lambda capture 'this' is not used

[cpanse]

cp@lilith:~ > R CMD INSTALL recmap_1.0.3.tar.gz 
* installing to library ‘/Library/Frameworks/R.framework/Versions/3.5/Resources/library’
* installing *source* package ‘recmap’ ...
** libs
clang++ -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include/ -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include   -fPIC  -Wall -g -O2 -c RcppExports.cpp -o RcppExports.o
clang++ -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include/ -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include   -fPIC  -Wall -g -O2 -c Rrecmap.cpp -o Rrecmap.o
In file included from Rrecmap.cpp:26:
../inst/include/recmap.h:260:26: warning: lambda capture 'this' is not used [-Wunused-lambda-capture]
    each_unique_pair(M, [this](map_region &a, map_region &b,
                         ^~~~
1 warning generated.
clang -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include/ -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include   -fPIC  -Wall -g -O2  -c recmap_init.c -o recmap_init.o
clang++ -std=gnu++11 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/usr/local/lib -o recmap.so RcppExports.o Rrecmap.o recmap_init.o -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
installing to /Library/Frameworks/R.framework/Versions/3.5/Resources/library/recmap/libs
** R
** data
** inst
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** installing vignettes
** testing if installed package can be loaded
* DONE (recmap)