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;
  17 use resolve_imports::ImportDirective;
  18 use resolve_imports::ImportDirectiveSubclass::{self, SingleImport, GlobImport};
  19 use resolve_imports::{ImportResolution, ImportResolutionPerNamespace};
  20 use Module;
  21 use Namespace::{TypeNS, ValueNS};
  22 use NameBindings;
  23 use {names_to_string, module_to_string};
  24 use ParentLink::{self, ModuleParentLink, BlockParentLink};
  25 use Resolver;
  26 use resolve_imports::Shadowable;
  27 use {resolve_error, ResolutionError};
  28
  29 use self::DuplicateCheckingMode::*;
  30
  31 use rustc::middle::cstore::{CrateStore, ChildItem, DlDef, DlField, DlImpl};
  32 use rustc::middle::def::*;
  33 use rustc::middle::def_id::{CRATE_DEF_INDEX, DefId};
  34
  35 use syntax::ast::{Name, NodeId};
  36 use syntax::attr::AttrMetaMethods;
  37 use syntax::parse::token::special_idents;
  38 use syntax::codemap::{Span, DUMMY_SP};
  39
  40 use rustc_front::hir;
  41 use rustc_front::hir::{Block, DeclItem};
  42 use rustc_front::hir::{ForeignItem, ForeignItemFn, ForeignItemStatic};
  43 use rustc_front::hir::{Item, ItemConst, ItemEnum, ItemExternCrate, ItemFn};
  44 use rustc_front::hir::{ItemForeignMod, ItemImpl, ItemMod, ItemStatic, ItemDefaultImpl};
  45 use rustc_front::hir::{ItemStruct, ItemTrait, ItemTy, ItemUse};
  46 use rustc_front::hir::{NamedField, PathListIdent, PathListMod};
  47 use rustc_front::hir::StmtDecl;
  48 use rustc_front::hir::UnnamedField;
  49 use rustc_front::hir::{Variant, ViewPathGlob, ViewPathList, ViewPathSimple};
  50 use rustc_front::hir::Visibility;
  51 use rustc_front::intravisit::{self, Visitor};
  52
  53 use std::mem::replace;
  54 use std::ops::{Deref, DerefMut};
  55 use std::rc::Rc;
  56
  57 // Specifies how duplicates should be handled when adding a child item if
  58 // another item exists with the same name in some namespace.
  59 #[derive(Copy, Clone, PartialEq)]
  60 enum DuplicateCheckingMode {
  61     ForbidDuplicateTypes,
  62     ForbidDuplicateValues,
  63     ForbidDuplicateTypesAndValues,
  64     OverwriteDuplicates,
  65 }
  66
  67 struct GraphBuilder<'a, 'b: 'a, 'tcx: 'b> {
  68     resolver: &'a mut Resolver<'b, 'tcx>,
  69 }
  70
  71 impl<'a, 'b:'a, 'tcx:'b> Deref for GraphBuilder<'a, 'b, 'tcx> {
  72     type Target = Resolver<'b, 'tcx>;
  73
  74     fn deref(&self) -> &Resolver<'b, 'tcx> {
  75         &*self.resolver
  76     }
  77 }
  78
  79 impl<'a, 'b:'a, 'tcx:'b> DerefMut for GraphBuilder<'a, 'b, 'tcx> {
  80     fn deref_mut(&mut self) -> &mut Resolver<'b, 'tcx> {
  81         &mut *self.resolver
  82     }
  83 }
  84
  85 impl<'a, 'b:'a, 'tcx:'b> GraphBuilder<'a, 'b, 'tcx> {
  86     /// Constructs the reduced graph for the entire crate.
  87     fn build_reduced_graph(self, krate: &hir::Crate) {
  88         let mut visitor = BuildReducedGraphVisitor {
  89             parent: self.graph_root.clone(),
  90             builder: self,
  91         };
  92         intravisit::walk_crate(&mut visitor, krate);
  93     }
  94
  95     /// Adds a new child item to the module definition of the parent node,
  96     /// or if there is already a child, does duplicate checking on the child.
  97     /// Returns the child's corresponding name bindings.
  98     fn add_child(&self,
  99                  name: Name,
 100                  parent: &Rc<Module>,
 101                  duplicate_checking_mode: DuplicateCheckingMode,
 102                  // For printing errors
 103                  sp: Span)
 104                  -> NameBindings {
 105         self.check_for_conflicts_between_external_crates_and_items(&**parent, name, sp);
 106
 107         // Add or reuse the child.
 108         let child = parent.children.borrow().get(&name).cloned();
 109         match child {
 110             None => {
 111                 let child = NameBindings::new();
 112                 parent.children.borrow_mut().insert(name, child.clone());
 113                 child
 114             }
 115             Some(child) => {
 116                 // Enforce the duplicate checking mode:
 117                 //
 118                 // * If we're requesting duplicate type checking, check that
 119                 //   the name isn't defined in the type namespace.
 120                 //
 121                 // * If we're requesting duplicate value checking, check that
 122                 //   the name isn't defined in the value namespace.
 123                 //
 124                 // * If we're requesting duplicate type and value checking,
 125                 //   check that the name isn't defined in either namespace.
 126                 //
 127                 // * If no duplicate checking was requested at all, do
 128                 //   nothing.
 129
 130                 let ns = match duplicate_checking_mode {
 131                     ForbidDuplicateTypes if child.type_ns.defined() => TypeNS,
 132                     ForbidDuplicateValues if child.value_ns.defined() => ValueNS,
 133                     ForbidDuplicateTypesAndValues if child.type_ns.defined() => TypeNS,
 134                     ForbidDuplicateTypesAndValues if child.value_ns.defined() => ValueNS,
 135                     _ => return child,
 136                 };
 137
 138                 // Record an error here by looking up the namespace that had the duplicate
 139                 let ns_str = match ns { TypeNS => "type or module", ValueNS => "value" };
 140                 resolve_error(self, sp, ResolutionError::DuplicateDefinition(ns_str, name));
 141
 142                 if let Some(sp) = child[ns].span() {
 143                     let note = format!("first definition of {} `{}` here", ns_str, name);
 144                     self.session.span_note(sp, &note);
 145                 }
 146                 child
 147             }
 148         }
 149     }
 150
 151     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 152         // Check each statement.
 153         for statement in &block.stmts {
 154             match statement.node {
 155                 StmtDecl(ref declaration, _) => {
 156                     match declaration.node {
 157                         DeclItem(_) => {
 158                             return true;
 159                         }
 160                         _ => {
 161                             // Keep searching.
 162                         }
 163                     }
 164                 }
 165                 _ => {
 166                     // Keep searching.
 167                 }
 168             }
 169         }
 170
 171         // If we found no items, we don't need to create
 172         // an anonymous module.
 173
 174         return false;
 175     }
 176
 177     fn get_parent_link(&mut self, parent: &Rc<Module>, name: Name) -> ParentLink {
 178         ModuleParentLink(Rc::downgrade(parent), name)
 179     }
 180
 181     /// Constructs the reduced graph for one item.
 182     fn build_reduced_graph_for_item(&mut self, item: &Item, parent: &Rc<Module>) -> Rc<Module> {
 183         let name = item.name;
 184         let sp = item.span;
 185         let is_public = item.vis == hir::Public;
 186         let modifiers = if is_public {
 187             DefModifiers::PUBLIC
 188         } else {
 189             DefModifiers::empty()
 190         } | DefModifiers::IMPORTABLE;
 191
 192         match item.node {
 193             ItemUse(ref view_path) => {
 194                 // Extract and intern the module part of the path. For
 195                 // globs and lists, the path is found directly in the AST;
 196                 // for simple paths we have to munge the path a little.
 197                 let module_path = match view_path.node {
 198                     ViewPathSimple(_, ref full_path) => {
 199                         full_path.segments
 200                                  .split_last()
 201                                  .unwrap()
 202                                  .1
 203                                  .iter()
 204                                  .map(|seg| seg.identifier.name)
 205                                  .collect()
 206                     }
 207
 208                     ViewPathGlob(ref module_ident_path) |
 209                     ViewPathList(ref module_ident_path, _) => {
 210                         module_ident_path.segments
 211                                          .iter()
 212                                          .map(|seg| seg.identifier.name)
 213                                          .collect()
 214                     }
 215                 };
 216
 217                 // Build up the import directives.
 218                 let shadowable = item.attrs.iter().any(|attr| {
 219                     attr.name() == special_idents::prelude_import.name.as_str()
 220                 });
 221                 let shadowable = if shadowable {
 222                     Shadowable::Always
 223                 } else {
 224                     Shadowable::Never
 225                 };
 226
 227                 match view_path.node {
 228                     ViewPathSimple(binding, ref full_path) => {
 229                         let source_name = full_path.segments.last().unwrap().identifier.name;
 230                         if source_name.as_str() == "mod" || source_name.as_str() == "self" {
 231                             resolve_error(self,
 232                                           view_path.span,
 233                                           ResolutionError::SelfImportsOnlyAllowedWithin);
 234                         }
 235
 236                         let subclass = SingleImport(binding, source_name);
 237                         self.build_import_directive(&**parent,
 238                                                     module_path,
 239                                                     subclass,
 240                                                     view_path.span,
 241                                                     item.id,
 242                                                     is_public,
 243                                                     shadowable);
 244                     }
 245                     ViewPathList(_, ref source_items) => {
 246                         // Make sure there's at most one `mod` import in the list.
 247                         let mod_spans = source_items.iter()
 248                                                     .filter_map(|item| {
 249                                                         match item.node {
 250                                                             PathListMod { .. } => Some(item.span),
 251                                                             _ => None,
 252                                                         }
 253                                                     })
 254                                                     .collect::<Vec<Span>>();
 255                         if mod_spans.len() > 1 {
 256                             resolve_error(self,
 257                                           mod_spans[0],
 258                                           ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 259                             for other_span in mod_spans.iter().skip(1) {
 260                                 self.session
 261                                     .span_note(*other_span, "another `self` import appears here");
 262                             }
 263                         }
 264
 265                         for source_item in source_items {
 266                             let (module_path, name, rename) = match source_item.node {
 267                                 PathListIdent { name, rename, .. } =>
 268                                     (module_path.clone(), name, rename.unwrap_or(name)),
 269                                 PathListMod { rename, .. } => {
 270                                     let name = match module_path.last() {
 271                                         Some(name) => *name,
 272                                         None => {
 273                                             resolve_error(
 274                                                 self,
 275                                                 source_item.span,
 276                                                 ResolutionError::
 277                                                 SelfImportOnlyInImportListWithNonEmptyPrefix
 278                                             );
 279                                             continue;
 280                                         }
 281                                     };
 282                                     let module_path = module_path.split_last().unwrap().1;
 283                                     let rename = rename.unwrap_or(name);
 284                                     (module_path.to_vec(), name, rename)
 285                                 }
 286                             };
 287                             self.build_import_directive(&**parent,
 288                                                         module_path,
 289                                                         SingleImport(rename, name),
 290                                                         source_item.span,
 291                                                         source_item.node.id(),
 292                                                         is_public,
 293                                                         shadowable);
 294                         }
 295                     }
 296                     ViewPathGlob(_) => {
 297                         self.build_import_directive(&**parent,
 298                                                     module_path,
 299                                                     GlobImport,
 300                                                     view_path.span,
 301                                                     item.id,
 302                                                     is_public,
 303                                                     shadowable);
 304                     }
 305                 }
 306                 parent.clone()
 307             }
 308
 309             ItemExternCrate(_) => {
 310                 // n.b. we don't need to look at the path option here, because cstore already
 311                 // did
 312                 if let Some(crate_id) = self.session.cstore.extern_mod_stmt_cnum(item.id) {
 313                     let def_id = DefId {
 314                         krate: crate_id,
 315                         index: CRATE_DEF_INDEX,
 316                     };
 317                     self.external_exports.insert(def_id);
 318                     let parent_link = ModuleParentLink(Rc::downgrade(parent), name);
 319                     let def = DefMod(def_id);
 320                     let external_module = Module::new(parent_link, Some(def), false, true);
 321
 322                     debug!("(build reduced graph for item) found extern `{}`",
 323                            module_to_string(&*external_module));
 324                     self.check_for_conflicts_between_external_crates(&**parent, name, sp);
 325                     parent.external_module_children
 326                           .borrow_mut()
 327                           .insert(name, external_module.clone());
 328                     self.build_reduced_graph_for_external_crate(&external_module);
 329                 }
 330                 parent.clone()
 331             }
 332
 333             ItemMod(..) => {
 334                 let name_bindings = self.add_child(name, parent, ForbidDuplicateTypes, sp);
 335
 336                 let parent_link = self.get_parent_link(parent, name);
 337                 let def = DefMod(self.ast_map.local_def_id(item.id));
 338                 let module = Module::new(parent_link, Some(def), false, is_public);
 339                 name_bindings.define_module(module.clone(), sp);
 340                 module
 341             }
 342
 343             ItemForeignMod(..) => parent.clone(),
 344
 345             // These items live in the value namespace.
 346             ItemStatic(_, m, _) => {
 347                 let name_bindings = self.add_child(name, parent, ForbidDuplicateValues, sp);
 348                 let mutbl = m == hir::MutMutable;
 349
 350                 name_bindings.define_value(DefStatic(self.ast_map.local_def_id(item.id), mutbl),
 351                                            sp,
 352                                            modifiers);
 353                 parent.clone()
 354             }
 355             ItemConst(_, _) => {
 356                 self.add_child(name, parent, ForbidDuplicateValues, sp)
 357                     .define_value(DefConst(self.ast_map.local_def_id(item.id)), sp, modifiers);
 358                 parent.clone()
 359             }
 360             ItemFn(_, _, _, _, _, _) => {
 361                 let name_bindings = self.add_child(name, parent, ForbidDuplicateValues, sp);
 362
 363                 let def = DefFn(self.ast_map.local_def_id(item.id), false);
 364                 name_bindings.define_value(def, sp, modifiers);
 365                 parent.clone()
 366             }
 367
 368             // These items live in the type namespace.
 369             ItemTy(..) => {
 370                 let name_bindings = self.add_child(name,
 371                                                    parent,
 372                                                    ForbidDuplicateTypes,
 373                                                    sp);
 374
 375                 let parent_link = self.get_parent_link(parent, name);
 376                 let def = DefTy(self.ast_map.local_def_id(item.id), false);
 377                 let module = Module::new(parent_link, Some(def), false, is_public);
 378                 name_bindings.define_module(module, sp);
 379                 parent.clone()
 380             }
 381
 382             ItemEnum(ref enum_definition, _) => {
 383                 let name_bindings = self.add_child(name,
 384                                                    parent,
 385                                                    ForbidDuplicateTypes,
 386                                                    sp);
 387
 388                 let parent_link = self.get_parent_link(parent, name);
 389                 let def = DefTy(self.ast_map.local_def_id(item.id), true);
 390                 let module = Module::new(parent_link, Some(def), false, is_public);
 391                 name_bindings.define_module(module.clone(), sp);
 392
 393                 for variant in &(*enum_definition).variants {
 394                     let item_def_id = self.ast_map.local_def_id(item.id);
 395                     self.build_reduced_graph_for_variant(variant, item_def_id, &module);
 396                 }
 397                 parent.clone()
 398             }
 399
 400             // These items live in both the type and value namespaces.
 401             ItemStruct(ref struct_def, _) => {
 402                 // Adding to both Type and Value namespaces or just Type?
 403                 let (forbid, ctor_id) = if struct_def.is_struct() {
 404                     (ForbidDuplicateTypes, None)
 405                 } else {
 406                     (ForbidDuplicateTypesAndValues, Some(struct_def.id()))
 407                 };
 408
 409                 let name_bindings = self.add_child(name, parent, forbid, sp);
 410
 411                 // Define a name in the type namespace.
 412                 name_bindings.define_type(DefTy(self.ast_map.local_def_id(item.id), false),
 413                                           sp,
 414                                           modifiers);
 415
 416                 // If this is a newtype or unit-like struct, define a name
 417                 // in the value namespace as well
 418                 if let Some(cid) = ctor_id {
 419                     name_bindings.define_value(DefStruct(self.ast_map.local_def_id(cid)),
 420                                                sp,
 421                                                modifiers);
 422                 }
 423
 424                 // Record the def ID and fields of this struct.
 425                 let named_fields = struct_def.fields()
 426                                              .iter()
 427                                              .filter_map(|f| {
 428                                                  match f.node.kind {
 429                                                      NamedField(name, _) => Some(name),
 430                                                      UnnamedField(_) => None,
 431                                                  }
 432                                              })
 433                                              .collect();
 434                 let item_def_id = self.ast_map.local_def_id(item.id);
 435                 self.structs.insert(item_def_id, named_fields);
 436
 437                 parent.clone()
 438             }
 439
 440             ItemDefaultImpl(_, _) |
 441             ItemImpl(..) => parent.clone(),
 442
 443             ItemTrait(_, _, _, ref items) => {
 444                 let name_bindings = self.add_child(name,
 445                                                    parent,
 446                                                    ForbidDuplicateTypes,
 447                                                    sp);
 448
 449                 let def_id = self.ast_map.local_def_id(item.id);
 450
 451                 // Add all the items within to a new module.
 452                 let parent_link = self.get_parent_link(parent, name);
 453                 let def = DefTrait(def_id);
 454                 let module_parent = Module::new(parent_link, Some(def), false, is_public);
 455                 name_bindings.define_module(module_parent.clone(), sp);
 456
 457                 // Add the names of all the items to the trait info.
 458                 for trait_item in items {
 459                     let name_bindings = self.add_child(trait_item.name,
 460                                                        &module_parent,
 461                                                        ForbidDuplicateTypesAndValues,
 462                                                        trait_item.span);
 463
 464                     match trait_item.node {
 465                         hir::ConstTraitItem(..) => {
 466                             let def = DefAssociatedConst(self.ast_map.local_def_id(trait_item.id));
 467                             // NB: not DefModifiers::IMPORTABLE
 468                             name_bindings.define_value(def, trait_item.span, DefModifiers::PUBLIC);
 469                         }
 470                         hir::MethodTraitItem(..) => {
 471                             let def = DefMethod(self.ast_map.local_def_id(trait_item.id));
 472                             // NB: not DefModifiers::IMPORTABLE
 473                             name_bindings.define_value(def, trait_item.span, DefModifiers::PUBLIC);
 474                         }
 475                         hir::TypeTraitItem(..) => {
 476                             let def = DefAssociatedTy(self.ast_map.local_def_id(item.id),
 477                                                       self.ast_map.local_def_id(trait_item.id));
 478                             // NB: not DefModifiers::IMPORTABLE
 479                             name_bindings.define_type(def, trait_item.span, DefModifiers::PUBLIC);
 480                         }
 481                     }
 482
 483                     let trait_item_def_id = self.ast_map.local_def_id(trait_item.id);
 484                     self.trait_item_map.insert((trait_item.name, def_id), trait_item_def_id);
 485                 }
 486
 487                 parent.clone()
 488             }
 489         }
 490     }
 491
 492     // Constructs the reduced graph for one variant. Variants exist in the
 493     // type and value namespaces.
 494     fn build_reduced_graph_for_variant(&mut self,
 495                                        variant: &Variant,
 496                                        item_id: DefId,
 497                                        parent: &Rc<Module>) {
 498         let name = variant.node.name;
 499         let is_exported = if variant.node.data.is_struct() {
 500             // Not adding fields for variants as they are not accessed with a self receiver
 501             let variant_def_id = self.ast_map.local_def_id(variant.node.data.id());
 502             self.structs.insert(variant_def_id, Vec::new());
 503             true
 504         } else {
 505             false
 506         };
 507
 508         let child = self.add_child(name, parent, ForbidDuplicateTypesAndValues, variant.span);
 509         // variants are always treated as importable to allow them to be glob
 510         // used
 511         child.define_value(DefVariant(item_id,
 512                                       self.ast_map.local_def_id(variant.node.data.id()),
 513                                       is_exported),
 514                            variant.span,
 515                            DefModifiers::PUBLIC | DefModifiers::IMPORTABLE);
 516         child.define_type(DefVariant(item_id,
 517                                      self.ast_map.local_def_id(variant.node.data.id()),
 518                                      is_exported),
 519                           variant.span,
 520                           DefModifiers::PUBLIC | DefModifiers::IMPORTABLE);
 521     }
 522
 523     /// Constructs the reduced graph for one foreign item.
 524     fn build_reduced_graph_for_foreign_item(&mut self,
 525                                             foreign_item: &ForeignItem,
 526                                             parent: &Rc<Module>) {
 527         let name = foreign_item.name;
 528         let is_public = foreign_item.vis == hir::Public;
 529         let modifiers = if is_public {
 530             DefModifiers::PUBLIC
 531         } else {
 532             DefModifiers::empty()
 533         } | DefModifiers::IMPORTABLE;
 534         let name_bindings = self.add_child(name, parent, ForbidDuplicateValues, foreign_item.span);
 535
 536         let def = match foreign_item.node {
 537             ForeignItemFn(..) => {
 538                 DefFn(self.ast_map.local_def_id(foreign_item.id), false)
 539             }
 540             ForeignItemStatic(_, m) => {
 541                 DefStatic(self.ast_map.local_def_id(foreign_item.id), m)
 542             }
 543         };
 544         name_bindings.define_value(def, foreign_item.span, modifiers);
 545     }
 546
 547     fn build_reduced_graph_for_block(&mut self, block: &Block, parent: &Rc<Module>) -> Rc<Module> {
 548         if self.block_needs_anonymous_module(block) {
 549             let block_id = block.id;
 550
 551             debug!("(building reduced graph for block) creating a new anonymous module for block \
 552                     {}",
 553                    block_id);
 554
 555             let parent_link = BlockParentLink(Rc::downgrade(parent), block_id);
 556             let new_module = Module::new(parent_link, None, false, false);
 557             parent.anonymous_children.borrow_mut().insert(block_id, new_module.clone());
 558             new_module
 559         } else {
 560             parent.clone()
 561         }
 562     }
 563
 564     fn handle_external_def(&mut self,
 565                            def: Def,
 566                            vis: Visibility,
 567                            child_name_bindings: &NameBindings,
 568                            final_ident: &str,
 569                            name: Name,
 570                            new_parent: &Rc<Module>) {
 571         debug!("(building reduced graph for external crate) building external def {}, priv {:?}",
 572                final_ident,
 573                vis);
 574         let is_public = vis == hir::Public;
 575         let modifiers = if is_public {
 576             DefModifiers::PUBLIC
 577         } else {
 578             DefModifiers::empty()
 579         } | DefModifiers::IMPORTABLE;
 580         let is_exported = is_public &&
 581                           match new_parent.def_id() {
 582             None => true,
 583             Some(did) => self.external_exports.contains(&did),
 584         };
 585         if is_exported {
 586             self.external_exports.insert(def.def_id());
 587         }
 588
 589         match def {
 590             DefMod(_) |
 591             DefForeignMod(_) |
 592             DefStruct(_) |
 593             DefTy(..) => {
 594                 if let Some(module_def) = child_name_bindings.type_ns.module() {
 595                     debug!("(building reduced graph for external crate) already created module");
 596                     module_def.def.set(Some(def));
 597                 } else {
 598                     debug!("(building reduced graph for external crate) building module {} {}",
 599                            final_ident,
 600                            is_public);
 601                     let parent_link = self.get_parent_link(new_parent, name);
 602                     let module = Module::new(parent_link, Some(def), true, is_public);
 603                     child_name_bindings.define_module(module, DUMMY_SP);
 604                 }
 605             }
 606             _ => {}
 607         }
 608
 609         match def {
 610             DefMod(_) | DefForeignMod(_) => {}
 611             DefVariant(_, variant_id, is_struct) => {
 612                 debug!("(building reduced graph for external crate) building variant {}",
 613                        final_ident);
 614                 // variants are always treated as importable to allow them to be
 615                 // glob used
 616                 let modifiers = DefModifiers::PUBLIC | DefModifiers::IMPORTABLE;
 617                 if is_struct {
 618                     child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 619                     // Not adding fields for variants as they are not accessed with a self receiver
 620                     self.structs.insert(variant_id, Vec::new());
 621                 } else {
 622                     child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 623                 }
 624             }
 625             DefFn(ctor_id, true) => {
 626                 child_name_bindings.define_value(
 627                 self.session.cstore.tuple_struct_definition_if_ctor(ctor_id)
 628                     .map_or(def, |_| DefStruct(ctor_id)), DUMMY_SP, modifiers);
 629             }
 630             DefFn(..) |
 631             DefStatic(..) |
 632             DefConst(..) |
 633             DefAssociatedConst(..) |
 634             DefMethod(..) => {
 635                 debug!("(building reduced graph for external crate) building value (fn/static) {}",
 636                        final_ident);
 637                 // impl methods have already been defined with the correct importability
 638                 // modifier
 639                 let mut modifiers = match *child_name_bindings.value_ns.borrow() {
 640                     Some(ref def) => (modifiers & !DefModifiers::IMPORTABLE) |
 641                                      (def.modifiers & DefModifiers::IMPORTABLE),
 642                     None => modifiers,
 643                 };
 644                 if !new_parent.is_normal() {
 645                     modifiers = modifiers & !DefModifiers::IMPORTABLE;
 646                 }
 647                 child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 648             }
 649             DefTrait(def_id) => {
 650                 debug!("(building reduced graph for external crate) building type {}",
 651                        final_ident);
 652
 653                 // If this is a trait, add all the trait item names to the trait
 654                 // info.
 655
 656                 let trait_item_def_ids = self.session.cstore.trait_item_def_ids(def_id);
 657                 for trait_item_def in &trait_item_def_ids {
 658                     let trait_item_name =
 659                         self.session.cstore.item_name(trait_item_def.def_id());
 660
 661                     debug!("(building reduced graph for external crate) ... adding trait item \
 662                             '{}'",
 663                            trait_item_name);
 664
 665                     self.trait_item_map.insert((trait_item_name, def_id), trait_item_def.def_id());
 666
 667                     if is_exported {
 668                         self.external_exports.insert(trait_item_def.def_id());
 669                     }
 670                 }
 671
 672                 // Define a module if necessary.
 673                 let parent_link = self.get_parent_link(new_parent, name);
 674                 let module = Module::new(parent_link, Some(def), true, is_public);
 675                 child_name_bindings.define_module(module, DUMMY_SP);
 676             }
 677             DefTy(..) | DefAssociatedTy(..) => {
 678                 debug!("(building reduced graph for external crate) building type {}",
 679                        final_ident);
 680
 681                 let modifiers = match new_parent.is_normal() {
 682                     true => modifiers,
 683                     _ => modifiers & !DefModifiers::IMPORTABLE,
 684                 };
 685
 686                 if let DefTy(..) = def {
 687                     child_name_bindings.type_ns.set_modifiers(modifiers);
 688                 } else {
 689                     child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 690                 }
 691             }
 692             DefStruct(def_id) => {
 693                 debug!("(building reduced graph for external crate) building type and value for \
 694                         {}",
 695                        final_ident);
 696                 child_name_bindings.define_type(def, DUMMY_SP, modifiers);
 697                 let fields = self.session.cstore.struct_field_names(def_id);
 698
 699                 if fields.is_empty() {
 700                     child_name_bindings.define_value(def, DUMMY_SP, modifiers);
 701                 }
 702
 703                 // Record the def ID and fields of this struct.
 704                 self.structs.insert(def_id, fields);
 705             }
 706             DefLocal(..) |
 707             DefPrimTy(..) |
 708             DefTyParam(..) |
 709             DefUse(..) |
 710             DefUpvar(..) |
 711             DefLabel(..) |
 712             DefSelfTy(..) |
 713             DefErr => {
 714                 panic!("didn't expect `{:?}`", def);
 715             }
 716         }
 717     }
 718
 719     /// Builds the reduced graph for a single item in an external crate.
 720     fn build_reduced_graph_for_external_crate_def(&mut self,
 721                                                   root: &Rc<Module>,
 722                                                   xcdef: ChildItem) {
 723         match xcdef.def {
 724             DlDef(def) => {
 725                 // Add the new child item, if necessary.
 726                 match def {
 727                     DefForeignMod(def_id) => {
 728                         // Foreign modules have no names. Recur and populate
 729                         // eagerly.
 730                         for child in self.session.cstore.item_children(def_id) {
 731                             self.build_reduced_graph_for_external_crate_def(root, child)
 732                         }
 733                     }
 734                     _ => {
 735                         let child_name_bindings = self.add_child(xcdef.name,
 736                                                                  root,
 737                                                                  OverwriteDuplicates,
 738                                                                  DUMMY_SP);
 739
 740                         self.handle_external_def(def,
 741                                                  xcdef.vis,
 742                                                  &child_name_bindings,
 743                                                  &xcdef.name.as_str(),
 744                                                  xcdef.name,
 745                                                  root);
 746                     }
 747                 }
 748             }
 749             DlImpl(_) => {
 750                 debug!("(building reduced graph for external crate) ignoring impl");
 751             }
 752             DlField => {
 753                 debug!("(building reduced graph for external crate) ignoring field");
 754             }
 755         }
 756     }
 757
 758     /// Builds the reduced graph rooted at the given external module.
 759     fn populate_external_module(&mut self, module: &Rc<Module>) {
 760         debug!("(populating external module) attempting to populate {}",
 761                module_to_string(&**module));
 762
 763         let def_id = match module.def_id() {
 764             None => {
 765                 debug!("(populating external module) ... no def ID!");
 766                 return;
 767             }
 768             Some(def_id) => def_id,
 769         };
 770
 771         for child in self.session.cstore.item_children(def_id) {
 772             debug!("(populating external module) ... found ident: {}",
 773                    child.name);
 774             self.build_reduced_graph_for_external_crate_def(module, child);
 775         }
 776         module.populated.set(true)
 777     }
 778
 779     /// Ensures that the reduced graph rooted at the given external module
 780     /// is built, building it if it is not.
 781     fn populate_module_if_necessary(&mut self, module: &Rc<Module>) {
 782         if !module.populated.get() {
 783             self.populate_external_module(module)
 784         }
 785         assert!(module.populated.get())
 786     }
 787
 788     /// Builds the reduced graph rooted at the 'use' directive for an external
 789     /// crate.
 790     fn build_reduced_graph_for_external_crate(&mut self, root: &Rc<Module>) {
 791         let root_cnum = root.def_id().unwrap().krate;
 792         for child in self.session.cstore.crate_top_level_items(root_cnum) {
 793             self.build_reduced_graph_for_external_crate_def(root, child);
 794         }
 795     }
 796
 797     /// Creates and adds an import directive to the given module.
 798     fn build_import_directive(&mut self,
 799                               module_: &Module,
 800                               module_path: Vec<Name>,
 801                               subclass: ImportDirectiveSubclass,
 802                               span: Span,
 803                               id: NodeId,
 804                               is_public: bool,
 805                               shadowable: Shadowable) {
 806         module_.imports
 807                .borrow_mut()
 808                .push(ImportDirective::new(module_path, subclass, span, id, is_public, shadowable));
 809         self.unresolved_imports += 1;
 810
 811         if is_public {
 812             module_.inc_pub_count();
 813         }
 814
 815         // Bump the reference count on the name. Or, if this is a glob, set
 816         // the appropriate flag.
 817
 818         match subclass {
 819             SingleImport(target, _) => {
 820                 debug!("(building import directive) building import directive: {}::{}",
 821                        names_to_string(&module_.imports.borrow().last().unwrap().module_path),
 822                        target);
 823
 824                 let mut import_resolutions = module_.import_resolutions.borrow_mut();
 825                 match import_resolutions.get_mut(&target) {
 826                     Some(resolution_per_ns) => {
 827                         debug!("(building import directive) bumping reference");
 828                         resolution_per_ns.outstanding_references += 1;
 829
 830                         // the source of this name is different now
 831                         let resolution =
 832                             ImportResolution { id: id, is_public: is_public, target: None };
 833                         resolution_per_ns[TypeNS] = resolution.clone();
 834                         resolution_per_ns[ValueNS] = resolution;
 835                         return;
 836                     }
 837                     None => {}
 838                 }
 839                 debug!("(building import directive) creating new");
 840                 let mut import_resolution_per_ns = ImportResolutionPerNamespace::new(id, is_public);
 841                 import_resolution_per_ns.outstanding_references = 1;
 842                 import_resolutions.insert(target, import_resolution_per_ns);
 843             }
 844             GlobImport => {
 845                 // Set the glob flag. This tells us that we don't know the
 846                 // module's exports ahead of time.
 847
 848                 module_.inc_glob_count();
 849                 if is_public {
 850                     module_.inc_pub_glob_count();
 851                 }
 852             }
 853         }
 854     }
 855 }
 856
 857 struct BuildReducedGraphVisitor<'a, 'b: 'a, 'tcx: 'b> {
 858     builder: GraphBuilder<'a, 'b, 'tcx>,
 859     parent: Rc<Module>,
 860 }
 861
 862 impl<'a, 'b, 'v, 'tcx> Visitor<'v> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
 863     fn visit_nested_item(&mut self, item: hir::ItemId) {
 864         self.visit_item(self.builder.resolver.ast_map.expect_item(item.id))
 865     }
 866
 867     fn visit_item(&mut self, item: &Item) {
 868         let p = self.builder.build_reduced_graph_for_item(item, &self.parent);
 869         let old_parent = replace(&mut self.parent, p);
 870         intravisit::walk_item(self, item);
 871         self.parent = old_parent;
 872     }
 873
 874     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
 875         self.builder.build_reduced_graph_for_foreign_item(foreign_item, &self.parent);
 876     }
 877
 878     fn visit_block(&mut self, block: &Block) {
 879         let np = self.builder.build_reduced_graph_for_block(block, &self.parent);
 880         let old_parent = replace(&mut self.parent, np);
 881         intravisit::walk_block(self, block);
 882         self.parent = old_parent;
 883     }
 884 }
 885
 886 pub fn build_reduced_graph(resolver: &mut Resolver, krate: &hir::Crate) {
 887     GraphBuilder { resolver: resolver }.build_reduced_graph(krate);
 888 }
 889
 890 pub fn populate_module_if_necessary(resolver: &mut Resolver, module: &Rc<Module>) {
 891     GraphBuilder { resolver: resolver }.populate_module_if_necessary(module);
 892 }