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::AdtDef(adt_def, 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, _) => {
 641             // Check to see if this cast is a "coercion cast", where the cast is actually done
 642             // using a coercion (or is a no-op).
 643             if let Some(&TyCastKind::CoercionCast) = cx.tables()
 644                                                     .cast_kinds()
 645                                                     .get(source.hir_id) {
 646                 // Convert the lexpr to a vexpr.
 647                 ExprKind::Use { source: source.to_ref() }
 648             } else {
 649                 // check whether this is casting an enum variant discriminant
 650                 // to prevent cycles, we refer to the discriminant initializer
 651                 // which is always an integer and thus doesn't need to know the
 652                 // enum's layout (or its tag type) to compute it during const eval
 653                 // Example:
 654                 // enum Foo {
 655                 //     A,
 656                 //     B = A as isize + 4,
 657                 // }
 658                 // The correct solution would be to add symbolic computations to miri,
 659                 // so we wouldn't have to compute and store the actual value
 660                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 661                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 662                     cx
 663                         .tables()
 664                         .node_id_to_type(source.hir_id)
 665                         .ty_adt_def()
 666                         .and_then(|adt_def| {
 667                         match def {
 668                             Def::VariantCtor(variant_id, CtorKind::Const) => {
 669                                 let idx = adt_def.variant_index_with_id(variant_id);
 670                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 671                                 use rustc::ty::util::IntTypeExt;
 672                                 let ty = adt_def.repr.discr_type();
 673                                 let ty = ty.to_ty(cx.tcx());
 674                                 Some((d, o, ty))
 675                             }
 676                             _ => None,
 677                         }
 678                     })
 679                 } else {
 680                     None
 681                 };
 682                 let source = if let Some((did, offset, ty)) = var {
 683                     let mk_const = |literal| Expr {
 684                         temp_lifetime,
 685                         ty,
 686                         span: expr.span,
 687                         kind: ExprKind::Literal { literal, user_ty: None },
 688                     }.to_ref();
 689                     let offset = mk_const(ty::Const::from_bits(
 690                         cx.tcx,
 691                         offset as u128,
 692                         cx.param_env.and(ty),
 693                     ));
 694                     match did {
 695                         Some(did) => {
 696                             // in case we are offsetting from a computed discriminant
 697                             // and not the beginning of discriminants (which is always `0`)
 698                             let substs = Substs::identity_for_item(cx.tcx(), did);
 699                             let lhs = mk_const(ty::Const::unevaluated(cx.tcx(), did, substs, ty));
 700                             let bin = ExprKind::Binary {
 701                                 op: BinOp::Add,
 702                                 lhs,
 703                                 rhs: offset,
 704                             };
 705                             Expr {
 706                                 temp_lifetime,
 707                                 ty,
 708                                 span: expr.span,
 709                                 kind: bin,
 710                             }.to_ref()
 711                         },
 712                         None => offset,
 713                     }
 714                 } else {
 715                     source.to_ref()
 716                 };
 717                 ExprKind::Cast { source }
 718             }
 719         }
 720         hir::ExprKind::Type(ref source, ref ty) => {
 721             let user_provided_tys = cx.tables.user_provided_tys();
 722             let user_ty = UserTypeAnnotation::Ty(
 723                 *user_provided_tys
 724                     .get(ty.hir_id)
 725                     .expect(&format!(
 726                         "{:?} not found in user_provided_tys, source: {:?}",
 727                         ty,
 728                         source,
 729                     ))
 730             );
 731             if source.is_place_expr() {
 732                 ExprKind::PlaceTypeAscription {
 733                     source: source.to_ref(),
 734                     user_ty,
 735                 }
 736             } else {
 737                 ExprKind::ValueTypeAscription {
 738                     source: source.to_ref(),
 739                     user_ty,
 740                 }
 741             }
 742         }
 743         hir::ExprKind::Box(ref value) => {
 744             ExprKind::Box {
 745                 value: value.to_ref(),
 746             }
 747         }
 748         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 749         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 750
 751         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 752     };
 753
 754     Expr {
 755         temp_lifetime,
 756         ty: expr_ty,
 757         span: expr.span,
 758         kind,
 759     }
 760 }
 761
 762 fn user_substs_applied_to_def(
 763     cx: &mut Cx<'a, 'gcx, 'tcx>,
 764     hir_id: hir::HirId,
 765     def: &Def,
 766 ) -> Option<UserTypeAnnotation<'tcx>> {
 767     match def {
 768         // A reference to something callable -- e.g., a fn, method, or
 769         // a tuple-struct or tuple-variant. This has the type of a
 770         // `Fn` but with the user-given substitutions.
 771         Def::Fn(_) |
 772         Def::Method(_) |
 773         Def::StructCtor(_, CtorKind::Fn) |
 774         Def::VariantCtor(_, CtorKind::Fn) =>
 775             Some(UserTypeAnnotation::FnDef(def.def_id(), cx.tables().user_substs(hir_id)?)),
 776
 777         Def::Const(_def_id) |
 778         Def::AssociatedConst(_def_id) =>
 779             bug!("unimplemented"),
 780
 781         // A unit struct/variant which is used as a value (e.g.,
 782         // `None`). This has the type of the enum/struct that defines
 783         // this variant -- but with the substitutions given by the
 784         // user.
 785         Def::StructCtor(_def_id, CtorKind::Const) |
 786         Def::VariantCtor(_def_id, CtorKind::Const) =>
 787             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 788
 789         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 790         Def::SelfCtor(_) =>
 791             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 792
 793         _ =>
 794             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
 795     }
 796 }
 797
 798 fn method_callee<'a, 'gcx, 'tcx>(
 799     cx: &mut Cx<'a, 'gcx, 'tcx>,
 800     expr: &hir::Expr,
 801     span: Span,
 802     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
 803 ) -> Expr<'tcx> {
 804     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 805     let (def_id, substs, user_ty) = match overloaded_callee {
 806         Some((def_id, substs)) => (def_id, substs, None),
 807         None => {
 808             let type_dependent_defs = cx.tables().type_dependent_defs();
 809             let def = type_dependent_defs
 810                 .get(expr.hir_id)
 811                 .unwrap_or_else(|| {
 812                     span_bug!(expr.span, "no type-dependent def for method callee")
 813                 });
 814             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, def);
 815             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 816         }
 817     };
 818     let ty = cx.tcx().mk_fn_def(def_id, substs);
 819     Expr {
 820         temp_lifetime,
 821         ty,
 822         span,
 823         kind: ExprKind::Literal {
 824             literal: ty::Const::zero_sized(cx.tcx(), ty),
 825             user_ty,
 826         },
 827     }
 828 }
 829
 830 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 831
 832 impl ToBorrowKind for AutoBorrowMutability {
 833     fn to_borrow_kind(&self) -> BorrowKind {
 834         use rustc::ty::adjustment::AllowTwoPhase;
 835         match *self {
 836             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 837                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 838                     AllowTwoPhase::Yes => true,
 839                     AllowTwoPhase::No => false
 840                 }},
 841             AutoBorrowMutability::Immutable =>
 842                 BorrowKind::Shared,
 843         }
 844     }
 845 }
 846
 847 impl ToBorrowKind for hir::Mutability {
 848     fn to_borrow_kind(&self) -> BorrowKind {
 849         match *self {
 850             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 851             hir::MutImmutable => BorrowKind::Shared,
 852         }
 853     }
 854 }
 855
 856 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 857     Arm {
 858         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 859         guard: match arm.guard {
 860                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 861                 _ => None,
 862             },
 863         body: arm.body.to_ref(),
 864         // BUG: fix this
 865         lint_level: LintLevel::Inherited,
 866     }
 867 }
 868
 869 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 870                                      expr: &'tcx hir::Expr,
 871                                      def: Def)
 872                                      -> ExprKind<'tcx> {
 873     let substs = cx.tables().node_substs(expr.hir_id);
 874     match def {
 875         // A regular function, constructor function or a constant.
 876         Def::Fn(_) |
 877         Def::Method(_) |
 878         Def::StructCtor(_, CtorKind::Fn) |
 879         Def::VariantCtor(_, CtorKind::Fn) |
 880         Def::SelfCtor(..) => {
 881             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
 882             ExprKind::Literal {
 883                 literal: ty::Const::zero_sized(
 884                     cx.tcx,
 885                     cx.tables().node_id_to_type(expr.hir_id),
 886                 ),
 887                 user_ty,
 888             }
 889         },
 890
 891         Def::Const(def_id) |
 892         Def::AssociatedConst(def_id) => ExprKind::Literal {
 893             literal: ty::Const::unevaluated(
 894                 cx.tcx,
 895                 def_id,
 896                 substs,
 897                 cx.tables().node_id_to_type(expr.hir_id),
 898             ),
 899             user_ty: None, // FIXME(#47184) -- user given type annot on constants
 900         },
 901
 902         Def::StructCtor(def_id, CtorKind::Const) |
 903         Def::VariantCtor(def_id, CtorKind::Const) => {
 904             match cx.tables().node_id_to_type(expr.hir_id).sty {
 905                 // A unit struct/variant which is used as a value.
 906                 // We return a completely different ExprKind here to account for this special case.
 907                 ty::Adt(adt_def, substs) => {
 908                     ExprKind::Adt {
 909                         adt_def,
 910                         variant_index: adt_def.variant_index_with_id(def_id),
 911                         substs,
 912                         user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt_def),
 913                         fields: vec![],
 914                         base: None,
 915                     }
 916                 }
 917                 ref sty => bug!("unexpected sty: {:?}", sty),
 918             }
 919         }
 920
 921         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 922
 923         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 924
 925         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 926     }
 927 }
 928
 929 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 930                                expr: &'tcx hir::Expr,
 931                                def: Def)
 932                                -> ExprKind<'tcx> {
 933     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 934
 935     match def {
 936         Def::Local(id) => ExprKind::VarRef { id },
 937
 938         Def::Upvar(var_id, index, closure_expr_id) => {
 939             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 940                    var_id,
 941                    index,
 942                    closure_expr_id);
 943             let var_hir_id = cx.tcx.hir.node_to_hir_id(var_id);
 944             let var_ty = cx.tables().node_id_to_type(var_hir_id);
 945
 946             // FIXME free regions in closures are not right
 947             let closure_ty = cx.tables()
 948                                .node_id_to_type(cx.tcx.hir.node_to_hir_id(closure_expr_id));
 949
 950             // FIXME we're just hard-coding the idea that the
 951             // signature will be &self or &mut self and hence will
 952             // have a bound region with number 0
 953             let closure_def_id = cx.tcx.hir.local_def_id(closure_expr_id);
 954             let region = ty::ReFree(ty::FreeRegion {
 955                 scope: closure_def_id,
 956                 bound_region: ty::BoundRegion::BrAnon(0),
 957             });
 958             let region = cx.tcx.mk_region(region);
 959
 960             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
 961                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
 962                     ty::ClosureKind::Fn => {
 963                         let ref_closure_ty = cx.tcx.mk_ref(region,
 964                                                            ty::TypeAndMut {
 965                                                                ty: closure_ty,
 966                                                                mutbl: hir::MutImmutable,
 967                                                            });
 968                         Expr {
 969                             ty: closure_ty,
 970                             temp_lifetime: temp_lifetime,
 971                             span: expr.span,
 972                             kind: ExprKind::Deref {
 973                                 arg: Expr {
 974                                     ty: ref_closure_ty,
 975                                     temp_lifetime,
 976                                     span: expr.span,
 977                                     kind: ExprKind::SelfRef,
 978                                 }
 979                                 .to_ref(),
 980                             },
 981                         }
 982                     }
 983                     ty::ClosureKind::FnMut => {
 984                         let ref_closure_ty = cx.tcx.mk_ref(region,
 985                                                            ty::TypeAndMut {
 986                                                                ty: closure_ty,
 987                                                                mutbl: hir::MutMutable,
 988                                                            });
 989                         Expr {
 990                             ty: closure_ty,
 991                             temp_lifetime,
 992                             span: expr.span,
 993                             kind: ExprKind::Deref {
 994                                 arg: Expr {
 995                                     ty: ref_closure_ty,
 996                                     temp_lifetime,
 997                                     span: expr.span,
 998                                     kind: ExprKind::SelfRef,
 999                                 }.to_ref(),
1000                             },
1001                         }
1002                     }
1003                     ty::ClosureKind::FnOnce => {
1004                         Expr {
1005                             ty: closure_ty,
1006                             temp_lifetime,
1007                             span: expr.span,
1008                             kind: ExprKind::SelfRef,
1009                         }
1010                     }
1011                 }
1012             } else {
1013                 Expr {
1014                     ty: closure_ty,
1015                     temp_lifetime,
1016                     span: expr.span,
1017                     kind: ExprKind::SelfRef,
1018                 }
1019             };
1020
1021             // at this point we have `self.n`, which loads up the upvar
1022             let field_kind = ExprKind::Field {
1023                 lhs: self_expr.to_ref(),
1024                 name: Field::new(index),
1025             };
1026
1027             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1028             // point we need an implicit deref
1029             let upvar_id = ty::UpvarId {
1030                 var_id: var_hir_id,
1031                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1032             };
1033             match cx.tables().upvar_capture(upvar_id) {
1034                 ty::UpvarCapture::ByValue => field_kind,
1035                 ty::UpvarCapture::ByRef(borrow) => {
1036                     ExprKind::Deref {
1037                         arg: Expr {
1038                             temp_lifetime,
1039                             ty: cx.tcx.mk_ref(borrow.region,
1040                                               ty::TypeAndMut {
1041                                                   ty: var_ty,
1042                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1043                                               }),
1044                             span: expr.span,
1045                             kind: field_kind,
1046                         }.to_ref(),
1047                     }
1048                 }
1049             }
1050         }
1051
1052         _ => span_bug!(expr.span, "type of & not region"),
1053     }
1054 }
1055
1056
1057 fn bin_op(op: hir::BinOpKind) -> BinOp {
1058     match op {
1059         hir::BinOpKind::Add => BinOp::Add,
1060         hir::BinOpKind::Sub => BinOp::Sub,
1061         hir::BinOpKind::Mul => BinOp::Mul,
1062         hir::BinOpKind::Div => BinOp::Div,
1063         hir::BinOpKind::Rem => BinOp::Rem,
1064         hir::BinOpKind::BitXor => BinOp::BitXor,
1065         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1066         hir::BinOpKind::BitOr => BinOp::BitOr,
1067         hir::BinOpKind::Shl => BinOp::Shl,
1068         hir::BinOpKind::Shr => BinOp::Shr,
1069         hir::BinOpKind::Eq => BinOp::Eq,
1070         hir::BinOpKind::Lt => BinOp::Lt,
1071         hir::BinOpKind::Le => BinOp::Le,
1072         hir::BinOpKind::Ne => BinOp::Ne,
1073         hir::BinOpKind::Ge => BinOp::Ge,
1074         hir::BinOpKind::Gt => BinOp::Gt,
1075         _ => bug!("no equivalent for ast binop {:?}", op),
1076     }
1077 }
1078
1079 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1080                                        expr: &'tcx hir::Expr,
1081                                        args: Vec<ExprRef<'tcx>>)
1082                                        -> ExprKind<'tcx> {
1083     let fun = method_callee(cx, expr, expr.span, None);
1084     ExprKind::Call {
1085         ty: fun.ty,
1086         fun: fun.to_ref(),
1087         args,
1088         from_hir_call: false,
1089     }
1090 }
1091
1092 fn overloaded_place<'a, 'gcx, 'tcx>(
1093     cx: &mut Cx<'a, 'gcx, 'tcx>,
1094     expr: &'tcx hir::Expr,
1095     place_ty: Ty<'tcx>,
1096     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
1097     args: Vec<ExprRef<'tcx>>,
1098 ) -> ExprKind<'tcx> {
1099     // For an overloaded *x or x[y] expression of type T, the method
1100     // call returns an &T and we must add the deref so that the types
1101     // line up (this is because `*x` and `x[y]` represent places):
1102
1103     let recv_ty = match args[0] {
1104         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1105         ExprRef::Mirror(ref e) => e.ty
1106     };
1107
1108     // Reconstruct the output assuming it's a reference with the
1109     // same region and mutability as the receiver. This holds for
1110     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1111     let (region, mutbl) = match recv_ty.sty {
1112         ty::Ref(region, _, mutbl) => (region, mutbl),
1113         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1114     };
1115     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1116         ty: place_ty,
1117         mutbl,
1118     });
1119
1120     // construct the complete expression `foo()` for the overloaded call,
1121     // which will yield the &T type
1122     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1123     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1124     let ref_expr = Expr {
1125         temp_lifetime,
1126         ty: ref_ty,
1127         span: expr.span,
1128         kind: ExprKind::Call {
1129             ty: fun.ty,
1130             fun: fun.to_ref(),
1131             args,
1132             from_hir_call: false,
1133         },
1134     };
1135
1136     // construct and return a deref wrapper `*foo()`
1137     ExprKind::Deref { arg: ref_expr.to_ref() }
1138 }
1139
1140 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1141                                    closure_expr: &'tcx hir::Expr,
1142                                    freevar: &hir::Freevar,
1143                                    freevar_ty: Ty<'tcx>)
1144                                    -> ExprRef<'tcx> {
1145     let var_hir_id = cx.tcx.hir.node_to_hir_id(freevar.var_id());
1146     let upvar_id = ty::UpvarId {
1147         var_id: var_hir_id,
1148         closure_expr_id: cx.tcx.hir.local_def_id(closure_expr.id).to_local(),
1149     };
1150     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1151     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1152     let var_ty = cx.tables().node_id_to_type(var_hir_id);
1153     let captured_var = Expr {
1154         temp_lifetime,
1155         ty: var_ty,
1156         span: closure_expr.span,
1157         kind: convert_var(cx, closure_expr, freevar.def),
1158     };
1159     match upvar_capture {
1160         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1161         ty::UpvarCapture::ByRef(upvar_borrow) => {
1162             let borrow_kind = match upvar_borrow.kind {
1163                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1164                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1165                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1166             };
1167             Expr {
1168                 temp_lifetime,
1169                 ty: freevar_ty,
1170                 span: closure_expr.span,
1171                 kind: ExprKind::Borrow {
1172                     region: upvar_borrow.region,
1173                     borrow_kind,
1174                     arg: captured_var.to_ref(),
1175                 },
1176             }.to_ref()
1177         }
1178     }
1179 }
1180
1181 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
1182 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1183                               fields: &'tcx [hir::Field])
1184                               -> Vec<FieldExprRef<'tcx>> {
1185     fields.iter()
1186         .map(|field| {
1187             FieldExprRef {
1188                 name: Field::new(cx.tcx.field_index(field.id, cx.tables)),
1189                 expr: field.expr.to_ref(),
1190             }
1191         })
1192         .collect()
1193 }