src/librustc_resolve/build_reduced_graph.rs

   1 //! After we obtain a fresh AST fragment from a macro, code in this module helps to integrate
   2 //! that fragment into the module structures that are already partially built.
   3 //!
   4 //! Items from the fragment are placed into modules,
   5 //! unexpanded macros in the fragment are visited and registered.
   6 //! Imports are also considered items and placed into modules here, but not resolved yet.
   7
   8 use crate::def_collector::collect_definitions;
   9 use crate::imports::{Import, ImportKind};
  10 use crate::macros::{LegacyBinding, LegacyScope};
  11 use crate::Namespace::{self, MacroNS, TypeNS, ValueNS};
  12 use crate::{CrateLint, Determinacy, PathResult, ResolutionError, VisResolutionError};
  13 use crate::{
  14     ExternPreludeEntry, ModuleOrUniformRoot, ParentScope, PerNS, Resolver, ResolverArenas,
  15 };
  16 use crate::{Module, ModuleData, ModuleKind, NameBinding, NameBindingKind, Segment, ToNameBinding};
  17
  18 use rustc::bug;
  19 use rustc::hir::exports::Export;
  20 use rustc::middle::cstore::CrateStore;
  21 use rustc::ty;
  22 use rustc_ast::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
  23 use rustc_ast::ast::{AssocItem, AssocItemKind, MetaItemKind, StmtKind};
  24 use rustc_ast::ast::{Ident, Name};
  25 use rustc_ast::token::{self, Token};
  26 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  27 use rustc_attr as attr;
  28 use rustc_data_structures::sync::Lrc;
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_expand::base::SyntaxExtension;
  31 use rustc_expand::expand::AstFragment;
  32 use rustc_hir::def::{self, *};
  33 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
  34 use rustc_metadata::creader::LoadedMacro;
  35 use rustc_span::hygiene::{ExpnId, MacroKind};
  36 use rustc_span::source_map::{respan, Spanned};
  37 use rustc_span::symbol::{kw, sym};
  38 use rustc_span::{Span, DUMMY_SP};
  39
  40 use log::debug;
  41 use std::cell::Cell;
  42 use std::ptr;
  43
  44 type Res = def::Res<NodeId>;
  45
  46 impl<'a> ToNameBinding<'a> for (Module<'a>, ty::Visibility, Span, ExpnId) {
  47     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  48         arenas.alloc_name_binding(NameBinding {
  49             kind: NameBindingKind::Module(self.0),
  50             ambiguity: None,
  51             vis: self.1,
  52             span: self.2,
  53             expansion: self.3,
  54         })
  55     }
  56 }
  57
  58 impl<'a> ToNameBinding<'a> for (Res, ty::Visibility, Span, ExpnId) {
  59     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  60         arenas.alloc_name_binding(NameBinding {
  61             kind: NameBindingKind::Res(self.0, false),
  62             ambiguity: None,
  63             vis: self.1,
  64             span: self.2,
  65             expansion: self.3,
  66         })
  67     }
  68 }
  69
  70 struct IsMacroExport;
  71
  72 impl<'a> ToNameBinding<'a> for (Res, ty::Visibility, Span, ExpnId, IsMacroExport) {
  73     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  74         arenas.alloc_name_binding(NameBinding {
  75             kind: NameBindingKind::Res(self.0, true),
  76             ambiguity: None,
  77             vis: self.1,
  78             span: self.2,
  79             expansion: self.3,
  80         })
  81     }
  82 }
  83
  84 impl<'a> Resolver<'a> {
  85     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
  86     /// otherwise, reports an error.
  87     crate fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
  88     where
  89         T: ToNameBinding<'a>,
  90     {
  91         let binding = def.to_name_binding(self.arenas);
  92         let key = self.new_key(ident, ns);
  93         if let Err(old_binding) = self.try_define(parent, key, binding) {
  94             self.report_conflict(parent, ident, ns, old_binding, &binding);
  95         }
  96     }
  97
  98     crate fn get_module(&mut self, def_id: DefId) -> Module<'a> {
  99         if def_id.krate == LOCAL_CRATE {
 100             return self.module_map[&def_id];
 101         }
 102
 103         if let Some(&module) = self.extern_module_map.get(&def_id) {
 104             return module;
 105         }
 106
 107         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
 108             (self.cstore().crate_name_untracked(def_id.krate), None)
 109         } else {
 110             let def_key = self.cstore().def_key(def_id);
 111             (
 112                 def_key.disambiguated_data.data.get_opt_name().unwrap(),
 113                 Some(self.get_module(DefId { index: def_key.parent.unwrap(), ..def_id })),
 114             )
 115         };
 116
 117         let kind = ModuleKind::Def(DefKind::Mod, def_id, name);
 118         let module = self.arenas.alloc_module(ModuleData::new(
 119             parent,
 120             kind,
 121             def_id,
 122             ExpnId::root(),
 123             DUMMY_SP,
 124         ));
 125         self.extern_module_map.insert(def_id, module);
 126         module
 127     }
 128
 129     crate fn macro_def_scope(&mut self, expn_id: ExpnId) -> Module<'a> {
 130         let def_id = match self.macro_defs.get(&expn_id) {
 131             Some(def_id) => *def_id,
 132             None => return self.ast_transform_scopes.get(&expn_id).unwrap_or(&self.graph_root),
 133         };
 134         if let Some(id) = self.definitions.as_local_node_id(def_id) {
 135             self.local_macro_def_scopes[&id]
 136         } else {
 137             let module_def_id = ty::DefIdTree::parent(&*self, def_id).unwrap();
 138             self.get_module(module_def_id)
 139         }
 140     }
 141
 142     crate fn get_macro(&mut self, res: Res) -> Option<Lrc<SyntaxExtension>> {
 143         match res {
 144             Res::Def(DefKind::Macro(..), def_id) => self.get_macro_by_def_id(def_id),
 145             Res::NonMacroAttr(attr_kind) => Some(self.non_macro_attr(attr_kind.is_used())),
 146             _ => None,
 147         }
 148     }
 149
 150     crate fn get_macro_by_def_id(&mut self, def_id: DefId) -> Option<Lrc<SyntaxExtension>> {
 151         if let Some(ext) = self.macro_map.get(&def_id) {
 152             return Some(ext.clone());
 153         }
 154
 155         let ext = Lrc::new(match self.cstore().load_macro_untracked(def_id, &self.session) {
 156             LoadedMacro::MacroDef(item, edition) => self.compile_macro(&item, edition),
 157             LoadedMacro::ProcMacro(ext) => ext,
 158         });
 159
 160         self.macro_map.insert(def_id, ext.clone());
 161         Some(ext)
 162     }
 163
 164     crate fn build_reduced_graph(
 165         &mut self,
 166         fragment: &AstFragment,
 167         parent_scope: ParentScope<'a>,
 168     ) -> LegacyScope<'a> {
 169         collect_definitions(&mut self.definitions, fragment, parent_scope.expansion);
 170         let mut visitor = BuildReducedGraphVisitor { r: self, parent_scope };
 171         fragment.visit_with(&mut visitor);
 172         visitor.parent_scope.legacy
 173     }
 174
 175     crate fn build_reduced_graph_external(&mut self, module: Module<'a>) {
 176         let def_id = module.def_id().expect("unpopulated module without a def-id");
 177         for child in self.cstore().item_children_untracked(def_id, self.session) {
 178             let child = child.map_id(|_| panic!("unexpected id"));
 179             BuildReducedGraphVisitor { r: self, parent_scope: ParentScope::module(module) }
 180                 .build_reduced_graph_for_external_crate_res(child);
 181         }
 182     }
 183 }
 184
 185 struct BuildReducedGraphVisitor<'a, 'b> {
 186     r: &'b mut Resolver<'a>,
 187     parent_scope: ParentScope<'a>,
 188 }
 189
 190 impl<'a> AsMut<Resolver<'a>> for BuildReducedGraphVisitor<'a, '_> {
 191     fn as_mut(&mut self) -> &mut Resolver<'a> {
 192         self.r
 193     }
 194 }
 195
 196 impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
 197     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
 198         self.resolve_visibility_speculative(vis, false).unwrap_or_else(|err| {
 199             self.r.report_vis_error(err);
 200             ty::Visibility::Public
 201         })
 202     }
 203
 204     fn resolve_visibility_speculative<'ast>(
 205         &mut self,
 206         vis: &'ast ast::Visibility,
 207         speculative: bool,
 208     ) -> Result<ty::Visibility, VisResolutionError<'ast>> {
 209         let parent_scope = &self.parent_scope;
 210         match vis.node {
 211             ast::VisibilityKind::Public => Ok(ty::Visibility::Public),
 212             ast::VisibilityKind::Crate(..) => {
 213                 Ok(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)))
 214             }
 215             ast::VisibilityKind::Inherited => {
 216                 Ok(ty::Visibility::Restricted(parent_scope.module.normal_ancestor_id))
 217             }
 218             ast::VisibilityKind::Restricted { ref path, id, .. } => {
 219                 // For visibilities we are not ready to provide correct implementation of "uniform
 220                 // paths" right now, so on 2018 edition we only allow module-relative paths for now.
 221                 // On 2015 edition visibilities are resolved as crate-relative by default,
 222                 // so we are prepending a root segment if necessary.
 223                 let ident = path.segments.get(0).expect("empty path in visibility").ident;
 224                 let crate_root = if ident.is_path_segment_keyword() {
 225                     None
 226                 } else if ident.span.rust_2015() {
 227                     Some(Segment::from_ident(Ident::new(
 228                         kw::PathRoot,
 229                         path.span.shrink_to_lo().with_ctxt(ident.span.ctxt()),
 230                     )))
 231                 } else {
 232                     return Err(VisResolutionError::Relative2018(ident.span, path));
 233                 };
 234
 235                 let segments = crate_root
 236                     .into_iter()
 237                     .chain(path.segments.iter().map(|seg| seg.into()))
 238                     .collect::<Vec<_>>();
 239                 let expected_found_error = |res| {
 240                     Err(VisResolutionError::ExpectedFound(
 241                         path.span,
 242                         Segment::names_to_string(&segments),
 243                         res,
 244                     ))
 245                 };
 246                 match self.r.resolve_path(
 247                     &segments,
 248                     Some(TypeNS),
 249                     parent_scope,
 250                     !speculative,
 251                     path.span,
 252                     CrateLint::SimplePath(id),
 253                 ) {
 254                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
 255                         let res = module.res().expect("visibility resolved to unnamed block");
 256                         if !speculative {
 257                             self.r.record_partial_res(id, PartialRes::new(res));
 258                         }
 259                         if module.is_normal() {
 260                             if res == Res::Err {
 261                                 Ok(ty::Visibility::Public)
 262                             } else {
 263                                 let vis = ty::Visibility::Restricted(res.def_id());
 264                                 if self.r.is_accessible_from(vis, parent_scope.module) {
 265                                     Ok(vis)
 266                                 } else {
 267                                     Err(VisResolutionError::AncestorOnly(path.span))
 268                                 }
 269                             }
 270                         } else {
 271                             expected_found_error(res)
 272                         }
 273                     }
 274                     PathResult::Module(..) => Err(VisResolutionError::ModuleOnly(path.span)),
 275                     PathResult::NonModule(partial_res) => {
 276                         expected_found_error(partial_res.base_res())
 277                     }
 278                     PathResult::Failed { span, label, suggestion, .. } => {
 279                         Err(VisResolutionError::FailedToResolve(span, label, suggestion))
 280                     }
 281                     PathResult::Indeterminate => Err(VisResolutionError::Indeterminate(path.span)),
 282                 }
 283             }
 284         }
 285     }
 286
 287     fn insert_field_names_local(&mut self, def_id: DefId, vdata: &ast::VariantData) {
 288         let field_names = vdata
 289             .fields()
 290             .iter()
 291             .map(|field| respan(field.span, field.ident.map_or(kw::Invalid, |ident| ident.name)))
 292             .collect();
 293         self.insert_field_names(def_id, field_names);
 294     }
 295
 296     fn insert_field_names(&mut self, def_id: DefId, field_names: Vec<Spanned<Name>>) {
 297         if !field_names.is_empty() {
 298             self.r.field_names.insert(def_id, field_names);
 299         }
 300     }
 301
 302     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 303         // If any statements are items, we need to create an anonymous module
 304         block.stmts.iter().any(|statement| match statement.kind {
 305             StmtKind::Item(_) | StmtKind::Mac(_) => true,
 306             _ => false,
 307         })
 308     }
 309
 310     // Add an import to the current module.
 311     fn add_import(
 312         &mut self,
 313         module_path: Vec<Segment>,
 314         kind: ImportKind<'a>,
 315         span: Span,
 316         id: NodeId,
 317         item: &ast::Item,
 318         root_span: Span,
 319         root_id: NodeId,
 320         vis: ty::Visibility,
 321     ) {
 322         let current_module = self.parent_scope.module;
 323         let import = self.r.arenas.alloc_import(Import {
 324             kind,
 325             parent_scope: self.parent_scope,
 326             module_path,
 327             imported_module: Cell::new(None),
 328             span,
 329             id,
 330             use_span: item.span,
 331             use_span_with_attributes: item.span_with_attributes(),
 332             has_attributes: !item.attrs.is_empty(),
 333             root_span,
 334             root_id,
 335             vis: Cell::new(vis),
 336             used: Cell::new(false),
 337         });
 338
 339         debug!("add_import({:?})", import);
 340
 341         self.r.indeterminate_imports.push(import);
 342         match import.kind {
 343             // Don't add unresolved underscore imports to modules
 344             ImportKind::Single { target: Ident { name: kw::Underscore, .. }, .. } => {}
 345             ImportKind::Single { target, type_ns_only, .. } => {
 346                 self.r.per_ns(|this, ns| {
 347                     if !type_ns_only || ns == TypeNS {
 348                         let key = this.new_key(target, ns);
 349                         let mut resolution = this.resolution(current_module, key).borrow_mut();
 350                         resolution.add_single_import(import);
 351                     }
 352                 });
 353             }
 354             // We don't add prelude imports to the globs since they only affect lexical scopes,
 355             // which are not relevant to import resolution.
 356             ImportKind::Glob { is_prelude: true, .. } => {}
 357             ImportKind::Glob { .. } => current_module.globs.borrow_mut().push(import),
 358             _ => unreachable!(),
 359         }
 360     }
 361
 362     fn build_reduced_graph_for_use_tree(
 363         &mut self,
 364         // This particular use tree
 365         use_tree: &ast::UseTree,
 366         id: NodeId,
 367         parent_prefix: &[Segment],
 368         nested: bool,
 369         // The whole `use` item
 370         item: &Item,
 371         vis: ty::Visibility,
 372         root_span: Span,
 373     ) {
 374         debug!(
 375             "build_reduced_graph_for_use_tree(parent_prefix={:?}, use_tree={:?}, nested={})",
 376             parent_prefix, use_tree, nested
 377         );
 378
 379         let mut prefix_iter = parent_prefix
 380             .iter()
 381             .cloned()
 382             .chain(use_tree.prefix.segments.iter().map(|seg| seg.into()))
 383             .peekable();
 384
 385         // On 2015 edition imports are resolved as crate-relative by default,
 386         // so prefixes are prepended with crate root segment if necessary.
 387         // The root is prepended lazily, when the first non-empty prefix or terminating glob
 388         // appears, so imports in braced groups can have roots prepended independently.
 389         let is_glob = if let ast::UseTreeKind::Glob = use_tree.kind { true } else { false };
 390         let crate_root = match prefix_iter.peek() {
 391             Some(seg) if !seg.ident.is_path_segment_keyword() && seg.ident.span.rust_2015() => {
 392                 Some(seg.ident.span.ctxt())
 393             }
 394             None if is_glob && use_tree.span.rust_2015() => Some(use_tree.span.ctxt()),
 395             _ => None,
 396         }
 397         .map(|ctxt| {
 398             Segment::from_ident(Ident::new(
 399                 kw::PathRoot,
 400                 use_tree.prefix.span.shrink_to_lo().with_ctxt(ctxt),
 401             ))
 402         });
 403
 404         let prefix = crate_root.into_iter().chain(prefix_iter).collect::<Vec<_>>();
 405         debug!("build_reduced_graph_for_use_tree: prefix={:?}", prefix);
 406
 407         let empty_for_self = |prefix: &[Segment]| {
 408             prefix.is_empty() || prefix.len() == 1 && prefix[0].ident.name == kw::PathRoot
 409         };
 410         match use_tree.kind {
 411             ast::UseTreeKind::Simple(rename, ..) => {
 412                 let mut ident = use_tree.ident();
 413                 let mut module_path = prefix;
 414                 let mut source = module_path.pop().unwrap();
 415                 let mut type_ns_only = false;
 416
 417                 if nested {
 418                     // Correctly handle `self`
 419                     if source.ident.name == kw::SelfLower {
 420                         type_ns_only = true;
 421
 422                         if empty_for_self(&module_path) {
 423                             self.r.report_error(
 424                                 use_tree.span,
 425                                 ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix,
 426                             );
 427                             return;
 428                         }
 429
 430                         // Replace `use foo::self;` with `use foo;`
 431                         source = module_path.pop().unwrap();
 432                         if rename.is_none() {
 433                             ident = source.ident;
 434                         }
 435                     }
 436                 } else {
 437                     // Disallow `self`
 438                     if source.ident.name == kw::SelfLower {
 439                         self.r.report_error(
 440                             use_tree.span,
 441                             ResolutionError::SelfImportsOnlyAllowedWithin,
 442                         );
 443                     }
 444
 445                     // Disallow `use $crate;`
 446                     if source.ident.name == kw::DollarCrate && module_path.is_empty() {
 447                         let crate_root = self.r.resolve_crate_root(source.ident);
 448                         let crate_name = match crate_root.kind {
 449                             ModuleKind::Def(.., name) => name,
 450                             ModuleKind::Block(..) => unreachable!(),
 451                         };
 452                         // HACK(eddyb) unclear how good this is, but keeping `$crate`
 453                         // in `source` breaks `src/test/compile-fail/import-crate-var.rs`,
 454                         // while the current crate doesn't have a valid `crate_name`.
 455                         if crate_name != kw::Invalid {
 456                             // `crate_name` should not be interpreted as relative.
 457                             module_path.push(Segment {
 458                                 ident: Ident { name: kw::PathRoot, span: source.ident.span },
 459                                 id: Some(self.r.next_node_id()),
 460                             });
 461                             source.ident.name = crate_name;
 462                         }
 463                         if rename.is_none() {
 464                             ident.name = crate_name;
 465                         }
 466
 467                         self.r
 468                             .session
 469                             .struct_span_err(item.span, "`$crate` may not be imported")
 470                             .emit();
 471                     }
 472                 }
 473
 474                 if ident.name == kw::Crate {
 475                     self.r.session.span_err(
 476                         ident.span,
 477                         "crate root imports need to be explicitly named: \
 478                          `use crate as name;`",
 479                     );
 480                 }
 481
 482                 let kind = ImportKind::Single {
 483                     source: source.ident,
 484                     target: ident,
 485                     source_bindings: PerNS {
 486                         type_ns: Cell::new(Err(Determinacy::Undetermined)),
 487                         value_ns: Cell::new(Err(Determinacy::Undetermined)),
 488                         macro_ns: Cell::new(Err(Determinacy::Undetermined)),
 489                     },
 490                     target_bindings: PerNS {
 491                         type_ns: Cell::new(None),
 492                         value_ns: Cell::new(None),
 493                         macro_ns: Cell::new(None),
 494                     },
 495                     type_ns_only,
 496                     nested,
 497                 };
 498                 self.add_import(
 499                     module_path,
 500                     kind,
 501                     use_tree.span,
 502                     id,
 503                     item,
 504                     root_span,
 505                     item.id,
 506                     vis,
 507                 );
 508             }
 509             ast::UseTreeKind::Glob => {
 510                 let kind = ImportKind::Glob {
 511                     is_prelude: attr::contains_name(&item.attrs, sym::prelude_import),
 512                     max_vis: Cell::new(ty::Visibility::Invisible),
 513                 };
 514                 self.add_import(prefix, kind, use_tree.span, id, item, root_span, item.id, vis);
 515             }
 516             ast::UseTreeKind::Nested(ref items) => {
 517                 // Ensure there is at most one `self` in the list
 518                 let self_spans = items
 519                     .iter()
 520                     .filter_map(|&(ref use_tree, _)| {
 521                         if let ast::UseTreeKind::Simple(..) = use_tree.kind {
 522                             if use_tree.ident().name == kw::SelfLower {
 523                                 return Some(use_tree.span);
 524                             }
 525                         }
 526
 527                         None
 528                     })
 529                     .collect::<Vec<_>>();
 530                 if self_spans.len() > 1 {
 531                     let mut e = self.r.into_struct_error(
 532                         self_spans[0],
 533                         ResolutionError::SelfImportCanOnlyAppearOnceInTheList,
 534                     );
 535
 536                     for other_span in self_spans.iter().skip(1) {
 537                         e.span_label(*other_span, "another `self` import appears here");
 538                     }
 539
 540                     e.emit();
 541                 }
 542
 543                 for &(ref tree, id) in items {
 544                     self.build_reduced_graph_for_use_tree(
 545                         // This particular use tree
 546                         tree, id, &prefix, true, // The whole `use` item
 547                         item, vis, root_span,
 548                     );
 549                 }
 550
 551                 // Empty groups `a::b::{}` are turned into synthetic `self` imports
 552                 // `a::b::c::{self as _}`, so that their prefixes are correctly
 553                 // resolved and checked for privacy/stability/etc.
 554                 if items.is_empty() && !empty_for_self(&prefix) {
 555                     let new_span = prefix[prefix.len() - 1].ident.span;
 556                     let tree = ast::UseTree {
 557                         prefix: ast::Path::from_ident(Ident::new(kw::SelfLower, new_span)),
 558                         kind: ast::UseTreeKind::Simple(
 559                             Some(Ident::new(kw::Underscore, new_span)),
 560                             ast::DUMMY_NODE_ID,
 561                             ast::DUMMY_NODE_ID,
 562                         ),
 563                         span: use_tree.span,
 564                     };
 565                     self.build_reduced_graph_for_use_tree(
 566                         // This particular use tree
 567                         &tree,
 568                         id,
 569                         &prefix,
 570                         true,
 571                         // The whole `use` item
 572                         item,
 573                         ty::Visibility::Invisible,
 574                         root_span,
 575                     );
 576                 }
 577             }
 578         }
 579     }
 580
 581     /// Constructs the reduced graph for one item.
 582     fn build_reduced_graph_for_item(&mut self, item: &'b Item) {
 583         let parent_scope = &self.parent_scope;
 584         let parent = parent_scope.module;
 585         let expansion = parent_scope.expansion;
 586         let ident = item.ident;
 587         let sp = item.span;
 588         let vis = self.resolve_visibility(&item.vis);
 589
 590         match item.kind {
 591             ItemKind::Use(ref use_tree) => {
 592                 self.build_reduced_graph_for_use_tree(
 593                     // This particular use tree
 594                     use_tree,
 595                     item.id,
 596                     &[],
 597                     false,
 598                     // The whole `use` item
 599                     item,
 600                     vis,
 601                     use_tree.span,
 602                 );
 603             }
 604
 605             ItemKind::ExternCrate(orig_name) => {
 606                 let module = if orig_name.is_none() && ident.name == kw::SelfLower {
 607                     self.r
 608                         .session
 609                         .struct_span_err(item.span, "`extern crate self;` requires renaming")
 610                         .span_suggestion(
 611                             item.span,
 612                             "try",
 613                             "extern crate self as name;".into(),
 614                             Applicability::HasPlaceholders,
 615                         )
 616                         .emit();
 617                     return;
 618                 } else if orig_name == Some(kw::SelfLower) {
 619                     self.r.graph_root
 620                 } else {
 621                     let crate_id =
 622                         self.r.crate_loader.process_extern_crate(item, &self.r.definitions);
 623                     self.r.extern_crate_map.insert(item.id, crate_id);
 624                     self.r.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX })
 625                 };
 626
 627                 let used = self.process_legacy_macro_imports(item, module);
 628                 let binding =
 629                     (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.r.arenas);
 630                 let import = self.r.arenas.alloc_import(Import {
 631                     kind: ImportKind::ExternCrate { source: orig_name, target: ident },
 632                     root_id: item.id,
 633                     id: item.id,
 634                     parent_scope: self.parent_scope,
 635                     imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 636                     has_attributes: !item.attrs.is_empty(),
 637                     use_span_with_attributes: item.span_with_attributes(),
 638                     use_span: item.span,
 639                     root_span: item.span,
 640                     span: item.span,
 641                     module_path: Vec::new(),
 642                     vis: Cell::new(vis),
 643                     used: Cell::new(used),
 644                 });
 645                 self.r.potentially_unused_imports.push(import);
 646                 let imported_binding = self.r.import(binding, import);
 647                 if ptr::eq(parent, self.r.graph_root) {
 648                     if let Some(entry) = self.r.extern_prelude.get(&ident.modern()) {
 649                         if expansion != ExpnId::root()
 650                             && orig_name.is_some()
 651                             && entry.extern_crate_item.is_none()
 652                         {
 653                             let msg = "macro-expanded `extern crate` items cannot \
 654                                        shadow names passed with `--extern`";
 655                             self.r.session.span_err(item.span, msg);
 656                         }
 657                     }
 658                     let entry =
 659                         self.r.extern_prelude.entry(ident.modern()).or_insert(ExternPreludeEntry {
 660                             extern_crate_item: None,
 661                             introduced_by_item: true,
 662                         });
 663                     entry.extern_crate_item = Some(imported_binding);
 664                     if orig_name.is_some() {
 665                         entry.introduced_by_item = true;
 666                     }
 667                 }
 668                 self.r.define(parent, ident, TypeNS, imported_binding);
 669             }
 670
 671             ItemKind::Mod(..) if ident.name == kw::Invalid => {} // Crate root
 672
 673             ItemKind::Mod(..) => {
 674                 let def_id = self.r.definitions.local_def_id(item.id);
 675                 let module_kind = ModuleKind::Def(DefKind::Mod, def_id, ident.name);
 676                 let module = self.r.arenas.alloc_module(ModuleData {
 677                     no_implicit_prelude: parent.no_implicit_prelude || {
 678                         attr::contains_name(&item.attrs, sym::no_implicit_prelude)
 679                     },
 680                     ..ModuleData::new(Some(parent), module_kind, def_id, expansion, item.span)
 681                 });
 682                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 683                 self.r.module_map.insert(def_id, module);
 684
 685                 // Descend into the module.
 686                 self.parent_scope.module = module;
 687             }
 688
 689             // These items live in the value namespace.
 690             ItemKind::Static(..) => {
 691                 let res = Res::Def(DefKind::Static, self.r.definitions.local_def_id(item.id));
 692                 self.r.define(parent, ident, ValueNS, (res, vis, sp, expansion));
 693             }
 694             ItemKind::Const(..) => {
 695                 let res = Res::Def(DefKind::Const, self.r.definitions.local_def_id(item.id));
 696                 self.r.define(parent, ident, ValueNS, (res, vis, sp, expansion));
 697             }
 698             ItemKind::Fn(..) => {
 699                 let res = Res::Def(DefKind::Fn, self.r.definitions.local_def_id(item.id));
 700                 self.r.define(parent, ident, ValueNS, (res, vis, sp, expansion));
 701
 702                 // Functions introducing procedural macros reserve a slot
 703                 // in the macro namespace as well (see #52225).
 704                 self.define_macro(item);
 705             }
 706
 707             // These items live in the type namespace.
 708             ItemKind::TyAlias(_, _, _, ref ty) => {
 709                 let def_kind = match ty.as_deref().and_then(|ty| ty.kind.opaque_top_hack()) {
 710                     None => DefKind::TyAlias,
 711                     Some(_) => DefKind::OpaqueTy,
 712                 };
 713                 let res = Res::Def(def_kind, self.r.definitions.local_def_id(item.id));
 714                 self.r.define(parent, ident, TypeNS, (res, vis, sp, expansion));
 715             }
 716
 717             ItemKind::Enum(_, _) => {
 718                 let def_id = self.r.definitions.local_def_id(item.id);
 719                 self.r.variant_vis.insert(def_id, vis);
 720                 let module_kind = ModuleKind::Def(DefKind::Enum, def_id, ident.name);
 721                 let module = self.r.new_module(
 722                     parent,
 723                     module_kind,
 724                     parent.normal_ancestor_id,
 725                     expansion,
 726                     item.span,
 727                 );
 728                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 729                 self.parent_scope.module = module;
 730             }
 731
 732             ItemKind::TraitAlias(..) => {
 733                 let res = Res::Def(DefKind::TraitAlias, self.r.definitions.local_def_id(item.id));
 734                 self.r.define(parent, ident, TypeNS, (res, vis, sp, expansion));
 735             }
 736
 737             // These items live in both the type and value namespaces.
 738             ItemKind::Struct(ref vdata, _) => {
 739                 // Define a name in the type namespace.
 740                 let def_id = self.r.definitions.local_def_id(item.id);
 741                 let res = Res::Def(DefKind::Struct, def_id);
 742                 self.r.define(parent, ident, TypeNS, (res, vis, sp, expansion));
 743
 744                 // Record field names for error reporting.
 745                 self.insert_field_names_local(def_id, vdata);
 746
 747                 // If this is a tuple or unit struct, define a name
 748                 // in the value namespace as well.
 749                 if let Some(ctor_node_id) = vdata.ctor_id() {
 750                     let mut ctor_vis = vis;
 751                     // If the structure is marked as non_exhaustive then lower the visibility
 752                     // to within the crate.
 753                     if vis == ty::Visibility::Public
 754                         && attr::contains_name(&item.attrs, sym::non_exhaustive)
 755                     {
 756                         ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 757                     }
 758                     for field in vdata.fields() {
 759                         // NOTE: The field may be an expansion placeholder, but expansion sets
 760                         // correct visibilities for unnamed field placeholders specifically, so the
 761                         // constructor visibility should still be determined correctly.
 762                         if let Ok(field_vis) = self.resolve_visibility_speculative(&field.vis, true)
 763                         {
 764                             if ctor_vis.is_at_least(field_vis, &*self.r) {
 765                                 ctor_vis = field_vis;
 766                             }
 767                         }
 768                     }
 769                     let ctor_res = Res::Def(
 770                         DefKind::Ctor(CtorOf::Struct, CtorKind::from_ast(vdata)),
 771                         self.r.definitions.local_def_id(ctor_node_id),
 772                     );
 773                     self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, sp, expansion));
 774                     self.r.struct_constructors.insert(def_id, (ctor_res, ctor_vis));
 775                 }
 776             }
 777
 778             ItemKind::Union(ref vdata, _) => {
 779                 let def_id = self.r.definitions.local_def_id(item.id);
 780                 let res = Res::Def(DefKind::Union, def_id);
 781                 self.r.define(parent, ident, TypeNS, (res, vis, sp, expansion));
 782
 783                 // Record field names for error reporting.
 784                 self.insert_field_names_local(def_id, vdata);
 785             }
 786
 787             ItemKind::Trait(..) => {
 788                 let def_id = self.r.definitions.local_def_id(item.id);
 789
 790                 // Add all the items within to a new module.
 791                 let module_kind = ModuleKind::Def(DefKind::Trait, def_id, ident.name);
 792                 let module = self.r.new_module(
 793                     parent,
 794                     module_kind,
 795                     parent.normal_ancestor_id,
 796                     expansion,
 797                     item.span,
 798                 );
 799                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 800                 self.parent_scope.module = module;
 801             }
 802
 803             // These items do not add names to modules.
 804             ItemKind::Impl { .. } | ItemKind::ForeignMod(..) | ItemKind::GlobalAsm(..) => {}
 805
 806             ItemKind::MacroDef(..) | ItemKind::Mac(_) => unreachable!(),
 807         }
 808     }
 809
 810     /// Constructs the reduced graph for one foreign item.
 811     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem) {
 812         let (res, ns) = match item.kind {
 813             ForeignItemKind::Fn(..) => {
 814                 (Res::Def(DefKind::Fn, self.r.definitions.local_def_id(item.id)), ValueNS)
 815             }
 816             ForeignItemKind::Static(..) => {
 817                 (Res::Def(DefKind::Static, self.r.definitions.local_def_id(item.id)), ValueNS)
 818             }
 819             ForeignItemKind::TyAlias(..) => {
 820                 (Res::Def(DefKind::ForeignTy, self.r.definitions.local_def_id(item.id)), TypeNS)
 821             }
 822             ForeignItemKind::Macro(_) => unreachable!(),
 823         };
 824         let parent = self.parent_scope.module;
 825         let expansion = self.parent_scope.expansion;
 826         let vis = self.resolve_visibility(&item.vis);
 827         self.r.define(parent, item.ident, ns, (res, vis, item.span, expansion));
 828     }
 829
 830     fn build_reduced_graph_for_block(&mut self, block: &Block) {
 831         let parent = self.parent_scope.module;
 832         let expansion = self.parent_scope.expansion;
 833         if self.block_needs_anonymous_module(block) {
 834             let module = self.r.new_module(
 835                 parent,
 836                 ModuleKind::Block(block.id),
 837                 parent.normal_ancestor_id,
 838                 expansion,
 839                 block.span,
 840             );
 841             self.r.block_map.insert(block.id, module);
 842             self.parent_scope.module = module; // Descend into the block.
 843         }
 844     }
 845
 846     /// Builds the reduced graph for a single item in an external crate.
 847     fn build_reduced_graph_for_external_crate_res(&mut self, child: Export<NodeId>) {
 848         let parent = self.parent_scope.module;
 849         let Export { ident, res, vis, span } = child;
 850         let expansion = ExpnId::root(); // FIXME(jseyfried) intercrate hygiene
 851         // Record primary definitions.
 852         match res {
 853             Res::Def(kind @ DefKind::Mod, def_id)
 854             | Res::Def(kind @ DefKind::Enum, def_id)
 855             | Res::Def(kind @ DefKind::Trait, def_id) => {
 856                 let module = self.r.new_module(
 857                     parent,
 858                     ModuleKind::Def(kind, def_id, ident.name),
 859                     def_id,
 860                     expansion,
 861                     span,
 862                 );
 863                 self.r.define(parent, ident, TypeNS, (module, vis, span, expansion));
 864             }
 865             Res::Def(DefKind::Struct, _)
 866             | Res::Def(DefKind::Union, _)
 867             | Res::Def(DefKind::Variant, _)
 868             | Res::Def(DefKind::TyAlias, _)
 869             | Res::Def(DefKind::ForeignTy, _)
 870             | Res::Def(DefKind::OpaqueTy, _)
 871             | Res::Def(DefKind::TraitAlias, _)
 872             | Res::Def(DefKind::AssocTy, _)
 873             | Res::Def(DefKind::AssocOpaqueTy, _)
 874             | Res::PrimTy(..)
 875             | Res::ToolMod => self.r.define(parent, ident, TypeNS, (res, vis, span, expansion)),
 876             Res::Def(DefKind::Fn, _)
 877             | Res::Def(DefKind::Method, _)
 878             | Res::Def(DefKind::Static, _)
 879             | Res::Def(DefKind::Const, _)
 880             | Res::Def(DefKind::AssocConst, _)
 881             | Res::Def(DefKind::Ctor(..), _) => {
 882                 self.r.define(parent, ident, ValueNS, (res, vis, span, expansion))
 883             }
 884             Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => {
 885                 self.r.define(parent, ident, MacroNS, (res, vis, span, expansion))
 886             }
 887             Res::Def(DefKind::TyParam, _)
 888             | Res::Def(DefKind::ConstParam, _)
 889             | Res::Local(..)
 890             | Res::SelfTy(..)
 891             | Res::SelfCtor(..)
 892             | Res::Err => bug!("unexpected resolution: {:?}", res),
 893         }
 894         // Record some extra data for better diagnostics.
 895         let cstore = self.r.cstore();
 896         match res {
 897             Res::Def(DefKind::Struct, def_id) | Res::Def(DefKind::Union, def_id) => {
 898                 let field_names = cstore.struct_field_names_untracked(def_id, self.r.session);
 899                 self.insert_field_names(def_id, field_names);
 900             }
 901             Res::Def(DefKind::Method, def_id) => {
 902                 if cstore.associated_item_cloned_untracked(def_id).method_has_self_argument {
 903                     self.r.has_self.insert(def_id);
 904                 }
 905             }
 906             Res::Def(DefKind::Ctor(CtorOf::Struct, ..), def_id) => {
 907                 let parent = cstore.def_key(def_id).parent;
 908                 if let Some(struct_def_id) = parent.map(|index| DefId { index, ..def_id }) {
 909                     self.r.struct_constructors.insert(struct_def_id, (res, vis));
 910                 }
 911             }
 912             _ => {}
 913         }
 914     }
 915
 916     fn legacy_import_macro(
 917         &mut self,
 918         name: ast::Name,
 919         binding: &'a NameBinding<'a>,
 920         span: Span,
 921         allow_shadowing: bool,
 922     ) {
 923         if self.r.macro_use_prelude.insert(name, binding).is_some() && !allow_shadowing {
 924             let msg = format!("`{}` is already in scope", name);
 925             let note =
 926                 "macro-expanded `#[macro_use]`s may not shadow existing macros (see RFC 1560)";
 927             self.r.session.struct_span_err(span, &msg).note(note).emit();
 928         }
 929     }
 930
 931     /// Returns `true` if we should consider the underlying `extern crate` to be used.
 932     fn process_legacy_macro_imports(&mut self, item: &Item, module: Module<'a>) -> bool {
 933         let mut import_all = None;
 934         let mut single_imports = Vec::new();
 935         for attr in &item.attrs {
 936             if attr.check_name(sym::macro_use) {
 937                 if self.parent_scope.module.parent.is_some() {
 938                     struct_span_err!(
 939                         self.r.session,
 940                         item.span,
 941                         E0468,
 942                         "an `extern crate` loading macros must be at the crate root"
 943                     )
 944                     .emit();
 945                 }
 946                 if let ItemKind::ExternCrate(Some(orig_name)) = item.kind {
 947                     if orig_name == kw::SelfLower {
 948                         self.r
 949                             .session
 950                             .struct_span_err(
 951                                 attr.span,
 952                                 "`#[macro_use]` is not supported on `extern crate self`",
 953                             )
 954                             .emit();
 955                     }
 956                 }
 957                 let ill_formed =
 958                     |span| struct_span_err!(self.r.session, span, E0466, "bad macro import").emit();
 959                 match attr.meta() {
 960                     Some(meta) => match meta.kind {
 961                         MetaItemKind::Word => {
 962                             import_all = Some(meta.span);
 963                             break;
 964                         }
 965                         MetaItemKind::List(nested_metas) => {
 966                             for nested_meta in nested_metas {
 967                                 match nested_meta.ident() {
 968                                     Some(ident) if nested_meta.is_word() => {
 969                                         single_imports.push(ident)
 970                                     }
 971                                     _ => ill_formed(nested_meta.span()),
 972                                 }
 973                             }
 974                         }
 975                         MetaItemKind::NameValue(..) => ill_formed(meta.span),
 976                     },
 977                     None => ill_formed(attr.span),
 978                 }
 979             }
 980         }
 981
 982         let macro_use_import = |this: &Self, span| {
 983             this.r.arenas.alloc_import(Import {
 984                 kind: ImportKind::MacroUse,
 985                 root_id: item.id,
 986                 id: item.id,
 987                 parent_scope: this.parent_scope,
 988                 imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 989                 use_span_with_attributes: item.span_with_attributes(),
 990                 has_attributes: !item.attrs.is_empty(),
 991                 use_span: item.span,
 992                 root_span: span,
 993                 span,
 994                 module_path: Vec::new(),
 995                 vis: Cell::new(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))),
 996                 used: Cell::new(false),
 997             })
 998         };
 999
1000         let allow_shadowing = self.parent_scope.expansion == ExpnId::root();
1001         if let Some(span) = import_all {
1002             let import = macro_use_import(self, span);
1003             self.r.potentially_unused_imports.push(import);
1004             module.for_each_child(self, |this, ident, ns, binding| {
1005                 if ns == MacroNS {
1006                     let imported_binding = this.r.import(binding, import);
1007                     this.legacy_import_macro(ident.name, imported_binding, span, allow_shadowing);
1008                 }
1009             });
1010         } else {
1011             for ident in single_imports.iter().cloned() {
1012                 let result = self.r.resolve_ident_in_module(
1013                     ModuleOrUniformRoot::Module(module),
1014                     ident,
1015                     MacroNS,
1016                     &self.parent_scope,
1017                     false,
1018                     ident.span,
1019                 );
1020                 if let Ok(binding) = result {
1021                     let import = macro_use_import(self, ident.span);
1022                     self.r.potentially_unused_imports.push(import);
1023                     let imported_binding = self.r.import(binding, import);
1024                     self.legacy_import_macro(
1025                         ident.name,
1026                         imported_binding,
1027                         ident.span,
1028                         allow_shadowing,
1029                     );
1030                 } else {
1031                     struct_span_err!(self.r.session, ident.span, E0469, "imported macro not found")
1032                         .emit();
1033                 }
1034             }
1035         }
1036         import_all.is_some() || !single_imports.is_empty()
1037     }
1038
1039     /// Returns `true` if this attribute list contains `macro_use`.
1040     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
1041         for attr in attrs {
1042             if attr.check_name(sym::macro_escape) {
1043                 let msg = "`#[macro_escape]` is a deprecated synonym for `#[macro_use]`";
1044                 let mut err = self.r.session.struct_span_warn(attr.span, msg);
1045                 if let ast::AttrStyle::Inner = attr.style {
1046                     err.help("try an outer attribute: `#[macro_use]`").emit();
1047                 } else {
1048                     err.emit();
1049                 }
1050             } else if !attr.check_name(sym::macro_use) {
1051                 continue;
1052             }
1053
1054             if !attr.is_word() {
1055                 self.r.session.span_err(attr.span, "arguments to `macro_use` are not allowed here");
1056             }
1057             return true;
1058         }
1059
1060         false
1061     }
1062
1063     fn visit_invoc(&mut self, id: NodeId) -> LegacyScope<'a> {
1064         let invoc_id = id.placeholder_to_expn_id();
1065
1066         self.parent_scope.module.unexpanded_invocations.borrow_mut().insert(invoc_id);
1067
1068         let old_parent_scope = self.r.invocation_parent_scopes.insert(invoc_id, self.parent_scope);
1069         assert!(old_parent_scope.is_none(), "invocation data is reset for an invocation");
1070
1071         LegacyScope::Invocation(invoc_id)
1072     }
1073
1074     fn proc_macro_stub(item: &ast::Item) -> Option<(MacroKind, Ident, Span)> {
1075         if attr::contains_name(&item.attrs, sym::proc_macro) {
1076             return Some((MacroKind::Bang, item.ident, item.span));
1077         } else if attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
1078             return Some((MacroKind::Attr, item.ident, item.span));
1079         } else if let Some(attr) = attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
1080             if let Some(nested_meta) = attr.meta_item_list().and_then(|list| list.get(0).cloned()) {
1081                 if let Some(ident) = nested_meta.ident() {
1082                     return Some((MacroKind::Derive, ident, ident.span));
1083                 }
1084             }
1085         }
1086         None
1087     }
1088
1089     // Mark the given macro as unused unless its name starts with `_`.
1090     // Macro uses will remove items from this set, and the remaining
1091     // items will be reported as `unused_macros`.
1092     fn insert_unused_macro(&mut self, ident: Ident, node_id: NodeId, span: Span) {
1093         if !ident.as_str().starts_with('_') {
1094             self.r.unused_macros.insert(node_id, span);
1095         }
1096     }
1097
1098     fn define_macro(&mut self, item: &ast::Item) -> LegacyScope<'a> {
1099         let parent_scope = self.parent_scope;
1100         let expansion = parent_scope.expansion;
1101         let (ext, ident, span, is_legacy) = match &item.kind {
1102             ItemKind::MacroDef(def) => {
1103                 let ext = Lrc::new(self.r.compile_macro(item, self.r.session.edition()));
1104                 (ext, item.ident, item.span, def.legacy)
1105             }
1106             ItemKind::Fn(..) => match Self::proc_macro_stub(item) {
1107                 Some((macro_kind, ident, span)) => {
1108                     self.r.proc_macro_stubs.insert(item.id);
1109                     (self.r.dummy_ext(macro_kind), ident, span, false)
1110                 }
1111                 None => return parent_scope.legacy,
1112             },
1113             _ => unreachable!(),
1114         };
1115
1116         let def_id = self.r.definitions.local_def_id(item.id);
1117         let res = Res::Def(DefKind::Macro(ext.macro_kind()), def_id);
1118         self.r.macro_map.insert(def_id, ext);
1119         self.r.local_macro_def_scopes.insert(item.id, parent_scope.module);
1120
1121         if is_legacy {
1122             let ident = ident.modern();
1123             self.r.macro_names.insert(ident);
1124             let is_macro_export = attr::contains_name(&item.attrs, sym::macro_export);
1125             let vis = if is_macro_export {
1126                 ty::Visibility::Public
1127             } else {
1128                 ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
1129             };
1130             let binding = (res, vis, span, expansion).to_name_binding(self.r.arenas);
1131             self.r.set_binding_parent_module(binding, parent_scope.module);
1132             self.r.all_macros.insert(ident.name, res);
1133             if is_macro_export {
1134                 let module = self.r.graph_root;
1135                 self.r.define(module, ident, MacroNS, (res, vis, span, expansion, IsMacroExport));
1136             } else {
1137                 self.r.check_reserved_macro_name(ident, res);
1138                 self.insert_unused_macro(ident, item.id, span);
1139             }
1140             LegacyScope::Binding(self.r.arenas.alloc_legacy_binding(LegacyBinding {
1141                 parent_legacy_scope: parent_scope.legacy,
1142                 binding,
1143                 ident,
1144             }))
1145         } else {
1146             let module = parent_scope.module;
1147             let vis = self.resolve_visibility(&item.vis);
1148             if vis != ty::Visibility::Public {
1149                 self.insert_unused_macro(ident, item.id, span);
1150             }
1151             self.r.define(module, ident, MacroNS, (res, vis, span, expansion));
1152             self.parent_scope.legacy
1153         }
1154     }
1155 }
1156
1157 macro_rules! method {
1158     ($visit:ident: $ty:ty, $invoc:path, $walk:ident) => {
1159         fn $visit(&mut self, node: &'b $ty) {
1160             if let $invoc(..) = node.kind {
1161                 self.visit_invoc(node.id);
1162             } else {
1163                 visit::$walk(self, node);
1164             }
1165         }
1166     }
1167 }
1168
1169 impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
1170     method!(visit_expr: ast::Expr, ast::ExprKind::Mac, walk_expr);
1171     method!(visit_pat: ast::Pat, ast::PatKind::Mac, walk_pat);
1172     method!(visit_ty: ast::Ty, ast::TyKind::Mac, walk_ty);
1173
1174     fn visit_item(&mut self, item: &'b Item) {
1175         let macro_use = match item.kind {
1176             ItemKind::MacroDef(..) => {
1177                 self.parent_scope.legacy = self.define_macro(item);
1178                 return;
1179             }
1180             ItemKind::Mac(..) => {
1181                 self.parent_scope.legacy = self.visit_invoc(item.id);
1182                 return;
1183             }
1184             ItemKind::Mod(..) => self.contains_macro_use(&item.attrs),
1185             _ => false,
1186         };
1187         let orig_current_module = self.parent_scope.module;
1188         let orig_current_legacy_scope = self.parent_scope.legacy;
1189         self.build_reduced_graph_for_item(item);
1190         visit::walk_item(self, item);
1191         self.parent_scope.module = orig_current_module;
1192         if !macro_use {
1193             self.parent_scope.legacy = orig_current_legacy_scope;
1194         }
1195     }
1196
1197     fn visit_stmt(&mut self, stmt: &'b ast::Stmt) {
1198         if let ast::StmtKind::Mac(..) = stmt.kind {
1199             self.parent_scope.legacy = self.visit_invoc(stmt.id);
1200         } else {
1201             visit::walk_stmt(self, stmt);
1202         }
1203     }
1204
1205     fn visit_foreign_item(&mut self, foreign_item: &'b ForeignItem) {
1206         if let ForeignItemKind::Macro(_) = foreign_item.kind {
1207             self.visit_invoc(foreign_item.id);
1208             return;
1209         }
1210
1211         self.build_reduced_graph_for_foreign_item(foreign_item);
1212         visit::walk_foreign_item(self, foreign_item);
1213     }
1214
1215     fn visit_block(&mut self, block: &'b Block) {
1216         let orig_current_module = self.parent_scope.module;
1217         let orig_current_legacy_scope = self.parent_scope.legacy;
1218         self.build_reduced_graph_for_block(block);
1219         visit::walk_block(self, block);
1220         self.parent_scope.module = orig_current_module;
1221         self.parent_scope.legacy = orig_current_legacy_scope;
1222     }
1223
1224     fn visit_assoc_item(&mut self, item: &'b AssocItem, ctxt: AssocCtxt) {
1225         let parent = self.parent_scope.module;
1226
1227         if let AssocItemKind::Macro(_) = item.kind {
1228             self.visit_invoc(item.id);
1229             return;
1230         }
1231
1232         if let AssocCtxt::Impl = ctxt {
1233             self.resolve_visibility(&item.vis);
1234             visit::walk_assoc_item(self, item, ctxt);
1235             return;
1236         }
1237
1238         // Add the item to the trait info.
1239         let item_def_id = self.r.definitions.local_def_id(item.id);
1240         let (res, ns) = match item.kind {
1241             AssocItemKind::Const(..) => (Res::Def(DefKind::AssocConst, item_def_id), ValueNS),
1242             AssocItemKind::Fn(_, ref sig, _, _) => {
1243                 if sig.decl.has_self() {
1244                     self.r.has_self.insert(item_def_id);
1245                 }
1246                 (Res::Def(DefKind::Method, item_def_id), ValueNS)
1247             }
1248             AssocItemKind::TyAlias(..) => (Res::Def(DefKind::AssocTy, item_def_id), TypeNS),
1249             AssocItemKind::Macro(_) => bug!(), // handled above
1250         };
1251
1252         let vis = ty::Visibility::Public;
1253         let expansion = self.parent_scope.expansion;
1254         self.r.define(parent, item.ident, ns, (res, vis, item.span, expansion));
1255
1256         visit::walk_assoc_item(self, item, ctxt);
1257     }
1258
1259     fn visit_token(&mut self, t: Token) {
1260         if let token::Interpolated(nt) = t.kind {
1261             if let token::NtExpr(ref expr) = *nt {
1262                 if let ast::ExprKind::Mac(..) = expr.kind {
1263                     self.visit_invoc(expr.id);
1264                 }
1265             }
1266         }
1267     }
1268
1269     fn visit_attribute(&mut self, attr: &'b ast::Attribute) {
1270         if !attr.is_doc_comment() && attr::is_builtin_attr(attr) {
1271             self.r
1272                 .builtin_attrs
1273                 .push((attr.get_normal_item().path.segments[0].ident, self.parent_scope));
1274         }
1275         visit::walk_attribute(self, attr);
1276     }
1277
1278     fn visit_arm(&mut self, arm: &'b ast::Arm) {
1279         if arm.is_placeholder {
1280             self.visit_invoc(arm.id);
1281         } else {
1282             visit::walk_arm(self, arm);
1283         }
1284     }
1285
1286     fn visit_field(&mut self, f: &'b ast::Field) {
1287         if f.is_placeholder {
1288             self.visit_invoc(f.id);
1289         } else {
1290             visit::walk_field(self, f);
1291         }
1292     }
1293
1294     fn visit_field_pattern(&mut self, fp: &'b ast::FieldPat) {
1295         if fp.is_placeholder {
1296             self.visit_invoc(fp.id);
1297         } else {
1298             visit::walk_field_pattern(self, fp);
1299         }
1300     }
1301
1302     fn visit_generic_param(&mut self, param: &'b ast::GenericParam) {
1303         if param.is_placeholder {
1304             self.visit_invoc(param.id);
1305         } else {
1306             visit::walk_generic_param(self, param);
1307         }
1308     }
1309
1310     fn visit_param(&mut self, p: &'b ast::Param) {
1311         if p.is_placeholder {
1312             self.visit_invoc(p.id);
1313         } else {
1314             visit::walk_param(self, p);
1315         }
1316     }
1317
1318     fn visit_struct_field(&mut self, sf: &'b ast::StructField) {
1319         if sf.is_placeholder {
1320             self.visit_invoc(sf.id);
1321         } else {
1322             self.resolve_visibility(&sf.vis);
1323             visit::walk_struct_field(self, sf);
1324         }
1325     }
1326
1327     // Constructs the reduced graph for one variant. Variants exist in the
1328     // type and value namespaces.
1329     fn visit_variant(&mut self, variant: &'b ast::Variant) {
1330         if variant.is_placeholder {
1331             self.visit_invoc(variant.id);
1332             return;
1333         }
1334
1335         let parent = self.parent_scope.module;
1336         let vis = self.r.variant_vis[&parent.def_id().expect("enum without def-id")];
1337         let expn_id = self.parent_scope.expansion;
1338         let ident = variant.ident;
1339
1340         // Define a name in the type namespace.
1341         let def_id = self.r.definitions.local_def_id(variant.id);
1342         let res = Res::Def(DefKind::Variant, def_id);
1343         self.r.define(parent, ident, TypeNS, (res, vis, variant.span, expn_id));
1344
1345         // If the variant is marked as non_exhaustive then lower the visibility to within the
1346         // crate.
1347         let mut ctor_vis = vis;
1348         let has_non_exhaustive = attr::contains_name(&variant.attrs, sym::non_exhaustive);
1349         if has_non_exhaustive && vis == ty::Visibility::Public {
1350             ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
1351         }
1352
1353         // Define a constructor name in the value namespace.
1354         // Braced variants, unlike structs, generate unusable names in
1355         // value namespace, they are reserved for possible future use.
1356         // It's ok to use the variant's id as a ctor id since an
1357         // error will be reported on any use of such resolution anyway.
1358         let ctor_node_id = variant.data.ctor_id().unwrap_or(variant.id);
1359         let ctor_def_id = self.r.definitions.local_def_id(ctor_node_id);
1360         let ctor_kind = CtorKind::from_ast(&variant.data);
1361         let ctor_res = Res::Def(DefKind::Ctor(CtorOf::Variant, ctor_kind), ctor_def_id);
1362         self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, variant.span, expn_id));
1363
1364         visit::walk_variant(self, variant);
1365     }
1366 }