1 //! Borrow checker diagnostics.
3 use itertools::Itertools;
4 use rustc_const_eval::util::{call_kind, CallDesugaringKind};
5 use rustc_errors::{Applicability, Diagnostic};
7 use rustc_hir::def::{CtorKind, Namespace};
8 use rustc_hir::GeneratorKind;
9 use rustc_infer::infer::TyCtxtInferExt;
10 use rustc_middle::mir::tcx::PlaceTy;
11 use rustc_middle::mir::{
12 AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
13 Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
15 use rustc_middle::ty::print::Print;
16 use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
17 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
18 use rustc_span::def_id::LocalDefId;
19 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
20 use rustc_target::abi::VariantIdx;
21 use rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions;
23 use super::borrow_set::BorrowData;
24 use super::MirBorrowckCtxt;
26 mod find_all_local_uses;
28 mod outlives_suggestion;
32 mod bound_region_errors;
36 mod mutability_errors;
39 pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
40 pub(crate) use mutability_errors::AccessKind;
41 pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
42 pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
43 pub(crate) use region_name::{RegionName, RegionNameSource};
44 pub(crate) use rustc_const_eval::util::CallKind;
46 pub(super) struct DescribePlaceOpt {
47 pub including_downcast: bool,
49 /// Enable/Disable tuple fields.
50 /// For example `x` tuple. if it's `true` `x.0`. Otherwise `x`
51 pub including_tuple_field: bool,
54 pub(super) struct IncludingTupleField(pub(super) bool);
56 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
57 /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
58 /// is moved after being invoked.
61 /// note: closure cannot be invoked more than once because it moves the variable `dict` out of
63 /// --> $DIR/issue-42065.rs:16:29
65 /// LL | for (key, value) in dict {
68 pub(super) fn add_moved_or_invoked_closure_note(
71 place: PlaceRef<'tcx>,
72 diag: &mut Diagnostic,
74 debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
75 let mut target = place.local_or_deref_local();
76 for stmt in &self.body[location.block].statements[location.statement_index..] {
77 debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
78 if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind {
79 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
81 Operand::Copy(place) | Operand::Move(place)
82 if target == place.local_or_deref_local() =>
84 target = into.local_or_deref_local()
91 // Check if we are attempting to call a closure after it has been invoked.
92 let terminator = self.body[location.block].terminator();
93 debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator);
94 if let TerminatorKind::Call {
95 func: Operand::Constant(box Constant { literal, .. }),
100 if let ty::FnDef(id, _) = *literal.ty().kind() {
101 debug!("add_moved_or_invoked_closure_note: id={:?}", id);
102 if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() {
103 let closure = match args.first() {
104 Some(Operand::Copy(place) | Operand::Move(place))
105 if target == place.local_or_deref_local() =>
107 place.local_or_deref_local().unwrap()
112 debug!("add_moved_or_invoked_closure_note: closure={:?}", closure);
113 if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
114 let did = did.expect_local();
115 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
117 if let Some((span, hir_place)) =
118 self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
123 "closure cannot be invoked more than once because it moves the \
124 variable `{}` out of its environment",
125 ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
135 // Check if we are just moving a closure after it has been invoked.
136 if let Some(target) = target {
137 if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
138 let did = did.expect_local();
139 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
141 if let Some((span, hir_place)) =
142 self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
147 "closure cannot be moved more than once as it is not `Copy` due to \
148 moving the variable `{}` out of its environment",
149 ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
159 /// End-user visible description of `place` if one can be found.
160 /// If the place is a temporary for instance, `"value"` will be returned.
161 pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
162 match self.describe_place(place_ref) {
164 // Surround descr with `backticks`.
166 descr.insert(0, '`');
170 None => "value".to_string(),
174 /// End-user visible description of `place` if one can be found.
175 /// If the place is a temporary for instance, `None` will be returned.
176 pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> {
177 self.describe_place_with_options(
179 DescribePlaceOpt { including_downcast: false, including_tuple_field: true },
183 /// End-user visible description of `place` if one can be found. If the place is a temporary
184 /// for instance, `None` will be returned.
185 /// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is
186 /// `Downcast` and `IncludingDowncast` is true
187 pub(super) fn describe_place_with_options(
189 place: PlaceRef<'tcx>,
190 opt: DescribePlaceOpt,
191 ) -> Option<String> {
192 let local = place.local;
193 let mut autoderef_index = None;
194 let mut buf = String::new();
195 let mut ok = self.append_local_to_string(local, &mut buf);
197 for (index, elem) in place.projection.into_iter().enumerate() {
199 ProjectionElem::Deref => {
201 if self.body.local_decls[local].is_ref_for_guard() {
204 if let Some(box LocalInfo::StaticRef { def_id, .. }) =
205 &self.body.local_decls[local].local_info
207 buf.push_str(self.infcx.tcx.item_name(*def_id).as_str());
212 if let Some(field) = self.is_upvar_field_projection(PlaceRef {
214 projection: place.projection.split_at(index + 1).0,
216 let var_index = field.index();
217 buf = self.upvars[var_index].place.to_string(self.infcx.tcx);
219 if !self.upvars[var_index].by_ref {
223 if autoderef_index.is_none() {
225 match place.projection.into_iter().rev().find_position(|elem| {
228 ProjectionElem::Deref | ProjectionElem::Downcast(..)
231 Some((index, _)) => Some(place.projection.len() - index),
235 if index >= autoderef_index.unwrap() {
240 ProjectionElem::Downcast(..) if opt.including_downcast => return None,
241 ProjectionElem::Downcast(..) => (),
242 ProjectionElem::OpaqueCast(..) => (),
243 ProjectionElem::Field(field, _ty) => {
244 // FIXME(project-rfc_2229#36): print capture precisely here.
245 if let Some(field) = self.is_upvar_field_projection(PlaceRef {
247 projection: place.projection.split_at(index + 1).0,
249 buf = self.upvars[field.index()].place.to_string(self.infcx.tcx);
252 let field_name = self.describe_field(
253 PlaceRef { local, projection: place.projection.split_at(index).0 },
255 IncludingTupleField(opt.including_tuple_field),
257 if let Some(field_name_str) = field_name {
259 buf.push_str(&field_name_str);
263 ProjectionElem::Index(index) => {
265 if self.append_local_to_string(*index, &mut buf).is_err() {
270 ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
271 // Since it isn't possible to borrow an element on a particular index and
272 // then use another while the borrow is held, don't output indices details
273 // to avoid confusing the end-user
274 buf.push_str("[..]");
281 fn describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol> {
282 for elem in place.projection.into_iter() {
284 ProjectionElem::Downcast(Some(name), _) => {
293 /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have
294 /// a name, or its name was generated by the compiler, then `Err` is returned
295 fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> {
296 let decl = &self.body.local_decls[local];
297 match self.local_names[local] {
298 Some(name) if !decl.from_compiler_desugaring() => {
299 buf.push_str(name.as_str());
306 /// End-user visible description of the `field`nth field of `base`
309 place: PlaceRef<'tcx>,
311 including_tuple_field: IncludingTupleField,
312 ) -> Option<String> {
313 let place_ty = match place {
314 PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty),
315 PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
316 ProjectionElem::Deref
317 | ProjectionElem::Index(..)
318 | ProjectionElem::ConstantIndex { .. }
319 | ProjectionElem::Subslice { .. } => {
320 PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
322 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
323 ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
324 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
327 self.describe_field_from_ty(
330 place_ty.variant_index,
331 including_tuple_field,
335 /// End-user visible description of the `field_index`nth field of `ty`
336 fn describe_field_from_ty(
340 variant_index: Option<VariantIdx>,
341 including_tuple_field: IncludingTupleField,
342 ) -> Option<String> {
344 // If the type is a box, the field is described from the boxed type
345 self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field)
349 let variant = if let Some(idx) = variant_index {
350 assert!(def.is_enum());
353 def.non_enum_variant()
355 if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) {
358 Some(variant.fields[field.index()].name.to_string())
360 ty::Tuple(_) => Some(field.index().to_string()),
361 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
362 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
364 ty::Array(ty, _) | ty::Slice(ty) => {
365 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
367 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
368 // We won't be borrowck'ing here if the closure came from another crate,
369 // so it's safe to call `expect_local`.
371 // We know the field exists so it's safe to call operator[] and `unwrap` here.
372 let def_id = def_id.expect_local();
377 .closure_min_captures_flattened(def_id)
380 .get_root_variable();
382 Some(self.infcx.tcx.hir().name(var_id).to_string())
385 // Might need a revision when the fields in trait RFC is implemented
386 // (https://github.com/rust-lang/rfcs/pull/1546)
387 bug!("End-user description not implemented for field access on `{:?}`", ty);
393 /// Add a note that a type does not implement `Copy`
394 pub(super) fn note_type_does_not_implement_copy(
396 err: &mut Diagnostic,
402 let message = format!(
403 "{}move occurs because {} has type `{}`, which does not implement the `Copy` trait",
404 move_prefix, place_desc, ty,
406 if let Some(span) = span {
407 err.span_label(span, message);
413 pub(super) fn borrowed_content_source(
415 deref_base: PlaceRef<'tcx>,
416 ) -> BorrowedContentSource<'tcx> {
417 let tcx = self.infcx.tcx;
419 // Look up the provided place and work out the move path index for it,
420 // we'll use this to check whether it was originally from an overloaded
422 match self.move_data.rev_lookup.find(deref_base) {
423 LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
424 debug!("borrowed_content_source: mpi={:?}", mpi);
426 for i in &self.move_data.init_path_map[mpi] {
427 let init = &self.move_data.inits[*i];
428 debug!("borrowed_content_source: init={:?}", init);
429 // We're only interested in statements that initialized a value, not the
430 // initializations from arguments.
431 let InitLocation::Statement(loc) = init.location else { continue };
433 let bbd = &self.body[loc.block];
434 let is_terminator = bbd.statements.len() == loc.statement_index;
436 "borrowed_content_source: loc={:?} is_terminator={:?}",
441 } else if let Some(Terminator {
442 kind: TerminatorKind::Call { func, from_hir_call: false, .. },
446 if let Some(source) =
447 BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
454 // Base is a `static` so won't be from an overloaded operator
458 // If we didn't find an overloaded deref or index, then assume it's a
459 // built in deref and check the type of the base.
460 let base_ty = deref_base.ty(self.body, tcx).ty;
461 if base_ty.is_unsafe_ptr() {
462 BorrowedContentSource::DerefRawPointer
463 } else if base_ty.is_mutable_ptr() {
464 BorrowedContentSource::DerefMutableRef
466 BorrowedContentSource::DerefSharedRef
470 /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
471 /// name where required.
472 pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
473 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
475 // We need to add synthesized lifetimes where appropriate. We do
476 // this by hooking into the pretty printer and telling it to label the
477 // lifetimes without names with the value `'0`.
478 if let ty::Ref(region, ..) = ty.kind() {
480 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
481 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
482 printer.region_highlight_mode.highlighting_bound_region(br, counter)
488 ty.print(printer).unwrap().into_buffer()
491 /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
492 /// synthesized lifetime name where required.
493 pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
494 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
496 let region = if let ty::Ref(region, ..) = ty.kind() {
498 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
499 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
500 printer.region_highlight_mode.highlighting_bound_region(br, counter)
506 bug!("ty for annotation of borrow region is not a reference");
509 region.print(printer).unwrap().into_buffer()
513 /// The span(s) associated to a use of a place.
514 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
515 pub(super) enum UseSpans<'tcx> {
516 /// The access is caused by capturing a variable for a closure.
518 /// This is true if the captured variable was from a generator.
519 generator_kind: Option<GeneratorKind>,
520 /// The span of the args of the closure, including the `move` keyword if
523 /// The span of the use resulting in capture kind
524 /// Check `ty::CaptureInfo` for more details
525 capture_kind_span: Span,
526 /// The span of the use resulting in the captured path
527 /// Check `ty::CaptureInfo` for more details
530 /// The access is caused by using a variable as the receiver of a method
531 /// that takes 'self'
533 /// The span of the variable being moved
535 /// The span of the method call on the variable
537 /// The definition span of the method being called
539 kind: CallKind<'tcx>,
541 /// This access is caused by a `match` or `if let` pattern.
543 /// This access has a single span associated to it: common case.
548 pub(super) fn args_or_use(self) -> Span {
550 UseSpans::ClosureUse { args_span: span, .. }
551 | UseSpans::PatUse(span)
552 | UseSpans::OtherUse(span) => span,
553 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
556 UseSpans::FnSelfUse { var_span, .. } => var_span,
560 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
561 pub(super) fn var_or_use_path_span(self) -> Span {
563 UseSpans::ClosureUse { path_span: span, .. }
564 | UseSpans::PatUse(span)
565 | UseSpans::OtherUse(span) => span,
566 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
569 UseSpans::FnSelfUse { var_span, .. } => var_span,
573 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
574 pub(super) fn var_or_use(self) -> Span {
576 UseSpans::ClosureUse { capture_kind_span: span, .. }
577 | UseSpans::PatUse(span)
578 | UseSpans::OtherUse(span) => span,
579 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
582 UseSpans::FnSelfUse { var_span, .. } => var_span,
586 pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
588 UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
593 /// Add a span label to the arguments of the closure, if it exists.
594 pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into<String>) {
595 if let UseSpans::ClosureUse { args_span, .. } = self {
596 err.span_label(args_span, message);
600 /// Add a span label to the use of the captured variable, if it exists.
601 /// only adds label to the `path_span`
602 pub(super) fn var_path_only_subdiag(
604 err: &mut Diagnostic,
605 action: crate::InitializationRequiringAction,
607 use crate::session_diagnostics::CaptureVarPathUseCause::*;
608 use crate::InitializationRequiringAction::*;
609 if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self {
610 match generator_kind {
612 err.subdiagnostic(match action {
613 Borrow => BorrowInGenerator { path_span },
614 MatchOn | Use => UseInGenerator { path_span },
615 Assignment => AssignInGenerator { path_span },
616 PartialAssignment => AssignPartInGenerator { path_span },
620 err.subdiagnostic(match action {
621 Borrow => BorrowInClosure { path_span },
622 MatchOn | Use => UseInClosure { path_span },
623 Assignment => AssignInClosure { path_span },
624 PartialAssignment => AssignPartInClosure { path_span },
631 /// Add a span label to the use of the captured variable, if it exists.
632 pub(super) fn var_span_label(
634 err: &mut Diagnostic,
635 message: impl Into<String>,
636 kind_desc: impl Into<String>,
638 if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
639 if capture_kind_span == path_span {
640 err.span_label(capture_kind_span, message);
642 let capture_kind_label =
643 format!("capture is {} because of use here", kind_desc.into());
644 let path_label = message;
645 err.span_label(capture_kind_span, capture_kind_label);
646 err.span_label(path_span, path_label);
651 /// Add a subdiagnostic to the use of the captured variable, if it exists.
652 pub(super) fn var_subdiag(
654 err: &mut Diagnostic,
655 kind: Option<rustc_middle::mir::BorrowKind>,
656 f: impl Fn(Option<GeneratorKind>, Span) -> crate::session_diagnostics::CaptureVarCause,
658 use crate::session_diagnostics::CaptureVarKind::*;
659 if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self {
660 if capture_kind_span != path_span {
661 err.subdiagnostic(match kind {
662 Some(kd) => match kd {
663 rustc_middle::mir::BorrowKind::Shared
664 | rustc_middle::mir::BorrowKind::Shallow
665 | rustc_middle::mir::BorrowKind::Unique => {
666 Immute { kind_span: capture_kind_span }
669 rustc_middle::mir::BorrowKind::Mut { .. } => {
670 Mut { kind_span: capture_kind_span }
673 None => Move { kind_span: capture_kind_span },
676 err.subdiagnostic(f(generator_kind, path_span));
680 /// Returns `false` if this place is not used in a closure.
681 pub(super) fn for_closure(&self) -> bool {
683 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
688 /// Returns `false` if this place is not used in a generator.
689 pub(super) fn for_generator(&self) -> bool {
691 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
696 /// Describe the span associated with a use of a place.
697 pub(super) fn describe(&self) -> &str {
699 UseSpans::ClosureUse { generator_kind, .. } => {
700 if generator_kind.is_some() {
710 pub(super) fn or_else<F>(self, if_other: F) -> Self
715 closure @ UseSpans::ClosureUse { .. } => closure,
716 UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
717 fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
722 pub(super) enum BorrowedContentSource<'tcx> {
726 OverloadedDeref(Ty<'tcx>),
727 OverloadedIndex(Ty<'tcx>),
730 impl<'tcx> BorrowedContentSource<'tcx> {
731 pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
733 BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
734 BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
735 BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
736 BorrowedContentSource::OverloadedDeref(ty) => ty
738 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
739 name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
742 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
743 BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
747 pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
749 BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
750 BorrowedContentSource::DerefSharedRef => Some("shared reference"),
751 BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
752 // Overloaded deref and index operators should be evaluated into a
753 // temporary. So we don't need a description here.
754 BorrowedContentSource::OverloadedDeref(_)
755 | BorrowedContentSource::OverloadedIndex(_) => None,
759 pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
761 BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
762 BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
763 BorrowedContentSource::DerefMutableRef => {
764 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
766 BorrowedContentSource::OverloadedDeref(ty) => ty
768 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
769 name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
772 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
773 BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
777 fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
779 ty::FnDef(def_id, substs) => {
780 let trait_id = tcx.trait_of_item(def_id)?;
782 let lang_items = tcx.lang_items();
783 if Some(trait_id) == lang_items.deref_trait()
784 || Some(trait_id) == lang_items.deref_mut_trait()
786 Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
787 } else if Some(trait_id) == lang_items.index_trait()
788 || Some(trait_id) == lang_items.index_mut_trait()
790 Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
800 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
801 /// Finds the spans associated to a move or copy of move_place at location.
802 pub(super) fn move_spans(
804 moved_place: PlaceRef<'tcx>, // Could also be an upvar.
806 ) -> UseSpans<'tcx> {
807 use self::UseSpans::*;
809 let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
810 return OtherUse(self.body.source_info(location).span);
813 debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
814 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind
815 && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind
817 debug!("move_spans: def_id={:?} places={:?}", def_id, places);
818 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
819 self.closure_span(def_id, moved_place, places)
830 // StatementKind::FakeRead only contains a def_id if they are introduced as a result
831 // of pattern matching within a closure.
832 if let StatementKind::FakeRead(box (cause, place)) = stmt.kind {
834 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
835 | FakeReadCause::ForLet(Some(closure_def_id)) => {
836 debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
837 let places = &[Operand::Move(place)];
838 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
839 self.closure_span(closure_def_id, moved_place, places)
854 if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
855 PatUse(stmt.source_info.span)
857 OtherUse(stmt.source_info.span)
860 // We are trying to find MIR of the form:
862 // _temp = _moved_val;
864 // FnSelfCall(_temp, ...)
867 // where `_moved_val` is the place we generated the move error for,
868 // `_temp` is some other local, and `FnSelfCall` is a function
869 // that has a `self` parameter.
871 let target_temp = match stmt.kind {
872 StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
873 temp.as_local().unwrap()
875 _ => return normal_ret,
878 debug!("move_spans: target_temp = {:?}", target_temp);
880 if let Some(Terminator {
881 kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
882 }) = &self.body[location.block].terminator
884 let Some((method_did, method_substs)) =
885 rustc_const_eval::util::find_self_call(
895 let kind = call_kind(
902 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
906 var_span: stmt.source_info.span,
907 fn_call_span: *fn_span,
908 fn_span: self.infcx.tcx.def_span(method_did),
915 /// Finds the span of arguments of a closure (within `maybe_closure_span`)
916 /// and its usage of the local assigned at `location`.
917 /// This is done by searching in statements succeeding `location`
918 /// and originating from `maybe_closure_span`.
919 pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
920 use self::UseSpans::*;
921 debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
923 let target = match self.body[location.block].statements.get(location.statement_index) {
924 Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => {
925 if let Some(local) = place.as_local() {
928 return OtherUse(use_span);
931 _ => return OtherUse(use_span),
934 if self.body.local_kind(target) != LocalKind::Temp {
935 // operands are always temporaries.
936 return OtherUse(use_span);
939 for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
940 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind {
941 let (&def_id, is_generator) = match kind {
942 box AggregateKind::Closure(def_id, _) => (def_id, false),
943 box AggregateKind::Generator(def_id, _, _) => (def_id, true),
948 "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
949 def_id, is_generator, places
951 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
952 self.closure_span(def_id, Place::from(target).as_ref(), places)
954 return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
956 return OtherUse(use_span);
960 if use_span != stmt.source_info.span {
968 /// Finds the spans of a captured place within a closure or generator.
969 /// The first span is the location of the use resulting in the capture kind of the capture
970 /// The second span is the location the use resulting in the captured path of the capture
974 target_place: PlaceRef<'tcx>,
975 places: &[Operand<'tcx>],
976 ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
978 "closure_span: def_id={:?} target_place={:?} places={:?}",
979 def_id, target_place, places
981 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id);
982 let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
983 debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
984 if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr {
985 for (captured_place, place) in
986 self.infcx.tcx.typeck(def_id).closure_min_captures_flattened(def_id).zip(places)
989 Operand::Copy(place) | Operand::Move(place)
990 if target_place == place.as_ref() =>
992 debug!("closure_span: found captured local {:?}", place);
993 let body = self.infcx.tcx.hir().body(body);
994 let generator_kind = body.generator_kind();
999 captured_place.get_capture_kind_span(self.infcx.tcx),
1000 captured_place.get_path_span(self.infcx.tcx),
1010 /// Helper to retrieve span(s) of given borrow from the current MIR
1012 pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1013 let span = self.body.source_info(borrow.reserve_location).span;
1014 self.borrow_spans(span, borrow.reserve_location)
1017 fn explain_captures(
1019 err: &mut Diagnostic,
1022 move_spans: UseSpans<'tcx>,
1023 moved_place: Place<'tcx>,
1024 partially_str: &str,
1028 maybe_reinitialized_locations_is_empty: bool,
1030 if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
1031 let place_name = self
1032 .describe_place(moved_place.as_ref())
1033 .map(|n| format!("`{}`", n))
1034 .unwrap_or_else(|| "value".to_owned());
1036 CallKind::FnCall { fn_trait_id, .. }
1037 if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() =>
1042 "{} {}moved due to this call{}",
1043 place_name, partially_str, loop_message
1048 "this value implements `FnOnce`, which causes it to be moved when called",
1051 CallKind::Operator { self_arg, .. } => {
1052 let self_arg = self_arg.unwrap();
1056 "{} {}moved due to usage in operator{}",
1057 place_name, partially_str, loop_message
1060 if self.fn_self_span_reported.insert(fn_span) {
1063 "calling this operator moves the left-hand side",
1067 CallKind::Normal { self_arg, desugaring, method_did } => {
1068 let self_arg = self_arg.unwrap();
1069 if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
1070 let ty = moved_place.ty(self.body, self.infcx.tcx).ty;
1071 let suggest = match self.infcx.tcx.get_diagnostic_item(sym::IntoIterator) {
1073 let infcx = self.infcx.tcx.infer_ctxt().build();
1074 type_known_to_meet_bound_modulo_regions(
1077 infcx.tcx.mk_imm_ref(
1078 infcx.tcx.lifetimes.re_erased,
1079 infcx.tcx.erase_regions(ty),
1088 err.span_suggestion_verbose(
1089 move_span.shrink_to_lo(),
1091 "consider iterating over a slice of the `{}`'s content to \
1092 avoid moving into the `for` loop",
1096 Applicability::MaybeIncorrect,
1103 "{} {}moved due to this implicit call to `.into_iter()`{}",
1104 place_name, partially_str, loop_message
1107 // If the moved place was a `&mut` ref, then we can
1108 // suggest to reborrow it where it was moved, so it
1109 // will still be valid by the time we get to the usage.
1110 if let ty::Ref(_, _, hir::Mutability::Mut) =
1111 moved_place.ty(self.body, self.infcx.tcx).ty.kind()
1113 // If we are in a loop this will be suggested later.
1115 err.span_suggestion_verbose(
1116 move_span.shrink_to_lo(),
1118 "consider creating a fresh reborrow of {} here",
1119 self.describe_place(moved_place.as_ref())
1120 .map(|n| format!("`{}`", n))
1121 .unwrap_or_else(|| "the mutable reference".to_string()),
1124 Applicability::MachineApplicable,
1132 "{} {}moved due to this method call{}",
1133 place_name, partially_str, loop_message
1137 let tcx = self.infcx.tcx;
1138 // Avoid pointing to the same function in multiple different
1140 if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
1141 let func = tcx.def_path_str(method_did);
1144 &format!("`{func}` takes ownership of the receiver `self`, which moves {place_name}")
1147 let parent_did = tcx.parent(method_did);
1148 let parent_self_ty = (tcx.def_kind(parent_did)
1149 == rustc_hir::def::DefKind::Impl)
1150 .then_some(parent_did)
1151 .and_then(|did| match tcx.type_of(did).kind() {
1152 ty::Adt(def, ..) => Some(def.did()),
1155 let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
1156 matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
1158 if is_option_or_result && maybe_reinitialized_locations_is_empty {
1161 "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
1165 // Other desugarings takes &self, which cannot cause a move
1169 if move_span != span || !loop_message.is_empty() {
1172 format!("value {}moved{} here{}", partially_str, move_msg, loop_message),
1175 // If the move error occurs due to a loop, don't show
1176 // another message for the same span
1177 if loop_message.is_empty() {
1178 move_spans.var_span_label(
1180 format!("variable {}moved due to use{}", partially_str, move_spans.describe()),