{"ast_node_type":"other","tokens":[{"end":57,"kind":"keyword","start":0,"text":"mbe::TokenTree::MetaVarExpr(dspan,"}]}
            mbe::TokenTree::MetaVarExpr(dspan, expr) => {
            // Replace meta-variable expressions with the result of their expansion.
                transcribe_metavar_expr(&mut tscx, *dspan, expr)?;