src/librustc_resolve/lib.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![crate_name = "rustc_resolve"]
  12 #![unstable(feature = "rustc_private", issue = "27812")]
  13 #![crate_type = "dylib"]
  14 #![crate_type = "rlib"]
  15 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  16       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  17       html_root_url = "https://doc.rust-lang.org/nightly/")]
  18 #![cfg_attr(not(stage0), deny(warnings))]
  19
  20 #![feature(associated_consts)]
  21 #![feature(borrow_state)]
  22 #![feature(rustc_diagnostic_macros)]
  23 #![feature(rustc_private)]
  24 #![feature(staged_api)]
  25
  26 #[macro_use]
  27 extern crate log;
  28 #[macro_use]
  29 extern crate syntax;
  30 extern crate syntax_pos;
  31 extern crate rustc_errors as errors;
  32 extern crate arena;
  33 #[macro_use]
  34 extern crate rustc;
  35
  36 use self::Namespace::*;
  37 use self::ResolveResult::*;
  38 use self::FallbackSuggestion::*;
  39 use self::TypeParameters::*;
  40 use self::RibKind::*;
  41 use self::UseLexicalScopeFlag::*;
  42 use self::ModulePrefixResult::*;
  43 use self::ParentLink::*;
  44
  45 use rustc::hir::map::Definitions;
  46 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  47 use rustc::session::Session;
  48 use rustc::lint;
  49 use rustc::hir::def::*;
  50 use rustc::hir::def_id::DefId;
  51 use rustc::ty;
  52 use rustc::ty::subst::{ParamSpace, FnSpace, TypeSpace};
  53 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  54 use rustc::util::nodemap::{NodeMap, NodeSet, FnvHashMap, FnvHashSet};
  55
  56 use syntax::ext::mtwt;
  57 use syntax::ast::{self, FloatTy};
  58 use syntax::ast::{CRATE_NODE_ID, Name, NodeId, CrateNum, IntTy, UintTy};
  59 use syntax::parse::token::{self, keywords};
  60 use syntax::util::lev_distance::find_best_match_for_name;
  61
  62 use syntax::visit::{self, FnKind, Visitor};
  63 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  64 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  65 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  66 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  67 use syntax::ast::{PathSegment, PathParameters, QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  68
  69 use syntax_pos::Span;
  70 use errors::DiagnosticBuilder;
  71
  72 use std::collections::{HashMap, HashSet};
  73 use std::cell::{Cell, RefCell};
  74 use std::fmt;
  75 use std::mem::replace;
  76
  77 use resolve_imports::{ImportDirective, NameResolution};
  78
  79 // NB: This module needs to be declared first so diagnostics are
  80 // registered before they are used.
  81 mod diagnostics;
  82
  83 mod check_unused;
  84 mod build_reduced_graph;
  85 mod resolve_imports;
  86
  87 enum SuggestionType {
  88     Macro(String),
  89     Function(token::InternedString),
  90     NotFound,
  91 }
  92
  93 /// Candidates for a name resolution failure
  94 struct SuggestedCandidates {
  95     name: String,
  96     candidates: Vec<Path>,
  97 }
  98
  99 enum ResolutionError<'a> {
 100     /// error E0401: can't use type parameters from outer function
 101     TypeParametersFromOuterFunction,
 102     /// error E0402: cannot use an outer type parameter in this context
 103     OuterTypeParameterContext,
 104     /// error E0403: the name is already used for a type parameter in this type parameter list
 105     NameAlreadyUsedInTypeParameterList(Name),
 106     /// error E0404: is not a trait
 107     IsNotATrait(&'a str),
 108     /// error E0405: use of undeclared trait name
 109     UndeclaredTraitName(&'a str, SuggestedCandidates),
 110     /// error E0407: method is not a member of trait
 111     MethodNotMemberOfTrait(Name, &'a str),
 112     /// error E0437: type is not a member of trait
 113     TypeNotMemberOfTrait(Name, &'a str),
 114     /// error E0438: const is not a member of trait
 115     ConstNotMemberOfTrait(Name, &'a str),
 116     /// error E0408: variable `{}` from pattern #{} is not bound in pattern #{}
 117     VariableNotBoundInPattern(Name, usize, usize),
 118     /// error E0409: variable is bound with different mode in pattern #{} than in pattern #1
 119     VariableBoundWithDifferentMode(Name, usize),
 120     /// error E0411: use of `Self` outside of an impl or trait
 121     SelfUsedOutsideImplOrTrait,
 122     /// error E0412: use of undeclared
 123     UseOfUndeclared(&'a str, &'a str, SuggestedCandidates),
 124     /// error E0415: identifier is bound more than once in this parameter list
 125     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 126     /// error E0416: identifier is bound more than once in the same pattern
 127     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 128     /// error E0422: does not name a struct
 129     DoesNotNameAStruct(&'a str),
 130     /// error E0423: is a struct variant name, but this expression uses it like a function name
 131     StructVariantUsedAsFunction(&'a str),
 132     /// error E0424: `self` is not available in a static method
 133     SelfNotAvailableInStaticMethod,
 134     /// error E0425: unresolved name
 135     UnresolvedName {
 136         path: &'a str,
 137         message: &'a str,
 138         context: UnresolvedNameContext<'a>,
 139         is_static_method: bool,
 140         is_field: bool,
 141         def: Def,
 142     },
 143     /// error E0426: use of undeclared label
 144     UndeclaredLabel(&'a str),
 145     /// error E0429: `self` imports are only allowed within a { } list
 146     SelfImportsOnlyAllowedWithin,
 147     /// error E0430: `self` import can only appear once in the list
 148     SelfImportCanOnlyAppearOnceInTheList,
 149     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 150     SelfImportOnlyInImportListWithNonEmptyPrefix,
 151     /// error E0432: unresolved import
 152     UnresolvedImport(Option<(&'a str, &'a str)>),
 153     /// error E0433: failed to resolve
 154     FailedToResolve(&'a str),
 155     /// error E0434: can't capture dynamic environment in a fn item
 156     CannotCaptureDynamicEnvironmentInFnItem,
 157     /// error E0435: attempt to use a non-constant value in a constant
 158     AttemptToUseNonConstantValueInConstant,
 159     /// error E0530: X bindings cannot shadow Ys
 160     BindingShadowsSomethingUnacceptable(&'a str, &'a str, Name),
 161     /// error E0531: unresolved pattern path kind `name`
 162     PatPathUnresolved(&'a str, &'a Path),
 163     /// error E0532: expected pattern path kind, found another pattern path kind
 164     PatPathUnexpected(&'a str, &'a str, &'a Path),
 165 }
 166
 167 /// Context of where `ResolutionError::UnresolvedName` arose.
 168 #[derive(Clone, PartialEq, Eq, Debug)]
 169 enum UnresolvedNameContext<'a> {
 170     /// `PathIsMod(parent)` indicates that a given path, used in
 171     /// expression context, actually resolved to a module rather than
 172     /// a value. The optional expression attached to the variant is the
 173     /// the parent of the erroneous path expression.
 174     PathIsMod(Option<&'a Expr>),
 175
 176     /// `Other` means we have no extra information about the context
 177     /// of the unresolved name error. (Maybe we could eliminate all
 178     /// such cases; but for now, this is an information-free default.)
 179     Other,
 180 }
 181
 182 fn resolve_error<'b, 'a: 'b, 'c>(resolver: &'b Resolver<'a>,
 183                                  span: syntax_pos::Span,
 184                                  resolution_error: ResolutionError<'c>) {
 185     resolve_struct_error(resolver, span, resolution_error).emit();
 186 }
 187
 188 fn resolve_struct_error<'b, 'a: 'b, 'c>(resolver: &'b Resolver<'a>,
 189                                         span: syntax_pos::Span,
 190                                         resolution_error: ResolutionError<'c>)
 191                                         -> DiagnosticBuilder<'a> {
 192     if !resolver.emit_errors {
 193         return resolver.session.diagnostic().struct_dummy();
 194     }
 195
 196     match resolution_error {
 197         ResolutionError::TypeParametersFromOuterFunction => {
 198             let mut err = struct_span_err!(resolver.session,
 199                                            span,
 200                                            E0401,
 201                                            "can't use type parameters from outer function; \
 202                                            try using a local type parameter instead");
 203             err.span_label(span, &format!("use of type variable from outer function"));
 204             err
 205         }
 206         ResolutionError::OuterTypeParameterContext => {
 207             struct_span_err!(resolver.session,
 208                              span,
 209                              E0402,
 210                              "cannot use an outer type parameter in this context")
 211         }
 212         ResolutionError::NameAlreadyUsedInTypeParameterList(name) => {
 213             struct_span_err!(resolver.session,
 214                              span,
 215                              E0403,
 216                              "the name `{}` is already used for a type parameter in this type \
 217                               parameter list",
 218                              name)
 219         }
 220         ResolutionError::IsNotATrait(name) => {
 221             struct_span_err!(resolver.session, span, E0404, "`{}` is not a trait", name)
 222         }
 223         ResolutionError::UndeclaredTraitName(name, candidates) => {
 224             let mut err = struct_span_err!(resolver.session,
 225                                            span,
 226                                            E0405,
 227                                            "trait `{}` is not in scope",
 228                                            name);
 229             show_candidates(&mut err, &candidates);
 230             err.span_label(span, &format!("`{}` is not in scope", name));
 231             err
 232         }
 233         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 234             struct_span_err!(resolver.session,
 235                              span,
 236                              E0407,
 237                              "method `{}` is not a member of trait `{}`",
 238                              method,
 239                              trait_)
 240         }
 241         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 242             struct_span_err!(resolver.session,
 243                              span,
 244                              E0437,
 245                              "type `{}` is not a member of trait `{}`",
 246                              type_,
 247                              trait_)
 248         }
 249         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 250             struct_span_err!(resolver.session,
 251                              span,
 252                              E0438,
 253                              "const `{}` is not a member of trait `{}`",
 254                              const_,
 255                              trait_)
 256         }
 257         ResolutionError::VariableNotBoundInPattern(variable_name, from, to) => {
 258             struct_span_err!(resolver.session,
 259                              span,
 260                              E0408,
 261                              "variable `{}` from pattern #{} is not bound in pattern #{}",
 262                              variable_name,
 263                              from,
 264                              to)
 265         }
 266         ResolutionError::VariableBoundWithDifferentMode(variable_name, pattern_number) => {
 267             struct_span_err!(resolver.session,
 268                              span,
 269                              E0409,
 270                              "variable `{}` is bound with different mode in pattern #{} than in \
 271                               pattern #1",
 272                              variable_name,
 273                              pattern_number)
 274         }
 275         ResolutionError::SelfUsedOutsideImplOrTrait => {
 276             let mut err = struct_span_err!(resolver.session,
 277                                            span,
 278                                            E0411,
 279                                            "use of `Self` outside of an impl or trait");
 280             err.span_label(span, &format!("used outside of impl or trait"));
 281             err
 282         }
 283         ResolutionError::UseOfUndeclared(kind, name, candidates) => {
 284             let mut err = struct_span_err!(resolver.session,
 285                                            span,
 286                                            E0412,
 287                                            "{} `{}` is undefined or not in scope",
 288                                            kind,
 289                                            name);
 290             show_candidates(&mut err, &candidates);
 291             err.span_label(span, &format!("undefined or not in scope"));
 292             err
 293         }
 294         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 295             let mut err = struct_span_err!(resolver.session,
 296                              span,
 297                              E0415,
 298                              "identifier `{}` is bound more than once in this parameter list",
 299                              identifier);
 300             err.span_label(span, &format!("used as parameter more than once"));
 301             err
 302         }
 303         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 304             let mut err = struct_span_err!(resolver.session,
 305                              span,
 306                              E0416,
 307                              "identifier `{}` is bound more than once in the same pattern",
 308                              identifier);
 309             err.span_label(span, &format!("used in a pattern more than once"));
 310             err
 311         }
 312         ResolutionError::DoesNotNameAStruct(name) => {
 313             struct_span_err!(resolver.session,
 314                              span,
 315                              E0422,
 316                              "`{}` does not name a structure",
 317                              name)
 318         }
 319         ResolutionError::StructVariantUsedAsFunction(path_name) => {
 320             struct_span_err!(resolver.session,
 321                              span,
 322                              E0423,
 323                              "`{}` is the name of a struct or struct variant, but this expression \
 324                              uses it like a function name",
 325                              path_name)
 326         }
 327         ResolutionError::SelfNotAvailableInStaticMethod => {
 328             struct_span_err!(resolver.session,
 329                              span,
 330                              E0424,
 331                              "`self` is not available in a static method. Maybe a `self` \
 332                              argument is missing?")
 333         }
 334         ResolutionError::UnresolvedName { path, message: msg, context, is_static_method,
 335                                           is_field, def } => {
 336             let mut err = struct_span_err!(resolver.session,
 337                                            span,
 338                                            E0425,
 339                                            "unresolved name `{}`{}",
 340                                            path,
 341                                            msg);
 342             match context {
 343                 UnresolvedNameContext::Other => {
 344                     if msg.is_empty() && is_static_method && is_field {
 345                         err.help("this is an associated function, you don't have access to \
 346                                   this type's fields or methods");
 347                     }
 348                 }
 349                 UnresolvedNameContext::PathIsMod(parent) => {
 350                     err.help(&match parent.map(|parent| &parent.node) {
 351                         Some(&ExprKind::Field(_, ident)) => {
 352                             format!("to reference an item from the `{module}` module, \
 353                                      use `{module}::{ident}`",
 354                                     module = path,
 355                                     ident = ident.node)
 356                         }
 357                         Some(&ExprKind::MethodCall(ident, _, _)) => {
 358                             format!("to call a function from the `{module}` module, \
 359                                      use `{module}::{ident}(..)`",
 360                                     module = path,
 361                                     ident = ident.node)
 362                         }
 363                         _ => {
 364                             format!("{def} `{module}` cannot be used as an expression",
 365                                     def = def.kind_name(),
 366                                     module = path)
 367                         }
 368                     });
 369                 }
 370             }
 371             err
 372         }
 373         ResolutionError::UndeclaredLabel(name) => {
 374             struct_span_err!(resolver.session,
 375                              span,
 376                              E0426,
 377                              "use of undeclared label `{}`",
 378                              name)
 379         }
 380         ResolutionError::SelfImportsOnlyAllowedWithin => {
 381             struct_span_err!(resolver.session,
 382                              span,
 383                              E0429,
 384                              "{}",
 385                              "`self` imports are only allowed within a { } list")
 386         }
 387         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 388             struct_span_err!(resolver.session,
 389                              span,
 390                              E0430,
 391                              "`self` import can only appear once in the list")
 392         }
 393         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 394             struct_span_err!(resolver.session,
 395                              span,
 396                              E0431,
 397                              "`self` import can only appear in an import list with a \
 398                               non-empty prefix")
 399         }
 400         ResolutionError::UnresolvedImport(name) => {
 401             let msg = match name {
 402                 Some((n, p)) => format!("unresolved import `{}`{}", n, p),
 403                 None => "unresolved import".to_owned(),
 404             };
 405             struct_span_err!(resolver.session, span, E0432, "{}", msg)
 406         }
 407         ResolutionError::FailedToResolve(msg) => {
 408             struct_span_err!(resolver.session, span, E0433, "failed to resolve. {}", msg)
 409         }
 410         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 411             struct_span_err!(resolver.session,
 412                              span,
 413                              E0434,
 414                              "{}",
 415                              "can't capture dynamic environment in a fn item; use the || { ... } \
 416                               closure form instead")
 417         }
 418         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 419             struct_span_err!(resolver.session,
 420                              span,
 421                              E0435,
 422                              "attempt to use a non-constant value in a constant")
 423         }
 424         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, shadows_what, name) => {
 425             let mut err = struct_span_err!(resolver.session,
 426                                            span,
 427                                            E0530,
 428                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 429             err.span_label(span, &format!("cannot be named the same as a {}", shadows_what));
 430             if let Success(binding) = resolver.current_module.resolve_name(name, ValueNS, true) {
 431                 let participle = if binding.is_import() { "imported" } else { "defined" };
 432                 err.span_label(binding.span, &format!("a {} `{}` is {} here",
 433                                                       shadows_what, name, participle));
 434             }
 435             err
 436         }
 437         ResolutionError::PatPathUnresolved(expected_what, path) => {
 438             struct_span_err!(resolver.session,
 439                              span,
 440                              E0531,
 441                              "unresolved {} `{}`",
 442                              expected_what,
 443                              path.segments.last().unwrap().identifier)
 444         }
 445         ResolutionError::PatPathUnexpected(expected_what, found_what, path) => {
 446             struct_span_err!(resolver.session,
 447                              span,
 448                              E0532,
 449                              "expected {}, found {} `{}`",
 450                              expected_what,
 451                              found_what,
 452                              path.segments.last().unwrap().identifier)
 453         }
 454     }
 455 }
 456
 457 #[derive(Copy, Clone)]
 458 struct BindingInfo {
 459     span: Span,
 460     binding_mode: BindingMode,
 461 }
 462
 463 // Map from the name in a pattern to its binding mode.
 464 type BindingMap = HashMap<Name, BindingInfo>;
 465
 466 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 467 enum PatternSource {
 468     Match,
 469     IfLet,
 470     WhileLet,
 471     Let,
 472     For,
 473     FnParam,
 474 }
 475
 476 impl PatternSource {
 477     fn is_refutable(self) -> bool {
 478         match self {
 479             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 480             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 481         }
 482     }
 483     fn descr(self) -> &'static str {
 484         match self {
 485             PatternSource::Match => "match binding",
 486             PatternSource::IfLet => "if let binding",
 487             PatternSource::WhileLet => "while let binding",
 488             PatternSource::Let => "let binding",
 489             PatternSource::For => "for binding",
 490             PatternSource::FnParam => "function parameter",
 491         }
 492     }
 493 }
 494
 495 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 496 pub enum Namespace {
 497     TypeNS,
 498     ValueNS,
 499 }
 500
 501 impl<'a> Visitor for Resolver<'a> {
 502     fn visit_item(&mut self, item: &Item) {
 503         self.resolve_item(item);
 504     }
 505     fn visit_arm(&mut self, arm: &Arm) {
 506         self.resolve_arm(arm);
 507     }
 508     fn visit_block(&mut self, block: &Block) {
 509         self.resolve_block(block);
 510     }
 511     fn visit_expr(&mut self, expr: &Expr) {
 512         self.resolve_expr(expr, None);
 513     }
 514     fn visit_local(&mut self, local: &Local) {
 515         self.resolve_local(local);
 516     }
 517     fn visit_ty(&mut self, ty: &Ty) {
 518         self.resolve_type(ty);
 519     }
 520     fn visit_poly_trait_ref(&mut self, tref: &ast::PolyTraitRef, m: &ast::TraitBoundModifier) {
 521         match self.resolve_trait_reference(tref.trait_ref.ref_id, &tref.trait_ref.path, 0) {
 522             Ok(def) => self.record_def(tref.trait_ref.ref_id, def),
 523             Err(_) => {
 524                 // error already reported
 525                 self.record_def(tref.trait_ref.ref_id, err_path_resolution())
 526             }
 527         }
 528         visit::walk_poly_trait_ref(self, tref, m);
 529     }
 530     fn visit_variant(&mut self,
 531                      variant: &ast::Variant,
 532                      generics: &Generics,
 533                      item_id: ast::NodeId) {
 534         if let Some(ref dis_expr) = variant.node.disr_expr {
 535             // resolve the discriminator expr as a constant
 536             self.with_constant_rib(|this| {
 537                 this.visit_expr(dis_expr);
 538             });
 539         }
 540
 541         // `visit::walk_variant` without the discriminant expression.
 542         self.visit_variant_data(&variant.node.data,
 543                                 variant.node.name,
 544                                 generics,
 545                                 item_id,
 546                                 variant.span);
 547     }
 548     fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
 549         let type_parameters = match foreign_item.node {
 550             ForeignItemKind::Fn(_, ref generics) => {
 551                 HasTypeParameters(generics, FnSpace, ItemRibKind)
 552             }
 553             ForeignItemKind::Static(..) => NoTypeParameters,
 554         };
 555         self.with_type_parameter_rib(type_parameters, |this| {
 556             visit::walk_foreign_item(this, foreign_item);
 557         });
 558     }
 559     fn visit_fn(&mut self,
 560                 function_kind: FnKind,
 561                 declaration: &FnDecl,
 562                 block: &Block,
 563                 _: Span,
 564                 node_id: NodeId) {
 565         let rib_kind = match function_kind {
 566             FnKind::ItemFn(_, generics, _, _, _, _) => {
 567                 self.visit_generics(generics);
 568                 ItemRibKind
 569             }
 570             FnKind::Method(_, sig, _) => {
 571                 self.visit_generics(&sig.generics);
 572                 MethodRibKind(!sig.decl.has_self())
 573             }
 574             FnKind::Closure => ClosureRibKind(node_id),
 575         };
 576         self.resolve_function(rib_kind, declaration, block);
 577     }
 578 }
 579
 580 pub type ErrorMessage = Option<(Span, String)>;
 581
 582 #[derive(Clone, PartialEq, Eq)]
 583 pub enum ResolveResult<T> {
 584     Failed(ErrorMessage), // Failed to resolve the name, optional helpful error message.
 585     Indeterminate, // Couldn't determine due to unresolved globs.
 586     Success(T), // Successfully resolved the import.
 587 }
 588
 589 impl<T> ResolveResult<T> {
 590     fn and_then<U, F: FnOnce(T) -> ResolveResult<U>>(self, f: F) -> ResolveResult<U> {
 591         match self {
 592             Failed(msg) => Failed(msg),
 593             Indeterminate => Indeterminate,
 594             Success(t) => f(t),
 595         }
 596     }
 597
 598     fn success(self) -> Option<T> {
 599         match self {
 600             Success(t) => Some(t),
 601             _ => None,
 602         }
 603     }
 604 }
 605
 606 enum FallbackSuggestion {
 607     NoSuggestion,
 608     Field,
 609     TraitItem,
 610     TraitMethod(String),
 611 }
 612
 613 #[derive(Copy, Clone)]
 614 enum TypeParameters<'a, 'b> {
 615     NoTypeParameters,
 616     HasTypeParameters(// Type parameters.
 617                       &'b Generics,
 618
 619                       // Identifies the things that these parameters
 620                       // were declared on (type, fn, etc)
 621                       ParamSpace,
 622
 623                       // The kind of the rib used for type parameters.
 624                       RibKind<'a>),
 625 }
 626
 627 // The rib kind controls the translation of local
 628 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 629 #[derive(Copy, Clone, Debug)]
 630 enum RibKind<'a> {
 631     // No translation needs to be applied.
 632     NormalRibKind,
 633
 634     // We passed through a closure scope at the given node ID.
 635     // Translate upvars as appropriate.
 636     ClosureRibKind(NodeId /* func id */),
 637
 638     // We passed through an impl or trait and are now in one of its
 639     // methods. Allow references to ty params that impl or trait
 640     // binds. Disallow any other upvars (including other ty params that are
 641     // upvars).
 642     //
 643     // The boolean value represents the fact that this method is static or not.
 644     MethodRibKind(bool),
 645
 646     // We passed through an item scope. Disallow upvars.
 647     ItemRibKind,
 648
 649     // We're in a constant item. Can't refer to dynamic stuff.
 650     ConstantItemRibKind,
 651
 652     // We passed through a module.
 653     ModuleRibKind(Module<'a>),
 654 }
 655
 656 #[derive(Copy, Clone)]
 657 enum UseLexicalScopeFlag {
 658     DontUseLexicalScope,
 659     UseLexicalScope,
 660 }
 661
 662 enum ModulePrefixResult<'a> {
 663     NoPrefixFound,
 664     PrefixFound(Module<'a>, usize),
 665 }
 666
 667 /// One local scope.
 668 #[derive(Debug)]
 669 struct Rib<'a> {
 670     bindings: HashMap<Name, Def>,
 671     kind: RibKind<'a>,
 672 }
 673
 674 impl<'a> Rib<'a> {
 675     fn new(kind: RibKind<'a>) -> Rib<'a> {
 676         Rib {
 677             bindings: HashMap::new(),
 678             kind: kind,
 679         }
 680     }
 681 }
 682
 683 /// A definition along with the index of the rib it was found on
 684 struct LocalDef {
 685     ribs: Option<(Namespace, usize)>,
 686     def: Def,
 687 }
 688
 689 impl LocalDef {
 690     fn from_def(def: Def) -> Self {
 691         LocalDef {
 692             ribs: None,
 693             def: def,
 694         }
 695     }
 696 }
 697
 698 enum LexicalScopeBinding<'a> {
 699     Item(&'a NameBinding<'a>),
 700     LocalDef(LocalDef),
 701 }
 702
 703 impl<'a> LexicalScopeBinding<'a> {
 704     fn local_def(self) -> LocalDef {
 705         match self {
 706             LexicalScopeBinding::LocalDef(local_def) => local_def,
 707             LexicalScopeBinding::Item(binding) => LocalDef::from_def(binding.def().unwrap()),
 708         }
 709     }
 710
 711     fn module(self) -> Option<Module<'a>> {
 712         match self {
 713             LexicalScopeBinding::Item(binding) => binding.module(),
 714             _ => None,
 715         }
 716     }
 717 }
 718
 719 /// The link from a module up to its nearest parent node.
 720 #[derive(Clone,Debug)]
 721 enum ParentLink<'a> {
 722     NoParentLink,
 723     ModuleParentLink(Module<'a>, Name),
 724     BlockParentLink(Module<'a>, NodeId),
 725 }
 726
 727 /// One node in the tree of modules.
 728 pub struct ModuleS<'a> {
 729     parent_link: ParentLink<'a>,
 730     def: Option<Def>,
 731
 732     // If the module is an extern crate, `def` is root of the external crate and `extern_crate_id`
 733     // is the NodeId of the local `extern crate` item (otherwise, `extern_crate_id` is None).
 734     extern_crate_id: Option<NodeId>,
 735
 736     resolutions: RefCell<HashMap<(Name, Namespace), &'a RefCell<NameResolution<'a>>>>,
 737     unresolved_imports: RefCell<Vec<&'a ImportDirective<'a>>>,
 738
 739     no_implicit_prelude: Cell<bool>,
 740
 741     glob_importers: RefCell<Vec<(Module<'a>, &'a ImportDirective<'a>)>>,
 742     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 743
 744     // Used to memoize the traits in this module for faster searches through all traits in scope.
 745     traits: RefCell<Option<Box<[(Name, &'a NameBinding<'a>)]>>>,
 746
 747     // Whether this module is populated. If not populated, any attempt to
 748     // access the children must be preceded with a
 749     // `populate_module_if_necessary` call.
 750     populated: Cell<bool>,
 751
 752     arenas: &'a ResolverArenas<'a>,
 753 }
 754
 755 pub type Module<'a> = &'a ModuleS<'a>;
 756
 757 impl<'a> ModuleS<'a> {
 758     fn new(parent_link: ParentLink<'a>,
 759            def: Option<Def>,
 760            external: bool,
 761            arenas: &'a ResolverArenas<'a>) -> Self {
 762         ModuleS {
 763             parent_link: parent_link,
 764             def: def,
 765             extern_crate_id: None,
 766             resolutions: RefCell::new(HashMap::new()),
 767             unresolved_imports: RefCell::new(Vec::new()),
 768             no_implicit_prelude: Cell::new(false),
 769             glob_importers: RefCell::new(Vec::new()),
 770             globs: RefCell::new((Vec::new())),
 771             traits: RefCell::new(None),
 772             populated: Cell::new(!external),
 773             arenas: arenas
 774         }
 775     }
 776
 777     fn for_each_child<F: FnMut(Name, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 778         for (&(name, ns), name_resolution) in self.resolutions.borrow().iter() {
 779             name_resolution.borrow().binding.map(|binding| f(name, ns, binding));
 780         }
 781     }
 782
 783     fn def_id(&self) -> Option<DefId> {
 784         self.def.as_ref().map(Def::def_id)
 785     }
 786
 787     // `self` resolves to the first module ancestor that `is_normal`.
 788     fn is_normal(&self) -> bool {
 789         match self.def {
 790             Some(Def::Mod(_)) => true,
 791             _ => false,
 792         }
 793     }
 794
 795     fn is_trait(&self) -> bool {
 796         match self.def {
 797             Some(Def::Trait(_)) => true,
 798             _ => false,
 799         }
 800     }
 801 }
 802
 803 impl<'a> fmt::Debug for ModuleS<'a> {
 804     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 805         write!(f, "{:?}", self.def)
 806     }
 807 }
 808
 809 // Records a possibly-private value, type, or module definition.
 810 #[derive(Clone, Debug)]
 811 pub struct NameBinding<'a> {
 812     kind: NameBindingKind<'a>,
 813     span: Span,
 814     vis: ty::Visibility,
 815 }
 816
 817 #[derive(Clone, Debug)]
 818 enum NameBindingKind<'a> {
 819     Def(Def),
 820     Module(Module<'a>),
 821     Import {
 822         binding: &'a NameBinding<'a>,
 823         directive: &'a ImportDirective<'a>,
 824         // Some(error) if using this imported name causes the import to be a privacy error
 825         privacy_error: Option<Box<PrivacyError<'a>>>,
 826     },
 827 }
 828
 829 #[derive(Clone, Debug)]
 830 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
 831
 832 impl<'a> NameBinding<'a> {
 833     fn module(&self) -> Option<Module<'a>> {
 834         match self.kind {
 835             NameBindingKind::Module(module) => Some(module),
 836             NameBindingKind::Def(_) => None,
 837             NameBindingKind::Import { binding, .. } => binding.module(),
 838         }
 839     }
 840
 841     fn def(&self) -> Option<Def> {
 842         match self.kind {
 843             NameBindingKind::Def(def) => Some(def),
 844             NameBindingKind::Module(module) => module.def,
 845             NameBindingKind::Import { binding, .. } => binding.def(),
 846         }
 847     }
 848
 849     fn is_pseudo_public(&self) -> bool {
 850         self.pseudo_vis() == ty::Visibility::Public
 851     }
 852
 853     // We sometimes need to treat variants as `pub` for backwards compatibility
 854     fn pseudo_vis(&self) -> ty::Visibility {
 855         if self.is_variant() { ty::Visibility::Public } else { self.vis }
 856     }
 857
 858     fn is_variant(&self) -> bool {
 859         match self.kind {
 860             NameBindingKind::Def(Def::Variant(..)) => true,
 861             _ => false,
 862         }
 863     }
 864
 865     fn is_extern_crate(&self) -> bool {
 866         self.module().and_then(|module| module.extern_crate_id).is_some()
 867     }
 868
 869     fn is_import(&self) -> bool {
 870         match self.kind {
 871             NameBindingKind::Import { .. } => true,
 872             _ => false,
 873         }
 874     }
 875
 876     fn is_glob_import(&self) -> bool {
 877         match self.kind {
 878             NameBindingKind::Import { directive, .. } => directive.is_glob(),
 879             _ => false,
 880         }
 881     }
 882
 883     fn is_importable(&self) -> bool {
 884         match self.def().unwrap() {
 885             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
 886             _ => true,
 887         }
 888     }
 889 }
 890
 891 /// Interns the names of the primitive types.
 892 struct PrimitiveTypeTable {
 893     primitive_types: HashMap<Name, PrimTy>,
 894 }
 895
 896 impl PrimitiveTypeTable {
 897     fn new() -> PrimitiveTypeTable {
 898         let mut table = PrimitiveTypeTable { primitive_types: HashMap::new() };
 899
 900         table.intern("bool", TyBool);
 901         table.intern("char", TyChar);
 902         table.intern("f32", TyFloat(FloatTy::F32));
 903         table.intern("f64", TyFloat(FloatTy::F64));
 904         table.intern("isize", TyInt(IntTy::Is));
 905         table.intern("i8", TyInt(IntTy::I8));
 906         table.intern("i16", TyInt(IntTy::I16));
 907         table.intern("i32", TyInt(IntTy::I32));
 908         table.intern("i64", TyInt(IntTy::I64));
 909         table.intern("str", TyStr);
 910         table.intern("usize", TyUint(UintTy::Us));
 911         table.intern("u8", TyUint(UintTy::U8));
 912         table.intern("u16", TyUint(UintTy::U16));
 913         table.intern("u32", TyUint(UintTy::U32));
 914         table.intern("u64", TyUint(UintTy::U64));
 915
 916         table
 917     }
 918
 919     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
 920         self.primitive_types.insert(token::intern(string), primitive_type);
 921     }
 922 }
 923
 924 /// The main resolver class.
 925 pub struct Resolver<'a> {
 926     session: &'a Session,
 927
 928     definitions: &'a mut Definitions,
 929
 930     graph_root: Module<'a>,
 931
 932     prelude: Option<Module<'a>>,
 933
 934     trait_item_map: FnvHashMap<(Name, DefId), bool /* is static method? */>,
 935
 936     structs: FnvHashMap<DefId, Vec<Name>>,
 937
 938     // The number of imports that are currently unresolved.
 939     unresolved_imports: usize,
 940
 941     // The module that represents the current item scope.
 942     current_module: Module<'a>,
 943
 944     // The current set of local scopes, for values.
 945     // FIXME #4948: Reuse ribs to avoid allocation.
 946     value_ribs: Vec<Rib<'a>>,
 947
 948     // The current set of local scopes, for types.
 949     type_ribs: Vec<Rib<'a>>,
 950
 951     // The current set of local scopes, for labels.
 952     label_ribs: Vec<Rib<'a>>,
 953
 954     // The trait that the current context can refer to.
 955     current_trait_ref: Option<(DefId, TraitRef)>,
 956
 957     // The current self type if inside an impl (used for better errors).
 958     current_self_type: Option<Ty>,
 959
 960     // The idents for the primitive types.
 961     primitive_type_table: PrimitiveTypeTable,
 962
 963     pub def_map: DefMap,
 964     pub freevars: FreevarMap,
 965     freevars_seen: NodeMap<NodeMap<usize>>,
 966     pub export_map: ExportMap,
 967     pub trait_map: TraitMap,
 968
 969     // A map from nodes to modules, both normal (`mod`) modules and anonymous modules.
 970     // Anonymous modules are pseudo-modules that are implicitly created around items
 971     // contained within blocks.
 972     //
 973     // For example, if we have this:
 974     //
 975     //  fn f() {
 976     //      fn g() {
 977     //          ...
 978     //      }
 979     //  }
 980     //
 981     // There will be an anonymous module created around `g` with the ID of the
 982     // entry block for `f`.
 983     module_map: NodeMap<Module<'a>>,
 984
 985     // Whether or not to print error messages. Can be set to true
 986     // when getting additional info for error message suggestions,
 987     // so as to avoid printing duplicate errors
 988     emit_errors: bool,
 989
 990     pub make_glob_map: bool,
 991     // Maps imports to the names of items actually imported (this actually maps
 992     // all imports, but only glob imports are actually interesting).
 993     pub glob_map: GlobMap,
 994
 995     used_imports: HashSet<(NodeId, Namespace)>,
 996     used_crates: HashSet<CrateNum>,
 997     pub maybe_unused_trait_imports: NodeSet,
 998
 999     privacy_errors: Vec<PrivacyError<'a>>,
1000
1001     arenas: &'a ResolverArenas<'a>,
1002 }
1003
1004 struct ResolverArenas<'a> {
1005     modules: arena::TypedArena<ModuleS<'a>>,
1006     local_modules: RefCell<Vec<Module<'a>>>,
1007     name_bindings: arena::TypedArena<NameBinding<'a>>,
1008     import_directives: arena::TypedArena<ImportDirective<'a>>,
1009     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1010 }
1011
1012 impl<'a> ResolverArenas<'a> {
1013     fn alloc_module(&'a self, module: ModuleS<'a>) -> Module<'a> {
1014         let module = self.modules.alloc(module);
1015         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1016             self.local_modules.borrow_mut().push(module);
1017         }
1018         module
1019     }
1020     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1021         self.local_modules.borrow()
1022     }
1023     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1024         self.name_bindings.alloc(name_binding)
1025     }
1026     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1027                               -> &'a ImportDirective {
1028         self.import_directives.alloc(import_directive)
1029     }
1030     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1031         self.name_resolutions.alloc(Default::default())
1032     }
1033 }
1034
1035 impl<'a> ty::NodeIdTree for Resolver<'a> {
1036     fn is_descendant_of(&self, node: NodeId, ancestor: NodeId) -> bool {
1037         let ancestor = self.definitions.local_def_id(ancestor);
1038         let mut module = *self.module_map.get(&node).unwrap();
1039         while module.def_id() != Some(ancestor) {
1040             let module_parent = match self.get_nearest_normal_module_parent(module) {
1041                 Some(parent) => parent,
1042                 None => return false,
1043             };
1044             module = module_parent;
1045         }
1046         true
1047     }
1048 }
1049
1050 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1051     fn resolve_generated_global_path(&mut self, path: &hir::Path, is_value: bool) -> Def {
1052         let namespace = if is_value { ValueNS } else { TypeNS };
1053         match self.resolve_crate_relative_path(path.span, &path.segments, namespace) {
1054             Ok(binding) => binding.def().unwrap(),
1055             Err(true) => Def::Err,
1056             Err(false) => {
1057                 let path_name = &format!("{}", path);
1058                 let error =
1059                     ResolutionError::UnresolvedName {
1060                         path: path_name,
1061                         message: "",
1062                         context: UnresolvedNameContext::Other,
1063                         is_static_method: false,
1064                         is_field: false,
1065                         def: Def::Err,
1066                     };
1067                 resolve_error(self, path.span, error);
1068                 Def::Err
1069             }
1070         }
1071     }
1072
1073     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1074         self.def_map.get(&id).cloned()
1075     }
1076
1077     fn record_resolution(&mut self, id: NodeId, def: Def) {
1078         self.def_map.insert(id, PathResolution::new(def));
1079     }
1080
1081     fn definitions(&mut self) -> Option<&mut Definitions> {
1082         Some(self.definitions)
1083     }
1084 }
1085
1086 trait Named {
1087     fn name(&self) -> Name;
1088 }
1089
1090 impl Named for ast::PathSegment {
1091     fn name(&self) -> Name {
1092         self.identifier.name
1093     }
1094 }
1095
1096 impl Named for hir::PathSegment {
1097     fn name(&self) -> Name {
1098         self.name
1099     }
1100 }
1101
1102 impl<'a> Resolver<'a> {
1103     fn new(session: &'a Session,
1104            definitions: &'a mut Definitions,
1105            make_glob_map: MakeGlobMap,
1106            arenas: &'a ResolverArenas<'a>)
1107            -> Resolver<'a> {
1108         let root_def_id = definitions.local_def_id(CRATE_NODE_ID);
1109         let graph_root =
1110             ModuleS::new(NoParentLink, Some(Def::Mod(root_def_id)), false, arenas);
1111         let graph_root = arenas.alloc_module(graph_root);
1112         let mut module_map = NodeMap();
1113         module_map.insert(CRATE_NODE_ID, graph_root);
1114
1115         Resolver {
1116             session: session,
1117
1118             definitions: definitions,
1119
1120             // The outermost module has def ID 0; this is not reflected in the
1121             // AST.
1122             graph_root: graph_root,
1123             prelude: None,
1124
1125             trait_item_map: FnvHashMap(),
1126             structs: FnvHashMap(),
1127
1128             unresolved_imports: 0,
1129
1130             current_module: graph_root,
1131             value_ribs: vec![Rib::new(ModuleRibKind(graph_root))],
1132             type_ribs: vec![Rib::new(ModuleRibKind(graph_root))],
1133             label_ribs: Vec::new(),
1134
1135             current_trait_ref: None,
1136             current_self_type: None,
1137
1138             primitive_type_table: PrimitiveTypeTable::new(),
1139
1140             def_map: NodeMap(),
1141             freevars: NodeMap(),
1142             freevars_seen: NodeMap(),
1143             export_map: NodeMap(),
1144             trait_map: NodeMap(),
1145             module_map: module_map,
1146
1147             emit_errors: true,
1148             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1149             glob_map: NodeMap(),
1150
1151             used_imports: HashSet::new(),
1152             used_crates: HashSet::new(),
1153             maybe_unused_trait_imports: NodeSet(),
1154
1155             privacy_errors: Vec::new(),
1156
1157             arenas: arenas,
1158         }
1159     }
1160
1161     fn arenas() -> ResolverArenas<'a> {
1162         ResolverArenas {
1163             modules: arena::TypedArena::new(),
1164             local_modules: RefCell::new(Vec::new()),
1165             name_bindings: arena::TypedArena::new(),
1166             import_directives: arena::TypedArena::new(),
1167             name_resolutions: arena::TypedArena::new(),
1168         }
1169     }
1170
1171     fn new_module(&self, parent_link: ParentLink<'a>, def: Option<Def>, external: bool)
1172                   -> Module<'a> {
1173         self.arenas.alloc_module(ModuleS::new(parent_link, def, external, self.arenas))
1174     }
1175
1176     fn new_extern_crate_module(&self, parent_link: ParentLink<'a>, def: Def, local_node_id: NodeId)
1177                                -> Module<'a> {
1178         let mut module = ModuleS::new(parent_link, Some(def), false, self.arenas);
1179         module.extern_crate_id = Some(local_node_id);
1180         self.arenas.modules.alloc(module)
1181     }
1182
1183     fn get_ribs<'b>(&'b mut self, ns: Namespace) -> &'b mut Vec<Rib<'a>> {
1184         match ns { ValueNS => &mut self.value_ribs, TypeNS => &mut self.type_ribs }
1185     }
1186
1187     #[inline]
1188     fn record_use(&mut self, name: Name, binding: &'a NameBinding<'a>) {
1189         // track extern crates for unused_extern_crate lint
1190         if let Some(DefId { krate, .. }) = binding.module().and_then(ModuleS::def_id) {
1191             self.used_crates.insert(krate);
1192         }
1193
1194         let (directive, privacy_error) = match binding.kind {
1195             NameBindingKind::Import { directive, ref privacy_error, .. } =>
1196                 (directive, privacy_error),
1197             _ => return,
1198         };
1199
1200         if let Some(error) = privacy_error.as_ref() {
1201             self.privacy_errors.push((**error).clone());
1202         }
1203
1204         if !self.make_glob_map {
1205             return;
1206         }
1207         if self.glob_map.contains_key(&directive.id) {
1208             self.glob_map.get_mut(&directive.id).unwrap().insert(name);
1209             return;
1210         }
1211
1212         let mut new_set = FnvHashSet();
1213         new_set.insert(name);
1214         self.glob_map.insert(directive.id, new_set);
1215     }
1216
1217     /// Resolves the given module path from the given root `module_`.
1218     fn resolve_module_path_from_root(&mut self,
1219                                      module_: Module<'a>,
1220                                      module_path: &[Name],
1221                                      index: usize,
1222                                      span: Span)
1223                                      -> ResolveResult<Module<'a>> {
1224         fn search_parent_externals(needle: Name, module: Module) -> Option<Module> {
1225             match module.resolve_name(needle, TypeNS, false) {
1226                 Success(binding) if binding.is_extern_crate() => Some(module),
1227                 _ => match module.parent_link {
1228                     ModuleParentLink(ref parent, _) => {
1229                         search_parent_externals(needle, parent)
1230                     }
1231                     _ => None,
1232                 },
1233             }
1234         }
1235
1236         let mut search_module = module_;
1237         let mut index = index;
1238         let module_path_len = module_path.len();
1239
1240         // Resolve the module part of the path. This does not involve looking
1241         // upward though scope chains; we simply resolve names directly in
1242         // modules as we go.
1243         while index < module_path_len {
1244             let name = module_path[index];
1245             match self.resolve_name_in_module(search_module, name, TypeNS, false, true) {
1246                 Failed(None) => {
1247                     let segment_name = name.as_str();
1248                     let module_name = module_to_string(search_module);
1249                     let msg = if "???" == &module_name {
1250                         match search_parent_externals(name, &self.current_module) {
1251                             Some(module) => {
1252                                 let path_str = names_to_string(module_path);
1253                                 let target_mod_str = module_to_string(&module);
1254                                 let current_mod_str = module_to_string(&self.current_module);
1255
1256                                 let prefix = if target_mod_str == current_mod_str {
1257                                     "self::".to_string()
1258                                 } else {
1259                                     format!("{}::", target_mod_str)
1260                                 };
1261
1262                                 format!("Did you mean `{}{}`?", prefix, path_str)
1263                             }
1264                             None => format!("Maybe a missing `extern crate {}`?", segment_name),
1265                         }
1266                     } else {
1267                         format!("Could not find `{}` in `{}`", segment_name, module_name)
1268                     };
1269
1270                     return Failed(Some((span, msg)));
1271                 }
1272                 Failed(err) => return Failed(err),
1273                 Indeterminate => {
1274                     debug!("(resolving module path for import) module resolution is \
1275                             indeterminate: {}",
1276                            name);
1277                     return Indeterminate;
1278                 }
1279                 Success(binding) => {
1280                     // Check to see whether there are type bindings, and, if
1281                     // so, whether there is a module within.
1282                     if let Some(module_def) = binding.module() {
1283                         self.check_privacy(name, binding, span);
1284                         search_module = module_def;
1285                     } else {
1286                         let msg = format!("Not a module `{}`", name);
1287                         return Failed(Some((span, msg)));
1288                     }
1289                 }
1290             }
1291
1292             index += 1;
1293         }
1294
1295         return Success(search_module);
1296     }
1297
1298     /// Attempts to resolve the module part of an import directive or path
1299     /// rooted at the given module.
1300     fn resolve_module_path(&mut self,
1301                            module_path: &[Name],
1302                            use_lexical_scope: UseLexicalScopeFlag,
1303                            span: Span)
1304                            -> ResolveResult<Module<'a>> {
1305         if module_path.len() == 0 {
1306             return Success(self.graph_root) // Use the crate root
1307         }
1308
1309         debug!("(resolving module path for import) processing `{}` rooted at `{}`",
1310                names_to_string(module_path),
1311                module_to_string(self.current_module));
1312
1313         // Resolve the module prefix, if any.
1314         let module_prefix_result = self.resolve_module_prefix(module_path, span);
1315
1316         let search_module;
1317         let start_index;
1318         match module_prefix_result {
1319             Failed(err) => return Failed(err),
1320             Indeterminate => {
1321                 debug!("(resolving module path for import) indeterminate; bailing");
1322                 return Indeterminate;
1323             }
1324             Success(NoPrefixFound) => {
1325                 // There was no prefix, so we're considering the first element
1326                 // of the path. How we handle this depends on whether we were
1327                 // instructed to use lexical scope or not.
1328                 match use_lexical_scope {
1329                     DontUseLexicalScope => {
1330                         // This is a crate-relative path. We will start the
1331                         // resolution process at index zero.
1332                         search_module = self.graph_root;
1333                         start_index = 0;
1334                     }
1335                     UseLexicalScope => {
1336                         // This is not a crate-relative path. We resolve the
1337                         // first component of the path in the current lexical
1338                         // scope and then proceed to resolve below that.
1339                         let ident = ast::Ident::with_empty_ctxt(module_path[0]);
1340                         match self.resolve_ident_in_lexical_scope(ident, TypeNS, true)
1341                                   .and_then(LexicalScopeBinding::module) {
1342                             None => return Failed(None),
1343                             Some(containing_module) => {
1344                                 search_module = containing_module;
1345                                 start_index = 1;
1346                             }
1347                         }
1348                     }
1349                 }
1350             }
1351             Success(PrefixFound(ref containing_module, index)) => {
1352                 search_module = containing_module;
1353                 start_index = index;
1354             }
1355         }
1356
1357         self.resolve_module_path_from_root(search_module,
1358                                            module_path,
1359                                            start_index,
1360                                            span)
1361     }
1362
1363     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1364     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1365     /// `ident` in the first scope that defines it (or None if no scopes define it).
1366     ///
1367     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1368     /// the items are defined in the block. For example,
1369     /// ```rust
1370     /// fn f() {
1371     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1372     ///    let g = || {};
1373     ///    fn g() {}
1374     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1375     /// }
1376     /// ```
1377     ///
1378     /// Invariant: This must only be called during main resolution, not during
1379     /// import resolution.
1380     fn resolve_ident_in_lexical_scope(&mut self,
1381                                       ident: ast::Ident,
1382                                       ns: Namespace,
1383                                       record_used: bool)
1384                                       -> Option<LexicalScopeBinding<'a>> {
1385         let name = match ns { ValueNS => mtwt::resolve(ident), TypeNS => ident.name };
1386
1387         // Walk backwards up the ribs in scope.
1388         for i in (0 .. self.get_ribs(ns).len()).rev() {
1389             if let Some(def) = self.get_ribs(ns)[i].bindings.get(&name).cloned() {
1390                 // The ident resolves to a type parameter or local variable.
1391                 return Some(LexicalScopeBinding::LocalDef(LocalDef {
1392                     ribs: Some((ns, i)),
1393                     def: def,
1394                 }));
1395             }
1396
1397             if let ModuleRibKind(module) = self.get_ribs(ns)[i].kind {
1398                 let name = ident.name;
1399                 let item = self.resolve_name_in_module(module, name, ns, true, record_used);
1400                 if let Success(binding) = item {
1401                     // The ident resolves to an item.
1402                     return Some(LexicalScopeBinding::Item(binding));
1403                 }
1404
1405                 // We can only see through anonymous modules
1406                 if module.def.is_some() {
1407                     return match self.prelude {
1408                         Some(prelude) if !module.no_implicit_prelude.get() => {
1409                             prelude.resolve_name(name, ns, false).success()
1410                                    .map(LexicalScopeBinding::Item)
1411                         }
1412                         _ => None,
1413                     };
1414                 }
1415             }
1416         }
1417
1418         None
1419     }
1420
1421     /// Returns the nearest normal module parent of the given module.
1422     fn get_nearest_normal_module_parent(&self, module_: Module<'a>) -> Option<Module<'a>> {
1423         let mut module_ = module_;
1424         loop {
1425             match module_.parent_link {
1426                 NoParentLink => return None,
1427                 ModuleParentLink(new_module, _) |
1428                 BlockParentLink(new_module, _) => {
1429                     let new_module = new_module;
1430                     if new_module.is_normal() {
1431                         return Some(new_module);
1432                     }
1433                     module_ = new_module;
1434                 }
1435             }
1436         }
1437     }
1438
1439     /// Returns the nearest normal module parent of the given module, or the
1440     /// module itself if it is a normal module.
1441     fn get_nearest_normal_module_parent_or_self(&self, module_: Module<'a>) -> Module<'a> {
1442         if module_.is_normal() {
1443             return module_;
1444         }
1445         match self.get_nearest_normal_module_parent(module_) {
1446             None => module_,
1447             Some(new_module) => new_module,
1448         }
1449     }
1450
1451     /// Resolves a "module prefix". A module prefix is one or both of (a) `self::`;
1452     /// (b) some chain of `super::`.
1453     /// grammar: (SELF MOD_SEP ) ? (SUPER MOD_SEP) *
1454     fn resolve_module_prefix(&mut self, module_path: &[Name], span: Span)
1455                              -> ResolveResult<ModulePrefixResult<'a>> {
1456         // Start at the current module if we see `self` or `super`, or at the
1457         // top of the crate otherwise.
1458         let mut i = match &*module_path[0].as_str() {
1459             "self" => 1,
1460             "super" => 0,
1461             _ => return Success(NoPrefixFound),
1462         };
1463         let module_ = self.current_module;
1464         let mut containing_module = self.get_nearest_normal_module_parent_or_self(module_);
1465
1466         // Now loop through all the `super`s we find.
1467         while i < module_path.len() && "super" == module_path[i].as_str() {
1468             debug!("(resolving module prefix) resolving `super` at {}",
1469                    module_to_string(&containing_module));
1470             match self.get_nearest_normal_module_parent(containing_module) {
1471                 None => {
1472                     let msg = "There are too many initial `super`s.".into();
1473                     return Failed(Some((span, msg)));
1474                 }
1475                 Some(new_module) => {
1476                     containing_module = new_module;
1477                     i += 1;
1478                 }
1479             }
1480         }
1481
1482         debug!("(resolving module prefix) finished resolving prefix at {}",
1483                module_to_string(&containing_module));
1484
1485         return Success(PrefixFound(containing_module, i));
1486     }
1487
1488     /// Attempts to resolve the supplied name in the given module for the
1489     /// given namespace. If successful, returns the binding corresponding to
1490     /// the name.
1491     fn resolve_name_in_module(&mut self,
1492                               module: Module<'a>,
1493                               name: Name,
1494                               namespace: Namespace,
1495                               use_lexical_scope: bool,
1496                               record_used: bool)
1497                               -> ResolveResult<&'a NameBinding<'a>> {
1498         debug!("(resolving name in module) resolving `{}` in `{}`", name, module_to_string(module));
1499
1500         self.populate_module_if_necessary(module);
1501         module.resolve_name(name, namespace, use_lexical_scope).and_then(|binding| {
1502             if record_used {
1503                 if let NameBindingKind::Import { directive, .. } = binding.kind {
1504                     self.used_imports.insert((directive.id, namespace));
1505                 }
1506                 self.record_use(name, binding);
1507             }
1508             Success(binding)
1509         })
1510     }
1511
1512     // AST resolution
1513     //
1514     // We maintain a list of value ribs and type ribs.
1515     //
1516     // Simultaneously, we keep track of the current position in the module
1517     // graph in the `current_module` pointer. When we go to resolve a name in
1518     // the value or type namespaces, we first look through all the ribs and
1519     // then query the module graph. When we resolve a name in the module
1520     // namespace, we can skip all the ribs (since nested modules are not
1521     // allowed within blocks in Rust) and jump straight to the current module
1522     // graph node.
1523     //
1524     // Named implementations are handled separately. When we find a method
1525     // call, we consult the module node to find all of the implementations in
1526     // scope. This information is lazily cached in the module node. We then
1527     // generate a fake "implementation scope" containing all the
1528     // implementations thus found, for compatibility with old resolve pass.
1529
1530     fn with_scope<F>(&mut self, id: NodeId, f: F)
1531         where F: FnOnce(&mut Resolver)
1532     {
1533         let module = self.module_map.get(&id).cloned(); // clones a reference
1534         if let Some(module) = module {
1535             // Move down in the graph.
1536             let orig_module = ::std::mem::replace(&mut self.current_module, module);
1537             self.value_ribs.push(Rib::new(ModuleRibKind(module)));
1538             self.type_ribs.push(Rib::new(ModuleRibKind(module)));
1539
1540             f(self);
1541
1542             self.current_module = orig_module;
1543             self.value_ribs.pop();
1544             self.type_ribs.pop();
1545         } else {
1546             f(self);
1547         }
1548     }
1549
1550     /// Searches the current set of local scopes for labels.
1551     /// Stops after meeting a closure.
1552     fn search_label(&self, name: Name) -> Option<Def> {
1553         for rib in self.label_ribs.iter().rev() {
1554             match rib.kind {
1555                 NormalRibKind => {
1556                     // Continue
1557                 }
1558                 _ => {
1559                     // Do not resolve labels across function boundary
1560                     return None;
1561                 }
1562             }
1563             let result = rib.bindings.get(&name).cloned();
1564             if result.is_some() {
1565                 return result;
1566             }
1567         }
1568         None
1569     }
1570
1571     fn resolve_crate(&mut self, krate: &Crate) {
1572         debug!("(resolving crate) starting");
1573         self.current_module = self.graph_root;
1574         visit::walk_crate(self, krate);
1575     }
1576
1577     fn resolve_item(&mut self, item: &Item) {
1578         let name = item.ident.name;
1579
1580         debug!("(resolving item) resolving {}", name);
1581
1582         match item.node {
1583             ItemKind::Enum(_, ref generics) |
1584             ItemKind::Ty(_, ref generics) |
1585             ItemKind::Struct(_, ref generics) => {
1586                 self.with_type_parameter_rib(HasTypeParameters(generics, TypeSpace, ItemRibKind),
1587                                              |this| visit::walk_item(this, item));
1588             }
1589             ItemKind::Fn(_, _, _, _, ref generics, _) => {
1590                 self.with_type_parameter_rib(HasTypeParameters(generics, FnSpace, ItemRibKind),
1591                                              |this| visit::walk_item(this, item));
1592             }
1593
1594             ItemKind::DefaultImpl(_, ref trait_ref) => {
1595                 self.with_optional_trait_ref(Some(trait_ref), |_, _| {});
1596             }
1597             ItemKind::Impl(_, _, ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1598                 self.resolve_implementation(generics,
1599                                             opt_trait_ref,
1600                                             &self_type,
1601                                             item.id,
1602                                             impl_items),
1603
1604             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1605                 // Create a new rib for the trait-wide type parameters.
1606                 self.with_type_parameter_rib(HasTypeParameters(generics,
1607                                                                TypeSpace,
1608                                                                ItemRibKind),
1609                                              |this| {
1610                     let local_def_id = this.definitions.local_def_id(item.id);
1611                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1612                         this.visit_generics(generics);
1613                         walk_list!(this, visit_ty_param_bound, bounds);
1614
1615                         for trait_item in trait_items {
1616                             match trait_item.node {
1617                                 TraitItemKind::Const(_, ref default) => {
1618                                     // Only impose the restrictions of
1619                                     // ConstRibKind if there's an actual constant
1620                                     // expression in a provided default.
1621                                     if default.is_some() {
1622                                         this.with_constant_rib(|this| {
1623                                             visit::walk_trait_item(this, trait_item)
1624                                         });
1625                                     } else {
1626                                         visit::walk_trait_item(this, trait_item)
1627                                     }
1628                                 }
1629                                 TraitItemKind::Method(ref sig, _) => {
1630                                     let type_parameters =
1631                                         HasTypeParameters(&sig.generics,
1632                                                           FnSpace,
1633                                                           MethodRibKind(!sig.decl.has_self()));
1634                                     this.with_type_parameter_rib(type_parameters, |this| {
1635                                         visit::walk_trait_item(this, trait_item)
1636                                     });
1637                                 }
1638                                 TraitItemKind::Type(..) => {
1639                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1640                                         visit::walk_trait_item(this, trait_item)
1641                                     });
1642                                 }
1643                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1644                             };
1645                         }
1646                     });
1647                 });
1648             }
1649
1650             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1651                 self.with_scope(item.id, |this| {
1652                     visit::walk_item(this, item);
1653                 });
1654             }
1655
1656             ItemKind::Const(..) | ItemKind::Static(..) => {
1657                 self.with_constant_rib(|this| {
1658                     visit::walk_item(this, item);
1659                 });
1660             }
1661
1662             ItemKind::Use(ref view_path) => {
1663                 match view_path.node {
1664                     ast::ViewPathList(ref prefix, ref items) => {
1665                         // Resolve prefix of an import with empty braces (issue #28388)
1666                         if items.is_empty() && !prefix.segments.is_empty() {
1667                             match self.resolve_crate_relative_path(prefix.span,
1668                                                                    &prefix.segments,
1669                                                                    TypeNS) {
1670                                 Ok(binding) => {
1671                                     let def = binding.def().unwrap();
1672                                     self.record_def(item.id, PathResolution::new(def));
1673                                 }
1674                                 Err(true) => self.record_def(item.id, err_path_resolution()),
1675                                 Err(false) => {
1676                                     resolve_error(self,
1677                                                   prefix.span,
1678                                                   ResolutionError::FailedToResolve(
1679                                                       &path_names_to_string(prefix, 0)));
1680                                     self.record_def(item.id, err_path_resolution());
1681                                 }
1682                             }
1683                         }
1684                     }
1685                     _ => {}
1686                 }
1687             }
1688
1689             ItemKind::ExternCrate(_) => {
1690                 // do nothing, these are just around to be encoded
1691             }
1692
1693             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1694         }
1695     }
1696
1697     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1698         where F: FnOnce(&mut Resolver)
1699     {
1700         match type_parameters {
1701             HasTypeParameters(generics, space, rib_kind) => {
1702                 let mut function_type_rib = Rib::new(rib_kind);
1703                 let mut seen_bindings = HashSet::new();
1704                 for (index, type_parameter) in generics.ty_params.iter().enumerate() {
1705                     let name = type_parameter.ident.name;
1706                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1707
1708                     if seen_bindings.contains(&name) {
1709                         resolve_error(self,
1710                                       type_parameter.span,
1711                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name));
1712                     }
1713                     seen_bindings.insert(name);
1714
1715                     // plain insert (no renaming)
1716                     let def_id = self.definitions.local_def_id(type_parameter.id);
1717                     let def = Def::TyParam(space, index as u32, def_id, name);
1718                     function_type_rib.bindings.insert(name, def);
1719                 }
1720                 self.type_ribs.push(function_type_rib);
1721             }
1722
1723             NoTypeParameters => {
1724                 // Nothing to do.
1725             }
1726         }
1727
1728         f(self);
1729
1730         if let HasTypeParameters(..) = type_parameters {
1731             self.type_ribs.pop();
1732         }
1733     }
1734
1735     fn with_label_rib<F>(&mut self, f: F)
1736         where F: FnOnce(&mut Resolver)
1737     {
1738         self.label_ribs.push(Rib::new(NormalRibKind));
1739         f(self);
1740         self.label_ribs.pop();
1741     }
1742
1743     fn with_constant_rib<F>(&mut self, f: F)
1744         where F: FnOnce(&mut Resolver)
1745     {
1746         self.value_ribs.push(Rib::new(ConstantItemRibKind));
1747         self.type_ribs.push(Rib::new(ConstantItemRibKind));
1748         f(self);
1749         self.type_ribs.pop();
1750         self.value_ribs.pop();
1751     }
1752
1753     fn resolve_function(&mut self,
1754                         rib_kind: RibKind<'a>,
1755                         declaration: &FnDecl,
1756                         block: &Block) {
1757         // Create a value rib for the function.
1758         self.value_ribs.push(Rib::new(rib_kind));
1759
1760         // Create a label rib for the function.
1761         self.label_ribs.push(Rib::new(rib_kind));
1762
1763         // Add each argument to the rib.
1764         let mut bindings_list = HashMap::new();
1765         for argument in &declaration.inputs {
1766             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
1767
1768             self.visit_ty(&argument.ty);
1769
1770             debug!("(resolving function) recorded argument");
1771         }
1772         visit::walk_fn_ret_ty(self, &declaration.output);
1773
1774         // Resolve the function body.
1775         self.visit_block(block);
1776
1777         debug!("(resolving function) leaving function");
1778
1779         self.label_ribs.pop();
1780         self.value_ribs.pop();
1781     }
1782
1783     fn resolve_trait_reference(&mut self,
1784                                id: NodeId,
1785                                trait_path: &Path,
1786                                path_depth: usize)
1787                                -> Result<PathResolution, ()> {
1788         self.resolve_path(id, trait_path, path_depth, TypeNS).and_then(|path_res| {
1789             if let Def::Trait(_) = path_res.base_def {
1790                 debug!("(resolving trait) found trait def: {:?}", path_res);
1791                 Ok(path_res)
1792             } else {
1793                 let mut err =
1794                     resolve_struct_error(self,
1795                                   trait_path.span,
1796                                   ResolutionError::IsNotATrait(&path_names_to_string(trait_path,
1797                                                                                       path_depth)));
1798
1799                 // If it's a typedef, give a note
1800                 if let Def::TyAlias(..) = path_res.base_def {
1801                     let trait_name = trait_path.segments.last().unwrap().identifier.name;
1802                     err.span_label(trait_path.span,
1803                                    &format!("`{}` is not a trait", trait_name));
1804
1805                     let definition_site = {
1806                         let segments = &trait_path.segments;
1807                         if trait_path.global {
1808                             self.resolve_crate_relative_path(trait_path.span, segments, TypeNS)
1809                         } else {
1810                             self.resolve_module_relative_path(trait_path.span, segments, TypeNS)
1811                         }.map(|binding| binding.span).unwrap_or(syntax_pos::DUMMY_SP)
1812                     };
1813
1814                     if definition_site != syntax_pos::DUMMY_SP {
1815                         err.span_label(definition_site,
1816                                        &format!("type aliases cannot be used for traits"));
1817                     }
1818                 }
1819                 err.emit();
1820                 Err(true)
1821             }
1822         }).map_err(|error_reported| {
1823             if error_reported { return }
1824
1825             // find possible candidates
1826             let trait_name = trait_path.segments.last().unwrap().identifier.name;
1827             let candidates =
1828                 self.lookup_candidates(
1829                     trait_name,
1830                     TypeNS,
1831                     |def| match def {
1832                         Def::Trait(_) => true,
1833                         _             => false,
1834                     },
1835                 );
1836
1837             // create error object
1838             let name = &path_names_to_string(trait_path, path_depth);
1839             let error =
1840                 ResolutionError::UndeclaredTraitName(
1841                     name,
1842                     candidates,
1843                 );
1844
1845             resolve_error(self, trait_path.span, error);
1846         })
1847     }
1848
1849     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1850         where F: FnOnce(&mut Resolver) -> T
1851     {
1852         // Handle nested impls (inside fn bodies)
1853         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1854         let result = f(self);
1855         self.current_self_type = previous_value;
1856         result
1857     }
1858
1859     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1860         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1861     {
1862         let mut new_val = None;
1863         let mut new_id = None;
1864         if let Some(trait_ref) = opt_trait_ref {
1865             if let Ok(path_res) = self.resolve_trait_reference(trait_ref.ref_id,
1866                                                                &trait_ref.path,
1867                                                                0) {
1868                 assert!(path_res.depth == 0);
1869                 self.record_def(trait_ref.ref_id, path_res);
1870                 new_val = Some((path_res.base_def.def_id(), trait_ref.clone()));
1871                 new_id = Some(path_res.base_def.def_id());
1872             } else {
1873                 self.record_def(trait_ref.ref_id, err_path_resolution());
1874             }
1875             visit::walk_trait_ref(self, trait_ref);
1876         }
1877         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1878         let result = f(self, new_id);
1879         self.current_trait_ref = original_trait_ref;
1880         result
1881     }
1882
1883     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
1884         where F: FnOnce(&mut Resolver)
1885     {
1886         let mut self_type_rib = Rib::new(NormalRibKind);
1887
1888         // plain insert (no renaming, types are not currently hygienic....)
1889         self_type_rib.bindings.insert(keywords::SelfType.name(), self_def);
1890         self.type_ribs.push(self_type_rib);
1891         f(self);
1892         self.type_ribs.pop();
1893     }
1894
1895     fn resolve_implementation(&mut self,
1896                               generics: &Generics,
1897                               opt_trait_reference: &Option<TraitRef>,
1898                               self_type: &Ty,
1899                               item_id: NodeId,
1900                               impl_items: &[ImplItem]) {
1901         // If applicable, create a rib for the type parameters.
1902         self.with_type_parameter_rib(HasTypeParameters(generics,
1903                                                        TypeSpace,
1904                                                        ItemRibKind),
1905                                      |this| {
1906             // Resolve the type parameters.
1907             this.visit_generics(generics);
1908
1909             // Resolve the trait reference, if necessary.
1910             this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1911                 // Resolve the self type.
1912                 this.visit_ty(self_type);
1913
1914                 this.with_self_rib(Def::SelfTy(trait_id, Some(item_id)), |this| {
1915                     this.with_current_self_type(self_type, |this| {
1916                         for impl_item in impl_items {
1917                             this.resolve_visibility(&impl_item.vis);
1918                             match impl_item.node {
1919                                 ImplItemKind::Const(..) => {
1920                                     // If this is a trait impl, ensure the const
1921                                     // exists in trait
1922                                     this.check_trait_item(impl_item.ident.name,
1923                                                           impl_item.span,
1924                                         |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
1925                                     visit::walk_impl_item(this, impl_item);
1926                                 }
1927                                 ImplItemKind::Method(ref sig, _) => {
1928                                     // If this is a trait impl, ensure the method
1929                                     // exists in trait
1930                                     this.check_trait_item(impl_item.ident.name,
1931                                                           impl_item.span,
1932                                         |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
1933
1934                                     // We also need a new scope for the method-
1935                                     // specific type parameters.
1936                                     let type_parameters =
1937                                         HasTypeParameters(&sig.generics,
1938                                                           FnSpace,
1939                                                           MethodRibKind(!sig.decl.has_self()));
1940                                     this.with_type_parameter_rib(type_parameters, |this| {
1941                                         visit::walk_impl_item(this, impl_item);
1942                                     });
1943                                 }
1944                                 ImplItemKind::Type(ref ty) => {
1945                                     // If this is a trait impl, ensure the type
1946                                     // exists in trait
1947                                     this.check_trait_item(impl_item.ident.name,
1948                                                           impl_item.span,
1949                                         |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
1950
1951                                     this.visit_ty(ty);
1952                                 }
1953                                 ImplItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1954                             }
1955                         }
1956                     });
1957                 });
1958             });
1959         });
1960     }
1961
1962     fn check_trait_item<F>(&self, name: Name, span: Span, err: F)
1963         where F: FnOnce(Name, &str) -> ResolutionError
1964     {
1965         // If there is a TraitRef in scope for an impl, then the method must be in the
1966         // trait.
1967         if let Some((did, ref trait_ref)) = self.current_trait_ref {
1968             if !self.trait_item_map.contains_key(&(name, did)) {
1969                 let path_str = path_names_to_string(&trait_ref.path, 0);
1970                 resolve_error(self, span, err(name, &path_str));
1971             }
1972         }
1973     }
1974
1975     fn resolve_local(&mut self, local: &Local) {
1976         // Resolve the type.
1977         walk_list!(self, visit_ty, &local.ty);
1978
1979         // Resolve the initializer.
1980         walk_list!(self, visit_expr, &local.init);
1981
1982         // Resolve the pattern.
1983         self.resolve_pattern(&local.pat, PatternSource::Let, &mut HashMap::new());
1984     }
1985
1986     // build a map from pattern identifiers to binding-info's.
1987     // this is done hygienically. This could arise for a macro
1988     // that expands into an or-pattern where one 'x' was from the
1989     // user and one 'x' came from the macro.
1990     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1991         let mut binding_map = HashMap::new();
1992
1993         pat.walk(&mut |pat| {
1994             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
1995                 if sub_pat.is_some() || match self.def_map.get(&pat.id) {
1996                     Some(&PathResolution { base_def: Def::Local(..), .. }) => true,
1997                     _ => false,
1998                 } {
1999                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
2000                     binding_map.insert(mtwt::resolve(ident.node), binding_info);
2001                 }
2002             }
2003             true
2004         });
2005
2006         binding_map
2007     }
2008
2009     // check that all of the arms in an or-pattern have exactly the
2010     // same set of bindings, with the same binding modes for each.
2011     fn check_consistent_bindings(&mut self, arm: &Arm) {
2012         if arm.pats.is_empty() {
2013             return;
2014         }
2015         let map_0 = self.binding_mode_map(&arm.pats[0]);
2016         for (i, p) in arm.pats.iter().enumerate() {
2017             let map_i = self.binding_mode_map(&p);
2018
2019             for (&key, &binding_0) in &map_0 {
2020                 match map_i.get(&key) {
2021                     None => {
2022                         resolve_error(self,
2023                                       p.span,
2024                                       ResolutionError::VariableNotBoundInPattern(key, 1, i + 1));
2025                     }
2026                     Some(binding_i) => {
2027                         if binding_0.binding_mode != binding_i.binding_mode {
2028                             resolve_error(self,
2029                                           binding_i.span,
2030                                           ResolutionError::VariableBoundWithDifferentMode(key,
2031                                                                                           i + 1));
2032                         }
2033                     }
2034                 }
2035             }
2036
2037             for (&key, &binding) in &map_i {
2038                 if !map_0.contains_key(&key) {
2039                     resolve_error(self,
2040                                   binding.span,
2041                                   ResolutionError::VariableNotBoundInPattern(key, i + 1, 1));
2042                 }
2043             }
2044         }
2045     }
2046
2047     fn resolve_arm(&mut self, arm: &Arm) {
2048         self.value_ribs.push(Rib::new(NormalRibKind));
2049
2050         let mut bindings_list = HashMap::new();
2051         for pattern in &arm.pats {
2052             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2053         }
2054
2055         // This has to happen *after* we determine which
2056         // pat_idents are variants
2057         self.check_consistent_bindings(arm);
2058
2059         walk_list!(self, visit_expr, &arm.guard);
2060         self.visit_expr(&arm.body);
2061
2062         self.value_ribs.pop();
2063     }
2064
2065     fn resolve_block(&mut self, block: &Block) {
2066         debug!("(resolving block) entering block");
2067         // Move down in the graph, if there's an anonymous module rooted here.
2068         let orig_module = self.current_module;
2069         let anonymous_module = self.module_map.get(&block.id).cloned(); // clones a reference
2070
2071         if let Some(anonymous_module) = anonymous_module {
2072             debug!("(resolving block) found anonymous module, moving down");
2073             self.value_ribs.push(Rib::new(ModuleRibKind(anonymous_module)));
2074             self.type_ribs.push(Rib::new(ModuleRibKind(anonymous_module)));
2075             self.current_module = anonymous_module;
2076         } else {
2077             self.value_ribs.push(Rib::new(NormalRibKind));
2078         }
2079
2080         // Descend into the block.
2081         visit::walk_block(self, block);
2082
2083         // Move back up.
2084         self.current_module = orig_module;
2085         self.value_ribs.pop();
2086         if let Some(_) = anonymous_module {
2087             self.type_ribs.pop();
2088         }
2089         debug!("(resolving block) leaving block");
2090     }
2091
2092     fn resolve_type(&mut self, ty: &Ty) {
2093         match ty.node {
2094             TyKind::Path(ref maybe_qself, ref path) => {
2095                 // This is a path in the type namespace. Walk through scopes
2096                 // looking for it.
2097                 if let Some(def) = self.resolve_possibly_assoc_item(ty.id, maybe_qself.as_ref(),
2098                                                                     path, TypeNS) {
2099                     match def.base_def {
2100                         Def::Mod(..) if def.depth == 0 => {
2101                             self.session.span_err(path.span, "expected type, found module");
2102                             self.record_def(ty.id, err_path_resolution());
2103                         }
2104                         _ => {
2105                             // Write the result into the def map.
2106                             debug!("(resolving type) writing resolution for `{}` (id {}) = {:?}",
2107                                    path_names_to_string(path, 0), ty.id, def);
2108                             self.record_def(ty.id, def);
2109                         }
2110                     }
2111                 } else {
2112                     self.record_def(ty.id, err_path_resolution());
2113
2114                     // Keep reporting some errors even if they're ignored above.
2115                     if let Err(true) = self.resolve_path(ty.id, path, 0, TypeNS) {
2116                         // `resolve_path` already reported the error
2117                     } else {
2118                         let kind = if maybe_qself.is_some() {
2119                             "associated type"
2120                         } else {
2121                             "type name"
2122                         };
2123
2124                         let is_invalid_self_type_name = path.segments.len() > 0 &&
2125                                                         maybe_qself.is_none() &&
2126                                                         path.segments[0].identifier.name ==
2127                                                         keywords::SelfType.name();
2128                         if is_invalid_self_type_name {
2129                             resolve_error(self,
2130                                           ty.span,
2131                                           ResolutionError::SelfUsedOutsideImplOrTrait);
2132                         } else {
2133                             let segment = path.segments.last();
2134                             let segment = segment.expect("missing name in path");
2135                             let type_name = segment.identifier.name;
2136
2137                             let candidates =
2138                                 self.lookup_candidates(
2139                                     type_name,
2140                                     TypeNS,
2141                                     |def| match def {
2142                                         Def::Trait(_) |
2143                                         Def::Enum(_) |
2144                                         Def::Struct(_) |
2145                                         Def::TyAlias(_) => true,
2146                                         _               => false,
2147                                     },
2148                                 );
2149
2150                             // create error object
2151                             let name = &path_names_to_string(path, 0);
2152                             let error =
2153                                 ResolutionError::UseOfUndeclared(
2154                                     kind,
2155                                     name,
2156                                     candidates,
2157                                 );
2158
2159                             resolve_error(self, ty.span, error);
2160                         }
2161                     }
2162                 }
2163             }
2164             _ => {}
2165         }
2166         // Resolve embedded types.
2167         visit::walk_ty(self, ty);
2168     }
2169
2170     fn fresh_binding(&mut self,
2171                      ident: &ast::SpannedIdent,
2172                      pat_id: NodeId,
2173                      outer_pat_id: NodeId,
2174                      pat_src: PatternSource,
2175                      bindings: &mut HashMap<Name, NodeId>)
2176                      -> PathResolution {
2177         // Add the binding to the local ribs, if it
2178         // doesn't already exist in the bindings map. (We
2179         // must not add it if it's in the bindings map
2180         // because that breaks the assumptions later
2181         // passes make about or-patterns.)
2182         let renamed = mtwt::resolve(ident.node);
2183         let def = match bindings.get(&renamed).cloned() {
2184             Some(id) if id == outer_pat_id => {
2185                 // `Variant(a, a)`, error
2186                 resolve_error(
2187                     self,
2188                     ident.span,
2189                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2190                         &ident.node.name.as_str())
2191                 );
2192                 Def::Err
2193             }
2194             Some(..) if pat_src == PatternSource::FnParam => {
2195                 // `fn f(a: u8, a: u8)`, error
2196                 resolve_error(
2197                     self,
2198                     ident.span,
2199                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2200                         &ident.node.name.as_str())
2201                 );
2202                 Def::Err
2203             }
2204             Some(..) if pat_src == PatternSource::Match => {
2205                 // `Variant1(a) | Variant2(a)`, ok
2206                 // Reuse definition from the first `a`.
2207                 self.value_ribs.last_mut().unwrap().bindings[&renamed]
2208             }
2209             Some(..) => {
2210                 span_bug!(ident.span, "two bindings with the same name from \
2211                                        unexpected pattern source {:?}", pat_src);
2212             }
2213             None => {
2214                 // A completely fresh binding, add to the lists.
2215                 // FIXME: Later stages are not ready to deal with `Def::Err` here yet, so
2216                 // define `Invalid` bindings as `Def::Local`, just don't add them to the lists.
2217                 let def = Def::Local(self.definitions.local_def_id(pat_id), pat_id);
2218                 if ident.node.name != keywords::Invalid.name() {
2219                     bindings.insert(renamed, outer_pat_id);
2220                     self.value_ribs.last_mut().unwrap().bindings.insert(renamed, def);
2221                 }
2222                 def
2223             }
2224         };
2225
2226         PathResolution::new(def)
2227     }
2228
2229     fn resolve_pattern_path<ExpectedFn>(&mut self,
2230                                         pat_id: NodeId,
2231                                         qself: Option<&QSelf>,
2232                                         path: &Path,
2233                                         namespace: Namespace,
2234                                         expected_fn: ExpectedFn,
2235                                         expected_what: &str)
2236         where ExpectedFn: FnOnce(Def) -> bool
2237     {
2238         let resolution = if let Some(resolution) = self.resolve_possibly_assoc_item(pat_id,
2239                                                                         qself, path, namespace) {
2240             if resolution.depth == 0 {
2241                 if expected_fn(resolution.base_def) {
2242                     resolution
2243                 } else {
2244                     resolve_error(
2245                         self,
2246                         path.span,
2247                         ResolutionError::PatPathUnexpected(expected_what,
2248                                                            resolution.kind_name(), path)
2249                     );
2250                     err_path_resolution()
2251                 }
2252             } else {
2253                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2254                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2255                 // it needs to be added to the trait map.
2256                 if namespace == ValueNS {
2257                     let item_name = path.segments.last().unwrap().identifier.name;
2258                     let traits = self.get_traits_containing_item(item_name);
2259                     self.trait_map.insert(pat_id, traits);
2260                 }
2261                 resolution
2262             }
2263         } else {
2264             if let Err(false) = self.resolve_path(pat_id, path, 0, namespace) {
2265                 resolve_error(
2266                     self,
2267                     path.span,
2268                     ResolutionError::PatPathUnresolved(expected_what, path)
2269                 );
2270             }
2271             err_path_resolution()
2272         };
2273
2274         self.record_def(pat_id, resolution);
2275     }
2276
2277     fn resolve_pattern(&mut self,
2278                        pat: &Pat,
2279                        pat_src: PatternSource,
2280                        // Maps idents to the node ID for the
2281                        // outermost pattern that binds them.
2282                        bindings: &mut HashMap<Name, NodeId>) {
2283         // Visit all direct subpatterns of this pattern.
2284         let outer_pat_id = pat.id;
2285         pat.walk(&mut |pat| {
2286             match pat.node {
2287                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2288                     // First try to resolve the identifier as some existing
2289                     // entity, then fall back to a fresh binding.
2290                     let resolution = if let Ok(resolution) = self.resolve_path(pat.id,
2291                                 &Path::from_ident(ident.span, ident.node), 0, ValueNS) {
2292                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2293                                              bmode != BindingMode::ByValue(Mutability::Immutable);
2294                         match resolution.base_def {
2295                             Def::Struct(..) | Def::Variant(..) |
2296                             Def::Const(..) | Def::AssociatedConst(..) if !always_binding => {
2297                                 // A constant, unit variant, etc pattern.
2298                                 resolution
2299                             }
2300                             Def::Struct(..) | Def::Variant(..) |
2301                             Def::Const(..) | Def::AssociatedConst(..) | Def::Static(..) => {
2302                                 // A fresh binding that shadows something unacceptable.
2303                                 resolve_error(
2304                                     self,
2305                                     ident.span,
2306                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2307                                         pat_src.descr(), resolution.kind_name(), ident.node.name)
2308                                 );
2309                                 err_path_resolution()
2310                             }
2311                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2312                                 // These entities are explicitly allowed
2313                                 // to be shadowed by fresh bindings.
2314                                 self.fresh_binding(ident, pat.id, outer_pat_id,
2315                                                    pat_src, bindings)
2316                             }
2317                             def => {
2318                                 span_bug!(ident.span, "unexpected definition for an \
2319                                                        identifier in pattern {:?}", def);
2320                             }
2321                         }
2322                     } else {
2323                         // Fall back to a fresh binding.
2324                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2325                     };
2326
2327                     self.record_def(pat.id, resolution);
2328                 }
2329
2330                 PatKind::TupleStruct(ref path, _, _) => {
2331                     self.resolve_pattern_path(pat.id, None, path, ValueNS, |def| {
2332                         match def {
2333                             Def::Struct(..) | Def::Variant(..) | Def::Err => true,
2334                             _ => false,
2335                         }
2336                     }, "variant or struct");
2337                 }
2338
2339                 PatKind::Path(ref qself, ref path) => {
2340                     self.resolve_pattern_path(pat.id, qself.as_ref(), path, ValueNS, |def| {
2341                         match def {
2342                             Def::Struct(..) | Def::Variant(..) |
2343                             Def::Const(..) | Def::AssociatedConst(..) | Def::Err => true,
2344                             _ => false,
2345                         }
2346                     }, "variant, struct or constant");
2347                 }
2348
2349                 PatKind::Struct(ref path, _, _) => {
2350                     self.resolve_pattern_path(pat.id, None, path, TypeNS, |def| {
2351                         match def {
2352                             Def::Struct(..) | Def::Variant(..) |
2353                             Def::TyAlias(..) | Def::AssociatedTy(..) | Def::Err => true,
2354                             _ => false,
2355                         }
2356                     }, "variant, struct or type alias");
2357                 }
2358
2359                 _ => {}
2360             }
2361             true
2362         });
2363
2364         visit::walk_pat(self, pat);
2365     }
2366
2367     /// Handles paths that may refer to associated items
2368     fn resolve_possibly_assoc_item(&mut self,
2369                                    id: NodeId,
2370                                    maybe_qself: Option<&QSelf>,
2371                                    path: &Path,
2372                                    namespace: Namespace)
2373                                    -> Option<PathResolution> {
2374         let max_assoc_types;
2375
2376         match maybe_qself {
2377             Some(qself) => {
2378                 if qself.position == 0 {
2379                     // FIXME: Create some fake resolution that can't possibly be a type.
2380                     return Some(PathResolution {
2381                         base_def: Def::Mod(self.definitions.local_def_id(ast::CRATE_NODE_ID)),
2382                         depth: path.segments.len(),
2383                     });
2384                 }
2385                 max_assoc_types = path.segments.len() - qself.position;
2386                 // Make sure the trait is valid.
2387                 let _ = self.resolve_trait_reference(id, path, max_assoc_types);
2388             }
2389             None => {
2390                 max_assoc_types = path.segments.len();
2391             }
2392         }
2393
2394         let mut resolution = self.with_no_errors(|this| {
2395             this.resolve_path(id, path, 0, namespace).ok()
2396         });
2397         for depth in 1..max_assoc_types {
2398             if resolution.is_some() {
2399                 break;
2400             }
2401             self.with_no_errors(|this| {
2402                 let partial_resolution = this.resolve_path(id, path, depth, TypeNS).ok();
2403                 if let Some(Def::Mod(..)) = partial_resolution.map(|r| r.base_def) {
2404                     // Modules cannot have associated items
2405                 } else {
2406                     resolution = partial_resolution;
2407                 }
2408             });
2409         }
2410         resolution
2411     }
2412
2413     /// Skips `path_depth` trailing segments, which is also reflected in the
2414     /// returned value. See `hir::def::PathResolution` for more info.
2415     fn resolve_path(&mut self, id: NodeId, path: &Path, path_depth: usize, namespace: Namespace)
2416                     -> Result<PathResolution, bool /* true if an error was reported */ > {
2417         debug!("resolve_path(id={:?} path={:?}, path_depth={:?})", id, path, path_depth);
2418
2419         let span = path.span;
2420         let segments = &path.segments[..path.segments.len() - path_depth];
2421
2422         let mk_res = |def| PathResolution { base_def: def, depth: path_depth };
2423
2424         if path.global {
2425             let binding = self.resolve_crate_relative_path(span, segments, namespace);
2426             return binding.map(|binding| mk_res(binding.def().unwrap()));
2427         }
2428
2429         // Try to find a path to an item in a module.
2430         let last_ident = segments.last().unwrap().identifier;
2431         // Resolve a single identifier with fallback to primitive types
2432         let resolve_identifier_with_fallback = |this: &mut Self, record_used| {
2433             let def = this.resolve_identifier(last_ident, namespace, record_used);
2434             match def {
2435                 None | Some(LocalDef{def: Def::Mod(..), ..}) if namespace == TypeNS =>
2436                     this.primitive_type_table
2437                         .primitive_types
2438                         .get(&last_ident.name)
2439                         .map_or(def, |prim_ty| Some(LocalDef::from_def(Def::PrimTy(*prim_ty)))),
2440                 _ => def
2441             }
2442         };
2443
2444         if segments.len() == 1 {
2445             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2446             // don't report an error right away, but try to fallback to a primitive type.
2447             // So, we are still able to successfully resolve something like
2448             //
2449             // use std::u8; // bring module u8 in scope
2450             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2451             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2452             //                     // not to non-existent std::u8::max_value
2453             // }
2454             //
2455             // Such behavior is required for backward compatibility.
2456             // The same fallback is used when `a` resolves to nothing.
2457             let def = resolve_identifier_with_fallback(self, true).ok_or(false);
2458             return def.and_then(|def| self.adjust_local_def(def, span).ok_or(true)).map(mk_res);
2459         }
2460
2461         let unqualified_def = resolve_identifier_with_fallback(self, false);
2462         let qualified_binding = self.resolve_module_relative_path(span, segments, namespace);
2463         match (qualified_binding, unqualified_def) {
2464             (Ok(binding), Some(ref ud)) if binding.def().unwrap() == ud.def => {
2465                 self.session
2466                     .add_lint(lint::builtin::UNUSED_QUALIFICATIONS,
2467                               id,
2468                               span,
2469                               "unnecessary qualification".to_string());
2470             }
2471             _ => {}
2472         }
2473
2474         qualified_binding.map(|binding| mk_res(binding.def().unwrap()))
2475     }
2476
2477     // Resolve a single identifier
2478     fn resolve_identifier(&mut self,
2479                           identifier: ast::Ident,
2480                           namespace: Namespace,
2481                           record_used: bool)
2482                           -> Option<LocalDef> {
2483         if identifier.name == keywords::Invalid.name() {
2484             return Some(LocalDef::from_def(Def::Err));
2485         }
2486
2487         self.resolve_ident_in_lexical_scope(identifier, namespace, record_used)
2488             .map(LexicalScopeBinding::local_def)
2489     }
2490
2491     // Resolve a local definition, potentially adjusting for closures.
2492     fn adjust_local_def(&mut self, local_def: LocalDef, span: Span) -> Option<Def> {
2493         let ribs = match local_def.ribs {
2494             Some((TypeNS, i)) => &self.type_ribs[i + 1..],
2495             Some((ValueNS, i)) => &self.value_ribs[i + 1..],
2496             _ => &[] as &[_],
2497         };
2498         let mut def = local_def.def;
2499         match def {
2500             Def::Upvar(..) => {
2501                 span_bug!(span, "unexpected {:?} in bindings", def)
2502             }
2503             Def::Local(_, node_id) => {
2504                 for rib in ribs {
2505                     match rib.kind {
2506                         NormalRibKind | ModuleRibKind(..) => {
2507                             // Nothing to do. Continue.
2508                         }
2509                         ClosureRibKind(function_id) => {
2510                             let prev_def = def;
2511                             let node_def_id = self.definitions.local_def_id(node_id);
2512
2513                             let seen = self.freevars_seen
2514                                            .entry(function_id)
2515                                            .or_insert_with(|| NodeMap());
2516                             if let Some(&index) = seen.get(&node_id) {
2517                                 def = Def::Upvar(node_def_id, node_id, index, function_id);
2518                                 continue;
2519                             }
2520                             let vec = self.freevars
2521                                           .entry(function_id)
2522                                           .or_insert_with(|| vec![]);
2523                             let depth = vec.len();
2524                             vec.push(Freevar {
2525                                 def: prev_def,
2526                                 span: span,
2527                             });
2528
2529                             def = Def::Upvar(node_def_id, node_id, depth, function_id);
2530                             seen.insert(node_id, depth);
2531                         }
2532                         ItemRibKind | MethodRibKind(_) => {
2533                             // This was an attempt to access an upvar inside a
2534                             // named function item. This is not allowed, so we
2535                             // report an error.
2536                             resolve_error(self,
2537                                           span,
2538                                           ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2539                             return None;
2540                         }
2541                         ConstantItemRibKind => {
2542                             // Still doesn't deal with upvars
2543                             resolve_error(self,
2544                                           span,
2545                                           ResolutionError::AttemptToUseNonConstantValueInConstant);
2546                             return None;
2547                         }
2548                     }
2549                 }
2550             }
2551             Def::TyParam(..) | Def::SelfTy(..) => {
2552                 for rib in ribs {
2553                     match rib.kind {
2554                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
2555                         ModuleRibKind(..) => {
2556                             // Nothing to do. Continue.
2557                         }
2558                         ItemRibKind => {
2559                             // This was an attempt to use a type parameter outside
2560                             // its scope.
2561
2562                             resolve_error(self,
2563                                           span,
2564                                           ResolutionError::TypeParametersFromOuterFunction);
2565                             return None;
2566                         }
2567                         ConstantItemRibKind => {
2568                             // see #9186
2569                             resolve_error(self, span, ResolutionError::OuterTypeParameterContext);
2570                             return None;
2571                         }
2572                     }
2573                 }
2574             }
2575             _ => {}
2576         }
2577         return Some(def);
2578     }
2579
2580     // resolve a "module-relative" path, e.g. a::b::c
2581     fn resolve_module_relative_path(&mut self,
2582                                     span: Span,
2583                                     segments: &[ast::PathSegment],
2584                                     namespace: Namespace)
2585                                     -> Result<&'a NameBinding<'a>,
2586                                               bool /* true if an error was reported */> {
2587         let module_path = segments.split_last()
2588                                   .unwrap()
2589                                   .1
2590                                   .iter()
2591                                   .map(|ps| ps.identifier.name)
2592                                   .collect::<Vec<_>>();
2593
2594         let containing_module;
2595         match self.resolve_module_path(&module_path, UseLexicalScope, span) {
2596             Failed(err) => {
2597                 let (span, msg) = match err {
2598                     Some((span, msg)) => (span, msg),
2599                     None => {
2600                         let msg = format!("Use of undeclared type or module `{}`",
2601                                           names_to_string(&module_path));
2602                         (span, msg)
2603                     }
2604                 };
2605
2606                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2607                 return Err(true);
2608             }
2609             Indeterminate => return Err(false),
2610             Success(resulting_module) => {
2611                 containing_module = resulting_module;
2612             }
2613         }
2614
2615         let name = segments.last().unwrap().identifier.name;
2616         let result = self.resolve_name_in_module(containing_module, name, namespace, false, true);
2617         result.success().map(|binding| {
2618             self.check_privacy(name, binding, span);
2619             binding
2620         }).ok_or(false)
2621     }
2622
2623     /// Invariant: This must be called only during main resolution, not during
2624     /// import resolution.
2625     fn resolve_crate_relative_path<T>(&mut self, span: Span, segments: &[T], namespace: Namespace)
2626                                       -> Result<&'a NameBinding<'a>,
2627                                                 bool /* true if an error was reported */>
2628         where T: Named,
2629     {
2630         let module_path = segments.split_last().unwrap().1.iter().map(T::name).collect::<Vec<_>>();
2631         let root_module = self.graph_root;
2632
2633         let containing_module;
2634         match self.resolve_module_path_from_root(root_module,
2635                                                  &module_path,
2636                                                  0,
2637                                                  span) {
2638             Failed(err) => {
2639                 let (span, msg) = match err {
2640                     Some((span, msg)) => (span, msg),
2641                     None => {
2642                         let msg = format!("Use of undeclared module `::{}`",
2643                                           names_to_string(&module_path));
2644                         (span, msg)
2645                     }
2646                 };
2647
2648                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2649                 return Err(true);
2650             }
2651
2652             Indeterminate => return Err(false),
2653
2654             Success(resulting_module) => {
2655                 containing_module = resulting_module;
2656             }
2657         }
2658
2659         let name = segments.last().unwrap().name();
2660         let result = self.resolve_name_in_module(containing_module, name, namespace, false, true);
2661         result.success().map(|binding| {
2662             self.check_privacy(name, binding, span);
2663             binding
2664         }).ok_or(false)
2665     }
2666
2667     fn with_no_errors<T, F>(&mut self, f: F) -> T
2668         where F: FnOnce(&mut Resolver) -> T
2669     {
2670         self.emit_errors = false;
2671         let rs = f(self);
2672         self.emit_errors = true;
2673         rs
2674     }
2675
2676     fn find_fallback_in_self_type(&mut self, name: Name) -> FallbackSuggestion {
2677         fn extract_node_id(t: &Ty) -> Option<NodeId> {
2678             match t.node {
2679                 TyKind::Path(None, _) => Some(t.id),
2680                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
2681                 // This doesn't handle the remaining `Ty` variants as they are not
2682                 // that commonly the self_type, it might be interesting to provide
2683                 // support for those in future.
2684                 _ => None,
2685             }
2686         }
2687
2688         if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
2689             // Look for a field with the same name in the current self_type.
2690             if let Some(resolution) = self.def_map.get(&node_id) {
2691                 match resolution.base_def {
2692                     Def::Enum(did) | Def::TyAlias(did) |
2693                     Def::Struct(did) | Def::Variant(_, did) if resolution.depth == 0 => {
2694                         if let Some(fields) = self.structs.get(&did) {
2695                             if fields.iter().any(|&field_name| name == field_name) {
2696                                 return Field;
2697                             }
2698                         }
2699                     }
2700                     _ => {}
2701                 }
2702             }
2703         }
2704
2705         // Look for a method in the current trait.
2706         if let Some((trait_did, ref trait_ref)) = self.current_trait_ref {
2707             if let Some(&is_static_method) = self.trait_item_map.get(&(name, trait_did)) {
2708                 if is_static_method {
2709                     return TraitMethod(path_names_to_string(&trait_ref.path, 0));
2710                 } else {
2711                     return TraitItem;
2712                 }
2713             }
2714         }
2715
2716         NoSuggestion
2717     }
2718
2719     fn find_best_match(&mut self, name: &str) -> SuggestionType {
2720         if let Some(macro_name) = self.session.available_macros
2721                                   .borrow().iter().find(|n| n.as_str() == name) {
2722             return SuggestionType::Macro(format!("{}!", macro_name));
2723         }
2724
2725         let names = self.value_ribs
2726                     .iter()
2727                     .rev()
2728                     .flat_map(|rib| rib.bindings.keys());
2729
2730         if let Some(found) = find_best_match_for_name(names, name, None) {
2731             if name != found {
2732                 return SuggestionType::Function(found);
2733             }
2734         } SuggestionType::NotFound
2735     }
2736
2737     fn resolve_labeled_block(&mut self, label: Option<ast::Ident>, id: NodeId, block: &Block) {
2738         if let Some(label) = label {
2739             let (label, def) = (mtwt::resolve(label), Def::Label(id));
2740             self.with_label_rib(|this| {
2741                 this.label_ribs.last_mut().unwrap().bindings.insert(label, def);
2742                 this.visit_block(block);
2743             });
2744         } else {
2745             self.visit_block(block);
2746         }
2747     }
2748
2749     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
2750         // First, record candidate traits for this expression if it could
2751         // result in the invocation of a method call.
2752
2753         self.record_candidate_traits_for_expr_if_necessary(expr);
2754
2755         // Next, resolve the node.
2756         match expr.node {
2757             ExprKind::Path(ref maybe_qself, ref path) => {
2758                 // This is a local path in the value namespace. Walk through
2759                 // scopes looking for it.
2760                 if let Some(path_res) = self.resolve_possibly_assoc_item(expr.id,
2761                                                             maybe_qself.as_ref(), path, ValueNS) {
2762                     // Check if struct variant
2763                     let is_struct_variant = if let Def::Variant(_, variant_id) = path_res.base_def {
2764                         self.structs.contains_key(&variant_id)
2765                     } else {
2766                         false
2767                     };
2768                     if is_struct_variant {
2769                         let _ = self.structs.contains_key(&path_res.base_def.def_id());
2770                         let path_name = path_names_to_string(path, 0);
2771
2772                         let mut err = resolve_struct_error(self,
2773                                         expr.span,
2774                                         ResolutionError::StructVariantUsedAsFunction(&path_name));
2775
2776                         let msg = format!("did you mean to write: `{} {{ /* fields */ }}`?",
2777                                           path_name);
2778                         if self.emit_errors {
2779                             err.help(&msg);
2780                         } else {
2781                             err.span_help(expr.span, &msg);
2782                         }
2783                         err.emit();
2784                         self.record_def(expr.id, err_path_resolution());
2785                     } else {
2786                         // Write the result into the def map.
2787                         debug!("(resolving expr) resolved `{}`",
2788                                path_names_to_string(path, 0));
2789
2790                         // Partial resolutions will need the set of traits in scope,
2791                         // so they can be completed during typeck.
2792                         if path_res.depth != 0 {
2793                             let method_name = path.segments.last().unwrap().identifier.name;
2794                             let traits = self.get_traits_containing_item(method_name);
2795                             self.trait_map.insert(expr.id, traits);
2796                         }
2797
2798                         self.record_def(expr.id, path_res);
2799                     }
2800                 } else {
2801                     // Be helpful if the name refers to a struct
2802                     // (The pattern matching def_tys where the id is in self.structs
2803                     // matches on regular structs while excluding tuple- and enum-like
2804                     // structs, which wouldn't result in this error.)
2805                     let path_name = path_names_to_string(path, 0);
2806                     let type_res = self.with_no_errors(|this| {
2807                         this.resolve_path(expr.id, path, 0, TypeNS)
2808                     });
2809
2810                     self.record_def(expr.id, err_path_resolution());
2811
2812                     if let Ok(Def::Struct(..)) = type_res.map(|r| r.base_def) {
2813                         let error_variant =
2814                             ResolutionError::StructVariantUsedAsFunction(&path_name);
2815                         let mut err = resolve_struct_error(self, expr.span, error_variant);
2816
2817                         let msg = format!("did you mean to write: `{} {{ /* fields */ }}`?",
2818                                           path_name);
2819
2820                         if self.emit_errors {
2821                             err.help(&msg);
2822                         } else {
2823                             err.span_help(expr.span, &msg);
2824                         }
2825                         err.emit();
2826                     } else {
2827                         // Keep reporting some errors even if they're ignored above.
2828                         if let Err(true) = self.resolve_path(expr.id, path, 0, ValueNS) {
2829                             // `resolve_path` already reported the error
2830                         } else {
2831                             let mut method_scope = false;
2832                             let mut is_static = false;
2833                             self.value_ribs.iter().rev().all(|rib| {
2834                                 method_scope = match rib.kind {
2835                                     MethodRibKind(is_static_) => {
2836                                         is_static = is_static_;
2837                                         true
2838                                     }
2839                                     ItemRibKind | ConstantItemRibKind => false,
2840                                     _ => return true, // Keep advancing
2841                                 };
2842                                 false // Stop advancing
2843                             });
2844
2845                             if method_scope &&
2846                                     &path_name[..] == keywords::SelfValue.name().as_str() {
2847                                 resolve_error(self,
2848                                               expr.span,
2849                                               ResolutionError::SelfNotAvailableInStaticMethod);
2850                             } else {
2851                                 let last_name = path.segments.last().unwrap().identifier.name;
2852                                 let (mut msg, is_field) =
2853                                     match self.find_fallback_in_self_type(last_name) {
2854                                     NoSuggestion => {
2855                                         // limit search to 5 to reduce the number
2856                                         // of stupid suggestions
2857                                         (match self.find_best_match(&path_name) {
2858                                             SuggestionType::Macro(s) => {
2859                                                 format!("the macro `{}`", s)
2860                                             }
2861                                             SuggestionType::Function(s) => format!("`{}`", s),
2862                                             SuggestionType::NotFound => "".to_string(),
2863                                         }, false)
2864                                     }
2865                                     Field => {
2866                                         (if is_static && method_scope {
2867                                             "".to_string()
2868                                         } else {
2869                                             format!("`self.{}`", path_name)
2870                                         }, true)
2871                                     }
2872                                     TraitItem => (format!("to call `self.{}`", path_name), false),
2873                                     TraitMethod(path_str) =>
2874                                         (format!("to call `{}::{}`", path_str, path_name), false),
2875                                 };
2876
2877                                 let mut context =  UnresolvedNameContext::Other;
2878                                 let mut def = Def::Err;
2879                                 if !msg.is_empty() {
2880                                     msg = format!(". Did you mean {}?", msg);
2881                                 } else {
2882                                     // we check if this a module and if so, we display a help
2883                                     // message
2884                                     let name_path = path.segments.iter()
2885                                                         .map(|seg| seg.identifier.name)
2886                                                         .collect::<Vec<_>>();
2887
2888                                     match self.resolve_module_path(&name_path[..],
2889                                                                    UseLexicalScope,
2890                                                                    expr.span) {
2891                                         Success(e) => {
2892                                             if let Some(def_type) = e.def {
2893                                                 def = def_type;
2894                                             }
2895                                             context = UnresolvedNameContext::PathIsMod(parent);
2896                                         },
2897                                         _ => {},
2898                                     };
2899                                 }
2900
2901                                 resolve_error(self,
2902                                               expr.span,
2903                                               ResolutionError::UnresolvedName {
2904                                                   path: &path_name,
2905                                                   message: &msg,
2906                                                   context: context,
2907                                                   is_static_method: method_scope && is_static,
2908                                                   is_field: is_field,
2909                                                   def: def,
2910                                               });
2911                             }
2912                         }
2913                     }
2914                 }
2915
2916                 visit::walk_expr(self, expr);
2917             }
2918
2919             ExprKind::Struct(ref path, _, _) => {
2920                 // Resolve the path to the structure it goes to. We don't
2921                 // check to ensure that the path is actually a structure; that
2922                 // is checked later during typeck.
2923                 match self.resolve_path(expr.id, path, 0, TypeNS) {
2924                     Ok(definition) => self.record_def(expr.id, definition),
2925                     Err(true) => self.record_def(expr.id, err_path_resolution()),
2926                     Err(false) => {
2927                         debug!("(resolving expression) didn't find struct def",);
2928
2929                         resolve_error(self,
2930                                       path.span,
2931                                       ResolutionError::DoesNotNameAStruct(
2932                                                                 &path_names_to_string(path, 0))
2933                                      );
2934                         self.record_def(expr.id, err_path_resolution());
2935                     }
2936                 }
2937
2938                 visit::walk_expr(self, expr);
2939             }
2940
2941             ExprKind::Loop(_, Some(label)) | ExprKind::While(_, _, Some(label)) => {
2942                 self.with_label_rib(|this| {
2943                     let def = Def::Label(expr.id);
2944
2945                     {
2946                         let rib = this.label_ribs.last_mut().unwrap();
2947                         rib.bindings.insert(mtwt::resolve(label.node), def);
2948                     }
2949
2950                     visit::walk_expr(this, expr);
2951                 })
2952             }
2953
2954             ExprKind::Break(Some(label)) | ExprKind::Continue(Some(label)) => {
2955                 match self.search_label(mtwt::resolve(label.node)) {
2956                     None => {
2957                         self.record_def(expr.id, err_path_resolution());
2958                         resolve_error(self,
2959                                       label.span,
2960                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()))
2961                     }
2962                     Some(def @ Def::Label(_)) => {
2963                         // Since this def is a label, it is never read.
2964                         self.record_def(expr.id, PathResolution::new(def))
2965                     }
2966                     Some(_) => {
2967                         span_bug!(expr.span, "label wasn't mapped to a label def!")
2968                     }
2969                 }
2970             }
2971
2972             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
2973                 self.visit_expr(subexpression);
2974
2975                 self.value_ribs.push(Rib::new(NormalRibKind));
2976                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut HashMap::new());
2977                 self.visit_block(if_block);
2978                 self.value_ribs.pop();
2979
2980                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
2981             }
2982
2983             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
2984                 self.visit_expr(subexpression);
2985                 self.value_ribs.push(Rib::new(NormalRibKind));
2986                 self.resolve_pattern(pattern, PatternSource::WhileLet, &mut HashMap::new());
2987
2988                 self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
2989
2990                 self.value_ribs.pop();
2991             }
2992
2993             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
2994                 self.visit_expr(subexpression);
2995                 self.value_ribs.push(Rib::new(NormalRibKind));
2996                 self.resolve_pattern(pattern, PatternSource::For, &mut HashMap::new());
2997
2998                 self.resolve_labeled_block(label.map(|l| l.node), expr.id, block);
2999
3000                 self.value_ribs.pop();
3001             }
3002
3003             ExprKind::Field(ref subexpression, _) => {
3004                 self.resolve_expr(subexpression, Some(expr));
3005             }
3006             ExprKind::MethodCall(_, ref types, ref arguments) => {
3007                 let mut arguments = arguments.iter();
3008                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3009                 for argument in arguments {
3010                     self.resolve_expr(argument, None);
3011                 }
3012                 for ty in types.iter() {
3013                     self.visit_ty(ty);
3014                 }
3015             }
3016
3017             _ => {
3018                 visit::walk_expr(self, expr);
3019             }
3020         }
3021     }
3022
3023     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3024         match expr.node {
3025             ExprKind::Field(_, name) => {
3026                 // FIXME(#6890): Even though you can't treat a method like a
3027                 // field, we need to add any trait methods we find that match
3028                 // the field name so that we can do some nice error reporting
3029                 // later on in typeck.
3030                 let traits = self.get_traits_containing_item(name.node.name);
3031                 self.trait_map.insert(expr.id, traits);
3032             }
3033             ExprKind::MethodCall(name, _, _) => {
3034                 debug!("(recording candidate traits for expr) recording traits for {}",
3035                        expr.id);
3036                 let traits = self.get_traits_containing_item(name.node.name);
3037                 self.trait_map.insert(expr.id, traits);
3038             }
3039             _ => {
3040                 // Nothing to do.
3041             }
3042         }
3043     }
3044
3045     fn get_traits_containing_item(&mut self, name: Name) -> Vec<TraitCandidate> {
3046         debug!("(getting traits containing item) looking for '{}'", name);
3047
3048         fn add_trait_info(found_traits: &mut Vec<TraitCandidate>,
3049                           trait_def_id: DefId,
3050                           import_id: Option<NodeId>,
3051                           name: Name) {
3052             debug!("(adding trait info) found trait {:?} for method '{}'",
3053                    trait_def_id,
3054                    name);
3055             found_traits.push(TraitCandidate {
3056                 def_id: trait_def_id,
3057                 import_id: import_id,
3058             });
3059         }
3060
3061         let mut found_traits = Vec::new();
3062         // Look for the current trait.
3063         if let Some((trait_def_id, _)) = self.current_trait_ref {
3064             if self.trait_item_map.contains_key(&(name, trait_def_id)) {
3065                 add_trait_info(&mut found_traits, trait_def_id, None, name);
3066             }
3067         }
3068
3069         let mut search_module = self.current_module;
3070         loop {
3071             // Look for trait children.
3072             let mut search_in_module = |this: &mut Self, module: Module<'a>| {
3073                 let mut traits = module.traits.borrow_mut();
3074                 if traits.is_none() {
3075                     let mut collected_traits = Vec::new();
3076                     module.for_each_child(|name, ns, binding| {
3077                         if ns != TypeNS { return }
3078                         if let Some(Def::Trait(_)) = binding.def() {
3079                             collected_traits.push((name, binding));
3080                         }
3081                     });
3082                     *traits = Some(collected_traits.into_boxed_slice());
3083                 }
3084
3085                 for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3086                     let trait_def_id = binding.def().unwrap().def_id();
3087                     if this.trait_item_map.contains_key(&(name, trait_def_id)) {
3088                         let mut import_id = None;
3089                         if let NameBindingKind::Import { directive, .. } = binding.kind {
3090                             let id = directive.id;
3091                             this.maybe_unused_trait_imports.insert(id);
3092                             import_id = Some(id);
3093                         }
3094                         add_trait_info(&mut found_traits, trait_def_id, import_id, name);
3095                         this.record_use(trait_name, binding);
3096                     }
3097                 }
3098             };
3099             search_in_module(self, search_module);
3100
3101             match search_module.parent_link {
3102                 NoParentLink | ModuleParentLink(..) => {
3103                     if !search_module.no_implicit_prelude.get() {
3104                         self.prelude.map(|prelude| search_in_module(self, prelude));
3105                     }
3106                     break;
3107                 }
3108                 BlockParentLink(parent_module, _) => {
3109                     search_module = parent_module;
3110                 }
3111             }
3112         }
3113
3114         found_traits
3115     }
3116
3117     /// When name resolution fails, this method can be used to look up candidate
3118     /// entities with the expected name. It allows filtering them using the
3119     /// supplied predicate (which should be used to only accept the types of
3120     /// definitions expected e.g. traits). The lookup spans across all crates.
3121     ///
3122     /// NOTE: The method does not look into imports, but this is not a problem,
3123     /// since we report the definitions (thus, the de-aliased imports).
3124     fn lookup_candidates<FilterFn>(&mut self,
3125                                    lookup_name: Name,
3126                                    namespace: Namespace,
3127                                    filter_fn: FilterFn) -> SuggestedCandidates
3128         where FilterFn: Fn(Def) -> bool {
3129
3130         let mut lookup_results = Vec::new();
3131         let mut worklist = Vec::new();
3132         worklist.push((self.graph_root, Vec::new(), false));
3133
3134         while let Some((in_module,
3135                         path_segments,
3136                         in_module_is_extern)) = worklist.pop() {
3137             self.populate_module_if_necessary(in_module);
3138
3139             in_module.for_each_child(|name, ns, name_binding| {
3140
3141                 // avoid imports entirely
3142                 if name_binding.is_import() { return; }
3143
3144                 // collect results based on the filter function
3145                 if let Some(def) = name_binding.def() {
3146                     if name == lookup_name && ns == namespace && filter_fn(def) {
3147                         // create the path
3148                         let ident = ast::Ident::with_empty_ctxt(name);
3149                         let params = PathParameters::none();
3150                         let segment = PathSegment {
3151                             identifier: ident,
3152                             parameters: params,
3153                         };
3154                         let span = name_binding.span;
3155                         let mut segms = path_segments.clone();
3156                         segms.push(segment);
3157                         let path = Path {
3158                             span: span,
3159                             global: true,
3160                             segments: segms,
3161                         };
3162                         // the entity is accessible in the following cases:
3163                         // 1. if it's defined in the same crate, it's always
3164                         // accessible (since private entities can be made public)
3165                         // 2. if it's defined in another crate, it's accessible
3166                         // only if both the module is public and the entity is
3167                         // declared as public (due to pruning, we don't explore
3168                         // outside crate private modules => no need to check this)
3169                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3170                             lookup_results.push(path);
3171                         }
3172                     }
3173                 }
3174
3175                 // collect submodules to explore
3176                 if let Some(module) = name_binding.module() {
3177                     // form the path
3178                     let path_segments = match module.parent_link {
3179                         NoParentLink => path_segments.clone(),
3180                         ModuleParentLink(_, name) => {
3181                             let mut paths = path_segments.clone();
3182                             let ident = ast::Ident::with_empty_ctxt(name);
3183                             let params = PathParameters::none();
3184                             let segm = PathSegment {
3185                                 identifier: ident,
3186                                 parameters: params,
3187                             };
3188                             paths.push(segm);
3189                             paths
3190                         }
3191                         _ => bug!(),
3192                     };
3193
3194                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3195                         // add the module to the lookup
3196                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3197                         worklist.push((module, path_segments, is_extern));
3198                     }
3199                 }
3200             })
3201         }
3202
3203         SuggestedCandidates {
3204             name: lookup_name.as_str().to_string(),
3205             candidates: lookup_results,
3206         }
3207     }
3208
3209     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3210         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3211         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3212             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3213         }
3214     }
3215
3216     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3217         let (path, id) = match *vis {
3218             ast::Visibility::Public => return ty::Visibility::Public,
3219             ast::Visibility::Crate(_) => return ty::Visibility::Restricted(ast::CRATE_NODE_ID),
3220             ast::Visibility::Restricted { ref path, id } => (path, id),
3221             ast::Visibility::Inherited => {
3222                 let current_module =
3223                     self.get_nearest_normal_module_parent_or_self(self.current_module);
3224                 let id =
3225                     self.definitions.as_local_node_id(current_module.def_id().unwrap()).unwrap();
3226                 return ty::Visibility::Restricted(id);
3227             }
3228         };
3229
3230         let segments: Vec<_> = path.segments.iter().map(|seg| seg.identifier.name).collect();
3231         let mut path_resolution = err_path_resolution();
3232         let vis = match self.resolve_module_path(&segments, DontUseLexicalScope, path.span) {
3233             Success(module) => {
3234                 let def = module.def.unwrap();
3235                 path_resolution = PathResolution::new(def);
3236                 ty::Visibility::Restricted(self.definitions.as_local_node_id(def.def_id()).unwrap())
3237             }
3238             Failed(Some((span, msg))) => {
3239                 self.session.span_err(span, &format!("failed to resolve module path. {}", msg));
3240                 ty::Visibility::Public
3241             }
3242             _ => {
3243                 self.session.span_err(path.span, "unresolved module path");
3244                 ty::Visibility::Public
3245             }
3246         };
3247         self.def_map.insert(id, path_resolution);
3248         if !self.is_accessible(vis) {
3249             let msg = format!("visibilities can only be restricted to ancestor modules");
3250             self.session.span_err(path.span, &msg);
3251         }
3252         vis
3253     }
3254
3255     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3256         let current_module = self.get_nearest_normal_module_parent_or_self(self.current_module);
3257         let node_id = self.definitions.as_local_node_id(current_module.def_id().unwrap()).unwrap();
3258         vis.is_accessible_from(node_id, self)
3259     }
3260
3261     fn check_privacy(&mut self, name: Name, binding: &'a NameBinding<'a>, span: Span) {
3262         if !self.is_accessible(binding.vis) {
3263             self.privacy_errors.push(PrivacyError(span, name, binding));
3264         }
3265     }
3266
3267     fn report_privacy_errors(&self) {
3268         if self.privacy_errors.len() == 0 { return }
3269         let mut reported_spans = HashSet::new();
3270         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3271             if !reported_spans.insert(span) { continue }
3272             if binding.is_extern_crate() {
3273                 // Warn when using an inaccessible extern crate.
3274                 let node_id = binding.module().unwrap().extern_crate_id.unwrap();
3275                 let msg = format!("extern crate `{}` is private", name);
3276                 self.session.add_lint(lint::builtin::INACCESSIBLE_EXTERN_CRATE, node_id, span, msg);
3277             } else {
3278                 let def = binding.def().unwrap();
3279                 self.session.span_err(span, &format!("{} `{}` is private", def.kind_name(), name));
3280             }
3281         }
3282     }
3283
3284     fn report_conflict(&self,
3285                        parent: Module,
3286                        name: Name,
3287                        ns: Namespace,
3288                        binding: &NameBinding,
3289                        old_binding: &NameBinding) {
3290         // Error on the second of two conflicting names
3291         if old_binding.span.lo > binding.span.lo {
3292             return self.report_conflict(parent, name, ns, old_binding, binding);
3293         }
3294
3295         let container = match parent.def {
3296             Some(Def::Mod(_)) => "module",
3297             Some(Def::Trait(_)) => "trait",
3298             None => "block",
3299             _ => "enum",
3300         };
3301
3302         let (participle, noun) = match old_binding.is_import() || old_binding.is_extern_crate() {
3303             true => ("imported", "import"),
3304             false => ("defined", "definition"),
3305         };
3306
3307         let span = binding.span;
3308         let msg = {
3309             let kind = match (ns, old_binding.module()) {
3310                 (ValueNS, _) => "a value",
3311                 (TypeNS, Some(module)) if module.extern_crate_id.is_some() => "an extern crate",
3312                 (TypeNS, Some(module)) if module.is_normal() => "a module",
3313                 (TypeNS, Some(module)) if module.is_trait() => "a trait",
3314                 (TypeNS, _) => "a type",
3315             };
3316             format!("{} named `{}` has already been {} in this {}",
3317                     kind, name, participle, container)
3318         };
3319
3320         let mut err = match (old_binding.is_extern_crate(), binding.is_extern_crate()) {
3321             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3322             (true, _) | (_, true) if binding.is_import() || old_binding.is_import() =>
3323                 struct_span_err!(self.session, span, E0254, "{}", msg),
3324             (true, _) | (_, true) => struct_span_err!(self.session, span, E0260, "{}", msg),
3325             _ => match (old_binding.is_import(), binding.is_import()) {
3326                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3327                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3328                 _ => {
3329                     let mut e = struct_span_err!(self.session, span, E0255, "{}", msg);
3330                     e.span_label(span, &format!("`{}` was already imported", name));
3331                     e
3332                 }
3333             },
3334         };
3335
3336         if old_binding.span != syntax_pos::DUMMY_SP {
3337             err.span_label(old_binding.span, &format!("previous {} of `{}` here", noun, name));
3338         }
3339         err.emit();
3340     }
3341 }
3342
3343 fn names_to_string(names: &[Name]) -> String {
3344     let mut first = true;
3345     let mut result = String::new();
3346     for name in names {
3347         if first {
3348             first = false
3349         } else {
3350             result.push_str("::")
3351         }
3352         result.push_str(&name.as_str());
3353     }
3354     result
3355 }
3356
3357 fn path_names_to_string(path: &Path, depth: usize) -> String {
3358     let names: Vec<ast::Name> = path.segments[..path.segments.len() - depth]
3359                                     .iter()
3360                                     .map(|seg| seg.identifier.name)
3361                                     .collect();
3362     names_to_string(&names[..])
3363 }
3364
3365 /// When an entity with a given name is not available in scope, we search for
3366 /// entities with that name in all crates. This method allows outputting the
3367 /// results of this search in a programmer-friendly way
3368 fn show_candidates(session: &mut DiagnosticBuilder,
3369                    candidates: &SuggestedCandidates) {
3370
3371     let paths = &candidates.candidates;
3372
3373     if paths.len() > 0 {
3374         // don't show more than MAX_CANDIDATES results, so
3375         // we're consistent with the trait suggestions
3376         const MAX_CANDIDATES: usize = 5;
3377
3378         // we want consistent results across executions, but candidates are produced
3379         // by iterating through a hash map, so make sure they are ordered:
3380         let mut path_strings: Vec<_> = paths.into_iter()
3381                                             .map(|p| path_names_to_string(&p, 0))
3382                                             .collect();
3383         path_strings.sort();
3384
3385         // behave differently based on how many candidates we have:
3386         if !paths.is_empty() {
3387             if paths.len() == 1 {
3388                 session.help(
3389                     &format!("you can import it into scope: `use {};`.",
3390                         &path_strings[0]),
3391                 );
3392             } else {
3393                 session.help("you can import several candidates \
3394                     into scope (`use ...;`):");
3395                 let count = path_strings.len() as isize - MAX_CANDIDATES as isize + 1;
3396
3397                 for (idx, path_string) in path_strings.iter().enumerate() {
3398                     if idx == MAX_CANDIDATES - 1 && count > 1 {
3399                         session.help(
3400                             &format!("  and {} other candidates", count).to_string(),
3401                         );
3402                         break;
3403                     } else {
3404                         session.help(
3405                             &format!("  `{}`", path_string).to_string(),
3406                         );
3407                     }
3408                 }
3409             }
3410         }
3411     } else {
3412         // nothing found:
3413         session.help(
3414             &format!("no candidates by the name of `{}` found in your \
3415             project; maybe you misspelled the name or forgot to import \
3416             an external crate?", candidates.name.to_string()),
3417         );
3418     };
3419 }
3420
3421 /// A somewhat inefficient routine to obtain the name of a module.
3422 fn module_to_string(module: Module) -> String {
3423     let mut names = Vec::new();
3424
3425     fn collect_mod(names: &mut Vec<ast::Name>, module: Module) {
3426         match module.parent_link {
3427             NoParentLink => {}
3428             ModuleParentLink(ref module, name) => {
3429                 names.push(name);
3430                 collect_mod(names, module);
3431             }
3432             BlockParentLink(ref module, _) => {
3433                 // danger, shouldn't be ident?
3434                 names.push(token::intern("<opaque>"));
3435                 collect_mod(names, module);
3436             }
3437         }
3438     }
3439     collect_mod(&mut names, module);
3440
3441     if names.is_empty() {
3442         return "???".to_string();
3443     }
3444     names_to_string(&names.into_iter().rev().collect::<Vec<ast::Name>>())
3445 }
3446
3447 fn err_path_resolution() -> PathResolution {
3448     PathResolution::new(Def::Err)
3449 }
3450
3451 #[derive(PartialEq,Copy, Clone)]
3452 pub enum MakeGlobMap {
3453     Yes,
3454     No,
3455 }
3456
3457 /// Entry point to crate resolution.
3458 pub fn resolve_crate<'a, 'b>(resolver: &'b mut Resolver<'a>, krate: &'b Crate) {
3459     // Currently, we ignore the name resolution data structures for
3460     // the purposes of dependency tracking. Instead we will run name
3461     // resolution and include its output in the hash of each item,
3462     // much like we do for macro expansion. In other words, the hash
3463     // reflects not just its contents but the results of name
3464     // resolution on those contents. Hopefully we'll push this back at
3465     // some point.
3466     let _ignore = resolver.session.dep_graph.in_ignore();
3467
3468     resolver.build_reduced_graph(krate);
3469     resolve_imports::resolve_imports(resolver);
3470     resolver.resolve_crate(krate);
3471
3472     check_unused::check_crate(resolver, krate);
3473     resolver.report_privacy_errors();
3474 }
3475
3476 pub fn with_resolver<'a, T, F>(session: &'a Session,
3477                                definitions: &'a mut Definitions,
3478                                make_glob_map: MakeGlobMap,
3479                                f: F) -> T
3480     where F: for<'b> FnOnce(Resolver<'b>) -> T,
3481 {
3482     let arenas = Resolver::arenas();
3483     let resolver = Resolver::new(session, definitions, make_glob_map, &arenas);
3484     f(resolver)
3485 }
3486
3487 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }