hash a stylesheet of swc

main.rs

use std::hash::{Hash, Hasher};
use swc_common::{FileName, SourceMap};
use swc_common::input::StringInput;
use swc_common::sync::Lrc;
use std::borrow::Borrow;

fn main() {
    let cm: Lrc<SourceMap> = Default::default();

    let fm = cm
        .new_source_file(FileName::Real("test.css".into()), ".h1 {color : red; }".to_string());
        // .new_source_file(FileName::Real("test.css".into()), "".to_string());   // OK

    let lexer = swc_css_parser::lexer::Lexer::new(StringInput::from(&*fm), None, Default::default());
    let mut parser = swc_css_parser::parser::Parser::new(lexer, Default::default());
    let stylesheet = parser.parse_all().unwrap();

    let mut hasher = std::collections::hash_map::DefaultHasher::new();
    stylesheet.hash(&mut hasher);
    let h = hasher.finish();

    println!("hash: {}", h);
}