1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
use super::combine::CombineFields;
use super::type_variable::{BiTo};
use ty::{self, Ty, TyCtxt};
use ty::TyVar;
use ty::relate::{Relate, RelateResult, TypeRelation};
pub struct Bivariate<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>,
a_is_expected: bool,
}
impl<'combine, 'infcx, 'gcx, 'tcx> Bivariate<'combine, 'infcx, 'gcx, 'tcx> {
pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool)
-> Bivariate<'combine, 'infcx, 'gcx, 'tcx>
{
Bivariate { fields: fields, a_is_expected: a_is_expected }
}
}
impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
for Bivariate<'combine, 'infcx, 'gcx, 'tcx>
{
fn tag(&self) -> &'static str { "Bivariate" }
fn tcx(&self) -> TyCtxt<'infcx, 'gcx, 'tcx> { self.fields.tcx() }
fn a_is_expected(&self) -> bool { self.a_is_expected }
fn relate_with_variance<T: Relate<'tcx>>(&mut self,
variance: ty::Variance,
a: &T,
b: &T)
-> RelateResult<'tcx, T>
{
match variance {
ty::Invariant => self.relate(a, b),
ty::Covariant => self.relate(a, b),
ty::Bivariant => self.relate(a, b),
ty::Contravariant => self.relate(a, b),
}
}
fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
debug!("{}.tys({:?}, {:?})", self.tag(),
a, b);
if a == b { return Ok(a); }
let infcx = self.fields.infcx;
let a = infcx.type_variables.borrow_mut().replace_if_possible(a);
let b = infcx.type_variables.borrow_mut().replace_if_possible(b);
match (&a.sty, &b.sty) {
(&ty::TyInfer(TyVar(a_id)), &ty::TyInfer(TyVar(b_id))) => {
infcx.type_variables.borrow_mut().relate_vars(a_id, BiTo, b_id);
Ok(a)
}
(&ty::TyInfer(TyVar(a_id)), _) => {
self.fields.instantiate(b, BiTo, a_id, self.a_is_expected)?;
Ok(a)
}
(_, &ty::TyInfer(TyVar(b_id))) => {
self.fields.instantiate(a, BiTo, b_id, self.a_is_expected)?;
Ok(a)
}
_ => {
self.fields.infcx.super_combine_tys(self, a, b)
}
}
}
fn regions(&mut self, a: &'tcx ty::Region, _: &'tcx ty::Region)
-> RelateResult<'tcx, &'tcx ty::Region> {
Ok(a)
}
fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
-> RelateResult<'tcx, ty::Binder<T>>
where T: Relate<'tcx>
{
let a1 = self.tcx().erase_late_bound_regions(a);
let b1 = self.tcx().erase_late_bound_regions(b);
let c = self.relate(&a1, &b1)?;
Ok(ty::Binder(c))
}
}