compiler/rustc_borrowck/src/diagnostics/mod.rs

   1 //! Borrow checker diagnostics.
   2
   3 use rustc_const_eval::util::call_kind;
   4 use rustc_errors::DiagnosticBuilder;
   5 use rustc_hir as hir;
   6 use rustc_hir::def::Namespace;
   7 use rustc_hir::def_id::DefId;
   8 use rustc_hir::GeneratorKind;
   9 use rustc_middle::mir::{
  10     AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
  11     Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
  12 };
  13 use rustc_middle::ty::print::Print;
  14 use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
  15 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
  16 use rustc_span::{symbol::sym, Span};
  17 use rustc_target::abi::VariantIdx;
  18
  19 use super::borrow_set::BorrowData;
  20 use super::MirBorrowckCtxt;
  21
  22 mod find_all_local_uses;
  23 mod find_use;
  24 mod outlives_suggestion;
  25 mod region_name;
  26 mod var_name;
  27
  28 mod bound_region_errors;
  29 mod conflict_errors;
  30 mod explain_borrow;
  31 mod move_errors;
  32 mod mutability_errors;
  33 mod region_errors;
  34
  35 crate use bound_region_errors::{ToUniverseInfo, UniverseInfo};
  36 crate use mutability_errors::AccessKind;
  37 crate use outlives_suggestion::OutlivesSuggestionBuilder;
  38 crate use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
  39 crate use region_name::{RegionName, RegionNameSource};
  40 crate use rustc_const_eval::util::CallKind;
  41
  42 pub(super) struct IncludingDowncast(pub(super) bool);
  43
  44 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
  45     /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
  46     /// is moved after being invoked.
  47     ///
  48     /// ```text
  49     /// note: closure cannot be invoked more than once because it moves the variable `dict` out of
  50     ///       its environment
  51     ///   --> $DIR/issue-42065.rs:16:29
  52     ///    |
  53     /// LL |         for (key, value) in dict {
  54     ///    |                             ^^^^
  55     /// ```
  56     pub(super) fn add_moved_or_invoked_closure_note(
  57         &self,
  58         location: Location,
  59         place: PlaceRef<'tcx>,
  60         diag: &mut DiagnosticBuilder<'_>,
  61     ) {
  62         debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
  63         let mut target = place.local_or_deref_local();
  64         for stmt in &self.body[location.block].statements[location.statement_index..] {
  65             debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
  66             if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind {
  67                 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
  68                 match from {
  69                     Operand::Copy(ref place) | Operand::Move(ref place)
  70                         if target == place.local_or_deref_local() =>
  71                     {
  72                         target = into.local_or_deref_local()
  73                     }
  74                     _ => {}
  75                 }
  76             }
  77         }
  78
  79         // Check if we are attempting to call a closure after it has been invoked.
  80         let terminator = self.body[location.block].terminator();
  81         debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator);
  82         if let TerminatorKind::Call {
  83             func: Operand::Constant(box Constant { literal, .. }),
  84             args,
  85             ..
  86         } = &terminator.kind
  87         {
  88             if let ty::FnDef(id, _) = *literal.ty().kind() {
  89                 debug!("add_moved_or_invoked_closure_note: id={:?}", id);
  90                 if self.infcx.tcx.parent(id) == self.infcx.tcx.lang_items().fn_once_trait() {
  91                     let closure = match args.first() {
  92                         Some(Operand::Copy(ref place)) | Some(Operand::Move(ref place))
  93                             if target == place.local_or_deref_local() =>
  94                         {
  95                             place.local_or_deref_local().unwrap()
  96                         }
  97                         _ => return,
  98                     };
  99
 100                     debug!("add_moved_or_invoked_closure_note: closure={:?}", closure);
 101                     if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
 102                         let did = did.expect_local();
 103                         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
 104
 105                         if let Some((span, hir_place)) =
 106                             self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
 107                         {
 108                             diag.span_note(
 109                                 *span,
 110                                 &format!(
 111                                     "closure cannot be invoked more than once because it moves the \
 112                                     variable `{}` out of its environment",
 113                                     ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
 114                                 ),
 115                             );
 116                             return;
 117                         }
 118                     }
 119                 }
 120             }
 121         }
 122
 123         // Check if we are just moving a closure after it has been invoked.
 124         if let Some(target) = target {
 125             if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
 126                 let did = did.expect_local();
 127                 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
 128
 129                 if let Some((span, hir_place)) =
 130                     self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
 131                 {
 132                     diag.span_note(
 133                         *span,
 134                         &format!(
 135                             "closure cannot be moved more than once as it is not `Copy` due to \
 136                              moving the variable `{}` out of its environment",
 137                             ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
 138                         ),
 139                     );
 140                 }
 141             }
 142         }
 143     }
 144
 145     /// End-user visible description of `place` if one can be found.
 146     /// If the place is a temporary for instance, `"value"` will be returned.
 147     pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
 148         match self.describe_place(place_ref) {
 149             Some(mut descr) => {
 150                 // Surround descr with `backticks`.
 151                 descr.reserve(2);
 152                 descr.insert(0, '`');
 153                 descr.push('`');
 154                 descr
 155             }
 156             None => "value".to_string(),
 157         }
 158     }
 159
 160     /// End-user visible description of `place` if one can be found.
 161     /// If the place is a temporary for instance, None will be returned.
 162     pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> {
 163         self.describe_place_with_options(place_ref, IncludingDowncast(false))
 164     }
 165
 166     /// End-user visible description of `place` if one can be found. If the
 167     /// place is a temporary for instance, None will be returned.
 168     /// `IncludingDowncast` parameter makes the function return `Err` if `ProjectionElem` is
 169     /// `Downcast` and `IncludingDowncast` is true
 170     pub(super) fn describe_place_with_options(
 171         &self,
 172         place: PlaceRef<'tcx>,
 173         including_downcast: IncludingDowncast,
 174     ) -> Option<String> {
 175         let mut buf = String::new();
 176         match self.append_place_to_string(place, &mut buf, false, &including_downcast) {
 177             Ok(()) => Some(buf),
 178             Err(()) => None,
 179         }
 180     }
 181
 182     /// Appends end-user visible description of `place` to `buf`.
 183     fn append_place_to_string(
 184         &self,
 185         place: PlaceRef<'tcx>,
 186         buf: &mut String,
 187         mut autoderef: bool,
 188         including_downcast: &IncludingDowncast,
 189     ) -> Result<(), ()> {
 190         match place {
 191             PlaceRef { local, projection: [] } => {
 192                 self.append_local_to_string(local, buf)?;
 193             }
 194             PlaceRef { local, projection: [ProjectionElem::Deref] }
 195                 if self.body.local_decls[local].is_ref_for_guard() =>
 196             {
 197                 self.append_place_to_string(
 198                     PlaceRef { local, projection: &[] },
 199                     buf,
 200                     autoderef,
 201                     &including_downcast,
 202                 )?;
 203             }
 204             PlaceRef { local, projection: [ProjectionElem::Deref] }
 205                 if self.body.local_decls[local].is_ref_to_static() =>
 206             {
 207                 let local_info = &self.body.local_decls[local].local_info;
 208                 if let Some(box LocalInfo::StaticRef { def_id, .. }) = *local_info {
 209                     buf.push_str(self.infcx.tcx.item_name(def_id).as_str());
 210                 } else {
 211                     unreachable!();
 212                 }
 213             }
 214             PlaceRef { local, projection: [proj_base @ .., elem] } => {
 215                 match elem {
 216                     ProjectionElem::Deref => {
 217                         let upvar_field_projection = self.is_upvar_field_projection(place);
 218                         if let Some(field) = upvar_field_projection {
 219                             let var_index = field.index();
 220                             let name = self.upvars[var_index].place.to_string(self.infcx.tcx);
 221                             if self.upvars[var_index].by_ref {
 222                                 buf.push_str(&name);
 223                             } else {
 224                                 buf.push('*');
 225                                 buf.push_str(&name);
 226                             }
 227                         } else {
 228                             if autoderef {
 229                                 // FIXME turn this recursion into iteration
 230                                 self.append_place_to_string(
 231                                     PlaceRef { local, projection: proj_base },
 232                                     buf,
 233                                     autoderef,
 234                                     &including_downcast,
 235                                 )?;
 236                             } else {
 237                                 buf.push('*');
 238                                 self.append_place_to_string(
 239                                     PlaceRef { local, projection: proj_base },
 240                                     buf,
 241                                     autoderef,
 242                                     &including_downcast,
 243                                 )?;
 244                             }
 245                         }
 246                     }
 247                     ProjectionElem::Downcast(..) => {
 248                         self.append_place_to_string(
 249                             PlaceRef { local, projection: proj_base },
 250                             buf,
 251                             autoderef,
 252                             &including_downcast,
 253                         )?;
 254                         if including_downcast.0 {
 255                             return Err(());
 256                         }
 257                     }
 258                     ProjectionElem::Field(field, _ty) => {
 259                         autoderef = true;
 260
 261                         // FIXME(project-rfc_2229#36): print capture precisely here.
 262                         let upvar_field_projection = self.is_upvar_field_projection(place);
 263                         if let Some(field) = upvar_field_projection {
 264                             let var_index = field.index();
 265                             let name = self.upvars[var_index].place.to_string(self.infcx.tcx);
 266                             buf.push_str(&name);
 267                         } else {
 268                             let field_name = self
 269                                 .describe_field(PlaceRef { local, projection: proj_base }, *field);
 270                             self.append_place_to_string(
 271                                 PlaceRef { local, projection: proj_base },
 272                                 buf,
 273                                 autoderef,
 274                                 &including_downcast,
 275                             )?;
 276                             buf.push('.');
 277                             buf.push_str(&field_name);
 278                         }
 279                     }
 280                     ProjectionElem::Index(index) => {
 281                         autoderef = true;
 282
 283                         self.append_place_to_string(
 284                             PlaceRef { local, projection: proj_base },
 285                             buf,
 286                             autoderef,
 287                             &including_downcast,
 288                         )?;
 289                         buf.push('[');
 290                         if self.append_local_to_string(*index, buf).is_err() {
 291                             buf.push('_');
 292                         }
 293                         buf.push(']');
 294                     }
 295                     ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
 296                         autoderef = true;
 297                         // Since it isn't possible to borrow an element on a particular index and
 298                         // then use another while the borrow is held, don't output indices details
 299                         // to avoid confusing the end-user
 300                         self.append_place_to_string(
 301                             PlaceRef { local, projection: proj_base },
 302                             buf,
 303                             autoderef,
 304                             &including_downcast,
 305                         )?;
 306                         buf.push_str("[..]");
 307                     }
 308                 };
 309             }
 310         }
 311
 312         Ok(())
 313     }
 314
 315     /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have
 316     /// a name, or its name was generated by the compiler, then `Err` is returned
 317     fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> {
 318         let decl = &self.body.local_decls[local];
 319         match self.local_names[local] {
 320             Some(name) if !decl.from_compiler_desugaring() => {
 321                 buf.push_str(name.as_str());
 322                 Ok(())
 323             }
 324             _ => Err(()),
 325         }
 326     }
 327
 328     /// End-user visible description of the `field`nth field of `base`
 329     fn describe_field(&self, place: PlaceRef<'tcx>, field: Field) -> String {
 330         // FIXME Place2 Make this work iteratively
 331         match place {
 332             PlaceRef { local, projection: [] } => {
 333                 let local = &self.body.local_decls[local];
 334                 self.describe_field_from_ty(local.ty, field, None)
 335             }
 336             PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
 337                 ProjectionElem::Deref => {
 338                     self.describe_field(PlaceRef { local, projection: proj_base }, field)
 339                 }
 340                 ProjectionElem::Downcast(_, variant_index) => {
 341                     let base_ty = place.ty(self.body, self.infcx.tcx).ty;
 342                     self.describe_field_from_ty(base_ty, field, Some(*variant_index))
 343                 }
 344                 ProjectionElem::Field(_, field_type) => {
 345                     self.describe_field_from_ty(*field_type, field, None)
 346                 }
 347                 ProjectionElem::Index(..)
 348                 | ProjectionElem::ConstantIndex { .. }
 349                 | ProjectionElem::Subslice { .. } => {
 350                     self.describe_field(PlaceRef { local, projection: proj_base }, field)
 351                 }
 352             },
 353         }
 354     }
 355
 356     /// End-user visible description of the `field_index`nth field of `ty`
 357     fn describe_field_from_ty(
 358         &self,
 359         ty: Ty<'_>,
 360         field: Field,
 361         variant_index: Option<VariantIdx>,
 362     ) -> String {
 363         if ty.is_box() {
 364             // If the type is a box, the field is described from the boxed type
 365             self.describe_field_from_ty(ty.boxed_ty(), field, variant_index)
 366         } else {
 367             match *ty.kind() {
 368                 ty::Adt(def, _) => {
 369                     let variant = if let Some(idx) = variant_index {
 370                         assert!(def.is_enum());
 371                         &def.variants[idx]
 372                     } else {
 373                         def.non_enum_variant()
 374                     };
 375                     variant.fields[field.index()].name.to_string()
 376                 }
 377                 ty::Tuple(_) => field.index().to_string(),
 378                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 379                     self.describe_field_from_ty(ty, field, variant_index)
 380                 }
 381                 ty::Array(ty, _) | ty::Slice(ty) => {
 382                     self.describe_field_from_ty(ty, field, variant_index)
 383                 }
 384                 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
 385                     // We won't be borrowck'ing here if the closure came from another crate,
 386                     // so it's safe to call `expect_local`.
 387                     //
 388                     // We know the field exists so it's safe to call operator[] and `unwrap` here.
 389                     let var_id = self
 390                         .infcx
 391                         .tcx
 392                         .typeck(def_id.expect_local())
 393                         .closure_min_captures_flattened(def_id)
 394                         .nth(field.index())
 395                         .unwrap()
 396                         .get_root_variable();
 397
 398                     self.infcx.tcx.hir().name(var_id).to_string()
 399                 }
 400                 _ => {
 401                     // Might need a revision when the fields in trait RFC is implemented
 402                     // (https://github.com/rust-lang/rfcs/pull/1546)
 403                     bug!("End-user description not implemented for field access on `{:?}`", ty);
 404                 }
 405             }
 406         }
 407     }
 408
 409     /// Add a note that a type does not implement `Copy`
 410     pub(super) fn note_type_does_not_implement_copy(
 411         &self,
 412         err: &mut DiagnosticBuilder<'_>,
 413         place_desc: &str,
 414         ty: Ty<'tcx>,
 415         span: Option<Span>,
 416         move_prefix: &str,
 417     ) {
 418         let message = format!(
 419             "{}move occurs because {} has type `{}`, which does not implement the `Copy` trait",
 420             move_prefix, place_desc, ty,
 421         );
 422         if let Some(span) = span {
 423             err.span_label(span, message);
 424         } else {
 425             err.note(&message);
 426         }
 427     }
 428
 429     pub(super) fn borrowed_content_source(
 430         &self,
 431         deref_base: PlaceRef<'tcx>,
 432     ) -> BorrowedContentSource<'tcx> {
 433         let tcx = self.infcx.tcx;
 434
 435         // Look up the provided place and work out the move path index for it,
 436         // we'll use this to check whether it was originally from an overloaded
 437         // operator.
 438         match self.move_data.rev_lookup.find(deref_base) {
 439             LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
 440                 debug!("borrowed_content_source: mpi={:?}", mpi);
 441
 442                 for i in &self.move_data.init_path_map[mpi] {
 443                     let init = &self.move_data.inits[*i];
 444                     debug!("borrowed_content_source: init={:?}", init);
 445                     // We're only interested in statements that initialized a value, not the
 446                     // initializations from arguments.
 447                     let InitLocation::Statement(loc) = init.location else { continue };
 448
 449                     let bbd = &self.body[loc.block];
 450                     let is_terminator = bbd.statements.len() == loc.statement_index;
 451                     debug!(
 452                         "borrowed_content_source: loc={:?} is_terminator={:?}",
 453                         loc, is_terminator,
 454                     );
 455                     if !is_terminator {
 456                         continue;
 457                     } else if let Some(Terminator {
 458                         kind: TerminatorKind::Call { ref func, from_hir_call: false, .. },
 459                         ..
 460                     }) = bbd.terminator
 461                     {
 462                         if let Some(source) =
 463                             BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
 464                         {
 465                             return source;
 466                         }
 467                     }
 468                 }
 469             }
 470             // Base is a `static` so won't be from an overloaded operator
 471             _ => (),
 472         };
 473
 474         // If we didn't find an overloaded deref or index, then assume it's a
 475         // built in deref and check the type of the base.
 476         let base_ty = deref_base.ty(self.body, tcx).ty;
 477         if base_ty.is_unsafe_ptr() {
 478             BorrowedContentSource::DerefRawPointer
 479         } else if base_ty.is_mutable_ptr() {
 480             BorrowedContentSource::DerefMutableRef
 481         } else {
 482             BorrowedContentSource::DerefSharedRef
 483         }
 484     }
 485 }
 486
 487 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 488     /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
 489     /// name where required.
 490     pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 491         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 492
 493         // We need to add synthesized lifetimes where appropriate. We do
 494         // this by hooking into the pretty printer and telling it to label the
 495         // lifetimes without names with the value `'0`.
 496         if let ty::Ref(region, ..) = ty.kind() {
 497             match **region {
 498                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 499                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 500                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 501                 }
 502                 _ => {}
 503             }
 504         }
 505
 506         ty.print(printer).unwrap().into_buffer()
 507     }
 508
 509     /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
 510     /// synthesized lifetime name where required.
 511     pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 512         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 513
 514         let region = if let ty::Ref(region, ..) = ty.kind() {
 515             match **region {
 516                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 517                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 518                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 519                 }
 520                 _ => {}
 521             }
 522             region
 523         } else {
 524             bug!("ty for annotation of borrow region is not a reference");
 525         };
 526
 527         region.print(printer).unwrap().into_buffer()
 528     }
 529 }
 530
 531 /// The span(s) associated to a use of a place.
 532 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 533 pub(super) enum UseSpans<'tcx> {
 534     /// The access is caused by capturing a variable for a closure.
 535     ClosureUse {
 536         /// This is true if the captured variable was from a generator.
 537         generator_kind: Option<GeneratorKind>,
 538         /// The span of the args of the closure, including the `move` keyword if
 539         /// it's present.
 540         args_span: Span,
 541         /// The span of the use resulting in capture kind
 542         /// Check `ty::CaptureInfo` for more details
 543         capture_kind_span: Span,
 544         /// The span of the use resulting in the captured path
 545         /// Check `ty::CaptureInfo` for more details
 546         path_span: Span,
 547     },
 548     /// The access is caused by using a variable as the receiver of a method
 549     /// that takes 'self'
 550     FnSelfUse {
 551         /// The span of the variable being moved
 552         var_span: Span,
 553         /// The span of the method call on the variable
 554         fn_call_span: Span,
 555         /// The definition span of the method being called
 556         fn_span: Span,
 557         kind: CallKind<'tcx>,
 558     },
 559     /// This access is caused by a `match` or `if let` pattern.
 560     PatUse(Span),
 561     /// This access has a single span associated to it: common case.
 562     OtherUse(Span),
 563 }
 564
 565 impl UseSpans<'_> {
 566     pub(super) fn args_or_use(self) -> Span {
 567         match self {
 568             UseSpans::ClosureUse { args_span: span, .. }
 569             | UseSpans::PatUse(span)
 570             | UseSpans::OtherUse(span) => span,
 571             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 572                 fn_call_span
 573             }
 574             UseSpans::FnSelfUse { var_span, .. } => var_span,
 575         }
 576     }
 577
 578     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
 579     pub(super) fn var_or_use_path_span(self) -> Span {
 580         match self {
 581             UseSpans::ClosureUse { path_span: span, .. }
 582             | UseSpans::PatUse(span)
 583             | UseSpans::OtherUse(span) => span,
 584             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 585                 fn_call_span
 586             }
 587             UseSpans::FnSelfUse { var_span, .. } => var_span,
 588         }
 589     }
 590
 591     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
 592     pub(super) fn var_or_use(self) -> Span {
 593         match self {
 594             UseSpans::ClosureUse { capture_kind_span: span, .. }
 595             | UseSpans::PatUse(span)
 596             | UseSpans::OtherUse(span) => span,
 597             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 598                 fn_call_span
 599             }
 600             UseSpans::FnSelfUse { var_span, .. } => var_span,
 601         }
 602     }
 603
 604     pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
 605         match self {
 606             UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
 607             _ => None,
 608         }
 609     }
 610
 611     // Add a span label to the arguments of the closure, if it exists.
 612     pub(super) fn args_span_label(
 613         self,
 614         err: &mut DiagnosticBuilder<'_>,
 615         message: impl Into<String>,
 616     ) {
 617         if let UseSpans::ClosureUse { args_span, .. } = self {
 618             err.span_label(args_span, message);
 619         }
 620     }
 621
 622     // Add a span label to the use of the captured variable, if it exists.
 623     // only adds label to the `path_span`
 624     pub(super) fn var_span_label_path_only(
 625         self,
 626         err: &mut DiagnosticBuilder<'_>,
 627         message: impl Into<String>,
 628     ) {
 629         if let UseSpans::ClosureUse { path_span, .. } = self {
 630             err.span_label(path_span, message);
 631         }
 632     }
 633
 634     // Add a span label to the use of the captured variable, if it exists.
 635     pub(super) fn var_span_label(
 636         self,
 637         err: &mut DiagnosticBuilder<'_>,
 638         message: impl Into<String>,
 639         kind_desc: impl Into<String>,
 640     ) {
 641         if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
 642             if capture_kind_span == path_span {
 643                 err.span_label(capture_kind_span, message);
 644             } else {
 645                 let capture_kind_label =
 646                     format!("capture is {} because of use here", kind_desc.into());
 647                 let path_label = message;
 648                 err.span_label(capture_kind_span, capture_kind_label);
 649                 err.span_label(path_span, path_label);
 650             }
 651         }
 652     }
 653
 654     /// Returns `false` if this place is not used in a closure.
 655     pub(super) fn for_closure(&self) -> bool {
 656         match *self {
 657             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
 658             _ => false,
 659         }
 660     }
 661
 662     /// Returns `false` if this place is not used in a generator.
 663     pub(super) fn for_generator(&self) -> bool {
 664         match *self {
 665             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
 666             _ => false,
 667         }
 668     }
 669
 670     /// Describe the span associated with a use of a place.
 671     pub(super) fn describe(&self) -> String {
 672         match *self {
 673             UseSpans::ClosureUse { generator_kind, .. } => {
 674                 if generator_kind.is_some() {
 675                     " in generator".to_string()
 676                 } else {
 677                     " in closure".to_string()
 678                 }
 679             }
 680             _ => String::new(),
 681         }
 682     }
 683
 684     pub(super) fn or_else<F>(self, if_other: F) -> Self
 685     where
 686         F: FnOnce() -> Self,
 687     {
 688         match self {
 689             closure @ UseSpans::ClosureUse { .. } => closure,
 690             UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
 691             fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
 692         }
 693     }
 694 }
 695
 696 pub(super) enum BorrowedContentSource<'tcx> {
 697     DerefRawPointer,
 698     DerefMutableRef,
 699     DerefSharedRef,
 700     OverloadedDeref(Ty<'tcx>),
 701     OverloadedIndex(Ty<'tcx>),
 702 }
 703
 704 impl<'tcx> BorrowedContentSource<'tcx> {
 705     pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
 706         match *self {
 707             BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
 708             BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
 709             BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
 710             BorrowedContentSource::OverloadedDeref(ty) => ty
 711                 .ty_adt_def()
 712                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 713                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 714                     _ => None,
 715                 })
 716                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 717             BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
 718         }
 719     }
 720
 721     pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
 722         match *self {
 723             BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
 724             BorrowedContentSource::DerefSharedRef => Some("shared reference"),
 725             BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
 726             // Overloaded deref and index operators should be evaluated into a
 727             // temporary. So we don't need a description here.
 728             BorrowedContentSource::OverloadedDeref(_)
 729             | BorrowedContentSource::OverloadedIndex(_) => None,
 730         }
 731     }
 732
 733     pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
 734         match *self {
 735             BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
 736             BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
 737             BorrowedContentSource::DerefMutableRef => {
 738                 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
 739             }
 740             BorrowedContentSource::OverloadedDeref(ty) => ty
 741                 .ty_adt_def()
 742                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 743                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 744                     _ => None,
 745                 })
 746                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 747             BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
 748         }
 749     }
 750
 751     fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
 752         match *func.kind() {
 753             ty::FnDef(def_id, substs) => {
 754                 let trait_id = tcx.trait_of_item(def_id)?;
 755
 756                 let lang_items = tcx.lang_items();
 757                 if Some(trait_id) == lang_items.deref_trait()
 758                     || Some(trait_id) == lang_items.deref_mut_trait()
 759                 {
 760                     Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
 761                 } else if Some(trait_id) == lang_items.index_trait()
 762                     || Some(trait_id) == lang_items.index_mut_trait()
 763                 {
 764                     Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
 765                 } else {
 766                     None
 767                 }
 768             }
 769             _ => None,
 770         }
 771     }
 772 }
 773
 774 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 775     /// Finds the spans associated to a move or copy of move_place at location.
 776     pub(super) fn move_spans(
 777         &self,
 778         moved_place: PlaceRef<'tcx>, // Could also be an upvar.
 779         location: Location,
 780     ) -> UseSpans<'tcx> {
 781         use self::UseSpans::*;
 782
 783         let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
 784             return OtherUse(self.body.source_info(location).span);
 785         };
 786
 787         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
 788         if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) = stmt.kind {
 789             match kind {
 790                 box AggregateKind::Closure(def_id, _)
 791                 | box AggregateKind::Generator(def_id, _, _) => {
 792                     debug!("move_spans: def_id={:?} places={:?}", def_id, places);
 793                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 794                         self.closure_span(*def_id, moved_place, places)
 795                     {
 796                         return ClosureUse {
 797                             generator_kind,
 798                             args_span,
 799                             capture_kind_span,
 800                             path_span,
 801                         };
 802                     }
 803                 }
 804                 _ => {}
 805             }
 806         }
 807
 808         // StatementKind::FakeRead only contains a def_id if they are introduced as a result
 809         // of pattern matching within a closure.
 810         if let StatementKind::FakeRead(box (cause, ref place)) = stmt.kind {
 811             match cause {
 812                 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
 813                 | FakeReadCause::ForLet(Some(closure_def_id)) => {
 814                     debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
 815                     let places = &[Operand::Move(*place)];
 816                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 817                         self.closure_span(closure_def_id, moved_place, places)
 818                     {
 819                         return ClosureUse {
 820                             generator_kind,
 821                             args_span,
 822                             capture_kind_span,
 823                             path_span,
 824                         };
 825                     }
 826                 }
 827                 _ => {}
 828             }
 829         }
 830
 831         let normal_ret =
 832             if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
 833                 PatUse(stmt.source_info.span)
 834             } else {
 835                 OtherUse(stmt.source_info.span)
 836             };
 837
 838         // We are trying to find MIR of the form:
 839         // ```
 840         // _temp = _moved_val;
 841         // ...
 842         // FnSelfCall(_temp, ...)
 843         // ```
 844         //
 845         // where `_moved_val` is the place we generated the move error for,
 846         // `_temp` is some other local, and `FnSelfCall` is a function
 847         // that has a `self` parameter.
 848
 849         let target_temp = match stmt.kind {
 850             StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
 851                 temp.as_local().unwrap()
 852             }
 853             _ => return normal_ret,
 854         };
 855
 856         debug!("move_spans: target_temp = {:?}", target_temp);
 857
 858         if let Some(Terminator {
 859             kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
 860         }) = &self.body[location.block].terminator
 861         {
 862             let Some((method_did, method_substs)) =
 863                 rustc_const_eval::util::find_self_call(
 864                     self.infcx.tcx,
 865                     &self.body,
 866                     target_temp,
 867                     location.block,
 868                 )
 869             else {
 870                 return normal_ret;
 871             };
 872
 873             let kind = call_kind(
 874                 self.infcx.tcx,
 875                 self.param_env,
 876                 method_did,
 877                 method_substs,
 878                 *fn_span,
 879                 *from_hir_call,
 880                 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
 881             );
 882
 883             return FnSelfUse {
 884                 var_span: stmt.source_info.span,
 885                 fn_call_span: *fn_span,
 886                 fn_span: self
 887                     .infcx
 888                     .tcx
 889                     .sess
 890                     .source_map()
 891                     .guess_head_span(self.infcx.tcx.def_span(method_did)),
 892                 kind,
 893             };
 894         }
 895         normal_ret
 896     }
 897
 898     /// Finds the span of arguments of a closure (within `maybe_closure_span`)
 899     /// and its usage of the local assigned at `location`.
 900     /// This is done by searching in statements succeeding `location`
 901     /// and originating from `maybe_closure_span`.
 902     pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
 903         use self::UseSpans::*;
 904         debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
 905
 906         let target = match self.body[location.block].statements.get(location.statement_index) {
 907             Some(&Statement { kind: StatementKind::Assign(box (ref place, _)), .. }) => {
 908                 if let Some(local) = place.as_local() {
 909                     local
 910                 } else {
 911                     return OtherUse(use_span);
 912                 }
 913             }
 914             _ => return OtherUse(use_span),
 915         };
 916
 917         if self.body.local_kind(target) != LocalKind::Temp {
 918             // operands are always temporaries.
 919             return OtherUse(use_span);
 920         }
 921
 922         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
 923             if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) =
 924                 stmt.kind
 925             {
 926                 let (def_id, is_generator) = match kind {
 927                     box AggregateKind::Closure(def_id, _) => (def_id, false),
 928                     box AggregateKind::Generator(def_id, _, _) => (def_id, true),
 929                     _ => continue,
 930                 };
 931
 932                 debug!(
 933                     "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
 934                     def_id, is_generator, places
 935                 );
 936                 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 937                     self.closure_span(*def_id, Place::from(target).as_ref(), places)
 938                 {
 939                     return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
 940                 } else {
 941                     return OtherUse(use_span);
 942                 }
 943             }
 944
 945             if use_span != stmt.source_info.span {
 946                 break;
 947             }
 948         }
 949
 950         OtherUse(use_span)
 951     }
 952
 953     /// Finds the spans of a captured place within a closure or generator.
 954     /// The first span is the location of the use resulting in the capture kind of the capture
 955     /// The second span is the location the use resulting in the captured path of the capture
 956     fn closure_span(
 957         &self,
 958         def_id: DefId,
 959         target_place: PlaceRef<'tcx>,
 960         places: &[Operand<'tcx>],
 961     ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
 962         debug!(
 963             "closure_span: def_id={:?} target_place={:?} places={:?}",
 964             def_id, target_place, places
 965         );
 966         let local_did = def_id.as_local()?;
 967         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(local_did);
 968         let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
 969         debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
 970         if let hir::ExprKind::Closure(.., body_id, args_span, _) = expr {
 971             for (captured_place, place) in self
 972                 .infcx
 973                 .tcx
 974                 .typeck(def_id.expect_local())
 975                 .closure_min_captures_flattened(def_id)
 976                 .zip(places)
 977             {
 978                 match place {
 979                     Operand::Copy(place) | Operand::Move(place)
 980                         if target_place == place.as_ref() =>
 981                     {
 982                         debug!("closure_span: found captured local {:?}", place);
 983                         let body = self.infcx.tcx.hir().body(*body_id);
 984                         let generator_kind = body.generator_kind();
 985
 986                         return Some((
 987                             *args_span,
 988                             generator_kind,
 989                             captured_place.get_capture_kind_span(self.infcx.tcx),
 990                             captured_place.get_path_span(self.infcx.tcx),
 991                         ));
 992                     }
 993                     _ => {}
 994                 }
 995             }
 996         }
 997         None
 998     }
 999
1000     /// Helper to retrieve span(s) of given borrow from the current MIR
1001     /// representation
1002     pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1003         let span = self.body.source_info(borrow.reserve_location).span;
1004         self.borrow_spans(span, borrow.reserve_location)
1005     }
1006 }