//! A bunch of methods and structures more or less related to resolving imports. use std::cell::Cell; use std::mem; use rustc_ast::NodeId; use rustc_data_structures::fx::{FxHashSet, FxIndexSet}; use rustc_data_structures::intern::Interned; use rustc_errors::codes::*; use rustc_errors::{Applicability, MultiSpan, pluralize, struct_span_code_err}; use rustc_hir::def::{self, DefKind, PartialRes}; use rustc_hir::def_id::DefId; use rustc_middle::metadata::{ModChild, Reexport}; use rustc_middle::{span_bug, ty}; use rustc_session::lint::BuiltinLintDiag; use rustc_session::lint::builtin::{ AMBIGUOUS_GLOB_REEXPORTS, HIDDEN_GLOB_REEXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE, REDUNDANT_IMPORTS, UNUSED_IMPORTS, }; use rustc_session::parse::feature_err; use rustc_span::edit_distance::find_best_match_for_name; use rustc_span::hygiene::LocalExpnId; use rustc_span::{Ident, Span, Symbol, kw, sym}; use smallvec::SmallVec; use tracing::debug; use crate::Determinacy::{self, *}; use crate::Namespace::*; use crate::diagnostics::{DiagMode, Suggestion, import_candidates}; use crate::errors::{ CannotBeReexportedCratePublic, CannotBeReexportedCratePublicNS, CannotBeReexportedPrivate, CannotBeReexportedPrivateNS, CannotDetermineImportResolution, CannotGlobImportAllCrates, ConsiderAddingMacroExport, ConsiderMarkingAsPub, IsNotDirectlyImportable, ItemsInTraitsAreNotImportable, }; use crate::{ AmbiguityError, AmbiguityKind, BindingKey, Finalize, ImportSuggestion, Module, ModuleOrUniformRoot, NameBinding, NameBindingData, NameBindingKind, ParentScope, PathResult, PerNS, ResolutionError, Resolver, ScopeSet, Segment, Used, module_to_string, names_to_string, }; type Res = def::Res; /// Contains data for specific kinds of imports. #[derive(Clone)] pub(crate) enum ImportKind<'ra> { Single { /// `source` in `use prefix::source as target`. source: Ident, /// `target` in `use prefix::source as target`. /// It will directly use `source` when the format is `use prefix::source`. target: Ident, /// Bindings to which `source` refers to. source_bindings: PerNS, Determinacy>>>, /// Bindings introduced by `target`. target_bindings: PerNS>>>, /// `true` for `...::{self [as target]}` imports, `false` otherwise. type_ns_only: bool, /// Did this import result from a nested import? ie. `use foo::{bar, baz};` nested: bool, /// The ID of the `UseTree` that imported this `Import`. /// /// In the case where the `Import` was expanded from a "nested" use tree, /// this id is the ID of the leaf tree. For example: /// /// ```ignore (pacify the merciless tidy) /// use foo::bar::{a, b} /// ``` /// /// If this is the import for `foo::bar::a`, we would have the ID of the `UseTree` /// for `a` in this field. id: NodeId, }, Glob { is_prelude: bool, // The visibility of the greatest re-export. // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors. max_vis: Cell>, id: NodeId, }, ExternCrate { source: Option, target: Ident, id: NodeId, }, MacroUse { /// A field has been added indicating whether it should be reported as a lint, /// addressing issue#119301. warn_private: bool, }, MacroExport, } /// Manually implement `Debug` for `ImportKind` because the `source/target_bindings` /// contain `Cell`s which can introduce infinite loops while printing. impl<'ra> std::fmt::Debug for ImportKind<'ra> { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { use ImportKind::*; match self { Single { source, target, source_bindings, target_bindings, type_ns_only, nested, id, } => f .debug_struct("Single") .field("source", source) .field("target", target) // Ignore the nested bindings to avoid an infinite loop while printing. .field( "source_bindings", &source_bindings.clone().map(|b| b.into_inner().map(|_| format_args!(".."))), ) .field( "target_bindings", &target_bindings.clone().map(|b| b.into_inner().map(|_| format_args!(".."))), ) .field("type_ns_only", type_ns_only) .field("nested", nested) .field("id", id) .finish(), Glob { is_prelude, max_vis, id } => f .debug_struct("Glob") .field("is_prelude", is_prelude) .field("max_vis", max_vis) .field("id", id) .finish(), ExternCrate { source, target, id } => f .debug_struct("ExternCrate") .field("source", source) .field("target", target) .field("id", id) .finish(), MacroUse { .. } => f.debug_struct("MacroUse").finish(), MacroExport => f.debug_struct("MacroExport").finish(), } } } /// One import. #[derive(Debug, Clone)] pub(crate) struct ImportData<'ra> { pub kind: ImportKind<'ra>, /// Node ID of the "root" use item -- this is always the same as `ImportKind`'s `id` /// (if it exists) except in the case of "nested" use trees, in which case /// it will be the ID of the root use tree. e.g., in the example /// ```ignore (incomplete code) /// use foo::bar::{a, b} /// ``` /// this would be the ID of the `use foo::bar` `UseTree` node. /// In case of imports without their own node ID it's the closest node that can be used, /// for example, for reporting lints. pub root_id: NodeId, /// Span of the entire use statement. pub use_span: Span, /// Span of the entire use statement with attributes. pub use_span_with_attributes: Span, /// Did the use statement have any attributes? pub has_attributes: bool, /// Span of this use tree. pub span: Span, /// Span of the *root* use tree (see `root_id`). pub root_span: Span, pub parent_scope: ParentScope<'ra>, pub module_path: Vec, /// The resolution of `module_path`. pub imported_module: Cell>>, pub vis: ty::Visibility, } /// All imports are unique and allocated on a same arena, /// so we can use referential equality to compare them. pub(crate) type Import<'ra> = Interned<'ra, ImportData<'ra>>; // Allows us to use Interned without actually enforcing (via Hash/PartialEq/...) uniqueness of the // contained data. // FIXME: We may wish to actually have at least debug-level assertions that Interned's guarantees // are upheld. impl std::hash::Hash for ImportData<'_> { fn hash(&self, _: &mut H) where H: std::hash::Hasher, { unreachable!() } } impl<'ra> ImportData<'ra> { pub(crate) fn is_glob(&self) -> bool { matches!(self.kind, ImportKind::Glob { .. }) } pub(crate) fn is_nested(&self) -> bool { match self.kind { ImportKind::Single { nested, .. } => nested, _ => false, } } pub(crate) fn id(&self) -> Option { match self.kind { ImportKind::Single { id, .. } | ImportKind::Glob { id, .. } | ImportKind::ExternCrate { id, .. } => Some(id), ImportKind::MacroUse { .. } | ImportKind::MacroExport => None, } } fn simplify(&self, r: &Resolver<'_, '_>) -> Reexport { let to_def_id = |id| r.local_def_id(id).to_def_id(); match self.kind { ImportKind::Single { id, .. } => Reexport::Single(to_def_id(id)), ImportKind::Glob { id, .. } => Reexport::Glob(to_def_id(id)), ImportKind::ExternCrate { id, .. } => Reexport::ExternCrate(to_def_id(id)), ImportKind::MacroUse { .. } => Reexport::MacroUse, ImportKind::MacroExport => Reexport::MacroExport, } } } /// Records information about the resolution of a name in a namespace of a module. #[derive(Clone, Default, Debug)] pub(crate) struct NameResolution<'ra> { /// Single imports that may define the name in the namespace. /// Imports are arena-allocated, so it's ok to use pointers as keys. pub single_imports: FxIndexSet>, /// The least shadowable known binding for this name, or None if there are no known bindings. pub binding: Option>, pub shadowed_glob: Option>, } impl<'ra> NameResolution<'ra> { /// Returns the binding for the name if it is known or None if it not known. pub(crate) fn binding(&self) -> Option> { self.binding.and_then(|binding| { if !binding.is_glob_import() || self.single_imports.is_empty() { Some(binding) } else { None } }) } } /// An error that may be transformed into a diagnostic later. Used to combine multiple unresolved /// import errors within the same use tree into a single diagnostic. #[derive(Debug, Clone)] struct UnresolvedImportError { span: Span, label: Option, note: Option, suggestion: Option, candidates: Option>, segment: Option, /// comes from `PathRes::Failed { module }` module: Option, } // Reexports of the form `pub use foo as bar;` where `foo` is `extern crate foo;` // are permitted for backward-compatibility under a deprecation lint. fn pub_use_of_private_extern_crate_hack( import: Import<'_>, binding: NameBinding<'_>, ) -> Option { match (&import.kind, &binding.kind) { (ImportKind::Single { .. }, NameBindingKind::Import { import: binding_import, .. }) if let ImportKind::ExternCrate { id, .. } = binding_import.kind && import.vis.is_public() => { Some(id) } _ => None, } } impl<'ra, 'tcx> Resolver<'ra, 'tcx> { /// Given a binding and an import that resolves to it, /// return the corresponding binding defined by the import. pub(crate) fn import( &self, binding: NameBinding<'ra>, import: Import<'ra>, ) -> NameBinding<'ra> { let import_vis = import.vis.to_def_id(); let vis = if binding.vis.is_at_least(import_vis, self.tcx) || pub_use_of_private_extern_crate_hack(import, binding).is_some() { import_vis } else { binding.vis }; if let ImportKind::Glob { ref max_vis, .. } = import.kind && (vis == import_vis || max_vis.get().is_none_or(|max_vis| vis.is_at_least(max_vis, self.tcx))) { max_vis.set(Some(vis.expect_local())) } self.arenas.alloc_name_binding(NameBindingData { kind: NameBindingKind::Import { binding, import }, ambiguity: None, warn_ambiguity: false, span: import.span, vis, expansion: import.parent_scope.expansion, }) } /// Define the name or return the existing binding if there is a collision. /// `update` indicates if the definition is a redefinition of an existing binding. pub(crate) fn try_define( &mut self, module: Module<'ra>, key: BindingKey, binding: NameBinding<'ra>, warn_ambiguity: bool, ) -> Result<(), NameBinding<'ra>> { let res = binding.res(); self.check_reserved_macro_name(key.ident, res); self.set_binding_parent_module(binding, module); self.update_resolution(module, key, warn_ambiguity, |this, resolution| { if let Some(old_binding) = resolution.binding { if res == Res::Err && old_binding.res() != Res::Err { // Do not override real bindings with `Res::Err`s from error recovery. return Ok(()); } match (old_binding.is_glob_import(), binding.is_glob_import()) { (true, true) => { // FIXME: remove `!binding.is_ambiguity_recursive()` after delete the warning ambiguity. if !binding.is_ambiguity_recursive() && let NameBindingKind::Import { import: old_import, .. } = old_binding.kind && let NameBindingKind::Import { import, .. } = binding.kind && old_import == import { // We should replace the `old_binding` with `binding` regardless // of whether they has same resolution or not when they are // imported from the same glob-import statement. resolution.binding = Some(binding); } else if res != old_binding.res() { resolution.binding = Some(this.new_ambiguity_binding( AmbiguityKind::GlobVsGlob, old_binding, binding, warn_ambiguity, )); } else if !old_binding.vis.is_at_least(binding.vis, this.tcx) { // We are glob-importing the same item but with greater visibility. resolution.binding = Some(binding); } else if binding.is_ambiguity_recursive() { resolution.binding = Some(this.new_warn_ambiguity_binding(binding)); } } (old_glob @ true, false) | (old_glob @ false, true) => { let (glob_binding, nonglob_binding) = if old_glob { (old_binding, binding) } else { (binding, old_binding) }; if key.ns == MacroNS && nonglob_binding.expansion != LocalExpnId::ROOT && glob_binding.res() != nonglob_binding.res() { resolution.binding = Some(this.new_ambiguity_binding( AmbiguityKind::GlobVsExpanded, nonglob_binding, glob_binding, false, )); } else { resolution.binding = Some(nonglob_binding); } if let Some(old_shadowed_glob) = resolution.shadowed_glob { assert!(old_shadowed_glob.is_glob_import()); if glob_binding.res() != old_shadowed_glob.res() { resolution.shadowed_glob = Some(this.new_ambiguity_binding( AmbiguityKind::GlobVsGlob, old_shadowed_glob, glob_binding, false, )); } else if !old_shadowed_glob.vis.is_at_least(binding.vis, this.tcx) { resolution.shadowed_glob = Some(glob_binding); } } else { resolution.shadowed_glob = Some(glob_binding); } } (false, false) => { return Err(old_binding); } } } else { resolution.binding = Some(binding); } Ok(()) }) } fn new_ambiguity_binding( &self, ambiguity_kind: AmbiguityKind, primary_binding: NameBinding<'ra>, secondary_binding: NameBinding<'ra>, warn_ambiguity: bool, ) -> NameBinding<'ra> { let ambiguity = Some((secondary_binding, ambiguity_kind)); let data = NameBindingData { ambiguity, warn_ambiguity, ..*primary_binding }; self.arenas.alloc_name_binding(data) } fn new_warn_ambiguity_binding(&self, binding: NameBinding<'ra>) -> NameBinding<'ra> { assert!(binding.is_ambiguity_recursive()); self.arenas.alloc_name_binding(NameBindingData { warn_ambiguity: true, ..*binding }) } // Use `f` to mutate the resolution of the name in the module. // If the resolution becomes a success, define it in the module's glob importers. fn update_resolution( &mut self, module: Module<'ra>, key: BindingKey, warn_ambiguity: bool, f: F, ) -> T where F: FnOnce(&mut Resolver<'ra, 'tcx>, &mut NameResolution<'ra>) -> T, { // Ensure that `resolution` isn't borrowed when defining in the module's glob importers, // during which the resolution might end up getting re-defined via a glob cycle. let (binding, t, warn_ambiguity) = { let resolution = &mut *self.resolution(module, key).borrow_mut(); let old_binding = resolution.binding(); let t = f(self, resolution); if let Some(binding) = resolution.binding() && old_binding != Some(binding) { (binding, t, warn_ambiguity || old_binding.is_some()) } else { return t; } }; let Ok(glob_importers) = module.glob_importers.try_borrow_mut() else { return t; }; // Define or update `binding` in `module`s glob importers. for import in glob_importers.iter() { let mut ident = key.ident; let scope = match ident.span.reverse_glob_adjust(module.expansion, import.span) { Some(Some(def)) => self.expn_def_scope(def), Some(None) => import.parent_scope.module, None => continue, }; if self.is_accessible_from(binding.vis, scope) { let imported_binding = self.import(binding, *import); let key = BindingKey { ident, ..key }; let _ = self.try_define( import.parent_scope.module, key, imported_binding, warn_ambiguity, ); } } t } // Define a dummy resolution containing a `Res::Err` as a placeholder for a failed // or indeterminate resolution, also mark such failed imports as used to avoid duplicate diagnostics. fn import_dummy_binding(&mut self, import: Import<'ra>, is_indeterminate: bool) { if let ImportKind::Single { target, ref target_bindings, .. } = import.kind { if !(is_indeterminate || target_bindings.iter().all(|binding| binding.get().is_none())) { return; // Has resolution, do not create the dummy binding } let dummy_binding = self.dummy_binding; let dummy_binding = self.import(dummy_binding, import); self.per_ns(|this, ns| { let key = BindingKey::new(target, ns); let _ = this.try_define(import.parent_scope.module, key, dummy_binding, false); this.update_resolution(import.parent_scope.module, key, false, |_, resolution| { resolution.single_imports.swap_remove(&import); }) }); self.record_use(target, dummy_binding, Used::Other); } else if import.imported_module.get().is_none() { self.import_use_map.insert(import, Used::Other); if let Some(id) = import.id() { self.used_imports.insert(id); } } } // Import resolution // // This is a fixed-point algorithm. We resolve imports until our efforts // are stymied by an unresolved import; then we bail out of the current // module and continue. We terminate successfully once no more imports // remain or unsuccessfully when no forward progress in resolving imports // is made. /// Resolves all imports for the crate. This method performs the fixed- /// point iteration. pub(crate) fn resolve_imports(&mut self) { let mut prev_indeterminate_count = usize::MAX; let mut indeterminate_count = self.indeterminate_imports.len() * 3; while indeterminate_count < prev_indeterminate_count { prev_indeterminate_count = indeterminate_count; indeterminate_count = 0; for import in mem::take(&mut self.indeterminate_imports) { let import_indeterminate_count = self.resolve_import(import); indeterminate_count += import_indeterminate_count; match import_indeterminate_count { 0 => self.determined_imports.push(import), _ => self.indeterminate_imports.push(import), } } } } pub(crate) fn finalize_imports(&mut self) { for module in self.arenas.local_modules().iter() { self.finalize_resolutions_in(*module); } let mut seen_spans = FxHashSet::default(); let mut errors = vec![]; let mut prev_root_id: NodeId = NodeId::ZERO; let determined_imports = mem::take(&mut self.determined_imports); let indeterminate_imports = mem::take(&mut self.indeterminate_imports); let mut glob_error = false; for (is_indeterminate, import) in determined_imports .iter() .map(|i| (false, i)) .chain(indeterminate_imports.iter().map(|i| (true, i))) { let unresolved_import_error = self.finalize_import(*import); // If this import is unresolved then create a dummy import // resolution for it so that later resolve stages won't complain. self.import_dummy_binding(*import, is_indeterminate); let Some(err) = unresolved_import_error else { continue }; glob_error |= import.is_glob(); if let ImportKind::Single { source, ref source_bindings, .. } = import.kind && source.name == kw::SelfLower // Silence `unresolved import` error if E0429 is already emitted && let Err(Determined) = source_bindings.value_ns.get() { continue; } if prev_root_id != NodeId::ZERO && prev_root_id != import.root_id && !errors.is_empty() { // In the case of a new import line, throw a diagnostic message // for the previous line. self.throw_unresolved_import_error(errors, glob_error); errors = vec![]; } if seen_spans.insert(err.span) { errors.push((*import, err)); prev_root_id = import.root_id; } } if !errors.is_empty() { self.throw_unresolved_import_error(errors, glob_error); return; } for import in &indeterminate_imports { let path = import_path_to_string( &import.module_path.iter().map(|seg| seg.ident).collect::>(), &import.kind, import.span, ); // FIXME: there should be a better way of doing this than // formatting this as a string then checking for `::` if path.contains("::") { let err = UnresolvedImportError { span: import.span, label: None, note: None, suggestion: None, candidates: None, segment: None, module: None, }; errors.push((*import, err)) } } self.throw_unresolved_import_error(errors, glob_error); } pub(crate) fn check_hidden_glob_reexports( &mut self, exported_ambiguities: FxHashSet>, ) { for module in self.arenas.local_modules().iter() { for (key, resolution) in self.resolutions(*module).borrow().iter() { let resolution = resolution.borrow(); let Some(binding) = resolution.binding else { continue }; if let NameBindingKind::Import { import, .. } = binding.kind && let Some((amb_binding, _)) = binding.ambiguity && binding.res() != Res::Err && exported_ambiguities.contains(&binding) { self.lint_buffer.buffer_lint( AMBIGUOUS_GLOB_REEXPORTS, import.root_id, import.root_span, BuiltinLintDiag::AmbiguousGlobReexports { name: key.ident.to_string(), namespace: key.ns.descr().to_string(), first_reexport_span: import.root_span, duplicate_reexport_span: amb_binding.span, }, ); } if let Some(glob_binding) = resolution.shadowed_glob { if binding.res() != Res::Err && glob_binding.res() != Res::Err && let NameBindingKind::Import { import: glob_import, .. } = glob_binding.kind && let Some(glob_import_id) = glob_import.id() && let glob_import_def_id = self.local_def_id(glob_import_id) && self.effective_visibilities.is_exported(glob_import_def_id) && glob_binding.vis.is_public() && !binding.vis.is_public() { let binding_id = match binding.kind { NameBindingKind::Res(res) => { Some(self.def_id_to_node_id(res.def_id().expect_local())) } NameBindingKind::Module(module) => { Some(self.def_id_to_node_id(module.def_id().expect_local())) } NameBindingKind::Import { import, .. } => import.id(), }; if let Some(binding_id) = binding_id { self.lint_buffer.buffer_lint( HIDDEN_GLOB_REEXPORTS, binding_id, binding.span, BuiltinLintDiag::HiddenGlobReexports { name: key.ident.name.to_string(), namespace: key.ns.descr().to_owned(), glob_reexport_span: glob_binding.span, private_item_span: binding.span, }, ); } } } } } } fn throw_unresolved_import_error( &mut self, mut errors: Vec<(Import<'_>, UnresolvedImportError)>, glob_error: bool, ) { errors.retain(|(_import, err)| match err.module { // Skip `use` errors for `use foo::Bar;` if `foo.rs` has unrecovered parse errors. Some(def_id) if self.mods_with_parse_errors.contains(&def_id) => false, _ => true, }); if errors.is_empty() { return; } /// Upper limit on the number of `span_label` messages. const MAX_LABEL_COUNT: usize = 10; let span = MultiSpan::from_spans(errors.iter().map(|(_, err)| err.span).collect()); let paths = errors .iter() .map(|(import, err)| { let path = import_path_to_string( &import.module_path.iter().map(|seg| seg.ident).collect::>(), &import.kind, err.span, ); format!("`{path}`") }) .collect::>(); let msg = format!("unresolved import{} {}", pluralize!(paths.len()), paths.join(", "),); let mut diag = struct_span_code_err!(self.dcx(), span, E0432, "{msg}"); if let Some((_, UnresolvedImportError { note: Some(note), .. })) = errors.iter().last() { diag.note(note.clone()); } for (import, err) in errors.into_iter().take(MAX_LABEL_COUNT) { if let Some(label) = err.label { diag.span_label(err.span, label); } if let Some((suggestions, msg, applicability)) = err.suggestion { if suggestions.is_empty() { diag.help(msg); continue; } diag.multipart_suggestion(msg, suggestions, applicability); } if let Some(candidates) = &err.candidates { match &import.kind { ImportKind::Single { nested: false, source, target, .. } => import_candidates( self.tcx, &mut diag, Some(err.span), candidates, DiagMode::Import { append: false, unresolved_import: true }, (source != target) .then(|| format!(" as {target}")) .as_deref() .unwrap_or(""), ), ImportKind::Single { nested: true, source, target, .. } => { import_candidates( self.tcx, &mut diag, None, candidates, DiagMode::Normal, (source != target) .then(|| format!(" as {target}")) .as_deref() .unwrap_or(""), ); } _ => {} } } if matches!(import.kind, ImportKind::Single { .. }) && let Some(segment) = err.segment && let Some(module) = err.module { self.find_cfg_stripped(&mut diag, &segment, module) } } let guar = diag.emit(); if glob_error { self.glob_error = Some(guar); } } /// Attempts to resolve the given import, returning: /// - `0` means its resolution is determined. /// - Other values mean that indeterminate exists under certain namespaces. /// /// Meanwhile, if resolve successful, the resolved bindings are written /// into the module. fn resolve_import(&mut self, import: Import<'ra>) -> usize { debug!( "(resolving import for module) resolving import `{}::...` in `{}`", Segment::names_to_string(&import.module_path), module_to_string(import.parent_scope.module).unwrap_or_else(|| "???".to_string()), ); let module = if let Some(module) = import.imported_module.get() { module } else { let path_res = self.maybe_resolve_path( &import.module_path, None, &import.parent_scope, Some(import), ); match path_res { PathResult::Module(module) => module, PathResult::Indeterminate => return 3, PathResult::NonModule(..) | PathResult::Failed { .. } => return 0, } }; import.imported_module.set(Some(module)); let (source, target, source_bindings, target_bindings, type_ns_only) = match import.kind { ImportKind::Single { source, target, ref source_bindings, ref target_bindings, type_ns_only, .. } => (source, target, source_bindings, target_bindings, type_ns_only), ImportKind::Glob { .. } => { self.resolve_glob_import(import); return 0; } _ => unreachable!(), }; let mut indeterminate_count = 0; self.per_ns(|this, ns| { if !type_ns_only || ns == TypeNS { if let Err(Undetermined) = source_bindings[ns].get() { let binding = this.maybe_resolve_ident_in_module( module, source, ns, &import.parent_scope, Some(import), ); source_bindings[ns].set(binding); } else { return; }; let parent = import.parent_scope.module; match source_bindings[ns].get() { Err(Undetermined) => indeterminate_count += 1, // Don't update the resolution, because it was never added. Err(Determined) if target.name == kw::Underscore => {} Ok(binding) if binding.is_importable() => { if binding.is_assoc_const_or_fn() && !this.tcx.features().import_trait_associated_functions() { feature_err( this.tcx.sess, sym::import_trait_associated_functions, import.span, "`use` associated items of traits is unstable", ) .emit(); } let imported_binding = this.import(binding, import); target_bindings[ns].set(Some(imported_binding)); this.define(parent, target, ns, imported_binding); } source_binding @ (Ok(..) | Err(Determined)) => { if source_binding.is_ok() { this.dcx() .create_err(IsNotDirectlyImportable { span: import.span, target }) .emit(); } let key = BindingKey::new(target, ns); this.update_resolution(parent, key, false, |_, resolution| { resolution.single_imports.swap_remove(&import); }); } } } }); indeterminate_count } /// Performs final import resolution, consistency checks and error reporting. /// /// Optionally returns an unresolved import error. This error is buffered and used to /// consolidate multiple unresolved import errors into a single diagnostic. fn finalize_import(&mut self, import: Import<'ra>) -> Option { let ignore_binding = match &import.kind { ImportKind::Single { target_bindings, .. } => target_bindings[TypeNS].get(), _ => None, }; let ambiguity_errors_len = |errors: &Vec>| errors.iter().filter(|error| !error.warning).count(); let prev_ambiguity_errors_len = ambiguity_errors_len(&self.ambiguity_errors); let finalize = Finalize::with_root_span(import.root_id, import.span, import.root_span); // We'll provide more context to the privacy errors later, up to `len`. let privacy_errors_len = self.privacy_errors.len(); let path_res = self.resolve_path( &import.module_path, None, &import.parent_scope, Some(finalize), ignore_binding, Some(import), ); let no_ambiguity = ambiguity_errors_len(&self.ambiguity_errors) == prev_ambiguity_errors_len; let module = match path_res { PathResult::Module(module) => { // Consistency checks, analogous to `finalize_macro_resolutions`. if let Some(initial_module) = import.imported_module.get() { if module != initial_module && no_ambiguity { span_bug!(import.span, "inconsistent resolution for an import"); } } else if self.privacy_errors.is_empty() { self.dcx() .create_err(CannotDetermineImportResolution { span: import.span }) .emit(); } module } PathResult::Failed { is_error_from_last_segment: false, span, segment_name, label, suggestion, module, error_implied_by_parse_error: _, } => { if no_ambiguity { assert!(import.imported_module.get().is_none()); self.report_error( span, ResolutionError::FailedToResolve { segment: Some(segment_name), label, suggestion, module, }, ); } return None; } PathResult::Failed { is_error_from_last_segment: true, span, label, suggestion, module, segment_name, .. } => { if no_ambiguity { assert!(import.imported_module.get().is_none()); let module = if let Some(ModuleOrUniformRoot::Module(m)) = module { m.opt_def_id() } else { None }; let err = match self .make_path_suggestion(import.module_path.clone(), &import.parent_scope) { Some((suggestion, note)) => UnresolvedImportError { span, label: None, note, suggestion: Some(( vec![(span, Segment::names_to_string(&suggestion))], String::from("a similar path exists"), Applicability::MaybeIncorrect, )), candidates: None, segment: Some(segment_name), module, }, None => UnresolvedImportError { span, label: Some(label), note: None, suggestion, candidates: None, segment: Some(segment_name), module, }, }; return Some(err); } return None; } PathResult::NonModule(partial_res) => { if no_ambiguity && partial_res.full_res() != Some(Res::Err) { // Check if there are no ambiguities and the result is not dummy. assert!(import.imported_module.get().is_none()); } // The error was already reported earlier. return None; } PathResult::Indeterminate => unreachable!(), }; let (ident, target, source_bindings, target_bindings, type_ns_only, import_id) = match import.kind { ImportKind::Single { source, target, ref source_bindings, ref target_bindings, type_ns_only, id, .. } => (source, target, source_bindings, target_bindings, type_ns_only, id), ImportKind::Glob { is_prelude, ref max_vis, id } => { if import.module_path.len() <= 1 { // HACK(eddyb) `lint_if_path_starts_with_module` needs at least // 2 segments, so the `resolve_path` above won't trigger it. let mut full_path = import.module_path.clone(); full_path.push(Segment::from_ident(Ident::dummy())); self.lint_if_path_starts_with_module(Some(finalize), &full_path, None); } if let ModuleOrUniformRoot::Module(module) = module && module == import.parent_scope.module { // Importing a module into itself is not allowed. return Some(UnresolvedImportError { span: import.span, label: Some(String::from("cannot glob-import a module into itself")), note: None, suggestion: None, candidates: None, segment: None, module: None, }); } if !is_prelude && let Some(max_vis) = max_vis.get() && !max_vis.is_at_least(import.vis, self.tcx) { let def_id = self.local_def_id(id); self.lint_buffer.buffer_lint( UNUSED_IMPORTS, id, import.span, BuiltinLintDiag::RedundantImportVisibility { max_vis: max_vis.to_string(def_id, self.tcx), import_vis: import.vis.to_string(def_id, self.tcx), span: import.span, }, ); } return None; } _ => unreachable!(), }; if self.privacy_errors.len() != privacy_errors_len { // Get the Res for the last element, so that we can point to alternative ways of // importing it if available. let mut path = import.module_path.clone(); path.push(Segment::from_ident(ident)); if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path( &path, None, &import.parent_scope, Some(finalize), ignore_binding, None, ) { let res = module.res().map(|r| (r, ident)); for error in &mut self.privacy_errors[privacy_errors_len..] { error.outermost_res = res; } } } let mut all_ns_err = true; self.per_ns(|this, ns| { if !type_ns_only || ns == TypeNS { let binding = this.resolve_ident_in_module( module, ident, ns, &import.parent_scope, Some(Finalize { report_private: false, ..finalize }), target_bindings[ns].get(), Some(import), ); match binding { Ok(binding) => { // Consistency checks, analogous to `finalize_macro_resolutions`. let initial_res = source_bindings[ns].get().map(|initial_binding| { all_ns_err = false; if let Some(target_binding) = target_bindings[ns].get() && target.name == kw::Underscore && initial_binding.is_extern_crate() && !initial_binding.is_import() { let used = if import.module_path.is_empty() { Used::Scope } else { Used::Other }; this.record_use(ident, target_binding, used); } initial_binding.res() }); let res = binding.res(); let has_ambiguity_error = this.ambiguity_errors.iter().any(|error| !error.warning); if res == Res::Err || has_ambiguity_error { this.dcx() .span_delayed_bug(import.span, "some error happened for an import"); return; } if let Ok(initial_res) = initial_res { if res != initial_res { span_bug!(import.span, "inconsistent resolution for an import"); } } else if this.privacy_errors.is_empty() { this.dcx() .create_err(CannotDetermineImportResolution { span: import.span }) .emit(); } } Err(..) => { // FIXME: This assert may fire if public glob is later shadowed by a private // single import (see test `issue-55884-2.rs`). In theory single imports should // always block globs, even if they are not yet resolved, so that this kind of // self-inconsistent resolution never happens. // Re-enable the assert when the issue is fixed. // assert!(result[ns].get().is_err()); } } } }); if all_ns_err { let mut all_ns_failed = true; self.per_ns(|this, ns| { if !type_ns_only || ns == TypeNS { let binding = this.resolve_ident_in_module( module, ident, ns, &import.parent_scope, Some(finalize), None, None, ); if binding.is_ok() { all_ns_failed = false; } } }); return if all_ns_failed { let resolutions = match module { ModuleOrUniformRoot::Module(module) => Some(self.resolutions(module).borrow()), _ => None, }; let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter()); let names = resolutions .filter_map(|(BindingKey { ident: i, .. }, resolution)| { if i.name == ident.name { return None; } // Never suggest the same name match *resolution.borrow() { NameResolution { binding: Some(name_binding), .. } => { match name_binding.kind { NameBindingKind::Import { binding, .. } => { match binding.kind { // Never suggest the name that has binding error // i.e., the name that cannot be previously resolved NameBindingKind::Res(Res::Err) => None, _ => Some(i.name), } } _ => Some(i.name), } } NameResolution { ref single_imports, .. } if single_imports.is_empty() => { None } _ => Some(i.name), } }) .collect::>(); let lev_suggestion = find_best_match_for_name(&names, ident.name, None).map(|suggestion| { ( vec![(ident.span, suggestion.to_string())], String::from("a similar name exists in the module"), Applicability::MaybeIncorrect, ) }); let (suggestion, note) = match self.check_for_module_export_macro(import, module, ident) { Some((suggestion, note)) => (suggestion.or(lev_suggestion), note), _ => (lev_suggestion, None), }; let label = match module { ModuleOrUniformRoot::Module(module) => { let module_str = module_to_string(module); if let Some(module_str) = module_str { format!("no `{ident}` in `{module_str}`") } else { format!("no `{ident}` in the root") } } _ => { if !ident.is_path_segment_keyword() { format!("no external crate `{ident}`") } else { // HACK(eddyb) this shows up for `self` & `super`, which // should work instead - for now keep the same error message. format!("no `{ident}` in the root") } } }; let parent_suggestion = self.lookup_import_candidates(ident, TypeNS, &import.parent_scope, |_| true); Some(UnresolvedImportError { span: import.span, label: Some(label), note, suggestion, candidates: if !parent_suggestion.is_empty() { Some(parent_suggestion) } else { None }, module: import.imported_module.get().and_then(|module| { if let ModuleOrUniformRoot::Module(m) = module { m.opt_def_id() } else { None } }), segment: Some(ident.name), }) } else { // `resolve_ident_in_module` reported a privacy error. None }; } let mut reexport_error = None; let mut any_successful_reexport = false; let mut crate_private_reexport = false; self.per_ns(|this, ns| { let Ok(binding) = source_bindings[ns].get() else { return; }; if !binding.vis.is_at_least(import.vis, this.tcx) { reexport_error = Some((ns, binding)); if let ty::Visibility::Restricted(binding_def_id) = binding.vis && binding_def_id.is_top_level_module() { crate_private_reexport = true; } } else { any_successful_reexport = true; } }); // All namespaces must be re-exported with extra visibility for an error to occur. if !any_successful_reexport { let (ns, binding) = reexport_error.unwrap(); if let Some(extern_crate_id) = pub_use_of_private_extern_crate_hack(import, binding) { self.lint_buffer.buffer_lint( PUB_USE_OF_PRIVATE_EXTERN_CRATE, import_id, import.span, BuiltinLintDiag::PrivateExternCrateReexport { source: ident, extern_crate_span: self.tcx.source_span(self.local_def_id(extern_crate_id)), }, ); } else if ns == TypeNS { let err = if crate_private_reexport { self.dcx() .create_err(CannotBeReexportedCratePublicNS { span: import.span, ident }) } else { self.dcx().create_err(CannotBeReexportedPrivateNS { span: import.span, ident }) }; err.emit(); } else { let mut err = if crate_private_reexport { self.dcx() .create_err(CannotBeReexportedCratePublic { span: import.span, ident }) } else { self.dcx().create_err(CannotBeReexportedPrivate { span: import.span, ident }) }; match binding.kind { NameBindingKind::Res(Res::Def(DefKind::Macro(_), def_id)) // exclude decl_macro if self.get_macro_by_def_id(def_id).macro_rules => { err.subdiagnostic( ConsiderAddingMacroExport { span: binding.span, }); } _ => { err.subdiagnostic( ConsiderMarkingAsPub { span: import.span, ident, }); } } err.emit(); } } if import.module_path.len() <= 1 { // HACK(eddyb) `lint_if_path_starts_with_module` needs at least // 2 segments, so the `resolve_path` above won't trigger it. let mut full_path = import.module_path.clone(); full_path.push(Segment::from_ident(ident)); self.per_ns(|this, ns| { if let Ok(binding) = source_bindings[ns].get() { this.lint_if_path_starts_with_module(Some(finalize), &full_path, Some(binding)); } }); } // Record what this import resolves to for later uses in documentation, // this may resolve to either a value or a type, but for documentation // purposes it's good enough to just favor one over the other. self.per_ns(|this, ns| { if let Ok(binding) = source_bindings[ns].get() { this.import_res_map.entry(import_id).or_default()[ns] = Some(binding.res()); } }); debug!("(resolving single import) successfully resolved import"); None } pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'ra>) -> bool { // This function is only called for single imports. let ImportKind::Single { source, target, ref source_bindings, ref target_bindings, id, .. } = import.kind else { unreachable!() }; // Skip if the import is of the form `use source as target` and source != target. if source != target { return false; } // Skip if the import was produced by a macro. if import.parent_scope.expansion != LocalExpnId::ROOT { return false; } // Skip if we are inside a named module (in contrast to an anonymous // module defined by a block). // Skip if the import is public or was used through non scope-based resolution, // e.g. through a module-relative path. if self.import_use_map.get(&import) == Some(&Used::Other) || self.effective_visibilities.is_exported(self.local_def_id(id)) { return false; } let mut is_redundant = true; let mut redundant_span = PerNS { value_ns: None, type_ns: None, macro_ns: None }; self.per_ns(|this, ns| { if is_redundant && let Ok(binding) = source_bindings[ns].get() { if binding.res() == Res::Err { return; } match this.early_resolve_ident_in_lexical_scope( target, ScopeSet::All(ns), &import.parent_scope, None, false, target_bindings[ns].get(), None, ) { Ok(other_binding) => { is_redundant = binding.res() == other_binding.res() && !other_binding.is_ambiguity_recursive(); if is_redundant { redundant_span[ns] = Some((other_binding.span, other_binding.is_import())); } } Err(_) => is_redundant = false, } } }); if is_redundant && !redundant_span.is_empty() { let mut redundant_spans: Vec<_> = redundant_span.present_items().collect(); redundant_spans.sort(); redundant_spans.dedup(); self.lint_buffer.buffer_lint( REDUNDANT_IMPORTS, id, import.span, BuiltinLintDiag::RedundantImport(redundant_spans, source), ); return true; } false } fn resolve_glob_import(&mut self, import: Import<'ra>) { // This function is only called for glob imports. let ImportKind::Glob { id, is_prelude, .. } = import.kind else { unreachable!() }; let ModuleOrUniformRoot::Module(module) = import.imported_module.get().unwrap() else { self.dcx().emit_err(CannotGlobImportAllCrates { span: import.span }); return; }; if module.is_trait() { self.dcx().emit_err(ItemsInTraitsAreNotImportable { span: import.span }); return; } else if module == import.parent_scope.module { return; } else if is_prelude { self.prelude = Some(module); return; } // Add to module's glob_importers module.glob_importers.borrow_mut().push(import); // Ensure that `resolutions` isn't borrowed during `try_define`, // since it might get updated via a glob cycle. let bindings = self .resolutions(module) .borrow() .iter() .filter_map(|(key, resolution)| { resolution.borrow().binding().map(|binding| (*key, binding)) }) .collect::>(); for (mut key, binding) in bindings { let scope = match key.ident.span.reverse_glob_adjust(module.expansion, import.span) { Some(Some(def)) => self.expn_def_scope(def), Some(None) => import.parent_scope.module, None => continue, }; if self.is_accessible_from(binding.vis, scope) { let imported_binding = self.import(binding, import); let warn_ambiguity = self .resolution(import.parent_scope.module, key) .borrow() .binding() .is_some_and(|binding| binding.warn_ambiguity_recursive()); let _ = self.try_define( import.parent_scope.module, key, imported_binding, warn_ambiguity, ); } } // Record the destination of this import self.record_partial_res(id, PartialRes::new(module.res().unwrap())); } // Miscellaneous post-processing, including recording re-exports, // reporting conflicts, and reporting unresolved imports. fn finalize_resolutions_in(&mut self, module: Module<'ra>) { // Since import resolution is finished, globs will not define any more names. *module.globs.borrow_mut() = Vec::new(); let Some(def_id) = module.opt_def_id() else { return }; let mut children = Vec::new(); module.for_each_child(self, |this, ident, _, binding| { let res = binding.res().expect_non_local(); let error_ambiguity = binding.is_ambiguity_recursive() && !binding.warn_ambiguity; if res != def::Res::Err && !error_ambiguity { let mut reexport_chain = SmallVec::new(); let mut next_binding = binding; while let NameBindingKind::Import { binding, import, .. } = next_binding.kind { reexport_chain.push(import.simplify(this)); next_binding = binding; } children.push(ModChild { ident, res, vis: binding.vis, reexport_chain }); } }); if !children.is_empty() { // Should be fine because this code is only called for local modules. self.module_children.insert(def_id.expect_local(), children); } } } fn import_path_to_string(names: &[Ident], import_kind: &ImportKind<'_>, span: Span) -> String { let pos = names.iter().position(|p| span == p.span && p.name != kw::PathRoot); let global = !names.is_empty() && names[0].name == kw::PathRoot; if let Some(pos) = pos { let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] }; names_to_string(names.iter().map(|ident| ident.name)) } else { let names = if global { &names[1..] } else { names }; if names.is_empty() { import_kind_to_string(import_kind) } else { format!( "{}::{}", names_to_string(names.iter().map(|ident| ident.name)), import_kind_to_string(import_kind), ) } } } fn import_kind_to_string(import_kind: &ImportKind<'_>) -> String { match import_kind { ImportKind::Single { source, .. } => source.to_string(), ImportKind::Glob { .. } => "*".to_string(), ImportKind::ExternCrate { .. } => "".to_string(), ImportKind::MacroUse { .. } => "#[macro_use]".to_string(), ImportKind::MacroExport => "#[macro_export]".to_string(), } }