//! Borrow checker diagnostics. use itertools::Itertools; use rustc_const_eval::util::{call_kind, CallDesugaringKind}; use rustc_errors::{Applicability, Diagnostic}; use rustc_hir as hir; use rustc_hir::def::{CtorKind, Namespace}; use rustc_hir::GeneratorKind; use rustc_infer::infer::{LateBoundRegionConversionTime, TyCtxtInferExt}; use rustc_middle::mir::tcx::PlaceTy; use rustc_middle::mir::{ AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, }; use rustc_middle::ty::print::Print; use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt}; use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult}; use rustc_span::def_id::LocalDefId; use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP}; use rustc_target::abi::VariantIdx; use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt; use rustc_trait_selection::traits::{ type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause, }; use super::borrow_set::BorrowData; use super::MirBorrowckCtxt; mod find_all_local_uses; mod find_use; mod outlives_suggestion; mod region_name; mod var_name; mod bound_region_errors; mod conflict_errors; mod explain_borrow; mod move_errors; mod mutability_errors; mod region_errors; pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo}; pub(crate) use mutability_errors::AccessKind; pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder; pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors}; pub(crate) use region_name::{RegionName, RegionNameSource}; pub(crate) use rustc_const_eval::util::CallKind; pub(super) struct DescribePlaceOpt { pub including_downcast: bool, /// Enable/Disable tuple fields. /// For example `x` tuple. if it's `true` `x.0`. Otherwise `x` pub including_tuple_field: bool, } pub(super) struct IncludingTupleField(pub(super) bool); impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure /// is moved after being invoked. /// /// ```text /// note: closure cannot be invoked more than once because it moves the variable `dict` out of /// its environment /// --> $DIR/issue-42065.rs:16:29 /// | /// LL | for (key, value) in dict { /// | ^^^^ /// ``` pub(super) fn add_moved_or_invoked_closure_note( &self, location: Location, place: PlaceRef<'tcx>, diag: &mut Diagnostic, ) -> bool { debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place); let mut target = place.local_or_deref_local(); for stmt in &self.body[location.block].statements[location.statement_index..] { debug!("add_moved_or_invoked_closure_note: stmt={:?} target={:?}", stmt, target); if let StatementKind::Assign(box (into, Rvalue::Use(from))) = &stmt.kind { debug!("add_fnonce_closure_note: into={:?} from={:?}", into, from); match from { Operand::Copy(place) | Operand::Move(place) if target == place.local_or_deref_local() => { target = into.local_or_deref_local() } _ => {} } } } // Check if we are attempting to call a closure after it has been invoked. let terminator = self.body[location.block].terminator(); debug!("add_moved_or_invoked_closure_note: terminator={:?}", terminator); if let TerminatorKind::Call { func: Operand::Constant(box Constant { literal, .. }), args, .. } = &terminator.kind { if let ty::FnDef(id, _) = *literal.ty().kind() { debug!("add_moved_or_invoked_closure_note: id={:?}", id); if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() { let closure = match args.first() { Some(Operand::Copy(place) | Operand::Move(place)) if target == place.local_or_deref_local() => { place.local_or_deref_local().unwrap() } _ => return false, }; debug!("add_moved_or_invoked_closure_note: closure={:?}", closure); if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() { let did = did.expect_local(); if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) { diag.span_note( *span, &format!( "closure cannot be invoked more than once because it moves the \ variable `{}` out of its environment", ty::place_to_string_for_capture(self.infcx.tcx, hir_place) ), ); return true; } } } } } // Check if we are just moving a closure after it has been invoked. if let Some(target) = target { if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() { let did = did.expect_local(); if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) { diag.span_note( *span, &format!( "closure cannot be moved more than once as it is not `Copy` due to \ moving the variable `{}` out of its environment", ty::place_to_string_for_capture(self.infcx.tcx, hir_place) ), ); return true; } } } false } /// End-user visible description of `place` if one can be found. /// If the place is a temporary for instance, `"value"` will be returned. pub(super) fn describe_any_place(&self, place_ref: PlaceRef<'tcx>) -> String { match self.describe_place(place_ref) { Some(mut descr) => { // Surround descr with `backticks`. descr.reserve(2); descr.insert(0, '`'); descr.push('`'); descr } None => "value".to_string(), } } /// End-user visible description of `place` if one can be found. /// If the place is a temporary for instance, `None` will be returned. pub(super) fn describe_place(&self, place_ref: PlaceRef<'tcx>) -> Option { self.describe_place_with_options( place_ref, DescribePlaceOpt { including_downcast: false, including_tuple_field: true }, ) } /// End-user visible description of `place` if one can be found. If the place is a temporary /// for instance, `None` will be returned. /// `IncludingDowncast` parameter makes the function return `None` if `ProjectionElem` is /// `Downcast` and `IncludingDowncast` is true pub(super) fn describe_place_with_options( &self, place: PlaceRef<'tcx>, opt: DescribePlaceOpt, ) -> Option { let local = place.local; let mut autoderef_index = None; let mut buf = String::new(); let mut ok = self.append_local_to_string(local, &mut buf); for (index, elem) in place.projection.into_iter().enumerate() { match elem { ProjectionElem::Deref => { if index == 0 { if self.body.local_decls[local].is_ref_for_guard() { continue; } if let Some(box LocalInfo::StaticRef { def_id, .. }) = &self.body.local_decls[local].local_info { buf.push_str(self.infcx.tcx.item_name(*def_id).as_str()); ok = Ok(()); continue; } } if let Some(field) = self.is_upvar_field_projection(PlaceRef { local, projection: place.projection.split_at(index + 1).0, }) { let var_index = field.index(); buf = self.upvars[var_index].place.to_string(self.infcx.tcx); ok = Ok(()); if !self.upvars[var_index].by_ref { buf.insert(0, '*'); } } else { if autoderef_index.is_none() { autoderef_index = match place.projection.into_iter().rev().find_position(|elem| { !matches!( elem, ProjectionElem::Deref | ProjectionElem::Downcast(..) ) }) { Some((index, _)) => Some(place.projection.len() - index), None => Some(0), }; } if index >= autoderef_index.unwrap() { buf.insert(0, '*'); } } } ProjectionElem::Downcast(..) if opt.including_downcast => return None, ProjectionElem::Downcast(..) => (), ProjectionElem::OpaqueCast(..) => (), ProjectionElem::Field(field, _ty) => { // FIXME(project-rfc_2229#36): print capture precisely here. if let Some(field) = self.is_upvar_field_projection(PlaceRef { local, projection: place.projection.split_at(index + 1).0, }) { buf = self.upvars[field.index()].place.to_string(self.infcx.tcx); ok = Ok(()); } else { let field_name = self.describe_field( PlaceRef { local, projection: place.projection.split_at(index).0 }, *field, IncludingTupleField(opt.including_tuple_field), ); if let Some(field_name_str) = field_name { buf.push('.'); buf.push_str(&field_name_str); } } } ProjectionElem::Index(index) => { buf.push('['); if self.append_local_to_string(*index, &mut buf).is_err() { buf.push('_'); } buf.push(']'); } ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => { // Since it isn't possible to borrow an element on a particular index and // then use another while the borrow is held, don't output indices details // to avoid confusing the end-user buf.push_str("[..]"); } } } ok.ok().map(|_| buf) } fn describe_name(&self, place: PlaceRef<'tcx>) -> Option { for elem in place.projection.into_iter() { match elem { ProjectionElem::Downcast(Some(name), _) => { return Some(*name); } _ => {} } } None } /// Appends end-user visible description of the `local` place to `buf`. If `local` doesn't have /// a name, or its name was generated by the compiler, then `Err` is returned fn append_local_to_string(&self, local: Local, buf: &mut String) -> Result<(), ()> { let decl = &self.body.local_decls[local]; match self.local_names[local] { Some(name) if !decl.from_compiler_desugaring() => { buf.push_str(name.as_str()); Ok(()) } _ => Err(()), } } /// End-user visible description of the `field`nth field of `base` fn describe_field( &self, place: PlaceRef<'tcx>, field: Field, including_tuple_field: IncludingTupleField, ) -> Option { let place_ty = match place { PlaceRef { local, projection: [] } => PlaceTy::from_ty(self.body.local_decls[local].ty), PlaceRef { local, projection: [proj_base @ .., elem] } => match elem { ProjectionElem::Deref | ProjectionElem::Index(..) | ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => { PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx) } ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx), ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty), ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type), }, }; self.describe_field_from_ty( place_ty.ty, field, place_ty.variant_index, including_tuple_field, ) } /// End-user visible description of the `field_index`nth field of `ty` fn describe_field_from_ty( &self, ty: Ty<'_>, field: Field, variant_index: Option, including_tuple_field: IncludingTupleField, ) -> Option { if ty.is_box() { // If the type is a box, the field is described from the boxed type self.describe_field_from_ty(ty.boxed_ty(), field, variant_index, including_tuple_field) } else { match *ty.kind() { ty::Adt(def, _) => { let variant = if let Some(idx) = variant_index { assert!(def.is_enum()); &def.variant(idx) } else { def.non_enum_variant() }; if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) { return None; } Some(variant.fields[field.index()].name.to_string()) } ty::Tuple(_) => Some(field.index().to_string()), ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => { self.describe_field_from_ty(ty, field, variant_index, including_tuple_field) } ty::Array(ty, _) | ty::Slice(ty) => { self.describe_field_from_ty(ty, field, variant_index, including_tuple_field) } ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => { // We won't be borrowck'ing here if the closure came from another crate, // so it's safe to call `expect_local`. // // We know the field exists so it's safe to call operator[] and `unwrap` here. let def_id = def_id.expect_local(); let var_id = self.infcx.tcx.closure_captures(def_id)[field.index()].get_root_variable(); Some(self.infcx.tcx.hir().name(var_id).to_string()) } _ => { // Might need a revision when the fields in trait RFC is implemented // (https://github.com/rust-lang/rfcs/pull/1546) bug!("End-user description not implemented for field access on `{:?}`", ty); } } } } /// Add a note that a type does not implement `Copy` pub(super) fn note_type_does_not_implement_copy( &self, err: &mut Diagnostic, place_desc: &str, ty: Ty<'tcx>, span: Option, move_prefix: &str, ) { let message = format!( "{move_prefix}move occurs because {place_desc} has type `{ty}`, which does not implement the `Copy` trait", ); if let Some(span) = span { err.span_label(span, message); } else { err.note(&message); } } pub(super) fn borrowed_content_source( &self, deref_base: PlaceRef<'tcx>, ) -> BorrowedContentSource<'tcx> { let tcx = self.infcx.tcx; // Look up the provided place and work out the move path index for it, // we'll use this to check whether it was originally from an overloaded // operator. match self.move_data.rev_lookup.find(deref_base) { LookupResult::Exact(mpi) | LookupResult::Parent(Some(mpi)) => { debug!("borrowed_content_source: mpi={:?}", mpi); for i in &self.move_data.init_path_map[mpi] { let init = &self.move_data.inits[*i]; debug!("borrowed_content_source: init={:?}", init); // We're only interested in statements that initialized a value, not the // initializations from arguments. let InitLocation::Statement(loc) = init.location else { continue }; let bbd = &self.body[loc.block]; let is_terminator = bbd.statements.len() == loc.statement_index; debug!( "borrowed_content_source: loc={:?} is_terminator={:?}", loc, is_terminator, ); if !is_terminator { continue; } else if let Some(Terminator { kind: TerminatorKind::Call { func, from_hir_call: false, .. }, .. }) = &bbd.terminator { if let Some(source) = BorrowedContentSource::from_call(func.ty(self.body, tcx), tcx) { return source; } } } } // Base is a `static` so won't be from an overloaded operator _ => (), }; // If we didn't find an overloaded deref or index, then assume it's a // built in deref and check the type of the base. let base_ty = deref_base.ty(self.body, tcx).ty; if base_ty.is_unsafe_ptr() { BorrowedContentSource::DerefRawPointer } else if base_ty.is_mutable_ptr() { BorrowedContentSource::DerefMutableRef } else { BorrowedContentSource::DerefSharedRef } } /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime /// name where required. pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String { let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS); // We need to add synthesized lifetimes where appropriate. We do // this by hooking into the pretty printer and telling it to label the // lifetimes without names with the value `'0`. if let ty::Ref(region, ..) = ty.kind() { match **region { ty::ReLateBound(_, ty::BoundRegion { kind: br, .. }) | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => { printer.region_highlight_mode.highlighting_bound_region(br, counter) } _ => {} } } ty.print(printer).unwrap().into_buffer() } /// Returns the name of the provided `Ty` (that must be a reference)'s region with a /// synthesized lifetime name where required. pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String { let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS); let region = if let ty::Ref(region, ..) = ty.kind() { match **region { ty::ReLateBound(_, ty::BoundRegion { kind: br, .. }) | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => { printer.region_highlight_mode.highlighting_bound_region(br, counter) } _ => {} } region } else { bug!("ty for annotation of borrow region is not a reference"); }; region.print(printer).unwrap().into_buffer() } } /// The span(s) associated to a use of a place. #[derive(Copy, Clone, PartialEq, Eq, Debug)] pub(super) enum UseSpans<'tcx> { /// The access is caused by capturing a variable for a closure. ClosureUse { /// This is true if the captured variable was from a generator. generator_kind: Option, /// The span of the args of the closure, including the `move` keyword if /// it's present. args_span: Span, /// The span of the use resulting in capture kind /// Check `ty::CaptureInfo` for more details capture_kind_span: Span, /// The span of the use resulting in the captured path /// Check `ty::CaptureInfo` for more details path_span: Span, }, /// The access is caused by using a variable as the receiver of a method /// that takes 'self' FnSelfUse { /// The span of the variable being moved var_span: Span, /// The span of the method call on the variable fn_call_span: Span, /// The definition span of the method being called fn_span: Span, kind: CallKind<'tcx>, }, /// This access is caused by a `match` or `if let` pattern. PatUse(Span), /// This access has a single span associated to it: common case. OtherUse(Span), } impl UseSpans<'_> { pub(super) fn args_or_use(self) -> Span { match self { UseSpans::ClosureUse { args_span: span, .. } | UseSpans::PatUse(span) | UseSpans::OtherUse(span) => span, UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { fn_call_span } UseSpans::FnSelfUse { var_span, .. } => var_span, } } /// Returns the span of `self`, in the case of a `ClosureUse` returns the `path_span` pub(super) fn var_or_use_path_span(self) -> Span { match self { UseSpans::ClosureUse { path_span: span, .. } | UseSpans::PatUse(span) | UseSpans::OtherUse(span) => span, UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { fn_call_span } UseSpans::FnSelfUse { var_span, .. } => var_span, } } /// Returns the span of `self`, in the case of a `ClosureUse` returns the `capture_kind_span` pub(super) fn var_or_use(self) -> Span { match self { UseSpans::ClosureUse { capture_kind_span: span, .. } | UseSpans::PatUse(span) | UseSpans::OtherUse(span) => span, UseSpans::FnSelfUse { fn_call_span, kind: CallKind::DerefCoercion { .. }, .. } => { fn_call_span } UseSpans::FnSelfUse { var_span, .. } => var_span, } } pub(super) fn generator_kind(self) -> Option { match self { UseSpans::ClosureUse { generator_kind, .. } => generator_kind, _ => None, } } /// Add a span label to the arguments of the closure, if it exists. pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into) { if let UseSpans::ClosureUse { args_span, .. } = self { err.span_label(args_span, message); } } /// Add a span label to the use of the captured variable, if it exists. /// only adds label to the `path_span` pub(super) fn var_path_only_subdiag( self, err: &mut Diagnostic, action: crate::InitializationRequiringAction, ) { use crate::session_diagnostics::CaptureVarPathUseCause::*; use crate::InitializationRequiringAction::*; if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self { match generator_kind { Some(_) => { err.subdiagnostic(match action { Borrow => BorrowInGenerator { path_span }, MatchOn | Use => UseInGenerator { path_span }, Assignment => AssignInGenerator { path_span }, PartialAssignment => AssignPartInGenerator { path_span }, }); } None => { err.subdiagnostic(match action { Borrow => BorrowInClosure { path_span }, MatchOn | Use => UseInClosure { path_span }, Assignment => AssignInClosure { path_span }, PartialAssignment => AssignPartInClosure { path_span }, }); } } } } /// Add a span label to the use of the captured variable, if it exists. pub(super) fn var_span_label( self, err: &mut Diagnostic, message: impl Into, kind_desc: impl Into, ) { if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self { if capture_kind_span == path_span { err.span_label(capture_kind_span, message); } else { let capture_kind_label = format!("capture is {} because of use here", kind_desc.into()); let path_label = message; err.span_label(capture_kind_span, capture_kind_label); err.span_label(path_span, path_label); } } } /// Add a subdiagnostic to the use of the captured variable, if it exists. pub(super) fn var_subdiag( self, err: &mut Diagnostic, kind: Option, f: impl Fn(Option, Span) -> crate::session_diagnostics::CaptureVarCause, ) { use crate::session_diagnostics::CaptureVarKind::*; if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self { if capture_kind_span != path_span { err.subdiagnostic(match kind { Some(kd) => match kd { rustc_middle::mir::BorrowKind::Shared | rustc_middle::mir::BorrowKind::Shallow | rustc_middle::mir::BorrowKind::Unique => { Immute { kind_span: capture_kind_span } } rustc_middle::mir::BorrowKind::Mut { .. } => { Mut { kind_span: capture_kind_span } } }, None => Move { kind_span: capture_kind_span }, }); }; err.subdiagnostic(f(generator_kind, path_span)); } } /// Returns `false` if this place is not used in a closure. pub(super) fn for_closure(&self) -> bool { match *self { UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_none(), _ => false, } } /// Returns `false` if this place is not used in a generator. pub(super) fn for_generator(&self) -> bool { match *self { UseSpans::ClosureUse { generator_kind, .. } => generator_kind.is_some(), _ => false, } } /// Describe the span associated with a use of a place. pub(super) fn describe(&self) -> &str { match *self { UseSpans::ClosureUse { generator_kind, .. } => { if generator_kind.is_some() { " in generator" } else { " in closure" } } _ => "", } } pub(super) fn or_else(self, if_other: F) -> Self where F: FnOnce() -> Self, { match self { closure @ UseSpans::ClosureUse { .. } => closure, UseSpans::PatUse(_) | UseSpans::OtherUse(_) => if_other(), fn_self @ UseSpans::FnSelfUse { .. } => fn_self, } } } pub(super) enum BorrowedContentSource<'tcx> { DerefRawPointer, DerefMutableRef, DerefSharedRef, OverloadedDeref(Ty<'tcx>), OverloadedIndex(Ty<'tcx>), } impl<'tcx> BorrowedContentSource<'tcx> { pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String { match *self { BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(), BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(), BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(), BorrowedContentSource::OverloadedDeref(ty) => ty .ty_adt_def() .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? { name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")), _ => None, }) .unwrap_or_else(|| format!("dereference of `{ty}`")), BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{ty}`"), } } pub(super) fn describe_for_named_place(&self) -> Option<&'static str> { match *self { BorrowedContentSource::DerefRawPointer => Some("raw pointer"), BorrowedContentSource::DerefSharedRef => Some("shared reference"), BorrowedContentSource::DerefMutableRef => Some("mutable reference"), // Overloaded deref and index operators should be evaluated into a // temporary. So we don't need a description here. BorrowedContentSource::OverloadedDeref(_) | BorrowedContentSource::OverloadedIndex(_) => None, } } pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String { match *self { BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(), BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(), BorrowedContentSource::DerefMutableRef => { bug!("describe_for_immutable_place: DerefMutableRef isn't immutable") } BorrowedContentSource::OverloadedDeref(ty) => ty .ty_adt_def() .and_then(|adt| match tcx.get_diagnostic_name(adt.did())? { name @ (sym::Rc | sym::Arc) => Some(format!("an `{name}`")), _ => None, }) .unwrap_or_else(|| format!("dereference of `{ty}`")), BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{ty}`"), } } fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option { match *func.kind() { ty::FnDef(def_id, substs) => { let trait_id = tcx.trait_of_item(def_id)?; let lang_items = tcx.lang_items(); if Some(trait_id) == lang_items.deref_trait() || Some(trait_id) == lang_items.deref_mut_trait() { Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0))) } else if Some(trait_id) == lang_items.index_trait() || Some(trait_id) == lang_items.index_mut_trait() { Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0))) } else { None } } _ => None, } } } impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { /// Finds the spans associated to a move or copy of move_place at location. pub(super) fn move_spans( &self, moved_place: PlaceRef<'tcx>, // Could also be an upvar. location: Location, ) -> UseSpans<'tcx> { use self::UseSpans::*; let Some(stmt) = self.body[location.block].statements.get(location.statement_index) else { return OtherUse(self.body.source_info(location).span); }; debug!("move_spans: moved_place={:?} location={:?} stmt={:?}", moved_place, location, stmt); if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind && let AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) = **kind { debug!("move_spans: def_id={:?} places={:?}", def_id, places); let def_id = def_id.expect_local(); if let Some((args_span, generator_kind, capture_kind_span, path_span)) = self.closure_span(def_id, moved_place, places) { return ClosureUse { generator_kind, args_span, capture_kind_span, path_span, }; } } // StatementKind::FakeRead only contains a def_id if they are introduced as a result // of pattern matching within a closure. if let StatementKind::FakeRead(box (cause, place)) = stmt.kind { match cause { FakeReadCause::ForMatchedPlace(Some(closure_def_id)) | FakeReadCause::ForLet(Some(closure_def_id)) => { debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place); let places = &[Operand::Move(place)]; if let Some((args_span, generator_kind, capture_kind_span, path_span)) = self.closure_span(closure_def_id, moved_place, places) { return ClosureUse { generator_kind, args_span, capture_kind_span, path_span, }; } } _ => {} } } let normal_ret = if moved_place.projection.iter().any(|p| matches!(p, ProjectionElem::Downcast(..))) { PatUse(stmt.source_info.span) } else { OtherUse(stmt.source_info.span) }; // We are trying to find MIR of the form: // ``` // _temp = _moved_val; // ... // FnSelfCall(_temp, ...) // ``` // // where `_moved_val` is the place we generated the move error for, // `_temp` is some other local, and `FnSelfCall` is a function // that has a `self` parameter. let target_temp = match stmt.kind { StatementKind::Assign(box (temp, _)) if temp.as_local().is_some() => { temp.as_local().unwrap() } _ => return normal_ret, }; debug!("move_spans: target_temp = {:?}", target_temp); if let Some(Terminator { kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, .. }) = &self.body[location.block].terminator { let Some((method_did, method_substs)) = rustc_const_eval::util::find_self_call( self.infcx.tcx, &self.body, target_temp, location.block, ) else { return normal_ret; }; let kind = call_kind( self.infcx.tcx, self.param_env, method_did, method_substs, *fn_span, *from_hir_call, Some(self.infcx.tcx.fn_arg_names(method_did)[0]), ); return FnSelfUse { var_span: stmt.source_info.span, fn_call_span: *fn_span, fn_span: self.infcx.tcx.def_span(method_did), kind, }; } normal_ret } /// Finds the span of arguments of a closure (within `maybe_closure_span`) /// and its usage of the local assigned at `location`. /// This is done by searching in statements succeeding `location` /// and originating from `maybe_closure_span`. pub(super) fn borrow_spans(&self, use_span: Span, location: Location) -> UseSpans<'tcx> { use self::UseSpans::*; debug!("borrow_spans: use_span={:?} location={:?}", use_span, location); let target = match self.body[location.block].statements.get(location.statement_index) { Some(Statement { kind: StatementKind::Assign(box (place, _)), .. }) => { if let Some(local) = place.as_local() { local } else { return OtherUse(use_span); } } _ => return OtherUse(use_span), }; if self.body.local_kind(target) != LocalKind::Temp { // operands are always temporaries. return OtherUse(use_span); } for stmt in &self.body[location.block].statements[location.statement_index + 1..] { if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind { let (&def_id, is_generator) = match kind { box AggregateKind::Closure(def_id, _) => (def_id, false), box AggregateKind::Generator(def_id, _, _) => (def_id, true), _ => continue, }; let def_id = def_id.expect_local(); debug!( "borrow_spans: def_id={:?} is_generator={:?} places={:?}", def_id, is_generator, places ); if let Some((args_span, generator_kind, capture_kind_span, path_span)) = self.closure_span(def_id, Place::from(target).as_ref(), places) { return ClosureUse { generator_kind, args_span, capture_kind_span, path_span }; } else { return OtherUse(use_span); } } if use_span != stmt.source_info.span { break; } } OtherUse(use_span) } /// Finds the spans of a captured place within a closure or generator. /// The first span is the location of the use resulting in the capture kind of the capture /// The second span is the location the use resulting in the captured path of the capture fn closure_span( &self, def_id: LocalDefId, target_place: PlaceRef<'tcx>, places: &[Operand<'tcx>], ) -> Option<(Span, Option, Span, Span)> { debug!( "closure_span: def_id={:?} target_place={:?} places={:?}", def_id, target_place, places ); let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(def_id); let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind; debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr); if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr { for (captured_place, place) in self.infcx.tcx.closure_captures(def_id).iter().zip(places) { match place { Operand::Copy(place) | Operand::Move(place) if target_place == place.as_ref() => { debug!("closure_span: found captured local {:?}", place); let body = self.infcx.tcx.hir().body(body); let generator_kind = body.generator_kind(); return Some(( fn_decl_span, generator_kind, captured_place.get_capture_kind_span(self.infcx.tcx), captured_place.get_path_span(self.infcx.tcx), )); } _ => {} } } } None } /// Helper to retrieve span(s) of given borrow from the current MIR /// representation pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<'tcx> { let span = self.body.source_info(borrow.reserve_location).span; self.borrow_spans(span, borrow.reserve_location) } fn explain_captures( &mut self, err: &mut Diagnostic, span: Span, move_span: Span, move_spans: UseSpans<'tcx>, moved_place: Place<'tcx>, partially_str: &str, loop_message: &str, move_msg: &str, is_loop_move: bool, maybe_reinitialized_locations_is_empty: bool, ) { if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans { let place_name = self .describe_place(moved_place.as_ref()) .map(|n| format!("`{n}`")) .unwrap_or_else(|| "value".to_owned()); match kind { CallKind::FnCall { fn_trait_id, .. } if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() => { err.span_label( fn_call_span, &format!( "{place_name} {partially_str}moved due to this call{loop_message}", ), ); err.span_note( var_span, "this value implements `FnOnce`, which causes it to be moved when called", ); } CallKind::Operator { self_arg, .. } => { let self_arg = self_arg.unwrap(); err.span_label( fn_call_span, &format!( "{place_name} {partially_str}moved due to usage in operator{loop_message}", ), ); if self.fn_self_span_reported.insert(fn_span) { err.span_note( self_arg.span, "calling this operator moves the left-hand side", ); } } CallKind::Normal { self_arg, desugaring, method_did, method_substs } => { let self_arg = self_arg.unwrap(); let tcx = self.infcx.tcx; if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring { let ty = moved_place.ty(self.body, tcx).ty; let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) { Some(def_id) => { let infcx = self.infcx.tcx.infer_ctxt().build(); type_known_to_meet_bound_modulo_regions( &infcx, self.param_env, tcx.mk_imm_ref(tcx.lifetimes.re_erased, tcx.erase_regions(ty)), def_id, DUMMY_SP, ) } _ => false, }; if suggest { err.span_suggestion_verbose( move_span.shrink_to_lo(), &format!( "consider iterating over a slice of the `{ty}`'s content to \ avoid moving into the `for` loop", ), "&", Applicability::MaybeIncorrect, ); } err.span_label( fn_call_span, &format!( "{place_name} {partially_str}moved due to this implicit call to `.into_iter()`{loop_message}", ), ); // If the moved place was a `&mut` ref, then we can // suggest to reborrow it where it was moved, so it // will still be valid by the time we get to the usage. if let ty::Ref(_, _, hir::Mutability::Mut) = moved_place.ty(self.body, self.infcx.tcx).ty.kind() { // If we are in a loop this will be suggested later. if !is_loop_move { err.span_suggestion_verbose( move_span.shrink_to_lo(), &format!( "consider creating a fresh reborrow of {} here", self.describe_place(moved_place.as_ref()) .map(|n| format!("`{n}`")) .unwrap_or_else(|| "the mutable reference".to_string()), ), "&mut *", Applicability::MachineApplicable, ); } } } else { err.span_label( fn_call_span, &format!( "{place_name} {partially_str}moved due to this method call{loop_message}", ), ); let infcx = tcx.infer_ctxt().build(); // Erase and shadow everything that could be passed to the new infcx. let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty); let method_substs = tcx.erase_regions(method_substs); if let ty::Adt(def, substs) = ty.kind() && Some(def.did()) == tcx.lang_items().pin_type() && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind() && let self_ty = infcx.instantiate_binder_with_fresh_vars( fn_call_span, LateBoundRegionConversionTime::FnCall, tcx.fn_sig(method_did).subst(tcx, method_substs).input(0), ) && infcx.can_eq(self.param_env, ty, self_ty) { err.span_suggestion_verbose( fn_call_span.shrink_to_lo(), "consider reborrowing the `Pin` instead of moving it", "as_mut().".to_string(), Applicability::MaybeIncorrect, ); } if let Some(clone_trait) = tcx.lang_items().clone_trait() && let trait_ref = tcx.mk_trait_ref(clone_trait, [ty]) && let o = Obligation::new( tcx, ObligationCause::dummy(), self.param_env, ty::Binder::dummy(trait_ref), ) && infcx.predicate_must_hold_modulo_regions(&o) { err.span_suggestion_verbose( fn_call_span.shrink_to_lo(), "you can `clone` the value and consume it, but this might not be \ your desired behavior", "clone().".to_string(), Applicability::MaybeIncorrect, ); } } // Avoid pointing to the same function in multiple different // error messages. if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) { let func = tcx.def_path_str(method_did); err.span_note( self_arg.span, &format!("`{func}` takes ownership of the receiver `self`, which moves {place_name}") ); } let parent_did = tcx.parent(method_did); let parent_self_ty = matches!(tcx.def_kind(parent_did), rustc_hir::def::DefKind::Impl { .. }) .then_some(parent_did) .and_then(|did| match tcx.type_of(did).subst_identity().kind() { ty::Adt(def, ..) => Some(def.did()), _ => None, }); let is_option_or_result = parent_self_ty.map_or(false, |def_id| { matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result)) }); if is_option_or_result && maybe_reinitialized_locations_is_empty { err.span_label( var_span, "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents", ); } } // Other desugarings takes &self, which cannot cause a move _ => {} } } else { if move_span != span || !loop_message.is_empty() { err.span_label( move_span, format!("value {partially_str}moved{move_msg} here{loop_message}"), ); } // If the move error occurs due to a loop, don't show // another message for the same span if loop_message.is_empty() { move_spans.var_span_label( err, format!("variable {partially_str}moved due to use{}", move_spans.describe()), "moved", ); } } } }