{"ast_node_type":"other","tokens":[{"end":58,"kind":"keyword","start":0,"text":")"}]}
    ) -> InterpResult<'tcx, ImmTy<'tcx, CtfeProvenance>> {
        val: &ImmTy<'tcx, CtfeProvenance>,
        // If it's a frozen shared reference that's not already immutable, potentially make it immutable.