src/librustc_resolve/resolve_imports.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use self::ImportDirectiveSubclass::*;
  12
  13 use DefModifiers;
  14 use DefOrModule;
  15 use Module;
  16 use Namespace::{self, TypeNS, ValueNS};
  17 use NameBinding;
  18 use ResolveResult;
  19 use ResolveResult::*;
  20 use Resolver;
  21 use UseLexicalScopeFlag;
  22 use {names_to_string, module_to_string};
  23 use {resolve_error, ResolutionError};
  24
  25 use build_reduced_graph;
  26
  27 use rustc::lint;
  28 use rustc::middle::def::*;
  29 use rustc::middle::def_id::DefId;
  30 use rustc::middle::privacy::*;
  31
  32 use syntax::ast::{NodeId, Name};
  33 use syntax::attr::AttrMetaMethods;
  34 use syntax::codemap::Span;
  35 use syntax::util::lev_distance::find_best_match_for_name;
  36
  37 use std::mem::replace;
  38
  39 /// Contains data for specific types of import directives.
  40 #[derive(Copy, Clone,Debug)]
  41 pub enum ImportDirectiveSubclass {
  42     SingleImport(Name /* target */, Name /* source */),
  43     GlobImport,
  44 }
  45
  46 /// Whether an import can be shadowed by another import.
  47 #[derive(Debug,PartialEq,Clone,Copy)]
  48 pub enum Shadowable {
  49     Always,
  50     Never,
  51 }
  52
  53 /// One import directive.
  54 #[derive(Debug,Clone)]
  55 pub struct ImportDirective {
  56     pub module_path: Vec<Name>,
  57     pub subclass: ImportDirectiveSubclass,
  58     pub span: Span,
  59     pub id: NodeId,
  60     pub is_public: bool, // see note in ImportResolutionPerNamespace about how to use this
  61     pub shadowable: Shadowable,
  62 }
  63
  64 impl ImportDirective {
  65     pub fn new(module_path: Vec<Name>,
  66                subclass: ImportDirectiveSubclass,
  67                span: Span,
  68                id: NodeId,
  69                is_public: bool,
  70                shadowable: Shadowable)
  71                -> ImportDirective {
  72         ImportDirective {
  73             module_path: module_path,
  74             subclass: subclass,
  75             span: span,
  76             id: id,
  77             is_public: is_public,
  78             shadowable: shadowable,
  79         }
  80     }
  81
  82     // Given the binding to which this directive resolves in a particular namespace,
  83     // this returns the binding for the name this directive defines in that namespace.
  84     fn import<'a>(&self, mut binding: NameBinding<'a>) -> NameBinding<'a> {
  85         if self.shadowable == Shadowable::Always {
  86             binding.modifiers = binding.modifiers | DefModifiers::PRELUDE;
  87         }
  88         binding
  89     }
  90 }
  91
  92 #[derive(Debug)]
  93 /// An ImportResolution records what we know about an imported name in a given namespace.
  94 /// More specifically, it records the number of unresolved `use` directives that import the name,
  95 /// the `use` directive importing the name in the namespace, and the `NameBinding` to which the
  96 /// name in the namespace resolves (if applicable).
  97 /// Different `use` directives may import the same name in different namespaces.
  98 pub struct ImportResolution<'a> {
  99     // When outstanding_references reaches zero, outside modules can count on the targets being
 100     // correct. Before then, all bets are off; future `use` directives could override the name.
 101     // Since shadowing is forbidden, the only way outstanding_references > 1 in a legal program
 102     // is if the name is imported by exactly two `use` directives, one of which resolves to a
 103     // value and the other of which resolves to a type.
 104     pub outstanding_references: usize,
 105
 106     /// Whether this resolution came from a `use` or a `pub use`.
 107     pub is_public: bool,
 108
 109     /// Resolution of the name in the namespace
 110     pub binding: Option<NameBinding<'a>>,
 111
 112     /// The source node of the `use` directive
 113     pub id: NodeId,
 114 }
 115
 116 impl<'a> ImportResolution<'a> {
 117     pub fn new(id: NodeId, is_public: bool) -> Self {
 118         ImportResolution {
 119             outstanding_references: 0,
 120             id: id,
 121             binding: None,
 122             is_public: is_public,
 123         }
 124     }
 125
 126     pub fn shadowable(&self) -> Shadowable {
 127         match self.binding {
 128             Some(ref binding) if binding.defined_with(DefModifiers::PRELUDE) =>
 129                 Shadowable::Always,
 130             Some(_) => Shadowable::Never,
 131             None => Shadowable::Always,
 132         }
 133     }
 134 }
 135
 136 struct ImportResolvingError<'a> {
 137     /// Module where the error happened
 138     source_module: Module<'a>,
 139     import_directive: ImportDirective,
 140     span: Span,
 141     help: String,
 142 }
 143
 144 struct ImportResolver<'a, 'b: 'a, 'tcx: 'b> {
 145     resolver: &'a mut Resolver<'b, 'tcx>,
 146 }
 147
 148 impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
 149     // Import resolution
 150     //
 151     // This is a fixed-point algorithm. We resolve imports until our efforts
 152     // are stymied by an unresolved import; then we bail out of the current
 153     // module and continue. We terminate successfully once no more imports
 154     // remain or unsuccessfully when no forward progress in resolving imports
 155     // is made.
 156
 157     /// Resolves all imports for the crate. This method performs the fixed-
 158     /// point iteration.
 159     fn resolve_imports(&mut self) {
 160         let mut i = 0;
 161         let mut prev_unresolved_imports = 0;
 162         loop {
 163             debug!("(resolving imports) iteration {}, {} imports left",
 164                    i,
 165                    self.resolver.unresolved_imports);
 166
 167             let module_root = self.resolver.graph_root;
 168             let errors = self.resolve_imports_for_module_subtree(module_root);
 169
 170             if self.resolver.unresolved_imports == 0 {
 171                 debug!("(resolving imports) success");
 172                 break;
 173             }
 174
 175             if self.resolver.unresolved_imports == prev_unresolved_imports {
 176                 // resolving failed
 177                 if errors.len() > 0 {
 178                     for e in errors {
 179                         self.import_resolving_error(e)
 180                     }
 181                 } else {
 182                     // Report unresolved imports only if no hard error was already reported
 183                     // to avoid generating multiple errors on the same import.
 184                     // Imports that are still indeterminate at this point are actually blocked
 185                     // by errored imports, so there is no point reporting them.
 186                     self.resolver.report_unresolved_imports(module_root);
 187                 }
 188                 break;
 189             }
 190
 191             i += 1;
 192             prev_unresolved_imports = self.resolver.unresolved_imports;
 193         }
 194     }
 195
 196     /// Resolves an `ImportResolvingError` into the correct enum discriminant
 197     /// and passes that on to `resolve_error`.
 198     fn import_resolving_error(&self, e: ImportResolvingError) {
 199         // If it's a single failed import then create a "fake" import
 200         // resolution for it so that later resolve stages won't complain.
 201         if let SingleImport(target, _) = e.import_directive.subclass {
 202             let mut import_resolutions = e.source_module.import_resolutions.borrow_mut();
 203
 204             let resolution = import_resolutions.entry((target, ValueNS)).or_insert_with(|| {
 205                 debug!("(resolving import error) adding import resolution for `{}`",
 206                        target);
 207
 208                 ImportResolution::new(e.import_directive.id,
 209                                       e.import_directive.is_public)
 210             });
 211
 212             if resolution.binding.is_none() {
 213                 debug!("(resolving import error) adding fake target to import resolution of `{}`",
 214                        target);
 215
 216                 let dummy_binding = NameBinding {
 217                     modifiers: DefModifiers::IMPORTABLE,
 218                     def_or_module: DefOrModule::Def(Def::Err),
 219                     span: None,
 220                 };
 221
 222                 resolution.binding = Some(dummy_binding);
 223             }
 224         }
 225
 226         let path = import_path_to_string(&e.import_directive.module_path,
 227                                          e.import_directive.subclass);
 228
 229         resolve_error(self.resolver,
 230                       e.span,
 231                       ResolutionError::UnresolvedImport(Some((&path, &e.help))));
 232     }
 233
 234     /// Attempts to resolve imports for the given module and all of its
 235     /// submodules.
 236     fn resolve_imports_for_module_subtree(&mut self,
 237                                           module_: Module<'b>)
 238                                           -> Vec<ImportResolvingError<'b>> {
 239         let mut errors = Vec::new();
 240         debug!("(resolving imports for module subtree) resolving {}",
 241                module_to_string(&*module_));
 242         let orig_module = replace(&mut self.resolver.current_module, module_);
 243         errors.extend(self.resolve_imports_for_module(module_));
 244         self.resolver.current_module = orig_module;
 245
 246         build_reduced_graph::populate_module_if_necessary(self.resolver, module_);
 247         module_.for_each_local_child(|_, _, child_node| {
 248             match child_node.module() {
 249                 None => {
 250                     // Nothing to do.
 251                 }
 252                 Some(child_module) => {
 253                     errors.extend(self.resolve_imports_for_module_subtree(child_module));
 254                 }
 255             }
 256         });
 257
 258         for (_, child_module) in module_.anonymous_children.borrow().iter() {
 259             errors.extend(self.resolve_imports_for_module_subtree(child_module));
 260         }
 261
 262         errors
 263     }
 264
 265     /// Attempts to resolve imports for the given module only.
 266     fn resolve_imports_for_module(&mut self, module: Module<'b>) -> Vec<ImportResolvingError<'b>> {
 267         let mut errors = Vec::new();
 268
 269         if module.all_imports_resolved() {
 270             debug!("(resolving imports for module) all imports resolved for {}",
 271                    module_to_string(&*module));
 272             return errors;
 273         }
 274
 275         let mut imports = module.imports.borrow_mut();
 276         let import_count = imports.len();
 277         let mut indeterminate_imports = Vec::new();
 278         while module.resolved_import_count.get() + indeterminate_imports.len() < import_count {
 279             let import_index = module.resolved_import_count.get();
 280             match self.resolve_import_for_module(module, &imports[import_index]) {
 281                 ResolveResult::Failed(err) => {
 282                     let import_directive = &imports[import_index];
 283                     let (span, help) = match err {
 284                         Some((span, msg)) => (span, format!(". {}", msg)),
 285                         None => (import_directive.span, String::new()),
 286                     };
 287                     errors.push(ImportResolvingError {
 288                         source_module: module,
 289                         import_directive: import_directive.clone(),
 290                         span: span,
 291                         help: help,
 292                     });
 293                 }
 294                 ResolveResult::Indeterminate => {}
 295                 ResolveResult::Success(()) => {
 296                     // count success
 297                     module.resolved_import_count
 298                           .set(module.resolved_import_count.get() + 1);
 299                     continue;
 300                 }
 301             }
 302             // This resolution was not successful, keep it for later
 303             indeterminate_imports.push(imports.swap_remove(import_index));
 304
 305         }
 306
 307         imports.extend(indeterminate_imports);
 308
 309         errors
 310     }
 311
 312     /// Attempts to resolve the given import. The return value indicates
 313     /// failure if we're certain the name does not exist, indeterminate if we
 314     /// don't know whether the name exists at the moment due to other
 315     /// currently-unresolved imports, or success if we know the name exists.
 316     /// If successful, the resolved bindings are written into the module.
 317     fn resolve_import_for_module(&mut self,
 318                                  module_: Module<'b>,
 319                                  import_directive: &ImportDirective)
 320                                  -> ResolveResult<()> {
 321         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 322                names_to_string(&import_directive.module_path),
 323                module_to_string(&*module_));
 324
 325         self.resolver
 326             .resolve_module_path(module_,
 327                                  &import_directive.module_path,
 328                                  UseLexicalScopeFlag::DontUseLexicalScope,
 329                                  import_directive.span)
 330             .and_then(|(containing_module, lp)| {
 331                 // We found the module that the target is contained
 332                 // within. Attempt to resolve the import within it.
 333                 if let SingleImport(target, source) = import_directive.subclass {
 334                     self.resolve_single_import(module_,
 335                                                containing_module,
 336                                                target,
 337                                                source,
 338                                                import_directive,
 339                                                lp)
 340                 } else {
 341                     self.resolve_glob_import(module_, containing_module, import_directive, lp)
 342                 }
 343             })
 344             .and_then(|()| {
 345                 // Decrement the count of unresolved imports.
 346                 assert!(self.resolver.unresolved_imports >= 1);
 347                 self.resolver.unresolved_imports -= 1;
 348
 349                 if let GlobImport = import_directive.subclass {
 350                     module_.dec_glob_count();
 351                     if import_directive.is_public {
 352                         module_.dec_pub_glob_count();
 353                     }
 354                 }
 355                 if import_directive.is_public {
 356                     module_.dec_pub_count();
 357                 }
 358                 Success(())
 359             })
 360     }
 361
 362     /// Resolves the name in the namespace of the module because it is being imported by
 363     /// importing_module. Returns the name bindings defining the name
 364     /// and whether or not the name was imported.
 365     fn resolve_name_in_module(&mut self,
 366                               module: Module<'b>, // Module containing the name
 367                               name: Name,
 368                               ns: Namespace,
 369                               importing_module: Module<'b>) // Module importing the name
 370                               -> (ResolveResult<NameBinding<'b>>, bool) {
 371         build_reduced_graph::populate_module_if_necessary(self.resolver, module);
 372         if let Some(name_binding) = module.get_child(name, ns) {
 373             if name_binding.is_extern_crate() {
 374                 // track the extern crate as used.
 375                 if let Some(DefId { krate, .. }) = name_binding.module().unwrap().def_id() {
 376                     self.resolver.used_crates.insert(krate);
 377                 }
 378             }
 379             return (Success(name_binding), false)
 380         }
 381
 382         // If there is an unresolved glob at this point in the containing module, bail out.
 383         // We don't know enough to be able to resolve the name.
 384         if module.pub_glob_count.get() > 0 {
 385             return (Indeterminate, false);
 386         }
 387
 388         match module.import_resolutions.borrow().get(&(name, ns)) {
 389             // The containing module definitely doesn't have an exported import with the
 390             // name in question. We can therefore accurately report that names are unbound.
 391             None => (Failed(None), false),
 392
 393             // The name is an import which has been fully resolved, so we just follow it.
 394             Some(resolution) if resolution.outstanding_references == 0 => {
 395                 // Import resolutions must be declared with "pub" in order to be exported.
 396                 if !resolution.is_public {
 397                     return (Failed(None), false);
 398                 }
 399
 400                 if let Some(binding) = resolution.binding.clone() {
 401                     self.resolver.record_import_use(name, ns, &resolution);
 402                     (Success(binding), true)
 403                 } else {
 404                     (Failed(None), false)
 405                 }
 406             }
 407
 408             // If module is the same module whose import we are resolving and
 409             // it has an unresolved import with the same name as `name`, then the user
 410             // is actually trying to import an item that is declared in the same scope
 411             //
 412             // e.g
 413             // use self::submodule;
 414             // pub mod submodule;
 415             //
 416             // In this case we continue as if we resolved the import and let
 417             // check_for_conflicts_between_imports_and_items handle the conflict
 418             Some(_) => match (importing_module.def_id(), module.def_id()) {
 419                 (Some(id1), Some(id2)) if id1 == id2 => (Failed(None), false),
 420                 _ => (Indeterminate, false)
 421             },
 422         }
 423     }
 424
 425     fn resolve_single_import(&mut self,
 426                              module_: Module<'b>,
 427                              target_module: Module<'b>,
 428                              target: Name,
 429                              source: Name,
 430                              directive: &ImportDirective,
 431                              lp: LastPrivate)
 432                              -> ResolveResult<()> {
 433         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 434                 private {:?}",
 435                target,
 436                module_to_string(&*target_module),
 437                source,
 438                module_to_string(module_),
 439                directive.id,
 440                lp);
 441
 442         let lp = match lp {
 443             LastMod(lp) => lp,
 444             LastImport {..} => {
 445                 self.resolver
 446                     .session
 447                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 448             }
 449         };
 450
 451         // We need to resolve both namespaces for this to succeed.
 452         let (value_result, value_used_reexport) =
 453             self.resolve_name_in_module(target_module, source, ValueNS, module_);
 454         let (type_result, type_used_reexport) =
 455             self.resolve_name_in_module(target_module, source, TypeNS, module_);
 456
 457         match (&value_result, &type_result) {
 458             (&Success(ref name_binding), _) if !value_used_reexport &&
 459                                                directive.is_public &&
 460                                                !name_binding.is_public() => {
 461                 let msg = format!("`{}` is private, and cannot be reexported", source);
 462                 let note_msg = format!("Consider marking `{}` as `pub` in the imported module",
 463                                         source);
 464                 struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 465                     .span_note(directive.span, &note_msg)
 466                     .emit();
 467             }
 468
 469             (_, &Success(ref name_binding)) if !type_used_reexport &&
 470                                                directive.is_public => {
 471                 if !name_binding.is_public() {
 472                     let msg = format!("`{}` is private, and cannot be reexported", source);
 473                     let note_msg =
 474                         format!("Consider declaring type or module `{}` with `pub`", source);
 475                     struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 476                         .span_note(directive.span, &note_msg)
 477                         .emit();
 478                 } else if name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 479                     let msg = format!("variant `{}` is private, and cannot be reexported \
 480                                        (error E0364), consider declaring its enum as `pub`",
 481                                        source);
 482                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 483                                                    directive.id,
 484                                                    directive.span,
 485                                                    msg);
 486                 }
 487             }
 488
 489             _ => {}
 490         }
 491
 492         let mut lev_suggestion = "".to_owned();
 493         match (&value_result, &type_result) {
 494             (&Indeterminate, _) | (_, &Indeterminate) => return Indeterminate,
 495             (&Failed(_), &Failed(_)) => {
 496                 let children = target_module.children.borrow();
 497                 let names = children.keys().map(|&(ref name, _)| name);
 498                 if let Some(name) = find_best_match_for_name(names, &source.as_str(), None) {
 499                     lev_suggestion = format!(". Did you mean to use `{}`?", name);
 500                 } else {
 501                     let resolutions = target_module.import_resolutions.borrow();
 502                     let names = resolutions.keys().map(|&(ref name, _)| name);
 503                     if let Some(name) = find_best_match_for_name(names,
 504                                                                  &source.as_str(),
 505                                                                  None) {
 506                         lev_suggestion =
 507                             format!(". Did you mean to use the re-exported import `{}`?", name);
 508                     }
 509                 }
 510             }
 511             _ => (),
 512         }
 513
 514         let mut value_used_public = false;
 515         let mut type_used_public = false;
 516
 517         // We've successfully resolved the import. Write the results in.
 518         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 519
 520         {
 521             let mut check_and_write_import = |namespace, result, used_public: &mut bool| {
 522                 let result: &ResolveResult<NameBinding> = result;
 523
 524                 let import_resolution = import_resolutions.get_mut(&(target, namespace)).unwrap();
 525                 let namespace_name = match namespace {
 526                     TypeNS => "type",
 527                     ValueNS => "value",
 528                 };
 529
 530                 match *result {
 531                     Success(ref name_binding) => {
 532                         debug!("(resolving single import) found {:?} target: {:?}",
 533                                namespace_name,
 534                                name_binding.def());
 535                         self.check_for_conflicting_import(&import_resolution,
 536                                                           directive.span,
 537                                                           target,
 538                                                           namespace);
 539
 540                         self.check_that_import_is_importable(&name_binding,
 541                                                              directive.span,
 542                                                              target);
 543
 544                         import_resolution.binding = Some(directive.import(name_binding.clone()));
 545                         import_resolution.id = directive.id;
 546                         import_resolution.is_public = directive.is_public;
 547
 548                         self.add_export(module_, target, &import_resolution);
 549                         *used_public = name_binding.is_public();
 550                     }
 551                     Failed(_) => {
 552                         // Continue.
 553                     }
 554                     Indeterminate => {
 555                         panic!("{:?} result should be known at this point", namespace_name);
 556                     }
 557                 }
 558
 559                 self.check_for_conflicts_between_imports_and_items(module_,
 560                                                                    import_resolution,
 561                                                                    directive.span,
 562                                                                    (target, namespace));
 563             };
 564             check_and_write_import(ValueNS, &value_result, &mut value_used_public);
 565             check_and_write_import(TypeNS, &type_result, &mut type_used_public);
 566         }
 567
 568         if let (&Failed(_), &Failed(_)) = (&value_result, &type_result) {
 569             let msg = format!("There is no `{}` in `{}`{}",
 570                               source,
 571                               module_to_string(target_module), lev_suggestion);
 572             return Failed(Some((directive.span, msg)));
 573         }
 574
 575         let value_used_public = value_used_reexport || value_used_public;
 576         let type_used_public = type_used_reexport || type_used_public;
 577
 578         let value_def_and_priv = {
 579             let import_resolution_value = import_resolutions.get_mut(&(target, ValueNS)).unwrap();
 580             assert!(import_resolution_value.outstanding_references >= 1);
 581             import_resolution_value.outstanding_references -= 1;
 582
 583             // Record what this import resolves to for later uses in documentation,
 584             // this may resolve to either a value or a type, but for documentation
 585             // purposes it's good enough to just favor one over the other.
 586             import_resolution_value.binding.as_ref().map(|binding| {
 587                 let def = binding.def().unwrap();
 588                 let last_private = if value_used_public { lp } else { DependsOn(def.def_id()) };
 589                 (def, last_private)
 590             })
 591         };
 592
 593         let type_def_and_priv = {
 594             let import_resolution_type = import_resolutions.get_mut(&(target, TypeNS)).unwrap();
 595             assert!(import_resolution_type.outstanding_references >= 1);
 596             import_resolution_type.outstanding_references -= 1;
 597
 598             import_resolution_type.binding.as_ref().map(|binding| {
 599                 let def = binding.def().unwrap();
 600                 let last_private = if type_used_public { lp } else { DependsOn(def.def_id()) };
 601                 (def, last_private)
 602             })
 603         };
 604
 605         let import_lp = LastImport {
 606             value_priv: value_def_and_priv.map(|(_, p)| p),
 607             value_used: Used,
 608             type_priv: type_def_and_priv.map(|(_, p)| p),
 609             type_used: Used,
 610         };
 611
 612         if let Some((def, _)) = value_def_and_priv {
 613             self.resolver.def_map.borrow_mut().insert(directive.id,
 614                                                       PathResolution {
 615                                                           base_def: def,
 616                                                           last_private: import_lp,
 617                                                           depth: 0,
 618                                                       });
 619         }
 620         if let Some((def, _)) = type_def_and_priv {
 621             self.resolver.def_map.borrow_mut().insert(directive.id,
 622                                                       PathResolution {
 623                                                           base_def: def,
 624                                                           last_private: import_lp,
 625                                                           depth: 0,
 626                                                       });
 627         }
 628
 629         debug!("(resolving single import) successfully resolved import");
 630         return Success(());
 631     }
 632
 633     // Resolves a glob import. Note that this function cannot fail; it either
 634     // succeeds or bails out (as importing * from an empty module or a module
 635     // that exports nothing is valid). target_module is the module we are
 636     // actually importing, i.e., `foo` in `use foo::*`.
 637     fn resolve_glob_import(&mut self,
 638                            module_: Module<'b>,
 639                            target_module: Module<'b>,
 640                            import_directive: &ImportDirective,
 641                            lp: LastPrivate)
 642                            -> ResolveResult<()> {
 643         let id = import_directive.id;
 644         let is_public = import_directive.is_public;
 645
 646         // This function works in a highly imperative manner; it eagerly adds
 647         // everything it can to the list of import resolutions of the module
 648         // node.
 649         debug!("(resolving glob import) resolving glob import {}", id);
 650
 651         // We must bail out if the node has unresolved imports of any kind
 652         // (including globs).
 653         if (*target_module).pub_count.get() > 0 {
 654             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 655             return ResolveResult::Indeterminate;
 656         }
 657
 658         // Add all resolved imports from the containing module.
 659         let import_resolutions = target_module.import_resolutions.borrow();
 660
 661         if module_.import_resolutions.borrow_state() != ::std::cell::BorrowState::Unused {
 662             // In this case, target_module == module_
 663             // This means we are trying to glob import a module into itself,
 664             // and it is a no-go
 665             debug!("(resolving glob imports) target module is current module; giving up");
 666             return ResolveResult::Failed(Some((import_directive.span,
 667                                                "Cannot glob-import a module into itself.".into())));
 668         }
 669
 670         for (&(name, ns), target_import_resolution) in import_resolutions.iter() {
 671             debug!("(resolving glob import) writing module resolution {} into `{}`",
 672                    name,
 673                    module_to_string(module_));
 674
 675             // Here we merge two import resolutions.
 676             let mut import_resolutions = module_.import_resolutions.borrow_mut();
 677             let mut dest_import_resolution =
 678                 import_resolutions.entry((name, ns))
 679                                   .or_insert_with(|| ImportResolution::new(id, is_public));
 680
 681             match target_import_resolution.binding {
 682                 Some(ref binding) if target_import_resolution.is_public => {
 683                     self.check_for_conflicting_import(&dest_import_resolution,
 684                                                       import_directive.span,
 685                                                       name,
 686                                                       ns);
 687                     dest_import_resolution.id = id;
 688                     dest_import_resolution.is_public = is_public;
 689                     dest_import_resolution.binding = Some(import_directive.import(binding.clone()));
 690                     self.add_export(module_, name, &dest_import_resolution);
 691                 }
 692                 _ => {}
 693             }
 694         }
 695
 696         // Add all children from the containing module.
 697         build_reduced_graph::populate_module_if_necessary(self.resolver, target_module);
 698
 699         target_module.for_each_local_child(|name, ns, name_binding| {
 700             self.merge_import_resolution(module_,
 701                                          target_module,
 702                                          import_directive,
 703                                          (name, ns),
 704                                          name_binding.clone());
 705         });
 706
 707         // Record the destination of this import
 708         if let Some(did) = target_module.def_id() {
 709             self.resolver.def_map.borrow_mut().insert(id,
 710                                                       PathResolution {
 711                                                           base_def: Def::Mod(did),
 712                                                           last_private: lp,
 713                                                           depth: 0,
 714                                                       });
 715         }
 716
 717         debug!("(resolving glob import) successfully resolved import");
 718         return ResolveResult::Success(());
 719     }
 720
 721     fn merge_import_resolution(&mut self,
 722                                module_: Module<'b>,
 723                                containing_module: Module<'b>,
 724                                import_directive: &ImportDirective,
 725                                (name, ns): (Name, Namespace),
 726                                name_binding: NameBinding<'b>) {
 727         let id = import_directive.id;
 728         let is_public = import_directive.is_public;
 729
 730         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 731         let dest_import_resolution = import_resolutions.entry((name, ns)).or_insert_with(|| {
 732             ImportResolution::new(id, is_public)
 733         });
 734
 735         debug!("(resolving glob import) writing resolution `{}` in `{}` to `{}`",
 736                name,
 737                module_to_string(&*containing_module),
 738                module_to_string(module_));
 739
 740         // Merge the child item into the import resolution.
 741         let modifier = DefModifiers::IMPORTABLE | DefModifiers::PUBLIC;
 742
 743         if ns == TypeNS && is_public && name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 744             let msg = format!("variant `{}` is private, and cannot be reexported (error \
 745                                E0364), consider declaring its enum as `pub`", name);
 746             self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 747                                            import_directive.id,
 748                                            import_directive.span,
 749                                            msg);
 750         }
 751
 752         if name_binding.defined_with(modifier) {
 753             let namespace_name = match ns {
 754                 TypeNS => "type",
 755                 ValueNS => "value",
 756             };
 757             debug!("(resolving glob import) ... for {} target", namespace_name);
 758             if dest_import_resolution.shadowable() == Shadowable::Never {
 759                 let msg = format!("a {} named `{}` has already been imported in this module",
 760                                  namespace_name,
 761                                  name);
 762                 span_err!(self.resolver.session, import_directive.span, E0251, "{}", msg);
 763             } else {
 764                 dest_import_resolution.binding = Some(import_directive.import(name_binding.clone()));
 765                 dest_import_resolution.id = id;
 766                 dest_import_resolution.is_public = is_public;
 767                 self.add_export(module_, name, &dest_import_resolution);
 768             }
 769         }
 770
 771         self.check_for_conflicts_between_imports_and_items(module_,
 772                                                            dest_import_resolution,
 773                                                            import_directive.span,
 774                                                            (name, ns));
 775     }
 776
 777     fn add_export(&mut self, module: Module<'b>, name: Name, resolution: &ImportResolution<'b>) {
 778         if !resolution.is_public { return }
 779         let node_id = match module.def_id() {
 780             Some(def_id) => self.resolver.ast_map.as_local_node_id(def_id).unwrap(),
 781             None => return,
 782         };
 783         let export = match resolution.binding.as_ref().unwrap().def() {
 784             Some(def) => Export { name: name, def_id: def.def_id() },
 785             None => return,
 786         };
 787         self.resolver.export_map.entry(node_id).or_insert(Vec::new()).push(export);
 788     }
 789
 790     /// Checks that imported names and items don't have the same name.
 791     fn check_for_conflicting_import(&mut self,
 792                                     import_resolution: &ImportResolution,
 793                                     import_span: Span,
 794                                     name: Name,
 795                                     namespace: Namespace) {
 796         let binding = &import_resolution.binding;
 797         debug!("check_for_conflicting_import: {}; target exists: {}",
 798                name,
 799                binding.is_some());
 800
 801         match *binding {
 802             Some(ref binding) if !binding.defined_with(DefModifiers::PRELUDE) => {
 803                 let ns_word = match namespace {
 804                     TypeNS => {
 805                         match binding.module() {
 806                             Some(ref module) if module.is_normal() => "module",
 807                             Some(ref module) if module.is_trait() => "trait",
 808                             _ => "type",
 809                         }
 810                     }
 811                     ValueNS => "value",
 812                 };
 813                 let use_id = import_resolution.id;
 814                 let item = self.resolver.ast_map.expect_item(use_id);
 815                 let mut err = struct_span_err!(self.resolver.session,
 816                                                import_span,
 817                                                E0252,
 818                                                "a {} named `{}` has already been imported \
 819                                                 in this module",
 820                                                ns_word,
 821                                                name);
 822                 span_note!(&mut err,
 823                            item.span,
 824                            "previous import of `{}` here",
 825                            name);
 826                 err.emit();
 827             }
 828             Some(_) | None => {}
 829         }
 830     }
 831
 832     /// Checks that an import is actually importable
 833     fn check_that_import_is_importable(&mut self,
 834                                        name_binding: &NameBinding,
 835                                        import_span: Span,
 836                                        name: Name) {
 837         if !name_binding.defined_with(DefModifiers::IMPORTABLE) {
 838             let msg = format!("`{}` is not directly importable", name);
 839             span_err!(self.resolver.session, import_span, E0253, "{}", &msg[..]);
 840         }
 841     }
 842
 843     /// Checks that imported names and items don't have the same name.
 844     fn check_for_conflicts_between_imports_and_items(&mut self,
 845                                                      module: Module<'b>,
 846                                                      import: &ImportResolution<'b>,
 847                                                      import_span: Span,
 848                                                      (name, ns): (Name, Namespace)) {
 849         // Check for item conflicts.
 850         let name_binding = match module.get_child(name, ns) {
 851             None => {
 852                 // There can't be any conflicts.
 853                 return;
 854             }
 855             Some(name_binding) => name_binding,
 856         };
 857
 858         if ns == ValueNS {
 859             match import.binding {
 860                 Some(ref binding) if !binding.defined_with(DefModifiers::PRELUDE) => {
 861                     let mut err = struct_span_err!(self.resolver.session,
 862                                                    import_span,
 863                                                    E0255,
 864                                                    "import `{}` conflicts with \
 865                                                     value in this module",
 866                                                    name);
 867                     if let Some(span) = name_binding.span {
 868                         err.span_note(span, "conflicting value here");
 869                     }
 870                     err.emit();
 871                 }
 872                 Some(_) | None => {}
 873             }
 874         } else {
 875             match import.binding {
 876                 Some(ref binding) if !binding.defined_with(DefModifiers::PRELUDE) => {
 877                     if name_binding.is_extern_crate() {
 878                         let msg = format!("import `{0}` conflicts with imported crate \
 879                                            in this module (maybe you meant `use {0}::*`?)",
 880                                           name);
 881                         span_err!(self.resolver.session, import_span, E0254, "{}", &msg[..]);
 882                         return;
 883                     }
 884
 885                     let (what, note) = match name_binding.module() {
 886                         Some(ref module) if module.is_normal() =>
 887                             ("existing submodule", "note conflicting module here"),
 888                         Some(ref module) if module.is_trait() =>
 889                             ("trait in this module", "note conflicting trait here"),
 890                         _ => ("type in this module", "note conflicting type here"),
 891                     };
 892                     let mut err = struct_span_err!(self.resolver.session,
 893                                                    import_span,
 894                                                    E0256,
 895                                                    "import `{}` conflicts with {}",
 896                                                    name,
 897                                                    what);
 898                     if let Some(span) = name_binding.span {
 899                         err.span_note(span, note);
 900                     }
 901                     err.emit();
 902                 }
 903                 Some(_) | None => {}
 904             }
 905         }
 906     }
 907 }
 908
 909 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
 910     if names.is_empty() {
 911         import_directive_subclass_to_string(subclass)
 912     } else {
 913         (format!("{}::{}",
 914                  names_to_string(names),
 915                  import_directive_subclass_to_string(subclass)))
 916             .to_string()
 917     }
 918 }
 919
 920 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
 921     match subclass {
 922         SingleImport(_, source) => source.to_string(),
 923         GlobImport => "*".to_string(),
 924     }
 925 }
 926
 927 pub fn resolve_imports(resolver: &mut Resolver) {
 928     let mut import_resolver = ImportResolver { resolver: resolver };
 929     import_resolver.resolve_imports();
 930 }