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