| // Copyright 2012 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use super::combine::CombineFields; |
| use super::InferCtxt; |
| use super::lattice::{self, LatticeDir}; |
| use super::Subtype; |
| |
| use ty::{self, Ty, TyCtxt}; |
| use ty::relate::{Relate, RelateResult, TypeRelation}; |
| use traits::PredicateObligations; |
| |
| /// "Least upper bound" (common supertype) |
| pub struct Lub<'a, 'gcx: 'a+'tcx, 'tcx: 'a> { |
| fields: CombineFields<'a, 'gcx, 'tcx> |
| } |
| |
| impl<'a, 'gcx, 'tcx> Lub<'a, 'gcx, 'tcx> { |
| pub fn new(fields: CombineFields<'a, 'gcx, 'tcx>) -> Lub<'a, 'gcx, 'tcx> { |
| Lub { fields: fields } |
| } |
| |
| pub fn obligations(self) -> PredicateObligations<'tcx> { |
| self.fields.obligations |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> TypeRelation<'a, 'gcx, 'tcx> for Lub<'a, 'gcx, 'tcx> { |
| fn tag(&self) -> &'static str { "Lub" } |
| |
| fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> { self.fields.tcx() } |
| |
| fn a_is_expected(&self) -> bool { self.fields.a_is_expected } |
| |
| fn relate_with_variance<T: Relate<'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, |
| b); |
| |
| 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<'tcx> |
| { |
| self.fields.higher_ranked_lub(a, b) |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> LatticeDir<'a, 'gcx, 'tcx> for Lub<'a, 'gcx, 'tcx> { |
| fn infcx(&self) -> &'a InferCtxt<'a, 'gcx, '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(); |
| sub.relate(&a, &v)?; |
| sub.relate(&b, &v)?; |
| Ok(()) |
| } |
| } |