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From: "omer.rosler at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/99683] Deduction failure when using CTAD of CNTTP inside a
 deduction guide
Date: Thu, 15 Apr 2021 17:48:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99683

--- Comment #1 from Omer Rosler <omer.rosler at gmail dot com> ---
It seems that=20

Reduced:

template<typename>
struct A
{
    constexpr A(int) {}
};

A(int) -> A<int>;


template<A> //template<auto> works fine
struct B=20
{
    template<typename T>
    B(T);
};

template<typename T>
B(T) -> B<A{T{}}>; //see below


int main()
{
    B t(42);
}


specifying A<T> explicitly also works, it's the deduction that triggers the=
 bug

If the initializer of `A` is not dependent on the template parameter of the
guide (i.e `T`) than the bug isn't showing=