use crate::query::Providers;
use crate::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use crate::ty::{self, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
pub(super) fn provide(providers: &mut Providers) {
*providers = Providers { erase_regions_ty, ..*providers };
}
fn erase_regions_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
ty.super_fold_with(&mut RegionEraserVisitor { tcx })
}
impl<'tcx> TyCtxt<'tcx> {
pub fn erase_regions<T>(self, value: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if !value.has_type_flags(TypeFlags::HAS_LATE_BOUND | TypeFlags::HAS_FREE_REGIONS) {
return value;
}
debug!("erase_regions({:?})", value);
let value1 = value.fold_with(&mut RegionEraserVisitor { tcx: self });
debug!("erase_regions = {:?}", value1);
value1
}
}
struct RegionEraserVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
if ty.has_infer() { ty.super_fold_with(self) } else { self.tcx.erase_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> {
match *r {
ty::ReLateBound(..) => r,
_ => self.tcx.lifetimes.re_erased,
}
}
}