Make find_local iterate instead of recurse

Author: spastorino

src/librustc_mir/dataflow/impls/borrowed_locals.rs

@@ -91,16 +91,19 @@ struct BorrowedLocalsVisitor<'b, 'c: 'b> {
 }
 
 fn find_local<'tcx>(place: &Place<'tcx>) -> Option<Local> {
-    match *place {
-        Place::Base(PlaceBase::Local(l)) => Some(l),
-        Place::Base(PlaceBase::Static(..)) => None,
-        Place::Projection(ref proj) => {
-            match proj.elem {
-                ProjectionElem::Deref => None,
-                _ => find_local(&proj.base)
+    place.iterate(|place_base, place_projection| {
+        for proj in place_projection {
+            if proj.elem == ProjectionElem::Deref {
+                return None;
             }
         }
-    }
+
+        if let PlaceBase::Local(local) = place_base {
+            Some(*local)
+        } else {
+            None
+        }
+    })
 }
 
 impl<'tcx, 'b, 'c> Visitor<'tcx> for BorrowedLocalsVisitor<'b, 'c> {