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 DefModifiers;
  14 use Module;
  15 use Namespace::{self, TypeNS, ValueNS};
  16 use {NameBinding, NameBindingKind};
  17 use ResolveResult;
  18 use ResolveResult::*;
  19 use Resolver;
  20 use UseLexicalScopeFlag;
  21 use {names_to_string, module_to_string};
  22 use {resolve_error, ResolutionError};
  23
  24 use build_reduced_graph;
  25
  26 use rustc::lint;
  27 use rustc::middle::def::*;
  28 use rustc::middle::privacy::*;
  29
  30 use syntax::ast::{NodeId, Name};
  31 use syntax::attr::AttrMetaMethods;
  32 use syntax::codemap::Span;
  33 use syntax::util::lev_distance::find_best_match_for_name;
  34
  35 use std::mem::replace;
  36
  37 /// Contains data for specific types of import directives.
  38 #[derive(Copy, Clone,Debug)]
  39 pub enum ImportDirectiveSubclass {
  40     SingleImport(Name /* target */, Name /* source */),
  41     GlobImport,
  42 }
  43
  44 /// Whether an import can be shadowed by another import.
  45 #[derive(Debug,PartialEq,Clone,Copy)]
  46 pub enum Shadowable {
  47     Always,
  48     Never,
  49 }
  50
  51 /// One import directive.
  52 #[derive(Debug,Clone)]
  53 pub struct ImportDirective {
  54     pub module_path: Vec<Name>,
  55     pub subclass: ImportDirectiveSubclass,
  56     pub span: Span,
  57     pub id: NodeId,
  58     pub is_public: bool, // see note in ImportResolutionPerNamespace about how to use this
  59     pub shadowable: Shadowable,
  60 }
  61
  62 impl ImportDirective {
  63     pub fn new(module_path: Vec<Name>,
  64                subclass: ImportDirectiveSubclass,
  65                span: Span,
  66                id: NodeId,
  67                is_public: bool,
  68                shadowable: Shadowable)
  69                -> ImportDirective {
  70         ImportDirective {
  71             module_path: module_path,
  72             subclass: subclass,
  73             span: span,
  74             id: id,
  75             is_public: is_public,
  76             shadowable: shadowable,
  77         }
  78     }
  79
  80     // Given the binding to which this directive resolves in a particular namespace,
  81     // this returns the binding for the name this directive defines in that namespace.
  82     fn import<'a>(&self, binding: &'a NameBinding<'a>) -> NameBinding<'a> {
  83         let mut modifiers = match self.is_public {
  84             true => DefModifiers::PUBLIC | DefModifiers::IMPORTABLE,
  85             false => DefModifiers::empty(),
  86         };
  87         if let GlobImport = self.subclass {
  88             modifiers = modifiers | DefModifiers::GLOB_IMPORTED;
  89         }
  90         if self.shadowable == Shadowable::Always {
  91             modifiers = modifiers | DefModifiers::PRELUDE;
  92         }
  93
  94         NameBinding {
  95             kind: NameBindingKind::Import { binding: binding, id: self.id },
  96             span: Some(self.span),
  97             modifiers: modifiers,
  98         }
  99     }
 100 }
 101
 102 #[derive(Clone, Default)]
 103 /// Records information about the resolution of a name in a module.
 104 pub struct NameResolution<'a> {
 105     /// The number of unresolved single imports that could define the name.
 106     pub outstanding_references: usize,
 107     /// The least shadowable known binding for this name, or None if there are no known bindings.
 108     pub binding: Option<&'a NameBinding<'a>>,
 109 }
 110
 111 impl<'a> NameResolution<'a> {
 112     pub fn result(&self, outstanding_globs: usize) -> ResolveResult<&'a NameBinding<'a>> {
 113         // If no unresolved imports (single or glob) can define the name, self.binding is final.
 114         if self.outstanding_references == 0 && outstanding_globs == 0 {
 115             return self.binding.map(Success).unwrap_or(Failed(None));
 116         }
 117
 118         if let Some(binding) = self.binding {
 119             // Single imports will never be shadowable by other single or glob imports.
 120             if !binding.defined_with(DefModifiers::GLOB_IMPORTED) { return Success(binding); }
 121             // Non-PRELUDE glob imports will never be shadowable by other glob imports.
 122             if self.outstanding_references == 0 && !binding.defined_with(DefModifiers::PRELUDE) {
 123                 return Success(binding);
 124             }
 125         }
 126
 127         Indeterminate
 128     }
 129
 130     // Define the name or return the existing binding if there is a collision.
 131     pub fn try_define(&mut self, binding: &'a NameBinding<'a>) -> Result<(), &'a NameBinding<'a>> {
 132         let is_prelude = |binding: &NameBinding| binding.defined_with(DefModifiers::PRELUDE);
 133         let old_binding = match self.binding {
 134             Some(_) if is_prelude(binding) => return Ok(()),
 135             Some(old_binding) if !is_prelude(old_binding) => old_binding,
 136             _ => { self.binding = Some(binding); return Ok(()); }
 137         };
 138
 139         // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
 140         if !old_binding.is_import() && binding.defined_with(DefModifiers::GLOB_IMPORTED) {
 141             if let NameBindingKind::Import { binding, .. } = binding.kind {
 142                 if binding.is_import() { return Ok(()); }
 143             }
 144         }
 145
 146         Err(old_binding)
 147     }
 148 }
 149
 150 struct ImportResolvingError<'a> {
 151     /// Module where the error happened
 152     source_module: Module<'a>,
 153     import_directive: ImportDirective,
 154     span: Span,
 155     help: String,
 156 }
 157
 158 struct ImportResolver<'a, 'b: 'a, 'tcx: 'b> {
 159     resolver: &'a mut Resolver<'b, 'tcx>,
 160 }
 161
 162 impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
 163     // Import resolution
 164     //
 165     // This is a fixed-point algorithm. We resolve imports until our efforts
 166     // are stymied by an unresolved import; then we bail out of the current
 167     // module and continue. We terminate successfully once no more imports
 168     // remain or unsuccessfully when no forward progress in resolving imports
 169     // is made.
 170
 171     /// Resolves all imports for the crate. This method performs the fixed-
 172     /// point iteration.
 173     fn resolve_imports(&mut self) {
 174         let mut i = 0;
 175         let mut prev_unresolved_imports = 0;
 176         loop {
 177             debug!("(resolving imports) iteration {}, {} imports left",
 178                    i,
 179                    self.resolver.unresolved_imports);
 180
 181             let module_root = self.resolver.graph_root;
 182             let errors = self.resolve_imports_for_module_subtree(module_root);
 183
 184             if self.resolver.unresolved_imports == 0 {
 185                 debug!("(resolving imports) success");
 186                 break;
 187             }
 188
 189             if self.resolver.unresolved_imports == prev_unresolved_imports {
 190                 // resolving failed
 191                 if errors.len() > 0 {
 192                     for e in errors {
 193                         self.import_resolving_error(e)
 194                     }
 195                 } else {
 196                     // Report unresolved imports only if no hard error was already reported
 197                     // to avoid generating multiple errors on the same import.
 198                     // Imports that are still indeterminate at this point are actually blocked
 199                     // by errored imports, so there is no point reporting them.
 200                     self.resolver.report_unresolved_imports(module_root);
 201                 }
 202                 break;
 203             }
 204
 205             i += 1;
 206             prev_unresolved_imports = self.resolver.unresolved_imports;
 207         }
 208     }
 209
 210     /// Resolves an `ImportResolvingError` into the correct enum discriminant
 211     /// and passes that on to `resolve_error`.
 212     fn import_resolving_error(&self, e: ImportResolvingError<'b>) {
 213         // If it's a single failed import then create a "fake" import
 214         // resolution for it so that later resolve stages won't complain.
 215         if let SingleImport(target, _) = e.import_directive.subclass {
 216             let dummy_binding = self.resolver.new_name_binding(NameBinding {
 217                 modifiers: DefModifiers::PRELUDE,
 218                 kind: NameBindingKind::Def(Def::Err),
 219                 span: None,
 220             });
 221
 222             let _ = e.source_module.try_define_child(target, ValueNS, dummy_binding);
 223             let _ = e.source_module.try_define_child(target, TypeNS, dummy_binding);
 224         }
 225
 226         let path = import_path_to_string(&e.import_directive.module_path,
 227                                          e.import_directive.subclass);
 228
 229         resolve_error(self.resolver,
 230                       e.span,
 231                       ResolutionError::UnresolvedImport(Some((&path, &e.help))));
 232     }
 233
 234     /// Attempts to resolve imports for the given module and all of its
 235     /// submodules.
 236     fn resolve_imports_for_module_subtree(&mut self,
 237                                           module_: Module<'b>)
 238                                           -> Vec<ImportResolvingError<'b>> {
 239         let mut errors = Vec::new();
 240         debug!("(resolving imports for module subtree) resolving {}",
 241                module_to_string(&*module_));
 242         let orig_module = replace(&mut self.resolver.current_module, module_);
 243         errors.extend(self.resolve_imports_for_module(module_));
 244         self.resolver.current_module = orig_module;
 245
 246         build_reduced_graph::populate_module_if_necessary(self.resolver, module_);
 247         module_.for_each_local_child(|_, _, child_node| {
 248             match child_node.module() {
 249                 None => {
 250                     // Nothing to do.
 251                 }
 252                 Some(child_module) => {
 253                     errors.extend(self.resolve_imports_for_module_subtree(child_module));
 254                 }
 255             }
 256         });
 257
 258         for (_, child_module) in module_.anonymous_children.borrow().iter() {
 259             errors.extend(self.resolve_imports_for_module_subtree(child_module));
 260         }
 261
 262         errors
 263     }
 264
 265     /// Attempts to resolve imports for the given module only.
 266     fn resolve_imports_for_module(&mut self, module: Module<'b>) -> Vec<ImportResolvingError<'b>> {
 267         let mut errors = Vec::new();
 268
 269         if module.all_imports_resolved() {
 270             debug!("(resolving imports for module) all imports resolved for {}",
 271                    module_to_string(&*module));
 272             return errors;
 273         }
 274
 275         let mut imports = module.imports.borrow_mut();
 276         let import_count = imports.len();
 277         let mut indeterminate_imports = Vec::new();
 278         while module.resolved_import_count.get() + indeterminate_imports.len() < import_count {
 279             let import_index = module.resolved_import_count.get();
 280             match self.resolve_import_for_module(module, &imports[import_index]) {
 281                 ResolveResult::Failed(err) => {
 282                     let import_directive = &imports[import_index];
 283                     let (span, help) = match err {
 284                         Some((span, msg)) => (span, format!(". {}", msg)),
 285                         None => (import_directive.span, String::new()),
 286                     };
 287                     errors.push(ImportResolvingError {
 288                         source_module: module,
 289                         import_directive: import_directive.clone(),
 290                         span: span,
 291                         help: help,
 292                     });
 293                 }
 294                 ResolveResult::Indeterminate => {}
 295                 ResolveResult::Success(()) => {
 296                     // count success
 297                     module.resolved_import_count
 298                           .set(module.resolved_import_count.get() + 1);
 299                     continue;
 300                 }
 301             }
 302             // This resolution was not successful, keep it for later
 303             indeterminate_imports.push(imports.swap_remove(import_index));
 304
 305         }
 306
 307         imports.extend(indeterminate_imports);
 308
 309         errors
 310     }
 311
 312     /// Attempts to resolve the given import. The return value indicates
 313     /// failure if we're certain the name does not exist, indeterminate if we
 314     /// don't know whether the name exists at the moment due to other
 315     /// currently-unresolved imports, or success if we know the name exists.
 316     /// If successful, the resolved bindings are written into the module.
 317     fn resolve_import_for_module(&mut self,
 318                                  module_: Module<'b>,
 319                                  import_directive: &ImportDirective)
 320                                  -> ResolveResult<()> {
 321         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 322                names_to_string(&import_directive.module_path),
 323                module_to_string(&*module_));
 324
 325         self.resolver
 326             .resolve_module_path(module_,
 327                                  &import_directive.module_path,
 328                                  UseLexicalScopeFlag::DontUseLexicalScope,
 329                                  import_directive.span)
 330             .and_then(|(containing_module, lp)| {
 331                 // We found the module that the target is contained
 332                 // within. Attempt to resolve the import within it.
 333                 if let SingleImport(target, source) = import_directive.subclass {
 334                     self.resolve_single_import(module_,
 335                                                containing_module,
 336                                                target,
 337                                                source,
 338                                                import_directive,
 339                                                lp)
 340                 } else {
 341                     self.resolve_glob_import(module_, containing_module, import_directive, lp)
 342                 }
 343             })
 344             .and_then(|()| {
 345                 // Decrement the count of unresolved imports.
 346                 assert!(self.resolver.unresolved_imports >= 1);
 347                 self.resolver.unresolved_imports -= 1;
 348
 349                 if let GlobImport = import_directive.subclass {
 350                     module_.dec_glob_count();
 351                     if import_directive.is_public {
 352                         module_.dec_pub_glob_count();
 353                     }
 354                 }
 355                 if import_directive.is_public {
 356                     module_.dec_pub_count();
 357                 }
 358                 Success(())
 359             })
 360     }
 361
 362     fn resolve_single_import(&mut self,
 363                              module_: Module<'b>,
 364                              target_module: Module<'b>,
 365                              target: Name,
 366                              source: Name,
 367                              directive: &ImportDirective,
 368                              lp: LastPrivate)
 369                              -> ResolveResult<()> {
 370         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 371                 private {:?}",
 372                target,
 373                module_to_string(&*target_module),
 374                source,
 375                module_to_string(module_),
 376                directive.id,
 377                lp);
 378
 379         let lp = match lp {
 380             LastMod(lp) => lp,
 381             LastImport {..} => {
 382                 self.resolver
 383                     .session
 384                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 385             }
 386         };
 387
 388         // If this is a circular import, we temporarily count it as determined so that
 389         // it fails (as opposed to being indeterminate) when nothing else can define it.
 390         if target_module.def_id() == module_.def_id() && source == target {
 391             module_.decrement_outstanding_references_for(target, ValueNS);
 392             module_.decrement_outstanding_references_for(target, TypeNS);
 393         }
 394
 395         // We need to resolve both namespaces for this to succeed.
 396         let value_result =
 397             self.resolver.resolve_name_in_module(target_module, source, ValueNS, false, true);
 398         let type_result =
 399             self.resolver.resolve_name_in_module(target_module, source, TypeNS, false, true);
 400
 401         if target_module.def_id() == module_.def_id() && source == target {
 402             module_.increment_outstanding_references_for(target, ValueNS);
 403             module_.increment_outstanding_references_for(target, TypeNS);
 404         }
 405
 406         match (&value_result, &type_result) {
 407             (&Success(name_binding), _) if !name_binding.is_import() &&
 408                                            directive.is_public &&
 409                                            !name_binding.is_public() => {
 410                 let msg = format!("`{}` is private, and cannot be reexported", source);
 411                 let note_msg = format!("Consider marking `{}` as `pub` in the imported module",
 412                                         source);
 413                 struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 414                     .span_note(directive.span, &note_msg)
 415                     .emit();
 416             }
 417
 418             (_, &Success(name_binding)) if !name_binding.is_import() && directive.is_public => {
 419                 if !name_binding.is_public() {
 420                     let msg = format!("`{}` is private, and cannot be reexported", source);
 421                     let note_msg =
 422                         format!("Consider declaring type or module `{}` with `pub`", source);
 423                     struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 424                         .span_note(directive.span, &note_msg)
 425                         .emit();
 426                 } else if name_binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 427                     let msg = format!("variant `{}` is private, and cannot be reexported \
 428                                        (error E0364), consider declaring its enum as `pub`",
 429                                        source);
 430                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 431                                                    directive.id,
 432                                                    directive.span,
 433                                                    msg);
 434                 }
 435             }
 436
 437             _ => {}
 438         }
 439
 440         match (&value_result, &type_result) {
 441             (&Indeterminate, _) | (_, &Indeterminate) => return Indeterminate,
 442             (&Failed(_), &Failed(_)) => {
 443                 let children = target_module.children.borrow();
 444                 let names = children.keys().map(|&(ref name, _)| name);
 445                 let lev_suggestion = match find_best_match_for_name(names, &source.as_str(), None) {
 446                     Some(name) => format!(". Did you mean to use `{}`?", name),
 447                     None => "".to_owned(),
 448                 };
 449                 let msg = format!("There is no `{}` in `{}`{}",
 450                                   source,
 451                                   module_to_string(target_module), lev_suggestion);
 452                 return Failed(Some((directive.span, msg)));
 453             }
 454             _ => (),
 455         }
 456
 457         for &(ns, result) in &[(ValueNS, &value_result), (TypeNS, &type_result)] {
 458             if let Success(binding) = *result {
 459                 if !binding.defined_with(DefModifiers::IMPORTABLE) {
 460                     let msg = format!("`{}` is not directly importable", target);
 461                     span_err!(self.resolver.session, directive.span, E0253, "{}", &msg);
 462                 }
 463
 464                 self.define(module_, target, ns, directive.import(binding));
 465             }
 466         }
 467
 468         // Record what this import resolves to for later uses in documentation,
 469         // this may resolve to either a value or a type, but for documentation
 470         // purposes it's good enough to just favor one over the other.
 471         module_.decrement_outstanding_references_for(target, ValueNS);
 472         module_.decrement_outstanding_references_for(target, TypeNS);
 473
 474         let def_and_priv = |binding: &NameBinding| {
 475             let def = binding.def().unwrap();
 476             let last_private = if binding.is_public() { lp } else { DependsOn(def.def_id()) };
 477             (def, last_private)
 478         };
 479         let value_def_and_priv = value_result.success().map(&def_and_priv);
 480         let type_def_and_priv = type_result.success().map(&def_and_priv);
 481
 482         let import_lp = LastImport {
 483             value_priv: value_def_and_priv.map(|(_, p)| p),
 484             value_used: Used,
 485             type_priv: type_def_and_priv.map(|(_, p)| p),
 486             type_used: Used,
 487         };
 488
 489         let write_path_resolution = |(def, _)| {
 490             let path_resolution =
 491                 PathResolution { base_def: def, last_private: import_lp, depth: 0 };
 492             self.resolver.def_map.borrow_mut().insert(directive.id, path_resolution);
 493         };
 494         value_def_and_priv.map(&write_path_resolution);
 495         type_def_and_priv.map(&write_path_resolution);
 496
 497         debug!("(resolving single import) successfully resolved import");
 498         return Success(());
 499     }
 500
 501     // Resolves a glob import. Note that this function cannot fail; it either
 502     // succeeds or bails out (as importing * from an empty module or a module
 503     // that exports nothing is valid). target_module is the module we are
 504     // actually importing, i.e., `foo` in `use foo::*`.
 505     fn resolve_glob_import(&mut self,
 506                            module_: Module<'b>,
 507                            target_module: Module<'b>,
 508                            directive: &ImportDirective,
 509                            lp: LastPrivate)
 510                            -> ResolveResult<()> {
 511         // We must bail out if the node has unresolved imports of any kind (including globs).
 512         if target_module.pub_count.get() > 0 {
 513             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 514             return Indeterminate;
 515         }
 516
 517         if module_.def_id() == target_module.def_id() {
 518             // This means we are trying to glob import a module into itself, and it is a no-go
 519             let msg = "Cannot glob-import a module into itself.".into();
 520             return Failed(Some((directive.span, msg)));
 521         }
 522
 523         // Add all children from the containing module.
 524         build_reduced_graph::populate_module_if_necessary(self.resolver, target_module);
 525         target_module.for_each_child(|name, ns, binding| {
 526             if !binding.defined_with(DefModifiers::IMPORTABLE | DefModifiers::PUBLIC) { return }
 527             if binding.is_extern_crate() { return }
 528             self.define(module_, name, ns, directive.import(binding));
 529
 530             if ns == TypeNS && directive.is_public &&
 531                binding.defined_with(DefModifiers::PRIVATE_VARIANT) {
 532                 let msg = format!("variant `{}` is private, and cannot be reexported (error \
 533                                    E0364), consider declaring its enum as `pub`", name);
 534                 self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 535                                                directive.id,
 536                                                directive.span,
 537                                                msg);
 538             }
 539         });
 540
 541         // Record the destination of this import
 542         if let Some(did) = target_module.def_id() {
 543             self.resolver.def_map.borrow_mut().insert(directive.id,
 544                                                       PathResolution {
 545                                                           base_def: Def::Mod(did),
 546                                                           last_private: lp,
 547                                                           depth: 0,
 548                                                       });
 549         }
 550
 551         debug!("(resolving glob import) successfully resolved import");
 552         return Success(());
 553     }
 554
 555     fn define(&mut self,
 556               parent: Module<'b>,
 557               name: Name,
 558               ns: Namespace,
 559               binding: NameBinding<'b>) {
 560         let binding = self.resolver.new_name_binding(binding);
 561         if let Err(old_binding) = parent.try_define_child(name, ns, binding) {
 562             self.report_conflict(name, ns, binding, old_binding);
 563         } else if binding.is_public() { // Add to the export map
 564             if let (Some(parent_def_id), Some(def)) = (parent.def_id(), binding.def()) {
 565                 let parent_node_id = self.resolver.ast_map.as_local_node_id(parent_def_id).unwrap();
 566                 let export = Export { name: name, def_id: def.def_id() };
 567                 self.resolver.export_map.entry(parent_node_id).or_insert(Vec::new()).push(export);
 568             }
 569         }
 570     }
 571
 572     fn report_conflict(&mut self,
 573                        name: Name,
 574                        ns: Namespace,
 575                        binding: &'b NameBinding<'b>,
 576                        old_binding: &'b NameBinding<'b>) {
 577         if old_binding.is_extern_crate() {
 578             let msg = format!("import `{0}` conflicts with imported crate \
 579                                in this module (maybe you meant `use {0}::*`?)",
 580                               name);
 581             span_err!(self.resolver.session, binding.span.unwrap(), E0254, "{}", &msg);
 582         } else if old_binding.is_import() {
 583             let ns_word = match (ns, old_binding.module()) {
 584                 (ValueNS, _) => "value",
 585                 (TypeNS, Some(module)) if module.is_normal() => "module",
 586                 (TypeNS, Some(module)) if module.is_trait() => "trait",
 587                 (TypeNS, _) => "type",
 588             };
 589             let mut err = struct_span_err!(self.resolver.session,
 590                                            binding.span.unwrap(),
 591                                            E0252,
 592                                            "a {} named `{}` has already been imported \
 593                                             in this module",
 594                                            ns_word,
 595                                            name);
 596             err.span_note(old_binding.span.unwrap(),
 597                           &format!("previous import of `{}` here", name));
 598             err.emit();
 599         } else if ns == ValueNS { // Check for item conflicts in the value namespace
 600             let mut err = struct_span_err!(self.resolver.session,
 601                                            binding.span.unwrap(),
 602                                            E0255,
 603                                            "import `{}` conflicts with value in this module",
 604                                            name);
 605             err.span_note(old_binding.span.unwrap(), "conflicting value here");
 606             err.emit();
 607         } else { // Check for item conflicts in the type namespace
 608             let (what, note) = match old_binding.module() {
 609                 Some(ref module) if module.is_normal() =>
 610                     ("existing submodule", "note conflicting module here"),
 611                 Some(ref module) if module.is_trait() =>
 612                     ("trait in this module", "note conflicting trait here"),
 613                 _ => ("type in this module", "note conflicting type here"),
 614             };
 615             let mut err = struct_span_err!(self.resolver.session,
 616                                            binding.span.unwrap(),
 617                                            E0256,
 618                                            "import `{}` conflicts with {}",
 619                                            name,
 620                                            what);
 621             err.span_note(old_binding.span.unwrap(), note);
 622             err.emit();
 623         }
 624     }
 625 }
 626
 627 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
 628     if names.is_empty() {
 629         import_directive_subclass_to_string(subclass)
 630     } else {
 631         (format!("{}::{}",
 632                  names_to_string(names),
 633                  import_directive_subclass_to_string(subclass)))
 634             .to_string()
 635     }
 636 }
 637
 638 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
 639     match subclass {
 640         SingleImport(_, source) => source.to_string(),
 641         GlobImport => "*".to_string(),
 642     }
 643 }
 644
 645 pub fn resolve_imports(resolver: &mut Resolver) {
 646     let mut import_resolver = ImportResolver { resolver: resolver };
 647     import_resolver.resolve_imports();
 648 }