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 #![deny(warnings)]
  19
  20 #![feature(associated_consts)]
  21 #![feature(rustc_diagnostic_macros)]
  22 #![feature(rustc_private)]
  23 #![feature(staged_api)]
  24
  25 #[macro_use]
  26 extern crate log;
  27 #[macro_use]
  28 extern crate syntax;
  29 extern crate syntax_pos;
  30 extern crate rustc_errors as errors;
  31 extern crate arena;
  32 #[macro_use]
  33 extern crate rustc;
  34
  35 use self::Namespace::*;
  36 use self::TypeParameters::*;
  37 use self::RibKind::*;
  38
  39 use rustc::hir::map::{Definitions, DefCollector};
  40 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  41 use rustc::middle::cstore::CrateLoader;
  42 use rustc::session::Session;
  43 use rustc::lint;
  44 use rustc::hir::def::*;
  45 use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  46 use rustc::ty;
  47 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  48 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet};
  49
  50 use syntax::ext::hygiene::{Mark, SyntaxContext};
  51 use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
  52 use syntax::ext::base::SyntaxExtension;
  53 use syntax::ext::base::Determinacy::{Determined, Undetermined};
  54 use syntax::symbol::{Symbol, keywords};
  55 use syntax::util::lev_distance::find_best_match_for_name;
  56
  57 use syntax::visit::{self, FnKind, Visitor};
  58 use syntax::attr;
  59 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  60 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  61 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  62 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  63 use syntax::ast::{QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  64 use syntax::feature_gate::{feature_err, emit_feature_err, GateIssue};
  65
  66 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
  67 use errors::DiagnosticBuilder;
  68
  69 use std::cell::{Cell, RefCell};
  70 use std::cmp;
  71 use std::fmt;
  72 use std::mem::replace;
  73 use std::rc::Rc;
  74
  75 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
  76 use macros::{InvocationData, LegacyBinding, LegacyScope};
  77
  78 // NB: This module needs to be declared first so diagnostics are
  79 // registered before they are used.
  80 mod diagnostics;
  81
  82 mod macros;
  83 mod check_unused;
  84 mod build_reduced_graph;
  85 mod resolve_imports;
  86
  87 /// A free importable items suggested in case of resolution failure.
  88 struct ImportSuggestion {
  89     path: Path,
  90 }
  91
  92 /// A field or associated item from self type suggested in case of resolution failure.
  93 enum AssocSuggestion {
  94     Field,
  95     MethodWithSelf,
  96     AssocItem,
  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, &'a Span),
 106     /// error E0407: method is not a member of trait
 107     MethodNotMemberOfTrait(Name, &'a str),
 108     /// error E0437: type is not a member of trait
 109     TypeNotMemberOfTrait(Name, &'a str),
 110     /// error E0438: const is not a member of trait
 111     ConstNotMemberOfTrait(Name, &'a str),
 112     /// error E0408: variable `{}` from pattern #{} is not bound in pattern #{}
 113     VariableNotBoundInPattern(Name, usize, usize),
 114     /// error E0409: variable is bound with different mode in pattern #{} than in pattern #1
 115     VariableBoundWithDifferentMode(Name, usize, Span),
 116     /// error E0415: identifier is bound more than once in this parameter list
 117     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 118     /// error E0416: identifier is bound more than once in the same pattern
 119     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 120     /// error E0426: use of undeclared label
 121     UndeclaredLabel(&'a str),
 122     /// error E0429: `self` imports are only allowed within a { } list
 123     SelfImportsOnlyAllowedWithin,
 124     /// error E0430: `self` import can only appear once in the list
 125     SelfImportCanOnlyAppearOnceInTheList,
 126     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 127     SelfImportOnlyInImportListWithNonEmptyPrefix,
 128     /// error E0432: unresolved import
 129     UnresolvedImport(Option<(&'a str, &'a str)>),
 130     /// error E0433: failed to resolve
 131     FailedToResolve(&'a str),
 132     /// error E0434: can't capture dynamic environment in a fn item
 133     CannotCaptureDynamicEnvironmentInFnItem,
 134     /// error E0435: attempt to use a non-constant value in a constant
 135     AttemptToUseNonConstantValueInConstant,
 136     /// error E0530: X bindings cannot shadow Ys
 137     BindingShadowsSomethingUnacceptable(&'a str, Name, &'a NameBinding<'a>),
 138 }
 139
 140 fn resolve_error<'sess, 'a>(resolver: &'sess Resolver,
 141                             span: Span,
 142                             resolution_error: ResolutionError<'a>) {
 143     resolve_struct_error(resolver, span, resolution_error).emit();
 144 }
 145
 146 fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
 147                                    span: Span,
 148                                    resolution_error: ResolutionError<'a>)
 149                                    -> DiagnosticBuilder<'sess> {
 150     match resolution_error {
 151         ResolutionError::TypeParametersFromOuterFunction => {
 152             let mut err = struct_span_err!(resolver.session,
 153                                            span,
 154                                            E0401,
 155                                            "can't use type parameters from outer function; \
 156                                            try using a local type parameter instead");
 157             err.span_label(span, &format!("use of type variable from outer function"));
 158             err
 159         }
 160         ResolutionError::OuterTypeParameterContext => {
 161             struct_span_err!(resolver.session,
 162                              span,
 163                              E0402,
 164                              "cannot use an outer type parameter in this context")
 165         }
 166         ResolutionError::NameAlreadyUsedInTypeParameterList(name, first_use_span) => {
 167              let mut err = struct_span_err!(resolver.session,
 168                                             span,
 169                                             E0403,
 170                                             "the name `{}` is already used for a type parameter \
 171                                             in this type parameter list",
 172                                             name);
 173              err.span_label(span, &format!("already used"));
 174              err.span_label(first_use_span.clone(), &format!("first use of `{}`", name));
 175              err
 176         }
 177         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 178             let mut err = struct_span_err!(resolver.session,
 179                                            span,
 180                                            E0407,
 181                                            "method `{}` is not a member of trait `{}`",
 182                                            method,
 183                                            trait_);
 184             err.span_label(span, &format!("not a member of trait `{}`", trait_));
 185             err
 186         }
 187         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 188             let mut err = struct_span_err!(resolver.session,
 189                              span,
 190                              E0437,
 191                              "type `{}` is not a member of trait `{}`",
 192                              type_,
 193                              trait_);
 194             err.span_label(span, &format!("not a member of trait `{}`", trait_));
 195             err
 196         }
 197         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 198             let mut err = struct_span_err!(resolver.session,
 199                              span,
 200                              E0438,
 201                              "const `{}` is not a member of trait `{}`",
 202                              const_,
 203                              trait_);
 204             err.span_label(span, &format!("not a member of trait `{}`", trait_));
 205             err
 206         }
 207         ResolutionError::VariableNotBoundInPattern(variable_name, from, to) => {
 208             let mut err = struct_span_err!(resolver.session,
 209                              span,
 210                              E0408,
 211                              "variable `{}` from pattern #{} is not bound in pattern #{}",
 212                              variable_name,
 213                              from,
 214                              to);
 215             err.span_label(span, &format!("pattern doesn't bind `{}`", variable_name));
 216             err
 217         }
 218         ResolutionError::VariableBoundWithDifferentMode(variable_name,
 219                                                         pattern_number,
 220                                                         first_binding_span) => {
 221             let mut err = struct_span_err!(resolver.session,
 222                              span,
 223                              E0409,
 224                              "variable `{}` is bound with different mode in pattern #{} than in \
 225                               pattern #1",
 226                              variable_name,
 227                              pattern_number);
 228             err.span_label(span, &format!("bound in different ways"));
 229             err.span_label(first_binding_span, &format!("first binding"));
 230             err
 231         }
 232         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 233             let mut err = struct_span_err!(resolver.session,
 234                              span,
 235                              E0415,
 236                              "identifier `{}` is bound more than once in this parameter list",
 237                              identifier);
 238             err.span_label(span, &format!("used as parameter more than once"));
 239             err
 240         }
 241         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 242             let mut err = struct_span_err!(resolver.session,
 243                              span,
 244                              E0416,
 245                              "identifier `{}` is bound more than once in the same pattern",
 246                              identifier);
 247             err.span_label(span, &format!("used in a pattern more than once"));
 248             err
 249         }
 250         ResolutionError::UndeclaredLabel(name) => {
 251             let mut err = struct_span_err!(resolver.session,
 252                                            span,
 253                                            E0426,
 254                                            "use of undeclared label `{}`",
 255                                            name);
 256             err.span_label(span, &format!("undeclared label `{}`",&name));
 257             err
 258         }
 259         ResolutionError::SelfImportsOnlyAllowedWithin => {
 260             struct_span_err!(resolver.session,
 261                              span,
 262                              E0429,
 263                              "{}",
 264                              "`self` imports are only allowed within a { } list")
 265         }
 266         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 267             struct_span_err!(resolver.session,
 268                              span,
 269                              E0430,
 270                              "`self` import can only appear once in the list")
 271         }
 272         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 273             struct_span_err!(resolver.session,
 274                              span,
 275                              E0431,
 276                              "`self` import can only appear in an import list with a \
 277                               non-empty prefix")
 278         }
 279         ResolutionError::UnresolvedImport(name) => {
 280             let msg = match name {
 281                 Some((n, _)) => format!("unresolved import `{}`", n),
 282                 None => "unresolved import".to_owned(),
 283             };
 284             let mut err = struct_span_err!(resolver.session, span, E0432, "{}", msg);
 285             if let Some((_, p)) = name {
 286                 err.span_label(span, &p);
 287             }
 288             err
 289         }
 290         ResolutionError::FailedToResolve(msg) => {
 291             let mut err = struct_span_err!(resolver.session, span, E0433,
 292                                            "failed to resolve. {}", msg);
 293             err.span_label(span, &msg);
 294             err
 295         }
 296         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 297             struct_span_err!(resolver.session,
 298                              span,
 299                              E0434,
 300                              "{}",
 301                              "can't capture dynamic environment in a fn item; use the || { ... } \
 302                               closure form instead")
 303         }
 304         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 305             let mut err = struct_span_err!(resolver.session,
 306                              span,
 307                              E0435,
 308                              "attempt to use a non-constant value in a constant");
 309             err.span_label(span, &format!("non-constant used with constant"));
 310             err
 311         }
 312         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 313             let shadows_what = PathResolution::new(binding.def()).kind_name();
 314             let mut err = struct_span_err!(resolver.session,
 315                                            span,
 316                                            E0530,
 317                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 318             err.span_label(span, &format!("cannot be named the same as a {}", shadows_what));
 319             let participle = if binding.is_import() { "imported" } else { "defined" };
 320             let msg = &format!("a {} `{}` is {} here", shadows_what, name, participle);
 321             err.span_label(binding.span, msg);
 322             err
 323         }
 324     }
 325 }
 326
 327 #[derive(Copy, Clone)]
 328 struct BindingInfo {
 329     span: Span,
 330     binding_mode: BindingMode,
 331 }
 332
 333 // Map from the name in a pattern to its binding mode.
 334 type BindingMap = FxHashMap<Ident, BindingInfo>;
 335
 336 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 337 enum PatternSource {
 338     Match,
 339     IfLet,
 340     WhileLet,
 341     Let,
 342     For,
 343     FnParam,
 344 }
 345
 346 impl PatternSource {
 347     fn is_refutable(self) -> bool {
 348         match self {
 349             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 350             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 351         }
 352     }
 353     fn descr(self) -> &'static str {
 354         match self {
 355             PatternSource::Match => "match binding",
 356             PatternSource::IfLet => "if let binding",
 357             PatternSource::WhileLet => "while let binding",
 358             PatternSource::Let => "let binding",
 359             PatternSource::For => "for binding",
 360             PatternSource::FnParam => "function parameter",
 361         }
 362     }
 363 }
 364
 365 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 366 enum PathSource<'a> {
 367     // Type paths `Path`.
 368     Type,
 369     // Trait paths in bounds or impls.
 370     Trait,
 371     // Expression paths `path`, with optional parent context.
 372     Expr(Option<&'a ExprKind>),
 373     // Paths in path patterns `Path`.
 374     Pat,
 375     // Paths in struct expressions and patterns `Path { .. }`.
 376     Struct,
 377     // Paths in tuple struct patterns `Path(..)`.
 378     TupleStruct,
 379     // `m::A::B` in `<T as m::A>::B::C`.
 380     TraitItem(Namespace),
 381     // Path in `pub(path)`
 382     Visibility,
 383     // Path in `use a::b::{...};`
 384     ImportPrefix,
 385 }
 386
 387 impl<'a> PathSource<'a> {
 388     fn namespace(self) -> Namespace {
 389         match self {
 390             PathSource::Type | PathSource::Trait | PathSource::Struct |
 391             PathSource::Visibility | PathSource::ImportPrefix => TypeNS,
 392             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
 393             PathSource::TraitItem(ns) => ns,
 394         }
 395     }
 396
 397     fn global_by_default(self) -> bool {
 398         match self {
 399             PathSource::Visibility | PathSource::ImportPrefix => true,
 400             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 401             PathSource::Struct | PathSource::TupleStruct |
 402             PathSource::Trait | PathSource::TraitItem(..) => false,
 403         }
 404     }
 405
 406     fn defer_to_typeck(self) -> bool {
 407         match self {
 408             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 409             PathSource::Struct | PathSource::TupleStruct => true,
 410             PathSource::Trait | PathSource::TraitItem(..) |
 411             PathSource::Visibility | PathSource::ImportPrefix => false,
 412         }
 413     }
 414
 415     fn descr_expected(self) -> &'static str {
 416         match self {
 417             PathSource::Type => "type",
 418             PathSource::Trait => "trait",
 419             PathSource::Pat => "unit struct/variant or constant",
 420             PathSource::Struct => "struct, variant or union type",
 421             PathSource::TupleStruct => "tuple struct/variant",
 422             PathSource::Visibility => "module",
 423             PathSource::ImportPrefix => "module or enum",
 424             PathSource::TraitItem(ns) => match ns {
 425                 TypeNS => "associated type",
 426                 ValueNS => "method or associated constant",
 427                 MacroNS => bug!("associated macro"),
 428             },
 429             PathSource::Expr(parent) => match parent {
 430                 // "function" here means "anything callable" rather than `Def::Fn`,
 431                 // this is not precise but usually more helpful than just "value".
 432                 Some(&ExprKind::Call(..)) => "function",
 433                 _ => "value",
 434             },
 435         }
 436     }
 437
 438     fn is_expected(self, def: Def) -> bool {
 439         match self {
 440             PathSource::Type => match def {
 441                 Def::Struct(..) | Def::Union(..) | Def::Enum(..) |
 442                 Def::Trait(..) | Def::TyAlias(..) | Def::AssociatedTy(..) |
 443                 Def::PrimTy(..) | Def::TyParam(..) | Def::SelfTy(..) => true,
 444                 _ => false,
 445             },
 446             PathSource::Trait => match def {
 447                 Def::Trait(..) => true,
 448                 _ => false,
 449             },
 450             PathSource::Expr(..) => match def {
 451                 Def::StructCtor(_, CtorKind::Const) | Def::StructCtor(_, CtorKind::Fn) |
 452                 Def::VariantCtor(_, CtorKind::Const) | Def::VariantCtor(_, CtorKind::Fn) |
 453                 Def::Const(..) | Def::Static(..) | Def::Local(..) | Def::Upvar(..) |
 454                 Def::Fn(..) | Def::Method(..) | Def::AssociatedConst(..) => true,
 455                 _ => false,
 456             },
 457             PathSource::Pat => match def {
 458                 Def::StructCtor(_, CtorKind::Const) |
 459                 Def::VariantCtor(_, CtorKind::Const) |
 460                 Def::Const(..) | Def::AssociatedConst(..) => true,
 461                 _ => false,
 462             },
 463             PathSource::TupleStruct => match def {
 464                 Def::StructCtor(_, CtorKind::Fn) | Def::VariantCtor(_, CtorKind::Fn) => true,
 465                 _ => false,
 466             },
 467             PathSource::Struct => match def {
 468                 Def::Struct(..) | Def::Union(..) | Def::Variant(..) |
 469                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => true,
 470                 _ => false,
 471             },
 472             PathSource::TraitItem(ns) => match def {
 473                 Def::AssociatedConst(..) | Def::Method(..) if ns == ValueNS => true,
 474                 Def::AssociatedTy(..) if ns == TypeNS => true,
 475                 _ => false,
 476             },
 477             PathSource::ImportPrefix => match def {
 478                 Def::Mod(..) | Def::Enum(..) => true,
 479                 _ => false,
 480             },
 481             PathSource::Visibility => match def {
 482                 Def::Mod(..) => true,
 483                 _ => false,
 484             },
 485         }
 486     }
 487
 488     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
 489         __diagnostic_used!(E0404);
 490         __diagnostic_used!(E0405);
 491         __diagnostic_used!(E0412);
 492         __diagnostic_used!(E0422);
 493         __diagnostic_used!(E0423);
 494         __diagnostic_used!(E0425);
 495         __diagnostic_used!(E0531);
 496         __diagnostic_used!(E0532);
 497         __diagnostic_used!(E0573);
 498         __diagnostic_used!(E0574);
 499         __diagnostic_used!(E0575);
 500         __diagnostic_used!(E0576);
 501         __diagnostic_used!(E0577);
 502         __diagnostic_used!(E0578);
 503         match (self, has_unexpected_resolution) {
 504             (PathSource::Trait, true) => "E0404",
 505             (PathSource::Trait, false) => "E0405",
 506             (PathSource::Type, true) => "E0573",
 507             (PathSource::Type, false) => "E0412",
 508             (PathSource::Struct, true) => "E0574",
 509             (PathSource::Struct, false) => "E0422",
 510             (PathSource::Expr(..), true) => "E0423",
 511             (PathSource::Expr(..), false) => "E0425",
 512             (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
 513             (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
 514             (PathSource::TraitItem(..), true) => "E0575",
 515             (PathSource::TraitItem(..), false) => "E0576",
 516             (PathSource::Visibility, true) | (PathSource::ImportPrefix, true) => "E0577",
 517             (PathSource::Visibility, false) | (PathSource::ImportPrefix, false) => "E0578",
 518         }
 519     }
 520 }
 521
 522 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 523 pub enum Namespace {
 524     TypeNS,
 525     ValueNS,
 526     MacroNS,
 527 }
 528
 529 #[derive(Clone, Default, Debug)]
 530 pub struct PerNS<T> {
 531     value_ns: T,
 532     type_ns: T,
 533     macro_ns: Option<T>,
 534 }
 535
 536 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 537     type Output = T;
 538     fn index(&self, ns: Namespace) -> &T {
 539         match ns {
 540             ValueNS => &self.value_ns,
 541             TypeNS => &self.type_ns,
 542             MacroNS => self.macro_ns.as_ref().unwrap(),
 543         }
 544     }
 545 }
 546
 547 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 548     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 549         match ns {
 550             ValueNS => &mut self.value_ns,
 551             TypeNS => &mut self.type_ns,
 552             MacroNS => self.macro_ns.as_mut().unwrap(),
 553         }
 554     }
 555 }
 556
 557 impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
 558     fn visit_item(&mut self, item: &'tcx Item) {
 559         self.resolve_item(item);
 560     }
 561     fn visit_arm(&mut self, arm: &'tcx Arm) {
 562         self.resolve_arm(arm);
 563     }
 564     fn visit_block(&mut self, block: &'tcx Block) {
 565         self.resolve_block(block);
 566     }
 567     fn visit_expr(&mut self, expr: &'tcx Expr) {
 568         self.resolve_expr(expr, None);
 569     }
 570     fn visit_local(&mut self, local: &'tcx Local) {
 571         self.resolve_local(local);
 572     }
 573     fn visit_ty(&mut self, ty: &'tcx Ty) {
 574         if let TyKind::Path(ref qself, ref path) = ty.node {
 575             self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 576         } else if let TyKind::ImplicitSelf = ty.node {
 577             let self_ty = keywords::SelfType.ident();
 578             let def = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.span))
 579                           .map_or(Def::Err, |d| d.def());
 580             self.record_def(ty.id, PathResolution::new(def));
 581         } else if let TyKind::Array(ref element, ref length) = ty.node {
 582             self.visit_ty(element);
 583             self.with_constant_rib(|this| {
 584                 this.visit_expr(length);
 585             });
 586             return;
 587         }
 588         visit::walk_ty(self, ty);
 589     }
 590     fn visit_poly_trait_ref(&mut self,
 591                             tref: &'tcx ast::PolyTraitRef,
 592                             m: &'tcx ast::TraitBoundModifier) {
 593         self.smart_resolve_path(tref.trait_ref.ref_id, None,
 594                                 &tref.trait_ref.path, PathSource::Trait);
 595         visit::walk_poly_trait_ref(self, tref, m);
 596     }
 597     fn visit_variant(&mut self,
 598                      variant: &'tcx ast::Variant,
 599                      generics: &'tcx Generics,
 600                      item_id: ast::NodeId) {
 601         if let Some(ref dis_expr) = variant.node.disr_expr {
 602             // resolve the discriminator expr as a constant
 603             self.with_constant_rib(|this| {
 604                 this.visit_expr(dis_expr);
 605             });
 606         }
 607
 608         // `visit::walk_variant` without the discriminant expression.
 609         self.visit_variant_data(&variant.node.data,
 610                                 variant.node.name,
 611                                 generics,
 612                                 item_id,
 613                                 variant.span);
 614     }
 615     fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
 616         let type_parameters = match foreign_item.node {
 617             ForeignItemKind::Fn(_, ref generics) => {
 618                 HasTypeParameters(generics, ItemRibKind)
 619             }
 620             ForeignItemKind::Static(..) => NoTypeParameters,
 621         };
 622         self.with_type_parameter_rib(type_parameters, |this| {
 623             visit::walk_foreign_item(this, foreign_item);
 624         });
 625     }
 626     fn visit_fn(&mut self,
 627                 function_kind: FnKind<'tcx>,
 628                 declaration: &'tcx FnDecl,
 629                 _: Span,
 630                 node_id: NodeId) {
 631         let rib_kind = match function_kind {
 632             FnKind::ItemFn(_, generics, ..) => {
 633                 self.visit_generics(generics);
 634                 ItemRibKind
 635             }
 636             FnKind::Method(_, sig, _, _) => {
 637                 self.visit_generics(&sig.generics);
 638                 MethodRibKind(!sig.decl.has_self())
 639             }
 640             FnKind::Closure(_) => ClosureRibKind(node_id),
 641         };
 642
 643         // Create a value rib for the function.
 644         self.ribs[ValueNS].push(Rib::new(rib_kind));
 645
 646         // Create a label rib for the function.
 647         self.label_ribs.push(Rib::new(rib_kind));
 648
 649         // Add each argument to the rib.
 650         let mut bindings_list = FxHashMap();
 651         for argument in &declaration.inputs {
 652             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 653
 654             self.visit_ty(&argument.ty);
 655
 656             debug!("(resolving function) recorded argument");
 657         }
 658         visit::walk_fn_ret_ty(self, &declaration.output);
 659
 660         // Resolve the function body.
 661         match function_kind {
 662             FnKind::ItemFn(.., body) |
 663             FnKind::Method(.., body) => {
 664                 self.visit_block(body);
 665             }
 666             FnKind::Closure(body) => {
 667                 self.visit_expr(body);
 668             }
 669         };
 670
 671         debug!("(resolving function) leaving function");
 672
 673         self.label_ribs.pop();
 674         self.ribs[ValueNS].pop();
 675     }
 676 }
 677
 678 pub type ErrorMessage = Option<(Span, String)>;
 679
 680 #[derive(Copy, Clone)]
 681 enum TypeParameters<'a, 'b> {
 682     NoTypeParameters,
 683     HasTypeParameters(// Type parameters.
 684                       &'b Generics,
 685
 686                       // The kind of the rib used for type parameters.
 687                       RibKind<'a>),
 688 }
 689
 690 // The rib kind controls the translation of local
 691 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 692 #[derive(Copy, Clone, Debug)]
 693 enum RibKind<'a> {
 694     // No translation needs to be applied.
 695     NormalRibKind,
 696
 697     // We passed through a closure scope at the given node ID.
 698     // Translate upvars as appropriate.
 699     ClosureRibKind(NodeId /* func id */),
 700
 701     // We passed through an impl or trait and are now in one of its
 702     // methods. Allow references to ty params that impl or trait
 703     // binds. Disallow any other upvars (including other ty params that are
 704     // upvars).
 705     //
 706     // The boolean value represents the fact that this method is static or not.
 707     MethodRibKind(bool),
 708
 709     // We passed through an item scope. Disallow upvars.
 710     ItemRibKind,
 711
 712     // We're in a constant item. Can't refer to dynamic stuff.
 713     ConstantItemRibKind,
 714
 715     // We passed through a module.
 716     ModuleRibKind(Module<'a>),
 717
 718     // We passed through a `macro_rules!` statement with the given expansion
 719     MacroDefinition(Mark),
 720 }
 721
 722 /// One local scope.
 723 #[derive(Debug)]
 724 struct Rib<'a> {
 725     bindings: FxHashMap<Ident, Def>,
 726     kind: RibKind<'a>,
 727 }
 728
 729 impl<'a> Rib<'a> {
 730     fn new(kind: RibKind<'a>) -> Rib<'a> {
 731         Rib {
 732             bindings: FxHashMap(),
 733             kind: kind,
 734         }
 735     }
 736 }
 737
 738 /// A definition along with the index of the rib it was found on
 739 #[derive(Copy, Clone, Debug)]
 740 struct LocalDef {
 741     ribs: Option<(Namespace, usize)>,
 742     def: Def,
 743 }
 744
 745 enum LexicalScopeBinding<'a> {
 746     Item(&'a NameBinding<'a>),
 747     Def(Def),
 748 }
 749
 750 impl<'a> LexicalScopeBinding<'a> {
 751     fn item(self) -> Option<&'a NameBinding<'a>> {
 752         match self {
 753             LexicalScopeBinding::Item(binding) => Some(binding),
 754             _ => None,
 755         }
 756     }
 757
 758     fn def(self) -> Def {
 759         match self {
 760             LexicalScopeBinding::Item(binding) => binding.def(),
 761             LexicalScopeBinding::Def(def) => def,
 762         }
 763     }
 764 }
 765
 766 #[derive(Clone)]
 767 enum PathResult<'a> {
 768     Module(Module<'a>),
 769     NonModule(PathResolution),
 770     Indeterminate,
 771     Failed(String, bool /* is the error from the last segment? */),
 772 }
 773
 774 enum ModuleKind {
 775     Block(NodeId),
 776     Def(Def, Name),
 777 }
 778
 779 /// One node in the tree of modules.
 780 pub struct ModuleData<'a> {
 781     parent: Option<Module<'a>>,
 782     kind: ModuleKind,
 783
 784     // The def id of the closest normal module (`mod`) ancestor (including this module).
 785     normal_ancestor_id: DefId,
 786
 787     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
 788     legacy_macro_resolutions: RefCell<Vec<(Mark, Ident, Span)>>,
 789     macro_resolutions: RefCell<Vec<(Box<[Ident]>, Span)>>,
 790
 791     // Macro invocations that can expand into items in this module.
 792     unresolved_invocations: RefCell<FxHashSet<Mark>>,
 793
 794     no_implicit_prelude: bool,
 795
 796     glob_importers: RefCell<Vec<&'a ImportDirective<'a>>>,
 797     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 798
 799     // Used to memoize the traits in this module for faster searches through all traits in scope.
 800     traits: RefCell<Option<Box<[(Ident, &'a NameBinding<'a>)]>>>,
 801
 802     // Whether this module is populated. If not populated, any attempt to
 803     // access the children must be preceded with a
 804     // `populate_module_if_necessary` call.
 805     populated: Cell<bool>,
 806 }
 807
 808 pub type Module<'a> = &'a ModuleData<'a>;
 809
 810 impl<'a> ModuleData<'a> {
 811     fn new(parent: Option<Module<'a>>, kind: ModuleKind, normal_ancestor_id: DefId) -> Self {
 812         ModuleData {
 813             parent: parent,
 814             kind: kind,
 815             normal_ancestor_id: normal_ancestor_id,
 816             resolutions: RefCell::new(FxHashMap()),
 817             legacy_macro_resolutions: RefCell::new(Vec::new()),
 818             macro_resolutions: RefCell::new(Vec::new()),
 819             unresolved_invocations: RefCell::new(FxHashSet()),
 820             no_implicit_prelude: false,
 821             glob_importers: RefCell::new(Vec::new()),
 822             globs: RefCell::new((Vec::new())),
 823             traits: RefCell::new(None),
 824             populated: Cell::new(normal_ancestor_id.is_local()),
 825         }
 826     }
 827
 828     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 829         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 830             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 831         }
 832     }
 833
 834     fn def(&self) -> Option<Def> {
 835         match self.kind {
 836             ModuleKind::Def(def, _) => Some(def),
 837             _ => None,
 838         }
 839     }
 840
 841     fn def_id(&self) -> Option<DefId> {
 842         self.def().as_ref().map(Def::def_id)
 843     }
 844
 845     // `self` resolves to the first module ancestor that `is_normal`.
 846     fn is_normal(&self) -> bool {
 847         match self.kind {
 848             ModuleKind::Def(Def::Mod(_), _) => true,
 849             _ => false,
 850         }
 851     }
 852
 853     fn is_trait(&self) -> bool {
 854         match self.kind {
 855             ModuleKind::Def(Def::Trait(_), _) => true,
 856             _ => false,
 857         }
 858     }
 859
 860     fn is_local(&self) -> bool {
 861         self.normal_ancestor_id.is_local()
 862     }
 863 }
 864
 865 impl<'a> fmt::Debug for ModuleData<'a> {
 866     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 867         write!(f, "{:?}", self.def())
 868     }
 869 }
 870
 871 // Records a possibly-private value, type, or module definition.
 872 #[derive(Clone, Debug)]
 873 pub struct NameBinding<'a> {
 874     kind: NameBindingKind<'a>,
 875     expansion: Mark,
 876     span: Span,
 877     vis: ty::Visibility,
 878 }
 879
 880 pub trait ToNameBinding<'a> {
 881     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
 882 }
 883
 884 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
 885     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
 886         self
 887     }
 888 }
 889
 890 #[derive(Clone, Debug)]
 891 enum NameBindingKind<'a> {
 892     Def(Def),
 893     Module(Module<'a>),
 894     Import {
 895         binding: &'a NameBinding<'a>,
 896         directive: &'a ImportDirective<'a>,
 897         used: Cell<bool>,
 898         legacy_self_import: bool,
 899     },
 900     Ambiguity {
 901         b1: &'a NameBinding<'a>,
 902         b2: &'a NameBinding<'a>,
 903         legacy: bool,
 904     }
 905 }
 906
 907 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
 908
 909 struct AmbiguityError<'a> {
 910     span: Span,
 911     name: Name,
 912     lexical: bool,
 913     b1: &'a NameBinding<'a>,
 914     b2: &'a NameBinding<'a>,
 915     legacy: bool,
 916 }
 917
 918 impl<'a> NameBinding<'a> {
 919     fn module(&self) -> Option<Module<'a>> {
 920         match self.kind {
 921             NameBindingKind::Module(module) => Some(module),
 922             NameBindingKind::Import { binding, .. } => binding.module(),
 923             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
 924             _ => None,
 925         }
 926     }
 927
 928     fn def(&self) -> Def {
 929         match self.kind {
 930             NameBindingKind::Def(def) => def,
 931             NameBindingKind::Module(module) => module.def().unwrap(),
 932             NameBindingKind::Import { binding, .. } => binding.def(),
 933             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
 934             NameBindingKind::Ambiguity { .. } => Def::Err,
 935         }
 936     }
 937
 938     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
 939         match self.kind {
 940             NameBindingKind::Import { binding, .. } => binding.get_macro(resolver),
 941             NameBindingKind::Ambiguity { b1, .. } => b1.get_macro(resolver),
 942             _ => resolver.get_macro(self.def()),
 943         }
 944     }
 945
 946     // We sometimes need to treat variants as `pub` for backwards compatibility
 947     fn pseudo_vis(&self) -> ty::Visibility {
 948         if self.is_variant() { ty::Visibility::Public } else { self.vis }
 949     }
 950
 951     fn is_variant(&self) -> bool {
 952         match self.kind {
 953             NameBindingKind::Def(Def::Variant(..)) |
 954             NameBindingKind::Def(Def::VariantCtor(..)) => true,
 955             _ => false,
 956         }
 957     }
 958
 959     fn is_extern_crate(&self) -> bool {
 960         match self.kind {
 961             NameBindingKind::Import {
 962                 directive: &ImportDirective {
 963                     subclass: ImportDirectiveSubclass::ExternCrate, ..
 964                 }, ..
 965             } => true,
 966             _ => false,
 967         }
 968     }
 969
 970     fn is_import(&self) -> bool {
 971         match self.kind {
 972             NameBindingKind::Import { .. } => true,
 973             _ => false,
 974         }
 975     }
 976
 977     fn is_glob_import(&self) -> bool {
 978         match self.kind {
 979             NameBindingKind::Import { directive, .. } => directive.is_glob(),
 980             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
 981             _ => false,
 982         }
 983     }
 984
 985     fn is_importable(&self) -> bool {
 986         match self.def() {
 987             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
 988             _ => true,
 989         }
 990     }
 991 }
 992
 993 /// Interns the names of the primitive types.
 994 struct PrimitiveTypeTable {
 995     primitive_types: FxHashMap<Name, PrimTy>,
 996 }
 997
 998 impl PrimitiveTypeTable {
 999     fn new() -> PrimitiveTypeTable {
1000         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1001
1002         table.intern("bool", TyBool);
1003         table.intern("char", TyChar);
1004         table.intern("f32", TyFloat(FloatTy::F32));
1005         table.intern("f64", TyFloat(FloatTy::F64));
1006         table.intern("isize", TyInt(IntTy::Is));
1007         table.intern("i8", TyInt(IntTy::I8));
1008         table.intern("i16", TyInt(IntTy::I16));
1009         table.intern("i32", TyInt(IntTy::I32));
1010         table.intern("i64", TyInt(IntTy::I64));
1011         table.intern("i128", TyInt(IntTy::I128));
1012         table.intern("str", TyStr);
1013         table.intern("usize", TyUint(UintTy::Us));
1014         table.intern("u8", TyUint(UintTy::U8));
1015         table.intern("u16", TyUint(UintTy::U16));
1016         table.intern("u32", TyUint(UintTy::U32));
1017         table.intern("u64", TyUint(UintTy::U64));
1018         table.intern("u128", TyUint(UintTy::U128));
1019         table
1020     }
1021
1022     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1023         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1024     }
1025 }
1026
1027 /// The main resolver class.
1028 pub struct Resolver<'a> {
1029     session: &'a Session,
1030
1031     pub definitions: Definitions,
1032
1033     // Maps the node id of a statement to the expansions of the `macro_rules!`s
1034     // immediately above the statement (if appropriate).
1035     macros_at_scope: FxHashMap<NodeId, Vec<Mark>>,
1036
1037     graph_root: Module<'a>,
1038
1039     prelude: Option<Module<'a>>,
1040
1041     trait_item_map: FxHashMap<(DefId, Name, Namespace), (Def, bool /* has self */)>,
1042
1043     // Names of fields of an item `DefId` accessible with dot syntax.
1044     // Used for hints during error reporting.
1045     field_names: FxHashMap<DefId, Vec<Name>>,
1046
1047     // All imports known to succeed or fail.
1048     determined_imports: Vec<&'a ImportDirective<'a>>,
1049
1050     // All non-determined imports.
1051     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1052
1053     // The module that represents the current item scope.
1054     current_module: Module<'a>,
1055
1056     // The current set of local scopes for types and values.
1057     // FIXME #4948: Reuse ribs to avoid allocation.
1058     ribs: PerNS<Vec<Rib<'a>>>,
1059
1060     // The current set of local scopes, for labels.
1061     label_ribs: Vec<Rib<'a>>,
1062
1063     // The trait that the current context can refer to.
1064     current_trait_ref: Option<(DefId, TraitRef)>,
1065
1066     // The current self type if inside an impl (used for better errors).
1067     current_self_type: Option<Ty>,
1068
1069     // The idents for the primitive types.
1070     primitive_type_table: PrimitiveTypeTable,
1071
1072     def_map: DefMap,
1073     pub freevars: FreevarMap,
1074     freevars_seen: NodeMap<NodeMap<usize>>,
1075     pub export_map: ExportMap,
1076     pub trait_map: TraitMap,
1077
1078     // A map from nodes to anonymous modules.
1079     // Anonymous modules are pseudo-modules that are implicitly created around items
1080     // contained within blocks.
1081     //
1082     // For example, if we have this:
1083     //
1084     //  fn f() {
1085     //      fn g() {
1086     //          ...
1087     //      }
1088     //  }
1089     //
1090     // There will be an anonymous module created around `g` with the ID of the
1091     // entry block for `f`.
1092     block_map: NodeMap<Module<'a>>,
1093     module_map: FxHashMap<DefId, Module<'a>>,
1094     extern_crate_roots: FxHashMap<(CrateNum, bool /* MacrosOnly? */), Module<'a>>,
1095
1096     pub make_glob_map: bool,
1097     // Maps imports to the names of items actually imported (this actually maps
1098     // all imports, but only glob imports are actually interesting).
1099     pub glob_map: GlobMap,
1100
1101     used_imports: FxHashSet<(NodeId, Namespace)>,
1102     pub maybe_unused_trait_imports: NodeSet,
1103
1104     privacy_errors: Vec<PrivacyError<'a>>,
1105     ambiguity_errors: Vec<AmbiguityError<'a>>,
1106     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1107
1108     arenas: &'a ResolverArenas<'a>,
1109     dummy_binding: &'a NameBinding<'a>,
1110     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1111
1112     pub exported_macros: Vec<ast::MacroDef>,
1113     crate_loader: &'a mut CrateLoader,
1114     macro_names: FxHashSet<Name>,
1115     builtin_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1116     lexical_macro_resolutions: Vec<(Name, &'a Cell<LegacyScope<'a>>)>,
1117     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1118     macro_exports: Vec<Export>,
1119     pub whitelisted_legacy_custom_derives: Vec<Name>,
1120
1121     // Maps the `Mark` of an expansion to its containing module or block.
1122     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1123
1124     // Avoid duplicated errors for "name already defined".
1125     name_already_seen: FxHashMap<Name, Span>,
1126
1127     // If `#![feature(proc_macro)]` is set
1128     proc_macro_enabled: bool,
1129
1130     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1131     warned_proc_macros: FxHashSet<Name>,
1132
1133     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1134 }
1135
1136 pub struct ResolverArenas<'a> {
1137     modules: arena::TypedArena<ModuleData<'a>>,
1138     local_modules: RefCell<Vec<Module<'a>>>,
1139     name_bindings: arena::TypedArena<NameBinding<'a>>,
1140     import_directives: arena::TypedArena<ImportDirective<'a>>,
1141     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1142     invocation_data: arena::TypedArena<InvocationData<'a>>,
1143     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1144 }
1145
1146 impl<'a> ResolverArenas<'a> {
1147     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1148         let module = self.modules.alloc(module);
1149         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1150             self.local_modules.borrow_mut().push(module);
1151         }
1152         module
1153     }
1154     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1155         self.local_modules.borrow()
1156     }
1157     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1158         self.name_bindings.alloc(name_binding)
1159     }
1160     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1161                               -> &'a ImportDirective {
1162         self.import_directives.alloc(import_directive)
1163     }
1164     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1165         self.name_resolutions.alloc(Default::default())
1166     }
1167     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1168                              -> &'a InvocationData<'a> {
1169         self.invocation_data.alloc(expansion_data)
1170     }
1171     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1172         self.legacy_bindings.alloc(binding)
1173     }
1174 }
1175
1176 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1177     fn parent(self, id: DefId) -> Option<DefId> {
1178         match id.krate {
1179             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1180             _ => self.session.cstore.def_key(id).parent,
1181         }.map(|index| DefId { index: index, ..id })
1182     }
1183 }
1184
1185 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1186     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1187         let namespace = if is_value { ValueNS } else { TypeNS };
1188         let hir::Path { ref segments, span, ref mut def } = *path;
1189         let path: Vec<_> = segments.iter().map(|seg| Ident::with_empty_ctxt(seg.name)).collect();
1190         match self.resolve_path(&path, Some(namespace), Some(span)) {
1191             PathResult::Module(module) => *def = module.def().unwrap(),
1192             PathResult::NonModule(path_res) if path_res.depth == 0 => *def = path_res.base_def,
1193             PathResult::NonModule(..) => match self.resolve_path(&path, None, Some(span)) {
1194                 PathResult::Failed(msg, _) => {
1195                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1196                 }
1197                 _ => {}
1198             },
1199             PathResult::Indeterminate => unreachable!(),
1200             PathResult::Failed(msg, _) => {
1201                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1202             }
1203         }
1204     }
1205
1206     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1207         self.def_map.get(&id).cloned()
1208     }
1209
1210     fn definitions(&mut self) -> &mut Definitions {
1211         &mut self.definitions
1212     }
1213 }
1214
1215 impl<'a> Resolver<'a> {
1216     pub fn new(session: &'a Session,
1217                krate: &Crate,
1218                make_glob_map: MakeGlobMap,
1219                crate_loader: &'a mut CrateLoader,
1220                arenas: &'a ResolverArenas<'a>)
1221                -> Resolver<'a> {
1222         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1223         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1224         let graph_root = arenas.alloc_module(ModuleData {
1225             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1226             ..ModuleData::new(None, root_module_kind, root_def_id)
1227         });
1228         let mut module_map = FxHashMap();
1229         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1230
1231         let mut definitions = Definitions::new();
1232         DefCollector::new(&mut definitions).collect_root();
1233
1234         let mut invocations = FxHashMap();
1235         invocations.insert(Mark::root(),
1236                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1237
1238         let features = session.features.borrow();
1239
1240         Resolver {
1241             session: session,
1242
1243             definitions: definitions,
1244             macros_at_scope: FxHashMap(),
1245
1246             // The outermost module has def ID 0; this is not reflected in the
1247             // AST.
1248             graph_root: graph_root,
1249             prelude: None,
1250
1251             trait_item_map: FxHashMap(),
1252             field_names: FxHashMap(),
1253
1254             determined_imports: Vec::new(),
1255             indeterminate_imports: Vec::new(),
1256
1257             current_module: graph_root,
1258             ribs: PerNS {
1259                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1260                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1261                 macro_ns: None,
1262             },
1263             label_ribs: Vec::new(),
1264
1265             current_trait_ref: None,
1266             current_self_type: None,
1267
1268             primitive_type_table: PrimitiveTypeTable::new(),
1269
1270             def_map: NodeMap(),
1271             freevars: NodeMap(),
1272             freevars_seen: NodeMap(),
1273             export_map: NodeMap(),
1274             trait_map: NodeMap(),
1275             module_map: module_map,
1276             block_map: NodeMap(),
1277             extern_crate_roots: FxHashMap(),
1278
1279             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1280             glob_map: NodeMap(),
1281
1282             used_imports: FxHashSet(),
1283             maybe_unused_trait_imports: NodeSet(),
1284
1285             privacy_errors: Vec::new(),
1286             ambiguity_errors: Vec::new(),
1287             disallowed_shadowing: Vec::new(),
1288
1289             arenas: arenas,
1290             dummy_binding: arenas.alloc_name_binding(NameBinding {
1291                 kind: NameBindingKind::Def(Def::Err),
1292                 expansion: Mark::root(),
1293                 span: DUMMY_SP,
1294                 vis: ty::Visibility::Public,
1295             }),
1296
1297             // `#![feature(proc_macro)]` implies `#[feature(extern_macros)]`
1298             use_extern_macros: features.use_extern_macros || features.proc_macro,
1299
1300             exported_macros: Vec::new(),
1301             crate_loader: crate_loader,
1302             macro_names: FxHashSet(),
1303             builtin_macros: FxHashMap(),
1304             lexical_macro_resolutions: Vec::new(),
1305             macro_map: FxHashMap(),
1306             macro_exports: Vec::new(),
1307             invocations: invocations,
1308             name_already_seen: FxHashMap(),
1309             whitelisted_legacy_custom_derives: Vec::new(),
1310             proc_macro_enabled: features.proc_macro,
1311             warned_proc_macros: FxHashSet(),
1312             potentially_unused_imports: Vec::new(),
1313         }
1314     }
1315
1316     pub fn arenas() -> ResolverArenas<'a> {
1317         ResolverArenas {
1318             modules: arena::TypedArena::new(),
1319             local_modules: RefCell::new(Vec::new()),
1320             name_bindings: arena::TypedArena::new(),
1321             import_directives: arena::TypedArena::new(),
1322             name_resolutions: arena::TypedArena::new(),
1323             invocation_data: arena::TypedArena::new(),
1324             legacy_bindings: arena::TypedArena::new(),
1325         }
1326     }
1327
1328     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1329         PerNS {
1330             type_ns: f(self, TypeNS),
1331             value_ns: f(self, ValueNS),
1332             macro_ns: match self.use_extern_macros {
1333                 true => Some(f(self, MacroNS)),
1334                 false => None,
1335             },
1336         }
1337     }
1338
1339     /// Entry point to crate resolution.
1340     pub fn resolve_crate(&mut self, krate: &Crate) {
1341         ImportResolver { resolver: self }.finalize_imports();
1342         self.current_module = self.graph_root;
1343         self.finalize_current_module_macro_resolutions();
1344         visit::walk_crate(self, krate);
1345
1346         check_unused::check_crate(self, krate);
1347         self.report_errors();
1348         self.crate_loader.postprocess(krate);
1349     }
1350
1351     fn new_module(&self, parent: Module<'a>, kind: ModuleKind, normal_ancestor_id: DefId)
1352                   -> Module<'a> {
1353         self.arenas.alloc_module(ModuleData::new(Some(parent), kind, normal_ancestor_id))
1354     }
1355
1356     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1357                   -> bool /* true if an error was reported */ {
1358         match binding.kind {
1359             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1360                     if !used.get() => {
1361                 used.set(true);
1362                 directive.used.set(true);
1363                 if legacy_self_import {
1364                     self.warn_legacy_self_import(directive);
1365                     return false;
1366                 }
1367                 self.used_imports.insert((directive.id, ns));
1368                 self.add_to_glob_map(directive.id, ident);
1369                 self.record_use(ident, ns, binding, span)
1370             }
1371             NameBindingKind::Import { .. } => false,
1372             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1373                 self.ambiguity_errors.push(AmbiguityError {
1374                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy: legacy,
1375                 });
1376                 if legacy {
1377                     self.record_use(ident, ns, b1, span);
1378                 }
1379                 !legacy
1380             }
1381             _ => false
1382         }
1383     }
1384
1385     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1386         if self.make_glob_map {
1387             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1388         }
1389     }
1390
1391     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1392     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1393     /// `ident` in the first scope that defines it (or None if no scopes define it).
1394     ///
1395     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1396     /// the items are defined in the block. For example,
1397     /// ```rust
1398     /// fn f() {
1399     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1400     ///    let g = || {};
1401     ///    fn g() {}
1402     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1403     /// }
1404     /// ```
1405     ///
1406     /// Invariant: This must only be called during main resolution, not during
1407     /// import resolution.
1408     fn resolve_ident_in_lexical_scope(&mut self,
1409                                       mut ident: Ident,
1410                                       ns: Namespace,
1411                                       record_used: Option<Span>)
1412                                       -> Option<LexicalScopeBinding<'a>> {
1413         if ns == TypeNS {
1414             ident = ident.unhygienize();
1415         }
1416
1417         // Walk backwards up the ribs in scope.
1418         for i in (0 .. self.ribs[ns].len()).rev() {
1419             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1420                 // The ident resolves to a type parameter or local variable.
1421                 return Some(LexicalScopeBinding::Def(
1422                     self.adjust_local_def(LocalDef { ribs: Some((ns, i)), def: def }, record_used)
1423                 ));
1424             }
1425
1426             if let ModuleRibKind(module) = self.ribs[ns][i].kind {
1427                 let item = self.resolve_ident_in_module(module, ident, ns, false, record_used);
1428                 if let Ok(binding) = item {
1429                     // The ident resolves to an item.
1430                     return Some(LexicalScopeBinding::Item(binding));
1431                 }
1432
1433                 if let ModuleKind::Block(..) = module.kind { // We can see through blocks
1434                 } else if !module.no_implicit_prelude {
1435                     return self.prelude.and_then(|prelude| {
1436                         self.resolve_ident_in_module(prelude, ident, ns, false, None).ok()
1437                     }).map(LexicalScopeBinding::Item)
1438                 } else {
1439                     return None;
1440                 }
1441             }
1442
1443             if let MacroDefinition(mac) = self.ribs[ns][i].kind {
1444                 // If an invocation of this macro created `ident`, give up on `ident`
1445                 // and switch to `ident`'s source from the macro definition.
1446                 let (source_ctxt, source_macro) = ident.ctxt.source();
1447                 if source_macro == mac {
1448                     ident.ctxt = source_ctxt;
1449                 }
1450             }
1451         }
1452
1453         None
1454     }
1455
1456     fn resolve_crate_var(&mut self, mut crate_var_ctxt: SyntaxContext) -> Module<'a> {
1457         while crate_var_ctxt.source().0 != SyntaxContext::empty() {
1458             crate_var_ctxt = crate_var_ctxt.source().0;
1459         }
1460         let module = self.invocations[&crate_var_ctxt.source().1].module.get();
1461         if module.is_local() { self.graph_root } else { module }
1462     }
1463
1464     // AST resolution
1465     //
1466     // We maintain a list of value ribs and type ribs.
1467     //
1468     // Simultaneously, we keep track of the current position in the module
1469     // graph in the `current_module` pointer. When we go to resolve a name in
1470     // the value or type namespaces, we first look through all the ribs and
1471     // then query the module graph. When we resolve a name in the module
1472     // namespace, we can skip all the ribs (since nested modules are not
1473     // allowed within blocks in Rust) and jump straight to the current module
1474     // graph node.
1475     //
1476     // Named implementations are handled separately. When we find a method
1477     // call, we consult the module node to find all of the implementations in
1478     // scope. This information is lazily cached in the module node. We then
1479     // generate a fake "implementation scope" containing all the
1480     // implementations thus found, for compatibility with old resolve pass.
1481
1482     fn with_scope<F>(&mut self, id: NodeId, f: F)
1483         where F: FnOnce(&mut Resolver)
1484     {
1485         let id = self.definitions.local_def_id(id);
1486         let module = self.module_map.get(&id).cloned(); // clones a reference
1487         if let Some(module) = module {
1488             // Move down in the graph.
1489             let orig_module = replace(&mut self.current_module, module);
1490             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1491             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1492
1493             self.finalize_current_module_macro_resolutions();
1494             f(self);
1495
1496             self.current_module = orig_module;
1497             self.ribs[ValueNS].pop();
1498             self.ribs[TypeNS].pop();
1499         } else {
1500             f(self);
1501         }
1502     }
1503
1504     /// Searches the current set of local scopes for labels.
1505     /// Stops after meeting a closure.
1506     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1507         for rib in self.label_ribs.iter().rev() {
1508             match rib.kind {
1509                 NormalRibKind => {
1510                     // Continue
1511                 }
1512                 MacroDefinition(mac) => {
1513                     // If an invocation of this macro created `ident`, give up on `ident`
1514                     // and switch to `ident`'s source from the macro definition.
1515                     let (source_ctxt, source_macro) = ident.ctxt.source();
1516                     if source_macro == mac {
1517                         ident.ctxt = source_ctxt;
1518                     }
1519                 }
1520                 _ => {
1521                     // Do not resolve labels across function boundary
1522                     return None;
1523                 }
1524             }
1525             let result = rib.bindings.get(&ident).cloned();
1526             if result.is_some() {
1527                 return result;
1528             }
1529         }
1530         None
1531     }
1532
1533     fn resolve_item(&mut self, item: &Item) {
1534         let name = item.ident.name;
1535
1536         debug!("(resolving item) resolving {}", name);
1537
1538         self.check_proc_macro_attrs(&item.attrs);
1539
1540         match item.node {
1541             ItemKind::Enum(_, ref generics) |
1542             ItemKind::Ty(_, ref generics) |
1543             ItemKind::Struct(_, ref generics) |
1544             ItemKind::Union(_, ref generics) |
1545             ItemKind::Fn(.., ref generics, _) => {
1546                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1547                                              |this| visit::walk_item(this, item));
1548             }
1549
1550             ItemKind::DefaultImpl(_, ref trait_ref) => {
1551                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1552                     // Resolve type arguments in trait path
1553                     visit::walk_trait_ref(this, trait_ref);
1554                 });
1555             }
1556             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1557                 self.resolve_implementation(generics,
1558                                             opt_trait_ref,
1559                                             &self_type,
1560                                             item.id,
1561                                             impl_items),
1562
1563             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1564                 // Create a new rib for the trait-wide type parameters.
1565                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1566                     let local_def_id = this.definitions.local_def_id(item.id);
1567                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1568                         this.visit_generics(generics);
1569                         walk_list!(this, visit_ty_param_bound, bounds);
1570
1571                         for trait_item in trait_items {
1572                             this.check_proc_macro_attrs(&trait_item.attrs);
1573
1574                             match trait_item.node {
1575                                 TraitItemKind::Const(_, ref default) => {
1576                                     // Only impose the restrictions of
1577                                     // ConstRibKind if there's an actual constant
1578                                     // expression in a provided default.
1579                                     if default.is_some() {
1580                                         this.with_constant_rib(|this| {
1581                                             visit::walk_trait_item(this, trait_item)
1582                                         });
1583                                     } else {
1584                                         visit::walk_trait_item(this, trait_item)
1585                                     }
1586                                 }
1587                                 TraitItemKind::Method(ref sig, _) => {
1588                                     let type_parameters =
1589                                         HasTypeParameters(&sig.generics,
1590                                                           MethodRibKind(!sig.decl.has_self()));
1591                                     this.with_type_parameter_rib(type_parameters, |this| {
1592                                         visit::walk_trait_item(this, trait_item)
1593                                     });
1594                                 }
1595                                 TraitItemKind::Type(..) => {
1596                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1597                                         visit::walk_trait_item(this, trait_item)
1598                                     });
1599                                 }
1600                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1601                             };
1602                         }
1603                     });
1604                 });
1605             }
1606
1607             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1608                 self.with_scope(item.id, |this| {
1609                     visit::walk_item(this, item);
1610                 });
1611             }
1612
1613             ItemKind::Const(..) | ItemKind::Static(..) => {
1614                 self.with_constant_rib(|this| {
1615                     visit::walk_item(this, item);
1616                 });
1617             }
1618
1619             ItemKind::Use(ref view_path) => {
1620                 match view_path.node {
1621                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1622                         // Resolve prefix of an import with empty braces (issue #28388).
1623                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1624                     }
1625                     _ => {}
1626                 }
1627             }
1628
1629             ItemKind::ExternCrate(_) => {
1630                 // do nothing, these are just around to be encoded
1631             }
1632
1633             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1634         }
1635     }
1636
1637     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1638         where F: FnOnce(&mut Resolver)
1639     {
1640         match type_parameters {
1641             HasTypeParameters(generics, rib_kind) => {
1642                 let mut function_type_rib = Rib::new(rib_kind);
1643                 let mut seen_bindings = FxHashMap();
1644                 for type_parameter in &generics.ty_params {
1645                     let name = type_parameter.ident.name;
1646                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1647
1648                     if seen_bindings.contains_key(&name) {
1649                         let span = seen_bindings.get(&name).unwrap();
1650                         resolve_error(self,
1651                                       type_parameter.span,
1652                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name,
1653                                                                                           span));
1654                     }
1655                     seen_bindings.entry(name).or_insert(type_parameter.span);
1656
1657                     // plain insert (no renaming)
1658                     let def_id = self.definitions.local_def_id(type_parameter.id);
1659                     let def = Def::TyParam(def_id);
1660                     function_type_rib.bindings.insert(Ident::with_empty_ctxt(name), def);
1661                     self.record_def(type_parameter.id, PathResolution::new(def));
1662                 }
1663                 self.ribs[TypeNS].push(function_type_rib);
1664             }
1665
1666             NoTypeParameters => {
1667                 // Nothing to do.
1668             }
1669         }
1670
1671         f(self);
1672
1673         if let HasTypeParameters(..) = type_parameters {
1674             self.ribs[TypeNS].pop();
1675         }
1676     }
1677
1678     fn with_label_rib<F>(&mut self, f: F)
1679         where F: FnOnce(&mut Resolver)
1680     {
1681         self.label_ribs.push(Rib::new(NormalRibKind));
1682         f(self);
1683         self.label_ribs.pop();
1684     }
1685
1686     fn with_constant_rib<F>(&mut self, f: F)
1687         where F: FnOnce(&mut Resolver)
1688     {
1689         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1690         self.ribs[TypeNS].push(Rib::new(ConstantItemRibKind));
1691         f(self);
1692         self.ribs[TypeNS].pop();
1693         self.ribs[ValueNS].pop();
1694     }
1695
1696     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1697         where F: FnOnce(&mut Resolver) -> T
1698     {
1699         // Handle nested impls (inside fn bodies)
1700         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1701         let result = f(self);
1702         self.current_self_type = previous_value;
1703         result
1704     }
1705
1706     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1707         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1708     {
1709         let mut new_val = None;
1710         let mut new_id = None;
1711         if let Some(trait_ref) = opt_trait_ref {
1712             let def = self.smart_resolve_path(trait_ref.ref_id, None,
1713                                               &trait_ref.path, PathSource::Trait).base_def;
1714             if def != Def::Err {
1715                 new_val = Some((def.def_id(), trait_ref.clone()));
1716                 new_id = Some(def.def_id());
1717             }
1718         }
1719         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1720         let result = f(self, new_id);
1721         self.current_trait_ref = original_trait_ref;
1722         result
1723     }
1724
1725     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
1726         where F: FnOnce(&mut Resolver)
1727     {
1728         let mut self_type_rib = Rib::new(NormalRibKind);
1729
1730         // plain insert (no renaming, types are not currently hygienic....)
1731         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
1732         self.ribs[TypeNS].push(self_type_rib);
1733         f(self);
1734         self.ribs[TypeNS].pop();
1735     }
1736
1737     fn resolve_implementation(&mut self,
1738                               generics: &Generics,
1739                               opt_trait_reference: &Option<TraitRef>,
1740                               self_type: &Ty,
1741                               item_id: NodeId,
1742                               impl_items: &[ImplItem]) {
1743         // If applicable, create a rib for the type parameters.
1744         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1745             // Dummy self type for better errors if `Self` is used in the trait path.
1746             this.with_self_rib(Def::SelfTy(None, None), |this| {
1747                 // Resolve the trait reference, if necessary.
1748                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1749                     let item_def_id = this.definitions.local_def_id(item_id);
1750                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
1751                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
1752                             // Resolve type arguments in trait path
1753                             visit::walk_trait_ref(this, trait_ref);
1754                         }
1755                         // Resolve the self type.
1756                         this.visit_ty(self_type);
1757                         // Resolve the type parameters.
1758                         this.visit_generics(generics);
1759                         this.with_current_self_type(self_type, |this| {
1760                             for impl_item in impl_items {
1761                                 this.check_proc_macro_attrs(&impl_item.attrs);
1762                                 this.resolve_visibility(&impl_item.vis);
1763                                 match impl_item.node {
1764                                     ImplItemKind::Const(..) => {
1765                                         // If this is a trait impl, ensure the const
1766                                         // exists in trait
1767                                         this.check_trait_item(impl_item.ident.name,
1768                                                             ValueNS,
1769                                                             impl_item.span,
1770                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
1771                                         visit::walk_impl_item(this, impl_item);
1772                                     }
1773                                     ImplItemKind::Method(ref sig, _) => {
1774                                         // If this is a trait impl, ensure the method
1775                                         // exists in trait
1776                                         this.check_trait_item(impl_item.ident.name,
1777                                                             ValueNS,
1778                                                             impl_item.span,
1779                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
1780
1781                                         // We also need a new scope for the method-
1782                                         // specific type parameters.
1783                                         let type_parameters =
1784                                             HasTypeParameters(&sig.generics,
1785                                                             MethodRibKind(!sig.decl.has_self()));
1786                                         this.with_type_parameter_rib(type_parameters, |this| {
1787                                             visit::walk_impl_item(this, impl_item);
1788                                         });
1789                                     }
1790                                     ImplItemKind::Type(ref ty) => {
1791                                         // If this is a trait impl, ensure the type
1792                                         // exists in trait
1793                                         this.check_trait_item(impl_item.ident.name,
1794                                                             TypeNS,
1795                                                             impl_item.span,
1796                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
1797
1798                                         this.visit_ty(ty);
1799                                     }
1800                                     ImplItemKind::Macro(_) =>
1801                                         panic!("unexpanded macro in resolve!"),
1802                                 }
1803                             }
1804                         });
1805                     });
1806                 });
1807             });
1808         });
1809     }
1810
1811     fn check_trait_item<F>(&self, name: Name, ns: Namespace, span: Span, err: F)
1812         where F: FnOnce(Name, &str) -> ResolutionError
1813     {
1814         // If there is a TraitRef in scope for an impl, then the method must be in the
1815         // trait.
1816         if let Some((did, ref trait_ref)) = self.current_trait_ref {
1817             if !self.trait_item_map.contains_key(&(did, name, ns)) {
1818                 let path_str = path_names_to_string(&trait_ref.path);
1819                 resolve_error(self, span, err(name, &path_str));
1820             }
1821         }
1822     }
1823
1824     fn resolve_local(&mut self, local: &Local) {
1825         // Resolve the type.
1826         walk_list!(self, visit_ty, &local.ty);
1827
1828         // Resolve the initializer.
1829         walk_list!(self, visit_expr, &local.init);
1830
1831         // Resolve the pattern.
1832         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
1833     }
1834
1835     // build a map from pattern identifiers to binding-info's.
1836     // this is done hygienically. This could arise for a macro
1837     // that expands into an or-pattern where one 'x' was from the
1838     // user and one 'x' came from the macro.
1839     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1840         let mut binding_map = FxHashMap();
1841
1842         pat.walk(&mut |pat| {
1843             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
1844                 if sub_pat.is_some() || match self.def_map.get(&pat.id) {
1845                     Some(&PathResolution { base_def: Def::Local(..), .. }) => true,
1846                     _ => false,
1847                 } {
1848                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
1849                     binding_map.insert(ident.node, binding_info);
1850                 }
1851             }
1852             true
1853         });
1854
1855         binding_map
1856     }
1857
1858     // check that all of the arms in an or-pattern have exactly the
1859     // same set of bindings, with the same binding modes for each.
1860     fn check_consistent_bindings(&mut self, arm: &Arm) {
1861         if arm.pats.is_empty() {
1862             return;
1863         }
1864         let map_0 = self.binding_mode_map(&arm.pats[0]);
1865         for (i, p) in arm.pats.iter().enumerate() {
1866             let map_i = self.binding_mode_map(&p);
1867
1868             for (&key, &binding_0) in &map_0 {
1869                 match map_i.get(&key) {
1870                     None => {
1871                         let error = ResolutionError::VariableNotBoundInPattern(key.name, 1, i + 1);
1872                         resolve_error(self, p.span, error);
1873                     }
1874                     Some(binding_i) => {
1875                         if binding_0.binding_mode != binding_i.binding_mode {
1876                             resolve_error(self,
1877                                           binding_i.span,
1878                                           ResolutionError::VariableBoundWithDifferentMode(
1879                                               key.name,
1880                                               i + 1,
1881                                               binding_0.span));
1882                         }
1883                     }
1884                 }
1885             }
1886
1887             for (&key, &binding) in &map_i {
1888                 if !map_0.contains_key(&key) {
1889                     resolve_error(self,
1890                                   binding.span,
1891                                   ResolutionError::VariableNotBoundInPattern(key.name, i + 1, 1));
1892                 }
1893             }
1894         }
1895     }
1896
1897     fn resolve_arm(&mut self, arm: &Arm) {
1898         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
1899
1900         let mut bindings_list = FxHashMap();
1901         for pattern in &arm.pats {
1902             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
1903         }
1904
1905         // This has to happen *after* we determine which
1906         // pat_idents are variants
1907         self.check_consistent_bindings(arm);
1908
1909         walk_list!(self, visit_expr, &arm.guard);
1910         self.visit_expr(&arm.body);
1911
1912         self.ribs[ValueNS].pop();
1913     }
1914
1915     fn resolve_block(&mut self, block: &Block) {
1916         debug!("(resolving block) entering block");
1917         // Move down in the graph, if there's an anonymous module rooted here.
1918         let orig_module = self.current_module;
1919         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
1920
1921         let mut num_macro_definition_ribs = 0;
1922         if let Some(anonymous_module) = anonymous_module {
1923             debug!("(resolving block) found anonymous module, moving down");
1924             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1925             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1926             self.current_module = anonymous_module;
1927             self.finalize_current_module_macro_resolutions();
1928         } else {
1929             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
1930         }
1931
1932         // Descend into the block.
1933         for stmt in &block.stmts {
1934             if let Some(marks) = self.macros_at_scope.remove(&stmt.id) {
1935                 num_macro_definition_ribs += marks.len() as u32;
1936                 for mark in marks {
1937                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(mark)));
1938                     self.label_ribs.push(Rib::new(MacroDefinition(mark)));
1939                 }
1940             }
1941
1942             self.visit_stmt(stmt);
1943         }
1944
1945         // Move back up.
1946         self.current_module = orig_module;
1947         for _ in 0 .. num_macro_definition_ribs {
1948             self.ribs[ValueNS].pop();
1949             self.label_ribs.pop();
1950         }
1951         self.ribs[ValueNS].pop();
1952         if let Some(_) = anonymous_module {
1953             self.ribs[TypeNS].pop();
1954         }
1955         debug!("(resolving block) leaving block");
1956     }
1957
1958     fn fresh_binding(&mut self,
1959                      ident: &SpannedIdent,
1960                      pat_id: NodeId,
1961                      outer_pat_id: NodeId,
1962                      pat_src: PatternSource,
1963                      bindings: &mut FxHashMap<Ident, NodeId>)
1964                      -> PathResolution {
1965         // Add the binding to the local ribs, if it
1966         // doesn't already exist in the bindings map. (We
1967         // must not add it if it's in the bindings map
1968         // because that breaks the assumptions later
1969         // passes make about or-patterns.)
1970         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
1971         match bindings.get(&ident.node).cloned() {
1972             Some(id) if id == outer_pat_id => {
1973                 // `Variant(a, a)`, error
1974                 resolve_error(
1975                     self,
1976                     ident.span,
1977                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
1978                         &ident.node.name.as_str())
1979                 );
1980             }
1981             Some(..) if pat_src == PatternSource::FnParam => {
1982                 // `fn f(a: u8, a: u8)`, error
1983                 resolve_error(
1984                     self,
1985                     ident.span,
1986                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
1987                         &ident.node.name.as_str())
1988                 );
1989             }
1990             Some(..) if pat_src == PatternSource::Match => {
1991                 // `Variant1(a) | Variant2(a)`, ok
1992                 // Reuse definition from the first `a`.
1993                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
1994             }
1995             Some(..) => {
1996                 span_bug!(ident.span, "two bindings with the same name from \
1997                                        unexpected pattern source {:?}", pat_src);
1998             }
1999             None => {
2000                 // A completely fresh binding, add to the lists if it's valid.
2001                 if ident.node.name != keywords::Invalid.name() {
2002                     bindings.insert(ident.node, outer_pat_id);
2003                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2004                 }
2005             }
2006         }
2007
2008         PathResolution::new(def)
2009     }
2010
2011     fn resolve_pattern(&mut self,
2012                        pat: &Pat,
2013                        pat_src: PatternSource,
2014                        // Maps idents to the node ID for the
2015                        // outermost pattern that binds them.
2016                        bindings: &mut FxHashMap<Ident, NodeId>) {
2017         // Visit all direct subpatterns of this pattern.
2018         let outer_pat_id = pat.id;
2019         pat.walk(&mut |pat| {
2020             match pat.node {
2021                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2022                     // First try to resolve the identifier as some existing
2023                     // entity, then fall back to a fresh binding.
2024                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS, None)
2025                                       .and_then(LexicalScopeBinding::item);
2026                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2027                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2028                                              bmode != BindingMode::ByValue(Mutability::Immutable);
2029                         match def {
2030                             Def::StructCtor(_, CtorKind::Const) |
2031                             Def::VariantCtor(_, CtorKind::Const) |
2032                             Def::Const(..) if !always_binding => {
2033                                 // A unit struct/variant or constant pattern.
2034                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2035                                 Some(PathResolution::new(def))
2036                             }
2037                             Def::StructCtor(..) | Def::VariantCtor(..) |
2038                             Def::Const(..) | Def::Static(..) => {
2039                                 // A fresh binding that shadows something unacceptable.
2040                                 resolve_error(
2041                                     self,
2042                                     ident.span,
2043                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2044                                         pat_src.descr(), ident.node.name, binding.unwrap())
2045                                 );
2046                                 None
2047                             }
2048                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2049                                 // These entities are explicitly allowed
2050                                 // to be shadowed by fresh bindings.
2051                                 None
2052                             }
2053                             def => {
2054                                 span_bug!(ident.span, "unexpected definition for an \
2055                                                        identifier in pattern: {:?}", def);
2056                             }
2057                         }
2058                     }).unwrap_or_else(|| {
2059                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2060                     });
2061
2062                     self.record_def(pat.id, resolution);
2063                 }
2064
2065                 PatKind::TupleStruct(ref path, ..) => {
2066                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2067                 }
2068
2069                 PatKind::Path(ref qself, ref path) => {
2070                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2071                 }
2072
2073                 PatKind::Struct(ref path, ..) => {
2074                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2075                 }
2076
2077                 _ => {}
2078             }
2079             true
2080         });
2081
2082         visit::walk_pat(self, pat);
2083     }
2084
2085     // High-level and context dependent path resolution routine.
2086     // Resolves the path and records the resolution into definition map.
2087     // If resolution fails tries several techniques to find likely
2088     // resolution candidates, suggest imports or other help, and report
2089     // errors in user friendly way.
2090     fn smart_resolve_path(&mut self,
2091                           id: NodeId,
2092                           qself: Option<&QSelf>,
2093                           path: &Path,
2094                           source: PathSource)
2095                           -> PathResolution {
2096         let segments = &path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>();
2097         self.smart_resolve_path_fragment(id, qself, segments, path.span, source)
2098     }
2099
2100     fn smart_resolve_path_fragment(&mut self,
2101                                    id: NodeId,
2102                                    qself: Option<&QSelf>,
2103                                    path: &[Ident],
2104                                    span: Span,
2105                                    source: PathSource)
2106                                    -> PathResolution {
2107         let ns = source.namespace();
2108         let is_expected = &|def| source.is_expected(def);
2109
2110         // Base error is amended with one short label and possibly some longer helps/notes.
2111         let report_errors = |this: &mut Self, def: Option<Def>| {
2112             // Make the base error.
2113             let expected = source.descr_expected();
2114             let path_str = names_to_string(path);
2115             let code = source.error_code(def.is_some());
2116             let (base_msg, fallback_label) = if let Some(def) = def {
2117                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2118                  format!("not a {}", expected))
2119             } else {
2120                 let item_str = path[path.len() - 1];
2121                 let (mod_prefix, mod_str) = if path.len() == 1 {
2122                     (format!(""), format!("this scope"))
2123                 } else if path.len() == 2 && path[0].name == keywords::CrateRoot.name() {
2124                     (format!(""), format!("the crate root"))
2125                 } else {
2126                     let mod_path = &path[..path.len() - 1];
2127                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), None) {
2128                         PathResult::Module(module) => module.def(),
2129                         _ => None,
2130                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2131                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2132                 };
2133                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2134                  format!("not found in {}", mod_str))
2135             };
2136             let mut err = this.session.struct_span_err_with_code(span, &base_msg, code);
2137
2138             // Emit special messages for unresolved `Self` and `self`.
2139             if is_self_type(path, ns) {
2140                 __diagnostic_used!(E0411);
2141                 err.code("E0411".into());
2142                 err.span_label(span, &format!("`Self` is only available in traits and impls"));
2143                 return err;
2144             }
2145             if is_self_value(path, ns) {
2146                 __diagnostic_used!(E0424);
2147                 err.code("E0424".into());
2148                 err.span_label(span, &format!("`self` value is only available in \
2149                                                methods with `self` parameter"));
2150                 return err;
2151             }
2152
2153             // Try to lookup the name in more relaxed fashion for better error reporting.
2154             let name = path.last().unwrap().name;
2155             let candidates = this.lookup_import_candidates(name, ns, is_expected);
2156             if !candidates.is_empty() {
2157                 // Report import candidates as help and proceed searching for labels.
2158                 show_candidates(&mut err, &candidates, def.is_some());
2159             }
2160             if path.len() == 1 && this.self_type_is_available() {
2161                 if let Some(candidate) = this.lookup_assoc_candidate(name, ns, is_expected) {
2162                     let self_is_available = this.self_value_is_available(path[0].ctxt);
2163                     match candidate {
2164                         AssocSuggestion::Field => {
2165                             err.span_label(span, &format!("did you mean `self.{}`?", path_str));
2166                             if !self_is_available {
2167                                 err.span_label(span, &format!("`self` value is only available in \
2168                                                                methods with `self` parameter"));
2169                             }
2170                         }
2171                         AssocSuggestion::MethodWithSelf if self_is_available => {
2172                             err.span_label(span, &format!("did you mean `self.{}(...)`?",
2173                                                            path_str));
2174                         }
2175                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2176                             err.span_label(span, &format!("did you mean `Self::{}`?", path_str));
2177                         }
2178                     }
2179                     return err;
2180                 }
2181             }
2182
2183             // Try context dependent help if relaxed lookup didn't work.
2184             if let Some(def) = def {
2185                 match (def, source) {
2186                     (Def::Macro(..), _) => {
2187                         err.span_label(span, &format!("did you mean `{}!(...)`?", path_str));
2188                         return err;
2189                     }
2190                     (Def::TyAlias(..), PathSource::Trait) => {
2191                         err.span_label(span, &format!("type aliases cannot be used for traits"));
2192                         return err;
2193                     }
2194                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match *parent {
2195                         ExprKind::Field(_, ident) => {
2196                             err.span_label(span, &format!("did you mean `{}::{}`?",
2197                                                            path_str, ident.node));
2198                             return err;
2199                         }
2200                         ExprKind::MethodCall(ident, ..) => {
2201                             err.span_label(span, &format!("did you mean `{}::{}(...)`?",
2202                                                            path_str, ident.node));
2203                             return err;
2204                         }
2205                         _ => {}
2206                     },
2207                     _ if ns == ValueNS && is_struct_like(def) => {
2208                         err.span_label(span, &format!("did you mean `{} {{ /* fields */ }}`?",
2209                                                        path_str));
2210                         return err;
2211                     }
2212                     _ => {}
2213                 }
2214             }
2215
2216             // Try Levenshtein if nothing else worked.
2217             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected) {
2218                 err.span_label(span, &format!("did you mean `{}`?", candidate));
2219                 return err;
2220             }
2221
2222             // Fallback label.
2223             err.span_label(span, &fallback_label);
2224             err
2225         };
2226         let report_errors = |this: &mut Self, def: Option<Def>| {
2227             report_errors(this, def).emit();
2228             err_path_resolution()
2229         };
2230
2231         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2232                                                            source.defer_to_typeck(),
2233                                                            source.global_by_default()) {
2234             Some(resolution) if resolution.depth == 0 => {
2235                 if is_expected(resolution.base_def) || resolution.base_def == Def::Err {
2236                     resolution
2237                 } else {
2238                     report_errors(self, Some(resolution.base_def))
2239                 }
2240             }
2241             Some(resolution) if source.defer_to_typeck() => {
2242                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2243                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2244                 // it needs to be added to the trait map.
2245                 if ns == ValueNS {
2246                     let item_name = path.last().unwrap().name;
2247                     let traits = self.get_traits_containing_item(item_name, ns);
2248                     self.trait_map.insert(id, traits);
2249                 }
2250                 resolution
2251             }
2252             _ => report_errors(self, None)
2253         };
2254
2255         if let PathSource::TraitItem(..) = source {} else {
2256             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2257             self.record_def(id, resolution);
2258         }
2259         resolution
2260     }
2261
2262     fn self_type_is_available(&mut self) -> bool {
2263         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(), TypeNS, None);
2264         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2265     }
2266
2267     fn self_value_is_available(&mut self, ctxt: SyntaxContext) -> bool {
2268         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2269         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None);
2270         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2271     }
2272
2273     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2274     fn resolve_qpath_anywhere(&mut self,
2275                               id: NodeId,
2276                               qself: Option<&QSelf>,
2277                               path: &[Ident],
2278                               primary_ns: Namespace,
2279                               span: Span,
2280                               defer_to_typeck: bool,
2281                               global_by_default: bool)
2282                               -> Option<PathResolution> {
2283         let mut fin_res = None;
2284         // FIXME: can't resolve paths in macro namespace yet, macros are
2285         // processed by the little special hack below.
2286         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2287             if i == 0 || ns != primary_ns {
2288                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2289                     // If defer_to_typeck, then resolution > no resolution,
2290                     // otherwise full resolution > partial resolution > no resolution.
2291                     Some(res) if res.depth == 0 || defer_to_typeck => return Some(res),
2292                     res => if fin_res.is_none() { fin_res = res },
2293                 };
2294             }
2295         }
2296         if primary_ns != MacroNS && path.len() == 1 &&
2297                 self.macro_names.contains(&path[0].name) {
2298             // Return some dummy definition, it's enough for error reporting.
2299             return Some(PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX))));
2300         }
2301         fin_res
2302     }
2303
2304     /// Handles paths that may refer to associated items.
2305     fn resolve_qpath(&mut self,
2306                      id: NodeId,
2307                      qself: Option<&QSelf>,
2308                      path: &[Ident],
2309                      ns: Namespace,
2310                      span: Span,
2311                      global_by_default: bool)
2312                      -> Option<PathResolution> {
2313         if let Some(qself) = qself {
2314             if qself.position == 0 {
2315                 // FIXME: Create some fake resolution that can't possibly be a type.
2316                 return Some(PathResolution {
2317                     base_def: Def::Mod(DefId::local(CRATE_DEF_INDEX)),
2318                     depth: path.len(),
2319                 });
2320             }
2321             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2322             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2323             let mut res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2324                                                            span, PathSource::TraitItem(ns));
2325             if res.base_def != Def::Err {
2326                 res.depth += path.len() - qself.position - 1;
2327             }
2328             return Some(res);
2329         }
2330
2331         let result = match self.resolve_path(&path, Some(ns), Some(span)) {
2332             PathResult::NonModule(path_res) => path_res,
2333             PathResult::Module(module) if !module.is_normal() => {
2334                 PathResolution::new(module.def().unwrap())
2335             }
2336             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2337             // don't report an error right away, but try to fallback to a primitive type.
2338             // So, we are still able to successfully resolve something like
2339             //
2340             // use std::u8; // bring module u8 in scope
2341             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2342             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2343             //                     // not to non-existent std::u8::max_value
2344             // }
2345             //
2346             // Such behavior is required for backward compatibility.
2347             // The same fallback is used when `a` resolves to nothing.
2348             PathResult::Module(..) | PathResult::Failed(..)
2349                     if (ns == TypeNS || path.len() > 1) &&
2350                        self.primitive_type_table.primitive_types.contains_key(&path[0].name) => {
2351                 let prim = self.primitive_type_table.primitive_types[&path[0].name];
2352                 match prim {
2353                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2354                         if !self.session.features.borrow().i128_type {
2355                             emit_feature_err(&self.session.parse_sess,
2356                                                 "i128_type", span, GateIssue::Language,
2357                                                 "128-bit type is unstable");
2358
2359                         }
2360                     }
2361                     _ => {}
2362                 }
2363                 PathResolution {
2364                     base_def: Def::PrimTy(prim),
2365                     depth: path.len() - 1,
2366                 }
2367             }
2368             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2369             PathResult::Failed(msg, false) => {
2370                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2371                 err_path_resolution()
2372             }
2373             PathResult::Failed(..) => return None,
2374             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2375         };
2376
2377         if path.len() > 1 && !global_by_default && result.base_def != Def::Err &&
2378            path[0].name != keywords::CrateRoot.name() && path[0].name != "$crate" {
2379             let unqualified_result = {
2380                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
2381                     PathResult::NonModule(path_res) => path_res.base_def,
2382                     PathResult::Module(module) => module.def().unwrap(),
2383                     _ => return Some(result),
2384                 }
2385             };
2386             if result.base_def == unqualified_result {
2387                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2388                 self.session.add_lint(lint, id, span, "unnecessary qualification".to_string());
2389             }
2390         }
2391
2392         Some(result)
2393     }
2394
2395     fn resolve_path(&mut self,
2396                     path: &[Ident],
2397                     opt_ns: Option<Namespace>, // `None` indicates a module path
2398                     record_used: Option<Span>)
2399                     -> PathResult<'a> {
2400         let mut module = None;
2401         let mut allow_super = true;
2402
2403         for (i, &ident) in path.iter().enumerate() {
2404             let is_last = i == path.len() - 1;
2405             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2406
2407             if i == 0 && ns == TypeNS && ident.name == keywords::SelfValue.name() {
2408                 module = Some(self.module_map[&self.current_module.normal_ancestor_id]);
2409                 continue
2410             } else if allow_super && ns == TypeNS && ident.name == keywords::Super.name() {
2411                 let current_module = if i == 0 { self.current_module } else { module.unwrap() };
2412                 let self_module = self.module_map[&current_module.normal_ancestor_id];
2413                 if let Some(parent) = self_module.parent {
2414                     module = Some(self.module_map[&parent.normal_ancestor_id]);
2415                     continue
2416                 } else {
2417                     let msg = "There are too many initial `super`s.".to_string();
2418                     return PathResult::Failed(msg, false);
2419                 }
2420             }
2421             allow_super = false;
2422
2423             if i == 0 && ns == TypeNS && ident.name == keywords::CrateRoot.name() {
2424                 module = Some(self.graph_root);
2425                 continue
2426             } else if i == 0 && ns == TypeNS && ident.name == "$crate" {
2427                 module = Some(self.resolve_crate_var(ident.ctxt));
2428                 continue
2429             }
2430
2431             let binding = if let Some(module) = module {
2432                 self.resolve_ident_in_module(module, ident, ns, false, record_used)
2433             } else if opt_ns == Some(MacroNS) {
2434                 self.resolve_lexical_macro_path_segment(ident, ns, record_used)
2435             } else {
2436                 match self.resolve_ident_in_lexical_scope(ident, ns, record_used) {
2437                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2438                     Some(LexicalScopeBinding::Def(def))
2439                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2440                         return PathResult::NonModule(PathResolution {
2441                             base_def: def,
2442                             depth: path.len() - 1,
2443                         });
2444                     }
2445                     _ => Err(if record_used.is_some() { Determined } else { Undetermined }),
2446                 }
2447             };
2448
2449             match binding {
2450                 Ok(binding) => {
2451                     let def = binding.def();
2452                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2453                     if let Some(next_module) = binding.module() {
2454                         module = Some(next_module);
2455                     } else if def == Def::Err {
2456                         return PathResult::NonModule(err_path_resolution());
2457                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2458                         return PathResult::NonModule(PathResolution {
2459                             base_def: def,
2460                             depth: path.len() - i - 1,
2461                         });
2462                     } else {
2463                         return PathResult::Failed(format!("Not a module `{}`", ident), is_last);
2464                     }
2465                 }
2466                 Err(Undetermined) => return PathResult::Indeterminate,
2467                 Err(Determined) => {
2468                     if let Some(module) = module {
2469                         if opt_ns.is_some() && !module.is_normal() {
2470                             return PathResult::NonModule(PathResolution {
2471                                 base_def: module.def().unwrap(),
2472                                 depth: path.len() - i,
2473                             });
2474                         }
2475                     }
2476                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2477                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2478                         let mut candidates =
2479                             self.lookup_import_candidates(ident.name, TypeNS, is_mod);
2480                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2481                         if let Some(candidate) = candidates.get(0) {
2482                             format!("Did you mean `{}`?", candidate.path)
2483                         } else {
2484                             format!("Maybe a missing `extern crate {};`?", ident)
2485                         }
2486                     } else if i == 0 {
2487                         format!("Use of undeclared type or module `{}`", ident)
2488                     } else {
2489                         format!("Could not find `{}` in `{}`", ident, path[i - 1])
2490                     };
2491                     return PathResult::Failed(msg, is_last);
2492                 }
2493             }
2494         }
2495
2496         PathResult::Module(module.unwrap_or(self.graph_root))
2497     }
2498
2499     // Resolve a local definition, potentially adjusting for closures.
2500     fn adjust_local_def(&mut self, local_def: LocalDef, record_used: Option<Span>) -> Def {
2501         let ribs = match local_def.ribs {
2502             Some((ns, i)) => &self.ribs[ns][i + 1..],
2503             None => &[] as &[_],
2504         };
2505         let mut def = local_def.def;
2506         match def {
2507             Def::Upvar(..) => {
2508                 span_bug!(record_used.unwrap_or(DUMMY_SP), "unexpected {:?} in bindings", def)
2509             }
2510             Def::Local(def_id) => {
2511                 for rib in ribs {
2512                     match rib.kind {
2513                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) => {
2514                             // Nothing to do. Continue.
2515                         }
2516                         ClosureRibKind(function_id) => {
2517                             let prev_def = def;
2518                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2519
2520                             let seen = self.freevars_seen
2521                                            .entry(function_id)
2522                                            .or_insert_with(|| NodeMap());
2523                             if let Some(&index) = seen.get(&node_id) {
2524                                 def = Def::Upvar(def_id, index, function_id);
2525                                 continue;
2526                             }
2527                             let vec = self.freevars
2528                                           .entry(function_id)
2529                                           .or_insert_with(|| vec![]);
2530                             let depth = vec.len();
2531                             def = Def::Upvar(def_id, depth, function_id);
2532
2533                             if let Some(span) = record_used {
2534                                 vec.push(Freevar {
2535                                     def: prev_def,
2536                                     span: span,
2537                                 });
2538                                 seen.insert(node_id, depth);
2539                             }
2540                         }
2541                         ItemRibKind | MethodRibKind(_) => {
2542                             // This was an attempt to access an upvar inside a
2543                             // named function item. This is not allowed, so we
2544                             // report an error.
2545                             if let Some(span) = record_used {
2546                                 resolve_error(self, span,
2547                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2548                             }
2549                             return Def::Err;
2550                         }
2551                         ConstantItemRibKind => {
2552                             // Still doesn't deal with upvars
2553                             if let Some(span) = record_used {
2554                                 resolve_error(self, span,
2555                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
2556                             }
2557                             return Def::Err;
2558                         }
2559                     }
2560                 }
2561             }
2562             Def::TyParam(..) | Def::SelfTy(..) => {
2563                 for rib in ribs {
2564                     match rib.kind {
2565                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
2566                         ModuleRibKind(..) | MacroDefinition(..) => {
2567                             // Nothing to do. Continue.
2568                         }
2569                         ItemRibKind => {
2570                             // This was an attempt to use a type parameter outside
2571                             // its scope.
2572                             if let Some(span) = record_used {
2573                                 resolve_error(self, span,
2574                                               ResolutionError::TypeParametersFromOuterFunction);
2575                             }
2576                             return Def::Err;
2577                         }
2578                         ConstantItemRibKind => {
2579                             // see #9186
2580                             if let Some(span) = record_used {
2581                                 resolve_error(self, span,
2582                                               ResolutionError::OuterTypeParameterContext);
2583                             }
2584                             return Def::Err;
2585                         }
2586                     }
2587                 }
2588             }
2589             _ => {}
2590         }
2591         return def;
2592     }
2593
2594     // Calls `f` with a `Resolver` whose current lexical scope is `module`'s lexical scope,
2595     // i.e. the module's items and the prelude (unless the module is `#[no_implicit_prelude]`).
2596     // FIXME #34673: This needs testing.
2597     pub fn with_module_lexical_scope<T, F>(&mut self, module: Module<'a>, f: F) -> T
2598         where F: FnOnce(&mut Resolver<'a>) -> T,
2599     {
2600         self.with_empty_ribs(|this| {
2601             this.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
2602             this.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
2603             f(this)
2604         })
2605     }
2606
2607     fn with_empty_ribs<T, F>(&mut self, f: F) -> T
2608         where F: FnOnce(&mut Resolver<'a>) -> T,
2609     {
2610         let ribs = replace(&mut self.ribs, PerNS::<Vec<Rib>>::default());
2611         let label_ribs = replace(&mut self.label_ribs, Vec::new());
2612
2613         let result = f(self);
2614         self.ribs = ribs;
2615         self.label_ribs = label_ribs;
2616         result
2617     }
2618
2619     fn lookup_assoc_candidate<FilterFn>(&mut self,
2620                                         name: Name,
2621                                         ns: Namespace,
2622                                         filter_fn: FilterFn)
2623                                         -> Option<AssocSuggestion>
2624         where FilterFn: Fn(Def) -> bool
2625     {
2626         fn extract_node_id(t: &Ty) -> Option<NodeId> {
2627             match t.node {
2628                 TyKind::Path(None, _) => Some(t.id),
2629                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
2630                 // This doesn't handle the remaining `Ty` variants as they are not
2631                 // that commonly the self_type, it might be interesting to provide
2632                 // support for those in future.
2633                 _ => None,
2634             }
2635         }
2636
2637         // Fields are generally expected in the same contexts as locals.
2638         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
2639             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
2640                 // Look for a field with the same name in the current self_type.
2641                 if let Some(resolution) = self.def_map.get(&node_id) {
2642                     match resolution.base_def {
2643                         Def::Struct(did) | Def::Union(did) if resolution.depth == 0 => {
2644                             if let Some(field_names) = self.field_names.get(&did) {
2645                                 if field_names.iter().any(|&field_name| name == field_name) {
2646                                     return Some(AssocSuggestion::Field);
2647                                 }
2648                             }
2649                         }
2650                         _ => {}
2651                     }
2652                 }
2653             }
2654         }
2655
2656         // Look for associated items in the current trait.
2657         if let Some((trait_did, _)) = self.current_trait_ref {
2658             if let Some(&(def, has_self)) = self.trait_item_map.get(&(trait_did, name, ns)) {
2659                 if filter_fn(def) {
2660                     return Some(if has_self {
2661                         AssocSuggestion::MethodWithSelf
2662                     } else {
2663                         AssocSuggestion::AssocItem
2664                     });
2665                 }
2666             }
2667         }
2668
2669         None
2670     }
2671
2672     fn lookup_typo_candidate<FilterFn>(&mut self,
2673                                        path: &[Ident],
2674                                        ns: Namespace,
2675                                        filter_fn: FilterFn)
2676                                        -> Option<String>
2677         where FilterFn: Fn(Def) -> bool
2678     {
2679         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
2680             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
2681                 if let Some(binding) = resolution.borrow().binding {
2682                     if filter_fn(binding.def()) {
2683                         names.push(ident.name);
2684                     }
2685                 }
2686             }
2687         };
2688
2689         let mut names = Vec::new();
2690         let prefix_str = if path.len() == 1 {
2691             // Search in lexical scope.
2692             // Walk backwards up the ribs in scope and collect candidates.
2693             for rib in self.ribs[ns].iter().rev() {
2694                 // Locals and type parameters
2695                 for (ident, def) in &rib.bindings {
2696                     if filter_fn(*def) {
2697                         names.push(ident.name);
2698                     }
2699                 }
2700                 // Items in scope
2701                 if let ModuleRibKind(module) = rib.kind {
2702                     // Items from this module
2703                     add_module_candidates(module, &mut names);
2704
2705                     if let ModuleKind::Block(..) = module.kind {
2706                         // We can see through blocks
2707                     } else {
2708                         // Items from the prelude
2709                         if let Some(prelude) = self.prelude {
2710                             if !module.no_implicit_prelude {
2711                                 add_module_candidates(prelude, &mut names);
2712                             }
2713                         }
2714                         break;
2715                     }
2716                 }
2717             }
2718             // Add primitive types to the mix
2719             if filter_fn(Def::PrimTy(TyBool)) {
2720                 for (name, _) in &self.primitive_type_table.primitive_types {
2721                     names.push(*name);
2722                 }
2723             }
2724             String::new()
2725         } else {
2726             // Search in module.
2727             let mod_path = &path[..path.len() - 1];
2728             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS), None) {
2729                 add_module_candidates(module, &mut names);
2730             }
2731             names_to_string(mod_path) + "::"
2732         };
2733
2734         let name = path[path.len() - 1].name;
2735         // Make sure error reporting is deterministic.
2736         names.sort_by_key(|name| name.as_str());
2737         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
2738             Some(found) if found != name => Some(format!("{}{}", prefix_str, found)),
2739             _ => None,
2740         }
2741     }
2742
2743     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
2744         if let Some(label) = label {
2745             let def = Def::Label(id);
2746             self.with_label_rib(|this| {
2747                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
2748                 this.visit_block(block);
2749             });
2750         } else {
2751             self.visit_block(block);
2752         }
2753     }
2754
2755     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&ExprKind>) {
2756         // First, record candidate traits for this expression if it could
2757         // result in the invocation of a method call.
2758
2759         self.record_candidate_traits_for_expr_if_necessary(expr);
2760
2761         // Next, resolve the node.
2762         match expr.node {
2763             ExprKind::Path(ref qself, ref path) => {
2764                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
2765                 visit::walk_expr(self, expr);
2766             }
2767
2768             ExprKind::Struct(ref path, ..) => {
2769                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
2770                 visit::walk_expr(self, expr);
2771             }
2772
2773             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
2774                 match self.search_label(label.node) {
2775                     None => {
2776                         self.record_def(expr.id, err_path_resolution());
2777                         resolve_error(self,
2778                                       label.span,
2779                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
2780                     }
2781                     Some(def @ Def::Label(_)) => {
2782                         // Since this def is a label, it is never read.
2783                         self.record_def(expr.id, PathResolution::new(def));
2784                     }
2785                     Some(_) => {
2786                         span_bug!(expr.span, "label wasn't mapped to a label def!");
2787                     }
2788                 }
2789
2790                 // visit `break` argument if any
2791                 visit::walk_expr(self, expr);
2792             }
2793
2794             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
2795                 self.visit_expr(subexpression);
2796
2797                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2798                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
2799                 self.visit_block(if_block);
2800                 self.ribs[ValueNS].pop();
2801
2802                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
2803             }
2804
2805             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
2806
2807             ExprKind::While(ref subexpression, ref block, label) => {
2808                 self.visit_expr(subexpression);
2809                 self.resolve_labeled_block(label, expr.id, &block);
2810             }
2811
2812             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
2813                 self.visit_expr(subexpression);
2814                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2815                 self.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
2816
2817                 self.resolve_labeled_block(label, expr.id, block);
2818
2819                 self.ribs[ValueNS].pop();
2820             }
2821
2822             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
2823                 self.visit_expr(subexpression);
2824                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2825                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
2826
2827                 self.resolve_labeled_block(label, expr.id, block);
2828
2829                 self.ribs[ValueNS].pop();
2830             }
2831
2832             // Equivalent to `visit::walk_expr` + passing some context to children.
2833             ExprKind::Field(ref subexpression, _) => {
2834                 self.resolve_expr(subexpression, Some(&expr.node));
2835             }
2836             ExprKind::MethodCall(_, ref types, ref arguments) => {
2837                 let mut arguments = arguments.iter();
2838                 self.resolve_expr(arguments.next().unwrap(), Some(&expr.node));
2839                 for argument in arguments {
2840                     self.resolve_expr(argument, None);
2841                 }
2842                 for ty in types.iter() {
2843                     self.visit_ty(ty);
2844                 }
2845             }
2846
2847             ExprKind::Repeat(ref element, ref count) => {
2848                 self.visit_expr(element);
2849                 self.with_constant_rib(|this| {
2850                     this.visit_expr(count);
2851                 });
2852             }
2853             ExprKind::Call(ref callee, ref arguments) => {
2854                 self.resolve_expr(callee, Some(&expr.node));
2855                 for argument in arguments {
2856                     self.resolve_expr(argument, None);
2857                 }
2858             }
2859
2860             _ => {
2861                 visit::walk_expr(self, expr);
2862             }
2863         }
2864     }
2865
2866     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
2867         match expr.node {
2868             ExprKind::Field(_, name) => {
2869                 // FIXME(#6890): Even though you can't treat a method like a
2870                 // field, we need to add any trait methods we find that match
2871                 // the field name so that we can do some nice error reporting
2872                 // later on in typeck.
2873                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
2874                 self.trait_map.insert(expr.id, traits);
2875             }
2876             ExprKind::MethodCall(name, ..) => {
2877                 debug!("(recording candidate traits for expr) recording traits for {}",
2878                        expr.id);
2879                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
2880                 self.trait_map.insert(expr.id, traits);
2881             }
2882             _ => {
2883                 // Nothing to do.
2884             }
2885         }
2886     }
2887
2888     fn get_traits_containing_item(&mut self, name: Name, ns: Namespace) -> Vec<TraitCandidate> {
2889         debug!("(getting traits containing item) looking for '{}'", name);
2890
2891         let mut found_traits = Vec::new();
2892         // Look for the current trait.
2893         if let Some((trait_def_id, _)) = self.current_trait_ref {
2894             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
2895                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: None });
2896             }
2897         }
2898
2899         let mut search_module = self.current_module;
2900         loop {
2901             self.get_traits_in_module_containing_item(name, ns, search_module, &mut found_traits);
2902             match search_module.kind {
2903                 ModuleKind::Block(..) => search_module = search_module.parent.unwrap(),
2904                 _ => break,
2905             }
2906         }
2907
2908         if let Some(prelude) = self.prelude {
2909             if !search_module.no_implicit_prelude {
2910                 self.get_traits_in_module_containing_item(name, ns, prelude, &mut found_traits);
2911             }
2912         }
2913
2914         found_traits
2915     }
2916
2917     fn get_traits_in_module_containing_item(&mut self,
2918                                             name: Name,
2919                                             ns: Namespace,
2920                                             module: Module,
2921                                             found_traits: &mut Vec<TraitCandidate>) {
2922         let mut traits = module.traits.borrow_mut();
2923         if traits.is_none() {
2924             let mut collected_traits = Vec::new();
2925             module.for_each_child(|name, ns, binding| {
2926                 if ns != TypeNS { return }
2927                 if let Def::Trait(_) = binding.def() {
2928                     collected_traits.push((name, binding));
2929                 }
2930             });
2931             *traits = Some(collected_traits.into_boxed_slice());
2932         }
2933
2934         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
2935             let trait_def_id = binding.def().def_id();
2936             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
2937                 let import_id = match binding.kind {
2938                     NameBindingKind::Import { directive, .. } => {
2939                         self.maybe_unused_trait_imports.insert(directive.id);
2940                         self.add_to_glob_map(directive.id, trait_name);
2941                         Some(directive.id)
2942                     }
2943                     _ => None,
2944                 };
2945                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
2946             }
2947         }
2948     }
2949
2950     /// When name resolution fails, this method can be used to look up candidate
2951     /// entities with the expected name. It allows filtering them using the
2952     /// supplied predicate (which should be used to only accept the types of
2953     /// definitions expected e.g. traits). The lookup spans across all crates.
2954     ///
2955     /// NOTE: The method does not look into imports, but this is not a problem,
2956     /// since we report the definitions (thus, the de-aliased imports).
2957     fn lookup_import_candidates<FilterFn>(&mut self,
2958                                           lookup_name: Name,
2959                                           namespace: Namespace,
2960                                           filter_fn: FilterFn)
2961                                           -> Vec<ImportSuggestion>
2962         where FilterFn: Fn(Def) -> bool
2963     {
2964         let mut candidates = Vec::new();
2965         let mut worklist = Vec::new();
2966         let mut seen_modules = FxHashSet();
2967         worklist.push((self.graph_root, Vec::new(), false));
2968
2969         while let Some((in_module,
2970                         path_segments,
2971                         in_module_is_extern)) = worklist.pop() {
2972             self.populate_module_if_necessary(in_module);
2973
2974             in_module.for_each_child(|ident, ns, name_binding| {
2975
2976                 // avoid imports entirely
2977                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
2978                 // avoid non-importable candidates as well
2979                 if !name_binding.is_importable() { return; }
2980
2981                 // collect results based on the filter function
2982                 if ident.name == lookup_name && ns == namespace {
2983                     if filter_fn(name_binding.def()) {
2984                         // create the path
2985                         let span = name_binding.span;
2986                         let mut segms = path_segments.clone();
2987                         segms.push(ident.into());
2988                         let path = Path {
2989                             span: span,
2990                             segments: segms,
2991                         };
2992                         // the entity is accessible in the following cases:
2993                         // 1. if it's defined in the same crate, it's always
2994                         // accessible (since private entities can be made public)
2995                         // 2. if it's defined in another crate, it's accessible
2996                         // only if both the module is public and the entity is
2997                         // declared as public (due to pruning, we don't explore
2998                         // outside crate private modules => no need to check this)
2999                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3000                             candidates.push(ImportSuggestion { path: path });
3001                         }
3002                     }
3003                 }
3004
3005                 // collect submodules to explore
3006                 if let Some(module) = name_binding.module() {
3007                     // form the path
3008                     let mut path_segments = path_segments.clone();
3009                     path_segments.push(ident.into());
3010
3011                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3012                         // add the module to the lookup
3013                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3014                         if seen_modules.insert(module.def_id().unwrap()) {
3015                             worklist.push((module, path_segments, is_extern));
3016                         }
3017                     }
3018                 }
3019             })
3020         }
3021
3022         candidates
3023     }
3024
3025     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3026         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3027         assert!(resolution.depth == 0 || resolution.base_def != Def::Err);
3028         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3029             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3030         }
3031     }
3032
3033     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3034         match *vis {
3035             ast::Visibility::Public => ty::Visibility::Public,
3036             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3037             ast::Visibility::Inherited => {
3038                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3039             }
3040             ast::Visibility::Restricted { ref path, id } => {
3041                 let def = self.smart_resolve_path(id, None, path, PathSource::Visibility).base_def;
3042                 if def == Def::Err {
3043                     ty::Visibility::Public
3044                 } else {
3045                     let vis = ty::Visibility::Restricted(def.def_id());
3046                     if self.is_accessible(vis) {
3047                         vis
3048                     } else {
3049                         self.session.span_err(path.span, "visibilities can only be restricted \
3050                                                           to ancestor modules");
3051                         ty::Visibility::Public
3052                     }
3053                 }
3054             }
3055         }
3056     }
3057
3058     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3059         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3060     }
3061
3062     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3063         vis.is_accessible_from(module.normal_ancestor_id, self)
3064     }
3065
3066     fn report_errors(&mut self) {
3067         self.report_shadowing_errors();
3068         let mut reported_spans = FxHashSet();
3069
3070         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3071             if !reported_spans.insert(span) { continue }
3072             let participle = |binding: &NameBinding| {
3073                 if binding.is_import() { "imported" } else { "defined" }
3074             };
3075             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3076             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3077             let note = if !lexical && b1.is_glob_import() {
3078                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3079             } else if let Def::Macro(..) = b1.def() {
3080                 format!("macro-expanded {} do not shadow",
3081                         if b1.is_import() { "macro imports" } else { "macros" })
3082             } else {
3083                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3084                         if b1.is_import() { "imports" } else { "items" })
3085             };
3086             if legacy {
3087                 let id = match b2.kind {
3088                     NameBindingKind::Import { directive, .. } => directive.id,
3089                     _ => unreachable!(),
3090                 };
3091                 let mut span = MultiSpan::from_span(span);
3092                 span.push_span_label(b1.span, msg1);
3093                 span.push_span_label(b2.span, msg2);
3094                 let msg = format!("`{}` is ambiguous", name);
3095                 self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3096             } else {
3097                 self.session.struct_span_err(span, &format!("`{}` is ambiguous", name))
3098                     .span_note(b1.span, &msg1)
3099                     .span_note(b2.span, &msg2)
3100                     .note(&note)
3101                     .emit();
3102             }
3103         }
3104
3105         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3106             if !reported_spans.insert(span) { continue }
3107             if binding.is_extern_crate() {
3108                 // Warn when using an inaccessible extern crate.
3109                 let node_id = match binding.kind {
3110                     NameBindingKind::Import { directive, .. } => directive.id,
3111                     _ => unreachable!(),
3112                 };
3113                 let msg = format!("extern crate `{}` is private", name);
3114                 self.session.add_lint(lint::builtin::INACCESSIBLE_EXTERN_CRATE, node_id, span, msg);
3115             } else {
3116                 let def = binding.def();
3117                 self.session.span_err(span, &format!("{} `{}` is private", def.kind_name(), name));
3118             }
3119         }
3120     }
3121
3122     fn report_shadowing_errors(&mut self) {
3123         for (name, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3124             self.resolve_legacy_scope(scope, name, true);
3125         }
3126
3127         let mut reported_errors = FxHashSet();
3128         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3129             if self.resolve_legacy_scope(&binding.parent, binding.name, false).is_some() &&
3130                reported_errors.insert((binding.name, binding.span)) {
3131                 let msg = format!("`{}` is already in scope", binding.name);
3132                 self.session.struct_span_err(binding.span, &msg)
3133                     .note("macro-expanded `macro_rules!`s may not shadow \
3134                            existing macros (see RFC 1560)")
3135                     .emit();
3136             }
3137         }
3138     }
3139
3140     fn report_conflict(&mut self,
3141                        parent: Module,
3142                        ident: Ident,
3143                        ns: Namespace,
3144                        binding: &NameBinding,
3145                        old_binding: &NameBinding) {
3146         // Error on the second of two conflicting names
3147         if old_binding.span.lo > binding.span.lo {
3148             return self.report_conflict(parent, ident, ns, old_binding, binding);
3149         }
3150
3151         let container = match parent.kind {
3152             ModuleKind::Def(Def::Mod(_), _) => "module",
3153             ModuleKind::Def(Def::Trait(_), _) => "trait",
3154             ModuleKind::Block(..) => "block",
3155             _ => "enum",
3156         };
3157
3158         let (participle, noun) = match old_binding.is_import() {
3159             true => ("imported", "import"),
3160             false => ("defined", "definition"),
3161         };
3162
3163         let (name, span) = (ident.name, binding.span);
3164
3165         if let Some(s) = self.name_already_seen.get(&name) {
3166             if s == &span {
3167                 return;
3168             }
3169         }
3170
3171         let msg = {
3172             let kind = match (ns, old_binding.module()) {
3173                 (ValueNS, _) => "a value",
3174                 (MacroNS, _) => "a macro",
3175                 (TypeNS, _) if old_binding.is_extern_crate() => "an extern crate",
3176                 (TypeNS, Some(module)) if module.is_normal() => "a module",
3177                 (TypeNS, Some(module)) if module.is_trait() => "a trait",
3178                 (TypeNS, _) => "a type",
3179             };
3180             format!("{} named `{}` has already been {} in this {}",
3181                     kind, name, participle, container)
3182         };
3183
3184         let mut err = match (old_binding.is_extern_crate(), binding.is_extern_crate()) {
3185             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3186             (true, _) | (_, true) => match binding.is_import() && old_binding.is_import() {
3187                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3188                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3189             },
3190             _ => match (old_binding.is_import(), binding.is_import()) {
3191                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3192                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3193                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3194             },
3195         };
3196
3197         err.span_label(span, &format!("`{}` already {}", name, participle));
3198         if old_binding.span != syntax_pos::DUMMY_SP {
3199             err.span_label(old_binding.span, &format!("previous {} of `{}` here", noun, name));
3200         }
3201         err.emit();
3202         self.name_already_seen.insert(name, span);
3203     }
3204
3205     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3206         let (id, span) = (directive.id, directive.span);
3207         let msg = "`self` no longer imports values".to_string();
3208         self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3209     }
3210
3211     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3212         if self.proc_macro_enabled { return; }
3213
3214         for attr in attrs {
3215             let maybe_binding = self.builtin_macros.get(&attr.name()).cloned().or_else(|| {
3216                 let ident = Ident::with_empty_ctxt(attr.name());
3217                 self.resolve_lexical_macro_path_segment(ident, MacroNS, None).ok()
3218             });
3219
3220             if let Some(binding) = maybe_binding {
3221                 if let SyntaxExtension::AttrProcMacro(..) = *binding.get_macro(self) {
3222                     attr::mark_known(attr);
3223
3224                     let msg = "attribute procedural macros are experimental";
3225                     let feature = "proc_macro";
3226
3227                     feature_err(&self.session.parse_sess, feature,
3228                                 attr.span, GateIssue::Language, msg)
3229                         .span_note(binding.span, "procedural macro imported here")
3230                         .emit();
3231                 }
3232             }
3233         }
3234     }
3235 }
3236
3237 fn is_struct_like(def: Def) -> bool {
3238     match def {
3239         Def::VariantCtor(_, CtorKind::Fictive) => true,
3240         _ => PathSource::Struct.is_expected(def),
3241     }
3242 }
3243
3244 fn is_self_type(path: &[Ident], namespace: Namespace) -> bool {
3245     namespace == TypeNS && path.len() == 1 && path[0].name == keywords::SelfType.name()
3246 }
3247
3248 fn is_self_value(path: &[Ident], namespace: Namespace) -> bool {
3249     namespace == ValueNS && path.len() == 1 && path[0].name == keywords::SelfValue.name()
3250 }
3251
3252 fn names_to_string(idents: &[Ident]) -> String {
3253     let mut result = String::new();
3254     for (i, ident) in idents.iter().filter(|i| i.name != keywords::CrateRoot.name()).enumerate() {
3255         if i > 0 {
3256             result.push_str("::");
3257         }
3258         result.push_str(&ident.name.as_str());
3259     }
3260     result
3261 }
3262
3263 fn path_names_to_string(path: &Path) -> String {
3264     names_to_string(&path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>())
3265 }
3266
3267 /// When an entity with a given name is not available in scope, we search for
3268 /// entities with that name in all crates. This method allows outputting the
3269 /// results of this search in a programmer-friendly way
3270 fn show_candidates(session: &mut DiagnosticBuilder,
3271                    candidates: &[ImportSuggestion],
3272                    better: bool) {
3273     // don't show more than MAX_CANDIDATES results, so
3274     // we're consistent with the trait suggestions
3275     const MAX_CANDIDATES: usize = 4;
3276
3277     // we want consistent results across executions, but candidates are produced
3278     // by iterating through a hash map, so make sure they are ordered:
3279     let mut path_strings: Vec<_> =
3280         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3281     path_strings.sort();
3282
3283     let better = if better { "better " } else { "" };
3284     let msg_diff = match path_strings.len() {
3285         1 => " is found in another module, you can import it",
3286         _ => "s are found in other modules, you can import them",
3287     };
3288
3289     let end = cmp::min(MAX_CANDIDATES, path_strings.len());
3290     session.help(&format!("possible {}candidate{} into scope:{}{}",
3291                           better,
3292                           msg_diff,
3293                           &path_strings[0..end].iter().map(|candidate| {
3294                               format!("\n  `use {};`", candidate)
3295                           }).collect::<String>(),
3296                           if path_strings.len() > MAX_CANDIDATES {
3297                               format!("\nand {} other candidates",
3298                                       path_strings.len() - MAX_CANDIDATES)
3299                           } else {
3300                               "".to_owned()
3301                           }
3302                           ));
3303 }
3304
3305 /// A somewhat inefficient routine to obtain the name of a module.
3306 fn module_to_string(module: Module) -> String {
3307     let mut names = Vec::new();
3308
3309     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3310         if let ModuleKind::Def(_, name) = module.kind {
3311             if let Some(parent) = module.parent {
3312                 names.push(Ident::with_empty_ctxt(name));
3313                 collect_mod(names, parent);
3314             }
3315         } else {
3316             // danger, shouldn't be ident?
3317             names.push(Ident::from_str("<opaque>"));
3318             collect_mod(names, module.parent.unwrap());
3319         }
3320     }
3321     collect_mod(&mut names, module);
3322
3323     if names.is_empty() {
3324         return "???".to_string();
3325     }
3326     names_to_string(&names.into_iter().rev().collect::<Vec<_>>())
3327 }
3328
3329 fn err_path_resolution() -> PathResolution {
3330     PathResolution::new(Def::Err)
3331 }
3332
3333 #[derive(PartialEq,Copy, Clone)]
3334 pub enum MakeGlobMap {
3335     Yes,
3336     No,
3337 }
3338
3339 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }