syntax_data: {"ast_node_type":"variable","tokens":[{"end":81,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let trait_args_count = tcx.generics_of(trait_def_id).count();
context_before:                 Some(trait_def_id) => {
context_after:                     &GenericArgs::identity_for_item(tcx, def_id)[..trait_args_count]