I looked at the source. Doesn't seem to support class initialization properly. It models lambdas as just arrow functions, which won't work if you try to pass them as Objects to other Java functions (where is Object.getClass()/hashCode()/equals() ?) It doesn't handle runtime checks of Java interfaces at all, for example:

interface Foo {} class FooImpl implements Foo {}

Object o = new FooImpl(); if (o instanceof Foo) -> compile error

The inability to even handle Java interfaces should be a clue right off the bat that this won't compile any non-trivial Java code base.