Using the 1.4 javadoc and mifdoclet source that has the fix to 4521721 integrated, the following example results in a ClassCastException in MIFExecutableMembersObject.generateThrowsTags.

package foo;

import java.io.IOException;

public class Foo {
    /**
     * A method.
     *
     * @throws IOException because it does
     * @throws ClassNotFoundException because it does
     */
    public void foo() throws IOException, ClassNotFoundException {}

    public static class Bar extends Foo {
	/**
	 * Another method.
	 *
	 * @throws java.security.AccessControlException because it does
	 */
	public void foo() throws IOException, ClassNotFoundException {}
    }
}

Here's a stack trace:

javadoc: In doclet class com.sun.tools.doclets.mif.MIFDoclet,  method start has thrown an exception java.lang.reflect.InvocationTargetException
java.lang.ClassCastException: com.sun.tools.javadoc.ClassDocImpl
        at com.sun.tools.doclets.mif.MIFExecutableMembersObject.generateThrowsTags(MIFExecutableMembersObject.java:189)
        at com.sun.tools.doclets.mif.MIFExecutableMembersObject.generateExecutableMemberTags(MIFExecutableMembersObject.java:143)
        at com.sun.tools.doclets.mif.MIFObject.generateTagInfo(MIFObject.java:744)
        at com.sun.tools.doclets.mif.MIFMembersObject.buildMIFMembersObject(MIFMembersObject.java:139)
        at com.sun.tools.doclets.mif.MIFClassKindObject.buildMembersGroup(MIFClassKindObject.java:489)
        at com.sun.tools.doclets.mif.MIFClassKindObject.build(MIFClassKindObject.java:150)
        at com.sun.tools.doclets.mif.MIFSinglePackageObject.buildMIFClassObjects(MIFSinglePackageObject.java:147)
        at com.sun.tools.doclets.mif.MIFPackageObject.build(MIFPackageObject.java:110)
        at com.sun.tools.doclets.mif.MIFPackageObjectWriter.<init>(MIFPackageObjectWriter.java:55)
        at com.sun.tools.doclets.mif.MIFPackageObjectWriter.generate(MIFPackageObjectWriter.java:74)
        at com.sun.tools.doclets.mif.MIFDoclet.generatePackages(MIFDoclet.java:189)
        at com.sun.tools.doclets.mif.MIFDoclet.startGeneration(MIFDoclet.java:141)
        at com.sun.tools.doclets.mif.MIFDoclet.start(MIFDoclet.java:52)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:324)
        at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:196)
        at com.sun.tools.javadoc.DocletInvoker.start(DocletInvoker.java:95)
        at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:288)
        at com.sun.tools.javadoc.Start.begin(Start.java:114)
        at com.sun.tools.javadoc.Main.execute(Main.java:44)
        at com.sun.tools.javadoc.Main.main(Main.java:34)
1 error

N/A

Important for 1.4
  xxxxx@xxxxx   2002-03-01

This bug has been fixed.  A class cast exception is not thrown at the specified location in the code anymore.
  xxxxx@xxxxx   2002-03-04