[RFA] Emit a warning for ineffective set VAR = EXP command

[Maciej W. Rozycki]

On Wed, 9 May 2012, Paul_Koning@Dell.com wrote:

> > What do you mean by "work" here?  I think a warning for "i++ * 2" is 
> > expected as that's questionable use -- the result of the multiplication is 
> > discarded.  Did you mean anything else?
> 
> You're right, but it does perform an assignment (to "i") so a message 
> saying that the statement has no effect is not accurate.  Then again, 
> given that the statement doesn't make much sense, the fact that the 
> message is not completely accurate isn't all that interesting -- unlike 
> the simple "i++" it isn't a likely case in reality.

 I think it's all right -- "might have no effect" is weaker than "has no 
effect" and will draw one's attention in the case of a typo or suchlike.

  Maciej