compiler/rustc_mir_build/src/thir/cx/expr.rs

   1 use crate::thir::cx::Cx;
   2 use crate::thir::util::UserAnnotatedTyHelpers;
   3 use crate::thir::*;
   4 use rustc_data_structures::stack::ensure_sufficient_stack;
   5 use rustc_hir as hir;
   6 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
   7 use rustc_index::vec::Idx;
   8 use rustc_middle::hir::place::Place as HirPlace;
   9 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
  10 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
  11 use rustc_middle::mir::interpret::Scalar;
  12 use rustc_middle::mir::BorrowKind;
  13 use rustc_middle::ty::adjustment::{
  14     Adjust, Adjustment, AutoBorrow, AutoBorrowMutability, PointerCast,
  15 };
  16 use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
  17 use rustc_middle::ty::{self, AdtKind, Ty};
  18 use rustc_span::Span;
  19
  20 use std::iter;
  21
  22 impl<'thir, 'tcx> Cx<'thir, 'tcx> {
  23     /// Mirrors and allocates a single [`hir::Expr`]. If you need to mirror a whole slice
  24     /// of expressions, prefer using [`mirror_exprs`].
  25     ///
  26     /// [`mirror_exprs`]: Self::mirror_exprs
  27     crate fn mirror_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) -> &'thir Expr<'thir, 'tcx> {
  28         // `mirror_expr` is recursing very deep. Make sure the stack doesn't overflow.
  29         ensure_sufficient_stack(|| self.arena.alloc(self.mirror_expr_inner(expr)))
  30     }
  31
  32     /// Mirrors and allocates a slice of [`hir::Expr`]s. They will be allocated as a
  33     /// contiguous sequence in memory.
  34     crate fn mirror_exprs(&mut self, exprs: &'tcx [hir::Expr<'tcx>]) -> &'thir [Expr<'thir, 'tcx>] {
  35         self.arena.alloc_from_iter(exprs.iter().map(|expr| self.mirror_expr_inner(expr)))
  36     }
  37
  38     /// Mirrors a [`hir::Expr`] without allocating it into the arena.
  39     /// This is a separate, private function so that [`mirror_expr`] and [`mirror_exprs`] can
  40     /// decide how to allocate this expression (alone or within a slice).
  41     ///
  42     /// [`mirror_expr`]: Self::mirror_expr
  43     /// [`mirror_exprs`]: Self::mirror_exprs
  44     pub(super) fn mirror_expr_inner(
  45         &mut self,
  46         hir_expr: &'tcx hir::Expr<'tcx>,
  47     ) -> Expr<'thir, 'tcx> {
  48         let temp_lifetime = self.region_scope_tree.temporary_scope(hir_expr.hir_id.local_id);
  49         let expr_scope =
  50             region::Scope { id: hir_expr.hir_id.local_id, data: region::ScopeData::Node };
  51
  52         debug!("Expr::make_mirror(): id={}, span={:?}", hir_expr.hir_id, hir_expr.span);
  53
  54         let mut expr = self.make_mirror_unadjusted(hir_expr);
  55
  56         // Now apply adjustments, if any.
  57         for adjustment in self.typeck_results.expr_adjustments(hir_expr) {
  58             debug!("make_mirror: expr={:?} applying adjustment={:?}", expr, adjustment);
  59             expr = self.apply_adjustment(hir_expr, expr, adjustment);
  60         }
  61
  62         // Next, wrap this up in the expr's scope.
  63         expr = Expr {
  64             temp_lifetime,
  65             ty: expr.ty,
  66             span: hir_expr.span,
  67             kind: ExprKind::Scope {
  68                 region_scope: expr_scope,
  69                 value: self.arena.alloc(expr),
  70                 lint_level: LintLevel::Explicit(hir_expr.hir_id),
  71             },
  72         };
  73
  74         // Finally, create a destruction scope, if any.
  75         if let Some(region_scope) =
  76             self.region_scope_tree.opt_destruction_scope(hir_expr.hir_id.local_id)
  77         {
  78             expr = Expr {
  79                 temp_lifetime,
  80                 ty: expr.ty,
  81                 span: hir_expr.span,
  82                 kind: ExprKind::Scope {
  83                     region_scope,
  84                     value: self.arena.alloc(expr),
  85                     lint_level: LintLevel::Inherited,
  86                 },
  87             };
  88         }
  89
  90         // OK, all done!
  91         expr
  92     }
  93
  94     fn apply_adjustment(
  95         &mut self,
  96         hir_expr: &'tcx hir::Expr<'tcx>,
  97         mut expr: Expr<'thir, 'tcx>,
  98         adjustment: &Adjustment<'tcx>,
  99     ) -> Expr<'thir, 'tcx> {
 100         let Expr { temp_lifetime, mut span, .. } = expr;
 101
 102         // Adjust the span from the block, to the last expression of the
 103         // block. This is a better span when returning a mutable reference
 104         // with too short a lifetime. The error message will use the span
 105         // from the assignment to the return place, which should only point
 106         // at the returned value, not the entire function body.
 107         //
 108         // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
 109         //      x
 110         //   // ^ error message points at this expression.
 111         // }
 112         let mut adjust_span = |expr: &mut Expr<'thir, 'tcx>| {
 113             if let ExprKind::Block { body } = &expr.kind {
 114                 if let Some(ref last_expr) = body.expr {
 115                     span = last_expr.span;
 116                     expr.span = span;
 117                 }
 118             }
 119         };
 120
 121         let kind = match adjustment.kind {
 122             Adjust::Pointer(PointerCast::Unsize) => {
 123                 adjust_span(&mut expr);
 124                 ExprKind::Pointer { cast: PointerCast::Unsize, source: self.arena.alloc(expr) }
 125             }
 126             Adjust::Pointer(cast) => ExprKind::Pointer { cast, source: self.arena.alloc(expr) },
 127             Adjust::NeverToAny => ExprKind::NeverToAny { source: self.arena.alloc(expr) },
 128             Adjust::Deref(None) => {
 129                 adjust_span(&mut expr);
 130                 ExprKind::Deref { arg: self.arena.alloc(expr) }
 131             }
 132             Adjust::Deref(Some(deref)) => {
 133                 // We don't need to do call adjust_span here since
 134                 // deref coercions always start with a built-in deref.
 135                 let call = deref.method_call(self.tcx(), expr.ty);
 136
 137                 expr = Expr {
 138                     temp_lifetime,
 139                     ty: self
 140                         .tcx
 141                         .mk_ref(deref.region, ty::TypeAndMut { ty: expr.ty, mutbl: deref.mutbl }),
 142                     span,
 143                     kind: ExprKind::Borrow {
 144                         borrow_kind: deref.mutbl.to_borrow_kind(),
 145                         arg: self.arena.alloc(expr),
 146                     },
 147                 };
 148
 149                 self.overloaded_place(
 150                     hir_expr,
 151                     adjustment.target,
 152                     Some(call),
 153                     self.arena.alloc_from_iter(iter::once(expr)),
 154                     deref.span,
 155                 )
 156             }
 157             Adjust::Borrow(AutoBorrow::Ref(_, m)) => {
 158                 ExprKind::Borrow { borrow_kind: m.to_borrow_kind(), arg: self.arena.alloc(expr) }
 159             }
 160             Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
 161                 ExprKind::AddressOf { mutability, arg: self.arena.alloc(expr) }
 162             }
 163         };
 164
 165         Expr { temp_lifetime, ty: adjustment.target, span, kind }
 166     }
 167
 168     fn make_mirror_unadjusted(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Expr<'thir, 'tcx> {
 169         let expr_ty = self.typeck_results().expr_ty(expr);
 170         let temp_lifetime = self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 171
 172         let kind = match expr.kind {
 173             // Here comes the interesting stuff:
 174             hir::ExprKind::MethodCall(_, method_span, ref args, fn_span) => {
 175                 // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 176                 let expr = self.method_callee(expr, method_span, None);
 177                 let args = self.mirror_exprs(args);
 178                 ExprKind::Call {
 179                     ty: expr.ty,
 180                     fun: self.arena.alloc(expr),
 181                     args,
 182                     from_hir_call: true,
 183                     fn_span,
 184                 }
 185             }
 186
 187             hir::ExprKind::Call(ref fun, ref args) => {
 188                 if self.typeck_results().is_method_call(expr) {
 189                     // The callee is something implementing Fn, FnMut, or FnOnce.
 190                     // Find the actual method implementation being called and
 191                     // build the appropriate UFCS call expression with the
 192                     // callee-object as expr parameter.
 193
 194                     // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 195
 196                     let method = self.method_callee(expr, fun.span, None);
 197
 198                     let arg_tys = args.iter().map(|e| self.typeck_results().expr_ty_adjusted(e));
 199                     let tupled_args = Expr {
 200                         ty: self.tcx.mk_tup(arg_tys),
 201                         temp_lifetime,
 202                         span: expr.span,
 203                         kind: ExprKind::Tuple { fields: self.mirror_exprs(args) },
 204                     };
 205
 206                     ExprKind::Call {
 207                         ty: method.ty,
 208                         fun: self.arena.alloc(method),
 209                         args: self
 210                             .arena
 211                             .alloc_from_iter(vec![self.mirror_expr_inner(fun), tupled_args]),
 212                         from_hir_call: true,
 213                         fn_span: expr.span,
 214                     }
 215                 } else {
 216                     let adt_data =
 217                         if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = fun.kind {
 218                             // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
 219                             expr_ty.ty_adt_def().and_then(|adt_def| match path.res {
 220                                 Res::Def(DefKind::Ctor(_, CtorKind::Fn), ctor_id) => {
 221                                     Some((adt_def, adt_def.variant_index_with_ctor_id(ctor_id)))
 222                                 }
 223                                 Res::SelfCtor(..) => Some((adt_def, VariantIdx::new(0))),
 224                                 _ => None,
 225                             })
 226                         } else {
 227                             None
 228                         };
 229                     if let Some((adt_def, index)) = adt_data {
 230                         let substs = self.typeck_results().node_substs(fun.hir_id);
 231                         let user_provided_types = self.typeck_results().user_provided_types();
 232                         let user_ty =
 233                             user_provided_types.get(fun.hir_id).copied().map(|mut u_ty| {
 234                                 if let UserType::TypeOf(ref mut did, _) = &mut u_ty.value {
 235                                     *did = adt_def.did;
 236                                 }
 237                                 u_ty
 238                             });
 239                         debug!("make_mirror_unadjusted: (call) user_ty={:?}", user_ty);
 240
 241                         let field_refs =
 242                             self.arena.alloc_from_iter(args.iter().enumerate().map(|(idx, e)| {
 243                                 FieldExpr { name: Field::new(idx), expr: self.mirror_expr(e) }
 244                             }));
 245                         ExprKind::Adt {
 246                             adt_def,
 247                             substs,
 248                             variant_index: index,
 249                             fields: field_refs,
 250                             user_ty,
 251                             base: None,
 252                         }
 253                     } else {
 254                         ExprKind::Call {
 255                             ty: self.typeck_results().node_type(fun.hir_id),
 256                             fun: self.mirror_expr(fun),
 257                             args: self.mirror_exprs(args),
 258                             from_hir_call: true,
 259                             fn_span: expr.span,
 260                         }
 261                     }
 262                 }
 263             }
 264
 265             hir::ExprKind::AddrOf(hir::BorrowKind::Ref, mutbl, ref arg) => {
 266                 ExprKind::Borrow { borrow_kind: mutbl.to_borrow_kind(), arg: self.mirror_expr(arg) }
 267             }
 268
 269             hir::ExprKind::AddrOf(hir::BorrowKind::Raw, mutability, ref arg) => {
 270                 ExprKind::AddressOf { mutability, arg: self.mirror_expr(arg) }
 271             }
 272
 273             hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: self.mirror_block(blk) },
 274
 275             hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
 276                 ExprKind::Assign { lhs: self.mirror_expr(lhs), rhs: self.mirror_expr(rhs) }
 277             }
 278
 279             hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 280                 if self.typeck_results().is_method_call(expr) {
 281                     let lhs = self.mirror_expr_inner(lhs);
 282                     let rhs = self.mirror_expr_inner(rhs);
 283                     self.overloaded_operator(expr, self.arena.alloc_from_iter(vec![lhs, rhs]))
 284                 } else {
 285                     ExprKind::AssignOp {
 286                         op: bin_op(op.node),
 287                         lhs: self.mirror_expr(lhs),
 288                         rhs: self.mirror_expr(rhs),
 289                     }
 290                 }
 291             }
 292
 293             hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 294                 literal: self.const_eval_literal(&lit.node, expr_ty, lit.span, false),
 295                 user_ty: None,
 296                 const_id: None,
 297             },
 298
 299             hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 300                 if self.typeck_results().is_method_call(expr) {
 301                     let lhs = self.mirror_expr_inner(lhs);
 302                     let rhs = self.mirror_expr_inner(rhs);
 303                     self.overloaded_operator(expr, self.arena.alloc_from_iter(vec![lhs, rhs]))
 304                 } else {
 305                     // FIXME overflow
 306                     match op.node {
 307                         hir::BinOpKind::And => ExprKind::LogicalOp {
 308                             op: LogicalOp::And,
 309                             lhs: self.mirror_expr(lhs),
 310                             rhs: self.mirror_expr(rhs),
 311                         },
 312                         hir::BinOpKind::Or => ExprKind::LogicalOp {
 313                             op: LogicalOp::Or,
 314                             lhs: self.mirror_expr(lhs),
 315                             rhs: self.mirror_expr(rhs),
 316                         },
 317
 318                         _ => {
 319                             let op = bin_op(op.node);
 320                             ExprKind::Binary {
 321                                 op,
 322                                 lhs: self.mirror_expr(lhs),
 323                                 rhs: self.mirror_expr(rhs),
 324                             }
 325                         }
 326                     }
 327                 }
 328             }
 329
 330             hir::ExprKind::Index(ref lhs, ref index) => {
 331                 if self.typeck_results().is_method_call(expr) {
 332                     let lhs = self.mirror_expr_inner(lhs);
 333                     let index = self.mirror_expr_inner(index);
 334                     self.overloaded_place(
 335                         expr,
 336                         expr_ty,
 337                         None,
 338                         self.arena.alloc_from_iter(vec![lhs, index]),
 339                         expr.span,
 340                     )
 341                 } else {
 342                     ExprKind::Index { lhs: self.mirror_expr(lhs), index: self.mirror_expr(index) }
 343                 }
 344             }
 345
 346             hir::ExprKind::Unary(hir::UnOp::Deref, ref arg) => {
 347                 if self.typeck_results().is_method_call(expr) {
 348                     let arg = self.mirror_expr_inner(arg);
 349                     self.overloaded_place(
 350                         expr,
 351                         expr_ty,
 352                         None,
 353                         self.arena.alloc_from_iter(iter::once(arg)),
 354                         expr.span,
 355                     )
 356                 } else {
 357                     ExprKind::Deref { arg: self.mirror_expr(arg) }
 358                 }
 359             }
 360
 361             hir::ExprKind::Unary(hir::UnOp::Not, ref arg) => {
 362                 if self.typeck_results().is_method_call(expr) {
 363                     let arg = self.mirror_expr_inner(arg);
 364                     self.overloaded_operator(expr, self.arena.alloc_from_iter(iter::once(arg)))
 365                 } else {
 366                     ExprKind::Unary { op: UnOp::Not, arg: self.mirror_expr(arg) }
 367                 }
 368             }
 369
 370             hir::ExprKind::Unary(hir::UnOp::Neg, ref arg) => {
 371                 if self.typeck_results().is_method_call(expr) {
 372                     let arg = self.mirror_expr_inner(arg);
 373                     self.overloaded_operator(expr, self.arena.alloc_from_iter(iter::once(arg)))
 374                 } else if let hir::ExprKind::Lit(ref lit) = arg.kind {
 375                     ExprKind::Literal {
 376                         literal: self.const_eval_literal(&lit.node, expr_ty, lit.span, true),
 377                         user_ty: None,
 378                         const_id: None,
 379                     }
 380                 } else {
 381                     ExprKind::Unary { op: UnOp::Neg, arg: self.mirror_expr(arg) }
 382                 }
 383             }
 384
 385             hir::ExprKind::Struct(ref qpath, ref fields, ref base) => match expr_ty.kind() {
 386                 ty::Adt(adt, substs) => match adt.adt_kind() {
 387                     AdtKind::Struct | AdtKind::Union => {
 388                         let user_provided_types = self.typeck_results().user_provided_types();
 389                         let user_ty = user_provided_types.get(expr.hir_id).copied();
 390                         debug!("make_mirror_unadjusted: (struct/union) user_ty={:?}", user_ty);
 391                         ExprKind::Adt {
 392                             adt_def: adt,
 393                             variant_index: VariantIdx::new(0),
 394                             substs,
 395                             user_ty,
 396                             fields: self.field_refs(fields),
 397                             base: base.as_ref().map(|base| FruInfo {
 398                                 base: self.mirror_expr(base),
 399                                 field_types: self.arena.alloc_from_iter(
 400                                     self.typeck_results().fru_field_types()[expr.hir_id]
 401                                         .iter()
 402                                         .cloned(),
 403                                 ),
 404                             }),
 405                         }
 406                     }
 407                     AdtKind::Enum => {
 408                         let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
 409                         match res {
 410                             Res::Def(DefKind::Variant, variant_id) => {
 411                                 assert!(base.is_none());
 412
 413                                 let index = adt.variant_index_with_id(variant_id);
 414                                 let user_provided_types =
 415                                     self.typeck_results().user_provided_types();
 416                                 let user_ty = user_provided_types.get(expr.hir_id).copied();
 417                                 debug!("make_mirror_unadjusted: (variant) user_ty={:?}", user_ty);
 418                                 ExprKind::Adt {
 419                                     adt_def: adt,
 420                                     variant_index: index,
 421                                     substs,
 422                                     user_ty,
 423                                     fields: self.field_refs(fields),
 424                                     base: None,
 425                                 }
 426                             }
 427                             _ => {
 428                                 span_bug!(expr.span, "unexpected res: {:?}", res);
 429                             }
 430                         }
 431                     }
 432                 },
 433                 _ => {
 434                     span_bug!(expr.span, "unexpected type for struct literal: {:?}", expr_ty);
 435                 }
 436             },
 437
 438             hir::ExprKind::Closure(..) => {
 439                 let closure_ty = self.typeck_results().expr_ty(expr);
 440                 let (def_id, substs, movability) = match *closure_ty.kind() {
 441                     ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 442                     ty::Generator(def_id, substs, movability) => {
 443                         (def_id, UpvarSubsts::Generator(substs), Some(movability))
 444                     }
 445                     _ => {
 446                         span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 447                     }
 448                 };
 449
 450                 let upvars = self.arena.alloc_from_iter(
 451                     self.typeck_results
 452                         .closure_min_captures_flattened(def_id)
 453                         .zip(substs.upvar_tys())
 454                         .map(|(captured_place, ty)| self.capture_upvar(expr, captured_place, ty)),
 455                 );
 456
 457                 // Convert the closure fake reads, if any, from hir `Place` to ExprRef
 458                 let fake_reads = match self.typeck_results.closure_fake_reads.get(&def_id) {
 459                     Some(fake_reads) => fake_reads
 460                         .iter()
 461                         .map(|(place, cause, hir_id)| {
 462                             let expr = self.convert_captured_hir_place(expr, place.clone());
 463                             let expr_ref: &'thir Expr<'thir, 'tcx> = self.arena.alloc(expr);
 464                             (expr_ref, *cause, *hir_id)
 465                         })
 466                         .collect(),
 467                     None => Vec::new(),
 468                 };
 469
 470                 ExprKind::Closure { closure_id: def_id, substs, upvars, movability, fake_reads }
 471             }
 472
 473             hir::ExprKind::Path(ref qpath) => {
 474                 let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
 475                 self.convert_path_expr(expr, res)
 476             }
 477
 478             hir::ExprKind::InlineAsm(ref asm) => ExprKind::InlineAsm {
 479                 template: asm.template,
 480                 operands: self.arena.alloc_from_iter(asm.operands.iter().map(|(op, _op_sp)| {
 481                     match *op {
 482                         hir::InlineAsmOperand::In { reg, ref expr } => {
 483                             InlineAsmOperand::In { reg, expr: self.mirror_expr(expr) }
 484                         }
 485                         hir::InlineAsmOperand::Out { reg, late, ref expr } => {
 486                             InlineAsmOperand::Out {
 487                                 reg,
 488                                 late,
 489                                 expr: expr.as_ref().map(|expr| self.mirror_expr(expr)),
 490                             }
 491                         }
 492                         hir::InlineAsmOperand::InOut { reg, late, ref expr } => {
 493                             InlineAsmOperand::InOut { reg, late, expr: self.mirror_expr(expr) }
 494                         }
 495                         hir::InlineAsmOperand::SplitInOut {
 496                             reg,
 497                             late,
 498                             ref in_expr,
 499                             ref out_expr,
 500                         } => InlineAsmOperand::SplitInOut {
 501                             reg,
 502                             late,
 503                             in_expr: self.mirror_expr(in_expr),
 504                             out_expr: out_expr.as_ref().map(|expr| self.mirror_expr(expr)),
 505                         },
 506                         hir::InlineAsmOperand::Const { ref expr } => {
 507                             InlineAsmOperand::Const { expr: self.mirror_expr(expr) }
 508                         }
 509                         hir::InlineAsmOperand::Sym { ref expr } => {
 510                             let qpath = match expr.kind {
 511                                 hir::ExprKind::Path(ref qpath) => qpath,
 512                                 _ => span_bug!(
 513                                     expr.span,
 514                                     "asm `sym` operand should be a path, found {:?}",
 515                                     expr.kind
 516                                 ),
 517                             };
 518                             let temp_lifetime =
 519                                 self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 520                             let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
 521                             let ty;
 522                             match res {
 523                                 Res::Def(DefKind::Fn, _) | Res::Def(DefKind::AssocFn, _) => {
 524                                     ty = self.typeck_results().node_type(expr.hir_id);
 525                                     let user_ty = self.user_substs_applied_to_res(expr.hir_id, res);
 526                                     InlineAsmOperand::SymFn {
 527                                         expr: self.arena.alloc(Expr {
 528                                             ty,
 529                                             temp_lifetime,
 530                                             span: expr.span,
 531                                             kind: ExprKind::Literal {
 532                                                 literal: ty::Const::zero_sized(self.tcx, ty),
 533                                                 user_ty,
 534                                                 const_id: None,
 535                                             },
 536                                         }),
 537                                     }
 538                                 }
 539
 540                                 Res::Def(DefKind::Static, def_id) => {
 541                                     InlineAsmOperand::SymStatic { def_id }
 542                                 }
 543
 544                                 _ => {
 545                                     self.tcx.sess.span_err(
 546                                         expr.span,
 547                                         "asm `sym` operand must point to a fn or static",
 548                                     );
 549
 550                                     // Not a real fn, but we're not reaching codegen anyways...
 551                                     ty = self.tcx.ty_error();
 552                                     InlineAsmOperand::SymFn {
 553                                         expr: self.arena.alloc(Expr {
 554                                             ty,
 555                                             temp_lifetime,
 556                                             span: expr.span,
 557                                             kind: ExprKind::Literal {
 558                                                 literal: ty::Const::zero_sized(self.tcx, ty),
 559                                                 user_ty: None,
 560                                                 const_id: None,
 561                                             },
 562                                         }),
 563                                     }
 564                                 }
 565                             }
 566                         }
 567                     }
 568                 })),
 569                 options: asm.options,
 570                 line_spans: asm.line_spans,
 571             },
 572
 573             hir::ExprKind::LlvmInlineAsm(ref asm) => ExprKind::LlvmInlineAsm {
 574                 asm: &asm.inner,
 575                 outputs: self.mirror_exprs(asm.outputs_exprs),
 576                 inputs: self.mirror_exprs(asm.inputs_exprs),
 577             },
 578
 579             hir::ExprKind::ConstBlock(ref anon_const) => {
 580                 let anon_const_def_id = self.tcx.hir().local_def_id(anon_const.hir_id);
 581                 let value = ty::Const::from_anon_const(self.tcx, anon_const_def_id);
 582
 583                 ExprKind::ConstBlock { value }
 584             }
 585             // Now comes the rote stuff:
 586             hir::ExprKind::Repeat(ref v, ref count) => {
 587                 let count_def_id = self.tcx.hir().local_def_id(count.hir_id);
 588                 let count = ty::Const::from_anon_const(self.tcx, count_def_id);
 589
 590                 ExprKind::Repeat { value: self.mirror_expr(v), count }
 591             }
 592             hir::ExprKind::Ret(ref v) => {
 593                 ExprKind::Return { value: v.as_ref().map(|v| self.mirror_expr(v)) }
 594             }
 595             hir::ExprKind::Break(dest, ref value) => match dest.target_id {
 596                 Ok(target_id) => ExprKind::Break {
 597                     label: region::Scope { id: target_id.local_id, data: region::ScopeData::Node },
 598                     value: value.as_ref().map(|value| self.mirror_expr(value)),
 599                 },
 600                 Err(err) => bug!("invalid loop id for break: {}", err),
 601             },
 602             hir::ExprKind::Continue(dest) => match dest.target_id {
 603                 Ok(loop_id) => ExprKind::Continue {
 604                     label: region::Scope { id: loop_id.local_id, data: region::ScopeData::Node },
 605                 },
 606                 Err(err) => bug!("invalid loop id for continue: {}", err),
 607             },
 608             hir::ExprKind::If(cond, then, else_opt) => ExprKind::If {
 609                 cond: self.mirror_expr(cond),
 610                 then: self.mirror_expr(then),
 611                 else_opt: else_opt.map(|el| self.mirror_expr(el)),
 612             },
 613             hir::ExprKind::Match(ref discr, ref arms, _) => ExprKind::Match {
 614                 scrutinee: self.mirror_expr(discr),
 615                 arms: self.arena.alloc_from_iter(arms.iter().map(|a| self.convert_arm(a))),
 616             },
 617             hir::ExprKind::Loop(ref body, ..) => {
 618                 let block_ty = self.typeck_results().node_type(body.hir_id);
 619                 let temp_lifetime = self.region_scope_tree.temporary_scope(body.hir_id.local_id);
 620                 let block = self.mirror_block(body);
 621                 let body = self.arena.alloc(Expr {
 622                     ty: block_ty,
 623                     temp_lifetime,
 624                     span: block.span,
 625                     kind: ExprKind::Block { body: block },
 626                 });
 627                 ExprKind::Loop { body }
 628             }
 629             hir::ExprKind::Field(ref source, ..) => ExprKind::Field {
 630                 lhs: self.mirror_expr(source),
 631                 name: Field::new(self.tcx.field_index(expr.hir_id, self.typeck_results)),
 632             },
 633             hir::ExprKind::Cast(ref source, ref cast_ty) => {
 634                 // Check for a user-given type annotation on this `cast`
 635                 let user_provided_types = self.typeck_results.user_provided_types();
 636                 let user_ty = user_provided_types.get(cast_ty.hir_id);
 637
 638                 debug!(
 639                     "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 640                     expr, cast_ty.hir_id, user_ty,
 641                 );
 642
 643                 // Check to see if this cast is a "coercion cast", where the cast is actually done
 644                 // using a coercion (or is a no-op).
 645                 let cast = if self.typeck_results().is_coercion_cast(source.hir_id) {
 646                     // Convert the lexpr to a vexpr.
 647                     ExprKind::Use { source: self.mirror_expr(source) }
 648                 } else if self.typeck_results().expr_ty(source).is_region_ptr() {
 649                     // Special cased so that we can type check that the element
 650                     // type of the source matches the pointed to type of the
 651                     // destination.
 652                     ExprKind::Pointer {
 653                         source: self.mirror_expr(source),
 654                         cast: PointerCast::ArrayToPointer,
 655                     }
 656                 } else {
 657                     // check whether this is casting an enum variant discriminant
 658                     // to prevent cycles, we refer to the discriminant initializer
 659                     // which is always an integer and thus doesn't need to know the
 660                     // enum's layout (or its tag type) to compute it during const eval
 661                     // Example:
 662                     // enum Foo {
 663                     //     A,
 664                     //     B = A as isize + 4,
 665                     // }
 666                     // The correct solution would be to add symbolic computations to miri,
 667                     // so we wouldn't have to compute and store the actual value
 668                     let var = if let hir::ExprKind::Path(ref qpath) = source.kind {
 669                         let res = self.typeck_results().qpath_res(qpath, source.hir_id);
 670                         self.typeck_results().node_type(source.hir_id).ty_adt_def().and_then(
 671                             |adt_def| match res {
 672                                 Res::Def(
 673                                     DefKind::Ctor(CtorOf::Variant, CtorKind::Const),
 674                                     variant_ctor_id,
 675                                 ) => {
 676                                     let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
 677                                     let (d, o) = adt_def.discriminant_def_for_variant(idx);
 678                                     use rustc_middle::ty::util::IntTypeExt;
 679                                     let ty = adt_def.repr.discr_type();
 680                                     let ty = ty.to_ty(self.tcx());
 681                                     Some((d, o, ty))
 682                                 }
 683                                 _ => None,
 684                             },
 685                         )
 686                     } else {
 687                         None
 688                     };
 689
 690                     let source = if let Some((did, offset, var_ty)) = var {
 691                         let mk_const = |literal| {
 692                             self.arena.alloc(Expr {
 693                                 temp_lifetime,
 694                                 ty: var_ty,
 695                                 span: expr.span,
 696                                 kind: ExprKind::Literal { literal, user_ty: None, const_id: None },
 697                             })
 698                         };
 699                         let offset = mk_const(ty::Const::from_bits(
 700                             self.tcx,
 701                             offset as u128,
 702                             self.param_env.and(var_ty),
 703                         ));
 704                         match did {
 705                             Some(did) => {
 706                                 // in case we are offsetting from a computed discriminant
 707                                 // and not the beginning of discriminants (which is always `0`)
 708                                 let substs = InternalSubsts::identity_for_item(self.tcx(), did);
 709                                 let lhs = mk_const(self.tcx().mk_const(ty::Const {
 710                                     val: ty::ConstKind::Unevaluated(
 711                                         ty::WithOptConstParam::unknown(did),
 712                                         substs,
 713                                         None,
 714                                     ),
 715                                     ty: var_ty,
 716                                 }));
 717                                 let bin =
 718                                     ExprKind::Binary { op: BinOp::Add, lhs: lhs, rhs: offset };
 719                                 self.arena.alloc(Expr {
 720                                     temp_lifetime,
 721                                     ty: var_ty,
 722                                     span: expr.span,
 723                                     kind: bin,
 724                                 })
 725                             }
 726                             None => offset,
 727                         }
 728                     } else {
 729                         self.mirror_expr(source)
 730                     };
 731
 732                     ExprKind::Cast { source: source }
 733                 };
 734
 735                 if let Some(user_ty) = user_ty {
 736                     // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 737                     //       inefficient, revisit this when performance becomes an issue.
 738                     let cast_expr = self.arena.alloc(Expr {
 739                         temp_lifetime,
 740                         ty: expr_ty,
 741                         span: expr.span,
 742                         kind: cast,
 743                     });
 744                     debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
 745
 746                     ExprKind::ValueTypeAscription { source: cast_expr, user_ty: Some(*user_ty) }
 747                 } else {
 748                     cast
 749                 }
 750             }
 751             hir::ExprKind::Type(ref source, ref ty) => {
 752                 let user_provided_types = self.typeck_results.user_provided_types();
 753                 let user_ty = user_provided_types.get(ty.hir_id).copied();
 754                 debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
 755                 let mirrored = self.mirror_expr(source);
 756                 if source.is_syntactic_place_expr() {
 757                     ExprKind::PlaceTypeAscription { source: mirrored, user_ty }
 758                 } else {
 759                     ExprKind::ValueTypeAscription { source: mirrored, user_ty }
 760                 }
 761             }
 762             hir::ExprKind::DropTemps(ref source) => {
 763                 ExprKind::Use { source: self.mirror_expr(source) }
 764             }
 765             hir::ExprKind::Box(ref value) => ExprKind::Box { value: self.mirror_expr(value) },
 766             hir::ExprKind::Array(ref fields) => {
 767                 ExprKind::Array { fields: self.mirror_exprs(fields) }
 768             }
 769             hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: self.mirror_exprs(fields) },
 770
 771             hir::ExprKind::Yield(ref v, _) => ExprKind::Yield { value: self.mirror_expr(v) },
 772             hir::ExprKind::Err => unreachable!(),
 773         };
 774
 775         Expr { temp_lifetime, ty: expr_ty, span: expr.span, kind }
 776     }
 777
 778     fn user_substs_applied_to_res(
 779         &mut self,
 780         hir_id: hir::HirId,
 781         res: Res,
 782     ) -> Option<ty::CanonicalUserType<'tcx>> {
 783         debug!("user_substs_applied_to_res: res={:?}", res);
 784         let user_provided_type = match res {
 785             // A reference to something callable -- e.g., a fn, method, or
 786             // a tuple-struct or tuple-variant. This has the type of a
 787             // `Fn` but with the user-given substitutions.
 788             Res::Def(DefKind::Fn, _)
 789             | Res::Def(DefKind::AssocFn, _)
 790             | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
 791             | Res::Def(DefKind::Const, _)
 792             | Res::Def(DefKind::AssocConst, _) => {
 793                 self.typeck_results().user_provided_types().get(hir_id).copied()
 794             }
 795
 796             // A unit struct/variant which is used as a value (e.g.,
 797             // `None`). This has the type of the enum/struct that defines
 798             // this variant -- but with the substitutions given by the
 799             // user.
 800             Res::Def(DefKind::Ctor(_, CtorKind::Const), _) => {
 801                 self.user_substs_applied_to_ty_of_hir_id(hir_id)
 802             }
 803
 804             // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 805             Res::SelfCtor(_) => self.user_substs_applied_to_ty_of_hir_id(hir_id),
 806
 807             _ => bug!("user_substs_applied_to_res: unexpected res {:?} at {:?}", res, hir_id),
 808         };
 809         debug!("user_substs_applied_to_res: user_provided_type={:?}", user_provided_type);
 810         user_provided_type
 811     }
 812
 813     fn method_callee(
 814         &mut self,
 815         expr: &hir::Expr<'_>,
 816         span: Span,
 817         overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 818     ) -> Expr<'thir, 'tcx> {
 819         let temp_lifetime = self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 820         let (def_id, substs, user_ty) = match overloaded_callee {
 821             Some((def_id, substs)) => (def_id, substs, None),
 822             None => {
 823                 let (kind, def_id) =
 824                     self.typeck_results().type_dependent_def(expr.hir_id).unwrap_or_else(|| {
 825                         span_bug!(expr.span, "no type-dependent def for method callee")
 826                     });
 827                 let user_ty = self.user_substs_applied_to_res(expr.hir_id, Res::Def(kind, def_id));
 828                 debug!("method_callee: user_ty={:?}", user_ty);
 829                 (def_id, self.typeck_results().node_substs(expr.hir_id), user_ty)
 830             }
 831         };
 832         let ty = self.tcx().mk_fn_def(def_id, substs);
 833         Expr {
 834             temp_lifetime,
 835             ty,
 836             span,
 837             kind: ExprKind::Literal {
 838                 literal: ty::Const::zero_sized(self.tcx(), ty),
 839                 user_ty,
 840                 const_id: None,
 841             },
 842         }
 843     }
 844
 845     fn convert_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) -> Arm<'thir, 'tcx> {
 846         Arm {
 847             pattern: self.pattern_from_hir(&arm.pat),
 848             guard: arm.guard.as_ref().map(|g| match g {
 849                 hir::Guard::If(ref e) => Guard::If(self.mirror_expr(e)),
 850                 hir::Guard::IfLet(ref pat, ref e) => {
 851                     Guard::IfLet(self.pattern_from_hir(pat), self.mirror_expr(e))
 852                 }
 853             }),
 854             body: self.mirror_expr(arm.body),
 855             lint_level: LintLevel::Explicit(arm.hir_id),
 856             scope: region::Scope { id: arm.hir_id.local_id, data: region::ScopeData::Node },
 857             span: arm.span,
 858         }
 859     }
 860
 861     fn convert_path_expr(
 862         &mut self,
 863         expr: &'tcx hir::Expr<'tcx>,
 864         res: Res,
 865     ) -> ExprKind<'thir, 'tcx> {
 866         let substs = self.typeck_results().node_substs(expr.hir_id);
 867         match res {
 868             // A regular function, constructor function or a constant.
 869             Res::Def(DefKind::Fn, _)
 870             | Res::Def(DefKind::AssocFn, _)
 871             | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
 872             | Res::SelfCtor(..) => {
 873                 let user_ty = self.user_substs_applied_to_res(expr.hir_id, res);
 874                 debug!("convert_path_expr: user_ty={:?}", user_ty);
 875                 ExprKind::Literal {
 876                     literal: ty::Const::zero_sized(
 877                         self.tcx,
 878                         self.typeck_results().node_type(expr.hir_id),
 879                     ),
 880                     user_ty,
 881                     const_id: None,
 882                 }
 883             }
 884
 885             Res::Def(DefKind::ConstParam, def_id) => {
 886                 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 887                 let item_id = self.tcx.hir().get_parent_node(hir_id);
 888                 let item_def_id = self.tcx.hir().local_def_id(item_id);
 889                 let generics = self.tcx.generics_of(item_def_id);
 890                 let index = generics.param_def_id_to_index[&def_id];
 891                 let name = self.tcx.hir().name(hir_id);
 892                 let val = ty::ConstKind::Param(ty::ParamConst::new(index, name));
 893                 ExprKind::Literal {
 894                     literal: self.tcx.mk_const(ty::Const {
 895                         val,
 896                         ty: self.typeck_results().node_type(expr.hir_id),
 897                     }),
 898                     user_ty: None,
 899                     const_id: Some(def_id),
 900                 }
 901             }
 902
 903             Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
 904                 let user_ty = self.user_substs_applied_to_res(expr.hir_id, res);
 905                 debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
 906                 ExprKind::Literal {
 907                     literal: self.tcx.mk_const(ty::Const {
 908                         val: ty::ConstKind::Unevaluated(
 909                             ty::WithOptConstParam::unknown(def_id),
 910                             substs,
 911                             None,
 912                         ),
 913                         ty: self.typeck_results().node_type(expr.hir_id),
 914                     }),
 915                     user_ty,
 916                     const_id: Some(def_id),
 917                 }
 918             }
 919
 920             Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id) => {
 921                 let user_provided_types = self.typeck_results.user_provided_types();
 922                 let user_provided_type = user_provided_types.get(expr.hir_id).copied();
 923                 debug!("convert_path_expr: user_provided_type={:?}", user_provided_type);
 924                 let ty = self.typeck_results().node_type(expr.hir_id);
 925                 match ty.kind() {
 926                     // A unit struct/variant which is used as a value.
 927                     // We return a completely different ExprKind here to account for this special case.
 928                     ty::Adt(adt_def, substs) => ExprKind::Adt {
 929                         adt_def,
 930                         variant_index: adt_def.variant_index_with_ctor_id(def_id),
 931                         substs,
 932                         user_ty: user_provided_type,
 933                         fields: self.arena.alloc_from_iter(iter::empty()),
 934                         base: None,
 935                     },
 936                     _ => bug!("unexpected ty: {:?}", ty),
 937                 }
 938             }
 939
 940             // We encode uses of statics as a `*&STATIC` where the `&STATIC` part is
 941             // a constant reference (or constant raw pointer for `static mut`) in MIR
 942             Res::Def(DefKind::Static, id) => {
 943                 let ty = self.tcx.static_ptr_ty(id);
 944                 let temp_lifetime = self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 945                 let kind = if self.tcx.is_thread_local_static(id) {
 946                     ExprKind::ThreadLocalRef(id)
 947                 } else {
 948                     let ptr = self.tcx.create_static_alloc(id);
 949                     ExprKind::StaticRef {
 950                         literal: ty::Const::from_scalar(self.tcx, Scalar::Ptr(ptr.into()), ty),
 951                         def_id: id,
 952                     }
 953                 };
 954                 ExprKind::Deref {
 955                     arg: self.arena.alloc(Expr { ty, temp_lifetime, span: expr.span, kind }),
 956                 }
 957             }
 958
 959             Res::Local(var_hir_id) => self.convert_var(var_hir_id),
 960
 961             _ => span_bug!(expr.span, "res `{:?}` not yet implemented", res),
 962         }
 963     }
 964
 965     fn convert_var(&mut self, var_hir_id: hir::HirId) -> ExprKind<'thir, 'tcx> {
 966         // We want upvars here not captures.
 967         // Captures will be handled in MIR.
 968         let is_upvar = self
 969             .tcx
 970             .upvars_mentioned(self.body_owner)
 971             .map_or(false, |upvars| upvars.contains_key(&var_hir_id));
 972
 973         debug!(
 974             "convert_var({:?}): is_upvar={}, body_owner={:?}",
 975             var_hir_id, is_upvar, self.body_owner
 976         );
 977
 978         if is_upvar {
 979             ExprKind::UpvarRef { closure_def_id: self.body_owner, var_hir_id }
 980         } else {
 981             ExprKind::VarRef { id: var_hir_id }
 982         }
 983     }
 984
 985     fn overloaded_operator(
 986         &mut self,
 987         expr: &'tcx hir::Expr<'tcx>,
 988         args: &'thir [Expr<'thir, 'tcx>],
 989     ) -> ExprKind<'thir, 'tcx> {
 990         let fun = self.arena.alloc(self.method_callee(expr, expr.span, None));
 991         ExprKind::Call { ty: fun.ty, fun, args, from_hir_call: false, fn_span: expr.span }
 992     }
 993
 994     fn overloaded_place(
 995         &mut self,
 996         expr: &'tcx hir::Expr<'tcx>,
 997         place_ty: Ty<'tcx>,
 998         overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 999         args: &'thir [Expr<'thir, 'tcx>],
1000         span: Span,
1001     ) -> ExprKind<'thir, 'tcx> {
1002         // For an overloaded *x or x[y] expression of type T, the method
1003         // call returns an &T and we must add the deref so that the types
1004         // line up (this is because `*x` and `x[y]` represent places):
1005
1006         // Reconstruct the output assuming it's a reference with the
1007         // same region and mutability as the receiver. This holds for
1008         // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1009         let (region, mutbl) = match *args[0].ty.kind() {
1010             ty::Ref(region, _, mutbl) => (region, mutbl),
1011             _ => span_bug!(span, "overloaded_place: receiver is not a reference"),
1012         };
1013         let ref_ty = self.tcx.mk_ref(region, ty::TypeAndMut { ty: place_ty, mutbl });
1014
1015         // construct the complete expression `foo()` for the overloaded call,
1016         // which will yield the &T type
1017         let temp_lifetime = self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1018         let fun = self.arena.alloc(self.method_callee(expr, span, overloaded_callee));
1019         let ref_expr = self.arena.alloc(Expr {
1020             temp_lifetime,
1021             ty: ref_ty,
1022             span,
1023             kind: ExprKind::Call { ty: fun.ty, fun, args, from_hir_call: false, fn_span: span },
1024         });
1025
1026         // construct and return a deref wrapper `*foo()`
1027         ExprKind::Deref { arg: ref_expr }
1028     }
1029
1030     fn convert_captured_hir_place(
1031         &mut self,
1032         closure_expr: &'tcx hir::Expr<'tcx>,
1033         place: HirPlace<'tcx>,
1034     ) -> Expr<'thir, 'tcx> {
1035         let temp_lifetime = self.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1036         let var_ty = place.base_ty;
1037
1038         // The result of capture analysis in `rustc_typeck/check/upvar.rs`represents a captured path
1039         // as it's seen for use within the closure and not at the time of closure creation.
1040         //
1041         // That is we see expect to see it start from a captured upvar and not something that is local
1042         // to the closure's parent.
1043         let var_hir_id = match place.base {
1044             HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
1045             base => bug!("Expected an upvar, found {:?}", base),
1046         };
1047
1048         let mut captured_place_expr = Expr {
1049             temp_lifetime,
1050             ty: var_ty,
1051             span: closure_expr.span,
1052             kind: self.convert_var(var_hir_id),
1053         };
1054
1055         for proj in place.projections.iter() {
1056             let kind = match proj.kind {
1057                 HirProjectionKind::Deref => {
1058                     ExprKind::Deref { arg: self.arena.alloc(captured_place_expr) }
1059                 }
1060                 HirProjectionKind::Field(field, ..) => {
1061                     // Variant index will always be 0, because for multi-variant
1062                     // enums, we capture the enum entirely.
1063                     ExprKind::Field {
1064                         lhs: self.arena.alloc(captured_place_expr),
1065                         name: Field::new(field as usize),
1066                     }
1067                 }
1068                 HirProjectionKind::Index | HirProjectionKind::Subslice => {
1069                     // We don't capture these projections, so we can ignore them here
1070                     continue;
1071                 }
1072             };
1073
1074             captured_place_expr =
1075                 Expr { temp_lifetime, ty: proj.ty, span: closure_expr.span, kind };
1076         }
1077
1078         captured_place_expr
1079     }
1080
1081     fn capture_upvar(
1082         &mut self,
1083         closure_expr: &'tcx hir::Expr<'tcx>,
1084         captured_place: &'tcx ty::CapturedPlace<'tcx>,
1085         upvar_ty: Ty<'tcx>,
1086     ) -> Expr<'thir, 'tcx> {
1087         let upvar_capture = captured_place.info.capture_kind;
1088         let captured_place_expr =
1089             self.convert_captured_hir_place(closure_expr, captured_place.place.clone());
1090         let temp_lifetime = self.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1091
1092         match upvar_capture {
1093             ty::UpvarCapture::ByValue(_) => captured_place_expr,
1094             ty::UpvarCapture::ByRef(upvar_borrow) => {
1095                 let borrow_kind = match upvar_borrow.kind {
1096                     ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1097                     ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1098                     ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false },
1099                 };
1100                 Expr {
1101                     temp_lifetime,
1102                     ty: upvar_ty,
1103                     span: closure_expr.span,
1104                     kind: ExprKind::Borrow {
1105                         borrow_kind,
1106                         arg: self.arena.alloc(captured_place_expr),
1107                     },
1108                 }
1109             }
1110         }
1111     }
1112
1113     /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExpr.
1114     fn field_refs(
1115         &mut self,
1116         fields: &'tcx [hir::ExprField<'tcx>],
1117     ) -> &'thir [FieldExpr<'thir, 'tcx>] {
1118         self.arena.alloc_from_iter(fields.iter().map(|field| FieldExpr {
1119             name: Field::new(self.tcx.field_index(field.hir_id, self.typeck_results)),
1120             expr: self.mirror_expr(field.expr),
1121         }))
1122     }
1123 }
1124
1125 trait ToBorrowKind {
1126     fn to_borrow_kind(&self) -> BorrowKind;
1127 }
1128
1129 impl ToBorrowKind for AutoBorrowMutability {
1130     fn to_borrow_kind(&self) -> BorrowKind {
1131         use rustc_middle::ty::adjustment::AllowTwoPhase;
1132         match *self {
1133             AutoBorrowMutability::Mut { allow_two_phase_borrow } => BorrowKind::Mut {
1134                 allow_two_phase_borrow: match allow_two_phase_borrow {
1135                     AllowTwoPhase::Yes => true,
1136                     AllowTwoPhase::No => false,
1137                 },
1138             },
1139             AutoBorrowMutability::Not => BorrowKind::Shared,
1140         }
1141     }
1142 }
1143
1144 impl ToBorrowKind for hir::Mutability {
1145     fn to_borrow_kind(&self) -> BorrowKind {
1146         match *self {
1147             hir::Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false },
1148             hir::Mutability::Not => BorrowKind::Shared,
1149         }
1150     }
1151 }
1152
1153 fn bin_op(op: hir::BinOpKind) -> BinOp {
1154     match op {
1155         hir::BinOpKind::Add => BinOp::Add,
1156         hir::BinOpKind::Sub => BinOp::Sub,
1157         hir::BinOpKind::Mul => BinOp::Mul,
1158         hir::BinOpKind::Div => BinOp::Div,
1159         hir::BinOpKind::Rem => BinOp::Rem,
1160         hir::BinOpKind::BitXor => BinOp::BitXor,
1161         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1162         hir::BinOpKind::BitOr => BinOp::BitOr,
1163         hir::BinOpKind::Shl => BinOp::Shl,
1164         hir::BinOpKind::Shr => BinOp::Shr,
1165         hir::BinOpKind::Eq => BinOp::Eq,
1166         hir::BinOpKind::Lt => BinOp::Lt,
1167         hir::BinOpKind::Le => BinOp::Le,
1168         hir::BinOpKind::Ne => BinOp::Ne,
1169         hir::BinOpKind::Ge => BinOp::Ge,
1170         hir::BinOpKind::Gt => BinOp::Gt,
1171         _ => bug!("no equivalent for ast binop {:?}", op),
1172     }
1173 }