AntlrVSIX. AntlrVSIX is a language server for use with Visual Studio 2019, Visual Studio Code, and Gnu Emacs to support Antlr, Bison, and W3C EBNF grammars. In addition to the IDE extensions provided here, a command-line tool is available to refactor grammars in order to make them cleaner, more readable, and more efficient.