Crate java_lang 

Java AST Parser — a syn-style API for Java 25.

This crate provides a complete Java Abstract Syntax Tree parser that closely follows the Java Language Specification (JLS) SE 25. The API design is inspired by Rust’s [syn] crate.

Quick Start

use java_lang::ast::CompilationUnit;
use java_lang::parse_str;

let unit: CompilationUnit = parse_str(
    "package com.example;\n\npublic class Hello {\n    public static void main(String[] args) {\n        System.out.println(\"Hello, World!\");\n    }\n}\n"
).unwrap();

// Access parsed elements
if let Some(pkg) = &unit.package {
    println!("Package: {:?}", pkg.name);
}
for item in &unit.type_decls {
    println!("Type: {:?}", item);
}

Design Principles

• Syn-style API: Uses Parse trait and ParseStream similar to [syn].
• Complete coverage: Supports Java 25 features including records, sealed classes, pattern matching, switch expressions, text blocks, and unnamed variables.
• Span tracking: Every AST node carries span information for error reporting.
• Zero-copy identifiers: Uses Ident with interning for efficient comparison.

Re-exports

pub use ast::compilation_unit::CompilationUnit;

pub use ast::Comment;

pub use ast::CommentKind;

Modules

ast

Macros

format_ident

Construct an identifier from a string literal.

opt

Optionally parse something. Returns None if the next token doesn’t match.

peek

Peek at the next token and check if it matches.

peek_ident

Peek at the next token and check if it is an identifier.

Structs

Error

The error type for Java parsing.

Ident

A Java identifier.

ParseStream

The parsing cursor, similar to syn’s ParseBuffer.

Span

A span of source code, represented as a range of byte offsets.

Token

A token produced by the lexer.

Enums

TokenKind

The kind of token.

Traits

Parse

A trait for types that can be parsed from a ParseStream.

Functions

parse

Parse a string into a value of type T without checking for trailing tokens.

parse_file

Parse a Java source file into a value of type T.

parse_str

Parse a string into a value of type T that implements Parse.

Type Aliases

Result

A specialized Result type for Java parsing.