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 intercrate(&self) -> bool {
36 self.fields.infcx.intercrate
39 fn param_env(&self) -> ty::ParamEnv<'tcx> {
43 fn a_is_expected(&self) -> bool {
47 fn mark_ambiguous(&mut self) {
48 self.fields.mark_ambiguous();
51 fn relate_item_substs(
54 a_subst: SubstsRef<'tcx>,
55 b_subst: SubstsRef<'tcx>,
56 ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
57 // N.B., once we are equating types, we don't care about
58 // variance, so don't try to lookup the variance here. This
59 // also avoids some cycles (e.g., #41849) since looking up
60 // variance requires computing types which can require
61 // performing trait matching (which then performs equality
64 relate::relate_substs(self, a_subst, b_subst)
67 fn relate_with_variance<T: Relate<'tcx>>(
70 _info: ty::VarianceDiagInfo<'tcx>,
73 ) -> RelateResult<'tcx, T> {
77 #[instrument(skip(self), level = "debug")]
78 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
83 trace!(a = ?a.kind(), b = ?b.kind());
85 let infcx = self.fields.infcx;
87 let a = infcx.inner.borrow_mut().type_variables().replace_if_possible(a);
88 let b = infcx.inner.borrow_mut().type_variables().replace_if_possible(b);
90 match (a.kind(), b.kind()) {
91 (&ty::Infer(TyVar(a_id)), &ty::Infer(TyVar(b_id))) => {
92 infcx.inner.borrow_mut().type_variables().equate(a_id, b_id);
95 (&ty::Infer(TyVar(a_id)), _) => {
96 self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?;
99 (_, &ty::Infer(TyVar(b_id))) => {
100 self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?;
104 &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, .. }),
105 &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }),
106 ) if a_def_id == b_def_id => {
107 self.fields.infcx.super_combine_tys(self, a, b)?;
109 (&ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }), _)
110 | (_, &ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }))
111 if self.fields.define_opaque_types && def_id.is_local() =>
113 self.fields.obligations.extend(
118 self.a_is_expected(),
119 &self.fields.trace.cause,
125 // Optimization of GeneratorWitness relation since we know that all
126 // free regions are replaced with bound regions during construction.
127 // This greatly speeds up equating of GeneratorWitness.
128 (&ty::GeneratorWitness(a_types), &ty::GeneratorWitness(b_types)) => {
129 let a_types = infcx.tcx.anonymize_bound_vars(a_types);
130 let b_types = infcx.tcx.anonymize_bound_vars(b_types);
131 if a_types.bound_vars() == b_types.bound_vars() {
132 let (a_types, b_types) = infcx.replace_bound_vars_with_placeholders(
133 a_types.map_bound(|a_types| (a_types, b_types.skip_binder())),
135 for (a, b) in std::iter::zip(a_types, b_types) {
139 return Err(ty::error::TypeError::Sorts(ty::relate::expected_found(
146 self.fields.infcx.super_combine_tys(self, a, b)?;
157 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
158 debug!("{}.regions({:?}, {:?})", self.tag(), a, b);
159 let origin = Subtype(Box::new(self.fields.trace.clone()));
164 .unwrap_region_constraints()
165 .make_eqregion(origin, a, b);
173 ) -> RelateResult<'tcx, ty::Const<'tcx>> {
174 self.fields.infcx.super_combine_consts(self, a, b)
179 a: ty::Binder<'tcx, T>,
180 b: ty::Binder<'tcx, T>,
181 ) -> RelateResult<'tcx, ty::Binder<'tcx, T>>
185 // A binder is equal to itself if it's structually equal to itself
190 if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
191 self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
192 self.fields.higher_ranked_sub(b, a, self.a_is_expected)?;
194 // Fast path for the common case.
195 self.relate(a.skip_binder(), b.skip_binder())?;
201 impl<'tcx> ConstEquateRelation<'tcx> for Equate<'_, '_, 'tcx> {
202 fn const_equate_obligation(&mut self, a: ty::Const<'tcx>, b: ty::Const<'tcx>) {
203 self.fields.add_const_equate_obligation(self.a_is_expected, a, b);