Compiler Error C2061

syntax error : identifier 'identifier'

The compiler found an identifier where it wasn't expected. Make sure that identifier is declared before you use it.

An initializer may be enclosed by parentheses. To avoid this problem, enclose the declarator in parentheses or make it a typedef.

This error could also be caused when the compiler detects an expression as a class template argument; use typename to tell the compiler it is a type, as shown in the following example:

The following sample generates C2061:

// C2061.cpp
// compile with: /std:c++17

template <A a> // C2061
class C1 {};

template <typename A a> // ok
class C2 {};

template <typename T>
class C3
{
   // Both are valid since C++20
   using Type1 = T::Type; // C2061
   using Type2 = typename T::Type; // OK
};

int main()
{
   int x;
   unsigned a1 = alignof(x);   // C2061
   unsigned a2 = alignof(int); // OK
   unsigned a3 = alignof(decltype(x)); // OK
}

To resolve the error with template<A a> class C1{};, use template <typename a> class C1 {};
To resolve the issue with using Type1 = T::Type;, use using Type1 = typename T::Type;
To resolve the issue with alignof(x), replace the argument with the type of x. In this case, int or decltype(x);

C2061 can occur if you pass an instance name to typeid:

// C2061b.cpp
// compile with: /clr
ref struct G
{
   int i;
};

int main()
{
   G ^pG = gcnew G;
   System::Type ^ pType = typeid<pG>;   // C2061
   System::Type ^ pType2 = typeid<G>;   // OK
}