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