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