syntax_data: {"ast_node_type":"variable","tokens":[{"end":24,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let bound_vars =
context_before:         // 3) ['x] + ['b] -> ['x, 'b]
context_after:             tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(pred_bound_vars));