1 files changed, 83 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/renumber.rs b/compiler/rustc_borrowck/src/renumber.rs
new file mode 100644
index 000000000..7a8ce621c
--- /dev/null
+++ b/compiler/rustc_borrowck/src/renumber.rs
@@ -0,0 +1,83 @@
+use rustc_index::vec::IndexVec;
+use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
+use rustc_middle::mir::visit::{MutVisitor, TyContext};
+use rustc_middle::mir::{Body, Location, Promoted};
+use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
+
+/// Replaces all free regions appearing in the MIR with fresh
+/// inference variables, returning the number of variables created.
+#[instrument(skip(infcx, body, promoted), level = "debug")]
+pub fn renumber_mir<'tcx>(
+    infcx: &InferCtxt<'_, 'tcx>,
+    body: &mut Body<'tcx>,
+    promoted: &mut IndexVec<Promoted, Body<'tcx>>,
+) {
+    debug!(?body.arg_count);
+
+    let mut visitor = NllVisitor { infcx };
+
+    for body in promoted.iter_mut() {
+        visitor.visit_body(body);
+    }
+
+    visitor.visit_body(body);
+}
+
+/// Replaces all regions appearing in `value` with fresh inference
+/// variables.
+#[instrument(skip(infcx), level = "debug")]
+pub fn renumber_regions<'tcx, T>(infcx: &InferCtxt<'_, 'tcx>, value: T) -> T
+where
+    T: TypeFoldable<'tcx>,
+{
+    infcx.tcx.fold_regions(value, |_region, _depth| {
+        let origin = NllRegionVariableOrigin::Existential { from_forall: false };
+        infcx.next_nll_region_var(origin)
+    })
+}
+
+struct NllVisitor<'a, 'tcx> {
+    infcx: &'a InferCtxt<'a, 'tcx>,
+}
+
+impl<'a, 'tcx> NllVisitor<'a, 'tcx> {
+    fn renumber_regions<T>(&mut self, value: T) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        renumber_regions(self.infcx, value)
+    }
+}
+
+impl<'a, 'tcx> MutVisitor<'tcx> for NllVisitor<'a, 'tcx> {
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.infcx.tcx
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    fn visit_ty(&mut self, ty: &mut Ty<'tcx>, ty_context: TyContext) {
+        *ty = self.renumber_regions(*ty);
+
+        debug!(?ty);
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
+        *substs = self.renumber_regions(*substs);
+
+        debug!(?substs);
+    }
+
+    #[instrument(skip(self), level = "debug")]
+    fn visit_region(&mut self, region: &mut ty::Region<'tcx>, location: Location) {
+        let old_region = *region;
+        *region = self.renumber_regions(old_region);
+
+        debug!(?region);
+    }
+
+    fn visit_const(&mut self, constant: &mut ty::Const<'tcx>, _location: Location) {
+        *constant = self.renumber_regions(*constant);
+    }
+}