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, ExternPreludeEntry};
  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::{CrateNum, 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 std::ptr;
  32 use rustc_data_structures::sync::Lrc;
  33
  34 use syntax::ast::{Name, Ident};
  35 use syntax::attr;
  36
  37 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
  38 use syntax::ast::{Mutability, StmtKind, TraitItem, TraitItemKind, Variant};
  39 use syntax::ext::base::{MacroKind, SyntaxExtension};
  40 use syntax::ext::base::Determinacy::Undetermined;
  41 use syntax::ext::hygiene::Mark;
  42 use syntax::ext::tt::macro_rules;
  43 use syntax::feature_gate::is_builtin_attr;
  44 use syntax::parse::token::{self, Token};
  45 use syntax::std_inject::injected_crate_name;
  46 use syntax::symbol::keywords;
  47 use syntax::visit::{self, Visitor};
  48
  49 use syntax_pos::{Span, DUMMY_SP};
  50
  51 impl<'a> ToNameBinding<'a> for (Module<'a>, ty::Visibility, Span, Mark) {
  52     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  53         arenas.alloc_name_binding(NameBinding {
  54             kind: NameBindingKind::Module(self.0),
  55             vis: self.1,
  56             span: self.2,
  57             expansion: self.3,
  58         })
  59     }
  60 }
  61
  62 impl<'a> ToNameBinding<'a> for (Def, ty::Visibility, Span, Mark) {
  63     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  64         arenas.alloc_name_binding(NameBinding {
  65             kind: NameBindingKind::Def(self.0, false),
  66             vis: self.1,
  67             span: self.2,
  68             expansion: self.3,
  69         })
  70     }
  71 }
  72
  73 pub(crate) struct IsMacroExport;
  74
  75 impl<'a> ToNameBinding<'a> for (Def, ty::Visibility, Span, Mark, IsMacroExport) {
  76     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
  77         arenas.alloc_name_binding(NameBinding {
  78             kind: NameBindingKind::Def(self.0, true),
  79             vis: self.1,
  80             span: self.2,
  81             expansion: self.3,
  82         })
  83     }
  84 }
  85
  86 #[derive(Default, PartialEq, Eq)]
  87 struct LegacyMacroImports {
  88     import_all: Option<Span>,
  89     imports: Vec<(Name, Span)>,
  90 }
  91
  92 impl<'a, 'cl> Resolver<'a, 'cl> {
  93     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
  94     /// otherwise, reports an error.
  95     pub fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
  96         where T: ToNameBinding<'a>,
  97     {
  98         let binding = def.to_name_binding(self.arenas);
  99         if let Err(old_binding) = self.try_define(parent, ident, ns, binding) {
 100             self.report_conflict(parent, ident, ns, old_binding, &binding);
 101         }
 102     }
 103
 104     fn block_needs_anonymous_module(&mut self, block: &Block) -> bool {
 105         // If any statements are items, we need to create an anonymous module
 106         block.stmts.iter().any(|statement| match statement.node {
 107             StmtKind::Item(_) | StmtKind::Mac(_) => true,
 108             _ => false,
 109         })
 110     }
 111
 112     fn insert_field_names(&mut self, def_id: DefId, field_names: Vec<Name>) {
 113         if !field_names.is_empty() {
 114             self.field_names.insert(def_id, field_names);
 115         }
 116     }
 117
 118     fn build_reduced_graph_for_use_tree(
 119         &mut self,
 120         root_use_tree: &ast::UseTree,
 121         root_id: NodeId,
 122         use_tree: &ast::UseTree,
 123         id: NodeId,
 124         vis: ty::Visibility,
 125         parent_prefix: &[Ident],
 126         mut uniform_paths_canary_emitted: bool,
 127         nested: bool,
 128         item: &Item,
 129         expansion: Mark,
 130     ) {
 131         debug!("build_reduced_graph_for_use_tree(parent_prefix={:?}, \
 132                 uniform_paths_canary_emitted={}, \
 133                 use_tree={:?}, nested={})",
 134                parent_prefix, uniform_paths_canary_emitted, use_tree, nested);
 135
 136         let is_prelude = attr::contains_name(&item.attrs, "prelude_import");
 137         let uniform_paths =
 138             self.session.rust_2018() &&
 139             self.session.features_untracked().uniform_paths;
 140
 141         let prefix_iter = || parent_prefix.iter().cloned()
 142             .chain(use_tree.prefix.segments.iter().map(|seg| seg.ident));
 143         let prefix_start = prefix_iter().next();
 144         let starts_with_non_keyword = prefix_start.map_or(false, |ident| {
 145             !ident.is_path_segment_keyword()
 146         });
 147
 148         // Imports are resolved as global by default, prepend `CrateRoot`,
 149         // unless `#![feature(uniform_paths)]` is enabled.
 150         let inject_crate_root =
 151             !uniform_paths &&
 152             match use_tree.kind {
 153                 // HACK(eddyb) special-case `use *` to mean `use ::*`.
 154                 ast::UseTreeKind::Glob if prefix_start.is_none() => true,
 155                 _ => starts_with_non_keyword,
 156             };
 157         let root = if inject_crate_root {
 158             let span = use_tree.prefix.span.shrink_to_lo();
 159             Some(Ident::new(keywords::CrateRoot.name(), span))
 160         } else {
 161             None
 162         };
 163
 164         let prefix: Vec<_> = root.into_iter().chain(prefix_iter()).collect();
 165
 166         debug!("build_reduced_graph_for_use_tree: prefix={:?}", prefix);
 167
 168         // `#[feature(uniform_paths)]` allows an unqualified import path,
 169         // e.g. `use x::...;` to resolve not just globally (`use ::x::...;`)
 170         // but also relatively (`use self::x::...;`). To catch ambiguities
 171         // that might arise from both of these being available and resolution
 172         // silently picking one of them, an artificial `use self::x as _;`
 173         // import is injected as a "canary", and an error is emitted if it
 174         // successfully resolves while an `x` external crate exists.
 175         //
 176         // For each block scope around the `use` item, one special canary
 177         // import of the form `use x as _;` is also injected, having its
 178         // parent set to that scope; `resolve_imports` will only resolve
 179         // it within its appropriate scope; if any of them successfully
 180         // resolve, an ambiguity error is emitted, since the original
 181         // import can't see the item in the block scope (`self::x` only
 182         // looks in the enclosing module), but a non-`use` path could.
 183         //
 184         // Additionally, the canary might be able to catch limitations of the
 185         // current implementation, where `::x` may be chosen due to `self::x`
 186         // not existing, but `self::x` could appear later, from macro expansion.
 187         //
 188         // NB. The canary currently only errors if the `x::...` path *could*
 189         // resolve as a relative path through the extern crate, i.e. `x` is
 190         // in `extern_prelude`, *even though* `::x` might still forcefully
 191         // load a non-`extern_prelude` crate.
 192         // While always producing an ambiguity errors if `self::x` exists and
 193         // a crate *could* be loaded, would be more conservative, imports for
 194         // local modules named `test` (or less commonly, `syntax` or `log`),
 195         // would need to be qualified (e.g. `self::test`), which is considered
 196         // ergonomically unacceptable.
 197         let emit_uniform_paths_canary =
 198             !uniform_paths_canary_emitted &&
 199             self.session.rust_2018() &&
 200             starts_with_non_keyword;
 201         if emit_uniform_paths_canary {
 202             let source = prefix_start.unwrap();
 203
 204             // Helper closure to emit a canary with the given base path.
 205             let emit = |this: &mut Self, base: Option<Ident>| {
 206                 let subclass = SingleImport {
 207                     target: Ident {
 208                         name: keywords::Underscore.name().gensymed(),
 209                         span: source.span,
 210                     },
 211                     source,
 212                     result: PerNS {
 213                         type_ns: Cell::new(Err(Undetermined)),
 214                         value_ns: Cell::new(Err(Undetermined)),
 215                         macro_ns: Cell::new(Err(Undetermined)),
 216                     },
 217                     type_ns_only: false,
 218                 };
 219                 this.add_import_directive(
 220                     base.into_iter().collect(),
 221                     subclass.clone(),
 222                     source.span,
 223                     id,
 224                     root_use_tree.span,
 225                     root_id,
 226                     ty::Visibility::Invisible,
 227                     expansion,
 228                     true, // is_uniform_paths_canary
 229                 );
 230             };
 231
 232             // A single simple `self::x` canary.
 233             emit(self, Some(Ident {
 234                 name: keywords::SelfValue.name(),
 235                 span: source.span,
 236             }));
 237
 238             // One special unprefixed canary per block scope around
 239             // the import, to detect items unreachable by `self::x`.
 240             let orig_current_module = self.current_module;
 241             let mut span = source.span.modern();
 242             loop {
 243                 match self.current_module.kind {
 244                     ModuleKind::Block(..) => emit(self, None),
 245                     ModuleKind::Def(..) => break,
 246                 }
 247                 match self.hygienic_lexical_parent(self.current_module, &mut span) {
 248                     Some(module) => {
 249                         self.current_module = module;
 250                     }
 251                     None => break,
 252                 }
 253             }
 254             self.current_module = orig_current_module;
 255
 256             uniform_paths_canary_emitted = true;
 257         }
 258
 259         match use_tree.kind {
 260             ast::UseTreeKind::Simple(rename, ..) => {
 261                 let mut ident = use_tree.ident();
 262                 let mut module_path = prefix;
 263                 let mut source = module_path.pop().unwrap();
 264                 let mut type_ns_only = false;
 265
 266                 if nested {
 267                     // Correctly handle `self`
 268                     if source.name == keywords::SelfValue.name() {
 269                         type_ns_only = true;
 270
 271                         let empty_prefix = module_path.last().map_or(true, |ident| {
 272                             ident.name == keywords::CrateRoot.name()
 273                         });
 274                         if empty_prefix {
 275                             resolve_error(
 276                                 self,
 277                                 use_tree.span,
 278                                 ResolutionError::
 279                                 SelfImportOnlyInImportListWithNonEmptyPrefix
 280                             );
 281                             return;
 282                         }
 283
 284                         // Replace `use foo::self;` with `use foo;`
 285                         source = module_path.pop().unwrap();
 286                         if rename.is_none() {
 287                             ident = source;
 288                         }
 289                     }
 290                 } else {
 291                     // Disallow `self`
 292                     if source.name == keywords::SelfValue.name() {
 293                         resolve_error(self,
 294                                       use_tree.span,
 295                                       ResolutionError::SelfImportsOnlyAllowedWithin);
 296                     }
 297
 298                     // Disallow `use $crate;`
 299                     if source.name == keywords::DollarCrate.name() && module_path.is_empty() {
 300                         let crate_root = self.resolve_crate_root(source);
 301                         let crate_name = match crate_root.kind {
 302                             ModuleKind::Def(_, name) => name,
 303                             ModuleKind::Block(..) => unreachable!(),
 304                         };
 305                         // HACK(eddyb) unclear how good this is, but keeping `$crate`
 306                         // in `source` breaks `src/test/compile-fail/import-crate-var.rs`,
 307                         // while the current crate doesn't have a valid `crate_name`.
 308                         if crate_name != keywords::Invalid.name() {
 309                             // `crate_name` should not be interpreted as relative.
 310                             module_path.push(Ident {
 311                                 name: keywords::CrateRoot.name(),
 312                                 span: source.span,
 313                             });
 314                             source.name = crate_name;
 315                         }
 316                         if rename.is_none() {
 317                             ident.name = crate_name;
 318                         }
 319
 320                         self.session.struct_span_warn(item.span, "`$crate` may not be imported")
 321                             .note("`use $crate;` was erroneously allowed and \
 322                                    will become a hard error in a future release")
 323                             .emit();
 324                     }
 325                 }
 326
 327                 if ident.name == keywords::Crate.name() {
 328                     self.session.span_err(ident.span,
 329                         "crate root imports need to be explicitly named: \
 330                          `use crate as name;`");
 331                 }
 332
 333                 let subclass = SingleImport {
 334                     target: ident,
 335                     source,
 336                     result: PerNS {
 337                         type_ns: Cell::new(Err(Undetermined)),
 338                         value_ns: Cell::new(Err(Undetermined)),
 339                         macro_ns: Cell::new(Err(Undetermined)),
 340                     },
 341                     type_ns_only,
 342                 };
 343                 self.add_import_directive(
 344                     module_path,
 345                     subclass,
 346                     use_tree.span,
 347                     id,
 348                     root_use_tree.span,
 349                     root_id,
 350                     vis,
 351                     expansion,
 352                     false, // is_uniform_paths_canary
 353                 );
 354             }
 355             ast::UseTreeKind::Glob => {
 356                 let subclass = GlobImport {
 357                     is_prelude,
 358                     max_vis: Cell::new(ty::Visibility::Invisible),
 359                 };
 360                 self.add_import_directive(
 361                     prefix,
 362                     subclass,
 363                     use_tree.span,
 364                     id,
 365                     root_use_tree.span,
 366                     root_id,
 367                     vis,
 368                     expansion,
 369                     false, // is_uniform_paths_canary
 370                 );
 371             }
 372             ast::UseTreeKind::Nested(ref items) => {
 373                 // Ensure there is at most one `self` in the list
 374                 let self_spans = items.iter().filter_map(|&(ref use_tree, _)| {
 375                     if let ast::UseTreeKind::Simple(..) = use_tree.kind {
 376                         if use_tree.ident().name == keywords::SelfValue.name() {
 377                             return Some(use_tree.span);
 378                         }
 379                     }
 380
 381                     None
 382                 }).collect::<Vec<_>>();
 383                 if self_spans.len() > 1 {
 384                     let mut e = resolve_struct_error(self,
 385                         self_spans[0],
 386                         ResolutionError::SelfImportCanOnlyAppearOnceInTheList);
 387
 388                     for other_span in self_spans.iter().skip(1) {
 389                         e.span_label(*other_span, "another `self` import appears here");
 390                     }
 391
 392                     e.emit();
 393                 }
 394
 395                 for &(ref tree, id) in items {
 396                     self.build_reduced_graph_for_use_tree(
 397                         root_use_tree,
 398                         root_id,
 399                         tree,
 400                         id,
 401                         vis,
 402                         &prefix,
 403                         uniform_paths_canary_emitted,
 404                         true,
 405                         item,
 406                         expansion,
 407                     );
 408                 }
 409             }
 410         }
 411     }
 412
 413     /// Constructs the reduced graph for one item.
 414     fn build_reduced_graph_for_item(&mut self, item: &Item, expansion: Mark) {
 415         let parent = self.current_module;
 416         let ident = item.ident;
 417         let sp = item.span;
 418         let vis = self.resolve_visibility(&item.vis);
 419
 420         match item.node {
 421             ItemKind::Use(ref use_tree) => {
 422                 self.build_reduced_graph_for_use_tree(
 423                     use_tree,
 424                     item.id,
 425                     use_tree,
 426                     item.id,
 427                     vis,
 428                     &[],
 429                     false, // uniform_paths_canary_emitted
 430                     false,
 431                     item,
 432                     expansion,
 433                 );
 434             }
 435
 436             ItemKind::ExternCrate(orig_name) => {
 437                 let crate_id = self.crate_loader.process_extern_crate(item, &self.definitions);
 438                 let module =
 439                     self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 440                 self.populate_module_if_necessary(module);
 441                 if injected_crate_name().map_or(false, |name| ident.name == name) {
 442                     self.injected_crate = Some(module);
 443                 }
 444
 445                 let used = self.process_legacy_macro_imports(item, module, expansion);
 446                 let binding =
 447                     (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.arenas);
 448                 if ptr::eq(self.current_module, self.graph_root) {
 449                     self.extern_prelude.entry(ident.modern()).or_insert(ExternPreludeEntry {
 450                         extern_crate_item: None,
 451                         introduced_by_item: true,
 452                     }).extern_crate_item = Some(binding);
 453                 }
 454                 let directive = self.arenas.alloc_import_directive(ImportDirective {
 455                     root_id: item.id,
 456                     id: item.id,
 457                     parent,
 458                     imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 459                     subclass: ImportDirectiveSubclass::ExternCrate {
 460                         source: orig_name,
 461                         target: ident,
 462                     },
 463                     root_span: item.span,
 464                     span: item.span,
 465                     module_path: Vec::new(),
 466                     vis: Cell::new(vis),
 467                     expansion,
 468                     used: Cell::new(used),
 469                     is_uniform_paths_canary: false,
 470                 });
 471                 self.potentially_unused_imports.push(directive);
 472                 let imported_binding = self.import(binding, directive);
 473                 self.define(parent, ident, TypeNS, imported_binding);
 474             }
 475
 476             ItemKind::GlobalAsm(..) => {}
 477
 478             ItemKind::Mod(..) if ident == keywords::Invalid.ident() => {} // Crate root
 479
 480             ItemKind::Mod(..) => {
 481                 let def_id = self.definitions.local_def_id(item.id);
 482                 let module_kind = ModuleKind::Def(Def::Mod(def_id), ident.name);
 483                 let module = self.arenas.alloc_module(ModuleData {
 484                     no_implicit_prelude: parent.no_implicit_prelude || {
 485                         attr::contains_name(&item.attrs, "no_implicit_prelude")
 486                     },
 487                     ..ModuleData::new(Some(parent), module_kind, def_id, expansion, item.span)
 488                 });
 489                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 490                 self.module_map.insert(def_id, module);
 491
 492                 // Descend into the module.
 493                 self.current_module = module;
 494             }
 495
 496             // Handled in `rustc_metadata::{native_libs,link_args}`
 497             ItemKind::ForeignMod(..) => {}
 498
 499             // These items live in the value namespace.
 500             ItemKind::Static(_, m, _) => {
 501                 let mutbl = m == Mutability::Mutable;
 502                 let def = Def::Static(self.definitions.local_def_id(item.id), mutbl);
 503                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 504             }
 505             ItemKind::Const(..) => {
 506                 let def = Def::Const(self.definitions.local_def_id(item.id));
 507                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 508             }
 509             ItemKind::Fn(..) => {
 510                 let def = Def::Fn(self.definitions.local_def_id(item.id));
 511                 self.define(parent, ident, ValueNS, (def, vis, sp, expansion));
 512
 513                 // Functions introducing procedural macros reserve a slot
 514                 // in the macro namespace as well (see #52225).
 515                 if attr::contains_name(&item.attrs, "proc_macro") ||
 516                    attr::contains_name(&item.attrs, "proc_macro_attribute") {
 517                     let def = Def::Macro(def.def_id(), MacroKind::ProcMacroStub);
 518                     self.define(parent, ident, MacroNS, (def, vis, sp, expansion));
 519                 }
 520                 if let Some(attr) = attr::find_by_name(&item.attrs, "proc_macro_derive") {
 521                     if let Some(trait_attr) =
 522                             attr.meta_item_list().and_then(|list| list.get(0).cloned()) {
 523                         if let Some(ident) = trait_attr.name().map(Ident::with_empty_ctxt) {
 524                             let sp = trait_attr.span;
 525                             let def = Def::Macro(def.def_id(), MacroKind::ProcMacroStub);
 526                             self.define(parent, ident, MacroNS, (def, vis, sp, expansion));
 527                         }
 528                     }
 529                 }
 530             }
 531
 532             // These items live in the type namespace.
 533             ItemKind::Ty(..) => {
 534                 let def = Def::TyAlias(self.definitions.local_def_id(item.id));
 535                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 536             }
 537
 538             ItemKind::Existential(_, _) => {
 539                 let def = Def::Existential(self.definitions.local_def_id(item.id));
 540                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 541             }
 542
 543             ItemKind::Enum(ref enum_definition, _) => {
 544                 let def = Def::Enum(self.definitions.local_def_id(item.id));
 545                 let module_kind = ModuleKind::Def(def, ident.name);
 546                 let module = self.new_module(parent,
 547                                              module_kind,
 548                                              parent.normal_ancestor_id,
 549                                              expansion,
 550                                              item.span);
 551                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 552
 553                 for variant in &(*enum_definition).variants {
 554                     self.build_reduced_graph_for_variant(variant, module, vis, expansion);
 555                 }
 556             }
 557
 558             ItemKind::TraitAlias(..) => {
 559                 let def = Def::TraitAlias(self.definitions.local_def_id(item.id));
 560                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 561             }
 562
 563             // These items live in both the type and value namespaces.
 564             ItemKind::Struct(ref struct_def, _) => {
 565                 // Define a name in the type namespace.
 566                 let def_id = self.definitions.local_def_id(item.id);
 567                 let def = Def::Struct(def_id);
 568                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 569
 570                 let mut ctor_vis = vis;
 571
 572                 let has_non_exhaustive = attr::contains_name(&item.attrs, "non_exhaustive");
 573
 574                 // If the structure is marked as non_exhaustive then lower the visibility
 575                 // to within the crate.
 576                 if has_non_exhaustive && vis == ty::Visibility::Public {
 577                     ctor_vis = ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX));
 578                 }
 579
 580                 // Record field names for error reporting.
 581                 let field_names = struct_def.fields().iter().filter_map(|field| {
 582                     let field_vis = self.resolve_visibility(&field.vis);
 583                     if ctor_vis.is_at_least(field_vis, &*self) {
 584                         ctor_vis = field_vis;
 585                     }
 586                     field.ident.map(|ident| ident.name)
 587                 }).collect();
 588                 let item_def_id = self.definitions.local_def_id(item.id);
 589                 self.insert_field_names(item_def_id, field_names);
 590
 591                 // If this is a tuple or unit struct, define a name
 592                 // in the value namespace as well.
 593                 if !struct_def.is_struct() {
 594                     let ctor_def = Def::StructCtor(self.definitions.local_def_id(struct_def.id()),
 595                                                    CtorKind::from_ast(struct_def));
 596                     self.define(parent, ident, ValueNS, (ctor_def, ctor_vis, sp, expansion));
 597                     self.struct_constructors.insert(def.def_id(), (ctor_def, ctor_vis));
 598                 }
 599             }
 600
 601             ItemKind::Union(ref vdata, _) => {
 602                 let def = Def::Union(self.definitions.local_def_id(item.id));
 603                 self.define(parent, ident, TypeNS, (def, vis, sp, expansion));
 604
 605                 // Record field names for error reporting.
 606                 let field_names = vdata.fields().iter().filter_map(|field| {
 607                     self.resolve_visibility(&field.vis);
 608                     field.ident.map(|ident| ident.name)
 609                 }).collect();
 610                 let item_def_id = self.definitions.local_def_id(item.id);
 611                 self.insert_field_names(item_def_id, field_names);
 612             }
 613
 614             ItemKind::Impl(..) => {}
 615
 616             ItemKind::Trait(..) => {
 617                 let def_id = self.definitions.local_def_id(item.id);
 618
 619                 // Add all the items within to a new module.
 620                 let module_kind = ModuleKind::Def(Def::Trait(def_id), ident.name);
 621                 let module = self.new_module(parent,
 622                                              module_kind,
 623                                              parent.normal_ancestor_id,
 624                                              expansion,
 625                                              item.span);
 626                 self.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 627                 self.current_module = module;
 628             }
 629
 630             ItemKind::MacroDef(..) | ItemKind::Mac(_) => unreachable!(),
 631         }
 632     }
 633
 634     // Constructs the reduced graph for one variant. Variants exist in the
 635     // type and value namespaces.
 636     fn build_reduced_graph_for_variant(&mut self,
 637                                        variant: &Variant,
 638                                        parent: Module<'a>,
 639                                        vis: ty::Visibility,
 640                                        expansion: Mark) {
 641         let ident = variant.node.ident;
 642         let def_id = self.definitions.local_def_id(variant.node.data.id());
 643
 644         // Define a name in the type namespace.
 645         let def = Def::Variant(def_id);
 646         self.define(parent, ident, TypeNS, (def, vis, variant.span, expansion));
 647
 648         // Define a constructor name in the value namespace.
 649         // Braced variants, unlike structs, generate unusable names in
 650         // value namespace, they are reserved for possible future use.
 651         let ctor_kind = CtorKind::from_ast(&variant.node.data);
 652         let ctor_def = Def::VariantCtor(def_id, ctor_kind);
 653
 654         self.define(parent, ident, ValueNS, (ctor_def, vis, variant.span, expansion));
 655     }
 656
 657     /// Constructs the reduced graph for one foreign item.
 658     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem, expansion: Mark) {
 659         let (def, ns) = match item.node {
 660             ForeignItemKind::Fn(..) => {
 661                 (Def::Fn(self.definitions.local_def_id(item.id)), ValueNS)
 662             }
 663             ForeignItemKind::Static(_, m) => {
 664                 (Def::Static(self.definitions.local_def_id(item.id), m), ValueNS)
 665             }
 666             ForeignItemKind::Ty => {
 667                 (Def::ForeignTy(self.definitions.local_def_id(item.id)), TypeNS)
 668             }
 669             ForeignItemKind::Macro(_) => unreachable!(),
 670         };
 671         let parent = self.current_module;
 672         let vis = self.resolve_visibility(&item.vis);
 673         self.define(parent, item.ident, ns, (def, vis, item.span, expansion));
 674     }
 675
 676     fn build_reduced_graph_for_block(&mut self, block: &Block, expansion: Mark) {
 677         let parent = self.current_module;
 678         if self.block_needs_anonymous_module(block) {
 679             let module = self.new_module(parent,
 680                                          ModuleKind::Block(block.id),
 681                                          parent.normal_ancestor_id,
 682                                          expansion,
 683                                          block.span);
 684             self.block_map.insert(block.id, module);
 685             self.current_module = module; // Descend into the block.
 686         }
 687     }
 688
 689     /// Builds the reduced graph for a single item in an external crate.
 690     fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'a>, child: Export) {
 691         let Export { ident, def, vis, span, .. } = child;
 692         let def_id = def.def_id();
 693         let expansion = Mark::root(); // FIXME(jseyfried) intercrate hygiene
 694         match def {
 695             Def::Mod(..) | Def::Enum(..) => {
 696                 let module = self.new_module(parent,
 697                                              ModuleKind::Def(def, ident.name),
 698                                              def_id,
 699                                              expansion,
 700                                              span);
 701                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 702             }
 703             Def::Variant(..) | Def::TyAlias(..) | Def::ForeignTy(..) => {
 704                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 705             }
 706             Def::Fn(..) | Def::Static(..) | Def::Const(..) | Def::VariantCtor(..) => {
 707                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 708             }
 709             Def::StructCtor(..) => {
 710                 self.define(parent, ident, ValueNS, (def, vis, DUMMY_SP, expansion));
 711
 712                 if let Some(struct_def_id) =
 713                         self.cstore.def_key(def_id).parent
 714                             .map(|index| DefId { krate: def_id.krate, index: index }) {
 715                     self.struct_constructors.insert(struct_def_id, (def, vis));
 716                 }
 717             }
 718             Def::Trait(..) => {
 719                 let module_kind = ModuleKind::Def(def, ident.name);
 720                 let module = self.new_module(parent,
 721                                              module_kind,
 722                                              parent.normal_ancestor_id,
 723                                              expansion,
 724                                              span);
 725                 self.define(parent, ident, TypeNS, (module, vis, DUMMY_SP, expansion));
 726
 727                 for child in self.cstore.item_children_untracked(def_id, self.session) {
 728                     let ns = if let Def::AssociatedTy(..) = child.def { TypeNS } else { ValueNS };
 729                     self.define(module, child.ident, ns,
 730                                 (child.def, ty::Visibility::Public, DUMMY_SP, expansion));
 731
 732                     if self.cstore.associated_item_cloned_untracked(child.def.def_id())
 733                            .method_has_self_argument {
 734                         self.has_self.insert(child.def.def_id());
 735                     }
 736                 }
 737                 module.populated.set(true);
 738             }
 739             Def::Struct(..) | Def::Union(..) => {
 740                 self.define(parent, ident, TypeNS, (def, vis, DUMMY_SP, expansion));
 741
 742                 // Record field names for error reporting.
 743                 let field_names = self.cstore.struct_field_names_untracked(def_id);
 744                 self.insert_field_names(def_id, field_names);
 745             }
 746             Def::Macro(..) => {
 747                 self.define(parent, ident, MacroNS, (def, vis, DUMMY_SP, expansion));
 748             }
 749             _ => bug!("unexpected definition: {:?}", def)
 750         }
 751     }
 752
 753     pub fn get_module(&mut self, def_id: DefId) -> Module<'a> {
 754         if def_id.krate == LOCAL_CRATE {
 755             return self.module_map[&def_id]
 756         }
 757
 758         let macros_only = self.cstore.dep_kind_untracked(def_id.krate).macros_only();
 759         if let Some(&module) = self.extern_module_map.get(&(def_id, macros_only)) {
 760             return module;
 761         }
 762
 763         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
 764             (self.cstore.crate_name_untracked(def_id.krate).as_interned_str(), None)
 765         } else {
 766             let def_key = self.cstore.def_key(def_id);
 767             (def_key.disambiguated_data.data.get_opt_name().unwrap(),
 768              Some(self.get_module(DefId { index: def_key.parent.unwrap(), ..def_id })))
 769         };
 770
 771         let kind = ModuleKind::Def(Def::Mod(def_id), name.as_symbol());
 772         let module =
 773             self.arenas.alloc_module(ModuleData::new(parent, kind, def_id, Mark::root(), DUMMY_SP));
 774         self.extern_module_map.insert((def_id, macros_only), module);
 775         module
 776     }
 777
 778     pub fn macro_def_scope(&mut self, expansion: Mark) -> Module<'a> {
 779         let def_id = self.macro_defs[&expansion];
 780         if let Some(id) = self.definitions.as_local_node_id(def_id) {
 781             self.local_macro_def_scopes[&id]
 782         } else if def_id.krate == CrateNum::BuiltinMacros {
 783             self.injected_crate.unwrap_or(self.graph_root)
 784         } else {
 785             let module_def_id = ty::DefIdTree::parent(&*self, def_id).unwrap();
 786             self.get_module(module_def_id)
 787         }
 788     }
 789
 790     pub fn get_macro(&mut self, def: Def) -> Lrc<SyntaxExtension> {
 791         let def_id = match def {
 792             Def::Macro(def_id, ..) => def_id,
 793             Def::NonMacroAttr(attr_kind) => return Lrc::new(SyntaxExtension::NonMacroAttr {
 794                 mark_used: attr_kind == NonMacroAttrKind::Tool,
 795             }),
 796             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 797         };
 798         if let Some(ext) = self.macro_map.get(&def_id) {
 799             return ext.clone();
 800         }
 801
 802         let macro_def = match self.cstore.load_macro_untracked(def_id, &self.session) {
 803             LoadedMacro::MacroDef(macro_def) => macro_def,
 804             LoadedMacro::ProcMacro(ext) => return ext,
 805         };
 806
 807         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
 808                                                &self.session.features_untracked(),
 809                                                &macro_def,
 810                                                self.cstore.crate_edition_untracked(def_id.krate)));
 811         self.macro_map.insert(def_id, ext.clone());
 812         ext
 813     }
 814
 815     /// Ensures that the reduced graph rooted at the given external module
 816     /// is built, building it if it is not.
 817     pub fn populate_module_if_necessary(&mut self, module: Module<'a>) {
 818         if module.populated.get() { return }
 819         let def_id = module.def_id().unwrap();
 820         for child in self.cstore.item_children_untracked(def_id, self.session) {
 821             self.build_reduced_graph_for_external_crate_def(module, child);
 822         }
 823         module.populated.set(true)
 824     }
 825
 826     fn legacy_import_macro(&mut self,
 827                            name: Name,
 828                            binding: &'a NameBinding<'a>,
 829                            span: Span,
 830                            allow_shadowing: bool) {
 831         if self.macro_use_prelude.insert(name, binding).is_some() && !allow_shadowing {
 832             let msg = format!("`{}` is already in scope", name);
 833             let note =
 834                 "macro-expanded `#[macro_use]`s may not shadow existing macros (see RFC 1560)";
 835             self.session.struct_span_err(span, &msg).note(note).emit();
 836         }
 837     }
 838
 839     // This returns true if we should consider the underlying `extern crate` to be used.
 840     fn process_legacy_macro_imports(&mut self, item: &Item, module: Module<'a>, expansion: Mark)
 841                                     -> bool {
 842         let allow_shadowing = expansion == Mark::root();
 843         let legacy_imports = self.legacy_macro_imports(&item.attrs);
 844         let used = legacy_imports != LegacyMacroImports::default();
 845
 846         // `#[macro_use]` is only allowed at the crate root.
 847         if self.current_module.parent.is_some() && used {
 848             span_err!(self.session, item.span, E0468,
 849                       "an `extern crate` loading macros must be at the crate root");
 850         }
 851
 852         let (graph_root, arenas) = (self.graph_root, self.arenas);
 853         let macro_use_directive = |span| arenas.alloc_import_directive(ImportDirective {
 854             root_id: item.id,
 855             id: item.id,
 856             parent: graph_root,
 857             imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
 858             subclass: ImportDirectiveSubclass::MacroUse,
 859             root_span: span,
 860             span,
 861             module_path: Vec::new(),
 862             vis: Cell::new(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))),
 863             expansion,
 864             used: Cell::new(false),
 865             is_uniform_paths_canary: false,
 866         });
 867
 868         if let Some(span) = legacy_imports.import_all {
 869             let directive = macro_use_directive(span);
 870             self.potentially_unused_imports.push(directive);
 871             module.for_each_child(|ident, ns, binding| if ns == MacroNS {
 872                 let imported_binding = self.import(binding, directive);
 873                 self.legacy_import_macro(ident.name, imported_binding, span, allow_shadowing);
 874             });
 875         } else {
 876             for (name, span) in legacy_imports.imports {
 877                 let ident = Ident::with_empty_ctxt(name);
 878                 let result = self.resolve_ident_in_module(
 879                     ModuleOrUniformRoot::Module(module),
 880                     ident,
 881                     MacroNS,
 882                     false,
 883                     span,
 884                 );
 885                 if let Ok(binding) = result {
 886                     let directive = macro_use_directive(span);
 887                     self.potentially_unused_imports.push(directive);
 888                     let imported_binding = self.import(binding, directive);
 889                     self.legacy_import_macro(name, imported_binding, span, allow_shadowing);
 890                 } else {
 891                     span_err!(self.session, span, E0469, "imported macro not found");
 892                 }
 893             }
 894         }
 895         used
 896     }
 897
 898     // does this attribute list contain "macro_use"?
 899     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
 900         for attr in attrs {
 901             if attr.check_name("macro_escape") {
 902                 let msg = "macro_escape is a deprecated synonym for macro_use";
 903                 let mut err = self.session.struct_span_warn(attr.span, msg);
 904                 if let ast::AttrStyle::Inner = attr.style {
 905                     err.help("consider an outer attribute, #[macro_use] mod ...").emit();
 906                 } else {
 907                     err.emit();
 908                 }
 909             } else if !attr.check_name("macro_use") {
 910                 continue;
 911             }
 912
 913             if !attr.is_word() {
 914                 self.session.span_err(attr.span, "arguments to macro_use are not allowed here");
 915             }
 916             return true;
 917         }
 918
 919         false
 920     }
 921
 922     fn legacy_macro_imports(&mut self, attrs: &[ast::Attribute]) -> LegacyMacroImports {
 923         let mut imports = LegacyMacroImports::default();
 924         for attr in attrs {
 925             if attr.check_name("macro_use") {
 926                 match attr.meta_item_list() {
 927                     Some(names) => for attr in names {
 928                         if let Some(word) = attr.word() {
 929                             imports.imports.push((word.name(), attr.span()));
 930                         } else {
 931                             span_err!(self.session, attr.span(), E0466, "bad macro import");
 932                         }
 933                     },
 934                     None => imports.import_all = Some(attr.span),
 935                 }
 936             }
 937         }
 938         imports
 939     }
 940 }
 941
 942 pub struct BuildReducedGraphVisitor<'a, 'b: 'a, 'c: 'b> {
 943     pub resolver: &'a mut Resolver<'b, 'c>,
 944     pub current_legacy_scope: LegacyScope<'b>,
 945     pub expansion: Mark,
 946 }
 947
 948 impl<'a, 'b, 'cl> BuildReducedGraphVisitor<'a, 'b, 'cl> {
 949     fn visit_invoc(&mut self, id: ast::NodeId) -> &'b InvocationData<'b> {
 950         let mark = id.placeholder_to_mark();
 951         self.resolver.current_module.unresolved_invocations.borrow_mut().insert(mark);
 952         let invocation = self.resolver.invocations[&mark];
 953         invocation.module.set(self.resolver.current_module);
 954         invocation.parent_legacy_scope.set(self.current_legacy_scope);
 955         invocation.output_legacy_scope.set(self.current_legacy_scope);
 956         invocation
 957     }
 958 }
 959
 960 macro_rules! method {
 961     ($visit:ident: $ty:ty, $invoc:path, $walk:ident) => {
 962         fn $visit(&mut self, node: &'a $ty) {
 963             if let $invoc(..) = node.node {
 964                 self.visit_invoc(node.id);
 965             } else {
 966                 visit::$walk(self, node);
 967             }
 968         }
 969     }
 970 }
 971
 972 impl<'a, 'b, 'cl> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b, 'cl> {
 973     method!(visit_impl_item: ast::ImplItem, ast::ImplItemKind::Macro, walk_impl_item);
 974     method!(visit_expr:      ast::Expr,     ast::ExprKind::Mac,       walk_expr);
 975     method!(visit_pat:       ast::Pat,      ast::PatKind::Mac,        walk_pat);
 976     method!(visit_ty:        ast::Ty,       ast::TyKind::Mac,         walk_ty);
 977
 978     fn visit_item(&mut self, item: &'a Item) {
 979         let macro_use = match item.node {
 980             ItemKind::MacroDef(..) => {
 981                 self.resolver.define_macro(item, self.expansion, &mut self.current_legacy_scope);
 982                 return
 983             }
 984             ItemKind::Mac(..) => {
 985                 self.current_legacy_scope = LegacyScope::Invocation(self.visit_invoc(item.id));
 986                 return
 987             }
 988             ItemKind::Mod(..) => self.resolver.contains_macro_use(&item.attrs),
 989             _ => false,
 990         };
 991
 992         let orig_current_module = self.resolver.current_module;
 993         let orig_current_legacy_scope = self.current_legacy_scope;
 994         self.resolver.build_reduced_graph_for_item(item, self.expansion);
 995         visit::walk_item(self, item);
 996         self.resolver.current_module = orig_current_module;
 997         if !macro_use {
 998             self.current_legacy_scope = orig_current_legacy_scope;
 999         }
1000     }
1001
1002     fn visit_stmt(&mut self, stmt: &'a ast::Stmt) {
1003         if let ast::StmtKind::Mac(..) = stmt.node {
1004             self.current_legacy_scope = LegacyScope::Invocation(self.visit_invoc(stmt.id));
1005         } else {
1006             visit::walk_stmt(self, stmt);
1007         }
1008     }
1009
1010     fn visit_foreign_item(&mut self, foreign_item: &'a ForeignItem) {
1011         if let ForeignItemKind::Macro(_) = foreign_item.node {
1012             self.visit_invoc(foreign_item.id);
1013             return;
1014         }
1015
1016         self.resolver.build_reduced_graph_for_foreign_item(foreign_item, self.expansion);
1017         visit::walk_foreign_item(self, foreign_item);
1018     }
1019
1020     fn visit_block(&mut self, block: &'a Block) {
1021         let orig_current_module = self.resolver.current_module;
1022         let orig_current_legacy_scope = self.current_legacy_scope;
1023         self.resolver.build_reduced_graph_for_block(block, self.expansion);
1024         visit::walk_block(self, block);
1025         self.resolver.current_module = orig_current_module;
1026         self.current_legacy_scope = orig_current_legacy_scope;
1027     }
1028
1029     fn visit_trait_item(&mut self, item: &'a TraitItem) {
1030         let parent = self.resolver.current_module;
1031
1032         if let TraitItemKind::Macro(_) = item.node {
1033             self.visit_invoc(item.id);
1034             return
1035         }
1036
1037         // Add the item to the trait info.
1038         let item_def_id = self.resolver.definitions.local_def_id(item.id);
1039         let (def, ns) = match item.node {
1040             TraitItemKind::Const(..) => (Def::AssociatedConst(item_def_id), ValueNS),
1041             TraitItemKind::Method(ref sig, _) => {
1042                 if sig.decl.has_self() {
1043                     self.resolver.has_self.insert(item_def_id);
1044                 }
1045                 (Def::Method(item_def_id), ValueNS)
1046             }
1047             TraitItemKind::Type(..) => (Def::AssociatedTy(item_def_id), TypeNS),
1048             TraitItemKind::Macro(_) => bug!(),  // handled above
1049         };
1050
1051         let vis = ty::Visibility::Public;
1052         self.resolver.define(parent, item.ident, ns, (def, vis, item.span, self.expansion));
1053
1054         self.resolver.current_module = parent.parent.unwrap(); // nearest normal ancestor
1055         visit::walk_trait_item(self, item);
1056         self.resolver.current_module = parent;
1057     }
1058
1059     fn visit_token(&mut self, t: Token) {
1060         if let Token::Interpolated(nt) = t {
1061             if let token::NtExpr(ref expr) = nt.0 {
1062                 if let ast::ExprKind::Mac(..) = expr.node {
1063                     self.visit_invoc(expr.id);
1064                 }
1065             }
1066         }
1067     }
1068
1069     fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
1070         if !attr.is_sugared_doc && is_builtin_attr(attr) {
1071             let parent_scope = ParentScope {
1072                 module: self.resolver.current_module.nearest_item_scope(),
1073                 expansion: self.expansion,
1074                 legacy: self.current_legacy_scope,
1075                 // Let's hope discerning built-in attributes from derive helpers is not necessary
1076                 derives: Vec::new(),
1077             };
1078             parent_scope.module.builtin_attrs.borrow_mut().push((
1079                 attr.path.segments[0].ident, parent_scope
1080             ));
1081         }
1082         visit::walk_attribute(self, attr);
1083     }
1084 }