syntax_data: {"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let liberated_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
context_before:             let sig = tcx.fn_sig(def_id).instantiate_identity();
context_after:             let mut assumed_wf_types: Vec<_> =