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, true, 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     /// Span of the module itself. Used for error reporting.
 871     span: Span,
 872 }
 873
 874 pub type Module<'a> = &'a ModuleData<'a>;
 875
 876 impl<'a> ModuleData<'a> {
 877     fn new(parent: Option<Module<'a>>,
 878            kind: ModuleKind,
 879            normal_ancestor_id: DefId,
 880            span: Span) -> Self {
 881         ModuleData {
 882             parent: parent,
 883             kind: kind,
 884             normal_ancestor_id: normal_ancestor_id,
 885             resolutions: RefCell::new(FxHashMap()),
 886             legacy_macro_resolutions: RefCell::new(Vec::new()),
 887             macro_resolutions: RefCell::new(Vec::new()),
 888             unresolved_invocations: RefCell::new(FxHashSet()),
 889             no_implicit_prelude: false,
 890             glob_importers: RefCell::new(Vec::new()),
 891             globs: RefCell::new((Vec::new())),
 892             traits: RefCell::new(None),
 893             populated: Cell::new(normal_ancestor_id.is_local()),
 894             span: span,
 895         }
 896     }
 897
 898     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 899         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 900             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 901         }
 902     }
 903
 904     fn def(&self) -> Option<Def> {
 905         match self.kind {
 906             ModuleKind::Def(def, _) => Some(def),
 907             _ => None,
 908         }
 909     }
 910
 911     fn def_id(&self) -> Option<DefId> {
 912         self.def().as_ref().map(Def::def_id)
 913     }
 914
 915     // `self` resolves to the first module ancestor that `is_normal`.
 916     fn is_normal(&self) -> bool {
 917         match self.kind {
 918             ModuleKind::Def(Def::Mod(_), _) => true,
 919             _ => false,
 920         }
 921     }
 922
 923     fn is_trait(&self) -> bool {
 924         match self.kind {
 925             ModuleKind::Def(Def::Trait(_), _) => true,
 926             _ => false,
 927         }
 928     }
 929
 930     fn is_local(&self) -> bool {
 931         self.normal_ancestor_id.is_local()
 932     }
 933
 934     fn nearest_item_scope(&'a self) -> Module<'a> {
 935         if self.is_trait() { self.parent.unwrap() } else { self }
 936     }
 937 }
 938
 939 impl<'a> fmt::Debug for ModuleData<'a> {
 940     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 941         write!(f, "{:?}", self.def())
 942     }
 943 }
 944
 945 // Records a possibly-private value, type, or module definition.
 946 #[derive(Clone, Debug)]
 947 pub struct NameBinding<'a> {
 948     kind: NameBindingKind<'a>,
 949     expansion: Mark,
 950     span: Span,
 951     vis: ty::Visibility,
 952 }
 953
 954 pub trait ToNameBinding<'a> {
 955     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
 956 }
 957
 958 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
 959     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
 960         self
 961     }
 962 }
 963
 964 #[derive(Clone, Debug)]
 965 enum NameBindingKind<'a> {
 966     Def(Def),
 967     Module(Module<'a>),
 968     Import {
 969         binding: &'a NameBinding<'a>,
 970         directive: &'a ImportDirective<'a>,
 971         used: Cell<bool>,
 972         legacy_self_import: bool,
 973     },
 974     Ambiguity {
 975         b1: &'a NameBinding<'a>,
 976         b2: &'a NameBinding<'a>,
 977         legacy: bool,
 978     }
 979 }
 980
 981 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
 982
 983 struct AmbiguityError<'a> {
 984     span: Span,
 985     name: Name,
 986     lexical: bool,
 987     b1: &'a NameBinding<'a>,
 988     b2: &'a NameBinding<'a>,
 989     legacy: bool,
 990 }
 991
 992 impl<'a> NameBinding<'a> {
 993     fn module(&self) -> Option<Module<'a>> {
 994         match self.kind {
 995             NameBindingKind::Module(module) => Some(module),
 996             NameBindingKind::Import { binding, .. } => binding.module(),
 997             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
 998             _ => None,
 999         }
1000     }
1001
1002     fn def(&self) -> Def {
1003         match self.kind {
1004             NameBindingKind::Def(def) => def,
1005             NameBindingKind::Module(module) => module.def().unwrap(),
1006             NameBindingKind::Import { binding, .. } => binding.def(),
1007             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
1008             NameBindingKind::Ambiguity { .. } => Def::Err,
1009         }
1010     }
1011
1012     fn def_ignoring_ambiguity(&self) -> Def {
1013         match self.kind {
1014             NameBindingKind::Import { binding, .. } => binding.def_ignoring_ambiguity(),
1015             NameBindingKind::Ambiguity { b1, .. } => b1.def_ignoring_ambiguity(),
1016             _ => self.def(),
1017         }
1018     }
1019
1020     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
1021         resolver.get_macro(self.def_ignoring_ambiguity())
1022     }
1023
1024     // We sometimes need to treat variants as `pub` for backwards compatibility
1025     fn pseudo_vis(&self) -> ty::Visibility {
1026         if self.is_variant() { ty::Visibility::Public } else { self.vis }
1027     }
1028
1029     fn is_variant(&self) -> bool {
1030         match self.kind {
1031             NameBindingKind::Def(Def::Variant(..)) |
1032             NameBindingKind::Def(Def::VariantCtor(..)) => true,
1033             _ => false,
1034         }
1035     }
1036
1037     fn is_extern_crate(&self) -> bool {
1038         match self.kind {
1039             NameBindingKind::Import {
1040                 directive: &ImportDirective {
1041                     subclass: ImportDirectiveSubclass::ExternCrate, ..
1042                 }, ..
1043             } => true,
1044             _ => false,
1045         }
1046     }
1047
1048     fn is_import(&self) -> bool {
1049         match self.kind {
1050             NameBindingKind::Import { .. } => true,
1051             _ => false,
1052         }
1053     }
1054
1055     fn is_glob_import(&self) -> bool {
1056         match self.kind {
1057             NameBindingKind::Import { directive, .. } => directive.is_glob(),
1058             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
1059             _ => false,
1060         }
1061     }
1062
1063     fn is_importable(&self) -> bool {
1064         match self.def() {
1065             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
1066             _ => true,
1067         }
1068     }
1069 }
1070
1071 /// Interns the names of the primitive types.
1072 struct PrimitiveTypeTable {
1073     primitive_types: FxHashMap<Name, PrimTy>,
1074 }
1075
1076 impl PrimitiveTypeTable {
1077     fn new() -> PrimitiveTypeTable {
1078         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1079
1080         table.intern("bool", TyBool);
1081         table.intern("char", TyChar);
1082         table.intern("f32", TyFloat(FloatTy::F32));
1083         table.intern("f64", TyFloat(FloatTy::F64));
1084         table.intern("isize", TyInt(IntTy::Is));
1085         table.intern("i8", TyInt(IntTy::I8));
1086         table.intern("i16", TyInt(IntTy::I16));
1087         table.intern("i32", TyInt(IntTy::I32));
1088         table.intern("i64", TyInt(IntTy::I64));
1089         table.intern("i128", TyInt(IntTy::I128));
1090         table.intern("str", TyStr);
1091         table.intern("usize", TyUint(UintTy::Us));
1092         table.intern("u8", TyUint(UintTy::U8));
1093         table.intern("u16", TyUint(UintTy::U16));
1094         table.intern("u32", TyUint(UintTy::U32));
1095         table.intern("u64", TyUint(UintTy::U64));
1096         table.intern("u128", TyUint(UintTy::U128));
1097         table
1098     }
1099
1100     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1101         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1102     }
1103 }
1104
1105 /// The main resolver class.
1106 pub struct Resolver<'a> {
1107     session: &'a Session,
1108
1109     pub definitions: Definitions,
1110
1111     graph_root: Module<'a>,
1112
1113     prelude: Option<Module<'a>>,
1114
1115     trait_item_map: FxHashMap<(DefId, Name, Namespace), (Def, bool /* has self */)>,
1116
1117     // Names of fields of an item `DefId` accessible with dot syntax.
1118     // Used for hints during error reporting.
1119     field_names: FxHashMap<DefId, Vec<Name>>,
1120
1121     // All imports known to succeed or fail.
1122     determined_imports: Vec<&'a ImportDirective<'a>>,
1123
1124     // All non-determined imports.
1125     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1126
1127     // The module that represents the current item scope.
1128     current_module: Module<'a>,
1129
1130     // The current set of local scopes for types and values.
1131     // FIXME #4948: Reuse ribs to avoid allocation.
1132     ribs: PerNS<Vec<Rib<'a>>>,
1133
1134     // The current set of local scopes, for labels.
1135     label_ribs: Vec<Rib<'a>>,
1136
1137     // The trait that the current context can refer to.
1138     current_trait_ref: Option<(DefId, TraitRef)>,
1139
1140     // The current self type if inside an impl (used for better errors).
1141     current_self_type: Option<Ty>,
1142
1143     // The idents for the primitive types.
1144     primitive_type_table: PrimitiveTypeTable,
1145
1146     def_map: DefMap,
1147     pub freevars: FreevarMap,
1148     freevars_seen: NodeMap<NodeMap<usize>>,
1149     pub export_map: ExportMap,
1150     pub trait_map: TraitMap,
1151
1152     // A map from nodes to anonymous modules.
1153     // Anonymous modules are pseudo-modules that are implicitly created around items
1154     // contained within blocks.
1155     //
1156     // For example, if we have this:
1157     //
1158     //  fn f() {
1159     //      fn g() {
1160     //          ...
1161     //      }
1162     //  }
1163     //
1164     // There will be an anonymous module created around `g` with the ID of the
1165     // entry block for `f`.
1166     block_map: NodeMap<Module<'a>>,
1167     module_map: FxHashMap<DefId, Module<'a>>,
1168     extern_crate_roots: FxHashMap<(CrateNum, bool /* MacrosOnly? */), Module<'a>>,
1169
1170     pub make_glob_map: bool,
1171     // Maps imports to the names of items actually imported (this actually maps
1172     // all imports, but only glob imports are actually interesting).
1173     pub glob_map: GlobMap,
1174
1175     used_imports: FxHashSet<(NodeId, Namespace)>,
1176     pub maybe_unused_trait_imports: NodeSet,
1177
1178     privacy_errors: Vec<PrivacyError<'a>>,
1179     ambiguity_errors: Vec<AmbiguityError<'a>>,
1180     gated_errors: FxHashSet<Span>,
1181     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1182
1183     arenas: &'a ResolverArenas<'a>,
1184     dummy_binding: &'a NameBinding<'a>,
1185     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1186
1187     crate_loader: &'a mut CrateLoader,
1188     macro_names: FxHashSet<Name>,
1189     global_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1190     lexical_macro_resolutions: Vec<(Name, &'a Cell<LegacyScope<'a>>)>,
1191     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1192     macro_defs: FxHashMap<Mark, DefId>,
1193     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
1194     macro_exports: Vec<Export>,
1195     pub whitelisted_legacy_custom_derives: Vec<Name>,
1196     pub found_unresolved_macro: bool,
1197
1198     // List of macros that we need to warn about as being unused.
1199     // The bool is true if the macro is unused, and false if its used.
1200     // Setting a bool to false should be much faster than removing a single
1201     // element from a FxHashSet.
1202     unused_macros: FxHashMap<DefId, bool>,
1203
1204     // Maps the `Mark` of an expansion to its containing module or block.
1205     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1206
1207     // Avoid duplicated errors for "name already defined".
1208     name_already_seen: FxHashMap<Name, Span>,
1209
1210     // If `#![feature(proc_macro)]` is set
1211     proc_macro_enabled: bool,
1212
1213     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1214     warned_proc_macros: FxHashSet<Name>,
1215
1216     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1217
1218     // This table maps struct IDs into struct constructor IDs,
1219     // it's not used during normal resolution, only for better error reporting.
1220     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1221 }
1222
1223 pub struct ResolverArenas<'a> {
1224     modules: arena::TypedArena<ModuleData<'a>>,
1225     local_modules: RefCell<Vec<Module<'a>>>,
1226     name_bindings: arena::TypedArena<NameBinding<'a>>,
1227     import_directives: arena::TypedArena<ImportDirective<'a>>,
1228     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1229     invocation_data: arena::TypedArena<InvocationData<'a>>,
1230     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1231 }
1232
1233 impl<'a> ResolverArenas<'a> {
1234     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1235         let module = self.modules.alloc(module);
1236         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1237             self.local_modules.borrow_mut().push(module);
1238         }
1239         module
1240     }
1241     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1242         self.local_modules.borrow()
1243     }
1244     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1245         self.name_bindings.alloc(name_binding)
1246     }
1247     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1248                               -> &'a ImportDirective {
1249         self.import_directives.alloc(import_directive)
1250     }
1251     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1252         self.name_resolutions.alloc(Default::default())
1253     }
1254     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1255                              -> &'a InvocationData<'a> {
1256         self.invocation_data.alloc(expansion_data)
1257     }
1258     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1259         self.legacy_bindings.alloc(binding)
1260     }
1261 }
1262
1263 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1264     fn parent(self, id: DefId) -> Option<DefId> {
1265         match id.krate {
1266             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1267             _ => self.session.cstore.def_key(id).parent,
1268         }.map(|index| DefId { index: index, ..id })
1269     }
1270 }
1271
1272 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1273     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1274         let namespace = if is_value { ValueNS } else { TypeNS };
1275         let hir::Path { ref segments, span, ref mut def } = *path;
1276         let path: Vec<_> = segments.iter().map(|seg| Ident::with_empty_ctxt(seg.name)).collect();
1277         match self.resolve_path(&path, Some(namespace), true, span) {
1278             PathResult::Module(module) => *def = module.def().unwrap(),
1279             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 =>
1280                 *def = path_res.base_def(),
1281             PathResult::NonModule(..) => match self.resolve_path(&path, None, true, span) {
1282                 PathResult::Failed(msg, _) => {
1283                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1284                 }
1285                 _ => {}
1286             },
1287             PathResult::Indeterminate => unreachable!(),
1288             PathResult::Failed(msg, _) => {
1289                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1290             }
1291         }
1292     }
1293
1294     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1295         self.def_map.get(&id).cloned()
1296     }
1297
1298     fn definitions(&mut self) -> &mut Definitions {
1299         &mut self.definitions
1300     }
1301 }
1302
1303 impl<'a> Resolver<'a> {
1304     pub fn new(session: &'a Session,
1305                krate: &Crate,
1306                crate_name: &str,
1307                make_glob_map: MakeGlobMap,
1308                crate_loader: &'a mut CrateLoader,
1309                arenas: &'a ResolverArenas<'a>)
1310                -> Resolver<'a> {
1311         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1312         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1313         let graph_root = arenas.alloc_module(ModuleData {
1314             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1315             ..ModuleData::new(None, root_module_kind, root_def_id, krate.span)
1316         });
1317         let mut module_map = FxHashMap();
1318         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1319
1320         let mut definitions = Definitions::new();
1321         DefCollector::new(&mut definitions)
1322             .collect_root(crate_name, &session.local_crate_disambiguator().as_str());
1323
1324         let mut invocations = FxHashMap();
1325         invocations.insert(Mark::root(),
1326                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1327
1328         let features = session.features.borrow();
1329
1330         let mut macro_defs = FxHashMap();
1331         macro_defs.insert(Mark::root(), root_def_id);
1332
1333         Resolver {
1334             session: session,
1335
1336             definitions: definitions,
1337
1338             // The outermost module has def ID 0; this is not reflected in the
1339             // AST.
1340             graph_root: graph_root,
1341             prelude: None,
1342
1343             trait_item_map: FxHashMap(),
1344             field_names: FxHashMap(),
1345
1346             determined_imports: Vec::new(),
1347             indeterminate_imports: Vec::new(),
1348
1349             current_module: graph_root,
1350             ribs: PerNS {
1351                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1352                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1353                 macro_ns: Some(vec![Rib::new(ModuleRibKind(graph_root))]),
1354             },
1355             label_ribs: Vec::new(),
1356
1357             current_trait_ref: None,
1358             current_self_type: None,
1359
1360             primitive_type_table: PrimitiveTypeTable::new(),
1361
1362             def_map: NodeMap(),
1363             freevars: NodeMap(),
1364             freevars_seen: NodeMap(),
1365             export_map: NodeMap(),
1366             trait_map: NodeMap(),
1367             module_map: module_map,
1368             block_map: NodeMap(),
1369             extern_crate_roots: FxHashMap(),
1370
1371             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1372             glob_map: NodeMap(),
1373
1374             used_imports: FxHashSet(),
1375             maybe_unused_trait_imports: NodeSet(),
1376
1377             privacy_errors: Vec::new(),
1378             ambiguity_errors: Vec::new(),
1379             gated_errors: FxHashSet(),
1380             disallowed_shadowing: Vec::new(),
1381
1382             arenas: arenas,
1383             dummy_binding: arenas.alloc_name_binding(NameBinding {
1384                 kind: NameBindingKind::Def(Def::Err),
1385                 expansion: Mark::root(),
1386                 span: DUMMY_SP,
1387                 vis: ty::Visibility::Public,
1388             }),
1389
1390             // `#![feature(proc_macro)]` implies `#[feature(extern_macros)]`
1391             use_extern_macros: features.use_extern_macros || features.proc_macro,
1392
1393             crate_loader: crate_loader,
1394             macro_names: FxHashSet(),
1395             global_macros: FxHashMap(),
1396             lexical_macro_resolutions: Vec::new(),
1397             macro_map: FxHashMap(),
1398             macro_exports: Vec::new(),
1399             invocations: invocations,
1400             macro_defs: macro_defs,
1401             local_macro_def_scopes: FxHashMap(),
1402             name_already_seen: FxHashMap(),
1403             whitelisted_legacy_custom_derives: Vec::new(),
1404             proc_macro_enabled: features.proc_macro,
1405             warned_proc_macros: FxHashSet(),
1406             potentially_unused_imports: Vec::new(),
1407             struct_constructors: DefIdMap(),
1408             found_unresolved_macro: false,
1409             unused_macros: FxHashMap(),
1410         }
1411     }
1412
1413     pub fn arenas() -> ResolverArenas<'a> {
1414         ResolverArenas {
1415             modules: arena::TypedArena::new(),
1416             local_modules: RefCell::new(Vec::new()),
1417             name_bindings: arena::TypedArena::new(),
1418             import_directives: arena::TypedArena::new(),
1419             name_resolutions: arena::TypedArena::new(),
1420             invocation_data: arena::TypedArena::new(),
1421             legacy_bindings: arena::TypedArena::new(),
1422         }
1423     }
1424
1425     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1426         PerNS {
1427             type_ns: f(self, TypeNS),
1428             value_ns: f(self, ValueNS),
1429             macro_ns: match self.use_extern_macros {
1430                 true => Some(f(self, MacroNS)),
1431                 false => None,
1432             },
1433         }
1434     }
1435
1436     /// Entry point to crate resolution.
1437     pub fn resolve_crate(&mut self, krate: &Crate) {
1438         ImportResolver { resolver: self }.finalize_imports();
1439         self.current_module = self.graph_root;
1440         self.finalize_current_module_macro_resolutions();
1441         visit::walk_crate(self, krate);
1442
1443         check_unused::check_crate(self, krate);
1444         self.report_errors();
1445         self.crate_loader.postprocess(krate);
1446     }
1447
1448     fn new_module(
1449         &self,
1450         parent: Module<'a>,
1451         kind: ModuleKind,
1452         normal_ancestor_id: DefId,
1453         span: Span,
1454     ) -> Module<'a> {
1455         self.arenas.alloc_module(ModuleData::new(Some(parent), kind, normal_ancestor_id, span))
1456     }
1457
1458     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1459                   -> bool /* true if an error was reported */ {
1460         match binding.kind {
1461             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1462                     if !used.get() => {
1463                 used.set(true);
1464                 directive.used.set(true);
1465                 if legacy_self_import {
1466                     self.warn_legacy_self_import(directive);
1467                     return false;
1468                 }
1469                 self.used_imports.insert((directive.id, ns));
1470                 self.add_to_glob_map(directive.id, ident);
1471                 self.record_use(ident, ns, binding, span)
1472             }
1473             NameBindingKind::Import { .. } => false,
1474             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1475                 self.ambiguity_errors.push(AmbiguityError {
1476                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy: legacy,
1477                 });
1478                 if legacy {
1479                     self.record_use(ident, ns, b1, span);
1480                 }
1481                 !legacy
1482             }
1483             _ => false
1484         }
1485     }
1486
1487     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1488         if self.make_glob_map {
1489             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1490         }
1491     }
1492
1493     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1494     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1495     /// `ident` in the first scope that defines it (or None if no scopes define it).
1496     ///
1497     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1498     /// the items are defined in the block. For example,
1499     /// ```rust
1500     /// fn f() {
1501     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1502     ///    let g = || {};
1503     ///    fn g() {}
1504     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1505     /// }
1506     /// ```
1507     ///
1508     /// Invariant: This must only be called during main resolution, not during
1509     /// import resolution.
1510     fn resolve_ident_in_lexical_scope(&mut self,
1511                                       mut ident: Ident,
1512                                       ns: Namespace,
1513                                       record_used: bool,
1514                                       path_span: Span)
1515                                       -> Option<LexicalScopeBinding<'a>> {
1516         if ns == TypeNS {
1517             ident = ident.unhygienize();
1518         }
1519
1520         // Walk backwards up the ribs in scope.
1521         for i in (0 .. self.ribs[ns].len()).rev() {
1522             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1523                 // The ident resolves to a type parameter or local variable.
1524                 return Some(LexicalScopeBinding::Def(
1525                     self.adjust_local_def(ns, i, def, record_used, path_span)
1526                 ));
1527             }
1528
1529             if let ModuleRibKind(module) = self.ribs[ns][i].kind {
1530                 let item = self.resolve_ident_in_module(module, ident, ns, false,
1531                                                         record_used, path_span);
1532                 if let Ok(binding) = item {
1533                     // The ident resolves to an item.
1534                     return Some(LexicalScopeBinding::Item(binding));
1535                 }
1536
1537                 if let ModuleKind::Block(..) = module.kind { // We can see through blocks
1538                 } else if !module.no_implicit_prelude {
1539                     return self.prelude.and_then(|prelude| {
1540                         self.resolve_ident_in_module(prelude, ident, ns, false,
1541                                                      false, path_span).ok()
1542                     }).map(LexicalScopeBinding::Item)
1543                 } else {
1544                     return None;
1545                 }
1546             }
1547
1548             if let MacroDefinition(def) = self.ribs[ns][i].kind {
1549                 // If an invocation of this macro created `ident`, give up on `ident`
1550                 // and switch to `ident`'s source from the macro definition.
1551                 let ctxt_data = ident.ctxt.data();
1552                 if def == self.macro_defs[&ctxt_data.outer_mark] {
1553                     ident.ctxt = ctxt_data.prev_ctxt;
1554                 }
1555             }
1556         }
1557
1558         None
1559     }
1560
1561     fn resolve_crate_var(&mut self, crate_var_ctxt: SyntaxContext, span: Span) -> Module<'a> {
1562         let mut ctxt_data = crate_var_ctxt.data();
1563         while ctxt_data.prev_ctxt != SyntaxContext::empty() {
1564             ctxt_data = ctxt_data.prev_ctxt.data();
1565         }
1566         let module = self.macro_def_scope(ctxt_data.outer_mark, span);
1567         if module.is_local() { self.graph_root } else { module }
1568     }
1569
1570     // AST resolution
1571     //
1572     // We maintain a list of value ribs and type ribs.
1573     //
1574     // Simultaneously, we keep track of the current position in the module
1575     // graph in the `current_module` pointer. When we go to resolve a name in
1576     // the value or type namespaces, we first look through all the ribs and
1577     // then query the module graph. When we resolve a name in the module
1578     // namespace, we can skip all the ribs (since nested modules are not
1579     // allowed within blocks in Rust) and jump straight to the current module
1580     // graph node.
1581     //
1582     // Named implementations are handled separately. When we find a method
1583     // call, we consult the module node to find all of the implementations in
1584     // scope. This information is lazily cached in the module node. We then
1585     // generate a fake "implementation scope" containing all the
1586     // implementations thus found, for compatibility with old resolve pass.
1587
1588     fn with_scope<F>(&mut self, id: NodeId, f: F)
1589         where F: FnOnce(&mut Resolver)
1590     {
1591         let id = self.definitions.local_def_id(id);
1592         let module = self.module_map.get(&id).cloned(); // clones a reference
1593         if let Some(module) = module {
1594             // Move down in the graph.
1595             let orig_module = replace(&mut self.current_module, module);
1596             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1597             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1598
1599             self.finalize_current_module_macro_resolutions();
1600             f(self);
1601
1602             self.current_module = orig_module;
1603             self.ribs[ValueNS].pop();
1604             self.ribs[TypeNS].pop();
1605         } else {
1606             f(self);
1607         }
1608     }
1609
1610     /// Searches the current set of local scopes for labels.
1611     /// Stops after meeting a closure.
1612     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1613         for rib in self.label_ribs.iter().rev() {
1614             match rib.kind {
1615                 NormalRibKind => {
1616                     // Continue
1617                 }
1618                 MacroDefinition(def) => {
1619                     // If an invocation of this macro created `ident`, give up on `ident`
1620                     // and switch to `ident`'s source from the macro definition.
1621                     let ctxt_data = ident.ctxt.data();
1622                     if def == self.macro_defs[&ctxt_data.outer_mark] {
1623                         ident.ctxt = ctxt_data.prev_ctxt;
1624                     }
1625                 }
1626                 _ => {
1627                     // Do not resolve labels across function boundary
1628                     return None;
1629                 }
1630             }
1631             let result = rib.bindings.get(&ident).cloned();
1632             if result.is_some() {
1633                 return result;
1634             }
1635         }
1636         None
1637     }
1638
1639     fn resolve_item(&mut self, item: &Item) {
1640         let name = item.ident.name;
1641
1642         debug!("(resolving item) resolving {}", name);
1643
1644         self.check_proc_macro_attrs(&item.attrs);
1645
1646         match item.node {
1647             ItemKind::Enum(_, ref generics) |
1648             ItemKind::Ty(_, ref generics) |
1649             ItemKind::Struct(_, ref generics) |
1650             ItemKind::Union(_, ref generics) |
1651             ItemKind::Fn(.., ref generics, _) => {
1652                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1653                                              |this| visit::walk_item(this, item));
1654             }
1655
1656             ItemKind::DefaultImpl(_, ref trait_ref) => {
1657                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1658                     // Resolve type arguments in trait path
1659                     visit::walk_trait_ref(this, trait_ref);
1660                 });
1661             }
1662             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1663                 self.resolve_implementation(generics,
1664                                             opt_trait_ref,
1665                                             &self_type,
1666                                             item.id,
1667                                             impl_items),
1668
1669             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1670                 // Create a new rib for the trait-wide type parameters.
1671                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1672                     let local_def_id = this.definitions.local_def_id(item.id);
1673                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1674                         this.visit_generics(generics);
1675                         walk_list!(this, visit_ty_param_bound, bounds);
1676
1677                         for trait_item in trait_items {
1678                             this.check_proc_macro_attrs(&trait_item.attrs);
1679
1680                             match trait_item.node {
1681                                 TraitItemKind::Const(_, ref default) => {
1682                                     // Only impose the restrictions of
1683                                     // ConstRibKind if there's an actual constant
1684                                     // expression in a provided default.
1685                                     if default.is_some() {
1686                                         this.with_constant_rib(|this| {
1687                                             visit::walk_trait_item(this, trait_item)
1688                                         });
1689                                     } else {
1690                                         visit::walk_trait_item(this, trait_item)
1691                                     }
1692                                 }
1693                                 TraitItemKind::Method(ref sig, _) => {
1694                                     let type_parameters =
1695                                         HasTypeParameters(&sig.generics,
1696                                                           MethodRibKind(!sig.decl.has_self()));
1697                                     this.with_type_parameter_rib(type_parameters, |this| {
1698                                         visit::walk_trait_item(this, trait_item)
1699                                     });
1700                                 }
1701                                 TraitItemKind::Type(..) => {
1702                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1703                                         visit::walk_trait_item(this, trait_item)
1704                                     });
1705                                 }
1706                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1707                             };
1708                         }
1709                     });
1710                 });
1711             }
1712
1713             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1714                 self.with_scope(item.id, |this| {
1715                     visit::walk_item(this, item);
1716                 });
1717             }
1718
1719             ItemKind::Const(..) | ItemKind::Static(..) => {
1720                 self.with_constant_rib(|this| {
1721                     visit::walk_item(this, item);
1722                 });
1723             }
1724
1725             ItemKind::Use(ref view_path) => {
1726                 match view_path.node {
1727                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1728                         // Resolve prefix of an import with empty braces (issue #28388).
1729                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1730                     }
1731                     _ => {}
1732                 }
1733             }
1734
1735             ItemKind::ExternCrate(_) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(_)=> {
1736                 // do nothing, these are just around to be encoded
1737             }
1738
1739             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1740         }
1741     }
1742
1743     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1744         where F: FnOnce(&mut Resolver)
1745     {
1746         match type_parameters {
1747             HasTypeParameters(generics, rib_kind) => {
1748                 let mut function_type_rib = Rib::new(rib_kind);
1749                 let mut seen_bindings = FxHashMap();
1750                 for type_parameter in &generics.ty_params {
1751                     let name = type_parameter.ident.name;
1752                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1753
1754                     if seen_bindings.contains_key(&name) {
1755                         let span = seen_bindings.get(&name).unwrap();
1756                         resolve_error(self,
1757                                       type_parameter.span,
1758                                       ResolutionError::NameAlreadyUsedInTypeParameterList(name,
1759                                                                                           span));
1760                     }
1761                     seen_bindings.entry(name).or_insert(type_parameter.span);
1762
1763                     // plain insert (no renaming)
1764                     let def_id = self.definitions.local_def_id(type_parameter.id);
1765                     let def = Def::TyParam(def_id);
1766                     function_type_rib.bindings.insert(Ident::with_empty_ctxt(name), def);
1767                     self.record_def(type_parameter.id, PathResolution::new(def));
1768                 }
1769                 self.ribs[TypeNS].push(function_type_rib);
1770             }
1771
1772             NoTypeParameters => {
1773                 // Nothing to do.
1774             }
1775         }
1776
1777         f(self);
1778
1779         if let HasTypeParameters(..) = type_parameters {
1780             self.ribs[TypeNS].pop();
1781         }
1782     }
1783
1784     fn with_label_rib<F>(&mut self, f: F)
1785         where F: FnOnce(&mut Resolver)
1786     {
1787         self.label_ribs.push(Rib::new(NormalRibKind));
1788         f(self);
1789         self.label_ribs.pop();
1790     }
1791
1792     fn with_constant_rib<F>(&mut self, f: F)
1793         where F: FnOnce(&mut Resolver)
1794     {
1795         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1796         self.ribs[TypeNS].push(Rib::new(ConstantItemRibKind));
1797         f(self);
1798         self.ribs[TypeNS].pop();
1799         self.ribs[ValueNS].pop();
1800     }
1801
1802     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1803         where F: FnOnce(&mut Resolver) -> T
1804     {
1805         // Handle nested impls (inside fn bodies)
1806         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1807         let result = f(self);
1808         self.current_self_type = previous_value;
1809         result
1810     }
1811
1812     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1813         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1814     {
1815         let mut new_val = None;
1816         let mut new_id = None;
1817         if let Some(trait_ref) = opt_trait_ref {
1818             let def = self.smart_resolve_path(trait_ref.ref_id, None,
1819                                               &trait_ref.path, PathSource::Trait).base_def();
1820             if def != Def::Err {
1821                 new_val = Some((def.def_id(), trait_ref.clone()));
1822                 new_id = Some(def.def_id());
1823             }
1824         }
1825         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1826         let result = f(self, new_id);
1827         self.current_trait_ref = original_trait_ref;
1828         result
1829     }
1830
1831     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
1832         where F: FnOnce(&mut Resolver)
1833     {
1834         let mut self_type_rib = Rib::new(NormalRibKind);
1835
1836         // plain insert (no renaming, types are not currently hygienic....)
1837         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
1838         self.ribs[TypeNS].push(self_type_rib);
1839         f(self);
1840         self.ribs[TypeNS].pop();
1841     }
1842
1843     fn resolve_implementation(&mut self,
1844                               generics: &Generics,
1845                               opt_trait_reference: &Option<TraitRef>,
1846                               self_type: &Ty,
1847                               item_id: NodeId,
1848                               impl_items: &[ImplItem]) {
1849         // If applicable, create a rib for the type parameters.
1850         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1851             // Dummy self type for better errors if `Self` is used in the trait path.
1852             this.with_self_rib(Def::SelfTy(None, None), |this| {
1853                 // Resolve the trait reference, if necessary.
1854                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
1855                     let item_def_id = this.definitions.local_def_id(item_id);
1856                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
1857                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
1858                             // Resolve type arguments in trait path
1859                             visit::walk_trait_ref(this, trait_ref);
1860                         }
1861                         // Resolve the self type.
1862                         this.visit_ty(self_type);
1863                         // Resolve the type parameters.
1864                         this.visit_generics(generics);
1865                         this.with_current_self_type(self_type, |this| {
1866                             for impl_item in impl_items {
1867                                 this.check_proc_macro_attrs(&impl_item.attrs);
1868                                 this.resolve_visibility(&impl_item.vis);
1869                                 match impl_item.node {
1870                                     ImplItemKind::Const(..) => {
1871                                         // If this is a trait impl, ensure the const
1872                                         // exists in trait
1873                                         this.check_trait_item(impl_item.ident.name,
1874                                                             ValueNS,
1875                                                             impl_item.span,
1876                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
1877                                         visit::walk_impl_item(this, impl_item);
1878                                     }
1879                                     ImplItemKind::Method(ref sig, _) => {
1880                                         // If this is a trait impl, ensure the method
1881                                         // exists in trait
1882                                         this.check_trait_item(impl_item.ident.name,
1883                                                             ValueNS,
1884                                                             impl_item.span,
1885                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
1886
1887                                         // We also need a new scope for the method-
1888                                         // specific type parameters.
1889                                         let type_parameters =
1890                                             HasTypeParameters(&sig.generics,
1891                                                             MethodRibKind(!sig.decl.has_self()));
1892                                         this.with_type_parameter_rib(type_parameters, |this| {
1893                                             visit::walk_impl_item(this, impl_item);
1894                                         });
1895                                     }
1896                                     ImplItemKind::Type(ref ty) => {
1897                                         // If this is a trait impl, ensure the type
1898                                         // exists in trait
1899                                         this.check_trait_item(impl_item.ident.name,
1900                                                             TypeNS,
1901                                                             impl_item.span,
1902                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
1903
1904                                         this.visit_ty(ty);
1905                                     }
1906                                     ImplItemKind::Macro(_) =>
1907                                         panic!("unexpanded macro in resolve!"),
1908                                 }
1909                             }
1910                         });
1911                     });
1912                 });
1913             });
1914         });
1915     }
1916
1917     fn check_trait_item<F>(&self, name: Name, ns: Namespace, span: Span, err: F)
1918         where F: FnOnce(Name, &str) -> ResolutionError
1919     {
1920         // If there is a TraitRef in scope for an impl, then the method must be in the
1921         // trait.
1922         if let Some((did, ref trait_ref)) = self.current_trait_ref {
1923             if !self.trait_item_map.contains_key(&(did, name, ns)) {
1924                 let path_str = path_names_to_string(&trait_ref.path);
1925                 resolve_error(self, span, err(name, &path_str));
1926             }
1927         }
1928     }
1929
1930     fn resolve_local(&mut self, local: &Local) {
1931         // Resolve the type.
1932         walk_list!(self, visit_ty, &local.ty);
1933
1934         // Resolve the initializer.
1935         walk_list!(self, visit_expr, &local.init);
1936
1937         // Resolve the pattern.
1938         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
1939     }
1940
1941     // build a map from pattern identifiers to binding-info's.
1942     // this is done hygienically. This could arise for a macro
1943     // that expands into an or-pattern where one 'x' was from the
1944     // user and one 'x' came from the macro.
1945     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
1946         let mut binding_map = FxHashMap();
1947
1948         pat.walk(&mut |pat| {
1949             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
1950                 if sub_pat.is_some() || match self.def_map.get(&pat.id).map(|res| res.base_def()) {
1951                     Some(Def::Local(..)) => true,
1952                     _ => false,
1953                 } {
1954                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
1955                     binding_map.insert(ident.node, binding_info);
1956                 }
1957             }
1958             true
1959         });
1960
1961         binding_map
1962     }
1963
1964     // check that all of the arms in an or-pattern have exactly the
1965     // same set of bindings, with the same binding modes for each.
1966     fn check_consistent_bindings(&mut self, arm: &Arm) {
1967         if arm.pats.is_empty() {
1968             return;
1969         }
1970
1971         let mut missing_vars = FxHashMap();
1972         let mut inconsistent_vars = FxHashMap();
1973         for (i, p) in arm.pats.iter().enumerate() {
1974             let map_i = self.binding_mode_map(&p);
1975
1976             for (j, q) in arm.pats.iter().enumerate() {
1977                 if i == j {
1978                     continue;
1979                 }
1980
1981                 let map_j = self.binding_mode_map(&q);
1982                 for (&key, &binding_i) in &map_i {
1983                     if map_j.len() == 0 {                   // Account for missing bindings when
1984                         let binding_error = missing_vars    // map_j has none.
1985                             .entry(key.name)
1986                             .or_insert(BindingError {
1987                                 name: key.name,
1988                                 origin: BTreeSet::new(),
1989                                 target: BTreeSet::new(),
1990                             });
1991                         binding_error.origin.insert(binding_i.span);
1992                         binding_error.target.insert(q.span);
1993                     }
1994                     for (&key_j, &binding_j) in &map_j {
1995                         match map_i.get(&key_j) {
1996                             None => {  // missing binding
1997                                 let binding_error = missing_vars
1998                                     .entry(key_j.name)
1999                                     .or_insert(BindingError {
2000                                         name: key_j.name,
2001                                         origin: BTreeSet::new(),
2002                                         target: BTreeSet::new(),
2003                                     });
2004                                 binding_error.origin.insert(binding_j.span);
2005                                 binding_error.target.insert(p.span);
2006                             }
2007                             Some(binding_i) => {  // check consistent binding
2008                                 if binding_i.binding_mode != binding_j.binding_mode {
2009                                     inconsistent_vars
2010                                         .entry(key.name)
2011                                         .or_insert((binding_j.span, binding_i.span));
2012                                 }
2013                             }
2014                         }
2015                     }
2016                 }
2017             }
2018         }
2019         let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();
2020         missing_vars.sort();
2021         for (_, v) in missing_vars {
2022             resolve_error(self,
2023                           *v.origin.iter().next().unwrap(),
2024                           ResolutionError::VariableNotBoundInPattern(v));
2025         }
2026         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2027         inconsistent_vars.sort();
2028         for (name, v) in inconsistent_vars {
2029             resolve_error(self, v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2030         }
2031     }
2032
2033     fn resolve_arm(&mut self, arm: &Arm) {
2034         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2035
2036         let mut bindings_list = FxHashMap();
2037         for pattern in &arm.pats {
2038             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2039         }
2040
2041         // This has to happen *after* we determine which
2042         // pat_idents are variants
2043         self.check_consistent_bindings(arm);
2044
2045         walk_list!(self, visit_expr, &arm.guard);
2046         self.visit_expr(&arm.body);
2047
2048         self.ribs[ValueNS].pop();
2049     }
2050
2051     fn resolve_block(&mut self, block: &Block) {
2052         debug!("(resolving block) entering block");
2053         // Move down in the graph, if there's an anonymous module rooted here.
2054         let orig_module = self.current_module;
2055         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
2056
2057         let mut num_macro_definition_ribs = 0;
2058         if let Some(anonymous_module) = anonymous_module {
2059             debug!("(resolving block) found anonymous module, moving down");
2060             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2061             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2062             self.current_module = anonymous_module;
2063             self.finalize_current_module_macro_resolutions();
2064         } else {
2065             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2066         }
2067
2068         // Descend into the block.
2069         for stmt in &block.stmts {
2070             if let ast::StmtKind::Item(ref item) = stmt.node {
2071                 if let ast::ItemKind::MacroDef(..) = item.node {
2072                     num_macro_definition_ribs += 1;
2073                     let def = self.definitions.local_def_id(item.id);
2074                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(def)));
2075                     self.label_ribs.push(Rib::new(MacroDefinition(def)));
2076                 }
2077             }
2078
2079             self.visit_stmt(stmt);
2080         }
2081
2082         // Move back up.
2083         self.current_module = orig_module;
2084         for _ in 0 .. num_macro_definition_ribs {
2085             self.ribs[ValueNS].pop();
2086             self.label_ribs.pop();
2087         }
2088         self.ribs[ValueNS].pop();
2089         if let Some(_) = anonymous_module {
2090             self.ribs[TypeNS].pop();
2091         }
2092         debug!("(resolving block) leaving block");
2093     }
2094
2095     fn fresh_binding(&mut self,
2096                      ident: &SpannedIdent,
2097                      pat_id: NodeId,
2098                      outer_pat_id: NodeId,
2099                      pat_src: PatternSource,
2100                      bindings: &mut FxHashMap<Ident, NodeId>)
2101                      -> PathResolution {
2102         // Add the binding to the local ribs, if it
2103         // doesn't already exist in the bindings map. (We
2104         // must not add it if it's in the bindings map
2105         // because that breaks the assumptions later
2106         // passes make about or-patterns.)
2107         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
2108         match bindings.get(&ident.node).cloned() {
2109             Some(id) if id == outer_pat_id => {
2110                 // `Variant(a, a)`, error
2111                 resolve_error(
2112                     self,
2113                     ident.span,
2114                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2115                         &ident.node.name.as_str())
2116                 );
2117             }
2118             Some(..) if pat_src == PatternSource::FnParam => {
2119                 // `fn f(a: u8, a: u8)`, error
2120                 resolve_error(
2121                     self,
2122                     ident.span,
2123                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2124                         &ident.node.name.as_str())
2125                 );
2126             }
2127             Some(..) if pat_src == PatternSource::Match => {
2128                 // `Variant1(a) | Variant2(a)`, ok
2129                 // Reuse definition from the first `a`.
2130                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
2131             }
2132             Some(..) => {
2133                 span_bug!(ident.span, "two bindings with the same name from \
2134                                        unexpected pattern source {:?}", pat_src);
2135             }
2136             None => {
2137                 // A completely fresh binding, add to the lists if it's valid.
2138                 if ident.node.name != keywords::Invalid.name() {
2139                     bindings.insert(ident.node, outer_pat_id);
2140                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2141                 }
2142             }
2143         }
2144
2145         PathResolution::new(def)
2146     }
2147
2148     fn resolve_pattern(&mut self,
2149                        pat: &Pat,
2150                        pat_src: PatternSource,
2151                        // Maps idents to the node ID for the
2152                        // outermost pattern that binds them.
2153                        bindings: &mut FxHashMap<Ident, NodeId>) {
2154         // Visit all direct subpatterns of this pattern.
2155         let outer_pat_id = pat.id;
2156         pat.walk(&mut |pat| {
2157             match pat.node {
2158                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2159                     // First try to resolve the identifier as some existing
2160                     // entity, then fall back to a fresh binding.
2161                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS,
2162                                                                       false, pat.span)
2163                                       .and_then(LexicalScopeBinding::item);
2164                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2165                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2166                                              bmode != BindingMode::ByValue(Mutability::Immutable);
2167                         match def {
2168                             Def::StructCtor(_, CtorKind::Const) |
2169                             Def::VariantCtor(_, CtorKind::Const) |
2170                             Def::Const(..) if !always_binding => {
2171                                 // A unit struct/variant or constant pattern.
2172                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2173                                 Some(PathResolution::new(def))
2174                             }
2175                             Def::StructCtor(..) | Def::VariantCtor(..) |
2176                             Def::Const(..) | Def::Static(..) => {
2177                                 // A fresh binding that shadows something unacceptable.
2178                                 resolve_error(
2179                                     self,
2180                                     ident.span,
2181                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2182                                         pat_src.descr(), ident.node.name, binding.unwrap())
2183                                 );
2184                                 None
2185                             }
2186                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2187                                 // These entities are explicitly allowed
2188                                 // to be shadowed by fresh bindings.
2189                                 None
2190                             }
2191                             def => {
2192                                 span_bug!(ident.span, "unexpected definition for an \
2193                                                        identifier in pattern: {:?}", def);
2194                             }
2195                         }
2196                     }).unwrap_or_else(|| {
2197                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2198                     });
2199
2200                     self.record_def(pat.id, resolution);
2201                 }
2202
2203                 PatKind::TupleStruct(ref path, ..) => {
2204                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2205                 }
2206
2207                 PatKind::Path(ref qself, ref path) => {
2208                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2209                 }
2210
2211                 PatKind::Struct(ref path, ..) => {
2212                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2213                 }
2214
2215                 _ => {}
2216             }
2217             true
2218         });
2219
2220         visit::walk_pat(self, pat);
2221     }
2222
2223     // High-level and context dependent path resolution routine.
2224     // Resolves the path and records the resolution into definition map.
2225     // If resolution fails tries several techniques to find likely
2226     // resolution candidates, suggest imports or other help, and report
2227     // errors in user friendly way.
2228     fn smart_resolve_path(&mut self,
2229                           id: NodeId,
2230                           qself: Option<&QSelf>,
2231                           path: &Path,
2232                           source: PathSource)
2233                           -> PathResolution {
2234         let segments = &path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>();
2235         let ident_span = path.segments.last().map_or(path.span, |seg| seg.span);
2236         self.smart_resolve_path_fragment(id, qself, segments, path.span, ident_span, source)
2237     }
2238
2239     fn smart_resolve_path_fragment(&mut self,
2240                                    id: NodeId,
2241                                    qself: Option<&QSelf>,
2242                                    path: &[Ident],
2243                                    span: Span,
2244                                    ident_span: Span,
2245                                    source: PathSource)
2246                                    -> PathResolution {
2247         let ns = source.namespace();
2248         let is_expected = &|def| source.is_expected(def);
2249         let is_enum_variant = &|def| if let Def::Variant(..) = def { true } else { false };
2250
2251         // Base error is amended with one short label and possibly some longer helps/notes.
2252         let report_errors = |this: &mut Self, def: Option<Def>| {
2253             // Make the base error.
2254             let expected = source.descr_expected();
2255             let path_str = names_to_string(path);
2256             let code = source.error_code(def.is_some());
2257             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
2258                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2259                  format!("not a {}", expected), span)
2260             } else {
2261                 let item_str = path[path.len() - 1];
2262                 let (mod_prefix, mod_str) = if path.len() == 1 {
2263                     (format!(""), format!("this scope"))
2264                 } else if path.len() == 2 && path[0].name == keywords::CrateRoot.name() {
2265                     (format!(""), format!("the crate root"))
2266                 } else {
2267                     let mod_path = &path[..path.len() - 1];
2268                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), false, span) {
2269                         PathResult::Module(module) => module.def(),
2270                         _ => None,
2271                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2272                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2273                 };
2274                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2275                  format!("not found in {}", mod_str), ident_span)
2276             };
2277             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
2278
2279             // Emit special messages for unresolved `Self` and `self`.
2280             if is_self_type(path, ns) {
2281                 __diagnostic_used!(E0411);
2282                 err.code("E0411".into());
2283                 err.span_label(span, "`Self` is only available in traits and impls");
2284                 return err;
2285             }
2286             if is_self_value(path, ns) {
2287                 __diagnostic_used!(E0424);
2288                 err.code("E0424".into());
2289                 err.span_label(span, format!("`self` value is only available in \
2290                                                methods with `self` parameter"));
2291                 return err;
2292             }
2293
2294             // Try to lookup the name in more relaxed fashion for better error reporting.
2295             let name = path.last().unwrap().name;
2296             let candidates = this.lookup_import_candidates(name, ns, is_expected);
2297             if !candidates.is_empty() {
2298                 let mut module_span = this.current_module.span;
2299                 module_span.hi = module_span.lo;
2300                 // Report import candidates as help and proceed searching for labels.
2301                 show_candidates(&mut err, module_span, &candidates, def.is_some());
2302             } else if is_expected(Def::Enum(DefId::local(CRATE_DEF_INDEX))) {
2303                 let enum_candidates = this.lookup_import_candidates(name, ns, is_enum_variant);
2304                 let mut enum_candidates = enum_candidates.iter()
2305                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
2306                 enum_candidates.sort();
2307                 for (sp, variant_path, enum_path) in enum_candidates {
2308                     let msg = format!("there is an enum variant `{}`, did you mean to use `{}`?",
2309                                       variant_path,
2310                                       enum_path);
2311                     if sp == DUMMY_SP {
2312                         err.help(&msg);
2313                     } else {
2314                         err.span_help(sp, &msg);
2315                     }
2316                 }
2317             }
2318             if path.len() == 1 && this.self_type_is_available(span) {
2319                 if let Some(candidate) = this.lookup_assoc_candidate(name, ns, is_expected) {
2320                     let self_is_available = this.self_value_is_available(path[0].ctxt, span);
2321                     match candidate {
2322                         AssocSuggestion::Field => {
2323                             err.span_label(span, format!("did you mean `self.{}`?", path_str));
2324                             if !self_is_available {
2325                                 err.span_label(span, format!("`self` value is only available in \
2326                                                                methods with `self` parameter"));
2327                             }
2328                         }
2329                         AssocSuggestion::MethodWithSelf if self_is_available => {
2330                             err.span_label(span, format!("did you mean `self.{}(...)`?",
2331                                                            path_str));
2332                         }
2333                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2334                             err.span_label(span, format!("did you mean `Self::{}`?", path_str));
2335                         }
2336                     }
2337                     return err;
2338                 }
2339             }
2340
2341             let mut levenshtein_worked = false;
2342
2343             // Try Levenshtein.
2344             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected, span) {
2345                 err.span_label(ident_span, format!("did you mean `{}`?", candidate));
2346                 levenshtein_worked = true;
2347             }
2348
2349             // Try context dependent help if relaxed lookup didn't work.
2350             if let Some(def) = def {
2351                 match (def, source) {
2352                     (Def::Macro(..), _) => {
2353                         err.span_label(span, format!("did you mean `{}!(...)`?", path_str));
2354                         return err;
2355                     }
2356                     (Def::TyAlias(..), PathSource::Trait) => {
2357                         err.span_label(span, "type aliases cannot be used for traits");
2358                         return err;
2359                     }
2360                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match parent.node {
2361                         ExprKind::Field(_, ident) => {
2362                             err.span_label(parent.span, format!("did you mean `{}::{}`?",
2363                                                                  path_str, ident.node));
2364                             return err;
2365                         }
2366                         ExprKind::MethodCall(ident, ..) => {
2367                             err.span_label(parent.span, format!("did you mean `{}::{}(...)`?",
2368                                                                  path_str, ident.node));
2369                             return err;
2370                         }
2371                         _ => {}
2372                     },
2373                     _ if ns == ValueNS && is_struct_like(def) => {
2374                         if let Def::Struct(def_id) = def {
2375                             if let Some((ctor_def, ctor_vis))
2376                                     = this.struct_constructors.get(&def_id).cloned() {
2377                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2378                                     err.span_label(span, format!("constructor is not visible \
2379                                                                    here due to private fields"));
2380                                 }
2381                             }
2382                         }
2383                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
2384                                                        path_str));
2385                         return err;
2386                     }
2387                     _ => {}
2388                 }
2389             }
2390
2391             // Fallback label.
2392             if !levenshtein_worked {
2393                 err.span_label(base_span, fallback_label);
2394             }
2395             err
2396         };
2397         let report_errors = |this: &mut Self, def: Option<Def>| {
2398             report_errors(this, def).emit();
2399             err_path_resolution()
2400         };
2401
2402         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2403                                                            source.defer_to_typeck(),
2404                                                            source.global_by_default()) {
2405             Some(resolution) if resolution.unresolved_segments() == 0 => {
2406                 if is_expected(resolution.base_def()) || resolution.base_def() == Def::Err {
2407                     resolution
2408                 } else {
2409                     // Add a temporary hack to smooth the transition to new struct ctor
2410                     // visibility rules. See #38932 for more details.
2411                     let mut res = None;
2412                     if let Def::Struct(def_id) = resolution.base_def() {
2413                         if let Some((ctor_def, ctor_vis))
2414                                 = self.struct_constructors.get(&def_id).cloned() {
2415                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2416                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2417                                 self.session.add_lint(lint, id, span,
2418                                     "private struct constructors are not usable through \
2419                                      reexports in outer modules".to_string());
2420                                 res = Some(PathResolution::new(ctor_def));
2421                             }
2422                         }
2423                     }
2424
2425                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def())))
2426                 }
2427             }
2428             Some(resolution) if source.defer_to_typeck() => {
2429                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2430                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2431                 // it needs to be added to the trait map.
2432                 if ns == ValueNS {
2433                     let item_name = path.last().unwrap().name;
2434                     let traits = self.get_traits_containing_item(item_name, ns);
2435                     self.trait_map.insert(id, traits);
2436                 }
2437                 resolution
2438             }
2439             _ => report_errors(self, None)
2440         };
2441
2442         if let PathSource::TraitItem(..) = source {} else {
2443             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2444             self.record_def(id, resolution);
2445         }
2446         resolution
2447     }
2448
2449     fn self_type_is_available(&mut self, span: Span) -> bool {
2450         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(),
2451                                                           TypeNS, false, span);
2452         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2453     }
2454
2455     fn self_value_is_available(&mut self, ctxt: SyntaxContext, span: Span) -> bool {
2456         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2457         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, false, span);
2458         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2459     }
2460
2461     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2462     fn resolve_qpath_anywhere(&mut self,
2463                               id: NodeId,
2464                               qself: Option<&QSelf>,
2465                               path: &[Ident],
2466                               primary_ns: Namespace,
2467                               span: Span,
2468                               defer_to_typeck: bool,
2469                               global_by_default: bool)
2470                               -> Option<PathResolution> {
2471         let mut fin_res = None;
2472         // FIXME: can't resolve paths in macro namespace yet, macros are
2473         // processed by the little special hack below.
2474         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2475             if i == 0 || ns != primary_ns {
2476                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2477                     // If defer_to_typeck, then resolution > no resolution,
2478                     // otherwise full resolution > partial resolution > no resolution.
2479                     Some(res) if res.unresolved_segments() == 0 || defer_to_typeck =>
2480                         return Some(res),
2481                     res => if fin_res.is_none() { fin_res = res },
2482                 };
2483             }
2484         }
2485         let is_global = self.global_macros.get(&path[0].name).cloned()
2486             .map(|binding| binding.get_macro(self).kind() == MacroKind::Bang).unwrap_or(false);
2487         if primary_ns != MacroNS && (is_global || self.macro_names.contains(&path[0].name)) {
2488             // Return some dummy definition, it's enough for error reporting.
2489             return Some(
2490                 PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX), MacroKind::Bang))
2491             );
2492         }
2493         fin_res
2494     }
2495
2496     /// Handles paths that may refer to associated items.
2497     fn resolve_qpath(&mut self,
2498                      id: NodeId,
2499                      qself: Option<&QSelf>,
2500                      path: &[Ident],
2501                      ns: Namespace,
2502                      span: Span,
2503                      global_by_default: bool)
2504                      -> Option<PathResolution> {
2505         if let Some(qself) = qself {
2506             if qself.position == 0 {
2507                 // FIXME: Create some fake resolution that can't possibly be a type.
2508                 return Some(PathResolution::with_unresolved_segments(
2509                     Def::Mod(DefId::local(CRATE_DEF_INDEX)), path.len()
2510                 ));
2511             }
2512             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2513             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2514             let res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2515                                                        span, span, PathSource::TraitItem(ns));
2516             return Some(PathResolution::with_unresolved_segments(
2517                 res.base_def(), res.unresolved_segments() + path.len() - qself.position - 1
2518             ));
2519         }
2520
2521         let result = match self.resolve_path(&path, Some(ns), true, span) {
2522             PathResult::NonModule(path_res) => path_res,
2523             PathResult::Module(module) if !module.is_normal() => {
2524                 PathResolution::new(module.def().unwrap())
2525             }
2526             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2527             // don't report an error right away, but try to fallback to a primitive type.
2528             // So, we are still able to successfully resolve something like
2529             //
2530             // use std::u8; // bring module u8 in scope
2531             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2532             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2533             //                     // not to non-existent std::u8::max_value
2534             // }
2535             //
2536             // Such behavior is required for backward compatibility.
2537             // The same fallback is used when `a` resolves to nothing.
2538             PathResult::Module(..) | PathResult::Failed(..)
2539                     if (ns == TypeNS || path.len() > 1) &&
2540                        self.primitive_type_table.primitive_types.contains_key(&path[0].name) => {
2541                 let prim = self.primitive_type_table.primitive_types[&path[0].name];
2542                 match prim {
2543                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2544                         if !self.session.features.borrow().i128_type {
2545                             emit_feature_err(&self.session.parse_sess,
2546                                                 "i128_type", span, GateIssue::Language,
2547                                                 "128-bit type is unstable");
2548
2549                         }
2550                     }
2551                     _ => {}
2552                 }
2553                 PathResolution::with_unresolved_segments(Def::PrimTy(prim), path.len() - 1)
2554             }
2555             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2556             PathResult::Failed(msg, false) => {
2557                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2558                 err_path_resolution()
2559             }
2560             PathResult::Failed(..) => return None,
2561             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2562         };
2563
2564         if path.len() > 1 && !global_by_default && result.base_def() != Def::Err &&
2565            path[0].name != keywords::CrateRoot.name() && path[0].name != "$crate" {
2566             let unqualified_result = {
2567                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), false, span) {
2568                     PathResult::NonModule(path_res) => path_res.base_def(),
2569                     PathResult::Module(module) => module.def().unwrap(),
2570                     _ => return Some(result),
2571                 }
2572             };
2573             if result.base_def() == unqualified_result {
2574                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2575                 self.session.add_lint(lint, id, span, "unnecessary qualification".to_string());
2576             }
2577         }
2578
2579         Some(result)
2580     }
2581
2582     fn resolve_path(&mut self,
2583                     path: &[Ident],
2584                     opt_ns: Option<Namespace>, // `None` indicates a module path
2585                     record_used: bool,
2586                     path_span: Span)
2587                     -> PathResult<'a> {
2588         let mut module = None;
2589         let mut allow_super = true;
2590
2591         for (i, &ident) in path.iter().enumerate() {
2592             let is_last = i == path.len() - 1;
2593             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2594
2595             if i == 0 && ns == TypeNS && ident.name == keywords::SelfValue.name() {
2596                 module = Some(self.module_map[&self.current_module.normal_ancestor_id]);
2597                 continue
2598             } else if allow_super && ns == TypeNS && ident.name == keywords::Super.name() {
2599                 let current_module = if i == 0 { self.current_module } else { module.unwrap() };
2600                 let self_module = self.module_map[&current_module.normal_ancestor_id];
2601                 if let Some(parent) = self_module.parent {
2602                     module = Some(self.module_map[&parent.normal_ancestor_id]);
2603                     continue
2604                 } else {
2605                     let msg = "There are too many initial `super`s.".to_string();
2606                     return PathResult::Failed(msg, false);
2607                 }
2608             }
2609             allow_super = false;
2610
2611             if i == 0 && ns == TypeNS && ident.name == keywords::CrateRoot.name() {
2612                 module = Some(self.graph_root);
2613                 continue
2614             } else if i == 0 && ns == TypeNS && ident.name == "$crate" {
2615                 module = Some(self.resolve_crate_var(ident.ctxt, path_span));
2616                 continue
2617             }
2618
2619             let binding = if let Some(module) = module {
2620                 self.resolve_ident_in_module(module, ident, ns, false, record_used, path_span)
2621             } else if opt_ns == Some(MacroNS) {
2622                 self.resolve_lexical_macro_path_segment(ident, ns, record_used, path_span)
2623                     .map(MacroBinding::binding)
2624             } else {
2625                 match self.resolve_ident_in_lexical_scope(ident, ns, record_used, path_span) {
2626                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2627                     Some(LexicalScopeBinding::Def(def))
2628                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2629                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2630                             def, path.len() - 1
2631                         ));
2632                     }
2633                     _ => Err(if record_used { Determined } else { Undetermined }),
2634                 }
2635             };
2636
2637             match binding {
2638                 Ok(binding) => {
2639                     let def = binding.def();
2640                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2641                     if let Some(next_module) = binding.module() {
2642                         module = Some(next_module);
2643                     } else if def == Def::Err {
2644                         return PathResult::NonModule(err_path_resolution());
2645                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2646                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2647                             def, path.len() - i - 1
2648                         ));
2649                     } else {
2650                         return PathResult::Failed(format!("Not a module `{}`", ident), is_last);
2651                     }
2652                 }
2653                 Err(Undetermined) => return PathResult::Indeterminate,
2654                 Err(Determined) => {
2655                     if let Some(module) = module {
2656                         if opt_ns.is_some() && !module.is_normal() {
2657                             return PathResult::NonModule(PathResolution::with_unresolved_segments(
2658                                 module.def().unwrap(), path.len() - i
2659                             ));
2660                         }
2661                     }
2662                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2663                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2664                         let mut candidates =
2665                             self.lookup_import_candidates(ident.name, TypeNS, is_mod);
2666                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2667                         if let Some(candidate) = candidates.get(0) {
2668                             format!("Did you mean `{}`?", candidate.path)
2669                         } else {
2670                             format!("Maybe a missing `extern crate {};`?", ident)
2671                         }
2672                     } else if i == 0 {
2673                         format!("Use of undeclared type or module `{}`", ident)
2674                     } else {
2675                         format!("Could not find `{}` in `{}`", ident, path[i - 1])
2676                     };
2677                     return PathResult::Failed(msg, is_last);
2678                 }
2679             }
2680         }
2681
2682         PathResult::Module(module.unwrap_or(self.graph_root))
2683     }
2684
2685     // Resolve a local definition, potentially adjusting for closures.
2686     fn adjust_local_def(&mut self,
2687                         ns: Namespace,
2688                         rib_index: usize,
2689                         mut def: Def,
2690                         record_used: bool,
2691                         span: Span) -> Def {
2692         let ribs = &self.ribs[ns][rib_index + 1..];
2693
2694         // An invalid forward use of a type parameter from a previous default.
2695         if let ForwardTyParamBanRibKind = self.ribs[ns][rib_index].kind {
2696             if record_used {
2697                 resolve_error(self, span,
2698                         ResolutionError::ForwardDeclaredTyParam);
2699             }
2700             assert_eq!(def, Def::Err);
2701             return Def::Err;
2702         }
2703
2704         match def {
2705             Def::Upvar(..) => {
2706                 span_bug!(span, "unexpected {:?} in bindings", def)
2707             }
2708             Def::Local(def_id) => {
2709                 for rib in ribs {
2710                     match rib.kind {
2711                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
2712                         ForwardTyParamBanRibKind => {
2713                             // Nothing to do. Continue.
2714                         }
2715                         ClosureRibKind(function_id) => {
2716                             let prev_def = def;
2717                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2718
2719                             let seen = self.freevars_seen
2720                                            .entry(function_id)
2721                                            .or_insert_with(|| NodeMap());
2722                             if let Some(&index) = seen.get(&node_id) {
2723                                 def = Def::Upvar(def_id, index, function_id);
2724                                 continue;
2725                             }
2726                             let vec = self.freevars
2727                                           .entry(function_id)
2728                                           .or_insert_with(|| vec![]);
2729                             let depth = vec.len();
2730                             def = Def::Upvar(def_id, depth, function_id);
2731
2732                             if record_used {
2733                                 vec.push(Freevar {
2734                                     def: prev_def,
2735                                     span: span,
2736                                 });
2737                                 seen.insert(node_id, depth);
2738                             }
2739                         }
2740                         ItemRibKind | MethodRibKind(_) => {
2741                             // This was an attempt to access an upvar inside a
2742                             // named function item. This is not allowed, so we
2743                             // report an error.
2744                             if record_used {
2745                                 resolve_error(self, span,
2746                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2747                             }
2748                             return Def::Err;
2749                         }
2750                         ConstantItemRibKind => {
2751                             // Still doesn't deal with upvars
2752                             if record_used {
2753                                 resolve_error(self, span,
2754                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
2755                             }
2756                             return Def::Err;
2757                         }
2758                     }
2759                 }
2760             }
2761             Def::TyParam(..) | Def::SelfTy(..) => {
2762                 for rib in ribs {
2763                     match rib.kind {
2764                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
2765                         ModuleRibKind(..) | MacroDefinition(..) | ForwardTyParamBanRibKind => {
2766                             // Nothing to do. Continue.
2767                         }
2768                         ItemRibKind => {
2769                             // This was an attempt to use a type parameter outside
2770                             // its scope.
2771                             if record_used {
2772                                 resolve_error(self, span,
2773                                               ResolutionError::TypeParametersFromOuterFunction);
2774                             }
2775                             return Def::Err;
2776                         }
2777                         ConstantItemRibKind => {
2778                             // see #9186
2779                             if record_used {
2780                                 resolve_error(self, span,
2781                                               ResolutionError::OuterTypeParameterContext);
2782                             }
2783                             return Def::Err;
2784                         }
2785                     }
2786                 }
2787             }
2788             _ => {}
2789         }
2790         return def;
2791     }
2792
2793     // Calls `f` with a `Resolver` whose current lexical scope is `module`'s lexical scope,
2794     // i.e. the module's items and the prelude (unless the module is `#[no_implicit_prelude]`).
2795     // FIXME #34673: This needs testing.
2796     pub fn with_module_lexical_scope<T, F>(&mut self, module: Module<'a>, f: F) -> T
2797         where F: FnOnce(&mut Resolver<'a>) -> T,
2798     {
2799         self.with_empty_ribs(|this| {
2800             this.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
2801             this.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
2802             f(this)
2803         })
2804     }
2805
2806     fn with_empty_ribs<T, F>(&mut self, f: F) -> T
2807         where F: FnOnce(&mut Resolver<'a>) -> T,
2808     {
2809         let ribs = replace(&mut self.ribs, PerNS::<Vec<Rib>>::default());
2810         let label_ribs = replace(&mut self.label_ribs, Vec::new());
2811
2812         let result = f(self);
2813         self.ribs = ribs;
2814         self.label_ribs = label_ribs;
2815         result
2816     }
2817
2818     fn lookup_assoc_candidate<FilterFn>(&mut self,
2819                                         name: Name,
2820                                         ns: Namespace,
2821                                         filter_fn: FilterFn)
2822                                         -> Option<AssocSuggestion>
2823         where FilterFn: Fn(Def) -> bool
2824     {
2825         fn extract_node_id(t: &Ty) -> Option<NodeId> {
2826             match t.node {
2827                 TyKind::Path(None, _) => Some(t.id),
2828                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
2829                 // This doesn't handle the remaining `Ty` variants as they are not
2830                 // that commonly the self_type, it might be interesting to provide
2831                 // support for those in future.
2832                 _ => None,
2833             }
2834         }
2835
2836         // Fields are generally expected in the same contexts as locals.
2837         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
2838             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
2839                 // Look for a field with the same name in the current self_type.
2840                 if let Some(resolution) = self.def_map.get(&node_id) {
2841                     match resolution.base_def() {
2842                         Def::Struct(did) | Def::Union(did)
2843                                 if resolution.unresolved_segments() == 0 => {
2844                             if let Some(field_names) = self.field_names.get(&did) {
2845                                 if field_names.iter().any(|&field_name| name == field_name) {
2846                                     return Some(AssocSuggestion::Field);
2847                                 }
2848                             }
2849                         }
2850                         _ => {}
2851                     }
2852                 }
2853             }
2854         }
2855
2856         // Look for associated items in the current trait.
2857         if let Some((trait_did, _)) = self.current_trait_ref {
2858             if let Some(&(def, has_self)) = self.trait_item_map.get(&(trait_did, name, ns)) {
2859                 if filter_fn(def) {
2860                     return Some(if has_self {
2861                         AssocSuggestion::MethodWithSelf
2862                     } else {
2863                         AssocSuggestion::AssocItem
2864                     });
2865                 }
2866             }
2867         }
2868
2869         None
2870     }
2871
2872     fn lookup_typo_candidate<FilterFn>(&mut self,
2873                                        path: &[Ident],
2874                                        ns: Namespace,
2875                                        filter_fn: FilterFn,
2876                                        span: Span)
2877                                        -> Option<Symbol>
2878         where FilterFn: Fn(Def) -> bool
2879     {
2880         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
2881             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
2882                 if let Some(binding) = resolution.borrow().binding {
2883                     if filter_fn(binding.def()) {
2884                         names.push(ident.name);
2885                     }
2886                 }
2887             }
2888         };
2889
2890         let mut names = Vec::new();
2891         if path.len() == 1 {
2892             // Search in lexical scope.
2893             // Walk backwards up the ribs in scope and collect candidates.
2894             for rib in self.ribs[ns].iter().rev() {
2895                 // Locals and type parameters
2896                 for (ident, def) in &rib.bindings {
2897                     if filter_fn(*def) {
2898                         names.push(ident.name);
2899                     }
2900                 }
2901                 // Items in scope
2902                 if let ModuleRibKind(module) = rib.kind {
2903                     // Items from this module
2904                     add_module_candidates(module, &mut names);
2905
2906                     if let ModuleKind::Block(..) = module.kind {
2907                         // We can see through blocks
2908                     } else {
2909                         // Items from the prelude
2910                         if let Some(prelude) = self.prelude {
2911                             if !module.no_implicit_prelude {
2912                                 add_module_candidates(prelude, &mut names);
2913                             }
2914                         }
2915                         break;
2916                     }
2917                 }
2918             }
2919             // Add primitive types to the mix
2920             if filter_fn(Def::PrimTy(TyBool)) {
2921                 for (name, _) in &self.primitive_type_table.primitive_types {
2922                     names.push(*name);
2923                 }
2924             }
2925         } else {
2926             // Search in module.
2927             let mod_path = &path[..path.len() - 1];
2928             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS),
2929                                                                   false, span) {
2930                 add_module_candidates(module, &mut names);
2931             }
2932         }
2933
2934         let name = path[path.len() - 1].name;
2935         // Make sure error reporting is deterministic.
2936         names.sort_by_key(|name| name.as_str());
2937         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
2938             Some(found) if found != name => Some(found),
2939             _ => None,
2940         }
2941     }
2942
2943     fn with_resolved_label<F>(&mut self, label: Option<SpannedIdent>, id: NodeId, f: F)
2944         where F: FnOnce(&mut Resolver)
2945     {
2946         if let Some(label) = label {
2947             let def = Def::Label(id);
2948             self.with_label_rib(|this| {
2949                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
2950                 f(this);
2951             });
2952         } else {
2953             f(self);
2954         }
2955     }
2956
2957     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
2958         self.with_resolved_label(label, id, |this| this.visit_block(block));
2959     }
2960
2961     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
2962         // First, record candidate traits for this expression if it could
2963         // result in the invocation of a method call.
2964
2965         self.record_candidate_traits_for_expr_if_necessary(expr);
2966
2967         // Next, resolve the node.
2968         match expr.node {
2969             ExprKind::Path(ref qself, ref path) => {
2970                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
2971                 visit::walk_expr(self, expr);
2972             }
2973
2974             ExprKind::Struct(ref path, ..) => {
2975                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
2976                 visit::walk_expr(self, expr);
2977             }
2978
2979             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
2980                 match self.search_label(label.node) {
2981                     None => {
2982                         self.record_def(expr.id, err_path_resolution());
2983                         resolve_error(self,
2984                                       label.span,
2985                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
2986                     }
2987                     Some(def @ Def::Label(_)) => {
2988                         // Since this def is a label, it is never read.
2989                         self.record_def(expr.id, PathResolution::new(def));
2990                     }
2991                     Some(_) => {
2992                         span_bug!(expr.span, "label wasn't mapped to a label def!");
2993                     }
2994                 }
2995
2996                 // visit `break` argument if any
2997                 visit::walk_expr(self, expr);
2998             }
2999
3000             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
3001                 self.visit_expr(subexpression);
3002
3003                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3004                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
3005                 self.visit_block(if_block);
3006                 self.ribs[ValueNS].pop();
3007
3008                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
3009             }
3010
3011             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
3012
3013             ExprKind::While(ref subexpression, ref block, label) => {
3014                 self.with_resolved_label(label, expr.id, |this| {
3015                     this.visit_expr(subexpression);
3016                     this.visit_block(block);
3017                 });
3018             }
3019
3020             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
3021                 self.with_resolved_label(label, expr.id, |this| {
3022                     this.visit_expr(subexpression);
3023                     this.ribs[ValueNS].push(Rib::new(NormalRibKind));
3024                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
3025                     this.visit_block(block);
3026                     this.ribs[ValueNS].pop();
3027                 });
3028             }
3029
3030             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
3031                 self.visit_expr(subexpression);
3032                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3033                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
3034
3035                 self.resolve_labeled_block(label, expr.id, block);
3036
3037                 self.ribs[ValueNS].pop();
3038             }
3039
3040             // Equivalent to `visit::walk_expr` + passing some context to children.
3041             ExprKind::Field(ref subexpression, _) => {
3042                 self.resolve_expr(subexpression, Some(expr));
3043             }
3044             ExprKind::MethodCall(_, ref types, ref arguments) => {
3045                 let mut arguments = arguments.iter();
3046                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3047                 for argument in arguments {
3048                     self.resolve_expr(argument, None);
3049                 }
3050                 for ty in types.iter() {
3051                     self.visit_ty(ty);
3052                 }
3053             }
3054
3055             ExprKind::Repeat(ref element, ref count) => {
3056                 self.visit_expr(element);
3057                 self.with_constant_rib(|this| {
3058                     this.visit_expr(count);
3059                 });
3060             }
3061             ExprKind::Call(ref callee, ref arguments) => {
3062                 self.resolve_expr(callee, Some(expr));
3063                 for argument in arguments {
3064                     self.resolve_expr(argument, None);
3065                 }
3066             }
3067
3068             _ => {
3069                 visit::walk_expr(self, expr);
3070             }
3071         }
3072     }
3073
3074     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3075         match expr.node {
3076             ExprKind::Field(_, name) => {
3077                 // FIXME(#6890): Even though you can't treat a method like a
3078                 // field, we need to add any trait methods we find that match
3079                 // the field name so that we can do some nice error reporting
3080                 // later on in typeck.
3081                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
3082                 self.trait_map.insert(expr.id, traits);
3083             }
3084             ExprKind::MethodCall(name, ..) => {
3085                 debug!("(recording candidate traits for expr) recording traits for {}",
3086                        expr.id);
3087                 let traits = self.get_traits_containing_item(name.node.name, ValueNS);
3088                 self.trait_map.insert(expr.id, traits);
3089             }
3090             _ => {
3091                 // Nothing to do.
3092             }
3093         }
3094     }
3095
3096     fn get_traits_containing_item(&mut self, name: Name, ns: Namespace) -> Vec<TraitCandidate> {
3097         debug!("(getting traits containing item) looking for '{}'", name);
3098
3099         let mut found_traits = Vec::new();
3100         // Look for the current trait.
3101         if let Some((trait_def_id, _)) = self.current_trait_ref {
3102             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
3103                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: None });
3104             }
3105         }
3106
3107         let mut search_module = self.current_module;
3108         loop {
3109             self.get_traits_in_module_containing_item(name, ns, search_module, &mut found_traits);
3110             match search_module.kind {
3111                 ModuleKind::Block(..) => search_module = search_module.parent.unwrap(),
3112                 _ => break,
3113             }
3114         }
3115
3116         if let Some(prelude) = self.prelude {
3117             if !search_module.no_implicit_prelude {
3118                 self.get_traits_in_module_containing_item(name, ns, prelude, &mut found_traits);
3119             }
3120         }
3121
3122         found_traits
3123     }
3124
3125     fn get_traits_in_module_containing_item(&mut self,
3126                                             name: Name,
3127                                             ns: Namespace,
3128                                             module: Module,
3129                                             found_traits: &mut Vec<TraitCandidate>) {
3130         let mut traits = module.traits.borrow_mut();
3131         if traits.is_none() {
3132             let mut collected_traits = Vec::new();
3133             module.for_each_child(|name, ns, binding| {
3134                 if ns != TypeNS { return }
3135                 if let Def::Trait(_) = binding.def() {
3136                     collected_traits.push((name, binding));
3137                 }
3138             });
3139             *traits = Some(collected_traits.into_boxed_slice());
3140         }
3141
3142         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3143             let trait_def_id = binding.def().def_id();
3144             if self.trait_item_map.contains_key(&(trait_def_id, name, ns)) {
3145                 let import_id = match binding.kind {
3146                     NameBindingKind::Import { directive, .. } => {
3147                         self.maybe_unused_trait_imports.insert(directive.id);
3148                         self.add_to_glob_map(directive.id, trait_name);
3149                         Some(directive.id)
3150                     }
3151                     _ => None,
3152                 };
3153                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
3154             }
3155         }
3156     }
3157
3158     /// When name resolution fails, this method can be used to look up candidate
3159     /// entities with the expected name. It allows filtering them using the
3160     /// supplied predicate (which should be used to only accept the types of
3161     /// definitions expected e.g. traits). The lookup spans across all crates.
3162     ///
3163     /// NOTE: The method does not look into imports, but this is not a problem,
3164     /// since we report the definitions (thus, the de-aliased imports).
3165     fn lookup_import_candidates<FilterFn>(&mut self,
3166                                           lookup_name: Name,
3167                                           namespace: Namespace,
3168                                           filter_fn: FilterFn)
3169                                           -> Vec<ImportSuggestion>
3170         where FilterFn: Fn(Def) -> bool
3171     {
3172         let mut candidates = Vec::new();
3173         let mut worklist = Vec::new();
3174         let mut seen_modules = FxHashSet();
3175         worklist.push((self.graph_root, Vec::new(), false));
3176
3177         while let Some((in_module,
3178                         path_segments,
3179                         in_module_is_extern)) = worklist.pop() {
3180             self.populate_module_if_necessary(in_module);
3181
3182             in_module.for_each_child(|ident, ns, name_binding| {
3183
3184                 // avoid imports entirely
3185                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3186                 // avoid non-importable candidates as well
3187                 if !name_binding.is_importable() { return; }
3188
3189                 // collect results based on the filter function
3190                 if ident.name == lookup_name && ns == namespace {
3191                     if filter_fn(name_binding.def()) {
3192                         // create the path
3193                         let mut segms = path_segments.clone();
3194                         segms.push(ast::PathSegment::from_ident(ident, name_binding.span));
3195                         let path = Path {
3196                             span: name_binding.span,
3197                             segments: segms,
3198                         };
3199                         // the entity is accessible in the following cases:
3200                         // 1. if it's defined in the same crate, it's always
3201                         // accessible (since private entities can be made public)
3202                         // 2. if it's defined in another crate, it's accessible
3203                         // only if both the module is public and the entity is
3204                         // declared as public (due to pruning, we don't explore
3205                         // outside crate private modules => no need to check this)
3206                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3207                             candidates.push(ImportSuggestion { path: path });
3208                         }
3209                     }
3210                 }
3211
3212                 // collect submodules to explore
3213                 if let Some(module) = name_binding.module() {
3214                     // form the path
3215                     let mut path_segments = path_segments.clone();
3216                     path_segments.push(ast::PathSegment::from_ident(ident, name_binding.span));
3217
3218                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3219                         // add the module to the lookup
3220                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3221                         if seen_modules.insert(module.def_id().unwrap()) {
3222                             worklist.push((module, path_segments, is_extern));
3223                         }
3224                     }
3225                 }
3226             })
3227         }
3228
3229         candidates
3230     }
3231
3232     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3233         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3234         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3235             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3236         }
3237     }
3238
3239     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3240         match *vis {
3241             ast::Visibility::Public => ty::Visibility::Public,
3242             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3243             ast::Visibility::Inherited => {
3244                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3245             }
3246             ast::Visibility::Restricted { ref path, id } => {
3247                 let def = self.smart_resolve_path(id, None, path,
3248                                                   PathSource::Visibility).base_def();
3249                 if def == Def::Err {
3250                     ty::Visibility::Public
3251                 } else {
3252                     let vis = ty::Visibility::Restricted(def.def_id());
3253                     if self.is_accessible(vis) {
3254                         vis
3255                     } else {
3256                         self.session.span_err(path.span, "visibilities can only be restricted \
3257                                                           to ancestor modules");
3258                         ty::Visibility::Public
3259                     }
3260                 }
3261             }
3262         }
3263     }
3264
3265     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3266         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3267     }
3268
3269     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3270         vis.is_accessible_from(module.normal_ancestor_id, self)
3271     }
3272
3273     fn report_errors(&mut self) {
3274         self.report_shadowing_errors();
3275         let mut reported_spans = FxHashSet();
3276
3277         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3278             if !reported_spans.insert(span) { continue }
3279             let participle = |binding: &NameBinding| {
3280                 if binding.is_import() { "imported" } else { "defined" }
3281             };
3282             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3283             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3284             let note = if b1.expansion == Mark::root() || !lexical && b1.is_glob_import() {
3285                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3286             } else if let Def::Macro(..) = b1.def() {
3287                 format!("macro-expanded {} do not shadow",
3288                         if b1.is_import() { "macro imports" } else { "macros" })
3289             } else {
3290                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3291                         if b1.is_import() { "imports" } else { "items" })
3292             };
3293             if legacy {
3294                 let id = match b2.kind {
3295                     NameBindingKind::Import { directive, .. } => directive.id,
3296                     _ => unreachable!(),
3297                 };
3298                 let mut span = MultiSpan::from_span(span);
3299                 span.push_span_label(b1.span, msg1);
3300                 span.push_span_label(b2.span, msg2);
3301                 let msg = format!("`{}` is ambiguous", name);
3302                 self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3303             } else {
3304                 let mut err =
3305                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", name));
3306                 err.span_note(b1.span, &msg1);
3307                 match b2.def() {
3308                     Def::Macro(..) if b2.span == DUMMY_SP =>
3309                         err.note(&format!("`{}` is also a builtin macro", name)),
3310                     _ => err.span_note(b2.span, &msg2),
3311                 };
3312                 err.note(&note).emit();
3313             }
3314         }
3315
3316         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3317             if !reported_spans.insert(span) { continue }
3318             if binding.is_extern_crate() {
3319                 // Warn when using an inaccessible extern crate.
3320                 let node_id = match binding.kind {
3321                     NameBindingKind::Import { directive, .. } => directive.id,
3322                     _ => unreachable!(),
3323                 };
3324                 let msg = format!("extern crate `{}` is private", name);
3325                 self.session.add_lint(lint::builtin::INACCESSIBLE_EXTERN_CRATE, node_id, span, msg);
3326             } else {
3327                 let def = binding.def();
3328                 self.session.span_err(span, &format!("{} `{}` is private", def.kind_name(), name));
3329             }
3330         }
3331     }
3332
3333     fn report_shadowing_errors(&mut self) {
3334         for (name, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3335             self.resolve_legacy_scope(scope, name, true);
3336         }
3337
3338         let mut reported_errors = FxHashSet();
3339         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3340             if self.resolve_legacy_scope(&binding.parent, binding.name, false).is_some() &&
3341                reported_errors.insert((binding.name, binding.span)) {
3342                 let msg = format!("`{}` is already in scope", binding.name);
3343                 self.session.struct_span_err(binding.span, &msg)
3344                     .note("macro-expanded `macro_rules!`s may not shadow \
3345                            existing macros (see RFC 1560)")
3346                     .emit();
3347             }
3348         }
3349     }
3350
3351     fn report_conflict(&mut self,
3352                        parent: Module,
3353                        ident: Ident,
3354                        ns: Namespace,
3355                        binding: &NameBinding,
3356                        old_binding: &NameBinding) {
3357         // Error on the second of two conflicting names
3358         if old_binding.span.lo > binding.span.lo {
3359             return self.report_conflict(parent, ident, ns, old_binding, binding);
3360         }
3361
3362         let container = match parent.kind {
3363             ModuleKind::Def(Def::Mod(_), _) => "module",
3364             ModuleKind::Def(Def::Trait(_), _) => "trait",
3365             ModuleKind::Block(..) => "block",
3366             _ => "enum",
3367         };
3368
3369         let (participle, noun) = match old_binding.is_import() {
3370             true => ("imported", "import"),
3371             false => ("defined", "definition"),
3372         };
3373
3374         let (name, span) = (ident.name, binding.span);
3375
3376         if let Some(s) = self.name_already_seen.get(&name) {
3377             if s == &span {
3378                 return;
3379             }
3380         }
3381
3382         let msg = {
3383             let kind = match (ns, old_binding.module()) {
3384                 (ValueNS, _) => "a value",
3385                 (MacroNS, _) => "a macro",
3386                 (TypeNS, _) if old_binding.is_extern_crate() => "an extern crate",
3387                 (TypeNS, Some(module)) if module.is_normal() => "a module",
3388                 (TypeNS, Some(module)) if module.is_trait() => "a trait",
3389                 (TypeNS, _) => "a type",
3390             };
3391             format!("{} named `{}` has already been {} in this {}",
3392                     kind, name, participle, container)
3393         };
3394
3395         let mut err = match (old_binding.is_extern_crate(), binding.is_extern_crate()) {
3396             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3397             (true, _) | (_, true) => match binding.is_import() && old_binding.is_import() {
3398                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3399                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3400             },
3401             _ => match (old_binding.is_import(), binding.is_import()) {
3402                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3403                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3404                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3405             },
3406         };
3407
3408         err.span_label(span, format!("`{}` already {}", name, participle));
3409         if old_binding.span != syntax_pos::DUMMY_SP {
3410             err.span_label(old_binding.span, format!("previous {} of `{}` here", noun, name));
3411         }
3412         err.emit();
3413         self.name_already_seen.insert(name, span);
3414     }
3415
3416     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3417         let (id, span) = (directive.id, directive.span);
3418         let msg = "`self` no longer imports values".to_string();
3419         self.session.add_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3420     }
3421
3422     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3423         if self.proc_macro_enabled { return; }
3424
3425         for attr in attrs {
3426             if attr.path.segments.len() > 1 {
3427                 continue
3428             }
3429             let ident = attr.path.segments[0].identifier;
3430             let result = self.resolve_lexical_macro_path_segment(ident,
3431                                                                  MacroNS,
3432                                                                  false,
3433                                                                  attr.path.span);
3434             if let Ok(binding) = result {
3435                 if let SyntaxExtension::AttrProcMacro(..) = *binding.binding().get_macro(self) {
3436                     attr::mark_known(attr);
3437
3438                     let msg = "attribute procedural macros are experimental";
3439                     let feature = "proc_macro";
3440
3441                     feature_err(&self.session.parse_sess, feature,
3442                                 attr.span, GateIssue::Language, msg)
3443                         .span_note(binding.span(), "procedural macro imported here")
3444                         .emit();
3445                 }
3446             }
3447         }
3448     }
3449 }
3450
3451 fn is_struct_like(def: Def) -> bool {
3452     match def {
3453         Def::VariantCtor(_, CtorKind::Fictive) => true,
3454         _ => PathSource::Struct.is_expected(def),
3455     }
3456 }
3457
3458 fn is_self_type(path: &[Ident], namespace: Namespace) -> bool {
3459     namespace == TypeNS && path.len() == 1 && path[0].name == keywords::SelfType.name()
3460 }
3461
3462 fn is_self_value(path: &[Ident], namespace: Namespace) -> bool {
3463     namespace == ValueNS && path.len() == 1 && path[0].name == keywords::SelfValue.name()
3464 }
3465
3466 fn names_to_string(idents: &[Ident]) -> String {
3467     let mut result = String::new();
3468     for (i, ident) in idents.iter().filter(|i| i.name != keywords::CrateRoot.name()).enumerate() {
3469         if i > 0 {
3470             result.push_str("::");
3471         }
3472         result.push_str(&ident.name.as_str());
3473     }
3474     result
3475 }
3476
3477 fn path_names_to_string(path: &Path) -> String {
3478     names_to_string(&path.segments.iter().map(|seg| seg.identifier).collect::<Vec<_>>())
3479 }
3480
3481 /// Get the path for an enum and the variant from an `ImportSuggestion` for an enum variant.
3482 fn import_candidate_to_paths(suggestion: &ImportSuggestion) -> (Span, String, String) {
3483     let variant_path = &suggestion.path;
3484     let variant_path_string = path_names_to_string(variant_path);
3485
3486     let path_len = suggestion.path.segments.len();
3487     let enum_path = ast::Path {
3488         span: suggestion.path.span,
3489         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
3490     };
3491     let enum_path_string = path_names_to_string(&enum_path);
3492
3493     (suggestion.path.span, variant_path_string, enum_path_string)
3494 }
3495
3496
3497 /// When an entity with a given name is not available in scope, we search for
3498 /// entities with that name in all crates. This method allows outputting the
3499 /// results of this search in a programmer-friendly way
3500 fn show_candidates(err: &mut DiagnosticBuilder,
3501                    span: Span,
3502                    candidates: &[ImportSuggestion],
3503                    better: bool) {
3504
3505     // we want consistent results across executions, but candidates are produced
3506     // by iterating through a hash map, so make sure they are ordered:
3507     let mut path_strings: Vec<_> =
3508         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3509     path_strings.sort();
3510
3511     let better = if better { "better " } else { "" };
3512     let msg_diff = match path_strings.len() {
3513         1 => " is found in another module, you can import it",
3514         _ => "s are found in other modules, you can import them",
3515     };
3516     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
3517
3518     for candidate in &mut path_strings {
3519         *candidate = format!("use {};\n", candidate);
3520     }
3521
3522     err.span_suggestions(span, &msg, path_strings);
3523 }
3524
3525 /// A somewhat inefficient routine to obtain the name of a module.
3526 fn module_to_string(module: Module) -> String {
3527     let mut names = Vec::new();
3528
3529     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3530         if let ModuleKind::Def(_, name) = module.kind {
3531             if let Some(parent) = module.parent {
3532                 names.push(Ident::with_empty_ctxt(name));
3533                 collect_mod(names, parent);
3534             }
3535         } else {
3536             // danger, shouldn't be ident?
3537             names.push(Ident::from_str("<opaque>"));
3538             collect_mod(names, module.parent.unwrap());
3539         }
3540     }
3541     collect_mod(&mut names, module);
3542
3543     if names.is_empty() {
3544         return "???".to_string();
3545     }
3546     names_to_string(&names.into_iter().rev().collect::<Vec<_>>())
3547 }
3548
3549 fn err_path_resolution() -> PathResolution {
3550     PathResolution::new(Def::Err)
3551 }
3552
3553 #[derive(PartialEq,Copy, Clone)]
3554 pub enum MakeGlobMap {
3555     Yes,
3556     No,
3557 }
3558
3559 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }