[Checkers] Framework changes

[Michael Ernst]

> > and method  
> > invocation check (cannot call a method whose receiver type isn't a  
> > subtype of the expression receiver type, cannot call an immutable  
> > reference on a mutable reference).
> 
> Shouldn't this already be checked in the framework?  The framework is
> supposed to already handle assignments and pseudo-assignments (examples of
> pseudo-assignments are between method actuals and formals).

Here is another way to state this:  If something this simple is missing
from the framework, then it should be possible to write a test case for
which the Interned checker (which does very little to override the base
functionality) fails.  If that isn't possible, then maybe the framework
already does it and the IGJ checker should take advantage of that.

(But since Matt is currently in the middle of a change to the framework, it
does not make sense to try to make any changes until he is finished with
his and has the Interned tests working.  Then, you can try to write the
test that fails the Interned checker.)

                    -Mike