//! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros. //! It runs when the crate is fully expanded and its module structure is fully built. //! So it just walks through the crate and resolves all the expressions, types, etc. //! //! If you wonder why there's no `early.rs`, that's because it's split into three files - //! `build_reduced_graph.rs`, `macros.rs` and `resolve_imports.rs`. use GenericParameters::*; use RibKind::*; use crate::{path_names_to_string, BindingError, CrateLint, LexicalScopeBinding}; use crate::{Module, ModuleOrUniformRoot, NameBindingKind, ParentScope, PathResult}; use crate::{ResolutionError, Resolver, Segment, UseError}; use log::debug; use rustc::{bug, lint, span_bug}; use rustc::hir::def::{self, PartialRes, DefKind, CtorKind, PerNS}; use rustc::hir::def::Namespace::{self, *}; use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX}; use rustc::hir::TraitCandidate; use rustc::util::nodemap::{FxHashMap, FxHashSet}; use smallvec::{smallvec, SmallVec}; use syntax::{unwrap_or, walk_list}; use syntax::ast::*; use syntax::ptr::P; use syntax::symbol::{kw, sym}; use syntax::util::lev_distance::find_best_match_for_name; use syntax::visit::{self, Visitor, FnKind}; use syntax_pos::Span; use std::collections::BTreeSet; use std::mem::replace; mod diagnostics; type Res = def::Res; type IdentMap = FxHashMap; /// Map from the name in a pattern to its binding mode. type BindingMap = IdentMap; #[derive(Copy, Clone, Debug)] struct BindingInfo { span: Span, binding_mode: BindingMode, } #[derive(Copy, Clone)] enum GenericParameters<'a, 'b> { NoGenericParams, HasGenericParams(// Type parameters. &'b Generics, // The kind of the rib used for type parameters. RibKind<'a>), } #[derive(Copy, Clone, PartialEq, Eq, Debug)] enum PatternSource { Match, Let, For, FnParam, } impl PatternSource { fn descr(self) -> &'static str { match self { PatternSource::Match => "match binding", PatternSource::Let => "let binding", PatternSource::For => "for binding", PatternSource::FnParam => "function parameter", } } } /// The rib kind restricts certain accesses, /// e.g. to a `Res::Local` of an outer item. #[derive(Copy, Clone, Debug)] crate enum RibKind<'a> { /// No restriction needs to be applied. NormalRibKind, /// We passed through an impl or trait and are now in one of its /// methods or associated types. Allow references to ty params that impl or trait /// binds. Disallow any other upvars (including other ty params that are /// upvars). AssocItemRibKind, /// We passed through a function definition. Disallow upvars. /// Permit only those const parameters that are specified in the function's generics. FnItemRibKind, /// We passed through an item scope. Disallow upvars. ItemRibKind, /// We're in a constant item. Can't refer to dynamic stuff. ConstantItemRibKind, /// We passed through a module. ModuleRibKind(Module<'a>), /// We passed through a `macro_rules!` statement MacroDefinition(DefId), /// All bindings in this rib are type parameters that can't be used /// from the default of a type parameter because they're not declared /// before said type parameter. Also see the `visit_generics` override. ForwardTyParamBanRibKind, /// We forbid the use of type parameters as the types of const parameters. TyParamAsConstParamTy, } impl RibKind<'_> { // Whether this rib kind contains generic parameters, as opposed to local // variables. crate fn contains_params(&self) -> bool { match self { NormalRibKind | FnItemRibKind | ConstantItemRibKind | ModuleRibKind(_) | MacroDefinition(_) => false, AssocItemRibKind | ItemRibKind | ForwardTyParamBanRibKind | TyParamAsConstParamTy => true, } } } /// A single local scope. /// /// A rib represents a scope names can live in. Note that these appear in many places, not just /// around braces. At any place where the list of accessible names (of the given namespace) /// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a /// stack. This may be, for example, a `let` statement (because it introduces variables), a macro, /// etc. /// /// Different [rib kinds](enum.RibKind) are transparent for different names. /// /// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When /// resolving, the name is looked up from inside out. #[derive(Debug)] crate struct Rib<'a, R = Res> { pub bindings: IdentMap, pub kind: RibKind<'a>, } impl<'a, R> Rib<'a, R> { fn new(kind: RibKind<'a>) -> Rib<'a, R> { Rib { bindings: Default::default(), kind, } } } #[derive(Copy, Clone, PartialEq, Eq, Debug)] crate enum AliasPossibility { No, Maybe, } #[derive(Copy, Clone, Debug)] crate enum PathSource<'a> { // Type paths `Path`. Type, // Trait paths in bounds or impls. Trait(AliasPossibility), // Expression paths `path`, with optional parent context. Expr(Option<&'a Expr>), // Paths in path patterns `Path`. Pat, // Paths in struct expressions and patterns `Path { .. }`. Struct, // Paths in tuple struct patterns `Path(..)`. TupleStruct, // `m::A::B` in `::B::C`. TraitItem(Namespace), } impl<'a> PathSource<'a> { fn namespace(self) -> Namespace { match self { PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS, PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS, PathSource::TraitItem(ns) => ns, } } fn defer_to_typeck(self) -> bool { match self { PathSource::Type | PathSource::Expr(..) | PathSource::Pat | PathSource::Struct | PathSource::TupleStruct => true, PathSource::Trait(_) | PathSource::TraitItem(..) => false, } } fn descr_expected(self) -> &'static str { match self { PathSource::Type => "type", PathSource::Trait(_) => "trait", PathSource::Pat => "unit struct/variant or constant", PathSource::Struct => "struct, variant or union type", PathSource::TupleStruct => "tuple struct/variant", PathSource::TraitItem(ns) => match ns { TypeNS => "associated type", ValueNS => "method or associated constant", MacroNS => bug!("associated macro"), }, PathSource::Expr(parent) => match parent.map(|p| &p.node) { // "function" here means "anything callable" rather than `DefKind::Fn`, // this is not precise but usually more helpful than just "value". Some(&ExprKind::Call(..)) => "function", _ => "value", }, } } crate fn is_expected(self, res: Res) -> bool { match self { PathSource::Type => match res { Res::Def(DefKind::Struct, _) | Res::Def(DefKind::Union, _) | Res::Def(DefKind::Enum, _) | Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) | Res::Def(DefKind::TyAlias, _) | Res::Def(DefKind::AssocTy, _) | Res::PrimTy(..) | Res::Def(DefKind::TyParam, _) | Res::SelfTy(..) | Res::Def(DefKind::OpaqueTy, _) | Res::Def(DefKind::ForeignTy, _) => true, _ => false, }, PathSource::Trait(AliasPossibility::No) => match res { Res::Def(DefKind::Trait, _) => true, _ => false, }, PathSource::Trait(AliasPossibility::Maybe) => match res { Res::Def(DefKind::Trait, _) => true, Res::Def(DefKind::TraitAlias, _) => true, _ => false, }, PathSource::Expr(..) => match res { Res::Def(DefKind::Ctor(_, CtorKind::Const), _) | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) | Res::Def(DefKind::Const, _) | Res::Def(DefKind::Static, _) | Res::Local(..) | Res::Def(DefKind::Fn, _) | Res::Def(DefKind::Method, _) | Res::Def(DefKind::AssocConst, _) | Res::SelfCtor(..) | Res::Def(DefKind::ConstParam, _) => true, _ => false, }, PathSource::Pat => match res { Res::Def(DefKind::Ctor(_, CtorKind::Const), _) | Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) | Res::SelfCtor(..) => true, _ => false, }, PathSource::TupleStruct => match res { Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) | Res::SelfCtor(..) => true, _ => false, }, PathSource::Struct => match res { Res::Def(DefKind::Struct, _) | Res::Def(DefKind::Union, _) | Res::Def(DefKind::Variant, _) | Res::Def(DefKind::TyAlias, _) | Res::Def(DefKind::AssocTy, _) | Res::SelfTy(..) => true, _ => false, }, PathSource::TraitItem(ns) => match res { Res::Def(DefKind::AssocConst, _) | Res::Def(DefKind::Method, _) if ns == ValueNS => true, Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true, _ => false, }, } } fn error_code(self, has_unexpected_resolution: bool) -> &'static str { __diagnostic_used!(E0404); __diagnostic_used!(E0405); __diagnostic_used!(E0412); __diagnostic_used!(E0422); __diagnostic_used!(E0423); __diagnostic_used!(E0425); __diagnostic_used!(E0531); __diagnostic_used!(E0532); __diagnostic_used!(E0573); __diagnostic_used!(E0574); __diagnostic_used!(E0575); __diagnostic_used!(E0576); match (self, has_unexpected_resolution) { (PathSource::Trait(_), true) => "E0404", (PathSource::Trait(_), false) => "E0405", (PathSource::Type, true) => "E0573", (PathSource::Type, false) => "E0412", (PathSource::Struct, true) => "E0574", (PathSource::Struct, false) => "E0422", (PathSource::Expr(..), true) => "E0423", (PathSource::Expr(..), false) => "E0425", (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532", (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531", (PathSource::TraitItem(..), true) => "E0575", (PathSource::TraitItem(..), false) => "E0576", } } } struct LateResolutionVisitor<'a, 'b> { r: &'b mut Resolver<'a>, /// The module that represents the current item scope. parent_scope: ParentScope<'a>, /// The current set of local scopes for types and values. /// FIXME #4948: Reuse ribs to avoid allocation. ribs: PerNS>>, /// The current set of local scopes, for labels. label_ribs: Vec>, /// The trait that the current context can refer to. current_trait_ref: Option<(Module<'a>, TraitRef)>, /// The current trait's associated types' ident, used for diagnostic suggestions. current_trait_assoc_types: Vec, /// The current self type if inside an impl (used for better errors). current_self_type: Option, /// The current self item if inside an ADT (used for better errors). current_self_item: Option, /// A list of labels as of yet unused. Labels will be removed from this map when /// they are used (in a `break` or `continue` statement) unused_labels: FxHashMap, /// Only used for better errors on `fn(): fn()`. current_type_ascription: Vec, } /// Walks the whole crate in DFS order, visiting each item, resolving names as it goes. impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> { fn visit_item(&mut self, item: &'tcx Item) { self.resolve_item(item); } fn visit_arm(&mut self, arm: &'tcx Arm) { self.resolve_arm(arm); } fn visit_block(&mut self, block: &'tcx Block) { self.resolve_block(block); } fn visit_anon_const(&mut self, constant: &'tcx AnonConst) { debug!("visit_anon_const {:?}", constant); self.with_constant_rib(|this| { visit::walk_anon_const(this, constant); }); } fn visit_expr(&mut self, expr: &'tcx Expr) { self.resolve_expr(expr, None); } fn visit_local(&mut self, local: &'tcx Local) { self.resolve_local(local); } fn visit_ty(&mut self, ty: &'tcx Ty) { match ty.node { TyKind::Path(ref qself, ref path) => { self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type); } TyKind::ImplicitSelf => { let self_ty = Ident::with_dummy_span(kw::SelfUpper); let res = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.id), ty.span) .map_or(Res::Err, |d| d.res()); self.r.record_partial_res(ty.id, PartialRes::new(res)); } _ => (), } visit::walk_ty(self, ty); } fn visit_poly_trait_ref(&mut self, tref: &'tcx PolyTraitRef, m: &'tcx TraitBoundModifier) { self.smart_resolve_path(tref.trait_ref.ref_id, None, &tref.trait_ref.path, PathSource::Trait(AliasPossibility::Maybe)); visit::walk_poly_trait_ref(self, tref, m); } fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) { let generic_params = match foreign_item.node { ForeignItemKind::Fn(_, ref generics) => { HasGenericParams(generics, ItemRibKind) } ForeignItemKind::Static(..) => NoGenericParams, ForeignItemKind::Ty => NoGenericParams, ForeignItemKind::Macro(..) => NoGenericParams, }; self.with_generic_param_rib(generic_params, |this| { visit::walk_foreign_item(this, foreign_item); }); } fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, _: Span, _: NodeId) { debug!("(resolving function) entering function"); let rib_kind = match fn_kind { FnKind::ItemFn(..) => FnItemRibKind, FnKind::Method(..) | FnKind::Closure(_) => NormalRibKind, }; // Create a value rib for the function. self.with_rib(ValueNS, rib_kind, |this| { // Create a label rib for the function. this.with_label_rib(rib_kind, |this| { // Add each argument to the rib. this.resolve_params(&declaration.inputs); visit::walk_fn_ret_ty(this, &declaration.output); // Resolve the function body, potentially inside the body of an async closure match fn_kind { FnKind::ItemFn(.., body) | FnKind::Method(.., body) => this.visit_block(body), FnKind::Closure(body) => this.visit_expr(body), }; debug!("(resolving function) leaving function"); }) }); } fn visit_generics(&mut self, generics: &'tcx Generics) { // For type parameter defaults, we have to ban access // to following type parameters, as the InternalSubsts can only // provide previous type parameters as they're built. We // put all the parameters on the ban list and then remove // them one by one as they are processed and become available. let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind); let mut found_default = false; default_ban_rib.bindings.extend(generics.params.iter() .filter_map(|param| match param.kind { GenericParamKind::Const { .. } | GenericParamKind::Lifetime { .. } => None, GenericParamKind::Type { ref default, .. } => { found_default |= default.is_some(); if found_default { Some((Ident::with_dummy_span(param.ident.name), Res::Err)) } else { None } } })); // We also ban access to type parameters for use as the types of const parameters. let mut const_ty_param_ban_rib = Rib::new(TyParamAsConstParamTy); const_ty_param_ban_rib.bindings.extend(generics.params.iter() .filter(|param| { if let GenericParamKind::Type { .. } = param.kind { true } else { false } }) .map(|param| (Ident::with_dummy_span(param.ident.name), Res::Err))); for param in &generics.params { match param.kind { GenericParamKind::Lifetime { .. } => self.visit_generic_param(param), GenericParamKind::Type { ref default, .. } => { for bound in ¶m.bounds { self.visit_param_bound(bound); } if let Some(ref ty) = default { self.ribs[TypeNS].push(default_ban_rib); self.visit_ty(ty); default_ban_rib = self.ribs[TypeNS].pop().unwrap(); } // Allow all following defaults to refer to this type parameter. default_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name)); } GenericParamKind::Const { ref ty } => { self.ribs[TypeNS].push(const_ty_param_ban_rib); for bound in ¶m.bounds { self.visit_param_bound(bound); } self.visit_ty(ty); const_ty_param_ban_rib = self.ribs[TypeNS].pop().unwrap(); } } } for p in &generics.where_clause.predicates { self.visit_where_predicate(p); } } } impl<'a, 'b> LateResolutionVisitor<'a, '_> { fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b> { // During late resolution we only track the module component of the parent scope, // although it may be useful to track other components as well for diagnostics. let graph_root = resolver.graph_root; let parent_scope = ParentScope::module(graph_root); let start_rib_kind = ModuleRibKind(graph_root); LateResolutionVisitor { r: resolver, parent_scope, ribs: PerNS { value_ns: vec![Rib::new(start_rib_kind)], type_ns: vec![Rib::new(start_rib_kind)], macro_ns: vec![Rib::new(start_rib_kind)], }, label_ribs: Vec::new(), current_trait_ref: None, current_trait_assoc_types: Vec::new(), current_self_type: None, current_self_item: None, unused_labels: Default::default(), current_type_ascription: Vec::new(), } } fn resolve_ident_in_lexical_scope(&mut self, ident: Ident, ns: Namespace, record_used_id: Option, path_span: Span) -> Option> { self.r.resolve_ident_in_lexical_scope( ident, ns, &self.parent_scope, record_used_id, path_span, &self.ribs[ns] ) } fn resolve_path( &mut self, path: &[Segment], opt_ns: Option, // `None` indicates a module path in import record_used: bool, path_span: Span, crate_lint: CrateLint, ) -> PathResult<'a> { self.r.resolve_path_with_ribs( path, opt_ns, &self.parent_scope, record_used, path_span, crate_lint, Some(&self.ribs) ) } // AST resolution // // We maintain a list of value ribs and type ribs. // // Simultaneously, we keep track of the current position in the module // graph in the `parent_scope.module` pointer. When we go to resolve a name in // the value or type namespaces, we first look through all the ribs and // then query the module graph. When we resolve a name in the module // namespace, we can skip all the ribs (since nested modules are not // allowed within blocks in Rust) and jump straight to the current module // graph node. // // Named implementations are handled separately. When we find a method // call, we consult the module node to find all of the implementations in // scope. This information is lazily cached in the module node. We then // generate a fake "implementation scope" containing all the // implementations thus found, for compatibility with old resolve pass. /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`). fn with_rib( &mut self, ns: Namespace, kind: RibKind<'a>, work: impl FnOnce(&mut Self) -> T, ) -> T { self.ribs[ns].push(Rib::new(kind)); let ret = work(self); self.ribs[ns].pop(); ret } fn with_scope(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T { let id = self.r.definitions.local_def_id(id); let module = self.r.module_map.get(&id).cloned(); // clones a reference if let Some(module) = module { // Move down in the graph. let orig_module = replace(&mut self.parent_scope.module, module); self.with_rib(ValueNS, ModuleRibKind(module), |this| { this.with_rib(TypeNS, ModuleRibKind(module), |this| { let ret = f(this); this.parent_scope.module = orig_module; ret }) }) } else { f(self) } } /// Searches the current set of local scopes for labels. Returns the first non-`None` label that /// is returned by the given predicate function /// /// Stops after meeting a closure. fn search_label(&self, mut ident: Ident, pred: P) -> Option where P: Fn(&Rib<'_, NodeId>, Ident) -> Option { for rib in self.label_ribs.iter().rev() { match rib.kind { NormalRibKind => {} // If an invocation of this macro created `ident`, give up on `ident` // and switch to `ident`'s source from the macro definition. MacroDefinition(def) => { if def == self.r.macro_def(ident.span.ctxt()) { ident.span.remove_mark(); } } _ => { // Do not resolve labels across function boundary return None; } } let r = pred(rib, ident); if r.is_some() { return r; } } None } fn resolve_adt(&mut self, item: &Item, generics: &Generics) { debug!("resolve_adt"); self.with_current_self_item(item, |this| { this.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| { let item_def_id = this.r.definitions.local_def_id(item.id); this.with_self_rib(Res::SelfTy(None, Some(item_def_id)), |this| { visit::walk_item(this, item); }); }); }); } fn future_proof_import(&mut self, use_tree: &UseTree) { let segments = &use_tree.prefix.segments; if !segments.is_empty() { let ident = segments[0].ident; if ident.is_path_segment_keyword() || ident.span.rust_2015() { return; } let nss = match use_tree.kind { UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..], _ => &[TypeNS], }; let report_error = |this: &Self, ns| { let what = if ns == TypeNS { "type parameters" } else { "local variables" }; this.r.session.span_err(ident.span, &format!("imports cannot refer to {}", what)); }; for &ns in nss { match self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span) { Some(LexicalScopeBinding::Res(..)) => { report_error(self, ns); } Some(LexicalScopeBinding::Item(binding)) => { let orig_blacklisted_binding = replace(&mut self.r.blacklisted_binding, Some(binding)); if let Some(LexicalScopeBinding::Res(..)) = self.resolve_ident_in_lexical_scope(ident, ns, None, use_tree.prefix.span) { report_error(self, ns); } self.r.blacklisted_binding = orig_blacklisted_binding; } None => {} } } } else if let UseTreeKind::Nested(use_trees) = &use_tree.kind { for (use_tree, _) in use_trees { self.future_proof_import(use_tree); } } } fn resolve_item(&mut self, item: &Item) { let name = item.ident.name; debug!("(resolving item) resolving {} ({:?})", name, item.node); match item.node { ItemKind::TyAlias(_, ref generics) | ItemKind::OpaqueTy(_, ref generics) | ItemKind::Fn(_, _, ref generics, _) => { self.with_generic_param_rib( HasGenericParams(generics, ItemRibKind), |this| visit::walk_item(this, item) ); } ItemKind::Enum(_, ref generics) | ItemKind::Struct(_, ref generics) | ItemKind::Union(_, ref generics) => { self.resolve_adt(item, generics); } ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) => self.resolve_implementation(generics, opt_trait_ref, &self_type, item.id, impl_items), ItemKind::Trait(.., ref generics, ref bounds, ref trait_items) => { // Create a new rib for the trait-wide type parameters. self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| { let local_def_id = this.r.definitions.local_def_id(item.id); this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| { this.visit_generics(generics); walk_list!(this, visit_param_bound, bounds); for trait_item in trait_items { this.with_trait_items(trait_items, |this| { let generic_params = HasGenericParams( &trait_item.generics, AssocItemRibKind, ); this.with_generic_param_rib(generic_params, |this| { match trait_item.node { TraitItemKind::Const(ref ty, ref default) => { this.visit_ty(ty); // Only impose the restrictions of // ConstRibKind for an actual constant // expression in a provided default. if let Some(ref expr) = *default{ this.with_constant_rib(|this| { this.visit_expr(expr); }); } } TraitItemKind::Method(_, _) => { visit::walk_trait_item(this, trait_item) } TraitItemKind::Type(..) => { visit::walk_trait_item(this, trait_item) } TraitItemKind::Macro(_) => { panic!("unexpanded macro in resolve!") } }; }); }); } }); }); } ItemKind::TraitAlias(ref generics, ref bounds) => { // Create a new rib for the trait-wide type parameters. self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| { let local_def_id = this.r.definitions.local_def_id(item.id); this.with_self_rib(Res::SelfTy(Some(local_def_id), None), |this| { this.visit_generics(generics); walk_list!(this, visit_param_bound, bounds); }); }); } ItemKind::Mod(_) | ItemKind::ForeignMod(_) => { self.with_scope(item.id, |this| { visit::walk_item(this, item); }); } ItemKind::Static(ref ty, _, ref expr) | ItemKind::Const(ref ty, ref expr) => { debug!("resolve_item ItemKind::Const"); self.with_item_rib(|this| { this.visit_ty(ty); this.with_constant_rib(|this| { this.visit_expr(expr); }); }); } ItemKind::Use(ref use_tree) => { self.future_proof_import(use_tree); } ItemKind::ExternCrate(..) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(..) => { // do nothing, these are just around to be encoded } ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"), } } fn with_generic_param_rib<'c, F>(&'c mut self, generic_params: GenericParameters<'a, 'c>, f: F) where F: FnOnce(&mut Self) { debug!("with_generic_param_rib"); match generic_params { HasGenericParams(generics, rib_kind) => { let mut function_type_rib = Rib::new(rib_kind); let mut function_value_rib = Rib::new(rib_kind); let mut seen_bindings = FxHashMap::default(); // We also can't shadow bindings from the parent item if let AssocItemRibKind = rib_kind { let mut add_bindings_for_ns = |ns| { let parent_rib = self.ribs[ns].iter() .rfind(|rib| if let ItemRibKind = rib.kind { true } else { false }) .expect("associated item outside of an item"); seen_bindings.extend( parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)), ); }; add_bindings_for_ns(ValueNS); add_bindings_for_ns(TypeNS); } for param in &generics.params { match param.kind { GenericParamKind::Lifetime { .. } => {} GenericParamKind::Type { .. } => { let ident = param.ident.modern(); debug!("with_generic_param_rib: {}", param.id); if seen_bindings.contains_key(&ident) { let span = seen_bindings.get(&ident).unwrap(); let err = ResolutionError::NameAlreadyUsedInParameterList( ident.name, *span, ); self.r.report_error(param.ident.span, err); } seen_bindings.entry(ident).or_insert(param.ident.span); // Plain insert (no renaming). let res = Res::Def( DefKind::TyParam, self.r.definitions.local_def_id(param.id), ); function_type_rib.bindings.insert(ident, res); self.r.record_partial_res(param.id, PartialRes::new(res)); } GenericParamKind::Const { .. } => { let ident = param.ident.modern(); debug!("with_generic_param_rib: {}", param.id); if seen_bindings.contains_key(&ident) { let span = seen_bindings.get(&ident).unwrap(); let err = ResolutionError::NameAlreadyUsedInParameterList( ident.name, *span, ); self.r.report_error(param.ident.span, err); } seen_bindings.entry(ident).or_insert(param.ident.span); let res = Res::Def( DefKind::ConstParam, self.r.definitions.local_def_id(param.id), ); function_value_rib.bindings.insert(ident, res); self.r.record_partial_res(param.id, PartialRes::new(res)); } } } self.ribs[ValueNS].push(function_value_rib); self.ribs[TypeNS].push(function_type_rib); } NoGenericParams => { // Nothing to do. } } f(self); if let HasGenericParams(..) = generic_params { self.ribs[TypeNS].pop(); self.ribs[ValueNS].pop(); } } fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) { self.label_ribs.push(Rib::new(kind)); f(self); self.label_ribs.pop(); } fn with_item_rib(&mut self, f: impl FnOnce(&mut Self)) { self.with_rib(ValueNS, ItemRibKind, |this| this.with_rib(TypeNS, ItemRibKind, f)) } fn with_constant_rib(&mut self, f: impl FnOnce(&mut Self)) { debug!("with_constant_rib"); self.with_rib(ValueNS, ConstantItemRibKind, |this| { this.with_label_rib(ConstantItemRibKind, f); }); } fn with_current_self_type(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T { // Handle nested impls (inside fn bodies) let previous_value = replace(&mut self.current_self_type, Some(self_type.clone())); let result = f(self); self.current_self_type = previous_value; result } fn with_current_self_item(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T { let previous_value = replace(&mut self.current_self_item, Some(self_item.id)); let result = f(self); self.current_self_item = previous_value; result } /// When evaluating a `trait` use its associated types' idents for suggestionsa in E0412. fn with_trait_items( &mut self, trait_items: &Vec, f: impl FnOnce(&mut Self) -> T, ) -> T { let trait_assoc_types = replace( &mut self.current_trait_assoc_types, trait_items.iter().filter_map(|item| match &item.node { TraitItemKind::Type(bounds, _) if bounds.len() == 0 => Some(item.ident), _ => None, }).collect(), ); let result = f(self); self.current_trait_assoc_types = trait_assoc_types; result } /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`). fn with_optional_trait_ref( &mut self, opt_trait_ref: Option<&TraitRef>, f: impl FnOnce(&mut Self, Option) -> T ) -> T { let mut new_val = None; let mut new_id = None; if let Some(trait_ref) = opt_trait_ref { let path: Vec<_> = Segment::from_path(&trait_ref.path); let res = self.smart_resolve_path_fragment( trait_ref.ref_id, None, &path, trait_ref.path.span, PathSource::Trait(AliasPossibility::No), CrateLint::SimplePath(trait_ref.ref_id), ).base_res(); if res != Res::Err { new_id = Some(res.def_id()); let span = trait_ref.path.span; if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path( &path, Some(TypeNS), false, span, CrateLint::SimplePath(trait_ref.ref_id), ) { new_val = Some((module, trait_ref.clone())); } } } let original_trait_ref = replace(&mut self.current_trait_ref, new_val); let result = f(self, new_id); self.current_trait_ref = original_trait_ref; result } fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) { let mut self_type_rib = Rib::new(NormalRibKind); // Plain insert (no renaming, since types are not currently hygienic) self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res); self.ribs[ns].push(self_type_rib); f(self); self.ribs[ns].pop(); } fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) { self.with_self_rib_ns(TypeNS, self_res, f) } fn resolve_implementation(&mut self, generics: &Generics, opt_trait_reference: &Option, self_type: &Ty, item_id: NodeId, impl_items: &[ImplItem]) { debug!("resolve_implementation"); // If applicable, create a rib for the type parameters. self.with_generic_param_rib(HasGenericParams(generics, ItemRibKind), |this| { // Dummy self type for better errors if `Self` is used in the trait path. this.with_self_rib(Res::SelfTy(None, None), |this| { // Resolve the trait reference, if necessary. this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| { let item_def_id = this.r.definitions.local_def_id(item_id); this.with_self_rib(Res::SelfTy(trait_id, Some(item_def_id)), |this| { if let Some(trait_ref) = opt_trait_reference.as_ref() { // Resolve type arguments in the trait path. visit::walk_trait_ref(this, trait_ref); } // Resolve the self type. this.visit_ty(self_type); // Resolve the generic parameters. this.visit_generics(generics); // Resolve the items within the impl. this.with_current_self_type(self_type, |this| { this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| { debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)"); for impl_item in impl_items { // We also need a new scope for the impl item type parameters. let generic_params = HasGenericParams(&impl_item.generics, AssocItemRibKind); this.with_generic_param_rib(generic_params, |this| { use crate::ResolutionError::*; match impl_item.node { ImplItemKind::Const(..) => { debug!( "resolve_implementation ImplItemKind::Const", ); // If this is a trait impl, ensure the const // exists in trait this.check_trait_item( impl_item.ident, ValueNS, impl_item.span, |n, s| ConstNotMemberOfTrait(n, s), ); this.with_constant_rib(|this| { visit::walk_impl_item(this, impl_item) }); } ImplItemKind::Method(..) => { // If this is a trait impl, ensure the method // exists in trait this.check_trait_item(impl_item.ident, ValueNS, impl_item.span, |n, s| MethodNotMemberOfTrait(n, s)); visit::walk_impl_item(this, impl_item); } ImplItemKind::TyAlias(ref ty) => { // If this is a trait impl, ensure the type // exists in trait this.check_trait_item(impl_item.ident, TypeNS, impl_item.span, |n, s| TypeNotMemberOfTrait(n, s)); this.visit_ty(ty); } ImplItemKind::OpaqueTy(ref bounds) => { // If this is a trait impl, ensure the type // exists in trait this.check_trait_item(impl_item.ident, TypeNS, impl_item.span, |n, s| TypeNotMemberOfTrait(n, s)); for bound in bounds { this.visit_param_bound(bound); } } ImplItemKind::Macro(_) => panic!("unexpanded macro in resolve!"), } }); } }); }); }); }); }); }); } fn check_trait_item(&mut self, ident: Ident, ns: Namespace, span: Span, err: F) where F: FnOnce(Name, &str) -> ResolutionError<'_> { // If there is a TraitRef in scope for an impl, then the method must be in the // trait. if let Some((module, _)) = self.current_trait_ref { if self.r.resolve_ident_in_module( ModuleOrUniformRoot::Module(module), ident, ns, &self.parent_scope, false, span, ).is_err() { let path = &self.current_trait_ref.as_ref().unwrap().1.path; self.r.report_error(span, err(ident.name, &path_names_to_string(path))); } } } fn resolve_params(&mut self, params: &[Param]) { let mut bindings = smallvec![(false, Default::default())]; for Param { pat, ty, .. } in params { self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings); self.visit_ty(ty); debug!("(resolving function / closure) recorded parameter"); } } fn resolve_local(&mut self, local: &Local) { // Resolve the type. walk_list!(self, visit_ty, &local.ty); // Resolve the initializer. walk_list!(self, visit_expr, &local.init); // Resolve the pattern. self.resolve_pattern_top(&local.pat, PatternSource::Let); } /// build a map from pattern identifiers to binding-info's. /// this is done hygienically. This could arise for a macro /// that expands into an or-pattern where one 'x' was from the /// user and one 'x' came from the macro. fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap { let mut binding_map = FxHashMap::default(); pat.walk(&mut |pat| { match pat.node { PatKind::Ident(binding_mode, ident, ref sub_pat) if sub_pat.is_some() || self.is_base_res_local(pat.id) => { binding_map.insert(ident, BindingInfo { span: ident.span, binding_mode }); } PatKind::Or(ref ps) => { // Check the consistency of this or-pattern and // then add all bindings to the larger map. for bm in self.check_consistent_bindings(ps) { binding_map.extend(bm); } return false; } _ => {} } true }); binding_map } fn is_base_res_local(&self, nid: NodeId) -> bool { match self.r.partial_res_map.get(&nid).map(|res| res.base_res()) { Some(Res::Local(..)) => true, _ => false, } } /// Checks that all of the arms in an or-pattern have exactly the /// same set of bindings, with the same binding modes for each. fn check_consistent_bindings(&mut self, pats: &[P]) -> Vec { let mut missing_vars = FxHashMap::default(); let mut inconsistent_vars = FxHashMap::default(); // 1) Compute the binding maps of all arms. let maps = pats.iter() .map(|pat| self.binding_mode_map(pat)) .collect::>(); // 2) Record any missing bindings or binding mode inconsistencies. for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) { // Check against all arms except for the same pattern which is always self-consistent. let inners = pats.iter().enumerate() .filter(|(_, pat)| pat.id != pat_outer.id) .flat_map(|(idx, _)| maps[idx].iter()) .map(|(key, binding)| (key.name, map_outer.get(&key), binding)); for (name, info, &binding_inner) in inners { match info { None => { // The inner binding is missing in the outer. let binding_error = missing_vars .entry(name) .or_insert_with(|| BindingError { name, origin: BTreeSet::new(), target: BTreeSet::new(), could_be_path: name.as_str().starts_with(char::is_uppercase), }); binding_error.origin.insert(binding_inner.span); binding_error.target.insert(pat_outer.span); } Some(binding_outer) => { if binding_outer.binding_mode != binding_inner.binding_mode { // The binding modes in the outer and inner bindings differ. inconsistent_vars .entry(name) .or_insert((binding_inner.span, binding_outer.span)); } } } } } // 3) Report all missing variables we found. let mut missing_vars = missing_vars.iter_mut().collect::>(); missing_vars.sort(); for (name, mut v) in missing_vars { if inconsistent_vars.contains_key(name) { v.could_be_path = false; } self.r.report_error( *v.origin.iter().next().unwrap(), ResolutionError::VariableNotBoundInPattern(v)); } // 4) Report all inconsistencies in binding modes we found. let mut inconsistent_vars = inconsistent_vars.iter().collect::>(); inconsistent_vars.sort(); for (name, v) in inconsistent_vars { self.r.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1)); } // 5) Finally bubble up all the binding maps. maps } /// Check the consistency of the outermost or-patterns. fn check_consistent_bindings_top(&mut self, pat: &Pat) { pat.walk(&mut |pat| match pat.node { PatKind::Or(ref ps) => { self.check_consistent_bindings(ps); false }, _ => true, }) } fn resolve_arm(&mut self, arm: &Arm) { self.with_rib(ValueNS, NormalRibKind, |this| { this.resolve_pattern_top(&arm.pat, PatternSource::Match); walk_list!(this, visit_expr, &arm.guard); this.visit_expr(&arm.body); }); } /// Arising from `source`, resolve a top level pattern. fn resolve_pattern_top(&mut self, pat: &Pat, pat_src: PatternSource) { self.resolve_pattern(pat, pat_src, &mut smallvec![(false, Default::default())]); } fn resolve_pattern( &mut self, pat: &Pat, pat_src: PatternSource, bindings: &mut SmallVec<[(bool, FxHashSet); 1]>, ) { self.resolve_pattern_inner(pat, pat_src, bindings); // This has to happen *after* we determine which pat_idents are variants: self.check_consistent_bindings_top(pat); visit::walk_pat(self, pat); } /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`. /// /// ### `bindings` /// /// A stack of sets of bindings accumulated. /// /// In each set, `false` denotes that a found binding in it should be interpreted as /// re-binding an already bound binding. This results in an error. Meanwhile, `true` /// denotes that a found binding in the set should result in reusing this binding /// rather than creating a fresh one. In other words, `false` and `true` correspond /// to product (e.g., `(a, b)`) and sum/or contexts (e.g., `p_0 | ... | p_i`) respectively. /// /// When called at the top level, the stack should have a single element with `false`. /// Otherwise, pushing to the stack happens as or-patterns are encountered and the /// context needs to be switched to `true` and then `false` for each `p_i. /// When each `p_i` has been dealt with, the top set is merged with its parent. /// When a whole or-pattern has been dealt with, the thing happens. /// /// See the implementation and `fresh_binding` for more details. fn resolve_pattern_inner( &mut self, pat: &Pat, pat_src: PatternSource, bindings: &mut SmallVec<[(bool, FxHashSet); 1]>, ) { // Visit all direct subpatterns of this pattern. pat.walk(&mut |pat| { debug!("resolve_pattern pat={:?} node={:?}", pat, pat.node); match pat.node { PatKind::Ident(bmode, ident, ref sub) => { // First try to resolve the identifier as some existing entity, // then fall back to a fresh binding. let has_sub = sub.is_some(); let res = self.try_resolve_as_non_binding(pat_src, pat, bmode, ident, has_sub) .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings)); self.r.record_partial_res(pat.id, PartialRes::new(res)); } PatKind::TupleStruct(ref path, ..) => { self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct); } PatKind::Path(ref qself, ref path) => { self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat); } PatKind::Struct(ref path, ..) => { self.smart_resolve_path(pat.id, None, path, PathSource::Struct); } PatKind::Or(ref ps) => { // Add a new set of bindings to the stack. `true` here records that when a // binding already exists in this set, it should not result in an error because // `V1(a) | V2(a)` must be allowed and are checked for consistency later. bindings.push((true, Default::default())); for p in ps { // Now we need to switch back to a product context so that each // part of the or-pattern internally rejects already bound names. // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad. bindings.push((false, Default::default())); self.resolve_pattern_inner(p, pat_src, bindings); // Move up the non-overlapping bindings to the or-pattern. // Existing bindings just get "merged". let collected = bindings.pop().unwrap().1; bindings.last_mut().unwrap().1.extend(collected); } // This or-pattern itself can itself be part of a product, // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`. // Both cases bind `a` again in a product pattern and must be rejected. let collected = bindings.pop().unwrap().1; bindings.last_mut().unwrap().1.extend(collected); // Prevent visiting `ps` as we've already done so above. return false; } _ => {} } true }); } fn fresh_binding( &mut self, ident: Ident, pat_id: NodeId, pat_src: PatternSource, bindings: &mut SmallVec<[(bool, FxHashSet); 1]>, ) -> Res { // Add the binding to the local ribs, if it doesn't already exist in the bindings map. // (We must not add it if it's in the bindings map because that breaks the assumptions // later passes make about or-patterns.) let ident = ident.modern_and_legacy(); // Walk outwards the stack of products / or-patterns and // find out if the identifier has been bound in any of these. let mut already_bound_and = false; let mut already_bound_or = false; for (is_sum, set) in bindings.iter_mut().rev() { match (is_sum, set.get(&ident).cloned()) { // Already bound in a product pattern, e.g. `(a, a)` which is not allowed. (false, Some(..)) => already_bound_and = true, // Already bound in an or-pattern, e.g. `V1(a) | V2(a)`. // This is *required* for consistency which is checked later. (true, Some(..)) => already_bound_or = true, // Not already bound here. _ => {} } } if already_bound_and { // Overlap in a product pattern somewhere; report an error. use ResolutionError::*; let error = match pat_src { // `fn f(a: u8, a: u8)`: PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList, // `Variant(a, a)`: _ => IdentifierBoundMoreThanOnceInSamePattern, }; self.r.report_error(ident.span, error(&ident.as_str())); } // Record as bound if it's valid: let ident_valid = ident.name != kw::Invalid; if ident_valid { bindings.last_mut().unwrap().1.insert(ident); } if already_bound_or { // `Variant1(a) | Variant2(a)`, ok // Reuse definition from the first `a`. self.innermost_rib_bindings(ValueNS)[&ident] } else { let res = Res::Local(pat_id); if ident_valid { // A completely fresh binding add to the set if it's valid. self.innermost_rib_bindings(ValueNS).insert(ident, res); } res } } fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap { &mut self.ribs[ns].last_mut().unwrap().bindings } fn try_resolve_as_non_binding( &mut self, pat_src: PatternSource, pat: &Pat, bm: BindingMode, ident: Ident, has_sub: bool, ) -> Option { let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, pat.span)?.item()?; let res = binding.res(); // An immutable (no `mut`) by-value (no `ref`) binding pattern without // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could // also be interpreted as a path to e.g. a constant, variant, etc. let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Immutable); match res { Res::Def(DefKind::Ctor(_, CtorKind::Const), _) | Res::Def(DefKind::Const, _) if is_syntactic_ambiguity => { // Disambiguate in favor of a unit struct/variant or constant pattern. self.r.record_use(ident, ValueNS, binding, false); Some(res) } Res::Def(DefKind::Ctor(..), _) | Res::Def(DefKind::Const, _) | Res::Def(DefKind::Static, _) => { // This is unambiguously a fresh binding, either syntactically // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves // to something unusable as a pattern (e.g., constructor function), // but we still conservatively report an error, see // issues/33118#issuecomment-233962221 for one reason why. self.r.report_error( ident.span, ResolutionError::BindingShadowsSomethingUnacceptable( pat_src.descr(), ident.name, binding, ), ); None } Res::Def(DefKind::Fn, _) | Res::Err => { // These entities are explicitly allowed to be shadowed by fresh bindings. None } res => { span_bug!(ident.span, "unexpected resolution for an \ identifier in pattern: {:?}", res); } } } // High-level and context dependent path resolution routine. // Resolves the path and records the resolution into definition map. // If resolution fails tries several techniques to find likely // resolution candidates, suggest imports or other help, and report // errors in user friendly way. fn smart_resolve_path(&mut self, id: NodeId, qself: Option<&QSelf>, path: &Path, source: PathSource<'_>) { self.smart_resolve_path_fragment( id, qself, &Segment::from_path(path), path.span, source, CrateLint::SimplePath(id), ); } fn smart_resolve_path_fragment(&mut self, id: NodeId, qself: Option<&QSelf>, path: &[Segment], span: Span, source: PathSource<'_>, crate_lint: CrateLint) -> PartialRes { let ns = source.namespace(); let is_expected = &|res| source.is_expected(res); let report_errors = |this: &mut Self, res: Option| { let (err, candidates) = this.smart_resolve_report_errors(path, span, source, res); let def_id = this.parent_scope.module.normal_ancestor_id; let node_id = this.r.definitions.as_local_node_id(def_id).unwrap(); let better = res.is_some(); this.r.use_injections.push(UseError { err, candidates, node_id, better }); PartialRes::new(Res::Err) }; let partial_res = match self.resolve_qpath_anywhere( id, qself, path, ns, span, source.defer_to_typeck(), crate_lint, ) { Some(partial_res) if partial_res.unresolved_segments() == 0 => { if is_expected(partial_res.base_res()) || partial_res.base_res() == Res::Err { partial_res } else { // Add a temporary hack to smooth the transition to new struct ctor // visibility rules. See #38932 for more details. let mut res = None; if let Res::Def(DefKind::Struct, def_id) = partial_res.base_res() { if let Some((ctor_res, ctor_vis)) = self.r.struct_constructors.get(&def_id).cloned() { if is_expected(ctor_res) && self.r.is_accessible_from(ctor_vis, self.parent_scope.module) { let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY; self.r.session.buffer_lint(lint, id, span, "private struct constructors are not usable through \ re-exports in outer modules", ); res = Some(PartialRes::new(ctor_res)); } } } res.unwrap_or_else(|| report_errors(self, Some(partial_res.base_res()))) } } Some(partial_res) if source.defer_to_typeck() => { // Not fully resolved associated item `T::A::B` or `::A::B` // or `::A::B`. If `B` should be resolved in value namespace then // it needs to be added to the trait map. if ns == ValueNS { let item_name = path.last().unwrap().ident; let traits = self.get_traits_containing_item(item_name, ns); self.r.trait_map.insert(id, traits); } let mut std_path = vec![Segment::from_ident(Ident::with_dummy_span(sym::std))]; std_path.extend(path); if self.r.primitive_type_table.primitive_types.contains_key(&path[0].ident.name) { let cl = CrateLint::No; let ns = Some(ns); if let PathResult::Module(_) | PathResult::NonModule(_) = self.resolve_path(&std_path, ns, false, span, cl) { // check if we wrote `str::from_utf8` instead of `std::str::from_utf8` let item_span = path.iter().last().map(|segment| segment.ident.span) .unwrap_or(span); debug!("accessed item from `std` submodule as a bare type {:?}", std_path); let mut hm = self.r.session.confused_type_with_std_module.borrow_mut(); hm.insert(item_span, span); // In some places (E0223) we only have access to the full path hm.insert(span, span); } } partial_res } _ => report_errors(self, None) }; if let PathSource::TraitItem(..) = source {} else { // Avoid recording definition of `A::B` in `::B::C`. self.r.record_partial_res(id, partial_res); } partial_res } fn self_type_is_available(&mut self, span: Span) -> bool { let binding = self.resolve_ident_in_lexical_scope( Ident::with_dummy_span(kw::SelfUpper), TypeNS, None, span, ); if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false } } fn self_value_is_available(&mut self, self_span: Span, path_span: Span) -> bool { let ident = Ident::new(kw::SelfLower, self_span); let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None, path_span); if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false } } // Resolve in alternative namespaces if resolution in the primary namespace fails. fn resolve_qpath_anywhere( &mut self, id: NodeId, qself: Option<&QSelf>, path: &[Segment], primary_ns: Namespace, span: Span, defer_to_typeck: bool, crate_lint: CrateLint, ) -> Option { let mut fin_res = None; for (i, ns) in [primary_ns, TypeNS, ValueNS].iter().cloned().enumerate() { if i == 0 || ns != primary_ns { match self.resolve_qpath(id, qself, path, ns, span, crate_lint) { // If defer_to_typeck, then resolution > no resolution, // otherwise full resolution > partial resolution > no resolution. Some(partial_res) if partial_res.unresolved_segments() == 0 || defer_to_typeck => return Some(partial_res), partial_res => if fin_res.is_none() { fin_res = partial_res }, } } } // `MacroNS` assert!(primary_ns != MacroNS); if qself.is_none() { let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident); let path = Path { segments: path.iter().map(path_seg).collect(), span }; if let Ok((_, res)) = self.r.resolve_macro_path( &path, None, &self.parent_scope, false, false ) { return Some(PartialRes::new(res)); } } fin_res } /// Handles paths that may refer to associated items. fn resolve_qpath( &mut self, id: NodeId, qself: Option<&QSelf>, path: &[Segment], ns: Namespace, span: Span, crate_lint: CrateLint, ) -> Option { debug!( "resolve_qpath(id={:?}, qself={:?}, path={:?}, ns={:?}, span={:?})", id, qself, path, ns, span, ); if let Some(qself) = qself { if qself.position == 0 { // This is a case like `::B`, where there is no // trait to resolve. In that case, we leave the `B` // segment to be resolved by type-check. return Some(PartialRes::with_unresolved_segments( Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX)), path.len() )); } // Make sure `A::B` in `::C` is a trait item. // // Currently, `path` names the full item (`A::B::C`, in // our example). so we extract the prefix of that that is // the trait (the slice upto and including // `qself.position`). And then we recursively resolve that, // but with `qself` set to `None`. // // However, setting `qself` to none (but not changing the // span) loses the information about where this path // *actually* appears, so for the purposes of the crate // lint we pass along information that this is the trait // name from a fully qualified path, and this also // contains the full span (the `CrateLint::QPathTrait`). let ns = if qself.position + 1 == path.len() { ns } else { TypeNS }; let partial_res = self.smart_resolve_path_fragment( id, None, &path[..=qself.position], span, PathSource::TraitItem(ns), CrateLint::QPathTrait { qpath_id: id, qpath_span: qself.path_span, }, ); // The remaining segments (the `C` in our example) will // have to be resolved by type-check, since that requires doing // trait resolution. return Some(PartialRes::with_unresolved_segments( partial_res.base_res(), partial_res.unresolved_segments() + path.len() - qself.position - 1, )); } let result = match self.resolve_path(&path, Some(ns), true, span, crate_lint) { PathResult::NonModule(path_res) => path_res, PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => { PartialRes::new(module.res().unwrap()) } // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we // don't report an error right away, but try to fallback to a primitive type. // So, we are still able to successfully resolve something like // // use std::u8; // bring module u8 in scope // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8 // u8::max_value() // OK, resolves to associated function ::max_value, // // not to non-existent std::u8::max_value // } // // Such behavior is required for backward compatibility. // The same fallback is used when `a` resolves to nothing. PathResult::Module(ModuleOrUniformRoot::Module(_)) | PathResult::Failed { .. } if (ns == TypeNS || path.len() > 1) && self.r.primitive_type_table.primitive_types .contains_key(&path[0].ident.name) => { let prim = self.r.primitive_type_table.primitive_types[&path[0].ident.name]; PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1) } PathResult::Module(ModuleOrUniformRoot::Module(module)) => PartialRes::new(module.res().unwrap()), PathResult::Failed { is_error_from_last_segment: false, span, label, suggestion } => { self.r.report_error(span, ResolutionError::FailedToResolve { label, suggestion }); PartialRes::new(Res::Err) } PathResult::Module(..) | PathResult::Failed { .. } => return None, PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"), }; if path.len() > 1 && result.base_res() != Res::Err && path[0].ident.name != kw::PathRoot && path[0].ident.name != kw::DollarCrate { let unqualified_result = { match self.resolve_path( &[*path.last().unwrap()], Some(ns), false, span, CrateLint::No, ) { PathResult::NonModule(path_res) => path_res.base_res(), PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res().unwrap(), _ => return Some(result), } }; if result.base_res() == unqualified_result { let lint = lint::builtin::UNUSED_QUALIFICATIONS; self.r.session.buffer_lint(lint, id, span, "unnecessary qualification") } } Some(result) } fn with_resolved_label(&mut self, label: Option