syntax_data: {"ast_node_type":"other","tokens":[{"end":44,"kind":"keyword","start":0,"text":"coroutine_captures_by_ref_ty:"}]}
source_snippet:         coroutine_captures_by_ref_ty: I::Ty,
context_before:         closure_tupled_upvars_ty: I::Ty,
context_after:     ) -> I::Ty {