src/interpreter.rs

   1 use rustc::infer;
   2 use rustc::middle::const_val;
   3 use rustc::hir::def_id::DefId;
   4 use rustc::mir::mir_map::MirMap;
   5 use rustc::mir::repr as mir;
   6 use rustc::traits::{self, ProjectionMode};
   7 use rustc::ty::fold::TypeFoldable;
   8 use rustc::ty::layout::{self, Layout, Size};
   9 use rustc::ty::subst::{self, Subst, Substs};
  10 use rustc::ty::{self, TyCtxt};
  11 use rustc::util::nodemap::DefIdMap;
  12 use std::cell::RefCell;
  13 use std::ops::Deref;
  14 use std::rc::Rc;
  15 use std::{iter, mem};
  16 use syntax::ast;
  17 use syntax::attr;
  18 use syntax::codemap::{self, DUMMY_SP};
  19
  20 use error::{EvalError, EvalResult};
  21 use memory::{Memory, Pointer};
  22 use primval::{self, PrimVal};
  23
  24 const TRACE_EXECUTION: bool = false;
  25
  26 struct Interpreter<'a, 'tcx: 'a> {
  27     /// The results of the type checker, from rustc.
  28     tcx: &'a TyCtxt<'tcx>,
  29
  30     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  31     mir_map: &'a MirMap<'tcx>,
  32
  33     /// A local cache from DefIds to Mir for non-crate-local items.
  34     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  35
  36     /// The virtual memory system.
  37     memory: Memory,
  38
  39     /// The virtual call stack.
  40     stack: Vec<Frame<'a, 'tcx>>,
  41
  42     /// Another stack containing the type substitutions for the current function invocation. It
  43     /// exists separately from `stack` because it must contain the `Substs` for a function while
  44     /// *creating* the `Frame` for that same function.
  45     substs_stack: Vec<&'tcx Substs<'tcx>>,
  46
  47     // TODO(tsion): Merge with `substs_stack`. Also try restructuring `Frame` to accomodate.
  48     /// A stack of the things necessary to print good strack traces:
  49     ///   * Function DefIds and Substs to print proper substituted function names.
  50     ///   * Spans pointing to specific function calls in the source.
  51     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
  52 }
  53
  54 /// A stack frame.
  55 struct Frame<'a, 'tcx: 'a> {
  56     /// The MIR for the function called on this frame.
  57     mir: CachedMir<'a, 'tcx>,
  58
  59     /// The block this frame will execute when a function call returns back to this frame.
  60     next_block: mir::BasicBlock,
  61
  62     /// A pointer for writing the return value of the current call if it's not a diverging call.
  63     return_ptr: Option<Pointer>,
  64
  65     /// The list of locals for the current function, stored in order as
  66     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  67     /// and the temporaries at `self.temp_offset`.
  68     locals: Vec<Pointer>,
  69
  70     /// The offset of the first variable in `self.locals`.
  71     var_offset: usize,
  72
  73     /// The offset of the first temporary in `self.locals`.
  74     temp_offset: usize,
  75 }
  76
  77 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  78 struct Lvalue {
  79     ptr: Pointer,
  80     extra: LvalueExtra,
  81 }
  82
  83 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  84 enum LvalueExtra {
  85     None,
  86     Length(u64),
  87     // Vtable(memory::AllocId),
  88 }
  89
  90 #[derive(Clone)]
  91 enum CachedMir<'mir, 'tcx: 'mir> {
  92     Ref(&'mir mir::Mir<'tcx>),
  93     Owned(Rc<mir::Mir<'tcx>>)
  94 }
  95
  96 /// Represents the action to be taken in the main loop as a result of executing a terminator.
  97 enum TerminatorTarget {
  98     /// Make a local jump to the given block.
  99     Block(mir::BasicBlock),
 100
 101     /// Start executing from the new current frame. (For function calls.)
 102     Call,
 103
 104     /// Stop executing the current frame and resume the previous frame.
 105     Return,
 106 }
 107
 108 impl<'a, 'tcx: 'a> Interpreter<'a, 'tcx> {
 109     fn new(tcx: &'a TyCtxt<'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 110         Interpreter {
 111             tcx: tcx,
 112             mir_map: mir_map,
 113             mir_cache: RefCell::new(DefIdMap()),
 114             memory: Memory::new(),
 115             stack: Vec::new(),
 116             substs_stack: Vec::new(),
 117             name_stack: Vec::new(),
 118         }
 119     }
 120
 121     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 122         if let Err(ref e) = r {
 123             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 124             for &(def_id, substs, span) in self.name_stack.iter().rev() {
 125                 // FIXME(tsion): Find a way to do this without this Display impl hack.
 126                 use rustc::util::ppaux;
 127                 use std::fmt;
 128                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 129                 impl<'tcx> fmt::Display for Instance<'tcx> {
 130                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 131                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 132                             |tcx| tcx.lookup_item_type(self.0).generics)
 133                     }
 134                 }
 135                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 136             }
 137             err.emit();
 138         }
 139         r
 140     }
 141
 142     fn log<F>(&self, extra_indent: usize, f: F) where F: FnOnce() {
 143         let indent = self.stack.len() + extra_indent;
 144         if !TRACE_EXECUTION { return; }
 145         for _ in 0..indent { print!("    "); }
 146         f();
 147         println!("");
 148     }
 149
 150     fn run(&mut self) -> EvalResult<()> {
 151         'outer: while !self.stack.is_empty() {
 152             let mut current_block = self.frame().next_block;
 153
 154             loop {
 155                 self.log(0, || print!("// {:?}", current_block));
 156                 let current_mir = self.mir().clone(); // Cloning a reference.
 157                 let block_data = current_mir.basic_block_data(current_block);
 158
 159                 for stmt in &block_data.statements {
 160                     self.log(0, || print!("{:?}", stmt));
 161                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 162                     let result = self.eval_assignment(lvalue, rvalue);
 163                     try!(self.maybe_report(stmt.span, result));
 164                 }
 165
 166                 let terminator = block_data.terminator();
 167                 self.log(0, || print!("{:?}", terminator.kind));
 168
 169                 let result = self.eval_terminator(terminator);
 170                 match try!(self.maybe_report(terminator.span, result)) {
 171                     TerminatorTarget::Block(block) => current_block = block,
 172                     TerminatorTarget::Return => {
 173                         self.pop_stack_frame();
 174                         self.name_stack.pop();
 175                         continue 'outer;
 176                     }
 177                     TerminatorTarget::Call => continue 'outer,
 178                 }
 179             }
 180         }
 181
 182         Ok(())
 183     }
 184
 185     fn push_stack_frame(&mut self, mir: CachedMir<'a, 'tcx>, substs: &'tcx Substs<'tcx>,
 186         return_ptr: Option<Pointer>)
 187     {
 188         self.substs_stack.push(substs);
 189
 190         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 191         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 192         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 193
 194         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 195             let size = self.type_size(ty);
 196             self.memory.allocate(size)
 197         }).collect();
 198
 199         let num_args = mir.arg_decls.len();
 200         let num_vars = mir.var_decls.len();
 201
 202         self.stack.push(Frame {
 203             mir: mir.clone(),
 204             next_block: mir::START_BLOCK,
 205             return_ptr: return_ptr,
 206             locals: locals,
 207             var_offset: num_args,
 208             temp_offset: num_args + num_vars,
 209         });
 210     }
 211
 212     fn pop_stack_frame(&mut self) {
 213         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 214         // TODO(tsion): Deallocate local variables.
 215         self.substs_stack.pop();
 216     }
 217
 218     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 219             -> EvalResult<TerminatorTarget> {
 220         use rustc::mir::repr::TerminatorKind::*;
 221         let target = match terminator.kind {
 222             Return => TerminatorTarget::Return,
 223
 224             Goto { target } => TerminatorTarget::Block(target),
 225
 226             If { ref cond, targets: (then_target, else_target) } => {
 227                 let cond_ptr = try!(self.eval_operand(cond));
 228                 let cond_val = try!(self.memory.read_bool(cond_ptr));
 229                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 230             }
 231
 232             SwitchInt { ref discr, ref values, ref targets, .. } => {
 233                 let discr_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 234                 let discr_size =
 235                     self.lvalue_layout(discr).size(&self.tcx.data_layout).bytes() as usize;
 236                 let discr_val = try!(self.memory.read_uint(discr_ptr, discr_size));
 237
 238                 // Branch to the `otherwise` case by default, if no match is found.
 239                 let mut target_block = targets[targets.len() - 1];
 240
 241                 for (index, val_const) in values.iter().enumerate() {
 242                     let ptr = try!(self.const_to_ptr(val_const));
 243                     let val = try!(self.memory.read_uint(ptr, discr_size));
 244                     if discr_val == val {
 245                         target_block = targets[index];
 246                         break;
 247                     }
 248                 }
 249
 250                 TerminatorTarget::Block(target_block)
 251             }
 252
 253             Switch { ref discr, ref targets, adt_def } => {
 254                 let adt_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 255                 let adt_layout = self.lvalue_layout(discr);
 256                 let discr_size = match *adt_layout {
 257                     Layout::General { discr, .. } => discr.size().bytes(),
 258                     _ => panic!("attmpted to switch on non-aggregate type"),
 259                 };
 260                 let discr_val = try!(self.memory.read_uint(adt_ptr, discr_size as usize));
 261
 262                 let matching = adt_def.variants.iter()
 263                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 264
 265                 match matching {
 266                     Some(i) => TerminatorTarget::Block(targets[i]),
 267                     None => return Err(EvalError::InvalidDiscriminant),
 268                 }
 269             }
 270
 271             Call { ref func, ref args, ref destination, .. } => {
 272                 let mut return_ptr = None;
 273                 if let Some((ref lv, target)) = *destination {
 274                     self.frame_mut().next_block = target;
 275                     return_ptr = Some(try!(self.eval_lvalue(lv)).to_ptr());
 276                 }
 277
 278                 let func_ty = self.operand_ty(func);
 279                 match func_ty.sty {
 280                     ty::TyFnDef(def_id, substs, fn_ty) => {
 281                         use syntax::abi::Abi;
 282                         match fn_ty.abi {
 283                             Abi::RustIntrinsic => {
 284                                 let name = self.tcx.item_name(def_id).as_str();
 285                                 match fn_ty.sig.0.output {
 286                                     ty::FnConverging(ty) => {
 287                                         let size = self.type_size(ty);
 288                                         try!(self.call_intrinsic(&name, substs, args,
 289                                             return_ptr.unwrap(), size))
 290                                     }
 291                                     ty::FnDiverging => unimplemented!(),
 292                                 }
 293                             }
 294
 295                             Abi::C =>
 296                                 try!(self.call_c_abi(def_id, args, return_ptr.unwrap())),
 297
 298                             Abi::Rust | Abi::RustCall => {
 299                                 // TODO(tsion): Adjust the first argument when calling a Fn or
 300                                 // FnMut closure via FnOnce::call_once.
 301
 302                                 // Only trait methods can have a Self parameter.
 303                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 304                                     self.trait_method(def_id, substs)
 305                                 } else {
 306                                     (def_id, substs)
 307                                 };
 308
 309                                 let mut arg_srcs = Vec::new();
 310                                 for arg in args {
 311                                     let src = try!(self.eval_operand(arg));
 312                                     let src_ty = self.operand_ty(arg);
 313                                     arg_srcs.push((src, src_ty));
 314                                 }
 315
 316                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 317                                     arg_srcs.pop();
 318                                     let last_arg = args.last().unwrap();
 319                                     let last = try!(self.eval_operand(last_arg));
 320                                     let last_ty = self.operand_ty(last_arg);
 321                                     let last_layout = self.type_layout(last_ty);
 322                                     match (&last_ty.sty, last_layout) {
 323                                         (&ty::TyTuple(ref fields),
 324                                          &Layout::Univariant { ref variant, .. }) => {
 325                                             let offsets = iter::once(0)
 326                                                 .chain(variant.offset_after_field.iter()
 327                                                     .map(|s| s.bytes()));
 328                                             for (offset, ty) in offsets.zip(fields) {
 329                                                 let src = last.offset(offset as isize);
 330                                                 arg_srcs.push((src, ty));
 331                                             }
 332                                         }
 333                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 334                                     }
 335                                 }
 336
 337                                 let mir = self.load_mir(resolved_def_id);
 338                                 self.name_stack.push((def_id, substs, terminator.span));
 339                                 self.push_stack_frame(mir, resolved_substs, return_ptr);
 340
 341                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 342                                     let dest = self.frame().locals[i];
 343                                     try!(self.move_(src, dest, src_ty));
 344                                 }
 345
 346                                 TerminatorTarget::Call
 347                             }
 348
 349                             abi => panic!("can't handle function with {:?} ABI", abi),
 350                         }
 351                     }
 352
 353                     _ => panic!("can't handle callee of type {:?}", func_ty),
 354                 }
 355             }
 356
 357             Drop { ref value, target, .. } => {
 358                 let ptr = try!(self.eval_lvalue(value)).to_ptr();
 359                 let ty = self.lvalue_ty(value);
 360                 try!(self.drop(ptr, ty));
 361                 TerminatorTarget::Block(target)
 362             }
 363
 364             Resume => unimplemented!(),
 365         };
 366
 367         Ok(target)
 368     }
 369
 370     fn drop(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<()> {
 371         if !self.type_needs_drop(ty) {
 372             self.log(1, || print!("no need to drop {:?}", ty));
 373             return Ok(());
 374         }
 375         self.log(1, || print!("need to drop {:?}", ty));
 376
 377         // TODO(tsion): Call user-defined Drop::drop impls.
 378
 379         match ty.sty {
 380             ty::TyBox(contents_ty) => {
 381                 match self.memory.read_ptr(ptr) {
 382                     Ok(contents_ptr) => {
 383                         try!(self.drop(contents_ptr, contents_ty));
 384                         self.log(1, || print!("deallocating box"));
 385                         try!(self.memory.deallocate(contents_ptr));
 386                     }
 387                     Err(EvalError::ReadBytesAsPointer) => {
 388                         let size = self.memory.pointer_size;
 389                         let possible_drop_fill = try!(self.memory.read_bytes(ptr, size));
 390                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 391                             return Ok(());
 392                         } else {
 393                             return Err(EvalError::ReadBytesAsPointer);
 394                         }
 395                     }
 396                     Err(e) => return Err(e),
 397                 }
 398             }
 399
 400             // TODO(tsion): Implement drop for other relevant types (e.g. aggregates).
 401             _ => {}
 402         }
 403
 404         // Filling drop.
 405         // FIXME(tsion): Trait objects (with no static size) probably get filled, too.
 406         let size = self.type_size(ty);
 407         try!(self.memory.drop_fill(ptr, size));
 408
 409         Ok(())
 410     }
 411
 412     fn call_intrinsic(
 413         &mut self,
 414         name: &str,
 415         substs: &'tcx Substs<'tcx>,
 416         args: &[mir::Operand<'tcx>],
 417         dest: Pointer,
 418         dest_size: usize
 419     ) -> EvalResult<TerminatorTarget> {
 420         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 421             .map(|arg| self.eval_operand(arg))
 422             .collect();
 423         let args = try!(args_res);
 424
 425         match name {
 426             "assume" => {}
 427
 428             "copy_nonoverlapping" => {
 429                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 430                 let elem_size = self.type_size(elem_ty);
 431                 let src = try!(self.memory.read_ptr(args[0]));
 432                 let dest = try!(self.memory.read_ptr(args[1]));
 433                 let count = try!(self.memory.read_isize(args[2]));
 434                 try!(self.memory.copy(src, dest, count as usize * elem_size));
 435             }
 436
 437             "forget" => {
 438                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 439                 let arg_size = self.type_size(arg_ty);
 440                 try!(self.memory.drop_fill(args[0], arg_size));
 441             }
 442
 443             "init" => try!(self.memory.write_repeat(dest, 0, dest_size)),
 444
 445             "min_align_of" => {
 446                 try!(self.memory.write_int(dest, 1, dest_size));
 447             }
 448
 449             "move_val_init" => {
 450                 let ty = *substs.types.get(subst::FnSpace, 0);
 451                 let ptr = try!(self.memory.read_ptr(args[0]));
 452                 try!(self.move_(args[1], ptr, ty));
 453             }
 454
 455             // FIXME(tsion): Handle different integer types correctly.
 456             "add_with_overflow" => {
 457                 let ty = *substs.types.get(subst::FnSpace, 0);
 458                 let size = self.type_size(ty);
 459                 let left = try!(self.memory.read_int(args[0], size));
 460                 let right = try!(self.memory.read_int(args[1], size));
 461                 let (n, overflowed) = unsafe {
 462                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 463                 };
 464                 try!(self.memory.write_int(dest, n, size));
 465                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 466             }
 467
 468             // FIXME(tsion): Handle different integer types correctly.
 469             "mul_with_overflow" => {
 470                 let ty = *substs.types.get(subst::FnSpace, 0);
 471                 let size = self.type_size(ty);
 472                 let left = try!(self.memory.read_int(args[0], size));
 473                 let right = try!(self.memory.read_int(args[1], size));
 474                 let (n, overflowed) = unsafe {
 475                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 476                 };
 477                 try!(self.memory.write_int(dest, n, size));
 478                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 479             }
 480
 481             "offset" => {
 482                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 483                 let pointee_size = self.type_size(pointee_ty) as isize;
 484                 let ptr_arg = args[0];
 485                 let offset = try!(self.memory.read_isize(args[1]));
 486
 487                 match self.memory.read_ptr(ptr_arg) {
 488                     Ok(ptr) => {
 489                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 490                         try!(self.memory.write_ptr(dest, result_ptr));
 491                     }
 492                     Err(EvalError::ReadBytesAsPointer) => {
 493                         let addr = try!(self.memory.read_isize(ptr_arg));
 494                         let result_addr = addr + offset * pointee_size as i64;
 495                         try!(self.memory.write_isize(dest, result_addr));
 496                     }
 497                     Err(e) => return Err(e),
 498                 }
 499             }
 500
 501             // FIXME(tsion): Handle different integer types correctly. Use primvals?
 502             "overflowing_sub" => {
 503                 let ty = *substs.types.get(subst::FnSpace, 0);
 504                 let size = self.type_size(ty);
 505                 let left = try!(self.memory.read_int(args[0], size));
 506                 let right = try!(self.memory.read_int(args[1], size));
 507                 let n = left.wrapping_sub(right);
 508                 try!(self.memory.write_int(dest, n, size));
 509             }
 510
 511             "size_of" => {
 512                 let ty = *substs.types.get(subst::FnSpace, 0);
 513                 let size = self.type_size(ty) as u64;
 514                 try!(self.memory.write_uint(dest, size, dest_size));
 515             }
 516
 517             "transmute" => {
 518                 let ty = *substs.types.get(subst::FnSpace, 0);
 519                 try!(self.move_(args[0], dest, ty));
 520             }
 521             "uninit" => try!(self.memory.mark_definedness(dest, dest_size, false)),
 522
 523             name => panic!("can't handle intrinsic: {}", name),
 524         }
 525
 526         // Since we pushed no stack frame, the main loop will act
 527         // as if the call just completed and it's returning to the
 528         // current frame.
 529         Ok(TerminatorTarget::Call)
 530     }
 531
 532     fn call_c_abi(
 533         &mut self,
 534         def_id: DefId,
 535         args: &[mir::Operand<'tcx>],
 536         dest: Pointer
 537     ) -> EvalResult<TerminatorTarget> {
 538         let name = self.tcx.item_name(def_id);
 539         let attrs = self.tcx.get_attrs(def_id);
 540         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 541             Some(ln) => ln.clone(),
 542             None => name.as_str(),
 543         };
 544
 545         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 546             .map(|arg| self.eval_operand(arg))
 547             .collect();
 548         let args = try!(args_res);
 549
 550         match &link_name[..] {
 551             "__rust_allocate" => {
 552                 let size = try!(self.memory.read_usize(args[0]));
 553                 let ptr = self.memory.allocate(size as usize);
 554                 try!(self.memory.write_ptr(dest, ptr));
 555             }
 556
 557             "__rust_reallocate" => {
 558                 let ptr = try!(self.memory.read_ptr(args[0]));
 559                 let size = try!(self.memory.read_usize(args[2]));
 560                 try!(self.memory.reallocate(ptr, size as usize));
 561                 try!(self.memory.write_ptr(dest, ptr));
 562             }
 563
 564             _ => panic!("can't call C ABI function: {}", link_name),
 565         }
 566
 567         // Since we pushed no stack frame, the main loop will act
 568         // as if the call just completed and it's returning to the
 569         // current frame.
 570         Ok(TerminatorTarget::Call)
 571     }
 572
 573     fn assign_fields<I: IntoIterator<Item = u64>>(
 574         &mut self,
 575         dest: Pointer,
 576         offsets: I,
 577         operands: &[mir::Operand<'tcx>],
 578     ) -> EvalResult<()> {
 579         for (offset, operand) in offsets.into_iter().zip(operands) {
 580             let src = try!(self.eval_operand(operand));
 581             let src_ty = self.operand_ty(operand);
 582             let field_dest = dest.offset(offset as isize);
 583             try!(self.move_(src, field_dest, src_ty));
 584         }
 585         Ok(())
 586     }
 587
 588     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 589         -> EvalResult<()>
 590     {
 591         let dest = try!(self.eval_lvalue(lvalue)).to_ptr();
 592         let dest_ty = self.lvalue_ty(lvalue);
 593         let dest_layout = self.lvalue_layout(lvalue);
 594
 595         use rustc::mir::repr::Rvalue::*;
 596         match *rvalue {
 597             Use(ref operand) => {
 598                 let src = try!(self.eval_operand(operand));
 599                 try!(self.move_(src, dest, dest_ty));
 600             }
 601
 602             BinaryOp(bin_op, ref left, ref right) => {
 603                 let left_ptr = try!(self.eval_operand(left));
 604                 let left_ty = self.operand_ty(left);
 605                 let left_val = try!(self.read_primval(left_ptr, left_ty));
 606
 607                 let right_ptr = try!(self.eval_operand(right));
 608                 let right_ty = self.operand_ty(right);
 609                 let right_val = try!(self.read_primval(right_ptr, right_ty));
 610
 611                 let val = try!(primval::binary_op(bin_op, left_val, right_val));
 612                 try!(self.memory.write_primval(dest, val));
 613             }
 614
 615             UnaryOp(un_op, ref operand) => {
 616                 let ptr = try!(self.eval_operand(operand));
 617                 let ty = self.operand_ty(operand);
 618                 let val = try!(self.read_primval(ptr, ty));
 619                 try!(self.memory.write_primval(dest, primval::unary_op(un_op, val)));
 620             }
 621
 622             Aggregate(ref kind, ref operands) => {
 623                 match *dest_layout {
 624                     Layout::Univariant { ref variant, .. } => {
 625                         let offsets = iter::once(0)
 626                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 627                         try!(self.assign_fields(dest, offsets, operands));
 628                     }
 629
 630                     Layout::Array { .. } => {
 631                         let elem_size = match dest_ty.sty {
 632                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 633                             _ => panic!("tried to assign {:?} aggregate to non-array type {:?}",
 634                                         kind, dest_ty),
 635                         };
 636                         let offsets = (0..).map(|i| i * elem_size);
 637                         try!(self.assign_fields(dest, offsets, operands));
 638                     }
 639
 640                     Layout::General { discr, ref variants, .. } => {
 641                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 642                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 643                             let discr_size = discr.size().bytes() as usize;
 644                             try!(self.memory.write_uint(dest, discr_val, discr_size));
 645
 646                             let offsets = variants[variant].offset_after_field.iter()
 647                                 .map(|s| s.bytes());
 648                             try!(self.assign_fields(dest, offsets, operands));
 649                         } else {
 650                             panic!("tried to assign {:?} aggregate to Layout::General dest", kind);
 651                         }
 652                     }
 653
 654                     _ => panic!("can't handle destination layout {:?} when assigning {:?}",
 655                                 dest_layout, kind),
 656                 }
 657             }
 658
 659             Repeat(ref operand, _) => {
 660                 let (elem_size, length) = match dest_ty.sty {
 661                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
 662                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
 663                 };
 664
 665                 let src = try!(self.eval_operand(operand));
 666                 for i in 0..length {
 667                     let elem_dest = dest.offset((i * elem_size) as isize);
 668                     try!(self.memory.copy(src, elem_dest, elem_size));
 669                 }
 670             }
 671
 672             Len(ref lvalue) => {
 673                 let src = try!(self.eval_lvalue(lvalue));
 674                 let ty = self.lvalue_ty(lvalue);
 675                 let len = match ty.sty {
 676                     ty::TyArray(_, n) => n as u64,
 677                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 678                         n
 679                     } else {
 680                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 681                     },
 682                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 683                 };
 684                 try!(self.memory.write_usize(dest, len));
 685             }
 686
 687             Ref(_, _, ref lvalue) => {
 688                 let lv = try!(self.eval_lvalue(lvalue));
 689                 try!(self.memory.write_ptr(dest, lv.ptr));
 690                 match lv.extra {
 691                     LvalueExtra::None => {},
 692                     LvalueExtra::Length(len) => {
 693                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 694                         try!(self.memory.write_usize(len_ptr, len));
 695                     }
 696                 }
 697             }
 698
 699             Box(ty) => {
 700                 let size = self.type_size(ty);
 701                 let ptr = self.memory.allocate(size);
 702                 try!(self.memory.write_ptr(dest, ptr));
 703             }
 704
 705             Cast(kind, ref operand, dest_ty) => {
 706                 let src = try!(self.eval_operand(operand));
 707                 let src_ty = self.operand_ty(operand);
 708
 709                 use rustc::mir::repr::CastKind::*;
 710                 match kind {
 711                     Unsize => {
 712                         try!(self.move_(src, dest, src_ty));
 713                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 714                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 715
 716                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 717                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 718                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 719                                 try!(self.memory.write_usize(len_ptr, length as u64));
 720                             }
 721
 722                             _ => panic!("can't handle cast: {:?}", rvalue),
 723                         }
 724                     }
 725
 726                     Misc => {
 727                         // FIXME(tsion): Wrong for almost everything.
 728                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
 729                         try!(self.memory.copy(src, dest, size));
 730                     }
 731
 732                     _ => panic!("can't handle cast: {:?}", rvalue),
 733                 }
 734             }
 735
 736             Slice { .. } => unimplemented!(),
 737             InlineAsm { .. } => unimplemented!(),
 738         }
 739
 740         Ok(())
 741     }
 742
 743     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 744         self.eval_operand_and_layout(op).map(|(p, _)| p)
 745     }
 746
 747     fn eval_operand_and_layout(&mut self, op: &mir::Operand<'tcx>)
 748         -> EvalResult<(Pointer, &'tcx Layout)>
 749     {
 750         use rustc::mir::repr::Operand::*;
 751         match *op {
 752             Consume(ref lvalue) =>
 753                 Ok((try!(self.eval_lvalue(lvalue)).to_ptr(), self.lvalue_layout(lvalue))),
 754             Constant(mir::Constant { ref literal, ty, .. }) => {
 755                 use rustc::mir::repr::Literal::*;
 756                 match *literal {
 757                     Value { ref value } => Ok((
 758                         try!(self.const_to_ptr(value)),
 759                         self.type_layout(ty),
 760                     )),
 761                     Item { .. } => unimplemented!(),
 762                 }
 763             }
 764         }
 765     }
 766
 767     // TODO(tsion): Replace this inefficient hack with a wrapper like LvalueTy (e.g. LvalueLayout).
 768     fn lvalue_layout(&self, lvalue: &mir::Lvalue<'tcx>) -> &'tcx Layout {
 769         use rustc::mir::tcx::LvalueTy;
 770         match self.mir().lvalue_ty(self.tcx, lvalue) {
 771             LvalueTy::Ty { ty } => self.type_layout(ty),
 772             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 773                 let field_tys = adt_def.variants[variant_index].fields.iter()
 774                     .map(|f| f.ty(self.tcx, substs));
 775
 776                 // FIXME(tsion): Handle LvalueTy::Downcast better somehow...
 777                 unimplemented!();
 778                 // self.repr_arena.alloc(self.make_aggregate_layout(iter::once(field_tys)))
 779             }
 780         }
 781     }
 782
 783     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
 784         use rustc::mir::repr::Lvalue::*;
 785         let ptr = match *lvalue {
 786             ReturnPointer => self.frame().return_ptr
 787                 .expect("ReturnPointer used in a function with no return value"),
 788             Arg(i) => self.frame().locals[i as usize],
 789             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
 790             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
 791
 792             Static(_def_id) => unimplemented!(),
 793
 794             Projection(ref proj) => {
 795                 let base_ptr = try!(self.eval_lvalue(&proj.base)).to_ptr();
 796                 let base_layout = self.lvalue_layout(&proj.base);
 797                 let base_ty = self.lvalue_ty(&proj.base);
 798
 799                 use rustc::mir::repr::ProjectionElem::*;
 800                 match proj.elem {
 801                     Field(field, _) => match *base_layout {
 802                         Layout::Univariant { ref variant, .. } => {
 803                             let offset = variant.field_offset(field.index()).bytes();
 804                             base_ptr.offset(offset as isize)
 805                         }
 806                         _ => panic!("field access on non-product type: {:?}", base_layout),
 807                     },
 808
 809                     Downcast(..) => match *base_layout {
 810                         Layout::General { discr, .. } =>
 811                             base_ptr.offset(discr.size().bytes() as isize),
 812                         _ => panic!("variant downcast on non-aggregate type: {:?}", base_layout),
 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_layout(ty).size(&self.tcx.data_layout).bytes() as usize
 924     }
 925
 926     fn type_layout(&self, ty: ty::Ty<'tcx>) -> &'tcx Layout {
 927         // TODO(tsion): Is this inefficient? Needs investigation.
 928         let ty = self.monomorphize(ty);
 929
 930         let infcx = infer::normalizing_infer_ctxt(self.tcx, &self.tcx.tables, ProjectionMode::Any);
 931
 932         // TODO(tsion): Report this error properly.
 933         ty.layout(&infcx).unwrap()
 934     }
 935
 936     pub fn read_primval(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<PrimVal> {
 937         use syntax::ast::{IntTy, UintTy};
 938         let val = match ty.sty {
 939             ty::TyBool              => PrimVal::Bool(try!(self.memory.read_bool(ptr))),
 940             ty::TyInt(IntTy::I8)    => PrimVal::I8(try!(self.memory.read_int(ptr, 1)) as i8),
 941             ty::TyInt(IntTy::I16)   => PrimVal::I16(try!(self.memory.read_int(ptr, 2)) as i16),
 942             ty::TyInt(IntTy::I32)   => PrimVal::I32(try!(self.memory.read_int(ptr, 4)) as i32),
 943             ty::TyInt(IntTy::I64)   => PrimVal::I64(try!(self.memory.read_int(ptr, 8)) as i64),
 944             ty::TyUint(UintTy::U8)  => PrimVal::U8(try!(self.memory.read_uint(ptr, 1)) as u8),
 945             ty::TyUint(UintTy::U16) => PrimVal::U16(try!(self.memory.read_uint(ptr, 2)) as u16),
 946             ty::TyUint(UintTy::U32) => PrimVal::U32(try!(self.memory.read_uint(ptr, 4)) as u32),
 947             ty::TyUint(UintTy::U64) => PrimVal::U64(try!(self.memory.read_uint(ptr, 8)) as u64),
 948
 949             // TODO(tsion): Pick the PrimVal dynamically.
 950             ty::TyInt(IntTy::Is)   => PrimVal::I64(try!(self.memory.read_isize(ptr))),
 951             ty::TyUint(UintTy::Us) => PrimVal::U64(try!(self.memory.read_usize(ptr))),
 952
 953             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 954             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
 955                 if self.type_is_sized(ty) {
 956                     match self.memory.read_ptr(ptr) {
 957                         Ok(p) => PrimVal::AbstractPtr(p),
 958                         Err(EvalError::ReadBytesAsPointer) => {
 959                             let n = try!(self.memory.read_usize(ptr));
 960                             PrimVal::IntegerPtr(n)
 961                         }
 962                         Err(e) => return Err(e),
 963                     }
 964                 } else {
 965                     panic!("unimplemented: primitive read of fat pointer type: {:?}", ty);
 966                 }
 967             }
 968
 969             _ => panic!("primitive read of non-primitive type: {:?}", ty),
 970         };
 971         Ok(val)
 972     }
 973
 974     fn frame(&self) -> &Frame<'a, 'tcx> {
 975         self.stack.last().expect("no call frames exist")
 976     }
 977
 978     fn frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
 979         self.stack.last_mut().expect("no call frames exist")
 980     }
 981
 982     fn mir(&self) -> &mir::Mir<'tcx> {
 983         &self.frame().mir
 984     }
 985
 986     fn substs(&self) -> &'tcx Substs<'tcx> {
 987         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
 988     }
 989
 990     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
 991         match self.tcx.map.as_local_node_id(def_id) {
 992             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
 993             None => {
 994                 let mut mir_cache = self.mir_cache.borrow_mut();
 995                 if let Some(mir) = mir_cache.get(&def_id) {
 996                     return CachedMir::Owned(mir.clone());
 997                 }
 998
 999                 use rustc::middle::cstore::CrateStore;
1000                 let cs = &self.tcx.sess.cstore;
1001                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1002                     panic!("no mir for {:?}", def_id);
1003                 });
1004                 let cached = Rc::new(mir);
1005                 mir_cache.insert(def_id, cached.clone());
1006                 CachedMir::Owned(cached)
1007             }
1008         }
1009     }
1010
1011     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1012         // Do the initial selection for the obligation. This yields the shallow result we are
1013         // looking for -- that is, what specific impl.
1014         let infcx = infer::normalizing_infer_ctxt(self.tcx, &self.tcx.tables, ProjectionMode::Any);
1015         let mut selcx = traits::SelectionContext::new(&infcx);
1016
1017         let obligation = traits::Obligation::new(
1018             traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1019             trait_ref.to_poly_trait_predicate(),
1020         );
1021         let selection = selcx.select(&obligation).unwrap().unwrap();
1022
1023         // Currently, we use a fulfillment context to completely resolve all nested obligations.
1024         // This is because they can inform the inference of the impl's type parameters.
1025         let mut fulfill_cx = traits::FulfillmentContext::new();
1026         let vtable = selection.map(|predicate| {
1027             fulfill_cx.register_predicate_obligation(&infcx, predicate);
1028         });
1029         let vtable = infer::drain_fulfillment_cx_or_panic(
1030             DUMMY_SP, &infcx, &mut fulfill_cx, &vtable
1031         );
1032
1033         vtable
1034     }
1035
1036     /// Trait method, which has to be resolved to an impl method.
1037     pub fn trait_method(&self, def_id: DefId, substs: &'tcx Substs<'tcx>)
1038         -> (DefId, &'tcx Substs<'tcx>)
1039     {
1040         let method_item = self.tcx.impl_or_trait_item(def_id);
1041         let trait_id = method_item.container().id();
1042         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1043         match self.fulfill_obligation(trait_ref) {
1044             traits::VtableImpl(vtable_impl) => {
1045                 let impl_did = vtable_impl.impl_def_id;
1046                 let mname = self.tcx.item_name(def_id);
1047                 // Create a concatenated set of substitutions which includes those from the impl
1048                 // and those from the method:
1049                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1050                 let substs = self.tcx.mk_substs(impl_substs);
1051                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1052
1053                 (mth.method.def_id, mth.substs)
1054             }
1055
1056             traits::VtableClosure(vtable_closure) =>
1057                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1058
1059             traits::VtableFnPointer(_fn_ty) => {
1060                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1061                 unimplemented!()
1062                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1063
1064                 // let method_ty = def_ty(tcx, def_id, substs);
1065                 // let fn_ptr_ty = match method_ty.sty {
1066                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1067                 //     _ => unreachable!("expected fn item type, found {}",
1068                 //                       method_ty)
1069                 // };
1070                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1071             }
1072
1073             traits::VtableObject(ref _data) => {
1074                 unimplemented!()
1075                 // Callee {
1076                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1077                 //                   tcx, data, def_id)),
1078                 //                   ty: def_ty(tcx, def_id, substs)
1079                 // }
1080             }
1081             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1082         }
1083     }
1084 }
1085
1086 fn pointee_type<'tcx>(ptr_ty: ty::Ty<'tcx>) -> Option<ty::Ty<'tcx>> {
1087     match ptr_ty.sty {
1088         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1089         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1090         ty::TyBox(ty) => {
1091             Some(ty)
1092         }
1093         _ => None,
1094     }
1095 }
1096
1097 impl Lvalue {
1098     fn to_ptr(self) -> Pointer {
1099         assert_eq!(self.extra, LvalueExtra::None);
1100         self.ptr
1101     }
1102 }
1103
1104 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1105     type Target = mir::Mir<'tcx>;
1106     fn deref(&self) -> &mir::Mir<'tcx> {
1107         match *self {
1108             CachedMir::Ref(r) => r,
1109             CachedMir::Owned(ref rc) => &rc,
1110         }
1111     }
1112 }
1113
1114 #[derive(Debug)]
1115 pub struct ImplMethod<'tcx> {
1116     pub method: Rc<ty::Method<'tcx>>,
1117     pub substs: &'tcx Substs<'tcx>,
1118     pub is_provided: bool,
1119 }
1120
1121 /// Locates the applicable definition of a method, given its name.
1122 pub fn get_impl_method<'tcx>(
1123     tcx: &TyCtxt<'tcx>,
1124     impl_def_id: DefId,
1125     substs: &'tcx Substs<'tcx>,
1126     name: ast::Name,
1127 ) -> ImplMethod<'tcx> {
1128     assert!(!substs.types.needs_infer());
1129
1130     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1131     let trait_def = tcx.lookup_trait_def(trait_def_id);
1132     let infcx = infer::normalizing_infer_ctxt(tcx, &tcx.tables, ProjectionMode::Any);
1133
1134     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1135         Some(node_item) => {
1136             ImplMethod {
1137                 method: node_item.item,
1138                 substs: traits::translate_substs(&infcx, impl_def_id, substs, node_item.node),
1139                 is_provided: node_item.node.is_from_trait(),
1140             }
1141         }
1142         None => {
1143             bug!("method {:?} not found in {:?}", name, impl_def_id);
1144         }
1145     }
1146 }
1147
1148 pub fn interpret_start_points<'tcx>(tcx: &TyCtxt<'tcx>, mir_map: &MirMap<'tcx>) {
1149     for (&id, mir) in &mir_map.map {
1150         for attr in tcx.map.attrs(id) {
1151             use syntax::attr::AttrMetaMethods;
1152             if attr.check_name("miri_run") {
1153                 let item = tcx.map.expect_item(id);
1154
1155                 println!("Interpreting: {}", item.name);
1156
1157                 let mut miri = Interpreter::new(tcx, mir_map);
1158                 let return_ptr = match mir.return_ty {
1159                     ty::FnConverging(ty) => {
1160                         let size = miri.type_size(ty);
1161                         Some(miri.memory.allocate(size))
1162                     }
1163                     ty::FnDiverging => None,
1164                 };
1165                 let substs = miri.tcx.mk_substs(Substs::empty());
1166                 miri.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
1167                 if let Err(_e) = miri.run() {
1168                     // TODO(tsion): Detect whether the error was already reported or not.
1169                     // tcx.sess.err(&e.to_string());
1170                 } else if let Some(ret) = return_ptr {
1171                     miri.memory.dump(ret.alloc_id);
1172                 }
1173                 println!("");
1174             }
1175         }
1176     }
1177 }
1178
1179 // TODO(tsion): Upstream these methods into rustc::ty::layout.
1180
1181 trait IntegerExt {
1182     fn size(self) -> Size;
1183 }
1184
1185 impl IntegerExt for layout::Integer {
1186     fn size(self) -> Size {
1187         use rustc::ty::layout::Integer::*;
1188         match self {
1189             I1 | I8 => Size::from_bits(8),
1190             I16 => Size::from_bits(16),
1191             I32 => Size::from_bits(32),
1192             I64 => Size::from_bits(64),
1193         }
1194     }
1195 }
1196
1197 trait StructExt {
1198     fn field_offset(&self, index: usize) -> Size;
1199 }
1200
1201 impl StructExt for layout::Struct {
1202     fn field_offset(&self, index: usize) -> Size {
1203         if index == 0 {
1204             Size::from_bytes(0)
1205         } else {
1206             self.offset_after_field[index - 1]
1207         }
1208     }
1209 }