'Template cannot be specialized after it has been instantiated' error for inner class

koval

Studio 12.6 started giving error for the code which compiled fine with 12.5

#include <type_traits>template<typename>struct Traits {    enum { IsA = false, IsB = false };};struct A1{};struct A2{};template<typename T>class C {    // This is where Traits<T> gets instantiated    struct L: std::conditional<Traits<T>::isA || Traits<T>::isB, A1, A2>::type {};};struct D {    struct I {};    C<I> ci;};template<>struct Traits<D::I> {    enum { isA = true, isB = false };};

The error:

"test.cpp", line 23: Error: Template "Traits<D::I>" cannot be specialized after it was instantiated."test.cpp", line 23: Error: Invalid template nesting depth.

Is this a bug or a new interpretation of the standard?

Note that the error disappears when Traits is a forward declaration only before class C (template<typename> struct Traits;)

Steve.Clamage-Oracle

Thanks for reporting this problem. I have filed C++ compiler bug .26580982 for you.

If you have a service contract with Oracle, you can request a fix in a patch, via your support channel. In any case, we will fix it as resources permit.