src/librustc_resolve/resolve_imports.rs

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