Function format_references 

fn format_references<'a, R>(
    ty: &'a str,
    references: R,
    has_self_ref: bool,
) -> impl Display + 'a
where
    R: IntoIterator<Item = StorePathRef<'a>> + 'a,

This contains the Nix logic to create “reference strings”, used for the output path calculation of ca paths and text paths.