Make scalar to symbol promotion robust to node order in state (#1766)

Fixes #1727

dace/sdfg/analysis/schedule_tree/treenodes.py

@@ -41,6 +41,8 @@ def __init__(self, children: Optional[List['ScheduleTreeNode']] = None):
         if self.children:
             for child in children:
                 child.parent = self
+        self.containers = {}
+        self.symbols = {}
 
     def as_string(self, indent: int = 0):
         if not self.children:

dace/transformation/passes/scalar_to_symbol.py

@@ -522,6 +522,8 @@ def remove_scalar_reads(sdfg: sd.SDFG, array_names: Dict[str, str]):
     for state in sdfg.states():
         scalar_nodes = [n for n in state.nodes() if isinstance(n, nodes.AccessNode) and n.data in array_names]
         for node in scalar_nodes:
+            if node not in state:
+                continue
             symname = array_names[node.data]
             for out_edge in state.out_edges(node):
                 for e in state.memlet_tree(out_edge):
@@ -649,7 +651,7 @@ def apply_pass(self, sdfg: SDFG, _: Dict[Any, Any]) -> Set[str]:
             scalar_nodes = [n for n in state.nodes() if isinstance(n, nodes.AccessNode) and n.data in to_promote]
             # Step 2: Assignment tasklets
             for node in scalar_nodes:
-                if state.in_degree(node) == 0:
+                if node not in state or state.in_degree(node) == 0:
                     continue
                 in_edge = state.in_edges(node)[0]
                 input = in_edge.src

tests/passes/scalar_to_symbol_test.py

@@ -729,6 +729,35 @@ def test_double_index_bug():
                         assert getattr(sympy_node, "name", None) != "indices"
 
 
+def test_reversed_order():
+    """
+    Tests a failure reported in issue #1727.
+    """
+    sdfg = dace.SDFG('tester')
+    sdfg.add_array('inputs', [1], dace.int32)
+    sdfg.add_transient('a', [1], dace.int32)
+    sdfg.add_transient('b', [1], dace.int32)
+    sdfg.add_array('output', [1], dace.int32)
+    initstate = sdfg.add_state()
+    state = sdfg.add_state_after(initstate)
+    finistate = sdfg.add_state_after(state)
+
+    # Note the order here
+    w = state.add_write('b')
+    t = state.add_tasklet('assign', {'inp'}, {'out'}, 'out = inp')
+    r = state.add_read('a')
+    state.add_edge(t, 'out', w, None, dace.Memlet('b'))
+    state.add_edge(r, None, t, 'inp', dace.Memlet('a'))
+
+    initstate.add_nedge(initstate.add_read('inputs'), initstate.add_write('a'), dace.Memlet('inputs'))
+    finistate.add_nedge(finistate.add_read('b'), finistate.add_write('output'), dace.Memlet('output'))
+
+    sdfg.validate()
+    promoted = scalar_to_symbol.ScalarToSymbolPromotion().apply_pass(sdfg, {})
+    assert promoted == {'a', 'b'}
+    sdfg.compile()
+
+
 if __name__ == '__main__':
     test_find_promotable()
     test_promote_simple()
@@ -753,3 +782,4 @@ def test_double_index_bug():
     test_ternary_expression(False)
     test_ternary_expression(True)
     test_double_index_bug()
+    test_reversed_order()