compiler/rustc_borrowck/src/diagnostics/mod.rs

   1 //! Borrow checker diagnostics.
   2
   3 use itertools::Itertools;
   4 use rustc_const_eval::util::{call_kind, CallDesugaringKind};
   5 use rustc_errors::{Applicability, Diagnostic};
   6 use rustc_hir as hir;
   7 use rustc_hir::def::{CtorKind, Namespace};
   8 use rustc_hir::GeneratorKind;
   9 use rustc_infer::infer::TyCtxtInferExt;
  10 use rustc_middle::mir::tcx::PlaceTy;
  11 use rustc_middle::mir::{
  12     AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
  13     Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
  14 };
  15 use rustc_middle::ty::print::Print;
  16 use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
  17 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
  18 use rustc_span::def_id::LocalDefId;
  19 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
  20 use rustc_target::abi::VariantIdx;
  21 use rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions;
  22
  23 use super::borrow_set::BorrowData;
  24 use super::MirBorrowckCtxt;
  25
  26 mod find_all_local_uses;
  27 mod find_use;
  28 mod outlives_suggestion;
  29 mod region_name;
  30 mod var_name;
  31
  32 mod bound_region_errors;
  33 mod conflict_errors;
  34 mod explain_borrow;
  35 mod move_errors;
  36 mod mutability_errors;
  37 mod region_errors;
  38
  39 pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
  40 pub(crate) use mutability_errors::AccessKind;
  41 pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
  42 pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
  43 pub(crate) use region_name::{RegionName, RegionNameSource};
  44 pub(crate) use rustc_const_eval::util::CallKind;
  45
  46 pub(super) struct DescribePlaceOpt {
  47     pub including_downcast: bool,
  48
  49     /// Enable/Disable tuple fields.
  50     /// For example `x` tuple. if it's `true` `x.0`. Otherwise `x`
  51     pub including_tuple_field: bool,
  52 }
  53
  54 pub(super) struct IncludingTupleField(pub(super) bool);
  55
  56 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
  57     /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
  58     /// is moved after being invoked.
  59     ///
  60     /// ```text
  61     /// note: closure cannot be invoked more than once because it moves the variable `dict` out of
  62     ///       its environment
  63     ///   --> $DIR/issue-42065.rs:16:29
  64     ///    |
  65     /// LL |         for (key, value) in dict {
  66     ///    |                             ^^^^
  67     /// ```
  68     pub(super) fn add_moved_or_invoked_closure_note(
  69         &self,
  70         location: Location,
  71         place: PlaceRef<'tcx>,
  72         diag: &mut Diagnostic,
  73     ) {
  74         debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
  75         let mut target = place.local_or_deref_local();
  76         for stmt in &self.body[location.block].statements[location.statement_index..] {
  77             debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
  78             if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind {
  79                 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
  80                 match from {
  81                     Operand::Copy(ref place) | Operand::Move(ref place)
  82                         if target == place.local_or_deref_local() =>
  83                     {
  84                         target = into.local_or_deref_local()
  85                     }
  86                     _ => {}
  87                 }
  88             }
  89         }
  90
  91         // Check if we are attempting to call a closure after it has been invoked.
  92         let terminator = self.body[location.block].terminator();
  93         debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator);
  94         if let TerminatorKind::Call {
  95             func: Operand::Constant(box Constant { literal, .. }),
  96             args,
  97             ..
  98         } = &terminator.kind
  99         {
 100             if let ty::FnDef(id, _) = *literal.ty().kind() {
 101                 debug!("add_moved_or_invoked_closure_note: id={:?}", id);
 102                 if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() {
 103                     let closure = match args.first() {
 104                         Some(Operand::Copy(ref place)) | Some(Operand::Move(ref place))
 105                             if target == place.local_or_deref_local() =>
 106                         {
 107                             place.local_or_deref_local().unwrap()
 108                         }
 109                         _ => return,
 110                     };
 111
 112                     debug!("add_moved_or_invoked_closure_note: closure={:?}", closure);
 113                     if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
 114                         let did = did.expect_local();
 115                         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
 116
 117                         if let Some((span, hir_place)) =
 118                             self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
 119                         {
 120                             diag.span_note(
 121                                 *span,
 122                                 &format!(
 123                                     "closure cannot be invoked more than once because it moves the \
 124                                     variable `{}` out of its environment",
 125                                     ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
 126                                 ),
 127                             );
 128                             return;
 129                         }
 130                     }
 131                 }
 132             }
 133         }
 134
 135         // Check if we are just moving a closure after it has been invoked.
 136         if let Some(target) = target {
 137             if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
 138                 let did = did.expect_local();
 139                 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
 140
 141                 if let Some((span, hir_place)) =
 142                     self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
 143                 {
 144                     diag.span_note(
 145                         *span,
 146                         &format!(
 147                             "closure cannot be moved more than once as it is not `Copy` due to \
 148                              moving the variable `{}` out of its environment",
 149                             ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
 150                         ),
 151                     );
 152                 }
 153             }
 154         }
 155     }
 156
 157     /// End-user visible description of `place` if one can be found.
 158     /// If the place is a temporary for instance, `"value"` will be returned.
 159     pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
 160         match self.describe_place(place_ref) {
 161             Some(mut descr) => {
 162                 // Surround descr with `backticks`.
 163                 descr.reserve(2);
 164                 descr.insert(0, '`');
 165                 descr.push('`');
 166                 descr
 167             }
 168             None => "value".to_string(),
 169         }
 170     }
 171
 172     /// End-user visible description of `place` if one can be found.
 173     /// If the place is a temporary for instance, `None` will be returned.
 174     pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> {
 175         self.describe_place_with_options(
 176             place_ref,
 177             DescribePlaceOpt { including_downcast: false, including_tuple_field: true },
 178         )
 179     }
 180
 181     /// End-user visible description of `place` if one can be found. If the place is a temporary
 182     /// for instance, `None` will be returned.
 183     /// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is
 184     /// `Downcast` and `IncludingDowncast` is true
 185     pub(super) fn describe_place_with_options(
 186         &self,
 187         place: PlaceRef<'tcx>,
 188         opt: DescribePlaceOpt,
 189     ) -> Option<String> {
 190         let local = place.local;
 191         let mut autoderef_index = None;
 192         let mut buf = String::new();
 193         let mut ok = self.append_local_to_string(local, &mut buf);
 194
 195         for (index, elem) in place.projection.into_iter().enumerate() {
 196             match elem {
 197                 ProjectionElem::Deref => {
 198                     if index == 0 {
 199                         if self.body.local_decls[local].is_ref_for_guard() {
 200                             continue;
 201                         }
 202                         if let Some(box LocalInfo::StaticRef { def_id, .. }) =
 203                             &self.body.local_decls[local].local_info
 204                         {
 205                             buf.push_str(self.infcx.tcx.item_name(*def_id).as_str());
 206                             ok = Ok(());
 207                             continue;
 208                         }
 209                     }
 210                     if let Some(field) = self.is_upvar_field_projection(PlaceRef {
 211                         local,
 212                         projection: place.projection.split_at(index + 1).0,
 213                     }) {
 214                         let var_index = field.index();
 215                         buf = self.upvars[var_index].place.to_string(self.infcx.tcx);
 216                         ok = Ok(());
 217                         if !self.upvars[var_index].by_ref {
 218                             buf.insert(0, '*');
 219                         }
 220                     } else {
 221                         if autoderef_index.is_none() {
 222                             autoderef_index =
 223                                 match place.projection.into_iter().rev().find_position(|elem| {
 224                                     !matches!(
 225                                         elem,
 226                                         ProjectionElem::Deref | ProjectionElem::Downcast(..)
 227                                     )
 228                                 }) {
 229                                     Some((index, _)) => Some(place.projection.len() - index),
 230                                     None => Some(0),
 231                                 };
 232                         }
 233                         if index >= autoderef_index.unwrap() {
 234                             buf.insert(0, '*');
 235                         }
 236                     }
 237                 }
 238                 ProjectionElem::Downcast(..) if opt.including_downcast => return None,
 239                 ProjectionElem::Downcast(..) => (),
 240                 ProjectionElem::OpaqueCast(..) => (),
 241                 ProjectionElem::Field(field, _ty) => {
 242                     // FIXME(project-rfc_2229#36): print capture precisely here.
 243                     if let Some(field) = self.is_upvar_field_projection(PlaceRef {
 244                         local,
 245                         projection: place.projection.split_at(index + 1).0,
 246                     }) {
 247                         buf = self.upvars[field.index()].place.to_string(self.infcx.tcx);
 248                         ok = Ok(());
 249                     } else {
 250                         let field_name = self.describe_field(
 251                             PlaceRef { local, projection: place.projection.split_at(index).0 },
 252                             *field,
 253                             IncludingTupleField(opt.including_tuple_field),
 254                         );
 255                         if let Some(field_name_str) = field_name {
 256                             buf.push('.');
 257                             buf.push_str(&field_name_str);
 258                         }
 259                     }
 260                 }
 261                 ProjectionElem::Index(index) => {
 262                     buf.push('[');
 263                     if self.append_local_to_string(*index, &mut buf).is_err() {
 264                         buf.push('_');
 265                     }
 266                     buf.push(']');
 267                 }
 268                 ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
 269                     // Since it isn't possible to borrow an element on a particular index and
 270                     // then use another while the borrow is held, don't output indices details
 271                     // to avoid confusing the end-user
 272                     buf.push_str("[..]");
 273                 }
 274             }
 275         }
 276         ok.ok().map(|_| buf)
 277     }
 278
 279     fn describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol> {
 280         for elem in place.projection.into_iter() {
 281             match elem {
 282                 ProjectionElem::Downcast(Some(name), _) => {
 283                     return Some(*name);
 284                 }
 285                 _ => {}
 286             }
 287         }
 288         None
 289     }
 290
 291     /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have
 292     /// a name, or its name was generated by the compiler, then `Err` is returned
 293     fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> {
 294         let decl = &self.body.local_decls[local];
 295         match self.local_names[local] {
 296             Some(name) if !decl.from_compiler_desugaring() => {
 297                 buf.push_str(name.as_str());
 298                 Ok(())
 299             }
 300             _ => Err(()),
 301         }
 302     }
 303
 304     /// End-user visible description of the `field`nth field of `base`
 305     fn describe_field(
 306         &self,
 307         place: PlaceRef<'tcx>,
 308         field: Field,
 309         including_tuple_field: IncludingTupleField,
 310     ) -> Option<String> {
 311         let place_ty = match place {
 312             PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty),
 313             PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
 314                 ProjectionElem::Deref
 315                 | ProjectionElem::Index(..)
 316                 | ProjectionElem::ConstantIndex { .. }
 317                 | ProjectionElem::Subslice { .. } => {
 318                     PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
 319                 }
 320                 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
 321                 ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
 322                 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
 323             },
 324         };
 325         self.describe_field_from_ty(
 326             place_ty.ty,
 327             field,
 328             place_ty.variant_index,
 329             including_tuple_field,
 330         )
 331     }
 332
 333     /// End-user visible description of the `field_index`nth field of `ty`
 334     fn describe_field_from_ty(
 335         &self,
 336         ty: Ty<'_>,
 337         field: Field,
 338         variant_index: Option<VariantIdx>,
 339         including_tuple_field: IncludingTupleField,
 340     ) -> Option<String> {
 341         if ty.is_box() {
 342             // If the type is a box, the field is described from the boxed type
 343             self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field)
 344         } else {
 345             match *ty.kind() {
 346                 ty::Adt(def, _) => {
 347                     let variant = if let Some(idx) = variant_index {
 348                         assert!(def.is_enum());
 349                         &def.variant(idx)
 350                     } else {
 351                         def.non_enum_variant()
 352                     };
 353                     if !including_tuple_field.0 && variant.ctor_kind == CtorKind::Fn {
 354                         return None;
 355                     }
 356                     Some(variant.fields[field.index()].name.to_string())
 357                 }
 358                 ty::Tuple(_) => Some(field.index().to_string()),
 359                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 360                     self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
 361                 }
 362                 ty::Array(ty, _) | ty::Slice(ty) => {
 363                     self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
 364                 }
 365                 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
 366                     // We won't be borrowck'ing here if the closure came from another crate,
 367                     // so it's safe to call `expect_local`.
 368                     //
 369                     // We know the field exists so it's safe to call operator[] and `unwrap` here.
 370                     let def_id = def_id.expect_local();
 371                     let var_id = self
 372                         .infcx
 373                         .tcx
 374                         .typeck(def_id)
 375                         .closure_min_captures_flattened(def_id)
 376                         .nth(field.index())
 377                         .unwrap()
 378                         .get_root_variable();
 379
 380                     Some(self.infcx.tcx.hir().name(var_id).to_string())
 381                 }
 382                 _ => {
 383                     // Might need a revision when the fields in trait RFC is implemented
 384                     // (https://github.com/rust-lang/rfcs/pull/1546)
 385                     bug!("End-user description not implemented for field access on `{:?}`", ty);
 386                 }
 387             }
 388         }
 389     }
 390
 391     /// Add a note that a type does not implement `Copy`
 392     pub(super) fn note_type_does_not_implement_copy(
 393         &self,
 394         err: &mut Diagnostic,
 395         place_desc: &str,
 396         ty: Ty<'tcx>,
 397         span: Option<Span>,
 398         move_prefix: &str,
 399     ) {
 400         let message = format!(
 401             "{}move occurs because {} has type `{}`, which does not implement the `Copy` trait",
 402             move_prefix, place_desc, ty,
 403         );
 404         if let Some(span) = span {
 405             err.span_label(span, message);
 406         } else {
 407             err.note(&message);
 408         }
 409     }
 410
 411     pub(super) fn borrowed_content_source(
 412         &self,
 413         deref_base: PlaceRef<'tcx>,
 414     ) -> BorrowedContentSource<'tcx> {
 415         let tcx = self.infcx.tcx;
 416
 417         // Look up the provided place and work out the move path index for it,
 418         // we'll use this to check whether it was originally from an overloaded
 419         // operator.
 420         match self.move_data.rev_lookup.find(deref_base) {
 421             LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
 422                 debug!("borrowed_content_source: mpi={:?}", mpi);
 423
 424                 for i in &self.move_data.init_path_map[mpi] {
 425                     let init = &self.move_data.inits[*i];
 426                     debug!("borrowed_content_source: init={:?}", init);
 427                     // We're only interested in statements that initialized a value, not the
 428                     // initializations from arguments.
 429                     let InitLocation::Statement(loc) = init.location else { continue };
 430
 431                     let bbd = &self.body[loc.block];
 432                     let is_terminator = bbd.statements.len() == loc.statement_index;
 433                     debug!(
 434                         "borrowed_content_source: loc={:?} is_terminator={:?}",
 435                         loc, is_terminator,
 436                     );
 437                     if !is_terminator {
 438                         continue;
 439                     } else if let Some(Terminator {
 440                         kind: TerminatorKind::Call { ref func, from_hir_call: false, .. },
 441                         ..
 442                     }) = bbd.terminator
 443                     {
 444                         if let Some(source) =
 445                             BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
 446                         {
 447                             return source;
 448                         }
 449                     }
 450                 }
 451             }
 452             // Base is a `static` so won't be from an overloaded operator
 453             _ => (),
 454         };
 455
 456         // If we didn't find an overloaded deref or index, then assume it's a
 457         // built in deref and check the type of the base.
 458         let base_ty = deref_base.ty(self.body, tcx).ty;
 459         if base_ty.is_unsafe_ptr() {
 460             BorrowedContentSource::DerefRawPointer
 461         } else if base_ty.is_mutable_ptr() {
 462             BorrowedContentSource::DerefMutableRef
 463         } else {
 464             BorrowedContentSource::DerefSharedRef
 465         }
 466     }
 467
 468     /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
 469     /// name where required.
 470     pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 471         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 472
 473         // We need to add synthesized lifetimes where appropriate. We do
 474         // this by hooking into the pretty printer and telling it to label the
 475         // lifetimes without names with the value `'0`.
 476         if let ty::Ref(region, ..) = ty.kind() {
 477             match **region {
 478                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 479                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 480                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 481                 }
 482                 _ => {}
 483             }
 484         }
 485
 486         ty.print(printer).unwrap().into_buffer()
 487     }
 488
 489     /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
 490     /// synthesized lifetime name where required.
 491     pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 492         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 493
 494         let region = if let ty::Ref(region, ..) = ty.kind() {
 495             match **region {
 496                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 497                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 498                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 499                 }
 500                 _ => {}
 501             }
 502             region
 503         } else {
 504             bug!("ty for annotation of borrow region is not a reference");
 505         };
 506
 507         region.print(printer).unwrap().into_buffer()
 508     }
 509 }
 510
 511 /// The span(s) associated to a use of a place.
 512 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 513 pub(super) enum UseSpans<'tcx> {
 514     /// The access is caused by capturing a variable for a closure.
 515     ClosureUse {
 516         /// This is true if the captured variable was from a generator.
 517         generator_kind: Option<GeneratorKind>,
 518         /// The span of the args of the closure, including the `move` keyword if
 519         /// it's present.
 520         args_span: Span,
 521         /// The span of the use resulting in capture kind
 522         /// Check `ty::CaptureInfo` for more details
 523         capture_kind_span: Span,
 524         /// The span of the use resulting in the captured path
 525         /// Check `ty::CaptureInfo` for more details
 526         path_span: Span,
 527     },
 528     /// The access is caused by using a variable as the receiver of a method
 529     /// that takes 'self'
 530     FnSelfUse {
 531         /// The span of the variable being moved
 532         var_span: Span,
 533         /// The span of the method call on the variable
 534         fn_call_span: Span,
 535         /// The definition span of the method being called
 536         fn_span: Span,
 537         kind: CallKind<'tcx>,
 538     },
 539     /// This access is caused by a `match` or `if let` pattern.
 540     PatUse(Span),
 541     /// This access has a single span associated to it: common case.
 542     OtherUse(Span),
 543 }
 544
 545 impl UseSpans<'_> {
 546     pub(super) fn args_or_use(self) -> Span {
 547         match self {
 548             UseSpans::ClosureUse { args_span: span, .. }
 549             | UseSpans::PatUse(span)
 550             | UseSpans::OtherUse(span) => span,
 551             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 552                 fn_call_span
 553             }
 554             UseSpans::FnSelfUse { var_span, .. } => var_span,
 555         }
 556     }
 557
 558     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
 559     pub(super) fn var_or_use_path_span(self) -> Span {
 560         match self {
 561             UseSpans::ClosureUse { path_span: span, .. }
 562             | UseSpans::PatUse(span)
 563             | UseSpans::OtherUse(span) => span,
 564             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 565                 fn_call_span
 566             }
 567             UseSpans::FnSelfUse { var_span, .. } => var_span,
 568         }
 569     }
 570
 571     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
 572     pub(super) fn var_or_use(self) -> Span {
 573         match self {
 574             UseSpans::ClosureUse { capture_kind_span: span, .. }
 575             | UseSpans::PatUse(span)
 576             | UseSpans::OtherUse(span) => span,
 577             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 578                 fn_call_span
 579             }
 580             UseSpans::FnSelfUse { var_span, .. } => var_span,
 581         }
 582     }
 583
 584     pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
 585         match self {
 586             UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
 587             _ => None,
 588         }
 589     }
 590
 591     // Add a span label to the arguments of the closure, if it exists.
 592     pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into<String>) {
 593         if let UseSpans::ClosureUse { args_span, .. } = self {
 594             err.span_label(args_span, message);
 595         }
 596     }
 597
 598     // Add a span label to the use of the captured variable, if it exists.
 599     // only adds label to the `path_span`
 600     pub(super) fn var_span_label_path_only(self, err: &mut Diagnostic, message: impl Into<String>) {
 601         if let UseSpans::ClosureUse { path_span, .. } = self {
 602             err.span_label(path_span, message);
 603         }
 604     }
 605
 606     // Add a span label to the use of the captured variable, if it exists.
 607     pub(super) fn var_span_label(
 608         self,
 609         err: &mut Diagnostic,
 610         message: impl Into<String>,
 611         kind_desc: impl Into<String>,
 612     ) {
 613         if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
 614             if capture_kind_span == path_span {
 615                 err.span_label(capture_kind_span, message);
 616             } else {
 617                 let capture_kind_label =
 618                     format!("capture is {} because of use here", kind_desc.into());
 619                 let path_label = message;
 620                 err.span_label(capture_kind_span, capture_kind_label);
 621                 err.span_label(path_span, path_label);
 622             }
 623         }
 624     }
 625
 626     /// Returns `false` if this place is not used in a closure.
 627     pub(super) fn for_closure(&self) -> bool {
 628         match *self {
 629             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
 630             _ => false,
 631         }
 632     }
 633
 634     /// Returns `false` if this place is not used in a generator.
 635     pub(super) fn for_generator(&self) -> bool {
 636         match *self {
 637             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
 638             _ => false,
 639         }
 640     }
 641
 642     /// Describe the span associated with a use of a place.
 643     pub(super) fn describe(&self) -> &str {
 644         match *self {
 645             UseSpans::ClosureUse { generator_kind, .. } => {
 646                 if generator_kind.is_some() {
 647                     " in generator"
 648                 } else {
 649                     " in closure"
 650                 }
 651             }
 652             _ => "",
 653         }
 654     }
 655
 656     pub(super) fn or_else<F>(self, if_other: F) -> Self
 657     where
 658         F: FnOnce() -> Self,
 659     {
 660         match self {
 661             closure @ UseSpans::ClosureUse { .. } => closure,
 662             UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
 663             fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
 664         }
 665     }
 666 }
 667
 668 pub(super) enum BorrowedContentSource<'tcx> {
 669     DerefRawPointer,
 670     DerefMutableRef,
 671     DerefSharedRef,
 672     OverloadedDeref(Ty<'tcx>),
 673     OverloadedIndex(Ty<'tcx>),
 674 }
 675
 676 impl<'tcx> BorrowedContentSource<'tcx> {
 677     pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
 678         match *self {
 679             BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
 680             BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
 681             BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
 682             BorrowedContentSource::OverloadedDeref(ty) => ty
 683                 .ty_adt_def()
 684                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
 685                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 686                     _ => None,
 687                 })
 688                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 689             BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
 690         }
 691     }
 692
 693     pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
 694         match *self {
 695             BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
 696             BorrowedContentSource::DerefSharedRef => Some("shared reference"),
 697             BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
 698             // Overloaded deref and index operators should be evaluated into a
 699             // temporary. So we don't need a description here.
 700             BorrowedContentSource::OverloadedDeref(_)
 701             | BorrowedContentSource::OverloadedIndex(_) => None,
 702         }
 703     }
 704
 705     pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
 706         match *self {
 707             BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
 708             BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
 709             BorrowedContentSource::DerefMutableRef => {
 710                 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
 711             }
 712             BorrowedContentSource::OverloadedDeref(ty) => ty
 713                 .ty_adt_def()
 714                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
 715                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 716                     _ => None,
 717                 })
 718                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 719             BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
 720         }
 721     }
 722
 723     fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
 724         match *func.kind() {
 725             ty::FnDef(def_id, substs) => {
 726                 let trait_id = tcx.trait_of_item(def_id)?;
 727
 728                 let lang_items = tcx.lang_items();
 729                 if Some(trait_id) == lang_items.deref_trait()
 730                     || Some(trait_id) == lang_items.deref_mut_trait()
 731                 {
 732                     Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
 733                 } else if Some(trait_id) == lang_items.index_trait()
 734                     || Some(trait_id) == lang_items.index_mut_trait()
 735                 {
 736                     Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
 737                 } else {
 738                     None
 739                 }
 740             }
 741             _ => None,
 742         }
 743     }
 744 }
 745
 746 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 747     /// Finds the spans associated to a move or copy of move_place at location.
 748     pub(super) fn move_spans(
 749         &self,
 750         moved_place: PlaceRef<'tcx>, // Could also be an upvar.
 751         location: Location,
 752     ) -> UseSpans<'tcx> {
 753         use self::UseSpans::*;
 754
 755         let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
 756             return OtherUse(self.body.source_info(location).span);
 757         };
 758
 759         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
 760         if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) = stmt.kind {
 761             match **kind {
 762                 AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) => {
 763                     debug!("move_spans: def_id={:?} places={:?}", def_id, places);
 764                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 765                         self.closure_span(def_id, moved_place, places)
 766                     {
 767                         return ClosureUse {
 768                             generator_kind,
 769                             args_span,
 770                             capture_kind_span,
 771                             path_span,
 772                         };
 773                     }
 774                 }
 775                 _ => {}
 776             }
 777         }
 778
 779         // StatementKind::FakeRead only contains a def_id if they are introduced as a result
 780         // of pattern matching within a closure.
 781         if let StatementKind::FakeRead(box (cause, ref place)) = stmt.kind {
 782             match cause {
 783                 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
 784                 | FakeReadCause::ForLet(Some(closure_def_id)) => {
 785                     debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
 786                     let places = &[Operand::Move(*place)];
 787                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 788                         self.closure_span(closure_def_id, moved_place, places)
 789                     {
 790                         return ClosureUse {
 791                             generator_kind,
 792                             args_span,
 793                             capture_kind_span,
 794                             path_span,
 795                         };
 796                     }
 797                 }
 798                 _ => {}
 799             }
 800         }
 801
 802         let normal_ret =
 803             if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
 804                 PatUse(stmt.source_info.span)
 805             } else {
 806                 OtherUse(stmt.source_info.span)
 807             };
 808
 809         // We are trying to find MIR of the form:
 810         // ```
 811         // _temp = _moved_val;
 812         // ...
 813         // FnSelfCall(_temp, ...)
 814         // ```
 815         //
 816         // where `_moved_val` is the place we generated the move error for,
 817         // `_temp` is some other local, and `FnSelfCall` is a function
 818         // that has a `self` parameter.
 819
 820         let target_temp = match stmt.kind {
 821             StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
 822                 temp.as_local().unwrap()
 823             }
 824             _ => return normal_ret,
 825         };
 826
 827         debug!("move_spans: target_temp = {:?}", target_temp);
 828
 829         if let Some(Terminator {
 830             kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
 831         }) = &self.body[location.block].terminator
 832         {
 833             let Some((method_did, method_substs)) =
 834                 rustc_const_eval::util::find_self_call(
 835                     self.infcx.tcx,
 836                     &self.body,
 837                     target_temp,
 838                     location.block,
 839                 )
 840             else {
 841                 return normal_ret;
 842             };
 843
 844             let kind = call_kind(
 845                 self.infcx.tcx,
 846                 self.param_env,
 847                 method_did,
 848                 method_substs,
 849                 *fn_span,
 850                 *from_hir_call,
 851                 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
 852             );
 853
 854             return FnSelfUse {
 855                 var_span: stmt.source_info.span,
 856                 fn_call_span: *fn_span,
 857                 fn_span: self.infcx.tcx.def_span(method_did),
 858                 kind,
 859             };
 860         }
 861         normal_ret
 862     }
 863
 864     /// Finds the span of arguments of a closure (within `maybe_closure_span`)
 865     /// and its usage of the local assigned at `location`.
 866     /// This is done by searching in statements succeeding `location`
 867     /// and originating from `maybe_closure_span`.
 868     pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
 869         use self::UseSpans::*;
 870         debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
 871
 872         let target = match self.body[location.block].statements.get(location.statement_index) {
 873             Some(&Statement { kind: StatementKind::Assign(box (ref place, _)), .. }) => {
 874                 if let Some(local) = place.as_local() {
 875                     local
 876                 } else {
 877                     return OtherUse(use_span);
 878                 }
 879             }
 880             _ => return OtherUse(use_span),
 881         };
 882
 883         if self.body.local_kind(target) != LocalKind::Temp {
 884             // operands are always temporaries.
 885             return OtherUse(use_span);
 886         }
 887
 888         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
 889             if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) =
 890                 stmt.kind
 891             {
 892                 let (&def_id, is_generator) = match kind {
 893                     box AggregateKind::Closure(def_id, _) => (def_id, false),
 894                     box AggregateKind::Generator(def_id, _, _) => (def_id, true),
 895                     _ => continue,
 896                 };
 897
 898                 debug!(
 899                     "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
 900                     def_id, is_generator, places
 901                 );
 902                 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 903                     self.closure_span(def_id, Place::from(target).as_ref(), places)
 904                 {
 905                     return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
 906                 } else {
 907                     return OtherUse(use_span);
 908                 }
 909             }
 910
 911             if use_span != stmt.source_info.span {
 912                 break;
 913             }
 914         }
 915
 916         OtherUse(use_span)
 917     }
 918
 919     /// Finds the spans of a captured place within a closure or generator.
 920     /// The first span is the location of the use resulting in the capture kind of the capture
 921     /// The second span is the location the use resulting in the captured path of the capture
 922     fn closure_span(
 923         &self,
 924         def_id: LocalDefId,
 925         target_place: PlaceRef<'tcx>,
 926         places: &[Operand<'tcx>],
 927     ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
 928         debug!(
 929             "closure_span: def_id={:?} target_place={:?} places={:?}",
 930             def_id, target_place, places
 931         );
 932         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id);
 933         let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
 934         debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
 935         if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr {
 936             for (captured_place, place) in
 937                 self.infcx.tcx.typeck(def_id).closure_min_captures_flattened(def_id).zip(places)
 938             {
 939                 match place {
 940                     Operand::Copy(place) | Operand::Move(place)
 941                         if target_place == place.as_ref() =>
 942                     {
 943                         debug!("closure_span: found captured local {:?}", place);
 944                         let body = self.infcx.tcx.hir().body(body);
 945                         let generator_kind = body.generator_kind();
 946
 947                         return Some((
 948                             fn_decl_span,
 949                             generator_kind,
 950                             captured_place.get_capture_kind_span(self.infcx.tcx),
 951                             captured_place.get_path_span(self.infcx.tcx),
 952                         ));
 953                     }
 954                     _ => {}
 955                 }
 956             }
 957         }
 958         None
 959     }
 960
 961     /// Helper to retrieve span(s) of given borrow from the current MIR
 962     /// representation
 963     pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
 964         let span = self.body.source_info(borrow.reserve_location).span;
 965         self.borrow_spans(span, borrow.reserve_location)
 966     }
 967
 968     fn explain_captures(
 969         &mut self,
 970         err: &mut Diagnostic,
 971         span: Span,
 972         move_span: Span,
 973         move_spans: UseSpans<'tcx>,
 974         moved_place: Place<'tcx>,
 975         partially_str: &str,
 976         loop_message: &str,
 977         move_msg: &str,
 978         is_loop_move: bool,
 979         maybe_reinitialized_locations_is_empty: bool,
 980     ) {
 981         if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
 982             let place_name = self
 983                 .describe_place(moved_place.as_ref())
 984                 .map(|n| format!("`{}`", n))
 985                 .unwrap_or_else(|| "value".to_owned());
 986             match kind {
 987                 CallKind::FnCall { fn_trait_id, .. }
 988                     if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() =>
 989                 {
 990                     err.span_label(
 991                         fn_call_span,
 992                         &format!(
 993                             "{} {}moved due to this call{}",
 994                             place_name, partially_str, loop_message
 995                         ),
 996                     );
 997                     err.span_note(
 998                         var_span,
 999                         "this value implements `FnOnce`, which causes it to be moved when called",
1000                     );
1001                 }
1002                 CallKind::Operator { self_arg, .. } => {
1003                     let self_arg = self_arg.unwrap();
1004                     err.span_label(
1005                         fn_call_span,
1006                         &format!(
1007                             "{} {}moved due to usage in operator{}",
1008                             place_name, partially_str, loop_message
1009                         ),
1010                     );
1011                     if self.fn_self_span_reported.insert(fn_span) {
1012                         err.span_note(
1013                             // Check whether the source is accessible
1014                             if self.infcx.tcx.sess.source_map().is_span_accessible(self_arg.span) {
1015                                 self_arg.span
1016                             } else {
1017                                 fn_call_span
1018                             },
1019                             "calling this operator moves the left-hand side",
1020                         );
1021                     }
1022                 }
1023                 CallKind::Normal { self_arg, desugaring, is_option_or_result } => {
1024                     let self_arg = self_arg.unwrap();
1025                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
1026                         let ty = moved_place.ty(self.body, self.infcx.tcx).ty;
1027                         let suggest = match self.infcx.tcx.get_diagnostic_item(sym::IntoIterator) {
1028                             Some(def_id) => {
1029                                 let infcx = self.infcx.tcx.infer_ctxt().build();
1030                                 type_known_to_meet_bound_modulo_regions(
1031                                     &infcx,
1032                                     self.param_env,
1033                                     infcx.tcx.mk_imm_ref(
1034                                         infcx.tcx.lifetimes.re_erased,
1035                                         infcx.tcx.erase_regions(ty),
1036                                     ),
1037                                     def_id,
1038                                     DUMMY_SP,
1039                                 )
1040                             }
1041                             _ => false,
1042                         };
1043                         if suggest {
1044                             err.span_suggestion_verbose(
1045                                 move_span.shrink_to_lo(),
1046                                 &format!(
1047                                     "consider iterating over a slice of the `{}`'s content to \
1048                                      avoid moving into the `for` loop",
1049                                     ty,
1050                                 ),
1051                                 "&",
1052                                 Applicability::MaybeIncorrect,
1053                             );
1054                         }
1055
1056                         err.span_label(
1057                             fn_call_span,
1058                             &format!(
1059                                 "{} {}moved due to this implicit call to `.into_iter()`{}",
1060                                 place_name, partially_str, loop_message
1061                             ),
1062                         );
1063                         // If the moved place was a `&mut` ref, then we can
1064                         // suggest to reborrow it where it was moved, so it
1065                         // will still be valid by the time we get to the usage.
1066                         if let ty::Ref(_, _, hir::Mutability::Mut) =
1067                             moved_place.ty(self.body, self.infcx.tcx).ty.kind()
1068                         {
1069                             // If we are in a loop this will be suggested later.
1070                             if !is_loop_move {
1071                                 err.span_suggestion_verbose(
1072                                     move_span.shrink_to_lo(),
1073                                     &format!(
1074                                         "consider creating a fresh reborrow of {} here",
1075                                         self.describe_place(moved_place.as_ref())
1076                                             .map(|n| format!("`{}`", n))
1077                                             .unwrap_or_else(|| "the mutable reference".to_string()),
1078                                     ),
1079                                     "&mut *",
1080                                     Applicability::MachineApplicable,
1081                                 );
1082                             }
1083                         }
1084                     } else {
1085                         err.span_label(
1086                             fn_call_span,
1087                             &format!(
1088                                 "{} {}moved due to this method call{}",
1089                                 place_name, partially_str, loop_message
1090                             ),
1091                         );
1092                     }
1093                     // Avoid pointing to the same function in multiple different
1094                     // error messages.
1095                     if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
1096                         err.span_note(
1097                             self_arg.span,
1098                             &format!("this function takes ownership of the receiver `self`, which moves {}", place_name)
1099                         );
1100                     }
1101                     if is_option_or_result && maybe_reinitialized_locations_is_empty {
1102                         err.span_label(
1103                             var_span,
1104                             "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
1105                         );
1106                     }
1107                 }
1108                 // Other desugarings takes &self, which cannot cause a move
1109                 _ => {}
1110             }
1111         } else {
1112             if move_span != span || !loop_message.is_empty() {
1113                 err.span_label(
1114                     move_span,
1115                     format!("value {}moved{} here{}", partially_str, move_msg, loop_message),
1116                 );
1117             }
1118             // If the move error occurs due to a loop, don't show
1119             // another message for the same span
1120             if loop_message.is_empty() {
1121                 move_spans.var_span_label(
1122                     err,
1123                     format!("variable {}moved due to use{}", partially_str, move_spans.describe()),
1124                     "moved",
1125                 );
1126             }
1127         }
1128     }
1129 }