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1a4d82fc JJ |
1 | // Copyright 2014 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 | ||
cc61c64b | 11 | use super::combine::{CombineFields, RelationDir}; |
c34b1796 | 12 | use super::{Subtype}; |
cc61c64b XL |
13 | |
14 | use hir::def_id::DefId; | |
c34b1796 | 15 | |
54a0048b SL |
16 | use ty::{self, Ty, TyCtxt}; |
17 | use ty::TyVar; | |
cc61c64b XL |
18 | use ty::subst::Substs; |
19 | use ty::relate::{self, Relate, RelateResult, TypeRelation}; | |
1a4d82fc | 20 | |
b039eaaf | 21 | /// Ensures `a` is made equal to `b`. Returns `a` on success. |
5bcae85e SL |
22 | pub struct Equate<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> { |
23 | fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, | |
24 | a_is_expected: bool, | |
1a4d82fc JJ |
25 | } |
26 | ||
5bcae85e SL |
27 | impl<'combine, 'infcx, 'gcx, 'tcx> Equate<'combine, 'infcx, 'gcx, 'tcx> { |
28 | pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool) | |
29 | -> Equate<'combine, 'infcx, 'gcx, 'tcx> | |
30 | { | |
31 | Equate { fields: fields, a_is_expected: a_is_expected } | |
54a0048b | 32 | } |
c34b1796 | 33 | } |
1a4d82fc | 34 | |
5bcae85e SL |
35 | impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx> |
36 | for Equate<'combine, 'infcx, 'gcx, 'tcx> | |
37 | { | |
c34b1796 | 38 | fn tag(&self) -> &'static str { "Equate" } |
1a4d82fc | 39 | |
5bcae85e | 40 | fn tcx(&self) -> TyCtxt<'infcx, 'gcx, 'tcx> { self.fields.tcx() } |
1a4d82fc | 41 | |
5bcae85e | 42 | fn a_is_expected(&self) -> bool { self.a_is_expected } |
1a4d82fc | 43 | |
cc61c64b XL |
44 | fn relate_item_substs(&mut self, |
45 | _item_def_id: DefId, | |
46 | a_subst: &'tcx Substs<'tcx>, | |
47 | b_subst: &'tcx Substs<'tcx>) | |
48 | -> RelateResult<'tcx, &'tcx Substs<'tcx>> | |
49 | { | |
50 | // NB: Once we are equating types, we don't care about | |
51 | // variance, so don't try to lookup the variance here. This | |
52 | // also avoids some cycles (e.g. #41849) since looking up | |
53 | // variance requires computing types which can require | |
54 | // performing trait matching (which then performs equality | |
55 | // unification). | |
56 | ||
57 | relate::relate_substs(self, None, a_subst, b_subst) | |
58 | } | |
59 | ||
a7813a04 XL |
60 | fn relate_with_variance<T: Relate<'tcx>>(&mut self, |
61 | _: ty::Variance, | |
62 | a: &T, | |
63 | b: &T) | |
64 | -> RelateResult<'tcx, T> | |
1a4d82fc | 65 | { |
c34b1796 | 66 | self.relate(a, b) |
1a4d82fc JJ |
67 | } |
68 | ||
c34b1796 | 69 | fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { |
62682a34 SL |
70 | debug!("{}.tys({:?}, {:?})", self.tag(), |
71 | a, b); | |
1a4d82fc JJ |
72 | if a == b { return Ok(a); } |
73 | ||
74 | let infcx = self.fields.infcx; | |
54a0048b SL |
75 | let a = infcx.type_variables.borrow_mut().replace_if_possible(a); |
76 | let b = infcx.type_variables.borrow_mut().replace_if_possible(b); | |
1a4d82fc | 77 | match (&a.sty, &b.sty) { |
62682a34 | 78 | (&ty::TyInfer(TyVar(a_id)), &ty::TyInfer(TyVar(b_id))) => { |
cc61c64b | 79 | infcx.type_variables.borrow_mut().equate(a_id, b_id); |
1a4d82fc JJ |
80 | Ok(a) |
81 | } | |
82 | ||
62682a34 | 83 | (&ty::TyInfer(TyVar(a_id)), _) => { |
cc61c64b | 84 | self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?; |
1a4d82fc JJ |
85 | Ok(a) |
86 | } | |
87 | ||
62682a34 | 88 | (_, &ty::TyInfer(TyVar(b_id))) => { |
cc61c64b | 89 | self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?; |
1a4d82fc JJ |
90 | Ok(a) |
91 | } | |
92 | ||
93 | _ => { | |
a7813a04 | 94 | self.fields.infcx.super_combine_tys(self, a, b)?; |
b039eaaf | 95 | Ok(a) |
1a4d82fc JJ |
96 | } |
97 | } | |
98 | } | |
99 | ||
7cac9316 XL |
100 | fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>) |
101 | -> RelateResult<'tcx, ty::Region<'tcx>> { | |
62682a34 | 102 | debug!("{}.regions({:?}, {:?})", |
c34b1796 | 103 | self.tag(), |
62682a34 SL |
104 | a, |
105 | b); | |
c34b1796 | 106 | let origin = Subtype(self.fields.trace.clone()); |
abe05a73 XL |
107 | self.fields.infcx.borrow_region_constraints() |
108 | .make_eqregion(origin, a, b); | |
c34b1796 AL |
109 | Ok(a) |
110 | } | |
111 | ||
112 | fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>) | |
113 | -> RelateResult<'tcx, ty::Binder<T>> | |
a7813a04 | 114 | where T: Relate<'tcx> |
1a4d82fc | 115 | { |
5bcae85e SL |
116 | self.fields.higher_ranked_sub(a, b, self.a_is_expected)?; |
117 | self.fields.higher_ranked_sub(b, a, self.a_is_expected) | |
1a4d82fc JJ |
118 | } |
119 | } |