Re: C++17 and "Alice in Wonderland"

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2021-03-24 14:53:25

On 3/24/21 5:45 PM, Bjorn Reese via Boost wrote:
> 
> You can use C++20 std::type_identity (or roll your own) to prevent the
> second T from being deduced. In Richard Smith's example:
> 
> template<class T, bool (*F)(std::type_identity_t<T>), int> struct X;
> template<class T, bool (*F)(std::type_identity_t<T>)> struct X<T, F, 0> {};
> X<char const, nullptr, 0> x;

As I commented in the clang bug, I don't think you should have to do 
this. There is only one T this template, and it is explicitly specified 
at the point of template instantiation, so there's nothing to deduce.