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::{CtorOf, Def, CtorKind};
   8 use rustc::mir::interpret::{GlobalId, ErrorHandled, ConstValue};
   9 use rustc::ty::{self, AdtKind, Ty};
  10 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability, PointerCast};
  11 use rustc::ty::subst::{InternalSubsts, SubstsRef};
  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: LintLevel::Explicit(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::Pointer(PointerCast::ReifyFnPointer) => {
  79             ExprKind::ReifyFnPointer { source: expr.to_ref() }
  80         }
  81         Adjust::Pointer(PointerCast::UnsafeFnPointer) => {
  82             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
  83         }
  84         Adjust::Pointer(PointerCast::ClosureFnPointer(unsafety)) => {
  85             ExprKind::ClosureFnPointer { source: expr.to_ref(), unsafety }
  86         }
  87         Adjust::NeverToAny => {
  88             ExprKind::NeverToAny { source: expr.to_ref() }
  89         }
  90         Adjust::Pointer(PointerCast::MutToConstPointer) => {
  91             ExprKind::MutToConstPointer { 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::Pointer(PointerCast::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::Ctor(ctor_id, _, CtorKind::Fn) =>
 265                                 Some((adt_def, adt_def.variant_index_with_ctor_id(ctor_id))),
 266                             Def::SelfCtor(..) => Some((adt_def, VariantIdx::new(0))),
 267                             _ => None,
 268                         }
 269                     })
 270                 } else {
 271                     None
 272                 };
 273                 if let Some((adt_def, index)) = adt_data {
 274                     let substs = cx.tables().node_substs(fun.hir_id);
 275                     let user_provided_types = cx.tables().user_provided_types();
 276                     let user_ty = user_provided_types.get(fun.hir_id)
 277                         .map(|u_ty| *u_ty)
 278                         .map(|mut u_ty| {
 279                             if let UserType::TypeOf(ref mut did, _) = &mut u_ty.value {
 280                                 *did = adt_def.did;
 281                             }
 282                             u_ty
 283                         });
 284                     debug!("make_mirror_unadjusted: (call) user_ty={:?}", user_ty);
 285
 286                     let field_refs = args.iter()
 287                         .enumerate()
 288                         .map(|(idx, e)| {
 289                             FieldExprRef {
 290                                 name: Field::new(idx),
 291                                 expr: e.to_ref(),
 292                             }
 293                         })
 294                         .collect();
 295                     ExprKind::Adt {
 296                         adt_def,
 297                         substs,
 298                         variant_index: index,
 299                         fields: field_refs,
 300                         user_ty,
 301                         base: None,
 302                     }
 303                 } else {
 304                     ExprKind::Call {
 305                         ty: cx.tables().node_type(fun.hir_id),
 306                         fun: fun.to_ref(),
 307                         args: args.to_ref(),
 308                         from_hir_call: true,
 309                     }
 310                 }
 311             }
 312         }
 313
 314         hir::ExprKind::AddrOf(mutbl, ref expr) => {
 315             ExprKind::Borrow {
 316                 borrow_kind: mutbl.to_borrow_kind(),
 317                 arg: expr.to_ref(),
 318             }
 319         }
 320
 321         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
 322
 323         hir::ExprKind::Assign(ref lhs, ref rhs) => {
 324             ExprKind::Assign {
 325                 lhs: lhs.to_ref(),
 326                 rhs: rhs.to_ref(),
 327             }
 328         }
 329
 330         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 331             if cx.tables().is_method_call(expr) {
 332                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 333             } else {
 334                 ExprKind::AssignOp {
 335                     op: bin_op(op.node),
 336                     lhs: lhs.to_ref(),
 337                     rhs: rhs.to_ref(),
 338                 }
 339             }
 340         }
 341
 342         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 343             literal: cx.tcx.mk_const(
 344                 cx.const_eval_literal(&lit.node, expr_ty, lit.span, false)
 345             ),
 346             user_ty: None,
 347         },
 348
 349         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 350             if cx.tables().is_method_call(expr) {
 351                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 352             } else {
 353                 // FIXME overflow
 354                 match (op.node, cx.constness) {
 355                     // FIXME(eddyb) use logical ops in constants when
 356                     // they can handle that kind of control-flow.
 357                     (hir::BinOpKind::And, hir::Constness::Const) => {
 358                         cx.control_flow_destroyed.push((
 359                             op.span,
 360                             "`&&` operator".into(),
 361                         ));
 362                         ExprKind::Binary {
 363                             op: BinOp::BitAnd,
 364                             lhs: lhs.to_ref(),
 365                             rhs: rhs.to_ref(),
 366                         }
 367                     }
 368                     (hir::BinOpKind::Or, hir::Constness::Const) => {
 369                         cx.control_flow_destroyed.push((
 370                             op.span,
 371                             "`||` operator".into(),
 372                         ));
 373                         ExprKind::Binary {
 374                             op: BinOp::BitOr,
 375                             lhs: lhs.to_ref(),
 376                             rhs: rhs.to_ref(),
 377                         }
 378                     }
 379
 380                     (hir::BinOpKind::And, hir::Constness::NotConst) => {
 381                         ExprKind::LogicalOp {
 382                             op: LogicalOp::And,
 383                             lhs: lhs.to_ref(),
 384                             rhs: rhs.to_ref(),
 385                         }
 386                     }
 387                     (hir::BinOpKind::Or, hir::Constness::NotConst) => {
 388                         ExprKind::LogicalOp {
 389                             op: LogicalOp::Or,
 390                             lhs: lhs.to_ref(),
 391                             rhs: rhs.to_ref(),
 392                         }
 393                     }
 394
 395                     _ => {
 396                         let op = bin_op(op.node);
 397                         ExprKind::Binary {
 398                             op,
 399                             lhs: lhs.to_ref(),
 400                             rhs: rhs.to_ref(),
 401                         }
 402                     }
 403                 }
 404             }
 405         }
 406
 407         hir::ExprKind::Index(ref lhs, ref index) => {
 408             if cx.tables().is_method_call(expr) {
 409                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 410             } else {
 411                 ExprKind::Index {
 412                     lhs: lhs.to_ref(),
 413                     index: index.to_ref(),
 414                 }
 415             }
 416         }
 417
 418         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
 419             if cx.tables().is_method_call(expr) {
 420                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
 421             } else {
 422                 ExprKind::Deref { arg: arg.to_ref() }
 423             }
 424         }
 425
 426         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
 427             if cx.tables().is_method_call(expr) {
 428                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 429             } else {
 430                 ExprKind::Unary {
 431                     op: UnOp::Not,
 432                     arg: arg.to_ref(),
 433                 }
 434             }
 435         }
 436
 437         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
 438             if cx.tables().is_method_call(expr) {
 439                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 440             } else {
 441                 if let hir::ExprKind::Lit(ref lit) = arg.node {
 442                     ExprKind::Literal {
 443                         literal: cx.tcx.mk_const(
 444                             cx.const_eval_literal(&lit.node, expr_ty, lit.span, true)
 445                         ),
 446                         user_ty: None,
 447                     }
 448                 } else {
 449                     ExprKind::Unary {
 450                         op: UnOp::Neg,
 451                         arg: arg.to_ref(),
 452                     }
 453                 }
 454             }
 455         }
 456
 457         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => {
 458             match expr_ty.sty {
 459                 ty::Adt(adt, substs) => {
 460                     match adt.adt_kind() {
 461                         AdtKind::Struct | AdtKind::Union => {
 462                             let user_provided_types = cx.tables().user_provided_types();
 463                             let user_ty = user_provided_types.get(expr.hir_id).map(|u_ty| *u_ty);
 464                             debug!("make_mirror_unadjusted: (struct/union) user_ty={:?}", user_ty);
 465                             ExprKind::Adt {
 466                                 adt_def: adt,
 467                                 variant_index: VariantIdx::new(0),
 468                                 substs,
 469                                 user_ty,
 470                                 fields: field_refs(cx, fields),
 471                                 base: base.as_ref().map(|base| {
 472                                     FruInfo {
 473                                         base: base.to_ref(),
 474                                         field_types: cx.tables()
 475                                                        .fru_field_types()[expr.hir_id]
 476                                                        .clone(),
 477                                     }
 478                                 }),
 479                             }
 480                         }
 481                         AdtKind::Enum => {
 482                             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 483                             match def {
 484                                 Def::Variant(variant_id) => {
 485                                     assert!(base.is_none());
 486
 487                                     let index = adt.variant_index_with_id(variant_id);
 488                                     let user_provided_types = cx.tables().user_provided_types();
 489                                     let user_ty = user_provided_types.get(expr.hir_id)
 490                                         .map(|u_ty| *u_ty);
 491                                     debug!(
 492                                         "make_mirror_unadjusted: (variant) user_ty={:?}",
 493                                         user_ty
 494                                     );
 495                                     ExprKind::Adt {
 496                                         adt_def: adt,
 497                                         variant_index: index,
 498                                         substs,
 499                                         user_ty,
 500                                         fields: field_refs(cx, fields),
 501                                         base: None,
 502                                     }
 503                                 }
 504                                 _ => {
 505                                     span_bug!(expr.span, "unexpected def: {:?}", def);
 506                                 }
 507                             }
 508                         }
 509                     }
 510                 }
 511                 _ => {
 512                     span_bug!(expr.span,
 513                               "unexpected type for struct literal: {:?}",
 514                               expr_ty);
 515                 }
 516             }
 517         }
 518
 519         hir::ExprKind::Closure(..) => {
 520             let closure_ty = cx.tables().expr_ty(expr);
 521             let (def_id, substs, movability) = match closure_ty.sty {
 522                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 523                 ty::Generator(def_id, substs, movability) => {
 524                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
 525                 }
 526                 _ => {
 527                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 528                 }
 529             };
 530             let upvars = cx.tcx.with_freevars(expr.hir_id, |freevars| {
 531                 freevars.iter()
 532                     .zip(substs.upvar_tys(def_id, cx.tcx))
 533                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 534                     .collect()
 535             });
 536             ExprKind::Closure {
 537                 closure_id: def_id,
 538                 substs,
 539                 upvars,
 540                 movability,
 541             }
 542         }
 543
 544         hir::ExprKind::Path(ref qpath) => {
 545             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 546             convert_path_expr(cx, expr, def)
 547         }
 548
 549         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
 550             ExprKind::InlineAsm {
 551                 asm,
 552                 outputs: outputs.to_ref(),
 553                 inputs: inputs.to_ref(),
 554             }
 555         }
 556
 557         // Now comes the rote stuff:
 558         hir::ExprKind::Repeat(ref v, ref count) => {
 559             let def_id = cx.tcx.hir().local_def_id_from_hir_id(count.hir_id);
 560             let substs = InternalSubsts::identity_for_item(cx.tcx.global_tcx(), def_id);
 561             let instance = ty::Instance::resolve(
 562                 cx.tcx.global_tcx(),
 563                 cx.param_env,
 564                 def_id,
 565                 substs,
 566             ).unwrap();
 567             let global_id = GlobalId {
 568                 instance,
 569                 promoted: None
 570             };
 571             let span = cx.tcx.def_span(def_id);
 572             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
 573                 Ok(cv) => cv.unwrap_usize(cx.tcx),
 574                 Err(ErrorHandled::Reported) => 0,
 575                 Err(ErrorHandled::TooGeneric) => {
 576                     cx.tcx.sess.span_err(span, "array lengths can't depend on generic parameters");
 577                     0
 578                 },
 579             };
 580
 581             ExprKind::Repeat {
 582                 value: v.to_ref(),
 583                 count,
 584             }
 585         }
 586         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 587         hir::ExprKind::Break(dest, ref value) => {
 588             match dest.target_id {
 589                 Ok(target_id) => ExprKind::Break {
 590                     label: region::Scope {
 591                         id: target_id.local_id,
 592                         data: region::ScopeData::Node
 593                     },
 594                     value: value.to_ref(),
 595                 },
 596                 Err(err) => bug!("invalid loop id for break: {}", err)
 597             }
 598         }
 599         hir::ExprKind::Continue(dest) => {
 600             match dest.target_id {
 601                 Ok(loop_id) => ExprKind::Continue {
 602                     label: region::Scope {
 603                         id: loop_id.local_id,
 604                         data: region::ScopeData::Node
 605                     },
 606                 },
 607                 Err(err) => bug!("invalid loop id for continue: {}", err)
 608             }
 609         }
 610         hir::ExprKind::Match(ref discr, ref arms, _) => {
 611             ExprKind::Match {
 612                 scrutinee: discr.to_ref(),
 613                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 614             }
 615         }
 616         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
 617             ExprKind::If {
 618                 condition: cond.to_ref(),
 619                 then: then.to_ref(),
 620                 otherwise: otherwise.to_ref(),
 621             }
 622         }
 623         hir::ExprKind::While(ref cond, ref body, _) => {
 624             ExprKind::Loop {
 625                 condition: Some(cond.to_ref()),
 626                 body: block::to_expr_ref(cx, body),
 627             }
 628         }
 629         hir::ExprKind::Loop(ref body, _, _) => {
 630             ExprKind::Loop {
 631                 condition: None,
 632                 body: block::to_expr_ref(cx, body),
 633             }
 634         }
 635         hir::ExprKind::Field(ref source, ..) => {
 636             ExprKind::Field {
 637                 lhs: source.to_ref(),
 638                 name: Field::new(cx.tcx.field_index(expr.hir_id, cx.tables)),
 639             }
 640         }
 641         hir::ExprKind::Cast(ref source, ref cast_ty) => {
 642             // Check for a user-given type annotation on this `cast`
 643             let user_provided_types = cx.tables.user_provided_types();
 644             let user_ty = user_provided_types.get(cast_ty.hir_id);
 645
 646             debug!(
 647                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 648                 expr,
 649                 cast_ty.hir_id,
 650                 user_ty,
 651             );
 652
 653             // Check to see if this cast is a "coercion cast", where the cast is actually done
 654             // using a coercion (or is a no-op).
 655             let cast = if cx.tables().is_coercion_cast(source.hir_id) {
 656                 // Convert the lexpr to a vexpr.
 657                 ExprKind::Use { source: source.to_ref() }
 658             } else {
 659                 // check whether this is casting an enum variant discriminant
 660                 // to prevent cycles, we refer to the discriminant initializer
 661                 // which is always an integer and thus doesn't need to know the
 662                 // enum's layout (or its tag type) to compute it during const eval
 663                 // Example:
 664                 // enum Foo {
 665                 //     A,
 666                 //     B = A as isize + 4,
 667                 // }
 668                 // The correct solution would be to add symbolic computations to miri,
 669                 // so we wouldn't have to compute and store the actual value
 670                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 671                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 672                     cx
 673                         .tables()
 674                         .node_type(source.hir_id)
 675                         .ty_adt_def()
 676                         .and_then(|adt_def| {
 677                         match def {
 678                             Def::Ctor(variant_ctor_id, CtorOf::Variant, CtorKind::Const) => {
 679                                 let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
 680                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 681                                 use rustc::ty::util::IntTypeExt;
 682                                 let ty = adt_def.repr.discr_type();
 683                                 let ty = ty.to_ty(cx.tcx());
 684                                 Some((d, o, ty))
 685                             }
 686                             _ => None,
 687                         }
 688                     })
 689                 } else {
 690                     None
 691                 };
 692
 693                 let source = if let Some((did, offset, var_ty)) = var {
 694                     let mk_const = |literal| Expr {
 695                         temp_lifetime,
 696                         ty: var_ty,
 697                         span: expr.span,
 698                         kind: ExprKind::Literal {
 699                             literal: cx.tcx.mk_const(literal),
 700                             user_ty: None
 701                         },
 702                     }.to_ref();
 703                     let offset = mk_const(ty::Const::from_bits(
 704                         cx.tcx,
 705                         offset as u128,
 706                         cx.param_env.and(var_ty),
 707                     ));
 708                     match did {
 709                         Some(did) => {
 710                             // in case we are offsetting from a computed discriminant
 711                             // and not the beginning of discriminants (which is always `0`)
 712                             let substs = InternalSubsts::identity_for_item(cx.tcx(), did);
 713                             let lhs = mk_const(ty::Const {
 714                                 val: ConstValue::Unevaluated(did, substs),
 715                                 ty: var_ty,
 716                             });
 717                             let bin = ExprKind::Binary {
 718                                 op: BinOp::Add,
 719                                 lhs,
 720                                 rhs: offset,
 721                             };
 722                             Expr {
 723                                 temp_lifetime,
 724                                 ty: var_ty,
 725                                 span: expr.span,
 726                                 kind: bin,
 727                             }.to_ref()
 728                         },
 729                         None => offset,
 730                     }
 731                 } else {
 732                     source.to_ref()
 733                 };
 734
 735                 ExprKind::Cast { source }
 736             };
 737
 738             if let Some(user_ty) = user_ty {
 739                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 740                 //       inefficient, revisit this when performance becomes an issue.
 741                 let cast_expr = Expr {
 742                     temp_lifetime,
 743                     ty: expr_ty,
 744                     span: expr.span,
 745                     kind: cast,
 746                 };
 747                 debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
 748
 749                 ExprKind::ValueTypeAscription {
 750                     source: cast_expr.to_ref(),
 751                     user_ty: Some(*user_ty),
 752                 }
 753             } else {
 754                 cast
 755             }
 756         }
 757         hir::ExprKind::Type(ref source, ref ty) => {
 758             let user_provided_types = cx.tables.user_provided_types();
 759             let user_ty = user_provided_types.get(ty.hir_id).map(|u_ty| *u_ty);
 760             debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
 761             if source.is_place_expr() {
 762                 ExprKind::PlaceTypeAscription {
 763                     source: source.to_ref(),
 764                     user_ty,
 765                 }
 766             } else {
 767                 ExprKind::ValueTypeAscription {
 768                     source: source.to_ref(),
 769                     user_ty,
 770                 }
 771             }
 772         }
 773         hir::ExprKind::Box(ref value) => {
 774             ExprKind::Box {
 775                 value: value.to_ref(),
 776             }
 777         }
 778         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 779         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 780
 781         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 782         hir::ExprKind::Err => unreachable!(),
 783     };
 784
 785     Expr {
 786         temp_lifetime,
 787         ty: expr_ty,
 788         span: expr.span,
 789         kind,
 790     }
 791 }
 792
 793 fn user_substs_applied_to_def(
 794     cx: &mut Cx<'a, 'gcx, 'tcx>,
 795     hir_id: hir::HirId,
 796     def: &Def,
 797 ) -> Option<ty::CanonicalUserType<'tcx>> {
 798     debug!("user_substs_applied_to_def: def={:?}", def);
 799     let user_provided_type = match def {
 800         // A reference to something callable -- e.g., a fn, method, or
 801         // a tuple-struct or tuple-variant. This has the type of a
 802         // `Fn` but with the user-given substitutions.
 803         Def::Fn(_) |
 804         Def::Method(_) |
 805         Def::Ctor(_, _, CtorKind::Fn) |
 806         Def::Const(_) |
 807         Def::AssociatedConst(_) => cx.tables().user_provided_types().get(hir_id).map(|u_ty| *u_ty),
 808
 809         // A unit struct/variant which is used as a value (e.g.,
 810         // `None`). This has the type of the enum/struct that defines
 811         // this variant -- but with the substitutions given by the
 812         // user.
 813         Def::Ctor(_, _, CtorKind::Const) =>
 814             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 815
 816         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 817         Def::SelfCtor(_) =>
 818             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 819
 820         _ =>
 821             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
 822     };
 823     debug!("user_substs_applied_to_def: user_provided_type={:?}", user_provided_type);
 824     user_provided_type
 825 }
 826
 827 fn method_callee<'a, 'gcx, 'tcx>(
 828     cx: &mut Cx<'a, 'gcx, 'tcx>,
 829     expr: &hir::Expr,
 830     span: Span,
 831     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 832 ) -> Expr<'tcx> {
 833     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 834     let (def_id, substs, user_ty) = match overloaded_callee {
 835         Some((def_id, substs)) => (def_id, substs, None),
 836         None => {
 837             let def = cx.tables().type_dependent_def(expr.hir_id)
 838                 .unwrap_or_else(|| {
 839                     span_bug!(expr.span, "no type-dependent def for method callee")
 840                 });
 841             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 842             debug!("method_callee: user_ty={:?}", user_ty);
 843             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 844         }
 845     };
 846     let ty = cx.tcx().mk_fn_def(def_id, substs);
 847     Expr {
 848         temp_lifetime,
 849         ty,
 850         span,
 851         kind: ExprKind::Literal {
 852             literal: cx.tcx().mk_const(
 853                 ty::Const::zero_sized(ty)
 854             ),
 855             user_ty,
 856         },
 857     }
 858 }
 859
 860 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 861
 862 impl ToBorrowKind for AutoBorrowMutability {
 863     fn to_borrow_kind(&self) -> BorrowKind {
 864         use rustc::ty::adjustment::AllowTwoPhase;
 865         match *self {
 866             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 867                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 868                     AllowTwoPhase::Yes => true,
 869                     AllowTwoPhase::No => false
 870                 }},
 871             AutoBorrowMutability::Immutable =>
 872                 BorrowKind::Shared,
 873         }
 874     }
 875 }
 876
 877 impl ToBorrowKind for hir::Mutability {
 878     fn to_borrow_kind(&self) -> BorrowKind {
 879         match *self {
 880             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 881             hir::MutImmutable => BorrowKind::Shared,
 882         }
 883     }
 884 }
 885
 886 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 887     Arm {
 888         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 889         guard: match arm.guard {
 890                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 891                 _ => None,
 892             },
 893         body: arm.body.to_ref(),
 894         // BUG: fix this
 895         lint_level: LintLevel::Inherited,
 896     }
 897 }
 898
 899 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 900                                      expr: &'tcx hir::Expr,
 901                                      def: Def)
 902                                      -> ExprKind<'tcx> {
 903     let substs = cx.tables().node_substs(expr.hir_id);
 904     match def {
 905         // A regular function, constructor function or a constant.
 906         Def::Fn(_) |
 907         Def::Method(_) |
 908         Def::Ctor(_, _, CtorKind::Fn) |
 909         Def::SelfCtor(..) => {
 910             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 911             debug!("convert_path_expr: user_ty={:?}", user_ty);
 912             ExprKind::Literal {
 913                 literal: cx.tcx.mk_const(ty::Const::zero_sized(
 914                     cx.tables().node_type(expr.hir_id),
 915                 )),
 916                 user_ty,
 917             }
 918         }
 919
 920         Def::ConstParam(def_id) => {
 921             let node_id = cx.tcx.hir().as_local_node_id(def_id).unwrap();
 922             let item_id = cx.tcx.hir().get_parent_node(node_id);
 923             let item_def_id = cx.tcx.hir().local_def_id(item_id);
 924             let generics = cx.tcx.generics_of(item_def_id);
 925             let index = generics.param_def_id_to_index[&cx.tcx.hir().local_def_id(node_id)];
 926             let name = cx.tcx.hir().name(node_id).as_interned_str();
 927             let val = ConstValue::Param(ty::ParamConst::new(index, name));
 928             ExprKind::Literal {
 929                 literal: cx.tcx.mk_const(
 930                     ty::Const {
 931                         val,
 932                         ty: cx.tables().node_type(expr.hir_id),
 933                     }
 934                 ),
 935                 user_ty: None,
 936             }
 937         }
 938
 939         Def::Const(def_id) |
 940         Def::AssociatedConst(def_id) => {
 941             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 942             debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
 943             ExprKind::Literal {
 944                 literal: cx.tcx.mk_const(ty::Const {
 945                     val: ConstValue::Unevaluated(def_id, substs),
 946                     ty: cx.tcx.type_of(def_id),
 947                 }),
 948                 user_ty,
 949             }
 950         },
 951
 952         Def::Ctor(def_id, _, CtorKind::Const) => {
 953             let user_provided_types = cx.tables.user_provided_types();
 954             let user_provided_type = user_provided_types.get(expr.hir_id).map(|u_ty| *u_ty);
 955             debug!("convert_path_expr: user_provided_type={:?}", user_provided_type);
 956             let ty = cx.tables().node_type(expr.hir_id);
 957             match ty.sty {
 958                 // A unit struct/variant which is used as a value.
 959                 // We return a completely different ExprKind here to account for this special case.
 960                 ty::Adt(adt_def, substs) => {
 961                     ExprKind::Adt {
 962                         adt_def,
 963                         variant_index: adt_def.variant_index_with_ctor_id(def_id),
 964                         substs,
 965                         user_ty: user_provided_type,
 966                         fields: vec![],
 967                         base: None,
 968                     }
 969                 }
 970                 _ => bug!("unexpected ty: {:?}", ty),
 971             }
 972         }
 973
 974         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 975
 976         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 977
 978         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 979     }
 980 }
 981
 982 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 983                                expr: &'tcx hir::Expr,
 984                                def: Def)
 985                                -> ExprKind<'tcx> {
 986     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 987
 988     match def {
 989         Def::Local(id) => ExprKind::VarRef { id: cx.tcx.hir().node_to_hir_id(id) },
 990
 991         Def::Upvar(var_id, index, closure_expr_id) => {
 992             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 993                    var_id,
 994                    index,
 995                    closure_expr_id);
 996             let var_hir_id = cx.tcx.hir().node_to_hir_id(var_id);
 997             let var_ty = cx.tables().node_type(var_hir_id);
 998
 999             // FIXME free regions in closures are not right
1000             let closure_ty = cx.tables()
1001                                .node_type(cx.tcx.hir().node_to_hir_id(closure_expr_id));
1002
1003             // FIXME we're just hard-coding the idea that the
1004             // signature will be &self or &mut self and hence will
1005             // have a bound region with number 0
1006             let closure_def_id = cx.tcx.hir().local_def_id(closure_expr_id);
1007             let region = ty::ReFree(ty::FreeRegion {
1008                 scope: closure_def_id,
1009                 bound_region: ty::BoundRegion::BrAnon(0),
1010             });
1011             let region = cx.tcx.mk_region(region);
1012
1013             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
1014                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
1015                     ty::ClosureKind::Fn => {
1016                         let ref_closure_ty = cx.tcx.mk_ref(region,
1017                                                            ty::TypeAndMut {
1018                                                                ty: closure_ty,
1019                                                                mutbl: hir::MutImmutable,
1020                                                            });
1021                         Expr {
1022                             ty: closure_ty,
1023                             temp_lifetime: temp_lifetime,
1024                             span: expr.span,
1025                             kind: ExprKind::Deref {
1026                                 arg: Expr {
1027                                     ty: ref_closure_ty,
1028                                     temp_lifetime,
1029                                     span: expr.span,
1030                                     kind: ExprKind::SelfRef,
1031                                 }
1032                                 .to_ref(),
1033                             },
1034                         }
1035                     }
1036                     ty::ClosureKind::FnMut => {
1037                         let ref_closure_ty = cx.tcx.mk_ref(region,
1038                                                            ty::TypeAndMut {
1039                                                                ty: closure_ty,
1040                                                                mutbl: hir::MutMutable,
1041                                                            });
1042                         Expr {
1043                             ty: closure_ty,
1044                             temp_lifetime,
1045                             span: expr.span,
1046                             kind: ExprKind::Deref {
1047                                 arg: Expr {
1048                                     ty: ref_closure_ty,
1049                                     temp_lifetime,
1050                                     span: expr.span,
1051                                     kind: ExprKind::SelfRef,
1052                                 }.to_ref(),
1053                             },
1054                         }
1055                     }
1056                     ty::ClosureKind::FnOnce => {
1057                         Expr {
1058                             ty: closure_ty,
1059                             temp_lifetime,
1060                             span: expr.span,
1061                             kind: ExprKind::SelfRef,
1062                         }
1063                     }
1064                 }
1065             } else {
1066                 Expr {
1067                     ty: closure_ty,
1068                     temp_lifetime,
1069                     span: expr.span,
1070                     kind: ExprKind::SelfRef,
1071                 }
1072             };
1073
1074             // at this point we have `self.n`, which loads up the upvar
1075             let field_kind = ExprKind::Field {
1076                 lhs: self_expr.to_ref(),
1077                 name: Field::new(index),
1078             };
1079
1080             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1081             // point we need an implicit deref
1082             let upvar_id = ty::UpvarId {
1083                 var_path: ty::UpvarPath {hir_id: var_hir_id},
1084                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1085             };
1086             match cx.tables().upvar_capture(upvar_id) {
1087                 ty::UpvarCapture::ByValue => field_kind,
1088                 ty::UpvarCapture::ByRef(borrow) => {
1089                     ExprKind::Deref {
1090                         arg: Expr {
1091                             temp_lifetime,
1092                             ty: cx.tcx.mk_ref(borrow.region,
1093                                               ty::TypeAndMut {
1094                                                   ty: var_ty,
1095                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1096                                               }),
1097                             span: expr.span,
1098                             kind: field_kind,
1099                         }.to_ref(),
1100                     }
1101                 }
1102             }
1103         }
1104
1105         _ => span_bug!(expr.span, "type of & not region"),
1106     }
1107 }
1108
1109
1110 fn bin_op(op: hir::BinOpKind) -> BinOp {
1111     match op {
1112         hir::BinOpKind::Add => BinOp::Add,
1113         hir::BinOpKind::Sub => BinOp::Sub,
1114         hir::BinOpKind::Mul => BinOp::Mul,
1115         hir::BinOpKind::Div => BinOp::Div,
1116         hir::BinOpKind::Rem => BinOp::Rem,
1117         hir::BinOpKind::BitXor => BinOp::BitXor,
1118         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1119         hir::BinOpKind::BitOr => BinOp::BitOr,
1120         hir::BinOpKind::Shl => BinOp::Shl,
1121         hir::BinOpKind::Shr => BinOp::Shr,
1122         hir::BinOpKind::Eq => BinOp::Eq,
1123         hir::BinOpKind::Lt => BinOp::Lt,
1124         hir::BinOpKind::Le => BinOp::Le,
1125         hir::BinOpKind::Ne => BinOp::Ne,
1126         hir::BinOpKind::Ge => BinOp::Ge,
1127         hir::BinOpKind::Gt => BinOp::Gt,
1128         _ => bug!("no equivalent for ast binop {:?}", op),
1129     }
1130 }
1131
1132 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1133                                        expr: &'tcx hir::Expr,
1134                                        args: Vec<ExprRef<'tcx>>)
1135                                        -> ExprKind<'tcx> {
1136     let fun = method_callee(cx, expr, expr.span, None);
1137     ExprKind::Call {
1138         ty: fun.ty,
1139         fun: fun.to_ref(),
1140         args,
1141         from_hir_call: false,
1142     }
1143 }
1144
1145 fn overloaded_place<'a, 'gcx, 'tcx>(
1146     cx: &mut Cx<'a, 'gcx, 'tcx>,
1147     expr: &'tcx hir::Expr,
1148     place_ty: Ty<'tcx>,
1149     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
1150     args: Vec<ExprRef<'tcx>>,
1151 ) -> ExprKind<'tcx> {
1152     // For an overloaded *x or x[y] expression of type T, the method
1153     // call returns an &T and we must add the deref so that the types
1154     // line up (this is because `*x` and `x[y]` represent places):
1155
1156     let recv_ty = match args[0] {
1157         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1158         ExprRef::Mirror(ref e) => e.ty
1159     };
1160
1161     // Reconstruct the output assuming it's a reference with the
1162     // same region and mutability as the receiver. This holds for
1163     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1164     let (region, mutbl) = match recv_ty.sty {
1165         ty::Ref(region, _, mutbl) => (region, mutbl),
1166         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1167     };
1168     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1169         ty: place_ty,
1170         mutbl,
1171     });
1172
1173     // construct the complete expression `foo()` for the overloaded call,
1174     // which will yield the &T type
1175     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1176     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1177     let ref_expr = Expr {
1178         temp_lifetime,
1179         ty: ref_ty,
1180         span: expr.span,
1181         kind: ExprKind::Call {
1182             ty: fun.ty,
1183             fun: fun.to_ref(),
1184             args,
1185             from_hir_call: false,
1186         },
1187     };
1188
1189     // construct and return a deref wrapper `*foo()`
1190     ExprKind::Deref { arg: ref_expr.to_ref() }
1191 }
1192
1193 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1194                                    closure_expr: &'tcx hir::Expr,
1195                                    freevar: &hir::Freevar,
1196                                    freevar_ty: Ty<'tcx>)
1197                                    -> ExprRef<'tcx> {
1198     let var_hir_id = cx.tcx.hir().node_to_hir_id(freevar.var_id());
1199     let upvar_id = ty::UpvarId {
1200         var_path: ty::UpvarPath { hir_id: var_hir_id },
1201         closure_expr_id: cx.tcx.hir().local_def_id_from_hir_id(closure_expr.hir_id).to_local(),
1202     };
1203     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1204     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1205     let var_ty = cx.tables().node_type(var_hir_id);
1206     let captured_var = Expr {
1207         temp_lifetime,
1208         ty: var_ty,
1209         span: closure_expr.span,
1210         kind: convert_var(cx, closure_expr, freevar.def),
1211     };
1212     match upvar_capture {
1213         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1214         ty::UpvarCapture::ByRef(upvar_borrow) => {
1215             let borrow_kind = match upvar_borrow.kind {
1216                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1217                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1218                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1219             };
1220             Expr {
1221                 temp_lifetime,
1222                 ty: freevar_ty,
1223                 span: closure_expr.span,
1224                 kind: ExprKind::Borrow {
1225                     borrow_kind,
1226                     arg: captured_var.to_ref(),
1227                 },
1228             }.to_ref()
1229         }
1230     }
1231 }
1232
1233 /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExprRef.
1234 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1235                               fields: &'tcx [hir::Field])
1236                               -> Vec<FieldExprRef<'tcx>> {
1237     fields.iter()
1238         .map(|field| {
1239             FieldExprRef {
1240                 name: Field::new(cx.tcx.field_index(field.hir_id, cx.tables)),
1241                 expr: field.expr.to_ref(),
1242             }
1243         })
1244         .collect()
1245 }