compiler/rustc_borrowck/src/diagnostics/mod.rs

   1 //! Borrow checker diagnostics.
   2
   3 use rustc_errors::DiagnosticBuilder;
   4 use rustc_hir as hir;
   5 use rustc_hir::def::Namespace;
   6 use rustc_hir::def_id::DefId;
   7 use rustc_hir::lang_items::LangItemGroup;
   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::{hygiene::DesugaringKind, 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 use rustc_span::symbol::Ident;
  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()].ident.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<'a>,
 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         match ty.kind() {
 501             ty::Ref(
 502                 ty::RegionKind::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 503                 | ty::RegionKind::RePlaceholder(ty::PlaceholderRegion { name: br, .. }),
 504                 _,
 505                 _,
 506             ) => printer.region_highlight_mode.highlighting_bound_region(*br, counter),
 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 = match ty.kind() {
 521             ty::Ref(region, _, _) => {
 522                 match region {
 523                     ty::RegionKind::ReLateBound(_, ty::BoundRegion { kind: br, .. })
 524                     | ty::RegionKind::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
 525                         printer.region_highlight_mode.highlighting_bound_region(*br, counter)
 526                     }
 527                     _ => {}
 528                 }
 529
 530                 region
 531             }
 532             _ => bug!("ty for annotation of borrow region is not a reference"),
 533         };
 534
 535         let _ = region.print(printer);
 536         s
 537     }
 538 }
 539
 540 /// The span(s) associated to a use of a place.
 541 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 542 pub(super) enum UseSpans<'tcx> {
 543     /// The access is caused by capturing a variable for a closure.
 544     ClosureUse {
 545         /// This is true if the captured variable was from a generator.
 546         generator_kind: Option<GeneratorKind>,
 547         /// The span of the args of the closure, including the `move` keyword if
 548         /// it's present.
 549         args_span: Span,
 550         /// The span of the use resulting in capture kind
 551         /// Check `ty::CaptureInfo` for more details
 552         capture_kind_span: Span,
 553         /// The span of the use resulting in the captured path
 554         /// Check `ty::CaptureInfo` for more details
 555         path_span: Span,
 556     },
 557     /// The access is caused by using a variable as the receiver of a method
 558     /// that takes 'self'
 559     FnSelfUse {
 560         /// The span of the variable being moved
 561         var_span: Span,
 562         /// The span of the method call on the variable
 563         fn_call_span: Span,
 564         /// The definition span of the method being called
 565         fn_span: Span,
 566         kind: FnSelfUseKind<'tcx>,
 567     },
 568     /// This access is caused by a `match` or `if let` pattern.
 569     PatUse(Span),
 570     /// This access has a single span associated to it: common case.
 571     OtherUse(Span),
 572 }
 573
 574 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 575 pub(super) enum FnSelfUseKind<'tcx> {
 576     /// A normal method call of the form `receiver.foo(a, b, c)`
 577     Normal {
 578         self_arg: Ident,
 579         implicit_into_iter: bool,
 580         /// Whether the self type of the method call has an `.as_ref()` method.
 581         /// Used for better diagnostics.
 582         is_option_or_result: bool,
 583     },
 584     /// A call to `FnOnce::call_once`, desugared from `my_closure(a, b, c)`
 585     FnOnceCall,
 586     /// A call to an operator trait, desuraged from operator syntax (e.g. `a << b`)
 587     Operator { self_arg: Ident },
 588     DerefCoercion {
 589         /// The `Span` of the `Target` associated type
 590         /// in the `Deref` impl we are using.
 591         deref_target: Span,
 592         /// The type `T::Deref` we are dereferencing to
 593         deref_target_ty: Ty<'tcx>,
 594     },
 595 }
 596
 597 impl UseSpans<'_> {
 598     pub(super) fn args_or_use(self) -> Span {
 599         match self {
 600             UseSpans::ClosureUse { args_span: span, .. }
 601             | UseSpans::PatUse(span)
 602             | UseSpans::OtherUse(span) => span,
 603             UseSpans::FnSelfUse {
 604                 fn_call_span, kind: FnSelfUseKind::DerefCoercion { .. }, ..
 605             } => fn_call_span,
 606             UseSpans::FnSelfUse { var_span, .. } => var_span,
 607         }
 608     }
 609
 610     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
 611     pub(super) fn var_or_use_path_span(self) -> Span {
 612         match self {
 613             UseSpans::ClosureUse { path_span: span, .. }
 614             | UseSpans::PatUse(span)
 615             | UseSpans::OtherUse(span) => span,
 616             UseSpans::FnSelfUse {
 617                 fn_call_span, kind: FnSelfUseKind::DerefCoercion { .. }, ..
 618             } => fn_call_span,
 619             UseSpans::FnSelfUse { var_span, .. } => var_span,
 620         }
 621     }
 622
 623     /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
 624     pub(super) fn var_or_use(self) -> Span {
 625         match self {
 626             UseSpans::ClosureUse { capture_kind_span: span, .. }
 627             | UseSpans::PatUse(span)
 628             | UseSpans::OtherUse(span) => span,
 629             UseSpans::FnSelfUse {
 630                 fn_call_span, kind: FnSelfUseKind::DerefCoercion { .. }, ..
 631             } => fn_call_span,
 632             UseSpans::FnSelfUse { var_span, .. } => var_span,
 633         }
 634     }
 635
 636     pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
 637         match self {
 638             UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
 639             _ => None,
 640         }
 641     }
 642
 643     // Add a span label to the arguments of the closure, if it exists.
 644     pub(super) fn args_span_label(
 645         self,
 646         err: &mut DiagnosticBuilder<'_>,
 647         message: impl Into<String>,
 648     ) {
 649         if let UseSpans::ClosureUse { args_span, .. } = self {
 650             err.span_label(args_span, message);
 651         }
 652     }
 653
 654     // Add a span label to the use of the captured variable, if it exists.
 655     // only adds label to the `path_span`
 656     pub(super) fn var_span_label_path_only(
 657         self,
 658         err: &mut DiagnosticBuilder<'_>,
 659         message: impl Into<String>,
 660     ) {
 661         if let UseSpans::ClosureUse { path_span, .. } = self {
 662             err.span_label(path_span, message);
 663         }
 664     }
 665
 666     // Add a span label to the use of the captured variable, if it exists.
 667     pub(super) fn var_span_label(
 668         self,
 669         err: &mut DiagnosticBuilder<'_>,
 670         message: impl Into<String>,
 671         kind_desc: impl Into<String>,
 672     ) {
 673         if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
 674             if capture_kind_span == path_span {
 675                 err.span_label(capture_kind_span, message);
 676             } else {
 677                 let capture_kind_label =
 678                     format!("capture is {} because of use here", kind_desc.into());
 679                 let path_label = message;
 680                 err.span_label(capture_kind_span, capture_kind_label);
 681                 err.span_label(path_span, path_label);
 682             }
 683         }
 684     }
 685
 686     /// Returns `false` if this place is not used in a closure.
 687     pub(super) fn for_closure(&self) -> bool {
 688         match *self {
 689             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
 690             _ => false,
 691         }
 692     }
 693
 694     /// Returns `false` if this place is not used in a generator.
 695     pub(super) fn for_generator(&self) -> bool {
 696         match *self {
 697             UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
 698             _ => false,
 699         }
 700     }
 701
 702     /// Describe the span associated with a use of a place.
 703     pub(super) fn describe(&self) -> String {
 704         match *self {
 705             UseSpans::ClosureUse { generator_kind, .. } => {
 706                 if generator_kind.is_some() {
 707                     " in generator".to_string()
 708                 } else {
 709                     " in closure".to_string()
 710                 }
 711             }
 712             _ => String::new(),
 713         }
 714     }
 715
 716     pub(super) fn or_else<F>(self, if_other: F) -> Self
 717     where
 718         F: FnOnce() -> Self,
 719     {
 720         match self {
 721             closure @ UseSpans::ClosureUse { .. } => closure,
 722             UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
 723             fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
 724         }
 725     }
 726 }
 727
 728 pub(super) enum BorrowedContentSource<'tcx> {
 729     DerefRawPointer,
 730     DerefMutableRef,
 731     DerefSharedRef,
 732     OverloadedDeref(Ty<'tcx>),
 733     OverloadedIndex(Ty<'tcx>),
 734 }
 735
 736 impl BorrowedContentSource<'tcx> {
 737     pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
 738         match *self {
 739             BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
 740             BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
 741             BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
 742             BorrowedContentSource::OverloadedDeref(ty) => ty
 743                 .ty_adt_def()
 744                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 745                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 746                     _ => None,
 747                 })
 748                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 749             BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
 750         }
 751     }
 752
 753     pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
 754         match *self {
 755             BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
 756             BorrowedContentSource::DerefSharedRef => Some("shared reference"),
 757             BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
 758             // Overloaded deref and index operators should be evaluated into a
 759             // temporary. So we don't need a description here.
 760             BorrowedContentSource::OverloadedDeref(_)
 761             | BorrowedContentSource::OverloadedIndex(_) => None,
 762         }
 763     }
 764
 765     pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
 766         match *self {
 767             BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
 768             BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
 769             BorrowedContentSource::DerefMutableRef => {
 770                 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
 771             }
 772             BorrowedContentSource::OverloadedDeref(ty) => ty
 773                 .ty_adt_def()
 774                 .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
 775                     name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
 776                     _ => None,
 777                 })
 778                 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
 779             BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
 780         }
 781     }
 782
 783     fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
 784         match *func.kind() {
 785             ty::FnDef(def_id, substs) => {
 786                 let trait_id = tcx.trait_of_item(def_id)?;
 787
 788                 let lang_items = tcx.lang_items();
 789                 if Some(trait_id) == lang_items.deref_trait()
 790                     || Some(trait_id) == lang_items.deref_mut_trait()
 791                 {
 792                     Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
 793                 } else if Some(trait_id) == lang_items.index_trait()
 794                     || Some(trait_id) == lang_items.index_mut_trait()
 795                 {
 796                     Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
 797                 } else {
 798                     None
 799                 }
 800             }
 801             _ => None,
 802         }
 803     }
 804 }
 805
 806 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 807     /// Finds the spans associated to a move or copy of move_place at location.
 808     pub(super) fn move_spans(
 809         &self,
 810         moved_place: PlaceRef<'tcx>, // Could also be an upvar.
 811         location: Location,
 812     ) -> UseSpans<'tcx> {
 813         use self::UseSpans::*;
 814
 815         let stmt = match self.body[location.block].statements.get(location.statement_index) {
 816             Some(stmt) => stmt,
 817             None => return OtherUse(self.body.source_info(location).span),
 818         };
 819
 820         debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
 821         if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) = stmt.kind {
 822             match kind {
 823                 box AggregateKind::Closure(def_id, _)
 824                 | box AggregateKind::Generator(def_id, _, _) => {
 825                     debug!("move_spans: def_id={:?} places={:?}", def_id, places);
 826                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 827                         self.closure_span(*def_id, moved_place, places)
 828                     {
 829                         return ClosureUse {
 830                             generator_kind,
 831                             args_span,
 832                             capture_kind_span,
 833                             path_span,
 834                         };
 835                     }
 836                 }
 837                 _ => {}
 838             }
 839         }
 840
 841         // StatementKind::FakeRead only contains a def_id if they are introduced as a result
 842         // of pattern matching within a closure.
 843         if let StatementKind::FakeRead(box (cause, ref place)) = stmt.kind {
 844             match cause {
 845                 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
 846                 | FakeReadCause::ForLet(Some(closure_def_id)) => {
 847                     debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
 848                     let places = &[Operand::Move(*place)];
 849                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
 850                         self.closure_span(closure_def_id, moved_place, places)
 851                     {
 852                         return ClosureUse {
 853                             generator_kind,
 854                             args_span,
 855                             capture_kind_span,
 856                             path_span,
 857                         };
 858                     }
 859                 }
 860                 _ => {}
 861             }
 862         }
 863
 864         let normal_ret =
 865             if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
 866                 PatUse(stmt.source_info.span)
 867             } else {
 868                 OtherUse(stmt.source_info.span)
 869             };
 870
 871         // We are trying to find MIR of the form:
 872         // ```
 873         // _temp = _moved_val;
 874         // ...
 875         // FnSelfCall(_temp, ...)
 876         // ```
 877         //
 878         // where `_moved_val` is the place we generated the move error for,
 879         // `_temp` is some other local, and `FnSelfCall` is a function
 880         // that has a `self` parameter.
 881
 882         let target_temp = match stmt.kind {
 883             StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
 884                 temp.as_local().unwrap()
 885             }
 886             _ => return normal_ret,
 887         };
 888
 889         debug!("move_spans: target_temp = {:?}", target_temp);
 890
 891         if let Some(Terminator {
 892             kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
 893         }) = &self.body[location.block].terminator
 894         {
 895             let (method_did, method_substs) = if let Some(info) =
 896                 rustc_const_eval::util::find_self_call(
 897                     self.infcx.tcx,
 898                     &self.body,
 899                     target_temp,
 900                     location.block,
 901                 ) {
 902                 info
 903             } else {
 904                 return normal_ret;
 905             };
 906
 907             let tcx = self.infcx.tcx;
 908             let parent = tcx.parent(method_did);
 909             let is_fn_once = parent == tcx.lang_items().fn_once_trait();
 910             let is_operator = !from_hir_call
 911                 && parent.map_or(false, |p| tcx.lang_items().group(LangItemGroup::Op).contains(&p));
 912             let is_deref = !from_hir_call && tcx.is_diagnostic_item(sym::deref_method, method_did);
 913             let fn_call_span = *fn_span;
 914
 915             let self_arg = tcx.fn_arg_names(method_did)[0];
 916
 917             debug!(
 918                 "terminator = {:?} from_hir_call={:?}",
 919                 self.body[location.block].terminator, from_hir_call
 920             );
 921
 922             // Check for a 'special' use of 'self' -
 923             // an FnOnce call, an operator (e.g. `<<`), or a
 924             // deref coercion.
 925             let kind = if is_fn_once {
 926                 Some(FnSelfUseKind::FnOnceCall)
 927             } else if is_operator {
 928                 Some(FnSelfUseKind::Operator { self_arg })
 929             } else if is_deref {
 930                 let deref_target =
 931                     tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| {
 932                         Instance::resolve(tcx, self.param_env, deref_target, method_substs)
 933                             .transpose()
 934                     });
 935                 if let Some(Ok(instance)) = deref_target {
 936                     let deref_target_ty = instance.ty(tcx, self.param_env);
 937                     Some(FnSelfUseKind::DerefCoercion {
 938                         deref_target: tcx.def_span(instance.def_id()),
 939                         deref_target_ty,
 940                     })
 941                 } else {
 942                     None
 943                 }
 944             } else {
 945                 None
 946             };
 947
 948             let kind = kind.unwrap_or_else(|| {
 949                 // This isn't a 'special' use of `self`
 950                 debug!("move_spans: method_did={:?}, fn_call_span={:?}", method_did, fn_call_span);
 951                 let implicit_into_iter = Some(method_did) == tcx.lang_items().into_iter_fn()
 952                     && fn_call_span.desugaring_kind() == Some(DesugaringKind::ForLoop);
 953                 let parent_self_ty = parent
 954                     .filter(|did| tcx.def_kind(*did) == rustc_hir::def::DefKind::Impl)
 955                     .and_then(|did| match tcx.type_of(did).kind() {
 956                         ty::Adt(def, ..) => Some(def.did),
 957                         _ => None,
 958                     });
 959                 let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
 960                     matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
 961                 });
 962                 FnSelfUseKind::Normal { self_arg, implicit_into_iter, is_option_or_result }
 963             });
 964
 965             return FnSelfUse {
 966                 var_span: stmt.source_info.span,
 967                 fn_call_span,
 968                 fn_span: self
 969                     .infcx
 970                     .tcx
 971                     .sess
 972                     .source_map()
 973                     .guess_head_span(self.infcx.tcx.def_span(method_did)),
 974                 kind,
 975             };
 976         }
 977         normal_ret
 978     }
 979
 980     /// Finds the span of arguments of a closure (within `maybe_closure_span`)
 981     /// and its usage of the local assigned at `location`.
 982     /// This is done by searching in statements succeeding `location`
 983     /// and originating from `maybe_closure_span`.
 984     pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
 985         use self::UseSpans::*;
 986         debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
 987
 988         let target = match self.body[location.block].statements.get(location.statement_index) {
 989             Some(&Statement { kind: StatementKind::Assign(box (ref place, _)), .. }) => {
 990                 if let Some(local) = place.as_local() {
 991                     local
 992                 } else {
 993                     return OtherUse(use_span);
 994                 }
 995             }
 996             _ => return OtherUse(use_span),
 997         };
 998
 999         if self.body.local_kind(target) != LocalKind::Temp {
1000             // operands are always temporaries.
1001             return OtherUse(use_span);
1002         }
1003
1004         for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
1005             if let StatementKind::Assign(box (_, Rvalue::Aggregate(ref kind, ref places))) =
1006                 stmt.kind
1007             {
1008                 let (def_id, is_generator) = match kind {
1009                     box AggregateKind::Closure(def_id, _) => (def_id, false),
1010                     box AggregateKind::Generator(def_id, _, _) => (def_id, true),
1011                     _ => continue,
1012                 };
1013
1014                 debug!(
1015                     "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
1016                     def_id, is_generator, places
1017                 );
1018                 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
1019                     self.closure_span(*def_id, Place::from(target).as_ref(), places)
1020                 {
1021                     return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
1022                 } else {
1023                     return OtherUse(use_span);
1024                 }
1025             }
1026
1027             if use_span != stmt.source_info.span {
1028                 break;
1029             }
1030         }
1031
1032         OtherUse(use_span)
1033     }
1034
1035     /// Finds the spans of a captured place within a closure or generator.
1036     /// The first span is the location of the use resulting in the capture kind of the capture
1037     /// The second span is the location the use resulting in the captured path of the capture
1038     fn closure_span(
1039         &self,
1040         def_id: DefId,
1041         target_place: PlaceRef<'tcx>,
1042         places: &[Operand<'tcx>],
1043     ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
1044         debug!(
1045             "closure_span: def_id={:?} target_place={:?} places={:?}",
1046             def_id, target_place, places
1047         );
1048         let local_did = def_id.as_local()?;
1049         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(local_did);
1050         let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
1051         debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
1052         if let hir::ExprKind::Closure(.., body_id, args_span, _) = expr {
1053             for (captured_place, place) in self
1054                 .infcx
1055                 .tcx
1056                 .typeck(def_id.expect_local())
1057                 .closure_min_captures_flattened(def_id)
1058                 .zip(places)
1059             {
1060                 match place {
1061                     Operand::Copy(place) | Operand::Move(place)
1062                         if target_place == place.as_ref() =>
1063                     {
1064                         debug!("closure_span: found captured local {:?}", place);
1065                         let body = self.infcx.tcx.hir().body(*body_id);
1066                         let generator_kind = body.generator_kind();
1067
1068                         return Some((
1069                             *args_span,
1070                             generator_kind,
1071                             captured_place.get_capture_kind_span(self.infcx.tcx),
1072                             captured_place.get_path_span(self.infcx.tcx),
1073                         ));
1074                     }
1075                     _ => {}
1076                 }
1077             }
1078         }
1079         None
1080     }
1081
1082     /// Helper to retrieve span(s) of given borrow from the current MIR
1083     /// representation
1084     pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1085         let span = self.body.source_info(borrow.reserve_location).span;
1086         self.borrow_spans(span, borrow.reserve_location)
1087     }
1088 }