If there's a variable of any type declared in module header, like
int var;
and there is a structure declared in module body, which has a variable of the same name, like
struct A
{
int var;
};
compiler will treat this as error and will give following message:
"'var' is already defined".
This won't happen if structure is declared in module header, though.
Yes, this is a known issue with the script compiler. It's something that might get fixed if I get round to rewriting the script compiler at some point.