On Mon, Jan 30, 2017 at 9:36 PM Jonathan Wakely <jwak...@redhat.com> wrote: > > On 30/01/17 13:28 +0000, Jonathan Wakely wrote: > >On 30/01/17 13:47 +0200, Ville Voutilainen wrote: > >>Tested on Linux-x64. > > > >OK, thanks. > > To be clear: this isn't approved by LWG yet, but I think we can be a > bit adventurous with deduction guides and add them for experimental > C++17 features. Getting more usage experience before we standardise > these things will be good, and deduction guides are very new and > untried. If we find problems we can remove them again, and will have > invaluable feedback for the standards committee. >
My brain compiler says that this may cause problems with std::optional<int> o1; std::optional o2 = o1; // wanted optional<int>, deduced optional<optional<int>> Trunk GCC deduces optional<int>, but I don't think it implements P0512R0 yet, which prefers explicit guides to implicit ones before considering partial ordering. This example is very similar to the example in https://timsong-cpp.github.io/cppwp/over.match.best#1.6. Tim
