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1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 use hair::*;
12 use rustc_data_structures::indexed_vec::Idx;
13 use hair::cx::Cx;
14 use hair::cx::block;
15 use hair::cx::to_ref::ToRef;
16 use hair::util::UserAnnotatedTyHelpers;
17 use rustc::hir::def::{Def, CtorKind};
18 use rustc::mir::interpret::{GlobalId, ErrorHandled};
19 use rustc::ty::{self, AdtKind, Ty};
20 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability};
21 use rustc::ty::cast::CastKind as TyCastKind;
22 use rustc::hir;
23 use rustc::hir::def_id::LocalDefId;
24 use rustc::mir::{BorrowKind};
25 use syntax_pos::Span;
26
27 impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
28     type Output = Expr<'tcx>;
29
30     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
31         let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
32         let expr_scope = region::Scope {
33             id: self.hir_id.local_id,
34             data: region::ScopeData::Node
35         };
36
37         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
38
39         let mut expr = make_mirror_unadjusted(cx, self);
40
41         // Now apply adjustments, if any.
42         for adjustment in cx.tables().expr_adjustments(self) {
43             debug!("make_mirror: expr={:?} applying adjustment={:?}",
44                    expr,
45                    adjustment);
46             expr = apply_adjustment(cx, self, expr, adjustment);
47         }
48
49         // Next, wrap this up in the expr's scope.
50         expr = Expr {
51             temp_lifetime,
52             ty: expr.ty,
53             span: self.span,
54             kind: ExprKind::Scope {
55                 region_scope: expr_scope,
56                 value: expr.to_ref(),
57                 lint_level: cx.lint_level_of(self.id),
58             },
59         };
60
61         // Finally, create a destruction scope, if any.
62         if let Some(region_scope) =
63             cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id) {
64                 expr = Expr {
65                     temp_lifetime,
66                     ty: expr.ty,
67                     span: self.span,
68                     kind: ExprKind::Scope {
69                         region_scope,
70                         value: expr.to_ref(),
71                         lint_level: LintLevel::Inherited,
72                     },
73                 };
74             }
75
76         // OK, all done!
77         expr
78     }
79 }
80
81 fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
82                                     hir_expr: &'tcx hir::Expr,
83                                     mut expr: Expr<'tcx>,
84                                     adjustment: &Adjustment<'tcx>)
85                                     -> Expr<'tcx> {
86     let Expr { temp_lifetime, mut span, .. } = expr;
87     let kind = match adjustment.kind {
88         Adjust::ReifyFnPointer => {
89             ExprKind::ReifyFnPointer { source: expr.to_ref() }
90         }
91         Adjust::UnsafeFnPointer => {
92             ExprKind::UnsafeFnPointer { source: expr.to_ref() }
93         }
94         Adjust::ClosureFnPointer => {
95             ExprKind::ClosureFnPointer { source: expr.to_ref() }
96         }
97         Adjust::NeverToAny => {
98             ExprKind::NeverToAny { source: expr.to_ref() }
99         }
100         Adjust::MutToConstPointer => {
101             ExprKind::Cast { source: expr.to_ref() }
102         }
103         Adjust::Deref(None) => {
104             // Adjust the span from the block, to the last expression of the
105             // block. This is a better span when returning a mutable reference
106             // with too short a lifetime. The error message will use the span
107             // from the assignment to the return place, which should only point
108             // at the returned value, not the entire function body.
109             //
110             // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
111             //      x
112             //   // ^ error message points at this expression.
113             // }
114             //
115             // We don't need to do this adjustment in the next match arm since
116             // deref coercions always start with a built-in deref.
117             if let ExprKind::Block { body } = expr.kind {
118                 if let Some(ref last_expr) = body.expr {
119                     span = last_expr.span;
120                     expr.span = span;
121                 }
122             }
123             ExprKind::Deref { arg: expr.to_ref() }
124         }
125         Adjust::Deref(Some(deref)) => {
126             let call = deref.method_call(cx.tcx(), expr.ty);
127
128             expr = Expr {
129                 temp_lifetime,
130                 ty: cx.tcx.mk_ref(deref.region,
131                                   ty::TypeAndMut {
132                                     ty: expr.ty,
133                                     mutbl: deref.mutbl,
134                                   }),
135                 span,
136                 kind: ExprKind::Borrow {
137                     region: deref.region,
138                     borrow_kind: deref.mutbl.to_borrow_kind(),
139                     arg: expr.to_ref(),
140                 },
141             };
142
143             overloaded_place(cx, hir_expr, adjustment.target, Some(call), vec![expr.to_ref()])
144         }
145         Adjust::Borrow(AutoBorrow::Ref(r, m)) => {
146             ExprKind::Borrow {
147                 region: r,
148                 borrow_kind: m.to_borrow_kind(),
149                 arg: expr.to_ref(),
150             }
151         }
152         Adjust::Borrow(AutoBorrow::RawPtr(m)) => {
153             // Convert this to a suitable `&foo` and
154             // then an unsafe coercion. Limit the region to be just this
155             // expression.
156             let region = ty::ReScope(region::Scope {
157                 id: hir_expr.hir_id.local_id,
158                 data: region::ScopeData::Node
159             });
160             let region = cx.tcx.mk_region(region);
161             expr = Expr {
162                 temp_lifetime,
163                 ty: cx.tcx.mk_ref(region,
164                                   ty::TypeAndMut {
165                                     ty: expr.ty,
166                                     mutbl: m,
167                                   }),
168                 span,
169                 kind: ExprKind::Borrow {
170                     region,
171                     borrow_kind: m.to_borrow_kind(),
172                     arg: expr.to_ref(),
173                 },
174             };
175             let cast_expr = Expr {
176                 temp_lifetime,
177                 ty: adjustment.target,
178                 span,
179                 kind: ExprKind::Cast { source: expr.to_ref() }
180             };
181
182             // To ensure that both implicit and explicit coercions are
183             // handled the same way, we insert an extra layer of indirection here.
184             // For explicit casts (e.g. 'foo as *const T'), the source of the 'Use'
185             // will be an ExprKind::Hair with the appropriate cast expression. Here,
186             // we make our Use source the generated Cast from the original coercion.
187             //
188             // In both cases, this outer 'Use' ensures that the inner 'Cast' is handled by
189             // as_operand, not by as_rvalue - causing the cast result to be stored in a temporary.
190             // Ordinary, this is identical to using the cast directly as an rvalue. However, if the
191             // source of the cast was previously borrowed as mutable, storing the cast in a
192             // temporary gives the source a chance to expire before the cast is used. For
193             // structs with a self-referential *mut ptr, this allows assignment to work as
194             // expected.
195             //
196             // For example, consider the type 'struct Foo { field: *mut Foo }',
197             // The method 'fn bar(&mut self) { self.field = self }'
198             // triggers a coercion from '&mut self' to '*mut self'. In order
199             // for the assignment to be valid, the implicit borrow
200             // of 'self' involved in the coercion needs to end before the local
201             // containing the '*mut T' is assigned to 'self.field' - otherwise,
202             // we end up trying to assign to 'self.field' while we have another mutable borrow
203             // active.
204             //
205             // We only need to worry about this kind of thing for coercions from refs to ptrs,
206             // since they get rid of a borrow implicitly.
207             ExprKind::Use { source: cast_expr.to_ref() }
208         }
209         Adjust::Unsize => {
210             // See the above comment for Adjust::Deref
211             if let ExprKind::Block { body } = expr.kind {
212                 if let Some(ref last_expr) = body.expr {
213                     span = last_expr.span;
214                     expr.span = span;
215                 }
216             }
217             ExprKind::Unsize { source: expr.to_ref() }
218         }
219     };
220
221     Expr {
222         temp_lifetime,
223         ty: adjustment.target,
224         span,
225         kind,
226     }
227 }
228
229 fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
230                                           expr: &'tcx hir::Expr)
231                                           -> Expr<'tcx> {
232     let expr_ty = cx.tables().expr_ty(expr);
233     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
234
235     let kind = match expr.node {
236         // Here comes the interesting stuff:
237         hir::ExprKind::MethodCall(_, method_span, ref args) => {
238             // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
239             let expr = method_callee(cx, expr, method_span,None);
240             let args = args.iter()
241                 .map(|e| e.to_ref())
242                 .collect();
243             ExprKind::Call {
244                 ty: expr.ty,
245                 fun: expr.to_ref(),
246                 args,
247                 from_hir_call: true,
248             }
249         }
250
251         hir::ExprKind::Call(ref fun, ref args) => {
252             if cx.tables().is_method_call(expr) {
253                 // The callee is something implementing Fn, FnMut, or FnOnce.
254                 // Find the actual method implementation being called and
255                 // build the appropriate UFCS call expression with the
256                 // callee-object as expr parameter.
257
258                 // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
259
260                 let method = method_callee(cx, expr, fun.span,None);
261
262                 let arg_tys = args.iter().map(|e| cx.tables().expr_ty_adjusted(e));
263                 let tupled_args = Expr {
264                     ty: cx.tcx.mk_tup(arg_tys),
265                     temp_lifetime,
266                     span: expr.span,
267                     kind: ExprKind::Tuple { fields: args.iter().map(ToRef::to_ref).collect() },
268                 };
269
270                 ExprKind::Call {
271                     ty: method.ty,
272                     fun: method.to_ref(),
273                     args: vec![fun.to_ref(), tupled_args.to_ref()],
274                     from_hir_call: true,
275                 }
276             } else {
277                 let adt_data = if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) =
278                     fun.node
279                 {
280                     // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
281                     expr_ty.ty_adt_def().and_then(|adt_def| {
282                         match path.def {
283                             Def::VariantCtor(variant_id, CtorKind::Fn) => {
284                                 Some((adt_def, adt_def.variant_index_with_id(variant_id)))
285                             }
286                             Def::StructCtor(_, CtorKind::Fn) |
287                             Def::SelfCtor(..) => Some((adt_def, VariantIdx::new(0))),
288                             _ => None,
289                         }
290                     })
291                 } else {
292                     None
293                 };
294                 if let Some((adt_def, index)) = adt_data {
295                     let substs = cx.tables().node_substs(fun.hir_id);
296
297                     let user_ty = cx.tables().user_substs(fun.hir_id)
298                         .map(|user_substs| UserTypeAnnotation::TypeOf(adt_def.did, user_substs));
299
300                     let field_refs = args.iter()
301                         .enumerate()
302                         .map(|(idx, e)| {
303                             FieldExprRef {
304                                 name: Field::new(idx),
305                                 expr: e.to_ref(),
306                             }
307                         })
308                         .collect();
309                     ExprKind::Adt {
310                         adt_def,
311                         substs,
312                         variant_index: index,
313                         fields: field_refs,
314                         user_ty,
315                         base: None,
316                     }
317                 } else {
318                     ExprKind::Call {
319                         ty: cx.tables().node_id_to_type(fun.hir_id),
320                         fun: fun.to_ref(),
321                         args: args.to_ref(),
322                         from_hir_call: true,
323                     }
324                 }
325             }
326         }
327
328         hir::ExprKind::AddrOf(mutbl, ref expr) => {
329             let region = match expr_ty.sty {
330                 ty::Ref(r, _, _) => r,
331                 _ => span_bug!(expr.span, "type of & not region"),
332             };
333             ExprKind::Borrow {
334                 region,
335                 borrow_kind: mutbl.to_borrow_kind(),
336                 arg: expr.to_ref(),
337             }
338         }
339
340         hir::ExprKind::Block(ref blk, _) => ExprKind::Block { body: &blk },
341
342         hir::ExprKind::Assign(ref lhs, ref rhs) => {
343             ExprKind::Assign {
344                 lhs: lhs.to_ref(),
345                 rhs: rhs.to_ref(),
346             }
347         }
348
349         hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
350             if cx.tables().is_method_call(expr) {
351                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
352             } else {
353                 ExprKind::AssignOp {
354                     op: bin_op(op.node),
355                     lhs: lhs.to_ref(),
356                     rhs: rhs.to_ref(),
357                 }
358             }
359         }
360
361         hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
362             literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, false),
363             user_ty: None,
364         },
365
366         hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
367             if cx.tables().is_method_call(expr) {
368                 overloaded_operator(cx, expr, vec![lhs.to_ref(), rhs.to_ref()])
369             } else {
370                 // FIXME overflow
371                 match (op.node, cx.constness) {
372                     // FIXME(eddyb) use logical ops in constants when
373                     // they can handle that kind of control-flow.
374                     (hir::BinOpKind::And, hir::Constness::Const) => {
375                         ExprKind::Binary {
376                             op: BinOp::BitAnd,
377                             lhs: lhs.to_ref(),
378                             rhs: rhs.to_ref(),
379                         }
380                     }
381                     (hir::BinOpKind::Or, hir::Constness::Const) => {
382                         ExprKind::Binary {
383                             op: BinOp::BitOr,
384                             lhs: lhs.to_ref(),
385                             rhs: rhs.to_ref(),
386                         }
387                     }
388
389                     (hir::BinOpKind::And, hir::Constness::NotConst) => {
390                         ExprKind::LogicalOp {
391                             op: LogicalOp::And,
392                             lhs: lhs.to_ref(),
393                             rhs: rhs.to_ref(),
394                         }
395                     }
396                     (hir::BinOpKind::Or, hir::Constness::NotConst) => {
397                         ExprKind::LogicalOp {
398                             op: LogicalOp::Or,
399                             lhs: lhs.to_ref(),
400                             rhs: rhs.to_ref(),
401                         }
402                     }
403
404                     _ => {
405                         let op = bin_op(op.node);
406                         ExprKind::Binary {
407                             op,
408                             lhs: lhs.to_ref(),
409                             rhs: rhs.to_ref(),
410                         }
411                     }
412                 }
413             }
414         }
415
416         hir::ExprKind::Index(ref lhs, ref index) => {
417             if cx.tables().is_method_call(expr) {
418                 overloaded_place(cx, expr, expr_ty, None, vec![lhs.to_ref(), index.to_ref()])
419             } else {
420                 ExprKind::Index {
421                     lhs: lhs.to_ref(),
422                     index: index.to_ref(),
423                 }
424             }
425         }
426
427         hir::ExprKind::Unary(hir::UnOp::UnDeref, ref arg) => {
428             if cx.tables().is_method_call(expr) {
429                 overloaded_place(cx, expr, expr_ty, None, vec![arg.to_ref()])
430             } else {
431                 ExprKind::Deref { arg: arg.to_ref() }
432             }
433         }
434
435         hir::ExprKind::Unary(hir::UnOp::UnNot, ref arg) => {
436             if cx.tables().is_method_call(expr) {
437                 overloaded_operator(cx, expr, vec![arg.to_ref()])
438             } else {
439                 ExprKind::Unary {
440                     op: UnOp::Not,
441                     arg: arg.to_ref(),
442                 }
443             }
444         }
445
446         hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
447             if cx.tables().is_method_call(expr) {
448                 overloaded_operator(cx, expr, vec![arg.to_ref()])
449             } else {
450                 if let hir::ExprKind::Lit(ref lit) = arg.node {
451                     ExprKind::Literal {
452                         literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, true),
453                         user_ty: None,
454                     }
455                 } else {
456                     ExprKind::Unary {
457                         op: UnOp::Neg,
458                         arg: arg.to_ref(),
459                     }
460                 }
461             }
462         }
463
464         hir::ExprKind::Struct(ref qpath, ref fields, ref base) => {
465             match expr_ty.sty {
466                 ty::Adt(adt, substs) => {
467                     match adt.adt_kind() {
468                         AdtKind::Struct | AdtKind::Union => {
469                             ExprKind::Adt {
470                                 adt_def: adt,
471                                 variant_index: VariantIdx::new(0),
472                                 substs,
473                                 user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
474                                 fields: field_refs(cx, fields),
475                                 base: base.as_ref().map(|base| {
476                                     FruInfo {
477                                         base: base.to_ref(),
478                                         field_types: cx.tables()
479                                                        .fru_field_types()[expr.hir_id]
480                                                        .clone(),
481                                     }
482                                 }),
483                             }
484                         }
485                         AdtKind::Enum => {
486                             let def = match *qpath {
487                                 hir::QPath::Resolved(_, ref path) => path.def,
488                                 hir::QPath::TypeRelative(..) => Def::Err,
489                             };
490                             match def {
491                                 Def::Variant(variant_id) => {
492                                     assert!(base.is_none());
493
494                                     let index = adt.variant_index_with_id(variant_id);
495                                     ExprKind::Adt {
496                                         adt_def: adt,
497                                         variant_index: index,
498                                         substs,
499                                         user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
500                                         fields: field_refs(cx, fields),
501                                         base: None,
502                                     }
503                                 }
504                                 _ => {
505                                     span_bug!(expr.span, "unexpected def: {:?}", def);
506                                 }
507                             }
508                         }
509                     }
510                 }
511                 _ => {
512                     span_bug!(expr.span,
513                               "unexpected type for struct literal: {:?}",
514                               expr_ty);
515                 }
516             }
517         }
518
519         hir::ExprKind::Closure(..) => {
520             let closure_ty = cx.tables().expr_ty(expr);
521             let (def_id, substs, movability) = match closure_ty.sty {
522                 ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
523                 ty::Generator(def_id, substs, movability) => {
524                     (def_id, UpvarSubsts::Generator(substs), Some(movability))
525                 }
526                 _ => {
527                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
528                 }
529             };
530             let upvars = cx.tcx.with_freevars(expr.id, |freevars| {
531                 freevars.iter()
532                     .zip(substs.upvar_tys(def_id, cx.tcx))
533                     .map(|(fv, ty)| capture_freevar(cx, expr, fv, ty))
534                     .collect()
535             });
536             ExprKind::Closure {
537                 closure_id: def_id,
538                 substs,
539                 upvars,
540                 movability,
541             }
542         }
543
544         hir::ExprKind::Path(ref qpath) => {
545             let def = cx.tables().qpath_def(qpath, expr.hir_id);
546             convert_path_expr(cx, expr, def)
547         }
548
549         hir::ExprKind::InlineAsm(ref asm, ref outputs, ref inputs) => {
550             ExprKind::InlineAsm {
551                 asm,
552                 outputs: outputs.to_ref(),
553                 inputs: inputs.to_ref(),
554             }
555         }
556
557         // Now comes the rote stuff:
558         hir::ExprKind::Repeat(ref v, ref count) => {
559             let def_id = cx.tcx.hir().local_def_id(count.id);
560             let substs = Substs::identity_for_item(cx.tcx.global_tcx(), def_id);
561             let instance = ty::Instance::resolve(
562                 cx.tcx.global_tcx(),
563                 cx.param_env,
564                 def_id,
565                 substs,
566             ).unwrap();
567             let global_id = GlobalId {
568                 instance,
569                 promoted: None
570             };
571             let span = cx.tcx.def_span(def_id);
572             let count = match cx.tcx.at(span).const_eval(cx.param_env.and(global_id)) {
573                 Ok(cv) => cv.unwrap_usize(cx.tcx),
574                 Err(ErrorHandled::Reported) => 0,
575                 Err(ErrorHandled::TooGeneric) => {
576                     cx.tcx.sess.span_err(span, "array lengths can't depend on generic parameters");
577                     0
578                 },
579             };
580
581             ExprKind::Repeat {
582                 value: v.to_ref(),
583                 count,
584             }
585         }
586         hir::ExprKind::Ret(ref v) => ExprKind::Return { value: v.to_ref() },
587         hir::ExprKind::Break(dest, ref value) => {
588             match dest.target_id {
589                 Ok(target_id) => ExprKind::Break {
590                     label: region::Scope {
591                         id: cx.tcx.hir().node_to_hir_id(target_id).local_id,
592                         data: region::ScopeData::Node
593                     },
594                     value: value.to_ref(),
595                 },
596                 Err(err) => bug!("invalid loop id for break: {}", err)
597             }
598         }
599         hir::ExprKind::Continue(dest) => {
600             match dest.target_id {
601                 Ok(loop_id) => ExprKind::Continue {
602                     label: region::Scope {
603                         id: cx.tcx.hir().node_to_hir_id(loop_id).local_id,
604                         data: region::ScopeData::Node
605                     },
606                 },
607                 Err(err) => bug!("invalid loop id for continue: {}", err)
608             }
609         }
610         hir::ExprKind::Match(ref discr, ref arms, _) => {
611             ExprKind::Match {
612                 discriminant: discr.to_ref(),
613                 arms: arms.iter().map(|a| convert_arm(cx, a)).collect(),
614             }
615         }
616         hir::ExprKind::If(ref cond, ref then, ref otherwise) => {
617             ExprKind::If {
618                 condition: cond.to_ref(),
619                 then: then.to_ref(),
620                 otherwise: otherwise.to_ref(),
621             }
622         }
623         hir::ExprKind::While(ref cond, ref body, _) => {
624             ExprKind::Loop {
625                 condition: Some(cond.to_ref()),
626                 body: block::to_expr_ref(cx, body),
627             }
628         }
629         hir::ExprKind::Loop(ref body, _, _) => {
630             ExprKind::Loop {
631                 condition: None,
632                 body: block::to_expr_ref(cx, body),
633             }
634         }
635         hir::ExprKind::Field(ref source, ..) => {
636             ExprKind::Field {
637                 lhs: source.to_ref(),
638                 name: Field::new(cx.tcx.field_index(expr.id, cx.tables)),
639             }
640         }
641         hir::ExprKind::Cast(ref source, ref cast_ty) => {
642             // Check for a user-given type annotation on this `cast`
643             let user_ty = cx.tables.user_provided_tys().get(cast_ty.hir_id)
644                 .map(|&t| UserTypeAnnotation::Ty(t));
645
646             debug!(
647                 "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
648                 expr,
649                 cast_ty.hir_id,
650                 user_ty,
651             );
652
653             // Check to see if this cast is a "coercion cast", where the cast is actually done
654             // using a coercion (or is a no-op).
655             let cast = if let Some(&TyCastKind::CoercionCast) =
656                 cx.tables()
657                 .cast_kinds()
658                 .get(source.hir_id)
659             {
660                 // Convert the lexpr to a vexpr.
661                 ExprKind::Use { source: source.to_ref() }
662             } else {
663                 // check whether this is casting an enum variant discriminant
664                 // to prevent cycles, we refer to the discriminant initializer
665                 // which is always an integer and thus doesn't need to know the
666                 // enum's layout (or its tag type) to compute it during const eval
667                 // Example:
668                 // enum Foo {
669                 //     A,
670                 //     B = A as isize + 4,
671                 // }
672                 // The correct solution would be to add symbolic computations to miri,
673                 // so we wouldn't have to compute and store the actual value
674                 let var = if let hir::ExprKind::Path(ref qpath) = source.node {
675                     let def = cx.tables().qpath_def(qpath, source.hir_id);
676                     cx
677                         .tables()
678                         .node_id_to_type(source.hir_id)
679                         .ty_adt_def()
680                         .and_then(|adt_def| {
681                         match def {
682                             Def::VariantCtor(variant_id, CtorKind::Const) => {
683                                 let idx = adt_def.variant_index_with_id(variant_id);
684                                 let (d, o) = adt_def.discriminant_def_for_variant(idx);
685                                 use rustc::ty::util::IntTypeExt;
686                                 let ty = adt_def.repr.discr_type();
687                                 let ty = ty.to_ty(cx.tcx());
688                                 Some((d, o, ty))
689                             }
690                             _ => None,
691                         }
692                     })
693                 } else {
694                     None
695                 };
696
697                 let source = if let Some((did, offset, var_ty)) = var {
698                     let mk_const = |literal| Expr {
699                         temp_lifetime,
700                         ty: var_ty,
701                         span: expr.span,
702                         kind: ExprKind::Literal { literal, user_ty: None },
703                     }.to_ref();
704                     let offset = mk_const(ty::Const::from_bits(
705                         cx.tcx,
706                         offset as u128,
707                         cx.param_env.and(var_ty),
708                     ));
709                     match did {
710                         Some(did) => {
711                             // in case we are offsetting from a computed discriminant
712                             // and not the beginning of discriminants (which is always `0`)
713                             let substs = Substs::identity_for_item(cx.tcx(), did);
714                             let lhs = mk_const(ty::Const::unevaluated(
715                                 cx.tcx(),
716                                 did,
717                                 substs,
718                                 var_ty,
719                             ));
720                             let bin = ExprKind::Binary {
721                                 op: BinOp::Add,
722                                 lhs,
723                                 rhs: offset,
724                             };
725                             Expr {
726                                 temp_lifetime,
727                                 ty: var_ty,
728                                 span: expr.span,
729                                 kind: bin,
730                             }.to_ref()
731                         },
732                         None => offset,
733                     }
734                 } else {
735                     source.to_ref()
736                 };
737
738                 ExprKind::Cast { source }
739             };
740
741             if let Some(user_ty) = user_ty {
742                 // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
743                 //       inefficient, revisit this when performance becomes an issue.
744                 let cast_expr = Expr {
745                     temp_lifetime,
746                     ty: expr_ty,
747                     span: expr.span,
748                     kind: cast,
749                 };
750
751                 ExprKind::ValueTypeAscription {
752                     source: cast_expr.to_ref(),
753                     user_ty: Some(user_ty),
754                 }
755             } else {
756                 cast
757             }
758         }
759         hir::ExprKind::Type(ref source, ref ty) => {
760             let user_provided_tys = cx.tables.user_provided_tys();
761             let user_ty = user_provided_tys
762                 .get(ty.hir_id)
763                 .map(|&c_ty| UserTypeAnnotation::Ty(c_ty));
764             if source.is_place_expr() {
765                 ExprKind::PlaceTypeAscription {
766                     source: source.to_ref(),
767                     user_ty,
768                 }
769             } else {
770                 ExprKind::ValueTypeAscription {
771                     source: source.to_ref(),
772                     user_ty,
773                 }
774             }
775         }
776         hir::ExprKind::Box(ref value) => {
777             ExprKind::Box {
778                 value: value.to_ref(),
779             }
780         }
781         hir::ExprKind::Array(ref fields) => ExprKind::Array { fields: fields.to_ref() },
782         hir::ExprKind::Tup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
783
784         hir::ExprKind::Yield(ref v) => ExprKind::Yield { value: v.to_ref() },
785     };
786
787     Expr {
788         temp_lifetime,
789         ty: expr_ty,
790         span: expr.span,
791         kind,
792     }
793 }
794
795 fn user_substs_applied_to_def(
796     cx: &mut Cx<'a, 'gcx, 'tcx>,
797     hir_id: hir::HirId,
798     def: &Def,
799 ) -> Option<UserTypeAnnotation<'tcx>> {
800     match def {
801         // A reference to something callable -- e.g., a fn, method, or
802         // a tuple-struct or tuple-variant. This has the type of a
803         // `Fn` but with the user-given substitutions.
804         Def::Fn(_) |
805         Def::Method(_) |
806         Def::StructCtor(_, CtorKind::Fn) |
807         Def::VariantCtor(_, CtorKind::Fn) |
808         Def::Const(_) |
809         Def::AssociatedConst(_) =>
810             Some(UserTypeAnnotation::TypeOf(def.def_id(), cx.tables().user_substs(hir_id)?)),
811
812         // A unit struct/variant which is used as a value (e.g.,
813         // `None`). This has the type of the enum/struct that defines
814         // this variant -- but with the substitutions given by the
815         // user.
816         Def::StructCtor(_def_id, CtorKind::Const) |
817         Def::VariantCtor(_def_id, CtorKind::Const) =>
818             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
819
820         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
821         Def::SelfCtor(_) =>
822             cx.user_substs_applied_to_ty_of_hir_id(hir_id),
823
824         _ =>
825             bug!("user_substs_applied_to_def: unexpected def {:?} at {:?}", def, hir_id)
826     }
827 }
828
829 fn method_callee<'a, 'gcx, 'tcx>(
830     cx: &mut Cx<'a, 'gcx, 'tcx>,
831     expr: &hir::Expr,
832     span: Span,
833     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
834 ) -> Expr<'tcx> {
835     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
836     let (def_id, substs, user_ty) = match overloaded_callee {
837         Some((def_id, substs)) => (def_id, substs, None),
838         None => {
839             let type_dependent_defs = cx.tables().type_dependent_defs();
840             let def = type_dependent_defs
841                 .get(expr.hir_id)
842                 .unwrap_or_else(|| {
843                     span_bug!(expr.span, "no type-dependent def for method callee")
844                 });
845             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, def);
846             (def.def_id(), cx.tables().node_substs(expr.hir_id), user_ty)
847         }
848     };
849     let ty = cx.tcx().mk_fn_def(def_id, substs);
850     Expr {
851         temp_lifetime,
852         ty,
853         span,
854         kind: ExprKind::Literal {
855             literal: ty::Const::zero_sized(cx.tcx(), ty),
856             user_ty,
857         },
858     }
859 }
860
861 trait ToBorrowKind { fn to_borrow_kind(&self) -> BorrowKind; }
862
863 impl ToBorrowKind for AutoBorrowMutability {
864     fn to_borrow_kind(&self) -> BorrowKind {
865         use rustc::ty::adjustment::AllowTwoPhase;
866         match *self {
867             AutoBorrowMutability::Mutable { allow_two_phase_borrow } =>
868                 BorrowKind::Mut { allow_two_phase_borrow: match allow_two_phase_borrow {
869                     AllowTwoPhase::Yes => true,
870                     AllowTwoPhase::No => false
871                 }},
872             AutoBorrowMutability::Immutable =>
873                 BorrowKind::Shared,
874         }
875     }
876 }
877
878 impl ToBorrowKind for hir::Mutability {
879     fn to_borrow_kind(&self) -> BorrowKind {
880         match *self {
881             hir::MutMutable => BorrowKind::Mut { allow_two_phase_borrow: false },
882             hir::MutImmutable => BorrowKind::Shared,
883         }
884     }
885 }
886
887 fn convert_arm<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>, arm: &'tcx hir::Arm) -> Arm<'tcx> {
888     Arm {
889         patterns: arm.pats.iter().map(|p| cx.pattern_from_hir(p)).collect(),
890         guard: match arm.guard {
891                 Some(hir::Guard::If(ref e)) => Some(Guard::If(e.to_ref())),
892                 _ => None,
893             },
894         body: arm.body.to_ref(),
895         // BUG: fix this
896         lint_level: LintLevel::Inherited,
897     }
898 }
899
900 fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
901                                      expr: &'tcx hir::Expr,
902                                      def: Def)
903                                      -> ExprKind<'tcx> {
904     let substs = cx.tables().node_substs(expr.hir_id);
905     match def {
906         // A regular function, constructor function or a constant.
907         Def::Fn(_) |
908         Def::Method(_) |
909         Def::StructCtor(_, CtorKind::Fn) |
910         Def::VariantCtor(_, CtorKind::Fn) |
911         Def::SelfCtor(..) => {
912             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
913             ExprKind::Literal {
914                 literal: ty::Const::zero_sized(
915                     cx.tcx,
916                     cx.tables().node_id_to_type(expr.hir_id),
917                 ),
918                 user_ty,
919             }
920         },
921
922         Def::Const(def_id) |
923         Def::AssociatedConst(def_id) => {
924             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
925             ExprKind::Literal {
926                 literal: ty::Const::unevaluated(
927                     cx.tcx,
928                     def_id,
929                     substs,
930                     cx.tables().node_id_to_type(expr.hir_id),
931                 ),
932                 user_ty,
933             }
934         },
935
936         Def::StructCtor(def_id, CtorKind::Const) |
937         Def::VariantCtor(def_id, CtorKind::Const) => {
938             match cx.tables().node_id_to_type(expr.hir_id).sty {
939                 // A unit struct/variant which is used as a value.
940                 // We return a completely different ExprKind here to account for this special case.
941                 ty::Adt(adt_def, substs) => {
942                     ExprKind::Adt {
943                         adt_def,
944                         variant_index: adt_def.variant_index_with_id(def_id),
945                         substs,
946                         user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt_def),
947                         fields: vec![],
948                         base: None,
949                     }
950                 }
951                 ref sty => bug!("unexpected sty: {:?}", sty),
952             }
953         }
954
955         Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
956
957         Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
958
959         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
960     }
961 }
962
963 fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
964                                expr: &'tcx hir::Expr,
965                                def: Def)
966                                -> ExprKind<'tcx> {
967     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
968
969     match def {
970         Def::Local(id) => ExprKind::VarRef { id },
971
972         Def::Upvar(var_id, index, closure_expr_id) => {
973             debug!("convert_var(upvar({:?}, {:?}, {:?}))",
974                    var_id,
975                    index,
976                    closure_expr_id);
977             let var_hir_id = cx.tcx.hir().node_to_hir_id(var_id);
978             let var_ty = cx.tables().node_id_to_type(var_hir_id);
979
980             // FIXME free regions in closures are not right
981             let closure_ty = cx.tables()
982                                .node_id_to_type(cx.tcx.hir().node_to_hir_id(closure_expr_id));
983
984             // FIXME we're just hard-coding the idea that the
985             // signature will be &self or &mut self and hence will
986             // have a bound region with number 0
987             let closure_def_id = cx.tcx.hir().local_def_id(closure_expr_id);
988             let region = ty::ReFree(ty::FreeRegion {
989                 scope: closure_def_id,
990                 bound_region: ty::BoundRegion::BrAnon(0),
991             });
992             let region = cx.tcx.mk_region(region);
993
994             let self_expr = if let ty::Closure(_, closure_substs) = closure_ty.sty {
995                 match cx.infcx.closure_kind(closure_def_id, closure_substs).unwrap() {
996                     ty::ClosureKind::Fn => {
997                         let ref_closure_ty = cx.tcx.mk_ref(region,
998                                                            ty::TypeAndMut {
999                                                                ty: closure_ty,
1000                                                                mutbl: hir::MutImmutable,
1001                                                            });
1002                         Expr {
1003                             ty: closure_ty,
1004                             temp_lifetime: temp_lifetime,
1005                             span: expr.span,
1006                             kind: ExprKind::Deref {
1007                                 arg: Expr {
1008                                     ty: ref_closure_ty,
1009                                     temp_lifetime,
1010                                     span: expr.span,
1011                                     kind: ExprKind::SelfRef,
1012                                 }
1013                                 .to_ref(),
1014                             },
1015                         }
1016                     }
1017                     ty::ClosureKind::FnMut => {
1018                         let ref_closure_ty = cx.tcx.mk_ref(region,
1019                                                            ty::TypeAndMut {
1020                                                                ty: closure_ty,
1021                                                                mutbl: hir::MutMutable,
1022                                                            });
1023                         Expr {
1024                             ty: closure_ty,
1025                             temp_lifetime,
1026                             span: expr.span,
1027                             kind: ExprKind::Deref {
1028                                 arg: Expr {
1029                                     ty: ref_closure_ty,
1030                                     temp_lifetime,
1031                                     span: expr.span,
1032                                     kind: ExprKind::SelfRef,
1033                                 }.to_ref(),
1034                             },
1035                         }
1036                     }
1037                     ty::ClosureKind::FnOnce => {
1038                         Expr {
1039                             ty: closure_ty,
1040                             temp_lifetime,
1041                             span: expr.span,
1042                             kind: ExprKind::SelfRef,
1043                         }
1044                     }
1045                 }
1046             } else {
1047                 Expr {
1048                     ty: closure_ty,
1049                     temp_lifetime,
1050                     span: expr.span,
1051                     kind: ExprKind::SelfRef,
1052                 }
1053             };
1054
1055             // at this point we have `self.n`, which loads up the upvar
1056             let field_kind = ExprKind::Field {
1057                 lhs: self_expr.to_ref(),
1058                 name: Field::new(index),
1059             };
1060
1061             // ...but the upvar might be an `&T` or `&mut T` capture, at which
1062             // point we need an implicit deref
1063             let upvar_id = ty::UpvarId {
1064                 var_path: ty::UpvarPath {hir_id: var_hir_id},
1065                 closure_expr_id: LocalDefId::from_def_id(closure_def_id),
1066             };
1067             match cx.tables().upvar_capture(upvar_id) {
1068                 ty::UpvarCapture::ByValue => field_kind,
1069                 ty::UpvarCapture::ByRef(borrow) => {
1070                     ExprKind::Deref {
1071                         arg: Expr {
1072                             temp_lifetime,
1073                             ty: cx.tcx.mk_ref(borrow.region,
1074                                               ty::TypeAndMut {
1075                                                   ty: var_ty,
1076                                                   mutbl: borrow.kind.to_mutbl_lossy(),
1077                                               }),
1078                             span: expr.span,
1079                             kind: field_kind,
1080                         }.to_ref(),
1081                     }
1082                 }
1083             }
1084         }
1085
1086         _ => span_bug!(expr.span, "type of & not region"),
1087     }
1088 }
1089
1090
1091 fn bin_op(op: hir::BinOpKind) -> BinOp {
1092     match op {
1093         hir::BinOpKind::Add => BinOp::Add,
1094         hir::BinOpKind::Sub => BinOp::Sub,
1095         hir::BinOpKind::Mul => BinOp::Mul,
1096         hir::BinOpKind::Div => BinOp::Div,
1097         hir::BinOpKind::Rem => BinOp::Rem,
1098         hir::BinOpKind::BitXor => BinOp::BitXor,
1099         hir::BinOpKind::BitAnd => BinOp::BitAnd,
1100         hir::BinOpKind::BitOr => BinOp::BitOr,
1101         hir::BinOpKind::Shl => BinOp::Shl,
1102         hir::BinOpKind::Shr => BinOp::Shr,
1103         hir::BinOpKind::Eq => BinOp::Eq,
1104         hir::BinOpKind::Lt => BinOp::Lt,
1105         hir::BinOpKind::Le => BinOp::Le,
1106         hir::BinOpKind::Ne => BinOp::Ne,
1107         hir::BinOpKind::Ge => BinOp::Ge,
1108         hir::BinOpKind::Gt => BinOp::Gt,
1109         _ => bug!("no equivalent for ast binop {:?}", op),
1110     }
1111 }
1112
1113 fn overloaded_operator<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1114                                        expr: &'tcx hir::Expr,
1115                                        args: Vec<ExprRef<'tcx>>)
1116                                        -> ExprKind<'tcx> {
1117     let fun = method_callee(cx, expr, expr.span, None);
1118     ExprKind::Call {
1119         ty: fun.ty,
1120         fun: fun.to_ref(),
1121         args,
1122         from_hir_call: false,
1123     }
1124 }
1125
1126 fn overloaded_place<'a, 'gcx, 'tcx>(
1127     cx: &mut Cx<'a, 'gcx, 'tcx>,
1128     expr: &'tcx hir::Expr,
1129     place_ty: Ty<'tcx>,
1130     overloaded_callee: Option<(DefId, &'tcx Substs<'tcx>)>,
1131     args: Vec<ExprRef<'tcx>>,
1132 ) -> ExprKind<'tcx> {
1133     // For an overloaded *x or x[y] expression of type T, the method
1134     // call returns an &T and we must add the deref so that the types
1135     // line up (this is because `*x` and `x[y]` represent places):
1136
1137     let recv_ty = match args[0] {
1138         ExprRef::Hair(e) => cx.tables().expr_ty_adjusted(e),
1139         ExprRef::Mirror(ref e) => e.ty
1140     };
1141
1142     // Reconstruct the output assuming it's a reference with the
1143     // same region and mutability as the receiver. This holds for
1144     // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
1145     let (region, mutbl) = match recv_ty.sty {
1146         ty::Ref(region, _, mutbl) => (region, mutbl),
1147         _ => span_bug!(expr.span, "overloaded_place: receiver is not a reference"),
1148     };
1149     let ref_ty = cx.tcx.mk_ref(region, ty::TypeAndMut {
1150         ty: place_ty,
1151         mutbl,
1152     });
1153
1154     // construct the complete expression `foo()` for the overloaded call,
1155     // which will yield the &T type
1156     let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
1157     let fun = method_callee(cx, expr, expr.span, overloaded_callee);
1158     let ref_expr = Expr {
1159         temp_lifetime,
1160         ty: ref_ty,
1161         span: expr.span,
1162         kind: ExprKind::Call {
1163             ty: fun.ty,
1164             fun: fun.to_ref(),
1165             args,
1166             from_hir_call: false,
1167         },
1168     };
1169
1170     // construct and return a deref wrapper `*foo()`
1171     ExprKind::Deref { arg: ref_expr.to_ref() }
1172 }
1173
1174 fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1175                                    closure_expr: &'tcx hir::Expr,
1176                                    freevar: &hir::Freevar,
1177                                    freevar_ty: Ty<'tcx>)
1178                                    -> ExprRef<'tcx> {
1179     let var_hir_id = cx.tcx.hir().node_to_hir_id(freevar.var_id());
1180     let upvar_id = ty::UpvarId {
1181         var_path: ty::UpvarPath { hir_id: var_hir_id },
1182         closure_expr_id: cx.tcx.hir().local_def_id(closure_expr.id).to_local(),
1183     };
1184     let upvar_capture = cx.tables().upvar_capture(upvar_id);
1185     let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
1186     let var_ty = cx.tables().node_id_to_type(var_hir_id);
1187     let captured_var = Expr {
1188         temp_lifetime,
1189         ty: var_ty,
1190         span: closure_expr.span,
1191         kind: convert_var(cx, closure_expr, freevar.def),
1192     };
1193     match upvar_capture {
1194         ty::UpvarCapture::ByValue => captured_var.to_ref(),
1195         ty::UpvarCapture::ByRef(upvar_borrow) => {
1196             let borrow_kind = match upvar_borrow.kind {
1197                 ty::BorrowKind::ImmBorrow => BorrowKind::Shared,
1198                 ty::BorrowKind::UniqueImmBorrow => BorrowKind::Unique,
1199                 ty::BorrowKind::MutBorrow => BorrowKind::Mut { allow_two_phase_borrow: false }
1200             };
1201             Expr {
1202                 temp_lifetime,
1203                 ty: freevar_ty,
1204                 span: closure_expr.span,
1205                 kind: ExprKind::Borrow {
1206                     region: upvar_borrow.region,
1207                     borrow_kind,
1208                     arg: captured_var.to_ref(),
1209                 },
1210             }.to_ref()
1211         }
1212     }
1213 }
1214
1215 /// Converts a list of named fields (i.e. for struct-like struct/enum ADTs) into FieldExprRef.
1216 fn field_refs<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
1217                               fields: &'tcx [hir::Field])
1218                               -> Vec<FieldExprRef<'tcx>> {
1219     fields.iter()
1220         .map(|field| {
1221             FieldExprRef {
1222                 name: Field::new(cx.tcx.field_index(field.id, cx.tables)),
1223                 expr: field.expr.to_ref(),
1224             }
1225         })
1226         .collect()
1227 }