rewrite the hasher to not access depth field

Co-authored-by: csmoe <[email protected]>

Author: nikomatsakis

src/librustc/ich/impls_ty.rs

@@ -104,16 +104,16 @@ for ty::RegionKind {
                 c.hash_stable(hcx, hasher);
             }
             ty::ReLateBound(db, ty::BrAnon(i)) => {
-                db.depth.hash_stable(hcx, hasher);
+                db.hash_stable(hcx, hasher);
                 i.hash_stable(hcx, hasher);
             }
             ty::ReLateBound(db, ty::BrNamed(def_id, name)) => {
-                db.depth.hash_stable(hcx, hasher);
+                db.hash_stable(hcx, hasher);
                 def_id.hash_stable(hcx, hasher);
                 name.hash_stable(hcx, hasher);
             }
             ty::ReLateBound(db, ty::BrEnv) => {
-                db.depth.hash_stable(hcx, hasher);
+                db.hash_stable(hcx, hasher);
             }
             ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, index, name }) => {
                 def_id.hash_stable(hcx, hasher);
@@ -821,10 +821,6 @@ impl_stable_hash_for!(enum ::middle::resolve_lifetime::Region {
     Free(call_site_scope_data, decl)
 });
 
-impl_stable_hash_for!(struct ty::DebruijnIndex {
-    depth
-});
-
 impl_stable_hash_for!(enum ty::cast::CastKind {
     CoercionCast,
     PtrPtrCast,

src/librustc/ty/sty.rs

@@ -1319,6 +1319,10 @@ impl DebruijnIndex {
     }
 }
 
+impl_stable_hash_for!(struct DebruijnIndex {
+    depth
+});
+
 /// Region utilities
 impl RegionKind {
     pub fn is_late_bound(&self) -> bool {