[PATCH] D133683: [c++] implements tentative DR1432 for partial ordering of function template

[Matheus Izvekov via Phabricator via cfe-commits]

mizvekov added a comment.

In D133683#3818935 <https://reviews.llvm.org/D133683#3818935>, @ychen wrote:

> This is described in https://eel.is/c++draft/temp.deduct.partial#13. Parietal ordering currently doesn't consider the number of deduced arguments. During the partial ordering stage, by https://eel.is/c++draft/temp.func.order#3, `template <typename T, typename... U> void g(T, U...);` would become `void g(UniqueT1, UniqueT2);`. And then it applies https://eel.is/c++draft/temp.deduct.partial#3.1 to decide which parameters are compared for partial ordering.

Sure, one thing is, given that we deduced a pack, does the number of elements deduced for that pack matter in partial ordering. I think `temp.deduct.partial#13` answers that it doesn't.

The other thing is, is a given template parameter pack used, or deduced, as opposed to just not being used. and I think the answer here is yes for that second overload of `g`.

If a template parameter pack appears as a type of a function parameter in an expansion pattern, such as `void g(T, U...);`, then I think that, notionally, there is no way to not use it.

For any call to that overload, that parameter pack will be deduced, no matter if to an empty pack or otherwise.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133683/new/

https://reviews.llvm.org/D133683