src/librustc_mir/borrow_check/nll/type_check/mod.rs

   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.
   4 //
   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.
  10
  11 //! This pass type-checks the MIR to ensure it is not broken.
  12 #![allow(unreachable_code)]
  13
  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::{RegionValueElements, LivenessValues};
  19 use borrow_check::nll::region_infer::{ClosureRegionRequirementsExt, TypeTest};
  20 use borrow_check::nll::type_check::free_region_relations::{CreateResult, UniversalRegionRelations};
  21 use borrow_check::nll::universal_regions::UniversalRegions;
  22 use borrow_check::nll::LocalWithRegion;
  23 use borrow_check::nll::ToRegionVid;
  24 use dataflow::move_paths::MoveData;
  25 use dataflow::FlowAtLocation;
  26 use dataflow::MaybeInitializedPlaces;
  27 use rustc::hir;
  28 use rustc::hir::def_id::DefId;
  29 use rustc::infer::canonical::QueryRegionConstraint;
  30 use rustc::infer::region_constraints::GenericKind;
  31 use rustc::infer::{InferCtxt, LateBoundRegionConversionTime};
  32 use rustc::mir::interpret::EvalErrorKind::BoundsCheck;
  33 use rustc::mir::tcx::PlaceTy;
  34 use rustc::mir::visit::{PlaceContext, Visitor};
  35 use rustc::mir::*;
  36 use rustc::traits::query::type_op;
  37 use rustc::traits::query::{Fallible, NoSolution};
  38 use rustc::ty::fold::TypeFoldable;
  39 use rustc::ty::{self, CanonicalTy, RegionVid, ToPolyTraitRef, Ty, TyCtxt, TypeVariants};
  40 use rustc_errors::Diagnostic;
  41 use std::fmt;
  42 use std::rc::Rc;
  43 use syntax_pos::{Span, DUMMY_SP};
  44 use transform::{MirPass, MirSource};
  45 use util::liveness::LivenessResults;
  46
  47 use rustc_data_structures::fx::FxHashSet;
  48 use rustc_data_structures::indexed_vec::Idx;
  49
  50 macro_rules! span_mirbug {
  51     ($context:expr, $elem:expr, $($message:tt)*) => ({
  52         $crate::borrow_check::nll::type_check::mirbug(
  53             $context.tcx(),
  54             $context.last_span,
  55             &format!(
  56                 "broken MIR in {:?} ({:?}): {}",
  57                 $context.mir_def_id,
  58                 $elem,
  59                 format_args!($($message)*),
  60             ),
  61         )
  62     })
  63 }
  64
  65 macro_rules! span_mirbug_and_err {
  66     ($context:expr, $elem:expr, $($message:tt)*) => ({
  67         {
  68             span_mirbug!($context, $elem, $($message)*);
  69             $context.error()
  70         }
  71     })
  72 }
  73
  74 mod constraint_conversion;
  75 pub mod free_region_relations;
  76 mod input_output;
  77 mod liveness;
  78 mod relate_tys;
  79
  80 /// Type checks the given `mir` in the context of the inference
  81 /// context `infcx`. Returns any region constraints that have yet to
  82 /// be proven. This result is includes liveness constraints that
  83 /// ensure that regions appearing in the types of all local variables
  84 /// are live at all points where that local variable may later be
  85 /// used.
  86 ///
  87 /// This phase of type-check ought to be infallible -- this is because
  88 /// the original, HIR-based type-check succeeded. So if any errors
  89 /// occur here, we will get a `bug!` reported.
  90 ///
  91 /// # Parameters
  92 ///
  93 /// - `infcx` -- inference context to use
  94 /// - `param_env` -- parameter environment to use for trait solving
  95 /// - `mir` -- MIR to type-check
  96 /// - `mir_def_id` -- DefId from which the MIR is derived (must be local)
  97 /// - `region_bound_pairs` -- the implied outlives obligations between type parameters
  98 ///   and lifetimes (e.g., `&'a T` implies `T: 'a`)
  99 /// - `implicit_region_bound` -- a region which all generic parameters are assumed
 100 ///   to outlive; should represent the fn body
 101 /// - `input_tys` -- fully liberated, but **not** normalized, expected types of the arguments;
 102 ///   the types of the input parameters found in the MIR itself will be equated with these
 103 /// - `output_ty` -- fully liberaetd, but **not** normalized, expected return type;
 104 ///   the type for the RETURN_PLACE will be equated with this
 105 /// - `liveness` -- results of a liveness computation on the MIR; used to create liveness
 106 ///   constraints for the regions in the types of variables
 107 /// - `flow_inits` -- results of a maybe-init dataflow analysis
 108 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis
 109 /// - `errors_buffer` -- errors are sent here for future reporting
 110 pub(crate) fn type_check<'gcx, 'tcx>(
 111     infcx: &InferCtxt<'_, 'gcx, 'tcx>,
 112     param_env: ty::ParamEnv<'gcx>,
 113     mir: &Mir<'tcx>,
 114     mir_def_id: DefId,
 115     universal_regions: &Rc<UniversalRegions<'tcx>>,
 116     location_table: &LocationTable,
 117     borrow_set: &BorrowSet<'tcx>,
 118     liveness: &LivenessResults<LocalWithRegion>,
 119     all_facts: &mut Option<AllFacts>,
 120     flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
 121     move_data: &MoveData<'tcx>,
 122     elements: &Rc<RegionValueElements>,
 123     errors_buffer: &mut Vec<Diagnostic>,
 124 ) -> (
 125     MirTypeckRegionConstraints<'tcx>,
 126     Rc<UniversalRegionRelations<'tcx>>,
 127 ) {
 128     let implicit_region_bound = infcx.tcx.mk_region(ty::ReVar(universal_regions.fr_fn_body));
 129     let mut constraints = MirTypeckRegionConstraints {
 130         liveness_constraints: LivenessValues::new(elements),
 131         outlives_constraints: ConstraintSet::default(),
 132         type_tests: Vec::default(),
 133     };
 134
 135     let CreateResult {
 136         universal_region_relations,
 137         region_bound_pairs,
 138         normalized_inputs_and_output,
 139     } = free_region_relations::create(
 140         infcx,
 141         mir_def_id,
 142         param_env,
 143         location_table,
 144         Some(implicit_region_bound),
 145         universal_regions,
 146         &mut constraints,
 147         all_facts,
 148     );
 149
 150     {
 151         let mut borrowck_context = BorrowCheckContext {
 152             universal_regions,
 153             location_table,
 154             borrow_set,
 155             all_facts,
 156             constraints: &mut constraints,
 157         };
 158
 159         type_check_internal(
 160             infcx,
 161             mir_def_id,
 162             param_env,
 163             mir,
 164             &region_bound_pairs,
 165             Some(implicit_region_bound),
 166             Some(&mut borrowck_context),
 167             Some(errors_buffer),
 168             |cx| {
 169                 liveness::generate(cx, mir, liveness, flow_inits, move_data);
 170                 cx.equate_inputs_and_outputs(
 171                     mir,
 172                     mir_def_id,
 173                     universal_regions,
 174                     &universal_region_relations,
 175                     &normalized_inputs_and_output,
 176                 );
 177             },
 178         );
 179     }
 180
 181     (constraints, universal_region_relations)
 182 }
 183
 184 fn type_check_internal<'a, 'gcx, 'tcx, F>(
 185     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 186     mir_def_id: DefId,
 187     param_env: ty::ParamEnv<'gcx>,
 188     mir: &'a Mir<'tcx>,
 189     region_bound_pairs: &'a [(ty::Region<'tcx>, GenericKind<'tcx>)],
 190     implicit_region_bound: Option<ty::Region<'tcx>>,
 191     borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
 192     errors_buffer: Option<&mut Vec<Diagnostic>>,
 193     mut extra: F,
 194 ) where
 195     F: FnMut(&mut TypeChecker<'a, 'gcx, 'tcx>),
 196 {
 197     let mut checker = TypeChecker::new(
 198         infcx,
 199         mir,
 200         mir_def_id,
 201         param_env,
 202         region_bound_pairs,
 203         implicit_region_bound,
 204         borrowck_context,
 205     );
 206     let errors_reported = {
 207         let mut verifier = TypeVerifier::new(&mut checker, mir);
 208         verifier.visit_mir(mir);
 209         verifier.errors_reported
 210     };
 211
 212     if !errors_reported {
 213         // if verifier failed, don't do further checks to avoid ICEs
 214         checker.typeck_mir(mir, errors_buffer);
 215     }
 216
 217     extra(&mut checker);
 218 }
 219
 220 fn mirbug(tcx: TyCtxt, span: Span, msg: &str) {
 221     // We sometimes see MIR failures (notably predicate failures) due to
 222     // the fact that we check rvalue sized predicates here. So use `delay_span_bug`
 223     // to avoid reporting bugs in those cases.
 224     tcx.sess.diagnostic().delay_span_bug(span, msg);
 225 }
 226
 227 enum FieldAccessError {
 228     OutOfRange { field_count: usize },
 229 }
 230
 231 /// Verifies that MIR types are sane to not crash further checks.
 232 ///
 233 /// The sanitize_XYZ methods here take an MIR object and compute its
 234 /// type, calling `span_mirbug` and returning an error type if there
 235 /// is a problem.
 236 struct TypeVerifier<'a, 'b: 'a, 'gcx: 'tcx, 'tcx: 'b> {
 237     cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>,
 238     mir: &'a Mir<'tcx>,
 239     last_span: Span,
 240     mir_def_id: DefId,
 241     errors_reported: bool,
 242 }
 243
 244 impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 245     fn visit_span(&mut self, span: &Span) {
 246         if !span.is_dummy() {
 247             self.last_span = *span;
 248         }
 249     }
 250
 251     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
 252         self.sanitize_place(place, location, context);
 253     }
 254
 255     fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
 256         self.super_constant(constant, location);
 257         self.sanitize_constant(constant, location);
 258         self.sanitize_type(constant, constant.ty);
 259     }
 260
 261     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
 262         self.super_rvalue(rvalue, location);
 263         let rval_ty = rvalue.ty(self.mir, self.tcx());
 264         self.sanitize_type(rvalue, rval_ty);
 265     }
 266
 267     fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
 268         self.super_local_decl(local, local_decl);
 269         self.sanitize_type(local_decl, local_decl.ty);
 270     }
 271
 272     fn visit_mir(&mut self, mir: &Mir<'tcx>) {
 273         self.sanitize_type(&"return type", mir.return_ty());
 274         for local_decl in &mir.local_decls {
 275             self.sanitize_type(local_decl, local_decl.ty);
 276         }
 277         if self.errors_reported {
 278             return;
 279         }
 280         self.super_mir(mir);
 281     }
 282 }
 283
 284 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 285     fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
 286         TypeVerifier {
 287             mir,
 288             mir_def_id: cx.mir_def_id,
 289             cx,
 290             last_span: mir.span,
 291             errors_reported: false,
 292         }
 293     }
 294
 295     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 296         self.cx.infcx.tcx
 297     }
 298
 299     fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
 300         if ty.has_escaping_regions() || ty.references_error() {
 301             span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
 302         } else {
 303             ty
 304         }
 305     }
 306
 307     /// Checks that the constant's `ty` field matches up with what
 308     /// would be expected from its literal.
 309     fn sanitize_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
 310         debug!(
 311             "sanitize_constant(constant={:?}, location={:?})",
 312             constant, location
 313         );
 314
 315         // FIXME(#46702) -- We need some way to get the predicates
 316         // associated with the "pre-evaluated" form of the
 317         // constant. For example, consider that the constant
 318         // may have associated constant projections (`<Foo as
 319         // Trait<'a, 'b>>::SOME_CONST`) that impose
 320         // constraints on `'a` and `'b`. These constraints
 321         // would be lost if we just look at the normalized
 322         // value.
 323         if let ty::TyFnDef(def_id, substs) = constant.literal.ty.sty {
 324             let tcx = self.tcx();
 325             let type_checker = &mut self.cx;
 326
 327             // FIXME -- For now, use the substitutions from
 328             // `value.ty` rather than `value.val`. The
 329             // renumberer will rewrite them to independent
 330             // sets of regions; in principle, we ought to
 331             // derive the type of the `value.val` from "first
 332             // principles" and equate with value.ty, but as we
 333             // are transitioning to the miri-based system, we
 334             // don't have a handy function for that, so for
 335             // now we just ignore `value.val` regions.
 336
 337             let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
 338             type_checker.normalize_and_prove_instantiated_predicates(
 339                 instantiated_predicates,
 340                 location.boring(),
 341             );
 342         }
 343
 344         debug!("sanitize_constant: expected_ty={:?}", constant.literal.ty);
 345
 346         if let Err(terr) = self
 347             .cx
 348             .eq_types(constant.literal.ty, constant.ty, location.boring())
 349         {
 350             span_mirbug!(
 351                 self,
 352                 constant,
 353                 "constant {:?} should have type {:?} but has {:?} ({:?})",
 354                 constant,
 355                 constant.literal.ty,
 356                 constant.ty,
 357                 terr,
 358             );
 359         }
 360     }
 361
 362     /// Checks that the types internal to the `place` match up with
 363     /// what would be expected.
 364     fn sanitize_place(
 365         &mut self,
 366         place: &Place<'tcx>,
 367         location: Location,
 368         context: PlaceContext,
 369     ) -> PlaceTy<'tcx> {
 370         debug!("sanitize_place: {:?}", place);
 371         let place_ty = match *place {
 372             Place::Local(index) => PlaceTy::Ty {
 373                 ty: self.mir.local_decls[index].ty,
 374             },
 375             Place::Promoted(box (_index, sty)) => {
 376                 let sty = self.sanitize_type(place, sty);
 377                 // FIXME -- promoted MIR return types reference
 378                 // various "free regions" (e.g., scopes and things)
 379                 // that they ought not to do. We have to figure out
 380                 // how best to handle that -- probably we want treat
 381                 // promoted MIR much like closures, renumbering all
 382                 // their free regions and propagating constraints
 383                 // upwards. We have the same acyclic guarantees, so
 384                 // that should be possible. But for now, ignore them.
 385                 //
 386                 // let promoted_mir = &self.mir.promoted[index];
 387                 // promoted_mir.return_ty()
 388                 PlaceTy::Ty { ty: sty }
 389             }
 390             Place::Static(box Static { def_id, ty: sty }) => {
 391                 let sty = self.sanitize_type(place, sty);
 392                 let ty = self.tcx().type_of(def_id);
 393                 let ty = self.cx.normalize(ty, location);
 394                 if let Err(terr) = self.cx.eq_types(ty, sty, location.boring()) {
 395                     span_mirbug!(
 396                         self,
 397                         place,
 398                         "bad static type ({:?}: {:?}): {:?}",
 399                         ty,
 400                         sty,
 401                         terr
 402                     );
 403                 }
 404                 PlaceTy::Ty { ty: sty }
 405             }
 406             Place::Projection(ref proj) => {
 407                 let base_context = if context.is_mutating_use() {
 408                     PlaceContext::Projection(Mutability::Mut)
 409                 } else {
 410                     PlaceContext::Projection(Mutability::Not)
 411                 };
 412                 let base_ty = self.sanitize_place(&proj.base, location, base_context);
 413                 if let PlaceTy::Ty { ty } = base_ty {
 414                     if ty.references_error() {
 415                         assert!(self.errors_reported);
 416                         return PlaceTy::Ty {
 417                             ty: self.tcx().types.err,
 418                         };
 419                     }
 420                 }
 421                 self.sanitize_projection(base_ty, &proj.elem, place, location)
 422             }
 423         };
 424         if let PlaceContext::Copy = context {
 425             let tcx = self.tcx();
 426             let trait_ref = ty::TraitRef {
 427                 def_id: tcx.lang_items().copy_trait().unwrap(),
 428                 substs: tcx.mk_substs_trait(place_ty.to_ty(tcx), &[]),
 429             };
 430
 431             // In order to have a Copy operand, the type T of the value must be Copy. Note that we
 432             // prove that T: Copy, rather than using the type_moves_by_default test. This is
 433             // important because type_moves_by_default ignores the resulting region obligations and
 434             // assumes they pass. This can result in bounds from Copy impls being unsoundly ignored
 435             // (e.g., #29149). Note that we decide to use Copy before knowing whether the bounds
 436             // fully apply: in effect, the rule is that if a value of some type could implement
 437             // Copy, then it must.
 438             self.cx.prove_trait_ref(trait_ref, location.interesting());
 439         }
 440         place_ty
 441     }
 442
 443     fn sanitize_projection(
 444         &mut self,
 445         base: PlaceTy<'tcx>,
 446         pi: &PlaceElem<'tcx>,
 447         place: &Place<'tcx>,
 448         location: Location,
 449     ) -> PlaceTy<'tcx> {
 450         debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, place);
 451         let tcx = self.tcx();
 452         let base_ty = base.to_ty(tcx);
 453         match *pi {
 454             ProjectionElem::Deref => {
 455                 let deref_ty = base_ty.builtin_deref(true);
 456                 PlaceTy::Ty {
 457                     ty: deref_ty.map(|t| t.ty).unwrap_or_else(|| {
 458                         span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty)
 459                     }),
 460                 }
 461             }
 462             ProjectionElem::Index(i) => {
 463                 let index_ty = Place::Local(i).ty(self.mir, tcx).to_ty(tcx);
 464                 if index_ty != tcx.types.usize {
 465                     PlaceTy::Ty {
 466                         ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i),
 467                     }
 468                 } else {
 469                     PlaceTy::Ty {
 470                         ty: base_ty.builtin_index().unwrap_or_else(|| {
 471                             span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
 472                         }),
 473                     }
 474                 }
 475             }
 476             ProjectionElem::ConstantIndex { .. } => {
 477                 // consider verifying in-bounds
 478                 PlaceTy::Ty {
 479                     ty: base_ty.builtin_index().unwrap_or_else(|| {
 480                         span_mirbug_and_err!(self, place, "index of non-array {:?}", base_ty)
 481                     }),
 482                 }
 483             }
 484             ProjectionElem::Subslice { from, to } => PlaceTy::Ty {
 485                 ty: match base_ty.sty {
 486                     ty::TyArray(inner, size) => {
 487                         let size = size.unwrap_usize(tcx);
 488                         let min_size = (from as u64) + (to as u64);
 489                         if let Some(rest_size) = size.checked_sub(min_size) {
 490                             tcx.mk_array(inner, rest_size)
 491                         } else {
 492                             span_mirbug_and_err!(
 493                                 self,
 494                                 place,
 495                                 "taking too-small slice of {:?}",
 496                                 base_ty
 497                             )
 498                         }
 499                     }
 500                     ty::TySlice(..) => base_ty,
 501                     _ => span_mirbug_and_err!(self, place, "slice of non-array {:?}", base_ty),
 502                 },
 503             },
 504             ProjectionElem::Downcast(adt_def1, index) => match base_ty.sty {
 505                 ty::TyAdt(adt_def, substs) if adt_def.is_enum() && adt_def == adt_def1 => {
 506                     if index >= adt_def.variants.len() {
 507                         PlaceTy::Ty {
 508                             ty: span_mirbug_and_err!(
 509                                 self,
 510                                 place,
 511                                 "cast to variant #{:?} but enum only has {:?}",
 512                                 index,
 513                                 adt_def.variants.len()
 514                             ),
 515                         }
 516                     } else {
 517                         PlaceTy::Downcast {
 518                             adt_def,
 519                             substs,
 520                             variant_index: index,
 521                         }
 522                     }
 523                 }
 524                 _ => PlaceTy::Ty {
 525                     ty: span_mirbug_and_err!(
 526                         self,
 527                         place,
 528                         "can't downcast {:?} as {:?}",
 529                         base_ty,
 530                         adt_def1
 531                     ),
 532                 },
 533             },
 534             ProjectionElem::Field(field, fty) => {
 535                 let fty = self.sanitize_type(place, fty);
 536                 match self.field_ty(place, base, field, location) {
 537                     Ok(ty) => if let Err(terr) = self.cx.eq_types(ty, fty, location.boring()) {
 538                         span_mirbug!(
 539                             self,
 540                             place,
 541                             "bad field access ({:?}: {:?}): {:?}",
 542                             ty,
 543                             fty,
 544                             terr
 545                         );
 546                     },
 547                     Err(FieldAccessError::OutOfRange { field_count }) => span_mirbug!(
 548                         self,
 549                         place,
 550                         "accessed field #{} but variant only has {}",
 551                         field.index(),
 552                         field_count
 553                     ),
 554                 }
 555                 PlaceTy::Ty { ty: fty }
 556             }
 557         }
 558     }
 559
 560     fn error(&mut self) -> Ty<'tcx> {
 561         self.errors_reported = true;
 562         self.tcx().types.err
 563     }
 564
 565     fn field_ty(
 566         &mut self,
 567         parent: &dyn fmt::Debug,
 568         base_ty: PlaceTy<'tcx>,
 569         field: Field,
 570         location: Location,
 571     ) -> Result<Ty<'tcx>, FieldAccessError> {
 572         let tcx = self.tcx();
 573
 574         let (variant, substs) = match base_ty {
 575             PlaceTy::Downcast {
 576                 adt_def,
 577                 substs,
 578                 variant_index,
 579             } => (&adt_def.variants[variant_index], substs),
 580             PlaceTy::Ty { ty } => match ty.sty {
 581                 ty::TyAdt(adt_def, substs) if !adt_def.is_enum() => (&adt_def.variants[0], substs),
 582                 ty::TyClosure(def_id, substs) => {
 583                     return match substs.upvar_tys(def_id, tcx).nth(field.index()) {
 584                         Some(ty) => Ok(ty),
 585                         None => Err(FieldAccessError::OutOfRange {
 586                             field_count: substs.upvar_tys(def_id, tcx).count(),
 587                         }),
 588                     }
 589                 }
 590                 ty::TyGenerator(def_id, substs, _) => {
 591                     // Try pre-transform fields first (upvars and current state)
 592                     if let Some(ty) = substs.pre_transforms_tys(def_id, tcx).nth(field.index()) {
 593                         return Ok(ty);
 594                     }
 595
 596                     // Then try `field_tys` which contains all the fields, but it
 597                     // requires the final optimized MIR.
 598                     return match substs.field_tys(def_id, tcx).nth(field.index()) {
 599                         Some(ty) => Ok(ty),
 600                         None => Err(FieldAccessError::OutOfRange {
 601                             field_count: substs.field_tys(def_id, tcx).count(),
 602                         }),
 603                     };
 604                 }
 605                 ty::TyTuple(tys) => {
 606                     return match tys.get(field.index()) {
 607                         Some(&ty) => Ok(ty),
 608                         None => Err(FieldAccessError::OutOfRange {
 609                             field_count: tys.len(),
 610                         }),
 611                     }
 612                 }
 613                 _ => {
 614                     return Ok(span_mirbug_and_err!(
 615                         self,
 616                         parent,
 617                         "can't project out of {:?}",
 618                         base_ty
 619                     ))
 620                 }
 621             },
 622         };
 623
 624         if let Some(field) = variant.fields.get(field.index()) {
 625             Ok(self.cx.normalize(&field.ty(tcx, substs), location))
 626         } else {
 627             Err(FieldAccessError::OutOfRange {
 628                 field_count: variant.fields.len(),
 629             })
 630         }
 631     }
 632 }
 633
 634 /// The MIR type checker. Visits the MIR and enforces all the
 635 /// constraints needed for it to be valid and well-typed. Along the
 636 /// way, it accrues region constraints -- these can later be used by
 637 /// NLL region checking.
 638 struct TypeChecker<'a, 'gcx: 'tcx, 'tcx: 'a> {
 639     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 640     param_env: ty::ParamEnv<'gcx>,
 641     last_span: Span,
 642     mir: &'a Mir<'tcx>,
 643     mir_def_id: DefId,
 644     region_bound_pairs: &'a [(ty::Region<'tcx>, GenericKind<'tcx>)],
 645     implicit_region_bound: Option<ty::Region<'tcx>>,
 646     reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
 647     borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
 648 }
 649
 650 struct BorrowCheckContext<'a, 'tcx: 'a> {
 651     universal_regions: &'a UniversalRegions<'tcx>,
 652     location_table: &'a LocationTable,
 653     all_facts: &'a mut Option<AllFacts>,
 654     borrow_set: &'a BorrowSet<'tcx>,
 655     constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
 656 }
 657
 658 /// A collection of region constraints that must be satisfied for the
 659 /// program to be considered well-typed.
 660 crate struct MirTypeckRegionConstraints<'tcx> {
 661     /// In general, the type-checker is not responsible for enforcing
 662     /// liveness constraints; this job falls to the region inferencer,
 663     /// which performs a liveness analysis. However, in some limited
 664     /// cases, the MIR type-checker creates temporary regions that do
 665     /// not otherwise appear in the MIR -- in particular, the
 666     /// late-bound regions that it instantiates at call-sites -- and
 667     /// hence it must report on their liveness constraints.
 668     crate liveness_constraints: LivenessValues<RegionVid>,
 669
 670     crate outlives_constraints: ConstraintSet,
 671
 672     crate type_tests: Vec<TypeTest<'tcx>>,
 673 }
 674
 675 /// The `Locations` type summarizes *where* region constraints are
 676 /// required to hold. Normally, this is at a particular point which
 677 /// created the obligation, but for constraints that the user gave, we
 678 /// want the constraint to hold at all points.
 679 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 680 pub enum Locations {
 681     /// Indicates that a type constraint should always be true. This
 682     /// is particularly important in the new borrowck analysis for
 683     /// things like the type of the return slot. Consider this
 684     /// example:
 685     ///
 686     /// ```
 687     /// fn foo<'a>(x: &'a u32) -> &'a u32 {
 688     ///     let y = 22;
 689     ///     return &y; // error
 690     /// }
 691     /// ```
 692     ///
 693     /// Here, we wind up with the signature from the return type being
 694     /// something like `&'1 u32` where `'1` is a universal region. But
 695     /// the type of the return slot `_0` is something like `&'2 u32`
 696     /// where `'2` is an existential region variable. The type checker
 697     /// requires that `&'2 u32 = &'1 u32` -- but at what point? In the
 698     /// older NLL analysis, we required this only at the entry point
 699     /// to the function. By the nature of the constraints, this wound
 700     /// up propagating to all points reachable from start (because
 701     /// `'1` -- as a universal region -- is live everywhere).  In the
 702     /// newer analysis, though, this doesn't work: `_0` is considered
 703     /// dead at the start (it has no usable value) and hence this type
 704     /// equality is basically a no-op. Then, later on, when we do `_0
 705     /// = &'3 y`, that region `'3` never winds up related to the
 706     /// universal region `'1` and hence no error occurs. Therefore, we
 707     /// use Locations::All instead, which ensures that the `'1` and
 708     /// `'2` are equal everything. We also use this for other
 709     /// user-given type annotations; e.g., if the user wrote `let mut
 710     /// x: &'static u32 = ...`, we would ensure that all values
 711     /// assigned to `x` are of `'static` lifetime.
 712     All,
 713
 714     /// A "boring" constraint (caused by the given location) is one that
 715     /// the user probably doesn't want to see described in diagnostics,
 716     /// because it is kind of an artifact of the type system setup.
 717     ///
 718     /// Example: `x = Foo { field: y }` technically creates
 719     /// intermediate regions representing the "type of `Foo { field: y
 720     /// }`", and data flows from `y` into those variables, but they
 721     /// are not very interesting. The assignment into `x` on the other
 722     /// hand might be.
 723     Boring(Location),
 724
 725     /// An *important* outlives constraint (caused by the given
 726     /// location) is one that would be useful to highlight in
 727     /// diagnostics, because it represents a point where references
 728     /// flow from one spot to another (e.g., `x = y`)
 729     Interesting(Location),
 730 }
 731
 732 impl Locations {
 733     pub fn from_location(&self) -> Option<Location> {
 734         match self {
 735             Locations::All => None,
 736             Locations::Boring(from_location) | Locations::Interesting(from_location) => {
 737                 Some(*from_location)
 738             }
 739         }
 740     }
 741
 742     /// Gets a span representing the location.
 743     pub fn span(&self, mir: &Mir<'_>) -> Span {
 744         let span_location = match self {
 745             Locations::All => Location::START,
 746             Locations::Boring(l) | Locations::Interesting(l) => *l,
 747         };
 748         mir.source_info(span_location).span
 749     }
 750 }
 751
 752 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
 753     fn new(
 754         infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 755         mir: &'a Mir<'tcx>,
 756         mir_def_id: DefId,
 757         param_env: ty::ParamEnv<'gcx>,
 758         region_bound_pairs: &'a [(ty::Region<'tcx>, GenericKind<'tcx>)],
 759         implicit_region_bound: Option<ty::Region<'tcx>>,
 760         borrowck_context: Option<&'a mut BorrowCheckContext<'a, 'tcx>>,
 761     ) -> Self {
 762         TypeChecker {
 763             infcx,
 764             last_span: DUMMY_SP,
 765             mir,
 766             mir_def_id,
 767             param_env,
 768             region_bound_pairs,
 769             implicit_region_bound,
 770             borrowck_context,
 771             reported_errors: FxHashSet(),
 772         }
 773     }
 774
 775     /// Given some operation `op` that manipulates types, proves
 776     /// predicates, or otherwise uses the inference context, executes
 777     /// `op` and then executes all the further obligations that `op`
 778     /// returns. This will yield a set of outlives constraints amongst
 779     /// regions which are extracted and stored as having occured at
 780     /// `locations`.
 781     ///
 782     /// **Any `rustc::infer` operations that might generate region
 783     /// constraints should occur within this method so that those
 784     /// constraints can be properly localized!**
 785     fn fully_perform_op<R>(
 786         &mut self,
 787         locations: Locations,
 788         op: impl type_op::TypeOp<'gcx, 'tcx, Output = R>,
 789     ) -> Fallible<R> {
 790         let (r, opt_data) = op.fully_perform(self.infcx)?;
 791
 792         if let Some(data) = &opt_data {
 793             self.push_region_constraints(locations, data);
 794         }
 795
 796         Ok(r)
 797     }
 798
 799     fn push_region_constraints(
 800         &mut self,
 801         locations: Locations,
 802         data: &[QueryRegionConstraint<'tcx>],
 803     ) {
 804         debug!(
 805             "push_region_constraints: constraints generated at {:?} are {:#?}",
 806             locations, data
 807         );
 808
 809         if let Some(ref mut borrowck_context) = self.borrowck_context {
 810             constraint_conversion::ConstraintConversion::new(
 811                 self.infcx.tcx,
 812                 borrowck_context.universal_regions,
 813                 borrowck_context.location_table,
 814                 self.region_bound_pairs,
 815                 self.implicit_region_bound,
 816                 self.param_env,
 817                 locations,
 818                 &mut borrowck_context.constraints.outlives_constraints,
 819                 &mut borrowck_context.constraints.type_tests,
 820                 &mut borrowck_context.all_facts,
 821             ).convert_all(&data);
 822         }
 823     }
 824
 825     fn sub_types(&mut self, sub: Ty<'tcx>, sup: Ty<'tcx>, locations: Locations) -> Fallible<()> {
 826         relate_tys::sub_types(
 827             self.infcx,
 828             sub,
 829             sup,
 830             locations,
 831             self.borrowck_context.as_mut().map(|x| &mut **x),
 832         )
 833     }
 834
 835     fn eq_types(&mut self, a: Ty<'tcx>, b: Ty<'tcx>, locations: Locations) -> Fallible<()> {
 836         relate_tys::eq_types(
 837             self.infcx,
 838             a,
 839             b,
 840             locations,
 841             self.borrowck_context.as_mut().map(|x| &mut **x),
 842         )
 843     }
 844
 845     fn eq_canonical_type_and_type(
 846         &mut self,
 847         a: CanonicalTy<'tcx>,
 848         b: Ty<'tcx>,
 849         locations: Locations,
 850     ) -> Fallible<()> {
 851         relate_tys::eq_canonical_type_and_type(
 852             self.infcx,
 853             a,
 854             b,
 855             locations,
 856             self.borrowck_context.as_mut().map(|x| &mut **x),
 857         )
 858     }
 859
 860     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 861         self.infcx.tcx
 862     }
 863
 864     fn check_stmt(&mut self, mir: &Mir<'tcx>, stmt: &Statement<'tcx>, location: Location) {
 865         debug!("check_stmt: {:?}", stmt);
 866         let tcx = self.tcx();
 867         match stmt.kind {
 868             StatementKind::Assign(ref place, ref rv) => {
 869                 // Assignments to temporaries are not "interesting";
 870                 // they are not caused by the user, but rather artifacts
 871                 // of lowering. Assignments to other sorts of places *are* interesting
 872                 // though.
 873                 let is_temp = if let Place::Local(l) = place {
 874                     !mir.local_decls[*l].is_user_variable.is_some()
 875                 } else {
 876                     false
 877                 };
 878
 879                 let locations = if is_temp {
 880                     location.boring()
 881                 } else {
 882                     location.interesting()
 883                 };
 884
 885                 let place_ty = place.ty(mir, tcx).to_ty(tcx);
 886                 let rv_ty = rv.ty(mir, tcx);
 887                 if let Err(terr) = self.sub_types(rv_ty, place_ty, locations) {
 888                     span_mirbug!(
 889                         self,
 890                         stmt,
 891                         "bad assignment ({:?} = {:?}): {:?}",
 892                         place_ty,
 893                         rv_ty,
 894                         terr
 895                     );
 896                 }
 897                 self.check_rvalue(mir, rv, location);
 898                 let trait_ref = ty::TraitRef {
 899                     def_id: tcx.lang_items().sized_trait().unwrap(),
 900                     substs: tcx.mk_substs_trait(place_ty, &[]),
 901                 };
 902                 self.prove_trait_ref(trait_ref, location.interesting());
 903             }
 904             StatementKind::SetDiscriminant {
 905                 ref place,
 906                 variant_index,
 907             } => {
 908                 let place_type = place.ty(mir, tcx).to_ty(tcx);
 909                 let adt = match place_type.sty {
 910                     TypeVariants::TyAdt(adt, _) if adt.is_enum() => adt,
 911                     _ => {
 912                         span_bug!(
 913                             stmt.source_info.span,
 914                             "bad set discriminant ({:?} = {:?}): lhs is not an enum",
 915                             place,
 916                             variant_index
 917                         );
 918                     }
 919                 };
 920                 if variant_index >= adt.variants.len() {
 921                     span_bug!(
 922                         stmt.source_info.span,
 923                         "bad set discriminant ({:?} = {:?}): value of of range",
 924                         place,
 925                         variant_index
 926                     );
 927                 };
 928             }
 929             StatementKind::UserAssertTy(c_ty, local) => {
 930                 let local_ty = mir.local_decls()[local].ty;
 931                 if let Err(terr) = self.eq_canonical_type_and_type(c_ty, local_ty, Locations::All) {
 932                     span_mirbug!(
 933                         self,
 934                         stmt,
 935                         "bad type assert ({:?} = {:?}): {:?}",
 936                         c_ty,
 937                         local_ty,
 938                         terr
 939                     );
 940                 }
 941             }
 942             StatementKind::ReadForMatch(_)
 943             | StatementKind::StorageLive(_)
 944             | StatementKind::StorageDead(_)
 945             | StatementKind::InlineAsm { .. }
 946             | StatementKind::EndRegion(_)
 947             | StatementKind::Validate(..)
 948             | StatementKind::Nop => {}
 949         }
 950     }
 951
 952     fn check_terminator(
 953         &mut self,
 954         mir: &Mir<'tcx>,
 955         term: &Terminator<'tcx>,
 956         term_location: Location,
 957     ) {
 958         debug!("check_terminator: {:?}", term);
 959         let tcx = self.tcx();
 960         match term.kind {
 961             TerminatorKind::Goto { .. }
 962             | TerminatorKind::Resume
 963             | TerminatorKind::Abort
 964             | TerminatorKind::Return
 965             | TerminatorKind::GeneratorDrop
 966             | TerminatorKind::Unreachable
 967             | TerminatorKind::Drop { .. }
 968             | TerminatorKind::FalseEdges { .. }
 969             | TerminatorKind::FalseUnwind { .. } => {
 970                 // no checks needed for these
 971             }
 972
 973             TerminatorKind::DropAndReplace {
 974                 ref location,
 975                 ref value,
 976                 target: _,
 977                 unwind: _,
 978             } => {
 979                 let place_ty = location.ty(mir, tcx).to_ty(tcx);
 980                 let rv_ty = value.ty(mir, tcx);
 981
 982                 let locations = term_location.interesting();
 983                 if let Err(terr) = self.sub_types(rv_ty, place_ty, locations) {
 984                     span_mirbug!(
 985                         self,
 986                         term,
 987                         "bad DropAndReplace ({:?} = {:?}): {:?}",
 988                         place_ty,
 989                         rv_ty,
 990                         terr
 991                     );
 992                 }
 993             }
 994             TerminatorKind::SwitchInt {
 995                 ref discr,
 996                 switch_ty,
 997                 ..
 998             } => {
 999                 let discr_ty = discr.ty(mir, tcx);
1000                 if let Err(terr) = self.sub_types(discr_ty, switch_ty, term_location.boring()) {
1001                     span_mirbug!(
1002                         self,
1003                         term,
1004                         "bad SwitchInt ({:?} on {:?}): {:?}",
1005                         switch_ty,
1006                         discr_ty,
1007                         terr
1008                     );
1009                 }
1010                 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
1011                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
1012                 }
1013                 // FIXME: check the values
1014             }
1015             TerminatorKind::Call {
1016                 ref func,
1017                 ref args,
1018                 ref destination,
1019                 ..
1020             } => {
1021                 let func_ty = func.ty(mir, tcx);
1022                 debug!("check_terminator: call, func_ty={:?}", func_ty);
1023                 let sig = match func_ty.sty {
1024                     ty::TyFnDef(..) | ty::TyFnPtr(_) => func_ty.fn_sig(tcx),
1025                     _ => {
1026                         span_mirbug!(self, term, "call to non-function {:?}", func_ty);
1027                         return;
1028                     }
1029                 };
1030                 let (sig, map) = self.infcx.replace_late_bound_regions_with_fresh_var(
1031                     term.source_info.span,
1032                     LateBoundRegionConversionTime::FnCall,
1033                     &sig,
1034                 );
1035                 let sig = self.normalize(sig, term_location);
1036                 self.check_call_dest(mir, term, &sig, destination, term_location);
1037
1038                 self.prove_predicates(
1039                     sig.inputs().iter().map(|ty| ty::Predicate::WellFormed(ty)),
1040                     term_location.boring(),
1041                 );
1042
1043                 // The ordinary liveness rules will ensure that all
1044                 // regions in the type of the callee are live here. We
1045                 // then further constrain the late-bound regions that
1046                 // were instantiated at the call site to be live as
1047                 // well. The resulting is that all the input (and
1048                 // output) types in the signature must be live, since
1049                 // all the inputs that fed into it were live.
1050                 for &late_bound_region in map.values() {
1051                     if let Some(ref mut borrowck_context) = self.borrowck_context {
1052                         let region_vid = borrowck_context
1053                             .universal_regions
1054                             .to_region_vid(late_bound_region);
1055                         borrowck_context
1056                             .constraints
1057                             .liveness_constraints
1058                             .add_element(region_vid, term_location);
1059                     }
1060                 }
1061
1062                 self.check_call_inputs(mir, term, &sig, args, term_location);
1063             }
1064             TerminatorKind::Assert {
1065                 ref cond, ref msg, ..
1066             } => {
1067                 let cond_ty = cond.ty(mir, tcx);
1068                 if cond_ty != tcx.types.bool {
1069                     span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
1070                 }
1071
1072                 if let BoundsCheck { ref len, ref index } = *msg {
1073                     if len.ty(mir, tcx) != tcx.types.usize {
1074                         span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
1075                     }
1076                     if index.ty(mir, tcx) != tcx.types.usize {
1077                         span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
1078                     }
1079                 }
1080             }
1081             TerminatorKind::Yield { ref value, .. } => {
1082                 let value_ty = value.ty(mir, tcx);
1083                 match mir.yield_ty {
1084                     None => span_mirbug!(self, term, "yield in non-generator"),
1085                     Some(ty) => {
1086                         if let Err(terr) = self.sub_types(value_ty, ty, term_location.interesting())
1087                         {
1088                             span_mirbug!(
1089                                 self,
1090                                 term,
1091                                 "type of yield value is {:?}, but the yield type is {:?}: {:?}",
1092                                 value_ty,
1093                                 ty,
1094                                 terr
1095                             );
1096                         }
1097                     }
1098                 }
1099             }
1100         }
1101     }
1102
1103     fn check_call_dest(
1104         &mut self,
1105         mir: &Mir<'tcx>,
1106         term: &Terminator<'tcx>,
1107         sig: &ty::FnSig<'tcx>,
1108         destination: &Option<(Place<'tcx>, BasicBlock)>,
1109         term_location: Location,
1110     ) {
1111         let tcx = self.tcx();
1112         match *destination {
1113             Some((ref dest, _target_block)) => {
1114                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
1115                 let locations = term_location.interesting();
1116                 if let Err(terr) = self.sub_types(sig.output(), dest_ty, locations) {
1117                     span_mirbug!(
1118                         self,
1119                         term,
1120                         "call dest mismatch ({:?} <- {:?}): {:?}",
1121                         dest_ty,
1122                         sig.output(),
1123                         terr
1124                     );
1125                 }
1126             }
1127             None => {
1128                 // FIXME(canndrew): This is_never should probably be an is_uninhabited
1129                 if !sig.output().is_never() {
1130                     span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
1131                 }
1132             }
1133         }
1134     }
1135
1136     fn check_call_inputs(
1137         &mut self,
1138         mir: &Mir<'tcx>,
1139         term: &Terminator<'tcx>,
1140         sig: &ty::FnSig<'tcx>,
1141         args: &[Operand<'tcx>],
1142         term_location: Location,
1143     ) {
1144         debug!("check_call_inputs({:?}, {:?})", sig, args);
1145         if args.len() < sig.inputs().len() || (args.len() > sig.inputs().len() && !sig.variadic) {
1146             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
1147         }
1148         for (n, (fn_arg, op_arg)) in sig.inputs().iter().zip(args).enumerate() {
1149             let op_arg_ty = op_arg.ty(mir, self.tcx());
1150             if let Err(terr) = self.sub_types(op_arg_ty, fn_arg, term_location.interesting()) {
1151                 span_mirbug!(
1152                     self,
1153                     term,
1154                     "bad arg #{:?} ({:?} <- {:?}): {:?}",
1155                     n,
1156                     fn_arg,
1157                     op_arg_ty,
1158                     terr
1159                 );
1160             }
1161         }
1162     }
1163
1164     fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block_data: &BasicBlockData<'tcx>) {
1165         let is_cleanup = block_data.is_cleanup;
1166         self.last_span = block_data.terminator().source_info.span;
1167         match block_data.terminator().kind {
1168             TerminatorKind::Goto { target } => {
1169                 self.assert_iscleanup(mir, block_data, target, is_cleanup)
1170             }
1171             TerminatorKind::SwitchInt { ref targets, .. } => for target in targets {
1172                 self.assert_iscleanup(mir, block_data, *target, is_cleanup);
1173             },
1174             TerminatorKind::Resume => if !is_cleanup {
1175                 span_mirbug!(self, block_data, "resume on non-cleanup block!")
1176             },
1177             TerminatorKind::Abort => if !is_cleanup {
1178                 span_mirbug!(self, block_data, "abort on non-cleanup block!")
1179             },
1180             TerminatorKind::Return => if is_cleanup {
1181                 span_mirbug!(self, block_data, "return on cleanup block")
1182             },
1183             TerminatorKind::GeneratorDrop { .. } => if is_cleanup {
1184                 span_mirbug!(self, block_data, "generator_drop in cleanup block")
1185             },
1186             TerminatorKind::Yield { resume, drop, .. } => {
1187                 if is_cleanup {
1188                     span_mirbug!(self, block_data, "yield in cleanup block")
1189                 }
1190                 self.assert_iscleanup(mir, block_data, resume, is_cleanup);
1191                 if let Some(drop) = drop {
1192                     self.assert_iscleanup(mir, block_data, drop, is_cleanup);
1193                 }
1194             }
1195             TerminatorKind::Unreachable => {}
1196             TerminatorKind::Drop { target, unwind, .. }
1197             | TerminatorKind::DropAndReplace { target, unwind, .. }
1198             | TerminatorKind::Assert {
1199                 target,
1200                 cleanup: unwind,
1201                 ..
1202             } => {
1203                 self.assert_iscleanup(mir, block_data, target, is_cleanup);
1204                 if let Some(unwind) = unwind {
1205                     if is_cleanup {
1206                         span_mirbug!(self, block_data, "unwind on cleanup block")
1207                     }
1208                     self.assert_iscleanup(mir, block_data, unwind, true);
1209                 }
1210             }
1211             TerminatorKind::Call {
1212                 ref destination,
1213                 cleanup,
1214                 ..
1215             } => {
1216                 if let &Some((_, target)) = destination {
1217                     self.assert_iscleanup(mir, block_data, target, is_cleanup);
1218                 }
1219                 if let Some(cleanup) = cleanup {
1220                     if is_cleanup {
1221                         span_mirbug!(self, block_data, "cleanup on cleanup block")
1222                     }
1223                     self.assert_iscleanup(mir, block_data, cleanup, true);
1224                 }
1225             }
1226             TerminatorKind::FalseEdges {
1227                 real_target,
1228                 ref imaginary_targets,
1229             } => {
1230                 self.assert_iscleanup(mir, block_data, real_target, is_cleanup);
1231                 for target in imaginary_targets {
1232                     self.assert_iscleanup(mir, block_data, *target, is_cleanup);
1233                 }
1234             }
1235             TerminatorKind::FalseUnwind {
1236                 real_target,
1237                 unwind,
1238             } => {
1239                 self.assert_iscleanup(mir, block_data, real_target, is_cleanup);
1240                 if let Some(unwind) = unwind {
1241                     if is_cleanup {
1242                         span_mirbug!(
1243                             self,
1244                             block_data,
1245                             "cleanup in cleanup block via false unwind"
1246                         );
1247                     }
1248                     self.assert_iscleanup(mir, block_data, unwind, true);
1249                 }
1250             }
1251         }
1252     }
1253
1254     fn assert_iscleanup(
1255         &mut self,
1256         mir: &Mir<'tcx>,
1257         ctxt: &dyn fmt::Debug,
1258         bb: BasicBlock,
1259         iscleanuppad: bool,
1260     ) {
1261         if mir[bb].is_cleanup != iscleanuppad {
1262             span_mirbug!(
1263                 self,
1264                 ctxt,
1265                 "cleanuppad mismatch: {:?} should be {:?}",
1266                 bb,
1267                 iscleanuppad
1268             );
1269         }
1270     }
1271
1272     fn check_local(
1273         &mut self,
1274         mir: &Mir<'tcx>,
1275         local: Local,
1276         local_decl: &LocalDecl<'tcx>,
1277         errors_buffer: &mut Option<&mut Vec<Diagnostic>>,
1278     ) {
1279         match mir.local_kind(local) {
1280             LocalKind::ReturnPointer | LocalKind::Arg => {
1281                 // return values of normal functions are required to be
1282                 // sized by typeck, but return values of ADT constructors are
1283                 // not because we don't include a `Self: Sized` bounds on them.
1284                 //
1285                 // Unbound parts of arguments were never required to be Sized
1286                 // - maybe we should make that a warning.
1287                 return;
1288             }
1289             LocalKind::Var | LocalKind::Temp => {}
1290         }
1291
1292         let span = local_decl.source_info.span;
1293         let ty = local_decl.ty;
1294
1295         // Erase the regions from `ty` to get a global type.  The
1296         // `Sized` bound in no way depends on precise regions, so this
1297         // shouldn't affect `is_sized`.
1298         let gcx = self.tcx().global_tcx();
1299         let erased_ty = gcx.lift(&self.tcx().erase_regions(&ty)).unwrap();
1300         if !erased_ty.is_sized(gcx.at(span), self.param_env) {
1301             // in current MIR construction, all non-control-flow rvalue
1302             // expressions evaluate through `as_temp` or `into` a return
1303             // slot or local, so to find all unsized rvalues it is enough
1304             // to check all temps, return slots and locals.
1305             if let None = self.reported_errors.replace((ty, span)) {
1306                 let mut diag = struct_span_err!(
1307                     self.tcx().sess,
1308                     span,
1309                     E0161,
1310                     "cannot move a value of type {0}: the size of {0} \
1311                      cannot be statically determined",
1312                     ty
1313                 );
1314                 if let Some(ref mut errors_buffer) = *errors_buffer {
1315                     diag.buffer(errors_buffer);
1316                 } else {
1317                     // we're allowed to use emit() here because the
1318                     // NLL migration will be turned on (and thus
1319                     // errors will need to be buffered) *only if*
1320                     // errors_buffer is Some.
1321                     diag.emit();
1322                 }
1323             }
1324         }
1325     }
1326
1327     fn aggregate_field_ty(
1328         &mut self,
1329         ak: &AggregateKind<'tcx>,
1330         field_index: usize,
1331         location: Location,
1332     ) -> Result<Ty<'tcx>, FieldAccessError> {
1333         let tcx = self.tcx();
1334
1335         match *ak {
1336             AggregateKind::Adt(def, variant_index, substs, active_field_index) => {
1337                 let variant = &def.variants[variant_index];
1338                 let adj_field_index = active_field_index.unwrap_or(field_index);
1339                 if let Some(field) = variant.fields.get(adj_field_index) {
1340                     Ok(self.normalize(field.ty(tcx, substs), location))
1341                 } else {
1342                     Err(FieldAccessError::OutOfRange {
1343                         field_count: variant.fields.len(),
1344                     })
1345                 }
1346             }
1347             AggregateKind::Closure(def_id, substs) => {
1348                 match substs.upvar_tys(def_id, tcx).nth(field_index) {
1349                     Some(ty) => Ok(ty),
1350                     None => Err(FieldAccessError::OutOfRange {
1351                         field_count: substs.upvar_tys(def_id, tcx).count(),
1352                     }),
1353                 }
1354             }
1355             AggregateKind::Generator(def_id, substs, _) => {
1356                 // Try pre-transform fields first (upvars and current state)
1357                 if let Some(ty) = substs.pre_transforms_tys(def_id, tcx).nth(field_index) {
1358                     Ok(ty)
1359                 } else {
1360                     // Then try `field_tys` which contains all the fields, but it
1361                     // requires the final optimized MIR.
1362                     match substs.field_tys(def_id, tcx).nth(field_index) {
1363                         Some(ty) => Ok(ty),
1364                         None => Err(FieldAccessError::OutOfRange {
1365                             field_count: substs.field_tys(def_id, tcx).count(),
1366                         }),
1367                     }
1368                 }
1369             }
1370             AggregateKind::Array(ty) => Ok(ty),
1371             AggregateKind::Tuple => {
1372                 unreachable!("This should have been covered in check_rvalues");
1373             }
1374         }
1375     }
1376
1377     fn check_rvalue(&mut self, mir: &Mir<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
1378         let tcx = self.tcx();
1379
1380         match rvalue {
1381             Rvalue::Aggregate(ak, ops) => {
1382                 self.check_aggregate_rvalue(mir, rvalue, ak, ops, location)
1383             }
1384
1385             Rvalue::Repeat(operand, len) => if *len > 1 {
1386                 let operand_ty = operand.ty(mir, tcx);
1387
1388                 let trait_ref = ty::TraitRef {
1389                     def_id: tcx.lang_items().copy_trait().unwrap(),
1390                     substs: tcx.mk_substs_trait(operand_ty, &[]),
1391                 };
1392
1393                 self.prove_trait_ref(trait_ref, location.interesting());
1394             },
1395
1396             Rvalue::NullaryOp(_, ty) => {
1397                 let trait_ref = ty::TraitRef {
1398                     def_id: tcx.lang_items().sized_trait().unwrap(),
1399                     substs: tcx.mk_substs_trait(ty, &[]),
1400                 };
1401
1402                 self.prove_trait_ref(trait_ref, location.interesting());
1403             }
1404
1405             Rvalue::Cast(cast_kind, op, ty) => match cast_kind {
1406                 CastKind::ReifyFnPointer => {
1407                     let fn_sig = op.ty(mir, tcx).fn_sig(tcx);
1408
1409                     // The type that we see in the fcx is like
1410                     // `foo::<'a, 'b>`, where `foo` is the path to a
1411                     // function definition. When we extract the
1412                     // signature, it comes from the `fn_sig` query,
1413                     // and hence may contain unnormalized results.
1414                     let fn_sig = self.normalize(fn_sig, location);
1415
1416                     let ty_fn_ptr_from = tcx.mk_fn_ptr(fn_sig);
1417
1418                     if let Err(terr) = self.eq_types(ty_fn_ptr_from, ty, location.interesting()) {
1419                         span_mirbug!(
1420                             self,
1421                             rvalue,
1422                             "equating {:?} with {:?} yields {:?}",
1423                             ty_fn_ptr_from,
1424                             ty,
1425                             terr
1426                         );
1427                     }
1428                 }
1429
1430                 CastKind::ClosureFnPointer => {
1431                     let sig = match op.ty(mir, tcx).sty {
1432                         ty::TyClosure(def_id, substs) => {
1433                             substs.closure_sig_ty(def_id, tcx).fn_sig(tcx)
1434                         }
1435                         _ => bug!(),
1436                     };
1437                     let ty_fn_ptr_from = tcx.coerce_closure_fn_ty(sig);
1438
1439                     if let Err(terr) = self.eq_types(ty_fn_ptr_from, ty, location.interesting()) {
1440                         span_mirbug!(
1441                             self,
1442                             rvalue,
1443                             "equating {:?} with {:?} yields {:?}",
1444                             ty_fn_ptr_from,
1445                             ty,
1446                             terr
1447                         );
1448                     }
1449                 }
1450
1451                 CastKind::UnsafeFnPointer => {
1452                     let fn_sig = op.ty(mir, tcx).fn_sig(tcx);
1453
1454                     // The type that we see in the fcx is like
1455                     // `foo::<'a, 'b>`, where `foo` is the path to a
1456                     // function definition. When we extract the
1457                     // signature, it comes from the `fn_sig` query,
1458                     // and hence may contain unnormalized results.
1459                     let fn_sig = self.normalize(fn_sig, location);
1460
1461                     let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
1462
1463                     if let Err(terr) = self.eq_types(ty_fn_ptr_from, ty, location.interesting()) {
1464                         span_mirbug!(
1465                             self,
1466                             rvalue,
1467                             "equating {:?} with {:?} yields {:?}",
1468                             ty_fn_ptr_from,
1469                             ty,
1470                             terr
1471                         );
1472                     }
1473                 }
1474
1475                 CastKind::Unsize => {
1476                     let &ty = ty;
1477                     let trait_ref = ty::TraitRef {
1478                         def_id: tcx.lang_items().coerce_unsized_trait().unwrap(),
1479                         substs: tcx.mk_substs_trait(op.ty(mir, tcx), &[ty.into()]),
1480                     };
1481
1482                     self.prove_trait_ref(trait_ref, location.interesting());
1483                 }
1484
1485                 CastKind::Misc => {}
1486             },
1487
1488             Rvalue::Ref(region, _borrow_kind, borrowed_place) => {
1489                 self.add_reborrow_constraint(location, region, borrowed_place);
1490             }
1491
1492             // FIXME: These other cases have to be implemented in future PRs
1493             Rvalue::Use(..)
1494             | Rvalue::Len(..)
1495             | Rvalue::BinaryOp(..)
1496             | Rvalue::CheckedBinaryOp(..)
1497             | Rvalue::UnaryOp(..)
1498             | Rvalue::Discriminant(..) => {}
1499         }
1500     }
1501
1502     fn check_aggregate_rvalue(
1503         &mut self,
1504         mir: &Mir<'tcx>,
1505         rvalue: &Rvalue<'tcx>,
1506         aggregate_kind: &AggregateKind<'tcx>,
1507         operands: &[Operand<'tcx>],
1508         location: Location,
1509     ) {
1510         let tcx = self.tcx();
1511
1512         self.prove_aggregate_predicates(aggregate_kind, location);
1513
1514         if *aggregate_kind == AggregateKind::Tuple {
1515             // tuple rvalue field type is always the type of the op. Nothing to check here.
1516             return;
1517         }
1518
1519         for (i, operand) in operands.iter().enumerate() {
1520             let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
1521                 Ok(field_ty) => field_ty,
1522                 Err(FieldAccessError::OutOfRange { field_count }) => {
1523                     span_mirbug!(
1524                         self,
1525                         rvalue,
1526                         "accessed field #{} but variant only has {}",
1527                         i,
1528                         field_count
1529                     );
1530                     continue;
1531                 }
1532             };
1533             let operand_ty = operand.ty(mir, tcx);
1534
1535             if let Err(terr) = self.sub_types(operand_ty, field_ty, location.boring()) {
1536                 span_mirbug!(
1537                     self,
1538                     rvalue,
1539                     "{:?} is not a subtype of {:?}: {:?}",
1540                     operand_ty,
1541                     field_ty,
1542                     terr
1543                 );
1544             }
1545         }
1546     }
1547
1548     /// Add the constraints that arise from a borrow expression `&'a P` at the location `L`.
1549     ///
1550     /// # Parameters
1551     ///
1552     /// - `location`: the location `L` where the borrow expression occurs
1553     /// - `borrow_region`: the region `'a` associated with the borrow
1554     /// - `borrowed_place`: the place `P` being borrowed
1555     fn add_reborrow_constraint(
1556         &mut self,
1557         location: Location,
1558         borrow_region: ty::Region<'tcx>,
1559         borrowed_place: &Place<'tcx>,
1560     ) {
1561         // These constraints are only meaningful during borrowck:
1562         let BorrowCheckContext {
1563             borrow_set,
1564             location_table,
1565             all_facts,
1566             constraints,
1567             ..
1568         } = match self.borrowck_context {
1569             Some(ref mut borrowck_context) => borrowck_context,
1570             None => return,
1571         };
1572
1573         // In Polonius mode, we also push a `borrow_region` fact
1574         // linking the loan to the region (in some cases, though,
1575         // there is no loan associated with this borrow expression --
1576         // that occurs when we are borrowing an unsafe place, for
1577         // example).
1578         if let Some(all_facts) = all_facts {
1579             if let Some(borrow_index) = borrow_set.location_map.get(&location) {
1580                 let region_vid = borrow_region.to_region_vid();
1581                 all_facts.borrow_region.push((
1582                     region_vid,
1583                     *borrow_index,
1584                     location_table.mid_index(location),
1585                 ));
1586             }
1587         }
1588
1589         // If we are reborrowing the referent of another reference, we
1590         // need to add outlives relationships. In a case like `&mut
1591         // *p`, where the `p` has type `&'b mut Foo`, for example, we
1592         // need to ensure that `'b: 'a`.
1593
1594         let mut borrowed_place = borrowed_place;
1595
1596         debug!(
1597             "add_reborrow_constraint({:?}, {:?}, {:?})",
1598             location, borrow_region, borrowed_place
1599         );
1600         while let Place::Projection(box PlaceProjection { base, elem }) = borrowed_place {
1601             debug!("add_reborrow_constraint - iteration {:?}", borrowed_place);
1602
1603             match *elem {
1604                 ProjectionElem::Deref => {
1605                     let tcx = self.infcx.tcx;
1606                     let base_ty = base.ty(self.mir, tcx).to_ty(tcx);
1607
1608                     debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
1609                     match base_ty.sty {
1610                         ty::TyRef(ref_region, _, mutbl) => {
1611                             constraints.outlives_constraints.push(OutlivesConstraint {
1612                                 sup: ref_region.to_region_vid(),
1613                                 sub: borrow_region.to_region_vid(),
1614                                 locations: location.boring(),
1615                             });
1616
1617                             if let Some(all_facts) = all_facts {
1618                                 all_facts.outlives.push((
1619                                     ref_region.to_region_vid(),
1620                                     borrow_region.to_region_vid(),
1621                                     location_table.mid_index(location),
1622                                 ));
1623                             }
1624
1625                             match mutbl {
1626                                 hir::Mutability::MutImmutable => {
1627                                     // Immutable reference. We don't need the base
1628                                     // to be valid for the entire lifetime of
1629                                     // the borrow.
1630                                     break;
1631                                 }
1632                                 hir::Mutability::MutMutable => {
1633                                     // Mutable reference. We *do* need the base
1634                                     // to be valid, because after the base becomes
1635                                     // invalid, someone else can use our mutable deref.
1636
1637                                     // This is in order to make the following function
1638                                     // illegal:
1639                                     // ```
1640                                     // fn unsafe_deref<'a, 'b>(x: &'a &'b mut T) -> &'b mut T {
1641                                     //     &mut *x
1642                                     // }
1643                                     // ```
1644                                     //
1645                                     // As otherwise you could clone `&mut T` using the
1646                                     // following function:
1647                                     // ```
1648                                     // fn bad(x: &mut T) -> (&mut T, &mut T) {
1649                                     //     let my_clone = unsafe_deref(&'a x);
1650                                     //     ENDREGION 'a;
1651                                     //     (my_clone, x)
1652                                     // }
1653                                     // ```
1654                                 }
1655                             }
1656                         }
1657                         ty::TyRawPtr(..) => {
1658                             // deref of raw pointer, guaranteed to be valid
1659                             break;
1660                         }
1661                         ty::TyAdt(def, _) if def.is_box() => {
1662                             // deref of `Box`, need the base to be valid - propagate
1663                         }
1664                         _ => bug!("unexpected deref ty {:?} in {:?}", base_ty, borrowed_place),
1665                     }
1666                 }
1667                 ProjectionElem::Field(..)
1668                 | ProjectionElem::Downcast(..)
1669                 | ProjectionElem::Index(..)
1670                 | ProjectionElem::ConstantIndex { .. }
1671                 | ProjectionElem::Subslice { .. } => {
1672                     // other field access
1673                 }
1674             }
1675
1676             // The "propagate" case. We need to check that our base is valid
1677             // for the borrow's lifetime.
1678             borrowed_place = base;
1679         }
1680     }
1681
1682     fn prove_aggregate_predicates(
1683         &mut self,
1684         aggregate_kind: &AggregateKind<'tcx>,
1685         location: Location,
1686     ) {
1687         let tcx = self.tcx();
1688
1689         debug!(
1690             "prove_aggregate_predicates(aggregate_kind={:?}, location={:?})",
1691             aggregate_kind, location
1692         );
1693
1694         let instantiated_predicates = match aggregate_kind {
1695             AggregateKind::Adt(def, _, substs, _) => {
1696                 tcx.predicates_of(def.did).instantiate(tcx, substs)
1697             }
1698
1699             // For closures, we have some **extra requirements** we
1700             //
1701             // have to check. In particular, in their upvars and
1702             // signatures, closures often reference various regions
1703             // from the surrounding function -- we call those the
1704             // closure's free regions. When we borrow-check (and hence
1705             // region-check) closures, we may find that the closure
1706             // requires certain relationships between those free
1707             // regions. However, because those free regions refer to
1708             // portions of the CFG of their caller, the closure is not
1709             // in a position to verify those relationships. In that
1710             // case, the requirements get "propagated" to us, and so
1711             // we have to solve them here where we instantiate the
1712             // closure.
1713             //
1714             // Despite the opacity of the previous parapgrah, this is
1715             // actually relatively easy to understand in terms of the
1716             // desugaring. A closure gets desugared to a struct, and
1717             // these extra requirements are basically like where
1718             // clauses on the struct.
1719             AggregateKind::Closure(def_id, substs) => {
1720                 if let Some(closure_region_requirements) =
1721                     tcx.mir_borrowck(*def_id).closure_requirements
1722                 {
1723                     let closure_constraints = closure_region_requirements.apply_requirements(
1724                         self.infcx.tcx,
1725                         location,
1726                         *def_id,
1727                         *substs,
1728                     );
1729
1730                     // Hmm, are these constraints *really* boring?
1731                     self.push_region_constraints(location.boring(), &closure_constraints);
1732                 }
1733
1734                 tcx.predicates_of(*def_id).instantiate(tcx, substs.substs)
1735             }
1736
1737             AggregateKind::Generator(def_id, substs, _) => {
1738                 tcx.predicates_of(*def_id).instantiate(tcx, substs.substs)
1739             }
1740
1741             AggregateKind::Array(_) | AggregateKind::Tuple => ty::InstantiatedPredicates::empty(),
1742         };
1743
1744         self.normalize_and_prove_instantiated_predicates(
1745             instantiated_predicates,
1746             location.boring(),
1747         );
1748     }
1749
1750     fn prove_trait_ref(&mut self, trait_ref: ty::TraitRef<'tcx>, locations: Locations) {
1751         self.prove_predicates(
1752             Some(ty::Predicate::Trait(
1753                 trait_ref.to_poly_trait_ref().to_poly_trait_predicate(),
1754             )),
1755             locations,
1756         );
1757     }
1758
1759     fn normalize_and_prove_instantiated_predicates(
1760         &mut self,
1761         instantiated_predicates: ty::InstantiatedPredicates<'tcx>,
1762         locations: Locations,
1763     ) {
1764         for predicate in instantiated_predicates.predicates {
1765             let predicate = self.normalize(predicate, locations);
1766             self.prove_predicate(predicate, locations);
1767         }
1768     }
1769
1770     fn prove_predicates(
1771         &mut self,
1772         predicates: impl IntoIterator<Item = ty::Predicate<'tcx>>,
1773         locations: Locations,
1774     ) {
1775         for predicate in predicates {
1776             debug!(
1777                 "prove_predicates(predicate={:?}, locations={:?})",
1778                 predicate, locations,
1779             );
1780
1781             self.prove_predicate(predicate, locations);
1782         }
1783     }
1784
1785     fn prove_predicate(&mut self, predicate: ty::Predicate<'tcx>, locations: Locations) {
1786         debug!(
1787             "prove_predicate(predicate={:?}, location={:?})",
1788             predicate, locations,
1789         );
1790
1791         let param_env = self.param_env;
1792         self.fully_perform_op(
1793             locations,
1794             param_env.and(type_op::prove_predicate::ProvePredicate::new(predicate)),
1795         ).unwrap_or_else(|NoSolution| {
1796             span_mirbug!(self, NoSolution, "could not prove {:?}", predicate);
1797         })
1798     }
1799
1800     fn typeck_mir(&mut self, mir: &Mir<'tcx>, mut errors_buffer: Option<&mut Vec<Diagnostic>>) {
1801         self.last_span = mir.span;
1802         debug!("run_on_mir: {:?}", mir.span);
1803
1804         for (local, local_decl) in mir.local_decls.iter_enumerated() {
1805             self.check_local(mir, local, local_decl, &mut errors_buffer);
1806         }
1807
1808         for (block, block_data) in mir.basic_blocks().iter_enumerated() {
1809             let mut location = Location {
1810                 block,
1811                 statement_index: 0,
1812             };
1813             for stmt in &block_data.statements {
1814                 if !stmt.source_info.span.is_dummy() {
1815                     self.last_span = stmt.source_info.span;
1816                 }
1817                 self.check_stmt(mir, stmt, location);
1818                 location.statement_index += 1;
1819             }
1820
1821             self.check_terminator(mir, block_data.terminator(), location);
1822             self.check_iscleanup(mir, block_data);
1823         }
1824     }
1825
1826     fn normalize<T>(&mut self, value: T, location: impl NormalizeLocation) -> T
1827     where
1828         T: type_op::normalize::Normalizable<'gcx, 'tcx> + Copy,
1829     {
1830         debug!("normalize(value={:?}, location={:?})", value, location);
1831         let param_env = self.param_env;
1832         self.fully_perform_op(
1833             location.to_locations(),
1834             param_env.and(type_op::normalize::Normalize::new(value)),
1835         ).unwrap_or_else(|NoSolution| {
1836             span_mirbug!(self, NoSolution, "failed to normalize `{:?}`", value);
1837             value
1838         })
1839     }
1840 }
1841
1842 pub struct TypeckMir;
1843
1844 impl MirPass for TypeckMir {
1845     fn run_pass<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, src: MirSource, mir: &mut Mir<'tcx>) {
1846         let def_id = src.def_id;
1847         debug!("run_pass: {:?}", def_id);
1848
1849         // When NLL is enabled, the borrow checker runs the typeck
1850         // itself, so we don't need this MIR pass anymore.
1851         if tcx.use_mir_borrowck() {
1852             return;
1853         }
1854
1855         if tcx.sess.err_count() > 0 {
1856             // compiling a broken program can obviously result in a
1857             // broken MIR, so try not to report duplicate errors.
1858             return;
1859         }
1860
1861         if tcx.is_struct_constructor(def_id) {
1862             // We just assume that the automatically generated struct constructors are
1863             // correct. See the comment in the `mir_borrowck` implementation for an
1864             // explanation why we need this.
1865             return;
1866         }
1867
1868         let param_env = tcx.param_env(def_id);
1869         tcx.infer_ctxt().enter(|infcx| {
1870             type_check_internal(
1871                 &infcx,
1872                 def_id,
1873                 param_env,
1874                 mir,
1875                 &[],
1876                 None,
1877                 None,
1878                 None,
1879                 |_| (),
1880             );
1881
1882             // For verification purposes, we just ignore the resulting
1883             // region constraint sets. Not our problem. =)
1884         });
1885     }
1886 }
1887
1888 pub trait AtLocation {
1889     /// Indicates a "boring" constraint that the user probably
1890     /// woudln't want to see highlights.
1891     fn boring(self) -> Locations;
1892
1893     /// Indicates an "interesting" edge, which is of significance only
1894     /// for diagnostics.
1895     fn interesting(self) -> Locations;
1896 }
1897
1898 impl AtLocation for Location {
1899     fn boring(self) -> Locations {
1900         Locations::Boring(self)
1901     }
1902
1903     fn interesting(self) -> Locations {
1904         Locations::Interesting(self)
1905     }
1906 }
1907
1908 trait NormalizeLocation: fmt::Debug + Copy {
1909     fn to_locations(self) -> Locations;
1910 }
1911
1912 impl NormalizeLocation for Locations {
1913     fn to_locations(self) -> Locations {
1914         self
1915     }
1916 }
1917
1918 impl NormalizeLocation for Location {
1919     fn to_locations(self) -> Locations {
1920         self.boring()
1921     }
1922 }