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use super::combine::CombineFields;
use super::higher_ranked::HigherRankedRelations;
use super::InferCtxt;
use super::lattice::{self, LatticeDir};
use super::Subtype;
use middle::ty::{self, Ty};
use middle::ty_relate::{Relate, RelateResult, TypeRelation};
use util::ppaux::Repr;
pub struct Lub<'a, 'tcx: 'a> {
fields: CombineFields<'a, 'tcx>
}
impl<'a, 'tcx> Lub<'a, 'tcx> {
pub fn new(fields: CombineFields<'a, 'tcx>) -> Lub<'a, 'tcx> {
Lub { fields: fields }
}
}
impl<'a, 'tcx> TypeRelation<'a, 'tcx> for Lub<'a, 'tcx> {
fn tag(&self) -> &'static str { "Lub" }
fn tcx(&self) -> &'a ty::ctxt<'tcx> { self.fields.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.glb().relate(a, b),
}
}
fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
lattice::super_lattice_tys(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());
Ok(self.fields.infcx.region_vars.lub_regions(origin, a, b))
}
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_lub(a, b)
}
}
impl<'a, 'tcx> LatticeDir<'a,'tcx> for Lub<'a, 'tcx> {
fn infcx(&self) -> &'a InferCtxt<'a,'tcx> {
self.fields.infcx
}
fn relate_bound(&self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()> {
let mut sub = self.fields.sub();
try!(sub.relate(&a, &v));
try!(sub.relate(&b, &v));
Ok(())
}
}