src/librustc_resolve/resolve_imports.rs

   1 // Copyright 2015 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 use self::ImportDirectiveSubclass::*;
  12
  13 use DefModifiers;
  14 use Module;
  15 use Namespace::{self, TypeNS, ValueNS};
  16 use {NameBindings, NameBinding};
  17 use NamespaceResult::{BoundResult, UnboundResult, UnknownResult};
  18 use NamespaceResult;
  19 use NameSearchType;
  20 use ResolveResult;
  21 use Resolver;
  22 use UseLexicalScopeFlag;
  23 use {names_to_string, module_to_string};
  24 use {resolve_error, ResolutionError};
  25
  26 use build_reduced_graph;
  27
  28 use rustc::lint;
  29 use rustc::middle::def::*;
  30 use rustc::middle::def_id::DefId;
  31 use rustc::middle::privacy::*;
  32
  33 use syntax::ast::{NodeId, Name};
  34 use syntax::attr::AttrMetaMethods;
  35 use syntax::codemap::Span;
  36 use syntax::util::lev_distance::find_best_match_for_name;
  37
  38 use std::mem::replace;
  39
  40 /// Contains data for specific types of import directives.
  41 #[derive(Copy, Clone,Debug)]
  42 pub enum ImportDirectiveSubclass {
  43     SingleImport(Name /* target */, Name /* source */),
  44     GlobImport,
  45 }
  46
  47 /// Whether an import can be shadowed by another import.
  48 #[derive(Debug,PartialEq,Clone,Copy)]
  49 pub enum Shadowable {
  50     Always,
  51     Never,
  52 }
  53
  54 /// One import directive.
  55 #[derive(Debug)]
  56 pub struct ImportDirective {
  57     pub module_path: Vec<Name>,
  58     pub subclass: ImportDirectiveSubclass,
  59     pub span: Span,
  60     pub id: NodeId,
  61     pub is_public: bool, // see note in ImportResolutionPerNamespace about how to use this
  62     pub shadowable: Shadowable,
  63 }
  64
  65 impl ImportDirective {
  66     pub fn new(module_path: Vec<Name>,
  67                subclass: ImportDirectiveSubclass,
  68                span: Span,
  69                id: NodeId,
  70                is_public: bool,
  71                shadowable: Shadowable)
  72                -> ImportDirective {
  73         ImportDirective {
  74             module_path: module_path,
  75             subclass: subclass,
  76             span: span,
  77             id: id,
  78             is_public: is_public,
  79             shadowable: shadowable,
  80         }
  81     }
  82 }
  83
  84 /// The item that an import resolves to.
  85 #[derive(Clone,Debug)]
  86 pub struct Target<'a> {
  87     pub target_module: Module<'a>,
  88     pub binding: NameBinding<'a>,
  89     pub shadowable: Shadowable,
  90 }
  91
  92 impl<'a> Target<'a> {
  93     pub fn new(target_module: Module<'a>, binding: NameBinding<'a>, shadowable: Shadowable)
  94                -> Self {
  95         Target {
  96             target_module: target_module,
  97             binding: binding,
  98             shadowable: shadowable,
  99         }
 100     }
 101 }
 102
 103 #[derive(Debug)]
 104 /// An ImportResolutionPerNamespace records what we know about an imported name.
 105 /// More specifically, it records the number of unresolved `use` directives that import the name,
 106 /// and for each namespace, it records the `use` directive importing the name in the namespace
 107 /// and the `Target` to which the name in the namespace resolves (if applicable).
 108 /// Different `use` directives may import the same name in different namespaces.
 109 pub struct ImportResolutionPerNamespace<'a> {
 110     // When outstanding_references reaches zero, outside modules can count on the targets being
 111     // correct. Before then, all bets are off; future `use` directives could override the name.
 112     // Since shadowing is forbidden, the only way outstanding_references > 1 in a legal program
 113     // is if the name is imported by exactly two `use` directives, one of which resolves to a
 114     // value and the other of which resolves to a type.
 115     pub outstanding_references: usize,
 116     pub type_ns: ImportResolution<'a>,
 117     pub value_ns: ImportResolution<'a>,
 118 }
 119
 120 /// Records what we know about an imported name in a namespace (see `ImportResolutionPerNamespace`).
 121 #[derive(Clone,Debug)]
 122 pub struct ImportResolution<'a> {
 123     /// Whether the name in the namespace was imported with a `use` or a `pub use`.
 124     pub is_public: bool,
 125
 126     /// Resolution of the name in the namespace
 127     pub target: Option<Target<'a>>,
 128
 129     /// The source node of the `use` directive
 130     pub id: NodeId,
 131 }
 132
 133 impl<'a> ::std::ops::Index<Namespace> for ImportResolutionPerNamespace<'a> {
 134     type Output = ImportResolution<'a>;
 135     fn index(&self, ns: Namespace) -> &ImportResolution<'a> {
 136         match ns { TypeNS => &self.type_ns, ValueNS => &self.value_ns }
 137     }
 138 }
 139
 140 impl<'a> ::std::ops::IndexMut<Namespace> for ImportResolutionPerNamespace<'a> {
 141     fn index_mut(&mut self, ns: Namespace) -> &mut ImportResolution<'a> {
 142         match ns { TypeNS => &mut self.type_ns, ValueNS => &mut self.value_ns }
 143     }
 144 }
 145
 146 impl<'a> ImportResolutionPerNamespace<'a> {
 147     pub fn new(id: NodeId, is_public: bool) -> Self {
 148         let resolution = ImportResolution { id: id, is_public: is_public, target: None };
 149         ImportResolutionPerNamespace {
 150             outstanding_references: 0, type_ns: resolution.clone(), value_ns: resolution,
 151         }
 152     }
 153
 154     pub fn shadowable(&self, namespace: Namespace) -> Shadowable {
 155         match self[namespace].target {
 156             Some(ref target) => target.shadowable,
 157             None => Shadowable::Always,
 158         }
 159     }
 160 }
 161
 162 struct ImportResolvingError {
 163     span: Span,
 164     path: String,
 165     help: String,
 166 }
 167
 168 struct ImportResolver<'a, 'b: 'a, 'tcx: 'b> {
 169     resolver: &'a mut Resolver<'b, 'tcx>,
 170 }
 171
 172 impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
 173     // Import resolution
 174     //
 175     // This is a fixed-point algorithm. We resolve imports until our efforts
 176     // are stymied by an unresolved import; then we bail out of the current
 177     // module and continue. We terminate successfully once no more imports
 178     // remain or unsuccessfully when no forward progress in resolving imports
 179     // is made.
 180
 181     /// Resolves all imports for the crate. This method performs the fixed-
 182     /// point iteration.
 183     fn resolve_imports(&mut self) {
 184         let mut i = 0;
 185         let mut prev_unresolved_imports = 0;
 186         loop {
 187             debug!("(resolving imports) iteration {}, {} imports left",
 188                    i,
 189                    self.resolver.unresolved_imports);
 190
 191             let module_root = self.resolver.graph_root;
 192             let errors = self.resolve_imports_for_module_subtree(module_root);
 193
 194             if self.resolver.unresolved_imports == 0 {
 195                 debug!("(resolving imports) success");
 196                 break;
 197             }
 198
 199             if self.resolver.unresolved_imports == prev_unresolved_imports {
 200                 // resolving failed
 201                 if errors.len() > 0 {
 202                     for e in errors {
 203                         resolve_error(self.resolver,
 204                                       e.span,
 205                                       ResolutionError::UnresolvedImport(Some((&e.path, &e.help))));
 206                     }
 207                 } else {
 208                     // Report unresolved imports only if no hard error was already reported
 209                     // to avoid generating multiple errors on the same import.
 210                     // Imports that are still indeterminate at this point are actually blocked
 211                     // by errored imports, so there is no point reporting them.
 212                     self.resolver.report_unresolved_imports(module_root);
 213                 }
 214                 break;
 215             }
 216
 217             i += 1;
 218             prev_unresolved_imports = self.resolver.unresolved_imports;
 219         }
 220     }
 221
 222     /// Attempts to resolve imports for the given module and all of its
 223     /// submodules.
 224     fn resolve_imports_for_module_subtree(&mut self,
 225                                           module_: Module<'b>)
 226                                           -> Vec<ImportResolvingError> {
 227         let mut errors = Vec::new();
 228         debug!("(resolving imports for module subtree) resolving {}",
 229                module_to_string(&*module_));
 230         let orig_module = replace(&mut self.resolver.current_module, module_);
 231         errors.extend(self.resolve_imports_for_module(module_));
 232         self.resolver.current_module = orig_module;
 233
 234         build_reduced_graph::populate_module_if_necessary(self.resolver, &module_);
 235         for (_, child_node) in module_.children.borrow().iter() {
 236             match child_node.type_ns.module() {
 237                 None => {
 238                     // Nothing to do.
 239                 }
 240                 Some(child_module) => {
 241                     errors.extend(self.resolve_imports_for_module_subtree(child_module));
 242                 }
 243             }
 244         }
 245
 246         for (_, child_module) in module_.anonymous_children.borrow().iter() {
 247             errors.extend(self.resolve_imports_for_module_subtree(child_module));
 248         }
 249
 250         errors
 251     }
 252
 253     /// Attempts to resolve imports for the given module only.
 254     fn resolve_imports_for_module(&mut self, module: Module<'b>) -> Vec<ImportResolvingError> {
 255         let mut errors = Vec::new();
 256
 257         if module.all_imports_resolved() {
 258             debug!("(resolving imports for module) all imports resolved for {}",
 259                    module_to_string(&*module));
 260             return errors;
 261         }
 262
 263         let mut imports = module.imports.borrow_mut();
 264         let import_count = imports.len();
 265         let mut indeterminate_imports = Vec::new();
 266         while module.resolved_import_count.get() + indeterminate_imports.len() < import_count {
 267             let import_index = module.resolved_import_count.get();
 268             match self.resolve_import_for_module(module, &imports[import_index]) {
 269                 ResolveResult::Failed(err) => {
 270                     let import_directive = &imports[import_index];
 271                     let (span, help) = match err {
 272                         Some((span, msg)) => (span, format!(". {}", msg)),
 273                         None => (import_directive.span, String::new()),
 274                     };
 275                     errors.push(ImportResolvingError {
 276                         span: span,
 277                         path: import_path_to_string(&import_directive.module_path,
 278                                                     import_directive.subclass),
 279                         help: help,
 280                     });
 281                 }
 282                 ResolveResult::Indeterminate => {}
 283                 ResolveResult::Success(()) => {
 284                     // count success
 285                     module.resolved_import_count
 286                           .set(module.resolved_import_count.get() + 1);
 287                     continue;
 288                 }
 289             }
 290             // This resolution was not successful, keep it for later
 291             indeterminate_imports.push(imports.swap_remove(import_index));
 292
 293         }
 294
 295         imports.extend(indeterminate_imports);
 296
 297         errors
 298     }
 299
 300     /// Attempts to resolve the given import. The return value indicates
 301     /// failure if we're certain the name does not exist, indeterminate if we
 302     /// don't know whether the name exists at the moment due to other
 303     /// currently-unresolved imports, or success if we know the name exists.
 304     /// If successful, the resolved bindings are written into the module.
 305     fn resolve_import_for_module(&mut self,
 306                                  module_: Module<'b>,
 307                                  import_directive: &ImportDirective)
 308                                  -> ResolveResult<()> {
 309         let mut resolution_result = ResolveResult::Failed(None);
 310         let module_path = &import_directive.module_path;
 311
 312         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 313                names_to_string(&module_path[..]),
 314                module_to_string(&*module_));
 315
 316         // First, resolve the module path for the directive, if necessary.
 317         let container = if module_path.is_empty() {
 318             // Use the crate root.
 319             Some((self.resolver.graph_root, LastMod(AllPublic)))
 320         } else {
 321             match self.resolver.resolve_module_path(module_,
 322                                                     &module_path[..],
 323                                                     UseLexicalScopeFlag::DontUseLexicalScope,
 324                                                     import_directive.span,
 325                                                     NameSearchType::ImportSearch) {
 326                 ResolveResult::Failed(err) => {
 327                     resolution_result = ResolveResult::Failed(err);
 328                     None
 329                 }
 330                 ResolveResult::Indeterminate => {
 331                     resolution_result = ResolveResult::Indeterminate;
 332                     None
 333                 }
 334                 ResolveResult::Success(container) => Some(container),
 335             }
 336         };
 337
 338         match container {
 339             None => {}
 340             Some((containing_module, lp)) => {
 341                 // We found the module that the target is contained
 342                 // within. Attempt to resolve the import within it.
 343
 344                 match import_directive.subclass {
 345                     SingleImport(target, source) => {
 346                         resolution_result = self.resolve_single_import(&module_,
 347                                                                        containing_module,
 348                                                                        target,
 349                                                                        source,
 350                                                                        import_directive,
 351                                                                        lp);
 352                     }
 353                     GlobImport => {
 354                         resolution_result = self.resolve_glob_import(&module_,
 355                                                                      containing_module,
 356                                                                      import_directive,
 357                                                                      lp);
 358                     }
 359                 }
 360             }
 361         }
 362
 363         // Decrement the count of unresolved imports.
 364         match resolution_result {
 365             ResolveResult::Success(()) => {
 366                 assert!(self.resolver.unresolved_imports >= 1);
 367                 self.resolver.unresolved_imports -= 1;
 368             }
 369             _ => {
 370                 // Nothing to do here; just return the error.
 371             }
 372         }
 373
 374         // Decrement the count of unresolved globs if necessary. But only if
 375         // the resolution result is a success -- other cases will
 376         // be handled by the main loop.
 377
 378         if resolution_result.success() {
 379             match import_directive.subclass {
 380                 GlobImport => {
 381                     module_.dec_glob_count();
 382                     if import_directive.is_public {
 383                         module_.dec_pub_glob_count();
 384                     }
 385                 }
 386                 SingleImport(..) => {
 387                     // Ignore.
 388                 }
 389             }
 390             if import_directive.is_public {
 391                 module_.dec_pub_count();
 392             }
 393         }
 394
 395         return resolution_result;
 396     }
 397
 398     fn resolve_single_import(&mut self,
 399                              module_: Module<'b>,
 400                              target_module: Module<'b>,
 401                              target: Name,
 402                              source: Name,
 403                              directive: &ImportDirective,
 404                              lp: LastPrivate)
 405                              -> ResolveResult<()> {
 406         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 407                 private {:?}",
 408                target,
 409                module_to_string(&*target_module),
 410                source,
 411                module_to_string(module_),
 412                directive.id,
 413                lp);
 414
 415         let lp = match lp {
 416             LastMod(lp) => lp,
 417             LastImport {..} => {
 418                 self.resolver
 419                     .session
 420                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 421             }
 422         };
 423
 424         // We need to resolve both namespaces for this to succeed.
 425
 426         let mut value_result = UnknownResult;
 427         let mut type_result = UnknownResult;
 428         let mut lev_suggestion = "".to_owned();
 429
 430         // Search for direct children of the containing module.
 431         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 432
 433         match target_module.children.borrow().get(&source) {
 434             None => {
 435                 let names = target_module.children.borrow();
 436                 if let Some(name) = find_best_match_for_name(names.keys(),
 437                                                              &source.as_str(),
 438                                                              None) {
 439                     lev_suggestion = format!(". Did you mean to use `{}`?", name);
 440                 }
 441             }
 442             Some(ref child_name_bindings) => {
 443                 // pub_err makes sure we don't give the same error twice.
 444                 let mut pub_err = false;
 445                 if child_name_bindings.value_ns.defined() {
 446                     debug!("(resolving single import) found value binding");
 447                     value_result = BoundResult(target_module,
 448                                                child_name_bindings.value_ns.clone());
 449                     if directive.is_public && !child_name_bindings.value_ns.is_public() {
 450                         let msg = format!("`{}` is private, and cannot be reexported", source);
 451                         let note_msg = format!("Consider marking `{}` as `pub` in the imported \
 452                                                 module",
 453                                                source);
 454                         struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 455                             .span_note(directive.span, &note_msg)
 456                             .emit();
 457                         pub_err = true;
 458                     }
 459                     if directive.is_public && child_name_bindings.value_ns.
 460                                               defined_with(DefModifiers::PRIVATE_VARIANT) {
 461                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 462                                            error E0364), consider declaring its enum as `pub`",
 463                                            source);
 464                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 465                                                        directive.id,
 466                                                        directive.span,
 467                                                        msg);
 468                         pub_err = true;
 469                     }
 470                 }
 471                 if child_name_bindings.type_ns.defined() {
 472                     debug!("(resolving single import) found type binding");
 473                     type_result = BoundResult(target_module,
 474                                               child_name_bindings.type_ns.clone());
 475                     if !pub_err && directive.is_public &&
 476                        !child_name_bindings.type_ns.is_public() {
 477                         let msg = format!("`{}` is private, and cannot be reexported", source);
 478                         let note_msg = format!("Consider declaring module `{}` as a `pub mod`",
 479                                                source);
 480                         struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 481                             .span_note(directive.span, &note_msg)
 482                             .emit();
 483                     }
 484                     if !pub_err && directive.is_public && child_name_bindings.type_ns.
 485                                                     defined_with(DefModifiers::PRIVATE_VARIANT) {
 486                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 487                                            error E0365), consider declaring its enum as `pub`",
 488                                            source);
 489                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 490                                                        directive.id,
 491                                                        directive.span,
 492                                                        msg);
 493                     }
 494                 }
 495             }
 496         }
 497
 498         // Unless we managed to find a result in both namespaces (unlikely),
 499         // search imports as well.
 500         let mut value_used_reexport = false;
 501         let mut type_used_reexport = false;
 502         match (value_result.clone(), type_result.clone()) {
 503             (BoundResult(..), BoundResult(..)) => {} // Continue.
 504             _ => {
 505                 // If there is an unresolved glob at this point in the
 506                 // containing module, bail out. We don't know enough to be
 507                 // able to resolve this import.
 508
 509                 if target_module.pub_glob_count.get() > 0 {
 510                     debug!("(resolving single import) unresolved pub glob; bailing out");
 511                     return ResolveResult::Indeterminate;
 512                 }
 513
 514                 // Now search the exported imports within the containing module.
 515                 match target_module.import_resolutions.borrow().get(&source) {
 516                     None => {
 517                         debug!("(resolving single import) no import");
 518                         // The containing module definitely doesn't have an
 519                         // exported import with the name in question. We can
 520                         // therefore accurately report that the names are
 521                         // unbound.
 522
 523                         if lev_suggestion.is_empty() {  // skip if we already have a suggestion
 524                             let names = target_module.import_resolutions.borrow();
 525                             if let Some(name) = find_best_match_for_name(names.keys(),
 526                                                                          &source.as_str(),
 527                                                                          None) {
 528                                 lev_suggestion =
 529                                     format!(". Did you mean to use the re-exported import `{}`?",
 530                                             name);
 531                             }
 532                         }
 533
 534                         if value_result.is_unknown() {
 535                             value_result = UnboundResult;
 536                         }
 537                         if type_result.is_unknown() {
 538                             type_result = UnboundResult;
 539                         }
 540                     }
 541                     Some(import_resolution) if import_resolution.outstanding_references == 0 => {
 542
 543                         fn get_binding<'a>(this: &mut Resolver,
 544                                            import_resolution: &ImportResolutionPerNamespace<'a>,
 545                                            namespace: Namespace,
 546                                            source: Name)
 547                                            -> NamespaceResult<'a> {
 548
 549                             // Import resolutions must be declared with "pub"
 550                             // in order to be exported.
 551                             if !import_resolution[namespace].is_public {
 552                                 return UnboundResult;
 553                             }
 554
 555                             match import_resolution[namespace].target.clone() {
 556                                 None => {
 557                                     return UnboundResult;
 558                                 }
 559                                 Some(Target {
 560                                     target_module,
 561                                     binding,
 562                                     shadowable: _
 563                                 }) => {
 564                                     debug!("(resolving single import) found import in ns {:?}",
 565                                            namespace);
 566                                     let id = import_resolution[namespace].id;
 567                                     // track used imports and extern crates as well
 568                                     this.used_imports.insert((id, namespace));
 569                                     this.record_import_use(id, source);
 570                                     match target_module.def_id() {
 571                                         Some(DefId{krate: kid, ..}) => {
 572                                             this.used_crates.insert(kid);
 573                                         }
 574                                         _ => {}
 575                                     }
 576                                     return BoundResult(target_module, binding);
 577                                 }
 578                             }
 579                         }
 580
 581                         // The name is an import which has been fully
 582                         // resolved. We can, therefore, just follow it.
 583                         if value_result.is_unknown() {
 584                             value_result = get_binding(self.resolver,
 585                                                        import_resolution,
 586                                                        ValueNS,
 587                                                        source);
 588                             value_used_reexport = import_resolution.value_ns.is_public;
 589                         }
 590                         if type_result.is_unknown() {
 591                             type_result = get_binding(self.resolver,
 592                                                       import_resolution,
 593                                                       TypeNS,
 594                                                       source);
 595                             type_used_reexport = import_resolution.type_ns.is_public;
 596                         }
 597
 598                     }
 599                     Some(_) => {
 600                         // If target_module is the same module whose import we are resolving
 601                         // and there it has an unresolved import with the same name as `source`,
 602                         // then the user is actually trying to import an item that is declared
 603                         // in the same scope
 604                         //
 605                         // e.g
 606                         // use self::submodule;
 607                         // pub mod submodule;
 608                         //
 609                         // In this case we continue as if we resolved the import and let the
 610                         // check_for_conflicts_between_imports_and_items call below handle
 611                         // the conflict
 612                         match (module_.def_id(), target_module.def_id()) {
 613                             (Some(id1), Some(id2)) if id1 == id2 => {
 614                                 if value_result.is_unknown() {
 615                                     value_result = UnboundResult;
 616                                 }
 617                                 if type_result.is_unknown() {
 618                                     type_result = UnboundResult;
 619                                 }
 620                             }
 621                             _ => {
 622                                 // The import is unresolved. Bail out.
 623                                 debug!("(resolving single import) unresolved import; bailing out");
 624                                 return ResolveResult::Indeterminate;
 625                             }
 626                         }
 627                     }
 628                 }
 629             }
 630         }
 631
 632         let mut value_used_public = false;
 633         let mut type_used_public = false;
 634
 635         // If we didn't find a result in the type namespace, search the
 636         // external modules.
 637         match type_result {
 638             BoundResult(..) => {}
 639             _ => {
 640                 match target_module.external_module_children.borrow_mut().get(&source) {
 641                     None => {} // Continue.
 642                     Some(module) => {
 643                         debug!("(resolving single import) found external module");
 644                         // track the module as used.
 645                         match module.def_id() {
 646                             Some(DefId{krate: kid, ..}) => {
 647                                 self.resolver.used_crates.insert(kid);
 648                             }
 649                             _ => {}
 650                         }
 651                         let name_binding = NameBinding::create_from_module(module);
 652                         type_result = BoundResult(target_module, name_binding);
 653                         type_used_public = true;
 654                     }
 655                 }
 656             }
 657         }
 658
 659         // We've successfully resolved the import. Write the results in.
 660         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 661         let import_resolution = import_resolutions.get_mut(&target).unwrap();
 662
 663         {
 664             let mut check_and_write_import = |namespace, result: &_, used_public: &mut bool| {
 665                 let namespace_name = match namespace {
 666                     TypeNS => "type",
 667                     ValueNS => "value",
 668                 };
 669
 670                 match *result {
 671                     BoundResult(ref target_module, ref name_binding) => {
 672                         debug!("(resolving single import) found {:?} target: {:?}",
 673                                namespace_name,
 674                                name_binding.def());
 675                         self.check_for_conflicting_import(&import_resolution,
 676                                                           directive.span,
 677                                                           target,
 678                                                           namespace);
 679
 680                         self.check_that_import_is_importable(&name_binding,
 681                                                              directive.span,
 682                                                              target);
 683
 684                         import_resolution[namespace] = ImportResolution {
 685                             target: Some(Target::new(target_module,
 686                                                      name_binding.clone(),
 687                                                      directive.shadowable)),
 688                             id: directive.id,
 689                             is_public: directive.is_public
 690                         };
 691
 692                         self.add_export(module_, target, &import_resolution[namespace]);
 693                         *used_public = name_binding.is_public();
 694                     }
 695                     UnboundResult => {
 696                         // Continue.
 697                     }
 698                     UnknownResult => {
 699                         panic!("{:?} result should be known at this point", namespace_name);
 700                     }
 701                 }
 702             };
 703             check_and_write_import(ValueNS, &value_result, &mut value_used_public);
 704             check_and_write_import(TypeNS, &type_result, &mut type_used_public);
 705         }
 706
 707         self.check_for_conflicts_between_imports_and_items(module_,
 708                                                            import_resolution,
 709                                                            directive.span,
 710                                                            target);
 711
 712         if value_result.is_unbound() && type_result.is_unbound() {
 713             let msg = format!("There is no `{}` in `{}`{}",
 714                               source,
 715                               module_to_string(&target_module), lev_suggestion);
 716             return ResolveResult::Failed(Some((directive.span, msg)));
 717         }
 718         let value_used_public = value_used_reexport || value_used_public;
 719         let type_used_public = type_used_reexport || type_used_public;
 720
 721         assert!(import_resolution.outstanding_references >= 1);
 722         import_resolution.outstanding_references -= 1;
 723
 724         // Record what this import resolves to for later uses in documentation,
 725         // this may resolve to either a value or a type, but for documentation
 726         // purposes it's good enough to just favor one over the other.
 727         let value_def_and_priv = import_resolution.value_ns.target.as_ref().map(|target| {
 728             let def = target.binding.def().unwrap();
 729             (def,
 730              if value_used_public {
 731                 lp
 732             } else {
 733                 DependsOn(def.def_id())
 734             })
 735         });
 736         let type_def_and_priv = import_resolution.type_ns.target.as_ref().map(|target| {
 737             let def = target.binding.def().unwrap();
 738             (def,
 739              if type_used_public {
 740                 lp
 741             } else {
 742                 DependsOn(def.def_id())
 743             })
 744         });
 745
 746         let import_lp = LastImport {
 747             value_priv: value_def_and_priv.map(|(_, p)| p),
 748             value_used: Used,
 749             type_priv: type_def_and_priv.map(|(_, p)| p),
 750             type_used: Used,
 751         };
 752
 753         if let Some((def, _)) = value_def_and_priv {
 754             self.resolver.def_map.borrow_mut().insert(directive.id,
 755                                                       PathResolution {
 756                                                           base_def: def,
 757                                                           last_private: import_lp,
 758                                                           depth: 0,
 759                                                       });
 760         }
 761         if let Some((def, _)) = type_def_and_priv {
 762             self.resolver.def_map.borrow_mut().insert(directive.id,
 763                                                       PathResolution {
 764                                                           base_def: def,
 765                                                           last_private: import_lp,
 766                                                           depth: 0,
 767                                                       });
 768         }
 769
 770         debug!("(resolving single import) successfully resolved import");
 771         return ResolveResult::Success(());
 772     }
 773
 774     // Resolves a glob import. Note that this function cannot fail; it either
 775     // succeeds or bails out (as importing * from an empty module or a module
 776     // that exports nothing is valid). target_module is the module we are
 777     // actually importing, i.e., `foo` in `use foo::*`.
 778     fn resolve_glob_import(&mut self,
 779                            module_: Module<'b>,
 780                            target_module: Module<'b>,
 781                            import_directive: &ImportDirective,
 782                            lp: LastPrivate)
 783                            -> ResolveResult<()> {
 784         let id = import_directive.id;
 785         let is_public = import_directive.is_public;
 786
 787         // This function works in a highly imperative manner; it eagerly adds
 788         // everything it can to the list of import resolutions of the module
 789         // node.
 790         debug!("(resolving glob import) resolving glob import {}", id);
 791
 792         // We must bail out if the node has unresolved imports of any kind
 793         // (including globs).
 794         if (*target_module).pub_count.get() > 0 {
 795             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 796             return ResolveResult::Indeterminate;
 797         }
 798
 799         // Add all resolved imports from the containing module.
 800         let import_resolutions = target_module.import_resolutions.borrow();
 801
 802         if module_.import_resolutions.borrow_state() != ::std::cell::BorrowState::Unused {
 803             // In this case, target_module == module_
 804             // This means we are trying to glob import a module into itself,
 805             // and it is a no-go
 806             debug!("(resolving glob imports) target module is current module; giving up");
 807             return ResolveResult::Failed(Some((import_directive.span,
 808                                                "Cannot glob-import a module into itself.".into())));
 809         }
 810
 811         for (name, target_import_resolution) in import_resolutions.iter() {
 812             debug!("(resolving glob import) writing module resolution {} into `{}`",
 813                    *name,
 814                    module_to_string(module_));
 815
 816             // Here we merge two import resolutions.
 817             let mut import_resolutions = module_.import_resolutions.borrow_mut();
 818             let mut dest_import_resolution = import_resolutions.entry(*name).or_insert_with(|| {
 819                 ImportResolutionPerNamespace::new(id, is_public)
 820             });
 821
 822             for &ns in [TypeNS, ValueNS].iter() {
 823                 match target_import_resolution[ns].target {
 824                     Some(ref target) if target_import_resolution[ns].is_public => {
 825                         self.check_for_conflicting_import(&dest_import_resolution,
 826                                                           import_directive.span,
 827                                                           *name,
 828                                                           ns);
 829                         dest_import_resolution[ns] = ImportResolution {
 830                             id: id, is_public: is_public, target: Some(target.clone())
 831                         };
 832                         self.add_export(module_, *name, &dest_import_resolution[ns]);
 833                     }
 834                     _ => {}
 835                 }
 836             }
 837         }
 838
 839         // Add all children from the containing module.
 840         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 841
 842         for (&name, name_bindings) in target_module.children.borrow().iter() {
 843             self.merge_import_resolution(module_,
 844                                          target_module,
 845                                          import_directive,
 846                                          name,
 847                                          name_bindings.clone());
 848
 849         }
 850
 851         // Record the destination of this import
 852         if let Some(did) = target_module.def_id() {
 853             self.resolver.def_map.borrow_mut().insert(id,
 854                                                       PathResolution {
 855                                                           base_def: Def::Mod(did),
 856                                                           last_private: lp,
 857                                                           depth: 0,
 858                                                       });
 859         }
 860
 861         debug!("(resolving glob import) successfully resolved import");
 862         return ResolveResult::Success(());
 863     }
 864
 865     fn merge_import_resolution(&mut self,
 866                                module_: Module<'b>,
 867                                containing_module: Module<'b>,
 868                                import_directive: &ImportDirective,
 869                                name: Name,
 870                                name_bindings: NameBindings<'b>) {
 871         let id = import_directive.id;
 872         let is_public = import_directive.is_public;
 873
 874         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 875         let dest_import_resolution = import_resolutions.entry(name).or_insert_with(|| {
 876             ImportResolutionPerNamespace::new(id, is_public)
 877         });
 878
 879         debug!("(resolving glob import) writing resolution `{}` in `{}` to `{}`",
 880                name,
 881                module_to_string(&*containing_module),
 882                module_to_string(module_));
 883
 884         // Merge the child item into the import resolution.
 885         // pub_err makes sure we don't give the same error twice.
 886         let mut pub_err = false;
 887         {
 888             let mut merge_child_item = |namespace| {
 889                 if !pub_err && is_public &&
 890                         name_bindings[namespace].defined_with(DefModifiers::PRIVATE_VARIANT) {
 891                     let msg = format!("variant `{}` is private, and cannot be reexported (error \
 892                                        E0364), consider declaring its enum as `pub`", name);
 893                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 894                                                    import_directive.id,
 895                                                    import_directive.span,
 896                                                    msg);
 897                     pub_err = true;
 898                 }
 899
 900                 let modifier = DefModifiers::IMPORTABLE | DefModifiers::PUBLIC;
 901                 if name_bindings[namespace].defined_with(modifier) {
 902                     let namespace_name = match namespace {
 903                         TypeNS => "type",
 904                         ValueNS => "value",
 905                     };
 906                     debug!("(resolving glob import) ... for {} target", namespace_name);
 907                     if dest_import_resolution.shadowable(namespace) == Shadowable::Never {
 908                         let msg = format!("a {} named `{}` has already been imported in this \
 909                                            module",
 910                                           namespace_name,
 911                                           name);
 912                         span_err!(self.resolver.session,
 913                                   import_directive.span,
 914                                   E0251,
 915                                   "{}",
 916                                   msg);
 917                     } else {
 918                         dest_import_resolution[namespace] = ImportResolution {
 919                             target: Some(Target::new(containing_module,
 920                                                      name_bindings[namespace].clone(),
 921                                                      import_directive.shadowable)),
 922                             id: id,
 923                             is_public: is_public
 924                         };
 925                         self.add_export(module_, name, &dest_import_resolution[namespace]);
 926                     }
 927                 } else {
 928                     // FIXME #30159: This is required for backwards compatability.
 929                     dest_import_resolution[namespace].is_public |= is_public;
 930                 }
 931             };
 932             merge_child_item(ValueNS);
 933             merge_child_item(TypeNS);
 934         }
 935
 936         self.check_for_conflicts_between_imports_and_items(module_,
 937                                                            dest_import_resolution,
 938                                                            import_directive.span,
 939                                                            name);
 940     }
 941
 942     fn add_export(&mut self, module: Module<'b>, name: Name, resolution: &ImportResolution<'b>) {
 943         if !resolution.is_public { return }
 944         let node_id = match module.def_id() {
 945             Some(def_id) => self.resolver.ast_map.as_local_node_id(def_id).unwrap(),
 946             None => return,
 947         };
 948         let export = match resolution.target.as_ref().unwrap().binding.def() {
 949             Some(def) => Export { name: name, def_id: def.def_id() },
 950             None => return,
 951         };
 952         self.resolver.export_map.entry(node_id).or_insert(Vec::new()).push(export);
 953     }
 954
 955     /// Checks that imported names and items don't have the same name.
 956     fn check_for_conflicting_import(&mut self,
 957                                     import_resolution: &ImportResolutionPerNamespace,
 958                                     import_span: Span,
 959                                     name: Name,
 960                                     namespace: Namespace) {
 961         let target = &import_resolution[namespace].target;
 962         debug!("check_for_conflicting_import: {}; target exists: {}",
 963                name,
 964                target.is_some());
 965
 966         match *target {
 967             Some(ref target) if target.shadowable != Shadowable::Always => {
 968                 let ns_word = match namespace {
 969                     TypeNS => {
 970                         match target.binding.module() {
 971                             Some(ref module) if module.is_normal() => "module",
 972                             Some(ref module) if module.is_trait() => "trait",
 973                             _ => "type",
 974                         }
 975                     }
 976                     ValueNS => "value",
 977                 };
 978                 let use_id = import_resolution[namespace].id;
 979                 let item = self.resolver.ast_map.expect_item(use_id);
 980                 let mut err = struct_span_err!(self.resolver.session,
 981                                                import_span,
 982                                                E0252,
 983                                                "a {} named `{}` has already been imported \
 984                                                 in this module",
 985                                                ns_word,
 986                                                name);
 987                 span_note!(&mut err,
 988                            item.span,
 989                            "previous import of `{}` here",
 990                            name);
 991                 err.emit();
 992             }
 993             Some(_) | None => {}
 994         }
 995     }
 996
 997     /// Checks that an import is actually importable
 998     fn check_that_import_is_importable(&mut self,
 999                                        name_binding: &NameBinding,
1000                                        import_span: Span,
1001                                        name: Name) {
1002         if !name_binding.defined_with(DefModifiers::IMPORTABLE) {
1003             let msg = format!("`{}` is not directly importable", name);
1004             span_err!(self.resolver.session, import_span, E0253, "{}", &msg[..]);
1005         }
1006     }
1007
1008     /// Checks that imported names and items don't have the same name.
1009     fn check_for_conflicts_between_imports_and_items(&mut self,
1010                                                      module: Module<'b>,
1011                                                      import: &ImportResolutionPerNamespace<'b>,
1012                                                      import_span: Span,
1013                                                      name: Name) {
1014         // First, check for conflicts between imports and `extern crate`s.
1015         if module.external_module_children
1016                  .borrow()
1017                  .contains_key(&name) {
1018             match import.type_ns.target {
1019                 Some(ref target) if target.shadowable != Shadowable::Always => {
1020                     let msg = format!("import `{0}` conflicts with imported crate in this module \
1021                                        (maybe you meant `use {0}::*`?)",
1022                                       name);
1023                     span_err!(self.resolver.session, import_span, E0254, "{}", &msg[..]);
1024                 }
1025                 Some(_) | None => {}
1026             }
1027         }
1028
1029         // Check for item conflicts.
1030         let name_bindings = match module.children.borrow().get(&name) {
1031             None => {
1032                 // There can't be any conflicts.
1033                 return;
1034             }
1035             Some(ref name_bindings) => (*name_bindings).clone(),
1036         };
1037
1038         match import.value_ns.target {
1039             Some(ref target) if target.shadowable != Shadowable::Always => {
1040                 if let Some(ref value) = *name_bindings.value_ns.borrow() {
1041                     let mut err = struct_span_err!(self.resolver.session,
1042                                                    import_span,
1043                                                    E0255,
1044                                                    "import `{}` conflicts with \
1045                                                     value in this module",
1046                                                    name);
1047                     if let Some(span) = value.span {
1048                         err.span_note(span, "conflicting value here");
1049                     }
1050                     err.emit();
1051                 }
1052             }
1053             Some(_) | None => {}
1054         }
1055
1056         match import.type_ns.target {
1057             Some(ref target) if target.shadowable != Shadowable::Always => {
1058                 if let Some(ref ty) = *name_bindings.type_ns.borrow() {
1059                     let (what, note) = match ty.module() {
1060                         Some(ref module) if module.is_normal() =>
1061                             ("existing submodule", "note conflicting module here"),
1062                         Some(ref module) if module.is_trait() =>
1063                             ("trait in this module", "note conflicting trait here"),
1064                         _ => ("type in this module", "note conflicting type here"),
1065                     };
1066                     let mut err = struct_span_err!(self.resolver.session,
1067                                                    import_span,
1068                                                    E0256,
1069                                                    "import `{}` conflicts with {}",
1070                                                    name,
1071                                                    what);
1072                     if let Some(span) = ty.span {
1073                         err.span_note(span, note);
1074                     }
1075                     err.emit();
1076                 }
1077             }
1078             Some(_) | None => {}
1079         }
1080     }
1081 }
1082
1083 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
1084     if names.is_empty() {
1085         import_directive_subclass_to_string(subclass)
1086     } else {
1087         (format!("{}::{}",
1088                  names_to_string(names),
1089                  import_directive_subclass_to_string(subclass)))
1090             .to_string()
1091     }
1092 }
1093
1094 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
1095     match subclass {
1096         SingleImport(_, source) => source.to_string(),
1097         GlobImport => "*".to_string(),
1098     }
1099 }
1100
1101 pub fn resolve_imports(resolver: &mut Resolver) {
1102     let mut import_resolver = ImportResolver { resolver: resolver };
1103     import_resolver.resolve_imports();
1104 }