src/librustc_mir/hair/cx/expr.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use hair::*;
  12 use rustc_data_structures::indexed_vec::Idx;
  13 use hair::cx::Cx;
  14 use hair::cx::block;
  15 use hair::cx::to_ref::ToRef;
  16 use hair::util::UserAnnotatedTyHelpers;
  17 use rustc::hir::def::{Def, CtorKind};
  18 use rustc::mir::interpret::GlobalId;
  19 use rustc::ty::{self, AdtKind, Ty};
  20 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability};
  21 use rustc::ty::cast::CastKind as TyCastKind;
  22 use rustc::hir;
  23 use rustc::hir::def_id::LocalDefId;
  24 use rustc::mir::{BorrowKind};
  25 use syntax_pos::Span;
  26
  27 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
  28     type Output = Expr<'tcx>;
  29
  30     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
  31         let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
  32         let expr_scope = region::Scope {
  33             id: self.hir_id.local_id,
  34             data: region::ScopeData::Node
  35         };
  36
  37         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
  38
  39         let mut expr = make_mirror_unadjusted(cx, self);
  40
  41         // Now apply adjustments, if any.
  42         for adjustment in cx.tables().expr_adjustments(self) {
  43             debug!("make_mirror: expr={:?} applying adjustment={:?}",
  44                    expr,
  45                    adjustment);
  46             expr = apply_adjustment(cx, self, expr, adjustment);
  47         }
  48
  49         // Next, wrap this up in the expr's scope.
  50         expr = Expr {
  51             temp_lifetime,
  52             ty: expr.ty,
  53             span: self.span,
  54             kind: ExprKind::Scope {
  55                 region_scope: expr_scope,
  56                 value: expr.to_ref(),
  57                 lint_level: cx.lint_level_of(self.id),
  58             },
  59         };
  60
  61         // Finally, create a destruction scope, if any.
  62         if let Some(region_scope) =
  63             cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id) {
  64                 expr = Expr {
  65                     temp_lifetime,
  66                     ty: expr.ty,
  67                     span: self.span,
  68                     kind: ExprKind::Scope {
  69                         region_scope,
  70                         value: expr.to_ref(),
  71                         lint_level: LintLevel::Inherited,
  72                     },
  73                 };
  74             }
  75
  76         // OK, all done!
  77         expr
  78     }
  79 }
  80
  81 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
  82                                     hir_expr: &'tcx hir::Expr,
  83                                     mut expr: Expr<'tcx>,
  84                                     adjustment: &Adjustment<'tcx>)
  85                                     -> Expr<'tcx> {
  86     let Expr { temp_lifetime, mut span, .. } = expr;
  87     let kind = match adjustment.kind {
  88         Adjust::ReifyFnPointer => {
  89             ExprKind::ReifyFnPointer { source: expr.to_ref() }
  90         }
  91         Adjust::UnsafeFnPointer => {
  92             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
  93         }
  94         Adjust::ClosureFnPointer => {
  95             ExprKind::ClosureFnPointer { source: expr.to_ref() }
  96         }
  97         Adjust::NeverToAny => {
  98             ExprKind::NeverToAny { source: expr.to_ref() }
  99         }
 100         Adjust::MutToConstPointer => {
 101             ExprKind::Cast { source: expr.to_ref() }
 102         }
 103         Adjust::Deref(None) => {
 104             // Adjust the span from the block, to the last expression of the
 105             // block. This is a better span when returning a mutable reference
 106             // with too short a lifetime. The error message will use the span
 107             // from the assignment to the return place, which should only point
 108             // at the returned value, not the entire function body.
 109             //
 110             // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
 111             //      x
 112             //   // ^ error message points at this expression.
 113             // }
 114             //
 115             // We don't need to do this adjustment in the next match arm since
 116             // deref coercions always start with a built-in deref.
 117             if let ExprKind::Block { body } = expr.kind {
 118                 if let Some(ref last_expr) = body.expr {
 119                     span = last_expr.span;
 120                     expr.span = span;
 121                 }
 122             }
 123             ExprKind::Deref { arg: expr.to_ref() }
 124         }
 125         Adjust::Deref(Some(deref)) => {
 126             let call = deref.method_call(cx.tcx(), expr.ty);
 127
 128             expr = Expr {
 129                 temp_lifetime,
 130                 ty: cx.tcx.mk_ref(deref.region,
 131                                   ty::TypeAndMut {
 132                                     ty: expr.ty,
 133                                     mutbl: deref.mutbl,
 134                                   }),
 135                 span,
 136                 kind: ExprKind::Borrow {
 137                     region: deref.region,
 138                     borrow_kind: deref.mutbl.to_borrow_kind(),
 139                     arg: expr.to_ref(),
 140                 },
 141             };
 142
 143             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
 144         }
 145         Adjust::Borrow(AutoBorrow::Ref(r, m)) => {
 146             ExprKind::Borrow {
 147                 region: r,
 148                 borrow_kind: m.to_borrow_kind(),
 149                 arg: expr.to_ref(),
 150             }
 151         }
 152         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
 153             // Convert this to a suitable `&foo` and
 154             // then an unsafe coercion. Limit the region to be just this
 155             // expression.
 156             let region = ty::ReScope(region::Scope {
 157                 id: hir_expr.hir_id.local_id,
 158                 data: region::ScopeData::Node
 159             });
 160             let region = cx.tcx.mk_region(region);
 161             expr = Expr {
 162                 temp_lifetime,
 163                 ty: cx.tcx.mk_ref(region,
 164                                   ty::TypeAndMut {
 165                                     ty: expr.ty,
 166                                     mutbl: m,
 167                                   }),
 168                 span,
 169                 kind: ExprKind::Borrow {
 170                     region,
 171                     borrow_kind: m.to_borrow_kind(),
 172                     arg: expr.to_ref(),
 173                 },
 174             };
 175             let cast_expr = Expr {
 176                 temp_lifetime,
 177                 ty: adjustment.target,
 178                 span,
 179                 kind: ExprKind::Cast { source: expr.to_ref() }
 180             };
 181
 182             // To ensure that both implicit and explicit coercions are
 183             // handled the same way, we insert an extra layer of indirection here.
 184             // For explicit casts (e.g. 'foo as *const T'), the source of the 'Use'
 185             // will be an ExprKind::Hair with the appropriate cast expression. Here,
 186             // we make our Use source the generated Cast from the original coercion.
 187             //
 188             // In both cases, this outer 'Use' ensures that the inner 'Cast' is handled by
 189             // as_operand, not by as_rvalue - causing the cast result to be stored in a temporary.
 190             // Ordinary, this is identical to using the cast directly as an rvalue. However, if the
 191             // source of the cast was previously borrowed as mutable, storing the cast in a
 192             // temporary gives the source a chance to expire before the cast is used. For
 193             // structs with a self-referential *mut ptr, this allows assignment to work as
 194             // expected.
 195             //
 196             // For example, consider the type 'struct Foo { field: *mut Foo }',
 197             // The method 'fn bar(&mut self) { self.field = self }'
 198             // triggers a coercion from '&mut self' to '*mut self'. In order
 199             // for the assignment to be valid, the implicit borrow
 200             // of 'self' involved in the coercion needs to end before the local
 201             // containing the '*mut T' is assigned to 'self.field' - otherwise,
 202             // we end up trying to assign to 'self.field' while we have another mutable borrow
 203             // active.
 204             //
 205             // We only need to worry about this kind of thing for coercions from refs to ptrs,
 206             // since they get rid of a borrow implicitly.
 207             ExprKind::Use { source: cast_expr.to_ref() }
 208         }
 209         Adjust::Unsize => {
 210             // See the above comment for Adjust::Deref
 211             if let ExprKind::Block { body } = expr.kind {
 212                 if let Some(ref last_expr) = body.expr {
 213                     span = last_expr.span;
 214                     expr.span = span;
 215                 }
 216             }
 217             ExprKind::Unsize { source: expr.to_ref() }
 218         }
 219     };
 220
 221     Expr {
 222         temp_lifetime,
 223         ty: adjustment.target,
 224         span,
 225         kind,
 226     }
 227 }
 228
 229 fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 230                                           expr: &'tcx hir::Expr)
 231                                           -> Expr<'tcx> {
 232     let expr_ty = cx.tables().expr_ty(expr);
 233     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 234
 235     let kind = match expr.node {
 236         // Here comes the interesting stuff:
 237         hir::ExprKind::MethodCall(_, method_span, ref args) => {
 238             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 239             let expr = method_callee(cx, expr, method_span,None);
 240             let args = args.iter()
 241                 .map(|e| e.to_ref())
 242                 .collect();
 243             ExprKind::Call {
 244                 ty: expr.ty,
 245                 fun: expr.to_ref(),
 246                 args,
 247                 from_hir_call: true,
 248             }
 249         }
 250
 251         hir::ExprKind::Call(ref fun, ref args) => {
 252             if cx.tables().is_method_call(expr) {
 253                 // The callee is something implementing Fn, FnMut, or FnOnce.
 254                 // Find the actual method implementation being called and
 255                 // build the appropriate UFCS call expression with the
 256                 // callee-object as expr parameter.
 257
 258                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 259
 260                 let method = method_callee(cx, expr, fun.span,None);
 261
 262                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
 263                 let tupled_args = Expr {
 264                     ty: cx.tcx.mk_tup(arg_tys),
 265                     temp_lifetime,
 266                     span: expr.span,
 267                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
 268                 };
 269
 270                 ExprKind::Call {
 271                     ty: method.ty,
 272                     fun: method.to_ref(),
 273                     args: vec![fun.to_ref(), tupled_args.to_ref()],
 274                     from_hir_call: true,
 275                 }
 276             } else {
 277                 let adt_data = if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) =
 278                     fun.node
 279                 {
 280                     // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
 281                     expr_ty.ty_adt_def().and_then(|adt_def| {
 282                         match path.def {
 283                             Def::VariantCtor(variant_id, CtorKind::Fn) => {
 284                                 Some((adt_def, adt_def.variant_index_with_id(variant_id)))
 285                             }
 286                             Def::StructCtor(_, CtorKind::Fn) |
 287                             Def::SelfCtor(..) => Some((adt_def, 0)),
 288                             _ => None,
 289                         }
 290                     })
 291                 } else {
 292                     None
 293                 };
 294                 if let Some((adt_def, index)) = adt_data {
 295                     let substs = cx.tables().node_substs(fun.hir_id);
 296
 297                     let user_ty = cx.tables().user_substs(fun.hir_id)
 298                         .map(|user_substs| UserTypeAnnotation::TypeOf(adt_def.did, user_substs));
 299
 300                     let field_refs = args.iter()
 301                         .enumerate()
 302                         .map(|(idx, e)| {
 303                             FieldExprRef {
 304                                 name: Field::new(idx),
 305                                 expr: e.to_ref(),
 306                             }
 307                         })
 308                         .collect();
 309                     ExprKind::Adt {
 310                         adt_def,
 311                         substs,
 312                         variant_index: index,
 313                         fields: field_refs,
 314                         user_ty,
 315                         base: None,
 316                     }
 317                 } else {
 318                     ExprKind::Call {
 319                         ty: cx.tables().node_id_to_type(fun.hir_id),
 320                         fun: fun.to_ref(),
 321                         args: args.to_ref(),
 322                         from_hir_call: true,
 323                     }
 324                 }
 325             }
 326         }
 327
 328         hir::ExprKind::AddrOf(mutbl, ref expr) => {
 329             let region = match expr_ty.sty {
 330                 ty::Ref(r, _, _) => r,
 331                 _ => span_bug!(expr.span, "type of & not region"),
 332             };
 333             ExprKind::Borrow {
 334                 region,
 335                 borrow_kind: mutbl.to_borrow_kind(),
 336                 arg: expr.to_ref(),
 337             }
 338         }
 339
 340         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
 341
 342         hir::ExprKind::Assign(ref lhs, ref rhs) => {
 343             ExprKind::Assign {
 344                 lhs: lhs.to_ref(),
 345                 rhs: rhs.to_ref(),
 346             }
 347         }
 348
 349         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 350             if cx.tables().is_method_call(expr) {
 351                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 352             } else {
 353                 ExprKind::AssignOp {
 354                     op: bin_op(op.node),
 355                     lhs: lhs.to_ref(),
 356                     rhs: rhs.to_ref(),
 357                 }
 358             }
 359         }
 360
 361         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 362             literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, false),
 363             user_ty: None,
 364         },
 365
 366         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 367             if cx.tables().is_method_call(expr) {
 368                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 369             } else {
 370                 // FIXME overflow
 371                 match (op.node, cx.constness) {
 372                     // FIXME(eddyb) use logical ops in constants when
 373                     // they can handle that kind of control-flow.
 374                     (hir::BinOpKind::And, hir::Constness::Const) => {
 375                         ExprKind::Binary {
 376                             op: BinOp::BitAnd,
 377                             lhs: lhs.to_ref(),
 378                             rhs: rhs.to_ref(),
 379                         }
 380                     }
 381                     (hir::BinOpKind::Or, hir::Constness::Const) => {
 382                         ExprKind::Binary {
 383                             op: BinOp::BitOr,
 384                             lhs: lhs.to_ref(),
 385                             rhs: rhs.to_ref(),
 386                         }
 387                     }
 388
 389                     (hir::BinOpKind::And, hir::Constness::NotConst) => {
 390                         ExprKind::LogicalOp {
 391                             op: LogicalOp::And,
 392                             lhs: lhs.to_ref(),
 393                             rhs: rhs.to_ref(),
 394                         }
 395                     }
 396                     (hir::BinOpKind::Or, hir::Constness::NotConst) => {
 397                         ExprKind::LogicalOp {
 398                             op: LogicalOp::Or,
 399                             lhs: lhs.to_ref(),
 400                             rhs: rhs.to_ref(),
 401                         }
 402                     }
 403
 404                     _ => {
 405                         let op = bin_op(op.node);
 406                         ExprKind::Binary {
 407                             op,
 408                             lhs: lhs.to_ref(),
 409                             rhs: rhs.to_ref(),
 410                         }
 411                     }
 412                 }
 413             }
 414         }
 415
 416         hir::ExprKind::Index(ref lhs, ref index) => {
 417             if cx.tables().is_method_call(expr) {
 418                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 419             } else {
 420                 ExprKind::Index {
 421                     lhs: lhs.to_ref(),
 422                     index: index.to_ref(),
 423                 }
 424             }
 425         }
 426
 427         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
 428             if cx.tables().is_method_call(expr) {
 429                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
 430             } else {
 431                 ExprKind::Deref { arg: arg.to_ref() }
 432             }
 433         }
 434
 435         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
 436             if cx.tables().is_method_call(expr) {
 437                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 438             } else {
 439                 ExprKind::Unary {
 440                     op: UnOp::Not,
 441                     arg: arg.to_ref(),
 442                 }
 443             }
 444         }
 445
 446         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
 447             if cx.tables().is_method_call(expr) {
 448                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 449             } else {
 450                 if let hir::ExprKind::Lit(ref lit) = arg.node {
 451                     ExprKind::Literal {
 452                         literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, true),
 453                         user_ty: None,
 454                     }
 455                 } else {
 456                     ExprKind::Unary {
 457                         op: UnOp::Neg,
 458                         arg: arg.to_ref(),
 459                     }
 460                 }
 461             }
 462         }
 463
 464         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => {
 465             match expr_ty.sty {
 466                 ty::Adt(adt, substs) => {
 467                     match adt.adt_kind() {
 468                         AdtKind::Struct | AdtKind::Union => {
 469                             ExprKind::Adt {
 470                                 adt_def: adt,
 471                                 variant_index: 0,
 472                                 substs,
 473                                 user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
 474                                 fields: field_refs(cx, fields),
 475                                 base: base.as_ref().map(|base| {
 476                                     FruInfo {
 477                                         base: base.to_ref(),
 478                                         field_types: cx.tables()
 479                                                        .fru_field_types()[expr.hir_id]
 480                                                        .clone(),
 481                                     }
 482                                 }),
 483                             }
 484                         }
 485                         AdtKind::Enum => {
 486                             let def = match *qpath {
 487                                 hir::QPath::Resolved(_, ref path) => path.def,
 488                                 hir::QPath::TypeRelative(..) => Def::Err,
 489                             };
 490                             match def {
 491                                 Def::Variant(variant_id) => {
 492                                     assert!(base.is_none());
 493
 494                                     let index = adt.variant_index_with_id(variant_id);
 495                                     ExprKind::Adt {
 496                                         adt_def: adt,
 497                                         variant_index: index,
 498                                         substs,
 499                                         user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
 500                                         fields: field_refs(cx, fields),
 501                                         base: None,
 502                                     }
 503                                 }
 504                                 _ => {
 505                                     span_bug!(expr.span, "unexpected def: {:?}", def);
 506                                 }
 507                             }
 508                         }
 509                     }
 510                 }
 511                 _ => {
 512                     span_bug!(expr.span,
 513                               "unexpected type for struct literal: {:?}",
 514                               expr_ty);
 515                 }
 516             }
 517         }
 518
 519         hir::ExprKind::Closure(..) => {
 520             let closure_ty = cx.tables().expr_ty(expr);
 521             let (def_id, substs, movability) = match closure_ty.sty {
 522                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 523                 ty::Generator(def_id, substs, movability) => {
 524                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
 525                 }
 526                 _ => {
 527                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 528                 }
 529             };
 530             let upvars = cx.tcx.with_freevars(expr.id, |freevars| {
 531                 freevars.iter()
 532                     .zip(substs.upvar_tys(def_id, cx.tcx))
 533                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 534                     .collect()
 535             });
 536             ExprKind::Closure {
 537                 closure_id: def_id,
 538                 substs,
 539                 upvars,
 540                 movability,
 541             }
 542         }
 543
 544         hir::ExprKind::Path(ref qpath) => {
 545             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 546             convert_path_expr(cx, expr, def)
 547         }
 548
 549         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
 550             ExprKind::InlineAsm {
 551                 asm,
 552                 outputs: outputs.to_ref(),
 553                 inputs: inputs.to_ref(),
 554             }
 555         }
 556
 557         // Now comes the rote stuff:
 558         hir::ExprKind::Repeat(ref v, ref count) => {
 559             let def_id = cx.tcx.hir.local_def_id(count.id);
 560             let substs = Substs::identity_for_item(cx.tcx.global_tcx(), def_id);
 561             let instance = ty::Instance::resolve(
 562                 cx.tcx.global_tcx(),
 563                 cx.param_env,
 564                 def_id,
 565                 substs,
 566             ).unwrap();
 567             let global_id = GlobalId {
 568                 instance,
 569                 promoted: None
 570             };
 571             let span = cx.tcx.def_span(def_id);
 572             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
 573                 Ok(cv) => cv.unwrap_usize(cx.tcx),
 574                 Err(e) => {
 575                     e.report_as_error(cx.tcx.at(span), "could not evaluate array length");
 576                     0
 577                 },
 578             };
 579
 580             ExprKind::Repeat {
 581                 value: v.to_ref(),
 582                 count,
 583             }
 584         }
 585         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 586         hir::ExprKind::Break(dest, ref value) => {
 587             match dest.target_id {
 588                 Ok(target_id) => ExprKind::Break {
 589                     label: region::Scope {
 590                         id: cx.tcx.hir.node_to_hir_id(target_id).local_id,
 591                         data: region::ScopeData::Node
 592                     },
 593                     value: value.to_ref(),
 594                 },
 595                 Err(err) => bug!("invalid loop id for break: {}", err)
 596             }
 597         }
 598         hir::ExprKind::Continue(dest) => {
 599             match dest.target_id {
 600                 Ok(loop_id) => ExprKind::Continue {
 601                     label: region::Scope {
 602                         id: cx.tcx.hir.node_to_hir_id(loop_id).local_id,
 603                         data: region::ScopeData::Node
 604                     },
 605                 },
 606                 Err(err) => bug!("invalid loop id for continue: {}", err)
 607             }
 608         }
 609         hir::ExprKind::Match(ref discr, ref arms, _) => {
 610             ExprKind::Match {
 611                 discriminant: discr.to_ref(),
 612                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 613             }
 614         }
 615         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
 616             ExprKind::If {
 617                 condition: cond.to_ref(),
 618                 then: then.to_ref(),
 619                 otherwise: otherwise.to_ref(),
 620             }
 621         }
 622         hir::ExprKind::While(ref cond, ref body, _) => {
 623             ExprKind::Loop {
 624                 condition: Some(cond.to_ref()),
 625                 body: block::to_expr_ref(cx, body),
 626             }
 627         }
 628         hir::ExprKind::Loop(ref body, _, _) => {
 629             ExprKind::Loop {
 630                 condition: None,
 631                 body: block::to_expr_ref(cx, body),
 632             }
 633         }
 634         hir::ExprKind::Field(ref source, ..) => {
 635             ExprKind::Field {
 636                 lhs: source.to_ref(),
 637                 name: Field::new(cx.tcx.field_index(expr.id, cx.tables)),
 638             }
 639         }
 640         hir::ExprKind::Cast(ref source, ref cast_ty) => {
 641             // Check for a user-given type annotation on this `cast`
 642             let user_ty = cx.tables.user_provided_tys().get(cast_ty.hir_id)
 643                 .map(|&t| UserTypeAnnotation::Ty(t));
 644
 645             debug!(
 646                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 647                 expr,
 648                 cast_ty.hir_id,
 649                 user_ty,
 650             );
 651
 652             // Check to see if this cast is a "coercion cast", where the cast is actually done
 653             // using a coercion (or is a no-op).
 654             let cast = if let Some(&TyCastKind::CoercionCast) =
 655                 cx.tables()
 656                 .cast_kinds()
 657                 .get(source.hir_id)
 658             {
 659                 // Convert the lexpr to a vexpr.
 660                 ExprKind::Use { source: source.to_ref() }
 661             } else {
 662                 // check whether this is casting an enum variant discriminant
 663                 // to prevent cycles, we refer to the discriminant initializer
 664                 // which is always an integer and thus doesn't need to know the
 665                 // enum's layout (or its tag type) to compute it during const eval
 666                 // Example:
 667                 // enum Foo {
 668                 //     A,
 669                 //     B = A as isize + 4,
 670                 // }
 671                 // The correct solution would be to add symbolic computations to miri,
 672                 // so we wouldn't have to compute and store the actual value
 673                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 674                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 675                     cx
 676                         .tables()
 677                         .node_id_to_type(source.hir_id)
 678                         .ty_adt_def()
 679                         .and_then(|adt_def| {
 680                         match def {
 681                             Def::VariantCtor(variant_id, CtorKind::Const) => {
 682                                 let idx = adt_def.variant_index_with_id(variant_id);
 683                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 684                                 use rustc::ty::util::IntTypeExt;
 685                                 let ty = adt_def.repr.discr_type();
 686                                 let ty = ty.to_ty(cx.tcx());
 687                                 Some((d, o, ty))
 688                             }
 689                             _ => None,
 690                         }
 691                     })
 692                 } else {
 693                     None
 694                 };
 695
 696                 let source = if let Some((did, offset, var_ty)) = var {
 697                     let mk_const = |literal| Expr {
 698                         temp_lifetime,
 699                         ty: var_ty,
 700                         span: expr.span,
 701                         kind: ExprKind::Literal { literal, user_ty: None },
 702                     }.to_ref();
 703                     let offset = mk_const(ty::Const::from_bits(
 704                         cx.tcx,
 705                         offset as u128,
 706                         cx.param_env.and(var_ty),
 707                     ));
 708                     match did {
 709                         Some(did) => {
 710                             // in case we are offsetting from a computed discriminant
 711                             // and not the beginning of discriminants (which is always `0`)
 712                             let substs = Substs::identity_for_item(cx.tcx(), did);
 713                             let lhs = mk_const(ty::Const::unevaluated(
 714                                 cx.tcx(),
 715                                 did,
 716                                 substs,
 717                                 var_ty,
 718                             ));
 719                             let bin = ExprKind::Binary {
 720                                 op: BinOp::Add,
 721                                 lhs,
 722                                 rhs: offset,
 723                             };
 724                             Expr {
 725                                 temp_lifetime,
 726                                 ty: var_ty,
 727                                 span: expr.span,
 728                                 kind: bin,
 729                             }.to_ref()
 730                         },
 731                         None => offset,
 732                     }
 733                 } else {
 734                     source.to_ref()
 735                 };
 736
 737                 ExprKind::Cast { source }
 738             };
 739
 740             if let Some(user_ty) = user_ty {
 741                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 742                 //       inefficient, revisit this when performance becomes an issue.
 743                 let cast_expr = Expr {
 744                     temp_lifetime,
 745                     ty: expr_ty,
 746                     span: expr.span,
 747                     kind: cast,
 748                 };
 749
 750                 ExprKind::ValueTypeAscription {
 751                     source: cast_expr.to_ref(),
 752                     user_ty: Some(user_ty),
 753                 }
 754             } else {
 755                 cast
 756             }
 757         }
 758         hir::ExprKind::Type(ref source, ref ty) => {
 759             let user_provided_tys = cx.tables.user_provided_tys();
 760             let user_ty = user_provided_tys
 761                 .get(ty.hir_id)
 762                 .map(|&c_ty| UserTypeAnnotation::Ty(c_ty));
 763             if source.is_place_expr() {
 764                 ExprKind::PlaceTypeAscription {
 765                     source: source.to_ref(),
 766                     user_ty,
 767                 }
 768             } else {
 769                 ExprKind::ValueTypeAscription {
 770                     source: source.to_ref(),
 771                     user_ty,
 772                 }
 773             }
 774         }
 775         hir::ExprKind::Box(ref value) => {
 776             ExprKind::Box {
 777                 value: value.to_ref(),
 778             }
 779         }
 780         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 781         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 782
 783         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 784     };
 785
 786     Expr {
 787         temp_lifetime,
 788         ty: expr_ty,
 789         span: expr.span,
 790         kind,
 791     }
 792 }
 793
 794 fn user_substs_applied_to_def(
 795     cx: &mut Cx<'a, 'gcx, 'tcx>,
 796     hir_id: hir::HirId,
 797     def: &Def,
 798 ) -> Option<UserTypeAnnotation<'tcx>> {
 799     match def {
 800         // A reference to something callable -- e.g., a fn, method, or
 801         // a tuple-struct or tuple-variant. This has the type of a
 802         // `Fn` but with the user-given substitutions.
 803         Def::Fn(_) |
 804         Def::Method(_) |
 805         Def::StructCtor(_, CtorKind::Fn) |
 806         Def::VariantCtor(_, CtorKind::Fn) |
 807         Def::Const(_) |
 808         Def::AssociatedConst(_) =>
 809             Some(UserTypeAnnotation::TypeOf(def.def_id(), cx.tables().user_substs(hir_id)?)),
 810
 811         // A unit struct/variant which is used as a value (e.g.,
 812         // `None`). This has the type of the enum/struct that defines
 813         // this variant -- but with the substitutions given by the
 814         // user.
 815         Def::StructCtor(_def_id, CtorKind::Const) |
 816         Def::VariantCtor(_def_id, CtorKind::Const) =>
 817             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 818
 819         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 820         Def::SelfCtor(_) =>
 821             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 822
 823         _ =>
 824             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
 825     }
 826 }
 827
 828 fn method_callee<'a, 'gcx, 'tcx>(
 829     cx: &mut Cx<'a, 'gcx, 'tcx>,
 830     expr: &hir::Expr,
 831     span: Span,
 832     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
 833 ) -> Expr<'tcx> {
 834     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 835     let (def_id, substs, user_ty) = match overloaded_callee {
 836         Some((def_id, substs)) => (def_id, substs, None),
 837         None => {
 838             let type_dependent_defs = cx.tables().type_dependent_defs();
 839             let def = type_dependent_defs
 840                 .get(expr.hir_id)
 841                 .unwrap_or_else(|| {
 842                     span_bug!(expr.span, "no type-dependent def for method callee")
 843                 });
 844             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, def);
 845             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 846         }
 847     };
 848     let ty = cx.tcx().mk_fn_def(def_id, substs);
 849     Expr {
 850         temp_lifetime,
 851         ty,
 852         span,
 853         kind: ExprKind::Literal {
 854             literal: ty::Const::zero_sized(cx.tcx(), ty),
 855             user_ty,
 856         },
 857     }
 858 }
 859
 860 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 861
 862 impl ToBorrowKind for AutoBorrowMutability {
 863     fn to_borrow_kind(&self) -> BorrowKind {
 864         use rustc::ty::adjustment::AllowTwoPhase;
 865         match *self {
 866             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 867                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 868                     AllowTwoPhase::Yes => true,
 869                     AllowTwoPhase::No => false
 870                 }},
 871             AutoBorrowMutability::Immutable =>
 872                 BorrowKind::Shared,
 873         }
 874     }
 875 }
 876
 877 impl ToBorrowKind for hir::Mutability {
 878     fn to_borrow_kind(&self) -> BorrowKind {
 879         match *self {
 880             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 881             hir::MutImmutable => BorrowKind::Shared,
 882         }
 883     }
 884 }
 885
 886 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 887     Arm {
 888         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 889         guard: match arm.guard {
 890                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 891                 _ => None,
 892             },
 893         body: arm.body.to_ref(),
 894         // BUG: fix this
 895         lint_level: LintLevel::Inherited,
 896     }
 897 }
 898
 899 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 900                                      expr: &'tcx hir::Expr,
 901                                      def: Def)
 902                                      -> ExprKind<'tcx> {
 903     let substs = cx.tables().node_substs(expr.hir_id);
 904     match def {
 905         // A regular function, constructor function or a constant.
 906         Def::Fn(_) |
 907         Def::Method(_) |
 908         Def::StructCtor(_, CtorKind::Fn) |
 909         Def::VariantCtor(_, CtorKind::Fn) |
 910         Def::SelfCtor(..) => {
 911             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 912             ExprKind::Literal {
 913                 literal: ty::Const::zero_sized(
 914                     cx.tcx,
 915                     cx.tables().node_id_to_type(expr.hir_id),
 916                 ),
 917                 user_ty,
 918             }
 919         },
 920
 921         Def::Const(def_id) |
 922         Def::AssociatedConst(def_id) => {
 923             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 924             ExprKind::Literal {
 925                 literal: ty::Const::unevaluated(
 926                     cx.tcx,
 927                     def_id,
 928                     substs,
 929                     cx.tables().node_id_to_type(expr.hir_id),
 930                 ),
 931                 user_ty,
 932             }
 933         },
 934
 935         Def::StructCtor(def_id, CtorKind::Const) |
 936         Def::VariantCtor(def_id, CtorKind::Const) => {
 937             match cx.tables().node_id_to_type(expr.hir_id).sty {
 938                 // A unit struct/variant which is used as a value.
 939                 // We return a completely different ExprKind here to account for this special case.
 940                 ty::Adt(adt_def, substs) => {
 941                     ExprKind::Adt {
 942                         adt_def,
 943                         variant_index: adt_def.variant_index_with_id(def_id),
 944                         substs,
 945                         user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt_def),
 946                         fields: vec![],
 947                         base: None,
 948                     }
 949                 }
 950                 ref sty => bug!("unexpected sty: {:?}", sty),
 951             }
 952         }
 953
 954         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 955
 956         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 957
 958         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 959     }
 960 }
 961
 962 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 963                                expr: &'tcx hir::Expr,
 964                                def: Def)
 965                                -> ExprKind<'tcx> {
 966     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 967
 968     match def {
 969         Def::Local(id) => ExprKind::VarRef { id },
 970
 971         Def::Upvar(var_id, index, closure_expr_id) => {
 972             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 973                    var_id,
 974                    index,
 975                    closure_expr_id);
 976             let var_hir_id = cx.tcx.hir.node_to_hir_id(var_id);
 977             let var_ty = cx.tables().node_id_to_type(var_hir_id);
 978
 979             // FIXME free regions in closures are not right
 980             let closure_ty = cx.tables()
 981                                .node_id_to_type(cx.tcx.hir.node_to_hir_id(closure_expr_id));
 982
 983             // FIXME we're just hard-coding the idea that the
 984             // signature will be &self or &mut self and hence will
 985             // have a bound region with number 0
 986             let closure_def_id = cx.tcx.hir.local_def_id(closure_expr_id);
 987             let region = ty::ReFree(ty::FreeRegion {
 988                 scope: closure_def_id,
 989                 bound_region: ty::BoundRegion::BrAnon(0),
 990             });
 991             let region = cx.tcx.mk_region(region);
 992
 993             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
 994                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
 995                     ty::ClosureKind::Fn => {
 996                         let ref_closure_ty = cx.tcx.mk_ref(region,
 997                                                            ty::TypeAndMut {
 998                                                                ty: closure_ty,
 999                                                                mutbl: hir::MutImmutable,
1000                                                            });
1001                         Expr {
1002                             ty: closure_ty,
1003                             temp_lifetime: temp_lifetime,
1004                             span: expr.span,
1005                             kind: ExprKind::Deref {
1006                                 arg: Expr {
1007                                     ty: ref_closure_ty,
1008                                     temp_lifetime,
1009                                     span: expr.span,
1010                                     kind: ExprKind::SelfRef,
1011                                 }
1012                                 .to_ref(),
1013                             },
1014                         }
1015                     }
1016                     ty::ClosureKind::FnMut => {
1017                         let ref_closure_ty = cx.tcx.mk_ref(region,
1018                                                            ty::TypeAndMut {
1019                                                                ty: closure_ty,
1020                                                                mutbl: hir::MutMutable,
1021                                                            });
1022                         Expr {
1023                             ty: closure_ty,
1024                             temp_lifetime,
1025                             span: expr.span,
1026                             kind: ExprKind::Deref {
1027                                 arg: Expr {
1028                                     ty: ref_closure_ty,
1029                                     temp_lifetime,
1030                                     span: expr.span,
1031                                     kind: ExprKind::SelfRef,
1032                                 }.to_ref(),
1033                             },
1034                         }
1035                     }
1036                     ty::ClosureKind::FnOnce => {
1037                         Expr {
1038                             ty: closure_ty,
1039                             temp_lifetime,
1040                             span: expr.span,
1041                             kind: ExprKind::SelfRef,
1042                         }
1043                     }
1044                 }
1045             } else {
1046                 Expr {
1047                     ty: closure_ty,
1048                     temp_lifetime,
1049                     span: expr.span,
1050                     kind: ExprKind::SelfRef,
1051                 }
1052             };
1053
1054             // at this point we have `self.n`, which loads up the upvar
1055             let field_kind = ExprKind::Field {
1056                 lhs: self_expr.to_ref(),
1057                 name: Field::new(index),
1058             };
1059
1060             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1061             // point we need an implicit deref
1062             let upvar_id = ty::UpvarId {
1063                 var_id: var_hir_id,
1064                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1065             };
1066             match cx.tables().upvar_capture(upvar_id) {
1067                 ty::UpvarCapture::ByValue => field_kind,
1068                 ty::UpvarCapture::ByRef(borrow) => {
1069                     ExprKind::Deref {
1070                         arg: Expr {
1071                             temp_lifetime,
1072                             ty: cx.tcx.mk_ref(borrow.region,
1073                                               ty::TypeAndMut {
1074                                                   ty: var_ty,
1075                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1076                                               }),
1077                             span: expr.span,
1078                             kind: field_kind,
1079                         }.to_ref(),
1080                     }
1081                 }
1082             }
1083         }
1084
1085         _ => span_bug!(expr.span, "type of & not region"),
1086     }
1087 }
1088
1089
1090 fn bin_op(op: hir::BinOpKind) -> BinOp {
1091     match op {
1092         hir::BinOpKind::Add => BinOp::Add,
1093         hir::BinOpKind::Sub => BinOp::Sub,
1094         hir::BinOpKind::Mul => BinOp::Mul,
1095         hir::BinOpKind::Div => BinOp::Div,
1096         hir::BinOpKind::Rem => BinOp::Rem,
1097         hir::BinOpKind::BitXor => BinOp::BitXor,
1098         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1099         hir::BinOpKind::BitOr => BinOp::BitOr,
1100         hir::BinOpKind::Shl => BinOp::Shl,
1101         hir::BinOpKind::Shr => BinOp::Shr,
1102         hir::BinOpKind::Eq => BinOp::Eq,
1103         hir::BinOpKind::Lt => BinOp::Lt,
1104         hir::BinOpKind::Le => BinOp::Le,
1105         hir::BinOpKind::Ne => BinOp::Ne,
1106         hir::BinOpKind::Ge => BinOp::Ge,
1107         hir::BinOpKind::Gt => BinOp::Gt,
1108         _ => bug!("no equivalent for ast binop {:?}", op),
1109     }
1110 }
1111
1112 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1113                                        expr: &'tcx hir::Expr,
1114                                        args: Vec<ExprRef<'tcx>>)
1115                                        -> ExprKind<'tcx> {
1116     let fun = method_callee(cx, expr, expr.span, None);
1117     ExprKind::Call {
1118         ty: fun.ty,
1119         fun: fun.to_ref(),
1120         args,
1121         from_hir_call: false,
1122     }
1123 }
1124
1125 fn overloaded_place<'a, 'gcx, 'tcx>(
1126     cx: &mut Cx<'a, 'gcx, 'tcx>,
1127     expr: &'tcx hir::Expr,
1128     place_ty: Ty<'tcx>,
1129     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
1130     args: Vec<ExprRef<'tcx>>,
1131 ) -> ExprKind<'tcx> {
1132     // For an overloaded *x or x[y] expression of type T, the method
1133     // call returns an &T and we must add the deref so that the types
1134     // line up (this is because `*x` and `x[y]` represent places):
1135
1136     let recv_ty = match args[0] {
1137         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1138         ExprRef::Mirror(ref e) => e.ty
1139     };
1140
1141     // Reconstruct the output assuming it's a reference with the
1142     // same region and mutability as the receiver. This holds for
1143     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1144     let (region, mutbl) = match recv_ty.sty {
1145         ty::Ref(region, _, mutbl) => (region, mutbl),
1146         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1147     };
1148     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1149         ty: place_ty,
1150         mutbl,
1151     });
1152
1153     // construct the complete expression `foo()` for the overloaded call,
1154     // which will yield the &T type
1155     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1156     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1157     let ref_expr = Expr {
1158         temp_lifetime,
1159         ty: ref_ty,
1160         span: expr.span,
1161         kind: ExprKind::Call {
1162             ty: fun.ty,
1163             fun: fun.to_ref(),
1164             args,
1165             from_hir_call: false,
1166         },
1167     };
1168
1169     // construct and return a deref wrapper `*foo()`
1170     ExprKind::Deref { arg: ref_expr.to_ref() }
1171 }
1172
1173 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1174                                    closure_expr: &'tcx hir::Expr,
1175                                    freevar: &hir::Freevar,
1176                                    freevar_ty: Ty<'tcx>)
1177                                    -> ExprRef<'tcx> {
1178     let var_hir_id = cx.tcx.hir.node_to_hir_id(freevar.var_id());
1179     let upvar_id = ty::UpvarId {
1180         var_id: var_hir_id,
1181         closure_expr_id: cx.tcx.hir.local_def_id(closure_expr.id).to_local(),
1182     };
1183     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1184     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1185     let var_ty = cx.tables().node_id_to_type(var_hir_id);
1186     let captured_var = Expr {
1187         temp_lifetime,
1188         ty: var_ty,
1189         span: closure_expr.span,
1190         kind: convert_var(cx, closure_expr, freevar.def),
1191     };
1192     match upvar_capture {
1193         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1194         ty::UpvarCapture::ByRef(upvar_borrow) => {
1195             let borrow_kind = match upvar_borrow.kind {
1196                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1197                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1198                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1199             };
1200             Expr {
1201                 temp_lifetime,
1202                 ty: freevar_ty,
1203                 span: closure_expr.span,
1204                 kind: ExprKind::Borrow {
1205                     region: upvar_borrow.region,
1206                     borrow_kind,
1207                     arg: captured_var.to_ref(),
1208                 },
1209             }.to_ref()
1210         }
1211     }
1212 }
1213
1214 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
1215 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1216                               fields: &'tcx [hir::Field])
1217                               -> Vec<FieldExprRef<'tcx>> {
1218     fields.iter()
1219         .map(|field| {
1220             FieldExprRef {
1221                 name: Field::new(cx.tcx.field_index(field.id, cx.tables)),
1222                 expr: field.expr.to_ref(),
1223             }
1224         })
1225         .collect()
1226 }