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;
13 use super::lattice::{self, LatticeDir};
16 use ty::{self, Ty, TyCtxt};
17 use ty::relate::{Relate, RelateResult, TypeRelation};
19 /// "Least upper bound" (common supertype)
20 pub struct Lub<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
21 fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>,
25 impl<'combine, 'infcx, 'gcx, 'tcx> Lub<'combine, 'infcx, 'gcx, 'tcx> {
26 pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool)
27 -> Lub<'combine, 'infcx, 'gcx, 'tcx>
29 Lub { fields: fields, a_is_expected: a_is_expected }
33 impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
34 for Lub<'combine, 'infcx, 'gcx, 'tcx>
36 fn tag(&self) -> &'static str { "Lub" }
38 fn tcx(&self) -> TyCtxt<'infcx, 'gcx, 'tcx> { self.fields.tcx() }
40 fn a_is_expected(&self) -> bool { self.a_is_expected }
42 fn relate_with_variance<T: Relate<'tcx>>(&mut self,
43 variance: ty::Variance,
46 -> RelateResult<'tcx, T>
49 ty::Invariant => self.fields.equate(self.a_is_expected).relate(a, b),
50 ty::Covariant => self.relate(a, b),
51 ty::Bivariant => self.fields.bivariate(self.a_is_expected).relate(a, b),
52 ty::Contravariant => self.fields.glb(self.a_is_expected).relate(a, b),
56 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
57 lattice::super_lattice_tys(self, a, b)
60 fn regions(&mut self, a: ty::Region, b: ty::Region) -> RelateResult<'tcx, ty::Region> {
61 debug!("{}.regions({:?}, {:?})",
66 let origin = Subtype(self.fields.trace.clone());
67 Ok(self.fields.infcx.region_vars.lub_regions(origin, a, b))
70 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
71 -> RelateResult<'tcx, ty::Binder<T>>
74 self.fields.higher_ranked_lub(a, b, self.a_is_expected)
78 impl<'combine, 'infcx, 'gcx, 'tcx> LatticeDir<'infcx, 'gcx, 'tcx>
79 for Lub<'combine, 'infcx, 'gcx, 'tcx>
81 fn infcx(&self) -> &'infcx InferCtxt<'infcx, 'gcx, 'tcx> {
85 fn relate_bound(&mut self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()> {
86 let mut sub = self.fields.sub(self.a_is_expected);