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 loc = match init.location {
 448                         InitLocation::Statement(stmt) => stmt,
 449                         _ => continue,
 450                     };
 451
 452                     let bbd = &self.body[loc.block];
 453                     let is_terminator = bbd.statements.len() == loc.statement_index;
 454                     debug!(
 455                         "borrowed_content_source: loc={:?} is_terminator={:?}",
 456                         loc, is_terminator,
 457                     );
 458                     if !is_terminator {
 459                         continue;
 460                     } else if let Some(Terminator {
 461                         kind: TerminatorKind::Call { ref func, from_hir_call: false, .. },
 462                         ..
 463                     }) = bbd.terminator
 464                     {
 465                         if let Some(source) =
 466                             BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
 467                         {
 468                             return source;
 469                         }
 470                     }
 471                 }
 472             }
 473             // Base is a `static` so won't be from an overloaded operator
 474             _ => (),
 475         };
 476
 477         // If we didn't find an overloaded deref or index, then assume it's a
 478         // built in deref and check the type of the base.
 479         let base_ty = deref_base.ty(self.body, tcx).ty;
 480         if base_ty.is_unsafe_ptr() {
 481             BorrowedContentSource::DerefRawPointer
 482         } else if base_ty.is_mutable_ptr() {
 483             BorrowedContentSource::DerefMutableRef
 484         } else {
 485             BorrowedContentSource::DerefSharedRef
 486         }
 487     }
 488 }
 489
 490 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 491     /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
 492     /// name where required.
 493     pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 494         let mut s = String::new();
 495         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, &mut s, Namespace::TypeNS);
 496
 497         // We need to add synthesized lifetimes where appropriate. We do
 498         // this by hooking into the pretty printer and telling it to label the
 499         // lifetimes without names with the value `'0`.
 500         if let ty::Ref(region, ..) = ty.kind() {
 501             match **region {
 502                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 503                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 504                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 505                 }
 506                 _ => {}
 507             }
 508         }
 509
 510         let _ = ty.print(printer);
 511         s
 512     }
 513
 514     /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
 515     /// synthesized lifetime name where required.
 516     pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
 517         let mut s = String::new();
 518         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, &mut s, Namespace::TypeNS);
 519
 520         let region = if let ty::Ref(region, ..) = ty.kind() {
 521             match **region {
 522                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 523                 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 524                     printer.region_highlight_mode.highlighting_bound_region(br, counter)
 525                 }
 526                 _ => {}
 527             }
 528             region
 529         } else {
 530             bug!("ty for annotation of borrow region is not a reference");
 531         };
 532
 533         let _ = region.print(printer);
 534         s
 535     }
 536 }
 537
 538 /// The span(s) associated to a use of a place.
 539 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 540 pub(super) enum UseSpans<'tcx> {
 541     /// The access is caused by capturing a variable for a closure.
 542     ClosureUse {
 543         /// This is true if the captured variable was from a generator.
 544         generator_kind: Option<GeneratorKind>,
 545         /// The span of the args of the closure, including the `move` keyword if
 546         /// it's present.
 547         args_span: Span,
 548         /// The span of the use resulting in capture kind
 549         /// Check `ty::CaptureInfo` for more details
 550         capture_kind_span: Span,
 551         /// The span of the use resulting in the captured path
 552         /// Check `ty::CaptureInfo` for more details
 553         path_span: Span,
 554     },
 555     /// The access is caused by using a variable as the receiver of a method
 556     /// that takes 'self'
 557     FnSelfUse {
 558         /// The span of the variable being moved
 559         var_span: Span,
 560         /// The span of the method call on the variable
 561         fn_call_span: Span,
 562         /// The definition span of the method being called
 563         fn_span: Span,
 564         kind: CallKind<'tcx>,
 565     },
 566     /// This access is caused by a `match` or `if let` pattern.
 567     PatUse(Span),
 568     /// This access has a single span associated to it: common case.
 569     OtherUse(Span),
 570 }
 571
 572 impl UseSpans<'_> {
 573     pub(super) fn args_or_use(self) -> Span {
 574         match self {
 575             UseSpans::ClosureUse { args_span: span, .. }
 576             | UseSpans::PatUse(span)
 577             | UseSpans::OtherUse(span) => span,
 578             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 579                 fn_call_span
 580             }
 581             UseSpans::FnSelfUse { var_span, .. } => var_span,
 582         }
 583     }
 584
 585     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
 586     pub(super) fn var_or_use_path_span(self) -> Span {
 587         match self {
 588             UseSpans::ClosureUse { path_span: span, .. }
 589             | UseSpans::PatUse(span)
 590             | UseSpans::OtherUse(span) => span,
 591             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 592                 fn_call_span
 593             }
 594             UseSpans::FnSelfUse { var_span, .. } => var_span,
 595         }
 596     }
 597
 598     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
 599     pub(super) fn var_or_use(self) -> Span {
 600         match self {
 601             UseSpans::ClosureUse { capture_kind_span: span, .. }
 602             | UseSpans::PatUse(span)
 603             | UseSpans::OtherUse(span) => span,
 604             UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
 605                 fn_call_span
 606             }
 607             UseSpans::FnSelfUse { var_span, .. } => var_span,
 608         }
 609     }
 610
 611     pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
 612         match self {
 613             UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
 614             _ => None,
 615         }
 616     }
 617
 618     // Add a span label to the arguments of the closure, if it exists.
 619     pub(super) fn args_span_label(
 620         self,
 621         err: &mut DiagnosticBuilder<'_>,
 622         message: impl Into<String>,
 623     ) {
 624         if let UseSpans::ClosureUse { args_span, .. } = self {
 625             err.span_label(args_span, message);
 626         }
 627     }
 628
 629     // Add a span label to the use of the captured variable, if it exists.
 630     // only adds label to the `path_span`
 631     pub(super) fn var_span_label_path_only(
 632         self,
 633         err: &mut DiagnosticBuilder<'_>,
 634         message: impl Into<String>,
 635     ) {
 636         if let UseSpans::ClosureUse { path_span, .. } = self {
 637             err.span_label(path_span, message);
 638         }
 639     }
 640
 641     // Add a span label to the use of the captured variable, if it exists.
 642     pub(super) fn var_span_label(
 643         self,
 644         err: &mut DiagnosticBuilder<'_>,
 645         message: impl Into<String>,
 646         kind_desc: impl Into<String>,
 647     ) {
 648         if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
 649             if capture_kind_span == path_span {
 650                 err.span_label(capture_kind_span, message);
 651             } else {
 652                 let capture_kind_label =
 653                     format!("capture is {} because of use here", kind_desc.into());
 654                 let path_label = message;
 655                 err.span_label(capture_kind_span, capture_kind_label);
 656                 err.span_label(path_span, path_label);
 657             }
 658         }
 659     }
 660
 661     /// Returns `false` if this place is not used in a closure.
 662     pub(super) fn for_closure(&self) -> bool {
 663         match *self {
 664             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
 665             _ => false,
 666         }
 667     }
 668
 669     /// Returns `false` if this place is not used in a generator.
 670     pub(super) fn for_generator(&self) -> bool {
 671         match *self {
 672             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
 673             _ => false,
 674         }
 675     }
 676
 677     /// Describe the span associated with a use of a place.
 678     pub(super) fn describe(&self) -> String {
 679         match *self {
 680             UseSpans::ClosureUse { generator_kind, .. } => {
 681                 if generator_kind.is_some() {
 682                     " in generator".to_string()
 683                 } else {
 684                     " in closure".to_string()
 685                 }
 686             }
 687             _ => String::new(),
 688         }
 689     }
 690
 691     pub(super) fn or_else<F>(self, if_other: F) -> Self
 692     where
 693         F: FnOnce() -> Self,
 694     {
 695         match self {
 696             closure @ UseSpans::ClosureUse { .. } => closure,
 697             UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
 698             fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
 699         }
 700     }
 701 }
 702
 703 pub(super) enum BorrowedContentSource<'tcx> {
 704     DerefRawPointer,
 705     DerefMutableRef,
 706     DerefSharedRef,
 707     OverloadedDeref(Ty<'tcx>),
 708     OverloadedIndex(Ty<'tcx>),
 709 }
 710
 711 impl<'tcx> BorrowedContentSource<'tcx> {
 712     pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
 713         match *self {
 714             BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
 715             BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
 716             BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
 717             BorrowedContentSource::OverloadedDeref(ty) => ty
 718                 .ty_adt_def()
 719                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 720                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 721                     _ => None,
 722                 })
 723                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 724             BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
 725         }
 726     }
 727
 728     pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
 729         match *self {
 730             BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
 731             BorrowedContentSource::DerefSharedRef => Some("shared reference"),
 732             BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
 733             // Overloaded deref and index operators should be evaluated into a
 734             // temporary. So we don't need a description here.
 735             BorrowedContentSource::OverloadedDeref(_)
 736             | BorrowedContentSource::OverloadedIndex(_) => None,
 737         }
 738     }
 739
 740     pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
 741         match *self {
 742             BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
 743             BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
 744             BorrowedContentSource::DerefMutableRef => {
 745                 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
 746             }
 747             BorrowedContentSource::OverloadedDeref(ty) => ty
 748                 .ty_adt_def()
 749                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 750                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 751                     _ => None,
 752                 })
 753                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 754             BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
 755         }
 756     }
 757
 758     fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
 759         match *func.kind() {
 760             ty::FnDef(def_id, substs) => {
 761                 let trait_id = tcx.trait_of_item(def_id)?;
 762
 763                 let lang_items = tcx.lang_items();
 764                 if Some(trait_id) == lang_items.deref_trait()
 765                     || Some(trait_id) == lang_items.deref_mut_trait()
 766                 {
 767                     Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
 768                 } else if Some(trait_id) == lang_items.index_trait()
 769                     || Some(trait_id) == lang_items.index_mut_trait()
 770                 {
 771                     Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
 772                 } else {
 773                     None
 774                 }
 775             }
 776             _ => None,
 777         }
 778     }
 779 }
 780
 781 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 782     /// Finds the spans associated to a move or copy of move_place at location.
 783     pub(super) fn move_spans(
 784         &self,
 785         moved_place: PlaceRef<'tcx>, // Could also be an upvar.
 786         location: Location,
 787     ) -> UseSpans<'tcx> {
 788         use self::UseSpans::*;
 789
 790         let stmt = match self.body[location.block].statements.get(location.statement_index) {
 791             Some(stmt) => stmt,
 792             None => return OtherUse(self.body.source_info(location).span),
 793         };
 794
 795         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
 796         if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) = stmt.kind {
 797             match kind {
 798                 box AggregateKind::Closure(def_id, _)
 799                 | box AggregateKind::Generator(def_id, _, _) => {
 800                     debug!("move_spans: def_id={:?} places={:?}", def_id, places);
 801                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 802                         self.closure_span(*def_id, moved_place, places)
 803                     {
 804                         return ClosureUse {
 805                             generator_kind,
 806                             args_span,
 807                             capture_kind_span,
 808                             path_span,
 809                         };
 810                     }
 811                 }
 812                 _ => {}
 813             }
 814         }
 815
 816         // StatementKind::FakeRead only contains a def_id if they are introduced as a result
 817         // of pattern matching within a closure.
 818         if let StatementKind::FakeRead(box (cause, ref place)) = stmt.kind {
 819             match cause {
 820                 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
 821                 | FakeReadCause::ForLet(Some(closure_def_id)) => {
 822                     debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
 823                     let places = &[Operand::Move(*place)];
 824                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 825                         self.closure_span(closure_def_id, moved_place, places)
 826                     {
 827                         return ClosureUse {
 828                             generator_kind,
 829                             args_span,
 830                             capture_kind_span,
 831                             path_span,
 832                         };
 833                     }
 834                 }
 835                 _ => {}
 836             }
 837         }
 838
 839         let normal_ret =
 840             if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
 841                 PatUse(stmt.source_info.span)
 842             } else {
 843                 OtherUse(stmt.source_info.span)
 844             };
 845
 846         // We are trying to find MIR of the form:
 847         // ```
 848         // _temp = _moved_val;
 849         // ...
 850         // FnSelfCall(_temp, ...)
 851         // ```
 852         //
 853         // where `_moved_val` is the place we generated the move error for,
 854         // `_temp` is some other local, and `FnSelfCall` is a function
 855         // that has a `self` parameter.
 856
 857         let target_temp = match stmt.kind {
 858             StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
 859                 temp.as_local().unwrap()
 860             }
 861             _ => return normal_ret,
 862         };
 863
 864         debug!("move_spans: target_temp = {:?}", target_temp);
 865
 866         if let Some(Terminator {
 867             kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
 868         }) = &self.body[location.block].terminator
 869         {
 870             let Some((method_did, method_substs)) =
 871                 rustc_const_eval::util::find_self_call(
 872                     self.infcx.tcx,
 873                     &self.body,
 874                     target_temp,
 875                     location.block,
 876                 )
 877             else {
 878                 return normal_ret;
 879             };
 880
 881             let kind = call_kind(
 882                 self.infcx.tcx,
 883                 self.param_env,
 884                 method_did,
 885                 method_substs,
 886                 *fn_span,
 887                 *from_hir_call,
 888                 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
 889             );
 890
 891             return FnSelfUse {
 892                 var_span: stmt.source_info.span,
 893                 fn_call_span: *fn_span,
 894                 fn_span: self
 895                     .infcx
 896                     .tcx
 897                     .sess
 898                     .source_map()
 899                     .guess_head_span(self.infcx.tcx.def_span(method_did)),
 900                 kind,
 901             };
 902         }
 903         normal_ret
 904     }
 905
 906     /// Finds the span of arguments of a closure (within `maybe_closure_span`)
 907     /// and its usage of the local assigned at `location`.
 908     /// This is done by searching in statements succeeding `location`
 909     /// and originating from `maybe_closure_span`.
 910     pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
 911         use self::UseSpans::*;
 912         debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
 913
 914         let target = match self.body[location.block].statements.get(location.statement_index) {
 915             Some(&Statement { kind: StatementKind::Assign(box (ref place, _)), .. }) => {
 916                 if let Some(local) = place.as_local() {
 917                     local
 918                 } else {
 919                     return OtherUse(use_span);
 920                 }
 921             }
 922             _ => return OtherUse(use_span),
 923         };
 924
 925         if self.body.local_kind(target) != LocalKind::Temp {
 926             // operands are always temporaries.
 927             return OtherUse(use_span);
 928         }
 929
 930         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
 931             if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) =
 932                 stmt.kind
 933             {
 934                 let (def_id, is_generator) = match kind {
 935                     box AggregateKind::Closure(def_id, _) => (def_id, false),
 936                     box AggregateKind::Generator(def_id, _, _) => (def_id, true),
 937                     _ => continue,
 938                 };
 939
 940                 debug!(
 941                     "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
 942                     def_id, is_generator, places
 943                 );
 944                 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 945                     self.closure_span(*def_id, Place::from(target).as_ref(), places)
 946                 {
 947                     return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
 948                 } else {
 949                     return OtherUse(use_span);
 950                 }
 951             }
 952
 953             if use_span != stmt.source_info.span {
 954                 break;
 955             }
 956         }
 957
 958         OtherUse(use_span)
 959     }
 960
 961     /// Finds the spans of a captured place within a closure or generator.
 962     /// The first span is the location of the use resulting in the capture kind of the capture
 963     /// The second span is the location the use resulting in the captured path of the capture
 964     fn closure_span(
 965         &self,
 966         def_id: DefId,
 967         target_place: PlaceRef<'tcx>,
 968         places: &[Operand<'tcx>],
 969     ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
 970         debug!(
 971             "closure_span: def_id={:?} target_place={:?} places={:?}",
 972             def_id, target_place, places
 973         );
 974         let local_did = def_id.as_local()?;
 975         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(local_did);
 976         let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
 977         debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
 978         if let hir::ExprKind::Closure(.., body_id, args_span, _) = expr {
 979             for (captured_place, place) in self
 980                 .infcx
 981                 .tcx
 982                 .typeck(def_id.expect_local())
 983                 .closure_min_captures_flattened(def_id)
 984                 .zip(places)
 985             {
 986                 match place {
 987                     Operand::Copy(place) | Operand::Move(place)
 988                         if target_place == place.as_ref() =>
 989                     {
 990                         debug!("closure_span: found captured local {:?}", place);
 991                         let body = self.infcx.tcx.hir().body(*body_id);
 992                         let generator_kind = body.generator_kind();
 993
 994                         return Some((
 995                             *args_span,
 996                             generator_kind,
 997                             captured_place.get_capture_kind_span(self.infcx.tcx),
 998                             captured_place.get_path_span(self.infcx.tcx),
 999                         ));
1000                     }
1001                     _ => {}
1002                 }
1003             }
1004         }
1005         None
1006     }
1007
1008     /// Helper to retrieve span(s) of given borrow from the current MIR
1009     /// representation
1010     pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1011         let span = self.body.source_info(borrow.reserve_location).span;
1012         self.borrow_spans(span, borrow.reserve_location)
1013     }
1014 }