Error on line 2: the first operator "++" will work and will return (as postfix operator should do) rvalue, but applying operator "++" to the rvalue (both postfix or prefix) is not allowed. That's why an error arises here because of the presence of the second increment operator. Standard 5.2.6
Error on line 4: you can not use the "--" (both prefix and postfix) for variable of type bool. Standard 5.2.6