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 macros::{InvocationData, LegacyScope};
  17 use resolve_imports::ImportDirective;
  18 use resolve_imports::ImportDirectiveSubclass::{self, GlobImport, SingleImport};
  19 use {Module, ModuleData, ModuleKind, NameBinding, NameBindingKind, ToNameBinding};
  20 use {Resolver, ResolverArenas};
  21 use Namespace::{self, TypeNS, ValueNS, MacroNS};
  22 use {resolve_error, resolve_struct_error, ResolutionError};
  23
  24 use rustc::middle::cstore::LoadedMacro;
  25 use rustc::hir::def::*;
  26 use rustc::hir::def_id::{BUILTIN_MACROS_CRATE, CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  27 use rustc::ty;
  28
  29 use std::cell::Cell;
  30 use std::rc::Rc;
  31
  32 use syntax::ast::{Name, Ident};
  33 use syntax::attr;
  34
  35 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind};
  36 use syntax::ast::{Mutability, StmtKind, TraitItem, TraitItemKind};
  37 use syntax::ast::{Variant, ViewPathGlob, ViewPathList, ViewPathSimple};
  38 use syntax::ext::base::SyntaxExtension;
  39 use syntax::ext::base::Determinacy::Undetermined;
  40 use syntax::ext::hygiene::Mark;
  41 use syntax::ext::tt::macro_rules;
  42 use syntax::parse::token;
  43 use syntax::symbol::keywords;
  44 use syntax::visit::{self, Visitor};
  45
  46 use syntax_pos::{Span, DUMMY_SP};
  47
  48 impl<'a> ToNameBinding<'a> for (Module<'a>, ty::Visibility, Span, Mark) {
  49     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  50         arenas.alloc_name_binding(NameBinding {
  51             kind: NameBindingKind::Module(self.0),
  52             vis: self.1,
  53             span: self.2,
  54             expansion: self.3,
  55         })
  56     }
  57 }
  58
  59 impl<'a> ToNameBinding<'a> for (Def, ty::Visibility, Span, Mark) {
  60     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  61         arenas.alloc_name_binding(NameBinding {
  62             kind: NameBindingKind::Def(self.0),
  63             vis: self.1,
  64             span: self.2,
  65             expansion: self.3,
  66         })
  67     }
  68 }
  69
  70 #[derive(Default, PartialEq, Eq)]
  71 struct LegacyMacroImports {
  72     import_all: Option<Span>,
  73     imports: Vec<(Name, Span)>,
  74     reexports: Vec<(Name, Span)>,
  75 }
  76
  77 impl<'a> Resolver<'a> {
  78     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
  79     /// otherwise, reports an error.
  80     pub fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
  81         where T: ToNameBinding<'a>,
  82     {
  83         let binding = def.to_name_binding(self.arenas);
  84         if let Err(old_binding) = self.try_define(parent, ident, ns, binding) {
  85             self.report_conflict(parent, ident, ns, old_binding, &binding);
  86         }
  87     }
  88
  89     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
  90         // If any statements are items, we need to create an anonymous module
  91         block.stmts.iter().any(|statement| match statement.node {
  92             StmtKind::Item(_) | StmtKind::Mac(_) => true,
  93             _ => false,
  94         })
  95     }
  96
  97     fn insert_field_names(&mut self, def_id: DefId, field_names: Vec<Name>) {
  98         if !field_names.is_empty() {
  99             self.field_names.insert(def_id, field_names);
 100         }
 101     }
 102
 103     /// Constructs the reduced graph for one item.
 104     fn build_reduced_graph_for_item(&mut self, item: &Item, expansion: Mark) {
 105         let parent = self.current_module;
 106         let ident = item.ident;
 107         let sp = item.span;
 108         let vis = self.resolve_visibility(&item.vis);
 109
 110         match item.node {
 111             ItemKind::Use(ref view_path) => {
 112                 // Extract and intern the module part of the path. For
 113                 // globs and lists, the path is found directly in the AST;
 114                 // for simple paths we have to munge the path a little.
 115                 let mut module_path: Vec<_> = match view_path.node {
 116                     ViewPathSimple(_, ref full_path) => {
 117                         full_path.segments
 118                                  .split_last()
 119                                  .unwrap()
 120                                  .1
 121                                  .iter()
 122                                  .map(|seg| seg.identifier)
 123                                  .collect()
 124                     }
 125
 126                     ViewPathGlob(ref module_ident_path) |
 127                     ViewPathList(ref module_ident_path, _) => {
 128                         module_ident_path.segments
 129                                          .iter()
 130                                          .map(|seg| seg.identifier)
 131                                          .collect()
 132                     }
 133                 };
 134
 135                 // This can be removed once warning cycle #36888 is complete.
 136                 if module_path.len() >= 2 && module_path[0].name == keywords::CrateRoot.name() &&
 137                    token::Ident(module_path[1]).is_path_segment_keyword() {
 138                     module_path.remove(0);
 139                 }
 140
 141                 // Build up the import directives.
 142                 let is_prelude = attr::contains_name(&item.attrs, "prelude_import");
 143
 144                 match view_path.node {
 145                     ViewPathSimple(mut binding, ref full_path) => {
 146                         let mut source = full_path.segments.last().unwrap().identifier;
 147                         let source_name = source.name;
 148                         if source_name == "mod" || source_name == "self" {
 149                             resolve_error(self,
 150                                           view_path.span,
 151                                           ResolutionError::SelfImportsOnlyAllowedWithin);
 152                         } else if source_name == keywords::DollarCrate.name() &&
 153                                   full_path.segments.len() == 1 {
 154                             let crate_root = self.resolve_crate_root(source.ctxt);
 155                             let crate_name = match crate_root.kind {
 156                                 ModuleKind::Def(_, name) => name,
 157                                 ModuleKind::Block(..) => unreachable!(),
 158                             };
 159                             source.name = crate_name;
 160                             if binding.name == keywords::DollarCrate.name() {
 161                                 binding.name = crate_name;
 162                             }
 163
 164                             self.session.struct_span_warn(item.span, "`$crate` may not be imported")
 165                                 .note("`use $crate;` was erroneously allowed and \
 166                                        will become a hard error in a future release")
 167                                 .emit();
 168                         }
 169
 170                         let subclass = SingleImport {
 171                             target: binding,
 172                             source: source,
 173                             result: self.per_ns(|_, _| Cell::new(Err(Undetermined))),
 174                             type_ns_only: false,
 175                         };
 176                         self.add_import_directive(
 177                             module_path, subclass, view_path.span, item.id, vis, expansion,
 178                         );
 179                     }
 180                     ViewPathList(_, ref source_items) => {
 181                         // Make sure there's at most one `mod` import in the list.
 182                         let mod_spans = source_items.iter().filter_map(|item| {
 183                             if item.node.name.name == keywords::SelfValue.name() {
 184                                 Some(item.span)
 185                             } else {
 186                                 None
 187                             }
 188                         }).collect::<Vec<Span>>();
 189
 190                         if mod_spans.len() > 1 {
 191                             let mut e = resolve_struct_error(self,
 192                                           mod_spans[0],
 193                                           ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 194                             for other_span in mod_spans.iter().skip(1) {
 195                                 e.span_note(*other_span, "another `self` import appears here");
 196                             }
 197                             e.emit();
 198                         }
 199
 200                         for source_item in source_items {
 201                             let node = source_item.node;
 202                             let (module_path, ident, rename, type_ns_only) = {
 203                                 if node.name.name != keywords::SelfValue.name() {
 204                                     let rename = node.rename.unwrap_or(node.name);
 205                                     (module_path.clone(), node.name, rename, false)
 206                                 } else {
 207                                     let ident = *module_path.last().unwrap();
 208                                     if ident.name == keywords::CrateRoot.name() {
 209                                         resolve_error(
 210                                             self,
 211                                             source_item.span,
 212                                             ResolutionError::
 213                                             SelfImportOnlyInImportListWithNonEmptyPrefix
 214                                         );
 215                                         continue;
 216                                     }
 217                                     let module_path = module_path.split_last().unwrap().1;
 218                                     let rename = node.rename.unwrap_or(ident);
 219                                     (module_path.to_vec(), ident, rename, true)
 220                                 }
 221                             };
 222                             let subclass = SingleImport {
 223                                 target: rename,
 224                                 source: ident,
 225                                 result: self.per_ns(|_, _| Cell::new(Err(Undetermined))),
 226                                 type_ns_only: type_ns_only,
 227                             };
 228                             let id = source_item.node.id;
 229                             self.add_import_directive(
 230                                 module_path, subclass, source_item.span, id, vis, expansion,
 231                             );
 232                         }
 233                     }
 234                     ViewPathGlob(_) => {
 235                         let subclass = GlobImport {
 236                             is_prelude: is_prelude,
 237                             max_vis: Cell::new(ty::Visibility::Invisible),
 238                         };
 239                         self.add_import_directive(
 240                             module_path, subclass, view_path.span, item.id, vis, expansion,
 241                         );
 242                     }
 243                 }
 244             }
 245
 246             ItemKind::ExternCrate(_) => {
 247                 self.crate_loader.process_item(item, &self.definitions);
 248
 249                 // n.b. we don't need to look at the path option here, because cstore already did
 250                 let crate_id = self.session.cstore.extern_mod_stmt_cnum(item.id).unwrap();
 251                 let module =
 252                     self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 253                 self.populate_module_if_necessary(module);
 254                 let used = self.process_legacy_macro_imports(item, module, expansion);
 255                 let binding =
 256                     (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.arenas);
 257                 let directive = self.arenas.alloc_import_directive(ImportDirective {
 258                     id: item.id,
 259                     parent: parent,
 260                     imported_module: Cell::new(Some(module)),
 261                     subclass: ImportDirectiveSubclass::ExternCrate,
 262                     span: item.span,
 263                     module_path: Vec::new(),
 264                     vis: Cell::new(vis),
 265                     expansion: expansion,
 266                     used: Cell::new(used),
 267                 });
 268                 self.potentially_unused_imports.push(directive);
 269                 let imported_binding = self.import(binding, directive);
 270                 self.define(parent, ident, TypeNS, imported_binding);
 271             }
 272
 273             ItemKind::GlobalAsm(..) => {}
 274
 275             ItemKind::Mod(..) if item.ident == keywords::Invalid.ident() => {} // Crate root
 276
 277             ItemKind::Mod(..) => {
 278                 let def_id = self.definitions.local_def_id(item.id);
 279                 let module_kind = ModuleKind::Def(Def::Mod(def_id), ident.name);
 280                 let module = self.arenas.alloc_module(ModuleData {
 281                     no_implicit_prelude: parent.no_implicit_prelude || {
 282                         attr::contains_name(&item.attrs, "no_implicit_prelude")
 283                     },
 284                     ..ModuleData::new(Some(parent), module_kind, def_id, expansion, item.span)
 285                 });
 286                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 287                 self.module_map.insert(def_id, module);
 288
 289                 // Descend into the module.
 290                 self.current_module = module;
 291             }
 292
 293             ItemKind::ForeignMod(..) => self.crate_loader.process_item(item, &self.definitions),
 294
 295             // These items live in the value namespace.
 296             ItemKind::Static(_, m, _) => {
 297                 let mutbl = m == Mutability::Mutable;
 298                 let def = Def::Static(self.definitions.local_def_id(item.id), mutbl);
 299                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 300             }
 301             ItemKind::Const(..) => {
 302                 let def = Def::Const(self.definitions.local_def_id(item.id));
 303                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 304             }
 305             ItemKind::Fn(..) => {
 306                 let def = Def::Fn(self.definitions.local_def_id(item.id));
 307                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 308             }
 309
 310             // These items live in the type namespace.
 311             ItemKind::Ty(..) => {
 312                 let def = Def::TyAlias(self.definitions.local_def_id(item.id));
 313                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 314             }
 315
 316             ItemKind::Enum(ref enum_definition, _) => {
 317                 let def = Def::Enum(self.definitions.local_def_id(item.id));
 318                 let module_kind = ModuleKind::Def(def, ident.name);
 319                 let module = self.new_module(parent,
 320                                              module_kind,
 321                                              parent.normal_ancestor_id,
 322                                              expansion,
 323                                              item.span);
 324                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 325
 326                 for variant in &(*enum_definition).variants {
 327                     self.build_reduced_graph_for_variant(variant, module, vis, expansion);
 328                 }
 329             }
 330
 331             // These items live in both the type and value namespaces.
 332             ItemKind::Struct(ref struct_def, _) => {
 333                 // Define a name in the type namespace.
 334                 let def = Def::Struct(self.definitions.local_def_id(item.id));
 335                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 336
 337                 // Record field names for error reporting.
 338                 let mut ctor_vis = vis;
 339                 let field_names = struct_def.fields().iter().filter_map(|field| {
 340                     let field_vis = self.resolve_visibility(&field.vis);
 341                     if ctor_vis.is_at_least(field_vis, &*self) {
 342                         ctor_vis = field_vis;
 343                     }
 344                     field.ident.map(|ident| ident.name)
 345                 }).collect();
 346                 let item_def_id = self.definitions.local_def_id(item.id);
 347                 self.insert_field_names(item_def_id, field_names);
 348
 349                 // If this is a tuple or unit struct, define a name
 350                 // in the value namespace as well.
 351                 if !struct_def.is_struct() {
 352                     let ctor_def = Def::StructCtor(self.definitions.local_def_id(struct_def.id()),
 353                                                    CtorKind::from_ast(struct_def));
 354                     self.define(parent, ident, ValueNS, (ctor_def, ctor_vis, sp, expansion));
 355                     self.struct_constructors.insert(def.def_id(), (ctor_def, ctor_vis));
 356                 }
 357             }
 358
 359             ItemKind::Union(ref vdata, _) => {
 360                 let def = Def::Union(self.definitions.local_def_id(item.id));
 361                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 362
 363                 // Record field names for error reporting.
 364                 let field_names = vdata.fields().iter().filter_map(|field| {
 365                     self.resolve_visibility(&field.vis);
 366                     field.ident.map(|ident| ident.name)
 367                 }).collect();
 368                 let item_def_id = self.definitions.local_def_id(item.id);
 369                 self.insert_field_names(item_def_id, field_names);
 370             }
 371
 372             ItemKind::DefaultImpl(..) | ItemKind::Impl(..) => {}
 373
 374             ItemKind::Trait(..) => {
 375                 let def_id = self.definitions.local_def_id(item.id);
 376
 377                 // Add all the items within to a new module.
 378                 let module_kind = ModuleKind::Def(Def::Trait(def_id), ident.name);
 379                 let module = self.new_module(parent,
 380                                              module_kind,
 381                                              parent.normal_ancestor_id,
 382                                              expansion,
 383                                              item.span);
 384                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 385                 self.current_module = module;
 386             }
 387             ItemKind::MacroDef(..) | ItemKind::Mac(_) => unreachable!(),
 388         }
 389     }
 390
 391     // Constructs the reduced graph for one variant. Variants exist in the
 392     // type and value namespaces.
 393     fn build_reduced_graph_for_variant(&mut self,
 394                                        variant: &Variant,
 395                                        parent: Module<'a>,
 396                                        vis: ty::Visibility,
 397                                        expansion: Mark) {
 398         let ident = variant.node.name;
 399         let def_id = self.definitions.local_def_id(variant.node.data.id());
 400
 401         // Define a name in the type namespace.
 402         let def = Def::Variant(def_id);
 403         self.define(parent, ident, TypeNS, (def, vis, variant.span, expansion));
 404
 405         // Define a constructor name in the value namespace.
 406         // Braced variants, unlike structs, generate unusable names in
 407         // value namespace, they are reserved for possible future use.
 408         let ctor_kind = CtorKind::from_ast(&variant.node.data);
 409         let ctor_def = Def::VariantCtor(def_id, ctor_kind);
 410         self.define(parent, ident, ValueNS, (ctor_def, vis, variant.span, expansion));
 411     }
 412
 413     /// Constructs the reduced graph for one foreign item.
 414     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem, expansion: Mark) {
 415         let def = match item.node {
 416             ForeignItemKind::Fn(..) => {
 417                 Def::Fn(self.definitions.local_def_id(item.id))
 418             }
 419             ForeignItemKind::Static(_, m) => {
 420                 Def::Static(self.definitions.local_def_id(item.id), m)
 421             }
 422         };
 423         let parent = self.current_module;
 424         let vis = self.resolve_visibility(&item.vis);
 425         self.define(parent, item.ident, ValueNS, (def, vis, item.span, expansion));
 426     }
 427
 428     fn build_reduced_graph_for_block(&mut self, block: &Block, expansion: Mark) {
 429         let parent = self.current_module;
 430         if self.block_needs_anonymous_module(block) {
 431             let module = self.new_module(parent,
 432                                          ModuleKind::Block(block.id),
 433                                          parent.normal_ancestor_id,
 434                                          expansion,
 435                                          block.span);
 436             self.block_map.insert(block.id, module);
 437             self.current_module = module; // Descend into the block.
 438         }
 439     }
 440
 441     /// Builds the reduced graph for a single item in an external crate.
 442     fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'a>, child: Export) {
 443         let ident = child.ident;
 444         let def = child.def;
 445         let def_id = def.def_id();
 446         let vis = self.session.cstore.visibility(def_id);
 447         let span = child.span;
 448         let expansion = Mark::root(); // FIXME(jseyfried) intercrate hygiene
 449         match def {
 450             Def::Mod(..) | Def::Enum(..) => {
 451                 let module = self.new_module(parent,
 452                                              ModuleKind::Def(def, ident.name),
 453                                              def_id,
 454                                              expansion,
 455                                              span);
 456                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 457             }
 458             Def::Variant(..) | Def::TyAlias(..) => {
 459                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 460             }
 461             Def::Fn(..) | Def::Static(..) | Def::Const(..) | Def::VariantCtor(..) => {
 462                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 463             }
 464             Def::StructCtor(..) => {
 465                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 466
 467                 if let Some(struct_def_id) =
 468                         self.session.cstore.def_key(def_id).parent
 469                             .map(|index| DefId { krate: def_id.krate, index: index }) {
 470                     self.struct_constructors.insert(struct_def_id, (def, vis));
 471                 }
 472             }
 473             Def::Trait(..) => {
 474                 let module_kind = ModuleKind::Def(def, ident.name);
 475                 let module = self.new_module(parent,
 476                                              module_kind,
 477                                              parent.normal_ancestor_id,
 478                                              expansion,
 479                                              span);
 480                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 481
 482                 for child in self.session.cstore.item_children(def_id, self.session) {
 483                     let ns = if let Def::AssociatedTy(..) = child.def { TypeNS } else { ValueNS };
 484                     self.define(module, child.ident, ns,
 485                                 (child.def, ty::Visibility::Public, DUMMY_SP, expansion));
 486
 487                     if self.session.cstore.associated_item_cloned(child.def.def_id())
 488                            .method_has_self_argument {
 489                         self.has_self.insert(child.def.def_id());
 490                     }
 491                 }
 492                 module.populated.set(true);
 493             }
 494             Def::Struct(..) | Def::Union(..) => {
 495                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 496
 497                 // Record field names for error reporting.
 498                 let field_names = self.session.cstore.struct_field_names(def_id);
 499                 self.insert_field_names(def_id, field_names);
 500             }
 501             Def::Macro(..) => {
 502                 self.define(parent, ident, MacroNS, (def, vis, DUMMY_SP, expansion));
 503             }
 504             _ => bug!("unexpected definition: {:?}", def)
 505         }
 506     }
 507
 508     pub fn get_module(&mut self, def_id: DefId) -> Module<'a> {
 509         if def_id.krate == LOCAL_CRATE {
 510             return self.module_map[&def_id]
 511         }
 512
 513         let macros_only = self.session.cstore.dep_kind(def_id.krate).macros_only();
 514         if let Some(&module) = self.extern_module_map.get(&(def_id, macros_only)) {
 515             return module;
 516         }
 517
 518         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
 519             (self.session.cstore.crate_name(def_id.krate), None)
 520         } else {
 521             let def_key = self.session.cstore.def_key(def_id);
 522             (def_key.disambiguated_data.data.get_opt_name().unwrap(),
 523              Some(self.get_module(DefId { index: def_key.parent.unwrap(), ..def_id })))
 524         };
 525
 526         let kind = ModuleKind::Def(Def::Mod(def_id), name);
 527         let module =
 528             self.arenas.alloc_module(ModuleData::new(parent, kind, def_id, Mark::root(), DUMMY_SP));
 529         self.extern_module_map.insert((def_id, macros_only), module);
 530         module
 531     }
 532
 533     pub fn macro_def_scope(&mut self, expansion: Mark) -> Module<'a> {
 534         let def_id = self.macro_defs[&expansion];
 535         if let Some(id) = self.definitions.as_local_node_id(def_id) {
 536             self.local_macro_def_scopes[&id]
 537         } else if def_id.krate == BUILTIN_MACROS_CRATE {
 538             // FIXME(jseyfried): This happens when `include!()`ing a `$crate::` path, c.f, #40469.
 539             self.graph_root
 540         } else {
 541             let module_def_id = ty::DefIdTree::parent(&*self, def_id).unwrap();
 542             self.get_module(module_def_id)
 543         }
 544     }
 545
 546     pub fn get_macro(&mut self, def: Def) -> Rc<SyntaxExtension> {
 547         let def_id = match def {
 548             Def::Macro(def_id, ..) => def_id,
 549             _ => panic!("Expected Def::Macro(..)"),
 550         };
 551         if let Some(ext) = self.macro_map.get(&def_id) {
 552             return ext.clone();
 553         }
 554
 555         let macro_def = match self.session.cstore.load_macro(def_id, &self.session) {
 556             LoadedMacro::MacroDef(macro_def) => macro_def,
 557             LoadedMacro::ProcMacro(ext) => return ext,
 558         };
 559
 560         let ext = Rc::new(macro_rules::compile(&self.session.parse_sess,
 561                                                &self.session.features,
 562                                                &macro_def));
 563         self.macro_map.insert(def_id, ext.clone());
 564         ext
 565     }
 566
 567     /// Ensures that the reduced graph rooted at the given external module
 568     /// is built, building it if it is not.
 569     pub fn populate_module_if_necessary(&mut self, module: Module<'a>) {
 570         if module.populated.get() { return }
 571         for child in self.session.cstore.item_children(module.def_id().unwrap(), self.session) {
 572             self.build_reduced_graph_for_external_crate_def(module, child);
 573         }
 574         module.populated.set(true)
 575     }
 576
 577     fn legacy_import_macro(&mut self,
 578                            name: Name,
 579                            binding: &'a NameBinding<'a>,
 580                            span: Span,
 581                            allow_shadowing: bool) {
 582         if self.global_macros.insert(name, binding).is_some() && !allow_shadowing {
 583             let msg = format!("`{}` is already in scope", name);
 584             let note =
 585                 "macro-expanded `#[macro_use]`s may not shadow existing macros (see RFC 1560)";
 586             self.session.struct_span_err(span, &msg).note(note).emit();
 587         }
 588     }
 589
 590     // This returns true if we should consider the underlying `extern crate` to be used.
 591     fn process_legacy_macro_imports(&mut self, item: &Item, module: Module<'a>, expansion: Mark)
 592                                     -> bool {
 593         let allow_shadowing = expansion == Mark::root();
 594         let legacy_imports = self.legacy_macro_imports(&item.attrs);
 595         let mut used = legacy_imports != LegacyMacroImports::default();
 596
 597         // `#[macro_use]` and `#[macro_reexport]` are only allowed at the crate root.
 598         if self.current_module.parent.is_some() && used {
 599             span_err!(self.session, item.span, E0468,
 600                       "an `extern crate` loading macros must be at the crate root");
 601         } else if !self.use_extern_macros && !used &&
 602                   self.session.cstore.dep_kind(module.def_id().unwrap().krate).macros_only() {
 603             let msg = "proc macro crates and `#[no_link]` crates have no effect without \
 604                        `#[macro_use]`";
 605             self.session.span_warn(item.span, msg);
 606             used = true; // Avoid the normal unused extern crate warning
 607         }
 608
 609         let (graph_root, arenas) = (self.graph_root, self.arenas);
 610         let macro_use_directive = |span| arenas.alloc_import_directive(ImportDirective {
 611             id: item.id,
 612             parent: graph_root,
 613             imported_module: Cell::new(Some(module)),
 614             subclass: ImportDirectiveSubclass::MacroUse,
 615             span: span,
 616             module_path: Vec::new(),
 617             vis: Cell::new(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))),
 618             expansion: expansion,
 619             used: Cell::new(false),
 620         });
 621
 622         if let Some(span) = legacy_imports.import_all {
 623             let directive = macro_use_directive(span);
 624             self.potentially_unused_imports.push(directive);
 625             module.for_each_child(|ident, ns, binding| if ns == MacroNS {
 626                 let imported_binding = self.import(binding, directive);
 627                 self.legacy_import_macro(ident.name, imported_binding, span, allow_shadowing);
 628             });
 629         } else {
 630             for (name, span) in legacy_imports.imports {
 631                 let ident = Ident::with_empty_ctxt(name);
 632                 let result = self.resolve_ident_in_module(module, ident, MacroNS,
 633                                                           false, false, span);
 634                 if let Ok(binding) = result {
 635                     let directive = macro_use_directive(span);
 636                     self.potentially_unused_imports.push(directive);
 637                     let imported_binding = self.import(binding, directive);
 638                     self.legacy_import_macro(name, imported_binding, span, allow_shadowing);
 639                 } else {
 640                     span_err!(self.session, span, E0469, "imported macro not found");
 641                 }
 642             }
 643         }
 644         for (name, span) in legacy_imports.reexports {
 645             self.session.cstore.export_macros(module.def_id().unwrap().krate);
 646             let ident = Ident::with_empty_ctxt(name);
 647             let result = self.resolve_ident_in_module(module, ident, MacroNS, false, false, span);
 648             if let Ok(binding) = result {
 649                 self.macro_exports.push(Export { ident: ident, def: binding.def(), span: span });
 650             } else {
 651                 span_err!(self.session, span, E0470, "reexported macro not found");
 652             }
 653         }
 654         used
 655     }
 656
 657     // does this attribute list contain "macro_use"?
 658     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
 659         for attr in attrs {
 660             if attr.check_name("macro_escape") {
 661                 let msg = "macro_escape is a deprecated synonym for macro_use";
 662                 let mut err = self.session.struct_span_warn(attr.span, msg);
 663                 if let ast::AttrStyle::Inner = attr.style {
 664                     err.help("consider an outer attribute, #[macro_use] mod ...").emit();
 665                 } else {
 666                     err.emit();
 667                 }
 668             } else if !attr.check_name("macro_use") {
 669                 continue;
 670             }
 671
 672             if !attr.is_word() {
 673                 self.session.span_err(attr.span, "arguments to macro_use are not allowed here");
 674             }
 675             return true;
 676         }
 677
 678         false
 679     }
 680
 681     fn legacy_macro_imports(&mut self, attrs: &[ast::Attribute]) -> LegacyMacroImports {
 682         let mut imports = LegacyMacroImports::default();
 683         for attr in attrs {
 684             if attr.check_name("macro_use") {
 685                 match attr.meta_item_list() {
 686                     Some(names) => for attr in names {
 687                         if let Some(word) = attr.word() {
 688                             imports.imports.push((word.name(), attr.span()));
 689                         } else {
 690                             span_err!(self.session, attr.span(), E0466, "bad macro import");
 691                         }
 692                     },
 693                     None => imports.import_all = Some(attr.span),
 694                 }
 695             } else if attr.check_name("macro_reexport") {
 696                 let bad_macro_reexport = |this: &mut Self, span| {
 697                     span_err!(this.session, span, E0467, "bad macro reexport");
 698                 };
 699                 if let Some(names) = attr.meta_item_list() {
 700                     for attr in names {
 701                         if let Some(word) = attr.word() {
 702                             imports.reexports.push((word.name(), attr.span()));
 703                         } else {
 704                             bad_macro_reexport(self, attr.span());
 705                         }
 706                     }
 707                 } else {
 708                     bad_macro_reexport(self, attr.span());
 709                 }
 710             }
 711         }
 712         imports
 713     }
 714 }
 715
 716 pub struct BuildReducedGraphVisitor<'a, 'b: 'a> {
 717     pub resolver: &'a mut Resolver<'b>,
 718     pub legacy_scope: LegacyScope<'b>,
 719     pub expansion: Mark,
 720 }
 721
 722 impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
 723     fn visit_invoc(&mut self, id: ast::NodeId) -> &'b InvocationData<'b> {
 724         let mark = id.placeholder_to_mark();
 725         self.resolver.current_module.unresolved_invocations.borrow_mut().insert(mark);
 726         let invocation = self.resolver.invocations[&mark];
 727         invocation.module.set(self.resolver.current_module);
 728         invocation.legacy_scope.set(self.legacy_scope);
 729         invocation
 730     }
 731 }
 732
 733 macro_rules! method {
 734     ($visit:ident: $ty:ty, $invoc:path, $walk:ident) => {
 735         fn $visit(&mut self, node: &'a $ty) {
 736             if let $invoc(..) = node.node {
 737                 self.visit_invoc(node.id);
 738             } else {
 739                 visit::$walk(self, node);
 740             }
 741         }
 742     }
 743 }
 744
 745 impl<'a, 'b> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b> {
 746     method!(visit_impl_item: ast::ImplItem, ast::ImplItemKind::Macro, walk_impl_item);
 747     method!(visit_expr:      ast::Expr,     ast::ExprKind::Mac,       walk_expr);
 748     method!(visit_pat:       ast::Pat,      ast::PatKind::Mac,        walk_pat);
 749     method!(visit_ty:        ast::Ty,       ast::TyKind::Mac,         walk_ty);
 750
 751     fn visit_item(&mut self, item: &'a Item) {
 752         let macro_use = match item.node {
 753             ItemKind::MacroDef(..) => {
 754                 self.resolver.define_macro(item, self.expansion, &mut self.legacy_scope);
 755                 return
 756             }
 757             ItemKind::Mac(..) => {
 758                 self.legacy_scope = LegacyScope::Expansion(self.visit_invoc(item.id));
 759                 return
 760             }
 761             ItemKind::Mod(..) => self.resolver.contains_macro_use(&item.attrs),
 762             _ => false,
 763         };
 764
 765         let (parent, legacy_scope) = (self.resolver.current_module, self.legacy_scope);
 766         self.resolver.build_reduced_graph_for_item(item, self.expansion);
 767         visit::walk_item(self, item);
 768         self.resolver.current_module = parent;
 769         if !macro_use {
 770             self.legacy_scope = legacy_scope;
 771         }
 772     }
 773
 774     fn visit_stmt(&mut self, stmt: &'a ast::Stmt) {
 775         if let ast::StmtKind::Mac(..) = stmt.node {
 776             self.legacy_scope = LegacyScope::Expansion(self.visit_invoc(stmt.id));
 777         } else {
 778             visit::walk_stmt(self, stmt);
 779         }
 780     }
 781
 782     fn visit_foreign_item(&mut self, foreign_item: &'a ForeignItem) {
 783         self.resolver.build_reduced_graph_for_foreign_item(foreign_item, self.expansion);
 784         visit::walk_foreign_item(self, foreign_item);
 785     }
 786
 787     fn visit_block(&mut self, block: &'a Block) {
 788         let (parent, legacy_scope) = (self.resolver.current_module, self.legacy_scope);
 789         self.resolver.build_reduced_graph_for_block(block, self.expansion);
 790         visit::walk_block(self, block);
 791         self.resolver.current_module = parent;
 792         self.legacy_scope = legacy_scope;
 793     }
 794
 795     fn visit_trait_item(&mut self, item: &'a TraitItem) {
 796         let parent = self.resolver.current_module;
 797
 798         if let TraitItemKind::Macro(_) = item.node {
 799             self.visit_invoc(item.id);
 800             return
 801         }
 802
 803         // Add the item to the trait info.
 804         let item_def_id = self.resolver.definitions.local_def_id(item.id);
 805         let (def, ns) = match item.node {
 806             TraitItemKind::Const(..) => (Def::AssociatedConst(item_def_id), ValueNS),
 807             TraitItemKind::Method(ref sig, _) => {
 808                 if sig.decl.has_self() {
 809                     self.resolver.has_self.insert(item_def_id);
 810                 }
 811                 (Def::Method(item_def_id), ValueNS)
 812             }
 813             TraitItemKind::Type(..) => (Def::AssociatedTy(item_def_id), TypeNS),
 814             TraitItemKind::Macro(_) => bug!(),  // handled above
 815         };
 816
 817         let vis = ty::Visibility::Public;
 818         self.resolver.define(parent, item.ident, ns, (def, vis, item.span, self.expansion));
 819
 820         self.resolver.current_module = parent.parent.unwrap(); // nearest normal ancestor
 821         visit::walk_trait_item(self, item);
 822         self.resolver.current_module = parent;
 823     }
 824 }