JDK12beta2 build Z fails to pass JCK12beta2 test icls03903.
Compiler enters infinite loop trying to compile the following
example (which is actually reduced form of the JCK test):

------
class a {
class b extends c {}
class c extends b {}
}
-------
> jc a.java
a.java:3: Cyclic class inheritance.
        class c extends b {}
                        ^

That's where it hangs. Note that this is a new failure, JDK12beta2 build U
correctly reported error and did not enter infinite loop.