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<'a> {
45 value_result: Cell<Result<&'a NameBinding<'a>, bool /* determined? */>>,
46 type_result: Cell<Result<&'a NameBinding<'a>, bool /* determined? */>>,
48 GlobImport { is_prelude: bool },
51 impl<'a> ImportDirectiveSubclass<'a> {
52 pub fn single(target: Name, source: Name) -> Self {
56 type_result: Cell::new(Err(false)),
57 value_result: Cell::new(Err(false)),
62 /// One import directive.
63 #[derive(Debug,Clone)]
64 pub struct ImportDirective<'a> {
67 module_path: Vec<Name>,
68 target_module: Cell<Option<Module<'a>>>, // the resolution of `module_path`
69 subclass: ImportDirectiveSubclass<'a>,
71 vis: ty::Visibility, // see note in ImportResolutionPerNamespace about how to use this
74 impl<'a> ImportDirective<'a> {
75 pub fn is_glob(&self) -> bool {
76 match self.subclass { ImportDirectiveSubclass::GlobImport { .. } => true, _ => false }
80 #[derive(Clone, Default)]
81 /// Records information about the resolution of a name in a namespace of a module.
82 pub struct NameResolution<'a> {
83 /// The single imports that define the name in the namespace.
84 single_imports: SingleImports<'a>,
85 /// The least shadowable known binding for this name, or None if there are no known bindings.
86 pub binding: Option<&'a NameBinding<'a>>,
87 duplicate_globs: Vec<&'a NameBinding<'a>>,
90 #[derive(Clone, Debug)]
91 enum SingleImports<'a> {
92 /// No single imports can define the name in the namespace.
94 /// Only the given single import can define the name in the namespace.
95 MaybeOne(&'a ImportDirective<'a>),
96 /// At least one single import will define the name in the namespace.
100 impl<'a> Default for SingleImports<'a> {
101 fn default() -> Self {
106 impl<'a> SingleImports<'a> {
107 fn add_directive(&mut self, directive: &'a ImportDirective<'a>) {
109 SingleImports::None => *self = SingleImports::MaybeOne(directive),
110 // If two single imports can define the name in the namespace, we can assume that at
111 // least one of them will define it since otherwise both would have to define only one
112 // namespace, leading to a duplicate error.
113 SingleImports::MaybeOne(_) => *self = SingleImports::AtLeastOne,
114 SingleImports::AtLeastOne => {}
118 fn directive_failed(&mut self) {
120 SingleImports::None => unreachable!(),
121 SingleImports::MaybeOne(_) => *self = SingleImports::None,
122 SingleImports::AtLeastOne => {}
127 impl<'a> NameResolution<'a> {
128 // Returns the binding for the name if it is known or None if it not known.
129 fn binding(&self) -> Option<&'a NameBinding<'a>> {
130 self.binding.and_then(|binding| match self.single_imports {
131 SingleImports::None => Some(binding),
132 _ if !binding.is_glob_import() => Some(binding),
133 _ => None, // The binding could be shadowed by a single import, so it is not known.
138 impl<'a> Resolver<'a> {
139 fn resolution(&self, module: Module<'a>, name: Name, ns: Namespace)
140 -> &'a RefCell<NameResolution<'a>> {
141 *module.resolutions.borrow_mut().entry((name, ns))
142 .or_insert_with(|| self.arenas.alloc_name_resolution())
145 /// Attempts to resolve the supplied name in the given module for the given namespace.
146 /// If successful, returns the binding corresponding to the name.
147 pub fn resolve_name_in_module(&mut self,
151 allow_private_imports: bool,
152 record_used: Option<Span>)
153 -> ResolveResult<&'a NameBinding<'a>> {
154 self.populate_module_if_necessary(module);
156 let resolution = self.resolution(module, name, ns);
157 let resolution = match resolution.borrow_state() {
158 ::std::cell::BorrowState::Unused => resolution.borrow_mut(),
159 _ => return Failed(None), // This happens when there is a cycle of imports
162 if let Some(result) = self.try_result(&resolution, ns, allow_private_imports) {
163 // If the resolution doesn't depend on glob definability, check privacy and return.
164 return result.and_then(|binding| {
165 if !allow_private_imports && binding.is_import() && !binding.is_pseudo_public() {
168 if let Some(span) = record_used {
169 self.record_use(name, ns, binding);
170 if !self.is_accessible(binding.vis) {
171 self.privacy_errors.push(PrivacyError(span, name, binding));
178 // Check if the globs are determined
179 for directive in module.globs.borrow().iter() {
180 if !allow_private_imports && directive.vis != ty::Visibility::Public { continue }
181 if let Some(target_module) = directive.target_module.get() {
182 let result = self.resolve_name_in_module(target_module, name, ns, false, None);
183 if let Indeterminate = result {
184 return Indeterminate;
187 return Indeterminate;
194 // Returns Some(the resolution of the name), or None if the resolution depends
195 // on whether more globs can define the name.
196 fn try_result(&mut self,
197 resolution: &NameResolution<'a>,
199 allow_private_imports: bool)
200 -> Option<ResolveResult<&'a NameBinding<'a>>> {
201 match resolution.binding {
202 Some(binding) if !binding.is_glob_import() =>
203 return Some(Success(binding)), // Items and single imports are not shadowable.
207 // Check if a single import can still define the name.
208 match resolution.single_imports {
209 SingleImports::None => {},
210 SingleImports::AtLeastOne => return Some(Indeterminate),
211 SingleImports::MaybeOne(directive) => {
212 // If (1) we don't allow private imports, (2) no public single import can define
213 // the name, and (3) no public glob has defined the name, the resolution depends
214 // on whether more globs can define the name.
215 if !allow_private_imports && directive.vis != ty::Visibility::Public &&
216 !resolution.binding.map(NameBinding::is_pseudo_public).unwrap_or(false) {
220 let target_module = match directive.target_module.get() {
221 Some(target_module) => target_module,
222 None => return Some(Indeterminate),
224 let name = match directive.subclass {
225 SingleImport { source, .. } => source,
226 GlobImport { .. } => unreachable!(),
228 match self.resolve_name_in_module(target_module, name, ns, false, None) {
230 _ => return Some(Indeterminate),
235 resolution.binding.map(Success)
238 // Add an import directive to the current module.
239 pub fn add_import_directive(&mut self,
240 module_path: Vec<Name>,
241 subclass: ImportDirectiveSubclass<'a>,
244 vis: ty::Visibility) {
245 let current_module = self.current_module;
246 let directive = self.arenas.alloc_import_directive(ImportDirective {
247 parent: current_module,
248 module_path: module_path,
249 target_module: Cell::new(None),
256 self.indeterminate_imports.push(directive);
257 match directive.subclass {
258 SingleImport { target, .. } => {
259 for &ns in &[ValueNS, TypeNS] {
260 let mut resolution = self.resolution(current_module, target, ns).borrow_mut();
261 resolution.single_imports.add_directive(directive);
264 // We don't add prelude imports to the globs since they only affect lexical scopes,
265 // which are not relevant to import resolution.
266 GlobImport { is_prelude: true } => {}
267 GlobImport { .. } => self.current_module.globs.borrow_mut().push(directive),
271 // Given a binding and an import directive that resolves to it,
272 // return the corresponding binding defined by the import directive.
273 fn import(&mut self, binding: &'a NameBinding<'a>, directive: &'a ImportDirective<'a>)
276 kind: NameBindingKind::Import {
278 directive: directive,
280 span: directive.span,
285 // Define the name or return the existing binding if there is a collision.
286 pub fn try_define<T>(&mut self, module: Module<'a>, name: Name, ns: Namespace, binding: T)
287 -> Result<(), &'a NameBinding<'a>>
288 where T: ToNameBinding<'a>
290 let binding = self.arenas.alloc_name_binding(binding.to_name_binding());
291 self.update_resolution(module, name, ns, |_, resolution| {
292 if let Some(old_binding) = resolution.binding {
293 if binding.is_glob_import() {
294 resolution.duplicate_globs.push(binding);
295 } else if old_binding.is_glob_import() {
296 resolution.duplicate_globs.push(old_binding);
297 resolution.binding = Some(binding);
299 return Err(old_binding);
302 resolution.binding = Some(binding);
309 // Use `f` to mutate the resolution of the name in the module.
310 // If the resolution becomes a success, define it in the module's glob importers.
311 fn update_resolution<T, F>(&mut self, module: Module<'a>, name: Name, ns: Namespace, f: F) -> T
312 where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
314 // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
315 // during which the resolution might end up getting re-defined via a glob cycle.
316 let (new_binding, t) = {
317 let mut resolution = &mut *self.resolution(module, name, ns).borrow_mut();
318 let was_known = resolution.binding().is_some();
320 let t = f(self, resolution);
322 if was_known { return t; }
323 match resolution.binding() {
324 Some(binding) => (binding, t),
329 // Define `new_binding` in `module`s glob importers.
330 if new_binding.is_importable() && new_binding.is_pseudo_public() {
331 for directive in module.glob_importers.borrow_mut().iter() {
332 let imported_binding = self.import(new_binding, directive);
333 let _ = self.try_define(directive.parent, name, ns, imported_binding);
341 struct ImportResolvingError<'a> {
342 import_directive: &'a ImportDirective<'a>,
347 struct ImportResolver<'a, 'b: 'a> {
348 resolver: &'a mut Resolver<'b>,
351 impl<'a, 'b: 'a> ::std::ops::Deref for ImportResolver<'a, 'b> {
352 type Target = Resolver<'b>;
353 fn deref(&self) -> &Resolver<'b> {
358 impl<'a, 'b: 'a> ::std::ops::DerefMut for ImportResolver<'a, 'b> {
359 fn deref_mut(&mut self) -> &mut Resolver<'b> {
364 impl<'a, 'b: 'a> ty::NodeIdTree for ImportResolver<'a, 'b> {
365 fn is_descendant_of(&self, node: NodeId, ancestor: NodeId) -> bool {
366 self.resolver.is_descendant_of(node, ancestor)
370 impl<'a, 'b:'a> ImportResolver<'a, 'b> {
373 // This is a fixed-point algorithm. We resolve imports until our efforts
374 // are stymied by an unresolved import; then we bail out of the current
375 // module and continue. We terminate successfully once no more imports
376 // remain or unsuccessfully when no forward progress in resolving imports
379 fn set_current_module(&mut self, module: Module<'b>) {
380 self.current_module = module;
381 self.current_vis = ty::Visibility::Restricted({
382 let normal_module = self.get_nearest_normal_module_parent_or_self(module);
383 self.definitions.as_local_node_id(normal_module.def_id().unwrap()).unwrap()
387 /// Resolves all imports for the crate. This method performs the fixed-
389 fn resolve_imports(&mut self) {
391 let mut prev_num_indeterminates = self.indeterminate_imports.len() + 1;
392 let mut errors = Vec::new();
394 while self.indeterminate_imports.len() < prev_num_indeterminates {
395 prev_num_indeterminates = self.indeterminate_imports.len();
396 debug!("(resolving imports) iteration {}, {} imports left", i, prev_num_indeterminates);
398 let mut imports = Vec::new();
399 ::std::mem::swap(&mut imports, &mut self.indeterminate_imports);
401 for import in imports {
402 match self.resolve_import(&import) {
404 let (span, help) = match err {
405 Some((span, msg)) => (span, format!(". {}", msg)),
406 None => (import.span, String::new()),
408 errors.push(ImportResolvingError {
409 import_directive: import,
414 Indeterminate => self.indeterminate_imports.push(import),
422 for module in self.arenas.local_modules().iter() {
423 self.finalize_resolutions_in(module);
426 // Report unresolved imports only if no hard error was already reported
427 // to avoid generating multiple errors on the same import.
428 if errors.len() == 0 {
429 if let Some(import) = self.indeterminate_imports.iter().next() {
430 let error = ResolutionError::UnresolvedImport(None);
431 resolve_error(self.resolver, import.span, error);
436 self.import_resolving_error(e)
440 // Define a "dummy" resolution containing a Def::Err as a placeholder for a
442 fn import_dummy_binding(&mut self, directive: &'b ImportDirective<'b>) {
443 if let SingleImport { target, .. } = directive.subclass {
444 let dummy_binding = self.arenas.alloc_name_binding(NameBinding {
445 kind: NameBindingKind::Def(Def::Err),
447 vis: ty::Visibility::Public,
449 let dummy_binding = self.import(dummy_binding, directive);
451 let _ = self.try_define(directive.parent, target, ValueNS, dummy_binding.clone());
452 let _ = self.try_define(directive.parent, target, TypeNS, dummy_binding);
456 /// Resolves an `ImportResolvingError` into the correct enum discriminant
457 /// and passes that on to `resolve_error`.
458 fn import_resolving_error(&mut self, e: ImportResolvingError<'b>) {
459 // If the error is a single failed import then create a "fake" import
460 // resolution for it so that later resolve stages won't complain.
461 self.import_dummy_binding(e.import_directive);
462 let path = import_path_to_string(&e.import_directive.module_path,
463 &e.import_directive.subclass);
464 resolve_error(self.resolver,
466 ResolutionError::UnresolvedImport(Some((&path, &e.help))));
469 /// Attempts to resolve the given import. The return value indicates
470 /// failure if we're certain the name does not exist, indeterminate if we
471 /// don't know whether the name exists at the moment due to other
472 /// currently-unresolved imports, or success if we know the name exists.
473 /// If successful, the resolved bindings are written into the module.
474 fn resolve_import(&mut self, directive: &'b ImportDirective<'b>) -> ResolveResult<()> {
475 debug!("(resolving import for module) resolving import `{}::...` in `{}`",
476 names_to_string(&directive.module_path),
477 module_to_string(self.current_module));
479 let module = directive.parent;
480 self.set_current_module(module);
482 let target_module = match directive.target_module.get() {
483 Some(module) => module,
484 _ => match self.resolve_module_path(&directive.module_path,
486 Some(directive.span)) {
487 Success(module) => module,
488 Indeterminate => return Indeterminate,
489 Failed(err) => return Failed(err),
493 directive.target_module.set(Some(target_module));
494 let (source, target, value_result, type_result) = match directive.subclass {
495 SingleImport { source, target, ref value_result, ref type_result } =>
496 (source, target, value_result, type_result),
497 GlobImport { .. } => return self.resolve_glob_import(target_module, directive),
500 let mut privacy_error = true;
501 for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
502 let was_determined = if let Err(false) = result.get() {
504 let span = Some(directive.span);
505 match self.resolve_name_in_module(target_module, source, ns, false, span) {
506 Success(binding) => Ok(binding),
507 Indeterminate => Err(false),
508 Failed(_) => Err(true),
517 Err(true) if !was_determined => {
518 self.update_resolution(module, target, ns, |_, resolution| {
519 resolution.single_imports.directive_failed()
522 Ok(binding) if !binding.is_importable() => {
523 let msg = format!("`{}` is not directly importable", target);
524 struct_span_err!(self.session, directive.span, E0253, "{}", &msg)
525 .span_label(directive.span, &format!("cannot be imported directly"))
527 // Do not import this illegal binding. Import a dummy binding and pretend
528 // everything is fine
529 self.import_dummy_binding(directive);
532 Ok(binding) if !self.is_accessible(binding.vis) => {}
533 Ok(binding) if !was_determined => {
534 let imported_binding = self.import(binding, directive);
535 let conflict = self.try_define(module, target, ns, imported_binding);
536 if let Err(old_binding) = conflict {
537 let binding = &self.import(binding, directive);
538 self.report_conflict(module, target, ns, binding, old_binding);
540 privacy_error = false;
542 Ok(_) => privacy_error = false,
547 let (value_result, type_result) = (value_result.get(), type_result.get());
548 match (value_result, type_result) {
549 (Err(false), _) | (_, Err(false)) => return Indeterminate,
550 (Err(true), Err(true)) => {
551 let resolutions = target_module.resolutions.borrow();
552 let names = resolutions.iter().filter_map(|(&(ref name, _), resolution)| {
553 if *name == source { return None; } // Never suggest the same name
554 match *resolution.borrow() {
555 NameResolution { binding: Some(_), .. } => Some(name),
556 NameResolution { single_imports: SingleImports::None, .. } => None,
560 let lev_suggestion = match find_best_match_for_name(names, &source.as_str(), None) {
561 Some(name) => format!(". Did you mean to use `{}`?", name),
562 None => "".to_owned(),
564 let module_str = module_to_string(target_module);
565 let msg = if &module_str == "???" {
566 format!("There is no `{}` in the crate root{}", source, lev_suggestion)
568 format!("There is no `{}` in `{}`{}", source, module_str, lev_suggestion)
570 return Failed(Some((directive.span, msg)));
576 for &(ns, result) in &[(ValueNS, value_result), (TypeNS, type_result)] {
577 let binding = match result { Ok(binding) => binding, _ => continue };
578 self.privacy_errors.push(PrivacyError(directive.span, source, binding));
579 let imported_binding = self.import(binding, directive);
580 let _ = self.try_define(module, target, ns, imported_binding);
584 match (value_result, type_result) {
585 (Ok(binding), _) if !binding.pseudo_vis().is_at_least(directive.vis, self) &&
586 self.is_accessible(binding.vis) => {
587 let msg = format!("`{}` is private, and cannot be reexported", source);
588 let note_msg = format!("consider marking `{}` as `pub` in the imported module",
590 struct_span_err!(self.session, directive.span, E0364, "{}", &msg)
591 .span_note(directive.span, ¬e_msg)
595 (_, Ok(binding)) if !binding.pseudo_vis().is_at_least(directive.vis, self) &&
596 self.is_accessible(binding.vis) => {
597 if binding.is_extern_crate() {
598 let msg = format!("extern crate `{}` is private, and cannot be reexported \
599 (error E0364), consider declaring with `pub`",
601 self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, directive.span, msg);
603 let mut err = struct_span_err!(self.session, directive.span, E0365,
604 "`{}` is private, and cannot be reexported",
606 err.span_label(directive.span, &format!("reexport of private `{}`", source));
607 err.note(&format!("consider declaring type or module `{}` with `pub`", source));
615 // Record what this import resolves to for later uses in documentation,
616 // this may resolve to either a value or a type, but for documentation
617 // purposes it's good enough to just favor one over the other.
618 let def = match type_result.ok().and_then(NameBinding::def) {
620 None => value_result.ok().and_then(NameBinding::def).unwrap(),
622 let path_resolution = PathResolution::new(def);
623 self.def_map.insert(directive.id, path_resolution);
625 debug!("(resolving single import) successfully resolved import");
629 // Resolves a glob import. Note that this function cannot fail; it either
630 // succeeds or bails out (as importing * from an empty module or a module
631 // that exports nothing is valid). target_module is the module we are
632 // actually importing, i.e., `foo` in `use foo::*`.
633 fn resolve_glob_import(&mut self, target_module: Module<'b>, directive: &'b ImportDirective<'b>)
634 -> ResolveResult<()> {
635 if let Some(Def::Trait(_)) = target_module.def {
636 self.session.span_err(directive.span, "items in traits are not importable.");
639 let module = self.current_module;
640 if module.def_id() == target_module.def_id() {
641 // This means we are trying to glob import a module into itself, and it is a no-go
642 let msg = "Cannot glob-import a module into itself.".into();
643 return Failed(Some((directive.span, msg)));
645 self.populate_module_if_necessary(target_module);
647 if let GlobImport { is_prelude: true } = directive.subclass {
648 self.prelude = Some(target_module);
652 // Add to target_module's glob_importers
653 target_module.glob_importers.borrow_mut().push(directive);
655 // Ensure that `resolutions` isn't borrowed during `try_define`,
656 // since it might get updated via a glob cycle.
657 let bindings = target_module.resolutions.borrow().iter().filter_map(|(name, resolution)| {
658 resolution.borrow().binding().map(|binding| (*name, binding))
659 }).collect::<Vec<_>>();
660 for ((name, ns), binding) in bindings {
661 if binding.is_importable() && binding.is_pseudo_public() {
662 let imported_binding = self.import(binding, directive);
663 let _ = self.try_define(module, name, ns, imported_binding);
667 // Record the destination of this import
668 if let Some(did) = target_module.def_id() {
669 let resolution = PathResolution::new(Def::Mod(did));
670 self.def_map.insert(directive.id, resolution);
673 debug!("(resolving glob import) successfully resolved import");
677 // Miscellaneous post-processing, including recording reexports, reporting conflicts,
678 // reporting the PRIVATE_IN_PUBLIC lint, and reporting unresolved imports.
679 fn finalize_resolutions_in(&mut self, module: Module<'b>) {
680 // Since import resolution is finished, globs will not define any more names.
681 *module.globs.borrow_mut() = Vec::new();
683 let mut reexports = Vec::new();
684 for (&(name, ns), resolution) in module.resolutions.borrow().iter() {
685 let resolution = resolution.borrow();
686 let binding = match resolution.binding {
687 Some(binding) => binding,
692 for duplicate_glob in resolution.duplicate_globs.iter() {
693 // FIXME #31337: We currently allow items to shadow glob-imported re-exports.
694 if !binding.is_import() {
695 if let NameBindingKind::Import { binding, .. } = duplicate_glob.kind {
696 if binding.is_import() { continue }
700 self.report_conflict(module, name, ns, duplicate_glob, binding);
703 if binding.vis == ty::Visibility::Public &&
704 (binding.is_import() || binding.is_extern_crate()) {
705 if let Some(def) = binding.def() {
706 reexports.push(Export { name: name, def_id: def.def_id() });
710 if let NameBindingKind::Import { binding: orig_binding, directive, .. } = binding.kind {
711 if ns == TypeNS && orig_binding.is_variant() &&
712 !orig_binding.vis.is_at_least(binding.vis, self) {
713 let msg = format!("variant `{}` is private, and cannot be reexported \
714 (error E0364), consider declaring its enum as `pub`",
716 self.session.add_lint(PRIVATE_IN_PUBLIC, directive.id, binding.span, msg);
721 if reexports.len() > 0 {
722 if let Some(def_id) = module.def_id() {
723 let node_id = self.definitions.as_local_node_id(def_id).unwrap();
724 self.export_map.insert(node_id, reexports);
730 fn import_path_to_string(names: &[Name], subclass: &ImportDirectiveSubclass) -> String {
731 if names.is_empty() {
732 import_directive_subclass_to_string(subclass)
735 names_to_string(names),
736 import_directive_subclass_to_string(subclass)))
741 fn import_directive_subclass_to_string(subclass: &ImportDirectiveSubclass) -> String {
743 SingleImport { source, .. } => source.to_string(),
744 GlobImport { .. } => "*".to_string(),