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 // Do not remove on snapshot creation. Needed for bootstrap. (Issue #22364)
  12 #![cfg_attr(stage0, feature(custom_attribute))]
  13 #![crate_name = "rustc_resolve"]
  14 #![unstable(feature = "rustc_private", issue = "27812")]
  15 #![cfg_attr(stage0, staged_api)]
  16 #![crate_type = "dylib"]
  17 #![crate_type = "rlib"]
  18 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  19       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  20       html_root_url = "https://doc.rust-lang.org/nightly/")]
  21
  22 #![feature(associated_consts)]
  23 #![feature(borrow_state)]
  24 #![feature(rustc_diagnostic_macros)]
  25 #![feature(rustc_private)]
  26 #![feature(staged_api)]
  27
  28 #[macro_use]
  29 extern crate log;
  30 #[macro_use]
  31 extern crate syntax;
  32 #[macro_use]
  33 #[no_link]
  34 extern crate rustc_bitflags;
  35 extern crate rustc_front;
  36
  37 extern crate rustc;
  38
  39 use self::PatternBindingMode::*;
  40 use self::Namespace::*;
  41 use self::NamespaceResult::*;
  42 use self::ResolveResult::*;
  43 use self::FallbackSuggestion::*;
  44 use self::TypeParameters::*;
  45 use self::RibKind::*;
  46 use self::UseLexicalScopeFlag::*;
  47 use self::ModulePrefixResult::*;
  48 use self::AssocItemResolveResult::*;
  49 use self::NameSearchType::*;
  50 use self::BareIdentifierPatternResolution::*;
  51 use self::ParentLink::*;
  52 use self::FallbackChecks::*;
  53
  54 use rustc::front::map as hir_map;
  55 use rustc::session::Session;
  56 use rustc::lint;
  57 use rustc::middle::cstore::{CrateStore, DefLike, DlDef};
  58 use rustc::middle::def::*;
  59 use rustc::middle::def_id::DefId;
  60 use rustc::middle::pat_util::pat_bindings;
  61 use rustc::middle::privacy::*;
  62 use rustc::middle::subst::{ParamSpace, FnSpace, TypeSpace};
  63 use rustc::middle::ty::{Freevar, FreevarMap, TraitMap, GlobMap};
  64 use rustc::util::nodemap::{NodeMap, DefIdSet, FnvHashMap};
  65
  66 use syntax::ast;
  67 use syntax::ast::{CRATE_NODE_ID, Ident, Name, NodeId, CrateNum, TyIs, TyI8, TyI16, TyI32, TyI64};
  68 use syntax::ast::{TyUs, TyU8, TyU16, TyU32, TyU64, TyF64, TyF32};
  69 use syntax::attr::AttrMetaMethods;
  70 use syntax::parse::token::{self, special_names, special_idents};
  71 use syntax::codemap::{self, Span, Pos};
  72 use syntax::util::lev_distance::{lev_distance, max_suggestion_distance};
  73
  74 use rustc_front::intravisit::{self, FnKind, Visitor};
  75 use rustc_front::hir;
  76 use rustc_front::hir::{Arm, BindByRef, BindByValue, BindingMode, Block};
  77 use rustc_front::hir::Crate;
  78 use rustc_front::hir::{Expr, ExprAgain, ExprBreak, ExprField};
  79 use rustc_front::hir::{ExprLoop, ExprWhile, ExprMethodCall};
  80 use rustc_front::hir::{ExprPath, ExprStruct, FnDecl};
  81 use rustc_front::hir::{ForeignItemFn, ForeignItemStatic, Generics};
  82 use rustc_front::hir::{ImplItem, Item, ItemConst, ItemEnum, ItemExternCrate};
  83 use rustc_front::hir::{ItemFn, ItemForeignMod, ItemImpl, ItemMod, ItemStatic, ItemDefaultImpl};
  84 use rustc_front::hir::{ItemStruct, ItemTrait, ItemTy, ItemUse};
  85 use rustc_front::hir::Local;
  86 use rustc_front::hir::{Pat, PatEnum, PatIdent, PatLit, PatQPath};
  87 use rustc_front::hir::{PatRange, PatStruct, Path, PrimTy};
  88 use rustc_front::hir::{TraitRef, Ty, TyBool, TyChar, TyFloat, TyInt};
  89 use rustc_front::hir::{TyRptr, TyStr, TyUint, TyPath, TyPtr};
  90 use rustc_front::util::walk_pat;
  91
  92 use std::collections::{HashMap, HashSet};
  93 use std::cell::{Cell, RefCell};
  94 use std::fmt;
  95 use std::mem::replace;
  96 use std::rc::{Rc, Weak};
  97 use std::usize;
  98
  99 use resolve_imports::{Target, ImportDirective, ImportResolution};
 100 use resolve_imports::Shadowable;
 101
 102 // NB: This module needs to be declared first so diagnostics are
 103 // registered before they are used.
 104 pub mod diagnostics;
 105
 106 mod check_unused;
 107 mod record_exports;
 108 mod build_reduced_graph;
 109 mod resolve_imports;
 110
 111 // Perform the callback, not walking deeper if the return is true
 112 macro_rules! execute_callback {
 113     ($node: expr, $walker: expr) => (
 114         if let Some(ref callback) = $walker.callback {
 115             if callback($node, &mut $walker.resolved) {
 116                 return;
 117             }
 118         }
 119     )
 120 }
 121
 122 enum SuggestionType {
 123     Macro(String),
 124     Function(String),
 125     NotFound,
 126 }
 127
 128 pub enum ResolutionError<'a> {
 129     /// error E0401: can't use type parameters from outer function
 130     TypeParametersFromOuterFunction,
 131     /// error E0402: cannot use an outer type parameter in this context
 132     OuterTypeParameterContext,
 133     /// error E0403: the name is already used for a type parameter in this type parameter list
 134     NameAlreadyUsedInTypeParameterList(Name),
 135     /// error E0404: is not a trait
 136     IsNotATrait(&'a str),
 137     /// error E0405: use of undeclared trait name
 138     UndeclaredTraitName(&'a str),
 139     /// error E0406: undeclared associated type
 140     UndeclaredAssociatedType,
 141     /// error E0407: method is not a member of trait
 142     MethodNotMemberOfTrait(Name, &'a str),
 143     /// error E0437: type is not a member of trait
 144     TypeNotMemberOfTrait(Name, &'a str),
 145     /// error E0438: const is not a member of trait
 146     ConstNotMemberOfTrait(Name, &'a str),
 147     /// error E0408: variable `{}` from pattern #1 is not bound in pattern
 148     VariableNotBoundInPattern(Name, usize),
 149     /// error E0409: variable is bound with different mode in pattern #{} than in pattern #1
 150     VariableBoundWithDifferentMode(Name, usize),
 151     /// error E0410: variable from pattern is not bound in pattern #1
 152     VariableNotBoundInParentPattern(Name, usize),
 153     /// error E0411: use of `Self` outside of an impl or trait
 154     SelfUsedOutsideImplOrTrait,
 155     /// error E0412: use of undeclared
 156     UseOfUndeclared(&'a str, &'a str),
 157     /// error E0413: declaration shadows an enum variant or unit-like struct in scope
 158     DeclarationShadowsEnumVariantOrUnitLikeStruct(Name),
 159     /// error E0414: only irrefutable patterns allowed here
 160     OnlyIrrefutablePatternsAllowedHere(DefId, Name),
 161     /// error E0415: identifier is bound more than once in this parameter list
 162     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 163     /// error E0416: identifier is bound more than once in the same pattern
 164     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 165     /// error E0417: static variables cannot be referenced in a pattern
 166     StaticVariableReference,
 167     /// error E0418: is not an enum variant, struct or const
 168     NotAnEnumVariantStructOrConst(&'a str),
 169     /// error E0419: unresolved enum variant, struct or const
 170     UnresolvedEnumVariantStructOrConst(&'a str),
 171     /// error E0420: is not an associated const
 172     NotAnAssociatedConst(&'a str),
 173     /// error E0421: unresolved associated const
 174     UnresolvedAssociatedConst(&'a str),
 175     /// error E0422: does not name a struct
 176     DoesNotNameAStruct(&'a str),
 177     /// error E0423: is a struct variant name, but this expression uses it like a function name
 178     StructVariantUsedAsFunction(&'a str),
 179     /// error E0424: `self` is not available in a static method
 180     SelfNotAvailableInStaticMethod,
 181     /// error E0425: unresolved name
 182     UnresolvedName(&'a str, &'a str),
 183     /// error E0426: use of undeclared label
 184     UndeclaredLabel(&'a str),
 185     /// error E0427: cannot use `ref` binding mode with ...
 186     CannotUseRefBindingModeWith(&'a str),
 187     /// error E0428: duplicate definition
 188     DuplicateDefinition(&'a str, Name),
 189     /// error E0429: `self` imports are only allowed within a { } list
 190     SelfImportsOnlyAllowedWithin,
 191     /// error E0430: `self` import can only appear once in the list
 192     SelfImportCanOnlyAppearOnceInTheList,
 193     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 194     SelfImportOnlyInImportListWithNonEmptyPrefix,
 195     /// error E0432: unresolved import
 196     UnresolvedImport(Option<(&'a str, &'a str)>),
 197     /// error E0433: failed to resolve
 198     FailedToResolve(&'a str),
 199     /// error E0434: can't capture dynamic environment in a fn item
 200     CannotCaptureDynamicEnvironmentInFnItem,
 201     /// error E0435: attempt to use a non-constant value in a constant
 202     AttemptToUseNonConstantValueInConstant,
 203 }
 204
 205 fn resolve_error<'b, 'a: 'b, 'tcx: 'a>(resolver: &'b Resolver<'a, 'tcx>,
 206                                        span: syntax::codemap::Span,
 207                                        resolution_error: ResolutionError<'b>) {
 208     if !resolver.emit_errors {
 209         return;
 210     }
 211     match resolution_error {
 212         ResolutionError::TypeParametersFromOuterFunction => {
 213             span_err!(resolver.session,
 214                       span,
 215                       E0401,
 216                       "can't use type parameters from outer function; try using a local type \
 217                        parameter instead");
 218         }
 219         ResolutionError::OuterTypeParameterContext => {
 220             span_err!(resolver.session,
 221                       span,
 222                       E0402,
 223                       "cannot use an outer type parameter in this context");
 224         }
 225         ResolutionError::NameAlreadyUsedInTypeParameterList(name) => {
 226             span_err!(resolver.session,
 227                       span,
 228                       E0403,
 229                       "the name `{}` is already used for a type parameter in this type parameter \
 230                        list",
 231                       name);
 232         }
 233         ResolutionError::IsNotATrait(name) => {
 234             span_err!(resolver.session, span, E0404, "`{}` is not a trait", name);
 235         }
 236         ResolutionError::UndeclaredTraitName(name) => {
 237             span_err!(resolver.session,
 238                       span,
 239                       E0405,
 240                       "use of undeclared trait name `{}`",
 241                       name);
 242         }
 243         ResolutionError::UndeclaredAssociatedType => {
 244             span_err!(resolver.session, span, E0406, "undeclared associated type");
 245         }
 246         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 247             span_err!(resolver.session,
 248                       span,
 249                       E0407,
 250                       "method `{}` is not a member of trait `{}`",
 251                       method,
 252                       trait_);
 253         }
 254         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 255             span_err!(resolver.session,
 256                       span,
 257                       E0437,
 258                       "type `{}` is not a member of trait `{}`",
 259                       type_,
 260                       trait_);
 261         }
 262         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 263             span_err!(resolver.session,
 264                       span,
 265                       E0438,
 266                       "const `{}` is not a member of trait `{}`",
 267                       const_,
 268                       trait_);
 269         }
 270         ResolutionError::VariableNotBoundInPattern(variable_name, pattern_number) => {
 271             span_err!(resolver.session,
 272                       span,
 273                       E0408,
 274                       "variable `{}` from pattern #1 is not bound in pattern #{}",
 275                       variable_name,
 276                       pattern_number);
 277         }
 278         ResolutionError::VariableBoundWithDifferentMode(variable_name, pattern_number) => {
 279             span_err!(resolver.session,
 280                       span,
 281                       E0409,
 282                       "variable `{}` is bound with different mode in pattern #{} than in pattern \
 283                        #1",
 284                       variable_name,
 285                       pattern_number);
 286         }
 287         ResolutionError::VariableNotBoundInParentPattern(variable_name, pattern_number) => {
 288             span_err!(resolver.session,
 289                       span,
 290                       E0410,
 291                       "variable `{}` from pattern #{} is not bound in pattern #1",
 292                       variable_name,
 293                       pattern_number);
 294         }
 295         ResolutionError::SelfUsedOutsideImplOrTrait => {
 296             span_err!(resolver.session,
 297                       span,
 298                       E0411,
 299                       "use of `Self` outside of an impl or trait");
 300         }
 301         ResolutionError::UseOfUndeclared(kind, name) => {
 302             span_err!(resolver.session,
 303                       span,
 304                       E0412,
 305                       "use of undeclared {} `{}`",
 306                       kind,
 307                       name);
 308         }
 309         ResolutionError::DeclarationShadowsEnumVariantOrUnitLikeStruct(name) => {
 310             span_err!(resolver.session,
 311                       span,
 312                       E0413,
 313                       "declaration of `{}` shadows an enum variant or unit-like struct in scope",
 314                       name);
 315         }
 316         ResolutionError::OnlyIrrefutablePatternsAllowedHere(did, name) => {
 317             span_err!(resolver.session,
 318                       span,
 319                       E0414,
 320                       "only irrefutable patterns allowed here");
 321             resolver.session.span_note(span,
 322                                        "there already is a constant in scope sharing the same \
 323                                         name as this pattern");
 324             if let Some(sp) = resolver.ast_map.span_if_local(did) {
 325                 resolver.session.span_note(sp, "constant defined here");
 326             }
 327             if let Some(directive) = resolver.current_module
 328                                              .import_resolutions
 329                                              .borrow()
 330                                              .get(&name) {
 331                 let item = resolver.ast_map.expect_item(directive.value_id);
 332                 resolver.session.span_note(item.span, "constant imported here");
 333             }
 334         }
 335         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 336             span_err!(resolver.session,
 337                       span,
 338                       E0415,
 339                       "identifier `{}` is bound more than once in this parameter list",
 340                       identifier);
 341         }
 342         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 343             span_err!(resolver.session,
 344                       span,
 345                       E0416,
 346                       "identifier `{}` is bound more than once in the same pattern",
 347                       identifier);
 348         }
 349         ResolutionError::StaticVariableReference => {
 350             span_err!(resolver.session,
 351                       span,
 352                       E0417,
 353                       "static variables cannot be referenced in a pattern, use a `const` instead");
 354         }
 355         ResolutionError::NotAnEnumVariantStructOrConst(name) => {
 356             span_err!(resolver.session,
 357                       span,
 358                       E0418,
 359                       "`{}` is not an enum variant, struct or const",
 360                       name);
 361         }
 362         ResolutionError::UnresolvedEnumVariantStructOrConst(name) => {
 363             span_err!(resolver.session,
 364                       span,
 365                       E0419,
 366                       "unresolved enum variant, struct or const `{}`",
 367                       name);
 368         }
 369         ResolutionError::NotAnAssociatedConst(name) => {
 370             span_err!(resolver.session,
 371                       span,
 372                       E0420,
 373                       "`{}` is not an associated const",
 374                       name);
 375         }
 376         ResolutionError::UnresolvedAssociatedConst(name) => {
 377             span_err!(resolver.session,
 378                       span,
 379                       E0421,
 380                       "unresolved associated const `{}`",
 381                       name);
 382         }
 383         ResolutionError::DoesNotNameAStruct(name) => {
 384             span_err!(resolver.session,
 385                       span,
 386                       E0422,
 387                       "`{}` does not name a structure",
 388                       name);
 389         }
 390         ResolutionError::StructVariantUsedAsFunction(path_name) => {
 391             span_err!(resolver.session,
 392                       span,
 393                       E0423,
 394                       "`{}` is the name of a struct or struct variant, but this expression uses \
 395                        it like a function name",
 396                       path_name);
 397         }
 398         ResolutionError::SelfNotAvailableInStaticMethod => {
 399             span_err!(resolver.session,
 400                       span,
 401                       E0424,
 402                       "`self` is not available in a static method. Maybe a `self` argument is \
 403                        missing?");
 404         }
 405         ResolutionError::UnresolvedName(path, name) => {
 406             span_err!(resolver.session,
 407                       span,
 408                       E0425,
 409                       "unresolved name `{}`{}",
 410                       path,
 411                       name);
 412         }
 413         ResolutionError::UndeclaredLabel(name) => {
 414             span_err!(resolver.session,
 415                       span,
 416                       E0426,
 417                       "use of undeclared label `{}`",
 418                       name);
 419         }
 420         ResolutionError::CannotUseRefBindingModeWith(descr) => {
 421             span_err!(resolver.session,
 422                       span,
 423                       E0427,
 424                       "cannot use `ref` binding mode with {}",
 425                       descr);
 426         }
 427         ResolutionError::DuplicateDefinition(namespace, name) => {
 428             span_err!(resolver.session,
 429                       span,
 430                       E0428,
 431                       "duplicate definition of {} `{}`",
 432                       namespace,
 433                       name);
 434         }
 435         ResolutionError::SelfImportsOnlyAllowedWithin => {
 436             span_err!(resolver.session,
 437                       span,
 438                       E0429,
 439                       "{}",
 440                       "`self` imports are only allowed within a { } list");
 441         }
 442         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 443             span_err!(resolver.session,
 444                       span,
 445                       E0430,
 446                       "`self` import can only appear once in the list");
 447         }
 448         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 449             span_err!(resolver.session,
 450                       span,
 451                       E0431,
 452                       "`self` import can only appear in an import list with a non-empty prefix");
 453         }
 454         ResolutionError::UnresolvedImport(name) => {
 455             let msg = match name {
 456                 Some((n, p)) => format!("unresolved import `{}`{}", n, p),
 457                 None => "unresolved import".to_owned(),
 458             };
 459             span_err!(resolver.session, span, E0432, "{}", msg);
 460         }
 461         ResolutionError::FailedToResolve(msg) => {
 462             span_err!(resolver.session, span, E0433, "failed to resolve. {}", msg);
 463         }
 464         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 465             span_err!(resolver.session,
 466                       span,
 467                       E0434,
 468                       "{}",
 469                       "can't capture dynamic environment in a fn item; use the || { ... } \
 470                        closure form instead");
 471         }
 472         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 473             span_err!(resolver.session,
 474                       span,
 475                       E0435,
 476                       "attempt to use a non-constant value in a constant");
 477         }
 478     }
 479 }
 480
 481 #[derive(Copy, Clone)]
 482 struct BindingInfo {
 483     span: Span,
 484     binding_mode: BindingMode,
 485 }
 486
 487 // Map from the name in a pattern to its binding mode.
 488 type BindingMap = HashMap<Name, BindingInfo>;
 489
 490 #[derive(Copy, Clone, PartialEq)]
 491 enum PatternBindingMode {
 492     RefutableMode,
 493     LocalIrrefutableMode,
 494     ArgumentIrrefutableMode,
 495 }
 496
 497 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 498 pub enum Namespace {
 499     TypeNS,
 500     ValueNS,
 501 }
 502
 503 /// A NamespaceResult represents the result of resolving an import in
 504 /// a particular namespace. The result is either definitely-resolved,
 505 /// definitely- unresolved, or unknown.
 506 #[derive(Clone)]
 507 enum NamespaceResult {
 508     /// Means that resolve hasn't gathered enough information yet to determine
 509     /// whether the name is bound in this namespace. (That is, it hasn't
 510     /// resolved all `use` directives yet.)
 511     UnknownResult,
 512     /// Means that resolve has determined that the name is definitely
 513     /// not bound in the namespace.
 514     UnboundResult,
 515     /// Means that resolve has determined that the name is bound in the Module
 516     /// argument, and specified by the NameBinding argument.
 517     BoundResult(Rc<Module>, NameBinding),
 518 }
 519
 520 impl NamespaceResult {
 521     fn is_unknown(&self) -> bool {
 522         match *self {
 523             UnknownResult => true,
 524             _ => false,
 525         }
 526     }
 527     fn is_unbound(&self) -> bool {
 528         match *self {
 529             UnboundResult => true,
 530             _ => false,
 531         }
 532     }
 533 }
 534
 535 impl<'a, 'v, 'tcx> Visitor<'v> for Resolver<'a, 'tcx> {
 536     fn visit_nested_item(&mut self, item: hir::ItemId) {
 537         self.visit_item(self.ast_map.expect_item(item.id))
 538     }
 539     fn visit_item(&mut self, item: &Item) {
 540         execute_callback!(hir_map::Node::NodeItem(item), self);
 541         self.resolve_item(item);
 542     }
 543     fn visit_arm(&mut self, arm: &Arm) {
 544         self.resolve_arm(arm);
 545     }
 546     fn visit_block(&mut self, block: &Block) {
 547         execute_callback!(hir_map::Node::NodeBlock(block), self);
 548         self.resolve_block(block);
 549     }
 550     fn visit_expr(&mut self, expr: &Expr) {
 551         execute_callback!(hir_map::Node::NodeExpr(expr), self);
 552         self.resolve_expr(expr);
 553     }
 554     fn visit_local(&mut self, local: &Local) {
 555         execute_callback!(hir_map::Node::NodeLocal(&*local.pat), self);
 556         self.resolve_local(local);
 557     }
 558     fn visit_ty(&mut self, ty: &Ty) {
 559         self.resolve_type(ty);
 560     }
 561     fn visit_generics(&mut self, generics: &Generics) {
 562         self.resolve_generics(generics);
 563     }
 564     fn visit_poly_trait_ref(&mut self, tref: &hir::PolyTraitRef, m: &hir::TraitBoundModifier) {
 565         match self.resolve_trait_reference(tref.trait_ref.ref_id, &tref.trait_ref.path, 0) {
 566             Ok(def) => self.record_def(tref.trait_ref.ref_id, def),
 567             Err(_) => {
 568                 // error already reported
 569             }
 570         }
 571         intravisit::walk_poly_trait_ref(self, tref, m);
 572     }
 573     fn visit_variant(&mut self,
 574                      variant: &hir::Variant,
 575                      generics: &Generics,
 576                      item_id: ast::NodeId) {
 577         execute_callback!(hir_map::Node::NodeVariant(variant), self);
 578         if let Some(ref dis_expr) = variant.node.disr_expr {
 579             // resolve the discriminator expr as a constant
 580             self.with_constant_rib(|this| {
 581                 this.visit_expr(dis_expr);
 582             });
 583         }
 584
 585         // `intravisit::walk_variant` without the discriminant expression.
 586         self.visit_variant_data(&variant.node.data,
 587                                 variant.node.name,
 588                                 generics,
 589                                 item_id,
 590                                 variant.span);
 591     }
 592     fn visit_foreign_item(&mut self, foreign_item: &hir::ForeignItem) {
 593         execute_callback!(hir_map::Node::NodeForeignItem(foreign_item), self);
 594         let type_parameters = match foreign_item.node {
 595             ForeignItemFn(_, ref generics) => {
 596                 HasTypeParameters(generics, FnSpace, ItemRibKind)
 597             }
 598             ForeignItemStatic(..) => NoTypeParameters,
 599         };
 600         self.with_type_parameter_rib(type_parameters, |this| {
 601             intravisit::walk_foreign_item(this, foreign_item);
 602         });
 603     }
 604     fn visit_fn(&mut self,
 605                 function_kind: FnKind<'v>,
 606                 declaration: &'v FnDecl,
 607                 block: &'v Block,
 608                 _: Span,
 609                 node_id: NodeId) {
 610         let rib_kind = match function_kind {
 611             FnKind::ItemFn(_, generics, _, _, _, _) => {
 612                 self.visit_generics(generics);
 613                 ItemRibKind
 614             }
 615             FnKind::Method(_, sig, _) => {
 616                 self.visit_generics(&sig.generics);
 617                 self.visit_explicit_self(&sig.explicit_self);
 618                 MethodRibKind
 619             }
 620             FnKind::Closure => ClosureRibKind(node_id),
 621         };
 622         self.resolve_function(rib_kind, declaration, block);
 623     }
 624 }
 625
 626 type ErrorMessage = Option<(Span, String)>;
 627
 628 enum ResolveResult<T> {
 629     Failed(ErrorMessage), // Failed to resolve the name, optional helpful error message.
 630     Indeterminate, // Couldn't determine due to unresolved globs.
 631     Success(T), // Successfully resolved the import.
 632 }
 633
 634 impl<T> ResolveResult<T> {
 635     fn success(&self) -> bool {
 636         match *self {
 637             Success(_) => true,
 638             _ => false,
 639         }
 640     }
 641 }
 642
 643 enum FallbackSuggestion {
 644     NoSuggestion,
 645     Field,
 646     Method,
 647     TraitItem,
 648     StaticMethod(String),
 649     TraitMethod(String),
 650 }
 651
 652 #[derive(Copy, Clone)]
 653 enum TypeParameters<'a> {
 654     NoTypeParameters,
 655     HasTypeParameters(// Type parameters.
 656                       &'a Generics,
 657
 658                       // Identifies the things that these parameters
 659                       // were declared on (type, fn, etc)
 660                       ParamSpace,
 661
 662                       // The kind of the rib used for type parameters.
 663                       RibKind),
 664 }
 665
 666 // The rib kind controls the translation of local
 667 // definitions (`DefLocal`) to upvars (`DefUpvar`).
 668 #[derive(Copy, Clone, Debug)]
 669 enum RibKind {
 670     // No translation needs to be applied.
 671     NormalRibKind,
 672
 673     // We passed through a closure scope at the given node ID.
 674     // Translate upvars as appropriate.
 675     ClosureRibKind(NodeId /* func id */),
 676
 677     // We passed through an impl or trait and are now in one of its
 678     // methods. Allow references to ty params that impl or trait
 679     // binds. Disallow any other upvars (including other ty params that are
 680     // upvars).
 681     MethodRibKind,
 682
 683     // We passed through an item scope. Disallow upvars.
 684     ItemRibKind,
 685
 686     // We're in a constant item. Can't refer to dynamic stuff.
 687     ConstantItemRibKind,
 688 }
 689
 690 #[derive(Copy, Clone)]
 691 enum UseLexicalScopeFlag {
 692     DontUseLexicalScope,
 693     UseLexicalScope,
 694 }
 695
 696 enum ModulePrefixResult {
 697     NoPrefixFound,
 698     PrefixFound(Rc<Module>, usize),
 699 }
 700
 701 #[derive(Copy, Clone)]
 702 enum AssocItemResolveResult {
 703     /// Syntax such as `<T>::item`, which can't be resolved until type
 704     /// checking.
 705     TypecheckRequired,
 706     /// We should have been able to resolve the associated item.
 707     ResolveAttempt(Option<PathResolution>),
 708 }
 709
 710 #[derive(Copy, Clone, PartialEq)]
 711 enum NameSearchType {
 712     /// We're doing a name search in order to resolve a `use` directive.
 713     ImportSearch,
 714
 715     /// We're doing a name search in order to resolve a path type, a path
 716     /// expression, or a path pattern.
 717     PathSearch,
 718 }
 719
 720 #[derive(Copy, Clone)]
 721 enum BareIdentifierPatternResolution {
 722     FoundStructOrEnumVariant(Def, LastPrivate),
 723     FoundConst(Def, LastPrivate, Name),
 724     BareIdentifierPatternUnresolved,
 725 }
 726
 727 /// One local scope.
 728 #[derive(Debug)]
 729 struct Rib {
 730     bindings: HashMap<Name, DefLike>,
 731     kind: RibKind,
 732 }
 733
 734 impl Rib {
 735     fn new(kind: RibKind) -> Rib {
 736         Rib {
 737             bindings: HashMap::new(),
 738             kind: kind,
 739         }
 740     }
 741 }
 742
 743 /// A definition along with the index of the rib it was found on
 744 struct LocalDef {
 745     ribs: Option<(Namespace, usize)>,
 746     def: Def,
 747 }
 748
 749 impl LocalDef {
 750     fn from_def(def: Def) -> Self {
 751         LocalDef {
 752             ribs: None,
 753             def: def,
 754         }
 755     }
 756 }
 757
 758 /// The link from a module up to its nearest parent node.
 759 #[derive(Clone,Debug)]
 760 enum ParentLink {
 761     NoParentLink,
 762     ModuleParentLink(Weak<Module>, Name),
 763     BlockParentLink(Weak<Module>, NodeId),
 764 }
 765
 766 /// One node in the tree of modules.
 767 pub struct Module {
 768     parent_link: ParentLink,
 769     def: Cell<Option<Def>>,
 770     is_public: bool,
 771
 772     children: RefCell<HashMap<Name, NameBindings>>,
 773     imports: RefCell<Vec<ImportDirective>>,
 774
 775     // The external module children of this node that were declared with
 776     // `extern crate`.
 777     external_module_children: RefCell<HashMap<Name, Rc<Module>>>,
 778
 779     // The anonymous children of this node. Anonymous children are pseudo-
 780     // modules that are implicitly created around items contained within
 781     // blocks.
 782     //
 783     // For example, if we have this:
 784     //
 785     //  fn f() {
 786     //      fn g() {
 787     //          ...
 788     //      }
 789     //  }
 790     //
 791     // There will be an anonymous module created around `g` with the ID of the
 792     // entry block for `f`.
 793     anonymous_children: RefCell<NodeMap<Rc<Module>>>,
 794
 795     // The status of resolving each import in this module.
 796     import_resolutions: RefCell<HashMap<Name, ImportResolution>>,
 797
 798     // The number of unresolved globs that this module exports.
 799     glob_count: Cell<usize>,
 800
 801     // The number of unresolved pub imports (both regular and globs) in this module
 802     pub_count: Cell<usize>,
 803
 804     // The number of unresolved pub glob imports in this module
 805     pub_glob_count: Cell<usize>,
 806
 807     // The index of the import we're resolving.
 808     resolved_import_count: Cell<usize>,
 809
 810     // Whether this module is populated. If not populated, any attempt to
 811     // access the children must be preceded with a
 812     // `populate_module_if_necessary` call.
 813     populated: Cell<bool>,
 814 }
 815
 816 impl Module {
 817     fn new(parent_link: ParentLink,
 818            def: Option<Def>,
 819            external: bool,
 820            is_public: bool)
 821            -> Rc<Module> {
 822         Rc::new(Module {
 823             parent_link: parent_link,
 824             def: Cell::new(def),
 825             is_public: is_public,
 826             children: RefCell::new(HashMap::new()),
 827             imports: RefCell::new(Vec::new()),
 828             external_module_children: RefCell::new(HashMap::new()),
 829             anonymous_children: RefCell::new(NodeMap()),
 830             import_resolutions: RefCell::new(HashMap::new()),
 831             glob_count: Cell::new(0),
 832             pub_count: Cell::new(0),
 833             pub_glob_count: Cell::new(0),
 834             resolved_import_count: Cell::new(0),
 835             populated: Cell::new(!external),
 836         })
 837     }
 838
 839     fn def_id(&self) -> Option<DefId> {
 840         self.def.get().as_ref().map(Def::def_id)
 841     }
 842
 843     fn is_normal(&self) -> bool {
 844         match self.def.get() {
 845             Some(DefMod(_)) | Some(DefForeignMod(_)) => true,
 846             _ => false,
 847         }
 848     }
 849
 850     fn is_trait(&self) -> bool {
 851         match self.def.get() {
 852             Some(DefTrait(_)) => true,
 853             _ => false,
 854         }
 855     }
 856
 857     fn all_imports_resolved(&self) -> bool {
 858         if self.imports.borrow_state() == ::std::cell::BorrowState::Writing {
 859             // it is currently being resolved ! so nope
 860             false
 861         } else {
 862             self.imports.borrow().len() == self.resolved_import_count.get()
 863         }
 864     }
 865 }
 866
 867 impl Module {
 868     pub fn inc_glob_count(&self) {
 869         self.glob_count.set(self.glob_count.get() + 1);
 870     }
 871     pub fn dec_glob_count(&self) {
 872         assert!(self.glob_count.get() > 0);
 873         self.glob_count.set(self.glob_count.get() - 1);
 874     }
 875     pub fn inc_pub_count(&self) {
 876         self.pub_count.set(self.pub_count.get() + 1);
 877     }
 878     pub fn dec_pub_count(&self) {
 879         assert!(self.pub_count.get() > 0);
 880         self.pub_count.set(self.pub_count.get() - 1);
 881     }
 882     pub fn inc_pub_glob_count(&self) {
 883         self.pub_glob_count.set(self.pub_glob_count.get() + 1);
 884     }
 885     pub fn dec_pub_glob_count(&self) {
 886         assert!(self.pub_glob_count.get() > 0);
 887         self.pub_glob_count.set(self.pub_glob_count.get() - 1);
 888     }
 889 }
 890
 891 impl fmt::Debug for Module {
 892     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 893         write!(f,
 894                "{:?}, {}",
 895                self.def,
 896                if self.is_public {
 897                    "public"
 898                } else {
 899                    "private"
 900                })
 901     }
 902 }
 903
 904 bitflags! {
 905     #[derive(Debug)]
 906     flags DefModifiers: u8 {
 907         const PUBLIC     = 1 << 0,
 908         const IMPORTABLE = 1 << 1,
 909     }
 910 }
 911
 912 // Records a possibly-private value, type, or module definition.
 913 #[derive(Debug)]
 914 struct NsDef {
 915     modifiers: DefModifiers, // see note in ImportResolution about how to use this
 916     def_or_module: DefOrModule,
 917     span: Option<Span>,
 918 }
 919
 920 #[derive(Debug)]
 921 enum DefOrModule {
 922     Def(Def),
 923     Module(Rc<Module>),
 924 }
 925
 926 impl NsDef {
 927     fn create_from_module(module: Rc<Module>, span: Option<Span>) -> Self {
 928         let modifiers = if module.is_public {
 929             DefModifiers::PUBLIC
 930         } else {
 931             DefModifiers::empty()
 932         } | DefModifiers::IMPORTABLE;
 933
 934         NsDef { modifiers: modifiers, def_or_module: DefOrModule::Module(module), span: span }
 935     }
 936
 937     fn create_from_def(def: Def, modifiers: DefModifiers, span: Option<Span>) -> Self {
 938         NsDef { modifiers: modifiers, def_or_module: DefOrModule::Def(def), span: span }
 939     }
 940
 941     fn module(&self) -> Option<Rc<Module>> {
 942         match self.def_or_module {
 943             DefOrModule::Module(ref module) => Some(module.clone()),
 944             DefOrModule::Def(_) => None,
 945         }
 946     }
 947
 948     fn def(&self) -> Option<Def> {
 949         match self.def_or_module {
 950             DefOrModule::Def(def) => Some(def),
 951             DefOrModule::Module(ref module) => module.def.get(),
 952         }
 953     }
 954 }
 955
 956 // Records at most one definition that a name in a namespace is bound to
 957 #[derive(Clone,Debug)]
 958 pub struct NameBinding(Rc<RefCell<Option<NsDef>>>);
 959
 960 impl NameBinding {
 961     fn new() -> Self {
 962         NameBinding(Rc::new(RefCell::new(None)))
 963     }
 964
 965     fn create_from_module(module: Rc<Module>) -> Self {
 966         NameBinding(Rc::new(RefCell::new(Some(NsDef::create_from_module(module, None)))))
 967     }
 968
 969     fn set(&self, ns_def: NsDef) {
 970         *self.0.borrow_mut() = Some(ns_def);
 971     }
 972
 973     fn set_modifiers(&self, modifiers: DefModifiers) {
 974         if let Some(ref mut ns_def) = *self.0.borrow_mut() {
 975             ns_def.modifiers = modifiers
 976         }
 977     }
 978
 979     fn borrow(&self) -> ::std::cell::Ref<Option<NsDef>> {
 980         self.0.borrow()
 981     }
 982
 983     // Lifted versions of the NsDef methods and fields
 984     fn def(&self) -> Option<Def> {
 985         self.borrow().as_ref().and_then(NsDef::def)
 986     }
 987     fn module(&self) -> Option<Rc<Module>> {
 988         self.borrow().as_ref().and_then(NsDef::module)
 989     }
 990     fn span(&self) -> Option<Span> {
 991         self.borrow().as_ref().and_then(|def| def.span)
 992     }
 993     fn modifiers(&self) -> Option<DefModifiers> {
 994         self.borrow().as_ref().and_then(|def| Some(def.modifiers))
 995     }
 996
 997     fn defined(&self) -> bool {
 998         self.borrow().is_some()
 999     }
1000
1001     fn defined_with(&self, modifiers: DefModifiers) -> bool {
1002         self.modifiers().map(|m| m.contains(modifiers)).unwrap_or(false)
1003     }
1004
1005     fn is_public(&self) -> bool {
1006         self.defined_with(DefModifiers::PUBLIC)
1007     }
1008
1009     fn def_and_lp(&self) -> (Def, LastPrivate) {
1010         let def = self.def().unwrap();
1011         (def, LastMod(if self.is_public() { AllPublic } else { DependsOn(def.def_id()) }))
1012     }
1013 }
1014
1015 // Records the definitions (at most one for each namespace) that a name is
1016 // bound to.
1017 #[derive(Clone,Debug)]
1018 pub struct NameBindings {
1019     type_ns: NameBinding, // < Meaning in type namespace.
1020     value_ns: NameBinding, // < Meaning in value namespace.
1021 }
1022
1023 impl ::std::ops::Index<Namespace> for NameBindings {
1024     type Output = NameBinding;
1025     fn index(&self, namespace: Namespace) -> &NameBinding {
1026         match namespace { TypeNS => &self.type_ns, ValueNS => &self.value_ns }
1027     }
1028 }
1029
1030 impl NameBindings {
1031     fn new() -> NameBindings {
1032         NameBindings {
1033             type_ns: NameBinding::new(),
1034             value_ns: NameBinding::new(),
1035         }
1036     }
1037
1038     /// Creates a new module in this set of name bindings.
1039     fn define_module(&self, module: Rc<Module>, sp: Span) {
1040         self.type_ns.set(NsDef::create_from_module(module, Some(sp)));
1041     }
1042
1043     /// Records a type definition.
1044     fn define_type(&self, def: Def, sp: Span, modifiers: DefModifiers) {
1045         debug!("defining type for def {:?} with modifiers {:?}", def, modifiers);
1046         self.type_ns.set(NsDef::create_from_def(def, modifiers, Some(sp)));
1047     }
1048
1049     /// Records a value definition.
1050     fn define_value(&self, def: Def, sp: Span, modifiers: DefModifiers) {
1051         debug!("defining value for def {:?} with modifiers {:?}", def, modifiers);
1052         self.value_ns.set(NsDef::create_from_def(def, modifiers, Some(sp)));
1053     }
1054 }
1055
1056 /// Interns the names of the primitive types.
1057 struct PrimitiveTypeTable {
1058     primitive_types: HashMap<Name, PrimTy>,
1059 }
1060
1061 impl PrimitiveTypeTable {
1062     fn new() -> PrimitiveTypeTable {
1063         let mut table = PrimitiveTypeTable { primitive_types: HashMap::new() };
1064
1065         table.intern("bool", TyBool);
1066         table.intern("char", TyChar);
1067         table.intern("f32", TyFloat(TyF32));
1068         table.intern("f64", TyFloat(TyF64));
1069         table.intern("isize", TyInt(TyIs));
1070         table.intern("i8", TyInt(TyI8));
1071         table.intern("i16", TyInt(TyI16));
1072         table.intern("i32", TyInt(TyI32));
1073         table.intern("i64", TyInt(TyI64));
1074         table.intern("str", TyStr);
1075         table.intern("usize", TyUint(TyUs));
1076         table.intern("u8", TyUint(TyU8));
1077         table.intern("u16", TyUint(TyU16));
1078         table.intern("u32", TyUint(TyU32));
1079         table.intern("u64", TyUint(TyU64));
1080
1081         table
1082     }
1083
1084     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1085         self.primitive_types.insert(token::intern(string), primitive_type);
1086     }
1087 }
1088
1089 /// The main resolver class.
1090 pub struct Resolver<'a, 'tcx: 'a> {
1091     session: &'a Session,
1092
1093     ast_map: &'a hir_map::Map<'tcx>,
1094
1095     graph_root: Rc<Module>,
1096
1097     trait_item_map: FnvHashMap<(Name, DefId), DefId>,
1098
1099     structs: FnvHashMap<DefId, Vec<Name>>,
1100
1101     // The number of imports that are currently unresolved.
1102     unresolved_imports: usize,
1103
1104     // The module that represents the current item scope.
1105     current_module: Rc<Module>,
1106
1107     // The current set of local scopes, for values.
1108     // FIXME #4948: Reuse ribs to avoid allocation.
1109     value_ribs: Vec<Rib>,
1110
1111     // The current set of local scopes, for types.
1112     type_ribs: Vec<Rib>,
1113
1114     // The current set of local scopes, for labels.
1115     label_ribs: Vec<Rib>,
1116
1117     // The trait that the current context can refer to.
1118     current_trait_ref: Option<(DefId, TraitRef)>,
1119
1120     // The current self type if inside an impl (used for better errors).
1121     current_self_type: Option<Ty>,
1122
1123     // The idents for the primitive types.
1124     primitive_type_table: PrimitiveTypeTable,
1125
1126     def_map: RefCell<DefMap>,
1127     freevars: FreevarMap,
1128     freevars_seen: NodeMap<NodeMap<usize>>,
1129     export_map: ExportMap,
1130     trait_map: TraitMap,
1131     external_exports: ExternalExports,
1132
1133     // Whether or not to print error messages. Can be set to true
1134     // when getting additional info for error message suggestions,
1135     // so as to avoid printing duplicate errors
1136     emit_errors: bool,
1137
1138     make_glob_map: bool,
1139     // Maps imports to the names of items actually imported (this actually maps
1140     // all imports, but only glob imports are actually interesting).
1141     glob_map: GlobMap,
1142
1143     used_imports: HashSet<(NodeId, Namespace)>,
1144     used_crates: HashSet<CrateNum>,
1145
1146     // Callback function for intercepting walks
1147     callback: Option<Box<Fn(hir_map::Node, &mut bool) -> bool>>,
1148     // The intention is that the callback modifies this flag.
1149     // Once set, the resolver falls out of the walk, preserving the ribs.
1150     resolved: bool,
1151 }
1152
1153 #[derive(PartialEq)]
1154 enum FallbackChecks {
1155     Everything,
1156     OnlyTraitAndStatics,
1157 }
1158
1159 impl<'a, 'tcx> Resolver<'a, 'tcx> {
1160     fn new(session: &'a Session,
1161            ast_map: &'a hir_map::Map<'tcx>,
1162            make_glob_map: MakeGlobMap)
1163            -> Resolver<'a, 'tcx> {
1164         let root_def_id = ast_map.local_def_id(CRATE_NODE_ID);
1165         let graph_root = Module::new(NoParentLink, Some(DefMod(root_def_id)), false, true);
1166
1167         Resolver {
1168             session: session,
1169
1170             ast_map: ast_map,
1171
1172             // The outermost module has def ID 0; this is not reflected in the
1173             // AST.
1174             graph_root: graph_root.clone(),
1175
1176             trait_item_map: FnvHashMap(),
1177             structs: FnvHashMap(),
1178
1179             unresolved_imports: 0,
1180
1181             current_module: graph_root,
1182             value_ribs: Vec::new(),
1183             type_ribs: Vec::new(),
1184             label_ribs: Vec::new(),
1185
1186             current_trait_ref: None,
1187             current_self_type: None,
1188
1189             primitive_type_table: PrimitiveTypeTable::new(),
1190
1191             def_map: RefCell::new(NodeMap()),
1192             freevars: NodeMap(),
1193             freevars_seen: NodeMap(),
1194             export_map: NodeMap(),
1195             trait_map: NodeMap(),
1196             used_imports: HashSet::new(),
1197             used_crates: HashSet::new(),
1198             external_exports: DefIdSet(),
1199
1200             emit_errors: true,
1201             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1202             glob_map: HashMap::new(),
1203
1204             callback: None,
1205             resolved: false,
1206         }
1207     }
1208
1209     #[inline]
1210     fn record_import_use(&mut self, import_id: NodeId, name: Name) {
1211         if !self.make_glob_map {
1212             return;
1213         }
1214         if self.glob_map.contains_key(&import_id) {
1215             self.glob_map.get_mut(&import_id).unwrap().insert(name);
1216             return;
1217         }
1218
1219         let mut new_set = HashSet::new();
1220         new_set.insert(name);
1221         self.glob_map.insert(import_id, new_set);
1222     }
1223
1224     fn get_trait_name(&self, did: DefId) -> Name {
1225         if let Some(node_id) = self.ast_map.as_local_node_id(did) {
1226             self.ast_map.expect_item(node_id).name
1227         } else {
1228             self.session.cstore.item_name(did)
1229         }
1230     }
1231
1232     /// Checks that the names of external crates don't collide with other
1233     /// external crates.
1234     fn check_for_conflicts_between_external_crates(&self,
1235                                                    module: &Module,
1236                                                    name: Name,
1237                                                    span: Span) {
1238         if module.external_module_children.borrow().contains_key(&name) {
1239             span_err!(self.session,
1240                       span,
1241                       E0259,
1242                       "an external crate named `{}` has already been imported into this module",
1243                       name);
1244         }
1245     }
1246
1247     /// Checks that the names of items don't collide with external crates.
1248     fn check_for_conflicts_between_external_crates_and_items(&self,
1249                                                              module: &Module,
1250                                                              name: Name,
1251                                                              span: Span) {
1252         if module.external_module_children.borrow().contains_key(&name) {
1253             span_err!(self.session,
1254                       span,
1255                       E0260,
1256                       "the name `{}` conflicts with an external crate that has been imported \
1257                        into this module",
1258                       name);
1259         }
1260     }
1261
1262     /// Resolves the given module path from the given root `module_`.
1263     fn resolve_module_path_from_root(&mut self,
1264                                      module_: Rc<Module>,
1265                                      module_path: &[Name],
1266                                      index: usize,
1267                                      span: Span,
1268                                      name_search_type: NameSearchType,
1269                                      lp: LastPrivate)
1270                                      -> ResolveResult<(Rc<Module>, LastPrivate)> {
1271         fn search_parent_externals(needle: Name, module: &Rc<Module>) -> Option<Rc<Module>> {
1272             match module.external_module_children.borrow().get(&needle) {
1273                 Some(_) => Some(module.clone()),
1274                 None => match module.parent_link {
1275                     ModuleParentLink(ref parent, _) => {
1276                         search_parent_externals(needle, &parent.upgrade().unwrap())
1277                     }
1278                     _ => None,
1279                 },
1280             }
1281         }
1282
1283         let mut search_module = module_;
1284         let mut index = index;
1285         let module_path_len = module_path.len();
1286         let mut closest_private = lp;
1287
1288         // Resolve the module part of the path. This does not involve looking
1289         // upward though scope chains; we simply resolve names directly in
1290         // modules as we go.
1291         while index < module_path_len {
1292             let name = module_path[index];
1293             match self.resolve_name_in_module(search_module.clone(),
1294                                               name,
1295                                               TypeNS,
1296                                               name_search_type,
1297                                               false) {
1298                 Failed(None) => {
1299                     let segment_name = name.as_str();
1300                     let module_name = module_to_string(&*search_module);
1301                     let mut span = span;
1302                     let msg = if "???" == &module_name[..] {
1303                         span.hi = span.lo + Pos::from_usize(segment_name.len());
1304
1305                         match search_parent_externals(name, &self.current_module) {
1306                             Some(module) => {
1307                                 let path_str = names_to_string(module_path);
1308                                 let target_mod_str = module_to_string(&*module);
1309                                 let current_mod_str = module_to_string(&*self.current_module);
1310
1311                                 let prefix = if target_mod_str == current_mod_str {
1312                                     "self::".to_string()
1313                                 } else {
1314                                     format!("{}::", target_mod_str)
1315                                 };
1316
1317                                 format!("Did you mean `{}{}`?", prefix, path_str)
1318                             }
1319                             None => format!("Maybe a missing `extern crate {}`?", segment_name),
1320                         }
1321                     } else {
1322                         format!("Could not find `{}` in `{}`", segment_name, module_name)
1323                     };
1324
1325                     return Failed(Some((span, msg)));
1326                 }
1327                 Failed(err) => return Failed(err),
1328                 Indeterminate => {
1329                     debug!("(resolving module path for import) module resolution is \
1330                             indeterminate: {}",
1331                            name);
1332                     return Indeterminate;
1333                 }
1334                 Success((target, used_proxy)) => {
1335                     // Check to see whether there are type bindings, and, if
1336                     // so, whether there is a module within.
1337                     if let Some(module_def) = target.binding.module() {
1338                         // track extern crates for unused_extern_crate lint
1339                         if let Some(did) = module_def.def_id() {
1340                             self.used_crates.insert(did.krate);
1341                         }
1342
1343                         search_module = module_def;
1344
1345                         // Keep track of the closest private module used
1346                         // when resolving this import chain.
1347                         if !used_proxy && !search_module.is_public {
1348                             if let Some(did) = search_module.def_id() {
1349                                 closest_private = LastMod(DependsOn(did));
1350                             }
1351                         }
1352                     } else {
1353                         let msg = format!("Not a module `{}`", name);
1354                         return Failed(Some((span, msg)));
1355                     }
1356                 }
1357             }
1358
1359             index += 1;
1360         }
1361
1362         return Success((search_module, closest_private));
1363     }
1364
1365     /// Attempts to resolve the module part of an import directive or path
1366     /// rooted at the given module.
1367     ///
1368     /// On success, returns the resolved module, and the closest *private*
1369     /// module found to the destination when resolving this path.
1370     fn resolve_module_path(&mut self,
1371                            module_: Rc<Module>,
1372                            module_path: &[Name],
1373                            use_lexical_scope: UseLexicalScopeFlag,
1374                            span: Span,
1375                            name_search_type: NameSearchType)
1376                            -> ResolveResult<(Rc<Module>, LastPrivate)> {
1377         let module_path_len = module_path.len();
1378         assert!(module_path_len > 0);
1379
1380         debug!("(resolving module path for import) processing `{}` rooted at `{}`",
1381                names_to_string(module_path),
1382                module_to_string(&*module_));
1383
1384         // Resolve the module prefix, if any.
1385         let module_prefix_result = self.resolve_module_prefix(module_.clone(), module_path);
1386
1387         let search_module;
1388         let start_index;
1389         let last_private;
1390         match module_prefix_result {
1391             Failed(None) => {
1392                 let mpath = names_to_string(module_path);
1393                 let mpath = &mpath[..];
1394                 match mpath.rfind(':') {
1395                     Some(idx) => {
1396                         let msg = format!("Could not find `{}` in `{}`",
1397                                           // idx +- 1 to account for the
1398                                           // colons on either side
1399                                           &mpath[idx + 1..],
1400                                           &mpath[..idx - 1]);
1401                         return Failed(Some((span, msg)));
1402                     }
1403                     None => {
1404                         return Failed(None);
1405                     }
1406                 }
1407             }
1408             Failed(err) => return Failed(err),
1409             Indeterminate => {
1410                 debug!("(resolving module path for import) indeterminate; bailing");
1411                 return Indeterminate;
1412             }
1413             Success(NoPrefixFound) => {
1414                 // There was no prefix, so we're considering the first element
1415                 // of the path. How we handle this depends on whether we were
1416                 // instructed to use lexical scope or not.
1417                 match use_lexical_scope {
1418                     DontUseLexicalScope => {
1419                         // This is a crate-relative path. We will start the
1420                         // resolution process at index zero.
1421                         search_module = self.graph_root.clone();
1422                         start_index = 0;
1423                         last_private = LastMod(AllPublic);
1424                     }
1425                     UseLexicalScope => {
1426                         // This is not a crate-relative path. We resolve the
1427                         // first component of the path in the current lexical
1428                         // scope and then proceed to resolve below that.
1429                         match self.resolve_module_in_lexical_scope(module_, module_path[0]) {
1430                             Failed(err) => return Failed(err),
1431                             Indeterminate => {
1432                                 debug!("(resolving module path for import) indeterminate; bailing");
1433                                 return Indeterminate;
1434                             }
1435                             Success(containing_module) => {
1436                                 search_module = containing_module;
1437                                 start_index = 1;
1438                                 last_private = LastMod(AllPublic);
1439                             }
1440                         }
1441                     }
1442                 }
1443             }
1444             Success(PrefixFound(ref containing_module, index)) => {
1445                 search_module = containing_module.clone();
1446                 start_index = index;
1447                 last_private = LastMod(DependsOn(containing_module.def_id()
1448                                                                   .unwrap()));
1449             }
1450         }
1451
1452         self.resolve_module_path_from_root(search_module,
1453                                            module_path,
1454                                            start_index,
1455                                            span,
1456                                            name_search_type,
1457                                            last_private)
1458     }
1459
1460     /// Invariant: This must only be called during main resolution, not during
1461     /// import resolution.
1462     fn resolve_item_in_lexical_scope(&mut self,
1463                                      module_: Rc<Module>,
1464                                      name: Name,
1465                                      namespace: Namespace)
1466                                      -> ResolveResult<(Target, bool)> {
1467         debug!("(resolving item in lexical scope) resolving `{}` in namespace {:?} in `{}`",
1468                name,
1469                namespace,
1470                module_to_string(&*module_));
1471
1472         // The current module node is handled specially. First, check for
1473         // its immediate children.
1474         build_reduced_graph::populate_module_if_necessary(self, &module_);
1475
1476         match module_.children.borrow().get(&name) {
1477             Some(name_bindings) if name_bindings[namespace].defined() => {
1478                 debug!("top name bindings succeeded");
1479                 return Success((Target::new(module_.clone(),
1480                                             name_bindings[namespace].clone(),
1481                                             Shadowable::Never),
1482                                 false));
1483             }
1484             Some(_) | None => {
1485                 // Not found; continue.
1486             }
1487         }
1488
1489         // Now check for its import directives. We don't have to have resolved
1490         // all its imports in the usual way; this is because chains of
1491         // adjacent import statements are processed as though they mutated the
1492         // current scope.
1493         if let Some(import_resolution) = module_.import_resolutions.borrow().get(&name) {
1494             match (*import_resolution).target_for_namespace(namespace) {
1495                 None => {
1496                     // Not found; continue.
1497                     debug!("(resolving item in lexical scope) found import resolution, but not \
1498                             in namespace {:?}",
1499                            namespace);
1500                 }
1501                 Some(target) => {
1502                     debug!("(resolving item in lexical scope) using import resolution");
1503                     // track used imports and extern crates as well
1504                     let id = import_resolution.id(namespace);
1505                     self.used_imports.insert((id, namespace));
1506                     self.record_import_use(id, name);
1507                     if let Some(DefId{krate: kid, ..}) = target.target_module.def_id() {
1508                         self.used_crates.insert(kid);
1509                     }
1510                     return Success((target, false));
1511                 }
1512             }
1513         }
1514
1515         // Search for external modules.
1516         if namespace == TypeNS {
1517             // FIXME (21114): In principle unclear `child` *has* to be lifted.
1518             let child = module_.external_module_children.borrow().get(&name).cloned();
1519             if let Some(module) = child {
1520                 let name_binding = NameBinding::create_from_module(module);
1521                 debug!("lower name bindings succeeded");
1522                 return Success((Target::new(module_, name_binding, Shadowable::Never),
1523                                 false));
1524             }
1525         }
1526
1527         // Finally, proceed up the scope chain looking for parent modules.
1528         let mut search_module = module_;
1529         loop {
1530             // Go to the next parent.
1531             match search_module.parent_link.clone() {
1532                 NoParentLink => {
1533                     // No more parents. This module was unresolved.
1534                     debug!("(resolving item in lexical scope) unresolved module");
1535                     return Failed(None);
1536                 }
1537                 ModuleParentLink(parent_module_node, _) => {
1538                     if search_module.is_normal() {
1539                         // We stop the search here.
1540                         debug!("(resolving item in lexical scope) unresolved module: not \
1541                                 searching through module parents");
1542                             return Failed(None);
1543                     } else {
1544                         search_module = parent_module_node.upgrade().unwrap();
1545                     }
1546                 }
1547                 BlockParentLink(ref parent_module_node, _) => {
1548                     search_module = parent_module_node.upgrade().unwrap();
1549                 }
1550             }
1551
1552             // Resolve the name in the parent module.
1553             match self.resolve_name_in_module(search_module.clone(),
1554                                               name,
1555                                               namespace,
1556                                               PathSearch,
1557                                               true) {
1558                 Failed(Some((span, msg))) => {
1559                     resolve_error(self, span, ResolutionError::FailedToResolve(&*msg));
1560                 }
1561                 Failed(None) => (), // Continue up the search chain.
1562                 Indeterminate => {
1563                     // We couldn't see through the higher scope because of an
1564                     // unresolved import higher up. Bail.
1565
1566                     debug!("(resolving item in lexical scope) indeterminate higher scope; bailing");
1567                     return Indeterminate;
1568                 }
1569                 Success((target, used_reexport)) => {
1570                     // We found the module.
1571                     debug!("(resolving item in lexical scope) found name in module, done");
1572                     return Success((target, used_reexport));
1573                 }
1574             }
1575         }
1576     }
1577
1578     /// Resolves a module name in the current lexical scope.
1579     fn resolve_module_in_lexical_scope(&mut self,
1580                                        module_: Rc<Module>,
1581                                        name: Name)
1582                                        -> ResolveResult<Rc<Module>> {
1583         // If this module is an anonymous module, resolve the item in the
1584         // lexical scope. Otherwise, resolve the item from the crate root.
1585         let resolve_result = self.resolve_item_in_lexical_scope(module_, name, TypeNS);
1586         match resolve_result {
1587             Success((target, _)) => {
1588                 if let Some(module_def) = target.binding.module() {
1589                     return Success(module_def)
1590                 } else {
1591                     debug!("!!! (resolving module in lexical scope) module \
1592                             wasn't actually a module!");
1593                     return Failed(None);
1594                 }
1595             }
1596             Indeterminate => {
1597                 debug!("(resolving module in lexical scope) indeterminate; bailing");
1598                 return Indeterminate;
1599             }
1600             Failed(err) => {
1601                 debug!("(resolving module in lexical scope) failed to resolve");
1602                 return Failed(err);
1603             }
1604         }
1605     }
1606
1607     /// Returns the nearest normal module parent of the given module.
1608     fn get_nearest_normal_module_parent(&mut self, module_: Rc<Module>) -> Option<Rc<Module>> {
1609         let mut module_ = module_;
1610         loop {
1611             match module_.parent_link.clone() {
1612                 NoParentLink => return None,
1613                 ModuleParentLink(new_module, _) |
1614                 BlockParentLink(new_module, _) => {
1615                     let new_module = new_module.upgrade().unwrap();
1616                     if new_module.is_normal() {
1617                         return Some(new_module);
1618                     }
1619                     module_ = new_module;
1620                 }
1621             }
1622         }
1623     }
1624
1625     /// Returns the nearest normal module parent of the given module, or the
1626     /// module itself if it is a normal module.
1627     fn get_nearest_normal_module_parent_or_self(&mut self, module_: Rc<Module>) -> Rc<Module> {
1628         if module_.is_normal() {
1629             return module_;
1630         }
1631         match self.get_nearest_normal_module_parent(module_.clone()) {
1632             None => module_,
1633             Some(new_module) => new_module,
1634         }
1635     }
1636
1637     /// Resolves a "module prefix". A module prefix is one or both of (a) `self::`;
1638     /// (b) some chain of `super::`.
1639     /// grammar: (SELF MOD_SEP ) ? (SUPER MOD_SEP) *
1640     fn resolve_module_prefix(&mut self,
1641                              module_: Rc<Module>,
1642                              module_path: &[Name])
1643                              -> ResolveResult<ModulePrefixResult> {
1644         // Start at the current module if we see `self` or `super`, or at the
1645         // top of the crate otherwise.
1646         let mut i = match &*module_path[0].as_str() {
1647             "self" => 1,
1648             "super" => 0,
1649             _ => return Success(NoPrefixFound),
1650         };
1651         let mut containing_module = self.get_nearest_normal_module_parent_or_self(module_);
1652
1653         // Now loop through all the `super`s we find.
1654         while i < module_path.len() && "super" == module_path[i].as_str() {
1655             debug!("(resolving module prefix) resolving `super` at {}",
1656                    module_to_string(&*containing_module));
1657             match self.get_nearest_normal_module_parent(containing_module) {
1658                 None => return Failed(None),
1659                 Some(new_module) => {
1660                     containing_module = new_module;
1661                     i += 1;
1662                 }
1663             }
1664         }
1665
1666         debug!("(resolving module prefix) finished resolving prefix at {}",
1667                module_to_string(&*containing_module));
1668
1669         return Success(PrefixFound(containing_module, i));
1670     }
1671
1672     /// Attempts to resolve the supplied name in the given module for the
1673     /// given namespace. If successful, returns the target corresponding to
1674     /// the name.
1675     ///
1676     /// The boolean returned on success is an indicator of whether this lookup
1677     /// passed through a public re-export proxy.
1678     fn resolve_name_in_module(&mut self,
1679                               module_: Rc<Module>,
1680                               name: Name,
1681                               namespace: Namespace,
1682                               name_search_type: NameSearchType,
1683                               allow_private_imports: bool)
1684                               -> ResolveResult<(Target, bool)> {
1685         debug!("(resolving name in module) resolving `{}` in `{}`",
1686                name,
1687                module_to_string(&*module_));
1688
1689         // First, check the direct children of the module.
1690         build_reduced_graph::populate_module_if_necessary(self, &module_);
1691
1692         match module_.children.borrow().get(&name) {
1693             Some(name_bindings) if name_bindings[namespace].defined() => {
1694                 debug!("(resolving name in module) found node as child");
1695                 return Success((Target::new(module_.clone(),
1696                                             name_bindings[namespace].clone(),
1697                                             Shadowable::Never),
1698                                 false));
1699             }
1700             Some(_) | None => {
1701                 // Continue.
1702             }
1703         }
1704
1705         // Next, check the module's imports if necessary.
1706
1707         // If this is a search of all imports, we should be done with glob
1708         // resolution at this point.
1709         if name_search_type == PathSearch {
1710             assert_eq!(module_.glob_count.get(), 0);
1711         }
1712
1713         // Check the list of resolved imports.
1714         match module_.import_resolutions.borrow().get(&name) {
1715             Some(import_resolution) if allow_private_imports || import_resolution.is_public => {
1716
1717                 if import_resolution.is_public && import_resolution.outstanding_references != 0 {
1718                     debug!("(resolving name in module) import unresolved; bailing out");
1719                     return Indeterminate;
1720                 }
1721                 match import_resolution.target_for_namespace(namespace) {
1722                     None => {
1723                         debug!("(resolving name in module) name found, but not in namespace {:?}",
1724                                namespace);
1725                     }
1726                     Some(target) => {
1727                         debug!("(resolving name in module) resolved to import");
1728                         // track used imports and extern crates as well
1729                         let id = import_resolution.id(namespace);
1730                         self.used_imports.insert((id, namespace));
1731                         self.record_import_use(id, name);
1732                         if let Some(DefId{krate: kid, ..}) = target.target_module.def_id() {
1733                             self.used_crates.insert(kid);
1734                         }
1735                         return Success((target, true));
1736                     }
1737                 }
1738             }
1739             Some(..) | None => {} // Continue.
1740         }
1741
1742         // Finally, search through external children.
1743         if namespace == TypeNS {
1744             // FIXME (21114): In principle unclear `child` *has* to be lifted.
1745             let child = module_.external_module_children.borrow().get(&name).cloned();
1746             if let Some(module) = child {
1747                 let name_binding = NameBinding::create_from_module(module);
1748                 return Success((Target::new(module_, name_binding, Shadowable::Never),
1749                                 false));
1750             }
1751         }
1752
1753         // We're out of luck.
1754         debug!("(resolving name in module) failed to resolve `{}`", name);
1755         return Failed(None);
1756     }
1757
1758     fn report_unresolved_imports(&mut self, module_: Rc<Module>) {
1759         let index = module_.resolved_import_count.get();
1760         let imports = module_.imports.borrow();
1761         let import_count = imports.len();
1762         if index != import_count {
1763             resolve_error(self,
1764                           (*imports)[index].span,
1765                           ResolutionError::UnresolvedImport(None));
1766         }
1767
1768         // Descend into children and anonymous children.
1769         build_reduced_graph::populate_module_if_necessary(self, &module_);
1770
1771         for (_, child_node) in module_.children.borrow().iter() {
1772             match child_node.type_ns.module() {
1773                 None => {
1774                     // Continue.
1775                 }
1776                 Some(child_module) => {
1777                     self.report_unresolved_imports(child_module);
1778                 }
1779             }
1780         }
1781
1782         for (_, module_) in module_.anonymous_children.borrow().iter() {
1783             self.report_unresolved_imports(module_.clone());
1784         }
1785     }
1786
1787     // AST resolution
1788     //
1789     // We maintain a list of value ribs and type ribs.
1790     //
1791     // Simultaneously, we keep track of the current position in the module
1792     // graph in the `current_module` pointer. When we go to resolve a name in
1793     // the value or type namespaces, we first look through all the ribs and
1794     // then query the module graph. When we resolve a name in the module
1795     // namespace, we can skip all the ribs (since nested modules are not
1796     // allowed within blocks in Rust) and jump straight to the current module
1797     // graph node.
1798     //
1799     // Named implementations are handled separately. When we find a method
1800     // call, we consult the module node to find all of the implementations in
1801     // scope. This information is lazily cached in the module node. We then
1802     // generate a fake "implementation scope" containing all the
1803     // implementations thus found, for compatibility with old resolve pass.
1804
1805     fn with_scope<F>(&mut self, name: Option<Name>, f: F)
1806         where F: FnOnce(&mut Resolver)
1807     {
1808         let orig_module = self.current_module.clone();
1809
1810         // Move down in the graph.
1811         match name {
1812             None => {
1813                 // Nothing to do.
1814             }
1815             Some(name) => {
1816                 build_reduced_graph::populate_module_if_necessary(self, &orig_module);
1817
1818                 match orig_module.children.borrow().get(&name) {
1819                     None => {
1820                         debug!("!!! (with scope) didn't find `{}` in `{}`",
1821                                name,
1822                                module_to_string(&*orig_module));
1823                     }
1824                     Some(name_bindings) => {
1825                         match name_bindings.type_ns.module() {
1826                             None => {
1827                                 debug!("!!! (with scope) didn't find module for `{}` in `{}`",
1828                                        name,
1829                                        module_to_string(&*orig_module));
1830                             }
1831                             Some(module_) => {
1832                                 self.current_module = module_;
1833                             }
1834                         }
1835                     }
1836                 }
1837             }
1838         }
1839
1840         f(self);
1841
1842         self.current_module = orig_module;
1843     }
1844
1845     /// Searches the current set of local scopes for labels.
1846     /// Stops after meeting a closure.
1847     fn search_label(&self, name: Name) -> Option<DefLike> {
1848         for rib in self.label_ribs.iter().rev() {
1849             match rib.kind {
1850                 NormalRibKind => {
1851                     // Continue
1852                 }
1853                 _ => {
1854                     // Do not resolve labels across function boundary
1855                     return None;
1856                 }
1857             }
1858             let result = rib.bindings.get(&name).cloned();
1859             if result.is_some() {
1860                 return result;
1861             }
1862         }
1863         None
1864     }
1865
1866     fn resolve_crate(&mut self, krate: &hir::Crate) {
1867         debug!("(resolving crate) starting");
1868
1869         intravisit::walk_crate(self, krate);
1870     }
1871
1872     fn check_if_primitive_type_name(&self, name: Name, span: Span) {
1873         if let Some(_) = self.primitive_type_table.primitive_types.get(&name) {
1874             span_err!(self.session,
1875                       span,
1876                       E0317,
1877                       "user-defined types or type parameters cannot shadow the primitive types");
1878         }
1879     }
1880
1881     fn resolve_item(&mut self, item: &Item) {
1882         let name = item.name;
1883
1884         debug!("(resolving item) resolving {}", name);
1885
1886         match item.node {
1887             ItemEnum(_, ref generics) |
1888             ItemTy(_, ref generics) |
1889             ItemStruct(_, ref generics) => {
1890                 self.check_if_primitive_type_name(name, item.span);
1891
1892                 self.with_type_parameter_rib(HasTypeParameters(generics, TypeSpace, ItemRibKind),
1893                                              |this| intravisit::walk_item(this, item));
1894             }
1895             ItemFn(_, _, _, _, ref generics, _) => {
1896                 self.with_type_parameter_rib(HasTypeParameters(generics, FnSpace, ItemRibKind),
1897                                              |this| intravisit::walk_item(this, item));
1898             }
1899
1900             ItemDefaultImpl(_, ref trait_ref) => {
1901                 self.with_optional_trait_ref(Some(trait_ref), |_, _| {});
1902             }
1903             ItemImpl(_, _, ref generics, ref opt_trait_ref, ref self_type, ref impl_items) => {
1904                 self.resolve_implementation(generics,
1905                                             opt_trait_ref,
1906                                             &**self_type,
1907                                             item.id,
1908                                             impl_items);
1909             }
1910
1911             ItemTrait(_, ref generics, ref bounds, ref trait_items) => {
1912                 self.check_if_primitive_type_name(name, item.span);
1913
1914                 // Create a new rib for the trait-wide type parameters.
1915                 self.with_type_parameter_rib(HasTypeParameters(generics,
1916                                                                TypeSpace,
1917                                                                ItemRibKind),
1918                                              |this| {
1919                     let local_def_id = this.ast_map.local_def_id(item.id);
1920                     this.with_self_rib(DefSelfTy(Some(local_def_id), None), |this| {
1921                         this.visit_generics(generics);
1922                         walk_list!(this, visit_ty_param_bound, bounds);
1923
1924                         for trait_item in trait_items {
1925                             match trait_item.node {
1926                                 hir::ConstTraitItem(_, ref default) => {
1927                                     // Only impose the restrictions of
1928                                     // ConstRibKind if there's an actual constant
1929                                     // expression in a provided default.
1930                                     if default.is_some() {
1931                                         this.with_constant_rib(|this| {
1932                                             intravisit::walk_trait_item(this, trait_item)
1933                                         });
1934                                     } else {
1935                                         intravisit::walk_trait_item(this, trait_item)
1936                                     }
1937                                 }
1938                                 hir::MethodTraitItem(ref sig, _) => {
1939                                     let type_parameters =
1940                                         HasTypeParameters(&sig.generics,
1941                                                           FnSpace,
1942                                                           MethodRibKind);
1943                                     this.with_type_parameter_rib(type_parameters, |this| {
1944                                         intravisit::walk_trait_item(this, trait_item)
1945                                     });
1946                                 }
1947                                 hir::TypeTraitItem(..) => {
1948                                     this.check_if_primitive_type_name(trait_item.name,
1949                                                                       trait_item.span);
1950                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1951                                         intravisit::walk_trait_item(this, trait_item)
1952                                     });
1953                                 }
1954                             };
1955                         }
1956                     });
1957                 });
1958             }
1959
1960             ItemMod(_) | ItemForeignMod(_) => {
1961                 self.with_scope(Some(name), |this| {
1962                     intravisit::walk_item(this, item);
1963                 });
1964             }
1965
1966             ItemConst(..) | ItemStatic(..) => {
1967                 self.with_constant_rib(|this| {
1968                     intravisit::walk_item(this, item);
1969                 });
1970             }
1971
1972             ItemUse(ref view_path) => {
1973                 // check for imports shadowing primitive types
1974                 let check_rename = |this: &Self, id, name| {
1975                     match this.def_map.borrow().get(&id).map(|d| d.full_def()) {
1976                         Some(DefTy(..)) | Some(DefStruct(..)) | Some(DefTrait(..)) | None => {
1977                             this.check_if_primitive_type_name(name, item.span);
1978                         }
1979                         _ => {}
1980                     }
1981                 };
1982
1983                 match view_path.node {
1984                     hir::ViewPathSimple(name, _) => {
1985                         check_rename(self, item.id, name);
1986                     }
1987                     hir::ViewPathList(ref prefix, ref items) => {
1988                         for item in items {
1989                             if let Some(name) = item.node.rename() {
1990                                 check_rename(self, item.node.id(), name);
1991                             }
1992                         }
1993
1994                         // Resolve prefix of an import with empty braces (issue #28388)
1995                         if items.is_empty() && !prefix.segments.is_empty() {
1996                             match self.resolve_crate_relative_path(prefix.span,
1997                                                                    &prefix.segments,
1998                                                                    TypeNS) {
1999                                 Some((def, lp)) =>
2000                                     self.record_def(item.id, PathResolution::new(def, lp, 0)),
2001                                 None => {
2002                                     resolve_error(self,
2003                                                   prefix.span,
2004                                                   ResolutionError::FailedToResolve(
2005                                                       &path_names_to_string(prefix, 0)));
2006                                 }
2007                             }
2008                         }
2009                     }
2010                     _ => {}
2011                 }
2012             }
2013
2014             ItemExternCrate(_) => {
2015                 // do nothing, these are just around to be encoded
2016             }
2017         }
2018     }
2019
2020     fn with_type_parameter_rib<F>(&mut self, type_parameters: TypeParameters, f: F)
2021         where F: FnOnce(&mut Resolver)
2022     {
2023         match type_parameters {
2024             HasTypeParameters(generics, space, rib_kind) => {
2025                 let mut function_type_rib = Rib::new(rib_kind);
2026                 let mut seen_bindings = HashSet::new();
2027                 for (index, type_parameter) in generics.ty_params.iter().enumerate() {
2028                     let name = type_parameter.name;
2029                     debug!("with_type_parameter_rib: {}", type_parameter.id);
2030
2031                     if seen_bindings.contains(&name) {
2032                         resolve_error(self,
2033                                       type_parameter.span,
2034                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name));
2035                     }
2036                     seen_bindings.insert(name);
2037
2038                     // plain insert (no renaming)
2039                     function_type_rib.bindings
2040                                      .insert(name,
2041                                              DlDef(DefTyParam(space,
2042                                                               index as u32,
2043                                                               self.ast_map
2044                                                                   .local_def_id(type_parameter.id),
2045                                                               name)));
2046                 }
2047                 self.type_ribs.push(function_type_rib);
2048             }
2049
2050             NoTypeParameters => {
2051                 // Nothing to do.
2052             }
2053         }
2054
2055         f(self);
2056
2057         match type_parameters {
2058             HasTypeParameters(..) => {
2059                 if !self.resolved {
2060                     self.type_ribs.pop();
2061                 }
2062             }
2063             NoTypeParameters => {}
2064         }
2065     }
2066
2067     fn with_label_rib<F>(&mut self, f: F)
2068         where F: FnOnce(&mut Resolver)
2069     {
2070         self.label_ribs.push(Rib::new(NormalRibKind));
2071         f(self);
2072         if !self.resolved {
2073             self.label_ribs.pop();
2074         }
2075     }
2076
2077     fn with_constant_rib<F>(&mut self, f: F)
2078         where F: FnOnce(&mut Resolver)
2079     {
2080         self.value_ribs.push(Rib::new(ConstantItemRibKind));
2081         self.type_ribs.push(Rib::new(ConstantItemRibKind));
2082         f(self);
2083         if !self.resolved {
2084             self.type_ribs.pop();
2085             self.value_ribs.pop();
2086         }
2087     }
2088
2089     fn resolve_function(&mut self, rib_kind: RibKind, declaration: &FnDecl, block: &Block) {
2090         // Create a value rib for the function.
2091         self.value_ribs.push(Rib::new(rib_kind));
2092
2093         // Create a label rib for the function.
2094         self.label_ribs.push(Rib::new(rib_kind));
2095
2096         // Add each argument to the rib.
2097         let mut bindings_list = HashMap::new();
2098         for argument in &declaration.inputs {
2099             self.resolve_pattern(&*argument.pat, ArgumentIrrefutableMode, &mut bindings_list);
2100
2101             self.visit_ty(&*argument.ty);
2102
2103             debug!("(resolving function) recorded argument");
2104         }
2105         intravisit::walk_fn_ret_ty(self, &declaration.output);
2106
2107         // Resolve the function body.
2108         self.visit_block(block);
2109
2110         debug!("(resolving function) leaving function");
2111
2112         if !self.resolved {
2113             self.label_ribs.pop();
2114             self.value_ribs.pop();
2115         }
2116     }
2117
2118     fn resolve_trait_reference(&mut self,
2119                                id: NodeId,
2120                                trait_path: &Path,
2121                                path_depth: usize)
2122                                -> Result<PathResolution, ()> {
2123         if let Some(path_res) = self.resolve_path(id, trait_path, path_depth, TypeNS, true) {
2124             if let DefTrait(_) = path_res.base_def {
2125                 debug!("(resolving trait) found trait def: {:?}", path_res);
2126                 Ok(path_res)
2127             } else {
2128                 resolve_error(self,
2129                               trait_path.span,
2130                               ResolutionError::IsNotATrait(&*path_names_to_string(trait_path,
2131                                                                                   path_depth)));
2132
2133                 // If it's a typedef, give a note
2134                 if let DefTy(..) = path_res.base_def {
2135                     self.session
2136                         .span_note(trait_path.span, "`type` aliases cannot be used for traits");
2137                 }
2138                 Err(())
2139             }
2140         } else {
2141             resolve_error(self,
2142                           trait_path.span,
2143                           ResolutionError::UndeclaredTraitName(&*path_names_to_string(trait_path,
2144                                                                                       path_depth)));
2145             Err(())
2146         }
2147     }
2148
2149     fn resolve_generics(&mut self, generics: &Generics) {
2150         for type_parameter in generics.ty_params.iter() {
2151             self.check_if_primitive_type_name(type_parameter.name, type_parameter.span);
2152         }
2153         for predicate in &generics.where_clause.predicates {
2154             match predicate {
2155                 &hir::WherePredicate::BoundPredicate(_) |
2156                 &hir::WherePredicate::RegionPredicate(_) => {}
2157                 &hir::WherePredicate::EqPredicate(ref eq_pred) => {
2158                     let path_res = self.resolve_path(eq_pred.id, &eq_pred.path, 0, TypeNS, true);
2159                     if let Some(PathResolution { base_def: DefTyParam(..), .. }) = path_res {
2160                         self.record_def(eq_pred.id, path_res.unwrap());
2161                     } else {
2162                         resolve_error(self,
2163                                       eq_pred.span,
2164                                       ResolutionError::UndeclaredAssociatedType);
2165                     }
2166                 }
2167             }
2168         }
2169         intravisit::walk_generics(self, generics);
2170     }
2171
2172     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
2173         where F: FnOnce(&mut Resolver) -> T
2174     {
2175         // Handle nested impls (inside fn bodies)
2176         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
2177         let result = f(self);
2178         self.current_self_type = previous_value;
2179         result
2180     }
2181
2182     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
2183         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
2184     {
2185         let mut new_val = None;
2186         let mut new_id = None;
2187         if let Some(trait_ref) = opt_trait_ref {
2188             if let Ok(path_res) = self.resolve_trait_reference(trait_ref.ref_id,
2189                                                                &trait_ref.path,
2190                                                                0) {
2191                 assert!(path_res.depth == 0);
2192                 self.record_def(trait_ref.ref_id, path_res);
2193                 new_val = Some((path_res.base_def.def_id(), trait_ref.clone()));
2194                 new_id = Some(path_res.base_def.def_id());
2195             }
2196             intravisit::walk_trait_ref(self, trait_ref);
2197         }
2198         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
2199         let result = f(self, new_id);
2200         self.current_trait_ref = original_trait_ref;
2201         result
2202     }
2203
2204     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
2205         where F: FnOnce(&mut Resolver)
2206     {
2207         let mut self_type_rib = Rib::new(NormalRibKind);
2208
2209         // plain insert (no renaming, types are not currently hygienic....)
2210         let name = special_names::type_self;
2211         self_type_rib.bindings.insert(name, DlDef(self_def));
2212         self.type_ribs.push(self_type_rib);
2213         f(self);
2214         if !self.resolved {
2215             self.type_ribs.pop();
2216         }
2217     }
2218
2219     fn resolve_implementation(&mut self,
2220                               generics: &Generics,
2221                               opt_trait_reference: &Option<TraitRef>,
2222                               self_type: &Ty,
2223                               item_id: NodeId,
2224                               impl_items: &[ImplItem]) {
2225         // If applicable, create a rib for the type parameters.
2226         self.with_type_parameter_rib(HasTypeParameters(generics,
2227                                                        TypeSpace,
2228                                                        ItemRibKind),
2229                                      |this| {
2230             // Resolve the type parameters.
2231             this.visit_generics(generics);
2232
2233             // Resolve the trait reference, if necessary.
2234             this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
2235                 // Resolve the self type.
2236                 this.visit_ty(self_type);
2237
2238                 this.with_self_rib(DefSelfTy(trait_id, Some((item_id, self_type.id))), |this| {
2239                     this.with_current_self_type(self_type, |this| {
2240                         for impl_item in impl_items {
2241                             match impl_item.node {
2242                                 hir::ImplItemKind::Const(..) => {
2243                                     // If this is a trait impl, ensure the const
2244                                     // exists in trait
2245                                     this.check_trait_item(impl_item.name,
2246                                                           impl_item.span,
2247                                         |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
2248                                     this.with_constant_rib(|this| {
2249                                         intravisit::walk_impl_item(this, impl_item);
2250                                     });
2251                                 }
2252                                 hir::ImplItemKind::Method(ref sig, _) => {
2253                                     // If this is a trait impl, ensure the method
2254                                     // exists in trait
2255                                     this.check_trait_item(impl_item.name,
2256                                                           impl_item.span,
2257                                         |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
2258
2259                                     // We also need a new scope for the method-
2260                                     // specific type parameters.
2261                                     let type_parameters =
2262                                         HasTypeParameters(&sig.generics,
2263                                                           FnSpace,
2264                                                           MethodRibKind);
2265                                     this.with_type_parameter_rib(type_parameters, |this| {
2266                                         intravisit::walk_impl_item(this, impl_item);
2267                                     });
2268                                 }
2269                                 hir::ImplItemKind::Type(ref ty) => {
2270                                     // If this is a trait impl, ensure the type
2271                                     // exists in trait
2272                                     this.check_trait_item(impl_item.name,
2273                                                           impl_item.span,
2274                                         |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
2275
2276                                     this.visit_ty(ty);
2277                                 }
2278                             }
2279                         }
2280                     });
2281                 });
2282             });
2283         });
2284     }
2285
2286     fn check_trait_item<F>(&self, name: Name, span: Span, err: F)
2287         where F: FnOnce(Name, &str) -> ResolutionError
2288     {
2289         // If there is a TraitRef in scope for an impl, then the method must be in the
2290         // trait.
2291         if let Some((did, ref trait_ref)) = self.current_trait_ref {
2292             if !self.trait_item_map.contains_key(&(name, did)) {
2293                 let path_str = path_names_to_string(&trait_ref.path, 0);
2294                 resolve_error(self, span, err(name, &*path_str));
2295             }
2296         }
2297     }
2298
2299     fn resolve_local(&mut self, local: &Local) {
2300         // Resolve the type.
2301         walk_list!(self, visit_ty, &local.ty);
2302
2303         // Resolve the initializer.
2304         walk_list!(self, visit_expr, &local.init);
2305
2306         // Resolve the pattern.
2307         self.resolve_pattern(&*local.pat, LocalIrrefutableMode, &mut HashMap::new());
2308     }
2309
2310     // build a map from pattern identifiers to binding-info's.
2311     // this is done hygienically. This could arise for a macro
2312     // that expands into an or-pattern where one 'x' was from the
2313     // user and one 'x' came from the macro.
2314     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2315         let mut result = HashMap::new();
2316         pat_bindings(&self.def_map, pat, |binding_mode, _id, sp, path1| {
2317             let name = path1.node;
2318             result.insert(name,
2319                           BindingInfo {
2320                               span: sp,
2321                               binding_mode: binding_mode,
2322                           });
2323         });
2324         return result;
2325     }
2326
2327     // check that all of the arms in an or-pattern have exactly the
2328     // same set of bindings, with the same binding modes for each.
2329     fn check_consistent_bindings(&mut self, arm: &Arm) {
2330         if arm.pats.is_empty() {
2331             return;
2332         }
2333         let map_0 = self.binding_mode_map(&*arm.pats[0]);
2334         for (i, p) in arm.pats.iter().enumerate() {
2335             let map_i = self.binding_mode_map(&**p);
2336
2337             for (&key, &binding_0) in &map_0 {
2338                 match map_i.get(&key) {
2339                     None => {
2340                         resolve_error(self,
2341                                       p.span,
2342                                       ResolutionError::VariableNotBoundInPattern(key, i + 1));
2343                     }
2344                     Some(binding_i) => {
2345                         if binding_0.binding_mode != binding_i.binding_mode {
2346                             resolve_error(self,
2347                                           binding_i.span,
2348                                           ResolutionError::VariableBoundWithDifferentMode(key,
2349                                                                                           i + 1));
2350                         }
2351                     }
2352                 }
2353             }
2354
2355             for (&key, &binding) in &map_i {
2356                 if !map_0.contains_key(&key) {
2357                     resolve_error(self,
2358                                   binding.span,
2359                                   ResolutionError::VariableNotBoundInParentPattern(key, i + 1));
2360                 }
2361             }
2362         }
2363     }
2364
2365     fn resolve_arm(&mut self, arm: &Arm) {
2366         self.value_ribs.push(Rib::new(NormalRibKind));
2367
2368         let mut bindings_list = HashMap::new();
2369         for pattern in &arm.pats {
2370             self.resolve_pattern(&**pattern, RefutableMode, &mut bindings_list);
2371         }
2372
2373         // This has to happen *after* we determine which
2374         // pat_idents are variants
2375         self.check_consistent_bindings(arm);
2376
2377         walk_list!(self, visit_expr, &arm.guard);
2378         self.visit_expr(&*arm.body);
2379
2380         if !self.resolved {
2381             self.value_ribs.pop();
2382         }
2383     }
2384
2385     fn resolve_block(&mut self, block: &Block) {
2386         debug!("(resolving block) entering block");
2387         self.value_ribs.push(Rib::new(NormalRibKind));
2388
2389         // Move down in the graph, if there's an anonymous module rooted here.
2390         let orig_module = self.current_module.clone();
2391         match orig_module.anonymous_children.borrow().get(&block.id) {
2392             None => {
2393                 // Nothing to do.
2394             }
2395             Some(anonymous_module) => {
2396                 debug!("(resolving block) found anonymous module, moving down");
2397                 self.current_module = anonymous_module.clone();
2398             }
2399         }
2400
2401         // Check for imports appearing after non-item statements.
2402         let mut found_non_item = false;
2403         for statement in &block.stmts {
2404             if let hir::StmtDecl(ref declaration, _) = statement.node {
2405                 if let hir::DeclItem(i) = declaration.node {
2406                     let i = self.ast_map.expect_item(i.id);
2407                     match i.node {
2408                         ItemExternCrate(_) | ItemUse(_) if found_non_item => {
2409                             span_err!(self.session,
2410                                       i.span,
2411                                       E0154,
2412                                       "imports are not allowed after non-item statements");
2413                         }
2414                         _ => {}
2415                     }
2416                 } else {
2417                     found_non_item = true
2418                 }
2419             } else {
2420                 found_non_item = true;
2421             }
2422         }
2423
2424         // Descend into the block.
2425         intravisit::walk_block(self, block);
2426
2427         // Move back up.
2428         if !self.resolved {
2429             self.current_module = orig_module;
2430             self.value_ribs.pop();
2431         }
2432         debug!("(resolving block) leaving block");
2433     }
2434
2435     fn resolve_type(&mut self, ty: &Ty) {
2436         match ty.node {
2437             TyPath(ref maybe_qself, ref path) => {
2438                 let resolution = match self.resolve_possibly_assoc_item(ty.id,
2439                                                                         maybe_qself.as_ref(),
2440                                                                         path,
2441                                                                         TypeNS,
2442                                                                         true) {
2443                     // `<T>::a::b::c` is resolved by typeck alone.
2444                     TypecheckRequired => {
2445                         // Resolve embedded types.
2446                         intravisit::walk_ty(self, ty);
2447                         return;
2448                     }
2449                     ResolveAttempt(resolution) => resolution,
2450                 };
2451
2452                 // This is a path in the type namespace. Walk through scopes
2453                 // looking for it.
2454                 match resolution {
2455                     Some(def) => {
2456                         // Write the result into the def map.
2457                         debug!("(resolving type) writing resolution for `{}` (id {}) = {:?}",
2458                                path_names_to_string(path, 0),
2459                                ty.id,
2460                                def);
2461                         self.record_def(ty.id, def);
2462                     }
2463                     None => {
2464                         // Keep reporting some errors even if they're ignored above.
2465                         self.resolve_path(ty.id, path, 0, TypeNS, true);
2466
2467                         let kind = if maybe_qself.is_some() {
2468                             "associated type"
2469                         } else {
2470                             "type name"
2471                         };
2472
2473                         let self_type_name = special_idents::type_self.name;
2474                         let is_invalid_self_type_name = path.segments.len() > 0 &&
2475                                                         maybe_qself.is_none() &&
2476                                                         path.segments[0].identifier.name ==
2477                                                         self_type_name;
2478                         if is_invalid_self_type_name {
2479                             resolve_error(self,
2480                                           ty.span,
2481                                           ResolutionError::SelfUsedOutsideImplOrTrait);
2482                         } else {
2483                             resolve_error(self,
2484                                           ty.span,
2485                                           ResolutionError::UseOfUndeclared(
2486                                                                     kind,
2487                                                                     &*path_names_to_string(path,
2488                                                                                            0))
2489                                          );
2490                         }
2491                     }
2492                 }
2493             }
2494             _ => {}
2495         }
2496         // Resolve embedded types.
2497         intravisit::walk_ty(self, ty);
2498     }
2499
2500     fn resolve_pattern(&mut self,
2501                        pattern: &Pat,
2502                        mode: PatternBindingMode,
2503                        // Maps idents to the node ID for the (outermost)
2504                        // pattern that binds them
2505                        bindings_list: &mut HashMap<Name, NodeId>) {
2506         let pat_id = pattern.id;
2507         walk_pat(pattern, |pattern| {
2508             match pattern.node {
2509                 PatIdent(binding_mode, ref path1, ref at_rhs) => {
2510                     // The meaning of PatIdent with no type parameters
2511                     // depends on whether an enum variant or unit-like struct
2512                     // with that name is in scope. The probing lookup has to
2513                     // be careful not to emit spurious errors. Only matching
2514                     // patterns (match) can match nullary variants or
2515                     // unit-like structs. For binding patterns (let
2516                     // and the LHS of @-patterns), matching such a value is
2517                     // simply disallowed (since it's rarely what you want).
2518                     let const_ok = mode == RefutableMode && at_rhs.is_none();
2519
2520                     let ident = path1.node;
2521                     let renamed = ident.name;
2522
2523                     match self.resolve_bare_identifier_pattern(ident.unhygienic_name,
2524                                                                pattern.span) {
2525                         FoundStructOrEnumVariant(def, lp) if const_ok => {
2526                             debug!("(resolving pattern) resolving `{}` to struct or enum variant",
2527                                    renamed);
2528
2529                             self.enforce_default_binding_mode(pattern,
2530                                                               binding_mode,
2531                                                               "an enum variant");
2532                             self.record_def(pattern.id,
2533                                             PathResolution {
2534                                                 base_def: def,
2535                                                 last_private: lp,
2536                                                 depth: 0,
2537                                             });
2538                         }
2539                         FoundStructOrEnumVariant(..) => {
2540                             resolve_error(
2541                                 self,
2542                                 pattern.span,
2543                                 ResolutionError::DeclarationShadowsEnumVariantOrUnitLikeStruct(
2544                                     renamed)
2545                             );
2546                         }
2547                         FoundConst(def, lp, _) if const_ok => {
2548                             debug!("(resolving pattern) resolving `{}` to constant", renamed);
2549
2550                             self.enforce_default_binding_mode(pattern, binding_mode, "a constant");
2551                             self.record_def(pattern.id,
2552                                             PathResolution {
2553                                                 base_def: def,
2554                                                 last_private: lp,
2555                                                 depth: 0,
2556                                             });
2557                         }
2558                         FoundConst(def, _, name) => {
2559                             resolve_error(
2560                                 self,
2561                                 pattern.span,
2562                                 ResolutionError::OnlyIrrefutablePatternsAllowedHere(def.def_id(),
2563                                                                                     name)
2564                             );
2565                         }
2566                         BareIdentifierPatternUnresolved => {
2567                             debug!("(resolving pattern) binding `{}`", renamed);
2568
2569                             let def_id = self.ast_map.local_def_id(pattern.id);
2570                             let def = DefLocal(def_id, pattern.id);
2571
2572                             // Record the definition so that later passes
2573                             // will be able to distinguish variants from
2574                             // locals in patterns.
2575
2576                             self.record_def(pattern.id,
2577                                             PathResolution {
2578                                                 base_def: def,
2579                                                 last_private: LastMod(AllPublic),
2580                                                 depth: 0,
2581                                             });
2582
2583                             // Add the binding to the local ribs, if it
2584                             // doesn't already exist in the bindings list. (We
2585                             // must not add it if it's in the bindings list
2586                             // because that breaks the assumptions later
2587                             // passes make about or-patterns.)
2588                             if !bindings_list.contains_key(&renamed) {
2589                                 let this = &mut *self;
2590                                 let last_rib = this.value_ribs.last_mut().unwrap();
2591                                 last_rib.bindings.insert(renamed, DlDef(def));
2592                                 bindings_list.insert(renamed, pat_id);
2593                             } else if mode == ArgumentIrrefutableMode &&
2594                                bindings_list.contains_key(&renamed) {
2595                                 // Forbid duplicate bindings in the same
2596                                 // parameter list.
2597                                 resolve_error(
2598                                     self,
2599                                     pattern.span,
2600                                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2601                                         &ident.name.as_str())
2602                                 );
2603                             } else if bindings_list.get(&renamed) == Some(&pat_id) {
2604                                 // Then this is a duplicate variable in the
2605                                 // same disjunction, which is an error.
2606                                 resolve_error(
2607                                     self,
2608                                     pattern.span,
2609                                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2610                                         &ident.name.as_str())
2611                                 );
2612                             }
2613                             // Else, not bound in the same pattern: do
2614                             // nothing.
2615                         }
2616                     }
2617                 }
2618
2619                 PatEnum(ref path, _) => {
2620                     // This must be an enum variant, struct or const.
2621                     let resolution = match self.resolve_possibly_assoc_item(pat_id,
2622                                                                             None,
2623                                                                             path,
2624                                                                             ValueNS,
2625                                                                             false) {
2626                         // The below shouldn't happen because all
2627                         // qualified paths should be in PatQPath.
2628                         TypecheckRequired =>
2629                             self.session.span_bug(path.span,
2630                                                   "resolve_possibly_assoc_item claimed
2631                                      \
2632                                                    that a path in PatEnum requires typecheck
2633                                      \
2634                                                    to resolve, but qualified paths should be
2635                                      \
2636                                                    PatQPath"),
2637                         ResolveAttempt(resolution) => resolution,
2638                     };
2639                     if let Some(path_res) = resolution {
2640                         match path_res.base_def {
2641                             DefVariant(..) | DefStruct(..) | DefConst(..) => {
2642                                 self.record_def(pattern.id, path_res);
2643                             }
2644                             DefStatic(..) => {
2645                                 resolve_error(&self,
2646                                               path.span,
2647                                               ResolutionError::StaticVariableReference);
2648                             }
2649                             _ => {
2650                                 // If anything ends up here entirely resolved,
2651                                 // it's an error. If anything ends up here
2652                                 // partially resolved, that's OK, because it may
2653                                 // be a `T::CONST` that typeck will resolve.
2654                                 if path_res.depth == 0 {
2655                                     resolve_error(
2656                                         self,
2657                                         path.span,
2658                                         ResolutionError::NotAnEnumVariantStructOrConst(
2659                                             &path.segments
2660                                                  .last()
2661                                                  .unwrap()
2662                                                  .identifier
2663                                                  .name
2664                                                  .as_str())
2665                                     );
2666                                 } else {
2667                                     let const_name = path.segments
2668                                                          .last()
2669                                                          .unwrap()
2670                                                          .identifier
2671                                                          .name;
2672                                     let traits = self.get_traits_containing_item(const_name);
2673                                     self.trait_map.insert(pattern.id, traits);
2674                                     self.record_def(pattern.id, path_res);
2675                                 }
2676                             }
2677                         }
2678                     } else {
2679                         resolve_error(
2680                             self,
2681                             path.span,
2682                             ResolutionError::UnresolvedEnumVariantStructOrConst(
2683                                 &path.segments.last().unwrap().identifier.name.as_str())
2684                         );
2685                     }
2686                     intravisit::walk_path(self, path);
2687                 }
2688
2689                 PatQPath(ref qself, ref path) => {
2690                     // Associated constants only.
2691                     let resolution = match self.resolve_possibly_assoc_item(pat_id,
2692                                                                             Some(qself),
2693                                                                             path,
2694                                                                             ValueNS,
2695                                                                             false) {
2696                         TypecheckRequired => {
2697                             // All `<T>::CONST` should end up here, and will
2698                             // require use of the trait map to resolve
2699                             // during typechecking.
2700                             let const_name = path.segments
2701                                                  .last()
2702                                                  .unwrap()
2703                                                  .identifier
2704                                                  .name;
2705                             let traits = self.get_traits_containing_item(const_name);
2706                             self.trait_map.insert(pattern.id, traits);
2707                             intravisit::walk_pat(self, pattern);
2708                             return true;
2709                         }
2710                         ResolveAttempt(resolution) => resolution,
2711                     };
2712                     if let Some(path_res) = resolution {
2713                         match path_res.base_def {
2714                             // All `<T as Trait>::CONST` should end up here, and
2715                             // have the trait already selected.
2716                             DefAssociatedConst(..) => {
2717                                 self.record_def(pattern.id, path_res);
2718                             }
2719                             _ => {
2720                                 resolve_error(
2721                                     self,
2722                                     path.span,
2723                                     ResolutionError::NotAnAssociatedConst(
2724                                         &path.segments.last().unwrap().identifier.name.as_str()
2725                                     )
2726                                 );
2727                             }
2728                         }
2729                     } else {
2730                         resolve_error(self,
2731                                       path.span,
2732                                       ResolutionError::UnresolvedAssociatedConst(&path.segments
2733                                                                                       .last()
2734                                                                                       .unwrap()
2735                                                                                       .identifier
2736                                                                                       .name
2737                                                                                       .as_str()));
2738                     }
2739                     intravisit::walk_pat(self, pattern);
2740                 }
2741
2742                 PatStruct(ref path, _, _) => {
2743                     match self.resolve_path(pat_id, path, 0, TypeNS, false) {
2744                         Some(definition) => {
2745                             self.record_def(pattern.id, definition);
2746                         }
2747                         result => {
2748                             debug!("(resolving pattern) didn't find struct def: {:?}", result);
2749                             resolve_error(
2750                                 self,
2751                                 path.span,
2752                                 ResolutionError::DoesNotNameAStruct(
2753                                     &*path_names_to_string(path, 0))
2754                             );
2755                         }
2756                     }
2757                     intravisit::walk_path(self, path);
2758                 }
2759
2760                 PatLit(_) | PatRange(..) => {
2761                     intravisit::walk_pat(self, pattern);
2762                 }
2763
2764                 _ => {
2765                     // Nothing to do.
2766                 }
2767             }
2768             true
2769         });
2770     }
2771
2772     fn resolve_bare_identifier_pattern(&mut self,
2773                                        name: Name,
2774                                        span: Span)
2775                                        -> BareIdentifierPatternResolution {
2776         let module = self.current_module.clone();
2777         match self.resolve_item_in_lexical_scope(module, name, ValueNS) {
2778             Success((target, _)) => {
2779                 debug!("(resolve bare identifier pattern) succeeded in finding {} at {:?}",
2780                        name,
2781                        target.binding.borrow());
2782                 match target.binding.def() {
2783                     None => {
2784                         panic!("resolved name in the value namespace to a set of name bindings \
2785                                 with no def?!");
2786                     }
2787                     // For the two success cases, this lookup can be
2788                     // considered as not having a private component because
2789                     // the lookup happened only within the current module.
2790                     Some(def @ DefVariant(..)) | Some(def @ DefStruct(..)) => {
2791                         return FoundStructOrEnumVariant(def, LastMod(AllPublic));
2792                     }
2793                     Some(def @ DefConst(..)) | Some(def @ DefAssociatedConst(..)) => {
2794                         return FoundConst(def, LastMod(AllPublic), name);
2795                     }
2796                     Some(DefStatic(..)) => {
2797                         resolve_error(self, span, ResolutionError::StaticVariableReference);
2798                         return BareIdentifierPatternUnresolved;
2799                     }
2800                     _ => return BareIdentifierPatternUnresolved
2801                 }
2802             }
2803
2804             Indeterminate => {
2805                 panic!("unexpected indeterminate result");
2806             }
2807             Failed(err) => {
2808                 match err {
2809                     Some((span, msg)) => {
2810                         resolve_error(self, span, ResolutionError::FailedToResolve(&*msg));
2811                     }
2812                     None => (),
2813                 }
2814
2815                 debug!("(resolve bare identifier pattern) failed to find {}", name);
2816                 return BareIdentifierPatternUnresolved;
2817             }
2818         }
2819     }
2820
2821     /// Handles paths that may refer to associated items
2822     fn resolve_possibly_assoc_item(&mut self,
2823                                    id: NodeId,
2824                                    maybe_qself: Option<&hir::QSelf>,
2825                                    path: &Path,
2826                                    namespace: Namespace,
2827                                    check_ribs: bool)
2828                                    -> AssocItemResolveResult {
2829         let max_assoc_types;
2830
2831         match maybe_qself {
2832             Some(qself) => {
2833                 if qself.position == 0 {
2834                     return TypecheckRequired;
2835                 }
2836                 max_assoc_types = path.segments.len() - qself.position;
2837                 // Make sure the trait is valid.
2838                 let _ = self.resolve_trait_reference(id, path, max_assoc_types);
2839             }
2840             None => {
2841                 max_assoc_types = path.segments.len();
2842             }
2843         }
2844
2845         let mut resolution = self.with_no_errors(|this| {
2846             this.resolve_path(id, path, 0, namespace, check_ribs)
2847         });
2848         for depth in 1..max_assoc_types {
2849             if resolution.is_some() {
2850                 break;
2851             }
2852             self.with_no_errors(|this| {
2853                 resolution = this.resolve_path(id, path, depth, TypeNS, true);
2854             });
2855         }
2856         if let Some(DefMod(_)) = resolution.map(|r| r.base_def) {
2857             // A module is not a valid type or value.
2858             resolution = None;
2859         }
2860         ResolveAttempt(resolution)
2861     }
2862
2863     /// If `check_ribs` is true, checks the local definitions first; i.e.
2864     /// doesn't skip straight to the containing module.
2865     /// Skips `path_depth` trailing segments, which is also reflected in the
2866     /// returned value. See `middle::def::PathResolution` for more info.
2867     pub fn resolve_path(&mut self,
2868                         id: NodeId,
2869                         path: &Path,
2870                         path_depth: usize,
2871                         namespace: Namespace,
2872                         check_ribs: bool)
2873                         -> Option<PathResolution> {
2874         let span = path.span;
2875         let segments = &path.segments[..path.segments.len() - path_depth];
2876
2877         let mk_res = |(def, lp)| PathResolution::new(def, lp, path_depth);
2878
2879         if path.global {
2880             let def = self.resolve_crate_relative_path(span, segments, namespace);
2881             return def.map(mk_res);
2882         }
2883
2884         // Try to find a path to an item in a module.
2885         let unqualified_def = self.resolve_identifier(segments.last().unwrap().identifier,
2886                                                       namespace,
2887                                                       check_ribs);
2888
2889         if segments.len() <= 1 {
2890             return unqualified_def.and_then(|def| self.adjust_local_def(def, span))
2891                                   .map(|def| {
2892                                       PathResolution::new(def, LastMod(AllPublic), path_depth)
2893                                   });
2894         }
2895
2896         let def = self.resolve_module_relative_path(span, segments, namespace);
2897         match (def, unqualified_def) {
2898             (Some((ref d, _)), Some(ref ud)) if *d == ud.def => {
2899                 self.session
2900                     .add_lint(lint::builtin::UNUSED_QUALIFICATIONS,
2901                               id,
2902                               span,
2903                               "unnecessary qualification".to_string());
2904             }
2905             _ => {}
2906         }
2907
2908         def.map(mk_res)
2909     }
2910
2911     // Resolve a single identifier
2912     fn resolve_identifier(&mut self,
2913                           identifier: hir::Ident,
2914                           namespace: Namespace,
2915                           check_ribs: bool)
2916                           -> Option<LocalDef> {
2917         // First, check to see whether the name is a primitive type.
2918         if namespace == TypeNS {
2919             if let Some(&prim_ty) = self.primitive_type_table
2920                                         .primitive_types
2921                                         .get(&identifier.unhygienic_name) {
2922                 return Some(LocalDef::from_def(DefPrimTy(prim_ty)));
2923             }
2924         }
2925
2926         if check_ribs {
2927             if let Some(def) = self.resolve_identifier_in_local_ribs(identifier, namespace) {
2928                 return Some(def);
2929             }
2930         }
2931
2932         self.resolve_item_by_name_in_lexical_scope(identifier.unhygienic_name, namespace)
2933             .map(LocalDef::from_def)
2934     }
2935
2936     // Resolve a local definition, potentially adjusting for closures.
2937     fn adjust_local_def(&mut self, local_def: LocalDef, span: Span) -> Option<Def> {
2938         let ribs = match local_def.ribs {
2939             Some((TypeNS, i)) => &self.type_ribs[i + 1..],
2940             Some((ValueNS, i)) => &self.value_ribs[i + 1..],
2941             _ => &[] as &[_],
2942         };
2943         let mut def = local_def.def;
2944         match def {
2945             DefUpvar(..) => {
2946                 self.session.span_bug(span, &format!("unexpected {:?} in bindings", def))
2947             }
2948             DefLocal(_, node_id) => {
2949                 for rib in ribs {
2950                     match rib.kind {
2951                         NormalRibKind => {
2952                             // Nothing to do. Continue.
2953                         }
2954                         ClosureRibKind(function_id) => {
2955                             let prev_def = def;
2956                             let node_def_id = self.ast_map.local_def_id(node_id);
2957
2958                             let seen = self.freevars_seen
2959                                            .entry(function_id)
2960                                            .or_insert_with(|| NodeMap());
2961                             if let Some(&index) = seen.get(&node_id) {
2962                                 def = DefUpvar(node_def_id, node_id, index, function_id);
2963                                 continue;
2964                             }
2965                             let vec = self.freevars
2966                                           .entry(function_id)
2967                                           .or_insert_with(|| vec![]);
2968                             let depth = vec.len();
2969                             vec.push(Freevar {
2970                                 def: prev_def,
2971                                 span: span,
2972                             });
2973
2974                             def = DefUpvar(node_def_id, node_id, depth, function_id);
2975                             seen.insert(node_id, depth);
2976                         }
2977                         ItemRibKind | MethodRibKind => {
2978                             // This was an attempt to access an upvar inside a
2979                             // named function item. This is not allowed, so we
2980                             // report an error.
2981                             resolve_error(self,
2982                                           span,
2983                                           ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2984                             return None;
2985                         }
2986                         ConstantItemRibKind => {
2987                             // Still doesn't deal with upvars
2988                             resolve_error(self,
2989                                           span,
2990                                           ResolutionError::AttemptToUseNonConstantValueInConstant);
2991                             return None;
2992                         }
2993                     }
2994                 }
2995             }
2996             DefTyParam(..) | DefSelfTy(..) => {
2997                 for rib in ribs {
2998                     match rib.kind {
2999                         NormalRibKind | MethodRibKind | ClosureRibKind(..) => {
3000                             // Nothing to do. Continue.
3001                         }
3002                         ItemRibKind => {
3003                             // This was an attempt to use a type parameter outside
3004                             // its scope.
3005
3006                             resolve_error(self,
3007                                           span,
3008                                           ResolutionError::TypeParametersFromOuterFunction);
3009                             return None;
3010                         }
3011                         ConstantItemRibKind => {
3012                             // see #9186
3013                             resolve_error(self, span, ResolutionError::OuterTypeParameterContext);
3014                             return None;
3015                         }
3016                     }
3017                 }
3018             }
3019             _ => {}
3020         }
3021         return Some(def);
3022     }
3023
3024     // resolve a "module-relative" path, e.g. a::b::c
3025     fn resolve_module_relative_path(&mut self,
3026                                     span: Span,
3027                                     segments: &[hir::PathSegment],
3028                                     namespace: Namespace)
3029                                     -> Option<(Def, LastPrivate)> {
3030         let module_path = segments.split_last()
3031                                   .unwrap()
3032                                   .1
3033                                   .iter()
3034                                   .map(|ps| ps.identifier.name)
3035                                   .collect::<Vec<_>>();
3036
3037         let containing_module;
3038         let last_private;
3039         let current_module = self.current_module.clone();
3040         match self.resolve_module_path(current_module,
3041                                        &module_path[..],
3042                                        UseLexicalScope,
3043                                        span,
3044                                        PathSearch) {
3045             Failed(err) => {
3046                 let (span, msg) = match err {
3047                     Some((span, msg)) => (span, msg),
3048                     None => {
3049                         let msg = format!("Use of undeclared type or module `{}`",
3050                                           names_to_string(&module_path));
3051                         (span, msg)
3052                     }
3053                 };
3054
3055                 resolve_error(self, span, ResolutionError::FailedToResolve(&*msg));
3056                 return None;
3057             }
3058             Indeterminate => panic!("indeterminate unexpected"),
3059             Success((resulting_module, resulting_last_private)) => {
3060                 containing_module = resulting_module;
3061                 last_private = resulting_last_private;
3062             }
3063         }
3064
3065         let name = segments.last().unwrap().identifier.name;
3066         let def = match self.resolve_name_in_module(containing_module.clone(),
3067                                                     name,
3068                                                     namespace,
3069                                                     NameSearchType::PathSearch,
3070                                                     false) {
3071             Success((Target { binding, .. }, _)) => {
3072                 let (def, lp) = binding.def_and_lp();
3073                 (def, last_private.or(lp))
3074             }
3075             _ => return None,
3076         };
3077         if let Some(DefId{krate: kid, ..}) = containing_module.def_id() {
3078             self.used_crates.insert(kid);
3079         }
3080         return Some(def);
3081     }
3082
3083     /// Invariant: This must be called only during main resolution, not during
3084     /// import resolution.
3085     fn resolve_crate_relative_path(&mut self,
3086                                    span: Span,
3087                                    segments: &[hir::PathSegment],
3088                                    namespace: Namespace)
3089                                    -> Option<(Def, LastPrivate)> {
3090         let module_path = segments.split_last()
3091                                   .unwrap()
3092                                   .1
3093                                   .iter()
3094                                   .map(|ps| ps.identifier.name)
3095                                   .collect::<Vec<_>>();
3096
3097         let root_module = self.graph_root.clone();
3098
3099         let containing_module;
3100         let last_private;
3101         match self.resolve_module_path_from_root(root_module,
3102                                                  &module_path[..],
3103                                                  0,
3104                                                  span,
3105                                                  PathSearch,
3106                                                  LastMod(AllPublic)) {
3107             Failed(err) => {
3108                 let (span, msg) = match err {
3109                     Some((span, msg)) => (span, msg),
3110                     None => {
3111                         let msg = format!("Use of undeclared module `::{}`",
3112                                           names_to_string(&module_path[..]));
3113                         (span, msg)
3114                     }
3115                 };
3116
3117                 resolve_error(self, span, ResolutionError::FailedToResolve(&*msg));
3118                 return None;
3119             }
3120
3121             Indeterminate => {
3122                 panic!("indeterminate unexpected");
3123             }
3124
3125             Success((resulting_module, resulting_last_private)) => {
3126                 containing_module = resulting_module;
3127                 last_private = resulting_last_private;
3128             }
3129         }
3130
3131         let name = segments.last().unwrap().identifier.name;
3132         match self.resolve_name_in_module(containing_module,
3133                                           name,
3134                                           namespace,
3135                                           NameSearchType::PathSearch,
3136                                           false) {
3137             Success((Target { binding, .. }, _)) => {
3138                 let (def, lp) = binding.def_and_lp();
3139                 Some((def, last_private.or(lp)))
3140             }
3141             _ => None,
3142         }
3143     }
3144
3145     fn resolve_identifier_in_local_ribs(&mut self,
3146                                         ident: hir::Ident,
3147                                         namespace: Namespace)
3148                                         -> Option<LocalDef> {
3149         // Check the local set of ribs.
3150         let (name, ribs) = match namespace {
3151             ValueNS => (ident.name, &self.value_ribs),
3152             TypeNS => (ident.unhygienic_name, &self.type_ribs),
3153         };
3154
3155         for (i, rib) in ribs.iter().enumerate().rev() {
3156             if let Some(def_like) = rib.bindings.get(&name).cloned() {
3157                 match def_like {
3158                     DlDef(def) => {
3159                         debug!("(resolving path in local ribs) resolved `{}` to {:?} at {}",
3160                                name,
3161                                def,
3162                                i);
3163                         return Some(LocalDef {
3164                             ribs: Some((namespace, i)),
3165                             def: def,
3166                         });
3167                     }
3168                     def_like => {
3169                         debug!("(resolving path in local ribs) resolved `{}` to pseudo-def {:?}",
3170                                name,
3171                                def_like);
3172                         return None;
3173                     }
3174                 }
3175             }
3176         }
3177
3178         None
3179     }
3180
3181     fn resolve_item_by_name_in_lexical_scope(&mut self,
3182                                              name: Name,
3183                                              namespace: Namespace)
3184                                              -> Option<Def> {
3185         // Check the items.
3186         let module = self.current_module.clone();
3187         match self.resolve_item_in_lexical_scope(module, name, namespace) {
3188             Success((target, _)) => {
3189                 match target.binding.def() {
3190                     None => {
3191                         // This can happen if we were looking for a type and
3192                         // found a module instead. Modules don't have defs.
3193                         debug!("(resolving item path by identifier in lexical scope) failed to \
3194                                 resolve {} after success...",
3195                                name);
3196                         None
3197                     }
3198                     Some(def) => {
3199                         debug!("(resolving item path in lexical scope) resolved `{}` to item",
3200                                name);
3201                         // This lookup is "all public" because it only searched
3202                         // for one identifier in the current module (couldn't
3203                         // have passed through reexports or anything like that.
3204                         Some(def)
3205                     }
3206                 }
3207             }
3208             Indeterminate => {
3209                 panic!("unexpected indeterminate result");
3210             }
3211             Failed(err) => {
3212                 debug!("(resolving item path by identifier in lexical scope) failed to resolve {}",
3213                        name);
3214
3215                 if let Some((span, msg)) = err {
3216                     resolve_error(self, span, ResolutionError::FailedToResolve(&*msg))
3217                 }
3218
3219                 None
3220             }
3221         }
3222     }
3223
3224     fn with_no_errors<T, F>(&mut self, f: F) -> T
3225         where F: FnOnce(&mut Resolver) -> T
3226     {
3227         self.emit_errors = false;
3228         let rs = f(self);
3229         self.emit_errors = true;
3230         rs
3231     }
3232
3233     fn find_fallback_in_self_type(&mut self, name: Name) -> FallbackSuggestion {
3234         fn extract_path_and_node_id(t: &Ty,
3235                                     allow: FallbackChecks)
3236                                     -> Option<(Path, NodeId, FallbackChecks)> {
3237             match t.node {
3238                 TyPath(None, ref path) => Some((path.clone(), t.id, allow)),
3239                 TyPtr(ref mut_ty) => extract_path_and_node_id(&*mut_ty.ty, OnlyTraitAndStatics),
3240                 TyRptr(_, ref mut_ty) => extract_path_and_node_id(&*mut_ty.ty, allow),
3241                 // This doesn't handle the remaining `Ty` variants as they are not
3242                 // that commonly the self_type, it might be interesting to provide
3243                 // support for those in future.
3244                 _ => None,
3245             }
3246         }
3247
3248         fn get_module(this: &mut Resolver,
3249                       span: Span,
3250                       name_path: &[ast::Name])
3251                       -> Option<Rc<Module>> {
3252             let root = this.current_module.clone();
3253             let last_name = name_path.last().unwrap();
3254
3255             if name_path.len() == 1 {
3256                 match this.primitive_type_table.primitive_types.get(last_name) {
3257                     Some(_) => None,
3258                     None => {
3259                         match this.current_module.children.borrow().get(last_name) {
3260                             Some(child) => child.type_ns.module(),
3261                             None => None,
3262                         }
3263                     }
3264                 }
3265             } else {
3266                 match this.resolve_module_path(root,
3267                                                &name_path[..],
3268                                                UseLexicalScope,
3269                                                span,
3270                                                PathSearch) {
3271                     Success((module, _)) => Some(module),
3272                     _ => None,
3273                 }
3274             }
3275         }
3276
3277         fn is_static_method(this: &Resolver, did: DefId) -> bool {
3278             if let Some(node_id) = this.ast_map.as_local_node_id(did) {
3279                 let sig = match this.ast_map.get(node_id) {
3280                     hir_map::NodeTraitItem(trait_item) => match trait_item.node {
3281                         hir::MethodTraitItem(ref sig, _) => sig,
3282                         _ => return false,
3283                     },
3284                     hir_map::NodeImplItem(impl_item) => match impl_item.node {
3285                         hir::ImplItemKind::Method(ref sig, _) => sig,
3286                         _ => return false,
3287                     },
3288                     _ => return false,
3289                 };
3290                 sig.explicit_self.node == hir::SelfStatic
3291             } else {
3292                 this.session.cstore.is_static_method(did)
3293             }
3294         }
3295
3296         let (path, node_id, allowed) = match self.current_self_type {
3297             Some(ref ty) => match extract_path_and_node_id(ty, Everything) {
3298                 Some(x) => x,
3299                 None => return NoSuggestion,
3300             },
3301             None => return NoSuggestion,
3302         };
3303
3304         if allowed == Everything {
3305             // Look for a field with the same name in the current self_type.
3306             match self.def_map.borrow().get(&node_id).map(|d| d.full_def()) {
3307                 Some(DefTy(did, _)) |
3308                 Some(DefStruct(did)) |
3309                 Some(DefVariant(_, did, _)) => match self.structs.get(&did) {
3310                     None => {}
3311                     Some(fields) => {
3312                         if fields.iter().any(|&field_name| name == field_name) {
3313                             return Field;
3314                         }
3315                     }
3316                 },
3317                 _ => {} // Self type didn't resolve properly
3318             }
3319         }
3320
3321         let name_path = path.segments.iter().map(|seg| seg.identifier.name).collect::<Vec<_>>();
3322
3323         // Look for a method in the current self type's impl module.
3324         if let Some(module) = get_module(self, path.span, &name_path) {
3325             if let Some(binding) = module.children.borrow().get(&name) {
3326                 if let Some(DefMethod(did)) = binding.value_ns.def() {
3327                     if is_static_method(self, did) {
3328                         return StaticMethod(path_names_to_string(&path, 0));
3329                     }
3330                     if self.current_trait_ref.is_some() {
3331                         return TraitItem;
3332                     } else if allowed == Everything {
3333                         return Method;
3334                     }
3335                 }
3336             }
3337         }
3338
3339         // Look for a method in the current trait.
3340         if let Some((trait_did, ref trait_ref)) = self.current_trait_ref {
3341             if let Some(&did) = self.trait_item_map.get(&(name, trait_did)) {
3342                 if is_static_method(self, did) {
3343                     return TraitMethod(path_names_to_string(&trait_ref.path, 0));
3344                 } else {
3345                     return TraitItem;
3346                 }
3347             }
3348         }
3349
3350         NoSuggestion
3351     }
3352
3353     fn find_best_match_for_name(&mut self, name: &str) -> SuggestionType {
3354         let mut maybes: Vec<token::InternedString> = Vec::new();
3355         let mut values: Vec<usize> = Vec::new();
3356
3357         if let Some(macro_name) = self.session.available_macros
3358                                  .borrow().iter().find(|n| n.as_str() == name) {
3359             return SuggestionType::Macro(format!("{}!", macro_name));
3360         }
3361
3362         for rib in self.value_ribs.iter().rev() {
3363             for (&k, _) in &rib.bindings {
3364                 maybes.push(k.as_str());
3365                 values.push(usize::MAX);
3366             }
3367         }
3368
3369         let mut smallest = 0;
3370         for (i, other) in maybes.iter().enumerate() {
3371             values[i] = lev_distance(name, &other);
3372
3373             if values[i] <= values[smallest] {
3374                 smallest = i;
3375             }
3376         }
3377
3378         let max_distance = max_suggestion_distance(name);
3379         if !values.is_empty() && values[smallest] <= max_distance && name != &maybes[smallest][..] {
3380
3381             SuggestionType::Function(maybes[smallest].to_string())
3382
3383         } else {
3384             SuggestionType::NotFound
3385         }
3386     }
3387
3388     fn resolve_expr(&mut self, expr: &Expr) {
3389         // First, record candidate traits for this expression if it could
3390         // result in the invocation of a method call.
3391
3392         self.record_candidate_traits_for_expr_if_necessary(expr);
3393
3394         // Next, resolve the node.
3395         match expr.node {
3396             ExprPath(ref maybe_qself, ref path) => {
3397                 let resolution = match self.resolve_possibly_assoc_item(expr.id,
3398                                                                         maybe_qself.as_ref(),
3399                                                                         path,
3400                                                                         ValueNS,
3401                                                                         true) {
3402                     // `<T>::a::b::c` is resolved by typeck alone.
3403                     TypecheckRequired => {
3404                         let method_name = path.segments.last().unwrap().identifier.name;
3405                         let traits = self.get_traits_containing_item(method_name);
3406                         self.trait_map.insert(expr.id, traits);
3407                         intravisit::walk_expr(self, expr);
3408                         return;
3409                     }
3410                     ResolveAttempt(resolution) => resolution,
3411                 };
3412
3413                 // This is a local path in the value namespace. Walk through
3414                 // scopes looking for it.
3415                 if let Some(path_res) = resolution {
3416                     // Check if struct variant
3417                     if let DefVariant(_, _, true) = path_res.base_def {
3418                         let path_name = path_names_to_string(path, 0);
3419
3420                         resolve_error(self,
3421                                       expr.span,
3422                                       ResolutionError::StructVariantUsedAsFunction(&*path_name));
3423
3424                         let msg = format!("did you mean to write: `{} {{ /* fields */ }}`?",
3425                                           path_name);
3426                         if self.emit_errors {
3427                             self.session.fileline_help(expr.span, &msg);
3428                         } else {
3429                             self.session.span_help(expr.span, &msg);
3430                         }
3431                     } else {
3432                         // Write the result into the def map.
3433                         debug!("(resolving expr) resolved `{}`",
3434                                path_names_to_string(path, 0));
3435
3436                         // Partial resolutions will need the set of traits in scope,
3437                         // so they can be completed during typeck.
3438                         if path_res.depth != 0 {
3439                             let method_name = path.segments.last().unwrap().identifier.name;
3440                             let traits = self.get_traits_containing_item(method_name);
3441                             self.trait_map.insert(expr.id, traits);
3442                         }
3443
3444                         self.record_def(expr.id, path_res);
3445                     }
3446                 } else {
3447                     // Be helpful if the name refers to a struct
3448                     // (The pattern matching def_tys where the id is in self.structs
3449                     // matches on regular structs while excluding tuple- and enum-like
3450                     // structs, which wouldn't result in this error.)
3451                     let path_name = path_names_to_string(path, 0);
3452                     let type_res = self.with_no_errors(|this| {
3453                         this.resolve_path(expr.id, path, 0, TypeNS, false)
3454                     });
3455                     match type_res.map(|r| r.base_def) {
3456                         Some(DefTy(struct_id, _)) if self.structs.contains_key(&struct_id) => {
3457                             resolve_error(
3458                                     self,
3459                                     expr.span,
3460                                     ResolutionError::StructVariantUsedAsFunction(
3461                                         &*path_name)
3462                                 );
3463
3464                             let msg = format!("did you mean to write: `{} {{ /* fields */ }}`?",
3465                                               path_name);
3466                             if self.emit_errors {
3467                                 self.session.fileline_help(expr.span, &msg);
3468                             } else {
3469                                 self.session.span_help(expr.span, &msg);
3470                             }
3471                         }
3472                         _ => {
3473                             // Keep reporting some errors even if they're ignored above.
3474                             self.resolve_path(expr.id, path, 0, ValueNS, true);
3475
3476                             let mut method_scope = false;
3477                             self.value_ribs.iter().rev().all(|rib| {
3478                                 method_scope = match rib.kind {
3479                                     MethodRibKind => true,
3480                                     ItemRibKind | ConstantItemRibKind => false,
3481                                     _ => return true, // Keep advancing
3482                                 };
3483                                 false // Stop advancing
3484                             });
3485
3486                             if method_scope && special_names::self_.as_str() == &path_name[..] {
3487                                 resolve_error(self,
3488                                               expr.span,
3489                                               ResolutionError::SelfNotAvailableInStaticMethod);
3490                             } else {
3491                                 let last_name = path.segments.last().unwrap().identifier.name;
3492                                 let mut msg = match self.find_fallback_in_self_type(last_name) {
3493                                     NoSuggestion => {
3494                                         // limit search to 5 to reduce the number
3495                                         // of stupid suggestions
3496                                         match self.find_best_match_for_name(&path_name) {
3497                                             SuggestionType::Macro(s) => {
3498                                                 format!("the macro `{}`", s)
3499                                             }
3500                                             SuggestionType::Function(s) => format!("`{}`", s),
3501                                             SuggestionType::NotFound => "".to_string(),
3502                                         }
3503                                     }
3504                                     Field => format!("`self.{}`", path_name),
3505                                     Method |
3506                                     TraitItem => format!("to call `self.{}`", path_name),
3507                                     TraitMethod(path_str) |
3508                                     StaticMethod(path_str) =>
3509                                         format!("to call `{}::{}`", path_str, path_name),
3510                                 };
3511
3512                                 if !msg.is_empty() {
3513                                     msg = format!(". Did you mean {}?", msg)
3514                                 }
3515
3516                                 resolve_error(self,
3517                                               expr.span,
3518                                               ResolutionError::UnresolvedName(&*path_name, &*msg));
3519                             }
3520                         }
3521                     }
3522                 }
3523
3524                 intravisit::walk_expr(self, expr);
3525             }
3526
3527             ExprStruct(ref path, _, _) => {
3528                 // Resolve the path to the structure it goes to. We don't
3529                 // check to ensure that the path is actually a structure; that
3530                 // is checked later during typeck.
3531                 match self.resolve_path(expr.id, path, 0, TypeNS, false) {
3532                     Some(definition) => self.record_def(expr.id, definition),
3533                     None => {
3534                         debug!("(resolving expression) didn't find struct def",);
3535
3536                         resolve_error(self,
3537                                       path.span,
3538                                       ResolutionError::DoesNotNameAStruct(
3539                                                                 &*path_names_to_string(path, 0))
3540                                      );
3541                     }
3542                 }
3543
3544                 intravisit::walk_expr(self, expr);
3545             }
3546
3547             ExprLoop(_, Some(label)) | ExprWhile(_, _, Some(label)) => {
3548                 self.with_label_rib(|this| {
3549                     let def_like = DlDef(DefLabel(expr.id));
3550
3551                     {
3552                         let rib = this.label_ribs.last_mut().unwrap();
3553                         rib.bindings.insert(label.name, def_like);
3554                     }
3555
3556                     intravisit::walk_expr(this, expr);
3557                 })
3558             }
3559
3560             ExprBreak(Some(label)) | ExprAgain(Some(label)) => {
3561                 match self.search_label(label.node.name) {
3562                     None => {
3563                         resolve_error(self,
3564                                       label.span,
3565                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()))
3566                     }
3567                     Some(DlDef(def @ DefLabel(_))) => {
3568                         // Since this def is a label, it is never read.
3569                         self.record_def(expr.id,
3570                                         PathResolution {
3571                                             base_def: def,
3572                                             last_private: LastMod(AllPublic),
3573                                             depth: 0,
3574                                         })
3575                     }
3576                     Some(_) => {
3577                         self.session.span_bug(expr.span, "label wasn't mapped to a label def!")
3578                     }
3579                 }
3580             }
3581
3582             _ => {
3583                 intravisit::walk_expr(self, expr);
3584             }
3585         }
3586     }
3587
3588     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3589         match expr.node {
3590             ExprField(_, name) => {
3591                 // FIXME(#6890): Even though you can't treat a method like a
3592                 // field, we need to add any trait methods we find that match
3593                 // the field name so that we can do some nice error reporting
3594                 // later on in typeck.
3595                 let traits = self.get_traits_containing_item(name.node);
3596                 self.trait_map.insert(expr.id, traits);
3597             }
3598             ExprMethodCall(name, _, _) => {
3599                 debug!("(recording candidate traits for expr) recording traits for {}",
3600                        expr.id);
3601                 let traits = self.get_traits_containing_item(name.node);
3602                 self.trait_map.insert(expr.id, traits);
3603             }
3604             _ => {
3605                 // Nothing to do.
3606             }
3607         }
3608     }
3609
3610     fn get_traits_containing_item(&mut self, name: Name) -> Vec<DefId> {
3611         debug!("(getting traits containing item) looking for '{}'", name);
3612
3613         fn add_trait_info(found_traits: &mut Vec<DefId>, trait_def_id: DefId, name: Name) {
3614             debug!("(adding trait info) found trait {:?} for method '{}'",
3615                    trait_def_id,
3616                    name);
3617             found_traits.push(trait_def_id);
3618         }
3619
3620         let mut found_traits = Vec::new();
3621         let mut search_module = self.current_module.clone();
3622         loop {
3623             // Look for the current trait.
3624             match self.current_trait_ref {
3625                 Some((trait_def_id, _)) => {
3626                     if self.trait_item_map.contains_key(&(name, trait_def_id)) {
3627                         add_trait_info(&mut found_traits, trait_def_id, name);
3628                     }
3629                 }
3630                 None => {} // Nothing to do.
3631             }
3632
3633             // Look for trait children.
3634             build_reduced_graph::populate_module_if_necessary(self, &search_module);
3635
3636             {
3637                 for (_, child_names) in search_module.children.borrow().iter() {
3638                     let def = match child_names.type_ns.def() {
3639                         Some(def) => def,
3640                         None => continue,
3641                     };
3642                     let trait_def_id = match def {
3643                         DefTrait(trait_def_id) => trait_def_id,
3644                         _ => continue,
3645                     };
3646                     if self.trait_item_map.contains_key(&(name, trait_def_id)) {
3647                         add_trait_info(&mut found_traits, trait_def_id, name);
3648                     }
3649                 }
3650             }
3651
3652             // Look for imports.
3653             for (_, import) in search_module.import_resolutions.borrow().iter() {
3654                 let target = match import.target_for_namespace(TypeNS) {
3655                     None => continue,
3656                     Some(target) => target,
3657                 };
3658                 let did = match target.binding.def() {
3659                     Some(DefTrait(trait_def_id)) => trait_def_id,
3660                     Some(..) | None => continue,
3661                 };
3662                 if self.trait_item_map.contains_key(&(name, did)) {
3663                     add_trait_info(&mut found_traits, did, name);
3664                     let id = import.type_id;
3665                     self.used_imports.insert((id, TypeNS));
3666                     let trait_name = self.get_trait_name(did);
3667                     self.record_import_use(id, trait_name);
3668                     if let Some(DefId{krate: kid, ..}) = target.target_module.def_id() {
3669                         self.used_crates.insert(kid);
3670                     }
3671                 }
3672             }
3673
3674             match search_module.parent_link.clone() {
3675                 NoParentLink | ModuleParentLink(..) => break,
3676                 BlockParentLink(parent_module, _) => {
3677                     search_module = parent_module.upgrade().unwrap();
3678                 }
3679             }
3680         }
3681
3682         found_traits
3683     }
3684
3685     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3686         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3687         assert!(match resolution.last_private {
3688                     LastImport{..} => false,
3689                     _ => true,
3690                 },
3691                 "Import should only be used for `use` directives");
3692
3693         if let Some(prev_res) = self.def_map.borrow_mut().insert(node_id, resolution) {
3694             let span = self.ast_map.opt_span(node_id).unwrap_or(codemap::DUMMY_SP);
3695             self.session.span_bug(span,
3696                                   &format!("path resolved multiple times ({:?} before, {:?} now)",
3697                                            prev_res,
3698                                            resolution));
3699         }
3700     }
3701
3702     fn enforce_default_binding_mode(&mut self,
3703                                     pat: &Pat,
3704                                     pat_binding_mode: BindingMode,
3705                                     descr: &str) {
3706         match pat_binding_mode {
3707             BindByValue(_) => {}
3708             BindByRef(..) => {
3709                 resolve_error(self,
3710                               pat.span,
3711                               ResolutionError::CannotUseRefBindingModeWith(descr));
3712             }
3713         }
3714     }
3715
3716     //
3717     // Diagnostics
3718     //
3719     // Diagnostics are not particularly efficient, because they're rarely
3720     // hit.
3721     //
3722
3723     #[allow(dead_code)]   // useful for debugging
3724     fn dump_module(&mut self, module_: Rc<Module>) {
3725         debug!("Dump of module `{}`:", module_to_string(&*module_));
3726
3727         debug!("Children:");
3728         build_reduced_graph::populate_module_if_necessary(self, &module_);
3729         for (&name, _) in module_.children.borrow().iter() {
3730             debug!("* {}", name);
3731         }
3732
3733         debug!("Import resolutions:");
3734         let import_resolutions = module_.import_resolutions.borrow();
3735         for (&name, import_resolution) in import_resolutions.iter() {
3736             let value_repr;
3737             match import_resolution.target_for_namespace(ValueNS) {
3738                 None => {
3739                     value_repr = "".to_string();
3740                 }
3741                 Some(_) => {
3742                     value_repr = " value:?".to_string();
3743                     // FIXME #4954
3744                 }
3745             }
3746
3747             let type_repr;
3748             match import_resolution.target_for_namespace(TypeNS) {
3749                 None => {
3750                     type_repr = "".to_string();
3751                 }
3752                 Some(_) => {
3753                     type_repr = " type:?".to_string();
3754                     // FIXME #4954
3755                 }
3756             }
3757
3758             debug!("* {}:{}{}", name, value_repr, type_repr);
3759         }
3760     }
3761 }
3762
3763
3764 fn names_to_string(names: &[Name]) -> String {
3765     let mut first = true;
3766     let mut result = String::new();
3767     for name in names {
3768         if first {
3769             first = false
3770         } else {
3771             result.push_str("::")
3772         }
3773         result.push_str(&name.as_str());
3774     }
3775     result
3776 }
3777
3778 fn path_names_to_string(path: &Path, depth: usize) -> String {
3779     let names: Vec<ast::Name> = path.segments[..path.segments.len() - depth]
3780                                     .iter()
3781                                     .map(|seg| seg.identifier.name)
3782                                     .collect();
3783     names_to_string(&names[..])
3784 }
3785
3786 /// A somewhat inefficient routine to obtain the name of a module.
3787 fn module_to_string(module: &Module) -> String {
3788     let mut names = Vec::new();
3789
3790     fn collect_mod(names: &mut Vec<ast::Name>, module: &Module) {
3791         match module.parent_link {
3792             NoParentLink => {}
3793             ModuleParentLink(ref module, name) => {
3794                 names.push(name);
3795                 collect_mod(names, &*module.upgrade().unwrap());
3796             }
3797             BlockParentLink(ref module, _) => {
3798                 // danger, shouldn't be ident?
3799                 names.push(special_idents::opaque.name);
3800                 collect_mod(names, &*module.upgrade().unwrap());
3801             }
3802         }
3803     }
3804     collect_mod(&mut names, module);
3805
3806     if names.is_empty() {
3807         return "???".to_string();
3808     }
3809     names_to_string(&names.into_iter().rev().collect::<Vec<ast::Name>>())
3810 }
3811
3812
3813 pub struct CrateMap {
3814     pub def_map: RefCell<DefMap>,
3815     pub freevars: FreevarMap,
3816     pub export_map: ExportMap,
3817     pub trait_map: TraitMap,
3818     pub external_exports: ExternalExports,
3819     pub glob_map: Option<GlobMap>,
3820 }
3821
3822 #[derive(PartialEq,Copy, Clone)]
3823 pub enum MakeGlobMap {
3824     Yes,
3825     No,
3826 }
3827
3828 /// Entry point to crate resolution.
3829 pub fn resolve_crate<'a, 'tcx>(session: &'a Session,
3830                                ast_map: &'a hir_map::Map<'tcx>,
3831                                make_glob_map: MakeGlobMap)
3832                                -> CrateMap {
3833     let krate = ast_map.krate();
3834     let mut resolver = create_resolver(session, ast_map, krate, make_glob_map, None);
3835
3836     resolver.resolve_crate(krate);
3837     session.abort_if_errors();
3838
3839     check_unused::check_crate(&mut resolver, krate);
3840
3841     CrateMap {
3842         def_map: resolver.def_map,
3843         freevars: resolver.freevars,
3844         export_map: resolver.export_map,
3845         trait_map: resolver.trait_map,
3846         external_exports: resolver.external_exports,
3847         glob_map: if resolver.make_glob_map {
3848             Some(resolver.glob_map)
3849         } else {
3850             None
3851         },
3852     }
3853 }
3854
3855 /// Builds a name resolution walker to be used within this module,
3856 /// or used externally, with an optional callback function.
3857 ///
3858 /// The callback takes a &mut bool which allows callbacks to end a
3859 /// walk when set to true, passing through the rest of the walk, while
3860 /// preserving the ribs + current module. This allows resolve_path
3861 /// calls to be made with the correct scope info. The node in the
3862 /// callback corresponds to the current node in the walk.
3863 pub fn create_resolver<'a, 'tcx>(session: &'a Session,
3864                                  ast_map: &'a hir_map::Map<'tcx>,
3865                                  krate: &'a Crate,
3866                                  make_glob_map: MakeGlobMap,
3867                                  callback: Option<Box<Fn(hir_map::Node, &mut bool) -> bool>>)
3868                                  -> Resolver<'a, 'tcx> {
3869     let mut resolver = Resolver::new(session, ast_map, make_glob_map);
3870
3871     resolver.callback = callback;
3872
3873     build_reduced_graph::build_reduced_graph(&mut resolver, krate);
3874     session.abort_if_errors();
3875
3876     resolve_imports::resolve_imports(&mut resolver);
3877     session.abort_if_errors();
3878
3879     record_exports::record(&mut resolver);
3880     session.abort_if_errors();
3881
3882     resolver
3883 }
3884
3885 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }