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 hir::def_id::DefId;
16 use ty::{self, Ty, TyCtxt};
18 use ty::subst::Substs;
19 use ty::relate::{self, Relate, RelateResult, TypeRelation};
21 /// Ensures `a` is made equal to `b`. Returns `a` on success.
22 pub struct Equate<'combine, 'infcx: 'combine, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
23 fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>,
27 impl<'combine, 'infcx, 'gcx, 'tcx> Equate<'combine, 'infcx, 'gcx, 'tcx> {
28 pub fn new(fields: &'combine mut CombineFields<'infcx, 'gcx, 'tcx>, a_is_expected: bool)
29 -> Equate<'combine, 'infcx, 'gcx, 'tcx>
31 Equate { fields: fields, a_is_expected: a_is_expected }
35 impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
36 for Equate<'combine, 'infcx, 'gcx, 'tcx>
38 fn tag(&self) -> &'static str { "Equate" }
40 fn tcx(&self) -> TyCtxt<'infcx, 'gcx, 'tcx> { self.fields.tcx() }
42 fn a_is_expected(&self) -> bool { self.a_is_expected }
44 fn relate_item_substs(&mut self,
46 a_subst: &'tcx Substs<'tcx>,
47 b_subst: &'tcx Substs<'tcx>)
48 -> RelateResult<'tcx, &'tcx Substs<'tcx>>
50 // NB: Once we are equating types, we don't care about
51 // variance, so don't try to lookup the variance here. This
52 // also avoids some cycles (e.g. #41849) since looking up
53 // variance requires computing types which can require
54 // performing trait matching (which then performs equality
57 relate::relate_substs(self, None, a_subst, b_subst)
60 fn relate_with_variance<T: Relate<'tcx>>(&mut self,
64 -> RelateResult<'tcx, T>
69 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
70 debug!("{}.tys({:?}, {:?})", self.tag(),
72 if a == b { return Ok(a); }
74 let infcx = self.fields.infcx;
75 let a = infcx.type_variables.borrow_mut().replace_if_possible(a);
76 let b = infcx.type_variables.borrow_mut().replace_if_possible(b);
78 debug!("{}.tys: replacements ({:?}, {:?})", self.tag(), a, b);
80 match (&a.sty, &b.sty) {
81 (&ty::Infer(TyVar(a_id)), &ty::Infer(TyVar(b_id))) => {
82 infcx.type_variables.borrow_mut().equate(a_id, b_id);
85 (&ty::Infer(TyVar(a_id)), _) => {
86 self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?;
89 (_, &ty::Infer(TyVar(b_id))) => {
90 self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?;
94 self.fields.infcx.super_combine_tys(self, a, b)?;
101 fn regions(&mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>)
102 -> RelateResult<'tcx, ty::Region<'tcx>> {
103 debug!("{}.regions({:?}, {:?})",
107 let origin = Subtype(self.fields.trace.clone());
108 self.fields.infcx.borrow_region_constraints()
109 .make_eqregion(origin, a, b);
113 fn binders<T>(&mut self, a: &ty::Binder<T>, b: &ty::Binder<T>)
114 -> RelateResult<'tcx, ty::Binder<T>>
115 where T: Relate<'tcx>
117 self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
118 self.fields.higher_ranked_sub(b, a, self.a_is_expected)