syntax_data: {"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"ty::FnDef(def_id,"}]}
source_snippet:             ty::FnDef(def_id, args) => interner.fn_sig(def_id).instantiate(interner, args),
context_before:             ty::FnPtr(sig_tys, hdr) => sig_tys.with(hdr),
context_after:             ty::Error(_) => {