| use either::Either; |
| use hir::PatField; |
| use rustc_data_structures::captures::Captures; |
| use rustc_data_structures::fx::FxIndexSet; |
| use rustc_errors::{ |
| struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan, |
| }; |
| use rustc_hir as hir; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_hir::intravisit::{walk_block, walk_expr, Visitor}; |
| use rustc_hir::{AsyncGeneratorKind, GeneratorKind, LangItem}; |
| use rustc_infer::traits::ObligationCause; |
| use rustc_middle::hir::nested_filter::OnlyBodies; |
| use rustc_middle::mir::tcx::PlaceTy; |
| use rustc_middle::mir::{ |
| self, AggregateKind, BindingForm, BorrowKind, CallSource, ClearCrossCrate, ConstraintCategory, |
| FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, MutBorrowKind, Operand, Place, |
| PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, |
| VarBindingForm, |
| }; |
| use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty}; |
| use rustc_middle::util::CallKind; |
| use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex}; |
| use rustc_span::def_id::LocalDefId; |
| use rustc_span::hygiene::DesugaringKind; |
| use rustc_span::symbol::{kw, sym, Ident}; |
| use rustc_span::{BytePos, Span, Symbol}; |
| use rustc_trait_selection::infer::InferCtxtExt; |
| use rustc_trait_selection::traits::ObligationCtxt; |
| use std::iter; |
| |
| use crate::borrow_set::TwoPhaseActivation; |
| use crate::borrowck_errors; |
| use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead; |
| use crate::diagnostics::{find_all_local_uses, CapturedMessageOpt}; |
| use crate::{ |
| borrow_set::BorrowData, diagnostics::Instance, prefixes::IsPrefixOf, |
| InitializationRequiringAction, MirBorrowckCtxt, PrefixSet, WriteKind, |
| }; |
| |
| use super::{ |
| explain_borrow::{BorrowExplanation, LaterUseKind}, |
| DescribePlaceOpt, 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 err = self.report_use_of_uninitialized( |
| mpi, |
| used_place, |
| moved_place, |
| desired_action, |
| span, |
| use_spans, |
| ); |
| 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, |
| DescribePlaceOpt { including_downcast: true, including_tuple_field: 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 {reinits} reinitializations might get skipped") |
| } else { |
| format!( |
| "these 3 reinitializations and {} other{} might get skipped", |
| reinits - 3, |
| if reinits == 4 { "" } else { "s" } |
| ) |
| }, |
| ); |
| } |
| |
| let closure = self.add_moved_or_invoked_closure_note(location, used_place, &mut err); |
| |
| let mut is_loop_move = false; |
| let mut in_pattern = false; |
| let mut seen_spans = FxIndexSet::default(); |
| |
| 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 is_move_msg = move_spans.for_closure(); |
| |
| let is_loop_message = location == move_out.source || move_site.traversed_back_edge; |
| |
| if location == move_out.source { |
| is_loop_move = true; |
| } |
| |
| if !seen_spans.contains(&move_span) { |
| if !closure { |
| self.suggest_ref_or_clone( |
| mpi, |
| move_span, |
| &mut err, |
| &mut in_pattern, |
| move_spans, |
| ); |
| } |
| |
| let msg_opt = CapturedMessageOpt { |
| is_partial_move, |
| is_loop_message, |
| is_move_msg, |
| is_loop_move, |
| maybe_reinitialized_locations_is_empty: maybe_reinitialized_locations |
| .is_empty(), |
| }; |
| self.explain_captures( |
| &mut err, |
| span, |
| move_span, |
| move_spans, |
| *moved_place, |
| msg_opt, |
| ); |
| } |
| seen_spans.insert(move_span); |
| } |
| |
| use_spans.var_path_only_subdiag(&mut err, desired_action); |
| |
| if !is_loop_move { |
| err.span_label( |
| span, |
| format!( |
| "value {} here after {partial_str}move", |
| desired_action.as_verb_in_past_tense(), |
| ), |
| ); |
| } |
| |
| let ty = used_place.ty(self.body, self.infcx.tcx).ty; |
| let needs_note = match ty.kind() { |
| ty::Closure(id, _) => { |
| self.infcx.tcx.closure_kind_origin(id.expect_local()).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). |
| // Same for if we're in a loop, see #101119. |
| if is_loop_move & !in_pattern && !matches!(use_spans, UseSpans::ClosureUse { .. }) { |
| 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 *", |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| let opt_name = self.describe_place_with_options( |
| place.as_ref(), |
| DescribePlaceOpt { including_downcast: true, including_tuple_field: true }, |
| ); |
| let note_msg = match opt_name { |
| Some(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 { |
| if let Some(local) = place.as_local() { |
| let span = self.body.local_decls[local].source_info.span; |
| err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label { |
| is_partial_move, |
| ty, |
| place: ¬e_msg, |
| span, |
| }); |
| } else { |
| err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Note { |
| is_partial_move, |
| ty, |
| place: ¬e_msg, |
| }); |
| }; |
| } |
| |
| if let UseSpans::FnSelfUse { |
| kind: CallKind::DerefCoercion { deref_target, deref_target_ty, .. }, |
| .. |
| } = use_spans |
| { |
| err.note(format!( |
| "{} occurs due to deref coercion to `{deref_target_ty}`", |
| desired_action.as_noun(), |
| )); |
| |
| // Check first whether the source is accessible (issue #87060) |
| if self.infcx.tcx.sess.source_map().is_span_accessible(deref_target) { |
| err.span_note(deref_target, "deref defined here"); |
| } |
| } |
| |
| self.buffer_move_error(move_out_indices, (used_place, err)); |
| } |
| } |
| |
| fn suggest_ref_or_clone( |
| &mut self, |
| mpi: MovePathIndex, |
| move_span: Span, |
| err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>, |
| in_pattern: &mut bool, |
| move_spans: UseSpans<'_>, |
| ) { |
| struct ExpressionFinder<'hir> { |
| expr_span: Span, |
| expr: Option<&'hir hir::Expr<'hir>>, |
| pat: Option<&'hir hir::Pat<'hir>>, |
| parent_pat: Option<&'hir hir::Pat<'hir>>, |
| } |
| impl<'hir> Visitor<'hir> for ExpressionFinder<'hir> { |
| fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) { |
| if e.span == self.expr_span { |
| self.expr = Some(e); |
| } |
| hir::intravisit::walk_expr(self, e); |
| } |
| fn visit_pat(&mut self, p: &'hir hir::Pat<'hir>) { |
| if p.span == self.expr_span { |
| self.pat = Some(p); |
| } |
| if let hir::PatKind::Binding(hir::BindingAnnotation::NONE, _, i, sub) = p.kind { |
| if i.span == self.expr_span || p.span == self.expr_span { |
| self.pat = Some(p); |
| } |
| // Check if we are in a situation of `ident @ ident` where we want to suggest |
| // `ref ident @ ref ident` or `ref ident @ Struct { ref ident }`. |
| if let Some(subpat) = sub && self.pat.is_none() { |
| self.visit_pat(subpat); |
| if self.pat.is_some() { |
| self.parent_pat = Some(p); |
| } |
| return; |
| } |
| } |
| hir::intravisit::walk_pat(self, p); |
| } |
| } |
| let hir = self.infcx.tcx.hir(); |
| if let Some(body_id) = hir.maybe_body_owned_by(self.mir_def_id()) { |
| let expr = hir.body(body_id).value; |
| let place = &self.move_data.move_paths[mpi].place; |
| let span = place.as_local().map(|local| self.body.local_decls[local].source_info.span); |
| let mut finder = |
| ExpressionFinder { expr_span: move_span, expr: None, pat: None, parent_pat: None }; |
| finder.visit_expr(expr); |
| if let Some(span) = span && let Some(expr) = finder.expr { |
| for (_, expr) in hir.parent_iter(expr.hir_id) { |
| if let hir::Node::Expr(expr) = expr { |
| if expr.span.contains(span) { |
| // If the let binding occurs within the same loop, then that |
| // loop isn't relevant, like in the following, the outermost `loop` |
| // doesn't play into `x` being moved. |
| // ``` |
| // loop { |
| // let x = String::new(); |
| // loop { |
| // foo(x); |
| // } |
| // } |
| // ``` |
| break; |
| } |
| if let hir::ExprKind::Loop(.., loop_span) = expr.kind { |
| err.span_label(loop_span, "inside of this loop"); |
| } |
| } |
| } |
| let typeck = self.infcx.tcx.typeck(self.mir_def_id()); |
| let hir_id = hir.parent_id(expr.hir_id); |
| if let Some(parent) = hir.find(hir_id) { |
| let (def_id, args, offset) = if let hir::Node::Expr(parent_expr) = parent |
| && let hir::ExprKind::MethodCall(_, _, args, _) = parent_expr.kind |
| && let Some(def_id) = typeck.type_dependent_def_id(parent_expr.hir_id) |
| { |
| (def_id.as_local(), args, 1) |
| } else if let hir::Node::Expr(parent_expr) = parent |
| && let hir::ExprKind::Call(call, args) = parent_expr.kind |
| && let ty::FnDef(def_id, _) = typeck.node_type(call.hir_id).kind() |
| { |
| (def_id.as_local(), args, 0) |
| } else { |
| (None, &[][..], 0) |
| }; |
| if let Some(def_id) = def_id |
| && let Some(node) = hir.find(hir.local_def_id_to_hir_id(def_id)) |
| && let Some(fn_sig) = node.fn_sig() |
| && let Some(ident) = node.ident() |
| && let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id) |
| && let Some(arg) = fn_sig.decl.inputs.get(pos + offset) |
| { |
| let mut span: MultiSpan = arg.span.into(); |
| span.push_span_label( |
| arg.span, |
| "this parameter takes ownership of the value".to_string(), |
| ); |
| let descr = match node.fn_kind() { |
| Some(hir::intravisit::FnKind::ItemFn(..)) | None => "function", |
| Some(hir::intravisit::FnKind::Method(..)) => "method", |
| Some(hir::intravisit::FnKind::Closure) => "closure", |
| }; |
| span.push_span_label( |
| ident.span, |
| format!("in this {descr}"), |
| ); |
| err.span_note( |
| span, |
| format!( |
| "consider changing this parameter type in {descr} `{ident}` to \ |
| borrow instead if owning the value isn't necessary", |
| ), |
| ); |
| } |
| let place = &self.move_data.move_paths[mpi].place; |
| let ty = place.ty(self.body, self.infcx.tcx).ty; |
| if let hir::Node::Expr(parent_expr) = parent |
| && let hir::ExprKind::Call(call_expr, _) = parent_expr.kind |
| && let hir::ExprKind::Path( |
| hir::QPath::LangItem(LangItem::IntoIterIntoIter, _, _) |
| ) = call_expr.kind |
| { |
| // Do not suggest `.clone()` in a `for` loop, we already suggest borrowing. |
| } else if let UseSpans::FnSelfUse { |
| kind: CallKind::Normal { .. }, |
| .. |
| } = move_spans { |
| // We already suggest cloning for these cases in `explain_captures`. |
| } else { |
| self.suggest_cloning(err, ty, expr, move_span); |
| } |
| } |
| } |
| if let Some(pat) = finder.pat { |
| *in_pattern = true; |
| let mut sugg = vec![(pat.span.shrink_to_lo(), "ref ".to_string())]; |
| if let Some(pat) = finder.parent_pat { |
| sugg.insert(0, (pat.span.shrink_to_lo(), "ref ".to_string())); |
| } |
| err.multipart_suggestion_verbose( |
| "borrow this binding in the pattern to avoid moving the value", |
| sugg, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| } |
| |
| fn report_use_of_uninitialized( |
| &self, |
| mpi: MovePathIndex, |
| used_place: PlaceRef<'tcx>, |
| moved_place: PlaceRef<'tcx>, |
| desired_action: InitializationRequiringAction, |
| span: Span, |
| use_spans: UseSpans<'tcx>, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| // We need all statements in the body where the binding was assigned to to later find all |
| // the branching code paths where the binding *wasn't* assigned to. |
| let inits = &self.move_data.init_path_map[mpi]; |
| let move_path = &self.move_data.move_paths[mpi]; |
| let decl_span = self.body.local_decls[move_path.place.local].source_info.span; |
| let mut spans = vec![]; |
| for init_idx in inits { |
| let init = &self.move_data.inits[*init_idx]; |
| let span = init.span(&self.body); |
| if !span.is_dummy() { |
| spans.push(span); |
| } |
| } |
| |
| let (name, desc) = match self.describe_place_with_options( |
| moved_place, |
| DescribePlaceOpt { including_downcast: true, including_tuple_field: true }, |
| ) { |
| Some(name) => (format!("`{name}`"), format!("`{name}` ")), |
| None => ("the variable".to_string(), String::new()), |
| }; |
| let path = match self.describe_place_with_options( |
| used_place, |
| DescribePlaceOpt { including_downcast: true, including_tuple_field: true }, |
| ) { |
| Some(name) => format!("`{name}`"), |
| None => "value".to_string(), |
| }; |
| |
| // We use the statements were the binding was initialized, and inspect the HIR to look |
| // for the branching codepaths that aren't covered, to point at them. |
| let map = self.infcx.tcx.hir(); |
| let body_id = map.body_owned_by(self.mir_def_id()); |
| let body = map.body(body_id); |
| |
| let mut visitor = ConditionVisitor { spans: &spans, name: &name, errors: vec![] }; |
| visitor.visit_body(&body); |
| |
| let mut show_assign_sugg = false; |
| let isnt_initialized = if let InitializationRequiringAction::PartialAssignment |
| | InitializationRequiringAction::Assignment = desired_action |
| { |
| // The same error is emitted for bindings that are *sometimes* initialized and the ones |
| // that are *partially* initialized by assigning to a field of an uninitialized |
| // binding. We differentiate between them for more accurate wording here. |
| "isn't fully initialized" |
| } else if !spans.iter().any(|i| { |
| // We filter these to avoid misleading wording in cases like the following, |
| // where `x` has an `init`, but it is in the same place we're looking at: |
| // ``` |
| // let x; |
| // x += 1; |
| // ``` |
| !i.contains(span) |
| // We filter these to avoid incorrect main message on `match-cfg-fake-edges.rs` |
| && !visitor |
| .errors |
| .iter() |
| .map(|(sp, _)| *sp) |
| .any(|sp| span < sp && !sp.contains(span)) |
| }) { |
| show_assign_sugg = true; |
| "isn't initialized" |
| } else { |
| "is possibly-uninitialized" |
| }; |
| |
| let used = desired_action.as_general_verb_in_past_tense(); |
| let mut err = |
| struct_span_err!(self, span, E0381, "{used} binding {desc}{isnt_initialized}"); |
| use_spans.var_path_only_subdiag(&mut err, desired_action); |
| |
| if let InitializationRequiringAction::PartialAssignment |
| | InitializationRequiringAction::Assignment = desired_action |
| { |
| err.help( |
| "partial initialization isn't supported, fully initialize the binding with a \ |
| default value and mutate it, or use `std::mem::MaybeUninit`", |
| ); |
| } |
| err.span_label(span, format!("{path} {used} here but it {isnt_initialized}")); |
| |
| let mut shown = false; |
| for (sp, label) in visitor.errors { |
| if sp < span && !sp.overlaps(span) { |
| // When we have a case like `match-cfg-fake-edges.rs`, we don't want to mention |
| // match arms coming after the primary span because they aren't relevant: |
| // ``` |
| // let x; |
| // match y { |
| // _ if { x = 2; true } => {} |
| // _ if { |
| // x; //~ ERROR |
| // false |
| // } => {} |
| // _ => {} // We don't want to point to this. |
| // }; |
| // ``` |
| err.span_label(sp, label); |
| shown = true; |
| } |
| } |
| if !shown { |
| for sp in &spans { |
| if *sp < span && !sp.overlaps(span) { |
| err.span_label(*sp, "binding initialized here in some conditions"); |
| } |
| } |
| } |
| |
| err.span_label(decl_span, "binding declared here but left uninitialized"); |
| if show_assign_sugg { |
| struct LetVisitor { |
| decl_span: Span, |
| sugg_span: Option<Span>, |
| } |
| |
| impl<'v> Visitor<'v> for LetVisitor { |
| fn visit_stmt(&mut self, ex: &'v hir::Stmt<'v>) { |
| if self.sugg_span.is_some() { |
| return; |
| } |
| if let hir::StmtKind::Local(hir::Local { |
| span, ty, init: None, .. |
| }) = &ex.kind && span.contains(self.decl_span) { |
| self.sugg_span = ty.map_or(Some(self.decl_span), |ty| Some(ty.span)); |
| } |
| hir::intravisit::walk_stmt(self, ex); |
| } |
| } |
| |
| let mut visitor = LetVisitor { decl_span, sugg_span: None }; |
| visitor.visit_body(&body); |
| if let Some(span) = visitor.sugg_span { |
| self.suggest_assign_value(&mut err, moved_place, span); |
| } |
| } |
| err |
| } |
| |
| fn suggest_assign_value( |
| &self, |
| err: &mut Diagnostic, |
| moved_place: PlaceRef<'tcx>, |
| sugg_span: Span, |
| ) { |
| let ty = moved_place.ty(self.body, self.infcx.tcx).ty; |
| debug!("ty: {:?}, kind: {:?}", ty, ty.kind()); |
| |
| let tcx = self.infcx.tcx; |
| let implements_default = |ty, param_env| { |
| let Some(default_trait) = tcx.get_diagnostic_item(sym::Default) else { |
| return false; |
| }; |
| self.infcx |
| .type_implements_trait(default_trait, [ty], param_env) |
| .must_apply_modulo_regions() |
| }; |
| |
| let assign_value = match ty.kind() { |
| ty::Bool => "false", |
| ty::Float(_) => "0.0", |
| ty::Int(_) | ty::Uint(_) => "0", |
| ty::Never | ty::Error(_) => "", |
| ty::Adt(def, _) if Some(def.did()) == tcx.get_diagnostic_item(sym::Vec) => "vec![]", |
| ty::Adt(_, _) if implements_default(ty, self.param_env) => "Default::default()", |
| _ => "todo!()", |
| }; |
| |
| if !assign_value.is_empty() { |
| err.span_suggestion_verbose( |
| sugg_span.shrink_to_hi(), |
| "consider assigning a value", |
| format!(" = {assign_value}"), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| |
| fn suggest_borrow_fn_like( |
| &self, |
| err: &mut Diagnostic, |
| 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 = |(pred, _): (ty::Clause<'tcx>, _)| { |
| if let ty::ClauseKind::Trait(pred) = pred.kind().skip_binder() |
| && 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(_) => tcx |
| .explicit_predicates_of(self.mir_def_id().to_def_id()) |
| .predicates |
| .iter() |
| .copied() |
| .find_map(find_fn_kind_from_did), |
| ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => tcx |
| .explicit_item_bounds(def_id) |
| .iter_instantiated_copied(tcx, args) |
| .find_map(|(clause, span)| find_fn_kind_from_did((clause, span))), |
| ty::Closure(_, args) => match args.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 = borrow_level.ref_prefix_str().to_owned(); |
| (move_span.shrink_to_lo(), suggestion) |
| }) |
| .collect(); |
| err.multipart_suggestion_verbose( |
| format!("consider {}borrowing {value_name}", borrow_level.mutably_str()), |
| sugg, |
| Applicability::MaybeIncorrect, |
| ); |
| true |
| } |
| |
| fn suggest_cloning( |
| &self, |
| err: &mut Diagnostic, |
| ty: Ty<'tcx>, |
| expr: &hir::Expr<'_>, |
| span: Span, |
| ) { |
| let tcx = self.infcx.tcx; |
| // Try to find predicates on *generic params* that would allow copying `ty` |
| let suggestion = |
| if let Some(symbol) = tcx.hir().maybe_get_struct_pattern_shorthand_field(expr) { |
| format!(": {symbol}.clone()") |
| } else { |
| ".clone()".to_owned() |
| }; |
| if let Some(clone_trait_def) = tcx.lang_items().clone_trait() |
| && self.infcx |
| .type_implements_trait( |
| clone_trait_def, |
| [ty], |
| self.param_env, |
| ) |
| .must_apply_modulo_regions() |
| { |
| let msg = if let ty::Adt(def, _) = ty.kind() |
| && [ |
| tcx.get_diagnostic_item(sym::Arc), |
| tcx.get_diagnostic_item(sym::Rc), |
| ].contains(&Some(def.did())) |
| { |
| "clone the value to increment its reference count" |
| } else { |
| "consider cloning the value if the performance cost is acceptable" |
| }; |
| err.span_suggestion_verbose( |
| span.shrink_to_hi(), |
| msg, |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| fn suggest_adding_copy_bounds(&self, err: &mut Diagnostic, 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 ocx = ObligationCtxt::new(&self.infcx); |
| let copy_did = tcx.require_lang_item(LangItem::Copy, Some(span)); |
| let cause = ObligationCause::misc(span, self.mir_def_id()); |
| |
| ocx.register_bound(cause, self.param_env, ty, copy_did); |
| let errors = ocx.select_all_or_error(); |
| |
| // Only emit suggestion if all required predicates are on generic |
| let predicates: Result<Vec<_>, _> = errors |
| .into_iter() |
| .map(|err| match err.obligation.predicate.kind().skip_binder() { |
| PredicateKind::Clause(ty::ClauseKind::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)), |
| 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, |
| borrow_span, |
| &self.describe_any_place(place.as_ref()), |
| &borrow_msg, |
| &value_msg, |
| ); |
| |
| borrow_spans.var_path_only_subdiag(&mut err, crate::InitializationRequiringAction::Borrow); |
| |
| move_spans.var_subdiag(None, &mut err, None, |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => MoveUseInGenerator { var_span }, |
| None => MoveUseInClosure { var_span }, |
| } |
| }); |
| |
| 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_subdiag(None, &mut err, Some(borrow.kind), |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| let place = &borrow.borrowed_place; |
| let desc_place = self.describe_any_place(place.as_ref()); |
| match kind { |
| Some(_) => { |
| BorrowUsePlaceGenerator { place: desc_place, var_span, is_single_var: true } |
| } |
| None => BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: true }, |
| } |
| }); |
| |
| 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 { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, |
| ) => { |
| first_borrow_desc = "mutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| "immutable", |
| issued_span, |
| "it", |
| "mutable", |
| &msg_borrow, |
| None, |
| ) |
| } |
| ( |
| BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, |
| BorrowKind::Shared, |
| ) => { |
| first_borrow_desc = "immutable "; |
| let mut err = self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| "mutable", |
| issued_span, |
| "it", |
| "immutable", |
| &msg_borrow, |
| None, |
| ); |
| self.suggest_binding_for_closure_capture_self(&mut err, &issued_spans); |
| self.suggest_using_closure_argument_instead_of_capture( |
| &mut err, |
| issued_borrow.borrowed_place, |
| &issued_spans, |
| ); |
| err |
| } |
| |
| ( |
| BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, |
| BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, |
| ) => { |
| first_borrow_desc = "first "; |
| let mut err = self.cannot_mutably_borrow_multiply( |
| span, |
| &desc_place, |
| &msg_place, |
| issued_span, |
| &msg_borrow, |
| None, |
| ); |
| self.suggest_slice_method_if_applicable( |
| &mut err, |
| place, |
| issued_borrow.borrowed_place, |
| ); |
| self.suggest_using_closure_argument_instead_of_capture( |
| &mut err, |
| issued_borrow.borrowed_place, |
| &issued_spans, |
| ); |
| self.explain_iterator_advancement_in_for_loop_if_applicable( |
| &mut err, |
| span, |
| &issued_spans, |
| ); |
| err |
| } |
| |
| ( |
| BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }, |
| BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }, |
| ) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_two_closures(span, &desc_place, issued_span, None) |
| } |
| |
| (BorrowKind::Mut { .. }, 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_subdiag( |
| None, |
| &mut err, |
| Some(BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }), |
| |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => BorrowUsePlaceGenerator { |
| place: desc_place, |
| var_span, |
| is_single_var: true, |
| }, |
| None => BorrowUsePlaceClosure { |
| place: desc_place, |
| var_span, |
| is_single_var: true, |
| }, |
| } |
| }, |
| ); |
| 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::Mut { kind: MutBorrowKind::ClosureCapture }, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_one_closure( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| issued_span, |
| "it", |
| "", |
| None, |
| ) |
| } |
| |
| (BorrowKind::Shared, BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }) => { |
| 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::Mut { kind: MutBorrowKind::ClosureCapture }) => { |
| 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::Shared | BorrowKind::Shallow, |
| ) => unreachable!(), |
| }; |
| |
| if issued_spans == borrow_spans { |
| borrow_spans.var_subdiag(None, &mut err, Some(gen_borrow_kind), |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => BorrowUsePlaceGenerator { |
| place: desc_place, |
| var_span, |
| is_single_var: false, |
| }, |
| None => { |
| BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: false } |
| } |
| } |
| }); |
| } else { |
| issued_spans.var_subdiag( |
| Some(&self.infcx.tcx.sess.parse_sess.span_diagnostic), |
| &mut err, |
| Some(issued_borrow.kind), |
| |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| let borrow_place = &issued_borrow.borrowed_place; |
| let borrow_place_desc = self.describe_any_place(borrow_place.as_ref()); |
| match kind { |
| Some(_) => { |
| FirstBorrowUsePlaceGenerator { place: borrow_place_desc, var_span } |
| } |
| None => FirstBorrowUsePlaceClosure { place: borrow_place_desc, var_span }, |
| } |
| }, |
| ); |
| |
| borrow_spans.var_subdiag( |
| Some(&self.infcx.tcx.sess.parse_sess.span_diagnostic), |
| &mut err, |
| Some(gen_borrow_kind), |
| |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => SecondBorrowUsePlaceGenerator { place: desc_place, var_span }, |
| None => SecondBorrowUsePlaceClosure { place: desc_place, var_span }, |
| } |
| }, |
| ); |
| } |
| |
| if union_type_name != "" { |
| err.note(format!( |
| "{msg_place} is a field of the union `{union_type_name}`, so it overlaps the field {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<'tcx>, |
| ) { |
| 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); |
| args.contains(&Operand::Move(inner_param)).then_some((loc, term)) |
| }) |
| 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_slice_method_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", |
| ) |
| .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices"); |
| } |
| } |
| |
| /// Suggest using `while let` for call `next` on an iterator in a for loop. |
| /// |
| /// For example: |
| /// ```ignore (illustrative) |
| /// |
| /// for x in iter { |
| /// ... |
| /// iter.next() |
| /// } |
| /// ``` |
| pub(crate) fn explain_iterator_advancement_in_for_loop_if_applicable( |
| &self, |
| err: &mut Diagnostic, |
| span: Span, |
| issued_spans: &UseSpans<'tcx>, |
| ) { |
| let issue_span = issued_spans.args_or_use(); |
| let tcx = self.infcx.tcx; |
| let hir = tcx.hir(); |
| |
| let Some(body_id) = hir.get(self.mir_hir_id()).body_id() else { return }; |
| let typeck_results = tcx.typeck(self.mir_def_id()); |
| |
| struct ExprFinder<'hir> { |
| issue_span: Span, |
| expr_span: Span, |
| body_expr: Option<&'hir hir::Expr<'hir>>, |
| loop_bind: Option<Symbol>, |
| } |
| impl<'hir> Visitor<'hir> for ExprFinder<'hir> { |
| fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) { |
| if let hir::ExprKind::Loop(hir::Block{ stmts: [stmt, ..], ..}, _, hir::LoopSource::ForLoop, _) = ex.kind && |
| let hir::StmtKind::Expr(hir::Expr{ kind: hir::ExprKind::Match(call, [_, bind, ..], _), ..}) = stmt.kind && |
| let hir::ExprKind::Call(path, _args) = call.kind && |
| let hir::ExprKind::Path(hir::QPath::LangItem(LangItem::IteratorNext, _, _, )) = path.kind && |
| let hir::PatKind::Struct(path, [field, ..], _) = bind.pat.kind && |
| let hir::QPath::LangItem(LangItem::OptionSome, _, _) = path && |
| let PatField { pat: hir::Pat{ kind: hir::PatKind::Binding(_, _, ident, ..), .. }, ..} = field && |
| self.issue_span.source_equal(call.span) { |
| self.loop_bind = Some(ident.name); |
| } |
| |
| if let hir::ExprKind::MethodCall(body_call, _recv, ..) = ex.kind && |
| body_call.ident.name == sym::next && ex.span.source_equal(self.expr_span) { |
| self.body_expr = Some(ex); |
| } |
| |
| hir::intravisit::walk_expr(self, ex); |
| } |
| } |
| let mut finder = |
| ExprFinder { expr_span: span, issue_span, loop_bind: None, body_expr: None }; |
| finder.visit_expr(hir.body(body_id).value); |
| |
| if let Some(loop_bind) = finder.loop_bind && |
| let Some(body_expr) = finder.body_expr && |
| let Some(def_id) = typeck_results.type_dependent_def_id(body_expr.hir_id) && |
| let Some(trait_did) = tcx.trait_of_item(def_id) && |
| tcx.is_diagnostic_item(sym::Iterator, trait_did) { |
| err.note(format!( |
| "a for loop advances the iterator for you, the result is stored in `{loop_bind}`." |
| )); |
| err.help("if you want to call `next` on a iterator within the loop, consider using `while let`."); |
| } |
| } |
| |
| /// Suggest using closure argument instead of capture. |
| /// |
| /// For example: |
| /// ```ignore (illustrative) |
| /// struct S; |
| /// |
| /// impl S { |
| /// fn call(&mut self, f: impl Fn(&mut Self)) { /* ... */ } |
| /// fn x(&self) {} |
| /// } |
| /// |
| /// let mut v = S; |
| /// v.call(|this: &mut S| v.x()); |
| /// // ^\ ^-- help: try using the closure argument: `this` |
| /// // *-- error: cannot borrow `v` as mutable because it is also borrowed as immutable |
| /// ``` |
| fn suggest_using_closure_argument_instead_of_capture( |
| &self, |
| err: &mut Diagnostic, |
| borrowed_place: Place<'tcx>, |
| issued_spans: &UseSpans<'tcx>, |
| ) { |
| let &UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return }; |
| let tcx = self.infcx.tcx; |
| let hir = tcx.hir(); |
| |
| // Get the type of the local that we are trying to borrow |
| let local = borrowed_place.local; |
| let local_ty = self.body.local_decls[local].ty; |
| |
| // Get the body the error happens in |
| let Some(body_id) = hir.get(self.mir_hir_id()).body_id() else { return }; |
| |
| let body_expr = hir.body(body_id).value; |
| |
| struct ClosureFinder<'hir> { |
| hir: rustc_middle::hir::map::Map<'hir>, |
| borrow_span: Span, |
| res: Option<(&'hir hir::Expr<'hir>, &'hir hir::Closure<'hir>)>, |
| /// The path expression with the `borrow_span` span |
| error_path: Option<(&'hir hir::Expr<'hir>, &'hir hir::QPath<'hir>)>, |
| } |
| impl<'hir> Visitor<'hir> for ClosureFinder<'hir> { |
| type NestedFilter = OnlyBodies; |
| |
| fn nested_visit_map(&mut self) -> Self::Map { |
| self.hir |
| } |
| |
| fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) { |
| if let hir::ExprKind::Path(qpath) = &ex.kind |
| && ex.span == self.borrow_span |
| { |
| self.error_path = Some((ex, qpath)); |
| } |
| |
| if let hir::ExprKind::Closure(closure) = ex.kind |
| && ex.span.contains(self.borrow_span) |
| // To support cases like `|| { v.call(|this| v.get()) }` |
| // FIXME: actually support such cases (need to figure out how to move from the capture place to original local) |
| && self.res.as_ref().map_or(true, |(prev_res, _)| prev_res.span.contains(ex.span)) |
| { |
| self.res = Some((ex, closure)); |
| } |
| |
| hir::intravisit::walk_expr(self, ex); |
| } |
| } |
| |
| // Find the closure that most tightly wraps `capture_kind_span` |
| let mut finder = |
| ClosureFinder { hir, borrow_span: capture_kind_span, res: None, error_path: None }; |
| finder.visit_expr(body_expr); |
| let Some((closure_expr, closure)) = finder.res else { return }; |
| |
| let typeck_results = tcx.typeck(self.mir_def_id()); |
| |
| // Check that the parent of the closure is a method call, |
| // with receiver matching with local's type (modulo refs) |
| let parent = hir.parent_id(closure_expr.hir_id); |
| if let hir::Node::Expr(parent) = hir.get(parent) { |
| if let hir::ExprKind::MethodCall(_, recv, ..) = parent.kind { |
| let recv_ty = typeck_results.expr_ty(recv); |
| |
| if recv_ty.peel_refs() != local_ty { |
| return; |
| } |
| } |
| } |
| |
| // Get closure's arguments |
| let ty::Closure(_, args) = typeck_results.expr_ty(closure_expr).kind() else { |
| /* hir::Closure can be a generator too */ |
| return; |
| }; |
| let sig = args.as_closure().sig(); |
| let tupled_params = |
| tcx.erase_late_bound_regions(sig.inputs().iter().next().unwrap().map_bound(|&b| b)); |
| let ty::Tuple(params) = tupled_params.kind() else { return }; |
| |
| // Find the first argument with a matching type, get its name |
| let Some((_, this_name)) = |
| params.iter().zip(hir.body_param_names(closure.body)).find(|(param_ty, name)| { |
| // FIXME: also support deref for stuff like `Rc` arguments |
| param_ty.peel_refs() == local_ty && name != &Ident::empty() |
| }) |
| else { |
| return; |
| }; |
| |
| let spans; |
| if let Some((_path_expr, qpath)) = finder.error_path |
| && let hir::QPath::Resolved(_, path) = qpath |
| && let hir::def::Res::Local(local_id) = path.res |
| { |
| // Find all references to the problematic variable in this closure body |
| |
| struct VariableUseFinder { |
| local_id: hir::HirId, |
| spans: Vec<Span>, |
| } |
| impl<'hir> Visitor<'hir> for VariableUseFinder { |
| fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) { |
| if let hir::ExprKind::Path(qpath) = &ex.kind |
| && let hir::QPath::Resolved(_, path) = qpath |
| && let hir::def::Res::Local(local_id) = path.res |
| && local_id == self.local_id |
| { |
| self.spans.push(ex.span); |
| } |
| |
| hir::intravisit::walk_expr(self, ex); |
| } |
| } |
| |
| let mut finder = VariableUseFinder { local_id, spans: Vec::new() }; |
| finder.visit_expr(hir.body(closure.body).value); |
| |
| spans = finder.spans; |
| } else { |
| spans = vec![capture_kind_span]; |
| } |
| |
| err.multipart_suggestion( |
| "try using the closure argument", |
| iter::zip(spans, iter::repeat(this_name.to_string())).collect(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| |
| fn suggest_binding_for_closure_capture_self( |
| &self, |
| err: &mut Diagnostic, |
| issued_spans: &UseSpans<'tcx>, |
| ) { |
| let UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return }; |
| let hir = self.infcx.tcx.hir(); |
| |
| struct ExpressionFinder<'hir> { |
| capture_span: Span, |
| closure_change_spans: Vec<Span>, |
| closure_arg_span: Option<Span>, |
| in_closure: bool, |
| suggest_arg: String, |
| hir: rustc_middle::hir::map::Map<'hir>, |
| closure_local_id: Option<hir::HirId>, |
| closure_call_changes: Vec<(Span, String)>, |
| } |
| impl<'hir> Visitor<'hir> for ExpressionFinder<'hir> { |
| fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) { |
| if e.span.contains(self.capture_span) { |
| if let hir::ExprKind::Closure(&hir::Closure { |
| movability: None, |
| body, |
| fn_arg_span, |
| fn_decl: hir::FnDecl{ inputs, .. }, |
| .. |
| }) = e.kind && |
| let Some(hir::Node::Expr(body )) = self.hir.find(body.hir_id) { |
| self.suggest_arg = "this: &Self".to_string(); |
| if inputs.len() > 0 { |
| self.suggest_arg.push_str(", "); |
| } |
| self.in_closure = true; |
| self.closure_arg_span = fn_arg_span; |
| self.visit_expr(body); |
| self.in_closure = false; |
| } |
| } |
| if let hir::Expr { kind: hir::ExprKind::Path(path), .. } = e { |
| if let hir::QPath::Resolved(_, hir::Path { segments: [seg], ..}) = path && |
| seg.ident.name == kw::SelfLower && self.in_closure { |
| self.closure_change_spans.push(e.span); |
| } |
| } |
| hir::intravisit::walk_expr(self, e); |
| } |
| |
| fn visit_local(&mut self, local: &'hir hir::Local<'hir>) { |
| if let hir::Pat { kind: hir::PatKind::Binding(_, hir_id, _ident, _), .. } = local.pat && |
| let Some(init) = local.init |
| { |
| if let hir::Expr { kind: hir::ExprKind::Closure(&hir::Closure { |
| movability: None, |
| .. |
| }), .. } = init && |
| init.span.contains(self.capture_span) { |
| self.closure_local_id = Some(*hir_id); |
| } |
| } |
| hir::intravisit::walk_local(self, local); |
| } |
| |
| fn visit_stmt(&mut self, s: &'hir hir::Stmt<'hir>) { |
| if let hir::StmtKind::Semi(e) = s.kind && |
| let hir::ExprKind::Call(hir::Expr { kind: hir::ExprKind::Path(path), ..}, args) = e.kind && |
| let hir::QPath::Resolved(_, hir::Path { segments: [seg], ..}) = path && |
| let Res::Local(hir_id) = seg.res && |
| Some(hir_id) == self.closure_local_id { |
| let (span, arg_str) = if args.len() > 0 { |
| (args[0].span.shrink_to_lo(), "self, ".to_string()) |
| } else { |
| let span = e.span.trim_start(seg.ident.span).unwrap_or(e.span); |
| (span, "(self)".to_string()) |
| }; |
| self.closure_call_changes.push((span, arg_str)); |
| } |
| hir::intravisit::walk_stmt(self, s); |
| } |
| } |
| |
| if let Some(hir::Node::ImplItem( |
| hir::ImplItem { kind: hir::ImplItemKind::Fn(_fn_sig, body_id), .. } |
| )) = hir.find(self.mir_hir_id()) && |
| let Some(hir::Node::Expr(expr)) = hir.find(body_id.hir_id) { |
| let mut finder = ExpressionFinder { |
| capture_span: *capture_kind_span, |
| closure_change_spans: vec![], |
| closure_arg_span: None, |
| in_closure: false, |
| suggest_arg: String::new(), |
| closure_local_id: None, |
| closure_call_changes: vec![], |
| hir, |
| }; |
| finder.visit_expr(expr); |
| |
| if finder.closure_change_spans.is_empty() || finder.closure_call_changes.is_empty() { |
| return; |
| } |
| |
| let mut sugg = vec![]; |
| let sm = self.infcx.tcx.sess.source_map(); |
| |
| if let Some(span) = finder.closure_arg_span { |
| sugg.push((sm.next_point(span.shrink_to_lo()).shrink_to_hi(), finder.suggest_arg)); |
| } |
| for span in finder.closure_change_spans { |
| sugg.push((span, "this".to_string())); |
| } |
| |
| for (span, suggest) in finder.closure_call_changes { |
| sugg.push((span, suggest)); |
| } |
| |
| err.multipart_suggestion_verbose( |
| "try explicitly pass `&Self` into the Closure as an argument", |
| sugg, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| /// 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(), |
| ) |
| }) |
| } |
| |
| /// 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.) |
| #[instrument(level = "debug", skip(self))] |
| 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>, |
| ) { |
| 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.mk_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!(?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(name), |
| BorrowExplanation::UsedLater(LaterUseKind::ClosureCapture, var_or_use_span, _), |
| ) if borrow_spans.for_generator() || borrow_spans.for_closure() => self |
| .report_escaping_closure_capture( |
| borrow_spans, |
| borrow_span, |
| &RegionName { |
| name: self.synthesize_region_name(), |
| source: RegionNameSource::Static, |
| }, |
| ConstraintCategory::CallArgument(None), |
| var_or_use_span, |
| &format!("`{name}`"), |
| "block", |
| ), |
| ( |
| Some(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}`"), |
| "function", |
| ), |
| ( |
| name, |
| BorrowExplanation::MustBeValidFor { |
| category: ConstraintCategory::Assignment, |
| from_closure: false, |
| region_name: |
| RegionName { |
| source: RegionNameSource::AnonRegionFromUpvar(upvar_span, 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<'tcx>, |
| ) -> 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!("`{name}` would have to be valid for `{region_name}`..."), |
| ); |
| |
| err.span_label( |
| drop_span, |
| format!( |
| "...but `{}` will be dropped here, when the {} returns", |
| name, |
| self.infcx |
| .tcx |
| .opt_item_name(self.mir_def_id().to_def_id()) |
| .map(|name| format!("function `{name}`")) |
| .unwrap_or_else(|| { |
| match &self.infcx.tcx.def_kind(self.mir_def_id()) { |
| DefKind::Closure => "enclosing closure", |
| DefKind::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!("`{name}` dropped here while still borrowed")); |
| |
| borrow_spans.args_subdiag(&mut err, |args_span| { |
| crate::session_diagnostics::CaptureArgLabel::Capture { |
| is_within: borrow_spans.for_generator(), |
| args_span, |
| } |
| }); |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| Some(borrow_span), |
| 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 {what_was_dropped} needs exclusive access to `{borrowed}`, \ |
| because the type `{dropped_ty}` implements the `Drop` trait" |
| ), |
| None => format!( |
| "here is drop of {what_was_dropped}; whose type `{dropped_ty}` implements the `Drop` trait" |
| ), |
| }; |
| 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 |
| } |
| |
| #[instrument(level = "debug", skip(self))] |
| 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<'tcx>, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| 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 value 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. |
| let sm = self.infcx.tcx.sess.source_map(); |
| let mut suggested = false; |
| let msg = "consider using a `let` binding to create a longer lived value"; |
| |
| /// We check that there's a single level of block nesting to ensure always correct |
| /// suggestions. If we don't, then we only provide a free-form message to avoid |
| /// misleading users in cases like `tests/ui/nll/borrowed-temporary-error.rs`. |
| /// We could expand the analysis to suggest hoising all of the relevant parts of |
| /// the users' code to make the code compile, but that could be too much. |
| struct NestedStatementVisitor { |
| span: Span, |
| current: usize, |
| found: usize, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for NestedStatementVisitor { |
| fn visit_block(&mut self, block: &hir::Block<'tcx>) { |
| self.current += 1; |
| walk_block(self, block); |
| self.current -= 1; |
| } |
| fn visit_expr(&mut self, expr: &hir::Expr<'tcx>) { |
| if self.span == expr.span.source_callsite() { |
| self.found = self.current; |
| } |
| walk_expr(self, expr); |
| } |
| } |
| let source_info = self.body.source_info(location); |
| let proper_span = proper_span.source_callsite(); |
| if let Some(scope) = self.body.source_scopes.get(source_info.scope) |
| && let ClearCrossCrate::Set(scope_data) = &scope.local_data |
| && let Some(node) = self.infcx.tcx.hir().find(scope_data.lint_root) |
| && let Some(id) = node.body_id() |
| && let hir::ExprKind::Block(block, _) = self.infcx.tcx.hir().body(id).value.kind |
| { |
| for stmt in block.stmts { |
| let mut visitor = NestedStatementVisitor { |
| span: proper_span, |
| current: 0, |
| found: 0, |
| }; |
| visitor.visit_stmt(stmt); |
| if visitor.found == 0 |
| && stmt.span.contains(proper_span) |
| && let Some(p) = sm.span_to_margin(stmt.span) |
| && let Ok(s) = sm.span_to_snippet(proper_span) |
| { |
| let addition = format!("let binding = {};\n{}", s, " ".repeat(p)); |
| err.multipart_suggestion_verbose( |
| msg, |
| vec![ |
| (stmt.span.shrink_to_lo(), addition), |
| (proper_span, "binding".to_string()), |
| ], |
| Applicability::MaybeIncorrect, |
| ); |
| suggested = true; |
| break; |
| } |
| } |
| } |
| if !suggested { |
| err.note(msg); |
| } |
| } |
| _ => {} |
| } |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| &self.body, |
| &self.local_names, |
| &mut err, |
| "", |
| None, |
| None, |
| ); |
| |
| borrow_spans.args_subdiag(&mut err, |args_span| { |
| crate::session_diagnostics::CaptureArgLabel::Capture { |
| is_within: borrow_spans.for_generator(), |
| args_span, |
| } |
| }); |
| |
| err |
| } |
| |
| fn try_report_cannot_return_reference_to_local( |
| &self, |
| borrow: &BorrowData<'tcx>, |
| borrow_span: Span, |
| return_span: Span, |
| category: ConstraintCategory<'tcx>, |
| 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::Temp if self.body.local_decls[local].is_user_variable() => { |
| "local variable " |
| } |
| LocalKind::Arg |
| if !self.upvars.is_empty() && local == ty::CAPTURE_STRUCT_LOCAL => |
| { |
| "variable captured by `move` " |
| } |
| LocalKind::Arg => "function parameter ", |
| LocalKind::ReturnPointer | LocalKind::Temp => { |
| bug!("temporary or return pointer with a name") |
| } |
| } |
| } else { |
| "local data " |
| }; |
| (format!("{local_kind}`{place_desc}`"), format!("`{place_desc}` is borrowed here")) |
| } 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::Arg => ( |
| "function parameter".to_string(), |
| "function parameter borrowed here".to_string(), |
| ), |
| LocalKind::Temp if self.body.local_decls[local].is_user_variable() => { |
| ("local binding".to_string(), "local binding introduced here".to_string()) |
| } |
| LocalKind::ReturnPointer | LocalKind::Temp => { |
| ("temporary value".to_string(), "temporary value created 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 return_ty = self.regioncx.universal_regions().unnormalized_output_ty; |
| |
| // to avoid panics |
| if let Some(iter_trait) = tcx.get_diagnostic_item(sym::Iterator) |
| && self |
| .infcx |
| .type_implements_trait(iter_trait, [return_ty], self.param_env) |
| .must_apply_modulo_regions() |
| { |
| err.span_suggestion_hidden( |
| return_span.shrink_to_hi(), |
| "use `.collect()` to allocate the iterator", |
| ".collect::<Vec<_>>()", |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| |
| Some(err) |
| } |
| |
| #[instrument(level = "debug", skip(self))] |
| fn report_escaping_closure_capture( |
| &mut self, |
| use_span: UseSpans<'tcx>, |
| var_span: Span, |
| fr_name: &RegionName, |
| category: ConstraintCategory<'tcx>, |
| constraint_span: Span, |
| captured_var: &str, |
| scope: &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 ") |
| } else if string.starts_with("async|") { |
| let pos = args_span.lo() + BytePos(5); |
| (args_span.with_lo(pos).with_hi(pos), " move") |
| } else { |
| (args_span.shrink_to_lo(), "move ") |
| } |
| } |
| Err(_) => (args_span, "move |<args>| <body>"), |
| }; |
| 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, |
| scope, |
| ); |
| err.span_suggestion_verbose( |
| sugg_span, |
| format!( |
| "to force the {kind} to take ownership of {captured_var} (and any \ |
| other referenced variables), use the `move` keyword" |
| ), |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| |
| match category { |
| ConstraintCategory::Return(_) | ConstraintCategory::OpaqueType => { |
| let msg = format!("{kind} is returned here"); |
| 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!("{scope} 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: Symbol, |
| escape_span: Span, |
| ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> { |
| let tcx = self.infcx.tcx; |
| |
| let escapes_from = tcx.def_descr(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!("`{upvar_name}` declared here, outside of the {escapes_from} body"), |
| ); |
| |
| err.span_label(borrow_span, format!("borrow is only valid in the {escapes_from} body")); |
| |
| if let Some(name) = name { |
| err.span_label( |
| escape_span, |
| format!("reference to `{name}` escapes the {escapes_from} body here"), |
| ); |
| } else { |
| err.span_label(escape_span, format!("reference escapes the {escapes_from} body here")); |
| } |
| |
| err |
| } |
| |
| fn get_moved_indexes( |
| &mut self, |
| location: Location, |
| mpi: MovePathIndex, |
| ) -> (Vec<MoveSite>, Vec<Location>) { |
| fn predecessor_locations<'tcx, 'a>( |
| body: &'a mir::Body<'tcx>, |
| location: Location, |
| ) -> impl Iterator<Item = Location> + Captures<'tcx> + 'a { |
| if location.statement_index == 0 { |
| let predecessors = body.basic_blocks.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 = FxIndexSet::default(); |
| let mut move_locations = FxIndexSet::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 = FxIndexSet::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_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => BorrowUseInGenerator { var_span }, |
| None => BorrowUseInClosure { var_span }, |
| } |
| }); |
| |
| self.buffer_error(err); |
| |
| return; |
| } |
| } |
| |
| let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place); |
| |
| loan_spans.var_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| { |
| use crate::session_diagnostics::CaptureVarCause::*; |
| match kind { |
| Some(_) => BorrowUseInGenerator { var_span }, |
| None => BorrowUseInClosure { var_span }, |
| } |
| }); |
| |
| 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 { call_source: CallSource::OverloadedOperator, .. }, |
| .. |
| }), |
| Some((method_did, method_args)), |
| ) = ( |
| &self.body[loan.reserve_location.block].terminator, |
| rustc_middle::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_args) |
| .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: |
| ClearCrossCrate::Set( |
| box LocalInfo::User(BindingForm::Var(VarBindingForm { |
| opt_match_place: None, |
| .. |
| })) |
| | box LocalInfo::StaticRef { .. } |
| | box LocalInfo::Boring, |
| ), |
| .. |
| }) |
| | 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::OpaqueCast { .. } |
| | 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()).instantiate_identity(); |
| match ty.kind() { |
| ty::FnDef(_, _) | ty::FnPtr(_) => self.annotate_fn_sig( |
| self.mir_def_id(), |
| self.infcx.tcx.fn_sig(self.mir_def_id()).instantiate_identity(), |
| ), |
| _ => 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 (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, args), |
| operands, |
| ) = rvalue |
| { |
| let def_id = def_id.expect_local(); |
| 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, args.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, target: Some(_), args, .. } = |
| &terminator.kind |
| { |
| if let Some(assigned_to) = destination.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: LocalDefId, |
| sig: ty::PolyFnSig<'tcx>, |
| ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { |
| debug!("annotate_fn_sig: did={:?} sig={:?}", did, sig); |
| let is_closure = self.infcx.tcx.is_closure(did.to_def_id()); |
| let fn_hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(did); |
| 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::Ref(lifetime, _) = &fn_decl.inputs[index].kind { |
| // With access to the lifetime, we can get |
| // the span of it. |
| arguments.push((*argument, lifetime.ident.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::Ref(lifetime, _) = ty.kind { |
| return_span = lifetime.ident.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 `{region_name}` lifetime of \ |
| the return type", |
| )); |
| |
| region_name |
| } |
| } |
| } |
| } |
| |
| /// Detect whether one of the provided spans is a statement nested within the top-most visited expr |
| struct ReferencedStatementsVisitor<'a>(&'a [Span], bool); |
| |
| impl<'a, 'v> Visitor<'v> for ReferencedStatementsVisitor<'a> { |
| fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) { |
| match s.kind { |
| hir::StmtKind::Semi(expr) if self.0.contains(&expr.span) => { |
| self.1 = true; |
| } |
| _ => {} |
| } |
| } |
| } |
| |
| /// Given a set of spans representing statements initializing the relevant binding, visit all the |
| /// function expressions looking for branching code paths that *do not* initialize the binding. |
| struct ConditionVisitor<'b> { |
| spans: &'b [Span], |
| name: &'b str, |
| errors: Vec<(Span, String)>, |
| } |
| |
| impl<'b, 'v> Visitor<'v> for ConditionVisitor<'b> { |
| fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) { |
| match ex.kind { |
| hir::ExprKind::If(cond, body, None) => { |
| // `if` expressions with no `else` that initialize the binding might be missing an |
| // `else` arm. |
| let mut v = ReferencedStatementsVisitor(self.spans, false); |
| v.visit_expr(body); |
| if v.1 { |
| self.errors.push(( |
| cond.span, |
| format!( |
| "if this `if` condition is `false`, {} is not initialized", |
| self.name, |
| ), |
| )); |
| self.errors.push(( |
| ex.span.shrink_to_hi(), |
| format!("an `else` arm might be missing here, initializing {}", self.name), |
| )); |
| } |
| } |
| hir::ExprKind::If(cond, body, Some(other)) => { |
| // `if` expressions where the binding is only initialized in one of the two arms |
| // might be missing a binding initialization. |
| let mut a = ReferencedStatementsVisitor(self.spans, false); |
| a.visit_expr(body); |
| let mut b = ReferencedStatementsVisitor(self.spans, false); |
| b.visit_expr(other); |
| match (a.1, b.1) { |
| (true, true) | (false, false) => {} |
| (true, false) => { |
| if other.span.is_desugaring(DesugaringKind::WhileLoop) { |
| self.errors.push(( |
| cond.span, |
| format!( |
| "if this condition isn't met and the `while` loop runs 0 \ |
| times, {} is not initialized", |
| self.name |
| ), |
| )); |
| } else { |
| self.errors.push(( |
| body.span.shrink_to_hi().until(other.span), |
| format!( |
| "if the `if` condition is `false` and this `else` arm is \ |
| executed, {} is not initialized", |
| self.name |
| ), |
| )); |
| } |
| } |
| (false, true) => { |
| self.errors.push(( |
| cond.span, |
| format!( |
| "if this condition is `true`, {} is not initialized", |
| self.name |
| ), |
| )); |
| } |
| } |
| } |
| hir::ExprKind::Match(e, arms, loop_desugar) => { |
| // If the binding is initialized in one of the match arms, then the other match |
| // arms might be missing an initialization. |
| let results: Vec<bool> = arms |
| .iter() |
| .map(|arm| { |
| let mut v = ReferencedStatementsVisitor(self.spans, false); |
| v.visit_arm(arm); |
| v.1 |
| }) |
| .collect(); |
| if results.iter().any(|x| *x) && !results.iter().all(|x| *x) { |
| for (arm, seen) in arms.iter().zip(results) { |
| if !seen { |
| if loop_desugar == hir::MatchSource::ForLoopDesugar { |
| self.errors.push(( |
| e.span, |
| format!( |
| "if the `for` loop runs 0 times, {} is not initialized", |
| self.name |
| ), |
| )); |
| } else if let Some(guard) = &arm.guard { |
| self.errors.push(( |
| arm.pat.span.to(guard.body().span), |
| format!( |
| "if this pattern and condition are matched, {} is not \ |
| initialized", |
| self.name |
| ), |
| )); |
| } else { |
| self.errors.push(( |
| arm.pat.span, |
| format!( |
| "if this pattern is matched, {} is not initialized", |
| self.name |
| ), |
| )); |
| } |
| } |
| } |
| } |
| } |
| // FIXME: should we also account for binops, particularly `&&` and `||`? `try` should |
| // also be accounted for. For now it is fine, as if we don't find *any* relevant |
| // branching code paths, we point at the places where the binding *is* initialized for |
| // *some* context. |
| _ => {} |
| } |
| walk_expr(self, ex); |
| } |
| } |