--- /dev/null
+use rustc::hir;
+use rustc::hir::def_id::DefId;
+use rustc::middle::region::ScopeTree;
+use rustc::mir::{
+ self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory, Local,
+ LocalDecl, LocalKind, Location, Operand, Place, PlaceBase, PlaceProjection,
+ 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::CompilerDesugaringKind;
+
+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::{BorrowckErrors, Origin};
+
+#[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, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
+ pub(super) fn report_use_of_moved_or_uninitialized(
+ &mut self,
+ location: Location,
+ desired_action: InitializationRequiringAction,
+ (moved_place, used_place, span): (&Place<'tcx>, &Place<'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.clone());
+
+ 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.infcx.tcx.cannot_act_on_uninitialized_variable(
+ span,
+ desired_action.as_noun(),
+ &self.describe_place_with_options(moved_place, IncludingDowncast(true))
+ .unwrap_or_else(|| "_".to_owned()),
+ Origin::Mir,
+ );
+ 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()),
+ );
+
+ 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.infcx.tcx.cannot_act_on_moved_value(
+ span,
+ desired_action.as_noun(),
+ msg,
+ self.describe_place_with_options(&moved_place, IncludingDowncast(true)),
+ Origin::Mir,
+ );
+
+ 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 && used_place.is_prefix_of(moved_place)
+ });
+ 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, 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),
+ );
+ if Some(CompilerDesugaringKind::ForLoop) == span.compiler_desugaring_kind() {
+ if let Ok(snippet) = self.infcx.tcx.sess.source_map()
+ .span_to_snippet(span)
+ {
+ err.span_suggestion(
+ move_span,
+ "consider borrowing this to avoid moving it into the for loop",
+ format!("&{}", snippet),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ 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()),
+ );
+ };
+ }
+
+ 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 = used_place.ty(self.mir, 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.mir, self.infcx.tcx).ty;
+ let opt_name = self.describe_place_with_options(place, 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",
+ );
+ }
+ }
+ if let Place::Base(PlaceBase::Local(local)) = place {
+ let decl = &self.mir.local_decls[*local];
+ err.span_label(
+ decl.source_info.span,
+ format!(
+ "move occurs because {} has type `{}`, \
+ which does not implement the `Copy` trait",
+ note_msg, ty,
+ ));
+ } else {
+ err.note(&format!(
+ "move occurs because {} has type `{}`, \
+ which does not implement the `Copy` trait",
+ note_msg, ty
+ ));
+ }
+ }
+
+ if let Some((_, mut old_err)) = self.move_error_reported
+ .insert(move_out_indices, (used_place.clone(), 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 tcx = self.infcx.tcx;
+ let value_msg = match self.describe_place(place) {
+ Some(name) => format!("`{}`", name),
+ None => "value".to_owned(),
+ };
+ let borrow_msg = match self.describe_place(&borrow.borrowed_place) {
+ 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, location);
+ let span = move_spans.args_or_use();
+
+ let mut err = tcx.cannot_move_when_borrowed(
+ span,
+ &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
+ Origin::Mir,
+ );
+ 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.mir, &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 tcx = self.infcx.tcx;
+
+ 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, location);
+ let span = use_spans.var_or_use();
+
+ let mut err = tcx.cannot_use_when_mutably_borrowed(
+ span,
+ &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
+ borrow_span,
+ &self.describe_place(&borrow.borrowed_place)
+ .unwrap_or_else(|| "_".to_owned()),
+ Origin::Mir,
+ );
+
+ borrow_spans.var_span_label(&mut err, {
+ let place = &borrow.borrowed_place;
+ let desc_place = self.describe_place(place).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.mir, &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 tcx = self.infcx.tcx;
+ 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 ";
+ tcx.cannot_reborrow_already_borrowed(
+ span,
+ &desc_place,
+ &msg_place,
+ lft,
+ issued_span,
+ "it",
+ rgt,
+ &msg_borrow,
+ None,
+ Origin::Mir,
+ )
+ }
+ (BorrowKind::Mut { .. }, _, lft, BorrowKind::Shared, rgt, _) => {
+ first_borrow_desc = "immutable ";
+ tcx.cannot_reborrow_already_borrowed(
+ span,
+ &desc_place,
+ &msg_place,
+ lft,
+ issued_span,
+ "it",
+ rgt,
+ &msg_borrow,
+ None,
+ Origin::Mir,
+ )
+ }
+
+ (BorrowKind::Mut { .. }, _, _, BorrowKind::Mut { .. }, _, _) => {
+ first_borrow_desc = "first ";
+ tcx.cannot_mutably_borrow_multiply(
+ span,
+ &desc_place,
+ &msg_place,
+ issued_span,
+ &msg_borrow,
+ None,
+ Origin::Mir,
+ )
+ }
+
+ (BorrowKind::Unique, _, _, BorrowKind::Unique, _, _) => {
+ first_borrow_desc = "first ";
+ tcx.cannot_uniquely_borrow_by_two_closures(
+ span,
+ &desc_place,
+ issued_span,
+ None,
+ Origin::Mir,
+ )
+ }
+
+ (BorrowKind::Mut { .. }, _, _, BorrowKind::Shallow, _, _)
+ | (BorrowKind::Unique, _, _, BorrowKind::Shallow, _, _) => {
+ let mut err = tcx.cannot_mutate_in_match_guard(
+ span,
+ issued_span,
+ &desc_place,
+ "mutably borrow",
+ Origin::Mir,
+ );
+ 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 ";
+ tcx.cannot_uniquely_borrow_by_one_closure(
+ span,
+ container_name,
+ &desc_place,
+ "",
+ issued_span,
+ "it",
+ "",
+ None,
+ Origin::Mir,
+ )
+ },
+
+ (BorrowKind::Shared, lft, _, BorrowKind::Unique, _, _) => {
+ first_borrow_desc = "first ";
+ tcx.cannot_reborrow_already_uniquely_borrowed(
+ span,
+ container_name,
+ &desc_place,
+ "",
+ lft,
+ issued_span,
+ "",
+ None,
+ second_borrow_desc,
+ Origin::Mir,
+ )
+ }
+
+ (BorrowKind::Mut { .. }, _, lft, BorrowKind::Unique, _, _) => {
+ first_borrow_desc = "first ";
+ tcx.cannot_reborrow_already_uniquely_borrowed(
+ span,
+ container_name,
+ &desc_place,
+ "",
+ lft,
+ issued_span,
+ "",
+ None,
+ second_borrow_desc,
+ Origin::Mir,
+ )
+ }
+
+ (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)
+ .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.mir,
+ &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 is_union = |place: &Place<'tcx>| -> bool {
+ place.ty(self.mir, self.infcx.tcx).ty
+ .ty_adt_def()
+ .map(|adt| adt.is_union())
+ .unwrap_or(false)
+ };
+
+ // 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 mut current = first_borrowed_place;
+ while let Place::Projection(box PlaceProjection { base, elem }) = current {
+ match elem {
+ ProjectionElem::Field(field, _) if is_union(base) => {
+ return Some((base, field));
+ },
+ _ => current = base,
+ }
+ }
+ 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 mut current = second_borrowed_place;
+ while let Place::Projection(box PlaceProjection { base, elem }) = current {
+ match elem {
+ ProjectionElem::Field(field, _) if {
+ is_union(base) && field != target_field && base == target_base
+ } => {
+ let desc_base = self.describe_place(base)
+ .unwrap_or_else(|| "_".to_owned());
+ let desc_first = self.describe_place(first_borrowed_place)
+ .unwrap_or_else(|| "_".to_owned());
+ let desc_second = self.describe_place(second_borrowed_place)
+ .unwrap_or_else(|| "_".to_owned());
+
+ // Also compute the name of the union type, eg. `Foo` so we
+ // can add a helpful note with it.
+ let ty = base.ty(self.mir, self.infcx.tcx).ty;
+
+ return Some((desc_base, desc_first, desc_second, ty.to_string()));
+ },
+ _ => current = base,
+ }
+ }
+ 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.
+ let desc_place = self.describe_place(first_borrowed_place)
+ .unwrap_or_else(|| "_".to_owned());
+ (desc_place, "".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 scope_tree = self.infcx.tcx.region_scope_tree(self.mir_def_id);
+ let root_place = self.prefixes(&borrow.borrowed_place, PrefixSet::All)
+ .last()
+ .unwrap();
+
+ let borrow_spans = self.retrieve_borrow_spans(borrow);
+ let borrow_span = borrow_spans.var_or_use();
+
+ let proper_span = match *root_place {
+ Place::Base(PlaceBase::Local(local)) => self.mir.local_decls[local].source_info.span,
+ _ => drop_span,
+ };
+
+ if self.access_place_error_reported
+ .contains(&(root_place.clone(), borrow_span))
+ {
+ debug!(
+ "suppressing access_place error when borrow doesn't live long enough for {:?}",
+ borrow_span
+ );
+ return;
+ }
+
+ self.access_place_error_reported
+ .insert((root_place.clone(), borrow_span));
+
+ if let StorageDeadOrDrop::Destructor(dropped_ty) =
+ self.classify_drop_access_kind(&borrow.borrowed_place)
+ {
+ // 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.is_prefix_of(place_span.0) {
+ self.report_borrow_conflicts_with_destructor(
+ location, borrow, place_span, kind, dropped_ty,
+ );
+ return;
+ }
+ }
+
+ let place_desc = self.describe_place(&borrow.borrowed_place);
+
+ 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,
+ &scope_tree,
+ &borrow,
+ drop_span,
+ borrow_spans,
+ explanation,
+ ),
+ (None, explanation) => self.report_temporary_value_does_not_live_long_enough(
+ location,
+ &scope_tree,
+ &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,
+ scope_tree: &'tcx ScopeTree,
+ borrow: &BorrowData<'tcx>,
+ drop_span: Span,
+ borrow_spans: UseSpans,
+ explanation: BorrowExplanation,
+ ) -> DiagnosticBuilder<'cx> {
+ debug!(
+ "report_local_value_does_not_live_long_enough(\
+ {:?}, {:?}, {:?}, {:?}, {:?}, {:?}\
+ )",
+ location, name, scope_tree, 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.infcx.tcx.path_does_not_live_long_enough(
+ borrow_span,
+ &format!("`{}`", name),
+ Origin::Mir,
+ );
+
+ 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_by_hir_id(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.mir,
+ &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.mir, &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.infcx
+ .tcx
+ .cannot_borrow_across_destructor(borrow_span, Origin::Mir);
+
+ let what_was_dropped = match self.describe_place(place) {
+ Some(name) => format!("`{}`", name.as_str()),
+ None => String::from("temporary value"),
+ };
+
+ let label = match self.describe_place(&borrow.borrowed_place) {
+ 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.mir, &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.infcx
+ .tcx
+ .thread_local_value_does_not_live_long_enough(borrow_span, Origin::Mir);
+
+ 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,
+ scope_tree: &'tcx ScopeTree,
+ 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, scope_tree, 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 tcx = self.infcx.tcx;
+ let mut err = tcx.temporary_value_borrowed_for_too_long(proper_span, Origin::Mir);
+ 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.mir, &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 tcx = self.infcx.tcx;
+
+ 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.mir.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)) => {
+ match self.mir.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, PrefixSet::All)
+ .last()
+ .unwrap();
+ let local = if let Place::Base(PlaceBase::Local(local)) = *root_place {
+ local
+ } else {
+ bug!("try_report_cannot_return_reference_to_local: not a local")
+ };
+ match self.mir.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 => bug!("local variable without a name"),
+ }
+ };
+
+ let mut err = tcx.cannot_return_reference_to_local(
+ return_span,
+ return_kind,
+ reference_desc,
+ &place_desc,
+ Origin::Mir,
+ );
+
+ 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 = tcx.cannot_capture_in_long_lived_closure(
+ args_span,
+ captured_var,
+ var_span,
+ Origin::Mir,
+ );
+
+ let suggestion = match tcx.sess.source_map().span_to_snippet(args_span) {
+ Ok(string) => format!("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 = tcx.borrowed_data_escapes_closure(escape_span, escapes_from, Origin::Mir);
+
+ 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 mir = self.mir;
+
+ let mut stack = Vec::new();
+ stack.extend(mir.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 = mir[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.mir,
+ self.move_data,
+ location,
+ |m| {
+ if m == mpi {
+ any_match = true;
+ }
+ },
+ );
+ if any_match {
+ continue 'dfs;
+ }
+
+ stack.extend(mir.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();
+
+ let tcx = self.infcx.tcx;
+ if loan.kind == BorrowKind::Shallow {
+ let mut err = tcx.cannot_mutate_in_match_guard(
+ span,
+ loan_span,
+ &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
+ "assign",
+ Origin::Mir,
+ );
+ 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 = tcx.cannot_assign_to_borrowed(
+ span,
+ loan_span,
+ &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
+ Origin::Mir,
+ );
+
+ 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.mir, &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)) = *err_place {
+ if let LocalKind::Arg = self.mir.local_kind(local) {
+ (true, Some(&self.mir.local_decls[local]))
+ } else {
+ (false, Some(&self.mir.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), assigned_span),
+ Some(decl) => (self.describe_place(err_place), decl.source_info.span),
+ };
+
+ let mut err = self.infcx.tcx.cannot_reassign_immutable(
+ span,
+ place_description.as_ref().map(AsRef::as_ref).unwrap_or("_"),
+ from_arg,
+ Origin::Mir,
+ );
+ 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: &Place<'tcx>) -> StorageDeadOrDrop<'tcx> {
+ let tcx = self.infcx.tcx;
+ match place {
+ Place::Base(PlaceBase::Local(_)) |
+ Place::Base(PlaceBase::Static(_)) => {
+ StorageDeadOrDrop::LocalStorageDead
+ }
+ Place::Projection(box PlaceProjection { base, elem }) => {
+ let base_access = self.classify_drop_access_kind(base);
+ match elem {
+ ProjectionElem::Deref => match base_access {
+ StorageDeadOrDrop::LocalStorageDead
+ | StorageDeadOrDrop::BoxedStorageDead => {
+ assert!(
+ base.ty(self.mir, 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 = base.ty(self.mir, 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(ref reservation, _), ..})
+ = &self.mir[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))
+ if self.mir.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.mir[location.block].statements[location.statement_index + 1..] {
+ debug!(
+ "annotate_argument_and_return_for_borrow: target={:?} stmt={:?}",
+ target, stmt
+ );
+ if let StatementKind::Assign(
+ Place::Base(PlaceBase::Local(assigned_to)),
+ 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() {
+ 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() {
+ 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.mir[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)), _)),
+ 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() {
+ 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.into_inner().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
+ }
+ }
+ }
+}
-use crate::borrow_check::nll::explain_borrow::BorrowExplanation;
-use crate::borrow_check::nll::region_infer::{RegionName, RegionNameSource};
-use crate::borrow_check::prefixes::IsPrefixOf;
-use crate::borrow_check::WriteKind;
use rustc::hir;
use rustc::hir::def::Namespace;
use rustc::hir::def_id::DefId;
-use rustc::middle::region::ScopeTree;
use rustc::mir::{
- self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, Constant,
- ConstraintCategory, Field, Local, LocalDecl, LocalKind, Location, Operand,
- Place, PlaceBase, PlaceProjection, ProjectionElem, Rvalue, Statement, StatementKind,
- Static, StaticKind, TerminatorKind, VarBindingForm,
+ AggregateKind, BindingForm, ClearCrossCrate, Constant, Field, Local,
+ LocalKind, Location, Operand, Place, PlaceBase, ProjectionElem, Rvalue,
+ Statement, StatementKind, Static, StaticKind, TerminatorKind,
};
use rustc::ty::{self, DefIdTree, Ty};
use rustc::ty::layout::VariantIdx;
use rustc::ty::print::Print;
-use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::indexed_vec::Idx;
-use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_errors::DiagnosticBuilder;
use syntax_pos::Span;
-use syntax::source_map::CompilerDesugaringKind;
use syntax::symbol::sym;
use super::borrow_set::BorrowData;
use super::{MirBorrowckCtxt};
-use super::{InitializationRequiringAction, PrefixSet};
-use crate::dataflow::drop_flag_effects;
-use crate::dataflow::indexes::{MovePathIndex, MoveOutIndex};
-use crate::util::borrowck_errors::{BorrowckErrors, Origin};
-#[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
-}
-
-impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
- pub(super) fn report_use_of_moved_or_uninitialized(
- &mut self,
- location: Location,
- desired_action: InitializationRequiringAction,
- (moved_place, used_place, span): (&Place<'tcx>, &Place<'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.clone());
-
- 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.infcx.tcx.cannot_act_on_uninitialized_variable(
- span,
- desired_action.as_noun(),
- &self.describe_place_with_options(moved_place, IncludingDowncast(true))
- .unwrap_or_else(|| "_".to_owned()),
- Origin::Mir,
- );
- 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()),
- );
-
- 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.infcx.tcx.cannot_act_on_moved_value(
- span,
- desired_action.as_noun(),
- msg,
- self.describe_place_with_options(&moved_place, IncludingDowncast(true)),
- Origin::Mir,
- );
-
- 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 && used_place.is_prefix_of(moved_place)
- });
- 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, 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),
- );
- if Some(CompilerDesugaringKind::ForLoop) == span.compiler_desugaring_kind() {
- if let Ok(snippet) = self.infcx.tcx.sess.source_map()
- .span_to_snippet(span)
- {
- err.span_suggestion(
- move_span,
- "consider borrowing this to avoid moving it into the for loop",
- format!("&{}", snippet),
- Applicability::MaybeIncorrect,
- );
- }
- }
- 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()),
- );
- };
- }
-
- 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 = used_place.ty(self.mir, 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.mir, self.infcx.tcx).ty;
- let opt_name = self.describe_place_with_options(place, 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",
- );
- }
- }
- if let Place::Base(PlaceBase::Local(local)) = place {
- let decl = &self.mir.local_decls[*local];
- err.span_label(
- decl.source_info.span,
- format!(
- "move occurs because {} has type `{}`, \
- which does not implement the `Copy` trait",
- note_msg, ty,
- ));
- } else {
- err.note(&format!(
- "move occurs because {} has type `{}`, \
- which does not implement the `Copy` trait",
- note_msg, ty
- ));
- }
- }
-
- if let Some((_, mut old_err)) = self.move_error_reported
- .insert(move_out_indices, (used_place.clone(), 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 tcx = self.infcx.tcx;
- let value_msg = match self.describe_place(place) {
- Some(name) => format!("`{}`", name),
- None => "value".to_owned(),
- };
- let borrow_msg = match self.describe_place(&borrow.borrowed_place) {
- 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, location);
- let span = move_spans.args_or_use();
-
- let mut err = tcx.cannot_move_when_borrowed(
- span,
- &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
- Origin::Mir,
- );
- 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.mir, &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 tcx = self.infcx.tcx;
-
- 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, location);
- let span = use_spans.var_or_use();
-
- let mut err = tcx.cannot_use_when_mutably_borrowed(
- span,
- &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
- borrow_span,
- &self.describe_place(&borrow.borrowed_place)
- .unwrap_or_else(|| "_".to_owned()),
- Origin::Mir,
- );
-
- borrow_spans.var_span_label(&mut err, {
- let place = &borrow.borrowed_place;
- let desc_place = self.describe_place(place).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.mir, &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 tcx = self.infcx.tcx;
- 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 ";
- tcx.cannot_reborrow_already_borrowed(
- span,
- &desc_place,
- &msg_place,
- lft,
- issued_span,
- "it",
- rgt,
- &msg_borrow,
- None,
- Origin::Mir,
- )
- }
- (BorrowKind::Mut { .. }, _, lft, BorrowKind::Shared, rgt, _) => {
- first_borrow_desc = "immutable ";
- tcx.cannot_reborrow_already_borrowed(
- span,
- &desc_place,
- &msg_place,
- lft,
- issued_span,
- "it",
- rgt,
- &msg_borrow,
- None,
- Origin::Mir,
- )
- }
-
- (BorrowKind::Mut { .. }, _, _, BorrowKind::Mut { .. }, _, _) => {
- first_borrow_desc = "first ";
- tcx.cannot_mutably_borrow_multiply(
- span,
- &desc_place,
- &msg_place,
- issued_span,
- &msg_borrow,
- None,
- Origin::Mir,
- )
- }
-
- (BorrowKind::Unique, _, _, BorrowKind::Unique, _, _) => {
- first_borrow_desc = "first ";
- tcx.cannot_uniquely_borrow_by_two_closures(
- span,
- &desc_place,
- issued_span,
- None,
- Origin::Mir,
- )
- }
-
- (BorrowKind::Mut { .. }, _, _, BorrowKind::Shallow, _, _)
- | (BorrowKind::Unique, _, _, BorrowKind::Shallow, _, _) => {
- let mut err = tcx.cannot_mutate_in_match_guard(
- span,
- issued_span,
- &desc_place,
- "mutably borrow",
- Origin::Mir,
- );
- 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 ";
- tcx.cannot_uniquely_borrow_by_one_closure(
- span,
- container_name,
- &desc_place,
- "",
- issued_span,
- "it",
- "",
- None,
- Origin::Mir,
- )
- },
-
- (BorrowKind::Shared, lft, _, BorrowKind::Unique, _, _) => {
- first_borrow_desc = "first ";
- tcx.cannot_reborrow_already_uniquely_borrowed(
- span,
- container_name,
- &desc_place,
- "",
- lft,
- issued_span,
- "",
- None,
- second_borrow_desc,
- Origin::Mir,
- )
- }
-
- (BorrowKind::Mut { .. }, _, lft, BorrowKind::Unique, _, _) => {
- first_borrow_desc = "first ";
- tcx.cannot_reborrow_already_uniquely_borrowed(
- span,
- container_name,
- &desc_place,
- "",
- lft,
- issued_span,
- "",
- None,
- second_borrow_desc,
- Origin::Mir,
- )
- }
-
- (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)
- .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.mir,
- &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 is_union = |place: &Place<'tcx>| -> bool {
- place.ty(self.mir, self.infcx.tcx).ty
- .ty_adt_def()
- .map(|adt| adt.is_union())
- .unwrap_or(false)
- };
-
- // 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 mut current = first_borrowed_place;
- while let Place::Projection(box PlaceProjection { base, elem }) = current {
- match elem {
- ProjectionElem::Field(field, _) if is_union(base) => {
- return Some((base, field));
- },
- _ => current = base,
- }
- }
- 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 mut current = second_borrowed_place;
- while let Place::Projection(box PlaceProjection { base, elem }) = current {
- match elem {
- ProjectionElem::Field(field, _) if {
- is_union(base) && field != target_field && base == target_base
- } => {
- let desc_base = self.describe_place(base)
- .unwrap_or_else(|| "_".to_owned());
- let desc_first = self.describe_place(first_borrowed_place)
- .unwrap_or_else(|| "_".to_owned());
- let desc_second = self.describe_place(second_borrowed_place)
- .unwrap_or_else(|| "_".to_owned());
-
- // Also compute the name of the union type, eg. `Foo` so we
- // can add a helpful note with it.
- let ty = base.ty(self.mir, self.infcx.tcx).ty;
-
- return Some((desc_base, desc_first, desc_second, ty.to_string()));
- },
- _ => current = base,
- }
- }
- 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.
- let desc_place = self.describe_place(first_borrowed_place)
- .unwrap_or_else(|| "_".to_owned());
- (desc_place, "".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 scope_tree = self.infcx.tcx.region_scope_tree(self.mir_def_id);
- let root_place = self.prefixes(&borrow.borrowed_place, PrefixSet::All)
- .last()
- .unwrap();
-
- let borrow_spans = self.retrieve_borrow_spans(borrow);
- let borrow_span = borrow_spans.var_or_use();
-
- let proper_span = match *root_place {
- Place::Base(PlaceBase::Local(local)) => self.mir.local_decls[local].source_info.span,
- _ => drop_span,
- };
-
- if self.access_place_error_reported
- .contains(&(root_place.clone(), borrow_span))
- {
- debug!(
- "suppressing access_place error when borrow doesn't live long enough for {:?}",
- borrow_span
- );
- return;
- }
-
- self.access_place_error_reported
- .insert((root_place.clone(), borrow_span));
-
- if let StorageDeadOrDrop::Destructor(dropped_ty) =
- self.classify_drop_access_kind(&borrow.borrowed_place)
- {
- // 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.is_prefix_of(place_span.0) {
- self.report_borrow_conflicts_with_destructor(
- location, borrow, place_span, kind, dropped_ty,
- );
- return;
- }
- }
-
- let place_desc = self.describe_place(&borrow.borrowed_place);
-
- 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,
- &scope_tree,
- &borrow,
- drop_span,
- borrow_spans,
- explanation,
- ),
- (None, explanation) => self.report_temporary_value_does_not_live_long_enough(
- location,
- &scope_tree,
- &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,
- scope_tree: &'tcx ScopeTree,
- borrow: &BorrowData<'tcx>,
- drop_span: Span,
- borrow_spans: UseSpans,
- explanation: BorrowExplanation,
- ) -> DiagnosticBuilder<'cx> {
- debug!(
- "report_local_value_does_not_live_long_enough(\
- {:?}, {:?}, {:?}, {:?}, {:?}, {:?}\
- )",
- location, name, scope_tree, 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.infcx.tcx.path_does_not_live_long_enough(
- borrow_span,
- &format!("`{}`", name),
- Origin::Mir,
- );
-
- 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_by_hir_id(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.mir,
- &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.mir, &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.infcx
- .tcx
- .cannot_borrow_across_destructor(borrow_span, Origin::Mir);
-
- let what_was_dropped = match self.describe_place(place) {
- Some(name) => format!("`{}`", name.as_str()),
- None => String::from("temporary value"),
- };
-
- let label = match self.describe_place(&borrow.borrowed_place) {
- 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.mir, &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.infcx
- .tcx
- .thread_local_value_does_not_live_long_enough(borrow_span, Origin::Mir);
-
- 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,
- scope_tree: &'tcx ScopeTree,
- 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, scope_tree, 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 tcx = self.infcx.tcx;
- let mut err = tcx.temporary_value_borrowed_for_too_long(proper_span, Origin::Mir);
- 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.mir, &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 tcx = self.infcx.tcx;
-
- 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.mir.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)) => {
- match self.mir.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, PrefixSet::All)
- .last()
- .unwrap();
- let local = if let Place::Base(PlaceBase::Local(local)) = *root_place {
- local
- } else {
- bug!("try_report_cannot_return_reference_to_local: not a local")
- };
- match self.mir.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 => bug!("local variable without a name"),
- }
- };
-
- let mut err = tcx.cannot_return_reference_to_local(
- return_span,
- return_kind,
- reference_desc,
- &place_desc,
- Origin::Mir,
- );
-
- 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 = tcx.cannot_capture_in_long_lived_closure(
- args_span,
- captured_var,
- var_span,
- Origin::Mir,
- );
-
- let suggestion = match tcx.sess.source_map().span_to_snippet(args_span) {
- Ok(string) => format!("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 = tcx.borrowed_data_escapes_closure(escape_span, escapes_from, Origin::Mir);
-
- 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 mir = self.mir;
-
- let mut stack = Vec::new();
- stack.extend(mir.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 = mir[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.mir,
- self.move_data,
- location,
- |m| {
- if m == mpi {
- any_match = true;
- }
- },
- );
- if any_match {
- continue 'dfs;
- }
-
- stack.extend(mir.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();
-
- let tcx = self.infcx.tcx;
- if loan.kind == BorrowKind::Shallow {
- let mut err = tcx.cannot_mutate_in_match_guard(
- span,
- loan_span,
- &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
- "assign",
- Origin::Mir,
- );
- 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 = tcx.cannot_assign_to_borrowed(
- span,
- loan_span,
- &self.describe_place(place).unwrap_or_else(|| "_".to_owned()),
- Origin::Mir,
- );
-
- 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.mir, &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)) = *err_place {
- if let LocalKind::Arg = self.mir.local_kind(local) {
- (true, Some(&self.mir.local_decls[local]))
- } else {
- (false, Some(&self.mir.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), assigned_span),
- Some(decl) => (self.describe_place(err_place), decl.source_info.span),
- };
-
- let mut err = self.infcx.tcx.cannot_reassign_immutable(
- span,
- place_description.as_ref().map(AsRef::as_ref).unwrap_or("_"),
- from_arg,
- Origin::Mir,
- );
- 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);
- }
-}
-
-pub(super) struct IncludingDowncast(bool);
-
-/// Which case a StorageDeadOrDrop is for.
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
-enum StorageDeadOrDrop<'tcx> {
- LocalStorageDead,
- BoxedStorageDead,
- Destructor(Ty<'tcx>),
-}
+pub(super) struct IncludingDowncast(pub(super) bool);
impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
false
}
}
-
- fn classify_drop_access_kind(&self, place: &Place<'tcx>) -> StorageDeadOrDrop<'tcx> {
- let tcx = self.infcx.tcx;
- match place {
- Place::Base(PlaceBase::Local(_)) |
- Place::Base(PlaceBase::Static(_)) => {
- StorageDeadOrDrop::LocalStorageDead
- }
- Place::Projection(box PlaceProjection { base, elem }) => {
- let base_access = self.classify_drop_access_kind(base);
- match elem {
- ProjectionElem::Deref => match base_access {
- StorageDeadOrDrop::LocalStorageDead
- | StorageDeadOrDrop::BoxedStorageDead => {
- assert!(
- base.ty(self.mir, 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 = base.ty(self.mir, 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(ref reservation, _), ..})
- = &self.mir[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))
- if self.mir.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.mir[location.block].statements[location.statement_index + 1..] {
- debug!(
- "annotate_argument_and_return_for_borrow: target={:?} stmt={:?}",
- target, stmt
- );
- if let StatementKind::Assign(
- Place::Base(PlaceBase::Local(assigned_to)),
- 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() {
- 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() {
- 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.mir[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)), _)),
- 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() {
- 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.into_inner().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.
- 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
- }
- }
- }
}
impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
/// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
/// name where required.
- fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
+ pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
let mut s = String::new();
let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, &mut s, Namespace::TypeNS);
/// Returns the name of the provided `Ty` (that must be a reference)'s region with a
/// synthesized lifetime name where required.
- fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
+ pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
let mut s = String::new();
let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, &mut s, Namespace::TypeNS);
}
/// Returns `false` if this place is not used in a closure.
- fn for_closure(&self) -> bool {
+ pub(super) fn for_closure(&self) -> bool {
match *self {
UseSpans::ClosureUse { is_generator, .. } => !is_generator,
_ => false,
}
/// Returns `false` if this place is not used in a generator.
- fn for_generator(&self) -> bool {
+ pub(super) fn for_generator(&self) -> bool {
match *self {
UseSpans::ClosureUse { is_generator, .. } => is_generator,
_ => false,
}
/// Describe the span associated with a use of a place.
- fn describe(&self) -> String {
+ pub(super) fn describe(&self) -> String {
match *self {
UseSpans::ClosureUse { is_generator, .. } => if is_generator {
" in generator".to_string()
projects / rust.git / commitdiff