generic child class

[nblanpain@hotmail.com]

Hi,
I have a compilation error that i not understand. This is my example :

## Vec package ##
generic
type T_Real is digits <>;
package Vec is
end Vec;

## Mat package ##
with Vec;
generic
with package Vector is new Vec (<>);
package Mat is
end Mat;

## Mat.Child package ##
generic
type T_Tab is array (Integer) of Vector.T_Real;
package Mat.Child is
end Mat.Child;

## Test package ##
with Vec;
with Mat;
with Mat.Child;
package Test is
   package Vec_Float is new Vec (T_Real => Float);
   package Mat_Float is new Mat (Vector => Vec_Float);
   type T_Tableau is array (Integer) of Float;
   package Mat_Child_Float is new Mat_Float.Child (T_Tab => T_Tableau);
---- error !!!!!!!!!!
end Test;

The error message is :
"component subtype of actual does not match that of formal T_Tab "

have you an explaining ?

thanks,