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