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