Bug#570838: missing warning, false error

[Prohle Peter <prohlep@math.bme.hu>]

I think there are inconsistencies warnings.

#include <iostream>
int main( void ) {
  for ( int i=0, j=99 ; (++j) = 99 , i<9 ; ++i ) {
    std::cout << i << ' ' << j << std::endl;
  }
  return 0;
}

/usr/bin/g++ -Wall the source code above yields NO warning, while the 
increased value 100 of j is UNUSED, since the assigment will overwrite 
with 99 again.


In addition to the missing warning above, we have a false error below:


Swapping the timing of the ++ opertor, namely using the expression

	(j++) = 99

yields the ERROR below:

	In function 'int main()':
	3: error: lvalue required as left operand of assignment

Hence (++j) is a left value, while (j++) is not.  This is inconsistent.

Each of the expressions ++j, j++ and j has the same left value as the 
others.  It is an independent and different question how the value at the 
location in question is affected by the presence and the position of the 
operator ++.  But the both of ++j and j++ have a left value identical to 
the left value of j, not?


I have cheked, that omitting the parenthesis does not help.

Regards,
	Peter PROHLE.