syntax_data: {"ast_node_type":"other","tokens":[{"end":121,"kind":"keyword","start":0,"text":"($struct_name:ident,"}]}
source_snippet:     ($struct_name:ident, $tmod_enum_name:ident, $opt_name:ident, $opt_expr:expr, $init:expr, $mods:expr, $tmod_vals:expr,
context_before:     };
context_after:         [UNTRACKED], [TARGET_MODIFIER]) => {