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)
Barry
Hi Barry,
why not? At least the grammar allows for it, is there any paragraph that disallows this (I admit I did only lookup the grammar, which often allows more than the actual language)?
Also: why would auto be placed outside of the template argument?type-id <- type-specifier-seq <- type-specifier <- simple-type-specifier <- placeholder-type-specifier <- type-constraint_opt auto
https://eel.is/c++draft/dcl.type#nt:placeholder-type-specifier
Thanks!
Sebastian