Function expand_macro

fn expand_macro<'cx>(
    cx: &'cx mut ExtCtxt<'_>,
    sp: Span,
    def_span: Span,
    node_id: NodeId,
    name: Ident,
    transparency: Transparency,
    arg: TokenStream,
    lhses: &[Vec<MatcherLoc>],
    rhses: &[TokenTree],
) -> Box<dyn MacResult + 'cx>

Expands the rules based macro defined by lhses and rhses for a given input arg.