src/librustc_resolve/diagnostics.rs

   1 use std::cmp::Reverse;
   2
   3 use errors::{Applicability, DiagnosticBuilder};
   4 use log::debug;
   5 use rustc::bug;
   6 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
   7 use rustc::hir::def::Namespace::{self, *};
   8 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
   9 use rustc::session::Session;
  10 use rustc::ty::{self, DefIdTree};
  11 use rustc::util::nodemap::FxHashSet;
  12 use syntax::ast::{self, Ident, Path};
  13 use syntax::feature_gate::BUILTIN_ATTRIBUTES;
  14 use syntax::source_map::SourceMap;
  15 use syntax::struct_span_err;
  16 use syntax::symbol::{Symbol, kw};
  17 use syntax::util::lev_distance::find_best_match_for_name;
  18 use syntax_pos::hygiene::MacroKind;
  19 use syntax_pos::{BytePos, Span, MultiSpan};
  20
  21 use crate::resolve_imports::{ImportDirective, ImportDirectiveSubclass, ImportResolver};
  22 use crate::path_names_to_string;
  23 use crate::{BindingError, CrateLint, HasGenericParams, LegacyScope, Module, ModuleOrUniformRoot};
  24 use crate::{PathResult, ParentScope, ResolutionError, Resolver, Scope, ScopeSet, Segment};
  25
  26 use rustc_error_codes::*;
  27
  28 type Res = def::Res<ast::NodeId>;
  29
  30 /// A vector of spans and replacements, a message and applicability.
  31 crate type Suggestion = (Vec<(Span, String)>, String, Applicability);
  32
  33 crate struct TypoSuggestion {
  34     pub candidate: Symbol,
  35     pub res: Res,
  36 }
  37
  38 impl TypoSuggestion {
  39     crate fn from_res(candidate: Symbol, res: Res) -> TypoSuggestion {
  40         TypoSuggestion { candidate, res }
  41     }
  42 }
  43
  44 /// A free importable items suggested in case of resolution failure.
  45 crate struct ImportSuggestion {
  46     pub did: Option<DefId>,
  47     pub path: Path,
  48 }
  49
  50 /// Adjust the impl span so that just the `impl` keyword is taken by removing
  51 /// everything after `<` (`"impl<T> Iterator for A<T> {}" -> "impl"`) and
  52 /// everything after the first whitespace (`"impl Iterator for A" -> "impl"`).
  53 ///
  54 /// *Attention*: the method used is very fragile since it essentially duplicates the work of the
  55 /// parser. If you need to use this function or something similar, please consider updating the
  56 /// `source_map` functions and this function to something more robust.
  57 fn reduce_impl_span_to_impl_keyword(cm: &SourceMap, impl_span: Span) -> Span {
  58     let impl_span = cm.span_until_char(impl_span, '<');
  59     let impl_span = cm.span_until_whitespace(impl_span);
  60     impl_span
  61 }
  62
  63 impl<'a> Resolver<'a> {
  64     crate fn add_module_candidates(
  65         &mut self,
  66         module: Module<'a>,
  67         names: &mut Vec<TypoSuggestion>,
  68         filter_fn: &impl Fn(Res) -> bool,
  69     ) {
  70         for (key, resolution) in self.resolutions(module).borrow().iter() {
  71             if let Some(binding) = resolution.borrow().binding {
  72                 let res = binding.res();
  73                 if filter_fn(res) {
  74                     names.push(TypoSuggestion::from_res(key.ident.name, res));
  75                 }
  76             }
  77         }
  78     }
  79
  80     /// Combines an error with provided span and emits it.
  81     ///
  82     /// This takes the error provided, combines it with the span and any additional spans inside the
  83     /// error and emits it.
  84     crate fn report_error(&self, span: Span, resolution_error: ResolutionError<'_>) {
  85         self.into_struct_error(span, resolution_error).emit();
  86     }
  87
  88     crate fn into_struct_error(
  89         &self, span: Span, resolution_error: ResolutionError<'_>
  90     ) -> DiagnosticBuilder<'_> {
  91         match resolution_error {
  92             ResolutionError::GenericParamsFromOuterFunction(outer_res, has_generic_params) => {
  93                 let mut err = struct_span_err!(self.session,
  94                     span,
  95                     E0401,
  96                     "can't use generic parameters from outer function",
  97                 );
  98                 err.span_label(span, format!("use of generic parameter from outer function"));
  99
 100                 let cm = self.session.source_map();
 101                 match outer_res {
 102                     Res::SelfTy(maybe_trait_defid, maybe_impl_defid) => {
 103                         if let Some(impl_span) = maybe_impl_defid.and_then(|def_id| {
 104                             self.definitions.opt_span(def_id)
 105                         }) {
 106                             err.span_label(
 107                                 reduce_impl_span_to_impl_keyword(cm, impl_span),
 108                                 "`Self` type implicitly declared here, by this `impl`",
 109                             );
 110                         }
 111                         match (maybe_trait_defid, maybe_impl_defid) {
 112                             (Some(_), None) => {
 113                                 err.span_label(span, "can't use `Self` here");
 114                             }
 115                             (_, Some(_)) => {
 116                                 err.span_label(span, "use a type here instead");
 117                             }
 118                             (None, None) => bug!("`impl` without trait nor type?"),
 119                         }
 120                         return err;
 121                     },
 122                     Res::Def(DefKind::TyParam, def_id) => {
 123                         if let Some(span) = self.definitions.opt_span(def_id) {
 124                             err.span_label(span, "type parameter from outer function");
 125                         }
 126                     }
 127                     Res::Def(DefKind::ConstParam, def_id) => {
 128                         if let Some(span) = self.definitions.opt_span(def_id) {
 129                             err.span_label(span, "const parameter from outer function");
 130                         }
 131                     }
 132                     _ => {
 133                         bug!("GenericParamsFromOuterFunction should only be used with Res::SelfTy, \
 134                             DefKind::TyParam");
 135                     }
 136                 }
 137
 138                 if has_generic_params == HasGenericParams::Yes {
 139                     // Try to retrieve the span of the function signature and generate a new
 140                     // message with a local type or const parameter.
 141                     let sugg_msg = &format!("try using a local generic parameter instead");
 142                     if let Some((sugg_span, snippet)) = cm.generate_local_type_param_snippet(span) {
 143                         // Suggest the modification to the user
 144                         err.span_suggestion(
 145                             sugg_span,
 146                             sugg_msg,
 147                             snippet,
 148                             Applicability::MachineApplicable,
 149                         );
 150                     } else if let Some(sp) = cm.generate_fn_name_span(span) {
 151                         err.span_label(sp,
 152                             format!("try adding a local generic parameter in this method instead"));
 153                     } else {
 154                         err.help(&format!("try using a local generic parameter instead"));
 155                     }
 156                 }
 157
 158                 err
 159             }
 160             ResolutionError::NameAlreadyUsedInParameterList(name, first_use_span) => {
 161                 let mut err = struct_span_err!(
 162                     self.session,
 163                     span,
 164                     E0403,
 165                     "the name `{}` is already used for a generic \
 166                      parameter in this item's generic parameters",
 167                     name,
 168                 );
 169                 err.span_label(span, "already used");
 170                 err.span_label(first_use_span, format!("first use of `{}`", name));
 171                 err
 172             }
 173             ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 174                 let mut err = struct_span_err!(self.session,
 175                                             span,
 176                                             E0407,
 177                                             "method `{}` is not a member of trait `{}`",
 178                                             method,
 179                                             trait_);
 180                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 181                 err
 182             }
 183             ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 184                 let mut err = struct_span_err!(self.session,
 185                                 span,
 186                                 E0437,
 187                                 "type `{}` is not a member of trait `{}`",
 188                                 type_,
 189                                 trait_);
 190                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 191                 err
 192             }
 193             ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 194                 let mut err = struct_span_err!(self.session,
 195                                 span,
 196                                 E0438,
 197                                 "const `{}` is not a member of trait `{}`",
 198                                 const_,
 199                                 trait_);
 200                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 201                 err
 202             }
 203             ResolutionError::VariableNotBoundInPattern(binding_error) => {
 204                 let BindingError { name, target, origin, could_be_path } = binding_error;
 205
 206                 let target_sp = target.iter().copied().collect::<Vec<_>>();
 207                 let origin_sp = origin.iter().copied().collect::<Vec<_>>();
 208
 209                 let msp = MultiSpan::from_spans(target_sp.clone());
 210                 let mut err = struct_span_err!(
 211                     self.session,
 212                     msp,
 213                     E0408,
 214                     "variable `{}` is not bound in all patterns", name,
 215                 );
 216                 for sp in target_sp {
 217                     err.span_label(sp, format!("pattern doesn't bind `{}`", name));
 218                 }
 219                 for sp in origin_sp {
 220                     err.span_label(sp, "variable not in all patterns");
 221                 }
 222                 if *could_be_path {
 223                     let help_msg = format!(
 224                         "if you meant to match on a variant or a `const` item, consider \
 225                          making the path in the pattern qualified: `?::{}`",
 226                          name,
 227                      );
 228                     err.span_help(span, &help_msg);
 229                 }
 230                 err
 231             }
 232             ResolutionError::VariableBoundWithDifferentMode(variable_name,
 233                                                             first_binding_span) => {
 234                 let mut err = struct_span_err!(self.session,
 235                                 span,
 236                                 E0409,
 237                                 "variable `{}` is bound in inconsistent \
 238                                 ways within the same match arm",
 239                                 variable_name);
 240                 err.span_label(span, "bound in different ways");
 241                 err.span_label(first_binding_span, "first binding");
 242                 err
 243             }
 244             ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 245                 let mut err = struct_span_err!(self.session,
 246                                 span,
 247                                 E0415,
 248                                 "identifier `{}` is bound more than once in this parameter list",
 249                                 identifier);
 250                 err.span_label(span, "used as parameter more than once");
 251                 err
 252             }
 253             ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 254                 let mut err = struct_span_err!(self.session,
 255                                 span,
 256                                 E0416,
 257                                 "identifier `{}` is bound more than once in the same pattern",
 258                                 identifier);
 259                 err.span_label(span, "used in a pattern more than once");
 260                 err
 261             }
 262             ResolutionError::UndeclaredLabel(name, lev_candidate) => {
 263                 let mut err = struct_span_err!(self.session,
 264                                             span,
 265                                             E0426,
 266                                             "use of undeclared label `{}`",
 267                                             name);
 268                 if let Some(lev_candidate) = lev_candidate {
 269                     err.span_suggestion(
 270                         span,
 271                         "a label with a similar name exists in this scope",
 272                         lev_candidate.to_string(),
 273                         Applicability::MaybeIncorrect,
 274                     );
 275                 } else {
 276                     err.span_label(span, format!("undeclared label `{}`", name));
 277                 }
 278                 err
 279             }
 280             ResolutionError::SelfImportsOnlyAllowedWithin => {
 281                 struct_span_err!(self.session,
 282                                 span,
 283                                 E0429,
 284                                 "{}",
 285                                 "`self` imports are only allowed within a { } list")
 286             }
 287             ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 288                 let mut err = struct_span_err!(self.session, span, E0430,
 289                                             "`self` import can only appear once in an import list");
 290                 err.span_label(span, "can only appear once in an import list");
 291                 err
 292             }
 293             ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 294                 let mut err = struct_span_err!(self.session, span, E0431,
 295                                             "`self` import can only appear in an import list with \
 296                                                 a non-empty prefix");
 297                 err.span_label(span, "can only appear in an import list with a non-empty prefix");
 298                 err
 299             }
 300             ResolutionError::FailedToResolve { label, suggestion } => {
 301                 let mut err = struct_span_err!(self.session, span, E0433,
 302                                             "failed to resolve: {}", &label);
 303                 err.span_label(span, label);
 304
 305                 if let Some((suggestions, msg, applicability)) = suggestion {
 306                     err.multipart_suggestion(&msg, suggestions, applicability);
 307                 }
 308
 309                 err
 310             }
 311             ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 312                 let mut err = struct_span_err!(self.session,
 313                                             span,
 314                                             E0434,
 315                                             "{}",
 316                                             "can't capture dynamic environment in a fn item");
 317                 err.help("use the `|| { ... }` closure form instead");
 318                 err
 319             }
 320             ResolutionError::AttemptToUseNonConstantValueInConstant => {
 321                 let mut err = struct_span_err!(self.session, span, E0435,
 322                                             "attempt to use a non-constant value in a constant");
 323                 err.span_label(span, "non-constant value");
 324                 err
 325             }
 326             ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 327                 let res = binding.res();
 328                 let shadows_what = res.descr();
 329                 let mut err = struct_span_err!(self.session, span, E0530, "{}s cannot shadow {}s",
 330                                             what_binding, shadows_what);
 331                 err.span_label(span, format!("cannot be named the same as {} {}",
 332                                             res.article(), shadows_what));
 333                 let participle = if binding.is_import() { "imported" } else { "defined" };
 334                 let msg = format!("the {} `{}` is {} here", shadows_what, name, participle);
 335                 err.span_label(binding.span, msg);
 336                 err
 337             }
 338             ResolutionError::ForwardDeclaredTyParam => {
 339                 let mut err = struct_span_err!(self.session, span, E0128,
 340                                             "type parameters with a default cannot use \
 341                                                 forward declared identifiers");
 342                 err.span_label(
 343                     span, "defaulted type parameters cannot be forward declared".to_string());
 344                 err
 345             }
 346             ResolutionError::SelfInTyParamDefault => {
 347                 let mut err = struct_span_err!(
 348                     self.session,
 349                     span,
 350                     E0735,
 351                     "type parameters cannot use `Self` in their defaults"
 352                 );
 353                 err.span_label(
 354                     span, "`Self` in type parameter default".to_string());
 355                 err
 356             }
 357         }
 358     }
 359
 360     /// Lookup typo candidate in scope for a macro or import.
 361     fn early_lookup_typo_candidate(
 362         &mut self,
 363         scope_set: ScopeSet,
 364         parent_scope: &ParentScope<'a>,
 365         ident: Ident,
 366         filter_fn: &impl Fn(Res) -> bool,
 367     ) -> Option<TypoSuggestion> {
 368         let mut suggestions = Vec::new();
 369         self.visit_scopes(scope_set, parent_scope, ident, |this, scope, use_prelude, _| {
 370             match scope {
 371                 Scope::DeriveHelpers(expn_id) => {
 372                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 373                     if filter_fn(res) {
 374                         suggestions.extend(this.helper_attrs.get(&expn_id)
 375                                                .into_iter().flatten().map(|ident| {
 376                             TypoSuggestion::from_res(ident.name, res)
 377                         }));
 378                     }
 379                 }
 380                 Scope::DeriveHelpersCompat => {
 381                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 382                     if filter_fn(res) {
 383                         for derive in parent_scope.derives {
 384                             let parent_scope =
 385                                 &ParentScope { derives: &[], ..*parent_scope };
 386                             if let Ok((Some(ext), _)) = this.resolve_macro_path(
 387                                 derive, Some(MacroKind::Derive), parent_scope, false, false
 388                             ) {
 389                                 suggestions.extend(ext.helper_attrs.iter().map(|name| {
 390                                     TypoSuggestion::from_res(*name, res)
 391                                 }));
 392                             }
 393                         }
 394                     }
 395                 }
 396                 Scope::MacroRules(legacy_scope) => {
 397                     if let LegacyScope::Binding(legacy_binding) = legacy_scope {
 398                         let res = legacy_binding.binding.res();
 399                         if filter_fn(res) {
 400                             suggestions.push(
 401                                 TypoSuggestion::from_res(legacy_binding.ident.name, res)
 402                             )
 403                         }
 404                     }
 405                 }
 406                 Scope::CrateRoot => {
 407                     let root_ident = Ident::new(kw::PathRoot, ident.span);
 408                     let root_module = this.resolve_crate_root(root_ident);
 409                     this.add_module_candidates(root_module, &mut suggestions, filter_fn);
 410                 }
 411                 Scope::Module(module) => {
 412                     this.add_module_candidates(module, &mut suggestions, filter_fn);
 413                 }
 414                 Scope::RegisteredAttrs => {
 415                     let res = Res::NonMacroAttr(NonMacroAttrKind::Registered);
 416                     if filter_fn(res) {
 417                         suggestions.extend(this.registered_attrs.iter().map(|ident| {
 418                             TypoSuggestion::from_res(ident.name, res)
 419                         }));
 420                     }
 421                 }
 422                 Scope::MacroUsePrelude => {
 423                     suggestions.extend(this.macro_use_prelude.iter().filter_map(|(name, binding)| {
 424                         let res = binding.res();
 425                         if filter_fn(res) {
 426                             Some(TypoSuggestion::from_res(*name, res))
 427                         } else {
 428                             None
 429                         }
 430                     }));
 431                 }
 432                 Scope::BuiltinAttrs => {
 433                     let res = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 434                     if filter_fn(res) {
 435                         suggestions.extend(BUILTIN_ATTRIBUTES.iter().map(|(name, ..)| {
 436                             TypoSuggestion::from_res(*name, res)
 437                         }));
 438                     }
 439                 }
 440                 Scope::LegacyPluginHelpers => {
 441                     let res = Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 442                     if filter_fn(res) {
 443                         let plugin_attributes = this.session.plugin_attributes.borrow();
 444                         suggestions.extend(plugin_attributes.iter().map(|(name, _)| {
 445                             TypoSuggestion::from_res(*name, res)
 446                         }));
 447                     }
 448                 }
 449                 Scope::ExternPrelude => {
 450                     suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
 451                         let res = Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX));
 452                         if filter_fn(res) {
 453                             Some(TypoSuggestion::from_res(ident.name, res))
 454                         } else {
 455                             None
 456                         }
 457                     }));
 458                 }
 459                 Scope::ToolPrelude => {
 460                     let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
 461                     suggestions.extend(this.registered_tools.iter().map(|ident| {
 462                         TypoSuggestion::from_res(ident.name, res)
 463                     }));
 464                 }
 465                 Scope::StdLibPrelude => {
 466                     if let Some(prelude) = this.prelude {
 467                         let mut tmp_suggestions = Vec::new();
 468                         this.add_module_candidates(prelude, &mut tmp_suggestions, filter_fn);
 469                         suggestions.extend(tmp_suggestions.into_iter().filter(|s| {
 470                             use_prelude || this.is_builtin_macro(s.res)
 471                         }));
 472                     }
 473                 }
 474                 Scope::BuiltinTypes => {
 475                     let primitive_types = &this.primitive_type_table.primitive_types;
 476                     suggestions.extend(
 477                         primitive_types.iter().flat_map(|(name, prim_ty)| {
 478                             let res = Res::PrimTy(*prim_ty);
 479                             if filter_fn(res) {
 480                                 Some(TypoSuggestion::from_res(*name, res))
 481                             } else {
 482                                 None
 483                             }
 484                         })
 485                     )
 486                 }
 487             }
 488
 489             None::<()>
 490         });
 491
 492         // Make sure error reporting is deterministic.
 493         suggestions.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 494
 495         match find_best_match_for_name(
 496             suggestions.iter().map(|suggestion| &suggestion.candidate),
 497             &ident.as_str(),
 498             None,
 499         ) {
 500             Some(found) if found != ident.name => suggestions
 501                 .into_iter()
 502                 .find(|suggestion| suggestion.candidate == found),
 503             _ => None,
 504         }
 505     }
 506
 507     fn lookup_import_candidates_from_module<FilterFn>(&mut self,
 508                                           lookup_ident: Ident,
 509                                           namespace: Namespace,
 510                                           start_module: Module<'a>,
 511                                           crate_name: Ident,
 512                                           filter_fn: FilterFn)
 513                                           -> Vec<ImportSuggestion>
 514         where FilterFn: Fn(Res) -> bool
 515     {
 516         let mut candidates = Vec::new();
 517         let mut seen_modules = FxHashSet::default();
 518         let not_local_module = crate_name.name != kw::Crate;
 519         let mut worklist = vec![(start_module, Vec::<ast::PathSegment>::new(), not_local_module)];
 520
 521         while let Some((in_module,
 522                         path_segments,
 523                         in_module_is_extern)) = worklist.pop() {
 524             // We have to visit module children in deterministic order to avoid
 525             // instabilities in reported imports (#43552).
 526             in_module.for_each_child(self, |this, ident, ns, name_binding| {
 527                 // avoid imports entirely
 528                 if name_binding.is_import() && !name_binding.is_extern_crate() { return; }
 529                 // avoid non-importable candidates as well
 530                 if !name_binding.is_importable() { return; }
 531
 532                 // collect results based on the filter function
 533                 if ident.name == lookup_ident.name && ns == namespace {
 534                     let res = name_binding.res();
 535                     if filter_fn(res) {
 536                         // create the path
 537                         let mut segms = path_segments.clone();
 538                         if lookup_ident.span.rust_2018() {
 539                             // crate-local absolute paths start with `crate::` in edition 2018
 540                             // FIXME: may also be stabilized for Rust 2015 (Issues #45477, #44660)
 541                             segms.insert(
 542                                 0, ast::PathSegment::from_ident(crate_name)
 543                             );
 544                         }
 545
 546                         segms.push(ast::PathSegment::from_ident(ident));
 547                         let path = Path {
 548                             span: name_binding.span,
 549                             segments: segms,
 550                         };
 551                         // the entity is accessible in the following cases:
 552                         // 1. if it's defined in the same crate, it's always
 553                         // accessible (since private entities can be made public)
 554                         // 2. if it's defined in another crate, it's accessible
 555                         // only if both the module is public and the entity is
 556                         // declared as public (due to pruning, we don't explore
 557                         // outside crate private modules => no need to check this)
 558                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
 559                             let did = match res {
 560                                 Res::Def(DefKind::Ctor(..), did) => this.parent(did),
 561                                 _ => res.opt_def_id(),
 562                             };
 563                             candidates.push(ImportSuggestion { did, path });
 564                         }
 565                     }
 566                 }
 567
 568                 // collect submodules to explore
 569                 if let Some(module) = name_binding.module() {
 570                     // form the path
 571                     let mut path_segments = path_segments.clone();
 572                     path_segments.push(ast::PathSegment::from_ident(ident));
 573
 574                     let is_extern_crate_that_also_appears_in_prelude =
 575                         name_binding.is_extern_crate() &&
 576                         lookup_ident.span.rust_2018();
 577
 578                     let is_visible_to_user =
 579                         !in_module_is_extern || name_binding.vis == ty::Visibility::Public;
 580
 581                     if !is_extern_crate_that_also_appears_in_prelude && is_visible_to_user {
 582                         // add the module to the lookup
 583                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
 584                         if seen_modules.insert(module.def_id().unwrap()) {
 585                             worklist.push((module, path_segments, is_extern));
 586                         }
 587                     }
 588                 }
 589             })
 590         }
 591
 592         candidates
 593     }
 594
 595     /// When name resolution fails, this method can be used to look up candidate
 596     /// entities with the expected name. It allows filtering them using the
 597     /// supplied predicate (which should be used to only accept the types of
 598     /// definitions expected, e.g., traits). The lookup spans across all crates.
 599     ///
 600     /// N.B., the method does not look into imports, but this is not a problem,
 601     /// since we report the definitions (thus, the de-aliased imports).
 602     crate fn lookup_import_candidates<FilterFn>(
 603         &mut self, lookup_ident: Ident, namespace: Namespace, filter_fn: FilterFn
 604     ) -> Vec<ImportSuggestion>
 605         where FilterFn: Fn(Res) -> bool
 606     {
 607         let mut suggestions = self.lookup_import_candidates_from_module(
 608             lookup_ident, namespace, self.graph_root, Ident::with_dummy_span(kw::Crate), &filter_fn
 609         );
 610
 611         if lookup_ident.span.rust_2018() {
 612             let extern_prelude_names = self.extern_prelude.clone();
 613             for (ident, _) in extern_prelude_names.into_iter() {
 614                 if ident.span.from_expansion() {
 615                     // Idents are adjusted to the root context before being
 616                     // resolved in the extern prelude, so reporting this to the
 617                     // user is no help. This skips the injected
 618                     // `extern crate std` in the 2018 edition, which would
 619                     // otherwise cause duplicate suggestions.
 620                     continue;
 621                 }
 622                 if let Some(crate_id) = self.crate_loader.maybe_process_path_extern(ident.name,
 623                                                                                     ident.span) {
 624                     let crate_root = self.get_module(DefId {
 625                         krate: crate_id,
 626                         index: CRATE_DEF_INDEX,
 627                     });
 628                     suggestions.extend(self.lookup_import_candidates_from_module(
 629                         lookup_ident, namespace, crate_root, ident, &filter_fn));
 630                 }
 631             }
 632         }
 633
 634         suggestions
 635     }
 636
 637     crate fn unresolved_macro_suggestions(
 638         &mut self,
 639         err: &mut DiagnosticBuilder<'a>,
 640         macro_kind: MacroKind,
 641         parent_scope: &ParentScope<'a>,
 642         ident: Ident,
 643     ) {
 644         let is_expected = &|res: Res| res.macro_kind() == Some(macro_kind);
 645         let suggestion = self.early_lookup_typo_candidate(
 646             ScopeSet::Macro(macro_kind), parent_scope, ident, is_expected
 647         );
 648         self.add_typo_suggestion(err, suggestion, ident.span);
 649
 650         if macro_kind == MacroKind::Derive &&
 651            (ident.as_str() == "Send" || ident.as_str() == "Sync") {
 652             let msg = format!("unsafe traits like `{}` should be implemented explicitly", ident);
 653             err.span_note(ident.span, &msg);
 654         }
 655         if self.macro_names.contains(&ident.modern()) {
 656             err.help("have you added the `#[macro_use]` on the module/import?");
 657         }
 658     }
 659
 660     crate fn add_typo_suggestion(
 661         &self,
 662         err: &mut DiagnosticBuilder<'_>,
 663         suggestion: Option<TypoSuggestion>,
 664         span: Span,
 665     ) -> bool {
 666         if let Some(suggestion) = suggestion {
 667             let msg = format!(
 668                 "{} {} with a similar name exists", suggestion.res.article(), suggestion.res.descr()
 669             );
 670             err.span_suggestion(
 671                 span, &msg, suggestion.candidate.to_string(), Applicability::MaybeIncorrect
 672             );
 673             let def_span = suggestion.res.opt_def_id()
 674                 .and_then(|def_id| self.definitions.opt_span(def_id));
 675             if let Some(span) = def_span {
 676                 err.span_label(span, &format!(
 677                     "similarly named {} `{}` defined here",
 678                     suggestion.res.descr(),
 679                     suggestion.candidate.as_str(),
 680                 ));
 681             }
 682             return true;
 683         }
 684         false
 685     }
 686 }
 687
 688 impl<'a, 'b> ImportResolver<'a, 'b> {
 689     /// Adds suggestions for a path that cannot be resolved.
 690     pub(crate) fn make_path_suggestion(
 691         &mut self,
 692         span: Span,
 693         mut path: Vec<Segment>,
 694         parent_scope: &ParentScope<'b>,
 695     ) -> Option<(Vec<Segment>, Vec<String>)> {
 696         debug!("make_path_suggestion: span={:?} path={:?}", span, path);
 697
 698         match (path.get(0), path.get(1)) {
 699             // `{{root}}::ident::...` on both editions.
 700             // On 2015 `{{root}}` is usually added implicitly.
 701             (Some(fst), Some(snd)) if fst.ident.name == kw::PathRoot &&
 702                                       !snd.ident.is_path_segment_keyword() => {}
 703             // `ident::...` on 2018.
 704             (Some(fst), _) if fst.ident.span.rust_2018() &&
 705                               !fst.ident.is_path_segment_keyword() => {
 706                 // Insert a placeholder that's later replaced by `self`/`super`/etc.
 707                 path.insert(0, Segment::from_ident(Ident::invalid()));
 708             }
 709             _ => return None,
 710         }
 711
 712         self.make_missing_self_suggestion(span, path.clone(), parent_scope)
 713             .or_else(|| self.make_missing_crate_suggestion(span, path.clone(), parent_scope))
 714             .or_else(|| self.make_missing_super_suggestion(span, path.clone(), parent_scope))
 715             .or_else(|| self.make_external_crate_suggestion(span, path, parent_scope))
 716     }
 717
 718     /// Suggest a missing `self::` if that resolves to an correct module.
 719     ///
 720     /// ```
 721     ///    |
 722     /// LL | use foo::Bar;
 723     ///    |     ^^^ did you mean `self::foo`?
 724     /// ```
 725     fn make_missing_self_suggestion(
 726         &mut self,
 727         span: Span,
 728         mut path: Vec<Segment>,
 729         parent_scope: &ParentScope<'b>,
 730     ) -> Option<(Vec<Segment>, Vec<String>)> {
 731         // Replace first ident with `self` and check if that is valid.
 732         path[0].ident.name = kw::SelfLower;
 733         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
 734         debug!("make_missing_self_suggestion: path={:?} result={:?}", path, result);
 735         if let PathResult::Module(..) = result {
 736             Some((path, Vec::new()))
 737         } else {
 738             None
 739         }
 740     }
 741
 742     /// Suggests a missing `crate::` if that resolves to an correct module.
 743     ///
 744     /// ```
 745     ///    |
 746     /// LL | use foo::Bar;
 747     ///    |     ^^^ did you mean `crate::foo`?
 748     /// ```
 749     fn make_missing_crate_suggestion(
 750         &mut self,
 751         span: Span,
 752         mut path: Vec<Segment>,
 753         parent_scope: &ParentScope<'b>,
 754     ) -> Option<(Vec<Segment>, Vec<String>)> {
 755         // Replace first ident with `crate` and check if that is valid.
 756         path[0].ident.name = kw::Crate;
 757         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
 758         debug!("make_missing_crate_suggestion:  path={:?} result={:?}", path, result);
 759         if let PathResult::Module(..) = result {
 760             Some((
 761                 path,
 762                 vec![
 763                     "`use` statements changed in Rust 2018; read more at \
 764                      <https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-\
 765                      clarity.html>".to_string()
 766                 ],
 767             ))
 768         } else {
 769             None
 770         }
 771     }
 772
 773     /// Suggests a missing `super::` if that resolves to an correct module.
 774     ///
 775     /// ```
 776     ///    |
 777     /// LL | use foo::Bar;
 778     ///    |     ^^^ did you mean `super::foo`?
 779     /// ```
 780     fn make_missing_super_suggestion(
 781         &mut self,
 782         span: Span,
 783         mut path: Vec<Segment>,
 784         parent_scope: &ParentScope<'b>,
 785     ) -> Option<(Vec<Segment>, Vec<String>)> {
 786         // Replace first ident with `crate` and check if that is valid.
 787         path[0].ident.name = kw::Super;
 788         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
 789         debug!("make_missing_super_suggestion:  path={:?} result={:?}", path, result);
 790         if let PathResult::Module(..) = result {
 791             Some((path, Vec::new()))
 792         } else {
 793             None
 794         }
 795     }
 796
 797     /// Suggests a missing external crate name if that resolves to an correct module.
 798     ///
 799     /// ```
 800     ///    |
 801     /// LL | use foobar::Baz;
 802     ///    |     ^^^^^^ did you mean `baz::foobar`?
 803     /// ```
 804     ///
 805     /// Used when importing a submodule of an external crate but missing that crate's
 806     /// name as the first part of path.
 807     fn make_external_crate_suggestion(
 808         &mut self,
 809         span: Span,
 810         mut path: Vec<Segment>,
 811         parent_scope: &ParentScope<'b>,
 812     ) -> Option<(Vec<Segment>, Vec<String>)> {
 813         if path[1].ident.span.rust_2015() {
 814             return None;
 815         }
 816
 817         // Sort extern crate names in reverse order to get
 818         // 1) some consistent ordering for emitted dignostics, and
 819         // 2) `std` suggestions before `core` suggestions.
 820         let mut extern_crate_names =
 821             self.r.extern_prelude.iter().map(|(ident, _)| ident.name).collect::<Vec<_>>();
 822         extern_crate_names.sort_by_key(|name| Reverse(name.as_str()));
 823
 824         for name in extern_crate_names.into_iter() {
 825             // Replace first ident with a crate name and check if that is valid.
 826             path[0].ident.name = name;
 827             let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
 828             debug!("make_external_crate_suggestion: name={:?} path={:?} result={:?}",
 829                     name, path, result);
 830             if let PathResult::Module(..) = result {
 831                 return Some((path, Vec::new()));
 832             }
 833         }
 834
 835         None
 836     }
 837
 838     /// Suggests importing a macro from the root of the crate rather than a module within
 839     /// the crate.
 840     ///
 841     /// ```
 842     /// help: a macro with this name exists at the root of the crate
 843     ///    |
 844     /// LL | use issue_59764::makro;
 845     ///    |     ^^^^^^^^^^^^^^^^^^
 846     ///    |
 847     ///    = note: this could be because a macro annotated with `#[macro_export]` will be exported
 848     ///            at the root of the crate instead of the module where it is defined
 849     /// ```
 850     pub(crate) fn check_for_module_export_macro(
 851         &mut self,
 852         directive: &'b ImportDirective<'b>,
 853         module: ModuleOrUniformRoot<'b>,
 854         ident: Ident,
 855     ) -> Option<(Option<Suggestion>, Vec<String>)> {
 856         let mut crate_module = if let ModuleOrUniformRoot::Module(module) = module {
 857             module
 858         } else {
 859             return None;
 860         };
 861
 862         while let Some(parent) = crate_module.parent {
 863             crate_module = parent;
 864         }
 865
 866         if ModuleOrUniformRoot::same_def(ModuleOrUniformRoot::Module(crate_module), module) {
 867             // Don't make a suggestion if the import was already from the root of the
 868             // crate.
 869             return None;
 870         }
 871
 872         let resolutions = self.r.resolutions(crate_module).borrow();
 873         let resolution = resolutions.get(&self.r.new_key(ident, MacroNS))?;
 874         let binding = resolution.borrow().binding()?;
 875         if let Res::Def(DefKind::Macro(MacroKind::Bang), _) = binding.res() {
 876             let module_name = crate_module.kind.name().unwrap();
 877             let import = match directive.subclass {
 878                 ImportDirectiveSubclass::SingleImport { source, target, .. } if source != target =>
 879                     format!("{} as {}", source, target),
 880                 _ => format!("{}", ident),
 881             };
 882
 883             let mut corrections: Vec<(Span, String)> = Vec::new();
 884             if !directive.is_nested() {
 885                 // Assume this is the easy case of `use issue_59764::foo::makro;` and just remove
 886                 // intermediate segments.
 887                 corrections.push((directive.span, format!("{}::{}", module_name, import)));
 888             } else {
 889                 // Find the binding span (and any trailing commas and spaces).
 890                 //   ie. `use a::b::{c, d, e};`
 891                 //                      ^^^
 892                 let (found_closing_brace, binding_span) = find_span_of_binding_until_next_binding(
 893                     self.r.session, directive.span, directive.use_span,
 894                 );
 895                 debug!("check_for_module_export_macro: found_closing_brace={:?} binding_span={:?}",
 896                        found_closing_brace, binding_span);
 897
 898                 let mut removal_span = binding_span;
 899                 if found_closing_brace {
 900                     // If the binding span ended with a closing brace, as in the below example:
 901                     //   ie. `use a::b::{c, d};`
 902                     //                      ^
 903                     // Then expand the span of characters to remove to include the previous
 904                     // binding's trailing comma.
 905                     //   ie. `use a::b::{c, d};`
 906                     //                    ^^^
 907                     if let Some(previous_span) = extend_span_to_previous_binding(
 908                         self.r.session, binding_span,
 909                     ) {
 910                         debug!("check_for_module_export_macro: previous_span={:?}", previous_span);
 911                         removal_span = removal_span.with_lo(previous_span.lo());
 912                     }
 913                 }
 914                 debug!("check_for_module_export_macro: removal_span={:?}", removal_span);
 915
 916                 // Remove the `removal_span`.
 917                 corrections.push((removal_span, "".to_string()));
 918
 919                 // Find the span after the crate name and if it has nested imports immediatately
 920                 // after the crate name already.
 921                 //   ie. `use a::b::{c, d};`
 922                 //               ^^^^^^^^^
 923                 //   or  `use a::{b, c, d}};`
 924                 //               ^^^^^^^^^^^
 925                 let (has_nested, after_crate_name) = find_span_immediately_after_crate_name(
 926                     self.r.session, module_name, directive.use_span,
 927                 );
 928                 debug!("check_for_module_export_macro: has_nested={:?} after_crate_name={:?}",
 929                        has_nested, after_crate_name);
 930
 931                 let source_map = self.r.session.source_map();
 932
 933                 // Add the import to the start, with a `{` if required.
 934                 let start_point = source_map.start_point(after_crate_name);
 935                 if let Ok(start_snippet) = source_map.span_to_snippet(start_point) {
 936                     corrections.push((
 937                         start_point,
 938                         if has_nested {
 939                             // In this case, `start_snippet` must equal '{'.
 940                             format!("{}{}, ", start_snippet, import)
 941                         } else {
 942                             // In this case, add a `{`, then the moved import, then whatever
 943                             // was there before.
 944                             format!("{{{}, {}", import, start_snippet)
 945                         }
 946                     ));
 947                 }
 948
 949                 // Add a `};` to the end if nested, matching the `{` added at the start.
 950                 if !has_nested {
 951                     corrections.push((source_map.end_point(after_crate_name),
 952                                      "};".to_string()));
 953                 }
 954             }
 955
 956             let suggestion = Some((
 957                 corrections,
 958                 String::from("a macro with this name exists at the root of the crate"),
 959                 Applicability::MaybeIncorrect,
 960             ));
 961             let note = vec![
 962                 "this could be because a macro annotated with `#[macro_export]` will be exported \
 963                  at the root of the crate instead of the module where it is defined".to_string(),
 964             ];
 965             Some((suggestion, note))
 966         } else {
 967             None
 968         }
 969     }
 970 }
 971
 972 /// Given a `binding_span` of a binding within a use statement:
 973 ///
 974 /// ```
 975 /// use foo::{a, b, c};
 976 ///              ^
 977 /// ```
 978 ///
 979 /// then return the span until the next binding or the end of the statement:
 980 ///
 981 /// ```
 982 /// use foo::{a, b, c};
 983 ///              ^^^
 984 /// ```
 985 pub(crate) fn find_span_of_binding_until_next_binding(
 986     sess: &Session,
 987     binding_span: Span,
 988     use_span: Span,
 989 ) -> (bool, Span) {
 990     let source_map = sess.source_map();
 991
 992     // Find the span of everything after the binding.
 993     //   ie. `a, e};` or `a};`
 994     let binding_until_end = binding_span.with_hi(use_span.hi());
 995
 996     // Find everything after the binding but not including the binding.
 997     //   ie. `, e};` or `};`
 998     let after_binding_until_end = binding_until_end.with_lo(binding_span.hi());
 999
1000     // Keep characters in the span until we encounter something that isn't a comma or
1001     // whitespace.
1002     //   ie. `, ` or ``.
1003     //
1004     // Also note whether a closing brace character was encountered. If there
1005     // was, then later go backwards to remove any trailing commas that are left.
1006     let mut found_closing_brace = false;
1007     let after_binding_until_next_binding = source_map.span_take_while(
1008         after_binding_until_end,
1009         |&ch| {
1010             if ch == '}' { found_closing_brace = true; }
1011             ch == ' ' || ch == ','
1012         }
1013     );
1014
1015     // Combine the two spans.
1016     //   ie. `a, ` or `a`.
1017     //
1018     // Removing these would leave `issue_52891::{d, e};` or `issue_52891::{d, e, };`
1019     let span = binding_span.with_hi(after_binding_until_next_binding.hi());
1020
1021     (found_closing_brace, span)
1022 }
1023
1024 /// Given a `binding_span`, return the span through to the comma or opening brace of the previous
1025 /// binding.
1026 ///
1027 /// ```
1028 /// use foo::a::{a, b, c};
1029 ///               ^^--- binding span
1030 ///               |
1031 ///               returned span
1032 ///
1033 /// use foo::{a, b, c};
1034 ///           --- binding span
1035 /// ```
1036 pub(crate) fn extend_span_to_previous_binding(
1037     sess: &Session,
1038     binding_span: Span,
1039 ) -> Option<Span> {
1040     let source_map = sess.source_map();
1041
1042     // `prev_source` will contain all of the source that came before the span.
1043     // Then split based on a command and take the first (ie. closest to our span)
1044     // snippet. In the example, this is a space.
1045     let prev_source = source_map.span_to_prev_source(binding_span).ok()?;
1046
1047     let prev_comma = prev_source.rsplit(',').collect::<Vec<_>>();
1048     let prev_starting_brace = prev_source.rsplit('{').collect::<Vec<_>>();
1049     if prev_comma.len() <= 1 || prev_starting_brace.len() <= 1 {
1050         return None;
1051     }
1052
1053     let prev_comma = prev_comma.first().unwrap();
1054     let prev_starting_brace = prev_starting_brace.first().unwrap();
1055
1056     // If the amount of source code before the comma is greater than
1057     // the amount of source code before the starting brace then we've only
1058     // got one item in the nested item (eg. `issue_52891::{self}`).
1059     if prev_comma.len() > prev_starting_brace.len() {
1060         return None;
1061     }
1062
1063     Some(binding_span.with_lo(BytePos(
1064         // Take away the number of bytes for the characters we've found and an
1065         // extra for the comma.
1066         binding_span.lo().0 - (prev_comma.as_bytes().len() as u32) - 1
1067     )))
1068 }
1069
1070 /// Given a `use_span` of a binding within a use statement, returns the highlighted span and if
1071 /// it is a nested use tree.
1072 ///
1073 /// ```
1074 /// use foo::a::{b, c};
1075 ///          ^^^^^^^^^^ // false
1076 ///
1077 /// use foo::{a, b, c};
1078 ///          ^^^^^^^^^^ // true
1079 ///
1080 /// use foo::{a, b::{c, d}};
1081 ///          ^^^^^^^^^^^^^^^ // true
1082 /// ```
1083 fn find_span_immediately_after_crate_name(
1084     sess: &Session,
1085     module_name: Symbol,
1086     use_span: Span,
1087 ) -> (bool, Span) {
1088     debug!("find_span_immediately_after_crate_name: module_name={:?} use_span={:?}",
1089            module_name, use_span);
1090     let source_map = sess.source_map();
1091
1092     // Using `use issue_59764::foo::{baz, makro};` as an example throughout..
1093     let mut num_colons = 0;
1094     // Find second colon.. `use issue_59764:`
1095     let until_second_colon = source_map.span_take_while(use_span, |c| {
1096         if *c == ':' { num_colons += 1; }
1097         match c {
1098             ':' if num_colons == 2 => false,
1099             _ => true,
1100         }
1101     });
1102     // Find everything after the second colon.. `foo::{baz, makro};`
1103     let from_second_colon = use_span.with_lo(until_second_colon.hi() + BytePos(1));
1104
1105     let mut found_a_non_whitespace_character = false;
1106     // Find the first non-whitespace character in `from_second_colon`.. `f`
1107     let after_second_colon = source_map.span_take_while(from_second_colon, |c| {
1108         if found_a_non_whitespace_character { return false; }
1109         if !c.is_whitespace() { found_a_non_whitespace_character = true; }
1110         true
1111     });
1112
1113     // Find the first `{` in from_second_colon.. `foo::{`
1114     let next_left_bracket = source_map.span_through_char(from_second_colon, '{');
1115
1116     (next_left_bracket == after_second_colon, from_second_colon)
1117 }
1118
1119 /// When an entity with a given name is not available in scope, we search for
1120 /// entities with that name in all crates. This method allows outputting the
1121 /// results of this search in a programmer-friendly way
1122 crate fn show_candidates(
1123     err: &mut DiagnosticBuilder<'_>,
1124     // This is `None` if all placement locations are inside expansions
1125     span: Option<Span>,
1126     candidates: &[ImportSuggestion],
1127     better: bool,
1128     found_use: bool,
1129 ) {
1130     // we want consistent results across executions, but candidates are produced
1131     // by iterating through a hash map, so make sure they are ordered:
1132     let mut path_strings: Vec<_> =
1133         candidates.into_iter().map(|c| path_names_to_string(&c.path)).collect();
1134     path_strings.sort();
1135
1136     let better = if better { "better " } else { "" };
1137     let msg_diff = match path_strings.len() {
1138         1 => " is found in another module, you can import it",
1139         _ => "s are found in other modules, you can import them",
1140     };
1141     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
1142
1143     if let Some(span) = span {
1144         for candidate in &mut path_strings {
1145             // produce an additional newline to separate the new use statement
1146             // from the directly following item.
1147             let additional_newline = if found_use {
1148                 ""
1149             } else {
1150                 "\n"
1151             };
1152             *candidate = format!("use {};\n{}", candidate, additional_newline);
1153         }
1154
1155         err.span_suggestions(
1156             span,
1157             &msg,
1158             path_strings.into_iter(),
1159             Applicability::Unspecified,
1160         );
1161     } else {
1162         let mut msg = msg;
1163         msg.push(':');
1164         for candidate in path_strings {
1165             msg.push('\n');
1166             msg.push_str(&candidate);
1167         }
1168     }
1169 }