--- old/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java	2018-07-11 10:50:43.216000000 -0700
+++ new/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java	2018-07-11 10:50:43.056000000 -0700
@@ -131,6 +131,10 @@
         return tab.get(name);
     }
 
+    public boolean isSupported() {
+        return this.compareTo(MIN) >= 0;
+    }
+
     public Target requiredTarget() {
         if (this.compareTo(JDK12) >= 0) return Target.JDK1_12;
         if (this.compareTo(JDK11) >= 0) return Target.JDK1_11;