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_prefix}move occurs because {place_desc} has type `{ty}`, which does not implement the `Copy` trait",
408 if let Some(span) = span {
409 err.span_label(span, message);
415 pub(super) fn borrowed_content_source(
417 deref_base: PlaceRef<'tcx>,
418 ) -> BorrowedContentSource<'tcx> {
419 let tcx = self.infcx.tcx;
421 // Look up the provided place and work out the move path index for it,
422 // we'll use this to check whether it was originally from an overloaded
424 match self.move_data.rev_lookup.find(deref_base) {
425 LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => {
426 debug!("borrowed_content_source: mpi={:?}", mpi);
428 for i in &self.move_data.init_path_map[mpi] {
429 let init = &self.move_data.inits[*i];
430 debug!("borrowed_content_source: init={:?}", init);
431 // We're only interested in statements that initialized a value, not the
432 // initializations from arguments.
433 let InitLocation::Statement(loc) = init.location else { continue };
435 let bbd = &self.body[loc.block];
436 let is_terminator = bbd.statements.len() == loc.statement_index;
438 "borrowed_content_source: loc={:?} is_terminator={:?}",
443 } else if let Some(Terminator {
444 kind: TerminatorKind::Call { func, from_hir_call: false, .. },
448 if let Some(source) =
449 BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx)
456 // Base is a `static` so won't be from an overloaded operator
460 // If we didn't find an overloaded deref or index, then assume it's a
461 // built in deref and check the type of the base.
462 let base_ty = deref_base.ty(self.body, tcx).ty;
463 if base_ty.is_unsafe_ptr() {
464 BorrowedContentSource::DerefRawPointer
465 } else if base_ty.is_mutable_ptr() {
466 BorrowedContentSource::DerefMutableRef
468 BorrowedContentSource::DerefSharedRef
472 /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
473 /// name where required.
474 pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
475 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
477 // We need to add synthesized lifetimes where appropriate. We do
478 // this by hooking into the pretty printer and telling it to label the
479 // lifetimes without names with the value `'0`.
480 if let ty::Ref(region, ..) = ty.kind() {
482 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
483 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
484 printer.region_highlight_mode.highlighting_bound_region(br, counter)
490 ty.print(printer).unwrap().into_buffer()
493 /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
494 /// synthesized lifetime name where required.
495 pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
496 let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
498 let region = if let ty::Ref(region, ..) = ty.kind() {
500 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
501 | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
502 printer.region_highlight_mode.highlighting_bound_region(br, counter)
508 bug!("ty for annotation of borrow region is not a reference");
511 region.print(printer).unwrap().into_buffer()
515 /// The span(s) associated to a use of a place.
516 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
517 pub(super) enum UseSpans<'tcx> {
518 /// The access is caused by capturing a variable for a closure.
520 /// This is true if the captured variable was from a generator.
521 generator_kind: Option<GeneratorKind>,
522 /// The span of the args of the closure, including the `move` keyword if
525 /// The span of the use resulting in capture kind
526 /// Check `ty::CaptureInfo` for more details
527 capture_kind_span: Span,
528 /// The span of the use resulting in the captured path
529 /// Check `ty::CaptureInfo` for more details
532 /// The access is caused by using a variable as the receiver of a method
533 /// that takes 'self'
535 /// The span of the variable being moved
537 /// The span of the method call on the variable
539 /// The definition span of the method being called
541 kind: CallKind<'tcx>,
543 /// This access is caused by a `match` or `if let` pattern.
545 /// This access has a single span associated to it: common case.
550 pub(super) fn args_or_use(self) -> Span {
552 UseSpans::ClosureUse { args_span: span, .. }
553 | UseSpans::PatUse(span)
554 | UseSpans::OtherUse(span) => span,
555 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
558 UseSpans::FnSelfUse { var_span, .. } => var_span,
562 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span`
563 pub(super) fn var_or_use_path_span(self) -> Span {
565 UseSpans::ClosureUse { path_span: span, .. }
566 | UseSpans::PatUse(span)
567 | UseSpans::OtherUse(span) => span,
568 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
571 UseSpans::FnSelfUse { var_span, .. } => var_span,
575 /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span`
576 pub(super) fn var_or_use(self) -> Span {
578 UseSpans::ClosureUse { capture_kind_span: span, .. }
579 | UseSpans::PatUse(span)
580 | UseSpans::OtherUse(span) => span,
581 UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => {
584 UseSpans::FnSelfUse { var_span, .. } => var_span,
588 pub(super) fn generator_kind(self) -> Option<GeneratorKind> {
590 UseSpans::ClosureUse { generator_kind, .. } => generator_kind,
595 /// Add a span label to the arguments of the closure, if it exists.
596 pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into<String>) {
597 if let UseSpans::ClosureUse { args_span, .. } = self {
598 err.span_label(args_span, message);
602 /// Add a span label to the use of the captured variable, if it exists.
603 /// only adds label to the `path_span`
604 pub(super) fn var_path_only_subdiag(
606 err: &mut Diagnostic,
607 action: crate::InitializationRequiringAction,
609 use crate::session_diagnostics::CaptureVarPathUseCause::*;
610 use crate::InitializationRequiringAction::*;
611 if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self {
612 match generator_kind {
614 err.subdiagnostic(match action {
615 Borrow => BorrowInGenerator { path_span },
616 MatchOn | Use => UseInGenerator { path_span },
617 Assignment => AssignInGenerator { path_span },
618 PartialAssignment => AssignPartInGenerator { path_span },
622 err.subdiagnostic(match action {
623 Borrow => BorrowInClosure { path_span },
624 MatchOn | Use => UseInClosure { path_span },
625 Assignment => AssignInClosure { path_span },
626 PartialAssignment => AssignPartInClosure { path_span },
633 /// Add a span label to the use of the captured variable, if it exists.
634 pub(super) fn var_span_label(
636 err: &mut Diagnostic,
637 message: impl Into<String>,
638 kind_desc: impl Into<String>,
640 if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
641 if capture_kind_span == path_span {
642 err.span_label(capture_kind_span, message);
644 let capture_kind_label =
645 format!("capture is {} because of use here", kind_desc.into());
646 let path_label = message;
647 err.span_label(capture_kind_span, capture_kind_label);
648 err.span_label(path_span, path_label);
653 /// Add a subdiagnostic to the use of the captured variable, if it exists.
654 pub(super) fn var_subdiag(
656 err: &mut Diagnostic,
657 kind: Option<rustc_middle::mir::BorrowKind>,
658 f: impl Fn(Option<GeneratorKind>, Span) -> crate::session_diagnostics::CaptureVarCause,
660 use crate::session_diagnostics::CaptureVarKind::*;
661 if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self {
662 if capture_kind_span != path_span {
663 err.subdiagnostic(match kind {
664 Some(kd) => match kd {
665 rustc_middle::mir::BorrowKind::Shared
666 | rustc_middle::mir::BorrowKind::Shallow
667 | rustc_middle::mir::BorrowKind::Unique => {
668 Immute { kind_span: capture_kind_span }
671 rustc_middle::mir::BorrowKind::Mut { .. } => {
672 Mut { kind_span: capture_kind_span }
675 None => Move { kind_span: capture_kind_span },
678 err.subdiagnostic(f(generator_kind, path_span));
682 /// Returns `false` if this place is not used in a closure.
683 pub(super) fn for_closure(&self) -> bool {
685 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(),
690 /// Returns `false` if this place is not used in a generator.
691 pub(super) fn for_generator(&self) -> bool {
693 UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(),
698 /// Describe the span associated with a use of a place.
699 pub(super) fn describe(&self) -> &str {
701 UseSpans::ClosureUse { generator_kind, .. } => {
702 if generator_kind.is_some() {
712 pub(super) fn or_else<F>(self, if_other: F) -> Self
717 closure @ UseSpans::ClosureUse { .. } => closure,
718 UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(),
719 fn_self @ UseSpans::FnSelfUse { .. } => fn_self,
724 pub(super) enum BorrowedContentSource<'tcx> {
728 OverloadedDeref(Ty<'tcx>),
729 OverloadedIndex(Ty<'tcx>),
732 impl<'tcx> BorrowedContentSource<'tcx> {
733 pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
735 BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
736 BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
737 BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
738 BorrowedContentSource::OverloadedDeref(ty) => ty
740 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
741 name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")),
744 .unwrap_or_else(|| format!("dereference of `{ty}`")),
745 BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{ty}`"),
749 pub(super) fn describe_for_named_place(&self) -> Option<&'static str> {
751 BorrowedContentSource::DerefRawPointer => Some("raw pointer"),
752 BorrowedContentSource::DerefSharedRef => Some("shared reference"),
753 BorrowedContentSource::DerefMutableRef => Some("mutable reference"),
754 // Overloaded deref and index operators should be evaluated into a
755 // temporary. So we don't need a description here.
756 BorrowedContentSource::OverloadedDeref(_)
757 | BorrowedContentSource::OverloadedIndex(_) => None,
761 pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
763 BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
764 BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
765 BorrowedContentSource::DerefMutableRef => {
766 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
768 BorrowedContentSource::OverloadedDeref(ty) => ty
770 .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? {
771 name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")),
774 .unwrap_or_else(|| format!("dereference of `{ty}`")),
775 BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{ty}`"),
779 fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
781 ty::FnDef(def_id, substs) => {
782 let trait_id = tcx.trait_of_item(def_id)?;
784 let lang_items = tcx.lang_items();
785 if Some(trait_id) == lang_items.deref_trait()
786 || Some(trait_id) == lang_items.deref_mut_trait()
788 Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
789 } else if Some(trait_id) == lang_items.index_trait()
790 || Some(trait_id) == lang_items.index_mut_trait()
792 Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
802 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
803 /// Finds the spans associated to a move or copy of move_place at location.
804 pub(super) fn move_spans(
806 moved_place: PlaceRef<'tcx>, // Could also be an upvar.
808 ) -> UseSpans<'tcx> {
809 use self::UseSpans::*;
811 let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else {
812 return OtherUse(self.body.source_info(location).span);
815 debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt);
816 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind
817 && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind
819 debug!("move_spans: def_id={:?} places={:?}", def_id, places);
820 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
821 self.closure_span(def_id, moved_place, places)
832 // StatementKind::FakeRead only contains a def_id if they are introduced as a result
833 // of pattern matching within a closure.
834 if let StatementKind::FakeRead(box (cause, place)) = stmt.kind {
836 FakeReadCause::ForMatchedPlace(Some(closure_def_id))
837 | FakeReadCause::ForLet(Some(closure_def_id)) => {
838 debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
839 let places = &[Operand::Move(place)];
840 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
841 self.closure_span(closure_def_id, moved_place, places)
856 if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) {
857 PatUse(stmt.source_info.span)
859 OtherUse(stmt.source_info.span)
862 // We are trying to find MIR of the form:
864 // _temp = _moved_val;
866 // FnSelfCall(_temp, ...)
869 // where `_moved_val` is the place we generated the move error for,
870 // `_temp` is some other local, and `FnSelfCall` is a function
871 // that has a `self` parameter.
873 let target_temp = match stmt.kind {
874 StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => {
875 temp.as_local().unwrap()
877 _ => return normal_ret,
880 debug!("move_spans: target_temp = {:?}", target_temp);
882 if let Some(Terminator {
883 kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
884 }) = &self.body[location.block].terminator
886 let Some((method_did, method_substs)) =
887 rustc_const_eval::util::find_self_call(
897 let kind = call_kind(
904 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
908 var_span: stmt.source_info.span,
909 fn_call_span: *fn_span,
910 fn_span: self.infcx.tcx.def_span(method_did),
917 /// Finds the span of arguments of a closure (within `maybe_closure_span`)
918 /// and its usage of the local assigned at `location`.
919 /// This is done by searching in statements succeeding `location`
920 /// and originating from `maybe_closure_span`.
921 pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> {
922 use self::UseSpans::*;
923 debug!("borrow_spans: use_span={:?} location={:?}", use_span, location);
925 let target = match self.body[location.block].statements.get(location.statement_index) {
926 Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => {
927 if let Some(local) = place.as_local() {
930 return OtherUse(use_span);
933 _ => return OtherUse(use_span),
936 if self.body.local_kind(target) != LocalKind::Temp {
937 // operands are always temporaries.
938 return OtherUse(use_span);
941 for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
942 if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind {
943 let (&def_id, is_generator) = match kind {
944 box AggregateKind::Closure(def_id, _) => (def_id, false),
945 box AggregateKind::Generator(def_id, _, _) => (def_id, true),
950 "borrow_spans: def_id={:?} is_generator={:?} places={:?}",
951 def_id, is_generator, places
953 if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
954 self.closure_span(def_id, Place::from(target).as_ref(), places)
956 return ClosureUse { generator_kind, args_span, capture_kind_span, path_span };
958 return OtherUse(use_span);
962 if use_span != stmt.source_info.span {
970 /// Finds the spans of a captured place within a closure or generator.
971 /// The first span is the location of the use resulting in the capture kind of the capture
972 /// The second span is the location the use resulting in the captured path of the capture
976 target_place: PlaceRef<'tcx>,
977 places: &[Operand<'tcx>],
978 ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
980 "closure_span: def_id={:?} target_place={:?} places={:?}",
981 def_id, target_place, places
983 let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id);
984 let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
985 debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
986 if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr {
987 for (captured_place, place) in
988 self.infcx.tcx.typeck(def_id).closure_min_captures_flattened(def_id).zip(places)
991 Operand::Copy(place) | Operand::Move(place)
992 if target_place == place.as_ref() =>
994 debug!("closure_span: found captured local {:?}", place);
995 let body = self.infcx.tcx.hir().body(body);
996 let generator_kind = body.generator_kind();
1001 captured_place.get_capture_kind_span(self.infcx.tcx),
1002 captured_place.get_path_span(self.infcx.tcx),
1012 /// Helper to retrieve span(s) of given borrow from the current MIR
1014 pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> {
1015 let span = self.body.source_info(borrow.reserve_location).span;
1016 self.borrow_spans(span, borrow.reserve_location)
1019 fn explain_captures(
1021 err: &mut Diagnostic,
1024 move_spans: UseSpans<'tcx>,
1025 moved_place: Place<'tcx>,
1026 partially_str: &str,
1030 maybe_reinitialized_locations_is_empty: bool,
1032 if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
1033 let place_name = self
1034 .describe_place(moved_place.as_ref())
1035 .map(|n| format!("`{n}`"))
1036 .unwrap_or_else(|| "value".to_owned());
1038 CallKind::FnCall { fn_trait_id, .. }
1039 if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() =>
1044 "{place_name} {partially_str}moved due to this call{loop_message}",
1049 "this value implements `FnOnce`, which causes it to be moved when called",
1052 CallKind::Operator { self_arg, .. } => {
1053 let self_arg = self_arg.unwrap();
1057 "{place_name} {partially_str}moved due to usage in operator{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 let tcx = self.infcx.tcx;
1070 if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
1071 let ty = moved_place.ty(self.body, tcx).ty;
1072 let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) {
1074 let infcx = self.infcx.tcx.infer_ctxt().build();
1075 type_known_to_meet_bound_modulo_regions(
1078 tcx.mk_imm_ref(tcx.lifetimes.re_erased, tcx.erase_regions(ty)),
1086 err.span_suggestion_verbose(
1087 move_span.shrink_to_lo(),
1089 "consider iterating over a slice of the `{ty}`'s content to \
1090 avoid moving into the `for` loop",
1093 Applicability::MaybeIncorrect,
1100 "{place_name} {partially_str}moved due to this implicit call to `.into_iter()`{loop_message}",
1103 // If the moved place was a `&mut` ref, then we can
1104 // suggest to reborrow it where it was moved, so it
1105 // will still be valid by the time we get to the usage.
1106 if let ty::Ref(_, _, hir::Mutability::Mut) =
1107 moved_place.ty(self.body, self.infcx.tcx).ty.kind()
1109 // If we are in a loop this will be suggested later.
1111 err.span_suggestion_verbose(
1112 move_span.shrink_to_lo(),
1114 "consider creating a fresh reborrow of {} here",
1115 self.describe_place(moved_place.as_ref())
1116 .map(|n| format!("`{n}`"))
1117 .unwrap_or_else(|| "the mutable reference".to_string()),
1120 Applicability::MachineApplicable,
1128 "{place_name} {partially_str}moved due to this method call{loop_message}",
1131 let infcx = tcx.infer_ctxt().build();
1132 let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty);
1133 if let ty::Adt(def, substs) = ty.kind()
1134 && Some(def.did()) == tcx.lang_items().pin_type()
1135 && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
1136 && let self_ty = infcx.replace_bound_vars_with_fresh_vars(
1138 LateBoundRegionConversionTime::FnCall,
1139 tcx.fn_sig(method_did).input(0),
1141 && infcx.can_eq(self.param_env, ty, self_ty).is_ok()
1143 err.span_suggestion_verbose(
1144 fn_call_span.shrink_to_lo(),
1145 "consider reborrowing the `Pin` instead of moving it",
1146 "as_mut().".to_string(),
1147 Applicability::MaybeIncorrect,
1150 if let Some(clone_trait) = tcx.lang_items().clone_trait()
1151 && let trait_ref = tcx.mk_trait_ref(clone_trait, [ty])
1152 && let o = Obligation::new(
1154 ObligationCause::dummy(),
1156 ty::Binder::dummy(trait_ref),
1158 && infcx.predicate_must_hold_modulo_regions(&o)
1160 err.span_suggestion_verbose(
1161 fn_call_span.shrink_to_lo(),
1162 "you can `clone` the value and consume it, but this might not be \
1163 your desired behavior",
1164 "clone().".to_string(),
1165 Applicability::MaybeIncorrect,
1169 // Avoid pointing to the same function in multiple different
1171 if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
1172 let func = tcx.def_path_str(method_did);
1175 &format!("`{func}` takes ownership of the receiver `self`, which moves {place_name}")
1178 let parent_did = tcx.parent(method_did);
1179 let parent_self_ty = (tcx.def_kind(parent_did)
1180 == rustc_hir::def::DefKind::Impl)
1181 .then_some(parent_did)
1182 .and_then(|did| match tcx.type_of(did).kind() {
1183 ty::Adt(def, ..) => Some(def.did()),
1186 let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
1187 matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
1189 if is_option_or_result && maybe_reinitialized_locations_is_empty {
1192 "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
1196 // Other desugarings takes &self, which cannot cause a move
1200 if move_span != span || !loop_message.is_empty() {
1203 format!("value {partially_str}moved{move_msg} here{loop_message}"),
1206 // If the move error occurs due to a loop, don't show
1207 // another message for the same span
1208 if loop_message.is_empty() {
1209 move_spans.var_span_label(
1211 format!("variable {partially_str}moved due to use{}", move_spans.describe()),