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