rustc_resolve/
ident.rs

1use Determinacy::*;
2use Namespace::*;
3use rustc_ast::{self as ast, NodeId};
4use rustc_errors::ErrorGuaranteed;
5use rustc_hir::def::{DefKind, Namespace, NonMacroAttrKind, PartialRes, PerNS};
6use rustc_middle::{bug, ty};
7use rustc_session::lint::BuiltinLintDiag;
8use rustc_session::lint::builtin::PROC_MACRO_DERIVE_RESOLUTION_FALLBACK;
9use rustc_session::parse::feature_err;
10use rustc_span::def_id::LocalDefId;
11use rustc_span::hygiene::{ExpnId, ExpnKind, LocalExpnId, MacroKind, SyntaxContext};
12use rustc_span::{Ident, Span, kw, sym};
13use tracing::{debug, instrument};
14
15use crate::errors::{ParamKindInEnumDiscriminant, ParamKindInNonTrivialAnonConst};
16use crate::imports::Import;
17use crate::late::{ConstantHasGenerics, NoConstantGenericsReason, PathSource, Rib, RibKind};
18use crate::macros::{MacroRulesScope, sub_namespace_match};
19use crate::{
20    AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingKey, Determinacy, Finalize,
21    ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot, NameBinding,
22    NameBindingKind, ParentScope, PathResult, PrivacyError, Res, ResolutionError, Resolver, Scope,
23    ScopeSet, Segment, ToNameBinding, Used, Weak, errors,
24};
25
26type Visibility = ty::Visibility<LocalDefId>;
27
28#[derive(Copy, Clone)]
29pub enum UsePrelude {
30    No,
31    Yes,
32}
33
34impl From<UsePrelude> for bool {
35    fn from(up: UsePrelude) -> bool {
36        matches!(up, UsePrelude::Yes)
37    }
38}
39
40#[derive(Debug, PartialEq)]
41enum Shadowing {
42    Restricted,
43    Unrestricted,
44}
45
46impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
47    /// A generic scope visitor.
48    /// Visits scopes in order to resolve some identifier in them or perform other actions.
49    /// If the callback returns `Some` result, we stop visiting scopes and return it.
50    pub(crate) fn visit_scopes<T>(
51        &mut self,
52        scope_set: ScopeSet<'ra>,
53        parent_scope: &ParentScope<'ra>,
54        ctxt: SyntaxContext,
55        mut visitor: impl FnMut(&mut Self, Scope<'ra>, UsePrelude, SyntaxContext) -> Option<T>,
56    ) -> Option<T> {
57        // General principles:
58        // 1. Not controlled (user-defined) names should have higher priority than controlled names
59        //    built into the language or standard library. This way we can add new names into the
60        //    language or standard library without breaking user code.
61        // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
62        // Places to search (in order of decreasing priority):
63        // (Type NS)
64        // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
65        //    (open set, not controlled).
66        // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
67        //    (open, not controlled).
68        // 3. Extern prelude (open, the open part is from macro expansions, not controlled).
69        // 4. Tool modules (closed, controlled right now, but not in the future).
70        // 5. Standard library prelude (de-facto closed, controlled).
71        // 6. Language prelude (closed, controlled).
72        // (Value NS)
73        // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
74        //    (open set, not controlled).
75        // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
76        //    (open, not controlled).
77        // 3. Standard library prelude (de-facto closed, controlled).
78        // (Macro NS)
79        // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
80        //    are currently reported as errors. They should be higher in priority than preludes
81        //    and probably even names in modules according to the "general principles" above. They
82        //    also should be subject to restricted shadowing because are effectively produced by
83        //    derives (you need to resolve the derive first to add helpers into scope), but they
84        //    should be available before the derive is expanded for compatibility.
85        //    It's mess in general, so we are being conservative for now.
86        // 1-3. `macro_rules` (open, not controlled), loop through `macro_rules` scopes. Have higher
87        //    priority than prelude macros, but create ambiguities with macros in modules.
88        // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
89        //    (open, not controlled). Have higher priority than prelude macros, but create
90        //    ambiguities with `macro_rules`.
91        // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
92        // 4a. User-defined prelude from macro-use
93        //    (open, the open part is from macro expansions, not controlled).
94        // 4b. "Standard library prelude" part implemented through `macro-use` (closed, controlled).
95        // 4c. Standard library prelude (de-facto closed, controlled).
96        // 6. Language prelude: builtin attributes (closed, controlled).
97
98        let rust_2015 = ctxt.edition().is_rust_2015();
99        let (ns, macro_kind, is_absolute_path) = match scope_set {
100            ScopeSet::All(ns) => (ns, None, false),
101            ScopeSet::AbsolutePath(ns) => (ns, None, true),
102            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
103            ScopeSet::Late(ns, ..) => (ns, None, false),
104        };
105        let module = match scope_set {
106            // Start with the specified module.
107            ScopeSet::Late(_, module, _) => module,
108            // Jump out of trait or enum modules, they do not act as scopes.
109            _ => parent_scope.module.nearest_item_scope(),
110        };
111        let mut scope = match ns {
112            _ if is_absolute_path => Scope::CrateRoot,
113            TypeNS | ValueNS => Scope::Module(module, None),
114            MacroNS => Scope::DeriveHelpers(parent_scope.expansion),
115        };
116        let mut ctxt = ctxt.normalize_to_macros_2_0();
117        let mut use_prelude = !module.no_implicit_prelude;
118
119        loop {
120            let visit = match scope {
121                // Derive helpers are not in scope when resolving derives in the same container.
122                Scope::DeriveHelpers(expn_id) => {
123                    !(expn_id == parent_scope.expansion && macro_kind == Some(MacroKind::Derive))
124                }
125                Scope::DeriveHelpersCompat => true,
126                Scope::MacroRules(macro_rules_scope) => {
127                    // Use "path compression" on `macro_rules` scope chains. This is an optimization
128                    // used to avoid long scope chains, see the comments on `MacroRulesScopeRef`.
129                    // As another consequence of this optimization visitors never observe invocation
130                    // scopes for macros that were already expanded.
131                    while let MacroRulesScope::Invocation(invoc_id) = macro_rules_scope.get() {
132                        if let Some(next_scope) = self.output_macro_rules_scopes.get(&invoc_id) {
133                            macro_rules_scope.set(next_scope.get());
134                        } else {
135                            break;
136                        }
137                    }
138                    true
139                }
140                Scope::CrateRoot => true,
141                Scope::Module(..) => true,
142                Scope::MacroUsePrelude => use_prelude || rust_2015,
143                Scope::BuiltinAttrs => true,
144                Scope::ExternPrelude => use_prelude || is_absolute_path,
145                Scope::ToolPrelude => use_prelude,
146                Scope::StdLibPrelude => use_prelude || ns == MacroNS,
147                Scope::BuiltinTypes => true,
148            };
149
150            if visit {
151                let use_prelude = if use_prelude { UsePrelude::Yes } else { UsePrelude::No };
152                if let break_result @ Some(..) = visitor(self, scope, use_prelude, ctxt) {
153                    return break_result;
154                }
155            }
156
157            scope = match scope {
158                Scope::DeriveHelpers(LocalExpnId::ROOT) => Scope::DeriveHelpersCompat,
159                Scope::DeriveHelpers(expn_id) => {
160                    // Derive helpers are not visible to code generated by bang or derive macros.
161                    let expn_data = expn_id.expn_data();
162                    match expn_data.kind {
163                        ExpnKind::Root
164                        | ExpnKind::Macro(MacroKind::Bang | MacroKind::Derive, _) => {
165                            Scope::DeriveHelpersCompat
166                        }
167                        _ => Scope::DeriveHelpers(expn_data.parent.expect_local()),
168                    }
169                }
170                Scope::DeriveHelpersCompat => Scope::MacroRules(parent_scope.macro_rules),
171                Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
172                    MacroRulesScope::Binding(binding) => {
173                        Scope::MacroRules(binding.parent_macro_rules_scope)
174                    }
175                    MacroRulesScope::Invocation(invoc_id) => {
176                        Scope::MacroRules(self.invocation_parent_scopes[&invoc_id].macro_rules)
177                    }
178                    MacroRulesScope::Empty => Scope::Module(module, None),
179                },
180                Scope::CrateRoot => match ns {
181                    TypeNS => {
182                        ctxt.adjust(ExpnId::root());
183                        Scope::ExternPrelude
184                    }
185                    ValueNS | MacroNS => break,
186                },
187                Scope::Module(module, prev_lint_id) => {
188                    use_prelude = !module.no_implicit_prelude;
189                    let derive_fallback_lint_id = match scope_set {
190                        ScopeSet::Late(.., lint_id) => lint_id,
191                        _ => None,
192                    };
193                    match self.hygienic_lexical_parent(module, &mut ctxt, derive_fallback_lint_id) {
194                        Some((parent_module, lint_id)) => {
195                            Scope::Module(parent_module, lint_id.or(prev_lint_id))
196                        }
197                        None => {
198                            ctxt.adjust(ExpnId::root());
199                            match ns {
200                                TypeNS => Scope::ExternPrelude,
201                                ValueNS => Scope::StdLibPrelude,
202                                MacroNS => Scope::MacroUsePrelude,
203                            }
204                        }
205                    }
206                }
207                Scope::MacroUsePrelude => Scope::StdLibPrelude,
208                Scope::BuiltinAttrs => break, // nowhere else to search
209                Scope::ExternPrelude if is_absolute_path => break,
210                Scope::ExternPrelude => Scope::ToolPrelude,
211                Scope::ToolPrelude => Scope::StdLibPrelude,
212                Scope::StdLibPrelude => match ns {
213                    TypeNS => Scope::BuiltinTypes,
214                    ValueNS => break, // nowhere else to search
215                    MacroNS => Scope::BuiltinAttrs,
216                },
217                Scope::BuiltinTypes => break, // nowhere else to search
218            };
219        }
220
221        None
222    }
223
224    fn hygienic_lexical_parent(
225        &mut self,
226        module: Module<'ra>,
227        ctxt: &mut SyntaxContext,
228        derive_fallback_lint_id: Option<NodeId>,
229    ) -> Option<(Module<'ra>, Option<NodeId>)> {
230        if !module.expansion.outer_expn_is_descendant_of(*ctxt) {
231            return Some((self.expn_def_scope(ctxt.remove_mark()), None));
232        }
233
234        if let ModuleKind::Block = module.kind {
235            return Some((module.parent.unwrap().nearest_item_scope(), None));
236        }
237
238        // We need to support the next case under a deprecation warning
239        // ```
240        // struct MyStruct;
241        // ---- begin: this comes from a proc macro derive
242        // mod implementation_details {
243        //     // Note that `MyStruct` is not in scope here.
244        //     impl SomeTrait for MyStruct { ... }
245        // }
246        // ---- end
247        // ```
248        // So we have to fall back to the module's parent during lexical resolution in this case.
249        if derive_fallback_lint_id.is_some()
250            && let Some(parent) = module.parent
251            // Inner module is inside the macro
252            && module.expansion != parent.expansion
253            // Parent module is outside of the macro
254            && module.expansion.is_descendant_of(parent.expansion)
255            // The macro is a proc macro derive
256            && let Some(def_id) = module.expansion.expn_data().macro_def_id
257        {
258            let ext = &self.get_macro_by_def_id(def_id).ext;
259            if ext.builtin_name.is_none()
260                && ext.macro_kind() == MacroKind::Derive
261                && parent.expansion.outer_expn_is_descendant_of(*ctxt)
262            {
263                return Some((parent, derive_fallback_lint_id));
264            }
265        }
266
267        None
268    }
269
270    /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
271    /// More specifically, we proceed up the hierarchy of scopes and return the binding for
272    /// `ident` in the first scope that defines it (or None if no scopes define it).
273    ///
274    /// A block's items are above its local variables in the scope hierarchy, regardless of where
275    /// the items are defined in the block. For example,
276    /// ```rust
277    /// fn f() {
278    ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
279    ///    let g = || {};
280    ///    fn g() {}
281    ///    g(); // This resolves to the local variable `g` since it shadows the item.
282    /// }
283    /// ```
284    ///
285    /// Invariant: This must only be called during main resolution, not during
286    /// import resolution.
287    #[instrument(level = "debug", skip(self, ribs))]
288    pub(crate) fn resolve_ident_in_lexical_scope(
289        &mut self,
290        mut ident: Ident,
291        ns: Namespace,
292        parent_scope: &ParentScope<'ra>,
293        finalize: Option<Finalize>,
294        ribs: &[Rib<'ra>],
295        ignore_binding: Option<NameBinding<'ra>>,
296    ) -> Option<LexicalScopeBinding<'ra>> {
297        assert!(ns == TypeNS || ns == ValueNS);
298        let orig_ident = ident;
299        let (general_span, normalized_span) = if ident.name == kw::SelfUpper {
300            // FIXME(jseyfried) improve `Self` hygiene
301            let empty_span = ident.span.with_ctxt(SyntaxContext::root());
302            (empty_span, empty_span)
303        } else if ns == TypeNS {
304            let normalized_span = ident.span.normalize_to_macros_2_0();
305            (normalized_span, normalized_span)
306        } else {
307            (ident.span.normalize_to_macro_rules(), ident.span.normalize_to_macros_2_0())
308        };
309        ident.span = general_span;
310        let normalized_ident = Ident { span: normalized_span, ..ident };
311
312        // Walk backwards up the ribs in scope.
313        let mut module = self.graph_root;
314        for (i, rib) in ribs.iter().enumerate().rev() {
315            debug!("walk rib\n{:?}", rib.bindings);
316            // Use the rib kind to determine whether we are resolving parameters
317            // (macro 2.0 hygiene) or local variables (`macro_rules` hygiene).
318            let rib_ident = if rib.kind.contains_params() { normalized_ident } else { ident };
319            if let Some((original_rib_ident_def, res)) = rib.bindings.get_key_value(&rib_ident) {
320                // The ident resolves to a type parameter or local variable.
321                return Some(LexicalScopeBinding::Res(self.validate_res_from_ribs(
322                    i,
323                    rib_ident,
324                    *res,
325                    finalize.map(|finalize| finalize.path_span),
326                    *original_rib_ident_def,
327                    ribs,
328                )));
329            }
330
331            module = match rib.kind {
332                RibKind::Module(module) => module,
333                RibKind::MacroDefinition(def) if def == self.macro_def(ident.span.ctxt()) => {
334                    // If an invocation of this macro created `ident`, give up on `ident`
335                    // and switch to `ident`'s source from the macro definition.
336                    ident.span.remove_mark();
337                    continue;
338                }
339                _ => continue,
340            };
341
342            match module.kind {
343                ModuleKind::Block => {} // We can see through blocks
344                _ => break,
345            }
346
347            let item = self.resolve_ident_in_module_unadjusted(
348                ModuleOrUniformRoot::Module(module),
349                ident,
350                ns,
351                parent_scope,
352                Shadowing::Unrestricted,
353                finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
354                ignore_binding,
355                None,
356            );
357            if let Ok(binding) = item {
358                // The ident resolves to an item.
359                return Some(LexicalScopeBinding::Item(binding));
360            }
361        }
362        self.early_resolve_ident_in_lexical_scope(
363            orig_ident,
364            ScopeSet::Late(ns, module, finalize.map(|finalize| finalize.node_id)),
365            parent_scope,
366            finalize,
367            finalize.is_some(),
368            ignore_binding,
369            None,
370        )
371        .ok()
372        .map(LexicalScopeBinding::Item)
373    }
374
375    /// Resolve an identifier in lexical scope.
376    /// This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
377    /// expansion and import resolution (perhaps they can be merged in the future).
378    /// The function is used for resolving initial segments of macro paths (e.g., `foo` in
379    /// `foo::bar!();` or `foo!();`) and also for import paths on 2018 edition.
380    #[instrument(level = "debug", skip(self))]
381    pub(crate) fn early_resolve_ident_in_lexical_scope(
382        &mut self,
383        orig_ident: Ident,
384        scope_set: ScopeSet<'ra>,
385        parent_scope: &ParentScope<'ra>,
386        finalize: Option<Finalize>,
387        force: bool,
388        ignore_binding: Option<NameBinding<'ra>>,
389        ignore_import: Option<Import<'ra>>,
390    ) -> Result<NameBinding<'ra>, Determinacy> {
391        bitflags::bitflags! {
392            #[derive(Clone, Copy)]
393            struct Flags: u8 {
394                const MACRO_RULES          = 1 << 0;
395                const MODULE               = 1 << 1;
396                const MISC_SUGGEST_CRATE   = 1 << 2;
397                const MISC_SUGGEST_SELF    = 1 << 3;
398                const MISC_FROM_PRELUDE    = 1 << 4;
399            }
400        }
401
402        assert!(force || finalize.is_none()); // `finalize` implies `force`
403
404        // Make sure `self`, `super` etc produce an error when passed to here.
405        if orig_ident.is_path_segment_keyword() {
406            return Err(Determinacy::Determined);
407        }
408
409        let (ns, macro_kind) = match scope_set {
410            ScopeSet::All(ns) => (ns, None),
411            ScopeSet::AbsolutePath(ns) => (ns, None),
412            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
413            ScopeSet::Late(ns, ..) => (ns, None),
414        };
415
416        // This is *the* result, resolution from the scope closest to the resolved identifier.
417        // However, sometimes this result is "weak" because it comes from a glob import or
418        // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
419        // mod m { ... } // solution in outer scope
420        // {
421        //     use prefix::*; // imports another `m` - innermost solution
422        //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
423        //     m::mac!();
424        // }
425        // So we have to save the innermost solution and continue searching in outer scopes
426        // to detect potential ambiguities.
427        let mut innermost_result: Option<(NameBinding<'_>, Flags)> = None;
428        let mut determinacy = Determinacy::Determined;
429
430        // Go through all the scopes and try to resolve the name.
431        let break_result = self.visit_scopes(
432            scope_set,
433            parent_scope,
434            orig_ident.span.ctxt(),
435            |this, scope, use_prelude, ctxt| {
436                let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
437                let result = match scope {
438                    Scope::DeriveHelpers(expn_id) => {
439                        if let Some(binding) = this.helper_attrs.get(&expn_id).and_then(|attrs| {
440                            attrs.iter().rfind(|(i, _)| ident == *i).map(|(_, binding)| *binding)
441                        }) {
442                            Ok((binding, Flags::empty()))
443                        } else {
444                            Err(Determinacy::Determined)
445                        }
446                    }
447                    Scope::DeriveHelpersCompat => {
448                        // FIXME: Try running this logic earlier, to allocate name bindings for
449                        // legacy derive helpers when creating an attribute invocation with
450                        // following derives. Legacy derive helpers are not common, so it shouldn't
451                        // affect performance. It should also allow to remove the `derives`
452                        // component from `ParentScope`.
453                        let mut result = Err(Determinacy::Determined);
454                        for derive in parent_scope.derives {
455                            let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
456                            match this.resolve_macro_path(
457                                derive,
458                                Some(MacroKind::Derive),
459                                parent_scope,
460                                true,
461                                force,
462                                ignore_import,
463                            ) {
464                                Ok((Some(ext), _)) => {
465                                    if ext.helper_attrs.contains(&ident.name) {
466                                        let binding = (
467                                            Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat),
468                                            Visibility::Public,
469                                            derive.span,
470                                            LocalExpnId::ROOT,
471                                        )
472                                            .to_name_binding(this.arenas);
473                                        result = Ok((binding, Flags::empty()));
474                                        break;
475                                    }
476                                }
477                                Ok(_) | Err(Determinacy::Determined) => {}
478                                Err(Determinacy::Undetermined) => {
479                                    result = Err(Determinacy::Undetermined)
480                                }
481                            }
482                        }
483                        result
484                    }
485                    Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
486                        MacroRulesScope::Binding(macro_rules_binding)
487                            if ident == macro_rules_binding.ident =>
488                        {
489                            Ok((macro_rules_binding.binding, Flags::MACRO_RULES))
490                        }
491                        MacroRulesScope::Invocation(_) => Err(Determinacy::Undetermined),
492                        _ => Err(Determinacy::Determined),
493                    },
494                    Scope::CrateRoot => {
495                        let root_ident = Ident::new(kw::PathRoot, ident.span);
496                        let root_module = this.resolve_crate_root(root_ident);
497                        let binding = this.resolve_ident_in_module(
498                            ModuleOrUniformRoot::Module(root_module),
499                            ident,
500                            ns,
501                            parent_scope,
502                            finalize,
503                            ignore_binding,
504                            ignore_import,
505                        );
506                        match binding {
507                            Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
508                            Err((Determinacy::Undetermined, Weak::No)) => {
509                                return Some(Err(Determinacy::determined(force)));
510                            }
511                            Err((Determinacy::Undetermined, Weak::Yes)) => {
512                                Err(Determinacy::Undetermined)
513                            }
514                            Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
515                        }
516                    }
517                    Scope::Module(module, derive_fallback_lint_id) => {
518                        let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
519                        let binding = this.resolve_ident_in_module_unadjusted(
520                            ModuleOrUniformRoot::Module(module),
521                            ident,
522                            ns,
523                            adjusted_parent_scope,
524                            if matches!(scope_set, ScopeSet::Late(..)) {
525                                Shadowing::Unrestricted
526                            } else {
527                                Shadowing::Restricted
528                            },
529                            finalize.map(|finalize| Finalize { used: Used::Scope, ..finalize }),
530                            ignore_binding,
531                            ignore_import,
532                        );
533                        match binding {
534                            Ok(binding) => {
535                                if let Some(lint_id) = derive_fallback_lint_id {
536                                    this.lint_buffer.buffer_lint(
537                                        PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
538                                        lint_id,
539                                        orig_ident.span,
540                                        BuiltinLintDiag::ProcMacroDeriveResolutionFallback {
541                                            span: orig_ident.span,
542                                            ns,
543                                            ident,
544                                        },
545                                    );
546                                }
547                                let misc_flags = if module == this.graph_root {
548                                    Flags::MISC_SUGGEST_CRATE
549                                } else if module.is_normal() {
550                                    Flags::MISC_SUGGEST_SELF
551                                } else {
552                                    Flags::empty()
553                                };
554                                Ok((binding, Flags::MODULE | misc_flags))
555                            }
556                            Err((Determinacy::Undetermined, Weak::No)) => {
557                                return Some(Err(Determinacy::determined(force)));
558                            }
559                            Err((Determinacy::Undetermined, Weak::Yes)) => {
560                                Err(Determinacy::Undetermined)
561                            }
562                            Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
563                        }
564                    }
565                    Scope::MacroUsePrelude => {
566                        match this.macro_use_prelude.get(&ident.name).cloned() {
567                            Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
568                            None => Err(Determinacy::determined(
569                                this.graph_root.unexpanded_invocations.borrow().is_empty(),
570                            )),
571                        }
572                    }
573                    Scope::BuiltinAttrs => match this.builtin_attrs_bindings.get(&ident.name) {
574                        Some(binding) => Ok((*binding, Flags::empty())),
575                        None => Err(Determinacy::Determined),
576                    },
577                    Scope::ExternPrelude => {
578                        match this.extern_prelude_get(ident, finalize.is_some()) {
579                            Some(binding) => Ok((binding, Flags::empty())),
580                            None => Err(Determinacy::determined(
581                                this.graph_root.unexpanded_invocations.borrow().is_empty(),
582                            )),
583                        }
584                    }
585                    Scope::ToolPrelude => match this.registered_tool_bindings.get(&ident) {
586                        Some(binding) => Ok((*binding, Flags::empty())),
587                        None => Err(Determinacy::Determined),
588                    },
589                    Scope::StdLibPrelude => {
590                        let mut result = Err(Determinacy::Determined);
591                        if let Some(prelude) = this.prelude
592                            && let Ok(binding) = this.resolve_ident_in_module_unadjusted(
593                                ModuleOrUniformRoot::Module(prelude),
594                                ident,
595                                ns,
596                                parent_scope,
597                                Shadowing::Unrestricted,
598                                None,
599                                ignore_binding,
600                                ignore_import,
601                            )
602                            && (matches!(use_prelude, UsePrelude::Yes)
603                                || this.is_builtin_macro(binding.res()))
604                        {
605                            result = Ok((binding, Flags::MISC_FROM_PRELUDE));
606                        }
607
608                        result
609                    }
610                    Scope::BuiltinTypes => match this.builtin_types_bindings.get(&ident.name) {
611                        Some(binding) => {
612                            if matches!(ident.name, sym::f16)
613                                && !this.tcx.features().f16()
614                                && !ident.span.allows_unstable(sym::f16)
615                                && finalize.is_some()
616                                && innermost_result.is_none()
617                            {
618                                feature_err(
619                                    this.tcx.sess,
620                                    sym::f16,
621                                    ident.span,
622                                    "the type `f16` is unstable",
623                                )
624                                .emit();
625                            }
626                            if matches!(ident.name, sym::f128)
627                                && !this.tcx.features().f128()
628                                && !ident.span.allows_unstable(sym::f128)
629                                && finalize.is_some()
630                                && innermost_result.is_none()
631                            {
632                                feature_err(
633                                    this.tcx.sess,
634                                    sym::f128,
635                                    ident.span,
636                                    "the type `f128` is unstable",
637                                )
638                                .emit();
639                            }
640                            Ok((*binding, Flags::empty()))
641                        }
642                        None => Err(Determinacy::Determined),
643                    },
644                };
645
646                match result {
647                    Ok((binding, flags))
648                        if sub_namespace_match(binding.macro_kind(), macro_kind) =>
649                    {
650                        if finalize.is_none() || matches!(scope_set, ScopeSet::Late(..)) {
651                            return Some(Ok(binding));
652                        }
653
654                        if let Some((innermost_binding, innermost_flags)) = innermost_result {
655                            // Found another solution, if the first one was "weak", report an error.
656                            let (res, innermost_res) = (binding.res(), innermost_binding.res());
657                            if res != innermost_res {
658                                let is_builtin = |res| {
659                                    matches!(res, Res::NonMacroAttr(NonMacroAttrKind::Builtin(..)))
660                                };
661                                let derive_helper =
662                                    Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
663                                let derive_helper_compat =
664                                    Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
665
666                                let ambiguity_error_kind = if is_builtin(innermost_res)
667                                    || is_builtin(res)
668                                {
669                                    Some(AmbiguityKind::BuiltinAttr)
670                                } else if innermost_res == derive_helper_compat
671                                    || res == derive_helper_compat && innermost_res != derive_helper
672                                {
673                                    Some(AmbiguityKind::DeriveHelper)
674                                } else if innermost_flags.contains(Flags::MACRO_RULES)
675                                    && flags.contains(Flags::MODULE)
676                                    && !this.disambiguate_macro_rules_vs_modularized(
677                                        innermost_binding,
678                                        binding,
679                                    )
680                                    || flags.contains(Flags::MACRO_RULES)
681                                        && innermost_flags.contains(Flags::MODULE)
682                                        && !this.disambiguate_macro_rules_vs_modularized(
683                                            binding,
684                                            innermost_binding,
685                                        )
686                                {
687                                    Some(AmbiguityKind::MacroRulesVsModularized)
688                                } else if innermost_binding.is_glob_import() {
689                                    Some(AmbiguityKind::GlobVsOuter)
690                                } else if innermost_binding
691                                    .may_appear_after(parent_scope.expansion, binding)
692                                {
693                                    Some(AmbiguityKind::MoreExpandedVsOuter)
694                                } else {
695                                    None
696                                };
697                                if let Some(kind) = ambiguity_error_kind {
698                                    let misc = |f: Flags| {
699                                        if f.contains(Flags::MISC_SUGGEST_CRATE) {
700                                            AmbiguityErrorMisc::SuggestCrate
701                                        } else if f.contains(Flags::MISC_SUGGEST_SELF) {
702                                            AmbiguityErrorMisc::SuggestSelf
703                                        } else if f.contains(Flags::MISC_FROM_PRELUDE) {
704                                            AmbiguityErrorMisc::FromPrelude
705                                        } else {
706                                            AmbiguityErrorMisc::None
707                                        }
708                                    };
709                                    this.ambiguity_errors.push(AmbiguityError {
710                                        kind,
711                                        ident: orig_ident,
712                                        b1: innermost_binding,
713                                        b2: binding,
714                                        warning: false,
715                                        misc1: misc(innermost_flags),
716                                        misc2: misc(flags),
717                                    });
718                                    return Some(Ok(innermost_binding));
719                                }
720                            }
721                        } else {
722                            // Found the first solution.
723                            innermost_result = Some((binding, flags));
724                        }
725                    }
726                    Ok(..) | Err(Determinacy::Determined) => {}
727                    Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
728                }
729
730                None
731            },
732        );
733
734        if let Some(break_result) = break_result {
735            return break_result;
736        }
737
738        // The first found solution was the only one, return it.
739        if let Some((binding, _)) = innermost_result {
740            return Ok(binding);
741        }
742
743        Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
744    }
745
746    #[instrument(level = "debug", skip(self))]
747    pub(crate) fn maybe_resolve_ident_in_module(
748        &mut self,
749        module: ModuleOrUniformRoot<'ra>,
750        ident: Ident,
751        ns: Namespace,
752        parent_scope: &ParentScope<'ra>,
753        ignore_import: Option<Import<'ra>>,
754    ) -> Result<NameBinding<'ra>, Determinacy> {
755        self.resolve_ident_in_module(module, ident, ns, parent_scope, None, None, ignore_import)
756            .map_err(|(determinacy, _)| determinacy)
757    }
758
759    #[instrument(level = "debug", skip(self))]
760    pub(crate) fn resolve_ident_in_module(
761        &mut self,
762        module: ModuleOrUniformRoot<'ra>,
763        mut ident: Ident,
764        ns: Namespace,
765        parent_scope: &ParentScope<'ra>,
766        finalize: Option<Finalize>,
767        ignore_binding: Option<NameBinding<'ra>>,
768        ignore_import: Option<Import<'ra>>,
769    ) -> Result<NameBinding<'ra>, (Determinacy, Weak)> {
770        let tmp_parent_scope;
771        let mut adjusted_parent_scope = parent_scope;
772        match module {
773            ModuleOrUniformRoot::Module(m) => {
774                if let Some(def) = ident.span.normalize_to_macros_2_0_and_adjust(m.expansion) {
775                    tmp_parent_scope =
776                        ParentScope { module: self.expn_def_scope(def), ..*parent_scope };
777                    adjusted_parent_scope = &tmp_parent_scope;
778                }
779            }
780            ModuleOrUniformRoot::ExternPrelude => {
781                ident.span.normalize_to_macros_2_0_and_adjust(ExpnId::root());
782            }
783            ModuleOrUniformRoot::CrateRootAndExternPrelude | ModuleOrUniformRoot::CurrentScope => {
784                // No adjustments
785            }
786        }
787        self.resolve_ident_in_module_unadjusted(
788            module,
789            ident,
790            ns,
791            adjusted_parent_scope,
792            Shadowing::Unrestricted,
793            finalize,
794            ignore_binding,
795            ignore_import,
796        )
797    }
798
799    /// Attempts to resolve `ident` in namespaces `ns` of `module`.
800    /// Invariant: if `finalize` is `Some`, expansion and import resolution must be complete.
801    #[instrument(level = "debug", skip(self))]
802    fn resolve_ident_in_module_unadjusted(
803        &mut self,
804        module: ModuleOrUniformRoot<'ra>,
805        ident: Ident,
806        ns: Namespace,
807        parent_scope: &ParentScope<'ra>,
808        shadowing: Shadowing,
809        finalize: Option<Finalize>,
810        // This binding should be ignored during in-module resolution, so that we don't get
811        // "self-confirming" import resolutions during import validation and checking.
812        ignore_binding: Option<NameBinding<'ra>>,
813        ignore_import: Option<Import<'ra>>,
814    ) -> Result<NameBinding<'ra>, (Determinacy, Weak)> {
815        let module = match module {
816            ModuleOrUniformRoot::Module(module) => module,
817            ModuleOrUniformRoot::CrateRootAndExternPrelude => {
818                assert_eq!(shadowing, Shadowing::Unrestricted);
819                let binding = self.early_resolve_ident_in_lexical_scope(
820                    ident,
821                    ScopeSet::AbsolutePath(ns),
822                    parent_scope,
823                    finalize,
824                    finalize.is_some(),
825                    ignore_binding,
826                    ignore_import,
827                );
828                return binding.map_err(|determinacy| (determinacy, Weak::No));
829            }
830            ModuleOrUniformRoot::ExternPrelude => {
831                assert_eq!(shadowing, Shadowing::Unrestricted);
832                return if ns != TypeNS {
833                    Err((Determined, Weak::No))
834                } else if let Some(binding) = self.extern_prelude_get(ident, finalize.is_some()) {
835                    Ok(binding)
836                } else if !self.graph_root.unexpanded_invocations.borrow().is_empty() {
837                    // Macro-expanded `extern crate` items can add names to extern prelude.
838                    Err((Undetermined, Weak::No))
839                } else {
840                    Err((Determined, Weak::No))
841                };
842            }
843            ModuleOrUniformRoot::CurrentScope => {
844                assert_eq!(shadowing, Shadowing::Unrestricted);
845                if ns == TypeNS {
846                    if ident.name == kw::Crate || ident.name == kw::DollarCrate {
847                        let module = self.resolve_crate_root(ident);
848                        return Ok(self.module_self_bindings[&module]);
849                    } else if ident.name == kw::Super || ident.name == kw::SelfLower {
850                        // FIXME: Implement these with renaming requirements so that e.g.
851                        // `use super;` doesn't work, but `use super as name;` does.
852                        // Fall through here to get an error from `early_resolve_...`.
853                    }
854                }
855
856                let binding = self.early_resolve_ident_in_lexical_scope(
857                    ident,
858                    ScopeSet::All(ns),
859                    parent_scope,
860                    finalize,
861                    finalize.is_some(),
862                    ignore_binding,
863                    ignore_import,
864                );
865                return binding.map_err(|determinacy| (determinacy, Weak::No));
866            }
867        };
868
869        let key = BindingKey::new(ident, ns);
870        let resolution =
871            self.resolution(module, key).try_borrow_mut().map_err(|_| (Determined, Weak::No))?; // This happens when there is a cycle of imports.
872
873        // If the primary binding is unusable, search further and return the shadowed glob
874        // binding if it exists. What we really want here is having two separate scopes in
875        // a module - one for non-globs and one for globs, but until that's done use this
876        // hack to avoid inconsistent resolution ICEs during import validation.
877        let binding = [resolution.binding, resolution.shadowed_glob]
878            .into_iter()
879            .find_map(|binding| if binding == ignore_binding { None } else { binding });
880
881        if let Some(Finalize { path_span, report_private, used, root_span, .. }) = finalize {
882            let Some(binding) = binding else {
883                return Err((Determined, Weak::No));
884            };
885
886            if !self.is_accessible_from(binding.vis, parent_scope.module) {
887                if report_private {
888                    self.privacy_errors.push(PrivacyError {
889                        ident,
890                        binding,
891                        dedup_span: path_span,
892                        outermost_res: None,
893                        parent_scope: *parent_scope,
894                        single_nested: path_span != root_span,
895                    });
896                } else {
897                    return Err((Determined, Weak::No));
898                }
899            }
900
901            // Forbid expanded shadowing to avoid time travel.
902            if let Some(shadowed_glob) = resolution.shadowed_glob
903                && shadowing == Shadowing::Restricted
904                && binding.expansion != LocalExpnId::ROOT
905                && binding.res() != shadowed_glob.res()
906            {
907                self.ambiguity_errors.push(AmbiguityError {
908                    kind: AmbiguityKind::GlobVsExpanded,
909                    ident,
910                    b1: binding,
911                    b2: shadowed_glob,
912                    warning: false,
913                    misc1: AmbiguityErrorMisc::None,
914                    misc2: AmbiguityErrorMisc::None,
915                });
916            }
917
918            if shadowing == Shadowing::Unrestricted
919                && binding.expansion != LocalExpnId::ROOT
920                && let NameBindingKind::Import { import, .. } = binding.kind
921                && matches!(import.kind, ImportKind::MacroExport)
922            {
923                self.macro_expanded_macro_export_errors.insert((path_span, binding.span));
924            }
925
926            self.record_use(ident, binding, used);
927            return Ok(binding);
928        }
929
930        let check_usable = |this: &mut Self, binding: NameBinding<'ra>| {
931            let usable = this.is_accessible_from(binding.vis, parent_scope.module);
932            if usable { Ok(binding) } else { Err((Determined, Weak::No)) }
933        };
934
935        // Items and single imports are not shadowable, if we have one, then it's determined.
936        if let Some(binding) = binding
937            && !binding.is_glob_import()
938        {
939            return check_usable(self, binding);
940        }
941
942        // --- From now on we either have a glob resolution or no resolution. ---
943
944        // Check if one of single imports can still define the name,
945        // if it can then our result is not determined and can be invalidated.
946        for single_import in &resolution.single_imports {
947            if ignore_import == Some(*single_import) {
948                // This branch handles a cycle in single imports.
949                //
950                // For example:
951                // ```
952                // use a::b;
953                // use b as a;
954                // ```
955                // 1. Record `use a::b` as the `ignore_import` and attempt to locate `a` in the
956                //    current module.
957                // 2. Encounter the import `use b as a`, which is a `single_import` for `a`,
958                //    and try to find `b` in the current module.
959                // 3. Re-encounter the `use a::b` import since it's a `single_import` of `b`.
960                //    This leads to entering this branch.
961                continue;
962            }
963            if !self.is_accessible_from(single_import.vis, parent_scope.module) {
964                continue;
965            }
966            if let Some(ignored) = ignore_binding
967                && let NameBindingKind::Import { import, .. } = ignored.kind
968                && import == *single_import
969            {
970                // Ignore not just the binding itself, but if it has a shadowed_glob,
971                // ignore that, too, because this loop is supposed to only process
972                // named imports.
973                continue;
974            }
975
976            let Some(module) = single_import.imported_module.get() else {
977                return Err((Undetermined, Weak::No));
978            };
979            let ImportKind::Single { source, target, target_bindings, .. } = &single_import.kind
980            else {
981                unreachable!();
982            };
983            if source != target {
984                // This branch allows the binding to be defined or updated later if the target name
985                // can hide the source.
986                if target_bindings.iter().all(|binding| binding.get().is_none()) {
987                    // None of the target bindings are available, so we can't determine
988                    // if this binding is correct or not.
989                    // See more details in #124840
990                    return Err((Undetermined, Weak::No));
991                } else if target_bindings[ns].get().is_none() && binding.is_some() {
992                    // `binding.is_some()` avoids the condition where the binding
993                    // truly doesn't exist in this namespace and should return `Err(Determined)`.
994                    return Err((Undetermined, Weak::No));
995                }
996            }
997
998            match self.resolve_ident_in_module(
999                module,
1000                *source,
1001                ns,
1002                &single_import.parent_scope,
1003                None,
1004                ignore_binding,
1005                ignore_import,
1006            ) {
1007                Err((Determined, _)) => continue,
1008                Ok(binding)
1009                    if !self.is_accessible_from(binding.vis, single_import.parent_scope.module) =>
1010                {
1011                    continue;
1012                }
1013                Ok(_) | Err((Undetermined, _)) => return Err((Undetermined, Weak::No)),
1014            }
1015        }
1016
1017        // So we have a resolution that's from a glob import. This resolution is determined
1018        // if it cannot be shadowed by some new item/import expanded from a macro.
1019        // This happens either if there are no unexpanded macros, or expanded names cannot
1020        // shadow globs (that happens in macro namespace or with restricted shadowing).
1021        //
1022        // Additionally, any macro in any module can plant names in the root module if it creates
1023        // `macro_export` macros, so the root module effectively has unresolved invocations if any
1024        // module has unresolved invocations.
1025        // However, it causes resolution/expansion to stuck too often (#53144), so, to make
1026        // progress, we have to ignore those potential unresolved invocations from other modules
1027        // and prohibit access to macro-expanded `macro_export` macros instead (unless restricted
1028        // shadowing is enabled, see `macro_expanded_macro_export_errors`).
1029        if let Some(binding) = binding {
1030            if binding.determined() || ns == MacroNS || shadowing == Shadowing::Restricted {
1031                return check_usable(self, binding);
1032            } else {
1033                return Err((Undetermined, Weak::No));
1034            }
1035        }
1036
1037        // --- From now on we have no resolution. ---
1038
1039        // Now we are in situation when new item/import can appear only from a glob or a macro
1040        // expansion. With restricted shadowing names from globs and macro expansions cannot
1041        // shadow names from outer scopes, so we can freely fallback from module search to search
1042        // in outer scopes. For `early_resolve_ident_in_lexical_scope` to continue search in outer
1043        // scopes we return `Undetermined` with `Weak::Yes`.
1044
1045        // Check if one of unexpanded macros can still define the name,
1046        // if it can then our "no resolution" result is not determined and can be invalidated.
1047        if !module.unexpanded_invocations.borrow().is_empty() {
1048            return Err((Undetermined, Weak::Yes));
1049        }
1050
1051        // Check if one of glob imports can still define the name,
1052        // if it can then our "no resolution" result is not determined and can be invalidated.
1053        for glob_import in module.globs.borrow().iter() {
1054            if ignore_import == Some(*glob_import) {
1055                continue;
1056            }
1057            if !self.is_accessible_from(glob_import.vis, parent_scope.module) {
1058                continue;
1059            }
1060            let module = match glob_import.imported_module.get() {
1061                Some(ModuleOrUniformRoot::Module(module)) => module,
1062                Some(_) => continue,
1063                None => return Err((Undetermined, Weak::Yes)),
1064            };
1065            let tmp_parent_scope;
1066            let (mut adjusted_parent_scope, mut ident) =
1067                (parent_scope, ident.normalize_to_macros_2_0());
1068            match ident.span.glob_adjust(module.expansion, glob_import.span) {
1069                Some(Some(def)) => {
1070                    tmp_parent_scope =
1071                        ParentScope { module: self.expn_def_scope(def), ..*parent_scope };
1072                    adjusted_parent_scope = &tmp_parent_scope;
1073                }
1074                Some(None) => {}
1075                None => continue,
1076            };
1077            let result = self.resolve_ident_in_module_unadjusted(
1078                ModuleOrUniformRoot::Module(module),
1079                ident,
1080                ns,
1081                adjusted_parent_scope,
1082                Shadowing::Unrestricted,
1083                None,
1084                ignore_binding,
1085                ignore_import,
1086            );
1087
1088            match result {
1089                Err((Determined, _)) => continue,
1090                Ok(binding)
1091                    if !self.is_accessible_from(binding.vis, glob_import.parent_scope.module) =>
1092                {
1093                    continue;
1094                }
1095                Ok(_) | Err((Undetermined, _)) => return Err((Undetermined, Weak::Yes)),
1096            }
1097        }
1098
1099        // No resolution and no one else can define the name - determinate error.
1100        Err((Determined, Weak::No))
1101    }
1102
1103    /// Validate a local resolution (from ribs).
1104    #[instrument(level = "debug", skip(self, all_ribs))]
1105    fn validate_res_from_ribs(
1106        &mut self,
1107        rib_index: usize,
1108        rib_ident: Ident,
1109        mut res: Res,
1110        finalize: Option<Span>,
1111        original_rib_ident_def: Ident,
1112        all_ribs: &[Rib<'ra>],
1113    ) -> Res {
1114        debug!("validate_res_from_ribs({:?})", res);
1115        let ribs = &all_ribs[rib_index + 1..];
1116
1117        // An invalid forward use of a generic parameter from a previous default
1118        // or in a const param ty.
1119        if let RibKind::ForwardGenericParamBan(reason) = all_ribs[rib_index].kind {
1120            if let Some(span) = finalize {
1121                let res_error = if rib_ident.name == kw::SelfUpper {
1122                    ResolutionError::ForwardDeclaredSelf(reason)
1123                } else {
1124                    ResolutionError::ForwardDeclaredGenericParam(rib_ident.name, reason)
1125                };
1126                self.report_error(span, res_error);
1127            }
1128            assert_eq!(res, Res::Err);
1129            return Res::Err;
1130        }
1131
1132        match res {
1133            Res::Local(_) => {
1134                use ResolutionError::*;
1135                let mut res_err = None;
1136
1137                for rib in ribs {
1138                    match rib.kind {
1139                        RibKind::Normal
1140                        | RibKind::FnOrCoroutine
1141                        | RibKind::Module(..)
1142                        | RibKind::MacroDefinition(..)
1143                        | RibKind::ForwardGenericParamBan(_) => {
1144                            // Nothing to do. Continue.
1145                        }
1146                        RibKind::Item(..) | RibKind::AssocItem => {
1147                            // This was an attempt to access an upvar inside a
1148                            // named function item. This is not allowed, so we
1149                            // report an error.
1150                            if let Some(span) = finalize {
1151                                // We don't immediately trigger a resolve error, because
1152                                // we want certain other resolution errors (namely those
1153                                // emitted for `ConstantItemRibKind` below) to take
1154                                // precedence.
1155                                res_err = Some((span, CannotCaptureDynamicEnvironmentInFnItem));
1156                            }
1157                        }
1158                        RibKind::ConstantItem(_, item) => {
1159                            // Still doesn't deal with upvars
1160                            if let Some(span) = finalize {
1161                                let (span, resolution_error) = match item {
1162                                    None if rib_ident.name == kw::SelfLower => {
1163                                        (span, LowercaseSelf)
1164                                    }
1165                                    None => {
1166                                        // If we have a `let name = expr;`, we have the span for
1167                                        // `name` and use that to see if it is followed by a type
1168                                        // specifier. If not, then we know we need to suggest
1169                                        // `const name: Ty = expr;`. This is a heuristic, it will
1170                                        // break down in the presence of macros.
1171                                        let sm = self.tcx.sess.source_map();
1172                                        let type_span = match sm.span_look_ahead(
1173                                            original_rib_ident_def.span,
1174                                            ":",
1175                                            None,
1176                                        ) {
1177                                            None => {
1178                                                Some(original_rib_ident_def.span.shrink_to_hi())
1179                                            }
1180                                            Some(_) => None,
1181                                        };
1182                                        (
1183                                            rib_ident.span,
1184                                            AttemptToUseNonConstantValueInConstant {
1185                                                ident: original_rib_ident_def,
1186                                                suggestion: "const",
1187                                                current: "let",
1188                                                type_span,
1189                                            },
1190                                        )
1191                                    }
1192                                    Some((ident, kind)) => (
1193                                        span,
1194                                        AttemptToUseNonConstantValueInConstant {
1195                                            ident,
1196                                            suggestion: "let",
1197                                            current: kind.as_str(),
1198                                            type_span: None,
1199                                        },
1200                                    ),
1201                                };
1202                                self.report_error(span, resolution_error);
1203                            }
1204                            return Res::Err;
1205                        }
1206                        RibKind::ConstParamTy => {
1207                            if let Some(span) = finalize {
1208                                self.report_error(
1209                                    span,
1210                                    ParamInTyOfConstParam { name: rib_ident.name },
1211                                );
1212                            }
1213                            return Res::Err;
1214                        }
1215                        RibKind::InlineAsmSym => {
1216                            if let Some(span) = finalize {
1217                                self.report_error(span, InvalidAsmSym);
1218                            }
1219                            return Res::Err;
1220                        }
1221                    }
1222                }
1223                if let Some((span, res_err)) = res_err {
1224                    self.report_error(span, res_err);
1225                    return Res::Err;
1226                }
1227            }
1228            Res::Def(DefKind::TyParam, _) | Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } => {
1229                for rib in ribs {
1230                    let (has_generic_params, def_kind) = match rib.kind {
1231                        RibKind::Normal
1232                        | RibKind::FnOrCoroutine
1233                        | RibKind::Module(..)
1234                        | RibKind::MacroDefinition(..)
1235                        | RibKind::InlineAsmSym
1236                        | RibKind::AssocItem
1237                        | RibKind::ForwardGenericParamBan(_) => {
1238                            // Nothing to do. Continue.
1239                            continue;
1240                        }
1241
1242                        RibKind::ConstParamTy => {
1243                            if !self.tcx.features().generic_const_parameter_types() {
1244                                if let Some(span) = finalize {
1245                                    self.report_error(
1246                                        span,
1247                                        ResolutionError::ParamInTyOfConstParam {
1248                                            name: rib_ident.name,
1249                                        },
1250                                    );
1251                                }
1252                                return Res::Err;
1253                            } else {
1254                                continue;
1255                            }
1256                        }
1257
1258                        RibKind::ConstantItem(trivial, _) => {
1259                            if let ConstantHasGenerics::No(cause) = trivial {
1260                                // HACK(min_const_generics): If we encounter `Self` in an anonymous
1261                                // constant we can't easily tell if it's generic at this stage, so
1262                                // we instead remember this and then enforce the self type to be
1263                                // concrete later on.
1264                                if let Res::SelfTyAlias {
1265                                    alias_to: def,
1266                                    forbid_generic: _,
1267                                    is_trait_impl,
1268                                } = res
1269                                {
1270                                    res = Res::SelfTyAlias {
1271                                        alias_to: def,
1272                                        forbid_generic: true,
1273                                        is_trait_impl,
1274                                    }
1275                                } else {
1276                                    if let Some(span) = finalize {
1277                                        let error = match cause {
1278                                            NoConstantGenericsReason::IsEnumDiscriminant => {
1279                                                ResolutionError::ParamInEnumDiscriminant {
1280                                                    name: rib_ident.name,
1281                                                    param_kind: ParamKindInEnumDiscriminant::Type,
1282                                                }
1283                                            }
1284                                            NoConstantGenericsReason::NonTrivialConstArg => {
1285                                                ResolutionError::ParamInNonTrivialAnonConst {
1286                                                    name: rib_ident.name,
1287                                                    param_kind:
1288                                                        ParamKindInNonTrivialAnonConst::Type,
1289                                                }
1290                                            }
1291                                        };
1292                                        let _: ErrorGuaranteed = self.report_error(span, error);
1293                                    }
1294
1295                                    return Res::Err;
1296                                }
1297                            }
1298
1299                            continue;
1300                        }
1301
1302                        // This was an attempt to use a type parameter outside its scope.
1303                        RibKind::Item(has_generic_params, def_kind) => {
1304                            (has_generic_params, def_kind)
1305                        }
1306                    };
1307
1308                    if let Some(span) = finalize {
1309                        self.report_error(
1310                            span,
1311                            ResolutionError::GenericParamsFromOuterItem(
1312                                res,
1313                                has_generic_params,
1314                                def_kind,
1315                            ),
1316                        );
1317                    }
1318                    return Res::Err;
1319                }
1320            }
1321            Res::Def(DefKind::ConstParam, _) => {
1322                for rib in ribs {
1323                    let (has_generic_params, def_kind) = match rib.kind {
1324                        RibKind::Normal
1325                        | RibKind::FnOrCoroutine
1326                        | RibKind::Module(..)
1327                        | RibKind::MacroDefinition(..)
1328                        | RibKind::InlineAsmSym
1329                        | RibKind::AssocItem
1330                        | RibKind::ForwardGenericParamBan(_) => continue,
1331
1332                        RibKind::ConstParamTy => {
1333                            if !self.tcx.features().generic_const_parameter_types() {
1334                                if let Some(span) = finalize {
1335                                    self.report_error(
1336                                        span,
1337                                        ResolutionError::ParamInTyOfConstParam {
1338                                            name: rib_ident.name,
1339                                        },
1340                                    );
1341                                }
1342                                return Res::Err;
1343                            } else {
1344                                continue;
1345                            }
1346                        }
1347
1348                        RibKind::ConstantItem(trivial, _) => {
1349                            if let ConstantHasGenerics::No(cause) = trivial {
1350                                if let Some(span) = finalize {
1351                                    let error = match cause {
1352                                        NoConstantGenericsReason::IsEnumDiscriminant => {
1353                                            ResolutionError::ParamInEnumDiscriminant {
1354                                                name: rib_ident.name,
1355                                                param_kind: ParamKindInEnumDiscriminant::Const,
1356                                            }
1357                                        }
1358                                        NoConstantGenericsReason::NonTrivialConstArg => {
1359                                            ResolutionError::ParamInNonTrivialAnonConst {
1360                                                name: rib_ident.name,
1361                                                param_kind: ParamKindInNonTrivialAnonConst::Const {
1362                                                    name: rib_ident.name,
1363                                                },
1364                                            }
1365                                        }
1366                                    };
1367                                    self.report_error(span, error);
1368                                }
1369
1370                                return Res::Err;
1371                            }
1372
1373                            continue;
1374                        }
1375
1376                        RibKind::Item(has_generic_params, def_kind) => {
1377                            (has_generic_params, def_kind)
1378                        }
1379                    };
1380
1381                    // This was an attempt to use a const parameter outside its scope.
1382                    if let Some(span) = finalize {
1383                        self.report_error(
1384                            span,
1385                            ResolutionError::GenericParamsFromOuterItem(
1386                                res,
1387                                has_generic_params,
1388                                def_kind,
1389                            ),
1390                        );
1391                    }
1392                    return Res::Err;
1393                }
1394            }
1395            _ => {}
1396        }
1397
1398        res
1399    }
1400
1401    #[instrument(level = "debug", skip(self))]
1402    pub(crate) fn maybe_resolve_path(
1403        &mut self,
1404        path: &[Segment],
1405        opt_ns: Option<Namespace>, // `None` indicates a module path in import
1406        parent_scope: &ParentScope<'ra>,
1407        ignore_import: Option<Import<'ra>>,
1408    ) -> PathResult<'ra> {
1409        self.resolve_path_with_ribs(path, opt_ns, parent_scope, None, None, None, ignore_import)
1410    }
1411
1412    #[instrument(level = "debug", skip(self))]
1413    pub(crate) fn resolve_path(
1414        &mut self,
1415        path: &[Segment],
1416        opt_ns: Option<Namespace>, // `None` indicates a module path in import
1417        parent_scope: &ParentScope<'ra>,
1418        finalize: Option<Finalize>,
1419        ignore_binding: Option<NameBinding<'ra>>,
1420        ignore_import: Option<Import<'ra>>,
1421    ) -> PathResult<'ra> {
1422        self.resolve_path_with_ribs(
1423            path,
1424            opt_ns,
1425            parent_scope,
1426            finalize,
1427            None,
1428            ignore_binding,
1429            ignore_import,
1430        )
1431    }
1432
1433    pub(crate) fn resolve_path_with_ribs(
1434        &mut self,
1435        path: &[Segment],
1436        opt_ns: Option<Namespace>, // `None` indicates a module path in import
1437        parent_scope: &ParentScope<'ra>,
1438        finalize: Option<Finalize>,
1439        ribs: Option<&PerNS<Vec<Rib<'ra>>>>,
1440        ignore_binding: Option<NameBinding<'ra>>,
1441        ignore_import: Option<Import<'ra>>,
1442    ) -> PathResult<'ra> {
1443        let mut module = None;
1444        let mut module_had_parse_errors = false;
1445        let mut allow_super = true;
1446        let mut second_binding = None;
1447
1448        // We'll provide more context to the privacy errors later, up to `len`.
1449        let privacy_errors_len = self.privacy_errors.len();
1450
1451        for (segment_idx, &Segment { ident, id, .. }) in path.iter().enumerate() {
1452            debug!("resolve_path ident {} {:?} {:?}", segment_idx, ident, id);
1453            let record_segment_res = |this: &mut Self, res| {
1454                if finalize.is_some()
1455                    && let Some(id) = id
1456                    && !this.partial_res_map.contains_key(&id)
1457                {
1458                    assert!(id != ast::DUMMY_NODE_ID, "Trying to resolve dummy id");
1459                    this.record_partial_res(id, PartialRes::new(res));
1460                }
1461            };
1462
1463            let is_last = segment_idx + 1 == path.len();
1464            let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
1465            let name = ident.name;
1466
1467            allow_super &= ns == TypeNS && (name == kw::SelfLower || name == kw::Super);
1468
1469            if ns == TypeNS {
1470                if allow_super && name == kw::Super {
1471                    let mut ctxt = ident.span.ctxt().normalize_to_macros_2_0();
1472                    let self_module = match segment_idx {
1473                        0 => Some(self.resolve_self(&mut ctxt, parent_scope.module)),
1474                        _ => match module {
1475                            Some(ModuleOrUniformRoot::Module(module)) => Some(module),
1476                            _ => None,
1477                        },
1478                    };
1479                    if let Some(self_module) = self_module
1480                        && let Some(parent) = self_module.parent
1481                    {
1482                        module =
1483                            Some(ModuleOrUniformRoot::Module(self.resolve_self(&mut ctxt, parent)));
1484                        continue;
1485                    }
1486                    return PathResult::failed(
1487                        ident,
1488                        false,
1489                        finalize.is_some(),
1490                        module_had_parse_errors,
1491                        module,
1492                        || ("there are too many leading `super` keywords".to_string(), None),
1493                    );
1494                }
1495                if segment_idx == 0 {
1496                    if name == kw::SelfLower {
1497                        let mut ctxt = ident.span.ctxt().normalize_to_macros_2_0();
1498                        let self_mod = self.resolve_self(&mut ctxt, parent_scope.module);
1499                        if let Some(res) = self_mod.res() {
1500                            record_segment_res(self, res);
1501                        }
1502                        module = Some(ModuleOrUniformRoot::Module(self_mod));
1503                        continue;
1504                    }
1505                    if name == kw::PathRoot && ident.span.at_least_rust_2018() {
1506                        module = Some(ModuleOrUniformRoot::ExternPrelude);
1507                        continue;
1508                    }
1509                    if name == kw::PathRoot
1510                        && ident.span.is_rust_2015()
1511                        && self.tcx.sess.at_least_rust_2018()
1512                    {
1513                        // `::a::b` from 2015 macro on 2018 global edition
1514                        module = Some(ModuleOrUniformRoot::CrateRootAndExternPrelude);
1515                        continue;
1516                    }
1517                    if name == kw::PathRoot || name == kw::Crate || name == kw::DollarCrate {
1518                        // `::a::b`, `crate::a::b` or `$crate::a::b`
1519                        let crate_root = self.resolve_crate_root(ident);
1520                        if let Some(res) = crate_root.res() {
1521                            record_segment_res(self, res);
1522                        }
1523                        module = Some(ModuleOrUniformRoot::Module(crate_root));
1524                        continue;
1525                    }
1526                }
1527            }
1528
1529            // Report special messages for path segment keywords in wrong positions.
1530            if ident.is_path_segment_keyword() && segment_idx != 0 {
1531                return PathResult::failed(
1532                    ident,
1533                    false,
1534                    finalize.is_some(),
1535                    module_had_parse_errors,
1536                    module,
1537                    || {
1538                        let name_str = if name == kw::PathRoot {
1539                            "crate root".to_string()
1540                        } else {
1541                            format!("`{name}`")
1542                        };
1543                        let label = if segment_idx == 1 && path[0].ident.name == kw::PathRoot {
1544                            format!("global paths cannot start with {name_str}")
1545                        } else {
1546                            format!("{name_str} in paths can only be used in start position")
1547                        };
1548                        (label, None)
1549                    },
1550                );
1551            }
1552
1553            let binding = if let Some(module) = module {
1554                self.resolve_ident_in_module(
1555                    module,
1556                    ident,
1557                    ns,
1558                    parent_scope,
1559                    finalize,
1560                    ignore_binding,
1561                    ignore_import,
1562                )
1563                .map_err(|(determinacy, _)| determinacy)
1564            } else if let Some(ribs) = ribs
1565                && let Some(TypeNS | ValueNS) = opt_ns
1566            {
1567                assert!(ignore_import.is_none());
1568                match self.resolve_ident_in_lexical_scope(
1569                    ident,
1570                    ns,
1571                    parent_scope,
1572                    finalize,
1573                    &ribs[ns],
1574                    ignore_binding,
1575                ) {
1576                    // we found a locally-imported or available item/module
1577                    Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
1578                    // we found a local variable or type param
1579                    Some(LexicalScopeBinding::Res(res)) => {
1580                        record_segment_res(self, res);
1581                        return PathResult::NonModule(PartialRes::with_unresolved_segments(
1582                            res,
1583                            path.len() - 1,
1584                        ));
1585                    }
1586                    _ => Err(Determinacy::determined(finalize.is_some())),
1587                }
1588            } else {
1589                self.early_resolve_ident_in_lexical_scope(
1590                    ident,
1591                    ScopeSet::All(ns),
1592                    parent_scope,
1593                    finalize,
1594                    finalize.is_some(),
1595                    ignore_binding,
1596                    ignore_import,
1597                )
1598            };
1599
1600            match binding {
1601                Ok(binding) => {
1602                    if segment_idx == 1 {
1603                        second_binding = Some(binding);
1604                    }
1605                    let res = binding.res();
1606
1607                    // Mark every privacy error in this path with the res to the last element. This allows us
1608                    // to detect the item the user cares about and either find an alternative import, or tell
1609                    // the user it is not accessible.
1610                    for error in &mut self.privacy_errors[privacy_errors_len..] {
1611                        error.outermost_res = Some((res, ident));
1612                    }
1613
1614                    let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(res);
1615                    if let Some(next_module) = binding.module() {
1616                        if self.mods_with_parse_errors.contains(&next_module.def_id()) {
1617                            module_had_parse_errors = true;
1618                        }
1619                        module = Some(ModuleOrUniformRoot::Module(next_module));
1620                        record_segment_res(self, res);
1621                    } else if res == Res::ToolMod && !is_last && opt_ns.is_some() {
1622                        if binding.is_import() {
1623                            self.dcx().emit_err(errors::ToolModuleImported {
1624                                span: ident.span,
1625                                import: binding.span,
1626                            });
1627                        }
1628                        let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
1629                        return PathResult::NonModule(PartialRes::new(res));
1630                    } else if res == Res::Err {
1631                        return PathResult::NonModule(PartialRes::new(Res::Err));
1632                    } else if opt_ns.is_some() && (is_last || maybe_assoc) {
1633                        self.lint_if_path_starts_with_module(finalize, path, second_binding);
1634                        record_segment_res(self, res);
1635                        return PathResult::NonModule(PartialRes::with_unresolved_segments(
1636                            res,
1637                            path.len() - segment_idx - 1,
1638                        ));
1639                    } else {
1640                        return PathResult::failed(
1641                            ident,
1642                            is_last,
1643                            finalize.is_some(),
1644                            module_had_parse_errors,
1645                            module,
1646                            || {
1647                                let label = format!(
1648                                    "`{ident}` is {} {}, not a module",
1649                                    res.article(),
1650                                    res.descr()
1651                                );
1652                                (label, None)
1653                            },
1654                        );
1655                    }
1656                }
1657                Err(Undetermined) => return PathResult::Indeterminate,
1658                Err(Determined) => {
1659                    if let Some(ModuleOrUniformRoot::Module(module)) = module
1660                        && opt_ns.is_some()
1661                        && !module.is_normal()
1662                    {
1663                        return PathResult::NonModule(PartialRes::with_unresolved_segments(
1664                            module.res().unwrap(),
1665                            path.len() - segment_idx,
1666                        ));
1667                    }
1668
1669                    return PathResult::failed(
1670                        ident,
1671                        is_last,
1672                        finalize.is_some(),
1673                        module_had_parse_errors,
1674                        module,
1675                        || {
1676                            self.report_path_resolution_error(
1677                                path,
1678                                opt_ns,
1679                                parent_scope,
1680                                ribs,
1681                                ignore_binding,
1682                                ignore_import,
1683                                module,
1684                                segment_idx,
1685                                ident,
1686                            )
1687                        },
1688                    );
1689                }
1690            }
1691        }
1692
1693        self.lint_if_path_starts_with_module(finalize, path, second_binding);
1694
1695        PathResult::Module(match module {
1696            Some(module) => module,
1697            None if path.is_empty() => ModuleOrUniformRoot::CurrentScope,
1698            _ => bug!("resolve_path: non-empty path `{:?}` has no module", path),
1699        })
1700    }
1701}