antlr4-dev

ANTLR4 builds an AST by defining grammar rules in a .g4 file, then generating a parser and lexer that traverse input tokens and construct an Abstract Syntax Tree. The generated parser applies your grammar rules to produce AST nodes, which you can inspect and manipulate using visitor or listener patterns.

The visitor pattern in ANTLR4 lets you traverse AST nodes by defining visit methods for each grammar rule. Each visit method receives an AST node, processes it, and returns a result. ANTLR4 generates a base visitor class; you extend it and override visit methods to implement your custom logic for each node type.

Configure Maven with the ANTLR4 plugin in your pom.xml to run generate-sources during the build lifecycle. This generates parser, lexer, and visitor classes from your .g4 grammar file. Then compile and test your generated code using standard Maven compile and test phases.

Yes, ANTLR4 is designed for frontend language tooling. You define grammar rules to specify lexical tokens and syntax structures, generate a parser from those rules, build AST nodes with accept methods, and implement visitor-based traversal to analyze or transform the resulting tree.

ANTLR4 abstracts away parser implementation details, but understanding lexical analysis, syntax rules, and tree traversal concepts helps. The Skill provides templates and examples for common patterns like AST node creation and visitor methods, making it accessible for grammar design without deep compiler theory knowledge.

Use ANTLR4's TestRig tool to debug your grammar by visualizing the parse tree interactively. This reveals whether your lexical rules, grammar rules, or visitor logic are producing unexpected node structures, letting you refine your grammar and AST node implementation iteratively.