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 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  12       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  13       html_root_url = "https://doc.rust-lang.org/nightly/")]
  14 #![deny(warnings)]
  15
  16 #![feature(rustc_diagnostic_macros)]
  17
  18 #[macro_use]
  19 extern crate log;
  20 #[macro_use]
  21 extern crate syntax;
  22 extern crate syntax_pos;
  23 extern crate rustc_errors as errors;
  24 extern crate arena;
  25 #[macro_use]
  26 extern crate rustc;
  27 extern crate rustc_data_structures;
  28
  29 use self::Namespace::*;
  30 use self::TypeParameters::*;
  31 use self::RibKind::*;
  32
  33 use rustc::hir::map::{Definitions, DefCollector};
  34 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  35 use rustc::middle::cstore::{CrateStore, CrateLoader};
  36 use rustc::session::Session;
  37 use rustc::lint;
  38 use rustc::hir::def::*;
  39 use rustc::hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  40 use rustc::ty;
  41 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  42 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};
  43
  44 use syntax::codemap::{dummy_spanned, respan};
  45 use syntax::ext::hygiene::{Mark, SyntaxContext};
  46 use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
  47 use syntax::ext::base::SyntaxExtension;
  48 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  49 use syntax::ext::base::MacroKind;
  50 use syntax::symbol::{Symbol, keywords};
  51 use syntax::util::lev_distance::find_best_match_for_name;
  52
  53 use syntax::visit::{self, FnKind, Visitor};
  54 use syntax::attr;
  55 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  56 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  57 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  58 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  59 use syntax::ast::{QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  60 use syntax::feature_gate::{feature_err, emit_feature_err, GateIssue};
  61
  62 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
  63 use errors::{DiagnosticBuilder, DiagnosticId};
  64
  65 use std::cell::{Cell, RefCell};
  66 use std::cmp;
  67 use std::collections::BTreeSet;
  68 use std::fmt;
  69 use std::mem::replace;
  70 use std::rc::Rc;
  71
  72 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
  73 use macros::{InvocationData, LegacyBinding, LegacyScope, MacroBinding};
  74
  75 // NB: This module needs to be declared first so diagnostics are
  76 // registered before they are used.
  77 mod diagnostics;
  78
  79 mod macros;
  80 mod check_unused;
  81 mod build_reduced_graph;
  82 mod resolve_imports;
  83
  84 /// A free importable items suggested in case of resolution failure.
  85 struct ImportSuggestion {
  86     path: Path,
  87 }
  88
  89 /// A field or associated item from self type suggested in case of resolution failure.
  90 enum AssocSuggestion {
  91     Field,
  92     MethodWithSelf,
  93     AssocItem,
  94 }
  95
  96 #[derive(Eq)]
  97 struct BindingError {
  98     name: Name,
  99     origin: BTreeSet<Span>,
 100     target: BTreeSet<Span>,
 101 }
 102
 103 impl PartialOrd for BindingError {
 104     fn partial_cmp(&self, other: &BindingError) -> Option<cmp::Ordering> {
 105         Some(self.cmp(other))
 106     }
 107 }
 108
 109 impl PartialEq for BindingError {
 110     fn eq(&self, other: &BindingError) -> bool {
 111         self.name == other.name
 112     }
 113 }
 114
 115 impl Ord for BindingError {
 116     fn cmp(&self, other: &BindingError) -> cmp::Ordering {
 117         self.name.cmp(&other.name)
 118     }
 119 }
 120
 121 enum ResolutionError<'a> {
 122     /// error E0401: can't use type parameters from outer function
 123     TypeParametersFromOuterFunction,
 124     /// error E0403: the name is already used for a type parameter in this type parameter list
 125     NameAlreadyUsedInTypeParameterList(Name, &'a Span),
 126     /// error E0407: method is not a member of trait
 127     MethodNotMemberOfTrait(Name, &'a str),
 128     /// error E0437: type is not a member of trait
 129     TypeNotMemberOfTrait(Name, &'a str),
 130     /// error E0438: const is not a member of trait
 131     ConstNotMemberOfTrait(Name, &'a str),
 132     /// error E0408: variable `{}` is not bound in all patterns
 133     VariableNotBoundInPattern(&'a BindingError),
 134     /// error E0409: variable `{}` is bound in inconsistent ways within the same match arm
 135     VariableBoundWithDifferentMode(Name, Span),
 136     /// error E0415: identifier is bound more than once in this parameter list
 137     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 138     /// error E0416: identifier is bound more than once in the same pattern
 139     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 140     /// error E0426: use of undeclared label
 141     UndeclaredLabel(&'a str, Option<Name>),
 142     /// error E0429: `self` imports are only allowed within a { } list
 143     SelfImportsOnlyAllowedWithin,
 144     /// error E0430: `self` import can only appear once in the list
 145     SelfImportCanOnlyAppearOnceInTheList,
 146     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 147     SelfImportOnlyInImportListWithNonEmptyPrefix,
 148     /// error E0432: unresolved import
 149     UnresolvedImport(Option<(Span, &'a str, &'a str)>),
 150     /// error E0433: failed to resolve
 151     FailedToResolve(&'a str),
 152     /// error E0434: can't capture dynamic environment in a fn item
 153     CannotCaptureDynamicEnvironmentInFnItem,
 154     /// error E0435: attempt to use a non-constant value in a constant
 155     AttemptToUseNonConstantValueInConstant,
 156     /// error E0530: X bindings cannot shadow Ys
 157     BindingShadowsSomethingUnacceptable(&'a str, Name, &'a NameBinding<'a>),
 158     /// error E0128: type parameters with a default cannot use forward declared identifiers
 159     ForwardDeclaredTyParam,
 160 }
 161
 162 fn resolve_error<'sess, 'a>(resolver: &'sess Resolver,
 163                             span: Span,
 164                             resolution_error: ResolutionError<'a>) {
 165     resolve_struct_error(resolver, span, resolution_error).emit();
 166 }
 167
 168 fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
 169                                    span: Span,
 170                                    resolution_error: ResolutionError<'a>)
 171                                    -> DiagnosticBuilder<'sess> {
 172     match resolution_error {
 173         ResolutionError::TypeParametersFromOuterFunction => {
 174             let mut err = struct_span_err!(resolver.session,
 175                                            span,
 176                                            E0401,
 177                                            "can't use type parameters from outer function; \
 178                                            try using a local type parameter instead");
 179             err.span_label(span, "use of type variable from outer function");
 180             err
 181         }
 182         ResolutionError::NameAlreadyUsedInTypeParameterList(name, first_use_span) => {
 183              let mut err = struct_span_err!(resolver.session,
 184                                             span,
 185                                             E0403,
 186                                             "the name `{}` is already used for a type parameter \
 187                                             in this type parameter list",
 188                                             name);
 189              err.span_label(span, "already used");
 190              err.span_label(first_use_span.clone(), format!("first use of `{}`", name));
 191              err
 192         }
 193         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 194             let mut err = struct_span_err!(resolver.session,
 195                                            span,
 196                                            E0407,
 197                                            "method `{}` is not a member of trait `{}`",
 198                                            method,
 199                                            trait_);
 200             err.span_label(span, format!("not a member of trait `{}`", trait_));
 201             err
 202         }
 203         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 204             let mut err = struct_span_err!(resolver.session,
 205                              span,
 206                              E0437,
 207                              "type `{}` is not a member of trait `{}`",
 208                              type_,
 209                              trait_);
 210             err.span_label(span, format!("not a member of trait `{}`", trait_));
 211             err
 212         }
 213         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 214             let mut err = struct_span_err!(resolver.session,
 215                              span,
 216                              E0438,
 217                              "const `{}` is not a member of trait `{}`",
 218                              const_,
 219                              trait_);
 220             err.span_label(span, format!("not a member of trait `{}`", trait_));
 221             err
 222         }
 223         ResolutionError::VariableNotBoundInPattern(binding_error) => {
 224             let target_sp = binding_error.target.iter().map(|x| *x).collect::<Vec<_>>();
 225             let msp = MultiSpan::from_spans(target_sp.clone());
 226             let msg = format!("variable `{}` is not bound in all patterns", binding_error.name);
 227             let mut err = resolver.session.struct_span_err_with_code(
 228                 msp,
 229                 &msg,
 230                 DiagnosticId::Error("E0408".into()),
 231             );
 232             for sp in target_sp {
 233                 err.span_label(sp, format!("pattern doesn't bind `{}`", binding_error.name));
 234             }
 235             let origin_sp = binding_error.origin.iter().map(|x| *x).collect::<Vec<_>>();
 236             for sp in origin_sp {
 237                 err.span_label(sp, "variable not in all patterns");
 238             }
 239             err
 240         }
 241         ResolutionError::VariableBoundWithDifferentMode(variable_name,
 242                                                         first_binding_span) => {
 243             let mut err = struct_span_err!(resolver.session,
 244                              span,
 245                              E0409,
 246                              "variable `{}` is bound in inconsistent \
 247                              ways within the same match arm",
 248                              variable_name);
 249             err.span_label(span, "bound in different ways");
 250             err.span_label(first_binding_span, "first binding");
 251             err
 252         }
 253         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 254             let mut err = struct_span_err!(resolver.session,
 255                              span,
 256                              E0415,
 257                              "identifier `{}` is bound more than once in this parameter list",
 258                              identifier);
 259             err.span_label(span, "used as parameter more than once");
 260             err
 261         }
 262         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 263             let mut err = struct_span_err!(resolver.session,
 264                              span,
 265                              E0416,
 266                              "identifier `{}` is bound more than once in the same pattern",
 267                              identifier);
 268             err.span_label(span, "used in a pattern more than once");
 269             err
 270         }
 271         ResolutionError::UndeclaredLabel(name, lev_candidate) => {
 272             let mut err = struct_span_err!(resolver.session,
 273                                            span,
 274                                            E0426,
 275                                            "use of undeclared label `{}`",
 276                                            name);
 277             if let Some(lev_candidate) = lev_candidate {
 278                 err.span_label(span, format!("did you mean `{}`?", lev_candidate));
 279             } else {
 280                 err.span_label(span, format!("undeclared label `{}`", name));
 281             }
 282             err
 283         }
 284         ResolutionError::SelfImportsOnlyAllowedWithin => {
 285             struct_span_err!(resolver.session,
 286                              span,
 287                              E0429,
 288                              "{}",
 289                              "`self` imports are only allowed within a { } list")
 290         }
 291         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 292             struct_span_err!(resolver.session,
 293                              span,
 294                              E0430,
 295                              "`self` import can only appear once in the list")
 296         }
 297         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 298             struct_span_err!(resolver.session,
 299                              span,
 300                              E0431,
 301                              "`self` import can only appear in an import list with a \
 302                               non-empty prefix")
 303         }
 304         ResolutionError::UnresolvedImport(name) => {
 305             let (span, msg) = match name {
 306                 Some((sp, n, _)) => (sp, format!("unresolved import `{}`", n)),
 307                 None => (span, "unresolved import".to_owned()),
 308             };
 309             let mut err = struct_span_err!(resolver.session, span, E0432, "{}", msg);
 310             if let Some((_, _, p)) = name {
 311                 err.span_label(span, p);
 312             }
 313             err
 314         }
 315         ResolutionError::FailedToResolve(msg) => {
 316             let mut err = struct_span_err!(resolver.session, span, E0433,
 317                                            "failed to resolve. {}", msg);
 318             err.span_label(span, msg);
 319             err
 320         }
 321         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 322             struct_span_err!(resolver.session,
 323                              span,
 324                              E0434,
 325                              "{}",
 326                              "can't capture dynamic environment in a fn item; use the || { ... } \
 327                               closure form instead")
 328         }
 329         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 330             let mut err = struct_span_err!(resolver.session,
 331                              span,
 332                              E0435,
 333                              "attempt to use a non-constant value in a constant");
 334             err.span_label(span, "non-constant value");
 335             err
 336         }
 337         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 338             let shadows_what = PathResolution::new(binding.def()).kind_name();
 339             let mut err = struct_span_err!(resolver.session,
 340                                            span,
 341                                            E0530,
 342                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 343             err.span_label(span, format!("cannot be named the same as a {}", shadows_what));
 344             let participle = if binding.is_import() { "imported" } else { "defined" };
 345             let msg = format!("a {} `{}` is {} here", shadows_what, name, participle);
 346             err.span_label(binding.span, msg);
 347             err
 348         }
 349         ResolutionError::ForwardDeclaredTyParam => {
 350             let mut err = struct_span_err!(resolver.session, span, E0128,
 351                                            "type parameters with a default cannot use \
 352                                             forward declared identifiers");
 353             err.span_label(span, format!("defaulted type parameters \
 354                                            cannot be forward declared"));
 355             err
 356         }
 357     }
 358 }
 359
 360 #[derive(Copy, Clone, Debug)]
 361 struct BindingInfo {
 362     span: Span,
 363     binding_mode: BindingMode,
 364 }
 365
 366 // Map from the name in a pattern to its binding mode.
 367 type BindingMap = FxHashMap<Ident, BindingInfo>;
 368
 369 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 370 enum PatternSource {
 371     Match,
 372     IfLet,
 373     WhileLet,
 374     Let,
 375     For,
 376     FnParam,
 377 }
 378
 379 impl PatternSource {
 380     fn is_refutable(self) -> bool {
 381         match self {
 382             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 383             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 384         }
 385     }
 386     fn descr(self) -> &'static str {
 387         match self {
 388             PatternSource::Match => "match binding",
 389             PatternSource::IfLet => "if let binding",
 390             PatternSource::WhileLet => "while let binding",
 391             PatternSource::Let => "let binding",
 392             PatternSource::For => "for binding",
 393             PatternSource::FnParam => "function parameter",
 394         }
 395     }
 396 }
 397
 398 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 399 enum PathSource<'a> {
 400     // Type paths `Path`.
 401     Type,
 402     // Trait paths in bounds or impls.
 403     Trait,
 404     // Expression paths `path`, with optional parent context.
 405     Expr(Option<&'a Expr>),
 406     // Paths in path patterns `Path`.
 407     Pat,
 408     // Paths in struct expressions and patterns `Path { .. }`.
 409     Struct,
 410     // Paths in tuple struct patterns `Path(..)`.
 411     TupleStruct,
 412     // `m::A::B` in `<T as m::A>::B::C`.
 413     TraitItem(Namespace),
 414     // Path in `pub(path)`
 415     Visibility,
 416     // Path in `use a::b::{...};`
 417     ImportPrefix,
 418 }
 419
 420 impl<'a> PathSource<'a> {
 421     fn namespace(self) -> Namespace {
 422         match self {
 423             PathSource::Type | PathSource::Trait | PathSource::Struct |
 424             PathSource::Visibility | PathSource::ImportPrefix => TypeNS,
 425             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
 426             PathSource::TraitItem(ns) => ns,
 427         }
 428     }
 429
 430     fn global_by_default(self) -> bool {
 431         match self {
 432             PathSource::Visibility | PathSource::ImportPrefix => true,
 433             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 434             PathSource::Struct | PathSource::TupleStruct |
 435             PathSource::Trait | PathSource::TraitItem(..) => false,
 436         }
 437     }
 438
 439     fn defer_to_typeck(self) -> bool {
 440         match self {
 441             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 442             PathSource::Struct | PathSource::TupleStruct => true,
 443             PathSource::Trait | PathSource::TraitItem(..) |
 444             PathSource::Visibility | PathSource::ImportPrefix => false,
 445         }
 446     }
 447
 448     fn descr_expected(self) -> &'static str {
 449         match self {
 450             PathSource::Type => "type",
 451             PathSource::Trait => "trait",
 452             PathSource::Pat => "unit struct/variant or constant",
 453             PathSource::Struct => "struct, variant or union type",
 454             PathSource::TupleStruct => "tuple struct/variant",
 455             PathSource::Visibility => "module",
 456             PathSource::ImportPrefix => "module or enum",
 457             PathSource::TraitItem(ns) => match ns {
 458                 TypeNS => "associated type",
 459                 ValueNS => "method or associated constant",
 460                 MacroNS => bug!("associated macro"),
 461             },
 462             PathSource::Expr(parent) => match parent.map(|p| &p.node) {
 463                 // "function" here means "anything callable" rather than `Def::Fn`,
 464                 // this is not precise but usually more helpful than just "value".
 465                 Some(&ExprKind::Call(..)) => "function",
 466                 _ => "value",
 467             },
 468         }
 469     }
 470
 471     fn is_expected(self, def: Def) -> bool {
 472         match self {
 473             PathSource::Type => match def {
 474                 Def::Struct(..) | Def::Union(..) | Def::Enum(..) |
 475                 Def::Trait(..) | Def::TyAlias(..) | Def::AssociatedTy(..) |
 476                 Def::PrimTy(..) | Def::TyParam(..) | Def::SelfTy(..) |
 477                 Def::TyForeign(..) => true,
 478                 _ => false,
 479             },
 480             PathSource::Trait => match def {
 481                 Def::Trait(..) => true,
 482                 _ => false,
 483             },
 484             PathSource::Expr(..) => match def {
 485                 Def::StructCtor(_, CtorKind::Const) | Def::StructCtor(_, CtorKind::Fn) |
 486                 Def::VariantCtor(_, CtorKind::Const) | Def::VariantCtor(_, CtorKind::Fn) |
 487                 Def::Const(..) | Def::Static(..) | Def::Local(..) | Def::Upvar(..) |
 488                 Def::Fn(..) | Def::Method(..) | Def::AssociatedConst(..) => true,
 489                 _ => false,
 490             },
 491             PathSource::Pat => match def {
 492                 Def::StructCtor(_, CtorKind::Const) |
 493                 Def::VariantCtor(_, CtorKind::Const) |
 494                 Def::Const(..) | Def::AssociatedConst(..) => true,
 495                 _ => false,
 496             },
 497             PathSource::TupleStruct => match def {
 498                 Def::StructCtor(_, CtorKind::Fn) | Def::VariantCtor(_, CtorKind::Fn) => true,
 499                 _ => false,
 500             },
 501             PathSource::Struct => match def {
 502                 Def::Struct(..) | Def::Union(..) | Def::Variant(..) |
 503                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => true,
 504                 _ => false,
 505             },
 506             PathSource::TraitItem(ns) => match def {
 507                 Def::AssociatedConst(..) | Def::Method(..) if ns == ValueNS => true,
 508                 Def::AssociatedTy(..) if ns == TypeNS => true,
 509                 _ => false,
 510             },
 511             PathSource::ImportPrefix => match def {
 512                 Def::Mod(..) | Def::Enum(..) => true,
 513                 _ => false,
 514             },
 515             PathSource::Visibility => match def {
 516                 Def::Mod(..) => true,
 517                 _ => false,
 518             },
 519         }
 520     }
 521
 522     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
 523         __diagnostic_used!(E0404);
 524         __diagnostic_used!(E0405);
 525         __diagnostic_used!(E0412);
 526         __diagnostic_used!(E0422);
 527         __diagnostic_used!(E0423);
 528         __diagnostic_used!(E0425);
 529         __diagnostic_used!(E0531);
 530         __diagnostic_used!(E0532);
 531         __diagnostic_used!(E0573);
 532         __diagnostic_used!(E0574);
 533         __diagnostic_used!(E0575);
 534         __diagnostic_used!(E0576);
 535         __diagnostic_used!(E0577);
 536         __diagnostic_used!(E0578);
 537         match (self, has_unexpected_resolution) {
 538             (PathSource::Trait, true) => "E0404",
 539             (PathSource::Trait, false) => "E0405",
 540             (PathSource::Type, true) => "E0573",
 541             (PathSource::Type, false) => "E0412",
 542             (PathSource::Struct, true) => "E0574",
 543             (PathSource::Struct, false) => "E0422",
 544             (PathSource::Expr(..), true) => "E0423",
 545             (PathSource::Expr(..), false) => "E0425",
 546             (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
 547             (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
 548             (PathSource::TraitItem(..), true) => "E0575",
 549             (PathSource::TraitItem(..), false) => "E0576",
 550             (PathSource::Visibility, true) | (PathSource::ImportPrefix, true) => "E0577",
 551             (PathSource::Visibility, false) | (PathSource::ImportPrefix, false) => "E0578",
 552         }
 553     }
 554 }
 555
 556 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 557 pub enum Namespace {
 558     TypeNS,
 559     ValueNS,
 560     MacroNS,
 561 }
 562
 563 #[derive(Clone, Default, Debug)]
 564 pub struct PerNS<T> {
 565     value_ns: T,
 566     type_ns: T,
 567     macro_ns: Option<T>,
 568 }
 569
 570 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 571     type Output = T;
 572     fn index(&self, ns: Namespace) -> &T {
 573         match ns {
 574             ValueNS => &self.value_ns,
 575             TypeNS => &self.type_ns,
 576             MacroNS => self.macro_ns.as_ref().unwrap(),
 577         }
 578     }
 579 }
 580
 581 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 582     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 583         match ns {
 584             ValueNS => &mut self.value_ns,
 585             TypeNS => &mut self.type_ns,
 586             MacroNS => self.macro_ns.as_mut().unwrap(),
 587         }
 588     }
 589 }
 590
 591 struct UsePlacementFinder {
 592     target_module: NodeId,
 593     span: Option<Span>,
 594     found_use: bool,
 595 }
 596
 597 impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
 598     fn visit_mod(
 599         &mut self,
 600         module: &'tcx ast::Mod,
 601         _: Span,
 602         _: &[ast::Attribute],
 603         node_id: NodeId,
 604     ) {
 605         if self.span.is_some() {
 606             return;
 607         }
 608         if node_id != self.target_module {
 609             visit::walk_mod(self, module);
 610             return;
 611         }
 612         // find a use statement
 613         for item in &module.items {
 614             match item.node {
 615                 ItemKind::Use(..) => {
 616                     // don't suggest placing a use before the prelude
 617                     // import or other generated ones
 618                     if item.span.ctxt().outer().expn_info().is_none() {
 619                         self.span = Some(item.span.with_hi(item.span.lo()));
 620                         self.found_use = true;
 621                         return;
 622                     }
 623                 },
 624                 // don't place use before extern crate
 625                 ItemKind::ExternCrate(_) => {}
 626                 // but place them before the first other item
 627                 _ => if self.span.map_or(true, |span| item.span < span ) {
 628                     if item.span.ctxt().outer().expn_info().is_none() {
 629                         // don't insert between attributes and an item
 630                         if item.attrs.is_empty() {
 631                             self.span = Some(item.span.with_hi(item.span.lo()));
 632                         } else {
 633                             // find the first attribute on the item
 634                             for attr in &item.attrs {
 635                                 if self.span.map_or(true, |span| attr.span < span) {
 636                                     self.span = Some(attr.span.with_hi(attr.span.lo()));
 637                                 }
 638                             }
 639                         }
 640                     }
 641                 },
 642             }
 643         }
 644     }
 645 }
 646
 647 impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
 648     fn visit_item(&mut self, item: &'tcx Item) {
 649         self.resolve_item(item);
 650     }
 651     fn visit_arm(&mut self, arm: &'tcx Arm) {
 652         self.resolve_arm(arm);
 653     }
 654     fn visit_block(&mut self, block: &'tcx Block) {
 655         self.resolve_block(block);
 656     }
 657     fn visit_expr(&mut self, expr: &'tcx Expr) {
 658         self.resolve_expr(expr, None);
 659     }
 660     fn visit_local(&mut self, local: &'tcx Local) {
 661         self.resolve_local(local);
 662     }
 663     fn visit_ty(&mut self, ty: &'tcx Ty) {
 664         match ty.node {
 665             TyKind::Path(ref qself, ref path) => {
 666                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 667             }
 668             TyKind::ImplicitSelf => {
 669                 let self_ty = keywords::SelfType.ident();
 670                 let def = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, true, ty.span)
 671                               .map_or(Def::Err, |d| d.def());
 672                 self.record_def(ty.id, PathResolution::new(def));
 673             }
 674             TyKind::Array(ref element, ref length) => {
 675                 self.visit_ty(element);
 676                 self.with_constant_rib(|this| {
 677                     this.visit_expr(length);
 678                 });
 679                 return;
 680             }
 681             _ => (),
 682         }
 683         visit::walk_ty(self, ty);
 684     }
 685     fn visit_poly_trait_ref(&mut self,
 686                             tref: &'tcx ast::PolyTraitRef,
 687                             m: &'tcx ast::TraitBoundModifier) {
 688         self.smart_resolve_path(tref.trait_ref.ref_id, None,
 689                                 &tref.trait_ref.path, PathSource::Trait);
 690         visit::walk_poly_trait_ref(self, tref, m);
 691     }
 692     fn visit_variant(&mut self,
 693                      variant: &'tcx ast::Variant,
 694                      generics: &'tcx Generics,
 695                      item_id: ast::NodeId) {
 696         if let Some(ref dis_expr) = variant.node.disr_expr {
 697             // resolve the discriminator expr as a constant
 698             self.with_constant_rib(|this| {
 699                 this.visit_expr(dis_expr);
 700             });
 701         }
 702
 703         // `visit::walk_variant` without the discriminant expression.
 704         self.visit_variant_data(&variant.node.data,
 705                                 variant.node.name,
 706                                 generics,
 707                                 item_id,
 708                                 variant.span);
 709     }
 710     fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
 711         let type_parameters = match foreign_item.node {
 712             ForeignItemKind::Fn(_, ref generics) => {
 713                 HasTypeParameters(generics, ItemRibKind)
 714             }
 715             ForeignItemKind::Static(..) => NoTypeParameters,
 716             ForeignItemKind::Ty => NoTypeParameters,
 717         };
 718         self.with_type_parameter_rib(type_parameters, |this| {
 719             visit::walk_foreign_item(this, foreign_item);
 720         });
 721     }
 722     fn visit_fn(&mut self,
 723                 function_kind: FnKind<'tcx>,
 724                 declaration: &'tcx FnDecl,
 725                 _: Span,
 726                 node_id: NodeId) {
 727         let rib_kind = match function_kind {
 728             FnKind::ItemFn(..) => {
 729                 ItemRibKind
 730             }
 731             FnKind::Method(_, sig, _, _) => {
 732                 MethodRibKind(!sig.decl.has_self())
 733             }
 734             FnKind::Closure(_) => ClosureRibKind(node_id),
 735         };
 736
 737         // Create a value rib for the function.
 738         self.ribs[ValueNS].push(Rib::new(rib_kind));
 739
 740         // Create a label rib for the function.
 741         self.label_ribs.push(Rib::new(rib_kind));
 742
 743         // Add each argument to the rib.
 744         let mut bindings_list = FxHashMap();
 745         for argument in &declaration.inputs {
 746             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 747
 748             self.visit_ty(&argument.ty);
 749
 750             debug!("(resolving function) recorded argument");
 751         }
 752         visit::walk_fn_ret_ty(self, &declaration.output);
 753
 754         // Resolve the function body.
 755         match function_kind {
 756             FnKind::ItemFn(.., body) |
 757             FnKind::Method(.., body) => {
 758                 self.visit_block(body);
 759             }
 760             FnKind::Closure(body) => {
 761                 self.visit_expr(body);
 762             }
 763         };
 764
 765         debug!("(resolving function) leaving function");
 766
 767         self.label_ribs.pop();
 768         self.ribs[ValueNS].pop();
 769     }
 770     fn visit_generics(&mut self, generics: &'tcx Generics) {
 771         // For type parameter defaults, we have to ban access
 772         // to following type parameters, as the Substs can only
 773         // provide previous type parameters as they're built.
 774         let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
 775         default_ban_rib.bindings.extend(generics.ty_params.iter()
 776             .skip_while(|p| p.default.is_none())
 777             .map(|p| (Ident::with_empty_ctxt(p.ident.name), Def::Err)));
 778
 779         for param in &generics.ty_params {
 780             for bound in &param.bounds {
 781                 self.visit_ty_param_bound(bound);
 782             }
 783
 784             if let Some(ref ty) = param.default {
 785                 self.ribs[TypeNS].push(default_ban_rib);
 786                 self.visit_ty(ty);
 787                 default_ban_rib = self.ribs[TypeNS].pop().unwrap();
 788             }
 789
 790             // Allow all following defaults to refer to this type parameter.
 791             default_ban_rib.bindings.remove(&Ident::with_empty_ctxt(param.ident.name));
 792         }
 793         for lt in &generics.lifetimes { self.visit_lifetime_def(lt); }
 794         for p in &generics.where_clause.predicates { self.visit_where_predicate(p); }
 795     }
 796 }
 797
 798 #[derive(Copy, Clone)]
 799 enum TypeParameters<'a, 'b> {
 800     NoTypeParameters,
 801     HasTypeParameters(// Type parameters.
 802                       &'b Generics,
 803
 804                       // The kind of the rib used for type parameters.
 805                       RibKind<'a>),
 806 }
 807
 808 // The rib kind controls the translation of local
 809 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 810 #[derive(Copy, Clone, Debug)]
 811 enum RibKind<'a> {
 812     // No translation needs to be applied.
 813     NormalRibKind,
 814
 815     // We passed through a closure scope at the given node ID.
 816     // Translate upvars as appropriate.
 817     ClosureRibKind(NodeId /* func id */),
 818
 819     // We passed through an impl or trait and are now in one of its
 820     // methods. Allow references to ty params that impl or trait
 821     // binds. Disallow any other upvars (including other ty params that are
 822     // upvars).
 823     //
 824     // The boolean value represents the fact that this method is static or not.
 825     MethodRibKind(bool),
 826
 827     // We passed through an item scope. Disallow upvars.
 828     ItemRibKind,
 829
 830     // We're in a constant item. Can't refer to dynamic stuff.
 831     ConstantItemRibKind,
 832
 833     // We passed through a module.
 834     ModuleRibKind(Module<'a>),
 835
 836     // We passed through a `macro_rules!` statement
 837     MacroDefinition(DefId),
 838
 839     // All bindings in this rib are type parameters that can't be used
 840     // from the default of a type parameter because they're not declared
 841     // before said type parameter. Also see the `visit_generics` override.
 842     ForwardTyParamBanRibKind,
 843 }
 844
 845 /// One local scope.
 846 #[derive(Debug)]
 847 struct Rib<'a> {
 848     bindings: FxHashMap<Ident, Def>,
 849     kind: RibKind<'a>,
 850 }
 851
 852 impl<'a> Rib<'a> {
 853     fn new(kind: RibKind<'a>) -> Rib<'a> {
 854         Rib {
 855             bindings: FxHashMap(),
 856             kind,
 857         }
 858     }
 859 }
 860
 861 enum LexicalScopeBinding<'a> {
 862     Item(&'a NameBinding<'a>),
 863     Def(Def),
 864 }
 865
 866 impl<'a> LexicalScopeBinding<'a> {
 867     fn item(self) -> Option<&'a NameBinding<'a>> {
 868         match self {
 869             LexicalScopeBinding::Item(binding) => Some(binding),
 870             _ => None,
 871         }
 872     }
 873
 874     fn def(self) -> Def {
 875         match self {
 876             LexicalScopeBinding::Item(binding) => binding.def(),
 877             LexicalScopeBinding::Def(def) => def,
 878         }
 879     }
 880 }
 881
 882 #[derive(Clone)]
 883 enum PathResult<'a> {
 884     Module(Module<'a>),
 885     NonModule(PathResolution),
 886     Indeterminate,
 887     Failed(Span, String, bool /* is the error from the last segment? */),
 888 }
 889
 890 enum ModuleKind {
 891     Block(NodeId),
 892     Def(Def, Name),
 893 }
 894
 895 /// One node in the tree of modules.
 896 pub struct ModuleData<'a> {
 897     parent: Option<Module<'a>>,
 898     kind: ModuleKind,
 899
 900     // The def id of the closest normal module (`mod`) ancestor (including this module).
 901     normal_ancestor_id: DefId,
 902
 903     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
 904     legacy_macro_resolutions: RefCell<Vec<(Mark, Ident, Span, MacroKind)>>,
 905     macro_resolutions: RefCell<Vec<(Box<[Ident]>, Span)>>,
 906
 907     // Macro invocations that can expand into items in this module.
 908     unresolved_invocations: RefCell<FxHashSet<Mark>>,
 909
 910     no_implicit_prelude: bool,
 911
 912     glob_importers: RefCell<Vec<&'a ImportDirective<'a>>>,
 913     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 914
 915     // Used to memoize the traits in this module for faster searches through all traits in scope.
 916     traits: RefCell<Option<Box<[(Ident, &'a NameBinding<'a>)]>>>,
 917
 918     // Whether this module is populated. If not populated, any attempt to
 919     // access the children must be preceded with a
 920     // `populate_module_if_necessary` call.
 921     populated: Cell<bool>,
 922
 923     /// Span of the module itself. Used for error reporting.
 924     span: Span,
 925
 926     expansion: Mark,
 927 }
 928
 929 type Module<'a> = &'a ModuleData<'a>;
 930
 931 impl<'a> ModuleData<'a> {
 932     fn new(parent: Option<Module<'a>>,
 933            kind: ModuleKind,
 934            normal_ancestor_id: DefId,
 935            expansion: Mark,
 936            span: Span) -> Self {
 937         ModuleData {
 938             parent,
 939             kind,
 940             normal_ancestor_id,
 941             resolutions: RefCell::new(FxHashMap()),
 942             legacy_macro_resolutions: RefCell::new(Vec::new()),
 943             macro_resolutions: RefCell::new(Vec::new()),
 944             unresolved_invocations: RefCell::new(FxHashSet()),
 945             no_implicit_prelude: false,
 946             glob_importers: RefCell::new(Vec::new()),
 947             globs: RefCell::new((Vec::new())),
 948             traits: RefCell::new(None),
 949             populated: Cell::new(normal_ancestor_id.is_local()),
 950             span,
 951             expansion,
 952         }
 953     }
 954
 955     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 956         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 957             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 958         }
 959     }
 960
 961     fn for_each_child_stable<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 962         let resolutions = self.resolutions.borrow();
 963         let mut resolutions = resolutions.iter().map(|(&(ident, ns), &resolution)| {
 964                                                     // Pre-compute keys for sorting
 965                                                     (ident.name.as_str(), ns, ident, resolution)
 966                                                 })
 967                                                 .collect::<Vec<_>>();
 968         resolutions.sort_unstable_by_key(|&(str, ns, ..)| (str, ns));
 969         for &(_, ns, ident, resolution) in resolutions.iter() {
 970             resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 971         }
 972     }
 973
 974     fn def(&self) -> Option<Def> {
 975         match self.kind {
 976             ModuleKind::Def(def, _) => Some(def),
 977             _ => None,
 978         }
 979     }
 980
 981     fn def_id(&self) -> Option<DefId> {
 982         self.def().as_ref().map(Def::def_id)
 983     }
 984
 985     // `self` resolves to the first module ancestor that `is_normal`.
 986     fn is_normal(&self) -> bool {
 987         match self.kind {
 988             ModuleKind::Def(Def::Mod(_), _) => true,
 989             _ => false,
 990         }
 991     }
 992
 993     fn is_trait(&self) -> bool {
 994         match self.kind {
 995             ModuleKind::Def(Def::Trait(_), _) => true,
 996             _ => false,
 997         }
 998     }
 999
1000     fn is_local(&self) -> bool {
1001         self.normal_ancestor_id.is_local()
1002     }
1003
1004     fn nearest_item_scope(&'a self) -> Module<'a> {
1005         if self.is_trait() { self.parent.unwrap() } else { self }
1006     }
1007 }
1008
1009 impl<'a> fmt::Debug for ModuleData<'a> {
1010     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1011         write!(f, "{:?}", self.def())
1012     }
1013 }
1014
1015 // Records a possibly-private value, type, or module definition.
1016 #[derive(Clone, Debug)]
1017 pub struct NameBinding<'a> {
1018     kind: NameBindingKind<'a>,
1019     expansion: Mark,
1020     span: Span,
1021     vis: ty::Visibility,
1022 }
1023
1024 pub trait ToNameBinding<'a> {
1025     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
1026 }
1027
1028 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
1029     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
1030         self
1031     }
1032 }
1033
1034 #[derive(Clone, Debug)]
1035 enum NameBindingKind<'a> {
1036     Def(Def),
1037     Module(Module<'a>),
1038     Import {
1039         binding: &'a NameBinding<'a>,
1040         directive: &'a ImportDirective<'a>,
1041         used: Cell<bool>,
1042         legacy_self_import: bool,
1043     },
1044     Ambiguity {
1045         b1: &'a NameBinding<'a>,
1046         b2: &'a NameBinding<'a>,
1047         legacy: bool,
1048     }
1049 }
1050
1051 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
1052
1053 struct UseError<'a> {
1054     err: DiagnosticBuilder<'a>,
1055     /// Attach `use` statements for these candidates
1056     candidates: Vec<ImportSuggestion>,
1057     /// The node id of the module to place the use statements in
1058     node_id: NodeId,
1059     /// Whether the diagnostic should state that it's "better"
1060     better: bool,
1061 }
1062
1063 struct AmbiguityError<'a> {
1064     span: Span,
1065     name: Name,
1066     lexical: bool,
1067     b1: &'a NameBinding<'a>,
1068     b2: &'a NameBinding<'a>,
1069     legacy: bool,
1070 }
1071
1072 impl<'a> NameBinding<'a> {
1073     fn module(&self) -> Option<Module<'a>> {
1074         match self.kind {
1075             NameBindingKind::Module(module) => Some(module),
1076             NameBindingKind::Import { binding, .. } => binding.module(),
1077             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
1078             _ => None,
1079         }
1080     }
1081
1082     fn def(&self) -> Def {
1083         match self.kind {
1084             NameBindingKind::Def(def) => def,
1085             NameBindingKind::Module(module) => module.def().unwrap(),
1086             NameBindingKind::Import { binding, .. } => binding.def(),
1087             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
1088             NameBindingKind::Ambiguity { .. } => Def::Err,
1089         }
1090     }
1091
1092     fn def_ignoring_ambiguity(&self) -> Def {
1093         match self.kind {
1094             NameBindingKind::Import { binding, .. } => binding.def_ignoring_ambiguity(),
1095             NameBindingKind::Ambiguity { b1, .. } => b1.def_ignoring_ambiguity(),
1096             _ => self.def(),
1097         }
1098     }
1099
1100     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
1101         resolver.get_macro(self.def_ignoring_ambiguity())
1102     }
1103
1104     // We sometimes need to treat variants as `pub` for backwards compatibility
1105     fn pseudo_vis(&self) -> ty::Visibility {
1106         if self.is_variant() { ty::Visibility::Public } else { self.vis }
1107     }
1108
1109     fn is_variant(&self) -> bool {
1110         match self.kind {
1111             NameBindingKind::Def(Def::Variant(..)) |
1112             NameBindingKind::Def(Def::VariantCtor(..)) => true,
1113             _ => false,
1114         }
1115     }
1116
1117     fn is_extern_crate(&self) -> bool {
1118         match self.kind {
1119             NameBindingKind::Import {
1120                 directive: &ImportDirective {
1121                     subclass: ImportDirectiveSubclass::ExternCrate, ..
1122                 }, ..
1123             } => true,
1124             _ => false,
1125         }
1126     }
1127
1128     fn is_import(&self) -> bool {
1129         match self.kind {
1130             NameBindingKind::Import { .. } => true,
1131             _ => false,
1132         }
1133     }
1134
1135     fn is_glob_import(&self) -> bool {
1136         match self.kind {
1137             NameBindingKind::Import { directive, .. } => directive.is_glob(),
1138             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
1139             _ => false,
1140         }
1141     }
1142
1143     fn is_importable(&self) -> bool {
1144         match self.def() {
1145             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
1146             _ => true,
1147         }
1148     }
1149
1150     fn is_macro_def(&self) -> bool {
1151         match self.kind {
1152             NameBindingKind::Def(Def::Macro(..)) => true,
1153             _ => false,
1154         }
1155     }
1156
1157     fn descr(&self) -> &'static str {
1158         if self.is_extern_crate() { "extern crate" } else { self.def().kind_name() }
1159     }
1160 }
1161
1162 /// Interns the names of the primitive types.
1163 struct PrimitiveTypeTable {
1164     primitive_types: FxHashMap<Name, PrimTy>,
1165 }
1166
1167 impl PrimitiveTypeTable {
1168     fn new() -> PrimitiveTypeTable {
1169         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1170
1171         table.intern("bool", TyBool);
1172         table.intern("char", TyChar);
1173         table.intern("f32", TyFloat(FloatTy::F32));
1174         table.intern("f64", TyFloat(FloatTy::F64));
1175         table.intern("isize", TyInt(IntTy::Is));
1176         table.intern("i8", TyInt(IntTy::I8));
1177         table.intern("i16", TyInt(IntTy::I16));
1178         table.intern("i32", TyInt(IntTy::I32));
1179         table.intern("i64", TyInt(IntTy::I64));
1180         table.intern("i128", TyInt(IntTy::I128));
1181         table.intern("str", TyStr);
1182         table.intern("usize", TyUint(UintTy::Us));
1183         table.intern("u8", TyUint(UintTy::U8));
1184         table.intern("u16", TyUint(UintTy::U16));
1185         table.intern("u32", TyUint(UintTy::U32));
1186         table.intern("u64", TyUint(UintTy::U64));
1187         table.intern("u128", TyUint(UintTy::U128));
1188         table
1189     }
1190
1191     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1192         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1193     }
1194 }
1195
1196 /// The main resolver class.
1197 pub struct Resolver<'a> {
1198     session: &'a Session,
1199     cstore: &'a CrateStore,
1200
1201     pub definitions: Definitions,
1202
1203     graph_root: Module<'a>,
1204
1205     prelude: Option<Module<'a>>,
1206
1207     // n.b. This is used only for better diagnostics, not name resolution itself.
1208     has_self: FxHashSet<DefId>,
1209
1210     // Names of fields of an item `DefId` accessible with dot syntax.
1211     // Used for hints during error reporting.
1212     field_names: FxHashMap<DefId, Vec<Name>>,
1213
1214     // All imports known to succeed or fail.
1215     determined_imports: Vec<&'a ImportDirective<'a>>,
1216
1217     // All non-determined imports.
1218     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1219
1220     // The module that represents the current item scope.
1221     current_module: Module<'a>,
1222
1223     // The current set of local scopes for types and values.
1224     // FIXME #4948: Reuse ribs to avoid allocation.
1225     ribs: PerNS<Vec<Rib<'a>>>,
1226
1227     // The current set of local scopes, for labels.
1228     label_ribs: Vec<Rib<'a>>,
1229
1230     // The trait that the current context can refer to.
1231     current_trait_ref: Option<(Module<'a>, TraitRef)>,
1232
1233     // The current self type if inside an impl (used for better errors).
1234     current_self_type: Option<Ty>,
1235
1236     // The idents for the primitive types.
1237     primitive_type_table: PrimitiveTypeTable,
1238
1239     def_map: DefMap,
1240     pub freevars: FreevarMap,
1241     freevars_seen: NodeMap<NodeMap<usize>>,
1242     pub export_map: ExportMap,
1243     pub trait_map: TraitMap,
1244
1245     // A map from nodes to anonymous modules.
1246     // Anonymous modules are pseudo-modules that are implicitly created around items
1247     // contained within blocks.
1248     //
1249     // For example, if we have this:
1250     //
1251     //  fn f() {
1252     //      fn g() {
1253     //          ...
1254     //      }
1255     //  }
1256     //
1257     // There will be an anonymous module created around `g` with the ID of the
1258     // entry block for `f`.
1259     block_map: NodeMap<Module<'a>>,
1260     module_map: FxHashMap<DefId, Module<'a>>,
1261     extern_module_map: FxHashMap<(DefId, bool /* MacrosOnly? */), Module<'a>>,
1262
1263     pub make_glob_map: bool,
1264     /// Maps imports to the names of items actually imported (this actually maps
1265     /// all imports, but only glob imports are actually interesting).
1266     pub glob_map: GlobMap,
1267
1268     used_imports: FxHashSet<(NodeId, Namespace)>,
1269     pub maybe_unused_trait_imports: NodeSet,
1270     pub maybe_unused_extern_crates: Vec<(NodeId, Span)>,
1271
1272     /// privacy errors are delayed until the end in order to deduplicate them
1273     privacy_errors: Vec<PrivacyError<'a>>,
1274     /// ambiguity errors are delayed for deduplication
1275     ambiguity_errors: Vec<AmbiguityError<'a>>,
1276     /// `use` injections are delayed for better placement and deduplication
1277     use_injections: Vec<UseError<'a>>,
1278
1279     gated_errors: FxHashSet<Span>,
1280     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1281
1282     arenas: &'a ResolverArenas<'a>,
1283     dummy_binding: &'a NameBinding<'a>,
1284     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1285
1286     crate_loader: &'a mut CrateLoader,
1287     macro_names: FxHashSet<Ident>,
1288     global_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1289     lexical_macro_resolutions: Vec<(Ident, &'a Cell<LegacyScope<'a>>)>,
1290     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1291     macro_defs: FxHashMap<Mark, DefId>,
1292     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
1293     macro_exports: Vec<Export>,
1294     pub whitelisted_legacy_custom_derives: Vec<Name>,
1295     pub found_unresolved_macro: bool,
1296
1297     // List of crate local macros that we need to warn about as being unused.
1298     // Right now this only includes macro_rules! macros, and macros 2.0.
1299     unused_macros: FxHashSet<DefId>,
1300
1301     // Maps the `Mark` of an expansion to its containing module or block.
1302     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1303
1304     // Avoid duplicated errors for "name already defined".
1305     name_already_seen: FxHashMap<Name, Span>,
1306
1307     // If `#![feature(proc_macro)]` is set
1308     proc_macro_enabled: bool,
1309
1310     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1311     warned_proc_macros: FxHashSet<Name>,
1312
1313     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1314
1315     // This table maps struct IDs into struct constructor IDs,
1316     // it's not used during normal resolution, only for better error reporting.
1317     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1318
1319     // Only used for better errors on `fn(): fn()`
1320     current_type_ascription: Vec<Span>,
1321 }
1322
1323 pub struct ResolverArenas<'a> {
1324     modules: arena::TypedArena<ModuleData<'a>>,
1325     local_modules: RefCell<Vec<Module<'a>>>,
1326     name_bindings: arena::TypedArena<NameBinding<'a>>,
1327     import_directives: arena::TypedArena<ImportDirective<'a>>,
1328     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1329     invocation_data: arena::TypedArena<InvocationData<'a>>,
1330     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1331 }
1332
1333 impl<'a> ResolverArenas<'a> {
1334     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1335         let module = self.modules.alloc(module);
1336         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1337             self.local_modules.borrow_mut().push(module);
1338         }
1339         module
1340     }
1341     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1342         self.local_modules.borrow()
1343     }
1344     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1345         self.name_bindings.alloc(name_binding)
1346     }
1347     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1348                               -> &'a ImportDirective {
1349         self.import_directives.alloc(import_directive)
1350     }
1351     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1352         self.name_resolutions.alloc(Default::default())
1353     }
1354     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1355                              -> &'a InvocationData<'a> {
1356         self.invocation_data.alloc(expansion_data)
1357     }
1358     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1359         self.legacy_bindings.alloc(binding)
1360     }
1361 }
1362
1363 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1364     fn parent(self, id: DefId) -> Option<DefId> {
1365         match id.krate {
1366             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1367             _ => self.cstore.def_key(id).parent,
1368         }.map(|index| DefId { index: index, ..id })
1369     }
1370 }
1371
1372 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1373     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1374         let namespace = if is_value { ValueNS } else { TypeNS };
1375         let hir::Path { ref segments, span, ref mut def } = *path;
1376         let path: Vec<SpannedIdent> = segments.iter()
1377             .map(|seg| respan(span, Ident::with_empty_ctxt(seg.name)))
1378             .collect();
1379         match self.resolve_path(&path, Some(namespace), true, span) {
1380             PathResult::Module(module) => *def = module.def().unwrap(),
1381             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 =>
1382                 *def = path_res.base_def(),
1383             PathResult::NonModule(..) => match self.resolve_path(&path, None, true, span) {
1384                 PathResult::Failed(span, msg, _) => {
1385                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1386                 }
1387                 _ => {}
1388             },
1389             PathResult::Indeterminate => unreachable!(),
1390             PathResult::Failed(span, msg, _) => {
1391                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1392             }
1393         }
1394     }
1395
1396     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1397         self.def_map.get(&id).cloned()
1398     }
1399
1400     fn definitions(&mut self) -> &mut Definitions {
1401         &mut self.definitions
1402     }
1403 }
1404
1405 impl<'a> Resolver<'a> {
1406     pub fn new(session: &'a Session,
1407                cstore: &'a CrateStore,
1408                krate: &Crate,
1409                crate_name: &str,
1410                make_glob_map: MakeGlobMap,
1411                crate_loader: &'a mut CrateLoader,
1412                arenas: &'a ResolverArenas<'a>)
1413                -> Resolver<'a> {
1414         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1415         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1416         let graph_root = arenas.alloc_module(ModuleData {
1417             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1418             ..ModuleData::new(None, root_module_kind, root_def_id, Mark::root(), krate.span)
1419         });
1420         let mut module_map = FxHashMap();
1421         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1422
1423         let mut definitions = Definitions::new();
1424         DefCollector::new(&mut definitions, Mark::root())
1425             .collect_root(crate_name, session.local_crate_disambiguator());
1426
1427         let mut invocations = FxHashMap();
1428         invocations.insert(Mark::root(),
1429                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1430
1431         let features = session.features.borrow();
1432
1433         let mut macro_defs = FxHashMap();
1434         macro_defs.insert(Mark::root(), root_def_id);
1435
1436         Resolver {
1437             session,
1438
1439             cstore,
1440
1441             definitions,
1442
1443             // The outermost module has def ID 0; this is not reflected in the
1444             // AST.
1445             graph_root,
1446             prelude: None,
1447
1448             has_self: FxHashSet(),
1449             field_names: FxHashMap(),
1450
1451             determined_imports: Vec::new(),
1452             indeterminate_imports: Vec::new(),
1453
1454             current_module: graph_root,
1455             ribs: PerNS {
1456                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1457                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1458                 macro_ns: Some(vec![Rib::new(ModuleRibKind(graph_root))]),
1459             },
1460             label_ribs: Vec::new(),
1461
1462             current_trait_ref: None,
1463             current_self_type: None,
1464
1465             primitive_type_table: PrimitiveTypeTable::new(),
1466
1467             def_map: NodeMap(),
1468             freevars: NodeMap(),
1469             freevars_seen: NodeMap(),
1470             export_map: FxHashMap(),
1471             trait_map: NodeMap(),
1472             module_map,
1473             block_map: NodeMap(),
1474             extern_module_map: FxHashMap(),
1475
1476             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1477             glob_map: NodeMap(),
1478
1479             used_imports: FxHashSet(),
1480             maybe_unused_trait_imports: NodeSet(),
1481             maybe_unused_extern_crates: Vec::new(),
1482
1483             privacy_errors: Vec::new(),
1484             ambiguity_errors: Vec::new(),
1485             use_injections: Vec::new(),
1486             gated_errors: FxHashSet(),
1487             disallowed_shadowing: Vec::new(),
1488
1489             arenas,
1490             dummy_binding: arenas.alloc_name_binding(NameBinding {
1491                 kind: NameBindingKind::Def(Def::Err),
1492                 expansion: Mark::root(),
1493                 span: DUMMY_SP,
1494                 vis: ty::Visibility::Public,
1495             }),
1496
1497             // The `proc_macro` and `decl_macro` features imply `use_extern_macros`
1498             use_extern_macros:
1499                 features.use_extern_macros || features.proc_macro || features.decl_macro,
1500
1501             crate_loader,
1502             macro_names: FxHashSet(),
1503             global_macros: FxHashMap(),
1504             lexical_macro_resolutions: Vec::new(),
1505             macro_map: FxHashMap(),
1506             macro_exports: Vec::new(),
1507             invocations,
1508             macro_defs,
1509             local_macro_def_scopes: FxHashMap(),
1510             name_already_seen: FxHashMap(),
1511             whitelisted_legacy_custom_derives: Vec::new(),
1512             proc_macro_enabled: features.proc_macro,
1513             warned_proc_macros: FxHashSet(),
1514             potentially_unused_imports: Vec::new(),
1515             struct_constructors: DefIdMap(),
1516             found_unresolved_macro: false,
1517             unused_macros: FxHashSet(),
1518             current_type_ascription: Vec::new(),
1519         }
1520     }
1521
1522     pub fn arenas() -> ResolverArenas<'a> {
1523         ResolverArenas {
1524             modules: arena::TypedArena::new(),
1525             local_modules: RefCell::new(Vec::new()),
1526             name_bindings: arena::TypedArena::new(),
1527             import_directives: arena::TypedArena::new(),
1528             name_resolutions: arena::TypedArena::new(),
1529             invocation_data: arena::TypedArena::new(),
1530             legacy_bindings: arena::TypedArena::new(),
1531         }
1532     }
1533
1534     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1535         PerNS {
1536             type_ns: f(self, TypeNS),
1537             value_ns: f(self, ValueNS),
1538             macro_ns: match self.use_extern_macros {
1539                 true => Some(f(self, MacroNS)),
1540                 false => None,
1541             },
1542         }
1543     }
1544
1545     /// Entry point to crate resolution.
1546     pub fn resolve_crate(&mut self, krate: &Crate) {
1547         ImportResolver { resolver: self }.finalize_imports();
1548         self.current_module = self.graph_root;
1549         self.finalize_current_module_macro_resolutions();
1550
1551         visit::walk_crate(self, krate);
1552
1553         check_unused::check_crate(self, krate);
1554         self.report_errors(krate);
1555         self.crate_loader.postprocess(krate);
1556     }
1557
1558     fn new_module(
1559         &self,
1560         parent: Module<'a>,
1561         kind: ModuleKind,
1562         normal_ancestor_id: DefId,
1563         expansion: Mark,
1564         span: Span,
1565     ) -> Module<'a> {
1566         let module = ModuleData::new(Some(parent), kind, normal_ancestor_id, expansion, span);
1567         self.arenas.alloc_module(module)
1568     }
1569
1570     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1571                   -> bool /* true if an error was reported */ {
1572         match binding.kind {
1573             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1574                     if !used.get() => {
1575                 used.set(true);
1576                 directive.used.set(true);
1577                 if legacy_self_import {
1578                     self.warn_legacy_self_import(directive);
1579                     return false;
1580                 }
1581                 self.used_imports.insert((directive.id, ns));
1582                 self.add_to_glob_map(directive.id, ident);
1583                 self.record_use(ident, ns, binding, span)
1584             }
1585             NameBindingKind::Import { .. } => false,
1586             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1587                 self.ambiguity_errors.push(AmbiguityError {
1588                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy,
1589                 });
1590                 if legacy {
1591                     self.record_use(ident, ns, b1, span);
1592                 }
1593                 !legacy
1594             }
1595             _ => false
1596         }
1597     }
1598
1599     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1600         if self.make_glob_map {
1601             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1602         }
1603     }
1604
1605     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1606     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1607     /// `ident` in the first scope that defines it (or None if no scopes define it).
1608     ///
1609     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1610     /// the items are defined in the block. For example,
1611     /// ```rust
1612     /// fn f() {
1613     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1614     ///    let g = || {};
1615     ///    fn g() {}
1616     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1617     /// }
1618     /// ```
1619     ///
1620     /// Invariant: This must only be called during main resolution, not during
1621     /// import resolution.
1622     fn resolve_ident_in_lexical_scope(&mut self,
1623                                       mut ident: Ident,
1624                                       ns: Namespace,
1625                                       record_used: bool,
1626                                       path_span: Span)
1627                                       -> Option<LexicalScopeBinding<'a>> {
1628         if ns == TypeNS {
1629             ident.ctxt = if ident.name == keywords::SelfType.name() {
1630                 SyntaxContext::empty() // FIXME(jseyfried) improve `Self` hygiene
1631             } else {
1632                 ident.ctxt.modern()
1633             }
1634         }
1635
1636         // Walk backwards up the ribs in scope.
1637         let mut module = self.graph_root;
1638         for i in (0 .. self.ribs[ns].len()).rev() {
1639             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1640                 // The ident resolves to a type parameter or local variable.
1641                 return Some(LexicalScopeBinding::Def(
1642                     self.adjust_local_def(ns, i, def, record_used, path_span)
1643                 ));
1644             }
1645
1646             module = match self.ribs[ns][i].kind {
1647                 ModuleRibKind(module) => module,
1648                 MacroDefinition(def) if def == self.macro_defs[&ident.ctxt.outer()] => {
1649                     // If an invocation of this macro created `ident`, give up on `ident`
1650                     // and switch to `ident`'s source from the macro definition.
1651                     ident.ctxt.remove_mark();
1652                     continue
1653                 }
1654                 _ => continue,
1655             };
1656
1657             let item = self.resolve_ident_in_module_unadjusted(
1658                 module, ident, ns, false, record_used, path_span,
1659             );
1660             if let Ok(binding) = item {
1661                 // The ident resolves to an item.
1662                 return Some(LexicalScopeBinding::Item(binding));
1663             }
1664
1665             match module.kind {
1666                 ModuleKind::Block(..) => {}, // We can see through blocks
1667                 _ => break,
1668             }
1669         }
1670
1671         ident.ctxt = ident.ctxt.modern();
1672         loop {
1673             module = unwrap_or!(self.hygienic_lexical_parent(module, &mut ident.ctxt), break);
1674             let orig_current_module = self.current_module;
1675             self.current_module = module; // Lexical resolutions can never be a privacy error.
1676             let result = self.resolve_ident_in_module_unadjusted(
1677                 module, ident, ns, false, record_used, path_span,
1678             );
1679             self.current_module = orig_current_module;
1680
1681             match result {
1682                 Ok(binding) => return Some(LexicalScopeBinding::Item(binding)),
1683                 Err(Undetermined) => return None,
1684                 Err(Determined) => {}
1685             }
1686         }
1687
1688         match self.prelude {
1689             Some(prelude) if !module.no_implicit_prelude => {
1690                 self.resolve_ident_in_module_unadjusted(prelude, ident, ns, false, false, path_span)
1691                     .ok().map(LexicalScopeBinding::Item)
1692             }
1693             _ => None,
1694         }
1695     }
1696
1697     fn hygienic_lexical_parent(&mut self, mut module: Module<'a>, ctxt: &mut SyntaxContext)
1698                                -> Option<Module<'a>> {
1699         if !module.expansion.is_descendant_of(ctxt.outer()) {
1700             return Some(self.macro_def_scope(ctxt.remove_mark()));
1701         }
1702
1703         if let ModuleKind::Block(..) = module.kind {
1704             return Some(module.parent.unwrap());
1705         }
1706
1707         let mut module_expansion = module.expansion.modern(); // for backward compatibility
1708         while let Some(parent) = module.parent {
1709             let parent_expansion = parent.expansion.modern();
1710             if module_expansion.is_descendant_of(parent_expansion) &&
1711                parent_expansion != module_expansion {
1712                 return if parent_expansion.is_descendant_of(ctxt.outer()) {
1713                     Some(parent)
1714                 } else {
1715                     None
1716                 };
1717             }
1718             module = parent;
1719             module_expansion = parent_expansion;
1720         }
1721
1722         None
1723     }
1724
1725     fn resolve_ident_in_module(&mut self,
1726                                module: Module<'a>,
1727                                mut ident: Ident,
1728                                ns: Namespace,
1729                                ignore_unresolved_invocations: bool,
1730                                record_used: bool,
1731                                span: Span)
1732                                -> Result<&'a NameBinding<'a>, Determinacy> {
1733         ident.ctxt = ident.ctxt.modern();
1734         let orig_current_module = self.current_module;
1735         if let Some(def) = ident.ctxt.adjust(module.expansion) {
1736             self.current_module = self.macro_def_scope(def);
1737         }
1738         let result = self.resolve_ident_in_module_unadjusted(
1739             module, ident, ns, ignore_unresolved_invocations, record_used, span,
1740         );
1741         self.current_module = orig_current_module;
1742         result
1743     }
1744
1745     fn resolve_crate_root(&mut self, mut ctxt: SyntaxContext) -> Module<'a> {
1746         let module = match ctxt.adjust(Mark::root()) {
1747             Some(def) => self.macro_def_scope(def),
1748             None => return self.graph_root,
1749         };
1750         self.get_module(DefId { index: CRATE_DEF_INDEX, ..module.normal_ancestor_id })
1751     }
1752
1753     fn resolve_self(&mut self, ctxt: &mut SyntaxContext, module: Module<'a>) -> Module<'a> {
1754         let mut module = self.get_module(module.normal_ancestor_id);
1755         while module.span.ctxt().modern() != *ctxt {
1756             let parent = module.parent.unwrap_or_else(|| self.macro_def_scope(ctxt.remove_mark()));
1757             module = self.get_module(parent.normal_ancestor_id);
1758         }
1759         module
1760     }
1761
1762     // AST resolution
1763     //
1764     // We maintain a list of value ribs and type ribs.
1765     //
1766     // Simultaneously, we keep track of the current position in the module
1767     // graph in the `current_module` pointer. When we go to resolve a name in
1768     // the value or type namespaces, we first look through all the ribs and
1769     // then query the module graph. When we resolve a name in the module
1770     // namespace, we can skip all the ribs (since nested modules are not
1771     // allowed within blocks in Rust) and jump straight to the current module
1772     // graph node.
1773     //
1774     // Named implementations are handled separately. When we find a method
1775     // call, we consult the module node to find all of the implementations in
1776     // scope. This information is lazily cached in the module node. We then
1777     // generate a fake "implementation scope" containing all the
1778     // implementations thus found, for compatibility with old resolve pass.
1779
1780     fn with_scope<F>(&mut self, id: NodeId, f: F)
1781         where F: FnOnce(&mut Resolver)
1782     {
1783         let id = self.definitions.local_def_id(id);
1784         let module = self.module_map.get(&id).cloned(); // clones a reference
1785         if let Some(module) = module {
1786             // Move down in the graph.
1787             let orig_module = replace(&mut self.current_module, module);
1788             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1789             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1790
1791             self.finalize_current_module_macro_resolutions();
1792             f(self);
1793
1794             self.current_module = orig_module;
1795             self.ribs[ValueNS].pop();
1796             self.ribs[TypeNS].pop();
1797         } else {
1798             f(self);
1799         }
1800     }
1801
1802     /// Searches the current set of local scopes for labels. Returns the first non-None label that
1803     /// is returned by the given predicate function
1804     ///
1805     /// Stops after meeting a closure.
1806     fn search_label<P, R>(&self, mut ident: Ident, pred: P) -> Option<R>
1807         where P: Fn(&Rib, Ident) -> Option<R>
1808     {
1809         for rib in self.label_ribs.iter().rev() {
1810             match rib.kind {
1811                 NormalRibKind => {}
1812                 // If an invocation of this macro created `ident`, give up on `ident`
1813                 // and switch to `ident`'s source from the macro definition.
1814                 MacroDefinition(def) => {
1815                     if def == self.macro_defs[&ident.ctxt.outer()] {
1816                         ident.ctxt.remove_mark();
1817                     }
1818                 }
1819                 _ => {
1820                     // Do not resolve labels across function boundary
1821                     return None;
1822                 }
1823             }
1824             let r = pred(rib, ident);
1825             if r.is_some() {
1826                 return r;
1827             }
1828         }
1829         None
1830     }
1831
1832     fn resolve_item(&mut self, item: &Item) {
1833         let name = item.ident.name;
1834
1835         debug!("(resolving item) resolving {}", name);
1836
1837         self.check_proc_macro_attrs(&item.attrs);
1838
1839         match item.node {
1840             ItemKind::Enum(_, ref generics) |
1841             ItemKind::Ty(_, ref generics) |
1842             ItemKind::Struct(_, ref generics) |
1843             ItemKind::Union(_, ref generics) |
1844             ItemKind::Fn(.., ref generics, _) => {
1845                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1846                                              |this| visit::walk_item(this, item));
1847             }
1848
1849             ItemKind::AutoImpl(_, ref trait_ref) => {
1850                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1851                     // Resolve type arguments in trait path
1852                     visit::walk_trait_ref(this, trait_ref);
1853                 });
1854             }
1855             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1856                 self.resolve_implementation(generics,
1857                                             opt_trait_ref,
1858                                             &self_type,
1859                                             item.id,
1860                                             impl_items),
1861
1862             ItemKind::Trait(.., ref generics, ref bounds, ref trait_items) => {
1863                 // Create a new rib for the trait-wide type parameters.
1864                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1865                     let local_def_id = this.definitions.local_def_id(item.id);
1866                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1867                         this.visit_generics(generics);
1868                         walk_list!(this, visit_ty_param_bound, bounds);
1869
1870                         for trait_item in trait_items {
1871                             this.check_proc_macro_attrs(&trait_item.attrs);
1872
1873                             match trait_item.node {
1874                                 TraitItemKind::Const(ref ty, ref default) => {
1875                                     this.visit_ty(ty);
1876
1877                                     // Only impose the restrictions of
1878                                     // ConstRibKind for an actual constant
1879                                     // expression in a provided default.
1880                                     if let Some(ref expr) = *default{
1881                                         this.with_constant_rib(|this| {
1882                                             this.visit_expr(expr);
1883                                         });
1884                                     }
1885                                 }
1886                                 TraitItemKind::Method(ref sig, _) => {
1887                                     let type_parameters =
1888                                         HasTypeParameters(&trait_item.generics,
1889                                                           MethodRibKind(!sig.decl.has_self()));
1890                                     this.with_type_parameter_rib(type_parameters, |this| {
1891                                         visit::walk_trait_item(this, trait_item)
1892                                     });
1893                                 }
1894                                 TraitItemKind::Type(..) => {
1895                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1896                                         visit::walk_trait_item(this, trait_item)
1897                                     });
1898                                 }
1899                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1900                             };
1901                         }
1902                     });
1903                 });
1904             }
1905
1906             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1907                 self.with_scope(item.id, |this| {
1908                     visit::walk_item(this, item);
1909                 });
1910             }
1911
1912             ItemKind::Static(ref ty, _, ref expr) |
1913             ItemKind::Const(ref ty, ref expr) => {
1914                 self.with_item_rib(|this| {
1915                     this.visit_ty(ty);
1916                     this.with_constant_rib(|this| {
1917                         this.visit_expr(expr);
1918                     });
1919                 });
1920             }
1921
1922             ItemKind::Use(ref view_path) => {
1923                 match view_path.node {
1924                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1925                         // Resolve prefix of an import with empty braces (issue #28388).
1926                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1927                     }
1928                     _ => {}
1929                 }
1930             }
1931
1932             ItemKind::ExternCrate(_) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(_)=> {
1933                 // do nothing, these are just around to be encoded
1934             }
1935
1936             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1937         }
1938     }
1939
1940     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1941         where F: FnOnce(&mut Resolver)
1942     {
1943         match type_parameters {
1944             HasTypeParameters(generics, rib_kind) => {
1945                 let mut function_type_rib = Rib::new(rib_kind);
1946                 let mut seen_bindings = FxHashMap();
1947                 for type_parameter in &generics.ty_params {
1948                     let ident = type_parameter.ident.modern();
1949                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1950
1951                     if seen_bindings.contains_key(&ident) {
1952                         let span = seen_bindings.get(&ident).unwrap();
1953                         let err =
1954                             ResolutionError::NameAlreadyUsedInTypeParameterList(ident.name, span);
1955                         resolve_error(self, type_parameter.span, err);
1956                     }
1957                     seen_bindings.entry(ident).or_insert(type_parameter.span);
1958
1959                     // plain insert (no renaming)
1960                     let def_id = self.definitions.local_def_id(type_parameter.id);
1961                     let def = Def::TyParam(def_id);
1962                     function_type_rib.bindings.insert(ident, def);
1963                     self.record_def(type_parameter.id, PathResolution::new(def));
1964                 }
1965                 self.ribs[TypeNS].push(function_type_rib);
1966             }
1967
1968             NoTypeParameters => {
1969                 // Nothing to do.
1970             }
1971         }
1972
1973         f(self);
1974
1975         if let HasTypeParameters(..) = type_parameters {
1976             self.ribs[TypeNS].pop();
1977         }
1978     }
1979
1980     fn with_label_rib<F>(&mut self, f: F)
1981         where F: FnOnce(&mut Resolver)
1982     {
1983         self.label_ribs.push(Rib::new(NormalRibKind));
1984         f(self);
1985         self.label_ribs.pop();
1986     }
1987
1988     fn with_item_rib<F>(&mut self, f: F)
1989         where F: FnOnce(&mut Resolver)
1990     {
1991         self.ribs[ValueNS].push(Rib::new(ItemRibKind));
1992         self.ribs[TypeNS].push(Rib::new(ItemRibKind));
1993         f(self);
1994         self.ribs[TypeNS].pop();
1995         self.ribs[ValueNS].pop();
1996     }
1997
1998     fn with_constant_rib<F>(&mut self, f: F)
1999         where F: FnOnce(&mut Resolver)
2000     {
2001         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
2002         f(self);
2003         self.ribs[ValueNS].pop();
2004     }
2005
2006     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
2007         where F: FnOnce(&mut Resolver) -> T
2008     {
2009         // Handle nested impls (inside fn bodies)
2010         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
2011         let result = f(self);
2012         self.current_self_type = previous_value;
2013         result
2014     }
2015
2016     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
2017         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
2018     {
2019         let mut new_val = None;
2020         let mut new_id = None;
2021         if let Some(trait_ref) = opt_trait_ref {
2022             let path: Vec<_> = trait_ref.path.segments.iter()
2023                 .map(|seg| respan(seg.span, seg.identifier))
2024                 .collect();
2025             let def = self.smart_resolve_path_fragment(trait_ref.ref_id,
2026                                                        None,
2027                                                        &path,
2028                                                        trait_ref.path.span,
2029                                                        trait_ref.path.segments.last().unwrap().span,
2030                                                        PathSource::Trait)
2031                 .base_def();
2032             if def != Def::Err {
2033                 new_id = Some(def.def_id());
2034                 let span = trait_ref.path.span;
2035                 if let PathResult::Module(module) = self.resolve_path(&path, None, false, span) {
2036                     new_val = Some((module, trait_ref.clone()));
2037                 }
2038             }
2039         }
2040         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
2041         let result = f(self, new_id);
2042         self.current_trait_ref = original_trait_ref;
2043         result
2044     }
2045
2046     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
2047         where F: FnOnce(&mut Resolver)
2048     {
2049         let mut self_type_rib = Rib::new(NormalRibKind);
2050
2051         // plain insert (no renaming, types are not currently hygienic....)
2052         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
2053         self.ribs[TypeNS].push(self_type_rib);
2054         f(self);
2055         self.ribs[TypeNS].pop();
2056     }
2057
2058     fn resolve_implementation(&mut self,
2059                               generics: &Generics,
2060                               opt_trait_reference: &Option<TraitRef>,
2061                               self_type: &Ty,
2062                               item_id: NodeId,
2063                               impl_items: &[ImplItem]) {
2064         // If applicable, create a rib for the type parameters.
2065         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
2066             // Dummy self type for better errors if `Self` is used in the trait path.
2067             this.with_self_rib(Def::SelfTy(None, None), |this| {
2068                 // Resolve the trait reference, if necessary.
2069                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
2070                     let item_def_id = this.definitions.local_def_id(item_id);
2071                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
2072                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
2073                             // Resolve type arguments in trait path
2074                             visit::walk_trait_ref(this, trait_ref);
2075                         }
2076                         // Resolve the self type.
2077                         this.visit_ty(self_type);
2078                         // Resolve the type parameters.
2079                         this.visit_generics(generics);
2080                         this.with_current_self_type(self_type, |this| {
2081                             for impl_item in impl_items {
2082                                 this.check_proc_macro_attrs(&impl_item.attrs);
2083                                 this.resolve_visibility(&impl_item.vis);
2084                                 match impl_item.node {
2085                                     ImplItemKind::Const(..) => {
2086                                         // If this is a trait impl, ensure the const
2087                                         // exists in trait
2088                                         this.check_trait_item(impl_item.ident,
2089                                                             ValueNS,
2090                                                             impl_item.span,
2091                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
2092                                         this.with_constant_rib(|this|
2093                                             visit::walk_impl_item(this, impl_item)
2094                                         );
2095                                     }
2096                                     ImplItemKind::Method(ref sig, _) => {
2097                                         // If this is a trait impl, ensure the method
2098                                         // exists in trait
2099                                         this.check_trait_item(impl_item.ident,
2100                                                             ValueNS,
2101                                                             impl_item.span,
2102                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
2103
2104                                         // We also need a new scope for the method-
2105                                         // specific type parameters.
2106                                         let type_parameters =
2107                                             HasTypeParameters(&impl_item.generics,
2108                                                             MethodRibKind(!sig.decl.has_self()));
2109                                         this.with_type_parameter_rib(type_parameters, |this| {
2110                                             visit::walk_impl_item(this, impl_item);
2111                                         });
2112                                     }
2113                                     ImplItemKind::Type(ref ty) => {
2114                                         // If this is a trait impl, ensure the type
2115                                         // exists in trait
2116                                         this.check_trait_item(impl_item.ident,
2117                                                             TypeNS,
2118                                                             impl_item.span,
2119                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
2120
2121                                         this.visit_ty(ty);
2122                                     }
2123                                     ImplItemKind::Macro(_) =>
2124                                         panic!("unexpanded macro in resolve!"),
2125                                 }
2126                             }
2127                         });
2128                     });
2129                 });
2130             });
2131         });
2132     }
2133
2134     fn check_trait_item<F>(&mut self, ident: Ident, ns: Namespace, span: Span, err: F)
2135         where F: FnOnce(Name, &str) -> ResolutionError
2136     {
2137         // If there is a TraitRef in scope for an impl, then the method must be in the
2138         // trait.
2139         if let Some((module, _)) = self.current_trait_ref {
2140             if self.resolve_ident_in_module(module, ident, ns, false, false, span).is_err() {
2141                 let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2142                 resolve_error(self, span, err(ident.name, &path_names_to_string(path)));
2143             }
2144         }
2145     }
2146
2147     fn resolve_local(&mut self, local: &Local) {
2148         // Resolve the type.
2149         walk_list!(self, visit_ty, &local.ty);
2150
2151         // Resolve the initializer.
2152         walk_list!(self, visit_expr, &local.init);
2153
2154         // Resolve the pattern.
2155         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
2156     }
2157
2158     // build a map from pattern identifiers to binding-info's.
2159     // this is done hygienically. This could arise for a macro
2160     // that expands into an or-pattern where one 'x' was from the
2161     // user and one 'x' came from the macro.
2162     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2163         let mut binding_map = FxHashMap();
2164
2165         pat.walk(&mut |pat| {
2166             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
2167                 if sub_pat.is_some() || match self.def_map.get(&pat.id).map(|res| res.base_def()) {
2168                     Some(Def::Local(..)) => true,
2169                     _ => false,
2170                 } {
2171                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
2172                     binding_map.insert(ident.node, binding_info);
2173                 }
2174             }
2175             true
2176         });
2177
2178         binding_map
2179     }
2180
2181     // check that all of the arms in an or-pattern have exactly the
2182     // same set of bindings, with the same binding modes for each.
2183     fn check_consistent_bindings(&mut self, arm: &Arm) {
2184         if arm.pats.is_empty() {
2185             return;
2186         }
2187
2188         let mut missing_vars = FxHashMap();
2189         let mut inconsistent_vars = FxHashMap();
2190         for (i, p) in arm.pats.iter().enumerate() {
2191             let map_i = self.binding_mode_map(&p);
2192
2193             for (j, q) in arm.pats.iter().enumerate() {
2194                 if i == j {
2195                     continue;
2196                 }
2197
2198                 let map_j = self.binding_mode_map(&q);
2199                 for (&key, &binding_i) in &map_i {
2200                     if map_j.len() == 0 {                   // Account for missing bindings when
2201                         let binding_error = missing_vars    // map_j has none.
2202                             .entry(key.name)
2203                             .or_insert(BindingError {
2204                                 name: key.name,
2205                                 origin: BTreeSet::new(),
2206                                 target: BTreeSet::new(),
2207                             });
2208                         binding_error.origin.insert(binding_i.span);
2209                         binding_error.target.insert(q.span);
2210                     }
2211                     for (&key_j, &binding_j) in &map_j {
2212                         match map_i.get(&key_j) {
2213                             None => {  // missing binding
2214                                 let binding_error = missing_vars
2215                                     .entry(key_j.name)
2216                                     .or_insert(BindingError {
2217                                         name: key_j.name,
2218                                         origin: BTreeSet::new(),
2219                                         target: BTreeSet::new(),
2220                                     });
2221                                 binding_error.origin.insert(binding_j.span);
2222                                 binding_error.target.insert(p.span);
2223                             }
2224                             Some(binding_i) => {  // check consistent binding
2225                                 if binding_i.binding_mode != binding_j.binding_mode {
2226                                     inconsistent_vars
2227                                         .entry(key.name)
2228                                         .or_insert((binding_j.span, binding_i.span));
2229                                 }
2230                             }
2231                         }
2232                     }
2233                 }
2234             }
2235         }
2236         let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();
2237         missing_vars.sort();
2238         for (_, v) in missing_vars {
2239             resolve_error(self,
2240                           *v.origin.iter().next().unwrap(),
2241                           ResolutionError::VariableNotBoundInPattern(v));
2242         }
2243         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2244         inconsistent_vars.sort();
2245         for (name, v) in inconsistent_vars {
2246             resolve_error(self, v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2247         }
2248     }
2249
2250     fn resolve_arm(&mut self, arm: &Arm) {
2251         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2252
2253         let mut bindings_list = FxHashMap();
2254         for pattern in &arm.pats {
2255             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2256         }
2257
2258         // This has to happen *after* we determine which
2259         // pat_idents are variants
2260         self.check_consistent_bindings(arm);
2261
2262         walk_list!(self, visit_expr, &arm.guard);
2263         self.visit_expr(&arm.body);
2264
2265         self.ribs[ValueNS].pop();
2266     }
2267
2268     fn resolve_block(&mut self, block: &Block) {
2269         debug!("(resolving block) entering block");
2270         // Move down in the graph, if there's an anonymous module rooted here.
2271         let orig_module = self.current_module;
2272         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
2273
2274         let mut num_macro_definition_ribs = 0;
2275         if let Some(anonymous_module) = anonymous_module {
2276             debug!("(resolving block) found anonymous module, moving down");
2277             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2278             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2279             self.current_module = anonymous_module;
2280             self.finalize_current_module_macro_resolutions();
2281         } else {
2282             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2283         }
2284
2285         // Descend into the block.
2286         for stmt in &block.stmts {
2287             if let ast::StmtKind::Item(ref item) = stmt.node {
2288                 if let ast::ItemKind::MacroDef(..) = item.node {
2289                     num_macro_definition_ribs += 1;
2290                     let def = self.definitions.local_def_id(item.id);
2291                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(def)));
2292                     self.label_ribs.push(Rib::new(MacroDefinition(def)));
2293                 }
2294             }
2295
2296             self.visit_stmt(stmt);
2297         }
2298
2299         // Move back up.
2300         self.current_module = orig_module;
2301         for _ in 0 .. num_macro_definition_ribs {
2302             self.ribs[ValueNS].pop();
2303             self.label_ribs.pop();
2304         }
2305         self.ribs[ValueNS].pop();
2306         if let Some(_) = anonymous_module {
2307             self.ribs[TypeNS].pop();
2308         }
2309         debug!("(resolving block) leaving block");
2310     }
2311
2312     fn fresh_binding(&mut self,
2313                      ident: &SpannedIdent,
2314                      pat_id: NodeId,
2315                      outer_pat_id: NodeId,
2316                      pat_src: PatternSource,
2317                      bindings: &mut FxHashMap<Ident, NodeId>)
2318                      -> PathResolution {
2319         // Add the binding to the local ribs, if it
2320         // doesn't already exist in the bindings map. (We
2321         // must not add it if it's in the bindings map
2322         // because that breaks the assumptions later
2323         // passes make about or-patterns.)
2324         let mut def = Def::Local(pat_id);
2325         match bindings.get(&ident.node).cloned() {
2326             Some(id) if id == outer_pat_id => {
2327                 // `Variant(a, a)`, error
2328                 resolve_error(
2329                     self,
2330                     ident.span,
2331                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2332                         &ident.node.name.as_str())
2333                 );
2334             }
2335             Some(..) if pat_src == PatternSource::FnParam => {
2336                 // `fn f(a: u8, a: u8)`, error
2337                 resolve_error(
2338                     self,
2339                     ident.span,
2340                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2341                         &ident.node.name.as_str())
2342                 );
2343             }
2344             Some(..) if pat_src == PatternSource::Match => {
2345                 // `Variant1(a) | Variant2(a)`, ok
2346                 // Reuse definition from the first `a`.
2347                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
2348             }
2349             Some(..) => {
2350                 span_bug!(ident.span, "two bindings with the same name from \
2351                                        unexpected pattern source {:?}", pat_src);
2352             }
2353             None => {
2354                 // A completely fresh binding, add to the lists if it's valid.
2355                 if ident.node.name != keywords::Invalid.name() {
2356                     bindings.insert(ident.node, outer_pat_id);
2357                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2358                 }
2359             }
2360         }
2361
2362         PathResolution::new(def)
2363     }
2364
2365     fn resolve_pattern(&mut self,
2366                        pat: &Pat,
2367                        pat_src: PatternSource,
2368                        // Maps idents to the node ID for the
2369                        // outermost pattern that binds them.
2370                        bindings: &mut FxHashMap<Ident, NodeId>) {
2371         // Visit all direct subpatterns of this pattern.
2372         let outer_pat_id = pat.id;
2373         pat.walk(&mut |pat| {
2374             match pat.node {
2375                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2376                     // First try to resolve the identifier as some existing
2377                     // entity, then fall back to a fresh binding.
2378                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS,
2379                                                                       false, pat.span)
2380                                       .and_then(LexicalScopeBinding::item);
2381                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2382                         let ivmode = BindingMode::ByValue(Mutability::Immutable);
2383                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2384                                              bmode != ivmode;
2385                         match def {
2386                             Def::StructCtor(_, CtorKind::Const) |
2387                             Def::VariantCtor(_, CtorKind::Const) |
2388                             Def::Const(..) if !always_binding => {
2389                                 // A unit struct/variant or constant pattern.
2390                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2391                                 Some(PathResolution::new(def))
2392                             }
2393                             Def::StructCtor(..) | Def::VariantCtor(..) |
2394                             Def::Const(..) | Def::Static(..) => {
2395                                 // A fresh binding that shadows something unacceptable.
2396                                 resolve_error(
2397                                     self,
2398                                     ident.span,
2399                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2400                                         pat_src.descr(), ident.node.name, binding.unwrap())
2401                                 );
2402                                 None
2403                             }
2404                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2405                                 // These entities are explicitly allowed
2406                                 // to be shadowed by fresh bindings.
2407                                 None
2408                             }
2409                             def => {
2410                                 span_bug!(ident.span, "unexpected definition for an \
2411                                                        identifier in pattern: {:?}", def);
2412                             }
2413                         }
2414                     }).unwrap_or_else(|| {
2415                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2416                     });
2417
2418                     self.record_def(pat.id, resolution);
2419                 }
2420
2421                 PatKind::TupleStruct(ref path, ..) => {
2422                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2423                 }
2424
2425                 PatKind::Path(ref qself, ref path) => {
2426                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2427                 }
2428
2429                 PatKind::Struct(ref path, ..) => {
2430                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2431                 }
2432
2433                 _ => {}
2434             }
2435             true
2436         });
2437
2438         visit::walk_pat(self, pat);
2439     }
2440
2441     // High-level and context dependent path resolution routine.
2442     // Resolves the path and records the resolution into definition map.
2443     // If resolution fails tries several techniques to find likely
2444     // resolution candidates, suggest imports or other help, and report
2445     // errors in user friendly way.
2446     fn smart_resolve_path(&mut self,
2447                           id: NodeId,
2448                           qself: Option<&QSelf>,
2449                           path: &Path,
2450                           source: PathSource)
2451                           -> PathResolution {
2452         let segments = &path.segments.iter()
2453             .map(|seg| respan(seg.span, seg.identifier))
2454             .collect::<Vec<_>>();
2455         let ident_span = path.segments.last().map_or(path.span, |seg| seg.span);
2456         self.smart_resolve_path_fragment(id, qself, segments, path.span, ident_span, source)
2457     }
2458
2459     fn smart_resolve_path_fragment(&mut self,
2460                                    id: NodeId,
2461                                    qself: Option<&QSelf>,
2462                                    path: &[SpannedIdent],
2463                                    span: Span,
2464                                    ident_span: Span,
2465                                    source: PathSource)
2466                                    -> PathResolution {
2467         let ns = source.namespace();
2468         let is_expected = &|def| source.is_expected(def);
2469         let is_enum_variant = &|def| if let Def::Variant(..) = def { true } else { false };
2470
2471         // Base error is amended with one short label and possibly some longer helps/notes.
2472         let report_errors = |this: &mut Self, def: Option<Def>| {
2473             // Make the base error.
2474             let expected = source.descr_expected();
2475             let path_str = names_to_string(path);
2476             let code = source.error_code(def.is_some());
2477             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
2478                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2479                  format!("not a {}", expected), span)
2480             } else {
2481                 let item_str = path[path.len() - 1].node;
2482                 let item_span = path[path.len() - 1].span;
2483                 let (mod_prefix, mod_str) = if path.len() == 1 {
2484                     (format!(""), format!("this scope"))
2485                 } else if path.len() == 2 && path[0].node.name == keywords::CrateRoot.name() {
2486                     (format!(""), format!("the crate root"))
2487                 } else {
2488                     let mod_path = &path[..path.len() - 1];
2489                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), false, span) {
2490                         PathResult::Module(module) => module.def(),
2491                         _ => None,
2492                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2493                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2494                 };
2495                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2496                  format!("not found in {}", mod_str), item_span)
2497             };
2498             let code = DiagnosticId::Error(code.into());
2499             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
2500
2501             // Emit special messages for unresolved `Self` and `self`.
2502             if is_self_type(path, ns) {
2503                 __diagnostic_used!(E0411);
2504                 err.code(DiagnosticId::Error("E0411".into()));
2505                 err.span_label(span, "`Self` is only available in traits and impls");
2506                 return (err, Vec::new());
2507             }
2508             if is_self_value(path, ns) {
2509                 __diagnostic_used!(E0424);
2510                 err.code(DiagnosticId::Error("E0424".into()));
2511                 err.span_label(span, format!("`self` value is only available in \
2512                                                methods with `self` parameter"));
2513                 return (err, Vec::new());
2514             }
2515
2516             // Try to lookup the name in more relaxed fashion for better error reporting.
2517             let ident = *path.last().unwrap();
2518             let candidates = this.lookup_import_candidates(ident.node.name, ns, is_expected);
2519             if candidates.is_empty() && is_expected(Def::Enum(DefId::local(CRATE_DEF_INDEX))) {
2520                 let enum_candidates =
2521                     this.lookup_import_candidates(ident.node.name, ns, is_enum_variant);
2522                 let mut enum_candidates = enum_candidates.iter()
2523                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
2524                 enum_candidates.sort();
2525                 for (sp, variant_path, enum_path) in enum_candidates {
2526                     if sp == DUMMY_SP {
2527                         let msg = format!("there is an enum variant `{}`, \
2528                                         try using `{}`?",
2529                                         variant_path,
2530                                         enum_path);
2531                         err.help(&msg);
2532                     } else {
2533                         err.span_suggestion(span, "you can try using the variant's enum",
2534                                             enum_path);
2535                     }
2536                 }
2537             }
2538             if path.len() == 1 && this.self_type_is_available(span) {
2539                 if let Some(candidate) = this.lookup_assoc_candidate(ident.node, ns, is_expected) {
2540                     let self_is_available = this.self_value_is_available(path[0].node.ctxt, span);
2541                     match candidate {
2542                         AssocSuggestion::Field => {
2543                             err.span_suggestion(span, "try",
2544                                                 format!("self.{}", path_str));
2545                             if !self_is_available {
2546                                 err.span_label(span, format!("`self` value is only available in \
2547                                                                methods with `self` parameter"));
2548                             }
2549                         }
2550                         AssocSuggestion::MethodWithSelf if self_is_available => {
2551                             err.span_suggestion(span, "try",
2552                                                 format!("self.{}", path_str));
2553                         }
2554                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2555                             err.span_suggestion(span, "try",
2556                                                 format!("Self::{}", path_str));
2557                         }
2558                     }
2559                     return (err, candidates);
2560                 }
2561             }
2562
2563             let mut levenshtein_worked = false;
2564
2565             // Try Levenshtein.
2566             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected, span) {
2567                 err.span_label(ident_span, format!("did you mean `{}`?", candidate));
2568                 levenshtein_worked = true;
2569             }
2570
2571             // Try context dependent help if relaxed lookup didn't work.
2572             if let Some(def) = def {
2573                 match (def, source) {
2574                     (Def::Macro(..), _) => {
2575                         err.span_label(span, format!("did you mean `{}!(...)`?", path_str));
2576                         return (err, candidates);
2577                     }
2578                     (Def::TyAlias(..), PathSource::Trait) => {
2579                         err.span_label(span, "type aliases cannot be used for traits");
2580                         return (err, candidates);
2581                     }
2582                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match parent.node {
2583                         ExprKind::Field(_, ident) => {
2584                             err.span_label(parent.span, format!("did you mean `{}::{}`?",
2585                                                                  path_str, ident.node));
2586                             return (err, candidates);
2587                         }
2588                         ExprKind::MethodCall(ref segment, ..) => {
2589                             err.span_label(parent.span, format!("did you mean `{}::{}(...)`?",
2590                                                                  path_str, segment.identifier));
2591                             return (err, candidates);
2592                         }
2593                         _ => {}
2594                     },
2595                     _ if ns == ValueNS && is_struct_like(def) => {
2596                         if let Def::Struct(def_id) = def {
2597                             if let Some((ctor_def, ctor_vis))
2598                                     = this.struct_constructors.get(&def_id).cloned() {
2599                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2600                                     err.span_label(span, format!("constructor is not visible \
2601                                                                    here due to private fields"));
2602                                 }
2603                             }
2604                         }
2605                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
2606                                                      path_str));
2607                         return (err, candidates);
2608                     }
2609                     _ => {}
2610                 }
2611             }
2612
2613             // Fallback label.
2614             if !levenshtein_worked {
2615                 err.span_label(base_span, fallback_label);
2616                 this.type_ascription_suggestion(&mut err, base_span);
2617             }
2618             (err, candidates)
2619         };
2620         let report_errors = |this: &mut Self, def: Option<Def>| {
2621             let (err, candidates) = report_errors(this, def);
2622             let def_id = this.current_module.normal_ancestor_id;
2623             let node_id = this.definitions.as_local_node_id(def_id).unwrap();
2624             let better = def.is_some();
2625             this.use_injections.push(UseError { err, candidates, node_id, better });
2626             err_path_resolution()
2627         };
2628
2629         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2630                                                            source.defer_to_typeck(),
2631                                                            source.global_by_default()) {
2632             Some(resolution) if resolution.unresolved_segments() == 0 => {
2633                 if is_expected(resolution.base_def()) || resolution.base_def() == Def::Err {
2634                     resolution
2635                 } else {
2636                     // Add a temporary hack to smooth the transition to new struct ctor
2637                     // visibility rules. See #38932 for more details.
2638                     let mut res = None;
2639                     if let Def::Struct(def_id) = resolution.base_def() {
2640                         if let Some((ctor_def, ctor_vis))
2641                                 = self.struct_constructors.get(&def_id).cloned() {
2642                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2643                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2644                                 self.session.buffer_lint(lint, id, span,
2645                                     "private struct constructors are not usable through \
2646                                      reexports in outer modules",
2647                                 );
2648                                 res = Some(PathResolution::new(ctor_def));
2649                             }
2650                         }
2651                     }
2652
2653                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def())))
2654                 }
2655             }
2656             Some(resolution) if source.defer_to_typeck() => {
2657                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2658                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2659                 // it needs to be added to the trait map.
2660                 if ns == ValueNS {
2661                     let item_name = path.last().unwrap().node;
2662                     let traits = self.get_traits_containing_item(item_name, ns);
2663                     self.trait_map.insert(id, traits);
2664                 }
2665                 resolution
2666             }
2667             _ => report_errors(self, None)
2668         };
2669
2670         if let PathSource::TraitItem(..) = source {} else {
2671             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2672             self.record_def(id, resolution);
2673         }
2674         resolution
2675     }
2676
2677     fn type_ascription_suggestion(&self,
2678                                   err: &mut DiagnosticBuilder,
2679                                   base_span: Span) {
2680         debug!("type_ascription_suggetion {:?}", base_span);
2681         let cm = self.session.codemap();
2682         debug!("self.current_type_ascription {:?}", self.current_type_ascription);
2683         if let Some(sp) = self.current_type_ascription.last() {
2684             let mut sp = *sp;
2685             loop {  // try to find the `:`, bail on first non-':'/non-whitespace
2686                 sp = sp.next_point();
2687                 if let Ok(snippet) = cm.span_to_snippet(sp.to(sp.next_point())) {
2688                     debug!("snippet {:?}", snippet);
2689                     let line_sp = cm.lookup_char_pos(sp.hi()).line;
2690                     let line_base_sp = cm.lookup_char_pos(base_span.lo()).line;
2691                     debug!("{:?} {:?}", line_sp, line_base_sp);
2692                     if snippet == ":" {
2693                         err.span_label(base_span,
2694                                        "expecting a type here because of type ascription");
2695                         if line_sp != line_base_sp {
2696                             err.span_suggestion_short(sp,
2697                                                       "did you mean to use `;` here instead?",
2698                                                       ";".to_string());
2699                         }
2700                         break;
2701                     } else if snippet.trim().len() != 0  {
2702                         debug!("tried to find type ascription `:` token, couldn't find it");
2703                         break;
2704                     }
2705                 } else {
2706                     break;
2707                 }
2708             }
2709         }
2710     }
2711
2712     fn self_type_is_available(&mut self, span: Span) -> bool {
2713         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(),
2714                                                           TypeNS, false, span);
2715         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2716     }
2717
2718     fn self_value_is_available(&mut self, ctxt: SyntaxContext, span: Span) -> bool {
2719         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2720         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, false, span);
2721         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2722     }
2723
2724     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2725     fn resolve_qpath_anywhere(&mut self,
2726                               id: NodeId,
2727                               qself: Option<&QSelf>,
2728                               path: &[SpannedIdent],
2729                               primary_ns: Namespace,
2730                               span: Span,
2731                               defer_to_typeck: bool,
2732                               global_by_default: bool)
2733                               -> Option<PathResolution> {
2734         let mut fin_res = None;
2735         // FIXME: can't resolve paths in macro namespace yet, macros are
2736         // processed by the little special hack below.
2737         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2738             if i == 0 || ns != primary_ns {
2739                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2740                     // If defer_to_typeck, then resolution > no resolution,
2741                     // otherwise full resolution > partial resolution > no resolution.
2742                     Some(res) if res.unresolved_segments() == 0 || defer_to_typeck =>
2743                         return Some(res),
2744                     res => if fin_res.is_none() { fin_res = res },
2745                 };
2746             }
2747         }
2748         let is_global = self.global_macros.get(&path[0].node.name).cloned()
2749             .map(|binding| binding.get_macro(self).kind() == MacroKind::Bang).unwrap_or(false);
2750         if primary_ns != MacroNS && (is_global ||
2751                                      self.macro_names.contains(&path[0].node.modern())) {
2752             // Return some dummy definition, it's enough for error reporting.
2753             return Some(
2754                 PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX), MacroKind::Bang))
2755             );
2756         }
2757         fin_res
2758     }
2759
2760     /// Handles paths that may refer to associated items.
2761     fn resolve_qpath(&mut self,
2762                      id: NodeId,
2763                      qself: Option<&QSelf>,
2764                      path: &[SpannedIdent],
2765                      ns: Namespace,
2766                      span: Span,
2767                      global_by_default: bool)
2768                      -> Option<PathResolution> {
2769         if let Some(qself) = qself {
2770             if qself.position == 0 {
2771                 // FIXME: Create some fake resolution that can't possibly be a type.
2772                 return Some(PathResolution::with_unresolved_segments(
2773                     Def::Mod(DefId::local(CRATE_DEF_INDEX)), path.len()
2774                 ));
2775             }
2776             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2777             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2778             let res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2779                                                        span, span, PathSource::TraitItem(ns));
2780             return Some(PathResolution::with_unresolved_segments(
2781                 res.base_def(), res.unresolved_segments() + path.len() - qself.position - 1
2782             ));
2783         }
2784
2785         let result = match self.resolve_path(&path, Some(ns), true, span) {
2786             PathResult::NonModule(path_res) => path_res,
2787             PathResult::Module(module) if !module.is_normal() => {
2788                 PathResolution::new(module.def().unwrap())
2789             }
2790             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2791             // don't report an error right away, but try to fallback to a primitive type.
2792             // So, we are still able to successfully resolve something like
2793             //
2794             // use std::u8; // bring module u8 in scope
2795             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2796             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2797             //                     // not to non-existent std::u8::max_value
2798             // }
2799             //
2800             // Such behavior is required for backward compatibility.
2801             // The same fallback is used when `a` resolves to nothing.
2802             PathResult::Module(..) | PathResult::Failed(..)
2803                     if (ns == TypeNS || path.len() > 1) &&
2804                        self.primitive_type_table.primitive_types
2805                            .contains_key(&path[0].node.name) => {
2806                 let prim = self.primitive_type_table.primitive_types[&path[0].node.name];
2807                 match prim {
2808                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2809                         if !self.session.features.borrow().i128_type {
2810                             emit_feature_err(&self.session.parse_sess,
2811                                                 "i128_type", span, GateIssue::Language,
2812                                                 "128-bit type is unstable");
2813
2814                         }
2815                     }
2816                     _ => {}
2817                 }
2818                 PathResolution::with_unresolved_segments(Def::PrimTy(prim), path.len() - 1)
2819             }
2820             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2821             PathResult::Failed(span, msg, false) => {
2822                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2823                 err_path_resolution()
2824             }
2825             PathResult::Failed(..) => return None,
2826             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2827         };
2828
2829         if path.len() > 1 && !global_by_default && result.base_def() != Def::Err &&
2830            path[0].node.name != keywords::CrateRoot.name() &&
2831            path[0].node.name != keywords::DollarCrate.name() {
2832             let unqualified_result = {
2833                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), false, span) {
2834                     PathResult::NonModule(path_res) => path_res.base_def(),
2835                     PathResult::Module(module) => module.def().unwrap(),
2836                     _ => return Some(result),
2837                 }
2838             };
2839             if result.base_def() == unqualified_result {
2840                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2841                 self.session.buffer_lint(lint, id, span, "unnecessary qualification")
2842             }
2843         }
2844
2845         Some(result)
2846     }
2847
2848     fn resolve_path(&mut self,
2849                     path: &[SpannedIdent],
2850                     opt_ns: Option<Namespace>, // `None` indicates a module path
2851                     record_used: bool,
2852                     path_span: Span)
2853                     -> PathResult<'a> {
2854         let mut module = None;
2855         let mut allow_super = true;
2856
2857         for (i, &ident) in path.iter().enumerate() {
2858             debug!("resolve_path ident {} {:?}", i, ident);
2859             let is_last = i == path.len() - 1;
2860             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2861
2862             if i == 0 && ns == TypeNS && ident.node.name == keywords::SelfValue.name() {
2863                 let mut ctxt = ident.node.ctxt.modern();
2864                 module = Some(self.resolve_self(&mut ctxt, self.current_module));
2865                 continue
2866             } else if allow_super && ns == TypeNS && ident.node.name == keywords::Super.name() {
2867                 let mut ctxt = ident.node.ctxt.modern();
2868                 let self_module = match i {
2869                     0 => self.resolve_self(&mut ctxt, self.current_module),
2870                     _ => module.unwrap(),
2871                 };
2872                 if let Some(parent) = self_module.parent {
2873                     module = Some(self.resolve_self(&mut ctxt, parent));
2874                     continue
2875                 } else {
2876                     let msg = "There are too many initial `super`s.".to_string();
2877                     return PathResult::Failed(ident.span, msg, false);
2878                 }
2879             }
2880             allow_super = false;
2881
2882             if i == 0 && ns == TypeNS && ident.node.name == keywords::CrateRoot.name() {
2883                 module = Some(self.resolve_crate_root(ident.node.ctxt.modern()));
2884                 continue
2885             } else if i == 0 && ns == TypeNS && ident.node.name == keywords::DollarCrate.name() {
2886                 module = Some(self.resolve_crate_root(ident.node.ctxt));
2887                 continue
2888             }
2889
2890             let binding = if let Some(module) = module {
2891                 self.resolve_ident_in_module(module, ident.node, ns, false, record_used, path_span)
2892             } else if opt_ns == Some(MacroNS) {
2893                 self.resolve_lexical_macro_path_segment(ident.node, ns, record_used, path_span)
2894                     .map(MacroBinding::binding)
2895             } else {
2896                 match self.resolve_ident_in_lexical_scope(ident.node, ns, record_used, path_span) {
2897                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2898                     Some(LexicalScopeBinding::Def(def))
2899                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2900                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2901                             def, path.len() - 1
2902                         ));
2903                     }
2904                     _ => Err(if record_used { Determined } else { Undetermined }),
2905                 }
2906             };
2907
2908             match binding {
2909                 Ok(binding) => {
2910                     let def = binding.def();
2911                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2912                     if let Some(next_module) = binding.module() {
2913                         module = Some(next_module);
2914                     } else if def == Def::Err {
2915                         return PathResult::NonModule(err_path_resolution());
2916                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2917                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2918                             def, path.len() - i - 1
2919                         ));
2920                     } else {
2921                         return PathResult::Failed(ident.span,
2922                                                   format!("Not a module `{}`", ident.node),
2923                                                   is_last);
2924                     }
2925                 }
2926                 Err(Undetermined) => return PathResult::Indeterminate,
2927                 Err(Determined) => {
2928                     if let Some(module) = module {
2929                         if opt_ns.is_some() && !module.is_normal() {
2930                             return PathResult::NonModule(PathResolution::with_unresolved_segments(
2931                                 module.def().unwrap(), path.len() - i
2932                             ));
2933                         }
2934                     }
2935                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2936                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2937                         let mut candidates =
2938                             self.lookup_import_candidates(ident.node.name, TypeNS, is_mod);
2939                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2940                         if let Some(candidate) = candidates.get(0) {
2941                             format!("Did you mean `{}`?", candidate.path)
2942                         } else {
2943                             format!("Maybe a missing `extern crate {};`?", ident.node)
2944                         }
2945                     } else if i == 0 {
2946                         format!("Use of undeclared type or module `{}`", ident.node)
2947                     } else {
2948                         format!("Could not find `{}` in `{}`", ident.node, path[i - 1].node)
2949                     };
2950                     return PathResult::Failed(ident.span, msg, is_last);
2951                 }
2952             }
2953         }
2954
2955         PathResult::Module(module.unwrap_or(self.graph_root))
2956     }
2957
2958     // Resolve a local definition, potentially adjusting for closures.
2959     fn adjust_local_def(&mut self,
2960                         ns: Namespace,
2961                         rib_index: usize,
2962                         mut def: Def,
2963                         record_used: bool,
2964                         span: Span) -> Def {
2965         let ribs = &self.ribs[ns][rib_index + 1..];
2966
2967         // An invalid forward use of a type parameter from a previous default.
2968         if let ForwardTyParamBanRibKind = self.ribs[ns][rib_index].kind {
2969             if record_used {
2970                 resolve_error(self, span, ResolutionError::ForwardDeclaredTyParam);
2971             }
2972             assert_eq!(def, Def::Err);
2973             return Def::Err;
2974         }
2975
2976         match def {
2977             Def::Upvar(..) => {
2978                 span_bug!(span, "unexpected {:?} in bindings", def)
2979             }
2980             Def::Local(node_id) => {
2981                 for rib in ribs {
2982                     match rib.kind {
2983                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
2984                         ForwardTyParamBanRibKind => {
2985                             // Nothing to do. Continue.
2986                         }
2987                         ClosureRibKind(function_id) => {
2988                             let prev_def = def;
2989
2990                             let seen = self.freevars_seen
2991                                            .entry(function_id)
2992                                            .or_insert_with(|| NodeMap());
2993                             if let Some(&index) = seen.get(&node_id) {
2994                                 def = Def::Upvar(node_id, index, function_id);
2995                                 continue;
2996                             }
2997                             let vec = self.freevars
2998                                           .entry(function_id)
2999                                           .or_insert_with(|| vec![]);
3000                             let depth = vec.len();
3001                             def = Def::Upvar(node_id, depth, function_id);
3002
3003                             if record_used {
3004                                 vec.push(Freevar {
3005                                     def: prev_def,
3006                                     span,
3007                                 });
3008                                 seen.insert(node_id, depth);
3009                             }
3010                         }
3011                         ItemRibKind | MethodRibKind(_) => {
3012                             // This was an attempt to access an upvar inside a
3013                             // named function item. This is not allowed, so we
3014                             // report an error.
3015                             if record_used {
3016                                 resolve_error(self, span,
3017                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
3018                             }
3019                             return Def::Err;
3020                         }
3021                         ConstantItemRibKind => {
3022                             // Still doesn't deal with upvars
3023                             if record_used {
3024                                 resolve_error(self, span,
3025                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
3026                             }
3027                             return Def::Err;
3028                         }
3029                     }
3030                 }
3031             }
3032             Def::TyParam(..) | Def::SelfTy(..) => {
3033                 for rib in ribs {
3034                     match rib.kind {
3035                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
3036                         ModuleRibKind(..) | MacroDefinition(..) | ForwardTyParamBanRibKind |
3037                         ConstantItemRibKind => {
3038                             // Nothing to do. Continue.
3039                         }
3040                         ItemRibKind => {
3041                             // This was an attempt to use a type parameter outside
3042                             // its scope.
3043                             if record_used {
3044                                 resolve_error(self, span,
3045                                               ResolutionError::TypeParametersFromOuterFunction);
3046                             }
3047                             return Def::Err;
3048                         }
3049                     }
3050                 }
3051             }
3052             _ => {}
3053         }
3054         return def;
3055     }
3056
3057     fn lookup_assoc_candidate<FilterFn>(&mut self,
3058                                         ident: Ident,
3059                                         ns: Namespace,
3060                                         filter_fn: FilterFn)
3061                                         -> Option<AssocSuggestion>
3062         where FilterFn: Fn(Def) -> bool
3063     {
3064         fn extract_node_id(t: &Ty) -> Option<NodeId> {
3065             match t.node {
3066                 TyKind::Path(None, _) => Some(t.id),
3067                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
3068                 // This doesn't handle the remaining `Ty` variants as they are not
3069                 // that commonly the self_type, it might be interesting to provide
3070                 // support for those in future.
3071                 _ => None,
3072             }
3073         }
3074
3075         // Fields are generally expected in the same contexts as locals.
3076         if filter_fn(Def::Local(ast::DUMMY_NODE_ID)) {
3077             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
3078                 // Look for a field with the same name in the current self_type.
3079                 if let Some(resolution) = self.def_map.get(&node_id) {
3080                     match resolution.base_def() {
3081                         Def::Struct(did) | Def::Union(did)
3082                                 if resolution.unresolved_segments() == 0 => {
3083                             if let Some(field_names) = self.field_names.get(&did) {
3084                                 if field_names.iter().any(|&field_name| ident.name == field_name) {
3085                                     return Some(AssocSuggestion::Field);
3086                                 }
3087                             }
3088                         }
3089                         _ => {}
3090                     }
3091                 }
3092             }
3093         }
3094
3095         // Look for associated items in the current trait.
3096         if let Some((module, _)) = self.current_trait_ref {
3097             if let Ok(binding) =
3098                     self.resolve_ident_in_module(module, ident, ns, false, false, module.span) {
3099                 let def = binding.def();
3100                 if filter_fn(def) {
3101                     return Some(if self.has_self.contains(&def.def_id()) {
3102                         AssocSuggestion::MethodWithSelf
3103                     } else {
3104                         AssocSuggestion::AssocItem
3105                     });
3106                 }
3107             }
3108         }
3109
3110         None
3111     }
3112
3113     fn lookup_typo_candidate<FilterFn>(&mut self,
3114                                        path: &[SpannedIdent],
3115                                        ns: Namespace,
3116                                        filter_fn: FilterFn,
3117                                        span: Span)
3118                                        -> Option<Symbol>
3119         where FilterFn: Fn(Def) -> bool
3120     {
3121         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
3122             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
3123                 if let Some(binding) = resolution.borrow().binding {
3124                     if filter_fn(binding.def()) {
3125                         names.push(ident.name);
3126                     }
3127                 }
3128             }
3129         };
3130
3131         let mut names = Vec::new();
3132         if path.len() == 1 {
3133             // Search in lexical scope.
3134             // Walk backwards up the ribs in scope and collect candidates.
3135             for rib in self.ribs[ns].iter().rev() {
3136                 // Locals and type parameters
3137                 for (ident, def) in &rib.bindings {
3138                     if filter_fn(*def) {
3139                         names.push(ident.name);
3140                     }
3141                 }
3142                 // Items in scope
3143                 if let ModuleRibKind(module) = rib.kind {
3144                     // Items from this module
3145                     add_module_candidates(module, &mut names);
3146
3147                     if let ModuleKind::Block(..) = module.kind {
3148                         // We can see through blocks
3149                     } else {
3150                         // Items from the prelude
3151                         if let Some(prelude) = self.prelude {
3152                             if !module.no_implicit_prelude {
3153                                 add_module_candidates(prelude, &mut names);
3154                             }
3155                         }
3156                         break;
3157                     }
3158                 }
3159             }
3160             // Add primitive types to the mix
3161             if filter_fn(Def::PrimTy(TyBool)) {
3162                 for (name, _) in &self.primitive_type_table.primitive_types {
3163                     names.push(*name);
3164                 }
3165             }
3166         } else {
3167             // Search in module.
3168             let mod_path = &path[..path.len() - 1];
3169             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS),
3170                                                                   false, span) {
3171                 add_module_candidates(module, &mut names);
3172             }
3173         }
3174
3175         let name = path[path.len() - 1].node.name;
3176         // Make sure error reporting is deterministic.
3177         names.sort_by_key(|name| name.as_str());
3178         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
3179             Some(found) if found != name => Some(found),
3180             _ => None,
3181         }
3182     }
3183
3184     fn with_resolved_label<F>(&mut self, label: Option<SpannedIdent>, id: NodeId, f: F)
3185         where F: FnOnce(&mut Resolver)
3186     {
3187         if let Some(label) = label {
3188             let def = Def::Label(id);
3189             self.with_label_rib(|this| {
3190                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
3191                 f(this);
3192             });
3193         } else {
3194             f(self);
3195         }
3196     }
3197
3198     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
3199         self.with_resolved_label(label, id, |this| this.visit_block(block));
3200     }
3201
3202     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
3203         // First, record candidate traits for this expression if it could
3204         // result in the invocation of a method call.
3205
3206         self.record_candidate_traits_for_expr_if_necessary(expr);
3207
3208         // Next, resolve the node.
3209         match expr.node {
3210             ExprKind::Path(ref qself, ref path) => {
3211                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
3212                 visit::walk_expr(self, expr);
3213             }
3214
3215             ExprKind::Struct(ref path, ..) => {
3216                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
3217                 visit::walk_expr(self, expr);
3218             }
3219
3220             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
3221                 match self.search_label(label.node, |rib, id| rib.bindings.get(&id).cloned()) {
3222                     None => {
3223                         // Search again for close matches...
3224                         // Picks the first label that is "close enough", which is not necessarily
3225                         // the closest match
3226                         let close_match = self.search_label(label.node, |rib, ident| {
3227                             let names = rib.bindings.iter().map(|(id, _)| &id.name);
3228                             find_best_match_for_name(names, &*ident.name.as_str(), None)
3229                         });
3230                         self.record_def(expr.id, err_path_resolution());
3231                         resolve_error(self,
3232                                       label.span,
3233                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str(),
3234                                                                        close_match));
3235                     }
3236                     Some(def @ Def::Label(_)) => {
3237                         // Since this def is a label, it is never read.
3238                         self.record_def(expr.id, PathResolution::new(def));
3239                     }
3240                     Some(_) => {
3241                         span_bug!(expr.span, "label wasn't mapped to a label def!");
3242                     }
3243                 }
3244
3245                 // visit `break` argument if any
3246                 visit::walk_expr(self, expr);
3247             }
3248
3249             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
3250                 self.visit_expr(subexpression);
3251
3252                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3253                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
3254                 self.visit_block(if_block);
3255                 self.ribs[ValueNS].pop();
3256
3257                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
3258             }
3259
3260             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
3261
3262             ExprKind::While(ref subexpression, ref block, label) => {
3263                 self.with_resolved_label(label, expr.id, |this| {
3264                     this.visit_expr(subexpression);
3265                     this.visit_block(block);
3266                 });
3267             }
3268
3269             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
3270                 self.with_resolved_label(label, expr.id, |this| {
3271                     this.visit_expr(subexpression);
3272                     this.ribs[ValueNS].push(Rib::new(NormalRibKind));
3273                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
3274                     this.visit_block(block);
3275                     this.ribs[ValueNS].pop();
3276                 });
3277             }
3278
3279             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
3280                 self.visit_expr(subexpression);
3281                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3282                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
3283
3284                 self.resolve_labeled_block(label, expr.id, block);
3285
3286                 self.ribs[ValueNS].pop();
3287             }
3288
3289             // Equivalent to `visit::walk_expr` + passing some context to children.
3290             ExprKind::Field(ref subexpression, _) => {
3291                 self.resolve_expr(subexpression, Some(expr));
3292             }
3293             ExprKind::MethodCall(ref segment, ref arguments) => {
3294                 let mut arguments = arguments.iter();
3295                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3296                 for argument in arguments {
3297                     self.resolve_expr(argument, None);
3298                 }
3299                 self.visit_path_segment(expr.span, segment);
3300             }
3301
3302             ExprKind::Repeat(ref element, ref count) => {
3303                 self.visit_expr(element);
3304                 self.with_constant_rib(|this| {
3305                     this.visit_expr(count);
3306                 });
3307             }
3308             ExprKind::Call(ref callee, ref arguments) => {
3309                 self.resolve_expr(callee, Some(expr));
3310                 for argument in arguments {
3311                     self.resolve_expr(argument, None);
3312                 }
3313             }
3314             ExprKind::Type(ref type_expr, _) => {
3315                 self.current_type_ascription.push(type_expr.span);
3316                 visit::walk_expr(self, expr);
3317                 self.current_type_ascription.pop();
3318             }
3319             _ => {
3320                 visit::walk_expr(self, expr);
3321             }
3322         }
3323     }
3324
3325     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3326         match expr.node {
3327             ExprKind::Field(_, name) => {
3328                 // FIXME(#6890): Even though you can't treat a method like a
3329                 // field, we need to add any trait methods we find that match
3330                 // the field name so that we can do some nice error reporting
3331                 // later on in typeck.
3332                 let traits = self.get_traits_containing_item(name.node, ValueNS);
3333                 self.trait_map.insert(expr.id, traits);
3334             }
3335             ExprKind::MethodCall(ref segment, ..) => {
3336                 debug!("(recording candidate traits for expr) recording traits for {}",
3337                        expr.id);
3338                 let traits = self.get_traits_containing_item(segment.identifier, ValueNS);
3339                 self.trait_map.insert(expr.id, traits);
3340             }
3341             _ => {
3342                 // Nothing to do.
3343             }
3344         }
3345     }
3346
3347     fn get_traits_containing_item(&mut self, mut ident: Ident, ns: Namespace)
3348                                   -> Vec<TraitCandidate> {
3349         debug!("(getting traits containing item) looking for '{}'", ident.name);
3350
3351         let mut found_traits = Vec::new();
3352         // Look for the current trait.
3353         if let Some((module, _)) = self.current_trait_ref {
3354             if self.resolve_ident_in_module(module, ident, ns, false, false, module.span).is_ok() {
3355                 let def_id = module.def_id().unwrap();
3356                 found_traits.push(TraitCandidate { def_id: def_id, import_id: None });
3357             }
3358         }
3359
3360         ident.ctxt = ident.ctxt.modern();
3361         let mut search_module = self.current_module;
3362         loop {
3363             self.get_traits_in_module_containing_item(ident, ns, search_module, &mut found_traits);
3364             search_module =
3365                 unwrap_or!(self.hygienic_lexical_parent(search_module, &mut ident.ctxt), break);
3366         }
3367
3368         if let Some(prelude) = self.prelude {
3369             if !search_module.no_implicit_prelude {
3370                 self.get_traits_in_module_containing_item(ident, ns, prelude, &mut found_traits);
3371             }
3372         }
3373
3374         found_traits
3375     }
3376
3377     fn get_traits_in_module_containing_item(&mut self,
3378                                             ident: Ident,
3379                                             ns: Namespace,
3380                                             module: Module<'a>,
3381                                             found_traits: &mut Vec<TraitCandidate>) {
3382         let mut traits = module.traits.borrow_mut();
3383         if traits.is_none() {
3384             let mut collected_traits = Vec::new();
3385             module.for_each_child(|name, ns, binding| {
3386                 if ns != TypeNS { return }
3387                 if let Def::Trait(_) = binding.def() {
3388                     collected_traits.push((name, binding));
3389                 }
3390             });
3391             *traits = Some(collected_traits.into_boxed_slice());
3392         }
3393
3394         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3395             let module = binding.module().unwrap();
3396             let mut ident = ident;
3397             if ident.ctxt.glob_adjust(module.expansion, binding.span.ctxt().modern()).is_none() {
3398                 continue
3399             }
3400             if self.resolve_ident_in_module_unadjusted(module, ident, ns, false, false, module.span)
3401                    .is_ok() {
3402                 let import_id = match binding.kind {
3403                     NameBindingKind::Import { directive, .. } => {
3404                         self.maybe_unused_trait_imports.insert(directive.id);
3405                         self.add_to_glob_map(directive.id, trait_name);
3406                         Some(directive.id)
3407                     }
3408                     _ => None,
3409                 };
3410                 let trait_def_id = module.def_id().unwrap();
3411                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
3412             }
3413         }
3414     }
3415
3416     /// When name resolution fails, this method can be used to look up candidate
3417     /// entities with the expected name. It allows filtering them using the
3418     /// supplied predicate (which should be used to only accept the types of
3419     /// definitions expected e.g. traits). The lookup spans across all crates.
3420     ///
3421     /// NOTE: The method does not look into imports, but this is not a problem,
3422     /// since we report the definitions (thus, the de-aliased imports).
3423     fn lookup_import_candidates<FilterFn>(&mut self,
3424                                           lookup_name: Name,
3425                                           namespace: Namespace,
3426                                           filter_fn: FilterFn)
3427                                           -> Vec<ImportSuggestion>
3428         where FilterFn: Fn(Def) -> bool
3429     {
3430         let mut candidates = Vec::new();
3431         let mut worklist = Vec::new();
3432         let mut seen_modules = FxHashSet();
3433         worklist.push((self.graph_root, Vec::new(), false));
3434
3435         while let Some((in_module,
3436                         path_segments,
3437                         in_module_is_extern)) = worklist.pop() {
3438             self.populate_module_if_necessary(in_module);
3439
3440             // We have to visit module children in deterministic order to avoid
3441             // instabilities in reported imports (#43552).
3442             in_module.for_each_child_stable(|ident, ns, name_binding| {
3443                 // avoid imports entirely
3444                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3445                 // avoid non-importable candidates as well
3446                 if !name_binding.is_importable() { return; }
3447
3448                 // collect results based on the filter function
3449                 if ident.name == lookup_name && ns == namespace {
3450                     if filter_fn(name_binding.def()) {
3451                         // create the path
3452                         let mut segms = path_segments.clone();
3453                         segms.push(ast::PathSegment::from_ident(ident, name_binding.span));
3454                         let path = Path {
3455                             span: name_binding.span,
3456                             segments: segms,
3457                         };
3458                         // the entity is accessible in the following cases:
3459                         // 1. if it's defined in the same crate, it's always
3460                         // accessible (since private entities can be made public)
3461                         // 2. if it's defined in another crate, it's accessible
3462                         // only if both the module is public and the entity is
3463                         // declared as public (due to pruning, we don't explore
3464                         // outside crate private modules => no need to check this)
3465                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3466                             candidates.push(ImportSuggestion { path: path });
3467                         }
3468                     }
3469                 }
3470
3471                 // collect submodules to explore
3472                 if let Some(module) = name_binding.module() {
3473                     // form the path
3474                     let mut path_segments = path_segments.clone();
3475                     path_segments.push(ast::PathSegment::from_ident(ident, name_binding.span));
3476
3477                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3478                         // add the module to the lookup
3479                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3480                         if seen_modules.insert(module.def_id().unwrap()) {
3481                             worklist.push((module, path_segments, is_extern));
3482                         }
3483                     }
3484                 }
3485             })
3486         }
3487
3488         candidates
3489     }
3490
3491     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3492         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3493         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3494             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3495         }
3496     }
3497
3498     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3499         match *vis {
3500             ast::Visibility::Public => ty::Visibility::Public,
3501             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3502             ast::Visibility::Inherited => {
3503                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3504             }
3505             ast::Visibility::Restricted { ref path, id } => {
3506                 let def = self.smart_resolve_path(id, None, path,
3507                                                   PathSource::Visibility).base_def();
3508                 if def == Def::Err {
3509                     ty::Visibility::Public
3510                 } else {
3511                     let vis = ty::Visibility::Restricted(def.def_id());
3512                     if self.is_accessible(vis) {
3513                         vis
3514                     } else {
3515                         self.session.span_err(path.span, "visibilities can only be restricted \
3516                                                           to ancestor modules");
3517                         ty::Visibility::Public
3518                     }
3519                 }
3520             }
3521         }
3522     }
3523
3524     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3525         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3526     }
3527
3528     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3529         vis.is_accessible_from(module.normal_ancestor_id, self)
3530     }
3531
3532     fn report_errors(&mut self, krate: &Crate) {
3533         self.report_shadowing_errors();
3534         self.report_with_use_injections(krate);
3535         let mut reported_spans = FxHashSet();
3536
3537         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3538             if !reported_spans.insert(span) { continue }
3539             let participle = |binding: &NameBinding| {
3540                 if binding.is_import() { "imported" } else { "defined" }
3541             };
3542             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3543             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3544             let note = if b1.expansion == Mark::root() || !lexical && b1.is_glob_import() {
3545                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3546             } else if let Def::Macro(..) = b1.def() {
3547                 format!("macro-expanded {} do not shadow",
3548                         if b1.is_import() { "macro imports" } else { "macros" })
3549             } else {
3550                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3551                         if b1.is_import() { "imports" } else { "items" })
3552             };
3553             if legacy {
3554                 let id = match b2.kind {
3555                     NameBindingKind::Import { directive, .. } => directive.id,
3556                     _ => unreachable!(),
3557                 };
3558                 let mut span = MultiSpan::from_span(span);
3559                 span.push_span_label(b1.span, msg1);
3560                 span.push_span_label(b2.span, msg2);
3561                 let msg = format!("`{}` is ambiguous", name);
3562                 self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, &msg);
3563             } else {
3564                 let mut err =
3565                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", name));
3566                 err.span_note(b1.span, &msg1);
3567                 match b2.def() {
3568                     Def::Macro(..) if b2.span == DUMMY_SP =>
3569                         err.note(&format!("`{}` is also a builtin macro", name)),
3570                     _ => err.span_note(b2.span, &msg2),
3571                 };
3572                 err.note(&note).emit();
3573             }
3574         }
3575
3576         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3577             if !reported_spans.insert(span) { continue }
3578             span_err!(self.session, span, E0603, "{} `{}` is private", binding.descr(), name);
3579         }
3580     }
3581
3582     fn report_with_use_injections(&mut self, krate: &Crate) {
3583         for UseError { mut err, candidates, node_id, better } in self.use_injections.drain(..) {
3584             let mut finder = UsePlacementFinder {
3585                 target_module: node_id,
3586                 span: None,
3587                 found_use: false,
3588             };
3589             visit::walk_crate(&mut finder, krate);
3590             if !candidates.is_empty() {
3591                 show_candidates(&mut err, finder.span, &candidates, better, finder.found_use);
3592             }
3593             err.emit();
3594         }
3595     }
3596
3597     fn report_shadowing_errors(&mut self) {
3598         for (ident, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3599             self.resolve_legacy_scope(scope, ident, true);
3600         }
3601
3602         let mut reported_errors = FxHashSet();
3603         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3604             if self.resolve_legacy_scope(&binding.parent, binding.ident, false).is_some() &&
3605                reported_errors.insert((binding.ident, binding.span)) {
3606                 let msg = format!("`{}` is already in scope", binding.ident);
3607                 self.session.struct_span_err(binding.span, &msg)
3608                     .note("macro-expanded `macro_rules!`s may not shadow \
3609                            existing macros (see RFC 1560)")
3610                     .emit();
3611             }
3612         }
3613     }
3614
3615     fn report_conflict<'b>(&mut self,
3616                        parent: Module,
3617                        ident: Ident,
3618                        ns: Namespace,
3619                        new_binding: &NameBinding<'b>,
3620                        old_binding: &NameBinding<'b>) {
3621         // Error on the second of two conflicting names
3622         if old_binding.span.lo() > new_binding.span.lo() {
3623             return self.report_conflict(parent, ident, ns, old_binding, new_binding);
3624         }
3625
3626         let container = match parent.kind {
3627             ModuleKind::Def(Def::Mod(_), _) => "module",
3628             ModuleKind::Def(Def::Trait(_), _) => "trait",
3629             ModuleKind::Block(..) => "block",
3630             _ => "enum",
3631         };
3632
3633         let old_noun = match old_binding.is_import() {
3634             true => "import",
3635             false => "definition",
3636         };
3637
3638         let new_participle = match new_binding.is_import() {
3639             true => "imported",
3640             false => "defined",
3641         };
3642
3643         let (name, span) = (ident.name, new_binding.span);
3644
3645         if let Some(s) = self.name_already_seen.get(&name) {
3646             if s == &span {
3647                 return;
3648             }
3649         }
3650
3651         let old_kind = match (ns, old_binding.module()) {
3652             (ValueNS, _) => "value",
3653             (MacroNS, _) => "macro",
3654             (TypeNS, _) if old_binding.is_extern_crate() => "extern crate",
3655             (TypeNS, Some(module)) if module.is_normal() => "module",
3656             (TypeNS, Some(module)) if module.is_trait() => "trait",
3657             (TypeNS, _) => "type",
3658         };
3659
3660         let namespace = match ns {
3661             ValueNS => "value",
3662             MacroNS => "macro",
3663             TypeNS => "type",
3664         };
3665
3666         let msg = format!("the name `{}` is defined multiple times", name);
3667
3668         let mut err = match (old_binding.is_extern_crate(), new_binding.is_extern_crate()) {
3669             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3670             (true, _) | (_, true) => match new_binding.is_import() && old_binding.is_import() {
3671                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3672                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3673             },
3674             _ => match (old_binding.is_import(), new_binding.is_import()) {
3675                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3676                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3677                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3678             },
3679         };
3680
3681         err.note(&format!("`{}` must be defined only once in the {} namespace of this {}",
3682                           name,
3683                           namespace,
3684                           container));
3685
3686         err.span_label(span, format!("`{}` re{} here", name, new_participle));
3687         if old_binding.span != syntax_pos::DUMMY_SP {
3688             err.span_label(old_binding.span, format!("previous {} of the {} `{}` here",
3689                                                       old_noun, old_kind, name));
3690         }
3691
3692         // See https://github.com/rust-lang/rust/issues/32354
3693         if old_binding.is_import() || new_binding.is_import() {
3694             let binding = if new_binding.is_import() {
3695                 new_binding
3696             } else {
3697                 old_binding
3698             };
3699
3700             let cm = self.session.codemap();
3701             let rename_msg = "You can use `as` to change the binding name of the import";
3702
3703             if let Ok(snippet) = cm.span_to_snippet(binding.span) {
3704                 err.span_suggestion(binding.span,
3705                                     rename_msg,
3706                                     format!("{} as Other{}", snippet, name));
3707             } else {
3708                 err.span_label(binding.span, rename_msg);
3709             }
3710         }
3711
3712         err.emit();
3713         self.name_already_seen.insert(name, span);
3714     }
3715
3716     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3717         let (id, span) = (directive.id, directive.span);
3718         let msg = "`self` no longer imports values";
3719         self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3720     }
3721
3722     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3723         if self.proc_macro_enabled { return; }
3724
3725         for attr in attrs {
3726             if attr.path.segments.len() > 1 {
3727                 continue
3728             }
3729             let ident = attr.path.segments[0].identifier;
3730             let result = self.resolve_lexical_macro_path_segment(ident,
3731                                                                  MacroNS,
3732                                                                  false,
3733                                                                  attr.path.span);
3734             if let Ok(binding) = result {
3735                 if let SyntaxExtension::AttrProcMacro(..) = *binding.binding().get_macro(self) {
3736                     attr::mark_known(attr);
3737
3738                     let msg = "attribute procedural macros are experimental";
3739                     let feature = "proc_macro";
3740
3741                     feature_err(&self.session.parse_sess, feature,
3742                                 attr.span, GateIssue::Language, msg)
3743                         .span_note(binding.span(), "procedural macro imported here")
3744                         .emit();
3745                 }
3746             }
3747         }
3748     }
3749 }
3750
3751 fn is_struct_like(def: Def) -> bool {
3752     match def {
3753         Def::VariantCtor(_, CtorKind::Fictive) => true,
3754         _ => PathSource::Struct.is_expected(def),
3755     }
3756 }
3757
3758 fn is_self_type(path: &[SpannedIdent], namespace: Namespace) -> bool {
3759     namespace == TypeNS && path.len() == 1 && path[0].node.name == keywords::SelfType.name()
3760 }
3761
3762 fn is_self_value(path: &[SpannedIdent], namespace: Namespace) -> bool {
3763     namespace == ValueNS && path.len() == 1 && path[0].node.name == keywords::SelfValue.name()
3764 }
3765
3766 fn names_to_string(idents: &[SpannedIdent]) -> String {
3767     let mut result = String::new();
3768     for (i, ident) in idents.iter()
3769                             .filter(|i| i.node.name != keywords::CrateRoot.name())
3770                             .enumerate() {
3771         if i > 0 {
3772             result.push_str("::");
3773         }
3774         result.push_str(&ident.node.name.as_str());
3775     }
3776     result
3777 }
3778
3779 fn path_names_to_string(path: &Path) -> String {
3780     names_to_string(&path.segments.iter()
3781                         .map(|seg| respan(seg.span, seg.identifier))
3782                         .collect::<Vec<_>>())
3783 }
3784
3785 /// Get the path for an enum and the variant from an `ImportSuggestion` for an enum variant.
3786 fn import_candidate_to_paths(suggestion: &ImportSuggestion) -> (Span, String, String) {
3787     let variant_path = &suggestion.path;
3788     let variant_path_string = path_names_to_string(variant_path);
3789
3790     let path_len = suggestion.path.segments.len();
3791     let enum_path = ast::Path {
3792         span: suggestion.path.span,
3793         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
3794     };
3795     let enum_path_string = path_names_to_string(&enum_path);
3796
3797     (suggestion.path.span, variant_path_string, enum_path_string)
3798 }
3799
3800
3801 /// When an entity with a given name is not available in scope, we search for
3802 /// entities with that name in all crates. This method allows outputting the
3803 /// results of this search in a programmer-friendly way
3804 fn show_candidates(err: &mut DiagnosticBuilder,
3805                    // This is `None` if all placement locations are inside expansions
3806                    span: Option<Span>,
3807                    candidates: &[ImportSuggestion],
3808                    better: bool,
3809                    found_use: bool) {
3810
3811     // we want consistent results across executions, but candidates are produced
3812     // by iterating through a hash map, so make sure they are ordered:
3813     let mut path_strings: Vec<_> =
3814         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3815     path_strings.sort();
3816
3817     let better = if better { "better " } else { "" };
3818     let msg_diff = match path_strings.len() {
3819         1 => " is found in another module, you can import it",
3820         _ => "s are found in other modules, you can import them",
3821     };
3822     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
3823
3824     if let Some(span) = span {
3825         for candidate in &mut path_strings {
3826             // produce an additional newline to separate the new use statement
3827             // from the directly following item.
3828             let additional_newline = if found_use {
3829                 ""
3830             } else {
3831                 "\n"
3832             };
3833             *candidate = format!("use {};\n{}", candidate, additional_newline);
3834         }
3835
3836         err.span_suggestions(span, &msg, path_strings);
3837     } else {
3838         let mut msg = msg;
3839         msg.push(':');
3840         for candidate in path_strings {
3841             msg.push('\n');
3842             msg.push_str(&candidate);
3843         }
3844     }
3845 }
3846
3847 /// A somewhat inefficient routine to obtain the name of a module.
3848 fn module_to_string(module: Module) -> String {
3849     let mut names = Vec::new();
3850
3851     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3852         if let ModuleKind::Def(_, name) = module.kind {
3853             if let Some(parent) = module.parent {
3854                 names.push(Ident::with_empty_ctxt(name));
3855                 collect_mod(names, parent);
3856             }
3857         } else {
3858             // danger, shouldn't be ident?
3859             names.push(Ident::from_str("<opaque>"));
3860             collect_mod(names, module.parent.unwrap());
3861         }
3862     }
3863     collect_mod(&mut names, module);
3864
3865     if names.is_empty() {
3866         return "???".to_string();
3867     }
3868     names_to_string(&names.into_iter()
3869                         .rev()
3870                         .map(|n| dummy_spanned(n))
3871                         .collect::<Vec<_>>())
3872 }
3873
3874 fn err_path_resolution() -> PathResolution {
3875     PathResolution::new(Def::Err)
3876 }
3877
3878 #[derive(PartialEq,Copy, Clone)]
3879 pub enum MakeGlobMap {
3880     Yes,
3881     No,
3882 }
3883
3884 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }