Function companion_debug_clone 

pub(crate) fn companion_debug_clone(
    df_name: &Ident,
    generics: &Generics,
    fields: &[(Ident, TokenStream)],
) -> TokenStream

Debug and Clone for a companion, each implemented only when every field type has it. #[derive(Debug, Clone)] would demand both of every column’s element type (#2013). fields are the companion’s fields with their types.