fix deferred assignments

src/kyupy/verilog.py

@@ -144,6 +144,7 @@ class VerilogTransformer(Transformer):
                         c.io_nodes[positions[name]] = n
                     if sd.kind == 'input':
                         Line(c, n, Node(c, name))
+        deferred_assignments = set()
         while len(assignments) > 0:
             more_assignments = []
             for target, source in assignments:  # pass 1.5: process signal assignments
@@ -163,7 +164,7 @@ class VerilogTransformer(Transformer):
                         source_sigs.append(s)
                 for t, s in zip(target_sigs, source_sigs):
                     if t in c.forks:
-                        assert s not in c.forks, 'assignment between two driven signals'
+                        assert s not in c.forks, f'assignment between two driven signals: source={s} target={t}'
                         Line(c, c.forks[t], Node(c, s))
                     elif s in c.forks:
                         assert t not in c.forks, 'assignment between two driven signals'
@@ -173,7 +174,11 @@ class VerilogTransformer(Transformer):
                         const_count += 1
                         Line(c, cnode, Node(c, t))
                     else:
-                        more_assignments.append((target, source))
+                        if (t, s) in deferred_assignments:
+                            log.info(f'ignoring: assign {t} = {s}')
+                        else:
+                            more_assignments.append((t, s))
+                            deferred_assignments.add((t, s)) 
             assignments = more_assignments
         for stmt in args[2:]:  # pass 2: connect signals to readers
             if isinstance(stmt, Instantiation):