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 rustc_const_math::ConstInt;
  14 use hair::cx::Cx;
  15 use hair::cx::block;
  16 use hair::cx::to_ref::ToRef;
  17 use rustc::hir::def::{Def, CtorKind};
  18 use rustc::middle::const_val::ConstVal;
  19 use rustc::ty::{self, AdtKind, VariantDef, Ty};
  20 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow};
  21 use rustc::ty::cast::CastKind as TyCastKind;
  22 use rustc::ty::subst::Subst;
  23 use rustc::hir;
  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_maps.temporary_scope(self.id);
  30         let expr_extent = CodeExtent::Misc(self.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: temp_lifetime,
  47             ty: expr.ty,
  48             span: self.span,
  49             kind: ExprKind::Scope {
  50                 extent: expr_extent,
  51                 value: expr.to_ref(),
  52             },
  53         };
  54
  55         // Finally, create a destruction scope, if any.
  56         if let Some(extent) = cx.region_maps.opt_destruction_extent(self.id) {
  57             expr = Expr {
  58                 temp_lifetime: temp_lifetime,
  59                 ty: expr.ty,
  60                 span: self.span,
  61                 kind: ExprKind::Scope {
  62                     extent: extent,
  63                     value: expr.to_ref(),
  64                 },
  65             };
  66         }
  67
  68         // OK, all done!
  69         expr
  70     }
  71 }
  72
  73 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
  74                                     hir_expr: &'tcx hir::Expr,
  75                                     mut expr: Expr<'tcx>,
  76                                     adjustment: &Adjustment<'tcx>)
  77                                     -> Expr<'tcx> {
  78     let Expr { temp_lifetime, span, .. } = expr;
  79     let kind = match adjustment.kind {
  80         Adjust::ReifyFnPointer => {
  81             ExprKind::ReifyFnPointer { source: expr.to_ref() }
  82         }
  83         Adjust::UnsafeFnPointer => {
  84             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
  85         }
  86         Adjust::ClosureFnPointer => {
  87             ExprKind::ClosureFnPointer { source: expr.to_ref() }
  88         }
  89         Adjust::NeverToAny => {
  90             ExprKind::NeverToAny { source: expr.to_ref() }
  91         }
  92         Adjust::MutToConstPointer => {
  93             ExprKind::Cast { source: expr.to_ref() }
  94         }
  95         Adjust::Deref(None) => {
  96             ExprKind::Deref { arg: expr.to_ref() }
  97         }
  98         Adjust::Deref(Some(deref)) => {
  99             let call = deref.method_call(cx.tcx, expr.ty);
 100
 101             expr = Expr {
 102                 temp_lifetime,
 103                 ty: cx.tcx.mk_ref(deref.region,
 104                                   ty::TypeAndMut {
 105                                     ty: expr.ty,
 106                                     mutbl: deref.mutbl,
 107                                   }),
 108                 span,
 109                 kind: ExprKind::Borrow {
 110                     region: deref.region,
 111                     borrow_kind: to_borrow_kind(deref.mutbl),
 112                     arg: expr.to_ref(),
 113                 },
 114             };
 115
 116             overloaded_lvalue(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
 117         }
 118         Adjust::Borrow(AutoBorrow::Ref(r, m)) => {
 119             ExprKind::Borrow {
 120                 region: r,
 121                 borrow_kind: to_borrow_kind(m),
 122                 arg: expr.to_ref(),
 123             }
 124         }
 125         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
 126             // Convert this to a suitable `&foo` and
 127             // then an unsafe coercion. Limit the region to be just this
 128             // expression.
 129             let region = ty::ReScope(CodeExtent::Misc(hir_expr.id));
 130             let region = cx.tcx.mk_region(region);
 131             expr = Expr {
 132                 temp_lifetime,
 133                 ty: cx.tcx.mk_ref(region,
 134                                   ty::TypeAndMut {
 135                                     ty: expr.ty,
 136                                     mutbl: m,
 137                                   }),
 138                 span,
 139                 kind: ExprKind::Borrow {
 140                     region: region,
 141                     borrow_kind: to_borrow_kind(m),
 142                     arg: expr.to_ref(),
 143                 },
 144             };
 145             ExprKind::Cast { source: expr.to_ref() }
 146         }
 147         Adjust::Unsize => {
 148             ExprKind::Unsize { source: expr.to_ref() }
 149         }
 150     };
 151
 152     Expr {
 153         temp_lifetime,
 154         ty: adjustment.target,
 155         span,
 156         kind,
 157     }
 158 }
 159
 160 fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 161                                           expr: &'tcx hir::Expr)
 162                                           -> Expr<'tcx> {
 163     let expr_ty = cx.tables().expr_ty(expr);
 164     let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
 165
 166     let kind = match expr.node {
 167         // Here comes the interesting stuff:
 168         hir::ExprMethodCall(.., ref args) => {
 169             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 170             let expr = method_callee(cx, expr, None);
 171             let args = args.iter()
 172                 .map(|e| e.to_ref())
 173                 .collect();
 174             ExprKind::Call {
 175                 ty: expr.ty,
 176                 fun: expr.to_ref(),
 177                 args: args,
 178             }
 179         }
 180
 181         hir::ExprCall(ref fun, ref args) => {
 182             if cx.tables().is_method_call(expr) {
 183                 // The callee is something implementing Fn, FnMut, or FnOnce.
 184                 // Find the actual method implementation being called and
 185                 // build the appropriate UFCS call expression with the
 186                 // callee-object as expr parameter.
 187
 188                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 189
 190                 let method = method_callee(cx, expr, None);
 191
 192                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
 193                 let tupled_args = Expr {
 194                     ty: cx.tcx.mk_tup(arg_tys, false),
 195                     temp_lifetime: temp_lifetime,
 196                     span: expr.span,
 197                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
 198                 };
 199
 200                 ExprKind::Call {
 201                     ty: method.ty,
 202                     fun: method.to_ref(),
 203                     args: vec![fun.to_ref(), tupled_args.to_ref()],
 204                 }
 205             } else {
 206                 let adt_data = if let hir::ExprPath(hir::QPath::Resolved(_, ref path)) = fun.node {
 207                     // Tuple-like ADTs are represented as ExprCall. We convert them here.
 208                     expr_ty.ty_adt_def().and_then(|adt_def| {
 209                         match path.def {
 210                             Def::VariantCtor(variant_id, CtorKind::Fn) => {
 211                                 Some((adt_def, adt_def.variant_index_with_id(variant_id)))
 212                             }
 213                             Def::StructCtor(_, CtorKind::Fn) => Some((adt_def, 0)),
 214                             _ => None,
 215                         }
 216                     })
 217                 } else {
 218                     None
 219                 };
 220                 if let Some((adt_def, index)) = adt_data {
 221                     let substs = cx.tables().node_substs(fun.id);
 222                     let field_refs = args.iter()
 223                         .enumerate()
 224                         .map(|(idx, e)| {
 225                             FieldExprRef {
 226                                 name: Field::new(idx),
 227                                 expr: e.to_ref(),
 228                             }
 229                         })
 230                         .collect();
 231                     ExprKind::Adt {
 232                         adt_def: adt_def,
 233                         substs: substs,
 234                         variant_index: index,
 235                         fields: field_refs,
 236                         base: None,
 237                     }
 238                 } else {
 239                     ExprKind::Call {
 240                         ty: cx.tables().node_id_to_type(fun.id),
 241                         fun: fun.to_ref(),
 242                         args: args.to_ref(),
 243                     }
 244                 }
 245             }
 246         }
 247
 248         hir::ExprAddrOf(mutbl, ref expr) => {
 249             let region = match expr_ty.sty {
 250                 ty::TyRef(r, _) => r,
 251                 _ => span_bug!(expr.span, "type of & not region"),
 252             };
 253             ExprKind::Borrow {
 254                 region: region,
 255                 borrow_kind: to_borrow_kind(mutbl),
 256                 arg: expr.to_ref(),
 257             }
 258         }
 259
 260         hir::ExprBlock(ref blk) => ExprKind::Block { body: &blk },
 261
 262         hir::ExprAssign(ref lhs, ref rhs) => {
 263             ExprKind::Assign {
 264                 lhs: lhs.to_ref(),
 265                 rhs: rhs.to_ref(),
 266             }
 267         }
 268
 269         hir::ExprAssignOp(op, ref lhs, ref rhs) => {
 270             if cx.tables().is_method_call(expr) {
 271                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 272             } else {
 273                 ExprKind::AssignOp {
 274                     op: bin_op(op.node),
 275                     lhs: lhs.to_ref(),
 276                     rhs: rhs.to_ref(),
 277                 }
 278             }
 279         }
 280
 281         hir::ExprLit(..) => ExprKind::Literal { literal: cx.const_eval_literal(expr) },
 282
 283         hir::ExprBinary(op, ref lhs, ref rhs) => {
 284             if cx.tables().is_method_call(expr) {
 285                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 286             } else {
 287                 // FIXME overflow
 288                 match (op.node, cx.constness) {
 289                     // FIXME(eddyb) use logical ops in constants when
 290                     // they can handle that kind of control-flow.
 291                     (hir::BinOp_::BiAnd, hir::Constness::Const) => {
 292                         ExprKind::Binary {
 293                             op: BinOp::BitAnd,
 294                             lhs: lhs.to_ref(),
 295                             rhs: rhs.to_ref(),
 296                         }
 297                     }
 298                     (hir::BinOp_::BiOr, hir::Constness::Const) => {
 299                         ExprKind::Binary {
 300                             op: BinOp::BitOr,
 301                             lhs: lhs.to_ref(),
 302                             rhs: rhs.to_ref(),
 303                         }
 304                     }
 305
 306                     (hir::BinOp_::BiAnd, hir::Constness::NotConst) => {
 307                         ExprKind::LogicalOp {
 308                             op: LogicalOp::And,
 309                             lhs: lhs.to_ref(),
 310                             rhs: rhs.to_ref(),
 311                         }
 312                     }
 313                     (hir::BinOp_::BiOr, hir::Constness::NotConst) => {
 314                         ExprKind::LogicalOp {
 315                             op: LogicalOp::Or,
 316                             lhs: lhs.to_ref(),
 317                             rhs: rhs.to_ref(),
 318                         }
 319                     }
 320
 321                     _ => {
 322                         let op = bin_op(op.node);
 323                         ExprKind::Binary {
 324                             op: op,
 325                             lhs: lhs.to_ref(),
 326                             rhs: rhs.to_ref(),
 327                         }
 328                     }
 329                 }
 330             }
 331         }
 332
 333         hir::ExprIndex(ref lhs, ref index) => {
 334             if cx.tables().is_method_call(expr) {
 335                 overloaded_lvalue(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 336             } else {
 337                 ExprKind::Index {
 338                     lhs: lhs.to_ref(),
 339                     index: index.to_ref(),
 340                 }
 341             }
 342         }
 343
 344         hir::ExprUnary(hir::UnOp::UnDeref, ref arg) => {
 345             if cx.tables().is_method_call(expr) {
 346                 overloaded_lvalue(cx, expr, expr_ty, None, vec![arg.to_ref()])
 347             } else {
 348                 ExprKind::Deref { arg: arg.to_ref() }
 349             }
 350         }
 351
 352         hir::ExprUnary(hir::UnOp::UnNot, ref arg) => {
 353             if cx.tables().is_method_call(expr) {
 354                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 355             } else {
 356                 ExprKind::Unary {
 357                     op: UnOp::Not,
 358                     arg: arg.to_ref(),
 359                 }
 360             }
 361         }
 362
 363         hir::ExprUnary(hir::UnOp::UnNeg, ref arg) => {
 364             if cx.tables().is_method_call(expr) {
 365                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 366             } else {
 367                 // FIXME runtime-overflow
 368                 if let hir::ExprLit(_) = arg.node {
 369                     ExprKind::Literal { literal: cx.const_eval_literal(expr) }
 370                 } else {
 371                     ExprKind::Unary {
 372                         op: UnOp::Neg,
 373                         arg: arg.to_ref(),
 374                     }
 375                 }
 376             }
 377         }
 378
 379         hir::ExprStruct(ref qpath, ref fields, ref base) => {
 380             match expr_ty.sty {
 381                 ty::TyAdt(adt, substs) => {
 382                     match adt.adt_kind() {
 383                         AdtKind::Struct | AdtKind::Union => {
 384                             let field_refs = field_refs(&adt.variants[0], fields);
 385                             ExprKind::Adt {
 386                                 adt_def: adt,
 387                                 variant_index: 0,
 388                                 substs: substs,
 389                                 fields: field_refs,
 390                                 base: base.as_ref().map(|base| {
 391                                     FruInfo {
 392                                         base: base.to_ref(),
 393                                         field_types: cx.tables().fru_field_types[&expr.id].clone(),
 394                                     }
 395                                 }),
 396                             }
 397                         }
 398                         AdtKind::Enum => {
 399                             let def = match *qpath {
 400                                 hir::QPath::Resolved(_, ref path) => path.def,
 401                                 hir::QPath::TypeRelative(..) => Def::Err,
 402                             };
 403                             match def {
 404                                 Def::Variant(variant_id) => {
 405                                     assert!(base.is_none());
 406
 407                                     let index = adt.variant_index_with_id(variant_id);
 408                                     let field_refs = field_refs(&adt.variants[index], fields);
 409                                     ExprKind::Adt {
 410                                         adt_def: adt,
 411                                         variant_index: index,
 412                                         substs: substs,
 413                                         fields: field_refs,
 414                                         base: None,
 415                                     }
 416                                 }
 417                                 _ => {
 418                                     span_bug!(expr.span, "unexpected def: {:?}", def);
 419                                 }
 420                             }
 421                         }
 422                     }
 423                 }
 424                 _ => {
 425                     span_bug!(expr.span,
 426                               "unexpected type for struct literal: {:?}",
 427                               expr_ty);
 428                 }
 429             }
 430         }
 431
 432         hir::ExprClosure(..) => {
 433             let closure_ty = cx.tables().expr_ty(expr);
 434             let (def_id, substs) = match closure_ty.sty {
 435                 ty::TyClosure(def_id, substs) => (def_id, substs),
 436                 _ => {
 437                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 438                 }
 439             };
 440             let upvars = cx.tcx.with_freevars(expr.id, |freevars| {
 441                 freevars.iter()
 442                     .zip(substs.upvar_tys(def_id, cx.tcx))
 443                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
 444                     .collect()
 445             });
 446             ExprKind::Closure {
 447                 closure_id: def_id,
 448                 substs: substs,
 449                 upvars: upvars,
 450             }
 451         }
 452
 453         hir::ExprPath(ref qpath) => {
 454             let def = cx.tables().qpath_def(qpath, expr.id);
 455             convert_path_expr(cx, expr, def)
 456         }
 457
 458         hir::ExprInlineAsm(ref asm, ref outputs, ref inputs) => {
 459             ExprKind::InlineAsm {
 460                 asm: asm,
 461                 outputs: outputs.to_ref(),
 462                 inputs: inputs.to_ref(),
 463             }
 464         }
 465
 466         // Now comes the rote stuff:
 467         hir::ExprRepeat(ref v, count) => {
 468             let c = &cx.tcx.hir.body(count).value;
 469             let def_id = cx.tcx.hir.body_owner_def_id(count);
 470             let substs = Substs::empty();
 471             let count = match cx.tcx.at(c.span).const_eval((def_id, substs)) {
 472                 Ok(ConstVal::Integral(ConstInt::Usize(u))) => u,
 473                 Ok(other) => bug!("constant evaluation of repeat count yielded {:?}", other),
 474                 Err(s) => cx.fatal_const_eval_err(&s, c.span, "expression")
 475             };
 476
 477             ExprKind::Repeat {
 478                 value: v.to_ref(),
 479                 count: count,
 480             }
 481         }
 482         hir::ExprRet(ref v) => ExprKind::Return { value: v.to_ref() },
 483         hir::ExprBreak(dest, ref value) => {
 484             match dest.target_id {
 485                 hir::ScopeTarget::Block(target_id) |
 486                 hir::ScopeTarget::Loop(hir::LoopIdResult::Ok(target_id)) => ExprKind::Break {
 487                     label: CodeExtent::Misc(target_id),
 488                     value: value.to_ref(),
 489                 },
 490                 hir::ScopeTarget::Loop(hir::LoopIdResult::Err(err)) =>
 491                     bug!("invalid loop id for break: {}", err)
 492             }
 493         }
 494         hir::ExprAgain(dest) => {
 495             match dest.target_id {
 496                 hir::ScopeTarget::Block(_) => bug!("cannot continue to blocks"),
 497                 hir::ScopeTarget::Loop(hir::LoopIdResult::Ok(loop_id)) => ExprKind::Continue {
 498                     label: CodeExtent::Misc(loop_id),
 499                 },
 500                 hir::ScopeTarget::Loop(hir::LoopIdResult::Err(err)) =>
 501                     bug!("invalid loop id for continue: {}", err)
 502             }
 503         }
 504         hir::ExprMatch(ref discr, ref arms, _) => {
 505             ExprKind::Match {
 506                 discriminant: discr.to_ref(),
 507                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 508             }
 509         }
 510         hir::ExprIf(ref cond, ref then, ref otherwise) => {
 511             ExprKind::If {
 512                 condition: cond.to_ref(),
 513                 then: then.to_ref(),
 514                 otherwise: otherwise.to_ref(),
 515             }
 516         }
 517         hir::ExprWhile(ref cond, ref body, _) => {
 518             ExprKind::Loop {
 519                 condition: Some(cond.to_ref()),
 520                 body: block::to_expr_ref(cx, body),
 521             }
 522         }
 523         hir::ExprLoop(ref body, _, _) => {
 524             ExprKind::Loop {
 525                 condition: None,
 526                 body: block::to_expr_ref(cx, body),
 527             }
 528         }
 529         hir::ExprField(ref source, name) => {
 530             let index = match cx.tables().expr_ty_adjusted(source).sty {
 531                 ty::TyAdt(adt_def, _) => adt_def.variants[0].index_of_field_named(name.node),
 532                 ref ty => span_bug!(expr.span, "field of non-ADT: {:?}", ty),
 533             };
 534             let index =
 535                 index.unwrap_or_else(|| {
 536                     span_bug!(expr.span, "no index found for field `{}`", name.node)
 537                 });
 538             ExprKind::Field {
 539                 lhs: source.to_ref(),
 540                 name: Field::new(index),
 541             }
 542         }
 543         hir::ExprTupField(ref source, index) => {
 544             ExprKind::Field {
 545                 lhs: source.to_ref(),
 546                 name: Field::new(index.node as usize),
 547             }
 548         }
 549         hir::ExprCast(ref source, _) => {
 550             // Check to see if this cast is a "coercion cast", where the cast is actually done
 551             // using a coercion (or is a no-op).
 552             if let Some(&TyCastKind::CoercionCast) = cx.tables().cast_kinds.get(&source.id) {
 553                 // Convert the lexpr to a vexpr.
 554                 ExprKind::Use { source: source.to_ref() }
 555             } else {
 556                 ExprKind::Cast { source: source.to_ref() }
 557             }
 558         }
 559         hir::ExprType(ref source, _) => return source.make_mirror(cx),
 560         hir::ExprBox(ref value) => {
 561             ExprKind::Box {
 562                 value: value.to_ref(),
 563                 value_extents: CodeExtent::Misc(value.id),
 564             }
 565         }
 566         hir::ExprArray(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 567         hir::ExprTup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 568     };
 569
 570     Expr {
 571         temp_lifetime: temp_lifetime,
 572         ty: expr_ty,
 573         span: expr.span,
 574         kind: kind,
 575     }
 576 }
 577
 578 fn method_callee<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 579                                  expr: &hir::Expr,
 580                                  custom_callee: Option<(DefId, &'tcx Substs<'tcx>)>)
 581                                  -> Expr<'tcx> {
 582     let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
 583     let (def_id, substs) = custom_callee.unwrap_or_else(|| {
 584         (cx.tables().type_dependent_defs[&expr.id].def_id(),
 585          cx.tables().node_substs(expr.id))
 586     });
 587     Expr {
 588         temp_lifetime: temp_lifetime,
 589         ty: cx.tcx.type_of(def_id).subst(cx.tcx, substs),
 590         span: expr.span,
 591         kind: ExprKind::Literal {
 592             literal: Literal::Value {
 593                 value: ConstVal::Function(def_id, substs),
 594             },
 595         },
 596     }
 597 }
 598
 599 fn to_borrow_kind(m: hir::Mutability) -> BorrowKind {
 600     match m {
 601         hir::MutMutable => BorrowKind::Mut,
 602         hir::MutImmutable => BorrowKind::Shared,
 603     }
 604 }
 605
 606 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 607     Arm {
 608         patterns: arm.pats.iter().map(|p| Pattern::from_hir(cx.tcx, cx.tables(), p)).collect(),
 609         guard: arm.guard.to_ref(),
 610         body: arm.body.to_ref(),
 611     }
 612 }
 613
 614 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 615                                      expr: &'tcx hir::Expr,
 616                                      def: Def)
 617                                      -> ExprKind<'tcx> {
 618     let substs = cx.tables().node_substs(expr.id);
 619     match def {
 620         // A regular function, constructor function or a constant.
 621         Def::Fn(def_id) |
 622         Def::Method(def_id) |
 623         Def::StructCtor(def_id, CtorKind::Fn) |
 624         Def::VariantCtor(def_id, CtorKind::Fn) => ExprKind::Literal {
 625             literal: Literal::Value {
 626                 value: ConstVal::Function(def_id, substs),
 627             },
 628         },
 629
 630         Def::Const(def_id) |
 631         Def::AssociatedConst(def_id) => ExprKind::Literal {
 632             literal: Literal::Item {
 633                 def_id: def_id,
 634                 substs: substs,
 635             },
 636         },
 637
 638         Def::StructCtor(def_id, CtorKind::Const) |
 639         Def::VariantCtor(def_id, CtorKind::Const) => {
 640             match cx.tables().node_id_to_type(expr.id).sty {
 641                 // A unit struct/variant which is used as a value.
 642                 // We return a completely different ExprKind here to account for this special case.
 643                 ty::TyAdt(adt_def, substs) => {
 644                     ExprKind::Adt {
 645                         adt_def: adt_def,
 646                         variant_index: adt_def.variant_index_with_id(def_id),
 647                         substs: substs,
 648                         fields: vec![],
 649                         base: None,
 650                     }
 651                 }
 652                 ref sty => bug!("unexpected sty: {:?}", sty),
 653             }
 654         }
 655
 656         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 657
 658         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 659
 660         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
 661     }
 662 }
 663
 664 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 665                                expr: &'tcx hir::Expr,
 666                                def: Def)
 667                                -> ExprKind<'tcx> {
 668     let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
 669
 670     match def {
 671         Def::Local(def_id) => {
 672             let node_id = cx.tcx.hir.as_local_node_id(def_id).unwrap();
 673             ExprKind::VarRef { id: node_id }
 674         }
 675
 676         Def::Upvar(def_id, index, closure_expr_id) => {
 677             let id_var = cx.tcx.hir.as_local_node_id(def_id).unwrap();
 678             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
 679                    id_var,
 680                    index,
 681                    closure_expr_id);
 682             let var_ty = cx.tables().node_id_to_type(id_var);
 683
 684             // FIXME free regions in closures are not right
 685             let closure_ty = cx.tables().node_id_to_type(closure_expr_id);
 686
 687             // FIXME we're just hard-coding the idea that the
 688             // signature will be &self or &mut self and hence will
 689             // have a bound region with number 0
 690             let closure_def_id = cx.tcx.hir.local_def_id(closure_expr_id);
 691             let region = ty::ReFree(ty::FreeRegion {
 692                 scope: closure_def_id,
 693                 bound_region: ty::BoundRegion::BrAnon(0),
 694             });
 695             let region = cx.tcx.mk_region(region);
 696
 697             let self_expr = match cx.tcx.closure_kind(closure_def_id) {
 698                 ty::ClosureKind::Fn => {
 699                     let ref_closure_ty = cx.tcx.mk_ref(region,
 700                                                        ty::TypeAndMut {
 701                                                            ty: closure_ty,
 702                                                            mutbl: hir::MutImmutable,
 703                                                        });
 704                     Expr {
 705                         ty: closure_ty,
 706                         temp_lifetime: temp_lifetime,
 707                         span: expr.span,
 708                         kind: ExprKind::Deref {
 709                             arg: Expr {
 710                                 ty: ref_closure_ty,
 711                                 temp_lifetime: temp_lifetime,
 712                                 span: expr.span,
 713                                 kind: ExprKind::SelfRef,
 714                             }
 715                             .to_ref(),
 716                         },
 717                     }
 718                 }
 719                 ty::ClosureKind::FnMut => {
 720                     let ref_closure_ty = cx.tcx.mk_ref(region,
 721                                                        ty::TypeAndMut {
 722                                                            ty: closure_ty,
 723                                                            mutbl: hir::MutMutable,
 724                                                        });
 725                     Expr {
 726                         ty: closure_ty,
 727                         temp_lifetime: temp_lifetime,
 728                         span: expr.span,
 729                         kind: ExprKind::Deref {
 730                             arg: Expr {
 731                                 ty: ref_closure_ty,
 732                                 temp_lifetime: temp_lifetime,
 733                                 span: expr.span,
 734                                 kind: ExprKind::SelfRef,
 735                             }.to_ref(),
 736                         },
 737                     }
 738                 }
 739                 ty::ClosureKind::FnOnce => {
 740                     Expr {
 741                         ty: closure_ty,
 742                         temp_lifetime: temp_lifetime,
 743                         span: expr.span,
 744                         kind: ExprKind::SelfRef,
 745                     }
 746                 }
 747             };
 748
 749             // at this point we have `self.n`, which loads up the upvar
 750             let field_kind = ExprKind::Field {
 751                 lhs: self_expr.to_ref(),
 752                 name: Field::new(index),
 753             };
 754
 755             // ...but the upvar might be an `&T` or `&mut T` capture, at which
 756             // point we need an implicit deref
 757             let upvar_id = ty::UpvarId {
 758                 var_id: id_var,
 759                 closure_expr_id: closure_expr_id,
 760             };
 761             let upvar_capture = match cx.tables().upvar_capture(upvar_id) {
 762                 Some(c) => c,
 763                 None => {
 764                     span_bug!(expr.span, "no upvar_capture for {:?}", upvar_id);
 765                 }
 766             };
 767             match upvar_capture {
 768                 ty::UpvarCapture::ByValue => field_kind,
 769                 ty::UpvarCapture::ByRef(borrow) => {
 770                     ExprKind::Deref {
 771                         arg: Expr {
 772                             temp_lifetime: temp_lifetime,
 773                             ty: cx.tcx.mk_ref(borrow.region,
 774                                               ty::TypeAndMut {
 775                                                   ty: var_ty,
 776                                                   mutbl: borrow.kind.to_mutbl_lossy(),
 777                                               }),
 778                             span: expr.span,
 779                             kind: field_kind,
 780                         }.to_ref(),
 781                     }
 782                 }
 783             }
 784         }
 785
 786         _ => span_bug!(expr.span, "type of & not region"),
 787     }
 788 }
 789
 790
 791 fn bin_op(op: hir::BinOp_) -> BinOp {
 792     match op {
 793         hir::BinOp_::BiAdd => BinOp::Add,
 794         hir::BinOp_::BiSub => BinOp::Sub,
 795         hir::BinOp_::BiMul => BinOp::Mul,
 796         hir::BinOp_::BiDiv => BinOp::Div,
 797         hir::BinOp_::BiRem => BinOp::Rem,
 798         hir::BinOp_::BiBitXor => BinOp::BitXor,
 799         hir::BinOp_::BiBitAnd => BinOp::BitAnd,
 800         hir::BinOp_::BiBitOr => BinOp::BitOr,
 801         hir::BinOp_::BiShl => BinOp::Shl,
 802         hir::BinOp_::BiShr => BinOp::Shr,
 803         hir::BinOp_::BiEq => BinOp::Eq,
 804         hir::BinOp_::BiLt => BinOp::Lt,
 805         hir::BinOp_::BiLe => BinOp::Le,
 806         hir::BinOp_::BiNe => BinOp::Ne,
 807         hir::BinOp_::BiGe => BinOp::Ge,
 808         hir::BinOp_::BiGt => BinOp::Gt,
 809         _ => bug!("no equivalent for ast binop {:?}", op),
 810     }
 811 }
 812
 813 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 814                                        expr: &'tcx hir::Expr,
 815                                        args: Vec<ExprRef<'tcx>>)
 816                                        -> ExprKind<'tcx> {
 817     let fun = method_callee(cx, expr, None);
 818     ExprKind::Call {
 819         ty: fun.ty,
 820         fun: fun.to_ref(),
 821         args,
 822     }
 823 }
 824
 825 fn overloaded_lvalue<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 826                                      expr: &'tcx hir::Expr,
 827                                      lvalue_ty: Ty<'tcx>,
 828                                      custom_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
 829                                      args: Vec<ExprRef<'tcx>>)
 830                                      -> ExprKind<'tcx> {
 831     // For an overloaded *x or x[y] expression of type T, the method
 832     // call returns an &T and we must add the deref so that the types
 833     // line up (this is because `*x` and `x[y]` represent lvalues):
 834
 835     let recv_ty = match args[0] {
 836         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
 837         ExprRef::Mirror(ref e) => e.ty
 838     };
 839
 840     // Reconstruct the output assuming it's a reference with the
 841     // same region and mutability as the receiver. This holds for
 842     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
 843     let (region, mt) = match recv_ty.sty {
 844         ty::TyRef(region, mt) => (region, mt),
 845         _ => span_bug!(expr.span, "overloaded_lvalue: receiver is not a reference"),
 846     };
 847     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
 848         ty: lvalue_ty,
 849         mutbl: mt.mutbl,
 850     });
 851
 852     // construct the complete expression `foo()` for the overloaded call,
 853     // which will yield the &T type
 854     let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
 855     let fun = method_callee(cx, expr, custom_callee);
 856     let ref_expr = Expr {
 857         temp_lifetime: temp_lifetime,
 858         ty: ref_ty,
 859         span: expr.span,
 860         kind: ExprKind::Call {
 861             ty: fun.ty,
 862             fun: fun.to_ref(),
 863             args,
 864         },
 865     };
 866
 867     // construct and return a deref wrapper `*foo()`
 868     ExprKind::Deref { arg: ref_expr.to_ref() }
 869 }
 870
 871 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 872                                    closure_expr: &'tcx hir::Expr,
 873                                    freevar: &hir::Freevar,
 874                                    freevar_ty: Ty<'tcx>)
 875                                    -> ExprRef<'tcx> {
 876     let id_var = cx.tcx.hir.as_local_node_id(freevar.def.def_id()).unwrap();
 877     let upvar_id = ty::UpvarId {
 878         var_id: id_var,
 879         closure_expr_id: closure_expr.id,
 880     };
 881     let upvar_capture = cx.tables().upvar_capture(upvar_id).unwrap();
 882     let temp_lifetime = cx.region_maps.temporary_scope(closure_expr.id);
 883     let var_ty = cx.tables().node_id_to_type(id_var);
 884     let captured_var = Expr {
 885         temp_lifetime: temp_lifetime,
 886         ty: var_ty,
 887         span: closure_expr.span,
 888         kind: convert_var(cx, closure_expr, freevar.def),
 889     };
 890     match upvar_capture {
 891         ty::UpvarCapture::ByValue => captured_var.to_ref(),
 892         ty::UpvarCapture::ByRef(upvar_borrow) => {
 893             let borrow_kind = match upvar_borrow.kind {
 894                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
 895                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
 896                 ty::BorrowKind::MutBorrow => BorrowKind::Mut,
 897             };
 898             Expr {
 899                 temp_lifetime: temp_lifetime,
 900                 ty: freevar_ty,
 901                 span: closure_expr.span,
 902                 kind: ExprKind::Borrow {
 903                     region: upvar_borrow.region,
 904                     borrow_kind: borrow_kind,
 905                     arg: captured_var.to_ref(),
 906                 },
 907             }.to_ref()
 908         }
 909     }
 910 }
 911
 912 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
 913 fn field_refs<'tcx>(variant: &'tcx VariantDef,
 914                     fields: &'tcx [hir::Field])
 915                     -> Vec<FieldExprRef<'tcx>> {
 916     fields.iter()
 917         .map(|field| {
 918             FieldExprRef {
 919                 name: Field::new(variant.index_of_field_named(field.name.node).unwrap()),
 920                 expr: field.expr.to_ref(),
 921             }
 922         })
 923         .collect()
 924 }