src/librustc_resolve/diagnostics.rs

   1 use std::cmp::Reverse;
   2 use std::ptr;
   3
   4 use log::debug;
   5 use rustc::bug;
   6 use rustc::session::Session;
   7 use rustc::ty::{self, DefIdTree};
   8 use rustc_ast::ast::{self, Ident, Path};
   9 use rustc_ast::util::lev_distance::find_best_match_for_name;
  10 use rustc_ast_pretty::pprust;
  11 use rustc_data_structures::fx::FxHashSet;
  12 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
  13 use rustc_feature::BUILTIN_ATTRIBUTES;
  14 use rustc_hir::def::Namespace::{self, *};
  15 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind};
  16 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
  17 use rustc_span::hygiene::MacroKind;
  18 use rustc_span::source_map::SourceMap;
  19 use rustc_span::symbol::{kw, Symbol};
  20 use rustc_span::{BytePos, MultiSpan, Span};
  21
  22 use crate::imports::{Import, ImportKind, ImportResolver};
  23 use crate::path_names_to_string;
  24 use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind};
  25 use crate::{
  26     BindingError, CrateLint, HasGenericParams, MacroRulesScope, Module, ModuleOrUniformRoot,
  27 };
  28 use crate::{NameBinding, NameBindingKind, PrivacyError, VisResolutionError};
  29 use crate::{ParentScope, PathResult, ResolutionError, Resolver, Scope, ScopeSet, Segment};
  30
  31 type Res = def::Res<ast::NodeId>;
  32
  33 /// A vector of spans and replacements, a message and applicability.
  34 crate type Suggestion = (Vec<(Span, String)>, String, Applicability);
  35
  36 crate struct TypoSuggestion {
  37     pub candidate: Symbol,
  38     pub res: Res,
  39 }
  40
  41 impl TypoSuggestion {
  42     crate fn from_res(candidate: Symbol, res: Res) -> TypoSuggestion {
  43         TypoSuggestion { candidate, res }
  44     }
  45 }
  46
  47 /// A free importable items suggested in case of resolution failure.
  48 crate struct ImportSuggestion {
  49     pub did: Option<DefId>,
  50     pub path: Path,
  51 }
  52
  53 /// Adjust the impl span so that just the `impl` keyword is taken by removing
  54 /// everything after `<` (`"impl<T> Iterator for A<T> {}" -> "impl"`) and
  55 /// everything after the first whitespace (`"impl Iterator for A" -> "impl"`).
  56 ///
  57 /// *Attention*: the method used is very fragile since it essentially duplicates the work of the
  58 /// parser. If you need to use this function or something similar, please consider updating the
  59 /// `source_map` functions and this function to something more robust.
  60 fn reduce_impl_span_to_impl_keyword(sm: &SourceMap, impl_span: Span) -> Span {
  61     let impl_span = sm.span_until_char(impl_span, '<');
  62     let impl_span = sm.span_until_whitespace(impl_span);
  63     impl_span
  64 }
  65
  66 impl<'a> Resolver<'a> {
  67     crate fn add_module_candidates(
  68         &mut self,
  69         module: Module<'a>,
  70         names: &mut Vec<TypoSuggestion>,
  71         filter_fn: &impl Fn(Res) -> bool,
  72     ) {
  73         for (key, resolution) in self.resolutions(module).borrow().iter() {
  74             if let Some(binding) = resolution.borrow().binding {
  75                 let res = binding.res();
  76                 if filter_fn(res) {
  77                     names.push(TypoSuggestion::from_res(key.ident.name, res));
  78                 }
  79             }
  80         }
  81     }
  82
  83     /// Combines an error with provided span and emits it.
  84     ///
  85     /// This takes the error provided, combines it with the span and any additional spans inside the
  86     /// error and emits it.
  87     crate fn report_error(&self, span: Span, resolution_error: ResolutionError<'_>) {
  88         self.into_struct_error(span, resolution_error).emit();
  89     }
  90
  91     crate fn into_struct_error(
  92         &self,
  93         span: Span,
  94         resolution_error: ResolutionError<'_>,
  95     ) -> DiagnosticBuilder<'_> {
  96         match resolution_error {
  97             ResolutionError::GenericParamsFromOuterFunction(outer_res, has_generic_params) => {
  98                 let mut err = struct_span_err!(
  99                     self.session,
 100                     span,
 101                     E0401,
 102                     "can't use generic parameters from outer function",
 103                 );
 104                 err.span_label(span, "use of generic parameter from outer function".to_string());
 105
 106                 let sm = self.session.source_map();
 107                 match outer_res {
 108                     Res::SelfTy(maybe_trait_defid, maybe_impl_defid) => {
 109                         if let Some(impl_span) =
 110                             maybe_impl_defid.and_then(|def_id| self.definitions.opt_span(def_id))
 111                         {
 112                             err.span_label(
 113                                 reduce_impl_span_to_impl_keyword(sm, impl_span),
 114                                 "`Self` type implicitly declared here, by this `impl`",
 115                             );
 116                         }
 117                         match (maybe_trait_defid, maybe_impl_defid) {
 118                             (Some(_), None) => {
 119                                 err.span_label(span, "can't use `Self` here");
 120                             }
 121                             (_, Some(_)) => {
 122                                 err.span_label(span, "use a type here instead");
 123                             }
 124                             (None, None) => bug!("`impl` without trait nor type?"),
 125                         }
 126                         return err;
 127                     }
 128                     Res::Def(DefKind::TyParam, def_id) => {
 129                         if let Some(span) = self.definitions.opt_span(def_id) {
 130                             err.span_label(span, "type parameter from outer function");
 131                         }
 132                     }
 133                     Res::Def(DefKind::ConstParam, def_id) => {
 134                         if let Some(span) = self.definitions.opt_span(def_id) {
 135                             err.span_label(span, "const parameter from outer function");
 136                         }
 137                     }
 138                     _ => {
 139                         bug!(
 140                             "GenericParamsFromOuterFunction should only be used with Res::SelfTy, \
 141                             DefKind::TyParam"
 142                         );
 143                     }
 144                 }
 145
 146                 if has_generic_params == HasGenericParams::Yes {
 147                     // Try to retrieve the span of the function signature and generate a new
 148                     // message with a local type or const parameter.
 149                     let sugg_msg = "try using a local generic parameter instead";
 150                     if let Some((sugg_span, snippet)) = sm.generate_local_type_param_snippet(span) {
 151                         // Suggest the modification to the user
 152                         err.span_suggestion(
 153                             sugg_span,
 154                             sugg_msg,
 155                             snippet,
 156                             Applicability::MachineApplicable,
 157                         );
 158                     } else if let Some(sp) = sm.generate_fn_name_span(span) {
 159                         err.span_label(
 160                             sp,
 161                             "try adding a local generic parameter in this method instead"
 162                                 .to_string(),
 163                         );
 164                     } else {
 165                         err.help("try using a local generic parameter instead");
 166                     }
 167                 }
 168
 169                 err
 170             }
 171             ResolutionError::NameAlreadyUsedInParameterList(name, first_use_span) => {
 172                 let mut err = struct_span_err!(
 173                     self.session,
 174                     span,
 175                     E0403,
 176                     "the name `{}` is already used for a generic \
 177                      parameter in this item's generic parameters",
 178                     name,
 179                 );
 180                 err.span_label(span, "already used");
 181                 err.span_label(first_use_span, format!("first use of `{}`", name));
 182                 err
 183             }
 184             ResolutionError::MethodNotMemberOfTrait(method, trait_) => {
 185                 let mut err = struct_span_err!(
 186                     self.session,
 187                     span,
 188                     E0407,
 189                     "method `{}` is not a member of trait `{}`",
 190                     method,
 191                     trait_
 192                 );
 193                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 194                 err
 195             }
 196             ResolutionError::TypeNotMemberOfTrait(type_, trait_) => {
 197                 let mut err = struct_span_err!(
 198                     self.session,
 199                     span,
 200                     E0437,
 201                     "type `{}` is not a member of trait `{}`",
 202                     type_,
 203                     trait_
 204                 );
 205                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 206                 err
 207             }
 208             ResolutionError::ConstNotMemberOfTrait(const_, trait_) => {
 209                 let mut err = struct_span_err!(
 210                     self.session,
 211                     span,
 212                     E0438,
 213                     "const `{}` is not a member of trait `{}`",
 214                     const_,
 215                     trait_
 216                 );
 217                 err.span_label(span, format!("not a member of trait `{}`", trait_));
 218                 err
 219             }
 220             ResolutionError::VariableNotBoundInPattern(binding_error) => {
 221                 let BindingError { name, target, origin, could_be_path } = binding_error;
 222
 223                 let target_sp = target.iter().copied().collect::<Vec<_>>();
 224                 let origin_sp = origin.iter().copied().collect::<Vec<_>>();
 225
 226                 let msp = MultiSpan::from_spans(target_sp.clone());
 227                 let mut err = struct_span_err!(
 228                     self.session,
 229                     msp,
 230                     E0408,
 231                     "variable `{}` is not bound in all patterns",
 232                     name,
 233                 );
 234                 for sp in target_sp {
 235                     err.span_label(sp, format!("pattern doesn't bind `{}`", name));
 236                 }
 237                 for sp in origin_sp {
 238                     err.span_label(sp, "variable not in all patterns");
 239                 }
 240                 if *could_be_path {
 241                     let help_msg = format!(
 242                         "if you meant to match on a variant or a `const` item, consider \
 243                          making the path in the pattern qualified: `?::{}`",
 244                         name,
 245                     );
 246                     err.span_help(span, &help_msg);
 247                 }
 248                 err
 249             }
 250             ResolutionError::VariableBoundWithDifferentMode(variable_name, first_binding_span) => {
 251                 let mut err = struct_span_err!(
 252                     self.session,
 253                     span,
 254                     E0409,
 255                     "variable `{}` is bound inconsistently across alternatives separated by `|`",
 256                     variable_name
 257                 );
 258                 err.span_label(span, "bound in different ways");
 259                 err.span_label(first_binding_span, "first binding");
 260                 err
 261             }
 262             ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => {
 263                 let mut err = struct_span_err!(
 264                     self.session,
 265                     span,
 266                     E0415,
 267                     "identifier `{}` is bound more than once in this parameter list",
 268                     identifier
 269                 );
 270                 err.span_label(span, "used as parameter more than once");
 271                 err
 272             }
 273             ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => {
 274                 let mut err = struct_span_err!(
 275                     self.session,
 276                     span,
 277                     E0416,
 278                     "identifier `{}` is bound more than once in the same pattern",
 279                     identifier
 280                 );
 281                 err.span_label(span, "used in a pattern more than once");
 282                 err
 283             }
 284             ResolutionError::UndeclaredLabel(name, lev_candidate) => {
 285                 let mut err = struct_span_err!(
 286                     self.session,
 287                     span,
 288                     E0426,
 289                     "use of undeclared label `{}`",
 290                     name
 291                 );
 292                 if let Some(lev_candidate) = lev_candidate {
 293                     err.span_suggestion(
 294                         span,
 295                         "a label with a similar name exists in this scope",
 296                         lev_candidate.to_string(),
 297                         Applicability::MaybeIncorrect,
 298                     );
 299                 } else {
 300                     err.span_label(span, format!("undeclared label `{}`", name));
 301                 }
 302                 err
 303             }
 304             ResolutionError::SelfImportsOnlyAllowedWithin => struct_span_err!(
 305                 self.session,
 306                 span,
 307                 E0429,
 308                 "{}",
 309                 "`self` imports are only allowed within a { } list"
 310             ),
 311             ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
 312                 let mut err = struct_span_err!(
 313                     self.session,
 314                     span,
 315                     E0430,
 316                     "`self` import can only appear once in an import list"
 317                 );
 318                 err.span_label(span, "can only appear once in an import list");
 319                 err
 320             }
 321             ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
 322                 let mut err = struct_span_err!(
 323                     self.session,
 324                     span,
 325                     E0431,
 326                     "`self` import can only appear in an import list with \
 327                                                 a non-empty prefix"
 328                 );
 329                 err.span_label(span, "can only appear in an import list with a non-empty prefix");
 330                 err
 331             }
 332             ResolutionError::FailedToResolve { label, suggestion } => {
 333                 let mut err =
 334                     struct_span_err!(self.session, span, E0433, "failed to resolve: {}", &label);
 335                 err.span_label(span, label);
 336
 337                 if let Some((suggestions, msg, applicability)) = suggestion {
 338                     err.multipart_suggestion(&msg, suggestions, applicability);
 339                 }
 340
 341                 err
 342             }
 343             ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
 344                 let mut err = struct_span_err!(
 345                     self.session,
 346                     span,
 347                     E0434,
 348                     "{}",
 349                     "can't capture dynamic environment in a fn item"
 350                 );
 351                 err.help("use the `|| { ... }` closure form instead");
 352                 err
 353             }
 354             ResolutionError::AttemptToUseNonConstantValueInConstant => {
 355                 let mut err = struct_span_err!(
 356                     self.session,
 357                     span,
 358                     E0435,
 359                     "attempt to use a non-constant value in a constant"
 360                 );
 361                 err.span_label(span, "non-constant value");
 362                 err
 363             }
 364             ResolutionError::BindingShadowsSomethingUnacceptable(what_binding, name, binding) => {
 365                 let res = binding.res();
 366                 let shadows_what = res.descr();
 367                 let mut err = struct_span_err!(
 368                     self.session,
 369                     span,
 370                     E0530,
 371                     "{}s cannot shadow {}s",
 372                     what_binding,
 373                     shadows_what
 374                 );
 375                 err.span_label(
 376                     span,
 377                     format!("cannot be named the same as {} {}", res.article(), shadows_what),
 378                 );
 379                 let participle = if binding.is_import() { "imported" } else { "defined" };
 380                 let msg = format!("the {} `{}` is {} here", shadows_what, name, participle);
 381                 err.span_label(binding.span, msg);
 382                 err
 383             }
 384             ResolutionError::ForwardDeclaredTyParam => {
 385                 let mut err = struct_span_err!(
 386                     self.session,
 387                     span,
 388                     E0128,
 389                     "type parameters with a default cannot use \
 390                                                 forward declared identifiers"
 391                 );
 392                 err.span_label(
 393                     span,
 394                     "defaulted type parameters cannot be forward declared".to_string(),
 395                 );
 396                 err
 397             }
 398             ResolutionError::SelfInTyParamDefault => {
 399                 let mut err = struct_span_err!(
 400                     self.session,
 401                     span,
 402                     E0735,
 403                     "type parameters cannot use `Self` in their defaults"
 404                 );
 405                 err.span_label(span, "`Self` in type parameter default".to_string());
 406                 err
 407             }
 408         }
 409     }
 410
 411     crate fn report_vis_error(&self, vis_resolution_error: VisResolutionError<'_>) {
 412         match vis_resolution_error {
 413             VisResolutionError::Relative2018(span, path) => {
 414                 let mut err = self.session.struct_span_err(
 415                     span,
 416                     "relative paths are not supported in visibilities on 2018 edition",
 417                 );
 418                 err.span_suggestion(
 419                     path.span,
 420                     "try",
 421                     format!("crate::{}", pprust::path_to_string(&path)),
 422                     Applicability::MaybeIncorrect,
 423                 );
 424                 err
 425             }
 426             VisResolutionError::AncestorOnly(span) => struct_span_err!(
 427                 self.session,
 428                 span,
 429                 E0742,
 430                 "visibilities can only be restricted to ancestor modules"
 431             ),
 432             VisResolutionError::FailedToResolve(span, label, suggestion) => {
 433                 self.into_struct_error(span, ResolutionError::FailedToResolve { label, suggestion })
 434             }
 435             VisResolutionError::ExpectedFound(span, path_str, res) => {
 436                 let mut err = struct_span_err!(
 437                     self.session,
 438                     span,
 439                     E0577,
 440                     "expected module, found {} `{}`",
 441                     res.descr(),
 442                     path_str
 443                 );
 444                 err.span_label(span, "not a module");
 445                 err
 446             }
 447             VisResolutionError::Indeterminate(span) => struct_span_err!(
 448                 self.session,
 449                 span,
 450                 E0578,
 451                 "cannot determine resolution for the visibility"
 452             ),
 453             VisResolutionError::ModuleOnly(span) => {
 454                 self.session.struct_span_err(span, "visibility must resolve to a module")
 455             }
 456         }
 457         .emit()
 458     }
 459
 460     /// Lookup typo candidate in scope for a macro or import.
 461     fn early_lookup_typo_candidate(
 462         &mut self,
 463         scope_set: ScopeSet,
 464         parent_scope: &ParentScope<'a>,
 465         ident: Ident,
 466         filter_fn: &impl Fn(Res) -> bool,
 467     ) -> Option<TypoSuggestion> {
 468         let mut suggestions = Vec::new();
 469         self.visit_scopes(scope_set, parent_scope, ident, |this, scope, use_prelude, _| {
 470             match scope {
 471                 Scope::DeriveHelpers(expn_id) => {
 472                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 473                     if filter_fn(res) {
 474                         suggestions.extend(
 475                             this.helper_attrs
 476                                 .get(&expn_id)
 477                                 .into_iter()
 478                                 .flatten()
 479                                 .map(|ident| TypoSuggestion::from_res(ident.name, res)),
 480                         );
 481                     }
 482                 }
 483                 Scope::DeriveHelpersCompat => {
 484                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 485                     if filter_fn(res) {
 486                         for derive in parent_scope.derives {
 487                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 488                             if let Ok((Some(ext), _)) = this.resolve_macro_path(
 489                                 derive,
 490                                 Some(MacroKind::Derive),
 491                                 parent_scope,
 492                                 false,
 493                                 false,
 494                             ) {
 495                                 suggestions.extend(
 496                                     ext.helper_attrs
 497                                         .iter()
 498                                         .map(|name| TypoSuggestion::from_res(*name, res)),
 499                                 );
 500                             }
 501                         }
 502                     }
 503                 }
 504                 Scope::MacroRules(macro_rules_scope) => {
 505                     if let MacroRulesScope::Binding(macro_rules_binding) = macro_rules_scope {
 506                         let res = macro_rules_binding.binding.res();
 507                         if filter_fn(res) {
 508                             suggestions
 509                                 .push(TypoSuggestion::from_res(macro_rules_binding.ident.name, res))
 510                         }
 511                     }
 512                 }
 513                 Scope::CrateRoot => {
 514                     let root_ident = Ident::new(kw::PathRoot, ident.span);
 515                     let root_module = this.resolve_crate_root(root_ident);
 516                     this.add_module_candidates(root_module, &mut suggestions, filter_fn);
 517                 }
 518                 Scope::Module(module) => {
 519                     this.add_module_candidates(module, &mut suggestions, filter_fn);
 520                 }
 521                 Scope::RegisteredAttrs => {
 522                     let res = Res::NonMacroAttr(NonMacroAttrKind::Registered);
 523                     if filter_fn(res) {
 524                         suggestions.extend(
 525                             this.registered_attrs
 526                                 .iter()
 527                                 .map(|ident| TypoSuggestion::from_res(ident.name, res)),
 528                         );
 529                     }
 530                 }
 531                 Scope::MacroUsePrelude => {
 532                     suggestions.extend(this.macro_use_prelude.iter().filter_map(
 533                         |(name, binding)| {
 534                             let res = binding.res();
 535                             filter_fn(res).then_some(TypoSuggestion::from_res(*name, res))
 536                         },
 537                     ));
 538                 }
 539                 Scope::BuiltinAttrs => {
 540                     let res = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 541                     if filter_fn(res) {
 542                         suggestions.extend(
 543                             BUILTIN_ATTRIBUTES
 544                                 .iter()
 545                                 .map(|(name, ..)| TypoSuggestion::from_res(*name, res)),
 546                         );
 547                     }
 548                 }
 549                 Scope::ExternPrelude => {
 550                     suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
 551                         let res = Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX));
 552                         filter_fn(res).then_some(TypoSuggestion::from_res(ident.name, res))
 553                     }));
 554                 }
 555                 Scope::ToolPrelude => {
 556                     let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
 557                     suggestions.extend(
 558                         this.registered_tools
 559                             .iter()
 560                             .map(|ident| TypoSuggestion::from_res(ident.name, res)),
 561                     );
 562                 }
 563                 Scope::StdLibPrelude => {
 564                     if let Some(prelude) = this.prelude {
 565                         let mut tmp_suggestions = Vec::new();
 566                         this.add_module_candidates(prelude, &mut tmp_suggestions, filter_fn);
 567                         suggestions.extend(
 568                             tmp_suggestions
 569                                 .into_iter()
 570                                 .filter(|s| use_prelude || this.is_builtin_macro(s.res)),
 571                         );
 572                     }
 573                 }
 574                 Scope::BuiltinTypes => {
 575                     let primitive_types = &this.primitive_type_table.primitive_types;
 576                     suggestions.extend(primitive_types.iter().flat_map(|(name, prim_ty)| {
 577                         let res = Res::PrimTy(*prim_ty);
 578                         filter_fn(res).then_some(TypoSuggestion::from_res(*name, res))
 579                     }))
 580                 }
 581             }
 582
 583             None::<()>
 584         });
 585
 586         // Make sure error reporting is deterministic.
 587         suggestions.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 588
 589         match find_best_match_for_name(
 590             suggestions.iter().map(|suggestion| &suggestion.candidate),
 591             &ident.as_str(),
 592             None,
 593         ) {
 594             Some(found) if found != ident.name => {
 595                 suggestions.into_iter().find(|suggestion| suggestion.candidate == found)
 596             }
 597             _ => None,
 598         }
 599     }
 600
 601     fn lookup_import_candidates_from_module<FilterFn>(
 602         &mut self,
 603         lookup_ident: Ident,
 604         namespace: Namespace,
 605         start_module: Module<'a>,
 606         crate_name: Ident,
 607         filter_fn: FilterFn,
 608     ) -> Vec<ImportSuggestion>
 609     where
 610         FilterFn: Fn(Res) -> bool,
 611     {
 612         let mut candidates = Vec::new();
 613         let mut seen_modules = FxHashSet::default();
 614         let not_local_module = crate_name.name != kw::Crate;
 615         let mut worklist = vec![(start_module, Vec::<ast::PathSegment>::new(), not_local_module)];
 616
 617         while let Some((in_module, path_segments, in_module_is_extern)) = worklist.pop() {
 618             // We have to visit module children in deterministic order to avoid
 619             // instabilities in reported imports (#43552).
 620             in_module.for_each_child(self, |this, ident, ns, name_binding| {
 621                 // avoid imports entirely
 622                 if name_binding.is_import() && !name_binding.is_extern_crate() {
 623                     return;
 624                 }
 625                 // avoid non-importable candidates as well
 626                 if !name_binding.is_importable() {
 627                     return;
 628                 }
 629
 630                 // collect results based on the filter function
 631                 if ident.name == lookup_ident.name && ns == namespace {
 632                     let res = name_binding.res();
 633                     if filter_fn(res) {
 634                         // create the path
 635                         let mut segms = path_segments.clone();
 636                         if lookup_ident.span.rust_2018() {
 637                             // crate-local absolute paths start with `crate::` in edition 2018
 638                             // FIXME: may also be stabilized for Rust 2015 (Issues #45477, #44660)
 639                             segms.insert(0, ast::PathSegment::from_ident(crate_name));
 640                         }
 641
 642                         segms.push(ast::PathSegment::from_ident(ident));
 643                         let path = Path { span: name_binding.span, segments: segms };
 644                         // the entity is accessible in the following cases:
 645                         // 1. if it's defined in the same crate, it's always
 646                         // accessible (since private entities can be made public)
 647                         // 2. if it's defined in another crate, it's accessible
 648                         // only if both the module is public and the entity is
 649                         // declared as public (due to pruning, we don't explore
 650                         // outside crate private modules => no need to check this)
 651                         if !in_module_is_extern || name_binding.vis == ty::Visibility::Public {
 652                             let did = match res {
 653                                 Res::Def(DefKind::Ctor(..), did) => this.parent(did),
 654                                 _ => res.opt_def_id(),
 655                             };
 656                             candidates.push(ImportSuggestion { did, path });
 657                         }
 658                     }
 659                 }
 660
 661                 // collect submodules to explore
 662                 if let Some(module) = name_binding.module() {
 663                     // form the path
 664                     let mut path_segments = path_segments.clone();
 665                     path_segments.push(ast::PathSegment::from_ident(ident));
 666
 667                     let is_extern_crate_that_also_appears_in_prelude =
 668                         name_binding.is_extern_crate() && lookup_ident.span.rust_2018();
 669
 670                     let is_visible_to_user =
 671                         !in_module_is_extern || name_binding.vis == ty::Visibility::Public;
 672
 673                     if !is_extern_crate_that_also_appears_in_prelude && is_visible_to_user {
 674                         // add the module to the lookup
 675                         let is_extern = in_module_is_extern || name_binding.is_extern_crate();
 676                         if seen_modules.insert(module.def_id().unwrap()) {
 677                             worklist.push((module, path_segments, is_extern));
 678                         }
 679                     }
 680                 }
 681             })
 682         }
 683
 684         candidates
 685     }
 686
 687     /// When name resolution fails, this method can be used to look up candidate
 688     /// entities with the expected name. It allows filtering them using the
 689     /// supplied predicate (which should be used to only accept the types of
 690     /// definitions expected, e.g., traits). The lookup spans across all crates.
 691     ///
 692     /// N.B., the method does not look into imports, but this is not a problem,
 693     /// since we report the definitions (thus, the de-aliased imports).
 694     crate fn lookup_import_candidates<FilterFn>(
 695         &mut self,
 696         lookup_ident: Ident,
 697         namespace: Namespace,
 698         filter_fn: FilterFn,
 699     ) -> Vec<ImportSuggestion>
 700     where
 701         FilterFn: Fn(Res) -> bool,
 702     {
 703         let mut suggestions = self.lookup_import_candidates_from_module(
 704             lookup_ident,
 705             namespace,
 706             self.graph_root,
 707             Ident::with_dummy_span(kw::Crate),
 708             &filter_fn,
 709         );
 710
 711         if lookup_ident.span.rust_2018() {
 712             let extern_prelude_names = self.extern_prelude.clone();
 713             for (ident, _) in extern_prelude_names.into_iter() {
 714                 if ident.span.from_expansion() {
 715                     // Idents are adjusted to the root context before being
 716                     // resolved in the extern prelude, so reporting this to the
 717                     // user is no help. This skips the injected
 718                     // `extern crate std` in the 2018 edition, which would
 719                     // otherwise cause duplicate suggestions.
 720                     continue;
 721                 }
 722                 if let Some(crate_id) =
 723                     self.crate_loader.maybe_process_path_extern(ident.name, ident.span)
 724                 {
 725                     let crate_root =
 726                         self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 727                     suggestions.extend(self.lookup_import_candidates_from_module(
 728                         lookup_ident,
 729                         namespace,
 730                         crate_root,
 731                         ident,
 732                         &filter_fn,
 733                     ));
 734                 }
 735             }
 736         }
 737
 738         suggestions
 739     }
 740
 741     crate fn unresolved_macro_suggestions(
 742         &mut self,
 743         err: &mut DiagnosticBuilder<'a>,
 744         macro_kind: MacroKind,
 745         parent_scope: &ParentScope<'a>,
 746         ident: Ident,
 747     ) {
 748         let is_expected = &|res: Res| res.macro_kind() == Some(macro_kind);
 749         let suggestion = self.early_lookup_typo_candidate(
 750             ScopeSet::Macro(macro_kind),
 751             parent_scope,
 752             ident,
 753             is_expected,
 754         );
 755         self.add_typo_suggestion(err, suggestion, ident.span);
 756
 757         if macro_kind == MacroKind::Derive && (ident.as_str() == "Send" || ident.as_str() == "Sync")
 758         {
 759             let msg = format!("unsafe traits like `{}` should be implemented explicitly", ident);
 760             err.span_note(ident.span, &msg);
 761         }
 762         if self.macro_names.contains(&ident.normalize_to_macros_2_0()) {
 763             err.help("have you added the `#[macro_use]` on the module/import?");
 764         }
 765     }
 766
 767     crate fn add_typo_suggestion(
 768         &self,
 769         err: &mut DiagnosticBuilder<'_>,
 770         suggestion: Option<TypoSuggestion>,
 771         span: Span,
 772     ) -> bool {
 773         if let Some(suggestion) = suggestion {
 774             // We shouldn't suggest underscore.
 775             if suggestion.candidate == kw::Underscore {
 776                 return false;
 777             }
 778
 779             let msg = format!(
 780                 "{} {} with a similar name exists",
 781                 suggestion.res.article(),
 782                 suggestion.res.descr()
 783             );
 784             err.span_suggestion(
 785                 span,
 786                 &msg,
 787                 suggestion.candidate.to_string(),
 788                 Applicability::MaybeIncorrect,
 789             );
 790             let def_span = suggestion.res.opt_def_id().and_then(|def_id| match def_id.krate {
 791                 LOCAL_CRATE => self.definitions.opt_span(def_id),
 792                 _ => Some(
 793                     self.session
 794                         .source_map()
 795                         .def_span(self.cstore().get_span_untracked(def_id, self.session)),
 796                 ),
 797             });
 798             if let Some(span) = def_span {
 799                 err.span_label(
 800                     span,
 801                     &format!(
 802                         "similarly named {} `{}` defined here",
 803                         suggestion.res.descr(),
 804                         suggestion.candidate.as_str(),
 805                     ),
 806                 );
 807             }
 808             return true;
 809         }
 810         false
 811     }
 812
 813     fn binding_description(&self, b: &NameBinding<'_>, ident: Ident, from_prelude: bool) -> String {
 814         let res = b.res();
 815         if b.span.is_dummy() {
 816             let add_built_in = match b.res() {
 817                 // These already contain the "built-in" prefix or look bad with it.
 818                 Res::NonMacroAttr(..) | Res::PrimTy(..) | Res::ToolMod => false,
 819                 _ => true,
 820             };
 821             let (built_in, from) = if from_prelude {
 822                 ("", " from prelude")
 823             } else if b.is_extern_crate()
 824                 && !b.is_import()
 825                 && self.session.opts.externs.get(&ident.as_str()).is_some()
 826             {
 827                 ("", " passed with `--extern`")
 828             } else if add_built_in {
 829                 (" built-in", "")
 830             } else {
 831                 ("", "")
 832             };
 833
 834             let article = if built_in.is_empty() { res.article() } else { "a" };
 835             format!(
 836                 "{a}{built_in} {thing}{from}",
 837                 a = article,
 838                 thing = res.descr(),
 839                 built_in = built_in,
 840                 from = from
 841             )
 842         } else {
 843             let introduced = if b.is_import() { "imported" } else { "defined" };
 844             format!("the {thing} {introduced} here", thing = res.descr(), introduced = introduced)
 845         }
 846     }
 847
 848     crate fn report_ambiguity_error(&self, ambiguity_error: &AmbiguityError<'_>) {
 849         let AmbiguityError { kind, ident, b1, b2, misc1, misc2 } = *ambiguity_error;
 850         let (b1, b2, misc1, misc2, swapped) = if b2.span.is_dummy() && !b1.span.is_dummy() {
 851             // We have to print the span-less alternative first, otherwise formatting looks bad.
 852             (b2, b1, misc2, misc1, true)
 853         } else {
 854             (b1, b2, misc1, misc2, false)
 855         };
 856
 857         let mut err = struct_span_err!(
 858             self.session,
 859             ident.span,
 860             E0659,
 861             "`{ident}` is ambiguous ({why})",
 862             ident = ident,
 863             why = kind.descr()
 864         );
 865         err.span_label(ident.span, "ambiguous name");
 866
 867         let mut could_refer_to = |b: &NameBinding<'_>, misc: AmbiguityErrorMisc, also: &str| {
 868             let what = self.binding_description(b, ident, misc == AmbiguityErrorMisc::FromPrelude);
 869             let note_msg = format!(
 870                 "`{ident}` could{also} refer to {what}",
 871                 ident = ident,
 872                 also = also,
 873                 what = what
 874             );
 875
 876             let thing = b.res().descr();
 877             let mut help_msgs = Vec::new();
 878             if b.is_glob_import()
 879                 && (kind == AmbiguityKind::GlobVsGlob
 880                     || kind == AmbiguityKind::GlobVsExpanded
 881                     || kind == AmbiguityKind::GlobVsOuter && swapped != also.is_empty())
 882             {
 883                 help_msgs.push(format!(
 884                     "consider adding an explicit import of \
 885                      `{ident}` to disambiguate",
 886                     ident = ident
 887                 ))
 888             }
 889             if b.is_extern_crate() && ident.span.rust_2018() {
 890                 help_msgs.push(format!(
 891                     "use `::{ident}` to refer to this {thing} unambiguously",
 892                     ident = ident,
 893                     thing = thing,
 894                 ))
 895             }
 896             if misc == AmbiguityErrorMisc::SuggestCrate {
 897                 help_msgs.push(format!(
 898                     "use `crate::{ident}` to refer to this {thing} unambiguously",
 899                     ident = ident,
 900                     thing = thing,
 901                 ))
 902             } else if misc == AmbiguityErrorMisc::SuggestSelf {
 903                 help_msgs.push(format!(
 904                     "use `self::{ident}` to refer to this {thing} unambiguously",
 905                     ident = ident,
 906                     thing = thing,
 907                 ))
 908             }
 909
 910             err.span_note(b.span, &note_msg);
 911             for (i, help_msg) in help_msgs.iter().enumerate() {
 912                 let or = if i == 0 { "" } else { "or " };
 913                 err.help(&format!("{}{}", or, help_msg));
 914             }
 915         };
 916
 917         could_refer_to(b1, misc1, "");
 918         could_refer_to(b2, misc2, " also");
 919         err.emit();
 920     }
 921
 922     /// If the binding refers to a tuple struct constructor with fields,
 923     /// returns the span of its fields.
 924     fn ctor_fields_span(&self, binding: &NameBinding<'_>) -> Option<Span> {
 925         if let NameBindingKind::Res(
 926             Res::Def(DefKind::Ctor(CtorOf::Struct, CtorKind::Fn), ctor_def_id),
 927             _,
 928         ) = binding.kind
 929         {
 930             let def_id = (&*self).parent(ctor_def_id).expect("no parent for a constructor");
 931             if let Some(fields) = self.field_names.get(&def_id) {
 932                 let first_field = fields.first().expect("empty field list in the map");
 933                 return Some(fields.iter().fold(first_field.span, |acc, field| acc.to(field.span)));
 934             }
 935         }
 936         None
 937     }
 938
 939     crate fn report_privacy_error(&self, privacy_error: &PrivacyError<'_>) {
 940         let PrivacyError { ident, binding, .. } = *privacy_error;
 941
 942         let res = binding.res();
 943         let ctor_fields_span = self.ctor_fields_span(binding);
 944         let plain_descr = res.descr().to_string();
 945         let nonimport_descr =
 946             if ctor_fields_span.is_some() { plain_descr + " constructor" } else { plain_descr };
 947         let import_descr = nonimport_descr.clone() + " import";
 948         let get_descr =
 949             |b: &NameBinding<'_>| if b.is_import() { &import_descr } else { &nonimport_descr };
 950
 951         // Print the primary message.
 952         let descr = get_descr(binding);
 953         let mut err =
 954             struct_span_err!(self.session, ident.span, E0603, "{} `{}` is private", descr, ident);
 955         err.span_label(ident.span, &format!("this {} is private", descr));
 956         if let Some(span) = ctor_fields_span {
 957             err.span_label(span, "a constructor is private if any of the fields is private");
 958         }
 959
 960         // Print the whole import chain to make it easier to see what happens.
 961         let first_binding = binding;
 962         let mut next_binding = Some(binding);
 963         let mut next_ident = ident;
 964         while let Some(binding) = next_binding {
 965             let name = next_ident;
 966             next_binding = match binding.kind {
 967                 _ if res == Res::Err => None,
 968                 NameBindingKind::Import { binding, import, .. } => match import.kind {
 969                     _ if binding.span.is_dummy() => None,
 970                     ImportKind::Single { source, .. } => {
 971                         next_ident = source;
 972                         Some(binding)
 973                     }
 974                     ImportKind::Glob { .. } | ImportKind::MacroUse => Some(binding),
 975                     ImportKind::ExternCrate { .. } => None,
 976                 },
 977                 _ => None,
 978             };
 979
 980             let first = ptr::eq(binding, first_binding);
 981             let descr = get_descr(binding);
 982             let msg = format!(
 983                 "{and_refers_to}the {item} `{name}`{which} is defined here{dots}",
 984                 and_refers_to = if first { "" } else { "...and refers to " },
 985                 item = descr,
 986                 name = name,
 987                 which = if first { "" } else { " which" },
 988                 dots = if next_binding.is_some() { "..." } else { "" },
 989             );
 990             let def_span = self.session.source_map().def_span(binding.span);
 991             let mut note_span = MultiSpan::from_span(def_span);
 992             if !first && binding.vis == ty::Visibility::Public {
 993                 note_span.push_span_label(def_span, "consider importing it directly".into());
 994             }
 995             err.span_note(note_span, &msg);
 996         }
 997
 998         err.emit();
 999     }
1000 }
1001
1002 impl<'a, 'b> ImportResolver<'a, 'b> {
1003     /// Adds suggestions for a path that cannot be resolved.
1004     pub(crate) fn make_path_suggestion(
1005         &mut self,
1006         span: Span,
1007         mut path: Vec<Segment>,
1008         parent_scope: &ParentScope<'b>,
1009     ) -> Option<(Vec<Segment>, Vec<String>)> {
1010         debug!("make_path_suggestion: span={:?} path={:?}", span, path);
1011
1012         match (path.get(0), path.get(1)) {
1013             // `{{root}}::ident::...` on both editions.
1014             // On 2015 `{{root}}` is usually added implicitly.
1015             (Some(fst), Some(snd))
1016                 if fst.ident.name == kw::PathRoot && !snd.ident.is_path_segment_keyword() => {}
1017             // `ident::...` on 2018.
1018             (Some(fst), _)
1019                 if fst.ident.span.rust_2018() && !fst.ident.is_path_segment_keyword() =>
1020             {
1021                 // Insert a placeholder that's later replaced by `self`/`super`/etc.
1022                 path.insert(0, Segment::from_ident(Ident::invalid()));
1023             }
1024             _ => return None,
1025         }
1026
1027         self.make_missing_self_suggestion(span, path.clone(), parent_scope)
1028             .or_else(|| self.make_missing_crate_suggestion(span, path.clone(), parent_scope))
1029             .or_else(|| self.make_missing_super_suggestion(span, path.clone(), parent_scope))
1030             .or_else(|| self.make_external_crate_suggestion(span, path, parent_scope))
1031     }
1032
1033     /// Suggest a missing `self::` if that resolves to an correct module.
1034     ///
1035     /// ```
1036     ///    |
1037     /// LL | use foo::Bar;
1038     ///    |     ^^^ did you mean `self::foo`?
1039     /// ```
1040     fn make_missing_self_suggestion(
1041         &mut self,
1042         span: Span,
1043         mut path: Vec<Segment>,
1044         parent_scope: &ParentScope<'b>,
1045     ) -> Option<(Vec<Segment>, Vec<String>)> {
1046         // Replace first ident with `self` and check if that is valid.
1047         path[0].ident.name = kw::SelfLower;
1048         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
1049         debug!("make_missing_self_suggestion: path={:?} result={:?}", path, result);
1050         if let PathResult::Module(..) = result { Some((path, Vec::new())) } else { None }
1051     }
1052
1053     /// Suggests a missing `crate::` if that resolves to an correct module.
1054     ///
1055     /// ```
1056     ///    |
1057     /// LL | use foo::Bar;
1058     ///    |     ^^^ did you mean `crate::foo`?
1059     /// ```
1060     fn make_missing_crate_suggestion(
1061         &mut self,
1062         span: Span,
1063         mut path: Vec<Segment>,
1064         parent_scope: &ParentScope<'b>,
1065     ) -> Option<(Vec<Segment>, Vec<String>)> {
1066         // Replace first ident with `crate` and check if that is valid.
1067         path[0].ident.name = kw::Crate;
1068         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
1069         debug!("make_missing_crate_suggestion:  path={:?} result={:?}", path, result);
1070         if let PathResult::Module(..) = result {
1071             Some((
1072                 path,
1073                 vec![
1074                     "`use` statements changed in Rust 2018; read more at \
1075                      <https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-\
1076                      clarity.html>"
1077                         .to_string(),
1078                 ],
1079             ))
1080         } else {
1081             None
1082         }
1083     }
1084
1085     /// Suggests a missing `super::` if that resolves to an correct module.
1086     ///
1087     /// ```
1088     ///    |
1089     /// LL | use foo::Bar;
1090     ///    |     ^^^ did you mean `super::foo`?
1091     /// ```
1092     fn make_missing_super_suggestion(
1093         &mut self,
1094         span: Span,
1095         mut path: Vec<Segment>,
1096         parent_scope: &ParentScope<'b>,
1097     ) -> Option<(Vec<Segment>, Vec<String>)> {
1098         // Replace first ident with `crate` and check if that is valid.
1099         path[0].ident.name = kw::Super;
1100         let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
1101         debug!("make_missing_super_suggestion:  path={:?} result={:?}", path, result);
1102         if let PathResult::Module(..) = result { Some((path, Vec::new())) } else { None }
1103     }
1104
1105     /// Suggests a missing external crate name if that resolves to an correct module.
1106     ///
1107     /// ```
1108     ///    |
1109     /// LL | use foobar::Baz;
1110     ///    |     ^^^^^^ did you mean `baz::foobar`?
1111     /// ```
1112     ///
1113     /// Used when importing a submodule of an external crate but missing that crate's
1114     /// name as the first part of path.
1115     fn make_external_crate_suggestion(
1116         &mut self,
1117         span: Span,
1118         mut path: Vec<Segment>,
1119         parent_scope: &ParentScope<'b>,
1120     ) -> Option<(Vec<Segment>, Vec<String>)> {
1121         if path[1].ident.span.rust_2015() {
1122             return None;
1123         }
1124
1125         // Sort extern crate names in reverse order to get
1126         // 1) some consistent ordering for emitted diagnostics, and
1127         // 2) `std` suggestions before `core` suggestions.
1128         let mut extern_crate_names =
1129             self.r.extern_prelude.iter().map(|(ident, _)| ident.name).collect::<Vec<_>>();
1130         extern_crate_names.sort_by_key(|name| Reverse(name.as_str()));
1131
1132         for name in extern_crate_names.into_iter() {
1133             // Replace first ident with a crate name and check if that is valid.
1134             path[0].ident.name = name;
1135             let result = self.r.resolve_path(&path, None, parent_scope, false, span, CrateLint::No);
1136             debug!(
1137                 "make_external_crate_suggestion: name={:?} path={:?} result={:?}",
1138                 name, path, result
1139             );
1140             if let PathResult::Module(..) = result {
1141                 return Some((path, Vec::new()));
1142             }
1143         }
1144
1145         None
1146     }
1147
1148     /// Suggests importing a macro from the root of the crate rather than a module within
1149     /// the crate.
1150     ///
1151     /// ```
1152     /// help: a macro with this name exists at the root of the crate
1153     ///    |
1154     /// LL | use issue_59764::makro;
1155     ///    |     ^^^^^^^^^^^^^^^^^^
1156     ///    |
1157     ///    = note: this could be because a macro annotated with `#[macro_export]` will be exported
1158     ///            at the root of the crate instead of the module where it is defined
1159     /// ```
1160     pub(crate) fn check_for_module_export_macro(
1161         &mut self,
1162         import: &'b Import<'b>,
1163         module: ModuleOrUniformRoot<'b>,
1164         ident: Ident,
1165     ) -> Option<(Option<Suggestion>, Vec<String>)> {
1166         let mut crate_module = if let ModuleOrUniformRoot::Module(module) = module {
1167             module
1168         } else {
1169             return None;
1170         };
1171
1172         while let Some(parent) = crate_module.parent {
1173             crate_module = parent;
1174         }
1175
1176         if ModuleOrUniformRoot::same_def(ModuleOrUniformRoot::Module(crate_module), module) {
1177             // Don't make a suggestion if the import was already from the root of the
1178             // crate.
1179             return None;
1180         }
1181
1182         let resolutions = self.r.resolutions(crate_module).borrow();
1183         let resolution = resolutions.get(&self.r.new_key(ident, MacroNS))?;
1184         let binding = resolution.borrow().binding()?;
1185         if let Res::Def(DefKind::Macro(MacroKind::Bang), _) = binding.res() {
1186             let module_name = crate_module.kind.name().unwrap();
1187             let import_snippet = match import.kind {
1188                 ImportKind::Single { source, target, .. } if source != target => {
1189                     format!("{} as {}", source, target)
1190                 }
1191                 _ => format!("{}", ident),
1192             };
1193
1194             let mut corrections: Vec<(Span, String)> = Vec::new();
1195             if !import.is_nested() {
1196                 // Assume this is the easy case of `use issue_59764::foo::makro;` and just remove
1197                 // intermediate segments.
1198                 corrections.push((import.span, format!("{}::{}", module_name, import_snippet)));
1199             } else {
1200                 // Find the binding span (and any trailing commas and spaces).
1201                 //   ie. `use a::b::{c, d, e};`
1202                 //                      ^^^
1203                 let (found_closing_brace, binding_span) = find_span_of_binding_until_next_binding(
1204                     self.r.session,
1205                     import.span,
1206                     import.use_span,
1207                 );
1208                 debug!(
1209                     "check_for_module_export_macro: found_closing_brace={:?} binding_span={:?}",
1210                     found_closing_brace, binding_span
1211                 );
1212
1213                 let mut removal_span = binding_span;
1214                 if found_closing_brace {
1215                     // If the binding span ended with a closing brace, as in the below example:
1216                     //   ie. `use a::b::{c, d};`
1217                     //                      ^
1218                     // Then expand the span of characters to remove to include the previous
1219                     // binding's trailing comma.
1220                     //   ie. `use a::b::{c, d};`
1221                     //                    ^^^
1222                     if let Some(previous_span) =
1223                         extend_span_to_previous_binding(self.r.session, binding_span)
1224                     {
1225                         debug!("check_for_module_export_macro: previous_span={:?}", previous_span);
1226                         removal_span = removal_span.with_lo(previous_span.lo());
1227                     }
1228                 }
1229                 debug!("check_for_module_export_macro: removal_span={:?}", removal_span);
1230
1231                 // Remove the `removal_span`.
1232                 corrections.push((removal_span, "".to_string()));
1233
1234                 // Find the span after the crate name and if it has nested imports immediatately
1235                 // after the crate name already.
1236                 //   ie. `use a::b::{c, d};`
1237                 //               ^^^^^^^^^
1238                 //   or  `use a::{b, c, d}};`
1239                 //               ^^^^^^^^^^^
1240                 let (has_nested, after_crate_name) = find_span_immediately_after_crate_name(
1241                     self.r.session,
1242                     module_name,
1243                     import.use_span,
1244                 );
1245                 debug!(
1246                     "check_for_module_export_macro: has_nested={:?} after_crate_name={:?}",
1247                     has_nested, after_crate_name
1248                 );
1249
1250                 let source_map = self.r.session.source_map();
1251
1252                 // Add the import to the start, with a `{` if required.
1253                 let start_point = source_map.start_point(after_crate_name);
1254                 if let Ok(start_snippet) = source_map.span_to_snippet(start_point) {
1255                     corrections.push((
1256                         start_point,
1257                         if has_nested {
1258                             // In this case, `start_snippet` must equal '{'.
1259                             format!("{}{}, ", start_snippet, import_snippet)
1260                         } else {
1261                             // In this case, add a `{`, then the moved import, then whatever
1262                             // was there before.
1263                             format!("{{{}, {}", import_snippet, start_snippet)
1264                         },
1265                     ));
1266                 }
1267
1268                 // Add a `};` to the end if nested, matching the `{` added at the start.
1269                 if !has_nested {
1270                     corrections.push((source_map.end_point(after_crate_name), "};".to_string()));
1271                 }
1272             }
1273
1274             let suggestion = Some((
1275                 corrections,
1276                 String::from("a macro with this name exists at the root of the crate"),
1277                 Applicability::MaybeIncorrect,
1278             ));
1279             let note = vec![
1280                 "this could be because a macro annotated with `#[macro_export]` will be exported \
1281                  at the root of the crate instead of the module where it is defined"
1282                     .to_string(),
1283             ];
1284             Some((suggestion, note))
1285         } else {
1286             None
1287         }
1288     }
1289 }
1290
1291 /// Given a `binding_span` of a binding within a use statement:
1292 ///
1293 /// ```
1294 /// use foo::{a, b, c};
1295 ///              ^
1296 /// ```
1297 ///
1298 /// then return the span until the next binding or the end of the statement:
1299 ///
1300 /// ```
1301 /// use foo::{a, b, c};
1302 ///              ^^^
1303 /// ```
1304 pub(crate) fn find_span_of_binding_until_next_binding(
1305     sess: &Session,
1306     binding_span: Span,
1307     use_span: Span,
1308 ) -> (bool, Span) {
1309     let source_map = sess.source_map();
1310
1311     // Find the span of everything after the binding.
1312     //   ie. `a, e};` or `a};`
1313     let binding_until_end = binding_span.with_hi(use_span.hi());
1314
1315     // Find everything after the binding but not including the binding.
1316     //   ie. `, e};` or `};`
1317     let after_binding_until_end = binding_until_end.with_lo(binding_span.hi());
1318
1319     // Keep characters in the span until we encounter something that isn't a comma or
1320     // whitespace.
1321     //   ie. `, ` or ``.
1322     //
1323     // Also note whether a closing brace character was encountered. If there
1324     // was, then later go backwards to remove any trailing commas that are left.
1325     let mut found_closing_brace = false;
1326     let after_binding_until_next_binding =
1327         source_map.span_take_while(after_binding_until_end, |&ch| {
1328             if ch == '}' {
1329                 found_closing_brace = true;
1330             }
1331             ch == ' ' || ch == ','
1332         });
1333
1334     // Combine the two spans.
1335     //   ie. `a, ` or `a`.
1336     //
1337     // Removing these would leave `issue_52891::{d, e};` or `issue_52891::{d, e, };`
1338     let span = binding_span.with_hi(after_binding_until_next_binding.hi());
1339
1340     (found_closing_brace, span)
1341 }
1342
1343 /// Given a `binding_span`, return the span through to the comma or opening brace of the previous
1344 /// binding.
1345 ///
1346 /// ```
1347 /// use foo::a::{a, b, c};
1348 ///               ^^--- binding span
1349 ///               |
1350 ///               returned span
1351 ///
1352 /// use foo::{a, b, c};
1353 ///           --- binding span
1354 /// ```
1355 pub(crate) fn extend_span_to_previous_binding(sess: &Session, binding_span: Span) -> Option<Span> {
1356     let source_map = sess.source_map();
1357
1358     // `prev_source` will contain all of the source that came before the span.
1359     // Then split based on a command and take the first (ie. closest to our span)
1360     // snippet. In the example, this is a space.
1361     let prev_source = source_map.span_to_prev_source(binding_span).ok()?;
1362
1363     let prev_comma = prev_source.rsplit(',').collect::<Vec<_>>();
1364     let prev_starting_brace = prev_source.rsplit('{').collect::<Vec<_>>();
1365     if prev_comma.len() <= 1 || prev_starting_brace.len() <= 1 {
1366         return None;
1367     }
1368
1369     let prev_comma = prev_comma.first().unwrap();
1370     let prev_starting_brace = prev_starting_brace.first().unwrap();
1371
1372     // If the amount of source code before the comma is greater than
1373     // the amount of source code before the starting brace then we've only
1374     // got one item in the nested item (eg. `issue_52891::{self}`).
1375     if prev_comma.len() > prev_starting_brace.len() {
1376         return None;
1377     }
1378
1379     Some(binding_span.with_lo(BytePos(
1380         // Take away the number of bytes for the characters we've found and an
1381         // extra for the comma.
1382         binding_span.lo().0 - (prev_comma.as_bytes().len() as u32) - 1,
1383     )))
1384 }
1385
1386 /// Given a `use_span` of a binding within a use statement, returns the highlighted span and if
1387 /// it is a nested use tree.
1388 ///
1389 /// ```
1390 /// use foo::a::{b, c};
1391 ///          ^^^^^^^^^^ // false
1392 ///
1393 /// use foo::{a, b, c};
1394 ///          ^^^^^^^^^^ // true
1395 ///
1396 /// use foo::{a, b::{c, d}};
1397 ///          ^^^^^^^^^^^^^^^ // true
1398 /// ```
1399 fn find_span_immediately_after_crate_name(
1400     sess: &Session,
1401     module_name: Symbol,
1402     use_span: Span,
1403 ) -> (bool, Span) {
1404     debug!(
1405         "find_span_immediately_after_crate_name: module_name={:?} use_span={:?}",
1406         module_name, use_span
1407     );
1408     let source_map = sess.source_map();
1409
1410     // Using `use issue_59764::foo::{baz, makro};` as an example throughout..
1411     let mut num_colons = 0;
1412     // Find second colon.. `use issue_59764:`
1413     let until_second_colon = source_map.span_take_while(use_span, |c| {
1414         if *c == ':' {
1415             num_colons += 1;
1416         }
1417         match c {
1418             ':' if num_colons == 2 => false,
1419             _ => true,
1420         }
1421     });
1422     // Find everything after the second colon.. `foo::{baz, makro};`
1423     let from_second_colon = use_span.with_lo(until_second_colon.hi() + BytePos(1));
1424
1425     let mut found_a_non_whitespace_character = false;
1426     // Find the first non-whitespace character in `from_second_colon`.. `f`
1427     let after_second_colon = source_map.span_take_while(from_second_colon, |c| {
1428         if found_a_non_whitespace_character {
1429             return false;
1430         }
1431         if !c.is_whitespace() {
1432             found_a_non_whitespace_character = true;
1433         }
1434         true
1435     });
1436
1437     // Find the first `{` in from_second_colon.. `foo::{`
1438     let next_left_bracket = source_map.span_through_char(from_second_colon, '{');
1439
1440     (next_left_bracket == after_second_colon, from_second_colon)
1441 }
1442
1443 /// When an entity with a given name is not available in scope, we search for
1444 /// entities with that name in all crates. This method allows outputting the
1445 /// results of this search in a programmer-friendly way
1446 crate fn show_candidates(
1447     err: &mut DiagnosticBuilder<'_>,
1448     // This is `None` if all placement locations are inside expansions
1449     span: Option<Span>,
1450     candidates: &[ImportSuggestion],
1451     better: bool,
1452     found_use: bool,
1453 ) {
1454     if candidates.is_empty() {
1455         return;
1456     }
1457     // we want consistent results across executions, but candidates are produced
1458     // by iterating through a hash map, so make sure they are ordered:
1459     let mut path_strings: Vec<_> =
1460         candidates.iter().map(|c| path_names_to_string(&c.path)).collect();
1461     path_strings.sort();
1462     path_strings.dedup();
1463
1464     let better = if better { "better " } else { "" };
1465     let msg_diff = match path_strings.len() {
1466         1 => " is found in another module, you can import it",
1467         _ => "s are found in other modules, you can import them",
1468     };
1469     let msg = format!("possible {}candidate{} into scope", better, msg_diff);
1470
1471     if let Some(span) = span {
1472         for candidate in &mut path_strings {
1473             // produce an additional newline to separate the new use statement
1474             // from the directly following item.
1475             let additional_newline = if found_use { "" } else { "\n" };
1476             *candidate = format!("use {};\n{}", candidate, additional_newline);
1477         }
1478
1479         err.span_suggestions(span, &msg, path_strings.into_iter(), Applicability::Unspecified);
1480     } else {
1481         let mut msg = msg;
1482         msg.push(':');
1483         for candidate in path_strings {
1484             msg.push('\n');
1485             msg.push_str(&candidate);
1486         }
1487         err.note(&msg);
1488     }
1489 }