src/librustc_resolve/lib.rs

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