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::session::config::nightly_options;
   9 use rustc_data_structures::fx::FxHashSet;
  10 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
  11 use rustc_hir as hir;
  12 use rustc_hir::def::Namespace::{self, *};
  13 use rustc_hir::def::{self, CtorKind, DefKind};
  14 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
  15 use rustc_hir::PrimTy;
  16 use rustc_span::hygiene::MacroKind;
  17 use rustc_span::symbol::{kw, sym};
  18 use rustc_span::Span;
  19 use syntax::ast::{self, Expr, ExprKind, Ident, Item, ItemKind, NodeId, Path, Ty, TyKind};
  20 use syntax::util::lev_distance::find_best_match_for_name;
  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(DefKind::Ctor(..), _)
 127                     | Res::Def(DefKind::Method, _)
 128                     | Res::Def(DefKind::Const, _)
 129                     | Res::Def(DefKind::AssocConst, _)
 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                 format!("`Self` is only available in impls, traits, and type definitions"),
 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 => format!(
 190                     "`self` value is a keyword and may not be bound to variables or shadowed",
 191                 ),
 192                 _ => format!(
 193                     "`self` value is a keyword only available in methods with a `self` parameter",
 194                 ),
 195             });
 196             if let Some(span) = &self.diagnostic_metadata.current_function {
 197                 err.span_label(*span, "this function doesn't have a `self` parameter");
 198             }
 199             return (err, Vec::new());
 200         }
 201
 202         // Try to lookup name in more relaxed fashion for better error reporting.
 203         let ident = path.last().unwrap().ident;
 204         let candidates = self
 205             .r
 206             .lookup_import_candidates(ident, ns, is_expected)
 207             .drain(..)
 208             .filter(|ImportSuggestion { did, .. }| {
 209                 match (did, res.and_then(|res| res.opt_def_id())) {
 210                     (Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
 211                     _ => true,
 212                 }
 213             })
 214             .collect::<Vec<_>>();
 215         let crate_def_id = DefId::local(CRATE_DEF_INDEX);
 216         if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
 217             let enum_candidates = self.r.lookup_import_candidates(ident, ns, is_enum_variant);
 218             let mut enum_candidates = enum_candidates
 219                 .iter()
 220                 .map(|suggestion| import_candidate_to_enum_paths(&suggestion))
 221                 .collect::<Vec<_>>();
 222             enum_candidates.sort();
 223
 224             if !enum_candidates.is_empty() {
 225                 // Contextualize for E0412 "cannot find type", but don't belabor the point
 226                 // (that it's a variant) for E0573 "expected type, found variant".
 227                 let preamble = if res.is_none() {
 228                     let others = match enum_candidates.len() {
 229                         1 => String::new(),
 230                         2 => " and 1 other".to_owned(),
 231                         n => format!(" and {} others", n),
 232                     };
 233                     format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
 234                 } else {
 235                     String::new()
 236                 };
 237                 let msg = format!("{}try using the variant's enum", preamble);
 238
 239                 err.span_suggestions(
 240                     span,
 241                     &msg,
 242                     enum_candidates
 243                         .into_iter()
 244                         .map(|(_variant_path, enum_ty_path)| enum_ty_path)
 245                         // Variants re-exported in prelude doesn't mean `prelude::v1` is the
 246                         // type name!
 247                         // FIXME: is there a more principled way to do this that
 248                         // would work for other re-exports?
 249                         .filter(|enum_ty_path| enum_ty_path != "std::prelude::v1")
 250                         // Also write `Option` rather than `std::prelude::v1::Option`.
 251                         .map(|enum_ty_path| {
 252                             // FIXME #56861: DRY-er prelude filtering.
 253                             enum_ty_path.trim_start_matches("std::prelude::v1::").to_owned()
 254                         }),
 255                     Applicability::MachineApplicable,
 256                 );
 257             }
 258         }
 259         if path.len() == 1 && self.self_type_is_available(span) {
 260             if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) {
 261                 let self_is_available = self.self_value_is_available(path[0].ident.span, span);
 262                 match candidate {
 263                     AssocSuggestion::Field => {
 264                         if self_is_available {
 265                             err.span_suggestion(
 266                                 span,
 267                                 "you might have meant to use the available field",
 268                                 format!("self.{}", path_str),
 269                                 Applicability::MachineApplicable,
 270                             );
 271                         } else {
 272                             err.span_label(span, "a field by this name exists in `Self`");
 273                         }
 274                     }
 275                     AssocSuggestion::MethodWithSelf if self_is_available => {
 276                         err.span_suggestion(
 277                             span,
 278                             "try",
 279                             format!("self.{}", path_str),
 280                             Applicability::MachineApplicable,
 281                         );
 282                     }
 283                     AssocSuggestion::MethodWithSelf | AssocSuggestion::AssocItem => {
 284                         err.span_suggestion(
 285                             span,
 286                             "try",
 287                             format!("Self::{}", path_str),
 288                             Applicability::MachineApplicable,
 289                         );
 290                     }
 291                 }
 292                 return (err, candidates);
 293             }
 294
 295             // If the first argument in call is `self` suggest calling a method.
 296             if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
 297                 let mut args_snippet = String::new();
 298                 if let Some(args_span) = args_span {
 299                     if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) {
 300                         args_snippet = snippet;
 301                     }
 302                 }
 303
 304                 err.span_suggestion(
 305                     call_span,
 306                     &format!("try calling `{}` as a method", ident),
 307                     format!("self.{}({})", path_str, args_snippet),
 308                     Applicability::MachineApplicable,
 309                 );
 310                 return (err, candidates);
 311             }
 312         }
 313
 314         // Try Levenshtein algorithm.
 315         let typo_sugg = self.lookup_typo_candidate(path, ns, is_expected, span);
 316         let levenshtein_worked = self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
 317
 318         // Try context-dependent help if relaxed lookup didn't work.
 319         if let Some(res) = res {
 320             if self.smart_resolve_context_dependent_help(
 321                 &mut err,
 322                 span,
 323                 source,
 324                 res,
 325                 &path_str,
 326                 &fallback_label,
 327             ) {
 328                 return (err, candidates);
 329             }
 330         }
 331
 332         // Fallback label.
 333         if !levenshtein_worked {
 334             err.span_label(base_span, fallback_label);
 335             self.type_ascription_suggestion(&mut err, base_span);
 336             match self.diagnostic_metadata.current_let_binding {
 337                 Some((pat_sp, Some(ty_sp), None)) if ty_sp.contains(base_span) && could_be_expr => {
 338                     err.span_suggestion_short(
 339                         pat_sp.between(ty_sp),
 340                         "use `=` if you meant to assign",
 341                         " = ".to_string(),
 342                         Applicability::MaybeIncorrect,
 343                     );
 344                 }
 345                 _ => {}
 346             }
 347         }
 348         (err, candidates)
 349     }
 350
 351     /// Check if the source is call expression and the first argument is `self`. If true,
 352     /// return the span of whole call and the span for all arguments expect the first one (`self`).
 353     fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
 354         let mut has_self_arg = None;
 355         if let PathSource::Expr(parent) = source {
 356             match &parent?.kind {
 357                 ExprKind::Call(_, args) if args.len() > 0 => {
 358                     let mut expr_kind = &args[0].kind;
 359                     loop {
 360                         match expr_kind {
 361                             ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
 362                                 if arg_name.segments[0].ident.name == kw::SelfLower {
 363                                     let call_span = parent.unwrap().span;
 364                                     let tail_args_span = if args.len() > 1 {
 365                                         Some(Span::new(
 366                                             args[1].span.lo(),
 367                                             args.last().unwrap().span.hi(),
 368                                             call_span.ctxt(),
 369                                         ))
 370                                     } else {
 371                                         None
 372                                     };
 373                                     has_self_arg = Some((call_span, tail_args_span));
 374                                 }
 375                                 break;
 376                             }
 377                             ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
 378                             _ => break,
 379                         }
 380                     }
 381                 }
 382                 _ => (),
 383             }
 384         };
 385         return has_self_arg;
 386     }
 387
 388     fn followed_by_brace(&self, span: Span) -> (bool, Option<(Span, String)>) {
 389         // HACK(estebank): find a better way to figure out that this was a
 390         // parser issue where a struct literal is being used on an expression
 391         // where a brace being opened means a block is being started. Look
 392         // ahead for the next text to see if `span` is followed by a `{`.
 393         let sm = self.r.session.source_map();
 394         let mut sp = span;
 395         loop {
 396             sp = sm.next_point(sp);
 397             match sm.span_to_snippet(sp) {
 398                 Ok(ref snippet) => {
 399                     if snippet.chars().any(|c| !c.is_whitespace()) {
 400                         break;
 401                     }
 402                 }
 403                 _ => break,
 404             }
 405         }
 406         let followed_by_brace = match sm.span_to_snippet(sp) {
 407             Ok(ref snippet) if snippet == "{" => true,
 408             _ => false,
 409         };
 410         // In case this could be a struct literal that needs to be surrounded
 411         // by parenthesis, find the appropriate span.
 412         let mut i = 0;
 413         let mut closing_brace = None;
 414         loop {
 415             sp = sm.next_point(sp);
 416             match sm.span_to_snippet(sp) {
 417                 Ok(ref snippet) => {
 418                     if snippet == "}" {
 419                         let sp = span.to(sp);
 420                         if let Ok(snippet) = sm.span_to_snippet(sp) {
 421                             closing_brace = Some((sp, snippet));
 422                         }
 423                         break;
 424                     }
 425                 }
 426                 _ => break,
 427             }
 428             i += 1;
 429             // The bigger the span, the more likely we're incorrect --
 430             // bound it to 100 chars long.
 431             if i > 100 {
 432                 break;
 433             }
 434         }
 435         return (followed_by_brace, closing_brace);
 436     }
 437
 438     /// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
 439     /// function.
 440     /// Returns `true` if able to provide context-dependent help.
 441     fn smart_resolve_context_dependent_help(
 442         &mut self,
 443         err: &mut DiagnosticBuilder<'a>,
 444         span: Span,
 445         source: PathSource<'_>,
 446         res: Res,
 447         path_str: &str,
 448         fallback_label: &str,
 449     ) -> bool {
 450         let ns = source.namespace();
 451         let is_expected = &|res| source.is_expected(res);
 452
 453         let path_sep = |err: &mut DiagnosticBuilder<'_>, expr: &Expr| match expr.kind {
 454             ExprKind::Field(_, ident) => {
 455                 err.span_suggestion(
 456                     expr.span,
 457                     "use the path separator to refer to an item",
 458                     format!("{}::{}", path_str, ident),
 459                     Applicability::MaybeIncorrect,
 460                 );
 461                 true
 462             }
 463             ExprKind::MethodCall(ref segment, ..) => {
 464                 let span = expr.span.with_hi(segment.ident.span.hi());
 465                 err.span_suggestion(
 466                     span,
 467                     "use the path separator to refer to an item",
 468                     format!("{}::{}", path_str, segment.ident),
 469                     Applicability::MaybeIncorrect,
 470                 );
 471                 true
 472             }
 473             _ => false,
 474         };
 475
 476         let mut bad_struct_syntax_suggestion = |def_id: DefId| {
 477             let (followed_by_brace, closing_brace) = self.followed_by_brace(span);
 478             let mut suggested = false;
 479             match source {
 480                 PathSource::Expr(Some(parent)) => {
 481                     suggested = path_sep(err, &parent);
 482                 }
 483                 PathSource::Expr(None) if followed_by_brace == true => {
 484                     if let Some((sp, snippet)) = closing_brace {
 485                         err.span_suggestion(
 486                             sp,
 487                             "surround the struct literal with parenthesis",
 488                             format!("({})", snippet),
 489                             Applicability::MaybeIncorrect,
 490                         );
 491                     } else {
 492                         err.span_label(
 493                             span, // Note the parenthesis surrounding the suggestion below
 494                             format!("did you mean `({} {{ /* fields */ }})`?", path_str),
 495                         );
 496                     }
 497                     suggested = true;
 498                 }
 499                 _ => {}
 500             }
 501             if !suggested {
 502                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 503                     err.span_label(span, &format!("`{}` defined here", path_str));
 504                 }
 505                 err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?", path_str));
 506             }
 507         };
 508
 509         match (res, source) {
 510             (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
 511                 err.span_suggestion(
 512                     span,
 513                     "use `!` to invoke the macro",
 514                     format!("{}!", path_str),
 515                     Applicability::MaybeIncorrect,
 516                 );
 517                 if path_str == "try" && span.rust_2015() {
 518                     err.note("if you want the `try` keyword, you need to be in the 2018 edition");
 519                 }
 520             }
 521             (Res::Def(DefKind::TyAlias, _), PathSource::Trait(_)) => {
 522                 err.span_label(span, "type aliases cannot be used as traits");
 523                 if nightly_options::is_nightly_build() {
 524                     err.note("did you mean to use a trait alias?");
 525                 }
 526             }
 527             (Res::Def(DefKind::Mod, _), PathSource::Expr(Some(parent))) => {
 528                 if !path_sep(err, &parent) {
 529                     return false;
 530                 }
 531             }
 532             (Res::Def(DefKind::Enum, def_id), PathSource::TupleStruct)
 533             | (Res::Def(DefKind::Enum, def_id), PathSource::Expr(..)) => {
 534                 if let Some(variants) = self.collect_enum_variants(def_id) {
 535                     if !variants.is_empty() {
 536                         let msg = if variants.len() == 1 {
 537                             "try using the enum's variant"
 538                         } else {
 539                             "try using one of the enum's variants"
 540                         };
 541
 542                         err.span_suggestions(
 543                             span,
 544                             msg,
 545                             variants.iter().map(path_names_to_string),
 546                             Applicability::MaybeIncorrect,
 547                         );
 548                     }
 549                 } else {
 550                     err.note("did you mean to use one of the enum's variants?");
 551                 }
 552             }
 553             (Res::Def(DefKind::Struct, def_id), _) if ns == ValueNS => {
 554                 if let Some((ctor_def, ctor_vis)) = self.r.struct_constructors.get(&def_id).cloned()
 555                 {
 556                     let accessible_ctor =
 557                         self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
 558                     if is_expected(ctor_def) && !accessible_ctor {
 559                         err.span_label(
 560                             span,
 561                             format!("constructor is not visible here due to private fields"),
 562                         );
 563                     }
 564                 } else {
 565                     bad_struct_syntax_suggestion(def_id);
 566                 }
 567             }
 568             (Res::Def(DefKind::Union, def_id), _)
 569             | (Res::Def(DefKind::Variant, def_id), _)
 570             | (Res::Def(DefKind::Ctor(_, CtorKind::Fictive), def_id), _)
 571                 if ns == ValueNS =>
 572             {
 573                 bad_struct_syntax_suggestion(def_id);
 574             }
 575             (Res::Def(DefKind::Ctor(_, CtorKind::Fn), def_id), _) if ns == ValueNS => {
 576                 if let Some(span) = self.r.definitions.opt_span(def_id) {
 577                     err.span_label(span, &format!("`{}` defined here", path_str));
 578                 }
 579                 err.span_label(span, format!("did you mean `{}( /* fields */ )`?", path_str));
 580             }
 581             (Res::SelfTy(..), _) if ns == ValueNS => {
 582                 err.span_label(span, fallback_label);
 583                 err.note("can't use `Self` as a constructor, you must use the implemented struct");
 584             }
 585             (Res::Def(DefKind::TyAlias, _), _) | (Res::Def(DefKind::AssocTy, _), _)
 586                 if ns == ValueNS =>
 587             {
 588                 err.note("can't use a type alias as a constructor");
 589             }
 590             _ => return false,
 591         }
 592         true
 593     }
 594
 595     fn lookup_assoc_candidate<FilterFn>(
 596         &mut self,
 597         ident: Ident,
 598         ns: Namespace,
 599         filter_fn: FilterFn,
 600     ) -> Option<AssocSuggestion>
 601     where
 602         FilterFn: Fn(Res) -> bool,
 603     {
 604         fn extract_node_id(t: &Ty) -> Option<NodeId> {
 605             match t.kind {
 606                 TyKind::Path(None, _) => Some(t.id),
 607                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
 608                 // This doesn't handle the remaining `Ty` variants as they are not
 609                 // that commonly the self_type, it might be interesting to provide
 610                 // support for those in future.
 611                 _ => None,
 612             }
 613         }
 614
 615         // Fields are generally expected in the same contexts as locals.
 616         if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
 617             if let Some(node_id) =
 618                 self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id)
 619             {
 620                 // Look for a field with the same name in the current self_type.
 621                 if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
 622                     match resolution.base_res() {
 623                         Res::Def(DefKind::Struct, did) | Res::Def(DefKind::Union, did)
 624                             if resolution.unresolved_segments() == 0 =>
 625                         {
 626                             if let Some(field_names) = self.r.field_names.get(&did) {
 627                                 if field_names
 628                                     .iter()
 629                                     .any(|&field_name| ident.name == field_name.node)
 630                                 {
 631                                     return Some(AssocSuggestion::Field);
 632                                 }
 633                             }
 634                         }
 635                         _ => {}
 636                     }
 637                 }
 638             }
 639         }
 640
 641         for assoc_type_ident in &self.diagnostic_metadata.current_trait_assoc_types {
 642             if *assoc_type_ident == ident {
 643                 return Some(AssocSuggestion::AssocItem);
 644             }
 645         }
 646
 647         // Look for associated items in the current trait.
 648         if let Some((module, _)) = self.current_trait_ref {
 649             if let Ok(binding) = self.r.resolve_ident_in_module(
 650                 ModuleOrUniformRoot::Module(module),
 651                 ident,
 652                 ns,
 653                 &self.parent_scope,
 654                 false,
 655                 module.span,
 656             ) {
 657                 let res = binding.res();
 658                 if filter_fn(res) {
 659                     return Some(if self.r.has_self.contains(&res.def_id()) {
 660                         AssocSuggestion::MethodWithSelf
 661                     } else {
 662                         AssocSuggestion::AssocItem
 663                     });
 664                 }
 665             }
 666         }
 667
 668         None
 669     }
 670
 671     fn lookup_typo_candidate(
 672         &mut self,
 673         path: &[Segment],
 674         ns: Namespace,
 675         filter_fn: &impl Fn(Res) -> bool,
 676         span: Span,
 677     ) -> Option<TypoSuggestion> {
 678         let mut names = Vec::new();
 679         if path.len() == 1 {
 680             // Search in lexical scope.
 681             // Walk backwards up the ribs in scope and collect candidates.
 682             for rib in self.ribs[ns].iter().rev() {
 683                 // Locals and type parameters
 684                 for (ident, &res) in &rib.bindings {
 685                     if filter_fn(res) {
 686                         names.push(TypoSuggestion::from_res(ident.name, res));
 687                     }
 688                 }
 689                 // Items in scope
 690                 if let RibKind::ModuleRibKind(module) = rib.kind {
 691                     // Items from this module
 692                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 693
 694                     if let ModuleKind::Block(..) = module.kind {
 695                         // We can see through blocks
 696                     } else {
 697                         // Items from the prelude
 698                         if !module.no_implicit_prelude {
 699                             let extern_prelude = self.r.extern_prelude.clone();
 700                             names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
 701                                 self.r
 702                                     .crate_loader
 703                                     .maybe_process_path_extern(ident.name, ident.span)
 704                                     .and_then(|crate_id| {
 705                                         let crate_mod = Res::Def(
 706                                             DefKind::Mod,
 707                                             DefId { krate: crate_id, index: CRATE_DEF_INDEX },
 708                                         );
 709
 710                                         if filter_fn(crate_mod) {
 711                                             Some(TypoSuggestion::from_res(ident.name, crate_mod))
 712                                         } else {
 713                                             None
 714                                         }
 715                                     })
 716                             }));
 717
 718                             if let Some(prelude) = self.r.prelude {
 719                                 self.r.add_module_candidates(prelude, &mut names, &filter_fn);
 720                             }
 721                         }
 722                         break;
 723                     }
 724                 }
 725             }
 726             // Add primitive types to the mix
 727             if filter_fn(Res::PrimTy(PrimTy::Bool)) {
 728                 names.extend(
 729                     self.r.primitive_type_table.primitive_types.iter().map(|(name, prim_ty)| {
 730                         TypoSuggestion::from_res(*name, Res::PrimTy(*prim_ty))
 731                     }),
 732                 )
 733             }
 734         } else {
 735             // Search in module.
 736             let mod_path = &path[..path.len() - 1];
 737             if let PathResult::Module(module) =
 738                 self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No)
 739             {
 740                 if let ModuleOrUniformRoot::Module(module) = module {
 741                     self.r.add_module_candidates(module, &mut names, &filter_fn);
 742                 }
 743             }
 744         }
 745
 746         let name = path[path.len() - 1].ident.name;
 747         // Make sure error reporting is deterministic.
 748         names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
 749
 750         match find_best_match_for_name(
 751             names.iter().map(|suggestion| &suggestion.candidate),
 752             &name.as_str(),
 753             None,
 754         ) {
 755             Some(found) if found != name => {
 756                 names.into_iter().find(|suggestion| suggestion.candidate == found)
 757             }
 758             _ => None,
 759         }
 760     }
 761
 762     /// Only used in a specific case of type ascription suggestions
 763     fn get_colon_suggestion_span(&self, start: Span) -> Span {
 764         let sm = self.r.session.source_map();
 765         start.to(sm.next_point(start))
 766     }
 767
 768     fn type_ascription_suggestion(&self, err: &mut DiagnosticBuilder<'_>, base_span: Span) {
 769         let sm = self.r.session.source_map();
 770         let base_snippet = sm.span_to_snippet(base_span);
 771         if let Some(sp) = self.diagnostic_metadata.current_type_ascription.last() {
 772             let mut sp = *sp;
 773             loop {
 774                 // Try to find the `:`; bail on first non-':' / non-whitespace.
 775                 sp = sm.next_point(sp);
 776                 if let Ok(snippet) = sm.span_to_snippet(sp.to(sm.next_point(sp))) {
 777                     let line_sp = sm.lookup_char_pos(sp.hi()).line;
 778                     let line_base_sp = sm.lookup_char_pos(base_span.lo()).line;
 779                     if snippet == ":" {
 780                         let mut show_label = true;
 781                         if line_sp != line_base_sp {
 782                             err.span_suggestion_short(
 783                                 sp,
 784                                 "did you mean to use `;` here instead?",
 785                                 ";".to_string(),
 786                                 Applicability::MaybeIncorrect,
 787                             );
 788                         } else {
 789                             let colon_sp = self.get_colon_suggestion_span(sp);
 790                             let after_colon_sp =
 791                                 self.get_colon_suggestion_span(colon_sp.shrink_to_hi());
 792                             if !sm
 793                                 .span_to_snippet(after_colon_sp)
 794                                 .map(|s| s == " ")
 795                                 .unwrap_or(false)
 796                             {
 797                                 err.span_suggestion(
 798                                     colon_sp,
 799                                     "maybe you meant to write a path separator here",
 800                                     "::".to_string(),
 801                                     Applicability::MaybeIncorrect,
 802                                 );
 803                                 show_label = false;
 804                             }
 805                             if let Ok(base_snippet) = base_snippet {
 806                                 let mut sp = after_colon_sp;
 807                                 for _ in 0..100 {
 808                                     // Try to find an assignment
 809                                     sp = sm.next_point(sp);
 810                                     let snippet = sm.span_to_snippet(sp.to(sm.next_point(sp)));
 811                                     match snippet {
 812                                         Ok(ref x) if x.as_str() == "=" => {
 813                                             err.span_suggestion(
 814                                                 base_span,
 815                                                 "maybe you meant to write an assignment here",
 816                                                 format!("let {}", base_snippet),
 817                                                 Applicability::MaybeIncorrect,
 818                                             );
 819                                             show_label = false;
 820                                             break;
 821                                         }
 822                                         Ok(ref x) if x.as_str() == "\n" => break,
 823                                         Err(_) => break,
 824                                         Ok(_) => {}
 825                                     }
 826                                 }
 827                             }
 828                         }
 829                         if show_label {
 830                             err.span_label(
 831                                 base_span,
 832                                 "expecting a type here because of type ascription",
 833                             );
 834                         }
 835                         break;
 836                     } else if !snippet.trim().is_empty() {
 837                         debug!("tried to find type ascription `:` token, couldn't find it");
 838                         break;
 839                     }
 840                 } else {
 841                     break;
 842                 }
 843             }
 844         }
 845     }
 846
 847     fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
 848         let mut result = None;
 849         let mut seen_modules = FxHashSet::default();
 850         let mut worklist = vec![(self.r.graph_root, Vec::new())];
 851
 852         while let Some((in_module, path_segments)) = worklist.pop() {
 853             // abort if the module is already found
 854             if result.is_some() {
 855                 break;
 856             }
 857
 858             in_module.for_each_child(self.r, |_, ident, _, name_binding| {
 859                 // abort if the module is already found or if name_binding is private external
 860                 if result.is_some() || !name_binding.vis.is_visible_locally() {
 861                     return;
 862                 }
 863                 if let Some(module) = name_binding.module() {
 864                     // form the path
 865                     let mut path_segments = path_segments.clone();
 866                     path_segments.push(ast::PathSegment::from_ident(ident));
 867                     let module_def_id = module.def_id().unwrap();
 868                     if module_def_id == def_id {
 869                         let path = Path { span: name_binding.span, segments: path_segments };
 870                         result = Some((module, ImportSuggestion { did: Some(def_id), path }));
 871                     } else {
 872                         // add the module to the lookup
 873                         if seen_modules.insert(module_def_id) {
 874                             worklist.push((module, path_segments));
 875                         }
 876                     }
 877                 }
 878             });
 879         }
 880
 881         result
 882     }
 883
 884     fn collect_enum_variants(&mut self, def_id: DefId) -> Option<Vec<Path>> {
 885         self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
 886             let mut variants = Vec::new();
 887             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
 888                 if let Res::Def(DefKind::Variant, _) = name_binding.res() {
 889                     let mut segms = enum_import_suggestion.path.segments.clone();
 890                     segms.push(ast::PathSegment::from_ident(ident));
 891                     variants.push(Path { span: name_binding.span, segments: segms });
 892                 }
 893             });
 894             variants
 895         })
 896     }
 897
 898     crate fn report_missing_type_error(
 899         &self,
 900         path: &[Segment],
 901     ) -> Option<(Span, &'static str, String, Applicability)> {
 902         let ident = match path {
 903             [segment] => segment.ident,
 904             _ => return None,
 905         };
 906         match (
 907             self.diagnostic_metadata.current_item,
 908             self.diagnostic_metadata.currently_processing_generics,
 909         ) {
 910             (Some(Item { kind: ItemKind::Fn(..), ident, .. }), true) if ident.name == sym::main => {
 911                 // Ignore `fn main()` as we don't want to suggest `fn main<T>()`
 912             }
 913             (Some(Item { kind, .. }), true) => {
 914                 // Likely missing type parameter.
 915                 if let Some(generics) = kind.generics() {
 916                     let msg = "you might be missing a type parameter";
 917                     let (span, sugg) = if let [.., param] = &generics.params[..] {
 918                         let span = if let [.., bound] = &param.bounds[..] {
 919                             bound.span()
 920                         } else {
 921                             param.ident.span
 922                         };
 923                         (span, format!(", {}", ident))
 924                     } else {
 925                         (generics.span, format!("<{}>", ident))
 926                     };
 927                     // Do not suggest if this is coming from macro expansion.
 928                     if !span.from_expansion() {
 929                         return Some((
 930                             span.shrink_to_hi(),
 931                             msg,
 932                             sugg,
 933                             Applicability::MaybeIncorrect,
 934                         ));
 935                     }
 936                 }
 937             }
 938             _ => {}
 939         }
 940         None
 941     }
 942 }
 943
 944 impl<'tcx> LifetimeContext<'_, 'tcx> {
 945     crate fn report_missing_lifetime_specifiers(
 946         &self,
 947         span: Span,
 948         count: usize,
 949     ) -> DiagnosticBuilder<'tcx> {
 950         struct_span_err!(
 951             self.tcx.sess,
 952             span,
 953             E0106,
 954             "missing lifetime specifier{}",
 955             pluralize!(count)
 956         )
 957     }
 958
 959     crate fn emit_undeclared_lifetime_error(&self, lifetime_ref: &hir::Lifetime) {
 960         let mut err = struct_span_err!(
 961             self.tcx.sess,
 962             lifetime_ref.span,
 963             E0261,
 964             "use of undeclared lifetime name `{}`",
 965             lifetime_ref
 966         );
 967         err.span_label(lifetime_ref.span, "undeclared lifetime");
 968         for missing in &self.missing_named_lifetime_spots {
 969             match missing {
 970                 MissingLifetimeSpot::Generics(generics) => {
 971                     let (span, sugg) = if let Some(param) = generics
 972                         .params
 973                         .iter()
 974                         .filter(|p| match p.kind {
 975                             hir::GenericParamKind::Type {
 976                                 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
 977                                 ..
 978                             } => false,
 979                             _ => true,
 980                         })
 981                         .next()
 982                     {
 983                         (param.span.shrink_to_lo(), format!("{}, ", lifetime_ref))
 984                     } else {
 985                         (generics.span, format!("<{}>", lifetime_ref))
 986                     };
 987                     err.span_suggestion(
 988                         span,
 989                         &format!("consider introducing lifetime `{}` here", lifetime_ref),
 990                         sugg,
 991                         Applicability::MaybeIncorrect,
 992                     );
 993                 }
 994                 MissingLifetimeSpot::HigherRanked { span, span_type } => {
 995                     err.span_suggestion(
 996                         *span,
 997                         &format!(
 998                             "consider making the {} lifetime-generic with a new `{}` lifetime",
 999                             span_type.descr(),
1000                             lifetime_ref
1001                         ),
1002                         span_type.suggestion(&lifetime_ref.to_string()),
1003                         Applicability::MaybeIncorrect,
1004                     );
1005                     err.note(
1006                         "for more information on higher-ranked polymorphism, visit \
1007                             https://doc.rust-lang.org/nomicon/hrtb.html",
1008                     );
1009                 }
1010             }
1011         }
1012         err.emit();
1013     }
1014
1015     crate fn is_trait_ref_fn_scope(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) -> bool {
1016         if let def::Res::Def(_, did) = trait_ref.trait_ref.path.res {
1017             if [
1018                 self.tcx.lang_items().fn_once_trait(),
1019                 self.tcx.lang_items().fn_trait(),
1020                 self.tcx.lang_items().fn_mut_trait(),
1021             ]
1022             .contains(&Some(did))
1023             {
1024                 let (span, span_type) = match &trait_ref.bound_generic_params {
1025                     [] => (trait_ref.span.shrink_to_lo(), ForLifetimeSpanType::BoundEmpty),
1026                     [.., bound] => (bound.span.shrink_to_hi(), ForLifetimeSpanType::BoundTail),
1027                 };
1028                 self.missing_named_lifetime_spots
1029                     .push(MissingLifetimeSpot::HigherRanked { span, span_type });
1030                 return true;
1031             }
1032         };
1033         false
1034     }
1035
1036     crate fn add_missing_lifetime_specifiers_label(
1037         &self,
1038         err: &mut DiagnosticBuilder<'_>,
1039         span: Span,
1040         count: usize,
1041         lifetime_names: &FxHashSet<ast::Ident>,
1042         params: &[ElisionFailureInfo],
1043     ) {
1044         if count > 1 {
1045             err.span_label(span, format!("expected {} lifetime parameters", count));
1046         } else {
1047             let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
1048             let suggest_existing = |err: &mut DiagnosticBuilder<'_>, sugg| {
1049                 err.span_suggestion(
1050                     span,
1051                     "consider using the named lifetime",
1052                     sugg,
1053                     Applicability::MaybeIncorrect,
1054                 );
1055             };
1056             let suggest_new =
1057                 |err: &mut DiagnosticBuilder<'_>, sugg: &str| {
1058                     err.span_label(span, "expected named lifetime parameter");
1059
1060                     for missing in self.missing_named_lifetime_spots.iter().rev() {
1061                         let mut introduce_suggestion = vec![];
1062                         let msg;
1063                         let should_break;
1064                         introduce_suggestion.push(match missing {
1065                         MissingLifetimeSpot::Generics(generics) => {
1066                             msg = "consider introducing a named lifetime parameter".to_string();
1067                             should_break = true;
1068                             if let Some(param) = generics.params.iter().filter(|p| match p.kind {
1069                                 hir::GenericParamKind::Type {
1070                                     synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1071                                     ..
1072                                 } => false,
1073                                 _ => true,
1074                             }).next() {
1075                                 (param.span.shrink_to_lo(), "'a, ".to_string())
1076                             } else {
1077                                 (generics.span, "<'a>".to_string())
1078                             }
1079                         }
1080                         MissingLifetimeSpot::HigherRanked { span, span_type } => {
1081                             msg = format!(
1082                                 "consider making the {} lifetime-generic with a new `'a` lifetime",
1083                                 span_type.descr(),
1084                             );
1085                             should_break = false;
1086                             err.note(
1087                                 "for more information on higher-ranked polymorphism, visit \
1088                              https://doc.rust-lang.org/nomicon/hrtb.html",
1089                             );
1090                             (*span, span_type.suggestion("'a"))
1091                         }
1092                     });
1093                         for param in params {
1094                             if let Ok(snippet) =
1095                                 self.tcx.sess.source_map().span_to_snippet(param.span)
1096                             {
1097                                 if snippet.starts_with("&") && !snippet.starts_with("&'") {
1098                                     introduce_suggestion
1099                                         .push((param.span, format!("&'a {}", &snippet[1..])));
1100                                 } else if snippet.starts_with("&'_ ") {
1101                                     introduce_suggestion
1102                                         .push((param.span, format!("&'a {}", &snippet[4..])));
1103                                 }
1104                             }
1105                         }
1106                         introduce_suggestion.push((span, sugg.to_string()));
1107                         err.multipart_suggestion(
1108                             &msg,
1109                             introduce_suggestion,
1110                             Applicability::MaybeIncorrect,
1111                         );
1112                         if should_break {
1113                             break;
1114                         }
1115                     }
1116                 };
1117
1118             match (
1119                 lifetime_names.len(),
1120                 lifetime_names.iter().next(),
1121                 snippet.as_ref().map(|s| s.as_str()),
1122             ) {
1123                 (1, Some(name), Some("&")) => {
1124                     suggest_existing(err, format!("&{} ", name));
1125                 }
1126                 (1, Some(name), Some("'_")) => {
1127                     suggest_existing(err, name.to_string());
1128                 }
1129                 (1, Some(name), Some(snippet)) if !snippet.ends_with(">") => {
1130                     suggest_existing(err, format!("{}<{}>", snippet, name));
1131                 }
1132                 (0, _, Some("&")) => {
1133                     suggest_new(err, "&'a ");
1134                 }
1135                 (0, _, Some("'_")) => {
1136                     suggest_new(err, "'a");
1137                 }
1138                 (0, _, Some(snippet)) if !snippet.ends_with(">") => {
1139                     suggest_new(err, &format!("{}<'a>", snippet));
1140                 }
1141                 _ => {
1142                     err.span_label(span, "expected lifetime parameter");
1143                 }
1144             }
1145         }
1146     }
1147 }