syntax_data: {"ast_node_type":"other","tokens":[{"end":107,"kind":"keyword","start":0,"text":"($_opt_name:ident,"}]}
source_snippet:     ($_opt_name:ident, $opt_expr:expr, $mods:expr, $tmod_vals:expr, [SUBSTRUCT $substruct_enum:ident]) => {
context_before: macro_rules! gather_tmods_top_level {
context_after:         $opt_expr.gather_target_modifiers($mods, $tmod_vals);