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, ParentScope, LegacyScope};
  17 use resolve_imports::ImportDirective;
  18 use resolve_imports::ImportDirectiveSubclass::{self, GlobImport, SingleImport};
  19 use {Module, ModuleData, ModuleKind, NameBinding, NameBindingKind, ToNameBinding};
  20 use {ModuleOrUniformRoot, PerNS, Resolver, ResolverArenas};
  21 use Namespace::{self, TypeNS, ValueNS, MacroNS};
  22 use {resolve_error, resolve_struct_error, ResolutionError};
  23
  24 use rustc::hir::def::*;
  25 use rustc::hir::def_id::{BUILTIN_MACROS_CRATE, CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  26 use rustc::ty;
  27 use rustc::middle::cstore::CrateStore;
  28 use rustc_metadata::cstore::LoadedMacro;
  29
  30 use std::cell::Cell;
  31 use rustc_data_structures::sync::Lrc;
  32
  33 use syntax::ast::{Name, Ident};
  34 use syntax::attr;
  35
  36 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
  37 use syntax::ast::{Mutability, StmtKind, TraitItem, TraitItemKind, Variant};
  38 use syntax::ext::base::{MacroKind, SyntaxExtension};
  39 use syntax::ext::base::Determinacy::Undetermined;
  40 use syntax::ext::hygiene::Mark;
  41 use syntax::ext::tt::macro_rules;
  42 use syntax::feature_gate::is_builtin_attr;
  43 use syntax::parse::token::{self, Token};
  44 use syntax::std_inject::injected_crate_name;
  45 use syntax::symbol::keywords;
  46 use syntax::visit::{self, Visitor};
  47
  48 use syntax_pos::{Span, DUMMY_SP};
  49
  50 impl<'a> ToNameBinding<'a> for (Module<'a>, ty::Visibility, Span, Mark) {
  51     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  52         arenas.alloc_name_binding(NameBinding {
  53             kind: NameBindingKind::Module(self.0),
  54             vis: self.1,
  55             span: self.2,
  56             expansion: self.3,
  57         })
  58     }
  59 }
  60
  61 impl<'a> ToNameBinding<'a> for (Def, ty::Visibility, Span, Mark) {
  62     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  63         arenas.alloc_name_binding(NameBinding {
  64             kind: NameBindingKind::Def(self.0, false),
  65             vis: self.1,
  66             span: self.2,
  67             expansion: self.3,
  68         })
  69     }
  70 }
  71
  72 pub(crate) struct IsMacroExport;
  73
  74 impl<'a> ToNameBinding<'a> for (Def, ty::Visibility, Span, Mark, IsMacroExport) {
  75     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  76         arenas.alloc_name_binding(NameBinding {
  77             kind: NameBindingKind::Def(self.0, true),
  78             vis: self.1,
  79             span: self.2,
  80             expansion: self.3,
  81         })
  82     }
  83 }
  84
  85 #[derive(Default, PartialEq, Eq)]
  86 struct LegacyMacroImports {
  87     import_all: Option<Span>,
  88     imports: Vec<(Name, Span)>,
  89 }
  90
  91 impl<'a, 'cl> Resolver<'a, 'cl> {
  92     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
  93     /// otherwise, reports an error.
  94     pub fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
  95         where T: ToNameBinding<'a>,
  96     {
  97         let binding = def.to_name_binding(self.arenas);
  98         if let Err(old_binding) = self.try_define(parent, ident, ns, binding) {
  99             self.report_conflict(parent, ident, ns, old_binding, &binding);
 100         }
 101     }
 102
 103     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 104         // If any statements are items, we need to create an anonymous module
 105         block.stmts.iter().any(|statement| match statement.node {
 106             StmtKind::Item(_) | StmtKind::Mac(_) => true,
 107             _ => false,
 108         })
 109     }
 110
 111     fn insert_field_names(&mut self, def_id: DefId, field_names: Vec<Name>) {
 112         if !field_names.is_empty() {
 113             self.field_names.insert(def_id, field_names);
 114         }
 115     }
 116
 117     fn build_reduced_graph_for_use_tree(
 118         &mut self,
 119         root_use_tree: &ast::UseTree,
 120         root_id: NodeId,
 121         use_tree: &ast::UseTree,
 122         id: NodeId,
 123         vis: ty::Visibility,
 124         parent_prefix: &[Ident],
 125         mut uniform_paths_canary_emitted: bool,
 126         nested: bool,
 127         item: &Item,
 128         expansion: Mark,
 129     ) {
 130         debug!("build_reduced_graph_for_use_tree(parent_prefix={:?}, \
 131                 uniform_paths_canary_emitted={}, \
 132                 use_tree={:?}, nested={})",
 133                parent_prefix, uniform_paths_canary_emitted, use_tree, nested);
 134
 135         let is_prelude = attr::contains_name(&item.attrs, "prelude_import");
 136         let uniform_paths =
 137             self.session.rust_2018() &&
 138             self.session.features_untracked().uniform_paths;
 139
 140         let prefix_iter = || parent_prefix.iter().cloned()
 141             .chain(use_tree.prefix.segments.iter().map(|seg| seg.ident));
 142         let prefix_start = prefix_iter().nth(0);
 143         let starts_with_non_keyword = prefix_start.map_or(false, |ident| {
 144             !ident.is_path_segment_keyword()
 145         });
 146
 147         // Imports are resolved as global by default, prepend `CrateRoot`,
 148         // unless `#![feature(uniform_paths)]` is enabled.
 149         let inject_crate_root =
 150             !uniform_paths &&
 151             match use_tree.kind {
 152                 // HACK(eddyb) special-case `use *` to mean `use ::*`.
 153                 ast::UseTreeKind::Glob if prefix_start.is_none() => true,
 154                 _ => starts_with_non_keyword,
 155             };
 156         let root = if inject_crate_root {
 157             let span = use_tree.prefix.span.shrink_to_lo();
 158             Some(Ident::new(keywords::CrateRoot.name(), span))
 159         } else {
 160             None
 161         };
 162
 163         let prefix: Vec<_> = root.into_iter().chain(prefix_iter()).collect();
 164
 165         debug!("build_reduced_graph_for_use_tree: prefix={:?}", prefix);
 166
 167         // `#[feature(uniform_paths)]` allows an unqualified import path,
 168         // e.g. `use x::...;` to resolve not just globally (`use ::x::...;`)
 169         // but also relatively (`use self::x::...;`). To catch ambiguities
 170         // that might arise from both of these being available and resolution
 171         // silently picking one of them, an artificial `use self::x as _;`
 172         // import is injected as a "canary", and an error is emitted if it
 173         // successfully resolves while an `x` external crate exists.
 174         //
 175         // For each block scope around the `use` item, one special canary
 176         // import of the form `use x as _;` is also injected, having its
 177         // parent set to that scope; `resolve_imports` will only resolve
 178         // it within its appropriate scope; if any of them successfully
 179         // resolve, an ambiguity error is emitted, since the original
 180         // import can't see the item in the block scope (`self::x` only
 181         // looks in the enclosing module), but a non-`use` path could.
 182         //
 183         // Additionally, the canary might be able to catch limitations of the
 184         // current implementation, where `::x` may be chosen due to `self::x`
 185         // not existing, but `self::x` could appear later, from macro expansion.
 186         //
 187         // NB. The canary currently only errors if the `x::...` path *could*
 188         // resolve as a relative path through the extern crate, i.e. `x` is
 189         // in `extern_prelude`, *even though* `::x` might still forcefully
 190         // load a non-`extern_prelude` crate.
 191         // While always producing an ambiguity errors if `self::x` exists and
 192         // a crate *could* be loaded, would be more conservative, imports for
 193         // local modules named `test` (or less commonly, `syntax` or `log`),
 194         // would need to be qualified (e.g. `self::test`), which is considered
 195         // ergonomically unacceptable.
 196         let emit_uniform_paths_canary =
 197             !uniform_paths_canary_emitted &&
 198             self.session.rust_2018() &&
 199             starts_with_non_keyword;
 200         if emit_uniform_paths_canary {
 201             let source = prefix_start.unwrap();
 202
 203             // Helper closure to emit a canary with the given base path.
 204             let emit = |this: &mut Self, base: Option<Ident>| {
 205                 let subclass = SingleImport {
 206                     target: Ident {
 207                         name: keywords::Underscore.name().gensymed(),
 208                         span: source.span,
 209                     },
 210                     source,
 211                     result: PerNS {
 212                         type_ns: Cell::new(Err(Undetermined)),
 213                         value_ns: Cell::new(Err(Undetermined)),
 214                         macro_ns: Cell::new(Err(Undetermined)),
 215                     },
 216                     type_ns_only: false,
 217                 };
 218                 this.add_import_directive(
 219                     base.into_iter().collect(),
 220                     subclass.clone(),
 221                     source.span,
 222                     id,
 223                     root_use_tree.span,
 224                     root_id,
 225                     ty::Visibility::Invisible,
 226                     expansion,
 227                     true, // is_uniform_paths_canary
 228                 );
 229             };
 230
 231             // A single simple `self::x` canary.
 232             emit(self, Some(Ident {
 233                 name: keywords::SelfValue.name(),
 234                 span: source.span,
 235             }));
 236
 237             // One special unprefixed canary per block scope around
 238             // the import, to detect items unreachable by `self::x`.
 239             let orig_current_module = self.current_module;
 240             let mut span = source.span.modern();
 241             loop {
 242                 match self.current_module.kind {
 243                     ModuleKind::Block(..) => emit(self, None),
 244                     ModuleKind::Def(..) => break,
 245                 }
 246                 match self.hygienic_lexical_parent(self.current_module, &mut span) {
 247                     Some(module) => {
 248                         self.current_module = module;
 249                     }
 250                     None => break,
 251                 }
 252             }
 253             self.current_module = orig_current_module;
 254
 255             uniform_paths_canary_emitted = true;
 256         }
 257
 258         match use_tree.kind {
 259             ast::UseTreeKind::Simple(rename, ..) => {
 260                 let mut ident = use_tree.ident();
 261                 let mut module_path = prefix;
 262                 let mut source = module_path.pop().unwrap();
 263                 let mut type_ns_only = false;
 264
 265                 if nested {
 266                     // Correctly handle `self`
 267                     if source.name == keywords::SelfValue.name() {
 268                         type_ns_only = true;
 269
 270                         let empty_prefix = module_path.last().map_or(true, |ident| {
 271                             ident.name == keywords::CrateRoot.name()
 272                         });
 273                         if empty_prefix {
 274                             resolve_error(
 275                                 self,
 276                                 use_tree.span,
 277                                 ResolutionError::
 278                                 SelfImportOnlyInImportListWithNonEmptyPrefix
 279                             );
 280                             return;
 281                         }
 282
 283                         // Replace `use foo::self;` with `use foo;`
 284                         source = module_path.pop().unwrap();
 285                         if rename.is_none() {
 286                             ident = source;
 287                         }
 288                     }
 289                 } else {
 290                     // Disallow `self`
 291                     if source.name == keywords::SelfValue.name() {
 292                         resolve_error(self,
 293                                       use_tree.span,
 294                                       ResolutionError::SelfImportsOnlyAllowedWithin);
 295                     }
 296
 297                     // Disallow `use $crate;`
 298                     if source.name == keywords::DollarCrate.name() && module_path.is_empty() {
 299                         let crate_root = self.resolve_crate_root(source);
 300                         let crate_name = match crate_root.kind {
 301                             ModuleKind::Def(_, name) => name,
 302                             ModuleKind::Block(..) => unreachable!(),
 303                         };
 304                         // HACK(eddyb) unclear how good this is, but keeping `$crate`
 305                         // in `source` breaks `src/test/compile-fail/import-crate-var.rs`,
 306                         // while the current crate doesn't have a valid `crate_name`.
 307                         if crate_name != keywords::Invalid.name() {
 308                             // `crate_name` should not be interpreted as relative.
 309                             module_path.push(Ident {
 310                                 name: keywords::CrateRoot.name(),
 311                                 span: source.span,
 312                             });
 313                             source.name = crate_name;
 314                         }
 315                         if rename.is_none() {
 316                             ident.name = crate_name;
 317                         }
 318
 319                         self.session.struct_span_warn(item.span, "`$crate` may not be imported")
 320                             .note("`use $crate;` was erroneously allowed and \
 321                                    will become a hard error in a future release")
 322                             .emit();
 323                     }
 324                 }
 325
 326                 if ident.name == keywords::Crate.name() {
 327                     self.session.span_err(ident.span,
 328                         "crate root imports need to be explicitly named: \
 329                          `use crate as name;`");
 330                 }
 331
 332                 let subclass = SingleImport {
 333                     target: ident,
 334                     source,
 335                     result: PerNS {
 336                         type_ns: Cell::new(Err(Undetermined)),
 337                         value_ns: Cell::new(Err(Undetermined)),
 338                         macro_ns: Cell::new(Err(Undetermined)),
 339                     },
 340                     type_ns_only,
 341                 };
 342                 self.add_import_directive(
 343                     module_path,
 344                     subclass,
 345                     use_tree.span,
 346                     id,
 347                     root_use_tree.span,
 348                     root_id,
 349                     vis,
 350                     expansion,
 351                     false, // is_uniform_paths_canary
 352                 );
 353             }
 354             ast::UseTreeKind::Glob => {
 355                 let subclass = GlobImport {
 356                     is_prelude,
 357                     max_vis: Cell::new(ty::Visibility::Invisible),
 358                 };
 359                 self.add_import_directive(
 360                     prefix,
 361                     subclass,
 362                     use_tree.span,
 363                     id,
 364                     root_use_tree.span,
 365                     root_id,
 366                     vis,
 367                     expansion,
 368                     false, // is_uniform_paths_canary
 369                 );
 370             }
 371             ast::UseTreeKind::Nested(ref items) => {
 372                 // Ensure there is at most one `self` in the list
 373                 let self_spans = items.iter().filter_map(|&(ref use_tree, _)| {
 374                     if let ast::UseTreeKind::Simple(..) = use_tree.kind {
 375                         if use_tree.ident().name == keywords::SelfValue.name() {
 376                             return Some(use_tree.span);
 377                         }
 378                     }
 379
 380                     None
 381                 }).collect::<Vec<_>>();
 382                 if self_spans.len() > 1 {
 383                     let mut e = resolve_struct_error(self,
 384                         self_spans[0],
 385                         ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 386
 387                     for other_span in self_spans.iter().skip(1) {
 388                         e.span_label(*other_span, "another `self` import appears here");
 389                     }
 390
 391                     e.emit();
 392                 }
 393
 394                 for &(ref tree, id) in items {
 395                     self.build_reduced_graph_for_use_tree(
 396                         root_use_tree,
 397                         root_id,
 398                         tree,
 399                         id,
 400                         vis,
 401                         &prefix,
 402                         uniform_paths_canary_emitted,
 403                         true,
 404                         item,
 405                         expansion,
 406                     );
 407                 }
 408             }
 409         }
 410     }
 411
 412     /// Constructs the reduced graph for one item.
 413     fn build_reduced_graph_for_item(&mut self, item: &Item, expansion: Mark) {
 414         let parent = self.current_module;
 415         let ident = item.ident;
 416         let sp = item.span;
 417         let vis = self.resolve_visibility(&item.vis);
 418
 419         match item.node {
 420             ItemKind::Use(ref use_tree) => {
 421                 self.build_reduced_graph_for_use_tree(
 422                     use_tree,
 423                     item.id,
 424                     use_tree,
 425                     item.id,
 426                     vis,
 427                     &[],
 428                     false, // uniform_paths_canary_emitted
 429                     false,
 430                     item,
 431                     expansion,
 432                 );
 433             }
 434
 435             ItemKind::ExternCrate(orig_name) => {
 436                 let crate_id = self.crate_loader.process_extern_crate(item, &self.definitions);
 437                 let module =
 438                     self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 439                 self.populate_module_if_necessary(module);
 440                 if injected_crate_name().map_or(false, |name| item.ident.name == name) {
 441                     self.injected_crate = Some(module);
 442                 }
 443
 444                 let used = self.process_legacy_macro_imports(item, module, expansion);
 445                 let binding =
 446                     (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.arenas);
 447                 let directive = self.arenas.alloc_import_directive(ImportDirective {
 448                     root_id: item.id,
 449                     id: item.id,
 450                     parent,
 451                     imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 452                     subclass: ImportDirectiveSubclass::ExternCrate(orig_name),
 453                     root_span: item.span,
 454                     span: item.span,
 455                     module_path: Vec::new(),
 456                     vis: Cell::new(vis),
 457                     expansion,
 458                     used: Cell::new(used),
 459                     is_uniform_paths_canary: false,
 460                 });
 461                 self.potentially_unused_imports.push(directive);
 462                 let imported_binding = self.import(binding, directive);
 463                 self.define(parent, ident, TypeNS, imported_binding);
 464             }
 465
 466             ItemKind::GlobalAsm(..) => {}
 467
 468             ItemKind::Mod(..) if item.ident == keywords::Invalid.ident() => {} // Crate root
 469
 470             ItemKind::Mod(..) => {
 471                 let def_id = self.definitions.local_def_id(item.id);
 472                 let module_kind = ModuleKind::Def(Def::Mod(def_id), ident.name);
 473                 let module = self.arenas.alloc_module(ModuleData {
 474                     no_implicit_prelude: parent.no_implicit_prelude || {
 475                         attr::contains_name(&item.attrs, "no_implicit_prelude")
 476                     },
 477                     ..ModuleData::new(Some(parent), module_kind, def_id, expansion, item.span)
 478                 });
 479                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 480                 self.module_map.insert(def_id, module);
 481
 482                 // Descend into the module.
 483                 self.current_module = module;
 484             }
 485
 486             // Handled in `rustc_metadata::{native_libs,link_args}`
 487             ItemKind::ForeignMod(..) => {}
 488
 489             // These items live in the value namespace.
 490             ItemKind::Static(_, m, _) => {
 491                 let mutbl = m == Mutability::Mutable;
 492                 let def = Def::Static(self.definitions.local_def_id(item.id), mutbl);
 493                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 494             }
 495             ItemKind::Const(..) => {
 496                 let def = Def::Const(self.definitions.local_def_id(item.id));
 497                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 498             }
 499             ItemKind::Fn(..) => {
 500                 let def = Def::Fn(self.definitions.local_def_id(item.id));
 501                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 502
 503                 // Functions introducing procedural macros reserve a slot
 504                 // in the macro namespace as well (see #52225).
 505                 if attr::contains_name(&item.attrs, "proc_macro") ||
 506                    attr::contains_name(&item.attrs, "proc_macro_attribute") {
 507                     let def = Def::Macro(def.def_id(), MacroKind::ProcMacroStub);
 508                     self.define(parent, ident, MacroNS, (def, vis, sp, expansion));
 509                 }
 510                 if let Some(attr) = attr::find_by_name(&item.attrs, "proc_macro_derive") {
 511                     if let Some(trait_attr) =
 512                             attr.meta_item_list().and_then(|list| list.get(0).cloned()) {
 513                         if let Some(ident) = trait_attr.name().map(Ident::with_empty_ctxt) {
 514                             let sp = trait_attr.span;
 515                             let def = Def::Macro(def.def_id(), MacroKind::ProcMacroStub);
 516                             self.define(parent, ident, MacroNS, (def, vis, sp, expansion));
 517                         }
 518                     }
 519                 }
 520             }
 521
 522             // These items live in the type namespace.
 523             ItemKind::Ty(..) => {
 524                 let def = Def::TyAlias(self.definitions.local_def_id(item.id));
 525                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 526             }
 527
 528             ItemKind::Existential(_, _) => {
 529                 let def = Def::Existential(self.definitions.local_def_id(item.id));
 530                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 531             }
 532
 533             ItemKind::Enum(ref enum_definition, _) => {
 534                 let def = Def::Enum(self.definitions.local_def_id(item.id));
 535                 let module_kind = ModuleKind::Def(def, ident.name);
 536                 let module = self.new_module(parent,
 537                                              module_kind,
 538                                              parent.normal_ancestor_id,
 539                                              expansion,
 540                                              item.span);
 541                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 542
 543                 for variant in &(*enum_definition).variants {
 544                     self.build_reduced_graph_for_variant(variant, module, vis, expansion);
 545                 }
 546             }
 547
 548             ItemKind::TraitAlias(..) => {
 549                 let def = Def::TraitAlias(self.definitions.local_def_id(item.id));
 550                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 551             }
 552
 553             // These items live in both the type and value namespaces.
 554             ItemKind::Struct(ref struct_def, _) => {
 555                 // Define a name in the type namespace.
 556                 let def_id = self.definitions.local_def_id(item.id);
 557                 let def = Def::Struct(def_id);
 558                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 559
 560                 let mut ctor_vis = vis;
 561
 562                 let has_non_exhaustive = attr::contains_name(&item.attrs, "non_exhaustive");
 563
 564                 // If the structure is marked as non_exhaustive then lower the visibility
 565                 // to within the crate.
 566                 if has_non_exhaustive && vis == ty::Visibility::Public {
 567                     ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 568                 }
 569
 570                 // Record field names for error reporting.
 571                 let field_names = struct_def.fields().iter().filter_map(|field| {
 572                     let field_vis = self.resolve_visibility(&field.vis);
 573                     if ctor_vis.is_at_least(field_vis, &*self) {
 574                         ctor_vis = field_vis;
 575                     }
 576                     field.ident.map(|ident| ident.name)
 577                 }).collect();
 578                 let item_def_id = self.definitions.local_def_id(item.id);
 579                 self.insert_field_names(item_def_id, field_names);
 580
 581                 // If this is a tuple or unit struct, define a name
 582                 // in the value namespace as well.
 583                 if !struct_def.is_struct() {
 584                     let ctor_def = Def::StructCtor(self.definitions.local_def_id(struct_def.id()),
 585                                                    CtorKind::from_ast(struct_def));
 586                     self.define(parent, ident, ValueNS, (ctor_def, ctor_vis, sp, expansion));
 587                     self.struct_constructors.insert(def.def_id(), (ctor_def, ctor_vis));
 588                 }
 589             }
 590
 591             ItemKind::Union(ref vdata, _) => {
 592                 let def = Def::Union(self.definitions.local_def_id(item.id));
 593                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 594
 595                 // Record field names for error reporting.
 596                 let field_names = vdata.fields().iter().filter_map(|field| {
 597                     self.resolve_visibility(&field.vis);
 598                     field.ident.map(|ident| ident.name)
 599                 }).collect();
 600                 let item_def_id = self.definitions.local_def_id(item.id);
 601                 self.insert_field_names(item_def_id, field_names);
 602             }
 603
 604             ItemKind::Impl(..) => {}
 605
 606             ItemKind::Trait(..) => {
 607                 let def_id = self.definitions.local_def_id(item.id);
 608
 609                 // Add all the items within to a new module.
 610                 let module_kind = ModuleKind::Def(Def::Trait(def_id), ident.name);
 611                 let module = self.new_module(parent,
 612                                              module_kind,
 613                                              parent.normal_ancestor_id,
 614                                              expansion,
 615                                              item.span);
 616                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 617                 self.current_module = module;
 618             }
 619
 620             ItemKind::MacroDef(..) | ItemKind::Mac(_) => unreachable!(),
 621         }
 622     }
 623
 624     // Constructs the reduced graph for one variant. Variants exist in the
 625     // type and value namespaces.
 626     fn build_reduced_graph_for_variant(&mut self,
 627                                        variant: &Variant,
 628                                        parent: Module<'a>,
 629                                        vis: ty::Visibility,
 630                                        expansion: Mark) {
 631         let ident = variant.node.ident;
 632         let def_id = self.definitions.local_def_id(variant.node.data.id());
 633
 634         // Define a name in the type namespace.
 635         let def = Def::Variant(def_id);
 636         self.define(parent, ident, TypeNS, (def, vis, variant.span, expansion));
 637
 638         // Define a constructor name in the value namespace.
 639         // Braced variants, unlike structs, generate unusable names in
 640         // value namespace, they are reserved for possible future use.
 641         let ctor_kind = CtorKind::from_ast(&variant.node.data);
 642         let ctor_def = Def::VariantCtor(def_id, ctor_kind);
 643
 644         self.define(parent, ident, ValueNS, (ctor_def, vis, variant.span, expansion));
 645     }
 646
 647     /// Constructs the reduced graph for one foreign item.
 648     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem, expansion: Mark) {
 649         let (def, ns) = match item.node {
 650             ForeignItemKind::Fn(..) => {
 651                 (Def::Fn(self.definitions.local_def_id(item.id)), ValueNS)
 652             }
 653             ForeignItemKind::Static(_, m) => {
 654                 (Def::Static(self.definitions.local_def_id(item.id), m), ValueNS)
 655             }
 656             ForeignItemKind::Ty => {
 657                 (Def::ForeignTy(self.definitions.local_def_id(item.id)), TypeNS)
 658             }
 659             ForeignItemKind::Macro(_) => unreachable!(),
 660         };
 661         let parent = self.current_module;
 662         let vis = self.resolve_visibility(&item.vis);
 663         self.define(parent, item.ident, ns, (def, vis, item.span, expansion));
 664     }
 665
 666     fn build_reduced_graph_for_block(&mut self, block: &Block, expansion: Mark) {
 667         let parent = self.current_module;
 668         if self.block_needs_anonymous_module(block) {
 669             let module = self.new_module(parent,
 670                                          ModuleKind::Block(block.id),
 671                                          parent.normal_ancestor_id,
 672                                          expansion,
 673                                          block.span);
 674             self.block_map.insert(block.id, module);
 675             self.current_module = module; // Descend into the block.
 676         }
 677     }
 678
 679     /// Builds the reduced graph for a single item in an external crate.
 680     fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'a>, child: Export) {
 681         let Export { ident, def, vis, span, .. } = child;
 682         let def_id = def.def_id();
 683         let expansion = Mark::root(); // FIXME(jseyfried) intercrate hygiene
 684         match def {
 685             Def::Mod(..) | Def::Enum(..) => {
 686                 let module = self.new_module(parent,
 687                                              ModuleKind::Def(def, ident.name),
 688                                              def_id,
 689                                              expansion,
 690                                              span);
 691                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 692             }
 693             Def::Variant(..) | Def::TyAlias(..) | Def::ForeignTy(..) => {
 694                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 695             }
 696             Def::Fn(..) | Def::Static(..) | Def::Const(..) | Def::VariantCtor(..) => {
 697                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 698             }
 699             Def::StructCtor(..) => {
 700                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 701
 702                 if let Some(struct_def_id) =
 703                         self.cstore.def_key(def_id).parent
 704                             .map(|index| DefId { krate: def_id.krate, index: index }) {
 705                     self.struct_constructors.insert(struct_def_id, (def, vis));
 706                 }
 707             }
 708             Def::Trait(..) => {
 709                 let module_kind = ModuleKind::Def(def, ident.name);
 710                 let module = self.new_module(parent,
 711                                              module_kind,
 712                                              parent.normal_ancestor_id,
 713                                              expansion,
 714                                              span);
 715                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 716
 717                 for child in self.cstore.item_children_untracked(def_id, self.session) {
 718                     let ns = if let Def::AssociatedTy(..) = child.def { TypeNS } else { ValueNS };
 719                     self.define(module, child.ident, ns,
 720                                 (child.def, ty::Visibility::Public, DUMMY_SP, expansion));
 721
 722                     if self.cstore.associated_item_cloned_untracked(child.def.def_id())
 723                            .method_has_self_argument {
 724                         self.has_self.insert(child.def.def_id());
 725                     }
 726                 }
 727                 module.populated.set(true);
 728             }
 729             Def::Struct(..) | Def::Union(..) => {
 730                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 731
 732                 // Record field names for error reporting.
 733                 let field_names = self.cstore.struct_field_names_untracked(def_id);
 734                 self.insert_field_names(def_id, field_names);
 735             }
 736             Def::Macro(..) => {
 737                 self.define(parent, ident, MacroNS, (def, vis, DUMMY_SP, expansion));
 738             }
 739             _ => bug!("unexpected definition: {:?}", def)
 740         }
 741     }
 742
 743     pub fn get_module(&mut self, def_id: DefId) -> Module<'a> {
 744         if def_id.krate == LOCAL_CRATE {
 745             return self.module_map[&def_id]
 746         }
 747
 748         let macros_only = self.cstore.dep_kind_untracked(def_id.krate).macros_only();
 749         if let Some(&module) = self.extern_module_map.get(&(def_id, macros_only)) {
 750             return module;
 751         }
 752
 753         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
 754             (self.cstore.crate_name_untracked(def_id.krate).as_interned_str(), None)
 755         } else {
 756             let def_key = self.cstore.def_key(def_id);
 757             (def_key.disambiguated_data.data.get_opt_name().unwrap(),
 758              Some(self.get_module(DefId { index: def_key.parent.unwrap(), ..def_id })))
 759         };
 760
 761         let kind = ModuleKind::Def(Def::Mod(def_id), name.as_symbol());
 762         let module =
 763             self.arenas.alloc_module(ModuleData::new(parent, kind, def_id, Mark::root(), DUMMY_SP));
 764         self.extern_module_map.insert((def_id, macros_only), module);
 765         module
 766     }
 767
 768     pub fn macro_def_scope(&mut self, expansion: Mark) -> Module<'a> {
 769         let def_id = self.macro_defs[&expansion];
 770         if let Some(id) = self.definitions.as_local_node_id(def_id) {
 771             self.local_macro_def_scopes[&id]
 772         } else if def_id.krate == BUILTIN_MACROS_CRATE {
 773             self.injected_crate.unwrap_or(self.graph_root)
 774         } else {
 775             let module_def_id = ty::DefIdTree::parent(&*self, def_id).unwrap();
 776             self.get_module(module_def_id)
 777         }
 778     }
 779
 780     pub fn get_macro(&mut self, def: Def) -> Lrc<SyntaxExtension> {
 781         let def_id = match def {
 782             Def::Macro(def_id, ..) => def_id,
 783             Def::NonMacroAttr(attr_kind) => return Lrc::new(SyntaxExtension::NonMacroAttr {
 784                 mark_used: attr_kind == NonMacroAttrKind::Tool,
 785             }),
 786             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 787         };
 788         if let Some(ext) = self.macro_map.get(&def_id) {
 789             return ext.clone();
 790         }
 791
 792         let macro_def = match self.cstore.load_macro_untracked(def_id, &self.session) {
 793             LoadedMacro::MacroDef(macro_def) => macro_def,
 794             LoadedMacro::ProcMacro(ext) => return ext,
 795         };
 796
 797         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
 798                                                &self.session.features_untracked(),
 799                                                &macro_def,
 800                                                self.cstore.crate_edition_untracked(def_id.krate)));
 801         self.macro_map.insert(def_id, ext.clone());
 802         ext
 803     }
 804
 805     /// Ensures that the reduced graph rooted at the given external module
 806     /// is built, building it if it is not.
 807     pub fn populate_module_if_necessary(&mut self, module: Module<'a>) {
 808         if module.populated.get() { return }
 809         let def_id = module.def_id().unwrap();
 810         for child in self.cstore.item_children_untracked(def_id, self.session) {
 811             self.build_reduced_graph_for_external_crate_def(module, child);
 812         }
 813         module.populated.set(true)
 814     }
 815
 816     fn legacy_import_macro(&mut self,
 817                            name: Name,
 818                            binding: &'a NameBinding<'a>,
 819                            span: Span,
 820                            allow_shadowing: bool) {
 821         if self.macro_use_prelude.insert(name, binding).is_some() && !allow_shadowing {
 822             let msg = format!("`{}` is already in scope", name);
 823             let note =
 824                 "macro-expanded `#[macro_use]`s may not shadow existing macros (see RFC 1560)";
 825             self.session.struct_span_err(span, &msg).note(note).emit();
 826         }
 827     }
 828
 829     // This returns true if we should consider the underlying `extern crate` to be used.
 830     fn process_legacy_macro_imports(&mut self, item: &Item, module: Module<'a>, expansion: Mark)
 831                                     -> bool {
 832         let allow_shadowing = expansion == Mark::root();
 833         let legacy_imports = self.legacy_macro_imports(&item.attrs);
 834         let used = legacy_imports != LegacyMacroImports::default();
 835
 836         // `#[macro_use]` is only allowed at the crate root.
 837         if self.current_module.parent.is_some() && used {
 838             span_err!(self.session, item.span, E0468,
 839                       "an `extern crate` loading macros must be at the crate root");
 840         }
 841
 842         let (graph_root, arenas) = (self.graph_root, self.arenas);
 843         let macro_use_directive = |span| arenas.alloc_import_directive(ImportDirective {
 844             root_id: item.id,
 845             id: item.id,
 846             parent: graph_root,
 847             imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 848             subclass: ImportDirectiveSubclass::MacroUse,
 849             root_span: span,
 850             span,
 851             module_path: Vec::new(),
 852             vis: Cell::new(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))),
 853             expansion,
 854             used: Cell::new(false),
 855             is_uniform_paths_canary: false,
 856         });
 857
 858         if let Some(span) = legacy_imports.import_all {
 859             let directive = macro_use_directive(span);
 860             self.potentially_unused_imports.push(directive);
 861             module.for_each_child(|ident, ns, binding| if ns == MacroNS {
 862                 let imported_binding = self.import(binding, directive);
 863                 self.legacy_import_macro(ident.name, imported_binding, span, allow_shadowing);
 864             });
 865         } else {
 866             for (name, span) in legacy_imports.imports {
 867                 let ident = Ident::with_empty_ctxt(name);
 868                 let result = self.resolve_ident_in_module(
 869                     ModuleOrUniformRoot::Module(module),
 870                     ident,
 871                     MacroNS,
 872                     false,
 873                     span,
 874                 );
 875                 if let Ok(binding) = result {
 876                     let directive = macro_use_directive(span);
 877                     self.potentially_unused_imports.push(directive);
 878                     let imported_binding = self.import(binding, directive);
 879                     self.legacy_import_macro(name, imported_binding, span, allow_shadowing);
 880                 } else {
 881                     span_err!(self.session, span, E0469, "imported macro not found");
 882                 }
 883             }
 884         }
 885         used
 886     }
 887
 888     // does this attribute list contain "macro_use"?
 889     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
 890         for attr in attrs {
 891             if attr.check_name("macro_escape") {
 892                 let msg = "macro_escape is a deprecated synonym for macro_use";
 893                 let mut err = self.session.struct_span_warn(attr.span, msg);
 894                 if let ast::AttrStyle::Inner = attr.style {
 895                     err.help("consider an outer attribute, #[macro_use] mod ...").emit();
 896                 } else {
 897                     err.emit();
 898                 }
 899             } else if !attr.check_name("macro_use") {
 900                 continue;
 901             }
 902
 903             if !attr.is_word() {
 904                 self.session.span_err(attr.span, "arguments to macro_use are not allowed here");
 905             }
 906             return true;
 907         }
 908
 909         false
 910     }
 911
 912     fn legacy_macro_imports(&mut self, attrs: &[ast::Attribute]) -> LegacyMacroImports {
 913         let mut imports = LegacyMacroImports::default();
 914         for attr in attrs {
 915             if attr.check_name("macro_use") {
 916                 match attr.meta_item_list() {
 917                     Some(names) => for attr in names {
 918                         if let Some(word) = attr.word() {
 919                             imports.imports.push((word.name(), attr.span()));
 920                         } else {
 921                             span_err!(self.session, attr.span(), E0466, "bad macro import");
 922                         }
 923                     },
 924                     None => imports.import_all = Some(attr.span),
 925                 }
 926             }
 927         }
 928         imports
 929     }
 930 }
 931
 932 pub struct BuildReducedGraphVisitor<'a, 'b: 'a, 'c: 'b> {
 933     pub resolver: &'a mut Resolver<'b, 'c>,
 934     pub current_legacy_scope: LegacyScope<'b>,
 935     pub expansion: Mark,
 936 }
 937
 938 impl<'a, 'b, 'cl> BuildReducedGraphVisitor<'a, 'b, 'cl> {
 939     fn visit_invoc(&mut self, id: ast::NodeId) -> &'b InvocationData<'b> {
 940         let mark = id.placeholder_to_mark();
 941         self.resolver.current_module.unresolved_invocations.borrow_mut().insert(mark);
 942         let invocation = self.resolver.invocations[&mark];
 943         invocation.module.set(self.resolver.current_module);
 944         invocation.parent_legacy_scope.set(self.current_legacy_scope);
 945         invocation.output_legacy_scope.set(self.current_legacy_scope);
 946         invocation
 947     }
 948 }
 949
 950 macro_rules! method {
 951     ($visit:ident: $ty:ty, $invoc:path, $walk:ident) => {
 952         fn $visit(&mut self, node: &'a $ty) {
 953             if let $invoc(..) = node.node {
 954                 self.visit_invoc(node.id);
 955             } else {
 956                 visit::$walk(self, node);
 957             }
 958         }
 959     }
 960 }
 961
 962 impl<'a, 'b, 'cl> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b, 'cl> {
 963     method!(visit_impl_item: ast::ImplItem, ast::ImplItemKind::Macro, walk_impl_item);
 964     method!(visit_expr:      ast::Expr,     ast::ExprKind::Mac,       walk_expr);
 965     method!(visit_pat:       ast::Pat,      ast::PatKind::Mac,        walk_pat);
 966     method!(visit_ty:        ast::Ty,       ast::TyKind::Mac,         walk_ty);
 967
 968     fn visit_item(&mut self, item: &'a Item) {
 969         let macro_use = match item.node {
 970             ItemKind::MacroDef(..) => {
 971                 self.resolver.define_macro(item, self.expansion, &mut self.current_legacy_scope);
 972                 return
 973             }
 974             ItemKind::Mac(..) => {
 975                 self.current_legacy_scope = LegacyScope::Invocation(self.visit_invoc(item.id));
 976                 return
 977             }
 978             ItemKind::Mod(..) => self.resolver.contains_macro_use(&item.attrs),
 979             _ => false,
 980         };
 981
 982         let orig_current_module = self.resolver.current_module;
 983         let orig_current_legacy_scope = self.current_legacy_scope;
 984         self.resolver.build_reduced_graph_for_item(item, self.expansion);
 985         visit::walk_item(self, item);
 986         self.resolver.current_module = orig_current_module;
 987         if !macro_use {
 988             self.current_legacy_scope = orig_current_legacy_scope;
 989         }
 990     }
 991
 992     fn visit_stmt(&mut self, stmt: &'a ast::Stmt) {
 993         if let ast::StmtKind::Mac(..) = stmt.node {
 994             self.current_legacy_scope = LegacyScope::Invocation(self.visit_invoc(stmt.id));
 995         } else {
 996             visit::walk_stmt(self, stmt);
 997         }
 998     }
 999
1000     fn visit_foreign_item(&mut self, foreign_item: &'a ForeignItem) {
1001         if let ForeignItemKind::Macro(_) = foreign_item.node {
1002             self.visit_invoc(foreign_item.id);
1003             return;
1004         }
1005
1006         self.resolver.build_reduced_graph_for_foreign_item(foreign_item, self.expansion);
1007         visit::walk_foreign_item(self, foreign_item);
1008     }
1009
1010     fn visit_block(&mut self, block: &'a Block) {
1011         let orig_current_module = self.resolver.current_module;
1012         let orig_current_legacy_scope = self.current_legacy_scope;
1013         self.resolver.build_reduced_graph_for_block(block, self.expansion);
1014         visit::walk_block(self, block);
1015         self.resolver.current_module = orig_current_module;
1016         self.current_legacy_scope = orig_current_legacy_scope;
1017     }
1018
1019     fn visit_trait_item(&mut self, item: &'a TraitItem) {
1020         let parent = self.resolver.current_module;
1021
1022         if let TraitItemKind::Macro(_) = item.node {
1023             self.visit_invoc(item.id);
1024             return
1025         }
1026
1027         // Add the item to the trait info.
1028         let item_def_id = self.resolver.definitions.local_def_id(item.id);
1029         let (def, ns) = match item.node {
1030             TraitItemKind::Const(..) => (Def::AssociatedConst(item_def_id), ValueNS),
1031             TraitItemKind::Method(ref sig, _) => {
1032                 if sig.decl.has_self() {
1033                     self.resolver.has_self.insert(item_def_id);
1034                 }
1035                 (Def::Method(item_def_id), ValueNS)
1036             }
1037             TraitItemKind::Type(..) => (Def::AssociatedTy(item_def_id), TypeNS),
1038             TraitItemKind::Macro(_) => bug!(),  // handled above
1039         };
1040
1041         let vis = ty::Visibility::Public;
1042         self.resolver.define(parent, item.ident, ns, (def, vis, item.span, self.expansion));
1043
1044         self.resolver.current_module = parent.parent.unwrap(); // nearest normal ancestor
1045         visit::walk_trait_item(self, item);
1046         self.resolver.current_module = parent;
1047     }
1048
1049     fn visit_token(&mut self, t: Token) {
1050         if let Token::Interpolated(nt) = t {
1051             match nt.0 {
1052                 token::NtExpr(ref expr) => {
1053                     if let ast::ExprKind::Mac(..) = expr.node {
1054                         self.visit_invoc(expr.id);
1055                     }
1056                 }
1057                 _ => {}
1058             }
1059         }
1060     }
1061
1062     fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
1063         if !attr.is_sugared_doc && is_builtin_attr(attr) {
1064             let parent_scope = ParentScope {
1065                 module: self.resolver.current_module.nearest_item_scope(),
1066                 expansion: self.expansion,
1067                 legacy: self.current_legacy_scope,
1068                 // Let's hope discerning built-in attributes from derive helpers is not necessary
1069                 derives: Vec::new(),
1070             };
1071             parent_scope.module.builtin_attrs.borrow_mut().push((
1072                 attr.path.segments[0].ident, parent_scope
1073             ));
1074         }
1075         visit::walk_attribute(self, attr);
1076     }
1077 }