[Bug c++/69600] Incorrect use of copy-assignment instead of move assignment from function

[sshannin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69600

--- Comment #4 from sshannin at gmail dot com ---
FWIW, this seems to be fixed on trunk. Still fails for at least 6.2, 5.4, and
4.9.4, but does compile with 7/trunk and 4.8.5

https://godbolt.org/g/hx9q4S