Mismatched serialisation of Consts between rust and python

[aborgna-q]

This is the serialised repr of a hugr_core::std_extensions::arithmetic::float_types::ConstF64

{
    "parent": 1,
    "op": "Const",
    "v": {
        "v": "Extension",
        "typ": {
            "t": "Opaque",
            "extension": "arithmetic.float.types",
            "id": "float64",
            "args": [],
            "bound": "C"
        },
        "value": {
            "c": "ConstF64",
            "v": {
                "value": 0.5
            }
        },
        "extensions": [
            "arithmetic.float.types"
        ]
    }
}

Compare it to the encoding of a hugr.std.float.FloatVal for the same value

{
    "parent": 0,
    "op": "Const",
    "v": {
        "v": "Extension",
        "extensions": [],
        "typ": {
            "t": "Opaque",
            "extension": "arithmetic.float.types",
            "id": "float64",
            "args": [],
            "bound": "C"
        },
        "value": {
            "c": "float",
            "v": 0.5
        }
    }
},

Note:

• The Cost op missing its extensions
• The value encoded directly as a Value instead of a dict

Code used to generate the examples:

Rust 🦀

fn example_float_const() {
    let hugr = build_main(
        Signature::new(type_row![], type_row![FLOAT64_TYPE])
            .with_extension_delta(float_types::EXTENSION_ID)
            .into(),
        |mut f_build| {
            let float_val = f_build.add_load_const(Value::from(ConstF64::new(0.5)));
            f_build.finish_with_outputs([float_val])
        },
    )
    .unwrap();

    println!("{}", serde_json::to_string_pretty(&hugr).unwrap());
}

Python 🐍

def test_float_const():
    h = Dfg()
    val = h.load(FloatVal(0.5))
    h.set_outputs(val)

    print(h.hugr.to_json())