This analysis performs a simple abstract interpretation of all methods of a class
to identify fields that are always assigned
an object that is a subtype of the field's declared type.
WE IGNORE THOSE FIELDS WHICH SEEMS TO BE ALWAYS NULL.
THESE FIELDS ARE OFTEN INITIALZED - AT RUNTIME - BY SOME CODE OUTSIDE
THE SCOPE OF "PURE" JAVA BASED ANALYSES.
E.G., WE IGNORE THE FOLLOWING FIELDS FROM JAVA 8: