{"ast_node_type":"function","tokens":[{"end":78,"kind":"keyword","start":0,"text":"fn"}]}
    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
impl<'tcx> NonConstOp<'tcx> for RawPtrComparison {
        // FIXME(const_trait_impl): revert to span_bug?