syntax_data: {"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"[SUBSTRUCT"}]}
source_snippet:             [SUBSTRUCT $substruct_enum:ident $variant:ident] |
context_before:         @parse {$($eout:tt)*}, ($puser_value:ident){$($pout:tt)*};
context_after:         $($tail:tt)*