Add deepestGeneric Method to types and check whether Field declaration has generic more than two times nested

src/jdk.compiler/share/classes/com/sun/source/tree/VariableTree.java

@@ -71,6 +71,15 @@ public interface VariableTree extends StatementTree {
      */
     Tree getType();
 
+    /**
+     * 0 - no generic
+     * 1 - is a generic
+     * 2 - contains a generic
+     * 3 - contains a generic like List<List<X>>
+     * @return
+     */
+    int deepestGeneric();
+
     /**
      * Returns the initializer for the variable, or {@code null} if none.
      * @return the initializer

src/jdk.compiler/share/classes/com/sun/tools/javac/api/WildcardFinderPlugin.java

@@ -12,6 +12,7 @@ public class WildcardFinderPlugin extends TreeScanner<Void, Void> implements Plu
     private final Consumer<String> logger;
 
     public WildcardFinderPlugin(Consumer<String> logger){
+
         this.logger = logger;
     }
     @Override
@@ -38,6 +39,21 @@ public class WildcardFinderPlugin extends TreeScanner<Void, Void> implements Plu
         javacTask.addTaskListener(this);
     }
 
+    @Override
+    public Void visitClass(ClassTree node, Void unused) {
+        node.getMembers().forEach(typeDecl -> {
+            if (typeDecl instanceof VariableTree) {
+                logger.accept(preText + "Field Type: " + ((VariableTree) typeDecl).getType().toString());
+                logger.accept(preText + "deepestGeneric: " + ((VariableTree) typeDecl).deepestGeneric());
+                if( ((VariableTree) typeDecl).deepestGeneric() >= 3){
+                    logger.accept(preText + "Field not Wildcard compatible");
+                }
+                //logger.accept("deepestGeneric: " + ((VariableTree)((VariableTree) typeDecl).getType()).deepestGeneric());
+            }
+        });
+        return super.visitClass(node, unused);
+    }
+
     String currentSource = "";
     String currentClassContent = "";
     @Override

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java

@@ -82,6 +82,9 @@ import static com.sun.tools.javac.code.TypeTag.*;
  */
 public abstract class Type extends AnnoConstruct implements TypeMirror, PoolConstant {
 
+    public int deepestGeneric(){
+        return 0;
+    }
     /**
      * Type metadata,  Should be {@code null} for the default value.
      *
@@ -898,6 +901,11 @@ public abstract class Type extends AnnoConstruct implements TypeMirror, PoolCons
             };
         }
 
+        @Override
+        public int deepestGeneric() {
+            return 0;
+        }
+
         @Override
         public TypeTag getTag() {
             return WILDCARD;
@@ -1031,6 +1039,12 @@ public abstract class Type extends AnnoConstruct implements TypeMirror, PoolCons
             this.interfaces_field = null;
         }
 
+        @Override
+        public int deepestGeneric() {
+            int deepest = typarams_field.stream().mapToInt(t -> t.deepestGeneric()).max().orElse(0);
+            return deepest>0?1 + deepest:0;
+        }
+
         public int poolTag() {
             return ClassFile.CONSTANT_Class;
         }
@@ -1354,6 +1368,11 @@ public abstract class Type extends AnnoConstruct implements TypeMirror, PoolCons
             this(that.elemtype, that.tsym, that.getMetadata());
         }
 
+        @Override
+        public int deepestGeneric() {
+            return elemtype.deepestGeneric();
+        }
+
         public int poolTag() {
             return ClassFile.CONSTANT_Class;
         }
@@ -1699,6 +1718,11 @@ public abstract class Type extends AnnoConstruct implements TypeMirror, PoolCons
             };
         }
 
+        @Override
+        public int deepestGeneric() {
+            return 1;
+        }
+
         @Override
         public TypeTag getTag() {
             return TYPEVAR;

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/JCTree.java

@@ -1076,6 +1076,9 @@ public abstract class JCTree implements Tree, Cloneable, DiagnosticPosition {
         public JCExpression getNameExpression() { return nameexpr; }
         @DefinedBy(Api.COMPILER_TREE)
         public JCTree getType() { return vartype; }
+        public int deepestGeneric(){
+            return type.deepestGeneric();
+        }
         @DefinedBy(Api.COMPILER_TREE)
         public JCExpression getInitializer() {
             return init;