Marke SingletonByRef functions scope

source/tanya/algorithm/iteration.d

@@ -109,7 +109,7 @@ private struct SingletonByRef(E)
         this.element = &element;
     }
 
-    @property ref inout(E) front() inout return
+    @property ref inout(E) front() inout return scope
     in
     {
         assert(!empty);
@@ -148,7 +148,7 @@ private struct SingletonByRef(E)
         return typeof(this)(*this.element);
     }
 
-    ref inout(E) opIndex(size_t i) inout return
+    ref inout(E) opIndex(size_t i) inout return scope
     in
     {
         assert(!empty);