flow/network: handle default endpoints correctly in _infer_plumbing_layout

diff --git a/migen/flow/network.py b/migen/flow/network.py
index e33f04e9399e2499abda2b234461f075432d7c72..6ca01b94c3e26e07ae3085c673a7707ea1c98aee 100644 (file)
--- a/migen/flow/network.py
+++ b/migen/flow/network.py
@@ -161,18 +161,25 @@ class DataFlowGraph(MultiDiGraph):
                                        edges = self.in_edges(a, data=True)
                                        assert(len(edges) == 1)
                                        other, me, data = edges[0]
+                                       if other.is_abstract():
+                                               continue
                                        other_ep = data["source"]
+                                       if other_ep is None:
+                                               other_ep = other.actor.single_source()
                                elif a.actor_class in plumbing.layout_source:
                                        edges = self.out_edges(a, data=True)
                                        assert(len(edges) == 1)
                                        me, other, data = edges[0]
+                                       if other.is_abstract():
+                                               continue
                                        other_ep = data["sink"]
+                                       if other_ep is None:
+                                               other_ep = other.actor.single_sink()
                                else:
                                        raise AssertionError
-                               if not other.is_abstract():
-                                       layout = other.actor.token(other_ep).layout()
-                                       a.parameters["layout"] = layout
-                                       a.instantiate()
+                               layout = other.actor.token(other_ep).layout()
+                               a.parameters["layout"] = layout
+                               a.instantiate()
        
        def _instantiate_actors(self):
                # 1. instantiate all abstract non-plumbing actors
@@ -184,13 +191,9 @@ class DataFlowGraph(MultiDiGraph):
                # 3. resolve default eps
                for u, v, d in self.edges_iter(data=True):
                        if d["source"] is None:
-                               source_eps = u.actor.sources()
-                               assert(len(source_eps) == 1)
-                               d["source"] = source_eps[0]
+                               d["source"] = u.actor.single_source()
                        if d["sink"] is None:
-                               sink_eps = v.actor.sinks()
-                               assert(len(sink_eps) == 1)
-                               d["sink"] = sink_eps[0]
+                               d["sink"] = v.actor.single_sink()
        
        # Elaboration turns an abstract DFG into a concrete one.
        #   Pass 1: eliminate subrecords and divergences