1 //! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
2 //! It runs when the crate is fully expanded and its module structure is fully built.
3 //! So it just walks through the crate and resolves all the expressions, types, etc.
5 //! If you wonder why there's no `early.rs`, that's because it's split into three files -
6 //! `build_reduced_graph.rs`, `macros.rs` and `resolve_imports.rs`.
10 use crate::{path_names_to_string, BindingError, CrateLint, LexicalScopeBinding};
11 use crate::{Module, ModuleOrUniformRoot, NameBindingKind, ParentScope, PathResult};
12 use crate::{ResolutionError, Resolver, Segment, UseError};
15 use rustc::{bug, lint, span_bug};
16 use rustc::hir::def::{self, PartialRes, DefKind, CtorKind, PerNS};
17 use rustc::hir::def::Namespace::{self, *};
18 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
19 use rustc::hir::TraitCandidate;
20 use rustc::util::nodemap::{FxHashMap, FxHashSet};
21 use smallvec::{smallvec, SmallVec};
22 use syntax::{unwrap_or, walk_list};
25 use syntax::symbol::{kw, sym};
26 use syntax::util::lev_distance::find_best_match_for_name;
27 use syntax::visit::{self, Visitor, FnKind};
30 use std::collections::BTreeSet;
31 use std::mem::replace;
33 use rustc_error_codes::*;
37 type Res = def::Res<NodeId>;
39 type IdentMap<T> = FxHashMap<Ident, T>;
41 /// Map from the name in a pattern to its binding mode.
42 type BindingMap = IdentMap<BindingInfo>;
44 #[derive(Copy, Clone, Debug)]
47 binding_mode: BindingMode,
50 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
59 fn descr(self) -> &'static str {
61 PatternSource::Match => "match binding",
62 PatternSource::Let => "let binding",
63 PatternSource::For => "for binding",
64 PatternSource::FnParam => "function parameter",
69 /// Denotes whether the context for the set of already bound bindings is a `Product`
70 /// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
71 /// See those functions for more information.
73 /// A product pattern context, e.g., `Variant(a, b)`.
75 /// An or-pattern context, e.g., `p_0 | ... | p_n`.
79 /// Does this the item (from the item rib scope) allow generic parameters?
80 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
81 crate enum HasGenericParams { Yes, No }
83 /// The rib kind restricts certain accesses,
84 /// e.g. to a `Res::Local` of an outer item.
85 #[derive(Copy, Clone, Debug)]
86 crate enum RibKind<'a> {
87 /// No restriction needs to be applied.
90 /// We passed through an impl or trait and are now in one of its
91 /// methods or associated types. Allow references to ty params that impl or trait
92 /// binds. Disallow any other upvars (including other ty params that are
96 /// We passed through a function definition. Disallow upvars.
97 /// Permit only those const parameters that are specified in the function's generics.
100 /// We passed through an item scope. Disallow upvars.
101 ItemRibKind(HasGenericParams),
103 /// We're in a constant item. Can't refer to dynamic stuff.
106 /// We passed through a module.
107 ModuleRibKind(Module<'a>),
109 /// We passed through a `macro_rules!` statement
110 MacroDefinition(DefId),
112 /// All bindings in this rib are type parameters that can't be used
113 /// from the default of a type parameter because they're not declared
114 /// before said type parameter. Also see the `visit_generics` override.
115 ForwardTyParamBanRibKind,
119 // Whether this rib kind contains generic parameters, as opposed to local
121 crate fn contains_params(&self) -> bool {
125 | ConstantItemRibKind
127 | MacroDefinition(_) => false,
130 | ForwardTyParamBanRibKind => true,
135 /// A single local scope.
137 /// A rib represents a scope names can live in. Note that these appear in many places, not just
138 /// around braces. At any place where the list of accessible names (of the given namespace)
139 /// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a
140 /// stack. This may be, for example, a `let` statement (because it introduces variables), a macro,
143 /// Different [rib kinds](enum.RibKind) are transparent for different names.
145 /// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
146 /// resolving, the name is looked up from inside out.
148 crate struct Rib<'a, R = Res> {
149 pub bindings: IdentMap<R>,
150 pub kind: RibKind<'a>,
153 impl<'a, R> Rib<'a, R> {
154 fn new(kind: RibKind<'a>) -> Rib<'a, R> {
156 bindings: Default::default(),
162 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
163 crate enum AliasPossibility {
168 #[derive(Copy, Clone, Debug)]
169 crate enum PathSource<'a> {
170 // Type paths `Path`.
172 // Trait paths in bounds or impls.
173 Trait(AliasPossibility),
174 // Expression paths `path`, with optional parent context.
175 Expr(Option<&'a Expr>),
176 // Paths in path patterns `Path`.
178 // Paths in struct expressions and patterns `Path { .. }`.
180 // Paths in tuple struct patterns `Path(..)`.
182 // `m::A::B` in `<T as m::A>::B::C`.
183 TraitItem(Namespace),
186 impl<'a> PathSource<'a> {
187 fn namespace(self) -> Namespace {
189 PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS,
190 PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
191 PathSource::TraitItem(ns) => ns,
195 fn defer_to_typeck(self) -> bool {
197 PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
198 PathSource::Struct | PathSource::TupleStruct => true,
199 PathSource::Trait(_) | PathSource::TraitItem(..) => false,
203 fn descr_expected(self) -> &'static str {
205 PathSource::Type => "type",
206 PathSource::Trait(_) => "trait",
207 PathSource::Pat => "unit struct, unit variant or constant",
208 PathSource::Struct => "struct, variant or union type",
209 PathSource::TupleStruct => "tuple struct or tuple variant",
210 PathSource::TraitItem(ns) => match ns {
211 TypeNS => "associated type",
212 ValueNS => "method or associated constant",
213 MacroNS => bug!("associated macro"),
215 PathSource::Expr(parent) => match &parent.as_ref().map(|p| &p.kind) {
216 // "function" here means "anything callable" rather than `DefKind::Fn`,
217 // this is not precise but usually more helpful than just "value".
218 Some(ExprKind::Call(call_expr, _)) => {
219 match &call_expr.kind {
220 ExprKind::Path(_, path) => {
221 let mut msg = "function";
222 if let Some(segment) = path.segments.iter().last() {
223 if let Some(c) = segment.ident.to_string().chars().next() {
224 if c.is_uppercase() {
225 msg = "function, tuple struct or tuple variant";
239 crate fn is_expected(self, res: Res) -> bool {
241 PathSource::Type => match res {
242 Res::Def(DefKind::Struct, _)
243 | Res::Def(DefKind::Union, _)
244 | Res::Def(DefKind::Enum, _)
245 | Res::Def(DefKind::Trait, _)
246 | Res::Def(DefKind::TraitAlias, _)
247 | Res::Def(DefKind::TyAlias, _)
248 | Res::Def(DefKind::AssocTy, _)
250 | Res::Def(DefKind::TyParam, _)
252 | Res::Def(DefKind::OpaqueTy, _)
253 | Res::Def(DefKind::ForeignTy, _) => true,
256 PathSource::Trait(AliasPossibility::No) => match res {
257 Res::Def(DefKind::Trait, _) => true,
260 PathSource::Trait(AliasPossibility::Maybe) => match res {
261 Res::Def(DefKind::Trait, _) => true,
262 Res::Def(DefKind::TraitAlias, _) => true,
265 PathSource::Expr(..) => match res {
266 Res::Def(DefKind::Ctor(_, CtorKind::Const), _)
267 | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
268 | Res::Def(DefKind::Const, _)
269 | Res::Def(DefKind::Static, _)
271 | Res::Def(DefKind::Fn, _)
272 | Res::Def(DefKind::Method, _)
273 | Res::Def(DefKind::AssocConst, _)
275 | Res::Def(DefKind::ConstParam, _) => true,
278 PathSource::Pat => match res {
279 Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
280 Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) |
281 Res::SelfCtor(..) => true,
284 PathSource::TupleStruct => match res {
285 Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) | Res::SelfCtor(..) => true,
288 PathSource::Struct => match res {
289 Res::Def(DefKind::Struct, _)
290 | Res::Def(DefKind::Union, _)
291 | Res::Def(DefKind::Variant, _)
292 | Res::Def(DefKind::TyAlias, _)
293 | Res::Def(DefKind::AssocTy, _)
294 | Res::SelfTy(..) => true,
297 PathSource::TraitItem(ns) => match res {
298 Res::Def(DefKind::AssocConst, _)
299 | Res::Def(DefKind::Method, _) if ns == ValueNS => true,
300 Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
306 fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
307 syntax::diagnostic_used!(E0404);
308 syntax::diagnostic_used!(E0405);
309 syntax::diagnostic_used!(E0412);
310 syntax::diagnostic_used!(E0422);
311 syntax::diagnostic_used!(E0423);
312 syntax::diagnostic_used!(E0425);
313 syntax::diagnostic_used!(E0531);
314 syntax::diagnostic_used!(E0532);
315 syntax::diagnostic_used!(E0573);
316 syntax::diagnostic_used!(E0574);
317 syntax::diagnostic_used!(E0575);
318 syntax::diagnostic_used!(E0576);
319 match (self, has_unexpected_resolution) {
320 (PathSource::Trait(_), true) => "E0404",
321 (PathSource::Trait(_), false) => "E0405",
322 (PathSource::Type, true) => "E0573",
323 (PathSource::Type, false) => "E0412",
324 (PathSource::Struct, true) => "E0574",
325 (PathSource::Struct, false) => "E0422",
326 (PathSource::Expr(..), true) => "E0423",
327 (PathSource::Expr(..), false) => "E0425",
328 (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
329 (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
330 (PathSource::TraitItem(..), true) => "E0575",
331 (PathSource::TraitItem(..), false) => "E0576",
337 struct DiagnosticMetadata {
338 /// The current trait's associated types' ident, used for diagnostic suggestions.
339 current_trait_assoc_types: Vec<Ident>,
341 /// The current self type if inside an impl (used for better errors).
342 current_self_type: Option<Ty>,
344 /// The current self item if inside an ADT (used for better errors).
345 current_self_item: Option<NodeId>,
347 /// The current enclosing funciton (used for better errors).
348 current_function: Option<Span>,
350 /// A list of labels as of yet unused. Labels will be removed from this map when
351 /// they are used (in a `break` or `continue` statement)
352 unused_labels: FxHashMap<NodeId, Span>,
354 /// Only used for better errors on `fn(): fn()`.
355 current_type_ascription: Vec<Span>,
357 /// Only used for better errors on `let <pat>: <expr, not type>;`.
358 current_let_binding: Option<(Span, Option<Span>, Option<Span>)>,
361 struct LateResolutionVisitor<'a, 'b> {
362 r: &'b mut Resolver<'a>,
364 /// The module that represents the current item scope.
365 parent_scope: ParentScope<'a>,
367 /// The current set of local scopes for types and values.
368 /// FIXME #4948: Reuse ribs to avoid allocation.
369 ribs: PerNS<Vec<Rib<'a>>>,
371 /// The current set of local scopes, for labels.
372 label_ribs: Vec<Rib<'a, NodeId>>,
374 /// The trait that the current context can refer to.
375 current_trait_ref: Option<(Module<'a>, TraitRef)>,
377 /// Fields used to add information to diagnostic errors.
378 diagnostic_metadata: DiagnosticMetadata,
381 /// Walks the whole crate in DFS order, visiting each item, resolving names as it goes.
382 impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
383 fn visit_item(&mut self, item: &'tcx Item) {
384 self.resolve_item(item);
386 fn visit_arm(&mut self, arm: &'tcx Arm) {
387 self.resolve_arm(arm);
389 fn visit_block(&mut self, block: &'tcx Block) {
390 self.resolve_block(block);
392 fn visit_anon_const(&mut self, constant: &'tcx AnonConst) {
393 debug!("visit_anon_const {:?}", constant);
394 self.with_constant_rib(|this| {
395 visit::walk_anon_const(this, constant);
398 fn visit_expr(&mut self, expr: &'tcx Expr) {
399 self.resolve_expr(expr, None);
401 fn visit_local(&mut self, local: &'tcx Local) {
402 let local_spans = match local.pat.kind {
403 // We check for this to avoid tuple struct fields.
404 PatKind::Wild => None,
407 local.ty.as_ref().map(|ty| ty.span),
408 local.init.as_ref().map(|init| init.span),
411 let original = replace(&mut self.diagnostic_metadata.current_let_binding, local_spans);
412 self.resolve_local(local);
413 self.diagnostic_metadata.current_let_binding = original;
415 fn visit_ty(&mut self, ty: &'tcx Ty) {
417 TyKind::Path(ref qself, ref path) => {
418 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
420 TyKind::ImplicitSelf => {
421 let self_ty = Ident::with_dummy_span(kw::SelfUpper);
422 let res = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.id), ty.span)
423 .map_or(Res::Err, |d| d.res());
424 self.r.record_partial_res(ty.id, PartialRes::new(res));
428 visit::walk_ty(self, ty);
430 fn visit_poly_trait_ref(&mut self,
431 tref: &'tcx PolyTraitRef,
432 m: &'tcx TraitBoundModifier) {
433 self.smart_resolve_path(tref.trait_ref.ref_id, None,
434 &tref.trait_ref.path, PathSource::Trait(AliasPossibility::Maybe));
435 visit::walk_poly_trait_ref(self, tref, m);
437 fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
438 match foreign_item.kind {
439 ForeignItemKind::Fn(_, ref generics) => {
440 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
441 visit::walk_foreign_item(this, foreign_item);
444 ForeignItemKind::Static(..) => {
445 self.with_item_rib(HasGenericParams::No, |this| {
446 visit::walk_foreign_item(this, foreign_item);
449 ForeignItemKind::Ty | ForeignItemKind::Macro(..) => {
450 visit::walk_foreign_item(self, foreign_item);
454 fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, sp: Span, _: NodeId) {
455 let previous_value = replace(&mut self.diagnostic_metadata.current_function, Some(sp));
456 debug!("(resolving function) entering function");
457 let rib_kind = match fn_kind {
458 FnKind::ItemFn(..) => FnItemRibKind,
459 FnKind::Method(..) | FnKind::Closure(_) => NormalRibKind,
462 // Create a value rib for the function.
463 self.with_rib(ValueNS, rib_kind, |this| {
464 // Create a label rib for the function.
465 this.with_label_rib(rib_kind, |this| {
466 // Add each argument to the rib.
467 this.resolve_params(&declaration.inputs);
469 visit::walk_fn_ret_ty(this, &declaration.output);
471 // Resolve the function body, potentially inside the body of an async closure
473 FnKind::ItemFn(.., body) |
474 FnKind::Method(.., body) => this.visit_block(body),
475 FnKind::Closure(body) => this.visit_expr(body),
478 debug!("(resolving function) leaving function");
481 self.diagnostic_metadata.current_function = previous_value;
484 fn visit_generics(&mut self, generics: &'tcx Generics) {
485 // For type parameter defaults, we have to ban access
486 // to following type parameters, as the InternalSubsts can only
487 // provide previous type parameters as they're built. We
488 // put all the parameters on the ban list and then remove
489 // them one by one as they are processed and become available.
490 let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
491 let mut found_default = false;
492 default_ban_rib.bindings.extend(generics.params.iter()
493 .filter_map(|param| match param.kind {
494 GenericParamKind::Const { .. } |
495 GenericParamKind::Lifetime { .. } => None,
496 GenericParamKind::Type { ref default, .. } => {
497 found_default |= default.is_some();
499 Some((Ident::with_dummy_span(param.ident.name), Res::Err))
506 // rust-lang/rust#61631: The type `Self` is essentially
507 // another type parameter. For ADTs, we consider it
508 // well-defined only after all of the ADT type parameters have
509 // been provided. Therefore, we do not allow use of `Self`
510 // anywhere in ADT type parameter defaults.
512 // (We however cannot ban `Self` for defaults on *all* generic
513 // lists; e.g. trait generics can usefully refer to `Self`,
514 // such as in the case of `trait Add<Rhs = Self>`.)
515 if self.diagnostic_metadata.current_self_item.is_some() {
516 // (`Some` if + only if we are in ADT's generics.)
517 default_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
520 for param in &generics.params {
522 GenericParamKind::Lifetime { .. } => self.visit_generic_param(param),
523 GenericParamKind::Type { ref default, .. } => {
524 for bound in ¶m.bounds {
525 self.visit_param_bound(bound);
528 if let Some(ref ty) = default {
529 self.ribs[TypeNS].push(default_ban_rib);
531 default_ban_rib = self.ribs[TypeNS].pop().unwrap();
534 // Allow all following defaults to refer to this type parameter.
535 default_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name));
537 GenericParamKind::Const { ref ty } => {
538 for bound in ¶m.bounds {
539 self.visit_param_bound(bound);
545 for p in &generics.where_clause.predicates {
546 self.visit_where_predicate(p);
551 impl<'a, 'b> LateResolutionVisitor<'a, '_> {
552 fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b> {
553 // During late resolution we only track the module component of the parent scope,
554 // although it may be useful to track other components as well for diagnostics.
555 let graph_root = resolver.graph_root;
556 let parent_scope = ParentScope::module(graph_root);
557 let start_rib_kind = ModuleRibKind(graph_root);
558 LateResolutionVisitor {
562 value_ns: vec![Rib::new(start_rib_kind)],
563 type_ns: vec![Rib::new(start_rib_kind)],
564 macro_ns: vec![Rib::new(start_rib_kind)],
566 label_ribs: Vec::new(),
567 current_trait_ref: None,
568 diagnostic_metadata: DiagnosticMetadata::default(),
572 fn resolve_ident_in_lexical_scope(&mut self,
575 record_used_id: Option<NodeId>,
577 -> Option<LexicalScopeBinding<'a>> {
578 self.r.resolve_ident_in_lexical_scope(
579 ident, ns, &self.parent_scope, record_used_id, path_span, &self.ribs[ns]
586 opt_ns: Option<Namespace>, // `None` indicates a module path in import
589 crate_lint: CrateLint,
590 ) -> PathResult<'a> {
591 self.r.resolve_path_with_ribs(
592 path, opt_ns, &self.parent_scope, record_used, path_span, crate_lint, Some(&self.ribs)
598 // We maintain a list of value ribs and type ribs.
600 // Simultaneously, we keep track of the current position in the module
601 // graph in the `parent_scope.module` pointer. When we go to resolve a name in
602 // the value or type namespaces, we first look through all the ribs and
603 // then query the module graph. When we resolve a name in the module
604 // namespace, we can skip all the ribs (since nested modules are not
605 // allowed within blocks in Rust) and jump straight to the current module
608 // Named implementations are handled separately. When we find a method
609 // call, we consult the module node to find all of the implementations in
610 // scope. This information is lazily cached in the module node. We then
611 // generate a fake "implementation scope" containing all the
612 // implementations thus found, for compatibility with old resolve pass.
614 /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
619 work: impl FnOnce(&mut Self) -> T,
621 self.ribs[ns].push(Rib::new(kind));
622 let ret = work(self);
627 fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
628 let id = self.r.definitions.local_def_id(id);
629 let module = self.r.module_map.get(&id).cloned(); // clones a reference
630 if let Some(module) = module {
631 // Move down in the graph.
632 let orig_module = replace(&mut self.parent_scope.module, module);
633 self.with_rib(ValueNS, ModuleRibKind(module), |this| {
634 this.with_rib(TypeNS, ModuleRibKind(module), |this| {
636 this.parent_scope.module = orig_module;
645 /// Searches the current set of local scopes for labels. Returns the first non-`None` label that
646 /// is returned by the given predicate function
648 /// Stops after meeting a closure.
649 fn search_label<P, R>(&self, mut ident: Ident, pred: P) -> Option<R>
650 where P: Fn(&Rib<'_, NodeId>, Ident) -> Option<R>
652 for rib in self.label_ribs.iter().rev() {
655 // If an invocation of this macro created `ident`, give up on `ident`
656 // and switch to `ident`'s source from the macro definition.
657 MacroDefinition(def) => {
658 if def == self.r.macro_def(ident.span.ctxt()) {
659 ident.span.remove_mark();
663 // Do not resolve labels across function boundary
667 let r = pred(rib, ident);
675 fn resolve_adt(&mut self, item: &Item, generics: &Generics) {
676 debug!("resolve_adt");
677 self.with_current_self_item(item, |this| {
678 this.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
679 let item_def_id = this.r.definitions.local_def_id(item.id);
680 this.with_self_rib(Res::SelfTy(None, Some(item_def_id)), |this| {
681 visit::walk_item(this, item);
687 fn future_proof_import(&mut self, use_tree: &UseTree) {
688 let segments = &use_tree.prefix.segments;
689 if !segments.is_empty() {
690 let ident = segments[0].ident;
691 if ident.is_path_segment_keyword() || ident.span.rust_2015() {
695 let nss = match use_tree.kind {
696 UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..],
699 let report_error = |this: &Self, ns| {
700 let what = if ns == TypeNS { "type parameters" } else { "local variables" };
701 this.r.session.span_err(ident.span, &format!("imports cannot refer to {}", what));
705 match self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span) {
706 Some(LexicalScopeBinding::Res(..)) => {
707 report_error(self, ns);
709 Some(LexicalScopeBinding::Item(binding)) => {
710 let orig_blacklisted_binding =
711 replace(&mut self.r.blacklisted_binding, Some(binding));
712 if let Some(LexicalScopeBinding::Res(..)) =
713 self.resolve_ident_in_lexical_scope(ident, ns, None,
714 use_tree.prefix.span) {
715 report_error(self, ns);
717 self.r.blacklisted_binding = orig_blacklisted_binding;
722 } else if let UseTreeKind::Nested(use_trees) = &use_tree.kind {
723 for (use_tree, _) in use_trees {
724 self.future_proof_import(use_tree);
729 fn resolve_item(&mut self, item: &Item) {
730 let name = item.ident.name;
731 debug!("(resolving item) resolving {} ({:?})", name, item.kind);
734 ItemKind::TyAlias(_, ref generics) |
735 ItemKind::Fn(_, ref generics, _) => {
736 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes),
737 |this| visit::walk_item(this, item));
740 ItemKind::Enum(_, ref generics) |
741 ItemKind::Struct(_, ref generics) |
742 ItemKind::Union(_, ref generics) => {
743 self.resolve_adt(item, generics);
746 ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
747 self.resolve_implementation(generics,
753 ItemKind::Trait(.., ref generics, ref bounds, ref trait_items) => {
754 // Create a new rib for the trait-wide type parameters.
755 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
756 let local_def_id = this.r.definitions.local_def_id(item.id);
757 this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| {
758 this.visit_generics(generics);
759 walk_list!(this, visit_param_bound, bounds);
761 for trait_item in trait_items {
762 this.with_trait_items(trait_items, |this| {
763 this.with_generic_param_rib(&trait_item.generics, AssocItemRibKind,
765 match trait_item.kind {
766 TraitItemKind::Const(ref ty, ref default) => {
769 // Only impose the restrictions of
770 // ConstRibKind for an actual constant
771 // expression in a provided default.
772 if let Some(ref expr) = *default{
773 this.with_constant_rib(|this| {
774 this.visit_expr(expr);
778 TraitItemKind::Method(_, _) => {
779 visit::walk_trait_item(this, trait_item)
781 TraitItemKind::Type(..) => {
782 visit::walk_trait_item(this, trait_item)
784 TraitItemKind::Macro(_) => {
785 panic!("unexpanded macro in resolve!")
795 ItemKind::TraitAlias(ref generics, ref bounds) => {
796 // Create a new rib for the trait-wide type parameters.
797 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
798 let local_def_id = this.r.definitions.local_def_id(item.id);
799 this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| {
800 this.visit_generics(generics);
801 walk_list!(this, visit_param_bound, bounds);
806 ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
807 self.with_scope(item.id, |this| {
808 visit::walk_item(this, item);
812 ItemKind::Static(ref ty, _, ref expr) |
813 ItemKind::Const(ref ty, ref expr) => {
814 debug!("resolve_item ItemKind::Const");
815 self.with_item_rib(HasGenericParams::No, |this| {
817 this.with_constant_rib(|this| {
818 this.visit_expr(expr);
823 ItemKind::Use(ref use_tree) => {
824 self.future_proof_import(use_tree);
827 ItemKind::ExternCrate(..) |
828 ItemKind::MacroDef(..) | ItemKind::GlobalAsm(..) => {
829 // do nothing, these are just around to be encoded
832 ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
836 fn with_generic_param_rib<'c, F>(&'c mut self, generics: &'c Generics, kind: RibKind<'a>, f: F)
837 where F: FnOnce(&mut Self)
839 debug!("with_generic_param_rib");
840 let mut function_type_rib = Rib::new(kind);
841 let mut function_value_rib = Rib::new(kind);
842 let mut seen_bindings = FxHashMap::default();
844 // We also can't shadow bindings from the parent item
845 if let AssocItemRibKind = kind {
846 let mut add_bindings_for_ns = |ns| {
847 let parent_rib = self.ribs[ns].iter()
848 .rfind(|r| if let ItemRibKind(_) = r.kind { true } else { false })
849 .expect("associated item outside of an item");
850 seen_bindings.extend(
851 parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)),
854 add_bindings_for_ns(ValueNS);
855 add_bindings_for_ns(TypeNS);
858 for param in &generics.params {
859 if let GenericParamKind::Lifetime { .. } = param.kind {
863 let def_kind = match param.kind {
864 GenericParamKind::Type { .. } => DefKind::TyParam,
865 GenericParamKind::Const { .. } => DefKind::ConstParam,
869 let ident = param.ident.modern();
870 debug!("with_generic_param_rib: {}", param.id);
872 if seen_bindings.contains_key(&ident) {
873 let span = seen_bindings.get(&ident).unwrap();
874 let err = ResolutionError::NameAlreadyUsedInParameterList(
878 self.r.report_error(param.ident.span, err);
880 seen_bindings.entry(ident).or_insert(param.ident.span);
882 // Plain insert (no renaming).
883 let res = Res::Def(def_kind, self.r.definitions.local_def_id(param.id));
886 GenericParamKind::Type { .. } => {
887 function_type_rib.bindings.insert(ident, res);
888 self.r.record_partial_res(param.id, PartialRes::new(res));
890 GenericParamKind::Const { .. } => {
891 function_value_rib.bindings.insert(ident, res);
892 self.r.record_partial_res(param.id, PartialRes::new(res));
898 self.ribs[ValueNS].push(function_value_rib);
899 self.ribs[TypeNS].push(function_type_rib);
903 self.ribs[TypeNS].pop();
904 self.ribs[ValueNS].pop();
907 fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) {
908 self.label_ribs.push(Rib::new(kind));
910 self.label_ribs.pop();
913 fn with_item_rib(&mut self, has_generic_params: HasGenericParams, f: impl FnOnce(&mut Self)) {
914 let kind = ItemRibKind(has_generic_params);
915 self.with_rib(ValueNS, kind, |this| this.with_rib(TypeNS, kind, f))
918 fn with_constant_rib(&mut self, f: impl FnOnce(&mut Self)) {
919 debug!("with_constant_rib");
920 self.with_rib(ValueNS, ConstantItemRibKind, |this| {
921 this.with_label_rib(ConstantItemRibKind, f);
925 fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
926 // Handle nested impls (inside fn bodies)
927 let previous_value = replace(
928 &mut self.diagnostic_metadata.current_self_type,
929 Some(self_type.clone()),
931 let result = f(self);
932 self.diagnostic_metadata.current_self_type = previous_value;
936 fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
937 let previous_value = replace(
938 &mut self.diagnostic_metadata.current_self_item,
941 let result = f(self);
942 self.diagnostic_metadata.current_self_item = previous_value;
946 /// When evaluating a `trait` use its associated types' idents for suggestionsa in E0412.
947 fn with_trait_items<T>(
949 trait_items: &Vec<TraitItem>,
950 f: impl FnOnce(&mut Self) -> T,
952 let trait_assoc_types = replace(
953 &mut self.diagnostic_metadata.current_trait_assoc_types,
954 trait_items.iter().filter_map(|item| match &item.kind {
955 TraitItemKind::Type(bounds, _) if bounds.len() == 0 => Some(item.ident),
959 let result = f(self);
960 self.diagnostic_metadata.current_trait_assoc_types = trait_assoc_types;
964 /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
965 fn with_optional_trait_ref<T>(
967 opt_trait_ref: Option<&TraitRef>,
968 f: impl FnOnce(&mut Self, Option<DefId>) -> T
970 let mut new_val = None;
971 let mut new_id = None;
972 if let Some(trait_ref) = opt_trait_ref {
973 let path: Vec<_> = Segment::from_path(&trait_ref.path);
974 let res = self.smart_resolve_path_fragment(
979 PathSource::Trait(AliasPossibility::No),
980 CrateLint::SimplePath(trait_ref.ref_id),
983 new_id = Some(res.def_id());
984 let span = trait_ref.path.span;
985 if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
991 CrateLint::SimplePath(trait_ref.ref_id),
994 new_val = Some((module, trait_ref.clone()));
998 let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
999 let result = f(self, new_id);
1000 self.current_trait_ref = original_trait_ref;
1004 fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
1005 let mut self_type_rib = Rib::new(NormalRibKind);
1007 // Plain insert (no renaming, since types are not currently hygienic)
1008 self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
1009 self.ribs[ns].push(self_type_rib);
1011 self.ribs[ns].pop();
1014 fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
1015 self.with_self_rib_ns(TypeNS, self_res, f)
1018 fn resolve_implementation(&mut self,
1019 generics: &Generics,
1020 opt_trait_reference: &Option<TraitRef>,
1023 impl_items: &[ImplItem]) {
1024 debug!("resolve_implementation");
1025 // If applicable, create a rib for the type parameters.
1026 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
1027 // Dummy self type for better errors if `Self` is used in the trait path.
1028 this.with_self_rib(Res::SelfTy(None, None), |this| {
1029 // Resolve the trait reference, if necessary.
1030 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1031 let item_def_id = this.r.definitions.local_def_id(item_id);
1032 this.with_self_rib(Res::SelfTy(trait_id, Some(item_def_id)), |this| {
1033 if let Some(trait_ref) = opt_trait_reference.as_ref() {
1034 // Resolve type arguments in the trait path.
1035 visit::walk_trait_ref(this, trait_ref);
1037 // Resolve the self type.
1038 this.visit_ty(self_type);
1039 // Resolve the generic parameters.
1040 this.visit_generics(generics);
1041 // Resolve the items within the impl.
1042 this.with_current_self_type(self_type, |this| {
1043 this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
1044 debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
1045 for impl_item in impl_items {
1046 // We also need a new scope for the impl item type parameters.
1047 this.with_generic_param_rib(&impl_item.generics,
1050 use crate::ResolutionError::*;
1051 match impl_item.kind {
1052 ImplItemKind::Const(..) => {
1054 "resolve_implementation ImplItemKind::Const",
1056 // If this is a trait impl, ensure the const
1058 this.check_trait_item(
1062 |n, s| ConstNotMemberOfTrait(n, s),
1065 this.with_constant_rib(|this| {
1066 visit::walk_impl_item(this, impl_item)
1069 ImplItemKind::Method(..) => {
1070 // If this is a trait impl, ensure the method
1072 this.check_trait_item(impl_item.ident,
1075 |n, s| MethodNotMemberOfTrait(n, s));
1077 visit::walk_impl_item(this, impl_item);
1079 ImplItemKind::TyAlias(ref ty) => {
1080 // If this is a trait impl, ensure the type
1082 this.check_trait_item(impl_item.ident,
1085 |n, s| TypeNotMemberOfTrait(n, s));
1089 ImplItemKind::Macro(_) =>
1090 panic!("unexpanded macro in resolve!"),
1102 fn check_trait_item<F>(&mut self, ident: Ident, ns: Namespace, span: Span, err: F)
1103 where F: FnOnce(Name, &str) -> ResolutionError<'_>
1105 // If there is a TraitRef in scope for an impl, then the method must be in the
1107 if let Some((module, _)) = self.current_trait_ref {
1108 if self.r.resolve_ident_in_module(
1109 ModuleOrUniformRoot::Module(module),
1116 let path = &self.current_trait_ref.as_ref().unwrap().1.path;
1117 self.r.report_error(span, err(ident.name, &path_names_to_string(path)));
1122 fn resolve_params(&mut self, params: &[Param]) {
1123 let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
1124 for Param { pat, ty, .. } in params {
1125 self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
1127 debug!("(resolving function / closure) recorded parameter");
1131 fn resolve_local(&mut self, local: &Local) {
1132 // Resolve the type.
1133 walk_list!(self, visit_ty, &local.ty);
1135 // Resolve the initializer.
1136 walk_list!(self, visit_expr, &local.init);
1138 // Resolve the pattern.
1139 self.resolve_pattern_top(&local.pat, PatternSource::Let);
1142 /// build a map from pattern identifiers to binding-info's.
1143 /// this is done hygienically. This could arise for a macro
1144 /// that expands into an or-pattern where one 'x' was from the
1145 /// user and one 'x' came from the macro.
1146 fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1147 let mut binding_map = FxHashMap::default();
1149 pat.walk(&mut |pat| {
1151 PatKind::Ident(binding_mode, ident, ref sub_pat)
1152 if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
1154 binding_map.insert(ident, BindingInfo { span: ident.span, binding_mode });
1156 PatKind::Or(ref ps) => {
1157 // Check the consistency of this or-pattern and
1158 // then add all bindings to the larger map.
1159 for bm in self.check_consistent_bindings(ps) {
1160 binding_map.extend(bm);
1173 fn is_base_res_local(&self, nid: NodeId) -> bool {
1174 match self.r.partial_res_map.get(&nid).map(|res| res.base_res()) {
1175 Some(Res::Local(..)) => true,
1180 /// Checks that all of the arms in an or-pattern have exactly the
1181 /// same set of bindings, with the same binding modes for each.
1182 fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
1183 let mut missing_vars = FxHashMap::default();
1184 let mut inconsistent_vars = FxHashMap::default();
1186 // 1) Compute the binding maps of all arms.
1187 let maps = pats.iter()
1188 .map(|pat| self.binding_mode_map(pat))
1189 .collect::<Vec<_>>();
1191 // 2) Record any missing bindings or binding mode inconsistencies.
1192 for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) {
1193 // Check against all arms except for the same pattern which is always self-consistent.
1194 let inners = pats.iter().enumerate()
1195 .filter(|(_, pat)| pat.id != pat_outer.id)
1196 .flat_map(|(idx, _)| maps[idx].iter())
1197 .map(|(key, binding)| (key.name, map_outer.get(&key), binding));
1199 for (name, info, &binding_inner) in inners {
1201 None => { // The inner binding is missing in the outer.
1202 let binding_error = missing_vars
1204 .or_insert_with(|| BindingError {
1206 origin: BTreeSet::new(),
1207 target: BTreeSet::new(),
1208 could_be_path: name.as_str().starts_with(char::is_uppercase),
1210 binding_error.origin.insert(binding_inner.span);
1211 binding_error.target.insert(pat_outer.span);
1213 Some(binding_outer) => {
1214 if binding_outer.binding_mode != binding_inner.binding_mode {
1215 // The binding modes in the outer and inner bindings differ.
1218 .or_insert((binding_inner.span, binding_outer.span));
1225 // 3) Report all missing variables we found.
1226 let mut missing_vars = missing_vars.iter_mut().collect::<Vec<_>>();
1227 missing_vars.sort();
1228 for (name, mut v) in missing_vars {
1229 if inconsistent_vars.contains_key(name) {
1230 v.could_be_path = false;
1232 self.r.report_error(
1233 *v.origin.iter().next().unwrap(),
1234 ResolutionError::VariableNotBoundInPattern(v));
1237 // 4) Report all inconsistencies in binding modes we found.
1238 let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
1239 inconsistent_vars.sort();
1240 for (name, v) in inconsistent_vars {
1241 self.r.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
1244 // 5) Finally bubble up all the binding maps.
1248 /// Check the consistency of the outermost or-patterns.
1249 fn check_consistent_bindings_top(&mut self, pat: &Pat) {
1250 pat.walk(&mut |pat| match pat.kind {
1251 PatKind::Or(ref ps) => {
1252 self.check_consistent_bindings(ps);
1259 fn resolve_arm(&mut self, arm: &Arm) {
1260 self.with_rib(ValueNS, NormalRibKind, |this| {
1261 this.resolve_pattern_top(&arm.pat, PatternSource::Match);
1262 walk_list!(this, visit_expr, &arm.guard);
1263 this.visit_expr(&arm.body);
1267 /// Arising from `source`, resolve a top level pattern.
1268 fn resolve_pattern_top(&mut self, pat: &Pat, pat_src: PatternSource) {
1269 let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
1270 self.resolve_pattern(pat, pat_src, &mut bindings);
1276 pat_src: PatternSource,
1277 bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
1279 self.resolve_pattern_inner(pat, pat_src, bindings);
1280 // This has to happen *after* we determine which pat_idents are variants:
1281 self.check_consistent_bindings_top(pat);
1282 visit::walk_pat(self, pat);
1285 /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
1289 /// A stack of sets of bindings accumulated.
1291 /// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
1292 /// be interpreted as re-binding an already bound binding. This results in an error.
1293 /// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
1294 /// in reusing this binding rather than creating a fresh one.
1296 /// When called at the top level, the stack must have a single element
1297 /// with `PatBound::Product`. Otherwise, pushing to the stack happens as
1298 /// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
1299 /// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
1300 /// When each `p_i` has been dealt with, the top set is merged with its parent.
1301 /// When a whole or-pattern has been dealt with, the thing happens.
1303 /// See the implementation and `fresh_binding` for more details.
1304 fn resolve_pattern_inner(
1307 pat_src: PatternSource,
1308 bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
1310 // Visit all direct subpatterns of this pattern.
1311 pat.walk(&mut |pat| {
1312 debug!("resolve_pattern pat={:?} node={:?}", pat, pat.kind);
1314 PatKind::Ident(bmode, ident, ref sub) => {
1315 // First try to resolve the identifier as some existing entity,
1316 // then fall back to a fresh binding.
1317 let has_sub = sub.is_some();
1318 let res = self.try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub)
1319 .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
1320 self.r.record_partial_res(pat.id, PartialRes::new(res));
1322 PatKind::TupleStruct(ref path, ..) => {
1323 self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
1325 PatKind::Path(ref qself, ref path) => {
1326 self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
1328 PatKind::Struct(ref path, ..) => {
1329 self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
1331 PatKind::Or(ref ps) => {
1332 // Add a new set of bindings to the stack. `Or` here records that when a
1333 // binding already exists in this set, it should not result in an error because
1334 // `V1(a) | V2(a)` must be allowed and are checked for consistency later.
1335 bindings.push((PatBoundCtx::Or, Default::default()));
1337 // Now we need to switch back to a product context so that each
1338 // part of the or-pattern internally rejects already bound names.
1339 // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
1340 bindings.push((PatBoundCtx::Product, Default::default()));
1341 self.resolve_pattern_inner(p, pat_src, bindings);
1342 // Move up the non-overlapping bindings to the or-pattern.
1343 // Existing bindings just get "merged".
1344 let collected = bindings.pop().unwrap().1;
1345 bindings.last_mut().unwrap().1.extend(collected);
1347 // This or-pattern itself can itself be part of a product,
1348 // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
1349 // Both cases bind `a` again in a product pattern and must be rejected.
1350 let collected = bindings.pop().unwrap().1;
1351 bindings.last_mut().unwrap().1.extend(collected);
1353 // Prevent visiting `ps` as we've already done so above.
1366 pat_src: PatternSource,
1367 bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
1369 // Add the binding to the local ribs, if it doesn't already exist in the bindings map.
1370 // (We must not add it if it's in the bindings map because that breaks the assumptions
1371 // later passes make about or-patterns.)
1372 let ident = ident.modern_and_legacy();
1374 // Walk outwards the stack of products / or-patterns and
1375 // find out if the identifier has been bound in any of these.
1376 let mut already_bound_and = false;
1377 let mut already_bound_or = false;
1378 for (is_sum, set) in bindings.iter_mut().rev() {
1379 match (is_sum, set.get(&ident).cloned()) {
1380 // Already bound in a product pattern, e.g. `(a, a)` which is not allowed.
1381 (PatBoundCtx::Product, Some(..)) => already_bound_and = true,
1382 // Already bound in an or-pattern, e.g. `V1(a) | V2(a)`.
1383 // This is *required* for consistency which is checked later.
1384 (PatBoundCtx::Or, Some(..)) => already_bound_or = true,
1385 // Not already bound here.
1390 if already_bound_and {
1391 // Overlap in a product pattern somewhere; report an error.
1392 use ResolutionError::*;
1393 let error = match pat_src {
1394 // `fn f(a: u8, a: u8)`:
1395 PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
1397 _ => IdentifierBoundMoreThanOnceInSamePattern,
1399 self.r.report_error(ident.span, error(&ident.as_str()));
1402 // Record as bound if it's valid:
1403 let ident_valid = ident.name != kw::Invalid;
1405 bindings.last_mut().unwrap().1.insert(ident);
1408 if already_bound_or {
1409 // `Variant1(a) | Variant2(a)`, ok
1410 // Reuse definition from the first `a`.
1411 self.innermost_rib_bindings(ValueNS)[&ident]
1413 let res = Res::Local(pat_id);
1415 // A completely fresh binding add to the set if it's valid.
1416 self.innermost_rib_bindings(ValueNS).insert(ident, res);
1422 fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
1423 &mut self.ribs[ns].last_mut().unwrap().bindings
1426 fn try_resolve_as_non_binding(
1428 pat_src: PatternSource,
1434 let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?.item()?;
1435 let res = binding.res();
1437 // An immutable (no `mut`) by-value (no `ref`) binding pattern without
1438 // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
1439 // also be interpreted as a path to e.g. a constant, variant, etc.
1440 let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Immutable);
1443 Res::Def(DefKind::Ctor(_, CtorKind::Const), _) |
1444 Res::Def(DefKind::Const, _) if is_syntactic_ambiguity => {
1445 // Disambiguate in favor of a unit struct/variant or constant pattern.
1446 self.r.record_use(ident, ValueNS, binding, false);
1449 Res::Def(DefKind::Ctor(..), _)
1450 | Res::Def(DefKind::Const, _)
1451 | Res::Def(DefKind::Static, _) => {
1452 // This is unambiguously a fresh binding, either syntactically
1453 // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
1454 // to something unusable as a pattern (e.g., constructor function),
1455 // but we still conservatively report an error, see
1456 // issues/33118#issuecomment-233962221 for one reason why.
1457 self.r.report_error(
1459 ResolutionError::BindingShadowsSomethingUnacceptable(
1467 Res::Def(DefKind::Fn, _) | Res::Err => {
1468 // These entities are explicitly allowed to be shadowed by fresh bindings.
1472 span_bug!(ident.span, "unexpected resolution for an \
1473 identifier in pattern: {:?}", res);
1478 // High-level and context dependent path resolution routine.
1479 // Resolves the path and records the resolution into definition map.
1480 // If resolution fails tries several techniques to find likely
1481 // resolution candidates, suggest imports or other help, and report
1482 // errors in user friendly way.
1483 fn smart_resolve_path(&mut self,
1485 qself: Option<&QSelf>,
1487 source: PathSource<'_>) {
1488 self.smart_resolve_path_fragment(
1491 &Segment::from_path(path),
1494 CrateLint::SimplePath(id),
1498 fn smart_resolve_path_fragment(&mut self,
1500 qself: Option<&QSelf>,
1503 source: PathSource<'_>,
1504 crate_lint: CrateLint)
1506 let ns = source.namespace();
1507 let is_expected = &|res| source.is_expected(res);
1509 let report_errors = |this: &mut Self, res: Option<Res>| {
1510 let (err, candidates) = this.smart_resolve_report_errors(path, span, source, res);
1511 let def_id = this.parent_scope.module.normal_ancestor_id;
1512 let node_id = this.r.definitions.as_local_node_id(def_id).unwrap();
1513 let better = res.is_some();
1514 this.r.use_injections.push(UseError { err, candidates, node_id, better });
1515 PartialRes::new(Res::Err)
1518 let partial_res = match self.resolve_qpath_anywhere(
1524 source.defer_to_typeck(),
1527 Some(partial_res) if partial_res.unresolved_segments() == 0 => {
1528 if is_expected(partial_res.base_res()) || partial_res.base_res() == Res::Err {
1531 report_errors(self, Some(partial_res.base_res()))
1534 Some(partial_res) if source.defer_to_typeck() => {
1535 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
1536 // or `<T>::A::B`. If `B` should be resolved in value namespace then
1537 // it needs to be added to the trait map.
1539 let item_name = path.last().unwrap().ident;
1540 let traits = self.get_traits_containing_item(item_name, ns);
1541 self.r.trait_map.insert(id, traits);
1544 let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))];
1545 std_path.extend(path);
1546 if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) {
1547 let cl = CrateLint::No;
1549 if let PathResult::Module(_) | PathResult::NonModule(_) =
1550 self.resolve_path(&std_path, ns, false, span, cl) {
1551 // check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
1552 let item_span = path.iter().last().map(|segment| segment.ident.span)
1554 debug!("accessed item from `std` submodule as a bare type {:?}", std_path);
1555 let mut hm = self.r.session.confused_type_with_std_module.borrow_mut();
1556 hm.insert(item_span, span);
1557 // In some places (E0223) we only have access to the full path
1558 hm.insert(span, span);
1563 _ => report_errors(self, None)
1566 if let PathSource::TraitItem(..) = source {} else {
1567 // Avoid recording definition of `A::B` in `<T as A>::B::C`.
1568 self.r.record_partial_res(id, partial_res);
1573 fn self_type_is_available(&mut self, span: Span) -> bool {
1574 let binding = self.resolve_ident_in_lexical_scope(
1575 Ident::with_dummy_span(kw::SelfUpper),
1580 if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
1583 fn self_value_is_available(&mut self, self_span: Span, path_span: Span) -> bool {
1584 let ident = Ident::new(kw::SelfLower, self_span);
1585 let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, path_span);
1586 if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
1589 // Resolve in alternative namespaces if resolution in the primary namespace fails.
1590 fn resolve_qpath_anywhere(
1593 qself: Option<&QSelf>,
1595 primary_ns: Namespace,
1597 defer_to_typeck: bool,
1598 crate_lint: CrateLint,
1599 ) -> Option<PartialRes> {
1600 let mut fin_res = None;
1601 for (i, ns) in [primary_ns, TypeNS, ValueNS].iter().cloned().enumerate() {
1602 if i == 0 || ns != primary_ns {
1603 match self.resolve_qpath(id, qself, path, ns, span, crate_lint) {
1604 // If defer_to_typeck, then resolution > no resolution,
1605 // otherwise full resolution > partial resolution > no resolution.
1606 Some(partial_res) if partial_res.unresolved_segments() == 0 ||
1608 return Some(partial_res),
1609 partial_res => if fin_res.is_none() { fin_res = partial_res },
1615 assert!(primary_ns != MacroNS);
1616 if qself.is_none() {
1617 let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
1618 let path = Path { segments: path.iter().map(path_seg).collect(), span };
1619 if let Ok((_, res)) = self.r.resolve_macro_path(
1620 &path, None, &self.parent_scope, false, false
1622 return Some(PartialRes::new(res));
1629 /// Handles paths that may refer to associated items.
1633 qself: Option<&QSelf>,
1637 crate_lint: CrateLint,
1638 ) -> Option<PartialRes> {
1640 "resolve_qpath(id={:?}, qself={:?}, path={:?}, ns={:?}, span={:?})",
1648 if let Some(qself) = qself {
1649 if qself.position == 0 {
1650 // This is a case like `<T>::B`, where there is no
1651 // trait to resolve. In that case, we leave the `B`
1652 // segment to be resolved by type-check.
1653 return Some(PartialRes::with_unresolved_segments(
1654 Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX)), path.len()
1658 // Make sure `A::B` in `<T as A::B>::C` is a trait item.
1660 // Currently, `path` names the full item (`A::B::C`, in
1661 // our example). so we extract the prefix of that that is
1662 // the trait (the slice upto and including
1663 // `qself.position`). And then we recursively resolve that,
1664 // but with `qself` set to `None`.
1666 // However, setting `qself` to none (but not changing the
1667 // span) loses the information about where this path
1668 // *actually* appears, so for the purposes of the crate
1669 // lint we pass along information that this is the trait
1670 // name from a fully qualified path, and this also
1671 // contains the full span (the `CrateLint::QPathTrait`).
1672 let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
1673 let partial_res = self.smart_resolve_path_fragment(
1676 &path[..=qself.position],
1678 PathSource::TraitItem(ns),
1679 CrateLint::QPathTrait {
1681 qpath_span: qself.path_span,
1685 // The remaining segments (the `C` in our example) will
1686 // have to be resolved by type-check, since that requires doing
1687 // trait resolution.
1688 return Some(PartialRes::with_unresolved_segments(
1689 partial_res.base_res(),
1690 partial_res.unresolved_segments() + path.len() - qself.position - 1,
1694 let result = match self.resolve_path(&path, Some(ns), true, span, crate_lint) {
1695 PathResult::NonModule(path_res) => path_res,
1696 PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => {
1697 PartialRes::new(module.res().unwrap())
1699 // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
1700 // don't report an error right away, but try to fallback to a primitive type.
1701 // So, we are still able to successfully resolve something like
1703 // use std::u8; // bring module u8 in scope
1704 // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
1705 // u8::max_value() // OK, resolves to associated function <u8>::max_value,
1706 // // not to non-existent std::u8::max_value
1709 // Such behavior is required for backward compatibility.
1710 // The same fallback is used when `a` resolves to nothing.
1711 PathResult::Module(ModuleOrUniformRoot::Module(_)) |
1712 PathResult::Failed { .. }
1713 if (ns == TypeNS || path.len() > 1) &&
1714 self.r.primitive_type_table.primitive_types
1715 .contains_key(&path[0].ident.name) => {
1716 let prim = self.r.primitive_type_table.primitive_types[&path[0].ident.name];
1717 PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
1719 PathResult::Module(ModuleOrUniformRoot::Module(module)) =>
1720 PartialRes::new(module.res().unwrap()),
1721 PathResult::Failed { is_error_from_last_segment: false, span, label, suggestion } => {
1722 self.r.report_error(span, ResolutionError::FailedToResolve { label, suggestion });
1723 PartialRes::new(Res::Err)
1725 PathResult::Module(..) | PathResult::Failed { .. } => return None,
1726 PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
1729 if path.len() > 1 && result.base_res() != Res::Err &&
1730 path[0].ident.name != kw::PathRoot &&
1731 path[0].ident.name != kw::DollarCrate {
1732 let unqualified_result = {
1733 match self.resolve_path(
1734 &[*path.last().unwrap()],
1740 PathResult::NonModule(path_res) => path_res.base_res(),
1741 PathResult::Module(ModuleOrUniformRoot::Module(module)) =>
1742 module.res().unwrap(),
1743 _ => return Some(result),
1746 if result.base_res() == unqualified_result {
1747 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
1748 self.r.lint_buffer.buffer_lint(lint, id, span, "unnecessary qualification")
1755 fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
1756 if let Some(label) = label {
1757 if label.ident.as_str().as_bytes()[1] != b'_' {
1758 self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
1760 self.with_label_rib(NormalRibKind, |this| {
1761 let ident = label.ident.modern_and_legacy();
1762 this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
1770 fn resolve_labeled_block(&mut self, label: Option<Label>, id: NodeId, block: &Block) {
1771 self.with_resolved_label(label, id, |this| this.visit_block(block));
1774 fn resolve_block(&mut self, block: &Block) {
1775 debug!("(resolving block) entering block");
1776 // Move down in the graph, if there's an anonymous module rooted here.
1777 let orig_module = self.parent_scope.module;
1778 let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
1780 let mut num_macro_definition_ribs = 0;
1781 if let Some(anonymous_module) = anonymous_module {
1782 debug!("(resolving block) found anonymous module, moving down");
1783 self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1784 self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1785 self.parent_scope.module = anonymous_module;
1787 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
1790 // Descend into the block.
1791 for stmt in &block.stmts {
1792 if let StmtKind::Item(ref item) = stmt.kind {
1793 if let ItemKind::MacroDef(..) = item.kind {
1794 num_macro_definition_ribs += 1;
1795 let res = self.r.definitions.local_def_id(item.id);
1796 self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
1797 self.label_ribs.push(Rib::new(MacroDefinition(res)));
1801 self.visit_stmt(stmt);
1805 self.parent_scope.module = orig_module;
1806 for _ in 0 .. num_macro_definition_ribs {
1807 self.ribs[ValueNS].pop();
1808 self.label_ribs.pop();
1810 self.ribs[ValueNS].pop();
1811 if anonymous_module.is_some() {
1812 self.ribs[TypeNS].pop();
1814 debug!("(resolving block) leaving block");
1817 fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
1818 // First, record candidate traits for this expression if it could
1819 // result in the invocation of a method call.
1821 self.record_candidate_traits_for_expr_if_necessary(expr);
1823 // Next, resolve the node.
1825 ExprKind::Path(ref qself, ref path) => {
1826 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
1827 visit::walk_expr(self, expr);
1830 ExprKind::Struct(ref path, ..) => {
1831 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
1832 visit::walk_expr(self, expr);
1835 ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
1836 let node_id = self.search_label(label.ident, |rib, ident| {
1837 rib.bindings.get(&ident.modern_and_legacy()).cloned()
1841 // Search again for close matches...
1842 // Picks the first label that is "close enough", which is not necessarily
1843 // the closest match
1844 let close_match = self.search_label(label.ident, |rib, ident| {
1845 let names = rib.bindings.iter().filter_map(|(id, _)| {
1846 if id.span.ctxt() == label.ident.span.ctxt() {
1852 find_best_match_for_name(names, &ident.as_str(), None)
1854 self.r.record_partial_res(expr.id, PartialRes::new(Res::Err));
1855 self.r.report_error(
1857 ResolutionError::UndeclaredLabel(&label.ident.as_str(), close_match),
1861 // Since this res is a label, it is never read.
1862 self.r.label_res_map.insert(expr.id, node_id);
1863 self.diagnostic_metadata.unused_labels.remove(&node_id);
1867 // visit `break` argument if any
1868 visit::walk_expr(self, expr);
1871 ExprKind::Let(ref pat, ref scrutinee) => {
1872 self.visit_expr(scrutinee);
1873 self.resolve_pattern_top(pat, PatternSource::Let);
1876 ExprKind::If(ref cond, ref then, ref opt_else) => {
1877 self.with_rib(ValueNS, NormalRibKind, |this| {
1878 this.visit_expr(cond);
1879 this.visit_block(then);
1881 opt_else.as_ref().map(|expr| self.visit_expr(expr));
1884 ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
1886 ExprKind::While(ref cond, ref block, label) => {
1887 self.with_resolved_label(label, expr.id, |this| {
1888 this.with_rib(ValueNS, NormalRibKind, |this| {
1889 this.visit_expr(cond);
1890 this.visit_block(block);
1895 ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
1896 self.visit_expr(iter_expr);
1897 self.with_rib(ValueNS, NormalRibKind, |this| {
1898 this.resolve_pattern_top(pat, PatternSource::For);
1899 this.resolve_labeled_block(label, expr.id, block);
1903 ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
1905 // Equivalent to `visit::walk_expr` + passing some context to children.
1906 ExprKind::Field(ref subexpression, _) => {
1907 self.resolve_expr(subexpression, Some(expr));
1909 ExprKind::MethodCall(ref segment, ref arguments) => {
1910 let mut arguments = arguments.iter();
1911 self.resolve_expr(arguments.next().unwrap(), Some(expr));
1912 for argument in arguments {
1913 self.resolve_expr(argument, None);
1915 self.visit_path_segment(expr.span, segment);
1918 ExprKind::Call(ref callee, ref arguments) => {
1919 self.resolve_expr(callee, Some(expr));
1920 for argument in arguments {
1921 self.resolve_expr(argument, None);
1924 ExprKind::Type(ref type_expr, _) => {
1925 self.diagnostic_metadata.current_type_ascription.push(type_expr.span);
1926 visit::walk_expr(self, expr);
1927 self.diagnostic_metadata.current_type_ascription.pop();
1929 // `async |x| ...` gets desugared to `|x| future_from_generator(|| ...)`, so we need to
1930 // resolve the arguments within the proper scopes so that usages of them inside the
1931 // closure are detected as upvars rather than normal closure arg usages.
1932 ExprKind::Closure(_, IsAsync::Async { .. }, _, ref fn_decl, ref body, _span) => {
1933 self.with_rib(ValueNS, NormalRibKind, |this| {
1934 // Resolve arguments:
1935 this.resolve_params(&fn_decl.inputs);
1936 // No need to resolve return type --
1937 // the outer closure return type is `FunctionRetTy::Default`.
1939 // Now resolve the inner closure
1941 // No need to resolve arguments: the inner closure has none.
1942 // Resolve the return type:
1943 visit::walk_fn_ret_ty(this, &fn_decl.output);
1945 this.visit_expr(body);
1950 visit::walk_expr(self, expr);
1955 fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
1957 ExprKind::Field(_, ident) => {
1958 // FIXME(#6890): Even though you can't treat a method like a
1959 // field, we need to add any trait methods we find that match
1960 // the field name so that we can do some nice error reporting
1961 // later on in typeck.
1962 let traits = self.get_traits_containing_item(ident, ValueNS);
1963 self.r.trait_map.insert(expr.id, traits);
1965 ExprKind::MethodCall(ref segment, ..) => {
1966 debug!("(recording candidate traits for expr) recording traits for {}",
1968 let traits = self.get_traits_containing_item(segment.ident, ValueNS);
1969 self.r.trait_map.insert(expr.id, traits);
1977 fn get_traits_containing_item(&mut self, mut ident: Ident, ns: Namespace)
1978 -> Vec<TraitCandidate> {
1979 debug!("(getting traits containing item) looking for '{}'", ident.name);
1981 let mut found_traits = Vec::new();
1982 // Look for the current trait.
1983 if let Some((module, _)) = self.current_trait_ref {
1984 if self.r.resolve_ident_in_module(
1985 ModuleOrUniformRoot::Module(module),
1992 let def_id = module.def_id().unwrap();
1993 found_traits.push(TraitCandidate { def_id: def_id, import_ids: smallvec![] });
1997 ident.span = ident.span.modern();
1998 let mut search_module = self.parent_scope.module;
2000 self.get_traits_in_module_containing_item(ident, ns, search_module, &mut found_traits);
2001 search_module = unwrap_or!(
2002 self.r.hygienic_lexical_parent(search_module, &mut ident.span), break
2006 if let Some(prelude) = self.r.prelude {
2007 if !search_module.no_implicit_prelude {
2008 self.get_traits_in_module_containing_item(ident, ns, prelude, &mut found_traits);
2015 fn get_traits_in_module_containing_item(&mut self,
2019 found_traits: &mut Vec<TraitCandidate>) {
2020 assert!(ns == TypeNS || ns == ValueNS);
2021 let mut traits = module.traits.borrow_mut();
2022 if traits.is_none() {
2023 let mut collected_traits = Vec::new();
2024 module.for_each_child(self.r, |_, name, ns, binding| {
2025 if ns != TypeNS { return }
2026 match binding.res() {
2027 Res::Def(DefKind::Trait, _) |
2028 Res::Def(DefKind::TraitAlias, _) => collected_traits.push((name, binding)),
2032 *traits = Some(collected_traits.into_boxed_slice());
2035 for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
2036 // Traits have pseudo-modules that can be used to search for the given ident.
2037 if let Some(module) = binding.module() {
2038 let mut ident = ident;
2039 if ident.span.glob_adjust(
2045 if self.r.resolve_ident_in_module_unadjusted(
2046 ModuleOrUniformRoot::Module(module),
2053 let import_ids = self.find_transitive_imports(&binding.kind, trait_name);
2054 let trait_def_id = module.def_id().unwrap();
2055 found_traits.push(TraitCandidate { def_id: trait_def_id, import_ids });
2057 } else if let Res::Def(DefKind::TraitAlias, _) = binding.res() {
2058 // For now, just treat all trait aliases as possible candidates, since we don't
2059 // know if the ident is somewhere in the transitive bounds.
2060 let import_ids = self.find_transitive_imports(&binding.kind, trait_name);
2061 let trait_def_id = binding.res().def_id();
2062 found_traits.push(TraitCandidate { def_id: trait_def_id, import_ids });
2064 bug!("candidate is not trait or trait alias?")
2069 fn find_transitive_imports(&mut self, mut kind: &NameBindingKind<'_>,
2070 trait_name: Ident) -> SmallVec<[NodeId; 1]> {
2071 let mut import_ids = smallvec![];
2072 while let NameBindingKind::Import { directive, binding, .. } = kind {
2073 self.r.maybe_unused_trait_imports.insert(directive.id);
2074 self.r.add_to_glob_map(&directive, trait_name);
2075 import_ids.push(directive.id);
2076 kind = &binding.kind;
2082 impl<'a> Resolver<'a> {
2083 pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
2084 let mut late_resolution_visitor = LateResolutionVisitor::new(self);
2085 visit::walk_crate(&mut late_resolution_visitor, krate);
2086 for (id, span) in late_resolution_visitor.diagnostic_metadata.unused_labels.iter() {
2087 self.lint_buffer.buffer_lint(lint::builtin::UNUSED_LABELS, *id, *span, "unused label");