https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57533
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- Seems to be fixed on trunk since commit 1722e2013f05f1f1f99379dbaa0c0df356da731f Author: Jason Merrill Date: Tue Jul 21 05:19:49 2020 c++: Implement C++20 implicit move changes. [PR91427]