There's never SFINAE for invalid alias declarations.

*Brian Bi*

On Wed, Sep 16, 2026, 12:20 PM Bingzhi via Std-Discussion <
std-discussion_at_[hidden]> wrote:

> template <class T>
> struct X {
> static consteval std::meta::info evaluate()
> { if (std::meta::is_same_type(^^T, ^^int)) return { }; else ... }
>
> using type = [: evaluate() :];
> };
> template <class T> concept C = requires { typename X<T>::type; };
> static_assert(!C<int>); // *error: *cannot splice a null reflection
>
>
> I don't know why it is. Can somebody explain?
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