gcc 11.4 fails to compile this example with an error `template argument 1 is invalid` on this line: https://github.com/boostorg/bimap/blob/e5c2657a9e2d6184622ad4ccd1373e6c60a7efca/example/population_bimap.cpp#L46 Specifying the Boost namespace on `optional` fixes it (you cannot use std here).
gcc 11.4 fails to compile this example with an error
template argument 1 is invalidon this line:bimap/example/population_bimap.cpp
Line 46 in e5c2657
Specifying the Boost namespace on
optionalfixes it (you cannot use std here).