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::{CoerceUnsizedTraitLangItem, CopyTraitLangItem, SizedTraitLangItem};
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,
48 promote_consts::should_suggest_const_in_array_repeat_expressions_attribute,
51 use crate::borrow_check::{
52 borrow_set::BorrowSet,
53 constraints::{OutlivesConstraint, OutlivesConstraintSet},
55 location::LocationTable,
56 member_constraints::MemberConstraintSet,
59 region_infer::values::{
60 LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements,
62 region_infer::{ClosureRegionRequirementsExt, TypeTest},
64 type_check::free_region_relations::{CreateResult, UniversalRegionRelations},
65 universal_regions::{DefiningTy, UniversalRegions},
69 macro_rules! span_mirbug {
70 ($context:expr, $elem:expr, $($message:tt)*) => ({
71 $crate::borrow_check::type_check::mirbug(
75 "broken MIR in {:?} ({:?}): {}",
78 format_args!($($message)*),
84 macro_rules! span_mirbug_and_err {
85 ($context:expr, $elem:expr, $($message:tt)*) => ({
87 span_mirbug!($context, $elem, $($message)*);
93 mod constraint_conversion;
94 pub mod free_region_relations;
99 /// Type checks the given `mir` in the context of the inference
100 /// context `infcx`. Returns any region constraints that have yet to
101 /// be proven. This result is includes liveness constraints that
102 /// ensure that regions appearing in the types of all local variables
103 /// are live at all points where that local variable may later be
106 /// This phase of type-check ought to be infallible -- this is because
107 /// the original, HIR-based type-check succeeded. So if any errors
108 /// occur here, we will get a `bug!` reported.
112 /// - `infcx` -- inference context to use
113 /// - `param_env` -- parameter environment to use for trait solving
114 /// - `body` -- MIR body to type-check
115 /// - `promoted` -- map of promoted constants within `body`
116 /// - `mir_def_id` -- `LocalDefId` from which the MIR is derived
117 /// - `universal_regions` -- the universal regions from `body`s function signature
118 /// - `location_table` -- MIR location map of `body`
119 /// - `borrow_set` -- information about borrows occurring in `body`
120 /// - `all_facts` -- when using Polonius, this is the generated set of Polonius facts
121 /// - `flow_inits` -- results of a maybe-init dataflow analysis
122 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis
123 /// - `elements` -- MIR region map
124 pub(crate) fn type_check<'mir, 'tcx>(
125 infcx: &InferCtxt<'_, 'tcx>,
126 param_env: ty::ParamEnv<'tcx>,
128 promoted: &IndexVec<Promoted, Body<'tcx>>,
129 mir_def_id: LocalDefId,
130 universal_regions: &Rc<UniversalRegions<'tcx>>,
131 location_table: &LocationTable,
132 borrow_set: &BorrowSet<'tcx>,
133 all_facts: &mut Option<AllFacts>,
134 flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
135 move_data: &MoveData<'tcx>,
136 elements: &Rc<RegionValueElements>,
138 ) -> MirTypeckResults<'tcx> {
139 let implicit_region_bound = infcx.tcx.mk_region(ty::ReVar(universal_regions.fr_fn_body));
140 let mut constraints = MirTypeckRegionConstraints {
141 placeholder_indices: PlaceholderIndices::default(),
142 placeholder_index_to_region: IndexVec::default(),
143 liveness_constraints: LivenessValues::new(elements.clone()),
144 outlives_constraints: OutlivesConstraintSet::default(),
145 member_constraints: MemberConstraintSet::default(),
146 closure_bounds_mapping: Default::default(),
147 type_tests: Vec::default(),
151 universal_region_relations,
153 normalized_inputs_and_output,
154 } = free_region_relations::create(
157 Some(implicit_region_bound),
162 let mut borrowck_context = BorrowCheckContext {
167 constraints: &mut constraints,
171 let opaque_type_values = type_check_internal(
178 implicit_region_bound,
179 &mut borrowck_context,
180 &universal_region_relations,
182 cx.equate_inputs_and_outputs(&body, universal_regions, &normalized_inputs_and_output);
183 liveness::generate(&mut cx, body, elements, flow_inits, move_data, location_table);
185 translate_outlives_facts(&mut cx);
186 cx.opaque_type_values
190 MirTypeckResults { constraints, universal_region_relations, opaque_type_values }
193 fn type_check_internal<'a, 'tcx, R>(
194 infcx: &'a InferCtxt<'a, 'tcx>,
195 mir_def_id: LocalDefId,
196 param_env: ty::ParamEnv<'tcx>,
197 body: &'a Body<'tcx>,
198 promoted: &'a IndexVec<Promoted, Body<'tcx>>,
199 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
200 implicit_region_bound: ty::Region<'tcx>,
201 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
202 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
203 extra: impl FnOnce(TypeChecker<'a, 'tcx>) -> R,
205 let mut checker = TypeChecker::new(
211 implicit_region_bound,
213 universal_region_relations,
215 let errors_reported = {
216 let mut verifier = TypeVerifier::new(&mut checker, body, promoted);
217 verifier.visit_body(&body);
218 verifier.errors_reported
221 if !errors_reported {
222 // if verifier failed, don't do further checks to avoid ICEs
223 checker.typeck_mir(body);
229 fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) {
230 let cx = &mut typeck.borrowck_context;
231 if let Some(facts) = cx.all_facts {
232 let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
233 let location_table = cx.location_table;
234 facts.outlives.extend(cx.constraints.outlives_constraints.outlives().iter().flat_map(
235 |constraint: &OutlivesConstraint| {
236 if let Some(from_location) = constraint.locations.from_location() {
237 Either::Left(iter::once((
240 location_table.mid_index(from_location),
246 .map(move |location| (constraint.sup, constraint.sub, location)),
254 fn mirbug(tcx: TyCtxt<'_>, span: Span, msg: &str) {
255 // We sometimes see MIR failures (notably predicate failures) due to
256 // the fact that we check rvalue sized predicates here. So use `delay_span_bug`
257 // to avoid reporting bugs in those cases.
258 tcx.sess.diagnostic().delay_span_bug(span, msg);
261 enum FieldAccessError {
262 OutOfRange { field_count: usize },
265 /// Verifies that MIR types are sane to not crash further checks.
267 /// The sanitize_XYZ methods here take an MIR object and compute its
268 /// type, calling `span_mirbug` and returning an error type if there
270 struct TypeVerifier<'a, 'b, 'tcx> {
271 cx: &'a mut TypeChecker<'b, 'tcx>,
272 body: &'b Body<'tcx>,
273 promoted: &'b IndexVec<Promoted, Body<'tcx>>,
275 mir_def_id: LocalDefId,
276 errors_reported: bool,
279 impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
280 fn visit_span(&mut self, span: &Span) {
281 if !span.is_dummy() {
282 self.last_span = *span;
286 fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
287 self.sanitize_place(place, location, context);
290 fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
291 self.super_constant(constant, location);
292 let ty = self.sanitize_type(constant, constant.literal.ty);
294 self.cx.infcx.tcx.for_each_free_region(&ty, |live_region| {
295 let live_region_vid =
296 self.cx.borrowck_context.universal_regions.to_region_vid(live_region);
300 .liveness_constraints
301 .add_element(live_region_vid, location);
304 if let Some(annotation_index) = constant.user_ty {
305 if let Err(terr) = self.cx.relate_type_and_user_type(
307 ty::Variance::Invariant,
308 &UserTypeProjection { base: annotation_index, projs: vec![] },
309 location.to_locations(),
310 ConstraintCategory::Boring,
312 let annotation = &self.cx.user_type_annotations[annotation_index];
316 "bad constant user type {:?} vs {:?}: {:?}",
323 let tcx = self.tcx();
324 if let ty::ConstKind::Unevaluated(def, substs, promoted) = constant.literal.val {
325 if let Some(promoted) = promoted {
326 let check_err = |verifier: &mut TypeVerifier<'a, 'b, 'tcx>,
327 promoted: &Body<'tcx>,
330 if let Err(terr) = verifier.cx.eq_types(
333 location.to_locations(),
334 ConstraintCategory::Boring,
339 "bad promoted type ({:?}: {:?}): {:?}",
347 if !self.errors_reported {
348 let promoted_body = &self.promoted[promoted];
349 self.sanitize_promoted(promoted_body, location);
351 let promoted_ty = promoted_body.return_ty();
352 check_err(self, promoted_body, ty, promoted_ty);
355 if let Err(terr) = self.cx.fully_perform_op(
356 location.to_locations(),
357 ConstraintCategory::Boring,
358 self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
361 UserSubsts { substs, user_self_ty: None },
367 "bad constant type {:?} ({:?})",
373 } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
374 let unnormalized_ty = tcx.type_of(static_def_id);
375 let locations = location.to_locations();
376 let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
377 let literal_ty = constant.literal.ty.builtin_deref(true).unwrap().ty;
379 if let Err(terr) = self.cx.eq_types(
383 ConstraintCategory::Boring,
385 span_mirbug!(self, constant, "bad static type {:?} ({:?})", constant, terr);
389 if let ty::FnDef(def_id, substs) = constant.literal.ty.kind {
390 let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
391 self.cx.normalize_and_prove_instantiated_predicates(
392 instantiated_predicates,
393 location.to_locations(),
399 fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
400 self.super_rvalue(rvalue, location);
401 let rval_ty = rvalue.ty(self.body, self.tcx());
402 self.sanitize_type(rvalue, rval_ty);
405 fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
406 self.super_local_decl(local, local_decl);
407 self.sanitize_type(local_decl, local_decl.ty);
409 if let Some(user_ty) = &local_decl.user_ty {
410 for (user_ty, span) in user_ty.projections_and_spans() {
411 let ty = if !local_decl.is_nonref_binding() {
412 // If we have a binding of the form `let ref x: T = ..`
413 // then remove the outermost reference so we can check the
414 // type annotation for the remaining type.
415 if let ty::Ref(_, rty, _) = local_decl.ty.kind {
418 bug!("{:?} with ref binding has wrong type {}", local, local_decl.ty);
424 if let Err(terr) = self.cx.relate_type_and_user_type(
426 ty::Variance::Invariant,
428 Locations::All(*span),
429 ConstraintCategory::TypeAnnotation,
434 "bad user type on variable {:?}: {:?} != {:?} ({:?})",
445 fn visit_body(&mut self, body: &Body<'tcx>) {
446 self.sanitize_type(&"return type", body.return_ty());
447 for local_decl in &body.local_decls {
448 self.sanitize_type(local_decl, local_decl.ty);
450 if self.errors_reported {
453 self.super_body(body);
457 impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
459 cx: &'a mut TypeChecker<'b, 'tcx>,
460 body: &'b Body<'tcx>,
461 promoted: &'b IndexVec<Promoted, Body<'tcx>>,
466 mir_def_id: cx.mir_def_id,
468 last_span: body.span,
469 errors_reported: false,
473 fn tcx(&self) -> TyCtxt<'tcx> {
477 fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
478 if ty.has_escaping_bound_vars() || ty.references_error() {
479 span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
485 /// Checks that the types internal to the `place` match up with
486 /// what would be expected.
491 context: PlaceContext,
493 debug!("sanitize_place: {:?}", place);
495 let mut place_ty = PlaceTy::from_ty(self.body.local_decls[place.local].ty);
497 for elem in place.projection.iter() {
498 if place_ty.variant_index.is_none() {
499 if place_ty.ty.references_error() {
500 assert!(self.errors_reported);
501 return PlaceTy::from_ty(self.tcx().ty_error());
504 place_ty = self.sanitize_projection(place_ty, elem, place, location)
507 if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
508 let tcx = self.tcx();
509 let trait_ref = ty::TraitRef {
510 def_id: tcx.require_lang_item(CopyTraitLangItem, Some(self.last_span)),
511 substs: tcx.mk_substs_trait(place_ty.ty, &[]),
514 // To have a `Copy` operand, the type `T` of the
515 // value must be `Copy`. Note that we prove that `T: Copy`,
516 // rather than using the `is_copy_modulo_regions`
517 // test. This is important because
518 // `is_copy_modulo_regions` ignores the resulting region
519 // obligations and assumes they pass. This can result in
520 // bounds from `Copy` impls being unsoundly ignored (e.g.,
521 // #29149). Note that we decide to use `Copy` before knowing
522 // whether the bounds fully apply: in effect, the rule is
523 // that if a value of some type could implement `Copy`, then
525 self.cx.prove_trait_ref(
527 location.to_locations(),
528 ConstraintCategory::CopyBound,
535 fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Location) {
536 // Determine the constraints from the promoted MIR by running the type
537 // checker on the promoted MIR, then transfer the constraints back to
538 // the main MIR, changing the locations to the provided location.
540 let parent_body = mem::replace(&mut self.body, promoted_body);
542 // Use new sets of constraints and closure bounds so that we can
543 // modify their locations.
544 let all_facts = &mut None;
545 let mut constraints = Default::default();
546 let mut closure_bounds = Default::default();
547 let mut liveness_constraints =
548 LivenessValues::new(Rc::new(RegionValueElements::new(&promoted_body)));
549 // Don't try to add borrow_region facts for the promoted MIR
551 let mut swap_constraints = |this: &mut Self| {
552 mem::swap(this.cx.borrowck_context.all_facts, all_facts);
554 &mut this.cx.borrowck_context.constraints.outlives_constraints,
558 &mut this.cx.borrowck_context.constraints.closure_bounds_mapping,
562 &mut this.cx.borrowck_context.constraints.liveness_constraints,
563 &mut liveness_constraints,
567 swap_constraints(self);
569 self.visit_body(&promoted_body);
571 if !self.errors_reported {
572 // if verifier failed, don't do further checks to avoid ICEs
573 self.cx.typeck_mir(promoted_body);
576 self.body = parent_body;
577 // Merge the outlives constraints back in, at the given location.
578 swap_constraints(self);
580 let locations = location.to_locations();
581 for constraint in constraints.outlives().iter() {
582 let mut constraint = *constraint;
583 constraint.locations = locations;
584 if let ConstraintCategory::Return(_)
585 | ConstraintCategory::UseAsConst
586 | ConstraintCategory::UseAsStatic = constraint.category
588 // "Returning" from a promoted is an assignment to a
589 // temporary from the user's point of view.
590 constraint.category = ConstraintCategory::Boring;
592 self.cx.borrowck_context.constraints.outlives_constraints.push(constraint)
594 for live_region in liveness_constraints.rows() {
598 .liveness_constraints
599 .add_element(live_region, location);
602 if !closure_bounds.is_empty() {
603 let combined_bounds_mapping =
604 closure_bounds.into_iter().flat_map(|(_, value)| value).collect();
609 .closure_bounds_mapping
610 .insert(location, combined_bounds_mapping);
611 assert!(existing.is_none(), "Multiple promoteds/closures at the same location.");
615 fn sanitize_projection(
622 debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, place);
623 let tcx = self.tcx();
624 let base_ty = base.ty;
626 ProjectionElem::Deref => {
627 let deref_ty = base_ty.builtin_deref(true);
628 PlaceTy::from_ty(deref_ty.map(|t| t.ty).unwrap_or_else(|| {
629 span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty)
632 ProjectionElem::Index(i) => {
633 let index_ty = Place::from(i).ty(self.body, tcx).ty;
634 if index_ty != tcx.types.usize {
635 PlaceTy::from_ty(span_mirbug_and_err!(self, i, "index by non-usize {:?}", i))
637 PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| {
638 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
642 ProjectionElem::ConstantIndex { .. } => {
643 // consider verifying in-bounds
644 PlaceTy::from_ty(base_ty.builtin_index().unwrap_or_else(|| {
645 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
648 ProjectionElem::Subslice { from, to, from_end } => {
649 PlaceTy::from_ty(match base_ty.kind {
650 ty::Array(inner, _) => {
651 assert!(!from_end, "array subslices should not use from_end");
652 tcx.mk_array(inner, (to - from) as u64)
655 assert!(from_end, "slice subslices should use from_end");
658 _ => span_mirbug_and_err!(self, place, "slice of non-array {:?}", base_ty),
661 ProjectionElem::Downcast(maybe_name, index) => match base_ty.kind {
662 ty::Adt(adt_def, _substs) if adt_def.is_enum() => {
663 if index.as_usize() >= adt_def.variants.len() {
664 PlaceTy::from_ty(span_mirbug_and_err!(
667 "cast to variant #{:?} but enum only has {:?}",
669 adt_def.variants.len()
672 PlaceTy { ty: base_ty, variant_index: Some(index) }
675 // We do not need to handle generators here, because this runs
676 // before the generator transform stage.
678 let ty = if let Some(name) = maybe_name {
679 span_mirbug_and_err!(
682 "can't downcast {:?} as {:?}",
687 span_mirbug_and_err!(self, place, "can't downcast {:?}", base_ty)
692 ProjectionElem::Field(field, fty) => {
693 let fty = self.sanitize_type(place, fty);
694 match self.field_ty(place, base, field, location) {
696 let ty = self.cx.normalize(ty, location);
697 if let Err(terr) = self.cx.eq_types(
700 location.to_locations(),
701 ConstraintCategory::Boring,
706 "bad field access ({:?}: {:?}): {:?}",
713 Err(FieldAccessError::OutOfRange { field_count }) => span_mirbug!(
716 "accessed field #{} but variant only has {}",
721 PlaceTy::from_ty(fty)
726 fn error(&mut self) -> Ty<'tcx> {
727 self.errors_reported = true;
728 self.tcx().ty_error()
733 parent: &dyn fmt::Debug,
734 base_ty: PlaceTy<'tcx>,
737 ) -> Result<Ty<'tcx>, FieldAccessError> {
738 let tcx = self.tcx();
740 let (variant, substs) = match base_ty {
741 PlaceTy { ty, variant_index: Some(variant_index) } => match ty.kind {
742 ty::Adt(adt_def, substs) => (&adt_def.variants[variant_index], substs),
743 ty::Generator(def_id, substs, _) => {
744 let mut variants = substs.as_generator().state_tys(def_id, tcx);
745 let mut variant = match variants.nth(variant_index.into()) {
748 "variant_index of generator out of range: {:?}/{:?}",
750 substs.as_generator().state_tys(def_id, tcx).count()
753 return match variant.nth(field.index()) {
755 None => Err(FieldAccessError::OutOfRange { field_count: variant.count() }),
758 _ => bug!("can't have downcast of non-adt non-generator type"),
760 PlaceTy { ty, variant_index: None } => match ty.kind {
761 ty::Adt(adt_def, substs) if !adt_def.is_enum() => {
762 (&adt_def.variants[VariantIdx::new(0)], substs)
764 ty::Closure(_, substs) => {
765 return match substs.as_closure().upvar_tys().nth(field.index()) {
767 None => Err(FieldAccessError::OutOfRange {
768 field_count: substs.as_closure().upvar_tys().count(),
772 ty::Generator(_, substs, _) => {
773 // Only prefix fields (upvars and current state) are
774 // accessible without a variant index.
775 return match substs.as_generator().prefix_tys().nth(field.index()) {
777 None => Err(FieldAccessError::OutOfRange {
778 field_count: substs.as_generator().prefix_tys().count(),
783 return match tys.get(field.index()) {
784 Some(&ty) => Ok(ty.expect_ty()),
785 None => Err(FieldAccessError::OutOfRange { field_count: tys.len() }),
789 return Ok(span_mirbug_and_err!(
792 "can't project out of {:?}",
799 if let Some(field) = variant.fields.get(field.index()) {
800 Ok(self.cx.normalize(&field.ty(tcx, substs), location))
802 Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
807 /// The MIR type checker. Visits the MIR and enforces all the
808 /// constraints needed for it to be valid and well-typed. Along the
809 /// way, it accrues region constraints -- these can later be used by
810 /// NLL region checking.
811 struct TypeChecker<'a, 'tcx> {
812 infcx: &'a InferCtxt<'a, 'tcx>,
813 param_env: ty::ParamEnv<'tcx>,
815 body: &'a Body<'tcx>,
816 /// User type annotations are shared between the main MIR and the MIR of
817 /// all of the promoted items.
818 user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>,
819 mir_def_id: LocalDefId,
820 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
821 implicit_region_bound: ty::Region<'tcx>,
822 reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
823 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
824 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
825 opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
828 struct BorrowCheckContext<'a, 'tcx> {
829 universal_regions: &'a UniversalRegions<'tcx>,
830 location_table: &'a LocationTable,
831 all_facts: &'a mut Option<AllFacts>,
832 borrow_set: &'a BorrowSet<'tcx>,
833 constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
837 crate struct MirTypeckResults<'tcx> {
838 crate constraints: MirTypeckRegionConstraints<'tcx>,
839 pub(in crate::borrow_check) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
840 crate opaque_type_values: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
843 /// A collection of region constraints that must be satisfied for the
844 /// program to be considered well-typed.
845 crate struct MirTypeckRegionConstraints<'tcx> {
846 /// Maps from a `ty::Placeholder` to the corresponding
847 /// `PlaceholderIndex` bit that we will use for it.
849 /// To keep everything in sync, do not insert this set
850 /// directly. Instead, use the `placeholder_region` helper.
851 crate placeholder_indices: PlaceholderIndices,
853 /// Each time we add a placeholder to `placeholder_indices`, we
854 /// also create a corresponding "representative" region vid for
855 /// that wraps it. This vector tracks those. This way, when we
856 /// convert the same `ty::RePlaceholder(p)` twice, we can map to
857 /// the same underlying `RegionVid`.
858 crate placeholder_index_to_region: IndexVec<PlaceholderIndex, ty::Region<'tcx>>,
860 /// In general, the type-checker is not responsible for enforcing
861 /// liveness constraints; this job falls to the region inferencer,
862 /// which performs a liveness analysis. However, in some limited
863 /// cases, the MIR type-checker creates temporary regions that do
864 /// not otherwise appear in the MIR -- in particular, the
865 /// late-bound regions that it instantiates at call-sites -- and
866 /// hence it must report on their liveness constraints.
867 crate liveness_constraints: LivenessValues<RegionVid>,
869 crate outlives_constraints: OutlivesConstraintSet,
871 crate member_constraints: MemberConstraintSet<'tcx, RegionVid>,
873 crate closure_bounds_mapping:
874 FxHashMap<Location, FxHashMap<(RegionVid, RegionVid), (ConstraintCategory, Span)>>,
876 crate type_tests: Vec<TypeTest<'tcx>>,
879 impl MirTypeckRegionConstraints<'tcx> {
880 fn placeholder_region(
882 infcx: &InferCtxt<'_, 'tcx>,
883 placeholder: ty::PlaceholderRegion,
884 ) -> ty::Region<'tcx> {
885 let placeholder_index = self.placeholder_indices.insert(placeholder);
886 match self.placeholder_index_to_region.get(placeholder_index) {
889 let origin = NLLRegionVariableOrigin::Placeholder(placeholder);
890 let region = infcx.next_nll_region_var_in_universe(origin, placeholder.universe);
891 self.placeholder_index_to_region.push(region);
898 /// The `Locations` type summarizes *where* region constraints are
899 /// required to hold. Normally, this is at a particular point which
900 /// created the obligation, but for constraints that the user gave, we
901 /// want the constraint to hold at all points.
902 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
904 /// Indicates that a type constraint should always be true. This
905 /// is particularly important in the new borrowck analysis for
906 /// things like the type of the return slot. Consider this
910 /// fn foo<'a>(x: &'a u32) -> &'a u32 {
912 /// return &y; // error
916 /// Here, we wind up with the signature from the return type being
917 /// something like `&'1 u32` where `'1` is a universal region. But
918 /// the type of the return slot `_0` is something like `&'2 u32`
919 /// where `'2` is an existential region variable. The type checker
920 /// requires that `&'2 u32 = &'1 u32` -- but at what point? In the
921 /// older NLL analysis, we required this only at the entry point
922 /// to the function. By the nature of the constraints, this wound
923 /// up propagating to all points reachable from start (because
924 /// `'1` -- as a universal region -- is live everywhere). In the
925 /// newer analysis, though, this doesn't work: `_0` is considered
926 /// dead at the start (it has no usable value) and hence this type
927 /// equality is basically a no-op. Then, later on, when we do `_0
928 /// = &'3 y`, that region `'3` never winds up related to the
929 /// universal region `'1` and hence no error occurs. Therefore, we
930 /// use Locations::All instead, which ensures that the `'1` and
931 /// `'2` are equal everything. We also use this for other
932 /// user-given type annotations; e.g., if the user wrote `let mut
933 /// x: &'static u32 = ...`, we would ensure that all values
934 /// assigned to `x` are of `'static` lifetime.
936 /// The span points to the place the constraint arose. For example,
937 /// it points to the type in a user-given type annotation. If
938 /// there's no sensible span then it's DUMMY_SP.
941 /// An outlives constraint that only has to hold at a single location,
942 /// usually it represents a point where references flow from one spot to
943 /// another (e.g., `x = y`)
948 pub fn from_location(&self) -> Option<Location> {
950 Locations::All(_) => None,
951 Locations::Single(from_location) => Some(*from_location),
955 /// Gets a span representing the location.
956 pub fn span(&self, body: &Body<'_>) -> Span {
958 Locations::All(span) => *span,
959 Locations::Single(l) => body.source_info(*l).span,
964 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
966 infcx: &'a InferCtxt<'a, 'tcx>,
967 body: &'a Body<'tcx>,
968 mir_def_id: LocalDefId,
969 param_env: ty::ParamEnv<'tcx>,
970 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
971 implicit_region_bound: ty::Region<'tcx>,
972 borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
973 universal_region_relations: &'a UniversalRegionRelations<'tcx>,
975 let mut checker = Self {
980 user_type_annotations: &body.user_type_annotations,
983 implicit_region_bound,
985 reported_errors: Default::default(),
986 universal_region_relations,
987 opaque_type_values: FxHashMap::default(),
989 checker.check_user_type_annotations();
993 /// Equate the inferred type and the annotated type for user type annotations
994 fn check_user_type_annotations(&mut self) {
996 "check_user_type_annotations: user_type_annotations={:?}",
997 self.user_type_annotations
999 for user_annotation in self.user_type_annotations {
1000 let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation;
1001 let (annotation, _) =
1002 self.infcx.instantiate_canonical_with_fresh_inference_vars(span, user_ty);
1004 UserType::Ty(mut ty) => {
1005 ty = self.normalize(ty, Locations::All(span));
1007 if let Err(terr) = self.eq_types(
1010 Locations::All(span),
1011 ConstraintCategory::BoringNoLocation,
1016 "bad user type ({:?} = {:?}): {:?}",
1023 self.prove_predicate(
1024 ty::PredicateAtom::WellFormed(inferred_ty.into()).to_predicate(self.tcx()),
1025 Locations::All(span),
1026 ConstraintCategory::TypeAnnotation,
1029 UserType::TypeOf(def_id, user_substs) => {
1030 if let Err(terr) = self.fully_perform_op(
1031 Locations::All(span),
1032 ConstraintCategory::BoringNoLocation,
1033 self.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
1042 "bad user type AscribeUserType({:?}, {:?} {:?}): {:?}",
1054 /// Given some operation `op` that manipulates types, proves
1055 /// predicates, or otherwise uses the inference context, executes
1056 /// `op` and then executes all the further obligations that `op`
1057 /// returns. This will yield a set of outlives constraints amongst
1058 /// regions which are extracted and stored as having occurred at
1061 /// **Any `rustc_infer::infer` operations that might generate region
1062 /// constraints should occur within this method so that those
1063 /// constraints can be properly localized!**
1064 fn fully_perform_op<R>(
1066 locations: Locations,
1067 category: ConstraintCategory,
1068 op: impl type_op::TypeOp<'tcx, Output = R>,
1070 let (r, opt_data) = op.fully_perform(self.infcx)?;
1072 if let Some(data) = &opt_data {
1073 self.push_region_constraints(locations, category, data);
1079 fn push_region_constraints(
1081 locations: Locations,
1082 category: ConstraintCategory,
1083 data: &QueryRegionConstraints<'tcx>,
1085 debug!("push_region_constraints: constraints generated at {:?} are {:#?}", locations, data);
1087 constraint_conversion::ConstraintConversion::new(
1089 self.borrowck_context.universal_regions,
1090 self.region_bound_pairs,
1091 Some(self.implicit_region_bound),
1095 &mut self.borrowck_context.constraints,
1100 /// Convenient wrapper around `relate_tys::relate_types` -- see
1101 /// that fn for docs.
1107 locations: Locations,
1108 category: ConstraintCategory,
1110 relate_tys::relate_types(
1117 Some(self.borrowck_context),
1125 locations: Locations,
1126 category: ConstraintCategory,
1128 self.relate_types(sub, ty::Variance::Covariant, sup, locations, category)
1131 /// Try to relate `sub <: sup`; if this fails, instantiate opaque
1132 /// variables in `sub` with their inferred definitions and try
1133 /// again. This is used for opaque types in places (e.g., `let x:
1134 /// impl Foo = ..`).
1135 fn sub_types_or_anon(
1139 locations: Locations,
1140 category: ConstraintCategory,
1142 if let Err(terr) = self.sub_types(sub, sup, locations, category) {
1143 if let ty::Opaque(..) = sup.kind {
1144 // When you have `let x: impl Foo = ...` in a closure,
1145 // the resulting inferend values are stored with the
1146 // def-id of the base function.
1148 self.tcx().closure_base_def_id(self.mir_def_id.to_def_id()).expect_local();
1149 return self.eq_opaque_type_and_type(sub, sup, parent_def_id, locations, category);
1161 locations: Locations,
1162 category: ConstraintCategory,
1164 self.relate_types(a, ty::Variance::Invariant, b, locations, category)
1167 fn relate_type_and_user_type(
1171 user_ty: &UserTypeProjection,
1172 locations: Locations,
1173 category: ConstraintCategory,
1176 "relate_type_and_user_type(a={:?}, v={:?}, user_ty={:?}, locations={:?})",
1177 a, v, user_ty, locations,
1180 let annotated_type = self.user_type_annotations[user_ty.base].inferred_ty;
1181 let mut curr_projected_ty = PlaceTy::from_ty(annotated_type);
1183 let tcx = self.infcx.tcx;
1185 for proj in &user_ty.projs {
1186 let projected_ty = curr_projected_ty.projection_ty_core(
1190 |this, field, &()| {
1191 let ty = this.field_ty(tcx, field);
1192 self.normalize(ty, locations)
1195 curr_projected_ty = projected_ty;
1198 "user_ty base: {:?} freshened: {:?} projs: {:?} yields: {:?}",
1199 user_ty.base, annotated_type, user_ty.projs, curr_projected_ty
1202 let ty = curr_projected_ty.ty;
1203 self.relate_types(a, v, ty, locations, category)?;
1208 fn eq_opaque_type_and_type(
1210 revealed_ty: Ty<'tcx>,
1212 anon_owner_def_id: LocalDefId,
1213 locations: Locations,
1214 category: ConstraintCategory,
1217 "eq_opaque_type_and_type( \
1220 revealed_ty, anon_ty
1223 // Fast path for the common case.
1224 if !anon_ty.has_opaque_types() {
1225 if let Err(terr) = self.eq_types(anon_ty, revealed_ty, locations, category) {
1229 "eq_opaque_type_and_type: `{:?}=={:?}` failed with `{:?}`",
1238 let infcx = self.infcx;
1239 let tcx = infcx.tcx;
1240 let param_env = self.param_env;
1241 let body = self.body;
1242 let concrete_opaque_types = &tcx.typeck(anon_owner_def_id).concrete_opaque_types;
1243 let mut opaque_type_values = Vec::new();
1245 debug!("eq_opaque_type_and_type: mir_def_id={:?}", self.mir_def_id);
1246 let opaque_type_map = self.fully_perform_op(
1251 let mut obligations = ObligationAccumulator::default();
1253 let dummy_body_id = hir::CRATE_HIR_ID;
1254 let (output_ty, opaque_type_map) =
1255 obligations.add(infcx.instantiate_opaque_types(
1260 locations.span(body),
1263 "eq_opaque_type_and_type: \
1264 instantiated output_ty={:?} \
1265 opaque_type_map={:#?} \
1267 output_ty, opaque_type_map, revealed_ty
1269 // Make sure that the inferred types are well-formed. I'm
1270 // not entirely sure this is needed (the HIR type check
1271 // didn't do this) but it seems sensible to prevent opaque
1272 // types hiding ill-formed types.
1273 obligations.obligations.push(traits::Obligation::new(
1274 ObligationCause::dummy(),
1276 ty::PredicateAtom::WellFormed(revealed_ty.into()).to_predicate(infcx.tcx),
1280 .at(&ObligationCause::dummy(), param_env)
1281 .eq(output_ty, revealed_ty)?,
1284 for (&opaque_def_id, opaque_decl) in &opaque_type_map {
1285 let resolved_ty = infcx.resolve_vars_if_possible(&opaque_decl.concrete_ty);
1286 let concrete_is_opaque = if let ty::Opaque(def_id, _) = resolved_ty.kind {
1287 def_id == opaque_def_id
1291 let opaque_defn_ty = match concrete_opaque_types.get(&opaque_def_id) {
1293 if !concrete_is_opaque {
1294 tcx.sess.delay_span_bug(
1297 "Non-defining use of {:?} with revealed type",
1304 Some(opaque_defn_ty) => opaque_defn_ty,
1306 debug!("opaque_defn_ty = {:?}", opaque_defn_ty);
1307 let subst_opaque_defn_ty =
1308 opaque_defn_ty.concrete_type.subst(tcx, opaque_decl.substs);
1309 let renumbered_opaque_defn_ty =
1310 renumber::renumber_regions(infcx, &subst_opaque_defn_ty);
1313 "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?}",
1314 opaque_decl.concrete_ty, resolved_ty, renumbered_opaque_defn_ty,
1317 if !concrete_is_opaque {
1318 // Equate concrete_ty (an inference variable) with
1319 // the renumbered type from typeck.
1322 .at(&ObligationCause::dummy(), param_env)
1323 .eq(opaque_decl.concrete_ty, renumbered_opaque_defn_ty)?,
1325 opaque_type_values.push((
1327 ty::ResolvedOpaqueTy {
1328 concrete_type: renumbered_opaque_defn_ty,
1329 substs: opaque_decl.substs,
1333 // We're using an opaque `impl Trait` type without
1334 // 'revealing' it. For example, code like this:
1336 // type Foo = impl Debug;
1337 // fn foo1() -> Foo { ... }
1338 // fn foo2() -> Foo { foo1() }
1340 // In `foo2`, we're not revealing the type of `Foo` - we're
1341 // just treating it as the opaque type.
1343 // When this occurs, we do *not* want to try to equate
1344 // the concrete type with the underlying defining type
1345 // of the opaque type - this will always fail, since
1346 // the defining type of an opaque type is always
1347 // some other type (e.g. not itself)
1348 // Essentially, none of the normal obligations apply here -
1349 // we're just passing around some unknown opaque type,
1350 // without actually looking at the underlying type it
1351 // gets 'revealed' into
1353 "eq_opaque_type_and_type: non-defining use of {:?}",
1359 debug!("eq_opaque_type_and_type: equated");
1362 value: Some(opaque_type_map),
1363 obligations: obligations.into_vec(),
1366 || "input_output".to_string(),
1370 self.opaque_type_values.extend(opaque_type_values);
1372 let universal_region_relations = self.universal_region_relations;
1374 // Finally, if we instantiated the anon types successfully, we
1375 // have to solve any bounds (e.g., `-> impl Iterator` needs to
1376 // prove that `T: Iterator` where `T` is the type we
1377 // instantiated it with).
1378 if let Some(opaque_type_map) = opaque_type_map {
1379 for (opaque_def_id, opaque_decl) in opaque_type_map {
1380 self.fully_perform_op(
1382 ConstraintCategory::OpaqueType,
1385 infcx.constrain_opaque_type(
1388 GenerateMemberConstraints::IfNoStaticBound,
1389 universal_region_relations,
1391 Ok(InferOk { value: (), obligations: vec![] })
1393 || "opaque_type_map".to_string(),
1401 fn tcx(&self) -> TyCtxt<'tcx> {
1405 fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Location) {
1406 debug!("check_stmt: {:?}", stmt);
1407 let tcx = self.tcx();
1409 StatementKind::Assign(box (ref place, ref rv)) => {
1410 // Assignments to temporaries are not "interesting";
1411 // they are not caused by the user, but rather artifacts
1412 // of lowering. Assignments to other sorts of places *are* interesting
1414 let category = match place.as_local() {
1415 Some(RETURN_PLACE) => {
1416 if let BorrowCheckContext {
1418 UniversalRegions { defining_ty: DefiningTy::Const(def_id, _), .. },
1420 } = self.borrowck_context
1422 if tcx.is_static(*def_id) {
1423 ConstraintCategory::UseAsStatic
1425 ConstraintCategory::UseAsConst
1428 ConstraintCategory::Return(ReturnConstraint::Normal)
1431 Some(l) if !body.local_decls[l].is_user_variable() => {
1432 ConstraintCategory::Boring
1434 _ => ConstraintCategory::Assignment,
1437 let place_ty = place.ty(body, tcx).ty;
1438 let place_ty = self.normalize(place_ty, location);
1439 let rv_ty = rv.ty(body, tcx);
1440 let rv_ty = self.normalize(rv_ty, location);
1442 self.sub_types_or_anon(rv_ty, place_ty, location.to_locations(), category)
1447 "bad assignment ({:?} = {:?}): {:?}",
1454 if let Some(annotation_index) = self.rvalue_user_ty(rv) {
1455 if let Err(terr) = self.relate_type_and_user_type(
1457 ty::Variance::Invariant,
1458 &UserTypeProjection { base: annotation_index, projs: vec![] },
1459 location.to_locations(),
1460 ConstraintCategory::Boring,
1462 let annotation = &self.user_type_annotations[annotation_index];
1466 "bad user type on rvalue ({:?} = {:?}): {:?}",
1474 self.check_rvalue(body, rv, location);
1475 if !self.tcx().features().unsized_locals {
1476 let trait_ref = ty::TraitRef {
1477 def_id: tcx.require_lang_item(SizedTraitLangItem, Some(self.last_span)),
1478 substs: tcx.mk_substs_trait(place_ty, &[]),
1480 self.prove_trait_ref(
1482 location.to_locations(),
1483 ConstraintCategory::SizedBound,
1487 StatementKind::SetDiscriminant { ref place, variant_index } => {
1488 let place_type = place.ty(body, tcx).ty;
1489 let adt = match place_type.kind {
1490 ty::Adt(adt, _) if adt.is_enum() => adt,
1493 stmt.source_info.span,
1494 "bad set discriminant ({:?} = {:?}): lhs is not an enum",
1500 if variant_index.as_usize() >= adt.variants.len() {
1502 stmt.source_info.span,
1503 "bad set discriminant ({:?} = {:?}): value of of range",
1509 StatementKind::AscribeUserType(box (ref place, ref projection), variance) => {
1510 let place_ty = place.ty(body, tcx).ty;
1511 if let Err(terr) = self.relate_type_and_user_type(
1515 Locations::All(stmt.source_info.span),
1516 ConstraintCategory::TypeAnnotation,
1518 let annotation = &self.user_type_annotations[projection.base];
1522 "bad type assert ({:?} <: {:?} with projections {:?}): {:?}",
1530 StatementKind::FakeRead(..)
1531 | StatementKind::StorageLive(..)
1532 | StatementKind::StorageDead(..)
1533 | StatementKind::LlvmInlineAsm { .. }
1534 | StatementKind::Retag { .. }
1535 | StatementKind::Nop => {}
1539 fn check_terminator(
1542 term: &Terminator<'tcx>,
1543 term_location: Location,
1545 debug!("check_terminator: {:?}", term);
1546 let tcx = self.tcx();
1548 TerminatorKind::Goto { .. }
1549 | TerminatorKind::Resume
1550 | TerminatorKind::Abort
1551 | TerminatorKind::Return
1552 | TerminatorKind::GeneratorDrop
1553 | TerminatorKind::Unreachable
1554 | TerminatorKind::Drop { .. }
1555 | TerminatorKind::FalseEdge { .. }
1556 | TerminatorKind::FalseUnwind { .. }
1557 | TerminatorKind::InlineAsm { .. } => {
1558 // no checks needed for these
1561 TerminatorKind::DropAndReplace { ref place, ref value, target: _, unwind: _ } => {
1562 let place_ty = place.ty(body, tcx).ty;
1563 let rv_ty = value.ty(body, tcx);
1565 let locations = term_location.to_locations();
1567 self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
1572 "bad DropAndReplace ({:?} = {:?}): {:?}",
1579 TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
1580 let discr_ty = discr.ty(body, tcx);
1581 if let Err(terr) = self.sub_types(
1584 term_location.to_locations(),
1585 ConstraintCategory::Assignment,
1590 "bad SwitchInt ({:?} on {:?}): {:?}",
1596 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
1597 span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
1599 // FIXME: check the values
1601 TerminatorKind::Call { ref func, ref args, ref destination, from_hir_call, .. } => {
1602 let func_ty = func.ty(body, tcx);
1603 debug!("check_terminator: call, func_ty={:?}", func_ty);
1604 let sig = match func_ty.kind {
1605 ty::FnDef(..) | ty::FnPtr(_) => func_ty.fn_sig(tcx),
1607 span_mirbug!(self, term, "call to non-function {:?}", func_ty);
1611 let (sig, map) = self.infcx.replace_bound_vars_with_fresh_vars(
1612 term.source_info.span,
1613 LateBoundRegionConversionTime::FnCall,
1616 let sig = self.normalize(sig, term_location);
1617 self.check_call_dest(body, term, &sig, destination, term_location);
1619 self.prove_predicates(
1620 sig.inputs_and_output.iter().map(|ty| ty::PredicateAtom::WellFormed(ty.into())),
1621 term_location.to_locations(),
1622 ConstraintCategory::Boring,
1625 // The ordinary liveness rules will ensure that all
1626 // regions in the type of the callee are live here. We
1627 // then further constrain the late-bound regions that
1628 // were instantiated at the call site to be live as
1629 // well. The resulting is that all the input (and
1630 // output) types in the signature must be live, since
1631 // all the inputs that fed into it were live.
1632 for &late_bound_region in map.values() {
1634 self.borrowck_context.universal_regions.to_region_vid(late_bound_region);
1635 self.borrowck_context
1637 .liveness_constraints
1638 .add_element(region_vid, term_location);
1641 self.check_call_inputs(body, term, &sig, args, term_location, from_hir_call);
1643 TerminatorKind::Assert { ref cond, ref msg, .. } => {
1644 let cond_ty = cond.ty(body, tcx);
1645 if cond_ty != tcx.types.bool {
1646 span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
1649 if let AssertKind::BoundsCheck { ref len, ref index } = *msg {
1650 if len.ty(body, tcx) != tcx.types.usize {
1651 span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
1653 if index.ty(body, tcx) != tcx.types.usize {
1654 span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
1658 TerminatorKind::Yield { ref value, .. } => {
1659 let value_ty = value.ty(body, tcx);
1660 match body.yield_ty {
1661 None => span_mirbug!(self, term, "yield in non-generator"),
1663 if let Err(terr) = self.sub_types(
1666 term_location.to_locations(),
1667 ConstraintCategory::Yield,
1672 "type of yield value is {:?}, but the yield type is {:?}: {:?}",
1687 term: &Terminator<'tcx>,
1688 sig: &ty::FnSig<'tcx>,
1689 destination: &Option<(Place<'tcx>, BasicBlock)>,
1690 term_location: Location,
1692 let tcx = self.tcx();
1693 match *destination {
1694 Some((ref dest, _target_block)) => {
1695 let dest_ty = dest.ty(body, tcx).ty;
1696 let dest_ty = self.normalize(dest_ty, term_location);
1697 let category = match dest.as_local() {
1698 Some(RETURN_PLACE) => {
1699 if let BorrowCheckContext {
1701 UniversalRegions { defining_ty: DefiningTy::Const(def_id, _), .. },
1703 } = self.borrowck_context
1705 if tcx.is_static(*def_id) {
1706 ConstraintCategory::UseAsStatic
1708 ConstraintCategory::UseAsConst
1711 ConstraintCategory::Return(ReturnConstraint::Normal)
1714 Some(l) if !body.local_decls[l].is_user_variable() => {
1715 ConstraintCategory::Boring
1717 _ => ConstraintCategory::Assignment,
1720 let locations = term_location.to_locations();
1723 self.sub_types_or_anon(sig.output(), dest_ty, locations, category)
1728 "call dest mismatch ({:?} <- {:?}): {:?}",
1735 // When `#![feature(unsized_locals)]` is not enabled,
1736 // this check is done at `check_local`.
1737 if self.tcx().features().unsized_locals {
1738 let span = term.source_info.span;
1739 self.ensure_place_sized(dest_ty, span);
1743 if !sig.output().conservative_is_privately_uninhabited(self.tcx()) {
1744 span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
1750 fn check_call_inputs(
1753 term: &Terminator<'tcx>,
1754 sig: &ty::FnSig<'tcx>,
1755 args: &[Operand<'tcx>],
1756 term_location: Location,
1757 from_hir_call: bool,
1759 debug!("check_call_inputs({:?}, {:?})", sig, args);
1760 if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.c_variadic) {
1761 span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
1763 for (n, (fn_arg, op_arg)) in sig.inputs().iter().zip(args).enumerate() {
1764 let op_arg_ty = op_arg.ty(body, self.tcx());
1765 let op_arg_ty = self.normalize(op_arg_ty, term_location);
1766 let category = if from_hir_call {
1767 ConstraintCategory::CallArgument
1769 ConstraintCategory::Boring
1772 self.sub_types(op_arg_ty, fn_arg, term_location.to_locations(), category)
1777 "bad arg #{:?} ({:?} <- {:?}): {:?}",
1787 fn check_iscleanup(&mut self, body: &Body<'tcx>, block_data: &BasicBlockData<'tcx>) {
1788 let is_cleanup = block_data.is_cleanup;
1789 self.last_span = block_data.terminator().source_info.span;
1790 match block_data.terminator().kind {
1791 TerminatorKind::Goto { target } => {
1792 self.assert_iscleanup(body, block_data, target, is_cleanup)
1794 TerminatorKind::SwitchInt { ref targets, .. } => {
1795 for target in targets {
1796 self.assert_iscleanup(body, block_data, *target, is_cleanup);
1799 TerminatorKind::Resume => {
1801 span_mirbug!(self, block_data, "resume on non-cleanup block!")
1804 TerminatorKind::Abort => {
1806 span_mirbug!(self, block_data, "abort on non-cleanup block!")
1809 TerminatorKind::Return => {
1811 span_mirbug!(self, block_data, "return on cleanup block")
1814 TerminatorKind::GeneratorDrop { .. } => {
1816 span_mirbug!(self, block_data, "generator_drop in cleanup block")
1819 TerminatorKind::Yield { resume, drop, .. } => {
1821 span_mirbug!(self, block_data, "yield in cleanup block")
1823 self.assert_iscleanup(body, block_data, resume, is_cleanup);
1824 if let Some(drop) = drop {
1825 self.assert_iscleanup(body, block_data, drop, is_cleanup);
1828 TerminatorKind::Unreachable => {}
1829 TerminatorKind::Drop { target, unwind, .. }
1830 | TerminatorKind::DropAndReplace { target, unwind, .. }
1831 | TerminatorKind::Assert { target, cleanup: unwind, .. } => {
1832 self.assert_iscleanup(body, block_data, target, is_cleanup);
1833 if let Some(unwind) = unwind {
1835 span_mirbug!(self, block_data, "unwind on cleanup block")
1837 self.assert_iscleanup(body, block_data, unwind, true);
1840 TerminatorKind::Call { ref destination, cleanup, .. } => {
1841 if let &Some((_, target)) = destination {
1842 self.assert_iscleanup(body, block_data, target, is_cleanup);
1844 if let Some(cleanup) = cleanup {
1846 span_mirbug!(self, block_data, "cleanup on cleanup block")
1848 self.assert_iscleanup(body, block_data, cleanup, true);
1851 TerminatorKind::FalseEdge { real_target, imaginary_target } => {
1852 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
1853 self.assert_iscleanup(body, block_data, imaginary_target, is_cleanup);
1855 TerminatorKind::FalseUnwind { real_target, unwind } => {
1856 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
1857 if let Some(unwind) = unwind {
1859 span_mirbug!(self, block_data, "cleanup in cleanup block via false unwind");
1861 self.assert_iscleanup(body, block_data, unwind, true);
1864 TerminatorKind::InlineAsm { ref destination, .. } => {
1865 if let &Some(target) = destination {
1866 self.assert_iscleanup(body, block_data, target, is_cleanup);
1872 fn assert_iscleanup(
1875 ctxt: &dyn fmt::Debug,
1879 if body[bb].is_cleanup != iscleanuppad {
1880 span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}", bb, iscleanuppad);
1884 fn check_local(&mut self, body: &Body<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) {
1885 match body.local_kind(local) {
1886 LocalKind::ReturnPointer | LocalKind::Arg => {
1887 // return values of normal functions are required to be
1888 // sized by typeck, but return values of ADT constructors are
1889 // not because we don't include a `Self: Sized` bounds on them.
1891 // Unbound parts of arguments were never required to be Sized
1892 // - maybe we should make that a warning.
1895 LocalKind::Var | LocalKind::Temp => {}
1898 // When `#![feature(unsized_locals)]` is enabled, only function calls
1899 // and nullary ops are checked in `check_call_dest`.
1900 if !self.tcx().features().unsized_locals {
1901 let span = local_decl.source_info.span;
1902 let ty = local_decl.ty;
1903 self.ensure_place_sized(ty, span);
1907 fn ensure_place_sized(&mut self, ty: Ty<'tcx>, span: Span) {
1908 let tcx = self.tcx();
1910 // Erase the regions from `ty` to get a global type. The
1911 // `Sized` bound in no way depends on precise regions, so this
1912 // shouldn't affect `is_sized`.
1913 let erased_ty = tcx.erase_regions(&ty);
1914 if !erased_ty.is_sized(tcx.at(span), self.param_env) {
1915 // in current MIR construction, all non-control-flow rvalue
1916 // expressions evaluate through `as_temp` or `into` a return
1917 // slot or local, so to find all unsized rvalues it is enough
1918 // to check all temps, return slots and locals.
1919 if self.reported_errors.replace((ty, span)).is_none() {
1920 let mut diag = struct_span_err!(
1924 "cannot move a value of type {0}: the size of {0} \
1925 cannot be statically determined",
1929 // While this is located in `nll::typeck` this error is not
1930 // an NLL error, it's a required check to prevent creation
1931 // of unsized rvalues in certain cases:
1932 // * operand of a box expression
1933 // * callee in a call expression
1939 fn aggregate_field_ty(
1941 ak: &AggregateKind<'tcx>,
1944 ) -> Result<Ty<'tcx>, FieldAccessError> {
1945 let tcx = self.tcx();
1948 AggregateKind::Adt(def, variant_index, substs, _, active_field_index) => {
1949 let variant = &def.variants[variant_index];
1950 let adj_field_index = active_field_index.unwrap_or(field_index);
1951 if let Some(field) = variant.fields.get(adj_field_index) {
1952 Ok(self.normalize(field.ty(tcx, substs), location))
1954 Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
1957 AggregateKind::Closure(_, substs) => {
1958 match substs.as_closure().upvar_tys().nth(field_index) {
1960 None => Err(FieldAccessError::OutOfRange {
1961 field_count: substs.as_closure().upvar_tys().count(),
1965 AggregateKind::Generator(_, substs, _) => {
1966 // It doesn't make sense to look at a field beyond the prefix;
1967 // these require a variant index, and are not initialized in
1968 // aggregate rvalues.
1969 match substs.as_generator().prefix_tys().nth(field_index) {
1971 None => Err(FieldAccessError::OutOfRange {
1972 field_count: substs.as_generator().prefix_tys().count(),
1976 AggregateKind::Array(ty) => Ok(ty),
1977 AggregateKind::Tuple => {
1978 unreachable!("This should have been covered in check_rvalues");
1983 fn check_rvalue(&mut self, body: &Body<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
1984 let tcx = self.tcx();
1987 Rvalue::Aggregate(ak, ops) => {
1988 self.check_aggregate_rvalue(&body, rvalue, ak, ops, location)
1991 Rvalue::Repeat(operand, len) => {
1992 // If the length cannot be evaluated we must assume that the length can be larger
1994 // If the length is larger than 1, the repeat expression will need to copy the
1995 // element, so we require the `Copy` trait.
1996 if len.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1997 if let Operand::Move(_) = operand {
1998 // While this is located in `nll::typeck` this error is not an NLL error, it's
1999 // a required check to 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(
2009 // To determine if `const_in_array_repeat_expressions` feature gate should
2010 // be mentioned, need to check if the rvalue is promotable.
2011 let should_suggest =
2012 should_suggest_const_in_array_repeat_expressions_attribute(
2015 debug!("check_rvalue: should_suggest={:?}", should_suggest);
2017 self.infcx.report_selection_error(
2018 &traits::Obligation::new(
2019 ObligationCause::new(
2021 self.tcx().hir().local_def_id_to_hir_id(self.mir_def_id),
2022 traits::ObligationCauseCode::RepeatVec(should_suggest),
2025 ty::Binder::bind(ty::TraitRef::new(
2026 self.tcx().require_lang_item(
2028 Some(self.last_span),
2030 tcx.mk_substs_trait(ty, &[]),
2033 .to_predicate(self.tcx()),
2035 &traits::SelectionError::Unimplemented,
2044 Rvalue::NullaryOp(_, ty) => {
2045 // Even with unsized locals cannot box an unsized value.
2046 if self.tcx().features().unsized_locals {
2047 let span = body.source_info(location).span;
2048 self.ensure_place_sized(ty, span);
2051 let trait_ref = ty::TraitRef {
2052 def_id: tcx.require_lang_item(SizedTraitLangItem, Some(self.last_span)),
2053 substs: tcx.mk_substs_trait(ty, &[]),
2056 self.prove_trait_ref(
2058 location.to_locations(),
2059 ConstraintCategory::SizedBound,
2063 Rvalue::Cast(cast_kind, op, ty) => {
2065 CastKind::Pointer(PointerCast::ReifyFnPointer) => {
2066 let fn_sig = op.ty(body, tcx).fn_sig(tcx);
2068 // The type that we see in the fcx is like
2069 // `foo::<'a, 'b>`, where `foo` is the path to a
2070 // function definition. When we extract the
2071 // signature, it comes from the `fn_sig` query,
2072 // and hence may contain unnormalized results.
2073 let fn_sig = self.normalize(fn_sig, location);
2075 let ty_fn_ptr_from = tcx.mk_fn_ptr(fn_sig);
2077 if let Err(terr) = self.eq_types(
2080 location.to_locations(),
2081 ConstraintCategory::Cast,
2086 "equating {:?} with {:?} yields {:?}",
2094 CastKind::Pointer(PointerCast::ClosureFnPointer(unsafety)) => {
2095 let sig = match op.ty(body, tcx).kind {
2096 ty::Closure(_, substs) => substs.as_closure().sig(),
2099 let ty_fn_ptr_from = tcx.mk_fn_ptr(tcx.signature_unclosure(sig, *unsafety));
2101 if let Err(terr) = self.eq_types(
2104 location.to_locations(),
2105 ConstraintCategory::Cast,
2110 "equating {:?} with {:?} yields {:?}",
2118 CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
2119 let fn_sig = op.ty(body, tcx).fn_sig(tcx);
2121 // The type that we see in the fcx is like
2122 // `foo::<'a, 'b>`, where `foo` is the path to a
2123 // function definition. When we extract the
2124 // signature, it comes from the `fn_sig` query,
2125 // and hence may contain unnormalized results.
2126 let fn_sig = self.normalize(fn_sig, location);
2128 let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
2130 if let Err(terr) = self.eq_types(
2133 location.to_locations(),
2134 ConstraintCategory::Cast,
2139 "equating {:?} with {:?} yields {:?}",
2147 CastKind::Pointer(PointerCast::Unsize) => {
2149 let trait_ref = ty::TraitRef {
2150 def_id: tcx.require_lang_item(
2151 CoerceUnsizedTraitLangItem,
2152 Some(self.last_span),
2154 substs: tcx.mk_substs_trait(op.ty(body, tcx), &[ty.into()]),
2157 self.prove_trait_ref(
2159 location.to_locations(),
2160 ConstraintCategory::Cast,
2164 CastKind::Pointer(PointerCast::MutToConstPointer) => {
2165 let ty_from = match op.ty(body, tcx).kind {
2166 ty::RawPtr(ty::TypeAndMut {
2168 mutbl: hir::Mutability::Mut,
2174 "unexpected base type for cast {:?}",
2180 let ty_to = match ty.kind {
2181 ty::RawPtr(ty::TypeAndMut {
2183 mutbl: hir::Mutability::Not,
2189 "unexpected target type for cast {:?}",
2195 if let Err(terr) = self.sub_types(
2198 location.to_locations(),
2199 ConstraintCategory::Cast,
2204 "relating {:?} with {:?} yields {:?}",
2212 CastKind::Pointer(PointerCast::ArrayToPointer) => {
2213 let ty_from = op.ty(body, tcx);
2215 let opt_ty_elem = match ty_from.kind {
2216 ty::RawPtr(ty::TypeAndMut {
2217 mutbl: hir::Mutability::Not,
2219 }) => match array_ty.kind {
2220 ty::Array(ty_elem, _) => Some(ty_elem),
2226 let ty_elem = match opt_ty_elem {
2227 Some(ty_elem) => ty_elem,
2232 "ArrayToPointer cast from unexpected type {:?}",
2239 let ty_to = match ty.kind {
2240 ty::RawPtr(ty::TypeAndMut {
2241 mutbl: hir::Mutability::Not,
2248 "ArrayToPointer cast to unexpected type {:?}",
2255 if let Err(terr) = self.sub_types(
2258 location.to_locations(),
2259 ConstraintCategory::Cast,
2264 "relating {:?} with {:?} yields {:?}",
2273 let ty_from = op.ty(body, tcx);
2274 let cast_ty_from = CastTy::from_ty(ty_from);
2275 let cast_ty_to = CastTy::from_ty(ty);
2276 match (cast_ty_from, cast_ty_to) {
2278 | (_, None | Some(CastTy::FnPtr))
2279 | (Some(CastTy::Float), Some(CastTy::Ptr(_)))
2280 | (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Float)) => {
2281 span_mirbug!(self, rvalue, "Invalid cast {:?} -> {:?}", ty_from, ty,)
2284 Some(CastTy::Int(_)),
2285 Some(CastTy::Int(_) | CastTy::Float | CastTy::Ptr(_)),
2287 | (Some(CastTy::Float), Some(CastTy::Int(_) | CastTy::Float))
2288 | (Some(CastTy::Ptr(_)), Some(CastTy::Int(_) | CastTy::Ptr(_)))
2289 | (Some(CastTy::FnPtr), Some(CastTy::Int(_) | CastTy::Ptr(_))) => (),
2295 Rvalue::Ref(region, _borrow_kind, borrowed_place) => {
2296 self.add_reborrow_constraint(&body, location, region, borrowed_place);
2300 BinOp::Eq | BinOp::Ne | BinOp::Lt | BinOp::Le | BinOp::Gt | BinOp::Ge,
2304 let ty_left = left.ty(body, tcx);
2305 match ty_left.kind {
2306 // Types with regions are comparable if they have a common super-type.
2307 ty::RawPtr(_) | ty::FnPtr(_) => {
2308 let ty_right = right.ty(body, tcx);
2309 let common_ty = self.infcx.next_ty_var(TypeVariableOrigin {
2310 kind: TypeVariableOriginKind::MiscVariable,
2311 span: body.source_info(location).span,
2315 ty::Variance::Contravariant,
2317 location.to_locations(),
2318 ConstraintCategory::Boring,
2320 .unwrap_or_else(|err| {
2321 bug!("Could not equate type variable with {:?}: {:?}", ty_left, err)
2323 if let Err(terr) = self.relate_types(
2325 ty::Variance::Contravariant,
2327 location.to_locations(),
2328 ConstraintCategory::Boring,
2333 "unexpected comparison types {:?} and {:?} yields {:?}",
2340 // For types with no regions we can just check that the
2341 // both operands have the same type.
2342 ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char | ty::Float(_)
2343 if ty_left == right.ty(body, tcx) => {}
2344 // Other types are compared by trait methods, not by
2345 // `Rvalue::BinaryOp`.
2349 "unexpected comparison types {:?} and {:?}",
2356 Rvalue::AddressOf(..)
2357 | Rvalue::ThreadLocalRef(..)
2360 | Rvalue::BinaryOp(..)
2361 | Rvalue::CheckedBinaryOp(..)
2362 | Rvalue::UnaryOp(..)
2363 | Rvalue::Discriminant(..) => {}
2367 /// If this rvalue supports a user-given type annotation, then
2368 /// extract and return it. This represents the final type of the
2369 /// rvalue and will be unified with the inferred type.
2370 fn rvalue_user_ty(&self, rvalue: &Rvalue<'tcx>) -> Option<UserTypeAnnotationIndex> {
2373 | Rvalue::ThreadLocalRef(_)
2374 | Rvalue::Repeat(..)
2376 | Rvalue::AddressOf(..)
2379 | Rvalue::BinaryOp(..)
2380 | Rvalue::CheckedBinaryOp(..)
2381 | Rvalue::NullaryOp(..)
2382 | Rvalue::UnaryOp(..)
2383 | Rvalue::Discriminant(..) => None,
2385 Rvalue::Aggregate(aggregate, _) => match **aggregate {
2386 AggregateKind::Adt(_, _, _, user_ty, _) => user_ty,
2387 AggregateKind::Array(_) => None,
2388 AggregateKind::Tuple => None,
2389 AggregateKind::Closure(_, _) => None,
2390 AggregateKind::Generator(_, _, _) => None,
2395 fn check_aggregate_rvalue(
2398 rvalue: &Rvalue<'tcx>,
2399 aggregate_kind: &AggregateKind<'tcx>,
2400 operands: &[Operand<'tcx>],
2403 let tcx = self.tcx();
2405 self.prove_aggregate_predicates(aggregate_kind, location);
2407 if *aggregate_kind == AggregateKind::Tuple {
2408 // tuple rvalue field type is always the type of the op. Nothing to check here.
2412 for (i, operand) in operands.iter().enumerate() {
2413 let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
2414 Ok(field_ty) => field_ty,
2415 Err(FieldAccessError::OutOfRange { field_count }) => {
2419 "accessed field #{} but variant only has {}",
2426 let operand_ty = operand.ty(body, tcx);
2427 let operand_ty = self.normalize(operand_ty, location);
2429 if let Err(terr) = self.sub_types(
2432 location.to_locations(),
2433 ConstraintCategory::Boring,
2438 "{:?} is not a subtype of {:?}: {:?}",
2447 /// Adds the constraints that arise from a borrow expression `&'a P` at the location `L`.
2451 /// - `location`: the location `L` where the borrow expression occurs
2452 /// - `borrow_region`: the region `'a` associated with the borrow
2453 /// - `borrowed_place`: the place `P` being borrowed
2454 fn add_reborrow_constraint(
2458 borrow_region: ty::Region<'tcx>,
2459 borrowed_place: &Place<'tcx>,
2461 // These constraints are only meaningful during borrowck:
2462 let BorrowCheckContext { borrow_set, location_table, all_facts, constraints, .. } =
2463 self.borrowck_context;
2465 // In Polonius mode, we also push a `borrow_region` fact
2466 // linking the loan to the region (in some cases, though,
2467 // there is no loan associated with this borrow expression --
2468 // that occurs when we are borrowing an unsafe place, for
2470 if let Some(all_facts) = all_facts {
2471 let _prof_timer = self.infcx.tcx.prof.generic_activity("polonius_fact_generation");
2472 if let Some(borrow_index) = borrow_set.get_index_of(&location) {
2473 let region_vid = borrow_region.to_region_vid();
2474 all_facts.borrow_region.push((
2477 location_table.mid_index(location),
2482 // If we are reborrowing the referent of another reference, we
2483 // need to add outlives relationships. In a case like `&mut
2484 // *p`, where the `p` has type `&'b mut Foo`, for example, we
2485 // need to ensure that `'b: 'a`.
2488 "add_reborrow_constraint({:?}, {:?}, {:?})",
2489 location, borrow_region, borrowed_place
2492 let mut cursor = borrowed_place.projection.as_ref();
2493 let tcx = self.infcx.tcx;
2494 let field = path_utils::is_upvar_field_projection(
2496 &self.borrowck_context.upvars,
2497 borrowed_place.as_ref(),
2500 let category = if let Some(field) = field {
2501 ConstraintCategory::ClosureUpvar(self.borrowck_context.upvars[field.index()].var_hir_id)
2503 ConstraintCategory::Boring
2506 while let [proj_base @ .., elem] = cursor {
2509 debug!("add_reborrow_constraint - iteration {:?}", elem);
2512 ProjectionElem::Deref => {
2513 let base_ty = Place::ty_from(borrowed_place.local, proj_base, body, tcx).ty;
2515 debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
2516 match base_ty.kind {
2517 ty::Ref(ref_region, _, mutbl) => {
2518 constraints.outlives_constraints.push(OutlivesConstraint {
2519 sup: ref_region.to_region_vid(),
2520 sub: borrow_region.to_region_vid(),
2521 locations: location.to_locations(),
2526 hir::Mutability::Not => {
2527 // Immutable reference. We don't need the base
2528 // to be valid for the entire lifetime of
2532 hir::Mutability::Mut => {
2533 // Mutable reference. We *do* need the base
2534 // to be valid, because after the base becomes
2535 // invalid, someone else can use our mutable deref.
2537 // This is in order to make the following function
2540 // fn unsafe_deref<'a, 'b>(x: &'a &'b mut T) -> &'b mut T {
2545 // As otherwise you could clone `&mut T` using the
2546 // following function:
2548 // fn bad(x: &mut T) -> (&mut T, &mut T) {
2549 // let my_clone = unsafe_deref(&'a x);
2558 // deref of raw pointer, guaranteed to be valid
2561 ty::Adt(def, _) if def.is_box() => {
2562 // deref of `Box`, need the base to be valid - propagate
2564 _ => bug!("unexpected deref ty {:?} in {:?}", base_ty, borrowed_place),
2567 ProjectionElem::Field(..)
2568 | ProjectionElem::Downcast(..)
2569 | ProjectionElem::Index(..)
2570 | ProjectionElem::ConstantIndex { .. }
2571 | ProjectionElem::Subslice { .. } => {
2572 // other field access
2578 fn prove_aggregate_predicates(
2580 aggregate_kind: &AggregateKind<'tcx>,
2583 let tcx = self.tcx();
2586 "prove_aggregate_predicates(aggregate_kind={:?}, location={:?})",
2587 aggregate_kind, location
2590 let instantiated_predicates = match aggregate_kind {
2591 AggregateKind::Adt(def, _, substs, _, _) => {
2592 tcx.predicates_of(def.did).instantiate(tcx, substs)
2595 // For closures, we have some **extra requirements** we
2597 // have to check. In particular, in their upvars and
2598 // signatures, closures often reference various regions
2599 // from the surrounding function -- we call those the
2600 // closure's free regions. When we borrow-check (and hence
2601 // region-check) closures, we may find that the closure
2602 // requires certain relationships between those free
2603 // regions. However, because those free regions refer to
2604 // portions of the CFG of their caller, the closure is not
2605 // in a position to verify those relationships. In that
2606 // case, the requirements get "propagated" to us, and so
2607 // we have to solve them here where we instantiate the
2610 // Despite the opacity of the previous parapgrah, this is
2611 // actually relatively easy to understand in terms of the
2612 // desugaring. A closure gets desugared to a struct, and
2613 // these extra requirements are basically like where
2614 // clauses on the struct.
2615 AggregateKind::Closure(def_id, substs)
2616 | AggregateKind::Generator(def_id, substs, _) => {
2617 self.prove_closure_bounds(tcx, def_id.expect_local(), substs, location)
2620 AggregateKind::Array(_) | AggregateKind::Tuple => ty::InstantiatedPredicates::empty(),
2623 self.normalize_and_prove_instantiated_predicates(
2624 instantiated_predicates,
2625 location.to_locations(),
2629 fn prove_closure_bounds(
2633 substs: SubstsRef<'tcx>,
2635 ) -> ty::InstantiatedPredicates<'tcx> {
2636 if let Some(ref closure_region_requirements) = tcx.mir_borrowck(def_id).closure_requirements
2638 let closure_constraints = QueryRegionConstraints {
2639 outlives: closure_region_requirements.apply_requirements(
2645 // Presently, closures never propagate member
2646 // constraints to their parents -- they are enforced
2647 // locally. This is largely a non-issue as member
2648 // constraints only come from `-> impl Trait` and
2649 // friends which don't appear (thus far...) in
2651 member_constraints: vec![],
2654 let bounds_mapping = closure_constraints
2658 .filter_map(|(idx, constraint)| {
2659 let ty::OutlivesPredicate(k1, r2) =
2660 constraint.no_bound_vars().unwrap_or_else(|| {
2661 bug!("query_constraint {:?} contained bound vars", constraint,);
2665 GenericArgKind::Lifetime(r1) => {
2666 // constraint is r1: r2
2667 let r1_vid = self.borrowck_context.universal_regions.to_region_vid(r1);
2668 let r2_vid = self.borrowck_context.universal_regions.to_region_vid(r2);
2669 let outlives_requirements =
2670 &closure_region_requirements.outlives_requirements[idx];
2673 (outlives_requirements.category, outlives_requirements.blame_span),
2676 GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
2684 .closure_bounds_mapping
2685 .insert(location, bounds_mapping);
2686 assert!(existing.is_none(), "Multiple closures at the same location.");
2688 self.push_region_constraints(
2689 location.to_locations(),
2690 ConstraintCategory::ClosureBounds,
2691 &closure_constraints,
2695 tcx.predicates_of(def_id).instantiate(tcx, substs)
2700 trait_ref: ty::TraitRef<'tcx>,
2701 locations: Locations,
2702 category: ConstraintCategory,
2704 self.prove_predicates(
2705 Some(ty::PredicateAtom::Trait(
2706 ty::TraitPredicate { trait_ref },
2707 hir::Constness::NotConst,
2714 fn normalize_and_prove_instantiated_predicates(
2716 instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
2717 locations: Locations,
2719 for predicate in instantiated_predicates.predicates {
2720 let predicate = self.normalize(predicate, locations);
2721 self.prove_predicate(predicate, locations, ConstraintCategory::Boring);
2725 fn prove_predicates(
2727 predicates: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
2728 locations: Locations,
2729 category: ConstraintCategory,
2731 for predicate in predicates {
2732 let predicate = predicate.to_predicate(self.tcx());
2733 debug!("prove_predicates(predicate={:?}, locations={:?})", predicate, locations,);
2735 self.prove_predicate(predicate, locations, category);
2741 predicate: ty::Predicate<'tcx>,
2742 locations: Locations,
2743 category: ConstraintCategory,
2745 debug!("prove_predicate(predicate={:?}, location={:?})", predicate, locations,);
2747 let param_env = self.param_env;
2748 self.fully_perform_op(
2751 param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
2753 .unwrap_or_else(|NoSolution| {
2754 span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
2758 fn typeck_mir(&mut self, body: &Body<'tcx>) {
2759 self.last_span = body.span;
2760 debug!("run_on_mir: {:?}", body.span);
2762 for (local, local_decl) in body.local_decls.iter_enumerated() {
2763 self.check_local(&body, local, local_decl);
2766 for (block, block_data) in body.basic_blocks().iter_enumerated() {
2767 let mut location = Location { block, statement_index: 0 };
2768 for stmt in &block_data.statements {
2769 if !stmt.source_info.span.is_dummy() {
2770 self.last_span = stmt.source_info.span;
2772 self.check_stmt(body, stmt, location);
2773 location.statement_index += 1;
2776 self.check_terminator(&body, block_data.terminator(), location);
2777 self.check_iscleanup(&body, block_data);
2781 fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
2783 T: type_op::normalize::Normalizable<'tcx> + Copy + 'tcx,
2785 debug!("normalize(value={:?}, location={:?})", value, location);
2786 let param_env = self.param_env;
2787 self.fully_perform_op(
2788 location.to_locations(),
2789 ConstraintCategory::Boring,
2790 param_env.and(type_op::normalize::Normalize::new(value)),
2792 .unwrap_or_else(|NoSolution| {
2793 span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
2799 trait NormalizeLocation: fmt::Debug + Copy {
2800 fn to_locations(self) -> Locations;
2803 impl NormalizeLocation for Locations {
2804 fn to_locations(self) -> Locations {
2809 impl NormalizeLocation for Location {
2810 fn to_locations(self) -> Locations {
2811 Locations::Single(self)
2815 #[derive(Debug, Default)]
2816 struct ObligationAccumulator<'tcx> {
2817 obligations: PredicateObligations<'tcx>,
2820 impl<'tcx> ObligationAccumulator<'tcx> {
2821 fn add<T>(&mut self, value: InferOk<'tcx, T>) -> T {
2822 let InferOk { value, obligations } = value;
2823 self.obligations.extend(obligations);
2827 fn into_vec(self) -> PredicateObligations<'tcx> {