Edison Design Group Open-Sources Its C++ Front End
A front end that has quietly sat inside Visual Studio's IntelliSense is now public, and by the source's count it is one of only four left.
Visual Studio’s IntelliSense has been running on a front end whose source almost nobody has read. Intel’s compiler used the same code until it switched to Clang. Neither one published the source. At the November 2025 C++ ISO meeting, Edison Design Group announced it was winding down and would open-source that front end. The repository is up now, and anyone can clone it.
It carries the front end plus other pieces, among them C and C++ back ends. A second site covers the transition, and a third holds documentation. By the author’s own count, four still-extant C++ front ends remain: Clang, GCC, MSVC, and this one, easily the least visible of the four. It just became readable, and that is the whole news.
The part I keep returning to is export templates. Edison’s front end was the only one to implement C++98’s export feature, and that experience fed the argument for removing it from C++11. Herb Sutter backed deprecation in a 2009 blog post; which paper finally did the removal, I cannot pin down. The pull now is diagnostics: a different lineage will disagree with Clang and GCC about what is legal.
A compiler that shipped the one feature nobody else attempted, then watched the standard delete it, is now something I can read on a Sunday. I would rather find that disagreement myself than let a customer find it. Skip it if you need a supported toolchain with a road map; the group is winding down. Set aside an evening, compile one small project, and read the first error message.