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         for (_, child_node) in module_.children.borrow().iter() {
 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             return (Success((module, name_binding)), false);
 390         }
 391
 392         if ns == TypeNS {
 393             if let Some(extern_crate) = module.external_module_children.borrow().get(&name) {
 394                 // track the extern crate as used.
 395                 if let Some(DefId{ krate: kid, .. }) = extern_crate.def_id() {
 396                     self.resolver.used_crates.insert(kid);
 397                 }
 398                 let name_binding = NameBinding::create_from_module(extern_crate, None);
 399                 return (Success((module, name_binding)), false);
 400             }
 401         }
 402
 403         // If there is an unresolved glob at this point in the containing module, bail out.
 404         // We don't know enough to be able to resolve the name.
 405         if module.pub_glob_count.get() > 0 {
 406             return (Indeterminate, false);
 407         }
 408
 409         match module.import_resolutions.borrow().get(&(name, ns)) {
 410             // The containing module definitely doesn't have an exported import with the
 411             // name in question. We can therefore accurately report that names are unbound.
 412             None => (Failed(None), false),
 413
 414             // The name is an import which has been fully resolved, so we just follow it.
 415             Some(resolution) if resolution.outstanding_references == 0 => {
 416                 // Import resolutions must be declared with "pub" in order to be exported.
 417                 if !resolution.is_public {
 418                     return (Failed(None), false);
 419                 }
 420
 421                 let target = resolution.target.clone();
 422                 if let Some(Target { target_module, binding, shadowable: _ }) = target {
 423                     // track used imports and extern crates as well
 424                     self.resolver.used_imports.insert((resolution.id, ns));
 425                     self.resolver.record_import_use(resolution.id, name);
 426                     if let Some(DefId { krate, .. }) = target_module.def_id() {
 427                         self.resolver.used_crates.insert(krate);
 428                     }
 429                     (Success((target_module, binding)), true)
 430                 } else {
 431                     (Failed(None), false)
 432                 }
 433             }
 434
 435             // If module is the same module whose import we are resolving and
 436             // it has an unresolved import with the same name as `name`, then the user
 437             // is actually trying to import an item that is declared in the same scope
 438             //
 439             // e.g
 440             // use self::submodule;
 441             // pub mod submodule;
 442             //
 443             // In this case we continue as if we resolved the import and let
 444             // check_for_conflicts_between_imports_and_items handle the conflict
 445             Some(_) => match (importing_module.def_id(), module.def_id()) {
 446                 (Some(id1), Some(id2)) if id1 == id2 => (Failed(None), false),
 447                 _ => (Indeterminate, false)
 448             },
 449         }
 450     }
 451
 452     fn resolve_single_import(&mut self,
 453                              module_: Module<'b>,
 454                              target_module: Module<'b>,
 455                              target: Name,
 456                              source: Name,
 457                              directive: &ImportDirective,
 458                              lp: LastPrivate)
 459                              -> ResolveResult<()> {
 460         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 461                 private {:?}",
 462                target,
 463                module_to_string(&*target_module),
 464                source,
 465                module_to_string(module_),
 466                directive.id,
 467                lp);
 468
 469         let lp = match lp {
 470             LastMod(lp) => lp,
 471             LastImport {..} => {
 472                 self.resolver
 473                     .session
 474                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 475             }
 476         };
 477
 478         // We need to resolve both namespaces for this to succeed.
 479         let (value_result, value_used_reexport) =
 480             self.resolve_name_in_module(&target_module, source, ValueNS, module_);
 481         let (type_result, type_used_reexport) =
 482             self.resolve_name_in_module(&target_module, source, TypeNS, module_);
 483
 484         match (&value_result, &type_result) {
 485             (&Success((_, ref name_binding)), _) if !value_used_reexport &&
 486                                                     directive.is_public &&
 487                                                     !name_binding.is_public() => {
 488                 let msg = format!("`{}` is private, and cannot be reexported", source);
 489                 let note_msg = format!("Consider marking `{}` as `pub` in the imported module",
 490                                         source);
 491                 struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 492                     .span_note(directive.span, &note_msg)
 493                     .emit();
 494             }
 495
 496             (_, &Success((_, ref name_binding))) if !type_used_reexport &&
 497                                                     directive.is_public => {
 498                 if !name_binding.is_public() {
 499                     let msg = format!("`{}` is private, and cannot be reexported", source);
 500                     let note_msg =
 501                         format!("Consider declaring type or module `{}` with `pub`", source);
 502                     struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 503                         .span_note(directive.span, &note_msg)
 504                         .emit();
 505                 } else if name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 506                     let msg = format!("variant `{}` is private, and cannot be reexported \
 507                                        (error E0364), consider declaring its enum as `pub`",
 508                                        source);
 509                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 510                                                    directive.id,
 511                                                    directive.span,
 512                                                    msg);
 513                 }
 514             }
 515
 516             _ => {}
 517         }
 518
 519         let mut lev_suggestion = "".to_owned();
 520         match (&value_result, &type_result) {
 521             (&Indeterminate, _) | (_, &Indeterminate) => return Indeterminate,
 522             (&Failed(_), &Failed(_)) => {
 523                 let children = target_module.children.borrow();
 524                 let names = children.keys().map(|&(ref name, _)| name);
 525                 if let Some(name) = find_best_match_for_name(names, &source.as_str(), None) {
 526                     lev_suggestion = format!(". Did you mean to use `{}`?", name);
 527                 } else {
 528                     let resolutions = target_module.import_resolutions.borrow();
 529                     let names = resolutions.keys().map(|&(ref name, _)| name);
 530                     if let Some(name) = find_best_match_for_name(names,
 531                                                                  &source.as_str(),
 532                                                                  None) {
 533                         lev_suggestion =
 534                             format!(". Did you mean to use the re-exported import `{}`?", name);
 535                     }
 536                 }
 537             }
 538             _ => (),
 539         }
 540
 541         let mut value_used_public = false;
 542         let mut type_used_public = false;
 543
 544         // We've successfully resolved the import. Write the results in.
 545         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 546
 547         {
 548             let mut check_and_write_import = |namespace, result, used_public: &mut bool| {
 549                 let result: &ResolveResult<(Module<'b>, NameBinding)> = result;
 550
 551                 let import_resolution = import_resolutions.get_mut(&(target, namespace)).unwrap();
 552                 let namespace_name = match namespace {
 553                     TypeNS => "type",
 554                     ValueNS => "value",
 555                 };
 556
 557                 match *result {
 558                     Success((ref target_module, ref name_binding)) => {
 559                         debug!("(resolving single import) found {:?} target: {:?}",
 560                                namespace_name,
 561                                name_binding.def());
 562                         self.check_for_conflicting_import(&import_resolution,
 563                                                           directive.span,
 564                                                           target,
 565                                                           namespace);
 566
 567                         self.check_that_import_is_importable(&name_binding,
 568                                                              directive.span,
 569                                                              target);
 570
 571                         import_resolution.target = Some(Target::new(target_module,
 572                                                                     name_binding.clone(),
 573                                                                     directive.shadowable));
 574                         import_resolution.id = directive.id;
 575                         import_resolution.is_public = directive.is_public;
 576
 577                         self.add_export(module_, target, &import_resolution);
 578                         *used_public = name_binding.is_public();
 579                     }
 580                     Failed(_) => {
 581                         // Continue.
 582                     }
 583                     Indeterminate => {
 584                         panic!("{:?} result should be known at this point", namespace_name);
 585                     }
 586                 }
 587
 588                 self.check_for_conflicts_between_imports_and_items(module_,
 589                                                                    import_resolution,
 590                                                                    directive.span,
 591                                                                    (target, namespace));
 592             };
 593             check_and_write_import(ValueNS, &value_result, &mut value_used_public);
 594             check_and_write_import(TypeNS, &type_result, &mut type_used_public);
 595         }
 596
 597         if let (&Failed(_), &Failed(_)) = (&value_result, &type_result) {
 598             let msg = format!("There is no `{}` in `{}`{}",
 599                               source,
 600                               module_to_string(&target_module), lev_suggestion);
 601             return Failed(Some((directive.span, msg)));
 602         }
 603
 604         let value_used_public = value_used_reexport || value_used_public;
 605         let type_used_public = type_used_reexport || type_used_public;
 606
 607         let value_def_and_priv = {
 608             let import_resolution_value = import_resolutions.get_mut(&(target, ValueNS)).unwrap();
 609             assert!(import_resolution_value.outstanding_references >= 1);
 610             import_resolution_value.outstanding_references -= 1;
 611
 612             // Record what this import resolves to for later uses in documentation,
 613             // this may resolve to either a value or a type, but for documentation
 614             // purposes it's good enough to just favor one over the other.
 615             import_resolution_value.target.as_ref().map(|target| {
 616                 let def = target.binding.def().unwrap();
 617                 let last_private = if value_used_public { lp } else { DependsOn(def.def_id()) };
 618                 (def, last_private)
 619             })
 620         };
 621
 622         let type_def_and_priv = {
 623             let import_resolution_type = import_resolutions.get_mut(&(target, TypeNS)).unwrap();
 624             assert!(import_resolution_type.outstanding_references >= 1);
 625             import_resolution_type.outstanding_references -= 1;
 626
 627             import_resolution_type.target.as_ref().map(|target| {
 628                 let def = target.binding.def().unwrap();
 629                 let last_private = if type_used_public { lp } else { DependsOn(def.def_id()) };
 630                 (def, last_private)
 631             })
 632         };
 633
 634         let import_lp = LastImport {
 635             value_priv: value_def_and_priv.map(|(_, p)| p),
 636             value_used: Used,
 637             type_priv: type_def_and_priv.map(|(_, p)| p),
 638             type_used: Used,
 639         };
 640
 641         if let Some((def, _)) = value_def_and_priv {
 642             self.resolver.def_map.borrow_mut().insert(directive.id,
 643                                                       PathResolution {
 644                                                           base_def: def,
 645                                                           last_private: import_lp,
 646                                                           depth: 0,
 647                                                       });
 648         }
 649         if let Some((def, _)) = type_def_and_priv {
 650             self.resolver.def_map.borrow_mut().insert(directive.id,
 651                                                       PathResolution {
 652                                                           base_def: def,
 653                                                           last_private: import_lp,
 654                                                           depth: 0,
 655                                                       });
 656         }
 657
 658         debug!("(resolving single import) successfully resolved import");
 659         return Success(());
 660     }
 661
 662     // Resolves a glob import. Note that this function cannot fail; it either
 663     // succeeds or bails out (as importing * from an empty module or a module
 664     // that exports nothing is valid). target_module is the module we are
 665     // actually importing, i.e., `foo` in `use foo::*`.
 666     fn resolve_glob_import(&mut self,
 667                            module_: Module<'b>,
 668                            target_module: Module<'b>,
 669                            import_directive: &ImportDirective,
 670                            lp: LastPrivate)
 671                            -> ResolveResult<()> {
 672         let id = import_directive.id;
 673         let is_public = import_directive.is_public;
 674
 675         // This function works in a highly imperative manner; it eagerly adds
 676         // everything it can to the list of import resolutions of the module
 677         // node.
 678         debug!("(resolving glob import) resolving glob import {}", id);
 679
 680         // We must bail out if the node has unresolved imports of any kind
 681         // (including globs).
 682         if (*target_module).pub_count.get() > 0 {
 683             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 684             return ResolveResult::Indeterminate;
 685         }
 686
 687         // Add all resolved imports from the containing module.
 688         let import_resolutions = target_module.import_resolutions.borrow();
 689
 690         if module_.import_resolutions.borrow_state() != ::std::cell::BorrowState::Unused {
 691             // In this case, target_module == module_
 692             // This means we are trying to glob import a module into itself,
 693             // and it is a no-go
 694             debug!("(resolving glob imports) target module is current module; giving up");
 695             return ResolveResult::Failed(Some((import_directive.span,
 696                                                "Cannot glob-import a module into itself.".into())));
 697         }
 698
 699         for (&(name, ns), target_import_resolution) in import_resolutions.iter() {
 700             debug!("(resolving glob import) writing module resolution {} into `{}`",
 701                    name,
 702                    module_to_string(module_));
 703
 704             // Here we merge two import resolutions.
 705             let mut import_resolutions = module_.import_resolutions.borrow_mut();
 706             let mut dest_import_resolution =
 707                 import_resolutions.entry((name, ns))
 708                                   .or_insert_with(|| ImportResolution::new(id, is_public));
 709
 710             match target_import_resolution.target {
 711                 Some(ref target) if target_import_resolution.is_public => {
 712                     self.check_for_conflicting_import(&dest_import_resolution,
 713                                                       import_directive.span,
 714                                                       name,
 715                                                       ns);
 716                     dest_import_resolution.id = id;
 717                     dest_import_resolution.is_public = is_public;
 718                     dest_import_resolution.target = Some(target.clone());
 719                     self.add_export(module_, name, &dest_import_resolution);
 720                 }
 721                 _ => {}
 722             }
 723         }
 724
 725         // Add all children from the containing module.
 726         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 727
 728         for (&name, name_binding) in target_module.children.borrow().iter() {
 729             self.merge_import_resolution(module_,
 730                                          target_module,
 731                                          import_directive,
 732                                          name,
 733                                          name_binding.clone());
 734         }
 735
 736         // Record the destination of this import
 737         if let Some(did) = target_module.def_id() {
 738             self.resolver.def_map.borrow_mut().insert(id,
 739                                                       PathResolution {
 740                                                           base_def: Def::Mod(did),
 741                                                           last_private: lp,
 742                                                           depth: 0,
 743                                                       });
 744         }
 745
 746         debug!("(resolving glob import) successfully resolved import");
 747         return ResolveResult::Success(());
 748     }
 749
 750     fn merge_import_resolution(&mut self,
 751                                module_: Module<'b>,
 752                                containing_module: Module<'b>,
 753                                import_directive: &ImportDirective,
 754                                (name, ns): (Name, Namespace),
 755                                name_binding: NameBinding<'b>) {
 756         let id = import_directive.id;
 757         let is_public = import_directive.is_public;
 758
 759         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 760         let dest_import_resolution = import_resolutions.entry((name, ns)).or_insert_with(|| {
 761             ImportResolution::new(id, is_public)
 762         });
 763
 764         debug!("(resolving glob import) writing resolution `{}` in `{}` to `{}`",
 765                name,
 766                module_to_string(&*containing_module),
 767                module_to_string(module_));
 768
 769         // Merge the child item into the import resolution.
 770         let modifier = DefModifiers::IMPORTABLE | DefModifiers::PUBLIC;
 771
 772         if ns == TypeNS && is_public && name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 773             let msg = format!("variant `{}` is private, and cannot be reexported (error \
 774                                E0364), consider declaring its enum as `pub`", name);
 775             self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 776                                            import_directive.id,
 777                                            import_directive.span,
 778                                            msg);
 779         }
 780
 781         if name_binding.defined_with(modifier) {
 782             let namespace_name = match ns {
 783                 TypeNS => "type",
 784                 ValueNS => "value",
 785             };
 786             debug!("(resolving glob import) ... for {} target", namespace_name);
 787             if dest_import_resolution.shadowable() == Shadowable::Never {
 788                 let msg = format!("a {} named `{}` has already been imported in this module",
 789                                  namespace_name,
 790                                  name);
 791                 span_err!(self.resolver.session, import_directive.span, E0251, "{}", msg);
 792            } else {
 793                 let target = Target::new(containing_module,
 794                                          name_binding.clone(),
 795                                          import_directive.shadowable);
 796                 dest_import_resolution.target = Some(target);
 797                 dest_import_resolution.id = id;
 798                 dest_import_resolution.is_public = is_public;
 799                 self.add_export(module_, name, &dest_import_resolution);
 800             }
 801         } else {
 802             // FIXME #30159: This is required for backwards compatability.
 803             dest_import_resolution.is_public |= is_public;
 804         }
 805
 806         self.check_for_conflicts_between_imports_and_items(module_,
 807                                                            dest_import_resolution,
 808                                                            import_directive.span,
 809                                                            (name, ns));
 810     }
 811
 812     fn add_export(&mut self, module: Module<'b>, name: Name, resolution: &ImportResolution<'b>) {
 813         if !resolution.is_public { return }
 814         let node_id = match module.def_id() {
 815             Some(def_id) => self.resolver.ast_map.as_local_node_id(def_id).unwrap(),
 816             None => return,
 817         };
 818         let export = match resolution.target.as_ref().unwrap().binding.def() {
 819             Some(def) => Export { name: name, def_id: def.def_id() },
 820             None => return,
 821         };
 822         self.resolver.export_map.entry(node_id).or_insert(Vec::new()).push(export);
 823     }
 824
 825     /// Checks that imported names and items don't have the same name.
 826     fn check_for_conflicting_import(&mut self,
 827                                     import_resolution: &ImportResolution,
 828                                     import_span: Span,
 829                                     name: Name,
 830                                     namespace: Namespace) {
 831         let target = &import_resolution.target;
 832         debug!("check_for_conflicting_import: {}; target exists: {}",
 833                name,
 834                target.is_some());
 835
 836         match *target {
 837             Some(ref target) if target.shadowable != Shadowable::Always => {
 838                 let ns_word = match namespace {
 839                     TypeNS => {
 840                         match target.binding.module() {
 841                             Some(ref module) if module.is_normal() => "module",
 842                             Some(ref module) if module.is_trait() => "trait",
 843                             _ => "type",
 844                         }
 845                     }
 846                     ValueNS => "value",
 847                 };
 848                 let use_id = import_resolution.id;
 849                 let item = self.resolver.ast_map.expect_item(use_id);
 850                 let mut err = struct_span_err!(self.resolver.session,
 851                                                import_span,
 852                                                E0252,
 853                                                "a {} named `{}` has already been imported \
 854                                                 in this module",
 855                                                ns_word,
 856                                                name);
 857                 span_note!(&mut err,
 858                            item.span,
 859                            "previous import of `{}` here",
 860                            name);
 861                 err.emit();
 862             }
 863             Some(_) | None => {}
 864         }
 865     }
 866
 867     /// Checks that an import is actually importable
 868     fn check_that_import_is_importable(&mut self,
 869                                        name_binding: &NameBinding,
 870                                        import_span: Span,
 871                                        name: Name) {
 872         if !name_binding.defined_with(DefModifiers::IMPORTABLE) {
 873             let msg = format!("`{}` is not directly importable", name);
 874             span_err!(self.resolver.session, import_span, E0253, "{}", &msg[..]);
 875         }
 876     }
 877
 878     /// Checks that imported names and items don't have the same name.
 879     fn check_for_conflicts_between_imports_and_items(&mut self,
 880                                                      module: Module<'b>,
 881                                                      import: &ImportResolution<'b>,
 882                                                      import_span: Span,
 883                                                      (name, ns): (Name, Namespace)) {
 884         // First, check for conflicts between imports and `extern crate`s.
 885         if ns == TypeNS {
 886             if module.external_module_children.borrow().contains_key(&name) {
 887                 match import.target {
 888                     Some(ref target) if target.shadowable != Shadowable::Always => {
 889                         let msg = format!("import `{0}` conflicts with imported crate \
 890                                            in this module (maybe you meant `use {0}::*`?)",
 891                                           name);
 892                         span_err!(self.resolver.session, import_span, E0254, "{}", &msg[..]);
 893                     }
 894                     Some(_) | None => {}
 895                 }
 896             }
 897         }
 898
 899         // Check for item conflicts.
 900         let name_binding = match module.get_child(name, ns) {
 901             None => {
 902                 // There can't be any conflicts.
 903                 return;
 904             }
 905             Some(name_binding) => name_binding,
 906         };
 907
 908         if ns == ValueNS {
 909             match import.target {
 910                 Some(ref target) if target.shadowable != Shadowable::Always => {
 911                     let mut err = struct_span_err!(self.resolver.session,
 912                                                    import_span,
 913                                                    E0255,
 914                                                    "import `{}` conflicts with \
 915                                                     value in this module",
 916                                                    name);
 917                     if let Some(span) = name_binding.span {
 918                         err.span_note(span, "conflicting value here");
 919                     }
 920                     err.emit();
 921                 }
 922                 Some(_) | None => {}
 923             }
 924         } else {
 925             match import.target {
 926                 Some(ref target) if target.shadowable != Shadowable::Always => {
 927                     let (what, note) = match name_binding.module() {
 928                         Some(ref module) if module.is_normal() =>
 929                             ("existing submodule", "note conflicting module here"),
 930                         Some(ref module) if module.is_trait() =>
 931                             ("trait in this module", "note conflicting trait here"),
 932                         _ => ("type in this module", "note conflicting type here"),
 933                     };
 934                     let mut err = struct_span_err!(self.resolver.session,
 935                                                    import_span,
 936                                                    E0256,
 937                                                    "import `{}` conflicts with {}",
 938                                                    name,
 939                                                    what);
 940                     if let Some(span) = name_binding.span {
 941                         err.span_note(span, note);
 942                     }
 943                     err.emit();
 944                 }
 945                 Some(_) | None => {}
 946             }
 947         }
 948     }
 949 }
 950
 951 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
 952     if names.is_empty() {
 953         import_directive_subclass_to_string(subclass)
 954     } else {
 955         (format!("{}::{}",
 956                  names_to_string(names),
 957                  import_directive_subclass_to_string(subclass)))
 958             .to_string()
 959     }
 960 }
 961
 962 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
 963     match subclass {
 964         SingleImport(_, source) => source.to_string(),
 965         GlobImport => "*".to_string(),
 966     }
 967 }
 968
 969 pub fn resolve_imports(resolver: &mut Resolver) {
 970     let mut import_resolver = ImportResolver { resolver: resolver };
 971     import_resolver.resolve_imports();
 972 }