unused declaration: ensure refs on implicit constructor (IDEA-158585)

java/java-tests/testData/inspection/deadCode/defaultConstructor/src/A.java

@@ -0,0 +1,18 @@
+class A {
+   public A(int... i) {
+     System.out.println(i);
+   }
+}
+
+class B extends A {
+  public static void main(String[] args) {
+    System.out.println(new B());
+  }
+}
+
+class C {}
+class D extends C {
+  public static void main(String[] args) {
+    System.out.println(new D());
+  }
+}