src/librustc_resolve/late/diagnostics.rs

   1 use crate::diagnostics::{ImportSuggestion, TypoSuggestion};
   2 use crate::late::{LateResolutionVisitor, RibKind};
   3 use crate::path_names_to_string;
   4 use crate::{CrateLint, Module, ModuleKind, ModuleOrUniformRoot};
   5 use crate::{PathResult, PathSource, Segment};
   6
   7 use rustc::session::config::nightly_options;
   8 use rustc_data_structures::fx::FxHashSet;
   9 use rustc_error_codes::*;
  10 use rustc_errors::{Applicability, DiagnosticBuilder};
  11 use rustc_hir::def::Namespace::{self, *};
  12 use rustc_hir::def::{self, CtorKind, DefKind};
  13 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
  14 use rustc_hir::PrimTy;
  15 use rustc_span::hygiene::MacroKind;
  16 use rustc_span::symbol::kw;
  17 use rustc_span::Span;
  18 use syntax::ast::{self, Expr, ExprKind, Ident, NodeId, Path, Ty, TyKind};
  19 use syntax::util::lev_distance::find_best_match_for_name;
  20
  21 use log::debug;
  22
  23 type Res = def::Res<ast::NodeId>;
  24
  25 /// A field or associated item from self type suggested in case of resolution failure.
  26 enum AssocSuggestion {
  27     Field,
  28     MethodWithSelf,
  29     AssocItem,
  30 }
  31
  32 fn is_self_type(path: &[Segment], namespace: Namespace) -> bool {
  33     namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper
  34 }
  35
  36 fn is_self_value(path: &[Segment], namespace: Namespace) -> bool {
  37     namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower
  38 }
  39
  40 /// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant.
  41 fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) {
  42     let variant_path = &suggestion.path;
  43     let variant_path_string = path_names_to_string(variant_path);
  44
  45     let path_len = suggestion.path.segments.len();
  46     let enum_path = ast::Path {
  47         span: suggestion.path.span,
  48         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
  49     };
  50     let enum_path_string = path_names_to_string(&enum_path);
  51
  52     (variant_path_string, enum_path_string)
  53 }
  54
  55 impl<'a> LateResolutionVisitor<'a, '_> {
  56     /// Handles error reporting for `smart_resolve_path_fragment` function.
  57     /// Creates base error and amends it with one short label and possibly some longer helps/notes.
  58     pub(crate) fn smart_resolve_report_errors(
  59         &mut self,
  60         path: &[Segment],
  61         span: Span,
  62         source: PathSource<'_>,
  63         res: Option<Res>,
  64     ) -> (DiagnosticBuilder<'a>, Vec<ImportSuggestion>) {
  65         let ident_span = path.last().map_or(span, |ident| ident.ident.span);
  66         let ns = source.namespace();
  67         let is_expected = &|res| source.is_expected(res);
  68         let is_enum_variant = &|res| {
  69             if let Res::Def(DefKind::Variant, _) = res { true } else { false }
  70         };
  71
  72         // Make the base error.
  73         let expected = source.descr_expected();
  74         let path_str = Segment::names_to_string(path);
  75         let item_str = path.last().unwrap().ident;
  76         let (base_msg, fallback_label, base_span, could_be_expr) = if let Some(res) = res {
  77             (
  78                 format!("expected {}, found {} `{}`", expected, res.descr(), path_str),
  79                 format!("not a {}", expected),
  80                 span,
  81                 match res {
  82                     Res::Def(DefKind::Fn, _) => {
  83                         // Verify whether this is a fn call or an Fn used as a type.
  84                         self.r
  85                             .session
  86                             .source_map()
  87                             .span_to_snippet(span)
  88                             .map(|snippet| snippet.ends_with(')'))
  89                             .unwrap_or(false)
  90                     }
  91                     Res::Def(DefKind::Ctor(..), _)
  92                     | Res::Def(DefKind::Method, _)
  93                     | Res::Def(DefKind::Const, _)
  94                     | Res::Def(DefKind::AssocConst, _)
  95                     | Res::SelfCtor(_)
  96                     | Res::PrimTy(_)
  97                     | Res::Local(_) => true,
  98                     _ => false,
  99                 },
 100             )
 101         } else {
 102             let item_span = path.last().unwrap().ident.span;
 103             let (mod_prefix, mod_str) = if path.len() == 1 {
 104                 (String::new(), "this scope".to_string())
 105             } else if path.len() == 2 && path[0].ident.name == kw::PathRoot {
 106                 (String::new(), "the crate root".to_string())
 107             } else {
 108                 let mod_path = &path[..path.len() - 1];
 109                 let mod_prefix =
 110                     match self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No) {
 111                         PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
 112                         _ => None,
 113                     }
 114                     .map_or(String::new(), |res| format!("{} ", res.descr()));
 115                 (mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)))
 116             };
 117             (
 118                 format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
 119                 format!("not found in {}", mod_str),
 120                 item_span,
 121                 false,
 122             )
 123         };
 124
 125         let code = source.error_code(res.is_some());
 126         let mut err = self.r.session.struct_span_err_with_code(base_span, &base_msg, code);
 127
 128         // Emit help message for fake-self from other languages (e.g., `this` in Javascript).
 129         if ["this", "my"].contains(&&*item_str.as_str())
 130             && self.self_value_is_available(path[0].ident.span, span)
 131         {
 132             err.span_suggestion(
 133                 span,
 134                 "did you mean",
 135                 "self".to_string(),
 136                 Applicability::MaybeIncorrect,
 137             );
 138         }
 139
 140         // Emit special messages for unresolved `Self` and `self`.
 141         if is_self_type(path, ns) {
 142             err.code(rustc_errors::error_code!(E0411));
 143             err.span_label(
 144                 span,
 145                 format!("`Self` is only available in impls, traits, and type definitions"),
 146             );
 147             return (err, Vec::new());
 148         }
 149         if is_self_value(path, ns) {
 150             debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
 151
 152             err.code(rustc_errors::error_code!(E0424));
 153             err.span_label(span, match source {
 154                 PathSource::Pat => format!(
 155                     "`self` value is a keyword and may not be bound to variables or shadowed",
 156                 ),
 157                 _ => format!(
 158                     "`self` value is a keyword only available in methods with a `self` parameter",
 159                 ),
 160             });
 161             if let Some(span) = &self.diagnostic_metadata.current_function {
 162                 err.span_label(*span, "this function doesn't have a `self` parameter");
 163             }
 164             return (err, Vec::new());
 165         }
 166
 167         // Try to lookup name in more relaxed fashion for better error reporting.
 168         let ident = path.last().unwrap().ident;
 169         let candidates = self
 170             .r
 171             .lookup_import_candidates(ident, ns, is_expected)
 172             .drain(..)
 173             .filter(|ImportSuggestion { did, .. }| {
 174                 match (did, res.and_then(|res| res.opt_def_id())) {
 175                     (Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
 176                     _ => true,
 177                 }
 178             })
 179             .collect::<Vec<_>>();
 180         let crate_def_id = DefId::local(CRATE_DEF_INDEX);
 181         if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
 182             let enum_candidates = self.r.lookup_import_candidates(ident, ns, is_enum_variant);
 183             let mut enum_candidates = enum_candidates
 184                 .iter()
 185                 .map(|suggestion| import_candidate_to_enum_paths(&suggestion))
 186                 .collect::<Vec<_>>();
 187             enum_candidates.sort();
 188
 189             if !enum_candidates.is_empty() {
 190                 // Contextualize for E0412 "cannot find type", but don't belabor the point
 191                 // (that it's a variant) for E0573 "expected type, found variant".
 192                 let preamble = if res.is_none() {
 193                     let others = match enum_candidates.len() {
 194                         1 => String::new(),
 195                         2 => " and 1 other".to_owned(),
 196                         n => format!(" and {} others", n),
 197                     };
 198                     format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
 199                 } else {
 200                     String::new()
 201                 };
 202                 let msg = format!("{}try using the variant's enum", preamble);
 203
 204                 err.span_suggestions(
 205                     span,
 206                     &msg,
 207                     enum_candidates
 208                         .into_iter()
 209                         .map(|(_variant_path, enum_ty_path)| enum_ty_path)
 210                         // Variants re-exported in prelude doesn't mean `prelude::v1` is the
 211                         // type name!
 212                         // FIXME: is there a more principled way to do this that
 213                         // would work for other re-exports?
 214                         .filter(|enum_ty_path| enum_ty_path != "std::prelude::v1")
 215                         // Also write `Option` rather than `std::prelude::v1::Option`.
 216                         .map(|enum_ty_path| {
 217                             // FIXME #56861: DRY-er prelude filtering.
 218                             enum_ty_path.trim_start_matches("std::prelude::v1::").to_owned()
 219                         }),
 220                     Applicability::MachineApplicable,
 221                 );
 222             }
 223         }
 224         if path.len() == 1 && self.self_type_is_available(span) {
 225             if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) {
 226                 let self_is_available = self.self_value_is_available(path[0].ident.span, span);
 227                 match candidate {
 228                     AssocSuggestion::Field => {
 229                         if self_is_available {
 230                             err.span_suggestion(
 231                                 span,
 232                                 "you might have meant to use the available field",
 233                                 format!("self.{}", path_str),
 234                                 Applicability::MachineApplicable,
 235                             );
 236                         } else {
 237                             err.span_label(span, "a field by this name exists in `Self`");
 238                         }
 239                     }
 240                     AssocSuggestion::MethodWithSelf if self_is_available => {
 241                         err.span_suggestion(
 242                             span,
 243                             "try",
 244                             format!("self.{}", path_str),
 245                             Applicability::MachineApplicable,
 246                         );
 247                     }
 248                     AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
 249                         err.span_suggestion(
 250                             span,
 251                             "try",
 252                             format!("Self::{}", path_str),
 253                             Applicability::MachineApplicable,
 254                         );
 255                     }
 256                 }
 257                 return (err, candidates);
 258             }
 259
 260             // If the first argument in call is `self` suggest calling a method.
 261             if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
 262                 let mut args_snippet = String::new();
 263                 if let Some(args_span) = args_span {
 264                     if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) {
 265                         args_snippet = snippet;
 266                     }
 267                 }
 268
 269                 err.span_suggestion(
 270                     call_span,
 271                     &format!("try calling `{}` as a method", ident),
 272                     format!("self.{}({})", path_str, args_snippet),
 273                     Applicability::MachineApplicable,
 274                 );
 275                 return (err, candidates);
 276             }
 277         }
 278
 279         // Try Levenshtein algorithm.
 280         let typo_sugg = self.lookup_typo_candidate(path, ns, is_expected, span);
 281         let levenshtein_worked = self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
 282
 283         // Try context-dependent help if relaxed lookup didn't work.
 284         if let Some(res) = res {
 285             if self.smart_resolve_context_dependent_help(
 286                 &mut err,
 287                 span,
 288                 source,
 289                 res,
 290                 &path_str,
 291                 &fallback_label,
 292             ) {
 293                 return (err, candidates);
 294             }
 295         }
 296
 297         // Fallback label.
 298         if !levenshtein_worked {
 299             err.span_label(base_span, fallback_label);
 300             self.type_ascription_suggestion(&mut err, base_span);
 301             match self.diagnostic_metadata.current_let_binding {
 302                 Some((pat_sp, Some(ty_sp), None)) if ty_sp.contains(base_span) && could_be_expr => {
 303                     err.span_suggestion_short(
 304                         pat_sp.between(ty_sp),
 305                         "use `=` if you meant to assign",
 306                         " = ".to_string(),
 307                         Applicability::MaybeIncorrect,
 308                     );
 309                 }
 310                 _ => {}
 311             }
 312         }
 313         (err, candidates)
 314     }
 315
 316     /// Check if the source is call expression and the first argument is `self`. If true,
 317     /// return the span of whole call and the span for all arguments expect the first one (`self`).
 318     fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
 319         let mut has_self_arg = None;
 320         if let PathSource::Expr(parent) = source {
 321             match &parent?.kind {
 322                 ExprKind::Call(_, args) if args.len() > 0 => {
 323                     let mut expr_kind = &args[0].kind;
 324                     loop {
 325                         match expr_kind {
 326                             ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
 327                                 if arg_name.segments[0].ident.name == kw::SelfLower {
 328                                     let call_span = parent.unwrap().span;
 329                                     let tail_args_span = if args.len() > 1 {
 330                                         Some(Span::new(
 331                                             args[1].span.lo(),
 332                                             args.last().unwrap().span.hi(),
 333                                             call_span.ctxt(),
 334                                         ))
 335                                     } else {
 336                                         None
 337                                     };
 338                                     has_self_arg = Some((call_span, tail_args_span));
 339                                 }
 340                                 break;
 341                             }
 342                             ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
 343                             _ => break,
 344                         }
 345                     }
 346                 }
 347                 _ => (),
 348             }
 349         };
 350         return has_self_arg;
 351     }
 352
 353     fn followed_by_brace(&self, span: Span) -> (bool, Option<(Span, String)>) {
 354         // HACK(estebank): find a better way to figure out that this was a
 355         // parser issue where a struct literal is being used on an expression
 356         // where a brace being opened means a block is being started. Look
 357         // ahead for the next text to see if `span` is followed by a `{`.
 358         let sm = self.r.session.source_map();
 359         let mut sp = span;
 360         loop {
 361             sp = sm.next_point(sp);
 362             match sm.span_to_snippet(sp) {
 363                 Ok(ref snippet) => {
 364                     if snippet.chars().any(|c| !c.is_whitespace()) {
 365                         break;
 366                     }
 367                 }
 368                 _ => break,
 369             }
 370         }
 371         let followed_by_brace = match sm.span_to_snippet(sp) {
 372             Ok(ref snippet) if snippet == "{" => true,
 373             _ => false,
 374         };
 375         // In case this could be a struct literal that needs to be surrounded
 376         // by parenthesis, find the appropriate span.
 377         let mut i = 0;
 378         let mut closing_brace = None;
 379         loop {
 380             sp = sm.next_point(sp);
 381             match sm.span_to_snippet(sp) {
 382                 Ok(ref snippet) => {
 383                     if snippet == "}" {
 384                         let sp = span.to(sp);
 385                         if let Ok(snippet) = sm.span_to_snippet(sp) {
 386                             closing_brace = Some((sp, snippet));
 387                         }
 388                         break;
 389                     }
 390                 }
 391                 _ => break,
 392             }
 393             i += 1;
 394             // The bigger the span, the more likely we're incorrect --
 395             // bound it to 100 chars long.
 396             if i > 100 {
 397                 break;
 398             }
 399         }
 400         return (followed_by_brace, closing_brace);
 401     }
 402
 403     /// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
 404     /// function.
 405     /// Returns `true` if able to provide context-dependent help.
 406     fn smart_resolve_context_dependent_help(
 407         &mut self,
 408         err: &mut DiagnosticBuilder<'a>,
 409         span: Span,
 410         source: PathSource<'_>,
 411         res: Res,
 412         path_str: &str,
 413         fallback_label: &str,
 414     ) -> bool {
 415         let ns = source.namespace();
 416         let is_expected = &|res| source.is_expected(res);
 417
 418         let path_sep = |err: &mut DiagnosticBuilder<'_>, expr: &Expr| match expr.kind {
 419             ExprKind::Field(_, ident) => {
 420                 err.span_suggestion(
 421                     expr.span,
 422                     "use the path separator to refer to an item",
 423                     format!("{}::{}", path_str, ident),
 424                     Applicability::MaybeIncorrect,
 425                 );
 426                 true
 427             }
 428             ExprKind::MethodCall(ref segment, ..) => {
 429                 let span = expr.span.with_hi(segment.ident.span.hi());
 430                 err.span_suggestion(
 431                     span,
 432                     "use the path separator to refer to an item",
 433                     format!("{}::{}", path_str, segment.ident),
 434                     Applicability::MaybeIncorrect,
 435                 );
 436                 true
 437             }
 438             _ => false,
 439         };
 440
 441         let mut bad_struct_syntax_suggestion = |def_id: DefId| {
 442             let (followed_by_brace, closing_brace) = self.followed_by_brace(span);
 443             let mut suggested = false;
 444             match source {
 445                 PathSource::Expr(Some(parent)) => {
 446                     suggested = path_sep(err, &parent);
 447                 }
 448                 PathSource::Expr(None) if followed_by_brace == true => {
 449                     if let Some((sp, snippet)) = closing_brace {
 450                         err.span_suggestion(
 451                             sp,
 452                             "surround the struct literal with parenthesis",
 453                             format!("({})", snippet),
 454                             Applicability::MaybeIncorrect,
 455                         );
 456                     } else {
 457                         err.span_label(
 458                             span, // Note the parenthesis surrounding the suggestion below
 459                             format!("did you mean `({} {{ /* fields */ }})`?", path_str),
 460                         );
 461                     }
 462                     suggested = true;
 463                 }
 464                 _ => {}
 465             }
 466             if !suggested {
 467                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 468                     err.span_label(span, &format!("`{}` defined here", path_str));
 469                 }
 470                 err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?", path_str));
 471             }
 472         };
 473
 474         match (res, source) {
 475             (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
 476                 err.span_suggestion(
 477                     span,
 478                     "use `!` to invoke the macro",
 479                     format!("{}!", path_str),
 480                     Applicability::MaybeIncorrect,
 481                 );
 482                 if path_str == "try" && span.rust_2015() {
 483                     err.note("if you want the `try` keyword, you need to be in the 2018 edition");
 484                 }
 485             }
 486             (Res::Def(DefKind::TyAlias, _), PathSource::Trait(_)) => {
 487                 err.span_label(span, "type aliases cannot be used as traits");
 488                 if nightly_options::is_nightly_build() {
 489                     err.note("did you mean to use a trait alias?");
 490                 }
 491             }
 492             (Res::Def(DefKind::Mod, _), PathSource::Expr(Some(parent))) => {
 493                 if !path_sep(err, &parent) {
 494                     return false;
 495                 }
 496             }
 497             (Res::Def(DefKind::Enum, def_id), PathSource::TupleStruct)
 498             | (Res::Def(DefKind::Enum, def_id), PathSource::Expr(..)) => {
 499                 if let Some(variants) = self.collect_enum_variants(def_id) {
 500                     if !variants.is_empty() {
 501                         let msg = if variants.len() == 1 {
 502                             "try using the enum's variant"
 503                         } else {
 504                             "try using one of the enum's variants"
 505                         };
 506
 507                         err.span_suggestions(
 508                             span,
 509                             msg,
 510                             variants.iter().map(path_names_to_string),
 511                             Applicability::MaybeIncorrect,
 512                         );
 513                     }
 514                 } else {
 515                     err.note("did you mean to use one of the enum's variants?");
 516                 }
 517             }
 518             (Res::Def(DefKind::Struct, def_id), _) if ns == ValueNS => {
 519                 if let Some((ctor_def, ctor_vis)) = self.r.struct_constructors.get(&def_id).cloned()
 520                 {
 521                     let accessible_ctor =
 522                         self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
 523                     if is_expected(ctor_def) && !accessible_ctor {
 524                         err.span_label(
 525                             span,
 526                             format!("constructor is not visible here due to private fields"),
 527                         );
 528                     }
 529                 } else {
 530                     bad_struct_syntax_suggestion(def_id);
 531                 }
 532             }
 533             (Res::Def(DefKind::Union, def_id), _)
 534             | (Res::Def(DefKind::Variant, def_id), _)
 535             | (Res::Def(DefKind::Ctor(_, CtorKind::Fictive), def_id), _)
 536                 if ns == ValueNS =>
 537             {
 538                 bad_struct_syntax_suggestion(def_id);
 539             }
 540             (Res::Def(DefKind::Ctor(_, CtorKind::Fn), def_id), _) if ns == ValueNS => {
 541                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 542                     err.span_label(span, &format!("`{}` defined here", path_str));
 543                 }
 544                 err.span_label(span, format!("did you mean `{}( /* fields */ )`?", path_str));
 545             }
 546             (Res::SelfTy(..), _) if ns == ValueNS => {
 547                 err.span_label(span, fallback_label);
 548                 err.note("can't use `Self` as a constructor, you must use the implemented struct");
 549             }
 550             (Res::Def(DefKind::TyAlias, _), _) | (Res::Def(DefKind::AssocTy, _), _)
 551                 if ns == ValueNS =>
 552             {
 553                 err.note("can't use a type alias as a constructor");
 554             }
 555             _ => return false,
 556         }
 557         true
 558     }
 559
 560     fn lookup_assoc_candidate<FilterFn>(
 561         &mut self,
 562         ident: Ident,
 563         ns: Namespace,
 564         filter_fn: FilterFn,
 565     ) -> Option<AssocSuggestion>
 566     where
 567         FilterFn: Fn(Res) -> bool,
 568     {
 569         fn extract_node_id(t: &Ty) -> Option<NodeId> {
 570             match t.kind {
 571                 TyKind::Path(None, _) => Some(t.id),
 572                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
 573                 // This doesn't handle the remaining `Ty` variants as they are not
 574                 // that commonly the self_type, it might be interesting to provide
 575                 // support for those in future.
 576                 _ => None,
 577             }
 578         }
 579
 580         // Fields are generally expected in the same contexts as locals.
 581         if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
 582             if let Some(node_id) =
 583                 self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id)
 584             {
 585                 // Look for a field with the same name in the current self_type.
 586                 if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
 587                     match resolution.base_res() {
 588                         Res::Def(DefKind::Struct, did) | Res::Def(DefKind::Union, did)
 589                             if resolution.unresolved_segments() == 0 =>
 590                         {
 591                             if let Some(field_names) = self.r.field_names.get(&did) {
 592                                 if field_names
 593                                     .iter()
 594                                     .any(|&field_name| ident.name == field_name.node)
 595                                 {
 596                                     return Some(AssocSuggestion::Field);
 597                                 }
 598                             }
 599                         }
 600                         _ => {}
 601                     }
 602                 }
 603             }
 604         }
 605
 606         for assoc_type_ident in &self.diagnostic_metadata.current_trait_assoc_types {
 607             if *assoc_type_ident == ident {
 608                 return Some(AssocSuggestion::AssocItem);
 609             }
 610         }
 611
 612         // Look for associated items in the current trait.
 613         if let Some((module, _)) = self.current_trait_ref {
 614             if let Ok(binding) = self.r.resolve_ident_in_module(
 615                 ModuleOrUniformRoot::Module(module),
 616                 ident,
 617                 ns,
 618                 &self.parent_scope,
 619                 false,
 620                 module.span,
 621             ) {
 622                 let res = binding.res();
 623                 if filter_fn(res) {
 624                     return Some(if self.r.has_self.contains(&res.def_id()) {
 625                         AssocSuggestion::MethodWithSelf
 626                     } else {
 627                         AssocSuggestion::AssocItem
 628                     });
 629                 }
 630             }
 631         }
 632
 633         None
 634     }
 635
 636     fn lookup_typo_candidate(
 637         &mut self,
 638         path: &[Segment],
 639         ns: Namespace,
 640         filter_fn: &impl Fn(Res) -> bool,
 641         span: Span,
 642     ) -> Option<TypoSuggestion> {
 643         let mut names = Vec::new();
 644         if path.len() == 1 {
 645             // Search in lexical scope.
 646             // Walk backwards up the ribs in scope and collect candidates.
 647             for rib in self.ribs[ns].iter().rev() {
 648                 // Locals and type parameters
 649                 for (ident, &res) in &rib.bindings {
 650                     if filter_fn(res) {
 651                         names.push(TypoSuggestion::from_res(ident.name, res));
 652                     }
 653                 }
 654                 // Items in scope
 655                 if let RibKind::ModuleRibKind(module) = rib.kind {
 656                     // Items from this module
 657                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 658
 659                     if let ModuleKind::Block(..) = module.kind {
 660                         // We can see through blocks
 661                     } else {
 662                         // Items from the prelude
 663                         if !module.no_implicit_prelude {
 664                             let extern_prelude = self.r.extern_prelude.clone();
 665                             names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
 666                                 self.r
 667                                     .crate_loader
 668                                     .maybe_process_path_extern(ident.name, ident.span)
 669                                     .and_then(|crate_id| {
 670                                         let crate_mod = Res::Def(
 671                                             DefKind::Mod,
 672                                             DefId { krate: crate_id, index: CRATE_DEF_INDEX },
 673                                         );
 674
 675                                         if filter_fn(crate_mod) {
 676                                             Some(TypoSuggestion::from_res(ident.name, crate_mod))
 677                                         } else {
 678                                             None
 679                                         }
 680                                     })
 681                             }));
 682
 683                             if let Some(prelude) = self.r.prelude {
 684                                 self.r.add_module_candidates(prelude, &mut names, &filter_fn);
 685                             }
 686                         }
 687                         break;
 688                     }
 689                 }
 690             }
 691             // Add primitive types to the mix
 692             if filter_fn(Res::PrimTy(PrimTy::Bool)) {
 693                 names.extend(
 694                     self.r.primitive_type_table.primitive_types.iter().map(|(name, prim_ty)| {
 695                         TypoSuggestion::from_res(*name, Res::PrimTy(*prim_ty))
 696                     }),
 697                 )
 698             }
 699         } else {
 700             // Search in module.
 701             let mod_path = &path[..path.len() - 1];
 702             if let PathResult::Module(module) =
 703                 self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No)
 704             {
 705                 if let ModuleOrUniformRoot::Module(module) = module {
 706                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 707                 }
 708             }
 709         }
 710
 711         let name = path[path.len() - 1].ident.name;
 712         // Make sure error reporting is deterministic.
 713         names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 714
 715         match find_best_match_for_name(
 716             names.iter().map(|suggestion| &suggestion.candidate),
 717             &name.as_str(),
 718             None,
 719         ) {
 720             Some(found) if found != name => {
 721                 names.into_iter().find(|suggestion| suggestion.candidate == found)
 722             }
 723             _ => None,
 724         }
 725     }
 726
 727     /// Only used in a specific case of type ascription suggestions
 728     fn get_colon_suggestion_span(&self, start: Span) -> Span {
 729         let cm = self.r.session.source_map();
 730         start.to(cm.next_point(start))
 731     }
 732
 733     fn type_ascription_suggestion(&self, err: &mut DiagnosticBuilder<'_>, base_span: Span) {
 734         let cm = self.r.session.source_map();
 735         let base_snippet = cm.span_to_snippet(base_span);
 736         if let Some(sp) = self.diagnostic_metadata.current_type_ascription.last() {
 737             let mut sp = *sp;
 738             loop {
 739                 // Try to find the `:`; bail on first non-':' / non-whitespace.
 740                 sp = cm.next_point(sp);
 741                 if let Ok(snippet) = cm.span_to_snippet(sp.to(cm.next_point(sp))) {
 742                     let line_sp = cm.lookup_char_pos(sp.hi()).line;
 743                     let line_base_sp = cm.lookup_char_pos(base_span.lo()).line;
 744                     if snippet == ":" {
 745                         let mut show_label = true;
 746                         if line_sp != line_base_sp {
 747                             err.span_suggestion_short(
 748                                 sp,
 749                                 "did you mean to use `;` here instead?",
 750                                 ";".to_string(),
 751                                 Applicability::MaybeIncorrect,
 752                             );
 753                         } else {
 754                             let colon_sp = self.get_colon_suggestion_span(sp);
 755                             let after_colon_sp =
 756                                 self.get_colon_suggestion_span(colon_sp.shrink_to_hi());
 757                             if !cm
 758                                 .span_to_snippet(after_colon_sp)
 759                                 .map(|s| s == " ")
 760                                 .unwrap_or(false)
 761                             {
 762                                 err.span_suggestion(
 763                                     colon_sp,
 764                                     "maybe you meant to write a path separator here",
 765                                     "::".to_string(),
 766                                     Applicability::MaybeIncorrect,
 767                                 );
 768                                 show_label = false;
 769                             }
 770                             if let Ok(base_snippet) = base_snippet {
 771                                 let mut sp = after_colon_sp;
 772                                 for _ in 0..100 {
 773                                     // Try to find an assignment
 774                                     sp = cm.next_point(sp);
 775                                     let snippet = cm.span_to_snippet(sp.to(cm.next_point(sp)));
 776                                     match snippet {
 777                                         Ok(ref x) if x.as_str() == "=" => {
 778                                             err.span_suggestion(
 779                                                 base_span,
 780                                                 "maybe you meant to write an assignment here",
 781                                                 format!("let {}", base_snippet),
 782                                                 Applicability::MaybeIncorrect,
 783                                             );
 784                                             show_label = false;
 785                                             break;
 786                                         }
 787                                         Ok(ref x) if x.as_str() == "\n" => break,
 788                                         Err(_) => break,
 789                                         Ok(_) => {}
 790                                     }
 791                                 }
 792                             }
 793                         }
 794                         if show_label {
 795                             err.span_label(
 796                                 base_span,
 797                                 "expecting a type here because of type ascription",
 798                             );
 799                         }
 800                         break;
 801                     } else if !snippet.trim().is_empty() {
 802                         debug!("tried to find type ascription `:` token, couldn't find it");
 803                         break;
 804                     }
 805                 } else {
 806                     break;
 807                 }
 808             }
 809         }
 810     }
 811
 812     fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
 813         let mut result = None;
 814         let mut seen_modules = FxHashSet::default();
 815         let mut worklist = vec![(self.r.graph_root, Vec::new())];
 816
 817         while let Some((in_module, path_segments)) = worklist.pop() {
 818             // abort if the module is already found
 819             if result.is_some() {
 820                 break;
 821             }
 822
 823             in_module.for_each_child(self.r, |_, ident, _, name_binding| {
 824                 // abort if the module is already found or if name_binding is private external
 825                 if result.is_some() || !name_binding.vis.is_visible_locally() {
 826                     return;
 827                 }
 828                 if let Some(module) = name_binding.module() {
 829                     // form the path
 830                     let mut path_segments = path_segments.clone();
 831                     path_segments.push(ast::PathSegment::from_ident(ident));
 832                     let module_def_id = module.def_id().unwrap();
 833                     if module_def_id == def_id {
 834                         let path = Path { span: name_binding.span, segments: path_segments };
 835                         result = Some((module, ImportSuggestion { did: Some(def_id), path }));
 836                     } else {
 837                         // add the module to the lookup
 838                         if seen_modules.insert(module_def_id) {
 839                             worklist.push((module, path_segments));
 840                         }
 841                     }
 842                 }
 843             });
 844         }
 845
 846         result
 847     }
 848
 849     fn collect_enum_variants(&mut self, def_id: DefId) -> Option<Vec<Path>> {
 850         self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
 851             let mut variants = Vec::new();
 852             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
 853                 if let Res::Def(DefKind::Variant, _) = name_binding.res() {
 854                     let mut segms = enum_import_suggestion.path.segments.clone();
 855                     segms.push(ast::PathSegment::from_ident(ident));
 856                     variants.push(Path { span: name_binding.span, segments: segms });
 857                 }
 858             });
 859             variants
 860         })
 861     }
 862 }