Compiler Error C3860

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type argument list following class type name must list parameters in the order used in type parameter list

A generic or template argument list was ill formed.

The following sample generates C3860:

// C3860.cpp
// compile with: /LD
template <class T1, class T2>
struct A {
   void f();
};

template <class T2, class T1>
void A<T1, T2>::f() {}   // C3860

Possible resolution:

// C3860b.cpp
// compile with: /c
template <class T1, class T2>
struct A {
   void f();
};

template <class T2, class T1>
void A<T2, T1>::f() {}

C3860 can also occur when using generics:

// C3860c.cpp
// compile with: /clr
generic<class T,class U>
ref struct GC {
   void f();
};

generic<class T, class U>
void GC<T,T>::f() {}   // C3860

Possible resolution:

// C3860d.cpp
// compile with: /clr /c
generic<class T,class U>
ref struct GC {
   void f();
};

generic<class T, class U>
void GC<T,U>::f() {}