Let us consider the following nested templates case:

template<typename T>
class Outer{

public:
    template<typename U>
    class Inner{

    public:
      void f();
    };

};

Then the following specialization
template<> template<typename U> void Outer<int>::Inner<U>::f(){};
results in compile-time error (I've tried to compile it with gcc 3.2.2)

main.cpp:XXX: invalid use of undefined type `class Outer<int>::Inner<U>'
main.cpp:XXX: declaration of `class Outer<int>::Inner<U>'
main.cpp:XXX: template definition of non-template `void
   Outer<int>::Inner<U>::f()'

Can anyone help me to figure out the problem?

Thanks in advnace,
Andriy Shnyr

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On 12/03/2003 11:35 AM, Andriy Shnyr wrote:
[snip]
> main.cpp:XXX: invalid use of undefined type `class Outer<int>::Inner<U>'
> main.cpp:XXX: declaration of `class Outer<int>::Inner<U>'
> main.cpp:XXX: template definition of non-template `void
>    Outer<int>::Inner<U>::f()'
>
> Can anyone help me to figure out the problem?
IIRC, adding ::template Inner<U> solved the compile problem for me;
however, I found a problem with the produced code not selecting the
right specialization, as reported here:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13088

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