src/librustc_resolve/lib.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![crate_name = "rustc_resolve"]
  12 #![crate_type = "dylib"]
  13 #![crate_type = "rlib"]
  14 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  15       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  16       html_root_url = "https://doc.rust-lang.org/nightly/")]
  17 #![deny(warnings)]
  18
  19 #![feature(associated_consts)]
  20 #![feature(rustc_diagnostic_macros)]
  21
  22 #![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
  23 #![cfg_attr(stage0, feature(rustc_private))]
  24 #![cfg_attr(stage0, feature(staged_api))]
  25
  26 #[macro_use]
  27 extern crate log;
  28 #[macro_use]
  29 extern crate syntax;
  30 extern crate syntax_pos;
  31 extern crate rustc_errors as errors;
  32 extern crate arena;
  33 #[macro_use]
  34 extern crate rustc;
  35
  36 use self::Namespace::*;
  37 use self::TypeParameters::*;
  38 use self::RibKind::*;
  39
  40 use rustc::hir::map::{Definitions, DefCollector};
  41 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  42 use rustc::middle::cstore::CrateLoader;
  43 use rustc::session::Session;
  44 use rustc::lint;
  45 use rustc::hir::def::*;
  46 use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  47 use rustc::ty;
  48 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  49 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};
  50
  51 use syntax::ext::hygiene::{Mark, SyntaxContext};
  52 use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
  53 use syntax::ext::base::SyntaxExtension;
  54 use syntax::ext::base::Determinacy::{Determined, Undetermined};
  55 use syntax::ext::base::MacroKind;
  56 use syntax::symbol::{Symbol, keywords};
  57 use syntax::util::lev_distance::find_best_match_for_name;
  58
  59 use syntax::visit::{self, FnKind, Visitor};
  60 use syntax::attr;
  61 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  62 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  63 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  64 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  65 use syntax::ast::{QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  66 use syntax::feature_gate::{feature_err, emit_feature_err, GateIssue};
  67
  68 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
  69 use errors::DiagnosticBuilder;
  70
  71 use std::cell::{Cell, RefCell};
  72 use std::cmp;
  73 use std::collections::BTreeSet;
  74 use std::fmt;
  75 use std::mem::replace;
  76 use std::rc::Rc;
  77
  78 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
  79 use macros::{InvocationData, LegacyBinding, LegacyScope, MacroBinding};
  80
  81 // NB: This module needs to be declared first so diagnostics are
  82 // registered before they are used.
  83 mod diagnostics;
  84
  85 mod macros;
  86 mod check_unused;
  87 mod build_reduced_graph;
  88 mod resolve_imports;
  89
  90 /// A free importable items suggested in case of resolution failure.
  91 struct ImportSuggestion {
  92     path: Path,
  93 }
  94
  95 /// A field or associated item from self type suggested in case of resolution failure.
  96 enum AssocSuggestion {
  97     Field,
  98     MethodWithSelf,
  99     AssocItem,
 100 }
 101
 102 #[derive(Eq)]
 103 struct BindingError {
 104     name: Name,
 105     origin: BTreeSet<Span>,
 106     target: BTreeSet<Span>,
 107 }
 108
 109 impl PartialOrd for BindingError {
 110     fn partial_cmp(&self, other: &BindingError) -> Option<cmp::Ordering> {
 111         Some(self.cmp(other))
 112     }
 113 }
 114
 115 impl PartialEq for BindingError {
 116     fn eq(&self, other: &BindingError) -> bool {
 117         self.name == other.name
 118     }
 119 }
 120
 121 impl Ord for BindingError {
 122     fn cmp(&self, other: &BindingError) -> cmp::Ordering {
 123         self.name.cmp(&other.name)
 124     }
 125 }
 126
 127 enum ResolutionError<'a> {
 128     /// error E0401: can't use type parameters from outer function
 129     TypeParametersFromOuterFunction,
 130     /// error E0402: cannot use an outer type parameter in this context
 131     OuterTypeParameterContext,
 132     /// error E0403: the name is already used for a type parameter in this type parameter list
 133     NameAlreadyUsedInTypeParameterList(Name, &'a Span),
 134     /// error E0407: method is not a member of trait
 135     MethodNotMemberOfTrait(Name, &'a str),
 136     /// error E0437: type is not a member of trait
 137     TypeNotMemberOfTrait(Name, &'a str),
 138     /// error E0438: const is not a member of trait
 139     ConstNotMemberOfTrait(Name, &'a str),
 140     /// error E0408: variable `{}` is not bound in all patterns
 141     VariableNotBoundInPattern(&'a BindingError),
 142     /// error E0409: variable `{}` is bound in inconsistent ways within the same match arm
 143     VariableBoundWithDifferentMode(Name, Span),
 144     /// error E0415: identifier is bound more than once in this parameter list
 145     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 146     /// error E0416: identifier is bound more than once in the same pattern
 147     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 148     /// error E0426: use of undeclared label
 149     UndeclaredLabel(&'a str),
 150     /// error E0429: `self` imports are only allowed within a { } list
 151     SelfImportsOnlyAllowedWithin,
 152     /// error E0430: `self` import can only appear once in the list
 153     SelfImportCanOnlyAppearOnceInTheList,
 154     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 155     SelfImportOnlyInImportListWithNonEmptyPrefix,
 156     /// error E0432: unresolved import
 157     UnresolvedImport(Option<(&'a str, &'a str)>),
 158     /// error E0433: failed to resolve
 159     FailedToResolve(&'a str),
 160     /// error E0434: can't capture dynamic environment in a fn item
 161     CannotCaptureDynamicEnvironmentInFnItem,
 162     /// error E0435: attempt to use a non-constant value in a constant
 163     AttemptToUseNonConstantValueInConstant,
 164     /// error E0530: X bindings cannot shadow Ys
 165     BindingShadowsSomethingUnacceptable(&'a str, Name, &'a NameBinding<'a>),
 166     /// error E0128: type parameters with a default cannot use forward declared identifiers
 167     ForwardDeclaredTyParam,
 168 }
 169
 170 fn resolve_error<'sess, 'a>(resolver: &'sess Resolver,
 171                             span: Span,
 172                             resolution_error: ResolutionError<'a>) {
 173     resolve_struct_error(resolver, span, resolution_error).emit();
 174 }
 175
 176 fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
 177                                    span: Span,
 178                                    resolution_error: ResolutionError<'a>)
 179                                    -> DiagnosticBuilder<'sess> {
 180     match resolution_error {
 181         ResolutionError::TypeParametersFromOuterFunction => {
 182             let mut err = struct_span_err!(resolver.session,
 183                                            span,
 184                                            E0401,
 185                                            "can't use type parameters from outer function; \
 186                                            try using a local type parameter instead");
 187             err.span_label(span, "use of type variable from outer function");
 188             err
 189         }
 190         ResolutionError::OuterTypeParameterContext => {
 191             struct_span_err!(resolver.session,
 192                              span,
 193                              E0402,
 194                              "cannot use an outer type parameter in this context")
 195         }
 196         ResolutionError::NameAlreadyUsedInTypeParameterList(name, first_use_span) => {
 197              let mut err = struct_span_err!(resolver.session,
 198                                             span,
 199                                             E0403,
 200                                             "the name `{}` is already used for a type parameter \
 201                                             in this type parameter list",
 202                                             name);
 203              err.span_label(span, "already used");
 204              err.span_label(first_use_span.clone(), format!("first use of `{}`", name));
 205              err
 206         }
 207         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 208             let mut err = struct_span_err!(resolver.session,
 209                                            span,
 210                                            E0407,
 211                                            "method `{}` is not a member of trait `{}`",
 212                                            method,
 213                                            trait_);
 214             err.span_label(span, format!("not a member of trait `{}`", trait_));
 215             err
 216         }
 217         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 218             let mut err = struct_span_err!(resolver.session,
 219                              span,
 220                              E0437,
 221                              "type `{}` is not a member of trait `{}`",
 222                              type_,
 223                              trait_);
 224             err.span_label(span, format!("not a member of trait `{}`", trait_));
 225             err
 226         }
 227         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 228             let mut err = struct_span_err!(resolver.session,
 229                              span,
 230                              E0438,
 231                              "const `{}` is not a member of trait `{}`",
 232                              const_,
 233                              trait_);
 234             err.span_label(span, format!("not a member of trait `{}`", trait_));
 235             err
 236         }
 237         ResolutionError::VariableNotBoundInPattern(binding_error) => {
 238             let target_sp = binding_error.target.iter().map(|x| *x).collect::<Vec<_>>();
 239             let msp = MultiSpan::from_spans(target_sp.clone());
 240             let msg = format!("variable `{}` is not bound in all patterns", binding_error.name);
 241             let mut err = resolver.session.struct_span_err_with_code(msp, &msg, "E0408");
 242             for sp in target_sp {
 243                 err.span_label(sp, format!("pattern doesn't bind `{}`", binding_error.name));
 244             }
 245             let origin_sp = binding_error.origin.iter().map(|x| *x).collect::<Vec<_>>();
 246             for sp in origin_sp {
 247                 err.span_label(sp, "variable not in all patterns");
 248             }
 249             err
 250         }
 251         ResolutionError::VariableBoundWithDifferentMode(variable_name,
 252                                                         first_binding_span) => {
 253             let mut err = struct_span_err!(resolver.session,
 254                              span,
 255                              E0409,
 256                              "variable `{}` is bound in inconsistent \
 257                              ways within the same match arm",
 258                              variable_name);
 259             err.span_label(span, "bound in different ways");
 260             err.span_label(first_binding_span, "first binding");
 261             err
 262         }
 263         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 264             let mut err = struct_span_err!(resolver.session,
 265                              span,
 266                              E0415,
 267                              "identifier `{}` is bound more than once in this parameter list",
 268                              identifier);
 269             err.span_label(span, "used as parameter more than once");
 270             err
 271         }
 272         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 273             let mut err = struct_span_err!(resolver.session,
 274                              span,
 275                              E0416,
 276                              "identifier `{}` is bound more than once in the same pattern",
 277                              identifier);
 278             err.span_label(span, "used in a pattern more than once");
 279             err
 280         }
 281         ResolutionError::UndeclaredLabel(name) => {
 282             let mut err = struct_span_err!(resolver.session,
 283                                            span,
 284                                            E0426,
 285                                            "use of undeclared label `{}`",
 286                                            name);
 287             err.span_label(span, format!("undeclared label `{}`", name));
 288             err
 289         }
 290         ResolutionError::SelfImportsOnlyAllowedWithin => {
 291             struct_span_err!(resolver.session,
 292                              span,
 293                              E0429,
 294                              "{}",
 295                              "`self` imports are only allowed within a { } list")
 296         }
 297         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 298             struct_span_err!(resolver.session,
 299                              span,
 300                              E0430,
 301                              "`self` import can only appear once in the list")
 302         }
 303         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 304             struct_span_err!(resolver.session,
 305                              span,
 306                              E0431,
 307                              "`self` import can only appear in an import list with a \
 308                               non-empty prefix")
 309         }
 310         ResolutionError::UnresolvedImport(name) => {
 311             let msg = match name {
 312                 Some((n, _)) => format!("unresolved import `{}`", n),
 313                 None => "unresolved import".to_owned(),
 314             };
 315             let mut err = struct_span_err!(resolver.session, span, E0432, "{}", msg);
 316             if let Some((_, p)) = name {
 317                 err.span_label(span, p);
 318             }
 319             err
 320         }
 321         ResolutionError::FailedToResolve(msg) => {
 322             let mut err = struct_span_err!(resolver.session, span, E0433,
 323                                            "failed to resolve. {}", msg);
 324             err.span_label(span, msg);
 325             err
 326         }
 327         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 328             struct_span_err!(resolver.session,
 329                              span,
 330                              E0434,
 331                              "{}",
 332                              "can't capture dynamic environment in a fn item; use the || { ... } \
 333                               closure form instead")
 334         }
 335         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 336             let mut err = struct_span_err!(resolver.session,
 337                              span,
 338                              E0435,
 339                              "attempt to use a non-constant value in a constant");
 340             err.span_label(span, "non-constant used with constant");
 341             err
 342         }
 343         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 344             let shadows_what = PathResolution::new(binding.def()).kind_name();
 345             let mut err = struct_span_err!(resolver.session,
 346                                            span,
 347                                            E0530,
 348                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 349             err.span_label(span, format!("cannot be named the same as a {}", shadows_what));
 350             let participle = if binding.is_import() { "imported" } else { "defined" };
 351             let msg = format!("a {} `{}` is {} here", shadows_what, name, participle);
 352             err.span_label(binding.span, msg);
 353             err
 354         }
 355         ResolutionError::ForwardDeclaredTyParam => {
 356             let mut err = struct_span_err!(resolver.session, span, E0128,
 357                                            "type parameters with a default cannot use \
 358                                             forward declared identifiers");
 359             err.span_label(span, format!("defaulted type parameters \
 360                                            cannot be forward declared"));
 361             err
 362         }
 363     }
 364 }
 365
 366 #[derive(Copy, Clone, Debug)]
 367 struct BindingInfo {
 368     span: Span,
 369     binding_mode: BindingMode,
 370 }
 371
 372 // Map from the name in a pattern to its binding mode.
 373 type BindingMap = FxHashMap<Ident, BindingInfo>;
 374
 375 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 376 enum PatternSource {
 377     Match,
 378     IfLet,
 379     WhileLet,
 380     Let,
 381     For,
 382     FnParam,
 383 }
 384
 385 impl PatternSource {
 386     fn is_refutable(self) -> bool {
 387         match self {
 388             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 389             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 390         }
 391     }
 392     fn descr(self) -> &'static str {
 393         match self {
 394             PatternSource::Match => "match binding",
 395             PatternSource::IfLet => "if let binding",
 396             PatternSource::WhileLet => "while let binding",
 397             PatternSource::Let => "let binding",
 398             PatternSource::For => "for binding",
 399             PatternSource::FnParam => "function parameter",
 400         }
 401     }
 402 }
 403
 404 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 405 enum PathSource<'a> {
 406     // Type paths `Path`.
 407     Type,
 408     // Trait paths in bounds or impls.
 409     Trait,
 410     // Expression paths `path`, with optional parent context.
 411     Expr(Option<&'a Expr>),
 412     // Paths in path patterns `Path`.
 413     Pat,
 414     // Paths in struct expressions and patterns `Path { .. }`.
 415     Struct,
 416     // Paths in tuple struct patterns `Path(..)`.
 417     TupleStruct,
 418     // `m::A::B` in `<T as m::A>::B::C`.
 419     TraitItem(Namespace),
 420     // Path in `pub(path)`
 421     Visibility,
 422     // Path in `use a::b::{...};`
 423     ImportPrefix,
 424 }
 425
 426 impl<'a> PathSource<'a> {
 427     fn namespace(self) -> Namespace {
 428         match self {
 429             PathSource::Type | PathSource::Trait | PathSource::Struct |
 430             PathSource::Visibility | PathSource::ImportPrefix => TypeNS,
 431             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
 432             PathSource::TraitItem(ns) => ns,
 433         }
 434     }
 435
 436     fn global_by_default(self) -> bool {
 437         match self {
 438             PathSource::Visibility | PathSource::ImportPrefix => true,
 439             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 440             PathSource::Struct | PathSource::TupleStruct |
 441             PathSource::Trait | PathSource::TraitItem(..) => false,
 442         }
 443     }
 444
 445     fn defer_to_typeck(self) -> bool {
 446         match self {
 447             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 448             PathSource::Struct | PathSource::TupleStruct => true,
 449             PathSource::Trait | PathSource::TraitItem(..) |
 450             PathSource::Visibility | PathSource::ImportPrefix => false,
 451         }
 452     }
 453
 454     fn descr_expected(self) -> &'static str {
 455         match self {
 456             PathSource::Type => "type",
 457             PathSource::Trait => "trait",
 458             PathSource::Pat => "unit struct/variant or constant",
 459             PathSource::Struct => "struct, variant or union type",
 460             PathSource::TupleStruct => "tuple struct/variant",
 461             PathSource::Visibility => "module",
 462             PathSource::ImportPrefix => "module or enum",
 463             PathSource::TraitItem(ns) => match ns {
 464                 TypeNS => "associated type",
 465                 ValueNS => "method or associated constant",
 466                 MacroNS => bug!("associated macro"),
 467             },
 468             PathSource::Expr(parent) => match parent.map(|p| &p.node) {
 469                 // "function" here means "anything callable" rather than `Def::Fn`,
 470                 // this is not precise but usually more helpful than just "value".
 471                 Some(&ExprKind::Call(..)) => "function",
 472                 _ => "value",
 473             },
 474         }
 475     }
 476
 477     fn is_expected(self, def: Def) -> bool {
 478         match self {
 479             PathSource::Type => match def {
 480                 Def::Struct(..) | Def::Union(..) | Def::Enum(..) |
 481                 Def::Trait(..) | Def::TyAlias(..) | Def::AssociatedTy(..) |
 482                 Def::PrimTy(..) | Def::TyParam(..) | Def::SelfTy(..) => true,
 483                 _ => false,
 484             },
 485             PathSource::Trait => match def {
 486                 Def::Trait(..) => true,
 487                 _ => false,
 488             },
 489             PathSource::Expr(..) => match def {
 490                 Def::StructCtor(_, CtorKind::Const) | Def::StructCtor(_, CtorKind::Fn) |
 491                 Def::VariantCtor(_, CtorKind::Const) | Def::VariantCtor(_, CtorKind::Fn) |
 492                 Def::Const(..) | Def::Static(..) | Def::Local(..) | Def::Upvar(..) |
 493                 Def::Fn(..) | Def::Method(..) | Def::AssociatedConst(..) => true,
 494                 _ => false,
 495             },
 496             PathSource::Pat => match def {
 497                 Def::StructCtor(_, CtorKind::Const) |
 498                 Def::VariantCtor(_, CtorKind::Const) |
 499                 Def::Const(..) | Def::AssociatedConst(..) => true,
 500                 _ => false,
 501             },
 502             PathSource::TupleStruct => match def {
 503                 Def::StructCtor(_, CtorKind::Fn) | Def::VariantCtor(_, CtorKind::Fn) => true,
 504                 _ => false,
 505             },
 506             PathSource::Struct => match def {
 507                 Def::Struct(..) | Def::Union(..) | Def::Variant(..) |
 508                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => true,
 509                 _ => false,
 510             },
 511             PathSource::TraitItem(ns) => match def {
 512                 Def::AssociatedConst(..) | Def::Method(..) if ns == ValueNS => true,
 513                 Def::AssociatedTy(..) if ns == TypeNS => true,
 514                 _ => false,
 515             },
 516             PathSource::ImportPrefix => match def {
 517                 Def::Mod(..) | Def::Enum(..) => true,
 518                 _ => false,
 519             },
 520             PathSource::Visibility => match def {
 521                 Def::Mod(..) => true,
 522                 _ => false,
 523             },
 524         }
 525     }
 526
 527     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
 528         __diagnostic_used!(E0404);
 529         __diagnostic_used!(E0405);
 530         __diagnostic_used!(E0412);
 531         __diagnostic_used!(E0422);
 532         __diagnostic_used!(E0423);
 533         __diagnostic_used!(E0425);
 534         __diagnostic_used!(E0531);
 535         __diagnostic_used!(E0532);
 536         __diagnostic_used!(E0573);
 537         __diagnostic_used!(E0574);
 538         __diagnostic_used!(E0575);
 539         __diagnostic_used!(E0576);
 540         __diagnostic_used!(E0577);
 541         __diagnostic_used!(E0578);
 542         match (self, has_unexpected_resolution) {
 543             (PathSource::Trait, true) => "E0404",
 544             (PathSource::Trait, false) => "E0405",
 545             (PathSource::Type, true) => "E0573",
 546             (PathSource::Type, false) => "E0412",
 547             (PathSource::Struct, true) => "E0574",
 548             (PathSource::Struct, false) => "E0422",
 549             (PathSource::Expr(..), true) => "E0423",
 550             (PathSource::Expr(..), false) => "E0425",
 551             (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
 552             (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
 553             (PathSource::TraitItem(..), true) => "E0575",
 554             (PathSource::TraitItem(..), false) => "E0576",
 555             (PathSource::Visibility, true) | (PathSource::ImportPrefix, true) => "E0577",
 556             (PathSource::Visibility, false) | (PathSource::ImportPrefix, false) => "E0578",
 557         }
 558     }
 559 }
 560
 561 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 562 pub enum Namespace {
 563     TypeNS,
 564     ValueNS,
 565     MacroNS,
 566 }
 567
 568 #[derive(Clone, Default, Debug)]
 569 pub struct PerNS<T> {
 570     value_ns: T,
 571     type_ns: T,
 572     macro_ns: Option<T>,
 573 }
 574
 575 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 576     type Output = T;
 577     fn index(&self, ns: Namespace) -> &T {
 578         match ns {
 579             ValueNS => &self.value_ns,
 580             TypeNS => &self.type_ns,
 581             MacroNS => self.macro_ns.as_ref().unwrap(),
 582         }
 583     }
 584 }
 585
 586 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 587     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 588         match ns {
 589             ValueNS => &mut self.value_ns,
 590             TypeNS => &mut self.type_ns,
 591             MacroNS => self.macro_ns.as_mut().unwrap(),
 592         }
 593     }
 594 }
 595
 596 impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
 597     fn visit_item(&mut self, item: &'tcx Item) {
 598         self.resolve_item(item);
 599     }
 600     fn visit_arm(&mut self, arm: &'tcx Arm) {
 601         self.resolve_arm(arm);
 602     }
 603     fn visit_block(&mut self, block: &'tcx Block) {
 604         self.resolve_block(block);
 605     }
 606     fn visit_expr(&mut self, expr: &'tcx Expr) {
 607         self.resolve_expr(expr, None);
 608     }
 609     fn visit_local(&mut self, local: &'tcx Local) {
 610         self.resolve_local(local);
 611     }
 612     fn visit_ty(&mut self, ty: &'tcx Ty) {
 613         if let TyKind::Path(ref qself, ref path) = ty.node {
 614             self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 615         } else if let TyKind::ImplicitSelf = ty.node {
 616             let self_ty = keywords::SelfType.ident();
 617             let def = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, Some(ty.span))
 618                           .map_or(Def::Err, |d| d.def());
 619             self.record_def(ty.id, PathResolution::new(def));
 620         } else if let TyKind::Array(ref element, ref length) = ty.node {
 621             self.visit_ty(element);
 622             self.with_constant_rib(|this| {
 623                 this.visit_expr(length);
 624             });
 625             return;
 626         }
 627         visit::walk_ty(self, ty);
 628     }
 629     fn visit_poly_trait_ref(&mut self,
 630                             tref: &'tcx ast::PolyTraitRef,
 631                             m: &'tcx ast::TraitBoundModifier) {
 632         self.smart_resolve_path(tref.trait_ref.ref_id, None,
 633                                 &tref.trait_ref.path, PathSource::Trait);
 634         visit::walk_poly_trait_ref(self, tref, m);
 635     }
 636     fn visit_variant(&mut self,
 637                      variant: &'tcx ast::Variant,
 638                      generics: &'tcx Generics,
 639                      item_id: ast::NodeId) {
 640         if let Some(ref dis_expr) = variant.node.disr_expr {
 641             // resolve the discriminator expr as a constant
 642             self.with_constant_rib(|this| {
 643                 this.visit_expr(dis_expr);
 644             });
 645         }
 646
 647         // `visit::walk_variant` without the discriminant expression.
 648         self.visit_variant_data(&variant.node.data,
 649                                 variant.node.name,
 650                                 generics,
 651                                 item_id,
 652                                 variant.span);
 653     }
 654     fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
 655         let type_parameters = match foreign_item.node {
 656             ForeignItemKind::Fn(_, ref generics) => {
 657                 HasTypeParameters(generics, ItemRibKind)
 658             }
 659             ForeignItemKind::Static(..) => NoTypeParameters,
 660         };
 661         self.with_type_parameter_rib(type_parameters, |this| {
 662             visit::walk_foreign_item(this, foreign_item);
 663         });
 664     }
 665     fn visit_fn(&mut self,
 666                 function_kind: FnKind<'tcx>,
 667                 declaration: &'tcx FnDecl,
 668                 _: Span,
 669                 node_id: NodeId) {
 670         let rib_kind = match function_kind {
 671             FnKind::ItemFn(_, generics, ..) => {
 672                 self.visit_generics(generics);
 673                 ItemRibKind
 674             }
 675             FnKind::Method(_, sig, _, _) => {
 676                 self.visit_generics(&sig.generics);
 677                 MethodRibKind(!sig.decl.has_self())
 678             }
 679             FnKind::Closure(_) => ClosureRibKind(node_id),
 680         };
 681
 682         // Create a value rib for the function.
 683         self.ribs[ValueNS].push(Rib::new(rib_kind));
 684
 685         // Create a label rib for the function.
 686         self.label_ribs.push(Rib::new(rib_kind));
 687
 688         // Add each argument to the rib.
 689         let mut bindings_list = FxHashMap();
 690         for argument in &declaration.inputs {
 691             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 692
 693             self.visit_ty(&argument.ty);
 694
 695             debug!("(resolving function) recorded argument");
 696         }
 697         visit::walk_fn_ret_ty(self, &declaration.output);
 698
 699         // Resolve the function body.
 700         match function_kind {
 701             FnKind::ItemFn(.., body) |
 702             FnKind::Method(.., body) => {
 703                 self.visit_block(body);
 704             }
 705             FnKind::Closure(body) => {
 706                 self.visit_expr(body);
 707             }
 708         };
 709
 710         debug!("(resolving function) leaving function");
 711
 712         self.label_ribs.pop();
 713         self.ribs[ValueNS].pop();
 714     }
 715     fn visit_generics(&mut self, generics: &'tcx Generics) {
 716         // For type parameter defaults, we have to ban access
 717         // to following type parameters, as the Substs can only
 718         // provide previous type parameters as they're built.
 719         let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
 720         default_ban_rib.bindings.extend(generics.ty_params.iter()
 721             .skip_while(|p| p.default.is_none())
 722             .map(|p| (Ident::with_empty_ctxt(p.ident.name), Def::Err)));
 723
 724         for param in &generics.ty_params {
 725             for bound in &param.bounds {
 726                 self.visit_ty_param_bound(bound);
 727             }
 728
 729             if let Some(ref ty) = param.default {
 730                 self.ribs[TypeNS].push(default_ban_rib);
 731                 self.visit_ty(ty);
 732                 default_ban_rib = self.ribs[TypeNS].pop().unwrap();
 733             }
 734
 735             // Allow all following defaults to refer to this type parameter.
 736             default_ban_rib.bindings.remove(&Ident::with_empty_ctxt(param.ident.name));
 737         }
 738         for lt in &generics.lifetimes { self.visit_lifetime_def(lt); }
 739         for p in &generics.where_clause.predicates { self.visit_where_predicate(p); }
 740     }
 741 }
 742
 743 pub type ErrorMessage = Option<(Span, String)>;
 744
 745 #[derive(Copy, Clone)]
 746 enum TypeParameters<'a, 'b> {
 747     NoTypeParameters,
 748     HasTypeParameters(// Type parameters.
 749                       &'b Generics,
 750
 751                       // The kind of the rib used for type parameters.
 752                       RibKind<'a>),
 753 }
 754
 755 // The rib kind controls the translation of local
 756 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 757 #[derive(Copy, Clone, Debug)]
 758 enum RibKind<'a> {
 759     // No translation needs to be applied.
 760     NormalRibKind,
 761
 762     // We passed through a closure scope at the given node ID.
 763     // Translate upvars as appropriate.
 764     ClosureRibKind(NodeId /* func id */),
 765
 766     // We passed through an impl or trait and are now in one of its
 767     // methods. Allow references to ty params that impl or trait
 768     // binds. Disallow any other upvars (including other ty params that are
 769     // upvars).
 770     //
 771     // The boolean value represents the fact that this method is static or not.
 772     MethodRibKind(bool),
 773
 774     // We passed through an item scope. Disallow upvars.
 775     ItemRibKind,
 776
 777     // We're in a constant item. Can't refer to dynamic stuff.
 778     ConstantItemRibKind,
 779
 780     // We passed through a module.
 781     ModuleRibKind(Module<'a>),
 782
 783     // We passed through a `macro_rules!` statement
 784     MacroDefinition(DefId),
 785
 786     // All bindings in this rib are type parameters that can't be used
 787     // from the default of a type parameter because they're not declared
 788     // before said type parameter. Also see the `visit_generics` override.
 789     ForwardTyParamBanRibKind,
 790 }
 791
 792 /// One local scope.
 793 #[derive(Debug)]
 794 struct Rib<'a> {
 795     bindings: FxHashMap<Ident, Def>,
 796     kind: RibKind<'a>,
 797 }
 798
 799 impl<'a> Rib<'a> {
 800     fn new(kind: RibKind<'a>) -> Rib<'a> {
 801         Rib {
 802             bindings: FxHashMap(),
 803             kind: kind,
 804         }
 805     }
 806 }
 807
 808 enum LexicalScopeBinding<'a> {
 809     Item(&'a NameBinding<'a>),
 810     Def(Def),
 811 }
 812
 813 impl<'a> LexicalScopeBinding<'a> {
 814     fn item(self) -> Option<&'a NameBinding<'a>> {
 815         match self {
 816             LexicalScopeBinding::Item(binding) => Some(binding),
 817             _ => None,
 818         }
 819     }
 820
 821     fn def(self) -> Def {
 822         match self {
 823             LexicalScopeBinding::Item(binding) => binding.def(),
 824             LexicalScopeBinding::Def(def) => def,
 825         }
 826     }
 827 }
 828
 829 #[derive(Clone)]
 830 enum PathResult<'a> {
 831     Module(Module<'a>),
 832     NonModule(PathResolution),
 833     Indeterminate,
 834     Failed(String, bool /* is the error from the last segment? */),
 835 }
 836
 837 enum ModuleKind {
 838     Block(NodeId),
 839     Def(Def, Name),
 840 }
 841
 842 /// One node in the tree of modules.
 843 pub struct ModuleData<'a> {
 844     parent: Option<Module<'a>>,
 845     kind: ModuleKind,
 846
 847     // The def id of the closest normal module (`mod`) ancestor (including this module).
 848     normal_ancestor_id: DefId,
 849
 850     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
 851     legacy_macro_resolutions: RefCell<Vec<(Mark, Ident, Span, MacroKind)>>,
 852     macro_resolutions: RefCell<Vec<(Box<[Ident]>, Span)>>,
 853
 854     // Macro invocations that can expand into items in this module.
 855     unresolved_invocations: RefCell<FxHashSet<Mark>>,
 856
 857     no_implicit_prelude: bool,
 858
 859     glob_importers: RefCell<Vec<&'a ImportDirective<'a>>>,
 860     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 861
 862     // Used to memoize the traits in this module for faster searches through all traits in scope.
 863     traits: RefCell<Option<Box<[(Ident, &'a NameBinding<'a>)]>>>,
 864
 865     // Whether this module is populated. If not populated, any attempt to
 866     // access the children must be preceded with a
 867     // `populate_module_if_necessary` call.
 868     populated: Cell<bool>,
 869 }
 870
 871 pub type Module<'a> = &'a ModuleData<'a>;
 872
 873 impl<'a> ModuleData<'a> {
 874     fn new(parent: Option<Module<'a>>, kind: ModuleKind, normal_ancestor_id: DefId) -> Self {
 875         ModuleData {
 876             parent: parent,
 877             kind: kind,
 878             normal_ancestor_id: normal_ancestor_id,
 879             resolutions: RefCell::new(FxHashMap()),
 880             legacy_macro_resolutions: RefCell::new(Vec::new()),
 881             macro_resolutions: RefCell::new(Vec::new()),
 882             unresolved_invocations: RefCell::new(FxHashSet()),
 883             no_implicit_prelude: false,
 884             glob_importers: RefCell::new(Vec::new()),
 885             globs: RefCell::new((Vec::new())),
 886             traits: RefCell::new(None),
 887             populated: Cell::new(normal_ancestor_id.is_local()),
 888         }
 889     }
 890
 891     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 892         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 893             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 894         }
 895     }
 896
 897     fn def(&self) -> Option<Def> {
 898         match self.kind {
 899             ModuleKind::Def(def, _) => Some(def),
 900             _ => None,
 901         }
 902     }
 903
 904     fn def_id(&self) -> Option<DefId> {
 905         self.def().as_ref().map(Def::def_id)
 906     }
 907
 908     // `self` resolves to the first module ancestor that `is_normal`.
 909     fn is_normal(&self) -> bool {
 910         match self.kind {
 911             ModuleKind::Def(Def::Mod(_), _) => true,
 912             _ => false,
 913         }
 914     }
 915
 916     fn is_trait(&self) -> bool {
 917         match self.kind {
 918             ModuleKind::Def(Def::Trait(_), _) => true,
 919             _ => false,
 920         }
 921     }
 922
 923     fn is_local(&self) -> bool {
 924         self.normal_ancestor_id.is_local()
 925     }
 926
 927     fn nearest_item_scope(&'a self) -> Module<'a> {
 928         if self.is_trait() { self.parent.unwrap() } else { self }
 929     }
 930 }
 931
 932 impl<'a> fmt::Debug for ModuleData<'a> {
 933     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 934         write!(f, "{:?}", self.def())
 935     }
 936 }
 937
 938 // Records a possibly-private value, type, or module definition.
 939 #[derive(Clone, Debug)]
 940 pub struct NameBinding<'a> {
 941     kind: NameBindingKind<'a>,
 942     expansion: Mark,
 943     span: Span,
 944     vis: ty::Visibility,
 945 }
 946
 947 pub trait ToNameBinding<'a> {
 948     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
 949 }
 950
 951 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
 952     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
 953         self
 954     }
 955 }
 956
 957 #[derive(Clone, Debug)]
 958 enum NameBindingKind<'a> {
 959     Def(Def),
 960     Module(Module<'a>),
 961     Import {
 962         binding: &'a NameBinding<'a>,
 963         directive: &'a ImportDirective<'a>,
 964         used: Cell<bool>,
 965         legacy_self_import: bool,
 966     },
 967     Ambiguity {
 968         b1: &'a NameBinding<'a>,
 969         b2: &'a NameBinding<'a>,
 970         legacy: bool,
 971     }
 972 }
 973
 974 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
 975
 976 struct AmbiguityError<'a> {
 977     span: Span,
 978     name: Name,
 979     lexical: bool,
 980     b1: &'a NameBinding<'a>,
 981     b2: &'a NameBinding<'a>,
 982     legacy: bool,
 983 }
 984
 985 impl<'a> NameBinding<'a> {
 986     fn module(&self) -> Option<Module<'a>> {
 987         match self.kind {
 988             NameBindingKind::Module(module) => Some(module),
 989             NameBindingKind::Import { binding, .. } => binding.module(),
 990             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
 991             _ => None,
 992         }
 993     }
 994
 995     fn def(&self) -> Def {
 996         match self.kind {
 997             NameBindingKind::Def(def) => def,
 998             NameBindingKind::Module(module) => module.def().unwrap(),
 999             NameBindingKind::Import { binding, .. } => binding.def(),
1000             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
1001             NameBindingKind::Ambiguity { .. } => Def::Err,
1002         }
1003     }
1004
1005     fn def_ignoring_ambiguity(&self) -> Def {
1006         match self.kind {
1007             NameBindingKind::Import { binding, .. } => binding.def_ignoring_ambiguity(),
1008             NameBindingKind::Ambiguity { b1, .. } => b1.def_ignoring_ambiguity(),
1009             _ => self.def(),
1010         }
1011     }
1012
1013     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
1014         resolver.get_macro(self.def_ignoring_ambiguity())
1015     }
1016
1017     // We sometimes need to treat variants as `pub` for backwards compatibility
1018     fn pseudo_vis(&self) -> ty::Visibility {
1019         if self.is_variant() { ty::Visibility::Public } else { self.vis }
1020     }
1021
1022     fn is_variant(&self) -> bool {
1023         match self.kind {
1024             NameBindingKind::Def(Def::Variant(..)) |
1025             NameBindingKind::Def(Def::VariantCtor(..)) => true,
1026             _ => false,
1027         }
1028     }
1029
1030     fn is_extern_crate(&self) -> bool {
1031         match self.kind {
1032             NameBindingKind::Import {
1033                 directive: &ImportDirective {
1034                     subclass: ImportDirectiveSubclass::ExternCrate, ..
1035                 }, ..
1036             } => true,
1037             _ => false,
1038         }
1039     }
1040
1041     fn is_import(&self) -> bool {
1042         match self.kind {
1043             NameBindingKind::Import { .. } => true,
1044             _ => false,
1045         }
1046     }
1047
1048     fn is_glob_import(&self) -> bool {
1049         match self.kind {
1050             NameBindingKind::Import { directive, .. } => directive.is_glob(),
1051             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
1052             _ => false,
1053         }
1054     }
1055
1056     fn is_importable(&self) -> bool {
1057         match self.def() {
1058             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
1059             _ => true,
1060         }
1061     }
1062 }
1063
1064 /// Interns the names of the primitive types.
1065 struct PrimitiveTypeTable {
1066     primitive_types: FxHashMap<Name, PrimTy>,
1067 }
1068
1069 impl PrimitiveTypeTable {
1070     fn new() -> PrimitiveTypeTable {
1071         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1072
1073         table.intern("bool", TyBool);
1074         table.intern("char", TyChar);
1075         table.intern("f32", TyFloat(FloatTy::F32));
1076         table.intern("f64", TyFloat(FloatTy::F64));
1077         table.intern("isize", TyInt(IntTy::Is));
1078         table.intern("i8", TyInt(IntTy::I8));
1079         table.intern("i16", TyInt(IntTy::I16));
1080         table.intern("i32", TyInt(IntTy::I32));
1081         table.intern("i64", TyInt(IntTy::I64));
1082         table.intern("i128", TyInt(IntTy::I128));
1083         table.intern("str", TyStr);
1084         table.intern("usize", TyUint(UintTy::Us));
1085         table.intern("u8", TyUint(UintTy::U8));
1086         table.intern("u16", TyUint(UintTy::U16));
1087         table.intern("u32", TyUint(UintTy::U32));
1088         table.intern("u64", TyUint(UintTy::U64));
1089         table.intern("u128", TyUint(UintTy::U128));
1090         table
1091     }
1092
1093     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1094         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1095     }
1096 }
1097
1098 /// The main resolver class.
1099 pub struct Resolver<'a> {
1100     session: &'a Session,
1101
1102     pub definitions: Definitions,
1103
1104     graph_root: Module<'a>,
1105
1106     prelude: Option<Module<'a>>,
1107
1108     trait_item_map: FxHashMap<(DefId, Name, Namespace), (Def, bool /* has self */)>,
1109
1110     // Names of fields of an item `DefId` accessible with dot syntax.
1111     // Used for hints during error reporting.
1112     field_names: FxHashMap<DefId, Vec<Name>>,
1113
1114     // All imports known to succeed or fail.
1115     determined_imports: Vec<&'a ImportDirective<'a>>,
1116
1117     // All non-determined imports.
1118     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1119
1120     // The module that represents the current item scope.
1121     current_module: Module<'a>,
1122
1123     // The current set of local scopes for types and values.
1124     // FIXME #4948: Reuse ribs to avoid allocation.
1125     ribs: PerNS<Vec<Rib<'a>>>,
1126
1127     // The current set of local scopes, for labels.
1128     label_ribs: Vec<Rib<'a>>,
1129
1130     // The trait that the current context can refer to.
1131     current_trait_ref: Option<(DefId, TraitRef)>,
1132
1133     // The current self type if inside an impl (used for better errors).
1134     current_self_type: Option<Ty>,
1135
1136     // The idents for the primitive types.
1137     primitive_type_table: PrimitiveTypeTable,
1138
1139     def_map: DefMap,
1140     pub freevars: FreevarMap,
1141     freevars_seen: NodeMap<NodeMap<usize>>,
1142     pub export_map: ExportMap,
1143     pub trait_map: TraitMap,
1144
1145     // A map from nodes to anonymous modules.
1146     // Anonymous modules are pseudo-modules that are implicitly created around items
1147     // contained within blocks.
1148     //
1149     // For example, if we have this:
1150     //
1151     //  fn f() {
1152     //      fn g() {
1153     //          ...
1154     //      }
1155     //  }
1156     //
1157     // There will be an anonymous module created around `g` with the ID of the
1158     // entry block for `f`.
1159     block_map: NodeMap<Module<'a>>,
1160     module_map: FxHashMap<DefId, Module<'a>>,
1161     extern_crate_roots: FxHashMap<(CrateNum, bool /* MacrosOnly? */), Module<'a>>,
1162
1163     pub make_glob_map: bool,
1164     // Maps imports to the names of items actually imported (this actually maps
1165     // all imports, but only glob imports are actually interesting).
1166     pub glob_map: GlobMap,
1167
1168     used_imports: FxHashSet<(NodeId, Namespace)>,
1169     pub maybe_unused_trait_imports: NodeSet,
1170
1171     privacy_errors: Vec<PrivacyError<'a>>,
1172     ambiguity_errors: Vec<AmbiguityError<'a>>,
1173     gated_errors: FxHashSet<Span>,
1174     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1175
1176     arenas: &'a ResolverArenas<'a>,
1177     dummy_binding: &'a NameBinding<'a>,
1178     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1179
1180     crate_loader: &'a mut CrateLoader,
1181     macro_names: FxHashSet<Name>,
1182     global_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1183     lexical_macro_resolutions: Vec<(Name, &'a Cell<LegacyScope<'a>>)>,
1184     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1185     macro_defs: FxHashMap<Mark, DefId>,
1186     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
1187     macro_exports: Vec<Export>,
1188     pub whitelisted_legacy_custom_derives: Vec<Name>,
1189     pub found_unresolved_macro: bool,
1190
1191     // Maps the `Mark` of an expansion to its containing module or block.
1192     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1193
1194     // Avoid duplicated errors for "name already defined".
1195     name_already_seen: FxHashMap<Name, Span>,
1196
1197     // If `#![feature(proc_macro)]` is set
1198     proc_macro_enabled: bool,
1199
1200     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1201     warned_proc_macros: FxHashSet<Name>,
1202
1203     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1204
1205     // This table maps struct IDs into struct constructor IDs,
1206     // it's not used during normal resolution, only for better error reporting.
1207     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1208 }
1209
1210 pub struct ResolverArenas<'a> {
1211     modules: arena::TypedArena<ModuleData<'a>>,
1212     local_modules: RefCell<Vec<Module<'a>>>,
1213     name_bindings: arena::TypedArena<NameBinding<'a>>,
1214     import_directives: arena::TypedArena<ImportDirective<'a>>,
1215     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1216     invocation_data: arena::TypedArena<InvocationData<'a>>,
1217     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1218 }
1219
1220 impl<'a> ResolverArenas<'a> {
1221     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1222         let module = self.modules.alloc(module);
1223         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1224             self.local_modules.borrow_mut().push(module);
1225         }
1226         module
1227     }
1228     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1229         self.local_modules.borrow()
1230     }
1231     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1232         self.name_bindings.alloc(name_binding)
1233     }
1234     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1235                               -> &'a ImportDirective {
1236         self.import_directives.alloc(import_directive)
1237     }
1238     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1239         self.name_resolutions.alloc(Default::default())
1240     }
1241     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1242                              -> &'a InvocationData<'a> {
1243         self.invocation_data.alloc(expansion_data)
1244     }
1245     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1246         self.legacy_bindings.alloc(binding)
1247     }
1248 }
1249
1250 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1251     fn parent(self, id: DefId) -> Option<DefId> {
1252         match id.krate {
1253             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1254             _ => self.session.cstore.def_key(id).parent,
1255         }.map(|index| DefId { index: index, ..id })
1256     }
1257 }
1258
1259 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1260     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1261         let namespace = if is_value { ValueNS } else { TypeNS };
1262         let hir::Path { ref segments, span, ref mut def } = *path;
1263         let path: Vec<_> = segments.iter().map(|seg| Ident::with_empty_ctxt(seg.name)).collect();
1264         match self.resolve_path(&path, Some(namespace), Some(span)) {
1265             PathResult::Module(module) => *def = module.def().unwrap(),
1266             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 =>
1267                 *def = path_res.base_def(),
1268             PathResult::NonModule(..) => match self.resolve_path(&path, None, Some(span)) {
1269                 PathResult::Failed(msg, _) => {
1270                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1271                 }
1272                 _ => {}
1273             },
1274             PathResult::Indeterminate => unreachable!(),
1275             PathResult::Failed(msg, _) => {
1276                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1277             }
1278         }
1279     }
1280
1281     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1282         self.def_map.get(&id).cloned()
1283     }
1284
1285     fn definitions(&mut self) -> &mut Definitions {
1286         &mut self.definitions
1287     }
1288 }
1289
1290 impl<'a> Resolver<'a> {
1291     pub fn new(session: &'a Session,
1292                krate: &Crate,
1293                crate_name: &str,
1294                make_glob_map: MakeGlobMap,
1295                crate_loader: &'a mut CrateLoader,
1296                arenas: &'a ResolverArenas<'a>)
1297                -> Resolver<'a> {
1298         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1299         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1300         let graph_root = arenas.alloc_module(ModuleData {
1301             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1302             ..ModuleData::new(None, root_module_kind, root_def_id)
1303         });
1304         let mut module_map = FxHashMap();
1305         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1306
1307         let mut definitions = Definitions::new();
1308         DefCollector::new(&mut definitions)
1309             .collect_root(crate_name, &session.local_crate_disambiguator().as_str());
1310
1311         let mut invocations = FxHashMap();
1312         invocations.insert(Mark::root(),
1313                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1314
1315         let features = session.features.borrow();
1316
1317         let mut macro_defs = FxHashMap();
1318         macro_defs.insert(Mark::root(), root_def_id);
1319
1320         Resolver {
1321             session: session,
1322
1323             definitions: definitions,
1324
1325             // The outermost module has def ID 0; this is not reflected in the
1326             // AST.
1327             graph_root: graph_root,
1328             prelude: None,
1329
1330             trait_item_map: FxHashMap(),
1331             field_names: FxHashMap(),
1332
1333             determined_imports: Vec::new(),
1334             indeterminate_imports: Vec::new(),
1335
1336             current_module: graph_root,
1337             ribs: PerNS {
1338                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1339                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1340                 macro_ns: Some(vec![Rib::new(ModuleRibKind(graph_root))]),
1341             },
1342             label_ribs: Vec::new(),
1343
1344             current_trait_ref: None,
1345             current_self_type: None,
1346
1347             primitive_type_table: PrimitiveTypeTable::new(),
1348
1349             def_map: NodeMap(),
1350             freevars: NodeMap(),
1351             freevars_seen: NodeMap(),
1352             export_map: NodeMap(),
1353             trait_map: NodeMap(),
1354             module_map: module_map,
1355             block_map: NodeMap(),
1356             extern_crate_roots: FxHashMap(),
1357
1358             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1359             glob_map: NodeMap(),
1360
1361             used_imports: FxHashSet(),
1362             maybe_unused_trait_imports: NodeSet(),
1363
1364             privacy_errors: Vec::new(),
1365             ambiguity_errors: Vec::new(),
1366             gated_errors: FxHashSet(),
1367             disallowed_shadowing: Vec::new(),
1368
1369             arenas: arenas,
1370             dummy_binding: arenas.alloc_name_binding(NameBinding {
1371                 kind: NameBindingKind::Def(Def::Err),
1372                 expansion: Mark::root(),
1373                 span: DUMMY_SP,
1374                 vis: ty::Visibility::Public,
1375             }),
1376
1377             // `#![feature(proc_macro)]` implies `#[feature(extern_macros)]`
1378             use_extern_macros: features.use_extern_macros || features.proc_macro,
1379
1380             crate_loader: crate_loader,
1381             macro_names: FxHashSet(),
1382             global_macros: FxHashMap(),
1383             lexical_macro_resolutions: Vec::new(),
1384             macro_map: FxHashMap(),
1385             macro_exports: Vec::new(),
1386             invocations: invocations,
1387             macro_defs: macro_defs,
1388             local_macro_def_scopes: FxHashMap(),
1389             name_already_seen: FxHashMap(),
1390             whitelisted_legacy_custom_derives: Vec::new(),
1391             proc_macro_enabled: features.proc_macro,
1392             warned_proc_macros: FxHashSet(),
1393             potentially_unused_imports: Vec::new(),
1394             struct_constructors: DefIdMap(),
1395             found_unresolved_macro: false,
1396         }
1397     }
1398
1399     pub fn arenas() -> ResolverArenas<'a> {
1400         ResolverArenas {
1401             modules: arena::TypedArena::new(),
1402             local_modules: RefCell::new(Vec::new()),
1403             name_bindings: arena::TypedArena::new(),
1404             import_directives: arena::TypedArena::new(),
1405             name_resolutions: arena::TypedArena::new(),
1406             invocation_data: arena::TypedArena::new(),
1407             legacy_bindings: arena::TypedArena::new(),
1408         }
1409     }
1410
1411     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1412         PerNS {
1413             type_ns: f(self, TypeNS),
1414             value_ns: f(self, ValueNS),
1415             macro_ns: match self.use_extern_macros {
1416                 true => Some(f(self, MacroNS)),
1417                 false => None,
1418             },
1419         }
1420     }
1421
1422     /// Entry point to crate resolution.
1423     pub fn resolve_crate(&mut self, krate: &Crate) {
1424         ImportResolver { resolver: self }.finalize_imports();
1425         self.current_module = self.graph_root;
1426         self.finalize_current_module_macro_resolutions();
1427         visit::walk_crate(self, krate);
1428
1429         check_unused::check_crate(self, krate);
1430         self.report_errors();
1431         self.crate_loader.postprocess(krate);
1432     }
1433
1434     fn new_module(&self, parent: Module<'a>, kind: ModuleKind, normal_ancestor_id: DefId)
1435                   -> Module<'a> {
1436         self.arenas.alloc_module(ModuleData::new(Some(parent), kind, normal_ancestor_id))
1437     }
1438
1439     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1440                   -> bool /* true if an error was reported */ {
1441         match binding.kind {
1442             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1443                     if !used.get() => {
1444                 used.set(true);
1445                 directive.used.set(true);
1446                 if legacy_self_import {
1447                     self.warn_legacy_self_import(directive);
1448                     return false;
1449                 }
1450                 self.used_imports.insert((directive.id, ns));
1451                 self.add_to_glob_map(directive.id, ident);
1452                 self.record_use(ident, ns, binding, span)
1453             }
1454             NameBindingKind::Import { .. } => false,
1455             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1456                 self.ambiguity_errors.push(AmbiguityError {
1457                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy: legacy,
1458                 });
1459                 if legacy {
1460                     self.record_use(ident, ns, b1, span);
1461                 }
1462                 !legacy
1463             }
1464             _ => false
1465         }
1466     }
1467
1468     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1469         if self.make_glob_map {
1470             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1471         }
1472     }
1473
1474     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1475     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1476     /// `ident` in the first scope that defines it (or None if no scopes define it).
1477     ///
1478     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1479     /// the items are defined in the block. For example,
1480     /// ```rust
1481     /// fn f() {
1482     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1483     ///    let g = || {};
1484     ///    fn g() {}
1485     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1486     /// }
1487     /// ```
1488     ///
1489     /// Invariant: This must only be called during main resolution, not during
1490     /// import resolution.
1491     fn resolve_ident_in_lexical_scope(&mut self,
1492                                       mut ident: Ident,
1493                                       ns: Namespace,
1494                                       record_used: Option<Span>)
1495                                       -> Option<LexicalScopeBinding<'a>> {
1496         if ns == TypeNS {
1497             ident = ident.unhygienize();
1498         }
1499
1500         // Walk backwards up the ribs in scope.
1501         for i in (0 .. self.ribs[ns].len()).rev() {
1502             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1503                 // The ident resolves to a type parameter or local variable.
1504                 return Some(LexicalScopeBinding::Def(
1505                     self.adjust_local_def(ns, i, def, record_used)
1506                 ));
1507             }
1508
1509             if let ModuleRibKind(module) = self.ribs[ns][i].kind {
1510                 let item = self.resolve_ident_in_module(module, ident, ns, false, record_used);
1511                 if let Ok(binding) = item {
1512                     // The ident resolves to an item.
1513                     return Some(LexicalScopeBinding::Item(binding));
1514                 }
1515
1516                 if let ModuleKind::Block(..) = module.kind { // We can see through blocks
1517                 } else if !module.no_implicit_prelude {
1518                     return self.prelude.and_then(|prelude| {
1519                         self.resolve_ident_in_module(prelude, ident, ns, false, None).ok()
1520                     }).map(LexicalScopeBinding::Item)
1521                 } else {
1522                     return None;
1523                 }
1524             }
1525
1526             if let MacroDefinition(def) = self.ribs[ns][i].kind {
1527                 // If an invocation of this macro created `ident`, give up on `ident`
1528                 // and switch to `ident`'s source from the macro definition.
1529                 let ctxt_data = ident.ctxt.data();
1530                 if def == self.macro_defs[&ctxt_data.outer_mark] {
1531                     ident.ctxt = ctxt_data.prev_ctxt;
1532                 }
1533             }
1534         }
1535
1536         None
1537     }
1538
1539     fn resolve_crate_var(&mut self, crate_var_ctxt: SyntaxContext) -> Module<'a> {
1540         let mut ctxt_data = crate_var_ctxt.data();
1541         while ctxt_data.prev_ctxt != SyntaxContext::empty() {
1542             ctxt_data = ctxt_data.prev_ctxt.data();
1543         }
1544         let module = self.macro_def_scope(ctxt_data.outer_mark);
1545         if module.is_local() { self.graph_root } else { module }
1546     }
1547
1548     // AST resolution
1549     //
1550     // We maintain a list of value ribs and type ribs.
1551     //
1552     // Simultaneously, we keep track of the current position in the module
1553     // graph in the `current_module` pointer. When we go to resolve a name in
1554     // the value or type namespaces, we first look through all the ribs and
1555     // then query the module graph. When we resolve a name in the module
1556     // namespace, we can skip all the ribs (since nested modules are not
1557     // allowed within blocks in Rust) and jump straight to the current module
1558     // graph node.
1559     //
1560     // Named implementations are handled separately. When we find a method
1561     // call, we consult the module node to find all of the implementations in
1562     // scope. This information is lazily cached in the module node. We then
1563     // generate a fake "implementation scope" containing all the
1564     // implementations thus found, for compatibility with old resolve pass.
1565
1566     fn with_scope<F>(&mut self, id: NodeId, f: F)
1567         where F: FnOnce(&mut Resolver)
1568     {
1569         let id = self.definitions.local_def_id(id);
1570         let module = self.module_map.get(&id).cloned(); // clones a reference
1571         if let Some(module) = module {
1572             // Move down in the graph.
1573             let orig_module = replace(&mut self.current_module, module);
1574             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1575             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1576
1577             self.finalize_current_module_macro_resolutions();
1578             f(self);
1579
1580             self.current_module = orig_module;
1581             self.ribs[ValueNS].pop();
1582             self.ribs[TypeNS].pop();
1583         } else {
1584             f(self);
1585         }
1586     }
1587
1588     /// Searches the current set of local scopes for labels.
1589     /// Stops after meeting a closure.
1590     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1591         for rib in self.label_ribs.iter().rev() {
1592             match rib.kind {
1593                 NormalRibKind => {
1594                     // Continue
1595                 }
1596                 MacroDefinition(def) => {
1597                     // If an invocation of this macro created `ident`, give up on `ident`
1598                     // and switch to `ident`'s source from the macro definition.
1599                     let ctxt_data = ident.ctxt.data();
1600                     if def == self.macro_defs[&ctxt_data.outer_mark] {
1601                         ident.ctxt = ctxt_data.prev_ctxt;
1602                     }
1603                 }
1604                 _ => {
1605                     // Do not resolve labels across function boundary
1606                     return None;
1607                 }
1608             }
1609             let result = rib.bindings.get(&ident).cloned();
1610             if result.is_some() {
1611                 return result;
1612             }
1613         }
1614         None
1615     }
1616
1617     fn resolve_item(&mut self, item: &Item) {
1618         let name = item.ident.name;
1619
1620         debug!("(resolving item) resolving {}", name);
1621
1622         self.check_proc_macro_attrs(&item.attrs);
1623
1624         match item.node {
1625             ItemKind::Enum(_, ref generics) |
1626             ItemKind::Ty(_, ref generics) |
1627             ItemKind::Struct(_, ref generics) |
1628             ItemKind::Union(_, ref generics) |
1629             ItemKind::Fn(.., ref generics, _) => {
1630                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1631                                              |this| visit::walk_item(this, item));
1632             }
1633
1634             ItemKind::DefaultImpl(_, ref trait_ref) => {
1635                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1636                     // Resolve type arguments in trait path
1637                     visit::walk_trait_ref(this, trait_ref);
1638                 });
1639             }
1640             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1641                 self.resolve_implementation(generics,
1642                                             opt_trait_ref,
1643                                             &self_type,
1644                                             item.id,
1645                                             impl_items),
1646
1647             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1648                 // Create a new rib for the trait-wide type parameters.
1649                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1650                     let local_def_id = this.definitions.local_def_id(item.id);
1651                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1652                         this.visit_generics(generics);
1653                         walk_list!(this, visit_ty_param_bound, bounds);
1654
1655                         for trait_item in trait_items {
1656                             this.check_proc_macro_attrs(&trait_item.attrs);
1657
1658                             match trait_item.node {
1659                                 TraitItemKind::Const(_, ref default) => {
1660                                     // Only impose the restrictions of
1661                                     // ConstRibKind if there's an actual constant
1662                                     // expression in a provided default.
1663                                     if default.is_some() {
1664                                         this.with_constant_rib(|this| {
1665                                             visit::walk_trait_item(this, trait_item)
1666                                         });
1667                                     } else {
1668                                         visit::walk_trait_item(this, trait_item)
1669                                     }
1670                                 }
1671                                 TraitItemKind::Method(ref sig, _) => {
1672                                     let type_parameters =
1673                                         HasTypeParameters(&sig.generics,
1674                                                           MethodRibKind(!sig.decl.has_self()));
1675                                     this.with_type_parameter_rib(type_parameters, |this| {
1676                                         visit::walk_trait_item(this, trait_item)
1677                                     });
1678                                 }
1679                                 TraitItemKind::Type(..) => {
1680                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1681                                         visit::walk_trait_item(this, trait_item)
1682                                     });
1683                                 }
1684                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1685                             };
1686                         }
1687                     });
1688                 });
1689             }
1690
1691             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1692                 self.with_scope(item.id, |this| {
1693                     visit::walk_item(this, item);
1694                 });
1695             }
1696
1697             ItemKind::Const(..) | ItemKind::Static(..) => {
1698                 self.with_constant_rib(|this| {
1699                     visit::walk_item(this, item);
1700                 });
1701             }
1702
1703             ItemKind::Use(ref view_path) => {
1704                 match view_path.node {
1705                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1706                         // Resolve prefix of an import with empty braces (issue #28388).
1707                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1708                     }
1709                     _ => {}
1710                 }
1711             }
1712
1713             ItemKind::ExternCrate(_) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(_)=> {
1714                 // do nothing, these are just around to be encoded
1715             }
1716
1717             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1718         }
1719     }
1720
1721     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1722         where F: FnOnce(&mut Resolver)
1723     {
1724         match type_parameters {
1725             HasTypeParameters(generics, rib_kind) => {
1726                 let mut function_type_rib = Rib::new(rib_kind);
1727                 let mut seen_bindings = FxHashMap();
1728                 for type_parameter in &generics.ty_params {
1729                     let name = type_parameter.ident.name;
1730                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1731
1732                     if seen_bindings.contains_key(&name) {
1733                         let span = seen_bindings.get(&name).unwrap();
1734                         resolve_error(self,
1735                                       type_parameter.span,
1736                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name,
1737                                                                                           span));
1738                     }
1739                     seen_bindings.entry(name).or_insert(type_parameter.span);
1740
1741                     // plain insert (no renaming)
1742                     let def_id = self.definitions.local_def_id(type_parameter.id);
1743                     let def = Def::TyParam(def_id);
1744                     function_type_rib.bindings.insert(Ident::with_empty_ctxt(name), def);
1745                     self.record_def(type_parameter.id, PathResolution::new(def));
1746                 }
1747                 self.ribs[TypeNS].push(function_type_rib);
1748             }
1749
1750             NoTypeParameters => {
1751                 // Nothing to do.
1752             }
1753         }
1754
1755         f(self);
1756
1757         if let HasTypeParameters(..) = type_parameters {
1758             self.ribs[TypeNS].pop();
1759         }
1760     }
1761
1762     fn with_label_rib<F>(&mut self, f: F)
1763         where F: FnOnce(&mut Resolver)
1764     {
1765         self.label_ribs.push(Rib::new(NormalRibKind));
1766         f(self);
1767         self.label_ribs.pop();
1768     }
1769
1770     fn with_constant_rib<F>(&mut self, f: F)
1771         where F: FnOnce(&mut Resolver)
1772     {
1773         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1774         self.ribs[TypeNS].push(Rib::new(ConstantItemRibKind));
1775         f(self);
1776         self.ribs[TypeNS].pop();
1777         self.ribs[ValueNS].pop();
1778     }
1779
1780     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1781         where F: FnOnce(&mut Resolver) -> T
1782     {
1783         // Handle nested impls (inside fn bodies)
1784         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1785         let result = f(self);
1786         self.current_self_type = previous_value;
1787         result
1788     }
1789
1790     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1791         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1792     {
1793         let mut new_val = None;
1794         let mut new_id = None;
1795         if let Some(trait_ref) = opt_trait_ref {
1796             let def = self.smart_resolve_path(trait_ref.ref_id, None,
1797                                               &trait_ref.path, PathSource::Trait).base_def();
1798             if def != Def::Err {
1799                 new_val = Some((def.def_id(), trait_ref.clone()));
1800                 new_id = Some(def.def_id());
1801             }
1802         }
1803         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1804         let result = f(self, new_id);
1805         self.current_trait_ref = original_trait_ref;
1806         result
1807     }
1808
1809     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
1810         where F: FnOnce(&mut Resolver)
1811     {
1812         let mut self_type_rib = Rib::new(NormalRibKind);
1813
1814         // plain insert (no renaming, types are not currently hygienic....)
1815         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
1816         self.ribs[TypeNS].push(self_type_rib);
1817         f(self);
1818         self.ribs[TypeNS].pop();
1819     }
1820
1821     fn resolve_implementation(&mut self,
1822                               generics: &Generics,
1823                               opt_trait_reference: &Option<TraitRef>,
1824                               self_type: &Ty,
1825                               item_id: NodeId,
1826                               impl_items: &[ImplItem]) {
1827         // If applicable, create a rib for the type parameters.
1828         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1829             // Dummy self type for better errors if `Self` is used in the trait path.
1830             this.with_self_rib(Def::SelfTy(None, None), |this| {
1831                 // Resolve the trait reference, if necessary.
1832                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1833                     let item_def_id = this.definitions.local_def_id(item_id);
1834                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
1835                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
1836                             // Resolve type arguments in trait path
1837                             visit::walk_trait_ref(this, trait_ref);
1838                         }
1839                         // Resolve the self type.
1840                         this.visit_ty(self_type);
1841                         // Resolve the type parameters.
1842                         this.visit_generics(generics);
1843                         this.with_current_self_type(self_type, |this| {
1844                             for impl_item in impl_items {
1845                                 this.check_proc_macro_attrs(&impl_item.attrs);
1846                                 this.resolve_visibility(&impl_item.vis);
1847                                 match impl_item.node {
1848                                     ImplItemKind::Const(..) => {
1849                                         // If this is a trait impl, ensure the const
1850                                         // exists in trait
1851                                         this.check_trait_item(impl_item.ident.name,
1852                                                             ValueNS,
1853                                                             impl_item.span,
1854                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
1855                                         visit::walk_impl_item(this, impl_item);
1856                                     }
1857                                     ImplItemKind::Method(ref sig, _) => {
1858                                         // If this is a trait impl, ensure the method
1859                                         // exists in trait
1860                                         this.check_trait_item(impl_item.ident.name,
1861                                                             ValueNS,
1862                                                             impl_item.span,
1863                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
1864
1865                                         // We also need a new scope for the method-
1866                                         // specific type parameters.
1867                                         let type_parameters =
1868                                             HasTypeParameters(&sig.generics,
1869                                                             MethodRibKind(!sig.decl.has_self()));
1870                                         this.with_type_parameter_rib(type_parameters, |this| {
1871                                             visit::walk_impl_item(this, impl_item);
1872                                         });
1873                                     }
1874                                     ImplItemKind::Type(ref ty) => {
1875                                         // If this is a trait impl, ensure the type
1876                                         // exists in trait
1877                                         this.check_trait_item(impl_item.ident.name,
1878                                                             TypeNS,
1879                                                             impl_item.span,
1880                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
1881
1882                                         this.visit_ty(ty);
1883                                     }
1884                                     ImplItemKind::Macro(_) =>
1885                                         panic!("unexpanded macro in resolve!"),
1886                                 }
1887                             }
1888                         });
1889                     });
1890                 });
1891             });
1892         });
1893     }
1894
1895     fn check_trait_item<F>(&self, name: Name, ns: Namespace, span: Span, err: F)
1896         where F: FnOnce(Name, &str) -> ResolutionError
1897     {
1898         // If there is a TraitRef in scope for an impl, then the method must be in the
1899         // trait.
1900         if let Some((did, ref trait_ref)) = self.current_trait_ref {
1901             if !self.trait_item_map.contains_key(&(did, name, ns)) {
1902                 let path_str = path_names_to_string(&trait_ref.path);
1903                 resolve_error(self, span, err(name, &path_str));
1904             }
1905         }
1906     }
1907
1908     fn resolve_local(&mut self, local: &Local) {
1909         // Resolve the type.
1910         walk_list!(self, visit_ty, &local.ty);
1911
1912         // Resolve the initializer.
1913         walk_list!(self, visit_expr, &local.init);
1914
1915         // Resolve the pattern.
1916         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
1917     }
1918
1919     // build a map from pattern identifiers to binding-info's.
1920     // this is done hygienically. This could arise for a macro
1921     // that expands into an or-pattern where one 'x' was from the
1922     // user and one 'x' came from the macro.
1923     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1924         let mut binding_map = FxHashMap();
1925
1926         pat.walk(&mut |pat| {
1927             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
1928                 if sub_pat.is_some() || match self.def_map.get(&pat.id).map(|res| res.base_def()) {
1929                     Some(Def::Local(..)) => true,
1930                     _ => false,
1931                 } {
1932                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
1933                     binding_map.insert(ident.node, binding_info);
1934                 }
1935             }
1936             true
1937         });
1938
1939         binding_map
1940     }
1941
1942     // check that all of the arms in an or-pattern have exactly the
1943     // same set of bindings, with the same binding modes for each.
1944     fn check_consistent_bindings(&mut self, arm: &Arm) {
1945         if arm.pats.is_empty() {
1946             return;
1947         }
1948
1949         let mut missing_vars = FxHashMap();
1950         let mut inconsistent_vars = FxHashMap();
1951         for (i, p) in arm.pats.iter().enumerate() {
1952             let map_i = self.binding_mode_map(&p);
1953
1954             for (j, q) in arm.pats.iter().enumerate() {
1955                 if i == j {
1956                     continue;
1957                 }
1958
1959                 let map_j = self.binding_mode_map(&q);
1960                 for (&key, &binding_i) in &map_i {
1961                     if map_j.len() == 0 {                   // Account for missing bindings when
1962                         let binding_error = missing_vars    // map_j has none.
1963                             .entry(key.name)
1964                             .or_insert(BindingError {
1965                                 name: key.name,
1966                                 origin: BTreeSet::new(),
1967                                 target: BTreeSet::new(),
1968                             });
1969                         binding_error.origin.insert(binding_i.span);
1970                         binding_error.target.insert(q.span);
1971                     }
1972                     for (&key_j, &binding_j) in &map_j {
1973                         match map_i.get(&key_j) {
1974                             None => {  // missing binding
1975                                 let binding_error = missing_vars
1976                                     .entry(key_j.name)
1977                                     .or_insert(BindingError {
1978                                         name: key_j.name,
1979                                         origin: BTreeSet::new(),
1980                                         target: BTreeSet::new(),
1981                                     });
1982                                 binding_error.origin.insert(binding_j.span);
1983                                 binding_error.target.insert(p.span);
1984                             }
1985                             Some(binding_i) => {  // check consistent binding
1986                                 if binding_i.binding_mode != binding_j.binding_mode {
1987                                     inconsistent_vars
1988                                         .entry(key.name)
1989                                         .or_insert((binding_j.span, binding_i.span));
1990                                 }
1991                             }
1992                         }
1993                     }
1994                 }
1995             }
1996         }
1997         let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();
1998         missing_vars.sort();
1999         for (_, v) in missing_vars {
2000             resolve_error(self,
2001                           *v.origin.iter().next().unwrap(),
2002                           ResolutionError::VariableNotBoundInPattern(v));
2003         }
2004         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2005         inconsistent_vars.sort();
2006         for (name, v) in inconsistent_vars {
2007             resolve_error(self, v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2008         }
2009     }
2010
2011     fn resolve_arm(&mut self, arm: &Arm) {
2012         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2013
2014         let mut bindings_list = FxHashMap();
2015         for pattern in &arm.pats {
2016             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2017         }
2018
2019         // This has to happen *after* we determine which
2020         // pat_idents are variants
2021         self.check_consistent_bindings(arm);
2022
2023         walk_list!(self, visit_expr, &arm.guard);
2024         self.visit_expr(&arm.body);
2025
2026         self.ribs[ValueNS].pop();
2027     }
2028
2029     fn resolve_block(&mut self, block: &Block) {
2030         debug!("(resolving block) entering block");
2031         // Move down in the graph, if there's an anonymous module rooted here.
2032         let orig_module = self.current_module;
2033         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
2034
2035         let mut num_macro_definition_ribs = 0;
2036         if let Some(anonymous_module) = anonymous_module {
2037             debug!("(resolving block) found anonymous module, moving down");
2038             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2039             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2040             self.current_module = anonymous_module;
2041             self.finalize_current_module_macro_resolutions();
2042         } else {
2043             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2044         }
2045
2046         // Descend into the block.
2047         for stmt in &block.stmts {
2048             if let ast::StmtKind::Item(ref item) = stmt.node {
2049                 if let ast::ItemKind::MacroDef(..) = item.node {
2050                     num_macro_definition_ribs += 1;
2051                     let def = self.definitions.local_def_id(item.id);
2052                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(def)));
2053                     self.label_ribs.push(Rib::new(MacroDefinition(def)));
2054                 }
2055             }
2056
2057             self.visit_stmt(stmt);
2058         }
2059
2060         // Move back up.
2061         self.current_module = orig_module;
2062         for _ in 0 .. num_macro_definition_ribs {
2063             self.ribs[ValueNS].pop();
2064             self.label_ribs.pop();
2065         }
2066         self.ribs[ValueNS].pop();
2067         if let Some(_) = anonymous_module {
2068             self.ribs[TypeNS].pop();
2069         }
2070         debug!("(resolving block) leaving block");
2071     }
2072
2073     fn fresh_binding(&mut self,
2074                      ident: &SpannedIdent,
2075                      pat_id: NodeId,
2076                      outer_pat_id: NodeId,
2077                      pat_src: PatternSource,
2078                      bindings: &mut FxHashMap<Ident, NodeId>)
2079                      -> PathResolution {
2080         // Add the binding to the local ribs, if it
2081         // doesn't already exist in the bindings map. (We
2082         // must not add it if it's in the bindings map
2083         // because that breaks the assumptions later
2084         // passes make about or-patterns.)
2085         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
2086         match bindings.get(&ident.node).cloned() {
2087             Some(id) if id == outer_pat_id => {
2088                 // `Variant(a, a)`, error
2089                 resolve_error(
2090                     self,
2091                     ident.span,
2092                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2093                         &ident.node.name.as_str())
2094                 );
2095             }
2096             Some(..) if pat_src == PatternSource::FnParam => {
2097                 // `fn f(a: u8, a: u8)`, error
2098                 resolve_error(
2099                     self,
2100                     ident.span,
2101                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2102                         &ident.node.name.as_str())
2103                 );
2104             }
2105             Some(..) if pat_src == PatternSource::Match => {
2106                 // `Variant1(a) | Variant2(a)`, ok
2107                 // Reuse definition from the first `a`.
2108                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
2109             }
2110             Some(..) => {
2111                 span_bug!(ident.span, "two bindings with the same name from \
2112                                        unexpected pattern source {:?}", pat_src);
2113             }
2114             None => {
2115                 // A completely fresh binding, add to the lists if it's valid.
2116                 if ident.node.name != keywords::Invalid.name() {
2117                     bindings.insert(ident.node, outer_pat_id);
2118                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2119                 }
2120             }
2121         }
2122
2123         PathResolution::new(def)
2124     }
2125
2126     fn resolve_pattern(&mut self,
2127                        pat: &Pat,
2128                        pat_src: PatternSource,
2129                        // Maps idents to the node ID for the
2130                        // outermost pattern that binds them.
2131                        bindings: &mut FxHashMap<Ident, NodeId>) {
2132         // Visit all direct subpatterns of this pattern.
2133         let outer_pat_id = pat.id;
2134         pat.walk(&mut |pat| {
2135             match pat.node {
2136                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2137                     // First try to resolve the identifier as some existing
2138                     // entity, then fall back to a fresh binding.
2139                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS, None)
2140                                       .and_then(LexicalScopeBinding::item);
2141                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2142                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2143                                              bmode != BindingMode::ByValue(Mutability::Immutable);
2144                         match def {
2145                             Def::StructCtor(_, CtorKind::Const) |
2146                             Def::VariantCtor(_, CtorKind::Const) |
2147                             Def::Const(..) if !always_binding => {
2148                                 // A unit struct/variant or constant pattern.
2149                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2150                                 Some(PathResolution::new(def))
2151                             }
2152                             Def::StructCtor(..) | Def::VariantCtor(..) |
2153                             Def::Const(..) | Def::Static(..) => {
2154                                 // A fresh binding that shadows something unacceptable.
2155                                 resolve_error(
2156                                     self,
2157                                     ident.span,
2158                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2159                                         pat_src.descr(), ident.node.name, binding.unwrap())
2160                                 );
2161                                 None
2162                             }
2163                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2164                                 // These entities are explicitly allowed
2165                                 // to be shadowed by fresh bindings.
2166                                 None
2167                             }
2168                             def => {
2169                                 span_bug!(ident.span, "unexpected definition for an \
2170                                                        identifier in pattern: {:?}", def);
2171                             }
2172                         }
2173                     }).unwrap_or_else(|| {
2174                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2175                     });
2176
2177                     self.record_def(pat.id, resolution);
2178                 }
2179
2180                 PatKind::TupleStruct(ref path, ..) => {
2181                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2182                 }
2183
2184                 PatKind::Path(ref qself, ref path) => {
2185                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2186                 }
2187
2188                 PatKind::Struct(ref path, ..) => {
2189                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2190                 }
2191
2192                 _ => {}
2193             }
2194             true
2195         });
2196
2197         visit::walk_pat(self, pat);
2198     }
2199
2200     // High-level and context dependent path resolution routine.
2201     // Resolves the path and records the resolution into definition map.
2202     // If resolution fails tries several techniques to find likely
2203     // resolution candidates, suggest imports or other help, and report
2204     // errors in user friendly way.
2205     fn smart_resolve_path(&mut self,
2206                           id: NodeId,
2207                           qself: Option<&QSelf>,
2208                           path: &Path,
2209                           source: PathSource)
2210                           -> PathResolution {
2211         let segments = &path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>();
2212         let ident_span = path.segments.last().map_or(path.span, |seg| seg.span);
2213         self.smart_resolve_path_fragment(id, qself, segments, path.span, ident_span, source)
2214     }
2215
2216     fn smart_resolve_path_fragment(&mut self,
2217                                    id: NodeId,
2218                                    qself: Option<&QSelf>,
2219                                    path: &[Ident],
2220                                    span: Span,
2221                                    ident_span: Span,
2222                                    source: PathSource)
2223                                    -> PathResolution {
2224         let ns = source.namespace();
2225         let is_expected = &|def| source.is_expected(def);
2226         let is_enum_variant = &|def| if let Def::Variant(..) = def { true } else { false };
2227
2228         // Base error is amended with one short label and possibly some longer helps/notes.
2229         let report_errors = |this: &mut Self, def: Option<Def>| {
2230             // Make the base error.
2231             let expected = source.descr_expected();
2232             let path_str = names_to_string(path);
2233             let code = source.error_code(def.is_some());
2234             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
2235                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2236                  format!("not a {}", expected), span)
2237             } else {
2238                 let item_str = path[path.len() - 1];
2239                 let (mod_prefix, mod_str) = if path.len() == 1 {
2240                     (format!(""), format!("this scope"))
2241                 } else if path.len() == 2 && path[0].name == keywords::CrateRoot.name() {
2242                     (format!(""), format!("the crate root"))
2243                 } else {
2244                     let mod_path = &path[..path.len() - 1];
2245                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), None) {
2246                         PathResult::Module(module) => module.def(),
2247                         _ => None,
2248                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2249                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2250                 };
2251                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2252                  format!("not found in {}", mod_str), ident_span)
2253             };
2254             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
2255
2256             // Emit special messages for unresolved `Self` and `self`.
2257             if is_self_type(path, ns) {
2258                 __diagnostic_used!(E0411);
2259                 err.code("E0411".into());
2260                 err.span_label(span, "`Self` is only available in traits and impls");
2261                 return err;
2262             }
2263             if is_self_value(path, ns) {
2264                 __diagnostic_used!(E0424);
2265                 err.code("E0424".into());
2266                 err.span_label(span, format!("`self` value is only available in \
2267                                                methods with `self` parameter"));
2268                 return err;
2269             }
2270
2271             // Try to lookup the name in more relaxed fashion for better error reporting.
2272             let name = path.last().unwrap().name;
2273             let candidates = this.lookup_import_candidates(name, ns, is_expected);
2274             if !candidates.is_empty() {
2275                 // Report import candidates as help and proceed searching for labels.
2276                 show_candidates(&mut err, &candidates, def.is_some());
2277             } else if is_expected(Def::Enum(DefId::local(CRATE_DEF_INDEX))) {
2278                 let enum_candidates = this.lookup_import_candidates(name, ns, is_enum_variant);
2279                 let mut enum_candidates = enum_candidates.iter()
2280                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
2281                 enum_candidates.sort();
2282                 for (sp, variant_path, enum_path) in enum_candidates {
2283                     let msg = format!("there is an enum variant `{}`, did you mean to use `{}`?",
2284                                       variant_path,
2285                                       enum_path);
2286                     if sp == DUMMY_SP {
2287                         err.help(&msg);
2288                     } else {
2289                         err.span_help(sp, &msg);
2290                     }
2291                 }
2292             }
2293             if path.len() == 1 && this.self_type_is_available() {
2294                 if let Some(candidate) = this.lookup_assoc_candidate(name, ns, is_expected) {
2295                     let self_is_available = this.self_value_is_available(path[0].ctxt);
2296                     match candidate {
2297                         AssocSuggestion::Field => {
2298                             err.span_label(span, format!("did you mean `self.{}`?", path_str));
2299                             if !self_is_available {
2300                                 err.span_label(span, format!("`self` value is only available in \
2301                                                                methods with `self` parameter"));
2302                             }
2303                         }
2304                         AssocSuggestion::MethodWithSelf if self_is_available => {
2305                             err.span_label(span, format!("did you mean `self.{}(...)`?",
2306                                                            path_str));
2307                         }
2308                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2309                             err.span_label(span, format!("did you mean `Self::{}`?", path_str));
2310                         }
2311                     }
2312                     return err;
2313                 }
2314             }
2315
2316             let mut levenshtein_worked = false;
2317
2318             // Try Levenshtein.
2319             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected) {
2320                 err.span_label(ident_span, format!("did you mean `{}`?", candidate));
2321                 levenshtein_worked = true;
2322             }
2323
2324             // Try context dependent help if relaxed lookup didn't work.
2325             if let Some(def) = def {
2326                 match (def, source) {
2327                     (Def::Macro(..), _) => {
2328                         err.span_label(span, format!("did you mean `{}!(...)`?", path_str));
2329                         return err;
2330                     }
2331                     (Def::TyAlias(..), PathSource::Trait) => {
2332                         err.span_label(span, "type aliases cannot be used for traits");
2333                         return err;
2334                     }
2335                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match parent.node {
2336                         ExprKind::Field(_, ident) => {
2337                             err.span_label(parent.span, format!("did you mean `{}::{}`?",
2338                                                                  path_str, ident.node));
2339                             return err;
2340                         }
2341                         ExprKind::MethodCall(ident, ..) => {
2342                             err.span_label(parent.span, format!("did you mean `{}::{}(...)`?",
2343                                                                  path_str, ident.node));
2344                             return err;
2345                         }
2346                         _ => {}
2347                     },
2348                     _ if ns == ValueNS && is_struct_like(def) => {
2349                         if let Def::Struct(def_id) = def {
2350                             if let Some((ctor_def, ctor_vis))
2351                                     = this.struct_constructors.get(&def_id).cloned() {
2352                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2353                                     err.span_label(span, format!("constructor is not visible \
2354                                                                    here due to private fields"));
2355                                 }
2356                             }
2357                         }
2358                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
2359                                                        path_str));
2360                         return err;
2361                     }
2362                     _ => {}
2363                 }
2364             }
2365
2366             // Fallback label.
2367             if !levenshtein_worked {
2368                 err.span_label(base_span, fallback_label);
2369             }
2370             err
2371         };
2372         let report_errors = |this: &mut Self, def: Option<Def>| {
2373             report_errors(this, def).emit();
2374             err_path_resolution()
2375         };
2376
2377         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2378                                                            source.defer_to_typeck(),
2379                                                            source.global_by_default()) {
2380             Some(resolution) if resolution.unresolved_segments() == 0 => {
2381                 if is_expected(resolution.base_def()) || resolution.base_def() == Def::Err {
2382                     resolution
2383                 } else {
2384                     // Add a temporary hack to smooth the transition to new struct ctor
2385                     // visibility rules. See #38932 for more details.
2386                     let mut res = None;
2387                     if let Def::Struct(def_id) = resolution.base_def() {
2388                         if let Some((ctor_def, ctor_vis))
2389                                 = self.struct_constructors.get(&def_id).cloned() {
2390                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2391                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2392                                 self.session.add_lint(lint, id, span,
2393                                     "private struct constructors are not usable through \
2394                                      reexports in outer modules".to_string());
2395                                 res = Some(PathResolution::new(ctor_def));
2396                             }
2397                         }
2398                     }
2399
2400                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def())))
2401                 }
2402             }
2403             Some(resolution) if source.defer_to_typeck() => {
2404                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2405                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2406                 // it needs to be added to the trait map.
2407                 if ns == ValueNS {
2408                     let item_name = path.last().unwrap().name;
2409                     let traits = self.get_traits_containing_item(item_name, ns);
2410                     self.trait_map.insert(id, traits);
2411                 }
2412                 resolution
2413             }
2414             _ => report_errors(self, None)
2415         };
2416
2417         if let PathSource::TraitItem(..) = source {} else {
2418             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2419             self.record_def(id, resolution);
2420         }
2421         resolution
2422     }
2423
2424     fn self_type_is_available(&mut self) -> bool {
2425         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(), TypeNS, None);
2426         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2427     }
2428
2429     fn self_value_is_available(&mut self, ctxt: SyntaxContext) -> bool {
2430         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2431         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, None);
2432         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2433     }
2434
2435     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2436     fn resolve_qpath_anywhere(&mut self,
2437                               id: NodeId,
2438                               qself: Option<&QSelf>,
2439                               path: &[Ident],
2440                               primary_ns: Namespace,
2441                               span: Span,
2442                               defer_to_typeck: bool,
2443                               global_by_default: bool)
2444                               -> Option<PathResolution> {
2445         let mut fin_res = None;
2446         // FIXME: can't resolve paths in macro namespace yet, macros are
2447         // processed by the little special hack below.
2448         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2449             if i == 0 || ns != primary_ns {
2450                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2451                     // If defer_to_typeck, then resolution > no resolution,
2452                     // otherwise full resolution > partial resolution > no resolution.
2453                     Some(res) if res.unresolved_segments() == 0 || defer_to_typeck =>
2454                         return Some(res),
2455                     res => if fin_res.is_none() { fin_res = res },
2456                 };
2457             }
2458         }
2459         let is_global = self.global_macros.get(&path[0].name).cloned()
2460             .map(|binding| binding.get_macro(self).kind() == MacroKind::Bang).unwrap_or(false);
2461         if primary_ns != MacroNS && (is_global || self.macro_names.contains(&path[0].name)) {
2462             // Return some dummy definition, it's enough for error reporting.
2463             return Some(
2464                 PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX), MacroKind::Bang))
2465             );
2466         }
2467         fin_res
2468     }
2469
2470     /// Handles paths that may refer to associated items.
2471     fn resolve_qpath(&mut self,
2472                      id: NodeId,
2473                      qself: Option<&QSelf>,
2474                      path: &[Ident],
2475                      ns: Namespace,
2476                      span: Span,
2477                      global_by_default: bool)
2478                      -> Option<PathResolution> {
2479         if let Some(qself) = qself {
2480             if qself.position == 0 {
2481                 // FIXME: Create some fake resolution that can't possibly be a type.
2482                 return Some(PathResolution::with_unresolved_segments(
2483                     Def::Mod(DefId::local(CRATE_DEF_INDEX)), path.len()
2484                 ));
2485             }
2486             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2487             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2488             let res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2489                                                        span, span, PathSource::TraitItem(ns));
2490             return Some(PathResolution::with_unresolved_segments(
2491                 res.base_def(), res.unresolved_segments() + path.len() - qself.position - 1
2492             ));
2493         }
2494
2495         let result = match self.resolve_path(&path, Some(ns), Some(span)) {
2496             PathResult::NonModule(path_res) => path_res,
2497             PathResult::Module(module) if !module.is_normal() => {
2498                 PathResolution::new(module.def().unwrap())
2499             }
2500             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2501             // don't report an error right away, but try to fallback to a primitive type.
2502             // So, we are still able to successfully resolve something like
2503             //
2504             // use std::u8; // bring module u8 in scope
2505             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2506             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2507             //                     // not to non-existent std::u8::max_value
2508             // }
2509             //
2510             // Such behavior is required for backward compatibility.
2511             // The same fallback is used when `a` resolves to nothing.
2512             PathResult::Module(..) | PathResult::Failed(..)
2513                     if (ns == TypeNS || path.len() > 1) &&
2514                        self.primitive_type_table.primitive_types.contains_key(&path[0].name) => {
2515                 let prim = self.primitive_type_table.primitive_types[&path[0].name];
2516                 match prim {
2517                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2518                         if !self.session.features.borrow().i128_type {
2519                             emit_feature_err(&self.session.parse_sess,
2520                                                 "i128_type", span, GateIssue::Language,
2521                                                 "128-bit type is unstable");
2522
2523                         }
2524                     }
2525                     _ => {}
2526                 }
2527                 PathResolution::with_unresolved_segments(Def::PrimTy(prim), path.len() - 1)
2528             }
2529             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2530             PathResult::Failed(msg, false) => {
2531                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2532                 err_path_resolution()
2533             }
2534             PathResult::Failed(..) => return None,
2535             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2536         };
2537
2538         if path.len() > 1 && !global_by_default && result.base_def() != Def::Err &&
2539            path[0].name != keywords::CrateRoot.name() && path[0].name != "$crate" {
2540             let unqualified_result = {
2541                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
2542                     PathResult::NonModule(path_res) => path_res.base_def(),
2543                     PathResult::Module(module) => module.def().unwrap(),
2544                     _ => return Some(result),
2545                 }
2546             };
2547             if result.base_def() == unqualified_result {
2548                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2549                 self.session.add_lint(lint, id, span, "unnecessary qualification".to_string());
2550             }
2551         }
2552
2553         Some(result)
2554     }
2555
2556     fn resolve_path(&mut self,
2557                     path: &[Ident],
2558                     opt_ns: Option<Namespace>, // `None` indicates a module path
2559                     record_used: Option<Span>)
2560                     -> PathResult<'a> {
2561         let mut module = None;
2562         let mut allow_super = true;
2563
2564         for (i, &ident) in path.iter().enumerate() {
2565             let is_last = i == path.len() - 1;
2566             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2567
2568             if i == 0 && ns == TypeNS && ident.name == keywords::SelfValue.name() {
2569                 module = Some(self.module_map[&self.current_module.normal_ancestor_id]);
2570                 continue
2571             } else if allow_super && ns == TypeNS && ident.name == keywords::Super.name() {
2572                 let current_module = if i == 0 { self.current_module } else { module.unwrap() };
2573                 let self_module = self.module_map[&current_module.normal_ancestor_id];
2574                 if let Some(parent) = self_module.parent {
2575                     module = Some(self.module_map[&parent.normal_ancestor_id]);
2576                     continue
2577                 } else {
2578                     let msg = "There are too many initial `super`s.".to_string();
2579                     return PathResult::Failed(msg, false);
2580                 }
2581             }
2582             allow_super = false;
2583
2584             if i == 0 && ns == TypeNS && ident.name == keywords::CrateRoot.name() {
2585                 module = Some(self.graph_root);
2586                 continue
2587             } else if i == 0 && ns == TypeNS && ident.name == "$crate" {
2588                 module = Some(self.resolve_crate_var(ident.ctxt));
2589                 continue
2590             }
2591
2592             let binding = if let Some(module) = module {
2593                 self.resolve_ident_in_module(module, ident, ns, false, record_used)
2594             } else if opt_ns == Some(MacroNS) {
2595                 self.resolve_lexical_macro_path_segment(ident, ns, record_used)
2596                     .map(MacroBinding::binding)
2597             } else {
2598                 match self.resolve_ident_in_lexical_scope(ident, ns, record_used) {
2599                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2600                     Some(LexicalScopeBinding::Def(def))
2601                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2602                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2603                             def, path.len() - 1
2604                         ));
2605                     }
2606                     _ => Err(if record_used.is_some() { Determined } else { Undetermined }),
2607                 }
2608             };
2609
2610             match binding {
2611                 Ok(binding) => {
2612                     let def = binding.def();
2613                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2614                     if let Some(next_module) = binding.module() {
2615                         module = Some(next_module);
2616                     } else if def == Def::Err {
2617                         return PathResult::NonModule(err_path_resolution());
2618                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2619                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2620                             def, path.len() - i - 1
2621                         ));
2622                     } else {
2623                         return PathResult::Failed(format!("Not a module `{}`", ident), is_last);
2624                     }
2625                 }
2626                 Err(Undetermined) => return PathResult::Indeterminate,
2627                 Err(Determined) => {
2628                     if let Some(module) = module {
2629                         if opt_ns.is_some() && !module.is_normal() {
2630                             return PathResult::NonModule(PathResolution::with_unresolved_segments(
2631                                 module.def().unwrap(), path.len() - i
2632                             ));
2633                         }
2634                     }
2635                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2636                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2637                         let mut candidates =
2638                             self.lookup_import_candidates(ident.name, TypeNS, is_mod);
2639                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2640                         if let Some(candidate) = candidates.get(0) {
2641                             format!("Did you mean `{}`?", candidate.path)
2642                         } else {
2643                             format!("Maybe a missing `extern crate {};`?", ident)
2644                         }
2645                     } else if i == 0 {
2646                         format!("Use of undeclared type or module `{}`", ident)
2647                     } else {
2648                         format!("Could not find `{}` in `{}`", ident, path[i - 1])
2649                     };
2650                     return PathResult::Failed(msg, is_last);
2651                 }
2652             }
2653         }
2654
2655         PathResult::Module(module.unwrap_or(self.graph_root))
2656     }
2657
2658     // Resolve a local definition, potentially adjusting for closures.
2659     fn adjust_local_def(&mut self,
2660                         ns: Namespace,
2661                         rib_index: usize,
2662                         mut def: Def,
2663                         record_used: Option<Span>) -> Def {
2664         let ribs = &self.ribs[ns][rib_index + 1..];
2665
2666         // An invalid forward use of a type parameter from a previous default.
2667         if let ForwardTyParamBanRibKind = self.ribs[ns][rib_index].kind {
2668             if let Some(span) = record_used {
2669                 resolve_error(self, span,
2670                         ResolutionError::ForwardDeclaredTyParam);
2671             }
2672             assert_eq!(def, Def::Err);
2673             return Def::Err;
2674         }
2675
2676         match def {
2677             Def::Upvar(..) => {
2678                 span_bug!(record_used.unwrap_or(DUMMY_SP), "unexpected {:?} in bindings", def)
2679             }
2680             Def::Local(def_id) => {
2681                 for rib in ribs {
2682                     match rib.kind {
2683                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
2684                         ForwardTyParamBanRibKind => {
2685                             // Nothing to do. Continue.
2686                         }
2687                         ClosureRibKind(function_id) => {
2688                             let prev_def = def;
2689                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2690
2691                             let seen = self.freevars_seen
2692                                            .entry(function_id)
2693                                            .or_insert_with(|| NodeMap());
2694                             if let Some(&index) = seen.get(&node_id) {
2695                                 def = Def::Upvar(def_id, index, function_id);
2696                                 continue;
2697                             }
2698                             let vec = self.freevars
2699                                           .entry(function_id)
2700                                           .or_insert_with(|| vec![]);
2701                             let depth = vec.len();
2702                             def = Def::Upvar(def_id, depth, function_id);
2703
2704                             if let Some(span) = record_used {
2705                                 vec.push(Freevar {
2706                                     def: prev_def,
2707                                     span: span,
2708                                 });
2709                                 seen.insert(node_id, depth);
2710                             }
2711                         }
2712                         ItemRibKind | MethodRibKind(_) => {
2713                             // This was an attempt to access an upvar inside a
2714                             // named function item. This is not allowed, so we
2715                             // report an error.
2716                             if let Some(span) = record_used {
2717                                 resolve_error(self, span,
2718                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2719                             }
2720                             return Def::Err;
2721                         }
2722                         ConstantItemRibKind => {
2723                             // Still doesn't deal with upvars
2724                             if let Some(span) = record_used {
2725                                 resolve_error(self, span,
2726                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
2727                             }
2728                             return Def::Err;
2729                         }
2730                     }
2731                 }
2732             }
2733             Def::TyParam(..) | Def::SelfTy(..) => {
2734                 for rib in ribs {
2735                     match rib.kind {
2736                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
2737                         ModuleRibKind(..) | MacroDefinition(..) | ForwardTyParamBanRibKind => {
2738                             // Nothing to do. Continue.
2739                         }
2740                         ItemRibKind => {
2741                             // This was an attempt to use a type parameter outside
2742                             // its scope.
2743                             if let Some(span) = record_used {
2744                                 resolve_error(self, span,
2745                                               ResolutionError::TypeParametersFromOuterFunction);
2746                             }
2747                             return Def::Err;
2748                         }
2749                         ConstantItemRibKind => {
2750                             // see #9186
2751                             if let Some(span) = record_used {
2752                                 resolve_error(self, span,
2753                                               ResolutionError::OuterTypeParameterContext);
2754                             }
2755                             return Def::Err;
2756                         }
2757                     }
2758                 }
2759             }
2760             _ => {}
2761         }
2762         return def;
2763     }
2764
2765     // Calls `f` with a `Resolver` whose current lexical scope is `module`'s lexical scope,
2766     // i.e. the module's items and the prelude (unless the module is `#[no_implicit_prelude]`).
2767     // FIXME #34673: This needs testing.
2768     pub fn with_module_lexical_scope<T, F>(&mut self, module: Module<'a>, f: F) -> T
2769         where F: FnOnce(&mut Resolver<'a>) -> T,
2770     {
2771         self.with_empty_ribs(|this| {
2772             this.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
2773             this.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
2774             f(this)
2775         })
2776     }
2777
2778     fn with_empty_ribs<T, F>(&mut self, f: F) -> T
2779         where F: FnOnce(&mut Resolver<'a>) -> T,
2780     {
2781         let ribs = replace(&mut self.ribs, PerNS::<Vec<Rib>>::default());
2782         let label_ribs = replace(&mut self.label_ribs, Vec::new());
2783
2784         let result = f(self);
2785         self.ribs = ribs;
2786         self.label_ribs = label_ribs;
2787         result
2788     }
2789
2790     fn lookup_assoc_candidate<FilterFn>(&mut self,
2791                                         name: Name,
2792                                         ns: Namespace,
2793                                         filter_fn: FilterFn)
2794                                         -> Option<AssocSuggestion>
2795         where FilterFn: Fn(Def) -> bool
2796     {
2797         fn extract_node_id(t: &Ty) -> Option<NodeId> {
2798             match t.node {
2799                 TyKind::Path(None, _) => Some(t.id),
2800                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
2801                 // This doesn't handle the remaining `Ty` variants as they are not
2802                 // that commonly the self_type, it might be interesting to provide
2803                 // support for those in future.
2804                 _ => None,
2805             }
2806         }
2807
2808         // Fields are generally expected in the same contexts as locals.
2809         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
2810             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
2811                 // Look for a field with the same name in the current self_type.
2812                 if let Some(resolution) = self.def_map.get(&node_id) {
2813                     match resolution.base_def() {
2814                         Def::Struct(did) | Def::Union(did)
2815                                 if resolution.unresolved_segments() == 0 => {
2816                             if let Some(field_names) = self.field_names.get(&did) {
2817                                 if field_names.iter().any(|&field_name| name == field_name) {
2818                                     return Some(AssocSuggestion::Field);
2819                                 }
2820                             }
2821                         }
2822                         _ => {}
2823                     }
2824                 }
2825             }
2826         }
2827
2828         // Look for associated items in the current trait.
2829         if let Some((trait_did, _)) = self.current_trait_ref {
2830             if let Some(&(def, has_self)) = self.trait_item_map.get(&(trait_did, name, ns)) {
2831                 if filter_fn(def) {
2832                     return Some(if has_self {
2833                         AssocSuggestion::MethodWithSelf
2834                     } else {
2835                         AssocSuggestion::AssocItem
2836                     });
2837                 }
2838             }
2839         }
2840
2841         None
2842     }
2843
2844     fn lookup_typo_candidate<FilterFn>(&mut self,
2845                                        path: &[Ident],
2846                                        ns: Namespace,
2847                                        filter_fn: FilterFn)
2848                                        -> Option<Symbol>
2849         where FilterFn: Fn(Def) -> bool
2850     {
2851         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
2852             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
2853                 if let Some(binding) = resolution.borrow().binding {
2854                     if filter_fn(binding.def()) {
2855                         names.push(ident.name);
2856                     }
2857                 }
2858             }
2859         };
2860
2861         let mut names = Vec::new();
2862         if path.len() == 1 {
2863             // Search in lexical scope.
2864             // Walk backwards up the ribs in scope and collect candidates.
2865             for rib in self.ribs[ns].iter().rev() {
2866                 // Locals and type parameters
2867                 for (ident, def) in &rib.bindings {
2868                     if filter_fn(*def) {
2869                         names.push(ident.name);
2870                     }
2871                 }
2872                 // Items in scope
2873                 if let ModuleRibKind(module) = rib.kind {
2874                     // Items from this module
2875                     add_module_candidates(module, &mut names);
2876
2877                     if let ModuleKind::Block(..) = module.kind {
2878                         // We can see through blocks
2879                     } else {
2880                         // Items from the prelude
2881                         if let Some(prelude) = self.prelude {
2882                             if !module.no_implicit_prelude {
2883                                 add_module_candidates(prelude, &mut names);
2884                             }
2885                         }
2886                         break;
2887                     }
2888                 }
2889             }
2890             // Add primitive types to the mix
2891             if filter_fn(Def::PrimTy(TyBool)) {
2892                 for (name, _) in &self.primitive_type_table.primitive_types {
2893                     names.push(*name);
2894                 }
2895             }
2896         } else {
2897             // Search in module.
2898             let mod_path = &path[..path.len() - 1];
2899             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS), None) {
2900                 add_module_candidates(module, &mut names);
2901             }
2902         }
2903
2904         let name = path[path.len() - 1].name;
2905         // Make sure error reporting is deterministic.
2906         names.sort_by_key(|name| name.as_str());
2907         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
2908             Some(found) if found != name => Some(found),
2909             _ => None,
2910         }
2911     }
2912
2913     fn with_resolved_label<F>(&mut self, label: Option<SpannedIdent>, id: NodeId, f: F)
2914         where F: FnOnce(&mut Resolver)
2915     {
2916         if let Some(label) = label {
2917             let def = Def::Label(id);
2918             self.with_label_rib(|this| {
2919                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
2920                 f(this);
2921             });
2922         } else {
2923             f(self);
2924         }
2925     }
2926
2927     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
2928         self.with_resolved_label(label, id, |this| this.visit_block(block));
2929     }
2930
2931     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
2932         // First, record candidate traits for this expression if it could
2933         // result in the invocation of a method call.
2934
2935         self.record_candidate_traits_for_expr_if_necessary(expr);
2936
2937         // Next, resolve the node.
2938         match expr.node {
2939             ExprKind::Path(ref qself, ref path) => {
2940                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
2941                 visit::walk_expr(self, expr);
2942             }
2943
2944             ExprKind::Struct(ref path, ..) => {
2945                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
2946                 visit::walk_expr(self, expr);
2947             }
2948
2949             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
2950                 match self.search_label(label.node) {
2951                     None => {
2952                         self.record_def(expr.id, err_path_resolution());
2953                         resolve_error(self,
2954                                       label.span,
2955                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
2956                     }
2957                     Some(def @ Def::Label(_)) => {
2958                         // Since this def is a label, it is never read.
2959                         self.record_def(expr.id, PathResolution::new(def));
2960                     }
2961                     Some(_) => {
2962                         span_bug!(expr.span, "label wasn't mapped to a label def!");
2963                     }
2964                 }
2965
2966                 // visit `break` argument if any
2967                 visit::walk_expr(self, expr);
2968             }
2969
2970             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
2971                 self.visit_expr(subexpression);
2972
2973                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2974                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
2975                 self.visit_block(if_block);
2976                 self.ribs[ValueNS].pop();
2977
2978                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
2979             }
2980
2981             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
2982
2983             ExprKind::While(ref subexpression, ref block, label) => {
2984                 self.with_resolved_label(label, expr.id, |this| {
2985                     this.visit_expr(subexpression);
2986                     this.visit_block(block);
2987                 });
2988             }
2989
2990             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
2991                 self.with_resolved_label(label, expr.id, |this| {
2992                     this.visit_expr(subexpression);
2993                     this.ribs[ValueNS].push(Rib::new(NormalRibKind));
2994                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
2995                     this.visit_block(block);
2996                     this.ribs[ValueNS].pop();
2997                 });
2998             }
2999
3000             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
3001                 self.visit_expr(subexpression);
3002                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3003                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
3004
3005                 self.resolve_labeled_block(label, expr.id, block);
3006
3007                 self.ribs[ValueNS].pop();
3008             }
3009
3010             // Equivalent to `visit::walk_expr` + passing some context to children.
3011             ExprKind::Field(ref subexpression, _) => {
3012                 self.resolve_expr(subexpression, Some(expr));
3013             }
3014             ExprKind::MethodCall(_, ref types, ref arguments) => {
3015                 let mut arguments = arguments.iter();
3016                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3017                 for argument in arguments {
3018                     self.resolve_expr(argument, None);
3019                 }
3020                 for ty in types.iter() {
3021                     self.visit_ty(ty);
3022                 }
3023             }
3024
3025             ExprKind::Repeat(ref element, ref count) => {
3026                 self.visit_expr(element);
3027                 self.with_constant_rib(|this| {
3028                     this.visit_expr(count);
3029                 });
3030             }
3031             ExprKind::Call(ref callee, ref arguments) => {
3032                 self.resolve_expr(callee, Some(expr));
3033                 for argument in arguments {
3034                     self.resolve_expr(argument, None);
3035                 }
3036             }
3037
3038             _ => {
3039                 visit::walk_expr(self, expr);
3040             }
3041         }
3042     }
3043
3044     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3045         match expr.node {
3046             ExprKind::Field(_, name) => {
3047                 // FIXME(#6890): Even though you can't treat a method like a
3048                 // field, we need to add any trait methods we find that match
3049                 // the field name so that we can do some nice error reporting
3050                 // later on in typeck.
3051                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
3052                 self.trait_map.insert(expr.id, traits);
3053             }
3054             ExprKind::MethodCall(name, ..) => {
3055                 debug!("(recording candidate traits for expr) recording traits for {}",
3056                        expr.id);
3057                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
3058                 self.trait_map.insert(expr.id, traits);
3059             }
3060             _ => {
3061                 // Nothing to do.
3062             }
3063         }
3064     }
3065
3066     fn get_traits_containing_item(&mut self, name: Name, ns: Namespace) -> Vec<TraitCandidate> {
3067         debug!("(getting traits containing item) looking for '{}'", name);
3068
3069         let mut found_traits = Vec::new();
3070         // Look for the current trait.
3071         if let Some((trait_def_id, _)) = self.current_trait_ref {
3072             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
3073                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: None });
3074             }
3075         }
3076
3077         let mut search_module = self.current_module;
3078         loop {
3079             self.get_traits_in_module_containing_item(name, ns, search_module, &mut found_traits);
3080             match search_module.kind {
3081                 ModuleKind::Block(..) => search_module = search_module.parent.unwrap(),
3082                 _ => break,
3083             }
3084         }
3085
3086         if let Some(prelude) = self.prelude {
3087             if !search_module.no_implicit_prelude {
3088                 self.get_traits_in_module_containing_item(name, ns, prelude, &mut found_traits);
3089             }
3090         }
3091
3092         found_traits
3093     }
3094
3095     fn get_traits_in_module_containing_item(&mut self,
3096                                             name: Name,
3097                                             ns: Namespace,
3098                                             module: Module,
3099                                             found_traits: &mut Vec<TraitCandidate>) {
3100         let mut traits = module.traits.borrow_mut();
3101         if traits.is_none() {
3102             let mut collected_traits = Vec::new();
3103             module.for_each_child(|name, ns, binding| {
3104                 if ns != TypeNS { return }
3105                 if let Def::Trait(_) = binding.def() {
3106                     collected_traits.push((name, binding));
3107                 }
3108             });
3109             *traits = Some(collected_traits.into_boxed_slice());
3110         }
3111
3112         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3113             let trait_def_id = binding.def().def_id();
3114             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
3115                 let import_id = match binding.kind {
3116                     NameBindingKind::Import { directive, .. } => {
3117                         self.maybe_unused_trait_imports.insert(directive.id);
3118                         self.add_to_glob_map(directive.id, trait_name);
3119                         Some(directive.id)
3120                     }
3121                     _ => None,
3122                 };
3123                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
3124             }
3125         }
3126     }
3127
3128     /// When name resolution fails, this method can be used to look up candidate
3129     /// entities with the expected name. It allows filtering them using the
3130     /// supplied predicate (which should be used to only accept the types of
3131     /// definitions expected e.g. traits). The lookup spans across all crates.
3132     ///
3133     /// NOTE: The method does not look into imports, but this is not a problem,
3134     /// since we report the definitions (thus, the de-aliased imports).
3135     fn lookup_import_candidates<FilterFn>(&mut self,
3136                                           lookup_name: Name,
3137                                           namespace: Namespace,
3138                                           filter_fn: FilterFn)
3139                                           -> Vec<ImportSuggestion>
3140         where FilterFn: Fn(Def) -> bool
3141     {
3142         let mut candidates = Vec::new();
3143         let mut worklist = Vec::new();
3144         let mut seen_modules = FxHashSet();
3145         worklist.push((self.graph_root, Vec::new(), false));
3146
3147         while let Some((in_module,
3148                         path_segments,
3149                         in_module_is_extern)) = worklist.pop() {
3150             self.populate_module_if_necessary(in_module);
3151
3152             in_module.for_each_child(|ident, ns, name_binding| {
3153
3154                 // avoid imports entirely
3155                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3156                 // avoid non-importable candidates as well
3157                 if !name_binding.is_importable() { return; }
3158
3159                 // collect results based on the filter function
3160                 if ident.name == lookup_name && ns == namespace {
3161                     if filter_fn(name_binding.def()) {
3162                         // create the path
3163                         let mut segms = path_segments.clone();
3164                         segms.push(ast::PathSegment::from_ident(ident, name_binding.span));
3165                         let path = Path {
3166                             span: name_binding.span,
3167                             segments: segms,
3168                         };
3169                         // the entity is accessible in the following cases:
3170                         // 1. if it's defined in the same crate, it's always
3171                         // accessible (since private entities can be made public)
3172                         // 2. if it's defined in another crate, it's accessible
3173                         // only if both the module is public and the entity is
3174                         // declared as public (due to pruning, we don't explore
3175                         // outside crate private modules => no need to check this)
3176                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3177                             candidates.push(ImportSuggestion { path: path });
3178                         }
3179                     }
3180                 }
3181
3182                 // collect submodules to explore
3183                 if let Some(module) = name_binding.module() {
3184                     // form the path
3185                     let mut path_segments = path_segments.clone();
3186                     path_segments.push(ast::PathSegment::from_ident(ident, name_binding.span));
3187
3188                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3189                         // add the module to the lookup
3190                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3191                         if seen_modules.insert(module.def_id().unwrap()) {
3192                             worklist.push((module, path_segments, is_extern));
3193                         }
3194                     }
3195                 }
3196             })
3197         }
3198
3199         candidates
3200     }
3201
3202     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3203         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3204         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3205             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3206         }
3207     }
3208
3209     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3210         match *vis {
3211             ast::Visibility::Public => ty::Visibility::Public,
3212             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3213             ast::Visibility::Inherited => {
3214                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3215             }
3216             ast::Visibility::Restricted { ref path, id } => {
3217                 let def = self.smart_resolve_path(id, None, path,
3218                                                   PathSource::Visibility).base_def();
3219                 if def == Def::Err {
3220                     ty::Visibility::Public
3221                 } else {
3222                     let vis = ty::Visibility::Restricted(def.def_id());
3223                     if self.is_accessible(vis) {
3224                         vis
3225                     } else {
3226                         self.session.span_err(path.span, "visibilities can only be restricted \
3227                                                           to ancestor modules");
3228                         ty::Visibility::Public
3229                     }
3230                 }
3231             }
3232         }
3233     }
3234
3235     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3236         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3237     }
3238
3239     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3240         vis.is_accessible_from(module.normal_ancestor_id, self)
3241     }
3242
3243     fn report_errors(&mut self) {
3244         self.report_shadowing_errors();
3245         let mut reported_spans = FxHashSet();
3246
3247         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3248             if !reported_spans.insert(span) { continue }
3249             let participle = |binding: &NameBinding| {
3250                 if binding.is_import() { "imported" } else { "defined" }
3251             };
3252             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3253             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3254             let note = if b1.expansion == Mark::root() || !lexical && b1.is_glob_import() {
3255                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3256             } else if let Def::Macro(..) = b1.def() {
3257                 format!("macro-expanded {} do not shadow",
3258                         if b1.is_import() { "macro imports" } else { "macros" })
3259             } else {
3260                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3261                         if b1.is_import() { "imports" } else { "items" })
3262             };
3263             if legacy {
3264                 let id = match b2.kind {
3265                     NameBindingKind::Import { directive, .. } => directive.id,
3266                     _ => unreachable!(),
3267                 };
3268                 let mut span = MultiSpan::from_span(span);
3269                 span.push_span_label(b1.span, msg1);
3270                 span.push_span_label(b2.span, msg2);
3271                 let msg = format!("`{}` is ambiguous", name);
3272                 self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3273             } else {
3274                 let mut err =
3275                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", name));
3276                 err.span_note(b1.span, &msg1);
3277                 match b2.def() {
3278                     Def::Macro(..) if b2.span == DUMMY_SP =>
3279                         err.note(&format!("`{}` is also a builtin macro", name)),
3280                     _ => err.span_note(b2.span, &msg2),
3281                 };
3282                 err.note(&note).emit();
3283             }
3284         }
3285
3286         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3287             if !reported_spans.insert(span) { continue }
3288             if binding.is_extern_crate() {
3289                 // Warn when using an inaccessible extern crate.
3290                 let node_id = match binding.kind {
3291                     NameBindingKind::Import { directive, .. } => directive.id,
3292                     _ => unreachable!(),
3293                 };
3294                 let msg = format!("extern crate `{}` is private", name);
3295                 self.session.add_lint(lint::builtin::INACCESSIBLE_EXTERN_CRATE, node_id, span, msg);
3296             } else {
3297                 let def = binding.def();
3298                 self.session.span_err(span, &format!("{} `{}` is private", def.kind_name(), name));
3299             }
3300         }
3301     }
3302
3303     fn report_shadowing_errors(&mut self) {
3304         for (name, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3305             self.resolve_legacy_scope(scope, name, true);
3306         }
3307
3308         let mut reported_errors = FxHashSet();
3309         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3310             if self.resolve_legacy_scope(&binding.parent, binding.name, false).is_some() &&
3311                reported_errors.insert((binding.name, binding.span)) {
3312                 let msg = format!("`{}` is already in scope", binding.name);
3313                 self.session.struct_span_err(binding.span, &msg)
3314                     .note("macro-expanded `macro_rules!`s may not shadow \
3315                            existing macros (see RFC 1560)")
3316                     .emit();
3317             }
3318         }
3319     }
3320
3321     fn report_conflict(&mut self,
3322                        parent: Module,
3323                        ident: Ident,
3324                        ns: Namespace,
3325                        binding: &NameBinding,
3326                        old_binding: &NameBinding) {
3327         // Error on the second of two conflicting names
3328         if old_binding.span.lo > binding.span.lo {
3329             return self.report_conflict(parent, ident, ns, old_binding, binding);
3330         }
3331
3332         let container = match parent.kind {
3333             ModuleKind::Def(Def::Mod(_), _) => "module",
3334             ModuleKind::Def(Def::Trait(_), _) => "trait",
3335             ModuleKind::Block(..) => "block",
3336             _ => "enum",
3337         };
3338
3339         let (participle, noun) = match old_binding.is_import() {
3340             true => ("imported", "import"),
3341             false => ("defined", "definition"),
3342         };
3343
3344         let (name, span) = (ident.name, binding.span);
3345
3346         if let Some(s) = self.name_already_seen.get(&name) {
3347             if s == &span {
3348                 return;
3349             }
3350         }
3351
3352         let msg = {
3353             let kind = match (ns, old_binding.module()) {
3354                 (ValueNS, _) => "a value",
3355                 (MacroNS, _) => "a macro",
3356                 (TypeNS, _) if old_binding.is_extern_crate() => "an extern crate",
3357                 (TypeNS, Some(module)) if module.is_normal() => "a module",
3358                 (TypeNS, Some(module)) if module.is_trait() => "a trait",
3359                 (TypeNS, _) => "a type",
3360             };
3361             format!("{} named `{}` has already been {} in this {}",
3362                     kind, name, participle, container)
3363         };
3364
3365         let mut err = match (old_binding.is_extern_crate(), binding.is_extern_crate()) {
3366             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3367             (true, _) | (_, true) => match binding.is_import() && old_binding.is_import() {
3368                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3369                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3370             },
3371             _ => match (old_binding.is_import(), binding.is_import()) {
3372                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3373                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3374                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3375             },
3376         };
3377
3378         err.span_label(span, format!("`{}` already {}", name, participle));
3379         if old_binding.span != syntax_pos::DUMMY_SP {
3380             err.span_label(old_binding.span, format!("previous {} of `{}` here", noun, name));
3381         }
3382         err.emit();
3383         self.name_already_seen.insert(name, span);
3384     }
3385
3386     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3387         let (id, span) = (directive.id, directive.span);
3388         let msg = "`self` no longer imports values".to_string();
3389         self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3390     }
3391
3392     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3393         if self.proc_macro_enabled { return; }
3394
3395         for attr in attrs {
3396             if attr.path.segments.len() > 1 {
3397                 continue
3398             }
3399             let ident = attr.path.segments[0].identifier;
3400             let result = self.resolve_lexical_macro_path_segment(ident, MacroNS, None);
3401             if let Ok(binding) = result {
3402                 if let SyntaxExtension::AttrProcMacro(..) = *binding.binding().get_macro(self) {
3403                     attr::mark_known(attr);
3404
3405                     let msg = "attribute procedural macros are experimental";
3406                     let feature = "proc_macro";
3407
3408                     feature_err(&self.session.parse_sess, feature,
3409                                 attr.span, GateIssue::Language, msg)
3410                         .span_note(binding.span(), "procedural macro imported here")
3411                         .emit();
3412                 }
3413             }
3414         }
3415     }
3416 }
3417
3418 fn is_struct_like(def: Def) -> bool {
3419     match def {
3420         Def::VariantCtor(_, CtorKind::Fictive) => true,
3421         _ => PathSource::Struct.is_expected(def),
3422     }
3423 }
3424
3425 fn is_self_type(path: &[Ident], namespace: Namespace) -> bool {
3426     namespace == TypeNS && path.len() == 1 && path[0].name == keywords::SelfType.name()
3427 }
3428
3429 fn is_self_value(path: &[Ident], namespace: Namespace) -> bool {
3430     namespace == ValueNS && path.len() == 1 && path[0].name == keywords::SelfValue.name()
3431 }
3432
3433 fn names_to_string(idents: &[Ident]) -> String {
3434     let mut result = String::new();
3435     for (i, ident) in idents.iter().filter(|i| i.name != keywords::CrateRoot.name()).enumerate() {
3436         if i > 0 {
3437             result.push_str("::");
3438         }
3439         result.push_str(&ident.name.as_str());
3440     }
3441     result
3442 }
3443
3444 fn path_names_to_string(path: &Path) -> String {
3445     names_to_string(&path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>())
3446 }
3447
3448 /// Get the path for an enum and the variant from an `ImportSuggestion` for an enum variant.
3449 fn import_candidate_to_paths(suggestion: &ImportSuggestion) -> (Span, String, String) {
3450     let variant_path = &suggestion.path;
3451     let variant_path_string = path_names_to_string(variant_path);
3452
3453     let path_len = suggestion.path.segments.len();
3454     let enum_path = ast::Path {
3455         span: suggestion.path.span,
3456         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
3457     };
3458     let enum_path_string = path_names_to_string(&enum_path);
3459
3460     (suggestion.path.span, variant_path_string, enum_path_string)
3461 }
3462
3463
3464 /// When an entity with a given name is not available in scope, we search for
3465 /// entities with that name in all crates. This method allows outputting the
3466 /// results of this search in a programmer-friendly way
3467 fn show_candidates(session: &mut DiagnosticBuilder,
3468                    candidates: &[ImportSuggestion],
3469                    better: bool) {
3470     // don't show more than MAX_CANDIDATES results, so
3471     // we're consistent with the trait suggestions
3472     const MAX_CANDIDATES: usize = 4;
3473
3474     // we want consistent results across executions, but candidates are produced
3475     // by iterating through a hash map, so make sure they are ordered:
3476     let mut path_strings: Vec<_> =
3477         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3478     path_strings.sort();
3479
3480     let better = if better { "better " } else { "" };
3481     let msg_diff = match path_strings.len() {
3482         1 => " is found in another module, you can import it",
3483         _ => "s are found in other modules, you can import them",
3484     };
3485
3486     let end = cmp::min(MAX_CANDIDATES, path_strings.len());
3487     session.help(&format!("possible {}candidate{} into scope:{}{}",
3488                           better,
3489                           msg_diff,
3490                           &path_strings[0..end].iter().map(|candidate| {
3491                               format!("\n  `use {};`", candidate)
3492                           }).collect::<String>(),
3493                           if path_strings.len() > MAX_CANDIDATES {
3494                               format!("\nand {} other candidates",
3495                                       path_strings.len() - MAX_CANDIDATES)
3496                           } else {
3497                               "".to_owned()
3498                           }
3499                           ));
3500 }
3501
3502 /// A somewhat inefficient routine to obtain the name of a module.
3503 fn module_to_string(module: Module) -> String {
3504     let mut names = Vec::new();
3505
3506     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3507         if let ModuleKind::Def(_, name) = module.kind {
3508             if let Some(parent) = module.parent {
3509                 names.push(Ident::with_empty_ctxt(name));
3510                 collect_mod(names, parent);
3511             }
3512         } else {
3513             // danger, shouldn't be ident?
3514             names.push(Ident::from_str("<opaque>"));
3515             collect_mod(names, module.parent.unwrap());
3516         }
3517     }
3518     collect_mod(&mut names, module);
3519
3520     if names.is_empty() {
3521         return "???".to_string();
3522     }
3523     names_to_string(&names.into_iter().rev().collect::<Vec<_>>())
3524 }
3525
3526 fn err_path_resolution() -> PathResolution {
3527     PathResolution::new(Def::Err)
3528 }
3529
3530 #[derive(PartialEq,Copy, Clone)]
3531 pub enum MakeGlobMap {
3532     Yes,
3533     No,
3534 }
3535
3536 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }