add_edge hangs when trying to form a loop

[tim0s]

Describe the bug

In certain situations if the user attempts to construct an (incorrect) SDFG, state.add_edge(...) never returns.

To Reproduce

The following snippet demonstrates this

import dace

sdfg = dace.SDFG("foo")
state = sdfg.add_state()
sdfg.add_array("bla", shape=(10, ), dtype=dace.float32)
mentry_3, mexit_3 = state.add_map("map_3", dict(i="0:9"))
mentry_3.add_in_connector("IN_0")
mentry_3.add_out_connector("OUT_0")
state.add_edge(mentry_3, "OUT_0", mentry_3, "IN_0", dace.Memlet(data="bla", subset='0:9'))

Expected behavior

The function returns a value that indicates it was used erroneously or throws an exception in finite time.

Additional context

This was found while auto-generating edge-cases for dace usage in order to determine how DaCe handles them.

[tbennun]

Thanks, fixed in #1559.