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, ConstValue};
   9 use rustc::ty::{self, AdtKind, Ty};
  10 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability};
  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::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::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::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_const(
 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_const(
 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 upvars = cx.tcx.with_freevars(expr.hir_id, |freevars| {
 533                 freevars.iter()
 534                     .zip(substs.upvar_tys(def_id, cx.tcx))
 535                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 536                     .collect()
 537             });
 538             ExprKind::Closure {
 539                 closure_id: def_id,
 540                 substs,
 541                 upvars,
 542                 movability,
 543             }
 544         }
 545
 546         hir::ExprKind::Path(ref qpath) => {
 547             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 548             convert_path_expr(cx, expr, def)
 549         }
 550
 551         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
 552             ExprKind::InlineAsm {
 553                 asm,
 554                 outputs: outputs.to_ref(),
 555                 inputs: inputs.to_ref(),
 556             }
 557         }
 558
 559         // Now comes the rote stuff:
 560         hir::ExprKind::Repeat(ref v, ref count) => {
 561             let def_id = cx.tcx.hir().local_def_id_from_hir_id(count.hir_id);
 562             let substs = InternalSubsts::identity_for_item(cx.tcx.global_tcx(), def_id);
 563             let instance = ty::Instance::resolve(
 564                 cx.tcx.global_tcx(),
 565                 cx.param_env,
 566                 def_id,
 567                 substs,
 568             ).unwrap();
 569             let global_id = GlobalId {
 570                 instance,
 571                 promoted: None
 572             };
 573             let span = cx.tcx.def_span(def_id);
 574             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
 575                 Ok(cv) => cv.unwrap_usize(cx.tcx),
 576                 Err(ErrorHandled::Reported) => 0,
 577                 Err(ErrorHandled::TooGeneric) => {
 578                     cx.tcx.sess.span_err(span, "array lengths can't depend on generic parameters");
 579                     0
 580                 },
 581             };
 582
 583             ExprKind::Repeat {
 584                 value: v.to_ref(),
 585                 count,
 586             }
 587         }
 588         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 589         hir::ExprKind::Break(dest, ref value) => {
 590             match dest.target_id {
 591                 Ok(target_id) => ExprKind::Break {
 592                     label: region::Scope {
 593                         id: target_id.local_id,
 594                         data: region::ScopeData::Node
 595                     },
 596                     value: value.to_ref(),
 597                 },
 598                 Err(err) => bug!("invalid loop id for break: {}", err)
 599             }
 600         }
 601         hir::ExprKind::Continue(dest) => {
 602             match dest.target_id {
 603                 Ok(loop_id) => ExprKind::Continue {
 604                     label: region::Scope {
 605                         id: loop_id.local_id,
 606                         data: region::ScopeData::Node
 607                     },
 608                 },
 609                 Err(err) => bug!("invalid loop id for continue: {}", err)
 610             }
 611         }
 612         hir::ExprKind::Match(ref discr, ref arms, _) => {
 613             ExprKind::Match {
 614                 scrutinee: discr.to_ref(),
 615                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 616             }
 617         }
 618         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
 619             ExprKind::If {
 620                 condition: cond.to_ref(),
 621                 then: then.to_ref(),
 622                 otherwise: otherwise.to_ref(),
 623             }
 624         }
 625         hir::ExprKind::While(ref cond, ref body, _) => {
 626             ExprKind::Loop {
 627                 condition: Some(cond.to_ref()),
 628                 body: block::to_expr_ref(cx, body),
 629             }
 630         }
 631         hir::ExprKind::Loop(ref body, _, _) => {
 632             ExprKind::Loop {
 633                 condition: None,
 634                 body: block::to_expr_ref(cx, body),
 635             }
 636         }
 637         hir::ExprKind::Field(ref source, ..) => {
 638             ExprKind::Field {
 639                 lhs: source.to_ref(),
 640                 name: Field::new(cx.tcx.field_index(expr.hir_id, cx.tables)),
 641             }
 642         }
 643         hir::ExprKind::Cast(ref source, ref cast_ty) => {
 644             // Check for a user-given type annotation on this `cast`
 645             let user_provided_types = cx.tables.user_provided_types();
 646             let user_ty = user_provided_types.get(cast_ty.hir_id);
 647
 648             debug!(
 649                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 650                 expr,
 651                 cast_ty.hir_id,
 652                 user_ty,
 653             );
 654
 655             // Check to see if this cast is a "coercion cast", where the cast is actually done
 656             // using a coercion (or is a no-op).
 657             let cast = if cx.tables().is_coercion_cast(source.hir_id) {
 658                 // Convert the lexpr to a vexpr.
 659                 ExprKind::Use { source: source.to_ref() }
 660             } else {
 661                 // check whether this is casting an enum variant discriminant
 662                 // to prevent cycles, we refer to the discriminant initializer
 663                 // which is always an integer and thus doesn't need to know the
 664                 // enum's layout (or its tag type) to compute it during const eval
 665                 // Example:
 666                 // enum Foo {
 667                 //     A,
 668                 //     B = A as isize + 4,
 669                 // }
 670                 // The correct solution would be to add symbolic computations to miri,
 671                 // so we wouldn't have to compute and store the actual value
 672                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 673                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 674                     cx
 675                         .tables()
 676                         .node_type(source.hir_id)
 677                         .ty_adt_def()
 678                         .and_then(|adt_def| {
 679                         match def {
 680                             Def::VariantCtor(variant_id, CtorKind::Const) => {
 681                                 let idx = adt_def.variant_index_with_id(variant_id);
 682                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 683                                 use rustc::ty::util::IntTypeExt;
 684                                 let ty = adt_def.repr.discr_type();
 685                                 let ty = ty.to_ty(cx.tcx());
 686                                 Some((d, o, ty))
 687                             }
 688                             _ => None,
 689                         }
 690                     })
 691                 } else {
 692                     None
 693                 };
 694
 695                 let source = if let Some((did, offset, var_ty)) = var {
 696                     let mk_const = |literal| Expr {
 697                         temp_lifetime,
 698                         ty: var_ty,
 699                         span: expr.span,
 700                         kind: ExprKind::Literal {
 701                             literal: cx.tcx.mk_const(literal),
 702                             user_ty: None
 703                         },
 704                     }.to_ref();
 705                     let offset = mk_const(ty::Const::from_bits(
 706                         cx.tcx,
 707                         offset as u128,
 708                         cx.param_env.and(var_ty),
 709                     ));
 710                     match did {
 711                         Some(did) => {
 712                             // in case we are offsetting from a computed discriminant
 713                             // and not the beginning of discriminants (which is always `0`)
 714                             let substs = InternalSubsts::identity_for_item(cx.tcx(), did);
 715                             let lhs = mk_const(ty::Const {
 716                                 val: ConstValue::Unevaluated(did, substs),
 717                                 ty: var_ty,
 718                             });
 719                             let bin = ExprKind::Binary {
 720                                 op: BinOp::Add,
 721                                 lhs,
 722                                 rhs: offset,
 723                             };
 724                             Expr {
 725                                 temp_lifetime,
 726                                 ty: var_ty,
 727                                 span: expr.span,
 728                                 kind: bin,
 729                             }.to_ref()
 730                         },
 731                         None => offset,
 732                     }
 733                 } else {
 734                     source.to_ref()
 735                 };
 736
 737                 ExprKind::Cast { source }
 738             };
 739
 740             if let Some(user_ty) = user_ty {
 741                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 742                 //       inefficient, revisit this when performance becomes an issue.
 743                 let cast_expr = Expr {
 744                     temp_lifetime,
 745                     ty: expr_ty,
 746                     span: expr.span,
 747                     kind: cast,
 748                 };
 749                 debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
 750
 751                 ExprKind::ValueTypeAscription {
 752                     source: cast_expr.to_ref(),
 753                     user_ty: Some(*user_ty),
 754                 }
 755             } else {
 756                 cast
 757             }
 758         }
 759         hir::ExprKind::Type(ref source, ref ty) => {
 760             let user_provided_types = cx.tables.user_provided_types();
 761             let user_ty = user_provided_types.get(ty.hir_id).map(|u_ty| *u_ty);
 762             debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
 763             if source.is_place_expr() {
 764                 ExprKind::PlaceTypeAscription {
 765                     source: source.to_ref(),
 766                     user_ty,
 767                 }
 768             } else {
 769                 ExprKind::ValueTypeAscription {
 770                     source: source.to_ref(),
 771                     user_ty,
 772                 }
 773             }
 774         }
 775         hir::ExprKind::Box(ref value) => {
 776             ExprKind::Box {
 777                 value: value.to_ref(),
 778             }
 779         }
 780         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 781         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 782
 783         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 784         hir::ExprKind::Err => unreachable!(),
 785     };
 786
 787     Expr {
 788         temp_lifetime,
 789         ty: expr_ty,
 790         span: expr.span,
 791         kind,
 792     }
 793 }
 794
 795 fn user_substs_applied_to_def(
 796     cx: &mut Cx<'a, 'gcx, 'tcx>,
 797     hir_id: hir::HirId,
 798     def: &Def,
 799 ) -> Option<ty::CanonicalUserType<'tcx>> {
 800     debug!("user_substs_applied_to_def: def={:?}", def);
 801     let user_provided_type = match def {
 802         // A reference to something callable -- e.g., a fn, method, or
 803         // a tuple-struct or tuple-variant. This has the type of a
 804         // `Fn` but with the user-given substitutions.
 805         Def::Fn(_) |
 806         Def::Method(_) |
 807         Def::StructCtor(_, CtorKind::Fn) |
 808         Def::VariantCtor(_, CtorKind::Fn) |
 809         Def::Const(_) |
 810         Def::AssociatedConst(_) => cx.tables().user_provided_types().get(hir_id).map(|u_ty| *u_ty),
 811
 812         // A unit struct/variant which is used as a value (e.g.,
 813         // `None`). This has the type of the enum/struct that defines
 814         // this variant -- but with the substitutions given by the
 815         // user.
 816         Def::StructCtor(_def_id, CtorKind::Const) |
 817         Def::VariantCtor(_def_id, CtorKind::Const) =>
 818             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 819
 820         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 821         Def::SelfCtor(_) =>
 822             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 823
 824         _ =>
 825             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
 826     };
 827     debug!("user_substs_applied_to_def: user_provided_type={:?}", user_provided_type);
 828     user_provided_type
 829 }
 830
 831 fn method_callee<'a, 'gcx, 'tcx>(
 832     cx: &mut Cx<'a, 'gcx, 'tcx>,
 833     expr: &hir::Expr,
 834     span: Span,
 835     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 836 ) -> Expr<'tcx> {
 837     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 838     let (def_id, substs, user_ty) = match overloaded_callee {
 839         Some((def_id, substs)) => (def_id, substs, None),
 840         None => {
 841             let type_dependent_defs = cx.tables().type_dependent_defs();
 842             let def = type_dependent_defs
 843                 .get(expr.hir_id)
 844                 .unwrap_or_else(|| {
 845                     span_bug!(expr.span, "no type-dependent def for method callee")
 846                 });
 847             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, def);
 848             debug!("method_callee: user_ty={:?}", user_ty);
 849             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 850         }
 851     };
 852     let ty = cx.tcx().mk_fn_def(def_id, substs);
 853     Expr {
 854         temp_lifetime,
 855         ty,
 856         span,
 857         kind: ExprKind::Literal {
 858             literal: cx.tcx().mk_const(
 859                 ty::Const::zero_sized(ty)
 860             ),
 861             user_ty,
 862         },
 863     }
 864 }
 865
 866 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 867
 868 impl ToBorrowKind for AutoBorrowMutability {
 869     fn to_borrow_kind(&self) -> BorrowKind {
 870         use rustc::ty::adjustment::AllowTwoPhase;
 871         match *self {
 872             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 873                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 874                     AllowTwoPhase::Yes => true,
 875                     AllowTwoPhase::No => false
 876                 }},
 877             AutoBorrowMutability::Immutable =>
 878                 BorrowKind::Shared,
 879         }
 880     }
 881 }
 882
 883 impl ToBorrowKind for hir::Mutability {
 884     fn to_borrow_kind(&self) -> BorrowKind {
 885         match *self {
 886             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 887             hir::MutImmutable => BorrowKind::Shared,
 888         }
 889     }
 890 }
 891
 892 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 893     Arm {
 894         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 895         guard: match arm.guard {
 896                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 897                 _ => None,
 898             },
 899         body: arm.body.to_ref(),
 900         // BUG: fix this
 901         lint_level: LintLevel::Inherited,
 902     }
 903 }
 904
 905 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 906                                      expr: &'tcx hir::Expr,
 907                                      def: Def)
 908                                      -> ExprKind<'tcx> {
 909     let substs = cx.tables().node_substs(expr.hir_id);
 910     match def {
 911         // A regular function, constructor function or a constant.
 912         Def::Fn(_) |
 913         Def::Method(_) |
 914         Def::StructCtor(_, CtorKind::Fn) |
 915         Def::VariantCtor(_, CtorKind::Fn) |
 916         Def::SelfCtor(..) => {
 917             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 918             debug!("convert_path_expr: user_ty={:?}", user_ty);
 919             ExprKind::Literal {
 920                 literal: cx.tcx.mk_const(ty::Const::zero_sized(
 921                     cx.tables().node_type(expr.hir_id),
 922                 )),
 923                 user_ty,
 924             }
 925         }
 926
 927         Def::ConstParam(def_id) => {
 928             let node_id = cx.tcx.hir().as_local_node_id(def_id).unwrap();
 929             let item_id = cx.tcx.hir().get_parent_node(node_id);
 930             let item_def_id = cx.tcx.hir().local_def_id(item_id);
 931             let generics = cx.tcx.generics_of(item_def_id);
 932             let index = generics.param_def_id_to_index[&cx.tcx.hir().local_def_id(node_id)];
 933             let name = cx.tcx.hir().name(node_id).as_interned_str();
 934             let val = ConstValue::Param(ty::ParamConst::new(index, name));
 935             ExprKind::Literal {
 936                 literal: cx.tcx.mk_const(
 937                     ty::Const {
 938                         val,
 939                         ty: cx.tables().node_type(expr.hir_id),
 940                     }
 941                 ),
 942                 user_ty: None,
 943             }
 944         }
 945
 946         Def::Const(def_id) |
 947         Def::AssociatedConst(def_id) => {
 948             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 949             debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
 950             ExprKind::Literal {
 951                 literal: cx.tcx.mk_const(ty::Const {
 952                     val: ConstValue::Unevaluated(def_id, substs),
 953                     ty: cx.tcx.type_of(def_id),
 954                 }),
 955                 user_ty,
 956             }
 957         },
 958
 959         Def::StructCtor(def_id, CtorKind::Const) |
 960         Def::VariantCtor(def_id, CtorKind::Const) => {
 961             let user_provided_types = cx.tables.user_provided_types();
 962             let user_provided_type = user_provided_types.get(expr.hir_id).map(|u_ty| *u_ty);
 963             debug!("convert_path_expr: user_provided_type={:?}", user_provided_type);
 964             let ty = cx.tables().node_type(expr.hir_id);
 965             match ty.sty {
 966                 // A unit struct/variant which is used as a value.
 967                 // We return a completely different ExprKind here to account for this special case.
 968                 ty::Adt(adt_def, substs) => {
 969                     ExprKind::Adt {
 970                         adt_def,
 971                         variant_index: adt_def.variant_index_with_id(def_id),
 972                         substs,
 973                         user_ty: user_provided_type,
 974                         fields: vec![],
 975                         base: None,
 976                     }
 977                 }
 978                 _ => bug!("unexpected ty: {:?}", ty),
 979             }
 980         }
 981
 982         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 983
 984         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 985
 986         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 987     }
 988 }
 989
 990 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 991                                expr: &'tcx hir::Expr,
 992                                def: Def)
 993                                -> ExprKind<'tcx> {
 994     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 995
 996     match def {
 997         Def::Local(id) => ExprKind::VarRef { id: cx.tcx.hir().node_to_hir_id(id) },
 998
 999         Def::Upvar(var_id, index, closure_expr_id) => {
1000             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
1001                    var_id,
1002                    index,
1003                    closure_expr_id);
1004             let var_hir_id = cx.tcx.hir().node_to_hir_id(var_id);
1005             let var_ty = cx.tables().node_type(var_hir_id);
1006
1007             // FIXME free regions in closures are not right
1008             let closure_ty = cx.tables()
1009                                .node_type(cx.tcx.hir().node_to_hir_id(closure_expr_id));
1010
1011             // FIXME we're just hard-coding the idea that the
1012             // signature will be &self or &mut self and hence will
1013             // have a bound region with number 0
1014             let closure_def_id = cx.tcx.hir().local_def_id(closure_expr_id);
1015             let region = ty::ReFree(ty::FreeRegion {
1016                 scope: closure_def_id,
1017                 bound_region: ty::BoundRegion::BrAnon(0),
1018             });
1019             let region = cx.tcx.mk_region(region);
1020
1021             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
1022                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
1023                     ty::ClosureKind::Fn => {
1024                         let ref_closure_ty = cx.tcx.mk_ref(region,
1025                                                            ty::TypeAndMut {
1026                                                                ty: closure_ty,
1027                                                                mutbl: hir::MutImmutable,
1028                                                            });
1029                         Expr {
1030                             ty: closure_ty,
1031                             temp_lifetime: 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                                 }
1040                                 .to_ref(),
1041                             },
1042                         }
1043                     }
1044                     ty::ClosureKind::FnMut => {
1045                         let ref_closure_ty = cx.tcx.mk_ref(region,
1046                                                            ty::TypeAndMut {
1047                                                                ty: closure_ty,
1048                                                                mutbl: hir::MutMutable,
1049                                                            });
1050                         Expr {
1051                             ty: closure_ty,
1052                             temp_lifetime,
1053                             span: expr.span,
1054                             kind: ExprKind::Deref {
1055                                 arg: Expr {
1056                                     ty: ref_closure_ty,
1057                                     temp_lifetime,
1058                                     span: expr.span,
1059                                     kind: ExprKind::SelfRef,
1060                                 }.to_ref(),
1061                             },
1062                         }
1063                     }
1064                     ty::ClosureKind::FnOnce => {
1065                         Expr {
1066                             ty: closure_ty,
1067                             temp_lifetime,
1068                             span: expr.span,
1069                             kind: ExprKind::SelfRef,
1070                         }
1071                     }
1072                 }
1073             } else {
1074                 Expr {
1075                     ty: closure_ty,
1076                     temp_lifetime,
1077                     span: expr.span,
1078                     kind: ExprKind::SelfRef,
1079                 }
1080             };
1081
1082             // at this point we have `self.n`, which loads up the upvar
1083             let field_kind = ExprKind::Field {
1084                 lhs: self_expr.to_ref(),
1085                 name: Field::new(index),
1086             };
1087
1088             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1089             // point we need an implicit deref
1090             let upvar_id = ty::UpvarId {
1091                 var_path: ty::UpvarPath {hir_id: var_hir_id},
1092                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1093             };
1094             match cx.tables().upvar_capture(upvar_id) {
1095                 ty::UpvarCapture::ByValue => field_kind,
1096                 ty::UpvarCapture::ByRef(borrow) => {
1097                     ExprKind::Deref {
1098                         arg: Expr {
1099                             temp_lifetime,
1100                             ty: cx.tcx.mk_ref(borrow.region,
1101                                               ty::TypeAndMut {
1102                                                   ty: var_ty,
1103                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1104                                               }),
1105                             span: expr.span,
1106                             kind: field_kind,
1107                         }.to_ref(),
1108                     }
1109                 }
1110             }
1111         }
1112
1113         _ => span_bug!(expr.span, "type of & not region"),
1114     }
1115 }
1116
1117
1118 fn bin_op(op: hir::BinOpKind) -> BinOp {
1119     match op {
1120         hir::BinOpKind::Add => BinOp::Add,
1121         hir::BinOpKind::Sub => BinOp::Sub,
1122         hir::BinOpKind::Mul => BinOp::Mul,
1123         hir::BinOpKind::Div => BinOp::Div,
1124         hir::BinOpKind::Rem => BinOp::Rem,
1125         hir::BinOpKind::BitXor => BinOp::BitXor,
1126         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1127         hir::BinOpKind::BitOr => BinOp::BitOr,
1128         hir::BinOpKind::Shl => BinOp::Shl,
1129         hir::BinOpKind::Shr => BinOp::Shr,
1130         hir::BinOpKind::Eq => BinOp::Eq,
1131         hir::BinOpKind::Lt => BinOp::Lt,
1132         hir::BinOpKind::Le => BinOp::Le,
1133         hir::BinOpKind::Ne => BinOp::Ne,
1134         hir::BinOpKind::Ge => BinOp::Ge,
1135         hir::BinOpKind::Gt => BinOp::Gt,
1136         _ => bug!("no equivalent for ast binop {:?}", op),
1137     }
1138 }
1139
1140 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1141                                        expr: &'tcx hir::Expr,
1142                                        args: Vec<ExprRef<'tcx>>)
1143                                        -> ExprKind<'tcx> {
1144     let fun = method_callee(cx, expr, expr.span, None);
1145     ExprKind::Call {
1146         ty: fun.ty,
1147         fun: fun.to_ref(),
1148         args,
1149         from_hir_call: false,
1150     }
1151 }
1152
1153 fn overloaded_place<'a, 'gcx, 'tcx>(
1154     cx: &mut Cx<'a, 'gcx, 'tcx>,
1155     expr: &'tcx hir::Expr,
1156     place_ty: Ty<'tcx>,
1157     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
1158     args: Vec<ExprRef<'tcx>>,
1159 ) -> ExprKind<'tcx> {
1160     // For an overloaded *x or x[y] expression of type T, the method
1161     // call returns an &T and we must add the deref so that the types
1162     // line up (this is because `*x` and `x[y]` represent places):
1163
1164     let recv_ty = match args[0] {
1165         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1166         ExprRef::Mirror(ref e) => e.ty
1167     };
1168
1169     // Reconstruct the output assuming it's a reference with the
1170     // same region and mutability as the receiver. This holds for
1171     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1172     let (region, mutbl) = match recv_ty.sty {
1173         ty::Ref(region, _, mutbl) => (region, mutbl),
1174         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1175     };
1176     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1177         ty: place_ty,
1178         mutbl,
1179     });
1180
1181     // construct the complete expression `foo()` for the overloaded call,
1182     // which will yield the &T type
1183     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1184     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1185     let ref_expr = Expr {
1186         temp_lifetime,
1187         ty: ref_ty,
1188         span: expr.span,
1189         kind: ExprKind::Call {
1190             ty: fun.ty,
1191             fun: fun.to_ref(),
1192             args,
1193             from_hir_call: false,
1194         },
1195     };
1196
1197     // construct and return a deref wrapper `*foo()`
1198     ExprKind::Deref { arg: ref_expr.to_ref() }
1199 }
1200
1201 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1202                                    closure_expr: &'tcx hir::Expr,
1203                                    freevar: &hir::Freevar,
1204                                    freevar_ty: Ty<'tcx>)
1205                                    -> ExprRef<'tcx> {
1206     let var_hir_id = cx.tcx.hir().node_to_hir_id(freevar.var_id());
1207     let upvar_id = ty::UpvarId {
1208         var_path: ty::UpvarPath { hir_id: var_hir_id },
1209         closure_expr_id: cx.tcx.hir().local_def_id_from_hir_id(closure_expr.hir_id).to_local(),
1210     };
1211     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1212     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1213     let var_ty = cx.tables().node_type(var_hir_id);
1214     let captured_var = Expr {
1215         temp_lifetime,
1216         ty: var_ty,
1217         span: closure_expr.span,
1218         kind: convert_var(cx, closure_expr, freevar.def),
1219     };
1220     match upvar_capture {
1221         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1222         ty::UpvarCapture::ByRef(upvar_borrow) => {
1223             let borrow_kind = match upvar_borrow.kind {
1224                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1225                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1226                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1227             };
1228             Expr {
1229                 temp_lifetime,
1230                 ty: freevar_ty,
1231                 span: closure_expr.span,
1232                 kind: ExprKind::Borrow {
1233                     borrow_kind,
1234                     arg: captured_var.to_ref(),
1235                 },
1236             }.to_ref()
1237         }
1238     }
1239 }
1240
1241 /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExprRef.
1242 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1243                               fields: &'tcx [hir::Field])
1244                               -> Vec<FieldExprRef<'tcx>> {
1245     fields.iter()
1246         .map(|field| {
1247             FieldExprRef {
1248                 name: Field::new(cx.tcx.field_index(field.hir_id, cx.tables)),
1249                 expr: field.expr.to_ref(),
1250             }
1251         })
1252         .collect()
1253 }