1 use super::combine::{CombineFields, ConstEquateRelation, RelationDir};
4 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
5 use rustc_middle::ty::subst::SubstsRef;
6 use rustc_middle::ty::TyVar;
7 use rustc_middle::ty::{self, Ty, TyCtxt};
9 use rustc_hir::def_id::DefId;
11 /// Ensures `a` is made equal to `b`. Returns `a` on success.
12 pub struct Equate<'combine, 'infcx, 'tcx> {
13 fields: &'combine mut CombineFields<'infcx, 'tcx>,
17 impl<'combine, 'infcx, 'tcx> Equate<'combine, 'infcx, 'tcx> {
19 fields: &'combine mut CombineFields<'infcx, 'tcx>,
21 ) -> Equate<'combine, 'infcx, 'tcx> {
22 Equate { fields, a_is_expected }
26 impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
27 fn tag(&self) -> &'static str {
31 fn tcx(&self) -> TyCtxt<'tcx> {
35 fn param_env(&self) -> ty::ParamEnv<'tcx> {
39 fn a_is_expected(&self) -> bool {
43 fn relate_item_substs(
46 a_subst: SubstsRef<'tcx>,
47 b_subst: SubstsRef<'tcx>,
48 ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
49 // N.B., once we are equating types, we don't care about
50 // variance, so don't try to lookup the variance here. This
51 // also avoids some cycles (e.g., #41849) since looking up
52 // variance requires computing types which can require
53 // performing trait matching (which then performs equality
56 relate::relate_substs(self, None, a_subst, b_subst)
59 fn relate_with_variance<T: Relate<'tcx>>(
62 _info: ty::VarianceDiagInfo<'tcx>,
65 ) -> RelateResult<'tcx, T> {
69 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
70 debug!("{}.tys({:?}, {:?})", self.tag(), a, b);
75 let infcx = self.fields.infcx;
76 let a = infcx.inner.borrow_mut().type_variables().replace_if_possible(a);
77 let b = infcx.inner.borrow_mut().type_variables().replace_if_possible(b);
79 debug!("{}.tys: replacements ({:?}, {:?})", self.tag(), a, b);
81 match (a.kind(), b.kind()) {
82 (&ty::Infer(TyVar(a_id)), &ty::Infer(TyVar(b_id))) => {
83 infcx.inner.borrow_mut().type_variables().equate(a_id, b_id);
86 (&ty::Infer(TyVar(a_id)), _) => {
87 self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?;
90 (_, &ty::Infer(TyVar(b_id))) => {
91 self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?;
95 self.fields.infcx.super_combine_tys(self, a, b)?;
106 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
107 debug!("{}.regions({:?}, {:?})", self.tag(), a, b);
108 let origin = Subtype(Box::new(self.fields.trace.clone()));
113 .unwrap_region_constraints()
114 .make_eqregion(origin, a, b);
122 ) -> RelateResult<'tcx, ty::Const<'tcx>> {
123 self.fields.infcx.super_combine_consts(self, a, b)
128 a: ty::Binder<'tcx, T>,
129 b: ty::Binder<'tcx, T>,
130 ) -> RelateResult<'tcx, ty::Binder<'tcx, T>>
134 if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
135 self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
136 self.fields.higher_ranked_sub(b, a, self.a_is_expected)
138 // Fast path for the common case.
139 self.relate(a.skip_binder(), b.skip_binder())?;
145 impl<'tcx> ConstEquateRelation<'tcx> for Equate<'_, '_, 'tcx> {
146 fn const_equate_obligation(&mut self, a: ty::Const<'tcx>, b: ty::Const<'tcx>) {
147 self.fields.add_const_equate_obligation(self.a_is_expected, a, b);