--- old/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Lint.java	2019-09-04 13:03:47.949963468 -0700
+++ new/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Lint.java	2019-09-04 13:03:47.753963468 -0700
@@ -177,6 +177,11 @@
         DEPRECATION("deprecation"),
 
         /**
+         * Warn about compiler generation of a default constructor.
+         */
+        DEFAULT_CTOR("default-ctor"),
+
+        /**
          * Warn about items which are documented with an {@code @deprecated} JavaDoc
          * comment, but which do not have {@code @Deprecated} annotation.
          */
--- old/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java	2019-09-04 13:03:48.401963468 -0700
+++ new/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java	2019-09-04 13:03:48.241963468 -0700
@@ -3566,6 +3566,20 @@
         }
     }
 
+    /**
+     * 
+     */
+    void checkDefaultConstructor(ClassSymbol c) {
+        // Kick out anonymous and private?
+        if (lint.isEnabled(Lint.LintCategory.DEFAULT_CTOR) &&
+            (c.flags() & ENUM) == 0 &&
+            !c.isAnonymous() &&
+            (c.flags() & PUBLIC) != 0) {
+            System.out.println("Default ctor on " + c);
+        }
+        return;
+    }
+
     private class ConversionWarner extends Warner {
         final String uncheckedKey;
         final Type found;
--- old/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TypeEnter.java	2019-09-04 13:03:48.901963468 -0700
+++ new/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TypeEnter.java	2019-09-04 13:03:48.725963468 -0700
@@ -914,6 +914,8 @@
                     }
                 }
                 if (addConstructor) {
+                    // Lint check here
+                    chk.checkDefaultConstructor(sym);
                     MethodSymbol basedConstructor = nc != null ?
                             (MethodSymbol)nc.constructor : null;
                     JCTree constrDef = DefaultConstructor(make.at(tree.pos), sym,