syntax_data: {"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"sig.to_coroutine_given_kind_and_upvars("}]}
source_snippet:                 sig.to_coroutine_given_kind_and_upvars(
context_before:                 iter::once(env_ty).chain([sig.tupled_inputs_ty]),
context_after:                     tcx,