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, DefIdMap};
  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     // This table maps struct IDs into struct constructor IDs,
1136     // it's not used during normal resolution, only for better error reporting.
1137     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1138 }
1139
1140 pub struct ResolverArenas<'a> {
1141     modules: arena::TypedArena<ModuleData<'a>>,
1142     local_modules: RefCell<Vec<Module<'a>>>,
1143     name_bindings: arena::TypedArena<NameBinding<'a>>,
1144     import_directives: arena::TypedArena<ImportDirective<'a>>,
1145     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1146     invocation_data: arena::TypedArena<InvocationData<'a>>,
1147     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1148 }
1149
1150 impl<'a> ResolverArenas<'a> {
1151     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1152         let module = self.modules.alloc(module);
1153         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1154             self.local_modules.borrow_mut().push(module);
1155         }
1156         module
1157     }
1158     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1159         self.local_modules.borrow()
1160     }
1161     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1162         self.name_bindings.alloc(name_binding)
1163     }
1164     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1165                               -> &'a ImportDirective {
1166         self.import_directives.alloc(import_directive)
1167     }
1168     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1169         self.name_resolutions.alloc(Default::default())
1170     }
1171     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1172                              -> &'a InvocationData<'a> {
1173         self.invocation_data.alloc(expansion_data)
1174     }
1175     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1176         self.legacy_bindings.alloc(binding)
1177     }
1178 }
1179
1180 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1181     fn parent(self, id: DefId) -> Option<DefId> {
1182         match id.krate {
1183             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1184             _ => self.session.cstore.def_key(id).parent,
1185         }.map(|index| DefId { index: index, ..id })
1186     }
1187 }
1188
1189 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1190     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1191         let namespace = if is_value { ValueNS } else { TypeNS };
1192         let hir::Path { ref segments, span, ref mut def } = *path;
1193         let path: Vec<_> = segments.iter().map(|seg| Ident::with_empty_ctxt(seg.name)).collect();
1194         match self.resolve_path(&path, Some(namespace), Some(span)) {
1195             PathResult::Module(module) => *def = module.def().unwrap(),
1196             PathResult::NonModule(path_res) if path_res.depth == 0 => *def = path_res.base_def,
1197             PathResult::NonModule(..) => match self.resolve_path(&path, None, Some(span)) {
1198                 PathResult::Failed(msg, _) => {
1199                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1200                 }
1201                 _ => {}
1202             },
1203             PathResult::Indeterminate => unreachable!(),
1204             PathResult::Failed(msg, _) => {
1205                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1206             }
1207         }
1208     }
1209
1210     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1211         self.def_map.get(&id).cloned()
1212     }
1213
1214     fn definitions(&mut self) -> &mut Definitions {
1215         &mut self.definitions
1216     }
1217 }
1218
1219 impl<'a> Resolver<'a> {
1220     pub fn new(session: &'a Session,
1221                krate: &Crate,
1222                make_glob_map: MakeGlobMap,
1223                crate_loader: &'a mut CrateLoader,
1224                arenas: &'a ResolverArenas<'a>)
1225                -> Resolver<'a> {
1226         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1227         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1228         let graph_root = arenas.alloc_module(ModuleData {
1229             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1230             ..ModuleData::new(None, root_module_kind, root_def_id)
1231         });
1232         let mut module_map = FxHashMap();
1233         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1234
1235         let mut definitions = Definitions::new();
1236         DefCollector::new(&mut definitions).collect_root();
1237
1238         let mut invocations = FxHashMap();
1239         invocations.insert(Mark::root(),
1240                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1241
1242         let features = session.features.borrow();
1243
1244         Resolver {
1245             session: session,
1246
1247             definitions: definitions,
1248             macros_at_scope: FxHashMap(),
1249
1250             // The outermost module has def ID 0; this is not reflected in the
1251             // AST.
1252             graph_root: graph_root,
1253             prelude: None,
1254
1255             trait_item_map: FxHashMap(),
1256             field_names: FxHashMap(),
1257
1258             determined_imports: Vec::new(),
1259             indeterminate_imports: Vec::new(),
1260
1261             current_module: graph_root,
1262             ribs: PerNS {
1263                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1264                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1265                 macro_ns: None,
1266             },
1267             label_ribs: Vec::new(),
1268
1269             current_trait_ref: None,
1270             current_self_type: None,
1271
1272             primitive_type_table: PrimitiveTypeTable::new(),
1273
1274             def_map: NodeMap(),
1275             freevars: NodeMap(),
1276             freevars_seen: NodeMap(),
1277             export_map: NodeMap(),
1278             trait_map: NodeMap(),
1279             module_map: module_map,
1280             block_map: NodeMap(),
1281             extern_crate_roots: FxHashMap(),
1282
1283             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1284             glob_map: NodeMap(),
1285
1286             used_imports: FxHashSet(),
1287             maybe_unused_trait_imports: NodeSet(),
1288
1289             privacy_errors: Vec::new(),
1290             ambiguity_errors: Vec::new(),
1291             disallowed_shadowing: Vec::new(),
1292
1293             arenas: arenas,
1294             dummy_binding: arenas.alloc_name_binding(NameBinding {
1295                 kind: NameBindingKind::Def(Def::Err),
1296                 expansion: Mark::root(),
1297                 span: DUMMY_SP,
1298                 vis: ty::Visibility::Public,
1299             }),
1300
1301             // `#![feature(proc_macro)]` implies `#[feature(extern_macros)]`
1302             use_extern_macros: features.use_extern_macros || features.proc_macro,
1303
1304             exported_macros: Vec::new(),
1305             crate_loader: crate_loader,
1306             macro_names: FxHashSet(),
1307             builtin_macros: FxHashMap(),
1308             lexical_macro_resolutions: Vec::new(),
1309             macro_map: FxHashMap(),
1310             macro_exports: Vec::new(),
1311             invocations: invocations,
1312             name_already_seen: FxHashMap(),
1313             whitelisted_legacy_custom_derives: Vec::new(),
1314             proc_macro_enabled: features.proc_macro,
1315             warned_proc_macros: FxHashSet(),
1316             potentially_unused_imports: Vec::new(),
1317             struct_constructors: DefIdMap(),
1318         }
1319     }
1320
1321     pub fn arenas() -> ResolverArenas<'a> {
1322         ResolverArenas {
1323             modules: arena::TypedArena::new(),
1324             local_modules: RefCell::new(Vec::new()),
1325             name_bindings: arena::TypedArena::new(),
1326             import_directives: arena::TypedArena::new(),
1327             name_resolutions: arena::TypedArena::new(),
1328             invocation_data: arena::TypedArena::new(),
1329             legacy_bindings: arena::TypedArena::new(),
1330         }
1331     }
1332
1333     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1334         PerNS {
1335             type_ns: f(self, TypeNS),
1336             value_ns: f(self, ValueNS),
1337             macro_ns: match self.use_extern_macros {
1338                 true => Some(f(self, MacroNS)),
1339                 false => None,
1340             },
1341         }
1342     }
1343
1344     /// Entry point to crate resolution.
1345     pub fn resolve_crate(&mut self, krate: &Crate) {
1346         ImportResolver { resolver: self }.finalize_imports();
1347         self.current_module = self.graph_root;
1348         self.finalize_current_module_macro_resolutions();
1349         visit::walk_crate(self, krate);
1350
1351         check_unused::check_crate(self, krate);
1352         self.report_errors();
1353         self.crate_loader.postprocess(krate);
1354     }
1355
1356     fn new_module(&self, parent: Module<'a>, kind: ModuleKind, normal_ancestor_id: DefId)
1357                   -> Module<'a> {
1358         self.arenas.alloc_module(ModuleData::new(Some(parent), kind, normal_ancestor_id))
1359     }
1360
1361     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1362                   -> bool /* true if an error was reported */ {
1363         match binding.kind {
1364             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1365                     if !used.get() => {
1366                 used.set(true);
1367                 directive.used.set(true);
1368                 if legacy_self_import {
1369                     self.warn_legacy_self_import(directive);
1370                     return false;
1371                 }
1372                 self.used_imports.insert((directive.id, ns));
1373                 self.add_to_glob_map(directive.id, ident);
1374                 self.record_use(ident, ns, binding, span)
1375             }
1376             NameBindingKind::Import { .. } => false,
1377             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1378                 self.ambiguity_errors.push(AmbiguityError {
1379                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy: legacy,
1380                 });
1381                 if legacy {
1382                     self.record_use(ident, ns, b1, span);
1383                 }
1384                 !legacy
1385             }
1386             _ => false
1387         }
1388     }
1389
1390     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1391         if self.make_glob_map {
1392             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1393         }
1394     }
1395
1396     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1397     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1398     /// `ident` in the first scope that defines it (or None if no scopes define it).
1399     ///
1400     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1401     /// the items are defined in the block. For example,
1402     /// ```rust
1403     /// fn f() {
1404     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1405     ///    let g = || {};
1406     ///    fn g() {}
1407     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1408     /// }
1409     /// ```
1410     ///
1411     /// Invariant: This must only be called during main resolution, not during
1412     /// import resolution.
1413     fn resolve_ident_in_lexical_scope(&mut self,
1414                                       mut ident: Ident,
1415                                       ns: Namespace,
1416                                       record_used: Option<Span>)
1417                                       -> Option<LexicalScopeBinding<'a>> {
1418         if ns == TypeNS {
1419             ident = ident.unhygienize();
1420         }
1421
1422         // Walk backwards up the ribs in scope.
1423         for i in (0 .. self.ribs[ns].len()).rev() {
1424             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1425                 // The ident resolves to a type parameter or local variable.
1426                 return Some(LexicalScopeBinding::Def(
1427                     self.adjust_local_def(LocalDef { ribs: Some((ns, i)), def: def }, record_used)
1428                 ));
1429             }
1430
1431             if let ModuleRibKind(module) = self.ribs[ns][i].kind {
1432                 let item = self.resolve_ident_in_module(module, ident, ns, false, record_used);
1433                 if let Ok(binding) = item {
1434                     // The ident resolves to an item.
1435                     return Some(LexicalScopeBinding::Item(binding));
1436                 }
1437
1438                 if let ModuleKind::Block(..) = module.kind { // We can see through blocks
1439                 } else if !module.no_implicit_prelude {
1440                     return self.prelude.and_then(|prelude| {
1441                         self.resolve_ident_in_module(prelude, ident, ns, false, None).ok()
1442                     }).map(LexicalScopeBinding::Item)
1443                 } else {
1444                     return None;
1445                 }
1446             }
1447
1448             if let MacroDefinition(mac) = self.ribs[ns][i].kind {
1449                 // If an invocation of this macro created `ident`, give up on `ident`
1450                 // and switch to `ident`'s source from the macro definition.
1451                 let (source_ctxt, source_macro) = ident.ctxt.source();
1452                 if source_macro == mac {
1453                     ident.ctxt = source_ctxt;
1454                 }
1455             }
1456         }
1457
1458         None
1459     }
1460
1461     fn resolve_crate_var(&mut self, mut crate_var_ctxt: SyntaxContext) -> Module<'a> {
1462         while crate_var_ctxt.source().0 != SyntaxContext::empty() {
1463             crate_var_ctxt = crate_var_ctxt.source().0;
1464         }
1465         let module = self.invocations[&crate_var_ctxt.source().1].module.get();
1466         if module.is_local() { self.graph_root } else { module }
1467     }
1468
1469     // AST resolution
1470     //
1471     // We maintain a list of value ribs and type ribs.
1472     //
1473     // Simultaneously, we keep track of the current position in the module
1474     // graph in the `current_module` pointer. When we go to resolve a name in
1475     // the value or type namespaces, we first look through all the ribs and
1476     // then query the module graph. When we resolve a name in the module
1477     // namespace, we can skip all the ribs (since nested modules are not
1478     // allowed within blocks in Rust) and jump straight to the current module
1479     // graph node.
1480     //
1481     // Named implementations are handled separately. When we find a method
1482     // call, we consult the module node to find all of the implementations in
1483     // scope. This information is lazily cached in the module node. We then
1484     // generate a fake "implementation scope" containing all the
1485     // implementations thus found, for compatibility with old resolve pass.
1486
1487     fn with_scope<F>(&mut self, id: NodeId, f: F)
1488         where F: FnOnce(&mut Resolver)
1489     {
1490         let id = self.definitions.local_def_id(id);
1491         let module = self.module_map.get(&id).cloned(); // clones a reference
1492         if let Some(module) = module {
1493             // Move down in the graph.
1494             let orig_module = replace(&mut self.current_module, module);
1495             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1496             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1497
1498             self.finalize_current_module_macro_resolutions();
1499             f(self);
1500
1501             self.current_module = orig_module;
1502             self.ribs[ValueNS].pop();
1503             self.ribs[TypeNS].pop();
1504         } else {
1505             f(self);
1506         }
1507     }
1508
1509     /// Searches the current set of local scopes for labels.
1510     /// Stops after meeting a closure.
1511     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1512         for rib in self.label_ribs.iter().rev() {
1513             match rib.kind {
1514                 NormalRibKind => {
1515                     // Continue
1516                 }
1517                 MacroDefinition(mac) => {
1518                     // If an invocation of this macro created `ident`, give up on `ident`
1519                     // and switch to `ident`'s source from the macro definition.
1520                     let (source_ctxt, source_macro) = ident.ctxt.source();
1521                     if source_macro == mac {
1522                         ident.ctxt = source_ctxt;
1523                     }
1524                 }
1525                 _ => {
1526                     // Do not resolve labels across function boundary
1527                     return None;
1528                 }
1529             }
1530             let result = rib.bindings.get(&ident).cloned();
1531             if result.is_some() {
1532                 return result;
1533             }
1534         }
1535         None
1536     }
1537
1538     fn resolve_item(&mut self, item: &Item) {
1539         let name = item.ident.name;
1540
1541         debug!("(resolving item) resolving {}", name);
1542
1543         self.check_proc_macro_attrs(&item.attrs);
1544
1545         match item.node {
1546             ItemKind::Enum(_, ref generics) |
1547             ItemKind::Ty(_, ref generics) |
1548             ItemKind::Struct(_, ref generics) |
1549             ItemKind::Union(_, ref generics) |
1550             ItemKind::Fn(.., ref generics, _) => {
1551                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1552                                              |this| visit::walk_item(this, item));
1553             }
1554
1555             ItemKind::DefaultImpl(_, ref trait_ref) => {
1556                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1557                     // Resolve type arguments in trait path
1558                     visit::walk_trait_ref(this, trait_ref);
1559                 });
1560             }
1561             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1562                 self.resolve_implementation(generics,
1563                                             opt_trait_ref,
1564                                             &self_type,
1565                                             item.id,
1566                                             impl_items),
1567
1568             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1569                 // Create a new rib for the trait-wide type parameters.
1570                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1571                     let local_def_id = this.definitions.local_def_id(item.id);
1572                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1573                         this.visit_generics(generics);
1574                         walk_list!(this, visit_ty_param_bound, bounds);
1575
1576                         for trait_item in trait_items {
1577                             this.check_proc_macro_attrs(&trait_item.attrs);
1578
1579                             match trait_item.node {
1580                                 TraitItemKind::Const(_, ref default) => {
1581                                     // Only impose the restrictions of
1582                                     // ConstRibKind if there's an actual constant
1583                                     // expression in a provided default.
1584                                     if default.is_some() {
1585                                         this.with_constant_rib(|this| {
1586                                             visit::walk_trait_item(this, trait_item)
1587                                         });
1588                                     } else {
1589                                         visit::walk_trait_item(this, trait_item)
1590                                     }
1591                                 }
1592                                 TraitItemKind::Method(ref sig, _) => {
1593                                     let type_parameters =
1594                                         HasTypeParameters(&sig.generics,
1595                                                           MethodRibKind(!sig.decl.has_self()));
1596                                     this.with_type_parameter_rib(type_parameters, |this| {
1597                                         visit::walk_trait_item(this, trait_item)
1598                                     });
1599                                 }
1600                                 TraitItemKind::Type(..) => {
1601                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1602                                         visit::walk_trait_item(this, trait_item)
1603                                     });
1604                                 }
1605                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1606                             };
1607                         }
1608                     });
1609                 });
1610             }
1611
1612             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1613                 self.with_scope(item.id, |this| {
1614                     visit::walk_item(this, item);
1615                 });
1616             }
1617
1618             ItemKind::Const(..) | ItemKind::Static(..) => {
1619                 self.with_constant_rib(|this| {
1620                     visit::walk_item(this, item);
1621                 });
1622             }
1623
1624             ItemKind::Use(ref view_path) => {
1625                 match view_path.node {
1626                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1627                         // Resolve prefix of an import with empty braces (issue #28388).
1628                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1629                     }
1630                     _ => {}
1631                 }
1632             }
1633
1634             ItemKind::ExternCrate(_) => {
1635                 // do nothing, these are just around to be encoded
1636             }
1637
1638             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1639         }
1640     }
1641
1642     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1643         where F: FnOnce(&mut Resolver)
1644     {
1645         match type_parameters {
1646             HasTypeParameters(generics, rib_kind) => {
1647                 let mut function_type_rib = Rib::new(rib_kind);
1648                 let mut seen_bindings = FxHashMap();
1649                 for type_parameter in &generics.ty_params {
1650                     let name = type_parameter.ident.name;
1651                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1652
1653                     if seen_bindings.contains_key(&name) {
1654                         let span = seen_bindings.get(&name).unwrap();
1655                         resolve_error(self,
1656                                       type_parameter.span,
1657                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name,
1658                                                                                           span));
1659                     }
1660                     seen_bindings.entry(name).or_insert(type_parameter.span);
1661
1662                     // plain insert (no renaming)
1663                     let def_id = self.definitions.local_def_id(type_parameter.id);
1664                     let def = Def::TyParam(def_id);
1665                     function_type_rib.bindings.insert(Ident::with_empty_ctxt(name), def);
1666                     self.record_def(type_parameter.id, PathResolution::new(def));
1667                 }
1668                 self.ribs[TypeNS].push(function_type_rib);
1669             }
1670
1671             NoTypeParameters => {
1672                 // Nothing to do.
1673             }
1674         }
1675
1676         f(self);
1677
1678         if let HasTypeParameters(..) = type_parameters {
1679             self.ribs[TypeNS].pop();
1680         }
1681     }
1682
1683     fn with_label_rib<F>(&mut self, f: F)
1684         where F: FnOnce(&mut Resolver)
1685     {
1686         self.label_ribs.push(Rib::new(NormalRibKind));
1687         f(self);
1688         self.label_ribs.pop();
1689     }
1690
1691     fn with_constant_rib<F>(&mut self, f: F)
1692         where F: FnOnce(&mut Resolver)
1693     {
1694         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1695         self.ribs[TypeNS].push(Rib::new(ConstantItemRibKind));
1696         f(self);
1697         self.ribs[TypeNS].pop();
1698         self.ribs[ValueNS].pop();
1699     }
1700
1701     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1702         where F: FnOnce(&mut Resolver) -> T
1703     {
1704         // Handle nested impls (inside fn bodies)
1705         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1706         let result = f(self);
1707         self.current_self_type = previous_value;
1708         result
1709     }
1710
1711     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1712         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1713     {
1714         let mut new_val = None;
1715         let mut new_id = None;
1716         if let Some(trait_ref) = opt_trait_ref {
1717             let def = self.smart_resolve_path(trait_ref.ref_id, None,
1718                                               &trait_ref.path, PathSource::Trait).base_def;
1719             if def != Def::Err {
1720                 new_val = Some((def.def_id(), trait_ref.clone()));
1721                 new_id = Some(def.def_id());
1722             }
1723         }
1724         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1725         let result = f(self, new_id);
1726         self.current_trait_ref = original_trait_ref;
1727         result
1728     }
1729
1730     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
1731         where F: FnOnce(&mut Resolver)
1732     {
1733         let mut self_type_rib = Rib::new(NormalRibKind);
1734
1735         // plain insert (no renaming, types are not currently hygienic....)
1736         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
1737         self.ribs[TypeNS].push(self_type_rib);
1738         f(self);
1739         self.ribs[TypeNS].pop();
1740     }
1741
1742     fn resolve_implementation(&mut self,
1743                               generics: &Generics,
1744                               opt_trait_reference: &Option<TraitRef>,
1745                               self_type: &Ty,
1746                               item_id: NodeId,
1747                               impl_items: &[ImplItem]) {
1748         // If applicable, create a rib for the type parameters.
1749         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1750             // Dummy self type for better errors if `Self` is used in the trait path.
1751             this.with_self_rib(Def::SelfTy(None, None), |this| {
1752                 // Resolve the trait reference, if necessary.
1753                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1754                     let item_def_id = this.definitions.local_def_id(item_id);
1755                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
1756                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
1757                             // Resolve type arguments in trait path
1758                             visit::walk_trait_ref(this, trait_ref);
1759                         }
1760                         // Resolve the self type.
1761                         this.visit_ty(self_type);
1762                         // Resolve the type parameters.
1763                         this.visit_generics(generics);
1764                         this.with_current_self_type(self_type, |this| {
1765                             for impl_item in impl_items {
1766                                 this.check_proc_macro_attrs(&impl_item.attrs);
1767                                 this.resolve_visibility(&impl_item.vis);
1768                                 match impl_item.node {
1769                                     ImplItemKind::Const(..) => {
1770                                         // If this is a trait impl, ensure the const
1771                                         // exists in trait
1772                                         this.check_trait_item(impl_item.ident.name,
1773                                                             ValueNS,
1774                                                             impl_item.span,
1775                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
1776                                         visit::walk_impl_item(this, impl_item);
1777                                     }
1778                                     ImplItemKind::Method(ref sig, _) => {
1779                                         // If this is a trait impl, ensure the method
1780                                         // exists in trait
1781                                         this.check_trait_item(impl_item.ident.name,
1782                                                             ValueNS,
1783                                                             impl_item.span,
1784                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
1785
1786                                         // We also need a new scope for the method-
1787                                         // specific type parameters.
1788                                         let type_parameters =
1789                                             HasTypeParameters(&sig.generics,
1790                                                             MethodRibKind(!sig.decl.has_self()));
1791                                         this.with_type_parameter_rib(type_parameters, |this| {
1792                                             visit::walk_impl_item(this, impl_item);
1793                                         });
1794                                     }
1795                                     ImplItemKind::Type(ref ty) => {
1796                                         // If this is a trait impl, ensure the type
1797                                         // exists in trait
1798                                         this.check_trait_item(impl_item.ident.name,
1799                                                             TypeNS,
1800                                                             impl_item.span,
1801                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
1802
1803                                         this.visit_ty(ty);
1804                                     }
1805                                     ImplItemKind::Macro(_) =>
1806                                         panic!("unexpanded macro in resolve!"),
1807                                 }
1808                             }
1809                         });
1810                     });
1811                 });
1812             });
1813         });
1814     }
1815
1816     fn check_trait_item<F>(&self, name: Name, ns: Namespace, span: Span, err: F)
1817         where F: FnOnce(Name, &str) -> ResolutionError
1818     {
1819         // If there is a TraitRef in scope for an impl, then the method must be in the
1820         // trait.
1821         if let Some((did, ref trait_ref)) = self.current_trait_ref {
1822             if !self.trait_item_map.contains_key(&(did, name, ns)) {
1823                 let path_str = path_names_to_string(&trait_ref.path);
1824                 resolve_error(self, span, err(name, &path_str));
1825             }
1826         }
1827     }
1828
1829     fn resolve_local(&mut self, local: &Local) {
1830         // Resolve the type.
1831         walk_list!(self, visit_ty, &local.ty);
1832
1833         // Resolve the initializer.
1834         walk_list!(self, visit_expr, &local.init);
1835
1836         // Resolve the pattern.
1837         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
1838     }
1839
1840     // build a map from pattern identifiers to binding-info's.
1841     // this is done hygienically. This could arise for a macro
1842     // that expands into an or-pattern where one 'x' was from the
1843     // user and one 'x' came from the macro.
1844     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1845         let mut binding_map = FxHashMap();
1846
1847         pat.walk(&mut |pat| {
1848             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
1849                 if sub_pat.is_some() || match self.def_map.get(&pat.id) {
1850                     Some(&PathResolution { base_def: Def::Local(..), .. }) => true,
1851                     _ => false,
1852                 } {
1853                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
1854                     binding_map.insert(ident.node, binding_info);
1855                 }
1856             }
1857             true
1858         });
1859
1860         binding_map
1861     }
1862
1863     // check that all of the arms in an or-pattern have exactly the
1864     // same set of bindings, with the same binding modes for each.
1865     fn check_consistent_bindings(&mut self, arm: &Arm) {
1866         if arm.pats.is_empty() {
1867             return;
1868         }
1869         let map_0 = self.binding_mode_map(&arm.pats[0]);
1870         for (i, p) in arm.pats.iter().enumerate() {
1871             let map_i = self.binding_mode_map(&p);
1872
1873             for (&key, &binding_0) in &map_0 {
1874                 match map_i.get(&key) {
1875                     None => {
1876                         let error = ResolutionError::VariableNotBoundInPattern(key.name, 1, i + 1);
1877                         resolve_error(self, p.span, error);
1878                     }
1879                     Some(binding_i) => {
1880                         if binding_0.binding_mode != binding_i.binding_mode {
1881                             resolve_error(self,
1882                                           binding_i.span,
1883                                           ResolutionError::VariableBoundWithDifferentMode(
1884                                               key.name,
1885                                               i + 1,
1886                                               binding_0.span));
1887                         }
1888                     }
1889                 }
1890             }
1891
1892             for (&key, &binding) in &map_i {
1893                 if !map_0.contains_key(&key) {
1894                     resolve_error(self,
1895                                   binding.span,
1896                                   ResolutionError::VariableNotBoundInPattern(key.name, i + 1, 1));
1897                 }
1898             }
1899         }
1900     }
1901
1902     fn resolve_arm(&mut self, arm: &Arm) {
1903         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
1904
1905         let mut bindings_list = FxHashMap();
1906         for pattern in &arm.pats {
1907             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
1908         }
1909
1910         // This has to happen *after* we determine which
1911         // pat_idents are variants
1912         self.check_consistent_bindings(arm);
1913
1914         walk_list!(self, visit_expr, &arm.guard);
1915         self.visit_expr(&arm.body);
1916
1917         self.ribs[ValueNS].pop();
1918     }
1919
1920     fn resolve_block(&mut self, block: &Block) {
1921         debug!("(resolving block) entering block");
1922         // Move down in the graph, if there's an anonymous module rooted here.
1923         let orig_module = self.current_module;
1924         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
1925
1926         let mut num_macro_definition_ribs = 0;
1927         if let Some(anonymous_module) = anonymous_module {
1928             debug!("(resolving block) found anonymous module, moving down");
1929             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1930             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
1931             self.current_module = anonymous_module;
1932             self.finalize_current_module_macro_resolutions();
1933         } else {
1934             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
1935         }
1936
1937         // Descend into the block.
1938         for stmt in &block.stmts {
1939             if let Some(marks) = self.macros_at_scope.remove(&stmt.id) {
1940                 num_macro_definition_ribs += marks.len() as u32;
1941                 for mark in marks {
1942                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(mark)));
1943                     self.label_ribs.push(Rib::new(MacroDefinition(mark)));
1944                 }
1945             }
1946
1947             self.visit_stmt(stmt);
1948         }
1949
1950         // Move back up.
1951         self.current_module = orig_module;
1952         for _ in 0 .. num_macro_definition_ribs {
1953             self.ribs[ValueNS].pop();
1954             self.label_ribs.pop();
1955         }
1956         self.ribs[ValueNS].pop();
1957         if let Some(_) = anonymous_module {
1958             self.ribs[TypeNS].pop();
1959         }
1960         debug!("(resolving block) leaving block");
1961     }
1962
1963     fn fresh_binding(&mut self,
1964                      ident: &SpannedIdent,
1965                      pat_id: NodeId,
1966                      outer_pat_id: NodeId,
1967                      pat_src: PatternSource,
1968                      bindings: &mut FxHashMap<Ident, NodeId>)
1969                      -> PathResolution {
1970         // Add the binding to the local ribs, if it
1971         // doesn't already exist in the bindings map. (We
1972         // must not add it if it's in the bindings map
1973         // because that breaks the assumptions later
1974         // passes make about or-patterns.)
1975         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
1976         match bindings.get(&ident.node).cloned() {
1977             Some(id) if id == outer_pat_id => {
1978                 // `Variant(a, a)`, error
1979                 resolve_error(
1980                     self,
1981                     ident.span,
1982                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
1983                         &ident.node.name.as_str())
1984                 );
1985             }
1986             Some(..) if pat_src == PatternSource::FnParam => {
1987                 // `fn f(a: u8, a: u8)`, error
1988                 resolve_error(
1989                     self,
1990                     ident.span,
1991                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
1992                         &ident.node.name.as_str())
1993                 );
1994             }
1995             Some(..) if pat_src == PatternSource::Match => {
1996                 // `Variant1(a) | Variant2(a)`, ok
1997                 // Reuse definition from the first `a`.
1998                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
1999             }
2000             Some(..) => {
2001                 span_bug!(ident.span, "two bindings with the same name from \
2002                                        unexpected pattern source {:?}", pat_src);
2003             }
2004             None => {
2005                 // A completely fresh binding, add to the lists if it's valid.
2006                 if ident.node.name != keywords::Invalid.name() {
2007                     bindings.insert(ident.node, outer_pat_id);
2008                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2009                 }
2010             }
2011         }
2012
2013         PathResolution::new(def)
2014     }
2015
2016     fn resolve_pattern(&mut self,
2017                        pat: &Pat,
2018                        pat_src: PatternSource,
2019                        // Maps idents to the node ID for the
2020                        // outermost pattern that binds them.
2021                        bindings: &mut FxHashMap<Ident, NodeId>) {
2022         // Visit all direct subpatterns of this pattern.
2023         let outer_pat_id = pat.id;
2024         pat.walk(&mut |pat| {
2025             match pat.node {
2026                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2027                     // First try to resolve the identifier as some existing
2028                     // entity, then fall back to a fresh binding.
2029                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS, None)
2030                                       .and_then(LexicalScopeBinding::item);
2031                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2032                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2033                                              bmode != BindingMode::ByValue(Mutability::Immutable);
2034                         match def {
2035                             Def::StructCtor(_, CtorKind::Const) |
2036                             Def::VariantCtor(_, CtorKind::Const) |
2037                             Def::Const(..) if !always_binding => {
2038                                 // A unit struct/variant or constant pattern.
2039                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2040                                 Some(PathResolution::new(def))
2041                             }
2042                             Def::StructCtor(..) | Def::VariantCtor(..) |
2043                             Def::Const(..) | Def::Static(..) => {
2044                                 // A fresh binding that shadows something unacceptable.
2045                                 resolve_error(
2046                                     self,
2047                                     ident.span,
2048                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2049                                         pat_src.descr(), ident.node.name, binding.unwrap())
2050                                 );
2051                                 None
2052                             }
2053                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2054                                 // These entities are explicitly allowed
2055                                 // to be shadowed by fresh bindings.
2056                                 None
2057                             }
2058                             def => {
2059                                 span_bug!(ident.span, "unexpected definition for an \
2060                                                        identifier in pattern: {:?}", def);
2061                             }
2062                         }
2063                     }).unwrap_or_else(|| {
2064                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2065                     });
2066
2067                     self.record_def(pat.id, resolution);
2068                 }
2069
2070                 PatKind::TupleStruct(ref path, ..) => {
2071                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2072                 }
2073
2074                 PatKind::Path(ref qself, ref path) => {
2075                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2076                 }
2077
2078                 PatKind::Struct(ref path, ..) => {
2079                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2080                 }
2081
2082                 _ => {}
2083             }
2084             true
2085         });
2086
2087         visit::walk_pat(self, pat);
2088     }
2089
2090     // High-level and context dependent path resolution routine.
2091     // Resolves the path and records the resolution into definition map.
2092     // If resolution fails tries several techniques to find likely
2093     // resolution candidates, suggest imports or other help, and report
2094     // errors in user friendly way.
2095     fn smart_resolve_path(&mut self,
2096                           id: NodeId,
2097                           qself: Option<&QSelf>,
2098                           path: &Path,
2099                           source: PathSource)
2100                           -> PathResolution {
2101         let segments = &path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>();
2102         self.smart_resolve_path_fragment(id, qself, segments, path.span, source)
2103     }
2104
2105     fn smart_resolve_path_fragment(&mut self,
2106                                    id: NodeId,
2107                                    qself: Option<&QSelf>,
2108                                    path: &[Ident],
2109                                    span: Span,
2110                                    source: PathSource)
2111                                    -> PathResolution {
2112         let ns = source.namespace();
2113         let is_expected = &|def| source.is_expected(def);
2114
2115         // Base error is amended with one short label and possibly some longer helps/notes.
2116         let report_errors = |this: &mut Self, def: Option<Def>| {
2117             // Make the base error.
2118             let expected = source.descr_expected();
2119             let path_str = names_to_string(path);
2120             let code = source.error_code(def.is_some());
2121             let (base_msg, fallback_label) = if let Some(def) = def {
2122                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2123                  format!("not a {}", expected))
2124             } else {
2125                 let item_str = path[path.len() - 1];
2126                 let (mod_prefix, mod_str) = if path.len() == 1 {
2127                     (format!(""), format!("this scope"))
2128                 } else if path.len() == 2 && path[0].name == keywords::CrateRoot.name() {
2129                     (format!(""), format!("the crate root"))
2130                 } else {
2131                     let mod_path = &path[..path.len() - 1];
2132                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), None) {
2133                         PathResult::Module(module) => module.def(),
2134                         _ => None,
2135                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2136                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2137                 };
2138                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2139                  format!("not found in {}", mod_str))
2140             };
2141             let mut err = this.session.struct_span_err_with_code(span, &base_msg, code);
2142
2143             // Emit special messages for unresolved `Self` and `self`.
2144             if is_self_type(path, ns) {
2145                 __diagnostic_used!(E0411);
2146                 err.code("E0411".into());
2147                 err.span_label(span, &format!("`Self` is only available in traits and impls"));
2148                 return err;
2149             }
2150             if is_self_value(path, ns) {
2151                 __diagnostic_used!(E0424);
2152                 err.code("E0424".into());
2153                 err.span_label(span, &format!("`self` value is only available in \
2154                                                methods with `self` parameter"));
2155                 return err;
2156             }
2157
2158             // Try to lookup the name in more relaxed fashion for better error reporting.
2159             let name = path.last().unwrap().name;
2160             let candidates = this.lookup_import_candidates(name, ns, is_expected);
2161             if !candidates.is_empty() {
2162                 // Report import candidates as help and proceed searching for labels.
2163                 show_candidates(&mut err, &candidates, def.is_some());
2164             }
2165             if path.len() == 1 && this.self_type_is_available() {
2166                 if let Some(candidate) = this.lookup_assoc_candidate(name, ns, is_expected) {
2167                     let self_is_available = this.self_value_is_available(path[0].ctxt);
2168                     match candidate {
2169                         AssocSuggestion::Field => {
2170                             err.span_label(span, &format!("did you mean `self.{}`?", path_str));
2171                             if !self_is_available {
2172                                 err.span_label(span, &format!("`self` value is only available in \
2173                                                                methods with `self` parameter"));
2174                             }
2175                         }
2176                         AssocSuggestion::MethodWithSelf if self_is_available => {
2177                             err.span_label(span, &format!("did you mean `self.{}(...)`?",
2178                                                            path_str));
2179                         }
2180                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2181                             err.span_label(span, &format!("did you mean `Self::{}`?", path_str));
2182                         }
2183                     }
2184                     return err;
2185                 }
2186             }
2187
2188             // Try context dependent help if relaxed lookup didn't work.
2189             if let Some(def) = def {
2190                 match (def, source) {
2191                     (Def::Macro(..), _) => {
2192                         err.span_label(span, &format!("did you mean `{}!(...)`?", path_str));
2193                         return err;
2194                     }
2195                     (Def::TyAlias(..), PathSource::Trait) => {
2196                         err.span_label(span, &format!("type aliases cannot be used for traits"));
2197                         return err;
2198                     }
2199                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match *parent {
2200                         ExprKind::Field(_, ident) => {
2201                             err.span_label(span, &format!("did you mean `{}::{}`?",
2202                                                            path_str, ident.node));
2203                             return err;
2204                         }
2205                         ExprKind::MethodCall(ident, ..) => {
2206                             err.span_label(span, &format!("did you mean `{}::{}(...)`?",
2207                                                            path_str, ident.node));
2208                             return err;
2209                         }
2210                         _ => {}
2211                     },
2212                     _ if ns == ValueNS && is_struct_like(def) => {
2213                         if let Def::Struct(def_id) = def {
2214                             if let Some((ctor_def, ctor_vis))
2215                                     = this.struct_constructors.get(&def_id).cloned() {
2216                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2217                                     err.span_label(span, &format!("constructor is not visible \
2218                                                                    here due to private fields"));
2219                                 }
2220                             }
2221                         }
2222                         err.span_label(span, &format!("did you mean `{} {{ /* fields */ }}`?",
2223                                                        path_str));
2224                         return err;
2225                     }
2226                     _ => {}
2227                 }
2228             }
2229
2230             // Try Levenshtein if nothing else worked.
2231             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected) {
2232                 err.span_label(span, &format!("did you mean `{}`?", candidate));
2233                 return err;
2234             }
2235
2236             // Fallback label.
2237             err.span_label(span, &fallback_label);
2238             err
2239         };
2240         let report_errors = |this: &mut Self, def: Option<Def>| {
2241             report_errors(this, def).emit();
2242             err_path_resolution()
2243         };
2244
2245         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2246                                                            source.defer_to_typeck(),
2247                                                            source.global_by_default()) {
2248             Some(resolution) if resolution.depth == 0 => {
2249                 if is_expected(resolution.base_def) || resolution.base_def == Def::Err {
2250                     resolution
2251                 } else {
2252                     // Add a temporary hack to smooth the transition to new struct ctor
2253                     // visibility rules. See #38932 for more details.
2254                     let mut res = None;
2255                     if let Def::Struct(def_id) = resolution.base_def {
2256                         if let Some((ctor_def, ctor_vis))
2257                                 = self.struct_constructors.get(&def_id).cloned() {
2258                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2259                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2260                                 self.session.add_lint(lint, id, span,
2261                                     "private struct constructors are not usable through \
2262                                      reexports in outer modules".to_string());
2263                                 res = Some(PathResolution::new(ctor_def));
2264                             }
2265                         }
2266                     }
2267
2268                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def)))
2269                 }
2270             }
2271             Some(resolution) if source.defer_to_typeck() => {
2272                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2273                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2274                 // it needs to be added to the trait map.
2275                 if ns == ValueNS {
2276                     let item_name = path.last().unwrap().name;
2277                     let traits = self.get_traits_containing_item(item_name, ns);
2278                     self.trait_map.insert(id, traits);
2279                 }
2280                 resolution
2281             }
2282             _ => report_errors(self, None)
2283         };
2284
2285         if let PathSource::TraitItem(..) = source {} else {
2286             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2287             self.record_def(id, resolution);
2288         }
2289         resolution
2290     }
2291
2292     fn self_type_is_available(&mut self) -> bool {
2293         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(), TypeNS, None);
2294         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2295     }
2296
2297     fn self_value_is_available(&mut self, ctxt: SyntaxContext) -> bool {
2298         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2299         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None);
2300         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2301     }
2302
2303     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2304     fn resolve_qpath_anywhere(&mut self,
2305                               id: NodeId,
2306                               qself: Option<&QSelf>,
2307                               path: &[Ident],
2308                               primary_ns: Namespace,
2309                               span: Span,
2310                               defer_to_typeck: bool,
2311                               global_by_default: bool)
2312                               -> Option<PathResolution> {
2313         let mut fin_res = None;
2314         // FIXME: can't resolve paths in macro namespace yet, macros are
2315         // processed by the little special hack below.
2316         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2317             if i == 0 || ns != primary_ns {
2318                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2319                     // If defer_to_typeck, then resolution > no resolution,
2320                     // otherwise full resolution > partial resolution > no resolution.
2321                     Some(res) if res.depth == 0 || defer_to_typeck => return Some(res),
2322                     res => if fin_res.is_none() { fin_res = res },
2323                 };
2324             }
2325         }
2326         if primary_ns != MacroNS && path.len() == 1 &&
2327                 self.macro_names.contains(&path[0].name) {
2328             // Return some dummy definition, it's enough for error reporting.
2329             return Some(PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX))));
2330         }
2331         fin_res
2332     }
2333
2334     /// Handles paths that may refer to associated items.
2335     fn resolve_qpath(&mut self,
2336                      id: NodeId,
2337                      qself: Option<&QSelf>,
2338                      path: &[Ident],
2339                      ns: Namespace,
2340                      span: Span,
2341                      global_by_default: bool)
2342                      -> Option<PathResolution> {
2343         if let Some(qself) = qself {
2344             if qself.position == 0 {
2345                 // FIXME: Create some fake resolution that can't possibly be a type.
2346                 return Some(PathResolution {
2347                     base_def: Def::Mod(DefId::local(CRATE_DEF_INDEX)),
2348                     depth: path.len(),
2349                 });
2350             }
2351             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2352             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2353             let mut res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2354                                                            span, PathSource::TraitItem(ns));
2355             if res.base_def != Def::Err {
2356                 res.depth += path.len() - qself.position - 1;
2357             }
2358             return Some(res);
2359         }
2360
2361         let result = match self.resolve_path(&path, Some(ns), Some(span)) {
2362             PathResult::NonModule(path_res) => path_res,
2363             PathResult::Module(module) if !module.is_normal() => {
2364                 PathResolution::new(module.def().unwrap())
2365             }
2366             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2367             // don't report an error right away, but try to fallback to a primitive type.
2368             // So, we are still able to successfully resolve something like
2369             //
2370             // use std::u8; // bring module u8 in scope
2371             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2372             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2373             //                     // not to non-existent std::u8::max_value
2374             // }
2375             //
2376             // Such behavior is required for backward compatibility.
2377             // The same fallback is used when `a` resolves to nothing.
2378             PathResult::Module(..) | PathResult::Failed(..)
2379                     if (ns == TypeNS || path.len() > 1) &&
2380                        self.primitive_type_table.primitive_types.contains_key(&path[0].name) => {
2381                 let prim = self.primitive_type_table.primitive_types[&path[0].name];
2382                 match prim {
2383                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2384                         if !self.session.features.borrow().i128_type {
2385                             emit_feature_err(&self.session.parse_sess,
2386                                                 "i128_type", span, GateIssue::Language,
2387                                                 "128-bit type is unstable");
2388
2389                         }
2390                     }
2391                     _ => {}
2392                 }
2393                 PathResolution {
2394                     base_def: Def::PrimTy(prim),
2395                     depth: path.len() - 1,
2396                 }
2397             }
2398             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2399             PathResult::Failed(msg, false) => {
2400                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2401                 err_path_resolution()
2402             }
2403             PathResult::Failed(..) => return None,
2404             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2405         };
2406
2407         if path.len() > 1 && !global_by_default && result.base_def != Def::Err &&
2408            path[0].name != keywords::CrateRoot.name() && path[0].name != "$crate" {
2409             let unqualified_result = {
2410                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
2411                     PathResult::NonModule(path_res) => path_res.base_def,
2412                     PathResult::Module(module) => module.def().unwrap(),
2413                     _ => return Some(result),
2414                 }
2415             };
2416             if result.base_def == unqualified_result {
2417                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2418                 self.session.add_lint(lint, id, span, "unnecessary qualification".to_string());
2419             }
2420         }
2421
2422         Some(result)
2423     }
2424
2425     fn resolve_path(&mut self,
2426                     path: &[Ident],
2427                     opt_ns: Option<Namespace>, // `None` indicates a module path
2428                     record_used: Option<Span>)
2429                     -> PathResult<'a> {
2430         let mut module = None;
2431         let mut allow_super = true;
2432
2433         for (i, &ident) in path.iter().enumerate() {
2434             let is_last = i == path.len() - 1;
2435             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2436
2437             if i == 0 && ns == TypeNS && ident.name == keywords::SelfValue.name() {
2438                 module = Some(self.module_map[&self.current_module.normal_ancestor_id]);
2439                 continue
2440             } else if allow_super && ns == TypeNS && ident.name == keywords::Super.name() {
2441                 let current_module = if i == 0 { self.current_module } else { module.unwrap() };
2442                 let self_module = self.module_map[&current_module.normal_ancestor_id];
2443                 if let Some(parent) = self_module.parent {
2444                     module = Some(self.module_map[&parent.normal_ancestor_id]);
2445                     continue
2446                 } else {
2447                     let msg = "There are too many initial `super`s.".to_string();
2448                     return PathResult::Failed(msg, false);
2449                 }
2450             }
2451             allow_super = false;
2452
2453             if i == 0 && ns == TypeNS && ident.name == keywords::CrateRoot.name() {
2454                 module = Some(self.graph_root);
2455                 continue
2456             } else if i == 0 && ns == TypeNS && ident.name == "$crate" {
2457                 module = Some(self.resolve_crate_var(ident.ctxt));
2458                 continue
2459             }
2460
2461             let binding = if let Some(module) = module {
2462                 self.resolve_ident_in_module(module, ident, ns, false, record_used)
2463             } else if opt_ns == Some(MacroNS) {
2464                 self.resolve_lexical_macro_path_segment(ident, ns, record_used)
2465             } else {
2466                 match self.resolve_ident_in_lexical_scope(ident, ns, record_used) {
2467                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2468                     Some(LexicalScopeBinding::Def(def))
2469                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2470                         return PathResult::NonModule(PathResolution {
2471                             base_def: def,
2472                             depth: path.len() - 1,
2473                         });
2474                     }
2475                     _ => Err(if record_used.is_some() { Determined } else { Undetermined }),
2476                 }
2477             };
2478
2479             match binding {
2480                 Ok(binding) => {
2481                     let def = binding.def();
2482                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2483                     if let Some(next_module) = binding.module() {
2484                         module = Some(next_module);
2485                     } else if def == Def::Err {
2486                         return PathResult::NonModule(err_path_resolution());
2487                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2488                         return PathResult::NonModule(PathResolution {
2489                             base_def: def,
2490                             depth: path.len() - i - 1,
2491                         });
2492                     } else {
2493                         return PathResult::Failed(format!("Not a module `{}`", ident), is_last);
2494                     }
2495                 }
2496                 Err(Undetermined) => return PathResult::Indeterminate,
2497                 Err(Determined) => {
2498                     if let Some(module) = module {
2499                         if opt_ns.is_some() && !module.is_normal() {
2500                             return PathResult::NonModule(PathResolution {
2501                                 base_def: module.def().unwrap(),
2502                                 depth: path.len() - i,
2503                             });
2504                         }
2505                     }
2506                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2507                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2508                         let mut candidates =
2509                             self.lookup_import_candidates(ident.name, TypeNS, is_mod);
2510                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2511                         if let Some(candidate) = candidates.get(0) {
2512                             format!("Did you mean `{}`?", candidate.path)
2513                         } else {
2514                             format!("Maybe a missing `extern crate {};`?", ident)
2515                         }
2516                     } else if i == 0 {
2517                         format!("Use of undeclared type or module `{}`", ident)
2518                     } else {
2519                         format!("Could not find `{}` in `{}`", ident, path[i - 1])
2520                     };
2521                     return PathResult::Failed(msg, is_last);
2522                 }
2523             }
2524         }
2525
2526         PathResult::Module(module.unwrap_or(self.graph_root))
2527     }
2528
2529     // Resolve a local definition, potentially adjusting for closures.
2530     fn adjust_local_def(&mut self, local_def: LocalDef, record_used: Option<Span>) -> Def {
2531         let ribs = match local_def.ribs {
2532             Some((ns, i)) => &self.ribs[ns][i + 1..],
2533             None => &[] as &[_],
2534         };
2535         let mut def = local_def.def;
2536         match def {
2537             Def::Upvar(..) => {
2538                 span_bug!(record_used.unwrap_or(DUMMY_SP), "unexpected {:?} in bindings", def)
2539             }
2540             Def::Local(def_id) => {
2541                 for rib in ribs {
2542                     match rib.kind {
2543                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) => {
2544                             // Nothing to do. Continue.
2545                         }
2546                         ClosureRibKind(function_id) => {
2547                             let prev_def = def;
2548                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2549
2550                             let seen = self.freevars_seen
2551                                            .entry(function_id)
2552                                            .or_insert_with(|| NodeMap());
2553                             if let Some(&index) = seen.get(&node_id) {
2554                                 def = Def::Upvar(def_id, index, function_id);
2555                                 continue;
2556                             }
2557                             let vec = self.freevars
2558                                           .entry(function_id)
2559                                           .or_insert_with(|| vec![]);
2560                             let depth = vec.len();
2561                             def = Def::Upvar(def_id, depth, function_id);
2562
2563                             if let Some(span) = record_used {
2564                                 vec.push(Freevar {
2565                                     def: prev_def,
2566                                     span: span,
2567                                 });
2568                                 seen.insert(node_id, depth);
2569                             }
2570                         }
2571                         ItemRibKind | MethodRibKind(_) => {
2572                             // This was an attempt to access an upvar inside a
2573                             // named function item. This is not allowed, so we
2574                             // report an error.
2575                             if let Some(span) = record_used {
2576                                 resolve_error(self, span,
2577                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2578                             }
2579                             return Def::Err;
2580                         }
2581                         ConstantItemRibKind => {
2582                             // Still doesn't deal with upvars
2583                             if let Some(span) = record_used {
2584                                 resolve_error(self, span,
2585                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
2586                             }
2587                             return Def::Err;
2588                         }
2589                     }
2590                 }
2591             }
2592             Def::TyParam(..) | Def::SelfTy(..) => {
2593                 for rib in ribs {
2594                     match rib.kind {
2595                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
2596                         ModuleRibKind(..) | MacroDefinition(..) => {
2597                             // Nothing to do. Continue.
2598                         }
2599                         ItemRibKind => {
2600                             // This was an attempt to use a type parameter outside
2601                             // its scope.
2602                             if let Some(span) = record_used {
2603                                 resolve_error(self, span,
2604                                               ResolutionError::TypeParametersFromOuterFunction);
2605                             }
2606                             return Def::Err;
2607                         }
2608                         ConstantItemRibKind => {
2609                             // see #9186
2610                             if let Some(span) = record_used {
2611                                 resolve_error(self, span,
2612                                               ResolutionError::OuterTypeParameterContext);
2613                             }
2614                             return Def::Err;
2615                         }
2616                     }
2617                 }
2618             }
2619             _ => {}
2620         }
2621         return def;
2622     }
2623
2624     // Calls `f` with a `Resolver` whose current lexical scope is `module`'s lexical scope,
2625     // i.e. the module's items and the prelude (unless the module is `#[no_implicit_prelude]`).
2626     // FIXME #34673: This needs testing.
2627     pub fn with_module_lexical_scope<T, F>(&mut self, module: Module<'a>, f: F) -> T
2628         where F: FnOnce(&mut Resolver<'a>) -> T,
2629     {
2630         self.with_empty_ribs(|this| {
2631             this.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
2632             this.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
2633             f(this)
2634         })
2635     }
2636
2637     fn with_empty_ribs<T, F>(&mut self, f: F) -> T
2638         where F: FnOnce(&mut Resolver<'a>) -> T,
2639     {
2640         let ribs = replace(&mut self.ribs, PerNS::<Vec<Rib>>::default());
2641         let label_ribs = replace(&mut self.label_ribs, Vec::new());
2642
2643         let result = f(self);
2644         self.ribs = ribs;
2645         self.label_ribs = label_ribs;
2646         result
2647     }
2648
2649     fn lookup_assoc_candidate<FilterFn>(&mut self,
2650                                         name: Name,
2651                                         ns: Namespace,
2652                                         filter_fn: FilterFn)
2653                                         -> Option<AssocSuggestion>
2654         where FilterFn: Fn(Def) -> bool
2655     {
2656         fn extract_node_id(t: &Ty) -> Option<NodeId> {
2657             match t.node {
2658                 TyKind::Path(None, _) => Some(t.id),
2659                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
2660                 // This doesn't handle the remaining `Ty` variants as they are not
2661                 // that commonly the self_type, it might be interesting to provide
2662                 // support for those in future.
2663                 _ => None,
2664             }
2665         }
2666
2667         // Fields are generally expected in the same contexts as locals.
2668         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
2669             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
2670                 // Look for a field with the same name in the current self_type.
2671                 if let Some(resolution) = self.def_map.get(&node_id) {
2672                     match resolution.base_def {
2673                         Def::Struct(did) | Def::Union(did) if resolution.depth == 0 => {
2674                             if let Some(field_names) = self.field_names.get(&did) {
2675                                 if field_names.iter().any(|&field_name| name == field_name) {
2676                                     return Some(AssocSuggestion::Field);
2677                                 }
2678                             }
2679                         }
2680                         _ => {}
2681                     }
2682                 }
2683             }
2684         }
2685
2686         // Look for associated items in the current trait.
2687         if let Some((trait_did, _)) = self.current_trait_ref {
2688             if let Some(&(def, has_self)) = self.trait_item_map.get(&(trait_did, name, ns)) {
2689                 if filter_fn(def) {
2690                     return Some(if has_self {
2691                         AssocSuggestion::MethodWithSelf
2692                     } else {
2693                         AssocSuggestion::AssocItem
2694                     });
2695                 }
2696             }
2697         }
2698
2699         None
2700     }
2701
2702     fn lookup_typo_candidate<FilterFn>(&mut self,
2703                                        path: &[Ident],
2704                                        ns: Namespace,
2705                                        filter_fn: FilterFn)
2706                                        -> Option<String>
2707         where FilterFn: Fn(Def) -> bool
2708     {
2709         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
2710             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
2711                 if let Some(binding) = resolution.borrow().binding {
2712                     if filter_fn(binding.def()) {
2713                         names.push(ident.name);
2714                     }
2715                 }
2716             }
2717         };
2718
2719         let mut names = Vec::new();
2720         let prefix_str = if path.len() == 1 {
2721             // Search in lexical scope.
2722             // Walk backwards up the ribs in scope and collect candidates.
2723             for rib in self.ribs[ns].iter().rev() {
2724                 // Locals and type parameters
2725                 for (ident, def) in &rib.bindings {
2726                     if filter_fn(*def) {
2727                         names.push(ident.name);
2728                     }
2729                 }
2730                 // Items in scope
2731                 if let ModuleRibKind(module) = rib.kind {
2732                     // Items from this module
2733                     add_module_candidates(module, &mut names);
2734
2735                     if let ModuleKind::Block(..) = module.kind {
2736                         // We can see through blocks
2737                     } else {
2738                         // Items from the prelude
2739                         if let Some(prelude) = self.prelude {
2740                             if !module.no_implicit_prelude {
2741                                 add_module_candidates(prelude, &mut names);
2742                             }
2743                         }
2744                         break;
2745                     }
2746                 }
2747             }
2748             // Add primitive types to the mix
2749             if filter_fn(Def::PrimTy(TyBool)) {
2750                 for (name, _) in &self.primitive_type_table.primitive_types {
2751                     names.push(*name);
2752                 }
2753             }
2754             String::new()
2755         } else {
2756             // Search in module.
2757             let mod_path = &path[..path.len() - 1];
2758             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS), None) {
2759                 add_module_candidates(module, &mut names);
2760             }
2761             names_to_string(mod_path) + "::"
2762         };
2763
2764         let name = path[path.len() - 1].name;
2765         // Make sure error reporting is deterministic.
2766         names.sort_by_key(|name| name.as_str());
2767         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
2768             Some(found) if found != name => Some(format!("{}{}", prefix_str, found)),
2769             _ => None,
2770         }
2771     }
2772
2773     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
2774         if let Some(label) = label {
2775             let def = Def::Label(id);
2776             self.with_label_rib(|this| {
2777                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
2778                 this.visit_block(block);
2779             });
2780         } else {
2781             self.visit_block(block);
2782         }
2783     }
2784
2785     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&ExprKind>) {
2786         // First, record candidate traits for this expression if it could
2787         // result in the invocation of a method call.
2788
2789         self.record_candidate_traits_for_expr_if_necessary(expr);
2790
2791         // Next, resolve the node.
2792         match expr.node {
2793             ExprKind::Path(ref qself, ref path) => {
2794                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
2795                 visit::walk_expr(self, expr);
2796             }
2797
2798             ExprKind::Struct(ref path, ..) => {
2799                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
2800                 visit::walk_expr(self, expr);
2801             }
2802
2803             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
2804                 match self.search_label(label.node) {
2805                     None => {
2806                         self.record_def(expr.id, err_path_resolution());
2807                         resolve_error(self,
2808                                       label.span,
2809                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
2810                     }
2811                     Some(def @ Def::Label(_)) => {
2812                         // Since this def is a label, it is never read.
2813                         self.record_def(expr.id, PathResolution::new(def));
2814                     }
2815                     Some(_) => {
2816                         span_bug!(expr.span, "label wasn't mapped to a label def!");
2817                     }
2818                 }
2819
2820                 // visit `break` argument if any
2821                 visit::walk_expr(self, expr);
2822             }
2823
2824             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
2825                 self.visit_expr(subexpression);
2826
2827                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2828                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
2829                 self.visit_block(if_block);
2830                 self.ribs[ValueNS].pop();
2831
2832                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
2833             }
2834
2835             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
2836
2837             ExprKind::While(ref subexpression, ref block, label) => {
2838                 self.visit_expr(subexpression);
2839                 self.resolve_labeled_block(label, expr.id, &block);
2840             }
2841
2842             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
2843                 self.visit_expr(subexpression);
2844                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2845                 self.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
2846
2847                 self.resolve_labeled_block(label, expr.id, block);
2848
2849                 self.ribs[ValueNS].pop();
2850             }
2851
2852             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
2853                 self.visit_expr(subexpression);
2854                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2855                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
2856
2857                 self.resolve_labeled_block(label, expr.id, block);
2858
2859                 self.ribs[ValueNS].pop();
2860             }
2861
2862             // Equivalent to `visit::walk_expr` + passing some context to children.
2863             ExprKind::Field(ref subexpression, _) => {
2864                 self.resolve_expr(subexpression, Some(&expr.node));
2865             }
2866             ExprKind::MethodCall(_, ref types, ref arguments) => {
2867                 let mut arguments = arguments.iter();
2868                 self.resolve_expr(arguments.next().unwrap(), Some(&expr.node));
2869                 for argument in arguments {
2870                     self.resolve_expr(argument, None);
2871                 }
2872                 for ty in types.iter() {
2873                     self.visit_ty(ty);
2874                 }
2875             }
2876
2877             ExprKind::Repeat(ref element, ref count) => {
2878                 self.visit_expr(element);
2879                 self.with_constant_rib(|this| {
2880                     this.visit_expr(count);
2881                 });
2882             }
2883             ExprKind::Call(ref callee, ref arguments) => {
2884                 self.resolve_expr(callee, Some(&expr.node));
2885                 for argument in arguments {
2886                     self.resolve_expr(argument, None);
2887                 }
2888             }
2889
2890             _ => {
2891                 visit::walk_expr(self, expr);
2892             }
2893         }
2894     }
2895
2896     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
2897         match expr.node {
2898             ExprKind::Field(_, name) => {
2899                 // FIXME(#6890): Even though you can't treat a method like a
2900                 // field, we need to add any trait methods we find that match
2901                 // the field name so that we can do some nice error reporting
2902                 // later on in typeck.
2903                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
2904                 self.trait_map.insert(expr.id, traits);
2905             }
2906             ExprKind::MethodCall(name, ..) => {
2907                 debug!("(recording candidate traits for expr) recording traits for {}",
2908                        expr.id);
2909                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
2910                 self.trait_map.insert(expr.id, traits);
2911             }
2912             _ => {
2913                 // Nothing to do.
2914             }
2915         }
2916     }
2917
2918     fn get_traits_containing_item(&mut self, name: Name, ns: Namespace) -> Vec<TraitCandidate> {
2919         debug!("(getting traits containing item) looking for '{}'", name);
2920
2921         let mut found_traits = Vec::new();
2922         // Look for the current trait.
2923         if let Some((trait_def_id, _)) = self.current_trait_ref {
2924             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
2925                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: None });
2926             }
2927         }
2928
2929         let mut search_module = self.current_module;
2930         loop {
2931             self.get_traits_in_module_containing_item(name, ns, search_module, &mut found_traits);
2932             match search_module.kind {
2933                 ModuleKind::Block(..) => search_module = search_module.parent.unwrap(),
2934                 _ => break,
2935             }
2936         }
2937
2938         if let Some(prelude) = self.prelude {
2939             if !search_module.no_implicit_prelude {
2940                 self.get_traits_in_module_containing_item(name, ns, prelude, &mut found_traits);
2941             }
2942         }
2943
2944         found_traits
2945     }
2946
2947     fn get_traits_in_module_containing_item(&mut self,
2948                                             name: Name,
2949                                             ns: Namespace,
2950                                             module: Module,
2951                                             found_traits: &mut Vec<TraitCandidate>) {
2952         let mut traits = module.traits.borrow_mut();
2953         if traits.is_none() {
2954             let mut collected_traits = Vec::new();
2955             module.for_each_child(|name, ns, binding| {
2956                 if ns != TypeNS { return }
2957                 if let Def::Trait(_) = binding.def() {
2958                     collected_traits.push((name, binding));
2959                 }
2960             });
2961             *traits = Some(collected_traits.into_boxed_slice());
2962         }
2963
2964         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
2965             let trait_def_id = binding.def().def_id();
2966             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
2967                 let import_id = match binding.kind {
2968                     NameBindingKind::Import { directive, .. } => {
2969                         self.maybe_unused_trait_imports.insert(directive.id);
2970                         self.add_to_glob_map(directive.id, trait_name);
2971                         Some(directive.id)
2972                     }
2973                     _ => None,
2974                 };
2975                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
2976             }
2977         }
2978     }
2979
2980     /// When name resolution fails, this method can be used to look up candidate
2981     /// entities with the expected name. It allows filtering them using the
2982     /// supplied predicate (which should be used to only accept the types of
2983     /// definitions expected e.g. traits). The lookup spans across all crates.
2984     ///
2985     /// NOTE: The method does not look into imports, but this is not a problem,
2986     /// since we report the definitions (thus, the de-aliased imports).
2987     fn lookup_import_candidates<FilterFn>(&mut self,
2988                                           lookup_name: Name,
2989                                           namespace: Namespace,
2990                                           filter_fn: FilterFn)
2991                                           -> Vec<ImportSuggestion>
2992         where FilterFn: Fn(Def) -> bool
2993     {
2994         let mut candidates = Vec::new();
2995         let mut worklist = Vec::new();
2996         let mut seen_modules = FxHashSet();
2997         worklist.push((self.graph_root, Vec::new(), false));
2998
2999         while let Some((in_module,
3000                         path_segments,
3001                         in_module_is_extern)) = worklist.pop() {
3002             self.populate_module_if_necessary(in_module);
3003
3004             in_module.for_each_child(|ident, ns, name_binding| {
3005
3006                 // avoid imports entirely
3007                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3008                 // avoid non-importable candidates as well
3009                 if !name_binding.is_importable() { return; }
3010
3011                 // collect results based on the filter function
3012                 if ident.name == lookup_name && ns == namespace {
3013                     if filter_fn(name_binding.def()) {
3014                         // create the path
3015                         let span = name_binding.span;
3016                         let mut segms = path_segments.clone();
3017                         segms.push(ident.into());
3018                         let path = Path {
3019                             span: span,
3020                             segments: segms,
3021                         };
3022                         // the entity is accessible in the following cases:
3023                         // 1. if it's defined in the same crate, it's always
3024                         // accessible (since private entities can be made public)
3025                         // 2. if it's defined in another crate, it's accessible
3026                         // only if both the module is public and the entity is
3027                         // declared as public (due to pruning, we don't explore
3028                         // outside crate private modules => no need to check this)
3029                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3030                             candidates.push(ImportSuggestion { path: path });
3031                         }
3032                     }
3033                 }
3034
3035                 // collect submodules to explore
3036                 if let Some(module) = name_binding.module() {
3037                     // form the path
3038                     let mut path_segments = path_segments.clone();
3039                     path_segments.push(ident.into());
3040
3041                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3042                         // add the module to the lookup
3043                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3044                         if seen_modules.insert(module.def_id().unwrap()) {
3045                             worklist.push((module, path_segments, is_extern));
3046                         }
3047                     }
3048                 }
3049             })
3050         }
3051
3052         candidates
3053     }
3054
3055     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3056         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3057         assert!(resolution.depth == 0 || resolution.base_def != Def::Err);
3058         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3059             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3060         }
3061     }
3062
3063     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3064         match *vis {
3065             ast::Visibility::Public => ty::Visibility::Public,
3066             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3067             ast::Visibility::Inherited => {
3068                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3069             }
3070             ast::Visibility::Restricted { ref path, id } => {
3071                 let def = self.smart_resolve_path(id, None, path, PathSource::Visibility).base_def;
3072                 if def == Def::Err {
3073                     ty::Visibility::Public
3074                 } else {
3075                     let vis = ty::Visibility::Restricted(def.def_id());
3076                     if self.is_accessible(vis) {
3077                         vis
3078                     } else {
3079                         self.session.span_err(path.span, "visibilities can only be restricted \
3080                                                           to ancestor modules");
3081                         ty::Visibility::Public
3082                     }
3083                 }
3084             }
3085         }
3086     }
3087
3088     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3089         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3090     }
3091
3092     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3093         vis.is_accessible_from(module.normal_ancestor_id, self)
3094     }
3095
3096     fn report_errors(&mut self) {
3097         self.report_shadowing_errors();
3098         let mut reported_spans = FxHashSet();
3099
3100         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3101             if !reported_spans.insert(span) { continue }
3102             let participle = |binding: &NameBinding| {
3103                 if binding.is_import() { "imported" } else { "defined" }
3104             };
3105             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3106             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3107             let note = if !lexical && b1.is_glob_import() {
3108                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3109             } else if let Def::Macro(..) = b1.def() {
3110                 format!("macro-expanded {} do not shadow",
3111                         if b1.is_import() { "macro imports" } else { "macros" })
3112             } else {
3113                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3114                         if b1.is_import() { "imports" } else { "items" })
3115             };
3116             if legacy {
3117                 let id = match b2.kind {
3118                     NameBindingKind::Import { directive, .. } => directive.id,
3119                     _ => unreachable!(),
3120                 };
3121                 let mut span = MultiSpan::from_span(span);
3122                 span.push_span_label(b1.span, msg1);
3123                 span.push_span_label(b2.span, msg2);
3124                 let msg = format!("`{}` is ambiguous", name);
3125                 self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3126             } else {
3127                 self.session.struct_span_err(span, &format!("`{}` is ambiguous", name))
3128                     .span_note(b1.span, &msg1)
3129                     .span_note(b2.span, &msg2)
3130                     .note(&note)
3131                     .emit();
3132             }
3133         }
3134
3135         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3136             if !reported_spans.insert(span) { continue }
3137             if binding.is_extern_crate() {
3138                 // Warn when using an inaccessible extern crate.
3139                 let node_id = match binding.kind {
3140                     NameBindingKind::Import { directive, .. } => directive.id,
3141                     _ => unreachable!(),
3142                 };
3143                 let msg = format!("extern crate `{}` is private", name);
3144                 self.session.add_lint(lint::builtin::INACCESSIBLE_EXTERN_CRATE, node_id, span, msg);
3145             } else {
3146                 let def = binding.def();
3147                 self.session.span_err(span, &format!("{} `{}` is private", def.kind_name(), name));
3148             }
3149         }
3150     }
3151
3152     fn report_shadowing_errors(&mut self) {
3153         for (name, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3154             self.resolve_legacy_scope(scope, name, true);
3155         }
3156
3157         let mut reported_errors = FxHashSet();
3158         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3159             if self.resolve_legacy_scope(&binding.parent, binding.name, false).is_some() &&
3160                reported_errors.insert((binding.name, binding.span)) {
3161                 let msg = format!("`{}` is already in scope", binding.name);
3162                 self.session.struct_span_err(binding.span, &msg)
3163                     .note("macro-expanded `macro_rules!`s may not shadow \
3164                            existing macros (see RFC 1560)")
3165                     .emit();
3166             }
3167         }
3168     }
3169
3170     fn report_conflict(&mut self,
3171                        parent: Module,
3172                        ident: Ident,
3173                        ns: Namespace,
3174                        binding: &NameBinding,
3175                        old_binding: &NameBinding) {
3176         // Error on the second of two conflicting names
3177         if old_binding.span.lo > binding.span.lo {
3178             return self.report_conflict(parent, ident, ns, old_binding, binding);
3179         }
3180
3181         let container = match parent.kind {
3182             ModuleKind::Def(Def::Mod(_), _) => "module",
3183             ModuleKind::Def(Def::Trait(_), _) => "trait",
3184             ModuleKind::Block(..) => "block",
3185             _ => "enum",
3186         };
3187
3188         let (participle, noun) = match old_binding.is_import() {
3189             true => ("imported", "import"),
3190             false => ("defined", "definition"),
3191         };
3192
3193         let (name, span) = (ident.name, binding.span);
3194
3195         if let Some(s) = self.name_already_seen.get(&name) {
3196             if s == &span {
3197                 return;
3198             }
3199         }
3200
3201         let msg = {
3202             let kind = match (ns, old_binding.module()) {
3203                 (ValueNS, _) => "a value",
3204                 (MacroNS, _) => "a macro",
3205                 (TypeNS, _) if old_binding.is_extern_crate() => "an extern crate",
3206                 (TypeNS, Some(module)) if module.is_normal() => "a module",
3207                 (TypeNS, Some(module)) if module.is_trait() => "a trait",
3208                 (TypeNS, _) => "a type",
3209             };
3210             format!("{} named `{}` has already been {} in this {}",
3211                     kind, name, participle, container)
3212         };
3213
3214         let mut err = match (old_binding.is_extern_crate(), binding.is_extern_crate()) {
3215             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3216             (true, _) | (_, true) => match binding.is_import() && old_binding.is_import() {
3217                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3218                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3219             },
3220             _ => match (old_binding.is_import(), binding.is_import()) {
3221                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3222                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3223                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3224             },
3225         };
3226
3227         err.span_label(span, &format!("`{}` already {}", name, participle));
3228         if old_binding.span != syntax_pos::DUMMY_SP {
3229             err.span_label(old_binding.span, &format!("previous {} of `{}` here", noun, name));
3230         }
3231         err.emit();
3232         self.name_already_seen.insert(name, span);
3233     }
3234
3235     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3236         let (id, span) = (directive.id, directive.span);
3237         let msg = "`self` no longer imports values".to_string();
3238         self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3239     }
3240
3241     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3242         if self.proc_macro_enabled { return; }
3243
3244         for attr in attrs {
3245             let maybe_binding = self.builtin_macros.get(&attr.name()).cloned().or_else(|| {
3246                 let ident = Ident::with_empty_ctxt(attr.name());
3247                 self.resolve_lexical_macro_path_segment(ident, MacroNS, None).ok()
3248             });
3249
3250             if let Some(binding) = maybe_binding {
3251                 if let SyntaxExtension::AttrProcMacro(..) = *binding.get_macro(self) {
3252                     attr::mark_known(attr);
3253
3254                     let msg = "attribute procedural macros are experimental";
3255                     let feature = "proc_macro";
3256
3257                     feature_err(&self.session.parse_sess, feature,
3258                                 attr.span, GateIssue::Language, msg)
3259                         .span_note(binding.span, "procedural macro imported here")
3260                         .emit();
3261                 }
3262             }
3263         }
3264     }
3265 }
3266
3267 fn is_struct_like(def: Def) -> bool {
3268     match def {
3269         Def::VariantCtor(_, CtorKind::Fictive) => true,
3270         _ => PathSource::Struct.is_expected(def),
3271     }
3272 }
3273
3274 fn is_self_type(path: &[Ident], namespace: Namespace) -> bool {
3275     namespace == TypeNS && path.len() == 1 && path[0].name == keywords::SelfType.name()
3276 }
3277
3278 fn is_self_value(path: &[Ident], namespace: Namespace) -> bool {
3279     namespace == ValueNS && path.len() == 1 && path[0].name == keywords::SelfValue.name()
3280 }
3281
3282 fn names_to_string(idents: &[Ident]) -> String {
3283     let mut result = String::new();
3284     for (i, ident) in idents.iter().filter(|i| i.name != keywords::CrateRoot.name()).enumerate() {
3285         if i > 0 {
3286             result.push_str("::");
3287         }
3288         result.push_str(&ident.name.as_str());
3289     }
3290     result
3291 }
3292
3293 fn path_names_to_string(path: &Path) -> String {
3294     names_to_string(&path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>())
3295 }
3296
3297 /// When an entity with a given name is not available in scope, we search for
3298 /// entities with that name in all crates. This method allows outputting the
3299 /// results of this search in a programmer-friendly way
3300 fn show_candidates(session: &mut DiagnosticBuilder,
3301                    candidates: &[ImportSuggestion],
3302                    better: bool) {
3303     // don't show more than MAX_CANDIDATES results, so
3304     // we're consistent with the trait suggestions
3305     const MAX_CANDIDATES: usize = 4;
3306
3307     // we want consistent results across executions, but candidates are produced
3308     // by iterating through a hash map, so make sure they are ordered:
3309     let mut path_strings: Vec<_> =
3310         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3311     path_strings.sort();
3312
3313     let better = if better { "better " } else { "" };
3314     let msg_diff = match path_strings.len() {
3315         1 => " is found in another module, you can import it",
3316         _ => "s are found in other modules, you can import them",
3317     };
3318
3319     let end = cmp::min(MAX_CANDIDATES, path_strings.len());
3320     session.help(&format!("possible {}candidate{} into scope:{}{}",
3321                           better,
3322                           msg_diff,
3323                           &path_strings[0..end].iter().map(|candidate| {
3324                               format!("\n  `use {};`", candidate)
3325                           }).collect::<String>(),
3326                           if path_strings.len() > MAX_CANDIDATES {
3327                               format!("\nand {} other candidates",
3328                                       path_strings.len() - MAX_CANDIDATES)
3329                           } else {
3330                               "".to_owned()
3331                           }
3332                           ));
3333 }
3334
3335 /// A somewhat inefficient routine to obtain the name of a module.
3336 fn module_to_string(module: Module) -> String {
3337     let mut names = Vec::new();
3338
3339     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3340         if let ModuleKind::Def(_, name) = module.kind {
3341             if let Some(parent) = module.parent {
3342                 names.push(Ident::with_empty_ctxt(name));
3343                 collect_mod(names, parent);
3344             }
3345         } else {
3346             // danger, shouldn't be ident?
3347             names.push(Ident::from_str("<opaque>"));
3348             collect_mod(names, module.parent.unwrap());
3349         }
3350     }
3351     collect_mod(&mut names, module);
3352
3353     if names.is_empty() {
3354         return "???".to_string();
3355     }
3356     names_to_string(&names.into_iter().rev().collect::<Vec<_>>())
3357 }
3358
3359 fn err_path_resolution() -> PathResolution {
3360     PathResolution::new(Def::Err)
3361 }
3362
3363 #[derive(PartialEq,Copy, Clone)]
3364 pub enum MakeGlobMap {
3365     Yes,
3366     No,
3367 }
3368
3369 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }