{"ast_node_type":"variable","tokens":[{"end":99,"kind":"keyword","start":0,"text":"let"}]}
    let (sig, binders) = db.callable_item_signature(callable_def).into_value_and_skipped_binders();
    let generic_params = generics(db, generic_def);
    let bound_vars = generic_params.bound_vars_subst(db, DebruijnIndex::INNERMOST);