| use either::Either; |
| use rustc_const_eval::util::CallKind; |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan}; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::{AsyncGeneratorKind, GeneratorKind}; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_infer::traits::ObligationCause; |
| use rustc_middle::mir::tcx::PlaceTy; |
| use rustc_middle::mir::{ |
| self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory, |
| FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef, |
| ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm, |
| }; |
| use rustc_middle::ty::{ |
| self, subst::Subst, suggest_constraining_type_params, EarlyBinder, PredicateKind, Ty, |
| }; |
| use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex}; |
| use rustc_span::symbol::sym; |
| use rustc_span::{BytePos, Span}; |
| use rustc_trait_selection::infer::InferCtxtExt; |
| use rustc_trait_selection::traits::TraitEngineExt as _; |
| |
| use crate::borrow_set::TwoPhaseActivation; |
| use crate::borrowck_errors; |
| |
| use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead; |
| use crate::diagnostics::find_all_local_uses; |
| use crate::{ |
| borrow_set::BorrowData, diagnostics::Instance, prefixes::IsPrefixOf, |
| InitializationRequiringAction, MirBorrowckCtxt, PrefixSet, WriteKind, |
| }; |
| |
| use super::{ |
| explain_borrow::{BorrowExplanation, LaterUseKind}, |
| IncludingDowncast, RegionName, RegionNameSource, UseSpans, |
| }; |
| |
| #[derive(Debug)] |
| struct MoveSite { |
| /// Index of the "move out" that we found. The `MoveData` can |
| /// then tell us where the move occurred. |
| moi: MoveOutIndex, |
| |
| /// `true` if we traversed a back edge while walking from the point |
| /// of error to the move site. |
| traversed_back_edge: bool, |
| } |
| |
| /// Which case a StorageDeadOrDrop is for. |
| #[derive(Copy, Clone, PartialEq, Eq, Debug)] |
| enum StorageDeadOrDrop<'tcx> { |
| LocalStorageDead, |
| BoxedStorageDead, |
| Destructor(Ty<'tcx>), |
| } |
| |
| impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { |
| pub(crate) fn report_use_of_moved_or_uninitialized( |
| &mut self, |
| location: Location, |
| desired_action: InitializationRequiringAction, |
| (moved_place, used_place, span): (PlaceRef<'tcx>, PlaceRef<'tcx>, Span), |
| mpi: MovePathIndex, |
| ) { |
| debug!( |
| "report_use_of_moved_or_uninitialized: location={:?} desired_action={:?} \ |
| moved_place={:?} used_place={:?} span={:?} mpi={:?}", |
| location, desired_action, moved_place, used_place, span, mpi |
| ); |
| |
| let use_spans = |
| self.move_spans(moved_place, location).or_else(|| self.borrow_spans(span, location)); |
| let span = use_spans.args_or_use(); |
| |
| let (move_site_vec, maybe_reinitialized_locations) = self.get_moved_indexes(location, mpi); |
| debug!( |
| "report_use_of_moved_or_uninitialized: move_site_vec={:?} use_spans={:?}", |
| move_site_vec, use_spans |
| ); |
| let move_out_indices: Vec<_> = |
| move_site_vec.iter().map(|move_site| move_site.moi).collect(); |
| |
| if move_out_indices.is_empty() { |
| let root_place = PlaceRef { projection: &[], ..used_place }; |
| |
| if !self.uninitialized_error_reported.insert(root_place) { |
| debug!( |
| "report_use_of_moved_or_uninitialized place: error about {:?} suppressed", |
| root_place |
| ); |
| return; |
| } |
| |
| let item_msg = |
| match self.describe_place_with_options(used_place, IncludingDowncast(true)) { |
| Some(name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| let mut err = self.cannot_act_on_uninitialized_variable( |
| span, |
| desired_action.as_noun(), |
| &self |
| .describe_place_with_options(moved_place, IncludingDowncast(true)) |
| .unwrap_or_else(|| "_".to_owned()), |
| ); |
| err.span_label(span, format!("use of possibly-uninitialized {}", item_msg)); |
| |
| use_spans.var_span_label_path_only( |
| &mut err, |
| format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), |
| ); |
| |
| self.buffer_error(err); |
| } else { |
| if let Some((reported_place, _)) = self.has_move_error(&move_out_indices) { |
| if self.prefixes(*reported_place, PrefixSet::All).any(|p| p == used_place) { |
| debug!( |
| "report_use_of_moved_or_uninitialized place: error suppressed \ |
| mois={:?}", |
| move_out_indices |
| ); |
| return; |
| } |
| } |
| |
| let is_partial_move = move_site_vec.iter().any(|move_site| { |
| let move_out = self.move_data.moves[(*move_site).moi]; |
| let moved_place = &self.move_data.move_paths[move_out.path].place; |
| // `*(_1)` where `_1` is a `Box` is actually a move out. |
| let is_box_move = moved_place.as_ref().projection == [ProjectionElem::Deref] |
| && self.body.local_decls[moved_place.local].ty.is_box(); |
| |
| !is_box_move |
| && used_place != moved_place.as_ref() |
| && used_place.is_prefix_of(moved_place.as_ref()) |
| }); |
| |
| let partial_str = if is_partial_move { "partial " } else { "" }; |
| let partially_str = if is_partial_move { "partially " } else { "" }; |
| |
| let mut err = self.cannot_act_on_moved_value( |
| span, |
| desired_action.as_noun(), |
| partially_str, |
| self.describe_place_with_options(moved_place, IncludingDowncast(true)), |
| ); |
| |
| let reinit_spans = maybe_reinitialized_locations |
| .iter() |
| .take(3) |
| .map(|loc| { |
| self.move_spans(self.move_data.move_paths[mpi].place.as_ref(), *loc) |
| .args_or_use() |
| }) |
| .collect::<Vec<Span>>(); |
| |
| let reinits = maybe_reinitialized_locations.len(); |
| if reinits == 1 { |
| err.span_label(reinit_spans[0], "this reinitialization might get skipped"); |
| } else if reinits > 1 { |
| err.span_note( |
| MultiSpan::from_spans(reinit_spans), |
| &if reinits <= 3 { |
| format!("these {} reinitializations might get skipped", reinits) |
| } else { |
| format!( |
| "these 3 reinitializations and {} other{} might get skipped", |
| reinits - 3, |
| if reinits == 4 { "" } else { "s" } |
| ) |
| }, |
| ); |
| } |
| |
| self.add_moved_or_invoked_closure_note(location, used_place, &mut err); |
| |
| let mut is_loop_move = false; |
| let mut in_pattern = false; |
| |
| for move_site in &move_site_vec { |
| let move_out = self.move_data.moves[(*move_site).moi]; |
| let moved_place = &self.move_data.move_paths[move_out.path].place; |
| |
| let move_spans = self.move_spans(moved_place.as_ref(), move_out.source); |
| let move_span = move_spans.args_or_use(); |
| |
| let move_msg = if move_spans.for_closure() { " into closure" } else { "" }; |
| |
| let loop_message = if location == move_out.source || move_site.traversed_back_edge { |
| ", in previous iteration of loop" |
| } else { |
| "" |
| }; |
| |
| if location == move_out.source { |
| is_loop_move = true; |
| } |
| |
| self.explain_captures( |
| &mut err, |
| span, |
| move_span, |
| move_spans, |
| *moved_place, |
| Some(used_place), |
| partially_str, |
| loop_message, |
| move_msg, |
| is_loop_move, |
| maybe_reinitialized_locations.is_empty(), |
| ); |
| |
| if let (UseSpans::PatUse(span), []) = |
| (move_spans, &maybe_reinitialized_locations[..]) |
| { |
| if maybe_reinitialized_locations.is_empty() { |
| err.span_suggestion_verbose( |
| span.shrink_to_lo(), |
| &format!( |
| "borrow this field in the pattern to avoid moving {}", |
| self.describe_place(moved_place.as_ref()) |
| .map(|n| format!("`{}`", n)) |
| .unwrap_or_else(|| "the value".to_string()) |
| ), |
| "ref ".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| in_pattern = true; |
| } |
| } |
| } |
| |
| use_spans.var_span_label_path_only( |
| &mut err, |
| format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), |
| ); |
| |
| if !is_loop_move { |
| err.span_label( |
| span, |
| format!( |
| "value {} here after {}move", |
| desired_action.as_verb_in_past_tense(), |
| partial_str |
| ), |
| ); |
| } |
| |
| let ty = used_place.ty(self.body, self.infcx.tcx).ty; |
| let needs_note = match ty.kind() { |
| ty::Closure(id, _) => { |
| let tables = self.infcx.tcx.typeck(id.expect_local()); |
| let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(id.expect_local()); |
| |
| tables.closure_kind_origins().get(hir_id).is_none() |
| } |
| _ => true, |
| }; |
| |
| let mpi = self.move_data.moves[move_out_indices[0]].path; |
| let place = &self.move_data.move_paths[mpi].place; |
| let ty = place.ty(self.body, self.infcx.tcx).ty; |
| |
| // If we're in pattern, we do nothing in favor of the previous suggestion (#80913). |
| if is_loop_move & !in_pattern { |
| if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() { |
| // We have a `&mut` ref, we need to reborrow on each iteration (#62112). |
| err.span_suggestion_verbose( |
| span.shrink_to_lo(), |
| &format!( |
| "consider creating a fresh reborrow of {} here", |
| self.describe_place(moved_place) |
| .map(|n| format!("`{}`", n)) |
| .unwrap_or_else(|| "the mutable reference".to_string()), |
| ), |
| "&mut *".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| let opt_name = |
| self.describe_place_with_options(place.as_ref(), IncludingDowncast(true)); |
| let note_msg = match opt_name { |
| Some(ref name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| if self.suggest_borrow_fn_like(&mut err, ty, &move_site_vec, ¬e_msg) { |
| // Suppress the next suggestion since we don't want to put more bounds onto |
| // something that already has `Fn`-like bounds (or is a closure), so we can't |
| // restrict anyways. |
| } else { |
| self.suggest_adding_copy_bounds(&mut err, ty, span); |
| } |
| |
| if needs_note { |
| let span = if let Some(local) = place.as_local() { |
| Some(self.body.local_decls[local].source_info.span) |
| } else { |
| None |
| }; |
| self.note_type_does_not_implement_copy(&mut err, ¬e_msg, ty, span, partial_str); |
| } |
| |
| if let UseSpans::FnSelfUse { |
| kind: CallKind::DerefCoercion { deref_target, deref_target_ty, .. }, |
| .. |
| } = use_spans |
| { |
| err.note(&format!( |
| "{} occurs due to deref coercion to `{}`", |
| desired_action.as_noun(), |
| deref_target_ty |
| )); |
| |
| // Check first whether the source is accessible (issue #87060) |
| if self.infcx.tcx.sess.source_map().span_to_snippet(deref_target).is_ok() { |
| err.span_note(deref_target, "deref defined here"); |
| } |
| } |
| |
| self.buffer_move_error(move_out_indices, (used_place, err)); |
| } |
| } |
| |
| fn suggest_borrow_fn_like( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>, |
| ty: Ty<'tcx>, |
| move_sites: &[MoveSite], |
| value_name: &str, |
| ) -> bool { |
| let tcx = self.infcx.tcx; |
| |
| // Find out if the predicates show that the type is a Fn or FnMut |
| let find_fn_kind_from_did = |predicates: &[(ty::Predicate<'tcx>, Span)], substs| { |
| predicates.iter().find_map(|(pred, _)| { |
| let pred = if let Some(substs) = substs { |
| EarlyBinder(*pred).subst(tcx, substs).kind().skip_binder() |
| } else { |
| pred.kind().skip_binder() |
| }; |
| if let ty::PredicateKind::Trait(pred) = pred && pred.self_ty() == ty { |
| if Some(pred.def_id()) == tcx.lang_items().fn_trait() { |
| return Some(hir::Mutability::Not); |
| } else if Some(pred.def_id()) == tcx.lang_items().fn_mut_trait() { |
| return Some(hir::Mutability::Mut); |
| } |
| } |
| None |
| }) |
| }; |
| |
| // If the type is opaque/param/closure, and it is Fn or FnMut, let's suggest (mutably) |
| // borrowing the type, since `&mut F: FnMut` iff `F: FnMut` and similarly for `Fn`. |
| // These types seem reasonably opaque enough that they could be substituted with their |
| // borrowed variants in a function body when we see a move error. |
| let borrow_level = match ty.kind() { |
| ty::Param(_) => find_fn_kind_from_did( |
| tcx.explicit_predicates_of(self.mir_def_id().to_def_id()).predicates, |
| None, |
| ), |
| ty::Opaque(did, substs) => { |
| find_fn_kind_from_did(tcx.explicit_item_bounds(*did), Some(*substs)) |
| } |
| ty::Closure(_, substs) => match substs.as_closure().kind() { |
| ty::ClosureKind::Fn => Some(hir::Mutability::Not), |
| ty::ClosureKind::FnMut => Some(hir::Mutability::Mut), |
| _ => None, |
| }, |
| _ => None, |
| }; |
| |
| let Some(borrow_level) = borrow_level else { return false; }; |
| let sugg = move_sites |
| .iter() |
| .map(|move_site| { |
| let move_out = self.move_data.moves[(*move_site).moi]; |
| let moved_place = &self.move_data.move_paths[move_out.path].place; |
| let move_spans = self.move_spans(moved_place.as_ref(), move_out.source); |
| let move_span = move_spans.args_or_use(); |
| let suggestion = if borrow_level == hir::Mutability::Mut { |
| "&mut ".to_string() |
| } else { |
| "&".to_string() |
| }; |
| (move_span.shrink_to_lo(), suggestion) |
| }) |
| .collect(); |
| err.multipart_suggestion_verbose( |
| &format!( |
| "consider {}borrowing {value_name}", |
| if borrow_level == hir::Mutability::Mut { "mutably " } else { "" } |
| ), |
| sugg, |
| Applicability::MaybeIncorrect, |
| ); |
| true |
| } |
| |
| fn suggest_adding_copy_bounds( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>, |
| ty: Ty<'tcx>, |
| span: Span, |
| ) { |
| let tcx = self.infcx.tcx; |
| let generics = tcx.generics_of(self.mir_def_id()); |
| |
| let Some(hir_generics) = tcx |
| .typeck_root_def_id(self.mir_def_id().to_def_id()) |
| .as_local() |
| .and_then(|def_id| tcx.hir().get_generics(def_id)) |
| else { return; }; |
| // Try to find predicates on *generic params* that would allow copying `ty` |
| let predicates: Result<Vec<_>, _> = tcx.infer_ctxt().enter(|infcx| { |
| let mut fulfill_cx = <dyn rustc_infer::traits::TraitEngine<'_>>::new(infcx.tcx); |
| |
| let copy_did = infcx.tcx.lang_items().copy_trait().unwrap(); |
| let cause = ObligationCause::new( |
| span, |
| self.mir_hir_id(), |
| rustc_infer::traits::ObligationCauseCode::MiscObligation, |
| ); |
| fulfill_cx.register_bound( |
| &infcx, |
| self.param_env, |
| // Erase any region vids from the type, which may not be resolved |
| infcx.tcx.erase_regions(ty), |
| copy_did, |
| cause, |
| ); |
| // Select all, including ambiguous predicates |
| let errors = fulfill_cx.select_all_or_error(&infcx); |
| |
| // Only emit suggestion if all required predicates are on generic |
| errors |
| .into_iter() |
| .map(|err| match err.obligation.predicate.kind().skip_binder() { |
| PredicateKind::Trait(predicate) => match predicate.self_ty().kind() { |
| ty::Param(param_ty) => Ok(( |
| generics.type_param(param_ty, tcx), |
| predicate.trait_ref.print_only_trait_path().to_string(), |
| )), |
| _ => Err(()), |
| }, |
| _ => Err(()), |
| }) |
| .collect() |
| }); |
| |
| if let Ok(predicates) = predicates { |
| suggest_constraining_type_params( |
| tcx, |
| hir_generics, |
| err, |
| predicates |
| .iter() |
| .map(|(param, constraint)| (param.name.as_str(), &**constraint, None)), |
| ); |
| } |
| } |
| |
| pub(crate) fn report_move_out_while_borrowed( |
| &mut self, |
| location: Location, |
| (place, span): (Place<'tcx>, Span), |
| borrow: &BorrowData<'tcx>, |
| ) { |
| debug!( |
| "report_move_out_while_borrowed: location={:?} place={:?} span={:?} borrow={:?}", |
| location, place, span, borrow |
| ); |
| let value_msg = self.describe_any_place(place.as_ref()); |
| let borrow_msg = self.describe_any_place(borrow.borrowed_place.as_ref()); |
| |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.args_or_use(); |
| |
| let move_spans = self.move_spans(place.as_ref(), location); |
| let span = move_spans.args_or_use(); |
| |
| let mut err = |
| self.cannot_move_when_borrowed(span, &self.describe_any_place(place.as_ref())); |
| err.span_label(borrow_span, format!("borrow of {} occurs here", borrow_msg)); |
| err.span_label(span, format!("move out of {} occurs here", value_msg)); |
| |
| borrow_spans.var_span_label_path_only( |
| &mut err, |
| format!("borrow occurs due to use{}", borrow_spans.describe()), |
| ); |
| |
| move_spans.var_span_label( |
| &mut err, |
| format!("move occurs due to use{}", move_spans.describe()), |
| "moved", |
| ); |
| |
| self.explain_why_borrow_contains_point(location, borrow, None) |
| .add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| Some(borrow_span), |
| None, |
| ); |
| self.buffer_error(err); |
| } |
| |
| pub(crate) fn report_use_while_mutably_borrowed( |
| &mut self, |
| location: Location, |
| (place, _span): (Place<'tcx>, Span), |
| borrow: &BorrowData<'tcx>, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.args_or_use(); |
| |
| // Conflicting borrows are reported separately, so only check for move |
| // captures. |
| let use_spans = self.move_spans(place.as_ref(), location); |
| let span = use_spans.var_or_use(); |
| |
| // If the attempted use is in a closure then we do not care about the path span of the place we are currently trying to use |
| // we call `var_span_label` on `borrow_spans` to annotate if the existing borrow was in a closure |
| let mut err = self.cannot_use_when_mutably_borrowed( |
| span, |
| &self.describe_any_place(place.as_ref()), |
| borrow_span, |
| &self.describe_any_place(borrow.borrowed_place.as_ref()), |
| ); |
| |
| borrow_spans.var_span_label( |
| &mut err, |
| { |
| let place = &borrow.borrowed_place; |
| let desc_place = self.describe_any_place(place.as_ref()); |
| format!("borrow occurs due to use of {}{}", desc_place, borrow_spans.describe()) |
| }, |
| "mutable", |
| ); |
| |
| self.explain_why_borrow_contains_point(location, borrow, None) |
| .add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| err |
| } |
| |
| pub(crate) fn report_conflicting_borrow( |
| &mut self, |
| location: Location, |
| (place, span): (Place<'tcx>, Span), |
| gen_borrow_kind: BorrowKind, |
| issued_borrow: &BorrowData<'tcx>, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| let issued_spans = self.retrieve_borrow_spans(issued_borrow); |
| let issued_span = issued_spans.args_or_use(); |
| |
| let borrow_spans = self.borrow_spans(span, location); |
| let span = borrow_spans.args_or_use(); |
| |
| let container_name = if issued_spans.for_generator() || borrow_spans.for_generator() { |
| "generator" |
| } else { |
| "closure" |
| }; |
| |
| let (desc_place, msg_place, msg_borrow, union_type_name) = |
| self.describe_place_for_conflicting_borrow(place, issued_borrow.borrowed_place); |
| |
| let explanation = self.explain_why_borrow_contains_point(location, issued_borrow, None); |
| let second_borrow_desc = if explanation.is_explained() { "second " } else { "" }; |
| |
| // FIXME: supply non-"" `opt_via` when appropriate |
| let first_borrow_desc; |
| let mut err = match (gen_borrow_kind, issued_borrow.kind) { |
| (BorrowKind::Shared, BorrowKind::Mut { .. }) => { |
| first_borrow_desc = "mutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| "immutable", |
| issued_span, |
| "it", |
| "mutable", |
| &msg_borrow, |
| None, |
| ) |
| } |
| (BorrowKind::Mut { .. }, BorrowKind::Shared) => { |
| first_borrow_desc = "immutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| "mutable", |
| issued_span, |
| "it", |
| "immutable", |
| &msg_borrow, |
| None, |
| ) |
| } |
| |
| (BorrowKind::Mut { .. }, BorrowKind::Mut { .. }) => { |
| first_borrow_desc = "first "; |
| let mut err = self.cannot_mutably_borrow_multiply( |
| span, |
| &desc_place, |
| &msg_place, |
| issued_span, |
| &msg_borrow, |
| None, |
| ); |
| self.suggest_split_at_mut_if_applicable( |
| &mut err, |
| place, |
| issued_borrow.borrowed_place, |
| ); |
| err |
| } |
| |
| (BorrowKind::Unique, BorrowKind::Unique) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_two_closures(span, &desc_place, issued_span, None) |
| } |
| |
| (BorrowKind::Mut { .. } | BorrowKind::Unique, BorrowKind::Shallow) => { |
| if let Some(immutable_section_description) = |
| self.classify_immutable_section(issued_borrow.assigned_place) |
| { |
| let mut err = self.cannot_mutate_in_immutable_section( |
| span, |
| issued_span, |
| &desc_place, |
| immutable_section_description, |
| "mutably borrow", |
| ); |
| borrow_spans.var_span_label( |
| &mut err, |
| format!( |
| "borrow occurs due to use of {}{}", |
| desc_place, |
| borrow_spans.describe(), |
| ), |
| "immutable", |
| ); |
| |
| return err; |
| } else { |
| first_borrow_desc = "immutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| "mutable", |
| issued_span, |
| "it", |
| "immutable", |
| &msg_borrow, |
| None, |
| ) |
| } |
| } |
| |
| (BorrowKind::Unique, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_one_closure( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| issued_span, |
| "it", |
| "", |
| None, |
| ) |
| } |
| |
| (BorrowKind::Shared, BorrowKind::Unique) => { |
| first_borrow_desc = "first "; |
| self.cannot_reborrow_already_uniquely_borrowed( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| "immutable", |
| issued_span, |
| "", |
| None, |
| second_borrow_desc, |
| ) |
| } |
| |
| (BorrowKind::Mut { .. }, BorrowKind::Unique) => { |
| first_borrow_desc = "first "; |
| self.cannot_reborrow_already_uniquely_borrowed( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| "mutable", |
| issued_span, |
| "", |
| None, |
| second_borrow_desc, |
| ) |
| } |
| |
| (BorrowKind::Shared, BorrowKind::Shared | BorrowKind::Shallow) |
| | ( |
| BorrowKind::Shallow, |
| BorrowKind::Mut { .. } |
| | BorrowKind::Unique |
| | BorrowKind::Shared |
| | BorrowKind::Shallow, |
| ) => unreachable!(), |
| }; |
| |
| if issued_spans == borrow_spans { |
| borrow_spans.var_span_label( |
| &mut err, |
| format!("borrows occur due to use of {}{}", desc_place, borrow_spans.describe(),), |
| gen_borrow_kind.describe_mutability(), |
| ); |
| } else { |
| let borrow_place = &issued_borrow.borrowed_place; |
| let borrow_place_desc = self.describe_any_place(borrow_place.as_ref()); |
| issued_spans.var_span_label( |
| &mut err, |
| format!( |
| "first borrow occurs due to use of {}{}", |
| borrow_place_desc, |
| issued_spans.describe(), |
| ), |
| issued_borrow.kind.describe_mutability(), |
| ); |
| |
| borrow_spans.var_span_label( |
| &mut err, |
| format!( |
| "second borrow occurs due to use of {}{}", |
| desc_place, |
| borrow_spans.describe(), |
| ), |
| gen_borrow_kind.describe_mutability(), |
| ); |
| } |
| |
| if union_type_name != "" { |
| err.note(&format!( |
| "{} is a field of the union `{}`, so it overlaps the field {}", |
| msg_place, union_type_name, msg_borrow, |
| )); |
| } |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| first_borrow_desc, |
| None, |
| Some((issued_span, span)), |
| ); |
| |
| self.suggest_using_local_if_applicable(&mut err, location, issued_borrow, explanation); |
| |
| err |
| } |
| |
| #[instrument(level = "debug", skip(self, err))] |
| fn suggest_using_local_if_applicable( |
| &self, |
| err: &mut Diagnostic, |
| location: Location, |
| issued_borrow: &BorrowData<'tcx>, |
| explanation: BorrowExplanation, |
| ) { |
| let used_in_call = matches!( |
| explanation, |
| BorrowExplanation::UsedLater(LaterUseKind::Call | LaterUseKind::Other, _call_span, _) |
| ); |
| if !used_in_call { |
| debug!("not later used in call"); |
| return; |
| } |
| |
| let use_span = |
| if let BorrowExplanation::UsedLater(LaterUseKind::Other, use_span, _) = explanation { |
| Some(use_span) |
| } else { |
| None |
| }; |
| |
| let outer_call_loc = |
| if let TwoPhaseActivation::ActivatedAt(loc) = issued_borrow.activation_location { |
| loc |
| } else { |
| issued_borrow.reserve_location |
| }; |
| let outer_call_stmt = self.body.stmt_at(outer_call_loc); |
| |
| let inner_param_location = location; |
| let Some(inner_param_stmt) = self.body.stmt_at(inner_param_location).left() else { |
| debug!("`inner_param_location` {:?} is not for a statement", inner_param_location); |
| return; |
| }; |
| let Some(&inner_param) = inner_param_stmt.kind.as_assign().map(|(p, _)| p) else { |
| debug!( |
| "`inner_param_location` {:?} is not for an assignment: {:?}", |
| inner_param_location, inner_param_stmt |
| ); |
| return; |
| }; |
| let inner_param_uses = find_all_local_uses::find(self.body, inner_param.local); |
| let Some((inner_call_loc, inner_call_term)) = inner_param_uses.into_iter().find_map(|loc| { |
| let Either::Right(term) = self.body.stmt_at(loc) else { |
| debug!("{:?} is a statement, so it can't be a call", loc); |
| return None; |
| }; |
| let TerminatorKind::Call { args, .. } = &term.kind else { |
| debug!("not a call: {:?}", term); |
| return None; |
| }; |
| debug!("checking call args for uses of inner_param: {:?}", args); |
| if args.contains(&Operand::Move(inner_param)) { |
| Some((loc, term)) |
| } else { |
| None |
| } |
| }) else { |
| debug!("no uses of inner_param found as a by-move call arg"); |
| return; |
| }; |
| debug!("===> outer_call_loc = {:?}, inner_call_loc = {:?}", outer_call_loc, inner_call_loc); |
| |
| let inner_call_span = inner_call_term.source_info.span; |
| let outer_call_span = match use_span { |
| Some(span) => span, |
| None => outer_call_stmt.either(|s| s.source_info, |t| t.source_info).span, |
| }; |
| if outer_call_span == inner_call_span || !outer_call_span.contains(inner_call_span) { |
| // FIXME: This stops the suggestion in some cases where it should be emitted. |
| // Fix the spans for those cases so it's emitted correctly. |
| debug!( |
| "outer span {:?} does not strictly contain inner span {:?}", |
| outer_call_span, inner_call_span |
| ); |
| return; |
| } |
| err.span_help( |
| inner_call_span, |
| &format!( |
| "try adding a local storing this{}...", |
| if use_span.is_some() { "" } else { " argument" } |
| ), |
| ); |
| err.span_help( |
| outer_call_span, |
| &format!( |
| "...and then using that local {}", |
| if use_span.is_some() { "here" } else { "as the argument to this call" } |
| ), |
| ); |
| } |
| |
| fn suggest_split_at_mut_if_applicable( |
| &self, |
| err: &mut Diagnostic, |
| place: Place<'tcx>, |
| borrowed_place: Place<'tcx>, |
| ) { |
| if let ([ProjectionElem::Index(_)], [ProjectionElem::Index(_)]) = |
| (&place.projection[..], &borrowed_place.projection[..]) |
| { |
| err.help( |
| "consider using `.split_at_mut(position)` or similar method to obtain \ |
| two mutable non-overlapping sub-slices", |
| ); |
| } |
| } |
| |
| /// Returns the description of the root place for a conflicting borrow and the full |
| /// descriptions of the places that caused the conflict. |
| /// |
| /// In the simplest case, where there are no unions involved, if a mutable borrow of `x` is |
| /// attempted while a shared borrow is live, then this function will return: |
| /// ``` |
| /// ("x", "", "") |
| /// # ; |
| /// ``` |
| /// In the simple union case, if a mutable borrow of a union field `x.z` is attempted while |
| /// a shared borrow of another field `x.y`, then this function will return: |
| /// ``` |
| /// ("x", "x.z", "x.y") |
| /// # ; |
| /// ``` |
| /// In the more complex union case, where the union is a field of a struct, then if a mutable |
| /// borrow of a union field in a struct `x.u.z` is attempted while a shared borrow of |
| /// another field `x.u.y`, then this function will return: |
| /// ``` |
| /// ("x.u", "x.u.z", "x.u.y") |
| /// # ; |
| /// ``` |
| /// This is used when creating error messages like below: |
| /// |
| /// ```text |
| /// cannot borrow `a.u` (via `a.u.z.c`) as immutable because it is also borrowed as |
| /// mutable (via `a.u.s.b`) [E0502] |
| /// ``` |
| pub(crate) fn describe_place_for_conflicting_borrow( |
| &self, |
| first_borrowed_place: Place<'tcx>, |
| second_borrowed_place: Place<'tcx>, |
| ) -> (String, String, String, String) { |
| // Define a small closure that we can use to check if the type of a place |
| // is a union. |
| let union_ty = |place_base| { |
| // Need to use fn call syntax `PlaceRef::ty` to determine the type of `place_base`; |
| // using a type annotation in the closure argument instead leads to a lifetime error. |
| let ty = PlaceRef::ty(&place_base, self.body, self.infcx.tcx).ty; |
| ty.ty_adt_def().filter(|adt| adt.is_union()).map(|_| ty) |
| }; |
| |
| // Start with an empty tuple, so we can use the functions on `Option` to reduce some |
| // code duplication (particularly around returning an empty description in the failure |
| // case). |
| Some(()) |
| .filter(|_| { |
| // If we have a conflicting borrow of the same place, then we don't want to add |
| // an extraneous "via x.y" to our diagnostics, so filter out this case. |
| first_borrowed_place != second_borrowed_place |
| }) |
| .and_then(|_| { |
| // We're going to want to traverse the first borrowed place to see if we can find |
| // field access to a union. If we find that, then we will keep the place of the |
| // union being accessed and the field that was being accessed so we can check the |
| // second borrowed place for the same union and an access to a different field. |
| for (place_base, elem) in first_borrowed_place.iter_projections().rev() { |
| match elem { |
| ProjectionElem::Field(field, _) if union_ty(place_base).is_some() => { |
| return Some((place_base, field)); |
| } |
| _ => {} |
| } |
| } |
| None |
| }) |
| .and_then(|(target_base, target_field)| { |
| // With the place of a union and a field access into it, we traverse the second |
| // borrowed place and look for an access to a different field of the same union. |
| for (place_base, elem) in second_borrowed_place.iter_projections().rev() { |
| if let ProjectionElem::Field(field, _) = elem { |
| if let Some(union_ty) = union_ty(place_base) { |
| if field != target_field && place_base == target_base { |
| return Some(( |
| self.describe_any_place(place_base), |
| self.describe_any_place(first_borrowed_place.as_ref()), |
| self.describe_any_place(second_borrowed_place.as_ref()), |
| union_ty.to_string(), |
| )); |
| } |
| } |
| } |
| } |
| None |
| }) |
| .unwrap_or_else(|| { |
| // If we didn't find a field access into a union, or both places match, then |
| // only return the description of the first place. |
| ( |
| self.describe_any_place(first_borrowed_place.as_ref()), |
| "".to_string(), |
| "".to_string(), |
| "".to_string(), |
| ) |
| }) |
| } |
| |
| /// Reports StorageDeadOrDrop of `place` conflicts with `borrow`. |
| /// |
| /// This means that some data referenced by `borrow` needs to live |
| /// past the point where the StorageDeadOrDrop of `place` occurs. |
| /// This is usually interpreted as meaning that `place` has too |
| /// short a lifetime. (But sometimes it is more useful to report |
| /// it as a more direct conflict between the execution of a |
| /// `Drop::drop` with an aliasing borrow.) |
| pub(crate) fn report_borrowed_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| borrow: &BorrowData<'tcx>, |
| place_span: (Place<'tcx>, Span), |
| kind: Option<WriteKind>, |
| ) { |
| debug!( |
| "report_borrowed_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, borrow, place_span, kind |
| ); |
| |
| let drop_span = place_span.1; |
| let root_place = |
| self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap(); |
| |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.var_or_use_path_span(); |
| |
| assert!(root_place.projection.is_empty()); |
| let proper_span = self.body.local_decls[root_place.local].source_info.span; |
| |
| let root_place_projection = self.infcx.tcx.intern_place_elems(root_place.projection); |
| |
| if self.access_place_error_reported.contains(&( |
| Place { local: root_place.local, projection: root_place_projection }, |
| borrow_span, |
| )) { |
| debug!( |
| "suppressing access_place error when borrow doesn't live long enough for {:?}", |
| borrow_span |
| ); |
| return; |
| } |
| |
| self.access_place_error_reported.insert(( |
| Place { local: root_place.local, projection: root_place_projection }, |
| borrow_span, |
| )); |
| |
| let borrowed_local = borrow.borrowed_place.local; |
| if self.body.local_decls[borrowed_local].is_ref_to_thread_local() { |
| let err = |
| self.report_thread_local_value_does_not_live_long_enough(drop_span, borrow_span); |
| self.buffer_error(err); |
| return; |
| } |
| |
| if let StorageDeadOrDrop::Destructor(dropped_ty) = |
| self.classify_drop_access_kind(borrow.borrowed_place.as_ref()) |
| { |
| // If a borrow of path `B` conflicts with drop of `D` (and |
| // we're not in the uninteresting case where `B` is a |
| // prefix of `D`), then report this as a more interesting |
| // destructor conflict. |
| if !borrow.borrowed_place.as_ref().is_prefix_of(place_span.0.as_ref()) { |
| self.report_borrow_conflicts_with_destructor( |
| location, borrow, place_span, kind, dropped_ty, |
| ); |
| return; |
| } |
| } |
| |
| let place_desc = self.describe_place(borrow.borrowed_place.as_ref()); |
| |
| let kind_place = kind.filter(|_| place_desc.is_some()).map(|k| (k, place_span.0)); |
| let explanation = self.explain_why_borrow_contains_point(location, &borrow, kind_place); |
| |
| debug!( |
| "report_borrowed_value_does_not_live_long_enough(place_desc: {:?}, explanation: {:?})", |
| place_desc, explanation |
| ); |
| let err = match (place_desc, explanation) { |
| // If the outlives constraint comes from inside the closure, |
| // for example: |
| // |
| // let x = 0; |
| // let y = &x; |
| // Box::new(|| y) as Box<Fn() -> &'static i32> |
| // |
| // then just use the normal error. The closure isn't escaping |
| // and `move` will not help here. |
| ( |
| Some(ref name), |
| BorrowExplanation::MustBeValidFor { |
| category: |
| category @ (ConstraintCategory::Return(_) |
| | ConstraintCategory::CallArgument |
| | ConstraintCategory::OpaqueType), |
| from_closure: false, |
| ref region_name, |
| span, |
| .. |
| }, |
| ) if borrow_spans.for_generator() | borrow_spans.for_closure() => self |
| .report_escaping_closure_capture( |
| borrow_spans, |
| borrow_span, |
| region_name, |
| category, |
| span, |
| &format!("`{}`", name), |
| ), |
| ( |
| ref name, |
| BorrowExplanation::MustBeValidFor { |
| category: ConstraintCategory::Assignment, |
| from_closure: false, |
| region_name: |
| RegionName { |
| source: |
| RegionNameSource::AnonRegionFromUpvar(upvar_span, ref upvar_name), |
| .. |
| }, |
| span, |
| .. |
| }, |
| ) => self.report_escaping_data(borrow_span, name, upvar_span, upvar_name, span), |
| (Some(name), explanation) => self.report_local_value_does_not_live_long_enough( |
| location, |
| &name, |
| &borrow, |
| drop_span, |
| borrow_spans, |
| explanation, |
| ), |
| (None, explanation) => self.report_temporary_value_does_not_live_long_enough( |
| location, |
| &borrow, |
| drop_span, |
| borrow_spans, |
| proper_span, |
| explanation, |
| ), |
| }; |
| |
| self.buffer_error(err); |
| } |
| |
| fn report_local_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| name: &str, |
| borrow: &BorrowData<'tcx>, |
| drop_span: Span, |
| borrow_spans: UseSpans<'tcx>, |
| explanation: BorrowExplanation, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| debug!( |
| "report_local_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, name, borrow, drop_span, borrow_spans |
| ); |
| |
| let borrow_span = borrow_spans.var_or_use_path_span(); |
| if let BorrowExplanation::MustBeValidFor { |
| category, |
| span, |
| ref opt_place_desc, |
| from_closure: false, |
| .. |
| } = explanation |
| { |
| if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
| borrow, |
| borrow_span, |
| span, |
| category, |
| opt_place_desc.as_ref(), |
| ) { |
| return diag; |
| } |
| } |
| |
| let mut err = self.path_does_not_live_long_enough(borrow_span, &format!("`{}`", name)); |
| |
| if let Some(annotation) = self.annotate_argument_and_return_for_borrow(borrow) { |
| let region_name = annotation.emit(self, &mut err); |
| |
| err.span_label( |
| borrow_span, |
| format!("`{}` would have to be valid for `{}`...", name, region_name), |
| ); |
| |
| let fn_hir_id = self.mir_hir_id(); |
| err.span_label( |
| drop_span, |
| format!( |
| "...but `{}` will be dropped here, when the {} returns", |
| name, |
| self.infcx |
| .tcx |
| .hir() |
| .opt_name(fn_hir_id) |
| .map(|name| format!("function `{}`", name)) |
| .unwrap_or_else(|| { |
| match &self |
| .infcx |
| .tcx |
| .typeck(self.mir_def_id()) |
| .node_type(fn_hir_id) |
| .kind() |
| { |
| ty::Closure(..) => "enclosing closure", |
| ty::Generator(..) => "enclosing generator", |
| kind => bug!("expected closure or generator, found {:?}", kind), |
| } |
| .to_string() |
| }) |
| ), |
| ); |
| |
| err.note( |
| "functions cannot return a borrow to data owned within the function's scope, \ |
| functions can only return borrows to data passed as arguments", |
| ); |
| err.note( |
| "to learn more, visit <https://doc.rust-lang.org/book/ch04-02-\ |
| references-and-borrowing.html#dangling-references>", |
| ); |
| |
| if let BorrowExplanation::MustBeValidFor { .. } = explanation { |
| } else { |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| } |
| } else { |
| err.span_label(borrow_span, "borrowed value does not live long enough"); |
| err.span_label(drop_span, format!("`{}` dropped here while still borrowed", name)); |
| |
| let within = if borrow_spans.for_generator() { " by generator" } else { "" }; |
| |
| borrow_spans.args_span_label(&mut err, format!("value captured here{}", within)); |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| } |
| |
| err |
| } |
| |
| fn report_borrow_conflicts_with_destructor( |
| &mut self, |
| location: Location, |
| borrow: &BorrowData<'tcx>, |
| (place, drop_span): (Place<'tcx>, Span), |
| kind: Option<WriteKind>, |
| dropped_ty: Ty<'tcx>, |
| ) { |
| debug!( |
| "report_borrow_conflicts_with_destructor(\ |
| {:?}, {:?}, ({:?}, {:?}), {:?}\ |
| )", |
| location, borrow, place, drop_span, kind, |
| ); |
| |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.var_or_use(); |
| |
| let mut err = self.cannot_borrow_across_destructor(borrow_span); |
| |
| let what_was_dropped = match self.describe_place(place.as_ref()) { |
| Some(name) => format!("`{}`", name), |
| None => String::from("temporary value"), |
| }; |
| |
| let label = match self.describe_place(borrow.borrowed_place.as_ref()) { |
| Some(borrowed) => format!( |
| "here, drop of {D} needs exclusive access to `{B}`, \ |
| because the type `{T}` implements the `Drop` trait", |
| D = what_was_dropped, |
| T = dropped_ty, |
| B = borrowed |
| ), |
| None => format!( |
| "here is drop of {D}; whose type `{T}` implements the `Drop` trait", |
| D = what_was_dropped, |
| T = dropped_ty |
| ), |
| }; |
| err.span_label(drop_span, label); |
| |
| // Only give this note and suggestion if they could be relevant. |
| let explanation = |
| self.explain_why_borrow_contains_point(location, borrow, kind.map(|k| (k, place))); |
| match explanation { |
| BorrowExplanation::UsedLater { .. } |
| | BorrowExplanation::UsedLaterWhenDropped { .. } => { |
| err.note("consider using a `let` binding to create a longer lived value"); |
| } |
| _ => {} |
| } |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| |
| self.buffer_error(err); |
| } |
| |
| fn report_thread_local_value_does_not_live_long_enough( |
| &mut self, |
| drop_span: Span, |
| borrow_span: Span, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| debug!( |
| "report_thread_local_value_does_not_live_long_enough(\ |
| {:?}, {:?}\ |
| )", |
| drop_span, borrow_span |
| ); |
| |
| let mut err = self.thread_local_value_does_not_live_long_enough(borrow_span); |
| |
| err.span_label( |
| borrow_span, |
| "thread-local variables cannot be borrowed beyond the end of the function", |
| ); |
| err.span_label(drop_span, "end of enclosing function is here"); |
| |
| err |
| } |
| |
| fn report_temporary_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| borrow: &BorrowData<'tcx>, |
| drop_span: Span, |
| borrow_spans: UseSpans<'tcx>, |
| proper_span: Span, |
| explanation: BorrowExplanation, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| debug!( |
| "report_temporary_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, borrow, drop_span, proper_span |
| ); |
| |
| if let BorrowExplanation::MustBeValidFor { category, span, from_closure: false, .. } = |
| explanation |
| { |
| if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
| borrow, |
| proper_span, |
| span, |
| category, |
| None, |
| ) { |
| return diag; |
| } |
| } |
| |
| let mut err = self.temporary_value_borrowed_for_too_long(proper_span); |
| err.span_label(proper_span, "creates a temporary which is freed while still in use"); |
| err.span_label(drop_span, "temporary value is freed at the end of this statement"); |
| |
| match explanation { |
| BorrowExplanation::UsedLater(..) |
| | BorrowExplanation::UsedLaterInLoop(..) |
| | BorrowExplanation::UsedLaterWhenDropped { .. } => { |
| // Only give this note and suggestion if it could be relevant. |
| err.note("consider using a `let` binding to create a longer lived value"); |
| } |
| _ => {} |
| } |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| |
| let within = if borrow_spans.for_generator() { " by generator" } else { "" }; |
| |
| borrow_spans.args_span_label(&mut err, format!("value captured here{}", within)); |
| |
| err |
| } |
| |
| fn try_report_cannot_return_reference_to_local( |
| &self, |
| borrow: &BorrowData<'tcx>, |
| borrow_span: Span, |
| return_span: Span, |
| category: ConstraintCategory, |
| opt_place_desc: Option<&String>, |
| ) -> Option<DiagnosticBuilder<'cx, ErrorGuaranteed>> { |
| let return_kind = match category { |
| ConstraintCategory::Return(_) => "return", |
| ConstraintCategory::Yield => "yield", |
| _ => return None, |
| }; |
| |
| // FIXME use a better heuristic than Spans |
| let reference_desc = if return_span == self.body.source_info(borrow.reserve_location).span { |
| "reference to" |
| } else { |
| "value referencing" |
| }; |
| |
| let (place_desc, note) = if let Some(place_desc) = opt_place_desc { |
| let local_kind = if let Some(local) = borrow.borrowed_place.as_local() { |
| match self.body.local_kind(local) { |
| LocalKind::ReturnPointer | LocalKind::Temp => { |
| bug!("temporary or return pointer with a name") |
| } |
| LocalKind::Var => "local variable ", |
| LocalKind::Arg |
| if !self.upvars.is_empty() && local == ty::CAPTURE_STRUCT_LOCAL => |
| { |
| "variable captured by `move` " |
| } |
| LocalKind::Arg => "function parameter ", |
| } |
| } else { |
| "local data " |
| }; |
| ( |
| format!("{}`{}`", local_kind, place_desc), |
| format!("`{}` is borrowed here", place_desc), |
| ) |
| } else { |
| let root_place = |
| self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap(); |
| let local = root_place.local; |
| match self.body.local_kind(local) { |
| LocalKind::ReturnPointer | LocalKind::Temp => { |
| ("temporary value".to_string(), "temporary value created here".to_string()) |
| } |
| LocalKind::Arg => ( |
| "function parameter".to_string(), |
| "function parameter borrowed here".to_string(), |
| ), |
| LocalKind::Var => { |
| ("local binding".to_string(), "local binding introduced here".to_string()) |
| } |
| } |
| }; |
| |
| let mut err = self.cannot_return_reference_to_local( |
| return_span, |
| return_kind, |
| reference_desc, |
| &place_desc, |
| ); |
| |
| if return_span != borrow_span { |
| err.span_label(borrow_span, note); |
| |
| let tcx = self.infcx.tcx; |
| let ty_params = ty::List::empty(); |
| |
| let return_ty = self.regioncx.universal_regions().unnormalized_output_ty; |
| let return_ty = tcx.erase_regions(return_ty); |
| |
| // to avoid panics |
| if let Some(iter_trait) = tcx.get_diagnostic_item(sym::Iterator) { |
| if self |
| .infcx |
| .type_implements_trait(iter_trait, return_ty, ty_params, self.param_env) |
| .must_apply_modulo_regions() |
| { |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(return_span) { |
| err.span_suggestion_hidden( |
| return_span, |
| "use `.collect()` to allocate the iterator", |
| format!("{snippet}.collect::<Vec<_>>()"), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| } |
| } |
| |
| Some(err) |
| } |
| |
| fn report_escaping_closure_capture( |
| &mut self, |
| use_span: UseSpans<'tcx>, |
| var_span: Span, |
| fr_name: &RegionName, |
| category: ConstraintCategory, |
| constraint_span: Span, |
| captured_var: &str, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| let tcx = self.infcx.tcx; |
| let args_span = use_span.args_or_use(); |
| |
| let (sugg_span, suggestion) = match tcx.sess.source_map().span_to_snippet(args_span) { |
| Ok(string) => { |
| if string.starts_with("async ") { |
| let pos = args_span.lo() + BytePos(6); |
| (args_span.with_lo(pos).with_hi(pos), "move ".to_string()) |
| } else if string.starts_with("async|") { |
| let pos = args_span.lo() + BytePos(5); |
| (args_span.with_lo(pos).with_hi(pos), " move".to_string()) |
| } else { |
| (args_span.shrink_to_lo(), "move ".to_string()) |
| } |
| } |
| Err(_) => (args_span, "move |<args>| <body>".to_string()), |
| }; |
| let kind = match use_span.generator_kind() { |
| Some(generator_kind) => match generator_kind { |
| GeneratorKind::Async(async_kind) => match async_kind { |
| AsyncGeneratorKind::Block => "async block", |
| AsyncGeneratorKind::Closure => "async closure", |
| _ => bug!("async block/closure expected, but async function found."), |
| }, |
| GeneratorKind::Gen => "generator", |
| }, |
| None => "closure", |
| }; |
| |
| let mut err = |
| self.cannot_capture_in_long_lived_closure(args_span, kind, captured_var, var_span); |
| err.span_suggestion_verbose( |
| sugg_span, |
| &format!( |
| "to force the {} to take ownership of {} (and any \ |
| other referenced variables), use the `move` keyword", |
| kind, captured_var |
| ), |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| |
| match category { |
| ConstraintCategory::Return(_) | ConstraintCategory::OpaqueType => { |
| let msg = format!("{} is returned here", kind); |
| err.span_note(constraint_span, &msg); |
| } |
| ConstraintCategory::CallArgument => { |
| fr_name.highlight_region_name(&mut err); |
| if matches!(use_span.generator_kind(), Some(GeneratorKind::Async(_))) { |
| err.note( |
| "async blocks are not executed immediately and must either take a \ |
| reference or ownership of outside variables they use", |
| ); |
| } else { |
| let msg = format!("function requires argument type to outlive `{}`", fr_name); |
| err.span_note(constraint_span, &msg); |
| } |
| } |
| _ => bug!( |
| "report_escaping_closure_capture called with unexpected constraint \ |
| category: `{:?}`", |
| category |
| ), |
| } |
| |
| err |
| } |
| |
| fn report_escaping_data( |
| &mut self, |
| borrow_span: Span, |
| name: &Option<String>, |
| upvar_span: Span, |
| upvar_name: &str, |
| escape_span: Span, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| let tcx = self.infcx.tcx; |
| |
| let (_, escapes_from) = tcx.article_and_description(self.mir_def_id().to_def_id()); |
| |
| let mut err = |
| borrowck_errors::borrowed_data_escapes_closure(tcx, escape_span, escapes_from); |
| |
| err.span_label( |
| upvar_span, |
| format!("`{}` declared here, outside of the {} body", upvar_name, escapes_from), |
| ); |
| |
| err.span_label(borrow_span, format!("borrow is only valid in the {} body", escapes_from)); |
| |
| if let Some(name) = name { |
| err.span_label( |
| escape_span, |
| format!("reference to `{}` escapes the {} body here", name, escapes_from), |
| ); |
| } else { |
| err.span_label( |
| escape_span, |
| format!("reference escapes the {} body here", escapes_from), |
| ); |
| } |
| |
| err |
| } |
| |
| fn get_moved_indexes( |
| &mut self, |
| location: Location, |
| mpi: MovePathIndex, |
| ) -> (Vec<MoveSite>, Vec<Location>) { |
| fn predecessor_locations<'a>( |
| body: &'a mir::Body<'_>, |
| location: Location, |
| ) -> impl Iterator<Item = Location> + 'a { |
| if location.statement_index == 0 { |
| let predecessors = body.predecessors()[location.block].to_vec(); |
| Either::Left(predecessors.into_iter().map(move |bb| body.terminator_loc(bb))) |
| } else { |
| Either::Right(std::iter::once(Location { |
| statement_index: location.statement_index - 1, |
| ..location |
| })) |
| } |
| } |
| |
| let mut mpis = vec![mpi]; |
| let move_paths = &self.move_data.move_paths; |
| mpis.extend(move_paths[mpi].parents(move_paths).map(|(mpi, _)| mpi)); |
| |
| let mut stack = Vec::new(); |
| let mut back_edge_stack = Vec::new(); |
| |
| predecessor_locations(self.body, location).for_each(|predecessor| { |
| if location.dominates(predecessor, &self.dominators) { |
| back_edge_stack.push(predecessor) |
| } else { |
| stack.push(predecessor); |
| } |
| }); |
| |
| let mut reached_start = false; |
| |
| /* Check if the mpi is initialized as an argument */ |
| let mut is_argument = false; |
| for arg in self.body.args_iter() { |
| let path = self.move_data.rev_lookup.find_local(arg); |
| if mpis.contains(&path) { |
| is_argument = true; |
| } |
| } |
| |
| let mut visited = FxHashSet::default(); |
| let mut move_locations = FxHashSet::default(); |
| let mut reinits = vec![]; |
| let mut result = vec![]; |
| |
| let mut dfs_iter = |result: &mut Vec<MoveSite>, location: Location, is_back_edge: bool| { |
| debug!( |
| "report_use_of_moved_or_uninitialized: (current_location={:?}, back_edge={})", |
| location, is_back_edge |
| ); |
| |
| if !visited.insert(location) { |
| return true; |
| } |
| |
| // check for moves |
| let stmt_kind = |
| self.body[location.block].statements.get(location.statement_index).map(|s| &s.kind); |
| if let Some(StatementKind::StorageDead(..)) = stmt_kind { |
| // this analysis only tries to find moves explicitly |
| // written by the user, so we ignore the move-outs |
| // created by `StorageDead` and at the beginning |
| // of a function. |
| } else { |
| // If we are found a use of a.b.c which was in error, then we want to look for |
| // moves not only of a.b.c but also a.b and a. |
| // |
| // Note that the moves data already includes "parent" paths, so we don't have to |
| // worry about the other case: that is, if there is a move of a.b.c, it is already |
| // marked as a move of a.b and a as well, so we will generate the correct errors |
| // there. |
| for moi in &self.move_data.loc_map[location] { |
| debug!("report_use_of_moved_or_uninitialized: moi={:?}", moi); |
| let path = self.move_data.moves[*moi].path; |
| if mpis.contains(&path) { |
| debug!( |
| "report_use_of_moved_or_uninitialized: found {:?}", |
| move_paths[path].place |
| ); |
| result.push(MoveSite { moi: *moi, traversed_back_edge: is_back_edge }); |
| move_locations.insert(location); |
| |
| // Strictly speaking, we could continue our DFS here. There may be |
| // other moves that can reach the point of error. But it is kind of |
| // confusing to highlight them. |
| // |
| // Example: |
| // |
| // ``` |
| // let a = vec![]; |
| // let b = a; |
| // let c = a; |
| // drop(a); // <-- current point of error |
| // ``` |
| // |
| // Because we stop the DFS here, we only highlight `let c = a`, |
| // and not `let b = a`. We will of course also report an error at |
| // `let c = a` which highlights `let b = a` as the move. |
| return true; |
| } |
| } |
| } |
| |
| // check for inits |
| let mut any_match = false; |
| for ii in &self.move_data.init_loc_map[location] { |
| let init = self.move_data.inits[*ii]; |
| match init.kind { |
| InitKind::Deep | InitKind::NonPanicPathOnly => { |
| if mpis.contains(&init.path) { |
| any_match = true; |
| } |
| } |
| InitKind::Shallow => { |
| if mpi == init.path { |
| any_match = true; |
| } |
| } |
| } |
| } |
| if any_match { |
| reinits.push(location); |
| return true; |
| } |
| return false; |
| }; |
| |
| while let Some(location) = stack.pop() { |
| if dfs_iter(&mut result, location, false) { |
| continue; |
| } |
| |
| let mut has_predecessor = false; |
| predecessor_locations(self.body, location).for_each(|predecessor| { |
| if location.dominates(predecessor, &self.dominators) { |
| back_edge_stack.push(predecessor) |
| } else { |
| stack.push(predecessor); |
| } |
| has_predecessor = true; |
| }); |
| |
| if !has_predecessor { |
| reached_start = true; |
| } |
| } |
| if (is_argument || !reached_start) && result.is_empty() { |
| /* Process back edges (moves in future loop iterations) only if |
| the move path is definitely initialized upon loop entry, |
| to avoid spurious "in previous iteration" errors. |
| During DFS, if there's a path from the error back to the start |
| of the function with no intervening init or move, then the |
| move path may be uninitialized at loop entry. |
| */ |
| while let Some(location) = back_edge_stack.pop() { |
| if dfs_iter(&mut result, location, true) { |
| continue; |
| } |
| |
| predecessor_locations(self.body, location) |
| .for_each(|predecessor| back_edge_stack.push(predecessor)); |
| } |
| } |
| |
| // Check if we can reach these reinits from a move location. |
| let reinits_reachable = reinits |
| .into_iter() |
| .filter(|reinit| { |
| let mut visited = FxHashSet::default(); |
| let mut stack = vec![*reinit]; |
| while let Some(location) = stack.pop() { |
| if !visited.insert(location) { |
| continue; |
| } |
| if move_locations.contains(&location) { |
| return true; |
| } |
| stack.extend(predecessor_locations(self.body, location)); |
| } |
| false |
| }) |
| .collect::<Vec<Location>>(); |
| (result, reinits_reachable) |
| } |
| |
| pub(crate) fn report_illegal_mutation_of_borrowed( |
| &mut self, |
| location: Location, |
| (place, span): (Place<'tcx>, Span), |
| loan: &BorrowData<'tcx>, |
| ) { |
| let loan_spans = self.retrieve_borrow_spans(loan); |
| let loan_span = loan_spans.args_or_use(); |
| |
| let descr_place = self.describe_any_place(place.as_ref()); |
| if loan.kind == BorrowKind::Shallow { |
| if let Some(section) = self.classify_immutable_section(loan.assigned_place) { |
| let mut err = self.cannot_mutate_in_immutable_section( |
| span, |
| loan_span, |
| &descr_place, |
| section, |
| "assign", |
| ); |
| loan_spans.var_span_label( |
| &mut err, |
| format!("borrow occurs due to use{}", loan_spans.describe()), |
| loan.kind.describe_mutability(), |
| ); |
| |
| self.buffer_error(err); |
| |
| return; |
| } |
| } |
| |
| let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place); |
| |
| loan_spans.var_span_label( |
| &mut err, |
| format!("borrow occurs due to use{}", loan_spans.describe()), |
| loan.kind.describe_mutability(), |
| ); |
| |
| self.explain_why_borrow_contains_point(location, loan, None).add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| |
| self.explain_deref_coercion(loan, &mut err); |
| |
| self.buffer_error(err); |
| } |
| |
| fn explain_deref_coercion(&mut self, loan: &BorrowData<'tcx>, err: &mut Diagnostic) { |
| let tcx = self.infcx.tcx; |
| if let ( |
| Some(Terminator { kind: TerminatorKind::Call { from_hir_call: false, .. }, .. }), |
| Some((method_did, method_substs)), |
| ) = ( |
| &self.body[loan.reserve_location.block].terminator, |
| rustc_const_eval::util::find_self_call( |
| tcx, |
| self.body, |
| loan.assigned_place.local, |
| loan.reserve_location.block, |
| ), |
| ) { |
| if tcx.is_diagnostic_item(sym::deref_method, method_did) { |
| let deref_target = |
| tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| { |
| Instance::resolve(tcx, self.param_env, deref_target, method_substs) |
| .transpose() |
| }); |
| if let Some(Ok(instance)) = deref_target { |
| let deref_target_ty = instance.ty(tcx, self.param_env); |
| err.note(&format!( |
| "borrow occurs due to deref coercion to `{}`", |
| deref_target_ty |
| )); |
| err.span_note(tcx.def_span(instance.def_id()), "deref defined here"); |
| } |
| } |
| } |
| } |
| |
| /// Reports an illegal reassignment; for example, an assignment to |
| /// (part of) a non-`mut` local that occurs potentially after that |
| /// local has already been initialized. `place` is the path being |
| /// assigned; `err_place` is a place providing a reason why |
| /// `place` is not mutable (e.g., the non-`mut` local `x` in an |
| /// assignment to `x.f`). |
| pub(crate) fn report_illegal_reassignment( |
| &mut self, |
| _location: Location, |
| (place, span): (Place<'tcx>, Span), |
| assigned_span: Span, |
| err_place: Place<'tcx>, |
| ) { |
| let (from_arg, local_decl, local_name) = match err_place.as_local() { |
| Some(local) => ( |
| self.body.local_kind(local) == LocalKind::Arg, |
| Some(&self.body.local_decls[local]), |
| self.local_names[local], |
| ), |
| None => (false, None, None), |
| }; |
| |
| // If root local is initialized immediately (everything apart from let |
| // PATTERN;) then make the error refer to that local, rather than the |
| // place being assigned later. |
| let (place_description, assigned_span) = match local_decl { |
| Some(LocalDecl { |
| local_info: |
| Some(box LocalInfo::User( |
| ClearCrossCrate::Clear |
| | ClearCrossCrate::Set(BindingForm::Var(VarBindingForm { |
| opt_match_place: None, |
| .. |
| })), |
| )) |
| | Some(box LocalInfo::StaticRef { .. }) |
| | None, |
| .. |
| }) |
| | None => (self.describe_any_place(place.as_ref()), assigned_span), |
| Some(decl) => (self.describe_any_place(err_place.as_ref()), decl.source_info.span), |
| }; |
| |
| let mut err = self.cannot_reassign_immutable(span, &place_description, from_arg); |
| let msg = if from_arg { |
| "cannot assign to immutable argument" |
| } else { |
| "cannot assign twice to immutable variable" |
| }; |
| if span != assigned_span && !from_arg { |
| err.span_label(assigned_span, format!("first assignment to {}", place_description)); |
| } |
| if let Some(decl) = local_decl |
| && let Some(name) = local_name |
| && decl.can_be_made_mutable() |
| { |
| err.span_suggestion( |
| decl.source_info.span, |
| "consider making this binding mutable", |
| format!("mut {}", name), |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.span_label(span, msg); |
| self.buffer_error(err); |
| } |
| |
| fn classify_drop_access_kind(&self, place: PlaceRef<'tcx>) -> StorageDeadOrDrop<'tcx> { |
| let tcx = self.infcx.tcx; |
| let (kind, _place_ty) = place.projection.iter().fold( |
| (LocalStorageDead, PlaceTy::from_ty(self.body.local_decls[place.local].ty)), |
| |(kind, place_ty), &elem| { |
| ( |
| match elem { |
| ProjectionElem::Deref => match kind { |
| StorageDeadOrDrop::LocalStorageDead |
| | StorageDeadOrDrop::BoxedStorageDead => { |
| assert!( |
| place_ty.ty.is_box(), |
| "Drop of value behind a reference or raw pointer" |
| ); |
| StorageDeadOrDrop::BoxedStorageDead |
| } |
| StorageDeadOrDrop::Destructor(_) => kind, |
| }, |
| ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => { |
| match place_ty.ty.kind() { |
| ty::Adt(def, _) if def.has_dtor(tcx) => { |
| // Report the outermost adt with a destructor |
| match kind { |
| StorageDeadOrDrop::Destructor(_) => kind, |
| StorageDeadOrDrop::LocalStorageDead |
| | StorageDeadOrDrop::BoxedStorageDead => { |
| StorageDeadOrDrop::Destructor(place_ty.ty) |
| } |
| } |
| } |
| _ => kind, |
| } |
| } |
| ProjectionElem::ConstantIndex { .. } |
| | ProjectionElem::Subslice { .. } |
| | ProjectionElem::Index(_) => kind, |
| }, |
| place_ty.projection_ty(tcx, elem), |
| ) |
| }, |
| ); |
| kind |
| } |
| |
| /// Describe the reason for the fake borrow that was assigned to `place`. |
| fn classify_immutable_section(&self, place: Place<'tcx>) -> Option<&'static str> { |
| use rustc_middle::mir::visit::Visitor; |
| struct FakeReadCauseFinder<'tcx> { |
| place: Place<'tcx>, |
| cause: Option<FakeReadCause>, |
| } |
| impl<'tcx> Visitor<'tcx> for FakeReadCauseFinder<'tcx> { |
| fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) { |
| match statement { |
| Statement { kind: StatementKind::FakeRead(box (cause, place)), .. } |
| if *place == self.place => |
| { |
| self.cause = Some(*cause); |
| } |
| _ => (), |
| } |
| } |
| } |
| let mut visitor = FakeReadCauseFinder { place, cause: None }; |
| visitor.visit_body(&self.body); |
| match visitor.cause { |
| Some(FakeReadCause::ForMatchGuard) => Some("match guard"), |
| Some(FakeReadCause::ForIndex) => Some("indexing expression"), |
| _ => None, |
| } |
| } |
| |
| /// Annotate argument and return type of function and closure with (synthesized) lifetime for |
| /// borrow of local value that does not live long enough. |
| fn annotate_argument_and_return_for_borrow( |
| &self, |
| borrow: &BorrowData<'tcx>, |
| ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { |
| // Define a fallback for when we can't match a closure. |
| let fallback = || { |
| let is_closure = self.infcx.tcx.is_closure(self.mir_def_id().to_def_id()); |
| if is_closure { |
| None |
| } else { |
| let ty = self.infcx.tcx.type_of(self.mir_def_id()); |
| match ty.kind() { |
| ty::FnDef(_, _) | ty::FnPtr(_) => self.annotate_fn_sig( |
| self.mir_def_id().to_def_id(), |
| self.infcx.tcx.fn_sig(self.mir_def_id()), |
| ), |
| _ => None, |
| } |
| } |
| }; |
| |
| // In order to determine whether we need to annotate, we need to check whether the reserve |
| // place was an assignment into a temporary. |
| // |
| // If it was, we check whether or not that temporary is eventually assigned into the return |
| // place. If it was, we can add annotations about the function's return type and arguments |
| // and it'll make sense. |
| let location = borrow.reserve_location; |
| debug!("annotate_argument_and_return_for_borrow: location={:?}", location); |
| if let Some(&Statement { kind: StatementKind::Assign(box (ref reservation, _)), .. }) = |
| &self.body[location.block].statements.get(location.statement_index) |
| { |
| debug!("annotate_argument_and_return_for_borrow: reservation={:?}", reservation); |
| // Check that the initial assignment of the reserve location is into a temporary. |
| let mut target = match reservation.as_local() { |
| Some(local) if self.body.local_kind(local) == LocalKind::Temp => local, |
| _ => return None, |
| }; |
| |
| // Next, look through the rest of the block, checking if we are assigning the |
| // `target` (that is, the place that contains our borrow) to anything. |
| let mut annotated_closure = None; |
| for stmt in &self.body[location.block].statements[location.statement_index + 1..] { |
| debug!( |
| "annotate_argument_and_return_for_borrow: target={:?} stmt={:?}", |
| target, stmt |
| ); |
| if let StatementKind::Assign(box (place, rvalue)) = &stmt.kind { |
| if let Some(assigned_to) = place.as_local() { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_to={:?} \ |
| rvalue={:?}", |
| assigned_to, rvalue |
| ); |
| // Check if our `target` was captured by a closure. |
| if let Rvalue::Aggregate( |
| box AggregateKind::Closure(def_id, substs), |
| operands, |
| ) = rvalue |
| { |
| for operand in operands { |
| let (Operand::Copy(assigned_from) | Operand::Move(assigned_from)) = operand else { |
| continue; |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from={:?}", |
| assigned_from |
| ); |
| |
| // Find the local from the operand. |
| let Some(assigned_from_local) = assigned_from.local_or_deref_local() else { |
| continue; |
| }; |
| |
| if assigned_from_local != target { |
| continue; |
| } |
| |
| // If a closure captured our `target` and then assigned |
| // into a place then we should annotate the closure in |
| // case it ends up being assigned into the return place. |
| annotated_closure = |
| self.annotate_fn_sig(*def_id, substs.as_closure().sig()); |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| annotated_closure={:?} assigned_from_local={:?} \ |
| assigned_to={:?}", |
| annotated_closure, assigned_from_local, assigned_to |
| ); |
| |
| if assigned_to == mir::RETURN_PLACE { |
| // If it was assigned directly into the return place, then |
| // return now. |
| return annotated_closure; |
| } else { |
| // Otherwise, update the target. |
| target = assigned_to; |
| } |
| } |
| |
| // If none of our closure's operands matched, then skip to the next |
| // statement. |
| continue; |
| } |
| |
| // Otherwise, look at other types of assignment. |
| let assigned_from = match rvalue { |
| Rvalue::Ref(_, _, assigned_from) => assigned_from, |
| Rvalue::Use(operand) => match operand { |
| Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { |
| assigned_from |
| } |
| _ => continue, |
| }, |
| _ => continue, |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| assigned_from={:?}", |
| assigned_from, |
| ); |
| |
| // Find the local from the rvalue. |
| let Some(assigned_from_local) = assigned_from.local_or_deref_local() else { continue }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| assigned_from_local={:?}", |
| assigned_from_local, |
| ); |
| |
| // Check if our local matches the target - if so, we've assigned our |
| // borrow to a new place. |
| if assigned_from_local != target { |
| continue; |
| } |
| |
| // If we assigned our `target` into a new place, then we should |
| // check if it was the return place. |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| assigned_from_local={:?} assigned_to={:?}", |
| assigned_from_local, assigned_to |
| ); |
| if assigned_to == mir::RETURN_PLACE { |
| // If it was then return the annotated closure if there was one, |
| // else, annotate this function. |
| return annotated_closure.or_else(fallback); |
| } |
| |
| // If we didn't assign into the return place, then we just update |
| // the target. |
| target = assigned_to; |
| } |
| } |
| } |
| |
| // Check the terminator if we didn't find anything in the statements. |
| let terminator = &self.body[location.block].terminator(); |
| debug!( |
| "annotate_argument_and_return_for_borrow: target={:?} terminator={:?}", |
| target, terminator |
| ); |
| if let TerminatorKind::Call { destination: Some((place, _)), args, .. } = |
| &terminator.kind |
| { |
| if let Some(assigned_to) = place.as_local() { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_to={:?} args={:?}", |
| assigned_to, args |
| ); |
| for operand in args { |
| let (Operand::Copy(assigned_from) | Operand::Move(assigned_from)) = operand else { |
| continue; |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from={:?}", |
| assigned_from, |
| ); |
| |
| if let Some(assigned_from_local) = assigned_from.local_or_deref_local() { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from_local={:?}", |
| assigned_from_local, |
| ); |
| |
| if assigned_to == mir::RETURN_PLACE && assigned_from_local == target { |
| return annotated_closure.or_else(fallback); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| // If we haven't found an assignment into the return place, then we need not add |
| // any annotations. |
| debug!("annotate_argument_and_return_for_borrow: none found"); |
| None |
| } |
| |
| /// Annotate the first argument and return type of a function signature if they are |
| /// references. |
| fn annotate_fn_sig( |
| &self, |
| did: DefId, |
| sig: ty::PolyFnSig<'tcx>, |
| ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { |
| debug!("annotate_fn_sig: did={:?} sig={:?}", did, sig); |
| let is_closure = self.infcx.tcx.is_closure(did); |
| let fn_hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did.as_local()?); |
| let fn_decl = self.infcx.tcx.hir().fn_decl_by_hir_id(fn_hir_id)?; |
| |
| // We need to work out which arguments to highlight. We do this by looking |
| // at the return type, where there are three cases: |
| // |
| // 1. If there are named arguments, then we should highlight the return type and |
| // highlight any of the arguments that are also references with that lifetime. |
| // If there are no arguments that have the same lifetime as the return type, |
| // then don't highlight anything. |
| // 2. The return type is a reference with an anonymous lifetime. If this is |
| // the case, then we can take advantage of (and teach) the lifetime elision |
| // rules. |
| // |
| // We know that an error is being reported. So the arguments and return type |
| // must satisfy the elision rules. Therefore, if there is a single argument |
| // then that means the return type and first (and only) argument have the same |
| // lifetime and the borrow isn't meeting that, we can highlight the argument |
| // and return type. |
| // |
| // If there are multiple arguments then the first argument must be self (else |
| // it would not satisfy the elision rules), so we can highlight self and the |
| // return type. |
| // 3. The return type is not a reference. In this case, we don't highlight |
| // anything. |
| let return_ty = sig.output(); |
| match return_ty.skip_binder().kind() { |
| ty::Ref(return_region, _, _) if return_region.has_name() && !is_closure => { |
| // This is case 1 from above, return type is a named reference so we need to |
| // search for relevant arguments. |
| let mut arguments = Vec::new(); |
| for (index, argument) in sig.inputs().skip_binder().iter().enumerate() { |
| if let ty::Ref(argument_region, _, _) = argument.kind() { |
| if argument_region == return_region { |
| // Need to use the `rustc_middle::ty` types to compare against the |
| // `return_region`. Then use the `rustc_hir` type to get only |
| // the lifetime span. |
| if let hir::TyKind::Rptr(lifetime, _) = &fn_decl.inputs[index].kind { |
| // With access to the lifetime, we can get |
| // the span of it. |
| arguments.push((*argument, lifetime.span)); |
| } else { |
| bug!("ty type is a ref but hir type is not"); |
| } |
| } |
| } |
| } |
| |
| // We need to have arguments. This shouldn't happen, but it's worth checking. |
| if arguments.is_empty() { |
| return None; |
| } |
| |
| // We use a mix of the HIR and the Ty types to get information |
| // as the HIR doesn't have full types for closure arguments. |
| let return_ty = sig.output().skip_binder(); |
| let mut return_span = fn_decl.output.span(); |
| if let hir::FnRetTy::Return(ty) = &fn_decl.output { |
| if let hir::TyKind::Rptr(lifetime, _) = ty.kind { |
| return_span = lifetime.span; |
| } |
| } |
| |
| Some(AnnotatedBorrowFnSignature::NamedFunction { |
| arguments, |
| return_ty, |
| return_span, |
| }) |
| } |
| ty::Ref(_, _, _) if is_closure => { |
| // This is case 2 from above but only for closures, return type is anonymous |
| // reference so we select |
| // the first argument. |
| let argument_span = fn_decl.inputs.first()?.span; |
| let argument_ty = sig.inputs().skip_binder().first()?; |
| |
| // Closure arguments are wrapped in a tuple, so we need to get the first |
| // from that. |
| if let ty::Tuple(elems) = argument_ty.kind() { |
| let &argument_ty = elems.first()?; |
| if let ty::Ref(_, _, _) = argument_ty.kind() { |
| return Some(AnnotatedBorrowFnSignature::Closure { |
| argument_ty, |
| argument_span, |
| }); |
| } |
| } |
| |
| None |
| } |
| ty::Ref(_, _, _) => { |
| // This is also case 2 from above but for functions, return type is still an |
| // anonymous reference so we select the first argument. |
| let argument_span = fn_decl.inputs.first()?.span; |
| let argument_ty = *sig.inputs().skip_binder().first()?; |
| |
| let return_span = fn_decl.output.span(); |
| let return_ty = sig.output().skip_binder(); |
| |
| // We expect the first argument to be a reference. |
| match argument_ty.kind() { |
| ty::Ref(_, _, _) => {} |
| _ => return None, |
| } |
| |
| Some(AnnotatedBorrowFnSignature::AnonymousFunction { |
| argument_ty, |
| argument_span, |
| return_ty, |
| return_span, |
| }) |
| } |
| _ => { |
| // This is case 3 from above, return type is not a reference so don't highlight |
| // anything. |
| None |
| } |
| } |
| } |
| } |
| |
| #[derive(Debug)] |
| enum AnnotatedBorrowFnSignature<'tcx> { |
| NamedFunction { |
| arguments: Vec<(Ty<'tcx>, Span)>, |
| return_ty: Ty<'tcx>, |
| return_span: Span, |
| }, |
| AnonymousFunction { |
| argument_ty: Ty<'tcx>, |
| argument_span: Span, |
| return_ty: Ty<'tcx>, |
| return_span: Span, |
| }, |
| Closure { |
| argument_ty: Ty<'tcx>, |
| argument_span: Span, |
| }, |
| } |
| |
| impl<'tcx> AnnotatedBorrowFnSignature<'tcx> { |
| /// Annotate the provided diagnostic with information about borrow from the fn signature that |
| /// helps explain. |
| pub(crate) fn emit(&self, cx: &mut MirBorrowckCtxt<'_, 'tcx>, diag: &mut Diagnostic) -> String { |
| match self { |
| &AnnotatedBorrowFnSignature::Closure { argument_ty, argument_span } => { |
| diag.span_label( |
| argument_span, |
| format!("has type `{}`", cx.get_name_for_ty(argument_ty, 0)), |
| ); |
| |
| cx.get_region_name_for_ty(argument_ty, 0) |
| } |
| &AnnotatedBorrowFnSignature::AnonymousFunction { |
| argument_ty, |
| argument_span, |
| return_ty, |
| return_span, |
| } => { |
| let argument_ty_name = cx.get_name_for_ty(argument_ty, 0); |
| diag.span_label(argument_span, format!("has type `{}`", argument_ty_name)); |
| |
| let return_ty_name = cx.get_name_for_ty(return_ty, 0); |
| let types_equal = return_ty_name == argument_ty_name; |
| diag.span_label( |
| return_span, |
| format!( |
| "{}has type `{}`", |
| if types_equal { "also " } else { "" }, |
| return_ty_name, |
| ), |
| ); |
| |
| diag.note( |
| "argument and return type have the same lifetime due to lifetime elision rules", |
| ); |
| diag.note( |
| "to learn more, visit <https://doc.rust-lang.org/book/ch10-03-\ |
| lifetime-syntax.html#lifetime-elision>", |
| ); |
| |
| cx.get_region_name_for_ty(return_ty, 0) |
| } |
| AnnotatedBorrowFnSignature::NamedFunction { arguments, return_ty, return_span } => { |
| // Region of return type and arguments checked to be the same earlier. |
| let region_name = cx.get_region_name_for_ty(*return_ty, 0); |
| for (_, argument_span) in arguments { |
| diag.span_label(*argument_span, format!("has lifetime `{}`", region_name)); |
| } |
| |
| diag.span_label(*return_span, format!("also has lifetime `{}`", region_name,)); |
| |
| diag.help(&format!( |
| "use data from the highlighted arguments which match the `{}` lifetime of \ |
| the return type", |
| region_name, |
| )); |
| |
| region_name |
| } |
| } |
| } |
| } |
