Need help invoking a rust library with Typescript in Tauri

Question

In my project I want to analyze the source code of a PHP file and convert it to AST. There is already a javascript package for this, but it only works with node. So I tried to convert the PHP code to AST using a Rust library. However, I have no experience with Rust and do not get anywhere:

inside file src-tauri/src/main.rs:

#[tauri::command]
fn php_to_ast(code: &str) -> String {
    match parser::parse(code) {
        Ok(ast) => {
            format!("{:?}", ast)
        }
    }
}

invoke in typescript:

invoke('php_to_ast', { code: value }).then((result) => {
            this._ast = result;
            console.log({ast: this._ast});
        }).catch((error) => {
            console.error({error});
        });

the console error message is:

error[E0004]: non-exhaustive patterns: `Err(_)` not covered
 --> src/main.rs:8:11
  |
8 |     match parser::parse(code) {
  |           ^^^^^^^^^^^^^^^^^^^ pattern `Err(_)` not covered
  |
note: `Result<Vec<php_parser_rs::parser::ast::Statement>, ParseErrorStack>` defined here
  = note: the matched value is of type `Result<Vec<php_parser_rs::parser::ast::Statement>, ParseErrorStack>`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
11~         }
12+         Err(_) => todo!()
  |

I am aware that I am not fully processing the return values from parser::parse(). For comparison, in the Rust library example, the call looks like this:

fn main() -> Result<()> {
    match parser::parse(CODE) {
        Ok(ast) => {
            println!("{:#?}", ast);
        }
        Err(err) => {
            println!("{}", err.report(CODE, None, true, false)?);

            println!("parsed so far: {:#?}", err.partial);
        }
    }

    Ok(())
}

Presumably I should also still process and return the errors (as a string with an error message?).