4 files changed, 23 insertions, 12 deletions

diff --git a/src/librustc/middle/infer/higher_ranked/mod.rs b/src/librustc/middle/infer/higher_ranked/mod.rs
index 073052dd368..40f32a51e22 100644
--- a/src/librustc/middle/infer/higher_ranked/mod.rs
+++ b/src/librustc/middle/infer/higher_ranked/mod.rs
@@ -468,7 +468,7 @@ pub fn skolemize_late_bound_regions<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
      * when higher-ranked things are involved. See `doc.rs` for more details.
      */
 
-    let (result, map) = ty::replace_late_bound_regions(infcx.tcx, binder, |br, _| {
+    let (result, map) = ty::replace_late_bound_regions(infcx.tcx, binder, |br| {
         infcx.region_vars.new_skolemized(br, &snapshot.region_vars_snapshot)
     });
 
diff --git a/src/librustc/middle/infer/mod.rs b/src/librustc/middle/infer/mod.rs
index 3f18af3d768..c1f0c10e11f 100644
--- a/src/librustc/middle/infer/mod.rs
+++ b/src/librustc/middle/infer/mod.rs
@@ -1056,7 +1056,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         ty::replace_late_bound_regions(
             self.tcx,
             value,
-            |br, _| self.next_region_var(LateBoundRegion(span, br, lbrct)))
+            |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
     }
 
     /// See `verify_generic_bound` method in `region_inference`
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 9b9a58178cc..2c9ff35364b 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -6672,7 +6672,7 @@ pub fn liberate_late_bound_regions<'tcx, T>(
 {
     replace_late_bound_regions(
         tcx, value,
-        |br, _| ty::ReFree(ty::FreeRegion{scope: scope, bound_region: br})).0
+        |br| ty::ReFree(ty::FreeRegion{scope: scope, bound_region: br})).0
 }
 
 pub fn count_late_bound_regions<'tcx, T>(
@@ -6681,7 +6681,7 @@ pub fn count_late_bound_regions<'tcx, T>(
     -> uint
     where T : TypeFoldable<'tcx> + Repr<'tcx>
 {
-    let (_, skol_map) = replace_late_bound_regions(tcx, value, |_, _| ty::ReStatic);
+    let (_, skol_map) = replace_late_bound_regions(tcx, value, |_| ty::ReStatic);
     skol_map.len()
 }
 
@@ -6712,7 +6712,7 @@ pub fn erase_late_bound_regions<'tcx, T>(
     -> T
     where T : TypeFoldable<'tcx> + Repr<'tcx>
 {
-    replace_late_bound_regions(tcx, value, |_, _| ty::ReStatic).0
+    replace_late_bound_regions(tcx, value, |_| ty::ReStatic).0
 }
 
 /// Rewrite any late-bound regions so that they are anonymous.  Region numbers are
@@ -6730,9 +6730,9 @@ pub fn anonymize_late_bound_regions<'tcx, T>(
     where T : TypeFoldable<'tcx> + Repr<'tcx>,
 {
     let mut counter = 0;
-    ty::Binder(replace_late_bound_regions(tcx, sig, |_, db| {
+    ty::Binder(replace_late_bound_regions(tcx, sig, |_| {
         counter += 1;
-        ReLateBound(db, BrAnon(counter))
+        ReLateBound(ty::DebruijnIndex::new(1), BrAnon(counter))
     }).0)
 }
 
@@ -6743,7 +6743,7 @@ pub fn replace_late_bound_regions<'tcx, T, F>(
     mut mapf: F)
     -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
     where T : TypeFoldable<'tcx> + Repr<'tcx>,
-          F : FnMut(BoundRegion, DebruijnIndex) -> ty::Region,
+          F : FnMut(BoundRegion) -> ty::Region,
 {
     debug!("replace_late_bound_regions({})", binder.repr(tcx));
 
@@ -6755,8 +6755,19 @@ pub fn replace_late_bound_regions<'tcx, T, F>(
         debug!("region={}", region.repr(tcx));
         match region {
             ty::ReLateBound(debruijn, br) if debruijn.depth == current_depth => {
-                * map.entry(br).get().unwrap_or_else(
-                      |vacant_entry| vacant_entry.insert(mapf(br, debruijn)))
+                let region =
+                    * map.entry(br).get().unwrap_or_else(
+                        |vacant_entry| vacant_entry.insert(mapf(br)));
+
+                if let ty::ReLateBound(debruijn1, br) = region {
+                    // If the callback returns a late-bound region,
+                    // that region should always use depth 1. Then we
+                    // adjust it to the correct depth.
+                    assert_eq!(debruijn1.depth, 1);
+                    ty::ReLateBound(debruijn, br)
+                } else {
+                    region
+                }
             }
             _ => {
                 region
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 2d433369366..0cf676b7035 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -1182,8 +1182,8 @@ impl<'tcx, T> UserString<'tcx> for ty::Binder<T>
         // the output. We'll probably want to tweak this over time to
         // decide just how much information to give.
         let mut names = Vec::new();
-        let (unbound_value, _) = ty::replace_late_bound_regions(tcx, self, |br, debruijn| {
-            ty::ReLateBound(debruijn, match br {
+        let (unbound_value, _) = ty::replace_late_bound_regions(tcx, self, |br| {
+            ty::ReLateBound(ty::DebruijnIndex::new(1), match br {
                 ty::BrNamed(_, name) => {
                     names.push(token::get_name(name));
                     br