"using typedef-name ... as class" on a forward declaration

Question

I'm doing some policy-based designs here and I have the need to typedef lots of template types to shorten the names.
Now the problem comes that when I need to use a pointer to one of those types I try to just forward-declare it but the compiler complains with a test.cpp:8: error: using typedef-name ‘Test1’ after ‘class’
It's nothing to do with sizes as I don't need the obj at all, its just a pointer in a ".h" file where I don't want to bring the whole template in.
This is g++:

//Works
class Test{};
class Test;

//Doesn't work
class Test{};
typedef Test Test1;
class Test1;

Any hint?

Answer 1

typedef Test Test1;
class Test1;

fails because the typedef statement serves as the declaration for the Test1 type.

Basically, when the compiler sees the typedef, it remembers that Test1 is a synonym for Test. Then when it sees class Test1;, it thinks there's a new type you are declaring. But it can't treat that as a declaration because the name Test1 is already being used by the typedef.

If you want to use a forward declaration for Test1, for example, you have to put the typedef in each file using that typedef as a forward declaration. Therefore, instead of class Test1;, you'd do:

class Test;
typedef Test Test1;