2 use crate::ty::fold::{TypeFoldable, TypeFolder};
3 use crate::ty::{self, Ty, TyCtxt, TypeFlags};
5 pub(super) fn provide(providers: &mut ty::query::Providers) {
6 *providers = ty::query::Providers { erase_regions_ty, ..*providers };
9 fn erase_regions_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
10 // N.B., use `super_fold_with` here. If we used `fold_with`, it
11 // could invoke the `erase_regions_ty` query recursively.
12 ty.super_fold_with(&mut RegionEraserVisitor { tcx })
15 impl<'tcx> TyCtxt<'tcx> {
16 /// Returns an equivalent value with all free regions removed (note
17 /// that late-bound regions remain, because they are important for
18 /// subtyping, but they are anonymized and normalized as well)..
19 pub fn erase_regions<T>(self, value: T) -> T
21 T: TypeFoldable<'tcx>,
23 // If there's nothing to erase avoid performing the query at all
24 if !value.has_type_flags(TypeFlags::HAS_RE_LATE_BOUND | TypeFlags::HAS_FREE_REGIONS) {
27 debug!("erase_regions({:?})", value);
28 let value1 = value.fold_with(&mut RegionEraserVisitor { tcx: self });
29 debug!("erase_regions = {:?}", value1);
34 struct RegionEraserVisitor<'tcx> {
38 impl<'tcx> TypeFolder<'tcx> for RegionEraserVisitor<'tcx> {
39 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
43 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
44 if ty.needs_infer() { ty.super_fold_with(self) } else { self.tcx.erase_regions_ty(ty) }
47 fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
49 T: TypeFoldable<'tcx>,
51 let u = self.tcx.anonymize_late_bound_regions(t);
52 u.super_fold_with(self)
55 fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
56 // because late-bound regions affect subtyping, we can't
57 // erase the bound/free distinction, but we can replace
58 // all free regions with 'erased.
60 // Note that we *CAN* replace early-bound regions -- the
61 // type system never "sees" those, they get substituted
62 // away. In codegen, they will always be erased to 'erased
63 // whenever a substitution occurs.
65 ty::ReLateBound(..) => r,
66 _ => self.tcx.lifetimes.re_erased,
70 fn fold_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'tcx> {
71 c.super_fold_with(self)