Autocomplete does not have a syntax, it is just `name<tab>` for names, or `->` or `.` for for C/C++ and similar DOP languages, or `(` or `<ctrl><space>` for function calltips (not actually autocompletion).
It matches symbols that have to be parsed from the source language, which means for generating tags the language is important and you can't change names to anything not allowed in the language.