This sad little snippet, when compiled as bug.java, crashes javac in a way I haven't been able to find documented yet. I've worked it down to it's essential components.

class mug
{
   void m()
{
   bug b=new bug();
}
}

Here is the result:
hagen@mile[89]: javac bug.java
java.lang.NullPointerException
at sun.tools.tree.NewInstanceExpression.code(NewInstanceExpression.java:196)
at sun.tools.tree.ExpressionStatement.code(ExpressionStatement.java:77)
at sun.tools.tree.DeclarationStatement.code(DeclarationStatement.java:81)
at sun.tools.javac.SourceField.code(SourceField.java:406)
at sun.tools.javac.SourceField.code(SourceField.java:368)
at sun.tools.javac.SourceClass.compileClass(SourceClass.java:564)
at sun.tools.javac.SourceClass.compile(SourceClass.java:527)
at sun.tools.javac.Main.compile(Main.java:193)
at sun.tools.javac.Main.main(Main.java:289)
.//bug.java:2: Class mug already defined in bug.java.
class mug
      ^
.//bug.java:6: Class bug not found in type declaration.
   bug b=new bug();
   ^
.//bug.java:6: Class bug not found in new.
   bug b=new bug();
         ^
error: An exception has occurred in the compiler; please file a bug report (###@###.###).
4 errors