I'm a fan of antlr-ng. It's a solid upgrade if you're already using antlr. In my experience, they're fully compatible. antlr's ALL(*) parsing is relatively powerful for a parser generator, but it lacks support for incremental parsing. antlr-ng might improve things enough to be usable interactively in smaller settings, even if you need to reparse the document each time. It also comes with useful extensions like https://github.com/mike-lischke/antlr4-c3, which generates syntactic and semantic completions directly from the grammar.