Fix ECJ warnings

Author: eregon

src/main/java/org/truffleruby/parser/RubyDeferredWarnings.java

@@ -71,6 +71,7 @@ public String getWarningMessage() {
             return buffer.toString();
         }
 
+        @Override
         public String toString() {
             return "WarningMessage(" +
                     "message = '" + message + "'" +
@@ -117,6 +118,7 @@ public void warning(String fileName, int lineNumber, String message) {
                         message));
     }
 
+    @Override
     public String toString() {
         var strings = new ArrayList<String>();
 

src/main/java/org/truffleruby/parser/YARPTranslator.java

@@ -853,6 +853,7 @@ public RubyNode visitCallOrWriteNode(Nodes.CallOrWriteNode node) {
         return assignPositionAndFlags(node, rubyNode);
     }
 
+    @Override
     public RubyNode visitCallTargetNode(Nodes.CallTargetNode node) {
         // extra argument should be added before node translation
         // to trigger correctly replacement with inlined nodes (e.g. InlinedIndexSetNodeGen)
@@ -1990,6 +1991,7 @@ public RubyNode visitIndexOrWriteNode(Nodes.IndexOrWriteNode node) {
         return assignPositionAndFlags(node, rubyNode);
     }
 
+    @Override
     public RubyNode visitIndexTargetNode(Nodes.IndexTargetNode node) {
         // extra argument should be added before node translation
         // to trigger correctly replacement with inlined nodes (e.g. InlinedIndexSetNodeGen)