Handle primitives for ObjectSpace.reachable_objects_from

Author: eregon

src/main/java/org/truffleruby/stdlib/ObjSpaceNodes.java

@@ -11,6 +11,7 @@
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.dsl.Cached;
+import com.oracle.truffle.api.dsl.Fallback;
 import com.oracle.truffle.api.dsl.Specialization;
 import com.oracle.truffle.api.object.DynamicObject;
 import org.truffleruby.Layouts;
@@ -86,6 +87,11 @@ public DynamicObject adjacentObjects(DynamicObject object) {
             return createArray(objects.toArray());
         }
 
+        @Fallback
+        public DynamicObject adjacentObjectsPrimitive(Object object) {
+            return nil();
+        }
+
     }
 
     @CoreMethod(names = "root_objects", isModuleFunction = true)