src/librustc_resolve/resolve_imports.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use self::ImportDirectiveSubclass::*;
  12
  13 use {AmbiguityError, CrateLint, Module, ModuleOrUniformRoot, PerNS};
  14 use Namespace::{self, TypeNS, MacroNS};
  15 use {NameBinding, NameBindingKind, ToNameBinding, PathResult, PrivacyError};
  16 use Resolver;
  17 use {names_to_string, module_to_string};
  18 use {resolve_error, ResolutionError};
  19
  20 use rustc_data_structures::ptr_key::PtrKey;
  21 use rustc::ty;
  22 use rustc::lint::builtin::BuiltinLintDiagnostics;
  23 use rustc::lint::builtin::{DUPLICATE_MACRO_EXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE};
  24 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
  25 use rustc::hir::def::*;
  26 use rustc::session::DiagnosticMessageId;
  27 use rustc::util::nodemap::FxHashSet;
  28
  29 use syntax::ast::{Ident, Name, NodeId, CRATE_NODE_ID};
  30 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  31 use syntax::ext::hygiene::Mark;
  32 use syntax::symbol::keywords;
  33 use syntax::util::lev_distance::find_best_match_for_name;
  34 use syntax_pos::{MultiSpan, Span};
  35
  36 use std::cell::{Cell, RefCell};
  37 use std::collections::BTreeMap;
  38 use std::fmt::Write;
  39 use std::{mem, ptr};
  40
  41 /// Contains data for specific types of import directives.
  42 #[derive(Clone, Debug)]
  43 pub enum ImportDirectiveSubclass<'a> {
  44     SingleImport {
  45         target: Ident,
  46         source: Ident,
  47         result: PerNS<Cell<Result<&'a NameBinding<'a>, Determinacy>>>,
  48         type_ns_only: bool,
  49     },
  50     GlobImport {
  51         is_prelude: bool,
  52         max_vis: Cell<ty::Visibility>, // The visibility of the greatest re-export.
  53         // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.
  54     },
  55     ExternCrate(Option<Name>),
  56     MacroUse,
  57 }
  58
  59 /// One import directive.
  60 #[derive(Debug,Clone)]
  61 pub struct ImportDirective<'a> {
  62     /// The id of the `extern crate`, `UseTree` etc that imported this `ImportDirective`.
  63     ///
  64     /// In the case where the `ImportDirective` was expanded from a "nested" use tree,
  65     /// this id is the id of the leaf tree. For example:
  66     ///
  67     /// ```ignore (pacify the mercilous tidy)
  68     /// use foo::bar::{a, b}
  69     /// ```
  70     ///
  71     /// If this is the import directive for `foo::bar::a`, we would have the id of the `UseTree`
  72     /// for `a` in this field.
  73     pub id: NodeId,
  74
  75     /// The `id` of the "root" use-kind -- this is always the same as
  76     /// `id` except in the case of "nested" use trees, in which case
  77     /// it will be the `id` of the root use tree. e.g., in the example
  78     /// from `id`, this would be the id of the `use foo::bar`
  79     /// `UseTree` node.
  80     pub root_id: NodeId,
  81
  82     /// Span of this use tree.
  83     pub span: Span,
  84
  85     /// Span of the *root* use tree (see `root_id`).
  86     pub root_span: Span,
  87
  88     pub parent: Module<'a>,
  89     pub module_path: Vec<Ident>,
  90     /// The resolution of `module_path`.
  91     pub imported_module: Cell<Option<ModuleOrUniformRoot<'a>>>,
  92     pub subclass: ImportDirectiveSubclass<'a>,
  93     pub vis: Cell<ty::Visibility>,
  94     pub expansion: Mark,
  95     pub used: Cell<bool>,
  96
  97     /// Whether this import is a "canary" for the `uniform_paths` feature,
  98     /// i.e. `use x::...;` results in an `use self::x as _;` canary.
  99     /// This flag affects diagnostics: an error is reported if and only if
 100     /// the import resolves successfully and an external crate with the same
 101     /// name (`x` above) also exists; any resolution failures are ignored.
 102     pub is_uniform_paths_canary: bool,
 103 }
 104
 105 impl<'a> ImportDirective<'a> {
 106     pub fn is_glob(&self) -> bool {
 107         match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
 108     }
 109
 110     crate fn crate_lint(&self) -> CrateLint {
 111         CrateLint::UsePath { root_id: self.root_id, root_span: self.root_span }
 112     }
 113 }
 114
 115 #[derive(Clone, Default, Debug)]
 116 /// Records information about the resolution of a name in a namespace of a module.
 117 pub struct NameResolution<'a> {
 118     /// Single imports that may define the name in the namespace.
 119     /// Import directives are arena-allocated, so it's ok to use pointers as keys.
 120     single_imports: FxHashSet<PtrKey<'a, ImportDirective<'a>>>,
 121     /// The least shadowable known binding for this name, or None if there are no known bindings.
 122     pub binding: Option<&'a NameBinding<'a>>,
 123     shadowed_glob: Option<&'a NameBinding<'a>>,
 124 }
 125
 126 impl<'a> NameResolution<'a> {
 127     // Returns the binding for the name if it is known or None if it not known.
 128     fn binding(&self) -> Option<&'a NameBinding<'a>> {
 129         self.binding.and_then(|binding| {
 130             if !binding.is_glob_import() ||
 131                self.single_imports.is_empty() { Some(binding) } else { None }
 132         })
 133     }
 134 }
 135
 136 impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
 137     fn resolution(&self, module: Module<'a>, ident: Ident, ns: Namespace)
 138                   -> &'a RefCell<NameResolution<'a>> {
 139         *module.resolutions.borrow_mut().entry((ident.modern(), ns))
 140                .or_insert_with(|| self.arenas.alloc_name_resolution())
 141     }
 142
 143     /// Attempts to resolve `ident` in namespaces `ns` of `module`.
 144     /// Invariant: if `record_used` is `Some`, expansion and import resolution must be complete.
 145     pub fn resolve_ident_in_module_unadjusted(&mut self,
 146                                               module: ModuleOrUniformRoot<'a>,
 147                                               ident: Ident,
 148                                               ns: Namespace,
 149                                               restricted_shadowing: bool,
 150                                               record_used: bool,
 151                                               path_span: Span)
 152                                               -> Result<&'a NameBinding<'a>, Determinacy> {
 153         let module = match module {
 154             ModuleOrUniformRoot::Module(module) => module,
 155             ModuleOrUniformRoot::UniformRoot(root) => {
 156                 // HACK(eddyb): `resolve_path` uses `keywords::Invalid` to indicate
 157                 // paths of length 0, and currently these are relative `use` paths.
 158                 let can_be_relative = !ident.is_path_segment_keyword() &&
 159                     root == keywords::Invalid.name();
 160                 if can_be_relative {
 161                     // Relative paths should only get here if the feature-gate is on.
 162                     assert!(self.session.rust_2018() &&
 163                             self.session.features_untracked().uniform_paths);
 164
 165                     // Try first to resolve relatively.
 166                     let mut ctxt = ident.span.ctxt().modern();
 167                     let self_module = self.resolve_self(&mut ctxt, self.current_module);
 168
 169                     let binding = self.resolve_ident_in_module_unadjusted(
 170                         ModuleOrUniformRoot::Module(self_module),
 171                         ident,
 172                         ns,
 173                         restricted_shadowing,
 174                         record_used,
 175                         path_span,
 176                     );
 177
 178                     // FIXME(eddyb) This may give false negatives, specifically
 179                     // if a crate with the same name is found in `extern_prelude`,
 180                     // preventing the check below this one from returning `binding`
 181                     // in all cases.
 182                     //
 183                     // That is, if there's no crate with the same name, `binding`
 184                     // is always returned, which is the result of doing the exact
 185                     // same lookup of `ident`, in the `self` module.
 186                     // But when a crate does exist, it will get chosen even when
 187                     // macro expansion could result in a success from the lookup
 188                     // in the `self` module, later on.
 189                     //
 190                     // NB. This is currently alleviated by the "ambiguity canaries"
 191                     // (see `is_uniform_paths_canary`) that get introduced for the
 192                     // maybe-relative imports handled here: if the false negative
 193                     // case were to arise, it would *also* cause an ambiguity error.
 194                     if binding.is_ok() {
 195                         return binding;
 196                     }
 197
 198                     // Fall back to resolving to an external crate.
 199                     if !(
 200                         ns == TypeNS &&
 201                         !ident.is_path_segment_keyword() &&
 202                         self.extern_prelude.contains(&ident.name)
 203                     ) {
 204                         // ... unless the crate name is not in the `extern_prelude`.
 205                         return binding;
 206                     }
 207                 }
 208
 209                 let crate_root = if
 210                     ns == TypeNS &&
 211                     root != keywords::Extern.name() &&
 212                     (
 213                         ident.name == keywords::Crate.name() ||
 214                         ident.name == keywords::DollarCrate.name()
 215                     )
 216                 {
 217                     self.resolve_crate_root(ident)
 218                 } else if
 219                     ns == TypeNS &&
 220                     !ident.is_path_segment_keyword() &&
 221                     self.extern_prelude.contains(&ident.name)
 222                 {
 223                     let crate_id =
 224                         self.crate_loader.process_path_extern(ident.name, ident.span);
 225                     self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX })
 226                 } else {
 227                     return Err(Determined);
 228                 };
 229                 self.populate_module_if_necessary(crate_root);
 230                 let binding = (crate_root, ty::Visibility::Public,
 231                                ident.span, Mark::root()).to_name_binding(self.arenas);
 232                 return Ok(binding);
 233             }
 234         };
 235
 236         self.populate_module_if_necessary(module);
 237
 238         let resolution = self.resolution(module, ident, ns)
 239             .try_borrow_mut()
 240             .map_err(|_| Determined)?; // This happens when there is a cycle of imports
 241
 242         if let Some(binding) = resolution.binding {
 243             if !restricted_shadowing && binding.expansion != Mark::root() {
 244                 if let NameBindingKind::Def(_, true) = binding.kind {
 245                     self.macro_expanded_macro_export_errors.insert((path_span, binding.span));
 246                 }
 247             }
 248         }
 249
 250         if record_used {
 251             if let Some(binding) = resolution.binding {
 252                 if let Some(shadowed_glob) = resolution.shadowed_glob {
 253                     // Forbid expanded shadowing to avoid time travel.
 254                     if restricted_shadowing &&
 255                        binding.expansion != Mark::root() &&
 256                        ns != MacroNS && // In MacroNS, `try_define` always forbids this shadowing
 257                        binding.def() != shadowed_glob.def() {
 258                         self.ambiguity_errors.push(AmbiguityError {
 259                             ident,
 260                             b1: binding,
 261                             b2: shadowed_glob,
 262                         });
 263                     }
 264                 }
 265                 if self.record_use(ident, ns, binding) {
 266                     return Ok(self.dummy_binding);
 267                 }
 268                 if !self.is_accessible(binding.vis) {
 269                     self.privacy_errors.push(PrivacyError(path_span, ident.name, binding));
 270                 }
 271             }
 272
 273             return resolution.binding.ok_or(Determined);
 274         }
 275
 276         let check_usable = |this: &mut Self, binding: &'a NameBinding<'a>| {
 277             // `extern crate` are always usable for backwards compatibility, see issue #37020.
 278             let usable = this.is_accessible(binding.vis) || binding.is_extern_crate();
 279             if usable { Ok(binding) } else { Err(Determined) }
 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(), return Err(Undetermined));
 298             let ident = match single_import.subclass {
 299                 SingleImport { source, .. } => source,
 300                 _ => unreachable!(),
 301             };
 302             match self.resolve_ident_in_module(module, ident, ns, false, path_span) {
 303                 Err(Determined) => continue,
 304                 Ok(binding)
 305                     if !self.is_accessible_from(binding.vis, single_import.parent) => continue,
 306                 Ok(_) | Err(Undetermined) => return Err(Undetermined),
 307             }
 308         }
 309
 310         // So we have a resolution that's from a glob import. This resolution is determined
 311         // if it cannot be shadowed by some new item/import expanded from a macro.
 312         // This happens either if there are no unexpanded macros, or expanded names cannot
 313         // shadow globs (that happens in macro namespace or with restricted shadowing).
 314         //
 315         // Additionally, any macro in any module can plant names in the root module if it creates
 316         // `macro_export` macros, so the root module effectively has unresolved invocations if any
 317         // module has unresolved invocations.
 318         // However, it causes resolution/expansion to stuck too often (#53144), so, to make
 319         // progress, we have to ignore those potential unresolved invocations from other modules
 320         // and prohibit access to macro-expanded `macro_export` macros instead (unless restricted
 321         // shadowing is enabled, see `macro_expanded_macro_export_errors`).
 322         let unexpanded_macros = !module.unresolved_invocations.borrow().is_empty();
 323         if let Some(binding) = resolution.binding {
 324             if !unexpanded_macros || ns == MacroNS || restricted_shadowing {
 325                 return check_usable(self, binding);
 326             } else {
 327                 return Err(Undetermined);
 328             }
 329         }
 330
 331         // --- From now on we have no resolution. ---
 332
 333         // Now we are in situation when new item/import can appear only from a glob or a macro
 334         // expansion. With restricted shadowing names from globs and macro expansions cannot
 335         // shadow names from outer scopes, so we can freely fallback from module search to search
 336         // in outer scopes. To continue search in outer scopes we have to lie a bit and return
 337         // `Determined` to `resolve_lexical_macro_path_segment` even if the correct answer
 338         // for in-module resolution could be `Undetermined`.
 339         if restricted_shadowing {
 340             return Err(Determined);
 341         }
 342
 343         // Check if one of unexpanded macros can still define the name,
 344         // if it can then our "no resolution" result is not determined and can be invalidated.
 345         if unexpanded_macros {
 346             return Err(Undetermined);
 347         }
 348
 349         // Check if one of glob imports can still define the name,
 350         // if it can then our "no resolution" result is not determined and can be invalidated.
 351         for glob_import in module.globs.borrow().iter() {
 352             if !self.is_accessible(glob_import.vis.get()) {
 353                 continue
 354             }
 355             let module = match glob_import.imported_module.get() {
 356                 Some(ModuleOrUniformRoot::Module(module)) => module,
 357                 Some(ModuleOrUniformRoot::UniformRoot(_)) => continue,
 358                 None => return Err(Undetermined),
 359             };
 360             let (orig_current_module, mut ident) = (self.current_module, ident.modern());
 361             match ident.span.glob_adjust(module.expansion, glob_import.span.ctxt().modern()) {
 362                 Some(Some(def)) => self.current_module = self.macro_def_scope(def),
 363                 Some(None) => {}
 364                 None => continue,
 365             };
 366             let result = self.resolve_ident_in_module_unadjusted(
 367                 ModuleOrUniformRoot::Module(module),
 368                 ident,
 369                 ns,
 370                 false,
 371                 false,
 372                 path_span,
 373             );
 374             self.current_module = orig_current_module;
 375
 376             match result {
 377                 Err(Determined) => continue,
 378                 Ok(binding)
 379                     if !self.is_accessible_from(binding.vis, glob_import.parent) => continue,
 380                 Ok(_) | Err(Undetermined) => return Err(Undetermined),
 381             }
 382         }
 383
 384         // No resolution and no one else can define the name - determinate error.
 385         Err(Determined)
 386     }
 387
 388     // Add an import directive to the current module.
 389     pub fn add_import_directive(&mut self,
 390                                 module_path: Vec<Ident>,
 391                                 subclass: ImportDirectiveSubclass<'a>,
 392                                 span: Span,
 393                                 id: NodeId,
 394                                 root_span: Span,
 395                                 root_id: NodeId,
 396                                 vis: ty::Visibility,
 397                                 expansion: Mark,
 398                                 is_uniform_paths_canary: bool) {
 399         let current_module = self.current_module;
 400         let directive = self.arenas.alloc_import_directive(ImportDirective {
 401             parent: current_module,
 402             module_path,
 403             imported_module: Cell::new(None),
 404             subclass,
 405             span,
 406             id,
 407             root_span,
 408             root_id,
 409             vis: Cell::new(vis),
 410             expansion,
 411             used: Cell::new(false),
 412             is_uniform_paths_canary,
 413         });
 414
 415         debug!("add_import_directive({:?})", directive);
 416
 417         self.indeterminate_imports.push(directive);
 418         match directive.subclass {
 419             SingleImport { target, type_ns_only, .. } => {
 420                 self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 421                     let mut resolution = this.resolution(current_module, target, ns).borrow_mut();
 422                     resolution.single_imports.insert(PtrKey(directive));
 423                 });
 424             }
 425             // We don't add prelude imports to the globs since they only affect lexical scopes,
 426             // which are not relevant to import resolution.
 427             GlobImport { is_prelude: true, .. } => {}
 428             GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
 429             _ => unreachable!(),
 430         }
 431     }
 432
 433     // Given a binding and an import directive that resolves to it,
 434     // return the corresponding binding defined by the import directive.
 435     pub fn import(&self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
 436                   -> &'a NameBinding<'a> {
 437         let vis = if binding.pseudo_vis().is_at_least(directive.vis.get(), self) ||
 438                      // c.f. `PUB_USE_OF_PRIVATE_EXTERN_CRATE`
 439                      !directive.is_glob() && binding.is_extern_crate() {
 440             directive.vis.get()
 441         } else {
 442             binding.pseudo_vis()
 443         };
 444
 445         if let GlobImport { ref max_vis, .. } = directive.subclass {
 446             if vis == directive.vis.get() || vis.is_at_least(max_vis.get(), self) {
 447                 max_vis.set(vis)
 448             }
 449         }
 450
 451         self.arenas.alloc_name_binding(NameBinding {
 452             kind: NameBindingKind::Import {
 453                 binding,
 454                 directive,
 455                 used: Cell::new(false),
 456             },
 457             span: directive.span,
 458             vis,
 459             expansion: directive.expansion,
 460         })
 461     }
 462
 463     crate fn check_reserved_macro_name(&self, ident: Ident, ns: Namespace) {
 464         // Reserve some names that are not quite covered by the general check
 465         // performed on `Resolver::builtin_attrs`.
 466         if ns == MacroNS &&
 467            (ident.name == "cfg" || ident.name == "cfg_attr" || ident.name == "derive") {
 468             self.session.span_err(ident.span,
 469                                   &format!("name `{}` is reserved in macro namespace", ident));
 470         }
 471     }
 472
 473     // Define the name or return the existing binding if there is a collision.
 474     pub fn try_define(&mut self,
 475                       module: Module<'a>,
 476                       ident: Ident,
 477                       ns: Namespace,
 478                       binding: &'a NameBinding<'a>)
 479                       -> Result<(), &'a NameBinding<'a>> {
 480         self.check_reserved_macro_name(ident, ns);
 481         self.update_resolution(module, ident, ns, |this, resolution| {
 482             if let Some(old_binding) = resolution.binding {
 483                 if binding.is_glob_import() {
 484                     if !old_binding.is_glob_import() &&
 485                        !(ns == MacroNS && old_binding.expansion != Mark::root()) {
 486                         resolution.shadowed_glob = Some(binding);
 487                     } else if binding.def() != old_binding.def() {
 488                         resolution.binding = Some(this.ambiguity(old_binding, binding));
 489                     } else if !old_binding.vis.is_at_least(binding.vis, &*this) {
 490                         // We are glob-importing the same item but with greater visibility.
 491                         resolution.binding = Some(binding);
 492                     }
 493                 } else if old_binding.is_glob_import() {
 494                     if ns == MacroNS && binding.expansion != Mark::root() &&
 495                        binding.def() != old_binding.def() {
 496                         resolution.binding = Some(this.ambiguity(binding, old_binding));
 497                     } else {
 498                         resolution.binding = Some(binding);
 499                         resolution.shadowed_glob = Some(old_binding);
 500                     }
 501                 } else if let (&NameBindingKind::Def(_, true), &NameBindingKind::Def(_, true)) =
 502                         (&old_binding.kind, &binding.kind) {
 503
 504                     this.session.buffer_lint_with_diagnostic(
 505                         DUPLICATE_MACRO_EXPORTS,
 506                         CRATE_NODE_ID,
 507                         binding.span,
 508                         &format!("a macro named `{}` has already been exported", ident),
 509                         BuiltinLintDiagnostics::DuplicatedMacroExports(
 510                             ident, old_binding.span, binding.span));
 511
 512                     resolution.binding = Some(binding);
 513                 } else {
 514                     return Err(old_binding);
 515                 }
 516             } else {
 517                 resolution.binding = Some(binding);
 518             }
 519
 520             Ok(())
 521         })
 522     }
 523
 524     pub fn ambiguity(&self, b1: &'a NameBinding<'a>, b2: &'a NameBinding<'a>)
 525                      -> &'a NameBinding<'a> {
 526         self.arenas.alloc_name_binding(NameBinding {
 527             kind: NameBindingKind::Ambiguity { b1, b2 },
 528             vis: if b1.vis.is_at_least(b2.vis, self) { b1.vis } else { b2.vis },
 529             span: b1.span,
 530             expansion: Mark::root(),
 531         })
 532     }
 533
 534     // Use `f` to mutate the resolution of the name in the module.
 535     // If the resolution becomes a success, define it in the module's glob importers.
 536     fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Namespace, f: F)
 537                                -> T
 538         where F: FnOnce(&mut Resolver<'a, 'crateloader>, &mut NameResolution<'a>) -> T
 539     {
 540         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
 541         // during which the resolution might end up getting re-defined via a glob cycle.
 542         let (binding, t) = {
 543             let resolution = &mut *self.resolution(module, ident, ns).borrow_mut();
 544             let old_binding = resolution.binding();
 545
 546             let t = f(self, resolution);
 547
 548             match resolution.binding() {
 549                 _ if old_binding.is_some() => return t,
 550                 None => return t,
 551                 Some(binding) => match old_binding {
 552                     Some(old_binding) if ptr::eq(old_binding, binding) => return t,
 553                     _ => (binding, t),
 554                 }
 555             }
 556         };
 557
 558         // Define `binding` in `module`s glob importers.
 559         for directive in module.glob_importers.borrow_mut().iter() {
 560             let mut ident = ident.modern();
 561             let scope = match ident.span.reverse_glob_adjust(module.expansion,
 562                                                              directive.span.ctxt().modern()) {
 563                 Some(Some(def)) => self.macro_def_scope(def),
 564                 Some(None) => directive.parent,
 565                 None => continue,
 566             };
 567             if self.is_accessible_from(binding.vis, scope) {
 568                 let imported_binding = self.import(binding, directive);
 569                 let _ = self.try_define(directive.parent, ident, ns, imported_binding);
 570             }
 571         }
 572
 573         t
 574     }
 575
 576     // Define a "dummy" resolution containing a Def::Err as a placeholder for a
 577     // failed resolution
 578     fn import_dummy_binding(&mut self, directive: &'a ImportDirective<'a>) {
 579         if let SingleImport { target, .. } = directive.subclass {
 580             let dummy_binding = self.dummy_binding;
 581             let dummy_binding = self.import(dummy_binding, directive);
 582             self.per_ns(|this, ns| {
 583                 let _ = this.try_define(directive.parent, target, ns, dummy_binding);
 584             });
 585         }
 586     }
 587 }
 588
 589 pub struct ImportResolver<'a, 'b: 'a, 'c: 'a + 'b> {
 590     pub resolver: &'a mut Resolver<'b, 'c>,
 591 }
 592
 593 impl<'a, 'b: 'a, 'c: 'a + 'b> ::std::ops::Deref for ImportResolver<'a, 'b, 'c> {
 594     type Target = Resolver<'b, 'c>;
 595     fn deref(&self) -> &Resolver<'b, 'c> {
 596         self.resolver
 597     }
 598 }
 599
 600 impl<'a, 'b: 'a, 'c: 'a + 'b> ::std::ops::DerefMut for ImportResolver<'a, 'b, 'c> {
 601     fn deref_mut(&mut self) -> &mut Resolver<'b, 'c> {
 602         self.resolver
 603     }
 604 }
 605
 606 impl<'a, 'b: 'a, 'c: 'a + 'b> ty::DefIdTree for &'a ImportResolver<'a, 'b, 'c> {
 607     fn parent(self, id: DefId) -> Option<DefId> {
 608         self.resolver.parent(id)
 609     }
 610 }
 611
 612 impl<'a, 'b:'a, 'c: 'b> ImportResolver<'a, 'b, 'c> {
 613     // Import resolution
 614     //
 615     // This is a fixed-point algorithm. We resolve imports until our efforts
 616     // are stymied by an unresolved import; then we bail out of the current
 617     // module and continue. We terminate successfully once no more imports
 618     // remain or unsuccessfully when no forward progress in resolving imports
 619     // is made.
 620
 621     /// Resolves all imports for the crate. This method performs the fixed-
 622     /// point iteration.
 623     pub fn resolve_imports(&mut self) {
 624         let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
 625         while self.indeterminate_imports.len() < prev_num_indeterminates {
 626             prev_num_indeterminates = self.indeterminate_imports.len();
 627             for import in mem::replace(&mut self.indeterminate_imports, Vec::new()) {
 628                 match self.resolve_import(&import) {
 629                     true => self.determined_imports.push(import),
 630                     false => self.indeterminate_imports.push(import),
 631                 }
 632             }
 633         }
 634     }
 635
 636     pub fn finalize_imports(&mut self) {
 637         for module in self.arenas.local_modules().iter() {
 638             self.finalize_resolutions_in(module);
 639         }
 640
 641         struct UniformPathsCanaryResults<'a> {
 642             name: Name,
 643             module_scope: Option<&'a NameBinding<'a>>,
 644             block_scopes: Vec<&'a NameBinding<'a>>,
 645         }
 646
 647         // Collect all tripped `uniform_paths` canaries separately.
 648         let mut uniform_paths_canaries: BTreeMap<
 649             (Span, NodeId, Namespace),
 650             UniformPathsCanaryResults,
 651         > = BTreeMap::new();
 652
 653         let mut errors = false;
 654         let mut seen_spans = FxHashSet();
 655         let mut error_vec = Vec::new();
 656         let mut prev_root_id: NodeId = NodeId::new(0);
 657         for i in 0 .. self.determined_imports.len() {
 658             let import = self.determined_imports[i];
 659             let error = self.finalize_import(import);
 660
 661             // For a `#![feature(uniform_paths)]` `use self::x as _` canary,
 662             // failure is ignored, while success may cause an ambiguity error.
 663             if import.is_uniform_paths_canary {
 664                 if error.is_some() {
 665                     continue;
 666                 }
 667
 668                 let (name, result) = match import.subclass {
 669                     SingleImport { source, ref result, .. } => (source.name, result),
 670                     _ => bug!(),
 671                 };
 672
 673                 let has_explicit_self =
 674                     import.module_path.len() > 0 &&
 675                     import.module_path[0].name == keywords::SelfValue.name();
 676
 677                 self.per_ns(|_, ns| {
 678                     if let Some(result) = result[ns].get().ok() {
 679                         let canary_results =
 680                             uniform_paths_canaries.entry((import.span, import.id, ns))
 681                                 .or_insert(UniformPathsCanaryResults {
 682                                     name,
 683                                     module_scope: None,
 684                                     block_scopes: vec![],
 685                                 });
 686
 687                         // All the canaries with the same `id` should have the same `name`.
 688                         assert_eq!(canary_results.name, name);
 689
 690                         if has_explicit_self {
 691                             // There should only be one `self::x` (module-scoped) canary.
 692                             assert!(canary_results.module_scope.is_none());
 693                             canary_results.module_scope = Some(result);
 694                         } else {
 695                             canary_results.block_scopes.push(result);
 696                         }
 697                     }
 698                 });
 699             } else if let Some((span, err)) = error {
 700                 errors = true;
 701
 702                 if let SingleImport { source, ref result, .. } = import.subclass {
 703                     if source.name == "self" {
 704                         // Silence `unresolved import` error if E0429 is already emitted
 705                         match result.value_ns.get() {
 706                             Err(Determined) => continue,
 707                             _ => {},
 708                         }
 709                     }
 710                 }
 711
 712                 // If the error is a single failed import then create a "fake" import
 713                 // resolution for it so that later resolve stages won't complain.
 714                 self.import_dummy_binding(import);
 715                 if prev_root_id.as_u32() != 0 &&
 716                     prev_root_id.as_u32() != import.root_id.as_u32() &&
 717                     !error_vec.is_empty(){
 718                     // in case of new import line, throw diagnostic message
 719                     // for previous line.
 720                     let mut empty_vec = vec![];
 721                     mem::swap(&mut empty_vec, &mut error_vec);
 722                     self.throw_unresolved_import_error(empty_vec, None);
 723                 }
 724                 if !seen_spans.contains(&span) {
 725                     let path = import_path_to_string(&import.module_path[..],
 726                                                      &import.subclass,
 727                                                      span);
 728                     error_vec.push((span, path, err));
 729                     seen_spans.insert(span);
 730                     prev_root_id = import.root_id;
 731                 }
 732             }
 733         }
 734
 735         let uniform_paths_feature = self.session.features_untracked().uniform_paths;
 736         for ((span, _, ns), results) in uniform_paths_canaries {
 737             let name = results.name;
 738             let external_crate = if ns == TypeNS && self.extern_prelude.contains(&name) {
 739                 let crate_id =
 740                     self.crate_loader.process_path_extern(name, span);
 741                 Some(Def::Mod(DefId { krate: crate_id, index: CRATE_DEF_INDEX }))
 742             } else {
 743                 None
 744             };
 745
 746             // Currently imports can't resolve in non-module scopes,
 747             // we only have canaries in them for future-proofing.
 748             if external_crate.is_none() && results.module_scope.is_none() {
 749                 continue;
 750             }
 751
 752             {
 753                 let mut all_results = external_crate.into_iter().chain(
 754                     results.module_scope.iter()
 755                         .chain(&results.block_scopes)
 756                         .map(|binding| binding.def())
 757                 );
 758                 let first = all_results.next().unwrap();
 759
 760                 // An ambiguity requires more than one *distinct* possible resolution.
 761                 let possible_resultions =
 762                     1 + all_results.filter(|&def| def != first).count();
 763                 if possible_resultions <= 1 {
 764                     continue;
 765                 }
 766             }
 767
 768             errors = true;
 769
 770             let msg = format!("`{}` import is ambiguous", name);
 771             let mut err = self.session.struct_span_err(span, &msg);
 772             let mut suggestion_choices = String::new();
 773             if external_crate.is_some() {
 774                 write!(suggestion_choices, "`::{}`", name);
 775                 err.span_label(span,
 776                     format!("can refer to external crate `::{}`", name));
 777             }
 778             if let Some(result) = results.module_scope {
 779                 if !suggestion_choices.is_empty() {
 780                     suggestion_choices.push_str(" or ");
 781                 }
 782                 write!(suggestion_choices, "`self::{}`", name);
 783                 if uniform_paths_feature {
 784                     err.span_label(result.span,
 785                         format!("can refer to `self::{}`", name));
 786                 } else {
 787                     err.span_label(result.span,
 788                         format!("may refer to `self::{}` in the future", name));
 789                 }
 790             }
 791             for result in results.block_scopes {
 792                 err.span_label(result.span,
 793                     format!("shadowed by block-scoped `{}`", name));
 794             }
 795             err.help(&format!("write {} explicitly instead", suggestion_choices));
 796             if uniform_paths_feature {
 797                 err.note("relative `use` paths enabled by `#![feature(uniform_paths)]`");
 798             } else {
 799                 err.note("in the future, `#![feature(uniform_paths)]` may become the default");
 800             }
 801             err.emit();
 802         }
 803
 804         if !error_vec.is_empty() {
 805             self.throw_unresolved_import_error(error_vec.clone(), None);
 806         }
 807
 808         // Report unresolved imports only if no hard error was already reported
 809         // to avoid generating multiple errors on the same import.
 810         if !errors {
 811             for import in &self.indeterminate_imports {
 812                 if import.is_uniform_paths_canary {
 813                     continue;
 814                 }
 815                 self.throw_unresolved_import_error(error_vec, Some(MultiSpan::from(import.span)));
 816                 break;
 817             }
 818         }
 819     }
 820
 821     fn throw_unresolved_import_error(&self, error_vec: Vec<(Span, String, String)>,
 822                                      span: Option<MultiSpan>) {
 823         let max_span_label_msg_count = 10;  // upper limit on number of span_label message.
 824         let (span,msg) = match error_vec.is_empty() {
 825             true => (span.unwrap(), "unresolved import".to_string()),
 826             false => {
 827                 let span = MultiSpan::from_spans(error_vec.clone().into_iter()
 828                                     .map(|elem: (Span, String, String)| { elem.0 }
 829                                     ).collect());
 830                 let path_vec: Vec<String> = error_vec.clone().into_iter()
 831                                 .map(|elem: (Span, String, String)| { format!("`{}`", elem.1) }
 832                                 ).collect();
 833                 let path = path_vec.join(", ");
 834                 let msg = format!("unresolved import{} {}",
 835                                 if path_vec.len() > 1 { "s" } else { "" },  path);
 836                 (span, msg)
 837             }
 838         };
 839         let mut err = struct_span_err!(self.resolver.session, span, E0432, "{}", &msg);
 840         for span_error in error_vec.into_iter().take(max_span_label_msg_count) {
 841             err.span_label(span_error.0, span_error.2);
 842         }
 843         err.emit();
 844     }
 845
 846     /// Attempts to resolve the given import, returning true if its resolution is determined.
 847     /// If successful, the resolved bindings are written into the module.
 848     fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> bool {
 849         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 850                names_to_string(&directive.module_path[..]),
 851                module_to_string(self.current_module).unwrap_or("???".to_string()));
 852
 853         self.current_module = directive.parent;
 854
 855         let module = if let Some(module) = directive.imported_module.get() {
 856             module
 857         } else {
 858             let vis = directive.vis.get();
 859             // For better failure detection, pretend that the import will not define any names
 860             // while resolving its module path.
 861             directive.vis.set(ty::Visibility::Invisible);
 862             let result = self.resolve_path(
 863                 Some(if directive.is_uniform_paths_canary {
 864                     ModuleOrUniformRoot::Module(directive.parent)
 865                 } else {
 866                     ModuleOrUniformRoot::UniformRoot(keywords::Invalid.name())
 867                 }),
 868                 &directive.module_path[..],
 869                 None,
 870                 false,
 871                 directive.span,
 872                 directive.crate_lint(),
 873             );
 874             directive.vis.set(vis);
 875
 876             match result {
 877                 PathResult::Module(module) => module,
 878                 PathResult::Indeterminate => return false,
 879                 _ => return true,
 880             }
 881         };
 882
 883         directive.imported_module.set(Some(module));
 884         let (source, target, result, type_ns_only) = match directive.subclass {
 885             SingleImport { source, target, ref result, type_ns_only } =>
 886                 (source, target, result, type_ns_only),
 887             GlobImport { .. } => {
 888                 self.resolve_glob_import(directive);
 889                 return true;
 890             }
 891             _ => unreachable!(),
 892         };
 893
 894         let mut indeterminate = false;
 895         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
 896             if let Err(Undetermined) = result[ns].get() {
 897                 result[ns].set(this.resolve_ident_in_module(module,
 898                                                             source,
 899                                                             ns,
 900                                                             false,
 901                                                             directive.span));
 902             } else {
 903                 return
 904             };
 905
 906             let parent = directive.parent;
 907             match result[ns].get() {
 908                 Err(Undetermined) => indeterminate = true,
 909                 Err(Determined) => {
 910                     this.update_resolution(parent, target, ns, |_, resolution| {
 911                         resolution.single_imports.remove(&PtrKey(directive));
 912                     });
 913                 }
 914                 Ok(binding) if !binding.is_importable() => {
 915                     let msg = format!("`{}` is not directly importable", target);
 916                     struct_span_err!(this.session, directive.span, E0253, "{}", &msg)
 917                         .span_label(directive.span, "cannot be imported directly")
 918                         .emit();
 919                     // Do not import this illegal binding. Import a dummy binding and pretend
 920                     // everything is fine
 921                     this.import_dummy_binding(directive);
 922                 }
 923                 Ok(binding) => {
 924                     let imported_binding = this.import(binding, directive);
 925                     let conflict = this.try_define(parent, target, ns, imported_binding);
 926                     if let Err(old_binding) = conflict {
 927                         this.report_conflict(parent, target, ns, imported_binding, old_binding);
 928                     }
 929                 }
 930             }
 931         });
 932
 933         !indeterminate
 934     }
 935
 936     // If appropriate, returns an error to report.
 937     fn finalize_import(&mut self, directive: &'b ImportDirective<'b>) -> Option<(Span, String)> {
 938         self.current_module = directive.parent;
 939         let ImportDirective { ref module_path, span, .. } = *directive;
 940
 941         let module_result = self.resolve_path(
 942             Some(if directive.is_uniform_paths_canary {
 943                 ModuleOrUniformRoot::Module(directive.parent)
 944             } else {
 945                 ModuleOrUniformRoot::UniformRoot(keywords::Invalid.name())
 946             }),
 947             &module_path,
 948             None,
 949             true,
 950             span,
 951             directive.crate_lint(),
 952         );
 953         let module = match module_result {
 954             PathResult::Module(module) => module,
 955             PathResult::Failed(span, msg, false) => {
 956                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 957                 return None;
 958             }
 959             PathResult::Failed(span, msg, true) => {
 960                 let (mut self_path, mut self_result) = (module_path.clone(), None);
 961                 let is_special = |ident: Ident| ident.is_path_segment_keyword() &&
 962                                                 ident.name != keywords::CrateRoot.name();
 963                 if !self_path.is_empty() && !is_special(self_path[0]) &&
 964                    !(self_path.len() > 1 && is_special(self_path[1])) {
 965                     self_path[0].name = keywords::SelfValue.name();
 966                     self_result = Some(self.resolve_path(None, &self_path, None, false,
 967                                                          span, CrateLint::No));
 968                 }
 969                 return if let Some(PathResult::Module(..)) = self_result {
 970                     Some((span, format!("Did you mean `{}`?", names_to_string(&self_path[..]))))
 971                 } else {
 972                     Some((span, msg))
 973                 };
 974             },
 975             _ => return None,
 976         };
 977
 978         let (ident, result, type_ns_only) = match directive.subclass {
 979             SingleImport { source, ref result, type_ns_only, .. } => (source, result, type_ns_only),
 980             GlobImport { is_prelude, ref max_vis } => {
 981                 if module_path.len() <= 1 {
 982                     // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
 983                     // 2 segments, so the `resolve_path` above won't trigger it.
 984                     let mut full_path = module_path.clone();
 985                     full_path.push(keywords::Invalid.ident());
 986                     self.lint_if_path_starts_with_module(
 987                         directive.crate_lint(),
 988                         &full_path,
 989                         directive.span,
 990                         None,
 991                     );
 992                 }
 993
 994                 if let ModuleOrUniformRoot::Module(module) = module {
 995                     if module.def_id() == directive.parent.def_id() {
 996                         // Importing a module into itself is not allowed.
 997                         return Some((directive.span,
 998                             "Cannot glob-import a module into itself.".to_string()));
 999                     }
1000                 }
1001                 if !is_prelude &&
1002                    max_vis.get() != ty::Visibility::Invisible && // Allow empty globs.
1003                    !max_vis.get().is_at_least(directive.vis.get(), &*self) {
1004                     let msg = "A non-empty glob must import something with the glob's visibility";
1005                     self.session.span_err(directive.span, msg);
1006                 }
1007                 return None;
1008             }
1009             _ => unreachable!(),
1010         };
1011
1012         // Do not record uses from canaries, to avoid interfering with other
1013         // diagnostics or suggestions that rely on some items not being used.
1014         let record_used = !directive.is_uniform_paths_canary;
1015
1016         let mut all_ns_err = true;
1017         self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
1018             if let Ok(binding) = result[ns].get() {
1019                 all_ns_err = false;
1020                 if record_used && this.record_use(ident, ns, binding) {
1021                     if let ModuleOrUniformRoot::Module(module) = module {
1022                         this.resolution(module, ident, ns).borrow_mut().binding =
1023                             Some(this.dummy_binding);
1024                     }
1025                 }
1026             }
1027         });
1028
1029         if all_ns_err {
1030             let mut all_ns_failed = true;
1031             self.per_ns(|this, ns| if !type_ns_only || ns == TypeNS {
1032                 match this.resolve_ident_in_module(module, ident, ns, record_used, span) {
1033                     Ok(_) => all_ns_failed = false,
1034                     _ => {}
1035                 }
1036             });
1037
1038             return if all_ns_failed {
1039                 let resolutions = match module {
1040                     ModuleOrUniformRoot::Module(module) =>
1041                         Some(module.resolutions.borrow()),
1042                     ModuleOrUniformRoot::UniformRoot(_) => None,
1043                 };
1044                 let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter());
1045                 let names = resolutions.filter_map(|(&(ref i, _), resolution)| {
1046                     if *i == ident { return None; } // Never suggest the same name
1047                     match *resolution.borrow() {
1048                         NameResolution { binding: Some(name_binding), .. } => {
1049                             match name_binding.kind {
1050                                 NameBindingKind::Import { binding, .. } => {
1051                                     match binding.kind {
1052                                         // Never suggest the name that has binding error
1053                                         // i.e. the name that cannot be previously resolved
1054                                         NameBindingKind::Def(Def::Err, _) => return None,
1055                                         _ => Some(&i.name),
1056                                     }
1057                                 },
1058                                 _ => Some(&i.name),
1059                             }
1060                         },
1061                         NameResolution { ref single_imports, .. }
1062                             if single_imports.is_empty() => None,
1063                         _ => Some(&i.name),
1064                     }
1065                 });
1066                 let lev_suggestion =
1067                     match find_best_match_for_name(names, &ident.as_str(), None) {
1068                         Some(name) => format!(". Did you mean to use `{}`?", name),
1069                         None => String::new(),
1070                     };
1071                 let msg = match module {
1072                     ModuleOrUniformRoot::Module(module) => {
1073                         let module_str = module_to_string(module);
1074                         if let Some(module_str) = module_str {
1075                             format!("no `{}` in `{}`{}", ident, module_str, lev_suggestion)
1076                         } else {
1077                             format!("no `{}` in the root{}", ident, lev_suggestion)
1078                         }
1079                     }
1080                     ModuleOrUniformRoot::UniformRoot(_) => {
1081                         if !ident.is_path_segment_keyword() {
1082                             format!("no `{}` external crate{}", ident, lev_suggestion)
1083                         } else {
1084                             // HACK(eddyb) this shows up for `self` & `super`, which
1085                             // should work instead - for now keep the same error message.
1086                             format!("no `{}` in the root{}", ident, lev_suggestion)
1087                         }
1088                     }
1089                 };
1090                 Some((span, msg))
1091             } else {
1092                 // `resolve_ident_in_module` reported a privacy error.
1093                 self.import_dummy_binding(directive);
1094                 None
1095             }
1096         }
1097
1098         let mut reexport_error = None;
1099         let mut any_successful_reexport = false;
1100         self.per_ns(|this, ns| {
1101             if let Ok(binding) = result[ns].get() {
1102                 let vis = directive.vis.get();
1103                 if !binding.pseudo_vis().is_at_least(vis, &*this) {
1104                     reexport_error = Some((ns, binding));
1105                 } else {
1106                     any_successful_reexport = true;
1107                 }
1108             }
1109         });
1110
1111         // All namespaces must be re-exported with extra visibility for an error to occur.
1112         if !any_successful_reexport {
1113             let (ns, binding) = reexport_error.unwrap();
1114             if ns == TypeNS && binding.is_extern_crate() {
1115                 let msg = format!("extern crate `{}` is private, and cannot be \
1116                                    re-exported (error E0365), consider declaring with \
1117                                    `pub`",
1118                                    ident);
1119                 self.session.buffer_lint(PUB_USE_OF_PRIVATE_EXTERN_CRATE,
1120                                          directive.id,
1121                                          directive.span,
1122                                          &msg);
1123             } else if ns == TypeNS {
1124                 struct_span_err!(self.session, directive.span, E0365,
1125                                  "`{}` is private, and cannot be re-exported", ident)
1126                     .span_label(directive.span, format!("re-export of private `{}`", ident))
1127                     .note(&format!("consider declaring type or module `{}` with `pub`", ident))
1128                     .emit();
1129             } else {
1130                 let msg = format!("`{}` is private, and cannot be re-exported", ident);
1131                 let note_msg =
1132                     format!("consider marking `{}` as `pub` in the imported module", ident);
1133                 struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
1134                     .span_note(directive.span, &note_msg)
1135                     .emit();
1136             }
1137         }
1138
1139         if module_path.len() <= 1 {
1140             // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
1141             // 2 segments, so the `resolve_path` above won't trigger it.
1142             let mut full_path = module_path.clone();
1143             full_path.push(ident);
1144             self.per_ns(|this, ns| {
1145                 if let Ok(binding) = result[ns].get() {
1146                     this.lint_if_path_starts_with_module(
1147                         directive.crate_lint(),
1148                         &full_path,
1149                         directive.span,
1150                         Some(binding),
1151                     );
1152                 }
1153             });
1154         }
1155
1156         // Record what this import resolves to for later uses in documentation,
1157         // this may resolve to either a value or a type, but for documentation
1158         // purposes it's good enough to just favor one over the other.
1159         self.per_ns(|this, ns| if let Some(binding) = result[ns].get().ok() {
1160             let import = this.import_map.entry(directive.id).or_default();
1161             import[ns] = Some(PathResolution::new(binding.def()));
1162         });
1163
1164         debug!("(resolving single import) successfully resolved import");
1165         None
1166     }
1167
1168     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
1169         let module = match directive.imported_module.get().unwrap() {
1170             ModuleOrUniformRoot::Module(module) => module,
1171             ModuleOrUniformRoot::UniformRoot(_) => {
1172                 self.session.span_err(directive.span,
1173                     "cannot glob-import all possible crates");
1174                 return;
1175             }
1176         };
1177
1178         self.populate_module_if_necessary(module);
1179
1180         if let Some(Def::Trait(_)) = module.def() {
1181             self.session.span_err(directive.span, "items in traits are not importable.");
1182             return;
1183         } else if module.def_id() == directive.parent.def_id()  {
1184             return;
1185         } else if let GlobImport { is_prelude: true, .. } = directive.subclass {
1186             self.prelude = Some(module);
1187             return;
1188         }
1189
1190         // Add to module's glob_importers
1191         module.glob_importers.borrow_mut().push(directive);
1192
1193         // Ensure that `resolutions` isn't borrowed during `try_define`,
1194         // since it might get updated via a glob cycle.
1195         let bindings = module.resolutions.borrow().iter().filter_map(|(&ident, resolution)| {
1196             resolution.borrow().binding().map(|binding| (ident, binding))
1197         }).collect::<Vec<_>>();
1198         for ((mut ident, ns), binding) in bindings {
1199             let scope = match ident.span.reverse_glob_adjust(module.expansion,
1200                                                              directive.span.ctxt().modern()) {
1201                 Some(Some(def)) => self.macro_def_scope(def),
1202                 Some(None) => self.current_module,
1203                 None => continue,
1204             };
1205             if self.is_accessible_from(binding.pseudo_vis(), scope) {
1206                 let imported_binding = self.import(binding, directive);
1207                 let _ = self.try_define(directive.parent, ident, ns, imported_binding);
1208             }
1209         }
1210
1211         // Record the destination of this import
1212         self.record_def(directive.id, PathResolution::new(module.def().unwrap()));
1213     }
1214
1215     // Miscellaneous post-processing, including recording re-exports,
1216     // reporting conflicts, and reporting unresolved imports.
1217     fn finalize_resolutions_in(&mut self, module: Module<'b>) {
1218         // Since import resolution is finished, globs will not define any more names.
1219         *module.globs.borrow_mut() = Vec::new();
1220
1221         let mut reexports = Vec::new();
1222
1223         for (&(ident, ns), resolution) in module.resolutions.borrow().iter() {
1224             let resolution = &mut *resolution.borrow_mut();
1225             let binding = match resolution.binding {
1226                 Some(binding) => binding,
1227                 None => continue,
1228             };
1229
1230             // Don't reexport `uniform_path` canaries.
1231             let non_canary_import = match binding.kind {
1232                 NameBindingKind::Import { directive, .. } => {
1233                     !directive.is_uniform_paths_canary
1234                 }
1235                 _ => false,
1236             };
1237
1238             if non_canary_import || binding.is_macro_def() {
1239                 let def = binding.def();
1240                 if def != Def::Err {
1241                     if !def.def_id().is_local() {
1242                         self.cstore.export_macros_untracked(def.def_id().krate);
1243                     }
1244                     reexports.push(Export {
1245                         ident: ident.modern(),
1246                         def: def,
1247                         span: binding.span,
1248                         vis: binding.vis,
1249                     });
1250                 }
1251             }
1252
1253             match binding.kind {
1254                 NameBindingKind::Import { binding: orig_binding, directive, .. } => {
1255                     if ns == TypeNS && orig_binding.is_variant() &&
1256                         !orig_binding.vis.is_at_least(binding.vis, &*self) {
1257                             let msg = match directive.subclass {
1258                                 ImportDirectiveSubclass::SingleImport { .. } => {
1259                                     format!("variant `{}` is private and cannot be re-exported",
1260                                             ident)
1261                                 },
1262                                 ImportDirectiveSubclass::GlobImport { .. } => {
1263                                     let msg = "enum is private and its variants \
1264                                                cannot be re-exported".to_owned();
1265                                     let error_id = (DiagnosticMessageId::ErrorId(0), // no code?!
1266                                                     Some(binding.span),
1267                                                     msg.clone());
1268                                     let fresh = self.session.one_time_diagnostics
1269                                         .borrow_mut().insert(error_id);
1270                                     if !fresh {
1271                                         continue;
1272                                     }
1273                                     msg
1274                                 },
1275                                 ref s @ _ => bug!("unexpected import subclass {:?}", s)
1276                             };
1277                             let mut err = self.session.struct_span_err(binding.span, &msg);
1278
1279                             let imported_module = match directive.imported_module.get() {
1280                                 Some(ModuleOrUniformRoot::Module(module)) => module,
1281                                 _ => bug!("module should exist"),
1282                             };
1283                             let resolutions = imported_module.parent.expect("parent should exist")
1284                                 .resolutions.borrow();
1285                             let enum_path_segment_index = directive.module_path.len() - 1;
1286                             let enum_ident = directive.module_path[enum_path_segment_index];
1287
1288                             let enum_resolution = resolutions.get(&(enum_ident, TypeNS))
1289                                 .expect("resolution should exist");
1290                             let enum_span = enum_resolution.borrow()
1291                                 .binding.expect("binding should exist")
1292                                 .span;
1293                             let enum_def_span = self.session.source_map().def_span(enum_span);
1294                             let enum_def_snippet = self.session.source_map()
1295                                 .span_to_snippet(enum_def_span).expect("snippet should exist");
1296                             // potentially need to strip extant `crate`/`pub(path)` for suggestion
1297                             let after_vis_index = enum_def_snippet.find("enum")
1298                                 .expect("`enum` keyword should exist in snippet");
1299                             let suggestion = format!("pub {}",
1300                                                      &enum_def_snippet[after_vis_index..]);
1301
1302                             self.session
1303                                 .diag_span_suggestion_once(&mut err,
1304                                                            DiagnosticMessageId::ErrorId(0),
1305                                                            enum_def_span,
1306                                                            "consider making the enum public",
1307                                                            suggestion);
1308                             err.emit();
1309                     }
1310                 }
1311                 _ => {}
1312             }
1313         }
1314
1315         if reexports.len() > 0 {
1316             if let Some(def_id) = module.def_id() {
1317                 self.export_map.insert(def_id, reexports);
1318             }
1319         }
1320     }
1321 }
1322
1323 fn import_path_to_string(names: &[Ident],
1324                          subclass: &ImportDirectiveSubclass,
1325                          span: Span) -> String {
1326     let pos = names.iter()
1327         .position(|p| span == p.span && p.name != keywords::CrateRoot.name());
1328     let global = !names.is_empty() && names[0].name == keywords::CrateRoot.name();
1329     if let Some(pos) = pos {
1330         let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] };
1331         names_to_string(names)
1332     } else {
1333         let names = if global { &names[1..] } else { names };
1334         if names.is_empty() {
1335             import_directive_subclass_to_string(subclass)
1336         } else {
1337             format!("{}::{}",
1338                     names_to_string(names),
1339                     import_directive_subclass_to_string(subclass))
1340         }
1341     }
1342 }
1343
1344 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
1345     match *subclass {
1346         SingleImport { source, .. } => source.to_string(),
1347         GlobImport { .. } => "*".to_string(),
1348         ExternCrate(_) => "<extern crate>".to_string(),
1349         MacroUse => "#[macro_use]".to_string(),
1350     }
1351 }