1 //! This pass type-checks the MIR to ensure it is not broken.
4 use std::{fmt, iter, mem};
8 use rustc_data_structures::frozen::Frozen;
9 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
10 use rustc_errors::struct_span_err;
12 use rustc_hir::def_id::{DefId, LocalDefId};
13 use rustc_hir::lang_items::LangItem;
14 use rustc_index::vec::{Idx, IndexVec};
15 use rustc_infer::infer::canonical::QueryRegionConstraints;
16 use rustc_infer::infer::outlives::env::RegionBoundPairs;
17 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
18 use rustc_infer::infer::{
19 InferCtxt, InferOk, LateBoundRegionConversionTime, NllRegionVariableOrigin,
21 use rustc_middle::mir::tcx::PlaceTy;
22 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
23 use rustc_middle::mir::AssertKind;
24 use rustc_middle::mir::*;
25 use rustc_middle::ty::adjustment::PointerCast;
26 use rustc_middle::ty::cast::CastTy;
27 use rustc_middle::ty::fold::TypeFoldable;
28 use rustc_middle::ty::subst::{GenericArgKind, Subst, SubstsRef, UserSubsts};
29 use rustc_middle::ty::{
30 self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, RegionVid, ToPredicate, Ty,
31 TyCtxt, UserType, UserTypeAnnotationIndex, WithConstness,
33 use rustc_span::{Span, DUMMY_SP};
34 use rustc_target::abi::VariantIdx;
35 use rustc_trait_selection::infer::InferCtxtExt as _;
36 use rustc_trait_selection::opaque_types::{GenerateMemberConstraints, InferCtxtExt};
37 use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
38 use rustc_trait_selection::traits::query::type_op;
39 use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
40 use rustc_trait_selection::traits::query::{Fallible, NoSolution};
41 use rustc_trait_selection::traits::{self, ObligationCause, PredicateObligations};
43 use crate::dataflow::impls::MaybeInitializedPlaces;
44 use crate::dataflow::move_paths::MoveData;
45 use crate::dataflow::ResultsCursor;
46 use crate::transform::{
47 check_consts::ConstCx, promote_consts::is_const_fn_in_array_repeat_expression,
50 use crate::borrow_check::{
51 borrow_set::BorrowSet,
52 constraints::{OutlivesConstraint, OutlivesConstraintSet},
54 location::LocationTable,
55 member_constraints::MemberConstraintSet,
58 region_infer::values::{
59 LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements,
61 region_infer::{ClosureRegionRequirementsExt, TypeTest},
63 type_check::free_region_relations::{CreateResult, UniversalRegionRelations},
64 universal_regions::{DefiningTy, UniversalRegions},
68 macro_rules! span_mirbug {
69 ($context:expr, $elem:expr, $($message:tt)*) => ({
70 $crate::borrow_check::type_check::mirbug(
74 "broken MIR in {:?} ({:?}): {}",
75 $context.body.source.def_id(),
77 format_args!($($message)*),
83 macro_rules! span_mirbug_and_err {
84 ($context:expr, $elem:expr, $($message:tt)*) => ({
86 span_mirbug!($context, $elem, $($message)*);
92 mod constraint_conversion;
93 pub mod free_region_relations;
98 /// Type checks the given `mir` in the context of the inference
99 /// context `infcx`. Returns any region constraints that have yet to
100 /// be proven. This result is includes liveness constraints that
101 /// ensure that regions appearing in the types of all local variables
102 /// are live at all points where that local variable may later be
105 /// This phase of type-check ought to be infallible -- this is because
106 /// the original, HIR-based type-check succeeded. So if any errors
107 /// occur here, we will get a `bug!` reported.
111 /// - `infcx` -- inference context to use
112 /// - `param_env` -- parameter environment to use for trait solving
113 /// - `body` -- MIR body to type-check
114 /// - `promoted` -- map of promoted constants within `body`
115 /// - `universal_regions` -- the universal regions from `body`s function signature
116 /// - `location_table` -- MIR location map of `body`
117 /// - `borrow_set` -- information about borrows occurring in `body`
118 /// - `all_facts` -- when using Polonius, this is the generated set of Polonius facts
119 /// - `flow_inits` -- results of a maybe-init dataflow analysis
120 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis
121 /// - `elements` -- MIR region map
122 pub(crate) fn type_check<'mir, 'tcx>(
123 infcx: &InferCtxt<'_, 'tcx>,
124 param_env: ty::ParamEnv<'tcx>,
126 promoted: &IndexVec<Promoted, Body<'tcx>>,
127 universal_regions: &Rc<UniversalRegions<'tcx>>,
128 location_table: &LocationTable,
129 borrow_set: &BorrowSet<'tcx>,
130 all_facts: &mut Option<AllFacts>,
131 flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
132 move_data: &MoveData<'tcx>,
133 elements: &Rc<RegionValueElements>,
134 upvars: &[Upvar<'tcx>],
135 ) -> MirTypeckResults<'tcx> {
136 let implicit_region_bound = infcx.tcx.mk_region(ty::ReVar(universal_regions.fr_fn_body));
137 let mut constraints = MirTypeckRegionConstraints {
138 placeholder_indices: PlaceholderIndices::default(),
139 placeholder_index_to_region: IndexVec::default(),
140 liveness_constraints: LivenessValues::new(elements.clone()),
141 outlives_constraints: OutlivesConstraintSet::default(),
142 member_constraints: MemberConstraintSet::default(),
143 closure_bounds_mapping: Default::default(),
144 type_tests: Vec::default(),
148 universal_region_relations,
150 normalized_inputs_and_output,
151 } = free_region_relations::create(
154 Some(implicit_region_bound),
159 let mut borrowck_context = BorrowCheckContext {
164 constraints: &mut constraints,
168 let opaque_type_values = type_check_internal(
174 implicit_region_bound,
175 &mut borrowck_context,
176 &universal_region_relations,
178 cx.equate_inputs_and_outputs(&body, universal_regions, &normalized_inputs_and_output);
179 liveness::generate(&mut cx, body, elements, flow_inits, move_data, location_table);
181 translate_outlives_facts(&mut cx);
182 cx.opaque_type_values
186 MirTypeckResults { constraints, universal_region_relations, opaque_type_values }
189 fn type_check_internal<'a, 'tcx, R>(
190 infcx: &'a InferCtxt<'a, 'tcx>,
191 param_env: ty::ParamEnv<'tcx>,
192 body: &'a Body<'tcx>,
193 promoted: &'a IndexVec<Promoted, Body<'tcx>>,
194 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
195 implicit_region_bound: ty::Region<'tcx>,
196 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
197 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
198 extra: impl FnOnce(TypeChecker<'a, 'tcx>) -> R,
200 let mut checker = TypeChecker::new(
205 implicit_region_bound,
207 universal_region_relations,
209 let errors_reported = {
210 let mut verifier = TypeVerifier::new(&mut checker, body, promoted);
211 verifier.visit_body(&body);
212 verifier.errors_reported
215 if !errors_reported {
216 // if verifier failed, don't do further checks to avoid ICEs
217 checker.typeck_mir(body);
223 fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) {
224 let cx = &mut typeck.borrowck_context;
225 if let Some(facts) = cx.all_facts {
226 let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
227 let location_table = cx.location_table;
228 facts.outlives.extend(cx.constraints.outlives_constraints.outlives().iter().flat_map(
229 |constraint: &OutlivesConstraint| {
230 if let Some(from_location) = constraint.locations.from_location() {
231 Either::Left(iter::once((
234 location_table.mid_index(from_location),
240 .map(move |location| (constraint.sup, constraint.sub, location)),
248 fn mirbug(tcx: TyCtxt<'_>, span: Span, msg: &str) {
249 // We sometimes see MIR failures (notably predicate failures) due to
250 // the fact that we check rvalue sized predicates here. So use `delay_span_bug`
251 // to avoid reporting bugs in those cases.
252 tcx.sess.diagnostic().delay_span_bug(span, msg);
255 enum FieldAccessError {
256 OutOfRange { field_count: usize },
259 /// Verifies that MIR types are sane to not crash further checks.
261 /// The sanitize_XYZ methods here take an MIR object and compute its
262 /// type, calling `span_mirbug` and returning an error type if there
264 struct TypeVerifier<'a, 'b, 'tcx> {
265 cx: &'a mut TypeChecker<'b, 'tcx>,
266 body: &'b Body<'tcx>,
267 promoted: &'b IndexVec<Promoted, Body<'tcx>>,
269 errors_reported: bool,
272 impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
273 fn visit_span(&mut self, span: &Span) {
274 if !span.is_dummy() {
275 self.last_span = *span;
279 fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
280 self.sanitize_place(place, location, context);
283 fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
284 self.super_constant(constant, location);
285 let ty = self.sanitize_type(constant, constant.literal.ty);
287 self.cx.infcx.tcx.for_each_free_region(&ty, |live_region| {
288 let live_region_vid =
289 self.cx.borrowck_context.universal_regions.to_region_vid(live_region);
293 .liveness_constraints
294 .add_element(live_region_vid, location);
297 if let Some(annotation_index) = constant.user_ty {
298 if let Err(terr) = self.cx.relate_type_and_user_type(
300 ty::Variance::Invariant,
301 &UserTypeProjection { base: annotation_index, projs: vec![] },
302 location.to_locations(),
303 ConstraintCategory::Boring,
305 let annotation = &self.cx.user_type_annotations[annotation_index];
309 "bad constant user type {:?} vs {:?}: {:?}",
316 let tcx = self.tcx();
317 if let ty::ConstKind::Unevaluated(def, substs, promoted) = constant.literal.val {
318 if let Some(promoted) = promoted {
319 let check_err = |verifier: &mut TypeVerifier<'a, 'b, 'tcx>,
320 promoted: &Body<'tcx>,
323 if let Err(terr) = verifier.cx.eq_types(
326 location.to_locations(),
327 ConstraintCategory::Boring,
332 "bad promoted type ({:?}: {:?}): {:?}",
340 if !self.errors_reported {
341 let promoted_body = &self.promoted[promoted];
342 self.sanitize_promoted(promoted_body, location);
344 let promoted_ty = promoted_body.return_ty();
345 check_err(self, promoted_body, ty, promoted_ty);
348 if let Err(terr) = self.cx.fully_perform_op(
349 location.to_locations(),
350 ConstraintCategory::Boring,
351 self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
354 UserSubsts { substs, user_self_ty: None },
360 "bad constant type {:?} ({:?})",
366 } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
367 let unnormalized_ty = tcx.type_of(static_def_id);
368 let locations = location.to_locations();
369 let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
370 let literal_ty = constant.literal.ty.builtin_deref(true).unwrap().ty;
372 if let Err(terr) = self.cx.eq_types(
376 ConstraintCategory::Boring,
378 span_mirbug!(self, constant, "bad static type {:?} ({:?})", constant, terr);
382 if let ty::FnDef(def_id, substs) = *constant.literal.ty.kind() {
383 let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
384 self.cx.normalize_and_prove_instantiated_predicates(
385 instantiated_predicates,
386 location.to_locations(),
392 fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
393 self.super_rvalue(rvalue, location);
394 let rval_ty = rvalue.ty(self.body, self.tcx());
395 self.sanitize_type(rvalue, rval_ty);
398 fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
399 self.super_local_decl(local, local_decl);
400 self.sanitize_type(local_decl, local_decl.ty);
402 if let Some(user_ty) = &local_decl.user_ty {
403 for (user_ty, span) in user_ty.projections_and_spans() {
404 let ty = if !local_decl.is_nonref_binding() {
405 // If we have a binding of the form `let ref x: T = ..`
406 // then remove the outermost reference so we can check the
407 // type annotation for the remaining type.
408 if let ty::Ref(_, rty, _) = local_decl.ty.kind() {
411 bug!("{:?} with ref binding has wrong type {}", local, local_decl.ty);
417 if let Err(terr) = self.cx.relate_type_and_user_type(
419 ty::Variance::Invariant,
421 Locations::All(*span),
422 ConstraintCategory::TypeAnnotation,
427 "bad user type on variable {:?}: {:?} != {:?} ({:?})",
438 fn visit_body(&mut self, body: &Body<'tcx>) {
439 self.sanitize_type(&"return type", body.return_ty());
440 for local_decl in &body.local_decls {
441 self.sanitize_type(local_decl, local_decl.ty);
443 if self.errors_reported {
446 self.super_body(body);
450 impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
452 cx: &'a mut TypeChecker<'b, 'tcx>,
453 body: &'b Body<'tcx>,
454 promoted: &'b IndexVec<Promoted, Body<'tcx>>,
456 TypeVerifier { body, promoted, cx, last_span: body.span, errors_reported: false }
459 fn tcx(&self) -> TyCtxt<'tcx> {
463 fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
464 if ty.has_escaping_bound_vars() || ty.references_error() {
465 span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
471 /// Checks that the types internal to the `place` match up with
472 /// what would be expected.
477 context: PlaceContext,
479 debug!("sanitize_place: {:?}", place);
481 let mut place_ty = PlaceTy::from_ty(self.body.local_decls[place.local].ty);
483 for elem in place.projection.iter() {
484 if place_ty.variant_index.is_none() {
485 if place_ty.ty.references_error() {
486 assert!(self.errors_reported);
487 return PlaceTy::from_ty(self.tcx().ty_error());
490 place_ty = self.sanitize_projection(place_ty, elem, place, location)
493 if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
494 let tcx = self.tcx();
495 let trait_ref = ty::TraitRef {
496 def_id: tcx.require_lang_item(LangItem::Copy, Some(self.last_span)),
497 substs: tcx.mk_substs_trait(place_ty.ty, &[]),
500 // To have a `Copy` operand, the type `T` of the
501 // value must be `Copy`. Note that we prove that `T: Copy`,
502 // rather than using the `is_copy_modulo_regions`
503 // test. This is important because
504 // `is_copy_modulo_regions` ignores the resulting region
505 // obligations and assumes they pass. This can result in
506 // bounds from `Copy` impls being unsoundly ignored (e.g.,
507 // #29149). Note that we decide to use `Copy` before knowing
508 // whether the bounds fully apply: in effect, the rule is
509 // that if a value of some type could implement `Copy`, then
511 self.cx.prove_trait_ref(
513 location.to_locations(),
514 ConstraintCategory::CopyBound,
521 fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Location) {
522 // Determine the constraints from the promoted MIR by running the type
523 // checker on the promoted MIR, then transfer the constraints back to
524 // the main MIR, changing the locations to the provided location.
526 let parent_body = mem::replace(&mut self.body, promoted_body);
528 // Use new sets of constraints and closure bounds so that we can
529 // modify their locations.
530 let all_facts = &mut None;
531 let mut constraints = Default::default();
532 let mut closure_bounds = Default::default();
533 let mut liveness_constraints =
534 LivenessValues::new(Rc::new(RegionValueElements::new(&promoted_body)));
535 // Don't try to add borrow_region facts for the promoted MIR
537 let mut swap_constraints = |this: &mut Self| {
538 mem::swap(this.cx.borrowck_context.all_facts, all_facts);
540 &mut this.cx.borrowck_context.constraints.outlives_constraints,
544 &mut this.cx.borrowck_context.constraints.closure_bounds_mapping,
548 &mut this.cx.borrowck_context.constraints.liveness_constraints,
549 &mut liveness_constraints,
553 swap_constraints(self);
555 self.visit_body(&promoted_body);
557 if !self.errors_reported {
558 // if verifier failed, don't do further checks to avoid ICEs
559 self.cx.typeck_mir(promoted_body);
562 self.body = parent_body;
563 // Merge the outlives constraints back in, at the given location.
564 swap_constraints(self);
566 let locations = location.to_locations();
567 for constraint in constraints.outlives().iter() {
568 let mut constraint = *constraint;
569 constraint.locations = locations;
570 if let ConstraintCategory::Return(_)
571 | ConstraintCategory::UseAsConst
572 | ConstraintCategory::UseAsStatic = constraint.category
574 // "Returning" from a promoted is an assignment to a
575 // temporary from the user's point of view.
576 constraint.category = ConstraintCategory::Boring;
578 self.cx.borrowck_context.constraints.outlives_constraints.push(constraint)
580 for live_region in liveness_constraints.rows() {
584 .liveness_constraints
585 .add_element(live_region, location);
588 if !closure_bounds.is_empty() {
589 let combined_bounds_mapping =
590 closure_bounds.into_iter().flat_map(|(_, value)| value).collect();
595 .closure_bounds_mapping
596 .insert(location, combined_bounds_mapping);
597 assert!(existing.is_none(), "Multiple promoteds/closures at the same location.");
601 fn sanitize_projection(
608 debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, place);
609 let tcx = self.tcx();
610 let base_ty = base.ty;
612 ProjectionElem::Deref => {
613 let deref_ty = base_ty.builtin_deref(true);
614 PlaceTy::from_ty(deref_ty.map(|t| t.ty).unwrap_or_else(|| {
615 span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty)
618 ProjectionElem::Index(i) => {
619 let index_ty = Place::from(i).ty(self.body, tcx).ty;
620 if index_ty != tcx.types.usize {
621 PlaceTy::from_ty(span_mirbug_and_err!(self, i, "index by non-usize {:?}", i))
623 PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| {
624 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
628 ProjectionElem::ConstantIndex { .. } => {
629 // consider verifying in-bounds
630 PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| {
631 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
634 ProjectionElem::Subslice { from, to, from_end } => {
635 PlaceTy::from_ty(match base_ty.kind() {
636 ty::Array(inner, _) => {
637 assert!(!from_end, "array subslices should not use from_end");
638 tcx.mk_array(inner, to - from)
641 assert!(from_end, "slice subslices should use from_end");
644 _ => span_mirbug_and_err!(self, place, "slice of non-array {:?}", base_ty),
647 ProjectionElem::Downcast(maybe_name, index) => match base_ty.kind() {
648 ty::Adt(adt_def, _substs) if adt_def.is_enum() => {
649 if index.as_usize() >= adt_def.variants.len() {
650 PlaceTy::from_ty(span_mirbug_and_err!(
653 "cast to variant #{:?} but enum only has {:?}",
655 adt_def.variants.len()
658 PlaceTy { ty: base_ty, variant_index: Some(index) }
661 // We do not need to handle generators here, because this runs
662 // before the generator transform stage.
664 let ty = if let Some(name) = maybe_name {
665 span_mirbug_and_err!(
668 "can't downcast {:?} as {:?}",
673 span_mirbug_and_err!(self, place, "can't downcast {:?}", base_ty)
678 ProjectionElem::Field(field, fty) => {
679 let fty = self.sanitize_type(place, fty);
680 match self.field_ty(place, base, field, location) {
682 let ty = self.cx.normalize(ty, location);
683 if let Err(terr) = self.cx.eq_types(
686 location.to_locations(),
687 ConstraintCategory::Boring,
692 "bad field access ({:?}: {:?}): {:?}",
699 Err(FieldAccessError::OutOfRange { field_count }) => span_mirbug!(
702 "accessed field #{} but variant only has {}",
707 PlaceTy::from_ty(fty)
712 fn error(&mut self) -> Ty<'tcx> {
713 self.errors_reported = true;
714 self.tcx().ty_error()
719 parent: &dyn fmt::Debug,
720 base_ty: PlaceTy<'tcx>,
723 ) -> Result<Ty<'tcx>, FieldAccessError> {
724 let tcx = self.tcx();
726 let (variant, substs) = match base_ty {
727 PlaceTy { ty, variant_index: Some(variant_index) } => match *ty.kind() {
728 ty::Adt(adt_def, substs) => (&adt_def.variants[variant_index], substs),
729 ty::Generator(def_id, substs, _) => {
730 let mut variants = substs.as_generator().state_tys(def_id, tcx);
731 let mut variant = match variants.nth(variant_index.into()) {
734 "variant_index of generator out of range: {:?}/{:?}",
736 substs.as_generator().state_tys(def_id, tcx).count()
739 return match variant.nth(field.index()) {
741 None => Err(FieldAccessError::OutOfRange { field_count: variant.count() }),
744 _ => bug!("can't have downcast of non-adt non-generator type"),
746 PlaceTy { ty, variant_index: None } => match *ty.kind() {
747 ty::Adt(adt_def, substs) if !adt_def.is_enum() => {
748 (&adt_def.variants[VariantIdx::new(0)], substs)
750 ty::Closure(_, substs) => {
754 .tuple_element_ty(field.index())
757 None => Err(FieldAccessError::OutOfRange {
758 field_count: substs.as_closure().upvar_tys().count(),
762 ty::Generator(_, substs, _) => {
763 // Only prefix fields (upvars and current state) are
764 // accessible without a variant index.
765 return match substs.as_generator().prefix_tys().nth(field.index()) {
767 None => Err(FieldAccessError::OutOfRange {
768 field_count: substs.as_generator().prefix_tys().count(),
773 return match tys.get(field.index()) {
774 Some(&ty) => Ok(ty.expect_ty()),
775 None => Err(FieldAccessError::OutOfRange { field_count: tys.len() }),
779 return Ok(span_mirbug_and_err!(
782 "can't project out of {:?}",
789 if let Some(field) = variant.fields.get(field.index()) {
790 Ok(self.cx.normalize(field.ty(tcx, substs), location))
792 Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
797 /// The MIR type checker. Visits the MIR and enforces all the
798 /// constraints needed for it to be valid and well-typed. Along the
799 /// way, it accrues region constraints -- these can later be used by
800 /// NLL region checking.
801 struct TypeChecker<'a, 'tcx> {
802 infcx: &'a InferCtxt<'a, 'tcx>,
803 param_env: ty::ParamEnv<'tcx>,
805 body: &'a Body<'tcx>,
806 /// User type annotations are shared between the main MIR and the MIR of
807 /// all of the promoted items.
808 user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>,
809 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
810 implicit_region_bound: ty::Region<'tcx>,
811 reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
812 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
813 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
814 opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
817 struct BorrowCheckContext<'a, 'tcx> {
818 universal_regions: &'a UniversalRegions<'tcx>,
819 location_table: &'a LocationTable,
820 all_facts: &'a mut Option<AllFacts>,
821 borrow_set: &'a BorrowSet<'tcx>,
822 constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
823 upvars: &'a [Upvar<'tcx>],
826 crate struct MirTypeckResults<'tcx> {
827 crate constraints: MirTypeckRegionConstraints<'tcx>,
828 pub(in crate::borrow_check) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
829 crate opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
832 /// A collection of region constraints that must be satisfied for the
833 /// program to be considered well-typed.
834 crate struct MirTypeckRegionConstraints<'tcx> {
835 /// Maps from a `ty::Placeholder` to the corresponding
836 /// `PlaceholderIndex` bit that we will use for it.
838 /// To keep everything in sync, do not insert this set
839 /// directly. Instead, use the `placeholder_region` helper.
840 crate placeholder_indices: PlaceholderIndices,
842 /// Each time we add a placeholder to `placeholder_indices`, we
843 /// also create a corresponding "representative" region vid for
844 /// that wraps it. This vector tracks those. This way, when we
845 /// convert the same `ty::RePlaceholder(p)` twice, we can map to
846 /// the same underlying `RegionVid`.
847 crate placeholder_index_to_region: IndexVec<PlaceholderIndex, ty::Region<'tcx>>,
849 /// In general, the type-checker is not responsible for enforcing
850 /// liveness constraints; this job falls to the region inferencer,
851 /// which performs a liveness analysis. However, in some limited
852 /// cases, the MIR type-checker creates temporary regions that do
853 /// not otherwise appear in the MIR -- in particular, the
854 /// late-bound regions that it instantiates at call-sites -- and
855 /// hence it must report on their liveness constraints.
856 crate liveness_constraints: LivenessValues<RegionVid>,
858 crate outlives_constraints: OutlivesConstraintSet,
860 crate member_constraints: MemberConstraintSet<'tcx, RegionVid>,
862 crate closure_bounds_mapping:
863 FxHashMap<Location, FxHashMap<(RegionVid, RegionVid), (ConstraintCategory, Span)>>,
865 crate type_tests: Vec<TypeTest<'tcx>>,
868 impl MirTypeckRegionConstraints<'tcx> {
869 fn placeholder_region(
871 infcx: &InferCtxt<'_, 'tcx>,
872 placeholder: ty::PlaceholderRegion,
873 ) -> ty::Region<'tcx> {
874 let placeholder_index = self.placeholder_indices.insert(placeholder);
875 match self.placeholder_index_to_region.get(placeholder_index) {
878 let origin = NllRegionVariableOrigin::Placeholder(placeholder);
879 let region = infcx.next_nll_region_var_in_universe(origin, placeholder.universe);
880 self.placeholder_index_to_region.push(region);
887 /// The `Locations` type summarizes *where* region constraints are
888 /// required to hold. Normally, this is at a particular point which
889 /// created the obligation, but for constraints that the user gave, we
890 /// want the constraint to hold at all points.
891 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
893 /// Indicates that a type constraint should always be true. This
894 /// is particularly important in the new borrowck analysis for
895 /// things like the type of the return slot. Consider this
899 /// fn foo<'a>(x: &'a u32) -> &'a u32 {
901 /// return &y; // error
905 /// Here, we wind up with the signature from the return type being
906 /// something like `&'1 u32` where `'1` is a universal region. But
907 /// the type of the return slot `_0` is something like `&'2 u32`
908 /// where `'2` is an existential region variable. The type checker
909 /// requires that `&'2 u32 = &'1 u32` -- but at what point? In the
910 /// older NLL analysis, we required this only at the entry point
911 /// to the function. By the nature of the constraints, this wound
912 /// up propagating to all points reachable from start (because
913 /// `'1` -- as a universal region -- is live everywhere). In the
914 /// newer analysis, though, this doesn't work: `_0` is considered
915 /// dead at the start (it has no usable value) and hence this type
916 /// equality is basically a no-op. Then, later on, when we do `_0
917 /// = &'3 y`, that region `'3` never winds up related to the
918 /// universal region `'1` and hence no error occurs. Therefore, we
919 /// use Locations::All instead, which ensures that the `'1` and
920 /// `'2` are equal everything. We also use this for other
921 /// user-given type annotations; e.g., if the user wrote `let mut
922 /// x: &'static u32 = ...`, we would ensure that all values
923 /// assigned to `x` are of `'static` lifetime.
925 /// The span points to the place the constraint arose. For example,
926 /// it points to the type in a user-given type annotation. If
927 /// there's no sensible span then it's DUMMY_SP.
930 /// An outlives constraint that only has to hold at a single location,
931 /// usually it represents a point where references flow from one spot to
932 /// another (e.g., `x = y`)
937 pub fn from_location(&self) -> Option<Location> {
939 Locations::All(_) => None,
940 Locations::Single(from_location) => Some(*from_location),
944 /// Gets a span representing the location.
945 pub fn span(&self, body: &Body<'_>) -> Span {
947 Locations::All(span) => *span,
948 Locations::Single(l) => body.source_info(*l).span,
953 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
955 infcx: &'a InferCtxt<'a, 'tcx>,
956 body: &'a Body<'tcx>,
957 param_env: ty::ParamEnv<'tcx>,
958 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
959 implicit_region_bound: ty::Region<'tcx>,
960 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
961 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
963 let mut checker = Self {
967 user_type_annotations: &body.user_type_annotations,
970 implicit_region_bound,
972 reported_errors: Default::default(),
973 universal_region_relations,
974 opaque_type_values: FxHashMap::default(),
976 checker.check_user_type_annotations();
980 fn unsized_feature_enabled(&self) -> bool {
981 let features = self.tcx().features();
982 features.unsized_locals || features.unsized_fn_params
985 /// Equate the inferred type and the annotated type for user type annotations
986 fn check_user_type_annotations(&mut self) {
988 "check_user_type_annotations: user_type_annotations={:?}",
989 self.user_type_annotations
991 for user_annotation in self.user_type_annotations {
992 let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation;
993 let (annotation, _) =
994 self.infcx.instantiate_canonical_with_fresh_inference_vars(span, user_ty);
996 UserType::Ty(mut ty) => {
997 ty = self.normalize(ty, Locations::All(span));
999 if let Err(terr) = self.eq_types(
1002 Locations::All(span),
1003 ConstraintCategory::BoringNoLocation,
1008 "bad user type ({:?} = {:?}): {:?}",
1015 self.prove_predicate(
1016 ty::PredicateKind::WellFormed(inferred_ty.into()).to_predicate(self.tcx()),
1017 Locations::All(span),
1018 ConstraintCategory::TypeAnnotation,
1021 UserType::TypeOf(def_id, user_substs) => {
1022 if let Err(terr) = self.fully_perform_op(
1023 Locations::All(span),
1024 ConstraintCategory::BoringNoLocation,
1025 self.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
1034 "bad user type AscribeUserType({:?}, {:?} {:?}): {:?}",
1046 /// Given some operation `op` that manipulates types, proves
1047 /// predicates, or otherwise uses the inference context, executes
1048 /// `op` and then executes all the further obligations that `op`
1049 /// returns. This will yield a set of outlives constraints amongst
1050 /// regions which are extracted and stored as having occurred at
1053 /// **Any `rustc_infer::infer` operations that might generate region
1054 /// constraints should occur within this method so that those
1055 /// constraints can be properly localized!**
1056 fn fully_perform_op<R>(
1058 locations: Locations,
1059 category: ConstraintCategory,
1060 op: impl type_op::TypeOp<'tcx, Output = R>,
1062 let (r, opt_data) = op.fully_perform(self.infcx)?;
1064 if let Some(data) = &opt_data {
1065 self.push_region_constraints(locations, category, data);
1071 fn push_region_constraints(
1073 locations: Locations,
1074 category: ConstraintCategory,
1075 data: &QueryRegionConstraints<'tcx>,
1077 debug!("push_region_constraints: constraints generated at {:?} are {:#?}", locations, data);
1079 constraint_conversion::ConstraintConversion::new(
1081 self.borrowck_context.universal_regions,
1082 self.region_bound_pairs,
1083 Some(self.implicit_region_bound),
1087 &mut self.borrowck_context.constraints,
1092 /// Convenient wrapper around `relate_tys::relate_types` -- see
1093 /// that fn for docs.
1099 locations: Locations,
1100 category: ConstraintCategory,
1102 relate_tys::relate_types(
1110 Some(self.borrowck_context),
1118 locations: Locations,
1119 category: ConstraintCategory,
1121 self.relate_types(sub, ty::Variance::Covariant, sup, locations, category)
1124 /// Try to relate `sub <: sup`; if this fails, instantiate opaque
1125 /// variables in `sub` with their inferred definitions and try
1126 /// again. This is used for opaque types in places (e.g., `let x:
1127 /// impl Foo = ..`).
1128 fn sub_types_or_anon(
1132 locations: Locations,
1133 category: ConstraintCategory,
1135 if let Err(terr) = self.sub_types(sub, sup, locations, category) {
1136 if let ty::Opaque(..) = sup.kind() {
1137 // When you have `let x: impl Foo = ...` in a closure,
1138 // the resulting inferend values are stored with the
1139 // def-id of the base function.
1141 self.tcx().closure_base_def_id(self.body.source.def_id()).expect_local();
1142 return self.eq_opaque_type_and_type(sub, sup, parent_def_id, locations, category);
1154 locations: Locations,
1155 category: ConstraintCategory,
1157 self.relate_types(a, ty::Variance::Invariant, b, locations, category)
1160 fn relate_type_and_user_type(
1164 user_ty: &UserTypeProjection,
1165 locations: Locations,
1166 category: ConstraintCategory,
1169 "relate_type_and_user_type(a={:?}, v={:?}, user_ty={:?}, locations={:?})",
1170 a, v, user_ty, locations,
1173 let annotated_type = self.user_type_annotations[user_ty.base].inferred_ty;
1174 let mut curr_projected_ty = PlaceTy::from_ty(annotated_type);
1176 let tcx = self.infcx.tcx;
1178 for proj in &user_ty.projs {
1179 let projected_ty = curr_projected_ty.projection_ty_core(
1183 |this, field, &()| {
1184 let ty = this.field_ty(tcx, field);
1185 self.normalize(ty, locations)
1188 curr_projected_ty = projected_ty;
1191 "user_ty base: {:?} freshened: {:?} projs: {:?} yields: {:?}",
1192 user_ty.base, annotated_type, user_ty.projs, curr_projected_ty
1195 let ty = curr_projected_ty.ty;
1196 self.relate_types(a, v, ty, locations, category)?;
1201 fn eq_opaque_type_and_type(
1203 revealed_ty: Ty<'tcx>,
1205 anon_owner_def_id: LocalDefId,
1206 locations: Locations,
1207 category: ConstraintCategory,
1210 "eq_opaque_type_and_type( \
1213 revealed_ty, anon_ty
1216 // Fast path for the common case.
1217 if !anon_ty.has_opaque_types() {
1218 if let Err(terr) = self.eq_types(anon_ty, revealed_ty, locations, category) {
1222 "eq_opaque_type_and_type: `{:?}=={:?}` failed with `{:?}`",
1231 let infcx = self.infcx;
1232 let tcx = infcx.tcx;
1233 let param_env = self.param_env;
1234 let body = self.body;
1235 let concrete_opaque_types = &tcx.typeck(anon_owner_def_id).concrete_opaque_types;
1236 let mut opaque_type_values = Vec::new();
1238 debug!("eq_opaque_type_and_type: mir_def_id={:?}", body.source.def_id());
1239 let opaque_type_map = self.fully_perform_op(
1244 let mut obligations = ObligationAccumulator::default();
1246 let dummy_body_id = hir::CRATE_HIR_ID;
1247 let (output_ty, opaque_type_map) =
1248 obligations.add(infcx.instantiate_opaque_types(
1253 locations.span(body),
1256 "eq_opaque_type_and_type: \
1257 instantiated output_ty={:?} \
1258 opaque_type_map={:#?} \
1260 output_ty, opaque_type_map, revealed_ty
1262 // Make sure that the inferred types are well-formed. I'm
1263 // not entirely sure this is needed (the HIR type check
1264 // didn't do this) but it seems sensible to prevent opaque
1265 // types hiding ill-formed types.
1266 obligations.obligations.push(traits::Obligation::new(
1267 ObligationCause::dummy(),
1269 ty::PredicateKind::WellFormed(revealed_ty.into()).to_predicate(infcx.tcx),
1273 .at(&ObligationCause::dummy(), param_env)
1274 .eq(output_ty, revealed_ty)?,
1277 for (&opaque_def_id, opaque_decl) in &opaque_type_map {
1278 let resolved_ty = infcx.resolve_vars_if_possible(opaque_decl.concrete_ty);
1279 let concrete_is_opaque = if let ty::Opaque(def_id, _) = resolved_ty.kind() {
1280 *def_id == opaque_def_id
1284 let opaque_defn_ty = match concrete_opaque_types.get(&opaque_def_id) {
1286 if !concrete_is_opaque {
1287 tcx.sess.delay_span_bug(
1290 "Non-defining use of {:?} with revealed type",
1297 Some(opaque_defn_ty) => opaque_defn_ty,
1299 debug!("opaque_defn_ty = {:?}", opaque_defn_ty);
1300 let subst_opaque_defn_ty =
1301 opaque_defn_ty.concrete_type.subst(tcx, opaque_decl.substs);
1302 let renumbered_opaque_defn_ty =
1303 renumber::renumber_regions(infcx, subst_opaque_defn_ty);
1306 "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?}",
1307 opaque_decl.concrete_ty, resolved_ty, renumbered_opaque_defn_ty,
1310 if !concrete_is_opaque {
1311 // Equate concrete_ty (an inference variable) with
1312 // the renumbered type from typeck.
1315 .at(&ObligationCause::dummy(), param_env)
1316 .eq(opaque_decl.concrete_ty, renumbered_opaque_defn_ty)?,
1318 opaque_type_values.push((
1320 ty::ResolvedOpaqueTy {
1321 concrete_type: renumbered_opaque_defn_ty,
1322 substs: opaque_decl.substs,
1326 // We're using an opaque `impl Trait` type without
1327 // 'revealing' it. For example, code like this:
1329 // type Foo = impl Debug;
1330 // fn foo1() -> Foo { ... }
1331 // fn foo2() -> Foo { foo1() }
1333 // In `foo2`, we're not revealing the type of `Foo` - we're
1334 // just treating it as the opaque type.
1336 // When this occurs, we do *not* want to try to equate
1337 // the concrete type with the underlying defining type
1338 // of the opaque type - this will always fail, since
1339 // the defining type of an opaque type is always
1340 // some other type (e.g. not itself)
1341 // Essentially, none of the normal obligations apply here -
1342 // we're just passing around some unknown opaque type,
1343 // without actually looking at the underlying type it
1344 // gets 'revealed' into
1346 "eq_opaque_type_and_type: non-defining use of {:?}",
1352 debug!("eq_opaque_type_and_type: equated");
1355 value: Some(opaque_type_map),
1356 obligations: obligations.into_vec(),
1359 || "input_output".to_string(),
1363 self.opaque_type_values.extend(opaque_type_values);
1365 let universal_region_relations = self.universal_region_relations;
1367 // Finally, if we instantiated the anon types successfully, we
1368 // have to solve any bounds (e.g., `-> impl Iterator` needs to
1369 // prove that `T: Iterator` where `T` is the type we
1370 // instantiated it with).
1371 if let Some(opaque_type_map) = opaque_type_map {
1372 for (opaque_def_id, opaque_decl) in opaque_type_map {
1373 self.fully_perform_op(
1375 ConstraintCategory::OpaqueType,
1378 infcx.constrain_opaque_type(
1381 GenerateMemberConstraints::IfNoStaticBound,
1382 universal_region_relations,
1384 Ok(InferOk { value: (), obligations: vec![] })
1386 || "opaque_type_map".to_string(),
1394 fn tcx(&self) -> TyCtxt<'tcx> {
1398 fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Location) {
1399 debug!("check_stmt: {:?}", stmt);
1400 let tcx = self.tcx();
1402 StatementKind::Assign(box (ref place, ref rv)) => {
1403 // Assignments to temporaries are not "interesting";
1404 // they are not caused by the user, but rather artifacts
1405 // of lowering. Assignments to other sorts of places *are* interesting
1407 let category = match place.as_local() {
1408 Some(RETURN_PLACE) => {
1409 if let BorrowCheckContext {
1411 UniversalRegions { defining_ty: DefiningTy::Const(def_id, _), .. },
1413 } = self.borrowck_context
1415 if tcx.is_static(*def_id) {
1416 ConstraintCategory::UseAsStatic
1418 ConstraintCategory::UseAsConst
1421 ConstraintCategory::Return(ReturnConstraint::Normal)
1424 Some(l) if !body.local_decls[l].is_user_variable() => {
1425 ConstraintCategory::Boring
1427 _ => ConstraintCategory::Assignment,
1430 let place_ty = place.ty(body, tcx).ty;
1431 let place_ty = self.normalize(place_ty, location);
1432 let rv_ty = rv.ty(body, tcx);
1433 let rv_ty = self.normalize(rv_ty, location);
1435 self.sub_types_or_anon(rv_ty, place_ty, location.to_locations(), category)
1440 "bad assignment ({:?} = {:?}): {:?}",
1447 if let Some(annotation_index) = self.rvalue_user_ty(rv) {
1448 if let Err(terr) = self.relate_type_and_user_type(
1450 ty::Variance::Invariant,
1451 &UserTypeProjection { base: annotation_index, projs: vec![] },
1452 location.to_locations(),
1453 ConstraintCategory::Boring,
1455 let annotation = &self.user_type_annotations[annotation_index];
1459 "bad user type on rvalue ({:?} = {:?}): {:?}",
1467 self.check_rvalue(body, rv, location);
1468 if !self.unsized_feature_enabled() {
1469 let trait_ref = ty::TraitRef {
1470 def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)),
1471 substs: tcx.mk_substs_trait(place_ty, &[]),
1473 self.prove_trait_ref(
1475 location.to_locations(),
1476 ConstraintCategory::SizedBound,
1480 StatementKind::SetDiscriminant { ref place, variant_index } => {
1481 let place_type = place.ty(body, tcx).ty;
1482 let adt = match place_type.kind() {
1483 ty::Adt(adt, _) if adt.is_enum() => adt,
1486 stmt.source_info.span,
1487 "bad set discriminant ({:?} = {:?}): lhs is not an enum",
1493 if variant_index.as_usize() >= adt.variants.len() {
1495 stmt.source_info.span,
1496 "bad set discriminant ({:?} = {:?}): value of of range",
1502 StatementKind::AscribeUserType(box (ref place, ref projection), variance) => {
1503 let place_ty = place.ty(body, tcx).ty;
1504 if let Err(terr) = self.relate_type_and_user_type(
1508 Locations::All(stmt.source_info.span),
1509 ConstraintCategory::TypeAnnotation,
1511 let annotation = &self.user_type_annotations[projection.base];
1515 "bad type assert ({:?} <: {:?} with projections {:?}): {:?}",
1523 StatementKind::FakeRead(..)
1524 | StatementKind::StorageLive(..)
1525 | StatementKind::StorageDead(..)
1526 | StatementKind::LlvmInlineAsm { .. }
1527 | StatementKind::Retag { .. }
1528 | StatementKind::Coverage(..)
1529 | StatementKind::Nop => {}
1533 fn check_terminator(
1536 term: &Terminator<'tcx>,
1537 term_location: Location,
1539 debug!("check_terminator: {:?}", term);
1540 let tcx = self.tcx();
1542 TerminatorKind::Goto { .. }
1543 | TerminatorKind::Resume
1544 | TerminatorKind::Abort
1545 | TerminatorKind::Return
1546 | TerminatorKind::GeneratorDrop
1547 | TerminatorKind::Unreachable
1548 | TerminatorKind::Drop { .. }
1549 | TerminatorKind::FalseEdge { .. }
1550 | TerminatorKind::FalseUnwind { .. }
1551 | TerminatorKind::InlineAsm { .. } => {
1552 // no checks needed for these
1555 TerminatorKind::DropAndReplace { ref place, ref value, target: _, unwind: _ } => {
1556 let place_ty = place.ty(body, tcx).ty;
1557 let rv_ty = value.ty(body, tcx);
1559 let locations = term_location.to_locations();
1561 self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
1566 "bad DropAndReplace ({:?} = {:?}): {:?}",
1573 TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
1574 let discr_ty = discr.ty(body, tcx);
1575 if let Err(terr) = self.sub_types(
1578 term_location.to_locations(),
1579 ConstraintCategory::Assignment,
1584 "bad SwitchInt ({:?} on {:?}): {:?}",
1590 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
1591 span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
1593 // FIXME: check the values
1595 TerminatorKind::Call { ref func, ref args, ref destination, from_hir_call, .. } => {
1596 let func_ty = func.ty(body, tcx);
1597 debug!("check_terminator: call, func_ty={:?}", func_ty);
1598 let sig = match func_ty.kind() {
1599 ty::FnDef(..) | ty::FnPtr(_) => func_ty.fn_sig(tcx),
1601 span_mirbug!(self, term, "call to non-function {:?}", func_ty);
1605 let (sig, map) = self.infcx.replace_bound_vars_with_fresh_vars(
1606 term.source_info.span,
1607 LateBoundRegionConversionTime::FnCall,
1610 let sig = self.normalize(sig, term_location);
1611 self.check_call_dest(body, term, &sig, destination, term_location);
1613 self.prove_predicates(
1614 sig.inputs_and_output.iter().map(|ty| ty::PredicateKind::WellFormed(ty.into())),
1615 term_location.to_locations(),
1616 ConstraintCategory::Boring,
1619 // The ordinary liveness rules will ensure that all
1620 // regions in the type of the callee are live here. We
1621 // then further constrain the late-bound regions that
1622 // were instantiated at the call site to be live as
1623 // well. The resulting is that all the input (and
1624 // output) types in the signature must be live, since
1625 // all the inputs that fed into it were live.
1626 for &late_bound_region in map.values() {
1628 self.borrowck_context.universal_regions.to_region_vid(late_bound_region);
1629 self.borrowck_context
1631 .liveness_constraints
1632 .add_element(region_vid, term_location);
1635 self.check_call_inputs(body, term, &sig, args, term_location, from_hir_call);
1637 TerminatorKind::Assert { ref cond, ref msg, .. } => {
1638 let cond_ty = cond.ty(body, tcx);
1639 if cond_ty != tcx.types.bool {
1640 span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
1643 if let AssertKind::BoundsCheck { ref len, ref index } = *msg {
1644 if len.ty(body, tcx) != tcx.types.usize {
1645 span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
1647 if index.ty(body, tcx) != tcx.types.usize {
1648 span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
1652 TerminatorKind::Yield { ref value, .. } => {
1653 let value_ty = value.ty(body, tcx);
1654 match body.yield_ty {
1655 None => span_mirbug!(self, term, "yield in non-generator"),
1657 if let Err(terr) = self.sub_types(
1660 term_location.to_locations(),
1661 ConstraintCategory::Yield,
1666 "type of yield value is {:?}, but the yield type is {:?}: {:?}",
1681 term: &Terminator<'tcx>,
1682 sig: &ty::FnSig<'tcx>,
1683 destination: &Option<(Place<'tcx>, BasicBlock)>,
1684 term_location: Location,
1686 let tcx = self.tcx();
1687 match *destination {
1688 Some((ref dest, _target_block)) => {
1689 let dest_ty = dest.ty(body, tcx).ty;
1690 let dest_ty = self.normalize(dest_ty, term_location);
1691 let category = match dest.as_local() {
1692 Some(RETURN_PLACE) => {
1693 if let BorrowCheckContext {
1695 UniversalRegions { defining_ty: DefiningTy::Const(def_id, _), .. },
1697 } = self.borrowck_context
1699 if tcx.is_static(*def_id) {
1700 ConstraintCategory::UseAsStatic
1702 ConstraintCategory::UseAsConst
1705 ConstraintCategory::Return(ReturnConstraint::Normal)
1708 Some(l) if !body.local_decls[l].is_user_variable() => {
1709 ConstraintCategory::Boring
1711 _ => ConstraintCategory::Assignment,
1714 let locations = term_location.to_locations();
1717 self.sub_types_or_anon(sig.output(), dest_ty, locations, category)
1722 "call dest mismatch ({:?} <- {:?}): {:?}",
1729 // When `unsized_fn_params` and `unsized_locals` are both not enabled,
1730 // this check is done at `check_local`.
1731 if self.unsized_feature_enabled() {
1732 let span = term.source_info.span;
1733 self.ensure_place_sized(dest_ty, span);
1739 .conservative_is_privately_uninhabited(self.param_env.and(sig.output()))
1741 span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
1747 fn check_call_inputs(
1750 term: &Terminator<'tcx>,
1751 sig: &ty::FnSig<'tcx>,
1752 args: &[Operand<'tcx>],
1753 term_location: Location,
1754 from_hir_call: bool,
1756 debug!("check_call_inputs({:?}, {:?})", sig, args);
1757 if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.c_variadic) {
1758 span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
1760 for (n, (fn_arg, op_arg)) in sig.inputs().iter().zip(args).enumerate() {
1761 let op_arg_ty = op_arg.ty(body, self.tcx());
1762 let op_arg_ty = self.normalize(op_arg_ty, term_location);
1763 let category = if from_hir_call {
1764 ConstraintCategory::CallArgument
1766 ConstraintCategory::Boring
1769 self.sub_types(op_arg_ty, fn_arg, term_location.to_locations(), category)
1774 "bad arg #{:?} ({:?} <- {:?}): {:?}",
1784 fn check_iscleanup(&mut self, body: &Body<'tcx>, block_data: &BasicBlockData<'tcx>) {
1785 let is_cleanup = block_data.is_cleanup;
1786 self.last_span = block_data.terminator().source_info.span;
1787 match block_data.terminator().kind {
1788 TerminatorKind::Goto { target } => {
1789 self.assert_iscleanup(body, block_data, target, is_cleanup)
1791 TerminatorKind::SwitchInt { ref targets, .. } => {
1792 for target in targets.all_targets() {
1793 self.assert_iscleanup(body, block_data, *target, is_cleanup);
1796 TerminatorKind::Resume => {
1798 span_mirbug!(self, block_data, "resume on non-cleanup block!")
1801 TerminatorKind::Abort => {
1803 span_mirbug!(self, block_data, "abort on non-cleanup block!")
1806 TerminatorKind::Return => {
1808 span_mirbug!(self, block_data, "return on cleanup block")
1811 TerminatorKind::GeneratorDrop { .. } => {
1813 span_mirbug!(self, block_data, "generator_drop in cleanup block")
1816 TerminatorKind::Yield { resume, drop, .. } => {
1818 span_mirbug!(self, block_data, "yield in cleanup block")
1820 self.assert_iscleanup(body, block_data, resume, is_cleanup);
1821 if let Some(drop) = drop {
1822 self.assert_iscleanup(body, block_data, drop, is_cleanup);
1825 TerminatorKind::Unreachable => {}
1826 TerminatorKind::Drop { target, unwind, .. }
1827 | TerminatorKind::DropAndReplace { target, unwind, .. }
1828 | TerminatorKind::Assert { target, cleanup: unwind, .. } => {
1829 self.assert_iscleanup(body, block_data, target, is_cleanup);
1830 if let Some(unwind) = unwind {
1832 span_mirbug!(self, block_data, "unwind on cleanup block")
1834 self.assert_iscleanup(body, block_data, unwind, true);
1837 TerminatorKind::Call { ref destination, cleanup, .. } => {
1838 if let &Some((_, target)) = destination {
1839 self.assert_iscleanup(body, block_data, target, is_cleanup);
1841 if let Some(cleanup) = cleanup {
1843 span_mirbug!(self, block_data, "cleanup on cleanup block")
1845 self.assert_iscleanup(body, block_data, cleanup, true);
1848 TerminatorKind::FalseEdge { real_target, imaginary_target } => {
1849 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
1850 self.assert_iscleanup(body, block_data, imaginary_target, is_cleanup);
1852 TerminatorKind::FalseUnwind { real_target, unwind } => {
1853 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
1854 if let Some(unwind) = unwind {
1856 span_mirbug!(self, block_data, "cleanup in cleanup block via false unwind");
1858 self.assert_iscleanup(body, block_data, unwind, true);
1861 TerminatorKind::InlineAsm { destination, .. } => {
1862 if let Some(target) = destination {
1863 self.assert_iscleanup(body, block_data, target, is_cleanup);
1869 fn assert_iscleanup(
1872 ctxt: &dyn fmt::Debug,
1876 if body[bb].is_cleanup != iscleanuppad {
1877 span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}", bb, iscleanuppad);
1881 fn check_local(&mut self, body: &Body<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) {
1882 match body.local_kind(local) {
1883 LocalKind::ReturnPointer | LocalKind::Arg => {
1884 // return values of normal functions are required to be
1885 // sized by typeck, but return values of ADT constructors are
1886 // not because we don't include a `Self: Sized` bounds on them.
1888 // Unbound parts of arguments were never required to be Sized
1889 // - maybe we should make that a warning.
1892 LocalKind::Var | LocalKind::Temp => {}
1895 // When `unsized_fn_params` or `unsized_locals` is enabled, only function calls
1896 // and nullary ops are checked in `check_call_dest`.
1897 if !self.unsized_feature_enabled() {
1898 let span = local_decl.source_info.span;
1899 let ty = local_decl.ty;
1900 self.ensure_place_sized(ty, span);
1904 fn ensure_place_sized(&mut self, ty: Ty<'tcx>, span: Span) {
1905 let tcx = self.tcx();
1907 // Erase the regions from `ty` to get a global type. The
1908 // `Sized` bound in no way depends on precise regions, so this
1909 // shouldn't affect `is_sized`.
1910 let erased_ty = tcx.erase_regions(ty);
1911 if !erased_ty.is_sized(tcx.at(span), self.param_env) {
1912 // in current MIR construction, all non-control-flow rvalue
1913 // expressions evaluate through `as_temp` or `into` a return
1914 // slot or local, so to find all unsized rvalues it is enough
1915 // to check all temps, return slots and locals.
1916 if self.reported_errors.replace((ty, span)).is_none() {
1917 let mut diag = struct_span_err!(
1921 "cannot move a value of type {0}: the size of {0} \
1922 cannot be statically determined",
1926 // While this is located in `nll::typeck` this error is not
1927 // an NLL error, it's a required check to prevent creation
1928 // of unsized rvalues in certain cases:
1929 // * operand of a box expression
1930 // * callee in a call expression
1936 fn aggregate_field_ty(
1938 ak: &AggregateKind<'tcx>,
1941 ) -> Result<Ty<'tcx>, FieldAccessError> {
1942 let tcx = self.tcx();
1945 AggregateKind::Adt(def, variant_index, substs, _, active_field_index) => {
1946 let variant = &def.variants[variant_index];
1947 let adj_field_index = active_field_index.unwrap_or(field_index);
1948 if let Some(field) = variant.fields.get(adj_field_index) {
1949 Ok(self.normalize(field.ty(tcx, substs), location))
1951 Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
1954 AggregateKind::Closure(_, substs) => {
1955 match substs.as_closure().upvar_tys().nth(field_index) {
1957 None => Err(FieldAccessError::OutOfRange {
1958 field_count: substs.as_closure().upvar_tys().count(),
1962 AggregateKind::Generator(_, substs, _) => {
1963 // It doesn't make sense to look at a field beyond the prefix;
1964 // these require a variant index, and are not initialized in
1965 // aggregate rvalues.
1966 match substs.as_generator().prefix_tys().nth(field_index) {
1968 None => Err(FieldAccessError::OutOfRange {
1969 field_count: substs.as_generator().prefix_tys().count(),
1973 AggregateKind::Array(ty) => Ok(ty),
1974 AggregateKind::Tuple => {
1975 unreachable!("This should have been covered in check_rvalues");
1980 fn check_rvalue(&mut self, body: &Body<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
1981 let tcx = self.tcx();
1984 Rvalue::Aggregate(ak, ops) => {
1985 self.check_aggregate_rvalue(&body, rvalue, ak, ops, location)
1988 Rvalue::Repeat(operand, len) => {
1989 // If the length cannot be evaluated we must assume that the length can be larger
1991 // If the length is larger than 1, the repeat expression will need to copy the
1992 // element, so we require the `Copy` trait.
1993 if len.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1995 Operand::Copy(..) | Operand::Constant(..) => {
1996 // These are always okay: direct use of a const, or a value that can evidently be copied.
1998 Operand::Move(place) => {
1999 // Make sure that repeated elements implement `Copy`.
2000 let span = body.source_info(location).span;
2001 let ty = operand.ty(body, tcx);
2002 if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span) {
2003 let ccx = ConstCx::new_with_param_env(tcx, body, self.param_env);
2005 is_const_fn_in_array_repeat_expression(&ccx, &place, &body);
2007 debug!("check_rvalue: is_const_fn={:?}", is_const_fn);
2009 let def_id = body.source.def_id().expect_local();
2010 self.infcx.report_selection_error(
2011 &traits::Obligation::new(
2012 ObligationCause::new(
2014 self.tcx().hir().local_def_id_to_hir_id(def_id),
2015 traits::ObligationCauseCode::RepeatVec(is_const_fn),
2018 ty::Binder::bind(ty::TraitRef::new(
2019 self.tcx().require_lang_item(
2021 Some(self.last_span),
2023 tcx.mk_substs_trait(ty, &[]),
2026 .to_predicate(self.tcx()),
2028 &traits::SelectionError::Unimplemented,
2038 Rvalue::NullaryOp(_, ty) => {
2039 // Even with unsized locals cannot box an unsized value.
2040 if self.unsized_feature_enabled() {
2041 let span = body.source_info(location).span;
2042 self.ensure_place_sized(ty, span);
2045 let trait_ref = ty::TraitRef {
2046 def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)),
2047 substs: tcx.mk_substs_trait(ty, &[]),
2050 self.prove_trait_ref(
2052 location.to_locations(),
2053 ConstraintCategory::SizedBound,
2057 Rvalue::Cast(cast_kind, op, ty) => {
2059 CastKind::Pointer(PointerCast::ReifyFnPointer) => {
2060 let fn_sig = op.ty(body, tcx).fn_sig(tcx);
2062 // The type that we see in the fcx is like
2063 // `foo::<'a, 'b>`, where `foo` is the path to a
2064 // function definition. When we extract the
2065 // signature, it comes from the `fn_sig` query,
2066 // and hence may contain unnormalized results.
2067 let fn_sig = self.normalize(fn_sig, location);
2069 let ty_fn_ptr_from = tcx.mk_fn_ptr(fn_sig);
2071 if let Err(terr) = self.eq_types(
2074 location.to_locations(),
2075 ConstraintCategory::Cast,
2080 "equating {:?} with {:?} yields {:?}",
2088 CastKind::Pointer(PointerCast::ClosureFnPointer(unsafety)) => {
2089 let sig = match op.ty(body, tcx).kind() {
2090 ty::Closure(_, substs) => substs.as_closure().sig(),
2093 let ty_fn_ptr_from = tcx.mk_fn_ptr(tcx.signature_unclosure(sig, *unsafety));
2095 if let Err(terr) = self.eq_types(
2098 location.to_locations(),
2099 ConstraintCategory::Cast,
2104 "equating {:?} with {:?} yields {:?}",
2112 CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
2113 let fn_sig = op.ty(body, tcx).fn_sig(tcx);
2115 // The type that we see in the fcx is like
2116 // `foo::<'a, 'b>`, where `foo` is the path to a
2117 // function definition. When we extract the
2118 // signature, it comes from the `fn_sig` query,
2119 // and hence may contain unnormalized results.
2120 let fn_sig = self.normalize(fn_sig, location);
2122 let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
2124 if let Err(terr) = self.eq_types(
2127 location.to_locations(),
2128 ConstraintCategory::Cast,
2133 "equating {:?} with {:?} yields {:?}",
2141 CastKind::Pointer(PointerCast::Unsize) => {
2143 let trait_ref = ty::TraitRef {
2145 .require_lang_item(LangItem::CoerceUnsized, Some(self.last_span)),
2146 substs: tcx.mk_substs_trait(op.ty(body, tcx), &[ty.into()]),
2149 self.prove_trait_ref(
2151 location.to_locations(),
2152 ConstraintCategory::Cast,
2156 CastKind::Pointer(PointerCast::MutToConstPointer) => {
2157 let ty_from = match op.ty(body, tcx).kind() {
2158 ty::RawPtr(ty::TypeAndMut {
2160 mutbl: hir::Mutability::Mut,
2166 "unexpected base type for cast {:?}",
2172 let ty_to = match ty.kind() {
2173 ty::RawPtr(ty::TypeAndMut {
2175 mutbl: hir::Mutability::Not,
2181 "unexpected target type for cast {:?}",
2187 if let Err(terr) = self.sub_types(
2190 location.to_locations(),
2191 ConstraintCategory::Cast,
2196 "relating {:?} with {:?} yields {:?}",
2204 CastKind::Pointer(PointerCast::ArrayToPointer) => {
2205 let ty_from = op.ty(body, tcx);
2207 let opt_ty_elem_mut = match ty_from.kind() {
2208 ty::RawPtr(ty::TypeAndMut { mutbl: array_mut, ty: array_ty }) => {
2209 match array_ty.kind() {
2210 ty::Array(ty_elem, _) => Some((ty_elem, *array_mut)),
2217 let (ty_elem, ty_mut) = match opt_ty_elem_mut {
2218 Some(ty_elem_mut) => ty_elem_mut,
2223 "ArrayToPointer cast from unexpected type {:?}",
2230 let (ty_to, ty_to_mut) = match ty.kind() {
2231 ty::RawPtr(ty::TypeAndMut { mutbl: ty_to_mut, ty: ty_to }) => {
2238 "ArrayToPointer cast to unexpected type {:?}",
2245 if ty_to_mut == Mutability::Mut && ty_mut == Mutability::Not {
2249 "ArrayToPointer cast from const {:?} to mut {:?}",
2256 if let Err(terr) = self.sub_types(
2259 location.to_locations(),
2260 ConstraintCategory::Cast,
2265 "relating {:?} with {:?} yields {:?}",
2274 let ty_from = op.ty(body, tcx);
2275 let cast_ty_from = CastTy::from_ty(ty_from);
2276 let cast_ty_to = CastTy::from_ty(ty);
2277 match (cast_ty_from, cast_ty_to) {
2279 | (_, None | Some(CastTy::FnPtr))
2280 | (Some(CastTy::Float), Some(CastTy::Ptr(_)))
2281 | (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Float)) => {
2282 span_mirbug!(self, rvalue, "Invalid cast {:?} -> {:?}", ty_from, ty,)
2285 Some(CastTy::Int(_)),
2286 Some(CastTy::Int(_) | CastTy::Float | CastTy::Ptr(_)),
2288 | (Some(CastTy::Float), Some(CastTy::Int(_) | CastTy::Float))
2289 | (Some(CastTy::Ptr(_)), Some(CastTy::Int(_) | CastTy::Ptr(_)))
2290 | (Some(CastTy::FnPtr), Some(CastTy::Int(_) | CastTy::Ptr(_))) => (),
2296 Rvalue::Ref(region, _borrow_kind, borrowed_place) => {
2297 self.add_reborrow_constraint(&body, location, region, borrowed_place);
2301 BinOp::Eq | BinOp::Ne | BinOp::Lt | BinOp::Le | BinOp::Gt | BinOp::Ge,
2305 let ty_left = left.ty(body, tcx);
2306 match ty_left.kind() {
2307 // Types with regions are comparable if they have a common super-type.
2308 ty::RawPtr(_) | ty::FnPtr(_) => {
2309 let ty_right = right.ty(body, tcx);
2310 let common_ty = self.infcx.next_ty_var(TypeVariableOrigin {
2311 kind: TypeVariableOriginKind::MiscVariable,
2312 span: body.source_info(location).span,
2316 ty::Variance::Contravariant,
2318 location.to_locations(),
2319 ConstraintCategory::Boring,
2321 .unwrap_or_else(|err| {
2322 bug!("Could not equate type variable with {:?}: {:?}", ty_left, err)
2324 if let Err(terr) = self.relate_types(
2326 ty::Variance::Contravariant,
2328 location.to_locations(),
2329 ConstraintCategory::Boring,
2334 "unexpected comparison types {:?} and {:?} yields {:?}",
2341 // For types with no regions we can just check that the
2342 // both operands have the same type.
2343 ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char | ty::Float(_)
2344 if ty_left == right.ty(body, tcx) => {}
2345 // Other types are compared by trait methods, not by
2346 // `Rvalue::BinaryOp`.
2350 "unexpected comparison types {:?} and {:?}",
2357 Rvalue::AddressOf(..)
2358 | Rvalue::ThreadLocalRef(..)
2361 | Rvalue::BinaryOp(..)
2362 | Rvalue::CheckedBinaryOp(..)
2363 | Rvalue::UnaryOp(..)
2364 | Rvalue::Discriminant(..) => {}
2368 /// If this rvalue supports a user-given type annotation, then
2369 /// extract and return it. This represents the final type of the
2370 /// rvalue and will be unified with the inferred type.
2371 fn rvalue_user_ty(&self, rvalue: &Rvalue<'tcx>) -> Option<UserTypeAnnotationIndex> {
2374 | Rvalue::ThreadLocalRef(_)
2375 | Rvalue::Repeat(..)
2377 | Rvalue::AddressOf(..)
2380 | Rvalue::BinaryOp(..)
2381 | Rvalue::CheckedBinaryOp(..)
2382 | Rvalue::NullaryOp(..)
2383 | Rvalue::UnaryOp(..)
2384 | Rvalue::Discriminant(..) => None,
2386 Rvalue::Aggregate(aggregate, _) => match **aggregate {
2387 AggregateKind::Adt(_, _, _, user_ty, _) => user_ty,
2388 AggregateKind::Array(_) => None,
2389 AggregateKind::Tuple => None,
2390 AggregateKind::Closure(_, _) => None,
2391 AggregateKind::Generator(_, _, _) => None,
2396 fn check_aggregate_rvalue(
2399 rvalue: &Rvalue<'tcx>,
2400 aggregate_kind: &AggregateKind<'tcx>,
2401 operands: &[Operand<'tcx>],
2404 let tcx = self.tcx();
2406 self.prove_aggregate_predicates(aggregate_kind, location);
2408 if *aggregate_kind == AggregateKind::Tuple {
2409 // tuple rvalue field type is always the type of the op. Nothing to check here.
2413 for (i, operand) in operands.iter().enumerate() {
2414 let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
2415 Ok(field_ty) => field_ty,
2416 Err(FieldAccessError::OutOfRange { field_count }) => {
2420 "accessed field #{} but variant only has {}",
2427 let operand_ty = operand.ty(body, tcx);
2428 let operand_ty = self.normalize(operand_ty, location);
2430 if let Err(terr) = self.sub_types(
2433 location.to_locations(),
2434 ConstraintCategory::Boring,
2439 "{:?} is not a subtype of {:?}: {:?}",
2448 /// Adds the constraints that arise from a borrow expression `&'a P` at the location `L`.
2452 /// - `location`: the location `L` where the borrow expression occurs
2453 /// - `borrow_region`: the region `'a` associated with the borrow
2454 /// - `borrowed_place`: the place `P` being borrowed
2455 fn add_reborrow_constraint(
2459 borrow_region: ty::Region<'tcx>,
2460 borrowed_place: &Place<'tcx>,
2462 // These constraints are only meaningful during borrowck:
2463 let BorrowCheckContext { borrow_set, location_table, all_facts, constraints, .. } =
2464 self.borrowck_context;
2466 // In Polonius mode, we also push a `borrow_region` fact
2467 // linking the loan to the region (in some cases, though,
2468 // there is no loan associated with this borrow expression --
2469 // that occurs when we are borrowing an unsafe place, for
2471 if let Some(all_facts) = all_facts {
2472 let _prof_timer = self.infcx.tcx.prof.generic_activity("polonius_fact_generation");
2473 if let Some(borrow_index) = borrow_set.get_index_of(&location) {
2474 let region_vid = borrow_region.to_region_vid();
2475 all_facts.borrow_region.push((
2478 location_table.mid_index(location),
2483 // If we are reborrowing the referent of another reference, we
2484 // need to add outlives relationships. In a case like `&mut
2485 // *p`, where the `p` has type `&'b mut Foo`, for example, we
2486 // need to ensure that `'b: 'a`.
2489 "add_reborrow_constraint({:?}, {:?}, {:?})",
2490 location, borrow_region, borrowed_place
2493 let mut cursor = borrowed_place.projection.as_ref();
2494 let tcx = self.infcx.tcx;
2495 let field = path_utils::is_upvar_field_projection(
2497 &self.borrowck_context.upvars,
2498 borrowed_place.as_ref(),
2501 let category = if let Some(field) = field {
2502 let var_hir_id = self.borrowck_context.upvars[field.index()].place.get_root_variable();
2503 // FIXME(project-rfc-2229#8): Use Place for better diagnostics
2504 ConstraintCategory::ClosureUpvar(var_hir_id)
2506 ConstraintCategory::Boring
2509 while let [proj_base @ .., elem] = cursor {
2512 debug!("add_reborrow_constraint - iteration {:?}", elem);
2515 ProjectionElem::Deref => {
2516 let base_ty = Place::ty_from(borrowed_place.local, proj_base, body, tcx).ty;
2518 debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
2519 match base_ty.kind() {
2520 ty::Ref(ref_region, _, mutbl) => {
2521 constraints.outlives_constraints.push(OutlivesConstraint {
2522 sup: ref_region.to_region_vid(),
2523 sub: borrow_region.to_region_vid(),
2524 locations: location.to_locations(),
2529 hir::Mutability::Not => {
2530 // Immutable reference. We don't need the base
2531 // to be valid for the entire lifetime of
2535 hir::Mutability::Mut => {
2536 // Mutable reference. We *do* need the base
2537 // to be valid, because after the base becomes
2538 // invalid, someone else can use our mutable deref.
2540 // This is in order to make the following function
2543 // fn unsafe_deref<'a, 'b>(x: &'a &'b mut T) -> &'b mut T {
2548 // As otherwise you could clone `&mut T` using the
2549 // following function:
2551 // fn bad(x: &mut T) -> (&mut T, &mut T) {
2552 // let my_clone = unsafe_deref(&'a x);
2561 // deref of raw pointer, guaranteed to be valid
2564 ty::Adt(def, _) if def.is_box() => {
2565 // deref of `Box`, need the base to be valid - propagate
2567 _ => bug!("unexpected deref ty {:?} in {:?}", base_ty, borrowed_place),
2570 ProjectionElem::Field(..)
2571 | ProjectionElem::Downcast(..)
2572 | ProjectionElem::Index(..)
2573 | ProjectionElem::ConstantIndex { .. }
2574 | ProjectionElem::Subslice { .. } => {
2575 // other field access
2581 fn prove_aggregate_predicates(
2583 aggregate_kind: &AggregateKind<'tcx>,
2586 let tcx = self.tcx();
2589 "prove_aggregate_predicates(aggregate_kind={:?}, location={:?})",
2590 aggregate_kind, location
2593 let instantiated_predicates = match aggregate_kind {
2594 AggregateKind::Adt(def, _, substs, _, _) => {
2595 tcx.predicates_of(def.did).instantiate(tcx, substs)
2598 // For closures, we have some **extra requirements** we
2600 // have to check. In particular, in their upvars and
2601 // signatures, closures often reference various regions
2602 // from the surrounding function -- we call those the
2603 // closure's free regions. When we borrow-check (and hence
2604 // region-check) closures, we may find that the closure
2605 // requires certain relationships between those free
2606 // regions. However, because those free regions refer to
2607 // portions of the CFG of their caller, the closure is not
2608 // in a position to verify those relationships. In that
2609 // case, the requirements get "propagated" to us, and so
2610 // we have to solve them here where we instantiate the
2613 // Despite the opacity of the previous parapgrah, this is
2614 // actually relatively easy to understand in terms of the
2615 // desugaring. A closure gets desugared to a struct, and
2616 // these extra requirements are basically like where
2617 // clauses on the struct.
2618 AggregateKind::Closure(def_id, substs)
2619 | AggregateKind::Generator(def_id, substs, _) => {
2620 self.prove_closure_bounds(tcx, def_id.expect_local(), substs, location)
2623 AggregateKind::Array(_) | AggregateKind::Tuple => ty::InstantiatedPredicates::empty(),
2626 self.normalize_and_prove_instantiated_predicates(
2627 instantiated_predicates,
2628 location.to_locations(),
2632 fn prove_closure_bounds(
2636 substs: SubstsRef<'tcx>,
2638 ) -> ty::InstantiatedPredicates<'tcx> {
2639 if let Some(ref closure_region_requirements) = tcx.mir_borrowck(def_id).closure_requirements
2641 let closure_constraints = QueryRegionConstraints {
2642 outlives: closure_region_requirements.apply_requirements(
2648 // Presently, closures never propagate member
2649 // constraints to their parents -- they are enforced
2650 // locally. This is largely a non-issue as member
2651 // constraints only come from `-> impl Trait` and
2652 // friends which don't appear (thus far...) in
2654 member_constraints: vec![],
2657 let bounds_mapping = closure_constraints
2661 .filter_map(|(idx, constraint)| {
2662 let ty::OutlivesPredicate(k1, r2) =
2663 constraint.no_bound_vars().unwrap_or_else(|| {
2664 bug!("query_constraint {:?} contained bound vars", constraint,);
2668 GenericArgKind::Lifetime(r1) => {
2669 // constraint is r1: r2
2670 let r1_vid = self.borrowck_context.universal_regions.to_region_vid(r1);
2671 let r2_vid = self.borrowck_context.universal_regions.to_region_vid(r2);
2672 let outlives_requirements =
2673 &closure_region_requirements.outlives_requirements[idx];
2676 (outlives_requirements.category, outlives_requirements.blame_span),
2679 GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
2687 .closure_bounds_mapping
2688 .insert(location, bounds_mapping);
2689 assert!(existing.is_none(), "Multiple closures at the same location.");
2691 self.push_region_constraints(
2692 location.to_locations(),
2693 ConstraintCategory::ClosureBounds,
2694 &closure_constraints,
2698 tcx.predicates_of(def_id).instantiate(tcx, substs)
2703 trait_ref: ty::TraitRef<'tcx>,
2704 locations: Locations,
2705 category: ConstraintCategory,
2707 self.prove_predicates(
2708 Some(ty::PredicateKind::Trait(
2709 ty::TraitPredicate { trait_ref },
2710 hir::Constness::NotConst,
2717 fn normalize_and_prove_instantiated_predicates(
2719 instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
2720 locations: Locations,
2722 for predicate in instantiated_predicates.predicates {
2723 let predicate = self.normalize(predicate, locations);
2724 self.prove_predicate(predicate, locations, ConstraintCategory::Boring);
2728 fn prove_predicates(
2730 predicates: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
2731 locations: Locations,
2732 category: ConstraintCategory,
2734 for predicate in predicates {
2735 let predicate = predicate.to_predicate(self.tcx());
2736 debug!("prove_predicates(predicate={:?}, locations={:?})", predicate, locations,);
2738 self.prove_predicate(predicate, locations, category);
2744 predicate: ty::Predicate<'tcx>,
2745 locations: Locations,
2746 category: ConstraintCategory,
2748 debug!("prove_predicate(predicate={:?}, location={:?})", predicate, locations,);
2750 let param_env = self.param_env;
2751 self.fully_perform_op(
2754 param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
2756 .unwrap_or_else(|NoSolution| {
2757 span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
2761 fn typeck_mir(&mut self, body: &Body<'tcx>) {
2762 self.last_span = body.span;
2763 debug!("run_on_mir: {:?}", body.span);
2765 for (local, local_decl) in body.local_decls.iter_enumerated() {
2766 self.check_local(&body, local, local_decl);
2769 for (block, block_data) in body.basic_blocks().iter_enumerated() {
2770 let mut location = Location { block, statement_index: 0 };
2771 for stmt in &block_data.statements {
2772 if !stmt.source_info.span.is_dummy() {
2773 self.last_span = stmt.source_info.span;
2775 self.check_stmt(body, stmt, location);
2776 location.statement_index += 1;
2779 self.check_terminator(&body, block_data.terminator(), location);
2780 self.check_iscleanup(&body, block_data);
2784 fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
2786 T: type_op::normalize::Normalizable<'tcx> + Copy + 'tcx,
2788 debug!("normalize(value={:?}, location={:?})", value, location);
2789 let param_env = self.param_env;
2790 self.fully_perform_op(
2791 location.to_locations(),
2792 ConstraintCategory::Boring,
2793 param_env.and(type_op::normalize::Normalize::new(value)),
2795 .unwrap_or_else(|NoSolution| {
2796 span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
2802 trait NormalizeLocation: fmt::Debug + Copy {
2803 fn to_locations(self) -> Locations;
2806 impl NormalizeLocation for Locations {
2807 fn to_locations(self) -> Locations {
2812 impl NormalizeLocation for Location {
2813 fn to_locations(self) -> Locations {
2814 Locations::Single(self)
2818 #[derive(Debug, Default)]
2819 struct ObligationAccumulator<'tcx> {
2820 obligations: PredicateObligations<'tcx>,
2823 impl<'tcx> ObligationAccumulator<'tcx> {
2824 fn add<T>(&mut self, value: InferOk<'tcx, T>) -> T {
2825 let InferOk { value, obligations } = value;
2826 self.obligations.extend(obligations);
2830 fn into_vec(self) -> PredicateObligations<'tcx> {