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};
19 use util::ppaux::Repr;
21 /// "Least upper bound" (common supertype)
22 pub struct Lub<'a, 'tcx: 'a> {
23 fields: CombineFields<'a, 'tcx>
26 impl<'a, 'tcx> Lub<'a, 'tcx> {
27 pub fn new(fields: CombineFields<'a, 'tcx>) -> Lub<'a, 'tcx> {
28 Lub { fields: fields }
32 impl<'a, 'tcx> TypeRelation<'a, 'tcx> for Lub<'a, 'tcx> {
33 fn tag(&self) -> &'static str { "Lub" }
35 fn tcx(&self) -> &'a ty::ctxt<'tcx> { self.fields.tcx() }
37 fn a_is_expected(&self) -> bool { self.fields.a_is_expected }
39 fn relate_with_variance<T:Relate<'a,'tcx>>(&mut self,
40 variance: ty::Variance,
43 -> RelateResult<'tcx, T>
46 ty::Invariant => self.fields.equate().relate(a, b),
47 ty::Covariant => self.relate(a, b),
48 ty::Bivariant => self.fields.bivariate().relate(a, b),
49 ty::Contravariant => self.fields.glb().relate(a, b),
53 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
54 lattice::super_lattice_tys(self, a, b)
57 fn regions(&mut self, a: ty::Region, b: ty::Region) -> RelateResult<'tcx, ty::Region> {
58 debug!("{}.regions({}, {})",
63 let origin = Subtype(self.fields.trace.clone());
64 Ok(self.fields.infcx.region_vars.lub_regions(origin, a, b))
67 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
68 -> RelateResult<'tcx, ty::Binder<T>>
69 where T: Relate<'a, 'tcx>
71 self.fields.higher_ranked_lub(a, b)
75 impl<'a, 'tcx> LatticeDir<'a,'tcx> for Lub<'a, 'tcx> {
76 fn infcx(&self) -> &'a InferCtxt<'a,'tcx> {
80 fn relate_bound(&self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()> {
81 let mut sub = self.fields.sub();
82 try!(sub.relate(&a, &v));
83 try!(sub.relate(&b, &v));