syntax_data: {"ast_node_type":"other","tokens":[{"end":32,"kind":"keyword","start":0,"text":"outer_expn:"}]}
source_snippet:             outer_expn: expn_id,
context_before:         self.syntax_context_data[ctxt.as_u32() as usize] = SyntaxContextData {
context_after:             outer_transparency: transparency,