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         if let ty::FnConverging(t) = mir.return_ty {
  89             self.sanitize_type(&"return type", t);
  90         }
  91         for var_decl in &mir.var_decls {
  92             self.sanitize_type(var_decl, var_decl.ty);
  93         }
  94         for (n, arg_decl) in mir.arg_decls.iter().enumerate() {
  95             self.sanitize_type(&(n, arg_decl), arg_decl.ty);
  96         }
  97         for (n, tmp_decl) in mir.temp_decls.iter().enumerate() {
  98             self.sanitize_type(&(n, tmp_decl), tmp_decl.ty);
  99         }
 100         if self.errors_reported {
 101             return;
 102         }
 103         self.super_mir(mir);
 104     }
 105 }
 106
 107 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 108     fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
 109         TypeVerifier {
 110             cx: cx,
 111             mir: mir,
 112             last_span: mir.span,
 113             errors_reported: false
 114         }
 115     }
 116
 117     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 118         self.cx.infcx.tcx
 119     }
 120
 121     fn sanitize_type(&mut self, parent: &fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
 122         if ty.needs_infer() || ty.has_escaping_regions() || ty.references_error() {
 123             span_mirbug_and_err!(self, parent, "bad type {:?}", ty)
 124         } else {
 125             ty
 126         }
 127     }
 128
 129     fn sanitize_lvalue(&mut self, lvalue: &Lvalue<'tcx>) -> LvalueTy<'tcx> {
 130         debug!("sanitize_lvalue: {:?}", lvalue);
 131         match *lvalue {
 132             Lvalue::Var(index) => LvalueTy::Ty { ty: self.mir.var_decls[index].ty },
 133             Lvalue::Temp(index) => LvalueTy::Ty { ty: self.mir.temp_decls[index].ty },
 134             Lvalue::Arg(index) => LvalueTy::Ty { ty: self.mir.arg_decls[index].ty },
 135             Lvalue::Static(def_id) =>
 136                 LvalueTy::Ty { ty: self.tcx().lookup_item_type(def_id).ty },
 137             Lvalue::ReturnPointer => {
 138                 if let ty::FnConverging(return_ty) = self.mir.return_ty {
 139                     LvalueTy::Ty { ty: return_ty }
 140                 } else {
 141                     LvalueTy::Ty {
 142                         ty: span_mirbug_and_err!(
 143                             self, lvalue, "return in diverging function")
 144                     }
 145                 }
 146             }
 147             Lvalue::Projection(ref proj) => {
 148                 let base_ty = self.sanitize_lvalue(&proj.base);
 149                 if let LvalueTy::Ty { ty } = base_ty {
 150                     if ty.references_error() {
 151                         assert!(self.errors_reported);
 152                         return LvalueTy::Ty { ty: self.tcx().types.err };
 153                     }
 154                 }
 155                 self.sanitize_projection(base_ty, &proj.elem, lvalue)
 156             }
 157         }
 158     }
 159
 160     fn sanitize_projection(&mut self,
 161                            base: LvalueTy<'tcx>,
 162                            pi: &LvalueElem<'tcx>,
 163                            lvalue: &Lvalue<'tcx>)
 164                            -> LvalueTy<'tcx> {
 165         debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, lvalue);
 166         let tcx = self.tcx();
 167         let base_ty = base.to_ty(tcx);
 168         let span = self.last_span;
 169         match *pi {
 170             ProjectionElem::Deref => {
 171                 let deref_ty = base_ty.builtin_deref(true, ty::LvaluePreference::NoPreference);
 172                 LvalueTy::Ty {
 173                     ty: deref_ty.map(|t| t.ty).unwrap_or_else(|| {
 174                         span_mirbug_and_err!(
 175                             self, lvalue, "deref of non-pointer {:?}", base_ty)
 176                     })
 177                 }
 178             }
 179             ProjectionElem::Index(ref i) => {
 180                 self.visit_operand(i);
 181                 let index_ty = i.ty(self.mir, tcx);
 182                 if index_ty != tcx.types.usize {
 183                     LvalueTy::Ty {
 184                         ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i)
 185                     }
 186                 } else {
 187                     LvalueTy::Ty {
 188                         ty: base_ty.builtin_index().unwrap_or_else(|| {
 189                             span_mirbug_and_err!(
 190                                 self, lvalue, "index of non-array {:?}", base_ty)
 191                         })
 192                     }
 193                 }
 194             }
 195             ProjectionElem::ConstantIndex { .. } => {
 196                 // consider verifying in-bounds
 197                 LvalueTy::Ty {
 198                     ty: base_ty.builtin_index().unwrap_or_else(|| {
 199                         span_mirbug_and_err!(
 200                             self, lvalue, "index of non-array {:?}", base_ty)
 201                     })
 202                 }
 203             }
 204             ProjectionElem::Subslice { from, to } => {
 205                 LvalueTy::Ty {
 206                     ty: match base_ty.sty {
 207                         ty::TyArray(inner, size) => {
 208                             let min_size = (from as usize) + (to as usize);
 209                             if let Some(rest_size) = size.checked_sub(min_size) {
 210                                 tcx.mk_array(inner, rest_size)
 211                             } else {
 212                                 span_mirbug_and_err!(
 213                                     self, lvalue, "taking too-small slice of {:?}", base_ty)
 214                             }
 215                         }
 216                         ty::TySlice(..) => base_ty,
 217                         _ => {
 218                             span_mirbug_and_err!(
 219                                 self, lvalue, "slice of non-array {:?}", base_ty)
 220                         }
 221                     }
 222                 }
 223             }
 224             ProjectionElem::Downcast(adt_def1, index) =>
 225                 match base_ty.sty {
 226                     ty::TyEnum(adt_def, substs) if adt_def == adt_def1 => {
 227                         if index >= adt_def.variants.len() {
 228                             LvalueTy::Ty {
 229                                 ty: span_mirbug_and_err!(
 230                                     self,
 231                                     lvalue,
 232                                     "cast to variant #{:?} but enum only has {:?}",
 233                                     index,
 234                                     adt_def.variants.len())
 235                             }
 236                         } else {
 237                             LvalueTy::Downcast {
 238                                 adt_def: adt_def,
 239                                 substs: substs,
 240                                 variant_index: index
 241                             }
 242                         }
 243                     }
 244                     _ => LvalueTy::Ty {
 245                         ty: span_mirbug_and_err!(
 246                             self, lvalue, "can't downcast {:?} as {:?}",
 247                             base_ty, adt_def1)
 248                     }
 249                 },
 250             ProjectionElem::Field(field, fty) => {
 251                 let fty = self.sanitize_type(lvalue, fty);
 252                 match self.field_ty(lvalue, base, field) {
 253                     Ok(ty) => {
 254                         if let Err(terr) = self.cx.eq_types(span, ty, fty) {
 255                             span_mirbug!(
 256                                 self, lvalue, "bad field access ({:?}: {:?}): {:?}",
 257                                 ty, fty, terr);
 258                         }
 259                     }
 260                     Err(FieldAccessError::OutOfRange { field_count }) => {
 261                         span_mirbug!(
 262                             self, lvalue, "accessed field #{} but variant only has {}",
 263                             field.index(), field_count)
 264                     }
 265                 }
 266                 LvalueTy::Ty { ty: fty }
 267             }
 268         }
 269     }
 270
 271     fn error(&mut self) -> Ty<'tcx> {
 272         self.errors_reported = true;
 273         self.tcx().types.err
 274     }
 275
 276     fn field_ty(&mut self,
 277                 parent: &fmt::Debug,
 278                 base_ty: LvalueTy<'tcx>,
 279                 field: Field)
 280                 -> Result<Ty<'tcx>, FieldAccessError>
 281     {
 282         let tcx = self.tcx();
 283
 284         let (variant, substs) = match base_ty {
 285             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 286                 (&adt_def.variants[variant_index], substs)
 287             }
 288             LvalueTy::Ty { ty } => match ty.sty {
 289                 ty::TyStruct(adt_def, substs) | ty::TyEnum(adt_def, substs)
 290                     if adt_def.is_univariant() => {
 291                         (&adt_def.variants[0], substs)
 292                     }
 293                 ty::TyTuple(tys) | ty::TyClosure(_, ty::ClosureSubsts {
 294                     upvar_tys: tys, ..
 295                 }) => {
 296                     return match tys.get(field.index()) {
 297                         Some(&ty) => Ok(ty),
 298                         None => Err(FieldAccessError::OutOfRange {
 299                             field_count: tys.len()
 300                         })
 301                     }
 302                 }
 303                 _ => return Ok(span_mirbug_and_err!(
 304                     self, parent, "can't project out of {:?}", base_ty))
 305             }
 306         };
 307
 308         if let Some(field) = variant.fields.get(field.index()) {
 309             Ok(self.cx.normalize(&field.ty(tcx, substs)))
 310         } else {
 311             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
 312         }
 313     }
 314 }
 315
 316 pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 317     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 318     fulfillment_cx: traits::FulfillmentContext<'tcx>,
 319     last_span: Span
 320 }
 321
 322 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
 323     fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>) -> Self {
 324         TypeChecker {
 325             infcx: infcx,
 326             fulfillment_cx: traits::FulfillmentContext::new(),
 327             last_span: DUMMY_SP
 328         }
 329     }
 330
 331     fn sub_types(&self, span: Span, sup: Ty<'tcx>, sub: Ty<'tcx>)
 332                  -> infer::UnitResult<'tcx>
 333     {
 334         self.infcx.sub_types(false, infer::TypeOrigin::Misc(span), sup, sub)
 335             // FIXME(#32730) propagate obligations
 336             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 337     }
 338
 339     fn eq_types(&self, span: Span, a: Ty<'tcx>, b: Ty<'tcx>)
 340                 -> infer::UnitResult<'tcx>
 341     {
 342         self.infcx.eq_types(false, infer::TypeOrigin::Misc(span), a, b)
 343             // FIXME(#32730) propagate obligations
 344             .map(|InferOk { obligations, .. }| assert!(obligations.is_empty()))
 345     }
 346
 347     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 348         self.infcx.tcx
 349     }
 350
 351     fn check_stmt(&mut self, mir: &Mir<'tcx>, stmt: &Statement<'tcx>) {
 352         debug!("check_stmt: {:?}", stmt);
 353         let tcx = self.tcx();
 354         match stmt.kind {
 355             StatementKind::Assign(ref lv, ref rv) => {
 356                 let lv_ty = lv.ty(mir, tcx).to_ty(tcx);
 357                 let rv_ty = rv.ty(mir, tcx);
 358                 if let Some(rv_ty) = rv_ty {
 359                     if let Err(terr) = self.sub_types(self.last_span, rv_ty, lv_ty) {
 360                         span_mirbug!(self, stmt, "bad assignment ({:?} = {:?}): {:?}",
 361                                      lv_ty, rv_ty, terr);
 362                     }
 363                 // FIXME: rvalue with undeterminable type - e.g. inline
 364                 // asm.
 365                 }
 366             }
 367             StatementKind::SetDiscriminant{ ref lvalue, variant_index } => {
 368                 let lvalue_type = lvalue.ty(mir, tcx).to_ty(tcx);
 369                 let adt = match lvalue_type.sty {
 370                     TypeVariants::TyEnum(adt, _) => adt,
 371                     _ => {
 372                         span_bug!(stmt.source_info.span,
 373                                   "bad set discriminant ({:?} = {:?}): lhs is not an enum",
 374                                   lvalue,
 375                                   variant_index);
 376                     }
 377                 };
 378                 if variant_index >= adt.variants.len() {
 379                      span_bug!(stmt.source_info.span,
 380                                "bad set discriminant ({:?} = {:?}): value of of range",
 381                                lvalue,
 382                                variant_index);
 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, sig.output) {
 495             (&Some(..), ty::FnDiverging) => {
 496                 span_mirbug!(self, term, "call to diverging function {:?} with dest", sig);
 497             }
 498             (&Some((ref dest, _)), ty::FnConverging(ty)) => {
 499                 let dest_ty = dest.ty(mir, tcx).to_ty(tcx);
 500                 if let Err(terr) = self.sub_types(self.last_span, ty, dest_ty) {
 501                     span_mirbug!(self, term,
 502                                  "call dest mismatch ({:?} <- {:?}): {:?}",
 503                                  dest_ty, ty, terr);
 504                 }
 505             }
 506             (&None, ty::FnDiverging) => {}
 507             (&None, ty::FnConverging(..)) => {
 508                 span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
 509              }
 510         }
 511     }
 512
 513     fn check_call_inputs(&self,
 514                          mir: &Mir<'tcx>,
 515                          term: &Terminator<'tcx>,
 516                          sig: &ty::FnSig<'tcx>,
 517                          args: &[Operand<'tcx>])
 518     {
 519         debug!("check_call_inputs({:?}, {:?})", sig, args);
 520         if args.len() < sig.inputs.len() ||
 521            (args.len() > sig.inputs.len() && !sig.variadic) {
 522             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
 523         }
 524         for (n, (fn_arg, op_arg)) in sig.inputs.iter().zip(args).enumerate() {
 525             let op_arg_ty = op_arg.ty(mir, self.tcx());
 526             if let Err(terr) = self.sub_types(self.last_span, op_arg_ty, fn_arg) {
 527                 span_mirbug!(self, term, "bad arg #{:?} ({:?} <- {:?}): {:?}",
 528                              n, fn_arg, op_arg_ty, terr);
 529             }
 530         }
 531     }
 532
 533     fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
 534         match operand {
 535             &Operand::Constant(Constant {
 536                 literal: Literal::Item { def_id, .. }, ..
 537             }) => {
 538                 Some(def_id) == self.tcx().lang_items.box_free_fn()
 539             }
 540             _ => false,
 541         }
 542     }
 543
 544     fn check_box_free_inputs(&self,
 545                              mir: &Mir<'tcx>,
 546                              term: &Terminator<'tcx>,
 547                              sig: &ty::FnSig<'tcx>,
 548                              args: &[Operand<'tcx>])
 549     {
 550         debug!("check_box_free_inputs");
 551
 552         // box_free takes a Box as a pointer. Allow for that.
 553
 554         if sig.inputs.len() != 1 {
 555             span_mirbug!(self, term, "box_free should take 1 argument");
 556             return;
 557         }
 558
 559         let pointee_ty = match sig.inputs[0].sty {
 560             ty::TyRawPtr(mt) => mt.ty,
 561             _ => {
 562                 span_mirbug!(self, term, "box_free should take a raw ptr");
 563                 return;
 564             }
 565         };
 566
 567         if args.len() != 1 {
 568             span_mirbug!(self, term, "box_free called with wrong # of args");
 569             return;
 570         }
 571
 572         let arg_ty = match args[0].ty(mir, self.tcx()).sty {
 573             ty::TyRawPtr(mt) => mt.ty,
 574             ty::TyBox(ty) => ty,
 575             _ => {
 576                 span_mirbug!(self, term, "box_free called with bad arg ty");
 577                 return;
 578             }
 579         };
 580
 581         if let Err(terr) = self.sub_types(self.last_span, arg_ty, pointee_ty) {
 582             span_mirbug!(self, term, "bad box_free arg ({:?} <- {:?}): {:?}",
 583                          pointee_ty, arg_ty, terr);
 584         }
 585     }
 586
 587     fn check_iscleanup(&mut self, mir: &Mir<'tcx>, block: &BasicBlockData<'tcx>)
 588     {
 589         let is_cleanup = block.is_cleanup;
 590         self.last_span = block.terminator().source_info.span;
 591         match block.terminator().kind {
 592             TerminatorKind::Goto { target } =>
 593                 self.assert_iscleanup(mir, block, target, is_cleanup),
 594             TerminatorKind::If { targets: (on_true, on_false), .. } => {
 595                 self.assert_iscleanup(mir, block, on_true, is_cleanup);
 596                 self.assert_iscleanup(mir, block, on_false, is_cleanup);
 597             }
 598             TerminatorKind::Switch { ref targets, .. } |
 599             TerminatorKind::SwitchInt { ref targets, .. } => {
 600                 for target in targets {
 601                     self.assert_iscleanup(mir, block, *target, is_cleanup);
 602                 }
 603             }
 604             TerminatorKind::Resume => {
 605                 if !is_cleanup {
 606                     span_mirbug!(self, block, "resume on non-cleanup block!")
 607                 }
 608             }
 609             TerminatorKind::Return => {
 610                 if is_cleanup {
 611                     span_mirbug!(self, block, "return on cleanup block")
 612                 }
 613             }
 614             TerminatorKind::Unreachable => {}
 615             TerminatorKind::Drop { target, unwind, .. } |
 616             TerminatorKind::DropAndReplace { target, unwind, .. } |
 617             TerminatorKind::Assert { target, cleanup: unwind, .. } => {
 618                 self.assert_iscleanup(mir, block, target, is_cleanup);
 619                 if let Some(unwind) = unwind {
 620                     if is_cleanup {
 621                         span_mirbug!(self, block, "unwind on cleanup block")
 622                     }
 623                     self.assert_iscleanup(mir, block, unwind, true);
 624                 }
 625             }
 626             TerminatorKind::Call { ref destination, cleanup, .. } => {
 627                 if let &Some((_, target)) = destination {
 628                     self.assert_iscleanup(mir, block, target, is_cleanup);
 629                 }
 630                 if let Some(cleanup) = cleanup {
 631                     if is_cleanup {
 632                         span_mirbug!(self, block, "cleanup on cleanup block")
 633                     }
 634                     self.assert_iscleanup(mir, block, cleanup, true);
 635                 }
 636             }
 637         }
 638     }
 639
 640     fn assert_iscleanup(&mut self,
 641                         mir: &Mir<'tcx>,
 642                         ctxt: &fmt::Debug,
 643                         bb: BasicBlock,
 644                         iscleanuppad: bool)
 645     {
 646         if mir[bb].is_cleanup != iscleanuppad {
 647             span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}",
 648                          bb, iscleanuppad);
 649         }
 650     }
 651
 652     fn typeck_mir(&mut self, mir: &Mir<'tcx>) {
 653         self.last_span = mir.span;
 654         debug!("run_on_mir: {:?}", mir.span);
 655         for block in mir.basic_blocks() {
 656             for stmt in &block.statements {
 657                 if stmt.source_info.span != DUMMY_SP {
 658                     self.last_span = stmt.source_info.span;
 659                 }
 660                 self.check_stmt(mir, stmt);
 661             }
 662
 663             self.check_terminator(mir, block.terminator());
 664             self.check_iscleanup(mir, block);
 665         }
 666     }
 667
 668
 669     fn normalize<T>(&mut self, value: &T) -> T
 670         where T: fmt::Debug + TypeFoldable<'tcx>
 671     {
 672         let mut selcx = traits::SelectionContext::new(self.infcx);
 673         let cause = traits::ObligationCause::misc(self.last_span, 0);
 674         let traits::Normalized { value, obligations } =
 675             traits::normalize(&mut selcx, cause, value);
 676
 677         debug!("normalize: value={:?} obligations={:?}",
 678                value,
 679                obligations);
 680
 681         let mut fulfill_cx = &mut self.fulfillment_cx;
 682         for obligation in obligations {
 683             fulfill_cx.register_predicate_obligation(self.infcx, obligation);
 684         }
 685
 686         value
 687     }
 688
 689     fn verify_obligations(&mut self, mir: &Mir<'tcx>) {
 690         self.last_span = mir.span;
 691         if let Err(e) = self.fulfillment_cx.select_all_or_error(self.infcx) {
 692             span_mirbug!(self, "", "errors selecting obligation: {:?}",
 693                          e);
 694         }
 695     }
 696 }
 697
 698 pub struct TypeckMir;
 699
 700 impl TypeckMir {
 701     pub fn new() -> Self {
 702         TypeckMir
 703     }
 704 }
 705
 706 impl<'tcx> MirPass<'tcx> for TypeckMir {
 707     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
 708                     src: MirSource, mir: &mut Mir<'tcx>) {
 709         if tcx.sess.err_count() > 0 {
 710             // compiling a broken program can obviously result in a
 711             // broken MIR, so try not to report duplicate errors.
 712             return;
 713         }
 714         let param_env = ty::ParameterEnvironment::for_item(tcx, src.item_id());
 715         tcx.infer_ctxt(None, Some(param_env), Reveal::NotSpecializable).enter(|infcx| {
 716             let mut checker = TypeChecker::new(&infcx);
 717             {
 718                 let mut verifier = TypeVerifier::new(&mut checker, mir);
 719                 verifier.visit_mir(mir);
 720                 if verifier.errors_reported {
 721                     // don't do further checks to avoid ICEs
 722                     return;
 723                 }
 724             }
 725             checker.typeck_mir(mir);
 726             checker.verify_obligations(mir);
 727         });
 728     }
 729 }
 730
 731 impl Pass for TypeckMir {
 732 }