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::fnv::FnvHashMap;
  13 use hair::cx::Cx;
  14 use hair::cx::block;
  15 use hair::cx::to_ref::ToRef;
  16 use rustc::front::map;
  17 use rustc::middle::def::Def;
  18 use rustc::middle::const_eval;
  19 use rustc::middle::region::CodeExtent;
  20 use rustc::middle::pat_util;
  21 use rustc::middle::ty::{self, VariantDef, Ty};
  22 use rustc::mir::repr::*;
  23 use rustc_front::hir;
  24 use rustc_front::util as hir_util;
  25 use syntax::parse::token;
  26 use syntax::ptr::P;
  27
  28 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
  29     type Output = Expr<'tcx>;
  30
  31     fn make_mirror<'a>(self, cx: &mut Cx<'a, 'tcx>) -> Expr<'tcx> {
  32         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
  33
  34         let expr_ty = cx.tcx.expr_ty(self); // note: no adjustments (yet)!
  35
  36         let kind = match self.node {
  37             // Here comes the interesting stuff:
  38             hir::ExprMethodCall(_, _, ref args) => {
  39                 // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
  40                 let expr = method_callee(cx, self, ty::MethodCall::expr(self.id));
  41                 let args = args.iter()
  42                                .map(|e| e.to_ref())
  43                                .collect();
  44                 ExprKind::Call {
  45                     ty: expr.ty,
  46                     fun: expr.to_ref(),
  47                     args: args,
  48                 }
  49             }
  50
  51             hir::ExprCall(ref fun, ref args) => {
  52                 if cx.tcx.is_method_call(self.id) {
  53                     // The callee is something implementing Fn, FnMut, or FnOnce.
  54                     // Find the actual method implementation being called and
  55                     // build the appropriate UFCS call expression with the
  56                     // callee-object as self parameter.
  57
  58                     // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
  59
  60                     let method = method_callee(cx, self, ty::MethodCall::expr(self.id));
  61
  62                     let sig = match method.ty.sty {
  63                         ty::TyBareFn(_, fn_ty) => &fn_ty.sig,
  64                         _ => cx.tcx.sess.span_bug(self.span, "type of method is not an fn")
  65                     };
  66
  67                     let sig = cx.tcx.no_late_bound_regions(sig).unwrap_or_else(|| {
  68                         cx.tcx.sess.span_bug(self.span, "method call has late-bound regions")
  69                     });
  70
  71                     assert_eq!(sig.inputs.len(), 2);
  72
  73                     let tupled_args = Expr {
  74                         ty: sig.inputs[1],
  75                         temp_lifetime: cx.tcx.region_maps.temporary_scope(self.id),
  76                         span: self.span,
  77                         kind: ExprKind::Tuple {
  78                             fields: args.iter().map(ToRef::to_ref).collect()
  79                         }
  80                     };
  81
  82                     ExprKind::Call {
  83                         ty: method.ty,
  84                         fun: method.to_ref(),
  85                         args: vec![fun.to_ref(), tupled_args.to_ref()]
  86                     }
  87                 } else {
  88                     let adt_data = if let hir::ExprPath(..) = fun.node {
  89                         // Tuple-like ADTs are represented as ExprCall. We convert them here.
  90                         expr_ty.ty_adt_def().and_then(|adt_def|{
  91                             match cx.tcx.def_map.borrow()[&fun.id].full_def() {
  92                                 Def::Variant(_, variant_id) => {
  93                                     Some((adt_def, adt_def.variant_index_with_id(variant_id)))
  94                                 },
  95                                 Def::Struct(..) => {
  96                                     Some((adt_def, 0))
  97                                 },
  98                                 _ => None
  99                             }
 100                         })
 101                     } else { None };
 102                     if let Some((adt_def, index)) = adt_data {
 103                         let substs = cx.tcx.mk_substs(cx.tcx.node_id_item_substs(fun.id).substs);
 104                         let field_refs = args.iter().enumerate().map(|(idx, e)| FieldExprRef {
 105                             name: Field::new(idx),
 106                             expr: e.to_ref()
 107                         }).collect();
 108                         ExprKind::Adt {
 109                             adt_def: adt_def,
 110                             substs: substs,
 111                             variant_index: index,
 112                             fields: field_refs,
 113                             base: None
 114                         }
 115                     } else {
 116                         ExprKind::Call {
 117                             ty: cx.tcx.node_id_to_type(fun.id),
 118                             fun: fun.to_ref(),
 119                             args: args.to_ref(),
 120                         }
 121                     }
 122                 }
 123             }
 124
 125             hir::ExprAddrOf(mutbl, ref expr) => {
 126                 let region = match expr_ty.sty {
 127                     ty::TyRef(r, _) => r,
 128                     _ => cx.tcx.sess.span_bug(expr.span, "type of & not region"),
 129                 };
 130                 ExprKind::Borrow {
 131                     region: *region,
 132                     borrow_kind: to_borrow_kind(mutbl),
 133                     arg: expr.to_ref(),
 134                 }
 135             }
 136
 137             hir::ExprBlock(ref blk) => {
 138                 ExprKind::Block { body: &blk }
 139             }
 140
 141             hir::ExprAssign(ref lhs, ref rhs) => {
 142                 ExprKind::Assign {
 143                     lhs: lhs.to_ref(),
 144                     rhs: rhs.to_ref(),
 145                 }
 146             }
 147
 148             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
 149                 let op = bin_op(op.node);
 150                 ExprKind::AssignOp {
 151                     op: op,
 152                     lhs: lhs.to_ref(),
 153                     rhs: rhs.to_ref(),
 154                 }
 155             }
 156
 157             hir::ExprLit(..) => ExprKind::Literal {
 158                 literal: cx.const_eval_literal(self)
 159             },
 160
 161             hir::ExprBinary(op, ref lhs, ref rhs) => {
 162                 if cx.tcx.is_method_call(self.id) {
 163                     let pass_args = if hir_util::is_by_value_binop(op.node) {
 164                         PassArgs::ByValue
 165                     } else {
 166                         PassArgs::ByRef
 167                     };
 168                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 169                                         pass_args, lhs.to_ref(), vec![rhs])
 170                 } else {
 171                     // FIXME overflow
 172                     match op.node {
 173                         hir::BinOp_::BiAnd => {
 174                             ExprKind::LogicalOp {
 175                                 op: LogicalOp::And,
 176                                 lhs: lhs.to_ref(),
 177                                 rhs: rhs.to_ref(),
 178                             }
 179                         }
 180                         hir::BinOp_::BiOr => {
 181                             ExprKind::LogicalOp {
 182                                 op: LogicalOp::Or,
 183                                 lhs: lhs.to_ref(),
 184                                 rhs: rhs.to_ref(),
 185                             }
 186                         }
 187                         _ => {
 188                             let op = bin_op(op.node);
 189                             ExprKind::Binary {
 190                                 op: op,
 191                                 lhs: lhs.to_ref(),
 192                                 rhs: rhs.to_ref(),
 193                             }
 194                         }
 195                     }
 196                 }
 197             }
 198
 199             hir::ExprIndex(ref lhs, ref index) => {
 200                 if cx.tcx.is_method_call(self.id) {
 201                     overloaded_lvalue(cx, self, ty::MethodCall::expr(self.id),
 202                                       PassArgs::ByValue, lhs.to_ref(), vec![index])
 203                 } else {
 204                     ExprKind::Index {
 205                         lhs: lhs.to_ref(),
 206                         index: index.to_ref(),
 207                     }
 208                 }
 209             }
 210
 211             hir::ExprUnary(hir::UnOp::UnDeref, ref arg) => {
 212                 if cx.tcx.is_method_call(self.id) {
 213                     overloaded_lvalue(cx, self, ty::MethodCall::expr(self.id),
 214                                       PassArgs::ByValue, arg.to_ref(), vec![])
 215                 } else {
 216                     ExprKind::Deref { arg: arg.to_ref() }
 217                 }
 218             }
 219
 220             hir::ExprUnary(op, ref arg) => {
 221                 if cx.tcx.is_method_call(self.id) {
 222                     overloaded_operator(cx, self, ty::MethodCall::expr(self.id),
 223                                         PassArgs::ByValue, arg.to_ref(), vec![])
 224                 } else {
 225                     // FIXME overflow
 226                     let op = match op {
 227                         hir::UnOp::UnNot => UnOp::Not,
 228                         hir::UnOp::UnNeg => UnOp::Neg,
 229                         hir::UnOp::UnDeref => {
 230                             cx.tcx.sess.span_bug(
 231                                 self.span,
 232                                 "UnDeref should have been handled elsewhere");
 233                         }
 234                     };
 235                     ExprKind::Unary {
 236                         op: op,
 237                         arg: arg.to_ref(),
 238                     }
 239                 }
 240             }
 241
 242             hir::ExprStruct(_, ref fields, ref base) => {
 243                 match expr_ty.sty {
 244                     ty::TyStruct(adt, substs) => {
 245                         let field_refs = field_refs(&adt.variants[0], fields);
 246                         ExprKind::Adt {
 247                             adt_def: adt,
 248                             variant_index: 0,
 249                             substs: substs,
 250                             fields: field_refs,
 251                             base: base.to_ref(),
 252                         }
 253                     }
 254                     ty::TyEnum(adt, substs) => {
 255                         match cx.tcx.def_map.borrow()[&self.id].full_def() {
 256                             Def::Variant(enum_id, variant_id) => {
 257                                 debug_assert!(adt.did == enum_id);
 258                                 let index = adt.variant_index_with_id(variant_id);
 259                                 let field_refs = field_refs(&adt.variants[index], fields);
 260                                 ExprKind::Adt {
 261                                     adt_def: adt,
 262                                     variant_index: index,
 263                                     substs: substs,
 264                                     fields: field_refs,
 265                                     base: base.to_ref(),
 266                                 }
 267                             }
 268                             ref def => {
 269                                 cx.tcx.sess.span_bug(
 270                                     self.span,
 271                                     &format!("unexpected def: {:?}", def));
 272                             }
 273                         }
 274                     }
 275                     _ => {
 276                         cx.tcx.sess.span_bug(
 277                             self.span,
 278                             &format!("unexpected type for struct literal: {:?}", expr_ty));
 279                     }
 280                 }
 281             }
 282
 283             hir::ExprClosure(..) => {
 284                 let closure_ty = cx.tcx.expr_ty(self);
 285                 let (def_id, substs) = match closure_ty.sty {
 286                     ty::TyClosure(def_id, ref substs) => (def_id, substs),
 287                     _ => {
 288                         cx.tcx.sess.span_bug(self.span,
 289                                              &format!("closure expr w/o closure type: {:?}",
 290                                                       closure_ty));
 291                     }
 292                 };
 293                 let upvars = cx.tcx.with_freevars(self.id, |freevars| {
 294                     freevars.iter()
 295                             .enumerate()
 296                             .map(|(i, fv)| capture_freevar(cx, self, fv, substs.upvar_tys[i]))
 297                             .collect()
 298                 });
 299                 ExprKind::Closure {
 300                     closure_id: def_id,
 301                     substs: &substs,
 302                     upvars: upvars,
 303                 }
 304             }
 305
 306             hir::ExprRange(ref start, ref end) => {
 307                 let range_ty = cx.tcx.expr_ty(self);
 308                 let (adt_def, substs) = match range_ty.sty {
 309                     ty::TyStruct(adt_def, substs) => (adt_def, substs),
 310                     _ => {
 311                         cx.tcx.sess.span_bug(self.span, "unexpanded ast");
 312                     }
 313                 };
 314
 315                 let field_expr_ref = |s: &'tcx P<hir::Expr>, name: &str| {
 316                     let name = token::intern(name);
 317                     let index = adt_def.variants[0].index_of_field_named(name).unwrap();
 318                     FieldExprRef { name: Field::new(index), expr: s.to_ref() }
 319                 };
 320
 321                 let start_field = start.as_ref()
 322                                        .into_iter()
 323                                        .map(|s| field_expr_ref(s, "start"));
 324
 325                 let end_field = end.as_ref()
 326                                    .into_iter()
 327                                    .map(|e| field_expr_ref(e, "end"));
 328
 329                 ExprKind::Adt {
 330                     adt_def: adt_def,
 331                     variant_index: 0,
 332                     substs: substs,
 333                     fields: start_field.chain(end_field).collect(),
 334                     base: None,
 335                 }
 336             }
 337
 338             hir::ExprPath(..) => {
 339                 convert_path_expr(cx, self)
 340             }
 341
 342             hir::ExprInlineAsm(ref asm) => {
 343                 ExprKind::InlineAsm { asm: asm }
 344             }
 345
 346             // Now comes the rote stuff:
 347
 348             hir::ExprRepeat(ref v, ref c) => ExprKind::Repeat {
 349                 value: v.to_ref(),
 350                 count: TypedConstVal {
 351                     ty: cx.tcx.expr_ty(c),
 352                     span: c.span,
 353                     value: const_eval::eval_const_expr(cx.tcx, c)
 354                 }
 355             },
 356             hir::ExprRet(ref v) =>
 357                 ExprKind::Return { value: v.to_ref() },
 358             hir::ExprBreak(label) =>
 359                 ExprKind::Break { label: label.map(|_| loop_label(cx, self)) },
 360             hir::ExprAgain(label) =>
 361                 ExprKind::Continue { label: label.map(|_| loop_label(cx, self)) },
 362             hir::ExprMatch(ref discr, ref arms, _) =>
 363                 ExprKind::Match { discriminant: discr.to_ref(),
 364                                   arms: arms.iter().map(|a| convert_arm(cx, a)).collect() },
 365             hir::ExprIf(ref cond, ref then, ref otherwise) =>
 366                 ExprKind::If { condition: cond.to_ref(),
 367                                then: block::to_expr_ref(cx, then),
 368                                otherwise: otherwise.to_ref() },
 369             hir::ExprWhile(ref cond, ref body, _) =>
 370                 ExprKind::Loop { condition: Some(cond.to_ref()),
 371                                  body: block::to_expr_ref(cx, body) },
 372             hir::ExprLoop(ref body, _) =>
 373                 ExprKind::Loop { condition: None,
 374                                  body: block::to_expr_ref(cx, body) },
 375             hir::ExprField(ref source, name) => {
 376                 let index = match cx.tcx.expr_ty_adjusted(source).sty {
 377                     ty::TyStruct(adt_def, _) =>
 378                         adt_def.variants[0].index_of_field_named(name.node),
 379                     ref ty =>
 380                         cx.tcx.sess.span_bug(
 381                             self.span,
 382                             &format!("field of non-struct: {:?}", ty)),
 383                 };
 384                 let index = index.unwrap_or_else(|| {
 385                     cx.tcx.sess.span_bug(
 386                         self.span,
 387                         &format!("no index found for field `{}`", name.node));
 388                 });
 389                 ExprKind::Field { lhs: source.to_ref(), name: Field::new(index) }
 390             }
 391             hir::ExprTupField(ref source, index) =>
 392                 ExprKind::Field { lhs: source.to_ref(),
 393                                   name: Field::new(index.node as usize) },
 394             hir::ExprCast(ref source, _) =>
 395                 ExprKind::Cast { source: source.to_ref() },
 396             hir::ExprType(ref source, _) =>
 397                 return source.make_mirror(cx),
 398             hir::ExprBox(ref value) =>
 399                 ExprKind::Box {
 400                     value: value.to_ref(),
 401                     value_extents: cx.tcx.region_maps.node_extent(value.id)
 402                 },
 403             hir::ExprVec(ref fields) =>
 404                 ExprKind::Vec { fields: fields.to_ref() },
 405             hir::ExprTup(ref fields) =>
 406                 ExprKind::Tuple { fields: fields.to_ref() },
 407         };
 408
 409         let temp_lifetime = cx.tcx.region_maps.temporary_scope(self.id);
 410         let expr_extent = cx.tcx.region_maps.node_extent(self.id);
 411
 412         let mut expr = Expr {
 413             temp_lifetime: temp_lifetime,
 414             ty: expr_ty,
 415             span: self.span,
 416             kind: kind,
 417         };
 418
 419         // Now apply adjustments, if any.
 420         match cx.tcx.tables.borrow().adjustments.get(&self.id) {
 421             None => {}
 422             Some(&ty::adjustment::AdjustReifyFnPointer) => {
 423                 let adjusted_ty = cx.tcx.expr_ty_adjusted(self);
 424                 expr = Expr {
 425                     temp_lifetime: temp_lifetime,
 426                     ty: adjusted_ty,
 427                     span: self.span,
 428                     kind: ExprKind::ReifyFnPointer { source: expr.to_ref() },
 429                 };
 430             }
 431             Some(&ty::adjustment::AdjustUnsafeFnPointer) => {
 432                 let adjusted_ty = cx.tcx.expr_ty_adjusted(self);
 433                 expr = Expr {
 434                     temp_lifetime: temp_lifetime,
 435                     ty: adjusted_ty,
 436                     span: self.span,
 437                     kind: ExprKind::UnsafeFnPointer { source: expr.to_ref() },
 438                 };
 439             }
 440             Some(&ty::adjustment::AdjustDerefRef(ref adj)) => {
 441                 for i in 0..adj.autoderefs {
 442                     let i = i as u32;
 443                     let adjusted_ty =
 444                         expr.ty.adjust_for_autoderef(
 445                             cx.tcx,
 446                             self.id,
 447                             self.span,
 448                             i,
 449                             |mc| cx.tcx.tables.borrow().method_map.get(&mc).map(|m| m.ty));
 450                     let kind = if cx.tcx.is_overloaded_autoderef(self.id, i) {
 451                         overloaded_lvalue(cx, self, ty::MethodCall::autoderef(self.id, i),
 452                                           PassArgs::ByValue, expr.to_ref(), vec![])
 453                     } else {
 454                         ExprKind::Deref { arg: expr.to_ref() }
 455                     };
 456                     expr = Expr {
 457                         temp_lifetime: temp_lifetime,
 458                         ty: adjusted_ty,
 459                         span: self.span,
 460                         kind: kind,
 461                     };
 462                 }
 463
 464                 if let Some(autoref) = adj.autoref {
 465                     let adjusted_ty = expr.ty.adjust_for_autoref(cx.tcx, Some(autoref));
 466                     match autoref {
 467                         ty::adjustment::AutoPtr(r, m) => {
 468                             expr = Expr {
 469                                 temp_lifetime: temp_lifetime,
 470                                 ty: adjusted_ty,
 471                                 span: self.span,
 472                                 kind: ExprKind::Borrow {
 473                                     region: *r,
 474                                     borrow_kind: to_borrow_kind(m),
 475                                     arg: expr.to_ref(),
 476                                 },
 477                             };
 478                         }
 479                         ty::adjustment::AutoUnsafe(m) => {
 480                             // Convert this to a suitable `&foo` and
 481                             // then an unsafe coercion. Limit the region to be just this
 482                             // expression.
 483                             let region = ty::ReScope(expr_extent);
 484                             let region = cx.tcx.mk_region(region);
 485                             expr = Expr {
 486                                 temp_lifetime: temp_lifetime,
 487                                 ty: cx.tcx.mk_ref(region, ty::TypeAndMut { ty: expr.ty, mutbl: m }),
 488                                 span: self.span,
 489                                 kind: ExprKind::Borrow {
 490                                     region: *region,
 491                                     borrow_kind: to_borrow_kind(m),
 492                                     arg: expr.to_ref(),
 493                                 },
 494                             };
 495                             expr = Expr {
 496                                 temp_lifetime: temp_lifetime,
 497                                 ty: adjusted_ty,
 498                                 span: self.span,
 499                                 kind: ExprKind::Cast { source: expr.to_ref() },
 500                             };
 501                         }
 502                     }
 503                 }
 504
 505                 if let Some(target) = adj.unsize {
 506                     expr = Expr {
 507                         temp_lifetime: temp_lifetime,
 508                         ty: target,
 509                         span: self.span,
 510                         kind: ExprKind::Unsize { source: expr.to_ref() },
 511                     };
 512                 }
 513             }
 514         }
 515
 516         // Next, wrap this up in the expr's scope.
 517         expr = Expr {
 518             temp_lifetime: temp_lifetime,
 519             ty: expr.ty,
 520             span: self.span,
 521             kind: ExprKind::Scope {
 522                 extent: expr_extent,
 523                 value: expr.to_ref(),
 524             },
 525         };
 526
 527         // Finally, create a destruction scope, if any.
 528         if let Some(extent) = cx.tcx.region_maps.opt_destruction_extent(self.id) {
 529             expr = Expr {
 530                 temp_lifetime: temp_lifetime,
 531                 ty: expr.ty,
 532                 span: self.span,
 533                 kind: ExprKind::Scope {
 534                     extent: extent,
 535                     value: expr.to_ref(),
 536                 },
 537             };
 538         }
 539
 540         // OK, all done!
 541         expr
 542     }
 543 }
 544
 545 fn method_callee<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 546                                expr: &hir::Expr,
 547                                method_call: ty::MethodCall)
 548                                -> Expr<'tcx> {
 549     let tables = cx.tcx.tables.borrow();
 550     let callee = &tables.method_map[&method_call];
 551     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 552     Expr {
 553         temp_lifetime: temp_lifetime,
 554         ty: callee.ty,
 555         span: expr.span,
 556         kind: ExprKind::Literal {
 557             literal: Literal::Item {
 558                 def_id: callee.def_id,
 559                 kind: ItemKind::Method,
 560                 substs: callee.substs,
 561             },
 562         },
 563     }
 564 }
 565
 566 fn to_borrow_kind(m: hir::Mutability) -> BorrowKind {
 567     match m {
 568         hir::MutMutable => BorrowKind::Mut,
 569         hir::MutImmutable => BorrowKind::Shared,
 570     }
 571 }
 572
 573 fn convert_arm<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
 574     let mut map;
 575     let opt_map = if arm.pats.len() == 1 {
 576         None
 577     } else {
 578         map = FnvHashMap();
 579         pat_util::pat_bindings(&cx.tcx.def_map, &arm.pats[0], |_, p_id, _, path| {
 580             map.insert(path.node, p_id);
 581         });
 582         Some(&map)
 583     };
 584
 585     Arm {
 586         patterns: arm.pats.iter().map(|p| cx.refutable_pat(opt_map, p)).collect(),
 587         guard: arm.guard.to_ref(),
 588         body: arm.body.to_ref(),
 589     }
 590 }
 591
 592 fn convert_path_expr<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, expr: &'tcx hir::Expr) -> ExprKind<'tcx> {
 593     let substs = cx.tcx.mk_substs(cx.tcx.node_id_item_substs(expr.id).substs);
 594     // Otherwise there may be def_map borrow conflicts
 595     let def = cx.tcx.def_map.borrow()[&expr.id].full_def();
 596     let (def_id, kind) = match def {
 597         // A regular function.
 598         Def::Fn(def_id) => (def_id, ItemKind::Function),
 599         Def::Method(def_id) => (def_id, ItemKind::Method),
 600         Def::Struct(def_id) => match cx.tcx.node_id_to_type(expr.id).sty {
 601             // A tuple-struct constructor. Should only be reached if not called in the same
 602             // expression.
 603             ty::TyBareFn(..) => (def_id, ItemKind::Function),
 604             // A unit struct which is used as a value. We return a completely different ExprKind
 605             // here to account for this special case.
 606             ty::TyStruct(adt_def, substs) => return ExprKind::Adt {
 607                 adt_def: adt_def,
 608                 variant_index: 0,
 609                 substs: substs,
 610                 fields: vec![],
 611                 base: None
 612             },
 613             ref sty => panic!("unexpected sty: {:?}", sty)
 614         },
 615         Def::Variant(enum_id, variant_id) => match cx.tcx.node_id_to_type(expr.id).sty {
 616             // A variant constructor. Should only be reached if not called in the same
 617             // expression.
 618             ty::TyBareFn(..) => (variant_id, ItemKind::Function),
 619             // A unit variant, similar special case to the struct case above.
 620             ty::TyEnum(adt_def, substs) => {
 621                 debug_assert!(adt_def.did == enum_id);
 622                 let index = adt_def.variant_index_with_id(variant_id);
 623                 return ExprKind::Adt {
 624                     adt_def: adt_def,
 625                     substs: substs,
 626                     variant_index: index,
 627                     fields: vec![],
 628                     base: None
 629                 };
 630             },
 631             ref sty => panic!("unexpected sty: {:?}", sty)
 632         },
 633         Def::Const(def_id) |
 634         Def::AssociatedConst(def_id) => {
 635             if let Some(v) = cx.try_const_eval_literal(expr) {
 636                 return ExprKind::Literal { literal: v };
 637             } else {
 638                 (def_id, ItemKind::Constant)
 639             }
 640         }
 641
 642         Def::Static(node_id, _) => return ExprKind::StaticRef {
 643             id: node_id,
 644         },
 645
 646         def @ Def::Local(..) |
 647         def @ Def::Upvar(..) => return convert_var(cx, expr, def),
 648
 649         def =>
 650             cx.tcx.sess.span_bug(
 651                 expr.span,
 652                 &format!("def `{:?}` not yet implemented", def)),
 653     };
 654     ExprKind::Literal {
 655         literal: Literal::Item { def_id: def_id, kind: kind, substs: substs }
 656     }
 657 }
 658
 659 fn convert_var<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 660                              expr: &'tcx hir::Expr,
 661                              def: Def)
 662                              -> ExprKind<'tcx> {
 663     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 664
 665     match def {
 666         Def::Local(_, node_id) => {
 667             ExprKind::VarRef {
 668                 id: node_id,
 669             }
 670         }
 671
 672         Def::Upvar(_, id_var, index, closure_expr_id) => {
 673             debug!("convert_var(upvar({:?}, {:?}, {:?}))", id_var, index, closure_expr_id);
 674             let var_ty = cx.tcx.node_id_to_type(id_var);
 675
 676             let body_id = match cx.tcx.map.find(closure_expr_id) {
 677                 Some(map::NodeExpr(expr)) => {
 678                     match expr.node {
 679                         hir::ExprClosure(_, _, ref body) => body.id,
 680                         _ => {
 681                             cx.tcx.sess.span_bug(expr.span, "closure expr is not a closure expr");
 682                         }
 683                     }
 684                 }
 685                 _ => {
 686                     cx.tcx.sess.span_bug(expr.span, "ast-map has garbage for closure expr");
 687                 }
 688             };
 689
 690             // FIXME free regions in closures are not right
 691             let closure_ty = cx.tcx.node_id_to_type(closure_expr_id);
 692
 693             // FIXME we're just hard-coding the idea that the
 694             // signature will be &self or &mut self and hence will
 695             // have a bound region with number 0
 696             let region = ty::Region::ReFree(ty::FreeRegion {
 697                 scope: cx.tcx.region_maps.node_extent(body_id),
 698                 bound_region: ty::BoundRegion::BrAnon(0),
 699             });
 700             let region = cx.tcx.mk_region(region);
 701
 702             let self_expr = match cx.tcx.closure_kind(cx.tcx.map.local_def_id(closure_expr_id)) {
 703                 ty::ClosureKind::FnClosureKind => {
 704                     let ref_closure_ty =
 705                         cx.tcx.mk_ref(region,
 706                                    ty::TypeAndMut { ty: closure_ty,
 707                                                     mutbl: hir::MutImmutable });
 708                     Expr {
 709                         ty: closure_ty,
 710                         temp_lifetime: temp_lifetime,
 711                         span: expr.span,
 712                         kind: ExprKind::Deref {
 713                             arg: Expr {
 714                                 ty: ref_closure_ty,
 715                                 temp_lifetime: temp_lifetime,
 716                                 span: expr.span,
 717                                 kind: ExprKind::SelfRef
 718                             }.to_ref()
 719                         }
 720                     }
 721                 }
 722                 ty::ClosureKind::FnMutClosureKind => {
 723                     let ref_closure_ty =
 724                         cx.tcx.mk_ref(region,
 725                                    ty::TypeAndMut { ty: closure_ty,
 726                                                     mutbl: hir::MutMutable });
 727                     Expr {
 728                         ty: closure_ty,
 729                         temp_lifetime: temp_lifetime,
 730                         span: expr.span,
 731                         kind: ExprKind::Deref {
 732                             arg: Expr {
 733                                 ty: ref_closure_ty,
 734                                 temp_lifetime: temp_lifetime,
 735                                 span: expr.span,
 736                                 kind: ExprKind::SelfRef
 737                             }.to_ref()
 738                         }
 739                     }
 740                 }
 741                 ty::ClosureKind::FnOnceClosureKind => {
 742                     Expr {
 743                         ty: closure_ty,
 744                         temp_lifetime: temp_lifetime,
 745                         span: expr.span,
 746                         kind: ExprKind::SelfRef,
 747                     }
 748                 }
 749             };
 750
 751             // at this point we have `self.n`, which loads up the upvar
 752             let field_kind = ExprKind::Field {
 753                 lhs: self_expr.to_ref(),
 754                 name: Field::new(index),
 755             };
 756
 757             // ...but the upvar might be an `&T` or `&mut T` capture, at which
 758             // point we need an implicit deref
 759             let upvar_id = ty::UpvarId {
 760                 var_id: id_var,
 761                 closure_expr_id: closure_expr_id,
 762             };
 763             let upvar_capture = match cx.tcx.upvar_capture(upvar_id) {
 764                 Some(c) => c,
 765                 None => {
 766                     cx.tcx.sess.span_bug(
 767                         expr.span,
 768                         &format!("no upvar_capture for {:?}", upvar_id));
 769                 }
 770             };
 771             match upvar_capture {
 772                 ty::UpvarCapture::ByValue => field_kind,
 773                 ty::UpvarCapture::ByRef(_) => {
 774                     ExprKind::Deref {
 775                         arg: Expr {
 776                             temp_lifetime: temp_lifetime,
 777                             ty: var_ty,
 778                             span: expr.span,
 779                             kind: field_kind,
 780                         }.to_ref()
 781                     }
 782                 }
 783             }
 784         }
 785
 786         _ => cx.tcx.sess.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         _ => panic!("no equivalent for ast binop {:?}", op),
 810     }
 811 }
 812
 813 enum PassArgs {
 814     ByValue,
 815     ByRef,
 816 }
 817
 818 fn overloaded_operator<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 819                                      expr: &'tcx hir::Expr,
 820                                      method_call: ty::MethodCall,
 821                                      pass_args: PassArgs,
 822                                      receiver: ExprRef<'tcx>,
 823                                      args: Vec<&'tcx P<hir::Expr>>)
 824                                      -> ExprKind<'tcx> {
 825     // the receiver has all the adjustments that are needed, so we can
 826     // just push a reference to it
 827     let mut argrefs = vec![receiver];
 828
 829     // the arguments, unfortunately, do not, so if this is a ByRef
 830     // operator, we have to gin up the autorefs (but by value is easy)
 831     match pass_args {
 832         PassArgs::ByValue => {
 833             argrefs.extend(args.iter().map(|arg| arg.to_ref()))
 834         }
 835
 836         PassArgs::ByRef => {
 837             let scope = cx.tcx.region_maps.node_extent(expr.id);
 838             let region = cx.tcx.mk_region(ty::ReScope(scope));
 839             let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 840             argrefs.extend(
 841                 args.iter()
 842                     .map(|arg| {
 843                         let arg_ty = cx.tcx.expr_ty_adjusted(arg);
 844                         let adjusted_ty =
 845                             cx.tcx.mk_ref(region,
 846                                        ty::TypeAndMut { ty: arg_ty,
 847                                                         mutbl: hir::MutImmutable });
 848                         Expr {
 849                             temp_lifetime: temp_lifetime,
 850                             ty: adjusted_ty,
 851                             span: expr.span,
 852                             kind: ExprKind::Borrow { region: *region,
 853                                                      borrow_kind: BorrowKind::Shared,
 854                                                      arg: arg.to_ref() }
 855                         }.to_ref()
 856                     }))
 857         }
 858     }
 859
 860     // now create the call itself
 861     let fun = method_callee(cx, expr, method_call);
 862     ExprKind::Call {
 863         ty: fun.ty,
 864         fun: fun.to_ref(),
 865         args: argrefs,
 866     }
 867 }
 868
 869 fn overloaded_lvalue<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 870                                    expr: &'tcx hir::Expr,
 871                                    method_call: ty::MethodCall,
 872                                    pass_args: PassArgs,
 873                                    receiver: ExprRef<'tcx>,
 874                                    args: Vec<&'tcx P<hir::Expr>>)
 875                                    -> ExprKind<'tcx> {
 876     // For an overloaded *x or x[y] expression of type T, the method
 877     // call returns an &T and we must add the deref so that the types
 878     // line up (this is because `*x` and `x[y]` represent lvalues):
 879
 880     // to find the type &T of the content returned by the method;
 881     let tables = cx.tcx.tables.borrow();
 882     let callee = &tables.method_map[&method_call];
 883     let ref_ty = callee.ty.fn_ret();
 884     let ref_ty = cx.tcx.no_late_bound_regions(&ref_ty).unwrap().unwrap();
 885     //                                              1~~~~~   2~~~~~
 886     // (1) callees always have all late-bound regions fully instantiated,
 887     // (2) overloaded methods don't return `!`
 888
 889     // construct the complete expression `foo()` for the overloaded call,
 890     // which will yield the &T type
 891     let temp_lifetime = cx.tcx.region_maps.temporary_scope(expr.id);
 892     let ref_kind = overloaded_operator(cx, expr, method_call, pass_args, receiver, args);
 893     let ref_expr = Expr {
 894         temp_lifetime: temp_lifetime,
 895         ty: ref_ty,
 896         span: expr.span,
 897         kind: ref_kind,
 898     };
 899
 900     // construct and return a deref wrapper `*foo()`
 901     ExprKind::Deref { arg: ref_expr.to_ref() }
 902 }
 903
 904 fn capture_freevar<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>,
 905                                  closure_expr: &'tcx hir::Expr,
 906                                  freevar: &ty::Freevar,
 907                                  freevar_ty: Ty<'tcx>)
 908                                  -> ExprRef<'tcx> {
 909     let id_var = freevar.def.var_id();
 910     let upvar_id = ty::UpvarId {
 911         var_id: id_var,
 912         closure_expr_id: closure_expr.id,
 913     };
 914     let upvar_capture = cx.tcx.upvar_capture(upvar_id).unwrap();
 915     let temp_lifetime = cx.tcx.region_maps.temporary_scope(closure_expr.id);
 916     let var_ty = cx.tcx.node_id_to_type(id_var);
 917     let captured_var = Expr {
 918         temp_lifetime: temp_lifetime,
 919         ty: var_ty,
 920         span: closure_expr.span,
 921         kind: convert_var(cx, closure_expr, freevar.def),
 922     };
 923     match upvar_capture {
 924         ty::UpvarCapture::ByValue => {
 925             captured_var.to_ref()
 926         }
 927         ty::UpvarCapture::ByRef(upvar_borrow) => {
 928             let borrow_kind = match upvar_borrow.kind {
 929                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
 930                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
 931                 ty::BorrowKind::MutBorrow => BorrowKind::Mut,
 932             };
 933             Expr {
 934                 temp_lifetime: temp_lifetime,
 935                 ty: freevar_ty,
 936                 span: closure_expr.span,
 937                 kind: ExprKind::Borrow { region: upvar_borrow.region,
 938                                          borrow_kind: borrow_kind,
 939                                          arg: captured_var.to_ref() }
 940             }.to_ref()
 941         }
 942     }
 943 }
 944
 945 fn loop_label<'a, 'tcx: 'a>(cx: &mut Cx<'a, 'tcx>, expr: &'tcx hir::Expr) -> CodeExtent {
 946     match cx.tcx.def_map.borrow().get(&expr.id).map(|d| d.full_def()) {
 947         Some(Def::Label(loop_id)) => cx.tcx.region_maps.node_extent(loop_id),
 948         d => {
 949             cx.tcx.sess.span_bug(expr.span, &format!("loop scope resolved to {:?}", d));
 950         }
 951     }
 952 }
 953
 954 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
 955 fn field_refs<'tcx>(variant: VariantDef<'tcx>,
 956                     fields: &'tcx [hir::Field])
 957                     -> Vec<FieldExprRef<'tcx>>
 958 {
 959     fields.iter()
 960           .map(|field| FieldExprRef {
 961               name: Field::new(variant.index_of_field_named(field.name.node).unwrap()),
 962               expr: field.expr.to_ref(),
 963           })
 964           .collect()
 965 }