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 {AmbiguityError, Module, PerNS};
  14 use Namespace::{self, TypeNS, MacroNS};
  15 use {NameBinding, NameBindingKind, PathResult, PrivacyError};
  16 use Resolver;
  17 use {names_to_string, module_to_string};
  18 use {resolve_error, ResolutionError};
  19
  20 use rustc::ty;
  21 use rustc::lint::builtin::PRIVATE_IN_PUBLIC;
  22 use rustc::hir::def_id::DefId;
  23 use rustc::hir::def::*;
  24 use rustc::util::nodemap::FxHashMap;
  25
  26 use syntax::ast::{Ident, NodeId};
  27 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  28 use syntax::ext::hygiene::Mark;
  29 use syntax::parse::token;
  30 use syntax::symbol::keywords;
  31 use syntax::util::lev_distance::find_best_match_for_name;
  32 use syntax_pos::Span;
  33
  34 use std::cell::{Cell, RefCell};
  35 use std::mem;
  36
  37 /// Contains data for specific types of import directives.
  38 #[derive(Clone, Debug)]
  39 pub enum ImportDirectiveSubclass<'a> {
  40     SingleImport {
  41         target: Ident,
  42         source: Ident,
  43         result: PerNS<Cell<Result<&'a NameBinding<'a>, Determinacy>>>,
  44         type_ns_only: bool,
  45     },
  46     GlobImport {
  47         is_prelude: bool,
  48         max_vis: Cell<ty::Visibility>, // The visibility of the greatest reexport.
  49         // n.b. `max_vis` is only used in `finalize_import` to check for reexport errors.
  50     },
  51     ExternCrate,
  52     MacroUse,
  53 }
  54
  55 /// One import directive.
  56 #[derive(Debug,Clone)]
  57 pub struct ImportDirective<'a> {
  58     pub id: NodeId,
  59     pub parent: Module<'a>,
  60     pub module_path: Vec<Ident>,
  61     pub imported_module: Cell<Option<Module<'a>>>, // the resolution of `module_path`
  62     pub subclass: ImportDirectiveSubclass<'a>,
  63     pub span: Span,
  64     pub vis: Cell<ty::Visibility>,
  65     pub expansion: Mark,
  66     pub used: Cell<bool>,
  67 }
  68
  69 impl<'a> ImportDirective<'a> {
  70     pub fn is_glob(&self) -> bool {
  71         match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
  72     }
  73 }
  74
  75 #[derive(Clone, Default)]
  76 /// Records information about the resolution of a name in a namespace of a module.
  77 pub struct NameResolution<'a> {
  78     /// The single imports that define the name in the namespace.
  79     single_imports: SingleImports<'a>,
  80     /// The least shadowable known binding for this name, or None if there are no known bindings.
  81     pub binding: Option<&'a NameBinding<'a>>,
  82     shadows_glob: Option<&'a NameBinding<'a>>,
  83 }
  84
  85 #[derive(Clone, Debug)]
  86 enum SingleImports<'a> {
  87     /// No single imports can define the name in the namespace.
  88     None,
  89     /// Only the given single import can define the name in the namespace.
  90     MaybeOne(&'a ImportDirective<'a>),
  91     /// At least one single import will define the name in the namespace.
  92     AtLeastOne,
  93 }
  94
  95 impl<'a> Default for SingleImports<'a> {
  96     /// Creates a `SingleImports<'a>` of None type.
  97     fn default() -> Self {
  98         SingleImports::None
  99     }
 100 }
 101
 102 impl<'a> SingleImports<'a> {
 103     fn add_directive(&mut self, directive: &'a ImportDirective<'a>) {
 104         match *self {
 105             SingleImports::None => *self = SingleImports::MaybeOne(directive),
 106             // If two single imports can define the name in the namespace, we can assume that at
 107             // least one of them will define it since otherwise both would have to define only one
 108             // namespace, leading to a duplicate error.
 109             SingleImports::MaybeOne(_) => *self = SingleImports::AtLeastOne,
 110             SingleImports::AtLeastOne => {}
 111         };
 112     }
 113
 114     fn directive_failed(&mut self) {
 115         match *self {
 116             SingleImports::None => unreachable!(),
 117             SingleImports::MaybeOne(_) => *self = SingleImports::None,
 118             SingleImports::AtLeastOne => {}
 119         }
 120     }
 121 }
 122
 123 impl<'a> NameResolution<'a> {
 124     // Returns the binding for the name if it is known or None if it not known.
 125     fn binding(&self) -> Option<&'a NameBinding<'a>> {
 126         self.binding.and_then(|binding| match self.single_imports {
 127             SingleImports::None => Some(binding),
 128             _ if !binding.is_glob_import() => Some(binding),
 129             _ => None, // The binding could be shadowed by a single import, so it is not known.
 130         })
 131     }
 132 }
 133
 134 impl<'a> Resolver<'a> {
 135     fn resolution(&self, module: Module<'a>, ident: Ident, ns: Namespace)
 136                   -> &'a RefCell<NameResolution<'a>> {
 137         let ident = ident.unhygienize();
 138         *module.resolutions.borrow_mut().entry((ident, ns))
 139                .or_insert_with(|| self.arenas.alloc_name_resolution())
 140     }
 141
 142     /// Attempts to resolve `ident` in namespaces `ns` of `module`.
 143     /// Invariant: if `record_used` is `Some`, import resolution must be complete.
 144     pub fn resolve_ident_in_module(&mut self,
 145                                    module: Module<'a>,
 146                                    ident: Ident,
 147                                    ns: Namespace,
 148                                    restricted_shadowing: bool,
 149                                    record_used: Option<Span>)
 150                                    -> Result<&'a NameBinding<'a>, Determinacy> {
 151         self.populate_module_if_necessary(module);
 152
 153         let resolution = self.resolution(module, ident, ns)
 154             .try_borrow_mut()
 155             .map_err(|_| Determined)?; // This happens when there is a cycle of imports
 156
 157         if let Some(span) = record_used {
 158             if let Some(binding) = resolution.binding {
 159                 if let Some(shadowed_glob) = resolution.shadows_glob {
 160                     let name = ident.name;
 161                     // Forbid expanded shadowing to avoid time travel.
 162                     if restricted_shadowing &&
 163                        binding.expansion != Mark::root() &&
 164                        ns != MacroNS && // In MacroNS, `try_define` always forbids this shadowing
 165                        binding.def() != shadowed_glob.def() {
 166                         self.ambiguity_errors.push(AmbiguityError {
 167                             span: span, name: name, lexical: false, b1: binding, b2: shadowed_glob,
 168                             legacy: false,
 169                         });
 170                     }
 171                 }
 172                 if self.record_use(ident, ns, binding, span) {
 173                     return Ok(self.dummy_binding);
 174                 }
 175                 if !self.is_accessible(binding.vis) {
 176                     self.privacy_errors.push(PrivacyError(span, ident.name, binding));
 177                 }
 178             }
 179
 180             return resolution.binding.ok_or(Determined);
 181         }
 182
 183         let check_usable = |this: &mut Self, binding: &'a NameBinding<'a>| {
 184             // `extern crate` are always usable for backwards compatability, see issue #37020.
 185             let usable = this.is_accessible(binding.vis) || binding.is_extern_crate();
 186             if usable { Ok(binding) } else { Err(Determined) }
 187         };
 188
 189         // Items and single imports are not shadowable.
 190         if let Some(binding) = resolution.binding {
 191             if !binding.is_glob_import() {
 192                 return check_usable(self, binding);
 193             }
 194         }
 195
 196         // Check if a single import can still define the name.
 197         match resolution.single_imports {
 198             SingleImports::AtLeastOne => return Err(Undetermined),
 199             SingleImports::MaybeOne(directive) if self.is_accessible(directive.vis.get()) => {
 200                 let module = match directive.imported_module.get() {
 201                     Some(module) => module,
 202                     None => return Err(Undetermined),
 203                 };
 204                 let ident = match directive.subclass {
 205                     SingleImport { source, .. } => source,
 206                     _ => unreachable!(),
 207                 };
 208                 match self.resolve_ident_in_module(module, ident, ns, false, None) {
 209                     Err(Determined) => {}
 210                     _ => return Err(Undetermined),
 211                 }
 212             }
 213             SingleImports::MaybeOne(_) | SingleImports::None => {},
 214         }
 215
 216         let no_unresolved_invocations =
 217             restricted_shadowing || module.unresolved_invocations.borrow().is_empty();
 218         match resolution.binding {
 219             // In `MacroNS`, expanded bindings do not shadow (enforced in `try_define`).
 220             Some(binding) if no_unresolved_invocations || ns == MacroNS =>
 221                 return check_usable(self, binding),
 222             None if no_unresolved_invocations => {}
 223             _ => return Err(Undetermined),
 224         }
 225
 226         // Check if the globs are determined
 227         if restricted_shadowing && module.def().is_some() {
 228             return Err(Determined);
 229         }
 230         for directive in module.globs.borrow().iter() {
 231             if self.is_accessible(directive.vis.get()) {
 232                 if let Some(module) = directive.imported_module.get() {
 233                     let result = self.resolve_ident_in_module(module, ident, ns, false, None);
 234                     if let Err(Undetermined) = result {
 235                         return Err(Undetermined);
 236                     }
 237                 } else {
 238                     return Err(Undetermined);
 239                 }
 240             }
 241         }
 242
 243         Err(Determined)
 244     }
 245
 246     // Add an import directive to the current module.
 247     pub fn add_import_directive(&mut self,
 248                                 module_path: Vec<Ident>,
 249                                 subclass: ImportDirectiveSubclass<'a>,
 250                                 span: Span,
 251                                 id: NodeId,
 252                                 vis: ty::Visibility,
 253                                 expansion: Mark) {
 254         let current_module = self.current_module;
 255         let directive = self.arenas.alloc_import_directive(ImportDirective {
 256             parent: current_module,
 257             module_path: module_path,
 258             imported_module: Cell::new(None),
 259             subclass: subclass,
 260             span: span,
 261             id: id,
 262             vis: Cell::new(vis),
 263             expansion: expansion,
 264             used: Cell::new(false),
 265         });
 266
 267         self.indeterminate_imports.push(directive);
 268         match directive.subclass {
 269             SingleImport { target, .. } => {
 270                 self.per_ns(|this, ns| {
 271                     let mut resolution = this.resolution(current_module, target, ns).borrow_mut();
 272                     resolution.single_imports.add_directive(directive);
 273                 });
 274             }
 275             // We don't add prelude imports to the globs since they only affect lexical scopes,
 276             // which are not relevant to import resolution.
 277             GlobImport { is_prelude: true, .. } => {}
 278             GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
 279             _ => unreachable!(),
 280         }
 281     }
 282
 283     // Given a binding and an import directive that resolves to it,
 284     // return the corresponding binding defined by the import directive.
 285     pub fn import(&self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
 286                   -> &'a NameBinding<'a> {
 287         let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
 288                      !directive.is_glob() && binding.is_extern_crate() { // c.f. `PRIVATE_IN_PUBLIC`
 289             directive.vis.get()
 290         } else {
 291             binding.pseudo_vis()
 292         };
 293
 294         if let GlobImport { ref max_vis, .. } = directive.subclass {
 295             if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
 296                 max_vis.set(vis)
 297             }
 298         }
 299
 300         self.arenas.alloc_name_binding(NameBinding {
 301             kind: NameBindingKind::Import {
 302                 binding: binding,
 303                 directive: directive,
 304                 used: Cell::new(false),
 305                 legacy_self_import: false,
 306             },
 307             span: directive.span,
 308             vis: vis,
 309             expansion: directive.expansion,
 310         })
 311     }
 312
 313     // Define the name or return the existing binding if there is a collision.
 314     pub fn try_define(&mut self,
 315                       module: Module<'a>,
 316                       ident: Ident,
 317                       ns: Namespace,
 318                       binding: &'a NameBinding<'a>)
 319                       -> Result<(), &'a NameBinding<'a>> {
 320         self.update_resolution(module, ident, ns, |this, resolution| {
 321             if let Some(old_binding) = resolution.binding {
 322                 if binding.is_glob_import() {
 323                     if !old_binding.is_glob_import() &&
 324                        !(ns == MacroNS && old_binding.expansion != Mark::root()) {
 325                         resolution.shadows_glob = Some(binding);
 326                     } else if binding.def() != old_binding.def() {
 327                         resolution.binding = Some(this.ambiguity(old_binding, binding));
 328                     } else if !old_binding.vis.is_at_least(binding.vis, &*this) {
 329                         // We are glob-importing the same item but with greater visibility.
 330                         resolution.binding = Some(binding);
 331                     }
 332                 } else if old_binding.is_glob_import() {
 333                     if ns == MacroNS && binding.expansion != Mark::root() &&
 334                        binding.def() != old_binding.def() {
 335                         resolution.binding = Some(this.ambiguity(binding, old_binding));
 336                     } else {
 337                         resolution.binding = Some(binding);
 338                         resolution.shadows_glob = Some(old_binding);
 339                     }
 340                 } else {
 341                     return Err(old_binding);
 342                 }
 343             } else {
 344                 resolution.binding = Some(binding);
 345             }
 346
 347             Ok(())
 348         })
 349     }
 350
 351     pub fn ambiguity(&self, b1: &'a NameBinding<'a>, b2: &'a NameBinding<'a>)
 352                      -> &'a NameBinding<'a> {
 353         self.arenas.alloc_name_binding(NameBinding {
 354             kind: NameBindingKind::Ambiguity { b1: b1, b2: b2, legacy: false },
 355             vis: if b1.vis.is_at_least(b2.vis, self) { b1.vis } else { b2.vis },
 356             span: b1.span,
 357             expansion: Mark::root(),
 358         })
 359     }
 360
 361     // Use `f` to mutate the resolution of the name in the module.
 362     // If the resolution becomes a success, define it in the module's glob importers.
 363     fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Namespace, f: F)
 364                                -> T
 365         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
 366     {
 367         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
 368         // during which the resolution might end up getting re-defined via a glob cycle.
 369         let (binding, t) = {
 370             let mut resolution = &mut *self.resolution(module, ident, ns).borrow_mut();
 371             let old_binding = resolution.binding();
 372
 373             let t = f(self, resolution);
 374
 375             match resolution.binding() {
 376                 _ if old_binding.is_some() => return t,
 377                 None => return t,
 378                 Some(binding) => match old_binding {
 379                     Some(old_binding) if old_binding as *const _ == binding as *const _ => return t,
 380                     _ => (binding, t),
 381                 }
 382             }
 383         };
 384
 385         // Define `binding` in `module`s glob importers.
 386         for directive in module.glob_importers.borrow_mut().iter() {
 387             if self.is_accessible_from(binding.vis, directive.parent) {
 388                 let imported_binding = self.import(binding, directive);
 389                 let _ = self.try_define(directive.parent, ident, ns, imported_binding);
 390             }
 391         }
 392
 393         t
 394     }
 395
 396     // Define a "dummy" resolution containing a Def::Err as a placeholder for a
 397     // failed resolution
 398     fn import_dummy_binding(&mut self, directive: &'a ImportDirective<'a>) {
 399         if let SingleImport { target, .. } = directive.subclass {
 400             let dummy_binding = self.dummy_binding;
 401             let dummy_binding = self.import(dummy_binding, directive);
 402             self.per_ns(|this, ns| {
 403                 let _ = this.try_define(directive.parent, target, ns, dummy_binding);
 404             });
 405         }
 406     }
 407 }
 408
 409 pub struct ImportResolver<'a, 'b: 'a> {
 410     pub resolver: &'a mut Resolver<'b>,
 411 }
 412
 413 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
 414     type Target = Resolver<'b>;
 415     fn deref(&self) -> &Resolver<'b> {
 416         self.resolver
 417     }
 418 }
 419
 420 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
 421     fn deref_mut(&mut self) -> &mut Resolver<'b> {
 422         self.resolver
 423     }
 424 }
 425
 426 impl<'a, 'b: 'a> ty::DefIdTree for &'a ImportResolver<'a, 'b> {
 427     fn parent(self, id: DefId) -> Option<DefId> {
 428         self.resolver.parent(id)
 429     }
 430 }
 431
 432 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 433     // Import resolution
 434     //
 435     // This is a fixed-point algorithm. We resolve imports until our efforts
 436     // are stymied by an unresolved import; then we bail out of the current
 437     // module and continue. We terminate successfully once no more imports
 438     // remain or unsuccessfully when no forward progress in resolving imports
 439     // is made.
 440
 441     /// Resolves all imports for the crate. This method performs the fixed-
 442     /// point iteration.
 443     pub fn resolve_imports(&mut self) {
 444         let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
 445         while self.indeterminate_imports.len() < prev_num_indeterminates {
 446             prev_num_indeterminates = self.indeterminate_imports.len();
 447             for import in mem::replace(&mut self.indeterminate_imports, Vec::new()) {
 448                 match self.resolve_import(&import) {
 449                     true => self.determined_imports.push(import),
 450                     false => self.indeterminate_imports.push(import),
 451                 }
 452             }
 453         }
 454     }
 455
 456     pub fn finalize_imports(&mut self) {
 457         for module in self.arenas.local_modules().iter() {
 458             self.finalize_resolutions_in(module);
 459         }
 460
 461         let mut errors = false;
 462         for i in 0 .. self.determined_imports.len() {
 463             let import = self.determined_imports[i];
 464             if let Some(err) = self.finalize_import(import) {
 465                 errors = true;
 466
 467                 // If the error is a single failed import then create a "fake" import
 468                 // resolution for it so that later resolve stages won't complain.
 469                 self.import_dummy_binding(import);
 470                 let path = import_path_to_string(&import.module_path, &import.subclass);
 471                 let error = ResolutionError::UnresolvedImport(Some((&path, &err)));
 472                 resolve_error(self.resolver, import.span, error);
 473             }
 474         }
 475
 476         // Report unresolved imports only if no hard error was already reported
 477         // to avoid generating multiple errors on the same import.
 478         if !errors {
 479             if let Some(import) = self.indeterminate_imports.iter().next() {
 480                 let error = ResolutionError::UnresolvedImport(None);
 481                 resolve_error(self.resolver, import.span, error);
 482             }
 483         }
 484     }
 485
 486     /// Attempts to resolve the given import, returning true if its resolution is determined.
 487     /// If successful, the resolved bindings are written into the module.
 488     fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> bool {
 489         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 490                names_to_string(&directive.module_path),
 491                module_to_string(self.current_module));
 492
 493         self.current_module = directive.parent;
 494
 495         let module = if let Some(module) = directive.imported_module.get() {
 496             module
 497         } else {
 498             let vis = directive.vis.get();
 499             // For better failure detection, pretend that the import will not define any names
 500             // while resolving its module path.
 501             directive.vis.set(ty::Visibility::Invisible);
 502             let result = self.resolve_path(&directive.module_path, None, None);
 503             directive.vis.set(vis);
 504
 505             match result {
 506                 PathResult::Module(module) => module,
 507                 PathResult::Indeterminate => return false,
 508                 _ => return true,
 509             }
 510         };
 511
 512         directive.imported_module.set(Some(module));
 513         let (source, target, result, type_ns_only) = match directive.subclass {
 514             SingleImport { source, target, ref result, type_ns_only } =>
 515                 (source, target, result, type_ns_only),
 516             GlobImport { .. } => {
 517                 self.resolve_glob_import(directive);
 518                 return true;
 519             }
 520             _ => unreachable!(),
 521         };
 522
 523         let mut indeterminate = false;
 524         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 525             if let Err(Undetermined) = result[ns].get() {
 526                 result[ns].set(this.resolve_ident_in_module(module, source, ns, false, None));
 527             } else {
 528                 return
 529             };
 530
 531             let parent = directive.parent;
 532             match result[ns].get() {
 533                 Err(Undetermined) => indeterminate = true,
 534                 Err(Determined) => {
 535                     this.update_resolution(parent, target, ns, |_, resolution| {
 536                         resolution.single_imports.directive_failed()
 537                     });
 538                 }
 539                 Ok(binding) if !binding.is_importable() => {
 540                     let msg = format!("`{}` is not directly importable", target);
 541                     struct_span_err!(this.session, directive.span, E0253, "{}", &msg)
 542                         .span_label(directive.span, &format!("cannot be imported directly"))
 543                         .emit();
 544                     // Do not import this illegal binding. Import a dummy binding and pretend
 545                     // everything is fine
 546                     this.import_dummy_binding(directive);
 547                 }
 548                 Ok(binding) => {
 549                     let imported_binding = this.import(binding, directive);
 550                     let conflict = this.try_define(parent, target, ns, imported_binding);
 551                     if let Err(old_binding) = conflict {
 552                         this.report_conflict(parent, target, ns, imported_binding, old_binding);
 553                     }
 554                 }
 555             }
 556         });
 557
 558         !indeterminate
 559     }
 560
 561     // If appropriate, returns an error to report.
 562     fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> Option<String> {
 563         self.current_module = directive.parent;
 564
 565         let ImportDirective { ref module_path, span, .. } = *directive;
 566         let module_result = self.resolve_path(&module_path, None, Some(span));
 567         let module = match module_result {
 568             PathResult::Module(module) => module,
 569             PathResult::Failed(msg, _) => {
 570                 let (mut self_path, mut self_result) = (module_path.clone(), None);
 571                 if !self_path.is_empty() && !token::Ident(self_path[0]).is_path_segment_keyword() {
 572                     self_path[0].name = keywords::SelfValue.name();
 573                     self_result = Some(self.resolve_path(&self_path, None, None));
 574                 }
 575                 return if let Some(PathResult::Module(..)) = self_result {
 576                     Some(format!("Did you mean `{}`?", names_to_string(&self_path)))
 577                 } else {
 578                     Some(msg)
 579                 };
 580             },
 581             _ => return None,
 582         };
 583
 584         let (ident, result, type_ns_only) = match directive.subclass {
 585             SingleImport { source, ref result, type_ns_only, .. } => (source, result, type_ns_only),
 586             GlobImport { .. } if module.def_id() == directive.parent.def_id() => {
 587                 // Importing a module into itself is not allowed.
 588                 return Some("Cannot glob-import a module into itself.".to_string());
 589             }
 590             GlobImport { is_prelude, ref max_vis } => {
 591                 if !is_prelude &&
 592                    max_vis.get() != ty::Visibility::Invisible && // Allow empty globs.
 593                    !max_vis.get().is_at_least(directive.vis.get(), &*self) {
 594                     let msg = "A non-empty glob must import something with the glob's visibility";
 595                     self.session.span_err(directive.span, msg);
 596                 }
 597                 return None;
 598             }
 599             _ => unreachable!(),
 600         };
 601
 602         let mut all_ns_err = true;
 603         let mut legacy_self_import = None;
 604         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 605             if let Ok(binding) = result[ns].get() {
 606                 all_ns_err = false;
 607                 if this.record_use(ident, ns, binding, directive.span) {
 608                     this.resolution(module, ident, ns).borrow_mut().binding =
 609                         Some(this.dummy_binding);
 610                 }
 611             }
 612         } else if let Ok(binding) = this.resolve_ident_in_module(module, ident, ns, false, None) {
 613             legacy_self_import = Some(directive);
 614             let binding = this.arenas.alloc_name_binding(NameBinding {
 615                 kind: NameBindingKind::Import {
 616                     binding: binding,
 617                     directive: directive,
 618                     used: Cell::new(false),
 619                     legacy_self_import: true,
 620                 },
 621                 ..*binding
 622             });
 623             let _ = this.try_define(directive.parent, ident, ns, binding);
 624         });
 625
 626         if all_ns_err {
 627             if let Some(directive) = legacy_self_import {
 628                 self.warn_legacy_self_import(directive);
 629                 return None;
 630             }
 631             let mut all_ns_failed = true;
 632             self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 633                 match this.resolve_ident_in_module(module, ident, ns, false, Some(span)) {
 634                     Ok(_) => all_ns_failed = false,
 635                     _ => {}
 636                 }
 637             });
 638
 639             return if all_ns_failed {
 640                 let resolutions = module.resolutions.borrow();
 641                 let names = resolutions.iter().filter_map(|(&(ref i, _), resolution)| {
 642                     if *i == ident { return None; } // Never suggest the same name
 643                     match *resolution.borrow() {
 644                         NameResolution { binding: Some(name_binding), .. } => {
 645                             match name_binding.kind {
 646                                 NameBindingKind::Import { binding, .. } => {
 647                                     match binding.kind {
 648                                         // Never suggest the name that has binding error
 649                                         // i.e. the name that cannot be previously resolved
 650                                         NameBindingKind::Def(Def::Err) => return None,
 651                                         _ => Some(&i.name),
 652                                     }
 653                                 },
 654                                 _ => Some(&i.name),
 655                             }
 656                         },
 657                         NameResolution { single_imports: SingleImports::None, .. } => None,
 658                         _ => Some(&i.name),
 659                     }
 660                 });
 661                 let lev_suggestion =
 662                     match find_best_match_for_name(names, &ident.name.as_str(), None) {
 663                         Some(name) => format!(". Did you mean to use `{}`?", name),
 664                         None => "".to_owned(),
 665                     };
 666                 let module_str = module_to_string(module);
 667                 let msg = if &module_str == "???" {
 668                     format!("no `{}` in the root{}", ident, lev_suggestion)
 669                 } else {
 670                     format!("no `{}` in `{}`{}", ident, module_str, lev_suggestion)
 671                 };
 672                 Some(msg)
 673             } else {
 674                 // `resolve_ident_in_module` reported a privacy error.
 675                 self.import_dummy_binding(directive);
 676                 None
 677             }
 678         }
 679
 680         let mut reexport_error = None;
 681         let mut any_successful_reexport = false;
 682         self.per_ns(|this, ns| {
 683             if let Ok(binding) = result[ns].get() {
 684                 let vis = directive.vis.get();
 685                 if !binding.pseudo_vis().is_at_least(vis, &*this) {
 686                     reexport_error = Some((ns, binding));
 687                 } else {
 688                     any_successful_reexport = true;
 689                 }
 690             }
 691         });
 692
 693         // All namespaces must be re-exported with extra visibility for an error to occur.
 694         if !any_successful_reexport {
 695             let (ns, binding) = reexport_error.unwrap();
 696             if ns == TypeNS && binding.is_extern_crate() {
 697                 let msg = format!("extern crate `{}` is private, and cannot be reexported \
 698                                    (error E0364), consider declaring with `pub`",
 699                                    ident);
 700                 self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
 701             } else if ns == TypeNS {
 702                 struct_span_err!(self.session, directive.span, E0365,
 703                                  "`{}` is private, and cannot be reexported", ident)
 704                     .span_label(directive.span, &format!("reexport of private `{}`", ident))
 705                     .note(&format!("consider declaring type or module `{}` with `pub`", ident))
 706                     .emit();
 707             } else {
 708                 let msg = format!("`{}` is private, and cannot be reexported", ident);
 709                 let note_msg =
 710                     format!("consider marking `{}` as `pub` in the imported module", ident);
 711                 struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
 712                     .span_note(directive.span, &note_msg)
 713                     .emit();
 714             }
 715         }
 716
 717         // Record what this import resolves to for later uses in documentation,
 718         // this may resolve to either a value or a type, but for documentation
 719         // purposes it's good enough to just favor one over the other.
 720         self.per_ns(|this, ns| if let Some(binding) = result[ns].get().ok() {
 721             this.def_map.entry(directive.id).or_insert(PathResolution::new(binding.def()));
 722         });
 723
 724         debug!("(resolving single import) successfully resolved import");
 725         None
 726     }
 727
 728     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
 729         let module = directive.imported_module.get().unwrap();
 730         self.populate_module_if_necessary(module);
 731
 732         if let Some(Def::Trait(_)) = module.def() {
 733             self.session.span_err(directive.span, "items in traits are not importable.");
 734             return;
 735         } else if module.def_id() == directive.parent.def_id()  {
 736             return;
 737         } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
 738             self.prelude = Some(module);
 739             return;
 740         }
 741
 742         // Add to module's glob_importers
 743         module.glob_importers.borrow_mut().push(directive);
 744
 745         // Ensure that `resolutions` isn't borrowed during `try_define`,
 746         // since it might get updated via a glob cycle.
 747         let bindings = module.resolutions.borrow().iter().filter_map(|(&ident, resolution)| {
 748             resolution.borrow().binding().map(|binding| (ident, binding))
 749         }).collect::<Vec<_>>();
 750         for ((ident, ns), binding) in bindings {
 751             if binding.pseudo_vis() == ty::Visibility::Public || self.is_accessible(binding.vis) {
 752                 let imported_binding = self.import(binding, directive);
 753                 let _ = self.try_define(directive.parent, ident, ns, imported_binding);
 754             }
 755         }
 756
 757         // Record the destination of this import
 758         self.record_def(directive.id, PathResolution::new(module.def().unwrap()));
 759     }
 760
 761     // Miscellaneous post-processing, including recording reexports, reporting conflicts,
 762     // reporting the PRIVATE_IN_PUBLIC lint, and reporting unresolved imports.
 763     fn finalize_resolutions_in(&mut self, module: Module<'b>) {
 764         // Since import resolution is finished, globs will not define any more names.
 765         *module.globs.borrow_mut() = Vec::new();
 766
 767         let mut reexports = Vec::new();
 768         let mut exported_macro_names = FxHashMap();
 769         if module as *const _ == self.graph_root as *const _ {
 770             let macro_exports = mem::replace(&mut self.macro_exports, Vec::new());
 771             for export in macro_exports.into_iter().rev() {
 772                 if exported_macro_names.insert(export.name, export.span).is_none() {
 773                     reexports.push(export);
 774                 }
 775             }
 776         }
 777
 778         for (&(ident, ns), resolution) in module.resolutions.borrow().iter() {
 779             let resolution = &mut *resolution.borrow_mut();
 780             let binding = match resolution.binding {
 781                 Some(binding) => binding,
 782                 None => continue,
 783             };
 784
 785             if binding.vis == ty::Visibility::Public &&
 786                (binding.is_import() || binding.is_extern_crate()) {
 787                 let def = binding.def();
 788                 if def != Def::Err {
 789                     if !def.def_id().is_local() {
 790                         self.session.cstore.export_macros(def.def_id().krate);
 791                     }
 792                     if let Def::Macro(..) = def {
 793                         if let Some(&span) = exported_macro_names.get(&ident.name) {
 794                             let msg =
 795                                 format!("a macro named `{}` has already been exported", ident);
 796                             self.session.struct_span_err(span, &msg)
 797                                 .span_label(span, &format!("`{}` already exported", ident))
 798                                 .span_note(binding.span, "previous macro export here")
 799                                 .emit();
 800                         }
 801                     }
 802                     reexports.push(Export { name: ident.name, def: def, span: binding.span });
 803                 }
 804             }
 805
 806             match binding.kind {
 807                 NameBindingKind::Import { binding: orig_binding, directive, .. } => {
 808                     if ns == TypeNS && orig_binding.is_variant() &&
 809                        !orig_binding.vis.is_at_least(binding.vis, &*self) {
 810                         let msg = format!("variant `{}` is private, and cannot be reexported \
 811                                            (error E0364), consider declaring its enum as `pub`",
 812                                           ident);
 813                         self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, binding.span, msg);
 814                     }
 815                 }
 816                 NameBindingKind::Ambiguity { b1, b2, .. }
 817                         if b1.is_glob_import() && b2.is_glob_import() => {
 818                     let (orig_b1, orig_b2) = match (&b1.kind, &b2.kind) {
 819                         (&NameBindingKind::Import { binding: b1, .. },
 820                          &NameBindingKind::Import { binding: b2, .. }) => (b1, b2),
 821                         _ => continue,
 822                     };
 823                     let (b1, b2) = match (orig_b1.vis, orig_b2.vis) {
 824                         (ty::Visibility::Public, ty::Visibility::Public) => continue,
 825                         (ty::Visibility::Public, _) => (b1, b2),
 826                         (_, ty::Visibility::Public) => (b2, b1),
 827                         _ => continue,
 828                     };
 829                     resolution.binding = Some(self.arenas.alloc_name_binding(NameBinding {
 830                         kind: NameBindingKind::Ambiguity { b1: b1, b2: b2, legacy: true }, ..*b1
 831                     }));
 832                 }
 833                 _ => {}
 834             }
 835         }
 836
 837         if reexports.len() > 0 {
 838             if let Some(def_id) = module.def_id() {
 839                 let node_id = self.definitions.as_local_node_id(def_id).unwrap();
 840                 self.export_map.insert(node_id, reexports);
 841             }
 842         }
 843     }
 844 }
 845
 846 fn import_path_to_string(names: &[Ident], subclass: &ImportDirectiveSubclass) -> String {
 847     let global = !names.is_empty() && names[0].name == keywords::CrateRoot.name();
 848     let names = if global { &names[1..] } else { names };
 849     if names.is_empty() {
 850         import_directive_subclass_to_string(subclass)
 851     } else {
 852         (format!("{}::{}",
 853                  names_to_string(names),
 854                  import_directive_subclass_to_string(subclass)))
 855             .to_string()
 856     }
 857 }
 858
 859 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
 860     match *subclass {
 861         SingleImport { source, .. } => source.to_string(),
 862         GlobImport { .. } => "*".to_string(),
 863         ExternCrate => "<extern crate>".to_string(),
 864         MacroUse => "#[macro_use]".to_string(),
 865     }
 866 }