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 {NameBindings, NameBinding};
  17 use NamespaceResult::{BoundResult, UnboundResult, UnknownResult};
  18 use NamespaceResult;
  19 use NameSearchType;
  20 use ResolveResult;
  21 use Resolver;
  22 use UseLexicalScopeFlag;
  23 use {names_to_string, module_to_string};
  24 use {resolve_error, ResolutionError};
  25
  26 use build_reduced_graph;
  27
  28 use rustc::lint;
  29 use rustc::middle::def::*;
  30 use rustc::middle::def_id::DefId;
  31 use rustc::middle::privacy::*;
  32
  33 use syntax::ast::{NodeId, Name};
  34 use syntax::attr::AttrMetaMethods;
  35 use syntax::codemap::Span;
  36 use syntax::util::lev_distance::find_best_match_for_name;
  37
  38 use std::mem::replace;
  39 use std::rc::Rc;
  40
  41 /// Contains data for specific types of import directives.
  42 #[derive(Copy, Clone,Debug)]
  43 pub enum ImportDirectiveSubclass {
  44     SingleImport(Name /* target */, Name /* source */),
  45     GlobImport,
  46 }
  47
  48 /// Whether an import can be shadowed by another import.
  49 #[derive(Debug,PartialEq,Clone,Copy)]
  50 pub enum Shadowable {
  51     Always,
  52     Never,
  53 }
  54
  55 /// One import directive.
  56 #[derive(Debug)]
  57 pub struct ImportDirective {
  58     pub module_path: Vec<Name>,
  59     pub subclass: ImportDirectiveSubclass,
  60     pub span: Span,
  61     pub id: NodeId,
  62     pub is_public: bool, // see note in ImportResolutionPerNamespace about how to use this
  63     pub shadowable: Shadowable,
  64 }
  65
  66 impl ImportDirective {
  67     pub fn new(module_path: Vec<Name>,
  68                subclass: ImportDirectiveSubclass,
  69                span: Span,
  70                id: NodeId,
  71                is_public: bool,
  72                shadowable: Shadowable)
  73                -> ImportDirective {
  74         ImportDirective {
  75             module_path: module_path,
  76             subclass: subclass,
  77             span: span,
  78             id: id,
  79             is_public: is_public,
  80             shadowable: shadowable,
  81         }
  82     }
  83 }
  84
  85 /// The item that an import resolves to.
  86 #[derive(Clone,Debug)]
  87 pub struct Target {
  88     pub target_module: Rc<Module>,
  89     pub binding: NameBinding,
  90     pub shadowable: Shadowable,
  91 }
  92
  93 impl Target {
  94     pub fn new(target_module: Rc<Module>,
  95                binding: NameBinding,
  96                shadowable: Shadowable)
  97                -> Target {
  98         Target {
  99             target_module: target_module,
 100             binding: binding,
 101             shadowable: shadowable,
 102         }
 103     }
 104 }
 105
 106 #[derive(Debug)]
 107 /// An ImportResolutionPerNamespace records what we know about an imported name.
 108 /// More specifically, it records the number of unresolved `use` directives that import the name,
 109 /// and for each namespace, it records the `use` directive importing the name in the namespace
 110 /// and the `Target` to which the name in the namespace resolves (if applicable).
 111 /// Different `use` directives may import the same name in different namespaces.
 112 pub struct ImportResolutionPerNamespace {
 113     // When outstanding_references reaches zero, outside modules can count on the targets being
 114     // correct. Before then, all bets are off; future `use` directives could override the name.
 115     // Since shadowing is forbidden, the only way outstanding_references > 1 in a legal program
 116     // is if the name is imported by exactly two `use` directives, one of which resolves to a
 117     // value and the other of which resolves to a type.
 118     pub outstanding_references: usize,
 119     pub type_ns: ImportResolution,
 120     pub value_ns: ImportResolution,
 121 }
 122
 123 /// Records what we know about an imported name in a namespace (see `ImportResolutionPerNamespace`).
 124 #[derive(Clone,Debug)]
 125 pub struct ImportResolution {
 126     /// Whether the name in the namespace was imported with a `use` or a `pub use`.
 127     pub is_public: bool,
 128
 129     /// Resolution of the name in the namespace
 130     pub target: Option<Target>,
 131
 132     /// The source node of the `use` directive
 133     pub id: NodeId,
 134 }
 135
 136 impl ::std::ops::Index<Namespace> for ImportResolutionPerNamespace {
 137     type Output = ImportResolution;
 138     fn index(&self, ns: Namespace) -> &ImportResolution {
 139         match ns { TypeNS => &self.type_ns, ValueNS => &self.value_ns }
 140     }
 141 }
 142
 143 impl ::std::ops::IndexMut<Namespace> for ImportResolutionPerNamespace {
 144     fn index_mut(&mut self, ns: Namespace) -> &mut ImportResolution {
 145         match ns { TypeNS => &mut self.type_ns, ValueNS => &mut self.value_ns }
 146     }
 147 }
 148
 149 impl ImportResolutionPerNamespace {
 150     pub fn new(id: NodeId, is_public: bool) -> Self {
 151         let resolution = ImportResolution { id: id, is_public: is_public, target: None };
 152         ImportResolutionPerNamespace {
 153             outstanding_references: 0, type_ns: resolution.clone(), value_ns: resolution,
 154         }
 155     }
 156
 157     pub fn shadowable(&self, namespace: Namespace) -> Shadowable {
 158         match self[namespace].target {
 159             Some(ref target) => target.shadowable,
 160             None => Shadowable::Always,
 161         }
 162     }
 163 }
 164
 165 struct ImportResolvingError {
 166     span: Span,
 167     path: String,
 168     help: String,
 169 }
 170
 171 struct ImportResolver<'a, 'b: 'a, 'tcx: 'b> {
 172     resolver: &'a mut Resolver<'b, 'tcx>,
 173 }
 174
 175 impl<'a, 'b:'a, 'tcx:'b> ImportResolver<'a, 'b, 'tcx> {
 176     // Import resolution
 177     //
 178     // This is a fixed-point algorithm. We resolve imports until our efforts
 179     // are stymied by an unresolved import; then we bail out of the current
 180     // module and continue. We terminate successfully once no more imports
 181     // remain or unsuccessfully when no forward progress in resolving imports
 182     // is made.
 183
 184     /// Resolves all imports for the crate. This method performs the fixed-
 185     /// point iteration.
 186     fn resolve_imports(&mut self) {
 187         let mut i = 0;
 188         let mut prev_unresolved_imports = 0;
 189         loop {
 190             debug!("(resolving imports) iteration {}, {} imports left",
 191                    i,
 192                    self.resolver.unresolved_imports);
 193
 194             let module_root = self.resolver.graph_root.clone();
 195             let errors = self.resolve_imports_for_module_subtree(module_root.clone());
 196
 197             if self.resolver.unresolved_imports == 0 {
 198                 debug!("(resolving imports) success");
 199                 break;
 200             }
 201
 202             if self.resolver.unresolved_imports == prev_unresolved_imports {
 203                 // resolving failed
 204                 if errors.len() > 0 {
 205                     for e in errors {
 206                         resolve_error(self.resolver,
 207                                       e.span,
 208                                       ResolutionError::UnresolvedImport(Some((&e.path, &e.help))));
 209                     }
 210                 } else {
 211                     // Report unresolved imports only if no hard error was already reported
 212                     // to avoid generating multiple errors on the same import.
 213                     // Imports that are still indeterminate at this point are actually blocked
 214                     // by errored imports, so there is no point reporting them.
 215                     self.resolver.report_unresolved_imports(module_root);
 216                 }
 217                 break;
 218             }
 219
 220             i += 1;
 221             prev_unresolved_imports = self.resolver.unresolved_imports;
 222         }
 223     }
 224
 225     /// Attempts to resolve imports for the given module and all of its
 226     /// submodules.
 227     fn resolve_imports_for_module_subtree(&mut self,
 228                                           module_: Rc<Module>)
 229                                           -> Vec<ImportResolvingError> {
 230         let mut errors = Vec::new();
 231         debug!("(resolving imports for module subtree) resolving {}",
 232                module_to_string(&*module_));
 233         let orig_module = replace(&mut self.resolver.current_module, module_.clone());
 234         errors.extend(self.resolve_imports_for_module(module_.clone()));
 235         self.resolver.current_module = orig_module;
 236
 237         build_reduced_graph::populate_module_if_necessary(self.resolver, &module_);
 238         for (_, child_node) in module_.children.borrow().iter() {
 239             match child_node.type_ns.module() {
 240                 None => {
 241                     // Nothing to do.
 242                 }
 243                 Some(child_module) => {
 244                     errors.extend(self.resolve_imports_for_module_subtree(child_module));
 245                 }
 246             }
 247         }
 248
 249         for (_, child_module) in module_.anonymous_children.borrow().iter() {
 250             errors.extend(self.resolve_imports_for_module_subtree(child_module.clone()));
 251         }
 252
 253         errors
 254     }
 255
 256     /// Attempts to resolve imports for the given module only.
 257     fn resolve_imports_for_module(&mut self, module: Rc<Module>) -> Vec<ImportResolvingError> {
 258         let mut errors = Vec::new();
 259
 260         if module.all_imports_resolved() {
 261             debug!("(resolving imports for module) all imports resolved for {}",
 262                    module_to_string(&*module));
 263             return errors;
 264         }
 265
 266         let mut imports = module.imports.borrow_mut();
 267         let import_count = imports.len();
 268         let mut indeterminate_imports = Vec::new();
 269         while module.resolved_import_count.get() + indeterminate_imports.len() < import_count {
 270             let import_index = module.resolved_import_count.get();
 271             match self.resolve_import_for_module(module.clone(), &imports[import_index]) {
 272                 ResolveResult::Failed(err) => {
 273                     let import_directive = &imports[import_index];
 274                     let (span, help) = match err {
 275                         Some((span, msg)) => (span, format!(". {}", msg)),
 276                         None => (import_directive.span, String::new()),
 277                     };
 278                     errors.push(ImportResolvingError {
 279                         span: span,
 280                         path: import_path_to_string(&import_directive.module_path,
 281                                                     import_directive.subclass),
 282                         help: help,
 283                     });
 284                 }
 285                 ResolveResult::Indeterminate => {}
 286                 ResolveResult::Success(()) => {
 287                     // count success
 288                     module.resolved_import_count
 289                           .set(module.resolved_import_count.get() + 1);
 290                     continue;
 291                 }
 292             }
 293             // This resolution was not successful, keep it for later
 294             indeterminate_imports.push(imports.swap_remove(import_index));
 295
 296         }
 297
 298         imports.extend(indeterminate_imports);
 299
 300         errors
 301     }
 302
 303     /// Attempts to resolve the given import. The return value indicates
 304     /// failure if we're certain the name does not exist, indeterminate if we
 305     /// don't know whether the name exists at the moment due to other
 306     /// currently-unresolved imports, or success if we know the name exists.
 307     /// If successful, the resolved bindings are written into the module.
 308     fn resolve_import_for_module(&mut self,
 309                                  module_: Rc<Module>,
 310                                  import_directive: &ImportDirective)
 311                                  -> ResolveResult<()> {
 312         let mut resolution_result = ResolveResult::Failed(None);
 313         let module_path = &import_directive.module_path;
 314
 315         debug!("(resolving import for module) resolving import `{}::...` in `{}`",
 316                names_to_string(&module_path[..]),
 317                module_to_string(&*module_));
 318
 319         // First, resolve the module path for the directive, if necessary.
 320         let container = if module_path.is_empty() {
 321             // Use the crate root.
 322             Some((self.resolver.graph_root.clone(), LastMod(AllPublic)))
 323         } else {
 324             match self.resolver.resolve_module_path(module_.clone(),
 325                                                     &module_path[..],
 326                                                     UseLexicalScopeFlag::DontUseLexicalScope,
 327                                                     import_directive.span,
 328                                                     NameSearchType::ImportSearch) {
 329                 ResolveResult::Failed(err) => {
 330                     resolution_result = ResolveResult::Failed(err);
 331                     None
 332                 }
 333                 ResolveResult::Indeterminate => {
 334                     resolution_result = ResolveResult::Indeterminate;
 335                     None
 336                 }
 337                 ResolveResult::Success(container) => Some(container),
 338             }
 339         };
 340
 341         match container {
 342             None => {}
 343             Some((containing_module, lp)) => {
 344                 // We found the module that the target is contained
 345                 // within. Attempt to resolve the import within it.
 346
 347                 match import_directive.subclass {
 348                     SingleImport(target, source) => {
 349                         resolution_result = self.resolve_single_import(&module_,
 350                                                                        containing_module,
 351                                                                        target,
 352                                                                        source,
 353                                                                        import_directive,
 354                                                                        lp);
 355                     }
 356                     GlobImport => {
 357                         resolution_result = self.resolve_glob_import(&module_,
 358                                                                      containing_module,
 359                                                                      import_directive,
 360                                                                      lp);
 361                     }
 362                 }
 363             }
 364         }
 365
 366         // Decrement the count of unresolved imports.
 367         match resolution_result {
 368             ResolveResult::Success(()) => {
 369                 assert!(self.resolver.unresolved_imports >= 1);
 370                 self.resolver.unresolved_imports -= 1;
 371             }
 372             _ => {
 373                 // Nothing to do here; just return the error.
 374             }
 375         }
 376
 377         // Decrement the count of unresolved globs if necessary. But only if
 378         // the resolution result is a success -- other cases will
 379         // be handled by the main loop.
 380
 381         if resolution_result.success() {
 382             match import_directive.subclass {
 383                 GlobImport => {
 384                     module_.dec_glob_count();
 385                     if import_directive.is_public {
 386                         module_.dec_pub_glob_count();
 387                     }
 388                 }
 389                 SingleImport(..) => {
 390                     // Ignore.
 391                 }
 392             }
 393             if import_directive.is_public {
 394                 module_.dec_pub_count();
 395             }
 396         }
 397
 398         return resolution_result;
 399     }
 400
 401     fn resolve_single_import(&mut self,
 402                              module_: &Module,
 403                              target_module: Rc<Module>,
 404                              target: Name,
 405                              source: Name,
 406                              directive: &ImportDirective,
 407                              lp: LastPrivate)
 408                              -> ResolveResult<()> {
 409         debug!("(resolving single import) resolving `{}` = `{}::{}` from `{}` id {}, last \
 410                 private {:?}",
 411                target,
 412                module_to_string(&*target_module),
 413                source,
 414                module_to_string(module_),
 415                directive.id,
 416                lp);
 417
 418         let lp = match lp {
 419             LastMod(lp) => lp,
 420             LastImport {..} => {
 421                 self.resolver
 422                     .session
 423                     .span_bug(directive.span, "not expecting Import here, must be LastMod")
 424             }
 425         };
 426
 427         // We need to resolve both namespaces for this to succeed.
 428
 429         let mut value_result = UnknownResult;
 430         let mut type_result = UnknownResult;
 431         let mut lev_suggestion = "".to_owned();
 432
 433         // Search for direct children of the containing module.
 434         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 435
 436         match target_module.children.borrow().get(&source) {
 437             None => {
 438                 let names = target_module.children.borrow();
 439                 if let Some(name) = find_best_match_for_name(names.keys(),
 440                                                              &source.as_str(),
 441                                                              None) {
 442                     lev_suggestion = format!(". Did you mean to use `{}`?", name);
 443                 }
 444             }
 445             Some(ref child_name_bindings) => {
 446                 // pub_err makes sure we don't give the same error twice.
 447                 let mut pub_err = false;
 448                 if child_name_bindings.value_ns.defined() {
 449                     debug!("(resolving single import) found value binding");
 450                     value_result = BoundResult(target_module.clone(),
 451                                                child_name_bindings.value_ns.clone());
 452                     if directive.is_public && !child_name_bindings.value_ns.is_public() {
 453                         let msg = format!("`{}` is private, and cannot be reexported", source);
 454                         let note_msg = format!("Consider marking `{}` as `pub` in the imported \
 455                                                 module",
 456                                                source);
 457                         struct_span_err!(self.resolver.session, directive.span, E0364, "{}", &msg)
 458                             .span_note(directive.span, &note_msg)
 459                             .emit();
 460                         pub_err = true;
 461                     }
 462                     if directive.is_public && child_name_bindings.value_ns.
 463                                               defined_with(DefModifiers::PRIVATE_VARIANT) {
 464                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 465                                            error E0364), consider declaring its enum as `pub`",
 466                                            source);
 467                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 468                                                        directive.id,
 469                                                        directive.span,
 470                                                        msg);
 471                         pub_err = true;
 472                     }
 473                 }
 474                 if child_name_bindings.type_ns.defined() {
 475                     debug!("(resolving single import) found type binding");
 476                     type_result = BoundResult(target_module.clone(),
 477                                               child_name_bindings.type_ns.clone());
 478                     if !pub_err && directive.is_public &&
 479                        !child_name_bindings.type_ns.is_public() {
 480                         let msg = format!("`{}` is private, and cannot be reexported", source);
 481                         let note_msg = format!("Consider declaring module `{}` as a `pub mod`",
 482                                                source);
 483                         struct_span_err!(self.resolver.session, directive.span, E0365, "{}", &msg)
 484                             .span_note(directive.span, &note_msg)
 485                             .emit();
 486                     }
 487                     if !pub_err && directive.is_public && child_name_bindings.type_ns.
 488                                                     defined_with(DefModifiers::PRIVATE_VARIANT) {
 489                         let msg = format!("variant `{}` is private, and cannot be reexported ( \
 490                                            error E0365), consider declaring its enum as `pub`",
 491                                            source);
 492                         self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 493                                                        directive.id,
 494                                                        directive.span,
 495                                                        msg);
 496                     }
 497                 }
 498             }
 499         }
 500
 501         // Unless we managed to find a result in both namespaces (unlikely),
 502         // search imports as well.
 503         let mut value_used_reexport = false;
 504         let mut type_used_reexport = false;
 505         match (value_result.clone(), type_result.clone()) {
 506             (BoundResult(..), BoundResult(..)) => {} // Continue.
 507             _ => {
 508                 // If there is an unresolved glob at this point in the
 509                 // containing module, bail out. We don't know enough to be
 510                 // able to resolve this import.
 511
 512                 if target_module.pub_glob_count.get() > 0 {
 513                     debug!("(resolving single import) unresolved pub glob; bailing out");
 514                     return ResolveResult::Indeterminate;
 515                 }
 516
 517                 // Now search the exported imports within the containing module.
 518                 match target_module.import_resolutions.borrow().get(&source) {
 519                     None => {
 520                         debug!("(resolving single import) no import");
 521                         // The containing module definitely doesn't have an
 522                         // exported import with the name in question. We can
 523                         // therefore accurately report that the names are
 524                         // unbound.
 525
 526                         if lev_suggestion.is_empty() {  // skip if we already have a suggestion
 527                             let names = target_module.import_resolutions.borrow();
 528                             if let Some(name) = find_best_match_for_name(names.keys(),
 529                                                                          &source.as_str(),
 530                                                                          None) {
 531                                 lev_suggestion =
 532                                     format!(". Did you mean to use the re-exported import `{}`?",
 533                                             name);
 534                             }
 535                         }
 536
 537                         if value_result.is_unknown() {
 538                             value_result = UnboundResult;
 539                         }
 540                         if type_result.is_unknown() {
 541                             type_result = UnboundResult;
 542                         }
 543                     }
 544                     Some(import_resolution) if import_resolution.outstanding_references == 0 => {
 545
 546                         fn get_binding(this: &mut Resolver,
 547                                        import_resolution: &ImportResolutionPerNamespace,
 548                                        namespace: Namespace,
 549                                        source: Name)
 550                                        -> NamespaceResult {
 551
 552                             // Import resolutions must be declared with "pub"
 553                             // in order to be exported.
 554                             if !import_resolution[namespace].is_public {
 555                                 return UnboundResult;
 556                             }
 557
 558                             match import_resolution[namespace].target.clone() {
 559                                 None => {
 560                                     return UnboundResult;
 561                                 }
 562                                 Some(Target {
 563                                     target_module,
 564                                     binding,
 565                                     shadowable: _
 566                                 }) => {
 567                                     debug!("(resolving single import) found import in ns {:?}",
 568                                            namespace);
 569                                     let id = import_resolution[namespace].id;
 570                                     // track used imports and extern crates as well
 571                                     this.used_imports.insert((id, namespace));
 572                                     this.record_import_use(id, source);
 573                                     match target_module.def_id() {
 574                                         Some(DefId{krate: kid, ..}) => {
 575                                             this.used_crates.insert(kid);
 576                                         }
 577                                         _ => {}
 578                                     }
 579                                     return BoundResult(target_module, binding);
 580                                 }
 581                             }
 582                         }
 583
 584                         // The name is an import which has been fully
 585                         // resolved. We can, therefore, just follow it.
 586                         if value_result.is_unknown() {
 587                             value_result = get_binding(self.resolver,
 588                                                        import_resolution,
 589                                                        ValueNS,
 590                                                        source);
 591                             value_used_reexport = import_resolution.value_ns.is_public;
 592                         }
 593                         if type_result.is_unknown() {
 594                             type_result = get_binding(self.resolver,
 595                                                       import_resolution,
 596                                                       TypeNS,
 597                                                       source);
 598                             type_used_reexport = import_resolution.type_ns.is_public;
 599                         }
 600
 601                     }
 602                     Some(_) => {
 603                         // If target_module is the same module whose import we are resolving
 604                         // and there it has an unresolved import with the same name as `source`,
 605                         // then the user is actually trying to import an item that is declared
 606                         // in the same scope
 607                         //
 608                         // e.g
 609                         // use self::submodule;
 610                         // pub mod submodule;
 611                         //
 612                         // In this case we continue as if we resolved the import and let the
 613                         // check_for_conflicts_between_imports_and_items call below handle
 614                         // the conflict
 615                         match (module_.def_id(), target_module.def_id()) {
 616                             (Some(id1), Some(id2)) if id1 == id2 => {
 617                                 if value_result.is_unknown() {
 618                                     value_result = UnboundResult;
 619                                 }
 620                                 if type_result.is_unknown() {
 621                                     type_result = UnboundResult;
 622                                 }
 623                             }
 624                             _ => {
 625                                 // The import is unresolved. Bail out.
 626                                 debug!("(resolving single import) unresolved import; bailing out");
 627                                 return ResolveResult::Indeterminate;
 628                             }
 629                         }
 630                     }
 631                 }
 632             }
 633         }
 634
 635         let mut value_used_public = false;
 636         let mut type_used_public = false;
 637
 638         // If we didn't find a result in the type namespace, search the
 639         // external modules.
 640         match type_result {
 641             BoundResult(..) => {}
 642             _ => {
 643                 match target_module.external_module_children.borrow_mut().get(&source).cloned() {
 644                     None => {} // Continue.
 645                     Some(module) => {
 646                         debug!("(resolving single import) found external module");
 647                         // track the module as used.
 648                         match module.def_id() {
 649                             Some(DefId{krate: kid, ..}) => {
 650                                 self.resolver.used_crates.insert(kid);
 651                             }
 652                             _ => {}
 653                         }
 654                         let name_binding = NameBinding::create_from_module(module);
 655                         type_result = BoundResult(target_module.clone(), name_binding);
 656                         type_used_public = true;
 657                     }
 658                 }
 659             }
 660         }
 661
 662         // We've successfully resolved the import. Write the results in.
 663         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 664         let import_resolution = import_resolutions.get_mut(&target).unwrap();
 665
 666         {
 667             let mut check_and_write_import = |namespace, result: &_, used_public: &mut bool| {
 668                 let namespace_name = match namespace {
 669                     TypeNS => "type",
 670                     ValueNS => "value",
 671                 };
 672
 673                 match *result {
 674                     BoundResult(ref target_module, ref name_binding) => {
 675                         debug!("(resolving single import) found {:?} target: {:?}",
 676                                namespace_name,
 677                                name_binding.def());
 678                         self.check_for_conflicting_import(&import_resolution,
 679                                                           directive.span,
 680                                                           target,
 681                                                           namespace);
 682
 683                         self.check_that_import_is_importable(&name_binding,
 684                                                              directive.span,
 685                                                              target);
 686
 687                         import_resolution[namespace] = ImportResolution {
 688                             target: Some(Target::new(target_module.clone(),
 689                                                      name_binding.clone(),
 690                                                      directive.shadowable)),
 691                             id: directive.id,
 692                             is_public: directive.is_public
 693                         };
 694                         *used_public = name_binding.is_public();
 695                     }
 696                     UnboundResult => {
 697                         // Continue.
 698                     }
 699                     UnknownResult => {
 700                         panic!("{:?} result should be known at this point", namespace_name);
 701                     }
 702                 }
 703             };
 704             check_and_write_import(ValueNS, &value_result, &mut value_used_public);
 705             check_and_write_import(TypeNS, &type_result, &mut type_used_public);
 706         }
 707
 708         self.check_for_conflicts_between_imports_and_items(module_,
 709                                                            import_resolution,
 710                                                            directive.span,
 711                                                            target);
 712
 713         if value_result.is_unbound() && type_result.is_unbound() {
 714             let msg = format!("There is no `{}` in `{}`{}",
 715                               source,
 716                               module_to_string(&target_module), lev_suggestion);
 717             return ResolveResult::Failed(Some((directive.span, msg)));
 718         }
 719         let value_used_public = value_used_reexport || value_used_public;
 720         let type_used_public = type_used_reexport || type_used_public;
 721
 722         assert!(import_resolution.outstanding_references >= 1);
 723         import_resolution.outstanding_references -= 1;
 724
 725         // Record what this import resolves to for later uses in documentation,
 726         // this may resolve to either a value or a type, but for documentation
 727         // purposes it's good enough to just favor one over the other.
 728         let value_def_and_priv = import_resolution.value_ns.target.as_ref().map(|target| {
 729             let def = target.binding.def().unwrap();
 730             (def,
 731              if value_used_public {
 732                 lp
 733             } else {
 734                 DependsOn(def.def_id())
 735             })
 736         });
 737         let type_def_and_priv = import_resolution.type_ns.target.as_ref().map(|target| {
 738             let def = target.binding.def().unwrap();
 739             (def,
 740              if type_used_public {
 741                 lp
 742             } else {
 743                 DependsOn(def.def_id())
 744             })
 745         });
 746
 747         let import_lp = LastImport {
 748             value_priv: value_def_and_priv.map(|(_, p)| p),
 749             value_used: Used,
 750             type_priv: type_def_and_priv.map(|(_, p)| p),
 751             type_used: Used,
 752         };
 753
 754         if let Some((def, _)) = value_def_and_priv {
 755             self.resolver.def_map.borrow_mut().insert(directive.id,
 756                                                       PathResolution {
 757                                                           base_def: def,
 758                                                           last_private: import_lp,
 759                                                           depth: 0,
 760                                                       });
 761         }
 762         if let Some((def, _)) = type_def_and_priv {
 763             self.resolver.def_map.borrow_mut().insert(directive.id,
 764                                                       PathResolution {
 765                                                           base_def: def,
 766                                                           last_private: import_lp,
 767                                                           depth: 0,
 768                                                       });
 769         }
 770
 771         debug!("(resolving single import) successfully resolved import");
 772         return ResolveResult::Success(());
 773     }
 774
 775     // Resolves a glob import. Note that this function cannot fail; it either
 776     // succeeds or bails out (as importing * from an empty module or a module
 777     // that exports nothing is valid). target_module is the module we are
 778     // actually importing, i.e., `foo` in `use foo::*`.
 779     fn resolve_glob_import(&mut self,
 780                            module_: &Module,
 781                            target_module: Rc<Module>,
 782                            import_directive: &ImportDirective,
 783                            lp: LastPrivate)
 784                            -> ResolveResult<()> {
 785         let id = import_directive.id;
 786         let is_public = import_directive.is_public;
 787
 788         // This function works in a highly imperative manner; it eagerly adds
 789         // everything it can to the list of import resolutions of the module
 790         // node.
 791         debug!("(resolving glob import) resolving glob import {}", id);
 792
 793         // We must bail out if the node has unresolved imports of any kind
 794         // (including globs).
 795         if (*target_module).pub_count.get() > 0 {
 796             debug!("(resolving glob import) target module has unresolved pub imports; bailing out");
 797             return ResolveResult::Indeterminate;
 798         }
 799
 800         // Add all resolved imports from the containing module.
 801         let import_resolutions = target_module.import_resolutions.borrow();
 802
 803         if module_.import_resolutions.borrow_state() != ::std::cell::BorrowState::Unused {
 804             // In this case, target_module == module_
 805             // This means we are trying to glob import a module into itself,
 806             // and it is a no-go
 807             debug!("(resolving glob imports) target module is current module; giving up");
 808             return ResolveResult::Failed(Some((import_directive.span,
 809                                                "Cannot glob-import a module into itself.".into())));
 810         }
 811
 812         for (name, target_import_resolution) in import_resolutions.iter() {
 813             debug!("(resolving glob import) writing module resolution {} into `{}`",
 814                    *name,
 815                    module_to_string(module_));
 816
 817             // Here we merge two import resolutions.
 818             let mut import_resolutions = module_.import_resolutions.borrow_mut();
 819             let mut dest_import_resolution = import_resolutions.entry(*name).or_insert_with(|| {
 820                 ImportResolutionPerNamespace::new(id, is_public)
 821             });
 822
 823             for &ns in [TypeNS, ValueNS].iter() {
 824                 match target_import_resolution[ns].target {
 825                     Some(ref target) if target_import_resolution[ns].is_public => {
 826                         self.check_for_conflicting_import(&dest_import_resolution,
 827                                                           import_directive.span,
 828                                                           *name,
 829                                                           ns);
 830                         dest_import_resolution[ns] = ImportResolution {
 831                             id: id, is_public: is_public, target: Some(target.clone())
 832                         };
 833                     }
 834                     _ => {}
 835                 }
 836             }
 837         }
 838
 839         // Add all children from the containing module.
 840         build_reduced_graph::populate_module_if_necessary(self.resolver, &target_module);
 841
 842         for (&name, name_bindings) in target_module.children.borrow().iter() {
 843             self.merge_import_resolution(module_,
 844                                          target_module.clone(),
 845                                          import_directive,
 846                                          name,
 847                                          name_bindings.clone());
 848
 849         }
 850
 851         // Record the destination of this import
 852         if let Some(did) = target_module.def_id() {
 853             self.resolver.def_map.borrow_mut().insert(id,
 854                                                       PathResolution {
 855                                                           base_def: DefMod(did),
 856                                                           last_private: lp,
 857                                                           depth: 0,
 858                                                       });
 859         }
 860
 861         debug!("(resolving glob import) successfully resolved import");
 862         return ResolveResult::Success(());
 863     }
 864
 865     fn merge_import_resolution(&mut self,
 866                                module_: &Module,
 867                                containing_module: Rc<Module>,
 868                                import_directive: &ImportDirective,
 869                                name: Name,
 870                                name_bindings: NameBindings) {
 871         let id = import_directive.id;
 872         let is_public = import_directive.is_public;
 873
 874         let mut import_resolutions = module_.import_resolutions.borrow_mut();
 875         let dest_import_resolution = import_resolutions.entry(name).or_insert_with(|| {
 876             ImportResolutionPerNamespace::new(id, is_public)
 877         });
 878
 879         debug!("(resolving glob import) writing resolution `{}` in `{}` to `{}`",
 880                name,
 881                module_to_string(&*containing_module),
 882                module_to_string(module_));
 883
 884         // Merge the child item into the import resolution.
 885         // pub_err makes sure we don't give the same error twice.
 886         let mut pub_err = false;
 887         {
 888             let mut merge_child_item = |namespace| {
 889                 if !pub_err && is_public &&
 890                         name_bindings[namespace].defined_with(DefModifiers::PRIVATE_VARIANT) {
 891                     let msg = format!("variant `{}` is private, and cannot be reexported (error \
 892                                        E0364), consider declaring its enum as `pub`", name);
 893                     self.resolver.session.add_lint(lint::builtin::PRIVATE_IN_PUBLIC,
 894                                                    import_directive.id,
 895                                                    import_directive.span,
 896                                                    msg);
 897                     pub_err = true;
 898                 }
 899
 900                 let modifier = DefModifiers::IMPORTABLE | DefModifiers::PUBLIC;
 901                 if name_bindings[namespace].defined_with(modifier) {
 902                     let namespace_name = match namespace {
 903                         TypeNS => "type",
 904                         ValueNS => "value",
 905                     };
 906                     debug!("(resolving glob import) ... for {} target", namespace_name);
 907                     if dest_import_resolution.shadowable(namespace) == Shadowable::Never {
 908                         let msg = format!("a {} named `{}` has already been imported in this \
 909                                            module",
 910                                           namespace_name,
 911                                           name);
 912                         span_err!(self.resolver.session,
 913                                   import_directive.span,
 914                                   E0251,
 915                                   "{}",
 916                                   msg);
 917                     } else {
 918                         dest_import_resolution[namespace] = ImportResolution {
 919                             target: Some(Target::new(containing_module.clone(),
 920                                                      name_bindings[namespace].clone(),
 921                                                      import_directive.shadowable)),
 922                             id: id,
 923                             is_public: is_public
 924                         };
 925                     }
 926                 } else {
 927                     // FIXME #30159: This is required for backwards compatability.
 928                     dest_import_resolution[namespace].is_public |= is_public;
 929                 }
 930             };
 931             merge_child_item(ValueNS);
 932             merge_child_item(TypeNS);
 933         }
 934
 935         self.check_for_conflicts_between_imports_and_items(module_,
 936                                                            dest_import_resolution,
 937                                                            import_directive.span,
 938                                                            name);
 939     }
 940
 941     /// Checks that imported names and items don't have the same name.
 942     fn check_for_conflicting_import(&mut self,
 943                                     import_resolution: &ImportResolutionPerNamespace,
 944                                     import_span: Span,
 945                                     name: Name,
 946                                     namespace: Namespace) {
 947         let target = &import_resolution[namespace].target;
 948         debug!("check_for_conflicting_import: {}; target exists: {}",
 949                name,
 950                target.is_some());
 951
 952         match *target {
 953             Some(ref target) if target.shadowable != Shadowable::Always => {
 954                 let ns_word = match namespace {
 955                     TypeNS => {
 956                         match target.binding.module() {
 957                             Some(ref module) if module.is_normal() => "module",
 958                             Some(ref module) if module.is_trait() => "trait",
 959                             _ => "type",
 960                         }
 961                     }
 962                     ValueNS => "value",
 963                 };
 964                 let use_id = import_resolution[namespace].id;
 965                 let item = self.resolver.ast_map.expect_item(use_id);
 966                 let mut err = struct_span_err!(self.resolver.session,
 967                                                import_span,
 968                                                E0252,
 969                                                "a {} named `{}` has already been imported \
 970                                                 in this module",
 971                                                ns_word,
 972                                                name);
 973                 span_note!(&mut err,
 974                            item.span,
 975                            "previous import of `{}` here",
 976                            name);
 977                 err.emit();
 978             }
 979             Some(_) | None => {}
 980         }
 981     }
 982
 983     /// Checks that an import is actually importable
 984     fn check_that_import_is_importable(&mut self,
 985                                        name_binding: &NameBinding,
 986                                        import_span: Span,
 987                                        name: Name) {
 988         if !name_binding.defined_with(DefModifiers::IMPORTABLE) {
 989             let msg = format!("`{}` is not directly importable", name);
 990             span_err!(self.resolver.session, import_span, E0253, "{}", &msg[..]);
 991         }
 992     }
 993
 994     /// Checks that imported names and items don't have the same name.
 995     fn check_for_conflicts_between_imports_and_items(&mut self,
 996                                                      module: &Module,
 997                                                      import: &ImportResolutionPerNamespace,
 998                                                      import_span: Span,
 999                                                      name: Name) {
1000         // First, check for conflicts between imports and `extern crate`s.
1001         if module.external_module_children
1002                  .borrow()
1003                  .contains_key(&name) {
1004             match import.type_ns.target {
1005                 Some(ref target) if target.shadowable != Shadowable::Always => {
1006                     let msg = format!("import `{0}` conflicts with imported crate in this module \
1007                                        (maybe you meant `use {0}::*`?)",
1008                                       name);
1009                     span_err!(self.resolver.session, import_span, E0254, "{}", &msg[..]);
1010                 }
1011                 Some(_) | None => {}
1012             }
1013         }
1014
1015         // Check for item conflicts.
1016         let children = module.children.borrow();
1017         let name_bindings = match children.get(&name) {
1018             None => {
1019                 // There can't be any conflicts.
1020                 return;
1021             }
1022             Some(ref name_bindings) => (*name_bindings).clone(),
1023         };
1024
1025         match import.value_ns.target {
1026             Some(ref target) if target.shadowable != Shadowable::Always => {
1027                 if let Some(ref value) = *name_bindings.value_ns.borrow() {
1028                     let mut err = struct_span_err!(self.resolver.session,
1029                                                    import_span,
1030                                                    E0255,
1031                                                    "import `{}` conflicts with \
1032                                                     value in this module",
1033                                                    name);
1034                     if let Some(span) = value.span {
1035                         err.span_note(span, "conflicting value here");
1036                     }
1037                     err.emit();
1038                 }
1039             }
1040             Some(_) | None => {}
1041         }
1042
1043         match import.type_ns.target {
1044             Some(ref target) if target.shadowable != Shadowable::Always => {
1045                 if let Some(ref ty) = *name_bindings.type_ns.borrow() {
1046                     let (what, note) = match ty.module() {
1047                         Some(ref module) if module.is_normal() =>
1048                             ("existing submodule", "note conflicting module here"),
1049                         Some(ref module) if module.is_trait() =>
1050                             ("trait in this module", "note conflicting trait here"),
1051                         _ => ("type in this module", "note conflicting type here"),
1052                     };
1053                     let mut err = struct_span_err!(self.resolver.session,
1054                                                    import_span,
1055                                                    E0256,
1056                                                    "import `{}` conflicts with {}",
1057                                                    name,
1058                                                    what);
1059                     if let Some(span) = ty.span {
1060                         err.span_note(span, note);
1061                     }
1062                     err.emit();
1063                 }
1064             }
1065             Some(_) | None => {}
1066         }
1067     }
1068 }
1069
1070 fn import_path_to_string(names: &[Name], subclass: ImportDirectiveSubclass) -> String {
1071     if names.is_empty() {
1072         import_directive_subclass_to_string(subclass)
1073     } else {
1074         (format!("{}::{}",
1075                  names_to_string(names),
1076                  import_directive_subclass_to_string(subclass)))
1077             .to_string()
1078     }
1079 }
1080
1081 fn import_directive_subclass_to_string(subclass: ImportDirectiveSubclass) -> String {
1082     match subclass {
1083         SingleImport(_, source) => source.to_string(),
1084         GlobImport => "*".to_string(),
1085     }
1086 }
1087
1088 pub fn resolve_imports(resolver: &mut Resolver) {
1089     let mut import_resolver = ImportResolver { resolver: resolver };
1090     import_resolver.resolve_imports();
1091 }