1 // Copyright 2012 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.
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.
11 use super::combine
::CombineFields
;
12 use super::higher_ranked
::HigherRankedRelations
;
14 use super::lattice
::{self, LatticeDir}
;
17 use middle
::ty
::{self, Ty}
;
18 use middle
::ty
::relate
::{Relate, RelateResult, TypeRelation}
;
20 /// "Greatest lower bound" (common subtype)
21 pub struct Glb
<'a
, 'tcx
: 'a
> {
22 fields
: CombineFields
<'a
, 'tcx
>
25 impl<'a
, 'tcx
> Glb
<'a
, 'tcx
> {
26 pub fn new(fields
: CombineFields
<'a
, 'tcx
>) -> Glb
<'a
, 'tcx
> {
27 Glb { fields: fields }
31 impl<'a
, 'tcx
> TypeRelation
<'a
, 'tcx
> for Glb
<'a
, 'tcx
> {
32 fn tag(&self) -> &'
static str { "Glb" }
34 fn tcx(&self) -> &'a ty
::ctxt
<'tcx
> { self.fields.tcx() }
36 fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
38 fn relate_with_variance
<T
:Relate
<'a
,'tcx
>>(&mut self,
39 variance
: ty
::Variance
,
42 -> RelateResult
<'tcx
, T
>
45 ty
::Invariant
=> self.fields
.equate().relate(a
, b
),
46 ty
::Covariant
=> self.relate(a
, b
),
47 ty
::Bivariant
=> self.fields
.bivariate().relate(a
, b
),
48 ty
::Contravariant
=> self.fields
.lub().relate(a
, b
),
52 fn tys(&mut self, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>) -> RelateResult
<'tcx
, Ty
<'tcx
>> {
53 lattice
::super_lattice_tys(self, a
, b
)
56 fn regions(&mut self, a
: ty
::Region
, b
: ty
::Region
) -> RelateResult
<'tcx
, ty
::Region
> {
57 debug
!("{}.regions({:?}, {:?})",
62 let origin
= Subtype(self.fields
.trace
.clone());
63 Ok(self.fields
.infcx
.region_vars
.glb_regions(origin
, a
, b
))
66 fn binders
<T
>(&mut self, a
: &ty
::Binder
<T
>, b
: &ty
::Binder
<T
>)
67 -> RelateResult
<'tcx
, ty
::Binder
<T
>>
68 where T
: Relate
<'a
, 'tcx
>
70 self.fields
.higher_ranked_glb(a
, b
)
74 impl<'a
, 'tcx
> LatticeDir
<'a
,'tcx
> for Glb
<'a
, 'tcx
> {
75 fn infcx(&self) -> &'a InferCtxt
<'a
,'tcx
> {
79 fn relate_bound(&self, v
: Ty
<'tcx
>, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>) -> RelateResult
<'tcx
, ()> {
80 let mut sub
= self.fields
.sub();
81 try
!(sub
.relate(&v
, &a
));
82 try
!(sub
.relate(&v
, &b
));