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::Determinacy::*;
  12 use self::ImportDirectiveSubclass::*;
  13
  14 use Module;
  15 use Namespace::{self, TypeNS, ValueNS};
  16 use {NameBinding, NameBindingKind, PrivacyError, ToNameBinding};
  17 use ResolveResult;
  18 use ResolveResult::*;
  19 use Resolver;
  20 use UseLexicalScopeFlag::DontUseLexicalScope;
  21 use {names_to_string, module_to_string};
  22 use {resolve_error, ResolutionError};
  23
  24 use rustc::ty;
  25 use rustc::lint::builtin::PRIVATE_IN_PUBLIC;
  26 use rustc::hir::def::*;
  27
  28 use syntax::ast::{NodeId, Name};
  29 use syntax::util::lev_distance::find_best_match_for_name;
  30 use syntax_pos::Span;
  31
  32 use std::cell::{Cell, RefCell};
  33
  34 impl<'a> Resolver<'a> {
  35     pub fn resolve_imports(&mut self) {
  36         ImportResolver { resolver: self }.resolve_imports();
  37     }
  38 }
  39
  40 #[derive(Copy, Clone, Debug)]
  41 pub enum Determinacy {
  42     Determined,
  43     Undetermined,
  44 }
  45
  46 /// Contains data for specific types of import directives.
  47 #[derive(Clone, Debug)]
  48 pub enum ImportDirectiveSubclass<'a> {
  49     SingleImport {
  50         target: Name,
  51         source: Name,
  52         value_result: Cell<Result<&'a NameBinding<'a>, Determinacy>>,
  53         type_result: Cell<Result<&'a NameBinding<'a>, Determinacy>>,
  54     },
  55     GlobImport {
  56         is_prelude: bool,
  57         max_vis: Cell<ty::Visibility>, // The visibility of the greatest reexport.
  58     },
  59 }
  60
  61 impl<'a> ImportDirectiveSubclass<'a> {
  62     pub fn single(target: Name, source: Name) -> Self {
  63         SingleImport {
  64             target: target,
  65             source: source,
  66             type_result: Cell::new(Err(Undetermined)),
  67             value_result: Cell::new(Err(Undetermined)),
  68         }
  69     }
  70 }
  71
  72 /// One import directive.
  73 #[derive(Debug,Clone)]
  74 pub struct ImportDirective<'a> {
  75     pub id: NodeId,
  76     parent: Module<'a>,
  77     module_path: Vec<Name>,
  78     imported_module: Cell<Option<Module<'a>>>, // the resolution of `module_path`
  79     subclass: ImportDirectiveSubclass<'a>,
  80     span: Span,
  81     vis: Cell<ty::Visibility>,
  82 }
  83
  84 impl<'a> ImportDirective<'a> {
  85     pub fn is_glob(&self) -> bool {
  86         match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
  87     }
  88 }
  89
  90 #[derive(Clone, Default)]
  91 /// Records information about the resolution of a name in a namespace of a module.
  92 pub struct NameResolution<'a> {
  93     /// The single imports that define the name in the namespace.
  94     single_imports: SingleImports<'a>,
  95     /// The least shadowable known binding for this name, or None if there are no known bindings.
  96     pub binding: Option<&'a NameBinding<'a>>,
  97     duplicate_globs: Vec<&'a NameBinding<'a>>,
  98 }
  99
 100 #[derive(Clone, Debug)]
 101 enum SingleImports<'a> {
 102     /// No single imports can define the name in the namespace.
 103     None,
 104     /// Only the given single import can define the name in the namespace.
 105     MaybeOne(&'a ImportDirective<'a>),
 106     /// At least one single import will define the name in the namespace.
 107     AtLeastOne,
 108 }
 109
 110 impl<'a> Default for SingleImports<'a> {
 111     fn default() -> Self {
 112         SingleImports::None
 113     }
 114 }
 115
 116 impl<'a> SingleImports<'a> {
 117     fn add_directive(&mut self, directive: &'a ImportDirective<'a>) {
 118         match *self {
 119             SingleImports::None => *self = SingleImports::MaybeOne(directive),
 120             // If two single imports can define the name in the namespace, we can assume that at
 121             // least one of them will define it since otherwise both would have to define only one
 122             // namespace, leading to a duplicate error.
 123             SingleImports::MaybeOne(_) => *self = SingleImports::AtLeastOne,
 124             SingleImports::AtLeastOne => {}
 125         };
 126     }
 127
 128     fn directive_failed(&mut self) {
 129         match *self {
 130             SingleImports::None => unreachable!(),
 131             SingleImports::MaybeOne(_) => *self = SingleImports::None,
 132             SingleImports::AtLeastOne => {}
 133         }
 134     }
 135 }
 136
 137 impl<'a> NameResolution<'a> {
 138     // Returns the binding for the name if it is known or None if it not known.
 139     fn binding(&self) -> Option<&'a NameBinding<'a>> {
 140         self.binding.and_then(|binding| match self.single_imports {
 141             SingleImports::None => Some(binding),
 142             _ if !binding.is_glob_import() => Some(binding),
 143             _ => None, // The binding could be shadowed by a single import, so it is not known.
 144         })
 145     }
 146 }
 147
 148 impl<'a> Resolver<'a> {
 149     fn resolution(&self, module: Module<'a>, name: Name, ns: Namespace)
 150                   -> &'a RefCell<NameResolution<'a>> {
 151         *module.resolutions.borrow_mut().entry((name, ns))
 152                .or_insert_with(|| self.arenas.alloc_name_resolution())
 153     }
 154
 155     /// Attempts to resolve the supplied name in the given module for the given namespace.
 156     /// If successful, returns the binding corresponding to the name.
 157     /// Invariant: if `record_used` is `Some`, import resolution must be complete.
 158     pub fn resolve_name_in_module(&mut self,
 159                                   module: Module<'a>,
 160                                   name: Name,
 161                                   ns: Namespace,
 162                                   allow_private_imports: bool,
 163                                   record_used: Option<Span>)
 164                                   -> ResolveResult<&'a NameBinding<'a>> {
 165         self.populate_module_if_necessary(module);
 166
 167         let resolution = self.resolution(module, name, ns);
 168         let resolution = match resolution.borrow_state() {
 169             ::std::cell::BorrowState::Unused => resolution.borrow_mut(),
 170             _ => return Failed(None), // This happens when there is a cycle of imports
 171         };
 172
 173         let new_import_semantics = self.new_import_semantics;
 174         let is_disallowed_private_import = |binding: &NameBinding| {
 175             !new_import_semantics && !allow_private_imports && // disallowed
 176             binding.vis != ty::Visibility::Public && binding.is_import() // non-`pub` import
 177         };
 178
 179         if let Some(span) = record_used {
 180             if let Some(binding) = resolution.binding {
 181                 if is_disallowed_private_import(binding) {
 182                     return Failed(None);
 183                 }
 184                 if self.record_use(name, ns, binding, span) {
 185                     return Success(self.dummy_binding);
 186                 }
 187                 if !self.is_accessible(binding.vis) {
 188                     self.privacy_errors.push(PrivacyError(span, name, binding));
 189                 }
 190             }
 191
 192             return resolution.binding.map(Success).unwrap_or(Failed(None));
 193         }
 194
 195         // If the resolution doesn't depend on glob definability, check privacy and return.
 196         if let Some(result) = self.try_result(&resolution, ns) {
 197             return result.and_then(|binding| {
 198                 if self.is_accessible(binding.vis) && !is_disallowed_private_import(binding) {
 199                     Success(binding)
 200                 } else {
 201                     Failed(None)
 202                 }
 203             });
 204         }
 205
 206         // Check if the globs are determined
 207         for directive in module.globs.borrow().iter() {
 208             if self.is_accessible(directive.vis.get()) {
 209                 if let Some(module) = directive.imported_module.get() {
 210                     let result = self.resolve_name_in_module(module, name, ns, true, None);
 211                     if let Indeterminate = result {
 212                         return Indeterminate;
 213                     }
 214                 } else {
 215                     return Indeterminate;
 216                 }
 217             }
 218         }
 219
 220         Failed(None)
 221     }
 222
 223     // Returns Some(the resolution of the name), or None if the resolution depends
 224     // on whether more globs can define the name.
 225     fn try_result(&mut self, resolution: &NameResolution<'a>, ns: Namespace)
 226                   -> Option<ResolveResult<&'a NameBinding<'a>>> {
 227         match resolution.binding {
 228             Some(binding) if !binding.is_glob_import() =>
 229                 return Some(Success(binding)), // Items and single imports are not shadowable.
 230             _ => {}
 231         };
 232
 233         // Check if a single import can still define the name.
 234         match resolution.single_imports {
 235             SingleImports::AtLeastOne => return Some(Indeterminate),
 236             SingleImports::MaybeOne(directive) if self.is_accessible(directive.vis.get()) => {
 237                 let module = match directive.imported_module.get() {
 238                     Some(module) => module,
 239                     None => return Some(Indeterminate),
 240                 };
 241                 let name = match directive.subclass {
 242                     SingleImport { source, .. } => source,
 243                     GlobImport { .. } => unreachable!(),
 244                 };
 245                 match self.resolve_name_in_module(module, name, ns, true, None) {
 246                     Failed(_) => {}
 247                     _ => return Some(Indeterminate),
 248                 }
 249             }
 250             SingleImports::MaybeOne(_) | SingleImports::None => {},
 251         }
 252
 253         resolution.binding.map(Success)
 254     }
 255
 256     // Add an import directive to the current module.
 257     pub fn add_import_directive(&mut self,
 258                                 module_path: Vec<Name>,
 259                                 subclass: ImportDirectiveSubclass<'a>,
 260                                 span: Span,
 261                                 id: NodeId,
 262                                 vis: ty::Visibility) {
 263         let current_module = self.current_module;
 264         let directive = self.arenas.alloc_import_directive(ImportDirective {
 265             parent: current_module,
 266             module_path: module_path,
 267             imported_module: Cell::new(None),
 268             subclass: subclass,
 269             span: span,
 270             id: id,
 271             vis: Cell::new(vis),
 272         });
 273
 274         self.indeterminate_imports.push(directive);
 275         match directive.subclass {
 276             SingleImport { target, .. } => {
 277                 for &ns in &[ValueNS, TypeNS] {
 278                     let mut resolution = self.resolution(current_module, target, ns).borrow_mut();
 279                     resolution.single_imports.add_directive(directive);
 280                 }
 281             }
 282             // We don't add prelude imports to the globs since they only affect lexical scopes,
 283             // which are not relevant to import resolution.
 284             GlobImport { is_prelude: true, .. } => {}
 285             GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
 286         }
 287     }
 288
 289     // Given a binding and an import directive that resolves to it,
 290     // return the corresponding binding defined by the import directive.
 291     fn import(&mut self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
 292               -> NameBinding<'a> {
 293         let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
 294                      !directive.is_glob() && binding.is_extern_crate() { // c.f. `PRIVATE_IN_PUBLIC`
 295             directive.vis.get()
 296         } else {
 297             binding.pseudo_vis()
 298         };
 299
 300         if let GlobImport { ref max_vis, .. } = directive.subclass {
 301             if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
 302                 max_vis.set(vis)
 303             }
 304         }
 305
 306         NameBinding {
 307             kind: NameBindingKind::Import {
 308                 binding: binding,
 309                 directive: directive,
 310             },
 311             span: directive.span,
 312             vis: vis,
 313         }
 314     }
 315
 316     // Define the name or return the existing binding if there is a collision.
 317     pub fn try_define<T>(&mut self, module: Module<'a>, name: Name, ns: Namespace, binding: T)
 318                          -> Result<(), &'a NameBinding<'a>>
 319         where T: ToNameBinding<'a>
 320     {
 321         let binding = self.arenas.alloc_name_binding(binding.to_name_binding());
 322         self.update_resolution(module, name, ns, |this, resolution| {
 323             if let Some(old_binding) = resolution.binding {
 324                 if binding.is_glob_import() {
 325                     if !this.new_import_semantics || !old_binding.is_glob_import() {
 326                         resolution.duplicate_globs.push(binding);
 327                     } else if binding.def() != old_binding.def() {
 328                         resolution.binding = Some(this.arenas.alloc_name_binding(NameBinding {
 329                             kind: NameBindingKind::Ambiguity {
 330                                 b1: old_binding,
 331                                 b2: binding,
 332                             },
 333                             vis: if old_binding.vis.is_at_least(binding.vis, this) {
 334                                 old_binding.vis
 335                             } else {
 336                                 binding.vis
 337                             },
 338                             span: old_binding.span,
 339                         }));
 340                     } else if !old_binding.vis.is_at_least(binding.vis, this) {
 341                         // We are glob-importing the same item but with greater visibility.
 342                         resolution.binding = Some(binding);
 343                     }
 344                 } else if old_binding.is_glob_import() {
 345                     resolution.duplicate_globs.push(old_binding);
 346                     resolution.binding = Some(binding);
 347                 } else {
 348                     return Err(old_binding);
 349                 }
 350             } else {
 351                 resolution.binding = Some(binding);
 352             }
 353
 354             Ok(())
 355         })
 356     }
 357
 358     // Use `f` to mutate the resolution of the name in the module.
 359     // If the resolution becomes a success, define it in the module's glob importers.
 360     fn update_resolution<T, F>(&mut self, module: Module<'a>, name: Name, ns: Namespace, f: F) -> T
 361         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
 362     {
 363         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
 364         // during which the resolution might end up getting re-defined via a glob cycle.
 365         let (binding, t) = {
 366             let mut resolution = &mut *self.resolution(module, name, ns).borrow_mut();
 367             let old_binding = resolution.binding();
 368
 369             let t = f(self, resolution);
 370
 371             match resolution.binding() {
 372                 _ if !self.new_import_semantics && old_binding.is_some() => return t,
 373                 None => return t,
 374                 Some(binding) => match old_binding {
 375                     Some(old_binding) if old_binding as *const _ == binding as *const _ => return t,
 376                     _ => (binding, t),
 377                 }
 378             }
 379         };
 380
 381         // Define `binding` in `module`s glob importers.
 382         for directive in module.glob_importers.borrow_mut().iter() {
 383             if match self.new_import_semantics {
 384                 true => self.is_accessible_from(binding.vis, directive.parent),
 385                 false => binding.vis == ty::Visibility::Public,
 386             } {
 387                 let imported_binding = self.import(binding, directive);
 388                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
 389             }
 390         }
 391
 392         t
 393     }
 394 }
 395
 396 struct ImportResolver<'a, 'b: 'a> {
 397     resolver: &'a mut Resolver<'b>,
 398 }
 399
 400 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
 401     type Target = Resolver<'b>;
 402     fn deref(&self) -> &Resolver<'b> {
 403         self.resolver
 404     }
 405 }
 406
 407 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
 408     fn deref_mut(&mut self) -> &mut Resolver<'b> {
 409         self.resolver
 410     }
 411 }
 412
 413 impl<'a, 'b: 'a> ty::NodeIdTree for ImportResolver<'a, 'b> {
 414     fn is_descendant_of(&self, node: NodeId, ancestor: NodeId) -> bool {
 415         self.resolver.is_descendant_of(node, ancestor)
 416     }
 417 }
 418
 419 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 420     // Import resolution
 421     //
 422     // This is a fixed-point algorithm. We resolve imports until our efforts
 423     // are stymied by an unresolved import; then we bail out of the current
 424     // module and continue. We terminate successfully once no more imports
 425     // remain or unsuccessfully when no forward progress in resolving imports
 426     // is made.
 427
 428     /// Resolves all imports for the crate. This method performs the fixed-
 429     /// point iteration.
 430     fn resolve_imports(&mut self) {
 431         let mut i = 0;
 432         let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
 433
 434         while self.indeterminate_imports.len() < prev_num_indeterminates {
 435             prev_num_indeterminates = self.indeterminate_imports.len();
 436             debug!("(resolving imports) iteration {}, {} imports left", i, prev_num_indeterminates);
 437
 438             let mut imports = Vec::new();
 439             ::std::mem::swap(&mut imports, &mut self.indeterminate_imports);
 440
 441             for import in imports {
 442                 match self.resolve_import(&import) {
 443                     Failed(_) => self.determined_imports.push(import),
 444                     Indeterminate => self.indeterminate_imports.push(import),
 445                     Success(()) => self.determined_imports.push(import),
 446                 }
 447             }
 448
 449             i += 1;
 450         }
 451
 452         for module in self.arenas.local_modules().iter() {
 453             self.finalize_resolutions_in(module);
 454         }
 455
 456         let mut errors = false;
 457         for i in 0 .. self.determined_imports.len() {
 458             let import = self.determined_imports[i];
 459             if let Failed(err) = self.finalize_import(import) {
 460                 errors = true;
 461                 let (span, help) = match err {
 462                     Some((span, msg)) => (span, msg),
 463                     None => continue,
 464                 };
 465
 466                 // If the error is a single failed import then create a "fake" import
 467                 // resolution for it so that later resolve stages won't complain.
 468                 self.import_dummy_binding(import);
 469                 let path = import_path_to_string(&import.module_path, &import.subclass);
 470                 let error = ResolutionError::UnresolvedImport(Some((&path, &help)));
 471                 resolve_error(self.resolver, span, error);
 472             }
 473         }
 474
 475         // Report unresolved imports only if no hard error was already reported
 476         // to avoid generating multiple errors on the same import.
 477         if !errors {
 478             if let Some(import) = self.indeterminate_imports.iter().next() {
 479                 let error = ResolutionError::UnresolvedImport(None);
 480                 resolve_error(self.resolver, import.span, error);
 481             }
 482         }
 483     }
 484
 485     // Define a "dummy" resolution containing a Def::Err as a placeholder for a
 486     // failed resolution
 487     fn import_dummy_binding(&mut self, directive: &'b ImportDirective<'b>) {
 488         if let SingleImport { target, .. } = directive.subclass {
 489             let dummy_binding = self.dummy_binding;
 490             let dummy_binding = self.import(dummy_binding, directive);
 491             let _ = self.try_define(directive.parent, target, ValueNS, dummy_binding.clone());
 492             let _ = self.try_define(directive.parent, target, TypeNS, dummy_binding);
 493         }
 494     }
 495
 496     /// Attempts to resolve the given import. The return value indicates
 497     /// failure if we're certain the name does not exist, indeterminate if we
 498     /// don't know whether the name exists at the moment due to other
 499     /// currently-unresolved imports, or success if we know the name exists.
 500     /// If successful, the resolved bindings are written into the module.
 501     fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
 502         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 503                names_to_string(&directive.module_path),
 504                module_to_string(self.current_module));
 505
 506         self.current_module = directive.parent;
 507
 508         let module = if let Some(module) = directive.imported_module.get() {
 509             module
 510         } else {
 511             let vis = directive.vis.get();
 512             // For better failure detection, pretend that the import will not define any names
 513             // while resolving its module path.
 514             directive.vis.set(ty::Visibility::PrivateExternal);
 515             let result =
 516                 self.resolve_module_path(&directive.module_path, DontUseLexicalScope, None);
 517             directive.vis.set(vis);
 518
 519             match result {
 520                 Success(module) => module,
 521                 Indeterminate => return Indeterminate,
 522                 Failed(err) => return Failed(err),
 523             }
 524         };
 525
 526         directive.imported_module.set(Some(module));
 527         let (source, target, value_result, type_result) = match directive.subclass {
 528             SingleImport { source, target, ref value_result, ref type_result } =>
 529                 (source, target, value_result, type_result),
 530             GlobImport { .. } => {
 531                 self.resolve_glob_import(directive);
 532                 return Success(());
 533             }
 534         };
 535
 536         let mut indeterminate = false;
 537         for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
 538             if let Err(Undetermined) = result.get() {
 539                 result.set({
 540                     match self.resolve_name_in_module(module, source, ns, false, None) {
 541                         Success(binding) => Ok(binding),
 542                         Indeterminate => Err(Undetermined),
 543                         Failed(_) => Err(Determined),
 544                     }
 545                 });
 546             } else {
 547                 continue
 548             };
 549
 550             match result.get() {
 551                 Err(Undetermined) => indeterminate = true,
 552                 Err(Determined) => {
 553                     self.update_resolution(directive.parent, target, ns, |_, resolution| {
 554                         resolution.single_imports.directive_failed()
 555                     });
 556                 }
 557                 Ok(binding) if !binding.is_importable() => {
 558                     let msg = format!("`{}` is not directly importable", target);
 559                     struct_span_err!(self.session, directive.span, E0253, "{}", &msg)
 560                         .span_label(directive.span, &format!("cannot be imported directly"))
 561                         .emit();
 562                     // Do not import this illegal binding. Import a dummy binding and pretend
 563                     // everything is fine
 564                     self.import_dummy_binding(directive);
 565                     return Success(());
 566                 }
 567                 Ok(binding) => {
 568                     let imported_binding = self.import(binding, directive);
 569                     let conflict = self.try_define(directive.parent, target, ns, imported_binding);
 570                     if let Err(old_binding) = conflict {
 571                         let binding = &self.import(binding, directive);
 572                         self.report_conflict(directive.parent, target, ns, binding, old_binding);
 573                     }
 574                 }
 575             }
 576         }
 577
 578         if indeterminate { Indeterminate } else { Success(()) }
 579     }
 580
 581     fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
 582         self.current_module = directive.parent;
 583
 584         let ImportDirective { ref module_path, span, .. } = *directive;
 585         let module_result = self.resolve_module_path(&module_path, DontUseLexicalScope, Some(span));
 586         let module = match module_result {
 587             Success(module) => module,
 588             Indeterminate => return Indeterminate,
 589             Failed(err) => return Failed(err),
 590         };
 591
 592         let (name, value_result, type_result) = match directive.subclass {
 593             SingleImport { source, ref value_result, ref type_result, .. } =>
 594                 (source, value_result.get(), type_result.get()),
 595             GlobImport { .. } if module.def_id() == directive.parent.def_id() => {
 596                 // Importing a module into itself is not allowed.
 597                 let msg = "Cannot glob-import a module into itself.".into();
 598                 return Failed(Some((directive.span, msg)));
 599             }
 600             GlobImport { is_prelude, ref max_vis } => {
 601                 if !is_prelude &&
 602                    max_vis.get() != ty::Visibility::PrivateExternal && // Allow empty globs.
 603                    !max_vis.get().is_at_least(directive.vis.get(), self) {
 604                     let msg = "A non-empty glob must import something with the glob's visibility";
 605                     self.session.span_err(directive.span, msg);
 606                 }
 607                 return Success(());
 608             }
 609         };
 610
 611         for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
 612             if let Ok(binding) = result {
 613                 if self.record_use(name, ns, binding, directive.span) {
 614                     self.resolution(module, name, ns).borrow_mut().binding =
 615                         Some(self.dummy_binding);
 616                 }
 617             }
 618         }
 619
 620         if value_result.is_err() && type_result.is_err() {
 621             let (value_result, type_result);
 622             value_result = self.resolve_name_in_module(module, name, ValueNS, false, Some(span));
 623             type_result = self.resolve_name_in_module(module, name, TypeNS, false, Some(span));
 624
 625             return if let (Failed(_), Failed(_)) = (value_result, type_result) {
 626                 let resolutions = module.resolutions.borrow();
 627                 let names = resolutions.iter().filter_map(|(&(ref n, _), resolution)| {
 628                     if *n == name { return None; } // Never suggest the same name
 629                     match *resolution.borrow() {
 630                         NameResolution { binding: Some(_), .. } => Some(n),
 631                         NameResolution { single_imports: SingleImports::None, .. } => None,
 632                         _ => Some(n),
 633                     }
 634                 });
 635                 let lev_suggestion = match find_best_match_for_name(names, &name.as_str(), None) {
 636                     Some(name) => format!(". Did you mean to use `{}`?", name),
 637                     None => "".to_owned(),
 638                 };
 639                 let module_str = module_to_string(module);
 640                 let msg = if &module_str == "???" {
 641                     format!("no `{}` in the root{}", name, lev_suggestion)
 642                 } else {
 643                     format!("no `{}` in `{}`{}", name, module_str, lev_suggestion)
 644                 };
 645                 Failed(Some((directive.span, msg)))
 646             } else {
 647                 // `resolve_name_in_module` reported a privacy error.
 648                 self.import_dummy_binding(directive);
 649                 Success(())
 650             }
 651         }
 652
 653         let session = self.session;
 654         let reexport_error = || {
 655             let msg = format!("`{}` is private, and cannot be reexported", name);
 656             let note_msg =
 657                 format!("consider marking `{}` as `pub` in the imported module", name);
 658             struct_span_err!(session, directive.span, E0364, "{}", &msg)
 659                 .span_note(directive.span, &note_msg)
 660                 .emit();
 661         };
 662
 663         let extern_crate_lint = || {
 664             let msg = format!("extern crate `{}` is private, and cannot be reexported \
 665                                (error E0364), consider declaring with `pub`",
 666                                name);
 667             session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
 668         };
 669
 670         match (value_result, type_result) {
 671             // With `#![feature(item_like_imports)]`, all namespaces
 672             // must be re-exported with extra visibility for an error to occur.
 673             (Ok(value_binding), Ok(type_binding)) if self.new_import_semantics => {
 674                 let vis = directive.vis.get();
 675                 if !value_binding.pseudo_vis().is_at_least(vis, self) &&
 676                    !type_binding.pseudo_vis().is_at_least(vis, self) {
 677                     reexport_error();
 678                 } else if type_binding.is_extern_crate() &&
 679                           !type_binding.vis.is_at_least(vis, self) {
 680                     extern_crate_lint();
 681                 }
 682             }
 683
 684             (Ok(binding), _) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
 685                 reexport_error();
 686             }
 687
 688             (_, Ok(binding)) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
 689                 if binding.is_extern_crate() {
 690                     extern_crate_lint();
 691                 } else {
 692                     struct_span_err!(self.session, directive.span, E0365,
 693                                      "`{}` is private, and cannot be reexported", name)
 694                         .span_label(directive.span, &format!("reexport of private `{}`", name))
 695                         .note(&format!("consider declaring type or module `{}` with `pub`", name))
 696                         .emit();
 697                 }
 698             }
 699
 700             _ => {}
 701         }
 702
 703         // Record what this import resolves to for later uses in documentation,
 704         // this may resolve to either a value or a type, but for documentation
 705         // purposes it's good enough to just favor one over the other.
 706         let def = match type_result.ok().map(NameBinding::def) {
 707             Some(def) => def,
 708             None => value_result.ok().map(NameBinding::def).unwrap(),
 709         };
 710         let path_resolution = PathResolution::new(def);
 711         self.def_map.insert(directive.id, path_resolution);
 712
 713         debug!("(resolving single import) successfully resolved import");
 714         return Success(());
 715     }
 716
 717     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
 718         let module = directive.imported_module.get().unwrap();
 719         self.populate_module_if_necessary(module);
 720
 721         if let Some(Def::Trait(_)) = module.def {
 722             self.session.span_err(directive.span, "items in traits are not importable.");
 723             return;
 724         } else if module.def_id() == directive.parent.def_id()  {
 725             return;
 726         } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
 727             self.prelude = Some(module);
 728             return;
 729         }
 730
 731         // Add to module's glob_importers
 732         module.glob_importers.borrow_mut().push(directive);
 733
 734         // Ensure that `resolutions` isn't borrowed during `try_define`,
 735         // since it might get updated via a glob cycle.
 736         let bindings = module.resolutions.borrow().iter().filter_map(|(name, resolution)| {
 737             resolution.borrow().binding().map(|binding| (*name, binding))
 738         }).collect::<Vec<_>>();
 739         for ((name, ns), binding) in bindings {
 740             if binding.pseudo_vis() == ty::Visibility::Public ||
 741                self.new_import_semantics && self.is_accessible(binding.vis) {
 742                 let imported_binding = self.import(binding, directive);
 743                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
 744             }
 745         }
 746
 747         // Record the destination of this import
 748         if let Some(did) = module.def_id() {
 749             let resolution = PathResolution::new(Def::Mod(did));
 750             self.def_map.insert(directive.id, resolution);
 751         }
 752     }
 753
 754     // Miscellaneous post-processing, including recording reexports, reporting conflicts,
 755     // reporting the PRIVATE_IN_PUBLIC lint, and reporting unresolved imports.
 756     fn finalize_resolutions_in(&mut self, module: Module<'b>) {
 757         // Since import resolution is finished, globs will not define any more names.
 758         *module.globs.borrow_mut() = Vec::new();
 759
 760         let mut reexports = Vec::new();
 761         for (&(name, ns), resolution) in module.resolutions.borrow().iter() {
 762             let resolution = resolution.borrow();
 763             let binding = match resolution.binding {
 764                 Some(binding) => binding,
 765                 None => continue,
 766             };
 767
 768             // Report conflicts
 769             if !self.new_import_semantics {
 770                 for duplicate_glob in resolution.duplicate_globs.iter() {
 771                     // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
 772                     if !binding.is_import() {
 773                         if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
 774                             if binding.is_import() { continue }
 775                         }
 776                     }
 777
 778                     self.report_conflict(module, name, ns, duplicate_glob, binding);
 779                 }
 780             }
 781
 782             if binding.vis == ty::Visibility::Public &&
 783                (binding.is_import() || binding.is_extern_crate()) {
 784                 let def = binding.def();
 785                 if def != Def::Err {
 786                     reexports.push(Export { name: name, def_id: def.def_id() });
 787                 }
 788             }
 789
 790             if let NameBindingKind::Import { binding: orig_binding, directive, .. } = binding.kind {
 791                 if ns == TypeNS && orig_binding.is_variant() &&
 792                    !orig_binding.vis.is_at_least(binding.vis, self) {
 793                     let msg = format!("variant `{}` is private, and cannot be reexported \
 794                                        (error E0364), consider declaring its enum as `pub`",
 795                                       name);
 796                     self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, binding.span, msg);
 797                 }
 798             }
 799         }
 800
 801         if reexports.len() > 0 {
 802             if let Some(def_id) = module.def_id() {
 803                 let node_id = self.definitions.as_local_node_id(def_id).unwrap();
 804                 self.export_map.insert(node_id, reexports);
 805             }
 806         }
 807     }
 808 }
 809
 810 fn import_path_to_string(names: &[Name], subclass: &ImportDirectiveSubclass) -> String {
 811     if names.is_empty() {
 812         import_directive_subclass_to_string(subclass)
 813     } else {
 814         (format!("{}::{}",
 815                  names_to_string(names),
 816                  import_directive_subclass_to_string(subclass)))
 817             .to_string()
 818     }
 819 }
 820
 821 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
 822     match *subclass {
 823         SingleImport { source, .. } => source.to_string(),
 824         GlobImport { .. } => "*".to_string(),
 825     }
 826 }