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