Compiler Warning (level 1) C4346

Visual Studio 2015
 

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The latest version of this topic can be found at Compiler Warning (level 1) C4346.

name' : dependent name is not a type

The typename keyword is required if a dependent name is to be treated as a type. This is a breaking change in the Visual C++ .NET 2003 compiler, made in order to conform to the ISO C++ standard.

For code that works the same in all versions of Visual C++, add typename to the declaration.

The following sample generates C4346:

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// C4346.cpp  
// compile with: /WX /LD  
template<class T>  
struct C {  
   T::X* x;   // C4346  
   // try the following line instead  
   // typename T::X* x;  
};

The following samples shows other examples where the typename keyword is required:

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// C4346b.cpp  
// compile with: /LD /W1  
template<class T>  
const typename T::X& f(typename T::Z* p);   // Required in both places  
  
template<class T, int N>  
struct L{};  
  
template<class T>  
struct M : public L<typename T::Type, T::Value>   
{   // required on type argument, not on non-type argument  
   typedef typename T::X   Type;  
   Type f();   // OK: "Type" is a type-specifer  
   typename T::X g();   // typename required  
   operator typename T::Z();   // typename required      
};

and this,

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// C4346c.cpp  
// compile with: /LD /WX  
struct Y {  
   typedef int Y_t;  
};  
  
template<class T>  
struct A {  
   typedef Y A_t;  
};  
  
template<class T>  
struct B {  
   typedef /*typename*/ A<T>::A_t B_t;   // C4346 typename needed here  
   typedef /*typename*/ B_t::Y_t  B_t2;   // typename also needed here  
};
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