src/interpreter.rs

   1 use arena::TypedArena;
   2 use rustc::infer;
   3 use rustc::middle::const_val;
   4 use rustc::middle::def_id::DefId;
   5 use rustc::mir::mir_map::MirMap;
   6 use rustc::mir::repr as mir;
   7 use rustc::traits::{self, ProjectionMode};
   8 use rustc::ty::fold::TypeFoldable;
   9 use rustc::ty::subst::{self, Subst, Substs};
  10 use rustc::ty::{self, TyCtxt};
  11 use rustc::util::nodemap::DefIdMap;
  12 use rustc_data_structures::fnv::FnvHashMap;
  13 use std::cell::RefCell;
  14 use std::ops::Deref;
  15 use std::rc::Rc;
  16 use std::{iter, mem};
  17 use syntax::ast;
  18 use syntax::attr;
  19 use syntax::codemap::{self, DUMMY_SP};
  20
  21 use error::{EvalError, EvalResult};
  22 use memory::{FieldRepr, Memory, Pointer, Repr};
  23 use primval::{self, PrimVal};
  24
  25 const TRACE_EXECUTION: bool = false;
  26
  27 struct Interpreter<'a, 'tcx: 'a, 'arena> {
  28     /// The results of the type checker, from rustc.
  29     tcx: &'a TyCtxt<'tcx>,
  30
  31     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  32     mir_map: &'a MirMap<'tcx>,
  33
  34     /// A local cache from DefIds to Mir for non-crate-local items.
  35     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  36
  37     /// An arena allocator for type representations.
  38     repr_arena: &'arena TypedArena<Repr>,
  39
  40     /// A cache for in-memory representations of types.
  41     repr_cache: RefCell<FnvHashMap<ty::Ty<'tcx>, &'arena Repr>>,
  42
  43     /// The virtual memory system.
  44     memory: Memory,
  45
  46     /// The virtual call stack.
  47     stack: Vec<Frame<'a, 'tcx>>,
  48
  49     /// Another stack containing the type substitutions for the current function invocation. It
  50     /// exists separately from `stack` because it must contain the `Substs` for a function while
  51     /// *creating* the `Frame` for that same function.
  52     substs_stack: Vec<&'tcx Substs<'tcx>>,
  53
  54     // TODO(tsion): Merge with `substs_stack`. Also try restructuring `Frame` to accomodate.
  55     /// A stack of the things necessary to print good strack traces:
  56     ///   * Function DefIds and Substs to print proper substituted function names.
  57     ///   * Spans pointing to specific function calls in the source.
  58     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
  59 }
  60
  61 /// A stack frame.
  62 struct Frame<'a, 'tcx: 'a> {
  63     /// The MIR for the function called on this frame.
  64     mir: CachedMir<'a, 'tcx>,
  65
  66     /// The block this frame will execute when a function call returns back to this frame.
  67     next_block: mir::BasicBlock,
  68
  69     /// A pointer for writing the return value of the current call if it's not a diverging call.
  70     return_ptr: Option<Pointer>,
  71
  72     /// The list of locals for the current function, stored in order as
  73     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  74     /// and the temporaries at `self.temp_offset`.
  75     locals: Vec<Pointer>,
  76
  77     /// The offset of the first variable in `self.locals`.
  78     var_offset: usize,
  79
  80     /// The offset of the first temporary in `self.locals`.
  81     temp_offset: usize,
  82 }
  83
  84 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  85 struct Lvalue {
  86     ptr: Pointer,
  87     extra: LvalueExtra,
  88 }
  89
  90 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  91 enum LvalueExtra {
  92     None,
  93     Length(u64),
  94     // Vtable(memory::AllocId),
  95 }
  96
  97 #[derive(Clone)]
  98 enum CachedMir<'mir, 'tcx: 'mir> {
  99     Ref(&'mir mir::Mir<'tcx>),
 100     Owned(Rc<mir::Mir<'tcx>>)
 101 }
 102
 103 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 104 enum TerminatorTarget {
 105     /// Make a local jump to the given block.
 106     Block(mir::BasicBlock),
 107
 108     /// Start executing from the new current frame. (For function calls.)
 109     Call,
 110
 111     /// Stop executing the current frame and resume the previous frame.
 112     Return,
 113 }
 114
 115 impl<'a, 'tcx: 'a, 'arena> Interpreter<'a, 'tcx, 'arena> {
 116     fn new(tcx: &'a TyCtxt<'tcx>, mir_map: &'a MirMap<'tcx>, repr_arena: &'arena TypedArena<Repr>)
 117         -> Self
 118     {
 119         Interpreter {
 120             tcx: tcx,
 121             mir_map: mir_map,
 122             mir_cache: RefCell::new(DefIdMap()),
 123             repr_arena: repr_arena,
 124             repr_cache: RefCell::new(FnvHashMap()),
 125             memory: Memory::new(),
 126             stack: Vec::new(),
 127             substs_stack: Vec::new(),
 128             name_stack: Vec::new(),
 129         }
 130     }
 131
 132     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 133         if let Err(ref e) = r {
 134             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 135             for &(def_id, substs, span) in self.name_stack.iter().rev() {
 136                 // FIXME(tsion): Find a way to do this without this Display impl hack.
 137                 use rustc::util::ppaux;
 138                 use std::fmt;
 139                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 140                 impl<'tcx> fmt::Display for Instance<'tcx> {
 141                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 142                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 143                             |tcx| tcx.lookup_item_type(self.0).generics)
 144                     }
 145                 }
 146                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 147             }
 148             err.emit();
 149         }
 150         r
 151     }
 152
 153     fn log<F>(&self, extra_indent: usize, f: F) where F: FnOnce() {
 154         let indent = self.stack.len() + extra_indent;
 155         if !TRACE_EXECUTION { return; }
 156         for _ in 0..indent { print!("    "); }
 157         f();
 158         println!("");
 159     }
 160
 161     fn run(&mut self) -> EvalResult<()> {
 162         'outer: while !self.stack.is_empty() {
 163             let mut current_block = self.frame().next_block;
 164
 165             loop {
 166                 self.log(0, || print!("// {:?}", current_block));
 167                 let current_mir = self.mir().clone(); // Cloning a reference.
 168                 let block_data = current_mir.basic_block_data(current_block);
 169
 170                 for stmt in &block_data.statements {
 171                     self.log(0, || print!("{:?}", stmt));
 172                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 173                     let result = self.eval_assignment(lvalue, rvalue);
 174                     try!(self.maybe_report(stmt.span, result));
 175                 }
 176
 177                 let terminator = block_data.terminator();
 178                 self.log(0, || print!("{:?}", terminator.kind));
 179
 180                 let result = self.eval_terminator(terminator);
 181                 match try!(self.maybe_report(terminator.span, result)) {
 182                     TerminatorTarget::Block(block) => current_block = block,
 183                     TerminatorTarget::Return => {
 184                         self.pop_stack_frame();
 185                         self.name_stack.pop();
 186                         continue 'outer;
 187                     }
 188                     TerminatorTarget::Call => continue 'outer,
 189                 }
 190             }
 191         }
 192
 193         Ok(())
 194     }
 195
 196     fn push_stack_frame(&mut self, mir: CachedMir<'a, 'tcx>, substs: &'tcx Substs<'tcx>,
 197         return_ptr: Option<Pointer>)
 198     {
 199         self.substs_stack.push(substs);
 200
 201         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 202         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 203         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 204
 205         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 206             let size = self.type_size(ty);
 207             self.memory.allocate(size)
 208         }).collect();
 209
 210         let num_args = mir.arg_decls.len();
 211         let num_vars = mir.var_decls.len();
 212
 213         self.stack.push(Frame {
 214             mir: mir.clone(),
 215             next_block: mir::START_BLOCK,
 216             return_ptr: return_ptr,
 217             locals: locals,
 218             var_offset: num_args,
 219             temp_offset: num_args + num_vars,
 220         });
 221     }
 222
 223     fn pop_stack_frame(&mut self) {
 224         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 225         // TODO(tsion): Deallocate local variables.
 226         self.substs_stack.pop();
 227     }
 228
 229     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 230             -> EvalResult<TerminatorTarget> {
 231         use rustc::mir::repr::TerminatorKind::*;
 232         let target = match terminator.kind {
 233             Return => TerminatorTarget::Return,
 234
 235             Goto { target } => TerminatorTarget::Block(target),
 236
 237             If { ref cond, targets: (then_target, else_target) } => {
 238                 let cond_ptr = try!(self.eval_operand(cond));
 239                 let cond_val = try!(self.memory.read_bool(cond_ptr));
 240                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 241             }
 242
 243             SwitchInt { ref discr, ref values, ref targets, .. } => {
 244                 let discr_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 245                 let discr_size = self.lvalue_repr(discr).size();
 246                 let discr_val = try!(self.memory.read_uint(discr_ptr, discr_size));
 247
 248                 // Branch to the `otherwise` case by default, if no match is found.
 249                 let mut target_block = targets[targets.len() - 1];
 250
 251                 for (index, val_const) in values.iter().enumerate() {
 252                     let ptr = try!(self.const_to_ptr(val_const));
 253                     let val = try!(self.memory.read_uint(ptr, discr_size));
 254                     if discr_val == val {
 255                         target_block = targets[index];
 256                         break;
 257                     }
 258                 }
 259
 260                 TerminatorTarget::Block(target_block)
 261             }
 262
 263             Switch { ref discr, ref targets, adt_def } => {
 264                 let adt_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 265                 let adt_repr = self.lvalue_repr(discr);
 266                 let discr_size = match *adt_repr {
 267                     Repr::Aggregate { discr_size, .. } => discr_size,
 268                     _ => panic!("attmpted to switch on non-aggregate type"),
 269                 };
 270                 let discr_val = try!(self.memory.read_uint(adt_ptr, discr_size));
 271
 272                 let matching = adt_def.variants.iter()
 273                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 274
 275                 match matching {
 276                     Some(i) => TerminatorTarget::Block(targets[i]),
 277                     None => return Err(EvalError::InvalidDiscriminant),
 278                 }
 279             }
 280
 281             Call { ref func, ref args, ref destination, .. } => {
 282                 let mut return_ptr = None;
 283                 if let Some((ref lv, target)) = *destination {
 284                     self.frame_mut().next_block = target;
 285                     return_ptr = Some(try!(self.eval_lvalue(lv)).to_ptr());
 286                 }
 287
 288                 let func_ty = self.operand_ty(func);
 289                 match func_ty.sty {
 290                     ty::TyFnDef(def_id, substs, fn_ty) => {
 291                         use syntax::abi::Abi;
 292                         match fn_ty.abi {
 293                             Abi::RustIntrinsic => {
 294                                 let name = self.tcx.item_name(def_id).as_str();
 295                                 match fn_ty.sig.0.output {
 296                                     ty::FnConverging(ty) => {
 297                                         let size = self.type_size(ty);
 298                                         try!(self.call_intrinsic(&name, substs, args,
 299                                             return_ptr.unwrap(), size))
 300                                     }
 301                                     ty::FnDiverging => unimplemented!(),
 302                                 }
 303                             }
 304
 305                             Abi::C =>
 306                                 try!(self.call_c_abi(def_id, args, return_ptr.unwrap())),
 307
 308                             Abi::Rust | Abi::RustCall => {
 309                                 // TODO(tsion): Adjust the first argument when calling a Fn or
 310                                 // FnMut closure via FnOnce::call_once.
 311
 312                                 // Only trait methods can have a Self parameter.
 313                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 314                                     self.trait_method(def_id, substs)
 315                                 } else {
 316                                     (def_id, substs)
 317                                 };
 318
 319                                 let mut arg_srcs = Vec::new();
 320                                 for arg in args {
 321                                     let src = try!(self.eval_operand(arg));
 322                                     let src_ty = self.operand_ty(arg);
 323                                     arg_srcs.push((src, src_ty));
 324                                 }
 325
 326                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 327                                     arg_srcs.pop();
 328                                     let last_arg = args.last().unwrap();
 329                                     let last = try!(self.eval_operand(last_arg));
 330                                     let last_ty = self.operand_ty(last_arg);
 331                                     let last_repr = self.type_repr(last_ty);
 332                                     match (&last_ty.sty, last_repr) {
 333                                         (&ty::TyTuple(ref fields),
 334                                          &Repr::Aggregate { discr_size: 0, ref variants, .. }) => {
 335                                             assert_eq!(variants.len(), 1);
 336                                             for (repr, ty) in variants[0].iter().zip(fields) {
 337                                                 let src = last.offset(repr.offset as isize);
 338                                                 arg_srcs.push((src, ty));
 339                                             }
 340                                         }
 341                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 342                                     }
 343                                 }
 344
 345                                 let mir = self.load_mir(resolved_def_id);
 346                                 self.name_stack.push((def_id, substs, terminator.span));
 347                                 self.push_stack_frame(mir, resolved_substs, return_ptr);
 348
 349                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 350                                     let dest = self.frame().locals[i];
 351                                     try!(self.move_(src, dest, src_ty));
 352                                 }
 353
 354                                 TerminatorTarget::Call
 355                             }
 356
 357                             abi => panic!("can't handle function with {:?} ABI", abi),
 358                         }
 359                     }
 360
 361                     _ => panic!("can't handle callee of type {:?}", func_ty),
 362                 }
 363             }
 364
 365             Drop { ref value, target, .. } => {
 366                 let ptr = try!(self.eval_lvalue(value)).to_ptr();
 367                 let ty = self.lvalue_ty(value);
 368                 try!(self.drop(ptr, ty));
 369                 TerminatorTarget::Block(target)
 370             }
 371
 372             Resume => unimplemented!(),
 373         };
 374
 375         Ok(target)
 376     }
 377
 378     fn drop(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<()> {
 379         if !self.type_needs_drop(ty) {
 380             self.log(1, || print!("no need to drop {:?}", ty));
 381             return Ok(());
 382         }
 383         self.log(1, || print!("need to drop {:?}", ty));
 384
 385         // TODO(tsion): Call user-defined Drop::drop impls.
 386
 387         match ty.sty {
 388             ty::TyBox(contents_ty) => {
 389                 match self.memory.read_ptr(ptr) {
 390                     Ok(contents_ptr) => {
 391                         try!(self.drop(contents_ptr, contents_ty));
 392                         self.log(1, || print!("deallocating box"));
 393                         try!(self.memory.deallocate(contents_ptr));
 394                     }
 395                     Err(EvalError::ReadBytesAsPointer) => {
 396                         let possible_drop_fill = try!(self.memory.read_usize(ptr));
 397                         if possible_drop_fill == mem::POST_DROP_U64 {
 398                             return Ok(());
 399                         } else {
 400                             return Err(EvalError::ReadBytesAsPointer);
 401                         }
 402                     }
 403                     Err(e) => return Err(e),
 404                 }
 405             }
 406
 407             // TODO(tsion): Implement drop for other relevant types (e.g. aggregates).
 408             _ => {}
 409         }
 410
 411         // Filling drop.
 412         // FIXME(tsion): Trait objects (with no static size) probably get filled, too.
 413         let size = self.type_size(ty);
 414         try!(self.memory.drop_fill(ptr, size));
 415
 416         Ok(())
 417     }
 418
 419     fn call_intrinsic(
 420         &mut self,
 421         name: &str,
 422         substs: &'tcx Substs<'tcx>,
 423         args: &[mir::Operand<'tcx>],
 424         dest: Pointer,
 425         dest_size: usize
 426     ) -> EvalResult<TerminatorTarget> {
 427         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 428             .map(|arg| self.eval_operand(arg))
 429             .collect();
 430         let args = try!(args_res);
 431
 432         match name {
 433             "assume" => {}
 434
 435             "copy_nonoverlapping" => {
 436                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 437                 let elem_size = self.type_size(elem_ty);
 438                 let src = try!(self.memory.read_ptr(args[0]));
 439                 let dest = try!(self.memory.read_ptr(args[1]));
 440                 let count = try!(self.memory.read_isize(args[2]));
 441                 try!(self.memory.copy(src, dest, count as usize * elem_size));
 442             }
 443
 444             "forget" => {
 445                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 446                 let arg_size = self.type_size(arg_ty);
 447                 try!(self.memory.drop_fill(args[0], arg_size));
 448             }
 449
 450             "init" => try!(self.memory.write_repeat(dest, 0, dest_size)),
 451
 452             "min_align_of" => {
 453                 try!(self.memory.write_int(dest, 1, dest_size));
 454             }
 455
 456             "move_val_init" => {
 457                 let ty = *substs.types.get(subst::FnSpace, 0);
 458                 let ptr = try!(self.memory.read_ptr(args[0]));
 459                 try!(self.move_(args[1], ptr, ty));
 460             }
 461
 462             // FIXME(tsion): Handle different integer types correctly.
 463             "add_with_overflow" => {
 464                 let ty = *substs.types.get(subst::FnSpace, 0);
 465                 let size = self.type_size(ty);
 466                 let left = try!(self.memory.read_int(args[0], size));
 467                 let right = try!(self.memory.read_int(args[1], size));
 468                 let (n, overflowed) = unsafe {
 469                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 470                 };
 471                 try!(self.memory.write_int(dest, n, size));
 472                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 473             }
 474
 475             // FIXME(tsion): Handle different integer types correctly.
 476             "mul_with_overflow" => {
 477                 let ty = *substs.types.get(subst::FnSpace, 0);
 478                 let size = self.type_size(ty);
 479                 let left = try!(self.memory.read_int(args[0], size));
 480                 let right = try!(self.memory.read_int(args[1], size));
 481                 let (n, overflowed) = unsafe {
 482                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 483                 };
 484                 try!(self.memory.write_int(dest, n, size));
 485                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 486             }
 487
 488             "offset" => {
 489                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 490                 let pointee_size = self.type_size(pointee_ty) as isize;
 491                 let ptr_arg = args[0];
 492                 let offset = try!(self.memory.read_isize(args[1]));
 493
 494                 match self.memory.read_ptr(ptr_arg) {
 495                     Ok(ptr) => {
 496                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 497                         try!(self.memory.write_ptr(dest, result_ptr));
 498                     }
 499                     Err(EvalError::ReadBytesAsPointer) => {
 500                         let addr = try!(self.memory.read_isize(ptr_arg));
 501                         let result_addr = addr + offset * pointee_size as i64;
 502                         try!(self.memory.write_isize(dest, result_addr));
 503                     }
 504                     Err(e) => return Err(e),
 505                 }
 506             }
 507
 508             // FIXME(tsion): Handle different integer types correctly. Use primvals?
 509             "overflowing_sub" => {
 510                 let ty = *substs.types.get(subst::FnSpace, 0);
 511                 let size = self.type_size(ty);
 512                 let left = try!(self.memory.read_int(args[0], size));
 513                 let right = try!(self.memory.read_int(args[1], size));
 514                 let n = left.wrapping_sub(right);
 515                 try!(self.memory.write_int(dest, n, size));
 516             }
 517
 518             "size_of" => {
 519                 let ty = *substs.types.get(subst::FnSpace, 0);
 520                 let size = self.type_size(ty) as u64;
 521                 try!(self.memory.write_uint(dest, size, dest_size));
 522             }
 523
 524             "transmute" => {
 525                 let ty = *substs.types.get(subst::FnSpace, 0);
 526                 try!(self.move_(args[0], dest, ty));
 527             }
 528             "uninit" => try!(self.memory.mark_definedness(dest, dest_size, false)),
 529
 530             name => panic!("can't handle intrinsic: {}", name),
 531         }
 532
 533         // Since we pushed no stack frame, the main loop will act
 534         // as if the call just completed and it's returning to the
 535         // current frame.
 536         Ok(TerminatorTarget::Call)
 537     }
 538
 539     fn call_c_abi(
 540         &mut self,
 541         def_id: DefId,
 542         args: &[mir::Operand<'tcx>],
 543         dest: Pointer
 544     ) -> EvalResult<TerminatorTarget> {
 545         let name = self.tcx.item_name(def_id);
 546         let attrs = self.tcx.get_attrs(def_id);
 547         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 548             Some(ln) => ln.clone(),
 549             None => name.as_str(),
 550         };
 551
 552         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 553             .map(|arg| self.eval_operand(arg))
 554             .collect();
 555         let args = try!(args_res);
 556
 557         match &link_name[..] {
 558             "__rust_allocate" => {
 559                 let size = try!(self.memory.read_usize(args[0]));
 560                 let ptr = self.memory.allocate(size as usize);
 561                 try!(self.memory.write_ptr(dest, ptr));
 562             }
 563
 564             "__rust_reallocate" => {
 565                 let ptr = try!(self.memory.read_ptr(args[0]));
 566                 let size = try!(self.memory.read_usize(args[2]));
 567                 try!(self.memory.reallocate(ptr, size as usize));
 568                 try!(self.memory.write_ptr(dest, ptr));
 569             }
 570
 571             _ => panic!("can't call C ABI function: {}", link_name),
 572         }
 573
 574         // Since we pushed no stack frame, the main loop will act
 575         // as if the call just completed and it's returning to the
 576         // current frame.
 577         Ok(TerminatorTarget::Call)
 578     }
 579
 580     fn assign_to_aggregate(
 581         &mut self,
 582         dest: Pointer,
 583         dest_repr: &Repr,
 584         variant: usize,
 585         discr: Option<u64>,
 586         operands: &[mir::Operand<'tcx>],
 587     ) -> EvalResult<()> {
 588         match *dest_repr {
 589             Repr::Aggregate { discr_size, ref variants, .. } => {
 590                 if discr_size > 0 {
 591                     try!(self.memory.write_uint(dest, discr.unwrap(), discr_size));
 592                 }
 593                 let after_discr = dest.offset(discr_size as isize);
 594                 for (field, operand) in variants[variant].iter().zip(operands) {
 595                     let src = try!(self.eval_operand(operand));
 596                     let src_ty = self.operand_ty(operand);
 597                     let field_dest = after_discr.offset(field.offset as isize);
 598                     try!(self.move_(src, field_dest, src_ty));
 599                 }
 600             }
 601             _ => panic!("expected Repr::Aggregate target"),
 602         }
 603         Ok(())
 604     }
 605
 606     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 607         -> EvalResult<()>
 608     {
 609         let dest = try!(self.eval_lvalue(lvalue)).to_ptr();
 610         let dest_ty = self.lvalue_ty(lvalue);
 611         let dest_repr = self.lvalue_repr(lvalue);
 612
 613         use rustc::mir::repr::Rvalue::*;
 614         match *rvalue {
 615             Use(ref operand) => {
 616                 let src = try!(self.eval_operand(operand));
 617                 try!(self.move_(src, dest, dest_ty));
 618             }
 619
 620             BinaryOp(bin_op, ref left, ref right) => {
 621                 let left_ptr = try!(self.eval_operand(left));
 622                 let left_ty = self.operand_ty(left);
 623                 let left_val = try!(self.read_primval(left_ptr, left_ty));
 624
 625                 let right_ptr = try!(self.eval_operand(right));
 626                 let right_ty = self.operand_ty(right);
 627                 let right_val = try!(self.read_primval(right_ptr, right_ty));
 628
 629                 let val = try!(primval::binary_op(bin_op, left_val, right_val));
 630                 try!(self.memory.write_primval(dest, val));
 631             }
 632
 633             UnaryOp(un_op, ref operand) => {
 634                 let ptr = try!(self.eval_operand(operand));
 635                 let ty = self.operand_ty(operand);
 636                 let val = try!(self.read_primval(ptr, ty));
 637                 try!(self.memory.write_primval(dest, primval::unary_op(un_op, val)));
 638             }
 639
 640             Aggregate(ref kind, ref operands) => {
 641                 use rustc::mir::repr::AggregateKind::*;
 642                 match *kind {
 643                     Tuple | Closure(..) =>
 644                         try!(self.assign_to_aggregate(dest, &dest_repr, 0, None, operands)),
 645
 646                     Adt(adt_def, variant, _) => {
 647                         let discr = Some(adt_def.variants[variant].disr_val.to_u64_unchecked());
 648                         try!(self.assign_to_aggregate(dest, &dest_repr, variant, discr, operands));
 649                     }
 650
 651                     Vec => if let Repr::Array { elem_size, length } = *dest_repr {
 652                         assert_eq!(length, operands.len());
 653                         for (i, operand) in operands.iter().enumerate() {
 654                             let src = try!(self.eval_operand(operand));
 655                             let src_ty = self.operand_ty(operand);
 656                             let elem_dest = dest.offset((i * elem_size) as isize);
 657                             try!(self.move_(src, elem_dest, src_ty));
 658                         }
 659                     } else {
 660                         panic!("expected Repr::Array target");
 661                     },
 662                 }
 663             }
 664
 665             Repeat(ref operand, _) => {
 666                 if let Repr::Array { elem_size, length } = *dest_repr {
 667                     let src = try!(self.eval_operand(operand));
 668                     for i in 0..length {
 669                         let elem_dest = dest.offset((i * elem_size) as isize);
 670                         try!(self.memory.copy(src, elem_dest, elem_size));
 671                     }
 672                 } else {
 673                     panic!("expected Repr::Array target");
 674                 }
 675             }
 676
 677             Len(ref lvalue) => {
 678                 let src = try!(self.eval_lvalue(lvalue));
 679                 let ty = self.lvalue_ty(lvalue);
 680                 let len = match ty.sty {
 681                     ty::TyArray(_, n) => n as u64,
 682                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 683                         n
 684                     } else {
 685                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 686                     },
 687                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 688                 };
 689                 try!(self.memory.write_usize(dest, len));
 690             }
 691
 692             Ref(_, _, ref lvalue) => {
 693                 let lv = try!(self.eval_lvalue(lvalue));
 694                 try!(self.memory.write_ptr(dest, lv.ptr));
 695                 match lv.extra {
 696                     LvalueExtra::None => {},
 697                     LvalueExtra::Length(len) => {
 698                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 699                         try!(self.memory.write_usize(len_ptr, len));
 700                     }
 701                 }
 702             }
 703
 704             Box(ty) => {
 705                 let size = self.type_size(ty);
 706                 let ptr = self.memory.allocate(size);
 707                 try!(self.memory.write_ptr(dest, ptr));
 708             }
 709
 710             Cast(kind, ref operand, dest_ty) => {
 711                 let src = try!(self.eval_operand(operand));
 712                 let src_ty = self.operand_ty(operand);
 713
 714                 use rustc::mir::repr::CastKind::*;
 715                 match kind {
 716                     Unsize => {
 717                         try!(self.move_(src, dest, src_ty));
 718                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 719                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 720
 721                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 722                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 723                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 724                                 try!(self.memory.write_usize(len_ptr, length as u64));
 725                             }
 726
 727                             _ => panic!("can't handle cast: {:?}", rvalue),
 728                         }
 729                     }
 730
 731                     Misc => {
 732                         // FIXME(tsion): Wrong for almost everything.
 733                         let size = dest_repr.size();
 734                         try!(self.memory.copy(src, dest, size));
 735                     }
 736
 737                     _ => panic!("can't handle cast: {:?}", rvalue),
 738                 }
 739             }
 740
 741             Slice { .. } => unimplemented!(),
 742             InlineAsm { .. } => unimplemented!(),
 743         }
 744
 745         Ok(())
 746     }
 747
 748     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 749         self.eval_operand_and_repr(op).map(|(p, _)| p)
 750     }
 751
 752     fn eval_operand_and_repr(&mut self, op: &mir::Operand<'tcx>)
 753         -> EvalResult<(Pointer, &'arena Repr)>
 754     {
 755         use rustc::mir::repr::Operand::*;
 756         match *op {
 757             Consume(ref lvalue) =>
 758                 Ok((try!(self.eval_lvalue(lvalue)).to_ptr(), self.lvalue_repr(lvalue))),
 759             Constant(mir::Constant { ref literal, ty, .. }) => {
 760                 use rustc::mir::repr::Literal::*;
 761                 match *literal {
 762                     Value { ref value } => Ok((
 763                         try!(self.const_to_ptr(value)),
 764                         self.type_repr(ty),
 765                     )),
 766                     Item { .. } => unimplemented!(),
 767                 }
 768             }
 769         }
 770     }
 771
 772     // TODO(tsion): Replace this inefficient hack with a wrapper like LvalueTy (e.g. LvalueRepr).
 773     fn lvalue_repr(&self, lvalue: &mir::Lvalue<'tcx>) -> &'arena Repr {
 774         use rustc::mir::tcx::LvalueTy;
 775         match self.mir().lvalue_ty(self.tcx, lvalue) {
 776             LvalueTy::Ty { ty } => self.type_repr(ty),
 777             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 778                 let field_tys = adt_def.variants[variant_index].fields.iter()
 779                     .map(|f| f.ty(self.tcx, substs));
 780                 self.repr_arena.alloc(self.make_aggregate_repr(iter::once(field_tys)))
 781             }
 782         }
 783     }
 784
 785     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
 786         use rustc::mir::repr::Lvalue::*;
 787         let ptr = match *lvalue {
 788             ReturnPointer => self.frame().return_ptr
 789                 .expect("ReturnPointer used in a function with no return value"),
 790             Arg(i) => self.frame().locals[i as usize],
 791             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
 792             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
 793
 794             Static(_def_id) => unimplemented!(),
 795
 796             Projection(ref proj) => {
 797                 let base_ptr = try!(self.eval_lvalue(&proj.base)).to_ptr();
 798                 let base_repr = self.lvalue_repr(&proj.base);
 799                 let base_ty = self.lvalue_ty(&proj.base);
 800                 use rustc::mir::repr::ProjectionElem::*;
 801                 match proj.elem {
 802                     Field(field, _) => match *base_repr {
 803                         Repr::Aggregate { discr_size: 0, ref variants, .. } => {
 804                             let fields = &variants[0];
 805                             base_ptr.offset(fields[field.index()].offset as isize)
 806                         }
 807                         _ => panic!("field access on non-product type: {:?}", base_repr),
 808                     },
 809
 810                     Downcast(..) => match *base_repr {
 811                         Repr::Aggregate { discr_size, .. } => base_ptr.offset(discr_size as isize),
 812                         _ => panic!("variant downcast on non-aggregate type: {:?}", base_repr),
 813                     },
 814
 815                     Deref => {
 816                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
 817                         let ptr = try!(self.memory.read_ptr(base_ptr));
 818                         let extra = match pointee_ty.sty {
 819                             ty::TySlice(_) | ty::TyStr => {
 820                                 let len_ptr = base_ptr.offset(self.memory.pointer_size as isize);
 821                                 let len = try!(self.memory.read_usize(len_ptr));
 822                                 LvalueExtra::Length(len)
 823                             }
 824                             ty::TyTrait(_) => unimplemented!(),
 825                             _ => LvalueExtra::None,
 826                         };
 827                         return Ok(Lvalue { ptr: ptr, extra: extra });
 828                     }
 829
 830                     Index(ref operand) => {
 831                         let elem_size = match base_ty.sty {
 832                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty),
 833                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
 834                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
 835                         };
 836                         let n_ptr = try!(self.eval_operand(operand));
 837                         let n = try!(self.memory.read_usize(n_ptr));
 838                         base_ptr.offset(n as isize * elem_size as isize)
 839                     }
 840
 841                     ConstantIndex { .. } => unimplemented!(),
 842                 }
 843             }
 844         };
 845
 846         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
 847     }
 848
 849     // TODO(tsion): Try making const_to_primval instead.
 850     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
 851         use rustc::middle::const_val::ConstVal::*;
 852         match *const_val {
 853             Float(_f) => unimplemented!(),
 854             Integral(int) => {
 855                 // TODO(tsion): Check int constant type.
 856                 let ptr = self.memory.allocate(8);
 857                 try!(self.memory.write_uint(ptr, int.to_u64_unchecked(), 8));
 858                 Ok(ptr)
 859             }
 860             Str(ref s) => {
 861                 let psize = self.memory.pointer_size;
 862                 let static_ptr = self.memory.allocate(s.len());
 863                 let ptr = self.memory.allocate(psize * 2);
 864                 try!(self.memory.write_bytes(static_ptr, s.as_bytes()));
 865                 try!(self.memory.write_ptr(ptr, static_ptr));
 866                 try!(self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64));
 867                 Ok(ptr)
 868             }
 869             ByteStr(ref bs) => {
 870                 let psize = self.memory.pointer_size;
 871                 let static_ptr = self.memory.allocate(bs.len());
 872                 let ptr = self.memory.allocate(psize);
 873                 try!(self.memory.write_bytes(static_ptr, bs));
 874                 try!(self.memory.write_ptr(ptr, static_ptr));
 875                 Ok(ptr)
 876             }
 877             Bool(b) => {
 878                 let ptr = self.memory.allocate(1);
 879                 try!(self.memory.write_bool(ptr, b));
 880                 Ok(ptr)
 881             }
 882             Char(_c)          => unimplemented!(),
 883             Struct(_node_id)  => unimplemented!(),
 884             Tuple(_node_id)   => unimplemented!(),
 885             Function(_def_id) => unimplemented!(),
 886             Array(_, _)       => unimplemented!(),
 887             Repeat(_, _)      => unimplemented!(),
 888             Dummy             => unimplemented!(),
 889         }
 890     }
 891
 892     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> ty::Ty<'tcx> {
 893         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
 894     }
 895
 896     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> ty::Ty<'tcx> {
 897         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
 898     }
 899
 900     fn monomorphize(&self, ty: ty::Ty<'tcx>) -> ty::Ty<'tcx> {
 901         let substituted = ty.subst(self.tcx, self.substs());
 902         infer::normalize_associated_type(self.tcx, &substituted)
 903     }
 904
 905     fn type_needs_drop(&self, ty: ty::Ty<'tcx>) -> bool {
 906         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
 907     }
 908
 909     fn move_(&mut self, src: Pointer, dest: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<()> {
 910         let size = self.type_size(ty);
 911         try!(self.memory.copy(src, dest, size));
 912         if self.type_needs_drop(ty) {
 913             try!(self.memory.drop_fill(src, size));
 914         }
 915         Ok(())
 916     }
 917
 918     fn type_is_sized(&self, ty: ty::Ty<'tcx>) -> bool {
 919         ty.is_sized(&self.tcx.empty_parameter_environment(), DUMMY_SP)
 920     }
 921
 922     fn type_size(&self, ty: ty::Ty<'tcx>) -> usize {
 923         self.type_repr(ty).size()
 924     }
 925
 926     fn type_repr(&self, ty: ty::Ty<'tcx>) -> &'arena Repr {
 927         let ty = self.monomorphize(ty);
 928
 929         if let Some(repr) = self.repr_cache.borrow().get(ty) {
 930             return repr;
 931         }
 932
 933         use syntax::ast::{IntTy, UintTy};
 934         let repr = match ty.sty {
 935             ty::TyBool => Repr::Primitive { size: 1 },
 936
 937             ty::TyInt(IntTy::I8)  | ty::TyUint(UintTy::U8)  => Repr::Primitive { size: 1 },
 938             ty::TyInt(IntTy::I16) | ty::TyUint(UintTy::U16) => Repr::Primitive { size: 2 },
 939             ty::TyInt(IntTy::I32) | ty::TyUint(UintTy::U32) => Repr::Primitive { size: 4 },
 940             ty::TyInt(IntTy::I64) | ty::TyUint(UintTy::U64) => Repr::Primitive { size: 8 },
 941
 942             ty::TyInt(IntTy::Is) | ty::TyUint(UintTy::Us) =>
 943                 Repr::Primitive { size: self.memory.pointer_size },
 944
 945             ty::TyTuple(ref fields) =>
 946                 self.make_aggregate_repr(iter::once(fields.iter().cloned())),
 947
 948             ty::TyEnum(adt_def, substs) | ty::TyStruct(adt_def, substs) => {
 949                 let variants = adt_def.variants.iter().map(|v| {
 950                     v.fields.iter().map(|f| f.ty(self.tcx, substs))
 951                 });
 952                 self.make_aggregate_repr(variants)
 953             }
 954
 955             ty::TyArray(elem_ty, length) => Repr::Array {
 956                 elem_size: self.type_size(elem_ty),
 957                 length: length,
 958             },
 959
 960             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 961             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 962             ty::TyBox(ty) => {
 963                 if self.type_is_sized(ty) {
 964                     Repr::Primitive { size: self.memory.pointer_size }
 965                 } else {
 966                     Repr::Primitive { size: self.memory.pointer_size * 2 }
 967                 }
 968             }
 969
 970             ty::TyFnPtr(..) => Repr::Primitive { size: self.memory.pointer_size },
 971
 972             ty::TyClosure(_, ref closure_substs) =>
 973                 self.make_aggregate_repr(iter::once(closure_substs.upvar_tys.iter().cloned())),
 974
 975             ref t => panic!("can't convert type to repr: {:?}", t),
 976         };
 977
 978         let repr_ref = self.repr_arena.alloc(repr);
 979         self.repr_cache.borrow_mut().insert(ty, repr_ref);
 980         repr_ref
 981     }
 982
 983     fn make_aggregate_repr<V>(&self, variant_fields: V) -> Repr
 984         where V: IntoIterator, V::Item: IntoIterator<Item = ty::Ty<'tcx>>
 985     {
 986         let mut variants = Vec::new();
 987         let mut max_variant_size = 0;
 988
 989         for field_tys in variant_fields {
 990             let mut fields = Vec::new();
 991             let mut size = 0;
 992
 993             for ty in field_tys {
 994                 let field_size = self.type_size(ty);
 995                 let offest = size;
 996                 size += field_size;
 997                 fields.push(FieldRepr { offset: offest, size: field_size });
 998             }
 999
1000             if size > max_variant_size { max_variant_size = size; }
1001             variants.push(fields);
1002         }
1003
1004         let discr_size = match variants.len() {
1005             n if n <= 1       => 0,
1006             n if n <= 1 << 8  => 1,
1007             n if n <= 1 << 16 => 2,
1008             n if n <= 1 << 32 => 4,
1009             _                 => 8,
1010         };
1011         Repr::Aggregate {
1012             discr_size: discr_size,
1013             size: max_variant_size + discr_size,
1014             variants: variants,
1015         }
1016     }
1017
1018     pub fn read_primval(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<PrimVal> {
1019         use syntax::ast::{IntTy, UintTy};
1020         let val = match ty.sty {
1021             ty::TyBool              => PrimVal::Bool(try!(self.memory.read_bool(ptr))),
1022             ty::TyInt(IntTy::I8)    => PrimVal::I8(try!(self.memory.read_int(ptr, 1)) as i8),
1023             ty::TyInt(IntTy::I16)   => PrimVal::I16(try!(self.memory.read_int(ptr, 2)) as i16),
1024             ty::TyInt(IntTy::I32)   => PrimVal::I32(try!(self.memory.read_int(ptr, 4)) as i32),
1025             ty::TyInt(IntTy::I64)   => PrimVal::I64(try!(self.memory.read_int(ptr, 8)) as i64),
1026             ty::TyUint(UintTy::U8)  => PrimVal::U8(try!(self.memory.read_uint(ptr, 1)) as u8),
1027             ty::TyUint(UintTy::U16) => PrimVal::U16(try!(self.memory.read_uint(ptr, 2)) as u16),
1028             ty::TyUint(UintTy::U32) => PrimVal::U32(try!(self.memory.read_uint(ptr, 4)) as u32),
1029             ty::TyUint(UintTy::U64) => PrimVal::U64(try!(self.memory.read_uint(ptr, 8)) as u64),
1030
1031             // TODO(tsion): Pick the PrimVal dynamically.
1032             ty::TyInt(IntTy::Is)   => PrimVal::I64(try!(self.memory.read_isize(ptr))),
1033             ty::TyUint(UintTy::Us) => PrimVal::U64(try!(self.memory.read_usize(ptr))),
1034
1035             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1036             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
1037                 if self.type_is_sized(ty) {
1038                     match self.memory.read_ptr(ptr) {
1039                         Ok(p) => PrimVal::AbstractPtr(p),
1040                         Err(EvalError::ReadBytesAsPointer) => {
1041                             let n = try!(self.memory.read_usize(ptr));
1042                             PrimVal::IntegerPtr(n)
1043                         }
1044                         Err(e) => return Err(e),
1045                     }
1046                 } else {
1047                     panic!("unimplemented: primitive read of fat pointer type: {:?}", ty);
1048                 }
1049             }
1050
1051             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1052         };
1053         Ok(val)
1054     }
1055
1056     fn frame(&self) -> &Frame<'a, 'tcx> {
1057         self.stack.last().expect("no call frames exist")
1058     }
1059
1060     fn frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
1061         self.stack.last_mut().expect("no call frames exist")
1062     }
1063
1064     fn mir(&self) -> &mir::Mir<'tcx> {
1065         &self.frame().mir
1066     }
1067
1068     fn substs(&self) -> &'tcx Substs<'tcx> {
1069         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
1070     }
1071
1072     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
1073         match self.tcx.map.as_local_node_id(def_id) {
1074             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
1075             None => {
1076                 let mut mir_cache = self.mir_cache.borrow_mut();
1077                 if let Some(mir) = mir_cache.get(&def_id) {
1078                     return CachedMir::Owned(mir.clone());
1079                 }
1080
1081                 use rustc::middle::cstore::CrateStore;
1082                 let cs = &self.tcx.sess.cstore;
1083                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1084                     panic!("no mir for {:?}", def_id);
1085                 });
1086                 let cached = Rc::new(mir);
1087                 mir_cache.insert(def_id, cached.clone());
1088                 CachedMir::Owned(cached)
1089             }
1090         }
1091     }
1092
1093     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1094         // Do the initial selection for the obligation. This yields the shallow result we are
1095         // looking for -- that is, what specific impl.
1096         let infcx = infer::normalizing_infer_ctxt(self.tcx, &self.tcx.tables, ProjectionMode::Any);
1097         let mut selcx = traits::SelectionContext::new(&infcx);
1098
1099         let obligation = traits::Obligation::new(
1100             traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1101             trait_ref.to_poly_trait_predicate(),
1102         );
1103         let selection = selcx.select(&obligation).unwrap().unwrap();
1104
1105         // Currently, we use a fulfillment context to completely resolve all nested obligations.
1106         // This is because they can inform the inference of the impl's type parameters.
1107         let mut fulfill_cx = traits::FulfillmentContext::new();
1108         let vtable = selection.map(|predicate| {
1109             fulfill_cx.register_predicate_obligation(&infcx, predicate);
1110         });
1111         let vtable = infer::drain_fulfillment_cx_or_panic(
1112             DUMMY_SP, &infcx, &mut fulfill_cx, &vtable
1113         );
1114
1115         vtable
1116     }
1117
1118     /// Trait method, which has to be resolved to an impl method.
1119     pub fn trait_method(&self, def_id: DefId, substs: &'tcx Substs<'tcx>)
1120         -> (DefId, &'tcx Substs<'tcx>)
1121     {
1122         let method_item = self.tcx.impl_or_trait_item(def_id);
1123         let trait_id = method_item.container().id();
1124         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1125         match self.fulfill_obligation(trait_ref) {
1126             traits::VtableImpl(vtable_impl) => {
1127                 let impl_did = vtable_impl.impl_def_id;
1128                 let mname = self.tcx.item_name(def_id);
1129                 // Create a concatenated set of substitutions which includes those from the impl
1130                 // and those from the method:
1131                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1132                 let substs = self.tcx.mk_substs(impl_substs);
1133                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1134
1135                 (mth.method.def_id, mth.substs)
1136             }
1137
1138             traits::VtableClosure(vtable_closure) =>
1139                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1140
1141             traits::VtableFnPointer(_fn_ty) => {
1142                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1143                 unimplemented!()
1144                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1145
1146                 // let method_ty = def_ty(tcx, def_id, substs);
1147                 // let fn_ptr_ty = match method_ty.sty {
1148                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1149                 //     _ => unreachable!("expected fn item type, found {}",
1150                 //                       method_ty)
1151                 // };
1152                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1153             }
1154
1155             traits::VtableObject(ref _data) => {
1156                 unimplemented!()
1157                 // Callee {
1158                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1159                 //                   tcx, data, def_id)),
1160                 //                   ty: def_ty(tcx, def_id, substs)
1161                 // }
1162             }
1163             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1164         }
1165     }
1166 }
1167
1168 fn pointee_type<'tcx>(ptr_ty: ty::Ty<'tcx>) -> Option<ty::Ty<'tcx>> {
1169     match ptr_ty.sty {
1170         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1171         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1172         ty::TyBox(ty) => {
1173             Some(ty)
1174         }
1175         _ => None,
1176     }
1177 }
1178
1179 impl Lvalue {
1180     fn to_ptr(self) -> Pointer {
1181         assert_eq!(self.extra, LvalueExtra::None);
1182         self.ptr
1183     }
1184 }
1185
1186 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1187     type Target = mir::Mir<'tcx>;
1188     fn deref(&self) -> &mir::Mir<'tcx> {
1189         match *self {
1190             CachedMir::Ref(r) => r,
1191             CachedMir::Owned(ref rc) => &rc,
1192         }
1193     }
1194 }
1195
1196 #[derive(Debug)]
1197 pub struct ImplMethod<'tcx> {
1198     pub method: Rc<ty::Method<'tcx>>,
1199     pub substs: &'tcx Substs<'tcx>,
1200     pub is_provided: bool,
1201 }
1202
1203 /// Locates the applicable definition of a method, given its name.
1204 pub fn get_impl_method<'tcx>(
1205     tcx: &TyCtxt<'tcx>,
1206     impl_def_id: DefId,
1207     substs: &'tcx Substs<'tcx>,
1208     name: ast::Name,
1209 ) -> ImplMethod<'tcx> {
1210     assert!(!substs.types.needs_infer());
1211
1212     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1213     let trait_def = tcx.lookup_trait_def(trait_def_id);
1214     let infcx = infer::normalizing_infer_ctxt(tcx, &tcx.tables, ProjectionMode::Any);
1215
1216     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1217         Some(node_item) => {
1218             ImplMethod {
1219                 method: node_item.item,
1220                 substs: traits::translate_substs(&infcx, impl_def_id, substs, node_item.node),
1221                 is_provided: node_item.node.is_from_trait(),
1222             }
1223         }
1224         None => {
1225             bug!("method {:?} not found in {:?}", name, impl_def_id);
1226         }
1227     }
1228 }
1229
1230 pub fn interpret_start_points<'tcx>(tcx: &TyCtxt<'tcx>, mir_map: &MirMap<'tcx>) {
1231     for (&id, mir) in &mir_map.map {
1232         for attr in tcx.map.attrs(id) {
1233             use syntax::attr::AttrMetaMethods;
1234             if attr.check_name("miri_run") {
1235                 let item = tcx.map.expect_item(id);
1236
1237                 println!("Interpreting: {}", item.name);
1238
1239                 let repr_arena = TypedArena::new();
1240                 let mut miri = Interpreter::new(tcx, mir_map, &repr_arena);
1241                 let return_ptr = match mir.return_ty {
1242                     ty::FnConverging(ty) => {
1243                         let size = miri.type_size(ty);
1244                         Some(miri.memory.allocate(size))
1245                     }
1246                     ty::FnDiverging => None,
1247                 };
1248                 let substs = miri.tcx.mk_substs(Substs::empty());
1249                 miri.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
1250                 if let Err(_e) = miri.run() {
1251                     // TODO(tsion): Detect whether the error was already reported or not.
1252                     // tcx.sess.err(&e.to_string());
1253                 } else if let Some(ret) = return_ptr {
1254                     miri.memory.dump(ret.alloc_id);
1255                 }
1256                 println!("");
1257             }
1258         }
1259     }
1260 }