One of two supplied operator* is not found

Hi,

I'm confused because of a forward declaration problem I have. I tried to
reduce the problem but now it even fails without forward declarations at
all.

This is my test code:

// main.cpp
#include "vector1.h" // unused but still required at least in my project
#include "vector2.h"
#include "sparsematrix.h"

int main()
{
  sparsematrix A;
  vector2 x;
  vector2 y = A*x; // here is the error
  return 0;
}

$ g++ main.cpp -o main
main.cpp: In function ???????int main()????????:
main.cpp:9: error: no match for ???????operator*???????? in ???????A * x????????
sparsematrix.h:7: note: candidates are: virtual const vector1
sparsematrix::operator*(const vector1&) const

// matrix.h
#include "vector1.h"
#include "vector2.h"

class matrix
{
  public:
    virtual const vector1 operator*(const vector1 &) const = 0;
            const vector2 operator*(const vector2 &) const
             { return vector2(); }
};

// sparsematrix
#include "matrix.h"
#include "vector1.h"

class sparsematrix : public matrix
{
  public:
    const vector1 operator*(const vector1 &) const { return vector1(); }
};

vector1 and vector2 are just two unrelated dummy classes (same for vector2):
class vector1
{
  public:
    vector1() {}
};

I'm really confused that operator* is not found for vector2 (but works for
vector1). I just tried to get feedback whether it's really necessary to
include vector1.h in main but now even my simple and reduced code fails to
compile :-(

Any ideas?
Jens

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