Should we warn if we detect null derefernces or void value uses ?

[Stefan Koch via Digitalmars-d]

Hi Guys,
What is your opinion, should we warn if we unambiguously detect 
something that is clearly unwanted ?

int fn(int y)
{
   int x = void;
   ++x;
   return x+y;
}

  This requires data-flow analysis (The same kind that tells you 
if you are skipping a statement)
And will slow down compilation a little if we enable such a 
warning.