Function parse_and_resolve_includes

pub fn parse_and_resolve_includes<S>(
    report: &mut Report,
    span: Option<Span>,
    fileserver: &mut dyn FileServer,
    root_filename: S,
    seen_filenames: &mut Vec<String>,
    once_filenames: &mut HashSet<String>,
) -> Result<AstTopLevel, ()>
where
    S: Borrow<str>,