compiler-error-c2139.md

description	title	ms.date	f1_keywords	helpviewer_keywords
Learn more about: Compiler Error C2139	Compiler Error C2139	05/03/2021	C2139	C2139

Compiler Error C2139

'type' : an undefined class is not allowed as an argument to compiler intrinsic type trait 'trait'

An invalid argument was passed to a type trait.

Remarks

For more information, see Compiler Support for Type Traits.

Example

The following sample generates C2139.

// C2139.cpp
// compile with: /EHsc
#include <iostream>
using namespace std;

template <class T>
struct is_polymorphic {
   static const bool value = __is_polymorphic(T);
};

class C;
class D {};

class E {
public:
   virtual void Test() {}
};

int main() {
   cout << is_polymorphic<C>::value << endl;   // C2139
   cout << is_polymorphic<D>::value << endl;   // OK
   cout << is_polymorphic<E>::value << endl;   // OK
}