I'm on why typeid isn't recognized

[Patrick Horgan <phorgan1@xxxxxxxxx>]

Building with these arguments:

g++ -fPIC -g -O0 -Wall -std=c++0x

I get this error:

/include/element.hh:101:26: error: ISO C++ forbids declaration of 
‘typeof’ with no type
.../include/element.hh:101:28: error: expected ‘;’ before ‘differenceType’


Here's line 101:

typedef typeof(T() - T()) differenceType;

I've tried to create a small program to reproduce it but can't make it 
fail! I build my example with the same arguments as the big one.

template<typename T>
struct foo
{
typedef typeof(T()-T()) difference_type;
};

int main()
{
foo<int> f;
}