On Wed, 4 Mar 2020 at 19:34, Barry Revzin via Std-Proposals
<std-proposals@lists.isocpp.org> wrote:
>
> On Wed, Mar 4, 2020, 11:11 AM Sebastian Büttner via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
>>
>> Sure! You can do this (you were missing the "auto" of the placeholder-type-specifier):
>>
>> void f(std::basic_string<any_of<char, uint8_t> auto> x);
>
>
> This one is not valid in C++20, but hopefully will become valid in C++23 (although the auto would go outside the template - basic_string<Concept> auto)

I don't think it would go outside.