{"ast_node_type":"impl","tokens":[{"end":78,"kind":"keyword","start":0,"text":"//"}]}
    // it, to validate whether or not the impl is legal to instantiate at all.
    // we use the ReErased, which has no lifetime information associated with
    let only_region_params = |param: &ty::GenericParamDef, _: &_| match param.kind {