Pancake while loop/if-statement conditions with function calls

Currently there isn't a direct way to put function calls into while loop and if-statement conditions. For example:
```c
fun return0() {return 0;}

fun main() {
if (return0() != 0)
{
return 1;
}
return 0;
}
```
doesn't work. Would be a lot more convenient if this can be supported.