{"ast_node_type":"variable","tokens":[{"end":87,"kind":"keyword","start":0,"text":"let"}]}
    let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
    .with_type_param_mode(ParamLoweringMode::Variable);
    let target_trait = impl_data.target_trait.as_ref()?;