syntax_data: {"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"fn_sig_for_fn_abi(tcx,"}]}
source_snippet:         fn_sig_for_fn_abi(tcx, instance, typing_env),
context_before:         &LayoutCx::new(tcx, typing_env),
context_after:         extra_args,