src/librustc_mir/transform/type_check.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 rustc::infer::{self, InferCtxt, InferOk};
  15 use rustc::traits::{self, Reveal};
  16 use rustc::ty::fold::TypeFoldable;
  17 use rustc::ty::{self, Ty, TyCtxt, TypeVariants};
  18 use rustc::mir::repr::*;
  19 use rustc::mir::tcx::LvalueTy;
  20 use rustc::mir::transform::{MirPass, MirSource, Pass};
  21 use rustc::mir::visit::{self, Visitor};
  22 use std::fmt;
  23 use syntax::ast;
  24 use syntax_pos::{Span, DUMMY_SP};
  25
  26 use rustc_data_structures::indexed_vec::Idx;
  27
  28 macro_rules! span_mirbug {
  29     ($context:expr, $elem:expr, $($message:tt)*) => ({
  30         $context.tcx().sess.span_warn(
  31             $context.last_span,
  32             &format!("broken MIR ({:?}): {}", $elem, format!($($message)*))
  33         )
  34     })
  35 }
  36
  37 macro_rules! span_mirbug_and_err {
  38     ($context:expr, $elem:expr, $($message:tt)*) => ({
  39         {
  40             $context.tcx().sess.span_warn(
  41                 $context.last_span,
  42                 &format!("broken MIR ({:?}): {:?}", $elem, format!($($message)*))
  43             );
  44             $context.error()
  45         }
  46     })
  47 }
  48
  49 enum FieldAccessError {
  50     OutOfRange { field_count: usize }
  51 }
  52
  53 /// Verifies that MIR types are sane to not crash further checks.
  54 ///
  55 /// The sanitize_XYZ methods here take an MIR object and compute its
  56 /// type, calling `span_mirbug` and returning an error type if there
  57 /// is a problem.
  58 struct TypeVerifier<'a, 'b: 'a, 'gcx: 'b+'tcx, 'tcx: 'b> {
  59     cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>,
  60     mir: &'a Mir<'tcx>,
  61     last_span: Span,
  62     errors_reported: bool
  63 }
  64
  65 impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
  66     fn visit_span(&mut self, span: &Span) {
  67         if *span != DUMMY_SP {
  68             self.last_span = *span;
  69         }
  70     }
  71
  72     fn visit_lvalue(&mut self,
  73                     lvalue: &Lvalue<'tcx>,
  74                     _context: visit::LvalueContext,
  75                     location: Location) {
  76         self.sanitize_lvalue(lvalue, location);
  77     }
  78
  79     fn visit_constant(&mut self, constant: &Constant<'tcx>, location: Location) {
  80         self.super_constant(constant, location);
  81         self.sanitize_type(constant, constant.ty);
  82     }
  83
  84     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
  85         self.super_rvalue(rvalue, location);
  86         if let Some(ty) = rvalue.ty(self.mir, self.tcx()) {
  87             self.sanitize_type(rvalue, ty);
  88         }
  89     }
  90
  91     fn visit_mir(&mut self, mir: &Mir<'tcx>) {
  92         self.sanitize_type(&"return type", mir.return_ty);
  93         for local_decl in &mir.local_decls {
  94             self.sanitize_type(local_decl, local_decl.ty);
  95         }
  96         if self.errors_reported {
  97             return;
  98         }
  99         self.super_mir(mir);
 100     }
 101 }
 102
 103 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 104     fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
 105         TypeVerifier {
 106             cx: cx,
 107             mir: mir,
 108             last_span: mir.span,
 109             errors_reported: false
 110         }
 111     }
 112
 113     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 114         self.cx.infcx.tcx
 115     }
 116
 117     fn sanitize_type(&mut self, parent: &fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
 118         if ty.needs_infer() || ty.has_escaping_regions() || ty.references_error() {
 119             span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
 120         } else {
 121             ty
 122         }
 123     }
 124
 125     fn sanitize_lvalue(&mut self, lvalue: &Lvalue<'tcx>, location: Location) -> LvalueTy<'tcx> {
 126         debug!("sanitize_lvalue: {:?}", lvalue);
 127         match *lvalue {
 128             Lvalue::Local(index) => LvalueTy::Ty { ty: self.mir.local_decls[index].ty },
 129             Lvalue::Static(def_id) =>
 130                 LvalueTy::Ty { ty: self.tcx().lookup_item_type(def_id).ty },
 131             Lvalue::Projection(ref proj) => {
 132                 let base_ty = self.sanitize_lvalue(&proj.base, location);
 133                 if let LvalueTy::Ty { ty } = base_ty {
 134                     if ty.references_error() {
 135                         assert!(self.errors_reported);
 136                         return LvalueTy::Ty { ty: self.tcx().types.err };
 137                     }
 138                 }
 139                 self.sanitize_projection(base_ty, &proj.elem, lvalue, location)
 140             }
 141         }
 142     }
 143
 144     fn sanitize_projection(&mut self,
 145                            base: LvalueTy<'tcx>,
 146                            pi: &LvalueElem<'tcx>,
 147                            lvalue: &Lvalue<'tcx>,
 148                            location: Location)
 149                            -> LvalueTy<'tcx> {
 150         debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, lvalue);
 151         let tcx = self.tcx();
 152         let base_ty = base.to_ty(tcx);
 153         let span = self.last_span;
 154         match *pi {
 155             ProjectionElem::Deref => {
 156                 let deref_ty = base_ty.builtin_deref(true, ty::LvaluePreference::NoPreference);
 157                 LvalueTy::Ty {
 158                     ty: deref_ty.map(|t| t.ty).unwrap_or_else(|| {
 159                         span_mirbug_and_err!(
 160                             self, lvalue, "deref of non-pointer {:?}", base_ty)
 161                     })
 162                 }
 163             }
 164             ProjectionElem::Index(ref i) => {
 165                 self.visit_operand(i, location);
 166                 let index_ty = i.ty(self.mir, tcx);
 167                 if index_ty != tcx.types.usize {
 168                     LvalueTy::Ty {
 169                         ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i)
 170                     }
 171                 } else {
 172                     LvalueTy::Ty {
 173                         ty: base_ty.builtin_index().unwrap_or_else(|| {
 174                             span_mirbug_and_err!(
 175                                 self, lvalue, "index of non-array {:?}", base_ty)
 176                         })
 177                     }
 178                 }
 179             }
 180             ProjectionElem::ConstantIndex { .. } => {
 181                 // consider verifying in-bounds
 182                 LvalueTy::Ty {
 183                     ty: base_ty.builtin_index().unwrap_or_else(|| {
 184                         span_mirbug_and_err!(
 185                             self, lvalue, "index of non-array {:?}", base_ty)
 186                     })
 187                 }
 188             }
 189             ProjectionElem::Subslice { from, to } => {
 190                 LvalueTy::Ty {
 191                     ty: match base_ty.sty {
 192                         ty::TyArray(inner, size) => {
 193                             let min_size = (from as usize) + (to as usize);
 194                             if let Some(rest_size) = size.checked_sub(min_size) {
 195                                 tcx.mk_array(inner, rest_size)
 196                             } else {
 197                                 span_mirbug_and_err!(
 198                                     self, lvalue, "taking too-small slice of {:?}", base_ty)
 199                             }
 200                         }
 201                         ty::TySlice(..) => base_ty,
 202                         _ => {
 203                             span_mirbug_and_err!(
 204                                 self, lvalue, "slice of non-array {:?}", base_ty)
 205                         }
 206                     }
 207                 }
 208             }
 209             ProjectionElem::Downcast(adt_def1, index) =>
 210                 match base_ty.sty {
 211                     ty::TyAdt(adt_def, substs) if adt_def.is_enum() && adt_def == adt_def1 => {
 212                         if index >= adt_def.variants.len() {
 213                             LvalueTy::Ty {
 214                                 ty: span_mirbug_and_err!(
 215                                     self,
 216                                     lvalue,
 217                                     "cast to variant #{:?} but enum only has {:?}",
 218                                     index,
 219                                     adt_def.variants.len())
 220                             }
 221                         } else {
 222                             LvalueTy::Downcast {
 223                                 adt_def: adt_def,
 224                                 substs: substs,
 225                                 variant_index: index
 226                             }
 227                         }
 228                     }
 229                     _ => LvalueTy::Ty {
 230                         ty: span_mirbug_and_err!(
 231                             self, lvalue, "can't downcast {:?} as {:?}",
 232                             base_ty, adt_def1)
 233                     }
 234                 },
 235             ProjectionElem::Field(field, fty) => {
 236                 let fty = self.sanitize_type(lvalue, fty);
 237                 match self.field_ty(lvalue, base, field) {
 238                     Ok(ty) => {
 239                         if let Err(terr) = self.cx.eq_types(span, ty, fty) {
 240                             span_mirbug!(
 241                                 self, lvalue, "bad field access ({:?}: {:?}): {:?}",
 242                                 ty, fty, terr);
 243                         }
 244                     }
 245                     Err(FieldAccessError::OutOfRange { field_count }) => {
 246                         span_mirbug!(
 247                             self, lvalue, "accessed field #{} but variant only has {}",
 248                             field.index(), field_count)
 249                     }
 250                 }
 251                 LvalueTy::Ty { ty: fty }
 252             }
 253         }
 254     }
 255
 256     fn error(&mut self) -> Ty<'tcx> {
 257         self.errors_reported = true;
 258         self.tcx().types.err
 259     }
 260
 261     fn field_ty(&mut self,
 262                 parent: &fmt::Debug,
 263                 base_ty: LvalueTy<'tcx>,
 264                 field: Field)
 265                 -> Result<Ty<'tcx>, FieldAccessError>
 266     {
 267         let tcx = self.tcx();
 268
 269         let (variant, substs) = match base_ty {
 270             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 271                 (&adt_def.variants[variant_index], substs)
 272             }
 273             LvalueTy::Ty { ty } => match ty.sty {
 274                 ty::TyAdt(adt_def, substs) if adt_def.is_univariant() => {
 275                         (&adt_def.variants[0], substs)
 276                     }
 277                 ty::TyTuple(tys) | ty::TyClosure(_, ty::ClosureSubsts {
 278                     upvar_tys: tys, ..
 279                 }) => {
 280                     return match tys.get(field.index()) {
 281                         Some(&ty) => Ok(ty),
 282                         None => Err(FieldAccessError::OutOfRange {
 283                             field_count: tys.len()
 284                         })
 285                     }
 286                 }
 287                 _ => return Ok(span_mirbug_and_err!(
 288                     self, parent, "can't project out of {:?}", base_ty))
 289             }
 290         };
 291
 292         if let Some(field) = variant.fields.get(field.index()) {
 293             Ok(self.cx.normalize(&field.ty(tcx, substs)))
 294         } else {
 295             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
 296         }
 297     }
 298 }
 299
 300 pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 301     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 302     fulfillment_cx: traits::FulfillmentContext<'tcx>,
 303     last_span: Span
 304 }
 305
 306 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
 307     fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>) -> Self {
 308         TypeChecker {
 309             infcx: infcx,
 310             fulfillment_cx: traits::FulfillmentContext::new(),
 311             last_span: DUMMY_SP
 312         }
 313     }
 314
 315     fn sub_types(&self, span: Span, sup: Ty<'tcx>, sub: Ty<'tcx>)
 316                  -> infer::UnitResult<'tcx>
 317     {
 318         self.infcx.sub_types(false, infer::TypeOrigin::Misc(span), sup, sub)
 319             // FIXME(#32730) propagate obligations
 320             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 321     }
 322
 323     fn eq_types(&self, span: Span, a: Ty<'tcx>, b: Ty<'tcx>)
 324                 -> infer::UnitResult<'tcx>
 325     {
 326         self.infcx.eq_types(false, infer::TypeOrigin::Misc(span), a, b)
 327             // FIXME(#32730) propagate obligations
 328             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 329     }
 330
 331     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 332         self.infcx.tcx
 333     }
 334
 335     fn check_stmt(&mut self, mir: &Mir<'tcx>, stmt: &Statement<'tcx>) {
 336         debug!("check_stmt: {:?}", stmt);
 337         let tcx = self.tcx();
 338         match stmt.kind {
 339             StatementKind::Assign(ref lv, ref rv) => {
 340                 let lv_ty = lv.ty(mir, tcx).to_ty(tcx);
 341                 let rv_ty = rv.ty(mir, tcx);
 342                 if let Some(rv_ty) = rv_ty {
 343                     if let Err(terr) = self.sub_types(self.last_span, rv_ty, lv_ty) {
 344                         span_mirbug!(self, stmt, "bad assignment ({:?} = {:?}): {:?}",
 345                                      lv_ty, rv_ty, terr);
 346                     }
 347                 // FIXME: rvalue with undeterminable type - e.g. inline
 348                 // asm.
 349                 }
 350             }
 351             StatementKind::SetDiscriminant{ ref lvalue, variant_index } => {
 352                 let lvalue_type = lvalue.ty(mir, tcx).to_ty(tcx);
 353                 let adt = match lvalue_type.sty {
 354                     TypeVariants::TyAdt(adt, _) if adt.is_enum() => adt,
 355                     _ => {
 356                         span_bug!(stmt.source_info.span,
 357                                   "bad set discriminant ({:?} = {:?}): lhs is not an enum",
 358                                   lvalue,
 359                                   variant_index);
 360                     }
 361                 };
 362                 if variant_index >= adt.variants.len() {
 363                      span_bug!(stmt.source_info.span,
 364                                "bad set discriminant ({:?} = {:?}): value of of range",
 365                                lvalue,
 366                                variant_index);
 367                 };
 368             }
 369             StatementKind::StorageLive(ref lv) |
 370             StatementKind::StorageDead(ref lv) => {
 371                 match *lv {
 372                     Lvalue::Local(_) => {}
 373                     _ => {
 374                         span_mirbug!(self, stmt, "bad lvalue: expected local");
 375                     }
 376                 }
 377             }
 378             StatementKind::Nop => {}
 379         }
 380     }
 381
 382     fn check_terminator(&mut self,
 383                         mir: &Mir<'tcx>,
 384                         term: &Terminator<'tcx>) {
 385         debug!("check_terminator: {:?}", term);
 386         let tcx = self.tcx();
 387         match term.kind {
 388             TerminatorKind::Goto { .. } |
 389             TerminatorKind::Resume |
 390             TerminatorKind::Return |
 391             TerminatorKind::Unreachable |
 392             TerminatorKind::Drop { .. } => {
 393                 // no checks needed for these
 394             }
 395
 396
 397             TerminatorKind::DropAndReplace {
 398                 ref location,
 399                 ref value,
 400                 ..
 401             } => {
 402                 let lv_ty = location.ty(mir, tcx).to_ty(tcx);
 403                 let rv_ty = value.ty(mir, tcx);
 404                 if let Err(terr) = self.sub_types(self.last_span, rv_ty, lv_ty) {
 405                     span_mirbug!(self, term, "bad DropAndReplace ({:?} = {:?}): {:?}",
 406                                  lv_ty, rv_ty, terr);
 407                 }
 408             }
 409
 410             TerminatorKind::If { ref cond, .. } => {
 411                 let cond_ty = cond.ty(mir, tcx);
 412                 match cond_ty.sty {
 413                     ty::TyBool => {}
 414                     _ => {
 415                         span_mirbug!(self, term, "bad If ({:?}, not bool", cond_ty);
 416                     }
 417                 }
 418             }
 419             TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
 420                 let discr_ty = discr.ty(mir, tcx).to_ty(tcx);
 421                 if let Err(terr) = self.sub_types(self.last_span, discr_ty, switch_ty) {
 422                     span_mirbug!(self, term, "bad SwitchInt ({:?} on {:?}): {:?}",
 423                                  switch_ty, discr_ty, terr);
 424                 }
 425                 if !switch_ty.is_integral() && !switch_ty.is_char() &&
 426                     !switch_ty.is_bool()
 427                 {
 428                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}",switch_ty);
 429                 }
 430                 // FIXME: check the values
 431             }
 432             TerminatorKind::Switch { ref discr, adt_def, ref targets } => {
 433                 let discr_ty = discr.ty(mir, tcx).to_ty(tcx);
 434                 match discr_ty.sty {
 435                     ty::TyAdt(def, _) if def.is_enum() &&
 436                                          def == adt_def &&
 437                                          adt_def.variants.len() == targets.len()
 438                       => {},
 439                     _ => {
 440                         span_mirbug!(self, term, "bad Switch ({:?} on {:?})",
 441                                      adt_def, discr_ty);
 442                     }
 443                 }
 444             }
 445             TerminatorKind::Call { ref func, ref args, ref destination, .. } => {
 446                 let func_ty = func.ty(mir, tcx);
 447                 debug!("check_terminator: call, func_ty={:?}", func_ty);
 448                 let func_ty = match func_ty.sty {
 449                     ty::TyFnDef(.., func_ty) | ty::TyFnPtr(func_ty) => func_ty,
 450                     _ => {
 451                         span_mirbug!(self, term, "call to non-function {:?}", func_ty);
 452                         return;
 453                     }
 454                 };
 455                 let sig = tcx.erase_late_bound_regions(&func_ty.sig);
 456                 let sig = self.normalize(&sig);
 457                 self.check_call_dest(mir, term, &sig, destination);
 458
 459                 if self.is_box_free(func) {
 460                     self.check_box_free_inputs(mir, term, &sig, args);
 461                 } else {
 462                     self.check_call_inputs(mir, term, &sig, args);
 463                 }
 464             }
 465             TerminatorKind::Assert { ref cond, ref msg, .. } => {
 466                 let cond_ty = cond.ty(mir, tcx);
 467                 if cond_ty != tcx.types.bool {
 468                     span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
 469                 }
 470
 471                 if let AssertMessage::BoundsCheck { ref len, ref index } = *msg {
 472                     if len.ty(mir, tcx) != tcx.types.usize {
 473                         span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
 474                     }
 475                     if index.ty(mir, tcx) != tcx.types.usize {
 476                         span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
 477                     }
 478                 }
 479             }
 480         }
 481     }
 482
 483     fn check_call_dest(&self,
 484                        mir: &Mir<'tcx>,
 485                        term: &Terminator<'tcx>,
 486                        sig: &ty::FnSig<'tcx>,
 487                        destination: &Option<(Lvalue<'tcx>, BasicBlock)>) {
 488         let tcx = self.tcx();
 489         match *destination {
 490             Some((ref dest, _)) => {
 491                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
 492                 if let Err(terr) = self.sub_types(self.last_span, sig.output, dest_ty) {
 493                     span_mirbug!(self, term,
 494                                  "call dest mismatch ({:?} <- {:?}): {:?}",
 495                                  dest_ty, sig.output, terr);
 496                 }
 497             },
 498             None => {
 499                 // FIXME(canndrew): This is_never should probably be an is_uninhabited
 500                 if !sig.output.is_never() {
 501                     span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
 502                 }
 503             },
 504         }
 505     }
 506
 507     fn check_call_inputs(&self,
 508                          mir: &Mir<'tcx>,
 509                          term: &Terminator<'tcx>,
 510                          sig: &ty::FnSig<'tcx>,
 511                          args: &[Operand<'tcx>])
 512     {
 513         debug!("check_call_inputs({:?}, {:?})", sig, args);
 514         if args.len() < sig.inputs.len() ||
 515            (args.len() > sig.inputs.len() && !sig.variadic) {
 516             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
 517         }
 518         for (n, (fn_arg, op_arg)) in sig.inputs.iter().zip(args).enumerate() {
 519             let op_arg_ty = op_arg.ty(mir, self.tcx());
 520             if let Err(terr) = self.sub_types(self.last_span, op_arg_ty, fn_arg) {
 521                 span_mirbug!(self, term, "bad arg #{:?} ({:?} <- {:?}): {:?}",
 522                              n, fn_arg, op_arg_ty, terr);
 523             }
 524         }
 525     }
 526
 527     fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
 528         match operand {
 529             &Operand::Constant(Constant {
 530                 literal: Literal::Item { def_id, .. }, ..
 531             }) => {
 532                 Some(def_id) == self.tcx().lang_items.box_free_fn()
 533             }
 534             _ => false,
 535         }
 536     }
 537
 538     fn check_box_free_inputs(&self,
 539                              mir: &Mir<'tcx>,
 540                              term: &Terminator<'tcx>,
 541                              sig: &ty::FnSig<'tcx>,
 542                              args: &[Operand<'tcx>])
 543     {
 544         debug!("check_box_free_inputs");
 545
 546         // box_free takes a Box as a pointer. Allow for that.
 547
 548         if sig.inputs.len() != 1 {
 549             span_mirbug!(self, term, "box_free should take 1 argument");
 550             return;
 551         }
 552
 553         let pointee_ty = match sig.inputs[0].sty {
 554             ty::TyRawPtr(mt) => mt.ty,
 555             _ => {
 556                 span_mirbug!(self, term, "box_free should take a raw ptr");
 557                 return;
 558             }
 559         };
 560
 561         if args.len() != 1 {
 562             span_mirbug!(self, term, "box_free called with wrong # of args");
 563             return;
 564         }
 565
 566         let arg_ty = match args[0].ty(mir, self.tcx()).sty {
 567             ty::TyRawPtr(mt) => mt.ty,
 568             ty::TyBox(ty) => ty,
 569             _ => {
 570                 span_mirbug!(self, term, "box_free called with bad arg ty");
 571                 return;
 572             }
 573         };
 574
 575         if let Err(terr) = self.sub_types(self.last_span, arg_ty, pointee_ty) {
 576             span_mirbug!(self, term, "bad box_free arg ({:?} <- {:?}): {:?}",
 577                          pointee_ty, arg_ty, terr);
 578         }
 579     }
 580
 581     fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block: &BasicBlockData<'tcx>)
 582     {
 583         let is_cleanup = block.is_cleanup;
 584         self.last_span = block.terminator().source_info.span;
 585         match block.terminator().kind {
 586             TerminatorKind::Goto { target } =>
 587                 self.assert_iscleanup(mir, block, target, is_cleanup),
 588             TerminatorKind::If { targets: (on_true, on_false), .. } => {
 589                 self.assert_iscleanup(mir, block, on_true, is_cleanup);
 590                 self.assert_iscleanup(mir, block, on_false, is_cleanup);
 591             }
 592             TerminatorKind::Switch { ref targets, .. } |
 593             TerminatorKind::SwitchInt { ref targets, .. } => {
 594                 for target in targets {
 595                     self.assert_iscleanup(mir, block, *target, is_cleanup);
 596                 }
 597             }
 598             TerminatorKind::Resume => {
 599                 if !is_cleanup {
 600                     span_mirbug!(self, block, "resume on non-cleanup block!")
 601                 }
 602             }
 603             TerminatorKind::Return => {
 604                 if is_cleanup {
 605                     span_mirbug!(self, block, "return on cleanup block")
 606                 }
 607             }
 608             TerminatorKind::Unreachable => {}
 609             TerminatorKind::Drop { target, unwind, .. } |
 610             TerminatorKind::DropAndReplace { target, unwind, .. } |
 611             TerminatorKind::Assert { target, cleanup: unwind, .. } => {
 612                 self.assert_iscleanup(mir, block, target, is_cleanup);
 613                 if let Some(unwind) = unwind {
 614                     if is_cleanup {
 615                         span_mirbug!(self, block, "unwind on cleanup block")
 616                     }
 617                     self.assert_iscleanup(mir, block, unwind, true);
 618                 }
 619             }
 620             TerminatorKind::Call { ref destination, cleanup, .. } => {
 621                 if let &Some((_, target)) = destination {
 622                     self.assert_iscleanup(mir, block, target, is_cleanup);
 623                 }
 624                 if let Some(cleanup) = cleanup {
 625                     if is_cleanup {
 626                         span_mirbug!(self, block, "cleanup on cleanup block")
 627                     }
 628                     self.assert_iscleanup(mir, block, cleanup, true);
 629                 }
 630             }
 631         }
 632     }
 633
 634     fn assert_iscleanup(&mut self,
 635                         mir: &Mir<'tcx>,
 636                         ctxt: &fmt::Debug,
 637                         bb: BasicBlock,
 638                         iscleanuppad: bool)
 639     {
 640         if mir[bb].is_cleanup != iscleanuppad {
 641             span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}",
 642                          bb, iscleanuppad);
 643         }
 644     }
 645
 646     fn typeck_mir(&mut self, mir: &Mir<'tcx>) {
 647         self.last_span = mir.span;
 648         debug!("run_on_mir: {:?}", mir.span);
 649         for block in mir.basic_blocks() {
 650             for stmt in &block.statements {
 651                 if stmt.source_info.span != DUMMY_SP {
 652                     self.last_span = stmt.source_info.span;
 653                 }
 654                 self.check_stmt(mir, stmt);
 655             }
 656
 657             self.check_terminator(mir, block.terminator());
 658             self.check_iscleanup(mir, block);
 659         }
 660     }
 661
 662
 663     fn normalize<T>(&mut self, value: &T) -> T
 664         where T: fmt::Debug + TypeFoldable<'tcx>
 665     {
 666         let mut selcx = traits::SelectionContext::new(self.infcx);
 667         let cause = traits::ObligationCause::misc(self.last_span, ast::CRATE_NODE_ID);
 668         let traits::Normalized { value, obligations } =
 669             traits::normalize(&mut selcx, cause, value);
 670
 671         debug!("normalize: value={:?} obligations={:?}",
 672                value,
 673                obligations);
 674
 675         let mut fulfill_cx = &mut self.fulfillment_cx;
 676         for obligation in obligations {
 677             fulfill_cx.register_predicate_obligation(self.infcx, obligation);
 678         }
 679
 680         value
 681     }
 682
 683     fn verify_obligations(&mut self, mir: &Mir<'tcx>) {
 684         self.last_span = mir.span;
 685         if let Err(e) = self.fulfillment_cx.select_all_or_error(self.infcx) {
 686             span_mirbug!(self, "", "errors selecting obligation: {:?}",
 687                          e);
 688         }
 689     }
 690 }
 691
 692 pub struct TypeckMir;
 693
 694 impl TypeckMir {
 695     pub fn new() -> Self {
 696         TypeckMir
 697     }
 698 }
 699
 700 impl<'tcx> MirPass<'tcx> for TypeckMir {
 701     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
 702                     src: MirSource, mir: &mut Mir<'tcx>) {
 703         debug!("run_pass: {}", tcx.node_path_str(src.item_id()));
 704
 705         if tcx.sess.err_count() > 0 {
 706             // compiling a broken program can obviously result in a
 707             // broken MIR, so try not to report duplicate errors.
 708             return;
 709         }
 710         let param_env = ty::ParameterEnvironment::for_item(tcx, src.item_id());
 711         tcx.infer_ctxt(None, Some(param_env), Reveal::NotSpecializable).enter(|infcx| {
 712             let mut checker = TypeChecker::new(&infcx);
 713             {
 714                 let mut verifier = TypeVerifier::new(&mut checker, mir);
 715                 verifier.visit_mir(mir);
 716                 if verifier.errors_reported {
 717                     // don't do further checks to avoid ICEs
 718                     return;
 719                 }
 720             }
 721             checker.typeck_mir(mir);
 722             checker.verify_obligations(mir);
 723         });
 724     }
 725 }
 726
 727 impl Pass for TypeckMir {
 728 }