[Bug c++/83591] -Wduplicated-branches fires in system headers in template instantiation

[twan at vitestro dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83591

--- Comment #6 from twan at vitestro dot com ---
I ran into this same issue on gcc 7.2.0. 

This issue seems to be resolved in gcc 9.3.0.