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use tracing::debug;
use crate::query::Providers;
use crate::ty::{
self, Ty, TyCtxt, TypeFlags, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
};
pub(super) fn provide(providers: &mut Providers) {
*providers = Providers { erase_and_anonymize_regions_ty, ..*providers };
}
fn erase_and_anonymize_regions_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
// N.B., use `super_fold_with` here. If we used `fold_with`, it
// could invoke the `erase_and_anonymize_regions_ty` query recursively.
ty.super_fold_with(&mut RegionEraserAndAnonymizerVisitor { tcx })
}
impl<'tcx> TyCtxt<'tcx> {
/// Returns an equivalent value with all free regions removed and
/// bound regions anonymized. (note that bound regions are important
/// for subtyping and generally type equality so *cannot* be removed)
pub fn erase_and_anonymize_regions<T>(self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
// If there's nothing to erase or anonymize, avoid performing the query at all
if !value.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
return value;
}
debug!("erase_and_anonymize_regions({:?})", value);
let value1 = value.fold_with(&mut RegionEraserAndAnonymizerVisitor { tcx: self });
debug!("erase_and_anonymize_regions = {:?}", value1);
value1
}
}
struct RegionEraserAndAnonymizerVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserAndAnonymizerVisitor<'tcx> {
fn cx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
if !ty.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
ty
} else if ty.has_infer() {
ty.super_fold_with(self)
} else {
self.tcx.erase_and_anonymize_regions_ty(ty)
}
}
fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
let u = self.tcx.anonymize_bound_vars(t);
u.super_fold_with(self)
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
// We must not erase bound regions. `for<'a> fn(&'a ())` and
// `fn(&'free ())` are different types: they may implement different
// traits and have a different `TypeId`.
match r.kind() {
ty::ReBound(..) => r,
_ => self.tcx.lifetimes.re_erased,
}
}
fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
if ct.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
ct.super_fold_with(self)
} else {
ct
}
}
fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
if p.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
p.super_fold_with(self)
} else {
p
}
}
fn fold_clauses(&mut self, c: ty::Clauses<'tcx>) -> ty::Clauses<'tcx> {
if c.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
c.super_fold_with(self)
} else {
c
}
}
}
|
