src/librustc_mir/hair/cx/expr.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use hair::*;
  12 use rustc_data_structures::fnv::FnvHashMap;
  13 use rustc_const_eval::ConstInt;
  14 use hair::cx::Cx;
  15 use hair::cx::block;
  16 use hair::cx::to_ref::ToRef;
  17 use rustc::front::map;
  18 use rustc::middle::def::Def;
  19 use rustc::middle::const_eval::{self, ConstVal};
  20 use rustc::middle::region::CodeExtent;
  21 use rustc::middle::pat_util;
  22 use rustc::middle::ty::{self, VariantDef, Ty};
  23 use rustc::mir::repr::*;
  24 use rustc_front::hir;
  25 use rustc_front::util as hir_util;
  26 use syntax::ptr::P;
  27
  28 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
  29     type Output = Expr<'tcx>;
  30
  31     fn make_mirror<'a>(self, cx: &mut Cx<'a, 'tcx>) -> Expr<'tcx> {
  32         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
  33
  34         let expr_ty = cx.tcx.expr_ty(self); // note: no adjustments (yet)!
  35         let temp_lifetime = cx.tcx.region_maps.temporary_scope(self.id);
  36         let expr_extent = cx.tcx.region_maps.node_extent(self.id);
  37
  38         let kind = match self.node {
  39             // Here comes the interesting stuff:
  40             hir::ExprMethodCall(_, _, ref args) => {
  41                 // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
  42                 let expr = method_callee(cx, self, ty::MethodCall::expr(self.id));
  43                 let args = args.iter()
  44                                .map(|e| e.to_ref())
  45                                .collect();
  46                 ExprKind::Call {
  47                     ty: expr.ty,
  48                     fun: expr.to_ref(),
  49                     args: args,
  50                 }
  51             }
  52
  53             hir::ExprCall(ref fun, ref args) => {
  54                 if cx.tcx.is_method_call(self.id) {
  55                     // The callee is something implementing Fn, FnMut, or FnOnce.
  56                     // Find the actual method implementation being called and
  57                     // build the appropriate UFCS call expression with the
  58                     // callee-object as self parameter.
  59
  60                     // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
  61
  62                     let method = method_callee(cx, self, ty::MethodCall::expr(self.id));
  63
  64                     let sig = match method.ty.sty {
  65                         ty::TyFnDef(_, _, fn_ty) => &fn_ty.sig,
  66                         _ => cx.tcx.sess.span_bug(self.span, "type of method is not an fn")
  67                     };
  68
  69                     let sig = cx.tcx.no_late_bound_regions(sig).unwrap_or_else(|| {
  70                         cx.tcx.sess.span_bug(self.span, "method call has late-bound regions")
  71                     });
  72
  73                     assert_eq!(sig.inputs.len(), 2);
  74
  75                     let tupled_args = Expr {
  76                         ty: sig.inputs[1],
  77                         temp_lifetime: temp_lifetime,
  78                         span: self.span,
  79                         kind: ExprKind::Tuple {
  80                             fields: args.iter().map(ToRef::to_ref).collect()
  81                         }
  82                     };
  83
  84                     ExprKind::Call {
  85                         ty: method.ty,
  86                         fun: method.to_ref(),
  87                         args: vec![fun.to_ref(), tupled_args.to_ref()]
  88                     }
  89                 } else {
  90                     let adt_data = if let hir::ExprPath(..) = fun.node {
  91                         // Tuple-like ADTs are represented as ExprCall. We convert them here.
  92                         expr_ty.ty_adt_def().and_then(|adt_def|{
  93                             match cx.tcx.def_map.borrow()[&fun.id].full_def() {
  94                                 Def::Variant(_, variant_id) => {
  95                                     Some((adt_def, adt_def.variant_index_with_id(variant_id)))
  96                                 },
  97                                 Def::Struct(..) => {
  98                                     Some((adt_def, 0))
  99                                 },
 100                                 _ => None
 101                             }
 102                         })
 103                     } else { None };
 104                     if let Some((adt_def, index)) = adt_data {
 105                         let substs = cx.tcx.mk_substs(cx.tcx.node_id_item_substs(fun.id).substs);
 106                         let field_refs = args.iter().enumerate().map(|(idx, e)| FieldExprRef {
 107                             name: Field::new(idx),
 108                             expr: e.to_ref()
 109                         }).collect();
 110                         ExprKind::Adt {
 111                             adt_def: adt_def,
 112                             substs: substs,
 113                             variant_index: index,
 114                             fields: field_refs,
 115                             base: None
 116                         }
 117                     } else {
 118                         ExprKind::Call {
 119                             ty: cx.tcx.node_id_to_type(fun.id),
 120                             fun: fun.to_ref(),
 121                             args: args.to_ref(),
 122                         }
 123                     }
 124                 }
 125             }
 126
 127             hir::ExprAddrOf(mutbl, ref expr) => {
 128                 let region = match expr_ty.sty {
 129                     ty::TyRef(r, _) => r,
 130                     _ => cx.tcx.sess.span_bug(expr.span, "type of & not region"),
 131                 };
 132                 ExprKind::Borrow {
 133                     region: *region,
 134                     borrow_kind: to_borrow_kind(mutbl),
 135                     arg: expr.to_ref(),
 136                 }
 137             }
 138
 139             hir::ExprBlock(ref blk) => {
 140                 ExprKind::Block { body: &blk }
 141             }
 142
 143             hir::ExprAssign(ref lhs, ref rhs) => {
 144                 ExprKind::Assign {
 145                     lhs: lhs.to_ref(),
 146                     rhs: rhs.to_ref(),
 147                 }
 148             }
 149
 150             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
 151                 if cx.tcx.is_method_call(self.id) {
 152                     let pass_args = if hir_util::is_by_value_binop(op.node) {
 153                         PassArgs::ByValue
 154                     } else {
 155                         PassArgs::ByRef
 156                     };
 157                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 158                                         pass_args, lhs.to_ref(), vec![rhs])
 159                 } else {
 160                     ExprKind::AssignOp {
 161                         op: bin_op(op.node),
 162                         lhs: lhs.to_ref(),
 163                         rhs: rhs.to_ref(),
 164                     }
 165                 }
 166             }
 167
 168             hir::ExprLit(..) => ExprKind::Literal {
 169                 literal: cx.const_eval_literal(self)
 170             },
 171
 172             hir::ExprBinary(op, ref lhs, ref rhs) => {
 173                 if cx.tcx.is_method_call(self.id) {
 174                     let pass_args = if hir_util::is_by_value_binop(op.node) {
 175                         PassArgs::ByValue
 176                     } else {
 177                         PassArgs::ByRef
 178                     };
 179                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 180                                         pass_args, lhs.to_ref(), vec![rhs])
 181                 } else {
 182                     // FIXME overflow
 183                     match op.node {
 184                         hir::BinOp_::BiAnd => {
 185                             ExprKind::LogicalOp {
 186                                 op: LogicalOp::And,
 187                                 lhs: lhs.to_ref(),
 188                                 rhs: rhs.to_ref(),
 189                             }
 190                         }
 191                         hir::BinOp_::BiOr => {
 192                             ExprKind::LogicalOp {
 193                                 op: LogicalOp::Or,
 194                                 lhs: lhs.to_ref(),
 195                                 rhs: rhs.to_ref(),
 196                             }
 197                         }
 198                         _ => {
 199                             let op = bin_op(op.node);
 200                             ExprKind::Binary {
 201                                 op: op,
 202                                 lhs: lhs.to_ref(),
 203                                 rhs: rhs.to_ref(),
 204                             }
 205                         }
 206                     }
 207                 }
 208             }
 209
 210             hir::ExprIndex(ref lhs, ref index) => {
 211                 if cx.tcx.is_method_call(self.id) {
 212                     overloaded_lvalue(cx, self, ty::MethodCall::expr(self.id),
 213                                       PassArgs::ByValue, lhs.to_ref(), vec![index])
 214                 } else {
 215                     ExprKind::Index {
 216                         lhs: lhs.to_ref(),
 217                         index: index.to_ref(),
 218                     }
 219                 }
 220             }
 221
 222             hir::ExprUnary(hir::UnOp::UnDeref, ref arg) => {
 223                 if cx.tcx.is_method_call(self.id) {
 224                     overloaded_lvalue(cx, self, ty::MethodCall::expr(self.id),
 225                                       PassArgs::ByValue, arg.to_ref(), vec![])
 226                 } else {
 227                     ExprKind::Deref { arg: arg.to_ref() }
 228                 }
 229             }
 230
 231             hir::ExprUnary(hir::UnOp::UnNot, ref arg) => {
 232                 if cx.tcx.is_method_call(self.id) {
 233                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 234                                         PassArgs::ByValue, arg.to_ref(), vec![])
 235                 } else {
 236                     ExprKind::Unary {
 237                         op: UnOp::Not,
 238                         arg: arg.to_ref(),
 239                     }
 240                 }
 241             }
 242
 243             hir::ExprUnary(hir::UnOp::UnNeg, ref arg) => {
 244                 if cx.tcx.is_method_call(self.id) {
 245                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 246                                         PassArgs::ByValue, arg.to_ref(), vec![])
 247                 } else {
 248                     // FIXME runtime-overflow
 249                     if let hir::ExprLit(_) = arg.node {
 250                         ExprKind::Literal {
 251                             literal: cx.const_eval_literal(self),
 252                         }
 253                     } else {
 254                         ExprKind::Unary {
 255                             op: UnOp::Neg,
 256                             arg: arg.to_ref(),
 257                         }
 258                     }
 259                 }
 260             }
 261
 262             hir::ExprStruct(_, ref fields, ref base) => {
 263                 match expr_ty.sty {
 264                     ty::TyStruct(adt, substs) => {
 265                         let field_refs = field_refs(&adt.variants[0], fields);
 266                         ExprKind::Adt {
 267                             adt_def: adt,
 268                             variant_index: 0,
 269                             substs: substs,
 270                             fields: field_refs,
 271                             base: base.as_ref().map(|base| {
 272                                 FruInfo {
 273                                     base: base.to_ref(),
 274                                     field_types: cx.tcx.tables
 275                                         .borrow()
 276                                         .fru_field_types[&self.id]
 277                                         .clone()
 278                                 }
 279                             })
 280                         }
 281                     }
 282                     ty::TyEnum(adt, substs) => {
 283                         match cx.tcx.def_map.borrow()[&self.id].full_def() {
 284                             Def::Variant(enum_id, variant_id) => {
 285                                 debug_assert!(adt.did == enum_id);
 286                                 assert!(base.is_none());
 287
 288                                 let index = adt.variant_index_with_id(variant_id);
 289                                 let field_refs = field_refs(&adt.variants[index], fields);
 290                                 ExprKind::Adt {
 291                                     adt_def: adt,
 292                                     variant_index: index,
 293                                     substs: substs,
 294                                     fields: field_refs,
 295                                     base: None
 296                                 }
 297                             }
 298                             ref def => {
 299                                 cx.tcx.sess.span_bug(
 300                                     self.span,
 301                                     &format!("unexpected def: {:?}", def));
 302                             }
 303                         }
 304                     }
 305                     _ => {
 306                         cx.tcx.sess.span_bug(
 307                             self.span,
 308                             &format!("unexpected type for struct literal: {:?}", expr_ty));
 309                     }
 310                 }
 311             }
 312
 313             hir::ExprClosure(..) => {
 314                 let closure_ty = cx.tcx.expr_ty(self);
 315                 let (def_id, substs) = match closure_ty.sty {
 316                     ty::TyClosure(def_id, ref substs) => (def_id, substs),
 317                     _ => {
 318                         cx.tcx.sess.span_bug(self.span,
 319                                              &format!("closure expr w/o closure type: {:?}",
 320                                                       closure_ty));
 321                     }
 322                 };
 323                 let upvars = cx.tcx.with_freevars(self.id, |freevars| {
 324                     freevars.iter()
 325                             .enumerate()
 326                             .map(|(i, fv)| capture_freevar(cx, self, fv, substs.upvar_tys[i]))
 327                             .collect()
 328                 });
 329                 ExprKind::Closure {
 330                     closure_id: def_id,
 331                     substs: &substs,
 332                     upvars: upvars,
 333                 }
 334             }
 335
 336             hir::ExprPath(..) => {
 337                 convert_path_expr(cx, self)
 338             }
 339
 340             hir::ExprInlineAsm(ref asm, ref outputs, ref inputs) => {
 341                 ExprKind::InlineAsm {
 342                     asm: asm,
 343                     outputs: outputs.to_ref(),
 344                     inputs: inputs.to_ref()
 345                 }
 346             }
 347
 348             // Now comes the rote stuff:
 349
 350             hir::ExprRepeat(ref v, ref c) => ExprKind::Repeat {
 351                 value: v.to_ref(),
 352                 count: TypedConstVal {
 353                     ty: cx.tcx.expr_ty(c),
 354                     span: c.span,
 355                     value: match const_eval::eval_const_expr(cx.tcx, c) {
 356                         ConstVal::Integral(ConstInt::Usize(u)) => u,
 357                         other => panic!("constant evaluation of repeat count yielded {:?}", other),
 358                     },
 359                 }
 360             },
 361             hir::ExprRet(ref v) =>
 362                 ExprKind::Return { value: v.to_ref() },
 363             hir::ExprBreak(label) =>
 364                 ExprKind::Break { label: label.map(|_| loop_label(cx, self)) },
 365             hir::ExprAgain(label) =>
 366                 ExprKind::Continue { label: label.map(|_| loop_label(cx, self)) },
 367             hir::ExprMatch(ref discr, ref arms, _) =>
 368                 ExprKind::Match { discriminant: discr.to_ref(),
 369                                   arms: arms.iter().map(|a| convert_arm(cx, a)).collect() },
 370             hir::ExprIf(ref cond, ref then, ref otherwise) =>
 371                 ExprKind::If { condition: cond.to_ref(),
 372                                then: block::to_expr_ref(cx, then),
 373                                otherwise: otherwise.to_ref() },
 374             hir::ExprWhile(ref cond, ref body, _) =>
 375                 ExprKind::Loop { condition: Some(cond.to_ref()),
 376                                  body: block::to_expr_ref(cx, body) },
 377             hir::ExprLoop(ref body, _) =>
 378                 ExprKind::Loop { condition: None,
 379                                  body: block::to_expr_ref(cx, body) },
 380             hir::ExprField(ref source, name) => {
 381                 let index = match cx.tcx.expr_ty_adjusted(source).sty {
 382                     ty::TyStruct(adt_def, _) =>
 383                         adt_def.variants[0].index_of_field_named(name.node),
 384                     ref ty =>
 385                         cx.tcx.sess.span_bug(
 386                             self.span,
 387                             &format!("field of non-struct: {:?}", ty)),
 388                 };
 389                 let index = index.unwrap_or_else(|| {
 390                     cx.tcx.sess.span_bug(
 391                         self.span,
 392                         &format!("no index found for field `{}`", name.node));
 393                 });
 394                 ExprKind::Field { lhs: source.to_ref(), name: Field::new(index) }
 395             }
 396             hir::ExprTupField(ref source, index) =>
 397                 ExprKind::Field { lhs: source.to_ref(),
 398                                   name: Field::new(index.node as usize) },
 399             hir::ExprCast(ref source, _) =>
 400                 ExprKind::Cast { source: source.to_ref() },
 401             hir::ExprType(ref source, _) =>
 402                 return source.make_mirror(cx),
 403             hir::ExprBox(ref value) =>
 404                 ExprKind::Box {
 405                     value: value.to_ref(),
 406                     value_extents: cx.tcx.region_maps.node_extent(value.id)
 407                 },
 408             hir::ExprVec(ref fields) =>
 409                 ExprKind::Vec { fields: fields.to_ref() },
 410             hir::ExprTup(ref fields) =>
 411                 ExprKind::Tuple { fields: fields.to_ref() },
 412         };
 413
 414         let mut expr = Expr {
 415             temp_lifetime: temp_lifetime,
 416             ty: expr_ty,
 417             span: self.span,
 418             kind: kind,
 419         };
 420
 421         debug!("make_mirror: unadjusted-expr={:?} applying adjustments={:?}",
 422                expr, cx.tcx.tables.borrow().adjustments.get(&self.id));
 423
 424         // Now apply adjustments, if any.
 425         match cx.tcx.tables.borrow().adjustments.get(&self.id) {
 426             None => {}
 427             Some(&ty::adjustment::AdjustReifyFnPointer) => {
 428                 let adjusted_ty = cx.tcx.expr_ty_adjusted(self);
 429                 expr = Expr {
 430                     temp_lifetime: temp_lifetime,
 431                     ty: adjusted_ty,
 432                     span: self.span,
 433                     kind: ExprKind::ReifyFnPointer { source: expr.to_ref() },
 434                 };
 435             }
 436             Some(&ty::adjustment::AdjustUnsafeFnPointer) => {
 437                 let adjusted_ty = cx.tcx.expr_ty_adjusted(self);
 438                 expr = Expr {
 439                     temp_lifetime: temp_lifetime,
 440                     ty: adjusted_ty,
 441                     span: self.span,
 442                     kind: ExprKind::UnsafeFnPointer { source: expr.to_ref() },
 443                 };
 444             }
 445             Some(&ty::adjustment::AdjustMutToConstPointer) => {
 446                 let adjusted_ty = cx.tcx.expr_ty_adjusted(self);
 447                 expr = Expr {
 448                     temp_lifetime: temp_lifetime,
 449                     ty: adjusted_ty,
 450                     span: self.span,
 451                     kind: ExprKind::Cast { source: expr.to_ref() },
 452                 };
 453             }
 454             Some(&ty::adjustment::AdjustDerefRef(ref adj)) => {
 455                 for i in 0..adj.autoderefs {
 456                     let i = i as u32;
 457                     let adjusted_ty =
 458                         expr.ty.adjust_for_autoderef(
 459                             cx.tcx,
 460                             self.id,
 461                             self.span,
 462                             i,
 463                             |mc| cx.tcx.tables.borrow().method_map.get(&mc).map(|m| m.ty));
 464                     debug!("make_mirror: autoderef #{}, adjusted_ty={:?}", i, adjusted_ty);
 465                     let method_key = ty::MethodCall::autoderef(self.id, i);
 466                     let meth_ty =
 467                         cx.tcx.tables.borrow().method_map.get(&method_key).map(|m| m.ty);
 468                     let kind = if let Some(meth_ty) = meth_ty {
 469                         debug!("make_mirror: overloaded autoderef (meth_ty={:?})", meth_ty);
 470
 471                         let ref_ty = cx.tcx.no_late_bound_regions(&meth_ty.fn_ret());
 472                         let (region, mutbl) = match ref_ty {
 473                             Some(ty::FnConverging(&ty::TyS {
 474                                 sty: ty::TyRef(region, mt), ..
 475                             })) => (region, mt.mutbl),
 476                             _ => cx.tcx.sess.span_bug(
 477                                 expr.span, "autoderef returned bad type")
 478                         };
 479
 480                         expr = Expr {
 481                             temp_lifetime: temp_lifetime,
 482                             ty: cx.tcx.mk_ref(
 483                                 region, ty::TypeAndMut { ty: expr.ty, mutbl: mutbl }),
 484                             span: expr.span,
 485                             kind: ExprKind::Borrow {
 486                                 region: *region,
 487                                 borrow_kind: to_borrow_kind(mutbl),
 488                                 arg: expr.to_ref()
 489                             }
 490                         };
 491
 492                         overloaded_lvalue(cx, self, method_key,
 493                                           PassArgs::ByRef, expr.to_ref(), vec![])
 494                     } else {
 495                         debug!("make_mirror: built-in autoderef");
 496                         ExprKind::Deref { arg: expr.to_ref() }
 497                     };
 498                     expr = Expr {
 499                         temp_lifetime: temp_lifetime,
 500                         ty: adjusted_ty,
 501                         span: self.span,
 502                         kind: kind,
 503                     };
 504                 }
 505
 506                 if let Some(autoref) = adj.autoref {
 507                     let adjusted_ty = expr.ty.adjust_for_autoref(cx.tcx, Some(autoref));
 508                     match autoref {
 509                         ty::adjustment::AutoPtr(r, m) => {
 510                             expr = Expr {
 511                                 temp_lifetime: temp_lifetime,
 512                                 ty: adjusted_ty,
 513                                 span: self.span,
 514                                 kind: ExprKind::Borrow {
 515                                     region: *r,
 516                                     borrow_kind: to_borrow_kind(m),
 517                                     arg: expr.to_ref(),
 518                                 },
 519                             };
 520                         }
 521                         ty::adjustment::AutoUnsafe(m) => {
 522                             // Convert this to a suitable `&foo` and
 523                             // then an unsafe coercion. Limit the region to be just this
 524                             // expression.
 525                             let region = ty::ReScope(expr_extent);
 526                             let region = cx.tcx.mk_region(region);
 527                             expr = Expr {
 528                                 temp_lifetime: temp_lifetime,
 529                                 ty: cx.tcx.mk_ref(region, ty::TypeAndMut { ty: expr.ty, mutbl: m }),
 530                                 span: self.span,
 531                                 kind: ExprKind::Borrow {
 532                                     region: *region,
 533                                     borrow_kind: to_borrow_kind(m),
 534                                     arg: expr.to_ref(),
 535                                 },
 536                             };
 537                             expr = Expr {
 538                                 temp_lifetime: temp_lifetime,
 539                                 ty: adjusted_ty,
 540                                 span: self.span,
 541                                 kind: ExprKind::Cast { source: expr.to_ref() },
 542                             };
 543                         }
 544                     }
 545                 }
 546
 547                 if let Some(target) = adj.unsize {
 548                     expr = Expr {
 549                         temp_lifetime: temp_lifetime,
 550                         ty: target,
 551                         span: self.span,
 552                         kind: ExprKind::Unsize { source: expr.to_ref() },
 553                     };
 554                 }
 555             }
 556         }
 557
 558         // Next, wrap this up in the expr's scope.
 559         expr = Expr {
 560             temp_lifetime: temp_lifetime,
 561             ty: expr.ty,
 562             span: self.span,
 563             kind: ExprKind::Scope {
 564                 extent: expr_extent,
 565                 value: expr.to_ref(),
 566             },
 567         };
 568
 569         // Finally, create a destruction scope, if any.
 570         if let Some(extent) = cx.tcx.region_maps.opt_destruction_extent(self.id) {
 571             expr = Expr {
 572                 temp_lifetime: temp_lifetime,
 573                 ty: expr.ty,
 574                 span: self.span,
 575                 kind: ExprKind::Scope {
 576                     extent: extent,
 577                     value: expr.to_ref(),
 578                 },
 579             };
 580         }
 581
 582         // OK, all done!
 583         expr
 584     }
 585 }
 586
 587 fn method_callee<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 588                                expr: &hir::Expr,
 589                                method_call: ty::MethodCall)
 590                                -> Expr<'tcx> {
 591     let tables = cx.tcx.tables.borrow();
 592     let callee = &tables.method_map[&method_call];
 593     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 594     Expr {
 595         temp_lifetime: temp_lifetime,
 596         ty: callee.ty,
 597         span: expr.span,
 598         kind: ExprKind::Literal {
 599             literal: Literal::Item {
 600                 def_id: callee.def_id,
 601                 substs: callee.substs,
 602             },
 603         },
 604     }
 605 }
 606
 607 fn to_borrow_kind(m: hir::Mutability) -> BorrowKind {
 608     match m {
 609         hir::MutMutable => BorrowKind::Mut,
 610         hir::MutImmutable => BorrowKind::Shared,
 611     }
 612 }
 613
 614 fn convert_arm<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 615     let mut map;
 616     let opt_map = if arm.pats.len() == 1 {
 617         None
 618     } else {
 619         map = FnvHashMap();
 620         pat_util::pat_bindings(&cx.tcx.def_map, &arm.pats[0], |_, p_id, _, path| {
 621             map.insert(path.node, p_id);
 622         });
 623         Some(&map)
 624     };
 625
 626     Arm {
 627         patterns: arm.pats.iter().map(|p| cx.refutable_pat(opt_map, p)).collect(),
 628         guard: arm.guard.to_ref(),
 629         body: arm.body.to_ref(),
 630     }
 631 }
 632
 633 fn convert_path_expr<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, expr: &'tcx hir::Expr) -> ExprKind<'tcx> {
 634     let substs = cx.tcx.mk_substs(cx.tcx.node_id_item_substs(expr.id).substs);
 635     // Otherwise there may be def_map borrow conflicts
 636     let def = cx.tcx.def_map.borrow()[&expr.id].full_def();
 637     let def_id = match def {
 638         // A regular function.
 639         Def::Fn(def_id) | Def::Method(def_id) => def_id,
 640         Def::Struct(def_id) => match cx.tcx.node_id_to_type(expr.id).sty {
 641             // A tuple-struct constructor. Should only be reached if not called in the same
 642             // expression.
 643             ty::TyFnDef(..) => def_id,
 644             // A unit struct which is used as a value. We return a completely different ExprKind
 645             // here to account for this special case.
 646             ty::TyStruct(adt_def, substs) => return ExprKind::Adt {
 647                 adt_def: adt_def,
 648                 variant_index: 0,
 649                 substs: substs,
 650                 fields: vec![],
 651                 base: None
 652             },
 653             ref sty => panic!("unexpected sty: {:?}", sty)
 654         },
 655         Def::Variant(enum_id, variant_id) => match cx.tcx.node_id_to_type(expr.id).sty {
 656             // A variant constructor. Should only be reached if not called in the same
 657             // expression.
 658             ty::TyFnDef(..) => variant_id,
 659             // A unit variant, similar special case to the struct case above.
 660             ty::TyEnum(adt_def, substs) => {
 661                 debug_assert!(adt_def.did == enum_id);
 662                 let index = adt_def.variant_index_with_id(variant_id);
 663                 return ExprKind::Adt {
 664                     adt_def: adt_def,
 665                     substs: substs,
 666                     variant_index: index,
 667                     fields: vec![],
 668                     base: None
 669                 };
 670             },
 671             ref sty => panic!("unexpected sty: {:?}", sty)
 672         },
 673         Def::Const(def_id) |
 674         Def::AssociatedConst(def_id) => {
 675             if let Some(e) = const_eval::lookup_const_by_id(cx.tcx, def_id, Some(expr.id), None) {
 676                 // FIXME ConstVal can't be yet used with adjustments, as they would be lost.
 677                 if !cx.tcx.tables.borrow().adjustments.contains_key(&e.id) {
 678                     if let Some(v) = cx.try_const_eval_literal(e) {
 679                         return ExprKind::Literal { literal: v };
 680                     }
 681                 }
 682             }
 683             def_id
 684         }
 685
 686         Def::Static(node_id, _) => return ExprKind::StaticRef {
 687             id: node_id,
 688         },
 689
 690         def @ Def::Local(..) |
 691         def @ Def::Upvar(..) => return convert_var(cx, expr, def),
 692
 693         def =>
 694             cx.tcx.sess.span_bug(
 695                 expr.span,
 696                 &format!("def `{:?}` not yet implemented", def)),
 697     };
 698     ExprKind::Literal {
 699         literal: Literal::Item { def_id: def_id, substs: substs }
 700     }
 701 }
 702
 703 fn convert_var<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 704                              expr: &'tcx hir::Expr,
 705                              def: Def)
 706                              -> ExprKind<'tcx> {
 707     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 708
 709     match def {
 710         Def::Local(_, node_id) => {
 711             ExprKind::VarRef {
 712                 id: node_id,
 713             }
 714         }
 715
 716         Def::Upvar(_, id_var, index, closure_expr_id) => {
 717             debug!("convert_var(upvar({:?}, {:?}, {:?}))", id_var, index, closure_expr_id);
 718             let var_ty = cx.tcx.node_id_to_type(id_var);
 719
 720             let body_id = match cx.tcx.map.find(closure_expr_id) {
 721                 Some(map::NodeExpr(expr)) => {
 722                     match expr.node {
 723                         hir::ExprClosure(_, _, ref body) => body.id,
 724                         _ => {
 725                             cx.tcx.sess.span_bug(expr.span, "closure expr is not a closure expr");
 726                         }
 727                     }
 728                 }
 729                 _ => {
 730                     cx.tcx.sess.span_bug(expr.span, "ast-map has garbage for closure expr");
 731                 }
 732             };
 733
 734             // FIXME free regions in closures are not right
 735             let closure_ty = cx.tcx.node_id_to_type(closure_expr_id);
 736
 737             // FIXME we're just hard-coding the idea that the
 738             // signature will be &self or &mut self and hence will
 739             // have a bound region with number 0
 740             let region = ty::Region::ReFree(ty::FreeRegion {
 741                 scope: cx.tcx.region_maps.node_extent(body_id),
 742                 bound_region: ty::BoundRegion::BrAnon(0),
 743             });
 744             let region = cx.tcx.mk_region(region);
 745
 746             let self_expr = match cx.tcx.closure_kind(cx.tcx.map.local_def_id(closure_expr_id)) {
 747                 ty::ClosureKind::Fn => {
 748                     let ref_closure_ty =
 749                         cx.tcx.mk_ref(region,
 750                                    ty::TypeAndMut { ty: closure_ty,
 751                                                     mutbl: hir::MutImmutable });
 752                     Expr {
 753                         ty: closure_ty,
 754                         temp_lifetime: temp_lifetime,
 755                         span: expr.span,
 756                         kind: ExprKind::Deref {
 757                             arg: Expr {
 758                                 ty: ref_closure_ty,
 759                                 temp_lifetime: temp_lifetime,
 760                                 span: expr.span,
 761                                 kind: ExprKind::SelfRef
 762                             }.to_ref()
 763                         }
 764                     }
 765                 }
 766                 ty::ClosureKind::FnMut => {
 767                     let ref_closure_ty =
 768                         cx.tcx.mk_ref(region,
 769                                    ty::TypeAndMut { ty: closure_ty,
 770                                                     mutbl: hir::MutMutable });
 771                     Expr {
 772                         ty: closure_ty,
 773                         temp_lifetime: temp_lifetime,
 774                         span: expr.span,
 775                         kind: ExprKind::Deref {
 776                             arg: Expr {
 777                                 ty: ref_closure_ty,
 778                                 temp_lifetime: temp_lifetime,
 779                                 span: expr.span,
 780                                 kind: ExprKind::SelfRef
 781                             }.to_ref()
 782                         }
 783                     }
 784                 }
 785                 ty::ClosureKind::FnOnce => {
 786                     Expr {
 787                         ty: closure_ty,
 788                         temp_lifetime: temp_lifetime,
 789                         span: expr.span,
 790                         kind: ExprKind::SelfRef,
 791                     }
 792                 }
 793             };
 794
 795             // at this point we have `self.n`, which loads up the upvar
 796             let field_kind = ExprKind::Field {
 797                 lhs: self_expr.to_ref(),
 798                 name: Field::new(index),
 799             };
 800
 801             // ...but the upvar might be an `&T` or `&mut T` capture, at which
 802             // point we need an implicit deref
 803             let upvar_id = ty::UpvarId {
 804                 var_id: id_var,
 805                 closure_expr_id: closure_expr_id,
 806             };
 807             let upvar_capture = match cx.tcx.upvar_capture(upvar_id) {
 808                 Some(c) => c,
 809                 None => {
 810                     cx.tcx.sess.span_bug(
 811                         expr.span,
 812                         &format!("no upvar_capture for {:?}", upvar_id));
 813                 }
 814             };
 815             match upvar_capture {
 816                 ty::UpvarCapture::ByValue => field_kind,
 817                 ty::UpvarCapture::ByRef(borrow) => {
 818                     ExprKind::Deref {
 819                         arg: Expr {
 820                             temp_lifetime: temp_lifetime,
 821                             ty: cx.tcx.mk_ref(
 822                                 cx.tcx.mk_region(borrow.region),
 823                                 ty::TypeAndMut {
 824                                     ty: var_ty,
 825                                     mutbl: borrow.kind.to_mutbl_lossy()
 826                                 }),
 827                             span: expr.span,
 828                             kind: field_kind,
 829                         }.to_ref()
 830                     }
 831                 }
 832             }
 833         }
 834
 835         _ => cx.tcx.sess.span_bug(expr.span, "type of & not region"),
 836     }
 837 }
 838
 839
 840 fn bin_op(op: hir::BinOp_) -> BinOp {
 841     match op {
 842         hir::BinOp_::BiAdd => BinOp::Add,
 843         hir::BinOp_::BiSub => BinOp::Sub,
 844         hir::BinOp_::BiMul => BinOp::Mul,
 845         hir::BinOp_::BiDiv => BinOp::Div,
 846         hir::BinOp_::BiRem => BinOp::Rem,
 847         hir::BinOp_::BiBitXor => BinOp::BitXor,
 848         hir::BinOp_::BiBitAnd => BinOp::BitAnd,
 849         hir::BinOp_::BiBitOr => BinOp::BitOr,
 850         hir::BinOp_::BiShl => BinOp::Shl,
 851         hir::BinOp_::BiShr => BinOp::Shr,
 852         hir::BinOp_::BiEq => BinOp::Eq,
 853         hir::BinOp_::BiLt => BinOp::Lt,
 854         hir::BinOp_::BiLe => BinOp::Le,
 855         hir::BinOp_::BiNe => BinOp::Ne,
 856         hir::BinOp_::BiGe => BinOp::Ge,
 857         hir::BinOp_::BiGt => BinOp::Gt,
 858         _ => panic!("no equivalent for ast binop {:?}", op),
 859     }
 860 }
 861
 862 enum PassArgs {
 863     ByValue,
 864     ByRef,
 865 }
 866
 867 fn overloaded_operator<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 868                                      expr: &'tcx hir::Expr,
 869                                      method_call: ty::MethodCall,
 870                                      pass_args: PassArgs,
 871                                      receiver: ExprRef<'tcx>,
 872                                      args: Vec<&'tcx P<hir::Expr>>)
 873                                      -> ExprKind<'tcx> {
 874     // the receiver has all the adjustments that are needed, so we can
 875     // just push a reference to it
 876     let mut argrefs = vec![receiver];
 877
 878     // the arguments, unfortunately, do not, so if this is a ByRef
 879     // operator, we have to gin up the autorefs (but by value is easy)
 880     match pass_args {
 881         PassArgs::ByValue => {
 882             argrefs.extend(args.iter().map(|arg| arg.to_ref()))
 883         }
 884
 885         PassArgs::ByRef => {
 886             let scope = cx.tcx.region_maps.node_extent(expr.id);
 887             let region = cx.tcx.mk_region(ty::ReScope(scope));
 888             let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 889             argrefs.extend(
 890                 args.iter()
 891                     .map(|arg| {
 892                         let arg_ty = cx.tcx.expr_ty_adjusted(arg);
 893                         let adjusted_ty =
 894                             cx.tcx.mk_ref(region,
 895                                        ty::TypeAndMut { ty: arg_ty,
 896                                                         mutbl: hir::MutImmutable });
 897                         Expr {
 898                             temp_lifetime: temp_lifetime,
 899                             ty: adjusted_ty,
 900                             span: expr.span,
 901                             kind: ExprKind::Borrow { region: *region,
 902                                                      borrow_kind: BorrowKind::Shared,
 903                                                      arg: arg.to_ref() }
 904                         }.to_ref()
 905                     }))
 906         }
 907     }
 908
 909     // now create the call itself
 910     let fun = method_callee(cx, expr, method_call);
 911     ExprKind::Call {
 912         ty: fun.ty,
 913         fun: fun.to_ref(),
 914         args: argrefs,
 915     }
 916 }
 917
 918 fn overloaded_lvalue<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 919                                    expr: &'tcx hir::Expr,
 920                                    method_call: ty::MethodCall,
 921                                    pass_args: PassArgs,
 922                                    receiver: ExprRef<'tcx>,
 923                                    args: Vec<&'tcx P<hir::Expr>>)
 924                                    -> ExprKind<'tcx> {
 925     // For an overloaded *x or x[y] expression of type T, the method
 926     // call returns an &T and we must add the deref so that the types
 927     // line up (this is because `*x` and `x[y]` represent lvalues):
 928
 929     // to find the type &T of the content returned by the method;
 930     let tables = cx.tcx.tables.borrow();
 931     let callee = &tables.method_map[&method_call];
 932     let ref_ty = callee.ty.fn_ret();
 933     let ref_ty = cx.tcx.no_late_bound_regions(&ref_ty).unwrap().unwrap();
 934     //                                              1~~~~~   2~~~~~
 935     // (1) callees always have all late-bound regions fully instantiated,
 936     // (2) overloaded methods don't return `!`
 937
 938     // construct the complete expression `foo()` for the overloaded call,
 939     // which will yield the &T type
 940     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 941     let ref_kind = overloaded_operator(cx, expr, method_call, pass_args, receiver, args);
 942     let ref_expr = Expr {
 943         temp_lifetime: temp_lifetime,
 944         ty: ref_ty,
 945         span: expr.span,
 946         kind: ref_kind,
 947     };
 948
 949     // construct and return a deref wrapper `*foo()`
 950     ExprKind::Deref { arg: ref_expr.to_ref() }
 951 }
 952
 953 fn capture_freevar<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 954                                  closure_expr: &'tcx hir::Expr,
 955                                  freevar: &ty::Freevar,
 956                                  freevar_ty: Ty<'tcx>)
 957                                  -> ExprRef<'tcx> {
 958     let id_var = freevar.def.var_id();
 959     let upvar_id = ty::UpvarId {
 960         var_id: id_var,
 961         closure_expr_id: closure_expr.id,
 962     };
 963     let upvar_capture = cx.tcx.upvar_capture(upvar_id).unwrap();
 964     let temp_lifetime = cx.tcx.region_maps.temporary_scope(closure_expr.id);
 965     let var_ty = cx.tcx.node_id_to_type(id_var);
 966     let captured_var = Expr {
 967         temp_lifetime: temp_lifetime,
 968         ty: var_ty,
 969         span: closure_expr.span,
 970         kind: convert_var(cx, closure_expr, freevar.def),
 971     };
 972     match upvar_capture {
 973         ty::UpvarCapture::ByValue => {
 974             captured_var.to_ref()
 975         }
 976         ty::UpvarCapture::ByRef(upvar_borrow) => {
 977             let borrow_kind = match upvar_borrow.kind {
 978                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
 979                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
 980                 ty::BorrowKind::MutBorrow => BorrowKind::Mut,
 981             };
 982             Expr {
 983                 temp_lifetime: temp_lifetime,
 984                 ty: freevar_ty,
 985                 span: closure_expr.span,
 986                 kind: ExprKind::Borrow { region: upvar_borrow.region,
 987                                          borrow_kind: borrow_kind,
 988                                          arg: captured_var.to_ref() }
 989             }.to_ref()
 990         }
 991     }
 992 }
 993
 994 fn loop_label<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, expr: &'tcx hir::Expr) -> CodeExtent {
 995     match cx.tcx.def_map.borrow().get(&expr.id).map(|d| d.full_def()) {
 996         Some(Def::Label(loop_id)) => cx.tcx.region_maps.node_extent(loop_id),
 997         d => {
 998             cx.tcx.sess.span_bug(expr.span, &format!("loop scope resolved to {:?}", d));
 999         }
1000     }
1001 }
1002
1003 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
1004 fn field_refs<'tcx>(variant: VariantDef<'tcx>,
1005                     fields: &'tcx [hir::Field])
1006                     -> Vec<FieldExprRef<'tcx>>
1007 {
1008     fields.iter()
1009           .map(|field| FieldExprRef {
1010               name: Field::new(variant.index_of_field_named(field.name.node).unwrap()),
1011               expr: field.expr.to_ref(),
1012           })
1013           .collect()
1014 }