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Diffstat (limited to 'compiler/rustc_borrowck/src/type_check/mod.rs')
| -rw-r--r-- | compiler/rustc_borrowck/src/type_check/mod.rs | 2721 |
1 files changed, 2721 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs new file mode 100644 index 000000000..d32b1edcd --- /dev/null +++ b/compiler/rustc_borrowck/src/type_check/mod.rs @@ -0,0 +1,2721 @@ +//! This pass type-checks the MIR to ensure it is not broken. + +use std::rc::Rc; +use std::{fmt, iter, mem}; + +use either::Either; + +use hir::OpaqueTyOrigin; +use rustc_data_structures::frozen::Frozen; +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_data_structures::vec_map::VecMap; +use rustc_hir as hir; +use rustc_hir::def::DefKind; +use rustc_hir::def_id::LocalDefId; +use rustc_hir::lang_items::LangItem; +use rustc_index::vec::{Idx, IndexVec}; +use rustc_infer::infer::canonical::QueryRegionConstraints; +use rustc_infer::infer::outlives::env::RegionBoundPairs; +use rustc_infer::infer::region_constraints::RegionConstraintData; +use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use rustc_infer::infer::{ + InferCtxt, InferOk, LateBoundRegion, LateBoundRegionConversionTime, NllRegionVariableOrigin, +}; +use rustc_middle::mir::tcx::PlaceTy; +use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor}; +use rustc_middle::mir::AssertKind; +use rustc_middle::mir::*; +use rustc_middle::ty::adjustment::PointerCast; +use rustc_middle::ty::cast::CastTy; +use rustc_middle::ty::subst::{GenericArgKind, SubstsRef, UserSubsts}; +use rustc_middle::ty::visit::TypeVisitable; +use rustc_middle::ty::{ + self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, OpaqueHiddenType, + OpaqueTypeKey, RegionVid, ToPredicate, Ty, TyCtxt, UserType, UserTypeAnnotationIndex, +}; +use rustc_span::def_id::CRATE_DEF_ID; +use rustc_span::{Span, DUMMY_SP}; +use rustc_target::abi::VariantIdx; +use rustc_trait_selection::traits::query::type_op; +use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints; +use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp; +use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput}; +use rustc_trait_selection::traits::query::Fallible; +use rustc_trait_selection::traits::PredicateObligation; + +use rustc_mir_dataflow::impls::MaybeInitializedPlaces; +use rustc_mir_dataflow::move_paths::MoveData; +use rustc_mir_dataflow::ResultsCursor; + +use crate::session_diagnostics::MoveUnsized; +use crate::{ + borrow_set::BorrowSet, + constraints::{OutlivesConstraint, OutlivesConstraintSet}, + diagnostics::UniverseInfo, + facts::AllFacts, + location::LocationTable, + member_constraints::MemberConstraintSet, + nll::ToRegionVid, + path_utils, + region_infer::values::{ + LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements, + }, + region_infer::{ClosureRegionRequirementsExt, TypeTest}, + type_check::free_region_relations::{CreateResult, UniversalRegionRelations}, + universal_regions::{DefiningTy, UniversalRegions}, + Upvar, +}; + +macro_rules! span_mirbug { + ($context:expr, $elem:expr, $($message:tt)*) => ({ + $crate::type_check::mirbug( + $context.tcx(), + $context.last_span, + &format!( + "broken MIR in {:?} ({:?}): {}", + $context.body().source.def_id(), + $elem, + format_args!($($message)*), + ), + ) + }) +} + +macro_rules! span_mirbug_and_err { + ($context:expr, $elem:expr, $($message:tt)*) => ({ + { + span_mirbug!($context, $elem, $($message)*); + $context.error() + } + }) +} + +mod canonical; +mod constraint_conversion; +pub mod free_region_relations; +mod input_output; +pub(crate) mod liveness; +mod relate_tys; + +/// Type checks the given `mir` in the context of the inference +/// context `infcx`. Returns any region constraints that have yet to +/// be proven. This result includes liveness constraints that +/// ensure that regions appearing in the types of all local variables +/// are live at all points where that local variable may later be +/// used. +/// +/// This phase of type-check ought to be infallible -- this is because +/// the original, HIR-based type-check succeeded. So if any errors +/// occur here, we will get a `bug!` reported. +/// +/// # Parameters +/// +/// - `infcx` -- inference context to use +/// - `param_env` -- parameter environment to use for trait solving +/// - `body` -- MIR body to type-check +/// - `promoted` -- map of promoted constants within `body` +/// - `universal_regions` -- the universal regions from `body`s function signature +/// - `location_table` -- MIR location map of `body` +/// - `borrow_set` -- information about borrows occurring in `body` +/// - `all_facts` -- when using Polonius, this is the generated set of Polonius facts +/// - `flow_inits` -- results of a maybe-init dataflow analysis +/// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis +/// - `elements` -- MIR region map +pub(crate) fn type_check<'mir, 'tcx>( + infcx: &InferCtxt<'_, 'tcx>, + param_env: ty::ParamEnv<'tcx>, + body: &Body<'tcx>, + promoted: &IndexVec<Promoted, Body<'tcx>>, + universal_regions: &Rc<UniversalRegions<'tcx>>, + location_table: &LocationTable, + borrow_set: &BorrowSet<'tcx>, + all_facts: &mut Option<AllFacts>, + flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>, + move_data: &MoveData<'tcx>, + elements: &Rc<RegionValueElements>, + upvars: &[Upvar<'tcx>], + use_polonius: bool, +) -> MirTypeckResults<'tcx> { + let implicit_region_bound = infcx.tcx.mk_region(ty::ReVar(universal_regions.fr_fn_body)); + let mut universe_causes = FxHashMap::default(); + universe_causes.insert(ty::UniverseIndex::from_u32(0), UniverseInfo::other()); + let mut constraints = MirTypeckRegionConstraints { + placeholder_indices: PlaceholderIndices::default(), + placeholder_index_to_region: IndexVec::default(), + liveness_constraints: LivenessValues::new(elements.clone()), + outlives_constraints: OutlivesConstraintSet::default(), + member_constraints: MemberConstraintSet::default(), + closure_bounds_mapping: Default::default(), + type_tests: Vec::default(), + universe_causes, + }; + + let CreateResult { + universal_region_relations, + region_bound_pairs, + normalized_inputs_and_output, + } = free_region_relations::create( + infcx, + param_env, + implicit_region_bound, + universal_regions, + &mut constraints, + ); + + debug!(?normalized_inputs_and_output); + + for u in ty::UniverseIndex::ROOT..infcx.universe() { + let info = UniverseInfo::other(); + constraints.universe_causes.insert(u, info); + } + + let mut borrowck_context = BorrowCheckContext { + universal_regions, + location_table, + borrow_set, + all_facts, + constraints: &mut constraints, + upvars, + }; + + let opaque_type_values = type_check_internal( + infcx, + param_env, + body, + promoted, + ®ion_bound_pairs, + implicit_region_bound, + &mut borrowck_context, + |mut cx| { + debug!("inside extra closure of type_check_internal"); + cx.equate_inputs_and_outputs(&body, universal_regions, &normalized_inputs_and_output); + liveness::generate( + &mut cx, + body, + elements, + flow_inits, + move_data, + location_table, + use_polonius, + ); + + translate_outlives_facts(&mut cx); + let opaque_type_values = + infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types(); + + opaque_type_values + .into_iter() + .map(|(opaque_type_key, decl)| { + cx.fully_perform_op( + Locations::All(body.span), + ConstraintCategory::OpaqueType, + CustomTypeOp::new( + |infcx| { + infcx.register_member_constraints( + param_env, + opaque_type_key, + decl.hidden_type.ty, + decl.hidden_type.span, + ); + Ok(InferOk { value: (), obligations: vec![] }) + }, + || "opaque_type_map".to_string(), + ), + ) + .unwrap(); + let mut hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type); + trace!( + "finalized opaque type {:?} to {:#?}", + opaque_type_key, + hidden_type.ty.kind() + ); + if hidden_type.has_infer_types_or_consts() { + infcx.tcx.sess.delay_span_bug( + decl.hidden_type.span, + &format!("could not resolve {:#?}", hidden_type.ty.kind()), + ); + hidden_type.ty = infcx.tcx.ty_error(); + } + + (opaque_type_key, (hidden_type, decl.origin)) + }) + .collect() + }, + ); + + MirTypeckResults { constraints, universal_region_relations, opaque_type_values } +} + +#[instrument( + skip(infcx, body, promoted, region_bound_pairs, borrowck_context, extra), + level = "debug" +)] +fn type_check_internal<'a, 'tcx, R>( + infcx: &'a InferCtxt<'a, 'tcx>, + param_env: ty::ParamEnv<'tcx>, + body: &'a Body<'tcx>, + promoted: &'a IndexVec<Promoted, Body<'tcx>>, + region_bound_pairs: &'a RegionBoundPairs<'tcx>, + implicit_region_bound: ty::Region<'tcx>, + borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>, + extra: impl FnOnce(TypeChecker<'a, 'tcx>) -> R, +) -> R { + debug!("body: {:#?}", body); + let mut checker = TypeChecker::new( + infcx, + body, + param_env, + region_bound_pairs, + implicit_region_bound, + borrowck_context, + ); + let errors_reported = { + let mut verifier = TypeVerifier::new(&mut checker, promoted); + verifier.visit_body(&body); + verifier.errors_reported + }; + + if !errors_reported { + // if verifier failed, don't do further checks to avoid ICEs + checker.typeck_mir(body); + } + + extra(checker) +} + +fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) { + let cx = &mut typeck.borrowck_context; + if let Some(facts) = cx.all_facts { + let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation"); + let location_table = cx.location_table; + facts.subset_base.extend(cx.constraints.outlives_constraints.outlives().iter().flat_map( + |constraint: &OutlivesConstraint<'_>| { + if let Some(from_location) = constraint.locations.from_location() { + Either::Left(iter::once(( + constraint.sup, + constraint.sub, + location_table.mid_index(from_location), + ))) + } else { + Either::Right( + location_table + .all_points() + .map(move |location| (constraint.sup, constraint.sub, location)), + ) + } + }, + )); + } +} + +#[track_caller] +fn mirbug(tcx: TyCtxt<'_>, span: Span, msg: &str) { + // We sometimes see MIR failures (notably predicate failures) due to + // the fact that we check rvalue sized predicates here. So use `delay_span_bug` + // to avoid reporting bugs in those cases. + tcx.sess.diagnostic().delay_span_bug(span, msg); +} + +enum FieldAccessError { + OutOfRange { field_count: usize }, +} + +/// Verifies that MIR types are sane to not crash further checks. +/// +/// The sanitize_XYZ methods here take an MIR object and compute its +/// type, calling `span_mirbug` and returning an error type if there +/// is a problem. +struct TypeVerifier<'a, 'b, 'tcx> { + cx: &'a mut TypeChecker<'b, 'tcx>, + promoted: &'b IndexVec<Promoted, Body<'tcx>>, + last_span: Span, + errors_reported: bool, +} + +impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> { + fn visit_span(&mut self, span: Span) { + if !span.is_dummy() { + self.last_span = span; + } + } + + fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) { + self.sanitize_place(place, location, context); + } + + fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) { + self.super_constant(constant, location); + let ty = self.sanitize_type(constant, constant.literal.ty()); + + self.cx.infcx.tcx.for_each_free_region(&ty, |live_region| { + let live_region_vid = + self.cx.borrowck_context.universal_regions.to_region_vid(live_region); + self.cx + .borrowck_context + .constraints + .liveness_constraints + .add_element(live_region_vid, location); + }); + + // HACK(compiler-errors): Constants that are gathered into Body.required_consts + // have their locations erased... + let locations = if location != Location::START { + location.to_locations() + } else { + Locations::All(constant.span) + }; + + if let Some(annotation_index) = constant.user_ty { + if let Err(terr) = self.cx.relate_type_and_user_type( + constant.literal.ty(), + ty::Variance::Invariant, + &UserTypeProjection { base: annotation_index, projs: vec![] }, + locations, + ConstraintCategory::Boring, + ) { + let annotation = &self.cx.user_type_annotations[annotation_index]; + span_mirbug!( + self, + constant, + "bad constant user type {:?} vs {:?}: {:?}", + annotation, + constant.literal.ty(), + terr, + ); + } + } else { + let tcx = self.tcx(); + let maybe_uneval = match constant.literal { + ConstantKind::Ty(ct) => match ct.kind() { + ty::ConstKind::Unevaluated(uv) => Some(uv), + _ => None, + }, + _ => None, + }; + if let Some(uv) = maybe_uneval { + if let Some(promoted) = uv.promoted { + let check_err = |verifier: &mut TypeVerifier<'a, 'b, 'tcx>, + promoted: &Body<'tcx>, + ty, + san_ty| { + if let Err(terr) = + verifier.cx.eq_types(ty, san_ty, locations, ConstraintCategory::Boring) + { + span_mirbug!( + verifier, + promoted, + "bad promoted type ({:?}: {:?}): {:?}", + ty, + san_ty, + terr + ); + }; + }; + + if !self.errors_reported { + let promoted_body = &self.promoted[promoted]; + self.sanitize_promoted(promoted_body, location); + + let promoted_ty = promoted_body.return_ty(); + check_err(self, promoted_body, ty, promoted_ty); + } + } else { + if let Err(terr) = self.cx.fully_perform_op( + locations, + ConstraintCategory::Boring, + self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new( + constant.literal.ty(), + uv.def.did, + UserSubsts { substs: uv.substs, user_self_ty: None }, + )), + ) { + span_mirbug!( + self, + constant, + "bad constant type {:?} ({:?})", + constant, + terr + ); + } + } + } else if let Some(static_def_id) = constant.check_static_ptr(tcx) { + let unnormalized_ty = tcx.type_of(static_def_id); + let normalized_ty = self.cx.normalize(unnormalized_ty, locations); + let literal_ty = constant.literal.ty().builtin_deref(true).unwrap().ty; + + if let Err(terr) = self.cx.eq_types( + literal_ty, + normalized_ty, + locations, + ConstraintCategory::Boring, + ) { + span_mirbug!(self, constant, "bad static type {:?} ({:?})", constant, terr); + } + } + + if let ty::FnDef(def_id, substs) = *constant.literal.ty().kind() { + let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs); + self.cx.normalize_and_prove_instantiated_predicates( + def_id, + instantiated_predicates, + locations, + ); + } + } + } + + fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { + self.super_rvalue(rvalue, location); + let rval_ty = rvalue.ty(self.body(), self.tcx()); + self.sanitize_type(rvalue, rval_ty); + } + + fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) { + self.super_local_decl(local, local_decl); + self.sanitize_type(local_decl, local_decl.ty); + + if let Some(user_ty) = &local_decl.user_ty { + for (user_ty, span) in user_ty.projections_and_spans() { + let ty = if !local_decl.is_nonref_binding() { + // If we have a binding of the form `let ref x: T = ..` + // then remove the outermost reference so we can check the + // type annotation for the remaining type. + if let ty::Ref(_, rty, _) = local_decl.ty.kind() { + *rty + } else { + bug!("{:?} with ref binding has wrong type {}", local, local_decl.ty); + } + } else { + local_decl.ty + }; + + if let Err(terr) = self.cx.relate_type_and_user_type( + ty, + ty::Variance::Invariant, + user_ty, + Locations::All(*span), + ConstraintCategory::TypeAnnotation, + ) { + span_mirbug!( + self, + local, + "bad user type on variable {:?}: {:?} != {:?} ({:?})", + local, + local_decl.ty, + local_decl.user_ty, + terr, + ); + } + } + } + } + + fn visit_body(&mut self, body: &Body<'tcx>) { + self.sanitize_type(&"return type", body.return_ty()); + for local_decl in &body.local_decls { + self.sanitize_type(local_decl, local_decl.ty); + } + if self.errors_reported { + return; + } + self.super_body(body); + } +} + +impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> { + fn new( + cx: &'a mut TypeChecker<'b, 'tcx>, + promoted: &'b IndexVec<Promoted, Body<'tcx>>, + ) -> Self { + TypeVerifier { promoted, last_span: cx.body.span, cx, errors_reported: false } + } + + fn body(&self) -> &Body<'tcx> { + self.cx.body + } + + fn tcx(&self) -> TyCtxt<'tcx> { + self.cx.infcx.tcx + } + + fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> { + if ty.has_escaping_bound_vars() || ty.references_error() { + span_mirbug_and_err!(self, parent, "bad type {:?}", ty) + } else { + ty + } + } + + /// Checks that the types internal to the `place` match up with + /// what would be expected. + fn sanitize_place( + &mut self, + place: &Place<'tcx>, + location: Location, + context: PlaceContext, + ) -> PlaceTy<'tcx> { + debug!("sanitize_place: {:?}", place); + + let mut place_ty = PlaceTy::from_ty(self.body().local_decls[place.local].ty); + + for elem in place.projection.iter() { + if place_ty.variant_index.is_none() { + if place_ty.ty.references_error() { + assert!(self.errors_reported); + return PlaceTy::from_ty(self.tcx().ty_error()); + } + } + place_ty = self.sanitize_projection(place_ty, elem, place, location); + } + + if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context { + let tcx = self.tcx(); + let trait_ref = ty::TraitRef { + def_id: tcx.require_lang_item(LangItem::Copy, Some(self.last_span)), + substs: tcx.mk_substs_trait(place_ty.ty, &[]), + }; + + // To have a `Copy` operand, the type `T` of the + // value must be `Copy`. Note that we prove that `T: Copy`, + // rather than using the `is_copy_modulo_regions` + // test. This is important because + // `is_copy_modulo_regions` ignores the resulting region + // obligations and assumes they pass. This can result in + // bounds from `Copy` impls being unsoundly ignored (e.g., + // #29149). Note that we decide to use `Copy` before knowing + // whether the bounds fully apply: in effect, the rule is + // that if a value of some type could implement `Copy`, then + // it must. + self.cx.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::CopyBound, + ); + } + + place_ty + } + + fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Location) { + // Determine the constraints from the promoted MIR by running the type + // checker on the promoted MIR, then transfer the constraints back to + // the main MIR, changing the locations to the provided location. + + let parent_body = mem::replace(&mut self.cx.body, promoted_body); + + // Use new sets of constraints and closure bounds so that we can + // modify their locations. + let all_facts = &mut None; + let mut constraints = Default::default(); + let mut closure_bounds = Default::default(); + let mut liveness_constraints = + LivenessValues::new(Rc::new(RegionValueElements::new(&promoted_body))); + // Don't try to add borrow_region facts for the promoted MIR + + let mut swap_constraints = |this: &mut Self| { + mem::swap(this.cx.borrowck_context.all_facts, all_facts); + mem::swap( + &mut this.cx.borrowck_context.constraints.outlives_constraints, + &mut constraints, + ); + mem::swap( + &mut this.cx.borrowck_context.constraints.closure_bounds_mapping, + &mut closure_bounds, + ); + mem::swap( + &mut this.cx.borrowck_context.constraints.liveness_constraints, + &mut liveness_constraints, + ); + }; + + swap_constraints(self); + + self.visit_body(&promoted_body); + + if !self.errors_reported { + // if verifier failed, don't do further checks to avoid ICEs + self.cx.typeck_mir(promoted_body); + } + + self.cx.body = parent_body; + // Merge the outlives constraints back in, at the given location. + swap_constraints(self); + + let locations = location.to_locations(); + for constraint in constraints.outlives().iter() { + let mut constraint = constraint.clone(); + constraint.locations = locations; + if let ConstraintCategory::Return(_) + | ConstraintCategory::UseAsConst + | ConstraintCategory::UseAsStatic = constraint.category + { + // "Returning" from a promoted is an assignment to a + // temporary from the user's point of view. + constraint.category = ConstraintCategory::Boring; + } + self.cx.borrowck_context.constraints.outlives_constraints.push(constraint) + } + for region in liveness_constraints.rows() { + // If the region is live at at least one location in the promoted MIR, + // then add a liveness constraint to the main MIR for this region + // at the location provided as an argument to this method + if liveness_constraints.get_elements(region).next().is_some() { + self.cx + .borrowck_context + .constraints + .liveness_constraints + .add_element(region, location); + } + } + + if !closure_bounds.is_empty() { + let combined_bounds_mapping = + closure_bounds.into_iter().flat_map(|(_, value)| value).collect(); + let existing = self + .cx + .borrowck_context + .constraints + .closure_bounds_mapping + .insert(location, combined_bounds_mapping); + assert!(existing.is_none(), "Multiple promoteds/closures at the same location."); + } + } + + fn sanitize_projection( + &mut self, + base: PlaceTy<'tcx>, + pi: PlaceElem<'tcx>, + place: &Place<'tcx>, + location: Location, + ) -> PlaceTy<'tcx> { + debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, place); + let tcx = self.tcx(); + let base_ty = base.ty; + match pi { + ProjectionElem::Deref => { + let deref_ty = base_ty.builtin_deref(true); + PlaceTy::from_ty(deref_ty.map(|t| t.ty).unwrap_or_else(|| { + span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty) + })) + } + ProjectionElem::Index(i) => { + let index_ty = Place::from(i).ty(self.body(), tcx).ty; + if index_ty != tcx.types.usize { + PlaceTy::from_ty(span_mirbug_and_err!(self, i, "index by non-usize {:?}", i)) + } else { + PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| { + span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty) + })) + } + } + ProjectionElem::ConstantIndex { .. } => { + // consider verifying in-bounds + PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| { + span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty) + })) + } + ProjectionElem::Subslice { from, to, from_end } => { + PlaceTy::from_ty(match base_ty.kind() { + ty::Array(inner, _) => { + assert!(!from_end, "array subslices should not use from_end"); + tcx.mk_array(*inner, to - from) + } + ty::Slice(..) => { + assert!(from_end, "slice subslices should use from_end"); + base_ty + } + _ => span_mirbug_and_err!(self, place, "slice of non-array {:?}", base_ty), + }) + } + ProjectionElem::Downcast(maybe_name, index) => match base_ty.kind() { + ty::Adt(adt_def, _substs) if adt_def.is_enum() => { + if index.as_usize() >= adt_def.variants().len() { + PlaceTy::from_ty(span_mirbug_and_err!( + self, + place, + "cast to variant #{:?} but enum only has {:?}", + index, + adt_def.variants().len() + )) + } else { + PlaceTy { ty: base_ty, variant_index: Some(index) } + } + } + // We do not need to handle generators here, because this runs + // before the generator transform stage. + _ => { + let ty = if let Some(name) = maybe_name { + span_mirbug_and_err!( + self, + place, + "can't downcast {:?} as {:?}", + base_ty, + name + ) + } else { + span_mirbug_and_err!(self, place, "can't downcast {:?}", base_ty) + }; + PlaceTy::from_ty(ty) + } + }, + ProjectionElem::Field(field, fty) => { + let fty = self.sanitize_type(place, fty); + let fty = self.cx.normalize(fty, location); + match self.field_ty(place, base, field, location) { + Ok(ty) => { + let ty = self.cx.normalize(ty, location); + if let Err(terr) = self.cx.eq_types( + ty, + fty, + location.to_locations(), + ConstraintCategory::Boring, + ) { + span_mirbug!( + self, + place, + "bad field access ({:?}: {:?}): {:?}", + ty, + fty, + terr + ); + } + } + Err(FieldAccessError::OutOfRange { field_count }) => span_mirbug!( + self, + place, + "accessed field #{} but variant only has {}", + field.index(), + field_count + ), + } + PlaceTy::from_ty(fty) + } + } + } + + fn error(&mut self) -> Ty<'tcx> { + self.errors_reported = true; + self.tcx().ty_error() + } + + fn field_ty( + &mut self, + parent: &dyn fmt::Debug, + base_ty: PlaceTy<'tcx>, + field: Field, + location: Location, + ) -> Result<Ty<'tcx>, FieldAccessError> { + let tcx = self.tcx(); + + let (variant, substs) = match base_ty { + PlaceTy { ty, variant_index: Some(variant_index) } => match *ty.kind() { + ty::Adt(adt_def, substs) => (adt_def.variant(variant_index), substs), + ty::Generator(def_id, substs, _) => { + let mut variants = substs.as_generator().state_tys(def_id, tcx); + let Some(mut variant) = variants.nth(variant_index.into()) else { + bug!( + "variant_index of generator out of range: {:?}/{:?}", + variant_index, + substs.as_generator().state_tys(def_id, tcx).count() + ); + }; + return match variant.nth(field.index()) { + Some(ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { field_count: variant.count() }), + }; + } + _ => bug!("can't have downcast of non-adt non-generator type"), + }, + PlaceTy { ty, variant_index: None } => match *ty.kind() { + ty::Adt(adt_def, substs) if !adt_def.is_enum() => { + (adt_def.variant(VariantIdx::new(0)), substs) + } + ty::Closure(_, substs) => { + return match substs + .as_closure() + .tupled_upvars_ty() + .tuple_fields() + .get(field.index()) + { + Some(&ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { + field_count: substs.as_closure().upvar_tys().count(), + }), + }; + } + ty::Generator(_, substs, _) => { + // Only prefix fields (upvars and current state) are + // accessible without a variant index. + return match substs.as_generator().prefix_tys().nth(field.index()) { + Some(ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { + field_count: substs.as_generator().prefix_tys().count(), + }), + }; + } + ty::Tuple(tys) => { + return match tys.get(field.index()) { + Some(&ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { field_count: tys.len() }), + }; + } + _ => { + return Ok(span_mirbug_and_err!( + self, + parent, + "can't project out of {:?}", + base_ty + )); + } + }, + }; + + if let Some(field) = variant.fields.get(field.index()) { + Ok(self.cx.normalize(field.ty(tcx, substs), location)) + } else { + Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() }) + } + } +} + +/// The MIR type checker. Visits the MIR and enforces all the +/// constraints needed for it to be valid and well-typed. Along the +/// way, it accrues region constraints -- these can later be used by +/// NLL region checking. +struct TypeChecker<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, + param_env: ty::ParamEnv<'tcx>, + last_span: Span, + body: &'a Body<'tcx>, + /// User type annotations are shared between the main MIR and the MIR of + /// all of the promoted items. + user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>, + region_bound_pairs: &'a RegionBoundPairs<'tcx>, + implicit_region_bound: ty::Region<'tcx>, + reported_errors: FxHashSet<(Ty<'tcx>, Span)>, + borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>, +} + +struct BorrowCheckContext<'a, 'tcx> { + pub(crate) universal_regions: &'a UniversalRegions<'tcx>, + location_table: &'a LocationTable, + all_facts: &'a mut Option<AllFacts>, + borrow_set: &'a BorrowSet<'tcx>, + pub(crate) constraints: &'a mut MirTypeckRegionConstraints<'tcx>, + upvars: &'a [Upvar<'tcx>], +} + +pub(crate) struct MirTypeckResults<'tcx> { + pub(crate) constraints: MirTypeckRegionConstraints<'tcx>, + pub(crate) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>, + pub(crate) opaque_type_values: + VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>, +} + +/// A collection of region constraints that must be satisfied for the +/// program to be considered well-typed. +pub(crate) struct MirTypeckRegionConstraints<'tcx> { + /// Maps from a `ty::Placeholder` to the corresponding + /// `PlaceholderIndex` bit that we will use for it. + /// + /// To keep everything in sync, do not insert this set + /// directly. Instead, use the `placeholder_region` helper. + pub(crate) placeholder_indices: PlaceholderIndices, + + /// Each time we add a placeholder to `placeholder_indices`, we + /// also create a corresponding "representative" region vid for + /// that wraps it. This vector tracks those. This way, when we + /// convert the same `ty::RePlaceholder(p)` twice, we can map to + /// the same underlying `RegionVid`. + pub(crate) placeholder_index_to_region: IndexVec<PlaceholderIndex, ty::Region<'tcx>>, + + /// In general, the type-checker is not responsible for enforcing + /// liveness constraints; this job falls to the region inferencer, + /// which performs a liveness analysis. However, in some limited + /// cases, the MIR type-checker creates temporary regions that do + /// not otherwise appear in the MIR -- in particular, the + /// late-bound regions that it instantiates at call-sites -- and + /// hence it must report on their liveness constraints. + pub(crate) liveness_constraints: LivenessValues<RegionVid>, + + pub(crate) outlives_constraints: OutlivesConstraintSet<'tcx>, + + pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>, + + pub(crate) closure_bounds_mapping: + FxHashMap<Location, FxHashMap<(RegionVid, RegionVid), (ConstraintCategory<'tcx>, Span)>>, + + pub(crate) universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>, + + pub(crate) type_tests: Vec<TypeTest<'tcx>>, +} + +impl<'tcx> MirTypeckRegionConstraints<'tcx> { + fn placeholder_region( + &mut self, + infcx: &InferCtxt<'_, 'tcx>, + placeholder: ty::PlaceholderRegion, + ) -> ty::Region<'tcx> { + let placeholder_index = self.placeholder_indices.insert(placeholder); + match self.placeholder_index_to_region.get(placeholder_index) { + Some(&v) => v, + None => { + let origin = NllRegionVariableOrigin::Placeholder(placeholder); + let region = infcx.next_nll_region_var_in_universe(origin, placeholder.universe); + self.placeholder_index_to_region.push(region); + region + } + } + } +} + +/// The `Locations` type summarizes *where* region constraints are +/// required to hold. Normally, this is at a particular point which +/// created the obligation, but for constraints that the user gave, we +/// want the constraint to hold at all points. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] +pub enum Locations { + /// Indicates that a type constraint should always be true. This + /// is particularly important in the new borrowck analysis for + /// things like the type of the return slot. Consider this + /// example: + /// + /// ```compile_fail,E0515 + /// fn foo<'a>(x: &'a u32) -> &'a u32 { + /// let y = 22; + /// return &y; // error + /// } + /// ``` + /// + /// Here, we wind up with the signature from the return type being + /// something like `&'1 u32` where `'1` is a universal region. But + /// the type of the return slot `_0` is something like `&'2 u32` + /// where `'2` is an existential region variable. The type checker + /// requires that `&'2 u32 = &'1 u32` -- but at what point? In the + /// older NLL analysis, we required this only at the entry point + /// to the function. By the nature of the constraints, this wound + /// up propagating to all points reachable from start (because + /// `'1` -- as a universal region -- is live everywhere). In the + /// newer analysis, though, this doesn't work: `_0` is considered + /// dead at the start (it has no usable value) and hence this type + /// equality is basically a no-op. Then, later on, when we do `_0 + /// = &'3 y`, that region `'3` never winds up related to the + /// universal region `'1` and hence no error occurs. Therefore, we + /// use Locations::All instead, which ensures that the `'1` and + /// `'2` are equal everything. We also use this for other + /// user-given type annotations; e.g., if the user wrote `let mut + /// x: &'static u32 = ...`, we would ensure that all values + /// assigned to `x` are of `'static` lifetime. + /// + /// The span points to the place the constraint arose. For example, + /// it points to the type in a user-given type annotation. If + /// there's no sensible span then it's DUMMY_SP. + All(Span), + + /// An outlives constraint that only has to hold at a single location, + /// usually it represents a point where references flow from one spot to + /// another (e.g., `x = y`) + Single(Location), +} + +impl Locations { + pub fn from_location(&self) -> Option<Location> { + match self { + Locations::All(_) => None, + Locations::Single(from_location) => Some(*from_location), + } + } + + /// Gets a span representing the location. + pub fn span(&self, body: &Body<'_>) -> Span { + match self { + Locations::All(span) => *span, + Locations::Single(l) => body.source_info(*l).span, + } + } +} + +impl<'a, 'tcx> TypeChecker<'a, 'tcx> { + fn new( + infcx: &'a InferCtxt<'a, 'tcx>, + body: &'a Body<'tcx>, + param_env: ty::ParamEnv<'tcx>, + region_bound_pairs: &'a RegionBoundPairs<'tcx>, + implicit_region_bound: ty::Region<'tcx>, + borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>, + ) -> Self { + let mut checker = Self { + infcx, + last_span: DUMMY_SP, + body, + user_type_annotations: &body.user_type_annotations, + param_env, + region_bound_pairs, + implicit_region_bound, + borrowck_context, + reported_errors: Default::default(), + }; + checker.check_user_type_annotations(); + checker + } + + fn body(&self) -> &Body<'tcx> { + self.body + } + + fn unsized_feature_enabled(&self) -> bool { + let features = self.tcx().features(); + features.unsized_locals || features.unsized_fn_params + } + + /// Equate the inferred type and the annotated type for user type annotations + #[instrument(skip(self), level = "debug")] + fn check_user_type_annotations(&mut self) { + debug!(?self.user_type_annotations); + for user_annotation in self.user_type_annotations { + let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation; + let inferred_ty = self.normalize(inferred_ty, Locations::All(span)); + let annotation = self.instantiate_canonical_with_fresh_inference_vars(span, user_ty); + match annotation { + UserType::Ty(mut ty) => { + ty = self.normalize(ty, Locations::All(span)); + + if let Err(terr) = self.eq_types( + ty, + inferred_ty, + Locations::All(span), + ConstraintCategory::BoringNoLocation, + ) { + span_mirbug!( + self, + user_annotation, + "bad user type ({:?} = {:?}): {:?}", + ty, + inferred_ty, + terr + ); + } + + self.prove_predicate( + ty::Binder::dummy(ty::PredicateKind::WellFormed(inferred_ty.into())) + .to_predicate(self.tcx()), + Locations::All(span), + ConstraintCategory::TypeAnnotation, + ); + } + UserType::TypeOf(def_id, user_substs) => { + if let Err(terr) = self.fully_perform_op( + Locations::All(span), + ConstraintCategory::BoringNoLocation, + self.param_env.and(type_op::ascribe_user_type::AscribeUserType::new( + inferred_ty, + def_id, + user_substs, + )), + ) { + span_mirbug!( + self, + user_annotation, + "bad user type AscribeUserType({:?}, {:?} {:?}, type_of={:?}): {:?}", + inferred_ty, + def_id, + user_substs, + self.tcx().type_of(def_id), + terr, + ); + } + } + } + } + } + + #[instrument(skip(self, data), level = "debug")] + fn push_region_constraints( + &mut self, + locations: Locations, + category: ConstraintCategory<'tcx>, + data: &QueryRegionConstraints<'tcx>, + ) { + debug!("constraints generated: {:#?}", data); + + constraint_conversion::ConstraintConversion::new( + self.infcx, + self.borrowck_context.universal_regions, + self.region_bound_pairs, + self.implicit_region_bound, + self.param_env, + locations, + locations.span(self.body), + category, + &mut self.borrowck_context.constraints, + ) + .convert_all(data); + } + + /// Try to relate `sub <: sup` + fn sub_types( + &mut self, + sub: Ty<'tcx>, + sup: Ty<'tcx>, + locations: Locations, + category: ConstraintCategory<'tcx>, + ) -> Fallible<()> { + // Use this order of parameters because the sup type is usually the + // "expected" type in diagnostics. + self.relate_types(sup, ty::Variance::Contravariant, sub, locations, category) + } + + #[instrument(skip(self, category), level = "debug")] + fn eq_types( + &mut self, + expected: Ty<'tcx>, + found: Ty<'tcx>, + locations: Locations, + category: ConstraintCategory<'tcx>, + ) -> Fallible<()> { + self.relate_types(expected, ty::Variance::Invariant, found, locations, category) + } + + #[instrument(skip(self), level = "debug")] + fn relate_type_and_user_type( + &mut self, + a: Ty<'tcx>, + v: ty::Variance, + user_ty: &UserTypeProjection, + locations: Locations, + category: ConstraintCategory<'tcx>, + ) -> Fallible<()> { + let annotated_type = self.user_type_annotations[user_ty.base].inferred_ty; + let mut curr_projected_ty = PlaceTy::from_ty(annotated_type); + + let tcx = self.infcx.tcx; + + for proj in &user_ty.projs { + let projected_ty = curr_projected_ty.projection_ty_core( + tcx, + self.param_env, + proj, + |this, field, ()| { + let ty = this.field_ty(tcx, field); + self.normalize(ty, locations) + }, + ); + curr_projected_ty = projected_ty; + } + debug!( + "user_ty base: {:?} freshened: {:?} projs: {:?} yields: {:?}", + user_ty.base, annotated_type, user_ty.projs, curr_projected_ty + ); + + let ty = curr_projected_ty.ty; + self.relate_types(ty, v.xform(ty::Variance::Contravariant), a, locations, category)?; + + Ok(()) + } + + fn tcx(&self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + #[instrument(skip(self, body, location), level = "debug")] + fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Location) { + let tcx = self.tcx(); + debug!("stmt kind: {:?}", stmt.kind); + match stmt.kind { + StatementKind::Assign(box (ref place, ref rv)) => { + // Assignments to temporaries are not "interesting"; + // they are not caused by the user, but rather artifacts + // of lowering. Assignments to other sorts of places *are* interesting + // though. + let category = match place.as_local() { + Some(RETURN_PLACE) => { + let defining_ty = &self.borrowck_context.universal_regions.defining_ty; + if defining_ty.is_const() { + if tcx.is_static(defining_ty.def_id()) { + ConstraintCategory::UseAsStatic + } else { + ConstraintCategory::UseAsConst + } + } else { + ConstraintCategory::Return(ReturnConstraint::Normal) + } + } + Some(l) + if matches!( + body.local_decls[l].local_info, + Some(box LocalInfo::AggregateTemp) + ) => + { + ConstraintCategory::Usage + } + Some(l) if !body.local_decls[l].is_user_variable() => { + ConstraintCategory::Boring + } + _ => ConstraintCategory::Assignment, + }; + debug!( + "assignment category: {:?} {:?}", + category, + place.as_local().map(|l| &body.local_decls[l]) + ); + + let place_ty = place.ty(body, tcx).ty; + debug!(?place_ty); + let place_ty = self.normalize(place_ty, location); + debug!("place_ty normalized: {:?}", place_ty); + let rv_ty = rv.ty(body, tcx); + debug!(?rv_ty); + let rv_ty = self.normalize(rv_ty, location); + debug!("normalized rv_ty: {:?}", rv_ty); + if let Err(terr) = + self.sub_types(rv_ty, place_ty, location.to_locations(), category) + { + span_mirbug!( + self, + stmt, + "bad assignment ({:?} = {:?}): {:?}", + place_ty, + rv_ty, + terr + ); + } + + if let Some(annotation_index) = self.rvalue_user_ty(rv) { + if let Err(terr) = self.relate_type_and_user_type( + rv_ty, + ty::Variance::Invariant, + &UserTypeProjection { base: annotation_index, projs: vec![] }, + location.to_locations(), + ConstraintCategory::Boring, + ) { + let annotation = &self.user_type_annotations[annotation_index]; + span_mirbug!( + self, + stmt, + "bad user type on rvalue ({:?} = {:?}): {:?}", + annotation, + rv_ty, + terr + ); + } + } + + self.check_rvalue(body, rv, location); + if !self.unsized_feature_enabled() { + let trait_ref = ty::TraitRef { + def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)), + substs: tcx.mk_substs_trait(place_ty, &[]), + }; + self.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::SizedBound, + ); + } + } + StatementKind::AscribeUserType(box (ref place, ref projection), variance) => { + let place_ty = place.ty(body, tcx).ty; + if let Err(terr) = self.relate_type_and_user_type( + place_ty, + variance, + projection, + Locations::All(stmt.source_info.span), + ConstraintCategory::TypeAnnotation, + ) { + let annotation = &self.user_type_annotations[projection.base]; + span_mirbug!( + self, + stmt, + "bad type assert ({:?} <: {:?} with projections {:?}): {:?}", + place_ty, + annotation, + projection.projs, + terr + ); + } + } + StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping { + .. + }) => span_bug!( + stmt.source_info.span, + "Unexpected StatementKind::CopyNonOverlapping, should only appear after lowering_intrinsics", + ), + StatementKind::FakeRead(..) + | StatementKind::StorageLive(..) + | StatementKind::StorageDead(..) + | StatementKind::Retag { .. } + | StatementKind::Coverage(..) + | StatementKind::Nop => {} + StatementKind::Deinit(..) | StatementKind::SetDiscriminant { .. } => { + bug!("Statement not allowed in this MIR phase") + } + } + } + + #[instrument(skip(self, body, term_location), level = "debug")] + fn check_terminator( + &mut self, + body: &Body<'tcx>, + term: &Terminator<'tcx>, + term_location: Location, + ) { + let tcx = self.tcx(); + debug!("terminator kind: {:?}", term.kind); + match term.kind { + TerminatorKind::Goto { .. } + | TerminatorKind::Resume + | TerminatorKind::Abort + | TerminatorKind::Return + | TerminatorKind::GeneratorDrop + | TerminatorKind::Unreachable + | TerminatorKind::Drop { .. } + | TerminatorKind::FalseEdge { .. } + | TerminatorKind::FalseUnwind { .. } + | TerminatorKind::InlineAsm { .. } => { + // no checks needed for these + } + + TerminatorKind::DropAndReplace { ref place, ref value, target: _, unwind: _ } => { + let place_ty = place.ty(body, tcx).ty; + let rv_ty = value.ty(body, tcx); + + let locations = term_location.to_locations(); + if let Err(terr) = + self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment) + { + span_mirbug!( + self, + term, + "bad DropAndReplace ({:?} = {:?}): {:?}", + place_ty, + rv_ty, + terr + ); + } + } + TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => { + self.check_operand(discr, term_location); + + let discr_ty = discr.ty(body, tcx); + if let Err(terr) = self.sub_types( + discr_ty, + switch_ty, + term_location.to_locations(), + ConstraintCategory::Assignment, + ) { + span_mirbug!( + self, + term, + "bad SwitchInt ({:?} on {:?}): {:?}", + switch_ty, + discr_ty, + terr + ); + } + if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() { + span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty); + } + // FIXME: check the values + } + TerminatorKind::Call { + ref func, + ref args, + ref destination, + from_hir_call, + target, + .. + } => { + self.check_operand(func, term_location); + for arg in args { + self.check_operand(arg, term_location); + } + + let func_ty = func.ty(body, tcx); + debug!("func_ty.kind: {:?}", func_ty.kind()); + + let sig = match func_ty.kind() { + ty::FnDef(..) | ty::FnPtr(_) => func_ty.fn_sig(tcx), + _ => { + span_mirbug!(self, term, "call to non-function {:?}", func_ty); + return; + } + }; + let (sig, map) = tcx.replace_late_bound_regions(sig, |br| { + self.infcx.next_region_var(LateBoundRegion( + term.source_info.span, + br.kind, + LateBoundRegionConversionTime::FnCall, + )) + }); + debug!(?sig); + let sig = self.normalize(sig, term_location); + self.check_call_dest(body, term, &sig, *destination, target, term_location); + + self.prove_predicates( + sig.inputs_and_output + .iter() + .map(|ty| ty::Binder::dummy(ty::PredicateKind::WellFormed(ty.into()))), + term_location.to_locations(), + ConstraintCategory::Boring, + ); + + // The ordinary liveness rules will ensure that all + // regions in the type of the callee are live here. We + // then further constrain the late-bound regions that + // were instantiated at the call site to be live as + // well. The resulting is that all the input (and + // output) types in the signature must be live, since + // all the inputs that fed into it were live. + for &late_bound_region in map.values() { + let region_vid = + self.borrowck_context.universal_regions.to_region_vid(late_bound_region); + self.borrowck_context + .constraints + .liveness_constraints + .add_element(region_vid, term_location); + } + + self.check_call_inputs(body, term, &sig, args, term_location, from_hir_call); + } + TerminatorKind::Assert { ref cond, ref msg, .. } => { + self.check_operand(cond, term_location); + + let cond_ty = cond.ty(body, tcx); + if cond_ty != tcx.types.bool { + span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty); + } + + if let AssertKind::BoundsCheck { ref len, ref index } = *msg { + if len.ty(body, tcx) != tcx.types.usize { + span_mirbug!(self, len, "bounds-check length non-usize {:?}", len) + } + if index.ty(body, tcx) != tcx.types.usize { + span_mirbug!(self, index, "bounds-check index non-usize {:?}", index) + } + } + } + TerminatorKind::Yield { ref value, .. } => { + self.check_operand(value, term_location); + + let value_ty = value.ty(body, tcx); + match body.yield_ty() { + None => span_mirbug!(self, term, "yield in non-generator"), + Some(ty) => { + if let Err(terr) = self.sub_types( + value_ty, + ty, + term_location.to_locations(), + ConstraintCategory::Yield, + ) { + span_mirbug!( + self, + term, + "type of yield value is {:?}, but the yield type is {:?}: {:?}", + value_ty, + ty, + terr + ); + } + } + } + } + } + } + + fn check_call_dest( + &mut self, + body: &Body<'tcx>, + term: &Terminator<'tcx>, + sig: &ty::FnSig<'tcx>, + destination: Place<'tcx>, + target: Option<BasicBlock>, + term_location: Location, + ) { + let tcx = self.tcx(); + match target { + Some(_) => { + let dest_ty = destination.ty(body, tcx).ty; + let dest_ty = self.normalize(dest_ty, term_location); + let category = match destination.as_local() { + Some(RETURN_PLACE) => { + if let BorrowCheckContext { + universal_regions: + UniversalRegions { + defining_ty: + DefiningTy::Const(def_id, _) + | DefiningTy::InlineConst(def_id, _), + .. + }, + .. + } = self.borrowck_context + { + if tcx.is_static(*def_id) { + ConstraintCategory::UseAsStatic + } else { + ConstraintCategory::UseAsConst + } + } else { + ConstraintCategory::Return(ReturnConstraint::Normal) + } + } + Some(l) if !body.local_decls[l].is_user_variable() => { + ConstraintCategory::Boring + } + _ => ConstraintCategory::Assignment, + }; + + let locations = term_location.to_locations(); + + if let Err(terr) = self.sub_types(sig.output(), dest_ty, locations, category) { + span_mirbug!( + self, + term, + "call dest mismatch ({:?} <- {:?}): {:?}", + dest_ty, + sig.output(), + terr + ); + } + + // When `unsized_fn_params` and `unsized_locals` are both not enabled, + // this check is done at `check_local`. + if self.unsized_feature_enabled() { + let span = term.source_info.span; + self.ensure_place_sized(dest_ty, span); + } + } + None => { + if !self + .tcx() + .conservative_is_privately_uninhabited(self.param_env.and(sig.output())) + { + span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig); + } + } + } + } + + fn check_call_inputs( + &mut self, + body: &Body<'tcx>, + term: &Terminator<'tcx>, + sig: &ty::FnSig<'tcx>, + args: &[Operand<'tcx>], + term_location: Location, + from_hir_call: bool, + ) { + debug!("check_call_inputs({:?}, {:?})", sig, args); + if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.c_variadic) { + span_mirbug!(self, term, "call to {:?} with wrong # of args", sig); + } + + let func_ty = if let TerminatorKind::Call { func, .. } = &term.kind { + Some(func.ty(body, self.infcx.tcx)) + } else { + None + }; + debug!(?func_ty); + + for (n, (fn_arg, op_arg)) in iter::zip(sig.inputs(), args).enumerate() { + let op_arg_ty = op_arg.ty(body, self.tcx()); + + let op_arg_ty = self.normalize(op_arg_ty, term_location); + let category = if from_hir_call { + ConstraintCategory::CallArgument(func_ty) + } else { + ConstraintCategory::Boring + }; + if let Err(terr) = + self.sub_types(op_arg_ty, *fn_arg, term_location.to_locations(), category) + { + span_mirbug!( + self, + term, + "bad arg #{:?} ({:?} <- {:?}): {:?}", + n, + fn_arg, + op_arg_ty, + terr + ); + } + } + } + + fn check_iscleanup(&mut self, body: &Body<'tcx>, block_data: &BasicBlockData<'tcx>) { + let is_cleanup = block_data.is_cleanup; + self.last_span = block_data.terminator().source_info.span; + match block_data.terminator().kind { + TerminatorKind::Goto { target } => { + self.assert_iscleanup(body, block_data, target, is_cleanup) + } + TerminatorKind::SwitchInt { ref targets, .. } => { + for target in targets.all_targets() { + self.assert_iscleanup(body, block_data, *target, is_cleanup); + } + } + TerminatorKind::Resume => { + if !is_cleanup { + span_mirbug!(self, block_data, "resume on non-cleanup block!") + } + } + TerminatorKind::Abort => { + if !is_cleanup { + span_mirbug!(self, block_data, "abort on non-cleanup block!") + } + } + TerminatorKind::Return => { + if is_cleanup { + span_mirbug!(self, block_data, "return on cleanup block") + } + } + TerminatorKind::GeneratorDrop { .. } => { + if is_cleanup { + span_mirbug!(self, block_data, "generator_drop in cleanup block") + } + } + TerminatorKind::Yield { resume, drop, .. } => { + if is_cleanup { + span_mirbug!(self, block_data, "yield in cleanup block") + } + self.assert_iscleanup(body, block_data, resume, is_cleanup); + if let Some(drop) = drop { + self.assert_iscleanup(body, block_data, drop, is_cleanup); + } + } + TerminatorKind::Unreachable => {} + TerminatorKind::Drop { target, unwind, .. } + | TerminatorKind::DropAndReplace { target, unwind, .. } + | TerminatorKind::Assert { target, cleanup: unwind, .. } => { + self.assert_iscleanup(body, block_data, target, is_cleanup); + if let Some(unwind) = unwind { + if is_cleanup { + span_mirbug!(self, block_data, "unwind on cleanup block") + } + self.assert_iscleanup(body, block_data, unwind, true); + } + } + TerminatorKind::Call { ref target, cleanup, .. } => { + if let &Some(target) = target { + self.assert_iscleanup(body, block_data, target, is_cleanup); + } + if let Some(cleanup) = cleanup { + if is_cleanup { + span_mirbug!(self, block_data, "cleanup on cleanup block") + } + self.assert_iscleanup(body, block_data, cleanup, true); + } + } + TerminatorKind::FalseEdge { real_target, imaginary_target } => { + self.assert_iscleanup(body, block_data, real_target, is_cleanup); + self.assert_iscleanup(body, block_data, imaginary_target, is_cleanup); + } + TerminatorKind::FalseUnwind { real_target, unwind } => { + self.assert_iscleanup(body, block_data, real_target, is_cleanup); + if let Some(unwind) = unwind { + if is_cleanup { + span_mirbug!(self, block_data, "cleanup in cleanup block via false unwind"); + } + self.assert_iscleanup(body, block_data, unwind, true); + } + } + TerminatorKind::InlineAsm { destination, cleanup, .. } => { + if let Some(target) = destination { + self.assert_iscleanup(body, block_data, target, is_cleanup); + } + if let Some(cleanup) = cleanup { + if is_cleanup { + span_mirbug!(self, block_data, "cleanup on cleanup block") + } + self.assert_iscleanup(body, block_data, cleanup, true); + } + } + } + } + + fn assert_iscleanup( + &mut self, + body: &Body<'tcx>, + ctxt: &dyn fmt::Debug, + bb: BasicBlock, + iscleanuppad: bool, + ) { + if body[bb].is_cleanup != iscleanuppad { + span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}", bb, iscleanuppad); + } + } + + fn check_local(&mut self, body: &Body<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) { + match body.local_kind(local) { + LocalKind::ReturnPointer | LocalKind::Arg => { + // return values of normal functions are required to be + // sized by typeck, but return values of ADT constructors are + // not because we don't include a `Self: Sized` bounds on them. + // + // Unbound parts of arguments were never required to be Sized + // - maybe we should make that a warning. + return; + } + LocalKind::Var | LocalKind::Temp => {} + } + + // When `unsized_fn_params` or `unsized_locals` is enabled, only function calls + // and nullary ops are checked in `check_call_dest`. + if !self.unsized_feature_enabled() { + let span = local_decl.source_info.span; + let ty = local_decl.ty; + self.ensure_place_sized(ty, span); + } + } + + fn ensure_place_sized(&mut self, ty: Ty<'tcx>, span: Span) { + let tcx = self.tcx(); + + // Erase the regions from `ty` to get a global type. The + // `Sized` bound in no way depends on precise regions, so this + // shouldn't affect `is_sized`. + let erased_ty = tcx.erase_regions(ty); + if !erased_ty.is_sized(tcx.at(span), self.param_env) { + // in current MIR construction, all non-control-flow rvalue + // expressions evaluate through `as_temp` or `into` a return + // slot or local, so to find all unsized rvalues it is enough + // to check all temps, return slots and locals. + if self.reported_errors.replace((ty, span)).is_none() { + // While this is located in `nll::typeck` this error is not + // an NLL error, it's a required check to prevent creation + // of unsized rvalues in a call expression. + self.tcx().sess.emit_err(MoveUnsized { ty, span }); + } + } + } + + fn aggregate_field_ty( + &mut self, + ak: &AggregateKind<'tcx>, + field_index: usize, + location: Location, + ) -> Result<Ty<'tcx>, FieldAccessError> { + let tcx = self.tcx(); + + match *ak { + AggregateKind::Adt(adt_did, variant_index, substs, _, active_field_index) => { + let def = tcx.adt_def(adt_did); + let variant = &def.variant(variant_index); + let adj_field_index = active_field_index.unwrap_or(field_index); + if let Some(field) = variant.fields.get(adj_field_index) { + Ok(self.normalize(field.ty(tcx, substs), location)) + } else { + Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() }) + } + } + AggregateKind::Closure(_, substs) => { + match substs.as_closure().upvar_tys().nth(field_index) { + Some(ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { + field_count: substs.as_closure().upvar_tys().count(), + }), + } + } + AggregateKind::Generator(_, substs, _) => { + // It doesn't make sense to look at a field beyond the prefix; + // these require a variant index, and are not initialized in + // aggregate rvalues. + match substs.as_generator().prefix_tys().nth(field_index) { + Some(ty) => Ok(ty), + None => Err(FieldAccessError::OutOfRange { + field_count: substs.as_generator().prefix_tys().count(), + }), + } + } + AggregateKind::Array(ty) => Ok(ty), + AggregateKind::Tuple => { + unreachable!("This should have been covered in check_rvalues"); + } + } + } + + fn check_operand(&mut self, op: &Operand<'tcx>, location: Location) { + if let Operand::Constant(constant) = op { + let maybe_uneval = match constant.literal { + ConstantKind::Ty(ct) => match ct.kind() { + ty::ConstKind::Unevaluated(uv) => Some(uv), + _ => None, + }, + _ => None, + }; + if let Some(uv) = maybe_uneval { + if uv.promoted.is_none() { + let tcx = self.tcx(); + let def_id = uv.def.def_id_for_type_of(); + if tcx.def_kind(def_id) == DefKind::InlineConst { + let def_id = def_id.expect_local(); + let predicates = + self.prove_closure_bounds(tcx, def_id, uv.substs, location); + self.normalize_and_prove_instantiated_predicates( + def_id.to_def_id(), + predicates, + location.to_locations(), + ); + } + } + } + } + } + + #[instrument(skip(self, body), level = "debug")] + fn check_rvalue(&mut self, body: &Body<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) { + let tcx = self.tcx(); + + match rvalue { + Rvalue::Aggregate(ak, ops) => { + for op in ops { + self.check_operand(op, location); + } + self.check_aggregate_rvalue(&body, rvalue, ak, ops, location) + } + + Rvalue::Repeat(operand, len) => { + self.check_operand(operand, location); + + // If the length cannot be evaluated we must assume that the length can be larger + // than 1. + // If the length is larger than 1, the repeat expression will need to copy the + // element, so we require the `Copy` trait. + if len.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) { + match operand { + Operand::Copy(..) | Operand::Constant(..) => { + // These are always okay: direct use of a const, or a value that can evidently be copied. + } + Operand::Move(place) => { + // Make sure that repeated elements implement `Copy`. + let span = body.source_info(location).span; + let ty = place.ty(body, tcx).ty; + let trait_ref = ty::TraitRef::new( + tcx.require_lang_item(LangItem::Copy, Some(span)), + tcx.mk_substs_trait(ty, &[]), + ); + + self.prove_trait_ref( + trait_ref, + Locations::Single(location), + ConstraintCategory::CopyBound, + ); + } + } + } + } + + &Rvalue::NullaryOp(_, ty) => { + let trait_ref = ty::TraitRef { + def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)), + substs: tcx.mk_substs_trait(ty, &[]), + }; + + self.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::SizedBound, + ); + } + + Rvalue::ShallowInitBox(operand, ty) => { + self.check_operand(operand, location); + + let trait_ref = ty::TraitRef { + def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)), + substs: tcx.mk_substs_trait(*ty, &[]), + }; + + self.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::SizedBound, + ); + } + + Rvalue::Cast(cast_kind, op, ty) => { + self.check_operand(op, location); + + match cast_kind { + CastKind::Pointer(PointerCast::ReifyFnPointer) => { + let fn_sig = op.ty(body, tcx).fn_sig(tcx); + + // The type that we see in the fcx is like + // `foo::<'a, 'b>`, where `foo` is the path to a + // function definition. When we extract the + // signature, it comes from the `fn_sig` query, + // and hence may contain unnormalized results. + let fn_sig = self.normalize(fn_sig, location); + + let ty_fn_ptr_from = tcx.mk_fn_ptr(fn_sig); + + if let Err(terr) = self.eq_types( + *ty, + ty_fn_ptr_from, + location.to_locations(), + ConstraintCategory::Cast, + ) { + span_mirbug!( + self, + rvalue, + "equating {:?} with {:?} yields {:?}", + ty_fn_ptr_from, + ty, + terr + ); + } + } + + CastKind::Pointer(PointerCast::ClosureFnPointer(unsafety)) => { + let sig = match op.ty(body, tcx).kind() { + ty::Closure(_, substs) => substs.as_closure().sig(), + _ => bug!(), + }; + let ty_fn_ptr_from = tcx.mk_fn_ptr(tcx.signature_unclosure(sig, *unsafety)); + + if let Err(terr) = self.eq_types( + *ty, + ty_fn_ptr_from, + location.to_locations(), + ConstraintCategory::Cast, + ) { + span_mirbug!( + self, + rvalue, + "equating {:?} with {:?} yields {:?}", + ty_fn_ptr_from, + ty, + terr + ); + } + } + + CastKind::Pointer(PointerCast::UnsafeFnPointer) => { + let fn_sig = op.ty(body, tcx).fn_sig(tcx); + + // The type that we see in the fcx is like + // `foo::<'a, 'b>`, where `foo` is the path to a + // function definition. When we extract the + // signature, it comes from the `fn_sig` query, + // and hence may contain unnormalized results. + let fn_sig = self.normalize(fn_sig, location); + + let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig); + + if let Err(terr) = self.eq_types( + *ty, + ty_fn_ptr_from, + location.to_locations(), + ConstraintCategory::Cast, + ) { + span_mirbug!( + self, + rvalue, + "equating {:?} with {:?} yields {:?}", + ty_fn_ptr_from, + ty, + terr + ); + } + } + + CastKind::Pointer(PointerCast::Unsize) => { + let &ty = ty; + let trait_ref = ty::TraitRef { + def_id: tcx + .require_lang_item(LangItem::CoerceUnsized, Some(self.last_span)), + substs: tcx.mk_substs_trait(op.ty(body, tcx), &[ty.into()]), + }; + + self.prove_trait_ref( + trait_ref, + location.to_locations(), + ConstraintCategory::Cast, + ); + } + + CastKind::Pointer(PointerCast::MutToConstPointer) => { + let ty::RawPtr(ty::TypeAndMut { + ty: ty_from, + mutbl: hir::Mutability::Mut, + }) = op.ty(body, tcx).kind() else { + span_mirbug!( + self, + rvalue, + "unexpected base type for cast {:?}", + ty, + ); + return; + }; + let ty::RawPtr(ty::TypeAndMut { + ty: ty_to, + mutbl: hir::Mutability::Not, + }) = ty.kind() else { + span_mirbug!( + self, + rvalue, + "unexpected target type for cast {:?}", + ty, + ); + return; + }; + if let Err(terr) = self.sub_types( + *ty_from, + *ty_to, + location.to_locations(), + ConstraintCategory::Cast, + ) { + span_mirbug!( + self, + rvalue, + "relating {:?} with {:?} yields {:?}", + ty_from, + ty_to, + terr + ); + } + } + + CastKind::Pointer(PointerCast::ArrayToPointer) => { + let ty_from = op.ty(body, tcx); + + let opt_ty_elem_mut = match ty_from.kind() { + ty::RawPtr(ty::TypeAndMut { mutbl: array_mut, ty: array_ty }) => { + match array_ty.kind() { + ty::Array(ty_elem, _) => Some((ty_elem, *array_mut)), + _ => None, + } + } + _ => None, + }; + + let Some((ty_elem, ty_mut)) = opt_ty_elem_mut else { + span_mirbug!( + self, + rvalue, + "ArrayToPointer cast from unexpected type {:?}", + ty_from, + ); + return; + }; + + let (ty_to, ty_to_mut) = match ty.kind() { + ty::RawPtr(ty::TypeAndMut { mutbl: ty_to_mut, ty: ty_to }) => { + (ty_to, *ty_to_mut) + } + _ => { + span_mirbug!( + self, + rvalue, + "ArrayToPointer cast to unexpected type {:?}", + ty, + ); + return; + } + }; + + if ty_to_mut == Mutability::Mut && ty_mut == Mutability::Not { + span_mirbug!( + self, + rvalue, + "ArrayToPointer cast from const {:?} to mut {:?}", + ty, + ty_to + ); + return; + } + + if let Err(terr) = self.sub_types( + *ty_elem, + *ty_to, + location.to_locations(), + ConstraintCategory::Cast, + ) { + span_mirbug!( + self, + rvalue, + "relating {:?} with {:?} yields {:?}", + ty_elem, + ty_to, + terr + ) + } + } + + CastKind::PointerExposeAddress => { + let ty_from = op.ty(body, tcx); + let cast_ty_from = CastTy::from_ty(ty_from); + let cast_ty_to = CastTy::from_ty(*ty); + match (cast_ty_from, cast_ty_to) { + (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => (), + _ => { + span_mirbug!( + self, + rvalue, + "Invalid PointerExposeAddress cast {:?} -> {:?}", + ty_from, + ty + ) + } + } + } + + CastKind::PointerFromExposedAddress => { + let ty_from = op.ty(body, tcx); + let cast_ty_from = CastTy::from_ty(ty_from); + let cast_ty_to = CastTy::from_ty(*ty); + match (cast_ty_from, cast_ty_to) { + (Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => (), + _ => { + span_mirbug!( + self, + rvalue, + "Invalid PointerFromExposedAddress cast {:?} -> {:?}", + ty_from, + ty + ) + } + } + } + + CastKind::Misc => { + let ty_from = op.ty(body, tcx); + let cast_ty_from = CastTy::from_ty(ty_from); + let cast_ty_to = CastTy::from_ty(*ty); + // Misc casts are either between floats and ints, or one ptr type to another. + match (cast_ty_from, cast_ty_to) { + ( + Some(CastTy::Int(_) | CastTy::Float), + Some(CastTy::Int(_) | CastTy::Float), + ) + | (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Ptr(_))) => (), + _ => { + span_mirbug!( + self, + rvalue, + "Invalid Misc cast {:?} -> {:?}", + ty_from, + ty, + ) + } + } + } + } + } + + Rvalue::Ref(region, _borrow_kind, borrowed_place) => { + self.add_reborrow_constraint(&body, location, *region, borrowed_place); + } + + Rvalue::BinaryOp( + BinOp::Eq | BinOp::Ne | BinOp::Lt | BinOp::Le | BinOp::Gt | BinOp::Ge, + box (left, right), + ) => { + self.check_operand(left, location); + self.check_operand(right, location); + + let ty_left = left.ty(body, tcx); + match ty_left.kind() { + // Types with regions are comparable if they have a common super-type. + ty::RawPtr(_) | ty::FnPtr(_) => { + let ty_right = right.ty(body, tcx); + let common_ty = self.infcx.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::MiscVariable, + span: body.source_info(location).span, + }); + self.sub_types( + ty_left, + common_ty, + location.to_locations(), + ConstraintCategory::Boring, + ) + .unwrap_or_else(|err| { + bug!("Could not equate type variable with {:?}: {:?}", ty_left, err) + }); + if let Err(terr) = self.sub_types( + ty_right, + common_ty, + location.to_locations(), + ConstraintCategory::Boring, + ) { + span_mirbug!( + self, + rvalue, + "unexpected comparison types {:?} and {:?} yields {:?}", + ty_left, + ty_right, + terr + ) + } + } + // For types with no regions we can just check that the + // both operands have the same type. + ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char | ty::Float(_) + if ty_left == right.ty(body, tcx) => {} + // Other types are compared by trait methods, not by + // `Rvalue::BinaryOp`. + _ => span_mirbug!( + self, + rvalue, + "unexpected comparison types {:?} and {:?}", + ty_left, + right.ty(body, tcx) + ), + } + } + + Rvalue::Use(operand) | Rvalue::UnaryOp(_, operand) => { + self.check_operand(operand, location); + } + Rvalue::CopyForDeref(place) => { + let op = &Operand::Copy(*place); + self.check_operand(op, location); + } + + Rvalue::BinaryOp(_, box (left, right)) + | Rvalue::CheckedBinaryOp(_, box (left, right)) => { + self.check_operand(left, location); + self.check_operand(right, location); + } + + Rvalue::AddressOf(..) + | Rvalue::ThreadLocalRef(..) + | Rvalue::Len(..) + | Rvalue::Discriminant(..) => {} + } + } + + /// If this rvalue supports a user-given type annotation, then + /// extract and return it. This represents the final type of the + /// rvalue and will be unified with the inferred type. + fn rvalue_user_ty(&self, rvalue: &Rvalue<'tcx>) -> Option<UserTypeAnnotationIndex> { + match rvalue { + Rvalue::Use(_) + | Rvalue::ThreadLocalRef(_) + | Rvalue::Repeat(..) + | Rvalue::Ref(..) + | Rvalue::AddressOf(..) + | Rvalue::Len(..) + | Rvalue::Cast(..) + | Rvalue::ShallowInitBox(..) + | Rvalue::BinaryOp(..) + | Rvalue::CheckedBinaryOp(..) + | Rvalue::NullaryOp(..) + | Rvalue::CopyForDeref(..) + | Rvalue::UnaryOp(..) + | Rvalue::Discriminant(..) => None, + + Rvalue::Aggregate(aggregate, _) => match **aggregate { + AggregateKind::Adt(_, _, _, user_ty, _) => user_ty, + AggregateKind::Array(_) => None, + AggregateKind::Tuple => None, + AggregateKind::Closure(_, _) => None, + AggregateKind::Generator(_, _, _) => None, + }, + } + } + + fn check_aggregate_rvalue( + &mut self, + body: &Body<'tcx>, + rvalue: &Rvalue<'tcx>, + aggregate_kind: &AggregateKind<'tcx>, + operands: &[Operand<'tcx>], + location: Location, + ) { + let tcx = self.tcx(); + + self.prove_aggregate_predicates(aggregate_kind, location); + + if *aggregate_kind == AggregateKind::Tuple { + // tuple rvalue field type is always the type of the op. Nothing to check here. + return; + } + + for (i, operand) in operands.iter().enumerate() { + let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) { + Ok(field_ty) => field_ty, + Err(FieldAccessError::OutOfRange { field_count }) => { + span_mirbug!( + self, + rvalue, + "accessed field #{} but variant only has {}", + i, + field_count + ); + continue; + } + }; + let operand_ty = operand.ty(body, tcx); + let operand_ty = self.normalize(operand_ty, location); + + if let Err(terr) = self.sub_types( + operand_ty, + field_ty, + location.to_locations(), + ConstraintCategory::Boring, + ) { + span_mirbug!( + self, + rvalue, + "{:?} is not a subtype of {:?}: {:?}", + operand_ty, + field_ty, + terr + ); + } + } + } + + /// Adds the constraints that arise from a borrow expression `&'a P` at the location `L`. + /// + /// # Parameters + /// + /// - `location`: the location `L` where the borrow expression occurs + /// - `borrow_region`: the region `'a` associated with the borrow + /// - `borrowed_place`: the place `P` being borrowed + fn add_reborrow_constraint( + &mut self, + body: &Body<'tcx>, + location: Location, + borrow_region: ty::Region<'tcx>, + borrowed_place: &Place<'tcx>, + ) { + // These constraints are only meaningful during borrowck: + let BorrowCheckContext { borrow_set, location_table, all_facts, constraints, .. } = + self.borrowck_context; + + // In Polonius mode, we also push a `loan_issued_at` fact + // linking the loan to the region (in some cases, though, + // there is no loan associated with this borrow expression -- + // that occurs when we are borrowing an unsafe place, for + // example). + if let Some(all_facts) = all_facts { + let _prof_timer = self.infcx.tcx.prof.generic_activity("polonius_fact_generation"); + if let Some(borrow_index) = borrow_set.get_index_of(&location) { + let region_vid = borrow_region.to_region_vid(); + all_facts.loan_issued_at.push(( + region_vid, + borrow_index, + location_table.mid_index(location), + )); + } + } + + // If we are reborrowing the referent of another reference, we + // need to add outlives relationships. In a case like `&mut + // *p`, where the `p` has type `&'b mut Foo`, for example, we + // need to ensure that `'b: 'a`. + + debug!( + "add_reborrow_constraint({:?}, {:?}, {:?})", + location, borrow_region, borrowed_place + ); + + let mut cursor = borrowed_place.projection.as_ref(); + let tcx = self.infcx.tcx; + let field = path_utils::is_upvar_field_projection( + tcx, + &self.borrowck_context.upvars, + borrowed_place.as_ref(), + body, + ); + let category = if let Some(field) = field { + ConstraintCategory::ClosureUpvar(field) + } else { + ConstraintCategory::Boring + }; + + while let [proj_base @ .., elem] = cursor { + cursor = proj_base; + + debug!("add_reborrow_constraint - iteration {:?}", elem); + + match elem { + ProjectionElem::Deref => { + let base_ty = Place::ty_from(borrowed_place.local, proj_base, body, tcx).ty; + + debug!("add_reborrow_constraint - base_ty = {:?}", base_ty); + match base_ty.kind() { + ty::Ref(ref_region, _, mutbl) => { + constraints.outlives_constraints.push(OutlivesConstraint { + sup: ref_region.to_region_vid(), + sub: borrow_region.to_region_vid(), + locations: location.to_locations(), + span: location.to_locations().span(body), + category, + variance_info: ty::VarianceDiagInfo::default(), + }); + + match mutbl { + hir::Mutability::Not => { + // Immutable reference. We don't need the base + // to be valid for the entire lifetime of + // the borrow. + break; + } + hir::Mutability::Mut => { + // Mutable reference. We *do* need the base + // to be valid, because after the base becomes + // invalid, someone else can use our mutable deref. + + // This is in order to make the following function + // illegal: + // ``` + // fn unsafe_deref<'a, 'b>(x: &'a &'b mut T) -> &'b mut T { + // &mut *x + // } + // ``` + // + // As otherwise you could clone `&mut T` using the + // following function: + // ``` + // fn bad(x: &mut T) -> (&mut T, &mut T) { + // let my_clone = unsafe_deref(&'a x); + // ENDREGION 'a; + // (my_clone, x) + // } + // ``` + } + } + } + ty::RawPtr(..) => { + // deref of raw pointer, guaranteed to be valid + break; + } + ty::Adt(def, _) if def.is_box() => { + // deref of `Box`, need the base to be valid - propagate + } + _ => bug!("unexpected deref ty {:?} in {:?}", base_ty, borrowed_place), + } + } + ProjectionElem::Field(..) + | ProjectionElem::Downcast(..) + | ProjectionElem::Index(..) + | ProjectionElem::ConstantIndex { .. } + | ProjectionElem::Subslice { .. } => { + // other field access + } + } + } + } + + fn prove_aggregate_predicates( + &mut self, + aggregate_kind: &AggregateKind<'tcx>, + location: Location, + ) { + let tcx = self.tcx(); + + debug!( + "prove_aggregate_predicates(aggregate_kind={:?}, location={:?})", + aggregate_kind, location + ); + + let (def_id, instantiated_predicates) = match *aggregate_kind { + AggregateKind::Adt(adt_did, _, substs, _, _) => { + (adt_did, tcx.predicates_of(adt_did).instantiate(tcx, substs)) + } + + // For closures, we have some **extra requirements** we + // + // have to check. In particular, in their upvars and + // signatures, closures often reference various regions + // from the surrounding function -- we call those the + // closure's free regions. When we borrow-check (and hence + // region-check) closures, we may find that the closure + // requires certain relationships between those free + // regions. However, because those free regions refer to + // portions of the CFG of their caller, the closure is not + // in a position to verify those relationships. In that + // case, the requirements get "propagated" to us, and so + // we have to solve them here where we instantiate the + // closure. + // + // Despite the opacity of the previous paragraph, this is + // actually relatively easy to understand in terms of the + // desugaring. A closure gets desugared to a struct, and + // these extra requirements are basically like where + // clauses on the struct. + AggregateKind::Closure(def_id, substs) + | AggregateKind::Generator(def_id, substs, _) => { + (def_id.to_def_id(), self.prove_closure_bounds(tcx, def_id, substs, location)) + } + + AggregateKind::Array(_) | AggregateKind::Tuple => { + (CRATE_DEF_ID.to_def_id(), ty::InstantiatedPredicates::empty()) + } + }; + + self.normalize_and_prove_instantiated_predicates( + def_id, + instantiated_predicates, + location.to_locations(), + ); + } + + fn prove_closure_bounds( + &mut self, + tcx: TyCtxt<'tcx>, + def_id: LocalDefId, + substs: SubstsRef<'tcx>, + location: Location, + ) -> ty::InstantiatedPredicates<'tcx> { + if let Some(ref closure_region_requirements) = tcx.mir_borrowck(def_id).closure_requirements + { + let closure_constraints = QueryRegionConstraints { + outlives: closure_region_requirements.apply_requirements( + tcx, + def_id.to_def_id(), + substs, + ), + + // Presently, closures never propagate member + // constraints to their parents -- they are enforced + // locally. This is largely a non-issue as member + // constraints only come from `-> impl Trait` and + // friends which don't appear (thus far...) in + // closures. + member_constraints: vec![], + }; + + let bounds_mapping = closure_constraints + .outlives + .iter() + .enumerate() + .filter_map(|(idx, constraint)| { + let ty::OutlivesPredicate(k1, r2) = + constraint.no_bound_vars().unwrap_or_else(|| { + bug!("query_constraint {:?} contained bound vars", constraint,); + }); + + match k1.unpack() { + GenericArgKind::Lifetime(r1) => { + // constraint is r1: r2 + let r1_vid = self.borrowck_context.universal_regions.to_region_vid(r1); + let r2_vid = self.borrowck_context.universal_regions.to_region_vid(r2); + let outlives_requirements = + &closure_region_requirements.outlives_requirements[idx]; + Some(( + (r1_vid, r2_vid), + (outlives_requirements.category, outlives_requirements.blame_span), + )) + } + GenericArgKind::Type(_) | GenericArgKind::Const(_) => None, + } + }) + .collect(); + + let existing = self + .borrowck_context + .constraints + .closure_bounds_mapping + .insert(location, bounds_mapping); + assert!(existing.is_none(), "Multiple closures at the same location."); + + self.push_region_constraints( + location.to_locations(), + ConstraintCategory::ClosureBounds, + &closure_constraints, + ); + } + + // Now equate closure substs to regions inherited from `typeck_root_def_id`. Fixes #98589. + let typeck_root_def_id = tcx.typeck_root_def_id(self.body.source.def_id()); + let typeck_root_substs = ty::InternalSubsts::identity_for_item(tcx, typeck_root_def_id); + + let parent_substs = match tcx.def_kind(def_id) { + DefKind::Closure => substs.as_closure().parent_substs(), + DefKind::Generator => substs.as_generator().parent_substs(), + DefKind::InlineConst => substs.as_inline_const().parent_substs(), + other => bug!("unexpected item {:?}", other), + }; + let parent_substs = tcx.mk_substs(parent_substs.iter()); + + assert_eq!(typeck_root_substs.len(), parent_substs.len()); + if let Err(_) = self.eq_substs( + typeck_root_substs, + parent_substs, + location.to_locations(), + ConstraintCategory::BoringNoLocation, + ) { + span_mirbug!( + self, + def_id, + "could not relate closure to parent {:?} != {:?}", + typeck_root_substs, + parent_substs + ); + } + + tcx.predicates_of(def_id).instantiate(tcx, substs) + } + + #[instrument(skip(self, body), level = "debug")] + fn typeck_mir(&mut self, body: &Body<'tcx>) { + self.last_span = body.span; + debug!(?body.span); + + for (local, local_decl) in body.local_decls.iter_enumerated() { + self.check_local(&body, local, local_decl); + } + + for (block, block_data) in body.basic_blocks().iter_enumerated() { + let mut location = Location { block, statement_index: 0 }; + for stmt in &block_data.statements { + if !stmt.source_info.span.is_dummy() { + self.last_span = stmt.source_info.span; + } + self.check_stmt(body, stmt, location); + location.statement_index += 1; + } + + self.check_terminator(&body, block_data.terminator(), location); + self.check_iscleanup(&body, block_data); + } + } +} + +trait NormalizeLocation: fmt::Debug + Copy { + fn to_locations(self) -> Locations; +} + +impl NormalizeLocation for Locations { + fn to_locations(self) -> Locations { + self + } +} + +impl NormalizeLocation for Location { + fn to_locations(self) -> Locations { + Locations::Single(self) + } +} + +/// Runs `infcx.instantiate_opaque_types`. Unlike other `TypeOp`s, +/// this is not canonicalized - it directly affects the main `InferCtxt` +/// that we use during MIR borrowchecking. +#[derive(Debug)] +pub(super) struct InstantiateOpaqueType<'tcx> { + pub base_universe: Option<ty::UniverseIndex>, + pub region_constraints: Option<RegionConstraintData<'tcx>>, + pub obligations: Vec<PredicateObligation<'tcx>>, +} + +impl<'tcx> TypeOp<'tcx> for InstantiateOpaqueType<'tcx> { + type Output = (); + /// We use this type itself to store the information used + /// when reporting errors. Since this is not a query, we don't + /// re-run anything during error reporting - we just use the information + /// we saved to help extract an error from the already-existing region + /// constraints in our `InferCtxt` + type ErrorInfo = InstantiateOpaqueType<'tcx>; + + fn fully_perform(mut self, infcx: &InferCtxt<'_, 'tcx>) -> Fallible<TypeOpOutput<'tcx, Self>> { + let (mut output, region_constraints) = scrape_region_constraints(infcx, || { + Ok(InferOk { value: (), obligations: self.obligations.clone() }) + })?; + self.region_constraints = Some(region_constraints); + output.error_info = Some(self); + Ok(output) + } +} |