Why is that case incorrect (it's logical)
template <typename T>
struct Der: public Base
{
typedef int T;
T val;
};
, but that case is correct?
struct Base
{
typedef int T;
};
template <typename T>
struct Der: public Base
{
T val;
};
The Standard 14.6.1/7 says:
In the definition of a class template or in the definition of a member of such a template that appears outside of the template definition, for each base class which does not depend on a template-parameter (14.6.2), if the name of the base class or the name of a member of the base class is the same as the name of a template-parameter, the base class name or member name hides the template-parameter name (3.3.7).
Why is it not ambiguous in here?
The first example is incorrect according to [temp.local]/6:
A template-parameter shall not be redeclared within its scope (including nested scopes).
However, in
template <typename T>
struct Der: public Base
{
T val;
};
T is hidden by the name inherited from Base - as specified by your quote.
[..] if the name of the base class or the name of a member of the base class is the same as the name of a template-parameter, the base class name or member name hides the template-parameter name (3.3.7).
That is, the member val is of type int. Demo.