So I'm working on this package that uses C++11 via Rcpp. Its DESCRIPTION has "SystemRequirements: C++11" and the files in question have "// [[Rcpp::plugins(cpp11)]]" at the top. And the whole things build fine. Despite all that, the syntax highlighting tells me that it's never heard of C++11 constructions like "std::unordered_map". Now, clearly the compiler has, because everything works. So how do I persuade RStudio (1.1.383) to provide diagnostics for this version of C++ rather than the previous one? Where does it take its cue for syntax highlighting?