compiler/rustc_resolve/src/late/diagnostics.rs

   1 use crate::diagnostics::{ImportSuggestion, LabelSuggestion, TypoSuggestion};
   2 use crate::late::lifetimes::{ElisionFailureInfo, LifetimeContext};
   3 use crate::late::{AliasPossibility, 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::visit::FnKind;
   9 use rustc_ast::{self as ast, Expr, ExprKind, Item, ItemKind, NodeId, Path, Ty, TyKind};
  10 use rustc_ast_pretty::pprust::path_segment_to_string;
  11 use rustc_data_structures::fx::FxHashSet;
  12 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
  13 use rustc_hir as hir;
  14 use rustc_hir::def::Namespace::{self, *};
  15 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
  16 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
  17 use rustc_hir::PrimTy;
  18 use rustc_session::parse::feature_err;
  19 use rustc_span::hygiene::MacroKind;
  20 use rustc_span::lev_distance::find_best_match_for_name;
  21 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  22 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
  23
  24 use tracing::debug;
  25
  26 type Res = def::Res<ast::NodeId>;
  27
  28 /// A field or associated item from self type suggested in case of resolution failure.
  29 enum AssocSuggestion {
  30     Field,
  31     MethodWithSelf,
  32     AssocFn,
  33     AssocType,
  34     AssocConst,
  35 }
  36
  37 impl AssocSuggestion {
  38     fn action(&self) -> &'static str {
  39         match self {
  40             AssocSuggestion::Field => "use the available field",
  41             AssocSuggestion::MethodWithSelf => "call the method with the fully-qualified path",
  42             AssocSuggestion::AssocFn => "call the associated function",
  43             AssocSuggestion::AssocConst => "use the associated `const`",
  44             AssocSuggestion::AssocType => "use the associated type",
  45         }
  46     }
  47 }
  48
  49 crate enum MissingLifetimeSpot<'tcx> {
  50     Generics(&'tcx hir::Generics<'tcx>),
  51     HigherRanked { span: Span, span_type: ForLifetimeSpanType },
  52     Static,
  53 }
  54
  55 crate enum ForLifetimeSpanType {
  56     BoundEmpty,
  57     BoundTail,
  58     TypeEmpty,
  59     TypeTail,
  60 }
  61
  62 impl ForLifetimeSpanType {
  63     crate fn descr(&self) -> &'static str {
  64         match self {
  65             Self::BoundEmpty | Self::BoundTail => "bound",
  66             Self::TypeEmpty | Self::TypeTail => "type",
  67         }
  68     }
  69
  70     crate fn suggestion(&self, sugg: &str) -> String {
  71         match self {
  72             Self::BoundEmpty | Self::TypeEmpty => format!("for<{}> ", sugg),
  73             Self::BoundTail | Self::TypeTail => format!(", {}", sugg),
  74         }
  75     }
  76 }
  77
  78 impl<'tcx> Into<MissingLifetimeSpot<'tcx>> for &'tcx hir::Generics<'tcx> {
  79     fn into(self) -> MissingLifetimeSpot<'tcx> {
  80         MissingLifetimeSpot::Generics(self)
  81     }
  82 }
  83
  84 fn is_self_type(path: &[Segment], namespace: Namespace) -> bool {
  85     namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper
  86 }
  87
  88 fn is_self_value(path: &[Segment], namespace: Namespace) -> bool {
  89     namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower
  90 }
  91
  92 /// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant.
  93 fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) {
  94     let variant_path = &suggestion.path;
  95     let variant_path_string = path_names_to_string(variant_path);
  96
  97     let path_len = suggestion.path.segments.len();
  98     let enum_path = ast::Path {
  99         span: suggestion.path.span,
 100         segments: suggestion.path.segments[0..path_len - 1].to_vec(),
 101         tokens: None,
 102     };
 103     let enum_path_string = path_names_to_string(&enum_path);
 104
 105     (variant_path_string, enum_path_string)
 106 }
 107
 108 impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
 109     fn def_span(&self, def_id: DefId) -> Option<Span> {
 110         match def_id.krate {
 111             LOCAL_CRATE => self.r.opt_span(def_id),
 112             _ => Some(
 113                 self.r
 114                     .session
 115                     .source_map()
 116                     .guess_head_span(self.r.cstore().get_span_untracked(def_id, self.r.session)),
 117             ),
 118         }
 119     }
 120
 121     /// Handles error reporting for `smart_resolve_path_fragment` function.
 122     /// Creates base error and amends it with one short label and possibly some longer helps/notes.
 123     pub(crate) fn smart_resolve_report_errors(
 124         &mut self,
 125         path: &[Segment],
 126         span: Span,
 127         source: PathSource<'_>,
 128         res: Option<Res>,
 129     ) -> (DiagnosticBuilder<'a>, Vec<ImportSuggestion>) {
 130         let ident_span = path.last().map_or(span, |ident| ident.ident.span);
 131         let ns = source.namespace();
 132         let is_expected = &|res| source.is_expected(res);
 133         let is_enum_variant = &|res| matches!(res, Res::Def(DefKind::Variant, _));
 134
 135         // Make the base error.
 136         let expected = source.descr_expected();
 137         let path_str = Segment::names_to_string(path);
 138         let item_str = path.last().unwrap().ident;
 139         let (base_msg, fallback_label, base_span, could_be_expr) = if let Some(res) = res {
 140             (
 141                 format!("expected {}, found {} `{}`", expected, res.descr(), path_str),
 142                 format!("not a {}", expected),
 143                 span,
 144                 match res {
 145                     Res::Def(DefKind::Fn, _) => {
 146                         // Verify whether this is a fn call or an Fn used as a type.
 147                         self.r
 148                             .session
 149                             .source_map()
 150                             .span_to_snippet(span)
 151                             .map(|snippet| snippet.ends_with(')'))
 152                             .unwrap_or(false)
 153                     }
 154                     Res::Def(
 155                         DefKind::Ctor(..) | DefKind::AssocFn | DefKind::Const | DefKind::AssocConst,
 156                         _,
 157                     )
 158                     | Res::SelfCtor(_)
 159                     | Res::PrimTy(_)
 160                     | Res::Local(_) => true,
 161                     _ => false,
 162                 },
 163             )
 164         } else {
 165             let item_span = path.last().unwrap().ident.span;
 166             let (mod_prefix, mod_str) = if path.len() == 1 {
 167                 (String::new(), "this scope".to_string())
 168             } else if path.len() == 2 && path[0].ident.name == kw::PathRoot {
 169                 (String::new(), "the crate root".to_string())
 170             } else {
 171                 let mod_path = &path[..path.len() - 1];
 172                 let mod_prefix =
 173                     match self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No) {
 174                         PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
 175                         _ => None,
 176                     }
 177                     .map_or(String::new(), |res| format!("{} ", res.descr()));
 178                 (mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)))
 179             };
 180             (
 181                 format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
 182                 if path_str == "async" && expected.starts_with("struct") {
 183                     "`async` blocks are only allowed in Rust 2018 or later".to_string()
 184                 } else {
 185                     format!("not found in {}", mod_str)
 186                 },
 187                 item_span,
 188                 false,
 189             )
 190         };
 191
 192         let code = source.error_code(res.is_some());
 193         let mut err = self.r.session.struct_span_err_with_code(base_span, &base_msg, code);
 194
 195         match (source, self.diagnostic_metadata.in_if_condition) {
 196             (PathSource::Expr(_), Some(Expr { span, kind: ExprKind::Assign(..), .. })) => {
 197                 err.span_suggestion_verbose(
 198                     span.shrink_to_lo(),
 199                     "you might have meant to use pattern matching",
 200                     "let ".to_string(),
 201                     Applicability::MaybeIncorrect,
 202                 );
 203                 self.r.session.if_let_suggestions.borrow_mut().insert(*span);
 204             }
 205             _ => {}
 206         }
 207
 208         let is_assoc_fn = self.self_type_is_available(span);
 209         // Emit help message for fake-self from other languages (e.g., `this` in Javascript).
 210         if ["this", "my"].contains(&&*item_str.as_str()) && is_assoc_fn {
 211             err.span_suggestion_short(
 212                 span,
 213                 "you might have meant to use `self` here instead",
 214                 "self".to_string(),
 215                 Applicability::MaybeIncorrect,
 216             );
 217             if !self.self_value_is_available(path[0].ident.span, span) {
 218                 if let Some((FnKind::Fn(_, _, sig, ..), fn_span)) =
 219                     &self.diagnostic_metadata.current_function
 220                 {
 221                     let (span, sugg) = if let Some(param) = sig.decl.inputs.get(0) {
 222                         (param.span.shrink_to_lo(), "&self, ")
 223                     } else {
 224                         (
 225                             self.r
 226                                 .session
 227                                 .source_map()
 228                                 .span_through_char(*fn_span, '(')
 229                                 .shrink_to_hi(),
 230                             "&self",
 231                         )
 232                     };
 233                     err.span_suggestion_verbose(
 234                         span,
 235                         "if you meant to use `self`, you are also missing a `self` receiver \
 236                          argument",
 237                         sugg.to_string(),
 238                         Applicability::MaybeIncorrect,
 239                     );
 240                 }
 241             }
 242         }
 243
 244         // Emit special messages for unresolved `Self` and `self`.
 245         if is_self_type(path, ns) {
 246             err.code(rustc_errors::error_code!(E0411));
 247             err.span_label(
 248                 span,
 249                 "`Self` is only available in impls, traits, and type definitions".to_string(),
 250             );
 251             return (err, Vec::new());
 252         }
 253         if is_self_value(path, ns) {
 254             debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
 255
 256             err.code(rustc_errors::error_code!(E0424));
 257             err.span_label(span, match source {
 258                 PathSource::Pat => "`self` value is a keyword and may not be bound to variables or shadowed"
 259                                    .to_string(),
 260                 _ => "`self` value is a keyword only available in methods with a `self` parameter"
 261                      .to_string(),
 262             });
 263             if let Some((fn_kind, span)) = &self.diagnostic_metadata.current_function {
 264                 // The current function has a `self' parameter, but we were unable to resolve
 265                 // a reference to `self`. This can only happen if the `self` identifier we
 266                 // are resolving came from a different hygiene context.
 267                 if fn_kind.decl().inputs.get(0).map_or(false, |p| p.is_self()) {
 268                     err.span_label(*span, "this function has a `self` parameter, but a macro invocation can only access identifiers it receives from parameters");
 269                 } else {
 270                     let doesnt = if is_assoc_fn {
 271                         let (span, sugg) = fn_kind
 272                             .decl()
 273                             .inputs
 274                             .get(0)
 275                             .map(|p| (p.span.shrink_to_lo(), "&self, "))
 276                             .unwrap_or_else(|| {
 277                                 (
 278                                     self.r
 279                                         .session
 280                                         .source_map()
 281                                         .span_through_char(*span, '(')
 282                                         .shrink_to_hi(),
 283                                     "&self",
 284                                 )
 285                             });
 286                         err.span_suggestion_verbose(
 287                             span,
 288                             "add a `self` receiver parameter to make the associated `fn` a method",
 289                             sugg.to_string(),
 290                             Applicability::MaybeIncorrect,
 291                         );
 292                         "doesn't"
 293                     } else {
 294                         "can't"
 295                     };
 296                     if let Some(ident) = fn_kind.ident() {
 297                         err.span_label(
 298                             ident.span,
 299                             &format!("this function {} have a `self` parameter", doesnt),
 300                         );
 301                     }
 302                 }
 303             }
 304             return (err, Vec::new());
 305         }
 306
 307         // Try to lookup name in more relaxed fashion for better error reporting.
 308         let ident = path.last().unwrap().ident;
 309         let candidates = self
 310             .r
 311             .lookup_import_candidates(ident, ns, &self.parent_scope, is_expected)
 312             .drain(..)
 313             .filter(|ImportSuggestion { did, .. }| {
 314                 match (did, res.and_then(|res| res.opt_def_id())) {
 315                     (Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did,
 316                     _ => true,
 317                 }
 318             })
 319             .collect::<Vec<_>>();
 320         let crate_def_id = DefId::local(CRATE_DEF_INDEX);
 321         if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
 322             let enum_candidates =
 323                 self.r.lookup_import_candidates(ident, ns, &self.parent_scope, is_enum_variant);
 324
 325             if !enum_candidates.is_empty() {
 326                 if let (PathSource::Type, Some(span)) =
 327                     (source, self.diagnostic_metadata.current_type_ascription.last())
 328                 {
 329                     if self
 330                         .r
 331                         .session
 332                         .parse_sess
 333                         .type_ascription_path_suggestions
 334                         .borrow()
 335                         .contains(span)
 336                     {
 337                         // Already reported this issue on the lhs of the type ascription.
 338                         err.delay_as_bug();
 339                         return (err, candidates);
 340                     }
 341                 }
 342
 343                 let mut enum_candidates = enum_candidates
 344                     .iter()
 345                     .map(|suggestion| import_candidate_to_enum_paths(&suggestion))
 346                     .collect::<Vec<_>>();
 347                 enum_candidates.sort();
 348
 349                 // Contextualize for E0412 "cannot find type", but don't belabor the point
 350                 // (that it's a variant) for E0573 "expected type, found variant".
 351                 let preamble = if res.is_none() {
 352                     let others = match enum_candidates.len() {
 353                         1 => String::new(),
 354                         2 => " and 1 other".to_owned(),
 355                         n => format!(" and {} others", n),
 356                     };
 357                     format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others)
 358                 } else {
 359                     String::new()
 360                 };
 361                 let msg = format!("{}try using the variant's enum", preamble);
 362
 363                 err.span_suggestions(
 364                     span,
 365                     &msg,
 366                     enum_candidates
 367                         .into_iter()
 368                         .map(|(_variant_path, enum_ty_path)| enum_ty_path)
 369                         // Variants re-exported in prelude doesn't mean `prelude::v1` is the
 370                         // type name!
 371                         // FIXME: is there a more principled way to do this that
 372                         // would work for other re-exports?
 373                         .filter(|enum_ty_path| enum_ty_path != "std::prelude::v1")
 374                         // Also write `Option` rather than `std::prelude::v1::Option`.
 375                         .map(|enum_ty_path| {
 376                             // FIXME #56861: DRY-er prelude filtering.
 377                             enum_ty_path.trim_start_matches("std::prelude::v1::").to_owned()
 378                         }),
 379                     Applicability::MachineApplicable,
 380                 );
 381             }
 382         }
 383         if path.len() == 1 && self.self_type_is_available(span) {
 384             if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) {
 385                 let self_is_available = self.self_value_is_available(path[0].ident.span, span);
 386                 match candidate {
 387                     AssocSuggestion::Field => {
 388                         if self_is_available {
 389                             err.span_suggestion(
 390                                 span,
 391                                 "you might have meant to use the available field",
 392                                 format!("self.{}", path_str),
 393                                 Applicability::MachineApplicable,
 394                             );
 395                         } else {
 396                             err.span_label(span, "a field by this name exists in `Self`");
 397                         }
 398                     }
 399                     AssocSuggestion::MethodWithSelf if self_is_available => {
 400                         err.span_suggestion(
 401                             span,
 402                             "you might have meant to call the method",
 403                             format!("self.{}", path_str),
 404                             Applicability::MachineApplicable,
 405                         );
 406                     }
 407                     AssocSuggestion::MethodWithSelf
 408                     | AssocSuggestion::AssocFn
 409                     | AssocSuggestion::AssocConst
 410                     | AssocSuggestion::AssocType => {
 411                         err.span_suggestion(
 412                             span,
 413                             &format!("you might have meant to {}", candidate.action()),
 414                             format!("Self::{}", path_str),
 415                             Applicability::MachineApplicable,
 416                         );
 417                     }
 418                 }
 419                 return (err, candidates);
 420             }
 421
 422             // If the first argument in call is `self` suggest calling a method.
 423             if let Some((call_span, args_span)) = self.call_has_self_arg(source) {
 424                 let mut args_snippet = String::new();
 425                 if let Some(args_span) = args_span {
 426                     if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) {
 427                         args_snippet = snippet;
 428                     }
 429                 }
 430
 431                 err.span_suggestion(
 432                     call_span,
 433                     &format!("try calling `{}` as a method", ident),
 434                     format!("self.{}({})", path_str, args_snippet),
 435                     Applicability::MachineApplicable,
 436                 );
 437                 return (err, candidates);
 438             }
 439         }
 440
 441         // Try Levenshtein algorithm.
 442         let typo_sugg = self.lookup_typo_candidate(path, ns, is_expected, span);
 443         // Try context-dependent help if relaxed lookup didn't work.
 444         if let Some(res) = res {
 445             if self.smart_resolve_context_dependent_help(
 446                 &mut err,
 447                 span,
 448                 source,
 449                 res,
 450                 &path_str,
 451                 &fallback_label,
 452             ) {
 453                 // We do this to avoid losing a secondary span when we override the main error span.
 454                 self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span);
 455                 return (err, candidates);
 456             }
 457         }
 458
 459         if !self.type_ascription_suggestion(&mut err, base_span) {
 460             let mut fallback = false;
 461             if let (
 462                 PathSource::Trait(AliasPossibility::Maybe),
 463                 Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)),
 464             ) = (source, res)
 465             {
 466                 if let Some(bounds @ [_, .., _]) = self.diagnostic_metadata.current_trait_object {
 467                     fallback = true;
 468                     let spans: Vec<Span> = bounds
 469                         .iter()
 470                         .map(|bound| bound.span())
 471                         .filter(|&sp| sp != base_span)
 472                         .collect();
 473
 474                     let start_span = bounds.iter().map(|bound| bound.span()).next().unwrap();
 475                     // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
 476                     let end_span = bounds.iter().map(|bound| bound.span()).last().unwrap();
 477                     // `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
 478                     let last_bound_span = spans.last().cloned().unwrap();
 479                     let mut multi_span: MultiSpan = spans.clone().into();
 480                     for sp in spans {
 481                         let msg = if sp == last_bound_span {
 482                             format!(
 483                                 "...because of {} bound{}",
 484                                 if bounds.len() <= 2 { "this" } else { "these" },
 485                                 if bounds.len() <= 2 { "" } else { "s" },
 486                             )
 487                         } else {
 488                             String::new()
 489                         };
 490                         multi_span.push_span_label(sp, msg);
 491                     }
 492                     multi_span.push_span_label(
 493                         base_span,
 494                         "expected this type to be a trait...".to_string(),
 495                     );
 496                     err.span_help(
 497                         multi_span,
 498                         "`+` is used to constrain a \"trait object\" type with lifetimes or \
 499                          auto-traits; structs and enums can't be bound in that way",
 500                     );
 501                     if bounds.iter().all(|bound| match bound {
 502                         ast::GenericBound::Outlives(_) => true,
 503                         ast::GenericBound::Trait(tr, _) => tr.span == base_span,
 504                     }) {
 505                         let mut sugg = vec![];
 506                         if base_span != start_span {
 507                             sugg.push((start_span.until(base_span), String::new()));
 508                         }
 509                         if base_span != end_span {
 510                             sugg.push((base_span.shrink_to_hi().to(end_span), String::new()));
 511                         }
 512
 513                         err.multipart_suggestion(
 514                             "if you meant to use a type and not a trait here, remove the bounds",
 515                             sugg,
 516                             Applicability::MaybeIncorrect,
 517                         );
 518                     }
 519                 }
 520             }
 521
 522             fallback |= self.restrict_assoc_type_in_where_clause(span, &mut err);
 523
 524             if !self.r.add_typo_suggestion(&mut err, typo_sugg, ident_span) {
 525                 fallback = true;
 526                 match self.diagnostic_metadata.current_let_binding {
 527                     Some((pat_sp, Some(ty_sp), None))
 528                         if ty_sp.contains(base_span) && could_be_expr =>
 529                     {
 530                         err.span_suggestion_short(
 531                             pat_sp.between(ty_sp),
 532                             "use `=` if you meant to assign",
 533                             " = ".to_string(),
 534                             Applicability::MaybeIncorrect,
 535                         );
 536                     }
 537                     _ => {}
 538                 }
 539             }
 540             if fallback {
 541                 // Fallback label.
 542                 err.span_label(base_span, fallback_label);
 543             }
 544         }
 545         if let Some(err_code) = &err.code {
 546             if err_code == &rustc_errors::error_code!(E0425) {
 547                 for label_rib in &self.label_ribs {
 548                     for (label_ident, node_id) in &label_rib.bindings {
 549                         if format!("'{}", ident) == label_ident.to_string() {
 550                             err.span_label(label_ident.span, "a label with a similar name exists");
 551                             if let PathSource::Expr(Some(Expr {
 552                                 kind: ExprKind::Break(None, Some(_)),
 553                                 ..
 554                             })) = source
 555                             {
 556                                 err.span_suggestion(
 557                                     span,
 558                                     "use the similarly named label",
 559                                     label_ident.name.to_string(),
 560                                     Applicability::MaybeIncorrect,
 561                                 );
 562                                 // Do not lint against unused label when we suggest them.
 563                                 self.diagnostic_metadata.unused_labels.remove(node_id);
 564                             }
 565                         }
 566                     }
 567                 }
 568             }
 569         }
 570
 571         (err, candidates)
 572     }
 573
 574     /// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
 575     fn restrict_assoc_type_in_where_clause(
 576         &mut self,
 577         span: Span,
 578         err: &mut DiagnosticBuilder<'_>,
 579     ) -> bool {
 580         // Detect that we are actually in a `where` predicate.
 581         let (bounded_ty, bounds, where_span) =
 582             if let Some(ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 583                 bounded_ty,
 584                 bound_generic_params,
 585                 bounds,
 586                 span,
 587             })) = self.diagnostic_metadata.current_where_predicate
 588             {
 589                 if !bound_generic_params.is_empty() {
 590                     return false;
 591                 }
 592                 (bounded_ty, bounds, span)
 593             } else {
 594                 return false;
 595             };
 596
 597         // Confirm that the target is an associated type.
 598         let (ty, position, path) = if let ast::TyKind::Path(
 599             Some(ast::QSelf { ty, position, .. }),
 600             path,
 601         ) = &bounded_ty.kind
 602         {
 603             // use this to verify that ident is a type param.
 604             let partial_res = if let Ok(Some(partial_res)) = self.resolve_qpath_anywhere(
 605                 bounded_ty.id,
 606                 None,
 607                 &Segment::from_path(path),
 608                 Namespace::TypeNS,
 609                 span,
 610                 true,
 611                 CrateLint::No,
 612             ) {
 613                 partial_res
 614             } else {
 615                 return false;
 616             };
 617             if !(matches!(
 618                 partial_res.base_res(),
 619                 hir::def::Res::Def(hir::def::DefKind::AssocTy, _)
 620             ) && partial_res.unresolved_segments() == 0)
 621             {
 622                 return false;
 623             }
 624             (ty, position, path)
 625         } else {
 626             return false;
 627         };
 628
 629         if let ast::TyKind::Path(None, type_param_path) = &ty.peel_refs().kind {
 630             // Confirm that the `SelfTy` is a type parameter.
 631             let partial_res = if let Ok(Some(partial_res)) = self.resolve_qpath_anywhere(
 632                 bounded_ty.id,
 633                 None,
 634                 &Segment::from_path(type_param_path),
 635                 Namespace::TypeNS,
 636                 span,
 637                 true,
 638                 CrateLint::No,
 639             ) {
 640                 partial_res
 641             } else {
 642                 return false;
 643             };
 644             if !(matches!(
 645                 partial_res.base_res(),
 646                 hir::def::Res::Def(hir::def::DefKind::TyParam, _)
 647             ) && partial_res.unresolved_segments() == 0)
 648             {
 649                 return false;
 650             }
 651             if let (
 652                 [ast::PathSegment { ident: constrain_ident, args: None, .. }],
 653                 [ast::GenericBound::Trait(poly_trait_ref, ast::TraitBoundModifier::None)],
 654             ) = (&type_param_path.segments[..], &bounds[..])
 655             {
 656                 if let [ast::PathSegment { ident, args: None, .. }] =
 657                     &poly_trait_ref.trait_ref.path.segments[..]
 658                 {
 659                     if ident.span == span {
 660                         err.span_suggestion_verbose(
 661                             *where_span,
 662                             &format!("constrain the associated type to `{}`", ident),
 663                             format!(
 664                                 "{}: {}<{} = {}>",
 665                                 self.r
 666                                     .session
 667                                     .source_map()
 668                                     .span_to_snippet(ty.span) // Account for `<&'a T as Foo>::Bar`.
 669                                     .unwrap_or_else(|_| constrain_ident.to_string()),
 670                                 path.segments[..*position]
 671                                     .iter()
 672                                     .map(|segment| path_segment_to_string(segment))
 673                                     .collect::<Vec<_>>()
 674                                     .join("::"),
 675                                 path.segments[*position..]
 676                                     .iter()
 677                                     .map(|segment| path_segment_to_string(segment))
 678                                     .collect::<Vec<_>>()
 679                                     .join("::"),
 680                                 ident,
 681                             ),
 682                             Applicability::MaybeIncorrect,
 683                         );
 684                     }
 685                     return true;
 686                 }
 687             }
 688         }
 689         false
 690     }
 691
 692     /// Check if the source is call expression and the first argument is `self`. If true,
 693     /// return the span of whole call and the span for all arguments expect the first one (`self`).
 694     fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option<Span>)> {
 695         let mut has_self_arg = None;
 696         if let PathSource::Expr(Some(parent)) = source {
 697             match &parent.kind {
 698                 ExprKind::Call(_, args) if !args.is_empty() => {
 699                     let mut expr_kind = &args[0].kind;
 700                     loop {
 701                         match expr_kind {
 702                             ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => {
 703                                 if arg_name.segments[0].ident.name == kw::SelfLower {
 704                                     let call_span = parent.span;
 705                                     let tail_args_span = if args.len() > 1 {
 706                                         Some(Span::new(
 707                                             args[1].span.lo(),
 708                                             args.last().unwrap().span.hi(),
 709                                             call_span.ctxt(),
 710                                         ))
 711                                     } else {
 712                                         None
 713                                     };
 714                                     has_self_arg = Some((call_span, tail_args_span));
 715                                 }
 716                                 break;
 717                             }
 718                             ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind,
 719                             _ => break,
 720                         }
 721                     }
 722                 }
 723                 _ => (),
 724             }
 725         };
 726         has_self_arg
 727     }
 728
 729     fn followed_by_brace(&self, span: Span) -> (bool, Option<Span>) {
 730         // HACK(estebank): find a better way to figure out that this was a
 731         // parser issue where a struct literal is being used on an expression
 732         // where a brace being opened means a block is being started. Look
 733         // ahead for the next text to see if `span` is followed by a `{`.
 734         let sm = self.r.session.source_map();
 735         let mut sp = span;
 736         loop {
 737             sp = sm.next_point(sp);
 738             match sm.span_to_snippet(sp) {
 739                 Ok(ref snippet) => {
 740                     if snippet.chars().any(|c| !c.is_whitespace()) {
 741                         break;
 742                     }
 743                 }
 744                 _ => break,
 745             }
 746         }
 747         let followed_by_brace = matches!(sm.span_to_snippet(sp), Ok(ref snippet) if snippet == "{");
 748         // In case this could be a struct literal that needs to be surrounded
 749         // by parentheses, find the appropriate span.
 750         let mut i = 0;
 751         let mut closing_brace = None;
 752         loop {
 753             sp = sm.next_point(sp);
 754             match sm.span_to_snippet(sp) {
 755                 Ok(ref snippet) => {
 756                     if snippet == "}" {
 757                         closing_brace = Some(span.to(sp));
 758                         break;
 759                     }
 760                 }
 761                 _ => break,
 762             }
 763             i += 1;
 764             // The bigger the span, the more likely we're incorrect --
 765             // bound it to 100 chars long.
 766             if i > 100 {
 767                 break;
 768             }
 769         }
 770         (followed_by_brace, closing_brace)
 771     }
 772
 773     /// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment`
 774     /// function.
 775     /// Returns `true` if able to provide context-dependent help.
 776     fn smart_resolve_context_dependent_help(
 777         &mut self,
 778         err: &mut DiagnosticBuilder<'a>,
 779         span: Span,
 780         source: PathSource<'_>,
 781         res: Res,
 782         path_str: &str,
 783         fallback_label: &str,
 784     ) -> bool {
 785         let ns = source.namespace();
 786         let is_expected = &|res| source.is_expected(res);
 787
 788         let path_sep = |err: &mut DiagnosticBuilder<'_>, expr: &Expr| match expr.kind {
 789             ExprKind::Field(_, ident) => {
 790                 err.span_suggestion(
 791                     expr.span,
 792                     "use the path separator to refer to an item",
 793                     format!("{}::{}", path_str, ident),
 794                     Applicability::MaybeIncorrect,
 795                 );
 796                 true
 797             }
 798             ExprKind::MethodCall(ref segment, ..) => {
 799                 let span = expr.span.with_hi(segment.ident.span.hi());
 800                 err.span_suggestion(
 801                     span,
 802                     "use the path separator to refer to an item",
 803                     format!("{}::{}", path_str, segment.ident),
 804                     Applicability::MaybeIncorrect,
 805                 );
 806                 true
 807             }
 808             _ => false,
 809         };
 810
 811         let mut bad_struct_syntax_suggestion = |def_id: DefId| {
 812             let (followed_by_brace, closing_brace) = self.followed_by_brace(span);
 813
 814             match source {
 815                 PathSource::Expr(Some(
 816                     parent @ Expr { kind: ExprKind::Field(..) | ExprKind::MethodCall(..), .. },
 817                 )) if path_sep(err, &parent) => {}
 818                 PathSource::Expr(
 819                     None
 820                     | Some(Expr {
 821                         kind:
 822                             ExprKind::Path(..)
 823                             | ExprKind::Binary(..)
 824                             | ExprKind::Unary(..)
 825                             | ExprKind::If(..)
 826                             | ExprKind::While(..)
 827                             | ExprKind::ForLoop(..)
 828                             | ExprKind::Match(..),
 829                         ..
 830                     }),
 831                 ) if followed_by_brace => {
 832                     if let Some(sp) = closing_brace {
 833                         err.span_label(span, fallback_label);
 834                         err.multipart_suggestion(
 835                             "surround the struct literal with parentheses",
 836                             vec![
 837                                 (sp.shrink_to_lo(), "(".to_string()),
 838                                 (sp.shrink_to_hi(), ")".to_string()),
 839                             ],
 840                             Applicability::MaybeIncorrect,
 841                         );
 842                     } else {
 843                         err.span_label(
 844                             span, // Note the parentheses surrounding the suggestion below
 845                             format!(
 846                                 "you might want to surround a struct literal with parentheses: \
 847                                  `({} {{ /* fields */ }})`?",
 848                                 path_str
 849                             ),
 850                         );
 851                     }
 852                 }
 853                 PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => {
 854                     let span = match &source {
 855                         PathSource::Expr(Some(Expr {
 856                             span, kind: ExprKind::Call(_, _), ..
 857                         }))
 858                         | PathSource::TupleStruct(span, _) => {
 859                             // We want the main underline to cover the suggested code as well for
 860                             // cleaner output.
 861                             err.set_span(*span);
 862                             *span
 863                         }
 864                         _ => span,
 865                     };
 866                     if let Some(span) = self.def_span(def_id) {
 867                         err.span_label(span, &format!("`{}` defined here", path_str));
 868                     }
 869                     let (tail, descr, applicability) = match source {
 870                         PathSource::Pat | PathSource::TupleStruct(..) => {
 871                             ("", "pattern", Applicability::MachineApplicable)
 872                         }
 873                         _ => (": val", "literal", Applicability::HasPlaceholders),
 874                     };
 875                     let (fields, applicability) = match self.r.field_names.get(&def_id) {
 876                         Some(fields) => (
 877                             fields
 878                                 .iter()
 879                                 .map(|f| format!("{}{}", f.node, tail))
 880                                 .collect::<Vec<String>>()
 881                                 .join(", "),
 882                             applicability,
 883                         ),
 884                         None => ("/* fields */".to_string(), Applicability::HasPlaceholders),
 885                     };
 886                     let pad = match self.r.field_names.get(&def_id) {
 887                         Some(fields) if fields.is_empty() => "",
 888                         _ => " ",
 889                     };
 890                     err.span_suggestion(
 891                         span,
 892                         &format!("use struct {} syntax instead", descr),
 893                         format!("{path_str} {{{pad}{fields}{pad}}}"),
 894                         applicability,
 895                     );
 896                 }
 897                 _ => {
 898                     err.span_label(span, fallback_label);
 899                 }
 900             }
 901         };
 902
 903         match (res, source) {
 904             (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
 905                 err.span_label(span, fallback_label);
 906                 err.span_suggestion_verbose(
 907                     span.shrink_to_hi(),
 908                     "use `!` to invoke the macro",
 909                     "!".to_string(),
 910                     Applicability::MaybeIncorrect,
 911                 );
 912                 if path_str == "try" && span.rust_2015() {
 913                     err.note("if you want the `try` keyword, you need Rust 2018 or later");
 914                 }
 915             }
 916             (Res::Def(DefKind::TyAlias, def_id), PathSource::Trait(_)) => {
 917                 err.span_label(span, "type aliases cannot be used as traits");
 918                 if self.r.session.is_nightly_build() {
 919                     let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \
 920                                `type` alias";
 921                     if let Some(span) = self.def_span(def_id) {
 922                         err.span_help(span, msg);
 923                     } else {
 924                         err.help(msg);
 925                     }
 926                 }
 927             }
 928             (Res::Def(DefKind::Mod, _), PathSource::Expr(Some(parent))) => {
 929                 if !path_sep(err, &parent) {
 930                     return false;
 931                 }
 932             }
 933             (
 934                 Res::Def(DefKind::Enum, def_id),
 935                 PathSource::TupleStruct(..) | PathSource::Expr(..),
 936             ) => {
 937                 if self
 938                     .diagnostic_metadata
 939                     .current_type_ascription
 940                     .last()
 941                     .map(|sp| {
 942                         self.r
 943                             .session
 944                             .parse_sess
 945                             .type_ascription_path_suggestions
 946                             .borrow()
 947                             .contains(&sp)
 948                     })
 949                     .unwrap_or(false)
 950                 {
 951                     err.delay_as_bug();
 952                     // We already suggested changing `:` into `::` during parsing.
 953                     return false;
 954                 }
 955
 956                 self.suggest_using_enum_variant(err, source, def_id, span);
 957             }
 958             (Res::Def(DefKind::Struct, def_id), _) if ns == ValueNS => {
 959                 let (ctor_def, ctor_vis, fields) =
 960                     if let Some(struct_ctor) = self.r.struct_constructors.get(&def_id).cloned() {
 961                         struct_ctor
 962                     } else {
 963                         bad_struct_syntax_suggestion(def_id);
 964                         return true;
 965                     };
 966
 967                 let is_accessible = self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
 968                 if !is_expected(ctor_def) || is_accessible {
 969                     return true;
 970                 }
 971
 972                 let field_spans = match source {
 973                     // e.g. `if let Enum::TupleVariant(field1, field2) = _`
 974                     PathSource::TupleStruct(_, pattern_spans) => {
 975                         err.set_primary_message(
 976                             "cannot match against a tuple struct which contains private fields",
 977                         );
 978
 979                         // Use spans of the tuple struct pattern.
 980                         Some(Vec::from(pattern_spans))
 981                     }
 982                     // e.g. `let _ = Enum::TupleVariant(field1, field2);`
 983                     _ if source.is_call() => {
 984                         err.set_primary_message(
 985                             "cannot initialize a tuple struct which contains private fields",
 986                         );
 987
 988                         // Use spans of the tuple struct definition.
 989                         self.r
 990                             .field_names
 991                             .get(&def_id)
 992                             .map(|fields| fields.iter().map(|f| f.span).collect::<Vec<_>>())
 993                     }
 994                     _ => None,
 995                 };
 996
 997                 if let Some(spans) =
 998                     field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len())
 999                 {
1000                     let non_visible_spans: Vec<Span> = fields
1001                         .iter()
1002                         .zip(spans.iter())
1003                         .filter(|(vis, _)| {
1004                             !self.r.is_accessible_from(**vis, self.parent_scope.module)
1005                         })
1006                         .map(|(_, span)| *span)
1007                         .collect();
1008
1009                     if non_visible_spans.len() > 0 {
1010                         let mut m: rustc_span::MultiSpan = non_visible_spans.clone().into();
1011                         non_visible_spans
1012                             .into_iter()
1013                             .for_each(|s| m.push_span_label(s, "private field".to_string()));
1014                         err.span_note(m, "constructor is not visible here due to private fields");
1015                     }
1016
1017                     return true;
1018                 }
1019
1020                 err.span_label(
1021                     span,
1022                     "constructor is not visible here due to private fields".to_string(),
1023                 );
1024             }
1025             (
1026                 Res::Def(
1027                     DefKind::Union | DefKind::Variant | DefKind::Ctor(_, CtorKind::Fictive),
1028                     def_id,
1029                 ),
1030                 _,
1031             ) if ns == ValueNS => {
1032                 bad_struct_syntax_suggestion(def_id);
1033             }
1034             (Res::Def(DefKind::Ctor(_, CtorKind::Fn), def_id), _) if ns == ValueNS => {
1035                 if let Some(span) = self.def_span(def_id) {
1036                     err.span_label(span, &format!("`{}` defined here", path_str));
1037                 }
1038                 let fields =
1039                     self.r.field_names.get(&def_id).map_or("/* fields */".to_string(), |fields| {
1040                         vec!["_"; fields.len()].join(", ")
1041                     });
1042                 err.span_suggestion(
1043                     span,
1044                     "use the tuple variant pattern syntax instead",
1045                     format!("{}({})", path_str, fields),
1046                     Applicability::HasPlaceholders,
1047                 );
1048             }
1049             (Res::SelfTy(..), _) if ns == ValueNS => {
1050                 err.span_label(span, fallback_label);
1051                 err.note("can't use `Self` as a constructor, you must use the implemented struct");
1052             }
1053             (Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => {
1054                 err.note("can't use a type alias as a constructor");
1055             }
1056             _ => return false,
1057         }
1058         true
1059     }
1060
1061     fn lookup_assoc_candidate<FilterFn>(
1062         &mut self,
1063         ident: Ident,
1064         ns: Namespace,
1065         filter_fn: FilterFn,
1066     ) -> Option<AssocSuggestion>
1067     where
1068         FilterFn: Fn(Res) -> bool,
1069     {
1070         fn extract_node_id(t: &Ty) -> Option<NodeId> {
1071             match t.kind {
1072                 TyKind::Path(None, _) => Some(t.id),
1073                 TyKind::Rptr(_, ref mut_ty) => extract_node_id(&mut_ty.ty),
1074                 // This doesn't handle the remaining `Ty` variants as they are not
1075                 // that commonly the self_type, it might be interesting to provide
1076                 // support for those in future.
1077                 _ => None,
1078             }
1079         }
1080
1081         // Fields are generally expected in the same contexts as locals.
1082         if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) {
1083             if let Some(node_id) =
1084                 self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id)
1085             {
1086                 // Look for a field with the same name in the current self_type.
1087                 if let Some(resolution) = self.r.partial_res_map.get(&node_id) {
1088                     match resolution.base_res() {
1089                         Res::Def(DefKind::Struct | DefKind::Union, did)
1090                             if resolution.unresolved_segments() == 0 =>
1091                         {
1092                             if let Some(field_names) = self.r.field_names.get(&did) {
1093                                 if field_names
1094                                     .iter()
1095                                     .any(|&field_name| ident.name == field_name.node)
1096                                 {
1097                                     return Some(AssocSuggestion::Field);
1098                                 }
1099                             }
1100                         }
1101                         _ => {}
1102                     }
1103                 }
1104             }
1105         }
1106
1107         if let Some(items) = self.diagnostic_metadata.current_trait_assoc_items {
1108             for assoc_item in &items[..] {
1109                 if assoc_item.ident == ident {
1110                     return Some(match &assoc_item.kind {
1111                         ast::AssocItemKind::Const(..) => AssocSuggestion::AssocConst,
1112                         ast::AssocItemKind::Fn(box ast::FnKind(_, sig, ..))
1113                             if sig.decl.has_self() =>
1114                         {
1115                             AssocSuggestion::MethodWithSelf
1116                         }
1117                         ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn,
1118                         ast::AssocItemKind::TyAlias(..) => AssocSuggestion::AssocType,
1119                         ast::AssocItemKind::MacCall(_) => continue,
1120                     });
1121                 }
1122             }
1123         }
1124
1125         // Look for associated items in the current trait.
1126         if let Some((module, _)) = self.current_trait_ref {
1127             if let Ok(binding) = self.r.resolve_ident_in_module(
1128                 ModuleOrUniformRoot::Module(module),
1129                 ident,
1130                 ns,
1131                 &self.parent_scope,
1132                 false,
1133                 module.span,
1134             ) {
1135                 let res = binding.res();
1136                 if filter_fn(res) {
1137                     if self.r.has_self.contains(&res.def_id()) {
1138                         return Some(AssocSuggestion::MethodWithSelf);
1139                     } else {
1140                         match res {
1141                             Res::Def(DefKind::AssocFn, _) => return Some(AssocSuggestion::AssocFn),
1142                             Res::Def(DefKind::AssocConst, _) => {
1143                                 return Some(AssocSuggestion::AssocConst);
1144                             }
1145                             Res::Def(DefKind::AssocTy, _) => {
1146                                 return Some(AssocSuggestion::AssocType);
1147                             }
1148                             _ => {}
1149                         }
1150                     }
1151                 }
1152             }
1153         }
1154
1155         None
1156     }
1157
1158     fn lookup_typo_candidate(
1159         &mut self,
1160         path: &[Segment],
1161         ns: Namespace,
1162         filter_fn: &impl Fn(Res) -> bool,
1163         span: Span,
1164     ) -> Option<TypoSuggestion> {
1165         let mut names = Vec::new();
1166         if path.len() == 1 {
1167             // Search in lexical scope.
1168             // Walk backwards up the ribs in scope and collect candidates.
1169             for rib in self.ribs[ns].iter().rev() {
1170                 // Locals and type parameters
1171                 for (ident, &res) in &rib.bindings {
1172                     if filter_fn(res) {
1173                         names.push(TypoSuggestion::from_res(ident.name, res));
1174                     }
1175                 }
1176                 // Items in scope
1177                 if let RibKind::ModuleRibKind(module) = rib.kind {
1178                     // Items from this module
1179                     self.r.add_module_candidates(module, &mut names, &filter_fn);
1180
1181                     if let ModuleKind::Block(..) = module.kind {
1182                         // We can see through blocks
1183                     } else {
1184                         // Items from the prelude
1185                         if !module.no_implicit_prelude {
1186                             let extern_prelude = self.r.extern_prelude.clone();
1187                             names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
1188                                 self.r.crate_loader.maybe_process_path_extern(ident.name).and_then(
1189                                     |crate_id| {
1190                                         let crate_mod = Res::Def(
1191                                             DefKind::Mod,
1192                                             DefId { krate: crate_id, index: CRATE_DEF_INDEX },
1193                                         );
1194
1195                                         if filter_fn(crate_mod) {
1196                                             Some(TypoSuggestion::from_res(ident.name, crate_mod))
1197                                         } else {
1198                                             None
1199                                         }
1200                                     },
1201                                 )
1202                             }));
1203
1204                             if let Some(prelude) = self.r.prelude {
1205                                 self.r.add_module_candidates(prelude, &mut names, &filter_fn);
1206                             }
1207                         }
1208                         break;
1209                     }
1210                 }
1211             }
1212             // Add primitive types to the mix
1213             if filter_fn(Res::PrimTy(PrimTy::Bool)) {
1214                 names.extend(
1215                     self.r.primitive_type_table.primitive_types.iter().map(|(name, prim_ty)| {
1216                         TypoSuggestion::from_res(*name, Res::PrimTy(*prim_ty))
1217                     }),
1218                 )
1219             }
1220         } else {
1221             // Search in module.
1222             let mod_path = &path[..path.len() - 1];
1223             if let PathResult::Module(module) =
1224                 self.resolve_path(mod_path, Some(TypeNS), false, span, CrateLint::No)
1225             {
1226                 if let ModuleOrUniformRoot::Module(module) = module {
1227                     self.r.add_module_candidates(module, &mut names, &filter_fn);
1228                 }
1229             }
1230         }
1231
1232         let name = path[path.len() - 1].ident.name;
1233         // Make sure error reporting is deterministic.
1234         names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
1235
1236         match find_best_match_for_name(
1237             &names.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
1238             name,
1239             None,
1240         ) {
1241             Some(found) if found != name => {
1242                 names.into_iter().find(|suggestion| suggestion.candidate == found)
1243             }
1244             _ => None,
1245         }
1246     }
1247
1248     /// Only used in a specific case of type ascription suggestions
1249     fn get_colon_suggestion_span(&self, start: Span) -> Span {
1250         let sm = self.r.session.source_map();
1251         start.to(sm.next_point(start))
1252     }
1253
1254     fn type_ascription_suggestion(&self, err: &mut DiagnosticBuilder<'_>, base_span: Span) -> bool {
1255         let sm = self.r.session.source_map();
1256         let base_snippet = sm.span_to_snippet(base_span);
1257         if let Some(&sp) = self.diagnostic_metadata.current_type_ascription.last() {
1258             if let Ok(snippet) = sm.span_to_snippet(sp) {
1259                 let len = snippet.trim_end().len() as u32;
1260                 if snippet.trim() == ":" {
1261                     let colon_sp =
1262                         sp.with_lo(sp.lo() + BytePos(len - 1)).with_hi(sp.lo() + BytePos(len));
1263                     let mut show_label = true;
1264                     if sm.is_multiline(sp) {
1265                         err.span_suggestion_short(
1266                             colon_sp,
1267                             "maybe you meant to write `;` here",
1268                             ";".to_string(),
1269                             Applicability::MaybeIncorrect,
1270                         );
1271                     } else {
1272                         let after_colon_sp =
1273                             self.get_colon_suggestion_span(colon_sp.shrink_to_hi());
1274                         if snippet.len() == 1 {
1275                             // `foo:bar`
1276                             err.span_suggestion(
1277                                 colon_sp,
1278                                 "maybe you meant to write a path separator here",
1279                                 "::".to_string(),
1280                                 Applicability::MaybeIncorrect,
1281                             );
1282                             show_label = false;
1283                             if !self
1284                                 .r
1285                                 .session
1286                                 .parse_sess
1287                                 .type_ascription_path_suggestions
1288                                 .borrow_mut()
1289                                 .insert(colon_sp)
1290                             {
1291                                 err.delay_as_bug();
1292                             }
1293                         }
1294                         if let Ok(base_snippet) = base_snippet {
1295                             let mut sp = after_colon_sp;
1296                             for _ in 0..100 {
1297                                 // Try to find an assignment
1298                                 sp = sm.next_point(sp);
1299                                 let snippet = sm.span_to_snippet(sp.to(sm.next_point(sp)));
1300                                 match snippet {
1301                                     Ok(ref x) if x.as_str() == "=" => {
1302                                         err.span_suggestion(
1303                                             base_span,
1304                                             "maybe you meant to write an assignment here",
1305                                             format!("let {}", base_snippet),
1306                                             Applicability::MaybeIncorrect,
1307                                         );
1308                                         show_label = false;
1309                                         break;
1310                                     }
1311                                     Ok(ref x) if x.as_str() == "\n" => break,
1312                                     Err(_) => break,
1313                                     Ok(_) => {}
1314                                 }
1315                             }
1316                         }
1317                     }
1318                     if show_label {
1319                         err.span_label(
1320                             base_span,
1321                             "expecting a type here because of type ascription",
1322                         );
1323                     }
1324                     return show_label;
1325                 }
1326             }
1327         }
1328         false
1329     }
1330
1331     fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
1332         let mut result = None;
1333         let mut seen_modules = FxHashSet::default();
1334         let mut worklist = vec![(self.r.graph_root, Vec::new())];
1335
1336         while let Some((in_module, path_segments)) = worklist.pop() {
1337             // abort if the module is already found
1338             if result.is_some() {
1339                 break;
1340             }
1341
1342             in_module.for_each_child(self.r, |_, ident, _, name_binding| {
1343                 // abort if the module is already found or if name_binding is private external
1344                 if result.is_some() || !name_binding.vis.is_visible_locally() {
1345                     return;
1346                 }
1347                 if let Some(module) = name_binding.module() {
1348                     // form the path
1349                     let mut path_segments = path_segments.clone();
1350                     path_segments.push(ast::PathSegment::from_ident(ident));
1351                     let module_def_id = module.def_id().unwrap();
1352                     if module_def_id == def_id {
1353                         let path =
1354                             Path { span: name_binding.span, segments: path_segments, tokens: None };
1355                         result = Some((
1356                             module,
1357                             ImportSuggestion {
1358                                 did: Some(def_id),
1359                                 descr: "module",
1360                                 path,
1361                                 accessible: true,
1362                             },
1363                         ));
1364                     } else {
1365                         // add the module to the lookup
1366                         if seen_modules.insert(module_def_id) {
1367                             worklist.push((module, path_segments));
1368                         }
1369                     }
1370                 }
1371             });
1372         }
1373
1374         result
1375     }
1376
1377     fn collect_enum_ctors(&mut self, def_id: DefId) -> Option<Vec<(Path, DefId, CtorKind)>> {
1378         self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| {
1379             let mut variants = Vec::new();
1380             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
1381                 if let Res::Def(DefKind::Ctor(CtorOf::Variant, kind), def_id) = name_binding.res() {
1382                     let mut segms = enum_import_suggestion.path.segments.clone();
1383                     segms.push(ast::PathSegment::from_ident(ident));
1384                     let path = Path { span: name_binding.span, segments: segms, tokens: None };
1385                     variants.push((path, def_id, kind));
1386                 }
1387             });
1388             variants
1389         })
1390     }
1391
1392     /// Adds a suggestion for using an enum's variant when an enum is used instead.
1393     fn suggest_using_enum_variant(
1394         &mut self,
1395         err: &mut DiagnosticBuilder<'a>,
1396         source: PathSource<'_>,
1397         def_id: DefId,
1398         span: Span,
1399     ) {
1400         let variants = match self.collect_enum_ctors(def_id) {
1401             Some(variants) => variants,
1402             None => {
1403                 err.note("you might have meant to use one of the enum's variants");
1404                 return;
1405             }
1406         };
1407
1408         let suggest_only_tuple_variants =
1409             matches!(source, PathSource::TupleStruct(..)) || source.is_call();
1410         if suggest_only_tuple_variants {
1411             // Suggest only tuple variants regardless of whether they have fields and do not
1412             // suggest path with added parenthesis.
1413             let mut suggestable_variants = variants
1414                 .iter()
1415                 .filter(|(.., kind)| *kind == CtorKind::Fn)
1416                 .map(|(variant, ..)| path_names_to_string(variant))
1417                 .collect::<Vec<_>>();
1418
1419             let non_suggestable_variant_count = variants.len() - suggestable_variants.len();
1420
1421             let source_msg = if source.is_call() {
1422                 "to construct"
1423             } else if matches!(source, PathSource::TupleStruct(..)) {
1424                 "to match against"
1425             } else {
1426                 unreachable!()
1427             };
1428
1429             if !suggestable_variants.is_empty() {
1430                 let msg = if non_suggestable_variant_count == 0 && suggestable_variants.len() == 1 {
1431                     format!("try {} the enum's variant", source_msg)
1432                 } else {
1433                     format!("try {} one of the enum's variants", source_msg)
1434                 };
1435
1436                 err.span_suggestions(
1437                     span,
1438                     &msg,
1439                     suggestable_variants.drain(..),
1440                     Applicability::MaybeIncorrect,
1441                 );
1442             }
1443
1444             // If the enum has no tuple variants..
1445             if non_suggestable_variant_count == variants.len() {
1446                 err.help(&format!("the enum has no tuple variants {}", source_msg));
1447             }
1448
1449             // If there are also non-tuple variants..
1450             if non_suggestable_variant_count == 1 {
1451                 err.help(&format!(
1452                     "you might have meant {} the enum's non-tuple variant",
1453                     source_msg
1454                 ));
1455             } else if non_suggestable_variant_count >= 1 {
1456                 err.help(&format!(
1457                     "you might have meant {} one of the enum's non-tuple variants",
1458                     source_msg
1459                 ));
1460             }
1461         } else {
1462             let needs_placeholder = |def_id: DefId, kind: CtorKind| {
1463                 let has_no_fields = self.r.field_names.get(&def_id).map_or(false, |f| f.is_empty());
1464                 match kind {
1465                     CtorKind::Const => false,
1466                     CtorKind::Fn | CtorKind::Fictive if has_no_fields => false,
1467                     _ => true,
1468                 }
1469             };
1470
1471             let mut suggestable_variants = variants
1472                 .iter()
1473                 .filter(|(_, def_id, kind)| !needs_placeholder(*def_id, *kind))
1474                 .map(|(variant, _, kind)| (path_names_to_string(variant), kind))
1475                 .map(|(variant, kind)| match kind {
1476                     CtorKind::Const => variant,
1477                     CtorKind::Fn => format!("({}())", variant),
1478                     CtorKind::Fictive => format!("({} {{}})", variant),
1479                 })
1480                 .collect::<Vec<_>>();
1481
1482             if !suggestable_variants.is_empty() {
1483                 let msg = if suggestable_variants.len() == 1 {
1484                     "you might have meant to use the following enum variant"
1485                 } else {
1486                     "you might have meant to use one of the following enum variants"
1487                 };
1488
1489                 err.span_suggestions(
1490                     span,
1491                     msg,
1492                     suggestable_variants.drain(..),
1493                     Applicability::MaybeIncorrect,
1494                 );
1495             }
1496
1497             let mut suggestable_variants_with_placeholders = variants
1498                 .iter()
1499                 .filter(|(_, def_id, kind)| needs_placeholder(*def_id, *kind))
1500                 .map(|(variant, _, kind)| (path_names_to_string(variant), kind))
1501                 .filter_map(|(variant, kind)| match kind {
1502                     CtorKind::Fn => Some(format!("({}(/* fields */))", variant)),
1503                     CtorKind::Fictive => Some(format!("({} {{ /* fields */ }})", variant)),
1504                     _ => None,
1505                 })
1506                 .collect::<Vec<_>>();
1507
1508             if !suggestable_variants_with_placeholders.is_empty() {
1509                 let msg = match (
1510                     suggestable_variants.is_empty(),
1511                     suggestable_variants_with_placeholders.len(),
1512                 ) {
1513                     (true, 1) => "the following enum variant is available",
1514                     (true, _) => "the following enum variants are available",
1515                     (false, 1) => "alternatively, the following enum variant is available",
1516                     (false, _) => "alternatively, the following enum variants are also available",
1517                 };
1518
1519                 err.span_suggestions(
1520                     span,
1521                     msg,
1522                     suggestable_variants_with_placeholders.drain(..),
1523                     Applicability::HasPlaceholders,
1524                 );
1525             }
1526         };
1527
1528         if def_id.is_local() {
1529             if let Some(span) = self.def_span(def_id) {
1530                 err.span_note(span, "the enum is defined here");
1531             }
1532         }
1533     }
1534
1535     crate fn report_missing_type_error(
1536         &self,
1537         path: &[Segment],
1538     ) -> Option<(Span, &'static str, String, Applicability)> {
1539         let (ident, span) = match path {
1540             [segment] if !segment.has_generic_args => {
1541                 (segment.ident.to_string(), segment.ident.span)
1542             }
1543             _ => return None,
1544         };
1545         let mut iter = ident.chars().map(|c| c.is_uppercase());
1546         let single_uppercase_char =
1547             matches!(iter.next(), Some(true)) && matches!(iter.next(), None);
1548         if !self.diagnostic_metadata.currently_processing_generics && !single_uppercase_char {
1549             return None;
1550         }
1551         match (self.diagnostic_metadata.current_item, single_uppercase_char) {
1552             (Some(Item { kind: ItemKind::Fn(..), ident, .. }), _) if ident.name == sym::main => {
1553                 // Ignore `fn main()` as we don't want to suggest `fn main<T>()`
1554             }
1555             (
1556                 Some(Item {
1557                     kind:
1558                         kind @ ItemKind::Fn(..)
1559                         | kind @ ItemKind::Enum(..)
1560                         | kind @ ItemKind::Struct(..)
1561                         | kind @ ItemKind::Union(..),
1562                     ..
1563                 }),
1564                 true,
1565             )
1566             | (Some(Item { kind, .. }), false) => {
1567                 // Likely missing type parameter.
1568                 if let Some(generics) = kind.generics() {
1569                     if span.overlaps(generics.span) {
1570                         // Avoid the following:
1571                         // error[E0405]: cannot find trait `A` in this scope
1572                         //  --> $DIR/typo-suggestion-named-underscore.rs:CC:LL
1573                         //   |
1574                         // L | fn foo<T: A>(x: T) {} // Shouldn't suggest underscore
1575                         //   |           ^- help: you might be missing a type parameter: `, A`
1576                         //   |           |
1577                         //   |           not found in this scope
1578                         return None;
1579                     }
1580                     let msg = "you might be missing a type parameter";
1581                     let (span, sugg) = if let [.., param] = &generics.params[..] {
1582                         let span = if let [.., bound] = &param.bounds[..] {
1583                             bound.span()
1584                         } else {
1585                             param.ident.span
1586                         };
1587                         (span, format!(", {}", ident))
1588                     } else {
1589                         (generics.span, format!("<{}>", ident))
1590                     };
1591                     // Do not suggest if this is coming from macro expansion.
1592                     if !span.from_expansion() {
1593                         return Some((
1594                             span.shrink_to_hi(),
1595                             msg,
1596                             sugg,
1597                             Applicability::MaybeIncorrect,
1598                         ));
1599                     }
1600                 }
1601             }
1602             _ => {}
1603         }
1604         None
1605     }
1606
1607     /// Given the target `label`, search the `rib_index`th label rib for similarly named labels,
1608     /// optionally returning the closest match and whether it is reachable.
1609     crate fn suggestion_for_label_in_rib(
1610         &self,
1611         rib_index: usize,
1612         label: Ident,
1613     ) -> Option<LabelSuggestion> {
1614         // Are ribs from this `rib_index` within scope?
1615         let within_scope = self.is_label_valid_from_rib(rib_index);
1616
1617         let rib = &self.label_ribs[rib_index];
1618         let names = rib
1619             .bindings
1620             .iter()
1621             .filter(|(id, _)| id.span.ctxt() == label.span.ctxt())
1622             .map(|(id, _)| id.name)
1623             .collect::<Vec<Symbol>>();
1624
1625         find_best_match_for_name(&names, label.name, None).map(|symbol| {
1626             // Upon finding a similar name, get the ident that it was from - the span
1627             // contained within helps make a useful diagnostic. In addition, determine
1628             // whether this candidate is within scope.
1629             let (ident, _) = rib.bindings.iter().find(|(ident, _)| ident.name == symbol).unwrap();
1630             (*ident, within_scope)
1631         })
1632     }
1633 }
1634
1635 impl<'tcx> LifetimeContext<'_, 'tcx> {
1636     crate fn report_missing_lifetime_specifiers(
1637         &self,
1638         span: Span,
1639         count: usize,
1640     ) -> DiagnosticBuilder<'tcx> {
1641         struct_span_err!(
1642             self.tcx.sess,
1643             span,
1644             E0106,
1645             "missing lifetime specifier{}",
1646             pluralize!(count)
1647         )
1648     }
1649
1650     crate fn emit_undeclared_lifetime_error(&self, lifetime_ref: &hir::Lifetime) {
1651         let mut err = struct_span_err!(
1652             self.tcx.sess,
1653             lifetime_ref.span,
1654             E0261,
1655             "use of undeclared lifetime name `{}`",
1656             lifetime_ref
1657         );
1658         err.span_label(lifetime_ref.span, "undeclared lifetime");
1659         let mut suggests_in_band = false;
1660         for missing in &self.missing_named_lifetime_spots {
1661             match missing {
1662                 MissingLifetimeSpot::Generics(generics) => {
1663                     let (span, sugg) = if let Some(param) = generics.params.iter().find(|p| {
1664                         !matches!(
1665                             p.kind,
1666                             hir::GenericParamKind::Type {
1667                                 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1668                                 ..
1669                             } | hir::GenericParamKind::Lifetime {
1670                                 kind: hir::LifetimeParamKind::Elided,
1671                             }
1672                         )
1673                     }) {
1674                         (param.span.shrink_to_lo(), format!("{}, ", lifetime_ref))
1675                     } else {
1676                         suggests_in_band = true;
1677                         (generics.span, format!("<{}>", lifetime_ref))
1678                     };
1679                     err.span_suggestion(
1680                         span,
1681                         &format!("consider introducing lifetime `{}` here", lifetime_ref),
1682                         sugg,
1683                         Applicability::MaybeIncorrect,
1684                     );
1685                 }
1686                 MissingLifetimeSpot::HigherRanked { span, span_type } => {
1687                     err.span_suggestion(
1688                         *span,
1689                         &format!(
1690                             "consider making the {} lifetime-generic with a new `{}` lifetime",
1691                             span_type.descr(),
1692                             lifetime_ref
1693                         ),
1694                         span_type.suggestion(&lifetime_ref.to_string()),
1695                         Applicability::MaybeIncorrect,
1696                     );
1697                     err.note(
1698                         "for more information on higher-ranked polymorphism, visit \
1699                             https://doc.rust-lang.org/nomicon/hrtb.html",
1700                     );
1701                 }
1702                 _ => {}
1703             }
1704         }
1705         if self.tcx.sess.is_nightly_build()
1706             && !self.tcx.features().in_band_lifetimes
1707             && suggests_in_band
1708         {
1709             err.help(
1710                 "if you want to experiment with in-band lifetime bindings, \
1711                     add `#![feature(in_band_lifetimes)]` to the crate attributes",
1712             );
1713         }
1714         err.emit();
1715     }
1716
1717     // FIXME(const_generics): This patches over a ICE caused by non-'static lifetimes in const
1718     // generics. We are disallowing this until we can decide on how we want to handle non-'static
1719     // lifetimes in const generics. See issue #74052 for discussion.
1720     crate fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &hir::Lifetime) {
1721         let mut err = struct_span_err!(
1722             self.tcx.sess,
1723             lifetime_ref.span,
1724             E0771,
1725             "use of non-static lifetime `{}` in const generic",
1726             lifetime_ref
1727         );
1728         err.note(
1729             "for more information, see issue #74052 \
1730             <https://github.com/rust-lang/rust/issues/74052>",
1731         );
1732         err.emit();
1733     }
1734
1735     crate fn is_trait_ref_fn_scope(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) -> bool {
1736         if let def::Res::Def(_, did) = trait_ref.trait_ref.path.res {
1737             if [
1738                 self.tcx.lang_items().fn_once_trait(),
1739                 self.tcx.lang_items().fn_trait(),
1740                 self.tcx.lang_items().fn_mut_trait(),
1741             ]
1742             .contains(&Some(did))
1743             {
1744                 let (span, span_type) = match &trait_ref.bound_generic_params {
1745                     [] => (trait_ref.span.shrink_to_lo(), ForLifetimeSpanType::BoundEmpty),
1746                     [.., bound] => (bound.span.shrink_to_hi(), ForLifetimeSpanType::BoundTail),
1747                 };
1748                 self.missing_named_lifetime_spots
1749                     .push(MissingLifetimeSpot::HigherRanked { span, span_type });
1750                 return true;
1751             }
1752         };
1753         false
1754     }
1755
1756     crate fn add_missing_lifetime_specifiers_label(
1757         &self,
1758         err: &mut DiagnosticBuilder<'_>,
1759         span: Span,
1760         count: usize,
1761         lifetime_names: &FxHashSet<Symbol>,
1762         lifetime_spans: Vec<Span>,
1763         params: &[ElisionFailureInfo],
1764     ) {
1765         let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok();
1766
1767         err.span_label(
1768             span,
1769             &format!(
1770                 "expected {} lifetime parameter{}",
1771                 if count == 1 { "named".to_string() } else { count.to_string() },
1772                 pluralize!(count)
1773             ),
1774         );
1775
1776         let suggest_existing = |err: &mut DiagnosticBuilder<'_>,
1777                                 name: &str,
1778                                 formatter: &dyn Fn(&str) -> String| {
1779             if let Some(MissingLifetimeSpot::HigherRanked { span: for_span, span_type }) =
1780                 self.missing_named_lifetime_spots.iter().rev().next()
1781             {
1782                 // When we have `struct S<'a>(&'a dyn Fn(&X) -> &X);` we want to not only suggest
1783                 // using `'a`, but also introduce the concept of HRLTs by suggesting
1784                 // `struct S<'a>(&'a dyn for<'b> Fn(&X) -> &'b X);`. (#72404)
1785                 let mut introduce_suggestion = vec![];
1786
1787                 let a_to_z_repeat_n = |n| {
1788                     (b'a'..=b'z').map(move |c| {
1789                         let mut s = '\''.to_string();
1790                         s.extend(std::iter::repeat(char::from(c)).take(n));
1791                         s
1792                     })
1793                 };
1794
1795                 // If all single char lifetime names are present, we wrap around and double the chars.
1796                 let lt_name = (1..)
1797                     .flat_map(a_to_z_repeat_n)
1798                     .find(|lt| !lifetime_names.contains(&Symbol::intern(&lt)))
1799                     .unwrap();
1800                 let msg = format!(
1801                     "consider making the {} lifetime-generic with a new `{}` lifetime",
1802                     span_type.descr(),
1803                     lt_name,
1804                 );
1805                 err.note(
1806                     "for more information on higher-ranked polymorphism, visit \
1807                     https://doc.rust-lang.org/nomicon/hrtb.html",
1808                 );
1809                 let for_sugg = span_type.suggestion(&lt_name);
1810                 for param in params {
1811                     if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(param.span) {
1812                         if snippet.starts_with('&') && !snippet.starts_with("&'") {
1813                             introduce_suggestion
1814                                 .push((param.span, format!("&{} {}", lt_name, &snippet[1..])));
1815                         } else if let Some(stripped) = snippet.strip_prefix("&'_ ") {
1816                             introduce_suggestion
1817                                 .push((param.span, format!("&{} {}", lt_name, stripped)));
1818                         }
1819                     }
1820                 }
1821                 introduce_suggestion.push((*for_span, for_sugg));
1822                 introduce_suggestion.push((span, formatter(&lt_name)));
1823                 err.multipart_suggestion(&msg, introduce_suggestion, Applicability::MaybeIncorrect);
1824             }
1825
1826             err.span_suggestion_verbose(
1827                 span,
1828                 &format!("consider using the `{}` lifetime", lifetime_names.iter().next().unwrap()),
1829                 formatter(name),
1830                 Applicability::MaybeIncorrect,
1831             );
1832         };
1833         let suggest_new = |err: &mut DiagnosticBuilder<'_>, sugg: &str| {
1834             for missing in self.missing_named_lifetime_spots.iter().rev() {
1835                 let mut introduce_suggestion = vec![];
1836                 let msg;
1837                 let should_break;
1838                 introduce_suggestion.push(match missing {
1839                     MissingLifetimeSpot::Generics(generics) => {
1840                         if generics.span == DUMMY_SP {
1841                             // Account for malformed generics in the HIR. This shouldn't happen,
1842                             // but if we make a mistake elsewhere, mainly by keeping something in
1843                             // `missing_named_lifetime_spots` that we shouldn't, like associated
1844                             // `const`s or making a mistake in the AST lowering we would provide
1845                             // non-sensical suggestions. Guard against that by skipping these.
1846                             // (#74264)
1847                             continue;
1848                         }
1849                         msg = "consider introducing a named lifetime parameter".to_string();
1850                         should_break = true;
1851                         if let Some(param) = generics.params.iter().find(|p| {
1852                             !matches!(
1853                                 p.kind,
1854                                 hir::GenericParamKind::Type {
1855                                     synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1856                                     ..
1857                                 }
1858                             )
1859                         }) {
1860                             (param.span.shrink_to_lo(), "'a, ".to_string())
1861                         } else {
1862                             (generics.span, "<'a>".to_string())
1863                         }
1864                     }
1865                     MissingLifetimeSpot::HigherRanked { span, span_type } => {
1866                         msg = format!(
1867                             "consider making the {} lifetime-generic with a new `'a` lifetime",
1868                             span_type.descr(),
1869                         );
1870                         should_break = false;
1871                         err.note(
1872                             "for more information on higher-ranked polymorphism, visit \
1873                             https://doc.rust-lang.org/nomicon/hrtb.html",
1874                         );
1875                         (*span, span_type.suggestion("'a"))
1876                     }
1877                     MissingLifetimeSpot::Static => {
1878                         let (span, sugg) = match snippet.as_deref() {
1879                             Some("&") => (span.shrink_to_hi(), "'static ".to_owned()),
1880                             Some("'_") => (span, "'static".to_owned()),
1881                             Some(snippet) if !snippet.ends_with('>') => {
1882                                 if snippet == "" {
1883                                     (
1884                                         span,
1885                                         std::iter::repeat("'static")
1886                                             .take(count)
1887                                             .collect::<Vec<_>>()
1888                                             .join(", "),
1889                                     )
1890                                 } else {
1891                                     (
1892                                         span.shrink_to_hi(),
1893                                         format!(
1894                                             "<{}>",
1895                                             std::iter::repeat("'static")
1896                                                 .take(count)
1897                                                 .collect::<Vec<_>>()
1898                                                 .join(", ")
1899                                         ),
1900                                     )
1901                                 }
1902                             }
1903                             _ => continue,
1904                         };
1905                         err.span_suggestion_verbose(
1906                             span,
1907                             "consider using the `'static` lifetime",
1908                             sugg.to_string(),
1909                             Applicability::MaybeIncorrect,
1910                         );
1911                         continue;
1912                     }
1913                 });
1914                 for param in params {
1915                     if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(param.span) {
1916                         if snippet.starts_with('&') && !snippet.starts_with("&'") {
1917                             introduce_suggestion
1918                                 .push((param.span, format!("&'a {}", &snippet[1..])));
1919                         } else if let Some(stripped) = snippet.strip_prefix("&'_ ") {
1920                             introduce_suggestion.push((param.span, format!("&'a {}", &stripped)));
1921                         }
1922                     }
1923                 }
1924                 introduce_suggestion.push((span, sugg.to_string()));
1925                 err.multipart_suggestion(&msg, introduce_suggestion, Applicability::MaybeIncorrect);
1926                 if should_break {
1927                     break;
1928                 }
1929             }
1930         };
1931
1932         let lifetime_names: Vec<_> = lifetime_names.iter().collect();
1933         match (&lifetime_names[..], snippet.as_deref()) {
1934             ([name], Some("&")) => {
1935                 suggest_existing(err, &name.as_str()[..], &|name| format!("&{} ", name));
1936             }
1937             ([name], Some("'_")) => {
1938                 suggest_existing(err, &name.as_str()[..], &|n| n.to_string());
1939             }
1940             ([name], Some("")) => {
1941                 suggest_existing(err, &name.as_str()[..], &|n| format!("{}, ", n).repeat(count));
1942             }
1943             ([name], Some(snippet)) if !snippet.ends_with('>') => {
1944                 let f = |name: &str| {
1945                     format!(
1946                         "{}<{}>",
1947                         snippet,
1948                         std::iter::repeat(name.to_string())
1949                             .take(count)
1950                             .collect::<Vec<_>>()
1951                             .join(", ")
1952                     )
1953                 };
1954                 suggest_existing(err, &name.as_str()[..], &f);
1955             }
1956             ([], Some("&")) if count == 1 => {
1957                 suggest_new(err, "&'a ");
1958             }
1959             ([], Some("'_")) if count == 1 => {
1960                 suggest_new(err, "'a");
1961             }
1962             ([], Some(snippet)) if !snippet.ends_with('>') => {
1963                 if snippet == "" {
1964                     // This happens when we have `type Bar<'a> = Foo<T>` where we point at the space
1965                     // before `T`. We will suggest `type Bar<'a> = Foo<'a, T>`.
1966                     suggest_new(
1967                         err,
1968                         &std::iter::repeat("'a, ").take(count).collect::<Vec<_>>().join(""),
1969                     );
1970                 } else {
1971                     suggest_new(
1972                         err,
1973                         &format!(
1974                             "{}<{}>",
1975                             snippet,
1976                             std::iter::repeat("'a").take(count).collect::<Vec<_>>().join(", ")
1977                         ),
1978                     );
1979                 }
1980             }
1981             (lts, ..) if lts.len() > 1 => {
1982                 err.span_note(lifetime_spans, "these named lifetimes are available to use");
1983                 if Some("") == snippet.as_deref() {
1984                     // This happens when we have `Foo<T>` where we point at the space before `T`,
1985                     // but this can be confusing so we give a suggestion with placeholders.
1986                     err.span_suggestion_verbose(
1987                         span,
1988                         "consider using one of the available lifetimes here",
1989                         "'lifetime, ".repeat(count),
1990                         Applicability::HasPlaceholders,
1991                     );
1992                 }
1993             }
1994             _ => {}
1995         }
1996     }
1997
1998     /// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
1999     /// This function will emit an error if `const_generics` is not enabled, the body identified by
2000     /// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
2001     crate fn maybe_emit_forbidden_non_static_lifetime_error(
2002         &self,
2003         body_id: hir::BodyId,
2004         lifetime_ref: &'tcx hir::Lifetime,
2005     ) {
2006         let is_anon_const = matches!(
2007             self.tcx.def_kind(self.tcx.hir().body_owner_def_id(body_id)),
2008             hir::def::DefKind::AnonConst
2009         );
2010         let is_allowed_lifetime = matches!(
2011             lifetime_ref.name,
2012             hir::LifetimeName::Implicit | hir::LifetimeName::Static | hir::LifetimeName::Underscore
2013         );
2014
2015         if !self.tcx.lazy_normalization() && is_anon_const && !is_allowed_lifetime {
2016             feature_err(
2017                 &self.tcx.sess.parse_sess,
2018                 sym::const_generics,
2019                 lifetime_ref.span,
2020                 "a non-static lifetime is not allowed in a `const`",
2021             )
2022             .emit();
2023         }
2024     }
2025 }