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 rustc::hir::def::{Def, CtorKind};
  17 use rustc::mir::interpret::GlobalId;
  18 use rustc::ty::{self, AdtKind, Ty};
  19 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability};
  20 use rustc::ty::cast::CastKind as TyCastKind;
  21 use rustc::hir;
  22 use rustc::hir::def_id::LocalDefId;
  23 use rustc::mir::{BorrowKind};
  24
  25 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
  26     type Output = Expr<'tcx>;
  27
  28     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
  29         let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
  30         let expr_scope = region::Scope::Node(self.hir_id.local_id);
  31
  32         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
  33
  34         let mut expr = make_mirror_unadjusted(cx, self);
  35
  36         // Now apply adjustments, if any.
  37         for adjustment in cx.tables().expr_adjustments(self) {
  38             debug!("make_mirror: expr={:?} applying adjustment={:?}",
  39                    expr,
  40                    adjustment);
  41             expr = apply_adjustment(cx, self, expr, adjustment);
  42         }
  43
  44         // Next, wrap this up in the expr's scope.
  45         expr = Expr {
  46             temp_lifetime,
  47             ty: expr.ty,
  48             span: self.span,
  49             kind: ExprKind::Scope {
  50                 region_scope: expr_scope,
  51                 value: expr.to_ref(),
  52                 lint_level: cx.lint_level_of(self.id),
  53             },
  54         };
  55
  56         // Finally, create a destruction scope, if any.
  57         if let Some(region_scope) =
  58             cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id) {
  59                 expr = Expr {
  60                     temp_lifetime,
  61                     ty: expr.ty,
  62                     span: self.span,
  63                     kind: ExprKind::Scope {
  64                         region_scope,
  65                         value: expr.to_ref(),
  66                         lint_level: LintLevel::Inherited,
  67                     },
  68                 };
  69             }
  70
  71         // OK, all done!
  72         expr
  73     }
  74 }
  75
  76 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
  77                                     hir_expr: &'tcx hir::Expr,
  78                                     mut expr: Expr<'tcx>,
  79                                     adjustment: &Adjustment<'tcx>)
  80                                     -> Expr<'tcx> {
  81     let Expr { temp_lifetime, mut span, .. } = expr;
  82     let kind = match adjustment.kind {
  83         Adjust::ReifyFnPointer => {
  84             ExprKind::ReifyFnPointer { source: expr.to_ref() }
  85         }
  86         Adjust::UnsafeFnPointer => {
  87             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
  88         }
  89         Adjust::ClosureFnPointer => {
  90             ExprKind::ClosureFnPointer { source: expr.to_ref() }
  91         }
  92         Adjust::NeverToAny => {
  93             ExprKind::NeverToAny { source: expr.to_ref() }
  94         }
  95         Adjust::MutToConstPointer => {
  96             ExprKind::Cast { source: expr.to_ref() }
  97         }
  98         Adjust::Deref(None) => {
  99             // Adjust the span from the block, to the last expression of the
 100             // block. This is a better span when returning a mutable reference
 101             // with too short a lifetime. The error message will use the span
 102             // from the assignment to the return place, which should only point
 103             // at the returned value, not the entire function body.
 104             //
 105             // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
 106             //      x
 107             //   // ^ error message points at this expression.
 108             // }
 109             //
 110             // We don't need to do this adjustment in the next match arm since
 111             // deref coercions always start with a built-in deref.
 112             if let ExprKind::Block { body } = expr.kind {
 113                 if let Some(ref last_expr) = body.expr {
 114                     span = last_expr.span;
 115                     expr.span = span;
 116                 }
 117             }
 118             ExprKind::Deref { arg: expr.to_ref() }
 119         }
 120         Adjust::Deref(Some(deref)) => {
 121             let call = deref.method_call(cx.tcx(), expr.ty);
 122
 123             expr = Expr {
 124                 temp_lifetime,
 125                 ty: cx.tcx.mk_ref(deref.region,
 126                                   ty::TypeAndMut {
 127                                     ty: expr.ty,
 128                                     mutbl: deref.mutbl,
 129                                   }),
 130                 span,
 131                 kind: ExprKind::Borrow {
 132                     region: deref.region,
 133                     borrow_kind: deref.mutbl.to_borrow_kind(),
 134                     arg: expr.to_ref(),
 135                 },
 136             };
 137
 138             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
 139         }
 140         Adjust::Borrow(AutoBorrow::Ref(r, m)) => {
 141             ExprKind::Borrow {
 142                 region: r,
 143                 borrow_kind: m.to_borrow_kind(),
 144                 arg: expr.to_ref(),
 145             }
 146         }
 147         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
 148             // Convert this to a suitable `&foo` and
 149             // then an unsafe coercion. Limit the region to be just this
 150             // expression.
 151             let region = ty::ReScope(region::Scope::Node(hir_expr.hir_id.local_id));
 152             let region = cx.tcx.mk_region(region);
 153             expr = Expr {
 154                 temp_lifetime,
 155                 ty: cx.tcx.mk_ref(region,
 156                                   ty::TypeAndMut {
 157                                     ty: expr.ty,
 158                                     mutbl: m,
 159                                   }),
 160                 span,
 161                 kind: ExprKind::Borrow {
 162                     region,
 163                     borrow_kind: m.to_borrow_kind(),
 164                     arg: expr.to_ref(),
 165                 },
 166             };
 167             let cast_expr = Expr {
 168                 temp_lifetime,
 169                 ty: adjustment.target,
 170                 span,
 171                 kind: ExprKind::Cast { source: expr.to_ref() }
 172             };
 173
 174             // To ensure that both implicit and explicit coercions are
 175             // handled the same way, we insert an extra layer of indirection here.
 176             // For explicit casts (e.g. 'foo as *const T'), the source of the 'Use'
 177             // will be an ExprKind::Hair with the appropriate cast expression. Here,
 178             // we make our Use source the generated Cast from the original coercion.
 179             //
 180             // In both cases, this outer 'Use' ensures that the inner 'Cast' is handled by
 181             // as_operand, not by as_rvalue - causing the cast result to be stored in a temporary.
 182             // Ordinary, this is identical to using the cast directly as an rvalue. However, if the
 183             // source of the cast was previously borrowed as mutable, storing the cast in a
 184             // temporary gives the source a chance to expire before the cast is used. For
 185             // structs with a self-referential *mut ptr, this allows assignment to work as
 186             // expected.
 187             //
 188             // For example, consider the type 'struct Foo { field: *mut Foo }',
 189             // The method 'fn bar(&mut self) { self.field = self }'
 190             // triggers a coercion from '&mut self' to '*mut self'. In order
 191             // for the assignment to be valid, the implicit borrow
 192             // of 'self' involved in the coercion needs to end before the local
 193             // containing the '*mut T' is assigned to 'self.field' - otherwise,
 194             // we end up trying to assign to 'self.field' while we have another mutable borrow
 195             // active.
 196             //
 197             // We only need to worry about this kind of thing for coercions from refs to ptrs,
 198             // since they get rid of a borrow implicitly.
 199             ExprKind::Use { source: cast_expr.to_ref() }
 200         }
 201         Adjust::Unsize => {
 202             // See the above comment for Adjust::Deref
 203             if let ExprKind::Block { body } = expr.kind {
 204                 if let Some(ref last_expr) = body.expr {
 205                     span = last_expr.span;
 206                     expr.span = span;
 207                 }
 208             }
 209             ExprKind::Unsize { source: expr.to_ref() }
 210         }
 211     };
 212
 213     Expr {
 214         temp_lifetime,
 215         ty: adjustment.target,
 216         span,
 217         kind,
 218     }
 219 }
 220
 221 fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 222                                           expr: &'tcx hir::Expr)
 223                                           -> Expr<'tcx> {
 224     let expr_ty = cx.tables().expr_ty(expr);
 225     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 226
 227     let kind = match expr.node {
 228         // Here comes the interesting stuff:
 229         hir::ExprKind::MethodCall(.., ref args) => {
 230             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 231             let expr = method_callee(cx, expr, None);
 232             let args = args.iter()
 233                 .map(|e| e.to_ref())
 234                 .collect();
 235             ExprKind::Call {
 236                 ty: expr.ty,
 237                 fun: expr.to_ref(),
 238                 args,
 239             }
 240         }
 241
 242         hir::ExprKind::Call(ref fun, ref args) => {
 243             if cx.tables().is_method_call(expr) {
 244                 // The callee is something implementing Fn, FnMut, or FnOnce.
 245                 // Find the actual method implementation being called and
 246                 // build the appropriate UFCS call expression with the
 247                 // callee-object as expr parameter.
 248
 249                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 250
 251                 let method = method_callee(cx, expr, None);
 252
 253                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
 254                 let tupled_args = Expr {
 255                     ty: cx.tcx.mk_tup(arg_tys),
 256                     temp_lifetime,
 257                     span: expr.span,
 258                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
 259                 };
 260
 261                 ExprKind::Call {
 262                     ty: method.ty,
 263                     fun: method.to_ref(),
 264                     args: vec![fun.to_ref(), tupled_args.to_ref()],
 265                 }
 266             } else {
 267                 let adt_data = if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) =
 268                     fun.node
 269                 {
 270                     // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
 271                     expr_ty.ty_adt_def().and_then(|adt_def| {
 272                         match path.def {
 273                             Def::VariantCtor(variant_id, CtorKind::Fn) => {
 274                                 Some((adt_def, adt_def.variant_index_with_id(variant_id)))
 275                             }
 276                             Def::StructCtor(_, CtorKind::Fn) => Some((adt_def, 0)),
 277                             _ => None,
 278                         }
 279                     })
 280                 } else {
 281                     None
 282                 };
 283                 if let Some((adt_def, index)) = adt_data {
 284                     let substs = cx.tables().node_substs(fun.hir_id);
 285
 286                     let user_ty = cx.tables().user_substs(fun.hir_id)
 287                         .map(|user_substs| {
 288                             user_substs.unchecked_map(|user_substs| {
 289                                 // Here, we just pair an `AdtDef` with the
 290                                 // `user_substs`, so no new types etc are introduced.
 291                                 cx.tcx().mk_adt(adt_def, user_substs)
 292                             })
 293                         });
 294
 295                     let field_refs = args.iter()
 296                         .enumerate()
 297                         .map(|(idx, e)| {
 298                             FieldExprRef {
 299                                 name: Field::new(idx),
 300                                 expr: e.to_ref(),
 301                             }
 302                         })
 303                         .collect();
 304                     ExprKind::Adt {
 305                         adt_def,
 306                         substs,
 307                         variant_index: index,
 308                         fields: field_refs,
 309                         user_ty,
 310                         base: None,
 311                     }
 312                 } else {
 313                     ExprKind::Call {
 314                         ty: cx.tables().node_id_to_type(fun.hir_id),
 315                         fun: fun.to_ref(),
 316                         args: args.to_ref(),
 317                     }
 318                 }
 319             }
 320         }
 321
 322         hir::ExprKind::AddrOf(mutbl, ref expr) => {
 323             let region = match expr_ty.sty {
 324                 ty::Ref(r, _, _) => r,
 325                 _ => span_bug!(expr.span, "type of & not region"),
 326             };
 327             ExprKind::Borrow {
 328                 region,
 329                 borrow_kind: mutbl.to_borrow_kind(),
 330                 arg: expr.to_ref(),
 331             }
 332         }
 333
 334         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
 335
 336         hir::ExprKind::Assign(ref lhs, ref rhs) => {
 337             ExprKind::Assign {
 338                 lhs: lhs.to_ref(),
 339                 rhs: rhs.to_ref(),
 340             }
 341         }
 342
 343         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 344             if cx.tables().is_method_call(expr) {
 345                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 346             } else {
 347                 ExprKind::AssignOp {
 348                     op: bin_op(op.node),
 349                     lhs: lhs.to_ref(),
 350                     rhs: rhs.to_ref(),
 351                 }
 352             }
 353         }
 354
 355         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 356             literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, false),
 357             user_ty: None,
 358         },
 359
 360         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 361             if cx.tables().is_method_call(expr) {
 362                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 363             } else {
 364                 // FIXME overflow
 365                 match (op.node, cx.constness) {
 366                     // FIXME(eddyb) use logical ops in constants when
 367                     // they can handle that kind of control-flow.
 368                     (hir::BinOpKind::And, hir::Constness::Const) => {
 369                         ExprKind::Binary {
 370                             op: BinOp::BitAnd,
 371                             lhs: lhs.to_ref(),
 372                             rhs: rhs.to_ref(),
 373                         }
 374                     }
 375                     (hir::BinOpKind::Or, hir::Constness::Const) => {
 376                         ExprKind::Binary {
 377                             op: BinOp::BitOr,
 378                             lhs: lhs.to_ref(),
 379                             rhs: rhs.to_ref(),
 380                         }
 381                     }
 382
 383                     (hir::BinOpKind::And, hir::Constness::NotConst) => {
 384                         ExprKind::LogicalOp {
 385                             op: LogicalOp::And,
 386                             lhs: lhs.to_ref(),
 387                             rhs: rhs.to_ref(),
 388                         }
 389                     }
 390                     (hir::BinOpKind::Or, hir::Constness::NotConst) => {
 391                         ExprKind::LogicalOp {
 392                             op: LogicalOp::Or,
 393                             lhs: lhs.to_ref(),
 394                             rhs: rhs.to_ref(),
 395                         }
 396                     }
 397
 398                     _ => {
 399                         let op = bin_op(op.node);
 400                         ExprKind::Binary {
 401                             op,
 402                             lhs: lhs.to_ref(),
 403                             rhs: rhs.to_ref(),
 404                         }
 405                     }
 406                 }
 407             }
 408         }
 409
 410         hir::ExprKind::Index(ref lhs, ref index) => {
 411             if cx.tables().is_method_call(expr) {
 412                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 413             } else {
 414                 ExprKind::Index {
 415                     lhs: lhs.to_ref(),
 416                     index: index.to_ref(),
 417                 }
 418             }
 419         }
 420
 421         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
 422             if cx.tables().is_method_call(expr) {
 423                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
 424             } else {
 425                 ExprKind::Deref { arg: arg.to_ref() }
 426             }
 427         }
 428
 429         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
 430             if cx.tables().is_method_call(expr) {
 431                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 432             } else {
 433                 ExprKind::Unary {
 434                     op: UnOp::Not,
 435                     arg: arg.to_ref(),
 436                 }
 437             }
 438         }
 439
 440         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
 441             if cx.tables().is_method_call(expr) {
 442                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 443             } else {
 444                 if let hir::ExprKind::Lit(ref lit) = arg.node {
 445                     ExprKind::Literal {
 446                         literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, true),
 447                         user_ty: None,
 448                     }
 449                 } else {
 450                     ExprKind::Unary {
 451                         op: UnOp::Neg,
 452                         arg: arg.to_ref(),
 453                     }
 454                 }
 455             }
 456         }
 457
 458         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => {
 459             match expr_ty.sty {
 460                 ty::Adt(adt, substs) => {
 461                     match adt.adt_kind() {
 462                         AdtKind::Struct | AdtKind::Union => {
 463                             ExprKind::Adt {
 464                                 adt_def: adt,
 465                                 variant_index: 0,
 466                                 substs,
 467                                 user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt),
 468                                 fields: field_refs(cx, fields),
 469                                 base: base.as_ref().map(|base| {
 470                                     FruInfo {
 471                                         base: base.to_ref(),
 472                                         field_types: cx.tables()
 473                                                        .fru_field_types()[expr.hir_id]
 474                                                        .clone(),
 475                                     }
 476                                 }),
 477                             }
 478                         }
 479                         AdtKind::Enum => {
 480                             let def = match *qpath {
 481                                 hir::QPath::Resolved(_, ref path) => path.def,
 482                                 hir::QPath::TypeRelative(..) => Def::Err,
 483                             };
 484                             match def {
 485                                 Def::Variant(variant_id) => {
 486                                     assert!(base.is_none());
 487
 488                                     let index = adt.variant_index_with_id(variant_id);
 489                                     ExprKind::Adt {
 490                                         adt_def: adt,
 491                                         variant_index: index,
 492                                         substs,
 493                                         user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt),
 494                                         fields: field_refs(cx, fields),
 495                                         base: None,
 496                                     }
 497                                 }
 498                                 _ => {
 499                                     span_bug!(expr.span, "unexpected def: {:?}", def);
 500                                 }
 501                             }
 502                         }
 503                     }
 504                 }
 505                 _ => {
 506                     span_bug!(expr.span,
 507                               "unexpected type for struct literal: {:?}",
 508                               expr_ty);
 509                 }
 510             }
 511         }
 512
 513         hir::ExprKind::Closure(..) => {
 514             let closure_ty = cx.tables().expr_ty(expr);
 515             let (def_id, substs, movability) = match closure_ty.sty {
 516                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 517                 ty::Generator(def_id, substs, movability) => {
 518                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
 519                 }
 520                 _ => {
 521                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 522                 }
 523             };
 524             let upvars = cx.tcx.with_freevars(expr.id, |freevars| {
 525                 freevars.iter()
 526                     .zip(substs.upvar_tys(def_id, cx.tcx))
 527                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 528                     .collect()
 529             });
 530             ExprKind::Closure {
 531                 closure_id: def_id,
 532                 substs,
 533                 upvars,
 534                 movability,
 535             }
 536         }
 537
 538         hir::ExprKind::Path(ref qpath) => {
 539             let def = cx.tables().qpath_def(qpath, expr.hir_id);
 540             convert_path_expr(cx, expr, def)
 541         }
 542
 543         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
 544             ExprKind::InlineAsm {
 545                 asm,
 546                 outputs: outputs.to_ref(),
 547                 inputs: inputs.to_ref(),
 548             }
 549         }
 550
 551         // Now comes the rote stuff:
 552         hir::ExprKind::Repeat(ref v, ref count) => {
 553             let def_id = cx.tcx.hir.local_def_id(count.id);
 554             let substs = Substs::identity_for_item(cx.tcx.global_tcx(), def_id);
 555             let instance = ty::Instance::resolve(
 556                 cx.tcx.global_tcx(),
 557                 cx.param_env,
 558                 def_id,
 559                 substs,
 560             ).unwrap();
 561             let global_id = GlobalId {
 562                 instance,
 563                 promoted: None
 564             };
 565             let span = cx.tcx.def_span(def_id);
 566             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
 567                 Ok(cv) => cv.unwrap_usize(cx.tcx),
 568                 Err(e) => {
 569                     e.report_as_error(cx.tcx.at(span), "could not evaluate array length");
 570                     0
 571                 },
 572             };
 573
 574             ExprKind::Repeat {
 575                 value: v.to_ref(),
 576                 count,
 577             }
 578         }
 579         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 580         hir::ExprKind::Break(dest, ref value) => {
 581             match dest.target_id {
 582                 Ok(target_id) => ExprKind::Break {
 583                     label: region::Scope::Node(cx.tcx.hir.node_to_hir_id(target_id).local_id),
 584                     value: value.to_ref(),
 585                 },
 586                 Err(err) => bug!("invalid loop id for break: {}", err)
 587             }
 588         }
 589         hir::ExprKind::Continue(dest) => {
 590             match dest.target_id {
 591                 Ok(loop_id) => ExprKind::Continue {
 592                     label: region::Scope::Node(cx.tcx.hir.node_to_hir_id(loop_id).local_id),
 593                 },
 594                 Err(err) => bug!("invalid loop id for continue: {}", err)
 595             }
 596         }
 597         hir::ExprKind::Match(ref discr, ref arms, _) => {
 598             ExprKind::Match {
 599                 discriminant: discr.to_ref(),
 600                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 601             }
 602         }
 603         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
 604             ExprKind::If {
 605                 condition: cond.to_ref(),
 606                 then: then.to_ref(),
 607                 otherwise: otherwise.to_ref(),
 608             }
 609         }
 610         hir::ExprKind::While(ref cond, ref body, _) => {
 611             ExprKind::Loop {
 612                 condition: Some(cond.to_ref()),
 613                 body: block::to_expr_ref(cx, body),
 614             }
 615         }
 616         hir::ExprKind::Loop(ref body, _, _) => {
 617             ExprKind::Loop {
 618                 condition: None,
 619                 body: block::to_expr_ref(cx, body),
 620             }
 621         }
 622         hir::ExprKind::Field(ref source, ..) => {
 623             ExprKind::Field {
 624                 lhs: source.to_ref(),
 625                 name: Field::new(cx.tcx.field_index(expr.id, cx.tables)),
 626             }
 627         }
 628         hir::ExprKind::Cast(ref source, _) => {
 629             // Check to see if this cast is a "coercion cast", where the cast is actually done
 630             // using a coercion (or is a no-op).
 631             if let Some(&TyCastKind::CoercionCast) = cx.tables()
 632                                                     .cast_kinds()
 633                                                     .get(source.hir_id) {
 634                 // Convert the lexpr to a vexpr.
 635                 ExprKind::Use { source: source.to_ref() }
 636             } else {
 637                 // check whether this is casting an enum variant discriminant
 638                 // to prevent cycles, we refer to the discriminant initializer
 639                 // which is always an integer and thus doesn't need to know the
 640                 // enum's layout (or its tag type) to compute it during const eval
 641                 // Example:
 642                 // enum Foo {
 643                 //     A,
 644                 //     B = A as isize + 4,
 645                 // }
 646                 // The correct solution would be to add symbolic computations to miri,
 647                 // so we wouldn't have to compute and store the actual value
 648                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
 649                     let def = cx.tables().qpath_def(qpath, source.hir_id);
 650                     cx
 651                         .tables()
 652                         .node_id_to_type(source.hir_id)
 653                         .ty_adt_def()
 654                         .and_then(|adt_def| {
 655                         match def {
 656                             Def::VariantCtor(variant_id, CtorKind::Const) => {
 657                                 let idx = adt_def.variant_index_with_id(variant_id);
 658                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 659                                 use rustc::ty::util::IntTypeExt;
 660                                 let ty = adt_def.repr.discr_type();
 661                                 let ty = ty.to_ty(cx.tcx());
 662                                 Some((d, o, ty))
 663                             }
 664                             _ => None,
 665                         }
 666                     })
 667                 } else {
 668                     None
 669                 };
 670                 let source = if let Some((did, offset, ty)) = var {
 671                     let mk_const = |literal| Expr {
 672                         temp_lifetime,
 673                         ty,
 674                         span: expr.span,
 675                         kind: ExprKind::Literal { literal, user_ty: None },
 676                     }.to_ref();
 677                     let offset = mk_const(ty::Const::from_bits(
 678                         cx.tcx,
 679                         offset as u128,
 680                         cx.param_env.and(ty),
 681                     ));
 682                     match did {
 683                         Some(did) => {
 684                             // in case we are offsetting from a computed discriminant
 685                             // and not the beginning of discriminants (which is always `0`)
 686                             let substs = Substs::identity_for_item(cx.tcx(), did);
 687                             let lhs = mk_const(ty::Const::unevaluated(cx.tcx(), did, substs, ty));
 688                             let bin = ExprKind::Binary {
 689                                 op: BinOp::Add,
 690                                 lhs,
 691                                 rhs: offset,
 692                             };
 693                             Expr {
 694                                 temp_lifetime,
 695                                 ty,
 696                                 span: expr.span,
 697                                 kind: bin,
 698                             }.to_ref()
 699                         },
 700                         None => offset,
 701                     }
 702                 } else {
 703                     source.to_ref()
 704                 };
 705                 ExprKind::Cast { source }
 706             }
 707         }
 708         hir::ExprKind::Type(ref source, _) => return source.make_mirror(cx),
 709         hir::ExprKind::Box(ref value) => {
 710             ExprKind::Box {
 711                 value: value.to_ref(),
 712             }
 713         }
 714         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 715         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 716
 717         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
 718     };
 719
 720     Expr {
 721         temp_lifetime,
 722         ty: expr_ty,
 723         span: expr.span,
 724         kind,
 725     }
 726 }
 727
 728 fn user_annotated_ty_for_def(
 729     cx: &mut Cx<'a, 'gcx, 'tcx>,
 730     hir_id: hir::HirId,
 731     def: &Def,
 732 ) -> Option<CanonicalTy<'tcx>> {
 733     match def {
 734         // A reference to something callable -- e.g., a fn, method, or
 735         // a tuple-struct or tuple-variant. This has the type of a
 736         // `Fn` but with the user-given substitutions.
 737         Def::Fn(_) |
 738         Def::Method(_) |
 739         Def::StructCtor(_, CtorKind::Fn) |
 740         Def::VariantCtor(_, CtorKind::Fn) =>
 741             Some(cx.tables().user_substs(hir_id)?.unchecked_map(|user_substs| {
 742                 // Here, we just pair a `DefId` with the
 743                 // `user_substs`, so no new types etc are introduced.
 744                 cx.tcx().mk_fn_def(def.def_id(), user_substs)
 745             })),
 746
 747         Def::Const(_def_id) |
 748         Def::AssociatedConst(_def_id) =>
 749             bug!("unimplemented"),
 750
 751         // A unit struct/variant which is used as a value (e.g.,
 752         // `None`). This has the type of the enum/struct that defines
 753         // this variant -- but with the substitutions given by the
 754         // user.
 755         Def::StructCtor(_def_id, CtorKind::Const) |
 756         Def::VariantCtor(_def_id, CtorKind::Const) =>
 757             match &cx.tables().node_id_to_type(hir_id).sty {
 758                 ty::Adt(adt_def, _) => user_annotated_ty_for_adt(cx, hir_id, adt_def),
 759                 sty => bug!("unexpected sty: {:?}", sty),
 760             },
 761
 762         _ =>
 763             bug!("user_annotated_ty_for_def: unexpected def {:?} at {:?}", def, hir_id)
 764     }
 765 }
 766
 767 fn user_annotated_ty_for_adt(
 768     cx: &mut Cx<'a, 'gcx, 'tcx>,
 769     hir_id: hir::HirId,
 770     adt_def: &'tcx AdtDef,
 771 ) -> Option<CanonicalTy<'tcx>> {
 772     let user_substs = cx.tables().user_substs(hir_id)?;
 773     Some(user_substs.unchecked_map(|user_substs| {
 774         // Here, we just pair an `AdtDef` with the
 775         // `user_substs`, so no new types etc are introduced.
 776         cx.tcx().mk_adt(adt_def, user_substs)
 777     }))
 778 }
 779
 780 fn method_callee<'a, 'gcx, 'tcx>(
 781     cx: &mut Cx<'a, 'gcx, 'tcx>,
 782     expr: &hir::Expr,
 783     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
 784 ) -> Expr<'tcx> {
 785     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 786     let (def_id, substs, user_ty) = match overloaded_callee {
 787         Some((def_id, substs)) => (def_id, substs, None),
 788         None => {
 789             let type_dependent_defs = cx.tables().type_dependent_defs();
 790             let def = type_dependent_defs
 791                 .get(expr.hir_id)
 792                 .unwrap_or_else(|| {
 793                     span_bug!(expr.span, "no type-dependent def for method callee")
 794                 });
 795             let user_ty = user_annotated_ty_for_def(cx, expr.hir_id, def);
 796             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
 797         }
 798     };
 799     let ty = cx.tcx().mk_fn_def(def_id, substs);
 800     Expr {
 801         temp_lifetime,
 802         ty,
 803         span: expr.span,
 804         kind: ExprKind::Literal {
 805             literal: ty::Const::zero_sized(cx.tcx(), ty),
 806             user_ty,
 807         },
 808     }
 809 }
 810
 811 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
 812
 813 impl ToBorrowKind for AutoBorrowMutability {
 814     fn to_borrow_kind(&self) -> BorrowKind {
 815         use rustc::ty::adjustment::AllowTwoPhase;
 816         match *self {
 817             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
 818                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
 819                     AllowTwoPhase::Yes => true,
 820                     AllowTwoPhase::No => false
 821                 }},
 822             AutoBorrowMutability::Immutable =>
 823                 BorrowKind::Shared,
 824         }
 825     }
 826 }
 827
 828 impl ToBorrowKind for hir::Mutability {
 829     fn to_borrow_kind(&self) -> BorrowKind {
 830         match *self {
 831             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
 832             hir::MutImmutable => BorrowKind::Shared,
 833         }
 834     }
 835 }
 836
 837 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 838     Arm {
 839         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
 840         guard: match arm.guard {
 841                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 842                 _ => None,
 843             },
 844         body: arm.body.to_ref(),
 845         // BUG: fix this
 846         lint_level: LintLevel::Inherited,
 847     }
 848 }
 849
 850 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 851                                      expr: &'tcx hir::Expr,
 852                                      def: Def)
 853                                      -> ExprKind<'tcx> {
 854     let substs = cx.tables().node_substs(expr.hir_id);
 855     match def {
 856         // A regular function, constructor function or a constant.
 857         Def::Fn(_) |
 858         Def::Method(_) |
 859         Def::StructCtor(_, CtorKind::Fn) |
 860         Def::VariantCtor(_, CtorKind::Fn) => {
 861             let user_ty = user_annotated_ty_for_def(cx, expr.hir_id, &def);
 862             ExprKind::Literal {
 863                 literal: ty::Const::zero_sized(
 864                     cx.tcx,
 865                     cx.tables().node_id_to_type(expr.hir_id),
 866                 ),
 867                 user_ty,
 868             }
 869         },
 870
 871         Def::Const(def_id) |
 872         Def::AssociatedConst(def_id) => ExprKind::Literal {
 873             literal: ty::Const::unevaluated(
 874                 cx.tcx,
 875                 def_id,
 876                 substs,
 877                 cx.tables().node_id_to_type(expr.hir_id),
 878             ),
 879             user_ty: None, // FIXME(#47184) -- user given type annot on constants
 880         },
 881
 882         Def::StructCtor(def_id, CtorKind::Const) |
 883         Def::VariantCtor(def_id, CtorKind::Const) => {
 884             match cx.tables().node_id_to_type(expr.hir_id).sty {
 885                 // A unit struct/variant which is used as a value.
 886                 // We return a completely different ExprKind here to account for this special case.
 887                 ty::Adt(adt_def, substs) => {
 888                     ExprKind::Adt {
 889                         adt_def,
 890                         variant_index: adt_def.variant_index_with_id(def_id),
 891                         substs,
 892                         user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt_def),
 893                         fields: vec![],
 894                         base: None,
 895                     }
 896                 }
 897                 ref sty => bug!("unexpected sty: {:?}", sty),
 898             }
 899         }
 900
 901         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 902
 903         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 904
 905         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 906     }
 907 }
 908
 909 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 910                                expr: &'tcx hir::Expr,
 911                                def: Def)
 912                                -> ExprKind<'tcx> {
 913     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 914
 915     match def {
 916         Def::Local(id) => ExprKind::VarRef { id },
 917
 918         Def::Upvar(var_id, index, closure_expr_id) => {
 919             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 920                    var_id,
 921                    index,
 922                    closure_expr_id);
 923             let var_hir_id = cx.tcx.hir.node_to_hir_id(var_id);
 924             let var_ty = cx.tables().node_id_to_type(var_hir_id);
 925
 926             // FIXME free regions in closures are not right
 927             let closure_ty = cx.tables()
 928                                .node_id_to_type(cx.tcx.hir.node_to_hir_id(closure_expr_id));
 929
 930             // FIXME we're just hard-coding the idea that the
 931             // signature will be &self or &mut self and hence will
 932             // have a bound region with number 0
 933             let closure_def_id = cx.tcx.hir.local_def_id(closure_expr_id);
 934             let region = ty::ReFree(ty::FreeRegion {
 935                 scope: closure_def_id,
 936                 bound_region: ty::BoundRegion::BrAnon(0),
 937             });
 938             let region = cx.tcx.mk_region(region);
 939
 940             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
 941                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
 942                     ty::ClosureKind::Fn => {
 943                         let ref_closure_ty = cx.tcx.mk_ref(region,
 944                                                            ty::TypeAndMut {
 945                                                                ty: closure_ty,
 946                                                                mutbl: hir::MutImmutable,
 947                                                            });
 948                         Expr {
 949                             ty: closure_ty,
 950                             temp_lifetime: temp_lifetime,
 951                             span: expr.span,
 952                             kind: ExprKind::Deref {
 953                                 arg: Expr {
 954                                     ty: ref_closure_ty,
 955                                     temp_lifetime,
 956                                     span: expr.span,
 957                                     kind: ExprKind::SelfRef,
 958                                 }
 959                                 .to_ref(),
 960                             },
 961                         }
 962                     }
 963                     ty::ClosureKind::FnMut => {
 964                         let ref_closure_ty = cx.tcx.mk_ref(region,
 965                                                            ty::TypeAndMut {
 966                                                                ty: closure_ty,
 967                                                                mutbl: hir::MutMutable,
 968                                                            });
 969                         Expr {
 970                             ty: closure_ty,
 971                             temp_lifetime,
 972                             span: expr.span,
 973                             kind: ExprKind::Deref {
 974                                 arg: Expr {
 975                                     ty: ref_closure_ty,
 976                                     temp_lifetime,
 977                                     span: expr.span,
 978                                     kind: ExprKind::SelfRef,
 979                                 }.to_ref(),
 980                             },
 981                         }
 982                     }
 983                     ty::ClosureKind::FnOnce => {
 984                         Expr {
 985                             ty: closure_ty,
 986                             temp_lifetime,
 987                             span: expr.span,
 988                             kind: ExprKind::SelfRef,
 989                         }
 990                     }
 991                 }
 992             } else {
 993                 Expr {
 994                     ty: closure_ty,
 995                     temp_lifetime,
 996                     span: expr.span,
 997                     kind: ExprKind::SelfRef,
 998                 }
 999             };
1000
1001             // at this point we have `self.n`, which loads up the upvar
1002             let field_kind = ExprKind::Field {
1003                 lhs: self_expr.to_ref(),
1004                 name: Field::new(index),
1005             };
1006
1007             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1008             // point we need an implicit deref
1009             let upvar_id = ty::UpvarId {
1010                 var_id: var_hir_id,
1011                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1012             };
1013             match cx.tables().upvar_capture(upvar_id) {
1014                 ty::UpvarCapture::ByValue => field_kind,
1015                 ty::UpvarCapture::ByRef(borrow) => {
1016                     ExprKind::Deref {
1017                         arg: Expr {
1018                             temp_lifetime,
1019                             ty: cx.tcx.mk_ref(borrow.region,
1020                                               ty::TypeAndMut {
1021                                                   ty: var_ty,
1022                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1023                                               }),
1024                             span: expr.span,
1025                             kind: field_kind,
1026                         }.to_ref(),
1027                     }
1028                 }
1029             }
1030         }
1031
1032         _ => span_bug!(expr.span, "type of & not region"),
1033     }
1034 }
1035
1036
1037 fn bin_op(op: hir::BinOpKind) -> BinOp {
1038     match op {
1039         hir::BinOpKind::Add => BinOp::Add,
1040         hir::BinOpKind::Sub => BinOp::Sub,
1041         hir::BinOpKind::Mul => BinOp::Mul,
1042         hir::BinOpKind::Div => BinOp::Div,
1043         hir::BinOpKind::Rem => BinOp::Rem,
1044         hir::BinOpKind::BitXor => BinOp::BitXor,
1045         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1046         hir::BinOpKind::BitOr => BinOp::BitOr,
1047         hir::BinOpKind::Shl => BinOp::Shl,
1048         hir::BinOpKind::Shr => BinOp::Shr,
1049         hir::BinOpKind::Eq => BinOp::Eq,
1050         hir::BinOpKind::Lt => BinOp::Lt,
1051         hir::BinOpKind::Le => BinOp::Le,
1052         hir::BinOpKind::Ne => BinOp::Ne,
1053         hir::BinOpKind::Ge => BinOp::Ge,
1054         hir::BinOpKind::Gt => BinOp::Gt,
1055         _ => bug!("no equivalent for ast binop {:?}", op),
1056     }
1057 }
1058
1059 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1060                                        expr: &'tcx hir::Expr,
1061                                        args: Vec<ExprRef<'tcx>>)
1062                                        -> ExprKind<'tcx> {
1063     let fun = method_callee(cx, expr, None);
1064     ExprKind::Call {
1065         ty: fun.ty,
1066         fun: fun.to_ref(),
1067         args,
1068     }
1069 }
1070
1071 fn overloaded_place<'a, 'gcx, 'tcx>(
1072     cx: &mut Cx<'a, 'gcx, 'tcx>,
1073     expr: &'tcx hir::Expr,
1074     place_ty: Ty<'tcx>,
1075     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
1076     args: Vec<ExprRef<'tcx>>,
1077 ) -> ExprKind<'tcx> {
1078     // For an overloaded *x or x[y] expression of type T, the method
1079     // call returns an &T and we must add the deref so that the types
1080     // line up (this is because `*x` and `x[y]` represent places):
1081
1082     let recv_ty = match args[0] {
1083         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1084         ExprRef::Mirror(ref e) => e.ty
1085     };
1086
1087     // Reconstruct the output assuming it's a reference with the
1088     // same region and mutability as the receiver. This holds for
1089     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1090     let (region, mutbl) = match recv_ty.sty {
1091         ty::Ref(region, _, mutbl) => (region, mutbl),
1092         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1093     };
1094     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1095         ty: place_ty,
1096         mutbl,
1097     });
1098
1099     // construct the complete expression `foo()` for the overloaded call,
1100     // which will yield the &T type
1101     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1102     let fun = method_callee(cx, expr, overloaded_callee);
1103     let ref_expr = Expr {
1104         temp_lifetime,
1105         ty: ref_ty,
1106         span: expr.span,
1107         kind: ExprKind::Call {
1108             ty: fun.ty,
1109             fun: fun.to_ref(),
1110             args,
1111         },
1112     };
1113
1114     // construct and return a deref wrapper `*foo()`
1115     ExprKind::Deref { arg: ref_expr.to_ref() }
1116 }
1117
1118 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1119                                    closure_expr: &'tcx hir::Expr,
1120                                    freevar: &hir::Freevar,
1121                                    freevar_ty: Ty<'tcx>)
1122                                    -> ExprRef<'tcx> {
1123     let var_hir_id = cx.tcx.hir.node_to_hir_id(freevar.var_id());
1124     let upvar_id = ty::UpvarId {
1125         var_id: var_hir_id,
1126         closure_expr_id: cx.tcx.hir.local_def_id(closure_expr.id).to_local(),
1127     };
1128     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1129     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1130     let var_ty = cx.tables().node_id_to_type(var_hir_id);
1131     let captured_var = Expr {
1132         temp_lifetime,
1133         ty: var_ty,
1134         span: closure_expr.span,
1135         kind: convert_var(cx, closure_expr, freevar.def),
1136     };
1137     match upvar_capture {
1138         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1139         ty::UpvarCapture::ByRef(upvar_borrow) => {
1140             let borrow_kind = match upvar_borrow.kind {
1141                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1142                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1143                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1144             };
1145             Expr {
1146                 temp_lifetime,
1147                 ty: freevar_ty,
1148                 span: closure_expr.span,
1149                 kind: ExprKind::Borrow {
1150                     region: upvar_borrow.region,
1151                     borrow_kind,
1152                     arg: captured_var.to_ref(),
1153                 },
1154             }.to_ref()
1155         }
1156     }
1157 }
1158
1159 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
1160 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1161                               fields: &'tcx [hir::Field])
1162                               -> Vec<FieldExprRef<'tcx>> {
1163     fields.iter()
1164         .map(|field| {
1165             FieldExprRef {
1166                 name: Field::new(cx.tcx.field_index(field.id, cx.tables)),
1167                 expr: field.expr.to_ref(),
1168             }
1169         })
1170         .collect()
1171 }