ast-utils Command
The ast-utils command generates and displays the Abstract Syntax Tree (AST) representation of Rust source files in
JSON format.
It uses the syn crate to parse Rust code and syn-serde for JSON serialization.
Usage
cargo run -- ast-utils --file-path ./src/main.rs
Arguments:
--file-path(or ): Path to the Rust source file to parse-f
Behavior
The tool performs the following operations:
- File Reading: Reads the specified Rust source file
- AST Parsing: Uses
syn::parse_file()to generate the AST - JSON Output: Converts the AST to pretty-printed JSON using
syn-serde
The output includes detailed structural information about:
- Function definitions
- Struct and enum declarations
- Import statements
- Type definitions
- Expression trees
- And all other Rust language constructs
Output
The command outputs a JSON representation of the AST directly to stdout. The JSON contains:
- Structural Information: Complete syntax tree with all language constructs
- Pretty Formatting: Human-readable JSON with proper indentation
- Comprehensive Details: All tokens, spans, and syntactic elements
Example
cargo run -- ast-utils --file-path examples/simple_program.rs
This would output something like:
{
"shebang": null,
"attrs": [],
"items": [
{
"Fn": {
"attrs": [],
"vis": {
"Public": {
"pub_token": {
"span": {
"start": 0,
"end": 3
}
}
}
},
"sig": {
"constness": null,
"asyncness": null,
"unsafety": null,
"abi": null,
"fn_token": {
"span": {
"start": 4,
"end": 6
}
},
"ident": "main",
// ... more AST structure
}
}
}
]
}
Use Cases
- Code Analysis: Understanding the structure of Rust source code
- Tooling Development: Building custom analysis tools that work with Rust AST
- Educational: Learning about Rust's syntax tree representation
- Debugging: Inspecting how the compiler parses your code