| use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; |
| use rustc_middle::mir::*; |
| use rustc_middle::ty; |
| use rustc_mir_dataflow::move_paths::{ |
| IllegalMoveOrigin, IllegalMoveOriginKind, LookupResult, MoveError, MovePathIndex, |
| }; |
| use rustc_span::Span; |
| |
| use crate::diagnostics::{DescribePlaceOpt, UseSpans}; |
| use crate::prefixes::PrefixSet; |
| use crate::MirBorrowckCtxt; |
| |
| // Often when desugaring a pattern match we may have many individual moves in |
| // MIR that are all part of one operation from the user's point-of-view. For |
| // example: |
| // |
| // let (x, y) = foo() |
| // |
| // would move x from the 0 field of some temporary, and y from the 1 field. We |
| // group such errors together for cleaner error reporting. |
| // |
| // Errors are kept separate if they are from places with different parent move |
| // paths. For example, this generates two errors: |
| // |
| // let (&x, &y) = (&String::new(), &String::new()); |
| #[derive(Debug)] |
| enum GroupedMoveError<'tcx> { |
| // Place expression can't be moved from, |
| // e.g., match x[0] { s => (), } where x: &[String] |
| MovesFromPlace { |
| original_path: Place<'tcx>, |
| span: Span, |
| move_from: Place<'tcx>, |
| kind: IllegalMoveOriginKind<'tcx>, |
| binds_to: Vec<Local>, |
| }, |
| // Part of a value expression can't be moved from, |
| // e.g., match &String::new() { &x => (), } |
| MovesFromValue { |
| original_path: Place<'tcx>, |
| span: Span, |
| move_from: MovePathIndex, |
| kind: IllegalMoveOriginKind<'tcx>, |
| binds_to: Vec<Local>, |
| }, |
| // Everything that isn't from pattern matching. |
| OtherIllegalMove { |
| original_path: Place<'tcx>, |
| use_spans: UseSpans<'tcx>, |
| kind: IllegalMoveOriginKind<'tcx>, |
| }, |
| } |
| |
| impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> { |
| pub(crate) fn report_move_errors(&mut self, move_errors: Vec<(Place<'tcx>, MoveError<'tcx>)>) { |
| let grouped_errors = self.group_move_errors(move_errors); |
| for error in grouped_errors { |
| self.report(error); |
| } |
| } |
| |
| fn group_move_errors( |
| &self, |
| errors: Vec<(Place<'tcx>, MoveError<'tcx>)>, |
| ) -> Vec<GroupedMoveError<'tcx>> { |
| let mut grouped_errors = Vec::new(); |
| for (original_path, error) in errors { |
| self.append_to_grouped_errors(&mut grouped_errors, original_path, error); |
| } |
| grouped_errors |
| } |
| |
| fn append_to_grouped_errors( |
| &self, |
| grouped_errors: &mut Vec<GroupedMoveError<'tcx>>, |
| original_path: Place<'tcx>, |
| error: MoveError<'tcx>, |
| ) { |
| match error { |
| MoveError::UnionMove { .. } => { |
| unimplemented!("don't know how to report union move errors yet.") |
| } |
| MoveError::IllegalMove { cannot_move_out_of: IllegalMoveOrigin { location, kind } } => { |
| // Note: that the only time we assign a place isn't a temporary |
| // to a user variable is when initializing it. |
| // If that ever stops being the case, then the ever initialized |
| // flow could be used. |
| if let Some(StatementKind::Assign(box ( |
| place, |
| Rvalue::Use(Operand::Move(move_from)), |
| ))) = self.body.basic_blocks[location.block] |
| .statements |
| .get(location.statement_index) |
| .map(|stmt| &stmt.kind) |
| { |
| if let Some(local) = place.as_local() { |
| let local_decl = &self.body.local_decls[local]; |
| // opt_match_place is the |
| // match_span is the span of the expression being matched on |
| // match *x.y { ... } match_place is Some(*x.y) |
| // ^^^^ match_span is the span of *x.y |
| // |
| // opt_match_place is None for let [mut] x = ... statements, |
| // whether or not the right-hand side is a place expression |
| if let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var( |
| VarBindingForm { |
| opt_match_place: Some((opt_match_place, match_span)), |
| binding_mode: _, |
| opt_ty_info: _, |
| pat_span: _, |
| }, |
| )))) = local_decl.local_info |
| { |
| let stmt_source_info = self.body.source_info(location); |
| self.append_binding_error( |
| grouped_errors, |
| kind, |
| original_path, |
| *move_from, |
| local, |
| opt_match_place, |
| match_span, |
| stmt_source_info.span, |
| ); |
| return; |
| } |
| } |
| } |
| |
| let move_spans = self.move_spans(original_path.as_ref(), location); |
| grouped_errors.push(GroupedMoveError::OtherIllegalMove { |
| use_spans: move_spans, |
| original_path, |
| kind, |
| }); |
| } |
| } |
| } |
| |
| fn append_binding_error( |
| &self, |
| grouped_errors: &mut Vec<GroupedMoveError<'tcx>>, |
| kind: IllegalMoveOriginKind<'tcx>, |
| original_path: Place<'tcx>, |
| move_from: Place<'tcx>, |
| bind_to: Local, |
| match_place: Option<Place<'tcx>>, |
| match_span: Span, |
| statement_span: Span, |
| ) { |
| debug!("append_binding_error(match_place={:?}, match_span={:?})", match_place, match_span); |
| |
| let from_simple_let = match_place.is_none(); |
| let match_place = match_place.unwrap_or(move_from); |
| |
| match self.move_data.rev_lookup.find(match_place.as_ref()) { |
| // Error with the match place |
| LookupResult::Parent(_) => { |
| for ge in &mut *grouped_errors { |
| if let GroupedMoveError::MovesFromPlace { span, binds_to, .. } = ge |
| && match_span == *span |
| { |
| debug!("appending local({:?}) to list", bind_to); |
| if !binds_to.is_empty() { |
| binds_to.push(bind_to); |
| } |
| return; |
| } |
| } |
| debug!("found a new move error location"); |
| |
| // Don't need to point to x in let x = ... . |
| let (binds_to, span) = if from_simple_let { |
| (vec![], statement_span) |
| } else { |
| (vec![bind_to], match_span) |
| }; |
| grouped_errors.push(GroupedMoveError::MovesFromPlace { |
| span, |
| move_from, |
| original_path, |
| kind, |
| binds_to, |
| }); |
| } |
| // Error with the pattern |
| LookupResult::Exact(_) => { |
| let LookupResult::Parent(Some(mpi)) = self.move_data.rev_lookup.find(move_from.as_ref()) else { |
| // move_from should be a projection from match_place. |
| unreachable!("Probably not unreachable..."); |
| }; |
| for ge in &mut *grouped_errors { |
| if let GroupedMoveError::MovesFromValue { |
| span, |
| move_from: other_mpi, |
| binds_to, |
| .. |
| } = ge |
| { |
| if match_span == *span && mpi == *other_mpi { |
| debug!("appending local({:?}) to list", bind_to); |
| binds_to.push(bind_to); |
| return; |
| } |
| } |
| } |
| debug!("found a new move error location"); |
| grouped_errors.push(GroupedMoveError::MovesFromValue { |
| span: match_span, |
| move_from: mpi, |
| original_path, |
| kind, |
| binds_to: vec![bind_to], |
| }); |
| } |
| }; |
| } |
| |
| fn report(&mut self, error: GroupedMoveError<'tcx>) { |
| let (mut err, err_span) = { |
| let (span, use_spans, original_path, kind) = match error { |
| GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. } |
| | GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => { |
| (span, None, original_path, kind) |
| } |
| GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => { |
| (use_spans.args_or_use(), Some(use_spans), original_path, kind) |
| } |
| }; |
| debug!( |
| "report: original_path={:?} span={:?}, kind={:?} \ |
| original_path.is_upvar_field_projection={:?}", |
| original_path, |
| span, |
| kind, |
| self.is_upvar_field_projection(original_path.as_ref()) |
| ); |
| ( |
| match kind { |
| &IllegalMoveOriginKind::BorrowedContent { target_place } => self |
| .report_cannot_move_from_borrowed_content( |
| original_path, |
| target_place, |
| span, |
| use_spans, |
| ), |
| &IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => { |
| self.cannot_move_out_of_interior_of_drop(span, ty) |
| } |
| &IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } => { |
| self.cannot_move_out_of_interior_noncopy(span, ty, Some(is_index)) |
| } |
| }, |
| span, |
| ) |
| }; |
| |
| self.add_move_hints(error, &mut err, err_span); |
| self.buffer_error(err); |
| } |
| |
| fn report_cannot_move_from_static( |
| &mut self, |
| place: Place<'tcx>, |
| span: Span, |
| ) -> DiagnosticBuilder<'a, ErrorGuaranteed> { |
| let description = if place.projection.len() == 1 { |
| format!("static item {}", self.describe_any_place(place.as_ref())) |
| } else { |
| let base_static = PlaceRef { local: place.local, projection: &[ProjectionElem::Deref] }; |
| |
| format!( |
| "{} as {} is a static item", |
| self.describe_any_place(place.as_ref()), |
| self.describe_any_place(base_static), |
| ) |
| }; |
| |
| self.cannot_move_out_of(span, &description) |
| } |
| |
| fn report_cannot_move_from_borrowed_content( |
| &mut self, |
| move_place: Place<'tcx>, |
| deref_target_place: Place<'tcx>, |
| span: Span, |
| use_spans: Option<UseSpans<'tcx>>, |
| ) -> DiagnosticBuilder<'a, ErrorGuaranteed> { |
| // Inspect the type of the content behind the |
| // borrow to provide feedback about why this |
| // was a move rather than a copy. |
| let ty = deref_target_place.ty(self.body, self.infcx.tcx).ty; |
| let upvar_field = self |
| .prefixes(move_place.as_ref(), PrefixSet::All) |
| .find_map(|p| self.is_upvar_field_projection(p)); |
| |
| let deref_base = match deref_target_place.projection.as_ref() { |
| [proj_base @ .., ProjectionElem::Deref] => { |
| PlaceRef { local: deref_target_place.local, projection: &proj_base } |
| } |
| _ => bug!("deref_target_place is not a deref projection"), |
| }; |
| |
| if let PlaceRef { local, projection: [] } = deref_base { |
| let decl = &self.body.local_decls[local]; |
| if decl.is_ref_for_guard() { |
| let mut err = self.cannot_move_out_of( |
| span, |
| &format!("`{}` in pattern guard", self.local_names[local].unwrap()), |
| ); |
| err.note( |
| "variables bound in patterns cannot be moved from \ |
| until after the end of the pattern guard", |
| ); |
| return err; |
| } else if decl.is_ref_to_static() { |
| return self.report_cannot_move_from_static(move_place, span); |
| } |
| } |
| |
| debug!("report: ty={:?}", ty); |
| let mut err = match ty.kind() { |
| ty::Array(..) | ty::Slice(..) => { |
| self.cannot_move_out_of_interior_noncopy(span, ty, None) |
| } |
| ty::Closure(def_id, closure_substs) |
| if def_id.as_local() == Some(self.mir_def_id()) && upvar_field.is_some() => |
| { |
| let closure_kind_ty = closure_substs.as_closure().kind_ty(); |
| let closure_kind = match closure_kind_ty.to_opt_closure_kind() { |
| Some(kind @ (ty::ClosureKind::Fn | ty::ClosureKind::FnMut)) => kind, |
| Some(ty::ClosureKind::FnOnce) => { |
| bug!("closure kind does not match first argument type") |
| } |
| None => bug!("closure kind not inferred by borrowck"), |
| }; |
| let capture_description = |
| format!("captured variable in an `{closure_kind}` closure"); |
| |
| let upvar = &self.upvars[upvar_field.unwrap().index()]; |
| let upvar_hir_id = upvar.place.get_root_variable(); |
| let upvar_name = upvar.place.to_string(self.infcx.tcx); |
| let upvar_span = self.infcx.tcx.hir().span(upvar_hir_id); |
| |
| let place_name = self.describe_any_place(move_place.as_ref()); |
| |
| let place_description = |
| if self.is_upvar_field_projection(move_place.as_ref()).is_some() { |
| format!("{place_name}, a {capture_description}") |
| } else { |
| format!("{place_name}, as `{upvar_name}` is a {capture_description}") |
| }; |
| |
| debug!( |
| "report: closure_kind_ty={:?} closure_kind={:?} place_description={:?}", |
| closure_kind_ty, closure_kind, place_description, |
| ); |
| |
| let mut diag = self.cannot_move_out_of(span, &place_description); |
| |
| diag.span_label(upvar_span, "captured outer variable"); |
| diag.span_label( |
| self.infcx.tcx.def_span(def_id), |
| format!("captured by this `{closure_kind}` closure"), |
| ); |
| |
| diag |
| } |
| _ => { |
| let source = self.borrowed_content_source(deref_base); |
| let move_place_ref = move_place.as_ref(); |
| match ( |
| self.describe_place_with_options( |
| move_place_ref, |
| DescribePlaceOpt { |
| including_downcast: false, |
| including_tuple_field: false, |
| }, |
| ), |
| self.describe_name(move_place_ref), |
| source.describe_for_named_place(), |
| ) { |
| (Some(place_desc), Some(name), Some(source_desc)) => self.cannot_move_out_of( |
| span, |
| &format!("`{place_desc}` as enum variant `{name}` which is behind a {source_desc}"), |
| ), |
| (Some(place_desc), Some(name), None) => self.cannot_move_out_of( |
| span, |
| &format!("`{place_desc}` as enum variant `{name}`"), |
| ), |
| (Some(place_desc), _, Some(source_desc)) => self.cannot_move_out_of( |
| span, |
| &format!("`{place_desc}` which is behind a {source_desc}"), |
| ), |
| (_, _, _) => self.cannot_move_out_of( |
| span, |
| &source.describe_for_unnamed_place(self.infcx.tcx), |
| ), |
| } |
| } |
| }; |
| if let Some(use_spans) = use_spans { |
| self.explain_captures( |
| &mut err, span, span, use_spans, move_place, "", "", "", false, true, |
| ); |
| } |
| err |
| } |
| |
| fn add_move_hints(&self, error: GroupedMoveError<'tcx>, err: &mut Diagnostic, span: Span) { |
| match error { |
| GroupedMoveError::MovesFromPlace { mut binds_to, move_from, .. } => { |
| if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) { |
| err.span_suggestion( |
| span, |
| "consider borrowing here", |
| format!("&{snippet}"), |
| Applicability::Unspecified, |
| ); |
| } |
| |
| if binds_to.is_empty() { |
| let place_ty = move_from.ty(self.body, self.infcx.tcx).ty; |
| let place_desc = match self.describe_place(move_from.as_ref()) { |
| Some(desc) => format!("`{desc}`"), |
| None => "value".to_string(), |
| }; |
| |
| self.note_type_does_not_implement_copy( |
| err, |
| &place_desc, |
| place_ty, |
| Some(span), |
| "", |
| ); |
| } else { |
| binds_to.sort(); |
| binds_to.dedup(); |
| |
| self.add_move_error_details(err, &binds_to); |
| } |
| } |
| GroupedMoveError::MovesFromValue { mut binds_to, .. } => { |
| binds_to.sort(); |
| binds_to.dedup(); |
| self.add_move_error_suggestions(err, &binds_to); |
| self.add_move_error_details(err, &binds_to); |
| } |
| // No binding. Nothing to suggest. |
| GroupedMoveError::OtherIllegalMove { ref original_path, use_spans, .. } => { |
| let span = use_spans.var_or_use(); |
| let place_ty = original_path.ty(self.body, self.infcx.tcx).ty; |
| let place_desc = match self.describe_place(original_path.as_ref()) { |
| Some(desc) => format!("`{desc}`"), |
| None => "value".to_string(), |
| }; |
| self.note_type_does_not_implement_copy(err, &place_desc, place_ty, Some(span), ""); |
| |
| use_spans.args_span_label(err, format!("move out of {place_desc} occurs here")); |
| } |
| } |
| } |
| |
| fn add_move_error_suggestions(&self, err: &mut Diagnostic, binds_to: &[Local]) { |
| let mut suggestions: Vec<(Span, &str, String)> = Vec::new(); |
| for local in binds_to { |
| let bind_to = &self.body.local_decls[*local]; |
| if let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var( |
| VarBindingForm { pat_span, .. }, |
| )))) = bind_to.local_info |
| { |
| if let Ok(pat_snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(pat_span) |
| { |
| if let Some(stripped) = pat_snippet.strip_prefix('&') { |
| let pat_snippet = stripped.trim_start(); |
| let (suggestion, to_remove) = if pat_snippet.starts_with("mut") |
| && pat_snippet["mut".len()..].starts_with(rustc_lexer::is_whitespace) |
| { |
| (pat_snippet["mut".len()..].trim_start(), "&mut") |
| } else { |
| (pat_snippet, "&") |
| }; |
| suggestions.push((pat_span, to_remove, suggestion.to_owned())); |
| } |
| } |
| } |
| } |
| suggestions.sort_unstable_by_key(|&(span, _, _)| span); |
| suggestions.dedup_by_key(|&mut (span, _, _)| span); |
| for (span, to_remove, suggestion) in suggestions { |
| err.span_suggestion( |
| span, |
| &format!("consider removing the `{to_remove}`"), |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| fn add_move_error_details(&self, err: &mut Diagnostic, binds_to: &[Local]) { |
| for (j, local) in binds_to.iter().enumerate() { |
| let bind_to = &self.body.local_decls[*local]; |
| let binding_span = bind_to.source_info.span; |
| |
| if j == 0 { |
| err.span_label(binding_span, "data moved here"); |
| } else { |
| err.span_label(binding_span, "...and here"); |
| } |
| |
| if binds_to.len() == 1 { |
| self.note_type_does_not_implement_copy( |
| err, |
| &format!("`{}`", self.local_names[*local].unwrap()), |
| bind_to.ty, |
| Some(binding_span), |
| "", |
| ); |
| } |
| } |
| |
| if binds_to.len() > 1 { |
| err.note( |
| "move occurs because these variables have types that \ |
| don't implement the `Copy` trait", |
| ); |
| } |
| } |
| } |
