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