| use rustc::hir; |
| use rustc::hir::def_id::DefId; |
| use rustc::mir::{ |
| self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory, Local, |
| LocalDecl, LocalKind, Location, Operand, Place, PlaceBase, PlaceRef, ProjectionElem, Rvalue, |
| Statement, StatementKind, TerminatorKind, VarBindingForm, |
| }; |
| use rustc::ty::{self, Ty}; |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_data_structures::indexed_vec::Idx; |
| use rustc_errors::{Applicability, DiagnosticBuilder}; |
| use syntax_pos::Span; |
| use syntax::source_map::DesugaringKind; |
| |
| use super::nll::explain_borrow::BorrowExplanation; |
| use super::nll::region_infer::{RegionName, RegionNameSource}; |
| use super::prefixes::IsPrefixOf; |
| use super::WriteKind; |
| use super::borrow_set::BorrowData; |
| use super::MirBorrowckCtxt; |
| use super::{InitializationRequiringAction, PrefixSet}; |
| use super::error_reporting::{IncludingDowncast, UseSpans}; |
| use crate::dataflow::drop_flag_effects; |
| use crate::dataflow::indexes::{MovePathIndex, MoveOutIndex}; |
| use crate::util::borrowck_errors; |
| |
| #[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(super) fn report_use_of_moved_or_uninitialized( |
| &mut self, |
| location: Location, |
| desired_action: InitializationRequiringAction, |
| (moved_place, used_place, span): (PlaceRef<'cx, 'tcx>, PlaceRef<'cx, '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 = self.get_moved_indexes(location, mpi); |
| debug!( |
| "report_use_of_moved_or_uninitialized: move_site_vec={:?}", |
| move_site_vec |
| ); |
| 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 = self |
| .prefixes(used_place, PrefixSet::All) |
| .last() |
| .unwrap(); |
| |
| if self.uninitialized_error_reported.contains(&root_place) { |
| debug!( |
| "report_use_of_moved_or_uninitialized place: error about {:?} suppressed", |
| root_place |
| ); |
| return; |
| } |
| |
| self.uninitialized_error_reported.insert(root_place); |
| |
| let item_msg = match self.describe_place_with_options(used_place, |
| IncludingDowncast(true)) { |
| Some(name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| let mut err = self.cannot_act_on_uninitialized_variable( |
| span, |
| desired_action.as_noun(), |
| &self.describe_place_with_options(moved_place, IncludingDowncast(true)) |
| .unwrap_or_else(|| "_".to_owned()), |
| ); |
| err.span_label(span, format!("use of possibly-uninitialized {}", item_msg)); |
| |
| use_spans.var_span_label( |
| &mut err, |
| format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), |
| ); |
| |
| // This error should not be downgraded to a warning, |
| // even in migrate mode. |
| self.disable_error_downgrading(); |
| err.buffer(&mut self.errors_buffer); |
| } else { |
| if let Some((reported_place, _)) = self.move_error_reported.get(&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 msg = ""; //FIXME: add "partially " or "collaterally " |
| |
| let mut err = self.cannot_act_on_moved_value( |
| span, |
| desired_action.as_noun(), |
| msg, |
| self.describe_place_with_options(moved_place, IncludingDowncast(true)), |
| ); |
| |
| self.add_moved_or_invoked_closure_note( |
| location, |
| used_place, |
| &mut err, |
| ); |
| |
| let mut is_loop_move = false; |
| 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; |
| used_place != moved_place.as_ref() |
| && used_place.is_prefix_of(moved_place.as_ref()) |
| }); |
| for move_site in &move_site_vec { |
| let move_out = self.move_data.moves[(*move_site).moi]; |
| let moved_place = &self.move_data.move_paths[move_out.path].place; |
| |
| let move_spans = self.move_spans(moved_place.as_ref(), move_out.source); |
| let move_span = move_spans.args_or_use(); |
| |
| let move_msg = if move_spans.for_closure() { |
| " into closure" |
| } else { |
| "" |
| }; |
| |
| if span == move_span { |
| err.span_label( |
| span, |
| format!("value moved{} here, in previous iteration of loop", move_msg), |
| ); |
| is_loop_move = true; |
| } else if move_site.traversed_back_edge { |
| err.span_label( |
| move_span, |
| format!( |
| "value moved{} here, in previous iteration of loop", |
| move_msg |
| ), |
| ); |
| } else { |
| err.span_label(move_span, format!("value moved{} here", move_msg)); |
| move_spans.var_span_label( |
| &mut err, |
| format!("variable moved due to use{}", move_spans.describe()), |
| ); |
| } |
| if Some(DesugaringKind::ForLoop) == move_span.desugaring_kind() { |
| if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) { |
| err.span_suggestion( |
| move_span, |
| "consider borrowing to avoid moving into the for loop", |
| format!("&{}", snippet), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| } |
| |
| use_spans.var_span_label( |
| &mut err, |
| format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), |
| ); |
| |
| if !is_loop_move { |
| err.span_label( |
| span, |
| format!( |
| "value {} here {}", |
| desired_action.as_verb_in_past_tense(), |
| if is_partial_move { "after partial move" } else { "after move" }, |
| ), |
| ); |
| } |
| |
| let ty = |
| Place::ty_from(used_place.base, used_place.projection, self.body, self.infcx.tcx) |
| .ty; |
| let needs_note = match ty.sty { |
| ty::Closure(id, _) => { |
| let tables = self.infcx.tcx.typeck_tables_of(id); |
| let hir_id = self.infcx.tcx.hir().as_local_hir_id(id).unwrap(); |
| |
| tables.closure_kind_origins().get(hir_id).is_none() |
| } |
| _ => true, |
| }; |
| |
| if needs_note { |
| 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; |
| let opt_name = |
| self.describe_place_with_options(place.as_ref(), IncludingDowncast(true)); |
| let note_msg = match opt_name { |
| Some(ref name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| if let ty::Param(param_ty) = ty.sty { |
| let tcx = self.infcx.tcx; |
| let generics = tcx.generics_of(self.mir_def_id); |
| let def_id = generics.type_param(¶m_ty, tcx).def_id; |
| if let Some(sp) = tcx.hir().span_if_local(def_id) { |
| err.span_label( |
| sp, |
| "consider adding a `Copy` constraint to this type argument", |
| ); |
| } |
| } |
| let span = if let Place { |
| base: PlaceBase::Local(local), |
| projection: box [], |
| } = place { |
| let decl = &self.body.local_decls[*local]; |
| Some(decl.source_info.span) |
| } else { |
| None |
| }; |
| self.note_type_does_not_implement_copy( |
| &mut err, |
| ¬e_msg, |
| ty, |
| span, |
| ); |
| } |
| |
| if let Some((_, mut old_err)) = self.move_error_reported |
| .insert(move_out_indices, (used_place, err)) |
| { |
| // Cancel the old error so it doesn't ICE. |
| old_err.cancel(); |
| } |
| } |
| } |
| |
| pub(super) 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 = match self.describe_place(place.as_ref()) { |
| Some(name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| let borrow_msg = match self.describe_place(borrow.borrowed_place.as_ref()) { |
| Some(name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.args_or_use(); |
| |
| let move_spans = self.move_spans(place.as_ref(), location); |
| let span = move_spans.args_or_use(); |
| |
| let mut err = self.cannot_move_when_borrowed( |
| span, |
| &self.describe_place(place.as_ref()).unwrap_or_else(|| "_".to_owned()), |
| ); |
| err.span_label(borrow_span, format!("borrow of {} occurs here", borrow_msg)); |
| err.span_label(span, format!("move out of {} occurs here", value_msg)); |
| |
| borrow_spans.var_span_label( |
| &mut err, |
| format!("borrow occurs due to use{}", borrow_spans.describe()) |
| ); |
| |
| move_spans.var_span_label( |
| &mut err, |
| format!("move occurs due to use{}", move_spans.describe()) |
| ); |
| |
| self.explain_why_borrow_contains_point( |
| location, |
| borrow, |
| None, |
| ).add_explanation_to_diagnostic(self.infcx.tcx, self.body, &mut err, "", Some(borrow_span)); |
| err.buffer(&mut self.errors_buffer); |
| } |
| |
| pub(super) fn report_use_while_mutably_borrowed( |
| &mut self, |
| location: Location, |
| (place, _span): (&Place<'tcx>, Span), |
| borrow: &BorrowData<'tcx>, |
| ) -> DiagnosticBuilder<'cx> { |
| 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(); |
| |
| let mut err = self.cannot_use_when_mutably_borrowed( |
| span, |
| &self.describe_place(place.as_ref()).unwrap_or_else(|| "_".to_owned()), |
| borrow_span, |
| &self.describe_place(borrow.borrowed_place.as_ref()) |
| .unwrap_or_else(|| "_".to_owned()), |
| ); |
| |
| borrow_spans.var_span_label(&mut err, { |
| let place = &borrow.borrowed_place; |
| let desc_place = |
| self.describe_place(place.as_ref()).unwrap_or_else(|| "_".to_owned()); |
| |
| format!("borrow occurs due to use of `{}`{}", desc_place, borrow_spans.describe()) |
| }); |
| |
| self.explain_why_borrow_contains_point(location, borrow, None) |
| .add_explanation_to_diagnostic(self.infcx.tcx, self.body, &mut err, "", None); |
| err |
| } |
| |
| pub(super) fn report_conflicting_borrow( |
| &mut self, |
| location: Location, |
| (place, span): (&Place<'tcx>, Span), |
| gen_borrow_kind: BorrowKind, |
| issued_borrow: &BorrowData<'tcx>, |
| ) -> DiagnosticBuilder<'cx> { |
| 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, |
| "immutable", |
| "mutable", |
| issued_borrow.kind, |
| "immutable", |
| "mutable", |
| ) { |
| (BorrowKind::Shared, lft, _, BorrowKind::Mut { .. }, _, rgt) => { |
| first_borrow_desc = "mutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| lft, |
| issued_span, |
| "it", |
| rgt, |
| &msg_borrow, |
| None, |
| ) |
| } |
| (BorrowKind::Mut { .. }, _, lft, BorrowKind::Shared, rgt, _) => { |
| first_borrow_desc = "immutable "; |
| self.cannot_reborrow_already_borrowed( |
| span, |
| &desc_place, |
| &msg_place, |
| lft, |
| issued_span, |
| "it", |
| rgt, |
| &msg_borrow, |
| None, |
| ) |
| } |
| |
| (BorrowKind::Mut { .. }, _, _, BorrowKind::Mut { .. }, _, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_mutably_borrow_multiply( |
| span, |
| &desc_place, |
| &msg_place, |
| issued_span, |
| &msg_borrow, |
| None, |
| ) |
| } |
| |
| (BorrowKind::Unique, _, _, BorrowKind::Unique, _, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_two_closures( |
| span, |
| &desc_place, |
| issued_span, |
| None, |
| ) |
| } |
| |
| (BorrowKind::Mut { .. }, _, _, BorrowKind::Shallow, _, _) |
| | (BorrowKind::Unique, _, _, BorrowKind::Shallow, _, _) => { |
| let mut err = self.cannot_mutate_in_match_guard( |
| span, |
| issued_span, |
| &desc_place, |
| "mutably borrow", |
| ); |
| borrow_spans.var_span_label( |
| &mut err, |
| format!( |
| "borrow occurs due to use of `{}`{}", desc_place, borrow_spans.describe() |
| ), |
| ); |
| |
| return err; |
| } |
| |
| (BorrowKind::Unique, _, _, _, _, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_uniquely_borrow_by_one_closure( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| issued_span, |
| "it", |
| "", |
| None, |
| ) |
| }, |
| |
| (BorrowKind::Shared, lft, _, BorrowKind::Unique, _, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_reborrow_already_uniquely_borrowed( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| lft, |
| issued_span, |
| "", |
| None, |
| second_borrow_desc, |
| ) |
| } |
| |
| (BorrowKind::Mut { .. }, _, lft, BorrowKind::Unique, _, _) => { |
| first_borrow_desc = "first "; |
| self.cannot_reborrow_already_uniquely_borrowed( |
| span, |
| container_name, |
| &desc_place, |
| "", |
| lft, |
| issued_span, |
| "", |
| None, |
| second_borrow_desc, |
| ) |
| } |
| |
| (BorrowKind::Shared, _, _, BorrowKind::Shared, _, _) |
| | (BorrowKind::Shared, _, _, BorrowKind::Shallow, _, _) |
| | (BorrowKind::Shallow, _, _, BorrowKind::Mut { .. }, _, _) |
| | (BorrowKind::Shallow, _, _, BorrowKind::Unique, _, _) |
| | (BorrowKind::Shallow, _, _, BorrowKind::Shared, _, _) |
| | (BorrowKind::Shallow, _, _, BorrowKind::Shallow, _, _) => unreachable!(), |
| }; |
| |
| if issued_spans == borrow_spans { |
| borrow_spans.var_span_label( |
| &mut err, |
| format!("borrows occur due to use of `{}`{}", desc_place, borrow_spans.describe()), |
| ); |
| } else { |
| let borrow_place = &issued_borrow.borrowed_place; |
| let borrow_place_desc = self.describe_place(borrow_place.as_ref()) |
| .unwrap_or_else(|| "_".to_owned()); |
| issued_spans.var_span_label( |
| &mut err, |
| format!( |
| "first borrow occurs due to use of `{}`{}", |
| borrow_place_desc, |
| issued_spans.describe(), |
| ), |
| ); |
| |
| borrow_spans.var_span_label( |
| &mut err, |
| format!( |
| "second borrow occurs due to use of `{}`{}", |
| desc_place, |
| borrow_spans.describe(), |
| ), |
| ); |
| } |
| |
| if union_type_name != "" { |
| err.note(&format!( |
| "`{}` is a field of the union `{}`, so it overlaps the field `{}`", |
| msg_place, union_type_name, msg_borrow, |
| )); |
| } |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| self.body, |
| &mut err, |
| first_borrow_desc, |
| None, |
| ); |
| |
| err |
| } |
| |
| /// 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: |
| /// |
| /// > 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(super) 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, place_projection| { |
| let ty = Place::ty_from(place_base, place_projection, self.body, self.infcx.tcx).ty; |
| ty.ty_adt_def().filter(|adt| adt.is_union()).map(|_| ty) |
| }; |
| let describe_place = |place| self.describe_place(place).unwrap_or_else(|| "_".to_owned()); |
| |
| // 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 a access to a different field. |
| let Place { |
| base, |
| projection, |
| } = first_borrowed_place; |
| |
| for (i, elem) in projection.iter().enumerate().rev() { |
| let proj_base = &projection[..i]; |
| |
| match elem { |
| ProjectionElem::Field(field, _) if union_ty(base, proj_base).is_some() => { |
| return Some((PlaceRef { |
| base: base, |
| projection: proj_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 a access to a different field of the same union. |
| let Place { |
| base, |
| projection, |
| } = second_borrowed_place; |
| |
| for (i, elem) in projection.iter().enumerate().rev() { |
| let proj_base = &projection[..i]; |
| |
| if let ProjectionElem::Field(field, _) = elem { |
| if let Some(union_ty) = union_ty(base, proj_base) { |
| if field != target_field |
| && base == target_base.base |
| && proj_base == target_base.projection { |
| // FIXME when we avoid clone reuse describe_place closure |
| let describe_base_place = self.describe_place(PlaceRef { |
| base: base, |
| projection: proj_base, |
| }).unwrap_or_else(|| "_".to_owned()); |
| |
| return Some(( |
| describe_base_place, |
| describe_place(first_borrowed_place.as_ref()), |
| describe_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. |
| ( |
| describe_place(first_borrowed_place.as_ref()), |
| "".to_string(), |
| "".to_string(), |
| "".to_string(), |
| ) |
| }) |
| } |
| |
| /// Reports StorageDeadOrDrop of `place` conflicts with `borrow`. |
| /// |
| /// This means that some data referenced by `borrow` needs to live |
| /// past the point where the StorageDeadOrDrop of `place` occurs. |
| /// This is usually interpreted as meaning that `place` has too |
| /// short a lifetime. (But sometimes it is more useful to report |
| /// it as a more direct conflict between the execution of a |
| /// `Drop::drop` with an aliasing borrow.) |
| pub(super) fn report_borrowed_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| borrow: &BorrowData<'tcx>, |
| place_span: (&Place<'tcx>, Span), |
| kind: Option<WriteKind>, |
| ) { |
| debug!( |
| "report_borrowed_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, borrow, place_span, kind |
| ); |
| |
| let drop_span = place_span.1; |
| let root_place = self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All) |
| .last() |
| .unwrap(); |
| |
| let borrow_spans = self.retrieve_borrow_spans(borrow); |
| let borrow_span = borrow_spans.var_or_use(); |
| |
| assert!(root_place.projection.is_empty()); |
| let proper_span = match root_place.base { |
| PlaceBase::Local(local) => self.body.local_decls[*local].source_info.span, |
| _ => drop_span, |
| }; |
| |
| if self.access_place_error_reported |
| .contains(&(Place { |
| base: root_place.base.clone(), |
| projection: root_place.projection.to_vec().into_boxed_slice(), |
| }, 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 { |
| base: root_place.base.clone(), |
| projection: root_place.projection.to_vec().into_boxed_slice(), |
| }, borrow_span)); |
| |
| 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); |
| |
| let err = match (place_desc, explanation) { |
| (Some(_), _) if self.is_place_thread_local(root_place) => { |
| self.report_thread_local_value_does_not_live_long_enough(drop_span, borrow_span) |
| } |
| // If the outlives constraint comes from inside the closure, |
| // for example: |
| // |
| // let x = 0; |
| // let y = &x; |
| // Box::new(|| y) as Box<Fn() -> &'static i32> |
| // |
| // then just use the normal error. The closure isn't escaping |
| // and `move` will not help here. |
| ( |
| Some(ref name), |
| BorrowExplanation::MustBeValidFor { |
| category: category @ ConstraintCategory::Return, |
| from_closure: false, |
| ref region_name, |
| span, |
| .. |
| }, |
| ) |
| | ( |
| Some(ref name), |
| BorrowExplanation::MustBeValidFor { |
| category: category @ ConstraintCategory::CallArgument, |
| from_closure: false, |
| ref region_name, |
| span, |
| .. |
| }, |
| ) if borrow_spans.for_closure() => self.report_escaping_closure_capture( |
| borrow_spans.args_or_use(), |
| borrow_span, |
| region_name, |
| category, |
| span, |
| &format!("`{}`", name), |
| ), |
| ( |
| ref name, |
| BorrowExplanation::MustBeValidFor { |
| category: ConstraintCategory::Assignment, |
| from_closure: false, |
| region_name: RegionName { |
| source: RegionNameSource::AnonRegionFromUpvar(upvar_span, ref upvar_name), |
| .. |
| }, |
| span, |
| .. |
| }, |
| ) => self.report_escaping_data(borrow_span, name, upvar_span, upvar_name, span), |
| (Some(name), explanation) => self.report_local_value_does_not_live_long_enough( |
| location, |
| &name, |
| &borrow, |
| drop_span, |
| borrow_spans, |
| explanation, |
| ), |
| (None, explanation) => self.report_temporary_value_does_not_live_long_enough( |
| location, |
| &borrow, |
| drop_span, |
| borrow_spans, |
| proper_span, |
| explanation, |
| ), |
| }; |
| |
| err.buffer(&mut self.errors_buffer); |
| } |
| |
| fn report_local_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| name: &str, |
| borrow: &BorrowData<'tcx>, |
| drop_span: Span, |
| borrow_spans: UseSpans, |
| explanation: BorrowExplanation, |
| ) -> DiagnosticBuilder<'cx> { |
| debug!( |
| "report_local_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, name, borrow, drop_span, borrow_spans |
| ); |
| |
| let borrow_span = borrow_spans.var_or_use(); |
| if let BorrowExplanation::MustBeValidFor { |
| category, |
| span, |
| ref opt_place_desc, |
| from_closure: false, |
| .. |
| } = explanation { |
| if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
| borrow, |
| borrow_span, |
| span, |
| category, |
| opt_place_desc.as_ref(), |
| ) { |
| return diag; |
| } |
| } |
| |
| let mut err = self.path_does_not_live_long_enough( |
| borrow_span, |
| &format!("`{}`", name), |
| ); |
| |
| if let Some(annotation) = self.annotate_argument_and_return_for_borrow(borrow) { |
| let region_name = annotation.emit(self, &mut err); |
| |
| err.span_label( |
| borrow_span, |
| format!("`{}` would have to be valid for `{}`...", name, region_name), |
| ); |
| |
| if let Some(fn_hir_id) = self.infcx.tcx.hir().as_local_hir_id(self.mir_def_id) { |
| err.span_label( |
| drop_span, |
| format!( |
| "...but `{}` will be dropped here, when the function `{}` returns", |
| name, |
| self.infcx.tcx.hir().name(fn_hir_id), |
| ), |
| ); |
| |
| 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>", |
| ); |
| } else { |
| err.span_label( |
| drop_span, |
| format!("...but `{}` dropped here while still borrowed", name), |
| ); |
| } |
| |
| if let BorrowExplanation::MustBeValidFor { .. } = explanation { |
| } else { |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, |
| self.body, |
| &mut err, |
| "", |
| None, |
| ); |
| } |
| } else { |
| err.span_label(borrow_span, "borrowed value does not live long enough"); |
| err.span_label( |
| drop_span, |
| format!("`{}` dropped here while still borrowed", name), |
| ); |
| |
| let within = if borrow_spans.for_generator() { |
| " by generator" |
| } else { |
| "" |
| }; |
| |
| borrow_spans.args_span_label( |
| &mut err, |
| format!("value captured here{}", within), |
| ); |
| |
| explanation.add_explanation_to_diagnostic( |
| self.infcx.tcx, self.body, &mut err, "", 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.as_str()), |
| None => String::from("temporary value"), |
| }; |
| |
| let label = match self.describe_place(borrow.borrowed_place.as_ref()) { |
| Some(borrowed) => format!( |
| "here, drop of {D} needs exclusive access to `{B}`, \ |
| because the type `{T}` implements the `Drop` trait", |
| D = what_was_dropped, |
| T = dropped_ty, |
| B = borrowed |
| ), |
| None => format!( |
| "here is drop of {D}; whose type `{T}` implements the `Drop` trait", |
| D = what_was_dropped, |
| T = dropped_ty |
| ), |
| }; |
| err.span_label(drop_span, label); |
| |
| // Only give this note and suggestion if they could be relevant. |
| let explanation = |
| self.explain_why_borrow_contains_point(location, borrow, kind.map(|k| (k, place))); |
| match explanation { |
| BorrowExplanation::UsedLater { .. } |
| | BorrowExplanation::UsedLaterWhenDropped { .. } => { |
| err.note("consider using a `let` binding to create a longer lived value"); |
| } |
| _ => {} |
| } |
| |
| explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.body, &mut err, "", None); |
| |
| err.buffer(&mut self.errors_buffer); |
| } |
| |
| fn report_thread_local_value_does_not_live_long_enough( |
| &mut self, |
| drop_span: Span, |
| borrow_span: Span, |
| ) -> DiagnosticBuilder<'cx> { |
| debug!( |
| "report_thread_local_value_does_not_live_long_enough(\ |
| {:?}, {:?}\ |
| )", |
| drop_span, borrow_span |
| ); |
| |
| let mut err = self.thread_local_value_does_not_live_long_enough(borrow_span); |
| |
| err.span_label( |
| borrow_span, |
| "thread-local variables cannot be borrowed beyond the end of the function", |
| ); |
| err.span_label(drop_span, "end of enclosing function is here"); |
| |
| err |
| } |
| |
| fn report_temporary_value_does_not_live_long_enough( |
| &mut self, |
| location: Location, |
| borrow: &BorrowData<'tcx>, |
| drop_span: Span, |
| borrow_spans: UseSpans, |
| proper_span: Span, |
| explanation: BorrowExplanation, |
| ) -> DiagnosticBuilder<'cx> { |
| debug!( |
| "report_temporary_value_does_not_live_long_enough(\ |
| {:?}, {:?}, {:?}, {:?}\ |
| )", |
| location, borrow, drop_span, proper_span |
| ); |
| |
| if let BorrowExplanation::MustBeValidFor { |
| category, |
| span, |
| from_closure: false, |
| .. |
| } = explanation { |
| if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
| borrow, |
| proper_span, |
| span, |
| category, |
| None, |
| ) { |
| return diag; |
| } |
| } |
| |
| let mut err = self.temporary_value_borrowed_for_too_long(proper_span); |
| err.span_label( |
| proper_span, |
| "creates a temporary which is freed while still in use", |
| ); |
| err.span_label( |
| drop_span, |
| "temporary value is freed at the end of this statement", |
| ); |
| |
| match explanation { |
| BorrowExplanation::UsedLater(..) |
| | BorrowExplanation::UsedLaterInLoop(..) |
| | BorrowExplanation::UsedLaterWhenDropped { .. } => { |
| // Only give this note and suggestion if it could be relevant. |
| err.note("consider using a `let` binding to create a longer lived value"); |
| } |
| _ => {} |
| } |
| explanation.add_explanation_to_diagnostic(self.infcx.tcx, self.body, &mut err, "", None); |
| |
| let within = if borrow_spans.for_generator() { |
| " by generator" |
| } else { |
| "" |
| }; |
| |
| borrow_spans.args_span_label( |
| &mut err, |
| format!("value captured here{}", within), |
| ); |
| |
| err |
| } |
| |
| fn try_report_cannot_return_reference_to_local( |
| &self, |
| borrow: &BorrowData<'tcx>, |
| borrow_span: Span, |
| return_span: Span, |
| category: ConstraintCategory, |
| opt_place_desc: Option<&String>, |
| ) -> Option<DiagnosticBuilder<'cx>> { |
| 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 = match borrow.borrowed_place { |
| Place { |
| base: PlaceBase::Local(local), |
| projection: box [], |
| } => { |
| match self.body.local_kind(local) { |
| LocalKind::ReturnPointer |
| | LocalKind::Temp => bug!("temporary or return pointer with a name"), |
| LocalKind::Var => "local variable ", |
| LocalKind::Arg |
| if !self.upvars.is_empty() |
| && local == Local::new(1) => { |
| "variable captured by `move` " |
| } |
| LocalKind::Arg => { |
| "function parameter " |
| } |
| } |
| } |
| _ => "local data ", |
| }; |
| ( |
| format!("{}`{}`", local_kind, place_desc), |
| format!("`{}` is borrowed here", place_desc), |
| ) |
| } else { |
| let root_place = self.prefixes(borrow.borrowed_place.as_ref(), |
| PrefixSet::All) |
| .last() |
| .unwrap(); |
| let local = if let PlaceRef { |
| base: PlaceBase::Local(local), |
| projection: [], |
| } = root_place { |
| local |
| } else { |
| bug!("try_report_cannot_return_reference_to_local: not a local") |
| }; |
| match self.body.local_kind(*local) { |
| LocalKind::ReturnPointer | LocalKind::Temp => ( |
| "temporary value".to_string(), |
| "temporary value created here".to_string(), |
| ), |
| LocalKind::Arg => ( |
| "function parameter".to_string(), |
| "function parameter borrowed here".to_string(), |
| ), |
| LocalKind::Var => ( |
| "local binding".to_string(), |
| "local binding introduced here".to_string(), |
| ), |
| } |
| }; |
| |
| let mut err = self.cannot_return_reference_to_local( |
| return_span, |
| return_kind, |
| reference_desc, |
| &place_desc, |
| ); |
| |
| if return_span != borrow_span { |
| err.span_label(borrow_span, note); |
| } |
| |
| Some(err) |
| } |
| |
| fn report_escaping_closure_capture( |
| &mut self, |
| args_span: Span, |
| var_span: Span, |
| fr_name: &RegionName, |
| category: ConstraintCategory, |
| constraint_span: Span, |
| captured_var: &str, |
| ) -> DiagnosticBuilder<'cx> { |
| let tcx = self.infcx.tcx; |
| |
| let mut err = self.cannot_capture_in_long_lived_closure( |
| args_span, |
| captured_var, |
| var_span, |
| ); |
| |
| let suggestion = match tcx.sess.source_map().span_to_snippet(args_span) { |
| Ok(mut string) => { |
| if string.starts_with("async ") { |
| string.insert_str(6, "move "); |
| } else if string.starts_with("async|") { |
| string.insert_str(5, " move"); |
| } else { |
| string.insert_str(0, "move "); |
| }; |
| string |
| }, |
| Err(_) => "move |<args>| <body>".to_string() |
| }; |
| |
| err.span_suggestion( |
| args_span, |
| &format!("to force the closure to take ownership of {} (and any \ |
| other referenced variables), use the `move` keyword", |
| captured_var), |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| |
| match category { |
| ConstraintCategory::Return => { |
| err.span_note(constraint_span, "closure is returned here"); |
| } |
| ConstraintCategory::CallArgument => { |
| fr_name.highlight_region_name(&mut err); |
| err.span_note( |
| constraint_span, |
| &format!("function requires argument type to outlive `{}`", fr_name), |
| ); |
| } |
| _ => bug!("report_escaping_closure_capture called with unexpected constraint \ |
| category: `{:?}`", category), |
| } |
| err |
| } |
| |
| fn report_escaping_data( |
| &mut self, |
| borrow_span: Span, |
| name: &Option<String>, |
| upvar_span: Span, |
| upvar_name: &str, |
| escape_span: Span, |
| ) -> DiagnosticBuilder<'cx> { |
| let tcx = self.infcx.tcx; |
| |
| let escapes_from = if tcx.is_closure(self.mir_def_id) { |
| let tables = tcx.typeck_tables_of(self.mir_def_id); |
| let mir_hir_id = tcx.hir().def_index_to_hir_id(self.mir_def_id.index); |
| match tables.node_type(mir_hir_id).sty { |
| ty::Closure(..) => "closure", |
| ty::Generator(..) => "generator", |
| _ => bug!("Closure body doesn't have a closure or generator type"), |
| } |
| } else { |
| "function" |
| }; |
| |
| let mut err = borrowck_errors::borrowed_data_escapes_closure( |
| tcx, |
| escape_span, |
| escapes_from, |
| ); |
| |
| err.span_label( |
| upvar_span, |
| format!( |
| "`{}` is declared here, outside of the {} body", |
| upvar_name, escapes_from |
| ), |
| ); |
| |
| err.span_label( |
| borrow_span, |
| format!( |
| "borrow is only valid in the {} body", |
| escapes_from |
| ), |
| ); |
| |
| if let Some(name) = name { |
| err.span_label( |
| escape_span, |
| format!("reference to `{}` escapes the {} body here", name, escapes_from), |
| ); |
| } else { |
| err.span_label( |
| escape_span, |
| format!("reference escapes the {} body here", escapes_from), |
| ); |
| } |
| |
| err |
| } |
| |
| fn get_moved_indexes(&mut self, location: Location, mpi: MovePathIndex) -> Vec<MoveSite> { |
| let body = self.body; |
| |
| let mut stack = Vec::new(); |
| stack.extend(body.predecessor_locations(location).map(|predecessor| { |
| let is_back_edge = location.dominates(predecessor, &self.dominators); |
| (predecessor, is_back_edge) |
| })); |
| |
| let mut visited = FxHashSet::default(); |
| let mut result = vec![]; |
| |
| 'dfs: while let Some((location, is_back_edge)) = stack.pop() { |
| debug!( |
| "report_use_of_moved_or_uninitialized: (current_location={:?}, back_edge={})", |
| location, is_back_edge |
| ); |
| |
| if !visited.insert(location) { |
| continue; |
| } |
| |
| // check for moves |
| let stmt_kind = 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. |
| let mut mpis = vec![mpi]; |
| let move_paths = &self.move_data.move_paths; |
| mpis.extend(move_paths[mpi].parents(move_paths)); |
| |
| for moi in &self.move_data.loc_map[location] { |
| debug!("report_use_of_moved_or_uninitialized: moi={:?}", moi); |
| if mpis.contains(&self.move_data.moves[*moi].path) { |
| debug!("report_use_of_moved_or_uninitialized: found"); |
| result.push(MoveSite { |
| moi: *moi, |
| traversed_back_edge: is_back_edge, |
| }); |
| |
| // 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. |
| continue 'dfs; |
| } |
| } |
| } |
| |
| // check for inits |
| let mut any_match = false; |
| drop_flag_effects::for_location_inits( |
| self.infcx.tcx, |
| self.body, |
| self.move_data, |
| location, |
| |m| { |
| if m == mpi { |
| any_match = true; |
| } |
| }, |
| ); |
| if any_match { |
| continue 'dfs; |
| } |
| |
| stack.extend(body.predecessor_locations(location).map(|predecessor| { |
| let back_edge = location.dominates(predecessor, &self.dominators); |
| (predecessor, is_back_edge || back_edge) |
| })); |
| } |
| |
| result |
| } |
| |
| pub(super) 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(); |
| |
| if loan.kind == BorrowKind::Shallow { |
| let mut err = self.cannot_mutate_in_match_guard( |
| span, |
| loan_span, |
| &self.describe_place(place.as_ref()).unwrap_or_else(|| "_".to_owned()), |
| "assign", |
| ); |
| loan_spans.var_span_label( |
| &mut err, |
| format!("borrow occurs due to use{}", loan_spans.describe()), |
| ); |
| |
| err.buffer(&mut self.errors_buffer); |
| |
| return; |
| } |
| |
| let mut err = self.cannot_assign_to_borrowed( |
| span, |
| loan_span, |
| &self.describe_place(place.as_ref()).unwrap_or_else(|| "_".to_owned()), |
| ); |
| |
| loan_spans.var_span_label( |
| &mut err, |
| format!("borrow occurs due to use{}", loan_spans.describe()), |
| ); |
| |
| self.explain_why_borrow_contains_point(location, loan, None) |
| .add_explanation_to_diagnostic(self.infcx.tcx, self.body, &mut err, "", None); |
| |
| err.buffer(&mut self.errors_buffer); |
| } |
| |
| /// 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(super) 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) = if let Place { |
| base: PlaceBase::Local(local), |
| projection: box [], |
| } = *err_place { |
| if let LocalKind::Arg = self.body.local_kind(local) { |
| (true, Some(&self.body.local_decls[local])) |
| } else { |
| (false, Some(&self.body.local_decls[local])) |
| } |
| } else { |
| (false, 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 { |
| is_user_variable: Some(ClearCrossCrate::Clear), |
| .. |
| }) |
| | Some(LocalDecl { |
| is_user_variable: |
| Some(ClearCrossCrate::Set(BindingForm::Var(VarBindingForm { |
| opt_match_place: None, |
| .. |
| }))), |
| .. |
| }) |
| | Some(LocalDecl { |
| is_user_variable: None, |
| .. |
| }) |
| | None => (self.describe_place(place.as_ref()), assigned_span), |
| Some(decl) => (self.describe_place(err_place.as_ref()), decl.source_info.span), |
| }; |
| |
| let mut err = self.cannot_reassign_immutable( |
| span, |
| place_description.as_ref().map(AsRef::as_ref).unwrap_or("_"), |
| from_arg, |
| ); |
| let msg = if from_arg { |
| "cannot assign to immutable argument" |
| } else { |
| "cannot assign twice to immutable variable" |
| }; |
| if span != assigned_span { |
| if !from_arg { |
| let value_msg = match place_description { |
| Some(name) => format!("`{}`", name), |
| None => "value".to_owned(), |
| }; |
| err.span_label(assigned_span, format!("first assignment to {}", value_msg)); |
| } |
| } |
| if let Some(decl) = local_decl { |
| if let Some(name) = decl.name { |
| if decl.can_be_made_mutable() { |
| err.span_suggestion( |
| decl.source_info.span, |
| "make this binding mutable", |
| format!("mut {}", name), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| } |
| err.span_label(span, msg); |
| err.buffer(&mut self.errors_buffer); |
| } |
| |
| fn classify_drop_access_kind(&self, place: PlaceRef<'cx, 'tcx>) -> StorageDeadOrDrop<'tcx> { |
| let tcx = self.infcx.tcx; |
| match place.projection { |
| [] => { |
| StorageDeadOrDrop::LocalStorageDead |
| } |
| [proj_base @ .., elem] => { |
| // FIXME(spastorino) make this iterate |
| let base_access = self.classify_drop_access_kind(PlaceRef { |
| base: place.base, |
| projection: proj_base, |
| }); |
| match elem { |
| ProjectionElem::Deref => match base_access { |
| StorageDeadOrDrop::LocalStorageDead |
| | StorageDeadOrDrop::BoxedStorageDead => { |
| assert!( |
| Place::ty_from(&place.base, proj_base, self.body, tcx).ty.is_box(), |
| "Drop of value behind a reference or raw pointer" |
| ); |
| StorageDeadOrDrop::BoxedStorageDead |
| } |
| StorageDeadOrDrop::Destructor(_) => base_access, |
| }, |
| ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => { |
| let base_ty = Place::ty_from(&place.base, proj_base, self.body, tcx).ty; |
| match base_ty.sty { |
| ty::Adt(def, _) if def.has_dtor(tcx) => { |
| // Report the outermost adt with a destructor |
| match base_access { |
| StorageDeadOrDrop::Destructor(_) => base_access, |
| StorageDeadOrDrop::LocalStorageDead |
| | StorageDeadOrDrop::BoxedStorageDead => { |
| StorageDeadOrDrop::Destructor(base_ty) |
| } |
| } |
| } |
| _ => base_access, |
| } |
| } |
| |
| ProjectionElem::ConstantIndex { .. } |
| | ProjectionElem::Subslice { .. } |
| | ProjectionElem::Index(_) => base_access, |
| } |
| } |
| } |
| } |
| |
| /// 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); |
| if is_closure { |
| None |
| } else { |
| let ty = self.infcx.tcx.type_of(self.mir_def_id); |
| match ty.sty { |
| ty::FnDef(_, _) | ty::FnPtr(_) => self.annotate_fn_sig( |
| self.mir_def_id, |
| self.infcx.tcx.fn_sig(self.mir_def_id), |
| ), |
| _ => None, |
| } |
| } |
| }; |
| |
| // In order to determine whether we need to annotate, we need to check whether the reserve |
| // place was an assignment into a temporary. |
| // |
| // If it was, we check whether or not that temporary is eventually assigned into the return |
| // place. If it was, we can add annotations about the function's return type and arguments |
| // and it'll make sense. |
| let location = borrow.reserve_location; |
| debug!( |
| "annotate_argument_and_return_for_borrow: location={:?}", |
| location |
| ); |
| if let Some(&Statement { kind: StatementKind::Assign(box(ref reservation, _)), ..}) |
| = &self.body[location.block].statements.get(location.statement_index) |
| { |
| debug!( |
| "annotate_argument_and_return_for_borrow: reservation={:?}", |
| reservation |
| ); |
| // Check that the initial assignment of the reserve location is into a temporary. |
| let mut target = *match reservation { |
| Place { |
| base: PlaceBase::Local(local), |
| projection: box [], |
| } 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 { |
| base: PlaceBase::Local(assigned_to), |
| projection: box [], |
| }, |
| rvalue |
| ) |
| ) = &stmt.kind { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_to={:?} \ |
| rvalue={:?}", |
| assigned_to, rvalue |
| ); |
| // Check if our `target` was captured by a closure. |
| if let Rvalue::Aggregate( |
| box AggregateKind::Closure(def_id, substs), |
| operands, |
| ) = rvalue |
| { |
| for operand in operands { |
| let assigned_from = match operand { |
| Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { |
| assigned_from |
| } |
| _ => continue, |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from={:?}", |
| assigned_from |
| ); |
| |
| // Find the local from the operand. |
| let assigned_from_local = match assigned_from.local_or_deref_local() { |
| Some(local) => local, |
| None => 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, |
| self.infcx.closure_sig(*def_id, *substs), |
| ); |
| 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 assigned_from_local = match assigned_from.local_or_deref_local() { |
| Some(local) => local, |
| None => continue, |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| assigned_from_local={:?}", |
| assigned_from_local, |
| ); |
| |
| // Check if our local matches the target - if so, we've assigned our |
| // borrow to a new place. |
| if assigned_from_local != target { |
| continue; |
| } |
| |
| // If we assigned our `target` into a new place, then we should |
| // check if it was the return place. |
| debug!( |
| "annotate_argument_and_return_for_borrow: \ |
| assigned_from_local={:?} assigned_to={:?}", |
| assigned_from_local, assigned_to |
| ); |
| if *assigned_to == mir::RETURN_PLACE { |
| // If it was then return the annotated closure if there was one, |
| // else, annotate this function. |
| return annotated_closure.or_else(fallback); |
| } |
| |
| // If we didn't assign into the return place, then we just update |
| // the target. |
| target = *assigned_to; |
| } |
| } |
| |
| // Check the terminator if we didn't find anything in the statements. |
| let terminator = &self.body[location.block].terminator(); |
| debug!( |
| "annotate_argument_and_return_for_borrow: target={:?} terminator={:?}", |
| target, terminator |
| ); |
| if let TerminatorKind::Call { |
| destination: Some((Place { |
| base: PlaceBase::Local(assigned_to), |
| projection: box [], |
| }, _)), |
| args, |
| .. |
| } = &terminator.kind |
| { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_to={:?} args={:?}", |
| assigned_to, args |
| ); |
| for operand in args { |
| let assigned_from = match operand { |
| Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { |
| assigned_from |
| } |
| _ => continue, |
| }; |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from={:?}", |
| assigned_from, |
| ); |
| |
| if let Some(assigned_from_local) = assigned_from.local_or_deref_local() { |
| debug!( |
| "annotate_argument_and_return_for_borrow: assigned_from_local={:?}", |
| assigned_from_local, |
| ); |
| |
| if *assigned_to == mir::RETURN_PLACE && assigned_from_local == target { |
| return annotated_closure.or_else(fallback); |
| } |
| } |
| } |
| } |
| } |
| |
| // If we haven't found an assignment into the return place, then we need not add |
| // any annotations. |
| debug!("annotate_argument_and_return_for_borrow: none found"); |
| None |
| } |
| |
| /// Annotate the first argument and return type of a function signature if they are |
| /// references. |
| fn annotate_fn_sig( |
| &self, |
| did: DefId, |
| sig: ty::PolyFnSig<'tcx>, |
| ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { |
| debug!("annotate_fn_sig: did={:?} sig={:?}", did, sig); |
| let is_closure = self.infcx.tcx.is_closure(did); |
| let fn_hir_id = self.infcx.tcx.hir().as_local_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().sty { |
| 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.sty { |
| if argument_region == return_region { |
| // Need to use the `rustc::ty` types to compare against the |
| // `return_region`. Then use the `rustc::hir` type to get only |
| // the lifetime span. |
| if let hir::TyKind::Rptr(lifetime, _) = &fn_decl.inputs[index].node { |
| // With access to the lifetime, we can get |
| // the span of it. |
| arguments.push((*argument, lifetime.span)); |
| } else { |
| bug!("ty type is a ref but hir type is not"); |
| } |
| } |
| } |
| } |
| |
| // We need to have arguments. This shouldn't happen, but it's worth checking. |
| if arguments.is_empty() { |
| return None; |
| } |
| |
| // We use a mix of the HIR and the Ty types to get information |
| // as the HIR doesn't have full types for closure arguments. |
| let return_ty = *sig.output().skip_binder(); |
| let mut return_span = fn_decl.output.span(); |
| if let hir::FunctionRetTy::Return(ty) = &fn_decl.output { |
| if let hir::TyKind::Rptr(lifetime, _) = ty.node { |
| return_span = lifetime.span; |
| } |
| } |
| |
| Some(AnnotatedBorrowFnSignature::NamedFunction { |
| arguments, |
| return_ty, |
| return_span, |
| }) |
| } |
| ty::Ref(_, _, _) if is_closure => { |
| // This is case 2 from above but only for closures, return type is anonymous |
| // reference so we select |
| // the first argument. |
| let argument_span = fn_decl.inputs.first()?.span; |
| let argument_ty = sig.inputs().skip_binder().first()?; |
| |
| // Closure arguments are wrapped in a tuple, so we need to get the first |
| // from that. |
| if let ty::Tuple(elems) = argument_ty.sty { |
| let argument_ty = elems.first()?.expect_ty(); |
| if let ty::Ref(_, _, _) = argument_ty.sty { |
| 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.sty { |
| 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(super) fn emit( |
| &self, |
| cx: &mut MirBorrowckCtxt<'_, 'tcx>, |
| diag: &mut DiagnosticBuilder<'_>, |
| ) -> String { |
| match self { |
| AnnotatedBorrowFnSignature::Closure { |
| argument_ty, |
| argument_span, |
| } => { |
| diag.span_label( |
| *argument_span, |
| format!("has type `{}`", cx.get_name_for_ty(argument_ty, 0)), |
| ); |
| |
| cx.get_region_name_for_ty(argument_ty, 0) |
| } |
| AnnotatedBorrowFnSignature::AnonymousFunction { |
| argument_ty, |
| argument_span, |
| return_ty, |
| return_span, |
| } => { |
| let argument_ty_name = cx.get_name_for_ty(argument_ty, 0); |
| diag.span_label(*argument_span, format!("has type `{}`", argument_ty_name)); |
| |
| let return_ty_name = cx.get_name_for_ty(return_ty, 0); |
| let types_equal = return_ty_name == argument_ty_name; |
| diag.span_label( |
| *return_span, |
| format!( |
| "{}has type `{}`", |
| if types_equal { "also " } else { "" }, |
| return_ty_name, |
| ), |
| ); |
| |
| diag.note( |
| "argument and return type have the same lifetime due to lifetime elision rules", |
| ); |
| diag.note( |
| "to learn more, visit <https://doc.rust-lang.org/book/ch10-03-\ |
| lifetime-syntax.html#lifetime-elision>", |
| ); |
| |
| cx.get_region_name_for_ty(return_ty, 0) |
| } |
| AnnotatedBorrowFnSignature::NamedFunction { |
| arguments, |
| return_ty, |
| return_span, |
| } => { |
| // Region of return type and arguments checked to be the same earlier. |
| let region_name = cx.get_region_name_for_ty(return_ty, 0); |
| for (_, argument_span) in arguments { |
| diag.span_label(*argument_span, format!("has lifetime `{}`", region_name)); |
| } |
| |
| diag.span_label( |
| *return_span, |
| format!("also has lifetime `{}`", region_name,), |
| ); |
| |
| diag.help(&format!( |
| "use data from the highlighted arguments which match the `{}` lifetime of \ |
| the return type", |
| region_name, |
| )); |
| |
| region_name |
| } |
| } |
| } |
| } |
