syntax_data: {"ast_node_type":"other","tokens":[{"end":35,"kind":"keyword","start":0,"text":"def_id.to_def_id(),"}]}
source_snippet:                 def_id.to_def_id(),
context_before:             let sig = tcx.liberate_late_bound_regions(
context_after:                 tcx.fn_sig(def_id).instantiate_identity(),