VC++ Template Compiler Error C2244: Unable to Matc

问题:

I've encountered a compiler error using Visual Studio 2010 which I've reduced down to the following code:

template <int i> struct A
{
    typedef int T;
};

template<int i>
struct B
{
    static const int i = i; // <-- this seems to cause the problem
    typename A<i>::T F();
};


template<int i>
typename A<i>::T B<i>::F()       { return B<i>::i; }

This code produces this error:

repro.cpp(15): error C2244: 'B<i>::F' : unable to match function definition to an existing declaration
repro.cpp(12) : see declaration of 'B<i>::F'
      definition
      'A<i>::T B<i>::F(void)'
      existing declarations
      'A<i>::T B<i>::F(void)'

If the declaration for i in struct B is removed the compiler error goes away. I believe it's because the template parameter for the return type of F is binding to the static member i within B instead of B's template argument. Why do the return types for F 'differ' when the value for i is the same? Is this a bug?

I should also mention that if the function is declared inline the error goes away.

回答1:

The problem is you are declaring the same name twice in the same scope. If you rename the static const int i, or the template parameter it should work.