如何基于Java创建Swift语言的ANTLR解析器并生成AST（Windows环境）

Hey there, let's break down your questions step by step based on what you've done so far with ANTLR and Swift grammar:

SwiftSupport.java is an auto-generated helper class tightly linked to the Swift3.g4 grammar file. It holds custom logic and utility functions that the ANTLR-generated parser/lexer needs to handle Swift-specific syntax nuances. For example, it might include code to:

• Manage Swift's context-dependent keywords (some words act as keywords only in specific contexts)
• Parse Swift-unique literals like multi-line strings or numeric values with underscore separators
• Handle scope-related or symbol-processing helper operations defined in the grammar's embedded actions

This file isn't optional—you must include it in your project for the parser and lexer to work correctly with Swift code.

Exactly as you suspected, you just need to add them to your project's source and set up the package structure properly:

• Add a package declaration at the top of every generated .java file (e.g., package com.yourproject.swift.parser;—replace this with your actual project package path)
• Organize the files into a directory structure that matches the package (so if your package is com.yourproject.swift.parser, place the files in src/main/java/com/yourproject/swift/parser/)
• Ensure your project has the antlr4-runtime-4.7.2-SNAPSHOT.jar added as a dependency—this is mandatory for the generated classes to compile and run.

Let's clarify the difference first to avoid confusion:

• The lexer generates tokens (basic building blocks like keywords, identifiers, literals)
• The parser takes those tokens and builds a parse tree—a full, detailed tree of the code's syntax, including every grammar detail (like parentheses, commas, and even redundant keywords)

If you want a streamlined Abstract Syntax Tree (AST) (which strips out syntax noise and focuses on the code's logical structure), you do need to build it manually—but ANTLR gives you tools to simplify this:

• Use the generated Swift3BaseVisitor or Swift3BaseListener classes. These let you traverse the parse tree; in each step, you can create custom AST nodes, skip irrelevant parse tree nodes, and assemble the logical structure you need.
• For example, you could create a SwiftASTVisitor extending Swift3BaseVisitor<ASTNode>, then override methods like visitFunctionDeclaration to convert the parse tree node for a function into your custom FunctionASTNode.

Some grammar files include embedded actions that assist with AST construction, so check the Swift3.g4 file for any comments or code snippets related to ASTs—if they exist, SwiftSupport.java might already have helper methods to support this work.

内容的提问来源于stack exchange，提问作者Ivan