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
use super::combine::{self, CombineFields};
use super::higher_ranked::HigherRankedRelations;
use super::Subtype;
use super::type_variable::{SubtypeOf, SupertypeOf};
use middle::ty::{self, Ty};
use middle::ty::TyVar;
use middle::ty_relate::{Relate, RelateResult, TypeRelation};
use util::ppaux::{Repr};
pub struct Sub<'a, 'tcx: 'a> {
fields: CombineFields<'a, 'tcx>
}
impl<'a, 'tcx> Sub<'a, 'tcx> {
pub fn new(f: CombineFields<'a, 'tcx>) -> Sub<'a, 'tcx> {
Sub { fields: f }
}
}
impl<'a, 'tcx> TypeRelation<'a, 'tcx> for Sub<'a, 'tcx> {
fn tag(&self) -> &'static str { "Sub" }
fn tcx(&self) -> &'a ty::ctxt<'tcx> { self.fields.infcx.tcx }
fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
fn relate_with_variance<T:Relate<'a,'tcx>>(&mut self,
variance: ty::Variance,
a: &T,
b: &T)
-> RelateResult<'tcx, T>
{
match variance {
ty::Invariant => self.fields.equate().relate(a, b),
ty::Covariant => self.relate(a, b),
ty::Bivariant => self.fields.bivariate().relate(a, b),
ty::Contravariant => self.fields.switch_expected().sub().relate(b, a),
}
}
fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
debug!("{}.tys({}, {})", self.tag(), a.repr(self.tcx()), b.repr(self.tcx()));
if a == b { return Ok(a); }
let infcx = self.fields.infcx;
let a = infcx.type_variables.borrow().replace_if_possible(a);
let b = infcx.type_variables.borrow().replace_if_possible(b);
match (&a.sty, &b.sty) {
(&ty::ty_infer(TyVar(a_id)), &ty::ty_infer(TyVar(b_id))) => {
infcx.type_variables
.borrow_mut()
.relate_vars(a_id, SubtypeOf, b_id);
Ok(a)
}
(&ty::ty_infer(TyVar(a_id)), _) => {
try!(self.fields
.switch_expected()
.instantiate(b, SupertypeOf, a_id));
Ok(a)
}
(_, &ty::ty_infer(TyVar(b_id))) => {
try!(self.fields.instantiate(a, SubtypeOf, b_id));
Ok(a)
}
(&ty::ty_err, _) | (_, &ty::ty_err) => {
Ok(self.tcx().types.err)
}
_ => {
combine::super_combine_tys(self.fields.infcx, self, a, b)
}
}
}
fn regions(&mut self, a: ty::Region, b: ty::Region) -> RelateResult<'tcx, ty::Region> {
debug!("{}.regions({}, {})",
self.tag(),
a.repr(self.tcx()),
b.repr(self.tcx()));
let origin = Subtype(self.fields.trace.clone());
self.fields.infcx.region_vars.make_subregion(origin, a, b);
Ok(a)
}
fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
-> RelateResult<'tcx, ty::Binder<T>>
where T: Relate<'a,'tcx>
{
self.fields.higher_ranked_sub(a, b)
}
}