[ONOS-4563][ONOS-4564][ONOS-4551][ONOS-4538]defect fix

Change-Id: Ia3fe844e1e846d2e1d2c4359eefc815e7767aef9
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
index b0a3b69..fc5dfef 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
@@ -35,6 +35,7 @@
 
 import static org.onosproject.yangutils.datamodel.utils.GeneratedLanguage.JAVA_GENERATION;
 import static org.onosproject.yangutils.datamodel.utils.YangDataModelFactory.getYangTypeDefNode;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
@@ -117,6 +118,11 @@
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
 
+        // Check for identifier collision
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, TYPEDEF_DATA);
+
         /*
          * Create a derived type information, the base type must be set in type
          * listener.