src/librustc_resolve/lib.rs

   1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![crate_name = "rustc_resolve"]
  12 #![crate_type = "dylib"]
  13 #![crate_type = "rlib"]
  14 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  15       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  16       html_root_url = "https://doc.rust-lang.org/nightly/")]
  17 #![deny(warnings)]
  18
  19 #![feature(rustc_diagnostic_macros)]
  20
  21 #[macro_use]
  22 extern crate log;
  23 #[macro_use]
  24 extern crate syntax;
  25 extern crate syntax_pos;
  26 extern crate rustc_errors as errors;
  27 extern crate arena;
  28 #[macro_use]
  29 extern crate rustc;
  30
  31 use self::Namespace::*;
  32 use self::TypeParameters::*;
  33 use self::RibKind::*;
  34
  35 use rustc::hir::map::{Definitions, DefCollector};
  36 use rustc::hir::{self, PrimTy, TyBool, TyChar, TyFloat, TyInt, TyUint, TyStr};
  37 use rustc::middle::cstore::CrateLoader;
  38 use rustc::session::Session;
  39 use rustc::lint;
  40 use rustc::hir::def::*;
  41 use rustc::hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE, DefId};
  42 use rustc::ty;
  43 use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
  44 use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};
  45
  46 use syntax::codemap::{dummy_spanned, respan};
  47 use syntax::ext::hygiene::{Mark, SyntaxContext};
  48 use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
  49 use syntax::ext::base::SyntaxExtension;
  50 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
  51 use syntax::ext::base::MacroKind;
  52 use syntax::symbol::{Symbol, keywords};
  53 use syntax::util::lev_distance::find_best_match_for_name;
  54
  55 use syntax::visit::{self, FnKind, Visitor};
  56 use syntax::attr;
  57 use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
  58 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
  59 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
  60 use syntax::ast::{Local, Mutability, Pat, PatKind, Path};
  61 use syntax::ast::{QSelf, TraitItemKind, TraitRef, Ty, TyKind};
  62 use syntax::feature_gate::{feature_err, emit_feature_err, GateIssue};
  63
  64 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
  65 use errors::DiagnosticBuilder;
  66
  67 use std::cell::{Cell, RefCell};
  68 use std::cmp;
  69 use std::collections::BTreeSet;
  70 use std::fmt;
  71 use std::mem::replace;
  72 use std::rc::Rc;
  73
  74 use resolve_imports::{ImportDirective, ImportDirectiveSubclass, NameResolution, ImportResolver};
  75 use macros::{InvocationData, LegacyBinding, LegacyScope, MacroBinding};
  76
  77 // NB: This module needs to be declared first so diagnostics are
  78 // registered before they are used.
  79 mod diagnostics;
  80
  81 mod macros;
  82 mod check_unused;
  83 mod build_reduced_graph;
  84 mod resolve_imports;
  85
  86 /// A free importable items suggested in case of resolution failure.
  87 struct ImportSuggestion {
  88     path: Path,
  89 }
  90
  91 /// A field or associated item from self type suggested in case of resolution failure.
  92 enum AssocSuggestion {
  93     Field,
  94     MethodWithSelf,
  95     AssocItem,
  96 }
  97
  98 #[derive(Eq)]
  99 struct BindingError {
 100     name: Name,
 101     origin: BTreeSet<Span>,
 102     target: BTreeSet<Span>,
 103 }
 104
 105 impl PartialOrd for BindingError {
 106     fn partial_cmp(&self, other: &BindingError) -> Option<cmp::Ordering> {
 107         Some(self.cmp(other))
 108     }
 109 }
 110
 111 impl PartialEq for BindingError {
 112     fn eq(&self, other: &BindingError) -> bool {
 113         self.name == other.name
 114     }
 115 }
 116
 117 impl Ord for BindingError {
 118     fn cmp(&self, other: &BindingError) -> cmp::Ordering {
 119         self.name.cmp(&other.name)
 120     }
 121 }
 122
 123 enum ResolutionError<'a> {
 124     /// error E0401: can't use type parameters from outer function
 125     TypeParametersFromOuterFunction,
 126     /// error E0403: the name is already used for a type parameter in this type parameter list
 127     NameAlreadyUsedInTypeParameterList(Name, &'a Span),
 128     /// error E0407: method is not a member of trait
 129     MethodNotMemberOfTrait(Name, &'a str),
 130     /// error E0437: type is not a member of trait
 131     TypeNotMemberOfTrait(Name, &'a str),
 132     /// error E0438: const is not a member of trait
 133     ConstNotMemberOfTrait(Name, &'a str),
 134     /// error E0408: variable `{}` is not bound in all patterns
 135     VariableNotBoundInPattern(&'a BindingError),
 136     /// error E0409: variable `{}` is bound in inconsistent ways within the same match arm
 137     VariableBoundWithDifferentMode(Name, Span),
 138     /// error E0415: identifier is bound more than once in this parameter list
 139     IdentifierBoundMoreThanOnceInParameterList(&'a str),
 140     /// error E0416: identifier is bound more than once in the same pattern
 141     IdentifierBoundMoreThanOnceInSamePattern(&'a str),
 142     /// error E0426: use of undeclared label
 143     UndeclaredLabel(&'a str),
 144     /// error E0429: `self` imports are only allowed within a { } list
 145     SelfImportsOnlyAllowedWithin,
 146     /// error E0430: `self` import can only appear once in the list
 147     SelfImportCanOnlyAppearOnceInTheList,
 148     /// error E0431: `self` import can only appear in an import list with a non-empty prefix
 149     SelfImportOnlyInImportListWithNonEmptyPrefix,
 150     /// error E0432: unresolved import
 151     UnresolvedImport(Option<(Span, &'a str, &'a str)>),
 152     /// error E0433: failed to resolve
 153     FailedToResolve(&'a str),
 154     /// error E0434: can't capture dynamic environment in a fn item
 155     CannotCaptureDynamicEnvironmentInFnItem,
 156     /// error E0435: attempt to use a non-constant value in a constant
 157     AttemptToUseNonConstantValueInConstant,
 158     /// error E0530: X bindings cannot shadow Ys
 159     BindingShadowsSomethingUnacceptable(&'a str, Name, &'a NameBinding<'a>),
 160     /// error E0128: type parameters with a default cannot use forward declared identifiers
 161     ForwardDeclaredTyParam,
 162 }
 163
 164 fn resolve_error<'sess, 'a>(resolver: &'sess Resolver,
 165                             span: Span,
 166                             resolution_error: ResolutionError<'a>) {
 167     resolve_struct_error(resolver, span, resolution_error).emit();
 168 }
 169
 170 fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
 171                                    span: Span,
 172                                    resolution_error: ResolutionError<'a>)
 173                                    -> DiagnosticBuilder<'sess> {
 174     match resolution_error {
 175         ResolutionError::TypeParametersFromOuterFunction => {
 176             let mut err = struct_span_err!(resolver.session,
 177                                            span,
 178                                            E0401,
 179                                            "can't use type parameters from outer function; \
 180                                            try using a local type parameter instead");
 181             err.span_label(span, "use of type variable from outer function");
 182             err
 183         }
 184         ResolutionError::NameAlreadyUsedInTypeParameterList(name, first_use_span) => {
 185              let mut err = struct_span_err!(resolver.session,
 186                                             span,
 187                                             E0403,
 188                                             "the name `{}` is already used for a type parameter \
 189                                             in this type parameter list",
 190                                             name);
 191              err.span_label(span, "already used");
 192              err.span_label(first_use_span.clone(), format!("first use of `{}`", name));
 193              err
 194         }
 195         ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 196             let mut err = struct_span_err!(resolver.session,
 197                                            span,
 198                                            E0407,
 199                                            "method `{}` is not a member of trait `{}`",
 200                                            method,
 201                                            trait_);
 202             err.span_label(span, format!("not a member of trait `{}`", trait_));
 203             err
 204         }
 205         ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 206             let mut err = struct_span_err!(resolver.session,
 207                              span,
 208                              E0437,
 209                              "type `{}` is not a member of trait `{}`",
 210                              type_,
 211                              trait_);
 212             err.span_label(span, format!("not a member of trait `{}`", trait_));
 213             err
 214         }
 215         ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 216             let mut err = struct_span_err!(resolver.session,
 217                              span,
 218                              E0438,
 219                              "const `{}` is not a member of trait `{}`",
 220                              const_,
 221                              trait_);
 222             err.span_label(span, format!("not a member of trait `{}`", trait_));
 223             err
 224         }
 225         ResolutionError::VariableNotBoundInPattern(binding_error) => {
 226             let target_sp = binding_error.target.iter().map(|x| *x).collect::<Vec<_>>();
 227             let msp = MultiSpan::from_spans(target_sp.clone());
 228             let msg = format!("variable `{}` is not bound in all patterns", binding_error.name);
 229             let mut err = resolver.session.struct_span_err_with_code(msp, &msg, "E0408");
 230             for sp in target_sp {
 231                 err.span_label(sp, format!("pattern doesn't bind `{}`", binding_error.name));
 232             }
 233             let origin_sp = binding_error.origin.iter().map(|x| *x).collect::<Vec<_>>();
 234             for sp in origin_sp {
 235                 err.span_label(sp, "variable not in all patterns");
 236             }
 237             err
 238         }
 239         ResolutionError::VariableBoundWithDifferentMode(variable_name,
 240                                                         first_binding_span) => {
 241             let mut err = struct_span_err!(resolver.session,
 242                              span,
 243                              E0409,
 244                              "variable `{}` is bound in inconsistent \
 245                              ways within the same match arm",
 246                              variable_name);
 247             err.span_label(span, "bound in different ways");
 248             err.span_label(first_binding_span, "first binding");
 249             err
 250         }
 251         ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 252             let mut err = struct_span_err!(resolver.session,
 253                              span,
 254                              E0415,
 255                              "identifier `{}` is bound more than once in this parameter list",
 256                              identifier);
 257             err.span_label(span, "used as parameter more than once");
 258             err
 259         }
 260         ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 261             let mut err = struct_span_err!(resolver.session,
 262                              span,
 263                              E0416,
 264                              "identifier `{}` is bound more than once in the same pattern",
 265                              identifier);
 266             err.span_label(span, "used in a pattern more than once");
 267             err
 268         }
 269         ResolutionError::UndeclaredLabel(name) => {
 270             let mut err = struct_span_err!(resolver.session,
 271                                            span,
 272                                            E0426,
 273                                            "use of undeclared label `{}`",
 274                                            name);
 275             err.span_label(span, format!("undeclared label `{}`", name));
 276             err
 277         }
 278         ResolutionError::SelfImportsOnlyAllowedWithin => {
 279             struct_span_err!(resolver.session,
 280                              span,
 281                              E0429,
 282                              "{}",
 283                              "`self` imports are only allowed within a { } list")
 284         }
 285         ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 286             struct_span_err!(resolver.session,
 287                              span,
 288                              E0430,
 289                              "`self` import can only appear once in the list")
 290         }
 291         ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 292             struct_span_err!(resolver.session,
 293                              span,
 294                              E0431,
 295                              "`self` import can only appear in an import list with a \
 296                               non-empty prefix")
 297         }
 298         ResolutionError::UnresolvedImport(name) => {
 299             let (span, msg) = match name {
 300                 Some((sp, n, _)) => (sp, format!("unresolved import `{}`", n)),
 301                 None => (span, "unresolved import".to_owned()),
 302             };
 303             let mut err = struct_span_err!(resolver.session, span, E0432, "{}", msg);
 304             if let Some((_, _, p)) = name {
 305                 err.span_label(span, p);
 306             }
 307             err
 308         }
 309         ResolutionError::FailedToResolve(msg) => {
 310             let mut err = struct_span_err!(resolver.session, span, E0433,
 311                                            "failed to resolve. {}", msg);
 312             err.span_label(span, msg);
 313             err
 314         }
 315         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 316             struct_span_err!(resolver.session,
 317                              span,
 318                              E0434,
 319                              "{}",
 320                              "can't capture dynamic environment in a fn item; use the || { ... } \
 321                               closure form instead")
 322         }
 323         ResolutionError::AttemptToUseNonConstantValueInConstant => {
 324             let mut err = struct_span_err!(resolver.session,
 325                              span,
 326                              E0435,
 327                              "attempt to use a non-constant value in a constant");
 328             err.span_label(span, "non-constant value");
 329             err
 330         }
 331         ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 332             let shadows_what = PathResolution::new(binding.def()).kind_name();
 333             let mut err = struct_span_err!(resolver.session,
 334                                            span,
 335                                            E0530,
 336                                            "{}s cannot shadow {}s", what_binding, shadows_what);
 337             err.span_label(span, format!("cannot be named the same as a {}", shadows_what));
 338             let participle = if binding.is_import() { "imported" } else { "defined" };
 339             let msg = format!("a {} `{}` is {} here", shadows_what, name, participle);
 340             err.span_label(binding.span, msg);
 341             err
 342         }
 343         ResolutionError::ForwardDeclaredTyParam => {
 344             let mut err = struct_span_err!(resolver.session, span, E0128,
 345                                            "type parameters with a default cannot use \
 346                                             forward declared identifiers");
 347             err.span_label(span, format!("defaulted type parameters \
 348                                            cannot be forward declared"));
 349             err
 350         }
 351     }
 352 }
 353
 354 #[derive(Copy, Clone, Debug)]
 355 struct BindingInfo {
 356     span: Span,
 357     binding_mode: BindingMode,
 358 }
 359
 360 // Map from the name in a pattern to its binding mode.
 361 type BindingMap = FxHashMap<Ident, BindingInfo>;
 362
 363 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 364 enum PatternSource {
 365     Match,
 366     IfLet,
 367     WhileLet,
 368     Let,
 369     For,
 370     FnParam,
 371 }
 372
 373 impl PatternSource {
 374     fn is_refutable(self) -> bool {
 375         match self {
 376             PatternSource::Match | PatternSource::IfLet | PatternSource::WhileLet => true,
 377             PatternSource::Let | PatternSource::For | PatternSource::FnParam  => false,
 378         }
 379     }
 380     fn descr(self) -> &'static str {
 381         match self {
 382             PatternSource::Match => "match binding",
 383             PatternSource::IfLet => "if let binding",
 384             PatternSource::WhileLet => "while let binding",
 385             PatternSource::Let => "let binding",
 386             PatternSource::For => "for binding",
 387             PatternSource::FnParam => "function parameter",
 388         }
 389     }
 390 }
 391
 392 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 393 enum PathSource<'a> {
 394     // Type paths `Path`.
 395     Type,
 396     // Trait paths in bounds or impls.
 397     Trait,
 398     // Expression paths `path`, with optional parent context.
 399     Expr(Option<&'a Expr>),
 400     // Paths in path patterns `Path`.
 401     Pat,
 402     // Paths in struct expressions and patterns `Path { .. }`.
 403     Struct,
 404     // Paths in tuple struct patterns `Path(..)`.
 405     TupleStruct,
 406     // `m::A::B` in `<T as m::A>::B::C`.
 407     TraitItem(Namespace),
 408     // Path in `pub(path)`
 409     Visibility,
 410     // Path in `use a::b::{...};`
 411     ImportPrefix,
 412 }
 413
 414 impl<'a> PathSource<'a> {
 415     fn namespace(self) -> Namespace {
 416         match self {
 417             PathSource::Type | PathSource::Trait | PathSource::Struct |
 418             PathSource::Visibility | PathSource::ImportPrefix => TypeNS,
 419             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct => ValueNS,
 420             PathSource::TraitItem(ns) => ns,
 421         }
 422     }
 423
 424     fn global_by_default(self) -> bool {
 425         match self {
 426             PathSource::Visibility | PathSource::ImportPrefix => true,
 427             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 428             PathSource::Struct | PathSource::TupleStruct |
 429             PathSource::Trait | PathSource::TraitItem(..) => false,
 430         }
 431     }
 432
 433     fn defer_to_typeck(self) -> bool {
 434         match self {
 435             PathSource::Type | PathSource::Expr(..) | PathSource::Pat |
 436             PathSource::Struct | PathSource::TupleStruct => true,
 437             PathSource::Trait | PathSource::TraitItem(..) |
 438             PathSource::Visibility | PathSource::ImportPrefix => false,
 439         }
 440     }
 441
 442     fn descr_expected(self) -> &'static str {
 443         match self {
 444             PathSource::Type => "type",
 445             PathSource::Trait => "trait",
 446             PathSource::Pat => "unit struct/variant or constant",
 447             PathSource::Struct => "struct, variant or union type",
 448             PathSource::TupleStruct => "tuple struct/variant",
 449             PathSource::Visibility => "module",
 450             PathSource::ImportPrefix => "module or enum",
 451             PathSource::TraitItem(ns) => match ns {
 452                 TypeNS => "associated type",
 453                 ValueNS => "method or associated constant",
 454                 MacroNS => bug!("associated macro"),
 455             },
 456             PathSource::Expr(parent) => match parent.map(|p| &p.node) {
 457                 // "function" here means "anything callable" rather than `Def::Fn`,
 458                 // this is not precise but usually more helpful than just "value".
 459                 Some(&ExprKind::Call(..)) => "function",
 460                 _ => "value",
 461             },
 462         }
 463     }
 464
 465     fn is_expected(self, def: Def) -> bool {
 466         match self {
 467             PathSource::Type => match def {
 468                 Def::Struct(..) | Def::Union(..) | Def::Enum(..) |
 469                 Def::Trait(..) | Def::TyAlias(..) | Def::AssociatedTy(..) |
 470                 Def::PrimTy(..) | Def::TyParam(..) | Def::SelfTy(..) => true,
 471                 _ => false,
 472             },
 473             PathSource::Trait => match def {
 474                 Def::Trait(..) => true,
 475                 _ => false,
 476             },
 477             PathSource::Expr(..) => match def {
 478                 Def::StructCtor(_, CtorKind::Const) | Def::StructCtor(_, CtorKind::Fn) |
 479                 Def::VariantCtor(_, CtorKind::Const) | Def::VariantCtor(_, CtorKind::Fn) |
 480                 Def::Const(..) | Def::Static(..) | Def::Local(..) | Def::Upvar(..) |
 481                 Def::Fn(..) | Def::Method(..) | Def::AssociatedConst(..) => true,
 482                 _ => false,
 483             },
 484             PathSource::Pat => match def {
 485                 Def::StructCtor(_, CtorKind::Const) |
 486                 Def::VariantCtor(_, CtorKind::Const) |
 487                 Def::Const(..) | Def::AssociatedConst(..) => true,
 488                 _ => false,
 489             },
 490             PathSource::TupleStruct => match def {
 491                 Def::StructCtor(_, CtorKind::Fn) | Def::VariantCtor(_, CtorKind::Fn) => true,
 492                 _ => false,
 493             },
 494             PathSource::Struct => match def {
 495                 Def::Struct(..) | Def::Union(..) | Def::Variant(..) |
 496                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => true,
 497                 _ => false,
 498             },
 499             PathSource::TraitItem(ns) => match def {
 500                 Def::AssociatedConst(..) | Def::Method(..) if ns == ValueNS => true,
 501                 Def::AssociatedTy(..) if ns == TypeNS => true,
 502                 _ => false,
 503             },
 504             PathSource::ImportPrefix => match def {
 505                 Def::Mod(..) | Def::Enum(..) => true,
 506                 _ => false,
 507             },
 508             PathSource::Visibility => match def {
 509                 Def::Mod(..) => true,
 510                 _ => false,
 511             },
 512         }
 513     }
 514
 515     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
 516         __diagnostic_used!(E0404);
 517         __diagnostic_used!(E0405);
 518         __diagnostic_used!(E0412);
 519         __diagnostic_used!(E0422);
 520         __diagnostic_used!(E0423);
 521         __diagnostic_used!(E0425);
 522         __diagnostic_used!(E0531);
 523         __diagnostic_used!(E0532);
 524         __diagnostic_used!(E0573);
 525         __diagnostic_used!(E0574);
 526         __diagnostic_used!(E0575);
 527         __diagnostic_used!(E0576);
 528         __diagnostic_used!(E0577);
 529         __diagnostic_used!(E0578);
 530         match (self, has_unexpected_resolution) {
 531             (PathSource::Trait, true) => "E0404",
 532             (PathSource::Trait, false) => "E0405",
 533             (PathSource::Type, true) => "E0573",
 534             (PathSource::Type, false) => "E0412",
 535             (PathSource::Struct, true) => "E0574",
 536             (PathSource::Struct, false) => "E0422",
 537             (PathSource::Expr(..), true) => "E0423",
 538             (PathSource::Expr(..), false) => "E0425",
 539             (PathSource::Pat, true) | (PathSource::TupleStruct, true) => "E0532",
 540             (PathSource::Pat, false) | (PathSource::TupleStruct, false) => "E0531",
 541             (PathSource::TraitItem(..), true) => "E0575",
 542             (PathSource::TraitItem(..), false) => "E0576",
 543             (PathSource::Visibility, true) | (PathSource::ImportPrefix, true) => "E0577",
 544             (PathSource::Visibility, false) | (PathSource::ImportPrefix, false) => "E0578",
 545         }
 546     }
 547 }
 548
 549 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 550 pub enum Namespace {
 551     TypeNS,
 552     ValueNS,
 553     MacroNS,
 554 }
 555
 556 #[derive(Clone, Default, Debug)]
 557 pub struct PerNS<T> {
 558     value_ns: T,
 559     type_ns: T,
 560     macro_ns: Option<T>,
 561 }
 562
 563 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 564     type Output = T;
 565     fn index(&self, ns: Namespace) -> &T {
 566         match ns {
 567             ValueNS => &self.value_ns,
 568             TypeNS => &self.type_ns,
 569             MacroNS => self.macro_ns.as_ref().unwrap(),
 570         }
 571     }
 572 }
 573
 574 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 575     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 576         match ns {
 577             ValueNS => &mut self.value_ns,
 578             TypeNS => &mut self.type_ns,
 579             MacroNS => self.macro_ns.as_mut().unwrap(),
 580         }
 581     }
 582 }
 583
 584 struct UsePlacementFinder {
 585     target_module: NodeId,
 586     span: Option<Span>,
 587     found_use: bool,
 588 }
 589
 590 impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
 591     fn visit_mod(
 592         &mut self,
 593         module: &'tcx ast::Mod,
 594         _: Span,
 595         _: &[ast::Attribute],
 596         node_id: NodeId,
 597     ) {
 598         if self.span.is_some() {
 599             return;
 600         }
 601         if node_id != self.target_module {
 602             visit::walk_mod(self, module);
 603             return;
 604         }
 605         // find a use statement
 606         for item in &module.items {
 607             match item.node {
 608                 ItemKind::Use(..) => {
 609                     // don't suggest placing a use before the prelude
 610                     // import or other generated ones
 611                     if item.span == DUMMY_SP {
 612                         let mut span = item.span;
 613                         span.hi = span.lo;
 614                         self.span = Some(span);
 615                         self.found_use = true;
 616                         return;
 617                     }
 618                 },
 619                 // don't place use before extern crate
 620                 ItemKind::ExternCrate(_) => {}
 621                 // but place them before the first other item
 622                 _ => if self.span.map_or(true, |span| item.span < span ) {
 623                     let mut span = item.span;
 624                     span.hi = span.lo;
 625                     self.span = Some(span);
 626                 },
 627             }
 628         }
 629         assert!(self.span.is_some(), "a file can't have no items and emit suggestions");
 630     }
 631 }
 632
 633 impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
 634     fn visit_item(&mut self, item: &'tcx Item) {
 635         self.resolve_item(item);
 636     }
 637     fn visit_arm(&mut self, arm: &'tcx Arm) {
 638         self.resolve_arm(arm);
 639     }
 640     fn visit_block(&mut self, block: &'tcx Block) {
 641         self.resolve_block(block);
 642     }
 643     fn visit_expr(&mut self, expr: &'tcx Expr) {
 644         self.resolve_expr(expr, None);
 645     }
 646     fn visit_local(&mut self, local: &'tcx Local) {
 647         self.resolve_local(local);
 648     }
 649     fn visit_ty(&mut self, ty: &'tcx Ty) {
 650         match ty.node {
 651             TyKind::Path(ref qself, ref path) => {
 652                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 653             }
 654             TyKind::ImplicitSelf => {
 655                 let self_ty = keywords::SelfType.ident();
 656                 let def = self.resolve_ident_in_lexical_scope(self_ty, TypeNS, true, ty.span)
 657                               .map_or(Def::Err, |d| d.def());
 658                 self.record_def(ty.id, PathResolution::new(def));
 659             }
 660             TyKind::Array(ref element, ref length) => {
 661                 self.visit_ty(element);
 662                 self.with_constant_rib(|this| {
 663                     this.visit_expr(length);
 664                 });
 665                 return;
 666             }
 667             _ => (),
 668         }
 669         visit::walk_ty(self, ty);
 670     }
 671     fn visit_poly_trait_ref(&mut self,
 672                             tref: &'tcx ast::PolyTraitRef,
 673                             m: &'tcx ast::TraitBoundModifier) {
 674         self.smart_resolve_path(tref.trait_ref.ref_id, None,
 675                                 &tref.trait_ref.path, PathSource::Trait);
 676         visit::walk_poly_trait_ref(self, tref, m);
 677     }
 678     fn visit_variant(&mut self,
 679                      variant: &'tcx ast::Variant,
 680                      generics: &'tcx Generics,
 681                      item_id: ast::NodeId) {
 682         if let Some(ref dis_expr) = variant.node.disr_expr {
 683             // resolve the discriminator expr as a constant
 684             self.with_constant_rib(|this| {
 685                 this.visit_expr(dis_expr);
 686             });
 687         }
 688
 689         // `visit::walk_variant` without the discriminant expression.
 690         self.visit_variant_data(&variant.node.data,
 691                                 variant.node.name,
 692                                 generics,
 693                                 item_id,
 694                                 variant.span);
 695     }
 696     fn visit_foreign_item(&mut self, foreign_item: &'tcx ForeignItem) {
 697         let type_parameters = match foreign_item.node {
 698             ForeignItemKind::Fn(_, ref generics) => {
 699                 HasTypeParameters(generics, ItemRibKind)
 700             }
 701             ForeignItemKind::Static(..) => NoTypeParameters,
 702         };
 703         self.with_type_parameter_rib(type_parameters, |this| {
 704             visit::walk_foreign_item(this, foreign_item);
 705         });
 706     }
 707     fn visit_fn(&mut self,
 708                 function_kind: FnKind<'tcx>,
 709                 declaration: &'tcx FnDecl,
 710                 _: Span,
 711                 node_id: NodeId) {
 712         let rib_kind = match function_kind {
 713             FnKind::ItemFn(_, generics, ..) => {
 714                 self.visit_generics(generics);
 715                 ItemRibKind
 716             }
 717             FnKind::Method(_, sig, _, _) => {
 718                 self.visit_generics(&sig.generics);
 719                 MethodRibKind(!sig.decl.has_self())
 720             }
 721             FnKind::Closure(_) => ClosureRibKind(node_id),
 722         };
 723
 724         // Create a value rib for the function.
 725         self.ribs[ValueNS].push(Rib::new(rib_kind));
 726
 727         // Create a label rib for the function.
 728         self.label_ribs.push(Rib::new(rib_kind));
 729
 730         // Add each argument to the rib.
 731         let mut bindings_list = FxHashMap();
 732         for argument in &declaration.inputs {
 733             self.resolve_pattern(&argument.pat, PatternSource::FnParam, &mut bindings_list);
 734
 735             self.visit_ty(&argument.ty);
 736
 737             debug!("(resolving function) recorded argument");
 738         }
 739         visit::walk_fn_ret_ty(self, &declaration.output);
 740
 741         // Resolve the function body.
 742         match function_kind {
 743             FnKind::ItemFn(.., body) |
 744             FnKind::Method(.., body) => {
 745                 self.visit_block(body);
 746             }
 747             FnKind::Closure(body) => {
 748                 self.visit_expr(body);
 749             }
 750         };
 751
 752         debug!("(resolving function) leaving function");
 753
 754         self.label_ribs.pop();
 755         self.ribs[ValueNS].pop();
 756     }
 757     fn visit_generics(&mut self, generics: &'tcx Generics) {
 758         // For type parameter defaults, we have to ban access
 759         // to following type parameters, as the Substs can only
 760         // provide previous type parameters as they're built.
 761         let mut default_ban_rib = Rib::new(ForwardTyParamBanRibKind);
 762         default_ban_rib.bindings.extend(generics.ty_params.iter()
 763             .skip_while(|p| p.default.is_none())
 764             .map(|p| (Ident::with_empty_ctxt(p.ident.name), Def::Err)));
 765
 766         for param in &generics.ty_params {
 767             for bound in &param.bounds {
 768                 self.visit_ty_param_bound(bound);
 769             }
 770
 771             if let Some(ref ty) = param.default {
 772                 self.ribs[TypeNS].push(default_ban_rib);
 773                 self.visit_ty(ty);
 774                 default_ban_rib = self.ribs[TypeNS].pop().unwrap();
 775             }
 776
 777             // Allow all following defaults to refer to this type parameter.
 778             default_ban_rib.bindings.remove(&Ident::with_empty_ctxt(param.ident.name));
 779         }
 780         for lt in &generics.lifetimes { self.visit_lifetime_def(lt); }
 781         for p in &generics.where_clause.predicates { self.visit_where_predicate(p); }
 782     }
 783 }
 784
 785 pub type ErrorMessage = Option<(Span, String)>;
 786
 787 #[derive(Copy, Clone)]
 788 enum TypeParameters<'a, 'b> {
 789     NoTypeParameters,
 790     HasTypeParameters(// Type parameters.
 791                       &'b Generics,
 792
 793                       // The kind of the rib used for type parameters.
 794                       RibKind<'a>),
 795 }
 796
 797 // The rib kind controls the translation of local
 798 // definitions (`Def::Local`) to upvars (`Def::Upvar`).
 799 #[derive(Copy, Clone, Debug)]
 800 enum RibKind<'a> {
 801     // No translation needs to be applied.
 802     NormalRibKind,
 803
 804     // We passed through a closure scope at the given node ID.
 805     // Translate upvars as appropriate.
 806     ClosureRibKind(NodeId /* func id */),
 807
 808     // We passed through an impl or trait and are now in one of its
 809     // methods. Allow references to ty params that impl or trait
 810     // binds. Disallow any other upvars (including other ty params that are
 811     // upvars).
 812     //
 813     // The boolean value represents the fact that this method is static or not.
 814     MethodRibKind(bool),
 815
 816     // We passed through an item scope. Disallow upvars.
 817     ItemRibKind,
 818
 819     // We're in a constant item. Can't refer to dynamic stuff.
 820     ConstantItemRibKind,
 821
 822     // We passed through a module.
 823     ModuleRibKind(Module<'a>),
 824
 825     // We passed through a `macro_rules!` statement
 826     MacroDefinition(DefId),
 827
 828     // All bindings in this rib are type parameters that can't be used
 829     // from the default of a type parameter because they're not declared
 830     // before said type parameter. Also see the `visit_generics` override.
 831     ForwardTyParamBanRibKind,
 832 }
 833
 834 /// One local scope.
 835 #[derive(Debug)]
 836 struct Rib<'a> {
 837     bindings: FxHashMap<Ident, Def>,
 838     kind: RibKind<'a>,
 839 }
 840
 841 impl<'a> Rib<'a> {
 842     fn new(kind: RibKind<'a>) -> Rib<'a> {
 843         Rib {
 844             bindings: FxHashMap(),
 845             kind,
 846         }
 847     }
 848 }
 849
 850 enum LexicalScopeBinding<'a> {
 851     Item(&'a NameBinding<'a>),
 852     Def(Def),
 853 }
 854
 855 impl<'a> LexicalScopeBinding<'a> {
 856     fn item(self) -> Option<&'a NameBinding<'a>> {
 857         match self {
 858             LexicalScopeBinding::Item(binding) => Some(binding),
 859             _ => None,
 860         }
 861     }
 862
 863     fn def(self) -> Def {
 864         match self {
 865             LexicalScopeBinding::Item(binding) => binding.def(),
 866             LexicalScopeBinding::Def(def) => def,
 867         }
 868     }
 869 }
 870
 871 #[derive(Clone)]
 872 enum PathResult<'a> {
 873     Module(Module<'a>),
 874     NonModule(PathResolution),
 875     Indeterminate,
 876     Failed(Span, String, bool /* is the error from the last segment? */),
 877 }
 878
 879 enum ModuleKind {
 880     Block(NodeId),
 881     Def(Def, Name),
 882 }
 883
 884 /// One node in the tree of modules.
 885 pub struct ModuleData<'a> {
 886     parent: Option<Module<'a>>,
 887     kind: ModuleKind,
 888
 889     // The def id of the closest normal module (`mod`) ancestor (including this module).
 890     normal_ancestor_id: DefId,
 891
 892     resolutions: RefCell<FxHashMap<(Ident, Namespace), &'a RefCell<NameResolution<'a>>>>,
 893     legacy_macro_resolutions: RefCell<Vec<(Mark, Ident, Span, MacroKind)>>,
 894     macro_resolutions: RefCell<Vec<(Box<[Ident]>, Span)>>,
 895
 896     // Macro invocations that can expand into items in this module.
 897     unresolved_invocations: RefCell<FxHashSet<Mark>>,
 898
 899     no_implicit_prelude: bool,
 900
 901     glob_importers: RefCell<Vec<&'a ImportDirective<'a>>>,
 902     globs: RefCell<Vec<&'a ImportDirective<'a>>>,
 903
 904     // Used to memoize the traits in this module for faster searches through all traits in scope.
 905     traits: RefCell<Option<Box<[(Ident, &'a NameBinding<'a>)]>>>,
 906
 907     // Whether this module is populated. If not populated, any attempt to
 908     // access the children must be preceded with a
 909     // `populate_module_if_necessary` call.
 910     populated: Cell<bool>,
 911
 912     /// Span of the module itself. Used for error reporting.
 913     span: Span,
 914
 915     expansion: Mark,
 916 }
 917
 918 pub type Module<'a> = &'a ModuleData<'a>;
 919
 920 impl<'a> ModuleData<'a> {
 921     fn new(parent: Option<Module<'a>>,
 922            kind: ModuleKind,
 923            normal_ancestor_id: DefId,
 924            expansion: Mark,
 925            span: Span) -> Self {
 926         ModuleData {
 927             parent,
 928             kind,
 929             normal_ancestor_id,
 930             resolutions: RefCell::new(FxHashMap()),
 931             legacy_macro_resolutions: RefCell::new(Vec::new()),
 932             macro_resolutions: RefCell::new(Vec::new()),
 933             unresolved_invocations: RefCell::new(FxHashSet()),
 934             no_implicit_prelude: false,
 935             glob_importers: RefCell::new(Vec::new()),
 936             globs: RefCell::new((Vec::new())),
 937             traits: RefCell::new(None),
 938             populated: Cell::new(normal_ancestor_id.is_local()),
 939             span,
 940             expansion,
 941         }
 942     }
 943
 944     fn for_each_child<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 945         for (&(ident, ns), name_resolution) in self.resolutions.borrow().iter() {
 946             name_resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 947         }
 948     }
 949
 950     fn for_each_child_stable<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
 951         let resolutions = self.resolutions.borrow();
 952         let mut resolutions = resolutions.iter().map(|(&(ident, ns), &resolution)| {
 953                                                     // Pre-compute keys for sorting
 954                                                     (ident.name.as_str(), ns, ident, resolution)
 955                                                 })
 956                                                 .collect::<Vec<_>>();
 957         resolutions.sort_unstable_by_key(|&(str, ns, ..)| (str, ns));
 958         for &(_, ns, ident, resolution) in resolutions.iter() {
 959             resolution.borrow().binding.map(|binding| f(ident, ns, binding));
 960         }
 961     }
 962
 963     fn def(&self) -> Option<Def> {
 964         match self.kind {
 965             ModuleKind::Def(def, _) => Some(def),
 966             _ => None,
 967         }
 968     }
 969
 970     fn def_id(&self) -> Option<DefId> {
 971         self.def().as_ref().map(Def::def_id)
 972     }
 973
 974     // `self` resolves to the first module ancestor that `is_normal`.
 975     fn is_normal(&self) -> bool {
 976         match self.kind {
 977             ModuleKind::Def(Def::Mod(_), _) => true,
 978             _ => false,
 979         }
 980     }
 981
 982     fn is_trait(&self) -> bool {
 983         match self.kind {
 984             ModuleKind::Def(Def::Trait(_), _) => true,
 985             _ => false,
 986         }
 987     }
 988
 989     fn is_local(&self) -> bool {
 990         self.normal_ancestor_id.is_local()
 991     }
 992
 993     fn nearest_item_scope(&'a self) -> Module<'a> {
 994         if self.is_trait() { self.parent.unwrap() } else { self }
 995     }
 996 }
 997
 998 impl<'a> fmt::Debug for ModuleData<'a> {
 999     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1000         write!(f, "{:?}", self.def())
1001     }
1002 }
1003
1004 // Records a possibly-private value, type, or module definition.
1005 #[derive(Clone, Debug)]
1006 pub struct NameBinding<'a> {
1007     kind: NameBindingKind<'a>,
1008     expansion: Mark,
1009     span: Span,
1010     vis: ty::Visibility,
1011 }
1012
1013 pub trait ToNameBinding<'a> {
1014     fn to_name_binding(self, arenas: &'a ResolverArenas<'a>) -> &'a NameBinding<'a>;
1015 }
1016
1017 impl<'a> ToNameBinding<'a> for &'a NameBinding<'a> {
1018     fn to_name_binding(self, _: &'a ResolverArenas<'a>) -> &'a NameBinding<'a> {
1019         self
1020     }
1021 }
1022
1023 #[derive(Clone, Debug)]
1024 enum NameBindingKind<'a> {
1025     Def(Def),
1026     Module(Module<'a>),
1027     Import {
1028         binding: &'a NameBinding<'a>,
1029         directive: &'a ImportDirective<'a>,
1030         used: Cell<bool>,
1031         legacy_self_import: bool,
1032     },
1033     Ambiguity {
1034         b1: &'a NameBinding<'a>,
1035         b2: &'a NameBinding<'a>,
1036         legacy: bool,
1037     }
1038 }
1039
1040 struct PrivacyError<'a>(Span, Name, &'a NameBinding<'a>);
1041
1042 struct UseError<'a> {
1043     err: DiagnosticBuilder<'a>,
1044     /// Attach `use` statements for these candidates
1045     candidates: Vec<ImportSuggestion>,
1046     /// The node id of the module to place the use statements in
1047     node_id: NodeId,
1048     /// Whether the diagnostic should state that it's "better"
1049     better: bool,
1050 }
1051
1052 struct AmbiguityError<'a> {
1053     span: Span,
1054     name: Name,
1055     lexical: bool,
1056     b1: &'a NameBinding<'a>,
1057     b2: &'a NameBinding<'a>,
1058     legacy: bool,
1059 }
1060
1061 impl<'a> NameBinding<'a> {
1062     fn module(&self) -> Option<Module<'a>> {
1063         match self.kind {
1064             NameBindingKind::Module(module) => Some(module),
1065             NameBindingKind::Import { binding, .. } => binding.module(),
1066             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.module(),
1067             _ => None,
1068         }
1069     }
1070
1071     fn def(&self) -> Def {
1072         match self.kind {
1073             NameBindingKind::Def(def) => def,
1074             NameBindingKind::Module(module) => module.def().unwrap(),
1075             NameBindingKind::Import { binding, .. } => binding.def(),
1076             NameBindingKind::Ambiguity { legacy: true, b1, .. } => b1.def(),
1077             NameBindingKind::Ambiguity { .. } => Def::Err,
1078         }
1079     }
1080
1081     fn def_ignoring_ambiguity(&self) -> Def {
1082         match self.kind {
1083             NameBindingKind::Import { binding, .. } => binding.def_ignoring_ambiguity(),
1084             NameBindingKind::Ambiguity { b1, .. } => b1.def_ignoring_ambiguity(),
1085             _ => self.def(),
1086         }
1087     }
1088
1089     fn get_macro(&self, resolver: &mut Resolver<'a>) -> Rc<SyntaxExtension> {
1090         resolver.get_macro(self.def_ignoring_ambiguity())
1091     }
1092
1093     // We sometimes need to treat variants as `pub` for backwards compatibility
1094     fn pseudo_vis(&self) -> ty::Visibility {
1095         if self.is_variant() { ty::Visibility::Public } else { self.vis }
1096     }
1097
1098     fn is_variant(&self) -> bool {
1099         match self.kind {
1100             NameBindingKind::Def(Def::Variant(..)) |
1101             NameBindingKind::Def(Def::VariantCtor(..)) => true,
1102             _ => false,
1103         }
1104     }
1105
1106     fn is_extern_crate(&self) -> bool {
1107         match self.kind {
1108             NameBindingKind::Import {
1109                 directive: &ImportDirective {
1110                     subclass: ImportDirectiveSubclass::ExternCrate, ..
1111                 }, ..
1112             } => true,
1113             _ => false,
1114         }
1115     }
1116
1117     fn is_import(&self) -> bool {
1118         match self.kind {
1119             NameBindingKind::Import { .. } => true,
1120             _ => false,
1121         }
1122     }
1123
1124     fn is_glob_import(&self) -> bool {
1125         match self.kind {
1126             NameBindingKind::Import { directive, .. } => directive.is_glob(),
1127             NameBindingKind::Ambiguity { b1, .. } => b1.is_glob_import(),
1128             _ => false,
1129         }
1130     }
1131
1132     fn is_importable(&self) -> bool {
1133         match self.def() {
1134             Def::AssociatedConst(..) | Def::Method(..) | Def::AssociatedTy(..) => false,
1135             _ => true,
1136         }
1137     }
1138
1139     fn is_macro_def(&self) -> bool {
1140         match self.kind {
1141             NameBindingKind::Def(Def::Macro(..)) => true,
1142             _ => false,
1143         }
1144     }
1145
1146     fn descr(&self) -> &'static str {
1147         if self.is_extern_crate() { "extern crate" } else { self.def().kind_name() }
1148     }
1149 }
1150
1151 /// Interns the names of the primitive types.
1152 struct PrimitiveTypeTable {
1153     primitive_types: FxHashMap<Name, PrimTy>,
1154 }
1155
1156 impl PrimitiveTypeTable {
1157     fn new() -> PrimitiveTypeTable {
1158         let mut table = PrimitiveTypeTable { primitive_types: FxHashMap() };
1159
1160         table.intern("bool", TyBool);
1161         table.intern("char", TyChar);
1162         table.intern("f32", TyFloat(FloatTy::F32));
1163         table.intern("f64", TyFloat(FloatTy::F64));
1164         table.intern("isize", TyInt(IntTy::Is));
1165         table.intern("i8", TyInt(IntTy::I8));
1166         table.intern("i16", TyInt(IntTy::I16));
1167         table.intern("i32", TyInt(IntTy::I32));
1168         table.intern("i64", TyInt(IntTy::I64));
1169         table.intern("i128", TyInt(IntTy::I128));
1170         table.intern("str", TyStr);
1171         table.intern("usize", TyUint(UintTy::Us));
1172         table.intern("u8", TyUint(UintTy::U8));
1173         table.intern("u16", TyUint(UintTy::U16));
1174         table.intern("u32", TyUint(UintTy::U32));
1175         table.intern("u64", TyUint(UintTy::U64));
1176         table.intern("u128", TyUint(UintTy::U128));
1177         table
1178     }
1179
1180     fn intern(&mut self, string: &str, primitive_type: PrimTy) {
1181         self.primitive_types.insert(Symbol::intern(string), primitive_type);
1182     }
1183 }
1184
1185 /// The main resolver class.
1186 pub struct Resolver<'a> {
1187     session: &'a Session,
1188
1189     pub definitions: Definitions,
1190
1191     graph_root: Module<'a>,
1192
1193     prelude: Option<Module<'a>>,
1194
1195     // n.b. This is used only for better diagnostics, not name resolution itself.
1196     has_self: FxHashSet<DefId>,
1197
1198     // Names of fields of an item `DefId` accessible with dot syntax.
1199     // Used for hints during error reporting.
1200     field_names: FxHashMap<DefId, Vec<Name>>,
1201
1202     // All imports known to succeed or fail.
1203     determined_imports: Vec<&'a ImportDirective<'a>>,
1204
1205     // All non-determined imports.
1206     indeterminate_imports: Vec<&'a ImportDirective<'a>>,
1207
1208     // The module that represents the current item scope.
1209     current_module: Module<'a>,
1210
1211     // The current set of local scopes for types and values.
1212     // FIXME #4948: Reuse ribs to avoid allocation.
1213     ribs: PerNS<Vec<Rib<'a>>>,
1214
1215     // The current set of local scopes, for labels.
1216     label_ribs: Vec<Rib<'a>>,
1217
1218     // The trait that the current context can refer to.
1219     current_trait_ref: Option<(Module<'a>, TraitRef)>,
1220
1221     // The current self type if inside an impl (used for better errors).
1222     current_self_type: Option<Ty>,
1223
1224     // The idents for the primitive types.
1225     primitive_type_table: PrimitiveTypeTable,
1226
1227     def_map: DefMap,
1228     pub freevars: FreevarMap,
1229     freevars_seen: NodeMap<NodeMap<usize>>,
1230     pub export_map: ExportMap,
1231     pub trait_map: TraitMap,
1232
1233     // A map from nodes to anonymous modules.
1234     // Anonymous modules are pseudo-modules that are implicitly created around items
1235     // contained within blocks.
1236     //
1237     // For example, if we have this:
1238     //
1239     //  fn f() {
1240     //      fn g() {
1241     //          ...
1242     //      }
1243     //  }
1244     //
1245     // There will be an anonymous module created around `g` with the ID of the
1246     // entry block for `f`.
1247     block_map: NodeMap<Module<'a>>,
1248     module_map: FxHashMap<DefId, Module<'a>>,
1249     extern_module_map: FxHashMap<(DefId, bool /* MacrosOnly? */), Module<'a>>,
1250
1251     pub make_glob_map: bool,
1252     /// Maps imports to the names of items actually imported (this actually maps
1253     /// all imports, but only glob imports are actually interesting).
1254     pub glob_map: GlobMap,
1255
1256     used_imports: FxHashSet<(NodeId, Namespace)>,
1257     pub maybe_unused_trait_imports: NodeSet,
1258
1259     /// privacy errors are delayed until the end in order to deduplicate them
1260     privacy_errors: Vec<PrivacyError<'a>>,
1261     /// ambiguity errors are delayed for deduplication
1262     ambiguity_errors: Vec<AmbiguityError<'a>>,
1263     /// `use` injections are delayed for better placement and deduplication
1264     use_injections: Vec<UseError<'a>>,
1265
1266     gated_errors: FxHashSet<Span>,
1267     disallowed_shadowing: Vec<&'a LegacyBinding<'a>>,
1268
1269     arenas: &'a ResolverArenas<'a>,
1270     dummy_binding: &'a NameBinding<'a>,
1271     use_extern_macros: bool, // true if `#![feature(use_extern_macros)]`
1272
1273     crate_loader: &'a mut CrateLoader,
1274     macro_names: FxHashSet<Ident>,
1275     global_macros: FxHashMap<Name, &'a NameBinding<'a>>,
1276     lexical_macro_resolutions: Vec<(Ident, &'a Cell<LegacyScope<'a>>)>,
1277     macro_map: FxHashMap<DefId, Rc<SyntaxExtension>>,
1278     macro_defs: FxHashMap<Mark, DefId>,
1279     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
1280     macro_exports: Vec<Export>,
1281     pub whitelisted_legacy_custom_derives: Vec<Name>,
1282     pub found_unresolved_macro: bool,
1283
1284     // List of crate local macros that we need to warn about as being unused.
1285     // Right now this only includes macro_rules! macros, and macros 2.0.
1286     unused_macros: FxHashSet<DefId>,
1287
1288     // Maps the `Mark` of an expansion to its containing module or block.
1289     invocations: FxHashMap<Mark, &'a InvocationData<'a>>,
1290
1291     // Avoid duplicated errors for "name already defined".
1292     name_already_seen: FxHashMap<Name, Span>,
1293
1294     // If `#![feature(proc_macro)]` is set
1295     proc_macro_enabled: bool,
1296
1297     // A set of procedural macros imported by `#[macro_use]` that have already been warned about
1298     warned_proc_macros: FxHashSet<Name>,
1299
1300     potentially_unused_imports: Vec<&'a ImportDirective<'a>>,
1301
1302     // This table maps struct IDs into struct constructor IDs,
1303     // it's not used during normal resolution, only for better error reporting.
1304     struct_constructors: DefIdMap<(Def, ty::Visibility)>,
1305
1306     // Only used for better errors on `fn(): fn()`
1307     current_type_ascription: Vec<Span>,
1308 }
1309
1310 pub struct ResolverArenas<'a> {
1311     modules: arena::TypedArena<ModuleData<'a>>,
1312     local_modules: RefCell<Vec<Module<'a>>>,
1313     name_bindings: arena::TypedArena<NameBinding<'a>>,
1314     import_directives: arena::TypedArena<ImportDirective<'a>>,
1315     name_resolutions: arena::TypedArena<RefCell<NameResolution<'a>>>,
1316     invocation_data: arena::TypedArena<InvocationData<'a>>,
1317     legacy_bindings: arena::TypedArena<LegacyBinding<'a>>,
1318 }
1319
1320 impl<'a> ResolverArenas<'a> {
1321     fn alloc_module(&'a self, module: ModuleData<'a>) -> Module<'a> {
1322         let module = self.modules.alloc(module);
1323         if module.def_id().map(|def_id| def_id.is_local()).unwrap_or(true) {
1324             self.local_modules.borrow_mut().push(module);
1325         }
1326         module
1327     }
1328     fn local_modules(&'a self) -> ::std::cell::Ref<'a, Vec<Module<'a>>> {
1329         self.local_modules.borrow()
1330     }
1331     fn alloc_name_binding(&'a self, name_binding: NameBinding<'a>) -> &'a NameBinding<'a> {
1332         self.name_bindings.alloc(name_binding)
1333     }
1334     fn alloc_import_directive(&'a self, import_directive: ImportDirective<'a>)
1335                               -> &'a ImportDirective {
1336         self.import_directives.alloc(import_directive)
1337     }
1338     fn alloc_name_resolution(&'a self) -> &'a RefCell<NameResolution<'a>> {
1339         self.name_resolutions.alloc(Default::default())
1340     }
1341     fn alloc_invocation_data(&'a self, expansion_data: InvocationData<'a>)
1342                              -> &'a InvocationData<'a> {
1343         self.invocation_data.alloc(expansion_data)
1344     }
1345     fn alloc_legacy_binding(&'a self, binding: LegacyBinding<'a>) -> &'a LegacyBinding<'a> {
1346         self.legacy_bindings.alloc(binding)
1347     }
1348 }
1349
1350 impl<'a, 'b: 'a> ty::DefIdTree for &'a Resolver<'b> {
1351     fn parent(self, id: DefId) -> Option<DefId> {
1352         match id.krate {
1353             LOCAL_CRATE => self.definitions.def_key(id.index).parent,
1354             _ => self.session.cstore.def_key(id).parent,
1355         }.map(|index| DefId { index: index, ..id })
1356     }
1357 }
1358
1359 impl<'a> hir::lowering::Resolver for Resolver<'a> {
1360     fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool) {
1361         let namespace = if is_value { ValueNS } else { TypeNS };
1362         let hir::Path { ref segments, span, ref mut def } = *path;
1363         let path: Vec<SpannedIdent> = segments.iter()
1364             .map(|seg| respan(span, Ident::with_empty_ctxt(seg.name)))
1365             .collect();
1366         match self.resolve_path(&path, Some(namespace), true, span) {
1367             PathResult::Module(module) => *def = module.def().unwrap(),
1368             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 =>
1369                 *def = path_res.base_def(),
1370             PathResult::NonModule(..) => match self.resolve_path(&path, None, true, span) {
1371                 PathResult::Failed(span, msg, _) => {
1372                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1373                 }
1374                 _ => {}
1375             },
1376             PathResult::Indeterminate => unreachable!(),
1377             PathResult::Failed(span, msg, _) => {
1378                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1379             }
1380         }
1381     }
1382
1383     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution> {
1384         self.def_map.get(&id).cloned()
1385     }
1386
1387     fn definitions(&mut self) -> &mut Definitions {
1388         &mut self.definitions
1389     }
1390 }
1391
1392 impl<'a> Resolver<'a> {
1393     pub fn new(session: &'a Session,
1394                krate: &Crate,
1395                crate_name: &str,
1396                make_glob_map: MakeGlobMap,
1397                crate_loader: &'a mut CrateLoader,
1398                arenas: &'a ResolverArenas<'a>)
1399                -> Resolver<'a> {
1400         let root_def_id = DefId::local(CRATE_DEF_INDEX);
1401         let root_module_kind = ModuleKind::Def(Def::Mod(root_def_id), keywords::Invalid.name());
1402         let graph_root = arenas.alloc_module(ModuleData {
1403             no_implicit_prelude: attr::contains_name(&krate.attrs, "no_implicit_prelude"),
1404             ..ModuleData::new(None, root_module_kind, root_def_id, Mark::root(), krate.span)
1405         });
1406         let mut module_map = FxHashMap();
1407         module_map.insert(DefId::local(CRATE_DEF_INDEX), graph_root);
1408
1409         let mut definitions = Definitions::new();
1410         DefCollector::new(&mut definitions, Mark::root())
1411             .collect_root(crate_name, &session.local_crate_disambiguator().as_str());
1412
1413         let mut invocations = FxHashMap();
1414         invocations.insert(Mark::root(),
1415                            arenas.alloc_invocation_data(InvocationData::root(graph_root)));
1416
1417         let features = session.features.borrow();
1418
1419         let mut macro_defs = FxHashMap();
1420         macro_defs.insert(Mark::root(), root_def_id);
1421
1422         Resolver {
1423             session,
1424
1425             definitions,
1426
1427             // The outermost module has def ID 0; this is not reflected in the
1428             // AST.
1429             graph_root,
1430             prelude: None,
1431
1432             has_self: FxHashSet(),
1433             field_names: FxHashMap(),
1434
1435             determined_imports: Vec::new(),
1436             indeterminate_imports: Vec::new(),
1437
1438             current_module: graph_root,
1439             ribs: PerNS {
1440                 value_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1441                 type_ns: vec![Rib::new(ModuleRibKind(graph_root))],
1442                 macro_ns: Some(vec![Rib::new(ModuleRibKind(graph_root))]),
1443             },
1444             label_ribs: Vec::new(),
1445
1446             current_trait_ref: None,
1447             current_self_type: None,
1448
1449             primitive_type_table: PrimitiveTypeTable::new(),
1450
1451             def_map: NodeMap(),
1452             freevars: NodeMap(),
1453             freevars_seen: NodeMap(),
1454             export_map: NodeMap(),
1455             trait_map: NodeMap(),
1456             module_map,
1457             block_map: NodeMap(),
1458             extern_module_map: FxHashMap(),
1459
1460             make_glob_map: make_glob_map == MakeGlobMap::Yes,
1461             glob_map: NodeMap(),
1462
1463             used_imports: FxHashSet(),
1464             maybe_unused_trait_imports: NodeSet(),
1465
1466             privacy_errors: Vec::new(),
1467             ambiguity_errors: Vec::new(),
1468             use_injections: Vec::new(),
1469             gated_errors: FxHashSet(),
1470             disallowed_shadowing: Vec::new(),
1471
1472             arenas,
1473             dummy_binding: arenas.alloc_name_binding(NameBinding {
1474                 kind: NameBindingKind::Def(Def::Err),
1475                 expansion: Mark::root(),
1476                 span: DUMMY_SP,
1477                 vis: ty::Visibility::Public,
1478             }),
1479
1480             // The `proc_macro` and `decl_macro` features imply `use_extern_macros`
1481             use_extern_macros:
1482                 features.use_extern_macros || features.proc_macro || features.decl_macro,
1483
1484             crate_loader,
1485             macro_names: FxHashSet(),
1486             global_macros: FxHashMap(),
1487             lexical_macro_resolutions: Vec::new(),
1488             macro_map: FxHashMap(),
1489             macro_exports: Vec::new(),
1490             invocations,
1491             macro_defs,
1492             local_macro_def_scopes: FxHashMap(),
1493             name_already_seen: FxHashMap(),
1494             whitelisted_legacy_custom_derives: Vec::new(),
1495             proc_macro_enabled: features.proc_macro,
1496             warned_proc_macros: FxHashSet(),
1497             potentially_unused_imports: Vec::new(),
1498             struct_constructors: DefIdMap(),
1499             found_unresolved_macro: false,
1500             unused_macros: FxHashSet(),
1501             current_type_ascription: Vec::new(),
1502         }
1503     }
1504
1505     pub fn arenas() -> ResolverArenas<'a> {
1506         ResolverArenas {
1507             modules: arena::TypedArena::new(),
1508             local_modules: RefCell::new(Vec::new()),
1509             name_bindings: arena::TypedArena::new(),
1510             import_directives: arena::TypedArena::new(),
1511             name_resolutions: arena::TypedArena::new(),
1512             invocation_data: arena::TypedArena::new(),
1513             legacy_bindings: arena::TypedArena::new(),
1514         }
1515     }
1516
1517     fn per_ns<T, F: FnMut(&mut Self, Namespace) -> T>(&mut self, mut f: F) -> PerNS<T> {
1518         PerNS {
1519             type_ns: f(self, TypeNS),
1520             value_ns: f(self, ValueNS),
1521             macro_ns: match self.use_extern_macros {
1522                 true => Some(f(self, MacroNS)),
1523                 false => None,
1524             },
1525         }
1526     }
1527
1528     /// Entry point to crate resolution.
1529     pub fn resolve_crate(&mut self, krate: &Crate) {
1530         ImportResolver { resolver: self }.finalize_imports();
1531         self.current_module = self.graph_root;
1532         self.finalize_current_module_macro_resolutions();
1533
1534         visit::walk_crate(self, krate);
1535
1536         check_unused::check_crate(self, krate);
1537         self.report_errors(krate);
1538         self.crate_loader.postprocess(krate);
1539     }
1540
1541     fn new_module(
1542         &self,
1543         parent: Module<'a>,
1544         kind: ModuleKind,
1545         normal_ancestor_id: DefId,
1546         expansion: Mark,
1547         span: Span,
1548     ) -> Module<'a> {
1549         let module = ModuleData::new(Some(parent), kind, normal_ancestor_id, expansion, span);
1550         self.arenas.alloc_module(module)
1551     }
1552
1553     fn record_use(&mut self, ident: Ident, ns: Namespace, binding: &'a NameBinding<'a>, span: Span)
1554                   -> bool /* true if an error was reported */ {
1555         match binding.kind {
1556             NameBindingKind::Import { directive, binding, ref used, legacy_self_import }
1557                     if !used.get() => {
1558                 used.set(true);
1559                 directive.used.set(true);
1560                 if legacy_self_import {
1561                     self.warn_legacy_self_import(directive);
1562                     return false;
1563                 }
1564                 self.used_imports.insert((directive.id, ns));
1565                 self.add_to_glob_map(directive.id, ident);
1566                 self.record_use(ident, ns, binding, span)
1567             }
1568             NameBindingKind::Import { .. } => false,
1569             NameBindingKind::Ambiguity { b1, b2, legacy } => {
1570                 self.ambiguity_errors.push(AmbiguityError {
1571                     span: span, name: ident.name, lexical: false, b1: b1, b2: b2, legacy,
1572                 });
1573                 if legacy {
1574                     self.record_use(ident, ns, b1, span);
1575                 }
1576                 !legacy
1577             }
1578             _ => false
1579         }
1580     }
1581
1582     fn add_to_glob_map(&mut self, id: NodeId, ident: Ident) {
1583         if self.make_glob_map {
1584             self.glob_map.entry(id).or_insert_with(FxHashSet).insert(ident.name);
1585         }
1586     }
1587
1588     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
1589     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
1590     /// `ident` in the first scope that defines it (or None if no scopes define it).
1591     ///
1592     /// A block's items are above its local variables in the scope hierarchy, regardless of where
1593     /// the items are defined in the block. For example,
1594     /// ```rust
1595     /// fn f() {
1596     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
1597     ///    let g = || {};
1598     ///    fn g() {}
1599     ///    g(); // This resolves to the local variable `g` since it shadows the item.
1600     /// }
1601     /// ```
1602     ///
1603     /// Invariant: This must only be called during main resolution, not during
1604     /// import resolution.
1605     fn resolve_ident_in_lexical_scope(&mut self,
1606                                       mut ident: Ident,
1607                                       ns: Namespace,
1608                                       record_used: bool,
1609                                       path_span: Span)
1610                                       -> Option<LexicalScopeBinding<'a>> {
1611         if ns == TypeNS {
1612             ident.ctxt = if ident.name == keywords::SelfType.name() {
1613                 SyntaxContext::empty() // FIXME(jseyfried) improve `Self` hygiene
1614             } else {
1615                 ident.ctxt.modern()
1616             }
1617         }
1618
1619         // Walk backwards up the ribs in scope.
1620         let mut module = self.graph_root;
1621         for i in (0 .. self.ribs[ns].len()).rev() {
1622             if let Some(def) = self.ribs[ns][i].bindings.get(&ident).cloned() {
1623                 // The ident resolves to a type parameter or local variable.
1624                 return Some(LexicalScopeBinding::Def(
1625                     self.adjust_local_def(ns, i, def, record_used, path_span)
1626                 ));
1627             }
1628
1629             module = match self.ribs[ns][i].kind {
1630                 ModuleRibKind(module) => module,
1631                 MacroDefinition(def) if def == self.macro_defs[&ident.ctxt.outer()] => {
1632                     // If an invocation of this macro created `ident`, give up on `ident`
1633                     // and switch to `ident`'s source from the macro definition.
1634                     ident.ctxt.remove_mark();
1635                     continue
1636                 }
1637                 _ => continue,
1638             };
1639
1640             let item = self.resolve_ident_in_module_unadjusted(
1641                 module, ident, ns, false, record_used, path_span,
1642             );
1643             if let Ok(binding) = item {
1644                 // The ident resolves to an item.
1645                 return Some(LexicalScopeBinding::Item(binding));
1646             }
1647
1648             match module.kind {
1649                 ModuleKind::Block(..) => {}, // We can see through blocks
1650                 _ => break,
1651             }
1652         }
1653
1654         ident.ctxt = ident.ctxt.modern();
1655         loop {
1656             module = unwrap_or!(self.hygienic_lexical_parent(module, &mut ident.ctxt), break);
1657             let orig_current_module = self.current_module;
1658             self.current_module = module; // Lexical resolutions can never be a privacy error.
1659             let result = self.resolve_ident_in_module_unadjusted(
1660                 module, ident, ns, false, record_used, path_span,
1661             );
1662             self.current_module = orig_current_module;
1663
1664             match result {
1665                 Ok(binding) => return Some(LexicalScopeBinding::Item(binding)),
1666                 Err(Undetermined) => return None,
1667                 Err(Determined) => {}
1668             }
1669         }
1670
1671         match self.prelude {
1672             Some(prelude) if !module.no_implicit_prelude => {
1673                 self.resolve_ident_in_module_unadjusted(prelude, ident, ns, false, false, path_span)
1674                     .ok().map(LexicalScopeBinding::Item)
1675             }
1676             _ => None,
1677         }
1678     }
1679
1680     fn hygienic_lexical_parent(&mut self, mut module: Module<'a>, ctxt: &mut SyntaxContext)
1681                                -> Option<Module<'a>> {
1682         if !module.expansion.is_descendant_of(ctxt.outer()) {
1683             return Some(self.macro_def_scope(ctxt.remove_mark()));
1684         }
1685
1686         if let ModuleKind::Block(..) = module.kind {
1687             return Some(module.parent.unwrap());
1688         }
1689
1690         let mut module_expansion = module.expansion.modern(); // for backward compatibility
1691         while let Some(parent) = module.parent {
1692             let parent_expansion = parent.expansion.modern();
1693             if module_expansion.is_descendant_of(parent_expansion) &&
1694                parent_expansion != module_expansion {
1695                 return if parent_expansion.is_descendant_of(ctxt.outer()) {
1696                     Some(parent)
1697                 } else {
1698                     None
1699                 };
1700             }
1701             module = parent;
1702             module_expansion = parent_expansion;
1703         }
1704
1705         None
1706     }
1707
1708     fn resolve_ident_in_module(&mut self,
1709                                module: Module<'a>,
1710                                mut ident: Ident,
1711                                ns: Namespace,
1712                                ignore_unresolved_invocations: bool,
1713                                record_used: bool,
1714                                span: Span)
1715                                -> Result<&'a NameBinding<'a>, Determinacy> {
1716         ident.ctxt = ident.ctxt.modern();
1717         let orig_current_module = self.current_module;
1718         if let Some(def) = ident.ctxt.adjust(module.expansion) {
1719             self.current_module = self.macro_def_scope(def);
1720         }
1721         let result = self.resolve_ident_in_module_unadjusted(
1722             module, ident, ns, ignore_unresolved_invocations, record_used, span,
1723         );
1724         self.current_module = orig_current_module;
1725         result
1726     }
1727
1728     fn resolve_crate_root(&mut self, mut ctxt: SyntaxContext) -> Module<'a> {
1729         let module = match ctxt.adjust(Mark::root()) {
1730             Some(def) => self.macro_def_scope(def),
1731             None => return self.graph_root,
1732         };
1733         self.get_module(DefId { index: CRATE_DEF_INDEX, ..module.normal_ancestor_id })
1734     }
1735
1736     fn resolve_self(&mut self, ctxt: &mut SyntaxContext, module: Module<'a>) -> Module<'a> {
1737         let mut module = self.get_module(module.normal_ancestor_id);
1738         while module.span.ctxt.modern() != *ctxt {
1739             let parent = module.parent.unwrap_or_else(|| self.macro_def_scope(ctxt.remove_mark()));
1740             module = self.get_module(parent.normal_ancestor_id);
1741         }
1742         module
1743     }
1744
1745     // AST resolution
1746     //
1747     // We maintain a list of value ribs and type ribs.
1748     //
1749     // Simultaneously, we keep track of the current position in the module
1750     // graph in the `current_module` pointer. When we go to resolve a name in
1751     // the value or type namespaces, we first look through all the ribs and
1752     // then query the module graph. When we resolve a name in the module
1753     // namespace, we can skip all the ribs (since nested modules are not
1754     // allowed within blocks in Rust) and jump straight to the current module
1755     // graph node.
1756     //
1757     // Named implementations are handled separately. When we find a method
1758     // call, we consult the module node to find all of the implementations in
1759     // scope. This information is lazily cached in the module node. We then
1760     // generate a fake "implementation scope" containing all the
1761     // implementations thus found, for compatibility with old resolve pass.
1762
1763     fn with_scope<F>(&mut self, id: NodeId, f: F)
1764         where F: FnOnce(&mut Resolver)
1765     {
1766         let id = self.definitions.local_def_id(id);
1767         let module = self.module_map.get(&id).cloned(); // clones a reference
1768         if let Some(module) = module {
1769             // Move down in the graph.
1770             let orig_module = replace(&mut self.current_module, module);
1771             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
1772             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
1773
1774             self.finalize_current_module_macro_resolutions();
1775             f(self);
1776
1777             self.current_module = orig_module;
1778             self.ribs[ValueNS].pop();
1779             self.ribs[TypeNS].pop();
1780         } else {
1781             f(self);
1782         }
1783     }
1784
1785     /// Searches the current set of local scopes for labels.
1786     /// Stops after meeting a closure.
1787     fn search_label(&self, mut ident: Ident) -> Option<Def> {
1788         for rib in self.label_ribs.iter().rev() {
1789             match rib.kind {
1790                 NormalRibKind => {}
1791                 // If an invocation of this macro created `ident`, give up on `ident`
1792                 // and switch to `ident`'s source from the macro definition.
1793                 MacroDefinition(def) => {
1794                     if def == self.macro_defs[&ident.ctxt.outer()] {
1795                         ident.ctxt.remove_mark();
1796                     }
1797                 }
1798                 _ => {
1799                     // Do not resolve labels across function boundary
1800                     return None;
1801                 }
1802             }
1803             let result = rib.bindings.get(&ident).cloned();
1804             if result.is_some() {
1805                 return result;
1806             }
1807         }
1808         None
1809     }
1810
1811     fn resolve_item(&mut self, item: &Item) {
1812         let name = item.ident.name;
1813
1814         debug!("(resolving item) resolving {}", name);
1815
1816         self.check_proc_macro_attrs(&item.attrs);
1817
1818         match item.node {
1819             ItemKind::Enum(_, ref generics) |
1820             ItemKind::Ty(_, ref generics) |
1821             ItemKind::Struct(_, ref generics) |
1822             ItemKind::Union(_, ref generics) |
1823             ItemKind::Fn(.., ref generics, _) => {
1824                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind),
1825                                              |this| visit::walk_item(this, item));
1826             }
1827
1828             ItemKind::DefaultImpl(_, ref trait_ref) => {
1829                 self.with_optional_trait_ref(Some(trait_ref), |this, _| {
1830                     // Resolve type arguments in trait path
1831                     visit::walk_trait_ref(this, trait_ref);
1832                 });
1833             }
1834             ItemKind::Impl(.., ref generics, ref opt_trait_ref, ref self_type, ref impl_items) =>
1835                 self.resolve_implementation(generics,
1836                                             opt_trait_ref,
1837                                             &self_type,
1838                                             item.id,
1839                                             impl_items),
1840
1841             ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
1842                 // Create a new rib for the trait-wide type parameters.
1843                 self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
1844                     let local_def_id = this.definitions.local_def_id(item.id);
1845                     this.with_self_rib(Def::SelfTy(Some(local_def_id), None), |this| {
1846                         this.visit_generics(generics);
1847                         walk_list!(this, visit_ty_param_bound, bounds);
1848
1849                         for trait_item in trait_items {
1850                             this.check_proc_macro_attrs(&trait_item.attrs);
1851
1852                             match trait_item.node {
1853                                 TraitItemKind::Const(ref ty, ref default) => {
1854                                     this.visit_ty(ty);
1855
1856                                     // Only impose the restrictions of
1857                                     // ConstRibKind for an actual constant
1858                                     // expression in a provided default.
1859                                     if let Some(ref expr) = *default{
1860                                         this.with_constant_rib(|this| {
1861                                             this.visit_expr(expr);
1862                                         });
1863                                     }
1864                                 }
1865                                 TraitItemKind::Method(ref sig, _) => {
1866                                     let type_parameters =
1867                                         HasTypeParameters(&sig.generics,
1868                                                           MethodRibKind(!sig.decl.has_self()));
1869                                     this.with_type_parameter_rib(type_parameters, |this| {
1870                                         visit::walk_trait_item(this, trait_item)
1871                                     });
1872                                 }
1873                                 TraitItemKind::Type(..) => {
1874                                     this.with_type_parameter_rib(NoTypeParameters, |this| {
1875                                         visit::walk_trait_item(this, trait_item)
1876                                     });
1877                                 }
1878                                 TraitItemKind::Macro(_) => panic!("unexpanded macro in resolve!"),
1879                             };
1880                         }
1881                     });
1882                 });
1883             }
1884
1885             ItemKind::Mod(_) | ItemKind::ForeignMod(_) => {
1886                 self.with_scope(item.id, |this| {
1887                     visit::walk_item(this, item);
1888                 });
1889             }
1890
1891             ItemKind::Static(ref ty, _, ref expr) |
1892             ItemKind::Const(ref ty, ref expr) => {
1893                 self.with_item_rib(|this| {
1894                     this.visit_ty(ty);
1895                     this.with_constant_rib(|this| {
1896                         this.visit_expr(expr);
1897                     });
1898                 });
1899             }
1900
1901             ItemKind::Use(ref view_path) => {
1902                 match view_path.node {
1903                     ast::ViewPathList(ref prefix, ref items) if items.is_empty() => {
1904                         // Resolve prefix of an import with empty braces (issue #28388).
1905                         self.smart_resolve_path(item.id, None, prefix, PathSource::ImportPrefix);
1906                     }
1907                     _ => {}
1908                 }
1909             }
1910
1911             ItemKind::ExternCrate(_) | ItemKind::MacroDef(..) | ItemKind::GlobalAsm(_)=> {
1912                 // do nothing, these are just around to be encoded
1913             }
1914
1915             ItemKind::Mac(_) => panic!("unexpanded macro in resolve!"),
1916         }
1917     }
1918
1919     fn with_type_parameter_rib<'b, F>(&'b mut self, type_parameters: TypeParameters<'a, 'b>, f: F)
1920         where F: FnOnce(&mut Resolver)
1921     {
1922         match type_parameters {
1923             HasTypeParameters(generics, rib_kind) => {
1924                 let mut function_type_rib = Rib::new(rib_kind);
1925                 let mut seen_bindings = FxHashMap();
1926                 for type_parameter in &generics.ty_params {
1927                     let ident = type_parameter.ident.modern();
1928                     debug!("with_type_parameter_rib: {}", type_parameter.id);
1929
1930                     if seen_bindings.contains_key(&ident) {
1931                         let span = seen_bindings.get(&ident).unwrap();
1932                         let err =
1933                             ResolutionError::NameAlreadyUsedInTypeParameterList(ident.name, span);
1934                         resolve_error(self, type_parameter.span, err);
1935                     }
1936                     seen_bindings.entry(ident).or_insert(type_parameter.span);
1937
1938                     // plain insert (no renaming)
1939                     let def_id = self.definitions.local_def_id(type_parameter.id);
1940                     let def = Def::TyParam(def_id);
1941                     function_type_rib.bindings.insert(ident, def);
1942                     self.record_def(type_parameter.id, PathResolution::new(def));
1943                 }
1944                 self.ribs[TypeNS].push(function_type_rib);
1945             }
1946
1947             NoTypeParameters => {
1948                 // Nothing to do.
1949             }
1950         }
1951
1952         f(self);
1953
1954         if let HasTypeParameters(..) = type_parameters {
1955             self.ribs[TypeNS].pop();
1956         }
1957     }
1958
1959     fn with_label_rib<F>(&mut self, f: F)
1960         where F: FnOnce(&mut Resolver)
1961     {
1962         self.label_ribs.push(Rib::new(NormalRibKind));
1963         f(self);
1964         self.label_ribs.pop();
1965     }
1966
1967     fn with_item_rib<F>(&mut self, f: F)
1968         where F: FnOnce(&mut Resolver)
1969     {
1970         self.ribs[ValueNS].push(Rib::new(ItemRibKind));
1971         self.ribs[TypeNS].push(Rib::new(ItemRibKind));
1972         f(self);
1973         self.ribs[TypeNS].pop();
1974         self.ribs[ValueNS].pop();
1975     }
1976
1977     fn with_constant_rib<F>(&mut self, f: F)
1978         where F: FnOnce(&mut Resolver)
1979     {
1980         self.ribs[ValueNS].push(Rib::new(ConstantItemRibKind));
1981         f(self);
1982         self.ribs[ValueNS].pop();
1983     }
1984
1985     fn with_current_self_type<T, F>(&mut self, self_type: &Ty, f: F) -> T
1986         where F: FnOnce(&mut Resolver) -> T
1987     {
1988         // Handle nested impls (inside fn bodies)
1989         let previous_value = replace(&mut self.current_self_type, Some(self_type.clone()));
1990         let result = f(self);
1991         self.current_self_type = previous_value;
1992         result
1993     }
1994
1995     fn with_optional_trait_ref<T, F>(&mut self, opt_trait_ref: Option<&TraitRef>, f: F) -> T
1996         where F: FnOnce(&mut Resolver, Option<DefId>) -> T
1997     {
1998         let mut new_val = None;
1999         let mut new_id = None;
2000         if let Some(trait_ref) = opt_trait_ref {
2001             let path: Vec<_> = trait_ref.path.segments.iter()
2002                 .map(|seg| respan(seg.span, seg.identifier))
2003                 .collect();
2004             let def = self.smart_resolve_path_fragment(trait_ref.ref_id,
2005                                                        None,
2006                                                        &path,
2007                                                        trait_ref.path.span,
2008                                                        trait_ref.path.segments.last().unwrap().span,
2009                                                        PathSource::Trait)
2010                 .base_def();
2011             if def != Def::Err {
2012                 new_id = Some(def.def_id());
2013                 let span = trait_ref.path.span;
2014                 if let PathResult::Module(module) = self.resolve_path(&path, None, false, span) {
2015                     new_val = Some((module, trait_ref.clone()));
2016                 }
2017             }
2018         }
2019         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
2020         let result = f(self, new_id);
2021         self.current_trait_ref = original_trait_ref;
2022         result
2023     }
2024
2025     fn with_self_rib<F>(&mut self, self_def: Def, f: F)
2026         where F: FnOnce(&mut Resolver)
2027     {
2028         let mut self_type_rib = Rib::new(NormalRibKind);
2029
2030         // plain insert (no renaming, types are not currently hygienic....)
2031         self_type_rib.bindings.insert(keywords::SelfType.ident(), self_def);
2032         self.ribs[TypeNS].push(self_type_rib);
2033         f(self);
2034         self.ribs[TypeNS].pop();
2035     }
2036
2037     fn resolve_implementation(&mut self,
2038                               generics: &Generics,
2039                               opt_trait_reference: &Option<TraitRef>,
2040                               self_type: &Ty,
2041                               item_id: NodeId,
2042                               impl_items: &[ImplItem]) {
2043         // If applicable, create a rib for the type parameters.
2044         self.with_type_parameter_rib(HasTypeParameters(generics, ItemRibKind), |this| {
2045             // Dummy self type for better errors if `Self` is used in the trait path.
2046             this.with_self_rib(Def::SelfTy(None, None), |this| {
2047                 // Resolve the trait reference, if necessary.
2048                 this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
2049                     let item_def_id = this.definitions.local_def_id(item_id);
2050                     this.with_self_rib(Def::SelfTy(trait_id, Some(item_def_id)), |this| {
2051                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
2052                             // Resolve type arguments in trait path
2053                             visit::walk_trait_ref(this, trait_ref);
2054                         }
2055                         // Resolve the self type.
2056                         this.visit_ty(self_type);
2057                         // Resolve the type parameters.
2058                         this.visit_generics(generics);
2059                         this.with_current_self_type(self_type, |this| {
2060                             for impl_item in impl_items {
2061                                 this.check_proc_macro_attrs(&impl_item.attrs);
2062                                 this.resolve_visibility(&impl_item.vis);
2063                                 match impl_item.node {
2064                                     ImplItemKind::Const(..) => {
2065                                         // If this is a trait impl, ensure the const
2066                                         // exists in trait
2067                                         this.check_trait_item(impl_item.ident,
2068                                                             ValueNS,
2069                                                             impl_item.span,
2070                                             |n, s| ResolutionError::ConstNotMemberOfTrait(n, s));
2071                                         visit::walk_impl_item(this, impl_item);
2072                                     }
2073                                     ImplItemKind::Method(ref sig, _) => {
2074                                         // If this is a trait impl, ensure the method
2075                                         // exists in trait
2076                                         this.check_trait_item(impl_item.ident,
2077                                                             ValueNS,
2078                                                             impl_item.span,
2079                                             |n, s| ResolutionError::MethodNotMemberOfTrait(n, s));
2080
2081                                         // We also need a new scope for the method-
2082                                         // specific type parameters.
2083                                         let type_parameters =
2084                                             HasTypeParameters(&sig.generics,
2085                                                             MethodRibKind(!sig.decl.has_self()));
2086                                         this.with_type_parameter_rib(type_parameters, |this| {
2087                                             visit::walk_impl_item(this, impl_item);
2088                                         });
2089                                     }
2090                                     ImplItemKind::Type(ref ty) => {
2091                                         // If this is a trait impl, ensure the type
2092                                         // exists in trait
2093                                         this.check_trait_item(impl_item.ident,
2094                                                             TypeNS,
2095                                                             impl_item.span,
2096                                             |n, s| ResolutionError::TypeNotMemberOfTrait(n, s));
2097
2098                                         this.visit_ty(ty);
2099                                     }
2100                                     ImplItemKind::Macro(_) =>
2101                                         panic!("unexpanded macro in resolve!"),
2102                                 }
2103                             }
2104                         });
2105                     });
2106                 });
2107             });
2108         });
2109     }
2110
2111     fn check_trait_item<F>(&mut self, ident: Ident, ns: Namespace, span: Span, err: F)
2112         where F: FnOnce(Name, &str) -> ResolutionError
2113     {
2114         // If there is a TraitRef in scope for an impl, then the method must be in the
2115         // trait.
2116         if let Some((module, _)) = self.current_trait_ref {
2117             if self.resolve_ident_in_module(module, ident, ns, false, false, span).is_err() {
2118                 let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2119                 resolve_error(self, span, err(ident.name, &path_names_to_string(path)));
2120             }
2121         }
2122     }
2123
2124     fn resolve_local(&mut self, local: &Local) {
2125         // Resolve the type.
2126         walk_list!(self, visit_ty, &local.ty);
2127
2128         // Resolve the initializer.
2129         walk_list!(self, visit_expr, &local.init);
2130
2131         // Resolve the pattern.
2132         self.resolve_pattern(&local.pat, PatternSource::Let, &mut FxHashMap());
2133     }
2134
2135     // build a map from pattern identifiers to binding-info's.
2136     // this is done hygienically. This could arise for a macro
2137     // that expands into an or-pattern where one 'x' was from the
2138     // user and one 'x' came from the macro.
2139     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2140         let mut binding_map = FxHashMap();
2141
2142         pat.walk(&mut |pat| {
2143             if let PatKind::Ident(binding_mode, ident, ref sub_pat) = pat.node {
2144                 if sub_pat.is_some() || match self.def_map.get(&pat.id).map(|res| res.base_def()) {
2145                     Some(Def::Local(..)) => true,
2146                     _ => false,
2147                 } {
2148                     let binding_info = BindingInfo { span: ident.span, binding_mode: binding_mode };
2149                     binding_map.insert(ident.node, binding_info);
2150                 }
2151             }
2152             true
2153         });
2154
2155         binding_map
2156     }
2157
2158     // check that all of the arms in an or-pattern have exactly the
2159     // same set of bindings, with the same binding modes for each.
2160     fn check_consistent_bindings(&mut self, arm: &Arm) {
2161         if arm.pats.is_empty() {
2162             return;
2163         }
2164
2165         let mut missing_vars = FxHashMap();
2166         let mut inconsistent_vars = FxHashMap();
2167         for (i, p) in arm.pats.iter().enumerate() {
2168             let map_i = self.binding_mode_map(&p);
2169
2170             for (j, q) in arm.pats.iter().enumerate() {
2171                 if i == j {
2172                     continue;
2173                 }
2174
2175                 let map_j = self.binding_mode_map(&q);
2176                 for (&key, &binding_i) in &map_i {
2177                     if map_j.len() == 0 {                   // Account for missing bindings when
2178                         let binding_error = missing_vars    // map_j has none.
2179                             .entry(key.name)
2180                             .or_insert(BindingError {
2181                                 name: key.name,
2182                                 origin: BTreeSet::new(),
2183                                 target: BTreeSet::new(),
2184                             });
2185                         binding_error.origin.insert(binding_i.span);
2186                         binding_error.target.insert(q.span);
2187                     }
2188                     for (&key_j, &binding_j) in &map_j {
2189                         match map_i.get(&key_j) {
2190                             None => {  // missing binding
2191                                 let binding_error = missing_vars
2192                                     .entry(key_j.name)
2193                                     .or_insert(BindingError {
2194                                         name: key_j.name,
2195                                         origin: BTreeSet::new(),
2196                                         target: BTreeSet::new(),
2197                                     });
2198                                 binding_error.origin.insert(binding_j.span);
2199                                 binding_error.target.insert(p.span);
2200                             }
2201                             Some(binding_i) => {  // check consistent binding
2202                                 if binding_i.binding_mode != binding_j.binding_mode {
2203                                     inconsistent_vars
2204                                         .entry(key.name)
2205                                         .or_insert((binding_j.span, binding_i.span));
2206                                 }
2207                             }
2208                         }
2209                     }
2210                 }
2211             }
2212         }
2213         let mut missing_vars = missing_vars.iter().collect::<Vec<_>>();
2214         missing_vars.sort();
2215         for (_, v) in missing_vars {
2216             resolve_error(self,
2217                           *v.origin.iter().next().unwrap(),
2218                           ResolutionError::VariableNotBoundInPattern(v));
2219         }
2220         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2221         inconsistent_vars.sort();
2222         for (name, v) in inconsistent_vars {
2223             resolve_error(self, v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2224         }
2225     }
2226
2227     fn resolve_arm(&mut self, arm: &Arm) {
2228         self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2229
2230         let mut bindings_list = FxHashMap();
2231         for pattern in &arm.pats {
2232             self.resolve_pattern(&pattern, PatternSource::Match, &mut bindings_list);
2233         }
2234
2235         // This has to happen *after* we determine which
2236         // pat_idents are variants
2237         self.check_consistent_bindings(arm);
2238
2239         walk_list!(self, visit_expr, &arm.guard);
2240         self.visit_expr(&arm.body);
2241
2242         self.ribs[ValueNS].pop();
2243     }
2244
2245     fn resolve_block(&mut self, block: &Block) {
2246         debug!("(resolving block) entering block");
2247         // Move down in the graph, if there's an anonymous module rooted here.
2248         let orig_module = self.current_module;
2249         let anonymous_module = self.block_map.get(&block.id).cloned(); // clones a reference
2250
2251         let mut num_macro_definition_ribs = 0;
2252         if let Some(anonymous_module) = anonymous_module {
2253             debug!("(resolving block) found anonymous module, moving down");
2254             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2255             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
2256             self.current_module = anonymous_module;
2257             self.finalize_current_module_macro_resolutions();
2258         } else {
2259             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
2260         }
2261
2262         // Descend into the block.
2263         for stmt in &block.stmts {
2264             if let ast::StmtKind::Item(ref item) = stmt.node {
2265                 if let ast::ItemKind::MacroDef(..) = item.node {
2266                     num_macro_definition_ribs += 1;
2267                     let def = self.definitions.local_def_id(item.id);
2268                     self.ribs[ValueNS].push(Rib::new(MacroDefinition(def)));
2269                     self.label_ribs.push(Rib::new(MacroDefinition(def)));
2270                 }
2271             }
2272
2273             self.visit_stmt(stmt);
2274         }
2275
2276         // Move back up.
2277         self.current_module = orig_module;
2278         for _ in 0 .. num_macro_definition_ribs {
2279             self.ribs[ValueNS].pop();
2280             self.label_ribs.pop();
2281         }
2282         self.ribs[ValueNS].pop();
2283         if let Some(_) = anonymous_module {
2284             self.ribs[TypeNS].pop();
2285         }
2286         debug!("(resolving block) leaving block");
2287     }
2288
2289     fn fresh_binding(&mut self,
2290                      ident: &SpannedIdent,
2291                      pat_id: NodeId,
2292                      outer_pat_id: NodeId,
2293                      pat_src: PatternSource,
2294                      bindings: &mut FxHashMap<Ident, NodeId>)
2295                      -> PathResolution {
2296         // Add the binding to the local ribs, if it
2297         // doesn't already exist in the bindings map. (We
2298         // must not add it if it's in the bindings map
2299         // because that breaks the assumptions later
2300         // passes make about or-patterns.)
2301         let mut def = Def::Local(self.definitions.local_def_id(pat_id));
2302         match bindings.get(&ident.node).cloned() {
2303             Some(id) if id == outer_pat_id => {
2304                 // `Variant(a, a)`, error
2305                 resolve_error(
2306                     self,
2307                     ident.span,
2308                     ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(
2309                         &ident.node.name.as_str())
2310                 );
2311             }
2312             Some(..) if pat_src == PatternSource::FnParam => {
2313                 // `fn f(a: u8, a: u8)`, error
2314                 resolve_error(
2315                     self,
2316                     ident.span,
2317                     ResolutionError::IdentifierBoundMoreThanOnceInParameterList(
2318                         &ident.node.name.as_str())
2319                 );
2320             }
2321             Some(..) if pat_src == PatternSource::Match => {
2322                 // `Variant1(a) | Variant2(a)`, ok
2323                 // Reuse definition from the first `a`.
2324                 def = self.ribs[ValueNS].last_mut().unwrap().bindings[&ident.node];
2325             }
2326             Some(..) => {
2327                 span_bug!(ident.span, "two bindings with the same name from \
2328                                        unexpected pattern source {:?}", pat_src);
2329             }
2330             None => {
2331                 // A completely fresh binding, add to the lists if it's valid.
2332                 if ident.node.name != keywords::Invalid.name() {
2333                     bindings.insert(ident.node, outer_pat_id);
2334                     self.ribs[ValueNS].last_mut().unwrap().bindings.insert(ident.node, def);
2335                 }
2336             }
2337         }
2338
2339         PathResolution::new(def)
2340     }
2341
2342     fn resolve_pattern(&mut self,
2343                        pat: &Pat,
2344                        pat_src: PatternSource,
2345                        // Maps idents to the node ID for the
2346                        // outermost pattern that binds them.
2347                        bindings: &mut FxHashMap<Ident, NodeId>) {
2348         // Visit all direct subpatterns of this pattern.
2349         let outer_pat_id = pat.id;
2350         pat.walk(&mut |pat| {
2351             match pat.node {
2352                 PatKind::Ident(bmode, ref ident, ref opt_pat) => {
2353                     // First try to resolve the identifier as some existing
2354                     // entity, then fall back to a fresh binding.
2355                     let binding = self.resolve_ident_in_lexical_scope(ident.node, ValueNS,
2356                                                                       false, pat.span)
2357                                       .and_then(LexicalScopeBinding::item);
2358                     let resolution = binding.map(NameBinding::def).and_then(|def| {
2359                         let ivmode = BindingMode::ByValue(Mutability::Immutable);
2360                         let always_binding = !pat_src.is_refutable() || opt_pat.is_some() ||
2361                                              bmode != ivmode;
2362                         match def {
2363                             Def::StructCtor(_, CtorKind::Const) |
2364                             Def::VariantCtor(_, CtorKind::Const) |
2365                             Def::Const(..) if !always_binding => {
2366                                 // A unit struct/variant or constant pattern.
2367                                 self.record_use(ident.node, ValueNS, binding.unwrap(), ident.span);
2368                                 Some(PathResolution::new(def))
2369                             }
2370                             Def::StructCtor(..) | Def::VariantCtor(..) |
2371                             Def::Const(..) | Def::Static(..) => {
2372                                 // A fresh binding that shadows something unacceptable.
2373                                 resolve_error(
2374                                     self,
2375                                     ident.span,
2376                                     ResolutionError::BindingShadowsSomethingUnacceptable(
2377                                         pat_src.descr(), ident.node.name, binding.unwrap())
2378                                 );
2379                                 None
2380                             }
2381                             Def::Local(..) | Def::Upvar(..) | Def::Fn(..) | Def::Err => {
2382                                 // These entities are explicitly allowed
2383                                 // to be shadowed by fresh bindings.
2384                                 None
2385                             }
2386                             def => {
2387                                 span_bug!(ident.span, "unexpected definition for an \
2388                                                        identifier in pattern: {:?}", def);
2389                             }
2390                         }
2391                     }).unwrap_or_else(|| {
2392                         self.fresh_binding(ident, pat.id, outer_pat_id, pat_src, bindings)
2393                     });
2394
2395                     self.record_def(pat.id, resolution);
2396                 }
2397
2398                 PatKind::TupleStruct(ref path, ..) => {
2399                     self.smart_resolve_path(pat.id, None, path, PathSource::TupleStruct);
2400                 }
2401
2402                 PatKind::Path(ref qself, ref path) => {
2403                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2404                 }
2405
2406                 PatKind::Struct(ref path, ..) => {
2407                     self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
2408                 }
2409
2410                 _ => {}
2411             }
2412             true
2413         });
2414
2415         visit::walk_pat(self, pat);
2416     }
2417
2418     // High-level and context dependent path resolution routine.
2419     // Resolves the path and records the resolution into definition map.
2420     // If resolution fails tries several techniques to find likely
2421     // resolution candidates, suggest imports or other help, and report
2422     // errors in user friendly way.
2423     fn smart_resolve_path(&mut self,
2424                           id: NodeId,
2425                           qself: Option<&QSelf>,
2426                           path: &Path,
2427                           source: PathSource)
2428                           -> PathResolution {
2429         let segments = &path.segments.iter()
2430             .map(|seg| respan(seg.span, seg.identifier))
2431             .collect::<Vec<_>>();
2432         let ident_span = path.segments.last().map_or(path.span, |seg| seg.span);
2433         self.smart_resolve_path_fragment(id, qself, segments, path.span, ident_span, source)
2434     }
2435
2436     fn smart_resolve_path_fragment(&mut self,
2437                                    id: NodeId,
2438                                    qself: Option<&QSelf>,
2439                                    path: &[SpannedIdent],
2440                                    span: Span,
2441                                    ident_span: Span,
2442                                    source: PathSource)
2443                                    -> PathResolution {
2444         let ns = source.namespace();
2445         let is_expected = &|def| source.is_expected(def);
2446         let is_enum_variant = &|def| if let Def::Variant(..) = def { true } else { false };
2447
2448         // Base error is amended with one short label and possibly some longer helps/notes.
2449         let report_errors = |this: &mut Self, def: Option<Def>| {
2450             // Make the base error.
2451             let expected = source.descr_expected();
2452             let path_str = names_to_string(path);
2453             let code = source.error_code(def.is_some());
2454             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
2455                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
2456                  format!("not a {}", expected), span)
2457             } else {
2458                 let item_str = path[path.len() - 1].node;
2459                 let item_span = path[path.len() - 1].span;
2460                 let (mod_prefix, mod_str) = if path.len() == 1 {
2461                     (format!(""), format!("this scope"))
2462                 } else if path.len() == 2 && path[0].node.name == keywords::CrateRoot.name() {
2463                     (format!(""), format!("the crate root"))
2464                 } else {
2465                     let mod_path = &path[..path.len() - 1];
2466                     let mod_prefix = match this.resolve_path(mod_path, Some(TypeNS), false, span) {
2467                         PathResult::Module(module) => module.def(),
2468                         _ => None,
2469                     }.map_or(format!(""), |def| format!("{} ", def.kind_name()));
2470                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
2471                 };
2472                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
2473                  format!("not found in {}", mod_str), item_span)
2474             };
2475             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
2476
2477             // Emit special messages for unresolved `Self` and `self`.
2478             if is_self_type(path, ns) {
2479                 __diagnostic_used!(E0411);
2480                 err.code("E0411".into());
2481                 err.span_label(span, "`Self` is only available in traits and impls");
2482                 return (err, Vec::new());
2483             }
2484             if is_self_value(path, ns) {
2485                 __diagnostic_used!(E0424);
2486                 err.code("E0424".into());
2487                 err.span_label(span, format!("`self` value is only available in \
2488                                                methods with `self` parameter"));
2489                 return (err, Vec::new());
2490             }
2491
2492             // Try to lookup the name in more relaxed fashion for better error reporting.
2493             let ident = *path.last().unwrap();
2494             let candidates = this.lookup_import_candidates(ident.node.name, ns, is_expected);
2495             if candidates.is_empty() && is_expected(Def::Enum(DefId::local(CRATE_DEF_INDEX))) {
2496                 let enum_candidates =
2497                     this.lookup_import_candidates(ident.node.name, ns, is_enum_variant);
2498                 let mut enum_candidates = enum_candidates.iter()
2499                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
2500                 enum_candidates.sort();
2501                 for (sp, variant_path, enum_path) in enum_candidates {
2502                     if sp == DUMMY_SP {
2503                         let msg = format!("there is an enum variant `{}`, \
2504                                         try using `{}`?",
2505                                         variant_path,
2506                                         enum_path);
2507                         err.help(&msg);
2508                     } else {
2509                         err.span_suggestion(span, "you can try using the variant's enum",
2510                                             enum_path);
2511                     }
2512                 }
2513             }
2514             if path.len() == 1 && this.self_type_is_available(span) {
2515                 if let Some(candidate) = this.lookup_assoc_candidate(ident.node, ns, is_expected) {
2516                     let self_is_available = this.self_value_is_available(path[0].node.ctxt, span);
2517                     match candidate {
2518                         AssocSuggestion::Field => {
2519                             err.span_suggestion(span, "try",
2520                                                 format!("self.{}", path_str));
2521                             if !self_is_available {
2522                                 err.span_label(span, format!("`self` value is only available in \
2523                                                                methods with `self` parameter"));
2524                             }
2525                         }
2526                         AssocSuggestion::MethodWithSelf if self_is_available => {
2527                             err.span_suggestion(span, "try",
2528                                                 format!("self.{}", path_str));
2529                         }
2530                         AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
2531                             err.span_suggestion(span, "try",
2532                                                 format!("Self::{}", path_str));
2533                         }
2534                     }
2535                     return (err, candidates);
2536                 }
2537             }
2538
2539             let mut levenshtein_worked = false;
2540
2541             // Try Levenshtein.
2542             if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected, span) {
2543                 err.span_label(ident_span, format!("did you mean `{}`?", candidate));
2544                 levenshtein_worked = true;
2545             }
2546
2547             // Try context dependent help if relaxed lookup didn't work.
2548             if let Some(def) = def {
2549                 match (def, source) {
2550                     (Def::Macro(..), _) => {
2551                         err.span_label(span, format!("did you mean `{}!(...)`?", path_str));
2552                         return (err, candidates);
2553                     }
2554                     (Def::TyAlias(..), PathSource::Trait) => {
2555                         err.span_label(span, "type aliases cannot be used for traits");
2556                         return (err, candidates);
2557                     }
2558                     (Def::Mod(..), PathSource::Expr(Some(parent))) => match parent.node {
2559                         ExprKind::Field(_, ident) => {
2560                             err.span_label(parent.span, format!("did you mean `{}::{}`?",
2561                                                                  path_str, ident.node));
2562                             return (err, candidates);
2563                         }
2564                         ExprKind::MethodCall(ref segment, ..) => {
2565                             err.span_label(parent.span, format!("did you mean `{}::{}(...)`?",
2566                                                                  path_str, segment.identifier));
2567                             return (err, candidates);
2568                         }
2569                         _ => {}
2570                     },
2571                     _ if ns == ValueNS && is_struct_like(def) => {
2572                         if let Def::Struct(def_id) = def {
2573                             if let Some((ctor_def, ctor_vis))
2574                                     = this.struct_constructors.get(&def_id).cloned() {
2575                                 if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
2576                                     err.span_label(span, format!("constructor is not visible \
2577                                                                    here due to private fields"));
2578                                 }
2579                             }
2580                         }
2581                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
2582                                                        path_str));
2583                         return (err, candidates);
2584                     }
2585                     _ => {}
2586                 }
2587             }
2588
2589             // Fallback label.
2590             if !levenshtein_worked {
2591                 err.span_label(base_span, fallback_label);
2592                 this.type_ascription_suggestion(&mut err, base_span);
2593             }
2594             (err, candidates)
2595         };
2596         let report_errors = |this: &mut Self, def: Option<Def>| {
2597             let (err, candidates) = report_errors(this, def);
2598             let def_id = this.current_module.normal_ancestor_id;
2599             let node_id = this.definitions.as_local_node_id(def_id).unwrap();
2600             let better = def.is_some();
2601             this.use_injections.push(UseError { err, candidates, node_id, better });
2602             err_path_resolution()
2603         };
2604
2605         let resolution = match self.resolve_qpath_anywhere(id, qself, path, ns, span,
2606                                                            source.defer_to_typeck(),
2607                                                            source.global_by_default()) {
2608             Some(resolution) if resolution.unresolved_segments() == 0 => {
2609                 if is_expected(resolution.base_def()) || resolution.base_def() == Def::Err {
2610                     resolution
2611                 } else {
2612                     // Add a temporary hack to smooth the transition to new struct ctor
2613                     // visibility rules. See #38932 for more details.
2614                     let mut res = None;
2615                     if let Def::Struct(def_id) = resolution.base_def() {
2616                         if let Some((ctor_def, ctor_vis))
2617                                 = self.struct_constructors.get(&def_id).cloned() {
2618                             if is_expected(ctor_def) && self.is_accessible(ctor_vis) {
2619                                 let lint = lint::builtin::LEGACY_CONSTRUCTOR_VISIBILITY;
2620                                 self.session.buffer_lint(lint, id, span,
2621                                     "private struct constructors are not usable through \
2622                                      reexports in outer modules",
2623                                 );
2624                                 res = Some(PathResolution::new(ctor_def));
2625                             }
2626                         }
2627                     }
2628
2629                     res.unwrap_or_else(|| report_errors(self, Some(resolution.base_def())))
2630                 }
2631             }
2632             Some(resolution) if source.defer_to_typeck() => {
2633                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2634                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2635                 // it needs to be added to the trait map.
2636                 if ns == ValueNS {
2637                     let item_name = path.last().unwrap().node;
2638                     let traits = self.get_traits_containing_item(item_name, ns);
2639                     self.trait_map.insert(id, traits);
2640                 }
2641                 resolution
2642             }
2643             _ => report_errors(self, None)
2644         };
2645
2646         if let PathSource::TraitItem(..) = source {} else {
2647             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2648             self.record_def(id, resolution);
2649         }
2650         resolution
2651     }
2652
2653     fn type_ascription_suggestion(&self,
2654                                   err: &mut DiagnosticBuilder,
2655                                   base_span: Span) {
2656         debug!("type_ascription_suggetion {:?}", base_span);
2657         let cm = self.session.codemap();
2658         debug!("self.current_type_ascription {:?}", self.current_type_ascription);
2659         if let Some(sp) = self.current_type_ascription.last() {
2660             let mut sp = *sp;
2661             loop {  // try to find the `:`, bail on first non-':'/non-whitespace
2662                 sp = sp.next_point();
2663                 if let Ok(snippet) = cm.span_to_snippet(sp.to(sp.next_point())) {
2664                     debug!("snippet {:?}", snippet);
2665                     let line_sp = cm.lookup_char_pos(sp.hi).line;
2666                     let line_base_sp = cm.lookup_char_pos(base_span.lo).line;
2667                     debug!("{:?} {:?}", line_sp, line_base_sp);
2668                     if snippet == ":" {
2669                         err.span_label(base_span,
2670                                        "expecting a type here because of type ascription");
2671                         if line_sp != line_base_sp {
2672                             err.span_suggestion_short(sp,
2673                                                       "did you mean to use `;` here instead?",
2674                                                       ";".to_string());
2675                         }
2676                         break;
2677                     } else if snippet.trim().len() != 0  {
2678                         debug!("tried to find type ascription `:` token, couldn't find it");
2679                         break;
2680                     }
2681                 } else {
2682                     break;
2683                 }
2684             }
2685         }
2686     }
2687
2688     fn self_type_is_available(&mut self, span: Span) -> bool {
2689         let binding = self.resolve_ident_in_lexical_scope(keywords::SelfType.ident(),
2690                                                           TypeNS, false, span);
2691         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2692     }
2693
2694     fn self_value_is_available(&mut self, ctxt: SyntaxContext, span: Span) -> bool {
2695         let ident = Ident { name: keywords::SelfValue.name(), ctxt: ctxt };
2696         let binding = self.resolve_ident_in_lexical_scope(ident, ValueNS, false, span);
2697         if let Some(LexicalScopeBinding::Def(def)) = binding { def != Def::Err } else { false }
2698     }
2699
2700     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2701     fn resolve_qpath_anywhere(&mut self,
2702                               id: NodeId,
2703                               qself: Option<&QSelf>,
2704                               path: &[SpannedIdent],
2705                               primary_ns: Namespace,
2706                               span: Span,
2707                               defer_to_typeck: bool,
2708                               global_by_default: bool)
2709                               -> Option<PathResolution> {
2710         let mut fin_res = None;
2711         // FIXME: can't resolve paths in macro namespace yet, macros are
2712         // processed by the little special hack below.
2713         for (i, ns) in [primary_ns, TypeNS, ValueNS, /*MacroNS*/].iter().cloned().enumerate() {
2714             if i == 0 || ns != primary_ns {
2715                 match self.resolve_qpath(id, qself, path, ns, span, global_by_default) {
2716                     // If defer_to_typeck, then resolution > no resolution,
2717                     // otherwise full resolution > partial resolution > no resolution.
2718                     Some(res) if res.unresolved_segments() == 0 || defer_to_typeck =>
2719                         return Some(res),
2720                     res => if fin_res.is_none() { fin_res = res },
2721                 };
2722             }
2723         }
2724         let is_global = self.global_macros.get(&path[0].node.name).cloned()
2725             .map(|binding| binding.get_macro(self).kind() == MacroKind::Bang).unwrap_or(false);
2726         if primary_ns != MacroNS && (is_global ||
2727                                      self.macro_names.contains(&path[0].node.modern())) {
2728             // Return some dummy definition, it's enough for error reporting.
2729             return Some(
2730                 PathResolution::new(Def::Macro(DefId::local(CRATE_DEF_INDEX), MacroKind::Bang))
2731             );
2732         }
2733         fin_res
2734     }
2735
2736     /// Handles paths that may refer to associated items.
2737     fn resolve_qpath(&mut self,
2738                      id: NodeId,
2739                      qself: Option<&QSelf>,
2740                      path: &[SpannedIdent],
2741                      ns: Namespace,
2742                      span: Span,
2743                      global_by_default: bool)
2744                      -> Option<PathResolution> {
2745         if let Some(qself) = qself {
2746             if qself.position == 0 {
2747                 // FIXME: Create some fake resolution that can't possibly be a type.
2748                 return Some(PathResolution::with_unresolved_segments(
2749                     Def::Mod(DefId::local(CRATE_DEF_INDEX)), path.len()
2750                 ));
2751             }
2752             // Make sure `A::B` in `<T as A>::B::C` is a trait item.
2753             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2754             let res = self.smart_resolve_path_fragment(id, None, &path[..qself.position + 1],
2755                                                        span, span, PathSource::TraitItem(ns));
2756             return Some(PathResolution::with_unresolved_segments(
2757                 res.base_def(), res.unresolved_segments() + path.len() - qself.position - 1
2758             ));
2759         }
2760
2761         let result = match self.resolve_path(&path, Some(ns), true, span) {
2762             PathResult::NonModule(path_res) => path_res,
2763             PathResult::Module(module) if !module.is_normal() => {
2764                 PathResolution::new(module.def().unwrap())
2765             }
2766             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2767             // don't report an error right away, but try to fallback to a primitive type.
2768             // So, we are still able to successfully resolve something like
2769             //
2770             // use std::u8; // bring module u8 in scope
2771             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2772             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2773             //                     // not to non-existent std::u8::max_value
2774             // }
2775             //
2776             // Such behavior is required for backward compatibility.
2777             // The same fallback is used when `a` resolves to nothing.
2778             PathResult::Module(..) | PathResult::Failed(..)
2779                     if (ns == TypeNS || path.len() > 1) &&
2780                        self.primitive_type_table.primitive_types
2781                            .contains_key(&path[0].node.name) => {
2782                 let prim = self.primitive_type_table.primitive_types[&path[0].node.name];
2783                 match prim {
2784                     TyUint(UintTy::U128) | TyInt(IntTy::I128) => {
2785                         if !self.session.features.borrow().i128_type {
2786                             emit_feature_err(&self.session.parse_sess,
2787                                                 "i128_type", span, GateIssue::Language,
2788                                                 "128-bit type is unstable");
2789
2790                         }
2791                     }
2792                     _ => {}
2793                 }
2794                 PathResolution::with_unresolved_segments(Def::PrimTy(prim), path.len() - 1)
2795             }
2796             PathResult::Module(module) => PathResolution::new(module.def().unwrap()),
2797             PathResult::Failed(span, msg, false) => {
2798                 resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
2799                 err_path_resolution()
2800             }
2801             PathResult::Failed(..) => return None,
2802             PathResult::Indeterminate => bug!("indetermined path result in resolve_qpath"),
2803         };
2804
2805         if path.len() > 1 && !global_by_default && result.base_def() != Def::Err &&
2806            path[0].node.name != keywords::CrateRoot.name() &&
2807            path[0].node.name != keywords::DollarCrate.name() {
2808             let unqualified_result = {
2809                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), false, span) {
2810                     PathResult::NonModule(path_res) => path_res.base_def(),
2811                     PathResult::Module(module) => module.def().unwrap(),
2812                     _ => return Some(result),
2813                 }
2814             };
2815             if result.base_def() == unqualified_result {
2816                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
2817                 self.session.buffer_lint(lint, id, span, "unnecessary qualification")
2818             }
2819         }
2820
2821         Some(result)
2822     }
2823
2824     fn resolve_path(&mut self,
2825                     path: &[SpannedIdent],
2826                     opt_ns: Option<Namespace>, // `None` indicates a module path
2827                     record_used: bool,
2828                     path_span: Span)
2829                     -> PathResult<'a> {
2830         let mut module = None;
2831         let mut allow_super = true;
2832
2833         for (i, &ident) in path.iter().enumerate() {
2834             debug!("resolve_path ident {} {:?}", i, ident);
2835             let is_last = i == path.len() - 1;
2836             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
2837
2838             if i == 0 && ns == TypeNS && ident.node.name == keywords::SelfValue.name() {
2839                 let mut ctxt = ident.node.ctxt.modern();
2840                 module = Some(self.resolve_self(&mut ctxt, self.current_module));
2841                 continue
2842             } else if allow_super && ns == TypeNS && ident.node.name == keywords::Super.name() {
2843                 let mut ctxt = ident.node.ctxt.modern();
2844                 let self_module = match i {
2845                     0 => self.resolve_self(&mut ctxt, self.current_module),
2846                     _ => module.unwrap(),
2847                 };
2848                 if let Some(parent) = self_module.parent {
2849                     module = Some(self.resolve_self(&mut ctxt, parent));
2850                     continue
2851                 } else {
2852                     let msg = "There are too many initial `super`s.".to_string();
2853                     return PathResult::Failed(ident.span, msg, false);
2854                 }
2855             }
2856             allow_super = false;
2857
2858             if i == 0 && ns == TypeNS && ident.node.name == keywords::CrateRoot.name() {
2859                 module = Some(self.resolve_crate_root(ident.node.ctxt.modern()));
2860                 continue
2861             } else if i == 0 && ns == TypeNS && ident.node.name == keywords::DollarCrate.name() {
2862                 module = Some(self.resolve_crate_root(ident.node.ctxt));
2863                 continue
2864             }
2865
2866             let binding = if let Some(module) = module {
2867                 self.resolve_ident_in_module(module, ident.node, ns, false, record_used, path_span)
2868             } else if opt_ns == Some(MacroNS) {
2869                 self.resolve_lexical_macro_path_segment(ident.node, ns, record_used, path_span)
2870                     .map(MacroBinding::binding)
2871             } else {
2872                 match self.resolve_ident_in_lexical_scope(ident.node, ns, record_used, path_span) {
2873                     Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
2874                     Some(LexicalScopeBinding::Def(def))
2875                             if opt_ns == Some(TypeNS) || opt_ns == Some(ValueNS) => {
2876                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2877                             def, path.len() - 1
2878                         ));
2879                     }
2880                     _ => Err(if record_used { Determined } else { Undetermined }),
2881                 }
2882             };
2883
2884             match binding {
2885                 Ok(binding) => {
2886                     let def = binding.def();
2887                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(def);
2888                     if let Some(next_module) = binding.module() {
2889                         module = Some(next_module);
2890                     } else if def == Def::Err {
2891                         return PathResult::NonModule(err_path_resolution());
2892                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
2893                         return PathResult::NonModule(PathResolution::with_unresolved_segments(
2894                             def, path.len() - i - 1
2895                         ));
2896                     } else {
2897                         return PathResult::Failed(ident.span,
2898                                                   format!("Not a module `{}`", ident.node),
2899                                                   is_last);
2900                     }
2901                 }
2902                 Err(Undetermined) => return PathResult::Indeterminate,
2903                 Err(Determined) => {
2904                     if let Some(module) = module {
2905                         if opt_ns.is_some() && !module.is_normal() {
2906                             return PathResult::NonModule(PathResolution::with_unresolved_segments(
2907                                 module.def().unwrap(), path.len() - i
2908                             ));
2909                         }
2910                     }
2911                     let msg = if module.and_then(ModuleData::def) == self.graph_root.def() {
2912                         let is_mod = |def| match def { Def::Mod(..) => true, _ => false };
2913                         let mut candidates =
2914                             self.lookup_import_candidates(ident.node.name, TypeNS, is_mod);
2915                         candidates.sort_by_key(|c| (c.path.segments.len(), c.path.to_string()));
2916                         if let Some(candidate) = candidates.get(0) {
2917                             format!("Did you mean `{}`?", candidate.path)
2918                         } else {
2919                             format!("Maybe a missing `extern crate {};`?", ident.node)
2920                         }
2921                     } else if i == 0 {
2922                         format!("Use of undeclared type or module `{}`", ident.node)
2923                     } else {
2924                         format!("Could not find `{}` in `{}`", ident.node, path[i - 1].node)
2925                     };
2926                     return PathResult::Failed(ident.span, msg, is_last);
2927                 }
2928             }
2929         }
2930
2931         PathResult::Module(module.unwrap_or(self.graph_root))
2932     }
2933
2934     // Resolve a local definition, potentially adjusting for closures.
2935     fn adjust_local_def(&mut self,
2936                         ns: Namespace,
2937                         rib_index: usize,
2938                         mut def: Def,
2939                         record_used: bool,
2940                         span: Span) -> Def {
2941         let ribs = &self.ribs[ns][rib_index + 1..];
2942
2943         // An invalid forward use of a type parameter from a previous default.
2944         if let ForwardTyParamBanRibKind = self.ribs[ns][rib_index].kind {
2945             if record_used {
2946                 resolve_error(self, span, ResolutionError::ForwardDeclaredTyParam);
2947             }
2948             assert_eq!(def, Def::Err);
2949             return Def::Err;
2950         }
2951
2952         match def {
2953             Def::Upvar(..) => {
2954                 span_bug!(span, "unexpected {:?} in bindings", def)
2955             }
2956             Def::Local(def_id) => {
2957                 for rib in ribs {
2958                     match rib.kind {
2959                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
2960                         ForwardTyParamBanRibKind => {
2961                             // Nothing to do. Continue.
2962                         }
2963                         ClosureRibKind(function_id) => {
2964                             let prev_def = def;
2965                             let node_id = self.definitions.as_local_node_id(def_id).unwrap();
2966
2967                             let seen = self.freevars_seen
2968                                            .entry(function_id)
2969                                            .or_insert_with(|| NodeMap());
2970                             if let Some(&index) = seen.get(&node_id) {
2971                                 def = Def::Upvar(def_id, index, function_id);
2972                                 continue;
2973                             }
2974                             let vec = self.freevars
2975                                           .entry(function_id)
2976                                           .or_insert_with(|| vec![]);
2977                             let depth = vec.len();
2978                             def = Def::Upvar(def_id, depth, function_id);
2979
2980                             if record_used {
2981                                 vec.push(Freevar {
2982                                     def: prev_def,
2983                                     span,
2984                                 });
2985                                 seen.insert(node_id, depth);
2986                             }
2987                         }
2988                         ItemRibKind | MethodRibKind(_) => {
2989                             // This was an attempt to access an upvar inside a
2990                             // named function item. This is not allowed, so we
2991                             // report an error.
2992                             if record_used {
2993                                 resolve_error(self, span,
2994                                         ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
2995                             }
2996                             return Def::Err;
2997                         }
2998                         ConstantItemRibKind => {
2999                             // Still doesn't deal with upvars
3000                             if record_used {
3001                                 resolve_error(self, span,
3002                                         ResolutionError::AttemptToUseNonConstantValueInConstant);
3003                             }
3004                             return Def::Err;
3005                         }
3006                     }
3007                 }
3008             }
3009             Def::TyParam(..) | Def::SelfTy(..) => {
3010                 for rib in ribs {
3011                     match rib.kind {
3012                         NormalRibKind | MethodRibKind(_) | ClosureRibKind(..) |
3013                         ModuleRibKind(..) | MacroDefinition(..) | ForwardTyParamBanRibKind |
3014                         ConstantItemRibKind => {
3015                             // Nothing to do. Continue.
3016                         }
3017                         ItemRibKind => {
3018                             // This was an attempt to use a type parameter outside
3019                             // its scope.
3020                             if record_used {
3021                                 resolve_error(self, span,
3022                                               ResolutionError::TypeParametersFromOuterFunction);
3023                             }
3024                             return Def::Err;
3025                         }
3026                     }
3027                 }
3028             }
3029             _ => {}
3030         }
3031         return def;
3032     }
3033
3034     // Calls `f` with a `Resolver` whose current lexical scope is `module`'s lexical scope,
3035     // i.e. the module's items and the prelude (unless the module is `#[no_implicit_prelude]`).
3036     // FIXME #34673: This needs testing.
3037     pub fn with_module_lexical_scope<T, F>(&mut self, module: Module<'a>, f: F) -> T
3038         where F: FnOnce(&mut Resolver<'a>) -> T,
3039     {
3040         self.with_empty_ribs(|this| {
3041             this.ribs[ValueNS].push(Rib::new(ModuleRibKind(module)));
3042             this.ribs[TypeNS].push(Rib::new(ModuleRibKind(module)));
3043             f(this)
3044         })
3045     }
3046
3047     fn with_empty_ribs<T, F>(&mut self, f: F) -> T
3048         where F: FnOnce(&mut Resolver<'a>) -> T,
3049     {
3050         let ribs = replace(&mut self.ribs, PerNS::<Vec<Rib>>::default());
3051         let label_ribs = replace(&mut self.label_ribs, Vec::new());
3052
3053         let result = f(self);
3054         self.ribs = ribs;
3055         self.label_ribs = label_ribs;
3056         result
3057     }
3058
3059     fn lookup_assoc_candidate<FilterFn>(&mut self,
3060                                         ident: Ident,
3061                                         ns: Namespace,
3062                                         filter_fn: FilterFn)
3063                                         -> Option<AssocSuggestion>
3064         where FilterFn: Fn(Def) -> bool
3065     {
3066         fn extract_node_id(t: &Ty) -> Option<NodeId> {
3067             match t.node {
3068                 TyKind::Path(None, _) => Some(t.id),
3069                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
3070                 // This doesn't handle the remaining `Ty` variants as they are not
3071                 // that commonly the self_type, it might be interesting to provide
3072                 // support for those in future.
3073                 _ => None,
3074             }
3075         }
3076
3077         // Fields are generally expected in the same contexts as locals.
3078         if filter_fn(Def::Local(DefId::local(CRATE_DEF_INDEX))) {
3079             if let Some(node_id) = self.current_self_type.as_ref().and_then(extract_node_id) {
3080                 // Look for a field with the same name in the current self_type.
3081                 if let Some(resolution) = self.def_map.get(&node_id) {
3082                     match resolution.base_def() {
3083                         Def::Struct(did) | Def::Union(did)
3084                                 if resolution.unresolved_segments() == 0 => {
3085                             if let Some(field_names) = self.field_names.get(&did) {
3086                                 if field_names.iter().any(|&field_name| ident.name == field_name) {
3087                                     return Some(AssocSuggestion::Field);
3088                                 }
3089                             }
3090                         }
3091                         _ => {}
3092                     }
3093                 }
3094             }
3095         }
3096
3097         // Look for associated items in the current trait.
3098         if let Some((module, _)) = self.current_trait_ref {
3099             if let Ok(binding) =
3100                     self.resolve_ident_in_module(module, ident, ns, false, false, module.span) {
3101                 let def = binding.def();
3102                 if filter_fn(def) {
3103                     return Some(if self.has_self.contains(&def.def_id()) {
3104                         AssocSuggestion::MethodWithSelf
3105                     } else {
3106                         AssocSuggestion::AssocItem
3107                     });
3108                 }
3109             }
3110         }
3111
3112         None
3113     }
3114
3115     fn lookup_typo_candidate<FilterFn>(&mut self,
3116                                        path: &[SpannedIdent],
3117                                        ns: Namespace,
3118                                        filter_fn: FilterFn,
3119                                        span: Span)
3120                                        -> Option<Symbol>
3121         where FilterFn: Fn(Def) -> bool
3122     {
3123         let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
3124             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
3125                 if let Some(binding) = resolution.borrow().binding {
3126                     if filter_fn(binding.def()) {
3127                         names.push(ident.name);
3128                     }
3129                 }
3130             }
3131         };
3132
3133         let mut names = Vec::new();
3134         if path.len() == 1 {
3135             // Search in lexical scope.
3136             // Walk backwards up the ribs in scope and collect candidates.
3137             for rib in self.ribs[ns].iter().rev() {
3138                 // Locals and type parameters
3139                 for (ident, def) in &rib.bindings {
3140                     if filter_fn(*def) {
3141                         names.push(ident.name);
3142                     }
3143                 }
3144                 // Items in scope
3145                 if let ModuleRibKind(module) = rib.kind {
3146                     // Items from this module
3147                     add_module_candidates(module, &mut names);
3148
3149                     if let ModuleKind::Block(..) = module.kind {
3150                         // We can see through blocks
3151                     } else {
3152                         // Items from the prelude
3153                         if let Some(prelude) = self.prelude {
3154                             if !module.no_implicit_prelude {
3155                                 add_module_candidates(prelude, &mut names);
3156                             }
3157                         }
3158                         break;
3159                     }
3160                 }
3161             }
3162             // Add primitive types to the mix
3163             if filter_fn(Def::PrimTy(TyBool)) {
3164                 for (name, _) in &self.primitive_type_table.primitive_types {
3165                     names.push(*name);
3166                 }
3167             }
3168         } else {
3169             // Search in module.
3170             let mod_path = &path[..path.len() - 1];
3171             if let PathResult::Module(module) = self.resolve_path(mod_path, Some(TypeNS),
3172                                                                   false, span) {
3173                 add_module_candidates(module, &mut names);
3174             }
3175         }
3176
3177         let name = path[path.len() - 1].node.name;
3178         // Make sure error reporting is deterministic.
3179         names.sort_by_key(|name| name.as_str());
3180         match find_best_match_for_name(names.iter(), &name.as_str(), None) {
3181             Some(found) if found != name => Some(found),
3182             _ => None,
3183         }
3184     }
3185
3186     fn with_resolved_label<F>(&mut self, label: Option<SpannedIdent>, id: NodeId, f: F)
3187         where F: FnOnce(&mut Resolver)
3188     {
3189         if let Some(label) = label {
3190             let def = Def::Label(id);
3191             self.with_label_rib(|this| {
3192                 this.label_ribs.last_mut().unwrap().bindings.insert(label.node, def);
3193                 f(this);
3194             });
3195         } else {
3196             f(self);
3197         }
3198     }
3199
3200     fn resolve_labeled_block(&mut self, label: Option<SpannedIdent>, id: NodeId, block: &Block) {
3201         self.with_resolved_label(label, id, |this| this.visit_block(block));
3202     }
3203
3204     fn resolve_expr(&mut self, expr: &Expr, parent: Option<&Expr>) {
3205         // First, record candidate traits for this expression if it could
3206         // result in the invocation of a method call.
3207
3208         self.record_candidate_traits_for_expr_if_necessary(expr);
3209
3210         // Next, resolve the node.
3211         match expr.node {
3212             ExprKind::Path(ref qself, ref path) => {
3213                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
3214                 visit::walk_expr(self, expr);
3215             }
3216
3217             ExprKind::Struct(ref path, ..) => {
3218                 self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
3219                 visit::walk_expr(self, expr);
3220             }
3221
3222             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
3223                 match self.search_label(label.node) {
3224                     None => {
3225                         self.record_def(expr.id, err_path_resolution());
3226                         resolve_error(self,
3227                                       label.span,
3228                                       ResolutionError::UndeclaredLabel(&label.node.name.as_str()));
3229                     }
3230                     Some(def @ Def::Label(_)) => {
3231                         // Since this def is a label, it is never read.
3232                         self.record_def(expr.id, PathResolution::new(def));
3233                     }
3234                     Some(_) => {
3235                         span_bug!(expr.span, "label wasn't mapped to a label def!");
3236                     }
3237                 }
3238
3239                 // visit `break` argument if any
3240                 visit::walk_expr(self, expr);
3241             }
3242
3243             ExprKind::IfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
3244                 self.visit_expr(subexpression);
3245
3246                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3247                 self.resolve_pattern(pattern, PatternSource::IfLet, &mut FxHashMap());
3248                 self.visit_block(if_block);
3249                 self.ribs[ValueNS].pop();
3250
3251                 optional_else.as_ref().map(|expr| self.visit_expr(expr));
3252             }
3253
3254             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
3255
3256             ExprKind::While(ref subexpression, ref block, label) => {
3257                 self.with_resolved_label(label, expr.id, |this| {
3258                     this.visit_expr(subexpression);
3259                     this.visit_block(block);
3260                 });
3261             }
3262
3263             ExprKind::WhileLet(ref pattern, ref subexpression, ref block, label) => {
3264                 self.with_resolved_label(label, expr.id, |this| {
3265                     this.visit_expr(subexpression);
3266                     this.ribs[ValueNS].push(Rib::new(NormalRibKind));
3267                     this.resolve_pattern(pattern, PatternSource::WhileLet, &mut FxHashMap());
3268                     this.visit_block(block);
3269                     this.ribs[ValueNS].pop();
3270                 });
3271             }
3272
3273             ExprKind::ForLoop(ref pattern, ref subexpression, ref block, label) => {
3274                 self.visit_expr(subexpression);
3275                 self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3276                 self.resolve_pattern(pattern, PatternSource::For, &mut FxHashMap());
3277
3278                 self.resolve_labeled_block(label, expr.id, block);
3279
3280                 self.ribs[ValueNS].pop();
3281             }
3282
3283             // Equivalent to `visit::walk_expr` + passing some context to children.
3284             ExprKind::Field(ref subexpression, _) => {
3285                 self.resolve_expr(subexpression, Some(expr));
3286             }
3287             ExprKind::MethodCall(ref segment, ref arguments) => {
3288                 let mut arguments = arguments.iter();
3289                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3290                 for argument in arguments {
3291                     self.resolve_expr(argument, None);
3292                 }
3293                 self.visit_path_segment(expr.span, segment);
3294             }
3295
3296             ExprKind::Repeat(ref element, ref count) => {
3297                 self.visit_expr(element);
3298                 self.with_constant_rib(|this| {
3299                     this.visit_expr(count);
3300                 });
3301             }
3302             ExprKind::Call(ref callee, ref arguments) => {
3303                 self.resolve_expr(callee, Some(expr));
3304                 for argument in arguments {
3305                     self.resolve_expr(argument, None);
3306                 }
3307             }
3308             ExprKind::Type(ref type_expr, _) => {
3309                 self.current_type_ascription.push(type_expr.span);
3310                 visit::walk_expr(self, expr);
3311                 self.current_type_ascription.pop();
3312             }
3313             _ => {
3314                 visit::walk_expr(self, expr);
3315             }
3316         }
3317     }
3318
3319     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &Expr) {
3320         match expr.node {
3321             ExprKind::Field(_, name) => {
3322                 // FIXME(#6890): Even though you can't treat a method like a
3323                 // field, we need to add any trait methods we find that match
3324                 // the field name so that we can do some nice error reporting
3325                 // later on in typeck.
3326                 let traits = self.get_traits_containing_item(name.node, ValueNS);
3327                 self.trait_map.insert(expr.id, traits);
3328             }
3329             ExprKind::MethodCall(ref segment, ..) => {
3330                 debug!("(recording candidate traits for expr) recording traits for {}",
3331                        expr.id);
3332                 let traits = self.get_traits_containing_item(segment.identifier, ValueNS);
3333                 self.trait_map.insert(expr.id, traits);
3334             }
3335             _ => {
3336                 // Nothing to do.
3337             }
3338         }
3339     }
3340
3341     fn get_traits_containing_item(&mut self, mut ident: Ident, ns: Namespace)
3342                                   -> Vec<TraitCandidate> {
3343         debug!("(getting traits containing item) looking for '{}'", ident.name);
3344
3345         let mut found_traits = Vec::new();
3346         // Look for the current trait.
3347         if let Some((module, _)) = self.current_trait_ref {
3348             if self.resolve_ident_in_module(module, ident, ns, false, false, module.span).is_ok() {
3349                 let def_id = module.def_id().unwrap();
3350                 found_traits.push(TraitCandidate { def_id: def_id, import_id: None });
3351             }
3352         }
3353
3354         ident.ctxt = ident.ctxt.modern();
3355         let mut search_module = self.current_module;
3356         loop {
3357             self.get_traits_in_module_containing_item(ident, ns, search_module, &mut found_traits);
3358             search_module =
3359                 unwrap_or!(self.hygienic_lexical_parent(search_module, &mut ident.ctxt), break);
3360         }
3361
3362         if let Some(prelude) = self.prelude {
3363             if !search_module.no_implicit_prelude {
3364                 self.get_traits_in_module_containing_item(ident, ns, prelude, &mut found_traits);
3365             }
3366         }
3367
3368         found_traits
3369     }
3370
3371     fn get_traits_in_module_containing_item(&mut self,
3372                                             ident: Ident,
3373                                             ns: Namespace,
3374                                             module: Module<'a>,
3375                                             found_traits: &mut Vec<TraitCandidate>) {
3376         let mut traits = module.traits.borrow_mut();
3377         if traits.is_none() {
3378             let mut collected_traits = Vec::new();
3379             module.for_each_child(|name, ns, binding| {
3380                 if ns != TypeNS { return }
3381                 if let Def::Trait(_) = binding.def() {
3382                     collected_traits.push((name, binding));
3383                 }
3384             });
3385             *traits = Some(collected_traits.into_boxed_slice());
3386         }
3387
3388         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
3389             let module = binding.module().unwrap();
3390             let mut ident = ident;
3391             if ident.ctxt.glob_adjust(module.expansion, binding.span.ctxt.modern()).is_none() {
3392                 continue
3393             }
3394             if self.resolve_ident_in_module_unadjusted(module, ident, ns, false, false, module.span)
3395                    .is_ok() {
3396                 let import_id = match binding.kind {
3397                     NameBindingKind::Import { directive, .. } => {
3398                         self.maybe_unused_trait_imports.insert(directive.id);
3399                         self.add_to_glob_map(directive.id, trait_name);
3400                         Some(directive.id)
3401                     }
3402                     _ => None,
3403                 };
3404                 let trait_def_id = module.def_id().unwrap();
3405                 found_traits.push(TraitCandidate { def_id: trait_def_id, import_id: import_id });
3406             }
3407         }
3408     }
3409
3410     /// When name resolution fails, this method can be used to look up candidate
3411     /// entities with the expected name. It allows filtering them using the
3412     /// supplied predicate (which should be used to only accept the types of
3413     /// definitions expected e.g. traits). The lookup spans across all crates.
3414     ///
3415     /// NOTE: The method does not look into imports, but this is not a problem,
3416     /// since we report the definitions (thus, the de-aliased imports).
3417     fn lookup_import_candidates<FilterFn>(&mut self,
3418                                           lookup_name: Name,
3419                                           namespace: Namespace,
3420                                           filter_fn: FilterFn)
3421                                           -> Vec<ImportSuggestion>
3422         where FilterFn: Fn(Def) -> bool
3423     {
3424         let mut candidates = Vec::new();
3425         let mut worklist = Vec::new();
3426         let mut seen_modules = FxHashSet();
3427         worklist.push((self.graph_root, Vec::new(), false));
3428
3429         while let Some((in_module,
3430                         path_segments,
3431                         in_module_is_extern)) = worklist.pop() {
3432             self.populate_module_if_necessary(in_module);
3433
3434             // We have to visit module children in deterministic order to avoid
3435             // instabilities in reported imports (#43552).
3436             in_module.for_each_child_stable(|ident, ns, name_binding| {
3437                 // avoid imports entirely
3438                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
3439                 // avoid non-importable candidates as well
3440                 if !name_binding.is_importable() { return; }
3441
3442                 // collect results based on the filter function
3443                 if ident.name == lookup_name && ns == namespace {
3444                     if filter_fn(name_binding.def()) {
3445                         // create the path
3446                         let mut segms = path_segments.clone();
3447                         segms.push(ast::PathSegment::from_ident(ident, name_binding.span));
3448                         let path = Path {
3449                             span: name_binding.span,
3450                             segments: segms,
3451                         };
3452                         // the entity is accessible in the following cases:
3453                         // 1. if it's defined in the same crate, it's always
3454                         // accessible (since private entities can be made public)
3455                         // 2. if it's defined in another crate, it's accessible
3456                         // only if both the module is public and the entity is
3457                         // declared as public (due to pruning, we don't explore
3458                         // outside crate private modules => no need to check this)
3459                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3460                             candidates.push(ImportSuggestion { path: path });
3461                         }
3462                     }
3463                 }
3464
3465                 // collect submodules to explore
3466                 if let Some(module) = name_binding.module() {
3467                     // form the path
3468                     let mut path_segments = path_segments.clone();
3469                     path_segments.push(ast::PathSegment::from_ident(ident, name_binding.span));
3470
3471                     if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
3472                         // add the module to the lookup
3473                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
3474                         if seen_modules.insert(module.def_id().unwrap()) {
3475                             worklist.push((module, path_segments, is_extern));
3476                         }
3477                     }
3478                 }
3479             })
3480         }
3481
3482         candidates
3483     }
3484
3485     fn record_def(&mut self, node_id: NodeId, resolution: PathResolution) {
3486         debug!("(recording def) recording {:?} for {}", resolution, node_id);
3487         if let Some(prev_res) = self.def_map.insert(node_id, resolution) {
3488             panic!("path resolved multiple times ({:?} before, {:?} now)", prev_res, resolution);
3489         }
3490     }
3491
3492     fn resolve_visibility(&mut self, vis: &ast::Visibility) -> ty::Visibility {
3493         match *vis {
3494             ast::Visibility::Public => ty::Visibility::Public,
3495             ast::Visibility::Crate(..) => ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
3496             ast::Visibility::Inherited => {
3497                 ty::Visibility::Restricted(self.current_module.normal_ancestor_id)
3498             }
3499             ast::Visibility::Restricted { ref path, id } => {
3500                 let def = self.smart_resolve_path(id, None, path,
3501                                                   PathSource::Visibility).base_def();
3502                 if def == Def::Err {
3503                     ty::Visibility::Public
3504                 } else {
3505                     let vis = ty::Visibility::Restricted(def.def_id());
3506                     if self.is_accessible(vis) {
3507                         vis
3508                     } else {
3509                         self.session.span_err(path.span, "visibilities can only be restricted \
3510                                                           to ancestor modules");
3511                         ty::Visibility::Public
3512                     }
3513                 }
3514             }
3515         }
3516     }
3517
3518     fn is_accessible(&self, vis: ty::Visibility) -> bool {
3519         vis.is_accessible_from(self.current_module.normal_ancestor_id, self)
3520     }
3521
3522     fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
3523         vis.is_accessible_from(module.normal_ancestor_id, self)
3524     }
3525
3526     fn report_errors(&mut self, krate: &Crate) {
3527         self.report_shadowing_errors();
3528         self.report_with_use_injections(krate);
3529         let mut reported_spans = FxHashSet();
3530
3531         for &AmbiguityError { span, name, b1, b2, lexical, legacy } in &self.ambiguity_errors {
3532             if !reported_spans.insert(span) { continue }
3533             let participle = |binding: &NameBinding| {
3534                 if binding.is_import() { "imported" } else { "defined" }
3535             };
3536             let msg1 = format!("`{}` could refer to the name {} here", name, participle(b1));
3537             let msg2 = format!("`{}` could also refer to the name {} here", name, participle(b2));
3538             let note = if b1.expansion == Mark::root() || !lexical && b1.is_glob_import() {
3539                 format!("consider adding an explicit import of `{}` to disambiguate", name)
3540             } else if let Def::Macro(..) = b1.def() {
3541                 format!("macro-expanded {} do not shadow",
3542                         if b1.is_import() { "macro imports" } else { "macros" })
3543             } else {
3544                 format!("macro-expanded {} do not shadow when used in a macro invocation path",
3545                         if b1.is_import() { "imports" } else { "items" })
3546             };
3547             if legacy {
3548                 let id = match b2.kind {
3549                     NameBindingKind::Import { directive, .. } => directive.id,
3550                     _ => unreachable!(),
3551                 };
3552                 let mut span = MultiSpan::from_span(span);
3553                 span.push_span_label(b1.span, msg1);
3554                 span.push_span_label(b2.span, msg2);
3555                 let msg = format!("`{}` is ambiguous", name);
3556                 self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, &msg);
3557             } else {
3558                 let mut err =
3559                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", name));
3560                 err.span_note(b1.span, &msg1);
3561                 match b2.def() {
3562                     Def::Macro(..) if b2.span == DUMMY_SP =>
3563                         err.note(&format!("`{}` is also a builtin macro", name)),
3564                     _ => err.span_note(b2.span, &msg2),
3565                 };
3566                 err.note(&note).emit();
3567             }
3568         }
3569
3570         for &PrivacyError(span, name, binding) in &self.privacy_errors {
3571             if !reported_spans.insert(span) { continue }
3572             span_err!(self.session, span, E0603, "{} `{}` is private", binding.descr(), name);
3573         }
3574     }
3575
3576     fn report_with_use_injections(&mut self, krate: &Crate) {
3577         for UseError { mut err, candidates, node_id, better } in self.use_injections.drain(..) {
3578             let mut finder = UsePlacementFinder {
3579                 target_module: node_id,
3580                 span: None,
3581                 found_use: false,
3582             };
3583             visit::walk_crate(&mut finder, krate);
3584             if !candidates.is_empty() {
3585                 let span = finder.span.expect("did not find module");
3586                 show_candidates(&mut err, span, &candidates, better, finder.found_use);
3587             }
3588             err.emit();
3589         }
3590     }
3591
3592     fn report_shadowing_errors(&mut self) {
3593         for (ident, scope) in replace(&mut self.lexical_macro_resolutions, Vec::new()) {
3594             self.resolve_legacy_scope(scope, ident, true);
3595         }
3596
3597         let mut reported_errors = FxHashSet();
3598         for binding in replace(&mut self.disallowed_shadowing, Vec::new()) {
3599             if self.resolve_legacy_scope(&binding.parent, binding.ident, false).is_some() &&
3600                reported_errors.insert((binding.ident, binding.span)) {
3601                 let msg = format!("`{}` is already in scope", binding.ident);
3602                 self.session.struct_span_err(binding.span, &msg)
3603                     .note("macro-expanded `macro_rules!`s may not shadow \
3604                            existing macros (see RFC 1560)")
3605                     .emit();
3606             }
3607         }
3608     }
3609
3610     fn report_conflict(&mut self,
3611                        parent: Module,
3612                        ident: Ident,
3613                        ns: Namespace,
3614                        new_binding: &NameBinding,
3615                        old_binding: &NameBinding) {
3616         // Error on the second of two conflicting names
3617         if old_binding.span.lo > new_binding.span.lo {
3618             return self.report_conflict(parent, ident, ns, old_binding, new_binding);
3619         }
3620
3621         let container = match parent.kind {
3622             ModuleKind::Def(Def::Mod(_), _) => "module",
3623             ModuleKind::Def(Def::Trait(_), _) => "trait",
3624             ModuleKind::Block(..) => "block",
3625             _ => "enum",
3626         };
3627
3628         let old_noun = match old_binding.is_import() {
3629             true => "import",
3630             false => "definition",
3631         };
3632
3633         let new_participle = match new_binding.is_import() {
3634             true => "imported",
3635             false => "defined",
3636         };
3637
3638         let (name, span) = (ident.name, new_binding.span);
3639
3640         if let Some(s) = self.name_already_seen.get(&name) {
3641             if s == &span {
3642                 return;
3643             }
3644         }
3645
3646         let old_kind = match (ns, old_binding.module()) {
3647             (ValueNS, _) => "value",
3648             (MacroNS, _) => "macro",
3649             (TypeNS, _) if old_binding.is_extern_crate() => "extern crate",
3650             (TypeNS, Some(module)) if module.is_normal() => "module",
3651             (TypeNS, Some(module)) if module.is_trait() => "trait",
3652             (TypeNS, _) => "type",
3653         };
3654
3655         let namespace = match ns {
3656             ValueNS => "value",
3657             MacroNS => "macro",
3658             TypeNS => "type",
3659         };
3660
3661         let msg = format!("the name `{}` is defined multiple times", name);
3662
3663         let mut err = match (old_binding.is_extern_crate(), new_binding.is_extern_crate()) {
3664             (true, true) => struct_span_err!(self.session, span, E0259, "{}", msg),
3665             (true, _) | (_, true) => match new_binding.is_import() && old_binding.is_import() {
3666                 true => struct_span_err!(self.session, span, E0254, "{}", msg),
3667                 false => struct_span_err!(self.session, span, E0260, "{}", msg),
3668             },
3669             _ => match (old_binding.is_import(), new_binding.is_import()) {
3670                 (false, false) => struct_span_err!(self.session, span, E0428, "{}", msg),
3671                 (true, true) => struct_span_err!(self.session, span, E0252, "{}", msg),
3672                 _ => struct_span_err!(self.session, span, E0255, "{}", msg),
3673             },
3674         };
3675
3676         err.note(&format!("`{}` must be defined only once in the {} namespace of this {}",
3677                           name,
3678                           namespace,
3679                           container));
3680
3681         err.span_label(span, format!("`{}` re{} here", name, new_participle));
3682         if old_binding.span != syntax_pos::DUMMY_SP {
3683             err.span_label(old_binding.span, format!("previous {} of the {} `{}` here",
3684                                                       old_noun, old_kind, name));
3685         }
3686
3687         err.emit();
3688         self.name_already_seen.insert(name, span);
3689     }
3690
3691     fn warn_legacy_self_import(&self, directive: &'a ImportDirective<'a>) {
3692         let (id, span) = (directive.id, directive.span);
3693         let msg = "`self` no longer imports values";
3694         self.session.buffer_lint(lint::builtin::LEGACY_IMPORTS, id, span, msg);
3695     }
3696
3697     fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
3698         if self.proc_macro_enabled { return; }
3699
3700         for attr in attrs {
3701             if attr.path.segments.len() > 1 {
3702                 continue
3703             }
3704             let ident = attr.path.segments[0].identifier;
3705             let result = self.resolve_lexical_macro_path_segment(ident,
3706                                                                  MacroNS,
3707                                                                  false,
3708                                                                  attr.path.span);
3709             if let Ok(binding) = result {
3710                 if let SyntaxExtension::AttrProcMacro(..) = *binding.binding().get_macro(self) {
3711                     attr::mark_known(attr);
3712
3713                     let msg = "attribute procedural macros are experimental";
3714                     let feature = "proc_macro";
3715
3716                     feature_err(&self.session.parse_sess, feature,
3717                                 attr.span, GateIssue::Language, msg)
3718                         .span_note(binding.span(), "procedural macro imported here")
3719                         .emit();
3720                 }
3721             }
3722         }
3723     }
3724 }
3725
3726 fn is_struct_like(def: Def) -> bool {
3727     match def {
3728         Def::VariantCtor(_, CtorKind::Fictive) => true,
3729         _ => PathSource::Struct.is_expected(def),
3730     }
3731 }
3732
3733 fn is_self_type(path: &[SpannedIdent], namespace: Namespace) -> bool {
3734     namespace == TypeNS && path.len() == 1 && path[0].node.name == keywords::SelfType.name()
3735 }
3736
3737 fn is_self_value(path: &[SpannedIdent], namespace: Namespace) -> bool {
3738     namespace == ValueNS && path.len() == 1 && path[0].node.name == keywords::SelfValue.name()
3739 }
3740
3741 fn names_to_string(idents: &[SpannedIdent]) -> String {
3742     let mut result = String::new();
3743     for (i, ident) in idents.iter()
3744                             .filter(|i| i.node.name != keywords::CrateRoot.name())
3745                             .enumerate() {
3746         if i > 0 {
3747             result.push_str("::");
3748         }
3749         result.push_str(&ident.node.name.as_str());
3750     }
3751     result
3752 }
3753
3754 fn path_names_to_string(path: &Path) -> String {
3755     names_to_string(&path.segments.iter()
3756                         .map(|seg| respan(seg.span, seg.identifier))
3757                         .collect::<Vec<_>>())
3758 }
3759
3760 /// Get the path for an enum and the variant from an `ImportSuggestion` for an enum variant.
3761 fn import_candidate_to_paths(suggestion: &ImportSuggestion) -> (Span, String, String) {
3762     let variant_path = &suggestion.path;
3763     let variant_path_string = path_names_to_string(variant_path);
3764
3765     let path_len = suggestion.path.segments.len();
3766     let enum_path = ast::Path {
3767         span: suggestion.path.span,
3768         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
3769     };
3770     let enum_path_string = path_names_to_string(&enum_path);
3771
3772     (suggestion.path.span, variant_path_string, enum_path_string)
3773 }
3774
3775
3776 /// When an entity with a given name is not available in scope, we search for
3777 /// entities with that name in all crates. This method allows outputting the
3778 /// results of this search in a programmer-friendly way
3779 fn show_candidates(err: &mut DiagnosticBuilder,
3780                    span: Span,
3781                    candidates: &[ImportSuggestion],
3782                    better: bool,
3783                    found_use: bool) {
3784
3785     // we want consistent results across executions, but candidates are produced
3786     // by iterating through a hash map, so make sure they are ordered:
3787     let mut path_strings: Vec<_> =
3788         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
3789     path_strings.sort();
3790
3791     let better = if better { "better " } else { "" };
3792     let msg_diff = match path_strings.len() {
3793         1 => " is found in another module, you can import it",
3794         _ => "s are found in other modules, you can import them",
3795     };
3796     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
3797
3798     for candidate in &mut path_strings {
3799         // produce an additional newline to separate the new use statement
3800         // from the directly following item.
3801         let additional_newline = if found_use {
3802             ""
3803         } else {
3804             "\n"
3805         };
3806         *candidate = format!("use {};\n{}", candidate, additional_newline);
3807     }
3808
3809     err.span_suggestions(span, &msg, path_strings);
3810 }
3811
3812 /// A somewhat inefficient routine to obtain the name of a module.
3813 fn module_to_string(module: Module) -> String {
3814     let mut names = Vec::new();
3815
3816     fn collect_mod(names: &mut Vec<Ident>, module: Module) {
3817         if let ModuleKind::Def(_, name) = module.kind {
3818             if let Some(parent) = module.parent {
3819                 names.push(Ident::with_empty_ctxt(name));
3820                 collect_mod(names, parent);
3821             }
3822         } else {
3823             // danger, shouldn't be ident?
3824             names.push(Ident::from_str("<opaque>"));
3825             collect_mod(names, module.parent.unwrap());
3826         }
3827     }
3828     collect_mod(&mut names, module);
3829
3830     if names.is_empty() {
3831         return "???".to_string();
3832     }
3833     names_to_string(&names.into_iter()
3834                         .rev()
3835                         .map(|n| dummy_spanned(n))
3836                         .collect::<Vec<_>>())
3837 }
3838
3839 fn err_path_resolution() -> PathResolution {
3840     PathResolution::new(Def::Err)
3841 }
3842
3843 #[derive(PartialEq,Copy, Clone)]
3844 pub enum MakeGlobMap {
3845     Yes,
3846     No,
3847 }
3848
3849 __build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }