SiblingSubgraph does not handle Copies at output boundary

[lmondada]

The following test

    #[test]
    fn edge_both_output_and_copy() {
        let one_bit = type_row![BOOL_T];
        let two_bit = type_row![BOOL_T, BOOL_T];

        let mut builder =
            DFGBuilder::new(FunctionType::new(one_bit.clone(), two_bit.clone())).unwrap();
        let inw = builder.input_wires().exactly_one().unwrap();
        let outw1 = builder.add_dataflow_op(not_op(), [inw]).unwrap().out_wire(0);
        let outw2 = builder
            .add_dataflow_op(and_op(), [inw, outw1])
            .unwrap()
            .outputs();
        let outw = [outw1]
            .into_iter()
            .chain(outw2);
        let h = builder.finish_hugr_with_outputs(outw, &EMPTY_REG).unwrap();
        let view = SiblingGraph::<DfgID>::new(&h, h.root());
        let subg = SiblingSubgraph::try_new_dataflow_subgraph(&view).unwrap();
        assert_eq!(subg.nodes().len(), 1);
    }

encodes the computation

graph TD
IN --> NOT
IN --> AND
NOT --> AND
NOT --> OUT
AND --> OUT

Loading

This currently fails with the error NotConvex as the output of the NOT is taken to be an output of the subgraph, even though one copy is actually still within the subgraph and used for the AND gate.

[cqc-alec]

@lmondada I think the final assertion in that test should be

        assert_eq!(subg.nodes().len(), 2);

Am I right?

[lmondada]

Yes, absolutely!