syntax_data: {"ast_node_type":"other","tokens":[{"end":82,"kind":"keyword","start":0,"text":"args.as_coroutine_closure().signature_parts_ty().print(self)?;"}]}
source_snippet:                     args.as_coroutine_closure().signature_parts_ty().print(self)?;
context_before:                     write!(self, " signature_parts_ty=")?;
context_after:                     write!(self, " upvar_tys=")?;