Compiler Error C3857

  • Article

'type': multiple type parameter lists are not allowed

More than one template or generic was specified for the same type, which is not allowed.

The following sample generates C3857:

// C3857.cpp
template <class T, class TT>
template <class T2>    // C3857
struct B {};

Possible resolution:

// C3857b.cpp
// compile with: /c
template <class T, class TT, class T2> 
struct B {};

C3857 can also occur when using generics:

// C3857c.cpp
// compile with: /clr
generic <typename T>
generic <typename U>
ref class GC;   // C3857

Possible resolution:

// C3857d.cpp
// compile with: /clr /c
generic <typename U>
ref class GC;