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