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         // n.b. `max_vis` is only used in `finalize_import` to check for reexport errors.
  59     },
  60 }
  61
  62 impl<'a> ImportDirectiveSubclass<'a> {
  63     pub fn single(target: Name, source: Name) -> Self {
  64         SingleImport {
  65             target: target,
  66             source: source,
  67             type_result: Cell::new(Err(Undetermined)),
  68             value_result: Cell::new(Err(Undetermined)),
  69         }
  70     }
  71 }
  72
  73 /// One import directive.
  74 #[derive(Debug,Clone)]
  75 pub struct ImportDirective<'a> {
  76     pub id: NodeId,
  77     parent: Module<'a>,
  78     module_path: Vec<Name>,
  79     imported_module: Cell<Option<Module<'a>>>, // the resolution of `module_path`
  80     subclass: ImportDirectiveSubclass<'a>,
  81     span: Span,
  82     vis: Cell<ty::Visibility>,
  83 }
  84
  85 impl<'a> ImportDirective<'a> {
  86     pub fn is_glob(&self) -> bool {
  87         match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
  88     }
  89 }
  90
  91 #[derive(Clone, Default)]
  92 /// Records information about the resolution of a name in a namespace of a module.
  93 pub struct NameResolution<'a> {
  94     /// The single imports that define the name in the namespace.
  95     single_imports: SingleImports<'a>,
  96     /// The least shadowable known binding for this name, or None if there are no known bindings.
  97     pub binding: Option<&'a NameBinding<'a>>,
  98     duplicate_globs: Vec<&'a NameBinding<'a>>,
  99 }
 100
 101 #[derive(Clone, Debug)]
 102 enum SingleImports<'a> {
 103     /// No single imports can define the name in the namespace.
 104     None,
 105     /// Only the given single import can define the name in the namespace.
 106     MaybeOne(&'a ImportDirective<'a>),
 107     /// At least one single import will define the name in the namespace.
 108     AtLeastOne,
 109 }
 110
 111 impl<'a> Default for SingleImports<'a> {
 112     fn default() -> Self {
 113         SingleImports::None
 114     }
 115 }
 116
 117 impl<'a> SingleImports<'a> {
 118     fn add_directive(&mut self, directive: &'a ImportDirective<'a>) {
 119         match *self {
 120             SingleImports::None => *self = SingleImports::MaybeOne(directive),
 121             // If two single imports can define the name in the namespace, we can assume that at
 122             // least one of them will define it since otherwise both would have to define only one
 123             // namespace, leading to a duplicate error.
 124             SingleImports::MaybeOne(_) => *self = SingleImports::AtLeastOne,
 125             SingleImports::AtLeastOne => {}
 126         };
 127     }
 128
 129     fn directive_failed(&mut self) {
 130         match *self {
 131             SingleImports::None => unreachable!(),
 132             SingleImports::MaybeOne(_) => *self = SingleImports::None,
 133             SingleImports::AtLeastOne => {}
 134         }
 135     }
 136 }
 137
 138 impl<'a> NameResolution<'a> {
 139     // Returns the binding for the name if it is known or None if it not known.
 140     fn binding(&self) -> Option<&'a NameBinding<'a>> {
 141         self.binding.and_then(|binding| match self.single_imports {
 142             SingleImports::None => Some(binding),
 143             _ if !binding.is_glob_import() => Some(binding),
 144             _ => None, // The binding could be shadowed by a single import, so it is not known.
 145         })
 146     }
 147 }
 148
 149 impl<'a> Resolver<'a> {
 150     fn resolution(&self, module: Module<'a>, name: Name, ns: Namespace)
 151                   -> &'a RefCell<NameResolution<'a>> {
 152         *module.resolutions.borrow_mut().entry((name, ns))
 153                .or_insert_with(|| self.arenas.alloc_name_resolution())
 154     }
 155
 156     /// Attempts to resolve the supplied name in the given module for the given namespace.
 157     /// If successful, returns the binding corresponding to the name.
 158     /// Invariant: if `record_used` is `Some`, import resolution must be complete.
 159     pub fn resolve_name_in_module(&mut self,
 160                                   module: Module<'a>,
 161                                   name: Name,
 162                                   ns: Namespace,
 163                                   allow_private_imports: bool,
 164                                   record_used: Option<Span>)
 165                                   -> ResolveResult<&'a NameBinding<'a>> {
 166         self.populate_module_if_necessary(module);
 167
 168         let resolution = self.resolution(module, name, ns);
 169         let resolution = match resolution.borrow_state() {
 170             ::std::cell::BorrowState::Unused => resolution.borrow_mut(),
 171             _ => return Failed(None), // This happens when there is a cycle of imports
 172         };
 173
 174         let new_import_semantics = self.new_import_semantics;
 175         let is_disallowed_private_import = |binding: &NameBinding| {
 176             !new_import_semantics && !allow_private_imports && // disallowed
 177             binding.vis != ty::Visibility::Public && binding.is_import() // non-`pub` import
 178         };
 179
 180         if let Some(span) = record_used {
 181             if let Some(binding) = resolution.binding {
 182                 if is_disallowed_private_import(binding) {
 183                     return Failed(None);
 184                 }
 185                 if self.record_use(name, ns, binding, span) {
 186                     return Success(self.dummy_binding);
 187                 }
 188                 if !self.is_accessible(binding.vis) {
 189                     self.privacy_errors.push(PrivacyError(span, name, binding));
 190                 }
 191             }
 192
 193             return resolution.binding.map(Success).unwrap_or(Failed(None));
 194         }
 195
 196         // If the resolution doesn't depend on glob definability, check privacy and return.
 197         if let Some(result) = self.try_result(&resolution, ns) {
 198             return result.and_then(|binding| {
 199                 if self.is_accessible(binding.vis) && !is_disallowed_private_import(binding) {
 200                     Success(binding)
 201                 } else {
 202                     Failed(None)
 203                 }
 204             });
 205         }
 206
 207         // Check if the globs are determined
 208         for directive in module.globs.borrow().iter() {
 209             if self.is_accessible(directive.vis.get()) {
 210                 if let Some(module) = directive.imported_module.get() {
 211                     let result = self.resolve_name_in_module(module, name, ns, true, None);
 212                     if let Indeterminate = result {
 213                         return Indeterminate;
 214                     }
 215                 } else {
 216                     return Indeterminate;
 217                 }
 218             }
 219         }
 220
 221         Failed(None)
 222     }
 223
 224     // Returns Some(the resolution of the name), or None if the resolution depends
 225     // on whether more globs can define the name.
 226     fn try_result(&mut self, resolution: &NameResolution<'a>, ns: Namespace)
 227                   -> Option<ResolveResult<&'a NameBinding<'a>>> {
 228         match resolution.binding {
 229             Some(binding) if !binding.is_glob_import() =>
 230                 return Some(Success(binding)), // Items and single imports are not shadowable.
 231             _ => {}
 232         };
 233
 234         // Check if a single import can still define the name.
 235         match resolution.single_imports {
 236             SingleImports::AtLeastOne => return Some(Indeterminate),
 237             SingleImports::MaybeOne(directive) if self.is_accessible(directive.vis.get()) => {
 238                 let module = match directive.imported_module.get() {
 239                     Some(module) => module,
 240                     None => return Some(Indeterminate),
 241                 };
 242                 let name = match directive.subclass {
 243                     SingleImport { source, .. } => source,
 244                     GlobImport { .. } => unreachable!(),
 245                 };
 246                 match self.resolve_name_in_module(module, name, ns, true, None) {
 247                     Failed(_) => {}
 248                     _ => return Some(Indeterminate),
 249                 }
 250             }
 251             SingleImports::MaybeOne(_) | SingleImports::None => {},
 252         }
 253
 254         resolution.binding.map(Success)
 255     }
 256
 257     // Add an import directive to the current module.
 258     pub fn add_import_directive(&mut self,
 259                                 module_path: Vec<Name>,
 260                                 subclass: ImportDirectiveSubclass<'a>,
 261                                 span: Span,
 262                                 id: NodeId,
 263                                 vis: ty::Visibility) {
 264         let current_module = self.current_module;
 265         let directive = self.arenas.alloc_import_directive(ImportDirective {
 266             parent: current_module,
 267             module_path: module_path,
 268             imported_module: Cell::new(None),
 269             subclass: subclass,
 270             span: span,
 271             id: id,
 272             vis: Cell::new(vis),
 273         });
 274
 275         self.indeterminate_imports.push(directive);
 276         match directive.subclass {
 277             SingleImport { target, .. } => {
 278                 for &ns in &[ValueNS, TypeNS] {
 279                     let mut resolution = self.resolution(current_module, target, ns).borrow_mut();
 280                     resolution.single_imports.add_directive(directive);
 281                 }
 282             }
 283             // We don't add prelude imports to the globs since they only affect lexical scopes,
 284             // which are not relevant to import resolution.
 285             GlobImport { is_prelude: true, .. } => {}
 286             GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
 287         }
 288     }
 289
 290     // Given a binding and an import directive that resolves to it,
 291     // return the corresponding binding defined by the import directive.
 292     fn import(&mut self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
 293               -> NameBinding<'a> {
 294         let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
 295                      !directive.is_glob() && binding.is_extern_crate() { // c.f. `PRIVATE_IN_PUBLIC`
 296             directive.vis.get()
 297         } else {
 298             binding.pseudo_vis()
 299         };
 300
 301         if let GlobImport { ref max_vis, .. } = directive.subclass {
 302             if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
 303                 max_vis.set(vis)
 304             }
 305         }
 306
 307         NameBinding {
 308             kind: NameBindingKind::Import {
 309                 binding: binding,
 310                 directive: directive,
 311             },
 312             span: directive.span,
 313             vis: vis,
 314         }
 315     }
 316
 317     // Define the name or return the existing binding if there is a collision.
 318     pub fn try_define<T>(&mut self, module: Module<'a>, name: Name, ns: Namespace, binding: T)
 319                          -> Result<(), &'a NameBinding<'a>>
 320         where T: ToNameBinding<'a>
 321     {
 322         let binding = self.arenas.alloc_name_binding(binding.to_name_binding());
 323         self.update_resolution(module, name, ns, |this, resolution| {
 324             if let Some(old_binding) = resolution.binding {
 325                 if binding.is_glob_import() {
 326                     if !this.new_import_semantics || !old_binding.is_glob_import() {
 327                         resolution.duplicate_globs.push(binding);
 328                     } else if binding.def() != old_binding.def() {
 329                         resolution.binding = Some(this.arenas.alloc_name_binding(NameBinding {
 330                             kind: NameBindingKind::Ambiguity {
 331                                 b1: old_binding,
 332                                 b2: binding,
 333                             },
 334                             vis: if old_binding.vis.is_at_least(binding.vis, this) {
 335                                 old_binding.vis
 336                             } else {
 337                                 binding.vis
 338                             },
 339                             span: old_binding.span,
 340                         }));
 341                     } else if !old_binding.vis.is_at_least(binding.vis, this) {
 342                         // We are glob-importing the same item but with greater visibility.
 343                         resolution.binding = Some(binding);
 344                     }
 345                 } else if old_binding.is_glob_import() {
 346                     resolution.duplicate_globs.push(old_binding);
 347                     resolution.binding = Some(binding);
 348                 } else {
 349                     return Err(old_binding);
 350                 }
 351             } else {
 352                 resolution.binding = Some(binding);
 353             }
 354
 355             Ok(())
 356         })
 357     }
 358
 359     // Use `f` to mutate the resolution of the name in the module.
 360     // If the resolution becomes a success, define it in the module's glob importers.
 361     fn update_resolution<T, F>(&mut self, module: Module<'a>, name: Name, ns: Namespace, f: F) -> T
 362         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
 363     {
 364         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
 365         // during which the resolution might end up getting re-defined via a glob cycle.
 366         let (binding, t) = {
 367             let mut resolution = &mut *self.resolution(module, name, ns).borrow_mut();
 368             let old_binding = resolution.binding();
 369
 370             let t = f(self, resolution);
 371
 372             match resolution.binding() {
 373                 _ if !self.new_import_semantics && old_binding.is_some() => return t,
 374                 None => return t,
 375                 Some(binding) => match old_binding {
 376                     Some(old_binding) if old_binding as *const _ == binding as *const _ => return t,
 377                     _ => (binding, t),
 378                 }
 379             }
 380         };
 381
 382         // Define `binding` in `module`s glob importers.
 383         for directive in module.glob_importers.borrow_mut().iter() {
 384             if match self.new_import_semantics {
 385                 true => self.is_accessible_from(binding.vis, directive.parent),
 386                 false => binding.vis == ty::Visibility::Public,
 387             } {
 388                 let imported_binding = self.import(binding, directive);
 389                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
 390             }
 391         }
 392
 393         t
 394     }
 395 }
 396
 397 struct ImportResolver<'a, 'b: 'a> {
 398     resolver: &'a mut Resolver<'b>,
 399 }
 400
 401 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
 402     type Target = Resolver<'b>;
 403     fn deref(&self) -> &Resolver<'b> {
 404         self.resolver
 405     }
 406 }
 407
 408 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
 409     fn deref_mut(&mut self) -> &mut Resolver<'b> {
 410         self.resolver
 411     }
 412 }
 413
 414 impl<'a, 'b: 'a> ty::NodeIdTree for ImportResolver<'a, 'b> {
 415     fn is_descendant_of(&self, node: NodeId, ancestor: NodeId) -> bool {
 416         self.resolver.is_descendant_of(node, ancestor)
 417     }
 418 }
 419
 420 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 421     // Import resolution
 422     //
 423     // This is a fixed-point algorithm. We resolve imports until our efforts
 424     // are stymied by an unresolved import; then we bail out of the current
 425     // module and continue. We terminate successfully once no more imports
 426     // remain or unsuccessfully when no forward progress in resolving imports
 427     // is made.
 428
 429     /// Resolves all imports for the crate. This method performs the fixed-
 430     /// point iteration.
 431     fn resolve_imports(&mut self) {
 432         let mut i = 0;
 433         let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
 434
 435         while self.indeterminate_imports.len() < prev_num_indeterminates {
 436             prev_num_indeterminates = self.indeterminate_imports.len();
 437             debug!("(resolving imports) iteration {}, {} imports left", i, prev_num_indeterminates);
 438
 439             let mut imports = Vec::new();
 440             ::std::mem::swap(&mut imports, &mut self.indeterminate_imports);
 441
 442             for import in imports {
 443                 match self.resolve_import(&import) {
 444                     Failed(_) => self.determined_imports.push(import),
 445                     Indeterminate => self.indeterminate_imports.push(import),
 446                     Success(()) => self.determined_imports.push(import),
 447                 }
 448             }
 449
 450             i += 1;
 451         }
 452
 453         for module in self.arenas.local_modules().iter() {
 454             self.finalize_resolutions_in(module);
 455         }
 456
 457         let mut errors = false;
 458         for i in 0 .. self.determined_imports.len() {
 459             let import = self.determined_imports[i];
 460             if let Failed(err) = self.finalize_import(import) {
 461                 errors = true;
 462                 let (span, help) = match err {
 463                     Some((span, msg)) => (span, msg),
 464                     None => continue,
 465                 };
 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, &help)));
 472                 resolve_error(self.resolver, 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     // Define a "dummy" resolution containing a Def::Err as a placeholder for a
 487     // failed resolution
 488     fn import_dummy_binding(&mut self, directive: &'b ImportDirective<'b>) {
 489         if let SingleImport { target, .. } = directive.subclass {
 490             let dummy_binding = self.dummy_binding;
 491             let dummy_binding = self.import(dummy_binding, directive);
 492             let _ = self.try_define(directive.parent, target, ValueNS, dummy_binding.clone());
 493             let _ = self.try_define(directive.parent, target, TypeNS, dummy_binding);
 494         }
 495     }
 496
 497     /// Attempts to resolve the given import. The return value indicates
 498     /// failure if we're certain the name does not exist, indeterminate if we
 499     /// don't know whether the name exists at the moment due to other
 500     /// currently-unresolved imports, or success if we know the name exists.
 501     /// If successful, the resolved bindings are written into the module.
 502     fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
 503         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 504                names_to_string(&directive.module_path),
 505                module_to_string(self.current_module));
 506
 507         self.current_module = directive.parent;
 508
 509         let module = if let Some(module) = directive.imported_module.get() {
 510             module
 511         } else {
 512             let vis = directive.vis.get();
 513             // For better failure detection, pretend that the import will not define any names
 514             // while resolving its module path.
 515             directive.vis.set(ty::Visibility::PrivateExternal);
 516             let result =
 517                 self.resolve_module_path(&directive.module_path, DontUseLexicalScope, None);
 518             directive.vis.set(vis);
 519
 520             match result {
 521                 Success(module) => module,
 522                 Indeterminate => return Indeterminate,
 523                 Failed(err) => return Failed(err),
 524             }
 525         };
 526
 527         directive.imported_module.set(Some(module));
 528         let (source, target, value_result, type_result) = match directive.subclass {
 529             SingleImport { source, target, ref value_result, ref type_result } =>
 530                 (source, target, value_result, type_result),
 531             GlobImport { .. } => {
 532                 self.resolve_glob_import(directive);
 533                 return Success(());
 534             }
 535         };
 536
 537         let mut indeterminate = false;
 538         for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
 539             if let Err(Undetermined) = result.get() {
 540                 result.set({
 541                     match self.resolve_name_in_module(module, source, ns, false, None) {
 542                         Success(binding) => Ok(binding),
 543                         Indeterminate => Err(Undetermined),
 544                         Failed(_) => Err(Determined),
 545                     }
 546                 });
 547             } else {
 548                 continue
 549             };
 550
 551             match result.get() {
 552                 Err(Undetermined) => indeterminate = true,
 553                 Err(Determined) => {
 554                     self.update_resolution(directive.parent, target, ns, |_, resolution| {
 555                         resolution.single_imports.directive_failed()
 556                     });
 557                 }
 558                 Ok(binding) if !binding.is_importable() => {
 559                     let msg = format!("`{}` is not directly importable", target);
 560                     struct_span_err!(self.session, directive.span, E0253, "{}", &msg)
 561                         .span_label(directive.span, &format!("cannot be imported directly"))
 562                         .emit();
 563                     // Do not import this illegal binding. Import a dummy binding and pretend
 564                     // everything is fine
 565                     self.import_dummy_binding(directive);
 566                     return Success(());
 567                 }
 568                 Ok(binding) => {
 569                     let imported_binding = self.import(binding, directive);
 570                     let conflict = self.try_define(directive.parent, target, ns, imported_binding);
 571                     if let Err(old_binding) = conflict {
 572                         let binding = &self.import(binding, directive);
 573                         self.report_conflict(directive.parent, target, ns, binding, old_binding);
 574                     }
 575                 }
 576             }
 577         }
 578
 579         if indeterminate { Indeterminate } else { Success(()) }
 580     }
 581
 582     fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
 583         self.current_module = directive.parent;
 584
 585         let ImportDirective { ref module_path, span, .. } = *directive;
 586         let module_result = self.resolve_module_path(&module_path, DontUseLexicalScope, Some(span));
 587         let module = match module_result {
 588             Success(module) => module,
 589             Indeterminate => return Indeterminate,
 590             Failed(err) => return Failed(err),
 591         };
 592
 593         let (name, value_result, type_result) = match directive.subclass {
 594             SingleImport { source, ref value_result, ref type_result, .. } =>
 595                 (source, value_result.get(), type_result.get()),
 596             GlobImport { .. } if module.def_id() == directive.parent.def_id() => {
 597                 // Importing a module into itself is not allowed.
 598                 let msg = "Cannot glob-import a module into itself.".into();
 599                 return Failed(Some((directive.span, msg)));
 600             }
 601             GlobImport { is_prelude, ref max_vis } => {
 602                 if !is_prelude &&
 603                    max_vis.get() != ty::Visibility::PrivateExternal && // Allow empty globs.
 604                    !max_vis.get().is_at_least(directive.vis.get(), self) {
 605                     let msg = "A non-empty glob must import something with the glob's visibility";
 606                     self.session.span_err(directive.span, msg);
 607                 }
 608                 return Success(());
 609             }
 610         };
 611
 612         for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
 613             if let Ok(binding) = result {
 614                 if self.record_use(name, ns, binding, directive.span) {
 615                     self.resolution(module, name, ns).borrow_mut().binding =
 616                         Some(self.dummy_binding);
 617                 }
 618             }
 619         }
 620
 621         if value_result.is_err() && type_result.is_err() {
 622             let (value_result, type_result);
 623             value_result = self.resolve_name_in_module(module, name, ValueNS, false, Some(span));
 624             type_result = self.resolve_name_in_module(module, name, TypeNS, false, Some(span));
 625
 626             return if let (Failed(_), Failed(_)) = (value_result, type_result) {
 627                 let resolutions = module.resolutions.borrow();
 628                 let names = resolutions.iter().filter_map(|(&(ref n, _), resolution)| {
 629                     if *n == name { return None; } // Never suggest the same name
 630                     match *resolution.borrow() {
 631                         NameResolution { binding: Some(_), .. } => Some(n),
 632                         NameResolution { single_imports: SingleImports::None, .. } => None,
 633                         _ => Some(n),
 634                     }
 635                 });
 636                 let lev_suggestion = match find_best_match_for_name(names, &name.as_str(), None) {
 637                     Some(name) => format!(". Did you mean to use `{}`?", name),
 638                     None => "".to_owned(),
 639                 };
 640                 let module_str = module_to_string(module);
 641                 let msg = if &module_str == "???" {
 642                     format!("no `{}` in the root{}", name, lev_suggestion)
 643                 } else {
 644                     format!("no `{}` in `{}`{}", name, module_str, lev_suggestion)
 645                 };
 646                 Failed(Some((directive.span, msg)))
 647             } else {
 648                 // `resolve_name_in_module` reported a privacy error.
 649                 self.import_dummy_binding(directive);
 650                 Success(())
 651             }
 652         }
 653
 654         let session = self.session;
 655         let reexport_error = || {
 656             let msg = format!("`{}` is private, and cannot be reexported", name);
 657             let note_msg =
 658                 format!("consider marking `{}` as `pub` in the imported module", name);
 659             struct_span_err!(session, directive.span, E0364, "{}", &msg)
 660                 .span_note(directive.span, &note_msg)
 661                 .emit();
 662         };
 663
 664         let extern_crate_lint = || {
 665             let msg = format!("extern crate `{}` is private, and cannot be reexported \
 666                                (error E0364), consider declaring with `pub`",
 667                                name);
 668             session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
 669         };
 670
 671         match (value_result, type_result) {
 672             // With `#![feature(item_like_imports)]`, all namespaces
 673             // must be re-exported with extra visibility for an error to occur.
 674             (Ok(value_binding), Ok(type_binding)) if self.new_import_semantics => {
 675                 let vis = directive.vis.get();
 676                 if !value_binding.pseudo_vis().is_at_least(vis, self) &&
 677                    !type_binding.pseudo_vis().is_at_least(vis, self) {
 678                     reexport_error();
 679                 } else if type_binding.is_extern_crate() &&
 680                           !type_binding.vis.is_at_least(vis, self) {
 681                     extern_crate_lint();
 682                 }
 683             }
 684
 685             (Ok(binding), _) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
 686                 reexport_error();
 687             }
 688
 689             (_, Ok(binding)) if !binding.pseudo_vis().is_at_least(directive.vis.get(), self) => {
 690                 if binding.is_extern_crate() {
 691                     extern_crate_lint();
 692                 } else {
 693                     struct_span_err!(self.session, directive.span, E0365,
 694                                      "`{}` is private, and cannot be reexported", name)
 695                         .span_label(directive.span, &format!("reexport of private `{}`", name))
 696                         .note(&format!("consider declaring type or module `{}` with `pub`", name))
 697                         .emit();
 698                 }
 699             }
 700
 701             _ => {}
 702         }
 703
 704         // Record what this import resolves to for later uses in documentation,
 705         // this may resolve to either a value or a type, but for documentation
 706         // purposes it's good enough to just favor one over the other.
 707         let def = match type_result.ok().map(NameBinding::def) {
 708             Some(def) => def,
 709             None => value_result.ok().map(NameBinding::def).unwrap(),
 710         };
 711         let path_resolution = PathResolution::new(def);
 712         self.def_map.insert(directive.id, path_resolution);
 713
 714         debug!("(resolving single import) successfully resolved import");
 715         return Success(());
 716     }
 717
 718     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
 719         let module = directive.imported_module.get().unwrap();
 720         self.populate_module_if_necessary(module);
 721
 722         if let Some(Def::Trait(_)) = module.def {
 723             self.session.span_err(directive.span, "items in traits are not importable.");
 724             return;
 725         } else if module.def_id() == directive.parent.def_id()  {
 726             return;
 727         } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
 728             self.prelude = Some(module);
 729             return;
 730         }
 731
 732         // Add to module's glob_importers
 733         module.glob_importers.borrow_mut().push(directive);
 734
 735         // Ensure that `resolutions` isn't borrowed during `try_define`,
 736         // since it might get updated via a glob cycle.
 737         let bindings = module.resolutions.borrow().iter().filter_map(|(name, resolution)| {
 738             resolution.borrow().binding().map(|binding| (*name, binding))
 739         }).collect::<Vec<_>>();
 740         for ((name, ns), binding) in bindings {
 741             if binding.pseudo_vis() == ty::Visibility::Public ||
 742                self.new_import_semantics && self.is_accessible(binding.vis) {
 743                 let imported_binding = self.import(binding, directive);
 744                 let _ = self.try_define(directive.parent, name, ns, imported_binding);
 745             }
 746         }
 747
 748         // Record the destination of this import
 749         if let Some(did) = module.def_id() {
 750             let resolution = PathResolution::new(Def::Mod(did));
 751             self.def_map.insert(directive.id, resolution);
 752         }
 753     }
 754
 755     // Miscellaneous post-processing, including recording reexports, reporting conflicts,
 756     // reporting the PRIVATE_IN_PUBLIC lint, and reporting unresolved imports.
 757     fn finalize_resolutions_in(&mut self, module: Module<'b>) {
 758         // Since import resolution is finished, globs will not define any more names.
 759         *module.globs.borrow_mut() = Vec::new();
 760
 761         let mut reexports = Vec::new();
 762         for (&(name, ns), resolution) in module.resolutions.borrow().iter() {
 763             let resolution = resolution.borrow();
 764             let binding = match resolution.binding {
 765                 Some(binding) => binding,
 766                 None => continue,
 767             };
 768
 769             // Report conflicts
 770             if !self.new_import_semantics {
 771                 for duplicate_glob in resolution.duplicate_globs.iter() {
 772                     // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
 773                     if !binding.is_import() {
 774                         if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
 775                             if binding.is_import() { continue }
 776                         }
 777                     }
 778
 779                     self.report_conflict(module, name, ns, duplicate_glob, binding);
 780                 }
 781             }
 782
 783             if binding.vis == ty::Visibility::Public &&
 784                (binding.is_import() || binding.is_extern_crate()) {
 785                 let def = binding.def();
 786                 if def != Def::Err {
 787                     reexports.push(Export { name: name, def_id: def.def_id() });
 788                 }
 789             }
 790
 791             if let NameBindingKind::Import { binding: orig_binding, directive, .. } = binding.kind {
 792                 if ns == TypeNS && orig_binding.is_variant() &&
 793                    !orig_binding.vis.is_at_least(binding.vis, self) {
 794                     let msg = format!("variant `{}` is private, and cannot be reexported \
 795                                        (error E0364), consider declaring its enum as `pub`",
 796                                       name);
 797                     self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, binding.span, msg);
 798                 }
 799             }
 800         }
 801
 802         if reexports.len() > 0 {
 803             if let Some(def_id) = module.def_id() {
 804                 let node_id = self.definitions.as_local_node_id(def_id).unwrap();
 805                 self.export_map.insert(node_id, reexports);
 806             }
 807         }
 808     }
 809 }
 810
 811 fn import_path_to_string(names: &[Name], subclass: &ImportDirectiveSubclass) -> String {
 812     if names.is_empty() {
 813         import_directive_subclass_to_string(subclass)
 814     } else {
 815         (format!("{}::{}",
 816                  names_to_string(names),
 817                  import_directive_subclass_to_string(subclass)))
 818             .to_string()
 819     }
 820 }
 821
 822 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
 823     match *subclass {
 824         SingleImport { source, .. } => source.to_string(),
 825         GlobImport { .. } => "*".to_string(),
 826     }
 827 }