1 // Copyright 2014 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, RelationDir};
14 use ty::{self, Ty, TyCtxt};
16 use ty::relate::{Relate, RelateResult, TypeRelation};
18 /// Ensures `a` is made equal to `b`. Returns `a` on success.
19 pub struct Equate<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
20 fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>,
24 impl<'combine, 'infcx, 'gcx, 'tcx> Equate<'combine, 'infcx, 'gcx, 'tcx> {
25 pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool)
26 -> Equate<'combine, 'infcx, 'gcx, 'tcx>
28 Equate { fields: fields, a_is_expected: a_is_expected }
32 impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
33 for Equate<'combine, 'infcx, 'gcx, 'tcx>
35 fn tag(&self) -> &'static str { "Equate" }
37 fn tcx(&self) -> TyCtxt<'infcx, 'gcx, 'tcx> { self.fields.tcx() }
39 fn a_is_expected(&self) -> bool { self.a_is_expected }
41 fn relate_with_variance<T: Relate<'tcx>>(&mut self,
45 -> RelateResult<'tcx, T>
50 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
51 debug!("{}.tys({:?}, {:?})", self.tag(),
53 if a == b { return Ok(a); }
55 let infcx = self.fields.infcx;
56 let a = infcx.type_variables.borrow_mut().replace_if_possible(a);
57 let b = infcx.type_variables.borrow_mut().replace_if_possible(b);
58 match (&a.sty, &b.sty) {
59 (&ty::TyInfer(TyVar(a_id)), &ty::TyInfer(TyVar(b_id))) => {
60 infcx.type_variables.borrow_mut().equate(a_id, b_id);
64 (&ty::TyInfer(TyVar(a_id)), _) => {
65 self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?;
69 (_, &ty::TyInfer(TyVar(b_id))) => {
70 self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?;
75 self.fields.infcx.super_combine_tys(self, a, b)?;
81 fn regions(&mut self, a: &'tcx ty::Region, b: &'tcx ty::Region)
82 -> RelateResult<'tcx, &'tcx ty::Region> {
83 debug!("{}.regions({:?}, {:?})",
87 let origin = Subtype(self.fields.trace.clone());
88 self.fields.infcx.region_vars.make_eqregion(origin, a, b);
92 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
93 -> RelateResult<'tcx, ty::Binder<T>>
96 self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
97 self.fields.higher_ranked_sub(b, a, self.a_is_expected)