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