src/librustc_mir/hair/cx/expr.rs

   1 use crate::hair::*;
   2 use crate::hair::cx::Cx;
   3 use crate::hair::cx::block;
   4 use crate::hair::cx::to_ref::ToRef;
   5 use crate::hair::util::UserAnnotatedTyHelpers;
   6 use rustc_data_structures::indexed_vec::Idx;
   7 use rustc::hir::def::{Def, CtorKind};
   8 use rustc::mir::interpret::{GlobalId, ErrorHandled};
   9 use rustc::ty::{self, AdtKind, Ty};
  10 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability};
  11 use rustc::ty::cast::CastKind as TyCastKind;
  12 use rustc::hir;
  13 use rustc::hir::def_id::LocalDefId;
  14 use rustc::mir::BorrowKind;
  15 use syntax_pos::Span;
  16
  17 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
  18     type Output = Expr<'tcx>;
  19
  20     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
  21         let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
  22         let expr_scope = region::Scope {
  23             id: self.hir_id.local_id,
  24             data: region::ScopeData::Node
  25         };
  26
  27         debug!("Expr::make_mirror(): id={}, span={:?}", self.hir_id, self.span);
  28
  29         let mut expr = make_mirror_unadjusted(cx, self);
  30
  31         // Now apply adjustments, if any.
  32         for adjustment in cx.tables().expr_adjustments(self) {
  33             debug!("make_mirror: expr={:?} applying adjustment={:?}",
  34                    expr,
  35                    adjustment);
  36             expr = apply_adjustment(cx, self, expr, adjustment);
  37         }
  38
  39         // Next, wrap this up in the expr's scope.
  40         expr = Expr {
  41             temp_lifetime,
  42             ty: expr.ty,
  43             span: self.span,
  44             kind: ExprKind::Scope {
  45                 region_scope: expr_scope,
  46                 value: expr.to_ref(),
  47                 lint_level: cx.lint_level_of(self.hir_id),
  48             },
  49         };
  50
  51         // Finally, create a destruction scope, if any.
  52         if let Some(region_scope) =
  53             cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id) {
  54                 expr = Expr {
  55                     temp_lifetime,
  56                     ty: expr.ty,
  57                     span: self.span,
  58                     kind: ExprKind::Scope {
  59                         region_scope,
  60                         value: expr.to_ref(),
  61                         lint_level: LintLevel::Inherited,
  62                     },
  63                 };
  64             }
  65
  66         // OK, all done!
  67         expr
  68     }
  69 }
  70
  71 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
  72                                     hir_expr: &'tcx hir::Expr,
  73                                     mut expr: Expr<'tcx>,
  74                                     adjustment: &Adjustment<'tcx>)
  75                                     -> Expr<'tcx> {
  76     let Expr { temp_lifetime, mut span, .. } = expr;
  77     let kind = match adjustment.kind {
  78         Adjust::ReifyFnPointer => {
  79             ExprKind::ReifyFnPointer { source: expr.to_ref() }
  80         }
  81         Adjust::UnsafeFnPointer => {
  82             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
  83         }
  84         Adjust::ClosureFnPointer => {
  85             ExprKind::ClosureFnPointer { source: expr.to_ref() }
  86         }
  87         Adjust::NeverToAny => {
  88             ExprKind::NeverToAny { source: expr.to_ref() }
  89         }
  90         Adjust::MutToConstPointer => {
  91             ExprKind::Cast { source: expr.to_ref() }
  92         }
  93         Adjust::Deref(None) => {
  94             // Adjust the span from the block, to the last expression of the
  95             // block. This is a better span when returning a mutable reference
  96             // with too short a lifetime. The error message will use the span
  97             // from the assignment to the return place, which should only point
  98             // at the returned value, not the entire function body.
  99             //
 100             // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
 101             //      x
 102             //   // ^ error message points at this expression.
 103             // }
 104             //
 105             // We don't need to do this adjustment in the next match arm since
 106             // deref coercions always start with a built-in deref.
 107             if let ExprKind::Block { body } = expr.kind {
 108                 if let Some(ref last_expr) = body.expr {
 109                     span = last_expr.span;
 110                     expr.span = span;
 111                 }
 112             }
 113             ExprKind::Deref { arg: expr.to_ref() }
 114         }
 115         Adjust::Deref(Some(deref)) => {
 116             let call = deref.method_call(cx.tcx(), expr.ty);
 117
 118             expr = Expr {
 119                 temp_lifetime,
 120                 ty: cx.tcx.mk_ref(deref.region,
 121                                   ty::TypeAndMut {
 122                                     ty: expr.ty,
 123                                     mutbl: deref.mutbl,
 124                                   }),
 125                 span,
 126                 kind: ExprKind::Borrow {
 127                     borrow_kind: deref.mutbl.to_borrow_kind(),
 128                     arg: expr.to_ref(),
 129                 },
 130             };
 131
 132             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
 133         }
 134         Adjust::Borrow(AutoBorrow::Ref(_, m)) => {
 135             ExprKind::Borrow {
 136                 borrow_kind: m.to_borrow_kind(),
 137                 arg: expr.to_ref(),
 138             }
 139         }
 140         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
 141             // Convert this to a suitable `&foo` and
 142             // then an unsafe coercion.
 143             expr = Expr {
 144                 temp_lifetime,
 145                 ty: cx.tcx.mk_ref(cx.tcx.types.re_erased,
 146                                   ty::TypeAndMut {
 147                                     ty: expr.ty,
 148                                     mutbl: m,
 149                                   }),
 150                 span,
 151                 kind: ExprKind::Borrow {
 152                     borrow_kind: m.to_borrow_kind(),
 153                     arg: expr.to_ref(),
 154                 },
 155             };
 156             let cast_expr = Expr {
 157                 temp_lifetime,
 158                 ty: adjustment.target,
 159                 span,
 160                 kind: ExprKind::Cast { source: expr.to_ref() }
 161             };
 162
 163             // To ensure that both implicit and explicit coercions are
 164             // handled the same way, we insert an extra layer of indirection here.
 165             // For explicit casts (e.g., 'foo as *const T'), the source of the 'Use'
 166             // will be an ExprKind::Hair with the appropriate cast expression. Here,
 167             // we make our Use source the generated Cast from the original coercion.
 168             //
 169             // In both cases, this outer 'Use' ensures that the inner 'Cast' is handled by
 170             // as_operand, not by as_rvalue - causing the cast result to be stored in a temporary.
 171             // Ordinary, this is identical to using the cast directly as an rvalue. However, if the
 172             // source of the cast was previously borrowed as mutable, storing the cast in a
 173             // temporary gives the source a chance to expire before the cast is used. For
 174             // structs with a self-referential *mut ptr, this allows assignment to work as
 175             // expected.
 176             //
 177             // For example, consider the type 'struct Foo { field: *mut Foo }',
 178             // The method 'fn bar(&mut self) { self.field = self }'
 179             // triggers a coercion from '&mut self' to '*mut self'. In order
 180             // for the assignment to be valid, the implicit borrow
 181             // of 'self' involved in the coercion needs to end before the local
 182             // containing the '*mut T' is assigned to 'self.field' - otherwise,
 183             // we end up trying to assign to 'self.field' while we have another mutable borrow
 184             // active.
 185             //
 186             // We only need to worry about this kind of thing for coercions from refs to ptrs,
 187             // since they get rid of a borrow implicitly.
 188             ExprKind::Use { source: cast_expr.to_ref() }
 189         }
 190         Adjust::Unsize => {
 191             // See the above comment for Adjust::Deref
 192             if let ExprKind::Block { body } = expr.kind {
 193                 if let Some(ref last_expr) = body.expr {
 194                     span = last_expr.span;
 195                     expr.span = span;
 196                 }
 197             }
 198             ExprKind::Unsize { source: expr.to_ref() }
 199         }
 200     };
 201
 202     Expr {
 203         temp_lifetime,
 204         ty: adjustment.target,
 205         span,
 206         kind,
 207     }
 208 }
 209
 210 fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 211                                           expr: &'tcx hir::Expr)
 212                                           -> Expr<'tcx> {
 213     let expr_ty = cx.tables().expr_ty(expr);
 214     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 215
 216     let kind = match expr.node {
 217         // Here comes the interesting stuff:
 218         hir::ExprKind::MethodCall(_, method_span, ref args) => {
 219             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 220             let expr = method_callee(cx, expr, method_span,None);
 221             let args = args.iter()
 222                 .map(|e| e.to_ref())
 223                 .collect();
 224             ExprKind::Call {
 225                 ty: expr.ty,
 226                 fun: expr.to_ref(),
 227                 args,
 228                 from_hir_call: true,
 229             }
 230         }
 231
 232         hir::ExprKind::Call(ref fun, ref args) => {
 233             if cx.tables().is_method_call(expr) {
 234                 // The callee is something implementing Fn, FnMut, or FnOnce.
 235                 // Find the actual method implementation being called and
 236                 // build the appropriate UFCS call expression with the
 237                 // callee-object as expr parameter.
 238
 239                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 240
 241                 let method = method_callee(cx, expr, fun.span,None);
 242
 243                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
 244                 let tupled_args = Expr {
 245                     ty: cx.tcx.mk_tup(arg_tys),
 246                     temp_lifetime,
 247                     span: expr.span,
 248                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
 249                 };
 250
 251                 ExprKind::Call {
 252                     ty: method.ty,
 253                     fun: method.to_ref(),
 254                     args: vec![fun.to_ref(), tupled_args.to_ref()],
 255                     from_hir_call: true,
 256                 }
 257             } else {
 258                 let adt_data = if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) =
 259                     fun.node
 260                 {
 261                     // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
 262                     expr_ty.ty_adt_def().and_then(|adt_def| {
 263                         match path.def {
 264                             Def::VariantCtor(variant_id, CtorKind::Fn) => {
 265                                 Some((adt_def, adt_def.variant_index_with_id(variant_id)))
 266                             }
 267                             Def::StructCtor(_, CtorKind::Fn) |
 268                             Def::SelfCtor(..) => Some((adt_def, VariantIdx::new(0))),
 269                             _ => None,
 270                         }
 271                     })
 272                 } else {
 273                     None
 274                 };
 275                 if let Some((adt_def, index)) = adt_data {
 276                     let substs = cx.tables().node_substs(fun.hir_id);
 277                     let user_provided_types = cx.tables().user_provided_types();
 278                     let user_ty = user_provided_types.get(fun.hir_id)
 279                         .map(|u_ty| *u_ty)
 280                         .map(|mut u_ty| {
 281                             if let UserType::TypeOf(ref mut did, _) = &mut u_ty.value {
 282                                 *did = adt_def.did;
 283                             }
 284                             u_ty
 285                         });
 286                     debug!("make_mirror_unadjusted: (call) user_ty={:?}", user_ty);
 287
 288                     let field_refs = args.iter()
 289                         .enumerate()
 290                         .map(|(idx, e)| {
 291                             FieldExprRef {
 292                                 name: Field::new(idx),
 293                                 expr: e.to_ref(),
 294                             }
 295                         })
 296                         .collect();
 297                     ExprKind::Adt {
 298                         adt_def,
 299                         substs,
 300                         variant_index: index,
 301                         fields: field_refs,
 302                         user_ty,
 303                         base: None,
 304                     }
 305                 } else {
 306                     ExprKind::Call {
 307                         ty: cx.tables().node_type(fun.hir_id),
 308                         fun: fun.to_ref(),
 309                         args: args.to_ref(),
 310                         from_hir_call: true,
 311                     }
 312                 }
 313             }
 314         }
 315
 316         hir::ExprKind::AddrOf(mutbl, ref expr) => {
 317             ExprKind::Borrow {
 318                 borrow_kind: mutbl.to_borrow_kind(),
 319                 arg: expr.to_ref(),
 320             }
 321         }
 322
 323         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
 324
 325         hir::ExprKind::Assign(ref lhs, ref rhs) => {
 326             ExprKind::Assign {
 327                 lhs: lhs.to_ref(),
 328                 rhs: rhs.to_ref(),
 329             }
 330         }
 331
 332         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 333             if cx.tables().is_method_call(expr) {
 334                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 335             } else {
 336                 ExprKind::AssignOp {
 337                     op: bin_op(op.node),
 338                     lhs: lhs.to_ref(),
 339                     rhs: rhs.to_ref(),
 340                 }
 341             }
 342         }
 343
 344         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 345             literal: cx.tcx.mk_lazy_const(ty::LazyConst::Evaluated(
 346                 cx.const_eval_literal(&lit.node, expr_ty, lit.span, false)
 347             )),
 348             user_ty: None,
 349         },
 350
 351         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 352             if cx.tables().is_method_call(expr) {
 353                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 354             } else {
 355                 // FIXME overflow
 356                 match (op.node, cx.constness) {
 357                     // FIXME(eddyb) use logical ops in constants when
 358                     // they can handle that kind of control-flow.
 359                     (hir::BinOpKind::And, hir::Constness::Const) => {
 360                         cx.control_flow_destroyed.push((
 361                             op.span,
 362                             "`&&` operator".into(),
 363                         ));
 364                         ExprKind::Binary {
 365                             op: BinOp::BitAnd,
 366                             lhs: lhs.to_ref(),
 367                             rhs: rhs.to_ref(),
 368                         }
 369                     }
 370                     (hir::BinOpKind::Or, hir::Constness::Const) => {
 371                         cx.control_flow_destroyed.push((
 372                             op.span,
 373                             "`||` operator".into(),
 374                         ));
 375                         ExprKind::Binary {
 376                             op: BinOp::BitOr,
 377                             lhs: lhs.to_ref(),
 378                             rhs: rhs.to_ref(),
 379                         }
 380                     }
 381
 382                     (hir::BinOpKind::And, hir::Constness::NotConst) => {
 383                         ExprKind::LogicalOp {
 384                             op: LogicalOp::And,
 385                             lhs: lhs.to_ref(),
 386                             rhs: rhs.to_ref(),
 387                         }
 388                     }
 389                     (hir::BinOpKind::Or, hir::Constness::NotConst) => {
 390                         ExprKind::LogicalOp {
 391                             op: LogicalOp::Or,
 392                             lhs: lhs.to_ref(),
 393                             rhs: rhs.to_ref(),
 394                         }
 395                     }
 396
 397                     _ => {
 398                         let op = bin_op(op.node);
 399                         ExprKind::Binary {
 400                             op,
 401                             lhs: lhs.to_ref(),
 402                             rhs: rhs.to_ref(),
 403                         }
 404                     }
 405                 }
 406             }
 407         }
 408
 409         hir::ExprKind::Index(ref lhs, ref index) => {
 410             if cx.tables().is_method_call(expr) {
 411                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 412             } else {
 413                 ExprKind::Index {
 414                     lhs: lhs.to_ref(),
 415                     index: index.to_ref(),
 416                 }
 417             }
 418         }
 419
 420         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
 421             if cx.tables().is_method_call(expr) {
 422                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
 423             } else {
 424                 ExprKind::Deref { arg: arg.to_ref() }
 425             }
 426         }
 427
 428         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
 429             if cx.tables().is_method_call(expr) {
 430                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 431             } else {
 432                 ExprKind::Unary {
 433                     op: UnOp::Not,
 434                     arg: arg.to_ref(),
 435                 }
 436             }
 437         }
 438
 439         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
 440             if cx.tables().is_method_call(expr) {
 441                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 442             } else {
 443                 if let hir::ExprKind::Lit(ref lit) = arg.node {
 444                     ExprKind::Literal {
 445                         literal: cx.tcx.mk_lazy_const(ty::LazyConst::Evaluated(
 446                             cx.const_eval_literal(&lit.node, expr_ty, lit.span, true)
 447                         )),
 448                         user_ty: None,
 449                     }
 450                 } else {
 451                     ExprKind::Unary {
 452                         op: UnOp::Neg,
 453                         arg: arg.to_ref(),
 454                     }
 455                 }
 456             }
 457         }
 458
 459         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => {
 460             match expr_ty.sty {
 461                 ty::Adt(adt, substs) => {
 462                     match adt.adt_kind() {
 463                         AdtKind::Struct | AdtKind::Union => {
 464                             let user_provided_types = cx.tables().user_provided_types();
 465                             let user_ty = user_provided_types.get(expr.hir_id).map(|u_ty| *u_ty);
 466                             debug!("make_mirror_unadjusted: (struct/union) user_ty={:?}", user_ty);
 467                             ExprKind::Adt {
 468                                 adt_def: adt,
 469                                 variant_index: VariantIdx::new(0),
 470                                 substs,
 471                                 user_ty,
 472                                 fields: field_refs(cx, fields),
 473                                 base: base.as_ref().map(|base| {
 474                                     FruInfo {
 475                                         base: base.to_ref(),
 476                                         field_types: cx.tables()
 477                                                        .fru_field_types()[expr.hir_id]
 478                                                        .clone(),
 479                                     }
 480                                 }),
 481                             }
 482                         }
 483                         AdtKind::Enum => {
 484                             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 485                             match def {
 486                                 Def::Variant(variant_id) => {
 487                                     assert!(base.is_none());
 488
 489                                     let index = adt.variant_index_with_id(variant_id);
 490                                     let user_provided_types = cx.tables().user_provided_types();
 491                                     let user_ty = user_provided_types.get(expr.hir_id)
 492                                         .map(|u_ty| *u_ty);
 493                                     debug!(
 494                                         "make_mirror_unadjusted: (variant) user_ty={:?}",
 495                                         user_ty
 496                                     );
 497                                     ExprKind::Adt {
 498                                         adt_def: adt,
 499                                         variant_index: index,
 500                                         substs,
 501                                         user_ty,
 502                                         fields: field_refs(cx, fields),
 503                                         base: None,
 504                                     }
 505                                 }
 506                                 _ => {
 507                                     span_bug!(expr.span, "unexpected def: {:?}", def);
 508                                 }
 509                             }
 510                         }
 511                     }
 512                 }
 513                 _ => {
 514                     span_bug!(expr.span,
 515                               "unexpected type for struct literal: {:?}",
 516                               expr_ty);
 517                 }
 518             }
 519         }
 520
 521         hir::ExprKind::Closure(..) => {
 522             let closure_ty = cx.tables().expr_ty(expr);
 523             let (def_id, substs, movability) = match closure_ty.sty {
 524                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 525                 ty::Generator(def_id, substs, movability) => {
 526                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
 527                 }
 528                 _ => {
 529                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 530                 }
 531             };
 532             let expr_node_id = cx.tcx.hir().hir_to_node_id(expr.hir_id);
 533             let upvars = cx.tcx.with_freevars(expr_node_id, |freevars| {
 534                 freevars.iter()
 535                     .zip(substs.upvar_tys(def_id, cx.tcx))
 536                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 537                     .collect()
 538             });
 539             ExprKind::Closure {
 540                 closure_id: def_id,
 541                 substs,
 542                 upvars,
 543                 movability,
 544             }
 545         }
 546
 547         hir::ExprKind::Path(ref qpath) => {
 548             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 549             convert_path_expr(cx, expr, def)
 550         }
 551
 552         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
 553             ExprKind::InlineAsm {
 554                 asm,
 555                 outputs: outputs.to_ref(),
 556                 inputs: inputs.to_ref(),
 557             }
 558         }
 559
 560         // Now comes the rote stuff:
 561         hir::ExprKind::Repeat(ref v, ref count) => {
 562             let def_id = cx.tcx.hir().local_def_id(count.id);
 563             let substs = Substs::identity_for_item(cx.tcx.global_tcx(), def_id);
 564             let instance = ty::Instance::resolve(
 565                 cx.tcx.global_tcx(),
 566                 cx.param_env,
 567                 def_id,
 568                 substs,
 569             ).unwrap();
 570             let global_id = GlobalId {
 571                 instance,
 572                 promoted: None
 573             };
 574             let span = cx.tcx.def_span(def_id);
 575             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
 576                 Ok(cv) => cv.unwrap_usize(cx.tcx),
 577                 Err(ErrorHandled::Reported) => 0,
 578                 Err(ErrorHandled::TooGeneric) => {
 579                     cx.tcx.sess.span_err(span, "array lengths can't depend on generic parameters");
 580                     0
 581                 },
 582             };
 583
 584             ExprKind::Repeat {
 585                 value: v.to_ref(),
 586                 count,
 587             }
 588         }
 589         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 590         hir::ExprKind::Break(dest, ref value) => {
 591             match dest.target_id {
 592                 Ok(target_id) => ExprKind::Break {
 593                     label: region::Scope {
 594                         id: cx.tcx.hir().node_to_hir_id(target_id).local_id,
 595                         data: region::ScopeData::Node
 596                     },
 597                     value: value.to_ref(),
 598                 },
 599                 Err(err) => bug!("invalid loop id for break: {}", err)
 600             }
 601         }
 602         hir::ExprKind::Continue(dest) => {
 603             match dest.target_id {
 604                 Ok(loop_id) => ExprKind::Continue {
 605                     label: region::Scope {
 606                         id: cx.tcx.hir().node_to_hir_id(loop_id).local_id,
 607                         data: region::ScopeData::Node
 608                     },
 609                 },
 610                 Err(err) => bug!("invalid loop id for continue: {}", err)
 611             }
 612         }
 613         hir::ExprKind::Match(ref discr, ref arms, _) => {
 614             ExprKind::Match {
 615                 discriminant: discr.to_ref(),
 616                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 617             }
 618         }
 619         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
 620             ExprKind::If {
 621                 condition: cond.to_ref(),
 622                 then: then.to_ref(),
 623                 otherwise: otherwise.to_ref(),
 624             }
 625         }
 626         hir::ExprKind::While(ref cond, ref body, _) => {
 627             ExprKind::Loop {
 628                 condition: Some(cond.to_ref()),
 629                 body: block::to_expr_ref(cx, body),
 630             }
 631         }
 632         hir::ExprKind::Loop(ref body, _, _) => {
 633             ExprKind::Loop {
 634                 condition: None,
 635                 body: block::to_expr_ref(cx, body),
 636             }
 637         }
 638         hir::ExprKind::Field(ref source, ..) => {
 639             ExprKind::Field {
 640                 lhs: source.to_ref(),
 641                 name: Field::new(cx.tcx.field_index(expr.hir_id, cx.tables)),
 642             }
 643         }
 644         hir::ExprKind::Cast(ref source, ref cast_ty) => {
 645             // Check for a user-given type annotation on this `cast`
 646             let user_provided_types = cx.tables.user_provided_types();
 647             let user_ty = user_provided_types.get(cast_ty.hir_id);
 648
 649             debug!(
 650                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 651                 expr,
 652                 cast_ty.hir_id,
 653                 user_ty,
 654             );
 655
 656             // Check to see if this cast is a "coercion cast", where the cast is actually done
 657             // using a coercion (or is a no-op).
 658             let cast = if let Some(&TyCastKind::CoercionCast) =
 659                 cx.tables()
 660                 .cast_kinds()
 661                 .get(source.hir_id)
 662             {
 663                 // Convert the lexpr to a vexpr.
 664                 ExprKind::Use { source: source.to_ref() }
 665             } else {
 666                 // check whether this is casting an enum variant discriminant
 667                 // to prevent cycles, we refer to the discriminant initializer
 668                 // which is always an integer and thus doesn't need to know the
 669                 // enum's layout (or its tag type) to compute it during const eval
 670                 // Example:
 671                 // enum Foo {
 672                 //     A,
 673                 //     B = A as isize + 4,
 674                 // }
 675                 // The correct solution would be to add symbolic computations to miri,
 676                 // so we wouldn't have to compute and store the actual value
 677                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 678                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 679                     cx
 680                         .tables()
 681                         .node_type(source.hir_id)
 682                         .ty_adt_def()
 683                         .and_then(|adt_def| {
 684                         match def {
 685                             Def::VariantCtor(variant_id, CtorKind::Const) => {
 686                                 let idx = adt_def.variant_index_with_id(variant_id);
 687                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 688                                 use rustc::ty::util::IntTypeExt;
 689                                 let ty = adt_def.repr.discr_type();
 690                                 let ty = ty.to_ty(cx.tcx());
 691                                 Some((d, o, ty))
 692                             }
 693                             _ => None,
 694                         }
 695                     })
 696                 } else {
 697                     None
 698                 };
 699
 700                 let source = if let Some((did, offset, var_ty)) = var {
 701                     let mk_const = |literal| Expr {
 702                         temp_lifetime,
 703                         ty: var_ty,
 704                         span: expr.span,
 705                         kind: ExprKind::Literal {
 706                             literal: cx.tcx.mk_lazy_const(literal),
 707                             user_ty: None
 708                         },
 709                     }.to_ref();
 710                     let offset = mk_const(ty::LazyConst::Evaluated(ty::Const::from_bits(
 711                         cx.tcx,
 712                         offset as u128,
 713                         cx.param_env.and(var_ty),
 714                     )));
 715                     match did {
 716                         Some(did) => {
 717                             // in case we are offsetting from a computed discriminant
 718                             // and not the beginning of discriminants (which is always `0`)
 719                             let substs = Substs::identity_for_item(cx.tcx(), did);
 720                             let lhs = mk_const(ty::LazyConst::Unevaluated(did, substs));
 721                             let bin = ExprKind::Binary {
 722                                 op: BinOp::Add,
 723                                 lhs,
 724                                 rhs: offset,
 725                             };
 726                             Expr {
 727                                 temp_lifetime,
 728                                 ty: var_ty,
 729                                 span: expr.span,
 730                                 kind: bin,
 731                             }.to_ref()
 732                         },
 733                         None => offset,
 734                     }
 735                 } else {
 736                     source.to_ref()
 737                 };
 738
 739                 ExprKind::Cast { source }
 740             };
 741
 742             if let Some(user_ty) = user_ty {
 743                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 744                 //       inefficient, revisit this when performance becomes an issue.
 745                 let cast_expr = Expr {
 746                     temp_lifetime,
 747                     ty: expr_ty,
 748                     span: expr.span,
 749                     kind: cast,
 750                 };
 751                 debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
 752
 753                 ExprKind::ValueTypeAscription {
 754                     source: cast_expr.to_ref(),
 755                     user_ty: Some(*user_ty),
 756                 }
 757             } else {
 758                 cast
 759             }
 760         }
 761         hir::ExprKind::Type(ref source, ref ty) => {
 762             let user_provided_types = cx.tables.user_provided_types();
 763             let user_ty = user_provided_types.get(ty.hir_id).map(|u_ty| *u_ty);
 764             debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
 765             if source.is_place_expr() {
 766                 ExprKind::PlaceTypeAscription {
 767                     source: source.to_ref(),
 768                     user_ty,
 769                 }
 770             } else {
 771                 ExprKind::ValueTypeAscription {
 772                     source: source.to_ref(),
 773                     user_ty,
 774                 }
 775             }
 776         }
 777         hir::ExprKind::Box(ref value) => {
 778             ExprKind::Box {
 779                 value: value.to_ref(),
 780             }
 781         }
 782         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 783         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 784
 785         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 786         hir::ExprKind::Err => unreachable!(),
 787     };
 788
 789     Expr {
 790         temp_lifetime,
 791         ty: expr_ty,
 792         span: expr.span,
 793         kind,
 794     }
 795 }
 796
 797 fn user_substs_applied_to_def(
 798     cx: &mut Cx<'a, 'gcx, 'tcx>,
 799     hir_id: hir::HirId,
 800     def: &Def,
 801 ) -> Option<ty::CanonicalUserType<'tcx>> {
 802     debug!("user_substs_applied_to_def: def={:?}", def);
 803     let user_provided_type = match def {
 804         // A reference to something callable -- e.g., a fn, method, or
 805         // a tuple-struct or tuple-variant. This has the type of a
 806         // `Fn` but with the user-given substitutions.
 807         Def::Fn(_) |
 808         Def::Method(_) |
 809         Def::StructCtor(_, CtorKind::Fn) |
 810         Def::VariantCtor(_, CtorKind::Fn) |
 811         Def::Const(_) |
 812         Def::AssociatedConst(_) => cx.tables().user_provided_types().get(hir_id).map(|u_ty| *u_ty),
 813
 814         // A unit struct/variant which is used as a value (e.g.,
 815         // `None`). This has the type of the enum/struct that defines
 816         // this variant -- but with the substitutions given by the
 817         // user.
 818         Def::StructCtor(_def_id, CtorKind::Const) |
 819         Def::VariantCtor(_def_id, CtorKind::Const) =>
 820             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 821
 822         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 823         Def::SelfCtor(_) =>
 824             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 825
 826         _ =>
 827             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
 828     };
 829     debug!("user_substs_applied_to_def: user_provided_type={:?}", user_provided_type);
 830     user_provided_type
 831 }
 832
 833 fn method_callee<'a, 'gcx, 'tcx>(
 834     cx: &mut Cx<'a, 'gcx, 'tcx>,
 835     expr: &hir::Expr,
 836     span: Span,
 837     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
 838 ) -> Expr<'tcx> {
 839     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 840     let (def_id, substs, user_ty) = match overloaded_callee {
 841         Some((def_id, substs)) => (def_id, substs, None),
 842         None => {
 843             let type_dependent_defs = cx.tables().type_dependent_defs();
 844             let def = type_dependent_defs
 845                 .get(expr.hir_id)
 846                 .unwrap_or_else(|| {
 847                     span_bug!(expr.span, "no type-dependent def for method callee")
 848                 });
 849             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, def);
 850             debug!("method_callee: user_ty={:?}", user_ty);
 851             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 852         }
 853     };
 854     let ty = cx.tcx().mk_fn_def(def_id, substs);
 855     Expr {
 856         temp_lifetime,
 857         ty,
 858         span,
 859         kind: ExprKind::Literal {
 860             literal: cx.tcx().mk_lazy_const(ty::LazyConst::Evaluated(
 861                 ty::Const::zero_sized(ty)
 862             )),
 863             user_ty,
 864         },
 865     }
 866 }
 867
 868 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 869
 870 impl ToBorrowKind for AutoBorrowMutability {
 871     fn to_borrow_kind(&self) -> BorrowKind {
 872         use rustc::ty::adjustment::AllowTwoPhase;
 873         match *self {
 874             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 875                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 876                     AllowTwoPhase::Yes => true,
 877                     AllowTwoPhase::No => false
 878                 }},
 879             AutoBorrowMutability::Immutable =>
 880                 BorrowKind::Shared,
 881         }
 882     }
 883 }
 884
 885 impl ToBorrowKind for hir::Mutability {
 886     fn to_borrow_kind(&self) -> BorrowKind {
 887         match *self {
 888             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 889             hir::MutImmutable => BorrowKind::Shared,
 890         }
 891     }
 892 }
 893
 894 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 895     Arm {
 896         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 897         guard: match arm.guard {
 898                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 899                 _ => None,
 900             },
 901         body: arm.body.to_ref(),
 902         // BUG: fix this
 903         lint_level: LintLevel::Inherited,
 904     }
 905 }
 906
 907 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 908                                      expr: &'tcx hir::Expr,
 909                                      def: Def)
 910                                      -> ExprKind<'tcx> {
 911     let substs = cx.tables().node_substs(expr.hir_id);
 912     match def {
 913         // A regular function, constructor function or a constant.
 914         Def::Fn(_) |
 915         Def::Method(_) |
 916         Def::StructCtor(_, CtorKind::Fn) |
 917         Def::VariantCtor(_, CtorKind::Fn) |
 918         Def::SelfCtor(..) => {
 919             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 920             debug!("convert_path_expr: user_ty={:?}", user_ty);
 921             ExprKind::Literal {
 922                 literal: cx.tcx.mk_lazy_const(ty::LazyConst::Evaluated(ty::Const::zero_sized(
 923                     cx.tables().node_type(expr.hir_id),
 924                 ))),
 925                 user_ty,
 926             }
 927         },
 928
 929         Def::Const(def_id) |
 930         Def::AssociatedConst(def_id) => {
 931             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 932             debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
 933             ExprKind::Literal {
 934                 literal: cx.tcx.mk_lazy_const(ty::LazyConst::Unevaluated(def_id, substs)),
 935                 user_ty,
 936             }
 937         },
 938
 939         Def::StructCtor(def_id, CtorKind::Const) |
 940         Def::VariantCtor(def_id, CtorKind::Const) => {
 941             let user_provided_types = cx.tables.user_provided_types();
 942             let user_provided_type = user_provided_types.get(expr.hir_id).map(|u_ty| *u_ty);
 943             debug!("convert_path_expr: user_provided_type={:?}", user_provided_type);
 944             match cx.tables().node_type(expr.hir_id).sty {
 945                 // A unit struct/variant which is used as a value.
 946                 // We return a completely different ExprKind here to account for this special case.
 947                 ty::Adt(adt_def, substs) => {
 948                     ExprKind::Adt {
 949                         adt_def,
 950                         variant_index: adt_def.variant_index_with_id(def_id),
 951                         substs,
 952                         user_ty: user_provided_type,
 953                         fields: vec![],
 954                         base: None,
 955                     }
 956                 }
 957                 ref sty => bug!("unexpected sty: {:?}", sty),
 958             }
 959         }
 960
 961         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 962
 963         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 964
 965         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 966     }
 967 }
 968
 969 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 970                                expr: &'tcx hir::Expr,
 971                                def: Def)
 972                                -> ExprKind<'tcx> {
 973     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 974
 975     match def {
 976         Def::Local(id) => ExprKind::VarRef { id },
 977
 978         Def::Upvar(var_id, index, closure_expr_id) => {
 979             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 980                    var_id,
 981                    index,
 982                    closure_expr_id);
 983             let var_hir_id = cx.tcx.hir().node_to_hir_id(var_id);
 984             let var_ty = cx.tables().node_type(var_hir_id);
 985
 986             // FIXME free regions in closures are not right
 987             let closure_ty = cx.tables()
 988                                .node_type(cx.tcx.hir().node_to_hir_id(closure_expr_id));
 989
 990             // FIXME we're just hard-coding the idea that the
 991             // signature will be &self or &mut self and hence will
 992             // have a bound region with number 0
 993             let closure_def_id = cx.tcx.hir().local_def_id(closure_expr_id);
 994             let region = ty::ReFree(ty::FreeRegion {
 995                 scope: closure_def_id,
 996                 bound_region: ty::BoundRegion::BrAnon(0),
 997             });
 998             let region = cx.tcx.mk_region(region);
 999
1000             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
1001                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
1002                     ty::ClosureKind::Fn => {
1003                         let ref_closure_ty = cx.tcx.mk_ref(region,
1004                                                            ty::TypeAndMut {
1005                                                                ty: closure_ty,
1006                                                                mutbl: hir::MutImmutable,
1007                                                            });
1008                         Expr {
1009                             ty: closure_ty,
1010                             temp_lifetime: temp_lifetime,
1011                             span: expr.span,
1012                             kind: ExprKind::Deref {
1013                                 arg: Expr {
1014                                     ty: ref_closure_ty,
1015                                     temp_lifetime,
1016                                     span: expr.span,
1017                                     kind: ExprKind::SelfRef,
1018                                 }
1019                                 .to_ref(),
1020                             },
1021                         }
1022                     }
1023                     ty::ClosureKind::FnMut => {
1024                         let ref_closure_ty = cx.tcx.mk_ref(region,
1025                                                            ty::TypeAndMut {
1026                                                                ty: closure_ty,
1027                                                                mutbl: hir::MutMutable,
1028                                                            });
1029                         Expr {
1030                             ty: closure_ty,
1031                             temp_lifetime,
1032                             span: expr.span,
1033                             kind: ExprKind::Deref {
1034                                 arg: Expr {
1035                                     ty: ref_closure_ty,
1036                                     temp_lifetime,
1037                                     span: expr.span,
1038                                     kind: ExprKind::SelfRef,
1039                                 }.to_ref(),
1040                             },
1041                         }
1042                     }
1043                     ty::ClosureKind::FnOnce => {
1044                         Expr {
1045                             ty: closure_ty,
1046                             temp_lifetime,
1047                             span: expr.span,
1048                             kind: ExprKind::SelfRef,
1049                         }
1050                     }
1051                 }
1052             } else {
1053                 Expr {
1054                     ty: closure_ty,
1055                     temp_lifetime,
1056                     span: expr.span,
1057                     kind: ExprKind::SelfRef,
1058                 }
1059             };
1060
1061             // at this point we have `self.n`, which loads up the upvar
1062             let field_kind = ExprKind::Field {
1063                 lhs: self_expr.to_ref(),
1064                 name: Field::new(index),
1065             };
1066
1067             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1068             // point we need an implicit deref
1069             let upvar_id = ty::UpvarId {
1070                 var_path: ty::UpvarPath {hir_id: var_hir_id},
1071                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1072             };
1073             match cx.tables().upvar_capture(upvar_id) {
1074                 ty::UpvarCapture::ByValue => field_kind,
1075                 ty::UpvarCapture::ByRef(borrow) => {
1076                     ExprKind::Deref {
1077                         arg: Expr {
1078                             temp_lifetime,
1079                             ty: cx.tcx.mk_ref(borrow.region,
1080                                               ty::TypeAndMut {
1081                                                   ty: var_ty,
1082                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1083                                               }),
1084                             span: expr.span,
1085                             kind: field_kind,
1086                         }.to_ref(),
1087                     }
1088                 }
1089             }
1090         }
1091
1092         _ => span_bug!(expr.span, "type of & not region"),
1093     }
1094 }
1095
1096
1097 fn bin_op(op: hir::BinOpKind) -> BinOp {
1098     match op {
1099         hir::BinOpKind::Add => BinOp::Add,
1100         hir::BinOpKind::Sub => BinOp::Sub,
1101         hir::BinOpKind::Mul => BinOp::Mul,
1102         hir::BinOpKind::Div => BinOp::Div,
1103         hir::BinOpKind::Rem => BinOp::Rem,
1104         hir::BinOpKind::BitXor => BinOp::BitXor,
1105         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1106         hir::BinOpKind::BitOr => BinOp::BitOr,
1107         hir::BinOpKind::Shl => BinOp::Shl,
1108         hir::BinOpKind::Shr => BinOp::Shr,
1109         hir::BinOpKind::Eq => BinOp::Eq,
1110         hir::BinOpKind::Lt => BinOp::Lt,
1111         hir::BinOpKind::Le => BinOp::Le,
1112         hir::BinOpKind::Ne => BinOp::Ne,
1113         hir::BinOpKind::Ge => BinOp::Ge,
1114         hir::BinOpKind::Gt => BinOp::Gt,
1115         _ => bug!("no equivalent for ast binop {:?}", op),
1116     }
1117 }
1118
1119 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1120                                        expr: &'tcx hir::Expr,
1121                                        args: Vec<ExprRef<'tcx>>)
1122                                        -> ExprKind<'tcx> {
1123     let fun = method_callee(cx, expr, expr.span, None);
1124     ExprKind::Call {
1125         ty: fun.ty,
1126         fun: fun.to_ref(),
1127         args,
1128         from_hir_call: false,
1129     }
1130 }
1131
1132 fn overloaded_place<'a, 'gcx, 'tcx>(
1133     cx: &mut Cx<'a, 'gcx, 'tcx>,
1134     expr: &'tcx hir::Expr,
1135     place_ty: Ty<'tcx>,
1136     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
1137     args: Vec<ExprRef<'tcx>>,
1138 ) -> ExprKind<'tcx> {
1139     // For an overloaded *x or x[y] expression of type T, the method
1140     // call returns an &T and we must add the deref so that the types
1141     // line up (this is because `*x` and `x[y]` represent places):
1142
1143     let recv_ty = match args[0] {
1144         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1145         ExprRef::Mirror(ref e) => e.ty
1146     };
1147
1148     // Reconstruct the output assuming it's a reference with the
1149     // same region and mutability as the receiver. This holds for
1150     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1151     let (region, mutbl) = match recv_ty.sty {
1152         ty::Ref(region, _, mutbl) => (region, mutbl),
1153         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1154     };
1155     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1156         ty: place_ty,
1157         mutbl,
1158     });
1159
1160     // construct the complete expression `foo()` for the overloaded call,
1161     // which will yield the &T type
1162     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1163     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1164     let ref_expr = Expr {
1165         temp_lifetime,
1166         ty: ref_ty,
1167         span: expr.span,
1168         kind: ExprKind::Call {
1169             ty: fun.ty,
1170             fun: fun.to_ref(),
1171             args,
1172             from_hir_call: false,
1173         },
1174     };
1175
1176     // construct and return a deref wrapper `*foo()`
1177     ExprKind::Deref { arg: ref_expr.to_ref() }
1178 }
1179
1180 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1181                                    closure_expr: &'tcx hir::Expr,
1182                                    freevar: &hir::Freevar,
1183                                    freevar_ty: Ty<'tcx>)
1184                                    -> ExprRef<'tcx> {
1185     let var_hir_id = cx.tcx.hir().node_to_hir_id(freevar.var_id());
1186     let upvar_id = ty::UpvarId {
1187         var_path: ty::UpvarPath { hir_id: var_hir_id },
1188         closure_expr_id: cx.tcx.hir().local_def_id_from_hir_id(closure_expr.hir_id).to_local(),
1189     };
1190     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1191     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1192     let var_ty = cx.tables().node_type(var_hir_id);
1193     let captured_var = Expr {
1194         temp_lifetime,
1195         ty: var_ty,
1196         span: closure_expr.span,
1197         kind: convert_var(cx, closure_expr, freevar.def),
1198     };
1199     match upvar_capture {
1200         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1201         ty::UpvarCapture::ByRef(upvar_borrow) => {
1202             let borrow_kind = match upvar_borrow.kind {
1203                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1204                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1205                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1206             };
1207             Expr {
1208                 temp_lifetime,
1209                 ty: freevar_ty,
1210                 span: closure_expr.span,
1211                 kind: ExprKind::Borrow {
1212                     borrow_kind,
1213                     arg: captured_var.to_ref(),
1214                 },
1215             }.to_ref()
1216         }
1217     }
1218 }
1219
1220 /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExprRef.
1221 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1222                               fields: &'tcx [hir::Field])
1223                               -> Vec<FieldExprRef<'tcx>> {
1224     fields.iter()
1225         .map(|field| {
1226             FieldExprRef {
1227                 name: Field::new(cx.tcx.field_index(field.hir_id, cx.tables)),
1228                 expr: field.expr.to_ref(),
1229             }
1230         })
1231         .collect()
1232 }