1//! A bunch of methods and structures more or less related to resolving imports.23use std::cmp::Ordering;4use std::mem;56use itertools::Itertools;7use rustc_ast::{Item, NodeId};8use rustc_attr_parsing::AttributeParser;9use rustc_data_structures::fx::{FxHashSet, FxIndexSet};10use rustc_data_structures::intern::Interned;11use rustc_errors::codes::*;12use rustc_errors::{13    Applicability, BufferedEarlyLint, Diagnostic, MultiSpan, pluralize, struct_span_code_err,14};15use rustc_hir::Attribute;16use rustc_hir::attrs::AttributeKind;17use rustc_hir::attrs::diagnostic::{CustomDiagnostic, Directive, FormatArgs};18use rustc_hir::def::{self, DefKind, PartialRes};19use rustc_hir::def_id::{DefId, LocalDefIdMap};20use rustc_middle::metadata::{AmbigModChild, ModChild, Reexport};21use rustc_middle::span_bug;22use rustc_middle::ty::{TyCtxt, Visibility};23use rustc_session::errors::feature_err;24use rustc_session::lint::LintId;25use rustc_session::lint::builtin::{26    AMBIGUOUS_GLOB_REEXPORTS, EXPORTED_PRIVATE_DEPENDENCIES, HIDDEN_GLOB_REEXPORTS,27    PUB_USE_OF_PRIVATE_EXTERN_CRATE, REDUNDANT_IMPORTS, UNUSED_IMPORTS,28};29use rustc_span::edit_distance::find_best_match_for_name;30use rustc_span::hygiene::LocalExpnId;31use rustc_span::{Ident, Span, Symbol, kw, sym};32use tracing::debug;3334use crate::Namespace::{self, *};35use crate::diagnostics::{DiagMode, Suggestion, import_candidates};36use crate::errors::{37    self, CannotBeReexportedCratePublic, CannotBeReexportedCratePublicNS,38    CannotBeReexportedPrivate, CannotBeReexportedPrivateNS, CannotDetermineImportResolution,39    CannotGlobImportAllCrates, ConsiderAddingMacroExport, ConsiderMarkingAsPub,40    ConsiderMarkingAsPubCrate,41};42use crate::ref_mut::CmCell;43use crate::{44    AmbiguityError, BindingKey, CmResolver, Decl, DeclData, DeclKind, Determinacy, Finalize,45    IdentKey, ImportSuggestion, ImportSummary, LocalModule, ModuleOrUniformRoot, ParentScope,46    PathResult, PerNS, Res, ResolutionError, Resolver, ScopeSet, Segment, Used, module_to_string,47    names_to_string,48};4950/// A potential import declaration in the process of being planted into a module.51/// Also used for lazily planting names from `--extern` flags to extern prelude.52#[derive(Clone, Copy, Default, PartialEq, Debug)]53pub(crate) enum PendingDecl<'ra> {54    Ready(Option<Decl<'ra>>),55    #[default]56    Pending,57}5859impl<'ra> PendingDecl<'ra> {60    pub(crate) fn decl(self) -> Option<Decl<'ra>> {61        match self {62            PendingDecl::Ready(decl) => decl,63            PendingDecl::Pending => None,64        }65    }66}6768/// Contains data for specific kinds of imports.69#[derive(Clone)]70pub(crate) enum ImportKind<'ra> {71    Single {72        /// `source` in `use prefix::source as target`.73        source: Ident,74        /// `target` in `use prefix::source as target`.75        /// It will directly use `source` when the format is `use prefix::source`.76        target: Ident,77        /// Name declarations introduced by the import.78        decls: PerNS<CmCell<PendingDecl<'ra>>>,79        /// Did this import result from a nested import? i.e. `use foo::{bar, baz};`80        nested: bool,81        /// The ID of the `UseTree` that imported this `Import`.82        ///83        /// In the case where the `Import` was expanded from a "nested" use tree,84        /// this id is the ID of the leaf tree. For example:85        ///86        /// ```ignore (pacify the merciless tidy)87        /// use foo::bar::{a, b}88        /// ```89        ///90        /// If this is the import for `foo::bar::a`, we would have the ID of the `UseTree`91        /// for `a` in this field.92        id: NodeId,93    },94    Glob {95        // The visibility of the greatest re-export.96        // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.97        max_vis: CmCell<Option<Visibility>>,98        id: NodeId,99    },100    ExternCrate {101        source: Option<Symbol>,102        target: Ident,103        id: NodeId,104    },105    MacroUse {106        /// A field has been added indicating whether it should be reported as a lint,107        /// addressing issue#119301.108        warn_private: bool,109    },110    MacroExport,111}112113/// Manually implement `Debug` for `ImportKind` because the `source/target_bindings`114/// contain `Cell`s which can introduce infinite loops while printing.115impl<'ra> std::fmt::Debug for ImportKind<'ra> {116    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {117        use ImportKind::*;118        match self {119            Single { source, target, decls, nested, id, .. } => f120                .debug_struct("Single")121                .field("source", source)122                .field("target", target)123                // Ignore the nested bindings to avoid an infinite loop while printing.124                .field(125                    "decls",126                    &decls.clone().map(|b| b.into_inner().decl().map(|_| format_args!(".."))),127                )128                .field("nested", nested)129                .field("id", id)130                .finish(),131            Glob { max_vis, id } => {132                f.debug_struct("Glob").field("max_vis", max_vis).field("id", id).finish()133            }134            ExternCrate { source, target, id } => f135                .debug_struct("ExternCrate")136                .field("source", source)137                .field("target", target)138                .field("id", id)139                .finish(),140            MacroUse { warn_private } => {141                f.debug_struct("MacroUse").field("warn_private", warn_private).finish()142            }143            MacroExport => f.debug_struct("MacroExport").finish(),144        }145    }146}147148#[derive(Debug, Clone, Default)]149pub(crate) struct OnUnknownData {150    directive: Box<Directive>,151}152153impl OnUnknownData {154    pub(crate) fn from_attrs<'tcx>(tcx: TyCtxt<'tcx>, item: &Item) -> Option<OnUnknownData> {155        if tcx.features().diagnostic_on_unknown()156            && let Some(Attribute::Parsed(AttributeKind::OnUnknown { directive, .. })) =157                AttributeParser::parse_limited(158                    tcx.sess,159                    &item.attrs,160                    &[sym::diagnostic, sym::on_unknown],161                )162        {163            Some(Self { directive: directive? })164        } else {165            None166        }167    }168}169170/// One import.171#[derive(Debug, Clone)]172pub(crate) struct ImportData<'ra> {173    pub kind: ImportKind<'ra>,174175    /// Node ID of the "root" use item -- this is always the same as `ImportKind`'s `id`176    /// (if it exists) except in the case of "nested" use trees, in which case177    /// it will be the ID of the root use tree. e.g., in the example178    /// ```ignore (incomplete code)179    /// use foo::bar::{a, b}180    /// ```181    /// this would be the ID of the `use foo::bar` `UseTree` node.182    /// In case of imports without their own node ID it's the closest node that can be used,183    /// for example, for reporting lints.184    pub root_id: NodeId,185186    /// Span of the entire use statement.187    pub use_span: Span,188189    /// Span of the entire use statement with attributes.190    pub use_span_with_attributes: Span,191192    /// Did the use statement have any attributes?193    pub has_attributes: bool,194195    /// Span of this use tree.196    pub span: Span,197198    /// Span of the *root* use tree (see `root_id`).199    pub root_span: Span,200201    pub parent_scope: ParentScope<'ra>,202    pub module_path: Vec<Segment>,203    /// The resolution of `module_path`:204    ///205    /// | `module_path` | `imported_module` | remark |206    /// |-|-|-|207    /// |`use prefix::foo`| `ModuleOrUniformRoot::Module(prefix)`         | - |208    /// |`use ::foo`      | `ModuleOrUniformRoot::ExternPrelude`          | 2018+ editions |209    /// |`use ::foo`      | `ModuleOrUniformRoot::ModuleAndExternPrelude` | a special case in 2015 edition |210    /// |`use foo`        | `ModuleOrUniformRoot::CurrentScope`           | - |211    pub imported_module: CmCell<Option<ModuleOrUniformRoot<'ra>>>,212    pub vis: Visibility,213214    /// Span of the visibility.215    pub vis_span: Span,216217    /// A `#[diagnostic::on_unknown]` attribute applied218    /// to the given import. This allows crates to specify219    /// custom error messages for a specific import220    ///221    /// This is `None` if the feature flag for `diagnostic::on_unknown` is disabled.222    pub on_unknown_attr: Option<OnUnknownData>,223}224225/// All imports are unique and allocated on a same arena,226/// so we can use referential equality to compare them.227pub(crate) type Import<'ra> = Interned<'ra, ImportData<'ra>>;228229// Allows us to use Interned without actually enforcing (via Hash/PartialEq/...) uniqueness of the230// contained data.231// FIXME: We may wish to actually have at least debug-level assertions that Interned's guarantees232// are upheld.233impl std::hash::Hash for ImportData<'_> {234    fn hash<H>(&self, _: &mut H)235    where236        H: std::hash::Hasher,237    {238        unreachable!()239    }240}241242impl<'ra> ImportData<'ra> {243    pub(crate) fn is_glob(&self) -> bool {244        matches!(self.kind, ImportKind::Glob { .. })245    }246247    pub(crate) fn is_nested(&self) -> bool {248        match self.kind {249            ImportKind::Single { nested, .. } => nested,250            _ => false,251        }252    }253254    pub(crate) fn id(&self) -> Option<NodeId> {255        match self.kind {256            ImportKind::Single { id, .. }257            | ImportKind::Glob { id, .. }258            | ImportKind::ExternCrate { id, .. } => Some(id),259            ImportKind::MacroUse { .. } | ImportKind::MacroExport => None,260        }261    }262263    pub(crate) fn simplify(&self, r: &Resolver<'_, '_>) -> Reexport {264        let to_def_id = |id| r.local_def_id(id).to_def_id();265        match self.kind {266            ImportKind::Single { id, .. } => Reexport::Single(to_def_id(id)),267            ImportKind::Glob { id, .. } => Reexport::Glob(to_def_id(id)),268            ImportKind::ExternCrate { id, .. } => Reexport::ExternCrate(to_def_id(id)),269            ImportKind::MacroUse { .. } => Reexport::MacroUse,270            ImportKind::MacroExport => Reexport::MacroExport,271        }272    }273274    fn summary(&self) -> ImportSummary {275        ImportSummary {276            vis: self.vis,277            nearest_parent_mod: self.parent_scope.module.nearest_parent_mod().expect_local(),278            is_single: matches!(self.kind, ImportKind::Single { .. }),279            priv_macro_use: matches!(self.kind, ImportKind::MacroUse { warn_private: true }),280            span: self.span,281        }282    }283}284285/// Records information about the resolution of a name in a namespace of a module.286#[derive(Clone, Debug)]287pub(crate) struct NameResolution<'ra> {288    /// Single imports that may define the name in the namespace.289    /// Imports are arena-allocated, so it's ok to use pointers as keys.290    pub single_imports: FxIndexSet<Import<'ra>>,291    /// The non-glob declaration for this name, if it is known to exist.292    pub non_glob_decl: Option<Decl<'ra>> = None,293    /// The glob declaration for this name, if it is known to exist.294    pub glob_decl: Option<Decl<'ra>> = None,295    pub orig_ident_span: Span,296}297298impl<'ra> NameResolution<'ra> {299    pub(crate) fn new(orig_ident_span: Span) -> Self {300        NameResolution { single_imports: FxIndexSet::default(), orig_ident_span, .. }301    }302303    /// Returns the best declaration if it is not going to change, and `None` if the best304    /// declaration may still change to something else.305    /// FIXME: this function considers `single_imports`, but not `unexpanded_invocations`, so306    /// the returned declaration may actually change after expanding macros in the same module,307    /// because of this fact we have glob overwriting (`select_glob_decl`). Consider using308    /// `unexpanded_invocations` here and avoiding glob overwriting entirely, if it doesn't cause309    /// code breakage in practice.310    /// FIXME: relationship between this function and similar `DeclData::determined` is unclear.311    pub(crate) fn determined_decl(&self) -> Option<Decl<'ra>> {312        if self.non_glob_decl.is_some() {313            self.non_glob_decl314        } else if self.glob_decl.is_some() && self.single_imports.is_empty() {315            self.glob_decl316        } else {317            None318        }319    }320321    pub(crate) fn best_decl(&self) -> Option<Decl<'ra>> {322        self.non_glob_decl.or(self.glob_decl)323    }324}325326/// An error that may be transformed into a diagnostic later. Used to combine multiple unresolved327/// import errors within the same use tree into a single diagnostic.328#[derive(Debug, Clone)]329struct UnresolvedImportError {330    span: Span,331    label: Option<String>,332    note: Option<String>,333    suggestion: Option<Suggestion>,334    candidates: Option<Vec<ImportSuggestion>>,335    segment: Option<Symbol>,336    /// comes from `PathRes::Failed { module }`337    module: Option<DefId>,338    on_unknown_attr: Option<OnUnknownData>,339}340341// Reexports of the form `pub use foo as bar;` where `foo` is `extern crate foo;`342// are permitted for backward-compatibility under a deprecation lint.343fn pub_use_of_private_extern_crate_hack(import: ImportSummary, decl: Decl<'_>) -> Option<NodeId> {344    match (import.is_single, decl.kind) {345        (true, DeclKind::Import { import: decl_import, .. })346            if let ImportKind::ExternCrate { id, .. } = decl_import.kind347                && import.vis.is_public() =>348        {349            Some(id)350        }351        _ => None,352    }353}354355/// Removes identical import layers from two declarations.356fn remove_same_import<'ra>(d1: Decl<'ra>, d2: Decl<'ra>) -> (Decl<'ra>, Decl<'ra>) {357    if let DeclKind::Import { import: import1, source_decl: d1_next } = d1.kind358        && let DeclKind::Import { import: import2, source_decl: d2_next } = d2.kind359        && import1 == import2360    {361        assert_eq!(d1.expansion, d2.expansion);362        assert_eq!(d1.span, d2.span);363        if d1.ambiguity.get() != d2.ambiguity.get() {364            assert!(d1.ambiguity.get().is_some());365            assert!(d2.ambiguity.get().is_none());366        }367        // Visibility of the new import declaration may be different,368        // because it already incorporates the visibility of the source binding.369        // `warn_ambiguity` of a re-fetched glob can also change in both directions.370        remove_same_import(d1_next, d2_next)371    } else {372        (d1, d2)373    }374}375376impl<'ra, 'tcx> Resolver<'ra, 'tcx> {377    pub(crate) fn import_decl_vis(&self, decl: Decl<'ra>, import: ImportSummary) -> Visibility {378        self.import_decl_vis_ext(decl, import, false)379    }380381    pub(crate) fn import_decl_vis_ext(382        &self,383        decl: Decl<'ra>,384        import: ImportSummary,385        min: bool,386    ) -> Visibility {387        assert!(import.vis.is_accessible_from(import.nearest_parent_mod, self.tcx));388        let decl_vis = if min { decl.min_vis() } else { decl.vis() };389        let ord = decl_vis.partial_cmp(import.vis, self.tcx);390        let extern_crate_hack = pub_use_of_private_extern_crate_hack(import, decl).is_some();391        if ord == Some(Ordering::Less)392            && decl_vis.is_accessible_from(import.nearest_parent_mod, self.tcx)393            && !extern_crate_hack394        {395            // Imported declaration is less visible than the import, but is still visible396            // from the current module, use the declaration's visibility.397            decl_vis.expect_local()398        } else {399            // Good case - imported declaration is more visible than the import, or the same,400            // use the import's visibility.401            //402            // Bad case - imported declaration is too private for the current module.403            // It doesn't matter what visibility we choose here (except in the `PRIVATE_MACRO_USE`404            // and `PUB_USE_OF_PRIVATE_EXTERN_CRATE` cases), because an error will be reported.405            // Use import visibility to keep the all declaration visibilities in a module ordered.406            if !min407                && matches!(ord, None | Some(Ordering::Less))408                && !extern_crate_hack409                && !import.priv_macro_use410            {411                let msg = format!("cannot extend visibility from {decl_vis:?} to {:?}", import.vis);412                self.dcx().span_delayed_bug(import.span, msg);413            }414            import.vis415        }416    }417418    /// Given an import and the declaration that it points to,419    /// create the corresponding import declaration.420    pub(crate) fn new_import_decl(&self, decl: Decl<'ra>, import: Import<'ra>) -> Decl<'ra> {421        let vis = self.import_decl_vis(decl, import.summary());422423        if let ImportKind::Glob { ref max_vis, .. } = import.kind424            && (vis == import.vis425                || max_vis.get().is_none_or(|max_vis| vis.greater_than(max_vis, self.tcx)))426        {427            max_vis.set_unchecked(Some(vis))428        }429430        self.arenas.alloc_decl(DeclData {431            kind: DeclKind::Import { source_decl: decl, import },432            ambiguity: CmCell::new(None),433            warn_ambiguity: CmCell::new(false),434            span: import.span,435            initial_vis: vis.to_def_id(),436            ambiguity_vis_max: CmCell::new(None),437            ambiguity_vis_min: CmCell::new(None),438            expansion: import.parent_scope.expansion,439            parent_module: Some(import.parent_scope.module),440        })441    }442443    /// If `glob_decl` attempts to overwrite `old_glob_decl` in a module,444    /// decide which one to keep.445    fn select_glob_decl(446        &self,447        old_glob_decl: Decl<'ra>,448        glob_decl: Decl<'ra>,449        warn_ambiguity: bool,450    ) -> Decl<'ra> {451        assert!(glob_decl.is_glob_import());452        assert!(old_glob_decl.is_glob_import());453        assert_ne!(glob_decl, old_glob_decl);454        // `best_decl` with a given key in a module may be overwritten in a455        // number of cases (all of them can be seen below in the `match` in `try_define_local`),456        // all these overwrites will be re-fetched by glob imports importing457        // from that module without generating new ambiguities.458        // - A glob decl is overwritten by a non-glob decl arriving later.459        // - A glob decl is overwritten by its clone after setting ambiguity in it.460        //   FIXME: avoid this by removing `warn_ambiguity`, or by triggering glob re-fetch461        //   with the same decl in some way.462        // - A glob decl is overwritten by a glob decl re-fetching an463        //   overwritten decl from other module (the recursive case).464        // Here we are detecting all such re-fetches and overwrite old decls465        // with the re-fetched decls.466        // This is probably incorrect in corner cases, and the outdated decls still get467        // propagated to other places and get stuck there, but that's what we have at the moment.468        let (old_deep_decl, deep_decl) = remove_same_import(old_glob_decl, glob_decl);469        if deep_decl != glob_decl {470            // Some import layers have been removed, need to overwrite.471            assert_ne!(old_deep_decl, old_glob_decl);472            // FIXME: reenable the asserts when `warn_ambiguity` is removed (#149195).473            // assert_ne!(old_deep_decl, deep_decl);474            // assert!(old_deep_decl.is_glob_import());475            assert!(!deep_decl.is_glob_import());476            if old_glob_decl.ambiguity.get().is_some() && glob_decl.ambiguity.get().is_none() {477                // Do not lose glob ambiguities when re-fetching the glob.478                glob_decl.ambiguity.set_unchecked(old_glob_decl.ambiguity.get());479            }480            if glob_decl.is_ambiguity_recursive() {481                glob_decl.warn_ambiguity.set_unchecked(true);482            }483            glob_decl484        } else if glob_decl.res() != old_glob_decl.res() {485            old_glob_decl.ambiguity.set_unchecked(Some(glob_decl));486            old_glob_decl.warn_ambiguity.set_unchecked(warn_ambiguity);487            if warn_ambiguity {488                old_glob_decl489            } else {490                // Need a fresh decl so other glob imports importing it could re-fetch it491                // and set their own `warn_ambiguity` to true.492                // FIXME: remove this when `warn_ambiguity` is removed (#149195).493                self.arenas.alloc_decl((*old_glob_decl).clone())494            }495        } else if let old_vis = old_glob_decl.vis()496            && let vis = glob_decl.vis()497            && old_vis != vis498        {499            // We are glob-importing the same item but with a different visibility.500            // All visibilities here are ordered because all of them are ancestors of `module`.501            if vis.greater_than(old_vis, self.tcx) {502                old_glob_decl.ambiguity_vis_max.set_unchecked(Some(glob_decl));503            } else if let old_min_vis = old_glob_decl.min_vis()504                && old_min_vis != vis505                && old_min_vis.greater_than(vis, self.tcx)506            {507                old_glob_decl.ambiguity_vis_min.set_unchecked(Some(glob_decl));508            }509            old_glob_decl510        } else if glob_decl.is_ambiguity_recursive() && !old_glob_decl.is_ambiguity_recursive() {511            // Overwriting a non-ambiguous glob import with an ambiguous glob import.512            old_glob_decl.ambiguity.set_unchecked(Some(glob_decl));513            old_glob_decl.warn_ambiguity.set_unchecked(true);514            old_glob_decl515        } else {516            old_glob_decl517        }518    }519520    /// Attempt to put the declaration with the given name and namespace into the module,521    /// and return existing declaration if there is a collision.522    pub(crate) fn try_plant_decl_into_local_module(523        &mut self,524        ident: IdentKey,525        orig_ident_span: Span,526        ns: Namespace,527        decl: Decl<'ra>,528        warn_ambiguity: bool,529    ) -> Result<(), Decl<'ra>> {530        assert!(!decl.warn_ambiguity.get());531        assert!(decl.ambiguity.get().is_none());532        assert!(decl.ambiguity_vis_max.get().is_none());533        assert!(decl.ambiguity_vis_min.get().is_none());534        let module = decl.parent_module.unwrap().expect_local();535        assert!(self.is_accessible_from(decl.vis(), module.to_module()));536        let res = decl.res();537        self.check_reserved_macro_name(ident.name, orig_ident_span, res);538        // Even if underscore names cannot be looked up, we still need to add them to modules,539        // because they can be fetched by glob imports from those modules, and bring traits540        // into scope both directly and through glob imports.541        let key = BindingKey::new_disambiguated(ident, ns, || {542            module.underscore_disambiguator.update_unchecked(|d| d + 1);543            module.underscore_disambiguator.get()544        });545        self.update_local_resolution(546            module,547            key,548            orig_ident_span,549            warn_ambiguity,550            |this, resolution| {551                if decl.is_glob_import() {552                    resolution.glob_decl = Some(match resolution.glob_decl {553                        Some(old_decl) => this.select_glob_decl(554                            old_decl,555                            decl,556                            warn_ambiguity && resolution.non_glob_decl.is_none(),557                        ),558                        None => decl,559                    })560                } else {561                    resolution.non_glob_decl = Some(match resolution.non_glob_decl {562                        Some(old_decl) => return Err(old_decl),563                        None => decl,564                    })565                }566567                Ok(())568            },569        )570    }571572    // Use `f` to mutate the resolution of the name in the module.573    // If the resolution becomes a success, define it in the module's glob importers.574    fn update_local_resolution<T, F>(575        &mut self,576        module: LocalModule<'ra>,577        key: BindingKey,578        orig_ident_span: Span,579        warn_ambiguity: bool,580        f: F,581    ) -> T582    where583        F: FnOnce(&Resolver<'ra, 'tcx>, &mut NameResolution<'ra>) -> T,584    {585        // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,586        // during which the resolution might end up getting re-defined via a glob cycle.587        let (binding, t, warn_ambiguity) = {588            let resolution = &mut *self589                .resolution_or_default(module.to_module(), key, orig_ident_span)590                .borrow_mut_unchecked();591            let old_decl = resolution.determined_decl();592            let old_vis = old_decl.map(|d| d.vis());593594            let t = f(self, resolution);595596            if let Some(binding) = resolution.determined_decl()597                && (old_decl != Some(binding) || old_vis != Some(binding.vis()))598            {599                (binding, t, warn_ambiguity || old_decl.is_some())600            } else {601                return t;602            }603        };604605        let Ok(glob_importers) = module.glob_importers.try_borrow_mut_unchecked() else {606            return t;607        };608609        // Define or update `binding` in `module`s glob importers.610        for import in glob_importers.iter() {611            let mut ident = key.ident;612            let scope = match ident613                .ctxt614                .update_unchecked(|ctxt| ctxt.reverse_glob_adjust(module.expansion, import.span))615            {616                Some(Some(def)) => self.expn_def_scope(def),617                Some(None) => import.parent_scope.module,618                None => continue,619            };620            if self.is_accessible_from(binding.vis(), scope) {621                let import_decl = self.new_import_decl(binding, *import);622                self.try_plant_decl_into_local_module(623                    ident,624                    orig_ident_span,625                    key.ns,626                    import_decl,627                    warn_ambiguity,628                )629                .expect("planting a glob cannot fail");630            }631        }632633        t634    }635636    // Define a dummy resolution containing a `Res::Err` as a placeholder for a failed637    // or indeterminate resolution, also mark such failed imports as used to avoid duplicate diagnostics.638    fn import_dummy_binding(&mut self, import: Import<'ra>, is_indeterminate: bool) {639        if let ImportKind::Single { target, ref decls, .. } = import.kind {640            if !(is_indeterminate || decls.iter().all(|d| d.get().decl().is_none())) {641                return; // Has resolution, do not create the dummy binding642            }643            let dummy_decl = self.dummy_decl;644            let dummy_decl = self.new_import_decl(dummy_decl, import);645            self.per_ns(|this, ns| {646                let ident = IdentKey::new(target);647                // This can fail, dummies are inserted only in non-occupied slots.648                let _ = this.try_plant_decl_into_local_module(649                    ident,650                    target.span,651                    ns,652                    dummy_decl,653                    false,654                );655                // Don't remove underscores from `single_imports`, they were never added.656                if target.name != kw::Underscore {657                    let key = BindingKey::new(ident, ns);658                    this.update_local_resolution(659                        import.parent_scope.module.expect_local(),660                        key,661                        target.span,662                        false,663                        |_, resolution| {664                            resolution.single_imports.swap_remove(&import);665                        },666                    )667                }668            });669            self.record_use(target, dummy_decl, Used::Other);670        } else if import.imported_module.get().is_none() {671            self.import_use_map.insert(import, Used::Other);672            if let Some(id) = import.id() {673                self.used_imports.insert(id);674            }675        }676    }677678    // Import resolution679    //680    // This is a fixed-point algorithm. We resolve imports until our efforts681    // are stymied by an unresolved import; then we bail out of the current682    // module and continue. We terminate successfully once no more imports683    // remain or unsuccessfully when no forward progress in resolving imports684    // is made.685686    /// Resolves all imports for the crate. This method performs the fixed-687    /// point iteration.688    pub(crate) fn resolve_imports(&mut self) {689        let mut prev_indeterminate_count = usize::MAX;690        let mut indeterminate_count = self.indeterminate_imports.len() * 3;691        while indeterminate_count < prev_indeterminate_count {692            prev_indeterminate_count = indeterminate_count;693            indeterminate_count = 0;694            self.assert_speculative = true;695            for import in mem::take(&mut self.indeterminate_imports) {696                let import_indeterminate_count = self.cm().resolve_import(import);697                indeterminate_count += import_indeterminate_count;698                match import_indeterminate_count {699                    0 => self.determined_imports.push(import),700                    _ => self.indeterminate_imports.push(import),701                }702            }703            self.assert_speculative = false;704        }705    }706707    pub(crate) fn finalize_imports(&mut self) {708        let mut module_children = Default::default();709        let mut ambig_module_children = Default::default();710        for module in &self.local_modules {711            self.finalize_resolutions_in(*module, &mut module_children, &mut ambig_module_children);712        }713        self.module_children = module_children;714        self.ambig_module_children = ambig_module_children;715716        let mut seen_spans = FxHashSet::default();717        let mut errors = vec![];718        let mut prev_root_id: NodeId = NodeId::ZERO;719        let determined_imports = mem::take(&mut self.determined_imports);720        let indeterminate_imports = mem::take(&mut self.indeterminate_imports);721722        let mut glob_error = false;723        for (is_indeterminate, import) in determined_imports724            .iter()725            .map(|i| (false, i))726            .chain(indeterminate_imports.iter().map(|i| (true, i)))727        {728            let unresolved_import_error = self.finalize_import(*import);729            // If this import is unresolved then create a dummy import730            // resolution for it so that later resolve stages won't complain.731            self.import_dummy_binding(*import, is_indeterminate);732733            let Some(err) = unresolved_import_error else { continue };734735            glob_error |= import.is_glob();736737            if let ImportKind::Single { source, ref decls, .. } = import.kind738                && source.name == kw::SelfLower739                // Silence `unresolved import` error if E0429 is already emitted740                && let PendingDecl::Ready(None) = decls.value_ns.get()741            {742                continue;743            }744745            if prev_root_id != NodeId::ZERO && prev_root_id != import.root_id && !errors.is_empty()746            {747                // In the case of a new import line, throw a diagnostic message748                // for the previous line.749                self.throw_unresolved_import_error(errors, glob_error);750                errors = vec![];751            }752            if seen_spans.insert(err.span) {753                errors.push((*import, err));754                prev_root_id = import.root_id;755            }756        }757758        if self.cstore().had_extern_crate_load_failure() {759            self.tcx.sess.dcx().abort_if_errors();760        }761762        if !errors.is_empty() {763            self.throw_unresolved_import_error(errors, glob_error);764            return;765        }766767        for import in &indeterminate_imports {768            let path = import_path_to_string(769                &import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),770                &import.kind,771                import.span,772            );773            // FIXME: there should be a better way of doing this than774            // formatting this as a string then checking for `::`775            if path.contains("::") {776                let err = UnresolvedImportError {777                    span: import.span,778                    label: None,779                    note: None,780                    suggestion: None,781                    candidates: None,782                    segment: None,783                    module: None,784                    on_unknown_attr: import.on_unknown_attr.clone(),785                };786                errors.push((*import, err))787            }788        }789790        if !errors.is_empty() {791            self.throw_unresolved_import_error(errors, glob_error);792        }793    }794795    pub(crate) fn lint_reexports(&mut self, exported_ambiguities: FxHashSet<Decl<'ra>>) {796        for module in &self.local_modules {797            for (key, resolution) in self.resolutions(module.to_module()).borrow().iter() {798                let resolution = resolution.borrow();799                let Some(binding) = resolution.best_decl() else { continue };800801                // Report "cannot reexport" errors for exotic cases involving macros 2.0802                // privacy bending or invariant-breaking code under deprecation lints.803                for decl in [resolution.non_glob_decl, resolution.glob_decl] {804                    if let Some(decl) = decl805                        && let DeclKind::Import { source_decl, import } = decl.kind806                    {807                        // The source entity is too private to be reexported808                        // with the given import declaration's visibility.809                        let ord = source_decl.vis().partial_cmp(decl.vis(), self.tcx);810                        if matches!(ord, None | Some(Ordering::Less)) {811                            let ident = match import.kind {812                                ImportKind::Single { source, .. } => source,813                                _ => key.ident.orig(resolution.orig_ident_span),814                            };815                            if let Some(lint) =816                                self.report_cannot_reexport(import, source_decl, ident, key.ns)817                            {818                                self.lint_buffer.add_early_lint(lint);819                            }820                        }821                    }822                }823824                if let DeclKind::Import { import, .. } = binding.kind825                    && let Some(amb_binding) = binding.ambiguity.get()826                    && binding.res() != Res::Err827                    && exported_ambiguities.contains(&binding)828                {829                    self.lint_buffer.buffer_lint(830                        AMBIGUOUS_GLOB_REEXPORTS,831                        import.root_id,832                        import.root_span,833                        errors::AmbiguousGlobReexports {834                            name: key.ident.name.to_string(),835                            namespace: key.ns.descr().to_string(),836                            first_reexport: import.root_span,837                            duplicate_reexport: amb_binding.span,838                        },839                    );840                }841842                if let Some(glob_decl) = resolution.glob_decl843                    && resolution.non_glob_decl.is_some()844                {845                    if binding.res() != Res::Err846                        && glob_decl.res() != Res::Err847                        && let DeclKind::Import { import: glob_import, .. } = glob_decl.kind848                        && let Some(glob_import_id) = glob_import.id()849                        && let glob_import_def_id = self.local_def_id(glob_import_id)850                        && self.effective_visibilities.is_exported(glob_import_def_id)851                        && glob_decl.vis().is_public()852                        && !binding.vis().is_public()853                    {854                        let binding_id = match binding.kind {855                            DeclKind::Def(res) => {856                                Some(self.def_id_to_node_id(res.def_id().expect_local()))857                            }858                            DeclKind::Import { import, .. } => import.id(),859                        };860                        if let Some(binding_id) = binding_id {861                            self.lint_buffer.buffer_lint(862                                HIDDEN_GLOB_REEXPORTS,863                                binding_id,864                                binding.span,865                                errors::HiddenGlobReexports {866                                    name: key.ident.name.to_string(),867                                    namespace: key.ns.descr().to_owned(),868                                    glob_reexport: glob_decl.span,869                                    private_item: binding.span,870                                },871                            );872                        }873                    }874                }875876                if let DeclKind::Import { import, .. } = binding.kind877                    && let Some(binding_id) = import.id()878                    && let import_def_id = self.local_def_id(binding_id)879                    && self.effective_visibilities.is_exported(import_def_id)880                    && let Res::Def(reexported_kind, reexported_def_id) = binding.res()881                    && !matches!(reexported_kind, DefKind::Ctor(..))882                    && !reexported_def_id.is_local()883                    && self.tcx.is_private_dep(reexported_def_id.krate)884                {885                    self.lint_buffer.buffer_lint(886                        EXPORTED_PRIVATE_DEPENDENCIES,887                        binding_id,888                        binding.span,889                        crate::errors::ReexportPrivateDependency {890                            name: key.ident.name,891                            kind: binding.res().descr(),892                            krate: self.tcx.crate_name(reexported_def_id.krate),893                        },894                    );895                }896            }897        }898    }899900    fn throw_unresolved_import_error(901        &mut self,902        mut errors: Vec<(Import<'_>, UnresolvedImportError)>,903        glob_error: bool,904    ) {905        errors.retain(|(_import, err)| match err.module {906            // Skip `use` errors for `use foo::Bar;` if `foo.rs` has unrecovered parse errors.907            Some(def_id) if self.mods_with_parse_errors.contains(&def_id) => false,908            // If we've encountered something like `use _;`, we've already emitted an error stating909            // that `_` is not a valid identifier, so we ignore that resolve error.910            _ => err.segment != Some(kw::Underscore),911        });912        if errors.is_empty() {913            self.tcx.dcx().delayed_bug("expected a parse or \"`_` can't be an identifier\" error");914            return;915        }916917        let span = MultiSpan::from_spans(errors.iter().map(|(_, err)| err.span).collect());918919        let paths = errors920            .iter()921            .map(|(import, err)| {922                let path = import_path_to_string(923                    &import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),924                    &import.kind,925                    err.span,926                );927                format!("`{path}`")928            })929            .collect::<Vec<_>>();930        let default_message =931            format!("unresolved import{} {}", pluralize!(paths.len()), paths.join(", "),);932        let (message, label, notes) =933            // Feature gating for `on_unknown_attr` happens initialization of the field934            if let Some(directive) = errors[0].1.on_unknown_attr.as_ref().map(|a| &a.directive) {935                let this = errors.iter().map(|(_import, err)| {936937                    // Is this unwrap_or reachable?938                    err.segment.unwrap_or(kw::Underscore)939                }).join(", ");940941                let args = FormatArgs {942                    this,943                    ..944                };945                let CustomDiagnostic { message, label, notes, .. } = directive.eval(None, &args);946947                (message, label, notes)948            } else {949                (None, None, Vec::new())950            };951        let has_custom_message = message.is_some();952        let message = message.as_deref().unwrap_or(default_message.as_str());953954        let mut diag = struct_span_code_err!(self.dcx(), span, E0432, "{message}");955        if has_custom_message {956            diag.note(default_message);957        }958959        if !notes.is_empty() {960            for note in notes {961                diag.note(note);962            }963        } else if let Some((_, UnresolvedImportError { note: Some(note), .. })) =964            errors.iter().last()965        {966            diag.note(note.clone());967        }968969        /// Upper limit on the number of `span_label` messages.970        const MAX_LABEL_COUNT: usize = 10;971972        for (import, err) in errors.into_iter().take(MAX_LABEL_COUNT) {973            if let Some(label) = &label {974                diag.span_label(err.span, label.clone());975            } else if let Some(label) = &err.label {976                diag.span_label(err.span, label.clone());977            }978979            if let Some((suggestions, msg, applicability)) = err.suggestion {980                if suggestions.is_empty() {981                    diag.help(msg);982                    continue;983                }984                diag.multipart_suggestion(msg, suggestions, applicability);985            }986987            if let Some(candidates) = &err.candidates {988                match &import.kind {989                    ImportKind::Single { nested: false, source, target, .. } => import_candidates(990                        self.tcx,991                        &mut diag,992                        Some(err.span),993                        candidates,994                        DiagMode::Import { append: false, unresolved_import: true },995                        (source != target)996                            .then(|| format!(" as {target}"))997                            .as_deref()998                            .unwrap_or(""),999                    ),1000                    ImportKind::Single { nested: true, source, target, .. } => {1001                        import_candidates(1002                            self.tcx,1003                            &mut diag,1004                            None,1005                            candidates,1006                            DiagMode::Normal,1007                            (source != target)1008                                .then(|| format!(" as {target}"))1009                                .as_deref()1010                                .unwrap_or(""),1011                        );1012                    }1013                    _ => {}1014                }1015            }10161017            if matches!(import.kind, ImportKind::Single { .. })1018                && let Some(segment) = err.segment1019                && let Some(module) = err.module1020            {1021                self.find_cfg_stripped(&mut diag, &segment, module)1022            }1023        }10241025        let guar = diag.emit();1026        if glob_error {1027            self.glob_error = Some(guar);1028        }1029    }10301031    /// Attempts to resolve the given import, returning:1032    /// - `0` means its resolution is determined.1033    /// - Other values mean that indeterminate exists under certain namespaces.1034    ///1035    /// Meanwhile, if resolve successful, the resolved bindings are written1036    /// into the module.1037    fn resolve_import<'r>(mut self: CmResolver<'r, 'ra, 'tcx>, import: Import<'ra>) -> usize {1038        debug!(1039            "(resolving import for module) resolving import `{}::...` in `{}`",1040            Segment::names_to_string(&import.module_path),1041            module_to_string(import.parent_scope.module).unwrap_or_else(|| "???".to_string()),1042        );1043        let module = if let Some(module) = import.imported_module.get() {1044            module1045        } else {1046            let path_res = self.reborrow().maybe_resolve_path(1047                &import.module_path,1048                None,1049                &import.parent_scope,1050                Some(import),1051            );10521053            match path_res {1054                PathResult::Module(module) => module,1055                PathResult::Indeterminate => return 3,1056                PathResult::NonModule(..) | PathResult::Failed { .. } => return 0,1057            }1058        };10591060        import.imported_module.set_unchecked(Some(module));1061        let (source, target, bindings) = match import.kind {1062            ImportKind::Single { source, target, ref decls, .. } => (source, target, decls),1063            ImportKind::Glob { .. } => {1064                self.get_mut_unchecked().resolve_glob_import(import);1065                return 0;1066            }1067            _ => unreachable!(),1068        };10691070        let mut indeterminate_count = 0;1071        self.per_ns_cm(|mut this, ns| {1072            if bindings[ns].get() != PendingDecl::Pending {1073                return;1074            };1075            let binding_result = this.reborrow().maybe_resolve_ident_in_module(1076                module,1077                source,1078                ns,1079                &import.parent_scope,1080                Some(import),1081            );1082            let parent = import.parent_scope.module;1083            let binding = match binding_result {1084                Ok(binding) => {1085                    if binding.is_assoc_item()1086                        && !this.tcx.features().import_trait_associated_functions()1087                    {1088                        feature_err(1089                            this.tcx.sess,1090                            sym::import_trait_associated_functions,1091                            import.span,1092                            "`use` associated items of traits is unstable",1093                        )1094                        .emit();1095                    }1096                    // We need the `target`, `source` can be extracted.1097                    let import_decl = this.new_import_decl(binding, import);1098                    this.get_mut_unchecked().plant_decl_into_local_module(1099                        IdentKey::new(target),1100                        target.span,1101                        ns,1102                        import_decl,1103                    );1104                    PendingDecl::Ready(Some(import_decl))1105                }1106                Err(Determinacy::Determined) => {1107                    // Don't remove underscores from `single_imports`, they were never added.1108                    if target.name != kw::Underscore {1109                        let key = BindingKey::new(IdentKey::new(target), ns);1110                        this.get_mut_unchecked().update_local_resolution(1111                            parent.expect_local(),1112                            key,1113                            target.span,1114                            false,1115                            |_, resolution| {1116                                resolution.single_imports.swap_remove(&import);1117                            },1118                        );1119                    }1120                    PendingDecl::Ready(None)1121                }1122                Err(Determinacy::Undetermined) => {1123                    indeterminate_count += 1;1124                    PendingDecl::Pending1125                }1126            };1127            bindings[ns].set_unchecked(binding);1128        });11291130        indeterminate_count1131    }11321133    /// Performs final import resolution, consistency checks and error reporting.1134    ///1135    /// Optionally returns an unresolved import error. This error is buffered and used to1136    /// consolidate multiple unresolved import errors into a single diagnostic.1137    fn finalize_import(&mut self, import: Import<'ra>) -> Option<UnresolvedImportError> {1138        let ignore_decl = match &import.kind {1139            ImportKind::Single { decls, .. } => decls[TypeNS].get().decl(),1140            _ => None,1141        };1142        let ambiguity_errors_len = |errors: &Vec<AmbiguityError<'_>>| {1143            errors.iter().filter(|error| error.warning.is_none()).count()1144        };1145        let prev_ambiguity_errors_len = ambiguity_errors_len(&self.ambiguity_errors);1146        let finalize = Finalize::with_root_span(import.root_id, import.span, import.root_span);11471148        // We'll provide more context to the privacy errors later, up to `len`.1149        let privacy_errors_len = self.privacy_errors.len();11501151        let path_res = self.cm().resolve_path(1152            &import.module_path,1153            None,1154            &import.parent_scope,1155            Some(finalize),1156            ignore_decl,1157            Some(import),1158        );11591160        let no_ambiguity =1161            ambiguity_errors_len(&self.ambiguity_errors) == prev_ambiguity_errors_len;11621163        let module = match path_res {1164            PathResult::Module(module) => {1165                // Consistency checks, analogous to `finalize_macro_resolutions`.1166                if let Some(initial_module) = import.imported_module.get() {1167                    if module != initial_module && no_ambiguity && !self.issue_145575_hack_applied {1168                        span_bug!(import.span, "inconsistent resolution for an import");1169                    }1170                } else if self.privacy_errors.is_empty() {1171                    self.dcx()1172                        .create_err(CannotDetermineImportResolution { span: import.span })1173                        .emit();1174                }11751176                module1177            }1178            PathResult::Failed {1179                is_error_from_last_segment: false,1180                span,1181                segment_name,1182                label,1183                suggestion,1184                module,1185                error_implied_by_parse_error: _,1186                message,1187                note: _,1188            } => {1189                if no_ambiguity {1190                    if !self.issue_145575_hack_applied {1191                        assert!(import.imported_module.get().is_none());1192                    }1193                    self.report_error(1194                        span,1195                        ResolutionError::FailedToResolve {1196                            segment: segment_name,1197                            label,1198                            suggestion,1199                            module,1200                            message,1201                        },1202                    );1203                }1204                return None;1205            }1206            PathResult::Failed {1207                is_error_from_last_segment: true,1208                span,1209                label,1210                suggestion,1211                module,1212                segment_name,1213                note,1214                ..1215            } => {1216                if no_ambiguity {1217                    if !self.issue_145575_hack_applied {1218                        assert!(import.imported_module.get().is_none());1219                    }1220                    let module = if let Some(ModuleOrUniformRoot::Module(m)) = module {1221                        m.opt_def_id()1222                    } else {1223                        None1224                    };1225                    let err = match self1226                        .make_path_suggestion(import.module_path.clone(), &import.parent_scope)1227                    {1228                        Some((suggestion, note)) => UnresolvedImportError {1229                            span,1230                            label: None,1231                            note,1232                            suggestion: Some((1233                                vec![(span, Segment::names_to_string(&suggestion))],1234                                String::from("a similar path exists"),1235                                Applicability::MaybeIncorrect,1236                            )),1237                            candidates: None,1238                            segment: Some(segment_name),1239                            module,1240                            on_unknown_attr: import.on_unknown_attr.clone(),1241                        },1242                        None => UnresolvedImportError {1243                            span,1244                            label: Some(label),1245                            note,1246                            suggestion,1247                            candidates: None,1248                            segment: Some(segment_name),1249                            module,1250                            on_unknown_attr: import.on_unknown_attr.clone(),1251                        },1252                    };1253                    return Some(err);1254                }1255                return None;1256            }1257            PathResult::NonModule(partial_res) => {1258                if no_ambiguity && partial_res.full_res() != Some(Res::Err) {1259                    // Check if there are no ambiguities and the result is not dummy.1260                    assert!(import.imported_module.get().is_none());1261                }1262                // The error was already reported earlier.1263                return None;1264            }1265            PathResult::Indeterminate => unreachable!(),1266        };12671268        let (ident, target, bindings, import_id) = match import.kind {1269            ImportKind::Single { source, target, ref decls, id, .. } => (source, target, decls, id),1270            ImportKind::Glob { ref max_vis, id } => {1271                if import.module_path.len() <= 1 {1272                    // HACK(eddyb) `lint_if_path_starts_with_module` needs at least1273                    // 2 segments, so the `resolve_path` above won't trigger it.1274                    let mut full_path = import.module_path.clone();1275                    full_path.push(Segment::from_ident(Ident::dummy()));1276                    self.lint_if_path_starts_with_module(finalize, &full_path, None);1277                }12781279                if let ModuleOrUniformRoot::Module(module) = module1280                    && module == import.parent_scope.module1281                {1282                    // Importing a module into itself is not allowed.1283                    return Some(UnresolvedImportError {1284                        span: import.span,1285                        label: Some(String::from("cannot glob-import a module into itself")),1286                        note: None,1287                        suggestion: None,1288                        candidates: None,1289                        segment: None,1290                        module: None,1291                        on_unknown_attr: None,1292                    });1293                }1294                if let Some(max_vis) = max_vis.get()1295                    && import.vis.greater_than(max_vis, self.tcx)1296                {1297                    let def_id = self.local_def_id(id);1298                    self.lint_buffer.buffer_lint(1299                        UNUSED_IMPORTS,1300                        id,1301                        import.span,1302                        crate::errors::RedundantImportVisibility {1303                            span: import.span,1304                            help: (),1305                            max_vis: max_vis.to_string(def_id, self.tcx),1306                            import_vis: import.vis.to_string(def_id, self.tcx),1307                        },1308                    );1309                }1310                return None;1311            }1312            _ => unreachable!(),1313        };13141315        if self.privacy_errors.len() != privacy_errors_len {1316            // Get the Res for the last element, so that we can point to alternative ways of1317            // importing it if available.1318            let mut path = import.module_path.clone();1319            path.push(Segment::from_ident(ident));1320            if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.cm().resolve_path(1321                &path,1322                None,1323                &import.parent_scope,1324                Some(finalize),1325                ignore_decl,1326                None,1327            ) {1328                let res = module.res().map(|r| (r, ident));1329                for error in &mut self.privacy_errors[privacy_errors_len..] {1330                    error.outermost_res = res;1331                }1332            } else {1333                // The final item is not a module (e.g., a struct, function, or macro).1334                // Resolve it directly in the parent module to get its Res, so1335                // `report_privacy_error()` can search for public re-export paths.1336                for ns in [TypeNS, ValueNS, MacroNS] {1337                    if let Ok(binding) = self.cm().resolve_ident_in_module(1338                        module,1339                        ident,1340                        ns,1341                        &import.parent_scope,1342                        None,1343                        ignore_decl,1344                        None,1345                    ) {1346                        let res = binding.res();1347                        for error in &mut self.privacy_errors[privacy_errors_len..] {1348                            error.outermost_res = Some((res, ident));1349                        }1350                        break;1351                    }1352                }1353            }1354        }13551356        let mut all_ns_err = true;1357        self.per_ns(|this, ns| {1358            let binding = this.cm().resolve_ident_in_module(1359                module,1360                ident,1361                ns,1362                &import.parent_scope,1363                Some(Finalize {1364                    report_private: false,1365                    import: Some(import.summary()),1366                    ..finalize1367                }),1368                bindings[ns].get().decl(),1369                Some(import),1370            );13711372            match binding {1373                Ok(binding) => {1374                    // Consistency checks, analogous to `finalize_macro_resolutions`.1375                    let initial_res = bindings[ns].get().decl().map(|binding| {1376                        let initial_binding = binding.import_source();1377                        all_ns_err = false;1378                        if target.name == kw::Underscore1379                            && initial_binding.is_extern_crate()1380                            && !initial_binding.is_import()1381                        {1382                            let used = if import.module_path.is_empty() {1383                                Used::Scope1384                            } else {1385                                Used::Other1386                            };1387                            this.record_use(ident, binding, used);1388                        }1389                        initial_binding.res()1390                    });1391                    let res = binding.res();1392                    let has_ambiguity_error =1393                        this.ambiguity_errors.iter().any(|error| error.warning.is_none());1394                    if res == Res::Err || has_ambiguity_error {1395                        this.dcx()1396                            .span_delayed_bug(import.span, "some error happened for an import");1397                        return;1398                    }1399                    if let Some(initial_res) = initial_res {1400                        if res != initial_res && !this.issue_145575_hack_applied {1401                            span_bug!(import.span, "inconsistent resolution for an import");1402                        }1403                    } else if this.privacy_errors.is_empty() {1404                        this.dcx()1405                            .create_err(CannotDetermineImportResolution { span: import.span })1406                            .emit();1407                    }1408                }1409                Err(..) => {1410                    // FIXME: This assert may fire if public glob is later shadowed by a private1411                    // single import (see test `issue-55884-2.rs`). In theory single imports should1412                    // always block globs, even if they are not yet resolved, so that this kind of1413                    // self-inconsistent resolution never happens.1414                    // Re-enable the assert when the issue is fixed.1415                    // assert!(result[ns].get().is_err());1416                }1417            }1418        });14191420        if all_ns_err {1421            let mut all_ns_failed = true;1422            self.per_ns(|this, ns| {1423                let binding = this.cm().resolve_ident_in_module(1424                    module,1425                    ident,1426                    ns,1427                    &import.parent_scope,1428                    Some(finalize),1429                    None,1430                    None,1431                );1432                if binding.is_ok() {1433                    all_ns_failed = false;1434                }1435            });14361437            return if all_ns_failed {1438                let names = match module {1439                    ModuleOrUniformRoot::Module(module) => {1440                        self.resolutions(module)1441                            .borrow()1442                            .iter()1443                            .filter_map(|(BindingKey { ident: i, .. }, resolution)| {1444                                if i.name == ident.name {1445                                    return None;1446                                } // Never suggest the same name1447                                if i.name == kw::Underscore {1448                                    return None;1449                                } // `use _` is never valid14501451                                let resolution = resolution.borrow();1452                                if let Some(name_binding) = resolution.best_decl() {1453                                    match name_binding.kind {1454                                        DeclKind::Import { source_decl, .. } => {1455                                            match source_decl.kind {1456                                                // Never suggest names that previously could not1457                                                // be resolved.1458                                                DeclKind::Def(Res::Err) => None,1459                                                _ => Some(i.name),1460                                            }1461                                        }1462                                        _ => Some(i.name),1463                                    }1464                                } else if resolution.single_imports.is_empty() {1465                                    None1466                                } else {1467                                    Some(i.name)1468                                }1469                            })1470                            .collect()1471                    }1472                    _ => Vec::new(),1473                };14741475                let lev_suggestion =1476                    find_best_match_for_name(&names, ident.name, None).map(|suggestion| {1477                        (1478                            vec![(ident.span, suggestion.to_string())],1479                            String::from("a similar name exists in the module"),1480                            Applicability::MaybeIncorrect,1481                        )1482                    });14831484                let (suggestion, note) =1485                    match self.check_for_module_export_macro(import, module, ident) {1486                        Some((suggestion, note)) => (suggestion.or(lev_suggestion), note),1487                        _ => (lev_suggestion, None),1488                    };14891490                // If importing of trait asscoiated items is enabled, an also find an1491                // `Enum`, then note that inherent associated items cannot be imported.1492                let note = if self.tcx.features().import_trait_associated_functions()1493                    && let PathResult::Module(ModuleOrUniformRoot::Module(m)) = path_res1494                    && let Some(Res::Def(DefKind::Enum, _)) = m.res()1495                {1496                    note.or(Some(1497                        "cannot import inherent associated items, only trait associated items"1498                            .to_string(),1499                    ))1500                } else {1501                    note1502                };15031504                let label = match module {1505                    ModuleOrUniformRoot::Module(module) => {1506                        let module_str = module_to_string(module);1507                        if let Some(module_str) = module_str {1508                            format!("no `{ident}` in `{module_str}`")1509                        } else {1510                            format!("no `{ident}` in the root")1511                        }1512                    }1513                    _ => {1514                        if !ident.is_path_segment_keyword() {1515                            format!("no external crate `{ident}`")1516                        } else {1517                            // HACK(eddyb) this shows up for `self` & `super`, which1518                            // should work instead - for now keep the same error message.1519                            format!("no `{ident}` in the root")1520                        }1521                    }1522                };15231524                let parent_suggestion =1525                    self.lookup_import_candidates(ident, TypeNS, &import.parent_scope, |_| true);15261527                Some(UnresolvedImportError {1528                    span: import.span,1529                    label: Some(label),1530                    note,1531                    suggestion,1532                    candidates: if !parent_suggestion.is_empty() {1533                        Some(parent_suggestion)1534                    } else {1535                        None1536                    },1537                    module: import.imported_module.get().and_then(|module| {1538                        if let ModuleOrUniformRoot::Module(m) = module {1539                            m.opt_def_id()1540                        } else {1541                            None1542                        }1543                    }),1544                    segment: Some(ident.name),1545                    on_unknown_attr: import.on_unknown_attr.clone(),1546                })1547            } else {1548                // `resolve_ident_in_module` reported a privacy error.1549                None1550            };1551        }15521553        let mut reexport_error = None;1554        let mut any_successful_reexport = false;1555        self.per_ns(|this, ns| {1556            let Some(binding) = bindings[ns].get().decl() else {1557                return;1558            };15591560            if import.vis.greater_than(binding.vis(), this.tcx) {1561                // In isolation, a declaration like this is not an error, but if *all* 1-31562                // declarations introduced by the import are more private than the import item's1563                // nominal visibility, then it's an error.1564                reexport_error = Some((ns, binding.import_source()));1565            } else {1566                any_successful_reexport = true;1567            }1568        });15691570        if !any_successful_reexport {1571            let (ns, binding) = reexport_error.unwrap();1572            if let Some(lint) = self.report_cannot_reexport(import, binding, ident, ns) {1573                self.lint_buffer.add_early_lint(lint);1574            }1575        }15761577        if import.module_path.len() <= 1 {1578            // HACK(eddyb) `lint_if_path_starts_with_module` needs at least1579            // 2 segments, so the `resolve_path` above won't trigger it.1580            let mut full_path = import.module_path.clone();1581            full_path.push(Segment::from_ident(ident));1582            self.per_ns(|this, ns| {1583                if let Some(binding) = bindings[ns].get().decl().map(|b| b.import_source()) {1584                    this.lint_if_path_starts_with_module(finalize, &full_path, Some(binding));1585                }1586            });1587        }15881589        // Record what this import resolves to for later uses in documentation,1590        // this may resolve to either a value or a type, but for documentation1591        // purposes it's good enough to just favor one over the other.1592        self.per_ns(|this, ns| {1593            if let Some(binding) = bindings[ns].get().decl().map(|b| b.import_source()) {1594                this.import_res_map.entry(import_id).or_default()[ns] = Some(binding.res());1595            }1596        });15971598        debug!("(resolving single import) successfully resolved import");1599        None1600    }16011602    fn report_cannot_reexport(1603        &self,1604        import: Import<'ra>,1605        decl: Decl<'ra>,1606        ident: Ident,1607        ns: Namespace,1608    ) -> Option<BufferedEarlyLint> {1609        let crate_private_reexport = match decl.vis() {1610            Visibility::Restricted(def_id) if def_id.is_top_level_module() => true,1611            _ => false,1612        };16131614        if let Some(extern_crate_id) = pub_use_of_private_extern_crate_hack(import.summary(), decl)1615        {1616            let ImportKind::Single { id, .. } = import.kind else { unreachable!() };1617            let sugg = self.tcx.source_span(self.local_def_id(extern_crate_id)).shrink_to_lo();1618            let diagnostic = crate::errors::PrivateExternCrateReexport { ident, sugg };1619            return Some(BufferedEarlyLint {1620                lint_id: LintId::of(PUB_USE_OF_PRIVATE_EXTERN_CRATE),1621                node_id: id,1622                span: Some(import.span.into()),1623                diagnostic: diagnostic.into(),1624            });1625        } else if ns == TypeNS {1626            let err = if crate_private_reexport {1627                self.dcx().create_err(CannotBeReexportedCratePublicNS { span: import.span, ident })1628            } else {1629                self.dcx().create_err(CannotBeReexportedPrivateNS { span: import.span, ident })1630            };1631            err.emit();1632        } else {1633            let mut err = if crate_private_reexport {1634                self.dcx().create_err(CannotBeReexportedCratePublic { span: import.span, ident })1635            } else {1636                self.dcx().create_err(CannotBeReexportedPrivate { span: import.span, ident })1637            };16381639            match decl.kind {1640                // exclude decl_macro1641                DeclKind::Def(Res::Def(DefKind::Macro(_), def_id))1642                    if self.get_macro_by_def_id(def_id).macro_rules =>1643                {1644                    err.subdiagnostic(ConsiderAddingMacroExport { span: decl.span });1645                    err.subdiagnostic(ConsiderMarkingAsPubCrate { vis_span: import.vis_span });1646                }1647                _ => {1648                    err.subdiagnostic(ConsiderMarkingAsPub { span: import.span, ident });1649                }1650            }1651            err.emit();1652        }16531654        None1655    }16561657    pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'ra>) -> bool {1658        // This function is only called for single imports.1659        let ImportKind::Single { source, target, ref decls, id, .. } = import.kind else {1660            unreachable!()1661        };16621663        // Skip if the import is of the form `use source as target` and source != target.1664        if source != target {1665            return false;1666        }16671668        // Skip if the import was produced by a macro.1669        if import.parent_scope.expansion != LocalExpnId::ROOT {1670            return false;1671        }16721673        // Skip if we are inside a named module (in contrast to an anonymous1674        // module defined by a block).1675        // Skip if the import is public or was used through non scope-based resolution,1676        // e.g. through a module-relative path.1677        if self.import_use_map.get(&import) == Some(&Used::Other)1678            || self.effective_visibilities.is_exported(self.local_def_id(id))1679        {1680            return false;1681        }16821683        let mut is_redundant = true;1684        let mut redundant_span = PerNS { value_ns: None, type_ns: None, macro_ns: None };1685        self.per_ns(|this, ns| {1686            let binding = decls[ns].get().decl().map(|b| b.import_source());1687            if is_redundant && let Some(binding) = binding {1688                if binding.res() == Res::Err {1689                    return;1690                }16911692                match this.cm().resolve_ident_in_scope_set(1693                    target,1694                    ScopeSet::All(ns),1695                    &import.parent_scope,1696                    None,1697                    decls[ns].get().decl(),1698                    None,1699                ) {1700                    Ok(other_binding) => {1701                        is_redundant = binding.res() == other_binding.res()1702                            && !other_binding.is_ambiguity_recursive();1703                        if is_redundant {1704                            redundant_span[ns] =1705                                Some((other_binding.span, other_binding.is_import()));1706                        }1707                    }1708                    Err(_) => is_redundant = false,1709                }1710            }1711        });17121713        if is_redundant && !redundant_span.is_empty() {1714            let mut redundant_spans: Vec<_> = redundant_span.present_items().collect();1715            redundant_spans.sort();1716            redundant_spans.dedup();1717            self.lint_buffer.dyn_buffer_lint(1718                REDUNDANT_IMPORTS,1719                id,1720                import.span,1721                move |dcx, level| {1722                    let ident = source;1723                    let subs = redundant_spans1724                        .into_iter()1725                        .map(|(span, is_imported)| match (span.is_dummy(), is_imported) {1726                            (false, true) => {1727                                errors::RedundantImportSub::ImportedHere { span, ident }1728                            }1729                            (false, false) => {1730                                errors::RedundantImportSub::DefinedHere { span, ident }1731                            }1732                            (true, true) => {1733                                errors::RedundantImportSub::ImportedPrelude { span, ident }1734                            }1735                            (true, false) => {1736                                errors::RedundantImportSub::DefinedPrelude { span, ident }1737                            }1738                        })1739                        .collect();1740                    errors::RedundantImport { subs, ident }.into_diag(dcx, level)1741                },1742            );1743            return true;1744        }17451746        false1747    }17481749    fn resolve_glob_import(&mut self, import: Import<'ra>) {1750        // This function is only called for glob imports.1751        let ImportKind::Glob { id, .. } = import.kind else { unreachable!() };17521753        let ModuleOrUniformRoot::Module(module) = import.imported_module.get().unwrap() else {1754            self.dcx().emit_err(CannotGlobImportAllCrates { span: import.span });1755            return;1756        };17571758        if module.is_trait() && !self.tcx.features().import_trait_associated_functions() {1759            feature_err(1760                self.tcx.sess,1761                sym::import_trait_associated_functions,1762                import.span,1763                "`use` associated items of traits is unstable",1764            )1765            .emit();1766        }17671768        if module == import.parent_scope.module {1769            return;1770        }17711772        // Add to module's glob_importers1773        module.glob_importers.borrow_mut_unchecked().push(import);17741775        // Ensure that `resolutions` isn't borrowed during `try_define`,1776        // since it might get updated via a glob cycle.1777        let bindings = self1778            .resolutions(module)1779            .borrow()1780            .iter()1781            .filter_map(|(key, resolution)| {1782                let resolution = resolution.borrow();1783                resolution.determined_decl().map(|decl| (*key, decl, resolution.orig_ident_span))1784            })1785            .collect::<Vec<_>>();1786        for (mut key, binding, orig_ident_span) in bindings {1787            let scope =1788                match key.ident.ctxt.update_unchecked(|ctxt| {1789                    ctxt.reverse_glob_adjust(module.expansion, import.span)1790                }) {1791                    Some(Some(def)) => self.expn_def_scope(def),1792                    Some(None) => import.parent_scope.module,1793                    None => continue,1794                };1795            if self.is_accessible_from(binding.vis(), scope) {1796                let import_decl = self.new_import_decl(binding, import);1797                let warn_ambiguity = self1798                    .resolution(import.parent_scope.module, key)1799                    .and_then(|r| r.determined_decl())1800                    .is_some_and(|binding| binding.warn_ambiguity_recursive());1801                self.try_plant_decl_into_local_module(1802                    key.ident,1803                    orig_ident_span,1804                    key.ns,1805                    import_decl,1806                    warn_ambiguity,1807                )1808                .expect("planting a glob cannot fail");1809            }1810        }18111812        // Record the destination of this import1813        self.record_partial_res(id, PartialRes::new(module.res().unwrap()));1814    }18151816    // Miscellaneous post-processing, including recording re-exports,1817    // reporting conflicts, and reporting unresolved imports.1818    fn finalize_resolutions_in(1819        &self,1820        module: LocalModule<'ra>,1821        module_children: &mut LocalDefIdMap<Vec<ModChild>>,1822        ambig_module_children: &mut LocalDefIdMap<Vec<AmbigModChild>>,1823    ) {1824        // Since import resolution is finished, globs will not define any more names.1825        *module.globs.borrow_mut(self) = Vec::new();18261827        let Some(def_id) = module.opt_def_id() else { return };18281829        let mut children = Vec::new();1830        let mut ambig_children = Vec::new();18311832        module.to_module().for_each_child(self, |this, ident, orig_ident_span, _, binding| {1833            let res = binding.res().expect_non_local();1834            if res != def::Res::Err {1835                let ident = ident.orig(orig_ident_span);1836                let child =1837                    |reexport_chain| ModChild { ident, res, vis: binding.vis(), reexport_chain };1838                if let Some((ambig_binding1, ambig_binding2)) = binding.descent_to_ambiguity() {1839                    let main = child(ambig_binding1.reexport_chain(this));1840                    let second = ModChild {1841                        ident,1842                        res: ambig_binding2.res().expect_non_local(),1843                        vis: ambig_binding2.vis(),1844                        reexport_chain: ambig_binding2.reexport_chain(this),1845                    };1846                    ambig_children.push(AmbigModChild { main, second })1847                } else {1848                    children.push(child(binding.reexport_chain(this)));1849                }1850            }1851        });18521853        if !children.is_empty() {1854            module_children.insert(def_id.expect_local(), children);1855        }1856        if !ambig_children.is_empty() {1857            ambig_module_children.insert(def_id.expect_local(), ambig_children);1858        }1859    }1860}18611862fn import_path_to_string(names: &[Ident], import_kind: &ImportKind<'_>, span: Span) -> String {1863    let pos = names.iter().position(|p| span == p.span && p.name != kw::PathRoot);1864    let global = !names.is_empty() && names[0].name == kw::PathRoot;1865    if let Some(pos) = pos {1866        let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] };1867        names_to_string(names.iter().map(|ident| ident.name))1868    } else {1869        let names = if global { &names[1..] } else { names };1870        if names.is_empty() {1871            import_kind_to_string(import_kind)1872        } else {1873            format!(1874                "{}::{}",1875                names_to_string(names.iter().map(|ident| ident.name)),1876                import_kind_to_string(import_kind),1877            )1878        }1879    }1880}18811882fn import_kind_to_string(import_kind: &ImportKind<'_>) -> String {1883    match import_kind {1884        ImportKind::Single { source, .. } => source.to_string(),1885        ImportKind::Glob { .. } => "*".to_string(),1886        ImportKind::ExternCrate { .. } => "<extern crate>".to_string(),1887        ImportKind::MacroUse { .. } => "#[macro_use]".to_string(),1888        ImportKind::MacroExport => "#[macro_export]".to_string(),1889    }1890}