syntax_data: {"ast_node_type":"other","tokens":[{"end":111,"kind":"keyword","start":0,"text":"($opt_name:ident,"}]}
source_snippet:     ($opt_name:ident, $opt_expr:expr, $mods:expr, $tmod_vals:expr, [$non_substruct:ident TARGET_MODIFIER]) => {
context_before:     };
context_after:         compile_error!("Top level option can't be target modifier");