c++ (g++-4.x) problem with templates - c++

Question

I have this simple code:
template<template <class> class Generator>
class TestHelper {};
template<class Writer>
class Test
{
typedef TestHelper< Test > Helper;
};
It's works great on last g++ versions, but, in 4.4 or 4.5, I get this error:
test.cpp:7: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class> class Generator> class TestHelper'
test.cpp:7: error: expected a class template, got 'Test<Writer>'
What I'm doing wrong?

Answer 1

It's because inside the body of class Test<Writer>, naming Test without providing the template arguments automatically assumes the same arguments (e.g. Writer).
For example, this allows you to write the copy constructor as:
Test(const Test&);
instead of
Test::Test(const Test<Writer>&);
You can overcome this by qualifying Test with its namespace, e.g.
typedef TestHelper< ::Test > Helper;
NOTE: As Tomalek suggests, the original usage is valid in C++0x. Here is the relevant paragraph of the standard (emphasis mine), from section 14.6.1 ([temp.local]):
Like normal (non-template) classes, class templates have an injected-class-name (Clause 9). The injected-class-name can be used as a template-name or a type-name. When it is used with a template-argument-list, as a template-argument for a template template-parameter, or as the final identifier in the elaborated-type-specifier of a friend class template declaration, it refers to the class template itself. Otherwise, it is equivalent to the template-name followed by the template-parameters of the class template enclosed in <>.

Answer 2

#Ben is probably right, but here's a totally different way to get it to compile, that doesn't use templates as args to templates.
template<class Generator> // changed this to a simpler template
class TestHelper {};
template<class Writer>
class Test
{
typedef TestHelper< typename Test :: Writer > Helper; // 2nd change
};
I made two changes. #Hugo, maybe this is what you wanted, and maybe this is what older versions of g++ did?
It's easy to get code to compile, but that doesn't mean that it does what you think it does!