Incorrect warning in JDK 5.0 RC

Question

I get the following warning
warning: [unchecked] unchecked assignment to variable _cleanValue of raw type class com.globalrefund.db.psql.PsqlRow.ColumnImpl
for this statement:
column._cleanValue = null;
I think there should never be a warning when I set a reference to null (or do I miss something)

Answer 1

Alternatively - does it make sense for the compiler to NOT issue the warning for one particular expression that evaluates to the only value that could be determined safe?
It IS an assignment, and it IS unchecked, even tho', for this 1 particular value of the RHS, it will not cause a problem.
Even tho' for this particular RHS expression , the compiler could determine that the warning was not necessary, there are many other RHS expressions that evaluate to null where the compiler could not determine that.
If the language started incorporating special rules for these sorts of corner cases then I suggest the following would result
* The compiler would get more complex (i.e. more bugs - slower execution)
* The language spec would get more complex (i.e. more reading and understanding required)
With regard to the supplied code the actual coding "imperfection" ( I won't call it an error), is not even on this line, and at least the message gives you early warning that something is not 100% right with your code.
If you later copy and paste that loop and start assigning something else, you will heading into a danger zone.
You may have spent quite a bit some time determining that that you didn't really need the type argument on the loop variable, and it is a bit frustrating that that effort was wasted - however I would suggest that you embrace this message as a friend rather than as an enemy.