src/librustc_resolve/resolve_imports.rs

   1 use self::ImportDirectiveSubclass::*;
   2
   3 use {AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
   4 use {CrateLint, Module, ModuleOrUniformRoot, PerNS, ScopeSet, Weak};
   5 use Namespace::{self, TypeNS, MacroNS};
   6 use {NameBinding, NameBindingKind, ToNameBinding, PathResult, PrivacyError};
   7 use {Resolver, Segment};
   8 use {names_to_string, module_to_string};
   9 use {resolve_error, ResolutionError};
  10 use macros::ParentScope;
  11
  12 use rustc_data_structures::ptr_key::PtrKey;
  13 use rustc::ty;
  14 use rustc::lint::builtin::BuiltinLintDiagnostics;
  15 use rustc::lint::builtin::{DUPLICATE_MACRO_EXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE};
  16 use rustc::hir::def_id::{CrateNum, DefId};
  17 use rustc::hir::def::*;
  18 use rustc::session::DiagnosticMessageId;
  19 use rustc::util::nodemap::FxHashSet;
  20
  21 use syntax::ast::{Ident, Name, NodeId, CRATE_NODE_ID};
  22 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  23 use syntax::ext::hygiene::Mark;
  24 use syntax::symbol::keywords;
  25 use syntax::util::lev_distance::find_best_match_for_name;
  26 use syntax_pos::{MultiSpan, Span};
  27
  28 use std::cell::{Cell, RefCell};
  29 use std::{mem, ptr};
  30
  31 /// Contains data for specific types of import directives.
  32 #[derive(Clone, Debug)]
  33 pub enum ImportDirectiveSubclass<'a> {
  34     SingleImport {
  35         /// `source` in `use prefix::source as target`.
  36         source: Ident,
  37         /// `target` in `use prefix::source as target`.
  38         target: Ident,
  39         /// Bindings to which `source` refers to.
  40         source_bindings: PerNS<Cell<Result<&'a NameBinding<'a>, Determinacy>>>,
  41         /// Bindings introduced by `target`.
  42         target_bindings: PerNS<Cell<Option<&'a NameBinding<'a>>>>,
  43         /// `true` for `...::{self [as target]}` imports, `false` otherwise.
  44         type_ns_only: bool,
  45     },
  46     GlobImport {
  47         is_prelude: bool,
  48         max_vis: Cell<ty::Visibility>, // The visibility of the greatest re-export.
  49         // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.
  50     },
  51     ExternCrate {
  52         source: Option<Name>,
  53         target: Ident,
  54     },
  55     MacroUse,
  56 }
  57
  58 /// One import directive.
  59 #[derive(Debug,Clone)]
  60 crate struct ImportDirective<'a> {
  61     /// The id of the `extern crate`, `UseTree` etc that imported this `ImportDirective`.
  62     ///
  63     /// In the case where the `ImportDirective` was expanded from a "nested" use tree,
  64     /// this id is the id of the leaf tree. For example:
  65     ///
  66     /// ```ignore (pacify the mercilous tidy)
  67     /// use foo::bar::{a, b}
  68     /// ```
  69     ///
  70     /// If this is the import directive for `foo::bar::a`, we would have the id of the `UseTree`
  71     /// for `a` in this field.
  72     pub id: NodeId,
  73
  74     /// The `id` of the "root" use-kind -- this is always the same as
  75     /// `id` except in the case of "nested" use trees, in which case
  76     /// it will be the `id` of the root use tree. e.g., in the example
  77     /// from `id`, this would be the id of the `use foo::bar`
  78     /// `UseTree` node.
  79     pub root_id: NodeId,
  80
  81     /// Span of this use tree.
  82     pub span: Span,
  83
  84     /// Span of the *root* use tree (see `root_id`).
  85     pub root_span: Span,
  86
  87     pub parent_scope: ParentScope<'a>,
  88     pub module_path: Vec<Segment>,
  89     /// The resolution of `module_path`.
  90     pub imported_module: Cell<Option<ModuleOrUniformRoot<'a>>>,
  91     pub subclass: ImportDirectiveSubclass<'a>,
  92     pub vis: Cell<ty::Visibility>,
  93     pub used: Cell<bool>,
  94 }
  95
  96 impl<'a> ImportDirective<'a> {
  97     pub fn is_glob(&self) -> bool {
  98         match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
  99     }
 100
 101     crate fn crate_lint(&self) -> CrateLint {
 102         CrateLint::UsePath { root_id: self.root_id, root_span: self.root_span }
 103     }
 104 }
 105
 106 #[derive(Clone, Default, Debug)]
 107 /// Records information about the resolution of a name in a namespace of a module.
 108 pub struct NameResolution<'a> {
 109     /// Single imports that may define the name in the namespace.
 110     /// Import directives are arena-allocated, so it's ok to use pointers as keys.
 111     single_imports: FxHashSet<PtrKey<'a, ImportDirective<'a>>>,
 112     /// The least shadowable known binding for this name, or None if there are no known bindings.
 113     pub binding: Option<&'a NameBinding<'a>>,
 114     shadowed_glob: Option<&'a NameBinding<'a>>,
 115 }
 116
 117 impl<'a> NameResolution<'a> {
 118     // Returns the binding for the name if it is known or None if it not known.
 119     fn binding(&self) -> Option<&'a NameBinding<'a>> {
 120         self.binding.and_then(|binding| {
 121             if !binding.is_glob_import() ||
 122                self.single_imports.is_empty() { Some(binding) } else { None }
 123         })
 124     }
 125 }
 126
 127 impl<'a> Resolver<'a> {
 128     fn resolution(&self, module: Module<'a>, ident: Ident, ns: Namespace)
 129                   -> &'a RefCell<NameResolution<'a>> {
 130         *module.resolutions.borrow_mut().entry((ident.modern(), ns))
 131                .or_insert_with(|| self.arenas.alloc_name_resolution())
 132     }
 133
 134     crate fn resolve_ident_in_module_unadjusted(
 135         &mut self,
 136         module: ModuleOrUniformRoot<'a>,
 137         ident: Ident,
 138         ns: Namespace,
 139         record_used: bool,
 140         path_span: Span,
 141     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 142         self.resolve_ident_in_module_unadjusted_ext(
 143             module, ident, ns, None, false, record_used, path_span
 144         ).map_err(|(determinacy, _)| determinacy)
 145     }
 146
 147     /// Attempts to resolve `ident` in namespaces `ns` of `module`.
 148     /// Invariant: if `record_used` is `Some`, expansion and import resolution must be complete.
 149     crate fn resolve_ident_in_module_unadjusted_ext(
 150         &mut self,
 151         module: ModuleOrUniformRoot<'a>,
 152         ident: Ident,
 153         ns: Namespace,
 154         parent_scope: Option<&ParentScope<'a>>,
 155         restricted_shadowing: bool,
 156         record_used: bool,
 157         path_span: Span,
 158     ) -> Result<&'a NameBinding<'a>, (Determinacy, Weak)> {
 159         let module = match module {
 160             ModuleOrUniformRoot::Module(module) => module,
 161             ModuleOrUniformRoot::CrateRootAndExternPrelude => {
 162                 assert!(!restricted_shadowing);
 163                 let parent_scope = self.dummy_parent_scope();
 164                 let binding = self.early_resolve_ident_in_lexical_scope(
 165                     ident, ScopeSet::AbsolutePath(ns), &parent_scope,
 166                     record_used, record_used, path_span,
 167                 );
 168                 return binding.map_err(|determinacy| (determinacy, Weak::No));
 169             }
 170             ModuleOrUniformRoot::ExternPrelude => {
 171                 assert!(!restricted_shadowing);
 172                 return if ns != TypeNS {
 173                     Err((Determined, Weak::No))
 174                 } else if let Some(binding) = self.extern_prelude_get(ident, !record_used) {
 175                     Ok(binding)
 176                 } else if !self.graph_root.unresolved_invocations.borrow().is_empty() {
 177                     // Macro-expanded `extern crate` items can add names to extern prelude.
 178                     Err((Undetermined, Weak::No))
 179                 } else {
 180                     Err((Determined, Weak::No))
 181                 }
 182             }
 183             ModuleOrUniformRoot::CurrentScope => {
 184                 assert!(!restricted_shadowing);
 185                 let parent_scope =
 186                     parent_scope.expect("no parent scope for a single-segment import");
 187
 188                 if ns == TypeNS {
 189                     if ident.name == keywords::Crate.name() ||
 190                         ident.name == keywords::DollarCrate.name() {
 191                         let module = self.resolve_crate_root(ident);
 192                         let binding = (module, ty::Visibility::Public,
 193                                         module.span, Mark::root())
 194                                         .to_name_binding(self.arenas);
 195                         return Ok(binding);
 196                     } else if ident.name == keywords::Super.name() ||
 197                                 ident.name == keywords::SelfLower.name() {
 198                         // FIXME: Implement these with renaming requirements so that e.g.
 199                         // `use super;` doesn't work, but `use super as name;` does.
 200                         // Fall through here to get an error from `early_resolve_...`.
 201                     }
 202                 }
 203
 204                 let binding = self.early_resolve_ident_in_lexical_scope(
 205                     ident, ScopeSet::Import(ns), parent_scope, record_used, record_used, path_span
 206                 );
 207                 return binding.map_err(|determinacy| (determinacy, Weak::No));
 208             }
 209         };
 210
 211         self.populate_module_if_necessary(module);
 212
 213         let resolution = self.resolution(module, ident, ns)
 214             .try_borrow_mut()
 215             .map_err(|_| (Determined, Weak::No))?; // This happens when there is a cycle of imports.
 216
 217         if let Some(binding) = resolution.binding {
 218             if !restricted_shadowing && binding.expansion != Mark::root() {
 219                 if let NameBindingKind::Def(_, true) = binding.kind {
 220                     self.macro_expanded_macro_export_errors.insert((path_span, binding.span));
 221                 }
 222             }
 223         }
 224
 225         let check_usable = |this: &mut Self, binding: &'a NameBinding<'a>| {
 226             if let Some(blacklisted_binding) = this.blacklisted_binding {
 227                 if ptr::eq(binding, blacklisted_binding) {
 228                     return Err((Determined, Weak::No));
 229                 }
 230             }
 231             // `extern crate` are always usable for backwards compatibility, see issue #37020,
 232             // remove this together with `PUB_USE_OF_PRIVATE_EXTERN_CRATE`.
 233             let usable = this.is_accessible(binding.vis) || binding.is_extern_crate();
 234             if usable { Ok(binding) } else { Err((Determined, Weak::No)) }
 235         };
 236
 237         if record_used {
 238             return resolution.binding.and_then(|binding| {
 239                 // If the primary binding is blacklisted, search further and return the shadowed
 240                 // glob binding if it exists. What we really want here is having two separate
 241                 // scopes in a module - one for non-globs and one for globs, but until that's done
 242                 // use this hack to avoid inconsistent resolution ICEs during import validation.
 243                 if let Some(blacklisted_binding) = self.blacklisted_binding {
 244                     if ptr::eq(binding, blacklisted_binding) {
 245                         return resolution.shadowed_glob;
 246                     }
 247                 }
 248                 Some(binding)
 249             }).ok_or((Determined, Weak::No)).and_then(|binding| {
 250                 if self.last_import_segment && check_usable(self, binding).is_err() {
 251                     Err((Determined, Weak::No))
 252                 } else {
 253                     self.record_use(ident, ns, binding, restricted_shadowing);
 254
 255                     if let Some(shadowed_glob) = resolution.shadowed_glob {
 256                         // Forbid expanded shadowing to avoid time travel.
 257                         if restricted_shadowing &&
 258                         binding.expansion != Mark::root() &&
 259                         binding.def() != shadowed_glob.def() {
 260                             self.ambiguity_errors.push(AmbiguityError {
 261                                 kind: AmbiguityKind::GlobVsExpanded,
 262                                 ident,
 263                                 b1: binding,
 264                                 b2: shadowed_glob,
 265                                 misc1: AmbiguityErrorMisc::None,
 266                                 misc2: AmbiguityErrorMisc::None,
 267                             });
 268                         }
 269                     }
 270
 271                     if !self.is_accessible(binding.vis) &&
 272                        // Remove this together with `PUB_USE_OF_PRIVATE_EXTERN_CRATE`
 273                        !(self.last_import_segment && binding.is_extern_crate()) {
 274                         self.privacy_errors.push(PrivacyError(path_span, ident, binding));
 275                     }
 276
 277                     Ok(binding)
 278                 }
 279             })
 280         }
 281
 282         // Items and single imports are not shadowable, if we have one, then it's determined.
 283         if let Some(binding) = resolution.binding {
 284             if !binding.is_glob_import() {
 285                 return check_usable(self, binding);
 286             }
 287         }
 288
 289         // --- From now on we either have a glob resolution or no resolution. ---
 290
 291         // Check if one of single imports can still define the name,
 292         // if it can then our result is not determined and can be invalidated.
 293         for single_import in &resolution.single_imports {
 294             if !self.is_accessible(single_import.vis.get()) {
 295                 continue;
 296             }
 297             let module = unwrap_or!(single_import.imported_module.get(),
 298                                     return Err((Undetermined, Weak::No)));
 299             let ident = match single_import.subclass {
 300                 SingleImport { source, .. } => source,
 301                 _ => unreachable!(),
 302             };
 303             match self.resolve_ident_in_module(module, ident, ns, Some(&single_import.parent_scope),
 304                                                false, path_span) {
 305                 Err(Determined) => continue,
 306                 Ok(binding) if !self.is_accessible_from(
 307                     binding.vis, single_import.parent_scope.module
 308                 ) => continue,
 309                 Ok(_) | Err(Undetermined) => return Err((Undetermined, Weak::No)),
 310             }
 311         }
 312
 313         // So we have a resolution that's from a glob import. This resolution is determined
 314         // if it cannot be shadowed by some new item/import expanded from a macro.
 315         // This happens either if there are no unexpanded macros, or expanded names cannot
 316         // shadow globs (that happens in macro namespace or with restricted shadowing).
 317         //
 318         // Additionally, any macro in any module can plant names in the root module if it creates
 319         // `macro_export` macros, so the root module effectively has unresolved invocations if any
 320         // module has unresolved invocations.
 321         // However, it causes resolution/expansion to stuck too often (#53144), so, to make
 322         // progress, we have to ignore those potential unresolved invocations from other modules
 323         // and prohibit access to macro-expanded `macro_export` macros instead (unless restricted
 324         // shadowing is enabled, see `macro_expanded_macro_export_errors`).
 325         let unexpanded_macros = !module.unresolved_invocations.borrow().is_empty();
 326         if let Some(binding) = resolution.binding {
 327             if !unexpanded_macros || ns == MacroNS || restricted_shadowing {
 328                 return check_usable(self, binding);
 329             } else {
 330                 return Err((Undetermined, Weak::No));
 331             }
 332         }
 333
 334         // --- From now on we have no resolution. ---
 335
 336         // Now we are in situation when new item/import can appear only from a glob or a macro
 337         // expansion. With restricted shadowing names from globs and macro expansions cannot
 338         // shadow names from outer scopes, so we can freely fallback from module search to search
 339         // in outer scopes. For `early_resolve_ident_in_lexical_scope` to continue search in outer
 340         // scopes we return `Undetermined` with `Weak::Yes`.
 341
 342         // Check if one of unexpanded macros can still define the name,
 343         // if it can then our "no resolution" result is not determined and can be invalidated.
 344         if unexpanded_macros {
 345             return Err((Undetermined, Weak::Yes));
 346         }
 347
 348         // Check if one of glob imports can still define the name,
 349         // if it can then our "no resolution" result is not determined and can be invalidated.
 350         for glob_import in module.globs.borrow().iter() {
 351             if !self.is_accessible(glob_import.vis.get()) {
 352                 continue
 353             }
 354             let module = match glob_import.imported_module.get() {
 355                 Some(ModuleOrUniformRoot::Module(module)) => module,
 356                 Some(_) => continue,
 357                 None => return Err((Undetermined, Weak::Yes)),
 358             };
 359             let (orig_current_module, mut ident) = (self.current_module, ident.modern());
 360             match ident.span.glob_adjust(module.expansion, glob_import.span.ctxt().modern()) {
 361                 Some(Some(def)) => self.current_module = self.macro_def_scope(def),
 362                 Some(None) => {}
 363                 None => continue,
 364             };
 365             let result = self.resolve_ident_in_module_unadjusted(
 366                 ModuleOrUniformRoot::Module(module),
 367                 ident,
 368                 ns,
 369                 false,
 370                 path_span,
 371             );
 372             self.current_module = orig_current_module;
 373
 374             match result {
 375                 Err(Determined) => continue,
 376                 Ok(binding) if !self.is_accessible_from(
 377                     binding.vis, glob_import.parent_scope.module
 378                 ) => continue,
 379                 Ok(_) | Err(Undetermined) => return Err((Undetermined, Weak::Yes)),
 380             }
 381         }
 382
 383         // No resolution and no one else can define the name - determinate error.
 384         Err((Determined, Weak::No))
 385     }
 386
 387     // Add an import directive to the current module.
 388     pub fn add_import_directive(&mut self,
 389                                 module_path: Vec<Segment>,
 390                                 subclass: ImportDirectiveSubclass<'a>,
 391                                 span: Span,
 392                                 id: NodeId,
 393                                 root_span: Span,
 394                                 root_id: NodeId,
 395                                 vis: ty::Visibility,
 396                                 parent_scope: ParentScope<'a>) {
 397         let current_module = parent_scope.module;
 398         let directive = self.arenas.alloc_import_directive(ImportDirective {
 399             parent_scope,
 400             module_path,
 401             imported_module: Cell::new(None),
 402             subclass,
 403             span,
 404             id,
 405             root_span,
 406             root_id,
 407             vis: Cell::new(vis),
 408             used: Cell::new(false),
 409         });
 410
 411         debug!("add_import_directive({:?})", directive);
 412
 413         self.indeterminate_imports.push(directive);
 414         match directive.subclass {
 415             SingleImport { target, type_ns_only, .. } => {
 416                 self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 417                     let mut resolution = this.resolution(current_module, target, ns).borrow_mut();
 418                     resolution.single_imports.insert(PtrKey(directive));
 419                 });
 420             }
 421             // We don't add prelude imports to the globs since they only affect lexical scopes,
 422             // which are not relevant to import resolution.
 423             GlobImport { is_prelude: true, .. } => {}
 424             GlobImport { .. } => current_module.globs.borrow_mut().push(directive),
 425             _ => unreachable!(),
 426         }
 427     }
 428
 429     // Given a binding and an import directive that resolves to it,
 430     // return the corresponding binding defined by the import directive.
 431     crate fn import(&self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
 432                     -> &'a NameBinding<'a> {
 433         let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
 434                      // cf. `PUB_USE_OF_PRIVATE_EXTERN_CRATE`
 435                      !directive.is_glob() && binding.is_extern_crate() {
 436             directive.vis.get()
 437         } else {
 438             binding.pseudo_vis()
 439         };
 440
 441         if let GlobImport { ref max_vis, .. } = directive.subclass {
 442             if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
 443                 max_vis.set(vis)
 444             }
 445         }
 446
 447         self.arenas.alloc_name_binding(NameBinding {
 448             kind: NameBindingKind::Import {
 449                 binding,
 450                 directive,
 451                 used: Cell::new(false),
 452             },
 453             ambiguity: None,
 454             span: directive.span,
 455             vis,
 456             expansion: directive.parent_scope.expansion,
 457         })
 458     }
 459
 460     crate fn check_reserved_macro_name(&self, ident: Ident, ns: Namespace) {
 461         // Reserve some names that are not quite covered by the general check
 462         // performed on `Resolver::builtin_attrs`.
 463         if ns == MacroNS &&
 464            (ident.name == "cfg" || ident.name == "cfg_attr" || ident.name == "derive") {
 465             self.session.span_err(ident.span,
 466                                   &format!("name `{}` is reserved in macro namespace", ident));
 467         }
 468     }
 469
 470     // Define the name or return the existing binding if there is a collision.
 471     pub fn try_define(&mut self,
 472                       module: Module<'a>,
 473                       ident: Ident,
 474                       ns: Namespace,
 475                       binding: &'a NameBinding<'a>)
 476                       -> Result<(), &'a NameBinding<'a>> {
 477         self.check_reserved_macro_name(ident, ns);
 478         self.set_binding_parent_module(binding, module);
 479         self.update_resolution(module, ident, ns, |this, resolution| {
 480             if let Some(old_binding) = resolution.binding {
 481                 if binding.def() == Def::Err {
 482                     // Do not override real bindings with `Def::Err`s from error recovery.
 483                     return Ok(());
 484                 }
 485                 match (old_binding.is_glob_import(), binding.is_glob_import()) {
 486                     (true, true) => {
 487                         if binding.def() != old_binding.def() {
 488                             resolution.binding = Some(this.ambiguity(AmbiguityKind::GlobVsGlob,
 489                                                                      old_binding, binding));
 490                         } else if !old_binding.vis.is_at_least(binding.vis, &*this) {
 491                             // We are glob-importing the same item but with greater visibility.
 492                             resolution.binding = Some(binding);
 493                         }
 494                     }
 495                     (old_glob @ true, false) | (old_glob @ false, true) => {
 496                         let (glob_binding, nonglob_binding) = if old_glob {
 497                             (old_binding, binding)
 498                         } else {
 499                             (binding, old_binding)
 500                         };
 501                         if glob_binding.def() != nonglob_binding.def() &&
 502                            ns == MacroNS && nonglob_binding.expansion != Mark::root() {
 503                             resolution.binding = Some(this.ambiguity(AmbiguityKind::GlobVsExpanded,
 504                                                                     nonglob_binding, glob_binding));
 505                         } else {
 506                             resolution.binding = Some(nonglob_binding);
 507                         }
 508                         resolution.shadowed_glob = Some(glob_binding);
 509                     }
 510                     (false, false) => {
 511                         if let (&NameBindingKind::Def(_, true), &NameBindingKind::Def(_, true)) =
 512                                (&old_binding.kind, &binding.kind) {
 513
 514                             this.session.buffer_lint_with_diagnostic(
 515                                 DUPLICATE_MACRO_EXPORTS,
 516                                 CRATE_NODE_ID,
 517                                 binding.span,
 518                                 &format!("a macro named `{}` has already been exported", ident),
 519                                 BuiltinLintDiagnostics::DuplicatedMacroExports(
 520                                     ident, old_binding.span, binding.span));
 521
 522                             resolution.binding = Some(binding);
 523                         } else {
 524                             return Err(old_binding);
 525                         }
 526                     }
 527                 }
 528             } else {
 529                 resolution.binding = Some(binding);
 530             }
 531
 532             Ok(())
 533         })
 534     }
 535
 536     fn ambiguity(&self, kind: AmbiguityKind,
 537                  primary_binding: &'a NameBinding<'a>, secondary_binding: &'a NameBinding<'a>)
 538                  -> &'a NameBinding<'a> {
 539         self.arenas.alloc_name_binding(NameBinding {
 540             ambiguity: Some((secondary_binding, kind)),
 541             ..primary_binding.clone()
 542         })
 543     }
 544
 545     // Use `f` to mutate the resolution of the name in the module.
 546     // If the resolution becomes a success, define it in the module's glob importers.
 547     fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Namespace, f: F)
 548                                -> T
 549         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
 550     {
 551         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
 552         // during which the resolution might end up getting re-defined via a glob cycle.
 553         let (binding, t) = {
 554             let resolution = &mut *self.resolution(module, ident, ns).borrow_mut();
 555             let old_binding = resolution.binding();
 556
 557             let t = f(self, resolution);
 558
 559             match resolution.binding() {
 560                 _ if old_binding.is_some() => return t,
 561                 None => return t,
 562                 Some(binding) => match old_binding {
 563                     Some(old_binding) if ptr::eq(old_binding, binding) => return t,
 564                     _ => (binding, t),
 565                 }
 566             }
 567         };
 568
 569         // Define `binding` in `module`s glob importers.
 570         for directive in module.glob_importers.borrow_mut().iter() {
 571             let mut ident = ident.modern();
 572             let scope = match ident.span.reverse_glob_adjust(module.expansion,
 573                                                              directive.span.ctxt().modern()) {
 574                 Some(Some(def)) => self.macro_def_scope(def),
 575                 Some(None) => directive.parent_scope.module,
 576                 None => continue,
 577             };
 578             if self.is_accessible_from(binding.vis, scope) {
 579                 let imported_binding = self.import(binding, directive);
 580                 let _ = self.try_define(directive.parent_scope.module, ident, ns, imported_binding);
 581             }
 582         }
 583
 584         t
 585     }
 586
 587     // Define a "dummy" resolution containing a Def::Err as a placeholder for a
 588     // failed resolution
 589     fn import_dummy_binding(&mut self, directive: &'a ImportDirective<'a>) {
 590         if let SingleImport { target, .. } = directive.subclass {
 591             let dummy_binding = self.dummy_binding;
 592             let dummy_binding = self.import(dummy_binding, directive);
 593             self.per_ns(|this, ns| {
 594                 let _ = this.try_define(directive.parent_scope.module, target, ns, dummy_binding);
 595             });
 596         }
 597     }
 598 }
 599
 600 pub struct ImportResolver<'a, 'b: 'a> {
 601     pub resolver: &'a mut Resolver<'b>,
 602 }
 603
 604 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
 605     type Target = Resolver<'b>;
 606     fn deref(&self) -> &Resolver<'b> {
 607         self.resolver
 608     }
 609 }
 610
 611 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
 612     fn deref_mut(&mut self) -> &mut Resolver<'b> {
 613         self.resolver
 614     }
 615 }
 616
 617 impl<'a, 'b: 'a> ty::DefIdTree for &'a ImportResolver<'a, 'b> {
 618     fn parent(self, id: DefId) -> Option<DefId> {
 619         self.resolver.parent(id)
 620     }
 621 }
 622
 623 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 624     // Import resolution
 625     //
 626     // This is a fixed-point algorithm. We resolve imports until our efforts
 627     // are stymied by an unresolved import; then we bail out of the current
 628     // module and continue. We terminate successfully once no more imports
 629     // remain or unsuccessfully when no forward progress in resolving imports
 630     // is made.
 631
 632     /// Resolves all imports for the crate. This method performs the fixed-
 633     /// point iteration.
 634     pub fn resolve_imports(&mut self) {
 635         let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
 636         while self.indeterminate_imports.len() < prev_num_indeterminates {
 637             prev_num_indeterminates = self.indeterminate_imports.len();
 638             for import in mem::replace(&mut self.indeterminate_imports, Vec::new()) {
 639                 match self.resolve_import(&import) {
 640                     true => self.determined_imports.push(import),
 641                     false => self.indeterminate_imports.push(import),
 642                 }
 643             }
 644         }
 645     }
 646
 647     pub fn finalize_imports(&mut self) {
 648         for module in self.arenas.local_modules().iter() {
 649             self.finalize_resolutions_in(module);
 650         }
 651
 652         let mut errors = false;
 653         let mut seen_spans = FxHashSet::default();
 654         let mut error_vec = Vec::new();
 655         let mut prev_root_id: NodeId = NodeId::from_u32(0);
 656         for i in 0 .. self.determined_imports.len() {
 657             let import = self.determined_imports[i];
 658             if let Some((span, err, note)) = self.finalize_import(import) {
 659                 errors = true;
 660
 661                 if let SingleImport { source, ref source_bindings, .. } = import.subclass {
 662                     if source.name == "self" {
 663                         // Silence `unresolved import` error if E0429 is already emitted
 664                         if let Err(Determined) = source_bindings.value_ns.get() {
 665                             continue;
 666                         }
 667                     }
 668                 }
 669
 670                 // If the error is a single failed import then create a "fake" import
 671                 // resolution for it so that later resolve stages won't complain.
 672                 self.import_dummy_binding(import);
 673                 if prev_root_id.as_u32() != 0 &&
 674                     prev_root_id.as_u32() != import.root_id.as_u32() &&
 675                     !error_vec.is_empty(){
 676                     // in case of new import line, throw diagnostic message
 677                     // for previous line.
 678                     let mut empty_vec = vec![];
 679                     mem::swap(&mut empty_vec, &mut error_vec);
 680                     self.throw_unresolved_import_error(empty_vec, None);
 681                 }
 682                 if !seen_spans.contains(&span) {
 683                     let path = import_path_to_string(
 684                         &import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),
 685                         &import.subclass,
 686                         span,
 687                     );
 688                     error_vec.push((span, path, err, note));
 689                     seen_spans.insert(span);
 690                     prev_root_id = import.root_id;
 691                 }
 692             }
 693         }
 694
 695         if !error_vec.is_empty() {
 696             self.throw_unresolved_import_error(error_vec.clone(), None);
 697         }
 698
 699         // Report unresolved imports only if no hard error was already reported
 700         // to avoid generating multiple errors on the same import.
 701         if !errors {
 702             for import in &self.indeterminate_imports {
 703                 self.throw_unresolved_import_error(error_vec, Some(MultiSpan::from(import.span)));
 704                 break;
 705             }
 706         }
 707     }
 708
 709     fn throw_unresolved_import_error(
 710         &self,
 711         error_vec: Vec<(Span, String, String, Option<String>)>,
 712         span: Option<MultiSpan>,
 713     ) {
 714         let max_span_label_msg_count = 10;  // upper limit on number of span_label message.
 715         let (span, msg, note) = if error_vec.is_empty() {
 716             (span.unwrap(), "unresolved import".to_string(), None)
 717         } else {
 718             let span = MultiSpan::from_spans(
 719                 error_vec.clone().into_iter()
 720                 .map(|elem: (Span, String, String, Option<String>)| elem.0)
 721                 .collect()
 722             );
 723
 724             let note: Option<String> = error_vec.clone().into_iter()
 725                 .filter_map(|elem: (Span, String, String, Option<String>)| elem.3)
 726                 .last();
 727
 728             let path_vec: Vec<String> = error_vec.clone().into_iter()
 729                 .map(|elem: (Span, String, String, Option<String>)| format!("`{}`", elem.1))
 730                 .collect();
 731             let path = path_vec.join(", ");
 732             let msg = format!(
 733                 "unresolved import{} {}",
 734                 if path_vec.len() > 1 { "s" } else { "" },
 735                 path
 736             );
 737
 738             (span, msg, note)
 739         };
 740
 741         let mut err = struct_span_err!(self.resolver.session, span, E0432, "{}", &msg);
 742         for span_error in error_vec.into_iter().take(max_span_label_msg_count) {
 743             err.span_label(span_error.0, span_error.2);
 744         }
 745         if let Some(note) = note {
 746             err.note(&note);
 747         }
 748         err.emit();
 749     }
 750
 751     /// Attempts to resolve the given import, returning true if its resolution is determined.
 752     /// If successful, the resolved bindings are written into the module.
 753     fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> bool {
 754         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 755                Segment::names_to_string(&directive.module_path),
 756                module_to_string(self.current_module).unwrap_or_else(|| "???".to_string()));
 757
 758         self.current_module = directive.parent_scope.module;
 759
 760         let module = if let Some(module) = directive.imported_module.get() {
 761             module
 762         } else {
 763             // For better failure detection, pretend that the import will
 764             // not define any names while resolving its module path.
 765             let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
 766             let path_res = self.resolve_path(
 767                 &directive.module_path,
 768                 None,
 769                 &directive.parent_scope,
 770                 false,
 771                 directive.span,
 772                 directive.crate_lint(),
 773             );
 774             directive.vis.set(orig_vis);
 775
 776             match path_res {
 777                 PathResult::Module(module) => module,
 778                 PathResult::Indeterminate => return false,
 779                 PathResult::NonModule(..) | PathResult::Failed(..) => return true,
 780             }
 781         };
 782
 783         directive.imported_module.set(Some(module));
 784         let (source, target, source_bindings, target_bindings, type_ns_only) =
 785                 match directive.subclass {
 786             SingleImport { source, target, ref source_bindings,
 787                            ref target_bindings, type_ns_only } =>
 788                 (source, target, source_bindings, target_bindings, type_ns_only),
 789             GlobImport { .. } => {
 790                 self.resolve_glob_import(directive);
 791                 return true;
 792             }
 793             _ => unreachable!(),
 794         };
 795
 796         let mut indeterminate = false;
 797         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 798             if let Err(Undetermined) = source_bindings[ns].get() {
 799                 // For better failure detection, pretend that the import will
 800                 // not define any names while resolving its module path.
 801                 let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
 802                 let binding = this.resolve_ident_in_module(
 803                     module, source, ns, Some(&directive.parent_scope), false, directive.span
 804                 );
 805                 directive.vis.set(orig_vis);
 806
 807                 source_bindings[ns].set(binding);
 808             } else {
 809                 return
 810             };
 811
 812             let parent = directive.parent_scope.module;
 813             match source_bindings[ns].get() {
 814                 Err(Undetermined) => indeterminate = true,
 815                 Err(Determined) => {
 816                     this.update_resolution(parent, target, ns, |_, resolution| {
 817                         resolution.single_imports.remove(&PtrKey(directive));
 818                     });
 819                 }
 820                 Ok(binding) if !binding.is_importable() => {
 821                     let msg = format!("`{}` is not directly importable", target);
 822                     struct_span_err!(this.session, directive.span, E0253, "{}", &msg)
 823                         .span_label(directive.span, "cannot be imported directly")
 824                         .emit();
 825                     // Do not import this illegal binding. Import a dummy binding and pretend
 826                     // everything is fine
 827                     this.import_dummy_binding(directive);
 828                 }
 829                 Ok(binding) => {
 830                     let imported_binding = this.import(binding, directive);
 831                     target_bindings[ns].set(Some(imported_binding));
 832                     let conflict = this.try_define(parent, target, ns, imported_binding);
 833                     if let Err(old_binding) = conflict {
 834                         this.report_conflict(parent, target, ns, imported_binding, old_binding);
 835                     }
 836                 }
 837             }
 838         });
 839
 840         !indeterminate
 841     }
 842
 843     // If appropriate, returns an error to report.
 844     fn finalize_import(
 845         &mut self,
 846         directive: &'b ImportDirective<'b>
 847     ) -> Option<(Span, String, Option<String>)> {
 848         self.current_module = directive.parent_scope.module;
 849
 850         let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
 851         let prev_ambiguity_errors_len = self.ambiguity_errors.len();
 852         let path_res = self.resolve_path(&directive.module_path, None, &directive.parent_scope,
 853                                          true, directive.span, directive.crate_lint());
 854         let no_ambiguity = self.ambiguity_errors.len() == prev_ambiguity_errors_len;
 855         directive.vis.set(orig_vis);
 856         let module = match path_res {
 857             PathResult::Module(module) => {
 858                 // Consistency checks, analogous to `finalize_current_module_macro_resolutions`.
 859                 if let Some(initial_module) = directive.imported_module.get() {
 860                     if !ModuleOrUniformRoot::same_def(module, initial_module) && no_ambiguity {
 861                         span_bug!(directive.span, "inconsistent resolution for an import");
 862                     }
 863                 } else {
 864                     if self.privacy_errors.is_empty() {
 865                         let msg = "cannot determine resolution for the import";
 866                         let msg_note = "import resolution is stuck, try simplifying other imports";
 867                         self.session.struct_span_err(directive.span, msg).note(msg_note).emit();
 868                     }
 869                 }
 870
 871                 module
 872             }
 873             PathResult::Failed(span, msg, false) => {
 874                 if no_ambiguity {
 875                     assert!(directive.imported_module.get().is_none());
 876                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 877                 }
 878                 return None;
 879             }
 880             PathResult::Failed(span, msg, true) => {
 881                 if no_ambiguity {
 882                     assert!(directive.imported_module.get().is_none());
 883                     return Some(match self.make_path_suggestion(span, directive.module_path.clone(),
 884                                                                 &directive.parent_scope) {
 885                         Some((suggestion, note)) => (
 886                             span,
 887                             format!("did you mean `{}`?", Segment::names_to_string(&suggestion)),
 888                             note,
 889                         ),
 890                         None => (span, msg, None),
 891                     });
 892                 }
 893                 return None;
 894             }
 895             PathResult::NonModule(path_res) if path_res.base_def() == Def::Err => {
 896                 if no_ambiguity {
 897                     assert!(directive.imported_module.get().is_none());
 898                 }
 899                 // The error was already reported earlier.
 900                 return None;
 901             }
 902             PathResult::Indeterminate | PathResult::NonModule(..) => unreachable!(),
 903         };
 904
 905         let (ident, target, source_bindings, target_bindings, type_ns_only) =
 906                 match directive.subclass {
 907             SingleImport { source, target, ref source_bindings,
 908                            ref target_bindings, type_ns_only } =>
 909                 (source, target, source_bindings, target_bindings, type_ns_only),
 910             GlobImport { is_prelude, ref max_vis } => {
 911                 if directive.module_path.len() <= 1 {
 912                     // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
 913                     // 2 segments, so the `resolve_path` above won't trigger it.
 914                     let mut full_path = directive.module_path.clone();
 915                     full_path.push(Segment::from_ident(keywords::Invalid.ident()));
 916                     self.lint_if_path_starts_with_module(
 917                         directive.crate_lint(),
 918                         &full_path,
 919                         directive.span,
 920                         None,
 921                     );
 922                 }
 923
 924                 if let ModuleOrUniformRoot::Module(module) = module {
 925                     if module.def_id() == directive.parent_scope.module.def_id() {
 926                         // Importing a module into itself is not allowed.
 927                         return Some((
 928                             directive.span,
 929                             "Cannot glob-import a module into itself.".to_string(),
 930                             None,
 931                         ));
 932                     }
 933                 }
 934                 if !is_prelude &&
 935                    max_vis.get() != ty::Visibility::Invisible && // Allow empty globs.
 936                    !max_vis.get().is_at_least(directive.vis.get(), &*self) {
 937                     let msg = "A non-empty glob must import something with the glob's visibility";
 938                     self.session.span_err(directive.span, msg);
 939                 }
 940                 return None;
 941             }
 942             _ => unreachable!(),
 943         };
 944
 945         let mut all_ns_err = true;
 946         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 947             let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
 948             let orig_blacklisted_binding =
 949                 mem::replace(&mut this.blacklisted_binding, target_bindings[ns].get());
 950             let orig_last_import_segment = mem::replace(&mut this.last_import_segment, true);
 951             let binding = this.resolve_ident_in_module(
 952                 module, ident, ns, Some(&directive.parent_scope), true, directive.span
 953             );
 954             this.last_import_segment = orig_last_import_segment;
 955             this.blacklisted_binding = orig_blacklisted_binding;
 956             directive.vis.set(orig_vis);
 957
 958             match binding {
 959                 Ok(binding) => {
 960                     // Consistency checks, analogous to `finalize_current_module_macro_resolutions`.
 961                     let initial_def = source_bindings[ns].get().map(|initial_binding| {
 962                         all_ns_err = false;
 963                         if let Some(target_binding) = target_bindings[ns].get() {
 964                             if target.name == "_" &&
 965                                initial_binding.is_extern_crate() && !initial_binding.is_import() {
 966                                 this.record_use(ident, ns, target_binding,
 967                                                 directive.module_path.is_empty());
 968                             }
 969                         }
 970                         initial_binding.def()
 971                     });
 972                     let def = binding.def();
 973                     if let Ok(initial_def) = initial_def {
 974                         if def != initial_def && this.ambiguity_errors.is_empty() {
 975                             span_bug!(directive.span, "inconsistent resolution for an import");
 976                         }
 977                     } else {
 978                         if def != Def::Err &&
 979                            this.ambiguity_errors.is_empty() && this.privacy_errors.is_empty() {
 980                             let msg = "cannot determine resolution for the import";
 981                             let msg_note =
 982                                 "import resolution is stuck, try simplifying other imports";
 983                             this.session.struct_span_err(directive.span, msg).note(msg_note).emit();
 984                         }
 985                     }
 986                 }
 987                 Err(..) => {
 988                     // FIXME: This assert may fire if public glob is later shadowed by a private
 989                     // single import (see test `issue-55884-2.rs`). In theory single imports should
 990                     // always block globs, even if they are not yet resolved, so that this kind of
 991                     // self-inconsistent resolution never happens.
 992                     // Reenable the assert when the issue is fixed.
 993                     // assert!(result[ns].get().is_err());
 994                 }
 995             }
 996         });
 997
 998         if all_ns_err {
 999             let mut all_ns_failed = true;
1000             self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
1001                 let binding = this.resolve_ident_in_module(
1002                     module, ident, ns, Some(&directive.parent_scope), true, directive.span
1003                 );
1004                 if binding.is_ok() {
1005                     all_ns_failed = false;
1006                 }
1007             });
1008
1009             return if all_ns_failed {
1010                 let resolutions = match module {
1011                     ModuleOrUniformRoot::Module(module) => Some(module.resolutions.borrow()),
1012                     _ => None,
1013                 };
1014                 let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter());
1015                 let names = resolutions.filter_map(|(&(ref i, _), resolution)| {
1016                     if *i == ident { return None; } // Never suggest the same name
1017                     match *resolution.borrow() {
1018                         NameResolution { binding: Some(name_binding), .. } => {
1019                             match name_binding.kind {
1020                                 NameBindingKind::Import { binding, .. } => {
1021                                     match binding.kind {
1022                                         // Never suggest the name that has binding error
1023                                         // i.e., the name that cannot be previously resolved
1024                                         NameBindingKind::Def(Def::Err, _) => return None,
1025                                         _ => Some(&i.name),
1026                                     }
1027                                 },
1028                                 _ => Some(&i.name),
1029                             }
1030                         },
1031                         NameResolution { ref single_imports, .. }
1032                             if single_imports.is_empty() => None,
1033                         _ => Some(&i.name),
1034                     }
1035                 });
1036                 let lev_suggestion =
1037                     match find_best_match_for_name(names, &ident.as_str(), None) {
1038                         Some(name) => format!(". Did you mean to use `{}`?", name),
1039                         None => String::new(),
1040                     };
1041                 let msg = match module {
1042                     ModuleOrUniformRoot::Module(module) => {
1043                         let module_str = module_to_string(module);
1044                         if let Some(module_str) = module_str {
1045                             format!("no `{}` in `{}`{}", ident, module_str, lev_suggestion)
1046                         } else {
1047                             format!("no `{}` in the root{}", ident, lev_suggestion)
1048                         }
1049                     }
1050                     _ => {
1051                         if !ident.is_path_segment_keyword() {
1052                             format!("no `{}` external crate{}", ident, lev_suggestion)
1053                         } else {
1054                             // HACK(eddyb) this shows up for `self` & `super`, which
1055                             // should work instead - for now keep the same error message.
1056                             format!("no `{}` in the root{}", ident, lev_suggestion)
1057                         }
1058                     }
1059                 };
1060                 Some((directive.span, msg, None))
1061             } else {
1062                 // `resolve_ident_in_module` reported a privacy error.
1063                 self.import_dummy_binding(directive);
1064                 None
1065             }
1066         }
1067
1068         let mut reexport_error = None;
1069         let mut any_successful_reexport = false;
1070         self.per_ns(|this, ns| {
1071             if let Ok(binding) = source_bindings[ns].get() {
1072                 let vis = directive.vis.get();
1073                 if !binding.pseudo_vis().is_at_least(vis, &*this) {
1074                     reexport_error = Some((ns, binding));
1075                 } else {
1076                     any_successful_reexport = true;
1077                 }
1078             }
1079         });
1080
1081         // All namespaces must be re-exported with extra visibility for an error to occur.
1082         if !any_successful_reexport {
1083             let (ns, binding) = reexport_error.unwrap();
1084             if ns == TypeNS && binding.is_extern_crate() {
1085                 let msg = format!("extern crate `{}` is private, and cannot be \
1086                                    re-exported (error E0365), consider declaring with \
1087                                    `pub`",
1088                                    ident);
1089                 self.session.buffer_lint(PUB_USE_OF_PRIVATE_EXTERN_CRATE,
1090                                          directive.id,
1091                                          directive.span,
1092                                          &msg);
1093             } else if ns == TypeNS {
1094                 struct_span_err!(self.session, directive.span, E0365,
1095                                  "`{}` is private, and cannot be re-exported", ident)
1096                     .span_label(directive.span, format!("re-export of private `{}`", ident))
1097                     .note(&format!("consider declaring type or module `{}` with `pub`", ident))
1098                     .emit();
1099             } else {
1100                 let msg = format!("`{}` is private, and cannot be re-exported", ident);
1101                 let note_msg =
1102                     format!("consider marking `{}` as `pub` in the imported module", ident);
1103                 struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
1104                     .span_note(directive.span, &note_msg)
1105                     .emit();
1106             }
1107         }
1108
1109         if directive.module_path.len() <= 1 {
1110             // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
1111             // 2 segments, so the `resolve_path` above won't trigger it.
1112             let mut full_path = directive.module_path.clone();
1113             full_path.push(Segment::from_ident(ident));
1114             self.per_ns(|this, ns| {
1115                 if let Ok(binding) = source_bindings[ns].get() {
1116                     this.lint_if_path_starts_with_module(
1117                         directive.crate_lint(),
1118                         &full_path,
1119                         directive.span,
1120                         Some(binding),
1121                     );
1122                 }
1123             });
1124         }
1125
1126         // Record what this import resolves to for later uses in documentation,
1127         // this may resolve to either a value or a type, but for documentation
1128         // purposes it's good enough to just favor one over the other.
1129         self.per_ns(|this, ns| if let Some(binding) = source_bindings[ns].get().ok() {
1130             let mut def = binding.def();
1131             if let Def::Macro(def_id, _) = def {
1132                 // `DefId`s from the "built-in macro crate" should not leak from resolve because
1133                 // later stages are not ready to deal with them and produce lots of ICEs. Replace
1134                 // them with `Def::Err` until some saner scheme is implemented for built-in macros.
1135                 if def_id.krate == CrateNum::BuiltinMacros {
1136                     this.session.span_err(directive.span, "cannot import a built-in macro");
1137                     def = Def::Err;
1138                 }
1139             }
1140             let import = this.import_map.entry(directive.id).or_default();
1141             import[ns] = Some(PathResolution::new(def));
1142         });
1143
1144         debug!("(resolving single import) successfully resolved import");
1145         None
1146     }
1147
1148     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
1149         let module = match directive.imported_module.get().unwrap() {
1150             ModuleOrUniformRoot::Module(module) => module,
1151             _ => {
1152                 self.session.span_err(directive.span, "cannot glob-import all possible crates");
1153                 return;
1154             }
1155         };
1156
1157         self.populate_module_if_necessary(module);
1158
1159         if let Some(Def::Trait(_)) = module.def() {
1160             self.session.span_err(directive.span, "items in traits are not importable.");
1161             return;
1162         } else if module.def_id() == directive.parent_scope.module.def_id()  {
1163             return;
1164         } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
1165             self.prelude = Some(module);
1166             return;
1167         }
1168
1169         // Add to module's glob_importers
1170         module.glob_importers.borrow_mut().push(directive);
1171
1172         // Ensure that `resolutions` isn't borrowed during `try_define`,
1173         // since it might get updated via a glob cycle.
1174         let bindings = module.resolutions.borrow().iter().filter_map(|(&ident, resolution)| {
1175             resolution.borrow().binding().map(|binding| (ident, binding))
1176         }).collect::<Vec<_>>();
1177         for ((mut ident, ns), binding) in bindings {
1178             let scope = match ident.span.reverse_glob_adjust(module.expansion,
1179                                                              directive.span.ctxt().modern()) {
1180                 Some(Some(def)) => self.macro_def_scope(def),
1181                 Some(None) => self.current_module,
1182                 None => continue,
1183             };
1184             if self.is_accessible_from(binding.pseudo_vis(), scope) {
1185                 let imported_binding = self.import(binding, directive);
1186                 let _ = self.try_define(directive.parent_scope.module, ident, ns, imported_binding);
1187             }
1188         }
1189
1190         // Record the destination of this import
1191         self.record_def(directive.id, PathResolution::new(module.def().unwrap()));
1192     }
1193
1194     // Miscellaneous post-processing, including recording re-exports,
1195     // reporting conflicts, and reporting unresolved imports.
1196     fn finalize_resolutions_in(&mut self, module: Module<'b>) {
1197         // Since import resolution is finished, globs will not define any more names.
1198         *module.globs.borrow_mut() = Vec::new();
1199
1200         let mut reexports = Vec::new();
1201
1202         for (&(ident, ns), resolution) in module.resolutions.borrow().iter() {
1203             let resolution = &mut *resolution.borrow_mut();
1204             let binding = match resolution.binding {
1205                 Some(binding) => binding,
1206                 None => continue,
1207             };
1208
1209             // Filter away "empty import canaries" and ambiguous imports.
1210             let is_good_import = binding.is_import() && !binding.is_ambiguity() &&
1211                                  binding.vis != ty::Visibility::Invisible;
1212             if is_good_import || binding.is_macro_def() {
1213                 let def = binding.def();
1214                 if def != Def::Err {
1215                     if let Some(def_id) = def.opt_def_id() {
1216                         if !def_id.is_local() && def_id.krate != CrateNum::BuiltinMacros {
1217                             self.cstore.export_macros_untracked(def_id.krate);
1218                         }
1219                     }
1220                     reexports.push(Export {
1221                         ident: ident.modern(),
1222                         def: def,
1223                         span: binding.span,
1224                         vis: binding.vis,
1225                     });
1226                 }
1227             }
1228
1229             if let NameBindingKind::Import { binding: orig_binding, directive, .. } = binding.kind {
1230                 if ns == TypeNS && orig_binding.is_variant() &&
1231                     !orig_binding.vis.is_at_least(binding.vis, &*self) {
1232                         let msg = match directive.subclass {
1233                             ImportDirectiveSubclass::SingleImport { .. } => {
1234                                 format!("variant `{}` is private and cannot be re-exported",
1235                                         ident)
1236                             },
1237                             ImportDirectiveSubclass::GlobImport { .. } => {
1238                                 let msg = "enum is private and its variants \
1239                                            cannot be re-exported".to_owned();
1240                                 let error_id = (DiagnosticMessageId::ErrorId(0), // no code?!
1241                                                 Some(binding.span),
1242                                                 msg.clone());
1243                                 let fresh = self.session.one_time_diagnostics
1244                                     .borrow_mut().insert(error_id);
1245                                 if !fresh {
1246                                     continue;
1247                                 }
1248                                 msg
1249                             },
1250                             ref s @ _ => bug!("unexpected import subclass {:?}", s)
1251                         };
1252                         let mut err = self.session.struct_span_err(binding.span, &msg);
1253
1254                         let imported_module = match directive.imported_module.get() {
1255                             Some(ModuleOrUniformRoot::Module(module)) => module,
1256                             _ => bug!("module should exist"),
1257                         };
1258                         let resolutions = imported_module.parent.expect("parent should exist")
1259                             .resolutions.borrow();
1260                         let enum_path_segment_index = directive.module_path.len() - 1;
1261                         let enum_ident = directive.module_path[enum_path_segment_index].ident;
1262
1263                         let enum_resolution = resolutions.get(&(enum_ident, TypeNS))
1264                             .expect("resolution should exist");
1265                         let enum_span = enum_resolution.borrow()
1266                             .binding.expect("binding should exist")
1267                             .span;
1268                         let enum_def_span = self.session.source_map().def_span(enum_span);
1269                         let enum_def_snippet = self.session.source_map()
1270                             .span_to_snippet(enum_def_span).expect("snippet should exist");
1271                         // potentially need to strip extant `crate`/`pub(path)` for suggestion
1272                         let after_vis_index = enum_def_snippet.find("enum")
1273                             .expect("`enum` keyword should exist in snippet");
1274                         let suggestion = format!("pub {}",
1275                                                  &enum_def_snippet[after_vis_index..]);
1276
1277                         self.session
1278                             .diag_span_suggestion_once(&mut err,
1279                                                        DiagnosticMessageId::ErrorId(0),
1280                                                        enum_def_span,
1281                                                        "consider making the enum public",
1282                                                        suggestion);
1283                         err.emit();
1284                 }
1285             }
1286         }
1287
1288         if reexports.len() > 0 {
1289             if let Some(def_id) = module.def_id() {
1290                 self.export_map.insert(def_id, reexports);
1291             }
1292         }
1293     }
1294 }
1295
1296 fn import_path_to_string(names: &[Ident],
1297                          subclass: &ImportDirectiveSubclass,
1298                          span: Span) -> String {
1299     let pos = names.iter()
1300         .position(|p| span == p.span && p.name != keywords::PathRoot.name());
1301     let global = !names.is_empty() && names[0].name == keywords::PathRoot.name();
1302     if let Some(pos) = pos {
1303         let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] };
1304         names_to_string(names)
1305     } else {
1306         let names = if global { &names[1..] } else { names };
1307         if names.is_empty() {
1308             import_directive_subclass_to_string(subclass)
1309         } else {
1310             format!("{}::{}",
1311                     names_to_string(names),
1312                     import_directive_subclass_to_string(subclass))
1313         }
1314     }
1315 }
1316
1317 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
1318     match *subclass {
1319         SingleImport { source, .. } => source.to_string(),
1320         GlobImport { .. } => "*".to_string(),
1321         ExternCrate { .. } => "<extern crate>".to_string(),
1322         MacroUse => "#[macro_use]".to_string(),
1323     }
1324 }