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_pos::{Span, DUMMY_SP};
  24
  25 use rustc_data_structures::indexed_vec::Idx;
  26
  27 macro_rules! span_mirbug {
  28     ($context:expr, $elem:expr, $($message:tt)*) => ({
  29         $context.tcx().sess.span_warn(
  30             $context.last_span,
  31             &format!("broken MIR ({:?}): {}", $elem, format!($($message)*))
  32         )
  33     })
  34 }
  35
  36 macro_rules! span_mirbug_and_err {
  37     ($context:expr, $elem:expr, $($message:tt)*) => ({
  38         {
  39             $context.tcx().sess.span_warn(
  40                 $context.last_span,
  41                 &format!("broken MIR ({:?}): {:?}", $elem, format!($($message)*))
  42             );
  43             $context.error()
  44         }
  45     })
  46 }
  47
  48 enum FieldAccessError {
  49     OutOfRange { field_count: usize }
  50 }
  51
  52 /// Verifies that MIR types are sane to not crash further checks.
  53 ///
  54 /// The sanitize_XYZ methods here take an MIR object and compute its
  55 /// type, calling `span_mirbug` and returning an error type if there
  56 /// is a problem.
  57 struct TypeVerifier<'a, 'b: 'a, 'gcx: 'b+'tcx, 'tcx: 'b> {
  58     cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>,
  59     mir: &'a Mir<'tcx>,
  60     last_span: Span,
  61     errors_reported: bool
  62 }
  63
  64 impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
  65     fn visit_span(&mut self, span: &Span) {
  66         if *span != DUMMY_SP {
  67             self.last_span = *span;
  68         }
  69     }
  70
  71     fn visit_lvalue(&mut self, lvalue: &Lvalue<'tcx>, _context: visit::LvalueContext) {
  72         self.sanitize_lvalue(lvalue);
  73     }
  74
  75     fn visit_constant(&mut self, constant: &Constant<'tcx>) {
  76         self.super_constant(constant);
  77         self.sanitize_type(constant, constant.ty);
  78     }
  79
  80     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>) {
  81         self.super_rvalue(rvalue);
  82         if let Some(ty) = rvalue.ty(self.mir, self.tcx()) {
  83             self.sanitize_type(rvalue, ty);
  84         }
  85     }
  86
  87     fn visit_mir(&mut self, mir: &Mir<'tcx>) {
  88         self.sanitize_type(&"return type", mir.return_ty);
  89         for var_decl in &mir.var_decls {
  90             self.sanitize_type(var_decl, var_decl.ty);
  91         }
  92         for (n, arg_decl) in mir.arg_decls.iter().enumerate() {
  93             self.sanitize_type(&(n, arg_decl), arg_decl.ty);
  94         }
  95         for (n, tmp_decl) in mir.temp_decls.iter().enumerate() {
  96             self.sanitize_type(&(n, tmp_decl), tmp_decl.ty);
  97         }
  98         if self.errors_reported {
  99             return;
 100         }
 101         self.super_mir(mir);
 102     }
 103 }
 104
 105 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 106     fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
 107         TypeVerifier {
 108             cx: cx,
 109             mir: mir,
 110             last_span: mir.span,
 111             errors_reported: false
 112         }
 113     }
 114
 115     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 116         self.cx.infcx.tcx
 117     }
 118
 119     fn sanitize_type(&mut self, parent: &fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
 120         if ty.needs_infer() || ty.has_escaping_regions() || ty.references_error() {
 121             span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
 122         } else {
 123             ty
 124         }
 125     }
 126
 127     fn sanitize_lvalue(&mut self, lvalue: &Lvalue<'tcx>) -> LvalueTy<'tcx> {
 128         debug!("sanitize_lvalue: {:?}", lvalue);
 129         match *lvalue {
 130             Lvalue::Var(index) => LvalueTy::Ty { ty: self.mir.var_decls[index].ty },
 131             Lvalue::Temp(index) => LvalueTy::Ty { ty: self.mir.temp_decls[index].ty },
 132             Lvalue::Arg(index) => LvalueTy::Ty { ty: self.mir.arg_decls[index].ty },
 133             Lvalue::Static(def_id) =>
 134                 LvalueTy::Ty { ty: self.tcx().lookup_item_type(def_id).ty },
 135             Lvalue::ReturnPointer => {
 136                 LvalueTy::Ty { ty: self.mir.return_ty }
 137             }
 138             Lvalue::Projection(ref proj) => {
 139                 let base_ty = self.sanitize_lvalue(&proj.base);
 140                 if let LvalueTy::Ty { ty } = base_ty {
 141                     if ty.references_error() {
 142                         assert!(self.errors_reported);
 143                         return LvalueTy::Ty { ty: self.tcx().types.err };
 144                     }
 145                 }
 146                 self.sanitize_projection(base_ty, &proj.elem, lvalue)
 147             }
 148         }
 149     }
 150
 151     fn sanitize_projection(&mut self,
 152                            base: LvalueTy<'tcx>,
 153                            pi: &LvalueElem<'tcx>,
 154                            lvalue: &Lvalue<'tcx>)
 155                            -> LvalueTy<'tcx> {
 156         debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, lvalue);
 157         let tcx = self.tcx();
 158         let base_ty = base.to_ty(tcx);
 159         let span = self.last_span;
 160         match *pi {
 161             ProjectionElem::Deref => {
 162                 let deref_ty = base_ty.builtin_deref(true, ty::LvaluePreference::NoPreference);
 163                 LvalueTy::Ty {
 164                     ty: deref_ty.map(|t| t.ty).unwrap_or_else(|| {
 165                         span_mirbug_and_err!(
 166                             self, lvalue, "deref of non-pointer {:?}", base_ty)
 167                     })
 168                 }
 169             }
 170             ProjectionElem::Index(ref i) => {
 171                 self.visit_operand(i);
 172                 let index_ty = i.ty(self.mir, tcx);
 173                 if index_ty != tcx.types.usize {
 174                     LvalueTy::Ty {
 175                         ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i)
 176                     }
 177                 } else {
 178                     LvalueTy::Ty {
 179                         ty: base_ty.builtin_index().unwrap_or_else(|| {
 180                             span_mirbug_and_err!(
 181                                 self, lvalue, "index of non-array {:?}", base_ty)
 182                         })
 183                     }
 184                 }
 185             }
 186             ProjectionElem::ConstantIndex { .. } => {
 187                 // consider verifying in-bounds
 188                 LvalueTy::Ty {
 189                     ty: base_ty.builtin_index().unwrap_or_else(|| {
 190                         span_mirbug_and_err!(
 191                             self, lvalue, "index of non-array {:?}", base_ty)
 192                     })
 193                 }
 194             }
 195             ProjectionElem::Subslice { from, to } => {
 196                 LvalueTy::Ty {
 197                     ty: match base_ty.sty {
 198                         ty::TyArray(inner, size) => {
 199                             let min_size = (from as usize) + (to as usize);
 200                             if let Some(rest_size) = size.checked_sub(min_size) {
 201                                 tcx.mk_array(inner, rest_size)
 202                             } else {
 203                                 span_mirbug_and_err!(
 204                                     self, lvalue, "taking too-small slice of {:?}", base_ty)
 205                             }
 206                         }
 207                         ty::TySlice(..) => base_ty,
 208                         _ => {
 209                             span_mirbug_and_err!(
 210                                 self, lvalue, "slice of non-array {:?}", base_ty)
 211                         }
 212                     }
 213                 }
 214             }
 215             ProjectionElem::Downcast(adt_def1, index) =>
 216                 match base_ty.sty {
 217                     ty::TyEnum(adt_def, substs) if adt_def == adt_def1 => {
 218                         if index >= adt_def.variants.len() {
 219                             LvalueTy::Ty {
 220                                 ty: span_mirbug_and_err!(
 221                                     self,
 222                                     lvalue,
 223                                     "cast to variant #{:?} but enum only has {:?}",
 224                                     index,
 225                                     adt_def.variants.len())
 226                             }
 227                         } else {
 228                             LvalueTy::Downcast {
 229                                 adt_def: adt_def,
 230                                 substs: substs,
 231                                 variant_index: index
 232                             }
 233                         }
 234                     }
 235                     _ => LvalueTy::Ty {
 236                         ty: span_mirbug_and_err!(
 237                             self, lvalue, "can't downcast {:?} as {:?}",
 238                             base_ty, adt_def1)
 239                     }
 240                 },
 241             ProjectionElem::Field(field, fty) => {
 242                 let fty = self.sanitize_type(lvalue, fty);
 243                 match self.field_ty(lvalue, base, field) {
 244                     Ok(ty) => {
 245                         if let Err(terr) = self.cx.eq_types(span, ty, fty) {
 246                             span_mirbug!(
 247                                 self, lvalue, "bad field access ({:?}: {:?}): {:?}",
 248                                 ty, fty, terr);
 249                         }
 250                     }
 251                     Err(FieldAccessError::OutOfRange { field_count }) => {
 252                         span_mirbug!(
 253                             self, lvalue, "accessed field #{} but variant only has {}",
 254                             field.index(), field_count)
 255                     }
 256                 }
 257                 LvalueTy::Ty { ty: fty }
 258             }
 259         }
 260     }
 261
 262     fn error(&mut self) -> Ty<'tcx> {
 263         self.errors_reported = true;
 264         self.tcx().types.err
 265     }
 266
 267     fn field_ty(&mut self,
 268                 parent: &fmt::Debug,
 269                 base_ty: LvalueTy<'tcx>,
 270                 field: Field)
 271                 -> Result<Ty<'tcx>, FieldAccessError>
 272     {
 273         let tcx = self.tcx();
 274
 275         let (variant, substs) = match base_ty {
 276             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 277                 (&adt_def.variants[variant_index], substs)
 278             }
 279             LvalueTy::Ty { ty } => match ty.sty {
 280                 ty::TyStruct(adt_def, substs) | ty::TyEnum(adt_def, substs)
 281                     if adt_def.is_univariant() => {
 282                         (&adt_def.variants[0], substs)
 283                     }
 284                 ty::TyTuple(tys) | ty::TyClosure(_, ty::ClosureSubsts {
 285                     upvar_tys: tys, ..
 286                 }) => {
 287                     return match tys.get(field.index()) {
 288                         Some(&ty) => Ok(ty),
 289                         None => Err(FieldAccessError::OutOfRange {
 290                             field_count: tys.len()
 291                         })
 292                     }
 293                 }
 294                 _ => return Ok(span_mirbug_and_err!(
 295                     self, parent, "can't project out of {:?}", base_ty))
 296             }
 297         };
 298
 299         if let Some(field) = variant.fields.get(field.index()) {
 300             Ok(self.cx.normalize(&field.ty(tcx, substs)))
 301         } else {
 302             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
 303         }
 304     }
 305 }
 306
 307 pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 308     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 309     fulfillment_cx: traits::FulfillmentContext<'tcx>,
 310     last_span: Span
 311 }
 312
 313 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
 314     fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>) -> Self {
 315         TypeChecker {
 316             infcx: infcx,
 317             fulfillment_cx: traits::FulfillmentContext::new(),
 318             last_span: DUMMY_SP
 319         }
 320     }
 321
 322     fn sub_types(&self, span: Span, sup: Ty<'tcx>, sub: Ty<'tcx>)
 323                  -> infer::UnitResult<'tcx>
 324     {
 325         self.infcx.sub_types(false, infer::TypeOrigin::Misc(span), sup, sub)
 326             // FIXME(#32730) propagate obligations
 327             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 328     }
 329
 330     fn eq_types(&self, span: Span, a: Ty<'tcx>, b: Ty<'tcx>)
 331                 -> infer::UnitResult<'tcx>
 332     {
 333         self.infcx.eq_types(false, infer::TypeOrigin::Misc(span), a, b)
 334             // FIXME(#32730) propagate obligations
 335             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 336     }
 337
 338     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 339         self.infcx.tcx
 340     }
 341
 342     fn check_stmt(&mut self, mir: &Mir<'tcx>, stmt: &Statement<'tcx>) {
 343         debug!("check_stmt: {:?}", stmt);
 344         let tcx = self.tcx();
 345         match stmt.kind {
 346             StatementKind::Assign(ref lv, ref rv) => {
 347                 let lv_ty = lv.ty(mir, tcx).to_ty(tcx);
 348                 let rv_ty = rv.ty(mir, tcx);
 349                 if let Some(rv_ty) = rv_ty {
 350                     if let Err(terr) = self.sub_types(self.last_span, rv_ty, lv_ty) {
 351                         span_mirbug!(self, stmt, "bad assignment ({:?} = {:?}): {:?}",
 352                                      lv_ty, rv_ty, terr);
 353                     }
 354                 // FIXME: rvalue with undeterminable type - e.g. inline
 355                 // asm.
 356                 }
 357             }
 358             StatementKind::SetDiscriminant{ ref lvalue, variant_index } => {
 359                 let lvalue_type = lvalue.ty(mir, tcx).to_ty(tcx);
 360                 let adt = match lvalue_type.sty {
 361                     TypeVariants::TyEnum(adt, _) => adt,
 362                     _ => {
 363                         span_bug!(stmt.source_info.span,
 364                                   "bad set discriminant ({:?} = {:?}): lhs is not an enum",
 365                                   lvalue,
 366                                   variant_index);
 367                     }
 368                 };
 369                 if variant_index >= adt.variants.len() {
 370                      span_bug!(stmt.source_info.span,
 371                                "bad set discriminant ({:?} = {:?}): value of of range",
 372                                lvalue,
 373                                variant_index);
 374                 };
 375             }
 376             StatementKind::StorageLive(ref lv) |
 377             StatementKind::StorageDead(ref lv) => {
 378                 match *lv {
 379                     Lvalue::Temp(_) | Lvalue::Var(_) => {}
 380                     _ => {
 381                         span_mirbug!(self, stmt, "bad lvalue: expected temp or var");
 382                     }
 383                 }
 384             }
 385         }
 386     }
 387
 388     fn check_terminator(&mut self,
 389                         mir: &Mir<'tcx>,
 390                         term: &Terminator<'tcx>) {
 391         debug!("check_terminator: {:?}", term);
 392         let tcx = self.tcx();
 393         match term.kind {
 394             TerminatorKind::Goto { .. } |
 395             TerminatorKind::Resume |
 396             TerminatorKind::Return |
 397             TerminatorKind::Unreachable |
 398             TerminatorKind::Drop { .. } => {
 399                 // no checks needed for these
 400             }
 401
 402
 403             TerminatorKind::DropAndReplace {
 404                 ref location,
 405                 ref value,
 406                 ..
 407             } => {
 408                 let lv_ty = location.ty(mir, tcx).to_ty(tcx);
 409                 let rv_ty = value.ty(mir, tcx);
 410                 if let Err(terr) = self.sub_types(self.last_span, rv_ty, lv_ty) {
 411                     span_mirbug!(self, term, "bad DropAndReplace ({:?} = {:?}): {:?}",
 412                                  lv_ty, rv_ty, terr);
 413                 }
 414             }
 415
 416             TerminatorKind::If { ref cond, .. } => {
 417                 let cond_ty = cond.ty(mir, tcx);
 418                 match cond_ty.sty {
 419                     ty::TyBool => {}
 420                     _ => {
 421                         span_mirbug!(self, term, "bad If ({:?}, not bool", cond_ty);
 422                     }
 423                 }
 424             }
 425             TerminatorKind::SwitchInt { ref discr, switch_ty, .. } => {
 426                 let discr_ty = discr.ty(mir, tcx).to_ty(tcx);
 427                 if let Err(terr) = self.sub_types(self.last_span, discr_ty, switch_ty) {
 428                     span_mirbug!(self, term, "bad SwitchInt ({:?} on {:?}): {:?}",
 429                                  switch_ty, discr_ty, terr);
 430                 }
 431                 if !switch_ty.is_integral() && !switch_ty.is_char() &&
 432                     !switch_ty.is_bool()
 433                 {
 434                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}",switch_ty);
 435                 }
 436                 // FIXME: check the values
 437             }
 438             TerminatorKind::Switch { ref discr, adt_def, ref targets } => {
 439                 let discr_ty = discr.ty(mir, tcx).to_ty(tcx);
 440                 match discr_ty.sty {
 441                     ty::TyEnum(def, _)
 442                         if def == adt_def && adt_def.variants.len() == targets.len()
 443                         => {},
 444                     _ => {
 445                         span_mirbug!(self, term, "bad Switch ({:?} on {:?})",
 446                                      adt_def, discr_ty);
 447                     }
 448                 }
 449             }
 450             TerminatorKind::Call { ref func, ref args, ref destination, .. } => {
 451                 let func_ty = func.ty(mir, tcx);
 452                 debug!("check_terminator: call, func_ty={:?}", func_ty);
 453                 let func_ty = match func_ty.sty {
 454                     ty::TyFnDef(_, _, func_ty) | ty::TyFnPtr(func_ty) => func_ty,
 455                     _ => {
 456                         span_mirbug!(self, term, "call to non-function {:?}", func_ty);
 457                         return;
 458                     }
 459                 };
 460                 let sig = tcx.erase_late_bound_regions(&func_ty.sig);
 461                 let sig = self.normalize(&sig);
 462                 self.check_call_dest(mir, term, &sig, destination);
 463
 464                 if self.is_box_free(func) {
 465                     self.check_box_free_inputs(mir, term, &sig, args);
 466                 } else {
 467                     self.check_call_inputs(mir, term, &sig, args);
 468                 }
 469             }
 470             TerminatorKind::Assert { ref cond, ref msg, .. } => {
 471                 let cond_ty = cond.ty(mir, tcx);
 472                 if cond_ty != tcx.types.bool {
 473                     span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
 474                 }
 475
 476                 if let AssertMessage::BoundsCheck { ref len, ref index } = *msg {
 477                     if len.ty(mir, tcx) != tcx.types.usize {
 478                         span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
 479                     }
 480                     if index.ty(mir, tcx) != tcx.types.usize {
 481                         span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
 482                     }
 483                 }
 484             }
 485         }
 486     }
 487
 488     fn check_call_dest(&self,
 489                        mir: &Mir<'tcx>,
 490                        term: &Terminator<'tcx>,
 491                        sig: &ty::FnSig<'tcx>,
 492                        destination: &Option<(Lvalue<'tcx>, BasicBlock)>) {
 493         let tcx = self.tcx();
 494         match *destination {
 495             Some((ref dest, _)) => {
 496                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
 497                 if let Err(terr) = self.sub_types(self.last_span, sig.output, dest_ty) {
 498                     span_mirbug!(self, term,
 499                                  "call dest mismatch ({:?} <- {:?}): {:?}",
 500                                  dest_ty, sig.output, terr);
 501                 }
 502             },
 503             None => {
 504                 // FIXME(canndrew): This is_never should probably be an is_uninhabited
 505                 if !sig.output.is_never() {
 506                     span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
 507                 }
 508             },
 509         }
 510     }
 511
 512     fn check_call_inputs(&self,
 513                          mir: &Mir<'tcx>,
 514                          term: &Terminator<'tcx>,
 515                          sig: &ty::FnSig<'tcx>,
 516                          args: &[Operand<'tcx>])
 517     {
 518         debug!("check_call_inputs({:?}, {:?})", sig, args);
 519         if args.len() < sig.inputs.len() ||
 520            (args.len() > sig.inputs.len() && !sig.variadic) {
 521             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
 522         }
 523         for (n, (fn_arg, op_arg)) in sig.inputs.iter().zip(args).enumerate() {
 524             let op_arg_ty = op_arg.ty(mir, self.tcx());
 525             if let Err(terr) = self.sub_types(self.last_span, op_arg_ty, fn_arg) {
 526                 span_mirbug!(self, term, "bad arg #{:?} ({:?} <- {:?}): {:?}",
 527                              n, fn_arg, op_arg_ty, terr);
 528             }
 529         }
 530     }
 531
 532     fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
 533         match operand {
 534             &Operand::Constant(Constant {
 535                 literal: Literal::Item { def_id, .. }, ..
 536             }) => {
 537                 Some(def_id) == self.tcx().lang_items.box_free_fn()
 538             }
 539             _ => false,
 540         }
 541     }
 542
 543     fn check_box_free_inputs(&self,
 544                              mir: &Mir<'tcx>,
 545                              term: &Terminator<'tcx>,
 546                              sig: &ty::FnSig<'tcx>,
 547                              args: &[Operand<'tcx>])
 548     {
 549         debug!("check_box_free_inputs");
 550
 551         // box_free takes a Box as a pointer. Allow for that.
 552
 553         if sig.inputs.len() != 1 {
 554             span_mirbug!(self, term, "box_free should take 1 argument");
 555             return;
 556         }
 557
 558         let pointee_ty = match sig.inputs[0].sty {
 559             ty::TyRawPtr(mt) => mt.ty,
 560             _ => {
 561                 span_mirbug!(self, term, "box_free should take a raw ptr");
 562                 return;
 563             }
 564         };
 565
 566         if args.len() != 1 {
 567             span_mirbug!(self, term, "box_free called with wrong # of args");
 568             return;
 569         }
 570
 571         let arg_ty = match args[0].ty(mir, self.tcx()).sty {
 572             ty::TyRawPtr(mt) => mt.ty,
 573             ty::TyBox(ty) => ty,
 574             _ => {
 575                 span_mirbug!(self, term, "box_free called with bad arg ty");
 576                 return;
 577             }
 578         };
 579
 580         if let Err(terr) = self.sub_types(self.last_span, arg_ty, pointee_ty) {
 581             span_mirbug!(self, term, "bad box_free arg ({:?} <- {:?}): {:?}",
 582                          pointee_ty, arg_ty, terr);
 583         }
 584     }
 585
 586     fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block: &BasicBlockData<'tcx>)
 587     {
 588         let is_cleanup = block.is_cleanup;
 589         self.last_span = block.terminator().source_info.span;
 590         match block.terminator().kind {
 591             TerminatorKind::Goto { target } =>
 592                 self.assert_iscleanup(mir, block, target, is_cleanup),
 593             TerminatorKind::If { targets: (on_true, on_false), .. } => {
 594                 self.assert_iscleanup(mir, block, on_true, is_cleanup);
 595                 self.assert_iscleanup(mir, block, on_false, is_cleanup);
 596             }
 597             TerminatorKind::Switch { ref targets, .. } |
 598             TerminatorKind::SwitchInt { ref targets, .. } => {
 599                 for target in targets {
 600                     self.assert_iscleanup(mir, block, *target, is_cleanup);
 601                 }
 602             }
 603             TerminatorKind::Resume => {
 604                 if !is_cleanup {
 605                     span_mirbug!(self, block, "resume on non-cleanup block!")
 606                 }
 607             }
 608             TerminatorKind::Return => {
 609                 if is_cleanup {
 610                     span_mirbug!(self, block, "return on cleanup block")
 611                 }
 612             }
 613             TerminatorKind::Unreachable => {}
 614             TerminatorKind::Drop { target, unwind, .. } |
 615             TerminatorKind::DropAndReplace { target, unwind, .. } |
 616             TerminatorKind::Assert { target, cleanup: unwind, .. } => {
 617                 self.assert_iscleanup(mir, block, target, is_cleanup);
 618                 if let Some(unwind) = unwind {
 619                     if is_cleanup {
 620                         span_mirbug!(self, block, "unwind on cleanup block")
 621                     }
 622                     self.assert_iscleanup(mir, block, unwind, true);
 623                 }
 624             }
 625             TerminatorKind::Call { ref destination, cleanup, .. } => {
 626                 if let &Some((_, target)) = destination {
 627                     self.assert_iscleanup(mir, block, target, is_cleanup);
 628                 }
 629                 if let Some(cleanup) = cleanup {
 630                     if is_cleanup {
 631                         span_mirbug!(self, block, "cleanup on cleanup block")
 632                     }
 633                     self.assert_iscleanup(mir, block, cleanup, true);
 634                 }
 635             }
 636         }
 637     }
 638
 639     fn assert_iscleanup(&mut self,
 640                         mir: &Mir<'tcx>,
 641                         ctxt: &fmt::Debug,
 642                         bb: BasicBlock,
 643                         iscleanuppad: bool)
 644     {
 645         if mir[bb].is_cleanup != iscleanuppad {
 646             span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}",
 647                          bb, iscleanuppad);
 648         }
 649     }
 650
 651     fn typeck_mir(&mut self, mir: &Mir<'tcx>) {
 652         self.last_span = mir.span;
 653         debug!("run_on_mir: {:?}", mir.span);
 654         for block in mir.basic_blocks() {
 655             for stmt in &block.statements {
 656                 if stmt.source_info.span != DUMMY_SP {
 657                     self.last_span = stmt.source_info.span;
 658                 }
 659                 self.check_stmt(mir, stmt);
 660             }
 661
 662             self.check_terminator(mir, block.terminator());
 663             self.check_iscleanup(mir, block);
 664         }
 665     }
 666
 667
 668     fn normalize<T>(&mut self, value: &T) -> T
 669         where T: fmt::Debug + TypeFoldable<'tcx>
 670     {
 671         let mut selcx = traits::SelectionContext::new(self.infcx);
 672         let cause = traits::ObligationCause::misc(self.last_span, 0);
 673         let traits::Normalized { value, obligations } =
 674             traits::normalize(&mut selcx, cause, value);
 675
 676         debug!("normalize: value={:?} obligations={:?}",
 677                value,
 678                obligations);
 679
 680         let mut fulfill_cx = &mut self.fulfillment_cx;
 681         for obligation in obligations {
 682             fulfill_cx.register_predicate_obligation(self.infcx, obligation);
 683         }
 684
 685         value
 686     }
 687
 688     fn verify_obligations(&mut self, mir: &Mir<'tcx>) {
 689         self.last_span = mir.span;
 690         if let Err(e) = self.fulfillment_cx.select_all_or_error(self.infcx) {
 691             span_mirbug!(self, "", "errors selecting obligation: {:?}",
 692                          e);
 693         }
 694     }
 695 }
 696
 697 pub struct TypeckMir;
 698
 699 impl TypeckMir {
 700     pub fn new() -> Self {
 701         TypeckMir
 702     }
 703 }
 704
 705 impl<'tcx> MirPass<'tcx> for TypeckMir {
 706     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
 707                     src: MirSource, mir: &mut Mir<'tcx>) {
 708         if tcx.sess.err_count() > 0 {
 709             // compiling a broken program can obviously result in a
 710             // broken MIR, so try not to report duplicate errors.
 711             return;
 712         }
 713         let param_env = ty::ParameterEnvironment::for_item(tcx, src.item_id());
 714         tcx.infer_ctxt(None, Some(param_env), Reveal::NotSpecializable).enter(|infcx| {
 715             let mut checker = TypeChecker::new(&infcx);
 716             {
 717                 let mut verifier = TypeVerifier::new(&mut checker, mir);
 718                 verifier.visit_mir(mir);
 719                 if verifier.errors_reported {
 720                     // don't do further checks to avoid ICEs
 721                     return;
 722                 }
 723             }
 724             checker.typeck_mir(mir);
 725             checker.verify_obligations(mir);
 726         });
 727     }
 728 }
 729
 730 impl Pass for TypeckMir {
 731 }