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