src/librustc_resolve/resolve_imports.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use self::ImportDirectiveSubclass::*;
  12
  13 use DefModifiers;
  14 use Module;
  15 use Namespace::{self, TypeNS, ValueNS};
  16 use {NameBindings, NameBinding};
  17 use NamespaceResult::{BoundResult, UnboundResult, UnknownResult};
  18 use NamespaceResult;
  19 use 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)]
  55 pub struct ImportDirective {
  56     pub module_path: Vec<Name>,
  57     pub subclass: ImportDirectiveSubclass,
  58     pub span: Span,
  59     pub id: NodeId,
  60     pub is_public: bool, // see note in ImportResolutionPerNamespace about how to use this
  61     pub shadowable: Shadowable,
  62 }
  63
  64 impl ImportDirective {
  65     pub fn new(module_path: Vec<Name>,
  66                subclass: ImportDirectiveSubclass,
  67                span: Span,
  68                id: NodeId,
  69                is_public: bool,
  70                shadowable: Shadowable)
  71                -> ImportDirective {
  72         ImportDirective {
  73             module_path: module_path,
  74             subclass: subclass,
  75             span: span,
  76             id: id,
  77             is_public: is_public,
  78             shadowable: shadowable,
  79         }
  80     }
  81 }
  82
  83 /// The item that an import resolves to.
  84 #[derive(Clone,Debug)]
  85 pub struct Target<'a> {
  86     pub target_module: Module<'a>,
  87     pub binding: NameBinding<'a>,
  88     pub shadowable: Shadowable,
  89 }
  90
  91 impl<'a> Target<'a> {
  92     pub fn new(target_module: Module<'a>, binding: NameBinding<'a>, shadowable: Shadowable)
  93                -> Self {
  94         Target {
  95             target_module: target_module,
  96             binding: binding,
  97             shadowable: shadowable,
  98         }
  99     }
 100 }
 101
 102 #[derive(Debug)]
 103 /// An ImportResolutionPerNamespace records what we know about an imported name.
 104 /// More specifically, it records the number of unresolved `use` directives that import the name,
 105 /// and for each namespace, it records the `use` directive importing the name in the namespace
 106 /// and the `Target` to which the name in the namespace resolves (if applicable).
 107 /// Different `use` directives may import the same name in different namespaces.
 108 pub struct ImportResolutionPerNamespace<'a> {
 109     // When outstanding_references reaches zero, outside modules can count on the targets being
 110     // correct. Before then, all bets are off; future `use` directives could override the name.
 111     // Since shadowing is forbidden, the only way outstanding_references > 1 in a legal program
 112     // is if the name is imported by exactly two `use` directives, one of which resolves to a
 113     // value and the other of which resolves to a type.
 114     pub outstanding_references: usize,
 115     pub type_ns: ImportResolution<'a>,
 116     pub value_ns: ImportResolution<'a>,
 117 }
 118
 119 /// Records what we know about an imported name in a namespace (see `ImportResolutionPerNamespace`).
 120 #[derive(Clone,Debug)]
 121 pub struct ImportResolution<'a> {
 122     /// Whether the name in the namespace was imported with a `use` or a `pub use`.
 123     pub is_public: bool,
 124
 125     /// Resolution of the name in the namespace
 126     pub target: Option<Target<'a>>,
 127
 128     /// The source node of the `use` directive
 129     pub id: NodeId,
 130 }
 131
 132 impl<'a> ::std::ops::Index<Namespace> for ImportResolutionPerNamespace<'a> {
 133     type Output = ImportResolution<'a>;
 134     fn index(&self, ns: Namespace) -> &ImportResolution<'a> {
 135         match ns { TypeNS => &self.type_ns, ValueNS => &self.value_ns }
 136     }
 137 }
 138
 139 impl<'a> ::std::ops::IndexMut<Namespace> for ImportResolutionPerNamespace<'a> {
 140     fn index_mut(&mut self, ns: Namespace) -> &mut ImportResolution<'a> {
 141         match ns { TypeNS => &mut self.type_ns, ValueNS => &mut self.value_ns }
 142     }
 143 }
 144
 145 impl<'a> ImportResolutionPerNamespace<'a> {
 146     pub fn new(id: NodeId, is_public: bool) -> Self {
 147         let resolution = ImportResolution { id: id, is_public: is_public, target: None };
 148         ImportResolutionPerNamespace {
 149             outstanding_references: 0, type_ns: resolution.clone(), value_ns: resolution,
 150         }
 151     }
 152
 153     pub fn shadowable(&self, namespace: Namespace) -> Shadowable {
 154         match self[namespace].target {
 155             Some(ref target) => target.shadowable,
 156             None => Shadowable::Always,
 157         }
 158     }
 159 }
 160
 161 struct ImportResolvingError {
 162     span: Span,
 163     path: String,
 164     help: String,
 165 }
 166
 167 struct ImportResolver<'a, 'b: 'a, 'tcx: 'b> {
 168     resolver: &'a mut Resolver<'b, 'tcx>,
 169 }
 170
 171 impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
 172     // Import resolution
 173     //
 174     // This is a fixed-point algorithm. We resolve imports until our efforts
 175     // are stymied by an unresolved import; then we bail out of the current
 176     // module and continue. We terminate successfully once no more imports
 177     // remain or unsuccessfully when no forward progress in resolving imports
 178     // is made.
 179
 180     /// Resolves all imports for the crate. This method performs the fixed-
 181     /// point iteration.
 182     fn resolve_imports(&mut self) {
 183         let mut i = 0;
 184         let mut prev_unresolved_imports = 0;
 185         loop {
 186             debug!("(resolving imports) iteration {}, {} imports left",
 187                    i,
 188                    self.resolver.unresolved_imports);
 189
 190             let module_root = self.resolver.graph_root;
 191             let errors = self.resolve_imports_for_module_subtree(module_root);
 192
 193             if self.resolver.unresolved_imports == 0 {
 194                 debug!("(resolving imports) success");
 195                 break;
 196             }
 197
 198             if self.resolver.unresolved_imports == prev_unresolved_imports {
 199                 // resolving failed
 200                 if errors.len() > 0 {
 201                     for e in errors {
 202                         resolve_error(self.resolver,
 203                                       e.span,
 204                                       ResolutionError::UnresolvedImport(Some((&e.path, &e.help))));
 205                     }
 206                 } else {
 207                     // Report unresolved imports only if no hard error was already reported
 208                     // to avoid generating multiple errors on the same import.
 209                     // Imports that are still indeterminate at this point are actually blocked
 210                     // by errored imports, so there is no point reporting them.
 211                     self.resolver.report_unresolved_imports(module_root);
 212                 }
 213                 break;
 214             }
 215
 216             i += 1;
 217             prev_unresolved_imports = self.resolver.unresolved_imports;
 218         }
 219     }
 220
 221     /// Attempts to resolve imports for the given module and all of its
 222     /// submodules.
 223     fn resolve_imports_for_module_subtree(&mut self,
 224                                           module_: Module<'b>)
 225                                           -> Vec<ImportResolvingError> {
 226         let mut errors = Vec::new();
 227         debug!("(resolving imports for module subtree) resolving {}",
 228                module_to_string(&*module_));
 229         let orig_module = replace(&mut self.resolver.current_module, module_);
 230         errors.extend(self.resolve_imports_for_module(module_));
 231         self.resolver.current_module = orig_module;
 232
 233         build_reduced_graph::populate_module_if_necessary(self.resolver, &module_);
 234         for (_, child_node) in module_.children.borrow().iter() {
 235             match child_node.type_ns.module() {
 236                 None => {
 237                     // Nothing to do.
 238                 }
 239                 Some(child_module) => {
 240                     errors.extend(self.resolve_imports_for_module_subtree(child_module));
 241                 }
 242             }
 243         }
 244
 245         for (_, child_module) in module_.anonymous_children.borrow().iter() {
 246             errors.extend(self.resolve_imports_for_module_subtree(child_module));
 247         }
 248
 249         errors
 250     }
 251
 252     /// Attempts to resolve imports for the given module only.
 253     fn resolve_imports_for_module(&mut self, module: Module<'b>) -> Vec<ImportResolvingError> {
 254         let mut errors = Vec::new();
 255
 256         if module.all_imports_resolved() {
 257             debug!("(resolving imports for module) all imports resolved for {}",
 258                    module_to_string(&*module));
 259             return errors;
 260         }
 261
 262         let mut imports = module.imports.borrow_mut();
 263         let import_count = imports.len();
 264         let mut indeterminate_imports = Vec::new();
 265         while module.resolved_import_count.get() + indeterminate_imports.len() < import_count {
 266             let import_index = module.resolved_import_count.get();
 267             match self.resolve_import_for_module(module, &imports[import_index]) {
 268                 ResolveResult::Failed(err) => {
 269                     let import_directive = &imports[import_index];
 270                     let (span, help) = match err {
 271                         Some((span, msg)) => (span, format!(". {}", msg)),
 272                         None => (import_directive.span, String::new()),
 273                     };
 274                     errors.push(ImportResolvingError {
 275                         span: span,
 276                         path: import_path_to_string(&import_directive.module_path,
 277                                                     import_directive.subclass),
 278                         help: help,
 279                     });
 280                 }
 281                 ResolveResult::Indeterminate => {}
 282                 ResolveResult::Success(()) => {
 283                     // count success
 284                     module.resolved_import_count
 285                           .set(module.resolved_import_count.get() + 1);
 286                     continue;
 287                 }
 288             }
 289             // This resolution was not successful, keep it for later
 290             indeterminate_imports.push(imports.swap_remove(import_index));
 291
 292         }
 293
 294         imports.extend(indeterminate_imports);
 295
 296         errors
 297     }
 298
 299     /// Attempts to resolve the given import. The return value indicates
 300     /// failure if we're certain the name does not exist, indeterminate if we
 301     /// don't know whether the name exists at the moment due to other
 302     /// currently-unresolved imports, or success if we know the name exists.
 303     /// If successful, the resolved bindings are written into the module.
 304     fn resolve_import_for_module(&mut self,
 305                                  module_: Module<'b>,
 306                                  import_directive: &ImportDirective)
 307                                  -> ResolveResult<()> {
 308         let mut resolution_result = ResolveResult::Failed(None);
 309         let module_path = &import_directive.module_path;
 310
 311         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 312                names_to_string(&module_path[..]),
 313                module_to_string(&*module_));
 314
 315         // First, resolve the module path for the directive, if necessary.
 316         let container = if module_path.is_empty() {
 317             // Use the crate root.
 318             Some((self.resolver.graph_root, LastMod(AllPublic)))
 319         } else {
 320             match self.resolver.resolve_module_path(module_,
 321                                                     &module_path[..],
 322                                                     UseLexicalScopeFlag::DontUseLexicalScope,
 323                                                     import_directive.span) {
 324                 ResolveResult::Failed(err) => {
 325                     resolution_result = ResolveResult::Failed(err);
 326                     None
 327                 }
 328                 ResolveResult::Indeterminate => {
 329                     resolution_result = ResolveResult::Indeterminate;
 330                     None
 331                 }
 332                 ResolveResult::Success(container) => Some(container),
 333             }
 334         };
 335
 336         match container {
 337             None => {}
 338             Some((containing_module, lp)) => {
 339                 // We found the module that the target is contained
 340                 // within. Attempt to resolve the import within it.
 341
 342                 match import_directive.subclass {
 343                     SingleImport(target, source) => {
 344                         resolution_result = self.resolve_single_import(&module_,
 345                                                                        containing_module,
 346                                                                        target,
 347                                                                        source,
 348                                                                        import_directive,
 349                                                                        lp);
 350                     }
 351                     GlobImport => {
 352                         resolution_result = self.resolve_glob_import(&module_,
 353                                                                      containing_module,
 354                                                                      import_directive,
 355                                                                      lp);
 356                     }
 357                 }
 358             }
 359         }
 360
 361         // Decrement the count of unresolved imports.
 362         match resolution_result {
 363             ResolveResult::Success(()) => {
 364                 assert!(self.resolver.unresolved_imports >= 1);
 365                 self.resolver.unresolved_imports -= 1;
 366             }
 367             _ => {
 368                 // Nothing to do here; just return the error.
 369             }
 370         }
 371
 372         // Decrement the count of unresolved globs if necessary. But only if
 373         // the resolution result is a success -- other cases will
 374         // be handled by the main loop.
 375
 376         if resolution_result.success() {
 377             match import_directive.subclass {
 378                 GlobImport => {
 379                     module_.dec_glob_count();
 380                     if import_directive.is_public {
 381                         module_.dec_pub_glob_count();
 382                     }
 383                 }
 384                 SingleImport(..) => {
 385                     // Ignore.
 386                 }
 387             }
 388             if import_directive.is_public {
 389                 module_.dec_pub_count();
 390             }
 391         }
 392
 393         return resolution_result;
 394     }
 395
 396     fn resolve_single_import(&mut self,
 397                              module_: Module<'b>,
 398                              target_module: Module<'b>,
 399                              target: Name,
 400                              source: Name,
 401                              directive: &ImportDirective,
 402                              lp: LastPrivate)
 403                              -> ResolveResult<()> {
 404         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 405                 private {:?}",
 406                target,
 407                module_to_string(&*target_module),
 408                source,
 409                module_to_string(module_),
 410                directive.id,
 411                lp);
 412
 413         let lp = match lp {
 414             LastMod(lp) => lp,
 415             LastImport {..} => {
 416                 self.resolver
 417                     .session
 418                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 419             }
 420         };
 421
 422         // We need to resolve both namespaces for this to succeed.
 423
 424         let mut value_result = UnknownResult;
 425         let mut type_result = UnknownResult;
 426         let mut lev_suggestion = "".to_owned();
 427
 428         // Search for direct children of the containing module.
 429         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 430
 431         match target_module.children.borrow().get(&source) {
 432             None => {
 433                 let names = target_module.children.borrow();
 434                 if let Some(name) = find_best_match_for_name(names.keys(),
 435                                                              &source.as_str(),
 436                                                              None) {
 437                     lev_suggestion = format!(". Did you mean to use `{}`?", name);
 438                 }
 439             }
 440             Some(ref child_name_bindings) => {
 441                 // pub_err makes sure we don't give the same error twice.
 442                 let mut pub_err = false;
 443                 if child_name_bindings.value_ns.defined() {
 444                     debug!("(resolving single import) found value binding");
 445                     value_result = BoundResult(target_module,
 446                                                child_name_bindings.value_ns.clone());
 447                     if directive.is_public && !child_name_bindings.value_ns.is_public() {
 448                         let msg = format!("`{}` is private, and cannot be reexported", source);
 449                         let note_msg = format!("Consider marking `{}` as `pub` in the imported \
 450                                                 module",
 451                                                source);
 452                         struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 453                             .span_note(directive.span, &note_msg)
 454                             .emit();
 455                         pub_err = true;
 456                     }
 457                     if directive.is_public && child_name_bindings.value_ns.
 458                                               defined_with(DefModifiers::PRIVATE_VARIANT) {
 459                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 460                                            error E0364), consider declaring its enum as `pub`",
 461                                            source);
 462                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 463                                                        directive.id,
 464                                                        directive.span,
 465                                                        msg);
 466                         pub_err = true;
 467                     }
 468                 }
 469                 if child_name_bindings.type_ns.defined() {
 470                     debug!("(resolving single import) found type binding");
 471                     type_result = BoundResult(target_module,
 472                                               child_name_bindings.type_ns.clone());
 473                     if !pub_err && directive.is_public &&
 474                        !child_name_bindings.type_ns.is_public() {
 475                         let msg = format!("`{}` is private, and cannot be reexported", source);
 476                         let note_msg = format!("Consider declaring module `{}` as a `pub mod`",
 477                                                source);
 478                         struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 479                             .span_note(directive.span, &note_msg)
 480                             .emit();
 481                     }
 482                     if !pub_err && directive.is_public && child_name_bindings.type_ns.
 483                                                     defined_with(DefModifiers::PRIVATE_VARIANT) {
 484                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 485                                            error E0365), consider declaring its enum as `pub`",
 486                                            source);
 487                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 488                                                        directive.id,
 489                                                        directive.span,
 490                                                        msg);
 491                     }
 492                 }
 493             }
 494         }
 495
 496         // Unless we managed to find a result in both namespaces (unlikely),
 497         // search imports as well.
 498         let mut value_used_reexport = false;
 499         let mut type_used_reexport = false;
 500         match (value_result.clone(), type_result.clone()) {
 501             (BoundResult(..), BoundResult(..)) => {} // Continue.
 502             _ => {
 503                 // If there is an unresolved glob at this point in the
 504                 // containing module, bail out. We don't know enough to be
 505                 // able to resolve this import.
 506
 507                 if target_module.pub_glob_count.get() > 0 {
 508                     debug!("(resolving single import) unresolved pub glob; bailing out");
 509                     return ResolveResult::Indeterminate;
 510                 }
 511
 512                 // Now search the exported imports within the containing module.
 513                 match target_module.import_resolutions.borrow().get(&source) {
 514                     None => {
 515                         debug!("(resolving single import) no import");
 516                         // The containing module definitely doesn't have an
 517                         // exported import with the name in question. We can
 518                         // therefore accurately report that the names are
 519                         // unbound.
 520
 521                         if lev_suggestion.is_empty() {  // skip if we already have a suggestion
 522                             let names = target_module.import_resolutions.borrow();
 523                             if let Some(name) = find_best_match_for_name(names.keys(),
 524                                                                          &source.as_str(),
 525                                                                          None) {
 526                                 lev_suggestion =
 527                                     format!(". Did you mean to use the re-exported import `{}`?",
 528                                             name);
 529                             }
 530                         }
 531
 532                         if value_result.is_unknown() {
 533                             value_result = UnboundResult;
 534                         }
 535                         if type_result.is_unknown() {
 536                             type_result = UnboundResult;
 537                         }
 538                     }
 539                     Some(import_resolution) if import_resolution.outstanding_references == 0 => {
 540
 541                         fn get_binding<'a>(this: &mut Resolver,
 542                                            import_resolution: &ImportResolutionPerNamespace<'a>,
 543                                            namespace: Namespace,
 544                                            source: Name)
 545                                            -> NamespaceResult<'a> {
 546
 547                             // Import resolutions must be declared with "pub"
 548                             // in order to be exported.
 549                             if !import_resolution[namespace].is_public {
 550                                 return UnboundResult;
 551                             }
 552
 553                             match import_resolution[namespace].target.clone() {
 554                                 None => {
 555                                     return UnboundResult;
 556                                 }
 557                                 Some(Target {
 558                                     target_module,
 559                                     binding,
 560                                     shadowable: _
 561                                 }) => {
 562                                     debug!("(resolving single import) found import in ns {:?}",
 563                                            namespace);
 564                                     let id = import_resolution[namespace].id;
 565                                     // track used imports and extern crates as well
 566                                     this.used_imports.insert((id, namespace));
 567                                     this.record_import_use(id, source);
 568                                     match target_module.def_id() {
 569                                         Some(DefId{krate: kid, ..}) => {
 570                                             this.used_crates.insert(kid);
 571                                         }
 572                                         _ => {}
 573                                     }
 574                                     return BoundResult(target_module, binding);
 575                                 }
 576                             }
 577                         }
 578
 579                         // The name is an import which has been fully
 580                         // resolved. We can, therefore, just follow it.
 581                         if value_result.is_unknown() {
 582                             value_result = get_binding(self.resolver,
 583                                                        import_resolution,
 584                                                        ValueNS,
 585                                                        source);
 586                             value_used_reexport = import_resolution.value_ns.is_public;
 587                         }
 588                         if type_result.is_unknown() {
 589                             type_result = get_binding(self.resolver,
 590                                                       import_resolution,
 591                                                       TypeNS,
 592                                                       source);
 593                             type_used_reexport = import_resolution.type_ns.is_public;
 594                         }
 595
 596                     }
 597                     Some(_) => {
 598                         // If target_module is the same module whose import we are resolving
 599                         // and there it has an unresolved import with the same name as `source`,
 600                         // then the user is actually trying to import an item that is declared
 601                         // in the same scope
 602                         //
 603                         // e.g
 604                         // use self::submodule;
 605                         // pub mod submodule;
 606                         //
 607                         // In this case we continue as if we resolved the import and let the
 608                         // check_for_conflicts_between_imports_and_items call below handle
 609                         // the conflict
 610                         match (module_.def_id(), target_module.def_id()) {
 611                             (Some(id1), Some(id2)) if id1 == id2 => {
 612                                 if value_result.is_unknown() {
 613                                     value_result = UnboundResult;
 614                                 }
 615                                 if type_result.is_unknown() {
 616                                     type_result = UnboundResult;
 617                                 }
 618                             }
 619                             _ => {
 620                                 // The import is unresolved. Bail out.
 621                                 debug!("(resolving single import) unresolved import; bailing out");
 622                                 return ResolveResult::Indeterminate;
 623                             }
 624                         }
 625                     }
 626                 }
 627             }
 628         }
 629
 630         let mut value_used_public = false;
 631         let mut type_used_public = false;
 632
 633         // If we didn't find a result in the type namespace, search the
 634         // external modules.
 635         match type_result {
 636             BoundResult(..) => {}
 637             _ => {
 638                 match target_module.external_module_children.borrow_mut().get(&source) {
 639                     None => {} // Continue.
 640                     Some(module) => {
 641                         debug!("(resolving single import) found external module");
 642                         // track the module as used.
 643                         match module.def_id() {
 644                             Some(DefId{krate: kid, ..}) => {
 645                                 self.resolver.used_crates.insert(kid);
 646                             }
 647                             _ => {}
 648                         }
 649                         let name_binding = NameBinding::create_from_module(module);
 650                         type_result = BoundResult(target_module, name_binding);
 651                         type_used_public = true;
 652                     }
 653                 }
 654             }
 655         }
 656
 657         // We've successfully resolved the import. Write the results in.
 658         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 659         let import_resolution = import_resolutions.get_mut(&target).unwrap();
 660
 661         {
 662             let mut check_and_write_import = |namespace, result: &_, used_public: &mut bool| {
 663                 let namespace_name = match namespace {
 664                     TypeNS => "type",
 665                     ValueNS => "value",
 666                 };
 667
 668                 match *result {
 669                     BoundResult(ref target_module, ref name_binding) => {
 670                         debug!("(resolving single import) found {:?} target: {:?}",
 671                                namespace_name,
 672                                name_binding.def());
 673                         self.check_for_conflicting_import(&import_resolution,
 674                                                           directive.span,
 675                                                           target,
 676                                                           namespace);
 677
 678                         self.check_that_import_is_importable(&name_binding,
 679                                                              directive.span,
 680                                                              target);
 681
 682                         import_resolution[namespace] = ImportResolution {
 683                             target: Some(Target::new(target_module,
 684                                                      name_binding.clone(),
 685                                                      directive.shadowable)),
 686                             id: directive.id,
 687                             is_public: directive.is_public
 688                         };
 689
 690                         self.add_export(module_, target, &import_resolution[namespace]);
 691                         *used_public = name_binding.is_public();
 692                     }
 693                     UnboundResult => {
 694                         // Continue.
 695                     }
 696                     UnknownResult => {
 697                         panic!("{:?} result should be known at this point", namespace_name);
 698                     }
 699                 }
 700             };
 701             check_and_write_import(ValueNS, &value_result, &mut value_used_public);
 702             check_and_write_import(TypeNS, &type_result, &mut type_used_public);
 703         }
 704
 705         self.check_for_conflicts_between_imports_and_items(module_,
 706                                                            import_resolution,
 707                                                            directive.span,
 708                                                            target);
 709
 710         if value_result.is_unbound() && type_result.is_unbound() {
 711             let msg = format!("There is no `{}` in `{}`{}",
 712                               source,
 713                               module_to_string(&target_module), lev_suggestion);
 714             return ResolveResult::Failed(Some((directive.span, msg)));
 715         }
 716         let value_used_public = value_used_reexport || value_used_public;
 717         let type_used_public = type_used_reexport || type_used_public;
 718
 719         assert!(import_resolution.outstanding_references >= 1);
 720         import_resolution.outstanding_references -= 1;
 721
 722         // Record what this import resolves to for later uses in documentation,
 723         // this may resolve to either a value or a type, but for documentation
 724         // purposes it's good enough to just favor one over the other.
 725         let value_def_and_priv = import_resolution.value_ns.target.as_ref().map(|target| {
 726             let def = target.binding.def().unwrap();
 727             (def,
 728              if value_used_public {
 729                 lp
 730             } else {
 731                 DependsOn(def.def_id())
 732             })
 733         });
 734         let type_def_and_priv = import_resolution.type_ns.target.as_ref().map(|target| {
 735             let def = target.binding.def().unwrap();
 736             (def,
 737              if type_used_public {
 738                 lp
 739             } else {
 740                 DependsOn(def.def_id())
 741             })
 742         });
 743
 744         let import_lp = LastImport {
 745             value_priv: value_def_and_priv.map(|(_, p)| p),
 746             value_used: Used,
 747             type_priv: type_def_and_priv.map(|(_, p)| p),
 748             type_used: Used,
 749         };
 750
 751         if let Some((def, _)) = value_def_and_priv {
 752             self.resolver.def_map.borrow_mut().insert(directive.id,
 753                                                       PathResolution {
 754                                                           base_def: def,
 755                                                           last_private: import_lp,
 756                                                           depth: 0,
 757                                                       });
 758         }
 759         if let Some((def, _)) = type_def_and_priv {
 760             self.resolver.def_map.borrow_mut().insert(directive.id,
 761                                                       PathResolution {
 762                                                           base_def: def,
 763                                                           last_private: import_lp,
 764                                                           depth: 0,
 765                                                       });
 766         }
 767
 768         debug!("(resolving single import) successfully resolved import");
 769         return ResolveResult::Success(());
 770     }
 771
 772     // Resolves a glob import. Note that this function cannot fail; it either
 773     // succeeds or bails out (as importing * from an empty module or a module
 774     // that exports nothing is valid). target_module is the module we are
 775     // actually importing, i.e., `foo` in `use foo::*`.
 776     fn resolve_glob_import(&mut self,
 777                            module_: Module<'b>,
 778                            target_module: Module<'b>,
 779                            import_directive: &ImportDirective,
 780                            lp: LastPrivate)
 781                            -> ResolveResult<()> {
 782         let id = import_directive.id;
 783         let is_public = import_directive.is_public;
 784
 785         // This function works in a highly imperative manner; it eagerly adds
 786         // everything it can to the list of import resolutions of the module
 787         // node.
 788         debug!("(resolving glob import) resolving glob import {}", id);
 789
 790         // We must bail out if the node has unresolved imports of any kind
 791         // (including globs).
 792         if (*target_module).pub_count.get() > 0 {
 793             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 794             return ResolveResult::Indeterminate;
 795         }
 796
 797         // Add all resolved imports from the containing module.
 798         let import_resolutions = target_module.import_resolutions.borrow();
 799
 800         if module_.import_resolutions.borrow_state() != ::std::cell::BorrowState::Unused {
 801             // In this case, target_module == module_
 802             // This means we are trying to glob import a module into itself,
 803             // and it is a no-go
 804             debug!("(resolving glob imports) target module is current module; giving up");
 805             return ResolveResult::Failed(Some((import_directive.span,
 806                                                "Cannot glob-import a module into itself.".into())));
 807         }
 808
 809         for (name, target_import_resolution) in import_resolutions.iter() {
 810             debug!("(resolving glob import) writing module resolution {} into `{}`",
 811                    *name,
 812                    module_to_string(module_));
 813
 814             // Here we merge two import resolutions.
 815             let mut import_resolutions = module_.import_resolutions.borrow_mut();
 816             let mut dest_import_resolution = import_resolutions.entry(*name).or_insert_with(|| {
 817                 ImportResolutionPerNamespace::new(id, is_public)
 818             });
 819
 820             for &ns in [TypeNS, ValueNS].iter() {
 821                 match target_import_resolution[ns].target {
 822                     Some(ref target) if target_import_resolution[ns].is_public => {
 823                         self.check_for_conflicting_import(&dest_import_resolution,
 824                                                           import_directive.span,
 825                                                           *name,
 826                                                           ns);
 827                         dest_import_resolution[ns] = ImportResolution {
 828                             id: id, is_public: is_public, target: Some(target.clone())
 829                         };
 830                         self.add_export(module_, *name, &dest_import_resolution[ns]);
 831                     }
 832                     _ => {}
 833                 }
 834             }
 835         }
 836
 837         // Add all children from the containing module.
 838         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 839
 840         for (&name, name_bindings) in target_module.children.borrow().iter() {
 841             self.merge_import_resolution(module_,
 842                                          target_module,
 843                                          import_directive,
 844                                          name,
 845                                          name_bindings.clone());
 846
 847         }
 848
 849         // Record the destination of this import
 850         if let Some(did) = target_module.def_id() {
 851             self.resolver.def_map.borrow_mut().insert(id,
 852                                                       PathResolution {
 853                                                           base_def: Def::Mod(did),
 854                                                           last_private: lp,
 855                                                           depth: 0,
 856                                                       });
 857         }
 858
 859         debug!("(resolving glob import) successfully resolved import");
 860         return ResolveResult::Success(());
 861     }
 862
 863     fn merge_import_resolution(&mut self,
 864                                module_: Module<'b>,
 865                                containing_module: Module<'b>,
 866                                import_directive: &ImportDirective,
 867                                name: Name,
 868                                name_bindings: NameBindings<'b>) {
 869         let id = import_directive.id;
 870         let is_public = import_directive.is_public;
 871
 872         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 873         let dest_import_resolution = import_resolutions.entry(name).or_insert_with(|| {
 874             ImportResolutionPerNamespace::new(id, is_public)
 875         });
 876
 877         debug!("(resolving glob import) writing resolution `{}` in `{}` to `{}`",
 878                name,
 879                module_to_string(&*containing_module),
 880                module_to_string(module_));
 881
 882         // Merge the child item into the import resolution.
 883         // pub_err makes sure we don't give the same error twice.
 884         let mut pub_err = false;
 885         {
 886             let mut merge_child_item = |namespace| {
 887                 if !pub_err && is_public &&
 888                         name_bindings[namespace].defined_with(DefModifiers::PRIVATE_VARIANT) {
 889                     let msg = format!("variant `{}` is private, and cannot be reexported (error \
 890                                        E0364), consider declaring its enum as `pub`", name);
 891                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 892                                                    import_directive.id,
 893                                                    import_directive.span,
 894                                                    msg);
 895                     pub_err = true;
 896                 }
 897
 898                 let modifier = DefModifiers::IMPORTABLE | DefModifiers::PUBLIC;
 899                 if name_bindings[namespace].defined_with(modifier) {
 900                     let namespace_name = match namespace {
 901                         TypeNS => "type",
 902                         ValueNS => "value",
 903                     };
 904                     debug!("(resolving glob import) ... for {} target", namespace_name);
 905                     if dest_import_resolution.shadowable(namespace) == Shadowable::Never {
 906                         let msg = format!("a {} named `{}` has already been imported in this \
 907                                            module",
 908                                           namespace_name,
 909                                           name);
 910                         span_err!(self.resolver.session,
 911                                   import_directive.span,
 912                                   E0251,
 913                                   "{}",
 914                                   msg);
 915                     } else {
 916                         dest_import_resolution[namespace] = ImportResolution {
 917                             target: Some(Target::new(containing_module,
 918                                                      name_bindings[namespace].clone(),
 919                                                      import_directive.shadowable)),
 920                             id: id,
 921                             is_public: is_public
 922                         };
 923                         self.add_export(module_, name, &dest_import_resolution[namespace]);
 924                     }
 925                 } else {
 926                     // FIXME #30159: This is required for backwards compatability.
 927                     dest_import_resolution[namespace].is_public |= is_public;
 928                 }
 929             };
 930             merge_child_item(ValueNS);
 931             merge_child_item(TypeNS);
 932         }
 933
 934         self.check_for_conflicts_between_imports_and_items(module_,
 935                                                            dest_import_resolution,
 936                                                            import_directive.span,
 937                                                            name);
 938     }
 939
 940     fn add_export(&mut self, module: Module<'b>, name: Name, resolution: &ImportResolution<'b>) {
 941         if !resolution.is_public { return }
 942         let node_id = match module.def_id() {
 943             Some(def_id) => self.resolver.ast_map.as_local_node_id(def_id).unwrap(),
 944             None => return,
 945         };
 946         let export = match resolution.target.as_ref().unwrap().binding.def() {
 947             Some(def) => Export { name: name, def_id: def.def_id() },
 948             None => return,
 949         };
 950         self.resolver.export_map.entry(node_id).or_insert(Vec::new()).push(export);
 951     }
 952
 953     /// Checks that imported names and items don't have the same name.
 954     fn check_for_conflicting_import(&mut self,
 955                                     import_resolution: &ImportResolutionPerNamespace,
 956                                     import_span: Span,
 957                                     name: Name,
 958                                     namespace: Namespace) {
 959         let target = &import_resolution[namespace].target;
 960         debug!("check_for_conflicting_import: {}; target exists: {}",
 961                name,
 962                target.is_some());
 963
 964         match *target {
 965             Some(ref target) if target.shadowable != Shadowable::Always => {
 966                 let ns_word = match namespace {
 967                     TypeNS => {
 968                         match target.binding.module() {
 969                             Some(ref module) if module.is_normal() => "module",
 970                             Some(ref module) if module.is_trait() => "trait",
 971                             _ => "type",
 972                         }
 973                     }
 974                     ValueNS => "value",
 975                 };
 976                 let use_id = import_resolution[namespace].id;
 977                 let item = self.resolver.ast_map.expect_item(use_id);
 978                 let mut err = struct_span_err!(self.resolver.session,
 979                                                import_span,
 980                                                E0252,
 981                                                "a {} named `{}` has already been imported \
 982                                                 in this module",
 983                                                ns_word,
 984                                                name);
 985                 span_note!(&mut err,
 986                            item.span,
 987                            "previous import of `{}` here",
 988                            name);
 989                 err.emit();
 990             }
 991             Some(_) | None => {}
 992         }
 993     }
 994
 995     /// Checks that an import is actually importable
 996     fn check_that_import_is_importable(&mut self,
 997                                        name_binding: &NameBinding,
 998                                        import_span: Span,
 999                                        name: Name) {
1000         if !name_binding.defined_with(DefModifiers::IMPORTABLE) {
1001             let msg = format!("`{}` is not directly importable", name);
1002             span_err!(self.resolver.session, import_span, E0253, "{}", &msg[..]);
1003         }
1004     }
1005
1006     /// Checks that imported names and items don't have the same name.
1007     fn check_for_conflicts_between_imports_and_items(&mut self,
1008                                                      module: Module<'b>,
1009                                                      import: &ImportResolutionPerNamespace<'b>,
1010                                                      import_span: Span,
1011                                                      name: Name) {
1012         // First, check for conflicts between imports and `extern crate`s.
1013         if module.external_module_children
1014                  .borrow()
1015                  .contains_key(&name) {
1016             match import.type_ns.target {
1017                 Some(ref target) if target.shadowable != Shadowable::Always => {
1018                     let msg = format!("import `{0}` conflicts with imported crate in this module \
1019                                        (maybe you meant `use {0}::*`?)",
1020                                       name);
1021                     span_err!(self.resolver.session, import_span, E0254, "{}", &msg[..]);
1022                 }
1023                 Some(_) | None => {}
1024             }
1025         }
1026
1027         // Check for item conflicts.
1028         let name_bindings = match module.children.borrow().get(&name) {
1029             None => {
1030                 // There can't be any conflicts.
1031                 return;
1032             }
1033             Some(ref name_bindings) => (*name_bindings).clone(),
1034         };
1035
1036         match import.value_ns.target {
1037             Some(ref target) if target.shadowable != Shadowable::Always => {
1038                 if let Some(ref value) = *name_bindings.value_ns.borrow() {
1039                     let mut err = struct_span_err!(self.resolver.session,
1040                                                    import_span,
1041                                                    E0255,
1042                                                    "import `{}` conflicts with \
1043                                                     value in this module",
1044                                                    name);
1045                     if let Some(span) = value.span {
1046                         err.span_note(span, "conflicting value here");
1047                     }
1048                     err.emit();
1049                 }
1050             }
1051             Some(_) | None => {}
1052         }
1053
1054         match import.type_ns.target {
1055             Some(ref target) if target.shadowable != Shadowable::Always => {
1056                 if let Some(ref ty) = *name_bindings.type_ns.borrow() {
1057                     let (what, note) = match ty.module() {
1058                         Some(ref module) if module.is_normal() =>
1059                             ("existing submodule", "note conflicting module here"),
1060                         Some(ref module) if module.is_trait() =>
1061                             ("trait in this module", "note conflicting trait here"),
1062                         _ => ("type in this module", "note conflicting type here"),
1063                     };
1064                     let mut err = struct_span_err!(self.resolver.session,
1065                                                    import_span,
1066                                                    E0256,
1067                                                    "import `{}` conflicts with {}",
1068                                                    name,
1069                                                    what);
1070                     if let Some(span) = ty.span {
1071                         err.span_note(span, note);
1072                     }
1073                     err.emit();
1074                 }
1075             }
1076             Some(_) | None => {}
1077         }
1078     }
1079 }
1080
1081 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
1082     if names.is_empty() {
1083         import_directive_subclass_to_string(subclass)
1084     } else {
1085         (format!("{}::{}",
1086                  names_to_string(names),
1087                  import_directive_subclass_to_string(subclass)))
1088             .to_string()
1089     }
1090 }
1091
1092 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
1093     match subclass {
1094         SingleImport(_, source) => source.to_string(),
1095         GlobImport => "*".to_string(),
1096     }
1097 }
1098
1099 pub fn resolve_imports(resolver: &mut Resolver) {
1100     let mut import_resolver = ImportResolver { resolver: resolver };
1101     import_resolver.resolve_imports();
1102 }