src/librustc_resolve/lib.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![crate_name = "rustc_resolve"]
  12 #![crate_type = "dylib"]
  13 #![crate_type = "rlib"]
  14 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  15       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  16       html_root_url = "https://doc.rust-lang.org/nightly/")]
  17 #![deny(warnings)]
  18
  19 #![feature(rustc_diagnostic_macros)]
  20
  21 #[macro_use]
  22 extern crate log;
  23 #[macro_use]
  24 extern crate syntax;
  25 extern crate syntax_pos;
  26 extern crate rustc_errors as errors;
  27 extern crate arena;
  28 #[macro_use]
  29 extern crate rustc;
  30
  31 use self::Namespace::*;
  32 use self::TypeParameters::*;
  33 use self::RibKind::*;
  34
  35 use rustc::hir::map::{Definitions, DefCollector};
  36 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  37 use rustc::middle::cstore::CrateLoader;
  38 use rustc::session::Session;
  39 use rustc::lint;
  40 use rustc::hir::def::*;
  41 use rustc::hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  42 use rustc::ty;
  43 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  44 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};
  45
  46 use syntax::codemap::{dummy_spanned, respan};
  47 use syntax::ext::hygiene::{Mark, SyntaxContext};
  48 use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
  49 use syntax::ext::base::SyntaxExtension;
  50 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  51 use syntax::ext::base::MacroKind;
  52 use syntax::symbol::{Symbol, keywords};
  53 use syntax::util::lev_distance::find_best_match_for_name;
  54
  55 use syntax::visit::{self, FnKind, Visitor};
  56 use syntax::attr;
  57 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  58 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  59 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  60 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  61 use syntax::ast::{QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  62 use syntax::feature_gate::{feature_err, emit_feature_err, GateIssue};
  63
  64 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
  65 use errors::DiagnosticBuilder;
  66
  67 use std::cell::{Cell, RefCell};
  68 use std::cmp;
  69 use std::collections::BTreeSet;
  70 use std::fmt;
  71 use std::mem::replace;
  72 use std::rc::Rc;
  73
  74 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
  75 use macros::{InvocationData, LegacyBinding, LegacyScope, MacroBinding};
  76
  77 // NB: This module needs to be declared first so diagnostics are
  78 // registered before they are used.
  79 mod diagnostics;
  80
  81 mod macros;
  82 mod check_unused;
  83 mod build_reduced_graph;
  84 mod resolve_imports;
  85
  86 /// A free importable items suggested in case of resolution failure.
  87 struct ImportSuggestion {
  88     path: Path,
  89 }
  90
  91 /// A field or associated item from self type suggested in case of resolution failure.
  92 enum AssocSuggestion {
  93     Field,
  94     MethodWithSelf,
  95     AssocItem,
  96 }
  97
  98 #[derive(Eq)]
  99 struct BindingError {
 100     name: Name,
 101     origin: BTreeSet<Span>,
 102     target: BTreeSet<Span>,
 103 }
 104
 105 impl PartialOrd for BindingError {
 106     fn partial_cmp(&self, other: &BindingError) -> Option<cmp::Ordering> {
 107         Some(self.cmp(other))
 108     }
 109 }
 110
 111 impl PartialEq for BindingError {
 112     fn eq(&self, other: &BindingError) -> bool {
 113         self.name == other.name
 114     }
 115 }
 116
 117 impl Ord for BindingError {
 118     fn cmp(&self, other: &BindingError) -> cmp::Ordering {
 119         self.name.cmp(&other.name)
 120     }
 121 }
 122
 123 enum ResolutionError<'a> {
 124     /// error E0401: can't use type parameters from outer function
 125     TypeParametersFromOuterFunction,
 126     /// error E0403: the name is already used for a type parameter in this type parameter list
 127     NameAlreadyUsedInTypeParameterList(Name, &'a Span),
 128     /// error E0407: method is not a member of trait
 129     MethodNotMemberOfTrait(Name, &'a str),
 130     /// error E0437: type is not a member of trait
 131     TypeNotMemberOfTrait(Name, &'a str),
 132     /// error E0438: const is not a member of trait
 133     ConstNotMemberOfTrait(Name, &'a str),
 134     /// error E0408: variable `{}` is not bound in all patterns
 135     VariableNotBoundInPattern(&'a BindingError),
 136     /// error E0409: variable `{}` is bound in inconsistent ways within the same match arm
 137     VariableBoundWithDifferentMode(Name, Span),
 138     /// error E0415: identifier is bound more than once in this parameter list
 139     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 140     /// error E0416: identifier is bound more than once in the same pattern
 141     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 142     /// error E0426: use of undeclared label
 143     UndeclaredLabel(&'a str),
 144     /// error E0429: `self` imports are only allowed within a { } list
 145     SelfImportsOnlyAllowedWithin,
 146     /// error E0430: `self` import can only appear once in the list
 147     SelfImportCanOnlyAppearOnceInTheList,
 148     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 149     SelfImportOnlyInImportListWithNonEmptyPrefix,
 150     /// error E0432: unresolved import
 151     UnresolvedImport(Option<(Span, &'a str, &'a str)>),
 152     /// error E0433: failed to resolve
 153     FailedToResolve(&'a str),
 154     /// error E0434: can't capture dynamic environment in a fn item
 155     CannotCaptureDynamicEnvironmentInFnItem,
 156     /// error E0435: attempt to use a non-constant value in a constant
 157     AttemptToUseNonConstantValueInConstant,
 158     /// error E0530: X bindings cannot shadow Ys
 159     BindingShadowsSomethingUnacceptable(&'a str, Name, &'a NameBinding<'a>),
 160     /// error E0128: type parameters with a default cannot use forward declared identifiers
 161     ForwardDeclaredTyParam,
 162 }
 163
 164 fn resolve_error<'sess, 'a>(resolver: &'sess Resolver,
 165                             span: Span,
 166                             resolution_error: ResolutionError<'a>) {
 167     resolve_struct_error(resolver, span, resolution_error).emit();
 168 }
 169
 170 fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
 171                                    span: Span,
 172                                    resolution_error: ResolutionError<'a>)
 173                                    -> DiagnosticBuilder<'sess> {
 174     match resolution_error {
 175         ResolutionError::TypeParametersFromOuterFunction => {
 176             let mut err = struct_span_err!(resolver.session,
 177                                            span,
 178                                            E0401,
 179                                            "can't use type parameters from outer function; \
 180                                            try using a local type parameter instead");
 181             err.span_label(span, "use of type variable from outer function");
 182             err
 183         }
 184         ResolutionError::NameAlreadyUsedInTypeParameterList(name, first_use_span) => {
 185              let mut err = struct_span_err!(resolver.session,
 186                                             span,
 187                                             E0403,
 188                                             "the name `{}` is already used for a type parameter \
 189                                             in this type parameter list",
 190                                             name);
 191              err.span_label(span, "already used");
 192              err.span_label(first_use_span.clone(), format!("first use of `{}`", name));
 193              err
 194         }
 195         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 196             let mut err = struct_span_err!(resolver.session,
 197                                            span,
 198                                            E0407,
 199                                            "method `{}` is not a member of trait `{}`",
 200                                            method,
 201                                            trait_);
 202             err.span_label(span, format!("not a member of trait `{}`", trait_));
 203             err
 204         }
 205         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 206             let mut err = struct_span_err!(resolver.session,
 207                              span,
 208                              E0437,
 209                              "type `{}` is not a member of trait `{}`",
 210                              type_,
 211                              trait_);
 212             err.span_label(span, format!("not a member of trait `{}`", trait_));
 213             err
 214         }
 215         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 216             let mut err = struct_span_err!(resolver.session,
 217                              span,
 218                              E0438,
 219                              "const `{}` is not a member of trait `{}`",
 220                              const_,
 221                              trait_);
 222             err.span_label(span, format!("not a member of trait `{}`", trait_));
 223             err
 224         }
 225         ResolutionError::VariableNotBoundInPattern(binding_error) => {
 226             let target_sp = binding_error.target.iter().map(|x| *x).collect::<Vec<_>>();
 227             let msp = MultiSpan::from_spans(target_sp.clone());
 228             let msg = format!("variable `{}` is not bound in all patterns", binding_error.name);
 229             let mut err = resolver.session.struct_span_err_with_code(msp, &msg, "E0408");
 230             for sp in target_sp {
 231                 err.span_label(sp, format!("pattern doesn't bind `{}`", binding_error.name));
 232             }
 233             let origin_sp = binding_error.origin.iter().map(|x| *x).collect::<Vec<_>>();
 234             for sp in origin_sp {
 235                 err.span_label(sp, "variable not in all patterns");
 236             }
 237             err
 238         }
 239         ResolutionError::VariableBoundWithDifferentMode(variable_name,
 240                                                         first_binding_span) => {
 241             let mut err = struct_span_err!(resolver.session,
 242                              span,
 243                              E0409,
 244                              "variable `{}` is bound in inconsistent \
 245                              ways within the same match arm",
 246                              variable_name);
 247             err.span_label(span, "bound in different ways");
 248             err.span_label(first_binding_span, "first binding");
 249             err
 250         }
 251         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 252             let mut err = struct_span_err!(resolver.session,
 253                              span,
 254                              E0415,
 255                              "identifier `{}` is bound more than once in this parameter list",
 256                              identifier);
 257             err.span_label(span, "used as parameter more than once");
 258             err
 259         }
 260         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 261             let mut err = struct_span_err!(resolver.session,
 262                              span,
 263                              E0416,
 264                              "identifier `{}` is bound more than once in the same pattern",
 265                              identifier);
 266             err.span_label(span, "used in a pattern more than once");
 267             err
 268         }
 269         ResolutionError::UndeclaredLabel(name) => {
 270             let mut err = struct_span_err!(resolver.session,
 271                                            span,
 272                                            E0426,
 273                                            "use of undeclared label `{}`",
 274                                            name);
 275             err.span_label(span, format!("undeclared label `{}`", name));
 276             err
 277         }
 278         ResolutionError::SelfImportsOnlyAllowedWithin => {
 279             struct_span_err!(resolver.session,
 280                              span,
 281                              E0429,
 282                              "{}",
 283                              "`self` imports are only allowed within a { } list")
 284         }
 285         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 286             struct_span_err!(resolver.session,
 287                              span,
 288                              E0430,
 289                              "`self` import can only appear once in the list")
 290         }
 291         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 292             struct_span_err!(resolver.session,
 293                              span,
 294                              E0431,
 295                              "`self` import can only appear in an import list with a \
 296                               non-empty prefix")
 297         }
 298         ResolutionError::UnresolvedImport(name) => {
 299             let (span, msg) = match name {
 300                 Some((sp, n, _)) => (sp, format!("unresolved import `{}`", n)),
 301                 None => (span, "unresolved import".to_owned()),
 302             };
 303             let mut err = struct_span_err!(resolver.session, span, E0432, "{}", msg);
 304             if let Some((_, _, p)) = name {
 305                 err.span_label(span, p);
 306             }
 307             err
 308         }
 309         ResolutionError::FailedToResolve(msg) => {
 310             let mut err = struct_span_err!(resolver.session, span, E0433,
 311                                            "failed to resolve. {}", msg);
 312             err.span_label(span, msg);
 313             err
 314         }
 315         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 316             struct_span_err!(resolver.session,
 317                              span,
 318                              E0434,
 319                              "{}",
 320                              "can't capture dynamic environment in a fn item; use the || { ... } \
 321                               closure form instead")
 322         }
 323         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 324             let mut err = struct_span_err!(resolver.session,
 325                              span,
 326                              E0435,
 327                              "attempt to use a non-constant value in a constant");
 328             err.span_label(span, "non-constant value");
 329             err
 330         }
 331         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 332             let shadows_what = PathResolution::new(binding.def()).kind_name();
 333             let mut err = struct_span_err!(resolver.session,
 334                                            span,
 335                                            E0530,
 336                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 337             err.span_label(span, format!("cannot be named the same as a {}", shadows_what));
 338             let participle = if binding.is_import() { "imported" } else { "defined" };
 339             let msg = format!("a {} `{}` is {} here", shadows_what, name, participle);
 340             err.span_label(binding.span, msg);
 341             err
 342         }
 343         ResolutionError::ForwardDeclaredTyParam => {
 344             let mut err = struct_span_err!(resolver.session, span, E0128,
 345                                            "type parameters with a default cannot use \
 346                                             forward declared identifiers");
 347             err.span_label(span, format!("defaulted type parameters \
 348                                            cannot be forward declared"));
 349             err
 350         }
 351     }
 352 }
 353
 354 #[derive(Copy, Clone, Debug)]
 355 struct BindingInfo {
 356     span: Span,
 357     binding_mode: BindingMode,
 358 }
 359
 360 // Map from the name in a pattern to its binding mode.
 361 type BindingMap = FxHashMap<Ident, BindingInfo>;
 362
 363 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 364 enum PatternSource {
 365     Match,
 366     IfLet,
 367     WhileLet,
 368     Let,
 369     For,
 370     FnParam,
 371 }
 372
 373 impl PatternSource {
 374     fn is_refutable(self) -> bool {
 375         match self {
 376             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 377             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 378         }
 379     }
 380     fn descr(self) -> &'static str {
 381         match self {
 382             PatternSource::Match => "match binding",
 383             PatternSource::IfLet => "if let binding",
 384             PatternSource::WhileLet => "while let binding",
 385             PatternSource::Let => "let binding",
 386             PatternSource::For => "for binding",
 387             PatternSource::FnParam => "function parameter",
 388         }
 389     }
 390 }
 391
 392 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 393 enum PathSource<'a> {
 394     // Type paths `Path`.
 395     Type,
 396     // Trait paths in bounds or impls.
 397     Trait,
 398     // Expression paths `path`, with optional parent context.
 399     Expr(Option<&'a Expr>),
 400     // Paths in path patterns `Path`.
 401     Pat,
 402     // Paths in struct expressions and patterns `Path { .. }`.
 403     Struct,
 404     // Paths in tuple struct patterns `Path(..)`.
 405     TupleStruct,
 406     // `m::A::B` in `<T as m::A>::B::C`.
 407     TraitItem(Namespace),
 408     // Path in `pub(path)`
 409     Visibility,
 410     // Path in `use a::b::{...};`
 411     ImportPrefix,
 412 }
 413
 414 impl<'a> PathSource<'a> {
 415     fn namespace(self) -> Namespace {
 416         match self {
 417             PathSource::Type | PathSource::Trait | PathSource::Struct |
 418             PathSource::Visibility | PathSource::ImportPrefix => TypeNS,
 419             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
 420             PathSource::TraitItem(ns) => ns,
 421         }
 422     }
 423
 424     fn global_by_default(self) -> bool {
 425         match self {
 426             PathSource::Visibility | PathSource::ImportPrefix => true,
 427             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 428             PathSource::Struct | PathSource::TupleStruct |
 429             PathSource::Trait | PathSource::TraitItem(..) => false,
 430         }
 431     }
 432
 433     fn defer_to_typeck(self) -> bool {
 434         match self {
 435             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 436             PathSource::Struct | PathSource::TupleStruct => true,
 437             PathSource::Trait | PathSource::TraitItem(..) |
 438             PathSource::Visibility | PathSource::ImportPrefix => false,
 439         }
 440     }
 441
 442     fn descr_expected(self) -> &'static str {
 443         match self {
 444             PathSource::Type => "type",
 445             PathSource::Trait => "trait",
 446             PathSource::Pat => "unit struct/variant or constant",
 447             PathSource::Struct => "struct, variant or union type",
 448             PathSource::TupleStruct => "tuple struct/variant",
 449             PathSource::Visibility => "module",
 450             PathSource::ImportPrefix => "module or enum",
 451             PathSource::TraitItem(ns) => match ns {
 452                 TypeNS => "associated type",
 453                 ValueNS => "method or associated constant",
 454                 MacroNS => bug!("associated macro"),
 455             },
 456             PathSource::Expr(parent) => match parent.map(|p| &p.node) {
 457                 // "function" here means "anything callable" rather than `Def::Fn`,
 458                 // this is not precise but usually more helpful than just "value".
 459                 Some(&ExprKind::Call(..)) => "function",
 460                 _ => "value",
 461             },
 462         }
 463     }
 464
 465     fn is_expected(self, def: Def) -> bool {
 466         match self {
 467             PathSource::Type => match def {
 468                 Def::Struct(..) | Def::Union(..) | Def::Enum(..) |
 469                 Def::Trait(..) | Def::TyAlias(..) | Def::AssociatedTy(..) |
 470                 Def::PrimTy(..) | Def::TyParam(..) | Def::SelfTy(..) => true,
 471                 _ => false,
 472             },
 473             PathSource::Trait => match def {
 474                 Def::Trait(..) => true,
 475                 _ => false,
 476             },
 477             PathSource::Expr(..) => match def {
 478                 Def::StructCtor(_, CtorKind::Const) | Def::StructCtor(_, CtorKind::Fn) |
 479                 Def::VariantCtor(_, CtorKind::Const) | Def::VariantCtor(_, CtorKind::Fn) |
 480                 Def::Const(..) | Def::Static(..) | Def::Local(..) | Def::Upvar(..) |
 481                 Def::Fn(..) | Def::Method(..) | Def::AssociatedConst(..) => true,
 482                 _ => false,
 483             },
 484             PathSource::Pat => match def {
 485                 Def::StructCtor(_, CtorKind::Const) |
 486                 Def::VariantCtor(_, CtorKind::Const) |
 487                 Def::Const(..) | Def::AssociatedConst(..) => true,
 488                 _ => false,
 489             },
 490             PathSource::TupleStruct => match def {
 491                 Def::StructCtor(_, CtorKind::Fn) | Def::VariantCtor(_, CtorKind::Fn) => true,
 492                 _ => false,
 493             },
 494             PathSource::Struct => match def {
 495                 Def::Struct(..) | Def::Union(..) | Def::Variant(..) |
 496                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => true,
 497                 _ => false,
 498             },
 499             PathSource::TraitItem(ns) => match def {
 500                 Def::AssociatedConst(..) | Def::Method(..) if ns == ValueNS => true,
 501                 Def::AssociatedTy(..) if ns == TypeNS => true,
 502                 _ => false,
 503             },
 504             PathSource::ImportPrefix => match def {
 505                 Def::Mod(..) | Def::Enum(..) => true,
 506                 _ => false,
 507             },
 508             PathSource::Visibility => match def {
 509                 Def::Mod(..) => true,
 510                 _ => false,
 511             },
 512         }
 513     }
 514
 515     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
 516         __diagnostic_used!(E0404);
 517         __diagnostic_used!(E0405);
 518         __diagnostic_used!(E0412);
 519         __diagnostic_used!(E0422);
 520         __diagnostic_used!(E0423);
 521         __diagnostic_used!(E0425);
 522         __diagnostic_used!(E0531);
 523         __diagnostic_used!(E0532);
 524         __diagnostic_used!(E0573);
 525         __diagnostic_used!(E0574);
 526         __diagnostic_used!(E0575);
 527         __diagnostic_used!(E0576);
 528         __diagnostic_used!(E0577);
 529         __diagnostic_used!(E0578);
 530         match (self, has_unexpected_resolution) {
 531             (PathSource::Trait, true) => "E0404",
 532             (PathSource::Trait, false) => "E0405",
 533             (PathSource::Type, true) => "E0573",
 534             (PathSource::Type, false) => "E0412",
 535             (PathSource::Struct, true) => "E0574",
 536             (PathSource::Struct, false) => "E0422",
 537             (PathSource::Expr(..), true) => "E0423",
 538             (PathSource::Expr(..), false) => "E0425",
 539             (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
 540             (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
 541             (PathSource::TraitItem(..), true) => "E0575",
 542             (PathSource::TraitItem(..), false) => "E0576",
 543             (PathSource::Visibility, true) | (PathSource::ImportPrefix, true) => "E0577",
 544             (PathSource::Visibility, false) | (PathSource::ImportPrefix, false) => "E0578",
 545         }
 546     }
 547 }
 548
 549 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 550 pub enum Namespace {
 551     TypeNS,
 552     ValueNS,
 553     MacroNS,
 554 }
 555
 556 #[derive(Clone, Default, Debug)]
 557 pub struct PerNS<T> {
 558     value_ns: T,
 559     type_ns: T,
 560     macro_ns: Option<T>,
 561 }
 562
 563 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 564     type Output = T;
 565     fn index(&self, ns: Namespace) -> &T {
 566         match ns {
 567             ValueNS => &self.value_ns,
 568             TypeNS => &self.type_ns,
 569             MacroNS => self.macro_ns.as_ref().unwrap(),
 570         }
 571     }
 572 }
 573
 574 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 575     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 576         match ns {
 577             ValueNS => &mut self.value_ns,
 578             TypeNS => &mut self.type_ns,
 579             MacroNS => self.macro_ns.as_mut().unwrap(),
 580         }
 581     }
 582 }
 583
 584 struct UsePlacementFinder {
 585     target_module: NodeId,
 586     span: Option<Span>,
 587     found_use: bool,
 588 }
 589
 590 impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
 591     fn visit_mod(
 592         &mut self,
 593         module: &'tcx ast::Mod,
 594         _: Span,
 595         _: &[ast::Attribute],
 596         node_id: NodeId,
 597     ) {
 598         if self.span.is_some() {
 599             return;
 600         }
 601         if node_id != self.target_module {
 602             visit::walk_mod(self, module);
 603             return;
 604         }
 605         // find a use statement
 606         for item in &module.items {
 607             match item.node {
 608                 ItemKind::Use(..) => {
 609                     // don't suggest placing a use before the prelude
 610                     // import or other generated ones
 611                     if item.span == DUMMY_SP {
 612                         let mut span = item.span;
 613                         span.hi = span.lo;
 614                         self.span = Some(span);
 615                         self.found_use = true;
 616                         return;
 617                     }
 618                 },
 619                 // don't place use before extern crate
 620                 ItemKind::ExternCrate(_) => {}
 621                 // but place them before the first other item
 622                 _ => if self.span.map_or(true, |span| item.span < span ) {
 623                     let mut span = item.span;
 624                     span.hi = span.lo;
 625                     self.span = Some(span);
 626                 },
 627             }
 628         }
 629         assert!(self.span.is_some(), "a file can't have no items and emit suggestions");
 630     }
 631 }
 632
 633 impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
 634     fn visit_item(&mut self, item: &'tcx Item) {
 635         self.resolve_item(item);
 636     }
 637     fn visit_arm(&mut self, arm: &'tcx Arm) {
 638         self.resolve_arm(arm);
 639     }
 640     fn visit_block(&mut self, block: &'tcx Block) {
 641         self.resolve_block(block);
 642     }
 643     fn visit_expr(&mut self, expr: &'tcx Expr) {
 644         self.resolve_expr(expr, None);
 645     }
 646     fn visit_local(&mut self, local: &'tcx Local) {
 647         self.resolve_local(local);
 648     }
 649     fn visit_ty(&mut self, ty: &'tcx Ty) {
 650         match ty.node {
 651             TyKind::Path(ref qself, ref path) => {
 652                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 653             }
 654             TyKind::ImplicitSelf => {
 655                 let self_ty = keywords::SelfType.ident();
 656                 let def = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, true, ty.span)
 657                               .map_or(Def::Err, |d| d.def());
 658                 self.record_def(ty.id, PathResolution::new(def));
 659             }
 660             TyKind::Array(ref element, ref length) => {
 661                 self.visit_ty(element);
 662                 self.with_constant_rib(|this| {
 663                     this.visit_expr(length);
 664                 });
 665                 return;
 666             }
 667             _ => (),
 668         }
 669         visit::walk_ty(self, ty);
 670     }
 671     fn visit_poly_trait_ref(&mut self,
 672                             tref: &'tcx ast::PolyTraitRef,
 673                             m: &'tcx ast::TraitBoundModifier) {
 674         self.smart_resolve_path(tref.trait_ref.ref_id, None,
 675                                 &tref.trait_ref.path, PathSource::Trait);
 676         visit::walk_poly_trait_ref(self, tref, m);
 677     }
 678     fn visit_variant(&mut self,
 679                      variant: &'tcx ast::Variant,
 680                      generics: &'tcx Generics,
 681                      item_id: ast::NodeId) {
 682         if let Some(ref dis_expr) = variant.node.disr_expr {
 683             // resolve the discriminator expr as a constant
 684             self.with_constant_rib(|this| {
 685                 this.visit_expr(dis_expr);
 686             });
 687         }
 688
 689         // `visit::walk_variant` without the discriminant expression.
 690         self.visit_variant_data(&variant.node.data,
 691                                 variant.node.name,
 692                                 generics,
 693                                 item_id,
 694                                 variant.span);
 695     }
 696     fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
 697         let type_parameters = match foreign_item.node {
 698             ForeignItemKind::Fn(_, ref generics) => {
 699                 HasTypeParameters(generics, ItemRibKind)
 700             }
 701             ForeignItemKind::Static(..) => NoTypeParameters,
 702         };
 703         self.with_type_parameter_rib(type_parameters, |this| {
 704             visit::walk_foreign_item(this, foreign_item);
 705         });
 706     }
 707     fn visit_fn(&mut self,
 708                 function_kind: FnKind<'tcx>,
 709                 declaration: &'tcx FnDecl,
 710                 _: Span,
 711                 node_id: NodeId) {
 712         let rib_kind = match function_kind {
 713             FnKind::ItemFn(_, generics, ..) => {
 714                 self.visit_generics(generics);
 715                 ItemRibKind
 716             }
 717             FnKind::Method(_, sig, _, _) => {
 718                 self.visit_generics(&sig.generics);
 719                 MethodRibKind(!sig.decl.has_self())
 720             }
 721             FnKind::Closure(_) => ClosureRibKind(node_id),
 722         };
 723
 724         // Create a value rib for the function.
 725         self.ribs[ValueNS].push(Rib::new(rib_kind));
 726
 727         // Create a label rib for the function.
 728         self.label_ribs.push(Rib::new(rib_kind));
 729
 730         // Add each argument to the rib.
 731         let mut bindings_list = FxHashMap();
 732         for argument in &declaration.inputs {
 733             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 734
 735             self.visit_ty(&argument.ty);
 736
 737             debug!("(resolving function) recorded argument");
 738         }
 739         visit::walk_fn_ret_ty(self, &declaration.output);
 740
 741         // Resolve the function body.
 742         match function_kind {
 743             FnKind::ItemFn(.., body) |
 744             FnKind::Method(.., body) => {
 745                 self.visit_block(body);
 746             }
 747             FnKind::Closure(body) => {
 748                 self.visit_expr(body);
 749             }
 750         };
 751
 752         debug!("(resolving function) leaving function");
 753
 754         self.label_ribs.pop();
 755         self.ribs[ValueNS].pop();
 756     }
 757     fn visit_generics(&mut self, generics: &'tcx Generics) {
 758         // For type parameter defaults, we have to ban access
 759         // to following type parameters, as the Substs can only
 760         // provide previous type parameters as they're built.
 761         let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
 762         default_ban_rib.bindings.extend(generics.ty_params.iter()
 763             .skip_while(|p| p.default.is_none())
 764             .map(|p| (Ident::with_empty_ctxt(p.ident.name), Def::Err)));
 765
 766         for param in &generics.ty_params {
 767             for bound in &param.bounds {
 768                 self.visit_ty_param_bound(bound);
 769             }
 770
 771             if let Some(ref ty) = param.default {
 772                 self.ribs[TypeNS].push(default_ban_rib);
 773                 self.visit_ty(ty);
 774                 default_ban_rib = self.ribs[TypeNS].pop().unwrap();
 775             }
 776
 777             // Allow all following defaults to refer to this type parameter.
 778             default_ban_rib.bindings.remove(&Ident::with_empty_ctxt(param.ident.name));
 779         }
 780         for lt in &generics.lifetimes { self.visit_lifetime_def(lt); }
 781         for p in &generics.where_clause.predicates { self.visit_where_predicate(p); }
 782     }
 783 }
 784
 785 #[derive(Copy, Clone)]
 786 enum TypeParameters<'a, 'b> {
 787     NoTypeParameters,
 788     HasTypeParameters(// Type parameters.
 789                       &'b Generics,
 790
 791                       // The kind of the rib used for type parameters.
 792                       RibKind<'a>),
 793 }
 794
 795 // The rib kind controls the translation of local
 796 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 797 #[derive(Copy, Clone, Debug)]
 798 enum RibKind<'a> {
 799     // No translation needs to be applied.
 800     NormalRibKind,
 801
 802     // We passed through a closure scope at the given node ID.
 803     // Translate upvars as appropriate.
 804     ClosureRibKind(NodeId /* func id */),
 805
 806     // We passed through an impl or trait and are now in one of its
 807     // methods. Allow references to ty params that impl or trait
 808     // binds. Disallow any other upvars (including other ty params that are
 809     // upvars).
 810     //
 811     // The boolean value represents the fact that this method is static or not.
 812     MethodRibKind(bool),
 813
 814     // We passed through an item scope. Disallow upvars.
 815     ItemRibKind,
 816
 817     // We're in a constant item. Can't refer to dynamic stuff.
 818     ConstantItemRibKind,
 819
 820     // We passed through a module.
 821     ModuleRibKind(Module<'a>),
 822
 823     // We passed through a `macro_rules!` statement
 824     MacroDefinition(DefId),
 825
 826     // All bindings in this rib are type parameters that can't be used
 827     // from the default of a type parameter because they're not declared
 828     // before said type parameter. Also see the `visit_generics` override.
 829     ForwardTyParamBanRibKind,
 830 }
 831
 832 /// One local scope.
 833 #[derive(Debug)]
 834 struct Rib<'a> {
 835     bindings: FxHashMap<Ident, Def>,
 836     kind: RibKind<'a>,
 837 }
 838
 839 impl<'a> Rib<'a> {
 840     fn new(kind: RibKind<'a>) -> Rib<'a> {
 841         Rib {
 842             bindings: FxHashMap(),
 843             kind,
 844         }
 845     }
 846 }
 847
 848 enum LexicalScopeBinding<'a> {
 849     Item(&'a NameBinding<'a>),
 850     Def(Def),
 851 }
 852
 853 impl<'a> LexicalScopeBinding<'a> {
 854     fn item(self) -> Option<&'a NameBinding<'a>> {
 855         match self {
 856             LexicalScopeBinding::Item(binding) => Some(binding),
 857             _ => None,
 858         }
 859     }
 860
 861     fn def(self) -> Def {
 862         match self {
 863             LexicalScopeBinding::Item(binding) => binding.def(),
 864             LexicalScopeBinding::Def(def) => def,
 865         }
 866     }
 867 }
 868
 869 #[derive(Clone)]
 870 enum PathResult<'a> {
 871     Module(Module<'a>),
 872     NonModule(PathResolution),
 873     Indeterminate,
 874     Failed(Span, String, bool /* is the error from the last segment? */),
 875 }
 876
 877 enum ModuleKind {
 878     Block(NodeId),
 879     Def(Def, Name),
 880 }
 881
 882 /// One node in the tree of modules.
 883 pub struct ModuleData<'a> {
 884     parent: Option<Module<'a>>,
 885     kind: ModuleKind,
 886
 887     // The def id of the closest normal module (`mod`) ancestor (including this module).
 888     normal_ancestor_id: DefId,
 889
 890     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
 891     legacy_macro_resolutions: RefCell<Vec<(Mark, Ident, Span, MacroKind)>>,
 892     macro_resolutions: RefCell<Vec<(Box<[Ident]>, Span)>>,
 893
 894     // Macro invocations that can expand into items in this module.
 895     unresolved_invocations: RefCell<FxHashSet<Mark>>,
 896
 897     no_implicit_prelude: bool,
 898
 899     glob_importers: RefCell<Vec<&'a ImportDirective<'a>>>,
 900     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 901
 902     // Used to memoize the traits in this module for faster searches through all traits in scope.
 903     traits: RefCell<Option<Box<[(Ident, &'a NameBinding<'a>)]>>>,
 904
 905     // Whether this module is populated. If not populated, any attempt to
 906     // access the children must be preceded with a
 907     // `populate_module_if_necessary` call.
 908     populated: Cell<bool>,
 909
 910     /// Span of the module itself. Used for error reporting.
 911     span: Span,
 912
 913     expansion: Mark,
 914 }
 915
 916 type Module<'a> = &'a ModuleData<'a>;
 917
 918 impl<'a> ModuleData<'a> {
 919     fn new(parent: Option<Module<'a>>,
 920            kind: ModuleKind,
 921            normal_ancestor_id: DefId,
 922            expansion: Mark,
 923            span: Span) -> Self {
 924         ModuleData {
 925             parent,
 926             kind,
 927             normal_ancestor_id,
 928             resolutions: RefCell::new(FxHashMap()),
 929             legacy_macro_resolutions: RefCell::new(Vec::new()),
 930             macro_resolutions: RefCell::new(Vec::new()),
 931             unresolved_invocations: RefCell::new(FxHashSet()),
 932             no_implicit_prelude: false,
 933             glob_importers: RefCell::new(Vec::new()),
 934             globs: RefCell::new((Vec::new())),
 935             traits: RefCell::new(None),
 936             populated: Cell::new(normal_ancestor_id.is_local()),
 937             span,
 938             expansion,
 939         }
 940     }
 941
 942     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 943         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 944             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 945         }
 946     }
 947
 948     fn for_each_child_stable<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 949         let resolutions = self.resolutions.borrow();
 950         let mut resolutions = resolutions.iter().map(|(&(ident, ns), &resolution)| {
 951                                                     // Pre-compute keys for sorting
 952                                                     (ident.name.as_str(), ns, ident, resolution)
 953                                                 })
 954                                                 .collect::<Vec<_>>();
 955         resolutions.sort_unstable_by_key(|&(str, ns, ..)| (str, ns));
 956         for &(_, ns, ident, resolution) in resolutions.iter() {
 957             resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 958         }
 959     }
 960
 961     fn def(&self) -> Option<Def> {
 962         match self.kind {
 963             ModuleKind::Def(def, _) => Some(def),
 964             _ => None,
 965         }
 966     }
 967
 968     fn def_id(&self) -> Option<DefId> {
 969         self.def().as_ref().map(Def::def_id)
 970     }
 971
 972     // `self` resolves to the first module ancestor that `is_normal`.
 973     fn is_normal(&self) -> bool {
 974         match self.kind {
 975             ModuleKind::Def(Def::Mod(_), _) => true,
 976             _ => false,
 977         }
 978     }
 979
 980     fn is_trait(&self) -> bool {
 981         match self.kind {
 982             ModuleKind::Def(Def::Trait(_), _) => true,
 983             _ => false,
 984         }
 985     }
 986
 987     fn is_local(&self) -> bool {
 988         self.normal_ancestor_id.is_local()
 989     }
 990
 991     fn nearest_item_scope(&'a self) -> Module<'a> {
 992         if self.is_trait() { self.parent.unwrap() } else { self }
 993     }
 994 }
 995
 996 impl<'a> fmt::Debug for ModuleData<'a> {
 997     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 998         write!(f, "{:?}", self.def())
 999     }
1000 }
1001
1002 // Records a possibly-private value, type, or module definition.
1003 #[derive(Clone, Debug)]
1004 pub struct NameBinding<'a> {
1005     kind: NameBindingKind<'a>,
1006     expansion: Mark,
1007     span: Span,
1008     vis: ty::Visibility,
1009 }
1010
1011 pub trait ToNameBinding<'a> {
1012     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
1013 }
1014
1015 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
1016     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
1017         self
1018     }
1019 }
1020
1021 #[derive(Clone, Debug)]
1022 enum NameBindingKind<'a> {
1023     Def(Def),
1024     Module(Module<'a>),
1025     Import {
1026         binding: &'a NameBinding<'a>,
1027         directive: &'a ImportDirective<'a>,
1028         used: Cell<bool>,
1029         legacy_self_import: bool,
1030     },
1031     Ambiguity {
1032         b1: &'a NameBinding<'a>,
1033         b2: &'a NameBinding<'a>,
1034         legacy: bool,
1035     }
1036 }
1037
1038 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
1039
1040 struct UseError<'a> {
1041     err: DiagnosticBuilder<'a>,
1042     /// Attach `use` statements for these candidates
1043     candidates: Vec<ImportSuggestion>,
1044     /// The node id of the module to place the use statements in
1045     node_id: NodeId,
1046     /// Whether the diagnostic should state that it's "better"
1047     better: bool,
1048 }
1049
1050 struct AmbiguityError<'a> {
1051     span: Span,
1052     name: Name,
1053     lexical: bool,
1054     b1: &'a NameBinding<'a>,
1055     b2: &'a NameBinding<'a>,
1056     legacy: bool,
1057 }
1058
1059 impl<'a> NameBinding<'a> {
1060     fn module(&self) -> Option<Module<'a>> {
1061         match self.kind {
1062             NameBindingKind::Module(module) => Some(module),
1063             NameBindingKind::Import { binding, .. } => binding.module(),
1064             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
1065             _ => None,
1066         }
1067     }
1068
1069     fn def(&self) -> Def {
1070         match self.kind {
1071             NameBindingKind::Def(def) => def,
1072             NameBindingKind::Module(module) => module.def().unwrap(),
1073             NameBindingKind::Import { binding, .. } => binding.def(),
1074             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
1075             NameBindingKind::Ambiguity { .. } => Def::Err,
1076         }
1077     }
1078
1079     fn def_ignoring_ambiguity(&self) -> Def {
1080         match self.kind {
1081             NameBindingKind::Import { binding, .. } => binding.def_ignoring_ambiguity(),
1082             NameBindingKind::Ambiguity { b1, .. } => b1.def_ignoring_ambiguity(),
1083             _ => self.def(),
1084         }
1085     }
1086
1087     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
1088         resolver.get_macro(self.def_ignoring_ambiguity())
1089     }
1090
1091     // We sometimes need to treat variants as `pub` for backwards compatibility
1092     fn pseudo_vis(&self) -> ty::Visibility {
1093         if self.is_variant() { ty::Visibility::Public } else { self.vis }
1094     }
1095
1096     fn is_variant(&self) -> bool {
1097         match self.kind {
1098             NameBindingKind::Def(Def::Variant(..)) |
1099             NameBindingKind::Def(Def::VariantCtor(..)) => true,
1100             _ => false,
1101         }
1102     }
1103
1104     fn is_extern_crate(&self) -> bool {
1105         match self.kind {
1106             NameBindingKind::Import {
1107                 directive: &ImportDirective {
1108                     subclass: ImportDirectiveSubclass::ExternCrate, ..
1109                 }, ..
1110             } => true,
1111             _ => false,
1112         }
1113     }
1114
1115     fn is_import(&self) -> bool {
1116         match self.kind {
1117             NameBindingKind::Import { .. } => true,
1118             _ => false,
1119         }
1120     }
1121
1122     fn is_glob_import(&self) -> bool {
1123         match self.kind {
1124             NameBindingKind::Import { directive, .. } => directive.is_glob(),
1125             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
1126             _ => false,
1127         }
1128     }
1129
1130     fn is_importable(&self) -> bool {
1131         match self.def() {
1132             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
1133             _ => true,
1134         }
1135     }
1136
1137     fn is_macro_def(&self) -> bool {
1138         match self.kind {
1139             NameBindingKind::Def(Def::Macro(..)) => true,
1140             _ => false,
1141         }
1142     }
1143
1144     fn descr(&self) -> &'static str {
1145         if self.is_extern_crate() { "extern crate" } else { self.def().kind_name() }
1146     }
1147 }
1148
1149 /// Interns the names of the primitive types.
1150 struct PrimitiveTypeTable {
1151     primitive_types: FxHashMap<Name, PrimTy>,
1152 }
1153
1154 impl PrimitiveTypeTable {
1155     fn new() -> PrimitiveTypeTable {
1156         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1157
1158         table.intern("bool", TyBool);
1159         table.intern("char", TyChar);
1160         table.intern("f32", TyFloat(FloatTy::F32));
1161         table.intern("f64", TyFloat(FloatTy::F64));
1162         table.intern("isize", TyInt(IntTy::Is));
1163         table.intern("i8", TyInt(IntTy::I8));
1164         table.intern("i16", TyInt(IntTy::I16));
1165         table.intern("i32", TyInt(IntTy::I32));
1166         table.intern("i64", TyInt(IntTy::I64));
1167         table.intern("i128", TyInt(IntTy::I128));
1168         table.intern("str", TyStr);
1169         table.intern("usize", TyUint(UintTy::Us));
1170         table.intern("u8", TyUint(UintTy::U8));
1171         table.intern("u16", TyUint(UintTy::U16));
1172         table.intern("u32", TyUint(UintTy::U32));
1173         table.intern("u64", TyUint(UintTy::U64));
1174         table.intern("u128", TyUint(UintTy::U128));
1175         table
1176     }
1177
1178     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1179         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1180     }
1181 }
1182
1183 /// The main resolver class.
1184 pub struct Resolver<'a> {
1185     session: &'a Session,
1186
1187     pub definitions: Definitions,
1188
1189     graph_root: Module<'a>,
1190
1191     prelude: Option<Module<'a>>,
1192
1193     // n.b. This is used only for better diagnostics, not name resolution itself.
1194     has_self: FxHashSet<DefId>,
1195
1196     // Names of fields of an item `DefId` accessible with dot syntax.
1197     // Used for hints during error reporting.
1198     field_names: FxHashMap<DefId, Vec<Name>>,
1199
1200     // All imports known to succeed or fail.
1201     determined_imports: Vec<&'a ImportDirective<'a>>,
1202
1203     // All non-determined imports.
1204     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1205
1206     // The module that represents the current item scope.
1207     current_module: Module<'a>,
1208
1209     // The current set of local scopes for types and values.
1210     // FIXME #4948: Reuse ribs to avoid allocation.
1211     ribs: PerNS<Vec<Rib<'a>>>,
1212
1213     // The current set of local scopes, for labels.
1214     label_ribs: Vec<Rib<'a>>,
1215
1216     // The trait that the current context can refer to.
1217     current_trait_ref: Option<(Module<'a>, TraitRef)>,
1218
1219     // The current self type if inside an impl (used for better errors).
1220     current_self_type: Option<Ty>,
1221
1222     // The idents for the primitive types.
1223     primitive_type_table: PrimitiveTypeTable,
1224
1225     def_map: DefMap,
1226     pub freevars: FreevarMap,
1227     freevars_seen: NodeMap<NodeMap<usize>>,
1228     pub export_map: ExportMap,
1229     pub trait_map: TraitMap,
1230
1231     // A map from nodes to anonymous modules.
1232     // Anonymous modules are pseudo-modules that are implicitly created around items
1233     // contained within blocks.
1234     //
1235     // For example, if we have this:
1236     //
1237     //  fn f() {
1238     //      fn g() {
1239     //          ...
1240     //      }
1241     //  }
1242     //
1243     // There will be an anonymous module created around `g` with the ID of the
1244     // entry block for `f`.
1245     block_map: NodeMap<Module<'a>>,
1246     module_map: FxHashMap<DefId, Module<'a>>,
1247     extern_module_map: FxHashMap<(DefId, bool /* MacrosOnly? */), Module<'a>>,
1248
1249     pub make_glob_map: bool,
1250     /// Maps imports to the names of items actually imported (this actually maps
1251     /// all imports, but only glob imports are actually interesting).
1252     pub glob_map: GlobMap,
1253
1254     used_imports: FxHashSet<(NodeId, Namespace)>,
1255     pub maybe_unused_trait_imports: NodeSet,
1256
1257     /// privacy errors are delayed until the end in order to deduplicate them
1258     privacy_errors: Vec<PrivacyError<'a>>,
1259     /// ambiguity errors are delayed for deduplication
1260     ambiguity_errors: Vec<AmbiguityError<'a>>,
1261     /// `use` injections are delayed for better placement and deduplication
1262     use_injections: Vec<UseError<'a>>,
1263
1264     gated_errors: FxHashSet<Span>,
1265     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1266
1267     arenas: &'a ResolverArenas<'a>,
1268     dummy_binding: &'a NameBinding<'a>,
1269     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1270
1271     crate_loader: &'a mut CrateLoader,
1272     macro_names: FxHashSet<Ident>,
1273     global_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1274     lexical_macro_resolutions: Vec<(Ident, &'a Cell<LegacyScope<'a>>)>,
1275     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1276     macro_defs: FxHashMap<Mark, DefId>,
1277     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
1278     macro_exports: Vec<Export>,
1279     pub whitelisted_legacy_custom_derives: Vec<Name>,
1280     pub found_unresolved_macro: bool,
1281
1282     // List of crate local macros that we need to warn about as being unused.
1283     // Right now this only includes macro_rules! macros, and macros 2.0.
1284     unused_macros: FxHashSet<DefId>,
1285
1286     // Maps the `Mark` of an expansion to its containing module or block.
1287     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1288
1289     // Avoid duplicated errors for "name already defined".
1290     name_already_seen: FxHashMap<Name, Span>,
1291
1292     // If `#![feature(proc_macro)]` is set
1293     proc_macro_enabled: bool,
1294
1295     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1296     warned_proc_macros: FxHashSet<Name>,
1297
1298     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1299
1300     // This table maps struct IDs into struct constructor IDs,
1301     // it's not used during normal resolution, only for better error reporting.
1302     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1303
1304     // Only used for better errors on `fn(): fn()`
1305     current_type_ascription: Vec<Span>,
1306 }
1307
1308 pub struct ResolverArenas<'a> {
1309     modules: arena::TypedArena<ModuleData<'a>>,
1310     local_modules: RefCell<Vec<Module<'a>>>,
1311     name_bindings: arena::TypedArena<NameBinding<'a>>,
1312     import_directives: arena::TypedArena<ImportDirective<'a>>,
1313     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1314     invocation_data: arena::TypedArena<InvocationData<'a>>,
1315     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1316 }
1317
1318 impl<'a> ResolverArenas<'a> {
1319     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1320         let module = self.modules.alloc(module);
1321         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1322             self.local_modules.borrow_mut().push(module);
1323         }
1324         module
1325     }
1326     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1327         self.local_modules.borrow()
1328     }
1329     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1330         self.name_bindings.alloc(name_binding)
1331     }
1332     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1333                               -> &'a ImportDirective {
1334         self.import_directives.alloc(import_directive)
1335     }
1336     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1337         self.name_resolutions.alloc(Default::default())
1338     }
1339     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1340                              -> &'a InvocationData<'a> {
1341         self.invocation_data.alloc(expansion_data)
1342     }
1343     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1344         self.legacy_bindings.alloc(binding)
1345     }
1346 }
1347
1348 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1349     fn parent(self, id: DefId) -> Option<DefId> {
1350         match id.krate {
1351             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1352             _ => self.session.cstore.def_key(id).parent,
1353         }.map(|index| DefId { index: index, ..id })
1354     }
1355 }
1356
1357 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1358     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1359         let namespace = if is_value { ValueNS } else { TypeNS };
1360         let hir::Path { ref segments, span, ref mut def } = *path;
1361         let path: Vec<SpannedIdent> = segments.iter()
1362             .map(|seg| respan(span, Ident::with_empty_ctxt(seg.name)))
1363             .collect();
1364         match self.resolve_path(&path, Some(namespace), true, span) {
1365             PathResult::Module(module) => *def = module.def().unwrap(),
1366             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 =>
1367                 *def = path_res.base_def(),
1368             PathResult::NonModule(..) => match self.resolve_path(&path, None, true, span) {
1369                 PathResult::Failed(span, msg, _) => {
1370                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1371                 }
1372                 _ => {}
1373             },
1374             PathResult::Indeterminate => unreachable!(),
1375             PathResult::Failed(span, msg, _) => {
1376                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1377             }
1378         }
1379     }
1380
1381     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1382         self.def_map.get(&id).cloned()
1383     }
1384
1385     fn definitions(&mut self) -> &mut Definitions {
1386         &mut self.definitions
1387     }
1388 }
1389
1390 impl<'a> Resolver<'a> {
1391     pub fn new(session: &'a Session,
1392                krate: &Crate,
1393                crate_name: &str,
1394                make_glob_map: MakeGlobMap,
1395                crate_loader: &'a mut CrateLoader,
1396                arenas: &'a ResolverArenas<'a>)
1397                -> Resolver<'a> {
1398         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1399         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1400         let graph_root = arenas.alloc_module(ModuleData {
1401             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1402             ..ModuleData::new(None, root_module_kind, root_def_id, Mark::root(), krate.span)
1403         });
1404         let mut module_map = FxHashMap();
1405         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1406
1407         let mut definitions = Definitions::new();
1408         DefCollector::new(&mut definitions, Mark::root())
1409             .collect_root(crate_name, &session.local_crate_disambiguator().as_str());
1410
1411         let mut invocations = FxHashMap();
1412         invocations.insert(Mark::root(),
1413                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1414
1415         let features = session.features.borrow();
1416
1417         let mut macro_defs = FxHashMap();
1418         macro_defs.insert(Mark::root(), root_def_id);
1419
1420         Resolver {
1421             session,
1422
1423             definitions,
1424
1425             // The outermost module has def ID 0; this is not reflected in the
1426             // AST.
1427             graph_root,
1428             prelude: None,
1429
1430             has_self: FxHashSet(),
1431             field_names: FxHashMap(),
1432
1433             determined_imports: Vec::new(),
1434             indeterminate_imports: Vec::new(),
1435
1436             current_module: graph_root,
1437             ribs: PerNS {
1438                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1439                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1440                 macro_ns: Some(vec![Rib::new(ModuleRibKind(graph_root))]),
1441             },
1442             label_ribs: Vec::new(),
1443
1444             current_trait_ref: None,
1445             current_self_type: None,
1446
1447             primitive_type_table: PrimitiveTypeTable::new(),
1448
1449             def_map: NodeMap(),
1450             freevars: NodeMap(),
1451             freevars_seen: NodeMap(),
1452             export_map: NodeMap(),
1453             trait_map: NodeMap(),
1454             module_map,
1455             block_map: NodeMap(),
1456             extern_module_map: FxHashMap(),
1457
1458             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1459             glob_map: NodeMap(),
1460
1461             used_imports: FxHashSet(),
1462             maybe_unused_trait_imports: NodeSet(),
1463
1464             privacy_errors: Vec::new(),
1465             ambiguity_errors: Vec::new(),
1466             use_injections: Vec::new(),
1467             gated_errors: FxHashSet(),
1468             disallowed_shadowing: Vec::new(),
1469
1470             arenas,
1471             dummy_binding: arenas.alloc_name_binding(NameBinding {
1472                 kind: NameBindingKind::Def(Def::Err),
1473                 expansion: Mark::root(),
1474                 span: DUMMY_SP,
1475                 vis: ty::Visibility::Public,
1476             }),
1477
1478             // The `proc_macro` and `decl_macro` features imply `use_extern_macros`
1479             use_extern_macros:
1480                 features.use_extern_macros || features.proc_macro || features.decl_macro,
1481
1482             crate_loader,
1483             macro_names: FxHashSet(),
1484             global_macros: FxHashMap(),
1485             lexical_macro_resolutions: Vec::new(),
1486             macro_map: FxHashMap(),
1487             macro_exports: Vec::new(),
1488             invocations,
1489             macro_defs,
1490             local_macro_def_scopes: FxHashMap(),
1491             name_already_seen: FxHashMap(),
1492             whitelisted_legacy_custom_derives: Vec::new(),
1493             proc_macro_enabled: features.proc_macro,
1494             warned_proc_macros: FxHashSet(),
1495             potentially_unused_imports: Vec::new(),
1496             struct_constructors: DefIdMap(),
1497             found_unresolved_macro: false,
1498             unused_macros: FxHashSet(),
1499             current_type_ascription: Vec::new(),
1500         }
1501     }
1502
1503     pub fn arenas() -> ResolverArenas<'a> {
1504         ResolverArenas {
1505             modules: arena::TypedArena::new(),
1506             local_modules: RefCell::new(Vec::new()),
1507             name_bindings: arena::TypedArena::new(),
1508             import_directives: arena::TypedArena::new(),
1509             name_resolutions: arena::TypedArena::new(),
1510             invocation_data: arena::TypedArena::new(),
1511             legacy_bindings: arena::TypedArena::new(),
1512         }
1513     }
1514
1515     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1516         PerNS {
1517             type_ns: f(self, TypeNS),
1518             value_ns: f(self, ValueNS),
1519             macro_ns: match self.use_extern_macros {
1520                 true => Some(f(self, MacroNS)),
1521                 false => None,
1522             },
1523         }
1524     }
1525
1526     /// Entry point to crate resolution.
1527     pub fn resolve_crate(&mut self, krate: &Crate) {
1528         ImportResolver { resolver: self }.finalize_imports();
1529         self.current_module = self.graph_root;
1530         self.finalize_current_module_macro_resolutions();
1531
1532         visit::walk_crate(self, krate);
1533
1534         check_unused::check_crate(self, krate);
1535         self.report_errors(krate);
1536         self.crate_loader.postprocess(krate);
1537     }
1538
1539     fn new_module(
1540         &self,
1541         parent: Module<'a>,
1542         kind: ModuleKind,
1543         normal_ancestor_id: DefId,
1544         expansion: Mark,
1545         span: Span,
1546     ) -> Module<'a> {
1547         let module = ModuleData::new(Some(parent), kind, normal_ancestor_id, expansion, span);
1548         self.arenas.alloc_module(module)
1549     }
1550
1551     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1552                   -> bool /* true if an error was reported */ {
1553         match binding.kind {
1554             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1555                     if !used.get() => {
1556                 used.set(true);
1557                 directive.used.set(true);
1558                 if legacy_self_import {
1559                     self.warn_legacy_self_import(directive);
1560                     return false;
1561                 }
1562                 self.used_imports.insert((directive.id, ns));
1563                 self.add_to_glob_map(directive.id, ident);
1564                 self.record_use(ident, ns, binding, span)
1565             }
1566             NameBindingKind::Import { .. } => false,
1567             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1568                 self.ambiguity_errors.push(AmbiguityError {
1569                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy,
1570                 });
1571                 if legacy {
1572                     self.record_use(ident, ns, b1, span);
1573                 }
1574                 !legacy
1575             }
1576             _ => false
1577         }
1578     }
1579
1580     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1581         if self.make_glob_map {
1582             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1583         }
1584     }
1585
1586     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1587     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1588     /// `ident` in the first scope that defines it (or None if no scopes define it).
1589     ///
1590     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1591     /// the items are defined in the block. For example,
1592     /// ```rust
1593     /// fn f() {
1594     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1595     ///    let g = || {};
1596     ///    fn g() {}
1597     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1598     /// }
1599     /// ```
1600     ///
1601     /// Invariant: This must only be called during main resolution, not during
1602     /// import resolution.
1603     fn resolve_ident_in_lexical_scope(&mut self,
1604                                       mut ident: Ident,
1605                                       ns: Namespace,
1606                                       record_used: bool,
1607                                       path_span: Span)
1608                                       -> Option<LexicalScopeBinding<'a>> {
1609         if ns == TypeNS {
1610             ident.ctxt = if ident.name == keywords::SelfType.name() {
1611                 SyntaxContext::empty() // FIXME(jseyfried) improve `Self` hygiene
1612             } else {
1613                 ident.ctxt.modern()
1614             }
1615         }
1616
1617         // Walk backwards up the ribs in scope.
1618         let mut module = self.graph_root;
1619         for i in (0 .. self.ribs[ns].len()).rev() {
1620             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1621                 // The ident resolves to a type parameter or local variable.
1622                 return Some(LexicalScopeBinding::Def(
1623                     self.adjust_local_def(ns, i, def, record_used, path_span)
1624                 ));
1625             }
1626
1627             module = match self.ribs[ns][i].kind {
1628                 ModuleRibKind(module) => module,
1629                 MacroDefinition(def) if def == self.macro_defs[&ident.ctxt.outer()] => {
1630                     // If an invocation of this macro created `ident`, give up on `ident`
1631                     // and switch to `ident`'s source from the macro definition.
1632                     ident.ctxt.remove_mark();
1633                     continue
1634                 }
1635                 _ => continue,
1636             };
1637
1638             let item = self.resolve_ident_in_module_unadjusted(
1639                 module, ident, ns, false, record_used, path_span,
1640             );
1641             if let Ok(binding) = item {
1642                 // The ident resolves to an item.
1643                 return Some(LexicalScopeBinding::Item(binding));
1644             }
1645
1646             match module.kind {
1647                 ModuleKind::Block(..) => {}, // We can see through blocks
1648                 _ => break,
1649             }
1650         }
1651
1652         ident.ctxt = ident.ctxt.modern();
1653         loop {
1654             module = unwrap_or!(self.hygienic_lexical_parent(module, &mut ident.ctxt), break);
1655             let orig_current_module = self.current_module;
1656             self.current_module = module; // Lexical resolutions can never be a privacy error.
1657             let result = self.resolve_ident_in_module_unadjusted(
1658                 module, ident, ns, false, record_used, path_span,
1659             );
1660             self.current_module = orig_current_module;
1661
1662             match result {
1663                 Ok(binding) => return Some(LexicalScopeBinding::Item(binding)),
1664                 Err(Undetermined) => return None,
1665                 Err(Determined) => {}
1666             }
1667         }
1668
1669         match self.prelude {
1670             Some(prelude) if !module.no_implicit_prelude => {
1671                 self.resolve_ident_in_module_unadjusted(prelude, ident, ns, false, false, path_span)
1672                     .ok().map(LexicalScopeBinding::Item)
1673             }
1674             _ => None,
1675         }
1676     }
1677
1678     fn hygienic_lexical_parent(&mut self, mut module: Module<'a>, ctxt: &mut SyntaxContext)
1679                                -> Option<Module<'a>> {
1680         if !module.expansion.is_descendant_of(ctxt.outer()) {
1681             return Some(self.macro_def_scope(ctxt.remove_mark()));
1682         }
1683
1684         if let ModuleKind::Block(..) = module.kind {
1685             return Some(module.parent.unwrap());
1686         }
1687
1688         let mut module_expansion = module.expansion.modern(); // for backward compatibility
1689         while let Some(parent) = module.parent {
1690             let parent_expansion = parent.expansion.modern();
1691             if module_expansion.is_descendant_of(parent_expansion) &&
1692                parent_expansion != module_expansion {
1693                 return if parent_expansion.is_descendant_of(ctxt.outer()) {
1694                     Some(parent)
1695                 } else {
1696                     None
1697                 };
1698             }
1699             module = parent;
1700             module_expansion = parent_expansion;
1701         }
1702
1703         None
1704     }
1705
1706     fn resolve_ident_in_module(&mut self,
1707                                module: Module<'a>,
1708                                mut ident: Ident,
1709                                ns: Namespace,
1710                                ignore_unresolved_invocations: bool,
1711                                record_used: bool,
1712                                span: Span)
1713                                -> Result<&'a NameBinding<'a>, Determinacy> {
1714         ident.ctxt = ident.ctxt.modern();
1715         let orig_current_module = self.current_module;
1716         if let Some(def) = ident.ctxt.adjust(module.expansion) {
1717             self.current_module = self.macro_def_scope(def);
1718         }
1719         let result = self.resolve_ident_in_module_unadjusted(
1720             module, ident, ns, ignore_unresolved_invocations, record_used, span,
1721         );
1722         self.current_module = orig_current_module;
1723         result
1724     }
1725
1726     fn resolve_crate_root(&mut self, mut ctxt: SyntaxContext) -> Module<'a> {
1727         let module = match ctxt.adjust(Mark::root()) {
1728             Some(def) => self.macro_def_scope(def),
1729             None => return self.graph_root,
1730         };
1731         self.get_module(DefId { index: CRATE_DEF_INDEX, ..module.normal_ancestor_id })
1732     }
1733
1734     fn resolve_self(&mut self, ctxt: &mut SyntaxContext, module: Module<'a>) -> Module<'a> {
1735         let mut module = self.get_module(module.normal_ancestor_id);
1736         while module.span.ctxt.modern() != *ctxt {
1737             let parent = module.parent.unwrap_or_else(|| self.macro_def_scope(ctxt.remove_mark()));
1738             module = self.get_module(parent.normal_ancestor_id);
1739         }
1740         module
1741     }
1742
1743     // AST resolution
1744     //
1745     // We maintain a list of value ribs and type ribs.
1746     //
1747     // Simultaneously, we keep track of the current position in the module
1748     // graph in the `current_module` pointer. When we go to resolve a name in
1749     // the value or type namespaces, we first look through all the ribs and
1750     // then query the module graph. When we resolve a name in the module
1751     // namespace, we can skip all the ribs (since nested modules are not
1752     // allowed within blocks in Rust) and jump straight to the current module
1753     // graph node.
1754     //
1755     // Named implementations are handled separately. When we find a method
1756     // call, we consult the module node to find all of the implementations in
1757     // scope. This information is lazily cached in the module node. We then
1758     // generate a fake "implementation scope" containing all the
1759     // implementations thus found, for compatibility with old resolve pass.
1760
1761     fn with_scope<F>(&mut self, id: NodeId, f: F)
1762         where F: FnOnce(&mut Resolver)
1763     {
1764         let id = self.definitions.local_def_id(id);
1765         let module = self.module_map.get(&id).cloned(); // clones a reference
1766         if let Some(module) = module {
1767             // Move down in the graph.
1768             let orig_module = replace(&mut self.current_module, module);
1769             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1770             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1771
1772             self.finalize_current_module_macro_resolutions();
1773             f(self);
1774
1775             self.current_module = orig_module;
1776             self.ribs[ValueNS].pop();
1777             self.ribs[TypeNS].pop();
1778         } else {
1779             f(self);
1780         }
1781     }
1782
1783     /// Searches the current set of local scopes for labels.
1784     /// Stops after meeting a closure.
1785     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1786         for rib in self.label_ribs.iter().rev() {
1787             match rib.kind {
1788                 NormalRibKind => {}
1789                 // If an invocation of this macro created `ident`, give up on `ident`
1790                 // and switch to `ident`'s source from the macro definition.
1791                 MacroDefinition(def) => {
1792                     if def == self.macro_defs[&ident.ctxt.outer()] {
1793                         ident.ctxt.remove_mark();
1794                     }
1795                 }
1796                 _ => {
1797                     // Do not resolve labels across function boundary
1798                     return None;
1799                 }
1800             }
1801             let result = rib.bindings.get(&ident).cloned();
1802             if result.is_some() {
1803                 return result;
1804             }
1805         }
1806         None
1807     }
1808
1809     fn resolve_item(&mut self, item: &Item) {
1810         let name = item.ident.name;
1811
1812         debug!("(resolving item) resolving {}", name);
1813
1814         self.check_proc_macro_attrs(&item.attrs);
1815
1816         match item.node {
1817             ItemKind::Enum(_, ref generics) |
1818             ItemKind::Ty(_, ref generics) |
1819             ItemKind::Struct(_, ref generics) |
1820             ItemKind::Union(_, ref generics) |
1821             ItemKind::Fn(.., ref generics, _) => {
1822                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1823                                              |this| visit::walk_item(this, item));
1824             }
1825
1826             ItemKind::DefaultImpl(_, ref trait_ref) => {
1827                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1828                     // Resolve type arguments in trait path
1829                     visit::walk_trait_ref(this, trait_ref);
1830                 });
1831             }
1832             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1833                 self.resolve_implementation(generics,
1834                                             opt_trait_ref,
1835                                             &self_type,
1836                                             item.id,
1837                                             impl_items),
1838
1839             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1840                 // Create a new rib for the trait-wide type parameters.
1841                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1842                     let local_def_id = this.definitions.local_def_id(item.id);
1843                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1844                         this.visit_generics(generics);
1845                         walk_list!(this, visit_ty_param_bound, bounds);
1846
1847                         for trait_item in trait_items {
1848                             this.check_proc_macro_attrs(&trait_item.attrs);
1849
1850                             match trait_item.node {
1851                                 TraitItemKind::Const(ref ty, ref default) => {
1852                                     this.visit_ty(ty);
1853
1854                                     // Only impose the restrictions of
1855                                     // ConstRibKind for an actual constant
1856                                     // expression in a provided default.
1857                                     if let Some(ref expr) = *default{
1858                                         this.with_constant_rib(|this| {
1859                                             this.visit_expr(expr);
1860                                         });
1861                                     }
1862                                 }
1863                                 TraitItemKind::Method(ref sig, _) => {
1864                                     let type_parameters =
1865                                         HasTypeParameters(&sig.generics,
1866                                                           MethodRibKind(!sig.decl.has_self()));
1867                                     this.with_type_parameter_rib(type_parameters, |this| {
1868                                         visit::walk_trait_item(this, trait_item)
1869                                     });
1870                                 }
1871                                 TraitItemKind::Type(..) => {
1872                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1873                                         visit::walk_trait_item(this, trait_item)
1874                                     });
1875                                 }
1876                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1877                             };
1878                         }
1879                     });
1880                 });
1881             }
1882
1883             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1884                 self.with_scope(item.id, |this| {
1885                     visit::walk_item(this, item);
1886                 });
1887             }
1888
1889             ItemKind::Static(ref ty, _, ref expr) |
1890             ItemKind::Const(ref ty, ref expr) => {
1891                 self.with_item_rib(|this| {
1892                     this.visit_ty(ty);
1893                     this.with_constant_rib(|this| {
1894                         this.visit_expr(expr);
1895                     });
1896                 });
1897             }
1898
1899             ItemKind::Use(ref view_path) => {
1900                 match view_path.node {
1901                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1902                         // Resolve prefix of an import with empty braces (issue #28388).
1903                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1904                     }
1905                     _ => {}
1906                 }
1907             }
1908
1909             ItemKind::ExternCrate(_) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(_)=> {
1910                 // do nothing, these are just around to be encoded
1911             }
1912
1913             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1914         }
1915     }
1916
1917     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1918         where F: FnOnce(&mut Resolver)
1919     {
1920         match type_parameters {
1921             HasTypeParameters(generics, rib_kind) => {
1922                 let mut function_type_rib = Rib::new(rib_kind);
1923                 let mut seen_bindings = FxHashMap();
1924                 for type_parameter in &generics.ty_params {
1925                     let ident = type_parameter.ident.modern();
1926                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1927
1928                     if seen_bindings.contains_key(&ident) {
1929                         let span = seen_bindings.get(&ident).unwrap();
1930                         let err =
1931                             ResolutionError::NameAlreadyUsedInTypeParameterList(ident.name, span);
1932                         resolve_error(self, type_parameter.span, err);
1933                     }
1934                     seen_bindings.entry(ident).or_insert(type_parameter.span);
1935
1936                     // plain insert (no renaming)
1937                     let def_id = self.definitions.local_def_id(type_parameter.id);
1938                     let def = Def::TyParam(def_id);
1939                     function_type_rib.bindings.insert(ident, def);
1940                     self.record_def(type_parameter.id, PathResolution::new(def));
1941                 }
1942                 self.ribs[TypeNS].push(function_type_rib);
1943             }
1944
1945             NoTypeParameters => {
1946                 // Nothing to do.
1947             }
1948         }
1949
1950         f(self);
1951
1952         if let HasTypeParameters(..) = type_parameters {
1953             self.ribs[TypeNS].pop();
1954         }
1955     }
1956
1957     fn with_label_rib<F>(&mut self, f: F)
1958         where F: FnOnce(&mut Resolver)
1959     {
1960         self.label_ribs.push(Rib::new(NormalRibKind));
1961         f(self);
1962         self.label_ribs.pop();
1963     }
1964
1965     fn with_item_rib<F>(&mut self, f: F)
1966         where F: FnOnce(&mut Resolver)
1967     {
1968         self.ribs[ValueNS].push(Rib::new(ItemRibKind));
1969         self.ribs[TypeNS].push(Rib::new(ItemRibKind));
1970         f(self);
1971         self.ribs[TypeNS].pop();
1972         self.ribs[ValueNS].pop();
1973     }
1974
1975     fn with_constant_rib<F>(&mut self, f: F)
1976         where F: FnOnce(&mut Resolver)
1977     {
1978         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1979         f(self);
1980         self.ribs[ValueNS].pop();
1981     }
1982
1983     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1984         where F: FnOnce(&mut Resolver) -> T
1985     {
1986         // Handle nested impls (inside fn bodies)
1987         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1988         let result = f(self);
1989         self.current_self_type = previous_value;
1990         result
1991     }
1992
1993     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1994         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1995     {
1996         let mut new_val = None;
1997         let mut new_id = None;
1998         if let Some(trait_ref) = opt_trait_ref {
1999             let path: Vec<_> = trait_ref.path.segments.iter()
2000                 .map(|seg| respan(seg.span, seg.identifier))
2001                 .collect();
2002             let def = self.smart_resolve_path_fragment(trait_ref.ref_id,
2003                                                        None,
2004                                                        &path,
2005                                                        trait_ref.path.span,
2006                                                        trait_ref.path.segments.last().unwrap().span,
2007                                                        PathSource::Trait)
2008                 .base_def();
2009             if def != Def::Err {
2010                 new_id = Some(def.def_id());
2011                 let span = trait_ref.path.span;
2012                 if let PathResult::Module(module) = self.resolve_path(&path, None, false, span) {
2013                     new_val = Some((module, trait_ref.clone()));
2014                 }
2015             }
2016         }
2017         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
2018         let result = f(self, new_id);
2019         self.current_trait_ref = original_trait_ref;
2020         result
2021     }
2022
2023     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
2024         where F: FnOnce(&mut Resolver)
2025     {
2026         let mut self_type_rib = Rib::new(NormalRibKind);
2027
2028         // plain insert (no renaming, types are not currently hygienic....)
2029         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
2030         self.ribs[TypeNS].push(self_type_rib);
2031         f(self);
2032         self.ribs[TypeNS].pop();
2033     }
2034
2035     fn resolve_implementation(&mut self,
2036                               generics: &Generics,
2037                               opt_trait_reference: &Option<TraitRef>,
2038                               self_type: &Ty,
2039                               item_id: NodeId,
2040                               impl_items: &[ImplItem]) {
2041         // If applicable, create a rib for the type parameters.
2042         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
2043             // Dummy self type for better errors if `Self` is used in the trait path.
2044             this.with_self_rib(Def::SelfTy(None, None), |this| {
2045                 // Resolve the trait reference, if necessary.
2046                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
2047                     let item_def_id = this.definitions.local_def_id(item_id);
2048                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
2049                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
2050                             // Resolve type arguments in trait path
2051                             visit::walk_trait_ref(this, trait_ref);
2052                         }
2053                         // Resolve the self type.
2054                         this.visit_ty(self_type);
2055                         // Resolve the type parameters.
2056                         this.visit_generics(generics);
2057                         this.with_current_self_type(self_type, |this| {
2058                             for impl_item in impl_items {
2059                                 this.check_proc_macro_attrs(&impl_item.attrs);
2060                                 this.resolve_visibility(&impl_item.vis);
2061                                 match impl_item.node {
2062                                     ImplItemKind::Const(..) => {
2063                                         // If this is a trait impl, ensure the const
2064                                         // exists in trait
2065                                         this.check_trait_item(impl_item.ident,
2066                                                             ValueNS,
2067                                                             impl_item.span,
2068                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
2069                                         visit::walk_impl_item(this, impl_item);
2070                                     }
2071                                     ImplItemKind::Method(ref sig, _) => {
2072                                         // If this is a trait impl, ensure the method
2073                                         // exists in trait
2074                                         this.check_trait_item(impl_item.ident,
2075                                                             ValueNS,
2076                                                             impl_item.span,
2077                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
2078
2079                                         // We also need a new scope for the method-
2080                                         // specific type parameters.
2081                                         let type_parameters =
2082                                             HasTypeParameters(&sig.generics,
2083                                                             MethodRibKind(!sig.decl.has_self()));
2084                                         this.with_type_parameter_rib(type_parameters, |this| {
2085                                             visit::walk_impl_item(this, impl_item);
2086                                         });
2087                                     }
2088                                     ImplItemKind::Type(ref ty) => {
2089                                         // If this is a trait impl, ensure the type
2090                                         // exists in trait
2091                                         this.check_trait_item(impl_item.ident,
2092                                                             TypeNS,
2093                                                             impl_item.span,
2094                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
2095
2096                                         this.visit_ty(ty);
2097                                     }
2098                                     ImplItemKind::Macro(_) =>
2099                                         panic!("unexpanded macro in resolve!"),
2100                                 }
2101                             }
2102                         });
2103                     });
2104                 });
2105             });
2106         });
2107     }
2108
2109     fn check_trait_item<F>(&mut self, ident: Ident, ns: Namespace, span: Span, err: F)
2110         where F: FnOnce(Name, &str) -> ResolutionError
2111     {
2112         // If there is a TraitRef in scope for an impl, then the method must be in the
2113         // trait.
2114         if let Some((module, _)) = self.current_trait_ref {
2115             if self.resolve_ident_in_module(module, ident, ns, false, false, span).is_err() {
2116                 let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2117                 resolve_error(self, span, err(ident.name, &path_names_to_string(path)));
2118             }
2119         }
2120     }
2121
2122     fn resolve_local(&mut self, local: &Local) {
2123         // Resolve the type.
2124         walk_list!(self, visit_ty, &local.ty);
2125
2126         // Resolve the initializer.
2127         walk_list!(self, visit_expr, &local.init);
2128
2129         // Resolve the pattern.
2130         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
2131     }
2132
2133     // build a map from pattern identifiers to binding-info's.
2134     // this is done hygienically. This could arise for a macro
2135     // that expands into an or-pattern where one 'x' was from the
2136     // user and one 'x' came from the macro.
2137     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2138         let mut binding_map = FxHashMap();
2139
2140         pat.walk(&mut |pat| {
2141             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
2142                 if sub_pat.is_some() || match self.def_map.get(&pat.id).map(|res| res.base_def()) {
2143                     Some(Def::Local(..)) => true,
2144                     _ => false,
2145                 } {
2146                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
2147                     binding_map.insert(ident.node, binding_info);
2148                 }
2149             }
2150             true
2151         });
2152
2153         binding_map
2154     }
2155
2156     // check that all of the arms in an or-pattern have exactly the
2157     // same set of bindings, with the same binding modes for each.
2158     fn check_consistent_bindings(&mut self, arm: &Arm) {
2159         if arm.pats.is_empty() {
2160             return;
2161         }
2162
2163         let mut missing_vars = FxHashMap();
2164         let mut inconsistent_vars = FxHashMap();
2165         for (i, p) in arm.pats.iter().enumerate() {
2166             let map_i = self.binding_mode_map(&p);
2167
2168             for (j, q) in arm.pats.iter().enumerate() {
2169                 if i == j {
2170                     continue;
2171                 }
2172
2173                 let map_j = self.binding_mode_map(&q);
2174                 for (&key, &binding_i) in &map_i {
2175                     if map_j.len() == 0 {                   // Account for missing bindings when
2176                         let binding_error = missing_vars    // map_j has none.
2177                             .entry(key.name)
2178                             .or_insert(BindingError {
2179                                 name: key.name,
2180                                 origin: BTreeSet::new(),
2181                                 target: BTreeSet::new(),
2182                             });
2183                         binding_error.origin.insert(binding_i.span);
2184                         binding_error.target.insert(q.span);
2185                     }
2186                     for (&key_j, &binding_j) in &map_j {
2187                         match map_i.get(&key_j) {
2188                             None => {  // missing binding
2189                                 let binding_error = missing_vars
2190                                     .entry(key_j.name)
2191                                     .or_insert(BindingError {
2192                                         name: key_j.name,
2193                                         origin: BTreeSet::new(),
2194                                         target: BTreeSet::new(),
2195                                     });
2196                                 binding_error.origin.insert(binding_j.span);
2197                                 binding_error.target.insert(p.span);
2198                             }
2199                             Some(binding_i) => {  // check consistent binding
2200                                 if binding_i.binding_mode != binding_j.binding_mode {
2201                                     inconsistent_vars
2202                                         .entry(key.name)
2203                                         .or_insert((binding_j.span, binding_i.span));
2204                                 }
2205                             }
2206                         }
2207                     }
2208                 }
2209             }
2210         }
2211         let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();
2212         missing_vars.sort();
2213         for (_, v) in missing_vars {
2214             resolve_error(self,
2215                           *v.origin.iter().next().unwrap(),
2216                           ResolutionError::VariableNotBoundInPattern(v));
2217         }
2218         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2219         inconsistent_vars.sort();
2220         for (name, v) in inconsistent_vars {
2221             resolve_error(self, v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2222         }
2223     }
2224
2225     fn resolve_arm(&mut self, arm: &Arm) {
2226         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2227
2228         let mut bindings_list = FxHashMap();
2229         for pattern in &arm.pats {
2230             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2231         }
2232
2233         // This has to happen *after* we determine which
2234         // pat_idents are variants
2235         self.check_consistent_bindings(arm);
2236
2237         walk_list!(self, visit_expr, &arm.guard);
2238         self.visit_expr(&arm.body);
2239
2240         self.ribs[ValueNS].pop();
2241     }
2242
2243     fn resolve_block(&mut self, block: &Block) {
2244         debug!("(resolving block) entering block");
2245         // Move down in the graph, if there's an anonymous module rooted here.
2246         let orig_module = self.current_module;
2247         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
2248
2249         let mut num_macro_definition_ribs = 0;
2250         if let Some(anonymous_module) = anonymous_module {
2251             debug!("(resolving block) found anonymous module, moving down");
2252             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2253             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2254             self.current_module = anonymous_module;
2255             self.finalize_current_module_macro_resolutions();
2256         } else {
2257             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2258         }
2259
2260         // Descend into the block.
2261         for stmt in &block.stmts {
2262             if let ast::StmtKind::Item(ref item) = stmt.node {
2263                 if let ast::ItemKind::MacroDef(..) = item.node {
2264                     num_macro_definition_ribs += 1;
2265                     let def = self.definitions.local_def_id(item.id);
2266                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(def)));
2267                     self.label_ribs.push(Rib::new(MacroDefinition(def)));
2268                 }
2269             }
2270
2271             self.visit_stmt(stmt);
2272         }
2273
2274         // Move back up.
2275         self.current_module = orig_module;
2276         for _ in 0 .. num_macro_definition_ribs {
2277             self.ribs[ValueNS].pop();
2278             self.label_ribs.pop();
2279         }
2280         self.ribs[ValueNS].pop();
2281         if let Some(_) = anonymous_module {
2282             self.ribs[TypeNS].pop();
2283         }
2284         debug!("(resolving block) leaving block");
2285     }
2286
2287     fn fresh_binding(&mut self,
2288                      ident: &SpannedIdent,
2289                      pat_id: NodeId,
2290                      outer_pat_id: NodeId,
2291                      pat_src: PatternSource,
2292                      bindings: &mut FxHashMap<Ident, NodeId>)
2293                      -> PathResolution {
2294         // Add the binding to the local ribs, if it
2295         // doesn't already exist in the bindings map. (We
2296         // must not add it if it's in the bindings map
2297         // because that breaks the assumptions later
2298         // passes make about or-patterns.)
2299         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
2300         match bindings.get(&ident.node).cloned() {
2301             Some(id) if id == outer_pat_id => {
2302                 // `Variant(a, a)`, error
2303                 resolve_error(
2304                     self,
2305                     ident.span,
2306                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2307                         &ident.node.name.as_str())
2308                 );
2309             }
2310             Some(..) if pat_src == PatternSource::FnParam => {
2311                 // `fn f(a: u8, a: u8)`, error
2312                 resolve_error(
2313                     self,
2314                     ident.span,
2315                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2316                         &ident.node.name.as_str())
2317                 );
2318             }
2319             Some(..) if pat_src == PatternSource::Match => {
2320                 // `Variant1(a) | Variant2(a)`, ok
2321                 // Reuse definition from the first `a`.
2322                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
2323             }
2324             Some(..) => {
2325                 span_bug!(ident.span, "two bindings with the same name from \
2326                                        unexpected pattern source {:?}", pat_src);
2327             }
2328             None => {
2329                 // A completely fresh binding, add to the lists if it's valid.
2330                 if ident.node.name != keywords::Invalid.name() {
2331                     bindings.insert(ident.node, outer_pat_id);
2332                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2333                 }
2334             }
2335         }
2336
2337         PathResolution::new(def)
2338     }
2339
2340     fn resolve_pattern(&mut self,
2341                        pat: &Pat,
2342                        pat_src: PatternSource,
2343                        // Maps idents to the node ID for the
2344                        // outermost pattern that binds them.
2345                        bindings: &mut FxHashMap<Ident, NodeId>) {
2346         // Visit all direct subpatterns of this pattern.
2347         let outer_pat_id = pat.id;
2348         pat.walk(&mut |pat| {
2349             match pat.node {
2350                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2351                     // First try to resolve the identifier as some existing
2352                     // entity, then fall back to a fresh binding.
2353                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS,
2354                                                                       false, pat.span)
2355                                       .and_then(LexicalScopeBinding::item);
2356                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2357                         let ivmode = BindingMode::ByValue(Mutability::Immutable);
2358                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2359                                              bmode != ivmode;
2360                         match def {
2361                             Def::StructCtor(_, CtorKind::Const) |
2362                             Def::VariantCtor(_, CtorKind::Const) |
2363                             Def::Const(..) if !always_binding => {
2364                                 // A unit struct/variant or constant pattern.
2365                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2366                                 Some(PathResolution::new(def))
2367                             }
2368                             Def::StructCtor(..) | Def::VariantCtor(..) |
2369                             Def::Const(..) | Def::Static(..) => {
2370                                 // A fresh binding that shadows something unacceptable.
2371                                 resolve_error(
2372                                     self,
2373                                     ident.span,
2374                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2375                                         pat_src.descr(), ident.node.name, binding.unwrap())
2376                                 );
2377                                 None
2378                             }
2379                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2380                                 // These entities are explicitly allowed
2381                                 // to be shadowed by fresh bindings.
2382                                 None
2383                             }
2384                             def => {
2385                                 span_bug!(ident.span, "unexpected definition for an \
2386                                                        identifier in pattern: {:?}", def);
2387                             }
2388                         }
2389                     }).unwrap_or_else(|| {
2390                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2391                     });
2392
2393                     self.record_def(pat.id, resolution);
2394                 }
2395
2396                 PatKind::TupleStruct(ref path, ..) => {
2397                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2398                 }
2399
2400                 PatKind::Path(ref qself, ref path) => {
2401                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2402                 }
2403
2404                 PatKind::Struct(ref path, ..) => {
2405                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2406                 }
2407
2408                 _ => {}
2409             }
2410             true
2411         });
2412
2413         visit::walk_pat(self, pat);
2414     }
2415
2416     // High-level and context dependent path resolution routine.
2417     // Resolves the path and records the resolution into definition map.
2418     // If resolution fails tries several techniques to find likely
2419     // resolution candidates, suggest imports or other help, and report
2420     // errors in user friendly way.
2421     fn smart_resolve_path(&mut self,
2422                           id: NodeId,
2423                           qself: Option<&QSelf>,
2424                           path: &Path,
2425                           source: PathSource)
2426                           -> PathResolution {
2427         let segments = &path.segments.iter()
2428             .map(|seg| respan(seg.span, seg.identifier))
2429             .collect::<Vec<_>>();
2430         let ident_span = path.segments.last().map_or(path.span, |seg| seg.span);
2431         self.smart_resolve_path_fragment(id, qself, segments, path.span, ident_span, source)
2432     }
2433
2434     fn smart_resolve_path_fragment(&mut self,
2435                                    id: NodeId,
2436                                    qself: Option<&QSelf>,
2437                                    path: &[SpannedIdent],
2438                                    span: Span,
2439                                    ident_span: Span,
2440                                    source: PathSource)
2441                                    -> PathResolution {
2442         let ns = source.namespace();
2443         let is_expected = &|def| source.is_expected(def);
2444         let is_enum_variant = &|def| if let Def::Variant(..) = def { true } else { false };
2445
2446         // Base error is amended with one short label and possibly some longer helps/notes.
2447         let report_errors = |this: &mut Self, def: Option<Def>| {
2448             // Make the base error.
2449             let expected = source.descr_expected();
2450             let path_str = names_to_string(path);
2451             let code = source.error_code(def.is_some());
2452             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
2453                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2454                  format!("not a {}", expected), span)
2455             } else {
2456                 let item_str = path[path.len() - 1].node;
2457                 let item_span = path[path.len() - 1].span;
2458                 let (mod_prefix, mod_str) = if path.len() == 1 {
2459                     (format!(""), format!("this scope"))
2460                 } else if path.len() == 2 && path[0].node.name == keywords::CrateRoot.name() {
2461                     (format!(""), format!("the crate root"))
2462                 } else {
2463                     let mod_path = &path[..path.len() - 1];
2464                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), false, span) {
2465                         PathResult::Module(module) => module.def(),
2466                         _ => None,
2467                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2468                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2469                 };
2470                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2471                  format!("not found in {}", mod_str), item_span)
2472             };
2473             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
2474
2475             // Emit special messages for unresolved `Self` and `self`.
2476             if is_self_type(path, ns) {
2477                 __diagnostic_used!(E0411);
2478                 err.code("E0411".into());
2479                 err.span_label(span, "`Self` is only available in traits and impls");
2480                 return (err, Vec::new());
2481             }
2482             if is_self_value(path, ns) {
2483                 __diagnostic_used!(E0424);
2484                 err.code("E0424".into());
2485                 err.span_label(span, format!("`self` value is only available in \
2486                                                methods with `self` parameter"));
2487                 return (err, Vec::new());
2488             }
2489
2490             // Try to lookup the name in more relaxed fashion for better error reporting.
2491             let ident = *path.last().unwrap();
2492             let candidates = this.lookup_import_candidates(ident.node.name, ns, is_expected);
2493             if candidates.is_empty() && is_expected(Def::Enum(DefId::local(CRATE_DEF_INDEX))) {
2494                 let enum_candidates =
2495                     this.lookup_import_candidates(ident.node.name, ns, is_enum_variant);
2496                 let mut enum_candidates = enum_candidates.iter()
2497                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
2498                 enum_candidates.sort();
2499                 for (sp, variant_path, enum_path) in enum_candidates {
2500                     if sp == DUMMY_SP {
2501                         let msg = format!("there is an enum variant `{}`, \
2502                                         try using `{}`?",
2503                                         variant_path,
2504                                         enum_path);
2505                         err.help(&msg);
2506                     } else {
2507                         err.span_suggestion(span, "you can try using the variant's enum",
2508                                             enum_path);
2509                     }
2510                 }
2511             }
2512             if path.len() == 1 && this.self_type_is_available(span) {
2513                 if let Some(candidate) = this.lookup_assoc_candidate(ident.node, ns, is_expected) {
2514                     let self_is_available = this.self_value_is_available(path[0].node.ctxt, span);
2515                     match candidate {
2516                         AssocSuggestion::Field => {
2517                             err.span_suggestion(span, "try",
2518                                                 format!("self.{}", path_str));
2519                             if !self_is_available {
2520                                 err.span_label(span, format!("`self` value is only available in \
2521                                                                methods with `self` parameter"));
2522                             }
2523                         }
2524                         AssocSuggestion::MethodWithSelf if self_is_available => {
2525                             err.span_suggestion(span, "try",
2526                                                 format!("self.{}", path_str));
2527                         }
2528                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2529                             err.span_suggestion(span, "try",
2530                                                 format!("Self::{}", path_str));
2531                         }
2532                     }
2533                     return (err, candidates);
2534                 }
2535             }
2536
2537             let mut levenshtein_worked = false;
2538
2539             // Try Levenshtein.
2540             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected, span) {
2541                 err.span_label(ident_span, format!("did you mean `{}`?", candidate));
2542                 levenshtein_worked = true;
2543             }
2544
2545             // Try context dependent help if relaxed lookup didn't work.
2546             if let Some(def) = def {
2547                 match (def, source) {
2548                     (Def::Macro(..), _) => {
2549                         err.span_label(span, format!("did you mean `{}!(...)`?", path_str));
2550                         return (err, candidates);
2551                     }
2552                     (Def::TyAlias(..), PathSource::Trait) => {
2553                         err.span_label(span, "type aliases cannot be used for traits");
2554                         return (err, candidates);
2555                     }
2556                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match parent.node {
2557                         ExprKind::Field(_, ident) => {
2558                             err.span_label(parent.span, format!("did you mean `{}::{}`?",
2559                                                                  path_str, ident.node));
2560                             return (err, candidates);
2561                         }
2562                         ExprKind::MethodCall(ref segment, ..) => {
2563                             err.span_label(parent.span, format!("did you mean `{}::{}(...)`?",
2564                                                                  path_str, segment.identifier));
2565                             return (err, candidates);
2566                         }
2567                         _ => {}
2568                     },
2569                     _ if ns == ValueNS && is_struct_like(def) => {
2570                         if let Def::Struct(def_id) = def {
2571                             if let Some((ctor_def, ctor_vis))
2572                                     = this.struct_constructors.get(&def_id).cloned() {
2573                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2574                                     err.span_label(span, format!("constructor is not visible \
2575                                                                    here due to private fields"));
2576                                 }
2577                             }
2578                         }
2579                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
2580                                                        path_str));
2581                         return (err, candidates);
2582                     }
2583                     _ => {}
2584                 }
2585             }
2586
2587             // Fallback label.
2588             if !levenshtein_worked {
2589                 err.span_label(base_span, fallback_label);
2590                 this.type_ascription_suggestion(&mut err, base_span);
2591             }
2592             (err, candidates)
2593         };
2594         let report_errors = |this: &mut Self, def: Option<Def>| {
2595             let (err, candidates) = report_errors(this, def);
2596             let def_id = this.current_module.normal_ancestor_id;
2597             let node_id = this.definitions.as_local_node_id(def_id).unwrap();
2598             let better = def.is_some();
2599             this.use_injections.push(UseError { err, candidates, node_id, better });
2600             err_path_resolution()
2601         };
2602
2603         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2604                                                            source.defer_to_typeck(),
2605                                                            source.global_by_default()) {
2606             Some(resolution) if resolution.unresolved_segments() == 0 => {
2607                 if is_expected(resolution.base_def()) || resolution.base_def() == Def::Err {
2608                     resolution
2609                 } else {
2610                     // Add a temporary hack to smooth the transition to new struct ctor
2611                     // visibility rules. See #38932 for more details.
2612                     let mut res = None;
2613                     if let Def::Struct(def_id) = resolution.base_def() {
2614                         if let Some((ctor_def, ctor_vis))
2615                                 = self.struct_constructors.get(&def_id).cloned() {
2616                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2617                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2618                                 self.session.buffer_lint(lint, id, span,
2619                                     "private struct constructors are not usable through \
2620                                      reexports in outer modules",
2621                                 );
2622                                 res = Some(PathResolution::new(ctor_def));
2623                             }
2624                         }
2625                     }
2626
2627                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def())))
2628                 }
2629             }
2630             Some(resolution) if source.defer_to_typeck() => {
2631                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2632                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2633                 // it needs to be added to the trait map.
2634                 if ns == ValueNS {
2635                     let item_name = path.last().unwrap().node;
2636                     let traits = self.get_traits_containing_item(item_name, ns);
2637                     self.trait_map.insert(id, traits);
2638                 }
2639                 resolution
2640             }
2641             _ => report_errors(self, None)
2642         };
2643
2644         if let PathSource::TraitItem(..) = source {} else {
2645             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2646             self.record_def(id, resolution);
2647         }
2648         resolution
2649     }
2650
2651     fn type_ascription_suggestion(&self,
2652                                   err: &mut DiagnosticBuilder,
2653                                   base_span: Span) {
2654         debug!("type_ascription_suggetion {:?}", base_span);
2655         let cm = self.session.codemap();
2656         debug!("self.current_type_ascription {:?}", self.current_type_ascription);
2657         if let Some(sp) = self.current_type_ascription.last() {
2658             let mut sp = *sp;
2659             loop {  // try to find the `:`, bail on first non-':'/non-whitespace
2660                 sp = sp.next_point();
2661                 if let Ok(snippet) = cm.span_to_snippet(sp.to(sp.next_point())) {
2662                     debug!("snippet {:?}", snippet);
2663                     let line_sp = cm.lookup_char_pos(sp.hi).line;
2664                     let line_base_sp = cm.lookup_char_pos(base_span.lo).line;
2665                     debug!("{:?} {:?}", line_sp, line_base_sp);
2666                     if snippet == ":" {
2667                         err.span_label(base_span,
2668                                        "expecting a type here because of type ascription");
2669                         if line_sp != line_base_sp {
2670                             err.span_suggestion_short(sp,
2671                                                       "did you mean to use `;` here instead?",
2672                                                       ";".to_string());
2673                         }
2674                         break;
2675                     } else if snippet.trim().len() != 0  {
2676                         debug!("tried to find type ascription `:` token, couldn't find it");
2677                         break;
2678                     }
2679                 } else {
2680                     break;
2681                 }
2682             }
2683         }
2684     }
2685
2686     fn self_type_is_available(&mut self, span: Span) -> bool {
2687         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(),
2688                                                           TypeNS, false, span);
2689         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2690     }
2691
2692     fn self_value_is_available(&mut self, ctxt: SyntaxContext, span: Span) -> bool {
2693         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2694         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, false, span);
2695         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2696     }
2697
2698     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2699     fn resolve_qpath_anywhere(&mut self,
2700                               id: NodeId,
2701                               qself: Option<&QSelf>,
2702                               path: &[SpannedIdent],
2703                               primary_ns: Namespace,
2704                               span: Span,
2705                               defer_to_typeck: bool,
2706                               global_by_default: bool)
2707                               -> Option<PathResolution> {
2708         let mut fin_res = None;
2709         // FIXME: can't resolve paths in macro namespace yet, macros are
2710         // processed by the little special hack below.
2711         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2712             if i == 0 || ns != primary_ns {
2713                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2714                     // If defer_to_typeck, then resolution > no resolution,
2715                     // otherwise full resolution > partial resolution > no resolution.
2716                     Some(res) if res.unresolved_segments() == 0 || defer_to_typeck =>
2717                         return Some(res),
2718                     res => if fin_res.is_none() { fin_res = res },
2719                 };
2720             }
2721         }
2722         let is_global = self.global_macros.get(&path[0].node.name).cloned()
2723             .map(|binding| binding.get_macro(self).kind() == MacroKind::Bang).unwrap_or(false);
2724         if primary_ns != MacroNS && (is_global ||
2725                                      self.macro_names.contains(&path[0].node.modern())) {
2726             // Return some dummy definition, it's enough for error reporting.
2727             return Some(
2728                 PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX), MacroKind::Bang))
2729             );
2730         }
2731         fin_res
2732     }
2733
2734     /// Handles paths that may refer to associated items.
2735     fn resolve_qpath(&mut self,
2736                      id: NodeId,
2737                      qself: Option<&QSelf>,
2738                      path: &[SpannedIdent],
2739                      ns: Namespace,
2740                      span: Span,
2741                      global_by_default: bool)
2742                      -> Option<PathResolution> {
2743         if let Some(qself) = qself {
2744             if qself.position == 0 {
2745                 // FIXME: Create some fake resolution that can't possibly be a type.
2746                 return Some(PathResolution::with_unresolved_segments(
2747                     Def::Mod(DefId::local(CRATE_DEF_INDEX)), path.len()
2748                 ));
2749             }
2750             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2751             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2752             let res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2753                                                        span, span, PathSource::TraitItem(ns));
2754             return Some(PathResolution::with_unresolved_segments(
2755                 res.base_def(), res.unresolved_segments() + path.len() - qself.position - 1
2756             ));
2757         }
2758
2759         let result = match self.resolve_path(&path, Some(ns), true, span) {
2760             PathResult::NonModule(path_res) => path_res,
2761             PathResult::Module(module) if !module.is_normal() => {
2762                 PathResolution::new(module.def().unwrap())
2763             }
2764             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2765             // don't report an error right away, but try to fallback to a primitive type.
2766             // So, we are still able to successfully resolve something like
2767             //
2768             // use std::u8; // bring module u8 in scope
2769             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2770             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2771             //                     // not to non-existent std::u8::max_value
2772             // }
2773             //
2774             // Such behavior is required for backward compatibility.
2775             // The same fallback is used when `a` resolves to nothing.
2776             PathResult::Module(..) | PathResult::Failed(..)
2777                     if (ns == TypeNS || path.len() > 1) &&
2778                        self.primitive_type_table.primitive_types
2779                            .contains_key(&path[0].node.name) => {
2780                 let prim = self.primitive_type_table.primitive_types[&path[0].node.name];
2781                 match prim {
2782                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2783                         if !self.session.features.borrow().i128_type {
2784                             emit_feature_err(&self.session.parse_sess,
2785                                                 "i128_type", span, GateIssue::Language,
2786                                                 "128-bit type is unstable");
2787
2788                         }
2789                     }
2790                     _ => {}
2791                 }
2792                 PathResolution::with_unresolved_segments(Def::PrimTy(prim), path.len() - 1)
2793             }
2794             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2795             PathResult::Failed(span, msg, false) => {
2796                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2797                 err_path_resolution()
2798             }
2799             PathResult::Failed(..) => return None,
2800             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2801         };
2802
2803         if path.len() > 1 && !global_by_default && result.base_def() != Def::Err &&
2804            path[0].node.name != keywords::CrateRoot.name() &&
2805            path[0].node.name != keywords::DollarCrate.name() {
2806             let unqualified_result = {
2807                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), false, span) {
2808                     PathResult::NonModule(path_res) => path_res.base_def(),
2809                     PathResult::Module(module) => module.def().unwrap(),
2810                     _ => return Some(result),
2811                 }
2812             };
2813             if result.base_def() == unqualified_result {
2814                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2815                 self.session.buffer_lint(lint, id, span, "unnecessary qualification")
2816             }
2817         }
2818
2819         Some(result)
2820     }
2821
2822     fn resolve_path(&mut self,
2823                     path: &[SpannedIdent],
2824                     opt_ns: Option<Namespace>, // `None` indicates a module path
2825                     record_used: bool,
2826                     path_span: Span)
2827                     -> PathResult<'a> {
2828         let mut module = None;
2829         let mut allow_super = true;
2830
2831         for (i, &ident) in path.iter().enumerate() {
2832             debug!("resolve_path ident {} {:?}", i, ident);
2833             let is_last = i == path.len() - 1;
2834             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2835
2836             if i == 0 && ns == TypeNS && ident.node.name == keywords::SelfValue.name() {
2837                 let mut ctxt = ident.node.ctxt.modern();
2838                 module = Some(self.resolve_self(&mut ctxt, self.current_module));
2839                 continue
2840             } else if allow_super && ns == TypeNS && ident.node.name == keywords::Super.name() {
2841                 let mut ctxt = ident.node.ctxt.modern();
2842                 let self_module = match i {
2843                     0 => self.resolve_self(&mut ctxt, self.current_module),
2844                     _ => module.unwrap(),
2845                 };
2846                 if let Some(parent) = self_module.parent {
2847                     module = Some(self.resolve_self(&mut ctxt, parent));
2848                     continue
2849                 } else {
2850                     let msg = "There are too many initial `super`s.".to_string();
2851                     return PathResult::Failed(ident.span, msg, false);
2852                 }
2853             }
2854             allow_super = false;
2855
2856             if i == 0 && ns == TypeNS && ident.node.name == keywords::CrateRoot.name() {
2857                 module = Some(self.resolve_crate_root(ident.node.ctxt.modern()));
2858                 continue
2859             } else if i == 0 && ns == TypeNS && ident.node.name == keywords::DollarCrate.name() {
2860                 module = Some(self.resolve_crate_root(ident.node.ctxt));
2861                 continue
2862             }
2863
2864             let binding = if let Some(module) = module {
2865                 self.resolve_ident_in_module(module, ident.node, ns, false, record_used, path_span)
2866             } else if opt_ns == Some(MacroNS) {
2867                 self.resolve_lexical_macro_path_segment(ident.node, ns, record_used, path_span)
2868                     .map(MacroBinding::binding)
2869             } else {
2870                 match self.resolve_ident_in_lexical_scope(ident.node, ns, record_used, path_span) {
2871                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2872                     Some(LexicalScopeBinding::Def(def))
2873                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2874                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2875                             def, path.len() - 1
2876                         ));
2877                     }
2878                     _ => Err(if record_used { Determined } else { Undetermined }),
2879                 }
2880             };
2881
2882             match binding {
2883                 Ok(binding) => {
2884                     let def = binding.def();
2885                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2886                     if let Some(next_module) = binding.module() {
2887                         module = Some(next_module);
2888                     } else if def == Def::Err {
2889                         return PathResult::NonModule(err_path_resolution());
2890                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2891                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2892                             def, path.len() - i - 1
2893                         ));
2894                     } else {
2895                         return PathResult::Failed(ident.span,
2896                                                   format!("Not a module `{}`", ident.node),
2897                                                   is_last);
2898                     }
2899                 }
2900                 Err(Undetermined) => return PathResult::Indeterminate,
2901                 Err(Determined) => {
2902                     if let Some(module) = module {
2903                         if opt_ns.is_some() && !module.is_normal() {
2904                             return PathResult::NonModule(PathResolution::with_unresolved_segments(
2905                                 module.def().unwrap(), path.len() - i
2906                             ));
2907                         }
2908                     }
2909                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2910                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2911                         let mut candidates =
2912                             self.lookup_import_candidates(ident.node.name, TypeNS, is_mod);
2913                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2914                         if let Some(candidate) = candidates.get(0) {
2915                             format!("Did you mean `{}`?", candidate.path)
2916                         } else {
2917                             format!("Maybe a missing `extern crate {};`?", ident.node)
2918                         }
2919                     } else if i == 0 {
2920                         format!("Use of undeclared type or module `{}`", ident.node)
2921                     } else {
2922                         format!("Could not find `{}` in `{}`", ident.node, path[i - 1].node)
2923                     };
2924                     return PathResult::Failed(ident.span, msg, is_last);
2925                 }
2926             }
2927         }
2928
2929         PathResult::Module(module.unwrap_or(self.graph_root))
2930     }
2931
2932     // Resolve a local definition, potentially adjusting for closures.
2933     fn adjust_local_def(&mut self,
2934                         ns: Namespace,
2935                         rib_index: usize,
2936                         mut def: Def,
2937                         record_used: bool,
2938                         span: Span) -> Def {
2939         let ribs = &self.ribs[ns][rib_index + 1..];
2940
2941         // An invalid forward use of a type parameter from a previous default.
2942         if let ForwardTyParamBanRibKind = self.ribs[ns][rib_index].kind {
2943             if record_used {
2944                 resolve_error(self, span, ResolutionError::ForwardDeclaredTyParam);
2945             }
2946             assert_eq!(def, Def::Err);
2947             return Def::Err;
2948         }
2949
2950         match def {
2951             Def::Upvar(..) => {
2952                 span_bug!(span, "unexpected {:?} in bindings", def)
2953             }
2954             Def::Local(def_id) => {
2955                 for rib in ribs {
2956                     match rib.kind {
2957                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
2958                         ForwardTyParamBanRibKind => {
2959                             // Nothing to do. Continue.
2960                         }
2961                         ClosureRibKind(function_id) => {
2962                             let prev_def = def;
2963                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2964
2965                             let seen = self.freevars_seen
2966                                            .entry(function_id)
2967                                            .or_insert_with(|| NodeMap());
2968                             if let Some(&index) = seen.get(&node_id) {
2969                                 def = Def::Upvar(def_id, index, function_id);
2970                                 continue;
2971                             }
2972                             let vec = self.freevars
2973                                           .entry(function_id)
2974                                           .or_insert_with(|| vec![]);
2975                             let depth = vec.len();
2976                             def = Def::Upvar(def_id, depth, function_id);
2977
2978                             if record_used {
2979                                 vec.push(Freevar {
2980                                     def: prev_def,
2981                                     span,
2982                                 });
2983                                 seen.insert(node_id, depth);
2984                             }
2985                         }
2986                         ItemRibKind | MethodRibKind(_) => {
2987                             // This was an attempt to access an upvar inside a
2988                             // named function item. This is not allowed, so we
2989                             // report an error.
2990                             if record_used {
2991                                 resolve_error(self, span,
2992                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2993                             }
2994                             return Def::Err;
2995                         }
2996                         ConstantItemRibKind => {
2997                             // Still doesn't deal with upvars
2998                             if record_used {
2999                                 resolve_error(self, span,
3000                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
3001                             }
3002                             return Def::Err;
3003                         }
3004                     }
3005                 }
3006             }
3007             Def::TyParam(..) | Def::SelfTy(..) => {
3008                 for rib in ribs {
3009                     match rib.kind {
3010                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
3011                         ModuleRibKind(..) | MacroDefinition(..) | ForwardTyParamBanRibKind |
3012                         ConstantItemRibKind => {
3013                             // Nothing to do. Continue.
3014                         }
3015                         ItemRibKind => {
3016                             // This was an attempt to use a type parameter outside
3017                             // its scope.
3018                             if record_used {
3019                                 resolve_error(self, span,
3020                                               ResolutionError::TypeParametersFromOuterFunction);
3021                             }
3022                             return Def::Err;
3023                         }
3024                     }
3025                 }
3026             }
3027             _ => {}
3028         }
3029         return def;
3030     }
3031
3032     fn lookup_assoc_candidate<FilterFn>(&mut self,
3033                                         ident: Ident,
3034                                         ns: Namespace,
3035                                         filter_fn: FilterFn)
3036                                         -> Option<AssocSuggestion>
3037         where FilterFn: Fn(Def) -> bool
3038     {
3039         fn extract_node_id(t: &Ty) -> Option<NodeId> {
3040             match t.node {
3041                 TyKind::Path(None, _) => Some(t.id),
3042                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
3043                 // This doesn't handle the remaining `Ty` variants as they are not
3044                 // that commonly the self_type, it might be interesting to provide
3045                 // support for those in future.
3046                 _ => None,
3047             }
3048         }
3049
3050         // Fields are generally expected in the same contexts as locals.
3051         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
3052             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
3053                 // Look for a field with the same name in the current self_type.
3054                 if let Some(resolution) = self.def_map.get(&node_id) {
3055                     match resolution.base_def() {
3056                         Def::Struct(did) | Def::Union(did)
3057                                 if resolution.unresolved_segments() == 0 => {
3058                             if let Some(field_names) = self.field_names.get(&did) {
3059                                 if field_names.iter().any(|&field_name| ident.name == field_name) {
3060                                     return Some(AssocSuggestion::Field);
3061                                 }
3062                             }
3063                         }
3064                         _ => {}
3065                     }
3066                 }
3067             }
3068         }
3069
3070         // Look for associated items in the current trait.
3071         if let Some((module, _)) = self.current_trait_ref {
3072             if let Ok(binding) =
3073                     self.resolve_ident_in_module(module, ident, ns, false, false, module.span) {
3074                 let def = binding.def();
3075                 if filter_fn(def) {
3076                     return Some(if self.has_self.contains(&def.def_id()) {
3077                         AssocSuggestion::MethodWithSelf
3078                     } else {
3079                         AssocSuggestion::AssocItem
3080                     });
3081                 }
3082             }
3083         }
3084
3085         None
3086     }
3087
3088     fn lookup_typo_candidate<FilterFn>(&mut self,
3089                                        path: &[SpannedIdent],
3090                                        ns: Namespace,
3091                                        filter_fn: FilterFn,
3092                                        span: Span)
3093                                        -> Option<Symbol>
3094         where FilterFn: Fn(Def) -> bool
3095     {
3096         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
3097             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
3098                 if let Some(binding) = resolution.borrow().binding {
3099                     if filter_fn(binding.def()) {
3100                         names.push(ident.name);
3101                     }
3102                 }
3103             }
3104         };
3105
3106         let mut names = Vec::new();
3107         if path.len() == 1 {
3108             // Search in lexical scope.
3109             // Walk backwards up the ribs in scope and collect candidates.
3110             for rib in self.ribs[ns].iter().rev() {
3111                 // Locals and type parameters
3112                 for (ident, def) in &rib.bindings {
3113                     if filter_fn(*def) {
3114                         names.push(ident.name);
3115                     }
3116                 }
3117                 // Items in scope
3118                 if let ModuleRibKind(module) = rib.kind {
3119                     // Items from this module
3120                     add_module_candidates(module, &mut names);
3121
3122                     if let ModuleKind::Block(..) = module.kind {
3123                         // We can see through blocks
3124                     } else {
3125                         // Items from the prelude
3126                         if let Some(prelude) = self.prelude {
3127                             if !module.no_implicit_prelude {
3128                                 add_module_candidates(prelude, &mut names);
3129                             }
3130                         }
3131                         break;
3132                     }
3133                 }
3134             }
3135             // Add primitive types to the mix
3136             if filter_fn(Def::PrimTy(TyBool)) {
3137                 for (name, _) in &self.primitive_type_table.primitive_types {
3138                     names.push(*name);
3139                 }
3140             }
3141         } else {
3142             // Search in module.
3143             let mod_path = &path[..path.len() - 1];
3144             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS),
3145                                                                   false, span) {
3146                 add_module_candidates(module, &mut names);
3147             }
3148         }
3149
3150         let name = path[path.len() - 1].node.name;
3151         // Make sure error reporting is deterministic.
3152         names.sort_by_key(|name| name.as_str());
3153         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
3154             Some(found) if found != name => Some(found),
3155             _ => None,
3156         }
3157     }
3158
3159     fn with_resolved_label<F>(&mut self, label: Option<SpannedIdent>, id: NodeId, f: F)
3160         where F: FnOnce(&mut Resolver)
3161     {
3162         if let Some(label) = label {
3163             let def = Def::Label(id);
3164             self.with_label_rib(|this| {
3165                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
3166                 f(this);
3167             });
3168         } else {
3169             f(self);
3170         }
3171     }
3172
3173     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
3174         self.with_resolved_label(label, id, |this| this.visit_block(block));
3175     }
3176
3177     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
3178         // First, record candidate traits for this expression if it could
3179         // result in the invocation of a method call.
3180
3181         self.record_candidate_traits_for_expr_if_necessary(expr);
3182
3183         // Next, resolve the node.
3184         match expr.node {
3185             ExprKind::Path(ref qself, ref path) => {
3186                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
3187                 visit::walk_expr(self, expr);
3188             }
3189
3190             ExprKind::Struct(ref path, ..) => {
3191                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
3192                 visit::walk_expr(self, expr);
3193             }
3194
3195             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
3196                 match self.search_label(label.node) {
3197                     None => {
3198                         self.record_def(expr.id, err_path_resolution());
3199                         resolve_error(self,
3200                                       label.span,
3201                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
3202                     }
3203                     Some(def @ Def::Label(_)) => {
3204                         // Since this def is a label, it is never read.
3205                         self.record_def(expr.id, PathResolution::new(def));
3206                     }
3207                     Some(_) => {
3208                         span_bug!(expr.span, "label wasn't mapped to a label def!");
3209                     }
3210                 }
3211
3212                 // visit `break` argument if any
3213                 visit::walk_expr(self, expr);
3214             }
3215
3216             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
3217                 self.visit_expr(subexpression);
3218
3219                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3220                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
3221                 self.visit_block(if_block);
3222                 self.ribs[ValueNS].pop();
3223
3224                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
3225             }
3226
3227             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
3228
3229             ExprKind::While(ref subexpression, ref block, label) => {
3230                 self.with_resolved_label(label, expr.id, |this| {
3231                     this.visit_expr(subexpression);
3232                     this.visit_block(block);
3233                 });
3234             }
3235
3236             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
3237                 self.with_resolved_label(label, expr.id, |this| {
3238                     this.visit_expr(subexpression);
3239                     this.ribs[ValueNS].push(Rib::new(NormalRibKind));
3240                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
3241                     this.visit_block(block);
3242                     this.ribs[ValueNS].pop();
3243                 });
3244             }
3245
3246             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
3247                 self.visit_expr(subexpression);
3248                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3249                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
3250
3251                 self.resolve_labeled_block(label, expr.id, block);
3252
3253                 self.ribs[ValueNS].pop();
3254             }
3255
3256             // Equivalent to `visit::walk_expr` + passing some context to children.
3257             ExprKind::Field(ref subexpression, _) => {
3258                 self.resolve_expr(subexpression, Some(expr));
3259             }
3260             ExprKind::MethodCall(ref segment, ref arguments) => {
3261                 let mut arguments = arguments.iter();
3262                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3263                 for argument in arguments {
3264                     self.resolve_expr(argument, None);
3265                 }
3266                 self.visit_path_segment(expr.span, segment);
3267             }
3268
3269             ExprKind::Repeat(ref element, ref count) => {
3270                 self.visit_expr(element);
3271                 self.with_constant_rib(|this| {
3272                     this.visit_expr(count);
3273                 });
3274             }
3275             ExprKind::Call(ref callee, ref arguments) => {
3276                 self.resolve_expr(callee, Some(expr));
3277                 for argument in arguments {
3278                     self.resolve_expr(argument, None);
3279                 }
3280             }
3281             ExprKind::Type(ref type_expr, _) => {
3282                 self.current_type_ascription.push(type_expr.span);
3283                 visit::walk_expr(self, expr);
3284                 self.current_type_ascription.pop();
3285             }
3286             _ => {
3287                 visit::walk_expr(self, expr);
3288             }
3289         }
3290     }
3291
3292     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3293         match expr.node {
3294             ExprKind::Field(_, name) => {
3295                 // FIXME(#6890): Even though you can't treat a method like a
3296                 // field, we need to add any trait methods we find that match
3297                 // the field name so that we can do some nice error reporting
3298                 // later on in typeck.
3299                 let traits = self.get_traits_containing_item(name.node, ValueNS);
3300                 self.trait_map.insert(expr.id, traits);
3301             }
3302             ExprKind::MethodCall(ref segment, ..) => {
3303                 debug!("(recording candidate traits for expr) recording traits for {}",
3304                        expr.id);
3305                 let traits = self.get_traits_containing_item(segment.identifier, ValueNS);
3306                 self.trait_map.insert(expr.id, traits);
3307             }
3308             _ => {
3309                 // Nothing to do.
3310             }
3311         }
3312     }
3313
3314     fn get_traits_containing_item(&mut self, mut ident: Ident, ns: Namespace)
3315                                   -> Vec<TraitCandidate> {
3316         debug!("(getting traits containing item) looking for '{}'", ident.name);
3317
3318         let mut found_traits = Vec::new();
3319         // Look for the current trait.
3320         if let Some((module, _)) = self.current_trait_ref {
3321             if self.resolve_ident_in_module(module, ident, ns, false, false, module.span).is_ok() {
3322                 let def_id = module.def_id().unwrap();
3323                 found_traits.push(TraitCandidate { def_id: def_id, import_id: None });
3324             }
3325         }
3326
3327         ident.ctxt = ident.ctxt.modern();
3328         let mut search_module = self.current_module;
3329         loop {
3330             self.get_traits_in_module_containing_item(ident, ns, search_module, &mut found_traits);
3331             search_module =
3332                 unwrap_or!(self.hygienic_lexical_parent(search_module, &mut ident.ctxt), break);
3333         }
3334
3335         if let Some(prelude) = self.prelude {
3336             if !search_module.no_implicit_prelude {
3337                 self.get_traits_in_module_containing_item(ident, ns, prelude, &mut found_traits);
3338             }
3339         }
3340
3341         found_traits
3342     }
3343
3344     fn get_traits_in_module_containing_item(&mut self,
3345                                             ident: Ident,
3346                                             ns: Namespace,
3347                                             module: Module<'a>,
3348                                             found_traits: &mut Vec<TraitCandidate>) {
3349         let mut traits = module.traits.borrow_mut();
3350         if traits.is_none() {
3351             let mut collected_traits = Vec::new();
3352             module.for_each_child(|name, ns, binding| {
3353                 if ns != TypeNS { return }
3354                 if let Def::Trait(_) = binding.def() {
3355                     collected_traits.push((name, binding));
3356                 }
3357             });
3358             *traits = Some(collected_traits.into_boxed_slice());
3359         }
3360
3361         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3362             let module = binding.module().unwrap();
3363             let mut ident = ident;
3364             if ident.ctxt.glob_adjust(module.expansion, binding.span.ctxt.modern()).is_none() {
3365                 continue
3366             }
3367             if self.resolve_ident_in_module_unadjusted(module, ident, ns, false, false, module.span)
3368                    .is_ok() {
3369                 let import_id = match binding.kind {
3370                     NameBindingKind::Import { directive, .. } => {
3371                         self.maybe_unused_trait_imports.insert(directive.id);
3372                         self.add_to_glob_map(directive.id, trait_name);
3373                         Some(directive.id)
3374                     }
3375                     _ => None,
3376                 };
3377                 let trait_def_id = module.def_id().unwrap();
3378                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
3379             }
3380         }
3381     }
3382
3383     /// When name resolution fails, this method can be used to look up candidate
3384     /// entities with the expected name. It allows filtering them using the
3385     /// supplied predicate (which should be used to only accept the types of
3386     /// definitions expected e.g. traits). The lookup spans across all crates.
3387     ///
3388     /// NOTE: The method does not look into imports, but this is not a problem,
3389     /// since we report the definitions (thus, the de-aliased imports).
3390     fn lookup_import_candidates<FilterFn>(&mut self,
3391                                           lookup_name: Name,
3392                                           namespace: Namespace,
3393                                           filter_fn: FilterFn)
3394                                           -> Vec<ImportSuggestion>
3395         where FilterFn: Fn(Def) -> bool
3396     {
3397         let mut candidates = Vec::new();
3398         let mut worklist = Vec::new();
3399         let mut seen_modules = FxHashSet();
3400         worklist.push((self.graph_root, Vec::new(), false));
3401
3402         while let Some((in_module,
3403                         path_segments,
3404                         in_module_is_extern)) = worklist.pop() {
3405             self.populate_module_if_necessary(in_module);
3406
3407             // We have to visit module children in deterministic order to avoid
3408             // instabilities in reported imports (#43552).
3409             in_module.for_each_child_stable(|ident, ns, name_binding| {
3410                 // avoid imports entirely
3411                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3412                 // avoid non-importable candidates as well
3413                 if !name_binding.is_importable() { return; }
3414
3415                 // collect results based on the filter function
3416                 if ident.name == lookup_name && ns == namespace {
3417                     if filter_fn(name_binding.def()) {
3418                         // create the path
3419                         let mut segms = path_segments.clone();
3420                         segms.push(ast::PathSegment::from_ident(ident, name_binding.span));
3421                         let path = Path {
3422                             span: name_binding.span,
3423                             segments: segms,
3424                         };
3425                         // the entity is accessible in the following cases:
3426                         // 1. if it's defined in the same crate, it's always
3427                         // accessible (since private entities can be made public)
3428                         // 2. if it's defined in another crate, it's accessible
3429                         // only if both the module is public and the entity is
3430                         // declared as public (due to pruning, we don't explore
3431                         // outside crate private modules => no need to check this)
3432                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3433                             candidates.push(ImportSuggestion { path: path });
3434                         }
3435                     }
3436                 }
3437
3438                 // collect submodules to explore
3439                 if let Some(module) = name_binding.module() {
3440                     // form the path
3441                     let mut path_segments = path_segments.clone();
3442                     path_segments.push(ast::PathSegment::from_ident(ident, name_binding.span));
3443
3444                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3445                         // add the module to the lookup
3446                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3447                         if seen_modules.insert(module.def_id().unwrap()) {
3448                             worklist.push((module, path_segments, is_extern));
3449                         }
3450                     }
3451                 }
3452             })
3453         }
3454
3455         candidates
3456     }
3457
3458     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3459         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3460         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3461             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3462         }
3463     }
3464
3465     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3466         match *vis {
3467             ast::Visibility::Public => ty::Visibility::Public,
3468             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3469             ast::Visibility::Inherited => {
3470                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3471             }
3472             ast::Visibility::Restricted { ref path, id } => {
3473                 let def = self.smart_resolve_path(id, None, path,
3474                                                   PathSource::Visibility).base_def();
3475                 if def == Def::Err {
3476                     ty::Visibility::Public
3477                 } else {
3478                     let vis = ty::Visibility::Restricted(def.def_id());
3479                     if self.is_accessible(vis) {
3480                         vis
3481                     } else {
3482                         self.session.span_err(path.span, "visibilities can only be restricted \
3483                                                           to ancestor modules");
3484                         ty::Visibility::Public
3485                     }
3486                 }
3487             }
3488         }
3489     }
3490
3491     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3492         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3493     }
3494
3495     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3496         vis.is_accessible_from(module.normal_ancestor_id, self)
3497     }
3498
3499     fn report_errors(&mut self, krate: &Crate) {
3500         self.report_shadowing_errors();
3501         self.report_with_use_injections(krate);
3502         let mut reported_spans = FxHashSet();
3503
3504         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3505             if !reported_spans.insert(span) { continue }
3506             let participle = |binding: &NameBinding| {
3507                 if binding.is_import() { "imported" } else { "defined" }
3508             };
3509             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3510             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3511             let note = if b1.expansion == Mark::root() || !lexical && b1.is_glob_import() {
3512                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3513             } else if let Def::Macro(..) = b1.def() {
3514                 format!("macro-expanded {} do not shadow",
3515                         if b1.is_import() { "macro imports" } else { "macros" })
3516             } else {
3517                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3518                         if b1.is_import() { "imports" } else { "items" })
3519             };
3520             if legacy {
3521                 let id = match b2.kind {
3522                     NameBindingKind::Import { directive, .. } => directive.id,
3523                     _ => unreachable!(),
3524                 };
3525                 let mut span = MultiSpan::from_span(span);
3526                 span.push_span_label(b1.span, msg1);
3527                 span.push_span_label(b2.span, msg2);
3528                 let msg = format!("`{}` is ambiguous", name);
3529                 self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, &msg);
3530             } else {
3531                 let mut err =
3532                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", name));
3533                 err.span_note(b1.span, &msg1);
3534                 match b2.def() {
3535                     Def::Macro(..) if b2.span == DUMMY_SP =>
3536                         err.note(&format!("`{}` is also a builtin macro", name)),
3537                     _ => err.span_note(b2.span, &msg2),
3538                 };
3539                 err.note(&note).emit();
3540             }
3541         }
3542
3543         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3544             if !reported_spans.insert(span) { continue }
3545             span_err!(self.session, span, E0603, "{} `{}` is private", binding.descr(), name);
3546         }
3547     }
3548
3549     fn report_with_use_injections(&mut self, krate: &Crate) {
3550         for UseError { mut err, candidates, node_id, better } in self.use_injections.drain(..) {
3551             let mut finder = UsePlacementFinder {
3552                 target_module: node_id,
3553                 span: None,
3554                 found_use: false,
3555             };
3556             visit::walk_crate(&mut finder, krate);
3557             if !candidates.is_empty() {
3558                 let span = finder.span.expect("did not find module");
3559                 show_candidates(&mut err, span, &candidates, better, finder.found_use);
3560             }
3561             err.emit();
3562         }
3563     }
3564
3565     fn report_shadowing_errors(&mut self) {
3566         for (ident, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3567             self.resolve_legacy_scope(scope, ident, true);
3568         }
3569
3570         let mut reported_errors = FxHashSet();
3571         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3572             if self.resolve_legacy_scope(&binding.parent, binding.ident, false).is_some() &&
3573                reported_errors.insert((binding.ident, binding.span)) {
3574                 let msg = format!("`{}` is already in scope", binding.ident);
3575                 self.session.struct_span_err(binding.span, &msg)
3576                     .note("macro-expanded `macro_rules!`s may not shadow \
3577                            existing macros (see RFC 1560)")
3578                     .emit();
3579             }
3580         }
3581     }
3582
3583     fn report_conflict(&mut self,
3584                        parent: Module,
3585                        ident: Ident,
3586                        ns: Namespace,
3587                        new_binding: &NameBinding,
3588                        old_binding: &NameBinding) {
3589         // Error on the second of two conflicting names
3590         if old_binding.span.lo > new_binding.span.lo {
3591             return self.report_conflict(parent, ident, ns, old_binding, new_binding);
3592         }
3593
3594         let container = match parent.kind {
3595             ModuleKind::Def(Def::Mod(_), _) => "module",
3596             ModuleKind::Def(Def::Trait(_), _) => "trait",
3597             ModuleKind::Block(..) => "block",
3598             _ => "enum",
3599         };
3600
3601         let old_noun = match old_binding.is_import() {
3602             true => "import",
3603             false => "definition",
3604         };
3605
3606         let new_participle = match new_binding.is_import() {
3607             true => "imported",
3608             false => "defined",
3609         };
3610
3611         let (name, span) = (ident.name, new_binding.span);
3612
3613         if let Some(s) = self.name_already_seen.get(&name) {
3614             if s == &span {
3615                 return;
3616             }
3617         }
3618
3619         let old_kind = match (ns, old_binding.module()) {
3620             (ValueNS, _) => "value",
3621             (MacroNS, _) => "macro",
3622             (TypeNS, _) if old_binding.is_extern_crate() => "extern crate",
3623             (TypeNS, Some(module)) if module.is_normal() => "module",
3624             (TypeNS, Some(module)) if module.is_trait() => "trait",
3625             (TypeNS, _) => "type",
3626         };
3627
3628         let namespace = match ns {
3629             ValueNS => "value",
3630             MacroNS => "macro",
3631             TypeNS => "type",
3632         };
3633
3634         let msg = format!("the name `{}` is defined multiple times", name);
3635
3636         let mut err = match (old_binding.is_extern_crate(), new_binding.is_extern_crate()) {
3637             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3638             (true, _) | (_, true) => match new_binding.is_import() && old_binding.is_import() {
3639                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3640                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3641             },
3642             _ => match (old_binding.is_import(), new_binding.is_import()) {
3643                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3644                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3645                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3646             },
3647         };
3648
3649         err.note(&format!("`{}` must be defined only once in the {} namespace of this {}",
3650                           name,
3651                           namespace,
3652                           container));
3653
3654         err.span_label(span, format!("`{}` re{} here", name, new_participle));
3655         if old_binding.span != syntax_pos::DUMMY_SP {
3656             err.span_label(old_binding.span, format!("previous {} of the {} `{}` here",
3657                                                       old_noun, old_kind, name));
3658         }
3659
3660         err.emit();
3661         self.name_already_seen.insert(name, span);
3662     }
3663
3664     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3665         let (id, span) = (directive.id, directive.span);
3666         let msg = "`self` no longer imports values";
3667         self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3668     }
3669
3670     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3671         if self.proc_macro_enabled { return; }
3672
3673         for attr in attrs {
3674             if attr.path.segments.len() > 1 {
3675                 continue
3676             }
3677             let ident = attr.path.segments[0].identifier;
3678             let result = self.resolve_lexical_macro_path_segment(ident,
3679                                                                  MacroNS,
3680                                                                  false,
3681                                                                  attr.path.span);
3682             if let Ok(binding) = result {
3683                 if let SyntaxExtension::AttrProcMacro(..) = *binding.binding().get_macro(self) {
3684                     attr::mark_known(attr);
3685
3686                     let msg = "attribute procedural macros are experimental";
3687                     let feature = "proc_macro";
3688
3689                     feature_err(&self.session.parse_sess, feature,
3690                                 attr.span, GateIssue::Language, msg)
3691                         .span_note(binding.span(), "procedural macro imported here")
3692                         .emit();
3693                 }
3694             }
3695         }
3696     }
3697 }
3698
3699 fn is_struct_like(def: Def) -> bool {
3700     match def {
3701         Def::VariantCtor(_, CtorKind::Fictive) => true,
3702         _ => PathSource::Struct.is_expected(def),
3703     }
3704 }
3705
3706 fn is_self_type(path: &[SpannedIdent], namespace: Namespace) -> bool {
3707     namespace == TypeNS && path.len() == 1 && path[0].node.name == keywords::SelfType.name()
3708 }
3709
3710 fn is_self_value(path: &[SpannedIdent], namespace: Namespace) -> bool {
3711     namespace == ValueNS && path.len() == 1 && path[0].node.name == keywords::SelfValue.name()
3712 }
3713
3714 fn names_to_string(idents: &[SpannedIdent]) -> String {
3715     let mut result = String::new();
3716     for (i, ident) in idents.iter()
3717                             .filter(|i| i.node.name != keywords::CrateRoot.name())
3718                             .enumerate() {
3719         if i > 0 {
3720             result.push_str("::");
3721         }
3722         result.push_str(&ident.node.name.as_str());
3723     }
3724     result
3725 }
3726
3727 fn path_names_to_string(path: &Path) -> String {
3728     names_to_string(&path.segments.iter()
3729                         .map(|seg| respan(seg.span, seg.identifier))
3730                         .collect::<Vec<_>>())
3731 }
3732
3733 /// Get the path for an enum and the variant from an `ImportSuggestion` for an enum variant.
3734 fn import_candidate_to_paths(suggestion: &ImportSuggestion) -> (Span, String, String) {
3735     let variant_path = &suggestion.path;
3736     let variant_path_string = path_names_to_string(variant_path);
3737
3738     let path_len = suggestion.path.segments.len();
3739     let enum_path = ast::Path {
3740         span: suggestion.path.span,
3741         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
3742     };
3743     let enum_path_string = path_names_to_string(&enum_path);
3744
3745     (suggestion.path.span, variant_path_string, enum_path_string)
3746 }
3747
3748
3749 /// When an entity with a given name is not available in scope, we search for
3750 /// entities with that name in all crates. This method allows outputting the
3751 /// results of this search in a programmer-friendly way
3752 fn show_candidates(err: &mut DiagnosticBuilder,
3753                    span: Span,
3754                    candidates: &[ImportSuggestion],
3755                    better: bool,
3756                    found_use: bool) {
3757
3758     // we want consistent results across executions, but candidates are produced
3759     // by iterating through a hash map, so make sure they are ordered:
3760     let mut path_strings: Vec<_> =
3761         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3762     path_strings.sort();
3763
3764     let better = if better { "better " } else { "" };
3765     let msg_diff = match path_strings.len() {
3766         1 => " is found in another module, you can import it",
3767         _ => "s are found in other modules, you can import them",
3768     };
3769     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
3770
3771     for candidate in &mut path_strings {
3772         // produce an additional newline to separate the new use statement
3773         // from the directly following item.
3774         let additional_newline = if found_use {
3775             ""
3776         } else {
3777             "\n"
3778         };
3779         *candidate = format!("use {};\n{}", candidate, additional_newline);
3780     }
3781
3782     err.span_suggestions(span, &msg, path_strings);
3783 }
3784
3785 /// A somewhat inefficient routine to obtain the name of a module.
3786 fn module_to_string(module: Module) -> String {
3787     let mut names = Vec::new();
3788
3789     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3790         if let ModuleKind::Def(_, name) = module.kind {
3791             if let Some(parent) = module.parent {
3792                 names.push(Ident::with_empty_ctxt(name));
3793                 collect_mod(names, parent);
3794             }
3795         } else {
3796             // danger, shouldn't be ident?
3797             names.push(Ident::from_str("<opaque>"));
3798             collect_mod(names, module.parent.unwrap());
3799         }
3800     }
3801     collect_mod(&mut names, module);
3802
3803     if names.is_empty() {
3804         return "???".to_string();
3805     }
3806     names_to_string(&names.into_iter()
3807                         .rev()
3808                         .map(|n| dummy_spanned(n))
3809                         .collect::<Vec<_>>())
3810 }
3811
3812 fn err_path_resolution() -> PathResolution {
3813     PathResolution::new(Def::Err)
3814 }
3815
3816 #[derive(PartialEq,Copy, Clone)]
3817 pub enum MakeGlobMap {
3818     Yes,
3819     No,
3820 }
3821
3822 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }