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