{"ast_node_type":"import","tokens":[{"end":37,"kind":"keyword","start":0,"text":"//"}]}
    // FIXME: use a proper span here?
    let typing_env = ty::TypingEnv::fully_monomorphized();
    let (ecx, op) = mk_eval_cx_for_const_val(tcx.at(rustc_span::DUMMY_SP), typing_env, val, ty)?;