| // Copyright 2014 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::{Subtype}; |
| use super::type_variable::{EqTo}; |
| |
| use ty::{self, Ty, TyCtxt}; |
| use ty::TyVar; |
| use ty::relate::{Relate, RelateResult, TypeRelation}; |
| use traits::PredicateObligations; |
| |
| /// Ensures `a` is made equal to `b`. Returns `a` on success. |
| pub struct Equate<'a, 'gcx: 'a+'tcx, 'tcx: 'a> { |
| fields: CombineFields<'a, 'gcx, 'tcx> |
| } |
| |
| impl<'a, 'gcx, 'tcx> Equate<'a, 'gcx, 'tcx> { |
| pub fn new(fields: CombineFields<'a, 'gcx, 'tcx>) -> Equate<'a, 'gcx, 'tcx> { |
| Equate { fields: fields } |
| } |
| |
| pub fn obligations(self) -> PredicateObligations<'tcx> { |
| self.fields.obligations |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> TypeRelation<'a, 'gcx, 'tcx> for Equate<'a, 'gcx, 'tcx> { |
| fn tag(&self) -> &'static str { "Equate" } |
| |
| 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, |
| _: ty::Variance, |
| a: &T, |
| b: &T) |
| -> RelateResult<'tcx, T> |
| { |
| self.relate(a, b) |
| } |
| |
| fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { |
| debug!("{}.tys({:?}, {:?})", self.tag(), |
| a, b); |
| if a == b { return Ok(a); } |
| |
| let infcx = self.fields.infcx; |
| let a = infcx.type_variables.borrow_mut().replace_if_possible(a); |
| let b = infcx.type_variables.borrow_mut().replace_if_possible(b); |
| match (&a.sty, &b.sty) { |
| (&ty::TyInfer(TyVar(a_id)), &ty::TyInfer(TyVar(b_id))) => { |
| infcx.type_variables.borrow_mut().relate_vars(a_id, EqTo, b_id); |
| Ok(a) |
| } |
| |
| (&ty::TyInfer(TyVar(a_id)), _) => { |
| self.fields.instantiate(b, EqTo, a_id)?; |
| Ok(a) |
| } |
| |
| (_, &ty::TyInfer(TyVar(b_id))) => { |
| self.fields.instantiate(a, EqTo, b_id)?; |
| Ok(a) |
| } |
| |
| _ => { |
| self.fields.infcx.super_combine_tys(self, a, b)?; |
| Ok(a) |
| } |
| } |
| } |
| |
| 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()); |
| self.fields.infcx.region_vars.make_eqregion(origin, a, b); |
| Ok(a) |
| } |
| |
| 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_sub(a, b)?; |
| self.fields.higher_ranked_sub(b, a) |
| } |
| } |