{"ast_node_type":"variable","tokens":[{"end":42,"kind":"keyword","start":0,"text":"//"}]}
        // let _: AssertParamIsCopy<Self>;
        // Just a single assertion for unions, that the union impls `Copy`.
        let self_ty = cx.ty_path(cx.path_ident(trait_span, Ident::with_dummy_span(kw::SelfUpper)));