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::{LateBoundRegionConversionTime, 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::query::evaluate_obligation::InferCtxtExt;
22 use rustc_trait_selection::traits::{
23 type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause,
26 use super::borrow_set::BorrowData;
27 use super::MirBorrowckCtxt;
29 mod find_all_local_uses;
31 mod outlives_suggestion;
35 mod bound_region_errors;
39 mod mutability_errors;
42 pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
43 pub(crate) use mutability_errors::AccessKind;
44 pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
45 pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
46 pub(crate) use region_name::{RegionName, RegionNameSource};
47 pub(crate) use rustc_const_eval::util::CallKind;
49 pub(super) struct DescribePlaceOpt {
50 pub including_downcast: bool,
52 /// Enable/Disable tuple fields.
53 /// For example `x` tuple. if it's `true` `x.0`. Otherwise `x`
54 pub including_tuple_field: bool,
57 pub(super) struct IncludingTupleField(pub(super) bool);
59 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
60 /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
61 /// is moved after being invoked.
64 /// note: closure cannot be invoked more than once because it moves the variable `dict` out of
66 /// --> $DIR/issue-42065.rs:16:29
68 /// LL | for (key, value) in dict {
71 pub(super) fn add_moved_or_invoked_closure_note(
74 place: PlaceRef<'tcx>,
75 diag: &mut Diagnostic,
77 debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
78 let mut target = place.local_or_deref_local();
79 for stmt in &self.body[location.block].statements[location.statement_index..] {
80 debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target);
81 if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind {
82 debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from);
84 Operand::Copy(place) | Operand::Move(place)
85 if target == place.local_or_deref_local() =>
87 target = into.local_or_deref_local()
94 // Check if we are attempting to call a closure after it has been invoked.
95 let terminator = self.body[location.block].terminator();
96 debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator);
97 if let TerminatorKind::Call {
98 func: Operand::Constant(box Constant { literal, .. }),
103 if let ty::FnDef(id, _) = *literal.ty().kind() {
104 debug!("add_moved_or_invoked_closure_note: id={:?}", id);
105 if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() {
106 let closure = match args.first() {
107 Some(Operand::Copy(place) | Operand::Move(place))
108 if target == place.local_or_deref_local() =>
110 place.local_or_deref_local().unwrap()
115 debug!("add_moved_or_invoked_closure_note: closure={:?}", closure);
116 if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
117 let did = did.expect_local();
118 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
120 if let Some((span, hir_place)) =
121 self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
126 "closure cannot be invoked more than once because it moves the \
127 variable `{}` out of its environment",
128 ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
138 // Check if we are just moving a closure after it has been invoked.
139 if let Some(target) = target {
140 if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
141 let did = did.expect_local();
142 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did);
144 if let Some((span, hir_place)) =
145 self.infcx.tcx.typeck(did).closure_kind_origins().get(hir_id)
150 "closure cannot be moved more than once as it is not `Copy` due to \
151 moving the variable `{}` out of its environment",
152 ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
162 /// End-user visible description of `place` if one can be found.
163 /// If the place is a temporary for instance, `"value"` will be returned.
164 pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String {
165 match self.describe_place(place_ref) {
167 // Surround descr with `backticks`.
169 descr.insert(0, '`');
173 None => "value".to_string(),
177 /// End-user visible description of `place` if one can be found.
178 /// If the place is a temporary for instance, `None` will be returned.
179 pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option<String> {
180 self.describe_place_with_options(
182 DescribePlaceOpt { including_downcast: false, including_tuple_field: true },
186 /// End-user visible description of `place` if one can be found. If the place is a temporary
187 /// for instance, `None` will be returned.
188 /// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is
189 /// `Downcast` and `IncludingDowncast` is true
190 pub(super) fn describe_place_with_options(
192 place: PlaceRef<'tcx>,
193 opt: DescribePlaceOpt,
194 ) -> Option<String> {
195 let local = place.local;
196 let mut autoderef_index = None;
197 let mut buf = String::new();
198 let mut ok = self.append_local_to_string(local, &mut buf);
200 for (index, elem) in place.projection.into_iter().enumerate() {
202 ProjectionElem::Deref => {
204 if self.body.local_decls[local].is_ref_for_guard() {
207 if let Some(box LocalInfo::StaticRef { def_id, .. }) =
208 &self.body.local_decls[local].local_info
210 buf.push_str(self.infcx.tcx.item_name(*def_id).as_str());
215 if let Some(field) = self.is_upvar_field_projection(PlaceRef {
217 projection: place.projection.split_at(index + 1).0,
219 let var_index = field.index();
220 buf = self.upvars[var_index].place.to_string(self.infcx.tcx);
222 if !self.upvars[var_index].by_ref {
226 if autoderef_index.is_none() {
228 match place.projection.into_iter().rev().find_position(|elem| {
231 ProjectionElem::Deref | ProjectionElem::Downcast(..)
234 Some((index, _)) => Some(place.projection.len() - index),
238 if index >= autoderef_index.unwrap() {
243 ProjectionElem::Downcast(..) if opt.including_downcast => return None,
244 ProjectionElem::Downcast(..) => (),
245 ProjectionElem::OpaqueCast(..) => (),
246 ProjectionElem::Field(field, _ty) => {
247 // FIXME(project-rfc_2229#36): print capture precisely here.
248 if let Some(field) = self.is_upvar_field_projection(PlaceRef {
250 projection: place.projection.split_at(index + 1).0,
252 buf = self.upvars[field.index()].place.to_string(self.infcx.tcx);
255 let field_name = self.describe_field(
256 PlaceRef { local, projection: place.projection.split_at(index).0 },
258 IncludingTupleField(opt.including_tuple_field),
260 if let Some(field_name_str) = field_name {
262 buf.push_str(&field_name_str);
266 ProjectionElem::Index(index) => {
268 if self.append_local_to_string(*index, &mut buf).is_err() {
273 ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
274 // Since it isn't possible to borrow an element on a particular index and
275 // then use another while the borrow is held, don't output indices details
276 // to avoid confusing the end-user
277 buf.push_str("[..]");
284 fn describe_name(&self, place: PlaceRef<'tcx>) -> Option<Symbol> {
285 for elem in place.projection.into_iter() {
287 ProjectionElem::Downcast(Some(name), _) => {
296 /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have
297 /// a name, or its name was generated by the compiler, then `Err` is returned
298 fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> {
299 let decl = &self.body.local_decls[local];
300 match self.local_names[local] {
301 Some(name) if !decl.from_compiler_desugaring() => {
302 buf.push_str(name.as_str());
309 /// End-user visible description of the `field`nth field of `base`
312 place: PlaceRef<'tcx>,
314 including_tuple_field: IncludingTupleField,
315 ) -> Option<String> {
316 let place_ty = match place {
317 PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty),
318 PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
319 ProjectionElem::Deref
320 | ProjectionElem::Index(..)
321 | ProjectionElem::ConstantIndex { .. }
322 | ProjectionElem::Subslice { .. } => {
323 PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
325 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
326 ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
327 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
330 self.describe_field_from_ty(
333 place_ty.variant_index,
334 including_tuple_field,
338 /// End-user visible description of the `field_index`nth field of `ty`
339 fn describe_field_from_ty(
343 variant_index: Option<VariantIdx>,
344 including_tuple_field: IncludingTupleField,
345 ) -> Option<String> {
347 // If the type is a box, the field is described from the boxed type
348 self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field)
352 let variant = if let Some(idx) = variant_index {
353 assert!(def.is_enum());
356 def.non_enum_variant()
358 if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) {
361 Some(variant.fields[field.index()].name.to_string())
363 ty::Tuple(_) => Some(field.index().to_string()),
364 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
365 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
367 ty::Array(ty, _) | ty::Slice(ty) => {
368 self.describe_field_from_ty(ty, field, variant_index, including_tuple_field)
370 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
371 // We won't be borrowck'ing here if the closure came from another crate,
372 // so it's safe to call `expect_local`.
374 // We know the field exists so it's safe to call operator[] and `unwrap` here.
375 let def_id = def_id.expect_local();
380 .closure_min_captures_flattened(def_id)
383 .get_root_variable();
385 Some(self.infcx.tcx.hir().name(var_id).to_string())
388 // Might need a revision when the fields in trait RFC is implemented
389 // (https://github.com/rust-lang/rfcs/pull/1546)
390 bug!("End-user description not implemented for field access on `{:?}`", ty);
396 /// Add a note that a type does not implement `Copy`
397 pub(super) fn note_type_does_not_implement_copy(
399 err: &mut Diagnostic,
405 let message = format!(
406 "{}move occurs because {} has type `{}`, which does not implement the `Copy` trait",
407 move_prefix, place_desc, ty,
409 if let Some(span) = span {
410 err.span_label(span, message);
416 pub(super) fn borrowed_content_source(
418 deref_base: PlaceRef<'tcx>,
419 ) -> BorrowedContentSource<'tcx> {
420 let tcx = self.infcx.tcx;
422 // Look up the provided place and work out the move path index for it,
423 // we'll use this to check whether it was originally from an overloaded
425 match self.move_data.rev_lookup.find(deref_base) {
426 LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
427 debug!("borrowed_content_source: mpi={:?}", mpi);
429 for i in &self.move_data.init_path_map[mpi] {
430 let init = &self.move_data.inits[*i];
431 debug!("borrowed_content_source: init={:?}", init);
432 // We're only interested in statements that initialized a value, not the
433 // initializations from arguments.
434 let InitLocation::Statement(loc) = init.location else { continue };
436 let bbd = &self.body[loc.block];
437 let is_terminator = bbd.statements.len() == loc.statement_index;
439 "borrowed_content_source: loc={:?} is_terminator={:?}",
444 } else if let Some(Terminator {
445 kind: TerminatorKind::Call { func, from_hir_call: false, .. },
449 if let Some(source) =
450 BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
457 // Base is a `static` so won't be from an overloaded operator
461 // If we didn't find an overloaded deref or index, then assume it's a
462 // built in deref and check the type of the base.
463 let base_ty = deref_base.ty(self.body, tcx).ty;
464 if base_ty.is_unsafe_ptr() {
465 BorrowedContentSource::DerefRawPointer
466 } else if base_ty.is_mutable_ptr() {
467 BorrowedContentSource::DerefMutableRef
469 BorrowedContentSource::DerefSharedRef
473 /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
474 /// name where required.
475 pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
476 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
478 // We need to add synthesized lifetimes where appropriate. We do
479 // this by hooking into the pretty printer and telling it to label the
480 // lifetimes without names with the value `'0`.
481 if let ty::Ref(region, ..) = ty.kind() {
483 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
484 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
485 printer.region_highlight_mode.highlighting_bound_region(br, counter)
491 ty.print(printer).unwrap().into_buffer()
494 /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
495 /// synthesized lifetime name where required.
496 pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
497 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
499 let region = if let ty::Ref(region, ..) = ty.kind() {
501 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
502 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
503 printer.region_highlight_mode.highlighting_bound_region(br, counter)
509 bug!("ty for annotation of borrow region is not a reference");
512 region.print(printer).unwrap().into_buffer()
516 /// The span(s) associated to a use of a place.
517 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
518 pub(super) enum UseSpans<'tcx> {
519 /// The access is caused by capturing a variable for a closure.
521 /// This is true if the captured variable was from a generator.
522 generator_kind: Option<GeneratorKind>,
523 /// The span of the args of the closure, including the `move` keyword if
526 /// The span of the use resulting in capture kind
527 /// Check `ty::CaptureInfo` for more details
528 capture_kind_span: Span,
529 /// The span of the use resulting in the captured path
530 /// Check `ty::CaptureInfo` for more details
533 /// The access is caused by using a variable as the receiver of a method
534 /// that takes 'self'
536 /// The span of the variable being moved
538 /// The span of the method call on the variable
540 /// The definition span of the method being called
542 kind: CallKind<'tcx>,
544 /// This access is caused by a `match` or `if let` pattern.
546 /// This access has a single span associated to it: common case.
551 pub(super) fn args_or_use(self) -> Span {
553 UseSpans::ClosureUse { args_span: span, .. }
554 | UseSpans::PatUse(span)
555 | UseSpans::OtherUse(span) => span,
556 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
559 UseSpans::FnSelfUse { var_span, .. } => var_span,
563 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
564 pub(super) fn var_or_use_path_span(self) -> Span {
566 UseSpans::ClosureUse { path_span: span, .. }
567 | UseSpans::PatUse(span)
568 | UseSpans::OtherUse(span) => span,
569 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
572 UseSpans::FnSelfUse { var_span, .. } => var_span,
576 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
577 pub(super) fn var_or_use(self) -> Span {
579 UseSpans::ClosureUse { capture_kind_span: span, .. }
580 | UseSpans::PatUse(span)
581 | UseSpans::OtherUse(span) => span,
582 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
585 UseSpans::FnSelfUse { var_span, .. } => var_span,
589 pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
591 UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
596 /// Add a span label to the arguments of the closure, if it exists.
597 pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into<String>) {
598 if let UseSpans::ClosureUse { args_span, .. } = self {
599 err.span_label(args_span, message);
603 /// Add a span label to the use of the captured variable, if it exists.
604 /// only adds label to the `path_span`
605 pub(super) fn var_path_only_subdiag(
607 err: &mut Diagnostic,
608 action: crate::InitializationRequiringAction,
610 use crate::session_diagnostics::CaptureVarPathUseCause::*;
611 use crate::InitializationRequiringAction::*;
612 if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self {
613 match generator_kind {
615 err.subdiagnostic(match action {
616 Borrow => BorrowInGenerator { path_span },
617 MatchOn | Use => UseInGenerator { path_span },
618 Assignment => AssignInGenerator { path_span },
619 PartialAssignment => AssignPartInGenerator { path_span },
623 err.subdiagnostic(match action {
624 Borrow => BorrowInClosure { path_span },
625 MatchOn | Use => UseInClosure { path_span },
626 Assignment => AssignInClosure { path_span },
627 PartialAssignment => AssignPartInClosure { path_span },
634 /// Add a span label to the use of the captured variable, if it exists.
635 pub(super) fn var_span_label(
637 err: &mut Diagnostic,
638 message: impl Into<String>,
639 kind_desc: impl Into<String>,
641 if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
642 if capture_kind_span == path_span {
643 err.span_label(capture_kind_span, message);
645 let capture_kind_label =
646 format!("capture is {} because of use here", kind_desc.into());
647 let path_label = message;
648 err.span_label(capture_kind_span, capture_kind_label);
649 err.span_label(path_span, path_label);
654 /// Add a subdiagnostic to the use of the captured variable, if it exists.
655 pub(super) fn var_subdiag(
657 err: &mut Diagnostic,
658 kind: Option<rustc_middle::mir::BorrowKind>,
659 f: impl Fn(Option<GeneratorKind>, Span) -> crate::session_diagnostics::CaptureVarCause,
661 use crate::session_diagnostics::CaptureVarKind::*;
662 if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self {
663 if capture_kind_span != path_span {
664 err.subdiagnostic(match kind {
665 Some(kd) => match kd {
666 rustc_middle::mir::BorrowKind::Shared
667 | rustc_middle::mir::BorrowKind::Shallow
668 | rustc_middle::mir::BorrowKind::Unique => {
669 Immute { kind_span: capture_kind_span }
672 rustc_middle::mir::BorrowKind::Mut { .. } => {
673 Mut { kind_span: capture_kind_span }
676 None => Move { kind_span: capture_kind_span },
679 err.subdiagnostic(f(generator_kind, path_span));
683 /// Returns `false` if this place is not used in a closure.
684 pub(super) fn for_closure(&self) -> bool {
686 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
691 /// Returns `false` if this place is not used in a generator.
692 pub(super) fn for_generator(&self) -> bool {
694 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
699 /// Describe the span associated with a use of a place.
700 pub(super) fn describe(&self) -> &str {
702 UseSpans::ClosureUse { generator_kind, .. } => {
703 if generator_kind.is_some() {
713 pub(super) fn or_else<F>(self, if_other: F) -> Self
718 closure @ UseSpans::ClosureUse { .. } => closure,
719 UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
720 fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
725 pub(super) enum BorrowedContentSource<'tcx> {
729 OverloadedDeref(Ty<'tcx>),
730 OverloadedIndex(Ty<'tcx>),
733 impl<'tcx> BorrowedContentSource<'tcx> {
734 pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
736 BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
737 BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
738 BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
739 BorrowedContentSource::OverloadedDeref(ty) => ty
741 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
742 name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
745 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
746 BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
750 pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
752 BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
753 BorrowedContentSource::DerefSharedRef => Some("shared reference"),
754 BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
755 // Overloaded deref and index operators should be evaluated into a
756 // temporary. So we don't need a description here.
757 BorrowedContentSource::OverloadedDeref(_)
758 | BorrowedContentSource::OverloadedIndex(_) => None,
762 pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
764 BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
765 BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
766 BorrowedContentSource::DerefMutableRef => {
767 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
769 BorrowedContentSource::OverloadedDeref(ty) => ty
771 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
772 name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
775 .unwrap_or_else(|| format!("dereference of `{}`", ty)),
776 BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
780 fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
782 ty::FnDef(def_id, substs) => {
783 let trait_id = tcx.trait_of_item(def_id)?;
785 let lang_items = tcx.lang_items();
786 if Some(trait_id) == lang_items.deref_trait()
787 || Some(trait_id) == lang_items.deref_mut_trait()
789 Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
790 } else if Some(trait_id) == lang_items.index_trait()
791 || Some(trait_id) == lang_items.index_mut_trait()
793 Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
803 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
804 /// Finds the spans associated to a move or copy of move_place at location.
805 pub(super) fn move_spans(
807 moved_place: PlaceRef<'tcx>, // Could also be an upvar.
809 ) -> UseSpans<'tcx> {
810 use self::UseSpans::*;
812 let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
813 return OtherUse(self.body.source_info(location).span);
816 debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
817 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind
818 && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind
820 debug!("move_spans: def_id={:?} places={:?}", def_id, places);
821 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
822 self.closure_span(def_id, moved_place, places)
833 // StatementKind::FakeRead only contains a def_id if they are introduced as a result
834 // of pattern matching within a closure.
835 if let StatementKind::FakeRead(box (cause, place)) = stmt.kind {
837 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
838 | FakeReadCause::ForLet(Some(closure_def_id)) => {
839 debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
840 let places = &[Operand::Move(place)];
841 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
842 self.closure_span(closure_def_id, moved_place, places)
857 if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
858 PatUse(stmt.source_info.span)
860 OtherUse(stmt.source_info.span)
863 // We are trying to find MIR of the form:
865 // _temp = _moved_val;
867 // FnSelfCall(_temp, ...)
870 // where `_moved_val` is the place we generated the move error for,
871 // `_temp` is some other local, and `FnSelfCall` is a function
872 // that has a `self` parameter.
874 let target_temp = match stmt.kind {
875 StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
876 temp.as_local().unwrap()
878 _ => return normal_ret,
881 debug!("move_spans: target_temp = {:?}", target_temp);
883 if let Some(Terminator {
884 kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
885 }) = &self.body[location.block].terminator
887 let Some((method_did, method_substs)) =
888 rustc_const_eval::util::find_self_call(
898 let kind = call_kind(
905 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
909 var_span: stmt.source_info.span,
910 fn_call_span: *fn_span,
911 fn_span: self.infcx.tcx.def_span(method_did),
918 /// Finds the span of arguments of a closure (within `maybe_closure_span`)
919 /// and its usage of the local assigned at `location`.
920 /// This is done by searching in statements succeeding `location`
921 /// and originating from `maybe_closure_span`.
922 pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
923 use self::UseSpans::*;
924 debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
926 let target = match self.body[location.block].statements.get(location.statement_index) {
927 Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => {
928 if let Some(local) = place.as_local() {
931 return OtherUse(use_span);
934 _ => return OtherUse(use_span),
937 if self.body.local_kind(target) != LocalKind::Temp {
938 // operands are always temporaries.
939 return OtherUse(use_span);
942 for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
943 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind {
944 let (&def_id, is_generator) = match kind {
945 box AggregateKind::Closure(def_id, _) => (def_id, false),
946 box AggregateKind::Generator(def_id, _, _) => (def_id, true),
951 "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
952 def_id, is_generator, places
954 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
955 self.closure_span(def_id, Place::from(target).as_ref(), places)
957 return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
959 return OtherUse(use_span);
963 if use_span != stmt.source_info.span {
971 /// Finds the spans of a captured place within a closure or generator.
972 /// The first span is the location of the use resulting in the capture kind of the capture
973 /// The second span is the location the use resulting in the captured path of the capture
977 target_place: PlaceRef<'tcx>,
978 places: &[Operand<'tcx>],
979 ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
981 "closure_span: def_id={:?} target_place={:?} places={:?}",
982 def_id, target_place, places
984 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id);
985 let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
986 debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
987 if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr {
988 for (captured_place, place) in
989 self.infcx.tcx.typeck(def_id).closure_min_captures_flattened(def_id).zip(places)
992 Operand::Copy(place) | Operand::Move(place)
993 if target_place == place.as_ref() =>
995 debug!("closure_span: found captured local {:?}", place);
996 let body = self.infcx.tcx.hir().body(body);
997 let generator_kind = body.generator_kind();
1002 captured_place.get_capture_kind_span(self.infcx.tcx),
1003 captured_place.get_path_span(self.infcx.tcx),
1013 /// Helper to retrieve span(s) of given borrow from the current MIR
1015 pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1016 let span = self.body.source_info(borrow.reserve_location).span;
1017 self.borrow_spans(span, borrow.reserve_location)
1020 fn explain_captures(
1022 err: &mut Diagnostic,
1025 move_spans: UseSpans<'tcx>,
1026 moved_place: Place<'tcx>,
1027 partially_str: &str,
1031 maybe_reinitialized_locations_is_empty: bool,
1033 if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
1034 let place_name = self
1035 .describe_place(moved_place.as_ref())
1036 .map(|n| format!("`{}`", n))
1037 .unwrap_or_else(|| "value".to_owned());
1039 CallKind::FnCall { fn_trait_id, .. }
1040 if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() =>
1045 "{} {}moved due to this call{}",
1046 place_name, partially_str, loop_message
1051 "this value implements `FnOnce`, which causes it to be moved when called",
1054 CallKind::Operator { self_arg, .. } => {
1055 let self_arg = self_arg.unwrap();
1059 "{} {}moved due to usage in operator{}",
1060 place_name, partially_str, loop_message
1063 if self.fn_self_span_reported.insert(fn_span) {
1066 "calling this operator moves the left-hand side",
1070 CallKind::Normal { self_arg, desugaring, method_did } => {
1071 let self_arg = self_arg.unwrap();
1072 let tcx = self.infcx.tcx;
1073 if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
1074 let ty = moved_place.ty(self.body, tcx).ty;
1075 let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) {
1077 let infcx = self.infcx.tcx.infer_ctxt().build();
1078 type_known_to_meet_bound_modulo_regions(
1081 tcx.mk_imm_ref(tcx.lifetimes.re_erased, tcx.erase_regions(ty)),
1089 err.span_suggestion_verbose(
1090 move_span.shrink_to_lo(),
1092 "consider iterating over a slice of the `{}`'s content to \
1093 avoid moving into the `for` loop",
1097 Applicability::MaybeIncorrect,
1104 "{} {}moved due to this implicit call to `.into_iter()`{}",
1105 place_name, partially_str, loop_message
1108 // If the moved place was a `&mut` ref, then we can
1109 // suggest to reborrow it where it was moved, so it
1110 // will still be valid by the time we get to the usage.
1111 if let ty::Ref(_, _, hir::Mutability::Mut) =
1112 moved_place.ty(self.body, self.infcx.tcx).ty.kind()
1114 // If we are in a loop this will be suggested later.
1116 err.span_suggestion_verbose(
1117 move_span.shrink_to_lo(),
1119 "consider creating a fresh reborrow of {} here",
1120 self.describe_place(moved_place.as_ref())
1121 .map(|n| format!("`{}`", n))
1122 .unwrap_or_else(|| "the mutable reference".to_string()),
1125 Applicability::MachineApplicable,
1133 "{} {}moved due to this method call{}",
1134 place_name, partially_str, loop_message
1137 let infcx = tcx.infer_ctxt().build();
1138 let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty);
1139 if let ty::Adt(def, substs) = ty.kind()
1140 && Some(def.did()) == tcx.lang_items().pin_type()
1141 && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
1142 && let self_ty = infcx.replace_bound_vars_with_fresh_vars(
1144 LateBoundRegionConversionTime::FnCall,
1145 tcx.fn_sig(method_did).input(0),
1147 && infcx.can_eq(self.param_env, ty, self_ty).is_ok()
1149 err.span_suggestion_verbose(
1150 fn_call_span.shrink_to_lo(),
1151 "consider reborrowing the `Pin` instead of moving it",
1152 "as_mut().".to_string(),
1153 Applicability::MaybeIncorrect,
1156 if let Some(clone_trait) = tcx.lang_items().clone_trait()
1157 && let trait_ref = tcx.mk_trait_ref(clone_trait, [ty])
1158 && let o = Obligation::new(
1160 ObligationCause::dummy(),
1162 ty::Binder::dummy(trait_ref),
1164 && infcx.predicate_must_hold_modulo_regions(&o)
1166 err.span_suggestion_verbose(
1167 fn_call_span.shrink_to_lo(),
1168 "you can `clone` the value and consume it, but this might not be \
1169 your desired behavior",
1170 "clone().".to_string(),
1171 Applicability::MaybeIncorrect,
1175 // Avoid pointing to the same function in multiple different
1177 if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
1178 let func = tcx.def_path_str(method_did);
1181 &format!("`{func}` takes ownership of the receiver `self`, which moves {place_name}")
1184 let parent_did = tcx.parent(method_did);
1185 let parent_self_ty = (tcx.def_kind(parent_did)
1186 == rustc_hir::def::DefKind::Impl)
1187 .then_some(parent_did)
1188 .and_then(|did| match tcx.type_of(did).kind() {
1189 ty::Adt(def, ..) => Some(def.did()),
1192 let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
1193 matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
1195 if is_option_or_result && maybe_reinitialized_locations_is_empty {
1198 "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
1202 // Other desugarings takes &self, which cannot cause a move
1206 if move_span != span || !loop_message.is_empty() {
1209 format!("value {}moved{} here{}", partially_str, move_msg, loop_message),
1212 // If the move error occurs due to a loop, don't show
1213 // another message for the same span
1214 if loop_message.is_empty() {
1215 move_spans.var_span_label(
1217 format!("variable {}moved due to use{}", partially_str, move_spans.describe()),