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 Module;
  20 use Namespace::{self, TypeNS, ValueNS};
  21 use {NameBinding, NameBindingKind};
  22 use module_to_string;
  23 use ParentLink::{ModuleParentLink, BlockParentLink};
  24 use Resolver;
  25 use resolve_imports::Shadowable;
  26 use {resolve_error, resolve_struct_error, ResolutionError};
  27
  28 use rustc::middle::cstore::{CrateStore, ChildItem, DlDef, DlField, DlImpl};
  29 use rustc::middle::def::*;
  30 use rustc::middle::def_id::{CRATE_DEF_INDEX, DefId};
  31 use rustc::middle::ty::VariantKind;
  32
  33 use syntax::ast::{Name, NodeId};
  34 use syntax::attr::AttrMetaMethods;
  35 use syntax::parse::token::special_idents;
  36 use syntax::codemap::{Span, DUMMY_SP};
  37
  38 use rustc_front::hir;
  39 use rustc_front::hir::{Block, DeclItem};
  40 use rustc_front::hir::{ForeignItem, ForeignItemFn, ForeignItemStatic};
  41 use rustc_front::hir::{Item, ItemConst, ItemEnum, ItemExternCrate, ItemFn};
  42 use rustc_front::hir::{ItemForeignMod, ItemImpl, ItemMod, ItemStatic, ItemDefaultImpl};
  43 use rustc_front::hir::{ItemStruct, ItemTrait, ItemTy, ItemUse};
  44 use rustc_front::hir::{PathListIdent, PathListMod, StmtDecl};
  45 use rustc_front::hir::{Variant, ViewPathGlob, ViewPathList, ViewPathSimple};
  46 use rustc_front::hir::Visibility;
  47 use rustc_front::intravisit::{self, Visitor};
  48
  49 use std::mem::replace;
  50 use std::ops::{Deref, DerefMut};
  51
  52 struct GraphBuilder<'a, 'b: 'a, 'tcx: 'b> {
  53     resolver: &'a mut Resolver<'b, 'tcx>,
  54 }
  55
  56 impl<'a, 'b:'a, 'tcx:'b> Deref for GraphBuilder<'a, 'b, 'tcx> {
  57     type Target = Resolver<'b, 'tcx>;
  58
  59     fn deref(&self) -> &Resolver<'b, 'tcx> {
  60         &*self.resolver
  61     }
  62 }
  63
  64 impl<'a, 'b:'a, 'tcx:'b> DerefMut for GraphBuilder<'a, 'b, 'tcx> {
  65     fn deref_mut(&mut self) -> &mut Resolver<'b, 'tcx> {
  66         &mut *self.resolver
  67     }
  68 }
  69
  70 trait ToNameBinding<'a> {
  71     fn to_name_binding(self) -> NameBinding<'a>;
  72 }
  73
  74 impl<'a> ToNameBinding<'a> for (Module<'a>, Span) {
  75     fn to_name_binding(self) -> NameBinding<'a> {
  76         NameBinding::create_from_module(self.0, Some(self.1))
  77     }
  78 }
  79
  80 impl<'a> ToNameBinding<'a> for (Def, Span, DefModifiers) {
  81     fn to_name_binding(self) -> NameBinding<'a> {
  82         let kind = NameBindingKind::Def(self.0);
  83         NameBinding { modifiers: self.2, kind: kind, span: Some(self.1) }
  84     }
  85 }
  86
  87 impl<'a, 'b:'a, 'tcx:'b> GraphBuilder<'a, 'b, 'tcx> {
  88     /// Constructs the reduced graph for the entire crate.
  89     fn build_reduced_graph(self, krate: &hir::Crate) {
  90         let mut visitor = BuildReducedGraphVisitor {
  91             parent: self.graph_root,
  92             builder: self,
  93         };
  94         intravisit::walk_crate(&mut visitor, krate);
  95     }
  96
  97     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined.
  98     fn try_define<T>(&self, parent: Module<'b>, name: Name, ns: Namespace, def: T)
  99         where T: ToNameBinding<'b>
 100     {
 101         let _ = parent.try_define_child(name, ns, self.new_name_binding(def.to_name_binding()));
 102     }
 103
 104     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
 105     /// otherwise, reports an error.
 106     fn define<T: ToNameBinding<'b>>(&self, parent: Module<'b>, name: Name, ns: Namespace, def: T) {
 107         let binding = self.new_name_binding(def.to_name_binding());
 108         let old_binding = match parent.try_define_child(name, ns, binding) {
 109             Ok(()) => return,
 110             Err(old_binding) => old_binding,
 111         };
 112
 113         let span = binding.span.unwrap_or(DUMMY_SP);
 114         if !old_binding.is_extern_crate() && !binding.is_extern_crate() {
 115             // Record an error here by looking up the namespace that had the duplicate
 116             let ns_str = match ns { TypeNS => "type or module", ValueNS => "value" };
 117             let resolution_error = ResolutionError::DuplicateDefinition(ns_str, name);
 118             let mut err = resolve_struct_error(self, span, resolution_error);
 119
 120             if let Some(sp) = old_binding.span {
 121                 let note = format!("first definition of {} `{}` here", ns_str, name);
 122                 err.span_note(sp, &note);
 123             }
 124             err.emit();
 125         } else if old_binding.is_extern_crate() && binding.is_extern_crate() {
 126             span_err!(self.session,
 127                       span,
 128                       E0259,
 129                       "an external crate named `{}` has already been imported into this module",
 130                       name);
 131         } else {
 132             span_err!(self.session,
 133                       span,
 134                       E0260,
 135                       "the name `{}` conflicts with an external crate \
 136                       that has been imported into this module",
 137                       name);
 138         }
 139     }
 140
 141     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 142         fn is_item(statement: &hir::Stmt) -> bool {
 143             if let StmtDecl(ref declaration, _) = statement.node {
 144                 if let DeclItem(_) = declaration.node {
 145                     return true;
 146                 }
 147             }
 148             false
 149         }
 150
 151         // If any statements are items, we need to create an anonymous module
 152         block.stmts.iter().any(is_item)
 153     }
 154
 155     /// Constructs the reduced graph for one item.
 156     fn build_reduced_graph_for_item(&mut self, item: &Item, parent: Module<'b>) -> Module<'b> {
 157         let name = item.name;
 158         let sp = item.span;
 159         let is_public = item.vis == hir::Public;
 160         let modifiers = if is_public {
 161             DefModifiers::PUBLIC
 162         } else {
 163             DefModifiers::empty()
 164         } | DefModifiers::IMPORTABLE;
 165
 166         match item.node {
 167             ItemUse(ref view_path) => {
 168                 // Extract and intern the module part of the path. For
 169                 // globs and lists, the path is found directly in the AST;
 170                 // for simple paths we have to munge the path a little.
 171                 let module_path = match view_path.node {
 172                     ViewPathSimple(_, ref full_path) => {
 173                         full_path.segments
 174                                  .split_last()
 175                                  .unwrap()
 176                                  .1
 177                                  .iter()
 178                                  .map(|seg| seg.identifier.name)
 179                                  .collect()
 180                     }
 181
 182                     ViewPathGlob(ref module_ident_path) |
 183                     ViewPathList(ref module_ident_path, _) => {
 184                         module_ident_path.segments
 185                                          .iter()
 186                                          .map(|seg| seg.identifier.name)
 187                                          .collect()
 188                     }
 189                 };
 190
 191                 // Build up the import directives.
 192                 let shadowable = item.attrs.iter().any(|attr| {
 193                     attr.name() == special_idents::prelude_import.name.as_str()
 194                 });
 195                 let shadowable = if shadowable {
 196                     Shadowable::Always
 197                 } else {
 198                     Shadowable::Never
 199                 };
 200
 201                 match view_path.node {
 202                     ViewPathSimple(binding, ref full_path) => {
 203                         let source_name = full_path.segments.last().unwrap().identifier.name;
 204                         if source_name.as_str() == "mod" || source_name.as_str() == "self" {
 205                             resolve_error(self,
 206                                           view_path.span,
 207                                           ResolutionError::SelfImportsOnlyAllowedWithin);
 208                         }
 209
 210                         let subclass = SingleImport(binding, source_name);
 211                         self.build_import_directive(parent,
 212                                                     module_path,
 213                                                     subclass,
 214                                                     view_path.span,
 215                                                     item.id,
 216                                                     is_public,
 217                                                     shadowable);
 218                     }
 219                     ViewPathList(_, ref source_items) => {
 220                         // Make sure there's at most one `mod` import in the list.
 221                         let mod_spans = source_items.iter()
 222                                                     .filter_map(|item| {
 223                                                         match item.node {
 224                                                             PathListMod { .. } => Some(item.span),
 225                                                             _ => None,
 226                                                         }
 227                                                     })
 228                                                     .collect::<Vec<Span>>();
 229                         if mod_spans.len() > 1 {
 230                             let mut e = resolve_struct_error(self,
 231                                           mod_spans[0],
 232                                           ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 233                             for other_span in mod_spans.iter().skip(1) {
 234                                 e.span_note(*other_span, "another `self` import appears here");
 235                             }
 236                             e.emit();
 237                         }
 238
 239                         for source_item in source_items {
 240                             let (module_path, name, rename) = match source_item.node {
 241                                 PathListIdent { name, rename, .. } =>
 242                                     (module_path.clone(), name, rename.unwrap_or(name)),
 243                                 PathListMod { rename, .. } => {
 244                                     let name = match module_path.last() {
 245                                         Some(name) => *name,
 246                                         None => {
 247                                             resolve_error(
 248                                                 self,
 249                                                 source_item.span,
 250                                                 ResolutionError::
 251                                                 SelfImportOnlyInImportListWithNonEmptyPrefix
 252                                             );
 253                                             continue;
 254                                         }
 255                                     };
 256                                     let module_path = module_path.split_last().unwrap().1;
 257                                     let rename = rename.unwrap_or(name);
 258                                     (module_path.to_vec(), name, rename)
 259                                 }
 260                             };
 261                             self.build_import_directive(parent,
 262                                                         module_path,
 263                                                         SingleImport(rename, name),
 264                                                         source_item.span,
 265                                                         source_item.node.id(),
 266                                                         is_public,
 267                                                         shadowable);
 268                         }
 269                     }
 270                     ViewPathGlob(_) => {
 271                         self.build_import_directive(parent,
 272                                                     module_path,
 273                                                     GlobImport,
 274                                                     view_path.span,
 275                                                     item.id,
 276                                                     is_public,
 277                                                     shadowable);
 278                     }
 279                 }
 280                 parent
 281             }
 282
 283             ItemExternCrate(_) => {
 284                 // n.b. we don't need to look at the path option here, because cstore already
 285                 // did
 286                 if let Some(crate_id) = self.session.cstore.extern_mod_stmt_cnum(item.id) {
 287                     let def_id = DefId {
 288                         krate: crate_id,
 289                         index: CRATE_DEF_INDEX,
 290                     };
 291                     self.external_exports.insert(def_id);
 292                     let parent_link = ModuleParentLink(parent, name);
 293                     let def = Def::Mod(def_id);
 294                     let local_def_id = self.ast_map.local_def_id(item.id);
 295                     let external_module =
 296                         self.new_extern_crate_module(parent_link, def, is_public, local_def_id);
 297                     self.define(parent, name, TypeNS, (external_module, sp));
 298
 299                     if is_public {
 300                         let export = Export { name: name, def_id: def_id };
 301                         if let Some(def_id) = parent.def_id() {
 302                             let node_id = self.resolver.ast_map.as_local_node_id(def_id).unwrap();
 303                             self.export_map.entry(node_id).or_insert(Vec::new()).push(export);
 304                         }
 305                     }
 306
 307                     self.build_reduced_graph_for_external_crate(external_module);
 308                 }
 309                 parent
 310             }
 311
 312             ItemMod(..) => {
 313                 let parent_link = ModuleParentLink(parent, name);
 314                 let def = Def::Mod(self.ast_map.local_def_id(item.id));
 315                 let module = self.new_module(parent_link, Some(def), false, is_public);
 316                 self.define(parent, name, TypeNS, (module, sp));
 317                 parent.module_children.borrow_mut().insert(item.id, module);
 318                 module
 319             }
 320
 321             ItemForeignMod(..) => parent,
 322
 323             // These items live in the value namespace.
 324             ItemStatic(_, m, _) => {
 325                 let mutbl = m == hir::MutMutable;
 326                 let def = Def::Static(self.ast_map.local_def_id(item.id), mutbl);
 327                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 328                 parent
 329             }
 330             ItemConst(_, _) => {
 331                 let def = Def::Const(self.ast_map.local_def_id(item.id));
 332                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 333                 parent
 334             }
 335             ItemFn(_, _, _, _, _, _) => {
 336                 let def = Def::Fn(self.ast_map.local_def_id(item.id));
 337                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 338                 parent
 339             }
 340
 341             // These items live in the type namespace.
 342             ItemTy(..) => {
 343                 let parent_link = ModuleParentLink(parent, name);
 344                 let def = Def::TyAlias(self.ast_map.local_def_id(item.id));
 345                 let module = self.new_module(parent_link, Some(def), false, is_public);
 346                 self.define(parent, name, TypeNS, (module, sp));
 347                 parent
 348             }
 349
 350             ItemEnum(ref enum_definition, _) => {
 351                 let parent_link = ModuleParentLink(parent, name);
 352                 let def = Def::Enum(self.ast_map.local_def_id(item.id));
 353                 let module = self.new_module(parent_link, Some(def), false, is_public);
 354                 self.define(parent, name, TypeNS, (module, sp));
 355
 356                 let variant_modifiers = if is_public {
 357                     DefModifiers::empty()
 358                 } else {
 359                     DefModifiers::PRIVATE_VARIANT
 360                 };
 361                 for variant in &(*enum_definition).variants {
 362                     let item_def_id = self.ast_map.local_def_id(item.id);
 363                     self.build_reduced_graph_for_variant(variant, item_def_id,
 364                                                          module, variant_modifiers);
 365                 }
 366                 parent
 367             }
 368
 369             // These items live in both the type and value namespaces.
 370             ItemStruct(ref struct_def, _) => {
 371                 // Define a name in the type namespace.
 372                 let def = Def::Struct(self.ast_map.local_def_id(item.id));
 373                 self.define(parent, name, TypeNS, (def, sp, modifiers));
 374
 375                 // If this is a newtype or unit-like struct, define a name
 376                 // in the value namespace as well
 377                 if !struct_def.is_struct() {
 378                     let def = Def::Struct(self.ast_map.local_def_id(struct_def.id()));
 379                     self.define(parent, name, ValueNS, (def, sp, modifiers));
 380                 }
 381
 382                 // Record the def ID and fields of this struct.
 383                 let named_fields = struct_def.fields()
 384                                              .iter()
 385                                              .filter_map(|f| f.node.name)
 386                                              .collect();
 387                 let item_def_id = self.ast_map.local_def_id(item.id);
 388                 self.structs.insert(item_def_id, named_fields);
 389
 390                 parent
 391             }
 392
 393             ItemDefaultImpl(_, _) |
 394             ItemImpl(..) => parent,
 395
 396             ItemTrait(_, _, _, ref items) => {
 397                 let def_id = self.ast_map.local_def_id(item.id);
 398
 399                 // Add all the items within to a new module.
 400                 let parent_link = ModuleParentLink(parent, name);
 401                 let def = Def::Trait(def_id);
 402                 let module_parent = self.new_module(parent_link, Some(def), false, is_public);
 403                 self.define(parent, name, TypeNS, (module_parent, sp));
 404
 405                 // Add the names of all the items to the trait info.
 406                 for item in items {
 407                     let item_def_id = self.ast_map.local_def_id(item.id);
 408                     let (def, ns) = match item.node {
 409                         hir::ConstTraitItem(..) => (Def::AssociatedConst(item_def_id), ValueNS),
 410                         hir::MethodTraitItem(..) => (Def::Method(item_def_id), ValueNS),
 411                         hir::TypeTraitItem(..) => (Def::AssociatedTy(def_id, item_def_id), TypeNS),
 412                     };
 413
 414                     let modifiers = DefModifiers::PUBLIC; // NB: not DefModifiers::IMPORTABLE
 415                     self.define(module_parent, item.name, ns, (def, item.span, modifiers));
 416
 417                     self.trait_item_map.insert((item.name, def_id), item_def_id);
 418                 }
 419
 420                 parent
 421             }
 422         }
 423     }
 424
 425     // Constructs the reduced graph for one variant. Variants exist in the
 426     // type and value namespaces.
 427     fn build_reduced_graph_for_variant(&mut self,
 428                                        variant: &Variant,
 429                                        item_id: DefId,
 430                                        parent: Module<'b>,
 431                                        variant_modifiers: DefModifiers) {
 432         let name = variant.node.name;
 433         if variant.node.data.is_struct() {
 434             // Not adding fields for variants as they are not accessed with a self receiver
 435             let variant_def_id = self.ast_map.local_def_id(variant.node.data.id());
 436             self.structs.insert(variant_def_id, Vec::new());
 437         }
 438
 439         // Variants are always treated as importable to allow them to be glob used.
 440         // All variants are defined in both type and value namespaces as future-proofing.
 441         let modifiers = DefModifiers::PUBLIC | DefModifiers::IMPORTABLE | variant_modifiers;
 442         let def = Def::Variant(item_id, self.ast_map.local_def_id(variant.node.data.id()));
 443
 444         self.define(parent, name, ValueNS, (def, variant.span, modifiers));
 445         self.define(parent, name, TypeNS, (def, variant.span, modifiers));
 446     }
 447
 448     /// Constructs the reduced graph for one foreign item.
 449     fn build_reduced_graph_for_foreign_item(&mut self,
 450                                             foreign_item: &ForeignItem,
 451                                             parent: Module<'b>) {
 452         let name = foreign_item.name;
 453         let is_public = foreign_item.vis == hir::Public;
 454         let modifiers = if is_public {
 455             DefModifiers::PUBLIC
 456         } else {
 457             DefModifiers::empty()
 458         } | DefModifiers::IMPORTABLE;
 459
 460         let def = match foreign_item.node {
 461             ForeignItemFn(..) => {
 462                 Def::Fn(self.ast_map.local_def_id(foreign_item.id))
 463             }
 464             ForeignItemStatic(_, m) => {
 465                 Def::Static(self.ast_map.local_def_id(foreign_item.id), m)
 466             }
 467         };
 468         self.define(parent, name, ValueNS, (def, foreign_item.span, modifiers));
 469     }
 470
 471     fn build_reduced_graph_for_block(&mut self, block: &Block, parent: Module<'b>) -> Module<'b> {
 472         if self.block_needs_anonymous_module(block) {
 473             let block_id = block.id;
 474
 475             debug!("(building reduced graph for block) creating a new anonymous module for block \
 476                     {}",
 477                    block_id);
 478
 479             let parent_link = BlockParentLink(parent, block_id);
 480             let new_module = self.new_module(parent_link, None, false, false);
 481             parent.module_children.borrow_mut().insert(block_id, new_module);
 482             new_module
 483         } else {
 484             parent
 485         }
 486     }
 487
 488     fn handle_external_def(&mut self,
 489                            def: Def,
 490                            vis: Visibility,
 491                            final_ident: &str,
 492                            name: Name,
 493                            new_parent: Module<'b>) {
 494         debug!("(building reduced graph for external crate) building external def {}, priv {:?}",
 495                final_ident,
 496                vis);
 497         let is_public = vis == hir::Public;
 498
 499         let mut modifiers = DefModifiers::empty();
 500         if is_public {
 501             modifiers = modifiers | DefModifiers::PUBLIC;
 502         }
 503         if new_parent.is_normal() {
 504             modifiers = modifiers | DefModifiers::IMPORTABLE;
 505         }
 506
 507         let is_exported = is_public &&
 508                           match new_parent.def_id() {
 509             None => true,
 510             Some(did) => self.external_exports.contains(&did),
 511         };
 512         if is_exported {
 513             self.external_exports.insert(def.def_id());
 514         }
 515
 516         match def {
 517             Def::Mod(_) | Def::ForeignMod(_) | Def::Enum(..) | Def::TyAlias(..) => {
 518                 debug!("(building reduced graph for external crate) building module {} {}",
 519                        final_ident,
 520                        is_public);
 521                 let parent_link = ModuleParentLink(new_parent, name);
 522                 let module = self.new_module(parent_link, Some(def), true, is_public);
 523                 self.try_define(new_parent, name, TypeNS, (module, DUMMY_SP));
 524             }
 525             Def::Variant(_, variant_id) => {
 526                 debug!("(building reduced graph for external crate) building variant {}",
 527                        final_ident);
 528                 // Variants are always treated as importable to allow them to be glob used.
 529                 // All variants are defined in both type and value namespaces as future-proofing.
 530                 let modifiers = DefModifiers::PUBLIC | DefModifiers::IMPORTABLE;
 531                 self.try_define(new_parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 532                 self.try_define(new_parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 533                 if self.session.cstore.variant_kind(variant_id) == Some(VariantKind::Struct) {
 534                     // Not adding fields for variants as they are not accessed with a self receiver
 535                     self.structs.insert(variant_id, Vec::new());
 536                 }
 537             }
 538             Def::Fn(..) |
 539             Def::Static(..) |
 540             Def::Const(..) |
 541             Def::AssociatedConst(..) |
 542             Def::Method(..) => {
 543                 debug!("(building reduced graph for external crate) building value (fn/static) {}",
 544                        final_ident);
 545                 self.try_define(new_parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 546             }
 547             Def::Trait(def_id) => {
 548                 debug!("(building reduced graph for external crate) building type {}",
 549                        final_ident);
 550
 551                 // If this is a trait, add all the trait item names to the trait
 552                 // info.
 553
 554                 let trait_item_def_ids = self.session.cstore.trait_item_def_ids(def_id);
 555                 for trait_item_def in &trait_item_def_ids {
 556                     let trait_item_name =
 557                         self.session.cstore.item_name(trait_item_def.def_id());
 558
 559                     debug!("(building reduced graph for external crate) ... adding trait item \
 560                             '{}'",
 561                            trait_item_name);
 562
 563                     self.trait_item_map.insert((trait_item_name, def_id), trait_item_def.def_id());
 564
 565                     if is_exported {
 566                         self.external_exports.insert(trait_item_def.def_id());
 567                     }
 568                 }
 569
 570                 let parent_link = ModuleParentLink(new_parent, name);
 571                 let module = self.new_module(parent_link, Some(def), true, is_public);
 572                 self.try_define(new_parent, name, TypeNS, (module, DUMMY_SP));
 573             }
 574             Def::AssociatedTy(..) => {
 575                 debug!("(building reduced graph for external crate) building type {}",
 576                        final_ident);
 577                 self.try_define(new_parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 578             }
 579             Def::Struct(def_id)
 580                 if self.session.cstore.tuple_struct_definition_if_ctor(def_id).is_none() => {
 581                 debug!("(building reduced graph for external crate) building type and value for \
 582                         {}",
 583                        final_ident);
 584                 self.try_define(new_parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 585                 if let Some(ctor_def_id) = self.session.cstore.struct_ctor_def_id(def_id) {
 586                     let def = Def::Struct(ctor_def_id);
 587                     self.try_define(new_parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 588                 }
 589
 590                 // Record the def ID and fields of this struct.
 591                 let fields = self.session.cstore.struct_field_names(def_id);
 592                 self.structs.insert(def_id, fields);
 593             }
 594             Def::Struct(..) => {}
 595             Def::Local(..) |
 596             Def::PrimTy(..) |
 597             Def::TyParam(..) |
 598             Def::Upvar(..) |
 599             Def::Label(..) |
 600             Def::SelfTy(..) |
 601             Def::Err => {
 602                 panic!("didn't expect `{:?}`", def);
 603             }
 604         }
 605     }
 606
 607     /// Builds the reduced graph for a single item in an external crate.
 608     fn build_reduced_graph_for_external_crate_def(&mut self,
 609                                                   root: Module<'b>,
 610                                                   xcdef: ChildItem) {
 611         match xcdef.def {
 612             DlDef(def) => {
 613                 // Add the new child item, if necessary.
 614                 match def {
 615                     Def::ForeignMod(def_id) => {
 616                         // Foreign modules have no names. Recur and populate
 617                         // eagerly.
 618                         for child in self.session.cstore.item_children(def_id) {
 619                             self.build_reduced_graph_for_external_crate_def(root, child)
 620                         }
 621                     }
 622                     _ => {
 623                         self.handle_external_def(def,
 624                                                  xcdef.vis,
 625                                                  &xcdef.name.as_str(),
 626                                                  xcdef.name,
 627                                                  root);
 628                     }
 629                 }
 630             }
 631             DlImpl(_) => {
 632                 debug!("(building reduced graph for external crate) ignoring impl");
 633             }
 634             DlField => {
 635                 debug!("(building reduced graph for external crate) ignoring field");
 636             }
 637         }
 638     }
 639
 640     /// Builds the reduced graph rooted at the given external module.
 641     fn populate_external_module(&mut self, module: Module<'b>) {
 642         debug!("(populating external module) attempting to populate {}",
 643                module_to_string(module));
 644
 645         let def_id = match module.def_id() {
 646             None => {
 647                 debug!("(populating external module) ... no def ID!");
 648                 return;
 649             }
 650             Some(def_id) => def_id,
 651         };
 652
 653         for child in self.session.cstore.item_children(def_id) {
 654             debug!("(populating external module) ... found ident: {}",
 655                    child.name);
 656             self.build_reduced_graph_for_external_crate_def(module, child);
 657         }
 658         module.populated.set(true)
 659     }
 660
 661     /// Ensures that the reduced graph rooted at the given external module
 662     /// is built, building it if it is not.
 663     fn populate_module_if_necessary(&mut self, module: Module<'b>) {
 664         if !module.populated.get() {
 665             self.populate_external_module(module)
 666         }
 667         assert!(module.populated.get())
 668     }
 669
 670     /// Builds the reduced graph rooted at the 'use' directive for an external
 671     /// crate.
 672     fn build_reduced_graph_for_external_crate(&mut self, root: Module<'b>) {
 673         let root_cnum = root.def_id().unwrap().krate;
 674         for child in self.session.cstore.crate_top_level_items(root_cnum) {
 675             self.build_reduced_graph_for_external_crate_def(root, child);
 676         }
 677     }
 678
 679     /// Creates and adds an import directive to the given module.
 680     fn build_import_directive(&mut self,
 681                               module_: Module<'b>,
 682                               module_path: Vec<Name>,
 683                               subclass: ImportDirectiveSubclass,
 684                               span: Span,
 685                               id: NodeId,
 686                               is_public: bool,
 687                               shadowable: Shadowable) {
 688         module_.unresolved_imports
 689                .borrow_mut()
 690                .push(ImportDirective::new(module_path, subclass, span, id, is_public, shadowable));
 691         self.unresolved_imports += 1;
 692
 693         if is_public {
 694             module_.inc_pub_count();
 695         }
 696
 697         // Bump the reference count on the name. Or, if this is a glob, set
 698         // the appropriate flag.
 699
 700         match subclass {
 701             SingleImport(target, _) => {
 702                 module_.increment_outstanding_references_for(target, ValueNS);
 703                 module_.increment_outstanding_references_for(target, TypeNS);
 704             }
 705             GlobImport => {
 706                 // Set the glob flag. This tells us that we don't know the
 707                 // module's exports ahead of time.
 708
 709                 module_.inc_glob_count();
 710                 if is_public {
 711                     module_.inc_pub_glob_count();
 712                 }
 713             }
 714         }
 715     }
 716 }
 717
 718 struct BuildReducedGraphVisitor<'a, 'b: 'a, 'tcx: 'b> {
 719     builder: GraphBuilder<'a, 'b, 'tcx>,
 720     parent: Module<'b>,
 721 }
 722
 723 impl<'a, 'b, 'v, 'tcx> Visitor<'v> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
 724     fn visit_nested_item(&mut self, item: hir::ItemId) {
 725         self.visit_item(self.builder.resolver.ast_map.expect_item(item.id))
 726     }
 727
 728     fn visit_item(&mut self, item: &Item) {
 729         let p = self.builder.build_reduced_graph_for_item(item, &self.parent);
 730         let old_parent = replace(&mut self.parent, p);
 731         intravisit::walk_item(self, item);
 732         self.parent = old_parent;
 733     }
 734
 735     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
 736         self.builder.build_reduced_graph_for_foreign_item(foreign_item, &self.parent);
 737     }
 738
 739     fn visit_block(&mut self, block: &Block) {
 740         let np = self.builder.build_reduced_graph_for_block(block, &self.parent);
 741         let old_parent = replace(&mut self.parent, np);
 742         intravisit::walk_block(self, block);
 743         self.parent = old_parent;
 744     }
 745 }
 746
 747 pub fn build_reduced_graph(resolver: &mut Resolver, krate: &hir::Crate) {
 748     GraphBuilder { resolver: resolver }.build_reduced_graph(krate);
 749 }
 750
 751 pub fn populate_module_if_necessary<'a, 'tcx>(resolver: &mut Resolver<'a, 'tcx>,
 752                                               module: Module<'a>) {
 753     GraphBuilder { resolver: resolver }.populate_module_if_necessary(module);
 754 }