Function expand_macro_attr 

fn expand_macro_attr(
    cx: &mut ExtCtxt<'_>,
    sp: Span,
    def_span: Span,
    node_id: NodeId,
    name: Ident,
    transparency: Transparency,
    args: TokenStream,
    body: TokenStream,
    rules: &[MacroRule],
) -> Result<TokenStream, ErrorGuaranteed>

Expands the rules based macro defined by rules for a given attribute args and body.