             true,
1093                                             true,
1094                                             DUMMY_SP);
1095                                         type_module =
1096                                             child_name_bindings.
1097                                                 get_module();
1098                                     }
1099                                 }
1100
1101                                 // Add each static method to the module.
1102                                 let new_parent = type_module;
1103                                 for method_info in methods.iter() {
1104                                     let name = method_info.name;
1105                                     debug!("(building reduced graph for \
1106                                              external crate) creating \
1107                                              static method '{}'",
1108                                            token::get_name(name));
1109
1110                                     let method_name_bindings =
1111                                         self.add_child(name,
1112                                                        &new_parent,
1113                                                        OverwriteDuplicates,
1114                                                        DUMMY_SP);
1115                                     let def = DefFn(method_info.def_id, false);
1116
1117                                     // NB: not IMPORTABLE
1118                                     let modifiers = if method_info.vis == ast::Public {
1119                                         PUBLIC
1120                                     } else {
1121                                         DefModifiers::empty()
1122                                     };
1123                                     method_name_bindings.define_value(
1124                                         def, DUMMY_SP, modifiers);
1125                                 }
1126                             }
1127
1128                             // Otherwise, do nothing.
1129                             Some(_) | None => {}
1130                         }
1131                     }
1132                 }
1133             }
1134             DlField => {
1135                 debug!("(building reduced graph for external crate) \
1136                         ignoring field");
1137             }
1138         }
1139     }
1140
1141     /// Builds the reduced graph rooted at the given external module.
1142     fn populate_external_module(&mut self, module: &Rc<Module>) {
1143         debug!("(populating external module) attempting to populate {}",
1144                self.module_to_string(&**module));
1145
1146         let def_id = match module.def_id.get() {
1147             None => {
1148                 debug!("(populating external module) ... no def ID!");
1149                 return
1150             }
1151             Some(def_id) => def_id,
1152         };
1153
1154         csearch::each_child_of_item(&self.session.cstore,
1155                                     def_id,
1156                                     |def_like, child_name, visibility| {
1157             debug!("(populating external module) ... found ident: {}",
1158                    token::get_name(child_name));
1159             self.build_reduced_graph_for_external_crate_def(module,
1160                                                             def_like,
1161                                                             child_name,
1162                                                             visibility)
1163         });
1164         module.populated.set(true)
1165     }
1166
1167     /// Ensures that the reduced graph rooted at the given external module
1168     /// is built, building it if it is not.
1169     fn populate_module_if_necessary(&mut self, module: &Rc<Module>) {
1170         if !module.populated.get() {
1171             self.populate_external_module(module)
1172         }
1173         assert!(module.populated.get())
1174     }
1175
1176     /// Builds the reduced graph rooted at the 'use' directive for an external
1177     /// crate.
1178     fn build_reduced_graph_for_external_crate(&mut self, root: &Rc<Module>) {
1179         csearch::each_top_level_item_of_crate(&self.session.cstore,
1180                                               root.def_id
1181                                                   .get()
1182                                                   .unwrap()
1183                                                   .krate,
1184                                               |def_like, name, visibility| {
1185             self.build_reduced_graph_for_external_crate_def(root, def_like, name, visibility)
1186         });
1187     }
1188
1189     /// Creates and adds an import directive to the given module.
1190     fn build_import_directive(&mut self,
1191                               module_: &Module,
1192                               module_path: Vec<Name>,
1193                               subclass: ImportDirectiveSubclass,
1194                               span: Span,
1195                               id: NodeId,
1196                               is_public: bool,
1197                               shadowable: Shadowable) {
1198         module_.imports.borrow_mut().push(ImportDirective::new(module_path,
1199                                                                subclass,
1200                                                                span,
1201                                                                id,
1202                                                                is_public,
1203                                                                shadowable));
1204         self.unresolved_imports += 1;
1205         // Bump the reference count on the name. Or, if this is a glob, set
1206         // the appropriate flag.
1207
1208         match subclass {
1209             SingleImport(target, _) => {
1210                 debug!("(building import directive) building import \
1211                         directive: {}::{}",
1212                        self.names_to_string(&module_.imports.borrow().last().unwrap().
1213                                                              module_path[]),
1214                        token::get_name(target));
1215
1216                 let mut import_resolutions = module_.import_resolutions
1217                                                     .borrow_mut();
1218                 match import_resolutions.get_mut(&target) {
1219                     Some(resolution) => {
1220                         debug!("(building import directive) bumping \
1221                                 reference");
1222                         resolution.outstanding_references += 1;
1223
1224                         // the source of this name is different now
1225                         resolution.type_id = id;
1226                         resolution.value_id = id;
1227                         resolution.is_public = is_public;
1228                         return;
1229                     }
1230                     None => {}
1231                 }
1232                 debug!("(building import directive) creating new");
1233                 let mut resolution = ImportResolution::new(id, is_public);
1234                 resolution.outstanding_references = 1;
1235                 import_resolutions.insert(target, resolution);
1236             }
1237             GlobImport => {
1238                 // Set the glob flag. This tells us that we don't know the
1239                 // module's exports ahead of time.
1240
1241                 module_.glob_count.set(module_.glob_count.get() + 1);
1242             }
1243         }
1244     }
1245 }
1246
1247 struct BuildReducedGraphVisitor<'a, 'b:'a, 'tcx:'b> {
1248     builder: GraphBuilder<'a, 'b, 'tcx>,
1249     parent: Rc<Module>
1250 }
1251
1252 impl<'a, 'b, 'v, 'tcx> Visitor<'v> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
1253     fn visit_item(&mut self, item: &Item) {
1254         let p = self.builder.build_reduced_graph_for_item(item, &self.parent);
1255         let old_parent = replace(&mut self.parent, p);
1256         visit::walk_item(self, item);
1257         self.parent = old_parent;
1258     }
1259
1260     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
1261         let parent = &self.parent;
1262         self.builder.build_reduced_graph_for_foreign_item(foreign_item,
1263                                                           parent,
1264                                                           |r| {
1265             let mut v = BuildReducedGraphVisitor {
1266                 builder: GraphBuilder { resolver: r },
1267                 parent: parent.clone()
1268             };
1269             visit::walk_foreign_item(&mut v, foreign_item);
1270         })
1271     }
1272
1273     fn visit_view_item(&mut self, view_item: &ViewItem) {
1274         self.builder.build_reduced_graph_for_view_item(view_item, &self.parent);
1275     }
1276
1277     fn visit_block(&mut self, block: &Block) {
1278         let np = self.builder.build_reduced_graph_for_block(block, &self.parent);
1279         let old_parent = replace(&mut self.parent, np);
1280         visit::walk_block(self, block);
1281         self.parent = old_parent;
1282     }
1283 }
1284
1285 pub fn build_reduced_graph(resolver: &mut Resolver, krate: &ast::Crate) {
1286     GraphBuilder {
1287         resolver: resolver
1288     }.build_reduced_graph(krate);
1289 }
1290
1291 pub fn populate_module_if_necessary(resolver: &mut Resolver, module: &Rc<Module>) {
1292     GraphBuilder {
1293         resolver: resolver
1294     }.populate_module_if_necessary(module);
1295 }