1 //! Borrow checker diagnostics. 2 3 use crate::session_diagnostics::{ 4 CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause, 5 CaptureVarKind, CaptureVarPathUseCause, OnClosureNote, 6 }; 7 use itertools::Itertools; 8 use rustc_errors::{Applicability, Diagnostic}; 9 use rustc_hir as hir; 10 use rustc_hir::def::{CtorKind, Namespace}; 11 use rustc_hir::GeneratorKind; 12 use rustc_index::IndexSlice; 13 use rustc_infer::infer::LateBoundRegionConversionTime; 14 use rustc_middle::mir::tcx::PlaceTy; 15 use rustc_middle::mir::{ 16 AggregateKind, CallSource, Constant, FakeReadCause, Local, LocalInfo, LocalKind, Location, 17 Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, 18 TerminatorKind, 19 }; 20 use rustc_middle::ty::print::Print; 21 use rustc_middle::ty::{self, Instance, Ty, TyCtxt}; 22 use rustc_middle::util::{call_kind, CallDesugaringKind}; 23 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult}; 24 use rustc_span::def_id::LocalDefId; 25 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP}; 26 use rustc_target::abi::{FieldIdx, VariantIdx}; 27 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt; 28 use rustc_trait_selection::traits::{ 29 type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause, 30 }; 31 32 use super::borrow_set::BorrowData; 33 use super::MirBorrowckCtxt; 34 35 mod find_all_local_uses; 36 mod find_use; 37 mod outlives_suggestion; 38 mod region_name; 39 mod var_name; 40 41 mod bound_region_errors; 42 mod conflict_errors; 43 mod explain_borrow; 44 mod move_errors; 45 mod mutability_errors; 46 mod region_errors; 47 48 pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo}; 49 pub(crate) use mutability_errors::AccessKind; 50 pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder; 51 pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors}; 52 pub(crate) use region_name::{RegionName, RegionNameSource}; 53 pub(crate) use rustc_middle::util::CallKind; 54 55 pub(super) struct DescribePlaceOpt { 56 pub including_downcast: bool, 57 58 /// Enable/Disable tuple fields. 59 /// For example `x` tuple. if it's `true` `x.0`. Otherwise `x` 60 pub including_tuple_field: bool, 61 } 62 63 pub(super) struct IncludingTupleField(pub(super) bool); 64 65 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { 66 /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure 67 /// is moved after being invoked. 68 /// 69 /// ```text 70 /// note: closure cannot be invoked more than once because it moves the variable `dict` out of 71 /// its environment 72 /// --> $DIR/issue-42065.rs:16:29 73 /// | 74 /// LL | for (key, value) in dict { 75 /// | ^^^^ 76 /// ``` add_moved_or_invoked_closure_note( &self, location: Location, place: PlaceRef<'tcx>, diag: &mut Diagnostic, ) -> bool77 pub(super) fn add_moved_or_invoked_closure_note( 78 &self, 79 location: Location, 80 place: PlaceRef<'tcx>, 81 diag: &mut Diagnostic, 82 ) -> bool { 83 debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place); 84 let mut target = place.local_or_deref_local(); 85 for stmt in &self.body[location.block].statements[location.statement_index..] { 86 debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target); 87 if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind { 88 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from); 89 match from { 90 Operand::Copy(place) | Operand::Move(place) 91 if target == place.local_or_deref_local() => 92 { 93 target = into.local_or_deref_local() 94 } 95 _ => {} 96 } 97 } 98 } 99 100 // Check if we are attempting to call a closure after it has been invoked. 101 let terminator = self.body[location.block].terminator(); 102 debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator); 103 if let TerminatorKind::Call { 104 func: Operand::Constant(box Constant { literal, .. }), 105 args, 106 .. 107 } = &terminator.kind 108 { 109 if let ty::FnDef(id, _) = *literal.ty().kind() { 110 debug!("add_moved_or_invoked_closure_note: id={:?}", id); 111 if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() { 112 let closure = match args.first() { 113 Some(Operand::Copy(place) | Operand::Move(place)) 114 if target == place.local_or_deref_local() => 115 { 116 place.local_or_deref_local().unwrap() 117 } 118 _ => return false, 119 }; 120 121 debug!("add_moved_or_invoked_closure_note: closure={:?}", closure); 122 if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() { 123 let did = did.expect_local(); 124 if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) { 125 diag.eager_subdiagnostic( 126 &self.infcx.tcx.sess.parse_sess.span_diagnostic, 127 OnClosureNote::InvokedTwice { 128 place_name: &ty::place_to_string_for_capture( 129 self.infcx.tcx, 130 hir_place, 131 ), 132 span: *span, 133 }, 134 ); 135 return true; 136 } 137 } 138 } 139 } 140 } 141 142 // Check if we are just moving a closure after it has been invoked. 143 if let Some(target) = target { 144 if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() { 145 let did = did.expect_local(); 146 if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) { 147 diag.eager_subdiagnostic( 148 &self.infcx.tcx.sess.parse_sess.span_diagnostic, 149 OnClosureNote::MovedTwice { 150 place_name: &ty::place_to_string_for_capture(self.infcx.tcx, hir_place), 151 span: *span, 152 }, 153 ); 154 return true; 155 } 156 } 157 } 158 false 159 } 160 161 /// End-user visible description of `place` if one can be found. 162 /// If the place is a temporary for instance, `"value"` will be returned. describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String163 pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String { 164 match self.describe_place(place_ref) { 165 Some(mut descr) => { 166 // Surround descr with `backticks`. 167 descr.reserve(2); 168 descr.insert(0, '`'); 169 descr.push('`'); 170 descr 171 } 172 None => "value".to_string(), 173 } 174 } 175 176 /// End-user visible description of `place` if one can be found. 177 /// If the place is a temporary for instance, `None` will be returned. describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String>178 pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> { 179 self.describe_place_with_options( 180 place_ref, 181 DescribePlaceOpt { including_downcast: false, including_tuple_field: true }, 182 ) 183 } 184 185 /// End-user visible description of `place` if one can be found. If the place is a temporary 186 /// for instance, `None` will be returned. 187 /// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is 188 /// `Downcast` and `IncludingDowncast` is true describe_place_with_options( &self, place: PlaceRef<'tcx>, opt: DescribePlaceOpt, ) -> Option<String>189 pub(super) fn describe_place_with_options( 190 &self, 191 place: PlaceRef<'tcx>, 192 opt: DescribePlaceOpt, 193 ) -> Option<String> { 194 let local = place.local; 195 let mut autoderef_index = None; 196 let mut buf = String::new(); 197 let mut ok = self.append_local_to_string(local, &mut buf); 198 199 for (index, elem) in place.projection.into_iter().enumerate() { 200 match elem { 201 ProjectionElem::Deref => { 202 if index == 0 { 203 if self.body.local_decls[local].is_ref_for_guard() { 204 continue; 205 } 206 if let LocalInfo::StaticRef { def_id, .. } = 207 *self.body.local_decls[local].local_info() 208 { 209 buf.push_str(self.infcx.tcx.item_name(def_id).as_str()); 210 ok = Ok(()); 211 continue; 212 } 213 } 214 if let Some(field) = self.is_upvar_field_projection(PlaceRef { 215 local, 216 projection: place.projection.split_at(index + 1).0, 217 }) { 218 let var_index = field.index(); 219 buf = self.upvars[var_index].place.to_string(self.infcx.tcx); 220 ok = Ok(()); 221 if !self.upvars[var_index].by_ref { 222 buf.insert(0, '*'); 223 } 224 } else { 225 if autoderef_index.is_none() { 226 autoderef_index = 227 match place.projection.into_iter().rev().find_position(|elem| { 228 !matches!( 229 elem, 230 ProjectionElem::Deref | ProjectionElem::Downcast(..) 231 ) 232 }) { 233 Some((index, _)) => Some(place.projection.len() - index), 234 None => Some(0), 235 }; 236 } 237 if index >= autoderef_index.unwrap() { 238 buf.insert(0, '*'); 239 } 240 } 241 } 242 ProjectionElem::Downcast(..) if opt.including_downcast => return None, 243 ProjectionElem::Downcast(..) => (), 244 ProjectionElem::OpaqueCast(..) => (), 245 ProjectionElem::Field(field, _ty) => { 246 // FIXME(project-rfc_2229#36): print capture precisely here. 247 if let Some(field) = self.is_upvar_field_projection(PlaceRef { 248 local, 249 projection: place.projection.split_at(index + 1).0, 250 }) { 251 buf = self.upvars[field.index()].place.to_string(self.infcx.tcx); 252 ok = Ok(()); 253 } else { 254 let field_name = self.describe_field( 255 PlaceRef { local, projection: place.projection.split_at(index).0 }, 256 *field, 257 IncludingTupleField(opt.including_tuple_field), 258 ); 259 if let Some(field_name_str) = field_name { 260 buf.push('.'); 261 buf.push_str(&field_name_str); 262 } 263 } 264 } 265 ProjectionElem::Index(index) => { 266 buf.push('['); 267 if self.append_local_to_string(*index, &mut buf).is_err() { 268 buf.push('_'); 269 } 270 buf.push(']'); 271 } 272 ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => { 273 // Since it isn't possible to borrow an element on a particular index and 274 // then use another while the borrow is held, don't output indices details 275 // to avoid confusing the end-user 276 buf.push_str("[..]"); 277 } 278 } 279 } 280 ok.ok().map(|_| buf) 281 } 282 describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol>283 fn describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol> { 284 for elem in place.projection.into_iter() { 285 match elem { 286 ProjectionElem::Downcast(Some(name), _) => { 287 return Some(*name); 288 } 289 _ => {} 290 } 291 } 292 None 293 } 294 295 /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have 296 /// a name, or its name was generated by the compiler, then `Err` is returned append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()>297 fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> { 298 let decl = &self.body.local_decls[local]; 299 match self.local_names[local] { 300 Some(name) if !decl.from_compiler_desugaring() => { 301 buf.push_str(name.as_str()); 302 Ok(()) 303 } 304 _ => Err(()), 305 } 306 } 307 308 /// End-user visible description of the `field`nth field of `base` describe_field( &self, place: PlaceRef<'tcx>, field: FieldIdx, including_tuple_field: IncludingTupleField, ) -> Option<String>309 fn describe_field( 310 &self, 311 place: PlaceRef<'tcx>, 312 field: FieldIdx, 313 including_tuple_field: IncludingTupleField, 314 ) -> Option<String> { 315 let place_ty = match place { 316 PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty), 317 PlaceRef { local, projection: [proj_base @ .., elem] } => match elem { 318 ProjectionElem::Deref 319 | ProjectionElem::Index(..) 320 | ProjectionElem::ConstantIndex { .. } 321 | ProjectionElem::Subslice { .. } => { 322 PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx) 323 } 324 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx), 325 ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty), 326 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type), 327 }, 328 }; 329 self.describe_field_from_ty( 330 place_ty.ty, 331 field, 332 place_ty.variant_index, 333 including_tuple_field, 334 ) 335 } 336 337 /// End-user visible description of the `field_index`nth field of `ty` describe_field_from_ty( &self, ty: Ty<'_>, field: FieldIdx, variant_index: Option<VariantIdx>, including_tuple_field: IncludingTupleField, ) -> Option<String>338 fn describe_field_from_ty( 339 &self, 340 ty: Ty<'_>, 341 field: FieldIdx, 342 variant_index: Option<VariantIdx>, 343 including_tuple_field: IncludingTupleField, 344 ) -> Option<String> { 345 if ty.is_box() { 346 // If the type is a box, the field is described from the boxed type 347 self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field) 348 } else { 349 match *ty.kind() { 350 ty::Adt(def, _) => { 351 let variant = if let Some(idx) = variant_index { 352 assert!(def.is_enum()); 353 &def.variant(idx) 354 } else { 355 def.non_enum_variant() 356 }; 357 if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) { 358 return None; 359 } 360 Some(variant.fields[field].name.to_string()) 361 } 362 ty::Tuple(_) => Some(field.index().to_string()), 363 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => { 364 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field) 365 } 366 ty::Array(ty, _) | ty::Slice(ty) => { 367 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field) 368 } 369 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => { 370 // We won't be borrowck'ing here if the closure came from another crate, 371 // so it's safe to call `expect_local`. 372 // 373 // We know the field exists so it's safe to call operator[] and `unwrap` here. 374 let def_id = def_id.expect_local(); 375 let var_id = 376 self.infcx.tcx.closure_captures(def_id)[field.index()].get_root_variable(); 377 378 Some(self.infcx.tcx.hir().name(var_id).to_string()) 379 } 380 _ => { 381 // Might need a revision when the fields in trait RFC is implemented 382 // (https://github.com/rust-lang/rfcs/pull/1546) 383 bug!("End-user description not implemented for field access on `{:?}`", ty); 384 } 385 } 386 } 387 } 388 borrowed_content_source( &self, deref_base: PlaceRef<'tcx>, ) -> BorrowedContentSource<'tcx>389 pub(super) fn borrowed_content_source( 390 &self, 391 deref_base: PlaceRef<'tcx>, 392 ) -> BorrowedContentSource<'tcx> { 393 let tcx = self.infcx.tcx; 394 395 // Look up the provided place and work out the move path index for it, 396 // we'll use this to check whether it was originally from an overloaded 397 // operator. 398 match self.move_data.rev_lookup.find(deref_base) { 399 LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => { 400 debug!("borrowed_content_source: mpi={:?}", mpi); 401 402 for i in &self.move_data.init_path_map[mpi] { 403 let init = &self.move_data.inits[*i]; 404 debug!("borrowed_content_source: init={:?}", init); 405 // We're only interested in statements that initialized a value, not the 406 // initializations from arguments. 407 let InitLocation::Statement(loc) = init.location else { continue }; 408 409 let bbd = &self.body[loc.block]; 410 let is_terminator = bbd.statements.len() == loc.statement_index; 411 debug!( 412 "borrowed_content_source: loc={:?} is_terminator={:?}", 413 loc, is_terminator, 414 ); 415 if !is_terminator { 416 continue; 417 } else if let Some(Terminator { 418 kind: 419 TerminatorKind::Call { 420 func, 421 call_source: CallSource::OverloadedOperator, 422 .. 423 }, 424 .. 425 }) = &bbd.terminator 426 { 427 if let Some(source) = 428 BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx) 429 { 430 return source; 431 } 432 } 433 } 434 } 435 // Base is a `static` so won't be from an overloaded operator 436 _ => (), 437 }; 438 439 // If we didn't find an overloaded deref or index, then assume it's a 440 // built in deref and check the type of the base. 441 let base_ty = deref_base.ty(self.body, tcx).ty; 442 if base_ty.is_unsafe_ptr() { 443 BorrowedContentSource::DerefRawPointer 444 } else if base_ty.is_mutable_ptr() { 445 BorrowedContentSource::DerefMutableRef 446 } else { 447 BorrowedContentSource::DerefSharedRef 448 } 449 } 450 451 /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime 452 /// name where required. get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String453 pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String { 454 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS); 455 456 // We need to add synthesized lifetimes where appropriate. We do 457 // this by hooking into the pretty printer and telling it to label the 458 // lifetimes without names with the value `'0`. 459 if let ty::Ref(region, ..) = ty.kind() { 460 match **region { 461 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. }) 462 | ty::RePlaceholder(ty::PlaceholderRegion { 463 bound: ty::BoundRegion { kind: br, .. }, 464 .. 465 }) => printer.region_highlight_mode.highlighting_bound_region(br, counter), 466 _ => {} 467 } 468 } 469 470 ty.print(printer).unwrap().into_buffer() 471 } 472 473 /// Returns the name of the provided `Ty` (that must be a reference)'s region with a 474 /// synthesized lifetime name where required. get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String475 pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String { 476 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS); 477 478 let region = if let ty::Ref(region, ..) = ty.kind() { 479 match **region { 480 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. }) 481 | ty::RePlaceholder(ty::PlaceholderRegion { 482 bound: ty::BoundRegion { kind: br, .. }, 483 .. 484 }) => printer.region_highlight_mode.highlighting_bound_region(br, counter), 485 _ => {} 486 } 487 region 488 } else { 489 bug!("ty for annotation of borrow region is not a reference"); 490 }; 491 492 region.print(printer).unwrap().into_buffer() 493 } 494 } 495 496 /// The span(s) associated to a use of a place. 497 #[derive(Copy, Clone, PartialEq, Eq, Debug)] 498 pub(super) enum UseSpans<'tcx> { 499 /// The access is caused by capturing a variable for a closure. 500 ClosureUse { 501 /// This is true if the captured variable was from a generator. 502 generator_kind: Option<GeneratorKind>, 503 /// The span of the args of the closure, including the `move` keyword if 504 /// it's present. 505 args_span: Span, 506 /// The span of the use resulting in capture kind 507 /// Check `ty::CaptureInfo` for more details 508 capture_kind_span: Span, 509 /// The span of the use resulting in the captured path 510 /// Check `ty::CaptureInfo` for more details 511 path_span: Span, 512 }, 513 /// The access is caused by using a variable as the receiver of a method 514 /// that takes 'self' 515 FnSelfUse { 516 /// The span of the variable being moved 517 var_span: Span, 518 /// The span of the method call on the variable 519 fn_call_span: Span, 520 /// The definition span of the method being called 521 fn_span: Span, 522 kind: CallKind<'tcx>, 523 }, 524 /// This access is caused by a `match` or `if let` pattern. 525 PatUse(Span), 526 /// This access has a single span associated to it: common case. 527 OtherUse(Span), 528 } 529 530 impl UseSpans<'_> { args_or_use(self) -> Span531 pub(super) fn args_or_use(self) -> Span { 532 match self { 533 UseSpans::ClosureUse { args_span: span, .. } 534 | UseSpans::PatUse(span) 535 | UseSpans::OtherUse(span) => span, 536 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { 537 fn_call_span 538 } 539 UseSpans::FnSelfUse { var_span, .. } => var_span, 540 } 541 } 542 543 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span` var_or_use_path_span(self) -> Span544 pub(super) fn var_or_use_path_span(self) -> Span { 545 match self { 546 UseSpans::ClosureUse { path_span: span, .. } 547 | UseSpans::PatUse(span) 548 | UseSpans::OtherUse(span) => span, 549 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { 550 fn_call_span 551 } 552 UseSpans::FnSelfUse { var_span, .. } => var_span, 553 } 554 } 555 556 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span` var_or_use(self) -> Span557 pub(super) fn var_or_use(self) -> Span { 558 match self { 559 UseSpans::ClosureUse { capture_kind_span: span, .. } 560 | UseSpans::PatUse(span) 561 | UseSpans::OtherUse(span) => span, 562 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { 563 fn_call_span 564 } 565 UseSpans::FnSelfUse { var_span, .. } => var_span, 566 } 567 } 568 generator_kind(self) -> Option<GeneratorKind>569 pub(super) fn generator_kind(self) -> Option<GeneratorKind> { 570 match self { 571 UseSpans::ClosureUse { generator_kind, .. } => generator_kind, 572 _ => None, 573 } 574 } 575 576 /// Add a span label to the arguments of the closure, if it exists. args_subdiag( self, err: &mut Diagnostic, f: impl FnOnce(Span) -> CaptureArgLabel, )577 pub(super) fn args_subdiag( 578 self, 579 err: &mut Diagnostic, 580 f: impl FnOnce(Span) -> CaptureArgLabel, 581 ) { 582 if let UseSpans::ClosureUse { args_span, .. } = self { 583 err.subdiagnostic(f(args_span)); 584 } 585 } 586 587 /// Add a span label to the use of the captured variable, if it exists. 588 /// only adds label to the `path_span` var_path_only_subdiag( self, err: &mut Diagnostic, action: crate::InitializationRequiringAction, )589 pub(super) fn var_path_only_subdiag( 590 self, 591 err: &mut Diagnostic, 592 action: crate::InitializationRequiringAction, 593 ) { 594 use crate::InitializationRequiringAction::*; 595 use CaptureVarPathUseCause::*; 596 if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self { 597 match generator_kind { 598 Some(_) => { 599 err.subdiagnostic(match action { 600 Borrow => BorrowInGenerator { path_span }, 601 MatchOn | Use => UseInGenerator { path_span }, 602 Assignment => AssignInGenerator { path_span }, 603 PartialAssignment => AssignPartInGenerator { path_span }, 604 }); 605 } 606 None => { 607 err.subdiagnostic(match action { 608 Borrow => BorrowInClosure { path_span }, 609 MatchOn | Use => UseInClosure { path_span }, 610 Assignment => AssignInClosure { path_span }, 611 PartialAssignment => AssignPartInClosure { path_span }, 612 }); 613 } 614 } 615 } 616 } 617 618 /// Add a subdiagnostic to the use of the captured variable, if it exists. var_subdiag( self, handler: Option<&rustc_errors::Handler>, err: &mut Diagnostic, kind: Option<rustc_middle::mir::BorrowKind>, f: impl FnOnce(Option<GeneratorKind>, Span) -> CaptureVarCause, )619 pub(super) fn var_subdiag( 620 self, 621 handler: Option<&rustc_errors::Handler>, 622 err: &mut Diagnostic, 623 kind: Option<rustc_middle::mir::BorrowKind>, 624 f: impl FnOnce(Option<GeneratorKind>, Span) -> CaptureVarCause, 625 ) { 626 if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self { 627 if capture_kind_span != path_span { 628 err.subdiagnostic(match kind { 629 Some(kd) => match kd { 630 rustc_middle::mir::BorrowKind::Shared 631 | rustc_middle::mir::BorrowKind::Shallow => { 632 CaptureVarKind::Immut { kind_span: capture_kind_span } 633 } 634 635 rustc_middle::mir::BorrowKind::Mut { .. } => { 636 CaptureVarKind::Mut { kind_span: capture_kind_span } 637 } 638 }, 639 None => CaptureVarKind::Move { kind_span: capture_kind_span }, 640 }); 641 }; 642 let diag = f(generator_kind, path_span); 643 match handler { 644 Some(hd) => err.eager_subdiagnostic(hd, diag), 645 None => err.subdiagnostic(diag), 646 }; 647 } 648 } 649 650 /// Returns `false` if this place is not used in a closure. for_closure(&self) -> bool651 pub(super) fn for_closure(&self) -> bool { 652 match *self { 653 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(), 654 _ => false, 655 } 656 } 657 658 /// Returns `false` if this place is not used in a generator. for_generator(&self) -> bool659 pub(super) fn for_generator(&self) -> bool { 660 match *self { 661 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(), 662 _ => false, 663 } 664 } 665 or_else<F>(self, if_other: F) -> Self where F: FnOnce() -> Self,666 pub(super) fn or_else<F>(self, if_other: F) -> Self 667 where 668 F: FnOnce() -> Self, 669 { 670 match self { 671 closure @ UseSpans::ClosureUse { .. } => closure, 672 UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(), 673 fn_self @ UseSpans::FnSelfUse { .. } => fn_self, 674 } 675 } 676 } 677 678 pub(super) enum BorrowedContentSource<'tcx> { 679 DerefRawPointer, 680 DerefMutableRef, 681 DerefSharedRef, 682 OverloadedDeref(Ty<'tcx>), 683 OverloadedIndex(Ty<'tcx>), 684 } 685 686 impl<'tcx> BorrowedContentSource<'tcx> { describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String687 pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String { 688 match *self { 689 BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(), 690 BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(), 691 BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(), 692 BorrowedContentSource::OverloadedDeref(ty) => ty 693 .ty_adt_def() 694 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? { 695 name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")), 696 _ => None, 697 }) 698 .unwrap_or_else(|| format!("dereference of `{ty}`")), 699 BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{ty}`"), 700 } 701 } 702 describe_for_named_place(&self) -> Option<&'static str>703 pub(super) fn describe_for_named_place(&self) -> Option<&'static str> { 704 match *self { 705 BorrowedContentSource::DerefRawPointer => Some("raw pointer"), 706 BorrowedContentSource::DerefSharedRef => Some("shared reference"), 707 BorrowedContentSource::DerefMutableRef => Some("mutable reference"), 708 // Overloaded deref and index operators should be evaluated into a 709 // temporary. So we don't need a description here. 710 BorrowedContentSource::OverloadedDeref(_) 711 | BorrowedContentSource::OverloadedIndex(_) => None, 712 } 713 } 714 describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String715 pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String { 716 match *self { 717 BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(), 718 BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(), 719 BorrowedContentSource::DerefMutableRef => { 720 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable") 721 } 722 BorrowedContentSource::OverloadedDeref(ty) => ty 723 .ty_adt_def() 724 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? { 725 name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")), 726 _ => None, 727 }) 728 .unwrap_or_else(|| format!("dereference of `{ty}`")), 729 BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{ty}`"), 730 } 731 } 732 from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self>733 fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> { 734 match *func.kind() { 735 ty::FnDef(def_id, substs) => { 736 let trait_id = tcx.trait_of_item(def_id)?; 737 738 let lang_items = tcx.lang_items(); 739 if Some(trait_id) == lang_items.deref_trait() 740 || Some(trait_id) == lang_items.deref_mut_trait() 741 { 742 Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0))) 743 } else if Some(trait_id) == lang_items.index_trait() 744 || Some(trait_id) == lang_items.index_mut_trait() 745 { 746 Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0))) 747 } else { 748 None 749 } 750 } 751 _ => None, 752 } 753 } 754 } 755 756 ///helper struct for explain_captures() 757 struct CapturedMessageOpt { 758 is_partial_move: bool, 759 is_loop_message: bool, 760 is_move_msg: bool, 761 is_loop_move: bool, 762 maybe_reinitialized_locations_is_empty: bool, 763 } 764 765 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { 766 /// Finds the spans associated to a move or copy of move_place at location. move_spans( &self, moved_place: PlaceRef<'tcx>, location: Location, ) -> UseSpans<'tcx>767 pub(super) fn move_spans( 768 &self, 769 moved_place: PlaceRef<'tcx>, // Could also be an upvar. 770 location: Location, 771 ) -> UseSpans<'tcx> { 772 use self::UseSpans::*; 773 774 let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else { 775 return OtherUse(self.body.source_info(location).span); 776 }; 777 778 debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt); 779 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind 780 && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind 781 { 782 debug!("move_spans: def_id={:?} places={:?}", def_id, places); 783 let def_id = def_id.expect_local(); 784 if let Some((args_span, generator_kind, capture_kind_span, path_span)) = 785 self.closure_span(def_id, moved_place, places) 786 { 787 return ClosureUse { 788 generator_kind, 789 args_span, 790 capture_kind_span, 791 path_span, 792 }; 793 } 794 } 795 796 // StatementKind::FakeRead only contains a def_id if they are introduced as a result 797 // of pattern matching within a closure. 798 if let StatementKind::FakeRead(box (cause, place)) = stmt.kind { 799 match cause { 800 FakeReadCause::ForMatchedPlace(Some(closure_def_id)) 801 | FakeReadCause::ForLet(Some(closure_def_id)) => { 802 debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place); 803 let places = &[Operand::Move(place)]; 804 if let Some((args_span, generator_kind, capture_kind_span, path_span)) = 805 self.closure_span(closure_def_id, moved_place, IndexSlice::from_raw(places)) 806 { 807 return ClosureUse { 808 generator_kind, 809 args_span, 810 capture_kind_span, 811 path_span, 812 }; 813 } 814 } 815 _ => {} 816 } 817 } 818 819 let normal_ret = 820 if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) { 821 PatUse(stmt.source_info.span) 822 } else { 823 OtherUse(stmt.source_info.span) 824 }; 825 826 // We are trying to find MIR of the form: 827 // ``` 828 // _temp = _moved_val; 829 // ... 830 // FnSelfCall(_temp, ...) 831 // ``` 832 // 833 // where `_moved_val` is the place we generated the move error for, 834 // `_temp` is some other local, and `FnSelfCall` is a function 835 // that has a `self` parameter. 836 837 let target_temp = match stmt.kind { 838 StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => { 839 temp.as_local().unwrap() 840 } 841 _ => return normal_ret, 842 }; 843 844 debug!("move_spans: target_temp = {:?}", target_temp); 845 846 if let Some(Terminator { 847 kind: TerminatorKind::Call { fn_span, call_source, .. }, .. 848 }) = &self.body[location.block].terminator 849 { 850 let Some((method_did, method_substs)) = 851 rustc_middle::util::find_self_call( 852 self.infcx.tcx, 853 &self.body, 854 target_temp, 855 location.block, 856 ) 857 else { 858 return normal_ret; 859 }; 860 861 let kind = call_kind( 862 self.infcx.tcx, 863 self.param_env, 864 method_did, 865 method_substs, 866 *fn_span, 867 call_source.from_hir_call(), 868 Some(self.infcx.tcx.fn_arg_names(method_did)[0]), 869 ); 870 871 return FnSelfUse { 872 var_span: stmt.source_info.span, 873 fn_call_span: *fn_span, 874 fn_span: self.infcx.tcx.def_span(method_did), 875 kind, 876 }; 877 } 878 normal_ret 879 } 880 881 /// Finds the span of arguments of a closure (within `maybe_closure_span`) 882 /// and its usage of the local assigned at `location`. 883 /// This is done by searching in statements succeeding `location` 884 /// and originating from `maybe_closure_span`. borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx>885 pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> { 886 use self::UseSpans::*; 887 debug!("borrow_spans: use_span={:?} location={:?}", use_span, location); 888 889 let target = match self.body[location.block].statements.get(location.statement_index) { 890 Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => { 891 if let Some(local) = place.as_local() { 892 local 893 } else { 894 return OtherUse(use_span); 895 } 896 } 897 _ => return OtherUse(use_span), 898 }; 899 900 if self.body.local_kind(target) != LocalKind::Temp { 901 // operands are always temporaries. 902 return OtherUse(use_span); 903 } 904 905 // drop and replace might have moved the assignment to the next block 906 let maybe_additional_statement = 907 if let TerminatorKind::Drop { target: drop_target, .. } = 908 self.body[location.block].terminator().kind 909 { 910 self.body[drop_target].statements.first() 911 } else { 912 None 913 }; 914 915 let statements = 916 self.body[location.block].statements[location.statement_index + 1..].iter(); 917 918 for stmt in statements.chain(maybe_additional_statement) { 919 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind { 920 let (&def_id, is_generator) = match kind { 921 box AggregateKind::Closure(def_id, _) => (def_id, false), 922 box AggregateKind::Generator(def_id, _, _) => (def_id, true), 923 _ => continue, 924 }; 925 let def_id = def_id.expect_local(); 926 927 debug!( 928 "borrow_spans: def_id={:?} is_generator={:?} places={:?}", 929 def_id, is_generator, places 930 ); 931 if let Some((args_span, generator_kind, capture_kind_span, path_span)) = 932 self.closure_span(def_id, Place::from(target).as_ref(), places) 933 { 934 return ClosureUse { generator_kind, args_span, capture_kind_span, path_span }; 935 } else { 936 return OtherUse(use_span); 937 } 938 } 939 940 if use_span != stmt.source_info.span { 941 break; 942 } 943 } 944 945 OtherUse(use_span) 946 } 947 948 /// Finds the spans of a captured place within a closure or generator. 949 /// The first span is the location of the use resulting in the capture kind of the capture 950 /// The second span is the location the use resulting in the captured path of the capture closure_span( &self, def_id: LocalDefId, target_place: PlaceRef<'tcx>, places: &IndexSlice<FieldIdx, Operand<'tcx>>, ) -> Option<(Span, Option<GeneratorKind>, Span, Span)>951 fn closure_span( 952 &self, 953 def_id: LocalDefId, 954 target_place: PlaceRef<'tcx>, 955 places: &IndexSlice<FieldIdx, Operand<'tcx>>, 956 ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> { 957 debug!( 958 "closure_span: def_id={:?} target_place={:?} places={:?}", 959 def_id, target_place, places 960 ); 961 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id); 962 let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind; 963 debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr); 964 if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr { 965 for (captured_place, place) in 966 self.infcx.tcx.closure_captures(def_id).iter().zip(places) 967 { 968 match place { 969 Operand::Copy(place) | Operand::Move(place) 970 if target_place == place.as_ref() => 971 { 972 debug!("closure_span: found captured local {:?}", place); 973 let body = self.infcx.tcx.hir().body(body); 974 let generator_kind = body.generator_kind(); 975 976 return Some(( 977 fn_decl_span, 978 generator_kind, 979 captured_place.get_capture_kind_span(self.infcx.tcx), 980 captured_place.get_path_span(self.infcx.tcx), 981 )); 982 } 983 _ => {} 984 } 985 } 986 } 987 None 988 } 989 990 /// Helper to retrieve span(s) of given borrow from the current MIR 991 /// representation retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx>992 pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> { 993 let span = self.body.source_info(borrow.reserve_location).span; 994 self.borrow_spans(span, borrow.reserve_location) 995 } 996 explain_captures( &mut self, err: &mut Diagnostic, span: Span, move_span: Span, move_spans: UseSpans<'tcx>, moved_place: Place<'tcx>, msg_opt: CapturedMessageOpt, )997 fn explain_captures( 998 &mut self, 999 err: &mut Diagnostic, 1000 span: Span, 1001 move_span: Span, 1002 move_spans: UseSpans<'tcx>, 1003 moved_place: Place<'tcx>, 1004 msg_opt: CapturedMessageOpt, 1005 ) { 1006 let CapturedMessageOpt { 1007 is_partial_move: is_partial, 1008 is_loop_message, 1009 is_move_msg, 1010 is_loop_move, 1011 maybe_reinitialized_locations_is_empty, 1012 } = msg_opt; 1013 if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans { 1014 let place_name = self 1015 .describe_place(moved_place.as_ref()) 1016 .map(|n| format!("`{n}`")) 1017 .unwrap_or_else(|| "value".to_owned()); 1018 match kind { 1019 CallKind::FnCall { fn_trait_id, .. } 1020 if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() => 1021 { 1022 err.subdiagnostic(CaptureReasonLabel::Call { 1023 fn_call_span, 1024 place_name: &place_name, 1025 is_partial, 1026 is_loop_message, 1027 }); 1028 err.subdiagnostic(CaptureReasonNote::FnOnceMoveInCall { var_span }); 1029 } 1030 CallKind::Operator { self_arg, .. } => { 1031 let self_arg = self_arg.unwrap(); 1032 err.subdiagnostic(CaptureReasonLabel::OperatorUse { 1033 fn_call_span, 1034 place_name: &place_name, 1035 is_partial, 1036 is_loop_message, 1037 }); 1038 if self.fn_self_span_reported.insert(fn_span) { 1039 err.subdiagnostic(CaptureReasonNote::LhsMoveByOperator { 1040 span: self_arg.span, 1041 }); 1042 } 1043 } 1044 CallKind::Normal { self_arg, desugaring, method_did, method_substs } => { 1045 let self_arg = self_arg.unwrap(); 1046 let tcx = self.infcx.tcx; 1047 if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring { 1048 let ty = moved_place.ty(self.body, tcx).ty; 1049 let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) { 1050 Some(def_id) => type_known_to_meet_bound_modulo_regions( 1051 &self.infcx, 1052 self.param_env, 1053 Ty::new_imm_ref(tcx, tcx.lifetimes.re_erased, ty), 1054 def_id, 1055 ), 1056 _ => false, 1057 }; 1058 if suggest { 1059 err.subdiagnostic(CaptureReasonSuggest::IterateSlice { 1060 ty, 1061 span: move_span.shrink_to_lo(), 1062 }); 1063 } 1064 1065 err.subdiagnostic(CaptureReasonLabel::ImplicitCall { 1066 fn_call_span, 1067 place_name: &place_name, 1068 is_partial, 1069 is_loop_message, 1070 }); 1071 // If the moved place was a `&mut` ref, then we can 1072 // suggest to reborrow it where it was moved, so it 1073 // will still be valid by the time we get to the usage. 1074 if let ty::Ref(_, _, hir::Mutability::Mut) = 1075 moved_place.ty(self.body, self.infcx.tcx).ty.kind() 1076 { 1077 // If we are in a loop this will be suggested later. 1078 if !is_loop_move { 1079 err.span_suggestion_verbose( 1080 move_span.shrink_to_lo(), 1081 format!( 1082 "consider creating a fresh reborrow of {} here", 1083 self.describe_place(moved_place.as_ref()) 1084 .map(|n| format!("`{n}`")) 1085 .unwrap_or_else(|| "the mutable reference".to_string()), 1086 ), 1087 "&mut *", 1088 Applicability::MachineApplicable, 1089 ); 1090 } 1091 } 1092 } else { 1093 if let Some((CallDesugaringKind::Await, _)) = desugaring { 1094 err.subdiagnostic(CaptureReasonLabel::Await { 1095 fn_call_span, 1096 place_name: &place_name, 1097 is_partial, 1098 is_loop_message, 1099 }); 1100 } else { 1101 err.subdiagnostic(CaptureReasonLabel::MethodCall { 1102 fn_call_span, 1103 place_name: &place_name, 1104 is_partial, 1105 is_loop_message, 1106 }); 1107 } 1108 // Erase and shadow everything that could be passed to the new infcx. 1109 let ty = moved_place.ty(self.body, tcx).ty; 1110 1111 if let ty::Adt(def, substs) = ty.kind() 1112 && Some(def.did()) == tcx.lang_items().pin_type() 1113 && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind() 1114 && let self_ty = self.infcx.instantiate_binder_with_fresh_vars( 1115 fn_call_span, 1116 LateBoundRegionConversionTime::FnCall, 1117 tcx.fn_sig(method_did).subst(tcx, method_substs).input(0), 1118 ) 1119 && self.infcx.can_eq(self.param_env, ty, self_ty) 1120 { 1121 err.eager_subdiagnostic( 1122 &self.infcx.tcx.sess.parse_sess.span_diagnostic, 1123 CaptureReasonSuggest::FreshReborrow { 1124 span: fn_call_span.shrink_to_lo(), 1125 }); 1126 } 1127 if let Some(clone_trait) = tcx.lang_items().clone_trait() 1128 && let trait_ref = ty::TraitRef::new(tcx, clone_trait, [ty]) 1129 && let o = Obligation::new( 1130 tcx, 1131 ObligationCause::dummy(), 1132 self.param_env, 1133 ty::Binder::dummy(trait_ref), 1134 ) 1135 && self.infcx.predicate_must_hold_modulo_regions(&o) 1136 { 1137 err.span_suggestion_verbose( 1138 fn_call_span.shrink_to_lo(), 1139 "you can `clone` the value and consume it, but this might not be \ 1140 your desired behavior", 1141 "clone().".to_string(), 1142 Applicability::MaybeIncorrect, 1143 ); 1144 } 1145 } 1146 // Avoid pointing to the same function in multiple different 1147 // error messages. 1148 if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) { 1149 self.explain_iterator_advancement_in_for_loop_if_applicable( 1150 err, 1151 span, 1152 &move_spans, 1153 ); 1154 1155 let func = tcx.def_path_str(method_did); 1156 err.subdiagnostic(CaptureReasonNote::FuncTakeSelf { 1157 func, 1158 place_name, 1159 span: self_arg.span, 1160 }); 1161 } 1162 let parent_did = tcx.parent(method_did); 1163 let parent_self_ty = 1164 matches!(tcx.def_kind(parent_did), rustc_hir::def::DefKind::Impl { .. }) 1165 .then_some(parent_did) 1166 .and_then(|did| match tcx.type_of(did).subst_identity().kind() { 1167 ty::Adt(def, ..) => Some(def.did()), 1168 _ => None, 1169 }); 1170 let is_option_or_result = parent_self_ty.is_some_and(|def_id| { 1171 matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result)) 1172 }); 1173 if is_option_or_result && maybe_reinitialized_locations_is_empty { 1174 err.subdiagnostic(CaptureReasonLabel::BorrowContent { var_span }); 1175 } 1176 } 1177 // Other desugarings takes &self, which cannot cause a move 1178 _ => {} 1179 } 1180 } else { 1181 if move_span != span || is_loop_message { 1182 err.subdiagnostic(CaptureReasonLabel::MovedHere { 1183 move_span, 1184 is_partial, 1185 is_move_msg, 1186 is_loop_message, 1187 }); 1188 } 1189 // If the move error occurs due to a loop, don't show 1190 // another message for the same span 1191 if !is_loop_message { 1192 move_spans.var_subdiag(None, err, None, |kind, var_span| match kind { 1193 Some(_) => CaptureVarCause::PartialMoveUseInGenerator { var_span, is_partial }, 1194 None => CaptureVarCause::PartialMoveUseInClosure { var_span, is_partial }, 1195 }) 1196 } 1197 } 1198 } 1199 } 1200