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.
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.
11 use self::ImportDirectiveSubclass::*;
14 use Namespace::{self, TypeNS, ValueNS};
15 use {NameBinding, NameBindingKind, PrivacyError, ToNameBinding};
19 use UseLexicalScopeFlag::DontUseLexicalScope;
20 use {names_to_string, module_to_string};
21 use {resolve_error, ResolutionError};
24 use rustc::lint::builtin::PRIVATE_IN_PUBLIC;
25 use rustc::hir::def::*;
27 use syntax::ast::{NodeId, Name};
28 use syntax::util::lev_distance::find_best_match_for_name;
29 use syntax_pos::{Span, DUMMY_SP};
31 use std::cell::{Cell, RefCell};
33 impl<'a> Resolver<'a> {
34 pub fn resolve_imports(&mut self) {
35 ImportResolver { resolver: self }.resolve_imports();
39 /// Contains data for specific types of import directives.
40 #[derive(Clone, Debug)]
41 pub enum ImportDirectiveSubclass {
45 type_determined: Cell<bool>,
46 value_determined: Cell<bool>,
48 GlobImport { is_prelude: bool },
51 impl ImportDirectiveSubclass {
52 pub fn single(target: Name, source: Name) -> Self {
56 type_determined: Cell::new(false),
57 value_determined: Cell::new(false),
62 /// One import directive.
63 #[derive(Debug,Clone)]
64 pub struct ImportDirective<'a> {
66 module_path: Vec<Name>,
67 target_module: Cell<Option<Module<'a>>>, // the resolution of `module_path`
68 subclass: ImportDirectiveSubclass,
70 vis: ty::Visibility, // see note in ImportResolutionPerNamespace about how to use this
73 impl<'a> ImportDirective<'a> {
74 pub fn is_glob(&self) -> bool {
75 match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
79 #[derive(Clone, Default)]
80 /// Records information about the resolution of a name in a namespace of a module.
81 pub struct NameResolution<'a> {
82 /// The single imports that define the name in the namespace.
83 single_imports: SingleImports<'a>,
84 /// The least shadowable known binding for this name, or None if there are no known bindings.
85 pub binding: Option<&'a NameBinding<'a>>,
86 duplicate_globs: Vec<&'a NameBinding<'a>>,
89 #[derive(Clone, Debug)]
90 enum SingleImports<'a> {
91 /// No single imports can define the name in the namespace.
93 /// Only the given single import can define the name in the namespace.
94 MaybeOne(&'a ImportDirective<'a>),
95 /// At least one single import will define the name in the namespace.
99 impl<'a> Default for SingleImports<'a> {
100 fn default() -> Self {
105 impl<'a> SingleImports<'a> {
106 fn add_directive(&mut self, directive: &'a ImportDirective<'a>) {
108 SingleImports::None => *self = SingleImports::MaybeOne(directive),
109 // If two single imports can define the name in the namespace, we can assume that at
110 // least one of them will define it since otherwise both would have to define only one
111 // namespace, leading to a duplicate error.
112 SingleImports::MaybeOne(_) => *self = SingleImports::AtLeastOne,
113 SingleImports::AtLeastOne => {}
117 fn directive_failed(&mut self) {
119 SingleImports::None => unreachable!(),
120 SingleImports::MaybeOne(_) => *self = SingleImports::None,
121 SingleImports::AtLeastOne => {}
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| match self.single_imports {
130 SingleImports::None => Some(binding),
131 _ if !binding.is_glob_import() => Some(binding),
132 _ => None, // The binding could be shadowed by a single import, so it is not known.
136 // Returns Some(the resolution of the name), or None if the resolution depends
137 // on whether more globs can define the name.
138 fn try_result(&self, ns: Namespace, allow_private_imports: bool)
139 -> Option<ResolveResult<&'a NameBinding<'a>>> {
141 Some(binding) if !binding.is_glob_import() =>
142 return Some(Success(binding)),
143 _ => {} // Items and single imports are not shadowable
146 // Check if a single import can still define the name.
147 match self.single_imports {
148 SingleImports::None => {},
149 SingleImports::AtLeastOne => return Some(Indeterminate),
150 SingleImports::MaybeOne(directive) => {
151 // If (1) we don't allow private imports, (2) no public single import can define
152 // the name, and (3) no public glob has defined the name, the resolution depends
153 // on whether more globs can define the name.
154 if !allow_private_imports && directive.vis != ty::Visibility::Public &&
155 !self.binding.map(NameBinding::is_pseudo_public).unwrap_or(false) {
159 let target_module = match directive.target_module.get() {
160 Some(target_module) => target_module,
161 None => return Some(Indeterminate),
163 let name = match directive.subclass {
164 SingleImport { source, .. } => source,
165 GlobImport { .. } => unreachable!(),
167 match target_module.resolve_name(name, ns, false) {
169 _ => return Some(Indeterminate),
174 self.binding.map(Success)
178 impl<'a> ::ModuleS<'a> {
179 fn resolution(&self, name: Name, ns: Namespace) -> &'a RefCell<NameResolution<'a>> {
180 *self.resolutions.borrow_mut().entry((name, ns))
181 .or_insert_with(|| self.arenas.alloc_name_resolution())
184 pub fn resolve_name(&self, name: Name, ns: Namespace, allow_private_imports: bool)
185 -> ResolveResult<&'a NameBinding<'a>> {
186 let resolution = self.resolution(name, ns);
187 let resolution = match resolution.borrow_state() {
188 ::std::cell::BorrowState::Unused => resolution.borrow_mut(),
189 _ => return Failed(None), // This happens when there is a cycle of imports
192 if let Some(result) = resolution.try_result(ns, allow_private_imports) {
193 // If the resolution doesn't depend on glob definability, check privacy and return.
194 return result.and_then(|binding| {
195 let allowed = allow_private_imports || !binding.is_import() ||
196 binding.is_pseudo_public();
197 if allowed { Success(binding) } else { Failed(None) }
201 // Check if the globs are determined
202 for directive in self.globs.borrow().iter() {
203 if !allow_private_imports && directive.vis != ty::Visibility::Public { continue }
204 match directive.target_module.get() {
205 None => return Indeterminate,
206 Some(target_module) => match target_module.resolve_name(name, ns, false) {
207 Indeterminate => return Indeterminate,
217 impl<'a> Resolver<'a> {
218 // Add an import directive to the current module.
219 pub fn add_import_directive(&mut self,
220 module_path: Vec<Name>,
221 subclass: ImportDirectiveSubclass,
224 vis: ty::Visibility) {
225 let directive = self.arenas.alloc_import_directive(ImportDirective {
226 module_path: module_path,
227 target_module: Cell::new(None),
234 self.current_module.unresolved_imports.borrow_mut().push(directive);
235 match directive.subclass {
236 SingleImport { target, .. } => {
237 for &ns in &[ValueNS, TypeNS] {
238 let mut resolution = self.current_module.resolution(target, ns).borrow_mut();
239 resolution.single_imports.add_directive(directive);
242 // We don't add prelude imports to the globs since they only affect lexical scopes,
243 // which are not relevant to import resolution.
244 GlobImport { is_prelude: true } => {}
245 GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
249 // Given a binding and an import directive that resolves to it,
250 // return the corresponding binding defined by the import directive.
251 fn import(&mut self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
254 kind: NameBindingKind::Import {
256 directive: directive,
258 span: directive.span,
263 // Define the name or return the existing binding if there is a collision.
264 pub fn try_define<T>(&mut self, module: Module<'a>, name: Name, ns: Namespace, binding: T)
265 -> Result<(), &'a NameBinding<'a>>
266 where T: ToNameBinding<'a>
268 let binding = self.arenas.alloc_name_binding(binding.to_name_binding());
269 self.update_resolution(module, name, ns, |_, resolution| {
270 if let Some(old_binding) = resolution.binding {
271 if binding.is_glob_import() {
272 resolution.duplicate_globs.push(binding);
273 } else if old_binding.is_glob_import() {
274 resolution.duplicate_globs.push(old_binding);
275 resolution.binding = Some(binding);
277 return Err(old_binding);
280 resolution.binding = Some(binding);
287 // Use `f` to mutate the resolution of the name in the module.
288 // If the resolution becomes a success, define it in the module's glob importers.
289 fn update_resolution<T, F>(&mut self, module: Module<'a>, name: Name, ns: Namespace, f: F) -> T
290 where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
292 // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
293 // during which the resolution might end up getting re-defined via a glob cycle.
294 let (new_binding, t) = {
295 let mut resolution = &mut *module.resolution(name, ns).borrow_mut();
296 let was_known = resolution.binding().is_some();
298 let t = f(self, resolution);
300 if was_known { return t; }
301 match resolution.binding() {
302 Some(binding) => (binding, t),
307 // Define `new_binding` in `module`s glob importers.
308 if new_binding.is_importable() && new_binding.is_pseudo_public() {
309 for &(importer, directive) in module.glob_importers.borrow_mut().iter() {
310 let imported_binding = self.import(new_binding, directive);
311 let _ = self.try_define(importer, name, ns, imported_binding);
319 struct ImportResolvingError<'a> {
320 /// Module where the error happened
321 source_module: Module<'a>,
322 import_directive: &'a ImportDirective<'a>,
327 struct ImportResolver<'a, 'b: 'a> {
328 resolver: &'a mut Resolver<'b>,
331 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
332 type Target = Resolver<'b>;
333 fn deref(&self) -> &Resolver<'b> {
338 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
339 fn deref_mut(&mut self) -> &mut Resolver<'b> {
344 impl<'a, 'b: 'a> ty::NodeIdTree for ImportResolver<'a, 'b> {
345 fn is_descendant_of(&self, node: NodeId, ancestor: NodeId) -> bool {
346 self.resolver.is_descendant_of(node, ancestor)
350 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
353 // This is a fixed-point algorithm. We resolve imports until our efforts
354 // are stymied by an unresolved import; then we bail out of the current
355 // module and continue. We terminate successfully once no more imports
356 // remain or unsuccessfully when no forward progress in resolving imports
359 /// Resolves all imports for the crate. This method performs the fixed-
361 fn resolve_imports(&mut self) {
363 let mut prev_unresolved_imports = 0;
364 let mut errors = Vec::new();
367 debug!("(resolving imports) iteration {}, {} imports left", i, self.unresolved_imports);
369 // Attempt to resolve imports in all local modules.
370 for module in self.arenas.local_modules().iter() {
371 self.current_module = module;
372 self.resolve_imports_in_current_module(&mut errors);
375 if self.unresolved_imports == 0 {
376 debug!("(resolving imports) success");
377 for module in self.arenas.local_modules().iter() {
378 self.finalize_resolutions_in(module, false);
383 if self.unresolved_imports == prev_unresolved_imports {
385 // Report unresolved imports only if no hard error was already reported
386 // to avoid generating multiple errors on the same import.
387 // Imports that are still indeterminate at this point are actually blocked
388 // by errored imports, so there is no point reporting them.
389 for module in self.arenas.local_modules().iter() {
390 self.finalize_resolutions_in(module, errors.len() == 0);
393 self.import_resolving_error(e)
399 prev_unresolved_imports = self.unresolved_imports;
403 // Define a "dummy" resolution containing a Def::Err as a placeholder for a
405 fn import_dummy_binding(&mut self,
406 source_module: Module<'b>,
407 directive: &'b ImportDirective<'b>) {
408 if let SingleImport { target, .. } = directive.subclass {
409 let dummy_binding = self.arenas.alloc_name_binding(NameBinding {
410 kind: NameBindingKind::Def(Def::Err),
412 vis: ty::Visibility::Public,
414 let dummy_binding = self.import(dummy_binding, directive);
416 let _ = self.try_define(source_module, target, ValueNS, dummy_binding.clone());
417 let _ = self.try_define(source_module, target, TypeNS, dummy_binding);
421 /// Resolves an `ImportResolvingError` into the correct enum discriminant
422 /// and passes that on to `resolve_error`.
423 fn import_resolving_error(&mut self, e: ImportResolvingError<'b>) {
424 // If the error is a single failed import then create a "fake" import
425 // resolution for it so that later resolve stages won't complain.
426 self.import_dummy_binding(e.source_module, e.import_directive);
427 let path = import_path_to_string(&e.import_directive.module_path,
428 &e.import_directive.subclass);
429 resolve_error(self.resolver,
431 ResolutionError::UnresolvedImport(Some((&path, &e.help))));
434 /// Attempts to resolve imports for the given module only.
435 fn resolve_imports_in_current_module(&mut self, errors: &mut Vec<ImportResolvingError<'b>>) {
436 let mut imports = Vec::new();
437 let mut unresolved_imports = self.current_module.unresolved_imports.borrow_mut();
438 ::std::mem::swap(&mut imports, &mut unresolved_imports);
440 for import_directive in imports {
441 match self.resolve_import(&import_directive) {
443 let (span, help) = match err {
444 Some((span, msg)) => (span, format!(". {}", msg)),
445 None => (import_directive.span, String::new()),
447 errors.push(ImportResolvingError {
448 source_module: self.current_module,
449 import_directive: import_directive,
454 Indeterminate => unresolved_imports.push(import_directive),
456 // Decrement the count of unresolved imports.
457 assert!(self.unresolved_imports >= 1);
458 self.unresolved_imports -= 1;
464 /// Attempts to resolve the given import. The return value indicates
465 /// failure if we're certain the name does not exist, indeterminate if we
466 /// don't know whether the name exists at the moment due to other
467 /// currently-unresolved imports, or success if we know the name exists.
468 /// If successful, the resolved bindings are written into the module.
469 fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
470 debug!("(resolving import for module) resolving import `{}::...` in `{}`",
471 names_to_string(&directive.module_path),
472 module_to_string(self.current_module));
474 let target_module = match directive.target_module.get() {
475 Some(module) => module,
476 _ => match self.resolve_module_path(&directive.module_path,
479 Success(module) => module,
480 Indeterminate => return Indeterminate,
481 Failed(err) => return Failed(err),
485 directive.target_module.set(Some(target_module));
486 let (source, target, value_determined, type_determined) = match directive.subclass {
487 SingleImport { source, target, ref value_determined, ref type_determined } =>
488 (source, target, value_determined, type_determined),
489 GlobImport { .. } => return self.resolve_glob_import(target_module, directive),
492 // We need to resolve both namespaces for this to succeed.
493 let value_result = self.resolve_name_in_module(target_module, source, ValueNS, false, true);
494 let type_result = self.resolve_name_in_module(target_module, source, TypeNS, false, true);
496 let module = self.current_module;
497 let mut privacy_error = true;
498 for &(ns, result, determined) in &[(ValueNS, &value_result, value_determined),
499 (TypeNS, &type_result, type_determined)] {
501 Failed(..) if !determined.get() => {
502 determined.set(true);
503 self.update_resolution(module, target, ns, |_, resolution| {
504 resolution.single_imports.directive_failed()
507 Success(binding) if !binding.is_importable() => {
508 let msg = format!("`{}` is not directly importable", target);
509 struct_span_err!(self.session, directive.span, E0253, "{}", &msg)
510 .span_label(directive.span, &format!("cannot be imported directly"))
512 // Do not import this illegal binding. Import a dummy binding and pretend
513 // everything is fine
514 self.import_dummy_binding(module, directive);
517 Success(binding) if !self.is_accessible(binding.vis) => {}
518 Success(binding) if !determined.get() => {
519 determined.set(true);
520 let imported_binding = self.import(binding, directive);
521 let conflict = self.try_define(module, target, ns, imported_binding);
522 if let Err(old_binding) = conflict {
523 let binding = &self.import(binding, directive);
524 self.report_conflict(module, target, ns, binding, old_binding);
526 privacy_error = false;
528 Success(_) => privacy_error = false,
533 match (&value_result, &type_result) {
534 (&Indeterminate, _) | (_, &Indeterminate) => return Indeterminate,
535 (&Failed(_), &Failed(_)) => {
536 let resolutions = target_module.resolutions.borrow();
537 let names = resolutions.iter().filter_map(|(&(ref name, _), resolution)| {
538 if *name == source { return None; } // Never suggest the same name
539 match *resolution.borrow() {
540 NameResolution { binding: Some(_), .. } => Some(name),
541 NameResolution { single_imports: SingleImports::None, .. } => None,
545 let lev_suggestion = match find_best_match_for_name(names, &source.as_str(), None) {
546 Some(name) => format!(". Did you mean to use `{}`?", name),
547 None => "".to_owned(),
549 let module_str = module_to_string(target_module);
550 let msg = if &module_str == "???" {
551 format!("There is no `{}` in the crate root{}", source, lev_suggestion)
553 format!("There is no `{}` in `{}`{}", source, module_str, lev_suggestion)
555 return Failed(Some((directive.span, msg)));
561 for &(ns, result) in &[(ValueNS, &value_result), (TypeNS, &type_result)] {
562 let binding = match *result { Success(binding) => binding, _ => continue };
563 self.privacy_errors.push(PrivacyError(directive.span, source, binding));
564 let imported_binding = self.import(binding, directive);
565 let _ = self.try_define(module, target, ns, imported_binding);
569 match (&value_result, &type_result) {
570 (&Success(binding), _) if !binding.pseudo_vis().is_at_least(directive.vis, self) &&
571 self.is_accessible(binding.vis) => {
572 let msg = format!("`{}` is private, and cannot be reexported", source);
573 let note_msg = format!("consider marking `{}` as `pub` in the imported module",
575 struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
576 .span_note(directive.span, ¬e_msg)
580 (_, &Success(binding)) if !binding.pseudo_vis().is_at_least(directive.vis, self) &&
581 self.is_accessible(binding.vis) => {
582 if binding.is_extern_crate() {
583 let msg = format!("extern crate `{}` is private, and cannot be reexported \
584 (error E0364), consider declaring with `pub`",
586 self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
588 let mut err = struct_span_err!(self.session, directive.span, E0365,
589 "`{}` is private, and cannot be reexported",
591 err.span_label(directive.span, &format!("reexport of private `{}`", source));
592 err.note(&format!("consider declaring type or module `{}` with `pub`", source));
600 // Record what this import resolves to for later uses in documentation,
601 // this may resolve to either a value or a type, but for documentation
602 // purposes it's good enough to just favor one over the other.
603 let def = match type_result.success().and_then(NameBinding::def) {
605 None => value_result.success().and_then(NameBinding::def).unwrap(),
607 let path_resolution = PathResolution::new(def);
608 self.def_map.insert(directive.id, path_resolution);
610 debug!("(resolving single import) successfully resolved import");
614 // Resolves a glob import. Note that this function cannot fail; it either
615 // succeeds or bails out (as importing * from an empty module or a module
616 // that exports nothing is valid). target_module is the module we are
617 // actually importing, i.e., `foo` in `use foo::*`.
618 fn resolve_glob_import(&mut self, target_module: Module<'b>, directive: &'b ImportDirective<'b>)
619 -> ResolveResult<()> {
620 if let Some(Def::Trait(_)) = target_module.def {
621 self.session.span_err(directive.span, "items in traits are not importable.");
624 let module = self.current_module;
625 if module.def_id() == target_module.def_id() {
626 // This means we are trying to glob import a module into itself, and it is a no-go
627 let msg = "Cannot glob-import a module into itself.".into();
628 return Failed(Some((directive.span, msg)));
630 self.populate_module_if_necessary(target_module);
632 if let GlobImport { is_prelude: true } = directive.subclass {
633 self.prelude = Some(target_module);
637 // Add to target_module's glob_importers
638 target_module.glob_importers.borrow_mut().push((module, directive));
640 // Ensure that `resolutions` isn't borrowed during `try_define`,
641 // since it might get updated via a glob cycle.
642 let bindings = target_module.resolutions.borrow().iter().filter_map(|(name, resolution)| {
643 resolution.borrow().binding().map(|binding| (*name, binding))
644 }).collect::<Vec<_>>();
645 for ((name, ns), binding) in bindings {
646 if binding.is_importable() && binding.is_pseudo_public() {
647 let imported_binding = self.import(binding, directive);
648 let _ = self.try_define(module, name, ns, imported_binding);
652 // Record the destination of this import
653 if let Some(did) = target_module.def_id() {
654 let resolution = PathResolution::new(Def::Mod(did));
655 self.def_map.insert(directive.id, resolution);
658 debug!("(resolving glob import) successfully resolved import");
662 // Miscellaneous post-processing, including recording reexports, reporting conflicts,
663 // reporting the PRIVATE_IN_PUBLIC lint, and reporting unresolved imports.
664 fn finalize_resolutions_in(&mut self, module: Module<'b>, report_unresolved_imports: bool) {
665 // Since import resolution is finished, globs will not define any more names.
666 *module.globs.borrow_mut() = Vec::new();
668 let mut reexports = Vec::new();
669 for (&(name, ns), resolution) in module.resolutions.borrow().iter() {
670 let resolution = resolution.borrow();
671 let binding = match resolution.binding {
672 Some(binding) => binding,
677 for duplicate_glob in resolution.duplicate_globs.iter() {
678 // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
679 if !binding.is_import() {
680 if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
681 if binding.is_import() { continue }
685 self.report_conflict(module, name, ns, duplicate_glob, binding);
688 if binding.vis == ty::Visibility::Public &&
689 (binding.is_import() || binding.is_extern_crate()) {
690 if let Some(def) = binding.def() {
691 reexports.push(Export { name: name, def_id: def.def_id() });
695 if let NameBindingKind::Import { binding: orig_binding, directive, .. } = binding.kind {
696 if ns == TypeNS && orig_binding.is_variant() &&
697 !orig_binding.vis.is_at_least(binding.vis, self) {
698 let msg = format!("variant `{}` is private, and cannot be reexported \
699 (error E0364), consider declaring its enum as `pub`",
701 self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, binding.span, msg);
706 if reexports.len() > 0 {
707 if let Some(def_id) = module.def_id() {
708 let node_id = self.definitions.as_local_node_id(def_id).unwrap();
709 self.export_map.insert(node_id, reexports);
713 if report_unresolved_imports {
714 for import in module.unresolved_imports.borrow().iter() {
715 resolve_error(self.resolver, import.span, ResolutionError::UnresolvedImport(None));
722 fn import_path_to_string(names: &[Name], subclass: &ImportDirectiveSubclass) -> String {
723 if names.is_empty() {
724 import_directive_subclass_to_string(subclass)
727 names_to_string(names),
728 import_directive_subclass_to_string(subclass)))
733 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
735 SingleImport { source, .. } => source.to_string(),
736 GlobImport { .. } => "*".to_string(),