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use super::combine::{CombineFields, ConstEquateRelation, RelationDir};
use super::Subtype;
use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::TyVar;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_hir::def_id::DefId;
/// Ensures `a` is made equal to `b`. Returns `a` on success.
pub struct Equate<'combine, 'infcx, 'tcx> {
fields: &'combine mut CombineFields<'infcx, 'tcx>,
a_is_expected: bool,
}
impl<'combine, 'infcx, 'tcx> Equate<'combine, 'infcx, 'tcx> {
pub fn new(
fields: &'combine mut CombineFields<'infcx, 'tcx>,
a_is_expected: bool,
) -> Equate<'combine, 'infcx, 'tcx> {
Equate { fields, a_is_expected }
}
}
impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
fn tag(&self) -> &'static str {
"Equate"
}
fn tcx(&self) -> TyCtxt<'tcx> {
self.fields.tcx()
}
fn param_env(&self) -> ty::ParamEnv<'tcx> {
self.fields.param_env
}
fn a_is_expected(&self) -> bool {
self.a_is_expected
}
fn relate_item_substs(
&mut self,
_item_def_id: DefId,
a_subst: SubstsRef<'tcx>,
b_subst: SubstsRef<'tcx>,
) -> RelateResult<'tcx, SubstsRef<'tcx>> {
// N.B., once we are equating types, we don't care about
// variance, so don't try to lookup the variance here. This
// also avoids some cycles (e.g., #41849) since looking up
// variance requires computing types which can require
// performing trait matching (which then performs equality
// unification).
relate::relate_substs(self, a_subst, b_subst)
}
fn relate_with_variance<T: Relate<'tcx>>(
&mut self,
_: ty::Variance,
_info: ty::VarianceDiagInfo<'tcx>,
a: T,
b: T,
) -> RelateResult<'tcx, T> {
self.relate(a, b)
}
#[instrument(skip(self), level = "debug")]
fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
if a == b {
return Ok(a);
}
trace!(a = ?a.kind(), b = ?b.kind());
let infcx = self.fields.infcx;
let a = infcx.inner.borrow_mut().type_variables().replace_if_possible(a);
let b = infcx.inner.borrow_mut().type_variables().replace_if_possible(b);
match (a.kind(), b.kind()) {
(&ty::Infer(TyVar(a_id)), &ty::Infer(TyVar(b_id))) => {
infcx.inner.borrow_mut().type_variables().equate(a_id, b_id);
}
(&ty::Infer(TyVar(a_id)), _) => {
self.fields.instantiate(b, RelationDir::EqTo, a_id, self.a_is_expected)?;
}
(_, &ty::Infer(TyVar(b_id))) => {
self.fields.instantiate(a, RelationDir::EqTo, b_id, self.a_is_expected)?;
}
(&ty::Opaque(a_def_id, _), &ty::Opaque(b_def_id, _)) if a_def_id == b_def_id => {
self.fields.infcx.super_combine_tys(self, a, b)?;
}
(&ty::Opaque(did, ..), _) | (_, &ty::Opaque(did, ..))
if self.fields.define_opaque_types && did.is_local() =>
{
self.fields.obligations.extend(
infcx
.handle_opaque_type(
a,
b,
self.a_is_expected(),
&self.fields.trace.cause,
self.param_env(),
)?
.obligations,
);
}
_ => {
self.fields.infcx.super_combine_tys(self, a, b)?;
}
}
Ok(a)
}
fn regions(
&mut self,
a: ty::Region<'tcx>,
b: ty::Region<'tcx>,
) -> RelateResult<'tcx, ty::Region<'tcx>> {
debug!("{}.regions({:?}, {:?})", self.tag(), a, b);
let origin = Subtype(Box::new(self.fields.trace.clone()));
self.fields
.infcx
.inner
.borrow_mut()
.unwrap_region_constraints()
.make_eqregion(origin, a, b);
Ok(a)
}
fn consts(
&mut self,
a: ty::Const<'tcx>,
b: ty::Const<'tcx>,
) -> RelateResult<'tcx, ty::Const<'tcx>> {
self.fields.infcx.super_combine_consts(self, a, b)
}
fn binders<T>(
&mut self,
a: ty::Binder<'tcx, T>,
b: ty::Binder<'tcx, T>,
) -> RelateResult<'tcx, ty::Binder<'tcx, T>>
where
T: Relate<'tcx>,
{
if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
self.fields.higher_ranked_sub(a, b, self.a_is_expected)?;
self.fields.higher_ranked_sub(b, a, self.a_is_expected)?;
} else {
// Fast path for the common case.
self.relate(a.skip_binder(), b.skip_binder())?;
}
Ok(a)
}
}
impl<'tcx> ConstEquateRelation<'tcx> for Equate<'_, '_, 'tcx> {
fn const_equate_obligation(&mut self, a: ty::Const<'tcx>, b: ty::Const<'tcx>) {
self.fields.add_const_equate_obligation(self.a_is_expected, a, b);
}
}
|
