6863465: javac doesn't detect circular subclass dependencies via qualified names
Summary: class inheritance circularity check should look at trees, not just symbols
Reviewed-by: jjg
5088624: cannot find symbol message should be more intelligent
Summary: Resolve.java should keep track of all candidates found during a method resolution sweep to generate more meaningful diagnostics
Reviewed-by: jjg
6980862: too aggressive compiler optimization causes stale results of Types.implementation()
Summary: use a scope counter in order to determine when/if the implementation cache entries are stale
Reviewed-by: jjg