src/librustc_mir_build/hair/cx/expr.rs

   1 use crate::hair::cx::block;
   2 use crate::hair::cx::to_ref::ToRef;
   3 use crate::hair::cx::Cx;
   4 use crate::hair::util::UserAnnotatedTyHelpers;
   5 use crate::hair::*;
   6 use rustc_hir as hir;
   7 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
   8 use rustc_index::vec::Idx;
   9 use rustc_middle::mir::interpret::Scalar;
  10 use rustc_middle::mir::BorrowKind;
  11 use rustc_middle::ty::adjustment::{
  12     Adjust, Adjustment, AutoBorrow, AutoBorrowMutability, PointerCast,
  13 };
  14 use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
  15 use rustc_middle::ty::{self, AdtKind, Ty};
  16 use rustc_span::Span;
  17
  18 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr<'tcx> {
  19     type Output = Expr<'tcx>;
  20
  21     fn make_mirror(self, cx: &mut Cx<'_, 'tcx>) -> Expr<'tcx> {
  22         let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
  23         let expr_scope = region::Scope { id: self.hir_id.local_id, data: region::ScopeData::Node };
  24
  25         debug!("Expr::make_mirror(): id={}, span={:?}", self.hir_id, self.span);
  26
  27         let mut expr = make_mirror_unadjusted(cx, self);
  28
  29         // Now apply adjustments, if any.
  30         for adjustment in cx.tables().expr_adjustments(self) {
  31             debug!("make_mirror: expr={:?} applying adjustment={:?}", expr, adjustment);
  32             expr = apply_adjustment(cx, self, expr, adjustment);
  33         }
  34
  35         // Next, wrap this up in the expr's scope.
  36         expr = Expr {
  37             temp_lifetime,
  38             ty: expr.ty,
  39             span: self.span,
  40             kind: ExprKind::Scope {
  41                 region_scope: expr_scope,
  42                 value: expr.to_ref(),
  43                 lint_level: LintLevel::Explicit(self.hir_id),
  44             },
  45         };
  46
  47         // Finally, create a destruction scope, if any.
  48         if let Some(region_scope) = cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id)
  49         {
  50             expr = Expr {
  51                 temp_lifetime,
  52                 ty: expr.ty,
  53                 span: self.span,
  54                 kind: ExprKind::Scope {
  55                     region_scope,
  56                     value: expr.to_ref(),
  57                     lint_level: LintLevel::Inherited,
  58                 },
  59             };
  60         }
  61
  62         // OK, all done!
  63         expr
  64     }
  65 }
  66
  67 fn apply_adjustment<'a, 'tcx>(
  68     cx: &mut Cx<'a, 'tcx>,
  69     hir_expr: &'tcx hir::Expr<'tcx>,
  70     mut expr: Expr<'tcx>,
  71     adjustment: &Adjustment<'tcx>,
  72 ) -> Expr<'tcx> {
  73     let Expr { temp_lifetime, mut span, .. } = expr;
  74
  75     // Adjust the span from the block, to the last expression of the
  76     // block. This is a better span when returning a mutable reference
  77     // with too short a lifetime. The error message will use the span
  78     // from the assignment to the return place, which should only point
  79     // at the returned value, not the entire function body.
  80     //
  81     // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
  82     //      x
  83     //   // ^ error message points at this expression.
  84     // }
  85     let mut adjust_span = |expr: &mut Expr<'tcx>| {
  86         if let ExprKind::Block { body } = expr.kind {
  87             if let Some(ref last_expr) = body.expr {
  88                 span = last_expr.span;
  89                 expr.span = span;
  90             }
  91         }
  92     };
  93
  94     let kind = match adjustment.kind {
  95         Adjust::Pointer(PointerCast::Unsize) => {
  96             adjust_span(&mut expr);
  97             ExprKind::Pointer { cast: PointerCast::Unsize, source: expr.to_ref() }
  98         }
  99         Adjust::Pointer(cast) => ExprKind::Pointer { cast, source: expr.to_ref() },
 100         Adjust::NeverToAny => ExprKind::NeverToAny { source: expr.to_ref() },
 101         Adjust::Deref(None) => {
 102             adjust_span(&mut expr);
 103             ExprKind::Deref { arg: expr.to_ref() }
 104         }
 105         Adjust::Deref(Some(deref)) => {
 106             // We don't need to do call adjust_span here since
 107             // deref coercions always start with a built-in deref.
 108             let call = deref.method_call(cx.tcx(), expr.ty);
 109
 110             expr = Expr {
 111                 temp_lifetime,
 112                 ty: cx.tcx.mk_ref(deref.region, ty::TypeAndMut { ty: expr.ty, mutbl: deref.mutbl }),
 113                 span,
 114                 kind: ExprKind::Borrow {
 115                     borrow_kind: deref.mutbl.to_borrow_kind(),
 116                     arg: expr.to_ref(),
 117                 },
 118             };
 119
 120             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
 121         }
 122         Adjust::Borrow(AutoBorrow::Ref(_, m)) => {
 123             ExprKind::Borrow { borrow_kind: m.to_borrow_kind(), arg: expr.to_ref() }
 124         }
 125         Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
 126             ExprKind::AddressOf { mutability, arg: expr.to_ref() }
 127         }
 128     };
 129
 130     Expr { temp_lifetime, ty: adjustment.target, span, kind }
 131 }
 132
 133 fn make_mirror_unadjusted<'a, 'tcx>(
 134     cx: &mut Cx<'a, 'tcx>,
 135     expr: &'tcx hir::Expr<'tcx>,
 136 ) -> Expr<'tcx> {
 137     let expr_ty = cx.tables().expr_ty(expr);
 138     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 139
 140     let kind = match expr.kind {
 141         // Here comes the interesting stuff:
 142         hir::ExprKind::MethodCall(_, method_span, ref args) => {
 143             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
 144             let expr = method_callee(cx, expr, method_span, None);
 145             let args = args.iter().map(|e| e.to_ref()).collect();
 146             ExprKind::Call { ty: expr.ty, fun: expr.to_ref(), args, from_hir_call: true }
 147         }
 148
 149         hir::ExprKind::Call(ref fun, ref args) => {
 150             if cx.tables().is_method_call(expr) {
 151                 // The callee is something implementing Fn, FnMut, or FnOnce.
 152                 // Find the actual method implementation being called and
 153                 // build the appropriate UFCS call expression with the
 154                 // callee-object as expr parameter.
 155
 156                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
 157
 158                 let method = method_callee(cx, expr, fun.span, None);
 159
 160                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
 161                 let tupled_args = Expr {
 162                     ty: cx.tcx.mk_tup(arg_tys),
 163                     temp_lifetime,
 164                     span: expr.span,
 165                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
 166                 };
 167
 168                 ExprKind::Call {
 169                     ty: method.ty,
 170                     fun: method.to_ref(),
 171                     args: vec![fun.to_ref(), tupled_args.to_ref()],
 172                     from_hir_call: true,
 173                 }
 174             } else {
 175                 let adt_data =
 176                     if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = fun.kind {
 177                         // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
 178                         expr_ty.ty_adt_def().and_then(|adt_def| match path.res {
 179                             Res::Def(DefKind::Ctor(_, CtorKind::Fn), ctor_id) => {
 180                                 Some((adt_def, adt_def.variant_index_with_ctor_id(ctor_id)))
 181                             }
 182                             Res::SelfCtor(..) => Some((adt_def, VariantIdx::new(0))),
 183                             _ => None,
 184                         })
 185                     } else {
 186                         None
 187                     };
 188                 if let Some((adt_def, index)) = adt_data {
 189                     let substs = cx.tables().node_substs(fun.hir_id);
 190                     let user_provided_types = cx.tables().user_provided_types();
 191                     let user_ty = user_provided_types.get(fun.hir_id).copied().map(|mut u_ty| {
 192                         if let UserType::TypeOf(ref mut did, _) = &mut u_ty.value {
 193                             *did = adt_def.did;
 194                         }
 195                         u_ty
 196                     });
 197                     debug!("make_mirror_unadjusted: (call) user_ty={:?}", user_ty);
 198
 199                     let field_refs = args
 200                         .iter()
 201                         .enumerate()
 202                         .map(|(idx, e)| FieldExprRef { name: Field::new(idx), expr: e.to_ref() })
 203                         .collect();
 204                     ExprKind::Adt {
 205                         adt_def,
 206                         substs,
 207                         variant_index: index,
 208                         fields: field_refs,
 209                         user_ty,
 210                         base: None,
 211                     }
 212                 } else {
 213                     ExprKind::Call {
 214                         ty: cx.tables().node_type(fun.hir_id),
 215                         fun: fun.to_ref(),
 216                         args: args.to_ref(),
 217                         from_hir_call: true,
 218                     }
 219                 }
 220             }
 221         }
 222
 223         hir::ExprKind::AddrOf(hir::BorrowKind::Ref, mutbl, ref arg) => {
 224             ExprKind::Borrow { borrow_kind: mutbl.to_borrow_kind(), arg: arg.to_ref() }
 225         }
 226
 227         hir::ExprKind::AddrOf(hir::BorrowKind::Raw, mutability, ref arg) => {
 228             ExprKind::AddressOf { mutability, arg: arg.to_ref() }
 229         }
 230
 231         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
 232
 233         hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
 234             ExprKind::Assign { lhs: lhs.to_ref(), rhs: rhs.to_ref() }
 235         }
 236
 237         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
 238             if cx.tables().is_method_call(expr) {
 239                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 240             } else {
 241                 ExprKind::AssignOp { op: bin_op(op.node), lhs: lhs.to_ref(), rhs: rhs.to_ref() }
 242             }
 243         }
 244
 245         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
 246             literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, false),
 247             user_ty: None,
 248         },
 249
 250         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
 251             if cx.tables().is_method_call(expr) {
 252                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
 253             } else {
 254                 // FIXME overflow
 255                 match (op.node, cx.constness) {
 256                     // Destroy control flow if `#![feature(const_if_match)]` is not enabled.
 257                     (hir::BinOpKind::And, hir::Constness::Const)
 258                         if !cx.tcx.features().const_if_match =>
 259                     {
 260                         cx.control_flow_destroyed.push((op.span, "`&&` operator".into()));
 261                         ExprKind::Binary { op: BinOp::BitAnd, lhs: lhs.to_ref(), rhs: rhs.to_ref() }
 262                     }
 263                     (hir::BinOpKind::Or, hir::Constness::Const)
 264                         if !cx.tcx.features().const_if_match =>
 265                     {
 266                         cx.control_flow_destroyed.push((op.span, "`||` operator".into()));
 267                         ExprKind::Binary { op: BinOp::BitOr, lhs: lhs.to_ref(), rhs: rhs.to_ref() }
 268                     }
 269
 270                     (hir::BinOpKind::And, _) => ExprKind::LogicalOp {
 271                         op: LogicalOp::And,
 272                         lhs: lhs.to_ref(),
 273                         rhs: rhs.to_ref(),
 274                     },
 275                     (hir::BinOpKind::Or, _) => ExprKind::LogicalOp {
 276                         op: LogicalOp::Or,
 277                         lhs: lhs.to_ref(),
 278                         rhs: rhs.to_ref(),
 279                     },
 280
 281                     _ => {
 282                         let op = bin_op(op.node);
 283                         ExprKind::Binary { op, lhs: lhs.to_ref(), rhs: rhs.to_ref() }
 284                     }
 285                 }
 286             }
 287         }
 288
 289         hir::ExprKind::Index(ref lhs, ref index) => {
 290             if cx.tables().is_method_call(expr) {
 291                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
 292             } else {
 293                 ExprKind::Index { lhs: lhs.to_ref(), index: index.to_ref() }
 294             }
 295         }
 296
 297         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
 298             if cx.tables().is_method_call(expr) {
 299                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
 300             } else {
 301                 ExprKind::Deref { arg: arg.to_ref() }
 302             }
 303         }
 304
 305         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
 306             if cx.tables().is_method_call(expr) {
 307                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 308             } else {
 309                 ExprKind::Unary { op: UnOp::Not, arg: arg.to_ref() }
 310             }
 311         }
 312
 313         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
 314             if cx.tables().is_method_call(expr) {
 315                 overloaded_operator(cx, expr, vec![arg.to_ref()])
 316             } else {
 317                 if let hir::ExprKind::Lit(ref lit) = arg.kind {
 318                     ExprKind::Literal {
 319                         literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, true),
 320                         user_ty: None,
 321                     }
 322                 } else {
 323                     ExprKind::Unary { op: UnOp::Neg, arg: arg.to_ref() }
 324                 }
 325             }
 326         }
 327
 328         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => match expr_ty.kind {
 329             ty::Adt(adt, substs) => match adt.adt_kind() {
 330                 AdtKind::Struct | AdtKind::Union => {
 331                     let user_provided_types = cx.tables().user_provided_types();
 332                     let user_ty = user_provided_types.get(expr.hir_id).copied();
 333                     debug!("make_mirror_unadjusted: (struct/union) user_ty={:?}", user_ty);
 334                     ExprKind::Adt {
 335                         adt_def: adt,
 336                         variant_index: VariantIdx::new(0),
 337                         substs,
 338                         user_ty,
 339                         fields: field_refs(cx, fields),
 340                         base: base.as_ref().map(|base| FruInfo {
 341                             base: base.to_ref(),
 342                             field_types: cx.tables().fru_field_types()[expr.hir_id].clone(),
 343                         }),
 344                     }
 345                 }
 346                 AdtKind::Enum => {
 347                     let res = cx.tables().qpath_res(qpath, expr.hir_id);
 348                     match res {
 349                         Res::Def(DefKind::Variant, variant_id) => {
 350                             assert!(base.is_none());
 351
 352                             let index = adt.variant_index_with_id(variant_id);
 353                             let user_provided_types = cx.tables().user_provided_types();
 354                             let user_ty = user_provided_types.get(expr.hir_id).copied();
 355                             debug!("make_mirror_unadjusted: (variant) user_ty={:?}", user_ty);
 356                             ExprKind::Adt {
 357                                 adt_def: adt,
 358                                 variant_index: index,
 359                                 substs,
 360                                 user_ty,
 361                                 fields: field_refs(cx, fields),
 362                                 base: None,
 363                             }
 364                         }
 365                         _ => {
 366                             span_bug!(expr.span, "unexpected res: {:?}", res);
 367                         }
 368                     }
 369                 }
 370             },
 371             _ => {
 372                 span_bug!(expr.span, "unexpected type for struct literal: {:?}", expr_ty);
 373             }
 374         },
 375
 376         hir::ExprKind::Closure(..) => {
 377             let closure_ty = cx.tables().expr_ty(expr);
 378             let (def_id, substs, movability) = match closure_ty.kind {
 379                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
 380                 ty::Generator(def_id, substs, movability) => {
 381                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
 382                 }
 383                 _ => {
 384                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
 385                 }
 386             };
 387             let upvars = cx
 388                 .tcx
 389                 .upvars(def_id)
 390                 .iter()
 391                 .flat_map(|upvars| upvars.iter())
 392                 .zip(substs.upvar_tys())
 393                 .map(|((&var_hir_id, _), ty)| capture_upvar(cx, expr, var_hir_id, ty))
 394                 .collect();
 395             ExprKind::Closure { closure_id: def_id, substs, upvars, movability }
 396         }
 397
 398         hir::ExprKind::Path(ref qpath) => {
 399             let res = cx.tables().qpath_res(qpath, expr.hir_id);
 400             convert_path_expr(cx, expr, res)
 401         }
 402
 403         hir::ExprKind::LlvmInlineAsm(ref asm) => ExprKind::LlvmInlineAsm {
 404             asm: &asm.inner,
 405             outputs: asm.outputs_exprs.to_ref(),
 406             inputs: asm.inputs_exprs.to_ref(),
 407         },
 408
 409         // Now comes the rote stuff:
 410         hir::ExprKind::Repeat(ref v, ref count) => {
 411             let count_def_id = cx.tcx.hir().local_def_id(count.hir_id).expect_local();
 412             let count = ty::Const::from_anon_const(cx.tcx, count_def_id);
 413
 414             ExprKind::Repeat { value: v.to_ref(), count }
 415         }
 416         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
 417         hir::ExprKind::Break(dest, ref value) => match dest.target_id {
 418             Ok(target_id) => ExprKind::Break {
 419                 label: region::Scope { id: target_id.local_id, data: region::ScopeData::Node },
 420                 value: value.to_ref(),
 421             },
 422             Err(err) => bug!("invalid loop id for break: {}", err),
 423         },
 424         hir::ExprKind::Continue(dest) => match dest.target_id {
 425             Ok(loop_id) => ExprKind::Continue {
 426                 label: region::Scope { id: loop_id.local_id, data: region::ScopeData::Node },
 427             },
 428             Err(err) => bug!("invalid loop id for continue: {}", err),
 429         },
 430         hir::ExprKind::Match(ref discr, ref arms, _) => ExprKind::Match {
 431             scrutinee: discr.to_ref(),
 432             arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
 433         },
 434         hir::ExprKind::Loop(ref body, _, _) => {
 435             ExprKind::Loop { body: block::to_expr_ref(cx, body) }
 436         }
 437         hir::ExprKind::Field(ref source, ..) => ExprKind::Field {
 438             lhs: source.to_ref(),
 439             name: Field::new(cx.tcx.field_index(expr.hir_id, cx.tables)),
 440         },
 441         hir::ExprKind::Cast(ref source, ref cast_ty) => {
 442             // Check for a user-given type annotation on this `cast`
 443             let user_provided_types = cx.tables.user_provided_types();
 444             let user_ty = user_provided_types.get(cast_ty.hir_id);
 445
 446             debug!(
 447                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
 448                 expr, cast_ty.hir_id, user_ty,
 449             );
 450
 451             // Check to see if this cast is a "coercion cast", where the cast is actually done
 452             // using a coercion (or is a no-op).
 453             let cast = if cx.tables().is_coercion_cast(source.hir_id) {
 454                 // Convert the lexpr to a vexpr.
 455                 ExprKind::Use { source: source.to_ref() }
 456             } else if cx.tables().expr_ty(source).is_region_ptr() {
 457                 // Special cased so that we can type check that the element
 458                 // type of the source matches the pointed to type of the
 459                 // destination.
 460                 ExprKind::Pointer { source: source.to_ref(), cast: PointerCast::ArrayToPointer }
 461             } else {
 462                 // check whether this is casting an enum variant discriminant
 463                 // to prevent cycles, we refer to the discriminant initializer
 464                 // which is always an integer and thus doesn't need to know the
 465                 // enum's layout (or its tag type) to compute it during const eval
 466                 // Example:
 467                 // enum Foo {
 468                 //     A,
 469                 //     B = A as isize + 4,
 470                 // }
 471                 // The correct solution would be to add symbolic computations to miri,
 472                 // so we wouldn't have to compute and store the actual value
 473                 let var = if let hir::ExprKind::Path(ref qpath) = source.kind {
 474                     let res = cx.tables().qpath_res(qpath, source.hir_id);
 475                     cx.tables().node_type(source.hir_id).ty_adt_def().and_then(
 476                         |adt_def| match res {
 477                             Res::Def(
 478                                 DefKind::Ctor(CtorOf::Variant, CtorKind::Const),
 479                                 variant_ctor_id,
 480                             ) => {
 481                                 let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
 482                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
 483                                 use rustc_middle::ty::util::IntTypeExt;
 484                                 let ty = adt_def.repr.discr_type();
 485                                 let ty = ty.to_ty(cx.tcx());
 486                                 Some((d, o, ty))
 487                             }
 488                             _ => None,
 489                         },
 490                     )
 491                 } else {
 492                     None
 493                 };
 494
 495                 let source = if let Some((did, offset, var_ty)) = var {
 496                     let mk_const = |literal| {
 497                         Expr {
 498                             temp_lifetime,
 499                             ty: var_ty,
 500                             span: expr.span,
 501                             kind: ExprKind::Literal { literal, user_ty: None },
 502                         }
 503                         .to_ref()
 504                     };
 505                     let offset = mk_const(ty::Const::from_bits(
 506                         cx.tcx,
 507                         offset as u128,
 508                         cx.param_env.and(var_ty),
 509                     ));
 510                     match did {
 511                         Some(did) => {
 512                             // in case we are offsetting from a computed discriminant
 513                             // and not the beginning of discriminants (which is always `0`)
 514                             let substs = InternalSubsts::identity_for_item(cx.tcx(), did);
 515                             let lhs = mk_const(cx.tcx().mk_const(ty::Const {
 516                                 val: ty::ConstKind::Unevaluated(did, substs, None),
 517                                 ty: var_ty,
 518                             }));
 519                             let bin = ExprKind::Binary { op: BinOp::Add, lhs, rhs: offset };
 520                             Expr { temp_lifetime, ty: var_ty, span: expr.span, kind: bin }.to_ref()
 521                         }
 522                         None => offset,
 523                     }
 524                 } else {
 525                     source.to_ref()
 526                 };
 527
 528                 ExprKind::Cast { source }
 529             };
 530
 531             if let Some(user_ty) = user_ty {
 532                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
 533                 //       inefficient, revisit this when performance becomes an issue.
 534                 let cast_expr = Expr { temp_lifetime, ty: expr_ty, span: expr.span, kind: cast };
 535                 debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
 536
 537                 ExprKind::ValueTypeAscription {
 538                     source: cast_expr.to_ref(),
 539                     user_ty: Some(*user_ty),
 540                 }
 541             } else {
 542                 cast
 543             }
 544         }
 545         hir::ExprKind::Type(ref source, ref ty) => {
 546             let user_provided_types = cx.tables.user_provided_types();
 547             let user_ty = user_provided_types.get(ty.hir_id).copied();
 548             debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
 549             if source.is_syntactic_place_expr() {
 550                 ExprKind::PlaceTypeAscription { source: source.to_ref(), user_ty }
 551             } else {
 552                 ExprKind::ValueTypeAscription { source: source.to_ref(), user_ty }
 553             }
 554         }
 555         hir::ExprKind::DropTemps(ref source) => ExprKind::Use { source: source.to_ref() },
 556         hir::ExprKind::Box(ref value) => ExprKind::Box { value: value.to_ref() },
 557         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
 558         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
 559
 560         hir::ExprKind::Yield(ref v, _) => ExprKind::Yield { value: v.to_ref() },
 561         hir::ExprKind::Err => unreachable!(),
 562     };
 563
 564     Expr { temp_lifetime, ty: expr_ty, span: expr.span, kind }
 565 }
 566
 567 fn user_substs_applied_to_res<'tcx>(
 568     cx: &mut Cx<'_, 'tcx>,
 569     hir_id: hir::HirId,
 570     res: Res,
 571 ) -> Option<ty::CanonicalUserType<'tcx>> {
 572     debug!("user_substs_applied_to_res: res={:?}", res);
 573     let user_provided_type = match res {
 574         // A reference to something callable -- e.g., a fn, method, or
 575         // a tuple-struct or tuple-variant. This has the type of a
 576         // `Fn` but with the user-given substitutions.
 577         Res::Def(DefKind::Fn, _)
 578         | Res::Def(DefKind::AssocFn, _)
 579         | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
 580         | Res::Def(DefKind::Const, _)
 581         | Res::Def(DefKind::AssocConst, _) => {
 582             cx.tables().user_provided_types().get(hir_id).copied()
 583         }
 584
 585         // A unit struct/variant which is used as a value (e.g.,
 586         // `None`). This has the type of the enum/struct that defines
 587         // this variant -- but with the substitutions given by the
 588         // user.
 589         Res::Def(DefKind::Ctor(_, CtorKind::Const), _) => {
 590             cx.user_substs_applied_to_ty_of_hir_id(hir_id)
 591         }
 592
 593         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
 594         Res::SelfCtor(_) => cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 595
 596         _ => bug!("user_substs_applied_to_res: unexpected res {:?} at {:?}", res, hir_id),
 597     };
 598     debug!("user_substs_applied_to_res: user_provided_type={:?}", user_provided_type);
 599     user_provided_type
 600 }
 601
 602 fn method_callee<'a, 'tcx>(
 603     cx: &mut Cx<'a, 'tcx>,
 604     expr: &hir::Expr<'_>,
 605     span: Span,
 606     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 607 ) -> Expr<'tcx> {
 608     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 609     let (def_id, substs, user_ty) = match overloaded_callee {
 610         Some((def_id, substs)) => (def_id, substs, None),
 611         None => {
 612             let (kind, def_id) = cx
 613                 .tables()
 614                 .type_dependent_def(expr.hir_id)
 615                 .unwrap_or_else(|| span_bug!(expr.span, "no type-dependent def for method callee"));
 616             let user_ty = user_substs_applied_to_res(cx, expr.hir_id, Res::Def(kind, def_id));
 617             debug!("method_callee: user_ty={:?}", user_ty);
 618             (def_id, cx.tables().node_substs(expr.hir_id), user_ty)
 619         }
 620     };
 621     let ty = cx.tcx().mk_fn_def(def_id, substs);
 622     Expr {
 623         temp_lifetime,
 624         ty,
 625         span,
 626         kind: ExprKind::Literal { literal: ty::Const::zero_sized(cx.tcx(), ty), user_ty },
 627     }
 628 }
 629
 630 trait ToBorrowKind {
 631     fn to_borrow_kind(&self) -> BorrowKind;
 632 }
 633
 634 impl ToBorrowKind for AutoBorrowMutability {
 635     fn to_borrow_kind(&self) -> BorrowKind {
 636         use rustc_middle::ty::adjustment::AllowTwoPhase;
 637         match *self {
 638             AutoBorrowMutability::Mut { allow_two_phase_borrow } => BorrowKind::Mut {
 639                 allow_two_phase_borrow: match allow_two_phase_borrow {
 640                     AllowTwoPhase::Yes => true,
 641                     AllowTwoPhase::No => false,
 642                 },
 643             },
 644             AutoBorrowMutability::Not => BorrowKind::Shared,
 645         }
 646     }
 647 }
 648
 649 impl ToBorrowKind for hir::Mutability {
 650     fn to_borrow_kind(&self) -> BorrowKind {
 651         match *self {
 652             hir::Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false },
 653             hir::Mutability::Not => BorrowKind::Shared,
 654         }
 655     }
 656 }
 657
 658 fn convert_arm<'tcx>(cx: &mut Cx<'_, 'tcx>, arm: &'tcx hir::Arm<'tcx>) -> Arm<'tcx> {
 659     Arm {
 660         pattern: cx.pattern_from_hir(&arm.pat),
 661         guard: match arm.guard {
 662             Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
 663             _ => None,
 664         },
 665         body: arm.body.to_ref(),
 666         lint_level: LintLevel::Explicit(arm.hir_id),
 667         scope: region::Scope { id: arm.hir_id.local_id, data: region::ScopeData::Node },
 668         span: arm.span,
 669     }
 670 }
 671
 672 fn convert_path_expr<'a, 'tcx>(
 673     cx: &mut Cx<'a, 'tcx>,
 674     expr: &'tcx hir::Expr<'tcx>,
 675     res: Res,
 676 ) -> ExprKind<'tcx> {
 677     let substs = cx.tables().node_substs(expr.hir_id);
 678     match res {
 679         // A regular function, constructor function or a constant.
 680         Res::Def(DefKind::Fn, _)
 681         | Res::Def(DefKind::AssocFn, _)
 682         | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
 683         | Res::SelfCtor(..) => {
 684             let user_ty = user_substs_applied_to_res(cx, expr.hir_id, res);
 685             debug!("convert_path_expr: user_ty={:?}", user_ty);
 686             ExprKind::Literal {
 687                 literal: ty::Const::zero_sized(cx.tcx, cx.tables().node_type(expr.hir_id)),
 688                 user_ty,
 689             }
 690         }
 691
 692         Res::Def(DefKind::ConstParam, def_id) => {
 693             let hir_id = cx.tcx.hir().as_local_hir_id(def_id).unwrap();
 694             let item_id = cx.tcx.hir().get_parent_node(hir_id);
 695             let item_def_id = cx.tcx.hir().local_def_id(item_id);
 696             let generics = cx.tcx.generics_of(item_def_id);
 697             let local_def_id = cx.tcx.hir().local_def_id(hir_id);
 698             let index = generics.param_def_id_to_index[&local_def_id];
 699             let name = cx.tcx.hir().name(hir_id);
 700             let val = ty::ConstKind::Param(ty::ParamConst::new(index, name));
 701             ExprKind::Literal {
 702                 literal: cx.tcx.mk_const(ty::Const { val, ty: cx.tables().node_type(expr.hir_id) }),
 703                 user_ty: None,
 704             }
 705         }
 706
 707         Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
 708             let user_ty = user_substs_applied_to_res(cx, expr.hir_id, res);
 709             debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
 710             ExprKind::Literal {
 711                 literal: cx.tcx.mk_const(ty::Const {
 712                     val: ty::ConstKind::Unevaluated(def_id, substs, None),
 713                     ty: cx.tables().node_type(expr.hir_id),
 714                 }),
 715                 user_ty,
 716             }
 717         }
 718
 719         Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id) => {
 720             let user_provided_types = cx.tables.user_provided_types();
 721             let user_provided_type = user_provided_types.get(expr.hir_id).copied();
 722             debug!("convert_path_expr: user_provided_type={:?}", user_provided_type);
 723             let ty = cx.tables().node_type(expr.hir_id);
 724             match ty.kind {
 725                 // A unit struct/variant which is used as a value.
 726                 // We return a completely different ExprKind here to account for this special case.
 727                 ty::Adt(adt_def, substs) => ExprKind::Adt {
 728                     adt_def,
 729                     variant_index: adt_def.variant_index_with_ctor_id(def_id),
 730                     substs,
 731                     user_ty: user_provided_type,
 732                     fields: vec![],
 733                     base: None,
 734                 },
 735                 _ => bug!("unexpected ty: {:?}", ty),
 736             }
 737         }
 738
 739         // We encode uses of statics as a `*&STATIC` where the `&STATIC` part is
 740         // a constant reference (or constant raw pointer for `static mut`) in MIR
 741         Res::Def(DefKind::Static, id) => {
 742             let ty = cx.tcx.static_ptr_ty(id);
 743             let ptr = cx.tcx.alloc_map.lock().create_static_alloc(id);
 744             let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 745             ExprKind::Deref {
 746                 arg: Expr {
 747                     ty,
 748                     temp_lifetime,
 749                     span: expr.span,
 750                     kind: ExprKind::StaticRef {
 751                         literal: ty::Const::from_scalar(cx.tcx, Scalar::Ptr(ptr.into()), ty),
 752                         def_id: id,
 753                     },
 754                 }
 755                 .to_ref(),
 756             }
 757         }
 758
 759         Res::Local(var_hir_id) => convert_var(cx, expr, var_hir_id),
 760
 761         _ => span_bug!(expr.span, "res `{:?}` not yet implemented", res),
 762     }
 763 }
 764
 765 fn convert_var<'tcx>(
 766     cx: &mut Cx<'_, 'tcx>,
 767     expr: &'tcx hir::Expr<'tcx>,
 768     var_hir_id: hir::HirId,
 769 ) -> ExprKind<'tcx> {
 770     let upvar_index = cx
 771         .tables()
 772         .upvar_list
 773         .get(&cx.body_owner)
 774         .and_then(|upvars| upvars.get_full(&var_hir_id).map(|(i, _, _)| i));
 775
 776     debug!(
 777         "convert_var({:?}): upvar_index={:?}, body_owner={:?}",
 778         var_hir_id, upvar_index, cx.body_owner
 779     );
 780
 781     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 782
 783     match upvar_index {
 784         None => ExprKind::VarRef { id: var_hir_id },
 785
 786         Some(upvar_index) => {
 787             let closure_def_id = cx.body_owner;
 788             let upvar_id = ty::UpvarId {
 789                 var_path: ty::UpvarPath { hir_id: var_hir_id },
 790                 closure_expr_id: closure_def_id.expect_local(),
 791             };
 792             let var_ty = cx.tables().node_type(var_hir_id);
 793
 794             // FIXME free regions in closures are not right
 795             let closure_ty = cx
 796                 .tables()
 797                 .node_type(cx.tcx.hir().local_def_id_to_hir_id(upvar_id.closure_expr_id));
 798
 799             // FIXME we're just hard-coding the idea that the
 800             // signature will be &self or &mut self and hence will
 801             // have a bound region with number 0
 802             let region = ty::ReFree(ty::FreeRegion {
 803                 scope: closure_def_id,
 804                 bound_region: ty::BoundRegion::BrAnon(0),
 805             });
 806             let region = cx.tcx.mk_region(region);
 807
 808             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.kind {
 809                 match cx.infcx.closure_kind(closure_substs).unwrap() {
 810                     ty::ClosureKind::Fn => {
 811                         let ref_closure_ty = cx.tcx.mk_ref(
 812                             region,
 813                             ty::TypeAndMut { ty: closure_ty, mutbl: hir::Mutability::Not },
 814                         );
 815                         Expr {
 816                             ty: closure_ty,
 817                             temp_lifetime,
 818                             span: expr.span,
 819                             kind: ExprKind::Deref {
 820                                 arg: Expr {
 821                                     ty: ref_closure_ty,
 822                                     temp_lifetime,
 823                                     span: expr.span,
 824                                     kind: ExprKind::SelfRef,
 825                                 }
 826                                 .to_ref(),
 827                             },
 828                         }
 829                     }
 830                     ty::ClosureKind::FnMut => {
 831                         let ref_closure_ty = cx.tcx.mk_ref(
 832                             region,
 833                             ty::TypeAndMut { ty: closure_ty, mutbl: hir::Mutability::Mut },
 834                         );
 835                         Expr {
 836                             ty: closure_ty,
 837                             temp_lifetime,
 838                             span: expr.span,
 839                             kind: ExprKind::Deref {
 840                                 arg: Expr {
 841                                     ty: ref_closure_ty,
 842                                     temp_lifetime,
 843                                     span: expr.span,
 844                                     kind: ExprKind::SelfRef,
 845                                 }
 846                                 .to_ref(),
 847                             },
 848                         }
 849                     }
 850                     ty::ClosureKind::FnOnce => Expr {
 851                         ty: closure_ty,
 852                         temp_lifetime,
 853                         span: expr.span,
 854                         kind: ExprKind::SelfRef,
 855                     },
 856                 }
 857             } else {
 858                 Expr { ty: closure_ty, temp_lifetime, span: expr.span, kind: ExprKind::SelfRef }
 859             };
 860
 861             // at this point we have `self.n`, which loads up the upvar
 862             let field_kind =
 863                 ExprKind::Field { lhs: self_expr.to_ref(), name: Field::new(upvar_index) };
 864
 865             // ...but the upvar might be an `&T` or `&mut T` capture, at which
 866             // point we need an implicit deref
 867             match cx.tables().upvar_capture(upvar_id) {
 868                 ty::UpvarCapture::ByValue => field_kind,
 869                 ty::UpvarCapture::ByRef(borrow) => ExprKind::Deref {
 870                     arg: Expr {
 871                         temp_lifetime,
 872                         ty: cx.tcx.mk_ref(
 873                             borrow.region,
 874                             ty::TypeAndMut { ty: var_ty, mutbl: borrow.kind.to_mutbl_lossy() },
 875                         ),
 876                         span: expr.span,
 877                         kind: field_kind,
 878                     }
 879                     .to_ref(),
 880                 },
 881             }
 882         }
 883     }
 884 }
 885
 886 fn bin_op(op: hir::BinOpKind) -> BinOp {
 887     match op {
 888         hir::BinOpKind::Add => BinOp::Add,
 889         hir::BinOpKind::Sub => BinOp::Sub,
 890         hir::BinOpKind::Mul => BinOp::Mul,
 891         hir::BinOpKind::Div => BinOp::Div,
 892         hir::BinOpKind::Rem => BinOp::Rem,
 893         hir::BinOpKind::BitXor => BinOp::BitXor,
 894         hir::BinOpKind::BitAnd => BinOp::BitAnd,
 895         hir::BinOpKind::BitOr => BinOp::BitOr,
 896         hir::BinOpKind::Shl => BinOp::Shl,
 897         hir::BinOpKind::Shr => BinOp::Shr,
 898         hir::BinOpKind::Eq => BinOp::Eq,
 899         hir::BinOpKind::Lt => BinOp::Lt,
 900         hir::BinOpKind::Le => BinOp::Le,
 901         hir::BinOpKind::Ne => BinOp::Ne,
 902         hir::BinOpKind::Ge => BinOp::Ge,
 903         hir::BinOpKind::Gt => BinOp::Gt,
 904         _ => bug!("no equivalent for ast binop {:?}", op),
 905     }
 906 }
 907
 908 fn overloaded_operator<'a, 'tcx>(
 909     cx: &mut Cx<'a, 'tcx>,
 910     expr: &'tcx hir::Expr<'tcx>,
 911     args: Vec<ExprRef<'tcx>>,
 912 ) -> ExprKind<'tcx> {
 913     let fun = method_callee(cx, expr, expr.span, None);
 914     ExprKind::Call { ty: fun.ty, fun: fun.to_ref(), args, from_hir_call: false }
 915 }
 916
 917 fn overloaded_place<'a, 'tcx>(
 918     cx: &mut Cx<'a, 'tcx>,
 919     expr: &'tcx hir::Expr<'tcx>,
 920     place_ty: Ty<'tcx>,
 921     overloaded_callee: Option<(DefId, SubstsRef<'tcx>)>,
 922     args: Vec<ExprRef<'tcx>>,
 923 ) -> ExprKind<'tcx> {
 924     // For an overloaded *x or x[y] expression of type T, the method
 925     // call returns an &T and we must add the deref so that the types
 926     // line up (this is because `*x` and `x[y]` represent places):
 927
 928     let recv_ty = match args[0] {
 929         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
 930         ExprRef::Mirror(ref e) => e.ty,
 931     };
 932
 933     // Reconstruct the output assuming it's a reference with the
 934     // same region and mutability as the receiver. This holds for
 935     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
 936     let (region, mutbl) = match recv_ty.kind {
 937         ty::Ref(region, _, mutbl) => (region, mutbl),
 938         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
 939     };
 940     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut { ty: place_ty, mutbl });
 941
 942     // construct the complete expression `foo()` for the overloaded call,
 943     // which will yield the &T type
 944     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 945     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
 946     let ref_expr = Expr {
 947         temp_lifetime,
 948         ty: ref_ty,
 949         span: expr.span,
 950         kind: ExprKind::Call { ty: fun.ty, fun: fun.to_ref(), args, from_hir_call: false },
 951     };
 952
 953     // construct and return a deref wrapper `*foo()`
 954     ExprKind::Deref { arg: ref_expr.to_ref() }
 955 }
 956
 957 fn capture_upvar<'tcx>(
 958     cx: &mut Cx<'_, 'tcx>,
 959     closure_expr: &'tcx hir::Expr<'tcx>,
 960     var_hir_id: hir::HirId,
 961     upvar_ty: Ty<'tcx>,
 962 ) -> ExprRef<'tcx> {
 963     let upvar_id = ty::UpvarId {
 964         var_path: ty::UpvarPath { hir_id: var_hir_id },
 965         closure_expr_id: cx.tcx.hir().local_def_id(closure_expr.hir_id).expect_local(),
 966     };
 967     let upvar_capture = cx.tables().upvar_capture(upvar_id);
 968     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
 969     let var_ty = cx.tables().node_type(var_hir_id);
 970     let captured_var = Expr {
 971         temp_lifetime,
 972         ty: var_ty,
 973         span: closure_expr.span,
 974         kind: convert_var(cx, closure_expr, var_hir_id),
 975     };
 976     match upvar_capture {
 977         ty::UpvarCapture::ByValue => captured_var.to_ref(),
 978         ty::UpvarCapture::ByRef(upvar_borrow) => {
 979             let borrow_kind = match upvar_borrow.kind {
 980                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
 981                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
 982                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false },
 983             };
 984             Expr {
 985                 temp_lifetime,
 986                 ty: upvar_ty,
 987                 span: closure_expr.span,
 988                 kind: ExprKind::Borrow { borrow_kind, arg: captured_var.to_ref() },
 989             }
 990             .to_ref()
 991         }
 992     }
 993 }
 994
 995 /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExprRef.
 996 fn field_refs<'a, 'tcx>(
 997     cx: &mut Cx<'a, 'tcx>,
 998     fields: &'tcx [hir::Field<'tcx>],
 999 ) -> Vec<FieldExprRef<'tcx>> {
1000     fields
1001         .iter()
1002         .map(|field| FieldExprRef {
1003             name: Field::new(cx.tcx.field_index(field.hir_id, cx.tables)),
1004             expr: field.expr.to_ref(),
1005         })
1006         .collect()
1007 }