IntelliSense in Visual Studio environment

From performance point of view, this might be C, C++ stuff, but this is purely a guess. These are multi-threaded applications which run in the background and keep analyzing the file you are modifying.

Even you can write one such plug in, if you have an idea to improve the product. Please refer to https://www.visualstudio.com/en-us/explore/explore-vside-vsi.aspx