{"ast_node_type":"other","tokens":[{"end":121,"kind":"keyword","start":0,"text":"//"}]}
        // We don't do what rustc does exactly, rustc does something clever when the spans have different syntax contexts
    fn merge_spans(a: SpanData<Ctx>, b: SpanData<Ctx>) -> SpanData<Ctx> {
        // but this runs afoul of our separation between `span` and `hir-expand`.