Influence of Unused Transient on the Signature

[philip-paul-mueller]

As far as I can tell the recent fix to LoopToMap introduced a change in behaviour.
The PR also modified how SDFG::_used_symbols_internal() works and in my opinion changed it in a non desirable way.

Consider the following script:

import dace
import pytest

def _make_sdfg_with_unused_transient(create_unused_transient: bool) -> dace.SDFG:
    sdfg = dace.SDFG("unused_transient")
    state = sdfg.add_state()

    for name in "ab":
        sdfg.add_array(
                name,
                shape=(10,),
                dtype=dace.float64,
                transient=False,
        )

    sdfg.add_symbol("x_shape", dace.int32)
    if create_unused_transient:
        sdfg.add_array(
                "x",
                shape=("x_shape",),
                dtype=dace.float32,
                transient=True,
        )

    state.add_mapped_tasklet(
            "map",
            map_ranges={"__i": "0:10"},
            inputs={"__in": dace.Memlet("a[__i]")},
            code="__out = __in + 1.90",
            outputs={"__out": dace.Memlet("b[__i]")},
            external_edges=True,
    )

    return sdfg

if __name__ == "__main__":
    create_unused_transient = True
    sdfg: dace.SDFG = _make_sdfg_with_unused_transient(create_unused_transient)

    print(f"Free Symbols: {sdfg.free_symbols}")
    print(f"arglist(): {sdfg.arglist()}")
    print(f"signature_arglist(): {sdfg.signature_arglist()}")
    print(f"signature_init_arglist(): {sdfg.init_signature()}")

As you can see depending on create_unused_transient the SDFG may or may not contain data descriptor with name x, that when it is present is not used.
Furthermore, the array has a symbolic size of x_shape, that symbol, however, is always present.
If you run that script using DaCe 2.0.0a3, then x_shape will not be part of the signature.

But if you use current main (a6717b608f497190205d) then x_shape will part of the signature if create_unused_transient is True.
However, if create_unused_transient is False then it will not be present.
It is important to notice that even if x_shape is present in the signature it is not used, i.e. the array is not allocated.

My question now is what is the correct behaviour?
In my opinion x_shape should not be part of the signature and this is an unintended side effect.