src/librustc_resolve/late/diagnostics.rs

   1 use crate::diagnostics::{ImportSuggestion, TypoSuggestion};
   2 use crate::late::lifetimes::{ElisionFailureInfo, LifetimeContext};
   3 use crate::late::{LateResolutionVisitor, RibKind};
   4 use crate::path_names_to_string;
   5 use crate::{CrateLint, Module, ModuleKind, ModuleOrUniformRoot};
   6 use crate::{PathResult, PathSource, Segment};
   7
   8 use rustc_ast::ast::{self, Expr, ExprKind, Ident, Item, ItemKind, NodeId, Path, Ty, TyKind};
   9 use rustc_ast::util::lev_distance::find_best_match_for_name;
  10 use rustc_data_structures::fx::FxHashSet;
  11 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
  12 use rustc_hir as hir;
  13 use rustc_hir::def::Namespace::{self, *};
  14 use rustc_hir::def::{self, CtorKind, DefKind};
  15 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
  16 use rustc_hir::PrimTy;
  17 use rustc_session::config::nightly_options;
  18 use rustc_span::hygiene::MacroKind;
  19 use rustc_span::symbol::{kw, sym};
  20 use rustc_span::Span;
  21
  22 use log::debug;
  23
  24 type Res = def::Res<ast::NodeId>;
  25
  26 /// A field or associated item from self type suggested in case of resolution failure.
  27 enum AssocSuggestion {
  28     Field,
  29     MethodWithSelf,
  30     AssocItem,
  31 }
  32
  33 crate enum MissingLifetimeSpot<'tcx> {
  34     Generics(&'tcx hir::Generics<'tcx>),
  35     HigherRanked { span: Span, span_type: ForLifetimeSpanType },
  36 }
  37
  38 crate enum ForLifetimeSpanType {
  39     BoundEmpty,
  40     BoundTail,
  41     TypeEmpty,
  42     TypeTail,
  43 }
  44
  45 impl ForLifetimeSpanType {
  46     crate fn descr(&self) -> &'static str {
  47         match self {
  48             Self::BoundEmpty | Self::BoundTail => "bound",
  49             Self::TypeEmpty | Self::TypeTail => "type",
  50         }
  51     }
  52
  53     crate fn suggestion(&self, sugg: &str) -> String {
  54         match self {
  55             Self::BoundEmpty | Self::TypeEmpty => format!("for<{}> ", sugg),
  56             Self::BoundTail | Self::TypeTail => format!(", {}", sugg),
  57         }
  58     }
  59 }
  60
  61 impl<'tcx> Into<MissingLifetimeSpot<'tcx>> for &'tcx hir::Generics<'tcx> {
  62     fn into(self) -> MissingLifetimeSpot<'tcx> {
  63         MissingLifetimeSpot::Generics(self)
  64     }
  65 }
  66
  67 fn is_self_type(path: &[Segment], namespace: Namespace) -> bool {
  68     namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper
  69 }
  70
  71 fn is_self_value(path: &[Segment], namespace: Namespace) -> bool {
  72     namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower
  73 }
  74
  75 /// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant.
  76 fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) {
  77     let variant_path = &suggestion.path;
  78     let variant_path_string = path_names_to_string(variant_path);
  79
  80     let path_len = suggestion.path.segments.len();
  81     let enum_path = ast::Path {
  82         span: suggestion.path.span,
  83         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
  84     };
  85     let enum_path_string = path_names_to_string(&enum_path);
  86
  87     (variant_path_string, enum_path_string)
  88 }
  89
  90 impl<'a> LateResolutionVisitor<'a, '_, '_> {
  91     /// Handles error reporting for `smart_resolve_path_fragment` function.
  92     /// Creates base error and amends it with one short label and possibly some longer helps/notes.
  93     pub(crate) fn smart_resolve_report_errors(
  94         &mut self,
  95         path: &[Segment],
  96         span: Span,
  97         source: PathSource<'_>,
  98         res: Option<Res>,
  99     ) -> (DiagnosticBuilder<'a>, Vec<ImportSuggestion>) {
 100         let ident_span = path.last().map_or(span, |ident| ident.ident.span);
 101         let ns = source.namespace();
 102         let is_expected = &|res| source.is_expected(res);
 103         let is_enum_variant = &|res| {
 104             if let Res::Def(DefKind::Variant, _) = res { true } else { false }
 105         };
 106
 107         // Make the base error.
 108         let expected = source.descr_expected();
 109         let path_str = Segment::names_to_string(path);
 110         let item_str = path.last().unwrap().ident;
 111         let (base_msg, fallback_label, base_span, could_be_expr) = if let Some(res) = res {
 112             (
 113                 format!("expected {}, found {} `{}`", expected, res.descr(), path_str),
 114                 format!("not a {}", expected),
 115                 span,
 116                 match res {
 117                     Res::Def(DefKind::Fn, _) => {
 118                         // Verify whether this is a fn call or an Fn used as a type.
 119                         self.r
 120                             .session
 121                             .source_map()
 122                             .span_to_snippet(span)
 123                             .map(|snippet| snippet.ends_with(')'))
 124                             .unwrap_or(false)
 125                     }
 126                     Res::Def(
 127                         DefKind::Ctor(..) | DefKind::AssocFn | DefKind::Const | DefKind::AssocConst,
 128                         _,
 129                     )
 130                     | Res::SelfCtor(_)
 131                     | Res::PrimTy(_)
 132                     | Res::Local(_) => true,
 133                     _ => false,
 134                 },
 135             )
 136         } else {
 137             let item_span = path.last().unwrap().ident.span;
 138             let (mod_prefix, mod_str) = if path.len() == 1 {
 139                 (String::new(), "this scope".to_string())
 140             } else if path.len() == 2 && path[0].ident.name == kw::PathRoot {
 141                 (String::new(), "the crate root".to_string())
 142             } else {
 143                 let mod_path = &path[..path.len() - 1];
 144                 let mod_prefix =
 145                     match self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No) {
 146                         PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
 147                         _ => None,
 148                     }
 149                     .map_or(String::new(), |res| format!("{} ", res.descr()));
 150                 (mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)))
 151             };
 152             (
 153                 format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
 154                 format!("not found in {}", mod_str),
 155                 item_span,
 156                 false,
 157             )
 158         };
 159
 160         let code = source.error_code(res.is_some());
 161         let mut err = self.r.session.struct_span_err_with_code(base_span, &base_msg, code);
 162
 163         // Emit help message for fake-self from other languages (e.g., `this` in Javascript).
 164         if ["this", "my"].contains(&&*item_str.as_str())
 165             && self.self_value_is_available(path[0].ident.span, span)
 166         {
 167             err.span_suggestion(
 168                 span,
 169                 "did you mean",
 170                 "self".to_string(),
 171                 Applicability::MaybeIncorrect,
 172             );
 173         }
 174
 175         // Emit special messages for unresolved `Self` and `self`.
 176         if is_self_type(path, ns) {
 177             err.code(rustc_errors::error_code!(E0411));
 178             err.span_label(
 179                 span,
 180                 "`Self` is only available in impls, traits, and type definitions".to_string(),
 181             );
 182             return (err, Vec::new());
 183         }
 184         if is_self_value(path, ns) {
 185             debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
 186
 187             err.code(rustc_errors::error_code!(E0424));
 188             err.span_label(span, match source {
 189                 PathSource::Pat => "`self` value is a keyword and may not be bound to variables or shadowed"
 190                                    .to_string(),
 191                 _ => "`self` value is a keyword only available in methods with a `self` parameter"
 192                      .to_string(),
 193             });
 194             if let Some(span) = &self.diagnostic_metadata.current_function {
 195                 err.span_label(*span, "this function doesn't have a `self` parameter");
 196             }
 197             return (err, Vec::new());
 198         }
 199
 200         // Try to lookup name in more relaxed fashion for better error reporting.
 201         let ident = path.last().unwrap().ident;
 202         let candidates = self
 203             .r
 204             .lookup_import_candidates(ident, ns, is_expected)
 205             .drain(..)
 206             .filter(|ImportSuggestion { did, .. }| {
 207                 match (did, res.and_then(|res| res.opt_def_id())) {
 208                     (Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
 209                     _ => true,
 210                 }
 211             })
 212             .collect::<Vec<_>>();
 213         let crate_def_id = DefId::local(CRATE_DEF_INDEX);
 214         if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
 215             let enum_candidates = self.r.lookup_import_candidates(ident, ns, is_enum_variant);
 216             let mut enum_candidates = enum_candidates
 217                 .iter()
 218                 .map(|suggestion| import_candidate_to_enum_paths(&suggestion))
 219                 .collect::<Vec<_>>();
 220             enum_candidates.sort();
 221
 222             if !enum_candidates.is_empty() {
 223                 // Contextualize for E0412 "cannot find type", but don't belabor the point
 224                 // (that it's a variant) for E0573 "expected type, found variant".
 225                 let preamble = if res.is_none() {
 226                     let others = match enum_candidates.len() {
 227                         1 => String::new(),
 228                         2 => " and 1 other".to_owned(),
 229                         n => format!(" and {} others", n),
 230                     };
 231                     format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
 232                 } else {
 233                     String::new()
 234                 };
 235                 let msg = format!("{}try using the variant's enum", preamble);
 236
 237                 err.span_suggestions(
 238                     span,
 239                     &msg,
 240                     enum_candidates
 241                         .into_iter()
 242                         .map(|(_variant_path, enum_ty_path)| enum_ty_path)
 243                         // Variants re-exported in prelude doesn't mean `prelude::v1` is the
 244                         // type name!
 245                         // FIXME: is there a more principled way to do this that
 246                         // would work for other re-exports?
 247                         .filter(|enum_ty_path| enum_ty_path != "std::prelude::v1")
 248                         // Also write `Option` rather than `std::prelude::v1::Option`.
 249                         .map(|enum_ty_path| {
 250                             // FIXME #56861: DRY-er prelude filtering.
 251                             enum_ty_path.trim_start_matches("std::prelude::v1::").to_owned()
 252                         }),
 253                     Applicability::MachineApplicable,
 254                 );
 255             }
 256         }
 257         if path.len() == 1 && self.self_type_is_available(span) {
 258             if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) {
 259                 let self_is_available = self.self_value_is_available(path[0].ident.span, span);
 260                 match candidate {
 261                     AssocSuggestion::Field => {
 262                         if self_is_available {
 263                             err.span_suggestion(
 264                                 span,
 265                                 "you might have meant to use the available field",
 266                                 format!("self.{}", path_str),
 267                                 Applicability::MachineApplicable,
 268                             );
 269                         } else {
 270                             err.span_label(span, "a field by this name exists in `Self`");
 271                         }
 272                     }
 273                     AssocSuggestion::MethodWithSelf if self_is_available => {
 274                         err.span_suggestion(
 275                             span,
 276                             "try",
 277                             format!("self.{}", path_str),
 278                             Applicability::MachineApplicable,
 279                         );
 280                     }
 281                     AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
 282                         err.span_suggestion(
 283                             span,
 284                             "try",
 285                             format!("Self::{}", path_str),
 286                             Applicability::MachineApplicable,
 287                         );
 288                     }
 289                 }
 290                 return (err, candidates);
 291             }
 292
 293             // If the first argument in call is `self` suggest calling a method.
 294             if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
 295                 let mut args_snippet = String::new();
 296                 if let Some(args_span) = args_span {
 297                     if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) {
 298                         args_snippet = snippet;
 299                     }
 300                 }
 301
 302                 err.span_suggestion(
 303                     call_span,
 304                     &format!("try calling `{}` as a method", ident),
 305                     format!("self.{}({})", path_str, args_snippet),
 306                     Applicability::MachineApplicable,
 307                 );
 308                 return (err, candidates);
 309             }
 310         }
 311
 312         // Try Levenshtein algorithm.
 313         let typo_sugg = self.lookup_typo_candidate(path, ns, is_expected, span);
 314         let levenshtein_worked = self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
 315
 316         // Try context-dependent help if relaxed lookup didn't work.
 317         if let Some(res) = res {
 318             if self.smart_resolve_context_dependent_help(
 319                 &mut err,
 320                 span,
 321                 source,
 322                 res,
 323                 &path_str,
 324                 &fallback_label,
 325             ) {
 326                 return (err, candidates);
 327             }
 328         }
 329
 330         // Fallback label.
 331         if !levenshtein_worked {
 332             err.span_label(base_span, fallback_label);
 333             self.type_ascription_suggestion(&mut err, base_span);
 334             match self.diagnostic_metadata.current_let_binding {
 335                 Some((pat_sp, Some(ty_sp), None)) if ty_sp.contains(base_span) && could_be_expr => {
 336                     err.span_suggestion_short(
 337                         pat_sp.between(ty_sp),
 338                         "use `=` if you meant to assign",
 339                         " = ".to_string(),
 340                         Applicability::MaybeIncorrect,
 341                     );
 342                 }
 343                 _ => {}
 344             }
 345         }
 346         (err, candidates)
 347     }
 348
 349     /// Check if the source is call expression and the first argument is `self`. If true,
 350     /// return the span of whole call and the span for all arguments expect the first one (`self`).
 351     fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
 352         let mut has_self_arg = None;
 353         if let PathSource::Expr(parent) = source {
 354             match &parent?.kind {
 355                 ExprKind::Call(_, args) if !args.is_empty() => {
 356                     let mut expr_kind = &args[0].kind;
 357                     loop {
 358                         match expr_kind {
 359                             ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
 360                                 if arg_name.segments[0].ident.name == kw::SelfLower {
 361                                     let call_span = parent.unwrap().span;
 362                                     let tail_args_span = if args.len() > 1 {
 363                                         Some(Span::new(
 364                                             args[1].span.lo(),
 365                                             args.last().unwrap().span.hi(),
 366                                             call_span.ctxt(),
 367                                         ))
 368                                     } else {
 369                                         None
 370                                     };
 371                                     has_self_arg = Some((call_span, tail_args_span));
 372                                 }
 373                                 break;
 374                             }
 375                             ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
 376                             _ => break,
 377                         }
 378                     }
 379                 }
 380                 _ => (),
 381             }
 382         };
 383         has_self_arg
 384     }
 385
 386     fn followed_by_brace(&self, span: Span) -> (bool, Option<(Span, String)>) {
 387         // HACK(estebank): find a better way to figure out that this was a
 388         // parser issue where a struct literal is being used on an expression
 389         // where a brace being opened means a block is being started. Look
 390         // ahead for the next text to see if `span` is followed by a `{`.
 391         let sm = self.r.session.source_map();
 392         let mut sp = span;
 393         loop {
 394             sp = sm.next_point(sp);
 395             match sm.span_to_snippet(sp) {
 396                 Ok(ref snippet) => {
 397                     if snippet.chars().any(|c| !c.is_whitespace()) {
 398                         break;
 399                     }
 400                 }
 401                 _ => break,
 402             }
 403         }
 404         let followed_by_brace = match sm.span_to_snippet(sp) {
 405             Ok(ref snippet) if snippet == "{" => true,
 406             _ => false,
 407         };
 408         // In case this could be a struct literal that needs to be surrounded
 409         // by parenthesis, find the appropriate span.
 410         let mut i = 0;
 411         let mut closing_brace = None;
 412         loop {
 413             sp = sm.next_point(sp);
 414             match sm.span_to_snippet(sp) {
 415                 Ok(ref snippet) => {
 416                     if snippet == "}" {
 417                         let sp = span.to(sp);
 418                         if let Ok(snippet) = sm.span_to_snippet(sp) {
 419                             closing_brace = Some((sp, snippet));
 420                         }
 421                         break;
 422                     }
 423                 }
 424                 _ => break,
 425             }
 426             i += 1;
 427             // The bigger the span, the more likely we're incorrect --
 428             // bound it to 100 chars long.
 429             if i > 100 {
 430                 break;
 431             }
 432         }
 433         (followed_by_brace, closing_brace)
 434     }
 435
 436     /// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
 437     /// function.
 438     /// Returns `true` if able to provide context-dependent help.
 439     fn smart_resolve_context_dependent_help(
 440         &mut self,
 441         err: &mut DiagnosticBuilder<'a>,
 442         span: Span,
 443         source: PathSource<'_>,
 444         res: Res,
 445         path_str: &str,
 446         fallback_label: &str,
 447     ) -> bool {
 448         let ns = source.namespace();
 449         let is_expected = &|res| source.is_expected(res);
 450
 451         let path_sep = |err: &mut DiagnosticBuilder<'_>, expr: &Expr| match expr.kind {
 452             ExprKind::Field(_, ident) => {
 453                 err.span_suggestion(
 454                     expr.span,
 455                     "use the path separator to refer to an item",
 456                     format!("{}::{}", path_str, ident),
 457                     Applicability::MaybeIncorrect,
 458                 );
 459                 true
 460             }
 461             ExprKind::MethodCall(ref segment, ..) => {
 462                 let span = expr.span.with_hi(segment.ident.span.hi());
 463                 err.span_suggestion(
 464                     span,
 465                     "use the path separator to refer to an item",
 466                     format!("{}::{}", path_str, segment.ident),
 467                     Applicability::MaybeIncorrect,
 468                 );
 469                 true
 470             }
 471             _ => false,
 472         };
 473
 474         let mut bad_struct_syntax_suggestion = |def_id: DefId| {
 475             let (followed_by_brace, closing_brace) = self.followed_by_brace(span);
 476             let mut suggested = false;
 477             match source {
 478                 PathSource::Expr(Some(parent)) => {
 479                     suggested = path_sep(err, &parent);
 480                 }
 481                 PathSource::Expr(None) if followed_by_brace => {
 482                     if let Some((sp, snippet)) = closing_brace {
 483                         err.span_suggestion(
 484                             sp,
 485                             "surround the struct literal with parenthesis",
 486                             format!("({})", snippet),
 487                             Applicability::MaybeIncorrect,
 488                         );
 489                     } else {
 490                         err.span_label(
 491                             span, // Note the parenthesis surrounding the suggestion below
 492                             format!("did you mean `({} {{ /* fields */ }})`?", path_str),
 493                         );
 494                     }
 495                     suggested = true;
 496                 }
 497                 _ => {}
 498             }
 499             if !suggested {
 500                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 501                     err.span_label(span, &format!("`{}` defined here", path_str));
 502                 }
 503                 err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?", path_str));
 504             }
 505         };
 506
 507         match (res, source) {
 508             (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
 509                 err.span_suggestion_verbose(
 510                     span.shrink_to_hi(),
 511                     "use `!` to invoke the macro",
 512                     "!".to_string(),
 513                     Applicability::MaybeIncorrect,
 514                 );
 515                 if path_str == "try" && span.rust_2015() {
 516                     err.note("if you want the `try` keyword, you need to be in the 2018 edition");
 517                 }
 518             }
 519             (Res::Def(DefKind::TyAlias, _), PathSource::Trait(_)) => {
 520                 err.span_label(span, "type aliases cannot be used as traits");
 521                 if nightly_options::is_nightly_build() {
 522                     err.note("did you mean to use a trait alias?");
 523                 }
 524             }
 525             (Res::Def(DefKind::Mod, _), PathSource::Expr(Some(parent))) => {
 526                 if !path_sep(err, &parent) {
 527                     return false;
 528                 }
 529             }
 530             (Res::Def(DefKind::Enum, def_id), PathSource::TupleStruct | PathSource::Expr(..)) => {
 531                 if let Some(variants) = self.collect_enum_variants(def_id) {
 532                     if !variants.is_empty() {
 533                         let msg = if variants.len() == 1 {
 534                             "try using the enum's variant"
 535                         } else {
 536                             "try using one of the enum's variants"
 537                         };
 538
 539                         err.span_suggestions(
 540                             span,
 541                             msg,
 542                             variants.iter().map(path_names_to_string),
 543                             Applicability::MaybeIncorrect,
 544                         );
 545                     }
 546                 } else {
 547                     err.note("did you mean to use one of the enum's variants?");
 548                 }
 549             }
 550             (Res::Def(DefKind::Struct, def_id), _) if ns == ValueNS => {
 551                 if let Some((ctor_def, ctor_vis)) = self.r.struct_constructors.get(&def_id).cloned()
 552                 {
 553                     let accessible_ctor =
 554                         self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
 555                     if is_expected(ctor_def) && !accessible_ctor {
 556                         err.span_label(
 557                             span,
 558                             "constructor is not visible here due to private fields".to_string(),
 559                         );
 560                     }
 561                 } else {
 562                     bad_struct_syntax_suggestion(def_id);
 563                 }
 564             }
 565             (
 566                 Res::Def(
 567                     DefKind::Union | DefKind::Variant | DefKind::Ctor(_, CtorKind::Fictive),
 568                     def_id,
 569                 ),
 570                 _,
 571             ) if ns == ValueNS => {
 572                 bad_struct_syntax_suggestion(def_id);
 573             }
 574             (Res::Def(DefKind::Ctor(_, CtorKind::Fn), def_id), _) if ns == ValueNS => {
 575                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 576                     err.span_label(span, &format!("`{}` defined here", path_str));
 577                 }
 578                 err.span_label(span, format!("did you mean `{}( /* fields */ )`?", path_str));
 579             }
 580             (Res::SelfTy(..), _) if ns == ValueNS => {
 581                 err.span_label(span, fallback_label);
 582                 err.note("can't use `Self` as a constructor, you must use the implemented struct");
 583             }
 584             (Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => {
 585                 err.note("can't use a type alias as a constructor");
 586             }
 587             _ => return false,
 588         }
 589         true
 590     }
 591
 592     fn lookup_assoc_candidate<FilterFn>(
 593         &mut self,
 594         ident: Ident,
 595         ns: Namespace,
 596         filter_fn: FilterFn,
 597     ) -> Option<AssocSuggestion>
 598     where
 599         FilterFn: Fn(Res) -> bool,
 600     {
 601         fn extract_node_id(t: &Ty) -> Option<NodeId> {
 602             match t.kind {
 603                 TyKind::Path(None, _) => Some(t.id),
 604                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
 605                 // This doesn't handle the remaining `Ty` variants as they are not
 606                 // that commonly the self_type, it might be interesting to provide
 607                 // support for those in future.
 608                 _ => None,
 609             }
 610         }
 611
 612         // Fields are generally expected in the same contexts as locals.
 613         if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
 614             if let Some(node_id) =
 615                 self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id)
 616             {
 617                 // Look for a field with the same name in the current self_type.
 618                 if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
 619                     match resolution.base_res() {
 620                         Res::Def(DefKind::Struct | DefKind::Union, did)
 621                             if resolution.unresolved_segments() == 0 =>
 622                         {
 623                             if let Some(field_names) = self.r.field_names.get(&did) {
 624                                 if field_names
 625                                     .iter()
 626                                     .any(|&field_name| ident.name == field_name.node)
 627                                 {
 628                                     return Some(AssocSuggestion::Field);
 629                                 }
 630                             }
 631                         }
 632                         _ => {}
 633                     }
 634                 }
 635             }
 636         }
 637
 638         for assoc_type_ident in &self.diagnostic_metadata.current_trait_assoc_types {
 639             if *assoc_type_ident == ident {
 640                 return Some(AssocSuggestion::AssocItem);
 641             }
 642         }
 643
 644         // Look for associated items in the current trait.
 645         if let Some((module, _)) = self.current_trait_ref {
 646             if let Ok(binding) = self.r.resolve_ident_in_module(
 647                 ModuleOrUniformRoot::Module(module),
 648                 ident,
 649                 ns,
 650                 &self.parent_scope,
 651                 false,
 652                 module.span,
 653             ) {
 654                 let res = binding.res();
 655                 if filter_fn(res) {
 656                     return Some(if self.r.has_self.contains(&res.def_id()) {
 657                         AssocSuggestion::MethodWithSelf
 658                     } else {
 659                         AssocSuggestion::AssocItem
 660                     });
 661                 }
 662             }
 663         }
 664
 665         None
 666     }
 667
 668     fn lookup_typo_candidate(
 669         &mut self,
 670         path: &[Segment],
 671         ns: Namespace,
 672         filter_fn: &impl Fn(Res) -> bool,
 673         span: Span,
 674     ) -> Option<TypoSuggestion> {
 675         let mut names = Vec::new();
 676         if path.len() == 1 {
 677             // Search in lexical scope.
 678             // Walk backwards up the ribs in scope and collect candidates.
 679             for rib in self.ribs[ns].iter().rev() {
 680                 // Locals and type parameters
 681                 for (ident, &res) in &rib.bindings {
 682                     if filter_fn(res) {
 683                         names.push(TypoSuggestion::from_res(ident.name, res));
 684                     }
 685                 }
 686                 // Items in scope
 687                 if let RibKind::ModuleRibKind(module) = rib.kind {
 688                     // Items from this module
 689                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 690
 691                     if let ModuleKind::Block(..) = module.kind {
 692                         // We can see through blocks
 693                     } else {
 694                         // Items from the prelude
 695                         if !module.no_implicit_prelude {
 696                             let extern_prelude = self.r.extern_prelude.clone();
 697                             names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
 698                                 self.r
 699                                     .crate_loader
 700                                     .maybe_process_path_extern(ident.name, ident.span)
 701                                     .and_then(|crate_id| {
 702                                         let crate_mod = Res::Def(
 703                                             DefKind::Mod,
 704                                             DefId { krate: crate_id, index: CRATE_DEF_INDEX },
 705                                         );
 706
 707                                         if filter_fn(crate_mod) {
 708                                             Some(TypoSuggestion::from_res(ident.name, crate_mod))
 709                                         } else {
 710                                             None
 711                                         }
 712                                     })
 713                             }));
 714
 715                             if let Some(prelude) = self.r.prelude {
 716                                 self.r.add_module_candidates(prelude, &mut names, &filter_fn);
 717                             }
 718                         }
 719                         break;
 720                     }
 721                 }
 722             }
 723             // Add primitive types to the mix
 724             if filter_fn(Res::PrimTy(PrimTy::Bool)) {
 725                 names.extend(
 726                     self.r.primitive_type_table.primitive_types.iter().map(|(name, prim_ty)| {
 727                         TypoSuggestion::from_res(*name, Res::PrimTy(*prim_ty))
 728                     }),
 729                 )
 730             }
 731         } else {
 732             // Search in module.
 733             let mod_path = &path[..path.len() - 1];
 734             if let PathResult::Module(module) =
 735                 self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No)
 736             {
 737                 if let ModuleOrUniformRoot::Module(module) = module {
 738                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 739                 }
 740             }
 741         }
 742
 743         let name = path[path.len() - 1].ident.name;
 744         // Make sure error reporting is deterministic.
 745         names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 746
 747         match find_best_match_for_name(
 748             names.iter().map(|suggestion| &suggestion.candidate),
 749             &name.as_str(),
 750             None,
 751         ) {
 752             Some(found) if found != name => {
 753                 names.into_iter().find(|suggestion| suggestion.candidate == found)
 754             }
 755             _ => None,
 756         }
 757     }
 758
 759     /// Only used in a specific case of type ascription suggestions
 760     fn get_colon_suggestion_span(&self, start: Span) -> Span {
 761         let sm = self.r.session.source_map();
 762         start.to(sm.next_point(start))
 763     }
 764
 765     fn type_ascription_suggestion(&self, err: &mut DiagnosticBuilder<'_>, base_span: Span) {
 766         let sm = self.r.session.source_map();
 767         let base_snippet = sm.span_to_snippet(base_span);
 768         if let Some(sp) = self.diagnostic_metadata.current_type_ascription.last() {
 769             let mut sp = *sp;
 770             loop {
 771                 // Try to find the `:`; bail on first non-':' / non-whitespace.
 772                 sp = sm.next_point(sp);
 773                 if let Ok(snippet) = sm.span_to_snippet(sp.to(sm.next_point(sp))) {
 774                     let line_sp = sm.lookup_char_pos(sp.hi()).line;
 775                     let line_base_sp = sm.lookup_char_pos(base_span.lo()).line;
 776                     if snippet == ":" {
 777                         let mut show_label = true;
 778                         if line_sp != line_base_sp {
 779                             err.span_suggestion_short(
 780                                 sp,
 781                                 "did you mean to use `;` here instead?",
 782                                 ";".to_string(),
 783                                 Applicability::MaybeIncorrect,
 784                             );
 785                         } else {
 786                             let colon_sp = self.get_colon_suggestion_span(sp);
 787                             let after_colon_sp =
 788                                 self.get_colon_suggestion_span(colon_sp.shrink_to_hi());
 789                             if !sm
 790                                 .span_to_snippet(after_colon_sp)
 791                                 .map(|s| s == " ")
 792                                 .unwrap_or(false)
 793                             {
 794                                 err.span_suggestion(
 795                                     colon_sp,
 796                                     "maybe you meant to write a path separator here",
 797                                     "::".to_string(),
 798                                     Applicability::MaybeIncorrect,
 799                                 );
 800                                 show_label = false;
 801                             }
 802                             if let Ok(base_snippet) = base_snippet {
 803                                 let mut sp = after_colon_sp;
 804                                 for _ in 0..100 {
 805                                     // Try to find an assignment
 806                                     sp = sm.next_point(sp);
 807                                     let snippet = sm.span_to_snippet(sp.to(sm.next_point(sp)));
 808                                     match snippet {
 809                                         Ok(ref x) if x.as_str() == "=" => {
 810                                             err.span_suggestion(
 811                                                 base_span,
 812                                                 "maybe you meant to write an assignment here",
 813                                                 format!("let {}", base_snippet),
 814                                                 Applicability::MaybeIncorrect,
 815                                             );
 816                                             show_label = false;
 817                                             break;
 818                                         }
 819                                         Ok(ref x) if x.as_str() == "\n" => break,
 820                                         Err(_) => break,
 821                                         Ok(_) => {}
 822                                     }
 823                                 }
 824                             }
 825                         }
 826                         if show_label {
 827                             err.span_label(
 828                                 base_span,
 829                                 "expecting a type here because of type ascription",
 830                             );
 831                         }
 832                         break;
 833                     } else if !snippet.trim().is_empty() {
 834                         debug!("tried to find type ascription `:` token, couldn't find it");
 835                         break;
 836                     }
 837                 } else {
 838                     break;
 839                 }
 840             }
 841         }
 842     }
 843
 844     fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
 845         let mut result = None;
 846         let mut seen_modules = FxHashSet::default();
 847         let mut worklist = vec![(self.r.graph_root, Vec::new())];
 848
 849         while let Some((in_module, path_segments)) = worklist.pop() {
 850             // abort if the module is already found
 851             if result.is_some() {
 852                 break;
 853             }
 854
 855             in_module.for_each_child(self.r, |_, ident, _, name_binding| {
 856                 // abort if the module is already found or if name_binding is private external
 857                 if result.is_some() || !name_binding.vis.is_visible_locally() {
 858                     return;
 859                 }
 860                 if let Some(module) = name_binding.module() {
 861                     // form the path
 862                     let mut path_segments = path_segments.clone();
 863                     path_segments.push(ast::PathSegment::from_ident(ident));
 864                     let module_def_id = module.def_id().unwrap();
 865                     if module_def_id == def_id {
 866                         let path = Path { span: name_binding.span, segments: path_segments };
 867                         result = Some((module, ImportSuggestion { did: Some(def_id), path }));
 868                     } else {
 869                         // add the module to the lookup
 870                         if seen_modules.insert(module_def_id) {
 871                             worklist.push((module, path_segments));
 872                         }
 873                     }
 874                 }
 875             });
 876         }
 877
 878         result
 879     }
 880
 881     fn collect_enum_variants(&mut self, def_id: DefId) -> Option<Vec<Path>> {
 882         self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
 883             let mut variants = Vec::new();
 884             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
 885                 if let Res::Def(DefKind::Variant, _) = name_binding.res() {
 886                     let mut segms = enum_import_suggestion.path.segments.clone();
 887                     segms.push(ast::PathSegment::from_ident(ident));
 888                     variants.push(Path { span: name_binding.span, segments: segms });
 889                 }
 890             });
 891             variants
 892         })
 893     }
 894
 895     crate fn report_missing_type_error(
 896         &self,
 897         path: &[Segment],
 898     ) -> Option<(Span, &'static str, String, Applicability)> {
 899         let ident = match path {
 900             [segment] => segment.ident,
 901             _ => return None,
 902         };
 903         match (
 904             self.diagnostic_metadata.current_item,
 905             self.diagnostic_metadata.currently_processing_generics,
 906         ) {
 907             (Some(Item { kind: ItemKind::Fn(..), ident, .. }), true) if ident.name == sym::main => {
 908                 // Ignore `fn main()` as we don't want to suggest `fn main<T>()`
 909             }
 910             (Some(Item { kind, .. }), true) => {
 911                 // Likely missing type parameter.
 912                 if let Some(generics) = kind.generics() {
 913                     let msg = "you might be missing a type parameter";
 914                     let (span, sugg) = if let [.., param] = &generics.params[..] {
 915                         let span = if let [.., bound] = &param.bounds[..] {
 916                             bound.span()
 917                         } else {
 918                             param.ident.span
 919                         };
 920                         (span, format!(", {}", ident))
 921                     } else {
 922                         (generics.span, format!("<{}>", ident))
 923                     };
 924                     // Do not suggest if this is coming from macro expansion.
 925                     if !span.from_expansion() {
 926                         return Some((
 927                             span.shrink_to_hi(),
 928                             msg,
 929                             sugg,
 930                             Applicability::MaybeIncorrect,
 931                         ));
 932                     }
 933                 }
 934             }
 935             _ => {}
 936         }
 937         None
 938     }
 939 }
 940
 941 impl<'tcx> LifetimeContext<'_, 'tcx> {
 942     crate fn report_missing_lifetime_specifiers(
 943         &self,
 944         span: Span,
 945         count: usize,
 946     ) -> DiagnosticBuilder<'tcx> {
 947         struct_span_err!(
 948             self.tcx.sess,
 949             span,
 950             E0106,
 951             "missing lifetime specifier{}",
 952             pluralize!(count)
 953         )
 954     }
 955
 956     crate fn emit_undeclared_lifetime_error(&self, lifetime_ref: &hir::Lifetime) {
 957         let mut err = struct_span_err!(
 958             self.tcx.sess,
 959             lifetime_ref.span,
 960             E0261,
 961             "use of undeclared lifetime name `{}`",
 962             lifetime_ref
 963         );
 964         err.span_label(lifetime_ref.span, "undeclared lifetime");
 965         for missing in &self.missing_named_lifetime_spots {
 966             match missing {
 967                 MissingLifetimeSpot::Generics(generics) => {
 968                     let (span, sugg) = if let Some(param) =
 969                         generics.params.iter().find(|p| match p.kind {
 970                             hir::GenericParamKind::Type {
 971                                 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
 972                                 ..
 973                             } => false,
 974                             _ => true,
 975                         }) {
 976                         (param.span.shrink_to_lo(), format!("{}, ", lifetime_ref))
 977                     } else {
 978                         (generics.span, format!("<{}>", lifetime_ref))
 979                     };
 980                     err.span_suggestion(
 981                         span,
 982                         &format!("consider introducing lifetime `{}` here", lifetime_ref),
 983                         sugg,
 984                         Applicability::MaybeIncorrect,
 985                     );
 986                 }
 987                 MissingLifetimeSpot::HigherRanked { span, span_type } => {
 988                     err.span_suggestion(
 989                         *span,
 990                         &format!(
 991                             "consider making the {} lifetime-generic with a new `{}` lifetime",
 992                             span_type.descr(),
 993                             lifetime_ref
 994                         ),
 995                         span_type.suggestion(&lifetime_ref.to_string()),
 996                         Applicability::MaybeIncorrect,
 997                     );
 998                     err.note(
 999                         "for more information on higher-ranked polymorphism, visit \
1000                             https://doc.rust-lang.org/nomicon/hrtb.html",
1001                     );
1002                 }
1003             }
1004         }
1005         err.emit();
1006     }
1007
1008     crate fn is_trait_ref_fn_scope(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) -> bool {
1009         if let def::Res::Def(_, did) = trait_ref.trait_ref.path.res {
1010             if [
1011                 self.tcx.lang_items().fn_once_trait(),
1012                 self.tcx.lang_items().fn_trait(),
1013                 self.tcx.lang_items().fn_mut_trait(),
1014             ]
1015             .contains(&Some(did))
1016             {
1017                 let (span, span_type) = match &trait_ref.bound_generic_params {
1018                     [] => (trait_ref.span.shrink_to_lo(), ForLifetimeSpanType::BoundEmpty),
1019                     [.., bound] => (bound.span.shrink_to_hi(), ForLifetimeSpanType::BoundTail),
1020                 };
1021                 self.missing_named_lifetime_spots
1022                     .push(MissingLifetimeSpot::HigherRanked { span, span_type });
1023                 return true;
1024             }
1025         };
1026         false
1027     }
1028
1029     crate fn add_missing_lifetime_specifiers_label(
1030         &self,
1031         err: &mut DiagnosticBuilder<'_>,
1032         span: Span,
1033         count: usize,
1034         lifetime_names: &FxHashSet<ast::Ident>,
1035         params: &[ElisionFailureInfo],
1036     ) {
1037         if count > 1 {
1038             err.span_label(span, format!("expected {} lifetime parameters", count));
1039         } else {
1040             let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
1041             let suggest_existing = |err: &mut DiagnosticBuilder<'_>, sugg| {
1042                 err.span_suggestion(
1043                     span,
1044                     "consider using the named lifetime",
1045                     sugg,
1046                     Applicability::MaybeIncorrect,
1047                 );
1048             };
1049             let suggest_new = |err: &mut DiagnosticBuilder<'_>, sugg: &str| {
1050                 err.span_label(span, "expected named lifetime parameter");
1051
1052                 for missing in self.missing_named_lifetime_spots.iter().rev() {
1053                     let mut introduce_suggestion = vec![];
1054                     let msg;
1055                     let should_break;
1056                     introduce_suggestion.push(match missing {
1057                         MissingLifetimeSpot::Generics(generics) => {
1058                             msg = "consider introducing a named lifetime parameter".to_string();
1059                             should_break = true;
1060                             if let Some(param) = generics.params.iter().find(|p| match p.kind {
1061                                 hir::GenericParamKind::Type {
1062                                     synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1063                                     ..
1064                                 } => false,
1065                                 _ => true,
1066                             }) {
1067                                 (param.span.shrink_to_lo(), "'a, ".to_string())
1068                             } else {
1069                                 (generics.span, "<'a>".to_string())
1070                             }
1071                         }
1072                         MissingLifetimeSpot::HigherRanked { span, span_type } => {
1073                             msg = format!(
1074                                 "consider making the {} lifetime-generic with a new `'a` lifetime",
1075                                 span_type.descr(),
1076                             );
1077                             should_break = false;
1078                             err.note(
1079                                 "for more information on higher-ranked polymorphism, visit \
1080                              https://doc.rust-lang.org/nomicon/hrtb.html",
1081                             );
1082                             (*span, span_type.suggestion("'a"))
1083                         }
1084                     });
1085                     for param in params {
1086                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(param.span)
1087                         {
1088                             if snippet.starts_with('&') && !snippet.starts_with("&'") {
1089                                 introduce_suggestion
1090                                     .push((param.span, format!("&'a {}", &snippet[1..])));
1091                             } else if snippet.starts_with("&'_ ") {
1092                                 introduce_suggestion
1093                                     .push((param.span, format!("&'a {}", &snippet[4..])));
1094                             }
1095                         }
1096                     }
1097                     introduce_suggestion.push((span, sugg.to_string()));
1098                     err.multipart_suggestion(
1099                         &msg,
1100                         introduce_suggestion,
1101                         Applicability::MaybeIncorrect,
1102                     );
1103                     if should_break {
1104                         break;
1105                     }
1106                 }
1107             };
1108
1109             match (lifetime_names.len(), lifetime_names.iter().next(), snippet.as_deref()) {
1110                 (1, Some(name), Some("&")) => {
1111                     suggest_existing(err, format!("&{} ", name));
1112                 }
1113                 (1, Some(name), Some("'_")) => {
1114                     suggest_existing(err, name.to_string());
1115                 }
1116                 (1, Some(name), Some(snippet)) if !snippet.ends_with('>') => {
1117                     suggest_existing(err, format!("{}<{}>", snippet, name));
1118                 }
1119                 (0, _, Some("&")) => {
1120                     suggest_new(err, "&'a ");
1121                 }
1122                 (0, _, Some("'_")) => {
1123                     suggest_new(err, "'a");
1124                 }
1125                 (0, _, Some(snippet)) if !snippet.ends_with('>') => {
1126                     suggest_new(err, &format!("{}<'a>", snippet));
1127                 }
1128                 _ => {
1129                     err.span_label(span, "expected lifetime parameter");
1130                 }
1131             }
1132         }
1133     }
1134 }