compiler/rustc_hir_typeck/src/method/suggest.rs

   1 //! Give useful errors and suggestions to users when an item can't be
   2 //! found or is otherwise invalid.
   3
   4 use crate::errors;
   5 use crate::FnCtxt;
   6 use rustc_ast::ast::Mutability;
   7 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   8 use rustc_errors::{
   9     pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
  10     MultiSpan,
  11 };
  12 use rustc_hir as hir;
  13 use rustc_hir::def::DefKind;
  14 use rustc_hir::def_id::DefId;
  15 use rustc_hir::lang_items::LangItem;
  16 use rustc_hir::{ExprKind, Node, QPath};
  17 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  18 use rustc_middle::traits::util::supertraits;
  19 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
  20 use rustc_middle::ty::print::with_crate_prefix;
  21 use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeVisitable};
  22 use rustc_middle::ty::{IsSuggestable, ToPolyTraitRef};
  23 use rustc_span::symbol::{kw, sym, Ident};
  24 use rustc_span::Symbol;
  25 use rustc_span::{lev_distance, source_map, ExpnKind, FileName, MacroKind, Span};
  26 use rustc_trait_selection::traits::error_reporting::on_unimplemented::TypeErrCtxtExt as _;
  27 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
  28 use rustc_trait_selection::traits::{
  29     FulfillmentError, Obligation, ObligationCause, ObligationCauseCode, OnUnimplementedNote,
  30 };
  31
  32 use std::cmp::Ordering;
  33 use std::iter;
  34
  35 use super::probe::{AutorefOrPtrAdjustment, IsSuggestion, Mode, ProbeScope};
  36 use super::{CandidateSource, MethodError, NoMatchData};
  37
  38 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  39     fn is_fn_ty(&self, ty: Ty<'tcx>, span: Span) -> bool {
  40         let tcx = self.tcx;
  41         match ty.kind() {
  42             // Not all of these (e.g., unsafe fns) implement `FnOnce`,
  43             // so we look for these beforehand.
  44             ty::Closure(..) | ty::FnDef(..) | ty::FnPtr(_) => true,
  45             // If it's not a simple function, look for things which implement `FnOnce`.
  46             _ => {
  47                 let Some(fn_once) = tcx.lang_items().fn_once_trait() else {
  48                     return false;
  49                 };
  50
  51                 // This conditional prevents us from asking to call errors and unresolved types.
  52                 // It might seem that we can use `predicate_must_hold_modulo_regions`,
  53                 // but since a Dummy binder is used to fill in the FnOnce trait's arguments,
  54                 // type resolution always gives a "maybe" here.
  55                 if self.autoderef(span, ty).any(|(ty, _)| {
  56                     info!("check deref {:?} error", ty);
  57                     matches!(ty.kind(), ty::Error(_) | ty::Infer(_))
  58                 }) {
  59                     return false;
  60                 }
  61
  62                 self.autoderef(span, ty).any(|(ty, _)| {
  63                     info!("check deref {:?} impl FnOnce", ty);
  64                     self.probe(|_| {
  65                         let fn_once_substs = tcx.mk_substs_trait(
  66                             ty,
  67                             &[self
  68                                 .next_ty_var(TypeVariableOrigin {
  69                                     kind: TypeVariableOriginKind::MiscVariable,
  70                                     span,
  71                                 })
  72                                 .into()],
  73                         );
  74                         let trait_ref = ty::TraitRef::new(fn_once, fn_once_substs);
  75                         let poly_trait_ref = ty::Binder::dummy(trait_ref);
  76                         let obligation = Obligation::misc(
  77                             span,
  78                             self.body_id,
  79                             self.param_env,
  80                             poly_trait_ref.without_const().to_predicate(tcx),
  81                         );
  82                         self.predicate_may_hold(&obligation)
  83                     })
  84                 })
  85             }
  86         }
  87     }
  88
  89     fn is_slice_ty(&self, ty: Ty<'tcx>, span: Span) -> bool {
  90         self.autoderef(span, ty).any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..)))
  91     }
  92
  93     pub fn report_method_error(
  94         &self,
  95         mut span: Span,
  96         rcvr_ty: Ty<'tcx>,
  97         item_name: Ident,
  98         source: SelfSource<'tcx>,
  99         error: MethodError<'tcx>,
 100         args: Option<(&'tcx hir::Expr<'tcx>, &'tcx [hir::Expr<'tcx>])>,
 101     ) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> {
 102         // Avoid suggestions when we don't know what's going on.
 103         if rcvr_ty.references_error() {
 104             return None;
 105         }
 106
 107         let report_candidates = |span: Span,
 108                                  err: &mut Diagnostic,
 109                                  mut sources: Vec<CandidateSource>,
 110                                  sugg_span: Span| {
 111             sources.sort();
 112             sources.dedup();
 113             // Dynamic limit to avoid hiding just one candidate, which is silly.
 114             let limit = if sources.len() == 5 { 5 } else { 4 };
 115
 116             for (idx, source) in sources.iter().take(limit).enumerate() {
 117                 match *source {
 118                     CandidateSource::Impl(impl_did) => {
 119                         // Provide the best span we can. Use the item, if local to crate, else
 120                         // the impl, if local to crate (item may be defaulted), else nothing.
 121                         let Some(item) = self.associated_value(impl_did, item_name).or_else(|| {
 122                             let impl_trait_ref = self.tcx.impl_trait_ref(impl_did)?;
 123                             self.associated_value(impl_trait_ref.def_id, item_name)
 124                         }) else {
 125                             continue;
 126                         };
 127
 128                         let note_span = if item.def_id.is_local() {
 129                             Some(self.tcx.def_span(item.def_id))
 130                         } else if impl_did.is_local() {
 131                             Some(self.tcx.def_span(impl_did))
 132                         } else {
 133                             None
 134                         };
 135
 136                         let impl_ty = self.tcx.at(span).type_of(impl_did);
 137
 138                         let insertion = match self.tcx.impl_trait_ref(impl_did) {
 139                             None => String::new(),
 140                             Some(trait_ref) => format!(
 141                                 " of the trait `{}`",
 142                                 self.tcx.def_path_str(trait_ref.def_id)
 143                             ),
 144                         };
 145
 146                         let (note_str, idx) = if sources.len() > 1 {
 147                             (
 148                                 format!(
 149                                     "candidate #{} is defined in an impl{} for the type `{}`",
 150                                     idx + 1,
 151                                     insertion,
 152                                     impl_ty,
 153                                 ),
 154                                 Some(idx + 1),
 155                             )
 156                         } else {
 157                             (
 158                                 format!(
 159                                     "the candidate is defined in an impl{} for the type `{}`",
 160                                     insertion, impl_ty,
 161                                 ),
 162                                 None,
 163                             )
 164                         };
 165                         if let Some(note_span) = note_span {
 166                             // We have a span pointing to the method. Show note with snippet.
 167                             err.span_note(note_span, &note_str);
 168                         } else {
 169                             err.note(&note_str);
 170                         }
 171                         if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_did) {
 172                             let path = self.tcx.def_path_str(trait_ref.def_id);
 173
 174                             let ty = match item.kind {
 175                                 ty::AssocKind::Const | ty::AssocKind::Type => rcvr_ty,
 176                                 ty::AssocKind::Fn => self
 177                                     .tcx
 178                                     .fn_sig(item.def_id)
 179                                     .inputs()
 180                                     .skip_binder()
 181                                     .get(0)
 182                                     .filter(|ty| ty.is_region_ptr() && !rcvr_ty.is_region_ptr())
 183                                     .copied()
 184                                     .unwrap_or(rcvr_ty),
 185                             };
 186                             print_disambiguation_help(
 187                                 item_name,
 188                                 args,
 189                                 err,
 190                                 path,
 191                                 ty,
 192                                 item.kind,
 193                                 item.def_id,
 194                                 sugg_span,
 195                                 idx,
 196                                 self.tcx.sess.source_map(),
 197                                 item.fn_has_self_parameter,
 198                             );
 199                         }
 200                     }
 201                     CandidateSource::Trait(trait_did) => {
 202                         let Some(item) = self.associated_value(trait_did, item_name) else { continue };
 203                         let item_span = self.tcx.def_span(item.def_id);
 204                         let idx = if sources.len() > 1 {
 205                             let msg = &format!(
 206                                 "candidate #{} is defined in the trait `{}`",
 207                                 idx + 1,
 208                                 self.tcx.def_path_str(trait_did)
 209                             );
 210                             err.span_note(item_span, msg);
 211                             Some(idx + 1)
 212                         } else {
 213                             let msg = &format!(
 214                                 "the candidate is defined in the trait `{}`",
 215                                 self.tcx.def_path_str(trait_did)
 216                             );
 217                             err.span_note(item_span, msg);
 218                             None
 219                         };
 220                         let path = self.tcx.def_path_str(trait_did);
 221                         print_disambiguation_help(
 222                             item_name,
 223                             args,
 224                             err,
 225                             path,
 226                             rcvr_ty,
 227                             item.kind,
 228                             item.def_id,
 229                             sugg_span,
 230                             idx,
 231                             self.tcx.sess.source_map(),
 232                             item.fn_has_self_parameter,
 233                         );
 234                     }
 235                 }
 236             }
 237             if sources.len() > limit {
 238                 err.note(&format!("and {} others", sources.len() - limit));
 239             }
 240         };
 241
 242         let sugg_span = if let SelfSource::MethodCall(expr) = source {
 243             // Given `foo.bar(baz)`, `expr` is `bar`, but we want to point to the whole thing.
 244             self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id)).span
 245         } else {
 246             span
 247         };
 248
 249         match error {
 250             MethodError::NoMatch(NoMatchData {
 251                 static_candidates: static_sources,
 252                 unsatisfied_predicates,
 253                 out_of_scope_traits,
 254                 lev_candidate,
 255                 mode,
 256             }) => {
 257                 let tcx = self.tcx;
 258
 259                 let actual = self.resolve_vars_if_possible(rcvr_ty);
 260                 let ty_str = self.ty_to_string(actual);
 261                 let is_method = mode == Mode::MethodCall;
 262                 let item_kind = if is_method {
 263                     "method"
 264                 } else if actual.is_enum() {
 265                     "variant or associated item"
 266                 } else {
 267                     match (item_name.as_str().chars().next(), actual.is_fresh_ty()) {
 268                         (Some(name), false) if name.is_lowercase() => "function or associated item",
 269                         (Some(_), false) => "associated item",
 270                         (Some(_), true) | (None, false) => "variant or associated item",
 271                         (None, true) => "variant",
 272                     }
 273                 };
 274
 275                 if self.suggest_wrapping_range_with_parens(
 276                     tcx, actual, source, span, item_name, &ty_str,
 277                 ) || self.suggest_constraining_numerical_ty(
 278                     tcx, actual, source, span, item_kind, item_name, &ty_str,
 279                 ) {
 280                     return None;
 281                 }
 282
 283                 span = item_name.span;
 284
 285                 // Don't show generic arguments when the method can't be found in any implementation (#81576).
 286                 let mut ty_str_reported = ty_str.clone();
 287                 if let ty::Adt(_, generics) = actual.kind() {
 288                     if generics.len() > 0 {
 289                         let mut autoderef = self.autoderef(span, actual);
 290                         let candidate_found = autoderef.any(|(ty, _)| {
 291                             if let ty::Adt(adt_deref, _) = ty.kind() {
 292                                 self.tcx
 293                                     .inherent_impls(adt_deref.did())
 294                                     .iter()
 295                                     .filter_map(|def_id| self.associated_value(*def_id, item_name))
 296                                     .count()
 297                                     >= 1
 298                             } else {
 299                                 false
 300                             }
 301                         });
 302                         let has_deref = autoderef.step_count() > 0;
 303                         if !candidate_found && !has_deref && unsatisfied_predicates.is_empty() {
 304                             if let Some((path_string, _)) = ty_str.split_once('<') {
 305                                 ty_str_reported = path_string.to_string();
 306                             }
 307                         }
 308                     }
 309                 }
 310
 311                 let mut err = struct_span_err!(
 312                     tcx.sess,
 313                     span,
 314                     E0599,
 315                     "no {} named `{}` found for {} `{}` in the current scope",
 316                     item_kind,
 317                     item_name,
 318                     actual.prefix_string(self.tcx),
 319                     ty_str_reported,
 320                 );
 321                 if actual.references_error() {
 322                     err.downgrade_to_delayed_bug();
 323                 }
 324
 325                 if let Mode::MethodCall = mode && let SelfSource::MethodCall(cal) = source {
 326                     self.suggest_await_before_method(
 327                         &mut err, item_name, actual, cal, span,
 328                     );
 329                 }
 330                 if let Some(span) = tcx.resolutions(()).confused_type_with_std_module.get(&span) {
 331                     err.span_suggestion(
 332                         span.shrink_to_lo(),
 333                         "you are looking for the module in `std`, not the primitive type",
 334                         "std::",
 335                         Applicability::MachineApplicable,
 336                     );
 337                 }
 338                 if let ty::RawPtr(_) = &actual.kind() {
 339                     err.note(
 340                         "try using `<*const T>::as_ref()` to get a reference to the \
 341                          type behind the pointer: https://doc.rust-lang.org/std/\
 342                          primitive.pointer.html#method.as_ref",
 343                     );
 344                     err.note(
 345                         "using `<*const T>::as_ref()` on a pointer which is unaligned or points \
 346                          to invalid or uninitialized memory is undefined behavior",
 347                     );
 348                 }
 349
 350                 let ty_span = match actual.kind() {
 351                     ty::Param(param_type) => {
 352                         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
 353                         let type_param = generics.type_param(param_type, self.tcx);
 354                         Some(self.tcx.def_span(type_param.def_id))
 355                     }
 356                     ty::Adt(def, _) if def.did().is_local() => Some(tcx.def_span(def.did())),
 357                     _ => None,
 358                 };
 359
 360                 if let Some(span) = ty_span {
 361                     err.span_label(
 362                         span,
 363                         format!(
 364                             "{item_kind} `{item_name}` not found for this {}",
 365                             actual.prefix_string(self.tcx)
 366                         ),
 367                     );
 368                 }
 369
 370                 if let SelfSource::MethodCall(rcvr_expr) = source {
 371                     self.suggest_fn_call(&mut err, rcvr_expr, rcvr_ty, |output_ty| {
 372                         let call_expr = self
 373                             .tcx
 374                             .hir()
 375                             .expect_expr(self.tcx.hir().get_parent_node(rcvr_expr.hir_id));
 376                         let probe = self.lookup_probe(
 377                             span,
 378                             item_name,
 379                             output_ty,
 380                             call_expr,
 381                             ProbeScope::AllTraits,
 382                         );
 383                         probe.is_ok()
 384                     });
 385                 }
 386
 387                 let mut custom_span_label = false;
 388
 389                 if !static_sources.is_empty() {
 390                     err.note(
 391                         "found the following associated functions; to be used as methods, \
 392                          functions must have a `self` parameter",
 393                     );
 394                     err.span_label(span, "this is an associated function, not a method");
 395                     custom_span_label = true;
 396                 }
 397                 if static_sources.len() == 1 {
 398                     let ty_str =
 399                         if let Some(CandidateSource::Impl(impl_did)) = static_sources.get(0) {
 400                             // When the "method" is resolved through dereferencing, we really want the
 401                             // original type that has the associated function for accurate suggestions.
 402                             // (#61411)
 403                             let ty = tcx.at(span).type_of(*impl_did);
 404                             match (&ty.peel_refs().kind(), &actual.peel_refs().kind()) {
 405                                 (ty::Adt(def, _), ty::Adt(def_actual, _)) if def == def_actual => {
 406                                     // Use `actual` as it will have more `substs` filled in.
 407                                     self.ty_to_value_string(actual.peel_refs())
 408                                 }
 409                                 _ => self.ty_to_value_string(ty.peel_refs()),
 410                             }
 411                         } else {
 412                             self.ty_to_value_string(actual.peel_refs())
 413                         };
 414                     if let SelfSource::MethodCall(expr) = source {
 415                         err.span_suggestion(
 416                             expr.span.to(span),
 417                             "use associated function syntax instead",
 418                             format!("{}::{}", ty_str, item_name),
 419                             Applicability::MachineApplicable,
 420                         );
 421                     } else {
 422                         err.help(&format!("try with `{}::{}`", ty_str, item_name,));
 423                     }
 424
 425                     report_candidates(span, &mut err, static_sources, sugg_span);
 426                 } else if static_sources.len() > 1 {
 427                     report_candidates(span, &mut err, static_sources, sugg_span);
 428                 }
 429
 430                 let mut bound_spans = vec![];
 431                 let mut restrict_type_params = false;
 432                 let mut unsatisfied_bounds = false;
 433                 if item_name.name == sym::count && self.is_slice_ty(actual, span) {
 434                     let msg = "consider using `len` instead";
 435                     if let SelfSource::MethodCall(_expr) = source {
 436                         err.span_suggestion_short(
 437                             span,
 438                             msg,
 439                             "len",
 440                             Applicability::MachineApplicable,
 441                         );
 442                     } else {
 443                         err.span_label(span, msg);
 444                     }
 445                     if let Some(iterator_trait) = self.tcx.get_diagnostic_item(sym::Iterator) {
 446                         let iterator_trait = self.tcx.def_path_str(iterator_trait);
 447                         err.note(&format!("`count` is defined on `{iterator_trait}`, which `{actual}` does not implement"));
 448                     }
 449                 } else if !unsatisfied_predicates.is_empty() {
 450                     let mut type_params = FxHashMap::default();
 451
 452                     // Pick out the list of unimplemented traits on the receiver.
 453                     // This is used for custom error messages with the `#[rustc_on_unimplemented]` attribute.
 454                     let mut unimplemented_traits = FxHashMap::default();
 455                     let mut unimplemented_traits_only = true;
 456                     for (predicate, _parent_pred, cause) in &unsatisfied_predicates {
 457                         if let (ty::PredicateKind::Trait(p), Some(cause)) =
 458                             (predicate.kind().skip_binder(), cause.as_ref())
 459                         {
 460                             if p.trait_ref.self_ty() != rcvr_ty {
 461                                 // This is necessary, not just to keep the errors clean, but also
 462                                 // because our derived obligations can wind up with a trait ref that
 463                                 // requires a different param_env to be correctly compared.
 464                                 continue;
 465                             }
 466                             unimplemented_traits.entry(p.trait_ref.def_id).or_insert((
 467                                 predicate.kind().rebind(p.trait_ref),
 468                                 Obligation {
 469                                     cause: cause.clone(),
 470                                     param_env: self.param_env,
 471                                     predicate: *predicate,
 472                                     recursion_depth: 0,
 473                                 },
 474                             ));
 475                         }
 476                     }
 477
 478                     // Make sure that, if any traits other than the found ones were involved,
 479                     // we don't don't report an unimplemented trait.
 480                     // We don't want to say that `iter::Cloned` is not an iterator, just
 481                     // because of some non-Clone item being iterated over.
 482                     for (predicate, _parent_pred, _cause) in &unsatisfied_predicates {
 483                         match predicate.kind().skip_binder() {
 484                             ty::PredicateKind::Trait(p)
 485                                 if unimplemented_traits.contains_key(&p.trait_ref.def_id) => {}
 486                             _ => {
 487                                 unimplemented_traits_only = false;
 488                                 break;
 489                             }
 490                         }
 491                     }
 492
 493                     let mut collect_type_param_suggestions =
 494                         |self_ty: Ty<'tcx>, parent_pred: ty::Predicate<'tcx>, obligation: &str| {
 495                             // We don't care about regions here, so it's fine to skip the binder here.
 496                             if let (ty::Param(_), ty::PredicateKind::Trait(p)) =
 497                                 (self_ty.kind(), parent_pred.kind().skip_binder())
 498                             {
 499                                 let node = match p.trait_ref.self_ty().kind() {
 500                                     ty::Param(_) => {
 501                                         // Account for `fn` items like in `issue-35677.rs` to
 502                                         // suggest restricting its type params.
 503                                         let did = self.tcx.hir().body_owner_def_id(hir::BodyId {
 504                                             hir_id: self.body_id,
 505                                         });
 506                                         Some(
 507                                             self.tcx
 508                                                 .hir()
 509                                                 .get(self.tcx.hir().local_def_id_to_hir_id(did)),
 510                                         )
 511                                     }
 512                                     ty::Adt(def, _) => def.did().as_local().map(|def_id| {
 513                                         self.tcx
 514                                             .hir()
 515                                             .get(self.tcx.hir().local_def_id_to_hir_id(def_id))
 516                                     }),
 517                                     _ => None,
 518                                 };
 519                                 if let Some(hir::Node::Item(hir::Item { kind, .. })) = node {
 520                                     if let Some(g) = kind.generics() {
 521                                         let key = (
 522                                             g.tail_span_for_predicate_suggestion(),
 523                                             g.add_where_or_trailing_comma(),
 524                                         );
 525                                         type_params
 526                                             .entry(key)
 527                                             .or_insert_with(FxHashSet::default)
 528                                             .insert(obligation.to_owned());
 529                                     }
 530                                 }
 531                             }
 532                         };
 533                     let mut bound_span_label = |self_ty: Ty<'_>, obligation: &str, quiet: &str| {
 534                         let msg = format!(
 535                             "doesn't satisfy `{}`",
 536                             if obligation.len() > 50 { quiet } else { obligation }
 537                         );
 538                         match &self_ty.kind() {
 539                             // Point at the type that couldn't satisfy the bound.
 540                             ty::Adt(def, _) => {
 541                                 bound_spans.push((self.tcx.def_span(def.did()), msg))
 542                             }
 543                             // Point at the trait object that couldn't satisfy the bound.
 544                             ty::Dynamic(preds, _, _) => {
 545                                 for pred in preds.iter() {
 546                                     match pred.skip_binder() {
 547                                         ty::ExistentialPredicate::Trait(tr) => bound_spans
 548                                             .push((self.tcx.def_span(tr.def_id), msg.clone())),
 549                                         ty::ExistentialPredicate::Projection(_)
 550                                         | ty::ExistentialPredicate::AutoTrait(_) => {}
 551                                     }
 552                                 }
 553                             }
 554                             // Point at the closure that couldn't satisfy the bound.
 555                             ty::Closure(def_id, _) => bound_spans.push((
 556                                 tcx.def_span(*def_id),
 557                                 format!("doesn't satisfy `{}`", quiet),
 558                             )),
 559                             _ => {}
 560                         }
 561                     };
 562                     let mut format_pred = |pred: ty::Predicate<'tcx>| {
 563                         let bound_predicate = pred.kind();
 564                         match bound_predicate.skip_binder() {
 565                             ty::PredicateKind::Projection(pred) => {
 566                                 let pred = bound_predicate.rebind(pred);
 567                                 // `<Foo as Iterator>::Item = String`.
 568                                 let projection_ty = pred.skip_binder().projection_ty;
 569
 570                                 let substs_with_infer_self = tcx.mk_substs(
 571                                     iter::once(tcx.mk_ty_var(ty::TyVid::from_u32(0)).into())
 572                                         .chain(projection_ty.substs.iter().skip(1)),
 573                                 );
 574
 575                                 let quiet_projection_ty = ty::ProjectionTy {
 576                                     substs: substs_with_infer_self,
 577                                     item_def_id: projection_ty.item_def_id,
 578                                 };
 579
 580                                 let term = pred.skip_binder().term;
 581
 582                                 let obligation = format!("{} = {}", projection_ty, term);
 583                                 let quiet = format!("{} = {}", quiet_projection_ty, term);
 584
 585                                 bound_span_label(projection_ty.self_ty(), &obligation, &quiet);
 586                                 Some((obligation, projection_ty.self_ty()))
 587                             }
 588                             ty::PredicateKind::Trait(poly_trait_ref) => {
 589                                 let p = poly_trait_ref.trait_ref;
 590                                 let self_ty = p.self_ty();
 591                                 let path = p.print_only_trait_path();
 592                                 let obligation = format!("{}: {}", self_ty, path);
 593                                 let quiet = format!("_: {}", path);
 594                                 bound_span_label(self_ty, &obligation, &quiet);
 595                                 Some((obligation, self_ty))
 596                             }
 597                             _ => None,
 598                         }
 599                     };
 600
 601                     // Find all the requirements that come from a local `impl` block.
 602                     let mut skip_list: FxHashSet<_> = Default::default();
 603                     let mut spanned_predicates: FxHashMap<MultiSpan, _> = Default::default();
 604                     for (data, p, parent_p, impl_def_id, cause) in unsatisfied_predicates
 605                         .iter()
 606                         .filter_map(|(p, parent, c)| c.as_ref().map(|c| (p, parent, c)))
 607                         .filter_map(|(p, parent, c)| match c.code() {
 608                             ObligationCauseCode::ImplDerivedObligation(ref data) => {
 609                                 Some((&data.derived, p, parent, data.impl_def_id, data))
 610                             }
 611                             _ => None,
 612                         })
 613                     {
 614                         let parent_trait_ref = data.parent_trait_pred;
 615                         let path = parent_trait_ref.print_modifiers_and_trait_path();
 616                         let tr_self_ty = parent_trait_ref.skip_binder().self_ty();
 617                         let unsatisfied_msg = "unsatisfied trait bound introduced here";
 618                         let derive_msg =
 619                             "unsatisfied trait bound introduced in this `derive` macro";
 620                         match self.tcx.hir().get_if_local(impl_def_id) {
 621                             // Unmet obligation comes from a `derive` macro, point at it once to
 622                             // avoid multiple span labels pointing at the same place.
 623                             Some(Node::Item(hir::Item {
 624                                 kind: hir::ItemKind::Trait(..),
 625                                 ident,
 626                                 ..
 627                             })) if matches!(
 628                                 ident.span.ctxt().outer_expn_data().kind,
 629                                 ExpnKind::Macro(MacroKind::Derive, _)
 630                             ) =>
 631                             {
 632                                 let span = ident.span.ctxt().outer_expn_data().call_site;
 633                                 let mut spans: MultiSpan = span.into();
 634                                 spans.push_span_label(span, derive_msg);
 635                                 let entry = spanned_predicates.entry(spans);
 636                                 entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p);
 637                             }
 638
 639                             Some(Node::Item(hir::Item {
 640                                 kind: hir::ItemKind::Impl(hir::Impl { of_trait, self_ty, .. }),
 641                                 ..
 642                             })) if matches!(
 643                                 self_ty.span.ctxt().outer_expn_data().kind,
 644                                 ExpnKind::Macro(MacroKind::Derive, _)
 645                             ) || matches!(
 646                                 of_trait.as_ref().map(|t| t
 647                                     .path
 648                                     .span
 649                                     .ctxt()
 650                                     .outer_expn_data()
 651                                     .kind),
 652                                 Some(ExpnKind::Macro(MacroKind::Derive, _))
 653                             ) =>
 654                             {
 655                                 let span = self_ty.span.ctxt().outer_expn_data().call_site;
 656                                 let mut spans: MultiSpan = span.into();
 657                                 spans.push_span_label(span, derive_msg);
 658                                 let entry = spanned_predicates.entry(spans);
 659                                 entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p);
 660                             }
 661
 662                             // Unmet obligation coming from a `trait`.
 663                             Some(Node::Item(hir::Item {
 664                                 kind: hir::ItemKind::Trait(..),
 665                                 ident,
 666                                 span: item_span,
 667                                 ..
 668                             })) if !matches!(
 669                                 ident.span.ctxt().outer_expn_data().kind,
 670                                 ExpnKind::Macro(MacroKind::Derive, _)
 671                             ) =>
 672                             {
 673                                 if let Some(pred) = parent_p {
 674                                     // Done to add the "doesn't satisfy" `span_label`.
 675                                     let _ = format_pred(*pred);
 676                                 }
 677                                 skip_list.insert(p);
 678                                 let mut spans = if cause.span != *item_span {
 679                                     let mut spans: MultiSpan = cause.span.into();
 680                                     spans.push_span_label(cause.span, unsatisfied_msg);
 681                                     spans
 682                                 } else {
 683                                     ident.span.into()
 684                                 };
 685                                 spans.push_span_label(ident.span, "in this trait");
 686                                 let entry = spanned_predicates.entry(spans);
 687                                 entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p);
 688                             }
 689
 690                             // Unmet obligation coming from an `impl`.
 691                             Some(Node::Item(hir::Item {
 692                                 kind:
 693                                     hir::ItemKind::Impl(hir::Impl {
 694                                         of_trait, self_ty, generics, ..
 695                                     }),
 696                                 span: item_span,
 697                                 ..
 698                             })) if !matches!(
 699                                 self_ty.span.ctxt().outer_expn_data().kind,
 700                                 ExpnKind::Macro(MacroKind::Derive, _)
 701                             ) && !matches!(
 702                                 of_trait.as_ref().map(|t| t
 703                                     .path
 704                                     .span
 705                                     .ctxt()
 706                                     .outer_expn_data()
 707                                     .kind),
 708                                 Some(ExpnKind::Macro(MacroKind::Derive, _))
 709                             ) =>
 710                             {
 711                                 let sized_pred =
 712                                     unsatisfied_predicates.iter().any(|(pred, _, _)| {
 713                                         match pred.kind().skip_binder() {
 714                                             ty::PredicateKind::Trait(pred) => {
 715                                                 Some(pred.def_id())
 716                                                     == self.tcx.lang_items().sized_trait()
 717                                                     && pred.polarity == ty::ImplPolarity::Positive
 718                                             }
 719                                             _ => false,
 720                                         }
 721                                     });
 722                                 for param in generics.params {
 723                                     if param.span == cause.span && sized_pred {
 724                                         let (sp, sugg) = match param.colon_span {
 725                                             Some(sp) => (sp.shrink_to_hi(), " ?Sized +"),
 726                                             None => (param.span.shrink_to_hi(), ": ?Sized"),
 727                                         };
 728                                         err.span_suggestion_verbose(
 729                                             sp,
 730                                             "consider relaxing the type parameter's implicit \
 731                                              `Sized` bound",
 732                                             sugg,
 733                                             Applicability::MachineApplicable,
 734                                         );
 735                                     }
 736                                 }
 737                                 if let Some(pred) = parent_p {
 738                                     // Done to add the "doesn't satisfy" `span_label`.
 739                                     let _ = format_pred(*pred);
 740                                 }
 741                                 skip_list.insert(p);
 742                                 let mut spans = if cause.span != *item_span {
 743                                     let mut spans: MultiSpan = cause.span.into();
 744                                     spans.push_span_label(cause.span, unsatisfied_msg);
 745                                     spans
 746                                 } else {
 747                                     let mut spans = Vec::with_capacity(2);
 748                                     if let Some(trait_ref) = of_trait {
 749                                         spans.push(trait_ref.path.span);
 750                                     }
 751                                     spans.push(self_ty.span);
 752                                     spans.into()
 753                                 };
 754                                 if let Some(trait_ref) = of_trait {
 755                                     spans.push_span_label(trait_ref.path.span, "");
 756                                 }
 757                                 spans.push_span_label(self_ty.span, "");
 758
 759                                 let entry = spanned_predicates.entry(spans);
 760                                 entry.or_insert_with(|| (path, tr_self_ty, Vec::new())).2.push(p);
 761                             }
 762                             _ => {}
 763                         }
 764                     }
 765                     let mut spanned_predicates: Vec<_> = spanned_predicates.into_iter().collect();
 766                     spanned_predicates.sort_by_key(|(span, (_, _, _))| span.primary_span());
 767                     for (span, (_path, _self_ty, preds)) in spanned_predicates {
 768                         let mut preds: Vec<_> = preds
 769                             .into_iter()
 770                             .filter_map(|pred| format_pred(*pred))
 771                             .map(|(p, _)| format!("`{}`", p))
 772                             .collect();
 773                         preds.sort();
 774                         preds.dedup();
 775                         let msg = if let [pred] = &preds[..] {
 776                             format!("trait bound {} was not satisfied", pred)
 777                         } else {
 778                             format!(
 779                                 "the following trait bounds were not satisfied:\n{}",
 780                                 preds.join("\n"),
 781                             )
 782                         };
 783                         err.span_note(span, &msg);
 784                         unsatisfied_bounds = true;
 785                     }
 786
 787                     // The requirements that didn't have an `impl` span to show.
 788                     let mut bound_list = unsatisfied_predicates
 789                         .iter()
 790                         .filter_map(|(pred, parent_pred, _cause)| {
 791                             format_pred(*pred).map(|(p, self_ty)| {
 792                                 collect_type_param_suggestions(self_ty, *pred, &p);
 793                                 (
 794                                     match parent_pred {
 795                                         None => format!("`{}`", &p),
 796                                         Some(parent_pred) => match format_pred(*parent_pred) {
 797                                             None => format!("`{}`", &p),
 798                                             Some((parent_p, _)) => {
 799                                                 collect_type_param_suggestions(
 800                                                     self_ty,
 801                                                     *parent_pred,
 802                                                     &p,
 803                                                 );
 804                                                 format!(
 805                                                     "`{}`\nwhich is required by `{}`",
 806                                                     p, parent_p
 807                                                 )
 808                                             }
 809                                         },
 810                                     },
 811                                     *pred,
 812                                 )
 813                             })
 814                         })
 815                         .filter(|(_, pred)| !skip_list.contains(&pred))
 816                         .map(|(t, _)| t)
 817                         .enumerate()
 818                         .collect::<Vec<(usize, String)>>();
 819
 820                     for ((span, add_where_or_comma), obligations) in type_params.into_iter() {
 821                         restrict_type_params = true;
 822                         // #74886: Sort here so that the output is always the same.
 823                         let mut obligations = obligations.into_iter().collect::<Vec<_>>();
 824                         obligations.sort();
 825                         err.span_suggestion_verbose(
 826                             span,
 827                             &format!(
 828                                 "consider restricting the type parameter{s} to satisfy the \
 829                                  trait bound{s}",
 830                                 s = pluralize!(obligations.len())
 831                             ),
 832                             format!("{} {}", add_where_or_comma, obligations.join(", ")),
 833                             Applicability::MaybeIncorrect,
 834                         );
 835                     }
 836
 837                     bound_list.sort_by(|(_, a), (_, b)| a.cmp(b)); // Sort alphabetically.
 838                     bound_list.dedup_by(|(_, a), (_, b)| a == b); // #35677
 839                     bound_list.sort_by_key(|(pos, _)| *pos); // Keep the original predicate order.
 840
 841                     if !bound_list.is_empty() || !skip_list.is_empty() {
 842                         let bound_list = bound_list
 843                             .into_iter()
 844                             .map(|(_, path)| path)
 845                             .collect::<Vec<_>>()
 846                             .join("\n");
 847                         let actual_prefix = actual.prefix_string(self.tcx);
 848                         info!("unimplemented_traits.len() == {}", unimplemented_traits.len());
 849                         let (primary_message, label) =
 850                             if unimplemented_traits.len() == 1 && unimplemented_traits_only {
 851                                 unimplemented_traits
 852                                     .into_iter()
 853                                     .next()
 854                                     .map(|(_, (trait_ref, obligation))| {
 855                                         if trait_ref.self_ty().references_error()
 856                                             || actual.references_error()
 857                                         {
 858                                             // Avoid crashing.
 859                                             return (None, None);
 860                                         }
 861                                         let OnUnimplementedNote { message, label, .. } = self
 862                                             .err_ctxt()
 863                                             .on_unimplemented_note(trait_ref, &obligation);
 864                                         (message, label)
 865                                     })
 866                                     .unwrap_or((None, None))
 867                             } else {
 868                                 (None, None)
 869                             };
 870                         let primary_message = primary_message.unwrap_or_else(|| format!(
 871                             "the {item_kind} `{item_name}` exists for {actual_prefix} `{ty_str}`, but its trait bounds were not satisfied"
 872                         ));
 873                         err.set_primary_message(&primary_message);
 874                         if let Some(label) = label {
 875                             custom_span_label = true;
 876                             err.span_label(span, label);
 877                         }
 878                         if !bound_list.is_empty() {
 879                             err.note(&format!(
 880                                 "the following trait bounds were not satisfied:\n{bound_list}"
 881                             ));
 882                         }
 883                         self.suggest_derive(&mut err, &unsatisfied_predicates);
 884
 885                         unsatisfied_bounds = true;
 886                     }
 887                 }
 888
 889                 let label_span_not_found = |err: &mut Diagnostic| {
 890                     if unsatisfied_predicates.is_empty() {
 891                         err.span_label(span, format!("{item_kind} not found in `{ty_str}`"));
 892                         let is_string_or_ref_str = match actual.kind() {
 893                             ty::Ref(_, ty, _) => {
 894                                 ty.is_str()
 895                                     || matches!(
 896                                         ty.kind(),
 897                                         ty::Adt(adt, _) if self.tcx.is_diagnostic_item(sym::String, adt.did())
 898                                     )
 899                             }
 900                             ty::Adt(adt, _) => self.tcx.is_diagnostic_item(sym::String, adt.did()),
 901                             _ => false,
 902                         };
 903                         if is_string_or_ref_str && item_name.name == sym::iter {
 904                             err.span_suggestion_verbose(
 905                                 item_name.span,
 906                                 "because of the in-memory representation of `&str`, to obtain \
 907                                  an `Iterator` over each of its codepoint use method `chars`",
 908                                 "chars",
 909                                 Applicability::MachineApplicable,
 910                             );
 911                         }
 912                         if let ty::Adt(adt, _) = rcvr_ty.kind() {
 913                             let mut inherent_impls_candidate = self
 914                                 .tcx
 915                                 .inherent_impls(adt.did())
 916                                 .iter()
 917                                 .copied()
 918                                 .filter(|def_id| {
 919                                     if let Some(assoc) = self.associated_value(*def_id, item_name) {
 920                                         // Check for both mode is the same so we avoid suggesting
 921                                         // incorrect associated item.
 922                                         match (mode, assoc.fn_has_self_parameter, source) {
 923                                             (Mode::MethodCall, true, SelfSource::MethodCall(_)) => {
 924                                                 // We check that the suggest type is actually
 925                                                 // different from the received one
 926                                                 // So we avoid suggestion method with Box<Self>
 927                                                 // for instance
 928                                                 self.tcx.at(span).type_of(*def_id) != actual
 929                                                     && self.tcx.at(span).type_of(*def_id) != rcvr_ty
 930                                             }
 931                                             (Mode::Path, false, _) => true,
 932                                             _ => false,
 933                                         }
 934                                     } else {
 935                                         false
 936                                     }
 937                                 })
 938                                 .collect::<Vec<_>>();
 939                             if !inherent_impls_candidate.is_empty() {
 940                                 inherent_impls_candidate.sort();
 941                                 inherent_impls_candidate.dedup();
 942
 943                                 // number of type to shows at most.
 944                                 let limit = if inherent_impls_candidate.len() == 5 { 5 } else { 4 };
 945                                 let type_candidates = inherent_impls_candidate
 946                                     .iter()
 947                                     .take(limit)
 948                                     .map(|impl_item| {
 949                                         format!("- `{}`", self.tcx.at(span).type_of(*impl_item))
 950                                     })
 951                                     .collect::<Vec<_>>()
 952                                     .join("\n");
 953                                 let additional_types = if inherent_impls_candidate.len() > limit {
 954                                     format!(
 955                                         "\nand {} more types",
 956                                         inherent_impls_candidate.len() - limit
 957                                     )
 958                                 } else {
 959                                     "".to_string()
 960                                 };
 961                                 err.note(&format!(
 962                                     "the {item_kind} was found for\n{}{}",
 963                                     type_candidates, additional_types
 964                                 ));
 965                             }
 966                         }
 967                     } else {
 968                         err.span_label(span, format!("{item_kind} cannot be called on `{ty_str}` due to unsatisfied trait bounds"));
 969                     }
 970                 };
 971
 972                 // If the method name is the name of a field with a function or closure type,
 973                 // give a helping note that it has to be called as `(x.f)(...)`.
 974                 if let SelfSource::MethodCall(expr) = source {
 975                     if !self.suggest_field_call(span, rcvr_ty, expr, item_name, &mut err)
 976                         && lev_candidate.is_none()
 977                         && !custom_span_label
 978                     {
 979                         label_span_not_found(&mut err);
 980                     }
 981                 } else if !custom_span_label {
 982                     label_span_not_found(&mut err);
 983                 }
 984
 985                 // Don't suggest (for example) `expr.field.method()` if `expr.method()`
 986                 // doesn't exist due to unsatisfied predicates.
 987                 if unsatisfied_predicates.is_empty() {
 988                     self.check_for_field_method(&mut err, source, span, actual, item_name);
 989                 }
 990
 991                 self.check_for_inner_self(&mut err, source, span, actual, item_name);
 992
 993                 bound_spans.sort();
 994                 bound_spans.dedup();
 995                 for (span, msg) in bound_spans.into_iter() {
 996                     err.span_label(span, &msg);
 997                 }
 998
 999                 if actual.is_numeric() && actual.is_fresh() || restrict_type_params {
1000                 } else {
1001                     self.suggest_traits_to_import(
1002                         &mut err,
1003                         span,
1004                         rcvr_ty,
1005                         item_name,
1006                         args.map(|(_, args)| args.len() + 1),
1007                         source,
1008                         out_of_scope_traits,
1009                         &unsatisfied_predicates,
1010                         unsatisfied_bounds,
1011                     );
1012                 }
1013
1014                 // Don't emit a suggestion if we found an actual method
1015                 // that had unsatisfied trait bounds
1016                 if unsatisfied_predicates.is_empty() && actual.is_enum() {
1017                     let adt_def = actual.ty_adt_def().expect("enum is not an ADT");
1018                     if let Some(suggestion) = lev_distance::find_best_match_for_name(
1019                         &adt_def.variants().iter().map(|s| s.name).collect::<Vec<_>>(),
1020                         item_name.name,
1021                         None,
1022                     ) {
1023                         err.span_suggestion(
1024                             span,
1025                             "there is a variant with a similar name",
1026                             suggestion,
1027                             Applicability::MaybeIncorrect,
1028                         );
1029                     }
1030                 }
1031
1032                 if item_name.name == sym::as_str && actual.peel_refs().is_str() {
1033                     let msg = "remove this method call";
1034                     let mut fallback_span = true;
1035                     if let SelfSource::MethodCall(expr) = source {
1036                         let call_expr =
1037                             self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id));
1038                         if let Some(span) = call_expr.span.trim_start(expr.span) {
1039                             err.span_suggestion(span, msg, "", Applicability::MachineApplicable);
1040                             fallback_span = false;
1041                         }
1042                     }
1043                     if fallback_span {
1044                         err.span_label(span, msg);
1045                     }
1046                 } else if let Some(lev_candidate) = lev_candidate {
1047                     // Don't emit a suggestion if we found an actual method
1048                     // that had unsatisfied trait bounds
1049                     if unsatisfied_predicates.is_empty() {
1050                         let def_kind = lev_candidate.kind.as_def_kind();
1051                         // Methods are defined within the context of a struct and their first parameter is always self,
1052                         // which represents the instance of the struct the method is being called on
1053                         // Associated functions don’t take self as a parameter and
1054                         // they are not methods because they don’t have an instance of the struct to work with.
1055                         if def_kind == DefKind::AssocFn && lev_candidate.fn_has_self_parameter {
1056                             err.span_suggestion(
1057                                 span,
1058                                 &format!("there is a method with a similar name",),
1059                                 lev_candidate.name,
1060                                 Applicability::MaybeIncorrect,
1061                             );
1062                         } else {
1063                             err.span_suggestion(
1064                                 span,
1065                                 &format!(
1066                                     "there is {} {} with a similar name",
1067                                     def_kind.article(),
1068                                     def_kind.descr(lev_candidate.def_id),
1069                                 ),
1070                                 lev_candidate.name,
1071                                 Applicability::MaybeIncorrect,
1072                             );
1073                         }
1074                     }
1075                 }
1076
1077                 self.check_for_deref_method(&mut err, source, rcvr_ty, item_name);
1078
1079                 return Some(err);
1080             }
1081
1082             MethodError::Ambiguity(sources) => {
1083                 let mut err = struct_span_err!(
1084                     self.sess(),
1085                     item_name.span,
1086                     E0034,
1087                     "multiple applicable items in scope"
1088                 );
1089                 err.span_label(item_name.span, format!("multiple `{}` found", item_name));
1090
1091                 report_candidates(span, &mut err, sources, sugg_span);
1092                 err.emit();
1093             }
1094
1095             MethodError::PrivateMatch(kind, def_id, out_of_scope_traits) => {
1096                 let kind = kind.descr(def_id);
1097                 let mut err = struct_span_err!(
1098                     self.tcx.sess,
1099                     item_name.span,
1100                     E0624,
1101                     "{} `{}` is private",
1102                     kind,
1103                     item_name
1104                 );
1105                 err.span_label(item_name.span, &format!("private {}", kind));
1106                 let sp = self
1107                     .tcx
1108                     .hir()
1109                     .span_if_local(def_id)
1110                     .unwrap_or_else(|| self.tcx.def_span(def_id));
1111                 err.span_label(sp, &format!("private {} defined here", kind));
1112                 self.suggest_valid_traits(&mut err, out_of_scope_traits);
1113                 err.emit();
1114             }
1115
1116             MethodError::IllegalSizedBound(candidates, needs_mut, bound_span) => {
1117                 let msg = format!("the `{}` method cannot be invoked on a trait object", item_name);
1118                 let mut err = self.sess().struct_span_err(span, &msg);
1119                 err.span_label(bound_span, "this has a `Sized` requirement");
1120                 if !candidates.is_empty() {
1121                     let help = format!(
1122                         "{an}other candidate{s} {were} found in the following trait{s}, perhaps \
1123                          add a `use` for {one_of_them}:",
1124                         an = if candidates.len() == 1 { "an" } else { "" },
1125                         s = pluralize!(candidates.len()),
1126                         were = pluralize!("was", candidates.len()),
1127                         one_of_them = if candidates.len() == 1 { "it" } else { "one_of_them" },
1128                     );
1129                     self.suggest_use_candidates(&mut err, help, candidates);
1130                 }
1131                 if let ty::Ref(region, t_type, mutability) = rcvr_ty.kind() {
1132                     if needs_mut {
1133                         let trait_type = self.tcx.mk_ref(
1134                             *region,
1135                             ty::TypeAndMut { ty: *t_type, mutbl: mutability.invert() },
1136                         );
1137                         err.note(&format!("you need `{}` instead of `{}`", trait_type, rcvr_ty));
1138                     }
1139                 }
1140                 err.emit();
1141             }
1142
1143             MethodError::BadReturnType => bug!("no return type expectations but got BadReturnType"),
1144         }
1145         None
1146     }
1147
1148     fn suggest_field_call(
1149         &self,
1150         span: Span,
1151         rcvr_ty: Ty<'tcx>,
1152         expr: &hir::Expr<'_>,
1153         item_name: Ident,
1154         err: &mut Diagnostic,
1155     ) -> bool {
1156         let tcx = self.tcx;
1157         let field_receiver = self.autoderef(span, rcvr_ty).find_map(|(ty, _)| match ty.kind() {
1158             ty::Adt(def, substs) if !def.is_enum() => {
1159                 let variant = &def.non_enum_variant();
1160                 tcx.find_field_index(item_name, variant).map(|index| {
1161                     let field = &variant.fields[index];
1162                     let field_ty = field.ty(tcx, substs);
1163                     (field, field_ty)
1164                 })
1165             }
1166             _ => None,
1167         });
1168         if let Some((field, field_ty)) = field_receiver {
1169             let scope = tcx.parent_module(self.body_id);
1170             let is_accessible = field.vis.is_accessible_from(scope, tcx);
1171
1172             if is_accessible {
1173                 if self.is_fn_ty(field_ty, span) {
1174                     let expr_span = expr.span.to(item_name.span);
1175                     err.multipart_suggestion(
1176                         &format!(
1177                             "to call the function stored in `{}`, \
1178                                          surround the field access with parentheses",
1179                             item_name,
1180                         ),
1181                         vec![
1182                             (expr_span.shrink_to_lo(), '('.to_string()),
1183                             (expr_span.shrink_to_hi(), ')'.to_string()),
1184                         ],
1185                         Applicability::MachineApplicable,
1186                     );
1187                 } else {
1188                     let call_expr = tcx.hir().expect_expr(tcx.hir().get_parent_node(expr.hir_id));
1189
1190                     if let Some(span) = call_expr.span.trim_start(item_name.span) {
1191                         err.span_suggestion(
1192                             span,
1193                             "remove the arguments",
1194                             "",
1195                             Applicability::MaybeIncorrect,
1196                         );
1197                     }
1198                 }
1199             }
1200
1201             let field_kind = if is_accessible { "field" } else { "private field" };
1202             err.span_label(item_name.span, format!("{}, not a method", field_kind));
1203             return true;
1204         }
1205         false
1206     }
1207
1208     /// Suggest possible range with adding parentheses, for example:
1209     /// when encountering `0..1.map(|i| i + 1)` suggest `(0..1).map(|i| i + 1)`.
1210     fn suggest_wrapping_range_with_parens(
1211         &self,
1212         tcx: TyCtxt<'tcx>,
1213         actual: Ty<'tcx>,
1214         source: SelfSource<'tcx>,
1215         span: Span,
1216         item_name: Ident,
1217         ty_str: &str,
1218     ) -> bool {
1219         if let SelfSource::MethodCall(expr) = source {
1220             for (_, parent) in tcx.hir().parent_iter(expr.hir_id).take(5) {
1221                 if let Node::Expr(parent_expr) = parent {
1222                     let lang_item = match parent_expr.kind {
1223                         ExprKind::Struct(ref qpath, _, _) => match **qpath {
1224                             QPath::LangItem(LangItem::Range, ..) => Some(LangItem::Range),
1225                             QPath::LangItem(LangItem::RangeTo, ..) => Some(LangItem::RangeTo),
1226                             QPath::LangItem(LangItem::RangeToInclusive, ..) => {
1227                                 Some(LangItem::RangeToInclusive)
1228                             }
1229                             _ => None,
1230                         },
1231                         ExprKind::Call(ref func, _) => match func.kind {
1232                             // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
1233                             ExprKind::Path(QPath::LangItem(LangItem::RangeInclusiveNew, ..)) => {
1234                                 Some(LangItem::RangeInclusiveStruct)
1235                             }
1236                             _ => None,
1237                         },
1238                         _ => None,
1239                     };
1240
1241                     if lang_item.is_none() {
1242                         continue;
1243                     }
1244
1245                     let span_included = match parent_expr.kind {
1246                         hir::ExprKind::Struct(_, eps, _) => {
1247                             eps.len() > 0 && eps.last().map_or(false, |ep| ep.span.contains(span))
1248                         }
1249                         // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
1250                         hir::ExprKind::Call(ref func, ..) => func.span.contains(span),
1251                         _ => false,
1252                     };
1253
1254                     if !span_included {
1255                         continue;
1256                     }
1257
1258                     let range_def_id = self.tcx.require_lang_item(lang_item.unwrap(), None);
1259                     let range_ty =
1260                         self.tcx.bound_type_of(range_def_id).subst(self.tcx, &[actual.into()]);
1261
1262                     let pick = self.probe_for_name(
1263                         span,
1264                         Mode::MethodCall,
1265                         item_name,
1266                         IsSuggestion(true),
1267                         range_ty,
1268                         expr.hir_id,
1269                         ProbeScope::AllTraits,
1270                     );
1271                     if pick.is_ok() {
1272                         let range_span = parent_expr.span.with_hi(expr.span.hi());
1273                         tcx.sess.emit_err(errors::MissingParentheseInRange {
1274                             span,
1275                             ty_str: ty_str.to_string(),
1276                             method_name: item_name.as_str().to_string(),
1277                             add_missing_parentheses: Some(errors::AddMissingParenthesesInRange {
1278                                 func_name: item_name.name.as_str().to_string(),
1279                                 left: range_span.shrink_to_lo(),
1280                                 right: range_span.shrink_to_hi(),
1281                             }),
1282                         });
1283                         return true;
1284                     }
1285                 }
1286             }
1287         }
1288         false
1289     }
1290
1291     fn suggest_constraining_numerical_ty(
1292         &self,
1293         tcx: TyCtxt<'tcx>,
1294         actual: Ty<'tcx>,
1295         source: SelfSource<'_>,
1296         span: Span,
1297         item_kind: &str,
1298         item_name: Ident,
1299         ty_str: &str,
1300     ) -> bool {
1301         let found_candidate = all_traits(self.tcx)
1302             .into_iter()
1303             .any(|info| self.associated_value(info.def_id, item_name).is_some());
1304         let found_assoc = |ty: Ty<'tcx>| {
1305             simplify_type(tcx, ty, TreatParams::AsInfer)
1306                 .and_then(|simp| {
1307                     tcx.incoherent_impls(simp)
1308                         .iter()
1309                         .find_map(|&id| self.associated_value(id, item_name))
1310                 })
1311                 .is_some()
1312         };
1313         let found_candidate = found_candidate
1314             || found_assoc(tcx.types.i8)
1315             || found_assoc(tcx.types.i16)
1316             || found_assoc(tcx.types.i32)
1317             || found_assoc(tcx.types.i64)
1318             || found_assoc(tcx.types.i128)
1319             || found_assoc(tcx.types.u8)
1320             || found_assoc(tcx.types.u16)
1321             || found_assoc(tcx.types.u32)
1322             || found_assoc(tcx.types.u64)
1323             || found_assoc(tcx.types.u128)
1324             || found_assoc(tcx.types.f32)
1325             || found_assoc(tcx.types.f32);
1326         if found_candidate
1327             && actual.is_numeric()
1328             && !actual.has_concrete_skeleton()
1329             && let SelfSource::MethodCall(expr) = source
1330         {
1331             let mut err = struct_span_err!(
1332                 tcx.sess,
1333                 span,
1334                 E0689,
1335                 "can't call {} `{}` on ambiguous numeric type `{}`",
1336                 item_kind,
1337                 item_name,
1338                 ty_str
1339             );
1340             let concrete_type = if actual.is_integral() { "i32" } else { "f32" };
1341             match expr.kind {
1342                 ExprKind::Lit(ref lit) => {
1343                     // numeric literal
1344                     let snippet = tcx
1345                         .sess
1346                         .source_map()
1347                         .span_to_snippet(lit.span)
1348                         .unwrap_or_else(|_| "<numeric literal>".to_owned());
1349
1350                     // If this is a floating point literal that ends with '.',
1351                     // get rid of it to stop this from becoming a member access.
1352                     let snippet = snippet.strip_suffix('.').unwrap_or(&snippet);
1353                     err.span_suggestion(
1354                         lit.span,
1355                         &format!(
1356                             "you must specify a concrete type for this numeric value, \
1357                                          like `{}`",
1358                             concrete_type
1359                         ),
1360                         format!("{snippet}_{concrete_type}"),
1361                         Applicability::MaybeIncorrect,
1362                     );
1363                 }
1364                 ExprKind::Path(QPath::Resolved(_, path)) => {
1365                     // local binding
1366                     if let hir::def::Res::Local(hir_id) = path.res {
1367                         let span = tcx.hir().span(hir_id);
1368                         let filename = tcx.sess.source_map().span_to_filename(span);
1369
1370                         let parent_node =
1371                             self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id));
1372                         let msg = format!(
1373                             "you must specify a type for this binding, like `{}`",
1374                             concrete_type,
1375                         );
1376
1377                         match (filename, parent_node) {
1378                             (
1379                                 FileName::Real(_),
1380                                 Node::Local(hir::Local {
1381                                     source: hir::LocalSource::Normal,
1382                                     ty,
1383                                     ..
1384                                 }),
1385                             ) => {
1386                                 let type_span = ty.map(|ty| ty.span.with_lo(span.hi())).unwrap_or(span.shrink_to_hi());
1387                                 err.span_suggestion(
1388                                     // account for `let x: _ = 42;`
1389                                     //                   ^^^
1390                                     type_span,
1391                                     &msg,
1392                                     format!(": {concrete_type}"),
1393                                     Applicability::MaybeIncorrect,
1394                                 );
1395                             }
1396                             _ => {
1397                                 err.span_label(span, msg);
1398                             }
1399                         }
1400                     }
1401                 }
1402                 _ => {}
1403             }
1404             err.emit();
1405             return true;
1406         }
1407         false
1408     }
1409
1410     fn check_for_field_method(
1411         &self,
1412         err: &mut Diagnostic,
1413         source: SelfSource<'tcx>,
1414         span: Span,
1415         actual: Ty<'tcx>,
1416         item_name: Ident,
1417     ) {
1418         if let SelfSource::MethodCall(expr) = source
1419         && let mod_id = self.tcx.parent_module(expr.hir_id).to_def_id()
1420         && let Some((fields, substs)) =
1421             self.get_field_candidates_considering_privacy(span, actual, mod_id)
1422         {
1423             let call_expr = self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id));
1424
1425             let lang_items = self.tcx.lang_items();
1426             let never_mention_traits = [
1427                 lang_items.clone_trait(),
1428                 lang_items.deref_trait(),
1429                 lang_items.deref_mut_trait(),
1430                 self.tcx.get_diagnostic_item(sym::AsRef),
1431                 self.tcx.get_diagnostic_item(sym::AsMut),
1432                 self.tcx.get_diagnostic_item(sym::Borrow),
1433                 self.tcx.get_diagnostic_item(sym::BorrowMut),
1434             ];
1435             let candidate_fields: Vec<_> = fields
1436                 .filter_map(|candidate_field| {
1437                     self.check_for_nested_field_satisfying(
1438                         span,
1439                         &|_, field_ty| {
1440                             self.lookup_probe(
1441                                 span,
1442                                 item_name,
1443                                 field_ty,
1444                                 call_expr,
1445                                 ProbeScope::TraitsInScope,
1446                             )
1447                             .map_or(false, |pick| {
1448                                 !never_mention_traits
1449                                     .iter()
1450                                     .flatten()
1451                                     .any(|def_id| self.tcx.parent(pick.item.def_id) == *def_id)
1452                             })
1453                         },
1454                         candidate_field,
1455                         substs,
1456                         vec![],
1457                         mod_id,
1458                     )
1459                 })
1460                 .map(|field_path| {
1461                     field_path
1462                         .iter()
1463                         .map(|id| id.name.to_ident_string())
1464                         .collect::<Vec<String>>()
1465                         .join(".")
1466                 })
1467                 .collect();
1468
1469             let len = candidate_fields.len();
1470             if len > 0 {
1471                 err.span_suggestions(
1472                     item_name.span.shrink_to_lo(),
1473                     format!(
1474                         "{} of the expressions' fields {} a method of the same name",
1475                         if len > 1 { "some" } else { "one" },
1476                         if len > 1 { "have" } else { "has" },
1477                     ),
1478                     candidate_fields.iter().map(|path| format!("{path}.")),
1479                     Applicability::MaybeIncorrect,
1480                 );
1481             }
1482         }
1483     }
1484
1485     fn check_for_inner_self(
1486         &self,
1487         err: &mut Diagnostic,
1488         source: SelfSource<'tcx>,
1489         span: Span,
1490         actual: Ty<'tcx>,
1491         item_name: Ident,
1492     ) {
1493         let tcx = self.tcx;
1494         let SelfSource::MethodCall(expr) = source else { return; };
1495         let call_expr = tcx.hir().expect_expr(tcx.hir().get_parent_node(expr.hir_id));
1496
1497         let ty::Adt(kind, substs) = actual.kind() else { return; };
1498         match kind.adt_kind() {
1499             ty::AdtKind::Enum => {
1500                 let matching_variants: Vec<_> = kind
1501                     .variants()
1502                     .iter()
1503                     .flat_map(|variant| {
1504                         let [field] = &variant.fields[..] else { return None; };
1505                         let field_ty = field.ty(tcx, substs);
1506
1507                         // Skip `_`, since that'll just lead to ambiguity.
1508                         if self.resolve_vars_if_possible(field_ty).is_ty_var() {
1509                             return None;
1510                         }
1511
1512                         self.lookup_probe(
1513                             span,
1514                             item_name,
1515                             field_ty,
1516                             call_expr,
1517                             ProbeScope::TraitsInScope,
1518                         )
1519                         .ok()
1520                         .map(|pick| (variant, field, pick))
1521                     })
1522                     .collect();
1523
1524                 let ret_ty_matches = |diagnostic_item| {
1525                     if let Some(ret_ty) = self
1526                         .ret_coercion
1527                         .as_ref()
1528                         .map(|c| self.resolve_vars_if_possible(c.borrow().expected_ty()))
1529                         && let ty::Adt(kind, _) = ret_ty.kind()
1530                         && tcx.get_diagnostic_item(diagnostic_item) == Some(kind.did())
1531                     {
1532                         true
1533                     } else {
1534                         false
1535                     }
1536                 };
1537
1538                 match &matching_variants[..] {
1539                     [(_, field, pick)] => {
1540                         let self_ty = field.ty(tcx, substs);
1541                         err.span_note(
1542                             tcx.def_span(pick.item.def_id),
1543                             &format!("the method `{item_name}` exists on the type `{self_ty}`"),
1544                         );
1545                         let (article, kind, variant, question) =
1546                             if tcx.is_diagnostic_item(sym::Result, kind.did()) {
1547                                 ("a", "Result", "Err", ret_ty_matches(sym::Result))
1548                             } else if tcx.is_diagnostic_item(sym::Option, kind.did()) {
1549                                 ("an", "Option", "None", ret_ty_matches(sym::Option))
1550                             } else {
1551                                 return;
1552                             };
1553                         if question {
1554                             err.span_suggestion_verbose(
1555                                 expr.span.shrink_to_hi(),
1556                                 format!(
1557                                     "use the `?` operator to extract the `{self_ty}` value, propagating \
1558                                     {article} `{kind}::{variant}` value to the caller"
1559                                 ),
1560                                 "?",
1561                                 Applicability::MachineApplicable,
1562                             );
1563                         } else {
1564                             err.span_suggestion_verbose(
1565                                 expr.span.shrink_to_hi(),
1566                                 format!(
1567                                     "consider using `{kind}::expect` to unwrap the `{self_ty}` value, \
1568                                     panicking if the value is {article} `{kind}::{variant}`"
1569                                 ),
1570                                 ".expect(\"REASON\")",
1571                                 Applicability::HasPlaceholders,
1572                             );
1573                         }
1574                     }
1575                     // FIXME(compiler-errors): Support suggestions for other matching enum variants
1576                     _ => {}
1577                 }
1578             }
1579             // Target wrapper types - types that wrap or pretend to wrap another type,
1580             // perhaps this inner type is meant to be called?
1581             ty::AdtKind::Struct | ty::AdtKind::Union => {
1582                 let [first] = ***substs else { return; };
1583                 let ty::GenericArgKind::Type(ty) = first.unpack() else { return; };
1584                 let Ok(pick) = self.lookup_probe(
1585                             span,
1586                             item_name,
1587                             ty,
1588                             call_expr,
1589                             ProbeScope::TraitsInScope,
1590                         )  else { return; };
1591
1592                 let name = self.ty_to_value_string(actual);
1593                 let inner_id = kind.did();
1594                 let mutable = if let Some(AutorefOrPtrAdjustment::Autoref { mutbl, .. }) =
1595                     pick.autoref_or_ptr_adjustment
1596                 {
1597                     Some(mutbl)
1598                 } else {
1599                     None
1600                 };
1601
1602                 if tcx.is_diagnostic_item(sym::LocalKey, inner_id) {
1603                     err.help("use `with` or `try_with` to access thread local storage");
1604                 } else if Some(kind.did()) == tcx.lang_items().maybe_uninit() {
1605                     err.help(format!(
1606                         "if this `{name}` has been initialized, \
1607                         use one of the `assume_init` methods to access the inner value"
1608                     ));
1609                 } else if tcx.is_diagnostic_item(sym::RefCell, inner_id) {
1610                     let (suggestion, borrow_kind, panic_if) = match mutable {
1611                         Some(Mutability::Not) => (".borrow()", "borrow", "a mutable borrow exists"),
1612                         Some(Mutability::Mut) => {
1613                             (".borrow_mut()", "mutably borrow", "any borrows exist")
1614                         }
1615                         None => return,
1616                     };
1617                     err.span_suggestion_verbose(
1618                         expr.span.shrink_to_hi(),
1619                         format!(
1620                             "use `{suggestion}` to {borrow_kind} the `{ty}`, \
1621                             panicking if {panic_if}"
1622                         ),
1623                         suggestion,
1624                         Applicability::MaybeIncorrect,
1625                     );
1626                 } else if tcx.is_diagnostic_item(sym::Mutex, inner_id) {
1627                     err.span_suggestion_verbose(
1628                         expr.span.shrink_to_hi(),
1629                         format!(
1630                             "use `.lock().unwrap()` to borrow the `{ty}`, \
1631                             blocking the current thread until it can be acquired"
1632                         ),
1633                         ".lock().unwrap()",
1634                         Applicability::MaybeIncorrect,
1635                     );
1636                 } else if tcx.is_diagnostic_item(sym::RwLock, inner_id) {
1637                     let (suggestion, borrow_kind) = match mutable {
1638                         Some(Mutability::Not) => (".read().unwrap()", "borrow"),
1639                         Some(Mutability::Mut) => (".write().unwrap()", "mutably borrow"),
1640                         None => return,
1641                     };
1642                     err.span_suggestion_verbose(
1643                         expr.span.shrink_to_hi(),
1644                         format!(
1645                             "use `{suggestion}` to {borrow_kind} the `{ty}`, \
1646                             blocking the current thread until it can be acquired"
1647                         ),
1648                         suggestion,
1649                         Applicability::MaybeIncorrect,
1650                     );
1651                 } else {
1652                     return;
1653                 };
1654
1655                 err.span_note(
1656                     tcx.def_span(pick.item.def_id),
1657                     &format!("the method `{item_name}` exists on the type `{ty}`"),
1658                 );
1659             }
1660         }
1661     }
1662
1663     pub(crate) fn note_unmet_impls_on_type(
1664         &self,
1665         err: &mut Diagnostic,
1666         errors: Vec<FulfillmentError<'tcx>>,
1667     ) {
1668         let all_local_types_needing_impls =
1669             errors.iter().all(|e| match e.obligation.predicate.kind().skip_binder() {
1670                 ty::PredicateKind::Trait(pred) => match pred.self_ty().kind() {
1671                     ty::Adt(def, _) => def.did().is_local(),
1672                     _ => false,
1673                 },
1674                 _ => false,
1675             });
1676         let mut preds: Vec<_> = errors
1677             .iter()
1678             .filter_map(|e| match e.obligation.predicate.kind().skip_binder() {
1679                 ty::PredicateKind::Trait(pred) => Some(pred),
1680                 _ => None,
1681             })
1682             .collect();
1683         preds.sort_by_key(|pred| (pred.def_id(), pred.self_ty()));
1684         let def_ids = preds
1685             .iter()
1686             .filter_map(|pred| match pred.self_ty().kind() {
1687                 ty::Adt(def, _) => Some(def.did()),
1688                 _ => None,
1689             })
1690             .collect::<FxHashSet<_>>();
1691         let mut spans: MultiSpan = def_ids
1692             .iter()
1693             .filter_map(|def_id| {
1694                 let span = self.tcx.def_span(*def_id);
1695                 if span.is_dummy() { None } else { Some(span) }
1696             })
1697             .collect::<Vec<_>>()
1698             .into();
1699
1700         for pred in &preds {
1701             match pred.self_ty().kind() {
1702                 ty::Adt(def, _) if def.did().is_local() => {
1703                     spans.push_span_label(
1704                         self.tcx.def_span(def.did()),
1705                         format!("must implement `{}`", pred.trait_ref.print_only_trait_path()),
1706                     );
1707                 }
1708                 _ => {}
1709             }
1710         }
1711
1712         if all_local_types_needing_impls && spans.primary_span().is_some() {
1713             let msg = if preds.len() == 1 {
1714                 format!(
1715                     "an implementation of `{}` might be missing for `{}`",
1716                     preds[0].trait_ref.print_only_trait_path(),
1717                     preds[0].self_ty()
1718                 )
1719             } else {
1720                 format!(
1721                     "the following type{} would have to `impl` {} required trait{} for this \
1722                      operation to be valid",
1723                     pluralize!(def_ids.len()),
1724                     if def_ids.len() == 1 { "its" } else { "their" },
1725                     pluralize!(preds.len()),
1726                 )
1727             };
1728             err.span_note(spans, &msg);
1729         }
1730
1731         let preds: Vec<_> = errors
1732             .iter()
1733             .map(|e| (e.obligation.predicate, None, Some(e.obligation.cause.clone())))
1734             .collect();
1735         self.suggest_derive(err, &preds);
1736     }
1737
1738     fn suggest_derive(
1739         &self,
1740         err: &mut Diagnostic,
1741         unsatisfied_predicates: &[(
1742             ty::Predicate<'tcx>,
1743             Option<ty::Predicate<'tcx>>,
1744             Option<ObligationCause<'tcx>>,
1745         )],
1746     ) {
1747         let mut derives = Vec::<(String, Span, Symbol)>::new();
1748         let mut traits = Vec::<Span>::new();
1749         for (pred, _, _) in unsatisfied_predicates {
1750             let ty::PredicateKind::Trait(trait_pred) = pred.kind().skip_binder() else { continue };
1751             let adt = match trait_pred.self_ty().ty_adt_def() {
1752                 Some(adt) if adt.did().is_local() => adt,
1753                 _ => continue,
1754             };
1755             if let Some(diagnostic_name) = self.tcx.get_diagnostic_name(trait_pred.def_id()) {
1756                 let can_derive = match diagnostic_name {
1757                     sym::Default => !adt.is_enum(),
1758                     sym::Eq
1759                     | sym::PartialEq
1760                     | sym::Ord
1761                     | sym::PartialOrd
1762                     | sym::Clone
1763                     | sym::Copy
1764                     | sym::Hash
1765                     | sym::Debug => true,
1766                     _ => false,
1767                 };
1768                 if can_derive {
1769                     let self_name = trait_pred.self_ty().to_string();
1770                     let self_span = self.tcx.def_span(adt.did());
1771                     if let Some(poly_trait_ref) = pred.to_opt_poly_trait_pred() {
1772                         for super_trait in supertraits(self.tcx, poly_trait_ref.to_poly_trait_ref())
1773                         {
1774                             if let Some(parent_diagnostic_name) =
1775                                 self.tcx.get_diagnostic_name(super_trait.def_id())
1776                             {
1777                                 derives.push((
1778                                     self_name.clone(),
1779                                     self_span,
1780                                     parent_diagnostic_name,
1781                                 ));
1782                             }
1783                         }
1784                     }
1785                     derives.push((self_name, self_span, diagnostic_name));
1786                 } else {
1787                     traits.push(self.tcx.def_span(trait_pred.def_id()));
1788                 }
1789             } else {
1790                 traits.push(self.tcx.def_span(trait_pred.def_id()));
1791             }
1792         }
1793         traits.sort();
1794         traits.dedup();
1795
1796         derives.sort();
1797         derives.dedup();
1798
1799         let mut derives_grouped = Vec::<(String, Span, String)>::new();
1800         for (self_name, self_span, trait_name) in derives.into_iter() {
1801             if let Some((last_self_name, _, ref mut last_trait_names)) = derives_grouped.last_mut()
1802             {
1803                 if last_self_name == &self_name {
1804                     last_trait_names.push_str(format!(", {}", trait_name).as_str());
1805                     continue;
1806                 }
1807             }
1808             derives_grouped.push((self_name, self_span, trait_name.to_string()));
1809         }
1810
1811         let len = traits.len();
1812         if len > 0 {
1813             let span: MultiSpan = traits.into();
1814             err.span_note(
1815                 span,
1816                 &format!("the following trait{} must be implemented", pluralize!(len),),
1817             );
1818         }
1819
1820         for (self_name, self_span, traits) in &derives_grouped {
1821             err.span_suggestion_verbose(
1822                 self_span.shrink_to_lo(),
1823                 &format!("consider annotating `{}` with `#[derive({})]`", self_name, traits),
1824                 format!("#[derive({})]\n", traits),
1825                 Applicability::MaybeIncorrect,
1826             );
1827         }
1828     }
1829
1830     fn check_for_deref_method(
1831         &self,
1832         err: &mut Diagnostic,
1833         self_source: SelfSource<'tcx>,
1834         rcvr_ty: Ty<'tcx>,
1835         item_name: Ident,
1836     ) {
1837         let SelfSource::QPath(ty) = self_source else { return; };
1838         for (deref_ty, _) in self.autoderef(rustc_span::DUMMY_SP, rcvr_ty).skip(1) {
1839             if let Ok(pick) = self.probe_for_name(
1840                 ty.span,
1841                 Mode::Path,
1842                 item_name,
1843                 IsSuggestion(true),
1844                 deref_ty,
1845                 ty.hir_id,
1846                 ProbeScope::TraitsInScope,
1847             ) {
1848                 if deref_ty.is_suggestable(self.tcx, true)
1849                     // If this method receives `&self`, then the provided
1850                     // argument _should_ coerce, so it's valid to suggest
1851                     // just changing the path.
1852                     && pick.item.fn_has_self_parameter
1853                     && let Some(self_ty) =
1854                         self.tcx.fn_sig(pick.item.def_id).inputs().skip_binder().get(0)
1855                     && self_ty.is_ref()
1856                 {
1857                     let suggested_path = match deref_ty.kind() {
1858                         ty::Bool
1859                         | ty::Char
1860                         | ty::Int(_)
1861                         | ty::Uint(_)
1862                         | ty::Float(_)
1863                         | ty::Adt(_, _)
1864                         | ty::Str
1865                         | ty::Projection(_)
1866                         | ty::Param(_) => format!("{deref_ty}"),
1867                         _ => format!("<{deref_ty}>"),
1868                     };
1869                     err.span_suggestion_verbose(
1870                         ty.span,
1871                         format!("the function `{item_name}` is implemented on `{deref_ty}`"),
1872                         suggested_path,
1873                         Applicability::MaybeIncorrect,
1874                     );
1875                 } else {
1876                     err.span_note(
1877                         ty.span,
1878                         format!("the function `{item_name}` is implemented on `{deref_ty}`"),
1879                     );
1880                 }
1881                 return;
1882             }
1883         }
1884     }
1885
1886     /// Print out the type for use in value namespace.
1887     fn ty_to_value_string(&self, ty: Ty<'tcx>) -> String {
1888         match ty.kind() {
1889             ty::Adt(def, substs) => format!("{}", ty::Instance::new(def.did(), substs)),
1890             _ => self.ty_to_string(ty),
1891         }
1892     }
1893
1894     fn suggest_await_before_method(
1895         &self,
1896         err: &mut Diagnostic,
1897         item_name: Ident,
1898         ty: Ty<'tcx>,
1899         call: &hir::Expr<'_>,
1900         span: Span,
1901     ) {
1902         let output_ty = match self.get_impl_future_output_ty(ty) {
1903             Some(output_ty) => self.resolve_vars_if_possible(output_ty).skip_binder(),
1904             _ => return,
1905         };
1906         let method_exists = self.method_exists(item_name, output_ty, call.hir_id, true);
1907         debug!("suggest_await_before_method: is_method_exist={}", method_exists);
1908         if method_exists {
1909             err.span_suggestion_verbose(
1910                 span.shrink_to_lo(),
1911                 "consider `await`ing on the `Future` and calling the method on its `Output`",
1912                 "await.",
1913                 Applicability::MaybeIncorrect,
1914             );
1915         }
1916     }
1917
1918     fn suggest_use_candidates(&self, err: &mut Diagnostic, msg: String, candidates: Vec<DefId>) {
1919         let parent_map = self.tcx.visible_parent_map(());
1920
1921         // Separate out candidates that must be imported with a glob, because they are named `_`
1922         // and cannot be referred with their identifier.
1923         let (candidates, globs): (Vec<_>, Vec<_>) = candidates.into_iter().partition(|trait_did| {
1924             if let Some(parent_did) = parent_map.get(trait_did) {
1925                 // If the item is re-exported as `_`, we should suggest a glob-import instead.
1926                 if *parent_did != self.tcx.parent(*trait_did)
1927                     && self
1928                         .tcx
1929                         .module_children(*parent_did)
1930                         .iter()
1931                         .filter(|child| child.res.opt_def_id() == Some(*trait_did))
1932                         .all(|child| child.ident.name == kw::Underscore)
1933                 {
1934                     return false;
1935                 }
1936             }
1937
1938             true
1939         });
1940
1941         let module_did = self.tcx.parent_module(self.body_id);
1942         let (module, _, _) = self.tcx.hir().get_module(module_did);
1943         let span = module.spans.inject_use_span;
1944
1945         let path_strings = candidates.iter().map(|trait_did| {
1946             format!("use {};\n", with_crate_prefix!(self.tcx.def_path_str(*trait_did)),)
1947         });
1948
1949         let glob_path_strings = globs.iter().map(|trait_did| {
1950             let parent_did = parent_map.get(trait_did).unwrap();
1951             format!(
1952                 "use {}::*; // trait {}\n",
1953                 with_crate_prefix!(self.tcx.def_path_str(*parent_did)),
1954                 self.tcx.item_name(*trait_did),
1955             )
1956         });
1957
1958         err.span_suggestions(
1959             span,
1960             &msg,
1961             path_strings.chain(glob_path_strings),
1962             Applicability::MaybeIncorrect,
1963         );
1964     }
1965
1966     fn suggest_valid_traits(
1967         &self,
1968         err: &mut Diagnostic,
1969         valid_out_of_scope_traits: Vec<DefId>,
1970     ) -> bool {
1971         if !valid_out_of_scope_traits.is_empty() {
1972             let mut candidates = valid_out_of_scope_traits;
1973             candidates.sort();
1974             candidates.dedup();
1975
1976             // `TryFrom` and `FromIterator` have no methods
1977             let edition_fix = candidates
1978                 .iter()
1979                 .find(|did| self.tcx.is_diagnostic_item(sym::TryInto, **did))
1980                 .copied();
1981
1982             err.help("items from traits can only be used if the trait is in scope");
1983             let msg = format!(
1984                 "the following {traits_are} implemented but not in scope; \
1985                  perhaps add a `use` for {one_of_them}:",
1986                 traits_are = if candidates.len() == 1 { "trait is" } else { "traits are" },
1987                 one_of_them = if candidates.len() == 1 { "it" } else { "one of them" },
1988             );
1989
1990             self.suggest_use_candidates(err, msg, candidates);
1991             if let Some(did) = edition_fix {
1992                 err.note(&format!(
1993                     "'{}' is included in the prelude starting in Edition 2021",
1994                     with_crate_prefix!(self.tcx.def_path_str(did))
1995                 ));
1996             }
1997
1998             true
1999         } else {
2000             false
2001         }
2002     }
2003
2004     fn suggest_traits_to_import(
2005         &self,
2006         err: &mut Diagnostic,
2007         span: Span,
2008         rcvr_ty: Ty<'tcx>,
2009         item_name: Ident,
2010         inputs_len: Option<usize>,
2011         source: SelfSource<'tcx>,
2012         valid_out_of_scope_traits: Vec<DefId>,
2013         unsatisfied_predicates: &[(
2014             ty::Predicate<'tcx>,
2015             Option<ty::Predicate<'tcx>>,
2016             Option<ObligationCause<'tcx>>,
2017         )],
2018         unsatisfied_bounds: bool,
2019     ) {
2020         let mut alt_rcvr_sugg = false;
2021         if let (SelfSource::MethodCall(rcvr), false) = (source, unsatisfied_bounds) {
2022             debug!(?span, ?item_name, ?rcvr_ty, ?rcvr);
2023             let skippable = [
2024                 self.tcx.lang_items().clone_trait(),
2025                 self.tcx.lang_items().deref_trait(),
2026                 self.tcx.lang_items().deref_mut_trait(),
2027                 self.tcx.lang_items().drop_trait(),
2028                 self.tcx.get_diagnostic_item(sym::AsRef),
2029             ];
2030             // Try alternative arbitrary self types that could fulfill this call.
2031             // FIXME: probe for all types that *could* be arbitrary self-types, not
2032             // just this list.
2033             for (rcvr_ty, post) in &[
2034                 (rcvr_ty, ""),
2035                 (self.tcx.mk_mut_ref(self.tcx.lifetimes.re_erased, rcvr_ty), "&mut "),
2036                 (self.tcx.mk_imm_ref(self.tcx.lifetimes.re_erased, rcvr_ty), "&"),
2037             ] {
2038                 match self.lookup_probe(span, item_name, *rcvr_ty, rcvr, ProbeScope::AllTraits) {
2039                     Ok(pick) => {
2040                         // If the method is defined for the receiver we have, it likely wasn't `use`d.
2041                         // We point at the method, but we just skip the rest of the check for arbitrary
2042                         // self types and rely on the suggestion to `use` the trait from
2043                         // `suggest_valid_traits`.
2044                         let did = Some(pick.item.container_id(self.tcx));
2045                         let skip = skippable.contains(&did);
2046                         if pick.autoderefs == 0 && !skip {
2047                             err.span_label(
2048                                 pick.item.ident(self.tcx).span,
2049                                 &format!("the method is available for `{}` here", rcvr_ty),
2050                             );
2051                         }
2052                         break;
2053                     }
2054                     Err(MethodError::Ambiguity(_)) => {
2055                         // If the method is defined (but ambiguous) for the receiver we have, it is also
2056                         // likely we haven't `use`d it. It may be possible that if we `Box`/`Pin`/etc.
2057                         // the receiver, then it might disambiguate this method, but I think these
2058                         // suggestions are generally misleading (see #94218).
2059                         break;
2060                     }
2061                     _ => {}
2062                 }
2063
2064                 for (rcvr_ty, pre) in &[
2065                     (self.tcx.mk_lang_item(*rcvr_ty, LangItem::OwnedBox), "Box::new"),
2066                     (self.tcx.mk_lang_item(*rcvr_ty, LangItem::Pin), "Pin::new"),
2067                     (self.tcx.mk_diagnostic_item(*rcvr_ty, sym::Arc), "Arc::new"),
2068                     (self.tcx.mk_diagnostic_item(*rcvr_ty, sym::Rc), "Rc::new"),
2069                 ] {
2070                     if let Some(new_rcvr_t) = *rcvr_ty
2071                         && let Ok(pick) = self.lookup_probe(
2072                             span,
2073                             item_name,
2074                             new_rcvr_t,
2075                             rcvr,
2076                             ProbeScope::AllTraits,
2077                         )
2078                     {
2079                         debug!("try_alt_rcvr: pick candidate {:?}", pick);
2080                         let did = Some(pick.item.container_id(self.tcx));
2081                         // We don't want to suggest a container type when the missing
2082                         // method is `.clone()` or `.deref()` otherwise we'd suggest
2083                         // `Arc::new(foo).clone()`, which is far from what the user wants.
2084                         // Explicitly ignore the `Pin::as_ref()` method as `Pin` does not
2085                         // implement the `AsRef` trait.
2086                         let skip = skippable.contains(&did)
2087                             || (("Pin::new" == *pre) && (sym::as_ref == item_name.name))
2088                             || inputs_len.map_or(false, |inputs_len| pick.item.kind == ty::AssocKind::Fn && self.tcx.fn_sig(pick.item.def_id).skip_binder().inputs().len() != inputs_len);
2089                         // Make sure the method is defined for the *actual* receiver: we don't
2090                         // want to treat `Box<Self>` as a receiver if it only works because of
2091                         // an autoderef to `&self`
2092                         if pick.autoderefs == 0 && !skip {
2093                             err.span_label(
2094                                 pick.item.ident(self.tcx).span,
2095                                 &format!("the method is available for `{}` here", new_rcvr_t),
2096                             );
2097                             err.multipart_suggestion(
2098                                 "consider wrapping the receiver expression with the \
2099                                     appropriate type",
2100                                 vec![
2101                                     (rcvr.span.shrink_to_lo(), format!("{}({}", pre, post)),
2102                                     (rcvr.span.shrink_to_hi(), ")".to_string()),
2103                                 ],
2104                                 Applicability::MaybeIncorrect,
2105                             );
2106                             // We don't care about the other suggestions.
2107                             alt_rcvr_sugg = true;
2108                         }
2109                     }
2110                 }
2111             }
2112         }
2113         if self.suggest_valid_traits(err, valid_out_of_scope_traits) {
2114             return;
2115         }
2116
2117         let type_is_local = self.type_derefs_to_local(span, rcvr_ty, source);
2118
2119         let mut arbitrary_rcvr = vec![];
2120         // There are no traits implemented, so lets suggest some traits to
2121         // implement, by finding ones that have the item name, and are
2122         // legal to implement.
2123         let mut candidates = all_traits(self.tcx)
2124             .into_iter()
2125             // Don't issue suggestions for unstable traits since they're
2126             // unlikely to be implementable anyway
2127             .filter(|info| match self.tcx.lookup_stability(info.def_id) {
2128                 Some(attr) => attr.level.is_stable(),
2129                 None => true,
2130             })
2131             .filter(|info| {
2132                 // We approximate the coherence rules to only suggest
2133                 // traits that are legal to implement by requiring that
2134                 // either the type or trait is local. Multi-dispatch means
2135                 // this isn't perfect (that is, there are cases when
2136                 // implementing a trait would be legal but is rejected
2137                 // here).
2138                 unsatisfied_predicates.iter().all(|(p, _, _)| {
2139                     match p.kind().skip_binder() {
2140                         // Hide traits if they are present in predicates as they can be fixed without
2141                         // having to implement them.
2142                         ty::PredicateKind::Trait(t) => t.def_id() == info.def_id,
2143                         ty::PredicateKind::Projection(p) => {
2144                             p.projection_ty.item_def_id == info.def_id
2145                         }
2146                         _ => false,
2147                     }
2148                 }) && (type_is_local || info.def_id.is_local())
2149                     && self
2150                         .associated_value(info.def_id, item_name)
2151                         .filter(|item| {
2152                             if let ty::AssocKind::Fn = item.kind {
2153                                 let id = item
2154                                     .def_id
2155                                     .as_local()
2156                                     .map(|def_id| self.tcx.hir().local_def_id_to_hir_id(def_id));
2157                                 if let Some(hir::Node::TraitItem(hir::TraitItem {
2158                                     kind: hir::TraitItemKind::Fn(fn_sig, method),
2159                                     ..
2160                                 })) = id.map(|id| self.tcx.hir().get(id))
2161                                 {
2162                                     let self_first_arg = match method {
2163                                         hir::TraitFn::Required([ident, ..]) => {
2164                                             ident.name == kw::SelfLower
2165                                         }
2166                                         hir::TraitFn::Provided(body_id) => {
2167                                             self.tcx.hir().body(*body_id).params.first().map_or(
2168                                                 false,
2169                                                 |param| {
2170                                                     matches!(
2171                                                         param.pat.kind,
2172                                                         hir::PatKind::Binding(_, _, ident, _)
2173                                                             if ident.name == kw::SelfLower
2174                                                     )
2175                                                 },
2176                                             )
2177                                         }
2178                                         _ => false,
2179                                     };
2180
2181                                     if !fn_sig.decl.implicit_self.has_implicit_self()
2182                                         && self_first_arg
2183                                     {
2184                                         if let Some(ty) = fn_sig.decl.inputs.get(0) {
2185                                             arbitrary_rcvr.push(ty.span);
2186                                         }
2187                                         return false;
2188                                     }
2189                                 }
2190                             }
2191                             // We only want to suggest public or local traits (#45781).
2192                             item.visibility(self.tcx).is_public() || info.def_id.is_local()
2193                         })
2194                         .is_some()
2195             })
2196             .collect::<Vec<_>>();
2197         for span in &arbitrary_rcvr {
2198             err.span_label(
2199                 *span,
2200                 "the method might not be found because of this arbitrary self type",
2201             );
2202         }
2203         if alt_rcvr_sugg {
2204             return;
2205         }
2206
2207         if !candidates.is_empty() {
2208             // Sort from most relevant to least relevant.
2209             candidates.sort_by(|a, b| a.cmp(b).reverse());
2210             candidates.dedup();
2211
2212             let param_type = match rcvr_ty.kind() {
2213                 ty::Param(param) => Some(param),
2214                 ty::Ref(_, ty, _) => match ty.kind() {
2215                     ty::Param(param) => Some(param),
2216                     _ => None,
2217                 },
2218                 _ => None,
2219             };
2220             err.help(if param_type.is_some() {
2221                 "items from traits can only be used if the type parameter is bounded by the trait"
2222             } else {
2223                 "items from traits can only be used if the trait is implemented and in scope"
2224             });
2225             let candidates_len = candidates.len();
2226             let message = |action| {
2227                 format!(
2228                     "the following {traits_define} an item `{name}`, perhaps you need to {action} \
2229                      {one_of_them}:",
2230                     traits_define =
2231                         if candidates_len == 1 { "trait defines" } else { "traits define" },
2232                     action = action,
2233                     one_of_them = if candidates_len == 1 { "it" } else { "one of them" },
2234                     name = item_name,
2235                 )
2236             };
2237             // Obtain the span for `param` and use it for a structured suggestion.
2238             if let Some(param) = param_type {
2239                 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2240                 let type_param = generics.type_param(param, self.tcx);
2241                 let hir = self.tcx.hir();
2242                 if let Some(def_id) = type_param.def_id.as_local() {
2243                     let id = hir.local_def_id_to_hir_id(def_id);
2244                     // Get the `hir::Param` to verify whether it already has any bounds.
2245                     // We do this to avoid suggesting code that ends up as `T: FooBar`,
2246                     // instead we suggest `T: Foo + Bar` in that case.
2247                     match hir.get(id) {
2248                         Node::GenericParam(param) => {
2249                             enum Introducer {
2250                                 Plus,
2251                                 Colon,
2252                                 Nothing,
2253                             }
2254                             let ast_generics = hir.get_generics(id.owner.def_id).unwrap();
2255                             let (sp, mut introducer) = if let Some(span) =
2256                                 ast_generics.bounds_span_for_suggestions(def_id)
2257                             {
2258                                 (span, Introducer::Plus)
2259                             } else if let Some(colon_span) = param.colon_span {
2260                                 (colon_span.shrink_to_hi(), Introducer::Nothing)
2261                             } else {
2262                                 (param.span.shrink_to_hi(), Introducer::Colon)
2263                             };
2264                             if matches!(
2265                                 param.kind,
2266                                 hir::GenericParamKind::Type { synthetic: true, .. },
2267                             ) {
2268                                 introducer = Introducer::Plus
2269                             }
2270                             let trait_def_ids: FxHashSet<DefId> = ast_generics
2271                                 .bounds_for_param(def_id)
2272                                 .flat_map(|bp| bp.bounds.iter())
2273                                 .filter_map(|bound| bound.trait_ref()?.trait_def_id())
2274                                 .collect();
2275                             if !candidates.iter().any(|t| trait_def_ids.contains(&t.def_id)) {
2276                                 err.span_suggestions(
2277                                     sp,
2278                                     &message(format!(
2279                                         "restrict type parameter `{}` with",
2280                                         param.name.ident(),
2281                                     )),
2282                                     candidates.iter().map(|t| {
2283                                         format!(
2284                                             "{} {}",
2285                                             match introducer {
2286                                                 Introducer::Plus => " +",
2287                                                 Introducer::Colon => ":",
2288                                                 Introducer::Nothing => "",
2289                                             },
2290                                             self.tcx.def_path_str(t.def_id),
2291                                         )
2292                                     }),
2293                                     Applicability::MaybeIncorrect,
2294                                 );
2295                             }
2296                             return;
2297                         }
2298                         Node::Item(hir::Item {
2299                             kind: hir::ItemKind::Trait(.., bounds, _),
2300                             ident,
2301                             ..
2302                         }) => {
2303                             let (sp, sep, article) = if bounds.is_empty() {
2304                                 (ident.span.shrink_to_hi(), ":", "a")
2305                             } else {
2306                                 (bounds.last().unwrap().span().shrink_to_hi(), " +", "another")
2307                             };
2308                             err.span_suggestions(
2309                                 sp,
2310                                 &message(format!("add {} supertrait for", article)),
2311                                 candidates.iter().map(|t| {
2312                                     format!("{} {}", sep, self.tcx.def_path_str(t.def_id),)
2313                                 }),
2314                                 Applicability::MaybeIncorrect,
2315                             );
2316                             return;
2317                         }
2318                         _ => {}
2319                     }
2320                 }
2321             }
2322
2323             let (potential_candidates, explicitly_negative) = if param_type.is_some() {
2324                 // FIXME: Even though negative bounds are not implemented, we could maybe handle
2325                 // cases where a positive bound implies a negative impl.
2326                 (candidates, Vec::new())
2327             } else if let Some(simp_rcvr_ty) =
2328                 simplify_type(self.tcx, rcvr_ty, TreatParams::AsPlaceholder)
2329             {
2330                 let mut potential_candidates = Vec::new();
2331                 let mut explicitly_negative = Vec::new();
2332                 for candidate in candidates {
2333                     // Check if there's a negative impl of `candidate` for `rcvr_ty`
2334                     if self
2335                         .tcx
2336                         .all_impls(candidate.def_id)
2337                         .filter(|imp_did| {
2338                             self.tcx.impl_polarity(*imp_did) == ty::ImplPolarity::Negative
2339                         })
2340                         .any(|imp_did| {
2341                             let imp = self.tcx.impl_trait_ref(imp_did).unwrap();
2342                             let imp_simp =
2343                                 simplify_type(self.tcx, imp.self_ty(), TreatParams::AsPlaceholder);
2344                             imp_simp.map_or(false, |s| s == simp_rcvr_ty)
2345                         })
2346                     {
2347                         explicitly_negative.push(candidate);
2348                     } else {
2349                         potential_candidates.push(candidate);
2350                     }
2351                 }
2352                 (potential_candidates, explicitly_negative)
2353             } else {
2354                 // We don't know enough about `recv_ty` to make proper suggestions.
2355                 (candidates, Vec::new())
2356             };
2357
2358             let action = if let Some(param) = param_type {
2359                 format!("restrict type parameter `{}` with", param)
2360             } else {
2361                 // FIXME: it might only need to be imported into scope, not implemented.
2362                 "implement".to_string()
2363             };
2364             match &potential_candidates[..] {
2365                 [] => {}
2366                 [trait_info] if trait_info.def_id.is_local() => {
2367                     err.span_note(
2368                         self.tcx.def_span(trait_info.def_id),
2369                         &format!(
2370                             "`{}` defines an item `{}`, perhaps you need to {} it",
2371                             self.tcx.def_path_str(trait_info.def_id),
2372                             item_name,
2373                             action
2374                         ),
2375                     );
2376                 }
2377                 trait_infos => {
2378                     let mut msg = message(action);
2379                     for (i, trait_info) in trait_infos.iter().enumerate() {
2380                         msg.push_str(&format!(
2381                             "\ncandidate #{}: `{}`",
2382                             i + 1,
2383                             self.tcx.def_path_str(trait_info.def_id),
2384                         ));
2385                     }
2386                     err.note(&msg);
2387                 }
2388             }
2389             match &explicitly_negative[..] {
2390                 [] => {}
2391                 [trait_info] => {
2392                     let msg = format!(
2393                         "the trait `{}` defines an item `{}`, but is explicitly unimplemented",
2394                         self.tcx.def_path_str(trait_info.def_id),
2395                         item_name
2396                     );
2397                     err.note(&msg);
2398                 }
2399                 trait_infos => {
2400                     let mut msg = format!(
2401                         "the following traits define an item `{}`, but are explicitly unimplemented:",
2402                         item_name
2403                     );
2404                     for trait_info in trait_infos {
2405                         msg.push_str(&format!("\n{}", self.tcx.def_path_str(trait_info.def_id)));
2406                     }
2407                     err.note(&msg);
2408                 }
2409             }
2410         }
2411     }
2412
2413     /// issue #102320, for `unwrap_or` with closure as argument, suggest `unwrap_or_else`
2414     /// FIXME: currently not working for suggesting `map_or_else`, see #102408
2415     pub(crate) fn suggest_else_fn_with_closure(
2416         &self,
2417         err: &mut Diagnostic,
2418         expr: &hir::Expr<'_>,
2419         found: Ty<'tcx>,
2420         expected: Ty<'tcx>,
2421     ) -> bool {
2422         let Some((_def_id_or_name, output, _inputs)) = self.extract_callable_info(expr, found)
2423         else { return false; };
2424
2425         if !self.can_coerce(output, expected) {
2426             return false;
2427         }
2428
2429         let parent = self.tcx.hir().get_parent_node(expr.hir_id);
2430         if  let Some(Node::Expr(call_expr)) = self.tcx.hir().find(parent) &&
2431             let hir::ExprKind::MethodCall(
2432                 hir::PathSegment { ident: method_name, .. },
2433                 self_expr,
2434                 args,
2435                 ..,
2436              ) = call_expr.kind &&
2437             let Some(self_ty) = self.typeck_results.borrow().expr_ty_opt(self_expr) {
2438             let new_name = Ident {
2439                 name: Symbol::intern(&format!("{}_else", method_name.as_str())),
2440                 span: method_name.span,
2441             };
2442             let probe = self.lookup_probe(
2443                 expr.span,
2444                 new_name,
2445                 self_ty,
2446                 self_expr,
2447                 ProbeScope::TraitsInScope,
2448             );
2449
2450             // check the method arguments number
2451             if let Ok(pick) = probe &&
2452                 let fn_sig = self.tcx.fn_sig(pick.item.def_id) &&
2453                 let fn_args = fn_sig.skip_binder().inputs() &&
2454                 fn_args.len() == args.len() + 1 {
2455                 err.span_suggestion_verbose(
2456                     method_name.span.shrink_to_hi(),
2457                     &format!("try calling `{}` instead", new_name.name.as_str()),
2458                     "_else",
2459                     Applicability::MaybeIncorrect,
2460                 );
2461                 return true;
2462             }
2463         }
2464         false
2465     }
2466
2467     /// Checks whether there is a local type somewhere in the chain of
2468     /// autoderefs of `rcvr_ty`.
2469     fn type_derefs_to_local(
2470         &self,
2471         span: Span,
2472         rcvr_ty: Ty<'tcx>,
2473         source: SelfSource<'tcx>,
2474     ) -> bool {
2475         fn is_local(ty: Ty<'_>) -> bool {
2476             match ty.kind() {
2477                 ty::Adt(def, _) => def.did().is_local(),
2478                 ty::Foreign(did) => did.is_local(),
2479                 ty::Dynamic(tr, ..) => tr.principal().map_or(false, |d| d.def_id().is_local()),
2480                 ty::Param(_) => true,
2481
2482                 // Everything else (primitive types, etc.) is effectively
2483                 // non-local (there are "edge" cases, e.g., `(LocalType,)`, but
2484                 // the noise from these sort of types is usually just really
2485                 // annoying, rather than any sort of help).
2486                 _ => false,
2487             }
2488         }
2489
2490         // This occurs for UFCS desugaring of `T::method`, where there is no
2491         // receiver expression for the method call, and thus no autoderef.
2492         if let SelfSource::QPath(_) = source {
2493             return is_local(self.resolve_vars_with_obligations(rcvr_ty));
2494         }
2495
2496         self.autoderef(span, rcvr_ty).any(|(ty, _)| is_local(ty))
2497     }
2498 }
2499
2500 #[derive(Copy, Clone, Debug)]
2501 pub enum SelfSource<'a> {
2502     QPath(&'a hir::Ty<'a>),
2503     MethodCall(&'a hir::Expr<'a> /* rcvr */),
2504 }
2505
2506 #[derive(Copy, Clone)]
2507 pub struct TraitInfo {
2508     pub def_id: DefId,
2509 }
2510
2511 impl PartialEq for TraitInfo {
2512     fn eq(&self, other: &TraitInfo) -> bool {
2513         self.cmp(other) == Ordering::Equal
2514     }
2515 }
2516 impl Eq for TraitInfo {}
2517 impl PartialOrd for TraitInfo {
2518     fn partial_cmp(&self, other: &TraitInfo) -> Option<Ordering> {
2519         Some(self.cmp(other))
2520     }
2521 }
2522 impl Ord for TraitInfo {
2523     fn cmp(&self, other: &TraitInfo) -> Ordering {
2524         // Local crates are more important than remote ones (local:
2525         // `cnum == 0`), and otherwise we throw in the defid for totality.
2526
2527         let lhs = (other.def_id.krate, other.def_id);
2528         let rhs = (self.def_id.krate, self.def_id);
2529         lhs.cmp(&rhs)
2530     }
2531 }
2532
2533 /// Retrieves all traits in this crate and any dependent crates,
2534 /// and wraps them into `TraitInfo` for custom sorting.
2535 pub fn all_traits(tcx: TyCtxt<'_>) -> Vec<TraitInfo> {
2536     tcx.all_traits().map(|def_id| TraitInfo { def_id }).collect()
2537 }
2538
2539 fn print_disambiguation_help<'tcx>(
2540     item_name: Ident,
2541     args: Option<(&'tcx hir::Expr<'tcx>, &'tcx [hir::Expr<'tcx>])>,
2542     err: &mut Diagnostic,
2543     trait_name: String,
2544     rcvr_ty: Ty<'_>,
2545     kind: ty::AssocKind,
2546     def_id: DefId,
2547     span: Span,
2548     candidate: Option<usize>,
2549     source_map: &source_map::SourceMap,
2550     fn_has_self_parameter: bool,
2551 ) {
2552     let mut applicability = Applicability::MachineApplicable;
2553     let (span, sugg) = if let (ty::AssocKind::Fn, Some((receiver, args))) = (kind, args) {
2554         let args = format!(
2555             "({}{})",
2556             if rcvr_ty.is_region_ptr() {
2557                 if rcvr_ty.is_mutable_ptr() { "&mut " } else { "&" }
2558             } else {
2559                 ""
2560             },
2561             std::iter::once(receiver)
2562                 .chain(args.iter())
2563                 .map(|arg| source_map.span_to_snippet(arg.span).unwrap_or_else(|_| {
2564                     applicability = Applicability::HasPlaceholders;
2565                     "_".to_owned()
2566                 }))
2567                 .collect::<Vec<_>>()
2568                 .join(", "),
2569         );
2570         let trait_name = if !fn_has_self_parameter {
2571             format!("<{} as {}>", rcvr_ty, trait_name)
2572         } else {
2573             trait_name
2574         };
2575         (span, format!("{}::{}{}", trait_name, item_name, args))
2576     } else {
2577         (span.with_hi(item_name.span.lo()), format!("<{} as {}>::", rcvr_ty, trait_name))
2578     };
2579     err.span_suggestion_verbose(
2580         span,
2581         &format!(
2582             "disambiguate the {} for {}",
2583             kind.as_def_kind().descr(def_id),
2584             if let Some(candidate) = candidate {
2585                 format!("candidate #{}", candidate)
2586             } else {
2587                 "the candidate".to_string()
2588             },
2589         ),
2590         sugg,
2591         applicability,
2592     );
2593 }