How is that not describing just a regular IDE like Intellij? The reason it has an indexing phase when you open a new project is because the IDE is building a database of your code base. You can then do many kinds of query against it.
They make IDEs for many languages but the indexability of languages varies a lot depending on (mostly) how strong their type system is and how easily parsed the code is. Check out their structured search feature for an example of how to do semantic queries over the indexed AST.
