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.
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
::{self, CombineFields}
;
12 use super::higher_ranked
::HigherRankedRelations
;
14 use super::type_variable
::{EqTo}
;
16 use middle
::ty
::{self, Ty}
;
17 use middle
::ty
::TyVar
;
18 use middle
::ty
::relate
::{Relate, RelateResult, TypeRelation}
;
20 /// Ensures `a` is made equal to `b`. Returns `a` on success.
21 pub struct Equate
<'a
, 'tcx
: 'a
> {
22 fields
: CombineFields
<'a
, 'tcx
>
25 impl<'a
, 'tcx
> Equate
<'a
, 'tcx
> {
26 pub fn new(fields
: CombineFields
<'a
, 'tcx
>) -> Equate
<'a
, 'tcx
> {
27 Equate { fields: fields }
31 impl<'a
, 'tcx
> TypeRelation
<'a
,'tcx
> for Equate
<'a
, 'tcx
> {
32 fn tag(&self) -> &'
static str { "Equate" }
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,
42 -> RelateResult
<'tcx
, T
>
47 fn tys(&mut self, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>) -> RelateResult
<'tcx
, Ty
<'tcx
>> {
48 debug
!("{}.tys({:?}, {:?})", self.tag(),
50 if a
== b { return Ok(a); }
52 let infcx
= self.fields
.infcx
;
53 let a
= infcx
.type_variables
.borrow().replace_if_possible(a
);
54 let b
= infcx
.type_variables
.borrow().replace_if_possible(b
);
55 match (&a
.sty
, &b
.sty
) {
56 (&ty
::TyInfer(TyVar(a_id
)), &ty
::TyInfer(TyVar(b_id
))) => {
57 infcx
.type_variables
.borrow_mut().relate_vars(a_id
, EqTo
, b_id
);
61 (&ty
::TyInfer(TyVar(a_id
)), _
) => {
62 try
!(self.fields
.instantiate(b
, EqTo
, a_id
));
66 (_
, &ty
::TyInfer(TyVar(b_id
))) => {
67 try
!(self.fields
.instantiate(a
, EqTo
, b_id
));
72 try
!(combine
::super_combine_tys(self.fields
.infcx
, self, a
, b
));
78 fn regions(&mut self, a
: ty
::Region
, b
: ty
::Region
) -> RelateResult
<'tcx
, ty
::Region
> {
79 debug
!("{}.regions({:?}, {:?})",
83 let origin
= Subtype(self.fields
.trace
.clone());
84 self.fields
.infcx
.region_vars
.make_eqregion(origin
, a
, b
);
88 fn binders
<T
>(&mut self, a
: &ty
::Binder
<T
>, b
: &ty
::Binder
<T
>)
89 -> RelateResult
<'tcx
, ty
::Binder
<T
>>
90 where T
: Relate
<'a
, 'tcx
>
92 try
!(self.fields
.higher_ranked_sub(a
, b
));
93 self.fields
.higher_ranked_sub(b
, a
)