1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! This pass type-checks the MIR to ensure it is not broken.
12 #![allow(unreachable_code)]
14 use borrow_check::borrow_set::BorrowSet;
15 use borrow_check::location::LocationTable;
16 use borrow_check::nll::constraints::{ConstraintSet, OutlivesConstraint};
17 use borrow_check::nll::facts::AllFacts;
18 use borrow_check::nll::region_infer::values::LivenessValues;
19 use borrow_check::nll::region_infer::values::PlaceholderIndices;
20 use borrow_check::nll::region_infer::values::RegionValueElements;
21 use borrow_check::nll::region_infer::{ClosureRegionRequirementsExt, TypeTest};
22 use borrow_check::nll::renumber;
23 use borrow_check::nll::type_check::free_region_relations::{
24 CreateResult, UniversalRegionRelations,
26 use borrow_check::nll::universal_regions::{DefiningTy, UniversalRegions};
27 use borrow_check::nll::ToRegionVid;
28 use dataflow::move_paths::MoveData;
29 use dataflow::FlowAtLocation;
30 use dataflow::MaybeInitializedPlaces;
32 use rustc::hir::def_id::DefId;
33 use rustc::infer::canonical::QueryRegionConstraint;
34 use rustc::infer::outlives::env::RegionBoundPairs;
35 use rustc::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
36 use rustc::mir::interpret::EvalErrorKind::BoundsCheck;
37 use rustc::mir::tcx::PlaceTy;
38 use rustc::mir::visit::{PlaceContext, Visitor};
40 use rustc::traits::query::type_op;
41 use rustc::traits::query::type_op::custom::CustomTypeOp;
42 use rustc::traits::query::{Fallible, NoSolution};
43 use rustc::traits::{ObligationCause, PredicateObligations};
44 use rustc::ty::fold::TypeFoldable;
45 use rustc::ty::subst::{Subst, Substs, UnpackedKind};
46 use rustc::ty::{self, RegionVid, ToPolyTraitRef, Ty, TyCtxt, TyKind};
49 use syntax_pos::{Span, DUMMY_SP};
50 use transform::{MirPass, MirSource};
53 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
55 macro_rules! span_mirbug {
56 ($context:expr, $elem:expr, $($message:tt)*) => ({
57 $crate::borrow_check::nll::type_check::mirbug(
61 "broken MIR in {:?} ({:?}): {}",
64 format_args!($($message)*),
70 macro_rules! span_mirbug_and_err {
71 ($context:expr, $elem:expr, $($message:tt)*) => ({
73 span_mirbug!($context, $elem, $($message)*);
79 mod constraint_conversion;
80 pub mod free_region_relations;
85 /// Type checks the given `mir` in the context of the inference
86 /// context `infcx`. Returns any region constraints that have yet to
87 /// be proven. This result is includes liveness constraints that
88 /// ensure that regions appearing in the types of all local variables
89 /// are live at all points where that local variable may later be
92 /// This phase of type-check ought to be infallible -- this is because
93 /// the original, HIR-based type-check succeeded. So if any errors
94 /// occur here, we will get a `bug!` reported.
98 /// - `infcx` -- inference context to use
99 /// - `param_env` -- parameter environment to use for trait solving
100 /// - `mir` -- MIR to type-check
101 /// - `mir_def_id` -- DefId from which the MIR is derived (must be local)
102 /// - `region_bound_pairs` -- the implied outlives obligations between type parameters
103 /// and lifetimes (e.g., `&'a T` implies `T: 'a`)
104 /// - `implicit_region_bound` -- a region which all generic parameters are assumed
105 /// to outlive; should represent the fn body
106 /// - `input_tys` -- fully liberated, but **not** normalized, expected types of the arguments;
107 /// the types of the input parameters found in the MIR itself will be equated with these
108 /// - `output_ty` -- fully liberated, but **not** normalized, expected return type;
109 /// the type for the RETURN_PLACE will be equated with this
110 /// - `liveness` -- results of a liveness computation on the MIR; used to create liveness
111 /// constraints for the regions in the types of variables
112 /// - `flow_inits` -- results of a maybe-init dataflow analysis
113 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysiss
114 pub(crate) fn type_check<'gcx, 'tcx>(
115 infcx: &InferCtxt<'_, 'gcx, 'tcx>,
116 param_env: ty::ParamEnv<'gcx>,
119 universal_regions: &Rc<UniversalRegions<'tcx>>,
120 location_table: &LocationTable,
121 borrow_set: &BorrowSet<'tcx>,
122 all_facts: &mut Option<AllFacts>,
123 flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
124 move_data: &MoveData<'tcx>,
125 elements: &Rc<RegionValueElements>,
126 ) -> MirTypeckResults<'tcx> {
127 let implicit_region_bound = infcx.tcx.mk_region(ty::ReVar(universal_regions.fr_fn_body));
128 let mut constraints = MirTypeckRegionConstraints {
129 liveness_constraints: LivenessValues::new(elements),
130 outlives_constraints: ConstraintSet::default(),
131 closure_bounds_mapping: Default::default(),
132 type_tests: Vec::default(),
134 let mut placeholder_indices = PlaceholderIndices::default();
137 universal_region_relations,
139 normalized_inputs_and_output,
140 } = free_region_relations::create(
143 Some(implicit_region_bound),
148 let mut borrowck_context = BorrowCheckContext {
153 constraints: &mut constraints,
154 placeholder_indices: &mut placeholder_indices,
163 Some(implicit_region_bound),
164 Some(&mut borrowck_context),
165 Some(&universal_region_relations),
167 cx.equate_inputs_and_outputs(mir, universal_regions, &normalized_inputs_and_output);
168 liveness::generate(cx, mir, elements, flow_inits, move_data, location_table);
172 .map(|bcx| translate_outlives_facts(bcx));
179 universal_region_relations,
183 fn type_check_internal<'a, 'gcx, 'tcx, R>(
184 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
186 param_env: ty::ParamEnv<'gcx>,
188 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
189 implicit_region_bound: Option<ty::Region<'tcx>>,
190 borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
191 universal_region_relations: Option<&'a UniversalRegionRelations<'tcx>>,
192 mut extra: impl FnMut(&mut TypeChecker<'a, 'gcx, 'tcx>) -> R,
194 let mut checker = TypeChecker::new(
200 implicit_region_bound,
202 universal_region_relations,
204 let errors_reported = {
205 let mut verifier = TypeVerifier::new(&mut checker, mir);
206 verifier.visit_mir(mir);
207 verifier.errors_reported
210 if !errors_reported {
211 // if verifier failed, don't do further checks to avoid ICEs
212 checker.typeck_mir(mir);
218 fn translate_outlives_facts(cx: &mut BorrowCheckContext) {
219 if let Some(facts) = cx.all_facts {
220 let location_table = cx.location_table;
223 .extend(cx.constraints.outlives_constraints.iter().flat_map(
224 |constraint: &OutlivesConstraint| {
225 if let Some(from_location) = constraint.locations.from_location() {
226 Either::Left(iter::once((
229 location_table.mid_index(from_location),
235 .map(move |location| (constraint.sup, constraint.sub, location)),
243 fn mirbug(tcx: TyCtxt, span: Span, msg: &str) {
244 // We sometimes see MIR failures (notably predicate failures) due to
245 // the fact that we check rvalue sized predicates here. So use `delay_span_bug`
246 // to avoid reporting bugs in those cases.
247 tcx.sess.diagnostic().delay_span_bug(span, msg);
250 enum FieldAccessError {
251 OutOfRange { field_count: usize },
254 /// Verifies that MIR types are sane to not crash further checks.
256 /// The sanitize_XYZ methods here take an MIR object and compute its
257 /// type, calling `span_mirbug` and returning an error type if there
259 struct TypeVerifier<'a, 'b: 'a, 'gcx: 'tcx, 'tcx: 'b> {
260 cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>,
264 errors_reported: bool,
267 impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
268 fn visit_span(&mut self, span: &Span) {
269 if !span.is_dummy() {
270 self.last_span = *span;
274 fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
275 self.sanitize_place(place, location, context);
278 fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
279 self.super_constant(constant, location);
280 self.sanitize_constant(constant, location);
281 self.sanitize_type(constant, constant.ty);
283 if let Some(user_ty) = constant.user_ty {
284 if let Err(terr) = self.cx.relate_type_and_user_type(
286 ty::Variance::Invariant,
288 location.to_locations(),
289 ConstraintCategory::Boring,
294 "bad constant user type {:?} vs {:?}: {:?}",
303 fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
304 self.super_rvalue(rvalue, location);
305 let rval_ty = rvalue.ty(self.mir, self.tcx());
306 self.sanitize_type(rvalue, rval_ty);
309 fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
310 self.super_local_decl(local, local_decl);
311 self.sanitize_type(local_decl, local_decl.ty);
313 if let Some((user_ty, span)) = local_decl.user_ty {
314 if let Err(terr) = self.cx.relate_type_and_user_type(
316 ty::Variance::Invariant,
318 Locations::All(span),
319 ConstraintCategory::TypeAnnotation,
324 "bad user type on variable {:?}: {:?} != {:?} ({:?})",
334 fn visit_mir(&mut self, mir: &Mir<'tcx>) {
335 self.sanitize_type(&"return type", mir.return_ty());
336 for local_decl in &mir.local_decls {
337 self.sanitize_type(local_decl, local_decl.ty);
339 if self.errors_reported {
346 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
347 fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
350 mir_def_id: cx.mir_def_id,
353 errors_reported: false,
357 fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
361 fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
362 if ty.has_escaping_regions() || ty.references_error() {
363 span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
369 /// Checks that the constant's `ty` field matches up with what
370 /// would be expected from its literal.
371 fn sanitize_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
373 "sanitize_constant(constant={:?}, location={:?})",
377 // FIXME(#46702) -- We need some way to get the predicates
378 // associated with the "pre-evaluated" form of the
379 // constant. For example, consider that the constant
380 // may have associated constant projections (`<Foo as
381 // Trait<'a, 'b>>::SOME_CONST`) that impose
382 // constraints on `'a` and `'b`. These constraints
383 // would be lost if we just look at the normalized
385 if let ty::FnDef(def_id, substs) = constant.literal.ty.sty {
386 let tcx = self.tcx();
387 let type_checker = &mut self.cx;
389 // FIXME -- For now, use the substitutions from
390 // `value.ty` rather than `value.val`. The
391 // renumberer will rewrite them to independent
392 // sets of regions; in principle, we ought to
393 // derive the type of the `value.val` from "first
394 // principles" and equate with value.ty, but as we
395 // are transitioning to the miri-based system, we
396 // don't have a handy function for that, so for
397 // now we just ignore `value.val` regions.
399 let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
400 type_checker.normalize_and_prove_instantiated_predicates(
401 instantiated_predicates,
402 location.to_locations(),
406 debug!("sanitize_constant: expected_ty={:?}", constant.literal.ty);
408 if let Err(terr) = self.cx.eq_types(
411 location.to_locations(),
412 ConstraintCategory::Boring,
417 "constant {:?} should have type {:?} but has {:?} ({:?})",
426 /// Checks that the types internal to the `place` match up with
427 /// what would be expected.
432 context: PlaceContext,
434 debug!("sanitize_place: {:?}", place);
435 let place_ty = match *place {
436 Place::Local(index) => PlaceTy::Ty {
437 ty: self.mir.local_decls[index].ty,
439 Place::Promoted(box (_index, sty)) => {
440 let sty = self.sanitize_type(place, sty);
441 // FIXME -- promoted MIR return types reference
442 // various "free regions" (e.g., scopes and things)
443 // that they ought not to do. We have to figure out
444 // how best to handle that -- probably we want treat
445 // promoted MIR much like closures, renumbering all
446 // their free regions and propagating constraints
447 // upwards. We have the same acyclic guarantees, so
448 // that should be possible. But for now, ignore them.
450 // let promoted_mir = &self.mir.promoted[index];
451 // promoted_mir.return_ty()
452 PlaceTy::Ty { ty: sty }
454 Place::Static(box Static { def_id, ty: sty }) => {
455 let sty = self.sanitize_type(place, sty);
456 let ty = self.tcx().type_of(def_id);
457 let ty = self.cx.normalize(ty, location);
460 .eq_types(ty, sty, location.to_locations(), ConstraintCategory::Boring)
465 "bad static type ({:?}: {:?}): {:?}",
471 PlaceTy::Ty { ty: sty }
473 Place::Projection(ref proj) => {
474 let base_context = if context.is_mutating_use() {
475 PlaceContext::Projection(Mutability::Mut)
477 PlaceContext::Projection(Mutability::Not)
479 let base_ty = self.sanitize_place(&proj.base, location, base_context);
480 if let PlaceTy::Ty { ty } = base_ty {
481 if ty.references_error() {
482 assert!(self.errors_reported);
484 ty: self.tcx().types.err,
488 self.sanitize_projection(base_ty, &proj.elem, place, location)
491 if let PlaceContext::Copy = context {
492 let tcx = self.tcx();
493 let trait_ref = ty::TraitRef {
494 def_id: tcx.lang_items().copy_trait().unwrap(),
495 substs: tcx.mk_substs_trait(place_ty.to_ty(tcx), &[]),
498 // In order to have a Copy operand, the type T of the value must be Copy. Note that we
499 // prove that T: Copy, rather than using the type_moves_by_default test. This is
500 // important because type_moves_by_default ignores the resulting region obligations and
501 // assumes they pass. This can result in bounds from Copy impls being unsoundly ignored
502 // (e.g., #29149). Note that we decide to use Copy before knowing whether the bounds
503 // fully apply: in effect, the rule is that if a value of some type could implement
504 // Copy, then it must.
505 self.cx.prove_trait_ref(
507 location.to_locations(),
508 ConstraintCategory::CopyBound,
514 fn sanitize_projection(
517 pi: &PlaceElem<'tcx>,
521 debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, place);
522 let tcx = self.tcx();
523 let base_ty = base.to_ty(tcx);
525 ProjectionElem::Deref => {
526 let deref_ty = base_ty.builtin_deref(true);
528 ty: deref_ty.map(|t| t.ty).unwrap_or_else(|| {
529 span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty)
533 ProjectionElem::Index(i) => {
534 let index_ty = Place::Local(i).ty(self.mir, tcx).to_ty(tcx);
535 if index_ty != tcx.types.usize {
537 ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i),
541 ty: base_ty.builtin_index().unwrap_or_else(|| {
542 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
547 ProjectionElem::ConstantIndex { .. } => {
548 // consider verifying in-bounds
550 ty: base_ty.builtin_index().unwrap_or_else(|| {
551 span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
555 ProjectionElem::Subslice { from, to } => PlaceTy::Ty {
556 ty: match base_ty.sty {
557 ty::Array(inner, size) => {
558 let size = size.unwrap_usize(tcx);
559 let min_size = (from as u64) + (to as u64);
560 if let Some(rest_size) = size.checked_sub(min_size) {
561 tcx.mk_array(inner, rest_size)
563 span_mirbug_and_err!(
566 "taking too-small slice of {:?}",
571 ty::Slice(..) => base_ty,
572 _ => span_mirbug_and_err!(self, place, "slice of non-array {:?}", base_ty),
575 ProjectionElem::Downcast(adt_def1, index) => match base_ty.sty {
576 ty::Adt(adt_def, substs) if adt_def.is_enum() && adt_def == adt_def1 => {
577 if index >= adt_def.variants.len() {
579 ty: span_mirbug_and_err!(
582 "cast to variant #{:?} but enum only has {:?}",
584 adt_def.variants.len()
591 variant_index: index,
596 ty: span_mirbug_and_err!(
599 "can't downcast {:?} as {:?}",
605 ProjectionElem::Field(field, fty) => {
606 let fty = self.sanitize_type(place, fty);
607 match self.field_ty(place, base, field, location) {
608 Ok(ty) => if let Err(terr) = self.cx.eq_types(
611 location.to_locations(),
612 ConstraintCategory::Boring,
617 "bad field access ({:?}: {:?}): {:?}",
623 Err(FieldAccessError::OutOfRange { field_count }) => span_mirbug!(
626 "accessed field #{} but variant only has {}",
631 PlaceTy::Ty { ty: fty }
636 fn error(&mut self) -> Ty<'tcx> {
637 self.errors_reported = true;
643 parent: &dyn fmt::Debug,
644 base_ty: PlaceTy<'tcx>,
647 ) -> Result<Ty<'tcx>, FieldAccessError> {
648 let tcx = self.tcx();
650 let (variant, substs) = match base_ty {
655 } => (&adt_def.variants[variant_index], substs),
656 PlaceTy::Ty { ty } => match ty.sty {
657 ty::Adt(adt_def, substs) if !adt_def.is_enum() => (&adt_def.variants[0], substs),
658 ty::Closure(def_id, substs) => {
659 return match substs.upvar_tys(def_id, tcx).nth(field.index()) {
661 None => Err(FieldAccessError::OutOfRange {
662 field_count: substs.upvar_tys(def_id, tcx).count(),
666 ty::Generator(def_id, substs, _) => {
667 // Try pre-transform fields first (upvars and current state)
668 if let Some(ty) = substs.pre_transforms_tys(def_id, tcx).nth(field.index()) {
672 // Then try `field_tys` which contains all the fields, but it
673 // requires the final optimized MIR.
674 return match substs.field_tys(def_id, tcx).nth(field.index()) {
676 None => Err(FieldAccessError::OutOfRange {
677 field_count: substs.field_tys(def_id, tcx).count(),
682 return match tys.get(field.index()) {
684 None => Err(FieldAccessError::OutOfRange {
685 field_count: tys.len(),
690 return Ok(span_mirbug_and_err!(
693 "can't project out of {:?}",
700 if let Some(field) = variant.fields.get(field.index()) {
701 Ok(self.cx.normalize(&field.ty(tcx, substs), location))
703 Err(FieldAccessError::OutOfRange {
704 field_count: variant.fields.len(),
710 /// The MIR type checker. Visits the MIR and enforces all the
711 /// constraints needed for it to be valid and well-typed. Along the
712 /// way, it accrues region constraints -- these can later be used by
713 /// NLL region checking.
714 struct TypeChecker<'a, 'gcx: 'tcx, 'tcx: 'a> {
715 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
716 param_env: ty::ParamEnv<'gcx>,
720 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
721 implicit_region_bound: Option<ty::Region<'tcx>>,
722 reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
723 borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
724 universal_region_relations: Option<&'a UniversalRegionRelations<'tcx>>,
727 struct BorrowCheckContext<'a, 'tcx: 'a> {
728 universal_regions: &'a UniversalRegions<'tcx>,
729 location_table: &'a LocationTable,
730 all_facts: &'a mut Option<AllFacts>,
731 borrow_set: &'a BorrowSet<'tcx>,
732 constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
733 placeholder_indices: &'a mut PlaceholderIndices,
736 crate struct MirTypeckResults<'tcx> {
737 crate constraints: MirTypeckRegionConstraints<'tcx>,
738 crate placeholder_indices: PlaceholderIndices,
739 crate universal_region_relations: Rc<UniversalRegionRelations<'tcx>>,
742 /// A collection of region constraints that must be satisfied for the
743 /// program to be considered well-typed.
744 crate struct MirTypeckRegionConstraints<'tcx> {
745 /// In general, the type-checker is not responsible for enforcing
746 /// liveness constraints; this job falls to the region inferencer,
747 /// which performs a liveness analysis. However, in some limited
748 /// cases, the MIR type-checker creates temporary regions that do
749 /// not otherwise appear in the MIR -- in particular, the
750 /// late-bound regions that it instantiates at call-sites -- and
751 /// hence it must report on their liveness constraints.
752 crate liveness_constraints: LivenessValues<RegionVid>,
754 crate outlives_constraints: ConstraintSet,
756 crate closure_bounds_mapping:
757 FxHashMap<Location, FxHashMap<(RegionVid, RegionVid), (ConstraintCategory, Span)>>,
759 crate type_tests: Vec<TypeTest<'tcx>>,
762 /// The `Locations` type summarizes *where* region constraints are
763 /// required to hold. Normally, this is at a particular point which
764 /// created the obligation, but for constraints that the user gave, we
765 /// want the constraint to hold at all points.
766 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
768 /// Indicates that a type constraint should always be true. This
769 /// is particularly important in the new borrowck analysis for
770 /// things like the type of the return slot. Consider this
774 /// fn foo<'a>(x: &'a u32) -> &'a u32 {
776 /// return &y; // error
780 /// Here, we wind up with the signature from the return type being
781 /// something like `&'1 u32` where `'1` is a universal region. But
782 /// the type of the return slot `_0` is something like `&'2 u32`
783 /// where `'2` is an existential region variable. The type checker
784 /// requires that `&'2 u32 = &'1 u32` -- but at what point? In the
785 /// older NLL analysis, we required this only at the entry point
786 /// to the function. By the nature of the constraints, this wound
787 /// up propagating to all points reachable from start (because
788 /// `'1` -- as a universal region -- is live everywhere). In the
789 /// newer analysis, though, this doesn't work: `_0` is considered
790 /// dead at the start (it has no usable value) and hence this type
791 /// equality is basically a no-op. Then, later on, when we do `_0
792 /// = &'3 y`, that region `'3` never winds up related to the
793 /// universal region `'1` and hence no error occurs. Therefore, we
794 /// use Locations::All instead, which ensures that the `'1` and
795 /// `'2` are equal everything. We also use this for other
796 /// user-given type annotations; e.g., if the user wrote `let mut
797 /// x: &'static u32 = ...`, we would ensure that all values
798 /// assigned to `x` are of `'static` lifetime.
800 /// The span points to the place the constraint arose. For example,
801 /// it points to the type in a user-given type annotation. If
802 /// there's no sensible span then it's DUMMY_SP.
805 /// An outlives constraint that only has to hold at a single location,
806 /// usually it represents a point where references flow from one spot to
807 /// another (e.g., `x = y`)
812 pub fn from_location(&self) -> Option<Location> {
814 Locations::All(_) => None,
815 Locations::Single(from_location) => Some(*from_location),
819 /// Gets a span representing the location.
820 pub fn span(&self, mir: &Mir<'_>) -> Span {
822 Locations::All(span) => *span,
823 Locations::Single(l) => mir.source_info(*l).span,
828 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
830 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
833 param_env: ty::ParamEnv<'gcx>,
834 region_bound_pairs: &'a RegionBoundPairs<'tcx>,
835 implicit_region_bound: Option<ty::Region<'tcx>>,
836 borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
837 universal_region_relations: Option<&'a UniversalRegionRelations<'tcx>>,
846 implicit_region_bound,
848 reported_errors: Default::default(),
849 universal_region_relations,
853 /// Given some operation `op` that manipulates types, proves
854 /// predicates, or otherwise uses the inference context, executes
855 /// `op` and then executes all the further obligations that `op`
856 /// returns. This will yield a set of outlives constraints amongst
857 /// regions which are extracted and stored as having occurred at
860 /// **Any `rustc::infer` operations that might generate region
861 /// constraints should occur within this method so that those
862 /// constraints can be properly localized!**
863 fn fully_perform_op<R>(
865 locations: Locations,
866 category: ConstraintCategory,
867 op: impl type_op::TypeOp<'gcx, 'tcx, Output = R>,
869 let (r, opt_data) = op.fully_perform(self.infcx)?;
871 if let Some(data) = &opt_data {
872 self.push_region_constraints(locations, category, data);
878 fn push_region_constraints(
880 locations: Locations,
881 category: ConstraintCategory,
882 data: &[QueryRegionConstraint<'tcx>],
885 "push_region_constraints: constraints generated at {:?} are {:#?}",
889 if let Some(ref mut borrowck_context) = self.borrowck_context {
890 constraint_conversion::ConstraintConversion::new(
892 borrowck_context.universal_regions,
893 self.region_bound_pairs,
894 self.implicit_region_bound,
898 &mut borrowck_context.constraints.outlives_constraints,
899 &mut borrowck_context.constraints.type_tests,
900 ).convert_all(&data);
904 /// Convenient wrapper around `relate_tys::relate_types` -- see
905 /// that fn for docs.
911 locations: Locations,
912 category: ConstraintCategory,
914 relate_tys::relate_types(
921 self.borrowck_context.as_mut().map(|x| &mut **x),
929 locations: Locations,
930 category: ConstraintCategory,
932 self.relate_types(sub, ty::Variance::Covariant, sup, locations, category)
935 /// Try to relate `sub <: sup`; if this fails, instantiate opaque
936 /// variables in `sub` with their inferred definitions and try
937 /// again. This is used for opaque types in places (e.g., `let x:
939 fn sub_types_or_anon(
943 locations: Locations,
944 category: ConstraintCategory,
946 if let Err(terr) = self.sub_types(sub, sup, locations, category) {
947 if let TyKind::Opaque(..) = sup.sty {
948 // When you have `let x: impl Foo = ...` in a closure,
949 // the resulting inferend values are stored with the
950 // def-id of the base function.
951 let parent_def_id = self.tcx().closure_base_def_id(self.mir_def_id);
952 return self.eq_opaque_type_and_type(sub, sup, parent_def_id, locations, category);
964 locations: Locations,
965 category: ConstraintCategory,
967 self.relate_types(a, ty::Variance::Invariant, b, locations, category)
970 fn relate_type_and_user_type(
974 user_ty: UserTypeAnnotation<'tcx>,
975 locations: Locations,
976 category: ConstraintCategory,
979 "relate_type_and_user_type(a={:?}, v={:?}, user_ty={:?}, locations={:?})",
980 a, v, user_ty, locations,
984 UserTypeAnnotation::Ty(canonical_ty) => {
985 let (ty, _) = self.infcx
986 .instantiate_canonical_with_fresh_inference_vars(DUMMY_SP, &canonical_ty);
988 // The `TypeRelating` code assumes that "unresolved inference
989 // variables" appear in the "a" side, so flip `Contravariant`
990 // ambient variance to get the right relationship.
991 let v1 = ty::Contravariant.xform(v);
993 self.relate_types(ty, v1, a, locations, category)?;
995 UserTypeAnnotation::TypeOf(def_id, canonical_substs) => {
1000 .instantiate_canonical_with_fresh_inference_vars(DUMMY_SP, &canonical_substs);
1002 self.fully_perform_op(
1005 self.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
1006 a, v, def_id, user_substs,
1015 fn eq_opaque_type_and_type(
1017 revealed_ty: Ty<'tcx>,
1019 anon_owner_def_id: DefId,
1020 locations: Locations,
1021 category: ConstraintCategory,
1024 "eq_opaque_type_and_type( \
1027 revealed_ty, anon_ty
1029 let infcx = self.infcx;
1030 let tcx = infcx.tcx;
1031 let param_env = self.param_env;
1032 debug!("eq_opaque_type_and_type: mir_def_id={:?}", self.mir_def_id);
1033 let opaque_type_map = self.fully_perform_op(
1038 let mut obligations = ObligationAccumulator::default();
1040 let dummy_body_id = ObligationCause::dummy().body_id;
1041 let (output_ty, opaque_type_map) =
1042 obligations.add(infcx.instantiate_opaque_types(
1049 "eq_opaque_type_and_type: \
1050 instantiated output_ty={:?} \
1051 opaque_type_map={:#?} \
1053 output_ty, opaque_type_map, revealed_ty
1055 obligations.add(infcx
1056 .at(&ObligationCause::dummy(), param_env)
1057 .eq(output_ty, revealed_ty)?);
1059 for (&opaque_def_id, opaque_decl) in &opaque_type_map {
1060 let opaque_defn_ty = tcx.type_of(opaque_def_id);
1061 let opaque_defn_ty = opaque_defn_ty.subst(tcx, opaque_decl.substs);
1062 let opaque_defn_ty = renumber::renumber_regions(infcx, &opaque_defn_ty);
1064 "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?}",
1065 opaque_decl.concrete_ty,
1066 infcx.resolve_type_vars_if_possible(&opaque_decl.concrete_ty),
1069 obligations.add(infcx
1070 .at(&ObligationCause::dummy(), param_env)
1071 .eq(opaque_decl.concrete_ty, opaque_defn_ty)?);
1074 debug!("eq_opaque_type_and_type: equated");
1077 value: Some(opaque_type_map),
1078 obligations: obligations.into_vec(),
1081 || "input_output".to_string(),
1085 let universal_region_relations = match self.universal_region_relations {
1087 None => return Ok(()),
1090 // Finally, if we instantiated the anon types successfully, we
1091 // have to solve any bounds (e.g., `-> impl Iterator` needs to
1092 // prove that `T: Iterator` where `T` is the type we
1093 // instantiated it with).
1094 if let Some(opaque_type_map) = opaque_type_map {
1095 for (opaque_def_id, opaque_decl) in opaque_type_map {
1096 self.fully_perform_op(
1098 ConstraintCategory::OpaqueType,
1101 infcx.constrain_opaque_type(
1104 universal_region_relations,
1108 obligations: vec![],
1111 || "opaque_type_map".to_string(),
1119 fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
1123 fn check_stmt(&mut self, mir: &Mir<'tcx>, stmt: &Statement<'tcx>, location: Location) {
1124 debug!("check_stmt: {:?}", stmt);
1125 let tcx = self.tcx();
1127 StatementKind::Assign(ref place, ref rv) => {
1128 // Assignments to temporaries are not "interesting";
1129 // they are not caused by the user, but rather artifacts
1130 // of lowering. Assignments to other sorts of places *are* interesting
1132 let category = match *place {
1133 Place::Local(RETURN_PLACE) => if let Some(BorrowCheckContext {
1136 defining_ty: DefiningTy::Const(def_id, _),
1140 }) = self.borrowck_context
1142 if tcx.is_static(*def_id).is_some() {
1143 ConstraintCategory::UseAsStatic
1145 ConstraintCategory::UseAsConst
1148 ConstraintCategory::Return
1150 Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
1151 ConstraintCategory::Boring
1153 _ => ConstraintCategory::Assignment,
1156 let place_ty = place.ty(mir, tcx).to_ty(tcx);
1157 let rv_ty = rv.ty(mir, tcx);
1159 self.sub_types_or_anon(rv_ty, place_ty, location.to_locations(), category)
1164 "bad assignment ({:?} = {:?}): {:?}",
1171 if let Some(user_ty) = self.rvalue_user_ty(rv) {
1172 if let Err(terr) = self.relate_type_and_user_type(
1174 ty::Variance::Invariant,
1176 location.to_locations(),
1177 ConstraintCategory::Boring,
1182 "bad user type on rvalue ({:?} = {:?}): {:?}",
1190 self.check_rvalue(mir, rv, location);
1191 if !self.tcx().features().unsized_locals {
1192 let trait_ref = ty::TraitRef {
1193 def_id: tcx.lang_items().sized_trait().unwrap(),
1194 substs: tcx.mk_substs_trait(place_ty, &[]),
1196 self.prove_trait_ref(
1198 location.to_locations(),
1199 ConstraintCategory::SizedBound,
1203 StatementKind::SetDiscriminant {
1207 let place_type = place.ty(mir, tcx).to_ty(tcx);
1208 let adt = match place_type.sty {
1209 TyKind::Adt(adt, _) if adt.is_enum() => adt,
1212 stmt.source_info.span,
1213 "bad set discriminant ({:?} = {:?}): lhs is not an enum",
1219 if variant_index >= adt.variants.len() {
1221 stmt.source_info.span,
1222 "bad set discriminant ({:?} = {:?}): value of of range",
1228 StatementKind::AscribeUserType(ref place, variance, c_ty) => {
1229 let place_ty = place.ty(mir, tcx).to_ty(tcx);
1230 if let Err(terr) = self.relate_type_and_user_type(
1234 Locations::All(stmt.source_info.span),
1235 ConstraintCategory::TypeAnnotation,
1240 "bad type assert ({:?} <: {:?}): {:?}",
1247 StatementKind::FakeRead(..)
1248 | StatementKind::StorageLive(_)
1249 | StatementKind::StorageDead(_)
1250 | StatementKind::InlineAsm { .. }
1251 | StatementKind::EndRegion(_)
1252 | StatementKind::Validate(..)
1253 | StatementKind::Nop => {}
1257 fn check_terminator(
1260 term: &Terminator<'tcx>,
1261 term_location: Location,
1263 debug!("check_terminator: {:?}", term);
1264 let tcx = self.tcx();
1266 TerminatorKind::Goto { .. }
1267 | TerminatorKind::Resume
1268 | TerminatorKind::Abort
1269 | TerminatorKind::Return
1270 | TerminatorKind::GeneratorDrop
1271 | TerminatorKind::Unreachable
1272 | TerminatorKind::Drop { .. }
1273 | TerminatorKind::FalseEdges { .. }
1274 | TerminatorKind::FalseUnwind { .. } => {
1275 // no checks needed for these
1278 TerminatorKind::DropAndReplace {
1284 let place_ty = location.ty(mir, tcx).to_ty(tcx);
1285 let rv_ty = value.ty(mir, tcx);
1287 let locations = term_location.to_locations();
1289 self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
1294 "bad DropAndReplace ({:?} = {:?}): {:?}",
1301 TerminatorKind::SwitchInt {
1306 let discr_ty = discr.ty(mir, tcx);
1307 if let Err(terr) = self.sub_types(
1310 term_location.to_locations(),
1311 ConstraintCategory::Assignment,
1316 "bad SwitchInt ({:?} on {:?}): {:?}",
1322 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
1323 span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
1325 // FIXME: check the values
1327 TerminatorKind::Call {
1334 let func_ty = func.ty(mir, tcx);
1335 debug!("check_terminator: call, func_ty={:?}", func_ty);
1336 let sig = match func_ty.sty {
1337 ty::FnDef(..) | ty::FnPtr(_) => func_ty.fn_sig(tcx),
1339 span_mirbug!(self, term, "call to non-function {:?}", func_ty);
1343 let (sig, map) = self.infcx.replace_late_bound_regions_with_fresh_var(
1344 term.source_info.span,
1345 LateBoundRegionConversionTime::FnCall,
1348 let sig = self.normalize(sig, term_location);
1349 self.check_call_dest(mir, term, &sig, destination, term_location);
1351 self.prove_predicates(
1352 sig.inputs().iter().map(|ty| ty::Predicate::WellFormed(ty)),
1353 term_location.to_locations(),
1354 ConstraintCategory::Boring,
1357 // The ordinary liveness rules will ensure that all
1358 // regions in the type of the callee are live here. We
1359 // then further constrain the late-bound regions that
1360 // were instantiated at the call site to be live as
1361 // well. The resulting is that all the input (and
1362 // output) types in the signature must be live, since
1363 // all the inputs that fed into it were live.
1364 for &late_bound_region in map.values() {
1365 if let Some(ref mut borrowck_context) = self.borrowck_context {
1366 let region_vid = borrowck_context
1368 .to_region_vid(late_bound_region);
1371 .liveness_constraints
1372 .add_element(region_vid, term_location);
1376 self.check_call_inputs(mir, term, &sig, args, term_location, from_hir_call);
1378 TerminatorKind::Assert {
1379 ref cond, ref msg, ..
1381 let cond_ty = cond.ty(mir, tcx);
1382 if cond_ty != tcx.types.bool {
1383 span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
1386 if let BoundsCheck { ref len, ref index } = *msg {
1387 if len.ty(mir, tcx) != tcx.types.usize {
1388 span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
1390 if index.ty(mir, tcx) != tcx.types.usize {
1391 span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
1395 TerminatorKind::Yield { ref value, .. } => {
1396 let value_ty = value.ty(mir, tcx);
1397 match mir.yield_ty {
1398 None => span_mirbug!(self, term, "yield in non-generator"),
1400 if let Err(terr) = self.sub_types(
1403 term_location.to_locations(),
1404 ConstraintCategory::Return,
1409 "type of yield value is {:?}, but the yield type is {:?}: {:?}",
1424 term: &Terminator<'tcx>,
1425 sig: &ty::FnSig<'tcx>,
1426 destination: &Option<(Place<'tcx>, BasicBlock)>,
1427 term_location: Location,
1429 let tcx = self.tcx();
1430 match *destination {
1431 Some((ref dest, _target_block)) => {
1432 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
1433 let category = match *dest {
1434 Place::Local(RETURN_PLACE) => {
1435 if let Some(BorrowCheckContext {
1438 defining_ty: DefiningTy::Const(def_id, _),
1442 }) = self.borrowck_context
1444 if tcx.is_static(*def_id).is_some() {
1445 ConstraintCategory::UseAsStatic
1447 ConstraintCategory::UseAsConst
1450 ConstraintCategory::Return
1453 Place::Local(l) if !mir.local_decls[l].is_user_variable.is_some() => {
1454 ConstraintCategory::Boring
1456 _ => ConstraintCategory::Assignment,
1459 let locations = term_location.to_locations();
1462 self.sub_types_or_anon(sig.output(), dest_ty, locations, category)
1467 "call dest mismatch ({:?} <- {:?}): {:?}",
1474 // When `#![feature(unsized_locals)]` is not enabled,
1475 // this check is done at `check_local`.
1476 if self.tcx().features().unsized_locals {
1477 let span = term.source_info.span;
1478 self.ensure_place_sized(dest_ty, span);
1482 // FIXME(canndrew): This is_never should probably be an is_uninhabited
1483 if !sig.output().is_never() {
1484 span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
1490 fn check_call_inputs(
1493 term: &Terminator<'tcx>,
1494 sig: &ty::FnSig<'tcx>,
1495 args: &[Operand<'tcx>],
1496 term_location: Location,
1497 from_hir_call: bool,
1499 debug!("check_call_inputs({:?}, {:?})", sig, args);
1500 if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.variadic) {
1501 span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
1503 for (n, (fn_arg, op_arg)) in sig.inputs().iter().zip(args).enumerate() {
1504 let op_arg_ty = op_arg.ty(mir, self.tcx());
1505 let category = if from_hir_call {
1506 ConstraintCategory::CallArgument
1508 ConstraintCategory::Boring
1511 self.sub_types(op_arg_ty, fn_arg, term_location.to_locations(), category)
1516 "bad arg #{:?} ({:?} <- {:?}): {:?}",
1526 fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block_data: &BasicBlockData<'tcx>) {
1527 let is_cleanup = block_data.is_cleanup;
1528 self.last_span = block_data.terminator().source_info.span;
1529 match block_data.terminator().kind {
1530 TerminatorKind::Goto { target } => {
1531 self.assert_iscleanup(mir, block_data, target, is_cleanup)
1533 TerminatorKind::SwitchInt { ref targets, .. } => for target in targets {
1534 self.assert_iscleanup(mir, block_data, *target, is_cleanup);
1536 TerminatorKind::Resume => if !is_cleanup {
1537 span_mirbug!(self, block_data, "resume on non-cleanup block!")
1539 TerminatorKind::Abort => if !is_cleanup {
1540 span_mirbug!(self, block_data, "abort on non-cleanup block!")
1542 TerminatorKind::Return => if is_cleanup {
1543 span_mirbug!(self, block_data, "return on cleanup block")
1545 TerminatorKind::GeneratorDrop { .. } => if is_cleanup {
1546 span_mirbug!(self, block_data, "generator_drop in cleanup block")
1548 TerminatorKind::Yield { resume, drop, .. } => {
1550 span_mirbug!(self, block_data, "yield in cleanup block")
1552 self.assert_iscleanup(mir, block_data, resume, is_cleanup);
1553 if let Some(drop) = drop {
1554 self.assert_iscleanup(mir, block_data, drop, is_cleanup);
1557 TerminatorKind::Unreachable => {}
1558 TerminatorKind::Drop { target, unwind, .. }
1559 | TerminatorKind::DropAndReplace { target, unwind, .. }
1560 | TerminatorKind::Assert {
1565 self.assert_iscleanup(mir, block_data, target, is_cleanup);
1566 if let Some(unwind) = unwind {
1568 span_mirbug!(self, block_data, "unwind on cleanup block")
1570 self.assert_iscleanup(mir, block_data, unwind, true);
1573 TerminatorKind::Call {
1578 if let &Some((_, target)) = destination {
1579 self.assert_iscleanup(mir, block_data, target, is_cleanup);
1581 if let Some(cleanup) = cleanup {
1583 span_mirbug!(self, block_data, "cleanup on cleanup block")
1585 self.assert_iscleanup(mir, block_data, cleanup, true);
1588 TerminatorKind::FalseEdges {
1590 ref imaginary_targets,
1592 self.assert_iscleanup(mir, block_data, real_target, is_cleanup);
1593 for target in imaginary_targets {
1594 self.assert_iscleanup(mir, block_data, *target, is_cleanup);
1597 TerminatorKind::FalseUnwind {
1601 self.assert_iscleanup(mir, block_data, real_target, is_cleanup);
1602 if let Some(unwind) = unwind {
1607 "cleanup in cleanup block via false unwind"
1610 self.assert_iscleanup(mir, block_data, unwind, true);
1616 fn assert_iscleanup(
1619 ctxt: &dyn fmt::Debug,
1623 if mir[bb].is_cleanup != iscleanuppad {
1627 "cleanuppad mismatch: {:?} should be {:?}",
1634 fn check_local(&mut self, mir: &Mir<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) {
1635 match mir.local_kind(local) {
1636 LocalKind::ReturnPointer | LocalKind::Arg => {
1637 // return values of normal functions are required to be
1638 // sized by typeck, but return values of ADT constructors are
1639 // not because we don't include a `Self: Sized` bounds on them.
1641 // Unbound parts of arguments were never required to be Sized
1642 // - maybe we should make that a warning.
1645 LocalKind::Var | LocalKind::Temp => {}
1648 // When `#![feature(unsized_locals)]` is enabled, only function calls
1649 // and nullary ops are checked in `check_call_dest`.
1650 if !self.tcx().features().unsized_locals {
1651 let span = local_decl.source_info.span;
1652 let ty = local_decl.ty;
1653 self.ensure_place_sized(ty, span);
1657 fn ensure_place_sized(&mut self, ty: Ty<'tcx>, span: Span) {
1658 let tcx = self.tcx();
1660 // Erase the regions from `ty` to get a global type. The
1661 // `Sized` bound in no way depends on precise regions, so this
1662 // shouldn't affect `is_sized`.
1663 let gcx = tcx.global_tcx();
1664 let erased_ty = gcx.lift(&tcx.erase_regions(&ty)).unwrap();
1665 if !erased_ty.is_sized(gcx.at(span), self.param_env) {
1666 // in current MIR construction, all non-control-flow rvalue
1667 // expressions evaluate through `as_temp` or `into` a return
1668 // slot or local, so to find all unsized rvalues it is enough
1669 // to check all temps, return slots and locals.
1670 if let None = self.reported_errors.replace((ty, span)) {
1671 let mut diag = struct_span_err!(
1675 "cannot move a value of type {0}: the size of {0} \
1676 cannot be statically determined",
1680 // While this is located in `nll::typeck` this error is not
1681 // an NLL error, it's a required check to prevent creation
1682 // of unsized rvalues in certain cases:
1683 // * operand of a box expression
1684 // * callee in a call expression
1690 fn aggregate_field_ty(
1692 ak: &AggregateKind<'tcx>,
1695 ) -> Result<Ty<'tcx>, FieldAccessError> {
1696 let tcx = self.tcx();
1699 AggregateKind::Adt(def, variant_index, substs, _, active_field_index) => {
1700 let variant = &def.variants[variant_index];
1701 let adj_field_index = active_field_index.unwrap_or(field_index);
1702 if let Some(field) = variant.fields.get(adj_field_index) {
1703 Ok(self.normalize(field.ty(tcx, substs), location))
1705 Err(FieldAccessError::OutOfRange {
1706 field_count: variant.fields.len(),
1710 AggregateKind::Closure(def_id, substs) => {
1711 match substs.upvar_tys(def_id, tcx).nth(field_index) {
1713 None => Err(FieldAccessError::OutOfRange {
1714 field_count: substs.upvar_tys(def_id, tcx).count(),
1718 AggregateKind::Generator(def_id, substs, _) => {
1719 // Try pre-transform fields first (upvars and current state)
1720 if let Some(ty) = substs.pre_transforms_tys(def_id, tcx).nth(field_index) {
1723 // Then try `field_tys` which contains all the fields, but it
1724 // requires the final optimized MIR.
1725 match substs.field_tys(def_id, tcx).nth(field_index) {
1727 None => Err(FieldAccessError::OutOfRange {
1728 field_count: substs.field_tys(def_id, tcx).count(),
1733 AggregateKind::Array(ty) => Ok(ty),
1734 AggregateKind::Tuple => {
1735 unreachable!("This should have been covered in check_rvalues");
1740 fn check_rvalue(&mut self, mir: &Mir<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
1741 let tcx = self.tcx();
1744 Rvalue::Aggregate(ak, ops) => {
1745 self.check_aggregate_rvalue(mir, rvalue, ak, ops, location)
1748 Rvalue::Repeat(operand, len) => if *len > 1 {
1749 let operand_ty = operand.ty(mir, tcx);
1751 let trait_ref = ty::TraitRef {
1752 def_id: tcx.lang_items().copy_trait().unwrap(),
1753 substs: tcx.mk_substs_trait(operand_ty, &[]),
1756 self.prove_trait_ref(
1758 location.to_locations(),
1759 ConstraintCategory::CopyBound,
1763 Rvalue::NullaryOp(_, ty) => {
1764 // Even with unsized locals cannot box an unsized value.
1765 if self.tcx().features().unsized_locals {
1766 let span = mir.source_info(location).span;
1767 self.ensure_place_sized(ty, span);
1770 let trait_ref = ty::TraitRef {
1771 def_id: tcx.lang_items().sized_trait().unwrap(),
1772 substs: tcx.mk_substs_trait(ty, &[]),
1775 self.prove_trait_ref(
1777 location.to_locations(),
1778 ConstraintCategory::SizedBound,
1782 Rvalue::Cast(cast_kind, op, ty) => {
1784 CastKind::ReifyFnPointer => {
1785 let fn_sig = op.ty(mir, tcx).fn_sig(tcx);
1787 // The type that we see in the fcx is like
1788 // `foo::<'a, 'b>`, where `foo` is the path to a
1789 // function definition. When we extract the
1790 // signature, it comes from the `fn_sig` query,
1791 // and hence may contain unnormalized results.
1792 let fn_sig = self.normalize(fn_sig, location);
1794 let ty_fn_ptr_from = tcx.mk_fn_ptr(fn_sig);
1796 if let Err(terr) = self.eq_types(
1799 location.to_locations(),
1800 ConstraintCategory::Cast,
1805 "equating {:?} with {:?} yields {:?}",
1813 CastKind::ClosureFnPointer => {
1814 let sig = match op.ty(mir, tcx).sty {
1815 ty::Closure(def_id, substs) => {
1816 substs.closure_sig_ty(def_id, tcx).fn_sig(tcx)
1820 let ty_fn_ptr_from = tcx.coerce_closure_fn_ty(sig);
1822 if let Err(terr) = self.eq_types(
1825 location.to_locations(),
1826 ConstraintCategory::Cast,
1831 "equating {:?} with {:?} yields {:?}",
1839 CastKind::UnsafeFnPointer => {
1840 let fn_sig = op.ty(mir, tcx).fn_sig(tcx);
1842 // The type that we see in the fcx is like
1843 // `foo::<'a, 'b>`, where `foo` is the path to a
1844 // function definition. When we extract the
1845 // signature, it comes from the `fn_sig` query,
1846 // and hence may contain unnormalized results.
1847 let fn_sig = self.normalize(fn_sig, location);
1849 let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
1851 if let Err(terr) = self.eq_types(
1854 location.to_locations(),
1855 ConstraintCategory::Cast,
1860 "equating {:?} with {:?} yields {:?}",
1868 CastKind::Unsize => {
1870 let trait_ref = ty::TraitRef {
1871 def_id: tcx.lang_items().coerce_unsized_trait().unwrap(),
1872 substs: tcx.mk_substs_trait(op.ty(mir, tcx), &[ty.into()]),
1875 self.prove_trait_ref(
1877 location.to_locations(),
1878 ConstraintCategory::Cast,
1882 CastKind::Misc => {}
1886 Rvalue::Ref(region, _borrow_kind, borrowed_place) => {
1887 self.add_reborrow_constraint(location, region, borrowed_place);
1890 // FIXME: These other cases have to be implemented in future PRs
1893 | Rvalue::BinaryOp(..)
1894 | Rvalue::CheckedBinaryOp(..)
1895 | Rvalue::UnaryOp(..)
1896 | Rvalue::Discriminant(..) => {}
1900 /// If this rvalue supports a user-given type annotation, then
1901 /// extract and return it. This represents the final type of the
1902 /// rvalue and will be unified with the inferred type.
1903 fn rvalue_user_ty(&self, rvalue: &Rvalue<'tcx>) -> Option<UserTypeAnnotation<'tcx>> {
1906 | Rvalue::Repeat(..)
1910 | Rvalue::BinaryOp(..)
1911 | Rvalue::CheckedBinaryOp(..)
1912 | Rvalue::NullaryOp(..)
1913 | Rvalue::UnaryOp(..)
1914 | Rvalue::Discriminant(..) => None,
1916 Rvalue::Aggregate(aggregate, _) => match **aggregate {
1917 AggregateKind::Adt(_, _, _, user_ty, _) => user_ty,
1918 AggregateKind::Array(_) => None,
1919 AggregateKind::Tuple => None,
1920 AggregateKind::Closure(_, _) => None,
1921 AggregateKind::Generator(_, _, _) => None,
1926 fn check_aggregate_rvalue(
1929 rvalue: &Rvalue<'tcx>,
1930 aggregate_kind: &AggregateKind<'tcx>,
1931 operands: &[Operand<'tcx>],
1934 let tcx = self.tcx();
1936 self.prove_aggregate_predicates(aggregate_kind, location);
1938 if *aggregate_kind == AggregateKind::Tuple {
1939 // tuple rvalue field type is always the type of the op. Nothing to check here.
1943 for (i, operand) in operands.iter().enumerate() {
1944 let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
1945 Ok(field_ty) => field_ty,
1946 Err(FieldAccessError::OutOfRange { field_count }) => {
1950 "accessed field #{} but variant only has {}",
1957 let operand_ty = operand.ty(mir, tcx);
1959 if let Err(terr) = self.sub_types(
1962 location.to_locations(),
1963 ConstraintCategory::Boring,
1968 "{:?} is not a subtype of {:?}: {:?}",
1977 /// Add the constraints that arise from a borrow expression `&'a P` at the location `L`.
1981 /// - `location`: the location `L` where the borrow expression occurs
1982 /// - `borrow_region`: the region `'a` associated with the borrow
1983 /// - `borrowed_place`: the place `P` being borrowed
1984 fn add_reborrow_constraint(
1987 borrow_region: ty::Region<'tcx>,
1988 borrowed_place: &Place<'tcx>,
1990 // These constraints are only meaningful during borrowck:
1991 let BorrowCheckContext {
1997 } = match self.borrowck_context {
1998 Some(ref mut borrowck_context) => borrowck_context,
2002 // In Polonius mode, we also push a `borrow_region` fact
2003 // linking the loan to the region (in some cases, though,
2004 // there is no loan associated with this borrow expression --
2005 // that occurs when we are borrowing an unsafe place, for
2007 if let Some(all_facts) = all_facts {
2008 if let Some(borrow_index) = borrow_set.location_map.get(&location) {
2009 let region_vid = borrow_region.to_region_vid();
2010 all_facts.borrow_region.push((
2013 location_table.mid_index(location),
2018 // If we are reborrowing the referent of another reference, we
2019 // need to add outlives relationships. In a case like `&mut
2020 // *p`, where the `p` has type `&'b mut Foo`, for example, we
2021 // need to ensure that `'b: 'a`.
2023 let mut borrowed_place = borrowed_place;
2026 "add_reborrow_constraint({:?}, {:?}, {:?})",
2027 location, borrow_region, borrowed_place
2029 while let Place::Projection(box PlaceProjection { base, elem }) = borrowed_place {
2030 debug!("add_reborrow_constraint - iteration {:?}", borrowed_place);
2033 ProjectionElem::Deref => {
2034 let tcx = self.infcx.tcx;
2035 let base_ty = base.ty(self.mir, tcx).to_ty(tcx);
2037 debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
2039 ty::Ref(ref_region, _, mutbl) => {
2040 constraints.outlives_constraints.push(OutlivesConstraint {
2041 sup: ref_region.to_region_vid(),
2042 sub: borrow_region.to_region_vid(),
2043 locations: location.to_locations(),
2044 category: ConstraintCategory::Boring,
2048 hir::Mutability::MutImmutable => {
2049 // Immutable reference. We don't need the base
2050 // to be valid for the entire lifetime of
2054 hir::Mutability::MutMutable => {
2055 // Mutable reference. We *do* need the base
2056 // to be valid, because after the base becomes
2057 // invalid, someone else can use our mutable deref.
2059 // This is in order to make the following function
2062 // fn unsafe_deref<'a, 'b>(x: &'a &'b mut T) -> &'b mut T {
2067 // As otherwise you could clone `&mut T` using the
2068 // following function:
2070 // fn bad(x: &mut T) -> (&mut T, &mut T) {
2071 // let my_clone = unsafe_deref(&'a x);
2080 // deref of raw pointer, guaranteed to be valid
2083 ty::Adt(def, _) if def.is_box() => {
2084 // deref of `Box`, need the base to be valid - propagate
2086 _ => bug!("unexpected deref ty {:?} in {:?}", base_ty, borrowed_place),
2089 ProjectionElem::Field(..)
2090 | ProjectionElem::Downcast(..)
2091 | ProjectionElem::Index(..)
2092 | ProjectionElem::ConstantIndex { .. }
2093 | ProjectionElem::Subslice { .. } => {
2094 // other field access
2098 // The "propagate" case. We need to check that our base is valid
2099 // for the borrow's lifetime.
2100 borrowed_place = base;
2104 fn prove_aggregate_predicates(
2106 aggregate_kind: &AggregateKind<'tcx>,
2109 let tcx = self.tcx();
2112 "prove_aggregate_predicates(aggregate_kind={:?}, location={:?})",
2113 aggregate_kind, location
2116 let instantiated_predicates = match aggregate_kind {
2117 AggregateKind::Adt(def, _, substs, _, _) => {
2118 tcx.predicates_of(def.did).instantiate(tcx, substs)
2121 // For closures, we have some **extra requirements** we
2123 // have to check. In particular, in their upvars and
2124 // signatures, closures often reference various regions
2125 // from the surrounding function -- we call those the
2126 // closure's free regions. When we borrow-check (and hence
2127 // region-check) closures, we may find that the closure
2128 // requires certain relationships between those free
2129 // regions. However, because those free regions refer to
2130 // portions of the CFG of their caller, the closure is not
2131 // in a position to verify those relationships. In that
2132 // case, the requirements get "propagated" to us, and so
2133 // we have to solve them here where we instantiate the
2136 // Despite the opacity of the previous parapgrah, this is
2137 // actually relatively easy to understand in terms of the
2138 // desugaring. A closure gets desugared to a struct, and
2139 // these extra requirements are basically like where
2140 // clauses on the struct.
2141 AggregateKind::Closure(def_id, ty::ClosureSubsts { substs })
2142 | AggregateKind::Generator(def_id, ty::GeneratorSubsts { substs }, _) => {
2143 self.prove_closure_bounds(tcx, *def_id, substs, location)
2146 AggregateKind::Array(_) | AggregateKind::Tuple => ty::InstantiatedPredicates::empty(),
2149 self.normalize_and_prove_instantiated_predicates(
2150 instantiated_predicates,
2151 location.to_locations(),
2155 fn prove_closure_bounds(
2157 tcx: TyCtxt<'a, 'gcx, 'tcx>,
2159 substs: &'tcx Substs<'tcx>,
2161 ) -> ty::InstantiatedPredicates<'tcx> {
2162 if let Some(closure_region_requirements) = tcx.mir_borrowck(def_id).closure_requirements {
2163 let closure_constraints =
2164 closure_region_requirements.apply_requirements(tcx, location, def_id, substs);
2166 if let Some(ref mut borrowck_context) = self.borrowck_context {
2167 let bounds_mapping = closure_constraints
2170 .filter_map(|(idx, constraint)| {
2171 let ty::OutlivesPredicate(k1, r2) =
2172 constraint.no_late_bound_regions().unwrap_or_else(|| {
2173 bug!("query_constraint {:?} contained bound regions", constraint,);
2177 UnpackedKind::Lifetime(r1) => {
2178 // constraint is r1: r2
2179 let r1_vid = borrowck_context.universal_regions.to_region_vid(r1);
2180 let r2_vid = borrowck_context.universal_regions.to_region_vid(r2);
2181 let outlives_requirements =
2182 &closure_region_requirements.outlives_requirements[idx];
2186 outlives_requirements.category,
2187 outlives_requirements.blame_span,
2191 UnpackedKind::Type(_) => None,
2196 let existing = borrowck_context
2198 .closure_bounds_mapping
2199 .insert(location, bounds_mapping);
2202 "Multiple closures at the same location."
2206 self.push_region_constraints(
2207 location.to_locations(),
2208 ConstraintCategory::ClosureBounds,
2209 &closure_constraints,
2213 tcx.predicates_of(def_id).instantiate(tcx, substs)
2218 trait_ref: ty::TraitRef<'tcx>,
2219 locations: Locations,
2220 category: ConstraintCategory,
2222 self.prove_predicates(
2223 Some(ty::Predicate::Trait(
2224 trait_ref.to_poly_trait_ref().to_poly_trait_predicate(),
2231 fn normalize_and_prove_instantiated_predicates(
2233 instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
2234 locations: Locations,
2236 for predicate in instantiated_predicates.predicates {
2237 let predicate = self.normalize(predicate, locations);
2238 self.prove_predicate(predicate, locations, ConstraintCategory::Boring);
2242 fn prove_predicates(
2244 predicates: impl IntoIterator<Item = ty::Predicate<'tcx>>,
2245 locations: Locations,
2246 category: ConstraintCategory,
2248 for predicate in predicates {
2250 "prove_predicates(predicate={:?}, locations={:?})",
2251 predicate, locations,
2254 self.prove_predicate(predicate, locations, category);
2260 predicate: ty::Predicate<'tcx>,
2261 locations: Locations,
2262 category: ConstraintCategory,
2265 "prove_predicate(predicate={:?}, location={:?})",
2266 predicate, locations,
2269 let param_env = self.param_env;
2270 self.fully_perform_op(
2273 param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
2274 ).unwrap_or_else(|NoSolution| {
2275 span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
2279 fn typeck_mir(&mut self, mir: &Mir<'tcx>) {
2280 self.last_span = mir.span;
2281 debug!("run_on_mir: {:?}", mir.span);
2283 for (local, local_decl) in mir.local_decls.iter_enumerated() {
2284 self.check_local(mir, local, local_decl);
2287 for (block, block_data) in mir.basic_blocks().iter_enumerated() {
2288 let mut location = Location {
2292 for stmt in &block_data.statements {
2293 if !stmt.source_info.span.is_dummy() {
2294 self.last_span = stmt.source_info.span;
2296 self.check_stmt(mir, stmt, location);
2297 location.statement_index += 1;
2300 self.check_terminator(mir, block_data.terminator(), location);
2301 self.check_iscleanup(mir, block_data);
2305 fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
2307 T: type_op::normalize::Normalizable<'gcx, 'tcx> + Copy,
2309 debug!("normalize(value={:?}, location={:?})", value, location);
2310 let param_env = self.param_env;
2311 self.fully_perform_op(
2312 location.to_locations(),
2313 ConstraintCategory::Boring,
2314 param_env.and(type_op::normalize::Normalize::new(value)),
2315 ).unwrap_or_else(|NoSolution| {
2316 span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
2322 pub struct TypeckMir;
2324 impl MirPass for TypeckMir {
2325 fn run_pass<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, src: MirSource, mir: &mut Mir<'tcx>) {
2326 let def_id = src.def_id;
2327 debug!("run_pass: {:?}", def_id);
2329 // When NLL is enabled, the borrow checker runs the typeck
2330 // itself, so we don't need this MIR pass anymore.
2331 if tcx.use_mir_borrowck() {
2335 if tcx.sess.err_count() > 0 {
2336 // compiling a broken program can obviously result in a
2337 // broken MIR, so try not to report duplicate errors.
2341 if tcx.is_struct_constructor(def_id) {
2342 // We just assume that the automatically generated struct constructors are
2343 // correct. See the comment in the `mir_borrowck` implementation for an
2344 // explanation why we need this.
2348 let param_env = tcx.param_env(def_id);
2349 tcx.infer_ctxt().enter(|infcx| {
2350 type_check_internal(
2362 // For verification purposes, we just ignore the resulting
2363 // region constraint sets. Not our problem. =)
2368 trait NormalizeLocation: fmt::Debug + Copy {
2369 fn to_locations(self) -> Locations;
2372 impl NormalizeLocation for Locations {
2373 fn to_locations(self) -> Locations {
2378 impl NormalizeLocation for Location {
2379 fn to_locations(self) -> Locations {
2380 Locations::Single(self)
2384 #[derive(Debug, Default)]
2385 struct ObligationAccumulator<'tcx> {
2386 obligations: PredicateObligations<'tcx>,
2389 impl<'tcx> ObligationAccumulator<'tcx> {
2390 fn add<T>(&mut self, value: InferOk<'tcx, T>) -> T {
2391 let InferOk { value, obligations } = value;
2392 self.obligations.extend(obligations);
2396 fn into_vec(self) -> PredicateObligations<'tcx> {