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;
13 use super::type_variable::{EqTo};
15 use ty::{self, Ty, TyCtxt};
17 use ty::relate::{Relate, RelateResult, TypeRelation};
19 /// Ensures `a` is made equal to `b`. Returns `a` on success.
20 pub struct Equate<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
21 fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>,
25 impl<'combine, 'infcx, 'gcx, 'tcx> Equate<'combine, 'infcx, 'gcx, 'tcx> {
26 pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool)
27 -> Equate<'combine, 'infcx, 'gcx, 'tcx>
29 Equate { fields: fields, a_is_expected: a_is_expected }
33 impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
34 for Equate<'combine, 'infcx, 'gcx, 'tcx>
36 fn tag(&self) -> &'static str { "Equate" }
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,
46 -> RelateResult<'tcx, T>
51 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
52 debug!("{}.tys({:?}, {:?})", self.tag(),
54 if a == b { return Ok(a); }
56 let infcx = self.fields.infcx;
57 let a = infcx.type_variables.borrow_mut().replace_if_possible(a);
58 let b = infcx.type_variables.borrow_mut().replace_if_possible(b);
59 match (&a.sty, &b.sty) {
60 (&ty::TyInfer(TyVar(a_id)), &ty::TyInfer(TyVar(b_id))) => {
61 infcx.type_variables.borrow_mut().relate_vars(a_id, EqTo, b_id);
65 (&ty::TyInfer(TyVar(a_id)), _) => {
66 self.fields.instantiate(b, EqTo, a_id, self.a_is_expected)?;
70 (_, &ty::TyInfer(TyVar(b_id))) => {
71 self.fields.instantiate(a, EqTo, b_id, self.a_is_expected)?;
76 self.fields.infcx.super_combine_tys(self, a, b)?;
82 fn regions(&mut self, a: &'tcx ty::Region, b: &'tcx ty::Region)
83 -> RelateResult<'tcx, &'tcx ty::Region> {
84 debug!("{}.regions({:?}, {:?})",
88 let origin = Subtype(self.fields.trace.clone());
89 self.fields.infcx.region_vars.make_eqregion(origin, a, b);
93 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
94 -> RelateResult<'tcx, ty::Binder<T>>
97 self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
98 self.fields.higher_ranked_sub(b, a, self.a_is_expected)