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::ImportDirectiveSubclass::{self, GlobImport};
  18 use Module;
  19 use Namespace::{self, TypeNS, ValueNS};
  20 use {NameBinding, NameBindingKind};
  21 use ParentLink::{ModuleParentLink, BlockParentLink};
  22 use Resolver;
  23 use {resolve_error, resolve_struct_error, ResolutionError};
  24
  25 use rustc::middle::cstore::{CrateStore, ChildItem, DlDef};
  26 use rustc::lint;
  27 use rustc::hir::def::*;
  28 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
  29 use rustc::ty::{self, VariantKind};
  30
  31 use syntax::ast::Name;
  32 use syntax::attr::AttrMetaMethods;
  33 use syntax::parse::token::{special_idents, SELF_KEYWORD_NAME, SUPER_KEYWORD_NAME};
  34 use syntax::codemap::{Span, DUMMY_SP};
  35
  36 use rustc::hir;
  37 use rustc::hir::{Block, DeclItem};
  38 use rustc::hir::{ForeignItem, ForeignItemFn, ForeignItemStatic};
  39 use rustc::hir::{Item, ItemConst, ItemEnum, ItemExternCrate, ItemFn};
  40 use rustc::hir::{ItemForeignMod, ItemImpl, ItemMod, ItemStatic, ItemDefaultImpl};
  41 use rustc::hir::{ItemStruct, ItemTrait, ItemTy, ItemUse};
  42 use rustc::hir::{PathListIdent, PathListMod, StmtDecl};
  43 use rustc::hir::{Variant, ViewPathGlob, ViewPathList, ViewPathSimple};
  44 use rustc::hir::intravisit::{self, Visitor};
  45
  46 trait ToNameBinding<'a> {
  47     fn to_name_binding(self) -> NameBinding<'a>;
  48 }
  49
  50 impl<'a> ToNameBinding<'a> for (Module<'a>, Span) {
  51     fn to_name_binding(self) -> NameBinding<'a> {
  52         NameBinding::create_from_module(self.0, Some(self.1))
  53     }
  54 }
  55
  56 impl<'a> ToNameBinding<'a> for (Def, Span, DefModifiers) {
  57     fn to_name_binding(self) -> NameBinding<'a> {
  58         let kind = NameBindingKind::Def(self.0);
  59         NameBinding { modifiers: self.2, kind: kind, span: Some(self.1) }
  60     }
  61 }
  62
  63 impl<'b, 'tcx:'b> Resolver<'b, 'tcx> {
  64     /// Constructs the reduced graph for the entire crate.
  65     pub fn build_reduced_graph(&mut self, krate: &hir::Crate) {
  66         let mut visitor = BuildReducedGraphVisitor {
  67             parent: self.graph_root,
  68             resolver: self,
  69         };
  70         intravisit::walk_crate(&mut visitor, krate);
  71     }
  72
  73     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined.
  74     fn try_define<T>(&self, parent: Module<'b>, name: Name, ns: Namespace, def: T)
  75         where T: ToNameBinding<'b>
  76     {
  77         let _ = parent.try_define_child(name, ns, def.to_name_binding());
  78     }
  79
  80     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
  81     /// otherwise, reports an error.
  82     fn define<T: ToNameBinding<'b>>(&self, parent: Module<'b>, name: Name, ns: Namespace, def: T) {
  83         let binding = def.to_name_binding();
  84         if let Err(old_binding) = parent.try_define_child(name, ns, binding.clone()) {
  85             self.report_conflict(parent, name, ns, old_binding, &binding);
  86         }
  87     }
  88
  89     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
  90         fn is_item(statement: &hir::Stmt) -> bool {
  91             if let StmtDecl(ref declaration, _) = statement.node {
  92                 if let DeclItem(_) = declaration.node {
  93                     return true;
  94                 }
  95             }
  96             false
  97         }
  98
  99         // If any statements are items, we need to create an anonymous module
 100         block.stmts.iter().any(is_item)
 101     }
 102
 103     /// Constructs the reduced graph for one item.
 104     fn build_reduced_graph_for_item(&mut self, item: &Item, parent_ref: &mut Module<'b>) {
 105         let parent = *parent_ref;
 106         let name = item.name;
 107         let sp = item.span;
 108         let is_public = item.vis == hir::Public;
 109         let modifiers = if is_public {
 110             DefModifiers::PUBLIC
 111         } else {
 112             DefModifiers::empty()
 113         } | DefModifiers::IMPORTABLE;
 114
 115         match item.node {
 116             ItemUse(ref view_path) => {
 117                 // Extract and intern the module part of the path. For
 118                 // globs and lists, the path is found directly in the AST;
 119                 // for simple paths we have to munge the path a little.
 120                 let is_global;
 121                 let module_path: Vec<Name> = match view_path.node {
 122                     ViewPathSimple(_, ref full_path) => {
 123                         is_global = full_path.global;
 124                         full_path.segments
 125                                  .split_last()
 126                                  .unwrap()
 127                                  .1
 128                                  .iter()
 129                                  .map(|seg| seg.identifier.name)
 130                                  .collect()
 131                     }
 132
 133                     ViewPathGlob(ref module_ident_path) |
 134                     ViewPathList(ref module_ident_path, _) => {
 135                         is_global = module_ident_path.global;
 136                         module_ident_path.segments
 137                                          .iter()
 138                                          .map(|seg| seg.identifier.name)
 139                                          .collect()
 140                     }
 141                 };
 142
 143                 // Checking for special identifiers in path
 144                 // prevent `self` or `super` at beginning of global path
 145                 if is_global && (module_path.first() == Some(&SELF_KEYWORD_NAME) ||
 146                                  module_path.first() == Some(&SUPER_KEYWORD_NAME)) {
 147                     self.session.add_lint(
 148                         lint::builtin::SUPER_OR_SELF_IN_GLOBAL_PATH,
 149                         item.id,
 150                         item.span,
 151                         format!("expected identifier, found keyword `{}`",
 152                                 module_path.first().unwrap().as_str()));
 153                 }
 154
 155                 // Build up the import directives.
 156                 let is_prelude = item.attrs.iter().any(|attr| {
 157                     attr.name() == special_idents::prelude_import.name.as_str()
 158                 });
 159
 160                 match view_path.node {
 161                     ViewPathSimple(binding, ref full_path) => {
 162                         let source_name = full_path.segments.last().unwrap().identifier.name;
 163                         if source_name.as_str() == "mod" || source_name.as_str() == "self" {
 164                             resolve_error(self,
 165                                           view_path.span,
 166                                           ResolutionError::SelfImportsOnlyAllowedWithin);
 167                         }
 168
 169                         let subclass = ImportDirectiveSubclass::single(binding, source_name);
 170                         self.unresolved_imports += 1;
 171                         parent.add_import_directive(module_path,
 172                                                     subclass,
 173                                                     view_path.span,
 174                                                     item.id,
 175                                                     is_public,
 176                                                     is_prelude);
 177                     }
 178                     ViewPathList(_, ref source_items) => {
 179                         // Make sure there's at most one `mod` import in the list.
 180                         let mod_spans = source_items.iter()
 181                                                     .filter_map(|item| {
 182                                                         match item.node {
 183                                                             PathListMod { .. } => Some(item.span),
 184                                                             _ => None,
 185                                                         }
 186                                                     })
 187                                                     .collect::<Vec<Span>>();
 188                         if mod_spans.len() > 1 {
 189                             let mut e = resolve_struct_error(self,
 190                                           mod_spans[0],
 191                                           ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 192                             for other_span in mod_spans.iter().skip(1) {
 193                                 e.span_note(*other_span, "another `self` import appears here");
 194                             }
 195                             e.emit();
 196                         }
 197
 198                         for source_item in source_items {
 199                             let (module_path, name, rename) = match source_item.node {
 200                                 PathListIdent { name, rename, .. } =>
 201                                     (module_path.clone(), name, rename.unwrap_or(name)),
 202                                 PathListMod { rename, .. } => {
 203                                     let name = match module_path.last() {
 204                                         Some(name) => *name,
 205                                         None => {
 206                                             resolve_error(
 207                                                 self,
 208                                                 source_item.span,
 209                                                 ResolutionError::
 210                                                 SelfImportOnlyInImportListWithNonEmptyPrefix
 211                                             );
 212                                             continue;
 213                                         }
 214                                     };
 215                                     let module_path = module_path.split_last().unwrap().1;
 216                                     let rename = rename.unwrap_or(name);
 217                                     (module_path.to_vec(), name, rename)
 218                                 }
 219                             };
 220                             let subclass = ImportDirectiveSubclass::single(rename, name);
 221                             self.unresolved_imports += 1;
 222                             parent.add_import_directive(module_path,
 223                                                         subclass,
 224                                                         source_item.span,
 225                                                         source_item.node.id(),
 226                                                         is_public,
 227                                                         is_prelude);
 228                         }
 229                     }
 230                     ViewPathGlob(_) => {
 231                         self.unresolved_imports += 1;
 232                         parent.add_import_directive(module_path,
 233                                                     GlobImport,
 234                                                     view_path.span,
 235                                                     item.id,
 236                                                     is_public,
 237                                                     is_prelude);
 238                     }
 239                 }
 240             }
 241
 242             ItemExternCrate(_) => {
 243                 // n.b. we don't need to look at the path option here, because cstore already
 244                 // did
 245                 if let Some(crate_id) = self.session.cstore.extern_mod_stmt_cnum(item.id) {
 246                     let def_id = DefId {
 247                         krate: crate_id,
 248                         index: CRATE_DEF_INDEX,
 249                     };
 250                     let parent_link = ModuleParentLink(parent, name);
 251                     let def = Def::Mod(def_id);
 252                     let module = self.new_extern_crate_module(parent_link, def, is_public, item.id);
 253                     self.define(parent, name, TypeNS, (module, sp));
 254
 255                     self.build_reduced_graph_for_external_crate(module);
 256                 }
 257             }
 258
 259             ItemMod(..) => {
 260                 let parent_link = ModuleParentLink(parent, name);
 261                 let def = Def::Mod(self.ast_map.local_def_id(item.id));
 262                 let module = self.new_module(parent_link, Some(def), false, is_public);
 263                 self.define(parent, name, TypeNS, (module, sp));
 264                 parent.module_children.borrow_mut().insert(item.id, module);
 265                 *parent_ref = module;
 266             }
 267
 268             ItemForeignMod(..) => {}
 269
 270             // These items live in the value namespace.
 271             ItemStatic(_, m, _) => {
 272                 let mutbl = m == hir::MutMutable;
 273                 let def = Def::Static(self.ast_map.local_def_id(item.id), mutbl);
 274                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 275             }
 276             ItemConst(_, _) => {
 277                 let def = Def::Const(self.ast_map.local_def_id(item.id));
 278                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 279             }
 280             ItemFn(_, _, _, _, _, _) => {
 281                 let def = Def::Fn(self.ast_map.local_def_id(item.id));
 282                 self.define(parent, name, ValueNS, (def, sp, modifiers));
 283             }
 284
 285             // These items live in the type namespace.
 286             ItemTy(..) => {
 287                 let def = Def::TyAlias(self.ast_map.local_def_id(item.id));
 288                 self.define(parent, name, TypeNS, (def, sp, modifiers));
 289             }
 290
 291             ItemEnum(ref enum_definition, _) => {
 292                 let parent_link = ModuleParentLink(parent, name);
 293                 let def = Def::Enum(self.ast_map.local_def_id(item.id));
 294                 let module = self.new_module(parent_link, Some(def), false, is_public);
 295                 self.define(parent, name, TypeNS, (module, sp));
 296
 297                 let variant_modifiers = if is_public {
 298                     DefModifiers::empty()
 299                 } else {
 300                     DefModifiers::PRIVATE_VARIANT
 301                 };
 302                 for variant in &(*enum_definition).variants {
 303                     let item_def_id = self.ast_map.local_def_id(item.id);
 304                     self.build_reduced_graph_for_variant(variant, item_def_id,
 305                                                          module, variant_modifiers);
 306                 }
 307             }
 308
 309             // These items live in both the type and value namespaces.
 310             ItemStruct(ref struct_def, _) => {
 311                 // Define a name in the type namespace.
 312                 let def = Def::Struct(self.ast_map.local_def_id(item.id));
 313                 self.define(parent, name, TypeNS, (def, sp, modifiers));
 314
 315                 // If this is a newtype or unit-like struct, define a name
 316                 // in the value namespace as well
 317                 if !struct_def.is_struct() {
 318                     let def = Def::Struct(self.ast_map.local_def_id(struct_def.id()));
 319                     self.define(parent, name, ValueNS, (def, sp, modifiers));
 320                 }
 321
 322                 // Record the def ID and fields of this struct.
 323                 let field_names = struct_def.fields()
 324                                             .iter()
 325                                             .map(|f| f.name)
 326                                             .collect();
 327                 let item_def_id = self.ast_map.local_def_id(item.id);
 328                 self.structs.insert(item_def_id, field_names);
 329             }
 330
 331             ItemDefaultImpl(_, _) | ItemImpl(..) => {}
 332
 333             ItemTrait(_, _, _, ref items) => {
 334                 let def_id = self.ast_map.local_def_id(item.id);
 335
 336                 // Add all the items within to a new module.
 337                 let parent_link = ModuleParentLink(parent, name);
 338                 let def = Def::Trait(def_id);
 339                 let module_parent = self.new_module(parent_link, Some(def), false, is_public);
 340                 self.define(parent, name, TypeNS, (module_parent, sp));
 341
 342                 // Add the names of all the items to the trait info.
 343                 for item in items {
 344                     let item_def_id = self.ast_map.local_def_id(item.id);
 345                     let (def, ns) = match item.node {
 346                         hir::ConstTraitItem(..) => (Def::AssociatedConst(item_def_id), ValueNS),
 347                         hir::MethodTraitItem(..) => (Def::Method(item_def_id), ValueNS),
 348                         hir::TypeTraitItem(..) => (Def::AssociatedTy(def_id, item_def_id), TypeNS),
 349                     };
 350
 351                     let modifiers = DefModifiers::PUBLIC; // NB: not DefModifiers::IMPORTABLE
 352                     self.define(module_parent, item.name, ns, (def, item.span, modifiers));
 353
 354                     self.trait_item_map.insert((item.name, def_id), item_def_id);
 355                 }
 356             }
 357         }
 358     }
 359
 360     // Constructs the reduced graph for one variant. Variants exist in the
 361     // type and value namespaces.
 362     fn build_reduced_graph_for_variant(&mut self,
 363                                        variant: &Variant,
 364                                        item_id: DefId,
 365                                        parent: Module<'b>,
 366                                        variant_modifiers: DefModifiers) {
 367         let name = variant.node.name;
 368         if variant.node.data.is_struct() {
 369             // Not adding fields for variants as they are not accessed with a self receiver
 370             let variant_def_id = self.ast_map.local_def_id(variant.node.data.id());
 371             self.structs.insert(variant_def_id, Vec::new());
 372         }
 373
 374         // Variants are always treated as importable to allow them to be glob used.
 375         // All variants are defined in both type and value namespaces as future-proofing.
 376         let modifiers = DefModifiers::PUBLIC | DefModifiers::IMPORTABLE | variant_modifiers;
 377         let def = Def::Variant(item_id, self.ast_map.local_def_id(variant.node.data.id()));
 378
 379         self.define(parent, name, ValueNS, (def, variant.span, modifiers));
 380         self.define(parent, name, TypeNS, (def, variant.span, modifiers));
 381     }
 382
 383     /// Constructs the reduced graph for one foreign item.
 384     fn build_reduced_graph_for_foreign_item(&mut self,
 385                                             foreign_item: &ForeignItem,
 386                                             parent: Module<'b>) {
 387         let name = foreign_item.name;
 388         let is_public = foreign_item.vis == hir::Public;
 389         let modifiers = if is_public {
 390             DefModifiers::PUBLIC
 391         } else {
 392             DefModifiers::empty()
 393         } | DefModifiers::IMPORTABLE;
 394
 395         let def = match foreign_item.node {
 396             ForeignItemFn(..) => {
 397                 Def::Fn(self.ast_map.local_def_id(foreign_item.id))
 398             }
 399             ForeignItemStatic(_, m) => {
 400                 Def::Static(self.ast_map.local_def_id(foreign_item.id), m)
 401             }
 402         };
 403         self.define(parent, name, ValueNS, (def, foreign_item.span, modifiers));
 404     }
 405
 406     fn build_reduced_graph_for_block(&mut self, block: &Block, parent: &mut Module<'b>) {
 407         if self.block_needs_anonymous_module(block) {
 408             let block_id = block.id;
 409
 410             debug!("(building reduced graph for block) creating a new anonymous module for block \
 411                     {}",
 412                    block_id);
 413
 414             let parent_link = BlockParentLink(parent, block_id);
 415             let new_module = self.new_module(parent_link, None, false, false);
 416             parent.module_children.borrow_mut().insert(block_id, new_module);
 417             *parent = new_module;
 418         }
 419     }
 420
 421     /// Builds the reduced graph for a single item in an external crate.
 422     fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'b>, xcdef: ChildItem) {
 423         let def = match xcdef.def {
 424             DlDef(def) => def,
 425             _ => return,
 426         };
 427
 428         if let Def::ForeignMod(def_id) = def {
 429             // Foreign modules have no names. Recur and populate eagerly.
 430             for child in self.session.cstore.item_children(def_id) {
 431                 self.build_reduced_graph_for_external_crate_def(parent, child);
 432             }
 433             return;
 434         }
 435
 436         let name = xcdef.name;
 437         let is_public = xcdef.vis == ty::Visibility::Public || parent.is_trait();
 438
 439         let mut modifiers = DefModifiers::empty();
 440         if is_public {
 441             modifiers = modifiers | DefModifiers::PUBLIC;
 442         }
 443         if parent.is_normal() {
 444             modifiers = modifiers | DefModifiers::IMPORTABLE;
 445         }
 446
 447         match def {
 448             Def::Mod(_) | Def::ForeignMod(_) | Def::Enum(..) => {
 449                 debug!("(building reduced graph for external crate) building module {} {}",
 450                        name,
 451                        is_public);
 452                 let parent_link = ModuleParentLink(parent, name);
 453                 let module = self.new_module(parent_link, Some(def), true, is_public);
 454                 self.try_define(parent, name, TypeNS, (module, DUMMY_SP));
 455             }
 456             Def::Variant(_, variant_id) => {
 457                 debug!("(building reduced graph for external crate) building variant {}", name);
 458                 // Variants are always treated as importable to allow them to be glob used.
 459                 // All variants are defined in both type and value namespaces as future-proofing.
 460                 let modifiers = DefModifiers::PUBLIC | DefModifiers::IMPORTABLE;
 461                 self.try_define(parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 462                 self.try_define(parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 463                 if self.session.cstore.variant_kind(variant_id) == Some(VariantKind::Struct) {
 464                     // Not adding fields for variants as they are not accessed with a self receiver
 465                     self.structs.insert(variant_id, Vec::new());
 466                 }
 467             }
 468             Def::Fn(..) |
 469             Def::Static(..) |
 470             Def::Const(..) |
 471             Def::AssociatedConst(..) |
 472             Def::Method(..) => {
 473                 debug!("(building reduced graph for external crate) building value (fn/static) {}",
 474                        name);
 475                 self.try_define(parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 476             }
 477             Def::Trait(def_id) => {
 478                 debug!("(building reduced graph for external crate) building type {}", name);
 479
 480                 // If this is a trait, add all the trait item names to the trait
 481                 // info.
 482
 483                 let trait_item_def_ids = self.session.cstore.trait_item_def_ids(def_id);
 484                 for trait_item_def in &trait_item_def_ids {
 485                     let trait_item_name =
 486                         self.session.cstore.item_name(trait_item_def.def_id());
 487
 488                     debug!("(building reduced graph for external crate) ... adding trait item \
 489                             '{}'",
 490                            trait_item_name);
 491
 492                     self.trait_item_map.insert((trait_item_name, def_id), trait_item_def.def_id());
 493                 }
 494
 495                 let parent_link = ModuleParentLink(parent, name);
 496                 let module = self.new_module(parent_link, Some(def), true, is_public);
 497                 self.try_define(parent, name, TypeNS, (module, DUMMY_SP));
 498             }
 499             Def::TyAlias(..) | Def::AssociatedTy(..) => {
 500                 debug!("(building reduced graph for external crate) building type {}", name);
 501                 self.try_define(parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 502             }
 503             Def::Struct(def_id)
 504                 if self.session.cstore.tuple_struct_definition_if_ctor(def_id).is_none() => {
 505                 debug!("(building reduced graph for external crate) building type and value for {}",
 506                        name);
 507                 self.try_define(parent, name, TypeNS, (def, DUMMY_SP, modifiers));
 508                 if let Some(ctor_def_id) = self.session.cstore.struct_ctor_def_id(def_id) {
 509                     let def = Def::Struct(ctor_def_id);
 510                     self.try_define(parent, name, ValueNS, (def, DUMMY_SP, modifiers));
 511                 }
 512
 513                 // Record the def ID and fields of this struct.
 514                 let fields = self.session.cstore.struct_field_names(def_id);
 515                 self.structs.insert(def_id, fields);
 516             }
 517             Def::Struct(..) => {}
 518             Def::Local(..) |
 519             Def::PrimTy(..) |
 520             Def::TyParam(..) |
 521             Def::Upvar(..) |
 522             Def::Label(..) |
 523             Def::SelfTy(..) |
 524             Def::Err => {
 525                 bug!("didn't expect `{:?}`", def);
 526             }
 527         }
 528     }
 529
 530     /// Builds the reduced graph rooted at the 'use' directive for an external
 531     /// crate.
 532     fn build_reduced_graph_for_external_crate(&mut self, root: Module<'b>) {
 533         let root_cnum = root.def_id().unwrap().krate;
 534         for child in self.session.cstore.crate_top_level_items(root_cnum) {
 535             self.build_reduced_graph_for_external_crate_def(root, child);
 536         }
 537     }
 538
 539     /// Ensures that the reduced graph rooted at the given external module
 540     /// is built, building it if it is not.
 541     pub fn populate_module_if_necessary(&mut self, module: Module<'b>) {
 542         if module.populated.get() { return }
 543         for child in self.session.cstore.item_children(module.def_id().unwrap()) {
 544             self.build_reduced_graph_for_external_crate_def(module, child);
 545         }
 546         module.populated.set(true)
 547     }
 548 }
 549
 550 struct BuildReducedGraphVisitor<'a, 'b: 'a, 'tcx: 'b> {
 551     resolver: &'a mut Resolver<'b, 'tcx>,
 552     parent: Module<'b>,
 553 }
 554
 555 impl<'a, 'b, 'v, 'tcx> Visitor<'v> for BuildReducedGraphVisitor<'a, 'b, 'tcx> {
 556     fn visit_nested_item(&mut self, item: hir::ItemId) {
 557         self.visit_item(self.resolver.ast_map.expect_item(item.id))
 558     }
 559
 560     fn visit_item(&mut self, item: &Item) {
 561         let old_parent = self.parent;
 562         self.resolver.build_reduced_graph_for_item(item, &mut self.parent);
 563         intravisit::walk_item(self, item);
 564         self.parent = old_parent;
 565     }
 566
 567     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
 568         self.resolver.build_reduced_graph_for_foreign_item(foreign_item, &self.parent);
 569     }
 570
 571     fn visit_block(&mut self, block: &Block) {
 572         let old_parent = self.parent;
 573         self.resolver.build_reduced_graph_for_block(block, &mut self.parent);
 574         intravisit::walk_block(self, block);
 575         self.parent = old_parent;
 576     }
 577 }