The way we generate code, the symbol for ":e" internal exception variable has type ECMAException, when it should have Throwable. Curiously, this passes the verifier and doesn't cause problems, but it's obviously wrong. This program works:

try {
   new java.io.FileInputStream("no-such-file");
} catch(e) {
   print(e.class)
   e.printStackTrace()
}

But the generated bytecode for the catch block is:

   FRAME FULL [jdk/nashorn/internal/runtime/ScriptFunction java/lang/Object jdk/nashorn/internal/runtime/ScriptObject java/lang/Object] [java/lang/Throwable]
    ASTORE 4
   L5
    ALOAD 4
    DUP
    INSTANCEOF jdk/nashorn/internal/runtime/ECMAException
    IFEQ L6
    CHECKCAST jdk/nashorn/internal/runtime/ECMAException
    GETFIELD jdk/nashorn/internal/runtime/ECMAException.thrown : Ljava/lang/Object;
    ...
    LOCALVARIABLE :e Ljdk/nashorn/internal/runtime/ECMAException; L0 L4 4

meaning, we can catch any Throwable and then set it into a lvar typed as ECMAException.

":e" should obviously be typed as Throwable.